bluuebunny/crossref_metadata_2025_split huggingface dataset:
Automatic Petri Net Simulation Model Generation for a Continuous Flow Transfer Line with Unreliable Machines
Authors: Sörensen Kenneth , Janssens Gerrit K. 
Published: May 2004

AbstractA production line is studied with several machines in series. The machines are separated with finite buffers. They can break down and have to be repaired. Production is assumed to be continuous, i.e. no individual products can be identified. Analytical models for the performance evaluation of such a system are scarce. Analytical results for the throughput can be obtained only under very restrictive assumptions. The performance study of longer transfer lines requires either approximation or simulation. A Petri net model is developed for an n‐machine $(n-1)$‐buffer system. The rules to design the Petri net transitions are given. The automatic generation of a discrete‐event simulation model from the Petri net model is explained. Finally, some potential applications of the Petri net are illustrated. These applications include the simulation of transfer lines with complex stochastic behaviour, the optimization of buffer size and allocation and the evaluation of approximation models for long transfer lines. Using the simulation model described in this paper, quality and reliability engineers can simulate the performance of a given continuous flow transfer line and evaluate the effect of performance‐increasing measures such as the insertion of extra buffer space or the use of more reliable machines. Copyright © 2004 John Wiley & Sons, Ltd.
Comparison of Methods to Estimate the Time‐to‐failure Distribution in Degradation Tests
Authors: de Oliveira Viviane Ribeiro Branco , Colosimo Enrico Antônio 
Published: May 2004

AbstractDegradation tests are alternative approaches to lifetime tests and accelerated lifetime tests in reliability studies. Based on a degradation process of a product quality characteristic over time, degradation tests provide enough information to estimate the time‐to‐failure distribution. Some estimation methods, such as analytical, the numerical or the approximated, can be used to obtain the time‐to‐failure distribution. They are chosen according to the complexity of the degradation model used in the data analysis. An example of the application and analysis of degradation tests is presented in this paper to characterize the durability of a product and compare the various estimation methods of the time‐to‐failure distribution. The example refers to a degradation process related to an automobile's tyre, and was carried out to estimate its average distance covered and some percentiles of interest. Copyright © 2004 John Wiley & Sons, Ltd.
Adaptive tracking control of flexible‐joint manipulators without overparametrization
Authors: Kim Min S. , Lee Jin S. 
Published: May 2004

AbstractIn this paper, an adaptive controller is designed for rigid‐link flexible‐joint robot manipulators based on link and actuator position measurements only. It is based on the adaptive integrator backstepping method and the link and actuator velocity filters are used to estimate the unknown velocity terms. Moreover, the proposed controller exploits the estimate of the joint stiffness matrix inverse to overcome the overparametrization problem, which has been a significant drawback in adaptive partial state feedback controllers. It achieves asymptotic tracking of link positions while keeping all states and signals bounded. The tracking capability of the presented method is shown through simulation results of one‐ and two‐link flexible joint manipulators. © 2004 Wiley Periodicals, Inc.
Dynamic process programming for a robotic manipulator based on hopfield NN monotonous optimization searching
Authors: Yu Zhongwei , Chen Huitang , Woo Peng‐Yung 
Published: May 2004

AbstractA new approach to programming the optimal dynamic process for an n‐joint
rigid robotic manipulator with the use of the monotonous optimization searching
ability of a Hopfield NN is presented. By combining robotic dynamics, this
paper designs a programmed controller, which satisfies the aforementioned
dynamic process. The convergence of the programmed controller is investigated.
Simulations and experiments demonstrate the effectiveness of the scheme described. ©
2004 Wiley Periodicals, Inc.
A new space and time sensor fusion method for mobile robot navigation
Authors: Jin TaeSeok , Lee JangMyung , Tso S. K. 
Published: May 2004

AbstractTo fully utilize the information from the sensors of mobile robot, this paper proposes a new sensor‐fusion technique where the sample data set obtained at a previous instant is properly transformed and fused with the current data sets to produce a reliable estimate for navigation control. Exploration of an unknown environment is an important task for the new generation of mobile service robots. The mobile robots may navigate by means of a number of monitoring systems such as the sonar‐sensing system or the visual‐sensing system. Notice that in the conventional fusion schemes, the measurement is dependent on the current data sets only. Therefore, more sensors are required to measure a given physical parameter or to improve the reliability of the measurement. However, in this approach, instead of adding more sensors to the system, the temporal sequences of the data sets are stored and utilized for the purpose. The basic principle is illustrated by examples and the effectiveness is proved through simulations and experiments. The newly proposed STSF (space and time sensor fusion) scheme is applied to the navigation of a mobile robot in an environment using landmarks, and the experimental results demonstrate the effective performance of the system. © 2004 Wiley Periodicals, Inc.
The distribution of the size of the ancestor‐tree and of the induced spanning subtree for random trees
Authors: Panholzer Alois 
Published: May 2004

AbstractWe consider two tree statistics that extend in a natural way the parameters depth of a node resp. distance between two nodes. The ancestor‐tree of p given nodes in a rooted tree T is the subtree of T, spanned by the root and these p nodes and generalizes the depth (ancestor‐tree of a single node), whereas the spanning subtree induced by p given nodes in a tree T generalizes the distance (induced spanning subtree of two nodes). We study the random variables size of the ancestor‐tree resp. spanning subtree size for two tree families, the simply generated trees and the recursive trees. We will assume here the random tree model and also that all () possibilities of selecting p nodes in a tree of size n are equally likely. For random simply generated trees we can then characterize for a fixed number p of chosen nodes the limiting distribution of both parameters as generalized Gamma distributions, where we prove the convergence of the moments too. For some specific simply generated tree families we can give exact formulæ for the first moments. In the instance of random recursive trees, we will show that the considered parameters are asymptotically normally distributed, where we can give also exact formulæ for the expectation and the variance. © 2004 Wiley Periodicals, Inc. Random Struct. Alg., 2004
Is the degree of fetal hepatosplenomegaly with transient abnormal myelopoiesis closely related to the postnatal severity of hematological abnormalities in Down syndrome?
Authors: Ogawa M. , Hosoya N. , Sato A. , Tanaka T. 
Published: May 2004

AbstractWe present three cases of transient abnormal myelopoiesis associated with trisomy 21 in which hepatomegaly was apparent during the fetal period. In the first case, the fetal hepatosplenomegaly was severe, multiple organ failure occurred in the neonatal period and death ensued at 4 weeks of age. In the second case, the hepatomegaly was moderate, and with conservative treatment in the neonatal period the outcome was good. In the third case, hepatomegaly was mild and improved spontaneously, and the hematological abnormalities required only conservative treatment in the neonatal period. Our experience raises the question of whether fetal hepatosplenomegaly is a predictor of transient myeloproliferative disorder with trisomy 21 and whether the degree of fetal hepatomegaly is a marker for the neonatal severity of hematological abnormalities. Copyright © 2004 ISUOG. Published by John Wiley & Sons, Ltd.
Smoothing effects of distributed wind turbines. Part 1. Coherence and smoothing effects at a wind farm
Authors: Nanahara Toshiya , Asari Masahiro , Sato Takamitsu , Yamaguchi Koji , Shibata Masaaki , Maejima Tsutomu 
Published: May 2004

AbstractRecently there has been a marked increase in wind power generation. From a power system point of view, because a wind turbine is an intermittent generator with large output fluctuation, any increase in the number of wind turbines gives rise to concerns about the adverse effects of wind turbines on power quality. The smoothing effects of wind turbine output fluctuation are of great importance in assessing the impacts of a large number of wind turbines. This article examines smoothing effects at a wind farm. First it presents a summary of wind measurements taken at two locations with six masts over a period of 1 year on both flat and complex terrain. Then the spatial coherence of wind speed is analysed, paying special attention to its dependence on the distance between observation points, wind direction, wind velocity and fluctuation frequency. Approximation equations for coherence of frequency and distance are obtained by applying Davenport's expression to the observed data. Second, coherence between turbine output at a wind farm is investigated; the results indicate that coherence for wind speed and turbine output shows a considerable resemblance. The article also examines smoothing effects at a wind farm using power spectral density through a theoretical approach. The study proves that smoothing effects can be approximated with a lowpass filter and that the effects at a wind farm should not be taken into account for periods of more than 10 min in case of assessing them on the safe side. Copyright © 2004 John Wiley & Sons, Ltd.
Grid impacts of wind power: a summary of recent studies in the United States
Authors: Parsons Brian , Milligan Michael , Zavadil Bob , Brooks Daniel , Kirby Brendan , Dragoon Ken , Caldwell Jim 
Published: May 2004

AbstractSeveral detailed technical investigations of grid ancillary service impacts of wind power plants in the United States have recently been performed. These studies were applied to Xcel Energy (in Minnesota) and PacifiCorp and the Bonneville Power Administration (both in the northwestern United States). Although the approaches vary, three utility time frames appear to be most at issue: regulation, load following and unit commitment. This article describes and compares the analytic frameworks from recent analysis and discusses the implications and cost estimates of wind integration. The findings of these studies indicate that relatively large‐scale wind generation will have an impact on power system operation and costs, but these impacts and costs are relatively low at penetration rates that are expected over the next several years. Published in 2004 by John Wiley & Sons, Ltd.
Experimental results of the variable speed, direct drive multipole synchronous wind turbine TWT1650
Authors: Torres Eduardo , Garcia‐Sanz Mario 
Published: May 2004

AbstractThis article presents details of the new variable speed multipole large wind turbine TWT1650 designed by the M. Torres group and summarizes some experimental results of the control system. After several years of multidisciplinary research the first prototype TWT1650 began to work at Cabanillas Wind Farm (Spain) in August 2001. Since then a large number of operational data have been collected and used to improve the behaviour of the machine. The design and controller tuning have been accomplished using advanced QFT (quantitative feedback theory) robust control strategies and have been optimized based on analysis of that information. This article introduces the main advantages of the multipole system and shows and evaluates some of the most representative experimental results under extreme wind conditions. Copyright © 2004 John Wiley & Sons, Ltd.
On‐line assessment of prediction risk for wind power production forecasts
Authors: Pinson P. , Kariniotakis G. 
Published: May 2004

AbstractThe article introduces a new methodology for assessing on‐line the prediction risk of short‐term wind power forecasts. The first stage of this methodology consists in computing confidence intervals with a confidence level defined by the end‐user. The resampling approach is used, which, in contrast to existing methods for wind forecasting, does not need to make a restrictive hypothesis on the distribution of the errors. To account for the non‐linearity of the power curve and the cut‐off effect, the errors are classified using appropriate fuzzy sets. The confidence intervals are then fine‐tuned to reduce their width in the case of stable weather conditions. For this purpose an appropriate index, called the ‘meteo‐risk index’ (MRI), is defined reflecting the spread of the available numerical weather predictions. A linear relation between that index and the resulting prediction error is shown. The second part of the methodology is to use the MRI itself as a preventive on‐line tool to derive signals for the operator on the meteorological risk, i.e. the probabilities of the occurrence of high prediction errors depending on the weather stability. Evaluation results of this methodology over a 1 year period on the case study of Ireland are given, where the output of several wind farms is predicted using a dynamic fuzzy neural network‐based model. The proposed methodology is generic and can be applied to all kinds of wind power prediction models. Copyright © 2004 John Wiley & Sons, Ltd.
Aeroelastic stability analysis of wind turbines using an eigenvalue approach
Authors: Hansen M. H. 
Published: May 2004

AbstractA design tool for performing aeroelastic stability analysis of wind turbines is presented in this paper. The method behind this tool is described in a general form, as independent of the particular aeroelastic modelling as possible. Here, the structure is modelled by a Finite beam Element Method, and the aerodynamic loads are modelled by the Blade Element Momentum method coupled with a Beddoes‐Leishman type dynamic stall model in a state‐space formulation. The linearization of the equations of motion is performed about a steady‐state equilibrium, where the deterministic forcing of the turbine is neglected. To eliminate the periodic coefficients and avoid using the Floquet Theory, the multi‐blade transformation is utilized. From the corresponding eigenvalue problem, the eigenvalues and eigenvectors can be computed at any operation condition to give the aeroelastic modal properties: Natural frequencies, damping and mode shapes. An example shows a good agreement between predicted and measured aeroelastic damping of a stall‐regulated 600 kW turbine. Copyright © 2004 John Wiley & Sons, Ltd.
Development of the Risø wind turbine airfoils
Authors: Fuglsang Peter , Bak Christian 
Published: May 2004

AbstractThis paper presents the wind turbine airfoil development at Risø. The design method is described together with our target characteristics for wind turbine airfoils. The use of the CFD code Ellipsys2D for prediction of final target characteristics is described together with the VELUX wind tunnel testing setup. Three airfoil families were developed; Risø‐A1, Risø‐P and Risø‐B1. The Risø‐A1 airfoil family was developed for rotors of 600 kW and larger. Wind tunnel testing and field testing showed that this airfoil family is well suited for stall and active stall control. However, sensitivity to roughness was higher than expected. Field tests of a 600 kW active stall wind turbine showed an estimated reduction in blade fatigue loading of up to 15% at the same annual energy yield and at the same time reduced blade weight and blade solidity. The Risø‐P airfoils were developed to replace the Risø‐A1 airfoils for use on pitch controlled wind turbines. Improved design objectives should reduce the sensitivity to roughness, but measurements are not yet available. The Risø‐B1 airfoil family was developed for variable speed operation with pitch control of large megawatt sized rotors. Wind tunnel testing verified the high maximum lift for these airfoils, and the airfoils were found to be very insensitive to leading edge roughness. Performance with vortex generators and Gurney flaps in combination was found to be attractive for the blade root part. Field testing of a 1·5 MW rotor is in progress. Copyright © 2004 John Wiley & Sons, Ltd.
Synthesis and Raman Spectroscopy of Nanoparticles of Crystalline and X‐ray Amorphous Germanium within Mesoporous SiO2
Authors: Schlecht Sabine , Yosef Maekele , Fröba Michael 
Published: May 2004

AbstractMesoporous hexagonally ordered SiO2 (SBA‐15) with a pore diameter of 7 nm was used as a host matrix for nanoparticles of amorphous and crystalline germanium. Raman spectra were recorded for these germanium nanoparticles and for bulk amorphous and crystalline germanium powder. The band shifts and line shapes of the Raman bands for the optical phonon at ∼300 cm—1 were analyzed and compared to the theoretical predictions derived from the phonon confinement model. In addition, the microstructure of amorphous hydrogenated germanium could be further elucidated by Raman spectroscopy and by thermal analysis.
On the Crystal Structure of K2Cu5Cl8(OH)4·2H2O
Authors: Kahlenberg Volker 
Published: May 2004

AbstractSingle crystals of K2Cu5Cl8(OH)4·2H2O were grown using hydrothermal techniques. The compound is monoclinic with a = 11.6424(11), b = 6.5639(4), c = 11.7710(10)Å, β = 91.09(1)°, V = 899.4(2)Å3, space group P21/c, Z = 2. The crystal structure was determined using single crystal X‐ray diffraction data and refined to a residual of R(|F|) = 0.025 for 1208 independent observed reflections with I > 2σ(I). Two out of three crystallographically independent Cu atoms are coordinated to four near hydroxyl groups or chlorine atoms and two more distant Cl atoms, giving an octahedrally Jahn‐Teller distorted (4+2)‐configuration. For the remaining third copper cation a square‐planar coordination can be found. Edge‐sharing of the octahedra results in the formation of kagome‐type sheets parallel to (100). The octahedral layers are decorated on both sides by planar [Cu(OH)2Cl2]‐units around the third Cu atom. The K atoms are located between adjacent sheets and are surrounded by six Cl atoms as well as two water molecules. The coordination polyhedra about the K‐atoms can be described as distorted bicapped trigonal prisms. Additional linkage is provided by intra‐ as well as inter‐layer hydrogen bonds (O—H···Cl, O—H···O).
Ramifications of metastability in bit variables explored via Simpson’s 4-slot mechanism
Authors: Paynter S. E. , Henderson N. , Armstrong J. M. 
Published: May 2004

Abstract.
Protocol descriptions often fail to take metastability into account. Metastability, however, can undermine protocols which depend on shared bits. In this paper a series of increasingly realistic models of bits are developed in CSP to explore the implications of metastability for Simpson’s 4-slot asynchronous communication mechanism. It is shown that the 4-slot mechanism with realistic bit models preserves data-coherence, freshness, and sequencing, and is Lamport-atomic. We demonstrate that metastability can undermine the correctness of protocols demonstrated correct on the assumption that bits are Lamport-safe; furthermore, realistic bit models can demonstrate that protocols are correct which Lamport-safe bit models would suggest were incorrect or impossible.
Dispersal distance of corn pollen under fluctuating diffusion coefficient
Authors: Yamamura Kohji 
Published: May 2004

AbstractI develop a mechanistic model for pollen dispersal by a generalization of the Brownian motion model. This model provides an explanation as to why the distribution of the dispersal distance is leptokurtic in most organisms. The pollen is assumed to move in a period betweenτandτ+Δτto the circumference of a circle of radius Δrτthat has a center at the current position. The angle of movement is chosen at random. Unlike the conventional Brownian motion model, the step length, Δrτ, fluctuates in a stochastic manner, obeying a generalized gamma distribution. The convection flow, i.e., the directional movement of pollen, is also considered. I show that this model is identical to the diffusion model where the dispersal duration weighted by the diffusion coefficient obeys a gamma distribution. Hence, the model is called the gamma model. The solution is given in an explicit form. The model is fitted to six data sets obtained from the literature by maximizing the quasi‐likelihood. Another model (the inverse gamma model), which is not a mechanistic model but a phenomenological model, is also fitted to the data to evaluate the validity of the gamma model.
Abortion laws and policies: challenges and opportunities
Authors: Cook Rebecca J. 
Published: May 2004

AbstractAn analysis of abortion law reform in all regions of the world in the past 20 years shows that countries have turned from a concentration upon criminality to a concern with women's health and family well‐being. Pragmatic approaches to achieve liberalization of abortion laws are described. Where legal reform is unlikely, specification of professional medical standards, clarification of laws and the scope of allowable action, as well as supportive statements by government officials, can facilitate services and may ultimately have a positive influence on legal reform.
Control of pain for women undergoing abortion
Authors: Stubblefield Phillip G. 
Published: May 2004

AbstractTo reduce the anxiety and pain experienced by women undergoing abortion, pre‐abortion psychological counseling should be given the first priority. Additional techniques for reducing pain are described, including the use of local anesthetic, sedatives, analgesics, and systemic anesthetic agents. Recommendations for practice include an improved technique for paracervical block, modified abortion technique to reduce painful stimulus, and safe use of low dose intravenous sedatives. General anesthesia should be avoided to improve abortion safety.
OPERATOR-VALUED FOURIER MULTIPLIERS ON PERIODIC BESOV SPACES AND APPLICATIONS
Authors: Arendt Wolfgang , Bu Shangquan 
Published: May 2004

AbstractLet $1\leq p,q\leq\infty$, $s\in\mathbb{R}$ and let $X$ be a Banach space. We show that the analogue of Marcinkiewicz’s Fourier multiplier theorem on $L^p(\mathbb{T})$ holds for the Besov space $B_{p,q}^s(\mathbb{T};X)$ if and only if $1\ltp\lt\infty$ and $X$ is a UMD-space. Introducing stronger conditions we obtain a periodic Fourier multiplier theorem which is valid without restriction on the indices or the space (which is analogous to Amann’s result (Math. Nachr.186 (1997), 5–56) on the real line). It is used to characterize maximal regularity of periodic Cauchy problems.AMS 2000 Mathematics subject classification: Primary 47D06; 42A45