船用件加工设备改造中步进电动机选择

文章主要研究在普通机床数控化改造中如何选择步进电动机的问题.提出了电动机的性能参数,包括最大转速、最大转矩、转动惯量等.给出了参数的计算方法和校核方法.     

桥式抓斗卸船机金属结构变形与调整

分析抓斗卸船机金属结构在不同工况下的变形,以及变形对小车运行功率的影响。通过对前大梁起拱,前后拉杆立柱进行调整,将结构变形对卸船机小车运行的不利影响变为有利的影响。     

单线铁路模板台车的结构分析

文章主要介绍了单线铁路模板台车的工作原理和结构,应用有限元软件对模板台车进行了整体的结构分析,并依据分析结果对模板台车的结构设计提出了改进建议,为其以后的优化设计和参数设计提供了理论依据.     

内河高桩码头大直径PHC管桩沉桩现场试验及参数优化*

依托安徽淮北港区孙疃作业区综合码头工程,开展内河高桩码头大直径预应力高强混凝土(PHC)管桩沉桩现场试验及参数优化研究。通过初始地勘报告获得沉桩参数后,进行沉桩可打性分析并优化施工工艺,进行试沉桩、高低应变和静载试验,并根据试验结果进行桩基设计参数优化。结果表明：结合沉桩现场试验中的桩端进入持力层深度和最后贯入度结果,验证了内河高桩码头大直径PHC管桩施工工艺、沉桩设备、沉桩控制参数和停锤标准的可行性;明确了内河高桩码头大直径PHC管桩单位面积极限侧摩阻力标准值和极限桩端阻力标准值的调整系数范围为5%~10%;采用⑦层粉细砂作为桩基持力层,同步优化桩基参数。     

Some remarks on the TKIP key mixing function of IEEE 802.11i

Temporal key integrity protocol (TKIP) is a sub-protocol of IEEE 802.11i. TKIP remedies some security flaws in wired equivalent privacy (WEP) protocol. TKIP adds four new algorithms to WEP: a message integrity code (MIC) called Michael, an initialization vector (IV) sequencing discipline, a key mixing function and a re-keying mechanism. The key mixing function, also called temporal key hash, de-correlates the IVs from weak keys. Some cryptographic properties of the substitution box (S-box) used in the key mixing function are investigated in this paper, such as regularity, avalanche effect, differ uniform and linear structure. Moen et al pointed out that there existed a temporal key recovery attack in TKIP key mixing function. In this paper a method is proposed to defend against the attack, and the resulting effect on performance is discussed.     

Filling the gap between voters and cryptography in e-voting

Cryptography is an important tool in the design and implementation of e-voting schemes since it can provide verifiability, which is not provided in the traditional voting. But in the real life, most voters can neither understand the profound theory of cryptography nor perform the complicated cryptographic computation. An e-voting system is presented in this paper to leverage the use of cryptography. It combines the advantages of voting scheme of Moran-Naor and voting scheme based on homomorphic encryption. It makes use of the cryptographic technique, but it hides the details of cryptographic computation from voters. Compared with voting scheme of Moran-Naor, the new system has three advantages: the ballots can be recovered when the voting machine breaks down, the costly cut-and-choose zero-knowledge proofs for shuffling votes made by the voting machine are avoided and the partial tally result in each voting machine can be kept secret. Foundation item: the National Natural Science Foundation of China (No. 60673076) and the National High Technology Research and Development Program (863) of China (No. 2008AA01Z403)     

基于道路网络交通平衡的动态拥挤收费分析

拥挤收费作为一项有效的交通需求管理手段得到许多国家及城市的重视。目前,大多数拥挤收费采取静态管理分析手段,不能真实有效的解决实际交通问题,在此提出道路网络交通平衡概念,以道路网络交通平衡为目标,提出卖时监控、及时反馈、动态实施的拥挤道路收费机制。     

基于居民出行需求的城市公共交通运营水平综合评价

分析影响城市公共交通运营水平的因素,在充分考虑居民出行需求的基础上,遵循科学性、合理性、客观性、完备性的原则,结合兰州市城市交通实际,建立城市公共交通运营水平的评价指标体系。运用灰色聚类分析法,构建城市公共交通运营水平评价的层次结构,建立综合评价数学模型,对兰州市公共交通运营水平纵向进行全面评价。     

NS1602型铁路起重机架设六四式铁路军用梁技术研究

介绍了利用NS1602型铁路起重机架设32m六四式铁路军用梁的主要过程,并对架梁过程中已架钢梁的安全问题进行了验算：确定不利工况下的起重机支腿反力,检算反力作用下钢梁的强度及稳定性。计算表明,利用铁路起重机架设抢修钢梁技术可行、安全可靠,为应急抢修架设军用梁提供了一个新的途径。     

卵砾石边坡坡脚泥沙起动试验研究

针对山区河流枯水卵石急滩的泥沙输移特点,通过对斜坡上卵砾石的实验现象观察和理论分析,发现卵砾石边坡坡脚处的泥沙首先起动。根据卵砾石边坡坡脚泥沙的受力状态,采用滚动模式进行理论推导,考虑了底部流速、阻力系数、卵砾石水下重力及其附加重力的影响,推导出了卵砾石边坡坡脚泥沙的起动流速公式,该公式与边坡坡度有关。通过水槽试验,拟合出卵砾石边坡坡脚泥沙的起动公式,并与沙莫夫公式进行了比较。