基于粗糙集的经济预警规则发现

应用粗糙集的理论和方法对经济预警有关数据进行分析,挖掘其中隐含的有用信息,提取规则并对规则进行约简,从而求取表达经济预警信息的最小决策规则,为经济预警有用信息的获取提供一种有效的方法.     

Highly enantioselective addition of methyl propiolate to aldehydes catalyzed by a titanium(IV) complex of a β-hydroxy amide

Three chiral β-hydroxy amide ligands were prepared by the reaction of benzyl chloride with amino alcohols derived from l-tyrosine. The titanium(IV) complex of chiral ligand 4a was found to be an effective catalyst for the asymmetric addition of methyl propiolate to aliphatic and aromatic aldehydes. The γ-hydroxy-α,β-acetylenic esters were obtained in excellent enantiomeric excesses (up to 94% ee) under optimized conditions.     

Anode spot plasma deposition of insulating layers on aluminum

The deposition of an insulating layer upon an aluminum plate in an argon plasma is described. The process is effected in a low-power DC discharge to which a small amount of sulfur hexafluoride (SF₆) has been added, causing the formation of anode spots at sharp metallic surfaces. The insulator is deposited in the region beneath the spot     

Lamb wave sensors array for nonviscous liquid sensing

The interdigital transducer (IDT) can excite Lamb wave in a piezoelectric plate loading with a liquid layer, and the phase velocity of Lamb wave is associated with the properties of the liquid layer. In this paper, the concept of effective permittivity is introduced to study the Lamb wave’s potential application in liquid sensing. Considering the measuring of ideal nonviscous liquid, the sensors array is designed to sense the density and the dielectric constant of the liquid layer simultaneously. Using LiNbO₃ as piezoelectric material, in order to improve the sensors array sensitivity and the electro-mechanical coupling coefficient, the optimized results including plate thicknesses and cut orientations are presented by numerical simulation. These studies show that the Lamb wave sensors array can be potential in liquid sensing.     

基于可控提前期和服务水平约束的(Q,r)库存问题

本文研究了存在顾客流失情况下，基于可控提前期和服务水平约束的连续盘点（Q，r）库存管理同题。当市场需求分布未知时采用MiniMax方法建立年总成本函数表达式，修正以往研究中对安全系数取值范围错误判断，推导出合理的安全系数取值范围，并给出最优解的计算方法。     

Two-stage autoignition and combustion mode evolution in boundary layer flows above a cold flat plate

Boundary layers are omnipresent in fundamental kinetic experimental facilities and practical combustion engines, which can cause ambiguity and misleading results in kinetic target acquisition and even abnormal engine combustion. In this paper, using n-heptane as a representative large hydrocarbon fuel exhibiting pronounced low-temperature chemistry (LTC), two-dimensional numerical simulation is conducted to resolve the transient autoignition phenomena affected by a boundary layer. We focus on the ignition characteristics and the subsequent combustion mode evolution of a hot combustible mixture flowing over a colder flat plate in an isobaric environment. For cases with autoignition occurring within the boundary layer, similarity is observed in the first-stage ignition as manifested by a constant temperature at all locations. The first-stage ignition is found to be rarely affected by heat and radical loss within the boundary layer. While for the main ignition event, an obvious dependence of ignition process on boundary layer thickness is identified, where the thermal-chemical process exhibits similarity at locations with similar boundary layer thickness, and the main ignition tends to first occur within the boundary layer at the domain end and generates a C-shape reaction front. It is found that sequential spontaneous autoignition is the dominant subsequent combustion mode at high-pressure conditions. At low to intermediate pressures, auto-ignition assisted flame propagation is nevertheless the dominant mode for combustion evolution. This research identifies novel features of autoignition and the subsequent combustion mode evolution affected by a cold, fully developed boundary layer, and provides useful guidance to the interpretation of abnormal combustion and combustion mode evolution in boundary layer flows.     

纳秒脉冲等离子体合成射流激励器的流场特性分析

采用一台高重频、快上升沿纳秒脉冲电源作为激励源,对典型的双电极合成射流激励器进行放电,通过粒子图像测速法（particle image velocimetry,PIV）测量放电实验中激励器稳定流场特性以及发展速度.分析实验结果发现,随着重复频率的提高,合成射流的平均发展速度也随之增大,1 kHz时的平均速度最高达到28.28 m/s,并在单脉冲能量远低于微秒脉冲的情况下,实现了更快的稳态流场控制,表明高重复频率下,更多次数的脉冲放电可提高激励总能量,有效地弥补纳秒脉冲单脉冲输出能量不足的缺点.而且频率越高,流场发展速度越快,说明高重频工作模式会对输出总能量有补偿作用.      

Research on a Rice Counting Algorithm Based on an Improved MCNN and a Density Map

The thousand grain weight is an index of size, fullness and quality in crop seed detection and is an important basis for field yield prediction. To detect the thousand grain weight of rice requires the accurate counting of rice. We collected a total of 5670 images of three different types of rice seeds with different qualities to construct a model. Considering the different shapes of different types of rice, this study used an adaptive Gaussian kernel to convolve with the rice coordinate function to obtain a more accurate density map, which was used as an important basis for determining the results of subsequent experiments. A Multi-Column Convolutional Neural Network was used to extract the features of different sizes of rice, and the features were fused by the fusion network to learn the mapping relationship from the original map features to the density map features. An advanced prior step was added to the original algorithm to estimate the density level of the image, which weakened the effect of the rice adhesion condition on the counting results. Extensive comparison experiments show that the proposed method is more accurate than the original MCNN algorithm.     

Termolecular chemistry facilitated by radical-radical recombinations and its impact on flame speed predictions

Recent theoretical studies have shown that termolecular chemistry can be facilitated through reactions of flame radicals (H, O, and OH) or O₂ with highly-energized collision complexes (either radical or stable species) formed in exothermic reactions. In this work, radical-radical recombination reaction induced termolecular chemistry and its impact on combustion modeling was studied. Two recombination reactions, H + CH₃ + M → CH₄ + M and H + OH + M → H₂O + M, were analyzed using ab-initio master equation analyses guided by quasiclassical trajectory results. The dynamics results and the master equation calculations indicate that CH₄^? and H₂O^? (formed in the two radical-radical reactions outlined above) react rapidly with flame radicals and O₂ at rates that are competitive with collisional cooling. The addition of these processes into conventional combustion modeling requires two modifications: the inclusion of the new nonthermal termolecular reaction rates and the simultaneous reduction of the competing recombination reaction rates. The former is described with newly derived Arrhenius expressions based on quasiclassical trajectories, and the latter is achieved by perturbing the recombination reaction rate during the simulation. Kinetic modeling was used to gauge the impact of including this nonthermal chemistry for H₂/CH₄-air laminar flames speeds. Inclusion of this nonthermal chemistry has a noticeable impact on simulated flame speeds. The procedure developed here can be utilized to properly quantify the effects of such nonthermal reactions in macroscopic kinetic models.     

凹凸棒石/硅橡胶复合材料的热氧化降解和老化性能研究

本文采用高压均质结合对辊挤压工艺对天然凹凸棒石进行棒晶解离得到了纯度较高和比表面积较大(133.7 m²/g)的纳米解离凹凸棒石. 进一步通过机械共混法分别将天然凹凸棒石和纳米解离凹凸棒石与硅橡胶生胶复合制备了天然凹凸棒石-硅橡胶和纳米解离凹凸棒石-硅橡胶材料,研究了天然凹凸棒石和纳米解离凹凸棒石对凹凸棒石/硅橡胶复合材料热氧化降解和老化性能的影响. 结果表明,天然凹凸棒石-硅橡胶和纳米解离凹凸棒石-硅橡胶在300 oC热氧老化处理0.5 h后,相比于纯硅橡胶,初始5%失重温度从385 oC提高至396∽399 oC. 系列表征结果表明,天然凹凸棒石和纳米解离凹凸棒石增强了纳米粒子与硅橡胶之间的相互作用从而抑制了纳米颗粒聚集,并且可显著提高硅橡胶侧链Si-CH₃的保存率,从而提高了该复合材料的热氧化降解和老化性能. 此外,纳米解离凹凸棒石可大大抑制纳米粒子的长大;因此老化后,纳米解离凹凸棒石-硅橡胶表现出了比硅橡胶(10.6%、7.4%和5.0%)更高的拉伸强度、断裂伸长率和撕裂强度保留率(40.6%、34.9% 和30.1%).