科创中国

车辆行驶引起的桥梁振动的动力响应数据是车桥耦合振动分析中重要参数.采用超声波测速仪、录像机及桥梁动态测试仪同人工记录相结合的方法,对高速公路交通荷载各要素进行24 h连续、全面调查,记录的数据包括车型、车速、行驶车道、车辆到达时间以及每辆过桥车辆引起的桥梁动力响应数据.本调查采集了8片梁的5 650单车过桥的动响应数据,研究了交通荷载调查样本中不同梁体的动力响应数据的统计规律,全面分析了高速公路交通荷载车辆过桥引起的桥梁动力响应的时空分布规律.研究结论能够给车桥耦合振动研究及相关研究提供有益的理论指导和数据支持.

In the field of aerospace, high-speed trains and automobile, etc, analysis of temperature filed and scuffing failure of tapered roller bearings are more important than ever, and the scuffing failure of elements of such rolling bearings under heavy load and high speed still cannot be effectively predicted yet. A simplified model of tapered roller bearings consisted of one inner raceway, one outer raceway and a tapered roller was established, in which the interaction of several heat sources is ignored. The contact mechanics model, temperature model and model of scuffing failure are synthesized, and the corresponding computer programs are developed to analyze the effects of bearings parameters, different material and operational conditions on thermal performance of bearings, and temperature distribution and the possibility of surface scuffing are obtained. The results show that load, speed, thermal conductivity and tapered roller materials influence temperature rise and scuffing failure of bearings. Ceramic material of tapered roller results in the decrease of scuffing possibility of bearings to a high extent than the conventional rolling bearing steel. Compared with bulk temperature, flash temperature on the surfaces of bearing elements has a little influence on maximum temperature rise of bearing elements. For the rolling bearings operated under high speed and heavy load, this paper proposes a method which can accurately calculate the possibility of scuffing failure of rolling bearings.

It is a common phenomenon that the cracks originating from a hole can cause structural damage in engineering.However,the fracture mechanics studies of hole edge crack problems are not sufficient.The problem of an elliptical hole with two collinear edge cracks of unequal length in an infinite plate under uniform tension at infinity is investigated.Based on the complex variable method,the analytical solutions of stress functions and stress intensity factors are provided.The stress distribution along the axes and the edge of the elliptical hole is given graphically.The numerical results show that there is obvious stress concentration near the hole and cracks,and the stresses tend to applied loads at distances far from the defect,which conform to Saint-Venant's principle.Hence,the stress functions are proved to be right.Under special conditions,the present configuration becomes the Griffith crack,two symmetrical cracks emanating from an elliptical hole,two cracks of unequal length emanating from a circular hole,a crack at the edge of a circular hole,or a crack emanating from an elliptical hole.Compared with available results,stress intensity factors for these special shapes of ellipses and cracks show good coincidence.The stress intensity factor for two cracks of unequal length at the edge of an elliptical hole increases with the crack length and the major-to-minor axis ratio of the elliptical hole.The stress distribution in an infinite plate containing an elliptic hole with unsymmetrical cracks is given for the first time.

首先对物流配送及相关理论进行了综述,提出了共同配送模式在广西-东盟物流中的应用,同时,对广西现行的自营配送模式与共同配送模式进行了比较,并从成本、路线、经营主体等方面进行了定性、定量分析,由此,得出了自营配送模式存在成本高、路线不完善、经济主体单一等一系列问题,而共同配送模式更适合于广西物流发展的现状,并提出了共同配送的三种组织模式在广西物流应用中的优势和劣势.最后,提出了共同配送模式在广西物流配送应用中需要注意的问题及其对策.

Now the optimization strategies for power distribution are researched widely,and most of them are aiming to the optimal fuel economy and the driving cycle must be preknown.Thus if the actual driving condition deviates from the scheduled driving cycle,the effect of optimal results will be declined greatly.Therefore,the instantaneous optimization strategy carried out on-line is studied in this paper.The power split path and the transmission efficiency are analyzed based on a special power-split scheme and the efficiency models of the power transmitting components are established.The synthetical efficiency optimization model is established for enhancing the transmission efficiency and the fuel economy.The identification of the synthetical efficiency as the optimization objective and the constrain group are discussed emphatically.The optimization is calculated by the adaptive simulated annealing(ASA)algorithm and realized on-line by the radial basis function(RBF)-based similar models.The optimization for power distribution of the hybrid vehicle in an actual driving condition is carried out and the road test results are presented.The test results indicate that the synthetical efficiency optimization method can enhance the transmission efficiency and the fuel economy of the power-split hybrid electric vehicle(HEV)observably.Compared to the rules-based strategy the optimization strategy is optimal and achieves the approximate global optimization solution for the power distribution.The synthetical efficiency optimization solved by ASA algorithm can give attentions to both optimization quality and calculation efficiency,thus it has good application foreground for the power distribution of power-split HEV.

Nondestructive techniques for appraising gas metal arc welding(GMAW) faults plays a very important role in on-line quality controllability and prediction of the GMAW process. On-line welding quality controllability and prediction have several disadvantages such as high cost, low efficiency, complication and greatly being affected by the environment. An enhanced, efficient evaluation technique for evaluating welding faults based on Mahalanobis distance(MD) and normal distribution is presented. In addition, a new piece of equipment, designated the weld quality tester(WQT), is developed based on the proposed evaluation technique. MD is superior to other multidimensional distances such as Euclidean distance because the covariance matrix used for calculating MD takes into account correlations in the data and scaling. The values of MD obtained from welding current and arc voltage are assumed to follow a normal distribution. The normal distribution has two parameters: the mean ? and standard deviation of the data. In the proposed evaluation technique used by the WQT, values of MD located in the range from zero to ?+3? are regarded as "good". Two experiments which involve changing the flow of shielding gas and smearing paint on the surface of the substrate are conducted in order to verify the sensitivity of the proposed evaluation technique and the feasibility of using WQT. The experimental results demonstrate the usefulness of the WQT for evaluating welding quality. The proposed technique can be applied to implement the on-line welding quality controllability and prediction, which is of great importance to design some novel equipment for weld quality detection.

在中国农村物流发展现状及特点分析的基础上,对中国邮政发展农村物流分销模式进行了研究和探讨,总结出邮政农村分销的四大模式,并对分销模式的进一步推广实施提出了相关建议.

应用粒子图像测速技术(PIV)对膜蒸馏系统热容腔结构参数影响近膜面处的流动情况进行正交试验,考察喷管前端距膜面的距离δ和喷管中心线与热容腔径向夹角β对流场的影响.试验结果表明,合理布置热容腔的结构参数组合可以使膜面冲刷速度增大,对膜面的有效冲刷面积也增大,更好的破坏温度极化和浓度极化,使系统的膜通量增加.对于试验中采用的膜蒸馏系统,最优的结构参数组合是第32组试验,δ1、δ2、δ3,β1、β2、β3的取值分别为4 mm、3mm、4 mm,50°、35°、25°.流量也是试验中一个重要的影响因素,随着流量的增加,膜面处切向速度增大,对膜面的作用力增大,但是在增大系统流量提高切向冲刷速度的同时,应该考虑膜的机械强度.试验为膜蒸馏系统内部流动的深入研究提供了试验数据和测试经验,可为膜蒸馏系统结构设计的改进和膜蒸馏系统效率的提高提供了参考.

简述流域水文模型的发展历程,介绍了集总式水文模型和分布式水文模型的概念和主要特点.在分析目前国内外分布式水文模型方面的研究现状的基础上,对国、内外具代表性的分布式模型进行对比,提出了分布式水文模型的分类及各自的特点,研究方面存在的问题和面临的挑战,指出了今后分布式水文模型的发展重点和方向.建议今后水文学界应在重视理论研究和实验研究的同时,积极开展分布式水文模型的应用研究.

论述了大型物流配送中心的基本构成,运营管理主要环节及要素,提出了提高大型物流配送中心运营管理效率和降低物流成本的主要方面和主要方法策略.