bluuebunny/crossref_metadata_2025 huggingface dataset:
THE ROLE OF TENURE SECURITY IN HOUSING SELF‐IMPROVEMENT: A CASE‐STUDY OF SURABAYA, INDONESIA
Authors: Mukoko Samba
Published: October 2007

Some developing countries are tapping into the opportunities offered by self‐help gradual improvement of houses in order to relieve the environmental problems besetting their urban areas. For decisionmakers and planners it is important to know the factors that can entice slum dwellers to improve their houses. Using Indonesian data, this paper has tested and verified the assumption that tenure security is a powerful factor that can entice slum dwellers to internalize the benefits from neighborhood environmental quality improvement.
URBANIZATION, URBAN CONCENTRATION AND ECONOMIC DEVELOPMENT
Authors: Sasaki Komei , Ito Taku , Kunihisa Sotaro , Kaiyama Michihiro
Published: October 2007

An international comparative study of the relations among the process of urbanization, urban concentration and economic development, and income distribution was performed by using data of developing and developed countries. Cross‐section analyses at certain time periods for capturing “long‐run” effects as well as time‐series analyses for some countries for “short‐run” effects were done taking advantage of the “rectangular” array of data. There were several interesting results: the pattern of unemployment rate in most developing countries shows an inverted‐U shaped curve with respect to the degree of urbanization; the pattern of urban concentration is in the form of an inverted‐U with respect to the economic development level; and the degree of inequality of income distribution seems to react in an inverted‐U form to the variances in the extent of urbanization.
SUSTAINABILITY OF POPULATION GROWTH: A CASE STUDY OF URBAN SETTLEMENTS IN ISRAEL
Authors: Portnov Boris A. , Pearlmutter David
Published: October 2007

One of the most sensitive criteria for gauging the degree of socio‐economic prosperity of an urban settlement is the ability to sustain stable rates of population growth by attracting newcomers and retaining existing population. The present paper argues that after reaching a particular size (on the average, 20–30, 000 residents), urban localities n Israel tend to experience substantial changes in components of their annual population growth. Starting with this inflection point, the growth of settlements gradually becomes less dependent on natural causes (birth and death rates) than on the ability to attract newcomers and retain current residents. On the basis of this conclusion, a strategy of “redirecting priorities” to developing the peripheral regions of the country is suggested. This strategy proposes the concentration of state and local financial resources on selected development Settlements until they reach the above population threshold and become more attractive for newcomers, followed by the sequential transfer of this support to other small urban localities in frontier areas. Although the present analysis was restricted to urban settlements in Israel, the mode of analysis and its applications for planning policy may be applicable to regional and urban physical planning elsewhere.
SPATIAL INTEGRATION OF URBAN WATER SERVICES AND ECONOMIES OF SCALE
Authors: Kim Euijune , Lee Hyun
Published: October 2007

This research attempts to analyze economic effects of spatial integration of urban water service markets in Korea, employing the notion of economies of scale in terms of cost‐effectiveness. The economies of scale are measured by the elasticity of supply with respect to the production cost from the translog cost function of urban water supply enterprises. It was found that the economies of scale in most urban water utility firms of Seoul Metropolitan region have continuously increased during the period 1989–1994. While the economies of scale would be hardly influenced by the changes in population density, they would tend to decrease marginally in response to the rise in employment density. If the urban water markets of the Seoul Metropolitan Region were consolidated into a single water service market without any changes to the current spatial network of water supply and regional economic attributes, the production cost would be reduced up to 47.1 percent of the actual cost in 1994. Those savings would be enough to make up for the financial deficit of the water production of the Seoul Metropolitan Region.
THE ECONOMIC EFFECT OF HIGHWAY CONSTRUCTION: A COMPARATIVE ANALYSIS FOR THE U.K., GERMANY AND JAPAN
Authors: Kunihisa Sotaro , Kaiyama Michihiro
Published: October 2007

This paper attempts to estimate the marginal productivity of highway construction in the U.K., Germany and Japan during the 15 years following the first oil crisis. In addition, highway‐improvement policy in Japan is evaluated using a simple macro‐economic regression model. The following conclusions were obtained: in every country the marginal productivity of highway construction decreased over the period 1975‐85, with the decrease most pronounced in Japan; subsequently, it increased slowly in the U.K. and Germany, with Japan leveling off though still having the highest value among the three countries; the U.K. maintained a high level of highway productivity largely as a result of a high degree of utilization. There is scope in Japan for attaining a higher level (approximately equal to that of the late 1970s) if the extent of highway utilization can be maintained by additional construction. This implies that future highway‐construction policy should be of efficiency‐seeking nature.
THE LOCAL EFFECTS OF LARGE DAM RESERVOIRS: U.S. EXPERIENCE, 1975–1995
Authors: Aleseyed Mostafa , Rephann Terance , Isserman Andrew
Published: October 2007

Dam construction has been an important component of economic development initiatives in the United States. However, few comprehensive empirical studies examine the effects of such projects on local employment and income. This paper employs quasi‐experimental control group methods to examine the effects of large dam reservoirs on county income, earnings, population and employment growth for dams opened in the U.S. during the period 1975–1984. The paper shows that large dam reservoirs have some statistically significant positive effects and tend to stimulate growth. There is considerable variation, however, with dams constructed for flood control purposes and dams further away from markets and large cities having less of an effect.
CLUSTERING OF THE URBAN FIELD AS A PRECONDITION FOR SUSTAINABLE POPULATION GROWTH IN PERIPHERAL AREAS: THE CASE OF ISRAEL
Authors: Portnov Boris A. , Erell Evyatar
Published: October 2007

Analysis of the development of urban communities suggests that sustainable population growth is based on a settlement's ability to attract and retain residents, rather than on natural causes (birth‐death rates). In the special case of small, peripheral urban communities, sustained growth was found to be related to the location of the settlement, and in particular to the spatial characteristics of a cluster of urban settlements of which it may be a part. An index of clustering was defined, which allows an analysis of the combined effect on population growth of spatial isolation and distance from major metropolitan centers of the country. Although the present analysis was restricted to urban settlements in Israel, the mode of analysis and its applications for planning policy may be applicable to regional and urban physical planning elsewhere.
THE IMPACT OF PUBLIC INFRASTRUCTURE ON MUNICIPAL ECONOMIC DEVELOPMENT: EMPIRICAL RESULTS FROM KENYA
Authors: Lewis Blane D.
Published: October 2007

This paper considers the role of public infrastructure in municipal economic development in Kenya. The primary objectives of the examination are to estimate the impact of roads and water infrastructure on municipal incomes, to ascertain the extent to which differences in institutional authority over water service delivery affect the quantity or quality of infrastructure, and to determine whether the presumed simultaneity between infrastructure and incomes matters for purposes of estimating the effect of the former on the latter. The analysis provides evidence to suggest that the impact of public infrastructure in the roads and water sectors on municipal economic development is significant. Also, the examination implies that local governments, when given authority over water services, do not appear to provide a larger quantity of water infrastructure than does the central government and/or its parastatal. On the other hand, and perhaps more significantly, the paper provides some initial evidence that the public water infrastructure services provided by local authorities are more accessible and reliable than those provided by central institutions. Finally, the results of the paper support the conclusion that possible simultaneity between public infrastructure and incomes does not seem to matter for estimating the quantitative impact of infrastructure on economic development.
COMPETITION BETWEEN PORTS AND INVESTMENT PLANNING
Authors: Garnett H. C.
Published: October 2007

The 1960s were a decade of rapid change in overseas transport technologies. That decade saw the introduction of container ships, hovercraft, massive tankers and ore carriers, LASH (lighter‐aboard‐ship) vessels, freightliners, and jumbo jets. Many of these will achieve their full potential in the 1970s. These new transport modes have not only had an effect upon the design of ports but also upon the procedures required to control their development at a national level. Whereas in the past there may have been no technological reason to exercise any national control at all, the current situation makes it unrealistic and inefficient to leave individual ports with power to plan and implement their own major developments. The basic theme of this paper is that the state of the technology for the transport of bulk and general cargoes is such that competition between ports for the business of British exporters and importers will result in higher than necessary overseas total distribution costs. Because inland transport costs and times are so much lower the effective hinterland of each port is much larger than it used to be. However, against this has to be weighed the fact that individual ports now can have the technical capacity to handle in a year a large proportion of British cargo of a given type and on a given trade route. Therefore, as the natural, long term tendency would be for port (and perhaps shipping) monopolies to develop it is in the best interests of the users of port facilities for national control to be exercised over them. In the past the threat of local port monopolies was thwarted by local user representation on port boards; now the likelihood of national monopolies requires control at a national level.
THE U.K. PERSONAL SAVINGS RATIO: PAST PRESENT AND FUTURE
Authors: Coghlan Richard T. , Jackson Peter M.
Published: October 2007

An earlier version of this paper was written in 1976 when both authors were members of the Economics Department of the University of Stirling; it should not be interpreted as reflecting the official position of the Bank of England in any way. We would like to thank Professor Jack Revell (University College, Bangor) and Dr Alan Budd (London Business School) who both read and commented upon an earlier version. The traditional disclaimer applies.
DICTIONARY OF SCOTTISH BUSINESS BIOGRAPHY
Authors: Jeremy David J.
Published: October 2007

Anthony Slaven and Sydney Checkland (eds.) Dictionary of Scottish Business Biography (1860–1960), Volume I. The Staple Industries.
FISCAL POLICY AND AGGREGATE CONSUMPTION: NEW EVIDENCE FROM THE UNITED STATES
Authors: Darby Julia , Malley Jim
Published: October 2007

Abstract

In this paper we estimate the marginal rate of substitution between aggregate per‐capita consumption and per‐capita government expenditure on goods and services using US quarterly data over the period 1953 to 1993. This estimate is an important input to any attempt to assess the overall effectiveness of fiscal policy since it directly affects the size of the fiscal policy multiplier. Other recent consumption studies which incorporate the effects of government expenditure have failed to establish a stable estimate of the marginal rate of substitution. We argue that this failure results from imposing the unrealistic assumption that this parameter is constant. In contrast, we allow the marginal rate of substitution to depend on both the level and composition of government spending.
SIR JAMES STEUART'S STATESMAN REVISITED IN LIGHT OF THE CONTINENTAL INFLUENCE1
Authors: Redman Deborah
Published: October 2007

Abstract

The author assesses the influence Continental thought had on Sir James Steuart and places him in the Continental setting in order to understand his most controversial message, his theory of the state, and how it differed from that of his contemporaries, above all from Adam Smith's
GROSS EXPENDITURE ON UK INDUSTRIAL ASSISTANCE: A RESEARCH NOTE
Authors: Wren Colin
Published: October 2007

Abstract

This note presents annual figures for gross expenditure on UK central government assistance to industry over the period 1960‐90. This is part of onging research on the determinants and effects of UK industrial assistance. All figures are at corrent prices and a breakdown is provided between various components of policy, comprising national assistance, industrial and firm specific assistance, technology support, civil aircraft aid, shipbuilding assistance and local employment and regional policy.
R&D COMPETITION WITH ASYMMETRIC FIRMS
Authors: Poyago‐Theotoky Joanna
Published: October 2007

Abstract

This paper considers a non‐tournament duopoly model of process innovation. Costs of production can be reduced by firms spending on R&D. Firms are asymmetric in the sense that they may differ in their initial costs of production. It is shown that the high‐cost firm may spend more (or less) in R&D than its low‐cost rival. This main result is dependent on the relative magnitude of two important forces: the incentive effect, whereby the low‐cost firm always has a stronger incentive to spend on cost‐reducing R&D, and the effectiveness factor, which favours the high‐cost firm.
AN ECONOMIC ANALYSIS OF THE BSE SCARE
Authors: Dnes Antony W.
Published: October 2007

Abstract

The economic aspects of the outbreak of Bovine Spongiform Encephalopathy (BSE) in British cattle herds are investigated. On balance, a non‐interventionist approach is most likely to be the least‐cost method of dealing with the BSE problem, where costs include the risks of humans contracting Creutzfeldt‐Jakob Disease (CJD). There is no case for compensating farmers for the historic cost of building up infected herds.
BLOCS, ZONES AND BANDS: INTERNATIONAL MONETARY HISTORY IN LIGHT OF RECENT THEORETICAL DEVELOPMENTS
Authors: Eichengreen Barry , Flandreau Marc
Published: October 2007

Abstract

Trends in international finance in recent decades have inspired considerable research on bloc‐ and band‐based international monetary arrangements. From this literature have emerged models providing the basis for much recent work in international monetary economics. To date, however, their application to historical experience has been rare. We therefore highlight parallels between modern‐day target zones on the one hand and the classical and inter‐war gold standards and Bretton Woods System on the other. We suggest that bloc‐based international monetary arrangements are in fact an historical commonplace; they have been the rule rather than the exception.
GIBSON'S PARADOX AND POLICY REGIMES: A COMPARISON OF THE EXPERIENCE IN THE US, UK AND ITALY
Authors: Muscatelli Vito Antonio , Spinelli Franco
Published: October 2007

Abstract

This paper compares the behaviour of long‐term interest rates and prices in Italy, the UK and the USA, and seeks to shed light into what has become known as the ‘Gibson Paradox’. We compare the various theoretical explanations for the observed positive correlation of interest rates and prices in the USA and the UK. Using both regression and frequency domain techniques, we demonstrate that there is little evidence for the occurrence of the paradox in the case of Italy. The key conclusion of the paper is that the comparative evidence from these three countries supports a gold standard interpretation of the Paradox.
FUND SUBSTITUTION AND THE INCENTIVE EFFECT OF PUBLIC INVESTMENT SUBSIDIES
Authors: Wren Colin
Published: October 2007

This paper analyses the observed phenomenon of public for private fund substitution in industrial assistance, by examining the public and private sector funding of investment under different assumptions about the nature of the private capital market. This bears on the effectiveness of industrial subsidies, and has implications for welfare and the design of optimal assistance contracts. It is shown that fund substitution depends crucially on the elasticity of investment with respect to the user cost of capital in the without‐subsidy position, and on the nature of any amount and rate constraints on the assistance contract.
Saint Augustine in History: A Review of Augustine the Bishop by F. Van der Meer Sheed and Ward, London, 1961
Authors: Austin M. N.
Published: October 2007

Augustine wrote and spoke for a small circle in a single province, which was soon to be engulfed in a sea of barbarism, and ultimately absorbed into the vast empire of Islam. He ruled no order; he founded no school: his immediate influence upon the Church, save in the matter of the Pelagian controversy, cannot have been great, and all traces of his presence upon earth soon dis‐appeared. It was not so with his writings. They remained to spread like oil in the centuries to come, and his many ideas germinated and blossomed far and wide like seeds from some famed garden of Europe broadcast upon the primeval virgin prairie.
Satan and His Persecutors: Two Recent Books
Authors: WARD JOHN O.
Published: October 2007

R. I. Moore: The Formation of a Persecuting Society: Power and Deviance in Western Europe 950–1250

H. A. Kelly: The Devil at Baptism: Ritual, Theology and Drama, Ithaca and London
‘Being Martin’: Saint and Successor in Sixth‐Century Tours
Authors: Brennan Brian
Published: October 2007

Utilising the poetry of Venantius Fortunatus (c. 530–600), this article explores the literary fashioning of an idealized episcopal identity for the sixth‐century bishops of Tours as successors to Martin, the celebrated fourth‐century saint of the city. It is argued that the poet’s deployment of the model was of political use to his patron, Bishop Gregory of Tours, both in the establishment of his authority in the town and in dealings with the Frankish kings about matters of taxation. It is suggested that this crafting of an episcopal identity allowed the poet to put pressure on Gregory himself to be Martin and intervene in such matters as a legal case or the affairs of a diocese outside his jurisdiction as metropolitan. The legitimating Martinian model of episcopal behaviour is presented therefore as potentially coercive.
The Protestant Work Ethic and the Australian Mercantile Elite, 1880–1914
Authors: Blackburn Kevin
Published: October 2007

This article tests, in the Australian context, Max Weber’s thesis that the work ethic of capitalism owed its origins to Protestantism. It studies the Australian Protestant churches for the presence of a work ethic, and investigates whether the Catholic Church also promoted such a moral precept to its members. The study then examines whether the work ethic of the Australian mercantile elite was drawn from that of the Protestant churches, from which most of its members came. The article proceeds to describe how the mercantile elite removed the religious origins of the work ethic and made it one of the foundations of its creed of economic individualism. This creed was based on the self‐righteous dogma that those who worked hard were rewarded by getting rich while those who were poor only had their own lack of hard work and thrift to blame. The article demonstrates that the work ethic of modern capitalism, as espoused by the Australian mercantile elite, was the result of the secularization of the work ethic of Protestantism, a process in which the religious content of the moral principle was removed.
Approximating a trivariate Normal probability that is of special relevance to the multifactorial model of disease transmission
Authors: HUTCHINSON T. P.
Published: October 2007

A study has been made of methods of approximating the probability of severe disease occurrence in the child of parents who both suffer from a mild (or subclinical) form of the disease in question. A wide range of parameter values has been considered. It has been found that

(i) The Mendell‐Elston formula is very accurate.

(ii) The simple pseudo‐Pareto formula is not quite as accurate as the Mendell‐Elston, but is still well within the range of acceptability.

(iii) A more elaborate pseudo‐Pareto formula is very accurate.
A note on the correct definition of additive deviation and dominance deviation
Authors: WILSON S. R.
Published: October 2007

It is shown that care must be taken to use the correct form of the definitions of additive deviation (representative value) and of dominance deviation. These values may vary depending on the population to which the individual is taken to belong.
Scheduling preventive maintenance for oil pumps using generalized proportional intensities models
Authors: Percy David F. , Alkali Babakalli M.
Published: October 2007

Percy and Alkali presented generalizations of the proportional intensities model introduced by Cox. They identified several features of these models that are particularly relevant for modelling complex repairable systems subject to preventive maintenance (PM). These include the baseline intensity, scaling factors and explanatory variables. We investigate these aspects in detail and apply the models to five sets of reliability data collected from the main pumps at oil refineries. We use likelihood methods to estimate the model parameters and compare how well the models fit the data. Our analyses suggest that a log‐linear baseline intensity function performs well and that an exponential deterministic scaling function is useful for corrective maintenance. The inclusion of explanatory variables to represent the quality of last maintenance and time since last maintenance also proves to be beneficial. We develop algorithms for simulating the reliability behaviour of a complex repairable system into the future, in order to schedule appropriate maintenance activities, identifying special cases that simplify the algebra. Applying these methods to the oil pump data, we derive recommendations for PM plans and demonstrate that adopting this strategy can lead to substantial savings.
A multi‐agent system for the decentralized resource‐constrained multi‐project scheduling problem
Authors: Homberger Jörg
Published: October 2007

A restart evolution strategy (RES) for the resource‐constrained project scheduling problem (RCPSP), as well as its integration in a multi‐agent system (MAS) for solving the decentralized resource‐constrained multi‐project scheduling problem (DRCMPSP) will be presented. To evaluate the developed approach, problem instances of the RCPSP taken from the literature with up to 300 activities are used, as well as 80 generated instances of the DRCMPSP, with up to 20 projects and with up to 120 activities each. For 73 instances of the RCPSP, the RES found better solutions than the best ones found so far. In addition, the MAS is suitable for solving large multi‐project instances decentrally. The results for the DRCMPSP instances show that the presented decentralized MAS is competitive with a central solution approach.
The Response of Articular Chondrocytes to Type II Collagen–Au Nanocomposites
Authors: Hsu Shan‐hui , Yen Hung‐Jen , Tsai Ching‐Lin
Published: October 2007

Abstract:  The nanocomposites (denoted “CII–Au”) of porcine type II collagen (CII) with 0.05, 0.1, 0.5, 1, or 2.5% (wt/wt) Au nanoparticles (∼5 nm) were fabricated for potential use in cartilage tissue engineering. Au formed clusters on the surface of all nanocomposites and appeared to distribute along the collagen fibrils inside the matrix. The addition of Au at low concentrations (≤0.5%) increased the modulus and viscosity, as well as the free radical‐scavenging ability. These effects decreased at higher concentrations of Au. The chondrocytes on CII–Au became spindle‐like with lamellipodia formation. Cell proliferation on CII–Au 0.1% was promoted. Nitric oxide (NO) in the culture medium was reduced by CII–Au 0.05% and CII–Au 0.1%. Type I collagen, aggrecan, and Sox 9 gene expressions increased with an increased Au content, but slightly decreased at 2.5% Au. There was no significant difference in the CII gene expression. The cellular uptake of Au was observed but less than that which occurred when 10 ppm of Au was added in culture medium. Chondrocytes cultured with ≤10 ppm of Au nanoparticles showed neither cytotoxicity nor change in gene expression. Au at an appropriate amount could be well dispersed in CII, and enhanced the material modulus, antioxidant effect, as well as the chondrocyte growth and matrix production.
Building a Better Rat Trap: Technological Innovation, Human Capital, and the Irula
Authors: Terjesen Siri
Published: October 2007

This case follows Sethu Sethunarayanan, Director of the nonprofit Center for Development of Disadvantaged People, which is dedicated to the improvement of the Irula tribe in rural villages of southeast India. The Irulas specialize in catching rats, an activity which provides the bulk of their income and food. Following a routine visit to a local village, Sethu recognized an opportunity for a “better rat trap” to aid the Irula rat catchers. With feedback from rat catchers, Sethu developed an innovative new trap. His innovation won the prestigious Global Development Marketplace award from the World Bank which provided the funding necessary to commercialize the new technology. The venture's implementation involved site visits to identify beneficiaries, health checks and treatment, preparatory workshops, factory establishment, factory training, production, women's micro–credit collectives, distribution, and project evaluation. The case focuses on the relationship between human capital and technological entrepreneurship, considering the knowledge and skills required to commercialize technology for the rural poor and the positive impact on this greatly disadvantaged population.
How Corporate Entrepreneurs Learn from Fledgling Innovation Initiatives: Cognition and the Development of a Termination Script
Authors: Corbett Andrew C. , Neck Heidi M. , DeTienne Dawn R.
Published: October 2007

Through a parallel examination of literatures on new product development termination and entrepreneurial cognition, this study explores a specific form of human capital development: learning from failure. Specifically we advance the literature on entrepreneurial human capital by linking cognitive scripts used by corporate entrepreneurs in project termination decisions to corresponding levels of learning. Our longitudinal investigation of technology–based firms suggests that corporate entrepreneurs use three types of termination scripts: (1) undisciplined termination, (2) strategic termination, and (3) innovation drift. We illustrate the presence of each script and analyze learning implications during innovation projects (action learning) and after termination (post–performance learning). Based on our analysis we suggest that organizational learning is dependent upon the type of termination script individuals employ.
Note to Instructors: Building a Better Rat Trap
Authors: Terjesen Siri
Published: October 2007

This case examines technological entrepreneurship and human capital in a remote village in southeast India. Sethu Sethunarayanan, director of the nongovernment organization (NGO) Center for Development of Disadvantaged People (CDDP), uses technology to improve the lives of impoverished people, focusing in particular on the indigenous Irula tribe. The Irulas’ rat catching activities constitute a primary source of income and food. However, the Irulas are often unsuccessful in catching rats and suffer many health problems from mouth–blowing a clay pot filled with smoke. Sethu developed a “better rat trap,” improving success rates and income and eliminating health hazards. In parallel, CDDP established a factory and self–help, micro–credit collectives to enable other villagers to improve their socioeconomic condition. The case chronicles the project's development, including opportunity recognition, and new technology development and implementation. An overview of the skills and experience of Sethu and the CDDP team, and the national, local, and community context is also provided.
The Use of Probabilistic Reasoning to Improve Least Squares Based Gas Path Diagnostics
Authors: Romessis C. , Kamboukos Ph. , Mathioudakis K.
Published: October 2007

A method is proposed to support least square type of methods for deriving health parameters from a small number of independent gas path measurements. The method derives statistical information using sets of solutions derived from a number of data records, to produce sets of candidate solutions with a lesser number of parameters. These sets can then be processed to derive an accurate component fault diagnosis. It could thus be classified as a new type of "concentrator" approach, which is shown to be more effective than previously existing schemes. The method's effectiveness is demonstrated by application to a number of typical jet engine component faults.
Numerical and Experimental Analysis of the Intake Flow in a High Performance Four-Stroke Motorcycle Engine: Influence of the Two-Equation Turbulence Models
Authors: Algieri Angelo , Bova Sergio , De Bartolo Carmine , Nigro Alessandra
Published: October 2007

An experimental and numerical analysis of the intake system of a production high performance four-stroke motorcycle engine was carried out. The aim of the work was to characterize the fluid dynamic behavior of the engine during the intake phase and to evaluate the capability of the most commonly used two-equation turbulence models to reproduce the in-cylinder flow field for a very complex engine head. Pressure and mass flow rates were measured on a steady-flow rig. Furthermore, velocity measurements were obtained within the combustion chamber using laser Doppler anemometry (LDA). The experimental data were compared to the numerical results using four two-equation turbulence models (standard k-ε, realizable k-ε, Wilcox k-ω, and SST k-ω models). All the investigated turbulence models well predicted the global performances of the intake system and the mean flow structure inside the cylinder. Some differences between measurements and computations were found close to the cylinder head while an improving agreement was evident moving away from the engine head. Furthermore, the Wilcox k-ω model permitted the flow field inside the combustion chamber of the engine to be reproduced and the overall angular momentum of the flux with respect to the cylinder axis to be quantified more properly.
Natural Gas Decarbonization Technologies for Advanced Power Plants
Authors: Gambini Marco , Vellini Michela
Published: October 2007

In this paper two options for H2 production, by means of natural gas, are presented and their performances are evaluated when they are integrated with advanced H2/air cycles. In this investigation two different schemes have been analyzed: an advanced combined cycle power plant (CC) and a new advanced mixed cycle power plant (AMC). The two methods for producing H2 are as follows: (1) steam methane reforming: it is the simplest and potentially the most economic method for producing hydrogen in the foreseeable future; and (2) partial oxidation of methane: it could offer an energy advantage because this method reduces the energy requirement of the reforming process. These hydrogen production plants require material and energetic integrations with power section and the best interconnections must be investigated in order to obtain good overall performance. With reference to thermodynamic and economic performance, significant comparisons have been made between the above introduced reference plants. An efficiency decrease and an increase in the cost of electricity has been obtained when power plants are equipped with a natural gas decarbonization section. The main results of the performed investigation are quite variable among the different H2 production technologies here considered: the efficiency decreases in a range of 5.5 percentage points to nearly 10 for the partial oxidation of the natural gas and in a range of about 9 percentage points to over 12 for the steam methane reforming. The electricity production cost increases in a range of about 41–42% for the first option and in a range of about 34–38% for the second one. The AMC, coupled with partial oxidation, stands out among the other power plant solutions here analyzed because it exhibits the highest net efficiency and the lowest final specific CO2 emission. In addition to this, economic impact is favorable when AMC is equipped with systems for H2 production based on partial oxidation of natural gas.
Rotary Kiln Slow Pyrolysis for Syngas and Char Production From Biomass and Waste—Part I: Working Envelope of the Reactor
Authors: Fantozzi Francesco , Colantoni Simone , Bartocci Pietro , Desideri Umberto
Published: October 2007

A microscale electrically heated rotary kiln for slow pyrolysis of biomass and waste was designed and built at the University of Perugia. The reactor is connected to a wet scrubbing section, for tar removal, and to a monitored combustion chamber to evaluate the lower heating value of the syngas. The system allows the evaluation of gas, tar, and char yields for different pyrolysis temperatures and residence times. The feeding screw conveyor and the kiln are rigidly connected; therefore, a modification of the flow rate implies a modification of the inside solid motion and of residence time. The paper provides the theoretical and experimental calculation of the relationships between residence time and flow rate used to determine the working envelope of the reactor as a function of the feedstock bulk density and moisture content, given the actual heat rate of the electric heaters. The methodology is extendable to any rotary kiln reactor with a rigidly connected feeding screw conveyor, given its geometric and energetic specifications. Part II of the paper will extend the energy balance, also introducing the yields of pyrolysis products.
Ignition of Lean Methane-Based Fuel Blends at Gas Turbine Pressures
Authors: Petersen Eric L. , Hall Joel M. , Smith Schuyler D. , de Vries Jaap , Amadio Anthony R. , Crofton Mark W.
Published: October 2007

Shock-tube experiments and chemical kinetics modeling were performed to further understand the ignition and oxidation kinetics of lean methane-based fuel blends at gas turbine pressures. Such data are required because the likelihood of gas turbine engines operating on CH4-based fuel blends with significant (>10%) amounts of hydrogen, ethane, and other hydrocarbons is very high. Ignition delay times were obtained behind reflected shock waves for fuel mixtures consisting of CH4, CH4∕H2, CH4∕C2H6, and CH4∕C3H8 in ratios ranging from 90/10% to 60/40%. Lean fuel/air equivalence ratios (ϕ=0.5) were utilized, and the test pressures ranged from 0.54 to 30.0atm. The test temperatures were from 1090K to 2001K. Significant reductions in ignition delay time were seen with the fuel blends relative to the CH4-only mixtures at all conditions. However, the temperature dependence (i.e., activation energy) of the ignition times was little affected by the additives for the range of mixtures and temperatures of this study. In general, the activation energy of ignition for all mixtures except the CH4∕C3H8 one was smaller at temperatures below approximately1300K(∼27kcal∕mol) than at temperatures above this value (∼41kcal∕mol). A methane/hydrocarbon–oxidation chemical kinetics mechanism developed in a recent study was able to reproduce the high-pressure, fuel-lean data for the fuel/air mixtures. The results herein extend the ignition delay time database for lean methane blends to higher pressures (30atm) and lower temperatures (1100K) than considered previously and represent a major step toward understanding the oxidation chemistry of such mixtures at gas turbine pressures. Extrapolation of the results to gas turbine premixer conditions at temperatures less than 800K should be avoided however because the temperature dependence of the ignition time may change dramatically from that obtained herein.
Combined First and Second-Law Analysis of Gas Turbine Cogeneration System With Inlet Air Cooling and Evaporative Aftercooling of the Compressor Discharge
Authors: Khaliq A. , Choudhary K.
Published: October 2007

A conceptual gas turbine based cogeneration cycle with compressor inlet air cooling and evaporative aftercooling of the compressor discharge is proposed to increase the cycle performance significantly and render it practically insensitive to seasonal temperature fluctuations. Combined first and second-law approach is applied for a cogeneration system having intercooled reheat regeneration in a gas turbine as well as inlet air cooling and evaporative aftercooling of the compressor discharge. Computational analysis is performed to investigate the effects of the overall pressure ratio rp, turbine inlet temperature (TIT), and ambient relative humidity φ on the exergy destruction in each component, first-law efficiency, power-to-heat ratio, and second-law efficiency of the cycle. Thermodynamic analysis indicates that exergy destruction in various components of the cogeneration cycle is significantly affected by overall pressure ratio and turbine inlet temperature, and not at all affected by the ambient relative humidity. It also indicates that the maximum exergy is destroyed during the combustion process, which represents over 60% of the total exergy destruction in the overall system. The first-law efficiency, power-to-heat ratio, and second-law efficiency of the cycle significantly vary with the change in the overall pressure ratio and turbine inlet temperature, but the change in relative humidity shows small variations in these parameters. Results clearly show that performance evaluation based on first-law analysis alone is not adequate, and hence, more meaningful evaluation must include second-law analysis. Decision makers should find the methodology contained in this paper useful in the comparison and selection of advanced combined heat and power systems.
Analysis of Combustion Induced Vortex Breakdown Driven Flame Flashback in a Premix Burner With Cylindrical Mixing Zone
Authors: Kiesewetter F. , Konle M. , Sattelmayer T.
Published: October 2007

In earlier experimental studies of the authors a previously unknown mechanism leading to flame flashback—combustion induced vortex breakdown (CIVB)—was discovered in premixed swirl burners. It exhibits the sudden formation of a recirculation bubble in vortical flows, which propagates upstream into the mixing zone after the equivalence ratio has exceeded a critical value. This bubble then stabilizes the chemical reaction and causes overheat with subsequent damage to the combustion system. Although it was shown earlier that the sudden change of the macroscopic character of the vortex flow leading to flashback can be qualitatively computed with three-dimensional as well as axisymmetric two-dimensional URANS-codes, the proper prediction of the flashback limits could not be achieved with this approach. For the first time, the paper shows quantitative predictions using a modified code with a combustion model, which covers the interaction of chemistry with vortex dynamics properly. Since the root cause for the macroscopic breakdown of the flow could not be explained on the basis of experiments or CFD results in the past, the vorticity transport equation is employed in the paper for the analysis of the source terms of the azimuthal component using the data delivered by the URANS-model. The analysis reveals that CIVB is initiated by the baroclinic torque in the flame and it is shown that CIVB is essentially a two-dimensional effect. As the most critical zone, the upstream part of the bubble was identified. The location and distribution of the heat release in this zone governs whether or not a flow field is prone to CIVB.
Dynamics of Multistage Bladed Disks Systems
Authors: Laxalde Denis , Lombard Jean-Pierre , Thouverez Fabrice
Published: October 2007

This paper presents a new and original method for dynamical analysis of multistage cyclic structures such as turbomachinery compressors or turbines. Each stage is modeled cyclically by its elementary sector and the interstage coupling is achieved through a cyclic recombination of the interface degrees of freedom. This method is quite simple to set up; it allows us to handle the finite element models of each stage’s sector directly and, as in classical cyclic symmetry analysis, to study the nodal diameter problems separately. The method is first validated on a simple case study which shows good agreements with a complete 360 deg reference calculation. An industrial example involving two HP compressor stages is then presented. Then the forced response application is presented in which synchronous engine order type excitations are considered.
An Investigation Into the Application of Fuzzy Logic Control to Industrial Gas Turbines
Authors: Nelson G. M. , Lakany H.
Published: October 2007

This paper investigates the feasibility benefits of applying fuzzy logic control (FLC) strategies for use with industrial gas turbines. Our main objective is to investigate different designs methods, design implement an FLC strategy, plant simulation in a test environment optimize the FLC, conduct tests to compare the FLC with conventional controls in scenarios relevant to the application. We have designed, implemented, and tested our simulation to the exhaust temperature control problem of a gas turbine problem. The FLC, plant simulation, existing control configuration, and integrated test environment were developed in Java. Heuristic methods were used to optimize the FLC, which proved time consuming. The paper illustrates that while implementation of the FLC is feasible, it requires more effort than the conventional controls examined.
Acoustic and perceptual cues for compound-phrasal contrasts in Vietnamese
Authors: Nguyễn Anh-Thu T. , Ingram John C. L.
Published: October 2007

This paper reports two series of experiments that examined the phonetic correlates of lexical stress in Vietnamese compounds in comparison to their phrasal constructions. In the first series of experiments, acoustic and perceptual characteristics of Vietnamese compound words and their phrasal counterparts were investigated on five likely acoustic correlates of stress or prominence (f0 range and contour, duration, intensity and spectral slope, vowel reduction), elicited under two distinct speaking conditions: a “normal speaking” condition and a “maximum contrast” condition which encouraged speakers to employ prosodic strategies for disambiguation. The results suggested that Vietnamese lacks phonetic resources for distinguishing compounds from phrases lexically and that native speakers may employ a phrase-level prosodic disambiguation strategy (juncture marking), when required to do so. However, in a second series of experiments, minimal pairs of bisyllabic coordinative compounds with reversible syllable positions were examined for acoustic evidence of asymmetrical prominence relations. Clear evidence of asymmetric prominences in coordinative compounds was found, supporting independent results obtained from an analysis of reduplicative compounds and tone sandhi in Vietnamese [Nguyễn and Ingram, 2006]. A reconciliation of these apparently conflicting findings on word stress in Vietnamese is presented and discussed.
The role of fundamental frequency contours in the perception of speech against interfering speech
Authors: Binns Christine , Culling John F.
Published: October 2007

Four experiments investigated the effect of the fundamental frequency (F0) contour on speech intelligibility against interfering sounds. Speech reception thresholds (SRTs) were measured for sentences with different manipulations of their F0 contours. These manipulations involved either reductions in F0 variation, or complete inversion of the F0 contour. Against speech-shaped noise, a flattened F0 contour had no significant impact on SRTs compared to a normal F0 contour; the mean SRT for the flattened contour was only 0.4dB higher. The mean SRT for the inverted contour, however, was 1.3dB higher than for the normal F0 contour. When the sentences were played against a single-talker interferer, the overall effect was greater, with a 2.0dB difference between normal and flattened conditions, and 3.8dB between normal and inverted. There was no effect of altering the F0 contour of the interferer, indicating that any abnormality of the F0 contour serves to reduce intelligibility of the target speech, but does not alter the masking produced by interfering speech. Low-pass filtering the F0 contour increased SRTs; elimination of frequencies between 2 and 4Hz had the greatest effect. Filtering sentences with inverted contours did not have a significant effect on SRTs.
Effects of periodic interruptions on the intelligibility of speech based on temporal fine-structure or envelope cues
Authors: Gilbert Gaëtan , Bergeras Isabelle , Voillery Dorothée , Lorenzi Christian
Published: October 2007

The intelligibility of speech signals processed to retain either temporal envelope (E) or fine structure (TFS) cues within 16 0.4-oct-wide frequency bands was evaluated when processed stimuli were periodically interrupted at different rates. The interrupted E- and TFS-coded stimuli were highly intelligible in all conditions. However, the different patterns of results obtained for E- and TFS-coded speech suggest that the two types of stimuli do not convey identical speech cues. When an effect of interruption rate was observed, the effect occurred at low interruption rates (<8Hz) and was stronger for E- than TFS-coded speech, suggesting larger involvement of modulation masking with E-coded speech.
Modal Doppler theory of an arbitrarily accelerating continuous-wave source applied to mode extraction in the oceanic waveguide
Authors: Walker S. C. , Roux Philippe , Kuperman W. A.
Published: October 2007

A Doppler-based method for using a moving narrow-band source to extract the modes of acoustic propagation in a range-independent shallow ocean waveguide over a partial-water-column spanning vertical line array (VLA) is introduced. Because the modal components propagate at distinct frequencies in the case of uniform radial source motion, the modal depth functions may be isolated and extracted from a frequency decomposition of the field. Because Doppler broadening due to radial source accelerations degrades the effectiveness of the extraction method, the method incorporates a technique to compensate for Doppler broadening. As the basis for the compensation technique, a theory is introduced for describing the VLA field from an accelerating cw source. By connecting the range of the source at the time a signal feature is emitted (the retarded time) to the range of the source at the time the signal feature arrives at the receiver (the contemporary time), the theory incorporates the Doppler effects associated with the finite group velocities of the modal components. The mode extraction method and compensation technique are applied to simulation and ocean data.