bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photoluminescence properties of Al‐rich AlXGa1‐XN grown on AlN/sapphire template by MOCVD
Authors: Zeng Jianping , Yan Jianchang , Wang Junxi , Cong Peipei , Li Jinmin , Sun Shuaishuai , Tao Ye 
Published: January 2012

AbstractOptical properties of the un‐doped and the Si‐doped AlGaN epilayers have been studied by using the deep ultraviolet photoluminescence (PL) spectrum. The samples were grown under the same conditions on a HT‐AlN template by low pressure metal‐organic chemical vapour deposition (LP‐MOCVD). The Al composition and the relaxation status were detected to be 0.654 and 42% for the un‐doped AlGaN, 0.657 and 63% for the Si‐doped AlGaN by use the high resolution XRD. The temperature dependent PL spectra of both AlGaN epilayers reveal a typical energy broadband around 2.85 eV involving the deep level impurity transitions and the different peak shift behaviour of localized excitons around 4.97 eV with temperature increasing from 13 K to 120 K. The luminescence intensity of the excitons in both samples indicated a thermal quenching process with two activation energies. The two activation energies Eact1 and Eact2 were assigned to the thermal barrier resulting from the strong composition fluctuation in AlGaN and the binding energy of the excitons, respectively. The different PL oscillation properties of two samples at the 2.85 eV emission band indicate the Si‐doped AlGaN epilayer has significant interference of interface and surface. The significant oscillations were attributed to less centres of nucleation in the Si‐doped AlGaN, as has been supported by atomic force microscopy (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of nitrogen precursor and its flow rate on the quality and the residual doping in GaN grown by molecular beam epitaxy
Authors: Cordier Yvon , Natali Franck , Chmielowska Magdalena , Leroux Mathieu , Chaix Catherine , Bouchaib Pierre 
Published: January 2012

AbstractThis work is dedicated to the growth of GaN layers by molecular beam epitaxy. Plasma assisted and ammonia growth techniques are compared. The influence of the nitrogen source (NH3 or N2 plasma) as well as its flow rate is investigated. In particular, we show how the amount of donors incorporated in the layers depends on the growth conditions. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
GaN on sapphire mesa technology
Authors: Herfurth Patrick , Men Yakiv , Rösch Rudolph , Carlin Jean‐Francois , Grandjean Nicolas , Kohn Erhard 
Published: January 2012

AbstractThis contribution reports on a GaN on sapphire mesa technology for lattice matched InAlN/GaN HEMTs similar to a silicon on insulator technology. Ultrathin buffer layers between 500 nm and 100 nm have been deep mesa etched down to the substrate to avoid cross talk between devices through the buffer and provide full transparency outside the active device area (of special interest to biochemical sensor applications).The heterostructure characteristics were: NS > 1.6 x 1013 cm‐2, Rsh < 600 Ω/□. 0.25 µm gate length HEMT device characteristics are moderate, but essentially similar down to 200 nm buffer thickness. Devices on 100 nm buffer layer are still difficult to reproduce. Ion/Ioff was up to 109 and sub‐threshold slopes down to 90 mV/dec (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Residual strain in recessed AlGaN/GaN heterostructure field‐effect transistors evaluated by micro photoluminescence measurements
Authors: Mikulics Martin , Hardtdegen Hilde , Winden Andreas , Fox Alfred , Marso Michel , Sofer Zdeněk , Lüth Hans , Grützmacher Detlev , Kordoš Peter 
Published: January 2012

AbstractThe residual strain in AlGaN/GaN heterostructure field‐effect transistors (HFETs) with recessed gates and their non‐recessed counterparts were investigated by micro photoluminescence measurements (µ‐PL). It is found that strain relaxation accounts for the observed sheet carrier density reduction after gate recessing. The usefulness of the method for device processing optimization is demonstrated. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of the optical properties of InGaN/GaN nanorods with different indium composition
Authors: Wang Q. , Bai J. , Gong Y. P. , Wang T. 
Published: January 2012

AbstractIn this paper, the optical properties of our nanorod array structures fabricated from InGaN/GaN multiple quantum wells (MQWs) epiwafers with two different kinds of indium compositions have been investigated. The optical performance of our nanorod samples are significantly enhanced compared to the as‐grown epiwafers, in particular, such improvement is much more pronounced in the nanorod array structure with a higher indium composition. This is mainly attributed to effective strain relaxation as a result of fabrication into nanorod structure, leading to significant reduction in quantum confined Stark effect (QCSE). X‐ray reciprocal space mapping (RSM) measurements have been performed in order to quantitatively evaluate the stain relaxation in the nanorod samples, confirming that the majority of the strain in InGaN/GaN MQWs can be relaxed as a result of fabrication into nanorods. Finally, excitation‐power dependant photoluminescence measurements performed at a low temperature also support the conclusion (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the origin of blue‐green emission from heteroepitaxial nonpolar a‐plane InGaN quantum wells
Authors: Kappers M. J. , Badcock T. J. , Hao R. , Moram M. A. , Hammersley S. , Dawson P. , Humphreys C. J. 
Published: January 2012

AbstractThe optical and structural properties of nonpolar a‐plane InGaN/GaN multiple quantum wells grown on r‐plane sapphire substrates were investigated as a function of defect density. The photoluminescence spectrum is characterised by a peak at 380 nm (3.24 eV) and a blue‐green emission band from 425‐550 nm (2.25‐3.10 eV). The near‐UV peak is assigned to carrier recombination in the quantum wells lying on the a‐plane. On the basis of microscopy, photoluminescence spectroscopy and cathodoluminescence imaging, the blue‐green emission band is attributed to emission from sidewall quantum wells formed on the various semipolar facets of small (∼100 nm) surface pits which form during quantum well growth at the lower temperatures and high NH3 flow in a nitrogen atmosphere. The density of the surface pits equals that of partial dislocations and threading dislocations in the quantum wells structure. Thus, the 300 K photoluminescence spectrum is dominated by the blue‐green emission band at a high defect density (>1010 cm‐2) and its intensity is reduced with lower defect densities. For a spectrum with a single emission from the nonpolar a‐plane InGaN/GaN quantum wells the defect density needs to be below ∼109 cm‐2. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Self‐assembled m ‐plane InGaN quantum dots: formation and shape evolution
Authors: Yang Xuelin , Arita Munetaka , Kako Satoshi , Arakawa Yasuhiko 
Published: January 2012

AbstractThe authors report the formation and shape evolution of m ‐plane InGaN quantum dots grown on GaN substrates. The formation of the quantum dots is enabled by introducing AlGaN/AlN interlayers prior to the GaN layer. The introduced compressive strain in the GaN layer promotes a growth mode transition during layer growth, from smooth InGaN layer to three dimensional quantum dot structures. The structural transition is consistent with optical properties. Furthermore, we also discuss the shape evolution with different growth conditions and find that the InGaN quantum dots are elongated with decreasing the indium concentration (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of carrier gas ratio and growth temperature on MOVPE growth of AlN
Authors: Miyagawa Reina , Yang Shibo , Miyake Hideto , Hiramatsu Kazumasa 
Published: January 2012

AbstractThe strong demand for high‐efficiency light‐emitting diodes in the deep‐ultraviolet region and for sensors has led to renewed interest in the growth of high‐quality AlN. However, the growth of high‐quality AlN is extremely difficult owing to the low surface migration rate of Al adatoms. In this study, the effects of the carrier gas ratio and growth temperature on the growth rate of AlN are examined with the aim of optimizing the growth conditions of high‐temperature AlN. AlN epilayers were grown on sapphire substrates by metal‐organic vapor phase epitaxy (MOVPE) at a growth temperature of 1430 °C with a medium‐temperature AlN layer grown at 1100 °C. A combination of H2 and N2 was used as the carrier gas in the growth of AlN, and the ratio of H2 to N2 in the carrier gas was changed to examine its effect on the growth of AlN. Under all growth conditions, crack‐free and smooth surfaces at the atomic level with an extremely small tilt were obtained. The growth rate decreased with increasing growth temperature and ratio of H2 in the carrier gas. This suggests that the high temperature and the H2 carrier gas inhibit the adsorption of atoms. Also, with increasing ratio of N2 in the carrier gas, the radius of curvature of the AlN layer increased and the compressive strain decreased. The reduction of compressive strain and increase in curvature of the AlN layer were due to an increase in the number of dislocations. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Teaching strategic thinking using system dynamics: lessons from a strategic development course
Authors: Kunc Martin 
Published: January 2012

AbstractThe use of System Dynamics within strategy courses aims to teach students dynamic theories to explain firm performance. This paper presents an analysis of the development of students' strategic systems thinking skills after taking a course on strategic development processes. Students that achieved the best performance employed graphs representing the performance of key variables, described how the strategy worked using verbal explanations of feedback processes, and validated the results obtained to detect poor or unreasonable strategies. However, a large group of students did not follow System Dynamics practices and performed poorly in their strategies. We extract two lessons: more emphasis on the areas shown by the best students, which are along the modeling for learning practices, are needed to improve students' strategic systems thinking skills, and it is important to adopt multidimensional tools to evaluate systems thinking skills given the diversity in learning preferences. Copyright © 2012 System Dynamics Society.
Bot detection evasion: a case study on local‐host alert correlation bot detection methods
Authors: Shirley Brandon , Babu Lokesh , Mano Chad 
Published: January 2012

ABSTRACTBotnets have continuously evolved since their inception as a malicious entity. Attackers come up with new botnet designs that exploit the weaknesses in existing defense mechanisms and continue to evade detection. It is necessary to analyze the weaknesses of existing defense mechanisms to find out the lacunae in them. This research exposes a weakness found in an existing bot detection method (BDM) by implementing a specialized P2P botnet model and carrying out experiments on it. Weaknesses that are found and validated can be used to predict the development path of botnets, and as a result, detection and mitigation measures can be implemented in a proactive fashion. The main contribution of this work is to demonstrate the exploitation pattern of an inherent weakness in local‐host alert correlation (LHAC) based methods and to assert that current LHAC implementations could allow pockets of cooperative bots to hide in an enterprise size network. This work suggests that additional monitoring capabilities must be added to current LHAC‐based methods in order for them to remain a viable bot detection mechanism. Copyright © 2012 John Wiley & Sons, Ltd.
Efficient identity‐based hierarchical access authentication protocol for mobile network
Authors: Liu He , Liang Mangui 
Published: January 2012

ABSTRACTThis paper presents a secure and efficient hierarchical identity‐based access authentication protocol for mobile network. First, a new mobile scheme is constructed to improve the registration performance by the port‐based vector switching; especially when there are multihops and bandwidth between the user and home network, the registration delay is greatly reduced. Second, an access authentication protocol is proposed by combining the designed mobile proposal with hierarchical identity‐based signature. It has the characteristics of identity based, local verification, concurrency and hierarchy. The whole authenticating process is divided into two phrases to precompute some time‐consuming parameters, which are important to decrease the effects of the signing/verifying. Besides, a new access router selection algorithm is given for the mobile user to choose optimal access point in this paper. The theoretical analysis and simulating results show that the proposed authentication protocol outperforms the previous ones in terms of the handover delay integrating the authentication with its security enhanced. For example, the falling speed of the new protocol's total latency is reduced about 50% and 83%, respectively, compared with the existing identity‐based‐signature‐based and Rivest–Shamir–Adleman‐based schemes. Copyright © 2012 John Wiley & Sons, Ltd.
Grammatical and context‐sensitive error correction using a statistical machine translation framework
Authors: Ehsan Nava , Faili Heshaam 
Published: January 2012

SUMMARYProducing electronic rather than paper documents has considerable benefits such as easier organizing and data management. Therefore, existence of automatic writing assistance tools such as spell and grammar checker/correctors can increase the quality of electronic texts by removing noise and correcting the erroneous sentences. Different kinds of errors in a text can be categorized into spelling, grammatical and real‐word errors. In this article, we present a language‐independent approach based on a statistical machine translation framework to develop a proofreading tool, which detects grammatical errors as well as context‐sensitive spelling mistakes (real‐word errors). A hybrid model for grammar checking is suggested by combining the mentioned approach with an existing rule‐based grammar checker. Experimental results on both English and Persian languages indicate that the proposed statistical method and the rule‐based grammar checker are complementary in detecting and correcting syntactic errors. The results of the hybrid grammar checker, applied to some English texts, show an improvement of about 24% with respect to the recall metric with almost similar value for precision. Experiments on real‐world data set show that state‐of‐the‐art results are achieved for grammar checking and context‐sensitive spell checking for Persian language. Copyright © 2012 John Wiley & Sons, Ltd.
A threat model‐based approach to security testing
Authors: Marback Aaron , Do Hyunsook , He Ke , Kondamarri Samuel , Xu Dianxiang 
Published: January 2012

SUMMARYSoftware security issues have been a major concern in the cyberspace community, so a great deal of research on security testing has been performed, and various security testing techniques have been developed. Threat modeling provides a systematic way to identify threats that might compromise security, and it has been a well‐accepted practice by the industry, but test case generation from threat models has not been addressed yet. Thus, in this paper, we propose a threat model‐based security testing approach that automatically generates security test sequences from threat trees and transforms them into executable tests. The security testing approach we consider consists of three activities in large: building threat models with threat trees; generating security test sequences from threat trees; and creating executable test cases by considering valid and invalid inputs. To support our approach, we implemented security test generation techniques, and we also conducted an empirical study to assess the effectiveness of our approach. The results of our study show that our threat tree‐based approach is effective in exposing vulnerabilities. Copyright © 2012 John Wiley & Sons, Ltd.
Estimating the annual probability of failure using improved progressive incremental dynamic analysis of structural systems
Authors: Kayhani Hossein , Azarbakht Alireza , Ghafory‐Ashtiany Mohsen 
Published: January 2012

SUMMARYA methodology based on the progressive incremental dynamic analysis has been introduced in this paper to estimate the structural response and the corresponding annual probability of failure. The proposed methodology employs the genetic algorithm optimisation technique and an equivalent single‐degree‐of‐freedom system corresponding to the first‐mode period of a considered structure. The proposed methodology can significantly reduce the number of ground motion records needed for estimating the annual probability of failure. The numerical results indicate that the proposed method can effectively reduce the computational effort needed for computation of probability of failure for the first‐mode dominated structures, which is advantageous as the structure becomes larger. A relatively huge set of single‐degree‐of‐freedom systems as well as three multi‐degree‐of‐freedom systems including 3, 8 and 12 storeyed reinforced concrete structures was taken into account to test the proposed methodology. It has been shown that the probability of failure can be estimated within ±15% error with 95% confidence. The proposed method can speed up the decision‐making process in the probability‐based seismic performance assessment of structures, and it also incorporates the randomness of strong ground motions explicitly. Copyright © 2012 John Wiley & Sons, Ltd.
Autonomous aggregation in location aware ad hoc wireless networks
Authors: Geibig Joanna , Bradler Dirk 
Published: January 2012

ABSTRACTGossip‐based epidemic protocols are used to aggregate data in distributed systems. This fault‐tolerant approach neither require maintenance of any global network state nor knowledge of network structure. However, although gossip‐based aggregation algorithms scale well for graphs with good expansion, their efficiency for sparse graphs is unexamined. In this paper, we analyze the feasibility and efficiency of a gossip aggregation protocol in wireless networks with low expansion. We propose a modification of the existing aggregation algorithm for use in locality‐aware, sparse, and static wireless networks. Our protocol terminates autonomously, uses less bandwidth than the original version, and removes the need for the leader election process while counting network nodes. Aggregates are calculated only over nodes placed in the vicinity, and nodes communicate only with their immediate neighbors by using a wireless broadcast. We evaluate our approach by simulation on sparse, irregular graphs with low expansion for the simplified system model. Furthermore, we analytically assess the worst‐case convergence time of this protocol for sparse wireless networks and also for the simplified system model. The proposed protocol can be used in the monitoring and alarming applications in wireless networks. Copyright © 2012 John Wiley & Sons, Ltd.
Understanding protein unfolding from molecular simulations
Authors: Toofanny Rudesh D. , Daggett Valerie 
Published: January 2012

AbstractExperimental biophysical techniques can probe the native, transition, intermediate, and denatured states of proteins. The characterization of these states and the conversion between states provide us with information about folding, dynamics, misfolding, and the origin of mechanical strength in response to force. Molecular dynamics (MD) simulations are a complementary theoretical technique that provides atomic detail to the experimental measurements particularly through careful benchmarking and validation against experiment. Furthermore, MD simulations often correctly predict the outcome of experiments and provide new and interesting avenues of investigation. Our understanding of protein unfolding is being pushed forward by the symbiosis of experimental and theoretical methods. Here, we review investigations of several protein systems and highlight the close interplay between experiment and simulation in providing an atomic resolution view of protein unfolding, which provide us with the general principles for folding and the origin of mechanical strength. © 2012 John Wiley & Sons, Ltd.This article is categorized under:

Structure and Mechanism > Reaction Mechanisms and Catalysis
Controversies Concerning the Use of Neoadjuvant Systemic Therapy for Primary Breast Cancer
Authors: Kaufmann Manfred , Karn Thomas , Ruckhäberle Eugen 
Published: January 2012

AbstractThe major aim of neoadjuvant systemic therapy is to improve prognosis by individualizing treatment. The proven benefits of neoadjuvant systemic therapy include reducing tumor burden, higher breast‐conserving surgery, and the possibility of in vivo monitoring of response to treatment. Other goals of neoadjuvant treatment are the detection of new prognostic and predictive biomarkers and the investigation of new drugs and imaging modalities. Although many prospective trials have answered important questions regarding neoadjuvant systemic therapy, several topics remain controversial.
Evliya Celebi’s Description of the Removal of a Musket Ball From the Brain of a Habsburg Prince: An Interesting Excerpt From the “Seyahatname”
Authors: Bilsel Yilmaz 
Published: January 2012

AbstractIn the 17th century an Ottoman traveler, Evliya Celebi, was inspired by a dream to embark on a journey across the Ottoman Empire. He traveled far and wide across Europe and North Africa and wrote extensively about his adventures in the Seyahatname. The Seyahatname, or “Book of Travels,” is the longest and most detailed travel account in Islamic (if not world) literature. It is a vast panorama of the Ottoman world in the mid‐17th century. This article is concerned with Celebi’s description of several surgeries that he claimed to have witnessed in Vienna during the year 1665. He describes several procedures, the first and most detailed of which is a fascinating brain operation that seems to be a highly unusual procedure for the time. His impressions of Central European medicine, as viewed by a Muslim from the East, offer an unexplored perspective. We examine what his description tells us about the perceptions and images of surgery and medicine.
Perception of Direct‐To‐Consumer Genetic Testing and Direct‐To‐Consumer Advertising of Genetic Tests among Members of a Large Managed Care Organization
Authors: Rahm Alanna Kulchak , Feigelson Heather Spencer , Wagner Nicole , Le Anh Quynh , Halterman Eve , Cornish Nadine , Dearing James W. 
Published: January 2012

AbstractThis small qualitative study was designed to determine possible attitudes toward and understanding of direct‐to‐consumer (DTC) genetic testing among members of a large managed care organization, and whether differences might exist between population groups. Ten focus groups were conducted by population type (high risk, White, African American, Hispanic/Latino) to determine knowledge, attitudes and beliefs about DTC genetics. Focus group transcripts were coded for attitudes toward and framing of the issue. Study results found participants were negative towards DTC genetic testing but they also found some aspects useful. Participants framed the issue mainly in terms of disease prevention and uncertainty of reaction to results, with some variation between population types. The concept of an “Informed Consumer,” or process to seek information when the issue becomes personally relevant, emerged. This concept suggests that individuals may seek additional assistance to make personally‐appropriate choices when faced with a DTC advertisement or genetic test.