1,591 research outputs found
The synthesis of monodisperse alkanes with long chains
No full textThis thesis discusses reasons for the interest in monodisperse long chain alkanes and describes attempts, past and present, to synthesise such molecules. Chapter 1 discusses why the synthesis of such molecules are important and the objectives of this project. Chapter 2 reviews the methods previous groups have devised to prepare pure samples of long chain alkanes. In particular, work carried out by Whiting et al. at Bristol, whose scheme formed the basis of the early work in Durham. Chapter 3 describes the work in Durham and improvements which were made to Whiting's method, allowing the synthesis of longer chain lengths and greater quantities of materials to be achieved. Chapter 4 provides a summary of the practical work carried out by the author. Chapter 5 gives experimental details of the work described in Chapter 4
Are apparent findings of nonlinearity due to structural instability in economic time series?
No full textMany modelling issues and policy debates in macroeconomics depend on whether macroeconomic times series are best characterized as linear or nonlinear. If departures from linearity exist, it is important to know whether these are endogenously generated (as in, e.g., a threshold autoregressive model) or whether they merely reflect changing structure over time. We advocate a Bayesian approach and show how such an approach can be implemented in practice. An empirical exercise involving several macroeconomic time series shows that apparent findings of threshold type nonlinearities could be due to structural instability
Towards the Theatre: Opasnyi Povorot (Dangerous Corner). The 1939 Production by G.M. Kozintsev at the Leningrad Comedy Theater
No full textThe subject of this research is the first production in a series of theatrical works by G.M. Kozintsev (1905–1973) of the late 1930s — early 1950s, which are fundamentally important both in his creative biography and in the history of Soviet theatre of that era. The author suggests that the entry of the famous film director into theatre was caused by the desire to find a way out of a creative impasse.
The director’s appeal to the play of the modern English novelist and playwright J.B. Priestley and its controversial interpretation were driven by the dramatic atmosphere of the late 1930s. The eccentric grotesque of the play and its pamphlet character, which was insisted on by the director, are considered as a parody of tragedy by the author of the research. This reveals a fundamental connection between the production under consideration and the subsequent successful experiments of G.M. Kozintsev in the field of theatrical Shakespeareana. The article draws attention to the fundamental connection between the style of the production and the general style of the Leningrad State Comedy Theatre developed by its director — the outstanding theatre director and set designer, G.M. Kozintsev and E.L. Schwartz’s friend and associate, N.P. Akimov. The research is based on the performance reviews, testimonies of the participants of the performance, contemporaries close to the director (especially the playwright and screenwriter E.L. Schwartz and the long-term G.M. Kozintsev’s co-author L.Z. Trauberg), as well as the surviving radio version of the play
Alternative efficiency measures for multiple-output production
No full textThis paper has two main purposes. Firstly, we develop various ways of defining efficiency in the case of multiple-output production. Our framework extends a previous model by allowing for nonseparability of inputs and outputs. We also specifically consider the case where some of the outputs are undesirable, such as pollutants. We investigate how these efficiency definitions relate to one another and to other approaches proposed in the literature. Secondly, we examine the behavior of these definitions in two examples of practically relevant size and complexity. One of these involves banking and the other agricultural data. Our main findings can be summarized as follows. For a given efficiency definition, efficiency rankings are found to be informative, despite the considerable uncertainty in the inference on efficiencies. It is, however, important for the researcher to select an efficiency concept appropriate to the particular issue under study, since different efficiency definitions can lead to quite different conclusions. (c) 2004 Elsevier B.V. All rights reserved
Semiparametric Bayesian inference in multiple equation models
No full textThis paper outlines an approach to Bayesian semiparametric regression in multiple equation models which can be used to carry out inference in seemingly unrelated regressions or simultaneous equations models with nonparametric components. The approach treats the points on each nonparametric regression line as unknown parameters and uses a prior on the degree of smoothness of each line to ensure valid posterior inference despite the fact that the number of parameters is greater than the number of observations. We develop an empirical Bayesian approach that allows us to estimate the prior smoothing hyperparameters from the data. An advantage of our semiparametric model is that it is written as a seemingly unrelated regressions model with independent normal-Wishart prior. Since this model is a common one, textbook results for posterior inference, model comparison, prediction and posterior computation are immediately available. We use this model in an application involving a two-equation structural model drawn from the labour and returns to schooling literatures
Does air pollution cause respiratory illness? A new look at Canadian cities
No full textIt is routinely asserted that urban air pollution is a major cause of acute respiratory conditions, leading to thousands of hospitalizations each year. The claim is based on inferences from partial correlations between ambient air pollution levels and hospitalization rates. Yet questions persist about the statistical robustness of the epidemiological findings, and controlled experiments have not confirmed the statistical findings. In this paper we present and analyze a new monthly data base showing concentrations of five major air contaminants in 11 large Canadian cities from 1974 to 1994, matched with monthly hospital admission rates by age group for all lung diagnostic categories; as well as a comprehensive set of socioeconomic and meteorological covariates. We compare two estimation approaches: model selection and Bayesian model averaging. Almost all of our estimates of the health effects of air pollution are insignificant. Two pollutant types have significantly negative coefficients, indicating, if interpreted in the standard way, that these pollutants are actually beneficial for health. We do not claim this, but we conclude that the perceived statistical relationship between air pollution and health is not robust
Stevin Outlet Sluices: Wave impact under a beam
No full textThe Dutch department of Public Works had a problem regarding wave impacts on a beam in the Stevin outlet sluices, located in the Afsluitdijk. Wave impacts on this beam could also cause a peak pressure on the barrier gate, just behind the beam. The numerical program ComFLOW and physical scale experiments were used to predict the wave impacts for different hydraulic conditions (i.e. wave height, wave period and water level). The research questions were: 1. How is the wave load on the northern gates depending on the presence of the military beam? 2. How large is a wave impact load on the bottom of the military beam in the Stevin outlet sluices? 3. How well can the numerical model ComFLOW and physical modelling be used to determine the wave impact on the bottom of the military beam in the Stevin outlet sluices? 2D scaled experiments were performed making use of a model with the (simplified) geometry of the Stevin outlet sluices and regular waves. It was found that the largest wave impacts occurred for water levels equal to the bottom plane of the beam or slightly under it. This happened for the shortest waves in the test domain. The largest pressure measured on the beam was approximately 50 kPa or 35H, with H representing the incident wave height in front of the model. It was also found that the spread in the peak pressures for one single experiment was large. The results of the measured impulse per peak showed far less spread. The effect of wave impacts under the beam was also found on the vertical wall under the beam. The actual pressures however were less and they were decreasing with increasing depth. Besides physical wave impact testing, a few experiments were performed with the beam removed from the model. This resulted in wave simply running up the vertical wall of the model. They did not cause a wave impact. The measurements of both type of experiments, with and without a beam, were compared. This revealed that the total wave impulse on the gate was not affected by the presence of the beam. However the distribution of the pressure within a single wave period was significantly different. In case of a beam, a large impact peak was observed, whereas the other wave only showed a small hump caused by the deflected flow against the vertical wall. When the calculated and measured wave impact results were compared it became clear that ComFLOW underestimated the peak pressures by a factor 2 to 20 for the pressures on the impact plane. The same was done for the peak impulse. This showed that the impulse of the peak on the impact plane were underestimated by a factor 2 at most. These results confirmed that the used grid was too coarse for the program to model the physics correctly. The main conclusions to the research questions were: 1. The presence of the military beam causes a different distribution of the force on the gate within a wave period. The total amount of impulse is more or less the same as for the situation without a beam. With the military beam, a wave impact results in a peak force on the gate. Without the beam, there will be no peak force. 2. The largest measured wave impact pressure is 35H. 3. Both ComFLOW and physical modelling can be used to predict wave impacts for the geometry of Stevin outlet sluices. Much care should be taken when modelling and much attention should go to the input parameters of the program.Hydraulic StructuresHydraulic EngineeringCivil Engineering and Geoscience
Analysis of economic data. 3rd edition
No full textEconometrics is concerned with the tasks of developing and applying quantitative or statistical methods to the study and elucidation of economic principles. Analysis of Economic Data teaches methods of data analysis to readers whose primary interest is not in econometrics, statistics or mathematics. It shows how to apply econometric techniques in the context of real-world empirical problems, and adopts a largely non-mathematical approach relying on verbal and graphical intuition. The book covers most of the tools used in modern econometrics research e.g. correlation, regression and extensions for time-series methods and contains extensive use of real data examples and involves readers in hands-on computer work
An introduction to econometrics
No full textIntroduction to Econometrics has been written as a core textbook for a first course in econometrics taken by undergraduate or graduate students. It is intended for students taking a single course in econometrics with a view towards doing practical data work. It will also be highly useful for students interested in understanding the basics of econometric theory with a view towards future study of advanced econometrics. To achieve this end, it has a practical emphasis, showing how a wide variety of models can be used with the types of data sets commonly used by economists. However, it also has enough discussion of the underlying econometric theory to give the student a knowledge of the statistical tools used in advanced econometrics courses
Bayesian econometrics
No full textResearchers in many fields are increasingly finding the Bayesian approach to statistics to be an attractive one. This book introduces the reader to the use of Bayesian methods in the field of econometrics at the advanced undergraduate or graduate level. The book is self-contained and does not require that readers have previous training in econometrics. The focus is on models used by applied economists and the computational techniques necessary to implement Bayesian methods when doing empirical work. Topics covered in the book include the regression model (and variants applicable for use with panel data), time series models, models for qualitative or censored data, nonparametric methods and Bayesian model averaging. The book includes numerous empirical examples and the website associated with it contains data sets and computer programs to help the student develop the computational skills of modern Bayesian econometrics
- …
