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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.
1

Concrete hydration, temperature development, and setting at early-ages

Schindler, Anton Karel 09 May 2011 (has links)
Not available / text
2

An adsorption based cooling solution for electronics used in thermally harsh environments

Sinha, Ashish 30 August 2010 (has links)
Growing need for application of electronics at temperatures beyond their rated limit, (usually > 150 °C) and the non availability of high temperature compatible electronics necessitates thermal management solutions that should be compact, scalable, reliable and be able to work in environments characterized by high temperature (150 -250 °C), mechanical shock and vibrations. In this backdrop the proposed research aims at realization of an adsorption cooling system for evaporator temperatures in the range of 140 °C-150 °C, and condenser temperature in the range of 160 °C-200 °C. Adsorption cooling systems have few moving parts (hence less maintenance issues), and the use of Thermo-Electric (TE) devices to regenerate heat of adsorption in between adsorbent beds enhances the compactness and efficiency of the overall 'ThermoElectric-Adsorption' (TEA) system. The work presented identifies the challenges involved and respective solutions for high temperature application. An experimental set up was fabricated to demonstrate system operation and mathematical models developed to benchmark experimental results. Also, it should be noted that TEA system comprises TE and adsorption chillers. A TE device can be a compact cooler in its own right. Hence a comparison of the performance of TEA and TE cooling systems has also been presented.
3

Effects Of Retempering With Superplasticizer On Properties Of Prolonged Mixed Mineral Admixture Containing Concrete At Hot Weather Conditions

Yazan, Kazim 01 November 2005 (has links) (PDF)
Concrete which is manufactured in a mixing plant to be delivered to construction site in unhardened and plastic stage is called ready-mixed concrete. Because of technical and economical reasons, many mineral and chemical admixtures are used in ready-mixed concrete production. As a result of extra mixing and delayed placing of ready-mixed concrete (especially at hot weather conditions), there can be many problems about concrete, like slump loss. Addition of water for retempering concrete is the usual procedure, but addition of water without proper adjustment in mixture proportions, adversely affects compressive strength. During this study, effects of prolonged mixing and retempering with superplasticizer on properties of fresh and hardened concrete at hot weather conditions are observed. Some of the properties of concrete inspected are compressive strength, splitting tensile strength, slump and air content. All mixes contain air entrainer and water reducer at a standard amount. The difference between mixes comes from kind and amount of mineral admixture which cement is replaced by. During the study, fly ash, blast furnace slag, ground clay brick and natural pozzolan are used at amounts, 25% and 50% of cement. Also, a mixture of pure cement is prepared as control concrete. 15 cm initial slump is planned in the experimental work. After five minutes and at the end of first, second, third and fourth hours of mixing process, if needed retempering process is proceeded with superplasticizer and samples are taken. As a result of retempering with superplasticizer, the aimed slump values are obtained. The effects are than, observed. As a result of this study, it has been observed that replacing Portland cement with certain mineral admixtures, especially fly ash at certain amounts, can be a solution for slump loss problem, by retarding the slump loss effect of prolonged mixing. Also it has been seen that ground clay brick causes better performance for slump values at lateral stages of mixing with respect to pure Portland cement. Another important observation has been about the increase in the amount of air caused by air entraining admixtures in fresh concrete based on prolonged mixing at hot weather conditions.
4

Three Essays on Environmental and Health Economics

Al-Azzam, Mohammad Sameer Ali 17 June 2022 (has links)
This thesis consists of three essays in applied microeconomics: First, heat and school absence: evidence from a survey of Indian children. Second, heatwaves and short-term morbidity in India. Third, intra-family marriage and pregnancy outcomes. Chapter 1. India is the second most populous country on earth with young people representing a significant number of the population resulting in data that indicates such figures at 38 per cent. With such high numbers, major consideration must be given into developing informed and targeted policies to ensure positive educational outcomes for young people. This paper contributes to existing literature by investigating the impact of high temperatures on students’ rates of absenteeism, relying on the short-term exogenous variation in daily maximum temperatures. The paper highlights the heterogeneity of the effect of temperature by climate zone. To create data, we link information on children’s school absences from the India Human Development Survey (IHDS-II) in combination with meteorological data from the ERA-Interim archive taken from a thirty day period prior to individual interview dates. Our findings suggest that high temperatures have a substantial negative impact on students’ attendance in rural areas. However, limited evidence of such an effect is found in urban areas. Our results therefore indicate a need to implement future in-depth studies. Chapter 2. Within this chapter, we investigate the impact of prolonged heat exposure on individuals short-term morbidity rates over a thirty day period prior to the interview date. We work with a broad dataset and use an econometric model that utilizes plausibly exogenous variation in high weather temperatures. We implement the percentile-based approach and three different heatwave metrics as a innovative way of defining and capturing the impact of heatwaves on health outcomes. Our results show that heatwave intensity of the eighty-fifth percentile over the duration of three consecutive days of extensive heat has a significant adverse effect on individuals short-term morbidity. More so, our findings indicate a disparity between genders in relation to the impact of heatwaves. Finally, it can be suggested that individuals having to travel an extensive distance in order to access water are most affected by high temperatures. Chapter 3. Millions of people worldwide are married to their blood relatives, yet the resulting impact on offspring health continues to be debated. Within this paper, we provide evidence around this debate by studying the birth outcomes from a large, representative sample of Indian women in varying marital circumstances. We explore the impact of intra-family marriage on negative pregnancy outcomes including stillbirth, miscarriage, and child death after birth. We utilize an ordinary least squares model (OLS), which controls for a wide range of financial and family factors. The results show that being a woman related to her husband by blood increases the probability of experiencing negative pregnancy outcomes by 2.8 percentage points. Our finding is robust using the instrumental variable approach (IV). The instrumental variable represents the ambient level of violence against women, which positively affects the probability of consanguineous marriage. The IV approach leads to a slightly smaller adverse impact of 2.2 percentage points. In addition, the OLS results provide suggestive evidence that intra-family marriage has no heterogeneous impact across religion types.
5

Essays in Environmental and Health Economics

Alishahi, Modjgan 18 July 2022 (has links)
This dissertation contains three distinct chapters considering different challenges faced by a developing country; India. Chapter 1. Food price spikes induced by hot weather could be a threat to food security, human health and poverty. It could exacerbate the health status of households by reducing the nutrient food choices, particularly among the vulnerable groups who already have a more frail status. This paper examines the first possible causal link between milk average market price and hot weather in the short run at the household level in India. Using Human Development Survey data, it is empirically showed that hot weather has a significant adverse impact on the price in rural India. The impacts are more pronounced for non-poor families in both rural and urban areas. The effects are robust to alternative heat metrics. The paper further investigates the effect of hot weather on households' milk consumption. Evidence suggests that low-income (poor) families with purchased consumption, both in rural and urban areas, are significantly adversely affected compared to those with homegrown product. Chapter 2. Health-related behaviour and, in particular, attending antenatal care during pregnancy is essential to reduce the risk of pregnancy complications, stillbirth, and maternal mortality. This paper estimates the causal effect of years of formal education on the likelihood that a pregnant woman in India attends natal care and screening services. Despite the importance, insufficient documents exist on the determinants of natal care usage in developing countries. The current study investigates for the first time the hypothesis that women’s schooling attainments might have a causal impact on natal care usage in India. Drawing on the nationally representative India Human Development Survey (IHDS-II) and instrumenting for years of schooling with plausibly exogenous variation in age at first menarche, I find that delayed age at menarche significantly increases formal education. Further, evidence suggests that an additional year of schooling significantly enhances the likelihood of uptaking the antenatal checkups. However, attending a sonogram/ultrasound does not appear to be significant. Chapter 3. Adolescent girls are amongst the vulnerable groups exposed to the risks that challenge their healthy development into young women. India's Rajiv Gandhi Scheme for Empowerment of Adolescent Girls (SABLA) program was designed to address such challenges by building health awareness and encouraging decision-making autonomy as the first steps towards real change in women’s development. Using data from the nationally representative India Demographic and Health Survey (IDHS), with plausibly exogenous variation in the program’s rollout across districts and birth cohorts, we provide evidence that exposure to SABLA increases the likelihood of having knowledge of family planning and diarrhoea treatment, using contraception, and autonomy in personal financial decision-making for exposed women. The effects are more pronounced for women residing in urban areas, for women who have secondary education or higher, and primarily for Muslim women.

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