Mechanical Properties of Robust Ultrathin Silk Fibroin Films

Robust ultrathin multilayer films of silk fibroin were fabricated by spin coating and spin‐assisted layer‐by‐layer assembly and their mechanical properties were studied both in tensile and compression modes for the first time. The ultrathin films were characterized by a high elastic modulus of 6–8 GPa (after treatment with methanol) with the ultimate tensile strength reaching 100 MPa. The superior toughness is also many times higher than that usually observed for conventional polymer composites (328 kJ m^–3 for the silk material studied here versus typical values of < 100 kJ m^–3). These outstanding properties are suggested to be caused by the gradual development of the self‐reinforcing microstructure of highly crystalline β‐sheets, serving as reinforcing fillers and physical crosslinks, a process that is well known for bulk silk materials but it is demonstrated here to occur in ultrathin films as well, despite their limited dimensions. However, the confined state within films thinner than the lengths of the extended domains causes a significantly reduced elasticity which should be considered in the design of nanosized films from silk materials. Such regenerated silk fibroin films with outstanding mechanical strength have potential applications in microscale biodevices, biocompatible implants, and synthetic coatings for artificial skin.     

仿真环境下的机器人足球决策系统

机器人足球系统是一类典型的多移动机器人合作的对抗系统．具有实时性要求高、环境高度动态、存在不可预测状态等特点．机器人足球系统是人工智能和智能控制领域的探究热点之一。主要研究在仿真环境下基于三层控制决策模型的机器人足球决策系统．为单个或多个足球机器人分配任务和执行任务。使机器人决策系统具有较好的应激性和协调性,实现有效攻防．探讨多智能机器人实时合作与对抗问题、以求验证和发展人工智能的有关理论和技术。     

某待建滨海核电厂厂址年均大气扩散因子计算模式与参数的实验研究

本文在某待建滨海核电厂厂趣现场野外实验基础上提出了计算该核电厂年均大气扩散因子的计算模型。此模型既考虑了向岸流与离岸流的差别，又考虑了混合层与热内边界层，混合释放与扩散参数随陆距变化等因素的综合影响。模型中所需要的各类参数，包括在１９９５，１９９６年间在该厂趣野外大气试验中获取的百米气象铁塔４个不同高度上的风，温逐时三维联合频率；湍流测量结合风洞实验获取的离岸流与向岸流的扩散参数。     

Carbon steel corrosion under anaerobic–aerobic cycling conditions in near-neutral pH saline solutions – Part 1: Long term corrosion behaviour

A corrosion mechanism has been developed to describe tubercle formation along pipeline steels during successive anaerobic–aerobic cycles. Small concentrations of O₂ under nominally anaerobic conditions can lead to the separation of anodes and cathodes. Under subsequent aerobic conditions localized corrosion is then promoted by O₂ reduction on the general magnetite-covered surface. Subsequently, the conversion of magnetite to maghemite passivates the general surface, and focuses corrosion within one major tubercle-covered pit. On switching from aerobic to anaerobic conditions, corrosion is temporarily supported by the galvanic coupling of lepidocrocite (γ-FeOOH) reduction (to γ-Fe-OH·OH) to steel dissolution primarily within the tubercle-covered pit.     

MP3音频解码速度优化

MP3采用MPEG-1 LayerIII层标准压缩编码格式,压缩率很高,失真也较小,算法也较为复杂.就MP3解码过程中,针对各解码模块的特点,通过浮点转定点运算、分段拟合、查找表等方法,对解码复杂度较高的模块进行算法优化,并且在16位定点DSP芯片实现,优化后解码每帧音频格式的指令数降到最初的1/ 20.     

迭加原理的错误及纠正—评PN结光生伏特效应

本文纠正了“迭加原理”的错误,建立了新的光伏理论。     

热成型陶瓷的晶粒取向

利用热成型技术(热压、热锻和热挤)结合粉料的熔盐合成工艺,加工含铋层状结构化合物 Bi_(?)PbNb_2O_(?)、Bi_2WO_6,Bi_2MoO_(?)和 Bi_4Ti_3O_(12),制得了晶粒取向良好的陶瓷材料。在热锻样品中(001)晶面取向度高达99%。本实验的主要工作是在 TEM 上进行的。对热成型样品的研究,得到了下列一些结果:(1)所有的热压和热锻样品的微观结构都非常致密,几乎不存在气孔;(2)晶粒生长良好,热锻样品的片状晶粒沿着锻压方向的一致排列产生了强烈的织构化的微观结构;(3)热锻 Bi_2PbNb_2O_(?)样品的片状晶粒尺寸和厚度分别为1～3μm 和<0.5μm。根据上述结果,结合样品制备过程中所观察到的一些现象,对层状结构化合物在热锻过程中的晶粒取向可以作出下述解释:在热锻的初期阶段,片状晶粒在热锻的单向压力作用下产生的剪切应力,加上热锻模具的特殊构造以及这些化合物相转变所引起的体积变化等因素,促使晶粒发生横向滑移,这一滑移过程伴随着显著的形变;在热锻的后期阶段,在热锻条件下晶粒的非对称生长过程进一步改善了陶瓷的晶粒取向度。     

互动的舞台——试论建筑的情理交织

建筑的演进，在某种意义上是情感与理性的交织发展过程，情感与理性的关系，从曾经相互抵触，逐渐发展到相互融合的阶段，建筑学领域中，情感与理性的界线正在变得模糊，该文通过解析几个重要时期建筑的形 特征，揭示出建筑发展的规律之一。     

Stresses between 3D fractures in infinite and layered elastic solids

Periodically distributed opening mode fractures are often found in layered sedimentary rocks. The stress analysis related to opening mode fractures in layered solids is solved by a new numerical approach combining (3D) fast Fourier transform with the theory of periodic eigenstrain and the conjugate gradient method. Results show that the fracture spacing to layer thickness ratio for embedded opening mode fractures, using a three-dimensional (3D) model, is in good comparison with that of the plane strain case (two-dimensional model). The critical value of the fracture spacing to layer thickness ratio increases for a stiff layer case and decreases for a stiff surrounding solid case. Out-of-plane fracture length is also studied as a parameter in the 3D modeling. Opening mode surface fractures in a layered half-space were also studied. The results show that a critical fracture saturation ratio exists for this case and occurs when the normal surface stress transitions from tensile to compressive. This stress state is shown to be caused by a bending effect in the layer.     

A corrosion prediction method for weathering steels

Japanese Specification for Highway Bridges [Japan Road Association: Specification for Highway Bridges—I & II, 2002.3] has been revised in 2002, which clearly states that degradation of bridge members, including those of weathering steels, to occur in prolonged period of time must be taken into account at the design stage to realize long term structural durability. To cope with the revised paradigm, SABI chemistry committee in Japan Society of Corrosion Engineers has proposed durable state concept [SABI Chemistry Committee of Japan Society of Corrosion Engineers, in: Proc. 132nd Symposium for Corrosion and Protection, 2001.6.25, p. 3], which is defined as a condition in which corrosion rate of steel is slow enough not to form thick rust [H. Kihira, K. Shiotani, H. Miyuki, T. Nakayama, M. Takemura, Y. Watanabe, Doboku Gakkai Ronbun-shu (J. Japan Soc. Civil Engineers) No. 745/I-65, 2003.10, pp.77-87]. Since corrosiveness of atmosphere differs by location, a corrosion prediction method for both conventional and advanced weathering steels [H. Kihira, A. Usami, K. Tanabe, M. Ito, G. Shigesato, Y. Tomita, T. Kusunoki, T. Tsuzuki, S. Ito, T. Murata, in: Electrochemical Society Proceedings, vol. 99-26, 2000, pp. 127-136] is needed to ensure structural durability for future. Thus, versatile computational scheme for it has been derived through mathematical modeling based upon the durable state concept.