Al-27Zn合金固溶时效后硬度及耐磨性研究

研究了两种Al-27Zn合金经425℃×8h固溶及125℃时效处理后组织结构、硬度和耐磨性的变化规律.结果表明,经时效处理后合金的组织形态为：Al基体上均匀分布着少量未溶树枝状晶组织以及大量细小弥散富锌的η相;合金的硬度随着时效时间的延长先升后降,合金元素Cu、Mg的加入提高了Al-27Zn的硬度;两种合金均具有良好的耐磨性,但合金元素Cu、Mg的加入降低了耐磨性;探讨了磨损机制及材料组织、硬度对合金耐磨性的影响.     

基于P89C668单片机的CAN总线接口设计

介绍了PHILIPS公司生产的P89C668单片机及其与CAN控制器SJA1000的CAN接口节点电路,并给出了CAN总线的基本通信程序:SJA1000初始化、发送和接收.     

基于P2P技术的信息获取方案研究

当前互联网的体系结构是客户/服务器模式,服务器集中了所有功能和资源,因此负荷很重,维护其上的信息检索越来越困难.对等网(P2P)技术可以解决这个问题.P2P网络是一种分布式系统结构,它将互联网的集中管理模式引向分散管理模式,将内容从中央单一节点引向网络的边缘,从而充分利用互联网中众多终端节点所蕴涵的处理能力和潜在资源.但是已有的P2P检索机制并不成功,分析指出,主要是缺少为web设计的、定义严密的、基本的数据模型,即信息定义和结构的质量很差.因此提出了一个基于P2P技术的信息获取方案-ICover,它建立在P2P网络上,提供信息建模、信息发布、信息网关、虚拟组织、信息端到端加密等关键部分,从而有效完成信息获取和共享.     

27t轴重通用货车应用下调车场连挂区调速控制研究

27 t轴重通用货车的应用给调车场连挂区调速控制提出了新问题。分析27 t轴重通用货车单位基本阻力更小、溜放动能更大等特点,减速顶对27 t轴重通用货车制动功的减小、临界制动速度的上浮等特性,以及与既有货车混合应用后超速连挂风险的增加、调速控制复杂性的增大等问题。通过模型建立、参数标定及仿真计算,得到减速顶对27 t轴重通用货车制动功的减幅及临界制动速度的漂移量。为解决27 t轴重与既有货车混合应用下调车场连挂区调速控制问题,提出3种调速控制方案,仿真计算显示,在满足27 t轴重通用货车调速控制、难行车不利溜放、最短溜放距离等约束下,增加布顶与调整坡度相结合的方案最优。     

海船重大改装的判别与规范指引

为对船舶改装是否属于"重大改装"进行有效判别,对中国船级社(CCS)《船舶重大改装实施指南》(2016)和有关部委、主管机关的有关规定进行研究分析。厘清这些规定中蕴含的船舶重大改装的判别原则和思路,为业界普遍性存在的及将来可能出现的各类海船改装提供"是否属于重大改装"的定性判断依据。     

预应力连续箱梁设计应注意的问题

预应力混凝土连续箱梁，由于设计和旋工方面对一些问题认识不足，有部分在建或已建结构出现腹板斜裂缝，齿板后底板横向裂缝或中跨跨中底板纵向裂缝等问题。主要从设计方面分析此类裂缝出现的原因，并探讨如何避免裂缝的发生。     

Surface chlorophyll in the Black Sea over 1978–1986 derived from satellite and in situ data

Absolute values of chlorophyll a concentration and its spatial and seasonal variations in the Black Sea were assessed by using satellite CZCS and in situ data. Since the satellite CZCS had operated for the 1978–1986 period, CZCS data was used for assessing the past state of the Black Sea just before the onset of drastic changes observed in late 1980s. The approach used for the calculation of the absolute values of chlorophyll a concentration from CZCS data was based on the direct comparison of in situ chlorophyll a data and those of CZCS and by applying the algorithm developed for the transformation of CZCS data into chlorophyll a values. CZCS Level 2 data related with pigment concentration having a spatial resolution of 1 km at nadir were used. The daily Level 3 files were derived by binning Level 2 values into 4-km grid cells and the monthly and seasonal Level 3 files were created by averaging the daily Level 3 files over the corresponding period. In situ chlorophyll a data were obtained by spectrophotometric and fluorometric methods in 15 scientific cruises over the 1978–1986 period. Total number of ship-measured data used for the comparison with those CZCS values was 590.Chlorophyll a concentration (Chl) was derived from CZCS values (C) with regression equations Chl=kC; the coefficient of transformation k was calculated from six different data sets by taking into account distinctions between subregions and seasons. The reasons for difference in the k values have been analyzed.Statistical comparison of the chlorophyll a values measured in situ and those derived from CZCS data was based on log-transformed data and gave the following results: regression SLOPE=0.842, regression INTERCEPT=−0.081, coefficient of determination (R²)=0.806, root–mean–square ERROR=0.195. The mean monthly chlorophyll a distributions derived from CZCS data over 1978–1986 have been constructed and the mean seasonal chlorophyll a values in different regions have been calculated and analyzed. The significant difference in chlorophyll concentration between the western shelf regions and the open part of the Black Sea has been demonstrated, especially in warm season. At almost all seasons, the highest chlorophyll concentration is observed in the western interior shelf region which is under strong influence of Danube. The summer mean chlorophyll concentration in this region is 18 times higher than that in the open parts and about nine times higher than in the eastern shelf region. The greatest seasonal variations are observed in the open part of the Black Sea: chlorophyll concentration in cold season is four to six times higher than in summer and three to five times higher than in April and October. To the contrary, in the western interior shelf regions, the concentration is higher in May–October (about twice than that in November–March). Seasonal variations in the western outer shelf regions are smoothed out as compared with both the western interior shelf and the open regions.     

一种自组织的P2P代理协议和搜索算法

针对当前互联网中大量使用的防火墙、代理技术和地址转换协议等给P2P (Peer to Peer)网络造成的通信障碍问题,提出了一种新型的P2P网络的代理协议(S4P),同时提出了对代理服务的搜索算法。该协议采用自组织的方式,使组成P2P网络的节点能够动态穿越双方所受到的通信障碍,解决网络中存在的对P2P连接的限制问题,增强了P2P网络的连接能力和资源访问与共享能力。仿真结果表明,S4P不仅可以完成节点间数据交换的要求,而且具有较好的性能。     

27SiMnMoV钢渗碳工艺性能的研究

本文采用真空渗碳方法,以20CrMnTi 钢为对比对象,研究了27SiMnMoV 钢的渗碳工艺性能.结果表明:27SiMnMoV 钢与20CrMnTi 钢相比,渗碳层中碳化物细小;碳浓度梯度小;硬度分布平缓;力学性能指标α_k、σ_(bb)、f 均要高些.故27SiMnMov 钢的渗碳工艺性能优于20CrMnTi钢.     

北京地铁5号线P＋R站交通组织研究

近年来,为了解决大城市交通问题,在周内外公认的一种交通模式,即P＋R交通模式,通过这种转换模式可有效减轻市中心的道路交通压力,减少环境污染,提高道路的使用率,让私家车使用者得到更大的实惠,给城市带来社会和经济效益。该文通过对北京市地铁5号线天通苑北站P＋R场站交通组织设计研究,分析了天通苑北站P＋R场站与外部道路之间、地铁站与社会停车场之间、地铁与公交换乘站之间的交通组织关系,说明解决好P＋R交通模式配套接口关系的重要性,可形成停车、换乘公共交通一体化,让更多的人主动选择公共交通。