bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of growth temperature on Eu‐doped GaN layers grown by organometallic vapor phase epitaxy
Authors: Kawasaki Takashi , Nishikawa Atsushi , Furukawa Naoki , Terai Yoshikazu , Fujiwara Yasufumi 
Published: April 2010

AbstractWe investigated the effect of growth temperature on the luminescence properties of Eu‐doped GaN layers grown by organometallic vapor phase epitaxy (OMVPE). The dominant photoluminescence (PL) peak intensity at 621 nm, due to the intra‐4f shell transitions of 5D0‐7F2 in Eu3+ ions, became the highest when the sample was grown at 1000 °C. We consider three reasons for this temperature dependence. Firstly, Eu concentration became the highest when the sample was grown at 1000 °C. Secondly, Eu‐doped GaN layer grown at 1000 °C had the local structure of Eu3+ ions, which emitted at 621 nm preferentially. Thirdly, the density of screw and mixed dislocations decreased with increasing growth temperature. These results indicated that an appropriate growth temperature exists for strong Eu‐related luminescence from Eu‐doped GaN layer grown by OMVPE. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Towards a deeper understanding of the reduced efficiency droop in low defect‐density GaInN wide‐well LEDs
Authors: Maier Markus , Passow Thorsten , Kunzer Michael , Pletschen Wilfried , Köhler Klaus , Wagner Joachim 
Published: April 2010

AbstractA series of 400 nm emitting GaInN/GaN single‐well light‐emitting diodes, grown on ultra‐low dislocation density GaN templates with well widths varying between 3 and 18 nm, were investigated by pulsed and time resolved electroluminescence measurements using small signal modulation technique for the latter. A reduction of the efficiency droop at high current densities with increasing well width was observed. The highest overall external quantum efficiency was obtained for LEDs with 11 nm thick double‐heterostructure (or wide well) active region at current densities above 70 A/cm2. Furthermore, carrier lifetime and volume carrier density in the wells were determined. A model based on the interplay between defect assisted recombination, depending on dislocation density, and strongly carrier density dependent loss processes is presented explaining the well‐thickness dependence of the efficiency droop. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Q‐factor measurements on planar nitride cavities
Authors: Collins Daniel P. , Holmes Mark J. , Taylor Robert A. , Oliver Rachel A. , Kappers Menno J. , Humphreys Colin J. 
Published: April 2010

AbstractTo enable the study of cavity quantum electro‐dynamical effects in nitride systems, it is essential to be able to fabricate high quality cavity structures that exhibit large Q‐values of the order of several thousands. A promising candidate for such a realisation is based around the micro‐pillar distributed Bragg reflector (DBR) cavity. The growth of nitride stacks is problematic due to such material issues as lattice mismatch and dislocation propagation which seem to be more pronounced when compared to similar arsenide structures. In this paper we report on our efforts to characterize the homogeneity of our first generation planar DBR structures through both reflectivity measurements using the broadband output of a photonic crystal fiber (PCF) and cryogenic photoluminescence under ultraviolet (UV) excitation. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Deep etch of GaN by laser micromachining
Authors: Mak Giuseppe Y. , Lam Edmund Y. , Choi H. W. 
Published: April 2010

AbstractTrench formation for device isolation on GaN light‐emitting diode (LED) wafers via nanosecond ultraviolet laser micromachining is demonstrated. Owing to the dissimilar ablation thresholds between GaN and sapphire, the etch process terminates automatically at the GaN/sapphire interface. It was found that optimal focus offset, optimal pulse energy and high repetition rate are essential for obtaining a trench with tapered sidewall and smooth bottom surface, which is suitable for the conformal deposition of interconnects across the trench. This technique has been successfully applied to the rapid prototyping of interconnected LED arrays on a single chip. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
GaN‐based light emitting diodes with periodic nano‐structures on the surface fabricated by nanoimprint lithography technique
Authors: Naoi Yoshiki , Matsumoto Masakazu , Tan Tianya , Tohno Mistuaki , Sakai Shiro , Fukano Atsuyuki , Tanaka Satoru 
Published: April 2010

AbstractWe investigated the characteristics of GaN‐based light emitting diodes (LEDs) with periodic nano‐structures on the surface by nanoimprint lithography technique. We measured the intensity emitted through nano‐structure on the p‐GaN surface into the forward side in an air/GaN‐LED/sapphire configuration, and also the intensity through nano‐structure fabricated between GaN/sapphire interfaces into the back side. Angular spatial distribution of electroluminescence intensity from GaN‐based 380 nm UV and 410 nm blue LED with nano‐structures were considerably different from that for the sample without nano processing, and the lobe near the horizontal direction in the surface side profile was observed. The results can be explained by a combination of diffracted light by the fabricated grating by NIL and transmitted light though the sidewall at the interface of the periodic structure. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Making available information from studies sponsored by the pharmaceutical industry: some current practices
Authors: O'Kelly Michael , Julious Steven A. , Pyke Stephen , Day Simon , Todd Sue , Seldrup Jorgen , Matcham James 
Published: April 2010

AbstractSince the web‐based registry ClinicalTrials.gov was launched on 29 February 2000, the pharmaceutical industry has made available an increasing amount of information about the clinical trials that it sponsors. The process has been spurred on by a number of factors including a wish by the industry to provide greater transparency regarding clinical trial data; and has been both aided and complicated by the number of institutions that have a legitimate interest in guiding and defining what should be made available. This article reviews the history of this process of making information about clinical trials publicly available. It provides a reader's guide to the study registries and the databases of results; and looks at some indicators of consistency in the posting of study information. Copyright © 2010 John Wiley & Sons, Ltd.
The effect of variability and carryover on average bioequivalence assessment: A simulation study
Authors: Sánchez O María Pilar , Ocaña Jordi , Carrasco Josep L. 
Published: April 2010

AbstractThe purpose of this study was to evaluate the effect of residual variability and carryover on average bioequivalence (ABE) studies performed under a 2×2 crossover design. ABE is usually assessed by means of the confidence interval inclusion principle. Here, the interval under consideration was the standard ‘shortest’ interval, which is the mainstream approach in practice.The evaluation was performed by means of a simulation study under different combinations of carryover and residual variability besides of formulation effect and sample size. The evaluation was made in terms of percentage of ABE declaration, coverage and interval precision.As is well known, high levels of variability distort the ABE procedures, particularly its type II error control (i.e. high variabilities make difficult to declare bioequivalence when it holds). The effect of carryover is modulated by variability and is especially disturbing for the type I error control. In the presence of carryover, the risk of erroneously declaring bioequivalence may become high, especially for low variabilities and large sample sizes. We end up with some hints concerning the controversy about pretesting for carryover before performing ABE analysis. Copyright © 2010 John Wiley & Sons, Ltd.
Organizing matters: how ‘the social dimension’ gets lost in sustainability projects
Authors: Vifell Åsa Casula , Soneryd Linda 
Published: April 2010

AbstractThis paper explores the conditions for taking the social dimension into consideration when trying to aim for increased sustainability through activities organized in projects. Among the three commonly accepted pillars of sustainable development – economic, ecological and social – the social dimension is often the most vague and least explicit in practical attempts to shape sustainable development. The aim with this study is to explore the role of organizing in shaping the balance between the pillars. The two cases examined are projects explicitly related to sustainable development goals set by the national government or parliament and implemented by other actors. The cases concern two topics: food production and electromagnetic fields. On the basis of relevant organizational dimensions and case analyses, the paper shows how the organization of sustainability shapes the ways in which the projects articulate the social dimension. This leads to practical advice for organizing new projects in the future. Copyright © 2010 John Wiley & Sons, Ltd and ERP Environment.
Strength of evidence of non‐inferiority trials—The adjustment of the type I error rate in non‐inferiority trials with the synthesis method
Authors: Kang Seung‐Ho , Tsong Yi 
Published: April 2010

AbstractIn non‐inferiority trials that employ the synthesis method several types of dependencies among test statistics occur due to sharing of the same information from the historical trial. The conditions under which the dependencies appear may be divided into three categories. The first case is when a new drug is approved with single non‐inferiority trial. The second case is when a new drug is approved if two independent non‐inferiority trials show positive results. The third case is when two new different drugs are approved with the same active control. The problem of the dependencies is that they can make the type I error rate deviate from the nominal level. In order to study such deviations, we introduce the unconditional and conditional across‐trial type I error rates when the non‐inferiority margin is estimated from the historical trial, and investigate how the dependencies affect the type I error rates. We show that the unconditional across‐trial type I error rate increases dramatically as does the correlation between two non‐inferiority tests when a new drug is approved based on the positive results of two non‐inferiority trials. We conclude that the conditional across‐trial type I error rate involves the unknown treatment effect in the historical trial. The formulae of the conditional across‐trial type I error rates provide us with a way of investigating the conditional across‐trial type I error rates for various assumed values of the treatment effect in the historical trial. Copyright © 2010 John Wiley & Sons, Ltd.
Likelihood‐based methods for estimating the association between a health outcome and left‐ or interval‐censored longitudinal exposure data
Authors: Wannemuehler Kathleen A. , Lyles Robert H. , Manatunga Amita K. , Terrell Metrecia L. , Marcus Michele 
Published: April 2010

AbstractThe Michigan Female Health Study (MFHS) conducted research focusing on reproductive health outcomes among women exposed to polybrominated biphenyls (PBBs). In the work presented here, the available longitudinal serum PBB exposure measurements are used to obtain predictions of PBB exposure for specific time points of interest via random effects models. In a two‐stage approach, a prediction of the PBB exposure is obtained and then used in a second‐stage health outcome model. This paper illustrates how a unified approach, which links the exposure and outcome in a joint model, provides an efficient adjustment for covariate measurement error. We compare the use of empirical Bayes predictions in the two‐stage approach with results from a joint modeling approach, with and without an adjustment for left‐ and interval‐censored data. The unified approach with the adjustment for left‐ and interval‐censored data resulted in little bias and near‐nominal confidence interval coverage in both the logistic and linear model setting. Published in 2010 by John Wiley & Sons, Ltd.
Space–time latent component modeling of geo‐referenced health data
Authors: Lawson Andrew B. , Song Hae‐Ryoung , Cai Bo , Hossain Md Monir , Huang Kun 
Published: April 2010

AbstractLatent structure models have been proposed in many applications. For space–time health data it is often important to be able to find the underlying trends in time, which are supported by subsets of small areas. Latent structure modeling is one such approach to this analysis. This paper presents a mixture‐based approach that can be applied to component selection. The analysis of a Georgia ambulatory asthma county‐level data set is presented and a simulation‐based evaluation is made. Copyright © 2010 John Wiley & Sons, Ltd.
Combining stratified and unstratified log‐rank tests in paired survival data
Authors: Oakes David , Feng Changyong 
Published: April 2010

AbstractThe log‐rank test is the most widely used nonparametric method for testing treatment differences in survival between two treatment groups due to its efficiency under the proportional hazards model. Most previous work on the log‐rank test has assumed that the samples from the two treatment groups are independent. This assumption is not always true. In multi‐center clinical trials, survival times of patients in the same medical center may be correlated due to factors specific to each center. For such data, we can construct both stratified and unstratified log‐rank tests. These two tests turn out to have very different powers for correlated samples. An appropriate linear combination of these two tests may give a more powerful test than either of the individual test. Under a bivariate frailty model, we obtain closed‐form asymptotic local alternative distributions and the correlation coefficient between these two tests. Based on these results we construct an optimal linear combination of the two test statistics to maximize the local power. Simulation studies with Hougaard's model confirm our construction. We also study the robustness of the combined test by simulations. Copyright © 2010 John Wiley & Sons, Ltd.
A linear exponent AR(1) family of correlation structures
Authors: Simpson Sean L. , Edwards Lloyd J. , Muller Keith E. , Sen Pranab K. , Styner Martin A. 
Published: April 2010

AbstractIn repeated measures settings, modeling the correlation pattern of the data can be immensely important for proper analyses. Accurate inference requires proper choice of the correlation model. Optimal efficiency of the estimation procedure demands a parsimonious parameterization of the correlation structure, with sufficient sensitivity to detect the range of correlation patterns that may occur. Many repeated measures settings have within‐subject correlation decreasing exponentially in time or space. Among the variety of correlation patterns available for this context, the continuous‐time first‐order autoregressive correlation structure, denoted AR(1), sees the most utilization. Despite its wide use, the AR(1) structure often poorly gauges within‐subject correlations that decay at a slower or faster rate than required by the AR(1) model. To address this deficiency we propose a two‐parameter generalization of the continuous‐time AR(1) model, termed the linear exponent autoregressive (LEAR) correlation structure, which accommodates much slower and much faster decay patterns. Special cases of the LEAR family include the AR(1), compound symmetry, and first‐order moving average correlation structures. Excellent analytic, numerical, and statistical properties help make the LEAR structure a valuable addition to the suite of parsimonious correlation models for repeated measures data. Both medical imaging data concerning neonate neurological development and longitudinal data concerning diet and hypertension [DASH (Dietary Approaches to Stop Hypertension) study] exemplify the utility of the LEAR correlation structure. Copyright © 2010 John Wiley & Sons, Ltd.
Effect of two horizontal components of earthquake on nonlinear response of torsionally coupled base isolated structures
Authors: Khoshnoudian Faramarz , Azad Ali Imani 
Published: April 2010

SUMMARYTorsion in base‐isolated structures using bilinear rubber isolators effected by two horizontal components of earthquake simultaneously is investigated under various principal parameters including number of storeys; ratio of uncoupled torsional frequency to lateral frequency in the superstructure; ratio of uncoupled torsional frequency to lateral frequency in the isolation system; mass eccentricity in the superstructure and isolation system; and, in addition, the direction of eccentricity. Structure was supposed a shear structure and it was modeled by using concentrated mass and springs. Isolators are modelled by using nonlinear springs considering the interaction of isolator behaviour in two directions. The effect of variation in considered parameters on the behaviour of the superstructure and isolation system is investigated under seven ground motions. It is demonstrated that the parameters affect asymmetric structure behaviour with respect to symmetric one. The results of our investigations help us to understand the asymmetric structure behaviour under bidirectional earthquake by comparing it with a symmetric one. These results demonstrate that asymmetry in the superstructure or isolation system could have a significant effect on the torsional behaviour of isolated structures. In addition, the results show that the use of rigid superstructures and calculation of dynamic torsion by multiplying eccentricity by the dynamic base shear are unacceptable assumptions. Torsional effect on the isolated structural behaviour is amplified by considering two horizontal components of earthquake and comparing them with just one horizontal component. Copyright © 2010 John Wiley & Sons, Ltd.
Dual criterion equivalent linearization approach for yielding structures under earthquake excitation
Authors: Rahmatabadi Payman , Khaloo Alireza 
Published: April 2010

AbstractIn order to estimate both maximum displacement and maximum inertia force of bilinear hysteretic system subjected to earthquake motions, an equivalent linearization approach with new effective parameters is presented. Effective mass and effective damping ratio as pair of effective parameters instead of the effective period and effective damping ratio in existing equivalent linear systems are introduced. Two error measures for displacement and inertia force are defined. Error distributions over a two‐dimensional parameter space of effective parameters are analysed, and the parameters are determined through a statistical approach with a dual optimization criterion for displacement and inertia force errors applicable to structural design. Single‐degree‐of‐freedom systems with bilinear hysteretic model; natural periods from 0.1 to 3.0 s; linear damping ratios from 3 to 50%; ductility ratios from 1.5 to 6; and post‐yield slope ratios 0, 0.05, 0.1 are considered. Analytical expressions for the effective parameters, and the ratio of the maximum inertia force to the maximum restoring force as functions of response ductility, elastic damping ratio and natural period of inelastic system are proposed for different site conditions and post‐yield slope ratios. Evaluation of proposed equations is performed, which reveals that the linear parameters lead to permissible error ranges. Copyright © 2010 John Wiley & Sons, Ltd.
Evaluation of seismic behaviour of steel special moment frame buildings with vertical irregularities
Authors: Le‐Trung Kien , Lee Kihak , Lee Jaehong , Lee Do Hyung 
Published: April 2010

AbstractThis paper concentrates on investigating the seismic behaviours of vertically irregular steel special moment frame (SMF) buildings by comparison with the regular counterpart. All buildings in this study were assumed to be located in Los Angeles, and subjected to 20 earthquake ground motions with a seismic hazard level of 2% probability of exceedance in 50 years. The beam–column connections of the buildings were modelled to consider the panel zone deformation. In addition, a ductile connection model accompanied by strength degradation was incorporated to the analysis programme in an effort to obtain more accurate response results. Three types of irregularities (mass, stiffness and strength irregularity) specified as vertical irregularities in the IBC 2000 provisions were imposed to the original building. Nonlinear static and dynamic analyses were performed, and the confidence levels of which the performance objective will be satisfied were calculated as well. The effects of different irregularity types and levels on the seismic behaviours of the buildings were investigated and discussed in terms of the height‐wise distribution of storey drifts, maximum storey drift demands, global collapse storey drift capacities and confidence levels. Copyright © 2010 John Wiley & Sons, Ltd.
Start of structural damage in stucco walls
Authors: Hart Gary C. , Jain Anurag , Dumortier Alexis , Simsir Can , Barnes Michael S. 
Published: April 2010

AbstractA wealth of data about the performance of stucco shear walls under cyclic loading has become available since 2001. Stucco and drywall are the only earthquake and wind lateral force‐resisting systems in many existing residential buildings, especially single and multi‐family homes built before 1980. This paper presents the results of an analysis of cyclic tests conducted at the University of California, Irvine, on solid stucco walls to determine the start of structural damage. Copyright © 2010 John Wiley & Sons, Ltd.
Seismic performance analysis of Wenchuan Hospital structure with viscous dampers
Authors: Chen Xue‐Wei , Li Jia‐Xuan , Cheang Jack 
Published: April 2010

AbstractAnalytical investigation was undertaken to assess the seismic performance of Wenchuan Hospital located in Wenchuan county, southwest China's Sichuan province, where a severe earthquake has occurred in May 2008. The structure consists of a four‐storey reinforced concrete frame with viscous dampers. The irregular building is 18·35‐m tall and has a total floor area of 17 000 m2. Viscous dampers are set along the outside surface of structure to get a more efficient reduction of structure responses. The design idea of performance‐based seismic design is presented in this paper. Seismic performance of the structure with and without viscous dampers under different levels of ground motion is analysed and verified by different methods, including elastic analysis under frequent earthquake, unyielding and elastic check of structure element under medium earthquake, static nonlinear analysis and dynamic nonlinear analysis under rare earthquake. And a comparative analysis is presented, such as results between elastic and inelastic analysis, static nonlinear analysis and dynamic nonlinear analysis, and structure with and without viscous dampers. The control effects of viscous dampers on internal force, deformation and energy dissipation of the structure are also studied. Meanwhile, a practical method to calculate the supplemental damping ratio added by viscous dampers is proposed for elastic analysis with dampers. After a series of analysis, the performance objective of the structure can be well verified. Copyright © 2010 John Wiley & Sons, Ltd.