bluuebunny/crossref_metadata_2025 huggingface dataset:
Renaissance City Singapore: a study of arts spaces
Authors: Chang T C , Lee W K
Published: June 2003

The study of ‘arts spaces’ has generally focused on physical spaces for the arts in the form of arts districts, cultural infrastructure and museum spaces. Apart from the provision of such physical spaces, we argue that the study of the arts should also focus on such aspects as the social environments and the creative spaces in which artists operate. Such a holistic approach not only facilitates an understanding of the myriad challenges artists face in society, but also opens greater research opportunities to geographers interested in the arts. Our case study of Singapore as a ‘Global City for the Arts’ provides insights into physical spaces of the arts as well as the social and creative environments in which the arts operate.
Imagining Strawberry Fields as a place of pilgrimage
Authors: Kruse Robert J
Published: June 2003

This paper examines the significance of Strawberry Fields, the memorial to John Lennon in Central Park, New York City, as a place of secular pilgrimage. Situated within postmodern conceptualizations of secular pilgrimage, Strawberry Fields is shown to be the spatial focus of a variety of discourses related to John Lennon's life and music. Furthermore, this paper illustrates how autobiography as a qualitative research method can reveal the sentiments that motivate particular pilgrims to places associated with major figures in popular music.
Street names and the scaling of memory: the politics of commemorating Martin Luther King, Jr within the African American community
Authors: Alderman Derek H
Published: June 2003

Streets named for Martin Luther King, Jr are common yet controversial features in cities across the United States. This paper analyses the politics of naming these streets as a ‘scaling of memory’– a socially contested process of determining the geographic extent to which the civil rights leader should be memorialized. Debates over the scaling of King's memory revolve around the size of the named street, the street's level of prominence within a hierarchy of roads, and the degree to which the street transcends the spatial confines of the black community. A street‐naming struggle in Eatonton, Georgia (USA) exposes how the scaling of memory can become a point of division and contest within the black community as activists seek to fulfil different political goals. Analysing these intra‐racial contests allows for a fuller appreciation of the historical consciousness and geographic agency of African Americans rather than seeing them as a single, monolithic group.
Imagining difference: the experiences of ‘transnational’ Indian IT professionals in Germany
Authors: Meijering Louise , Van Hoven Bettina
Published: June 2003

In this paper we explore the motivations to migrate and the migration experiences of 22 Indian IT professionals in Germany. When studying skilled migration, Germany is an interesting case as it struggled with waves of extreme right activities whilst trying to attract IT professionals from outside the European Union at the same time. In this context, we are interested in the conflicts that the migrants may experience as a result of their desire or obligation to move, their specific cultural baggage and the way in which they encounter the different sides of German society.
Entries and omissions: using solicited diaries in geographical research
Authors: Meth Paula
Published: June 2003

This paper explores the use of personal solicited diaries as a qualitative research tool within social geography. Diaries were used with women from South Africa who recorded their experiences of violence over a period of one month. The paper analyses diaries in terms of their longitudinal benefits, their socially constituted nature, their use in conjunction with interviews and finally their potential for empowerment. The paper concludes with a discussion of the limitations of the diary as a methodological tool.
Kut (informal rotating credit) in the livelihood strategies of urban households in Penang, Malaysia
Authors: Ghazali Suriati
Published: June 2003

The importance of social capital in both rural and urban communities is an often‐published topic. By representing the operation of social capital networks, this paper explores the persistence of informal rotating credit in the livelihoods of low‐income, urban households in Penang, Malaysia. It highlights the function of such credit and the ways in which it benefits poor women and their households. This paper suggests that informal credit reduces the probability of being poor, and the returns to household investment in social capital are higher for the poor than for the population at large. The downside of such social capital is also discussed. The paper concludes that informal credit is enhanced in the urban settings due to the increase in income opportunities, especially for women.
Modeling Fear of Crime and Perceived Victimization Risk: The (In)Significance of Neighborhood Integration
Authors: Kanan James W. , Pruitt Matthew V.
Published: June 2003

The bulk of fear–of–crime research has been limited to one questionnaire item that asks respondents to assess their personal safety by answering “how safe they feel alone in their neighborhoods at night.” More recently, however, studies have pointed to the multidimensional nature of fear of crime and perceived risk of victimization. Following this line of inquiry, we investigate the potential impact of several variable sets on three measures of fear of crime or risk perception—the traditional risk assessment of being alone at night, a measure of worry about crime, and a more general assessment of neighborhood safety. Of particular interest are the relative effects of neighborhood integration variables on the measures of fear/risk. A comparison of the effects of neighborhood integration variables with a set of perceived neighborhood disorder, routine activities, socio–demographic characteristics, and victimization experience variables reveals that the neighborhood disorder (incivilities), income, and crime prevention measures produce the most consistently significant effects on fear of crime and perceived risk. Contrary to our expectations, neighborhood integration variables appear to be relatively unimportant.
Mining the Data: Analyzing the Economic Implications of Mining for Nonmetropolitan Regions
Authors: Freudenburg William R. , Wilson Lisa J.
Published: June 2003

Extractive industries such as logging and mining are generally expected to bring significant economic benefits to rural regions, but a growing number of findings have now challenged that common expectation. Still, it is not clear whether the findings of less–than–desirable economic outcomes are isolated or representative. In this article, we assemble literally all of the relevant quantitative findings on mining that we have been able to identify in published and/or technical literature from the United States. In the interest of rigor, we limit the assessment to cases in which strictly nonmetropolitan mining regions are compared against other nonmetropolitan regions and/or against those regions’ own experiences over time. Overall, 301 findings meet the criteria for inclusion. Contrary to the long–established assumptions, but consistent with more recent critiques, roughly half of all published findings indicate negative economic outcomes in mining communities, with the remaining findings being split roughly evenly between favorable and neutral/indeterminate ones. Positive findings are more likely to be associated with incomes than with poverty or (especially) unemployment rates, and they are more likely to come from the western United States, where much of the mining involves relatively large, new coal strip mines. Over half of all positive findings come from the years prior to 1982. In virtually all other categories, the plurality or majority of findings have been negative. When the patterns of findings are subjected to one–sample means tests, the only way to produce a significantly positive outcome is by combining all neutral/indeterminate findings with the positive ones, while focusing exclusively on incomes; by contrast, in the case of poverty or unemployment rates—as well as for the overall body of findings—the results are consistently and significantly negative, whether the neutral/indeterminate findings are combined with negative ones or omitted from the equations altogether. Until or unless future studies produce dramatically different findings, there appears to be no scientific basis for accepting the widespread, “obvious” assumption that mining will lead to economic improvement.
The Institutionalization of U.S. Political Parties: Patronage Newspapers
Authors: Blau Judith R. , Elman Cheryl
Published: June 2003

There is general agreement that mass political parties emerged during the Jacksonian era, but there is no consensus about their precise origins. Institutional theorists within political science contend that political parties trace their beginnings to elite who nurtured them within the civil service bureaucracy, whereas theorists in political science who rely on microlevel explanations consider that parties developed to solve problems of social choice and collective action. Historians, in contrast, indicate that newspaper patronage in Washington, DC, beginning with Jefferson, was critical for the emergence of federal political parties. This study systematically examines the empirical implications of that assumption and considers both the organizational and political processes that underlie establishment of newspapers in the Capital, contributing to the understanding that newspapers provided a model both for the civil service and for political parties.
Dimensions of Participation in a Professional Social‐Movement Organization
Authors: Cohn Steven F. , Barkan Steven E. , Halteman William A.
Published: June 2003

Differential participation after recruitment remains a black box in the social‐movement and voluntary‐association literatures. This paper identifies several dimensions of membership participation in a professional social‐movement organization (SMO) with a national membership and analyzes the determinants of differential involvement in these forms. In general, members’ ideological beliefs, social and organizational ties, perceptions about their SMO, and communication with SMO officials all predict participation across the various forms. Our findings extend previous work on differential participation in three ways. First, we statistically isolate cultural dimensions of postrecruitment participation and, in so doing, complement recent ethnographic research. Second, our findings suggest that the distinct dimensions of external and internal participation found by Knoke (1988) in a national sample of voluntary associations may not generalize to national SMOs studied individually. Third, our results indicate that models combining ideological and microstructural factors should explain the multiple forms of participation in SMOs lacking these distinct dimensions.
The Forgotten Movement: The Vietnam Antiwar Movement
Authors: Fendrich James Max
Published: June 2003

Utilizing recent research and monographs from participants and observers, this paper reports on the underanalyzed Vietnam antiwar movement. Key events are placed in a historical context that help to explain the origins of the movement. Particular attention is given to the various responses of the state to the challengers and the complex interrelationships with the media. As the antiwar movement grew and developed, there were multiple factors that contributed to solidarity and factionalism within the movement. Despite state repressive actions and internal factionalism, the movement was successful in helping to end the war. The effects on U.S. policies were more indirect than direct. The antiwar movement mobilized millions of citizens to public protest. The demonstrations helped to shift public opinion away from supporting the war and activated third parties to question and demand an end to war policies. The political system did respond to the antiwar movement's demands.
Why Territorial Disintegration Has Not Occurred in Russia: Applying State Breakdown Theories to Explain Stability
Authors: Li Rebecca S. K.
Published: June 2003

Much has been written to explain the collapse of the former Soviet Union. Little attention, however, has been paid to understanding why post‐1991 Russia has maintained stability despite continued economic and political turmoil throughout the 1990s. This paper attempts to answer this question by applying an integrated model of territorial disintegration to examine the political, economic, demographic, and geopolitical changes in the pre‐1991 Soviet Union and post‐1991 Russia. The integrated model is constructed by synthesizing Goldstone's demographic‐structural model, Skocpol's and Collins’ geopolitical model, and a modified version of Collins’ argument of the destabilizing potential brought about by rapid market development as three alternative routes to territorial disintegration. It is found that improvement in Russia's geopolitical condition after 1991 is largely responsible for the decline in disintegrative potential. Slower population growth also rendered the demographic route less disintegrative during the 1990s. More effective taxation and the availability of foreign loans enabled the Russian state to handle its financial crises, thereby curbing the development of destabilizing forces through the dynamics proposed by Collins.
Competition, Race, and the Measurement of Female Labor Activity
Authors: Baunach Dawn Michelle , Barnes Sandra L.
Published: June 2003

Not all groups compete equally in the labor market. Here, we focus on women's competition with men for jobs. This competition assumes that women's employment is affected by men’s, and vice versa. We use two statistics—female labor force participation and share—to uncover this competition. 1990 U.S. census data on 281 metropolitan statistical areas were analyzed using weighted least squares regression. Supply‐side explanations of female labor activity (education, children, household headship, and government assistance) receive more support than demand‐side explanations (poverty, industrial mix, and region). Evidence of competition along gender and race lines is found. Men's employment is buttressed in metropolitan areas by higher wages, less poverty, and more women with children. Welfare benefits (AFDC) and deindustrialization lower black women's employment, while only white women benefit from advanced education and a “feminized” occupational structure. Implications for future research and policy are discussed.
Feminism and Military Gender Practices: Israeli Women Soldiers in “Masculine” Roles
Authors: Sasson‐Levy Orna
Published: June 2003

Women's military service is the focus of an ongoing controversy because of its implications for the gendered nature of citizenship. While liberal feminists endorse equal service as a venue for equal citizenship, radical feminists see women's service as a rei•cation of martial citizenship and cooperation with a hierarchical and sexist institution. These debates, however, tend to ignore the perspective of the women soldiers themselves.

This paper seeks to add to the contemporary debate on women's military service the subjective dimension of gender and national identities of women soldiers serving in “masculine” roles. I use a theory of identity practices in order to analyze the interaction between state institutions and identity construction. Based on in‐depth interviews, I argue that Israeli women soldiers in “masculine” roles shape their gender identities according to the hegemonic masculinity of the combat soldier through three interrelated practices: (1) mimicry of combat soldiers’ bodily and discursive practices; (2) distancing from “traditional femininity”; and (3) trivialization of sexual harassment.

These practices signify both resistance and compliance with the military dichotomized gender order. While these transgender performances subvert the hegemonic norms of masculinity and femininity, they also collaborate with the military androcentric norms. Thus, although these women soldiers individually transgress gender boundaries, they internalize the military's masculine ideology and values and learn to identify with the patriarchal order of the army and the state. This accounts for a pattern of “limited inclusion” that reaf•rms their marginalization, thus prohibiting them from developing a collective consciousness that would challenge the gendered structure of citizenship.
Book Review
Authors: Archibald Sarah
Published: June 2003

Book reviewed:

Jonathan H. Pincus, Basic Instincts: What Makes Killers Kill
The Plasma Membrane Calcium‐ATPase as a Major Mechanism for Intracellular Calcium Regulation in Neurones from the Rat Superior Cervical Ganglion
Authors: Wanaverbecq N. , Marsh S. J. , Al‐Qatari M. , Brown D. A.
Published: June 2003

Patch‐clamp recording combined with indo‐1 measurement of free intracellular calcium concentration ([Ca2+]i) was used to determine the homeostatic systems involved in the maintenance of resting [Ca2+]i and in the clearance of Ca2+ transients following activation of voltage‐gated Ca2+ channels in neurones cultured from rat superior cervical ganglion (SCG). The Ca2+ binding ratio was estimated to be ∼500 at 100 nM, decreasing to ∼250 at [Ca2+]i≈ 1 μM, and to involve at least two buffering systems with different affinities for Ca2+. Removal of extracellular Ca2+ led to a decrease in [Ca2+]i that was mimicked by the addition of La3+, and was more pronounced after inhibition of the endoplasmic reticulum Ca2+ uptake system (SERCA). Inhibition of the plasma membrane Ca2+ pump (PMCA) by extracellular alkalinisation (pH 9) or intracellular carboxyeosin both increased resting [Ca2+]i and prolonged the recovery of Ca2+ transients at peak [Ca2+]i⩽ 500 nM. For [Ca2+]i loads > 500 nM, recovery showed an additional plateau phase that was abolished in m‐chlorophenylhydrazone (CCCP) or on omitting intracellular Na+. Inhibition of the plasma membrane Na+ ‐Ca2+ exchanger (NCX) and of SERCA had a small but significant additional effect on the rate of decay of these larger Ca2+ transients. In conclusion, resting [Ca2+]i is maintained by passive Ca2+ influx and regulated by a large Ca2+ buffering system, Ca2+ extrusion via a PMCA and Ca2+ transport from the intracellular stores. PMCA is also the principal Ca2+ extrusion system at low Ca2+ loads, with additional participation of the NCX and intracellular organelles at high [Ca2+]i.
Sugar Transport by Mammalian Members of the SLC26 Superfamily of Anion‐Bicarbonate Exchangers
Authors: Chambard J‐M. , Ashmore J. F.
Published: June 2003

The mammalian cochlea contains a population of outer hair cells (OHCs) whose electromotility depends on an assembly of ‘motor’ molecules in the basolateral membrane of the cell. Named ‘prestin’, the molecule is a member of the SLC26 anion transporter superfamily. We show both directly and indirectly that SLC26A5, rat prestin, takes up hexoses when expressed in several cell lines. Direct measurements of labelled fructose transport into COS‐7 cells expessing prestin are reported here. Indirect measurements, using imaging techniques, show that transfected HEK‐293 or CHO‐K1 cells undergo reversible volume changes when exposed to isosmotic glucose‐fructose exchange. The observations are consistent with the sugar transport. A similar transport was observed using a C‐terminal green fluorescent protein (GFP)‐tagged pendrin (SLC26A4) construct. Cells transfected with GFP alone did not respond to sugars. The data are consistent with fructose being transported by prestin with an apparent Km= 24 mm. From the voltage‐dependent capacitance of transfected cells, we estimate that 250 000 prestin molecules were present and hence that the single transport rate is not more than 3000 fructose molecules s−1. Comparison of the transfected cell swelling rates induced by fructose and by osmotic steps indicates that water was co‐transported with sugar. We suggest that the structure of SLC26 family members allows them to act as neutral substrate transporters and may explain observed properties of cochlear hair cells.
Sex differences in the modulation of K+ currents in diabetic rat cardiac myocytes
Authors: Shimoni Yakhin , Liu Xiu‐Fang
Published: June 2003

A transient (Ipeak) and a sustained (Isus) outward K+ current were measured, using whole‐cell voltage‐clamp methods, in isolated rat ventricular myocytes obtained by enzymatic dispersion. A comparison was made between male and female rats following induction of (insulin‐deficient) diabetes with streptozotocin (STZ). In control (non‐diabetic) rats, both currents were smaller in cells obtained from females, as compared to males (P < 0.005). However, whereas inducing diabetes in male rats significantly attenuated both Ipeak and Isus (P < 0.005), Ipeak was unchanged in female diabetic rats. Isus was significantly (P < 0.005) reduced, but the extent of reduction was smaller (P < 0.02) than in males. The formation of angiotensin II (ATII) or endothelin‐1 (ET‐1) was blocked using inhibitors of angiotensin‐converting enzyme (ACE) and endothelin‐converting enzyme (ECE), respectively. In cells from diabetic males both inhibitors significantly (P < 0.005) enhanced K+ currents. In contrast, no effect was observed in cells from female diabetic rats. However, in ovariectomized (Ovx) diabetic females the in vitro inhibition of ATII and ET‐1 formation augmented the two K+ currents, but not when oestradiol was administered in vivo prior to cell isolation. In cells from diabetic males, incubation with 100 nM 17β‐oestradiol significantly (P < 0.005) enhanced both Ipeak and Isus. This effect was blocked if ATII or ET‐1 was added to the medium. These results show that autocrine modulation of K+ currents by renin‐angiotensin and endothelin systems is attenuated or absent in female diabetic rats. Oestradiol plays a key role in reducing this modulation. These results may underlie some of the sex differences associated with development of cardiac arrhythmias.
Hyperpolarizing Inhibition Develops without Trophic support by GABA in Cultured Rat Midbrain Neurons
Authors: Titz Stefan , Hans Michael , Kelsch Wolfgang , Lewen Andrea , Swandulla Dieter , Misgeld Ulrich
Published: June 2003

During a limited period of early neuronal development, GABA is depolarizing and elevates [Ca2+]i, which mediates the trophic action of GABA in neuronal maturation. We tested the attractive hypothesis that GABA itself promotes the developmental change of its response from depolarizing to hyperpolarizing (Ganguly et al. 2001). In cultured midbrain neurons we found that the GABA response changed from depolarizing to hyperpolarizing, although GABAA receptors had been blocked throughout development. In immature neurons prolonged exposure of the cells to nanomolar concentrations of GABA or brief repetitive applications of GABA strongly diminished the elevation of [Ca2+]i by GABA. As revealed by gramicidin perforated‐patch recording, reduced [Ca2+]i responses were due to a diminished driving force for Cl−. This suggests that immature neurons do not have an efficient inward transport that can compensate the loss of cytosolic Cl− resulting from sustained GABAA receptor activation by ambient GABA. Transient increases in external K+, which can induce voltage‐dependent Cl− entry, restored GABA‐induced [Ca2+]i elevations. In mature neurons, GABA reduced [Ca2+]i provided that background [Ca2+]i was elevated by the application of an L‐type Ca2+ channel agonist. This was probably due to a hyperpolarization of the membrane by Cl− currents. K+‐Cl− cotransport maintained the gradient for hyperpolarizing Cl− currents. We conclude that in immature midbrain neurons an inward Cl− transport is not effective although the GABA response is depolarizing. Further, GABA itself is not required for the developmental switch of GABAergic responses from depolarizing to hyperpolarizing in cultured midbrain neurons.
Presynaptic Rat Kv1.2 Channels Suppress Synaptic Terminal Hyperexcitability Following Action Potential Invasion
Authors: Dodson Paul D. , Billups Brian , Rusznák Zoltán , Szucs Géza , Barker Matthew C. , Forsythe Ian D.
Published: June 2003

Voltage‐gated K+ channels activating close to resting membrane potentials are widely expressed and differentially located in axons, presynaptic terminals and cell bodies. There is extensive evidence for localisation of Kv1 subunits at many central synaptic terminals but few clues to their presynaptic function. We have used the calyx of Held to investigate the role of presynaptic Kv1 channels in the rat by selectively blocking Kv1.1 and Kv1.2 containing channels with dendrotoxin‐K (DTX‐K) and tityustoxin‐Kα (TsTX‐Kα) respectively. We show that Kv1.2 homomers are responsible for two‐thirds of presynaptic low threshold current, whilst Kv1.1/Kv1.2 heteromers contribute the remaining current. These channels are located in the transition zone between the axon and synaptic terminal, contrasting with the high threshold K+ channel subunit Kv3.1 which is located on the synaptic terminal itself. Kv1 homomers were absent from bushy cell somata (from which the calyx axons arise); instead somatic low threshold channels consisted of heteromers containing Kv1.1, Kv1.2 and Kv1.6 subunits. Current‐clamp recording from the calyx showed that each presynaptic action potential (AP) was followed by a depolarising after‐potential (DAP) lasting around 50 ms. Kv1.1/Kv1.2 heteromers had little influence on terminal excitability, since DTX‐K did not alter AP firing. However TsTX‐Kα increased DAP amplitude, bringing the terminal closer to threshold for generating an additional AP. Paired pre‐ and postsynaptic recordings confirmed that this aberrant AP evoked an excitatory postsynaptic current (EPSC). We conclude that Kv1.2 channels have a general presynaptic function in suppressing terminal hyperexcitability during the depolarising after‐potential.
Experimental Investigation of Multiple Solutions for Liquid Holdup in Upward Inclined Stratified Flow
Authors: Smith Steven P. , Gregory Garry A. , Yarranton Harvey W.
Published: June 2003

The mechanistic model of Taitel and Dukler [1] has previously been reported to exhibit a region in which three solutions exist for the height of the gas-liquid interface in the stratified/wave flow regime. Most laboratory studies have not dealt with flow rates in the ranges where the multiple solutions occur. An experimental study has been carried out at the University of Calgary to obtain such data. The object of this work is to review the relevant theory, investigate situations where theory suggests that multiple solutions should exist, and attempt to show whether or not such solutions do physically exist.
Slug Detection as a Tool for Predictive Control of GLCC© Compact Separators
Authors: Earni Shankar , Wang Shoubo , Mohan Ram S. , Shoham Ovadia , Marrelli Jack D.
Published: June 2003

Current design and performance of the GLCC©1 separator is dependent on the prediction of the upstream inlet flow conditions based on available models. It is expected that early detection of terrain slugging (slug length, slug velocity and holdup) and controlling the liquid level in the GLCC using feed forward mechanism can improve the operational range of the GLCC, by decreasing the gas carry under and liquid carry over, and thereby decreasing the control valve dynamics. The conventional feedback control loops can seldom achieve perfect control considering the impact of huge slugs that are keeping the output of the process continuously away from desired set point value. The reason is simple: a feedback controller reacts only after it has detected a deviation in the value of the level from the set point. Unlike the feedback systems, a feed forward control configuration measures the disturbance directly and takes control action to negate the effect of the disturbance on liquid level in the GLCC. Therefore, a feed forward control system has the theoretical potential for perfect control if the slug detection and characterization are perfect. A strategy for GLCC predictive control has been proposed which integrates the feedback and feed forward loops to compensate for error due to modeling and slug characterization. A model has been developed for predictive control system design and simulated in MATLAB-Simulink®. Experimental results obtained demonstrate that the proposed strategy is a viable approach for GLCC predictive control.
Char Attrition from Australian Black Coals in Pressurized Fluidized Bed Combustion
Authors: Wang Alan L. T. , Stubington John F.
Published: June 2003

Char attrition is the main mechanism for the fine char generation in PFBC. The char attrition rates were significantly different for each of the two coal chars tested. Specific char attrition rate increased with the surface porosity of burning char particles. A coal with higher ratio of telocollinite/inertinite contents formed chars in PFBC with larger pores or higher porosity during devolatilization, which resulted in a higher specific attrition rate.
Possible Detection of Multiple Blockages Using Transients
Authors: Adewumi Michael A. , Eltohami E. S. , Solaja A.
Published: June 2003

This work explores the possibility of utilizing the interaction between a pressure pulse propagating in a pipe with the blockages therein, as a means of blockage detection and characterization. Whereas an earlier work focused on a single blockage, the present work attempts to extend the strategy to multiple blockages. A one-dimensional isothermal non-compositional single-phase Eulerian model was used to describe the propagation of a pressure pulse through a pipe with multiple blockages. Pressure variations at the inlet caused by reflections of the propagating transient are monitored and analyzed. This analysis is used to make deductions about the internal configuration of the pipe. The results demonstrate that the technique is feasible and that accurate characterization of multiple blockages is possible.
Modeling and Simulation of PEM Fuel Cells With CO Poisoning
Authors: Baschuk Jeffrey J. , Rowe Andrew M. , Li Xianguo
Published: June 2003

A polymer electrolyte membrane (PEM) fuel cell is analyzed by applying the conservation principle to the electrode backing, catalyst layers and polymer electrolyte. The conservation equations used are the conservation of species, momentum and energy, with the Nernst-Planck equation used for the electrolyte. Oxygen reduction at the cathode is modeled using the Butler-Volmer equation while the adsorption, desorption and electro-oxidation of hydrogen and CO at the anode are modeled by the Tafel-Volmer and “reactant-pair” mechanism, respectively. Temperature variations within the cell are minimized by decreasing current density or increasing temperature. An increase in pressure increases the cell voltage at low current density, but decreases the cell voltage at high current density. The electrochemical kinetics model used for the adsorption, desorption and electro-oxidation of hydrogen and CO is validated with published, experimental data.
Experimental Studies on a Heat Pump Operating With R22, R407C and R407A: Comparison From an Exergy Point of View
Authors: Rakhesh B. , Venkatarathnam G. , Murthy S. Srinivasa
Published: June 2003

Experiments are conducted on a heat pump with refrigerants R22, R407C and R407A. The performance is compared in terms of coefficient of performance, heating/cooling capacities, and exergy efficiency of the overall system. The results are analyzed from an exergy point of view to bring out the conditions under which the performance is maximum.
Stability of the Damped Mathieu Equation With Time Delay
Authors: Insperger T. , Ste´pa´n G.
Published: June 2003

In the space of the system parameters, the stability charts are determined for the delayed and damped Mathieu equation defined as x¨t+κx˙t+δ+ε cos txt=bxt−2π. This stability chart makes the connection between the Strutt-Ince chart of the damped Mathieu equation and the Hsu-Bhatt-Vyshnegradskii chart of the autonomous second order delay-differential equation. The combined charts describe the intriguing stability properties of an important class of delayed oscillatory systems subjected to parametric excitation.
Memoryless Adaptive Decentralized Sliding Mode Control for Uncertain Large-Scale Systems With Time-Varying Delays
Authors: Yan Jun-Juh
Published: June 2003

The problem of robust stabilization for uncertain large-scale systems with time-varying delays is investigated through sliding mode control. A memoryless adaptive decentralized sliding mode controller (ADSMC) is developed. The proposed controller ensures the occurrence of the sliding manifold of the composite system. It is worthy of note that the proposed ADSMC does not involve any information of coupling states and is a local controller. Furthermore, it also does not include any delayed state or the upperbounds of uncertainties. Thus, such ADSMC is memoryless, and the limitation of knowing the upperbounds of uncertainties in advance is certainly released. A numerical example is given to verify the validity of the developed memoryless ADSMC.
Output Feedback H∞ Control Problem for Linear Neutral Systems: Delay Independent Case
Authors: Bas¸er Ulviye
Published: June 2003

This paper presents the solution of output feedback H∞ control problem for linear neutral systems with unknown constant multiple state delays in delay independent case, without any restrictions on plant matrices D12 and D21. First, some sufficient conditions for the solution of this problem are obtained in closed-loop system matrices in both linear matrix inequality (LMI) and algebraic Riccati inequality (ARI) forms, by standard Lyapunov-Krazovskii functional in delay independent multi-delay case. Because of the complexity of the solution of the compensator from these inequalities, equivalent sufficient conditions are derived for designing output feedback controller which stabilizes the closed-loop neutral system under consideration and guarantees an H∞-norm bound constraint on the disturbance attenuation. These conditions are of the form two ARIs and, for simplicity in computation equivalent LMIs are given. Finally, output feedback H∞ controller design is achieved and the results are illustrated in some numerical examples.
Adaptive Control of a Class of Time-Delay Systems
Authors: Evesque S. , Annaswamy A. M. , Niculescu S. , Dowling A. P.
Published: June 2003

The control of physical systems in the presence of time-delays becomes particularly challenging when parametric uncertainties are present. To cope with these ubiquitous uncertainties, we propose an adaptive controller in this paper that can accommodate both a time-delay and parametric uncertainties. The controller includes a) a control architecture that is based on the plant relative degree rather than the plant order, b) an integral implementation of the well known Posicast Controller so as to accommodate unstable plants, c) high-order tuners for parameter adaptation, and d) a Lyapunov-Krasvoskii functional that allows adaptive stabilization. The controller is shown to be semi-global in the time-delay τ and to result in asymptotic tracking. The implications of the adaptive controller are explored in the context of combustion control through simulation studies. Robustness properties of the controller are briefly discussed.
Degenerate Cases in Using the Direct Method
Authors: Sipahi Rifat , Olgac Nejat
Published: June 2003

A recent stability analysis, the Direct Method, for linear time invariant, time delayed systems (LTI-TDS) is revisited in this work considering the degenerate system dynamics. The principal strengths and enabling novelties of the method are reviewed along with its structured steps involved for assessing the stability. Uncommon in the literature, the Direct Method can handle large dimensional systems (e.g., larger than two) very comfortably. It returns an explicit formula for the exact stability posture of the system for a given time delay, as such it reveals the possible detached stability pockets throughout the time delay axis. Both retarded and neutral classes of LTI-TDS are considered in this work. The main contribution here is to demonstrate the ability of the Direct Method in tackling degenerate cases. Along with the analytical arguments, example case studies are provided for a group of degeneracies. It is shown that the new method is capable of resolving them without any difficulty.
Annular Bounds for the Roots of Characteristic Equations of Uncertain Discrete Systems
Authors: Sun Yeong-Jeu
Published: June 2003

In this paper, we provide the annular bound, i.e., lower and upper circular bound, for the roots of characteristic equations of uncertain discrete systems. Such an annular bound can be easily obtained by estimating the largest nonnegative zero of the specific polynomial. Two examples are also provided to show that the proposed annular bound is less conservative than the existing one reported recently.
Control Techniques and Programming Issues for Time Delayed Internet Based Teleoperation
Authors: Munir Saghir , Book Wayne J.
Published: June 2003

This article focuses on Internet-based real time control, such as remote bilateral teleoperation. In such applications, it is required that the control loop be closed through a time delayed network. This paper focuses on two control strategies (based on wave variables and a time forward observer), bandwidth issues, and some related programming details. Experimental results of bilateral teleoperation via the Internet between Atlanta and Tokyo are given. The system used is a two-degree-of-freedom haptic interface, bilaterally coupled to a simulation (implemented on a windows NT based computer) of a similar system.
Analysis of a System of Linear Delay Differential Equations
Authors: Asl Farshid Maghami , Ulsoy A. Galip
Published: June 2003

A new analytic approach to obtain the complete solution for systems of delay differential equations (DDE) based on the concept of Lambert functions is presented. The similarity with the concept of the state transition matrix in linear ordinary differential equations enables the approach to be used for general classes of linear delay differential equations using the matrix form of DDEs. The solution is in the form of an infinite series of modes written in terms of Lambert functions. Stability criteria for the individual modes, free response, and forced response for delay equations in different examples are studied, and the results are presented. The new approach is applied to obtain the stability regions for the individual modes of the linearized chatter problem in turning. The results present a necessary condition to the stability in chatter for the whole system, since it only enables the study of the individual modes, and there are an infinite number of them that contribute to the stability of the system.
Optimal Sampled-Data Reconstruction of Stochastic Signals With Preview
Authors: Polyakov K. Yu. , Rosenwasser E. N. , Lampe B. P.
Published: June 2003

The problem of H2-optimal reconstruction of a continuous-time signal using a stable sampled-data filter is considered. The signal is corrupted by additive noise and is measured with preview of τ, i.e., it is known in advance over the interval τ. This problem is equivalent to delayed signal reconstruction. A rigorous solution of the problem is presented on the basis of the parametric transfer function approach. Explicit expressions are given for the order of the optimal filter. A lower bound is obtained for the cost function for τ→∞, and it is shown that this bound depends on the ratio of the preview interval to the sampling period.
Survey on Recent Results in the Stability and Control of Time-Delay Systems*
Authors: Gu Keqin , Niculescu Silviu-Iulian
Published: June 2003

This paper gives a broad overview of the stability and control of time-delay systems. Emphasis is on the more recent progress and engineering applications. Examples of practical problems, mathematical descriptions, stability and performance analysis, and feedback control are discussed.
Constructive Filtering Algorithms for Delayed Systems With Uncertain Statistics
Authors: Ahmedova N. K. , Kolmanovskii V. B. , Matasov A. I.
Published: June 2003

A stochastic optimal guaranteed estimation problem for dynamic delayed systems with uncertain statistics is considered. The solution of this problem reduces to a complex nonsmooth extremal problem. To obtain an approximate solution, the nonsmooth problem is replaced by a smooth one. Constructive filtering algorithms are obtained from an approximate solution of the smooth problem under the assumption that the delay is small in comparison with the observation time. Estimates for the nonoptimality levels of the proposed filtering algorithms are derived.
Exponential Stability for Continuous-Time Singular Systems With Multiple Time Delays
Authors: Sun Yeong-Jeu
Published: June 2003

In this paper, the global exponential stability for a class of singular systems with multiple time delays is investigated. Simple stability criterion is derived to guarantee the global exponential stability of such systems. Moreover, an estimate of the convergence rate of such stable systems is presented. A numerical example is also provided to illustrate the main result.
Delay-Dependent Anti-Windup Loops for Enlarging the Stability Region of Time Delay Systems With Saturating Inputs
Authors: Tarbouriech S. , da Silva, J. M. Gomes , Garcia G.
Published: June 2003

This paper addresses the problem of the determination of regions of stability for linear systems with delayed inputs and subject to input saturation through anti-windup strategies. Differently of the most anti-windup techniques, where the design of the anti-windup loop is introduced with the objective of minimizing the performance degradation, we are particularly interested in the synthesis of anti-windup gains in order to guarantee the stability of the closed-loop system for regions of admissible initial states as large as possible. With this aim, due to the presence of delay in the input we propose delay dependent results.
Chebyshev Expansion of Linear and Piecewise Linear Dynamic Systems With Time Delay and Periodic Coefficients Under Control Excitations
Authors: Ma Haitao , Butcher Eric A. , Bueler Ed
Published: June 2003

In this paper, a new efficient method is proposed to obtain the transient response of linear or piecewise linear dynamic systems with time delay and periodic coefficients under arbitrary control excitations via Chebyshev polynomial expansion. Since the time domain can be divided into intervals with length equal to the delay period, at each such interval the fundamental solution matrix for the corresponding periodic ordinary differential equation (without delay) is constructed in terms of shifted Chebyshev polynomials by using a previous technique that reduces the problem to a set of linear algebraic equations. By employing a convolution integral formula, the solution for each interval can be directly obtained in terms of the fundamental solution matrix. In addition, by combining the properties of the periodic system and Floquet theory, the computational processes are simplified and become very efficient. An alternate version, which does not employ Floquet theory, is also presented. Several examples of time-periodic delay systems, when the excitation period is equal to or larger than the delay period and for linear and piecewise linear systems, are studied. The numerical results obtained via this method are compared with those obtained from Matlab DDE23 software (Shampine, L. F., and Thompson, S., 2001, “Solving DDEs in MATLAB,” Appl. Numer. Math., 37(4), pp. 441–458.) An error bound analysis is also included. It is found that this method efficiently provides accurate results that find general application in areas such as machine tool vibrations and parametric control of robotic systems.
Synthesis of Controllers for Time-Delay Systems Subject to Actuator Saturation and Disturbance
Authors: Oucheriah Said
Published: June 2003

The problem of robust stabilization of a class of dynamic systems subject to time delays, external disturbance, and control saturation is addressed in this paper. Delay-dependent sufficient conditions via LMI formulation are derived to guarantee that the solutions of the system considered are uniformly bounded. The problem of designing memoryless linear state feedback controllers such that the domain of safe admissible initial states is enlarged is formulated and solved as an optimization problem with LMI constraints. Finally, an example is included to illustrate the results developed in this paper.
Mixed H2/H∞ Control for State-Delayed Linear Systems and a LMI Approach to the Solution of Coupled AREs
Authors: Aliyu M. D. S.
Published: June 2003

In this paper, the state-feedback mixed H2/H∞ control problem for state-delayed linear systems is considered. Sufficient conditions for the solvability of this problem are given in terms of the solution to a pair of algebraic Riccati equations similar to the nondelayed case. However, these Riccati equations are more difficult to solve than those arising in the pure H2, H∞ problems, and an alternative approach is to solve a pair of linear matrix inequalities (LMIs).
Sliding Mode Control for Nonlinear Systems with Output Delay Via Method of Stable System Center*
Authors: Shtessel Yuri B. , Zinober Alan S. I. , Shkolnikov Ilia A.
Published: June 2003

Output tracking in causal nonlinear systems with an output time delay is considered using sliding mode control. The problem is reduced to that of the tracking of the output reference profile given by an exogenous system in a causal non-minimum phase system without delay, where the delay is being replaced by its Pade’ approximation. The non-minimum phase output-tracking problem is transformed to a corresponding state tracking problem. Bounded state tracking profiles are generated by equations of the stable system center. A sliding mode control algorithm is developed. A numerical example demonstrates the effectiveness of the sliding mode control design.
Output-Feedback Model Reference Adaptive Control for Continuous State Delay Systems
Authors: Mirkin Boris M. , Gutman Per-Olof
Published: June 2003

This paper develops a new approach for the output model reference adaptive control of linear continuous-time plants with state delays. The main idea is to include into the control law a feedforward component that compensates for the delayed states, in addition to output feedback. The feedforward is formed by special adaptively adjusted prefilters as a function of the delayed state of the reference model. The output feedback component is designed as for a plant without delay, but applied to the time-delay plant. Such a controller structure containing adaptive output feedback and adaptive prefilters from the delayed reference model makes it possible to solve the problem of adaptive exact asymptotic output tracking under parametric uncertainties. The stability is analyzed using the Lyapunov-Krasovskii functional method. A simulated example illustrates the new controller.
Preservation of the Full Relative Degree for a Class of Delay Systems Under Sampling
Authors: Pepe P.
Published: June 2003

This paper addresses the problem of the preservation of the full relative degree under sampling, for a particular class of nonlinear time delay systems, on the basis of the work by Barbot, Monaco, and Normand-Cyrot, (“A Sampled Normal Form for Feedback Linearization,” Mathematics of Control, Signals and Systems, 1996. No. 9, pp. 162–188). The preservation of the relative degree, in order to build up the control law, has many advantages in the delayless case. The results of this paper are a first step in order to achieve the same advantages in the delayed case, too.