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1
Kočí, Kamila. "Separace azaarénů vysoceúčinnou kapalinovou chromatografií." Doctoral thesis, Vysoké učení technické v Brně. Fakulta chemická, 2008. http://www.nusl.cz/ntk/nusl-233281.
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Under the framework of this PhD project, a study on chromatographic behaviour of selected azaarenes on octadecylsilica stationary phases during their separation by reversed phase liquid chromatography was developed. The main goal was aimed at an application of the basic RPLC principles on the retention behaviour of azaarenes including the effects such as peak tailing, peak broadening, irreproducible retention or strong retention on a stationary phase. This study was particularly focused on basic azaarenes, also called acridines, which belong to a group of persistent organic pollutants providing mutagenic and/or carcinogenic activity. The retention patterns were studied on a group of eight acridines that are often present in environmental samples polluted with polycyclic aromatic compounds. The mixture of acridines was separated under isocratic elution conditions on three octadecylsilica stationary phases using two different binary mixtures as a mobile phase. Evaluation of the surface properties of the selected stationary phases was firstly performed, followed by the separation experiments. The structure of the experiments was designed to evaluate the effect of three different factors on the retention behaviour of acridines: properties of a stationary phase, composition of a mobile phase and physical-chemical properties of acridines. The treatment of the results was based on the capacity factor values providing the best fitting and repeatability of data, but other parameters that evaluate thermodynamic and kinetic aspects of the separation process were also given. Simple correlations between the three factors and a character of retention mechanism of acridines on the given separation system were found. Application of this knowledge simplifies an optimisation process and helps to solve common separation problems for acridines, but also for other basic analytes displaying similar physical-chemical properties (Mr and pKa).
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Goltra, Robert Joseph III. "Student Retention Matters| A Study of Community College Student Retention Characteristics, Models, and Programs." Thesis, Lindenwood University, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=13806283.
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The purpose of this study was to determine if retention of first-year college students was influenced by specific variables and programs at one Midwest community college. The study was focused on responses from the Community College Survey of Student Engagement (CCSSE) (Center for Community College Student Engagement, 2013) and peer mentoring program data. Data and retention were measured using Wald chi-square tests and t-tests, respectively. The CCSSE benchmarks were Academic Challenge, Active and Collaborative Learning, Student Effort, Student-Faculty Interactions, and Support for Learners. Benchmarks were analyzed using student variables age, gender, working for pay, student loans, and race/ethnicity. Benchmarks titled Student Effort and Support for Learners had a significant impact on retention. The relevance of this finding became clear through analyzing specific student variables to determine their impact on each specific benchmark. Also investigated were the retention rates of first-time students who participated in the college’s peer mentoring program and first-time students who did not participate in the college’s peer mentoring program. Following analysis of the data, there was a statistical difference in the retention rates of first-year, peer-mentored students and non-peer mentored, first-year students. The peer mentoring program was also studied by analyzing the effects peer mentoring had on students who were on academic probation. No statistically significant difference was found in retention rates of students who remained on academic probation and their peers who had moved off probation. Data for all aspects of peer mentoring suggested program consistency positively affects retention rates of first-year students.
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Batchelder, James P. "University Budget Models, Institutional Size, and Student Outcomes." Digital Commons @ East Tennessee State University, 2020. https://dc.etsu.edu/etd/3832.
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The purpose of the non-experimental quantitative research study was to identify if there is a significant difference between the types of budget model an institution utilizes, institutional size, and student enrollment, retention, and graduation rates. This study was to identify if there is significant difference between institutional size and the type budget model utilized.
Member institutions of the American Association of State Colleges and Universities (AASCU) were selected to participate in this study due to their similarities of mission and admissions policy. AASCU institutions share a common mission that focuses on access, innovation, regional support, and inclusion. AASCU institutions are all public regional institutions.
Larger institutions within the study presented significantly higher retention and graduation rates compared to medium size institutions. I used the Carnegie classification of size as institutions that have enrollments less than 3,000 as small, institutions that have enrollments less than 10,000 as medium, and institutions with enrollments greater than 10,000 as large. I study found no significant difference in the types of budget model utilized and the student outcomes related to enrollment, retention, or graduation rates. I did indicate that institutions that utilized a more decentralized budgeting approach had higher enrollment percentages and higher retention and graduation rates than institutions that utilized a centralized budget model. I also did not identify any significant difference in the size of an institution and the type of budget model utilized.
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Kumar, Neraj. "Detection of Variable Retention Time in DRAM." PDXScholar, 2014. https://pdxscholar.library.pdx.edu/open_access_etds/2103.
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This thesis investigates a test method to detect the presence of Variable Retention Time (VRT) bits in manufactured DRAM. The VRT bits retention time is modeled as a 2-state random telegraph process that includes miscorrelation between test and use. The VRT defect is particularly sensitive to test and use conditions. A new test method is proposed to screen the VRT bits by simulating the use conditions during manufacturing test. Evaluation of the proposed test method required a bit-level VRT model to be parameterized as a function of temperature and voltage conditions. The complete 2-state VRT bit model combines models for the time-in-state and for the retention-time including miscorrelation. A copula is used to model the eect of miscorrelation between test and use. The proposed VRT test algorithm runtime is estimated as a function of VRT test coverage, test temperature and test voltage.
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Russell, Bradley Steven. "A comparison of neural network and regression models for Navy retention modeling." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1993. http://handle.dtic.mil/100.2/ADA267132.
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Thesis (M.S. in Management) Naval Postgraduate School, March 1993.Thesis advisor(s): George W. Thomas ; Daniel R. Dolk ; Timothy R. Hill. "March 1993." Includes bibliographical references. Also available online.
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Holliday, Matthew R. "First Year Experience Seminars: How Contrasting Models Impact the College Transition and Retention." Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/316770.
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Most institutions of higher education utilize First Year Experience (FYE) coursework to facilitate college adjustment and student retention. FYE courses are designed to support the college transition by introducing freshman to campus resources that can help them achieve their educational and career goals; however, there is much variation in instructional design across college campuses depending on students' needs and institutional goals. This dissertation examined the differences in student outcomes based on enrollment in either academic content-specific or broad introductory FYE coursework. The first study used a qualitative method to examine resilient Honors students' perceptions of how their introductory FYE course impacted their college transition at the end of their first semester. The second study utilized several quantitative models to longitudinally assess the difference between FYE course enrollment and students' cumulative GPAs, retention, and perceptions during their junior year of college. Thematic analysis of questionnaire responses revealed that the resilient Honors students believed their broad introductory FYE course supported their social and academic transition to college by relieving stress that is commonly associated with the beginning of higher education. The quantitative study found that students who were enrolled in academic content-specific FYE courses had higher grades, retention, and scored higher on college success strategies and first-year satisfaction factor scores, compared to students who were enrolled in the broad introductory FYE courses. These findings were discussed in relation to the current literature on college adjustment, followed by a discussion of the implications for academic units, limitations of the study, and future directions for research in this area.
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Kockisch, Sandra. "Evolution and validation of bioadhesion models predictive of retention in the oral cavity." Thesis, University of Portsmouth, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247476.
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McDaniel, Cleve. "Retention classification models for an historically black university with an open admission policy /." free to MU campus, to others for purchase, 1997. http://wwwlib.umi.com/cr/mo/fullcit?p9841172.
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Miller, Donald C. "An analysis of economic retention models for excess stock in a stochastic demand environment." Thesis, Monterey, California. Naval Postgraduate School, 1994. http://hdl.handle.net/10945/27955.
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Approved for public release; distribution is unlimitedRetention policy for U.S. Navy wholesale inventories in long supply has been in a state of flux and under Congressional scrutiny since 1985. This thesis analyzes and compares the U.S. Navy's current economic retention process to four mathematical Economic Retention Decision Models designed to assist in making retention determinations with respect to excess inventories. The motivation for this research was based on several factors, the two primary factors were; the Navy does not currently use a classical economic retention decision model when making retention/disposal decisions for essential material, and U.S. Navy inventories in long supply were estimated to be as high as 3.4 billion dollars in March 1993. A Pascal based simulation was developed to compare the Navy's retention process and the mathematical models. The comparison was based on performance with respect to the Measures Of Effectiveness (MOE) of Total Cost and Average Customer Wait Time. The simulation was designed to emulate the portions of the Navy's consumable item inventory management system (UICP) applicable to the demand process for a Navy managed consumable item. The goal of this research was to determine how effective the Navy's retention process was as compared with economic retention decision models for both a steady state and a declining demand environment
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Besich, John. "Job embeddedness versus traditional models of voluntary turnover: A test of voluntary turnover prediction." Thesis, University of North Texas, 2005. https://digital.library.unt.edu/ark:/67531/metadc4977/.
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Voluntary turnover has historically been a problem for today's organizations. Traditional models of turnover continue to be utilized in a number of ways in both academia and industry. A newer model of turnover, job embeddedness, has recently been developed in an attempt to better predict voluntary turnover than existing models. Job embeddedness consists of organizational fit, organizational sacrifice, and organizational links. The purpose of this study is to two fold. First, psychometric analyses were conducted on the job embeddedness model. Exploratory factor analyses were conducted on the dimensions of job embeddedness, which revealed a combined model consisting of five factors. This structure was then analyzed using confirmatory factor analysis, assessing a 1, 3, and 5 factor model structure. The confirmatory factor analysis established the use of the 5 factor model structure in subsequent analysis in this study. The second purpose of this study is to compare the predictive power of the job embeddedness model versus that of the traditional models of turnover. The traditional model of turnover is comprised of job satisfaction, organizational commitment, and perceived job alternatives. In order to compare the predictive power of the job embeddedness and traditional model of voluntary turnover, a series of structural equation model analyses were conducting using LISREL. The job embeddedness model, alone, was found to be the best fit with the sample data. This fit was improved over the other two models tested (traditional model and the combination of the traditional and job embeddedness model). In addition to assessing which model better predicts voluntary turnover, it was tested which age group and gender is a better fit with the job embeddedness model. It was found that the job embeddedness model better predicts turnover intention for older respondents and males.
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Scott, Nathan A. "Models, analysis, and recommendations pertaining to the retention of Naval Special Warfare's mid-level officers." Thesis, Monterey, California: Naval Postgraduate School, 2013. http://hdl.handle.net/10945/39010.
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defined in Title 17, United States Code, Section 101. As such, it is in the public domain, and under the provisions of Title 17, United States Code, Section 105, it may not be copyrighted.Approved for public release; distribution is unlimited.Naval Special Warfare (NSW) is facing a substantial deficiency within its midgrade (815 years of active duty service) officer ranks. This thesis employs two different models in order to provide recommendations to the NSW Community Managers office for potential changes that might improve retention of these officers. The NSW Community Managers should use findings from the annualized-cost-of-leaving model to improve near-term retention, and they should use recommendations from the analytical hierarchy process for improving long-term retention.
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Quinn, Ruth. "Evaluation of flow models and pollutant retention isotherms for their application to rain garden bioretention." Thesis, University of Greenwich, 2015. http://gala.gre.ac.uk/14319/.
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The primary aims of this research was firstly to develop a computer modelling tool which could predict pollution retention in a rain garden and secondly to use the model and additional experiments to examine various aspects of rain garden design with respect to pollutant retention. Initially, the behaviour of all contaminants in urban runoff was examined including their retention and possible modelling methods. Heavy metals were then identified as the main focus of this project as this choice was the most beneficial addition to current research. The main factors affecting their retention were found to be macropore flow, pore water velocity, soil moisture content and soil characteristics and the primary method of modelling capture was identified as a sorption isotherm. Thus a dual-permeability heavy metal sorption model was developed; this was based on an intensive literature review of current best practice in both hydrological modelling and pollutant retention fields with respect to rain garden devices. The kinematic wave equation was chosen to model water movement in both the matrix and macropore regions as this provided a simpler alternative to more complex equations while still maintaining good accuracy. With regards to the modelling of heavy metal retention three isotherms were chosen: the linear, Langmuir and Freundlich equations as these were found from previous research to be the most accurate. These isotherms were incorporated into a one dimensional advection-dispersion-adsorption equation in order to model both transport and retention together. This model was tested against the appropriate literature and accurate comparisons were obtained thus validating it. Column experiments were designed to both provide a unique contribution to rain garden research and further validate the model. This was achieved by analysing past experiments and identifying an area where research is lacking; this area was the effect of macropore flow on heavy metal retention in rain garden systems under typical English climatic conditions. The findings of these experiments indicated that although macropore flow did not impact the hydraulic performance of the columns, retention of the most mobile of heavy metals, copper, was decreased slightly in one case. The overall retention of the columns was still high however at a value in excess of 99% for copper, lead and zinc. The results of the experiments were also used to further validate the model. The model was then applied to the development of a rain garden device for a planned roundabout in Kent, U.K. Preliminary design considered an upper root zone layer with organic soil and a sandy storage sublayer each 30 cm thick, for a rain garden area of 5 and 10% the size of the contributing impervious surface. Two scenarios were examined; the accumulation and movement of metals without macropores and the possibility of groundwater contamination due to preferential flow. It was shown that levels of lead can build up in the upper layers of the system, but only constituted a health hazard after 10 years. Simulations showed that copper was successfully retained (no significant concentrations below 50 cm of rain garden soil depth). Finally given concerns of preferential flow bypassing sustainable drainage systems, macropore flow was examined; results indicated that due to site conditions it was not a threat to groundwater at this location for the time frame considered. These actions successfully completed the objectives of this project and it was deemed successful.
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Chou, Po N. "The Asher and Dane School Districts' Mentoring Models: The Relationship Between Mentoring and Retention of Beginning Teachers." BYU ScholarsArchive, 2010. https://scholarsarchive.byu.edu/etd/2370.
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Diverse mentoring models have been implemented by educational organizations to address teacher retention, but debate continues over which mentoring model is most beneficial. Two school districts in Utah, USA, hereafter referred to as the Asher and Dane (pseudonyms) School Districts, provide distinct approaches to mentoring. Both the Asher and Dane School District have used veteran teachers with full-time teaching loads to mentor beginning teachers. The Dane School District, however, has recently implemented a unique and distinct mentoring model in addition to in-school mentors. In this model, full-time released teacher "coaches" with specialized mentoring responsibilities are assigned by the district to mentor several beginning elementary teachers in one grade band (K-3 or 4-6) throughout the district. This longitudinal research studied the Asher and Dane School Districts' mentoring models to develop a grounded theory to explain how these two distinct mentoring models were related to beginning teacher retention rates. A stratified, random sample was utilized, resulting in 23 participants selected for this study. Interview data were gathered from each participant during their first year of teaching, as well as follow-up survey and interview data in their third year. Beginning teacher attrition data were gathered from both the Asher and Dane School Districts. A constant comparative qualitative analysis method, using NVivo software, facilitated the development of the grounded theory. Findings describe and explain the sources and types of support that beginning teachers in these two distinct mentoring models found most beneficial in their induction, development and retention during their first three years. Beginning teachers reported that key mentoring characteristics included a mentor that had experience and knowledge, particularly in their same grade level, as well as a personal relationship with someone who was open to listening to them and who empowered others. Overall, collaborative teams and in-school mentors were a great source of support for beginning teachers, and teacher retention occurred most often when beginning teachers felt supported by their principals. Beginning teachers also experienced a decrease in stress and increase in both autonomy and confidence with time or years of teaching, experience, and support. Findings suggested that district coaches in the Dane School District lacked proximity, personal relationship, and knowledge of the grade being taught by those they mentored. As a result, they lacked the ability to help induct beginning teachers into their school culture and develop informal networks in the school and ensure retention.
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Forsgren, Mattias. "Further perceptions of probability : The perception-cognition gap and sequence retention models under continuously changing Bernoulli distributions." Thesis, Uppsala universitet, Institutionen för psykologi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-332983.
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Hyman Minsky’s Financial Instability Hypothesis (Minsky, 1977) proposes that cyclicality in the financial market is caused by a rational process of learning and inference of probabilities. Although a substantial literature is available on the perception of stationary probability distributions, the learning of non-stationary distributions has received less interest. The purpose of this thesis is to investigate people’s cognitive ability to learn cyclical changes in an underlying probability from feedback. Key aspects of the design of Gallistel et al. (2014) are replicated, but under continuously, rather than stepwise, changing Bernoulli distributions to establish: (i) if the learning process is continuous or discrete, (ii) if there is only local learning or if people induce the underlying functional form, and (iii) if there are any differences in performance between perceptual and cognitive formulations of the task. The step-hold updating model introduced by Gallistel et al. (2014) is compared to two simple trial by trial updating models. The results suggest that (i) the learning process is continuous, (ii) people perceive the functional form explicitly but do not extrapolate, and (iii) there are some differences depending on framing. One of the trial by trial models outperforms the step-hold model for the majority of subjects in this sample and version of the task.
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D'Angelo, Kathryn Peach. "ALCOHOL AND FIRST YEAR COLLEGE RETENTION: THE VALUE OF ALCOHOL DATA TO PREDICTIVE MODELS, POLICY, AND OTHER PREVENTION STRATEGIES." Diss., Temple University Libraries, 2012. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/164912.
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Educational AdministrationEd.D.
Through an examination of first year college students at a large, urban, public university, this study explored one university's use of alcohol course survey data from an online alcohol prevention program to determine whether it would increase the power of a predictive model for first year student retention. At a time when fiscal and human resources are both scarce and in high demand, institutions require policy and prevention strategies that promise to make a positive difference in the health, safety and academic persistence of its students. Using available data on 4,121 first year students this research identified key variables that, when combined with student attitudes about alcohol use, identify the significant predictors of first year college retention enabling university leaders to design more impactful strategies for intervention including a student-centered policy framework with an aim toward reducing harmful behaviors on campus.
Temple University--Theses
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Merriman, Carolyn S. "Promoting Nursing Student Success: Working With at-Risk Nursing Students: Using Success Courses as Models to Increase Retention." Digital Commons @ East Tennessee State University, 2009. https://dc.etsu.edu/etsu-works/8437.
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LoBasso, Thomas. "AN EVALUATION OF ENROLLMENT MANAGEMENT MODELS OF THE 28 FLORIDA COMMUNITY COLLEGES." Doctoral diss., University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2503.
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ABSTRACT The purpose of this study was to determine the extent to which enrollment management models have been successfully implemented within the 28 Florida community colleges. The study also sought to determine when enrollment management structures began and whether expected benefits were achieved. Analysis of the data collected in this study indicated the following five major findings. First, enrollment management concepts and practices have been implemented at some level within the 23 Florida community colleges surveyed. This was evident by the use of the word "enrollment" in the organizational titles as well as in the titles of the individuals who were responsible for the models. Second, enrollment management models reported were determined to be relatively new in comparison to four-year institutions. The literature on enrollment management demonstrated that four-year colleges began enrollment management practices in the early-to-mid 1970s. Much of the existing literature on enrollment management has been based on the experiences at four-year institutions. Third, some enrollment management divisions appeared to have key enrollment offices displaced. The key enrollment offices selected in this study were supported throughout the literature. Those offices represented were as follows: Admissions, Records and Registration, Financial aid, Orientation, and Advising. Fourth, increasing enrollment was the strongest reason for implementing the enrollment structure and subsequently was the strongest benefit realized. The anticipated decline in high school graduates, and the expectation of subsequent declining college enrollments during the 1970s, provided the impetus for the adoption of models of enrollment management. The fifth finding was that moving key enrollment offices such as financial aid into the enrollment management organizations would be an improvement to existing models. As enrollment management concepts are implemented into practice, the realignment of related offices may be necessary to effectively accomplish goals.Ed.D.
Department of Educational Research, Technology and Leadership
Education
Educational Leadership
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Sperry, Rita A. "Prediction of retention and probation status of first-year college students in learning communities using binary logistic regression models." Thesis, Texas A&M University - Corpus Christi, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3626219.
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The first year of college is a critical period of transition for incoming college students. Learning communities have been identified as an approach to link students together in courses that are intentionally integrated and designed with first-year students' needs in mind. Yet, learning community teaching teams are often not provided with data prior to the start of the semester about their students in order to target interventions. Also, it remains unclear as to which students are most benefitted by participating in learning communities. One question then becomes, what variables known on or before the first day of classes are predictive of first-year student success, in terms of retention and probation status, for first-year college students in learning communities?
The correlational study employed univariate and multivariate analyses on pre-college data about three consecutive cohorts of first-year students in learning communities at a regional public university in South Texas. Logistic regression models were developed to predict retention and probation status without respect to learning community membership, as well as for each learning community category.
Results indicated that group differences were not statistically significant based on either first-generation status or age for retention, while group differences were statistically significant for probation status on the basis of all of the pre-college variables except age. Although statistically significant differences were found among the learning community categories for each of the pre-college variables, there were no statistically significant group differences in their retention or probation rates.
The model to predict retention regardless of learning community membership included five variables, while the model to predict probation status included eight variables. The models for each learning community contained different sets of predictor variables; the most common predictors of retention or probation status were high school percentile and orientation date.
The study has practical implications for admissions officers, orientation planners, student support services, and learning community practitioners. It is recommended to replicate the study with more recent learning community cohorts and additional pre-college variables, as well as in programs across the nation, to contribute to the literature about the potential for learning communities to enhance first-year student success.
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Dong, Yu. "Application of integrated constructed wetlands for contaminant treatment and diffusion." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/7750.
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The sediment accumulation is an important characteristic in the ageing process of integrated constructed wetlands (ICW). Retained nutrient and other contaminants in wetland sediments have the potential to be remobilized and released to the overlying water column when environmental conditions change. In this study, mesocosms which filled with saturated sediments and planted with Phragmites australis and Agrostis stolonifera were set up to examine nutrient and other contaminants retention and/or release by wetland sediment and substrates. The effects of physico-chemical parameters on sediment-water contaminant exchange were also investigated through the application of multiple regression models, principal component analysis (PCA), redundancy analysis (RDA), and self-organizing map (SOM) model. The results demonstrated an average net release of chemical oxygen demand (COD), ammonianitrogen (NH3-N), nitrate-nitrogen (NO3-N) and molybdate reactive phosphorus (MRP) to the overlying water column, indicating that the ICW sediment and substrates acted as new contaminant sources. According to statistical analysis, electrical conductivity (EC) and redox potential (RP) values affected COD treatment efficiency. Chloride (Cl) concentration and RP value had an impact on NH3-N treatment performance. NO3-N removal was influenced by dissolved oxygen (DO) concentration and RP value. MRP treatment efficiency was related to DO concentration and EC value. The SOM model was selected as prediction tool to provide numerical estimations for the performance of ICW mesocosms. The model was validated, indicating that NH3-N, NO3-N, MRP, and COD treatment efficiencies could be predicted by input variables which are quick and cost-effective to measure. The SOM model can be seen as an appropriate method for monitoring the performance of mature ICWs. The type of vegetation played a minor role in releasing nutrients and other contaminants. However, the mesocosm planted with Phragmites australis outperformed the one planted with Agrostis stolonifera. No water reached bottom outlet of the mesocosm suggesting that there was little potential risk to contaminate groundwater. The clay liner and the biogeochemical processes taking place within sediments proved to be effective in preventing surface water from infiltration. Although no reduction in the overall performance has been observed for the full-scale ICW sites 7 and/or 11, this laboratory-scale study provided valuable warning signs regarding the loss of contaminant sequestration which may contribute to decline in wetland treatment performance over time. The impacts of hydraulic loading rate (HLR) and seasonal temperature fluctuations on contaminant removal efficiencies of a new ICW system receiving domestic wastewater were also assessed. The system showed good overall treatment performance in terms of effluent quality and removal efficiency. The influence of ICW removal efficiencies of the hydraulic loading rate, which was based on overall water balance, was negligible due to large footprint and multi-cellular configuration of the studied system. Relatively low temperature in autumns and winters resulted in decreased biological activities and lower contaminant removal efficiency. The long-term trends in nutrient removal have been investigated to five Wildfowl & Wetlands Trust constructed wetland systems. The results showed less effective removal even release of NO3-N, total oxidised nitrogen (TON), orthophosphate- phosphorus (PO4-P) and total phosphorus (TP) in many of the systems as a result of wetland aging and lack of sediment management.
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RODRIGUES, JUNIOR ORLANDO. "Aplicacao de modelos metabolicos para a determinacao de funcoes de excrecao e retencao." reponame:Repositório Institucional do IPEN, 1994. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10344.
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Made available in DSpace on 2014-10-09T12:37:35Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:03:23Z (GMT). No. of bitstreams: 1 02232.pdf: 3951264 bytes, checksum: dbd0c0050958a2578e3ec58da9f6ac83 (MD5)
Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Grimsrud, Anna Thora. "Loss to follow-up from South Africa's antiretroviral treatment programme: Trends, risk factors, and models of care to improve retention." Doctoral thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/14578.
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Includes bibliographical referencesOver the past decade, antiretroviral therapy (ART) programmes have rapidly expanded in resource-limited settings. Access to ART has been accelerated through a public health approach to reduce morbidity and mortality, thereby transforming HIV from a humanitarian crisis to a chronic disease. However, the benefits of ART to patients and communities are dependent on patients being retained in care. This thesis investigates loss to follow-up (LTFU) after ART initiation, in the context of scale-up and limited resources and evaluates models of ART delivery to improve retention. After a brief introduction that offers orientation to the key issues and concepts in the field, Chapter 2 provides a comprehensive literature review discussing the public health concerns related to LTFU in ART programmes, as well as the methodological concerns encountered in studying LTFU. Six results chapters (Chapters 3-8) are presented using complementary cohort data from two collaborative datasets (one from programmes in resource-limited settings and one including only South African cohorts) and from a single ART programme at a community health centre. How to define LTFU is the focus of Chapter 3, demonstrating that definitions can have an appreciable impact on estimates of LTFU. In Chapter 4, temporal factors related to the expansion of ART programmes are investigated, with evidence that the risk of patient LTFU increases with each successive calendar year of ART initiation, and that the rate of programme expansion has a stronger association with the risk of LTFU than absolute programme size. Analyses in Chapter 5 suggest that patients initiating ART at higher CD4 cell counts, above 300 cells/μl, may have an increased risk of LTFU compared to patients initiating ART with lower CD4 cell counts. Taken together, these findings underscore the notion that LTFU is a burgeoning threat to the long-term successes of ART programmes in South Africa and other resource-limited settings. Chapters 6-8 report on the implementation and outcomes from innovative models of ART delivery for stable ART patients. Patient outcomes from (i) a nurse-managed ART service and then (ii) community-based 'Adherence Clubs' highlight that comparable and, in some cases, favourable patient outcomes may be achieved when ART delivery is decentralised. This thesis concludes that LTFU is a significant challenge faced by ART programmes. In the context of ambitious targets and evidence of the potential benefits of ART for individuals and communities, concurrent changes to the health system are necessary to support retention in care. The successes of ART programmes in treating a chronic condition in resource-limited settings can be built upon by expanding community-based ART provision and potentially integrating management of other adulthood illnesses.
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Kane-Sellers, Marjorie Laura. "Predictive models of employee voluntary turnover in a North American professional sales force using data-mining analysis." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1486.
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DiGaudio, Lisa M. "Implications of the School Improvement Engine for Teacher Retention and School Organizational Health." ScholarWorks, 2017. https://scholarworks.waldenu.edu/dissertations/3292.
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Teachers working in urban schools in the United States are among those most at-risk for leaving the profession due to poor working conditions and lack of collegial relationships with school leaders and peers, among other factors. Use of professional development tools, such as the School Improvement Engine (SIE), may improve teacher retention and school organizational health; however, little research exists on the use of the SIE in charter schools. The purpose of this case study was to investigate New York City (NYC) school data on teacher retention and student achievement, how NYC charter school leaders participating in the program implemented the SIE, and how teachers and administrators perceived the impact of the implementation on their individual growth and desire to stay in their positions. Peter Senge's organizational learning theory was used to examine how SIE tools may promote a healthy organization in 5 areas (systems thinking, personal mastery, mental models, building shared vision, and team learning). Teacher retention and student achievement archived data for NYC schools were descriptively analyzed. Individual interviews were conducted with a purposeful sample of 10 teachers and 4 school leaders from NYC charter schools implementing the SIE. Interview data were analyzed using open coding to identify key themes. Results indicated that SIE schools outperformed other NYC schools (charter and public) in English Language Arts (ELA), math, and teacher retention. Participants stated that tools like peer review helped them to become more effective in their teaching. Positive social change impacts include providing data that support the use of the SIE to improve teacher effectiveness, teacher retention, and the overall school organizational health.
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Flöjs, Amanda, and Alexandra Hägg. "Churn Prediction : Predicting User Churn for a Subscription-based Service using Statistical Analysis and Machine Learning Models." Thesis, Umeå universitet, Institutionen för matematik och matematisk statistik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-171678.
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Subscription-based services are becoming more popular in today’s society. Therefore, any company that engages in the subscription-based business needs to understand the user behavior and minimize the number of users canceling their subscription, i.e. minimize churn. According to marketing metrics, the probability of selling to an existing user is markedly higher than selling to a brand new user. Nonetheless, it is of great importance that more focus is directed towards preventing users from leaving the service, in other words preventing user churn. To be able to prevent user churn the company needs to identify the users in the risk zone of churning. Therefore, this thesis project will treat this as a classification problem. The objective of the thesis project was to develop a statistical model to predict churn for a subscription-based service. Various statistical methods were used in order to identify patterns in user behavior using activity and engagement data including variables describing recency, frequency, and volume. The best performing statistical model for predicting churn was achieved by the Random Forest algorithm. The selected model is able to separate the two classes of churning users and the non-churning users with 73% probability and has a fairly low missclassification rate of 35%. The results show that it is possible to predict user churn using statistical models. Although, there are indications that it is difficult for the model to generalize a specific behavioral pattern for user churn. This is understandable since human behavior is hard to predict. The results show that variables describing how frequent the user is interacting with the service are explaining the most whether a user is likely to churn or not.Prenumerationstjänster blir alltmer populära i dagens samhälle. Därför är det viktigt för ett företag med en prenumerationsbaserad verksamhet att ha en god förståelse för sina användares beteendemönster på tjänsten, samt att de minskar antalet användare som avslutar sin prenumeration. Enligt marknads-föringsstatistik är sannolikheten att sälja till en redan existerande användare betydligt högre än att sälja till en helt ny. Av den anledningen, är det viktigt att ett stort fokus riktas mot att förebygga att användare lämnar tjänsten. För att förebygga att användare lämnar tjänsten måste företaget identifiera vilka användare som är i riskzonen att lämna. Därför har detta examensarbete behandlats som ett klassifikations problem. Syftet med arbetet var att utveckla en statistisk modell för att förutspå vilka användare som sannolikt kommer att lämna prenumerationstjänsten inom nästa månad. Olika statistiska metoder har prövats för att identifiera användares beteendemönster i aktivitet- och engagemangsdata, data som inkluderar variabler som beskriver senaste interaktion, frekvens och volym. Bäst prestanda för att förutspå om en användare kommer att lämna tjänsten gavs av Random Forest algoritmen. Den valda modellen kan separera de två klasserna av användare som lämnar tjänsten och de användare som stannar med 73% sannolikhet och har en relativt låg missfrekvens på 35%. Resultatet av arbetet visar att det går att förutspå vilka användare som befinner sig i riskzonen för att lämna tjänsten med hjälp av statistiska modeller, även om det är svårt för modellen att generalisera ett specifikt beteendemönster för de olika grupperna. Detta är dock förståeligt då det är mänskligt beteende som modellen försöker att förutspå. Resultatet av arbetet pekar mot att variabler som beskriver frekvensen av användandet av tjänsten beskriver mer om en användare är påväg att lämna tjänsten än variabler som beskriver användarens aktivitet i volym.
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Hansen, Tayler L. "Modeling Digestibility and Rate of Passage in Horses." UKnowledge, 2014. http://uknowledge.uky.edu/animalsci_etds/37.
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Horses consume large amounts of fiber in their diet, which may affect digestibility and digesta rate of passage. The objective of these studies was to assess the effects of diet composition on digestibility and rate of passage in horses using mathematical models. Using previously published data, forage dry matter digestibility (DMD) was related to forage neutral detergent fiber (NDF) concentrations and crude protein (CP) concentrations (DMD = 66.1178 – 0.3410*NDF + 0.6356*CP, DM basis; P < 0.001). In a second experiment, horses were fed diets formulated to have high fiber (HF, n= 3; NDF = 55.3%, CP = 11.8%) or low fiber (LF, n = 3; NDF = 40.5%, CP = 13.3%) concentrations. The LF treatment had greater DM, organic matter, and gross energy digestibilities (P < 0.05), whereas the HF treatment had greater NDF digestibility (P < 0.05). Mathematical models were useful to determine mean retention time (MRT) and there were no differences between model MRT and algebraic MRT, or treatment. Some compartmental parameters were different between treatments (P < 0.05), indicating that dietary fiber may alter some components of digesta passage in horses.
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Wack, Linda-Jacqueline [Verfasser], and Fritz [Akademischer Betreuer] Schick. "Simulation of Tracer Diffusion and Retention for Hypoxia Imaging with Positron Emission Tomography in Two- and Three-Dimensional Tumor Models / Linda-Jacqueline Wack ; Betreuer: Fritz Schick." Tübingen : Universitätsbibliothek Tübingen, 2017. http://d-nb.info/1167246888/34.
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Kucker, Sarah Christine. "The role of vocabulary knowledge and novelty biases in word learning: Exploring referent selection and retention in 18- to 24- month-old children and associative models." Diss., University of Iowa, 2013. https://ir.uiowa.edu/etd/2551.
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In order to learn a new word, a young child must extricate the correct object from multiple possible items in front of them, make an initial association between the specific word-form and the particular referent, robustly link the new word and referent and integrate the new word into their lexicon. Recent research suggests processes that focus attention on the most novel objects in a complex environment, as well as the child's own developing vocabulary play critical roles in this process. This thesis aims to understand the influence of novelty and prior vocabulary knowledge on referent selection and how the interaction of novelty and knowledge can lead to word learning.
A series of empirical studies first probed the use of children's endogenous novelty bias in a referent selection task, and then explored how the use of novelty was related to retention of newly mapped word-referent pairs. A second set of studies explored children's use of vocabulary knowledge in ambiguous learning situations by varying the strength of knowledge for competing items present during novel word learning. Finally, a Hebbian Normalized Recurrent Network model was used to explore the underlying associative process of referent selection and retention in novelty- or knowledge-based word learning tasks.
Counter to prior work, results here suggest that novelty can override knowledge and in fact, be a detriment to word learning. Children demonstrate a novelty bias across multiple contexts and tasks, but the dominant use of novelty does not translate to retention and does not appear to implicate the use of the child's lexicon. As novelty diminishes and vocabulary knowledge increases, some children can overcome this bias and demonstrate retention for new word-referent pairs. Moreover, the results also suggest that when disambiguation requires the use of weak prior knowledge, more cognitive processing is necessary. The increases in processing subsequently translate to retention for new word-referent pairs. The empirical and computational results together suggest potential limitations of these findings to word learning and suggest future directions exploring variability in object and word representations during learning.
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Hetrick, Todd M. "Development and Validation of a Modified Clean Agent Draining Model for Total Flooding Fire Suppression Systems." Digital WPI, 2009. https://digitalcommons.wpi.edu/etd-theses/121.
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This project analyzes the validity of theoretical models used to predict the duration (hold time) for which a halon-replacement suppression agent will remain within a protected enclosure. Two current models and one new formulation are investigated; the sharp descending interface model (as applied in NFPA 2001, Annex C), the wide descending interface model (implemented in ISO 14520.1, Annex E), and the thick descending interface model (introduced herein). The thick interface model develops the characteristic thickness as an additional input parameter. Experimental data from 34 full-scale tests designed to characterize the discharge and draining dynamics of seven clean extinguishing agents (CEA) is used to assess model validity. For purposes of model validation the characteristic thickness is regressed from the experimental data although further work may be required to establish the independence of this parameter to other system design and environmental variables. Results show that the wide and sharp interface models' validity is highly sensitive to the threshold of agent concentration decay being modeled; whereas the thick interface prediction method demonstrates increased robustness at any modeled threshold. When the hold time is defined as a 15% decay in agent concentration, experimentally obtained hold time values are roughly 10% shorter than sharp interface predictions, 60% longer than wide interface predictions, and 30% longer than the thick interface model predicts.
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Nayeb, Yazdi Mohammad. "Understanding the role of scale in assessing sediment and nutrient loads from Coastal Plain watersheds delivered to the Chesapeake Bay." Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/99377.
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Urban and agricultural runoff is the principal contributor to non-point source (NPS) pollution and subsequent impairments of streams, rivers, lakes, and estuaries. Urban and agricultural runoff is a major source of sediment, nitrogen (N) and phosphorus (P) loading to receiving waters. Coastal waters in the southeastern U.S. are vulnerable to human impacts due to the proximity to urban an agricultural land uses, and hydrologic connection of the Coastal Plain to receiving waters. To mitigate the impacts of urban and agricultural runoff, a variety of stormwater control measures (SCMs) are implemented. Despite the importance of the Coastal Plain on water quality and quantity, few studies are available that focus on prediction of nutrient and sediment runoff loads from Coastal Plain watersheds. The overall goals of my dissertation are to assess the effect of urban and agricultural watershed on coastal waters through monitoring and modeling, and to characterize treatment performance of SCMs. These goals are addressed in four independent studies. First, we developed the Storm Water Management Model (SWMM) and the Hydrologic Simulation Program-Fortran (HSPF) models for an urbanized watershed to compared the ability of these two models at simulating streamflow, peak flow, and baseflow. Three separate monitoring and modeling programs were conducted on: 1) six urban land uses (i.e. commercial, industrial, low density residential, high density residential, transportation, and open space); 2) container nursey; and 3) a Coastal Plain retention pond. This study provides methods for estimating watershed pollutant loads. This is a key missing link in implementing watershed improvement strategies and selecting the most appropriate urban BMPs at the local scale. Results of these projects will help urban planners, urban decision makers and ecological experts for long-term sustainable management of urbanized and agricultural watersheds.Doctor of Philosophy
Urban and agricultural runoff is a major source of sediment, nitrogen (N) and phosphorus (P) loading to receiving waters. When in excess, these pollutants degrade water quality and threaten aquatic ecosystems. Coastal waters in the southeastern U.S. are vulnerable to human impacts due to the proximity to urban an agricultural landuse. To mitigate the impacts of urban and agricultural runoff, a variety of stormwater control measures (SCMs) are implemented. The overall goals of my dissertation are to assess the effect of urban and agricultural watershed on coastal waters through monitoring and modeling, and to characterize treatment performance of SCMs. These goals are addressed in four independent studies. First, we developed two watershed models the Storm Water Management Model (SWMM) and the Hydrologic Simulation Program-Fortran (HSPF) to simulate streamflow, peak flow, and baseflow within an urbanized watershed. Three separate monitoring programs were conducted on: (1) urban land uses (i.e. commercial, industrial, low density residential, high density residential, transportation, and open space); (2) container nursey; and (3) a Coastal Plain retention pond. These studies provided methods for estimating watershed pollutant loads. Results of these projects will help urban planners and ecological experts for long-term sustainable management of urbanized and agricultural watersheds.
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Grau, Valldosera Josep. "A dropout definition for continuance intention and effective re-enrolment models in online distance learning." Doctoral thesis, Universitat Oberta de Catalunya, 2020. http://hdl.handle.net/10803/668911.
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Aquesta recerca intenta trobar una definició d'abandonament (dropout) empírica i adaptada als estudiants de la UOC i, per extensió, potencialment adaptable a altres institucions d'aprenentatge a distància en línia. Hem fet una anàlisi de la quantitat de semestres consecutius de descans (N) que fan que es consideri que un estudiant d'un programa determinat ha abandonat els estudis (amb una probabilitat inferior al 5% de retorn o error màxim). Aquesta N és diferent per a cada programa, com també ho és el percentatge global d'abandonament. Per a tots els programes hi ha una alta probabilitat d'abandonament després d'una pausa, especialment quan aquesta interrupció és durant el segon o tercer semestre (early dropout). La recerca continua posant el focus d'anàlisi en l'early dropout, amb la definició de dos models per al conjunt de nous estudiants de grau que descansen durant el segon semestre: el model d'intenció de continuar i el de rematrícula efectiva (o prolongació de descans), ambdós durant el tercer semestre.Esta investigación trata de encontrar una definición de abandono (dropout) empírica y adaptada a los estudiantes de la UOC y, por extensión, potencialmente adaptable a otras instituciones de aprendizaje a distancia en línea. Hemos realizado un análisis de la cantidad de semestres consecutivos de descanso (N) que hacen que se considere que un estudiante de un programa determinado ha abandonado los estudios (con una probabilidad inferior al 5 % de retorno o error máximo). Esta N es diferente para cada programa, así como el porcentaje global de abandono. Para todos los programas, hay una alta probabilidad de abandono tras una pausa, especialmente cuando esta interrupción es en el segundo o tercer semestre (early dropout). La investigación continúa poniendo el foco de análisis en el early dropout, con la definición de dos modelos para el conjunto de nuevos estudiantes de grado que descansan en el segundo semestre: el modelo de intención de continuar y el de rematrícula efectiva (o prolongación de descanso), ambos en el tercer semestre.
The aim of this research is to establish an empirical definition of dropout that is tailored to UOC students and can be adapted later on to other online distance learning institutions. To do so, we analyse the number of consecutive rest periods (N) needed for a student on a particular programme to be considered to have dropped out (with a probability of less than 5% return or maximum error). This N proves to be different for each programme, as does the overall dropout rate. All programmes show a high probability of students' leaving after a break, especially when this interruption in their studies takes place in the second or third semester (early dropout). The research then focuses on early dropout, defining two models for the total number of new bachelor's degree students taking a break in the second semester: the continuance intention model and the effective re-enrolment model (or extended rest period), both for the third semester.
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Maicu, Maria Christina. "Optimisation of retention of Mangiferin in Cyclopia Subternata during preparation for drying and storage of green honeybush and development of Nir Spectroscopy Calibration models for rapid quantification of Mangiferin and Xanthone contents." Thesis, Stellenbosch : Stellenbosch University, 2008. http://hdl.handle.net/10019.1/2468.
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Thesis (Msc Food Sc (Food Science))--Stellenbosch University, 2008.Extraction efficiency of soluble solids (SS), total polyphenols (TP) and xanthones (AlCl3 assay) from dried, green Cyclopia subternata, as affected by mass-solvent ratio, extraction time and solvents, was investigated. In addition the effect of solvent composition on extraction of mangiferin and hesperidin was determined. Extraction of 5 g plant material as opposed to 0.5 and 1 g resulted in lower recoveries of SS, TP and xanthones (P<0.05). Extraction of SS and TP increased during the initial 20 min of contact time, where after it remained constant (P>0.05). Water, 33% acetonitrile, ethanol (50, 80 and 100%), methanol (50 and 100%) and 70% acetone were investigated as extraction solvents. Extraction for 30 min with 33% acetonitrile on a steam bath or 50% ethanol at 64°C on a water bath proved to be the most effective for extraction of SS, TP and xanthones, while 33% acetonitrile was most effective in extracting hesperidin from C. subternata. However, 70% acetone was most effective in extracting mangiferin. A poor correlation (r = 0.54) was observed for the total antioxidant activity (TAA) of C. subternata, as determined for water extracts and with the mangiferin content determined by HPLC. A moderate correlation (r = 0.85) was, however, obtained for TAA and TP content. The mangiferin content of green C. subternata can be determined using the aluminium chloride (AlCl3) colorimetric method. A moderate correlation (r = 0.87) was found for the xanthone content of the plant material determined using the AlCl3 colorimetric method and mangiferin content quantified by HPLC (y = 1.2x + 0.54) following extraction with hot water. For extraction using 33% acetonitrile a weaker correlation (r = 0.74; y = 1.3x + 0.87) was found between the xanthone and mangiferin contents. The xanthone content (determined by AlCl3) of the plant material as extracted by the two solvents, correlated well (r = 0.91). Good correlations were also obtained, when comparing extractions with water and 33% acetonitrile, for determination of the SS (0.94) and mangiferin contents (r = 0.97) of the plant material. Near infrared (NIR) spectroscopy was investigated as a rapid and more economical method for prediction of mangiferin and xanthone contents of dried, green C. subternata plant material. NIR spectroscopy calibration models can be used for screening purposes for the mangiferin and (SEP = 0.21 g.100 g-1; r = 0.82) and xanthone (SEP = 0.27 g.100 g-1; r = 0.81) contents. The effect of various pre-drying treatments and storage temperatures on the colour, soluble SS, TP, mangiferin and hesperidin contents of green C. subternata was investigated. By steaming green C. subternata directly after maceration, its colour retention can be improved. Good stability was shown for mangiferin and hesperidin during manufacture and storage of C. subternata.
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Maicu, Maria Christina. "Optimisation of retention of mangiferin in Cyclopia subteranata during preparation for drying and storage of green honeybush and development of NIR spectroscopy calibration models for rapid quantification of mangiferin and xanthone contents /." Link to the online version, 2008. http://hdl.handle.net/10019/780.
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Hoglin, Phillip J. "Survival analysis and accession optimization of prior enlisted United States Marine Corps officers." Thesis, Monterey, California. Naval Postgraduate School, 2004. http://hdl.handle.net/10945/1673.
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Approved for public release, distribution is unlimitedThe purpose of this thesis is to firstly analyze the determinants on the survival of United States Marine Corps Officers, and secondly, to develop the methodology to optimize the accessions of prior and non-prior enlisted officers. Using data from the Marine Corps Officer Accession Career file (MCCOAC), the Cox Proportional Hazards Model is used to estimate the effects of officer characteristics on their survival as a commissioned officer in the USMC. A Markov model for career transition is combined with fiscal data to determine the optimum number of prior and non-prior enlisted officers under the constraints of force structure and budget. The findings indicate that prior enlisted officers have a better survival rate than their non-prior enlisted counterparts. Additionally, officers who are married, commissioned through MECEP, graduate in the top third of their TBS class, and are assigned to a combat support MOS have a better survival rate than officers who are unmarried, commissioned through USNA, graduate in the middle third of their TBS class, and are assigned to either combat or combat service support MOS. The findings also indicate that the optimum number of prior enlisted officer accessions may be considerably lower than recent trends and may differ across MOS. Based on the findings; it is recommended that prior enlisted officer accession figures be reviewed.
Major, Australian Army
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Romão, Joana Mendonça Vasconcelos. "Modelos para estimar taxas de retenção de clientes : aplicação a uma carteira de seguro automóvel." Master's thesis, Instituto Superior de Economia e Gestão, 2019. http://hdl.handle.net/10400.5/19740.
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Mestrado em Actuarial ScienceO acesso à informação tem-se tornado cada vez mais fácil. A comparação entre condições tarifárias de diferentes seguradoras é hoje mais frequente, com efeito nas taxas de retenção de clientes e respetivos contratos de seguro. A importância que é dada a este tema é cada vez maior e a construção de ferramentas para estimar as referidas taxas permite tomar medidas para a retenção de negócio rentável e o agravamento dos prémios de contratos menos rentáveis. Este trabalho teve como objetivo estimar a probabilidade de retenção à data de vencimento de uma apólice de seguro, numa carteira do ramo automóvel. Verificado o problema de desequilíbrio entre as classes da variável resposta, a escolha das metodologias a usar baseou-se essencialmente na procura de aumentar a exatidão do modelo final e contornar esse problema.
With an increasingly easy accessibility to information, there is a growing concern about customer retention rates. Insurers are giving more importance on having accurate tools to monitor the policies renewal process, making them allowed to keep with the profitable business and increase premiums on the less profitable one. The objective of this study was to estimate the probability of renewing a policy in a motor insurance portfolio. To be working with an imbalance data set made us try different modelling methodologies, where all of them were chosen based on the need to increase the predictive performance of the model.
info:eu-repo/semantics/publishedVersion
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Fonti, Mary L. "A Predictive Modeling System: Early identification of students at-risk enrolled in online learning programs." NSUWorks, 2015. http://nsuworks.nova.edu/gscis_etd/367.
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Predictive statistical modeling shows promise in accurately predicting academic performance for students enrolled in online programs. This approach has proven effective in accurately identifying students who are at-risk enabling instructors to provide instructional intervention. While the potential benefits of statistical modeling is significant, implementations have proven to be complex, costly, and difficult to maintain. To address these issues, the purpose of this study is to develop a fully integrated, automated predictive modeling system (PMS) that is flexible, easy to use, and portable to identify students who are potentially at-risk for not succeeding in a course they are currently enrolled in. Dynamic and static variables from a student system (edX) will be analyzed to predict academic performance of an individual student or entire class. The PMS model framework will include development of an open-source Web application, application programming interface (API), and SQL reporting services (SSRS). The model is based on knowledge discovery database (KDD) approach utilizing inductive logic programming language (ILP) to analyze student data. This alternative approach for predicting academic performance has several unique advantages over current predictive modeling techniques in use and is a promising new direction in educational research.
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Cox, Katrina M. "Understanding Brigham Young University's Technology Teacher Education Program's Sucess in Attracting and Retaining Female Students." Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1416.pdf.
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Undin, Torgny. "Development and improvement of methods for characterization of HPLC stationary phases." Licentiate thesis, Uppsala universitet, Analytisk kemi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-166978.
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High Performance Liquid Chromatography (HPLC) is a widely used tech-nique both for detecting and purifying substances in academy and in the industry. In order to facilitate the use of, and knowledge in HPLC, character-ization of stationary phases is of utmost importance. Tailor made characteri-zation methods and workflows are steadily increasing the speed and accura-cy in which new separation systems and methods are developed. In the field fundamental separation science and of preparative chromatography there is always the need for faster and more accurate methods of adsorption isotherm determination. Some of that demand are met with the steadily increase of computational power, but the practical aspects on models and methods must also be further developed. These nonlinear characterization methods will not only give models capable of describing the adsorption isotherm but also actual values of local adsorption energies and monolayer saturation capacity of an individual interaction sites etc.The studies presented in this thesis use modern alkali stable stationary phas-es as a model phase, which will give an insight in hybrid materials and their separation mechanism. This thesis will include an update and expansion in using the Elution by Characteristic Points (ECP) method for determination of adsorption isotherms. The precision is even further increased due to the ability to use slope data as well as an increase in usability by assigning a set of guidance rules to be applied when determine adsorption isotherms having inflection points. This thesis will further provide the reader with information about stationary phase characterization and the power of using existing tech-niques; combine them with each other, and also what the expansion of meth-ods can revile in terms of precision and increased usability. A more holistic view of what benefits that comes with combining a non-linear characteriza-tion of a stationary phase with more common linear characterization meth-ods are presented.
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Kuo, Che-Hung, and 郭哲宏. "Retention models for reverse phase liquid chromatography and elucidation of retention mechanisms in micellar liquid chromatography." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/n44555.
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碩士國立臺北科技大學
化學工程與生物科技系化學工程碩士班
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HPLC (high performance liquid chromatography) was widely used to separate mixture in pharmaceutical industry. Separation process design needs to determine the appropriate operating conditions, such as stationary phase, mobile phase and temperature. However, there was no straightforward approach to find these conditions. These separation conditions were always determined by trial and error in pharmaceutical industry. In order to understand solute retention mechanism in chromatography system, many researchers developed retention models to investigate the relationship between solute retention time and concentration of polar modifier. Tthere were a lot of retention models developed to predict solute retention mechanism in the normal phase. For the reverse phase (RP) linear solvent strength (LSS) retention model have been widely used to predict solute separation in reverse phase chromatography. However, LSS model was empirical model and was effectively only in the narrow range. The goal of this study was to develop a retention model which based on equilibrium constant theory to replace the LSS model. This RP retention model was developed herein to account for solute–water, modifier of solvent strength–water, solute–sorbent, and modifier–sorbent interactions. C18 was chosen as a column and acetonitrile (AN) was chosen as a modifier for this study. Nine solutes were chosen for this study, such as acetone, benzaldehyde, benzene, naphthalene, etc. The method to evaluate the model accuracy was using pulse experiment and frontal test to obtain data. From the frontal test results, equilibrium constant of the adsorptions was determined. The results of fits were excellent. The adsorption mechanisms could be investigated by plotting the logarithms of the retention factor versus the logarithms of concentration of AN, and results from the plotting can be fitted by the retention model. Various cases were considered to figure out which situation can solute obtain good fitting results. Various solute adsorption mechanisms were described by the RP retention model. Solute retention mechanism in MLC (micellar liquid chromatography) is the other topic in this thesis. Unlike general reverse phase liquid chromatography system. MLC is a reverse phase liquid chromatographic mode with mobile phase containing a surfactant above its cmc (critical micellar concentration). Micellar phase did not exist when concentration of surfactant is below cmc. Solute retention time can decrease by increasing concentration of surfactant in the system, meaning that surfactant in the HPLC system have same effect as modifier. HPLC, UV (UV-Vis Spectrophotometer) and DLS (Dynamic light scattering) were used to investigated solute retention mechanism in MLC system in this research. The data from the pulse experiment were fitted by Foley model, and equilibrium constants for solutes between three phases in MLC system were obtained. From the DLS experiment results, micelle size at different concentration of surfactant with different solutes were obtained. Solute-micelle interaction mechanisms were investigated by UV spectrogram at different concentrations of surfactant. By using DLS and UV experiments interactions between solute and micelle were investigated, and interactions for solutes with three phases in MLC system were investigated by HPLC. The results showed that the hydrophobic area of the stationary phase for DTAB system with solutes was larger than that for SDS system. The result of DLS experiments showed the micelles size decreased with increasing concentration of surfactant, probably because repulsive force between micelle were higher at higher concentration of surfactant. Micelle size at DTAB system is larger than that at SDS system. The results of UV spectrograms showed that AP, BZD and BA interaction mechanism with surfactant and micelle did not exhibit obvious difference, whereas interaction mechanism with surfactant and micelle for TBA showed obvious difference. The results of HPLC and DLS implied TBA might exist in micelle.
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Courteau, Lucie. "A two-period model of signaling with ownership retention." Thesis, 1992. http://hdl.handle.net/2429/2943.
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This dissertation is an extension of Leland and Pyle's (1977) signaling model. It introduces the
length of the retention period to which the entrepreneur commits in the prospectus as a signal
of firm value, in addition to the retention level.
The analysis uses concepts of game theory to examine a two-period model where an entrepreneur
seeks to issue shares on the market and invest in a productive project that generates
outcomes which are publicly announced at the end of the next two periods. The entrepreneur
can retain some of her firm's shares and trade them later on the secondary market, after
information has been released about the outcomes.
The length of the retention period is found to be a signaling mechanism that complements
ownership retention. Depending on the information structure of the firm, a longer retention
period may reduce or increase the retention level necessary for separation.
The model also shows that there are realistic situations in which entrepreneurs prefer to
retain a portion of their firm's shares for longer than the minimum retention period imposed
by regulations, and others in which she prefers the shortest period possible. The optimal
combination of under-diversification and commitment is shown to depend on the information
structure and the probability distribution of outcomes of the firm.
The empirical implications of the model are tested on the set of firms that made an initial
public offering in 1981. Although the results of the tests are generally consistent with the
predictions of the model, they are not strong enough to reject the null hypotheses.
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Wu, Li-Wei, and 吳立偉. "An Exploration of Relationship Quality, Customer Retention and Cross-buying: An Empirical Research of Contingent Models." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/43969557344714398427.
Full textAbstract:
博士國立成功大學
企業管理學系碩博士班
95
The relationships between relationship quality, customer retention and cross-buying are not as simple as expected. Prior studies examining the effects of trust and satisfaction on cross-buying and customer retention have drawn mixed results. Thus, there is a need for research that further examines the relationships between customer retention, cross-buying, satisfaction, and trust under different contingent conditions. This study develops and examines three contingent models to explore the mixed results of previous studies. First, this study considers how the effect of satisfaction on customer retention varies with differing levels of switching costs, alternative attractiveness, and relationship inertia. Second, this study examines how decision-making uncertainty partially mediates the effect of trust on customer retention, as well as how that partial mediation varies depending on the relationship length. Finally, this study aims to examine the joint moderating effects of category similarity and category complexity on the relationships between satisfaction, trust and cross-buying. With a sample of 470 customers of banks in Taiwan, this study used a hierarchical regression to test the moderating effects by incorporating two-way and three-way interaction effects of switching barriers and relationship inertia with satisfaction in the contingent model of relationship inertia. In the contingent model of relationship length, the sample was partitioned according to the relationship length using a median split for purposes of moderator analysis and comparison. A multigroup analysis was conducted using LISREL to estimate direct and indirect effects among constructs. The sample was also partitioned according to category similarity and complexity in the contingent model of category similarity and complexity. The moderating effects in the hypotheses were assessed by subgroup regression analysis. As expected, satisfaction, switching costs and relationship inertia positively affect customer retention, but alternative attractiveness negatively affects customer retention. In addition, satisfaction has a reduced effect on customer retention as switching costs and relationship inertia increase and alternative attractiveness decreases. More interestingly, relationship inertia has asymmetric effects on the moderating effects of switching costs and alternative attractiveness in the satisfaction-customer retention relationship. In other words, relationship inertia only strengthens the moderating effect of switching cost on the satisfaction-retention link, nevertheless has no significant effect to weaken the moderating effect of alternative attractiveness. On the other hand, trust, as a means of reducing decision-making uncertainty, is more associated with customer retention in earlier phase of relationships. Obviously, decision-making uncertainty is not a static concept. Decision-making uncertainty will be reduced as customers’ knowledge and familiarity is gained with repeated exposures from the service provider over time. As the relationship length increases, the indirect effect of trust via decision-making uncertainty diminishes. In contrast, the direct effect of trust on customer retention increases. Furthermore, our findings provide an explanation of how the introduction of dissimilar and complex product categories might be strategically managed to increase the possibility of cross-buying. The moderating effect of category similarity and complexity in this study extends previous studies by specifying the contingent conditions under which trust and satisfaction are different roles in cross-buying. Satisfaction has an effect on similar and simple cross-buying but does not have an effect on dissimilar and complex cross-buying. However, satisfaction and trust have equal effects on cross-buying under the joint conditions of high category similarity / high category complexity and low category similarity / low category complexity. Moreover, our results show that trust, rather than satisfaction, is a relatively more important antecedent of both dissimilar and complex cross-buying.
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Hsien-Tung, Tsai. "Three Essays on Customer Retention and Community-building: Integrative Models and Empirical Evidence in Online and Offline Contexts." 2006. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-0806200609474800.
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CHEN, JIAN-HONG, and 陳建宏. "Effects of mental models of a computer-aided instruction system on the acquisition and retention of cognitive skills." Thesis, 1990. http://ndltd.ncl.edu.tw/handle/75642313771306351010.
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Tsai, Hsien-Tung, and 蔡顯童. "Three Essays on Customer Retention and Community-building: Integrative Models and Empirical Evidence in Online and Offline Contexts." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/98531073697181228561.
Full textAbstract:
博士國立臺灣大學
國際企業學研究所
94
This thesis contains three essays to fill the research gaps mostly left unexplained in extant research and provide practitioners with guidelines for effectively managing customer relationships. In the first two essays, the author formulates and empirically tests conceptual frameworks that consider the antecedents of customer repurchase intentions in online settings. The author also incorporates the concept of relational orientations into the model to examine its moderating effect on the links between the drivers and repurchase intentions. To test the proposed hypotheses, the author uses structural equation modeling based on data obtained from a large online retailing store in Taiwan. The results strongly support most of the hypotheses. In the third essay, the author attempts to contribute to a better understanding of brand community participation (BCP) by addressing three important research gaps: First, the author elaborates on the dimensions of BCP and introduces a new measure of this construct. Second, the author examines the antecedents of BCP by three levels (individual-, group-, and relationship-level). Third, the author investigates the underestimated influence of BCP on firm-side outcomes (perceived legitimacy and consumer power), as well as its consumer-side consequences (word-of-mouth, imitation, and loyalty intentions). The empirical analysis is based on data collected from ten car brand communities. This study provides evidence for the proposed conceptualization of BCP and finds that the investigated antecedents account for some variance of BCP, which in turn positively affects consumer- and firm-side outcomes.
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"The differential effects of consistent and inconsistent multiple models on the facilitation and retention of children's donating behavior." Tulane University, 1989.
Find full textAbstract:
This study investigated the differential facilitative effects of single and consistent/inconsistent multiple models on children's donating behavior. One hundred and twenty eight students from four schools participated in the investigation which exposed the subjects to one of eight video taped modeling conditions (comprised of donating and/or non-donating models) in which the subjects observed generous and/or selfish behavior by the model(s). Subjects then played a game with the experimenter in which they earned chips. The immediate modeling effects were measured by the number of chips that the subjects donated to other children when given such an opportunity. Retention of such modeling effects was assessed in a follow-up measure where the children again played a game, earned chips, and had the opportunity to anonymously donate any or all of their chips The results of this investigation more closely approximate the results predicted by Bandura's social learning theory (the amalgam effect of multiple models) than previous studies. Subjects viewing single and multiple consistently donating models donated at significantly greater levels than did all other conditions. Subjects viewing single and multiple consistently non-donating models donated significantly less amounts than did all other conditions. The obtained order of the multiple inconsistent conditions supports Bandura's (1969, 1972) theory in that it appears that when multiple inconsistent models were observed, the response produced was an amalgam of the behaviors of the divergent models. That is, the subjects did not directly imitate either one or the other of the models, but instead produced a response that was the result of combinations of the observed behavior Therefore, this investigation lends further support to the theory that models serve to influence learning through their informative function. Results are further discussed in terms of how future investigations could attempt to answer questions raised in this studyacase@tulane.edu
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Mangat, Rabban. "The Role of Intestinal Derived Remnant Lipoproteins in the Progression of Atherosclerosis in Animal Models of Type 1 and Type 2 Diabetes." Phd thesis, 2011. http://hdl.handle.net/10048/1953.
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Introduction: Subjects with insulin resistance (IR) and diabetes are at increased risk of cardiovascular disease (CVD) than those without diabetes, however the mechanistic basis remains elusive. Despite LDL-cholesterol lowering by statin therapy, two-thirds of all CVD events remain, constituting a significant 'residual risk' for CVD. This ‘residual risk’ has been found to be greater for patients with diabetes than those without diabetes. This suggests the role for alternative sources of lipoprotein-derived cholesterol in CVD during diabetes. Both type-1 diabetic as well as IR subjects have been found to have increased plasma concentrations of fasting intestinal derived apoB48 containing remnants (CM-r). However it is not known if the diabetic metabolic milieu indeed increases the susceptibility of the arteries to CM-r and if these indeed bind to arterial proteoglycans (PGs).
Objectives: To determine arterial retention of CM-r in type-1 diabetes and IR using ex vivo perfusion methodology in a streptozotocin rat model of type 1 diabetes and JCR-LA-cp rat model of IR. To determine the direct binding affinity and capacity of CM-r to biglycan using an in vitro approach. Methods and Results: We observed increased arterial CM-R retention in type 1 diabetic vessels as well as in IR vessels when compared to control vessels. The retained CM-r colocalized with arterial biglycan in type 1 diabetic vessels and a direct correlation was observed between the CM-r and the presence of glycated proteins in type I diabetic arteries. The increased arterial CM-r retention in the IR rats was associated with increased arterial biglycan protein content. We have conclusively demonstrated for the first time that CM-r indeed bind to human biglycan. Conclusion: Tight glycemic control in patients with type 1 diabetes can alleviate CVD by reducing hyperglycemia and subsequent retention of CM-r. A significant increase in biglycan protein core content during IR is suggestive of early vascular remodeling and may help to explain how CM-r accumulate more readily during diabetes induced CVD. Based on the results from this study, individuals with IR may be at increased risk for atherogenesis due to increased atherogenicity of the post-prandial CM-r when compared to normal population.Nutrition and Metabolism
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Carvalho, Márcia Filipa Dias dos Santos. "The impact of online promotional efforts on customer acquisitiom and retention at continente.pt." Master's thesis, 2015. http://hdl.handle.net/10362/15694.
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Continente Online (COL) is the market leader of online grocery retailing in Portugal. Aiming at sustaining this position, it has been focusing its promotional efforts in acquiring and retaining customers.
This report intakes an extensive study on the impact of COL’s exclusive promotional efforts (free delivery offers and ten percent discounts on loyalty card) on customer acquisition and retention, as well as, a cost analysis on these offers.
Two econometric models were developed and the results were interesting. It was concluded that free delivery offers have a significant impact both in terms of customer acquisition and retention, having also a lower cost in comparison with ten percent on loyalty card discounts.
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Macias, Margarida Catalão Fontan. "How to improve customer retention and lifetime value on subscription-based models: In company project with "The Bam and Boo" toothbrush." Master's thesis, 2019. http://hdl.handle.net/10071/19168.
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The present In-Company project aims to study how subscription-based business models can improve their retention and customers lifetime value. This project was made in collaboration with ‘The Bam and Boo’ Toothbrush, a Portuguese brand bamboo toothbrushes subscription service that is in the market since June 2017 and currently accounts with more than 22.000 active subscribers.
To achieve these project results we have used quantitative data from the company database reports, and qualitative data collected on a focus group session with a group of participants that resembles the brand’s target. From this data we were able to trigger some critical stages of retention and consumption patterns, and valuable insights regarding consumers behaviors and purchase profiles. Some of the critical questions that needed to be answered were related to – understand the moment of customers churns, which are the motives that led customers to make this action, and how is the company able to improve its customers lifetime and value.
We present solutions on areas such as Communication, Customer Relationship Management, Product, and Organizational Strategy, in order to improve the company retention rates and overall results. For that the company should consider delivering a more personalized service and content to its customers, run a stronger email marketing strategy, rethink its portfolio, and share the company values and mission with its community.O presente projeto-empresa visa estudar de que forma conseguimos melhorar a retenção e o valor dos clientes em modelos de subscrição. Este projeto foi realizado em colaboração com a empresa 'The Bam and Boo', um serviço de subscrição de escovas de dentes de bambu. A marca portuguesa está no mercado desde Junho, 2017 e atualmente conta com mais de 22.000 subscritores ativos. De forma a alcançar os resultados propostos neste projeto recorremos a dados quantitativos, obtidos através da base de dados de clientes da empresa, e dados qualitativos, recolhidos de uma sessão com um grupo focal no qual os participantes representavam o target da marca. Assim, foi-nos possível detetar pontos críticos em relação aos padrões e comportamento dos consumidores, e os seus perfis de compra. As questões principais que pretendemos responder neste projeto são – compreender o momento em que os clientes desistem das suas subscrições, por que motivos o fazem e de que forma a marca pode aumentar o valor e a retenção dos seus clientes. Apresentamos soluções em áreas como – comunicação, gestão e relacionamento com os clientes, produto e estratégia da organização; com o fim de melhorar as taxas de retenção e os resultados da empresa como um todo. Para isso, a empresa deve reconsiderar algumas das suas políticas e oferecer um serviço mais personalizado e diversificado aos seus clientes, montar uma estratégia de email marketing mais forte, reconsiderar o seu portfólio de produtos, e a forma de partilha dos seus valores e missão com a sua comunidade.
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Alpuim, Ricardo Manuel Pires de. "Retenção de clientes pós-venda no setor automóvel : uma abordagem quantitativa." Master's thesis, 2012. http://hdl.handle.net/10400.14/11928.
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O âmbito global da presente tese é o da análise dos fatores de influência
na capacidade de retenção de clientes nos serviços pós-venda, do setor
automóvel. A modalidade do trabalho é do tipo projeto, uma vez que surgiu na
sequência da solicitação por parte da empresa de consultoria Viragem, S.A.
Em síntese, o trabalho desenvolvido pretende fundamentar como
preferível a opção pela assistência na marca, quando o cliente tem de decidir
entre os concessionários de marca ou as oficinas independentes.
O trabalho foi realizado numa abordagem de cariz quantitativo, em que
a principal medida foi a definição e validação de um modelo de previsão, que
pretende determinar a data da próxima visita de cada cliente aos
concessionários.
Foram, também, analisadas as respostas a dois questionários (um
realizado no Brasil e outro realizado pela empresa Viragem aos seus clientes)
para tentar encontrar nelas a resposta ao tema do trabalho. Os resultados
observados estão globalmente alinhados com a literatura recolhida e entendida
como importante para esta temática.
Nas conclusões são apresentadas algumas sugestões para fazer face às
lacunas identificadas, salientando-se a proposta de alteração do modelo de
previsão atualmente implementado, dados os resultados positivos obtidos com
um dos modelos matemáticos alternativos desenvolvidos no âmbito deste
trabalho de projeto.The purpose of this thesis is to analyze the ability to retain customers in after-sales service, particularly in the automobile sector. The type of work is a project type, as a result of a request from the consulting company Viragem, S.A. Indeed, the work developed aims to support as preferred option, the assistance in the brand when the customer has to decide between brand dealers or independent garages. The study was performed as an approach of a quantitative nature, in which the main outcome measure was the definition and validation of a forecasting model that pretends to determine the date of next visit of each customer to the brand workshop. We also analyzed two surveys (one conducted in Brazil and the other one made by the Viragem company to its customers) which allowed to remove important results in order to seek an answer to the issue of the work. The results are broadly in line with the literature collected and understood as important to this theme. In the conclusions are presented some suggestions to address the gaps identified, highlighting the proposed changing of the forecast model currently implemented, given the positive results obtained with one of the alternative mathematical models developed within this project work.
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Silva, Beatriz Corrêa da. "Métodos Analíticos como fonte de valor na área de gestão de Recursos Humanos em empresas de consultadoria em Portugal." Master's thesis, 2021. http://hdl.handle.net/10362/121113.
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Dissertation presented as the partial requirement for obtaining a Master's degree in Statistics and Information Management, specialization in Information Analysis and ManagementOs processos analíticos são um elemento-chave para o sucesso organizacional. Atualmente, a capacidade de analisar as informações das empresas fornece uma vantagem para qualquer departamento, nomeadamente para o departamento de Recursos Humanos. A revisão literária sobre o tema desta dissertação aponta fatores que precisam ser mais bem explorados e aperfeiçoados para que o desenvolvimento e implementação de processos analíticos nos RH possam ser aceites e melhor compreendidos, quer num contexto profissional, quer num contexto académico. Através dos processos analíticos de Recursos Humanos, surgirá um cenário em que a criação de conhecimento ocupa um papel central para toda a estrutura organizacional. Um dos fatores motivadores desta pesquisa é conseguir compreender que processos de análise de dados está a ser utilizado no departamento de Recursos Humanos nas consultoras em Portugal, como estas criam conhecimento, como o gerem e o impacto que estes processos têm nas áreas em que são postos em prática. Para isso, realizou-se um questionário junto destas empresas, para conseguir responder aos objetivos desta dissertação. Os dados foram obtidos por colaboradores de departamentos de RH, que utilizam processos analíticos nas suas funções. Os resultados demonstram as técnicas analíticas utilizadas, como é desenvolvido todo o processo de análise, assim como quais são as vantagens da realização das mesmas. Este estudo evidenciou a necessidade de potencializar mais os resultados destas análises que surgem dos departamentos de RH, permitindo ajudar de forma transversal os outros departamentos a atingir os seus objetivos, como também partilhar e evidenciar o impacto das tecnologias de informação nas organizações.
Analytical processes are a key element of the organizational success. Currently, the ability to analyze company information provides an advantage for any department, namely the Human Resources department. The literary review of this dissertation points out factors that need to be better explored and improved so that the development and implementation of analytical processes in HR can be accepted and better understood, both in a professional context and in an academic context. Through the Human Resources analytical processes, a scenario will arise in which the creation of knowledge plays a central role for the entire organizational structure. One of the motivating factors of this research is to be able to understand what data analysis processes are being used in the Human Resources department at consulting in Portugal, how they create knowledge, how they manage it and the impact that these processes have in the areas in which they are placed. For this, a questionnaire was carried out with consulting organizations, in order to answer the objectives of this dissertation. The data was obtained by employees of the HR departments that use analytical processes in their functions. The results demonstrate the analytical techniques used, how the entire analysis process is developed, as well as what are the advantages of performing it. This study highlighted the need to enhance the results of these analyzes that emerge from the HR departments, allowing to help other departments in a transversal way to achieve the organizational objectives, as well as to share and highlight the impact of information technologies in organizations.
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Costa, Guadalupe Filipa de Sousa Plácido. "Modelação estatística: um estudo sobre a retenção de clientes na indústria Health & Fitness." Master's thesis, 2018. http://hdl.handle.net/1822/65068.
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Dissertação de mestrado em EstatísticaCom o aumento da competitividade da indústria de Health&Fitness, a implementação de estratégias e táticas para evitar a perda de clientes é muito importante, especialmente porque a captação de novos clientes acarreta altos custos para as empresas. A sua retenção e fidelização podem ser vitais para a saúde financeira a médio e a longo prazo de uma empresa. É importante que, numa visão de marketing, sejam desenvolvidas estratégias para atrair clientes, fidelizá-los e aliciá-los a apadrinhar os produtos da empresa a longo prazo. Cabe às empresas e aos seus profissionais manterem-se em constante alerta de forma a saberem o que os clientes esperam dos seus serviços, para assim fornecerem um serviço que corresponda às suas expectativas e necessidades, conseguindo gerar satisfação e fidelização. Este estudo, realizado no contexto de uma empresa portuguesa de Health & Fitness (Solinca), tem como principal objetivo compreender o comportamento dos sócios (clientes) através da análise da sua retenção e respetivo ciclo de vida, que são os indicadores de desempenho (Key Performance Indicators (KPIs)) mais importantes nesta indústria. Pretende-se identificar os fatores que influenciam a sua retenção e o seu comportamento de mudança, identificando fatores de risco para o cancelamento do contrato e, assim, melhorar os pontos de contacto com o cliente. Assim, foram desenvolvidos modelos estatísticos num contexto de modelos Lineares/ Lineares Generalizados e de Análise de Sobrevivência (numa abordagem de modelação simples e múltipla) para estimar e prever a retenção de clientes – sócio ativo ou não ativo (desistente) – em dez clubes da Solinca Health & Fitness, no período entre janeiro de 2013 e dezembro de 2015. Os dados foram recolhidos a 1 de fevereiro de 2018.
With the increasing competitiveness of the Health & Fitness industry, implementing strategies and tactics to prevent the loss of customers is highly important, particularly because the recruitment of new customers entails high costs for companies. Their retention and loyalty may be vital in the medium- to long-term financial health of a company. It is important for marketing planners to develop initial strategies to attract customers and engage them to patronize the products in the long run. It is up to companies and their professionals to be constantly on the alert in order to know what customers expect from their services, and thus provide a service that meets their expectations and needs, hence generating client satisfaction and loyalty. In this work, in the context of a Portuguese Health & Fitness company (Solinca), the main objective is to understand customers’ behaviour by analyzing customer retention and customer lifecycle, which are the most important key performance indicators (KPI) in this industry. This study aims to identify the factors that influenced customers’ retention and their changing behaviours, by pinpointing the risk factors for contract cancellations and thus improving points of contact with customers. We developed statistical models within the context of Linear Models, Generalized Linear Models, and Survival Analysis (in a simple and multiple modelling) to predict and forecast customer retention–continuing (or active) customer or non-continuing (dropout)– in ten clubs of health Solinca - Health & Fitness in the period between January 2013 and December 2015. The data were collected on February 1, 2018.