bluuebunny/crossref_metadata_2025_split huggingface dataset:
Results on an optimality system in radiative transfer
Authors: Herty Michael 
Published: January 2007

AbstractOptimal control problems for the radiative transfer equation are introduced and formulated. We recall necessary and sufficient optimality conditions for a tracking–type optimization problem using the full radiative transfer equations. We present an optimization algorithms and examples on source inversion problems using the introduced optimality conditions. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nonlinear control of a variable displacement axial piston pump
Authors: Fuchshumer Franz , Kugi Andreas 
Published: January 2007

AbstractIn this contribution a mathematical model of a variable displacement axial piston pump controlled by a solenoid valve is derived. For the purpose of a controller design the mathematical model is simplified using singular perturbation arguments. The goal of the controller design is to track prescribed trajectories in the load pressure for arbitrary unknown load conditions. The control concept being proposed comprises a feedforward controller and a nonlinear backstepping controller combined with a load estimator for the trajectory error system. The feasibility of this control concept is shown by means of measurements on a test‐stand. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling, simulation and control a hydraulic servo system
Authors: Hancu Olimpiu , Maties Vistrian , Balan Radu 
Published: January 2007

AbstractHydraulic actuators are widely used in industrial applications due to several advantages like large force and torque, high power to weight ratio, rapid and accurate response. In this paper a nonlinear model of a hydraulic servo system is developed by means of the associated differential equations and then simulated using Matlab techniques. The model describes the behavior of a servo system FESTO TP511 with MOOG‐DDV633 servovalve and includes the nonlinearities of friction forces, valve dynamics, oil compressibility and load influence. The nonlinear model is used to design an optimal controller based on estimated state parameters through simulation. A digital control platform based on Atmel ATmega8535 microcontroller is used to compare the behavior of hydraulic system under PD and optimal control. The control platform was designed like an interface between PC and process: the control algorithm runs on PC and the digital platform assures amplifying, filtering and data communication functions. Both simulation and experimental results are provided to show the effectiveness of the proposed model and control method. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Integrated Motional Measurement for a Flexible Structure
Authors: Örtel Thorsten , Wagner Jörg F. 
Published: January 2007

AbstractIntegrated navigation systems based on gyros and accelerometers are well established devices for vehicle guidance. The system design is traditionally based on the assumption that the vehicle is a rigid body. However, generalizing such integrated systems to flexible structures is possible. The example of the motion of a simple beam being considered here is meant to be a first approach to obtain sophisticated motional measurements of a wing of a large airplane during flight.The principle of integrated navigation systems consists of combining different measuring methods by using their specific advantages. Gyros and accelerometers are used to obtain reliable signals within a short period of time. On the other hand, aiding sensors like radar units and strain gauges are used because of their long‐term accuracy. The kernel of the integrated system consists, however, of an extended Kalman filter that estimates the motion state of the structure. Besides the sensor signals, the basis for the filter is an additional kinematical model of the structure. By means of a model reduction, a kinematical model of the beam was developed.Based on simulation the paper presents this approach, the appropriate sensor set, and first estimated motion results. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An optimal control problem in image processing
Authors: Bredies Kristian , Lorenz Dirk A. , Maass Peter 
Published: January 2007

AbstractAs a starting point, we present a control problem in mammographic image processing which leads to non‐standard penalty terms and involves a degenerate parabolic PDE which has to be controlled in the coefficients. We then discuss the classical conditional gradient method from constrained optimization and propose a generalization for non‐convex functionals which covers the conditional gradient method as well as the recently proposed iterative shrinkage method of Daubechies, Defrise and De Mol for the solution of linear inverse problems with sparsity promoting penalty terms. We prove that this new algorithm converges. This also gives a deeper understanding of the iterative shrinkage method. Further, we show an application to the above‐mentioned control problem in image processing. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical simulation of stationary fluid flows in rivers with islands
Authors: Shokina Nina 
Published: January 2007

AbstractThe algorithm is presented for numerical solution of problems on stationary fluid flows with surface gravitational waves in multiply‐connected domains with complicated geometry using adaptive grids in the framework of plane shallow water model taking into account bottom irregularities, frictional force and Coriolis force. The stream function ‐ vorticity function statement in curvilinear coordinates is used. The alternating triangular iterative method is developed for solving the system of difference equations for the vorticity function. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Laboratory experiments on vortices colliding with multiple islands
Authors: Tanabe Aya , Cenedese Claudia 
Published: January 2007

AbstractLaboratory experiments have been performed to investigate the physical processes that govern the interaction of a self‐propagating barotropic cyclonic vortex with aligned circular cylinders. The motivation was to understand the dynamics which controls the interaction of North Brazil Current (NBC) rings with the Lesser Antilles (LA) in the Eastern Caribbean Sea. The geometrical parameter regulating the flow in the experiments was the ratio of the gap size to the diameter of the incident vortex, G /d. The range 0.03 ≤ G /d ≤ 0.4 was studied. Since the passages of the LA have values of 0.07 ≤ G /d ≤ 0.3 [2], the experimental results might explain recent oceanic observations [3]. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Natural fiber eco‐composites
Authors: Bogoeva‐Gaceva G. , Avella M. , Malinconico M. , Buzarovska A. , Grozdanov A. , Gentile G. , Errico M. E. 
Published: January 2007

AbstractThe natural fiber (NF) reinforced composites, so called eco‐composites, are subject of many scientific and research projects, as well as many commercial programs. The growing global environmental and social concern, high rate of depletion of petroleum resources, and new environmental regulations have forced the search for new composites and green materials, compatible with the environment. The aim of this article is to present a brief review of the most suitable and commonly used biodegradable polymer matrices and NF reinforcements in eco‐composites, as well as some of the already produced and commercialized NF eco‐composites. POLYM. COMPOS. 28:98–107, 2007. © 2007 Society of Plastics Engineers
Effects of organo‐montmorillonite on the mechanical and morphological properties of epoxy/glass fiber composites
Authors: Norkhairunnisa Mazlan , Azhar Abu Bakar , Shyang Chow Wen 
Published: January 2007

AbstractEpoxy composites filled with glass fiber and organo‐montmorillonite (OMMT) were prepared by the hand lay‐up method. The flexural properties of the epoxy/glass fiber/OMMT composites were characterized by a three‐point bending test. The flexural modulus and strength of epoxy/glass fiber were increased significantly in the presence of OMMT. The optimum loading of OMMT in the epoxy/glass fiber composites was attained at 3 wt%, where the improvement in flexural modulus and strength was approximately 66 and 95%, respectively. The fractured surface morphology of the epoxy/glass fiber/OMMT composites was investigated using field emission scanning electron microscopy. It was found that OMMT adheres on the epoxy/glass fiber interface, and this is also supported by evidence from energy dispersive X‐ray analysis. Copyright © 2007 Society of Chemical Industry
Value of surrogate tests to predict exercise‐induced bronchoconstriction in atopic childhood asthma
Authors: Lex Christiane , Dymek Sabine , Heying Ruth , Kovacevic Alexander , Kramm Christof M. , Schuster Antje 
Published: January 2007

AbstractExercise challenge tests are helpful in the diagnosis and management of childhood asthma, but methodology is complex and time‐consuming. The aim of this study was to investigate whether exercise‐induced bronchoconstriction (EIB) can be predicted by the results of different surrogate tests in a pediatric population. Eighty‐five children (mean age: 11 years, range: 5–16 years) with atopic asthma were studied. Measurements of exhaled nitric oxide (eNO), spirometry and whole body plethysmography were performed followed by a standardized exercise testing. Questionnaires were completed asking for respiratory symptoms within 2 weeks preceding the study protocol. In 12/85 children (14%), forced expiratory volume in 1 sec (FEV1) was significantly reduced by ≥15% after exercise testing. eNO was significantly elevated in this group of 12 patients as compared to patients without EIB (51.3 (31.1–67.3) parts per billion (ppb) versus 20.2 (10.9–42.3) ppb; P = 0.003). All children with normal eNO levels (≤25 ppb) had normal lung function results after exercise; hence the negative predictive value (NPV) of elevated eNO levels for prediction of EIB was 100%. However, the positive predictive value (PPV) was only 28%. The NPV and PPV for reported asthma symptoms within 2 weeks preceding the study were 96% and 26%, respectively. Considering recent symptom history in addition to elevated eNO improved the PPV to 40%, and resulted in the best combination of sensitivity and specificity. No baseline lung function parameter predicted whether a patient would develop EIB or not. In conclusion, eNO measurements, symptom questionnaires and most efficiently a combination of both surrogate tests can be used as time‐saving methods to exclude EIB in atopic childhood asthma. Pediatr Pulmonol. 2007; 42:225–230. © 2007 Wiley‐Liss, Inc.
Carbon‐film field‐emission cathodes in a compact orbitron‐type ionization vacuum sensor
Authors: Alexandrov S. Ye. , Arkhipov A. V. , Mishin M. V. , Sominski G. G. 
Published: January 2007

AbstractA possibility to using large‐area field‐emission cathodes as electron sources in ionic vacuum sensors was investigated. In the specially developed electron‐optic scheme, electrons are extracted from a box‐shaped cathode by the field of two anode strings. For a large part of the cathode, trajectories of emitted electrons are infinite (in theory), thus high efficiency of gas ionization and overall gauge sensitivity can be achieved. Experimental testing of a sensor prototype has demonstrated general viability of the proposed principle. For a residual gas pressure of about 10−5 Torr and a cathode emission current 10 µA, the current of collected ions had value of about 1 nA. The achieved sensitivity is sufficient for some of the possible practical applications of the sensor and can be further improved by simple design corrections. Besides the direct goals of the experiments, they yielded additional information on the performance of carbon emitters in high‐voltage devices. Copyright © 2007 John Wiley & Sons, Ltd.
Precipitation reactions during the early stages of aging in a Ni and Al alloyed martensitic medium carbon steel
Authors: Erlach S. , Danoix F. , Leitner H. , Auger P. , Siller I. , Clemens H. 
Published: January 2007

AbstractSteels in hot‐work applications are exposed to a complex combination of mechanical, thermal and creep loading conditions. Advanced hot‐work tool steels combine precipitation of alloy carbides and intermetallic phases and, therefore, exhibit a higher thermal stability than conventional tool steels.The mechanical and thermophysical properties of a Fe‐0.32C‐6.5Ni‐2.5Al wt% martensitic tool steel are mainly determined by the combined precipitation of secondary hardening carbides and of intermetallic NiAl precipitates of B2‐type. This alloy shows a large and rapid hardening reaction upon aging for as short as 60 s at a temperature of 610 °C.Atom probe field ion microscopy has been used to investigate both the composition and morphology of the fine precipitates and the matrix present after aging for 0, 30 and 60 s at 610 °C. In particular, chemical composition, particle radii and number density of the precipitates have been determined as a function of the aging time. The data obtained from these initial stages of the precipitation processes were analysed by means of statistical calculations. Copyright © 2007 John Wiley & Sons, Ltd.
Three‐dimensional atom probe analysis of chromium‐ and copper‐added nitriding steel
Authors: Takahashi J. , Kawasaki K. , Kawakami K. , Sugiyama M. 
Published: January 2007

AbstractDetailed analysis of fine precipitates in a soft‐nitrided steel containing chromium and copper was performed using an energy‐compensated three‐dimensional atom probe (3DAP). A high number density of copper precipitates, chromium nitride precipitates and their pairs were observed in the diffusion layer of the nitrided steel. The size and density of these precipitates dominated the hardness increment due to nitriding. From the characteristic distribution and morphology of these precipitates in the depth direction, the following three stages of precipitation are proposed: In heat treatment for nitriding, copper precipitates are generated first. Chromium nitrides are then nucleated on the surface of the copper precipitates heterogeneously, and their pairs are formed. Finally, single chromium nitrides were homogeneously nucleated. Copyright © 2007 John Wiley & Sons, Ltd.
Adaptive motion estimation schemes using maximum mutual information criterion
Authors: Zhao Jing , Wu Dapeng , Erdogmus Deniz , Fang Yuguang , He Zhihai 
Published: January 2007

AbstractWe consider the motion estimation problem in video coding. In our previous work, we proposed a new motion estimation method where motion estimation is formulated as an optimization problem and an adaptive system under the minimum error entropy (MEE) criterion is used for motion estimation. In this paper, we develop an adaptive system under the criterion of maximum mutual information to address the motion estimation problem. Our proposed motion estimation algorithms have very low encoding complexity and hence are ideally suited for wireless video sensor networks where limited bandwidth, restricted computational capability, and limited battery power supply impose stringent constraints on the video encoding system. Copyright © 2007 John Wiley & Sons, Ltd.
Video transport over multi‐hop directional wireless networks
Authors: Li Yang , Man Hong 
Published: January 2007

AbstractExploiting directional antenna technology in wireless networks has become an attractive option for multimedia applications because of the potential capacity increase through spatial reuse. However, it has also been recognized that multi‐hop directional networks may suffer long transmission delays and frequent link breakages if conventional routing protocols (e.g., AODV and DSR) are used. This is mainly caused by ‘node deafness’ in directional transmission. To address this problem, we propose a multi‐path routing scheme which focuses more on minimizing per‐hop delays instead of traditional route length. In this paper, an analytical and numerical analysis of link breakages in multi‐hop directional network is presented, along with an introduction to our multi‐path routing scheme and two implementations based on AODV and DSR protocols. We further propose a differentiated service (DiffServ) framework for layered video transport over multi‐hop directional network using QoS aware multi‐path routing. Both network layer and application layer simulation results are presented to demonstrate the effectiveness of the proposed video transport scheme over directional networks. Copyright © 2007 John Wiley & Sons, Ltd.
Modelling farmer decision-making: concepts, progress and challenges
Authors: Edwards-Jones G. 
Published: January 2007

AbstractDecisions made by farmers may have large influences beyond the farm boundary, and for this reason they are often of interest to Government and the public. The process of adoption of new technologies and policies has received considerable academic attention over many years, and this has highlighted the rôle of social influences in decision-making. In addition a range of purely economic-based models of farmer decision-making have been developed in order to predict potential changes in agriculture and land use under future policy and market scenarios. Since the 1990s these traditional approaches to understanding decision-making have been supplemented by an increasing input from psychology. As a result of this work it is clear that farmers' decisions are influenced by a range of factors which may be grouped under six headings: socio-demographics of the farmer, psychological make up of the farmer, the characteristics of the farm household, structure of the farm business, the wider social milieu and the characteristics of the innovation to be adopted. This paper presents a short review of the quantitative methods that seek to integrate insights from economics and social science within theoretical frameworks derived from psychology. Suggestions for further work include more empirical study in farmer decision-making related to animal health and welfare, the rôle of the farmers' own health status in decision-making and the formal integration of economic and psychological variables in simulation models.
The reopening of a collapsed fluid-filled elastic tube
Authors: JUEL ANNE , HEAP ALEXANDRA 
Published: January 2007

We present an experimental study of the reopening mechanics of a collapsed liquid-filled elastic tube. The experiment is a simple mechanical model of pulmonary airway reopening and aims to assess the robustness of existing theoretical models. A metre-long horizontal elastic tube of inner radius Ri=4.88 ± 0.14mm is filled with silicone oil and is carefully collapsed mechanically. The injection of nitrogen at a constant flow rate results in the steady propagation of an air finger, after the decay of initial transients. This behaviour is observed over the realizable range of the capillary numbers Ca, which measures the ratio of viscous and capillary forces. With increasing Ca, the transition region between the collapsed and reopened sections of the tube shortens, and the height of the tube behind the bubble tip increases. We also find that air fingers can propagate in partially reopened tubes, in which the transmural pressure is negative far behind the finger tip.The effect of viscosity on the reopening dynamics was explored by performing experiments using three different grades of silicone oil, with kinematic viscosities of 1000cS, 200cS and 100cS. A direct comparison between the experimental pressure dependence on Ca and numerical simulations of the zero-gravity three-dimensional airway-reopening model of Hazel & Heil (Trans. ASME: J. Biomech. Engng, vol. 128, 2006, p. 473) highlights some significant differences. Within the experimental parameter range, gravity profoundly influences the reopening mechanics in several ways. The reopening tube is supported by a rigid base, which induces an asymmetry about the horizontal mid-plane of the collapsed tube, resulting in distinct phases of reopening as Ca increases. In addition, buoyancy forces act on the air finger, which is observed to propagate near the top of the cross-section of the tube, leaving a thicker fluid-lining below. In the limit of small Ca, the height of the reopened tube increases significantly with viscosity. Experimental evidence suggests that this increase in viscosity leads to significant changes in the film configuration behind the propagating finger, caused by the increased contribution of buoyancy forces. The altered film configuration changes the mechanical load on the tube walls and, hence, the shape of the reopened tube.
Inhibitory effect of BIBN4096BS, CGRP8–37, a CGRP antibody and an RNA‐Spiegelmer on CGRP induced vasodilatation in the perfused and non‐perfused rat middle cerebral artery
Authors: Edvinsson L , Nilsson E , Jansen‐Olesen I 
Published: January 2007

Background and purpose:A new concept for the inhibition of CGRP signalling has been developed by interaction with the CGRP moleculeper seby using a CGRP antibody or a CGRP binding RNA‐Spiegelmer (NOX‐C89). We have compared these CGRP scavengers with two known receptor antagonists (CGRP8–37and BIBN4096BS) on CGRP‐induced relaxations in the rat middle cerebral artery (MCA). Furthermore, the role of the endothelial barrier has been studied.Experimental approach:We used the luminally perfused MCA in an arteriograph, pressurized to 85 mm Hg and myograph studies of isolated ring segments of the MCA.Key results:In myograph studies and in the perfusion system during abluminal application, αCGRP and βCGRP induced concentration‐dependent dilatation of the MCA. Given luminally neither peptide was significantly vasodilator. Adrenomedullin and amylin induced weak dilatations. In myograph experiments, relaxation induced by αCGRP was prevented by the four CGRP blockers (CGRP8–37, BIBN4096BS, the CGRP antibody and NOX‐C89.). In abluminal perfusion experiments, the relaxant response to αCGRP was prevented by these agents to a varying degree. Dilatation induced by abluminal application of αCGRP was inhibited by luminal CGRP8–37but not by luminal BIBN4096BS, CGRP antibody or NOX‐C89.Conclusions and Implications:α or βCGRP acted on smooth muscle cell CGRP receptors in rat MCA and were effectively prevented from reaching these receptors by the endothelial barrier. The CGRP blockers significantly inhibited αCGRP induced relaxation but were also prevented from reaching the CGRP receptors by the arterial endothelium.British Journal of Pharmacology(2007)150, 633–640. doi:10.1038/sj.bjp.0707134
Rimonabant: more than an anti‐obesity drug?
Authors: Costa B 
Published: January 2007

The endocannabinoid system modulates many pathophysiological functions, including the brain pathways involved in the regulation of body weight and adipose tissue function. The selective cannabinoid CB1 receptor antagonist, rimonabant, has undergone phase III clinical testing as anti‐obesity drug. Obesity is considered a mild inflammatory condition and predisposes individuals to an increased risk of developing many diseases. It has been recently suggested that a successful intervention to treat obesity is a therapy combining weight‐reducing drugs with anti‐inflammatory ones. In this scenario, rimonabant's anti‐obesity action is accompanied by favorable changes in markers for insulin resistance, C‐reactive protein, adiponectin, tumor necrosis factor α (TNFα). The results reported by Croci and Zarini in this issue highlight the anti‐inflammatory and anti‐hyperalgesic effect of rimonabant in obese animals, so suggesting that it could provide a more general and aggressive strategy to protect obese patients from many pathological risks.British Journal of Pharmacology (2007) 150, –. 22 January 2007; doi:10.1038/sj.bjp.0707139