• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 264
  • 147
  • 41
  • 30
  • 23
  • 14
  • 13
  • 6
  • 4
  • 4
  • 3
  • 3
  • 2
  • 2
  • 2
  • Tagged with
  • 626
  • 626
  • 210
  • 124
  • 114
  • 87
  • 86
  • 86
  • 75
  • 67
  • 61
  • 58
  • 58
  • 56
  • 55
  • 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.
21

Planning for the integrated refinery subsystems

Ejikeme-Ugwu, Edith January 2012 (has links)
In global energy and industrial market, petroleum refining industry accounts for a major share. Through proper planning and the use of adequate mathematical models for the different processing units, many profit improving opportunities can be realized. The increasing crude oil price has also made refining of crude oil blends to be a common practice. This thesis aims to provide useful insight for planning of the integrated refinery subsystems. The main subsystems referred to are (1) The crude oil unloading subsystem (2) The production and product blending subsystem and (3) The product distribution subsystem. Aspen HYSYS® was first used to develop a rigorous model for crude distillation unit (CDU) and vacuum distillation unit (VDU). The rigorous model was validated with pilot plant data from literature. The information obtained from the rigorous model is further used to develop a model for planning of the CDU and VDU. This was combined with models (obtained from empirical correlations) for fluid catalytic cracker (FCC) and hydrotreater (HDT) units to form a mathematical programming planning model used for refinery production and product blending subsystem planning. Since two different types of crude were considered, the optimum volumetric mixing ratio, the sulphur content at that mixing ratio and the CDU flow rate were determined. The yields fraction obtained from the rigorous model were then used to generate regression model using least square method. The sulphur composition of the crude oil was used as independent variable in the regression model. The generated regression models were then used to replace the regular fixed yield approach in a refinery planning model and the results compared. From the results obtained, the proposed method provided an alternative and convenient means for estimating yields from CDU and VDU than the regular fixed yield approach. The proposed aggregate model for the production and products blending subsystem was integrated with the modified scheduling model for the crude unloading subsystem developed by Lee et al. (1996) and products distribution model developed by Alabi and Castro (2009) for refinery planning. It was found that the regression model could be integrated in a refinery planning model and that the CDU flow rate was maximised as compared to the non- integrated system.
22

Analysis of Distresses in Asphalt Pavement Transitions on Bridge Approaches and Departures

Rajalingola, Manvitha 03 November 2017 (has links)
Some highway agencies in the United States are experiencing frequent distresses in asphalt pavements on bridge approaches/departures. Commonly observed distresses include alligator cracking and rutting, which reduce roadway smoothness and safety. To lessen the distresses in pavements it is needed to investigate the extent and root causes of the problem. Based on Florida highway conditions, this research study mainly focused on1. Literature review and identification of the extent of the problem; 2. Collection of relevant pavement condition data and descriptive analysis; 3. Development of statistical models to determine factors influencing the distresses in asphalt pavements on bridge approaches/departures. To the best of my knowledge, this is the first study that uses a statistical model to determine the factors that are responsible for causing asphalt pavement distresses on bridge approaches/departures. As part of the literature review, a nationwide questionnaire survey was targeted towards U.S state DOTs. The data collection and analysis specific to the Florida highways found that in 2015 on Florida Interstate highways, about 27% bridges with asphalt pavements on their approaches/departures showed signs of cracking, and about 20% bridges have noticeable rutting in their approach or departure pavements. A random parameter linear regression model was applied to examine the factors that may influence distresses in asphalt pavements in Florida. Pavement condition was evaluated based on the Florida Department of Transportation (FDOT) 2015 pavement condition data and video log images, and other relevant data were collected from various sources such as FDOT Roadway Characteristics Inventory (RCI) database, FDOT pavement management reports, and FDOT Ground Penetrating Radar (GPR) survey reports. A constraint existed in the availability of the GPR data that can give pavement layer thickness, which limited the number of bridge approach pavement sections included in the statistical modeling. Based on the limited data, the estimated results from the random parameter linear regression model showed that the variables influencing distresses in asphalt pavements on bridge approaches/departures, in terms of rutting and roughness, may include pavement age, annual average daily truck traffic, and surface friction course.
23

An outcomes-based framework for assessing the quality of transnational engineering education at a private college

Chong, Beng Keok January 2005 (has links)
The concept of "transnational" education has emerged over the past decade or more as a critical strategy for meeting the growing demand for higher education worldwide. Essentially, transnational higher education allows international providers with outstanding credentials to conduct degree programs at local sites in conjunction with local tertiary institutions. Due to the rapid expansion of transnational programmes and the proliferation of transnational education providers, both governments and parents have, however, raised questions about the quality of education provided through transnational mechanisms. Rapid technological development, coupled with the recent growth of new engineering specialty areas, has led to the development of outcomes-based criteria for engineering education by a range of international engineering professional bodies. The emergence of outcomes-based approaches requires new instruments to measure the success, or otherwise, of engineering programs offered by universities. This study was conducted at a Malaysian private college (pseudonym "Trans College" with the prime purpose of developing an authoritative measurement instrument for evaluating the quality of transnational engineering education. This study generated a theory-based 11-dimension Preliminary Conceptual Framework consisting of four Outcomes dimensions and seven Contributory dimensions for Transnational Engineering Education, and tested the integrity of the theoretical framework through surveys of enrolled students, staff, and representatives of employing agencies. The Preliminary Conceptual Framework was found to have a high degree of conceptual validity, as well as some limitations. The findings of the surveys enabled a Revised Conceptual Framework for Transnational Engineering Education to be developed through reliability test and validated by using confirmatory and exploratory factor analyses. The revised framework comprises five Outcomes and eight Contributory dimensions. It has been transposed into a 13-dimension revised survey instrument consisting of 25 Outcomes items clustered into five Outcomes dimensions, and 49 Contributory items clustered into eight Contributory dimensions. The developed survey instrument was then used to study the perceptions of students, staff, and employers regarding the quality of the transnational engineering education. Through performing t-tests, ANOVA, and other statistical analyses, the results of the study indicate that the quality of the transnational engineering education at Trans College was perceived by students, staff, and employers to be generally sound. It was also revealed that the Contributory construct can be adopted for measuring the satisfaction levels of students. Students, staff, and employers were also satisfied for the most part with their respective experiences of the programs in question. The study is believed to have considerable significance. First, it has generated a conceptual framework for measuring the quality of the transnational engineering education. The validated conceptual framework is transposed into a validated instrument that can be adapted for use by a range of other transnational educational providers. Second, it affirms the value of the "transnational" concept while also providing a number of recommendations for the enhancement of such programmes, particularly at Trans College. Third, the conceptual framework for the delivery of successful transnational engineering education derived from this study may help to improve the quality of transnational engineering programmes conducted in Malaysia, and make Malaysia "the centre of educational excellence" in the ASEAN region, with the transnational providers becoming hubs of tertiary education, and their networks spanning the globe.
24

The association of Exchange rates and Stock returns : Linear Regression analysis

Akumbu, Nshom Martin January 2007 (has links)
<p>The association of exchange rates with stock returns and performance in major trading markets is widely accepted. The world’s economy has seen unprecedented growth of interdependent; as such the magnitude of the effect of exchange rates on returns will be even stronger. Since the author perceives the importance of exchange rates on stock returns, the author found it interesting to study the effect of exchange rates on some stocks traded on the Stock exchange.</p><p>There has been a renewed interest to investigate the relationship between returns and exchange rates as such; the author has chosen to investigate the present study to focus in the United Kingdom with data from the London Stock exchange .The author carried out his research on 18 companies traded on the London Stock Exchange in the process, using linear regression analysis. Taking into account the fact that the magnitude of exchange rate movements on stock returns is governed by a series of factors, the author did set up a selection criteria which spread across a series of industries ranging from financial services, manufacturing, aviation, mining, tobacco, fashion and food processing. All selected companies are of the FTSE 100 companies.</p><p>The author produced results that to some degree are consistent with predictions in the theoretical framework. The author find significant exposure of stock returns to changes in exchange rates for some companies in the sample of FTSE 100 firms used in the study. The author equally finds out that particular currencies may be of more risk to certain companies than to others by introducing euro values in to his regression equation. This gives the compelling evidence that these companies rely heavily on external sales and revenue.</p><p>The author, further employed lagged values of exchange rates in to his regression and found significant evidence of the possibility of mispricing for certain stocks and the impact of the previous days trading figures on present stock prices. The author believes that the weak responds in certain cases was as a result of hedging strategies put in place by these companies and risk management strategies which tend to minimise the effect of exchange rates movements.</p>
25

Något om regressionsanalys

Pettersson, Angelica January 2009 (has links)
<p>En gren inom statistikteorin är den så kallade Regressionsanalysen där man studerar hur data från exempelvis ett stickprov kan anpassas till en graf. Skrivandet av denna uppsats har haft som syfte att studera några av de metoder som finns att tillgå vid bestämning av de ingående parametrarna i de enklare fallen av regression. Dessutom ges i de avslutande kapitlen exempel på den del inom regressionsanalysen som kallas Styckvis Linjär Regression eller <em>Piecewise Linear Regression.</em></p> / Presentationen är redan avklarad den 26 april 2010 kl. 11.30
26

The association of Exchange rates and Stock returns : Linear Regression analysis

Akumbu, Nshom Martin January 2007 (has links)
The association of exchange rates with stock returns and performance in major trading markets is widely accepted. The world’s economy has seen unprecedented growth of interdependent; as such the magnitude of the effect of exchange rates on returns will be even stronger. Since the author perceives the importance of exchange rates on stock returns, the author found it interesting to study the effect of exchange rates on some stocks traded on the Stock exchange. There has been a renewed interest to investigate the relationship between returns and exchange rates as such; the author has chosen to investigate the present study to focus in the United Kingdom with data from the London Stock exchange .The author carried out his research on 18 companies traded on the London Stock Exchange in the process, using linear regression analysis. Taking into account the fact that the magnitude of exchange rate movements on stock returns is governed by a series of factors, the author did set up a selection criteria which spread across a series of industries ranging from financial services, manufacturing, aviation, mining, tobacco, fashion and food processing. All selected companies are of the FTSE 100 companies. The author produced results that to some degree are consistent with predictions in the theoretical framework. The author find significant exposure of stock returns to changes in exchange rates for some companies in the sample of FTSE 100 firms used in the study. The author equally finds out that particular currencies may be of more risk to certain companies than to others by introducing euro values in to his regression equation. This gives the compelling evidence that these companies rely heavily on external sales and revenue. The author, further employed lagged values of exchange rates in to his regression and found significant evidence of the possibility of mispricing for certain stocks and the impact of the previous days trading figures on present stock prices. The author believes that the weak responds in certain cases was as a result of hedging strategies put in place by these companies and risk management strategies which tend to minimise the effect of exchange rates movements.
27

Planning for the integrated refinery subsystems

Ejikeme-Ugwu, Edith 06 1900 (has links)
In global energy and industrial market, petroleum refining industry accounts for a major share. Through proper planning and the use of adequate mathematical models for the different processing units, many profit improving opportunities can be realized. The increasing crude oil price has also made refining of crude oil blends to be a common practice. This thesis aims to provide useful insight for planning of the integrated refinery subsystems. The main subsystems referred to are (1) The crude oil unloading subsystem (2) The production and product blending subsystem and (3) The product distribution subsystem. Aspen HYSYS® was first used to develop a rigorous model for crude distillation unit (CDU) and vacuum distillation unit (VDU). The rigorous model was validated with pilot plant data from literature. The information obtained from the rigorous model is further used to develop a model for planning of the CDU and VDU. This was combined with models (obtained from empirical correlations) for fluid catalytic cracker (FCC) and hydrotreater (HDT) units to form a mathematical programming planning model used for refinery production and product blending subsystem planning. Since two different types of crude were considered, the optimum volumetric mixing ratio, the sulphur content at that mixing ratio and the CDU flow rate were determined. The yields fraction obtained from the rigorous model were then used to generate regression model using least square method. The sulphur composition of the crude oil was used as independent variable in the regression model. The generated regression models were then used to replace the regular fixed yield approach in a refinery planning model and the results compared. From the results obtained, the proposed method provided an alternative and convenient means for estimating yields from CDU and VDU than the regular fixed yield approach. The proposed aggregate model for the production and products blending subsystem was integrated with the modified scheduling model for the crude unloading subsystem developed by Lee et al. (1996) and products distribution model developed by Alabi and Castro (2009) for refinery planning. It was found that the regression model could be integrated in a refinery planning model and that the CDU flow rate was maximised as compared to the non- integrated system.
28

Predicting the Unit Appraisal Value of the Unimproved and Private Land in the City of Houston by LEED Sustainable Site Credits

Park, Young Jun 2009 December 1900 (has links)
The primary objectives of this research are to identify the relation between Leadership in Energy and Environmental Design (LEED) criteria regarding sustainable site credits and the appraised value of land parcels in the City of Houston, and additionally to analyze the effects of detail components which leverage the sustainable credits regarding the Public Transportation Access (PTA) in terms of economic issues. To accomplish these objectives, the approach to estimate sustainable ratings of specific parcels using Geographic Information Systems (GIS) was established. Green construction must be one of the most powerful trends in the construction industry. One of the main concepts to underlie the basis of this green construction is sustainability. This sustainability has to be considered in the process of the site selection prior to the actual activities to construct a building. Recently, the U.S. Green Building Council (USGBC) has suggested the modified guideline with "LEED 2009 for New Construction and Major Renovations". According to this metric, it is clear that this principle endeavors to block environmental abuses related to land development or restoration projects. On the other hand, it is not easy to check the serviceability of these rules to guarantee continuous economic merit through sustainable land development or restoration encouraged by these criteria. The criteria regarding the sustainable site selection in this LEED metric are Sustainable Site Credit (SSC) #1: Site Selection, SSC #3: Brownfield, and SSC #4.1: Public Transportation Access. Linear regression methods were used for predictive analysis. In this model, the unit appraisal value of the land was used as the dependent variable to reflect the economic values of the land, and LEED-sustainable-site criteria were used as the categorical independent variables. According to statistical results, the models to predict the appraisal parcel value using sustainable site components have relatively low R-square. Moreover, SSC #1 and SSC #3 were not significant factors affecting the unit value of land. This outcome means that there are no statistically significant effects of SSC #1 and SSC #3 on parcel value. On the other hand, SSC #4.1 was highly significant. Furthermore, the detail components of SSC #4.1 regarding the bus stops and railroad stations were also significant. These results can lead to improved environmental preservation by avoiding development which is far from the PTA as well as increasing economic value while enhancing the development density near the PTA corridors. Finally, GIS was used to determine the LEED ratings of individual parcels. The methods established to do this can be applied to other projects for the other regions, or the same region at different times.
29

Πολλαπλό γραμμικό μοντέλο παλινδρόμησης : στατιστικά συμπεράσματα και εκτιμήσεις

Κιουφεντζή, Όλγα 27 August 2008 (has links)
Η εργασία μου αναφέρεται στην ανάλυση της γραμμικής παλινδρόμησης και στην περαιτέρω ανάλυση των υποθέσεων του γραμμικού μοντέλου παλινδρόμησης σε συνδυασμό με παραδείγματα από την οικονομική θεωρία. Περιέχει ακόμη μια εφαρμογή για την ελαχιστοποίηση του κόστους παραγωγής ηλεκτρικής ενέργειας κάποιων επιχειρήσεων. / My paper concerns in Linear Regression analysis and the further analysis of the hypothesis of the Linear Regression model accompanied with many examples of econometric theory. Also, it concludes an application of minimization of the production cost of electric power of a specific number of companies.
30

Water Consumption Patterns in Australian Aboriginal Communities

emmayuen@hotmail.com, Emma Yuen January 2005 (has links)
Aboriginal Australians have a significantly lower health status than their non-Aboriginal counterparts. To facilitate healthy living practices necessary for good health, a high level investment is currently made in water services, on the assumption that there is a relationship between the volume and quality of water supplied with health outcomes, despite the high economic and environmental cost. This thesis investigates whether the current design supply criteria of 1000-1200 litres per person per day of water, meeting the Australian Drinking Water Quality Guidelines, is both sufficient and necessary to improve the health of Aboriginal Australians. The scope of the thesis is limited to the sufficiency of design guidelines although it necessarily also touches on the broader issues of Aboriginal health. Both qualitative and quantitative methods were used to explore current water consumption patterns of consumers at multiple hierarchical levels (community, household and individual) and hence the requirements of physical infrastructure on which consumers depend. Multiple linear regression was used to consider factors correlated with supply volume, while metering was used at both the domestic and appliance level to determine where and how water was used. Meters were installed on fixtures in two houses in a community near Alice Springs. This was then complemented by qualitative information obtained through focus group discussions, key informant interviews and observation in the field. The appropriateness of the supply of high quality water for all uses was addressed by considering the volume of drinking water intake and its impact on the derivation of water quality guidelines. This was achieved by a face-to-face survey involving 57 volunteers. Fieldwork was conducted predominantly in three communities near Alice Springs although some additional data was collected in other communities in Western Australia and the Northern Territory. The results showed that the factors influencing water consumption were highly complex and variable between communities and individuals. However, there were some culturally specific needs identified in Aboriginal communities, such as the need for temperature and dust control, as well as the reduction of losses. The unique characteristics of each community made it difficult to provide a more precise estimate for design supply. As a result, overly conservative guidelines such as those already used are necessary in the short term despite there being no guarantee of improved health. In the long term, issues of community governance and capacity building will start to be addressed, and the realisation that social systems are both complex and dynamic will need to be reflected in policy. These issues were represented in a systemic conceptual model at the end of the thesis, which also highlighted inadequacies of reductionist approaches such as design supply guidelines. The thesis concluded that complex problem situations such as that of health, require a systems approach.

Page generated in 0.0901 seconds