bluuebunny/crossref_metadata_2025_split huggingface dataset:
Observer‐based stabilization of linear switching systems
Authors: Caravani Paolo , De Santis Elena 
Published: November 2008

AbstractThe discrete component of the hybrid state of a discrete‐time linear switching system is assumed to be uncontrolled and unobserved. Conditions of stabilizability for this class of systems are given in terms of a new definition of control invariance, based on the realization of a discrete observer that permits reconstruction of the discrete‐state in certain intervals of the time basis. This paper highlights the relationship between the minimum dwell time of the system and its stabilizability. An almost complete characterization of stabilizability is offered in terms of certain subsets of the continuous‐state space. These sets are amenable to tractable parametric procedures for controller synthesis. Copyright © 2008 John Wiley & Sons, Ltd.
Kalman filter‐based adaptive control for networked systems with unknown parameters and randomly missing outputs
Authors: Shi Y. , Fang H. , Yan M. 
Published: November 2008

AbstractThis paper investigates the problem of adaptive control for networked control systems with unknown model parameters and randomly missing outputs. In particular, for a system with the autoregressive model with exogenous input placed in a network environment, the randomly missing output feature is modeled as a Bernoulli process. Then, an output estimator is designed to online estimate the missing output measurements, and further a Kalman filter‐based method is proposed for parameter estimation. Based on the estimated output and the available output, and the estimated model parameters, an adaptive control is designed to make the output track the desired signal. Convergence properties of the proposed algorithms are analyzed in detail. Simulation examples illustrate the effectiveness of the proposed method. Copyright © 2008 John Wiley & Sons, Ltd.
Asymmetric Ramsey properties of random graphs involving cliques
Authors: Marciniszyn Martin , Skokan Jozef , Spöhel Reto , Steger Angelika 
Published: November 2008

AbstractConsider the following problem: For given graphs G and F1,…,Fk, find a coloring of the edges of G with k colors such that G does not contain Fi in color i. Rödl and Ruciński studied this problem for the random graph Gn,p in the symmetric case when k is fixed and F1 = ··· = Fk = F. They proved that such a coloring exists asymptotically almost surely (a.a.s.) provided that p ≤ bn−β for some constants b = b(F,k) and β = β(F). This result is essentially best possible because for p ≥ Bn−β, where B = B(F,k) is a large constant, such an edge‐coloring does not exist. Kohayakawa and Kreuter conjectured a threshold function n for arbitrary F1,…,Fk.In this article we address the case when F1,…,Fk are cliques of different sizes and propose an algorithm that a.a.s. finds a valid k‐edge‐coloring of Gn,p with p ≤ bn−β for some constant b = b(F1,…,Fk), where β = β(F1,…,Fk) as conjectured. With a few exceptions, this algorithm also works in the general symmetric case. We also show that there exists a constant B = B(F1,…,Fk) such that for p ≥ Bn−β the random graph Gn,p a.a.s. does not have a valid k‐edge‐coloring provided the so‐called KŁR‐conjecture holds. © 2008 Wiley Periodicals, Inc. Random Struct. Alg., 2009
Computing in fault tolerant broadcast networks and noisy decision trees
Authors: Newman Ilan 
Published: November 2008

AbstractWe consider a fault tolerant broadcast network of n processors each holding one bit of information. The goal is to compute a given Boolean function on the n bits. In each step, a processor may broadcast one bit of information. Each listening processor receives the bit that was broadcast with error probability bounded by a fixed constant ϵ. The errors in different steps, as well as for different receiving processors in the same step, are mutually independent. The protocols that are considered in this model are oblivious protocols: At each step, the processors that broadcast are fixed in advanced and independent of the input and the outcome of previous steps.We present here the first linear complexity protocols for several classes of Boolean functions. This answer an open question of Yao (Invited talk in the 5th ISTCS Conf., 1997), considering this fault tolerant model that was introduced by El Gamal (Open problems presented at the 1984 workshop on Specific Problems in Communication and Computation sponsored by Bell Communication Research) and studied also by Gallager IEEE Tran Info Theory 34 (1988) 176–180. © 2008 Wiley Periodicals, Inc. Random Struct. Alg., 2009
Delaunay graphs of point sets in the plane with respect to axis‐parallel rectangles
Authors: Chen Xiaomin , Pach János , Szegedy Mario , Tardos Gábor 
Published: November 2008

AbstractGiven a point set P in the plane, the Delaunay graph with respect to axis‐parallel rectangles is a graph defined on the vertex set P, whose two points p,q ∈ P are connected by an edge if and only if there is a rectangle parallel to the coordinate axes that contains p and q, but no other elements of P. The following question of Even et al. (SIAM J Comput 33 (2003) 94–136) was motivated by a frequency assignment problem in cellular telephone networks: Does there exist a constant c > 0 such that the Delaunay graph of any set of n points in general position in the plane contains an independent set of size at least cn? We answer this question in the negative, by proving that the largest independent set in a randomly and uniformly selected point set in the unit square is O(nlog 2 log n/log n), with probability tending to 1. We also show that our bound is not far from optimal, as the Delaunay graph of a uniform random set of n points almost surely has an independent set of size at least cn log log n/(log n log log log n).We give two further applications of our methods: (1) We construct two‐dimensional n‐element partially ordered sets such that the size of the largest independent sets of vertices in their Hasse diagrams is o(n). This answers a question of Matoušek and Přívětivý (Combinat Probab Comput 15 (2006) 473–475) and improves a result of Kříž and Nešetřil (Order 8 (1991) 41–48). (2) For any positive integers c and d, we prove the existence of a planar point set with the property that no matter how we color its elements by c colors, we find an axis‐parallel rectangle containing at least d points, all of which have the same color. This solves an old problem from the work of Brass et al. (Research Problem in Discrete Geometry Springer‐Verlag, New York, 2005). © 2008 Wiley Periodicals, Inc. Random Struct. Alg., 2009
Induced subgraphs with distinct sizes
Authors: Alon Noga , Kostochka A.V. 
Published: November 2008

AbstractWe show that for every 0 < ϵ < 1/2, there is an n0 = n0(ϵ) such that if n > n0 then every n‐vertex graph G of size at least $\varepsilon \left( {\matrix{ {\matrix{ n \cr 2 \cr } } \cr } } \right)$ and at most $(1- \varepsilon) \left( {\matrix{ {\matrix{ n \cr 2 \cr } } \cr } } \right)$ contains induced k‐vertex subgraphs with at least 10−7k different sizes, for every $k \le {{\varepsilon n} \over 3}$. This is best possible, up to a constant factor. This is also a step toward a conjecture by Erdős, Faudree, and Sós on the number of distinct pairs (|V (H)|,|E(H)|) of induced subgraphs of Ramsey graphs. © 2008 Wiley Periodicals, Inc. Random Struct. Alg., 2009
Covariate adjustment in randomized trials with binary outcomes: Targeted maximum likelihood estimation
Authors: Moore K. L. , van der Laan M. J. 
Published: November 2008

AbstractCovariate adjustment using linear models for continuous outcomes in randomized trials has been shown to increase efficiency and power over the unadjusted method in estimating the marginal effect of treatment. However, for binary outcomes, investigators generally rely on the unadjusted estimate as the literature indicates that covariate‐adjusted estimates based on the logistic regression models are less efficient. The crucial step that has been missing when adjusting for covariates is that one must integrate/average the adjusted estimate over those covariates in order to obtain the marginal effect. We apply the method of targeted maximum likelihood estimation (tMLE) to obtain estimators for the marginal effect using covariate adjustment for binary outcomes. We show that the covariate adjustment in randomized trials using the logistic regression models can be mapped, by averaging over the covariate(s), to obtain a fully robust and efficient estimator of the marginal effect, which equals a targeted maximum likelihood estimator. This tMLE is obtained by simply adding a clever covariate to a fixed initial regression. We present simulation studies that demonstrate that this tMLE increases efficiency and power over the unadjusted method, particularly for smaller sample sizes, even when the regression model is mis‐specified. Copyright © 2008 John Wiley & Sons, Ltd.
A flexible strategy for testing subgroups and overall population
Authors: Alosh Mohamed , Huque Mohammad F. 
Published: November 2008

AbstractSubgroup analyses in addition to the total study population analysis are common in clinical trials. However, it is well recognized that findings from subgroup analyses do not provide confirmatory evidence for subgroup treatment effects without placing a priori criteria for ensuring that their findings are scientifically sound. In this paper we address some of the common pitfalls of subgroup analyses. Subgroups analyses inherently have low power for detecting treatment effects. We investigate the power interplay for a subgroup analysis and that for the total study population and list factors that impact the power of a subgroup analysis. Then we introduce a flexible statistical strategy for testing a pre‐specified sequence of hypotheses for both the overall and a subgroup. The proposed method strongly controls the familywise Type I error rate and enjoys higher power than other traditional methods. This testing strategy allows testing for a subgroup once a pre‐specified degree of consistency in the efficacy findings between the subgroup and the overall study population is met. In addition, it accounts for the dependency between test statistics for the subgroup and the overall study population. We discuss the power performance of this new method and provide significance levels for subgroup analysis. Finally, we illustrate its application through retrospective analysis of data from three published clinical trials. Copyright © 2008 John Wiley & Sons, Ltd.
Transformation‐invariant and nonparametric monotone smooth estimation of ROC curves
Authors: Du Pang , Tang Liansheng 
Published: November 2008

AbstractWhen a new diagnostic test is developed, it is of interest to evaluate its accuracy in distinguishing diseased subjects from non‐diseased subjects. The accuracy of the test is often evaluated by receiver operating characteristic (ROC) curves. Smooth ROC estimates are often preferable for continuous test results when the underlying ROC curves are in fact continuous. Nonparametric and parametric methods have been proposed by various authors to obtain smooth ROC curve estimates. However, there are certain drawbacks with the existing methods. Parametric methods need specific model assumptions. Nonparametric methods do not always satisfy the inherent properties of the ROC curves, such as monotonicity and transformation invariance. In this paper we propose a monotone spline approach to obtain smooth monotone ROC curves. Our method ensures important inherent properties of the underlying ROC curves, which include monotonicity, transformation invariance, and boundary constraints. We compare the finite sample performance of the newly proposed ROC method with other ROC smoothing methods in large‐scale simulation studies. We illustrate our method through a real life example. Copyright © 2008 John Wiley & Sons, Ltd.
Intercommunity relationships and community growth in China's high technology industries 1988–2000
Authors: Zhang Yan , Li Haiyang , Schoonhoven Claudia Bird 
Published: November 2008

AbstractIn this study, we examine how intercommunity relationships affect the growth of organizational communities. Using a unique panel dataset on 53 technology development communities in China spanning 1988–2000, we found that regional community density, a community's geographic proximity to the nearest community and its domain overlap with the nearest community have an inverted U‐shaped relationship with the community's growth. These non‐monotonic results suggest that adjacent communities have both mutualistic and competitive effects on each other. Theoretical and managerial implications are discussed. Copyright © 2008 John Wiley & Sons, Ltd.
An architecture‐centric software maintainability assessment using information theory
Authors: Anan Muhammad , Saiedian Hossein , Ryoo Jungwoo 
Published: November 2008

AbstractArchitecture‐based metrics can provide valuable information on whether or not one can localize the effects of modification (such as adjusting data flows or control flows) in software and can therefore be used to prevent the changes from adversely affecting other software components. This paper proposes an architecture‐centric metric using entropy for assessing structural dependencies among software components. The proposed metric is based on a mathematical model representing the maintainability snapshot of a system. The introduced architectural‐level metric includes measures for coupling and cohesion. From this model, the relative maintainability of a component, referred to as a maintainability profile, can be developed to identify architectural decisions that are detrimental to the maintainability of a system. Copyright © 2008 John Wiley & Sons, Ltd.
Nuchal translucency and nasal bone in first‐trimester ultrasound screening for aneuploidy in multiple pregnancies
Authors: Sepulveda W. , Wong A. E. , Casasbuenas A. 
Published: November 2008

AbstractObjectiveTo review our experience with first‐trimester screening of chromosomal abnormalities in multiple pregnancies using nuchal translucency (NT) thickness measurement and nasal bone assessment.MethodsCases of multiple pregnancy presenting for first‐trimester ultrasound evaluation and with viable fetuses measuring between 45 and 84 mm were recruited for this study. Crown–rump length, NT thickness, the presence or absence of the nasal bone and chorionicity were determined and the information prospectively collected in a dedicated database.ResultsThere were 206 twin pregnancies, eight sets of triplets, and one set of quadruplets, totalling 440 screened fetuses. Information on perinatal outcome was available in all cases. The NT thickness was measured in all cases and was found to be greater than the 95th percentile in six (8.6%) of the 70 monochorionic fetuses and in 10 (2.7%) of the 370 dichorionic fetuses (P < 0.05, Fisher's exact test). The nasal bone was successfully assessed in 421 of the 440 (95.7%) fetuses and found to be absent in only four cases, three of which were found to have aneuploidy. Chromosomal abnormalities were diagnosed in six fetuses from one monochorionic and four dichorionic twin pregnancies. Five of the six affected cases were associated with increased NT thickness (sensitivity 83.3%), whereas the nasal bone was absent in only three of the aneuploid fetuses (sensitivity 50%).ConclusionsFirst‐trimester ultrasound screening for chromosomal abnormalities using NT thickness in multiple pregnancies is highly sensitive. However, nasal bone assessment is not only limited in sensitivity but also more challenging in multiple than in singleton pregnancies owing to difficulties in obtaining adequate views of the fetal face. Copyright © 2008 ISUOG. Published by John Wiley & Sons, Ltd.
E‐CLEMA: A cross‐layer design for improved quality of service in mobile WiMAX networks
Authors: Triantafyllopoulou Dionysia , Passas Nikos , Merakos Lazaros , Sagias Nikos C. , Mathiopoulos P. Takis 
Published: November 2008

AbstractIn this paper, an efficient cross‐layer design that performs joint adaptation of the physical (PHY) and application layers of a mobile WiMAX network is proposed. The design takes into account channel state and performance information from the PHY and medium access control (MAC) layers, respectively. It uses a decision algorithm to evaluate this information, specify unfavorable conditions regarding low channel quality and increased congestion, and take measures by coordinating modulation order, transmission power, and media encoding rate, toward improved overall quality of service (QoS) offered to the user. Extensive simulation results show that the proposed design achieves considerably reduced packet loss and power consumption, combined with increased throughput as compared to a typical mobile WiMAX system. Copyright © 2008 John Wiley & Sons, Ltd.
E2SRT: enhanced event‐to‐sink reliable transport for wireless sensor networks
Authors: Kumar Sunil , Feng Zhenhua , Hu Fei , Xiao Yang 
Published: November 2008

AbstractAn event‐to‐sink reliable transport (ESRT) control scheme was recently proposed to address the event‐to‐sink reliability issues in wireless sensor network (WSN). In this paper, we study the performance of ESRT in the presence of ‘over‐demanding’ event reliability, using both the analytical and simulation approaches. We show that the ESRT protocol does not achieve optimum reliability and begins to fluctuate between two inefficient network states. With insights from update mechanism in ESRT, we propose a new algorithm, called enhanced ESRT (E2SRT), to solve the ‘over‐demanding’ event reliability problem and to stabilize the network. Simulation results show that E2SRT outperforms ESRT in terms of both reliability and energy consumption in the presence of ‘over‐demanding’ event reliability. Besides, it ensures robust convergence in the presence of dynamic network environments. Copyright © 2008 John Wiley & Sons, Ltd.
Chemical character of BCxNy layers grown by CVD with trimethylamine borane
Authors: Baake O. , Hoffmann P. S. , Klein A. , Pollakowski B. , Beckhoff B. , Ensinger W. , Kosinova M. , Fainer N. , Sulyaeva V. S. , Trunova V. 
Published: November 2008

AbstractLayers of BCxNy were produced in a chemical vapour deposition (CVD) process using trimethylamine borane with He, N2, and NH3, respectively, as precursor. These layers deposited on Si (100) wafers were characterized chemically by X‐ray photoelectron spectroscopy (XPS) and synchrotron radiation‐based total reflection X‐ray fluorescence analysis combined with near‐edge X‐ray absorption fine structure spectroscopy (TXRF‐NEXAFS). As a result, the composition of the material produced without NH3 is a B‐C bonds containing compound with an atomic relation 1:1. Adding NH3 with a partial pressure of up to about 1.3 Pa the product could be identified as B2C2N. Increasing the partial pressure of NH3 to 1.7 and 2.1 Pa the product was enriched in nitrogen yielding a compound characterized as h‐BCN. In all cases an impurity of oxygen was observed. Copyright © 2008 John Wiley & Sons, Ltd.
Qualitative urinary organic acid analysis: Methodological approaches and performance
Authors: Peters V. , Garbade S. F. , Langhans C. D. , Hoffmann G. F. , Pollitt R. J. , Downing M. , Bonham J. R. 
Published: November 2008

SummaryA programme for proficiency testing of biochemical genetics laboratories undertaking urinary qualitative organic acid analysis and its results for 50 samples examined for factors contributing to poor performance are described. Urine samples from patients in whom inherited metabolic disorders have been confirmed as well as control urines were circulated to participants and the results from 94 laboratories were evaluated. Laboratories showed variability both in terms of their individual performance and on a disease‐specific basis. In general, conditions including methylmalonic aciduria, propionic aciduria, isovaleric aciduria, mevalonic aciduria, Canavan disease and 3‐methylcrotonyl‐CoA carboxylase were readily identified. Detection was poorer for other diseases such as glutaric aciduria type II, glyceric aciduria and, in one sample, 3‐methylcrotonyl‐CoA carboxylase deficiency. To identify the factors that allow some laboratories to perform well on a consistent basis while others perform badly, we devised a questionnaire and compared the responses with the results for performance in the scheme. A trend towards better performance could be demonstrated for those laboratories that regularly use internal quality control (QC) samples in their sample preparation (p = 0.079) and those that participate in further external quality assurance (EQA) schemes (p = 0,040). Clinicians who depend upon these diagnostic services to identify patients with these defects and the laboratories that provide them should be aware of the potential for missed diagnoses and the factors that may lead to improved performance.
Xanthogranulomatous Pyelonephritis: No Longer A Contraindication for Laparoscopic Surgery?
Authors: Qadan Motaz , Wines Michael , Tolley David A. 
Published: November 2008

Background: Xanthogranulomatous pyelonephritis is a chronic renal inflammatory condition associated with significant renal and peri-renal inflammation. Consequently, operative treatment of this condition has traditionally been by open nephrectomy rather than the laparoscopic approach. We report our experience with the diagnosis and management of XGP in our department, which has subsequently been histologically confirmed. Patients and methods: We reviewed records of all patients with a histological diagnosis of XGP between 1984 and 2007. 20 patients with a diagnosis were included. Patient demographics, preoperative presentation, diagnostic imaging, operative details, post-operative recovery and complications were included in our data. Results: 13 patients underwent open nephrectomy and 7 patients underwent a laparoscopic procedure, of which 1 was subsequently converted to an open procedure. Blood loss, analgesic requirement, time to first meal and length of stay (LOS) in hospital were all lower in the laparoscopic group compared with the open group (362.5 ml vs. 723.6 ml, p = 0.049; 65.3 mg vs. 146.9 mg, p = 0.153; 2.8 days vs. 4.2 days, p= 0.184; 4.4 days vs. 9.8 days, p = 0.084). Operative times were similar in both groups (157.5 min vs. 154.2 min, p= 0.888). There were 5 complications in the laparoscopic group and 13 in the open group. Conclusion: The laparoscopic approach, although technically challenging, provides superior intra-operative and post-operative recovery results compared to the open approach with comparable operative times and incidences of complications. In specialised centres and in experienced hands, laparoscopic nephrectomy should be considered as the first choice procedure in those patients with a suspected diagnosis of XGP.