Dissertations / Theses on the topic 'Productivity enhancement'

A hierarchical procedure is developed to determine maximum overall yield of a process and optimize process changes to achieve such a yield. First, a targeting procedure is developed to identify an upper bound of the overall yield ahead of detailed design. Several mass integration strategies are proposed to attain maximum yield. These strategies include rerouting of raw materials, optimization of reaction yield, rerouting of product from undesirable outlets to desirable outlets, and recycling of unreacted raw materials. Path equations are tailored to provide the appropriate level of detail for modeling process performance as a function of the optimization variables pertaining to design and operating variables. Interval analysis is used as an inclusion technique that provides rigorous bounds regardless of the process nonlinearities and without enumeration. Then, a new approach for identification of cost-effective implementation of maximum attainable targets for yield is presented. In this approach, a mathematical program was developed to identify the maximum feasible yield using a combination of iterative additions of constraints and problem reformulation. Next, cost objectives were employed to identify a cost-effective solution with the details of design and operating variables. Constraint convexification was used to improve the quality of the solution towards globability. A trade-off procedure between the saving and expenses for yield maximization problem is presented. The proposed procedure is systematic, rigorous, and computationally efficient. A case study was solved to demonstrate the applicability and usefulness of the developed procedure.

Thesis (Ph.D)--Mechanical Engineering, Georgia Institute of Technology, 2010.
Committee Chair: Major, J. Rhett; Committee Member: Melkote, Shreyes; Committee Member: Ozdoganlar, Burak; Committee Member: Shi, Jan; Committee Member: Ume, I. Charles. Part of the SMARTech Electronic Thesis and Dissertation Collection.

The Productivity Measurement and Enhancement System (ProMES) is a human resource intervention that provides feedback to members of an organizational unit via a measurement system constructed by the unit personnel. The unit constructs the system by defining their objectives, identifying productivity indicators for each objective, and developing utility curves or contingencies for each indicator, specifying the overall and relative value to the organization of different performance levels on each indicator. Over the years, it has produced very positive results upon implementation. However, there has been great variability in the effectiveness of ProMES. This study attempted to identify the factors that contributed to this variability. Three major factors were proposed to influence the success of the intervention: feedback quality, the degree to which units prioritized their actions on the feedback, and the organizational social context. Additionally, the individual effects of the components of the organizational social context factor were analyzed; these components included the degree of employee participation in the intervention, unit attitudes towards productivity improvement, organizational support for the intervention, and organizational stability. Three productivity indices were used as dependent variables: the unit d-score (the difference between feedback productivity and baseline productivity divided by the pooled standard deviation), the rate of productivity change over the first third of the feedback stage, and the degree to which units were able to sustain prior productivity improvements over the last two thirds of the feedback stage. The degree of match with the original ProMES methodology was proposed as a moderator in the relationship between the three major factors and the criteria, and the degree of feedback interpretation training given to the unit was proposed as a moderator between the units? action on feedback and the criteria. Drawing on a database of 74 units from different industries and countries, scales were constructed to operationalize the factors. Results from multiple regression analyses indicated that favorable attitudes towards productivity improvement were associated with faster productivity improvements. Additionally, feedback quality and the action taken on feedback significantly predicted greater and faster productivity improvements. The implications for human resource professionals and researchers in industrial/organizational psychology are discussed.

Three Brazilian yeast strains, Saccharomyces cerevisiae 42 - F, Saccharomyces cereviaiae PLA 851 and Saccharomyces boulardli IZ 1904, all currently employed in the sugar fermentation industry, were evaluated with respect to their thermal tolerance and alcohol production kinetics. Best performance was found in Saccharomyces cerevisiae PLA 851 at temperatures up to 40 degrees (a common fermentation temperature in the Brazilian industry). This strain was further evaluated in chemostatic growth under sucrose limitation with biomass feedback on a 1 Litre scale in a specially constructed apparatus. At 30 degrees and 35 degrees under a dilution (growth) rate of 0.1 /h ethanol productivity increased by a factor of 2 with feedback and at 40 degrees by a factor of 3. The feedback factor (Beta) was 0.9. PLA 851 cells, heat - shocked at 45 degrees, resulted in a greater biomass productivity subsequently at 40 degrees coupled with a change in cell morphology. Highest ethanol productivity was found with 10% initial sucrose concentration at a dilution rate of 0.25 /h with feedback. Saccharomyces cerevisiae PLA 851 appears to be well adapted to the harsh physiological conditions in alcohol fermentations as currently practiced in Brazil.

There are unique challenges in the fabrication and testing of optical semiconductor devices because, unlike typical silicon semiconductor devices, which can be tested cost-effectively on the wafer, many optical devices can only be 'fully' tested once the individual die is bonded to a heat sink. As a result, both the manufacturing process and test strategy need to be capable of predicting yields and product quality attributes based on limited sampling from a batch of the product. The large number of product quality and process variables that are measured for each device when it is manufactured makes it almost impractical to manually analyze them for valuable decision-making information. There is a need for understanding the complex, interactive effects of process variables on the product quality variables as well as automated analysis and discovery tools for extracting useful knowledge from the raw data. Such knowledge could have a significant impact on productivity and quality improvement. The objective of the present study is to identify useful correlations amongst the numerous process variables and to develop simple empirical models to predict important process quality indicators. Quality is assessed using statistical data analysis, focusing on the primary functions of major failures. Validation of the data set also demonstrated that linear models were accurate in predicting new data points for some of the output variables, whereas the variation of some output variables could not be explained using the available industrial data bank. Some models were powerful in making predictions and to provide a clearer insight in determining the key factors in manufacturing of BHet. BHet is a directly modulated laser operating at 2.5 Gb/s and reaches up to 360 km. Application of this research for failure prediction at an early stage of the manufacturing line could result in a dramatic reduction in the number of defective wafers that are completely processed and thereby lowering the overall manufacturing cost.

This thesis examines the influence of local and regional governments in investment growth and productivity in Mexico. A combination of quantitative and qualitative analysis is used with the aim of assessing their influence and tools. Mexican municipalities and states have gained major participation in policy making, investment fostering and infrastructure building. The decentralised resources to meet these goals have increased considerably; as a consequence, it becomes imperative to measure the actual effects of such resources as well as to identify the opportunity areas to develop. The first part of the empirical analysis, attempts to measure the influence of local governments’ expenditures on private investment growth, as well as to identify the most important investment drivers. Likewise, given the increasing foreign investments landing in Mexico, there is a potential regional competition between cities, this is also evaluated. A panel data analysis consistent with cross section dependence is carried out for 63 Metropolitan Areas (MA)/cities for the period 1993-2008. The econometric analysis shows that, municipal governments’ expenditures have had a substantial effect on private capital. In addition, competition strategies matters. More importantly, public infrastructure stock is revealed as a central determinant for investment, especially for manufacturing firms. The second empirical chapter evaluates whether municipal and state expenditures in economic policies have boosted productivity of firms. Firms and regional features are also included in the estimation models. Panel data analysis consistent to cross section dependence is used, for 63 MA/cities and 29 states. The results showed that the policies implemented in municipalities have had little or even negative effects over firms’ productivity. Meanwhile, the policies implemented by states have had larger influence on productivity increases. In order to dig deeper into the role of local and regional governments in economic policies, two case studies –Hermosillo and Mexicali- are presented in the last part. Empirical models cannot tell about the local processes, as the data used is only expenditures. The fieldwork undertaken helped to identify the most significant policies followed in each city, as well as the leadership and organisation of stakeholders. The main finding suggests that local participation and overcoming political cycle is essential for the long-term success; and easing doing business for firms, rather than incentives, is more effective to spur private investment.

A study was carried out to determine the effects of oat (Avena sativa) and grazing vetch (Vicia darsycapa) winter cover crops and fertilizer application on SOM, phosphorus (P) pools, nutrient availability, nutrient uptake, maize yield and seedbanks of problematic weeds in an irrigated maize-based conservation agriculture (CA) system. A separate experiment was carried out to investigate the effects of the winter cover crops on nitrogen (N) management, N use efficiency and profitability. After four years of continuous rotation, the winter cover crops significantly (p<0.05) increased particulate SOM and hot water soluble carbon in the 0 – 5 and 5 – 20 cm soil depths. When fertilized, oat was better able to support SOM sequestration in water stable aggregates at 0 – 20 cm whilst grazing vetch was more effective at 20 – 50 cm. Where no fertilizer was invested, there were significant (p<0.01) reductions in biomass input and SOM on oat-maize and weedy fallow-maize rotations whereas vetch-maize rotations did not respond, both at 0 – 5 and 5 – 20 cm. Targeting fertilizer to the winter cover crop required less fertilizer, and yet gave a similar SOM response as targeting the fertilizer to the maize crop. In addition to increasing SOM in the surface soil (0 – 5 cm), the winter cover crops significantly (p<0.05) increased labile pools of P, including microbial P. The cover crops also significantly (p<0.05) increased maize P concentration during early growth, extractable soil P, Cu, Mn, and Zn but had no effect on Ca and K. Grazing vetch increased soil mineral N but reduced extractable soil Mg. Without fertilizer, there were sharp declines in maize grain yield on oat and weedy fallow rotations over the four year period, but less so, on the grazing vetch. Grazing vetch increased maize growth, grain yield response to N fertilizer, nitrogen use efficiency (NUE) and profitability for fertilizer rates below 180 kg N ha-1. Oat effects however on maize yield and NUE were generally similar to weedy fallow. Based on the partial factor productivity of N, the highest efficiencies in utilization of fertilizer N for maize yield improvement under grazing vetch and oat are obtained at 60 kg N ha-1 and would decline thereafter with any increases in fertilizer application rate. Grazing vetch gave N fertilizer replacement values of up to 120 kg N ha-1 as well as the highest marginal rates of return to increasing N fertilizer rate. The cover crops were more effective than the weedy fallow in reducing seedbank density of Digitaria sanguinalis, Eleusine indica, Amaranthus retroflexus and Datura stramonium at 0 – 5 cm soil depth, causing weed seed reductions of 30 - 70%. The winter cover crops however, selectively allowed emergence of the narrow leafed weeds; Cyperus esculentus and Digitaria sanguinalis in the maize crop. The findings of this study suggested that grazing vetch is suited for SOM improvement in low fertilizer input systems and that fertilizer is better invested on winter cover crops as opposed to maize crops. Oat, on the other hand, when fertilized, would be ideal for C sequestration in water stable aggregates of the surface soil. Grazing vetch is ideal for resource poor farmers who cannot afford mineral fertilizers as it gives grain yield improvement and high fertilizer replacement value. Grazing vetch can produce enough maize yield response to pay its way in the maize-based systems and oat may not require additional N than that applied to the weedy fallow. Phosphorus and Zn are some of the major limiting essential plant nutrients on South African soils and the winter cover crops could make a contribution. The cover crops also hasten depletion of some problematic weeds from seedbanks, leading to reduced weed pressure during maize growth.

Thesis (M.S.)--West Virginia University, 1999.
Title from document title page. Document formatted into pages; contains viii, 115 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 96-99).

Matrix acidizing is used in carbonate formations to create wormholes that connect the formation to the wellbore. Hydrochloric acid, organic acids, or mixtures of these acids are typically used in matrix acidizing treatments of carbonate reservoirs. However, the use of these acids in deep wells has some major drawbacks including high and uncontrolled reaction rate and corrosion to well tubulars, especially those made of chrome-based tubulars (Cr-13 and duplex steel), and these problems become severe at high temperatures. Hydrochloric acid (HCl) and its based fluids have a major drawback in stimulating shallow (low fracture gradient) formations as they may cause face dissolution (formation surface washout) if injected at low rates. The objective of stimulation of sandstone reservoirs is to remove the damage caused to the production zone during drilling or completion operations. Many problems may occur during sandstone acidizing with Hydrochloric/Hydrofluoric acids (HCl/HF) mud acid. Among those problems: decomposition of clays in HCl acids, precipitation of fluosilicates, the presence of carbonate can cause the precipitation of calcium fluorides, silica-gel filming, colloidal silica-gel precipitation, and mixing between various stages of the treatment. To overcome problems associated with strong acids, chelating agents were introduced and used in the field. However, major concerns with most of these chemicals are their limited dissolving power and negative environmental impact. Glutamic acid diacetic acid (GLDA) a newly developed environmentally friendly chelate was examined as stand-alone stimulation fluid in deep oil and gas wells. In this study we used GLDA to stimulate carbonate cores (calcite and dolomite). GLDA was also used to stimulate and remove the damage from different sandstone cores containing different compositions of clay minerals. Carbonate cores (calcite and dolomite) of 6 and 20 in. length and 1.5 in. diameter were used in the coreflood experiments. Coreflood experiments were run at temperatures ranging from 180 to 300oF. Ethylene diamine tetra acetic acid (EDTA), hydroxyl ethylethylene diaminetriacetic acid (HEDTA), and GLDA were used to stimulate and remove the damage from different sandstone cores at high temperatures. X-ray Computed Topography (CT) scans were used to determine the effectiveness of these fluids in stimulation calcite and dolomite cores and removing the damage from sandstone cores. The sandstone cores used in this study contain from 1 to 18 wt percent illite (swellable and migratable clay mineral). GLDA was found to be highly effective in creating wormholes over a wide range of pH (1.7-13) in calcite cores. Increasing temperature enhanced the reaction rate, more calcite was dissolved, and larger wormholes were formed for different pH with smaller volumes of GLDA solutions. GLDA has a prolonged activity and leads to a decreased surface spending resulting in face dissolution and therefore acts deeper in the formation. In addition, GLDA was very effective in creating wormholes in the dolomite core as it is a good chelate for magnesium. Coreflood experiments showed that at high pH values (pH =11) GLDA, HEDTA, and EDTA were almost the same in increasing the permeability of both Berea and Bandera sandstone cores. GLDA, HEDTA, and EDTA were compatible with Bandera sandstone cores which contains 10 wt percent Illite. The weight loss from the core was highest in case of HEDTA and lowest in case of GLDA at pH 11. At low pH values (pH =4) 0.6M GLDA performed better than 0.6M HEDTA in the coreflood experiments. The permeability ratio (final/initial) for Bandera sandstone cores was 2 in the case of GLDA and 1.2 in the case of HEDTA at pH of 4 and 300oF. At high pH HEDTA was the best chelating agent to stimulate different sandstone cores, and at low pH GLDA was the best one. For Berea sandstone cores EDTA at high pH of 11 was the best in increasing the permeability of the core at 300oF. The low pH GLDA based fluid has been especially designed for high temperature oil well stimulation in carbonate and sandstone rock. Extensive studies have proved that GLDA effectively created wormholes in carbonate cores, is gentle to most types of casing including Cr-based tubular, has a high thermal stability and gives no unwanted interactions with carbonate or sandstone formations. These unique properties ensure that it can be safely used under extreme conditions for which the current technologies do not give optimal results. Furthermore, this stimulation fluid contributes to a sustainable future as it based on readily biodegradable GLDA that is made from natural and renewable raw material.

碩士
國立臺灣科技大學
工業管理系
100
Business cycle is faster and faster in technology industries. It’s possible from 7~8 years to 2~3 year. Some business forecasts variance are too large to impact factory operation mode and resource planning. Factory should always adjust management mode, include less quantity and more various types, decrease line change time and lower inventory with WIP (work in process). Many companies hope to invite external consultant to adopt “Lean production”. But many cases fail at the beginning due to lower output, poor quality and employees quit. That’s because we are lack of internal production activities to support (or enhance) it. Employees are against when we want to elimate the waste and improve productivity. The study hopes to enhance lean production by factory improve activities. Encourage operators and techcian to join production improvement by IE tools and activities. The final purpose is to shift their thingking from reward, bonus to honor and self-fulfillment.

碩士
國立高雄海洋科技大學
海洋生物技術研究所
106
Wild type bacteria, Comamonas sp. L8U, was isolated from soil in Taiwan that was capable of growing from levulinic acid as sole carbon source. It accumulated poly(3-hydroxybutyrate-co-96 mol% 3-hydroxyvalerate) copolymer in the cell and produced 337 ± 40.1 mg/L 3-hydroxyvalerate (3HV) and a small amount of 3-hydroxybutyrate (3HB) (3.5 ± 3.17 mg/L) in the medium. Levulinic acid is a renewable feedstock that can be produced by heating cellulose from agricultural and forestry wastes under acidic conditions. The optimum condition for Comamonas sp. L8U to produce 3HV is the mineral salts medium (pH7.4) lacking of ferrous ion with 0.8% (w/v) levulinate and. The phaC1 deletion mutant L8UΔC1 failed to polyhydroxyalkanoate (PHA) accumulation, but produced 3HV of 1,357 ± 16.5 mg/L and 3HB of 41 ± 7.2 mg/L in the medium. Comamonas sp. L8UΔC1 deleting phaA or phaB genes decreased 3HB to 17±5.1 mg/L or non-dedetectable amount, respectively. L8UΔC1 produced 3HV of 3.25 g/L by batch fermetation in 2 L scale. The productivity of 3HV was further enhanced to 6.30 g/L by fed-batch culture approach. This study deleted five thioesterase genes in Comamonas sp. L8U. Mutant L8UΔTE2 had a higher PHA content (72 ± 0.6 dry wt%) compared with wild type (64 ± 1.3 dry wt%), but a lower 3HV in the medium (127 ± 12.1 mg/L). Mutant M70 was mini-Tn5 inserted in lexA gene and had a change in cell morphology, segmentation deficient, which showed a higher 3HV productivity than that of wild type.