Efficient expression and characterization of isolated structural domains of yeast phosphoglycerate kinase generated by site-directed mutagenesis

The two domains of yeast phosphoglycerate kinase were producedby recombinant techniques. The N-domain was obtained by theintroduction of a termination codon at the position coding forPhe185, and the C-domain by a deletion in the gene of the codingsequence between Serl and Leu186. Both domains were efficientlyexpressed in yeast, the level for the C-domain being greaterthan that for the N-domain. Both domains were found to havea quasi-native structure; the C-domain retained its abilityto bind nucleotides. Small local differences were detected indomain structure compared to that in the whole enzyme, probablydue to the lack of interdomain stabilizing interactions. Nevertheless,such an approach provides direct evidence for independent foldingof domains in a two-domain protein.     

氢化苯乙烯-丁二烯-苯乙烯嵌段共聚物研究进展

从相态结构、改性及共混等几个角度分别概述了氢化苯乙烯-丁二烯-苯乙烯嵌段共聚物(SEBS)的研究近况，并对SEBS在塑料加工中的应用研究进展作了较详报道。     

基于BP神经网络的红外透过率计算

针对实时条件下中红外波段平均大气透过率的计 算,提出了一种基于贝叶斯正则化BP神经网络的方法。 利用BP神经网络良好的非线性拟合特点,建立大气参数与中红外平均透过率之间的关系 模型,从而可以准确迅速 地得到计算结果。此网络模型是以实测温度、压强、湿度和气溶胶的后向散射系数作为输入 向量,分别以水蒸气和CO₂吸收透过率、气溶胶散射透过率和大气透过率作为输出。仿 真结果表明:在相同的大气参数下,本方法的计算 结果与期望值之间的相对误差较小,且远小于经验公式法,验证了本方法的可行性与有效性 。因此,本方法对大气透过率的准确地快捷计算提供了有益的借鉴。     

A cache invalidation scheme for continuous partial match queries in mobile computing environments

The continuous partial match query is a partial match query whose result remains consistently in the client’s memory. Conventional cache invalidation methods for mobile clients are record ID-based. However, since the partial match query uses content-based retrieval, the conventional ID-based approaches cannot efficiently manage the cache consistency of mobile clients. In this paper, we propose a predicate-based cache invalidation scheme for continuous partial match queries in mobile computing environments. We represent the cache state of a mobile client as a predicate, and also construct a cache invalidation report (CIR), which the server broadcasts to clients for cache management, with predicates. In order to reduce the amount of information that is needed for cache management, we propose a set of methods for CIR construction (in the server) and identification of invalidated data (in the client). Through experiments, we show that the predicate-based approach is very effective for the cache management of mobile clients.     

Motion pattern analysis of parallel kinematic machines: A case study

This paper looks at the “five-axis machines” for machining operations. These machines have five (or six at maximum) degrees of freedom (dof). The output motion must have at least three translational and two rotational dof. This output motion pattern can be obtained with different structural topologies: serial, parallel, hybrid and with serial and/or parallel manipulators working in co-operation. The latter allows higher motion ranges in rotational and translational dof. Moreover, it provides a good stiffness, a highly valued requisite in applications like machining. Manipulators of this type are characterized by their kinematics to be integrated in the CNC, which requires the study of the relative motion between their modules. This motion is usually complex, and in certain cases presents kinematic relations not evident. This work presents a methodology to solve the motion pattern out of the direct and inverse kinematics of the relative motion between the modules of which the manipulator is composed. On the one hand, the spindle is mounted on a parallel module. On the other hand, the working table is mounted on a serial module. This methodology was applied to the Hermes parallel manipulator in combination with rotary and linear tables. As a result, a series of considerations regarding other possible combinations between modules was made and a new machine is proposed.     

低成本可配置DTMB系统信道估计的VLSI实现

提出一种应用于DTMB系统信道估计的低成本可配置实现方案.在该方案中,本文所提出的基于快速Walsh变换的新型循环相关结构,在没有增加任何硬件成本的前提下,可以同时支持码长分别为256和512的两种PN序列进行相关运算.采用SMIC 0.18标准CMOS工艺综合,本文所提出的信道估计循环相关器可以稳定工作在50MHz的系统时钟频率下,逻辑资源消耗为41355等效门.电路仿真结果表明本文提出的结构比已有的设计结构节省了约60%的功耗,硬件开销减少了48%.     

Haptic Perception,Mechanics, and Material Technologies for Virtual Reality

Emerging virtual and augmented reality technologies can transform human activities in myriad domains, lending tangible, embodied form to digital data, services, and information. Haptic technologies will play a critical role in enabling human to touch and interact with the contents of these virtual environments. The immense variety of skilled manual tasks that humans perform in real environments are only possible through the coordination of touch sensation, perception, and movement that together comprise the haptic modality. Consequently, many research groups are vigorously investigating haptic technologies for virtual reality. A longstanding research goal in this area has been to create haptic interfaces that allow their users to touch and feel plausibly realistic virtual objects. In this progress report, the perspective on this unresolved research challenge is shared, guided by the observation that no technologies can even approximately match the capabilities of the human sense of touch. Factors that have it challenging to engineer haptic technologies for virtual reality, including the extraordinary spatial and temporal tactile acuity of the skin, and the complex interplay between continuum mechanics, haptic perception, and interaction are identified. The perspective on how these challenges may be overcome through convergent research on haptic perception, mechanics, electronics, and material technologies is presented.     

Miniature Soft Electromagnetic Actuators for Robotic Applications

Electromagnetic actuators (EMAs) serve the majority of motion control needs in fields ranging from industrial robotics to automotive systems and biomedical devices, due to their unmatched combination of speed, precision, force, and scalability. This paper describes the design and fabrication of miniature soft EMAs that operate based on the Lorentz force principle. The actuators are fabricated from silicone polymer, liquid metal (LM) alloy (eutectic gallium indium, EGaIn), and magnetic (NdFeB) powder. They are small, intrinsically deformable, and can be fabricated using simple techniques. The central elements of the actuators are fine, 3D helical coil conductors, which are used as electromagnetic inductors. The coils are formed from stretchable filaments that are filled with a LM alloy. To achieve high power densities, the filaments themselves may be fabricated from colloids of EGaIn microdroplets in a silicone polymer matrix, allowing them to dissipate heat and accommodate high currents, and thus high forces. Millimeter‐scale cylindrical actuators are demonstrated for linear high frequency motion and articulated devices for bending motion. These actuators are applied in a vibrotactile feedback display and in a miniature soft robotic gripper.     

国外聚苯醚合金市场现状

叙述了近年来国外聚苯醚合金的供需现状（包括美国、日本和西欧的生产能力、消费构成等），对聚苯醚及其合金的市场动态进行了介绍。     

物料温度和几何尺寸对动态干燥偏差活化能的影响

利用偏差活化能方法研究物料工业干燥动态特性和探索干燥机理的有效途径。通过实验和理论分析，研宛了被干燥物料的偏差活化能随其几何尺寸变化的规律，以及相同几何尺寸时偏差活化能随干燥环境温度变化的关系。研究表明，物料在干燥过程中，不同几何尺寸的试样其偏差活化能均呈现波动趋势，环境温度从低温到高温变化过程中出现偏差活化能最低的环境温度最佳区域。并非干燥环境温度越高，干燥率越高；在温度较低的干燥环境下，物料从泥状到小几何尺寸时，偏差活化能变化不大；偏差活化能随着被干燥物料几何尺寸的减小而降低，相对偏差活化能随着干燥温度的升高而较快地接近1。