基于MFO算法的全液压压裂车功率节能匹配

针对机械式压裂车油耗和成本较高的缺点,提出全液压压裂车概念,考虑到系统功率损失,提出使用"施工比油耗"衡量压裂车实际油耗,对全液压压裂车进行全局功率匹配,分别建立发动机万有特性、变量柱塞泵效率和整机辅助功率的数学模型,采用自适应惩罚函数法构建惩罚函数,以施工比油耗最低为优化目标建立目标函数,基于MFO算法,以压裂泵需输出的压力和流量作为优化输入参数,优化输出需启动的发动机数量、各发动机转速及其柱塞泵排量共计11个调整参数的最佳组合,结果表明,在全部工况下,全液压压裂车施工比油耗维持在4.55~9.91 L/（60 MPa·m³）,且随着负载压力和排量的增加而逐渐降低;与原方案相比,新方案最高可节油35.97%,且节油率随着负载压力的增大而逐渐减小;与机械式压裂车相比,同等工况下,采用新方案的全液压压裂车最高可节油53.74%。     

Tight Lower Bounds on the Size of a Maximum Matching in a Regular Graph

In this paper we study tight lower bounds on the size of a maximum matching in a regular graph. For k ≥3, let G be a connected k-regular graph of order n and let α′(G) be the size of a maximum matching in G. We show that if k is even, then , while if k is odd, then . We show that both bounds are tight. Research supported in part by the South African National Research Foundation and the University of KwaZulu-Natal.     

Reconstruction of Sparse Polynomials via Quasi-Orthogonal Matching Pursuit Method

In this paper, we propose a Quasi-Orthogonal Matching Pursuit (QOMP) algorithm for constructing a sparse approximation of functions in terms of expansion by orthonormal polynomials. For the two kinds of sampled data, data with noises and without noises, we apply the mutual coherence of measurement matrix to establish the convergence of the QOMP algorithm which can reconstruct $s$-sparse Legendre polynomials, Chebyshev polynomials and trigonometric polynomials in $s$ step iterations. The results are also extended to general bounded orthogonal system including tensor product of these three univariate orthogonal polynomials. Finally, numerical experiments will be presented to verify the effectiveness of the QOMP method.     

Stainless Steel Electrodes to Determine Biodiesel Content in Petroleum Diesel Fuel by Electrochemical Impedance Spectroscopy

The blending ratio of biodiesel in petroleum diesel has become one of the most important parameters to ensure the quality of diesel/biodiesel blend. This paper presents a fast and simple method based on electrochemical impedance spectroscopy to determine the biodiesel content in diesel fuel. Different from the method reported in the literature, using a pair of two identical screen printed carbon paste electrodes, in the present work we used two electrodes made from 304 stainless steel with dimensions of 0.8×0.3 cm for the EIS measurements. Improved results were obtained in terms of sensitivity, stability of measurements, electrode reuse, and cost. In this procedure the charge transfer resistance is proportionally related to the biodiesel content, which is used to construct a calibration curve for the analysis of biodiesel content. The procedure was validated by an official method, using two samples, being one of them, certified through an official interlaboratory program of the Brazilian government (Interlaboratory Program for Biodiesel of National Agency of Petroleum, Natural Gas and Biofuels (PIB)/ANP). Good results were obtained in terms of recovery (102.6 %‐102.8 %), precision (coefficient of variation lower than 2.3 %), limit of detection (0.24 %) and limit of quantification (0.80 %). These results indicate that this method is sufficiently suitable as an alternative method to the official method for determining biodiesel content in commercial diesel fuel.     

Synthesis,electrolyte properties and solar cell performance of hyperbranched poly(aryl-ether-urea)s

Hyperbranched poly(aryl-ether-urea)s with phenyl, N,N-dimethylamino ethyl and polyethylene oxide end-groups linked through urethane group – HBPEU-1, HBPEU-2 and HBPEU-3 respectively – were synthesized from an AB₂-type blocked isocyanate monomer and characterized by FT-IR, ¹H-NMR, SEC-MALLS, TGA and DSC techniques. The molecular weight of the polymers were found to be ranged from 4.9 × 10³ ? 1.96 × 10⁴ g/mol. The TGA results showed that the polymers decompose between 175°C – 220°C. In the DSC curves, HBPEU-1 and HBPEU-3 showed T_g at 160°C and 53°C respectively, whereas HBPEU-2 did not showed clear T_g. All the three polymers were converted into polymer electrolytes by doping with LiI/I₂. The doped polymers showed remarkably high ionic conductivity, up to 222 – 277 times compared to the un-doped polymers and the highest conductivity was observed with doped HBPEU-2. The TiO₂ based dye-sensitized solar cells (DSSCs) were fabricated using the doped polymer electrolytes and their performance was tested; HBPEU-2 showed good performance by yielding energy conversion efficiency (η) of 4.5%.     

On some structural properties of generalized fullerene graphs with 13 pentagonal faces

It is shown that every generalized fullerene graph G with 13 pentagons is 2-extendable, a brick, and cyclically 5-edge-connected, i.e., that G cannot be separated into two components, each containing a cycle, by deletion of fewer than five edges. New lower bound on the number of perfect matchings in such graphs are also established.     

(Un)stable matchings with blocking costs

We introduce and study weighted bipartite matching problems under strict preferences where blocking edges can be paid for, thus imposing costs rather than constraints as in classical models. We focus on the setting in which the weight of an edge represents the benefit from including it in the matching and/or the cost if it is a blocking edge. We show that this setting encompasses interesting special cases that remain polynomially-solvable, although it becomes APX-hard even in a quite restricted case.     

考虑产品与单元匹配的单元装配系统构建模型

针对日本式单元生产过程中流水装配线向单元装配系统转换的决策优化问题,本文以最小化总完工时间和工人总工时为目标,同时考虑产品与单元的匹配关系,构建了单元装配系统多目标优化模型,基于NSGA-II算法设计了适用于该问题的三段染色体的编码方式。通过算例分析了产品与单元匹配关系变化对总完工时间和工人总工时的影响,结果表明,在工人数不变的情况下,产品与单元匹配关系变化会导致总完工时间产生较大差异,随着工人数增多,这种差异逐渐变小。     

基于时间依赖网络的危险品运输路径选择研究

为合理选择危险品运输路径,降低危险品运输事故的发生概率,以危险品运输路径选择问题为研究对象,对运输网络的时变特性进行分析,提出了动态路阻运输路径的思想。考虑到危险品运输不一定满足时间依赖网络FIFO特性,因此本文建立了包括时间阻抗、费用阻抗和风险阻抗在内的综合阻抗最小的危险品运输路线模型,采用综合阻抗最小化与时间依赖非FIFO网络最短路径综合算法对模型优化求解。给出的算例表明,不同时间段内的最优路径会发生变化,验证了该模型方法的可行性。     

单电子束双波段同轴相对论返波管粒子模拟

设计了一种能在C波段和X波段实现稳定双频输出的带有非对称谐振反射腔的单电子束同轴相对论返波振荡器。采用耦合阻抗跃变型慢波结构,使用粒子PIC模拟软件进行了粒子模拟研究。模拟结果显示：轴向电场在系统中的分布得到改进,电子束的能散得到改善。在电子束电压511 kV,电流8.95 kA,引导磁场0.73 T的条件下,双频器件实现了8.09 GHz和9.91 GHz的双波段频率稳定输出,平均功率为1.0 GW,波束互作用效率为21.9%, 效率高于空心双波段返波管及其他双波段器件。器件辐射功率的拍频为1.82 GHz,拍波更为明显和稳定。模拟研究中同时发现, 随着慢波结构之间漂移段的变化,双频频率都呈现一种准周期的变化。