Lightweight design of automotive front side rails with TWB concept

Due to the continuous tightening of various regulations for conserving energy and protecting the environment, the weight reduction of and automobile body becomes an increasingly important issue. In order to reduce the weight of an automobile, we have brought forward a method of replacing the simple structure with the tailor-welded blank (TWB), in which a design process is appropriately defined for a front side rail. Focusing on the thickness determination of TWB, we have deduced the constraint inequalities of strength, bending stiffness, and torsion stiffness to prevent the thickness from decreasing unboundedly due to the lightweight requirement, thus reducing the weight of the front side rail satisfying the design demands of these three factors. The full-width frontal impact simulation of the whole car after redesign in the front side rails has been performed to verify vital performances such as deformation mode, energy absorption, and acceleration.     

基于LDAP的统一用户管理系统的设计和实现

统一的用户管理是电子政务信息基础架构的重要部分.文章讨论了基于LDAP目录服务的统一用户管理系统的设计和实现.通过利用LDAP的树状信息结构、快速响应大容量访问和广泛复制的能力，可以充分提高统一用户管理系统的可扩展性、可靠性和可伸缩性。     

Improving environmental sustainability of concrete products: Investigation on MWC thermal and mechanical properties

This research focuses on the possibility of constituting a more sustainable lightweight concrete, Mineralized Wood Concrete (MWC), substituting natural aggregates with wastes from woodworking activities. Exploiting this type of aggregates, a triple purpose has been achieved: preservation of natural raw materials, reuse of wastes and energy saving. Furthermore, the use of wood aggregates is a way to try to develop a sustainable concrete characterized by high thermal inertia, high thermal resistance and low weight.In this paper, effects of the addition of wood aggregates on mechanical and thermal properties of concrete are studied. Mechanical performances have been investigated with compressive strength tests, while a one-dimensional heat flow model has been used to predict the thermal conductivity of MWC.The use of MWC can be associated with the idea of a different typology of relatively heavy building envelope: this union could competitively answer to the demand of well-insulated building envelope and concurrently characterized by high thermal mass. From this union, a series of other values can be derived: low weight, environmentally friendly, easily industrialized and easy on-site casting. Consequently, applications of wood concrete in building constructions may be an interesting solution in order to improve sustainability and building energy efficiency.     

主反射镜的一种轻量化设计和加工

报告了φ354mm轻质主反射镜的设计和制作工艺方法.用有限元法对镜面进行了力学分析,确定了加工和检测状态下的镜子装夹方案.检测镜面的结果表明这种方法是实用的.     

On the polymer modified cement mortars with different lightweight aggregates in marine environment

Having a light weight is a design objective for offshore and coastal structures and in order to reach this aim, use of lightweight concrete consisting lightweight aggregates and polymers is a feasible solution. In this study, materials obtained from locally available crushed volcanic scoria as main aggregate and some additional lightweight aggregates with ceramic, perlite and andesite as well polymers were used in the mixtures with different proportions (totally 14 mixtures) to propose feasible alternatives for coastal structure designers. To evaluate the design performances of the mixtures, their properties such as density, cylinder compressive strength, capillarity, loss of mass under the effects of the agents in marine environment such as sodium sulphate and sodium chloride were obtained experimentally. It was found that mixtures with scoria aggregates showed more favourable results and additional aggregates gave flexibility to the designer to lower densities up to 40 % ‐ 60 % of normal‐weight mixtures. Polymer modification also improved the performance of the related materials.     

用不可能差分法分析12轮ESF算法

轻量级分组密码算法ESF是一种具有广义Feistel结构的32轮迭代型分组密码,轮函数具有SPN结构,分组长度为64比特,密钥长度为80比特。为了研究ESF算法抵抗不可能差分攻击的能力,基于一条8轮不可能差分路径,根据轮密钥之间的关系,通过向前增加2轮、向后增加2轮的方式,对12轮ESF算法进行了攻击。计算结果表明,攻击12轮ESF算法所需的数据复杂度为O(2⁵³),时间复杂度为O(260.43),由此说明12轮的ESF算法对不可能差分密码分析是不免疫的。     

The effects of air content on permeability of lightweight concrete

Air entraining agent is used to control the floatation of lightweight aggregate (LWA) in lightweight aggregate concrete (LWAC), therefore reducing the segregation of LWAC. At the same time, using an air entraining agent will affect the water sorption of the concrete. In this paper, two lightweight concrete mixes of density 1000 kg/m³ and air content of 13.5% and 31.9% were compared and the effects of entrained air on the strength, surface sorptivity, and chloride permeability of LWAC are presented. Results show that the use of porous LWA would not lower the permeability resistance of concrete. Entrained air had little effect on sorptivity but a major effect on chloride permeability. The weaker pores' network in the cement paste is the basic cause for the high chloride permeability of concrete than the use of porous LWA. Although chloride permeability of low density LWAC concrete decreased with age of concrete, it was found that the concrete was not dense enough to stop the chloride ion to penetrate through the concrete before the concrete mature at 90 days.