bluuebunny/crossref_metadata_2025_split huggingface dataset:
Flow–stress coupled permeability tensor for fractured rock masses
Authors: Zhou Chuang B. , Sharma Radhey S. , Chen Yi F. , Rong Guan 
Published: January 2008

AbstractIn this paper a new analytical model is proposed to determine the permeability tensor for fractured rock masses based on the superposition principle of liquid dissipation energy. This model relies on the geometrical characteristics of rock fractures and the corresponding fracture network, and demonstrates the coupling effect between fluid flow and stress/deformation. This model empirically considers the effect of pre‐peak shear dilation and shear contraction on the hydraulic behavior of rock fractures and can be used to determine the applicability of the continuum approach to hydro‐mechanical coupling analysis. Results of numerical analysis presented in this paper show that the new model can effectively describe the permeability of fractured rock masses, and can be applied to the coupling analysis of seepage and stress fields. Copyright © 2008 John Wiley & Sons, Ltd.
Optimal empty vehicle redistribution for hub‐and‐spoke transportation systems
Authors: Song Dong‐Ping , Carter Jonathan 
Published: January 2008

AbstractThis article considers the empty vehicle redistribution problem in a hub‐and‐spoke transportation system, with random demands and stochastic transportation times. An event‐driven model is formulated, which yields the implicit optimal control policy. Based on the analytical results for two‐depot systems, a dynamic decomposition procedure is presented which produces a near‐optimal policy with linear computational complexity in terms of the number of spokes. The resulting policy has the same asymptotic behavior as that of the optimal policy. It is found that the threshold‐type control policy is not usually optimal in such systems. The results are illustrated through small‐scale numerical examples. Through simulation the robustness of the dynamic decomposition policy is tested using a variety of scenarios: more spokes, more vehicles, different combinations of distribution types for the empty vehicle travel times and loaded vehicle arrivals. This shows that the dynamic decomposition policy is significantly better than a heuristics policy in all scenarios and appears to be robust to the assumptions of the distribution types. © 2008 Wiley Periodicals, Inc. Naval Research Logistics, 2008
Dynamic scheduling of network resources with advance reservations in optical grids
Authors: Tanwir Savera , Battestilli Lina , Perros Harry , Karmous‐Edwards Gigi 
Published: January 2008

AbstractAdvance reservation of lightpaths in grid environments is necessary to guarantee QoS and reliability. In this paper, we have evaluated and compared several algorithms for dynamic scheduling of lightpaths using a flexible advance reservation model. The main aim is to find the best scheduling policy for a grid network resource manager that improves network utilization and minimizes blocking. The scheduling of lightpaths involves both routing and wavelength assignment. Our simulation results show that minimum‐cost adaptive routing where link costs are determined by the current and future usage of the link provides the minimum blocking. For wavelength assignment, we have used a scheme that reduces fragmentation by minimizing unused gaps. We have also analyzed approaches for failure recovery and resource optimization. Copyright © 2008 John Wiley & Sons, Ltd.
Pinpointing users with location estimation techniques and Wi‐Fi hotspot technology
Authors: Curran Kevin , Furey Eoghan 
Published: January 2008

AbstractLocation awareness is becoming an important capability for mobile computing; however, it has not been possible until now to provide cheap pervasive positioning systems. Wide area coverage is most famously achieved by using global positioning systems (GPS). A constellation of low‐orbit satellites cover the earth's surface. Unfortunately GPS does not work indoors and has limited success in big cities because of the ‘urban canyon’ effect. PlaceLab is a research project that attempts to solve the ubiquity issues surrounding 802.11‐based location estimation. PlaceLab, like RADAR, uses a device's 802.11 interface; however, it does not require the area to be pre‐calibrated. It predicts location via the known positions of the access points detected by the device. Commonly used systems have a number of drawbacks, including cost, accuracy and the ability to work indoors. PlaceLab is a piece of open source software developed by Intel Research that can pinpoint a user within a Wi‐Fi network. We set out here to investigate whether PlaceLab can be used as a means of establishing a user's position. This type of investigation could, if successful, pave the way for the development of other location‐based applications. This report documents the efforts to answer the above question. PlaceLab was found to work, but only in ideal locations where factors such as the number of floors and the lack of available APs did not affect its use. It was concluded that these factors prevent the system from being effective as a means of establishing a user's position in most locations on campus. Copyright © 2008 John Wiley & Sons, Ltd.
QoS management in mobile IP networks using a terminal assistant
Authors: Benmammar Badr , Jrad Zeina , Krief Francine 
Published: January 2008

AbstractThis paper describes a signalling environment for Quality of Service (QoS) negotiation and advance resource reservation in mobile IP networks. This environment is built in conformance with the generic signalling environment, which is standardized by the NSIS IETF working group. The advanced resource reservation protocol, called MQoS NSLP, is based on the QoS NSLP signalling application. It provides to mobile terminals the QoS required based on the user's mobility and QoS profile. In this work, we investigate the use of some techniques of the AI (Artificial Intelligence) domain to implement a user interface called NIA (Negotiation Individual Assistant) in order to determine the QoS profile and negotiate the QoS parameters in the new domain after the handover. Therefore, we use connectionist learning in the management of the negotiation profiles and agent technology to help the user choose the best service provider, dynamically negotiate the QoS on the user's behalf, and follow the user's behaviour to be able to anticipate the negotiation and manage renegotiation. The advance resource reservation is based on an object MSpec (Mobility Specification) which determines the future location of the mobile terminal. The MSpec object is a part of the mobility and QoS profile and is determined by the NIA in the mobile terminal. Copyright © 2008 John Wiley & Sons, Ltd.
An analytical simulator for deploying IP telephony
Authors: Salah K. , Darwish N. , Saleem M. , Shaaban Y. 
Published: January 2008

AbstractDeploying IP telephony or voice over IP (VoIP) is a major and challenging task. This paper describes an analytical design and planning simulator to assess the readiness of existing IP networks for the deployment of VoIP. The analytical simulator utilizes techniques used for network flows and queuing network analysis to compute two key performance bounds for VoIP: delay and bandwidth. The simulator is GUI‐based and has an interface with drag‐and‐drop features to easily construct any generic network topology. The simulator has an engine that automates and implements the analytical techniques. The engine determines the number of VoIP calls that can be sustained by the constructed network while satisfying VoIP QoS requirements and leaving adequate capacity for future growth. As a case study, the paper illustrates how the simulator can be utilized to assess the readiness to deploy VoIP for a typical network of a small enterprise. We have made the analytical simulator publicly available in order to improve and ease the process of VoIP deployment. Copyright © 2008 John Wiley & Sons, Ltd.
A comparison of abstract versions of deflation, balancing and additive coarse grid correction preconditioners
Authors: Nabben R. , Vuik C. 
Published: January 2008

AbstractIn this paper we consider various preconditioners for the conjugate gradient (CG) method to solve large linear systems of equations with symmetric positive definite system matrix. We continue the comparison between abstract versions of the deflation, balancing and additive coarse grid correction preconditioning techniques started in (SIAM J. Numer. Anal.2004;42:1631–1647;SIAM J. Sci. Comput.2006;27:1742–1759). There the deflation method is compared with the abstract additive coarse grid correction preconditioner and the abstract balancing preconditioner. Here, we close the triangle between these three methods. First of all, we show that a theoretical comparison of the condition numbers of the abstract additive coarse grid correction and the condition number of the system preconditioned by the abstract balancing preconditioner is not possible. We present a counter example, for which the condition number of the abstract additive coarse grid correction preconditioned system is below the condition number of the system preconditioned with the abstract balancing preconditioner. However, if the CG method is preconditioned by the abstract balancing preconditioner and is started with a special starting vector, the asymptotic convergence behavior of the CG method can be described by the so‐called effective condition number with respect to the starting vector. We prove that this effective condition number of the system preconditioned by the abstract balancing preconditioner is less than or equal to the condition number of the system preconditioned by the abstract additive coarse grid correction method. We also provide a short proof of the relationship between the effective condition number and the convergence of CG. Moreover, we compare theA‐norm of the errors of the iterates given by the different preconditioners and establish the orthogonal invariants of all three types of preconditioners. Copyright © 2008 John Wiley & Sons, Ltd.
Crack tip enrichment in the XFEM using a cutoff function
Authors: Chahine Elie , Laborde Patrick , Renard Yves 
Published: January 2008

AbstractWe consider a variant of the eXtended Finite Element Method (XFEM) in which a cutoff function is used to localize the singular enrichment surface. The goal of this variant is to obtain numerically an optimal convergence rate while reducing the computational cost of the classical XFEM with a fixed enrichment area. We give a mathematical result of quasi‐optimal error estimate. One of the key points of this paper is to prove the optimality of the coupling between the singular and the discontinuous enrichments. Finally, we present some numerical computations validating the theoretical result. These computations are compared with those of the classical XFEM and a non‐enriched method. Copyright © 2008 John Wiley & Sons, Ltd.
Consistent linearization and finite element implementation of an incrementally objective canonical form return mapping algorithm for large deformation inelasticity
Authors: Seifert T. , Maier G. 
Published: January 2008

AbstractThe present paper focuses on the consistent linearization and finite element implementation of an incrementally objective canonical form return mapping algorithm. A general and modular algorithmic setting, suited for almost any rate constitutive equations, is presented where the finite deformation consistent tangent modulus is obtained as a by‐product of the integration algorithm. Numerical examples illustrate the good performance of the proposed formulation, especially for large deformation increments with noteworthy superimposed rotation, where the consistent formulation converges quadratically in a reasonable number of iterations. Copyright © 2008 John Wiley & Sons, Ltd.
A new crack tip element for the phantom‐node method with arbitrary cohesive cracks
Authors: Rabczuk Timon , Zi Goangseup , Gerstenberger Axel , Wall Wolfgang A. 
Published: January 2008

AbstractWe have developed a new crack tip element for the phantom‐node method. In this method, a crack tip can be placed inside an element. Therefore, cracks can propagate almost independent of the finite element mesh. We developed two different formulations for the three‐node triangular element and four‐node quadrilateral element, respectively. Although this method is well suited for the one‐point quadrature scheme, it can be used with other general quadrature schemes. We provide some numerical examples for some static and dynamic problems. Copyright © 2007 John Wiley & Sons, Ltd.
Comparison of symptomatology in Taiwanese women pregnant with and without assisted reproductive technology
Authors: Kuo Pi‐Chao , Chu Nancy L. , Chen Yueh‐Chih , Su Tsann‐Jun , Chen Chung‐Hey 
Published: January 2008

AbstractWe compared the symptoms of 91 Taiwanese women, 50 pregnant by assisted reproductive technology (ART), with those of 41 women, pregnant without assistance. They completed a self‐administered demographic questionnaire and symptomatology inventory (SI) during each trimester. The ART group had a higher frequency of complications and hospitalizations than the unassisted women. No significant differences were found in physical and affective symptoms in the ART group across three trimesters, but significant differences were found in the unassisted group. In addition, ART and non‐ART women differed in types of individual symptoms experienced each trimester. These findings suggest the need for nurses to assess each group for the presence of specific symptoms throughout pregnancy and to provide individualized symptom management. © 2008 Wiley Periodicals, Inc. Res Nurs Health 31:208–216, 2008
Is there a bias against telephone interviews in qualitative research?
Authors: Novick Gina 
Published: January 2008

AbstractTelephone interviews are largely neglected in the qualitative research literature and, when discussed, they are often depicted as a less attractive alternative to face‐to‐face interviewing. The absence of visual cues via telephone is thought to result in loss of contextual and nonverbal data and to compromise rapport, probing, and interpretation of responses. Yet, telephones may allow respondents to feel relaxed and able to disclose sensitive information, and evidence is lacking that they produce lower quality data. This apparent bias against telephone interviews contrasts with a growing interest in electronic qualitative interviews. Research is needed comparing these modalities, and examining their impact on data quality and their use for studying varying topics and populations. Such studies could contribute evidence‐based guidelines for optimizing interview data. © 2008 Wiley Periodicals, Inc. Res Nurs Health 31:391–398, 2008
Knock‐in murine models of familial gastrointestinal stromal tumours
Authors: Gunawan B 
Published: January 2008

AbstractIn recent years, gastrointestinal stromal tumour (GIST) has emerged from a poorly understood group of mesenchymal tumours to a distinct pathological entity that has become a leading model for new therapies targeting kinases. GIST pathogenesis is driven by receptor tyrosine kinase‐activating mutations most often in KIT or PDGFRA that may be sporadic or result in familial GIST syndromes. In a recent issue of The Journal of Pathology (J Pathol 2008;214:302–311), Nakai and colleagues report that mutation of the previously un‐modelled tyrosine kinase II domain of KIT generates a spectrum of features very similar to that in two human GIST families. Knock‐in mouse models of GIST may prove extremely useful in pre‐clinical evaluation of kinase‐targeted compounds and of the mechanism of drug resistance, but intriguingly it now seems clearer that the distribution of GIST in mouse models and humans is different. Copyright © 2008 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Increased MMP‐2 activity during intervertebral disc degeneration is correlated to MMP‐14 levels
Authors: Rutges JPHJ , Kummer JA , Oner FC , Verbout AJ , Castelein RJM , Roestenburg HJA , Dhert WJA , Creemers LB 
Published: January 2008

AbstractIntervertebral disc (IVD) degeneration is associated with the increased expression of several matrix metalloproteinases (MMPs), in particular MMP‐2. However, little is known about the actual activity of MMP‐2 in healthy and degenerated discs, or what mechanisms are involved in its activation. A major activation pathway involves complex formation with MMP‐14 and a tissue inhibitor of metalloproteinases‐2 (TIMP‐2). In a series of 56 human IVDs, obtained at autopsy and graded according to the Thompson score (I–V), we analysed whether MMP‐2 activity was increased in different stages of IVD degeneration and to what extent activation was related to the production of MMP‐14 and TIMP‐2. MMP‐2 activation and production were quantified by gelatin zymography. Immunohistochemical staining of MMP‐14 and TIMP‐2 was quantified with a video overlay‐based system. A positive correlation was observed between the amount of active MMP‐2 and pro‐MMP‐2 and degeneration grade (p < 0.001, correlation coefficient (CC) 0.557; and p < 0.001, CC 0.556, respectively). MMP‐2 activity correlated positively with MMP‐14 and less strongly with TIMP‐2 (p = 0.001, CC 0.436; and p = 0.03, CC 0.288, respectively). Moreover, immunopositivity for MMP‐14 correlated to degeneration grade (p = 0.002, CC 0.398). IVD degeneration was associated with the activity of MMP‐2 and the correlation of its activation with MMP‐14 production suggests MMP‐14 activates MMP‐2 during degeneration. As MMP‐14 is capable of activating several other enzymes that are also thought to be involved in IVD degeneration, it may be a key mediator of the degenerative process. Copyright © 2008 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Application of analytical and preparative high‐speed counter‐current chromatography for the separation of Z‐ligustilide from a crude extract of Angelica sinensis
Authors: Wang Xiao , Shi Xingang , Li Fuwei , Liu Jianhua , Cheng Chuange 
Published: January 2008

AbstractZ‐Ligustilide was separated and purified from the traditional Chinese medicinal plant Angelica sinensis by high‐speed counter‐current chromatography (HSCCC). Analytical HSCCC was first used for the systematic selection of the two‐phase solvent system. Preparative HSCCC separation was performed with a two‐phase solvent system composed of petroleum ether (60–90°C)–ethanol–water at an optimum volume ratio of 10:17:10 (v/v). A total of 38 mg Z‐ligustilide at 98.8% purity was obtained in one step from 200 mg crude extract as determined by HPLC analysis. The structure of the target compound was identified by electron impact ionisation mass spectrometry. Copyright © 2008 John Wiley & Sons, Ltd.
Validated method for the quantification of artepillin‐C in Brazilian propolis
Authors: Matsuda Adriana Hitomi , de Almeida‐Muradian Ligia Bicudo 
Published: January 2008

AbstractBrazilian propolis contains several phenolic compounds among which 5 diprenyl‐4‐hydroxycinnamic acid (artepillin‐C) is commonly found in areas where flora is rich in Baccharis species. The quantification of artepillin‐C has become an important factor as an indicator of Brazilian propolis quality and the compound may be used as a chemical marker for quality control in exportating green propolis. This work was to validate the method and evaluate the content of artepillin‐C from 33 samples collected in different Brazilian regions. The method used was HPLC with UV–vis detection and a reversed‐phase C18 column. The validation parameters studied were: linearity, accuracy, precision, quantification and detection limits. The results obtained were: detection limit = 0.0036 µg/mL, quantification limit = 0.012 µg/mL, accuracy = 0.0064 and 0.078, recovery 98–102%. Artepillin‐C content varied from 0 to 11% depending on the geographical origin. Propolis from the southeast region presented the highest level of artepillin‐C (5.0–11.0%). Whist that from the northeast region did not show any artepillin‐C. Copyright © 2008 John Wiley & Sons, Ltd.
Outpatient use of cardiovascular drugs during pregnancy
Authors: Andrade Susan E. , Raebel Marsha A. , Brown Jeffrey , Lane Kimberly , Livingston James , Boudreau Denise , Rolnick Sharon J. , Roblin Douglas , Smith David H. , Dal Pan Gerald J. , Scott Pamela E. , Platt Richard 
Published: January 2008

AbstractPurposeTo provide information on the prevalence of use of cardiovascular drugs, some of which may have fetotoxic or teratogenic effects, in the outpatient setting among pregnant women in the United States.MethodsA retrospective study was conducted using the automated databases of seven health plans participating in the HMO Research Network Center for Education and Research on Therapeutics (CERT). Women who delivered an infant from 1 January 2001 to 31 December 2005 were identified. Cardiovascular drug use was evaluated assuming a gestational duration of 270 days.ResultsDuring the period 2001 through 2005, 118 935 deliveries were identified that met the criteria for study; 3.1% of women (N = 3672) were dispensed an antihypertensive medication and 0.12% of women (N = 146) were dispensed an antihyperlipidemic medication at any time during pregnancy. The most common antihypertensive drugs dispensed during pregnancy were nifedipine (1219 deliveries; 1.0%), methyldopa (961 deliveries; 0.8%), atenolol (593 deliveries; 0.5%), and labetalol (576 deliveries; 0.5%). Overall, 134 women (0.11%) received an angiotensin converting enzyme (ACE) inhibitor and 7 women (0.006%) received an angiotensin II receptor blocker (ARB) during pregnancy. Statins were the most commonly dispensed antihyperlipidemic drugs (71 deliveries; 0.06%).ConclusionsThe prevalence of use of cardiovascular drugs that are suspected to be fetotoxic or teratogenic (ACE inhibitors, ARBs, and statins) was low in this cohort of pregnant women. Differing patterns of use across health plans suggests that further research is needed to evaluate the potential differential effects of cardiovascular drugs to assist prescribers and patients in making informed treatment decisions. Copyright © 2008 John Wiley & Sons, Ltd.
Calibration of the WCT‐100 photoconductance instrument at low conductance
Authors: McIntosh Keith R. , Guo Jiun‐Hua , Abbott Malcolm D. , Bardos Robert A. 
Published: January 2008

AbstractThe WCT‐100 photoconductance instrument is used throughout the photovoltaic industry providing a relatively simple and inexpensive means to assess recombination parameters. This paper presents a method to determine its output voltage VWCT over the conductance range, S = 0·002–20 mS, a range not easily attained by the conventional calibration method. The relationship between VWCT and S is found to transition from being non‐linear to linear at S ∼ 1 mS, which equates to the conductance of a 300 µm thick 30 Ω‐cm silicon wafer. For samples whose dark conductance is lower than the transition conductance, the non‐linear relationship between VWCT and S must be taken into account to prevent a gross underestimation of recombination rate. The method we describe can equally well be used to investigate the calibration of other photoconductance instruments. It involves the simultaneous measurement of a device's electrical conductance and the instrument's output voltage under a range of steady‐state illumination intensities. Copyright © 2008 John Wiley & Sons, Ltd.