Academic literature on the topic 'Catphan'
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Journal articles on the topic "Catphan"
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Nelson, G. "WE-D-204-06: An Open Source ImageJ CatPhan Analysis Tool." Medical Physics 42, no. 6Part38 (June 2015): 3671. http://dx.doi.org/10.1118/1.4925946.
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Santos, J., M. d. C. Batista, S. Foley, G. Paulo, M. F. McEntee, and L. Rainford. "Paediatric CT optimisation utilising Catphan(R) 600 and age-specific anthropomorphic phantoms." Radiation Protection Dosimetry 162, no. 4 (February 23, 2014): 586–96. http://dx.doi.org/10.1093/rpd/ncu018.
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Biondi, M., A. Bogi, L. N. Mazzoni, E. Vanzi, G. M. Belmonte, G. De Otto, R. Martini, et al. "A novel ImageJ macro for Catphan low contrast module analysis: Preliminary results." Physica Medica 32 (February 2016): 72. http://dx.doi.org/10.1016/j.ejmp.2016.01.247.
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Husby, Ellen, Elisabeth D. Svendsen, Hilde K. Andersen, and Anne Catrine T. Martinsen. "100 days with scans of the same Catphan phantom on the same CT scanner." Journal of Applied Clinical Medical Physics 18, no. 6 (September 18, 2017): 224–31. http://dx.doi.org/10.1002/acm2.12186.
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Geso, Moshi, Salem Saeed Alghamdi, Abdulrahman Tajaldeen, Rowa Aljondi, Hind Alghamdi, Ali Zailae, Essam H. Mattar, et al. "Modified Contrast-Detail Phantom for Determination of the CT Scanners Abilities for Low-Contrast Detection." Applied Sciences 11, no. 14 (July 20, 2021): 6661. http://dx.doi.org/10.3390/app11146661.
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Computerised tomography (CT) continues to be a corner stone medical and radiologic imaging modalities in radiology and radiotherapy departments. Its importance lies in its efficiency in low contrast detectability (LCD). The assessment of such capabilities requires rigorous image quality analysis using special designed phantoms with different densities as well as variation in atomic mass numbers (A) of the material. Absence of such ranges of densities and atomic mass numbers, limits the dynamic range of assessment. An example is Catphan phantom which represents only three subject contrast levels 0.3, 0.5 and 1 per cent. This project aims to present a phantom with extended range of available subject contrast to include very low-level values and to increase its dynamic scale. With this design, a relatively large number of different contrast objects (holes) can be presented for imaging by a CT scanner to assess its LCD ability. We shall thus introduce another LCD phantom to complement the existing ones, such as Catphan. The cylindrical phantom is constructed using Poly (methyl methacrylate) (PMMA), with craters (holes) having dimensions that gradually increase from 1.0 to 12.5 mm penetrated in configuration that extend from the centre to the corner. Each line of the drilled holes in the phantom is filled with contrast material of specific concentrations. As opposed to the phantom of low detail contrast used in planar imaging, the iodine (contrast material) in this phantom replaces the depth of the phantom holes. The iodine could be reduced to 0.2 l milli-Molar (mM) and can be varied for the next line of holes by a small increment depending on the required level of contrast detectability assessment required.
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Irvine, Denise, and Mark McJury. "Aspects of simulator cone-beam CT for radiotherapy treatment planning." Journal of Radiotherapy in Practice 9, no. 3 (September 2010): 165–74. http://dx.doi.org/10.1017/s1460396910000026.
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AbstractBackground and purpose: Following a recent major upgrade in cone-beam computed tomography (CBCT) software and functionality, we have reassessed aspects of our Varian Acuity simulator performance for use in treatment planning. The feasibility of using CBCT for treatment planning has been assessed and here we report specifically on Hounsfield number (HN) accuracy and related dose errors, and digitally reconstructed radiograph (DRR) image quality.Methods: Using a Catphan® 600 CT phantom, HN accuracy and uniformity were investigated for a range of CBCT imaging modes. This included the variation in HNs with scan length and phantom position. Results were compared with those acquired from conventional CT. Treatment plans for three sites were generated using the Rando phantom, and results from CBCT-based data were compared to that from CT-based data using a gamma analysis. Image quality of DRRs based on CBCT data were compared with those from CT data both quantitatively, by calculating the modulation transfer function (MTF) and qualitatively, by counting the number of line pairs visible on a phantom.Results and conclusions: Catphan data showed that for certain cases, the HN calibration of the Acuity CBCT was out of tolerance and could lead to errors in dose calculation of >2%. HNs were only acceptable for scan lengths >10 cm. In multi-scan mode, geometric shifts and differences in HNs were seen on CT slices on either side of the interface between the two acquisitions. However, comparisons between treatment plans calculated using CBCT data and conventional CT data from Rando phantoms showed that head, pelvis and thorax plans were acceptable. CBCT DRR image quality compared favourably with a conventional CT scanner in some respects; however, image uniformity and low contrast resolution were poorer due to the ‘cupping’ artefact obtained with CBCT scans.
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Volz, Lennart, Charles-Antoine Collins-Fekete, Pierluigi Piersimoni, Robert P. Johnson, Vladimir Bashkirov, Reinhard Schulte, and Joao Seco. "Stopping power accuracy and achievable spatial resolution of helium ion imaging using a prototype particle CT detector system." Current Directions in Biomedical Engineering 3, no. 2 (September 7, 2017): 401–4. http://dx.doi.org/10.1515/cdbme-2017-0084.
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AbstractA precise relative stopping power map of the patient is crucial for accurate particle therapy. Charged particle imaging determines the stopping power either tomographically – particle computed tomography (pCT) – or by combining prior knowledge from particle radiography (pRad) and x-ray CT. Generally, multiple Coulomb scattering limits the spatial resolution. Compared to protons, heavier particles scatter less due to their lower charge/mass ratio. A theoretical framework to predict the most likely trajectory of particles in matter was developed for light ions up to carbon and was found to be the most accurate for helium comparing for fixed initial velocity. To further investigate the potential of helium in particle imaging, helium computed tomography (HeCT) and radiography (HeRad) were studied at the Heidel-berg Ion-Beam Therapy Centre (HIT) using a prototype pCT detector system registering individual particles, originally developed by the U.S. pCT collaboration. Several phantoms were investigated: modules of the Catphan QA phantom for analysis of spatial resolution and achievable stopping power accuracy, a paediatric head phantom (CIRS) and a custom-made phantom comprised of animal meat enclosed in a 2 % agarose mixture representing human tissue. The pCT images were reconstructed applying the CARP iterative reconstruction algorithm. The MTF10% was investigated using a sharp edge gradient technique. HeRad provides a spatial resolution above that of protons (MTF1010%=6.07 lp/cm for HeRad versus MTF10%=3.35 lp/cm for proton radiography). For HeCT, the spatial resolution was limited by the number of projections acquired (90 projections for a full scan). The RSP accuracy for all inserts of the Catphan CTP404 module was found to be 2.5% or better and is subject to further optimisation. In conclusion, helium imaging appears to offer higher spatial resolution compared to proton imaging. In future studies, the advantage of helium imaging compared to other imaging modalities in clinical applications will be further explored.
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Zhang, Hong, Vic Kong, Ke Huang, and Jian-Yue Jin. "Correction of Bowtie-Filter Normalization and Crescent Artifacts for a Clinical CBCT System." Technology in Cancer Research & Treatment 16, no. 1 (June 23, 2016): 81–91. http://dx.doi.org/10.1177/1533034615627584.
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Purpose: To present our experiences in understanding and minimizing bowtie-filter crescent artifacts and bowtie-filter normalization artifacts in a clinical cone beam computed tomography system. Methods: Bowtie-filter position and profile variations during gantry rotation were studied. Two previously proposed strategies (A and B) were applied to the clinical cone beam computed tomography system to correct bowtie-filter crescent artifacts. Physical calibration and analytical approaches were used to minimize the norm phantom misalignment and to correct for bowtie-filter normalization artifacts. A combined procedure to reduce bowtie-filter crescent artifacts and bowtie-filter normalization artifacts was proposed and tested on a norm phantom, CatPhan, and a patient and evaluated using standard deviation of Hounsfield unit along a sampling line. Results: The bowtie-filter exhibited not only a translational shift but also an amplitude variation in its projection profile during gantry rotation. Strategy B was better than strategy A slightly in minimizing bowtie-filter crescent artifacts, possibly because it corrected the amplitude variation, suggesting that the amplitude variation plays a role in bowtie-filter crescent artifacts. The physical calibration largely reduced the misalignment-induced bowtie-filter normalization artifacts, and the analytical approach further reduced bowtie-filter normalization artifacts. The combined procedure minimized both bowtie-filter crescent artifacts and bowtie-filter normalization artifacts, with Hounsfield unit standard deviation being 63.2, 45.0, 35.0, and 18.8 Hounsfield unit for the best correction approaches of none, bowtie-filter crescent artifacts, bowtie-filter normalization artifacts, and bowtie-filter normalization artifacts + bowtie-filter crescent artifacts, respectively. The combined procedure also demonstrated reduction of bowtie-filter crescent artifacts and bowtie-filter normalization artifacts in a CatPhan and a patient. Conclusion: We have developed a step-by-step procedure that can be directly used in clinical cone beam computed tomography systems to minimize both bowtie-filter crescent artifacts and bowtie-filter normalization artifacts.
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Zarb, Francis, and Louise Rainford. "Psychophysical evaluation of Catphan®600 CT image quality findings using human observers and software analysis." Radiography 20, no. 4 (November 2014): 318–22. http://dx.doi.org/10.1016/j.radi.2014.03.014.
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Davis, Anne T., Antony L. Palmer, and Andrew Nisbet. "Can different Catphan phantoms be used in a multi-centre audit of radiotherapy CT image quality?" Physica Medica 78 (October 2020): 38–47. http://dx.doi.org/10.1016/j.ejmp.2020.09.003.
Full textDissertations / Theses on the topic "Catphan"
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Fucci, Laura. "Caratterizzazione dosimetrica e di qualità immagine del tomografo Philips Brilliance ICT 256-slice." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/8354/.
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In questo lavoro, svolto presso l'Istituto Scientifico Romagnolo per lo Studio e la Cura dei Tumori (I.R.S.T.) (I.R.C.C.S) di Meldola, si sono studiate le caratteristiche di un tomografo Philips Brilliance iCT 256 strati, con l'obiettivo di individuare le variazioni di qualità delle immagini e di dose in funzione dei parametri di acquisizione dello strumento, al fine di una successiva ottimizzazione dei protocolli degli esami tomografici.
Le valutazioni sono state fatte sul tomografo multistrato Philips mediante uso di diversi fantocci e dosimetri, seguendo le linee guida della pubblicazione per il controllo di qualità in tomografia computerizzata dell'International Atomic Energy Agency (IAEA).
Si è utilizzato il fantoccio Catphan per la caratterizzazione della qualità dell'immagine, acquisendo immagini sia in modalità assiale che spirale e variando parametri di acquisizione quali spessore di strato, kV, mAs e pitch.
Per le varie combinazioni di questi parametri sono state misurate, mediante l'utilizzo dei software ImageJ ed ImageOwl, grandezze oggettive quali risoluzione spaziale, risoluzione a basso contrasto e rumore dell'immagine acquisita.
Due fantocci di polimetilmetacrilato (PMMA) head e body sono serviti, insieme ad una camera a ionizzazione di tipo pencil, per la misura di indici di dose per la tomografia computerizzata (CTDI).
L'irraggiamento di questi strumenti è stato effettuato a diversi valori di tensione del tubo radiogeno e ha permesso di confrontare i valori CTDI misurati con quelli forniti dal tomografo.
Si sono quindi calcolate le dosi efficaci di alcuni protocolli della macchina per poi confrontarle con livelli di riferimento diagnostici (DRL), strumenti utilizzati con l'obiettivo di raggiungere valori di dose adeguati per lo scopo clinico dell'esame.
Come ulteriore valutazione dosimetrica, si è utilizzato il fantoccio antropomorfo Rando, in cui sono stati inseriti dei dosimetri a termoluminescenza (TLD) per la misura della dose organo.
Dai risultati si osserva un andamento inversamente proporzionale tra tensione del tubo radiogeno e contrasto dell'immagine. Impostando valori alti di kV si ottiene però un'immagine meno rumorosa. Oltre alla tensione del tubo, si è valutato come anche lo spessore di strato e la corrente influiscano sul rumore dell'immagine.
I risultati ottenuti dimostrano che i valori dei parametri oggettivi di qualità delle immagini rientrano nei limiti di attendibilità, così come i valori di CTDI visualizzati dal tomografo.
Lo studio della dipendenza di questi parametri oggettivi dalle impostazione di scansione permette di ottimizzare l'acquisizione TC, ottenendo un buon compromesso fra dose impartita e qualità dell'immagine.
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Freitas, Eduardo Nuno Pereira. "Optimização de análise de imagens para controlo de qualidade em imagem médica." Master's thesis, Faculdade de Ciências e Tecnologia, 2010. http://hdl.handle.net/10362/5302.
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Dissertação apresentada à Faculdade de Ciências e Tecnologia da Universidade Nova
de Lisboa para a obtenção do grau de Mestre em Engenharia BiomédicaA tomografia computorizada é um dos mais destacados e modernos métodos de diagnóstico de imagem médica. A sua crescente utilização exige um controlo adequado e rigoroso destes aparelhos.Actualmente, exige-se que o diagnóstico médico esteja sujeito a um controlo de qualidade, no sentido de assegurar a satisfação das expectativas do paciente no seu diagnóstico e tratamento. Assim, a proliferação da utilização da tomografia computorizada implica o controlo de qualidade da mesma. Um dos métodos utilizados no controlo de qualidade da imagem em tomografia computorizada é a utilização do fantoma Catphan® 500. Contudo, alguns dos testes apresentam grande subjectividade, não sendo portanto reprodutíveis. Por esse motivo, neste trabalho propõem-se a criação de um software de modo a facilitar o trabalho dos físicos médicos e tornar a análise dos diversos parâmetros reprodutível.O desenvolvimento deste software foi feito utilizando a linguagem de programação MatLab, e destinou-se a optimizar os testes de controlo de qualidade das tomografias computorizada para o Catphan® 500. Esta optimização é feita para todos os testes, nomeadamente para os de linearidade dos números TC, de espessura de corte, de calibração espacial, de obtenção da MTF, de alta resolução, de baixo contraste, de uniformidade e de ruído.
A presente dissertação foi preparada no âmbito da colaboração existente entre a Faculdade Ciências e Tecnologia e a MedicalConsult, S.A.
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Mehdi-Zodeh, Hamid. "Evaluation of platinum group metal Lewis acid complexes of the novel biaryl-like R2-CATPHOS diphosphines in catalysis." Thesis, University of Newcastle upon Tyne, 2013. http://hdl.handle.net/10443/2169.
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Recently, cationic ‘coordinately unsaturated’ square planar transition metal group Lewis acid complexes of the type [M(Ligand)]2+ (M = Pt, Pd,) have been shown to exhibit a number of advantageous features, which include well defined coordination geometries and wide functional group tolerance. They have proven to be efficient catalysts for a host of important enantioselective transformations including Diels-Alder reactions and 1,3-dipolar cycloadditions, as well as cycloisomerisations and various cyclisations. The supporting ligands and the metal centre each assert significant effects on the reactivity of the catalyst where, in particular, those complexes based on biaryl diphosphines such as BINAP, BIPHEP, MeO-BIPHEP, and NUPHOS are established as highly efficient catalysts for various couplings and cyclisations. The Doherty group has recently synthesised the novel biaryl-like R2-CATPHOS class of diphosphines and showed enantiopure (S)-Me2-CATPHOS to be markedly efficient ligand for rhodium catalysed asymmetric hydrogenation of dehydroamino esters and (E)-β-aryl-β-(enamido)phosphonates. This thesis reports details of a systematic evaluation of the efficiency of Lewis acid platinum and palladium metal complexes of enantiopure (S)-Me2-CATPHOS as catalysts for the asymmetric carbonyl-ene and Friedel-Crafts reaction and a comparison with their BINAP-based counterparts. The performance of R2-CATPHOS (R = H, Me, MeO) diphosphines as ligands for the palladium catalysed Suzuki-Miyaura cross-coupling, the Buchwald-Hartwig amination as well as a tandem carbopalladation-carbonylation sequence has also been investigated. Gold(I) complexes of R2-CATPHOS have also been shown to form efficient Lewis acid catalysts for the cycloisomerisation of a range of propargylamides. A range of platinum, palladium, and gold(I) precatalysts have been prepared and spectroscopically characterised, and catalytic conditions optimised in order to establish the extent to which R2-CATPHOS biaryl-like diphosphines are surrogates for their more conventional biaryl based counterparts such as BINAP and BIPHEP. The performance of catalysts based on R2-CATPHOS has also been compared for selected reactions to establish the influence of R on catalyst efficiency. This thesis evaluates the performance of R2-CATPHOS-based Lewis acid catalysts in chiral and achiral transformations with not only palladium and platinum but also with relatively new bis-gold catalysts that have only recently emerged in catalysis and offer great research potentials due to the unique properties of gold.
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Marques, Luís Miguel Valente. "E-government e participação política em Portugal." Master's thesis, Instituto Superior de Ciências Sociais e Políticas, 2016. http://hdl.handle.net/10400.5/11544.
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Dissertação de Mestrado em MPA - Administração PúblicaEsta dissertação pretende dar-nos um conhecimento mais fino sobre uma problemática ainda pouco desenvolvida no contexto da Ciência da Administração Pública, a relação entre o e-government e a participação política. Partindo da questão de partida “o e-government a nível local, em Portugal, contribui para uma maior participação política?”, realizou-se um trabalho de investigação quantitativa sobre a presença de funcionalidades de e-government destinadas a uma interação direta entre cidadãos e municípios. Pretendendo explorar as relações de associação entre e-government e participação política que decorrem do uso de ferramentas de e-participation, os conceitos de e-government, participação política e e-participation foram decompostos em dimensões, de acordo com a literatura de referência. As variáveis que constituem as dimensões foram escolhidas de acordo com o levantamento realizado sobre estudos acerca de local e-government e bases de dados nacionais, incidindo sobre os 308 municípios de Portugal, com dados referentes a 2011 e 2013. Estes foram analisados com recurso às técnicas estatísticas, Análise Categorial de Componentes Principais (CATPCA), Análise Fatorial e Análise de Clusters. Os resultados obtidos evidenciaram uma tendência de associação negativa entre a participação eleitoral e as dimensões e-information, capital humano e infraestruturas de telecomunicações. As ferramentas associadas à dimensão e-decision não se encontram significativamente desenvolvidas, neste contexto ainda nos encontramos num estado embrionário em direção ao New Public Service
This dissertation aims to give a finer understanding of a yet not very studied field in the context of Public Administration Science, the relation between e-government and political participation. Starting from the hypothesis “does local level e-government in Portugal contribute to a higher political participation?” a quantitative research was developed about the presence of e-government functionalities geared towards direct interaction between citizens and Municipalities. Aiming to explore the relation between e-government, political participation and e-participation derived from the use of e-participation applications, the concepts of e-government, political participation and e-participation were disaggregated into dimensions, based on current literature. The variables which compose the dimensions were chosen in accordance to the survey of studies on local e-government and national databases, encompassing the 308 Portuguese municipalities, using data from 2011 and 2013. The data was analyzed using the statistical techniques Categorical Principal Components Analysis (CATPCA), Factorial Analysis and Clusters Analysis. The results obtained uncovered a negative association tendency between electoral participation and the dimensions e-information, human capital and telecommunication infrastructures. The applications associated with the dimension e-decision are not significantly developed, in this context we are still in an embryonic stage of development towards New Public Service.
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Rijal, Jhalendra P. "Environmental and behavioral factors associated with the infestation of vineyards by larvae of grape root borer." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/46871.
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Grape root borer, Vitacea polistiformis (Harris), is an oligophagous pest of grapevines in the eastern USA. Neonates must burrow into the soil to find grape roots. In Virginia, larvae feed on roots for ~2 years, then pupate just beneath the soil surface. Emerging adults leave an empty pupal exuviae at the soil surface around the vine base. There was no relationship between weekly captures in pheromone traps and pupal exuviae counts, indicating that exuviae sampling is most appropriate to assess infestations. Exuviae sampling in Virginia vineyards revealed infestations that ranged from light to very heavy. Eighteen biotic and abiotic variables were measured and used in analyses that assessed their relative contributions to differences in exuviae density. Water holding capacity and clay/sand ratio were most strongly associated with pupal exuviae density; these variables were used to develop a model for predicting the extent of infestation of individual vineyards. The spatial distribution of pupal exuviae was characterized using non-spatial and geospatial techniques. Although the non-spatial method (Taylor's Power Law) indicated that exuviae showed an aggregated distribution in all blocks, spatial methods (variograms, SADIE) revealed aggregated distributions only in blocks with ≥ 0.5 pupal exuviae per vine. Independent pupal exuviae samples for population assessment in vineyards can be achieved using sampling points separated by >8.8 m. Combined results from geospatial analyses and the temporal distribution of pupal exuviae within years enabled the development of a practical and quantitative sampling protocol. Bioassays used to measure the behavioral response of larvae to host stimuli revealed that neonates were attracted to grape root volatiles. In soil column bioassays, larvae moved vertically and horizontally over distances of up to 120 cm and apparently perceived the presence of grape roots from a distance of 5 cm in soil. Results are discussed in relation to their potential implications for monitoring and managing grape root borer.Ph. D.
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Vasquez, Modesto Cal. "Eficiência e produtividade no ensino superior público." Doctoral thesis, Instituto Superior de Ciências Sociais e Políticas, 2013. http://hdl.handle.net/10400.5/6183.
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tese de Doutoramento em Ciências Sociais na Especialidade de Administração PúblicaNesta investigação foram estudadas as eficiências e as produtividades das instituições portuguesas do ensino superior público: universidades e institutos politécnicos. Na análise consideraram-se oito períodos académicos: 2000-2001 a 2007-2008. Recorrendo à metodologia Data Envelopment Analysis (DEA), propôs-se uma abordagem que, até à presente data, não foi utilizada para o ensino superior: Analisar a eficiência e a produtividade tendo como base os conceitos de eficiência e super eficiência não radial. Foi também analisado o impacto na eficiência de factores não discricionários. As análises foram efectuadas tendo como suporte o modelo desenvolvido e programado. As conclusões mais relevantes foram: Globalmente, no período 2000-2008, as universidades e os institutos politécnicos melhoraram as suas eficiências relativas e produtividades; A assimetria regional tem impacto na eficiência.
In this research efficiency and productivity of the Portuguese public higher education institutions were studied: universities and polytechnics. The analysis covered eight academic periods: 2000-2001 to 2007-2008. Using Data Envelopment Analysis methodology (DEA), proposed an approach that, to date, has not been used for higher education: Analyze the efficiency and productivity based on the concept of non-radial efficiency and super-efficiency. It was also analysed the impact on efficiency of non-discretionary factors. The analysis were carried out with support of the model developed and programmed. The most relevant conclusions were: overall, in the 2000-2008 period, universities and polytechnics have improved their relative efficiencies and productivity; regional development has impact on efficiency.
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Singh, Mukhbir. "Validating computer content analysis A case study of CATPAC /." 2005. http://proquest.umi.com/pqdweb?did=921017221&sid=16&Fmt=2&clientId=39334&RQT=309&VName=PQD.
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Thesis (Ph.D.)--State University of New York at Buffalo, 2005.Title from PDF title page (viewed on May 10, 2006) Available through UMI ProQuest Digital Dissertations. Thesis adviser: Jacobson, Thomas L. Includes bibliographical references.
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Luo, Ting, and 羅婷. "CatPaw: A Cloud-based Real-Time Mechanism to Protect End Hosts." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/287t6m.
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碩士國立中央大學
資訊工程學系
103
The rising of malicious software and network APT attacks severely brings the risk of security exploitation to all the enterprises and personal computers. Therefore, security vendors are dedicated to provide the service with more diversity in order to protect their customers from global malicious attacks. Antivirus actively provides a high quality service to protect computer security. However single security vendor may still be confronted with several problems, such as significant detection windows, antivirus self vulnerability, and tedious time consuming tasks on scanning whole system files. Actually, most users may pay closely attention to both the detection rate and the speed of scanning tasks of antivirus software. In this thesis, we propose a defense mechanism named CatPaw to resist the intrusion of malware and malicious contents. Windows operating system will be selected as the platform to verify our design. System software or others user applications will be scanned by sending them to VirusTotal on the Internet before executing by operating systems. If the test passes without hesitation, the file can be executed continuously. Real time scanning on VirusTotal can not only provide security service with more reliability and more accurately by using multiple antivirus engines, but also provide 24 hours real time protection for users. Furthermore, scanning the files only triggered by users instead of scanning all the files in the disk by traditional single antivirus software will make it as efficient as possible.
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Lavado, Nuno Filipe Jorge. "Extensões via splines da análise em componentes principais." Doctoral thesis, 2012. http://hdl.handle.net/10071/6202.
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Uma nova abordagem para generalizar a Análise em Componentes
Principais (ACP) para estruturas não-lineares é proposta
nesta tese: quasi-linear PCA (qlPCA). Esta inclui transformações
spline das variáveis originais optimizadas através de um processo
de Mínimos Quadrados Alternados sobre uma determinada
função perda. As transformações óptimas são explicitamente conhecidas
após a convergência, sendo o sumário do modelo semelhante
ao da ACP. Apesar do algoritmo proposto ser dedicado
a ambientes de variáveis contínuas com eventual presença
de relações não-lineares, a sua inspiração foram os algoritmos
que emergiram do sistema Gifi, tendo estes sido especialmente
concebidos para variáveis categoriais. Deste ponto de vista, pode
afirmar-se que esta tese propõe uma solução para o seguinte problema:
Tendo as variantes da ACP associadas ao sistema Gifi
sido desenvolvidas para variáveis categoriais, como adaptá-
-las de modo a serem consideradas como uma abordagem
não-linear em contexto de variáveis contínuas?
As variantes associadas ao sistema Gifi não são usualmente abordagens
a considerar pelos investigadores de áreas do conhecimento
que lidem com vari´aveis cont´ınuas. Nesse sentido, considera-se
que a qlPCA representa um contributo relevante, alargando o
leque de aplica¸c˜oes do referencial te´orico desenvolvido por Gifi.A new approach to generalize Principal Components Analysis (PCA) in order to handle nonlinear structures is proposed in this thesis: quasi-linear PCA (qlPCA). It includes spline transformations of the original variables, using Alternating Least Squares fitting of a suitable objective loss function to achieve optimal transformations. Optimal transformations are explicitly known after convergence and qlPCA reports model summary in a linear PCA fashion. Even though the proposed algorithm is designed for continuous variables eventually with nonlinear relationships, it was inspired by algorithms that emerged from the Gifi system, whose focus were categorical variables. Thus, this thesis proposes a solution for the following problem: Having Gifi’s related approaches been developed for categorical variables, how to adapt them in order to be considered a nonlinear option also in the context of continuous variables? Gifi’s related approaches are not usually a valid option for researchers dealing with continuous variables. The proposed approach, qlPCA, can enlarge the scope of applications of Gifi’s theoretical framework, being therefore a relevant contribution.
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Santos, José Fernando Fernandes. "Fatores chave de sucesso das equipas virtuais de tecnologias de informação e comunicação (TIC) em regime de outsourcing, do ponto de vista dos membros da equipa." Master's thesis, 2015. http://hdl.handle.net/10437/6011.
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Orientação : Isabel Duarte; co-orientação: Ana LorgaEste estudo pretende identificar quais os fatores que contribuem para o sucesso das equipas virtuais de tecnologias de informação e comunicação em ambiente de outsourcing. Sabendo, à priori, que as equipas participantes no estudo eram consideradas equipas de sucesso - de acordo com as métricas utilizadas internamente para medir os níveis de serviço – partiu-se de uma abordagem inovadora. Ao invés de se proceder à investigação segundo o modelo tradicional, optou-se por dar aos membros das equipas participantes parte ativa na investigação. Através de um questionário online feito a todos os membros das equipas participantes, e recorrendo a uma escala de Likert, foram analisadas trinta e nove variáveis cobrindo todo o espetro de uma equipa virtual: seleção, constituição da equipa, ambiente de trabalho e liderança. Os dados recolhidos foram analisados através de metodologias Estatísticas, tendo sido utilizado a Análise de Componentes Principais para Dados Categóricos (CATPCA) para validar as dimensões das hipóteses levantadas. Esperava-se que, do ponto de vista dos membros das equipas participantes, os temas cultura, comunicação, objetivos, oportunidades de carreira e gestão de conflitos tivessem uma maior relevância do que aqueles que efetivamente foram observados. No entanto, a tónica é colocada nas principais variáveis que afetam o seu dia-a-dia: ferramentas e processos estandardizados, definição clara de funções e responsabilidades e processo de escalonamento. Verificou-se que, em todas as hipóteses, a variável «Team members should know what is expected of them individually and collectively» obteve valores muito elevados, o que pode levar a concluir que os membros das equipas consideram a definição clara das tarefas a realizar por cada membro, em interação com os outros, o elemento central para a sua própria motivação e empenho no trabalho em equipa. O conhecimento, quer do papel que cada um desempenha, quer dos resultados esperados é o fator essencial que lhes permite ultrapassar dificuldades interpessoais, alcançar o sucesso individual e, em última análise, que promove o envolvimento pessoal e a satisfação profissional que geram o sucesso das equipas.
This study aims to identify the factors that contribute to the success of virtual teams in the information and communication technologies, working in outsourcing environment. Knowing in advance that the teams participating in the study were considered successful teams - according to the metrics used internally to measure the service levels - the option was to consider a different approach. Instead of proceeding to the study under the traditional model, it was decided that the members of the participating teams should play an active role in the research. Through an online questionnaire given to all members of the participating teams, and using a Likert scale, thirty-nine variables covering the entire spectrum of a virtual team were subject to analysis: selection, composition of the team, work environment and leadership. The data collected were analyzed using statistical methodologies, and the Analysis for Categorical Data (CATPCA) was used to validate the hypotheses’ dimensions. In terms of results it was expected that, from the members of the participating teams stand point, the themes culture, communication, goals, career opportunities and conflict management would have greater relevance than those that were observed. However, according to the respondents’ point of view, the emphasis was put on the main variables that affect their daily work: tools and standardized processes, clear roles and responsibilities and escalation process. It was found that, in all cases, the variable «Team members should know what is expected of them individually and collectively» got very high values, which may lead to the conclusion that the team members consider that the clear definition of their own tasks, in interaction with the other members, is the core for their self-motivation and commitment in team work. The members’ knowledge not only of each other’s role but also of the expected results is the essential factor that allows them to overcome interpersonal difficulties, to achieve individual success and, ultimately, fosters the personal involvement and the professional satisfaction that lead to the team success.
Conference papers on the topic "Catphan"
1
Olsson, Marie-Louise, and Kristina Norrgren. "An investigation of the iterative reconstruction method iDose4on a Philips CT Brilliance 64 using a Catphan 600 phantom." In SPIE Medical Imaging, edited by Norbert J. Pelc, Robert M. Nishikawa, and Bruce R. Whiting. SPIE, 2012. http://dx.doi.org/10.1117/12.910889.
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Dalkilic, Mehmet M., and Arijit Sengupta. "Design and evaluation of CATPA." In the 2005 ACM symposium. New York, New York, USA: ACM Press, 2005. http://dx.doi.org/10.1145/1066677.1066721.
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Gómez-Guerrero, Santiago, Miguel García-Torres, Gustavo Sosa-Cabrera, Emilio Sotto-Riveros, and Christian E. Schaerer. "Classifying dengue cases using CatPCA in combination with the MSU correlation." In Entropy 2021: The Scientific Tool of the 21st Century. Basel, Switzerland: MDPI, 2021. http://dx.doi.org/10.3390/entropy2021-09828.
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