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Characterizing the Separation and Reattachment of Suction Surface Boundary Layer in Low Pressure Turbine Using Massively Parallel Large Eddy SimulationsJagannathan, Shriram 2010 December 1900 (has links)
The separation and reattachment of the suction surface boundary layer in a low pressure turbine is characterized using large-eddy simulation at Re=68,000 based on freestream velocity and suction surface length. A high pass filtered Smagorinsky model is used for modeling the sub-grid scales. The onset of time mean separation is at s=so = 0:61 and reattachment at s=so = 0:81, extending over 20% of the suction surface. The boundary layer is convectively unstable with a maximum reverse flow velocity of about 13% of freestream. The breakdown to turbulence occurs over a very short distance of suction surface which is followed by reattachment. Detailed investigations into the structure and kinematics of the bubble and turbulence statistics are presented. The vortex shed from the bubble, convects downstream and interacts with the trailing edge vortices increasing the turbulence intensity. On the suction side, dominant hairpin structures near the transitional and turbulent flow regime are observed. These hairpin vortices are carried by the freestream even downstream of the trailing edge of the blade with a possibility of reaching the next stage. Longitudinal streaks that evolve from the breakdown of hairpin vortices formed near the leading edge are observed on the pressure surface.
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Theoretical And Experimental Investigation Of A Humidification-dehumidification Desalination System Using Solar EnergySolmus, Ismail 01 September 2006 (has links) (PDF)
In this thesis, experimental and numerical studies have been carried out to investigate the performance of a solar desalination system working on humidification-dehumidification principle under the climatological conditions of Ankara, Turkey. The desalination unit was configured mainly by a double-pass flat plate solar air heater with two glass covers, pad humidifier, storage tank and dehumidifying exchanger. The system used in this work is based on the idea of closed water and open air cycles. A computer simulation program based on the mathematical model was developed by means of MATLAB software to study the effect of different environmental, design, and operational parameters on the desalination system productivity. In this simulation program, the fourth order Runge-Kutta method was used to solve the energy balance equations simultaneously and numerically. In order to compare the obtained theoretical results with experimental ones and validate of the developed mathematical model of the system, an experimental study has been carried out. For that, an experimental set-up was designed, constructed and tested at the solar house of the Mechanical Engineering Department of METU. In addition, the existing solar desalination system was integrated with an evacuated tubular solar water heater unit (closed water circulation) and performance of the system has been studied experimentally.
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Roll pass design for improved flexibility and quality in wire rod rollingEriksson, Conny January 2004 (has links)
<p>The thesis treats roll pass design in wire rod rolling of stainless steel for sequences and series built up by two-symmetrical grooves. It is focused on predicting rolling flexibility, also called working range, as well as product quality. For analysing the flexibility a computer program has been developed. The minimum and maximum roll gap and corresponding bar areas for series of grooves including "oval", "round", "false round", "square" and "diamond" shapes are calculated. Six pass designs used in Swedish mills are analysed. Full-scale rolling is compared with laboratory experiments for the square-oval and false round (round)-oval series. The false round-oval series offers the largest working range and that the flexibility is smaller for pass sequences designed for high reductions. The false round-oval series are also acknowledged as a series for high quality steels and are usually better than the square-oval series having a tendency for defect formation. The thesis also includes high-speed rolling of wire rod in blocks. Here interstand tensions are utilised in order to keep the process stable. For obtaining the required dimensional tolerances of the product they are kept as low as possible. However interstand tensions could be used in order to increase the working range and move the product range towards smaller wire cross sections. For analysing this possibility, a narrow spread technology is utilised. At present time a practical problem is referred to the fixed gearings in the common blocks, which require a certain and given level of interstand tensions and corresponding reductions. This problem can however be solved by means of new block design and modern process control technology. Roll stands can be separately driven and controlled at very high speeds. Thus the eight stand blocks can be subdivided into four plus four passes blocks with a cooling line between enabling also higher productivity without violating the product quality because defect formations caused by a too high rolling temperature. The true working range of a series for a specific steel grade is however not only dependent on the possible spectrum of wire dimensions that can be obtained but might also depend on its ability to decrease or eliminate defects such as surface cracks. Thus, the behaviour of artificial V-shaped cracks in the longitudinal direction has been investigated and compared for the square-oval and false round (round)-oval series mentioned above. In agreement with other research works it was established that efficient rolling conditions for reducing the cracks are obtained when the cracks open up at the same time as their depth is reduced. If the V-shaped crack is closed by contact between its oxidized side surfaces the rolling schedule is not optimal for getting a high quality product. A deeper understanding of the experimental results was obtained by means of an FE-analysis</p>
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The effectiveness of social investment programmes to improve education in Gauteng / Fundile VusaniVusani, Humphrey Fundile January 2010 (has links)
The decisions and actions of management in organisations have an increasing
impact on individuals, other organisations and the community. The importance of
the exercise of corporate social responsibility can no longer be based on the
assumption that the self–interest of the owner of the property will lead to the
public good, or that self–interest and public good can be kept apart and have
nothing to do with each other. On the contrary, it requires of managers that they
assume responsibility for the public good, that they subordinate their actions to
an ethical code of conduct, that they restrain their authority wherever their
exercise would infringe upon the common will and upon the freedom of the individual.
South Africa is one of the countries with the highest illiteracy rate in the world.
There are more children dropping out of school in South Africa than any other
country in the world. The social and economic impact of the lack of education is
difficult to comprehend.
Lack of education affects company productivity and competitiveness adversely. A
lack of education increases the training costs of organisations immensely.
Hence, companies cannot sit on the sideline, but should rather be involved in
education through corporate social responsibility programs.
The primary objective of the study is to investigate the relationship between
corporate social responsibility spending by companies, especially on education,
and improvement in standards of education, thereby increasing the overall
annual Grade 12 pass rate. In order to address the primary objectives of the study, the following secondary
objectives were formulated:
* To understand and obtain insight into the dynamics of social responsibility programs of companies that are involved in education;
* To analyse and identify the main reason for companies to be involved in education;
* To analyse and assess corporate and school partnerships in and around the designated area;
* To measure output for different township high schools by using the grade 12 pass rate as a measuring tool;
* To establish the level of satisfaction within companies that have embarked on corporate social responsibility programs; and
* To establish the importance of mathematics and science as part of the school education.
The most important conclusions that could be drawn from the study are:
* Companies had endorsed corporate social responsibility as part of their strategy;
* It had been extremely difficult to obtain information about companies' corporate social responsibility programs due to information being
classified as confidential by companies. This could be a serious
impediment for advancement of literature and research in the country;
and
* Companies had contributed massive resources to the advancement of
education through their educational programs, but this had not yielded
the consistently desired results through improvement of the Grade 12
pass rate. / Thesis (M.B.A.)--North-West University, Potchefstroom Campus, 2011.
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The effectiveness of social investment programmes to improve education in Gauteng / Fundile VusaniVusani, Humphrey Fundile January 2010 (has links)
The decisions and actions of management in organisations have an increasing
impact on individuals, other organisations and the community. The importance of
the exercise of corporate social responsibility can no longer be based on the
assumption that the self–interest of the owner of the property will lead to the
public good, or that self–interest and public good can be kept apart and have
nothing to do with each other. On the contrary, it requires of managers that they
assume responsibility for the public good, that they subordinate their actions to
an ethical code of conduct, that they restrain their authority wherever their
exercise would infringe upon the common will and upon the freedom of the individual.
South Africa is one of the countries with the highest illiteracy rate in the world.
There are more children dropping out of school in South Africa than any other
country in the world. The social and economic impact of the lack of education is
difficult to comprehend.
Lack of education affects company productivity and competitiveness adversely. A
lack of education increases the training costs of organisations immensely.
Hence, companies cannot sit on the sideline, but should rather be involved in
education through corporate social responsibility programs.
The primary objective of the study is to investigate the relationship between
corporate social responsibility spending by companies, especially on education,
and improvement in standards of education, thereby increasing the overall
annual Grade 12 pass rate. In order to address the primary objectives of the study, the following secondary
objectives were formulated:
* To understand and obtain insight into the dynamics of social responsibility programs of companies that are involved in education;
* To analyse and identify the main reason for companies to be involved in education;
* To analyse and assess corporate and school partnerships in and around the designated area;
* To measure output for different township high schools by using the grade 12 pass rate as a measuring tool;
* To establish the level of satisfaction within companies that have embarked on corporate social responsibility programs; and
* To establish the importance of mathematics and science as part of the school education.
The most important conclusions that could be drawn from the study are:
* Companies had endorsed corporate social responsibility as part of their strategy;
* It had been extremely difficult to obtain information about companies' corporate social responsibility programs due to information being
classified as confidential by companies. This could be a serious
impediment for advancement of literature and research in the country;
and
* Companies had contributed massive resources to the advancement of
education through their educational programs, but this had not yielded
the consistently desired results through improvement of the Grade 12
pass rate. / Thesis (M.B.A.)--North-West University, Potchefstroom Campus, 2011.
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Assessing Binary Measurement SystemsDanila, Oana Mihaela January 2012 (has links)
Binary measurement systems (BMS) are widely used in both manufacturing industry and medicine. In industry, a BMS is often used to measure various characteristics of parts and then classify them as pass or fail, according to some quality standards. Good measurement systems are essential both for problem solving (i.e., reducing the rate of defectives) and to protect customers from receiving defective products. As a result, it is desirable to assess the performance of the BMS as well as to separate the effects of the measurement system and the production process on the observed classifications. In medicine, BMSs are known as diagnostic or screening tests, and are used to detect a target condition in subjects, thus classifying them as positive or negative. Assessing the performance of a medical test is essential in quantifying the costs due to misclassification of patients, and in the future prevention of these errors.
In both industry and medicine, the most commonly used characteristics to quantify the performance a BMS are the two misclassification rates, defined as the chance of passing a nonconforming (non-diseased) unit, called the consumer's risk (false positive), and the chance of failing a conforming (diseased) unit, called the producer's risk (false negative). In most assessment studies, it is also of interest to estimate the conforming (prevalence) rate, i.e. probability that a randomly selected unit is conforming (diseased).
There are two main approaches for assessing the performance of a BMS. Both approaches involve measuring a number of units one or more times with the BMS. The first one, called the "gold standard" approach, requires the use of a gold-standard measurement system that can determine the state of units with no classification errors. When a gold standard does not exist, is too expensive or time-consuming, another option is to repeatedly measure units with the BMS, and then use a latent class approach to estimate the parameters of interest. In industry, for both approaches, the standard sampling plan involves randomly selecting parts from the population of manufactured parts.
In this thesis, we focus on a specific context commonly found in the manufacturing industry. First, the BMS under study is nondestructive. Second, the BMS is used for 100% inspection or any kind of systematic inspection of the production yield. In this context, we are likely to have available a large number of previously passed and failed parts. Furthermore, the inspection system typically tracks the number of parts passed and failed; that is, we often have baseline data about the current pass rate, separate from the assessment study. Finally, we assume that during the time of the evaluation, the process is under statistical control and the BMS is stable.
Our main goal is to investigate the effect of using sampling plans that involve random selection of parts from the available populations of previously passed and failed parts, i.e. conditional selection, on the estimation procedure and the main characteristics of the estimators. Also, we demonstrate the value of combining the additional information provided by the baseline data with those collected in the assessment study, in improving the overall estimation procedure. We also examine how the availability of baseline data and using a conditional selection sampling plan affect recommendations on the design of the assessment study.
In Chapter 2, we give a summary of the existing estimation methods and sampling plans for a BMS assessment study in both industrial and medical settings, that are relevant in our context. In Chapters 3 and 4, we investigate the assessment of a BMS in the case where we assume that the misclassification rates are common for all conforming/nonconforming parts and that repeated measurements on the same part are independent, conditional on the true state of the part, i.e. conditional independence. We call models using these assumptions fixed-effects models. In Chapter 3, we look at the case where a gold standard is available, whereas in Chapter 4, we investigate the "no gold standard" case. In both cases, we show that using a conditional selection plan, along with the baseline information, substantially improves the accuracy and precision of the estimators, compared to the standard sampling plan.
In Chapters 5 and 6, we investigate the case where we allow for possible variation in the misclassification rates within conforming and nonconforming parts, by proposing some new random-effects models. These models relax the fixed-effects model assumptions regarding constant misclassification rates and conditional independence. As in the previous chapters, we focus on investigating the effect of using conditional selection and baseline information on the properties of the estimators, and give study design recommendations based on our findings.
In Chapter 7, we discuss other potential applications of the conditional selection plan, where the study data are augmented with the baseline information on the pass rate, especially in the context where there are multiple BMSs under investigation.
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Language Modeling For Turkish Continuous Speech RecognitionSahin, Serkan 01 December 2003 (has links) (PDF)
This study aims to build a new language model for Turkish continuous speech recognition. Turkish is very productive language in terms of word forms because of its agglutinative nature. For such languages like Turkish, the vocabulary size is far from being acceptable from only one simple stem, thousands of new words can be generated using inflectional and derivational suffixes. In this work, word are parsed into their stem and endings. First of all, we consider endings as words and we obtained bigram probabilities using stem and endings. Then, bigram probabilities are obtained using only the stems. Single pass recognition was performed by using bigram probabilities. As a second job, two pass recognition was performed. Firstly, previous bigram probabilities were used to create word lattices. Secondly, trigram probabilities were obtained from a larger text. Finally, one-best results were obtained by using word lattices and trigram probabilities. All work is done in Hidden Markov Model Toolkit (HTK) environment, except parsing and network transforming.
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Demonstration Of A Stabilized Hovering Platform For Undergraduate LaboratoryCamlica, Fahri Bugra 01 February 2005 (has links) (PDF)
This research work covers the design, manufacture and testing of an unmanned aerial vehicle for the purpose of testing various control systems by undergraduate students in the laboratory environment. The aerial vehicle under
consideration is a four-rotor propeller powered. Aluminum rod based mechanical structure is preferred. The stabilization of the hovering vehicle in its rotational axes in the air and navigation about the yaw axis are the accomplished goals of this study. The aerial vehicle is run in real time by using Matlab 6.5 Software&rsquo / s xPc module. The linear quadratic regulator and PD controllers are utilized to stabilize the aerial
vehicle in its rotation axes. To eliminate the measurement noise generated by the sensors, low-pass second order transfer function is designed and its implementation
to real time experiments is discussed.
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以數值高程模型辨識地形之研究宋秉憲, Soong,Bing Shang Unknown Date (has links)
本研究所要討論的是如何以局部區域的數值高程模型資料辨識出所在整體地形的相對應位置。數值高程模型是以網格式的方式描述地表上連續性的起伏變化,以二維陣列儲存地表高度的資料,包含三度空間的特性。
我們從區域地形萃取出線性特徵與點特徵,分別為水系河段與地形上較明顯的凸點與凹點,以水系作為識別每一區域地形的“指紋”,對於地形變化小或河段特徵不明顯之區域尋找其特徵點,配合相關地形參數與整體地形進行比對,並對不同之特徵採用不同比對演算法。我們以物件化的方式表達水系河段與特徵點,將許多圖層的資訊整合於物件中,除了方便資料的管理,也加快了比對的效率。實驗結果顯示,應用此兩種特徵值作為辨識地形依據,可有效辨識出正確位置,也節省許多不必要的比對時間。 / The main objective of this thesis is to identify a terrain using partial Digital Elevation Model (DEM) information. DEM is one of the most commonly used data representation models used in Geographical Information Systems. It is a digital model with an array of uniformly spaced elevation data in raster format. One can use DEM to analyze terrain measures including slope, aspect, and other features. In the thesis, we use hydrology analysis to extract the stream networks and use terrain parameter analysis to compute terrain features from the DEM of a small region. This information can be used as the “fingerprints” of the terrain and then compare them with the “fingerprints” in the whole data base in order to identify or to locate the correct location of the region. The KMP string matching algorithm is used to speed up the matching process.
Measurements extracted from DEM through hydrology analysis may not provide significant terrain information for the identification purpose. In this case, other mechanism such as VIP node and algorithm are used to facilitate the identification process.
We embed object oriented concepts in actual implementation. The experimental results show that our mechanism works successfully and the time used in the identification process reduced significantly.
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Monetary policy and the banking sector /Winistörfer, Patrick. January 2007 (has links) (PDF)
Univ., Diss.--Bern, 2007.
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