OALib Journal期刊

ISSN: 2333-9721




2018 ( 174 )

2017 ( 143 )

2016 ( 157 )

2015 ( 1914 )


匹配条件: “ Dongpo Yang” ,找到相关结果约55769条。
Noise Simulation Analysis of a Variable Displacement External Gear Pump and Unloading Groove Optimization  [PDF]
Yongkang Zhou, Wenwu Li, Dongpo Yang
Open Access Library Journal (OALib Journal) , 2018, DOI: 10.4236/oalib.1105030
The oil pump is an important part of vehicle engine, whose noise and vibration characteristics affect the engine performance significantly. The noises generat-ed by both the pressure and flow fluctuations are the main contributors to the oil pump noise. In this paper, noise analysis of an external gear pump is carried out by using the computational fluid dynamics (CFD) method and The Lighthill’s acoustic analogy (LAA) algorithm. The fluid pressure and velocity distributions of the flowfield are firstly calculated by using a CFD model. The noises generated by flowfield are simulated and their sound pressure spectra are obtained by using an LAA-based finite element model. By analyzing the phenomenon of oil trapping, the optimum design of unloading groove is put forward, and then the simulation analysis is carried out. According to the finite element model, the noise level of gear pump is reduced and the effect of noise reduction is achieved. The technique presented in this paper can be regarded as a useful tool for optimization design of gear pumps in vehicle engineering.
The Theory of Quaternion Matrix Derivatives
Dongpo Xu,Danilo P. Mandic
Mathematics , 2014, DOI: 10.1109/TSP.2015.2399865
Abstract: A systematic theory is introduced for calculating the derivatives of quaternion matrix function with respect to quaternion matrix variables. The proposed methodology is equipped with the matrix product rule and chain rule and it is able to handle both analytic and nonanalytic functions. This corrects a flaw in the existing methods, that is, the incorrect use of the traditional product rule. In the framework introduced, the derivatives of quaternion matrix functions can be calculated directly without the differential of this function. Key results are summarized in tables. Several examples show how the quaternion matrix derivatives can be used as an important tool for solving problems related to signal processing.
Quaternion Gradient and Hessian
Dongpo Xu,Danilo P. Mandic
Computer Science , 2014, DOI: 10.1109/TNNLS.2015.2440473
Abstract: The optimization of real scalar functions of quaternion variables, such as the mean square error or array output power, underpins many practical applications. Solutions often require the calculation of the gradient and Hessian, however, real functions of quaternion variables are essentially non-analytic. To address this issue, we propose new definitions of quaternion gradient and Hessian, based on the novel generalized HR (GHR) calculus, thus making possible efficient derivation of optimization algorithms directly in the quaternion field, rather than transforming the problem to the real domain, as is current practice. In addition, unlike the existing quaternion gradients, the GHR calculus allows for the product and chain rule, and for a one-to-one correspondence of the proposed quaternion gradient and Hessian with their real counterparts. Properties of the quaternion gradient and Hessian relevant to numerical applications are elaborated, and the results illuminate the usefulness of the GHR calculus in greatly simplifying the derivation of the quaternion least mean squares, and in quaternion least square and Newton algorithm. The proposed gradient and Hessian are also shown to enable the same generic forms as the corresponding real- and complex-valued algorithms, further illustrating the advantages in algorithm design and evaluation.
Convergence of an Online Split-Complex Gradient Algorithm for Complex-Valued Neural Networks
Huisheng Zhang,Dongpo Xu,Zhiping Wang
Discrete Dynamics in Nature and Society , 2010, DOI: 10.1155/2010/829692
Abstract: The online gradient method has been widely used in training neural networks. We consider in this paper an online split-complex gradient algorithm for complex-valued neural networks. We choose an adaptive learning rate during the training procedure. Under certain conditions, by firstly showing the monotonicity of the error function, it is proved that the gradient of the error function tends to zero and the weight sequence tends to a fixed point. A numerical example is given to support the theoretical findings. 1. Introduction In recent years, neural networks have been widely used because of their outstanding capability of approximating nonlinear models. As an important search method in optimization theory, gradient algorithm has been applied in various engineering fields, such as adaptive control and recursive parametrical estimation [1–3]. Gradient algorithm is also a popular training method for neural networks (when used to train neural networks with hidden layers, gradient algorithm is also called BP algorithm) and can be done either in the online or in the batch mode [4]. In online training, weights are updated after the presentation of each training example, while in batch training, weights are not updated until all of the examples are inputted into the networks. As a result, batch gradient training algorithm is always used when the number of training samples is relatively small. However, in the case that a very large number of training samples are available, online gradient training algorithm is preferred. Conventional neural networks' parameters are usually real numbers for dealing with real-valued signals [5, 6]. In many applications, however, the inputs and outputs of a system are best described as complex-valued signals and processing is done in complex space. In order to solve the problem in complex domain, complex-valued neural networks (CVNNs) have been proposed in recent years [7–9], which are the extensions of the usual real-valued neural networks to complex numbers. Accordingly, there are two types of generalized gradient training algorithm for complex-valued neural networks: fully complex gradient algorithm [10–12] and split-complex gradient algorithm [13, 14]; both of which can be processed in online mode and batch mode. It has been pointed out that the split-complex gradient algorithm can avoid the problems resulting from the singular points [14]. Convergence is of primary importance for a training algorithm to be successfully used. There have been extensive research results concerning the convergence of gradient algorithm for
catena-Poly[[[aquapyridinezinc(II)]-μ2-3,3′-(p-phenylene)diacrylato] pyridine solvate]
Dongpo Su,Desheng Song,Zhiyong Fu
Acta Crystallographica Section E , 2010, DOI: 10.1107/s1600536810033167
Abstract: The title compound, {[Zn(C12H8O4)(C5H5N)(H2O)]·C5H5N}n, has been prepared by hydrothermal reaction. The ZnII atom is six-coordinated by four carboxylate O atoms of two p-phenylenediacrylate (ppda2 ) ligands, one N atom of a pyridine molecule and one O atom of a water molecule in a distorted octahedral environment. The carboxylate groups of the ppda2 anions are in a bridging–chelating mode, in which two O atoms chelate one Zn2+ ion. These connections result in an extended chain structure. Parallel packing of the chains forms a two-dimensional network with intermolecular edge-to-face interactions. Further linkages between the layers through O—H...O hydrogen-bonding interactions result in a three-dimensional supramolecular architecture with one-dimensional rectanglar channels.
Zhiyong Fu,Dongpo Su,Desheng Song
Acta Crystallographica Section E , 2009, DOI: 10.1107/s1600536809036150
Abstract: The title PbII coordination polymer, [PbCl2(C13H14N2)], was prepared by the hydrothermal reaction of PbCl2 with 4,4,-trimethylenedipyridine in a 1:1 ratio. It exhibits a two-dimensional layered structural motif consisting of PbCl2 chains and the flexible bridged 4,4′-trimethylenedipyridine ligand. The connections result in a cavity of about 4 × 15 .
Network value and optimum analysis on the mode of networked marketing in TV media
Xiao Dongpo,Zhenji Zhang,Xiaolan Guan
Journal of Industrial Engineering and Management , 2012, DOI: 10.3926/jiem.615
Abstract: Purpose: With the development of the networked marketing in TV media, it is important to do the research on network value and optimum analysis in this field. Design/methodology/approach: According to the research on the mode of networked marketing in TV media and Correlation theory, the essence of media marketing is creating, spreading and transferring values. The Participants of marketing value activities are in network, and value activities proceed in networked form. Network capability is important to TV media marketing activities. Findings: This article raises the direction of research of analysis and optimization about network based on the mode of networked marketing in TV media by studying TV media marketing Development Mechanism , network analysis and network value structure.
Soil biological activities at maize seedling stage under application of slow/controlled release nitrogen fertilizers

LI Dongpo,WU Zhijie,CHEN Lijun,LIANG Chenghua,ZHANG Lili,WANG Weicheng,YANG Defu,

应用生态学报 , 2006,
Abstract: With pot experiment and simulating field ecological environment, this paper studied the effects of different slow/controlled release N fertilizers on the soil nitrate-reductase and urease activities and microbial biomass C and N at maize seedling stage. The results showed that granular urea amended with dicyandiamide (DCD) and N-(n-bultyl) thiophosphoric triamide (NBPT) induced the highest soil nitrate-reductase activity, granular urea brought about the highest soil urease activity and microbial biomass C and N, while starch acetate (SA)-coated granular urea, SA-coated granular urea amended with DCD, methyl methacrylate (MMA)-coated granular urea amended with DCD, and no N fertilization gave a higher soil urease activity. Soil microbial C and N had a similar variation trend after applying various kinds of test slow/controlled release N fertilizers, and were the lowest after applying SA-coated granular urea amended with DCD and NBPT. Coated granular urea amended with inhibitors had a stronger effect on soil biological activities than coated granular urea, and MMA-coating had a better effect than SA-coating.
Dynam ics of arease activity in a long-term fertilized black soil and its affecting factors

LI Dongpo,WU Zhijie,CHEN Lijun,YANG Jie,ZHU Ping,REN Jun,PENG Chang,GAO Hongjun,

应用生态学报 , 2003,
Abstract: The effect of long-term fertilization on the urease activity in a typical black soil in Northeastern China was examined in this paper. The soil has been fertilized since 1980, and the dynamics of its urease activity was monitored during crop growth season. The results showed that a significant difference in soil urease activity was found at each growth stage between soils treated by different fertilizations. In farmyard manure treated soil, the urease activity was > 160 mg.kg-1.h-1 and with a low seasonal fluctuations. The soil urease activity had a significant positive correlation with soil biological, physical and chemical properties, and the N, P and K contents in plants (P < 0.01), and with soil moisture content and grain crude protein (P < 0.05).
A Current-Mode DC-DC Buck Converter with High Stability and Fast Dynamic Response
Chen Dongpo,He Lenian,Yan Xiaolang,
Chen Dongpo
,He Lenian,Yan Xiaolang

半导体学报 , 2006,
Abstract: 提出了一种高稳定性的电流型DC-DC转换器.首先应用一种新型的电流型转换器的模型推导了控制环路的增益表达式,在分析其环路增益的基础上,提出了一种新颖的控制环路频率补偿的方法,从而使转换器的稳定性不受负载电流和电源电压变化的影响.其次应用这种新的频率补偿方法,使用0.5μm-CMOS工艺设计了一种电流模式的降压型转换器.仿真结果表明,该稳压器具有高度的稳定特性,其稳定性与负载和电源电压无关.并且由于这种新的频率补偿为环路提供了极高的带宽,所以该转换器具有优异的动态响应.其提供的全负载瞬态响应的建立时间小于5μs,过冲电压小于30mV.

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