A ctivation measurement of neutron distribution in intermediate energy heavy ion target area

The distribution of neutrons produced by the reaction of 50MeV/u ^12C-ion on a thick Cu target are studied.The neutrons are measured with threshold activation detectors.Al.F,C,Al and In activation samples were used to measure neutrons with energy greater than 7,11,20,50MeV and thermal neutrons,respectively,The fluence rate,energy and angular distributions of neutrons,total neutron yield of 12C-ion and the emission rate in the forward direction of neutrons over 11 and 20MeV were obtained.     

全球水能资源评估模型与方法研究

为在全球范围开展水能资源评估,提高评估与规划的准确性与效率,通过建立水能资源评估的全球尺度参数标准、一般技术流程与方法体系,构建河流水能资源理论蕴藏量、技术可开发量评估和电站开发经济性测算模型,提出一套适用于内业工作的数字化评估方法与流程。以非洲刚果河流域为例,应用水能评估模型与数字化方法,实证评估了刚果河流域及干流的水能资源的理论蕴藏量、干流下游河段的技术可开发量,完成了刚果河下游水电基地开发成本测算。     

我国矿井水资源化利用现状及前景展望

针对现阶段我国在矿井水资源化政策制定、科学研究、人才培养及宣传等方面存在的问题,在总结全国53处煤矿矿井水利用率、利用方式、利用价格等现状的基础上,分析了矿井水资源化利用的制约因素,提出了出台落地性政策、加强创新人才建设培养、分质分类利用、加大宣传和发挥行业协会作用等政策方面的建议,指出高质量矿井水的开发、矿井水资源热能利用、产业化和规模化经营、废弃矿矿井水资源化利用等是矿井水热能利用的方向。     

基于相图-BP网络相结合的发动机转子系统故障诊断方法研究

发动机故障诊断是飞机故障预测和健康管理的重要内容,为了充分利用发动机的相图特征对发动机转子系统进行故障诊断,提出了一种相图和神经网络相结合的发动机转子系统故障诊断方法;在分析不同状态下发动机的整机振动信号参数在不同范围随机变化导致相轨迹分布不同的基础上,提取发动机振动相图特征值,借助BP神经网络良好的状态分类功能,对发动机转子系统进行故障诊断;实践表明该方法能有效去除噪声对故障信息的干扰,诊断准确率较高,判别速度较快,具有一定的实用价值。     

Mining diversity on social media networks

The fast development of multimedia technology and increasing availability of network bandwidth has given rise to an abundance of network data as a result of all the ever-booming social media and social websites in recent years, e.g., Flickr, Youtube, MySpace, Facebook, etc. Social network analysis has therefore become a critical problem attracting enthusiasm from both academia and industry. However, an important measure that captures a participant’s diversity in the network has been largely neglected in previous studies. Namely, diversity characterizes how diverse a given node connects with its peers. In this paper, we give a comprehensive study of this concept. We first lay out two criteria that capture the semantic meaning of diversity, and then propose a compliant definition which is simple enough to embed the idea. Based on the approach, we can measure not only a user’s sociality and interest diversity but also a social media’s user diversity. An efficient top-k diversity ranking algorithm is developed for computation on dynamic networks. Experiments on both synthetic and real social media datasets give interesting results, where individual nodes identified with high diversities are intuitive.     

Delay‐dependent stability for Markovian genetic regulatory networks with time‐varying delays

This paper is concerned with the problem of stochastic stability analysis for a class of genetic regulatory networks with Markovian jump parameters and time‐varying delays. A delay‐dependent stability criterion is derived by using a novel mode‐dependent Lyapunov functional. The derived stability criterion is expressed in terms of linear matrix inequalities and is less conservative than the existing ones in the literature. A numerical example is provided to demonstrate the effectiveness of the proposed stability criterion. Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

Intelligent control of doubly‐fed induction generator systems using PIDNNs

An intelligent control for a stand‐alone doubly‐fed induction generator (DFIG) system using a proportional‐integral‐derivative neural network (PIDNN) is proposed in this study. This system can be applied as a stand‐alone power supply system or as the emergency power system when the electricity grid fails for all sub‐synchronous, synchronous, and super‐synchronous conditions. The rotor side converter is controlled using field‐oriented control to produce 3‐phase stator voltages with constant magnitude and frequency at different rotor speeds. Moreover, the grid side converter, which is also controlled using field‐oriented control, is primarily implemented to maintain the magnitude of the DC‐link voltage. Furthermore, the intelligent PIDNN controller is proposed for both the rotor and grid side converters to improve the transient and steady‐state responses of the DFIG system for different operating conditions. Both the network structure and online learning algorithm are introduced in detail. Finally, the feasibility of the proposed control scheme is verified through experimentation. Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

立式钻铣床动力头设计与三维造型

多工位钻铣床实现了一台机床对一个零件做不同加工的功能,节省了机床,也缩小了占地面积,同时提高了加工精度和生产率,对工人劳动强度也降低很多。本设计中,钻头的固定采用拉杆式楔形固定,钻头采用套筒及主轴轴面为拉杆的结构,套筒外侧用绝缘胶固定了一个支撑架,钻头的动力由同步齿形带传递到钻头,比起万向轴传递动力要准确且刚性好。动力采用行星轮的传递方式,保证了各工位的同步工作,节省空间,本机构紧凑,各啮合齿轮之间中心距不超过100 mm,因而,用齿轮传动可以满足要求,这样可以用标准件对机床快速装配完工,对缩短加工周期有很大好处。     

多壁碳纳米管/聚酰亚胺复合材料制备及其性能研究

聚酰亚胺的前聚体,聚酰胺酸,是通过4,4-二氨基二苯醚(ODA)与3,3,4,4二苯甲酮四羧酸二酐(BTDA)反应制备的。未改性的、酸改性和胺改性的多壁碳纳米管(MWCNT)被分别地单独加入到聚酰胺酸溶液中,并加热至300℃,从而制成聚酰亚胺/碳纳米管复合材料。扫描型电子显微镜(SEM)和透射电子显微镜(TEM)的显微照片表明,酸改性的多壁碳纳米管和胺改性多壁碳纳米管在聚酰亚胺基体中被均匀一致地分散开。通过对酸和胺改性的多壁碳纳米管MWCNTS对多壁碳纳米管/聚酰亚胺复合材料的表面和体积电阻率的影响进行了研究。了解到该纳米复合材料的表面电阻率ITES从1.28×10^(15)Ω/cm^(2)(纯聚酰亚胺),降到7.59×10^(6)Ω/cm^(2)(26.98%的未改性的多壁碳纳米管含量)。除此之外,添加多壁碳纳米管影响了纳米复合材料的玻璃化转变温度。改性多壁碳纳米管意义就是提高了纳米复合材料的机械性能。多壁碳纳米管/聚酰亚胺复合材料的拉伸强度从10^(2)MPa(纯的聚酰亚胺)增加到134 MPa(6.98%酸改性多壁碳纳米管/聚酰亚胺复合材料)。     

Method for using the blockchain to protect data privacy of IoV

With the rapid development of the Internet of Things,vehicle industry is undergoing a rapid transformation from the early vehicle Ad-Hoc network to the Internet of Vehicles (IoV) in which massive vehicles and on-board smart devices can realize data sharing and interaction.However,this brings about a big challenge for the security of shared data in a huge volume containing a lot of user privacy,especially the issues of access control,trust and key escrow.To address these problems,we propose an efficient blockchain-based distributed data sharing method in IoV.In our scheme,blockchain transactions are utilized for trustworthily data storage and access as well as user revocation.To realize end device verification,we introduce certificateless cryptography for transaction verification of blockchain nodes and the ease of the key escrow problem.Moreover,we propose an efficient partial policy-hidden CP-ABE scheme for data fine-grained access control with efficient user revocation.Security analysis and experiments demonstrate that our scheme is secure,efficient and practical.