Search | Engineering

订阅投稿

首页工程期刊工程焦点工程成就工程前沿关于我们 English

资源类型

期刊论文 74

年份

2023 3

2022 4

2021 6

2020 4

2019 8

2017 10

2016 4

2015 6

2014 2

2013 1

2012 1

2011 4

2010 4

2009 1

2008 3

2007 3

2006 5

2005 2

2004 1

2002 1

展开︾

关键词

平均功率 2

遗传算法 2

1) 1

GM(1 1

GVG农情采样系统 1

Gibbs抽样 1

LED灯具；加速老化测试；中位寿命；滑动平均误差 1

MCMC模拟 1

MapReduce；近似作业；时限；任务调度；掉队任务消除 1

PCB缺陷检测 1

Weibull分布 1

mcr 1

一致性 1

三维构造 1

井帮位移 1

人工智能 1

人脸建模 1

优化 1

作物灾情 1

展开︾

检索范围：

排序：展示方式：

A case study on sample average approximation method for stochastic supply chain network design problem

Yuan WANG, Ruyan SHOU, Loo Hay LEE, Ek Peng CHEW

《工程管理前沿（英文）》 2017年第4卷第3期页码 338-347 doi: 10.15302/J-FEM-2017032

摘要： This study aims to solve a typical long-term strategic decision problem on supply chain network design with consideration to uncertain demands. Existing methods for these problems are either deterministic or limited in scale. We analyze the impact of uncertainty on demand based on actual large data from industrial companies. Deterministic equivalent model with nonanticipativity constraints, branch-and-fix coordination, sample average approximation (SAA) with Bayesian bootstrap, and Latin hypercube sampling were adopted to analyze stochastic demands. A computational study of supply chain network with front-ends in Europe and back-ends in Asia is presented to highlight the importance of stochastic factors in these problems and the efficiency of our proposed solution approach.

关键词： supply chain network stochastic demand sampling average approximation Bayesian bootstrap Latin hypercube sampling

HTML PDF 收藏

Performance prediction of switched reluctance generator with time average and small signal models

Jyoti KOUJALAGI, B. UMAMAHESWARI, R. ARUMUGAM

《能源前沿（英文）》 2013年第7卷第1期页码 56-68 doi: 10.1007/s11708-012-0216-8

摘要： This paper presents the complete mathematical model and predicts the performance of switched reluctance generator with time average and small signal models. The complete mathematical model is developed in three stages. First, a switching model is developed based on quasi-linear inductance profile. Next, based on the switching behaviour, a time average model is obtained to measure the difference between the excitation and generation time in each switching cycle. Finally, to track control voltage and current wave shapes, a small signal model is designed. The effectiveness of the complete multilevel model combining electrical machine, power converter, load and control with programming language is demonstrated through simulations. A PI controller is used for controlling the voltage of the generator. The results presented show that the controller exhibits accurate tracking control of load voltage under different operating conditions. This demonstrates that the proposed model is able to perform an accurate control of the generated output voltage even in transient situations. The simulation is performed to choose the control parameters and study the performance of switched reluctance generator prior to its actual implementation. Initial experimental results are presented using NI-Data acquisition card to control the output power according to load requirements.

关键词： generator reluctance switching model small signal model time average model

HTML PDF 收藏

Experimental study on average movement characteristics of bed-load particles

Limo TANG, Xingkui WANG,

《结构与土木工程前沿（英文）》 2009年第3卷第4期页码 435-439 doi: 10.1007/s11709-009-0050-1

摘要： The three-dimensional movements of bed-load particles in an open channel with different grain diameters and different specific gravities under the conditions of different hydraulic gradient are measured by means of particle tracking velocimetry (PTV) technique. The average movement characteristics of the particles are analyzed by statistics. The results show that the longitudinal average velocities of the particles neither agree with the law suggested by Einstein nor obey the law assumed by Bagnold. Einstein’s law is that the particle velocity is equal to 11.6 times of shear velocity, and the Bagnold’s law assumes the velocity equal to the difference between flow velocity at corresponding water depth and settling velocity of particle. Two formulas for determining the velocity of particle in the forms of expression given by Einstein and Bagnold are obtained according to the statistical results of experimental data, respectively.

关键词： different longitudinal three-dimensional particle Bagnold

HTML PDF 收藏

Numerical simulation and experimental research on the wheel brush sampling process of an asteroid sampler

《机械工程前沿（英文）》 2023年第18卷第2期 doi: 10.1007/s11465-022-0732-0

摘要： To examine the environmental characteristics of the microgravity force and the weathered layer on an asteroid surface, a symmetric wheel brush asteroid sampler is proposed for the collection of particles on the asteroid surface. To study the influence of the wheel brush rotation speed on the sampling efficiency and the driving torque required for the wheel brush, the contact dynamics model between particles and sampling wheel brushes is established and a simulation and experimental verification of the sampling process are conducted. The parameter calibration of the sampled particles is studied first, and the calibrated particle parameters are used in the numerical simulation of the sampling process. The sampling results and the particle stream curves are obtained for the working conditions of different rotation speeds, and the effects of different parameter settings on the sampling efficiency are analyzed. In addition, a set of rotating symmetrical sampling wheel brush devices is built for the ground test, and the dynamic torque sensor is used to test the torque change of the wheel brush during the sampling process. The relationship between the speed of the wheel brush and the driving torque of the wheel brush motor is determined by comparing the simulation results with the test results. Results indicate that when the rotating speed of the wheel brush is faster, the sampling efficiency is higher, and the driving torque required for the sampling wheel brush is greater. Moreover, a numerical simulation analysis of the sampling process of the wheel brush sampler in a microgravity environment is conducted to determine the optimal speed condition, and the brushing test of the wheel brush sampler in the microgravity environment is verified with the drop tower method. This research proposes the structural optimization design and motor selection of a wheel brush asteroid sampler, which provides important reference value and engineering significance.

关键词： asteroid sampling wheel brush sampler discrete element method parameter calibration experimental research

HTML PDF 收藏

Investigation on sampling artifacts of particle associated PAHs using ozone denuder systems

Kai LIU, Fengkui DUAN, Kebin HE, Yongliang MA, Yuan CHENG

《环境科学与工程前沿（英文）》 2014年第8卷第2期页码 284-292 doi: 10.1007/s11783-013-0555-7

摘要： Polycyclic aromatic hydrocarbons (PAHs) are complex organic compounds which are identified as significant carcinogenic to human health. PAHs (mainly in particle phase) are susceptible to atmospheric oxidant gases, especially ozone, nitrogen oxides (NO ), hydroxyl radical (OH), and could be degraded on filters during sampling process, leading to an underestimation of ambient PAH concentrations. The goal of this work was to investigate particle associated PAHs sampling artifacts caused by ozone in summer of Beijing. Comparative sampling systems were operated simultaneously during the whole campaign, one with activated carbon ozone denuder, the other being set as conventional sampling system. Activated carbon denuder was testified to be highly efficient to eliminate ozone from air stream. In general, nine particle-bound PAHs observed from conventional sampler were all lower than those from ozone denuder system. The total PAHs (particle phase) concentration was averagely underestimated by 35.9% in conventional sampling procedure. Benzo[a]pyrene (BaP) had the highest percentage of mass loss. Ambient temperature was founded to have influences on PAHs sampling artifacts. High temperature can increase loss of particle associated PAHs during sampling.

关键词： particle associated polycyclic aromatic hydrocarbons (PAHs) ozone denuder sampling artifacts

HTML PDF 收藏

A sampling method based on URL clustering for fast web accessibility evaluation

Meng-ni ZHANG,Can WANG,Jia-jun BU,Zhi YU,Yu ZHOU,Chun CHEN

《信息与电子工程前沿（英文）》 2015年第16卷第6期页码 449-456 doi: 10.1631/FITEE.1400377

摘要： When evaluating the accessibility of a large website, we rely on sampling methods to reduce the cost of evaluation. This may lead to a biased evaluation when the distribution of checkpoint violations in a website is skewed and the selected samples do not provide a good representation of the entire website. To improve sampling quality, stratified sampling methods first cluster web pages in a site and then draw samples from each cluster. In existing stratified sampling methods, however, all the pages in a website need to be analyzed for clustering, causing huge I/O and computation costs. To address this issue, we propose a novel page sampling method based on URL clustering for web accessibility evaluation, namely URLSamp. Using only the URL information for stratified page sampling, URLSamp can efficiently scale to large websites. Meanwhile, by exploiting similarities in URL patterns, URLSamp cluster pages by their generating scripts and can thus effectively detect accessibility problems from web page templates. We use a data set of 45 web sites to validate our method. Experimental results show that our URLSamp method is both effective and efficient for web accessibility evaluation.

关键词： Page sampling URL clustering Web accessibility evaluation

HTML PDF 收藏

Shape reconstruction of parallelogram flaw

ZHENG Gangfeng, WU Bin, HE Cunfu

《机械工程前沿（英文）》 2008年第3卷第1期页码 17-22 doi: 10.1007/s11465-008-0015-4

摘要： To reconstruct the shape of the scatterer in elastic media, the authors deduce the Born approximation solution of the two-dimensional scattering problem, which includes the shape factor that embodies all information about the shape of the scatterer. Accordingly, the change in the shape of the scatterer only necessitates the number of the corresponding new shape factors. For a parallelogram void in a long Al rod, its shape factor can be obtained. In view of the definition of a characteristic function, the shape factor has a corresponding integral representation. Obviously, the shape factor can be considered as a Fourier transform of the characteristic function, which is reconstructed from the inverse Fourier transform. The integral equation is considered as the basic equation to reconstruct the shape of the scatterer. The identification of the geometrical character of a flaw is then given by the two dimensional inverse Born approximation in a low-frequency range. For the parallelogram void, a theoretical calculating identification is performed. At the same time, the numerical results are obtained by the finite element method.

关键词： approximation scatterer scattering problem information inverse

HTML PDF 收藏

Dilution sampling and analysis of particulate matter in biomass-derived syngas

Xiaoliang WANG, Curtis ROBBINS, S. Kent HOEKMAN, Judith C. CHOW, John G. WATSON, Dennis SCHUETZLE

《环境科学与工程前沿（英文）》 2011年第5卷第3期页码 320-330 doi: 10.1007/s11783-011-0347-x

摘要： Thermochemical biomass gasification, followed by conversion of the produced syngas to fuels and electrical power, is a promising energy alternative. Real-world characterization of particulate matter (PM) and other contaminants in the syngas is important to minimize damage and ensure efficient operation of the engines it powers and the fuels created from it. A dilution sampling system is demonstrated to quantify PM in syngas generated from two gasification plants utilizing different biomass feedstocks: a BioMax 15 Biopower System that uses raw and torrefied woodchips as feedstocks, and an integrated biorefinery (IBR) that uses rice hulls and woodchips as feedstocks. PM mass concentrations in syngas from the IBR downstream of the purification system were 12.8–13.7 μg·m , which were significantly lower than the maximum level for catalyst protection (500 μg·m ) and were 2–3 orders of magnitude lower than those in BioMax 15 syngas (2247–4835 μg·m ). Ultrafine particle number concentration and PM chemical constituents were also much lower in the IBR syngas than in the BioMax 15. The dilution sampling system enabled reliable measurements over a wide range of concentrations: the use of high sensitivity instruments allowed measurement at very low concentrations (~1 μg·m ), while the flexibility of dilution minimized sampling problems that are commonly encountered due to high levels of tars in raw syngas (~1 g·m ).

关键词： dilution source sampling syngas characterization biomass gasification ultrafine particles

HTML PDF 收藏

Accounting for the uncertainties in the estimation of average shear wave velocity using – correlations

《结构与土木工程前沿（英文）》 2021年第15卷第5期页码 1199-1208 doi: 10.1007/s11709-021-0749-1

摘要： Site-specific seismic hazard analysis is crucial for designing earthquake resistance structures, particularly in seismically active regions. Shear wave velocity ( V _S) is a key parameter in such analysis, although the economy and other factors restrict its direct field measurement in many cases. Various V _S–SPT– N correlations are routinely incorporated in seismic hazard analysis to estimate the value of V _S. However, many uncertainties question the reliability of these estimated V _S values. This paper comes up with a statistical approach to take care of such uncertainties involved in V _S calculations. The measured SPT– N values from all the critical boreholes were converted into statistical parameters and passed through various correlations to estimate V _S at different depths. The effect of different soil layers in the boreholes on the Vs estimation was also taken into account. Further, the average shear wave velocity of the top 30 m soil cover ( V _S30) is estimated after accounting for various epistemic and aleatoric uncertainties. The scattering nature of the V _S values estimated using different V _S– N correlations was reduced significantly with the application of the methodology. Study results further clearly demonstrated the potential of the approach to eliminate various uncertainties involved in the estimation of V _S30 using general and soil-specific correlations.

关键词： uncertainties V _S– N correlations V _S30 SPT data statistical methodology

HTML PDF 收藏

广义近似空间与粗糙分类代数

刘永红

《中国工程科学》 2006年第8卷第3期页码 39-48

摘要：

提出了广义近似空间、粗近似公理、干扰集公理、粗糙集的分类原则、粗选原则、不确定偶集原则、精选原则、对策分类、量子逻辑分类、bit量子对称分类、不可比集、bit空间集、协议关系、粗糙集函数、粗糙分类代数和粗糙单代数等基本概念，并提出了一个猜想；展示了一些新观点；基于协议关系构造了粗糙商代数和粗糙子代数，给出了回避-归并算法及算例。

关键词：广义近似空间粗糙集粗糙分类代数协议关系粗糙单代数粗糙商代数粗糙子代数

HTML PDF 收藏

连续非线性最优控制问题的勒让德—伽辽金逼近方法 Article

Xue-song CHEN

《信息与电子工程前沿（英文）》 2017年第18卷第10期页码 1479-1487 doi: 10.1631/FITEE.1601101

摘要：该方法基于伽辽金逼近理论（Galerkin approximation）求解广义哈密尔顿—雅可比—贝尔曼（Hamilton-Jacobi-Bellman, GHJB）方程。

关键词：广义哈密尔顿—雅可比—贝尔曼方程；非线性最优控制；伽辽金逼近（Galerkin approximation）；勒让德多项式（Legendre polynomials）

HTML PDF 收藏

Unified methodology for site-characterization and sampling of highway runoff

Jy S. WU, Craig J. ALLAN,

《环境科学与工程前沿（英文）》 2010年第4卷第1期页码 47-58 doi: 10.1007/s11783-010-0003-x

摘要： Hydrology, roadway traffic conditions, and atmospheric deposition are three essential data categories for the planning and implementation of highway-runoff monitoring and characterization programs. Causal variables pertaining to each data category could be site specific but have been shown to correlate with runoff pollutant loads. These data categories were combined to derive statistical relationships for characterization and prioritization of the respective pollutant loads at highway runoff sites. Storm runoff data of total suspended solids (TSS), total dissolved solid (TDS), chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN) and total phosphorus (TP) collected from three highway sites in Charlotte, North Carolina, USA, were used to illustrate the development of site-specific highway-runoff pollutant loading models. This unified methodology provides a basis for initial assessment of the pollutant-constituent loads from highway runoff using hydrologic component variables. Improved reliability is achievable when additional traffic and/or atmospheric component variables are incorporated into the basic hydrologic regression model. In addition, operational guidance is suggested for implementing highway-runoff monitoring programs that are subject to sampling and resources constraints.

关键词： highway runoff pollutant loads regression models non-point source pollution storm water permit

HTML PDF 收藏

满足MapReduce环境下近似处理的时限要求 Article

Ming-hao HU, Chang-jian WANG, Yu-xing PENG

《信息与电子工程前沿（英文）》 2017年第18卷第11期页码 1754-1772 doi: 10.1631/FITEE.1601056

摘要：为了向大数据分析提供实时结果，在现今的生产环境中满足MapReduce作业的时限要求是非常关键的。许多研究致力于解决时限要求的问题，目前存在两种代表性的方法。第一种是分配适量资源以在时限前完成整个作业，在时限紧迫或资源受限时，该方法会错过时限；另一种是在时限约束下运行预数据量的样本，该方法能满足时限但无法使数据量最大化。在本文中，我们提出一个时限–导向的任务调度方法来解决上述问题，称为“Dart”。给定具体的时限和可用资源量时，Dart使用基于历史数据和作业运行状态的迭代估计法准确预测作业完成时间。基于时间预测，Dart法采用接近–修改算法做出动态调度决策，在满足时限的情况下将可处理数据量最大化并消除掉队任务。同时Dart法可有效地避免任务失败和数据倾斜，防止其性能受影响。在包含64个虚拟机的集群上使用OpenCloud和Facebook的工作负载对Dart法进行评估。结果表明Dart法在时限紧迫和资源受限情况下能有效满足时限并将处理数据量最大化。

关键词： MapReduce；近似作业；时限；任务调度；掉队任务消除

HTML PDF 收藏

Uncertainty propagation in dynamics of composite plates: A semi-analytical non-sampling-based approach

Mahdi FAKOOR, Hadi PARVIZ

《结构与土木工程前沿（英文）》 2020年第14卷第6期页码 1359-1371 doi: 10.1007/s11709-020-0658-8

摘要： In this study, the influences of spatially varying stochastic properties on free vibration analysis of composite plates were investigated via development of a new approach named the deterministic-stochastic Galerkin-based semi-analytical method. The material properties including tensile modulus, shear modulus, and density of the plate were assumed to be spatially varying and uncertain. Gaussian fields with first-order Markov kernels were utilized to define the aforementioned material properties. The stochastic fields were decomposed via application of the Karhunen-Loeve theorem. A first-order shear deformation theory was assumed, following which the displacement field was defined using admissible trigonometric modes to derive the potential and kinetic energies. The stochastic equations of motion of the plate were obtained using the variational principle. The deterministic-stochastic Galerkin-based method was utilized to find the probability space of natural frequencies, and the corresponding mode shapes of the plate were determined using a polynomial chaos approach. The proposed method significantly reduced the size of the mathematical models of the structure, which is very useful for enhancing the computational efficiency of stochastic simulations. The methodology was verified using a stochastic finite element method and the available results in literature. The sensitivity of natural frequencies and corresponding mode shapes due to the uncertainty of material properties was investigated, and the results indicated that the higher-order modes are more sensitive to uncertainty propagation in spatially varying properties.

关键词： composite plate spatially varying stochastic properties Galerkin method polynomial chaos approach semi-analytical approach

HTML PDF 收藏

亚奈奎斯特采样的数据恢复：性能极限与恢复算法

罗茜倩,张朝阳

《信息与电子工程前沿（英文）》 2021年第22卷第2期页码 141-286 doi: 10.1631/FITEE.1900320

摘要：奈奎斯特频率是一般带限信号进行无损采样的采样率下界，然而在某些情景中，亚奈奎斯特频率也足以进行无损采样和信号恢复。以往对亚奈奎斯特采样的研究主要集中在利用信号变换来降低信号维度，但是亚奈奎斯特采样信号的结构并没有得到充分研究。本文针对线性调制基带信号的亚奈奎斯特采样，研究其信号恢复性能极限与算法。该问题中，原信号维度无法降低，因此亚奈奎斯特采样不可避免会带来信息损失，信号恢复也变成一个欠定线性问题。本文采用两种亚奈奎斯特采样方法对线性调制基带信号进行采样，分别研究了两种采样方法下的性能极限和信号恢复算法。首先，针对两种亚奈奎斯特采样方法，分别计算了采样序列之间的最小归一化欧氏距离，以此作为最优性能的指标。然后，在基带信号有限符号集的限制条件下，采用改进的时变维特比算法从亚奈奎斯特采样序列中恢复原信号。将仿真得到的亚奈奎斯特采样的误比特率与其性能的理论极限比较，并与奈奎斯特采样性能对比，验证了时变维特比算法在信号恢复问题中的优良性能。

关键词：奈奎斯特采样定理；亚奈奎斯特采样；最小欧式距离；欠定线性问题；时变维特比算法

HTML PDF 收藏

标题作者时间类型操作

A case study on sample average approximation method for stochastic supply chain network design problem

Yuan WANG, Ruyan SHOU, Loo Hay LEE, Ek Peng CHEW

期刊论文

Performance prediction of switched reluctance generator with time average and small signal models

Jyoti KOUJALAGI, B. UMAMAHESWARI, R. ARUMUGAM

期刊论文

Experimental study on average movement characteristics of bed-load particles

Limo TANG, Xingkui WANG,

期刊论文