bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tailoring the strong coupling regime in III‐nitride based microcavities for room temperature polariton laser applications
Authors: Levrat Jacques , Butté Raphaël , Christmann Gabriel , Feltin Eric , Carlin Jean‐François , Grandjean Nicolas 
Published: November 2009

AbstractWe report on the properties of III‐nitride based microcavities (MCs) operating in the strong coupling regime (SCR) up to room temperature. We first discuss why this class of materials is well suited to investigate the physics of cavity polaritons, which are admixed particles resulting from the coupling between cavity photons and excitons. In addition to the high quality of the different building blocks forming the MC, we point out the role of the active medium geometry, and in particular, the impact of the quantum well number and the distribution of the latter to maximize the vacuum Rabi splitting. Thanks to a well grounded SCR at high temperatures, we demonstrate polariton lasing in the 180‐340 K range whose threshold is mainly governed by thermally activated detrapping mechanisms. Since the trap depth formed by the lower polariton branch is fixed by the exciton‐cavity photon detuning (δ), it is shown that the polariton escape rate from the trap and hence the threshold power density strongly depend on this parameter. Experimental results are well accounted for when using a simplified thermodynamic model that reproduces the threshold behavior as a function of δ in the temperature range investigated. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photoluminescence properties of PbSe/PbS core‐shell quantum dots
Authors: Maikov Georgy I. , Vaxenburg Roman , Yanover Diana , Kigel Ariel , Sashchiuk Aldona , Lifshitz Efrat 
Published: November 2009

AbstractThe present study describes the investigation of the ground‐state exciton emission in the PbSe/PbS core‐shell colloidal quantum dots (CQDs) with different core‐radius/shell‐thickness ratio, by recording temperature dependence of ground‐state exciton photoluminescence (PL) properties, including line‐width, integrated PL intensity, and the temperature coefficient of energy band‐gap, over a temperature range from 1.4 K to 300 K. The obtained data reveal a reduction of the temperature coefficient of the energy band‐gap as well as slightly decrease of exciton and optical phonon coupling in the PbSe/PbS core‐shell CQDs with respect to that in the corresponding PbSe core. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Suppressed blinking in CdTe/CdSe core‐shell quantum dots
Authors: Kloper Viki , Osovsky Ruth , Cheskis Dima , Sashchiuk Aldona , Lifshitz Efrat 
Published: November 2009

AbstractCdTe/CdSe core‐shell colloidal quantum dots (CQDs) were synthesized by a unique colloidal procedure permitting the growth of spherical structures with the highest emission quantum efficiency (∼90%). The CQDs photoluminescence (PL) intensity shows only minor fluctuations (<10%) in time, revealing a blinking suppression in the CQDs, while the PL of a single CQD shows the occurrence of longer lived (ns) multiexcitons, important for the applications of CQDs also in gain devices. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Impact of Pr on the properties of InP based layers for light sources and detectors
Authors: Prochazkova Olga , Grym Jan , Zavadil Jiri , Zdansky Karel , Yatskiv Roman 
Published: November 2009

AbstractWe report the optimization of LPE growth technique for the preparation of InP and GaInAsP high quality and high purity layers by using Pr purification effect. We have found that Pr addition into the growth melt leads to the reduction of the layer defect density by a half order of magnitude and carrier concentrations diminished to 1014 cm–3. Three types of p‐n junction based radiation detection structures were prepared and their detection performance was assessed by using α‐particles emitted from the 241Am radioactive source. The type III structure, utilizing the p‐n junction with both components grown with Pr addition, exhibits the highest charge collection efficiency. Pr admixture was also exploited in the preparation of quaternary GaInAsP(Pr) active region in the double heterostructure GaInAsP/InP emitting at 1200 nm. Purification effect of Pr addition is demonstrated by measuring impurity concentrations deduced from C‐V curves and by low temperature PL spectra. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photoluminescence studies of MBE‐grown ZnO and MgZnO epitaxial layers
Authors: Kuokštis Edmundas , Karaliūnas Mindaugas , Juršėnas Saulius , Miasojedovas Saulius , Serevičius Tomas , Ting Shao‐Ying , Huang Jeng‐Jie , Yang Chih‐Chung 
Published: November 2009

AbstractPhotoluminescence (PL) and optical gain properties of ZnO and MgZnO epitaxial layers were investigated under different excitation conditions in a wide temperature range. The high‐quality layers were grown by molecular beam epitaxy technique. CW laser radiation, nano‐ and pico‐second light pulses were used as photoexcitation source. Spontaneous, stimulated, time‐resolved and time‐integrated PL of ZnO‐based layers are analyzed. The PL of the layers under low excitation is caused by annihilation of free excitons in the near‐band‐edge region. Increase of excitation in ZnO leads to radiative recombination due to non‐elastic collisions of excitons with typical P ‐line in the spectrum. Under extremely high levels of pumping excitons undergo the Mott transition and broad electron‐hole band predominates in the PL spectrum. The latter mechanism is responsible for optical gain of ZnO. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A density functional theory study of the enantioselective reduction of prochiral ketones promoted by chiral spiroborate esters
Authors: Wei Donghui , Tang Mingsheng , Zhang Wenjing , Zhao Jing , Sun Ling , Zhao Chufeng , Wang Homgming 
Published: November 2009

AbstractRecently, chiral spiroborate ester [(R)‐2‐((1,3,2‐dioxaborolan‐2‐yloxy)methyl)pyrrolidine] has been experimentally employed as an effective chiral catalyst in the borane‐mediated asymmetric reduction of prochiral ketones to produce the corresponding secondary alcohols. In this article, we have theoretically investigated the mechanism of the reduction using density functional theory. The results reveal that this reaction is accomplished via four steps. Fully geometry optimized reactants, products, transition states, and intermediates were obtained at the B3LYP/6‐31G (d, p) level. The analysis of these results reveals one pathway that is more energetically favorable, and its associated geometries correlate well with the final products of the reaction. The further calculations show that the solvent effect of THF has no great influence on enantioselectivity of this reduction. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
Localization in some discontinuously and randomly driven quantum systems
Authors: Ghosh S. , Bhattacharyya S. P. 
Published: November 2009

AbstractA charged particle moving in a harmonic, symmetric double well, a square well, or a Morse potential is allowed to interact with a discontinuously reversing spatially homogeneous electric field. Randomly reversing field is seen to cause localization in the quantum system. A critical reversal frequency is seen to exist below which no localization is manifested in the harmonic, double and square well. In the Morse case, there is dissociation if the upper limit of the interval between random kicks exceeds τmax. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
CASPT2 study on low‐lying states of HBN and HNB radicals
Authors: Li Wen‐Zuo , Cheng Jian‐Bo , Li Qing‐Zhong , Gong Bao‐An , Sun Jia‐Zhong 
Published: November 2009

AbstractIn this study, some low‐lying states of the HBN and HNB radicals have been studied using multiconfiguration second‐order perturbation theory. The geometries of all stationary points along the potential energy surfaces (PESs) were optimized at the CASPT2/cc‐pVQZ level. The ground and the first excited states of HBN were predicted to be X2Π and A2Σ+ states, respectively. It was predicted that the ground state of HNB is X2Σ+ state. The A2Π state of HNB has unique imaginary frequency, which was different from the previously published results. A bending local minimum M1 was found for the first time along the 12A″ PES, and the A2Π state of HNB should be the transition state of the isomerization reactions for M1 ↔ M1. The CASPT2/ANO potential energy curves (PECs) of isomerization reactions for HBN ↔ HNB were calculated as a function of HBN bond angle. By comparing the CASPT2 and CASSCF calculated results, we concluded that the influence of the dynamic electron correlation on HBN ↔ HNB system is not large. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2011
Whether electronegativity and hardness are manifest two different descriptors of the one and the same fundamental property of atoms—A quest
Authors: Ghosh Dulal C. , Islam Nazmul 
Published: November 2009

AbstractIn this report, we have tried to reveal that there is much conceptual commonality between the two fundamental theoretical descriptors of chemistry and physics—the electronegativity and the hardness. The physical hardness was introduced and theorized by condensed matter physicists. The chemical hardness was introduced by chemists to generalize and rationalize the HSAB principle. We have tried to establish that the physical hardness and the chemical hardness with evolution of time have converged to one and the same general principle—the hardness. We have also tried to understand the physical basis and operational significance of another very important descriptor arising out of theoretical constructs of chemistry—the electronegativity. We have relied upon the fact that, since these descriptors are not observables, there is no possibility of their quantum mechanical evaluation. These descriptors, therefore, should be and must be reified before suggesting ansatz for their evaluation. We have dwelt at length upon the effort of density functional definition and evaluation of electronegativity and hardness and discovered the inherent inner contradiction of the theory and measurement. We have also noted that a good number of scientists hold the opinion that the density functional formula of electronegativity is χ = I and that of hardness is η = I, where I is the ionization potential of the chemical system. This study concludes that the two fundamental descriptors—the hardness and the electronegativity originate from the same source—the electron attracting power of the screened nucleus upon valence electrons and discovers the surprising result that if one measures hardness, the electronegativity is simultaneously measured and vice versa. We have also explored the ansatz of semiempirical evaluation of electronegativity and hardness of atomic systems involving the radius of the atoms. We have noted that the ansatz for electronegativity and hardness is the same. To justify our statement that if one measures hardness, the electronegativity is simultaneously measured and vice versa, we have used the evaluated set of hardness for 103 elements of the periodic table as a scale of electronegativity and found that such set of hardness data satisfies the sine qua non of a satisfactory scale of electronegativity. The electronegativity and the hardness are two different appearances of the one and the same fundamental property of atoms. They are different and also nondifferent. They are different in their fields of application. They are nondifferent when we discuss the basic philosophical structures of their origin and development. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2011
Competence‐conscious associative classification
Authors: Veloso Adriano , Zaki Mohammed , Meira Wagner , Gonçalves Marcos 
Published: November 2009

AbstractThe classification performance of an associative classifier is strongly dependent on the statistic measure or metric that is used to quantify the strength of the association between features and classes (i.e. confidence, correlation, etc.). Previous studies have shown that classifiers produced by different metrics may provide conflicting predictions, and that the best metric to use is data‐dependent and rarely known while designing the classifier. This uncertainty concerning the optimal match between metrics and problems is a dilemma, and prevents associative classifiers to achieve their maximal performance. This dilemma is the focus of this paper. A possible solution to this dilemma is to learn the competence, expertise, or assertiveness of metrics. The basic idea is that each metric has a specific sub‐domain for which it is most competent (i.e. it consistently produces more accurate classifiers than the ones produced by other metrics). Particularly, we investigate stacking‐based meta‐learning methods, which use the training data to find the domain of competence of each metric. The meta‐classifier describes the domains of competence (or areas of expertise) of each metric, enabling a more sensible use of these metrics so that competence‐conscious classifiers can be produced (i.e. a metric is only used to produce classifiers for test instances that belong to its domain of competence). We conducted a systematic and comprehensive evaluation, using different datasets and evaluation measures, of classifiers produced by different metrics. The result is that, while no metric is always superior than all others, the selection of appropriate metrics according to their competence/expertise (i.e. competence‐conscious associative classifiers) seems very effective, showing gains that range from 1.2% to 26.3% when compared with the baselines (SVMs and an existing ensemble method). Copyright © 2009 Wiley Periodicals, Inc. Statistical Analysis and Data Mining 2: 361‐377, 2009
Roughly balanced bagging for imbalanced data
Authors: Hido Shohei , Kashima Hisashi , Takahashi Yutaka 
Published: November 2009

AbstractThe class imbalance problem appears in many real‐world applications of classification learning. We propose an ensemble algorithm “Roughly Balanced (RB) Bagging” using a novel sampling technique to improve the original bagging algorithm for data sets with skewed class distributions. For this sampling method, the number of samples in the largest and smallest classes are different, but they are effectively balanced when averaged over all of the subsets, which supports the approach of bagging in a more appropriate way. Individual models in RB Bagging tend to show larger diversity, which is one of the keys of ensemble models, compared with existing bagging‐based methods for imbalanced data that use exactly the same number of majority and minority examples for every training subset. In addition, the proposed method makes full use of all of the minority examples by under‐sampling, which is efficiently done by using negative binomial distributions. Numerical experiments using benchmark and real‐world data sets demonstrate that RB Bagging shows better performance than the existing “balanced” methods and other common methods for area under the ROC curve (AUC), which is a widely used metric in the class imbalance problem. Copyright © 2009 Wiley Periodicals, Inc. Statistical Analysis and Data Mining 2: 412‐426, 2009
Fault‐Tolerant Scheme on Partial Differential Equations with Nearest‐Neighbor Mesh‐Connected Machines
Authors: Osawa Gyo , Kawai Toshio , Aiso Hideo 
Published: November 2009

AbstractIn the numerical computation of a partial differential equation, it is useful to employ a parallel computer, where a large number of processors are connected in a mesh form. Such a scheme is now realizable with the advent of modern VLSI technology. On the other hand, there arises a request for the fault tolerancy with the increase of the processing units. When a partial differential equation is to be solved by such a computer, the requirement is not severe for the completeness of the data, since the iterative method usually is employed. This paper considers a problem of this nature, and discusses the recovery from the fault within the execution. The method is to detect the fault, to modify the connections among the processing units, separating the processing unit in fault, and to continue the computation by modifying a part of the discrete algorithm. By the proposed method, the dynamic recovery from the fault is easily realized, and the degradation of the computation accuracy due to the fault is suppressed. The proposed scheme is implemented on the parallel computer PAX‐32 with 32 processing units. The actual result of solving a two‐dimensional Poisson equation is presented, and a theoretical evaluation is made for the error in the one‐dimensional problem.
An Experimental Evaluation of Classifiers Using Spatial Context for Multispectral Images
Authors: Watanabe Takashi , Suzuki Hitoshi 
Published: November 2009

AbstractIn early classification of the multi‐spectral images obtained by remote sensing, pixelwise classification was used primarily. However, pixelwise classification is limited, noting only the spectral aspect of data. Several methods have been proposed to improve the classification performance by utilizing the spatial context, in addition to the spectral aspect. By contrast, few reports have been made which evaluate quantitatively those methods to present a systematic comparison. This paper considers the typical classifiers utilizing the local spatial context such as spatial continuity and spatial adjacency, which are compound decision theory, majority decision, adaptive classification and probabilistic relaxation, together with modified versions. An experiment was made to compare the classification accuracy of such classifiers. To make the quantitative evaluation objectively, artificial multispectral data simulating the LANDSAT image was used in the experiment. This paper presents the experimental result and its discussion.
A Validation Method for Communication Protocols Using Context–Free Language Theory
Authors: Kurosawa Kaoru , Kuwabara Yoshiki , Shigeno Takashi 
Published: November 2009

AbstractUsually, communication protocols are modelled as a communication between two finite‐state machines. Yu and Gouda [1] have shown that if the messages of a single type and the finite‐state machine have no mixed nodes, the verification of deadlock can be made in a polynomial time. This paper shows that if the messages are of a single type, the verification of deadlock can be made in a polynomial time, even if there does exist mixed nodes. The proof is derived by indicating that the communication sequences arriving at deadlock states form a context‐free language. If there does not exist a deadlock in the protocol obtained by converting all the messages into a single type, no deadlock exists in the original protocol (the converse is not always true). In this sense, the result in this paper is important.
3–D Object Data Input System Using Rearview Mirrors
Authors: Agui Takeshi , Saito Tomohito , Nakajima Masayuki 
Published: November 2009

AbstractThis paper introduces a noncontact measurement technique for 3‐D data acquisition. The conventional optical projection method cannot measure a 3‐D object when a dead angle is encountered. This paper investigates a methods using rearview mirrors to increase the observability and decrease the dead angle of the projection point on the object. The rearview mirrors provide multiple view of the object in the same image, thereby simplifying the 3‐D data acquisition process.
Implementation of a Small‐Scale Prototype for Software Service System (SSS)
Authors: Tashiro Shuichi , Mori Ryoichi 
Published: November 2009

AbstractThe software service system (SSS) is used for software protection and distribution, aiming at a balance between the protection of the rights of the proprietor and the convenience of utilization and distribution. The distributed software includes the permission provision program describing the condition of utilization. The record of the user's right (abbreviated as record of right) describing the user's rights, is stored in the nonvolatile memory of the computer. The permission provision program refers the right record, and verifies the user's right. Based on that result, the program controls the execution, termination, stop and restart of the corresponding software.This paper reports on the implementation of a small‐scale model for the software distribution environment by SSS. SSSBOX is constructed, which is an environment to execute the permission provision program, i.e., the proprietary management mechanism which manages the right record and provides the access of the permission provision program to the right record. The following facts were verified as the result of experiment. The permission provision program can describe various kinds of permission conditions, such as software rental, purchase, free trial and restricted permission only for specified users. On the other hand, the description aiming at construction of unreasonable right record or destruction of the right record constructed by another permission provision program, are detected during execution and is refused securely.
The Cellular Frame Model for Representation and Aggregation of Knowledge in Image Understanding
Authors: Oka Ryuichi 
Published: November 2009

AbstractThis paper proposes a computational model of hierarchical labeling based on cellular automaton “Cellular Frame Model.” The model of the objective world is described by defining a set of labels called Cellular Frame used for representing knowledge. The reliability of existence of labels for representation by state equations whose initial conditions are determined by input level patterns is described. The state equations are of the form of local, parallel and iterative operations. The computational process of the state equations is considered as a process of aggregation (based on input label patterns) of label knowledge introduced for model description. In this paper, model describability of Cellular Frame is discussed from two viewpoints: hierarchy of the set of labels, and graphic interpretation of aggregate model. Convergence of labeling is ensured by the fact that the state equations always converge. In addition, several hypotheses have been ascertained by showing examples of models and simulation of labeling processes by state equations.
Evaluation of Linear Interpolated Handwritten Image and an Adaptive Sampling Method for Telewriting Signal
Authors: Ohtsuka Sakuichi , Kishimoto Tomio , Sato Yuichi 
Published: November 2009

AbstractWhen a telewriting signal of handwritten text and graphics shares a common telephone channel with voice, the data rate of the telewriting must be curtailed to maintain the quality of the audio portion. A fixed rate sampling method with linear interpolation has been used in telewriting because of its simplicity. However, this method does not perform well when distortions are caused by higher drawing speed of line strokes. To overcome such a shortcoming, this paper: (1) investigates the distortions associated with the fixed rate sampling method; (2) derives quantitative measures of interpolation distortion and truncation distortion; and (3) proposes an adaptive sampling algorithm. A writing tablet (4 dots/mm resolution) was used in the experiments to validate the objective measures, and to assess the performance of the adaptive algorithm. Experimental results indicate that while the data rates of the fixed rate sampling method and the adaptive method are almost the same, the adaptive method scores higher in the subjective image quality assessment tests.