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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
281

Strategy, performance improvement, combined rail-truck transport

Muh, Patrick Tatambunkah January 2007 (has links)
With increasing trade, freight transport demand has grown tremendously and as sustainability has become an essential concern of our globe, interests in improving and achieving effective and efficient rail freight transport have become an essential needs and focus of the 21st century. However, achieving an improved rail freight transport service and an increased market share in a competitive environment is rather complex in several aspects as freight trains would need to operate with principles and characteristics resembling those of passenger’s traffic in order to attract new type of goods. In order to adopt the principles and characteristics used in passenger trains, airlines and hotel industries into intermodal line train systems, a simulation model has been developed and implemented. The principles for pricing which we have considered are base on the available train capacity along a travel sub-leg and our objective was to increase the performance of the intermodal line cargo train system. We adopted the yield management concept with rail freight customers given the possibility to change their start and/or end train stations (travel sub-leg) and/or to change their departure day in an intermodal line cargo train system. Using our developed simulation tool, we have examined the performance of an intermodal line cargo train system with respect to the dynamic and constant pricing strategy. Our prime objective was to investigate and answer the questions which pricing strategy leads to the best space utilization and performance of an intermodal line train cargo system? Our simulation results show that the dynamic pricing gives the best space utilization and rail freight performance. Dynamic pricing strategy appears good to both the train operators, in term of the revenue generated, and the freight transporters as they achieved reduced transport cost and freights accommodation at train stations different from their closest train stations. / JANNEBERGVÄGEN 37 374 50 ASARUM (+46)736 978 052
282

Combined effects of ocean acidification, ocean warming and oil spill on aspects of development of marine invertebrates

Arnberg, Maj January 2016 (has links)
For decades, humans have impacted marine ecosystems in a variety of ways including contamination by pollution, fishing, and physical destruction of habitats. Global change has, and will, lead to alterations in in a number of abiotic factors of our ocean in particular reduced oxygen saturation, salinity changes, elevated temperature (ocean warming or OW) and elevated carbon dioxide (ocean acidification or OA). Now and in the future, OA and OW will operate together with local anthropogenic drivers such as oil pollution. And yet, at present, very little is known about their potential combined interactive effects on physiological performance and tolerance of marine organisms. Therefore, multiple driver experiments are required if we are to understand and predict future vulnerability of species, populations and ecosystems. Early life stages of invertebrates are generally considered most vulnerable to environmental stress. However, few studies consider the combined effects OA and OW on survival and growth during early development of marine invertebrates, and to our knowledge, there is no information on the additional effects of oil pollution. Therefore, the aim of this thesis was to investigate the effects of combined exposure to OA, OW, and incorporating local drivers such as oil pollution on the development, morphology and physiology of three economically and ecologically important marine invertebrates. These are Northern shrimp Pandalus borealis, Northern krill Meganyctiphanes norvegica, and the green sea urchin Strongylocentrotus droebachiensis. All are cold-water species, assumed to have a narrower tolerance than more temperate species, and so could be particular sensitive to combined stressor affects. Both Northern krill and to a lesser extent Northern shrimp larvae survived experimental conditions, mirroring those predicted under a future global change scenario (combined OA and OW exposure). Neither was hatching success affected. Both shrimp and krill larvae exhibited accelerated developmental rates and incurred greater maintenance costs as a result of exposure to these stressors. Shrimp larvae showed accelerated developmental rates (-9 days), increased metabolic rates (+20 %), and increased feeding rates (+20 %), but reduced growth (- 9 %) when exposed to OW compared with the control. OA increased development rate but only at the control temperature. Although juvenile mortality of krill was not affected by predicted OA/OW conditions, metabolic rate increased significantly (+ 36 %), as did larval developmental rate, while number of moults, feeding rate and growth (- 67 %) decreased significantly (- 67 %, - 60 % and -8 % respectively). Accelerated development was accompanied by greater maintenance costs possibly due to experience a mismatch between energy supply and demand. Both species had an excess of food, and so growth reduction was more likely to be associated with higher metabolic demands in the future global change treatments. Food shortage in situ, due to variable food availability in the sea and/or mismatch with key prey species (algae and zooplankton) could result in more negative effects on growth and ultimately survival. Green sea urchins were also able to survive OA exposure, without detectable effects on hatching success. However, at day 44 post-fertilization, larval body length in the OA treatment was 9 % lower compared to the control. Furthermore, there was a significant tendency of urchin larvae to increase swimming activity in the OA conditions that might indicate compensatory feeding. Elevated maintenance and repair costs as a result of exposure to multi-stressors affected the energy budget of all the three species studied here resulting in reduced growth. Global drivers (OA and OW) resulted in trade-offs with more energy reallocated to swimming activity and metabolism, rather than growth. Exposure to oil reduced the acquisition of energy by reduced feeding which in turn resulted in less energy being available for growth. Both shrimp and sea urchin larvae showed reduced activity and feeding when exposed to oil. It is possible that the reduced swimming activity observed may be due to a narcotic effect of the oil. Furthermore, early stage sea urchin larvae showed increased mortality when exposed to oil while the older larvae did not, indicating a stage specific toxicity to oil for sea urchin larvae. The combination of global drivers and oil pollution acted additively on growth for both sea urchin and shrimp larvae. The impact of combined drivers on the size of shrimp larvae was equal the sum of the negative impacts observed for each driver: a 5 % reduction when exposed to OA and OW, a 9 % reduction when exposed to oil, and a cumulative 15 % reduction when exposed to all stressors. Similarly, the impact of combined drivers on the size of sea urchin larvae was equal to the sum of the negative impacts observed for each driver: a 14 % reduction when exposed to OA, a 9 % reduction when exposed to oil, and a 21 % reduction when exposed to all drivers. Therefore, the study demonstrated the additive physiological effects of OA, OW and a contaminant, and indicated that larval (sea urchin and shrimp) resilience to future changes (i.e. pollution) could be greatly reduced if larvae were already energy limited and severely stressed (reduced development) as a result of exposure to the global drivers. This study therefore shows the importance that the effective management of local drivers such as oil pollution could have against the backdrop of OA and OW, and emphasises that it is important to study impacts of toxicants, such as an oil pollution, in the context of predicted changes in the environment, as OW and OA are becoming major concerns. Finally, the fact that some local and global drivers seem to act additively should encourage local managers to act on local driver regulations, to obtain positive effects on local populations and environment and thereby rendering them more resilient to the negative impacts of future global drivers.
283

Energetický paroplynový zdroj na bázi spalování hutnických plynů / Gas steam cycle power plant using metelurgic gas

Kysel, Stanislav January 2011 (has links)
The main goal of my thesis is to carry out thermic calculations for adjusted conditions of electric and heat energy consumption. The power of the generator is 330 MW. In the proposal, you can find combustion trubines type GE 9171E. Steam-gas power plant is designed to combust metallurgical gases. Effort of the thesis focuses also on giving a new informations about trends in combinated production of electric and heat energy.
284

Effects of upper body concurrent training in trained individuals: a review

Hansson, Björn January 2017 (has links)
Concurrent training (CT) is defined as the development of both endurance and strength within the same exercise program. CT has been studied for decades, but the results has been diverse. However, very few have studied the effects of CT on the upper body musculature. Hence, this review set out to investigate the effects of combined strength and endurance training (ET) of the upper body on muscle hypertrophy, muscle strength and endurance variables. PubMed was searched with relevant search terms with varying combinations, such as concurrent training, combined strength and endurance training. After scanning the literature, a total of eight articles were included. The results suggest that muscle strength, exercise economy and time to exhaustion can effectively be improved by CT of the upper body. The effect of CT on upper body musculature were unclear. Some of the articles included suggests a decrease in whole body lean mass, which might simply be due to insufficient loading of the lower body musculature. In order to maintain muscle mass during a CT protocol, endurance athletes should aim to perform ST which targets muscles active during ET. However, the limited empiric literature available on CT of the upper body makes a conclusion hard to draw. This review shows that CT of the upper body is yet an unexplored and researchers should further investigate the effects of CT for the musculature of the upper body alone. If we gain more knowledge of the effects from concurrent training of the upper body, it could have several implications, both clinically and in a sport setting.
285

Study of power plant with carbon dioxide capture ability through modelling and simulation

Biliyok, Chechet 11 1900 (has links)
With an increased urgency for global action towards climate change mitigation, this research was undertaken with the aim of evaluating post-combustion CO2 capture as an emission abatement strategy for gas-fired power plants. A dynamic rate-based model of a capture plant with MEA solvent was built, with imposed chemical equilibrium, and validated at pilot scale under transient conditions. The model predicted plant behaviour under multiple process inputs and disturbances. The validated model was next used to analyse the process and it was found that CO2 absorption is mass transfer limited. The model was then improved by explicitly adding reactions rate in the model continuity, the first such dynamic model to be reported for the capture process. The model is again validated and is observed to provide better predictions than the previous model. Next, high fidelity models of a gas-fired power plant, a scaled-up capture plant and a compression train were built and integrated for 90% CO2 capture. Steam for solvent regeneration is extracted from the power plant IP/LP crossover pipe. Net efficiency drops from 59% to 49%, with increased cooling water demand. A 40% exhaust gas recirculation resulted in a recovery of 1% efficiency, proving that enhanced mass transfer in the capture plant reduces solvent regeneration energy demands. Economic analysis reveals that overnight cost increases by 58% with CO2 capture, and cost of electricity by 30%. While this discourages deployment of capture technology, natural gas prices remain the largest driver for cost of electricity. Other integration approaches – using a dedicated boiler and steam extraction from the LP steam drum – were explored for operational flexibility, and their net efficiencies were found to be 40 and 45% respectively. Supplementary firing of exhaust gas may be a viable option for retrofit, as it is shown to minimise integrated plant output losses at a net efficiency of 43.5%. Areas identified for further study are solvent substitution, integrated plant part load operation, flexible control and use of rotating packed beds for CO2 capture.
286

Estimation of treatment effects under combined sampling and experimental designs

Smith, Christina D. January 1900 (has links)
Doctor of Philosophy / Department of Statistics / Dallas E. Johnson / Over the years sampling and experimental design have developed independently with little mutual compatibility. However, many studies do (or should) involve both a sampling design and an experimental design. For example, a polluted site may be exhaustively partitioned into area plots, a random sample of plots selected, and the selected plots randomly assigned to three clean-up regimens. In this research the relationship between sampling design and experimental design is discussed and a basic review of each is given. An estimator that combines sampling and experimental design is presented and it's development explained. Properties of this estimator will be derived and some applications of the estimator will be examined. Finally, a simulation study comparing this estimator with the traditional estimator will be presented.
287

High quality coding and reconstruction for transmission of single video images

Barnard, Gerrit 31 October 2007 (has links)
Please read the abstract in the section 00front of this document Copyright 1990, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. Please cite as follows: Barnard, G 1990, High quality coding and reconstruction for transmission of single video images, MEng dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-10312007-110001/ > / Dissertation (M Eng (Electronic Engineering))--University of Pretoria, 2007. / Electrical, Electronic and Computer Engineering / unrestricted
288

Neuromuscular fatigue, muscle temperature and hypoxia : an integrative approach

Lloyd, Alex January 2016 (has links)
Real world exposures to physiologically and/or psychologically stressful environments are often multifactorial. For example, high-altitude typically combines exposure to hypobaric hypoxia, solar radiation and cold ambient temperatures, while sea level thermal stress is often combined with supplementary or transient stressors such as rain, solar radiation and wind. In such complex environments, the effect of one stressor on performance may be subject to change, simply due to the presence of another independent stressor. Such differential influences can occur in three basic forms; additive, antagonistic and synergistic, each term defining a fundamental concept of inter-parameter interactions. As well as the natural occurrence of stressors in combination, understanding interactions is fundamental to experimentally modelling how multiple physiological strains integrate in their influence on or regulation of - exercise intensity. In this thesis the current literature on neuromuscular fatigue and the influence of thermal and hypoxic stress is reviewed (Chapter 1). This is followed by an outline of the methodological developments used in the subsequent experiments (Chapter 2). In the first experimental study (Chapter 3) a novel approach was adopted to investigate the combined effect of muscle cooling and hypoxia on neuromuscular fatigue in humans. The results showed that the neuromuscular system s maximal force generating capacity declined by 8.1 and 13.9% during independent cold and hypoxic stress compared to control. Force generation decreased by 21.4% during combined hypoxic-cold compared to control, closely matching the additive value of hypoxia and cold individually (22%). This was also reflected in the measurement of mechanical fatigue (electromechanical ratio), demonstrating an additive response during combined hypoxic-cold. From this study, it was concluded that when moderate hypoxia and cold environmental temperatures are combined during low intensity exercise, the level of fatigue increases additively with no interaction between these stressors. Before conducting a more complex investigation on combined stressors, a better understanding of the role of muscle temperature on central fatigue - i.e. voluntary muscle activation via the afferent signalling pathways was sought. The focus of Chapter 4 was to quantify the relationship between muscle temperature and voluntary muscle activation (central fatigue) across a wide range of temperatures. The primary finding was that different muscle temperatures can induce significant changes in voluntary activation (0.5% reduction per-degree-centigrade increase in muscle temperature) when neural drive is sustained for a prolonged effort (e.g. 120-s); however this effect is not exhibited during efforts that are brief in duration (e.g. 3-s). To further explore this finding, Chapter 5 investigated the effect of metaboreceptive feedback at two different muscle temperatures, using post-exercise muscle ischemia, on voluntary activation of a remote muscle group. The results showed that at the same perceived mental effort, peripheral limb discomfort was significantly higher with increasing muscle temperature (2% increase per-degree-centigrade increase). However any influence of increased muscle temperature on leg muscle metaboreceptive feedback did not appear to inhibit voluntary muscle activation - i.e. central control - of a remote muscle group, as represented by an equal force output and voluntary activation in the thermoneutral, contralateral leg. In Chapter 6, the psycho-sensory effects of changes in muscle temperature on central fatigue during dynamic exercise were investigated. During sustained dynamic exercise, fatigue development appeared to occur at a faster rate in hot muscle (4% increase per-degree-centigrade increase) leading to a nullification of the beneficial effects of increased muscle temperature on peak power output after a period of ~60-s maximal exercise. In support of previous studies using isometric exercise (Chapter 4 and 6), participants reported significantly higher muscular pain and discomfort in hot muscle compared to cooler muscle during dynamic exercise (2 and 1% increase per-degree-centigrade increase respectively), however this did not result in a lower power output. From Chapters 4, 5 and 6 it was concluded that in addition to faster rates of metabolite accumulation due to cardiovascular strain, it is possible that a direct sensitisation of the metaboreceptive group III and IV muscle afferents occurs in warmer muscle. This likely contributes to the reduction in voluntary muscle activation during exercise in the heat, while it may attenuate central fatigue in the cold. It was also interpreted that muscle afferents may have a similar signalling role to cutaneous sensory afferents; the latter of which are recognised for their role in providing thermal feedback to the cognitive-behavioural centres of the brain and aiding exercise regulation under thermal stress. The impact of body core and active muscle temperature on voluntary muscle activation represented a similar ratio (5 to 1 respectively) to the temperature manipulated (single leg) to non-temperature manipulated mass (rest of body) in Chapters 4, 5 and 6. This indicates that voluntary muscle activation may also be regulated based on a central meta-representation of total body heat content i.e. the summed firing rates of all activated thermoreceptors in the brain, skin, muscle, viscera and spine. Building on the initial findings of Chapter 3, Chapter 7 investigated the causative factors behind the expression of different interaction types during exposure to multi-stressor environments. This was achieved by studying the interaction between thermal stress and hypoxia on the rate of peripheral and central fatigue development during a high intensity bout of knee extension exercise to exhaustion. The results showed that during combined exposure to moderate hypoxia and mild cold, the reductions in time to exhaustion were additive of the relative effects of hypoxia and cold independently. This differs from the findings in Chapter 3, in which fatigue was additive of the absolute effects of cold and hypoxia. In contrast, combining moderate hypoxia with severe heat stress resulted in a significant antagonistic interaction on both the absolute and relative reductions in time to exhaustion i.e. the combined effect being significantly less than the sum of the individual effects. Based on the results in Chapter 7, a quantitative paradigm for understanding of systematic integration of multifactorial stressors was proposed. This is, that the interaction type between stressors is influenced by the impact magnitude of the individual stressors effect on exercise capacity, whereby the greater the stressors impact, the greater the probability that one stressor will be cancelled out by the other. This is the first study to experimentally model the overarching principles characterising the presence of simultaneous physiological strains, suggesting multifactorial integration be subject to the worst strain takes precedence when the individual strains are severe.
289

Thermally and Chemically Induced Changes in Interface Shear Behavior of Landfill Liners

Li, Ling January 2015 (has links)
Composite liners are used in landfills to isolate solid waste from the local environment. The combination of a high-density polyethylene (HDPE) geomembrane and compacted clay liner (CCL) is commonly used worldwide. In the Ontario region, bentonite sand mixtures (BSMs) and the local clay i.e. Leda clay, can be considered as appropriate CCL materials. However, the interface failure between smooth HDPE and CCL is a critical issue for landfill safety. The shear stress behavior and strength parameters at the interface between the HDPE and CCL can be affected by many factors, such as temperature and chemicals. The temperature difference between winter and summer in the Ontario region is approximately 50°C, which causes a freeze-thaw (F-T) phenomenon in local landfills. Leachate and heat are generated during the solid waste stabilization process. Landfill leachate usually contains a high concentration of cations, which can carry heat, thus affecting the landfill liner properties. As a result, the interface shear stress behavior and strength parameters are affected by the aforementioned conditions. In this thesis, a series of experiments were conducted on the shear stress behavior at the interface of Leda clay / HDPE and bentonite sand mixture (BSM) / HDPE. In order to understand the influence of the F-T phenomenon, the samples were tested by varying the number of F-T cycles. Meanwhile, in order to understand the combined influence of cations and heat, the samples were saturated with different solutions, i.e. distilled water, potassium chloride and calcium chloride solutions. Then they were cured in an oven with different temperatures and room temperature, respectively. All of the laboratorial shear tests have been performed by using a direct shear machine. Results show that the BSM /HDPE and Leda clay/ HDPE interfaces are both influenced by the F-T cycles. The BSM/HDPE interface shear of the samples between 0 and 5 F-T cycles has more obvious differences, while the friction angle of compacted Leda clay/HDPE exhibits distinct reduction in the first 3 cycles, after which, the difference becomes hard to differentiate. The results also indicate that both high temperature and high concentration of cations from leachate can slight reduce the interface shear stress of BSM/HDPE. However, the combined influence of thermal-chemical conditions is not much more obvious compared to the effects of a single thermal or chemical condition. The BSM materials, which were saturated with different solutions, are also tested by using X-ray diffraction to examine the mineral changes in the BSM. The calcium and potassium cations convert sodium-bentonite into calcium-rich bentonite and illite/semectie mixtures, respectively. Nevertheless, the changess of clay part caused by the combined effect of heat and leachate have limited influence on the BSM/HDPE interface shear behavior.
290

Unilateral or Bilateral Training to Improve Amateur Female Handball Players’ Sprint Acceleration and Change of Direction Ability : A Quantitative Study Comparing Two Training Methods

Hawkins, Marcus January 2016 (has links)
Aim The aim of the study was to identify the difference between unilateral and bilateral training and their effect on female handball players sprint acceleration and change of direction (COD) ability. The research question was “What differences are there between the effect of combined training performed unilaterally and training performed bilaterally on female handball players’ sprint acceleration ability and COD ability?” Method 60 female (age: 20 ± 5yr) handball players participated in the study, 30 in each group. A loss of 30 subjects occurred, leaving total of 30 subjects finished the study, 15 in each group. The subjects performed two tests before initiating a combined training protocol, inducing strength and plyometric exercises. The first test consisted of a 10-meter straight sprint that was also divided into a 5-meter split, which measured their sprint acceleration by using Ivar Run System. The second test was a modified version of Spasic’s (2015) handball specific COD assessor. After the baseline-test, the subjects participated in a six-week long training protocol, one plyometric workout a week and one strength workout a week. Once the six weeks were completed, the same tests were performed. The data was recorded in Microsoft Excel (2016, Seattle, USA) and analyzed in IBM SPSS (2013, version 22.0, New York, USA).  Results Statistically, unilateral training has proven to be a more effective training method to improve the first 5-meters (p=0,013) of the 10-meter sprint acceleration test and not the other areas. Whilst bilateral training has proven to be more effective training method to improve the total time of the 10-meter sprint acceleration test (p=0,035). Both groups have statistically shown no significant difference in the COD-ability test. Conclusion Crucial standardization errors were made during this study, which in turn could have impaired the results greatly. A cautious approach to a solid conclusion should be considered, due to the standardization errors and the fact, that the subjects were not used to a training protocol being systematically structured. More research with a similar perspective has to be brought about, focusing on the long-term effect and maybe even on elite players. / Syfte och frågeställningar Studiens syfte var att ta reda på om unilateralt baserat träning eller om bilateralt baserat träning var effektivast för att förbättra sprint acceleration och riktningsförändringsförmåga (COD). Frågeställningen lyder; Skiljer sig effekten av kombinerat träning som utförs unilateralt från bilateralt på kvinnliga handbollsspelare som tävlar på amatörnivå. Metod 60 kvinnliga handbollsspelare (age: 20 ± 5yr) deltog i studien. Totalt genomförde 30 stycken deltagare hela studien, 15 per grupp, vilket innebär ett bortfall på 30 stycken. Innan träningsperioden började fick deltagarna genomföra två förtester. Första testet var ett 10-meters sprint accelerationstest, som hade splittider på 5-meter, andra testet var en modifierad Spasics (2015), som är ett riktningsförändringsförmågatest. De testades tider mättes med IVAR Run system. Efter testerna, genomförde deltagarna ett sex-veckors långt träningsprogram, varje vecka genomfördes ett styrkepass och ett plyometriskt träningpass. Eftertester genomfördes efter träningsperioden, resultatet från testerna antecknades i Microsoft Excell (2016, Seattle, USA) och analyserades i IBM SPSS (2013, version 22.0, New York, USA). Resultat Resultatet visar att unilateral träning är en mer effektive träningsmetod för att förbättra de första 5-meterna (p=0,013) i 10-meter sprint accelerationstestet, men inte i de andra delarna. Däremot visar det sig att bilateral träning har en statistiskskillnad (p=0,035) på hela 10-meters sprint accelerationstestet, men inte de första eller sista 5-meterna var för sig. Både grupperna visade ingen statistiskskillnad i riktningsförändringstestet. Slutsats Standardiseringsmisstag gjordes under studiens gång, som kan ha haft direkt påverkan på resultatet. Innan en slutsatsen dras, bör man ta hänsyn till misstagen som begåtts ur ett standardiseringsperspektiv och att deltagarna var ej vana att genomföra ett träningsprogram som var systematiskt strukturerat. Mer forskning inom samma område, utifrån samma perspektiv behövs göras, särskilt långsiktiga studier och kanske även på elitspelare.

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