bluuebunny/crossref_metadata_2025 huggingface dataset:
DEFENCE ECONOMICS REVIEW
Authors: Hilton Brian
Published: October 2007

Michael Brzoska and Thomas Ohlson, Arms Production in the Third World, London,

John Roper (editor), The Future of British Defence Policy London,

Christian Schmidt (editor), The Economics of Military Expenditure London, MacMillan 1987, pp. 520, (cloth).

Franklin C. Spinney edited by James Clay Thompson,
PORTFOLIO BEHAVIOUR AND ASSET PRICING IN A CHARACTERISTICS FRAMEWORK
Authors: BLAKE DAVID
Published: October 2007

We have applied the characteristics model to the problem of portfolio behaviour and asset pricing. By defining assets in terms of characteristics, we generated individual demands for assets which depended on the prices of assets, the technological relationship between assets and asset characteristics, and the individual's preferences for different characteristics. In general, the characteristics model cannot be readily aggregated across individuals. However, when we assumed that the assets‐characteristics technology had a simple form which was common to all individuals, market‐clearing conditions could be used to derive an asset pricing model. Finally, we showed that the characteristics model provides a unified approach to the problem of preference‐based portfolio behaviour and asset pricing. A number of existing models can be interpreted as characteristics models: the state‐preference model, the parameter‐preference model, the capital asset pricing model and the inter‐temporal capital asset pricing model.
FINANCIAL MARKET IMPERFECTIONS AND IRREGULAR GROWTH CYCLES
Authors: Gatti Domenico Delli , Gallegati Mauro
Published: October 2007

Abstract

In this paper we analyze the generation of endogenous growth and irregular fluctuations in a simple New Keynesian model whose background assumptions are borrowed from a class of asymmetric information models popularized by Greenwald and Stiglitz. We extend the framework put forward by Greenwald and stiglitz taking explicitly into account technological progress as the engine of growth. We show how irregular endogenous fluctuations can arise around an endogenous trend: the traditional view of fluctuations as ‘short run’ phenomena must be abandoned in favour of models of fluctuating growth.
CHOICE OF PRODUCT TYPE BY STRATEGICALLY INTERDEPENDENT FIRMS
Authors: Gee J. M. Alec
Published: October 2007

Astract

The paper analyses the degree of product differentiation between sigle product firms in alternative market equilibria. The equilibria are stable in the sense of Nash, and both non‐cooperative and tacitly collusive market outcomesare identified. The basic model follows the ‘address’ aproach to product differentiation, and the firms' strategic variables are choice of product type and price charged. When all firms are non‐cooperative, product gaps between firms are equal; but tacit collusion results in product gap variation between firms in Nash equilibrium. In all cases, profits for any firm are assumed to be proportional to the multiple of the product gaps between that firm and each of its two closest rivals.
SOME EVIDENCE ON MEAN REVERSION IN EX ANTE REAL INTEREST RATES
Authors: Moosa Imad A. , Bhatti Razzaque H.
Published: October 2007

Astract

Ex ante real interest rates and their differentials are tested for mean reversion using quarterly data on three‐month treasury bill rates and consumer prices for 12 major industrial countries over the period 1972:l‐1993:3. The results are strongly supportive of mean reversion, particularly when less conventional tests are employed. The conclusion that can be derived from the empirical evidence is that goods, capital and foreign exchange markets have become highly integrated in the countries under consideration.
THE PRICE‐QUALITY RELATIONSHIP UNDER MONOPOLY AND COMPETITION
Authors: George Donald A. R.
Published: October 2007

Abstract

The standard economic approaches (screening and signalling) to product quality imply an upward sloping relationship between price and product quality. In the case of screening models it is a relationship which applies to the product line of each individual firm. In the case of signalling models it applies across firms. Both types of model have their shortcomings. An alternative approach is presented which involves endogenising the quality control process. Firms voluntarily provide a warranty contract for their products and this, in turn generates an incentive to control quality. The model compares monopolistic and competitive markets in respect of warranties. quality control and the price‐quality relationship. Under monopoly, the price‐quality relationship is always upward‐sloping or flat. Under competition, however, cost shifts or certain demand side shifts can generate a downward‐sloping relationship between price and quality.
HORIZONTALISM, STRUCTURALISM, LIQUIDITY PREFERENCE AND THE PRINCIPLE OF INCREASING RISK
Authors: Lavoie Marc
Published: October 2007

Abstract

It is shown that the horizontal post‐Keynesian view of credit‐money endogeneity is reasonable rather than extreme. One can argue in favour of a horizontal credit‐money supply curve while still taking into account the non‐accommodating behaviour of the central bank, financial innovations, protfolio adjustments, liquidity perference theory, and the principle of increasing risk. The differences between horizontalists and other post‐Keynesian monetary theorists are matters of emphasis rather than substantial differences of opinion. The only real topic of contention is the ultimate determinant of the base rate of interest.
Das Opium des Volkes
Authors: COLLINSON PATRICK
Published: October 2007

G. J. Cuming and Derek Baker (Eds): Popular Belief and Practice: Papers Read at the Ninth Summer Meeting and the Tenth Winter Meeting of the Ecclesiastical History Society. Cambridge University Press, 1972; pp. xii+331.

Derek Baker (Ed.): Schism, Heresy and Religious Protest: Papers Read at the Tenth Summer Meeting and the Eleventh Winter Meeting of the Ecclesiastical History Society. Cambridge University Press, 1972; pp. xV&Plus;404.
The Religious Crisis of the 1960s: The Experience of the Australian Churches
Authors: Hilliard David
Published: October 2007

The decade of the 1960s in North America and Europe is generally seen by historians and sociologists as a time of sudden and unexpected religious upheaval. But was this the case in Australia? This article examines the changes in belief and behaviour within Australia’s major churches during the ‘remembered sixties’ from c. 1964 to c. 1972, in relation to the cultural and social context, and the extent to which these amounted to a religious turnaround or crisis. Areas examined include the impact of radical theology, symbolized by the book Honest to God, and the ‘new morality’; the changes in Australian Catholicism initiated by the Second Vatican Council; the debate among Catholics over birth control and the papal encyclical Humanae Vitae; the decline in weekly church attendance, Sunday school enrolments and the membership of church youth organizations; the ‘crisis’ in the ordained ministry; changing attitudes in the churches towards social issues; and the responses of the churches to the Vietnam War. The religious unsettlement that occurred in Australia during this period was very similar to North America and Europe, though there were distinctive local emphases. The central issues in debate were common to all major denominations: the relevance and authority of traditional institutions and formulations of belief.
Effect of maternal age on autosomal trisomies
Authors: HASSOLD TERRY , JACOBS PATRICIA , KLINE JENNIE , STEIN ZENA , WARBURTON DOROTHY
Published: October 2007

The effect of maternal age on the genesis of trisomy was studied by comparing data from 362 trisomic and 790 chromosomally normal spontaneous abortions. As a group the trisomies were associated with a substantial increase in maternal age but there were considerable differences in the magnitude of the effect for different trisomies. The effect of increasing maternal age was most pronounced for trisomies involving the small chromosomes, both acrocentric and non‐acrocentric. However, trisomy 16 was conspicuously different from trisomies for all the other small chromosomes, both in the reduced importance of increased maternal age and in the high frequency with which it occurred. The effect of increasing maternal age on trisomies for chromosomes in groups A, B and C was less clear than that for the small chromosomes. However, the evidence suggested that trisomy for these chromosomes was associated with a moderate increase in maternal age.

It was suggested that the maternal age‐dependent trisomies might result from precocious disjunction of the bivalents and random segregation of the resulting univalents, a process which would affect chromosomes with the fewest number of chiasmata and which might be more prevalent in oocytes of older women. It was further suggested that true non‐disjunction, that is, the failure of bivalents to separate at anaphase, might also result in the production of trisomies. This process might be independent of, or only slightly influenced by, increasing maternal age but be affected by the presence of large blocks of heterochromatin.
Subgroup studies of black admixture within a mixed population of Bahia, Brazil
Authors: AZEVÉDO ELIANE S.
Published: October 2007

Genetic, anthropological and medical data are shown to support the conclusion that subgroup studies of Black admixture within a mixed population are feasible, even if to some extent subjective. Thus, the use of subgroup racial classification for studies within mixed populations can be defended as the only choice to avoid excessive heterogeneity.
The effects of increased phenotypic variance on the evolutionary outcomes of generalized major‐gene models
Authors: CARMELLI DORIT , KARLIN SAMUEL
Published: October 2007

The study of generalized major‐gene models has been extended to accommodate selective, assortative mating mechanisms. In this formulation the consequences of amplified phenotypic variance on the major gene frequency are investigated. It is shown that the rate of approach to the equilibrium state is slowed under attenuated assortative mating tendencies and/or with increased environmental noise. Also, an increased phenotypic variance induces more skewness in the nature of the gene frequencies, i.e. a less ‘central’ polymorphic expression. Where strong positive assortative mating occurs, a population fixation state results. Negative assortment generally facilitates the stability of a ‘central’ polymorphism.
Reduced oxygen tension attenuates differentiation capacity of human mesenchymal stem cells and prolongs their lifespan
Authors: Fehrer Christine , Brunauer Regina , Laschober Gerhard , Unterluggauer Hermann , Reitinger Stephan , Kloss Frank , Gülly Christian , Gaßner Robert , Lepperdinger Günter
Published: October 2007

Mesenchymal stem cells (MSC) are capable of differentiating into bone, fat, cartilage, tendon and other organ progenitor cells. Despite the abundance of MSC within the organism, little is known about their in vivo properties or about their corresponding in vivo niches. We therefore isolated MSC from spongy (cancellous) bone biopsies of healthy adults. When compared with the surrounding marrow, a fourfold higher number of colony‐forming units was found within the tight meshwork of trabecular bone surface. At these sites, oxygen concentrations range from 1% to 7%. In MSC cultured at oxygen as low as 3%, rates for cell death and hypoxia‐induced gene transcription remained unchanged, while in vitro proliferative lifespan was significantly increased, with about 10 additional population doublings before reaching terminal growth arrest. However, differentiation capacity into adipogenic progeny was diminished and no osteogenic differentiation was detectable at 3% oxygen. In turn, MSC that had previously been cultured at 3% oxygen could subsequently be stimulated to successfully differentiate at 20% oxygen. These data support our preliminary finding that primary MSC are enriched at the surface of spongy bone. Low oxygen levels in this location provide a milieu that extends cellular lifespan and furthermore is instructive for the stemness of MSC allowing proliferation upon stimulation while suppressing differentiation.
Markov decision processes with a target set for minimum criteria
Authors: Ohtsubo Yoshio
Published: October 2007

We consider Markov decisions processes with a target set, where criterion function is an expectation of minimum function. We formulate the problem as an infinite horizon case with a recurrent class. We show under some conditions that an optimal value function is a unique solution to an optimality equation and there exists a stationary optimal policy. Also we give a policy improvement method.
Impact of Dialyzer Membrane on Apoptosis and Function of Polymorphonuclear Cells and Cytokine Synthesis by Peripheral Blood Mononuclear Cells in Hemodialysis Patients
Authors: Andreoli Maria C.C. , Dalboni Maria A. , Watanabe Renato , Manfredi Silvia R. , Canziani Maria E.F. , Kallás Esper G. , Sesso Ricardo C. , Draibe Sergio A. , Balakrishnan Vaidyanathapuram S. , Jaber Bertrand L. , Liangos Orfeas , Cendoroglo Miguel
Published: October 2007

Abstract:  In an in vivo crossover trial, we compared a cellulosic with a synthetic dialyzer with respect to polymorphonuclear cells (PMN) function and apoptosis, cytokine serum levels and synthesis by peripheral blood mononuclear cells (PBMC), and complement activation. Twenty hemodialysis (HD) patients were assigned in alternate order to HD with cellulose acetate (CA) or polysulfone (PS) dialyzer. After 2 weeks, patients were crossed over to the second dialyzer and treated for another 2 weeks. Apoptosis was assessed by flow cytometry in freshly isolated PMN. Phagocytosis and production of peroxide by PMN were studied by flow cytometry in whole blood. PBMC were isolated from blood samples and incubated for 24 h with or without lipopolysaccharide (LPS). There was no impact of dialyzer biocompatibility on PMN apoptosis and function, cytokine synthesis by PBMC or on their serum levels, serum levels of C3a, and terminal complement complex (TCC). Nevertheless, after HD, serum levels of complement correlated negatively with PMN phagocytosis and peroxide production, and positively with PMN apoptosis and cytokine production by PBMC. Although the results did not show a dialyzer advantage on the immunologic parameters, complement activation may have modulated cell function and apoptosis after HD.
Assessing the Relationship between Human Capital and Firm Performance: Evidence from Technology–Based New Ventures
Authors: Shrader Rod , Siegel Donald S.
Published: October 2007

We assess the role of human capital in the growth and development of new technology–based ventures, based on longitudinal data from 198 high–tech ventures. Our empirical results imply that there is a strong relationship between team experience and strategy. Although there is a weak direct link between team experience and venture performance, the findings strongly suggest that the fit between strategy and team experience is a key determinant of the long–term performance of high–tech entrepreneurial ventures. For small, technology–based new ventures, the team's technological experience appears to be the most important determinant of the success of a differentiation strategy.
Technology Entrepreneurs’ Human Capital and Its Effects on Innovation Radicalness
Authors: Marvel Matthew R. , Lumpkin G.T.
Published: October 2007

Radical innovations transform existing markets, create new markets, and stimulate economic growth. This study investigates how the experience, education, and prior knowledge of technology entrepreneurs relate to innovation radicalness. Findings from a sample of 145 technology entrepreneurs operating within university–affiliated incubators suggest that general and specific human capital are both vital to innovation outcomes. Innovation radicalness was positively associated with formal education and prior knowledge of technology, but negatively associated with prior knowledge of ways to serve markets. This suggests a counterintuitive conclusion—the less technology entrepreneurs know about ways to serve a market, the greater their chances of using technology knowledge to create breakthrough innovations within it. Finally, we discuss configurations of human capital that are likely to bestow unique advantages in the construction of radical innovations.
Expression of thermosensitive two‐pore domain K+ channels in human keratinocytes cell line HaCaT cells
Authors: Kang Dawon , Kim Sung‐Hee , Hwang Eun‐Mi , Kwon Oh‐Sang , Yang Hae‐Young , Kim Eun‐Sook , Choi Tae Hyun , Park Jae‐Yong , Hong Seong‐Geun , Han Jaehee
Published: October 2007

Abstract:  Recent studies have shown that keratinocytes can sense temperature via thermo‐transient receptor potential (TRP) channels. It is not known whether other thermosensitive ion channels such as TREK‐1, TREK‐2 and TRAAK (TREKs/TRAAK) that are members of the two‐pore domain K+ (K2P) channel family are expressed in human keratinocytes. Here, we identified the expression of TREKs/TRAAK in human keratinocytes‐derived cell line HaCaT cells using RT‐PCR, immunocytochemistry, Western blot analysis and patch‐clamp technique. RT‐PCR showed that all six K2P channels tested (TASK‐1, TASK‐3, TREK‐1, TREK‐2, TRAAK and TASK‐2) were expressed in HaCaT cells, as well as in skin and dorsal root ganglion (DRG) of rat. The expression of TREKs/TRAAK mRNA identified by RT‐PCR was further studied at the protein level. Using anti‐TREK‐1, ‐TREK‐2 and ‐TRAAK, bands of ∼46, ∼60 and ∼43 kDa, respectively, were observed at plasma membrane of HaCaT cells. Immunostaining also showed that TREK‐1, TREK‐2 and TRAAK were expressed in all area of cells including plasma membrane. Whole‐cell K+ currents recorded from HaCaT cells were activated by arachidonic acid and heat. These results suggest that TREKs/TRAAK channels could act as thermosensors in human keratinocytes.
Evolving FDI Legitimacy and Strategic Choice of Japanese Subsidiaries in China
Authors: Peng George Z. , Beamish Paul W.
Published: October 2007

We examine how evolving FDI legitimacy in China influences two strategic choices (entry mode and expatriate staffing) of Japanese subsidiaries there over the period 1993–2000, based on data aggregated from Toyo Keizai and the National Bureau of Statistics of China (various years). As FDI legitimacy improves over time, we find that smaller subsidiaries tend to choose the wholly owned subsidiary mode and deploy a higher percentage of expatriates, whereas larger subsidiaries tend to choose the joint venture mode and use a lower percentage of expatriates; and that Japanese subsidiaries are more likely to have a local manager, and this tendency may be stronger for larger subsidiaries. The theoretical and practical implications of these findings are discussed from a density dependence theory perspective.
Cultural Intelligence: Its Measurement and Effects on Cultural Judgment and Decision Making, Cultural Adaptation and Task Performance
Authors: Ang Soon , Van Dyne Linn , Koh Christine , Ng K. Yee , Templer Klaus J. , Tay Cheryl , Chandrasekar N. Anand
Published: October 2007

We enhance the theoretical precision of cultural intelligence (CQ: capability to function effectively in culturally diverse settings) by developing and testing a model that posits differential relationships between the four CQ, dimensions (metacognitive, cognitive, motivational and behavioural) and three intercultural effectiveness outcomes (cultural judgment and decision making, cultural adaptation and task performance in culturally diverse settings). Before testing the model, we describe development and cross-validation (N = 1,360) of the multidimensional cultural intelligence scale (CQS) across samples, time and country. We then describe three substantive studies (N = 794) in field and educational development settings across two national contexts, the USA and Singapore. The results demonstrate a consistent pattern of relationships where metacognitive CQ and cognitive CQ predicted cultural judgment and decision making; motivational CQ and behavioural CQ predicted cultural adaptation; and metacognitive CQ and behavioural CQ predicted task performance. We discuss theoretical and practical implications of our model and findings.
A Virtual Tool for Prediction of Turbocharger Nonlinear Dynamic Response: Validation Against Test Data
Authors: Andrés Luis San , Rivadeneira Juan Carlos , Gjika Kostandin , Groves Christopher , LaRue Gerry
Published: October 2007

Advances on the modeling of nonlinear rotor-bearing models for prediction of the dynamic shaft response of automotive turbochargers (TCs) supported on floating ring bearings (FRBs) are presented. Comprehensive test data for a TC unit operating at a top speed of 65krpm serves to validate the model predictions. The static forced performance of the support FRBs considers lubricant thermal effects, thermal expansion of the shaft and bearings, and entrance pressure losses due to centrifugal flow effects. The bearing analysis also yields linearized rotordynamic force coefficients for the inner and outer lubricant films. These coefficients are used with the rotor model to predict the synchronous response to imbalance and the system natural frequencies and stability. A method renders an accurate estimation of the test rotor imbalance by using the actual vibration measurements and influence coefficients derived from predictions using linearized bearing force coefficients. Predicted ring rotational speeds, operating radial clearances, and lubricant viscosities for the inner and outer films are the main input to the nonlinear time transient analysis. The nonlinear response model predicts the total shaft motion, with fast Fourier transforms showing the synchronous response, and amplitudes and whirl frequencies of subsynchronous motions. The predicted synchronous amplitudes are in good agreement with the measurements, in particular at high shaft speeds. The nonlinear analysis predicts multiple frequency subsynchronous motions for speeds ranging from 10krpmto55krpm (maximum speed 70krpm), with amplitudes and frequencies that correlate well with the test data. The comparisons validate the comprehensive rotor-bearings model whose ultimate aim is to save TC design time and accelerate product development.
Liquid Fuel Combustion Using Heat Recirculation Through Annular Porous Media
Authors: Newburn E. Ryan , Agrawal Ajay K.
Published: October 2007

A counter-flow annular heat recirculating burner was designed for lean prevaporized, premixed combustion. Prior to entering the combustor, the reactants are passed through a porous media-filled preheating annulus surrounding the combustor. Kerosene is dripped by gravity onto the porous media and vaporized by the heat conducted through the combustor wall. Experiments were conducted to evaluate heat transfer and combustion performance at various equivalence ratios, heat release rates, and inlet air temperatures. Results show low CO emissions over a range of equivalence ratios. NOx emissions were high at high heat release rates, indicating inadequate prevaporization and premixing of fuel with air. Heat recirculation and heat loss characteristics are presented at various operating conditions.
Buoyancy-Induced Flow in Open Rotating Cavities
Authors: Owen J. Michael , Abrahamsson Hans , Lindblad Klas
Published: October 2007

Buoyancy-induced flow can occur in the cavity between the co-rotating compressor disks in gas-turbine engines, where the Rayleigh numbers can be in excess of 1012. In most cases the cavity is open at the center, and an axial throughflow of cooling air can interact with the buoyancy-induced flow between the disks. Such flows can be modeled, computationally and experimentally, by a simple rotating cavity with an axial flow of air. This paper describes work conducted as part of ICAS-GT, a major European research project. Experimental measurements of velocity, temperature, and heat transfer were obtained on a purpose-built experimental rig, and these results have been reported in an earlier paper. In addition, 3D unsteady CFD computations were carried out using a commercial code (Fluent) and a RNG k‐ε turbulence model. The computed velocity vectors and contours of temperature reveal a flow structure in which, as seen by previous experimenters, “radial arms” transport cold air from the center to the periphery of the cavity, and regions of cyclonic and anticyclonic circulation are formed on either side of each arm. The computed radial distribution of the tangential velocity agrees reasonably well with the measurements in two of the three cases considered here. In the third case, the computations significantly overpredict the measurements; the reason for this is not understood. The computed and measured values of Nu for the heated disk show qualitatively similar radial distributions, with high values near the center and the periphery. In two of the cases, the quantitative agreement is reasonably good; in the third case, the computations significantly underpredict the measured values.
Friction Reduction by Piston Ring Pack Modifications of a Lean-Burn Four-Stroke Natural Gas Engine: Experimental Results
Authors: Quillen Kris , Stanglmaier Rudolf H. , Moughon Luke , Takata Rosalind , Wong Victor , Reinbold Ed , Donahue Rick
Published: October 2007

A project to reduce frictional losses from natural gas engines is currently being carried out by a collaborative team from Waukesha Engine Dresser, Massachusetts Institute of Technology (MIT), and Colorado State University (CSU). This project is part of the Advanced Reciprocating Engine System (ARES) program led by the U.S. Department of Energy. Previous papers have discussed the computational tools used to evaluate piston-ring/cylinder friction and described the effects of changing various ring pack parameters on engine friction. These computational tools were used to optimize the ring pack of a Waukesha VGF 18-liter engine, and this paper presents the experimental results obtained on the engine test bed. Measured reductions in friction mean effective pressure (FMEP) were observed with a low tension oil control ring (LTOCR) and a skewed barrel top ring (SBTR). A negative twist second ring (NTSR) was used to counteract the oil consumption increase due to the LTOCR. The LTOCR and SBTR each resulted in a ∼0.50% improvement in mechanical efficiency (ηmech).
Supersonic Virtual Valve Design for Numerical Simulation of a Large-Bore Natural Gas Engine
Authors: Kim Gi-Heon , Kirkpatrick Allan , Mitchell Charles
Published: October 2007

In many applications of supersonic injection devices, three-dimensional computation that can model a complex supersonic jet has become critical. However, in spite of its increasing necessity, it is computationally costly to capture the details of supersonic structures in intricate three-dimensional geometries with moving boundaries. In large-bore stationary natural gas fueled engine research, one of the most promising mixing enhancement technologies currently used for natural gas engines is high-pressure fuel injection. Consequently, this creates considerable interest in three-dimensional computational simulations that can examine the entire injection and mixing process in engines using high-pressure injection and can determine the impact of injector design on engine performance. However, the cost of three-dimensional engine simulations—including a moving piston and the kinetics of combustion and pollutant production—quickly becomes considerable in terms of simulation time requirements. One limiting factor is the modeling of the small length scales of the poppet valve flow. Such length scales can be three orders of magnitude smaller than cylinder length scales. The objective of this paper is to describe the development of a methodology for the design of a simple geometry supersonic virtual valve that can be substituted in three-dimensional numerical models for the complex shrouded poppet valve injection system actually installed in the engine to be simulated. Downstream flow characteristics of the jets from an actual valve and various virtual valves are compared. Relevant mixing parameters, such as local equivalent ratio and turbulence kinetic energy, are evaluated in full-scale moving piston simulations that include the effect of the jet-piston interaction. A comparison of the results has indicated that it is possible to design a simple converging-diverging fuel nozzle that will produce the same jet and, subsequently, the same large-scale and turbulent-scale mixing patterns in the engine cylinder as a real poppet valve.
Numerical Simulation of Liquid Jet Atomization Including Turbulence Effects
Authors: Trinh Huu P. , Chen C. P. , Balasubramanyam M. S.
Published: October 2007

This paper describes numerical implementation and validation of a newly developed hybrid model, T-blob/T-TAB, into an existing computational fluid dynamics (CFD) program for primary and secondary breakup simulation of liquid jet atomization. This model extends two widely used models, the Kelvin-Helmholtz (KH) instability of Reitz (the “blob” model) (1987, Atomization Spray Technol., 3, pp. 309–337) and the Taylor-Analogy-Breakup (TAB) secondary droplet breakup of O’Rourke and Amsden (1987, SAE Technical Paper No. 872089) to include liquid turbulence effects. In the primary breakup model, the level of the turbulence effect on the liquid breakup depends on the characteristic scales and flow conditions at the liquid nozzle exit. Transition to the secondary breakup was modeled based on energy balance, and an additional turbulence force acted on parent drops was modeled and integrated into the TAB governing equation. Several assessment studies are presented, and the results indicate that the existing KH and TAB models tend to underpredict the product drop size and spray angle, whereas the current model provides superior results when compared to the measured data.
Transient Modeling of the NETL Hybrid Fuel Cell/Gas Turbine Facility and Experimental Validation
Authors: Ferrari Mario L. , Liese Eric , Tucker David , Lawson Larry , Traverso Alberto , Massardo Aristide F.
Published: October 2007

This paper describes the experimental validation of two different transient models of the hybrid fuel cell/gas turbine facility of the U.S. DOE-NETL at Morgantown. The first part of this work is devoted to the description of the facility, designed to experimentally investigate these plants with real components, except the fuel cell. The behavior of the SOFC is obtained with apt volumes (for the stack and the off-gas burner) and using a combustor to generate similar thermal effects. The second part of this paper shows the facility real-time transient model developed at the U.S. DOE-NETL and the detailed transient modeling activity using the TRANSEO program developed at TPG. The results obtained with both models are successfully compared with the experimental data of two different load step decreases. The more detailed model agrees more closely with the experimental data, which, of course, is more time consuming than the real-time model (the detailed model operates with a calculation over calculated time ratio around 6). Finally, the TPG model has been used to discuss the importance of performance map precision for both compressor and turbine. This is an important analysis to better understand the steady-state difference between the two models.
Integration of On-Line and Off-Line Diagnostic Algorithms for Aircraft Engine Health Management
Authors: Kobayashi Takahisa , Simon Donald L.
Published: October 2007

This paper investigates the integration of on-line and off-line diagnostic algorithms for aircraft gas turbine engines. The on-line diagnostic algorithm is designed for in-flight fault detection. It continuously monitors engine outputs for anomalous signatures induced by faults. The off-line diagnostic algorithm is designed to track engine health degradation over the lifetime of an engine. It estimates engine health degradation periodically over the course of the engine’s life. The estimate generated by the off-line algorithm is used to “update” the on-line algorithm. Through this integration, the on-line algorithm becomes aware of engine health degradation, and its effectiveness to detect faults can be maintained while the engine continues to degrade. The benefit of this integration is investigated in a simulation environment using a nonlinear engine model.
Single- and multi-channel underwater acoustic communication channel capacity: A computational study
Authors: Hayward Thomas J. , Yang T. C.
Published: October 2007

Acoustic communication channel capacity determines the maximum data rate that can be supported by an acoustic channel for a given source power and source/receiver configuration. In this paper, broadband acoustic propagation modeling is applied to estimate the channel capacity for a time-invariant shallow-water waveguide for a single source-receiver pair and for vertical source and receiver arrays. Without bandwidth constraints, estimated single-input, single-output (SISO) capacities approach 10megabits∕s at 1km range, but beyond 2km range they decay at a rate consistent with previous estimates by Peloquin and Leinhos (unpublished, 1997), which were based on a sonar equation calculation. Channel capacities subject to source bandwidth constraints are approximately 30–90% lower than for the unconstrained case, and exhibit a significant wind speed dependence. Channel capacity is investigated for single-input, multi-output (SIMO) and multi-input, multi-output (MIMO) systems, both for finite arrays and in the limit of a dense array spanning the entire water column. The limiting values of the SIMO and MIMO channel capacities for the modeled environment are found to be about four times higher and up to 200–400 times higher, respectively, than for the SISO case. Implications for underwater acoustic communication systems are discussed.
Forward-masked monaural and interaural intensity discrimination
Authors: Stellmack Mark A. , Viemeister Neal F. , Byrne Andrew J.
Published: October 2007

Intensity-discrimination thresholds were measured for a 25-ms, 6-kHz pure tone for pedestal levels from 40 to 90dB sound pressure level (SPL) with and without a forward masker (100-ms narrowband Gaussian noise, N0=70dB). When the masker was present, the masker and probe were separated by 100ms of silence. Unmasked and masked thresholds were measured in a two-interval monaural procedure and, separately, in a single-interval interaural procedure in which the pedestal and incremented pedestals were presented simultaneously to opposite ears. While the monaural thresholds were elevated markedly by the forward masker for mid-level pedestals, interaural thresholds were nearly unaffected by the masker across pedestal levels. The results argue against the notion that the monaural elevation in forward-masked thresholds is due to degraded encoding of intensity information at early stages of auditory processing.
Proper orthogonal decomposition and cluster weighted modeling for sensitivity analysis of sound propagation in the atmospheric surface layer
Authors: Pettit Chris L. , Wilson D. Keith
Published: October 2007

Outdoor sound propagation predictions are compromised by uncertainty and error in the atmosphere and terrain representations, and sometimes also by simplified or incorrect physics. A model’s predictive power, i.e., its accurate representation of the sound propagation, cannot be assessed without first quantifying the ensemble sound pressure variability and sensitivity to uncertainties in the model’s governing parameters. This paper describes fundamental steps toward this goal for a single-frequency point source. The atmospheric surface layer is represented through Monin-Obukhov similarity theory and the acoustic ground properties with a relaxation model. Sound propagation is predicted with the parabolic equation method. Governing parameters are modeled as independent random variables across physically reasonable ranges. Latin hypercube sampling and proper orthogonal decomposition (POD) are employed in conjunction with cluster-weighted models to develop compact representations of the sound pressure random field. Full-field sensitivity of the sound pressure field is computed via the sensitivities of the POD mode coefficients to the system parameters. Ensemble statistics of the full-field sensitivities are computed to illustrate their relative importance at every down range location. The central role of sensitivity analysis in uncertainty quantification of outdoor sound propagation is discussed and pitfalls of sampling-based sensitivity analysis for outdoor sound propagation are described.
Effects of periodic masker interruption on the intelligibility of interrupted speech
Authors: Iyer Nandini , Brungart Douglas S. , Simpson Brian D.
Published: October 2007

When listeners hear a target signal in the presence of competing sounds, they are quite good at extracting information at instances when the local signal-to-noise ratio of the target is most favorable. Previous research suggests that listeners can easily understand a periodically interrupted target when it is interleaved with noise. It is not clear if this ability extends to the case where an interrupted target is alternated with a speech masker rather than noise. This study examined speech intelligibility in the presence of noise or speech maskers, which were either continuous or interrupted at one of six rates between 4 and 128Hz. Results indicated that with noise maskers, listeners performed significantly better with interrupted, rather than continuous maskers. With speech maskers, however, performance was better in continuous, rather than interrupted masker conditions. Presumably the listeners used continuity as a cue to distinguish the continuous masker from the interrupted target. Intelligibility in the interrupted masker condition was improved by introducing a pitch difference between the target and speech masker. These results highlight the role that target-masker differences in continuity and pitch play in the segregation of competing speech signals.
High frequency ultrasonic characterization of human vocal fold tissue
Authors: Huang Chih-Chung , Sun Lei , Dailey Seth H. , Wang Shyh-Hau , Shung K. Kirk
Published: October 2007

Recently, endolaryngeal sonography at frequencies ranging from 10 to 30MHz has been found to be useful in diagnosing diseases of the vocal folds (VFs). However, image resolution can be further improved by ultrasound at higher frequencies, necessitating the measurement of high-frequency acoustic properties of VF tissue. The ultrasonic parameters of integrated backscatter, sound velocity, and frequency-dependent attenuation coefficient were measured in both the lamina propria (LP) and vocalis muscle (VM) of human VFs using a 47MHz high-frequency ultrasonic transducer. The integrated backscatter was −173.44±6.14 (mean±s.d.) and −195.13±3.58dB in the LP and VM, respectively, the sound velocity was 1667.68±44.9 and 1595.07±39.33m∕s, and the attenuation coefficient at 47MHz was 8.28±1.72 and 7.17±1.30dB∕mm. The difference between these ultrasonic parameters may be attributed to variations in the structure and fiber concentrations in VF tissue. These results could serve as a useful clinical reference for the further development of high-frequency ultrasound devices for endolarynx sonography applications.
Subglottal coupling and its influence on vowel formants
Authors: Chi Xuemin , Sonderegger Morgan
Published: October 2007

A model of acoustic coupling between the oral and subglottal cavities is developed and predicts attenuation of and discontinuities in vowel formant prominence near resonances of the subglottal system. One discontinuity occurs near the second subglottal resonance (SubF2), at 1300–1600Hz, suggesting the hypothesis that this is a quantal effect [K. N. Stevens, J. Phonetics 17, 3–46 (1989)] dividing speakers’ front and back vowels. Recordings of English vowels (in /hVd/ environments) for three male and three female speakers were made, while an accelerometer attached to the neck area was used to capture the subglottal waveform. Average speaker SubF2 values range from 1280 to 1620Hz, in agreement with prior work. Attenuation of 5–12dB of second formant prominence near SubF2 is found to occur in all back-front diphthongs analyzed, while discontinuities in the range of 50–300Hz often occur, in good agreement with the resonator model. These coupling effects are found to be generally stronger for open-phase than for closed-phase measurements. The implications for a quantal relation between coupling effects near SubF2 and [back] are discussed.
Variation in spectral-shape discrimination weighting functions at different stimulus levels and signal strengths
Authors: Lentz Jennifer J.
Published: October 2007

This study evaluated whether weights for spectral-shape discrimination depend on overall stimulus level and signal strength (the degree of spectral-shape change between two stimuli). Five listeners discriminated between standard stimuli that were the sum of six equal-amplitude tones and signal stimuli created by decreasing the amplitudes of three low-frequency components and increasing the amplitudes of three high-frequency components. Weighting functions were influenced by stimulus level in that the relative contribution of the low-frequency (decremented) components to the high-frequency (incremented) components decreased with increasing stimulus level. Although individual variability was present, a follow-up experiment suggested that the level dependence was due to greater reliance on high-frequency components rather than incremented components. Excitation-pattern analyses indicated that the level dependence is primarily, but not solely, driven by cochlear factors. In general, different signal strengths had no effect on the weighting functions (when normalized), but two of the five listeners showed variability in the shape of the weighting function across signal strengths. Results suggest that the effects of stimulus level on weighting functions and individual variability in the shapes of the weighting functions should be considered when comparing weighting functions across conditions and groups that might require different stimulus levels and signal strengths.
Performance of artificial neural network-based classifiers to identify military impulse noise
Authors: Bucci Brian A. , Vipperman Jeffrey S.
Published: October 2007

Noise monitoring stations are in place around some military installations to provide records that assist in processing noise complaints and damage claims. However, they are known to produce false positives (by incorrectly attributing naturally occurring noise to military operations) and also fail to detect many impulse events. In this project, classifiers based on artificial neural networks were developed to improve the accuracy of military impulse noise identification. Two time-domain metrics—kurtosis and crest factor—and two custom frequency-domain metrics—spectral slope and weighted square error—were inputs to the artificial neural networks. The classification algorithm was able to achieve up to 100% accuracy on the training data and the validation data, while improving detection threshold by at least 40dB.
Use of perceptual weights to test a model of loudness summation
Authors: Leibold Lori J. , Jesteadt Walt
Published: October 2007

Leibold et al.[J. Acoust. Soc. Am. 121, 2822–2831 (2007)] examined the perceptual weight subjects assigned to individual components of a multitone complex while performing a loudness-matching task. Weights agreed with the Moore et al. loudness model [J. Audio Eng. Soc. 45, 224–237 (1997)], except when components were widely spaced in frequency. In an effort to account for the data, the just-noticeable-difference (jnd) for intensity discrimination was measured for each component and compared to the weight for that component. The model predicts greater improvement in intensity discrimination with increasing bandwidth than was observed in the data. jnds were not correlated with weights in the widest frequency-spacing condition.
Speech segregation in rooms: Effects of reverberation on both target and interferer
Authors: Lavandier Mathieu , Culling John F.
Published: October 2007

Speech reception thresholds were measured to investigate the influence of a room on speech segregation between a spatially separated target and interferer. The listening tests were realized under headphones. A room simulation allowed selected positioning of the interferer and target, as well as varying the absorption coefficient of the room internal surfaces. The measurements involved target sentences and speech-shaped noise or 2-voice interferers. Four experiments revealed that speech segregation in rooms was not only dependent on the azimuth separation of sound sources, but also on their direct-to-reverberant energy ratio at the listening position. This parameter was varied for interferer and target independently. Speech intelligibility decreased as the direct-to-reverberant ratio of sources was degraded by sound reflections in the room. The influence of the direct-to-reverberant ratio of the interferer was in agreement with binaural unmasking theories, through its effect on interaural coherence. The effect on the target occurred at higher levels of reverberation and was explained by the intrinsic degradation of speech intelligibility in reverberation.
Acoustic scattering from double-diffusive microstructure
Authors: Lavery Andone C. , Ross Tetjana
Published: October 2007

Laboratory measurements of high-frequency broadband acoustic backscattering (200–600kHz) from the diffusive regime of double-diffusive microstructure have been performed. This type of microstructure, which was characterized using direct microstructure and optical shadowgraph techniques, is identified by sharp density and sound speed interfaces separating well-mixed layers. Vertical acoustic backscattering measurements were performed for a range of physical parameters controlling the double-diffusive microstructure. The echoes have been analyzed in both the frequency domain, providing information on the spectral response of the scattering, and in the time domain, using pulse compression techniques. High levels of variability were observed, associated with interface oscillations and turbulent plumes, with many echoes showing significant spectral structure. Acoustic estimates of interface thickness (1–3cm), obtained for the echoes with exactly two peaks in the compressed pulse output, were in good agreement with estimates based on direct microstructure and optical shadowgraph measurements. Predictions based on a one-dimensional weak-scattering model that includes the actual density and sound speed profiles agree reasonably with the measured scattering. A remote-sensing tool for mapping oceanic microstructure, such as high-frequency broadband acoustic scattering, could lead to a better understanding of the extent and evolution of double-diffusive layering, and to the importance of double diffusion to oceanic mixing.
Measurements of mutual radiation impedance between baffled cylindrical shell transducers
Authors: Oishi Tetsuro , Brown David A.
Published: October 2007

The mutual radiation impedances between two baffled cylindrical shell transducers, made of PZT-4 piezoelectric rings with one half of the cylindrical surface covered by a compliant baffle, were determined in experiments as a function of separation distance using an experimental technique recently described [B. Aronov, J. Acoust. Soc. Am. 119, 3822–3830 (2006)]. Two baffled cylindrical shell transducers were connected electrically in parallel and the input electrical admittance was measured at different separations when the two transducers were operated in phase and then 180° out-of-phase in both the coaxial and horizontal (side-by-side) alignments. The mutual radiation impedances were then computed using an electrical equivalent circuit to determine the significance of interaction for cylindrical elements in these array geometries.