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关键词： Signal to noise ratio  

摘要： Abstract: In this paper, modified correlation detector based spectrum sensing technique is proposed assuming additive Laplacian noise. In the proposed modified detector, we consider a test statistic where the received signal at the cognitive terminal is correlated with primary user signal. Binary phase shift keying primary user signal is considered for simplicity. Then the received signal is raised to an arbitrary exponent P whose value ranges from 0 to 2 (0 © 2021, Pleiades Publishing, Ltd.

关键词： compressed natural gas   energy   exergy   gasoline   spark ignition engine  

摘要： A comparative energy and exergy analysis was experimentally performed using a bi-fuel compressed natural gas (CNG) spark ignition engine. The experiments were conducted for gasoline and CNG fuel at 1700 rpm and different operating loads from 5 to 30 Nm. The experiments were performed under stoichiometric air-fuel ratio and maximum brake torque ignition timing. Quantitative and qualitative analysis were conducted using the first and second law of thermodynamics, respectively. The effect of engine operating load on various energy and exergy parameters was compared for both the fuels. Output energy with respect to engine load was found higher for CNG compared to gasoline. Engine wall heat transfer was also higher in the CNG engine case due to its high combustion chamber temperature and lower burning velocity. The difference in heat transfer energy fraction between gasoline and CNG gradually increased with engine load. The exhaust energy was found maximum in the case of CNG under low operating load and reduced to a minimum at higher engine operating load. The unaccounted energy fraction was found lower for the CNG engine and reduced with respect to engine load. CNG exhibits the highest exergy efficiency (26.80%) compared to gasoline (25.50%) at 30 Nm load. On average, a 2% higher exergy efficiency was observed with the CNG engine at all operating load conditions. This indicates CNG has a higher potential to convert chemical energy present in the fuel into useful work output. CNG shows lower exergy destruction at all operating loads compared to gasoline, and it reduces significantly at higher engine loads. In all operating loads, exergy transfer due to exhaust gas and heat transfer to the wall was higher in the case of CNG.

关键词： V-groove quantum wire   Transition energy   Non-linear rectification   Second and third harmonic generation  

摘要： The non-linear rectification and generation of the second and third harmonic of a realistic single-electron Ga1-yAlyAs/GaAs/Ga1-xAlxAs V-groove quantum wire are calculated. The effects of the V-groove geometrical and physical parameters, such as the inter-sidewall angle, the thickness of the crescent, the position of the pinchoffs, the temperature of the sample, and the aluminum concentration on the optical coefficients are analyzed. In addition, the effect of the hydrostatic pressure and the applied external tilted static electric field on the overall configuration is determined. The results revealed that an increase in the temperature and the aluminum concentration allows fine blue-shift tuning of the coefficient peaks, while an increase of inter-sidewall angle, the thickness of the crescent, and the hydrostatic pressure allows coarse red-shift tuning. Furthermore, the polarization angle of the optic field significantly affects the peak values of the optical coefficients, while the strength of the static electric field and its orientation angle produce changes at most on the order of similar to 4%. The positioning of the peaks of the optical coefficients is in agreement with the calculated transition energies.

关键词： 量子力学  

ISBN: (纸本)9787113276966

摘要： 随着我国首颗量子实验卫星“墨子号”的成功发射，量子保密通信“京沪干线”的正式开通，量子计算机的出现，很多人开始关注量子的最新动态。什么是量子力学？它有多重要？它和经典物理学有什么不同?它又有哪些应用？为什么各国如此重视？就让这本书中的小豆丁，带你找寻答案吧。

关键词： Almost positivity   Powers of second order operators   Dirichlet problem   Green function estimates  

摘要： Estimates from above and below by the same positive prototype function for suitably modified Green functions in bounded smooth domains under Dirichlet boundary conditions for elliptic operators L of higher order 2m >= 4 have been shown so far only when the principal part of L is the polyharmonic operator (-Delta)(m). In the present note, it is shown that such kind of result still holds when the Laplacian is replaced by any second order uniformly elliptic operator in divergence form with smooth variable coefficients. For general higher order elliptic operators, whose principal part cannot be written as a power of second order operators, it was recently proved that such kind of result becomes false in general.

关键词： long-range effects   polarizable force fields   pseudobond   QM/MM  

摘要： Quantum mechanics/molecular mechanics (QM/MM) simulations are a popular approach to study various features of large systems. A common application of QM/MM calculations is in the investigation of reaction mechanisms in condensed-phase and biological systems. The combination of QM and MM methods to represent a system gives rise to several challenges that need to be addressed. The increase in computational speed has allowed the expanded use of more complicated and accurate methods for both QM and MM simulations. Here, we review some approaches that address several common challenges encountered in QM/MM simulations with advanced polarizable potentials, from methods to account for boundary across covalent bonds and long-range effects, to polarization and advanced embedding potentials. This article is categorized under: Electronic Structure Theory > Combined QM/MM Methods Molecular and Statistical Mechanics > Molecular Interactions Software > Simulation Methods

关键词： Laplacian Support Vector Machine   semi-supervised learning   primal solution   classification  

摘要： Laplacian support vector machine (LapSVM) is an extremely popular classification method and relies on a small number of labels and a Laplacian regularization to complete the training of the support vector machine (SVM). However, the training of SVM model and Laplacian matrix construction are usually two independent process. Therefore, In this paper, we propose a new adaptive LapSVM method to realize semi-supervised learning with a primal solution. Specifically, the hinge loss of unlabelled data is considered to maximize the distance between unlabelled samples from different classes and the process of dealing with labelled data are similar to other LapSVM methods. Besides, the proposed method embeds the Laplacian matrix acquisition into the SVM training process to improve the effectiveness of Laplacian matrix and the accuracy of new SVM model. Moreover, a novel optimization algorithm considering primal solver is proposed to our adaptive LapSVM model. Experimental results showed that our method outperformed all comparison methods in terms of different evaluation metrics on both real datasets and synthetic datasets.

关键词： Vehicle re-identification   Laplacian-regularized correlative sparse ranking   Multi-view   Deep feature  

摘要： Vehicle re-identification has gradually gained attention and widespread applications. However, most of the existing methods learn the discriminative features for identities by single-feature channel only. It is worth noting that visual cognition of the human eyes is a multi-channel system which usually seeks a sparse representation. Therefore, integrating the multi-view information in sparse representation is a natural way to boost computer vision tasks in challenging scenarios. In this paper, we propose to mine multi-view deep features via Laplacian-regularized correlative sparse ranking for vehicle re-identification. Specifically, first, we employ multiple baseline networks to generate features. Then, we explore the feature correlation via enforcing the correlation term into the multi-view Laplacian sparse ranking framework. The original rankings are obtained by the reconstruction coefficients between the probe and gallery. Finally, we utilize a re-ranking technique to further boost performance. Experimental results on public benchmark VeRi-776 and VehicleID datasets demonstrate that our approach outperforms state-of-the-art approaches. The Laplacian-regularized correlative sparse ranking as a general framework can be used in any multi-view feature fusion and will obtain more competitive results.

关键词： Hydrostatic pressure   Temperature   Laser field   Self-polarization   Binding energy   Quantum well  

摘要： In this study, the self-polarization and binding energy of the donor impurity atom in the laser field applied Ga1_xAlxAs/GaAs quantum well are investigated under the combined influence of hydrostatic pressure and temperature. Variation of self-polarization and binding energy depending on temperature, hydrostatic pressure, impurity position, well width and laser field parameters are shown. Using the effective mass approximation, subband energy has been found by finite difference method and impurity energy has been found by variation method. Our results showed that hydrostatic pressure and temperature have a noticeable effect on the calculated selfpolarization and binding energy in a quantum well under the effect of the laser field. We think that the results obtained will be useful in determining the physical properties of the quantum well under the influence of laser field, hydrostatic pressure and temperature.

关键词： Controllability   Laplace equations   Complex networks   Energy measurement   Eigenvalues and eigenfunctions   Control energy   network controllability   signed networks  

摘要： This article investigates energy-related controllability of complex networks. Specifically, our objective is to establish controllability characteristics on signed complex networks, where the network units interact via neighbor-based Laplacian feedback and the network admits positive and negative edges to capture cooperative and competitive interactions among these units. The network units can be classified into leaders and followers. This article focuses on characterizing the energy-related controllability in signed networks (i.e., the energy incurred by the leaders in the control of a network). To this end, controllability Gramian-based measures are exploited to quantify the difficulty of the control problem on signed networks in terms of the required control energy. Fundamental relationships between these measures and network topology are developed via graph Laplacian to characterize energy-related controllability. It is revealed that, for structurally unbalanced signed graphs, the energy-related controllability is closely related to the diagonal entries of the inverse of the graph Laplacian. It is also discovered that structurally balanced signed graphs and their corresponding unsigned graphs have the same energy-related controllability.