bluuebunny/crossref_metadata_2025 huggingface dataset:
Cat allergen‐induced cytokine secretion and Fel d 1–immunoglobulin G immune complexes in cord blood
Authors: Casas R. , Jenmalm M. C. , Björkstén B.
Published: April 2004

Background
We have recently obtained evidence for the presence of immune complexes (IC) in cord blood from allergic and non‐allergic mothers. Such complexes could conceivably provide the fetus with the initial trigger for the priming of the T cell system already in utero.

Objective
To relate the presence of Fel d 1–IgG IC to T cell cytokine production in cord blood mononuclear cells (CBMCs) after stimulation with cat allergen.

Methods
CBMC obtained from babies of 15 allergic and 22 non‐allergic mothers were cultured in the presence of cat allergen. The production of IFN‐γ, IL‐5, IL‐10 and IL‐13 was determined by ELISA. Furthermore, IgG1 and IgG4 antibodies to cat allergen in cord blood samples were measured by ELISA. A more sensitive ELISA was used to measure Fel d 1–IgG IC.

Results
The prevalence and levels of IC were similar in cord blood from children of allergic and non‐allergic mothers. The production of IL‐5, IL‐10. IL‐13 and IFN‐γ by CBMC was not influenced by maternal atopy, but IFN‐γ was less commonly detected in samples with IC. There was no association between the presence of IC and any other cytokines. The levels of IgG1 and IgG4 antibodies were similar in both groups, and tended to be associated with the presence of IC.

Conclusion
Immune complexes in cord blood may represent a normal mechanism for inducing primary immune responses, as the responses in babies from allergic and non‐allergic mothers were largely similar. Low levels of IFN‐γ seems to be related with the presence of IC in cord blood.
Intranasal treatment with ovalbumin but not the major T cell epitope ovalbumin 323–339 generates interleukin‐10 secreting T cells and results in the induction of allergen systemic tolerance
Authors: Barbey C. , Donatelli‐Dufour N. , Batard P. , Corradin G. , Spertini F.
Published: April 2004

Background
Nasal administration of major peptide T cell epitopes gives contradictory data on the induction of peripheral tolerance.

Objective
To compare the prophylactic effect of intranasal treatment (INT) on the development of an allergic response, using either ovalbumin (OVA) or its major T cell epitope OVA 323–339 (OVAp).

Methods
BALB/c mice were treated intranasally with OVA or OVAp and subsequently immunized s.c. with OVA. Anti‐OVA‐specific antibody, T cell proliferation and cytokine responses were analysed. In an adoptive transfer model using OVAp specific TCR transgenic (Tg) T cells from D011.10 mice, in vivo tracking and characterization of transferred T cells in the cervical, inguinal and bronchial lymph nodes (BLN) and in the spleen were determined by FACS analysis.

Results
Prophylactic INT with OVA induced T cell tolerance towards subsequent OVA s.c. immunizations, inhibiting OVA specific T cell proliferation, IgE and IgG1 production, in contrast to INT with OVAp, which was unable to induce tolerance. In vivo analysis of transferred OVA‐specific TCR Tg T cells showed that INT with OVA induced a preferential activation of T cells in BLN, as opposed to a broad, systemic activation with OVAp. In vivo, OVAp INT led to faster and more sustained cell division cycles than OVA INT. Ex vivo, tolerance to OVA was associated with the generation of IL‐10 secreting CD4+ T cells in BLN of OVA‐treated mice only.

Conclusion
INT with OVA but not with OVAp led to regional (as opposed to systemic) T cell activation and the induction of IL‐10 secreting CD4+ T cells in BLN, potentially critical steps in the induction of T cell‐specific tolerance via the nasal route.
Effect of high‐frequency gastric electrical stimulation on gastric myoelectric activity in gastroparetic patients
Authors: Lin Z. , Forster J. , Sarosiek I. , McCallum R. W.
Published: April 2004

Abstract  The aim of this study was to investigate the effect of gastric electrical stimulation (GES) on gastric myoelectric activity (GMA) and to identify possible mechanisms that could help explain how high‐frequency GES is effective in treating nausea and vomiting associated with gastroparesis. Fifteen gastroparetic patients who received high‐frequency GES were enrolled. Two pairs of temporary pacing wires were implanted on the serosa of the stomach along the greater curvature during surgery for placement of the permanent stimulation device. Two‐channel serosal recordings of GMA before and during GES were measured. A gastric emptying test and severity of nausea and vomiting were assessed at baseline and at 3 months of GES. Power spectral and cross correlation analyses revealed that impaired propagation of slow waves (50%), tachygastria (30%) and abnormal myoelectric responses to a meal (50%) were the main abnormalities observed at baseline. GES with a high frequency significantly enhanced the slow wave amplitude and propagation velocity, and resulted in a significant improvement in nausea and vomiting but did not entrain the gastric slow wave or improve gastric emptying after 3 months of GES.
Otilonium bromide inhibits muscle contractions via L‐type calcium channels in the rat colon
Authors: Martin M. T. , Hove‐Madsen L. , Jimenez M.
Published: April 2004

Abstract  The aim of this study is to evaluate in vitro the effect of otilonium bromide (OB) on the mechanical and electrical activities of the rat colonic smooth muscle using muscle bath, microelectrodes and patch‐clamp techniques. Otilonium bromide dose dependently inhibited the spontaneous activity (logIC50 ± SE: −5.31 ± 0.05). This effect was not modified by TTX (10−6 mol L−1). Cyclic depolarizations were abolished by OB (10−4 mol L−1). Electrical field stimulation induced inhibitory junction potentials (IJPs) followed by a depolarization with superimposed spikes causing a contraction. In the presence of OB (10−4 mol L−1) IJPs were recorded, but spikes and contractions were abolished. Otilonium bromide (3 × 10−6 mol L−1) inhibited inward current obtained in isolated cells (amphotericin perforated patch technique). The otilonium‐sensitive current amplitude was maximal (75pA) around 0 mV. The effect of different doses of OB was tested by depolarizing cells from −70 mV to 0 mV. OB dose dependently inhibited the inward current with an EC50 of 885 nmol L−1. Abolishment of the otilonium‐sensitive current by 3 × 10−6 mol L−1 nifedipine confirmed that it was an L‐type Ca2+ current. Our results show that OB inhibits the spontaneous and triggered muscular contractions. This effect is produced by the inhibition of muscular action potentials carried by L‐type calcium current, confirming the spasmolytic properties of OB.
School's out! Why earlier among children of lone parents?
Authors: Weitoft Gunilla Ringbäck , Hjern Anders , Rosén Måns
Published: April 2004

The aims of this population‐based study were to analyse educational attainment at ages 24–25 among children of lone parents in comparison with children living with two biological parents, to increase understanding of the factors that seem to be of major importance in increased risks of lower educational achievement and to examine how the life circumstances of non‐custodial parents influence possible differences. We found that children who grew up with only one parent showed lower educational attainment than did children in two‐parent families. Poorer educational performance on the part of the offspring of lone parents can be explained to a large extent by socio‐economic disadvantage, especially a lack of economic resources. However, achievement varies according to cause of lone parenting, and findings strongly indicate that adjusting solely for custodial parents’ circumstances may lead to under‐estimation of the relationship. Lone parenting seems to have a more detrimental effect on girls’ education, and also within groups of children with highly educated parents than among those with a relatively low level of education.
Financial Liberalisation in Southern Africa: An Assessment
Authors: Nyawata Obert , Bird Graham
Published: April 2004

In the early 1990s many Southern African economies embarked on financial liberalisation. Although it is too soon to carry out sophisticated econometric analysis of this change in policy, the available empirical evidence may be inspected to see whether it lends support to advocates of financial liberalisation. In this article we explore the avenues through which financial liberalisation might be expected to exert an influence. Consistent with much of the existing literature, we discover that a degree of agnosticism is warranted. Financial liberalisation is no panacea and will not improve economic performance unless accompanied by sound economic policies. It remains difficult to isolate the effects of financial liberalisation from the data available.
A Comparison of Fathers’ and Mothers’ Talk to Toddlers in Low‐income Families
Authors: Rowe Meredith L. , Coker David , Pan Barbara Alexander
Published: April 2004

The purpose of this study was to provide descriptive information about low‐income fathers’ and mothers’ talk to toddlers and to re‐examine the bridge hypothesis (Gleason, 1975) in light of current changes in family structure and childcare responsibilities. Thirty‐three father–child and mother–child dyads were videotaped during semi‐structured free play at home. Fathers’ and mothers’ talk to children did not differ in amount, diversity of vocabulary, or linguistic complexity as measured by mean length of utterance. However, fathers produced more wh‐questions and explicit clarification requests, thus presenting more conversational challenges to children. Resident fathers employed more direct forms of prohibitives. Results suggest the need for closer examination of factors related to child‐directed speech in varying family configurations.
The Fate of Jewish Historiography after the Bible: A New Interpretation
Authors: Tropper Amram
Published: April 2004

What caused the eventual decline in later Jewish history of the vibrant historiographical tradition of the biblical period? In contrast to the plethora of historical writings composed during the biblical period, the rabbis of the early common era apparently were not interested in writing history, and when they did relate to historical events they often introduced mythical and unrealistic elements into their writings. Scholars have offered various explanations for this phenomenon; a central goal of this article is to locate these explanations within both the immediate historical setting of Roman Palestine and the overarching cultural atmosphere of the Greco‐Roman Near East. In particular, I suggest that the largely ahistorical approach of the rabbis functioned as a local Jewish counterpart to the widespread classicizing tendencies of a contemporary Greek intellectual movement, the Second Sophistic. In both cases, eastern communities, whose political aspirations were stifled under Roman rule, sought to express their cognitive and spiritual identities by focusing on a glorious and idealized past rather than on contemporary history.

Interestingly, the apparent lack of rabbinic interest in historiography is not limited to the early rabbinic period. Throughout the Middle Ages and into the Renaissance, Jews essentially did not write their political, diplomatic, or military history. Instead, Jews composed “traditional historiography” which included various types of literary genres among which the rabbinic “chain of transmission” was the most important. The chain of transmission reconstructs (or fabricates) the links that connect later rabbinic sages with their predecessors. Robert Bonfil has noted the similarity between this rabbinic project and contemporary church histories. Adding a diachronic dimension to Bonfil's comparison, I suggest that rabbinic chains of transmission and church histories are not similar though entirely independent phenomena, but rather their shared project actually derives from a common origin, the Hellenistic succession list. The succession list literary genre, which sketches the history of an intellectual discipline, apparently thrived during the Second Sophistic and diffused then into both rabbinic Judaism and early Christianity. Thus, even though historiography was not terribly important to the early rabbis or to most Second Sophistic intellectuals, the succession list schematic, or the history of an intellectual discipline, was evaluated differently. Rabbis and early Christians absorbed the succession list from Second Sophistic culture and then continued to employ this historiographical genre for many centuries to come.
Re‐Enactment and Radical Interpretation
Authors: D'Oro Giuseppina
Published: April 2004

This article discusses R. G. Collingwood's account of re‐enactment and Donald Davidson's account of radical translation. Both Collingwood and Davidson are concerned with the question “how is understanding possible?” and both seek to answer the question transcendentally by asking after the heuristic principles that guide the historian and the radical translator. Further, they both agree that the possibility of understanding rests on the presumption of rationality. But whereas Davidson's principle of charity entails that truth is a presupposition or heuristic principle of understanding, for Collingwood understanding rests on a commitment to internal consistency alone. Collingwood and Davidson diverge over the scope of the principle of charity because they have radically different conceptions of meaning. Davidson endorses an extensional semantics that links meaning with truth in the attempt to extrude intensional notions from a theory of meaning. Since radical translation rests on a truth‐conditional semantics, it rules out the possibility that there may be statements that are intelligible even though based on false beliefs. Collingwood's account of re‐enactment, on the other hand, disconnects meaning from truth, thereby allowing for the possibility of understanding agents who have false beliefs. The paper argues, first, that Davidson's account of radical translation rests on inappropriately naturalistic assumptions about the nature of understanding, and that Davidson commits this error because he develops his account of radical interpretation in response to an epistemological question that is motivated by a skeptical concern: “how can we know whether we have provided the correct interpretation?” Second, that in the twentieth century far too much philosophizing has been driven by epistemological concerns that have obscured attempts to provide adequate answers to the sort of conceptual question with which Collingwood is concerned, namely: “what does it mean to understand?”
Can the New Imperialism Triumph in the Age of Nation‐States?
Authors: Mann Michael
Published: April 2004

The Shield of Achilles: War, Peace, and the Course of History. By Philip Bobbitt
A Place for History
Authors: Matsuda Matt
Published: April 2004

Representing Place: Landscape Painting and Maps. By Edward Casey

Landscape, Nature, and the Body Politic: From Britain's Renaissance to America's New World. By Kenneth Robert Olwig
Voices of Silence
Authors: Gossman Lionel
Published: April 2004

Imperfect Histories: The Elusive Past and the Legacy of Romantic Historicism. By Ann Rigney
Cutaneous manifestations in the cardiofaciocutaneous syndrome, a variant of the classical Noonan syndrome. Report of a case and review of the literature
Authors: Weiss G , Confino Y , Shemer A , Trau H
Published: April 2004

We report one patient with cardiofaciocutaneous (CFC) syndrome. He presented with clinical findings characteristic of this condition such as: cutaneous abnormalities, including ichthyosis, widespread keratosis pilaris, a peculiar craniofacial appearance with sparse, curly hair and low‐set posteriorly rotated ears; congenital heart defects; and mild mental and motor retardation. We submit a comprehensive review of previously published articles regarding the dermatological findings in CFC syndrome (recently shown to be a variant of Noonan syndrome) emphasizing diagnostic criteria and its differentiation from the Costello syndrome.
Lipodystrophy following hepatitis infection: A causative relationship?
Authors: Khanna N , Sirka C , Gupta S , Singh M
Published: April 2004

Progressive partial lipodystrophy is a clinical syndrome characterized by progressive loss of subcutaneous fat. A 27‐year‐old female developed progressive loss of fat from the face and upper part of the torso associated with increased bulkiness of the body below the pelvis following an attack of hepatitis. She had been persistently hepatitis B surface antigen positive and her serum was positive for IgG antibodies to hepatitis B core antigen. Although the woman had hypocomplementaemia of the C3 component of complement, there was no evidence of renal involvement.
Cutaneous mastocytosis in children: a clinical analysis of 71 cases
Authors: Kiszewski AE , Durán‐Mckinster C , Orozco‐Covarrubias L , Gutiérrez‐Castrellón P , Ruiz‐Maldonado R
Published: April 2004

Objective  To characterize the clinical features, response to therapy, evolution and prognosis of cutaneous mastocytosis in children.

Background  Mastocytosis in children, instead of being induced by a potentially oncogenic c‐kit mutation is probably a clonal disease with benign prognosis.

Methods  The clinicopathological features, evolution and response to treatment were analysed in 71 children with mastocytosis.

Results  There were 53 (75%) cases of urticaria pigmentosa, 12 (17%) cases of mastocytoma, and six (8%) cases of diffuse cutaneous mastocytosis. In 92% of cases disease onset was in the first year of life. There was a male predominance 1.8 : 1. Treatment did not modify the disease evolution. Eighty per cent of patients improved or had spontaneous resolution of the disease.

Conclusion  The most frequent clinical form of mastocytosis was urticaria pigmentosa followed by mastocytoma and diffuse cutaneous mastocytosis. Darier's sign was present in 94% of cases. A negative Darier's sign does not rule out mastocytosis. In contrast to adults, mastocytosis in children usually has a benign course making sophisticated or invasive diagnostic tests unnecessary. A classification of paediatric cutaneous mastocytosis is proposed.
Bilateral naevus of Ota: a rare manifestation in a Caucasian
Authors: Turnbull JR , Assaf Ch , Zouboulis ChC , Tebbe B
Published: April 2004

The naevus of Ota (naevus fusculocoeruleus ophthalmomaxillaris) was first described by the Japanese dermatologist M. T. Ota in 1939. It has a reported incidence of 0.2% to 1% in the Japanese population. It usually occurs in the skin innervated by the first or second branch of the trigeminal nerve. The naevus comprises dermal melanocytes and is congenital or acquired during adolescence. Commonly associated lesions include scleral melanocytosis and other ocular manifestations as well as lesions of the tympanic membrane, oral and intranasal mucosa and leptomeninges. Diseases associated with Ota's naevus in rare cases are open‐angle glaucomas and melanoma. The naevus of Ota in Europeans is a rare manifestation. We report the very rare case of a bilateral naevus of Ota associated with enoral melanocytosis in a white European person.
PM‐SCL autoantibody positive scleroderma with polymyositis (mechanic's hand: clinical aid in the diagnosis)
Authors: Török L , Dankó K , Cserni G , Szûcs G
Published: April 2004

This report concerns a 56‐year‐old‐woman presenting PM‐SCL autoantibody positive scleroderma with dermatomyositis (scleromyositis) and concomitant interstitial lung fibrosis. The recently observed overlapping syndrome is characterized by the presence of specific autoantibodies, HLA–type association and benign course. A new skin symptom (‘mechanic's hands’) predicts the disease, in particular the interstitial lung pathology, which is its most relevant internal manifestation.
Agminated histiocytomas in a 23‐year‐old patient
Authors: Pock L , Konkol’ová R , Dragon J , Holíková Z , Hercogová J
Published: April 2004

A 23‐year‐old patient presented with a group of 17 reddish‐brown papules and nodules on the left shoulder lasting for 4 years. The histopathologic examination after a punch biopsy was repetitively consistent with the diagnosis of fibrous histiocytoma (FH). We use the term agminate histiocytomas for the first time to stress the presence of grouped lesions in one skin segment. Intralesional corticosteroids and cryotherapy were partially successful in this patient.
Information Transparency and Coordination Failure: Theory and Experiment
Authors: ANCTIL REGINA M. , DICKHAUT JOHN , KANODIA CHANDRA , SHAPIRO BRIAN
Published: April 2004

We examine the effect of higher order beliefs on the ability of decentralized decision makers to coordinate and take advantage of improvements in information transparency that can increase welfare. Theories that address this question have not been empirically explored. We study coordination in a laboratory experiment with privately informed decision makers. Economic outcomes in the setting depend both on agents' rational beliefs regarding economic fundamentals and on their rational beliefs regarding the beliefs of other agents. Increasing information transparency mitigates uncertainty about economic fundamentals but may increase strategic uncertainty, precipitating multiple equilibria and less efficient group outcomes. We provide evidence that sometimes the equilibrium attained by creditors is inferior from a welfare perspective to other available equilibria. Risk dominance appears to determine equilibrium selection in our setting.
Underwater Options and the Dynamics of Executive Pay‐to‐Performance Sensitivities
Authors: HALL BRIAN J. , KNOX THOMAS A.
Published: April 2004

We empirically analyze the dynamics of executives' pay‐to‐performance sensitivities. Option pay‐to‐performance sensitivities become weaker as options fall underwater, often leading to pressures to reprice options or restore pay‐to‐performance sensitivity in other ways. Building a detailed data set on executives' portfolios of stock and options, we find that the responsiveness of pay‐to‐performance sensitivities (created by all executive holdings of stock and options) to changes in stock price is large. The elasticity of pay‐to‐performance sensitivities with respect to stock price decreases is about 0.7 and is larger for high‐option executives and for executives with high percentages of options already underwater. The dominant mechanism through which companies offset declines in option pay‐to‐performance sensitivities is larger option grants following stock price declines; on average, these larger grants restore approximately 40% of the stock‐price‐induced pay‐to‐performance sensitivity declines. Option repricings are inconsequential in this regard, despite the attention they have attracted. In looking at positive returns, we find the reverse: higher returns both directly increase pay‐to‐performance sensitivities and lead to larger option grants, which raise pay‐to‐performance sensitivities further. Thus, option grants to executives tend to be largest following large stock price increases or large stock price decreases.
Evidence‐based Medicine for Apheresis: An Ongoing Challenge
Authors: McCarthy Leo J
Published: April 2004

Abstract:  Although much has been learned about the pathophysiologic process of thrombotic thrombocytopenic purpura (TTP) since Moschcowitz's initial description in 1924, its etiology and treatments remain problematic. We treated our first patient with TTP by plasma exchange in 1975 and have now treated over 160 patients. We report our experience exchanging patients using FFP, solvent detergent (SD) and cryopoor plasma as the exchange media. Most patients experience allergic reactions, some severe, during the course of treatment. However, use of SD plasma virtually eliminates all allergic reactions. Splenectomy was a much more common treatment prior to plasma exchange, but can still be a useful treatment option for some refractory patients. Recombinant ADAMTS‐13 can hopefully provide not only more useful diagnostic assays but also could provide specific and more efficacious treatment of patients with both acquired and familial forms of TTP.
Drug‐induced Thrombotic Thrombocytopenic Purpura/Hemolytic Uremic Syndrome: A Concise Review
Authors: Dlott Jeffrey S , Danielson Constance FM , Blue‐Hnidy Deborah E , J McCarthy Leo
Published: April 2004

Abstract:  An extensive variety of drugs have been associated with thrombotic thrombocytopenic purpura and hemolytic uremic syndrome (TTP/HUS). Although a direct causal effect has usually not been proven, the cumulative evidence linking several drugs with TTP/HUS is strong. This paper reviews several categories of drugs including antineoplastics, immunotherapeutics and antiplatelet agents that have been reported to induce TTP/HUS. The pathogenesis of drug‐induced TTP/HUS and the effectiveness of treatment regimens are also reviewed. A consensus on diagnostic criteria to accurately and consistently diagnose drug‐induced TTP is needed.
Synchronizing Tracking Control for Flexible Joint Robots via Estimated State Feedback
Authors: Rodriguez-Angeles Alejandro , Nijmeijer Henk
Published: April 2004

In this paper, we propose a synchronization controller for flexible joint robots, which are interconnected in a master-slave scheme. The synchronization controller is based on feedback linearization and only requires measurements of the master and slave link positions, since the velocities and accelerations are estimated by means of model-based nonlinear observers. It is shown, using Lyapunov function based stability analysis, that the proposed synchronization controller yields local uniformly ultimately boundedness of the closed loop errors. A tuning gain procedure is presented. The results are supported by simulations in a one degree of freedom master-slave system.
Design and Control of Optimal Scan Trajectories: Scanning Tunneling Microscope Example
Authors: Perez Hector , Zou Qingze , Devasia Santosh
Published: April 2004

This article addresses the optimal (minimal input energy) design of scan trajectories, which is important in applications such as the imaging and manipulation of nano-scale surface phenomena using scanning tunneling microscopes (STM), MEMS-based micro-scanners, quick-return mechanisms and cams used in manufacturing, and general repeating processes. The contribution of this article is the systematic solution of the optimal scan-trajectory design problem. As opposed to existing techniques that require pre-specification of the desired output trajectory (such prespecifications can be ad hoc), the optimal output trajectory is found as a result of the proposed input-energy minimization approach. In this sense, the proposed approach leads to a systematic solution of the optimal output-trajectory-design problem. The proposed optimal scanning method is applied to an experimental scanning tunneling microscope; simulation and experimental results are presented to illustrate the efficacy of the proposed approach to design optimal scan-trajectories.
Shaped Time-Optimal Feedback Controllers for Flexible Structures
Authors: Pao Lucy Y. , La-orpacharapan Chanat
Published: April 2004

This paper describes the design of closed-loop control laws for servomechanisms with one dominant flexible mode. An input shaping technique is employed to alter the rigid body phase-plane trajectory that is used in time-optimal servomechanisms. The resulting controllers lead to near time-optimal performance without unwanted residual vibrations. After the basic technique is outlined for a system with one undamped flexible mode, extensions are given considering different acceleration and deceleration capabilities, damping, and slew rate limits.
Co-Simulation of Algebraically Coupled Dynamic Subsystems Without Disclosure of Proprietary Subsystem Models
Authors: Gu Bei , Asada H. Harry
Published: April 2004

A method for simultaneously running a collection of dynamic simulators coupled by algebraic boundary conditions is presented. Dynamic interactions between subsystems are simulated without disclosing proprietary information about the subsystem models, as all the computations are performed based on input-output numerical data of encapsulated subsystem simulators coded by independent groups. First, this paper describes a system of interacting subsystems with a causal conflict as a high-index, Differential-Algebraic Equation (DAE), and develops a systematic solution method using Discrete-Time Sliding Mode control. Stability and convergence conditions as well as error bounds are analyzed by using nonlinear control theory. Second, the algorithm is modified such that the subsystem simulator does not have to disclose its internal model and state variables for solving the overall DAE. The new algorithm is developed based on the generalized Kirchhoff Laws that allow us to represent algebraic boundary constraints as linear equations of the subsystems’ outputs interacting to each other. Third, a multi-rate algorithm is developed for improving efficiency, accuracy, and convergence characteristics. Numerical examples verify the major theoretical results and illustrate features of the proposed method.
Control-Oriented Modeling and Analysis for Automotive Fuel Cell Systems
Authors: Pukrushpan Jay T. , Peng Huei , Stefanopoulou Anna G.
Published: April 2004

Fuel Cells are electrochemical devices that convert the chemical energy of a gaseous fuel directly into electricity. They are widely regarded as a potential future stationary and mobile power source. The response of a fuel cell system depends on the air and hydrogen feed, flow and pressure regulation, and heat and water management. In this paper, we develop a dynamic model suitable for the control study of fuel cell systems. The transient phenomena captured in the model include the flow and inertia dynamics of the compressor, the manifold filling dynamics (both anode and cathode), reactant partial pressures, and membrane humidity. It is important to note, however, that the fuel cell stack temperature is treated as a parameter rather than a state variable of this model because of its long time constant. Limitations and several possible applications of this model are presented.
Sub-Optimal Longitudinal Control of Road Vehicles With Capacity and Safety Considerations
Authors: Sainte-Marie J. , Mammar S. , Nouvelie`re L. , Rouault V.
Published: April 2004

This paper presents a technique for longitudinal control of road vehicles. The technique is based on the calculation of safety distances between two vehicles and uses an optimal control strategy to regulate the speed and position of the controlled vehicle. The technique we propose can be used either for platooning strategies or for autonomous control, i.e., without cooperation or communication between vehicles or with the infrastructure required. We mainly focus on the latter aspect, in which case only measurements of the distance from the preceding vehicle are required, and can be obtained by means of a LiDAR or any equivalent system. First, we study the vehicle model and the control law, then we present simulations, stability results and evaluations.
Optimal Control for Bouncing Suppression of CNG Injectors
Authors: Dyntar D. , Guzzella L.
Published: April 2004

This paper describes the model-based design and the experimental validation of a control system which suppresses the bouncing behavior of Compressed Natural Gas (CNG) fuel injectors. First a detailed model of the system is developed, including temperature and supply-voltage variation effects. Using an optical position sensor, this model is experimentally validated in a second step. Based on this model a feed-forward controller is developed and tested which minimizes the bouncing energy of the system. Since in series applications position sensing would be too expensive to use, an observer-based iterative control algorithm is derived which uses coil current measurements instead of the position information to asymptotically suppress bouncing.
Control-Oriented Modeling of Transcritical Vapor Compression Systems
Authors: Rasmussen Bryan P. , Alleyne Andrew G.
Published: April 2004

This paper presents a methodology for developing a low order dynamic model of a transcritical air-conditioning system, specifically suited for multivariable controller design. An 11th-order nonlinear dynamic model of the system is derived using first principles. Analysis indicates that the system exhibits multiple time scale behavior, and that model reduction is appropriate. Model reduction using singular perturbation techniques yields physical insight as to which physical phenomena are relatively fast/slow, and a 5th-order dynamic model appropriate for multivariable controller design. Although all results shown are for a transcritical cycle, the methodology presented can easily be extended to subcritical cycles.
The Impact of Using a Secondary Swash-Plate Angle Within an Axial Piston Pump
Authors: Manring Noah D. , Dong Zhilin
Published: April 2004

In this paper, the control and containment forces acting on the swash plate of an axial-piston pump are examined. The most novel aspect of this research is that it includes the analysis of a secondary swash-plate angle that is occasionally used in aerospace pump applications. From a practical standpoint, swash-plate control and containment devices take on many different designs; however, they must all resist the same essential moments and forces that attempt to dislocate the swash plate from its proper position. By considering the basic machine design without its control and containment mechanisms, this work generally derives the needed forces and moments for insuring proper swash plate motion and thereby gives the designer of these machines a useful tool for designing control and containment devices of any type. In this research, the dynamic characteristics of the control and containment forces are studied by deriving instantaneous and average equations of motion for the swash plate. Results from this analysis are generated by holding the pump speed and discharge pressure constant, and by prescribing a typical second-order response for the primary swash plate angle. In conclusion, it is shown that the primary advantage of implementing a secondary swash-plate angle is that it can be used to reduce the overall control effort of the pump. Disadvantages of using the secondary swash-plate angle are associated with additional containment requirements for the swash plate.
Monopropellant-Driven Free Piston Hydraulic Pump for Mobile Robotic Systems
Authors: McGee Timothy G. , Raade Justin W. , Kazerooni H.
Published: April 2004

The authors present a novel power supply for mobile robotic systems. A monopropellant (e.g., hydrogen peroxide) decomposes into high temperature gases, which drive a free piston hydraulic pump (FPHP). The elimination of fuel/oxidizer mixing allows the design of simple, lightweight systems capable of operation in oxygen free environments. A thermodynamic analysis has been performed, and an experimental FPHP has been built and tested. The prototype successfully pumped hydraulic fluid, although the flow rate was limited by the off-the-shelf components used.
Output–Feedback Regulation of the Contact-Force in High-Speed Train Pantographs
Authors: Pisano Alessandro , Usai Elio
Published: April 2004

One of the main problems in high-speed train transportation systems is to counteract the fast variations of the contact force between the catenary and the pantograph collector end. The variation of the catenary equivalent stiffness, due to the suspending system, originates mechanical oscillations whose frequency and magnitude are larger and larger as the train speed increases. Such oscillations cause electric arcs that damage the mechanical structure and compromise the collection of the current from the supply wire, degradating the overall performance. Active pantographs offer the possibility of affecting the contact force evolution by suitably modifying a control torque applied at the lower arm of the pantograph. We consider the equivalent stiffness of the catenary as an uncertainty to compensate for by suitable robust control techniques, and, under the assumption that a noisy measure of the actual contact force is available, we propose an output-feedback control scheme based on higher-order sliding modes and high-gain observers. That combination allows for an almost-complete rejection of the undesired oscillations of the contact force, as confirmed by simulations, and is very attractive for real-time implementation purposes, due to its simplicity and robustness.
A Nonlinear State-Space Model of a Resonating Single Fiber Scanner for Tracking Control: Theory and Experiment
Authors: Smithwick Quinn Y. J. , Reinhall Per G. , Vagners Juris , Seibel Eric J.
Published: April 2004

A nonlinear state-space dynamic model of a resonating single fiber scanner is developed to understand scan distortion—jump, whirl, amplitude dependent amplitude and phase shifts—and as the basis for controllers to remove those distortions. The non-planar nonlinear continuum dynamics of a resonating base excited cantilever are reduced to a set of state-space coupled Duffing equations with centripetal acceleration. Methods for experimentally determining the model parameters are developed. The analytic frequency responses for raster, spiral and propeller scans are derived, and match experimental frequency responses for all three scan patterns, for various amplitudes, and using the same model parameters.
A New Model of Binocular Stereo Coordinate Measurement System Based on Skew Ray Tracing
Authors: Lin Psang Dain , Liao Te-tan
Published: April 2004

Two-CCD binocular stereo vision systems using pinhole model are attracting research interest in many important fields such as 3-D coordinate measurement. However, new system modeling is difficult because of lack of fundamental imaging formation theory. In this paper, in order to measure a 3-D surface, we demonstrate how a binocular stereo vision system can be modeled by the proposed skew ray tracing method to study the geometric relations between the binocular camera images and the 3-D surface. In order to investigate the overall accuracy and resolution of this system, the influence of infinitesimal camera reading errors on measured coordinate errors is determined by sensitivity analysis. Experimental verification demonstrates that the performance of the proposed system is excellent.
Rest-to-Rest Motion for Planar Multi-Link Flexible Manipulator Through Backward Recursion
Authors: Benosman M. , Le Vey G. , Lanari L. , De Luca A.
Published: April 2004

In this work is considered the problem of rest-to-rest motion in a desired pre-fixed time for planar flexible manipulators. We introduce a simple idea permitting the minimization of end-effector residual vibration when reaching a desired angular equilibrium position, in a pre-fixed desired travelling time. The results hold without considering internal elastic damping effect, using a classical controller with feedforward plus joint feedback terms. The new approach concerns the computation of the feedforward control, which is based on backward integration of the elastic dynamics, starting from a rest position of the flexible arms. This backward integration yields basically elastic trajectories permitting to reach the final desired end-effector position without oscillation. The feedback controller is then used to stabilize locally the actual states along these desired trajectories. However, for fast rest to rest motion, the feedback compensator fails to drive the system states along the desired trajectories, this being due to the relatively large initial elastic error. To overcome this limitation, proper joint motion is planned between the desired initial and final positions through optimization techniques, the goal being the minimization of the initial elastic error associated to these joint trajectories. The optimal planning technique is formulated as a Pontryagin optimal control problem. This scheme is validated via numerical tests as well as experiments on a flexible two-link planar manipulator.
Hamilton’s Equations With Euler Parameters for Rigid Body Dynamics Modeling
Authors: Shivarama Ravishankar , Fahrenthold Eric P.
Published: April 2004

A combination of Euler parameter kinematics and Hamiltonian mechanics provides a rigid body dynamics model well suited for use in strongly nonlinear problems involving arbitrarily large rotations. The model is unconstrained, free of singularities, includes a general potential energy function and a minimum set of momentum variables, and takes an explicit state space form convenient for numerical implementation. The general formulation may be specialized to address particular applications, as illustrated in several three dimensional example problems.
Pulse Width Control for Precise Positioning of Structurally Flexible Systems Subject to Stiction and Coulomb Friction
Authors: Rathbun David B. , Berg Martin C. , Buffinton Keith W.
Published: April 2004

Pulse width control refers to the use of a control law to determine the duration of fixed-height force pulses for point-to-point position control of a plant that is subject to mechanical friction, including stiction. The use of constant-gain pulse width control laws for precise positioning of structurally flexible plants subject to stiction and Coulomb friction is analyzed. It is shown that when the plant is a simple two-mass system subject to stiction and Coulomb friction, a position error limit cycle can result. Sufficient conditions for stability and self-sustained oscillation of this closed-loop system are derived. The sufficient conditions for stability are used to determine conditions on the plant parameters and the control gain that guarantee closed-loop stability and thus limit-cycle-free operation and zero steady-state position error. The analysis methods that are introduced are demonstrated in applications to the control of the position of the end-effector of an industrial robot.
Piecewise-Linear-Gain Pulse Width Control for Precise Positioning of Structurally Flexible Systems Subject to Stiction and Coulomb Friction
Authors: Rathbun David B. , Berg Martin C. , Buffinton Keith W.
Published: April 2004

Pulse width control refers to the use of a control law to determine the duration of fixed-height force pulses for point-to-point position control of a plant that is subject to mechanical friction, including stiction. A quantitative measure of the performance of a pulse width control system is introduced. Applications of this measure suggest that piecewise-linear-gain pulse width control laws will often provide better performance than constant-gain pulse width control laws. A method for designing piecewise-linear-gain pulse width control laws is introduced. The performance measure and piecewise-linear-gain control law design method are demonstrated in applications to the control of the position of the end-effector of an industrial robot.
A Hybrid Neural Network Approach for the Development of Friction Component Dynamic Model
Authors: Cao M. , Wang K. W. , Fujii Y. , Tobler W. E.
Published: April 2004

In this research, a new hybrid neural network is developed to model engagement behaviors of automotive transmission wet friction component. Utilizing known first principles on the physics of engagement, special modules are created to estimate viscous torque and asperity contact torque as preprocessors to a two-layer neural network. Inside these modules, all the physical parameters are represented by neurons with various activation functions derived from first principles. These new features contribute to the improved performance and trainability over a conventional two-layer network model. Both the hybrid and conventional neural net models are trained and tested with experimental data collected from an SAE#2 test stand. The results show that the performance of the hybrid model is much superior to that of the conventional model. It successfully captures detailed characteristics of the friction component engagement torque as a function of time over a wide operating range.
A Practical Robotic End-Effector for Grasping Postal Sacks
Authors: Kazerooni H.
Published: April 2004

This article describes a new class of end-effectors that can be used with robotic and material handling devices for grabbing and holding deformable objects with undefined shapes such as sacks and bags. These end-effectors can grab and hold filled sacks from any point on the sack and regardless of the sack orientation and position. The first prototype end-effector, designed for the U.S. Postal Service, has two rollers. The rollers are pushed toward each other by the force of a spring. When the rollers are powered to spin, the inward spinning of the rollers causes the sack material to be dragged in between the rollers due to the friction between the surfaces of the rollers and the sack material. The spring pushes the rollers toward each other with sufficient force to hold the sack material in place between the rollers. The end-effector described here has been evaluated and proven to be exceedingly effective in grabbing and holding postal sacks. This article describes the underlying principles of the design, grasp conditions and control of the end-effector.
Remote Vibration Control for Flexible Beams Subject to Harmonic Disturbances
Authors: Wu Shang-Teh
Published: April 2004

A low-order control algorithm is developed to regulate an infinitely dimensional flexible beam subject to nondecaying, harmonic disturbances of known frequency. The control input is applied at the boundary while the output of concern is at the opposite end of the flexible structure. Only local displacement and velocity at the boundary are required in the control algorithm, which emulates the behavior of a set of mechanical spring, mass, and damper. A virtual spring is integrated with the structure flexibility to establish an internal model for the external disturbance. Such a virtual passive algorithm ensures stability in the presence of structural and parameter uncertainties. It is shown that, by properly choosing the control gains, the output tends to a standstill while the other parts of the system oscillate in such a way as to counteract the harmonic disturbance.
A New Approach to Delay-Dependent H∞ Control of Linear State-Delayed Systems
Authors: Wang De-Jin
Published: April 2004

An alternative delay-dependent H∞ controller design is proposed for linear, continuous, time-invariant systems with unknown state delay. The resulting delay-dependent H∞ control criterion is obtained in terms of Park’s inequality for bounding cross term. The H∞ controller determined by a convex optimization algorithm with linear matrix inequality (LMI) constraints, guarantees the asymptotic stability of the closed-loop systems and reduces the effect of the disturbance input on the controlled output to within a prescribed level. A numerical example illustrates the effectiveness of our method.
On Zeros of Discrete-Time Models for Collocated Mass-Damper-Spring Systems
Authors: Ishitobi Mitsuaki , Liang Shan
Published: April 2004

When a continuous-time system is discretized using the zero-order hold, there is no simple relation which shows how the zeros of the continuous-time system are transformed by sampling. In this paper, for a discrete-time model of a collocated mass-damper-spring system, the asymptotic behavior of the zeros is analyzed with respect to the sampling period and the linear approximate expressions are given. In addition, the linear approximate expressions lead to a sufficient condition for all the zeros of the discrete-time model to lie inside the unit circle for sufficiently small sampling periods. The sufficient condition is satisfied when a damping matrix is positive definite. Moreover, an example is shown to illustrate the validity of the linear approximations. Finally, a comment for a noncollocated system is presented.