Thermal Stresses in a Cylinder Block Casting Due to Coupled Thermal and Mechanical Effects

Thermal stress in castings results from nonuniform cooling. The thermal stress and the deformation can change the casting and mold contact conditions which then alter the heat transfer between the casting and the mold. The contact element method was used to study the interaction between a sand mold and a casting. The contact status was then fed back to the heat transfer analysis between the sand mold and the casting to re-evaluate the heat transfer coefficient based on the gap size or pressure between surfaces. The thermal and mechanical phenomena are then coupled in two directions. The method was applied to analyze stress in a stress frame specimen casting and a cylinder block. The results are more accurate than without consideration of the contact effects on the heat transfer.     

Simplification of Template-free Method to Prepare Polyaniline Nanotubes

1 Introduction Conducting polymer nanostructures (e.g.nanotubes or nanofibers) have received considerable attention owing their unique properties and promising applications in technology and nano-devices[1]. Conducting polymer nanostructures can be generally synthesized through "hard" and "soft" template method.Usually an external hard template in a "hard-template" method is required and the post-treatment of removing template is rather tedious."Soft-template" method is advantageous of omitting external template and post-treatment of removing template,however,structure directors (e.g.surfactants and special organic solvent) are necessary to be introduced into the chemical polymerization bath,which result in complicating the synthesis and the extraction of the final product.Therefore,to reduce reagents of a reaction system might be a approach to simplify "soft-template" method that is challenge in preparation of conducting polymer nanostructures.     

Finite element models and molecular dynamic simulations for studying the response of mast cell under mechanical activation

In micropipette aspiration experiment, increasing mechanical stress applied to cell membrane induced degranulation of mast cell as well as a current that could be inhibited by an inhibitor, which is specific for the transient receptor potential vanilloid （TRPVs） channels. To determine the sensitivity of TRPVs to membrane strain and tension, and to gain new insights into the activation mechanism of TRPVs, finite element models of mast cell and molecular dynamic simulations of human aquaporin-1 are presented. During the finite element simulations, the cell membrane sustained to micropipette aspiration was simulated, and the strain distribution along membrane thickness direction was obtained. Besides, combining the finite element models of osteoblast aspirated into micro- pipette and other compared models, we examined the relationship between cell mechanical stimulations and mechanical attributes and presented a new perspective to determine the cell equivalent elastic modulus. Consid- ering the indetermination of TRPV crystal structure, human aquaporin-1, one kind of the channel membrane proteins, substituting for TRPV, has been studied with molecular dynamic （MD） simulations, under different external lateral tensions which have been obtained in mast cell finite ele- ment simulations, to investigate the mechanical stimulation effects on the membrane channels. The simulations show that human aquaporin-1 undergoes significant conforma- tional change and expands in accordance with lateraltension, which not only confirms the tendency of the pre- vious electrophysiological experiments but also leads us to a better understanding of TRPVs. The multi-scale study combining finite element simulation and MD simulation is a significant breakthrough in the field of mechanical mechanism in cell system.     

Solvent-assisted polymer micro-molding

The micro-molding technology has played an important role in fabrication of polymer micro-patterns and development of functional devices. In such a process, suitable solvent can swell or dissolve the polymer films to decrease their glass transition temperature （Tg） and viscosity and thereby improve flowing ability. Consequently, it is easy to obtain the 2D and 3D patterns with high fidelity by the solvent-assisted micro-molding. Compared with the high temperature molding, this technology overcomes some shortcomings such as shrinking after cooling, degradation at high temperature, difficulty in processing some functional materials having high Tg, etc. It can be applied to making patterns not only on polymer monolayers but also on polyelectrolyte multilayers. Moreover, the compressioninduced patterns on the multilayers are chemically homogenous but physically heterogeneous. In this review, the controlling factors on the pattern quality are also discussed, including materials of the mold, solvent, pressure, temperature and pattern density.     

Anthropomorphic Classification of Tactile Qualities of Woven Fabrics Based on Skin/Textile Friction-Induced Vibrations

The common method classifying tactile qualities of fabrics is indirectly based on their difference of purely mechanical and physical properties. When human skin slides across fabric surfaces, the friction interaction between fabrics and skin will occur and trigger the cutaneouS tactile receptors, which are responsible for perceived tactile sensation. By the extracted features from friction- induced vibration signals, this paper presents an anthropomorphic classification method classifying tactile qualities of fabrics. The friction-induced vibration signals are recorded by a three-axis accelerator sensor, and the entice testing procedure is conducted in an anthropomorphic way to obtain vibration signals. The fast Fourier transform （FFT） is applied to analyzing the recoded signals, and then the classification features are extracted from the FFT data by the neurophysiological properties of tactile receptors. The extracted features are used to classify fabric samples by the softness sensation and the roughness sensation, respectively, and the classification performance is checked by a comparison with those in a sensory evaluation procedure. The results showed that the anthropomorphic objective classification method was precise and efficient to clarify tactile qualities of woven fabrics.     

P(AN-MMA)/TiO_2 Nano-composite Polymer Electrolyte by in-situ Polymerization

1 Introduction With the development of portable electric devices,polymer lithium ion batteries (PLiBs) have been widely used as the power sources because of their high energy density and safe property[1].P(AN-MMA) copolymer is a kind of cheap macromolecules easily dissolving in the polar solvents such as carbonate,it has been applied as gel polymer electrolyte in PLiBs.Here we prepare a kind of highly conductive nano-composite polymer electrolytes using the P(AN-MMA) copolymer incorporated with TiO2 nanoparticles as polymer matrix.The nano-composite polymer materials are prepared by an in-situ polymerization method.Nano-composite polymer electrolytes (NCPEs) are prepared by immersing the obtained porous P(AN-MMA)/TiO2 nano-composite polymer membranes in non-aqueous electrolyte.Their electrochemical characteristics were discussed here.     

Preliminary results of direct cell-matrix assembly technology

Tissue loss and end-stage organ failure has been an emergent problem for humanity. Solving this problem at the most basic level is currently an area of great interest to many.researchers. At the end of the 20th century, tissue engineering technology began using formed scaffolds to indirectly control the assembly of cells. This technology has resulted in a new way to artificially fabricate tissues.But the method has been limited to simple tissue types,such as bone, skin, muscle and tendon. The fabrication of complex organs by this technology is still not possible.A possible alternative is assembling cells directly into a viable and predefined structure.     

Pure metal extraction from molten oxide slag by short-circuit galvanic cell

The oxygen-ion-permeable membrane galvanic short-circuit method has been developed, in which pure metal was directly extracted from the molten oxide slag, and no external voltage is applied. The galvanic cell employed in the experiment was as follows: graphite rod|[O]_{Fe+C saturation}|ZrO₂(MgO)|(FeO)_(siag)|Fe rod. The reduction current in the galvanic cell consisted of an external short-circuit current and an interior short-circuit current in the oxygen-ion-permeable membrane. The real-time variation of external circuit reduction ratio of the molten slag could be obtained from the curve of the external circuit current to the time.     

A Numerical Method for Cavity Identification in Beams on an Elastic Foundation

An analytical solution for the natural frequencies of a beam containing a cavity on an elastic foundation is presented. Based on the analytical solution, a numerical method for identifying cavities in the foundation is developed. The position and size of the cavities are identified by minimizing an objective function, which is formulated according to the difference between the computed and measured natural frequencies of the system. The conjugate gradient algorithm is adopted for minimizing the objective function. Some numerical examples are presented to demonstrate the applicability of the presented cavity determination method. The results show that the presented method can be used to identify the cavity position and size conveniently and efficiently.     

Information flow among neural networks with Bayesian estimation

Estimating the interaction among neural networks is an interesting issue in neuroscience. Some methods have been proposed to estimate the coupling strength among neural networks; however, few estimations of the coupling direction (information flow) among neural networks have been attempted. It is known that Bayesian estimator is based on a priori knowledge and a probability of event occurrence. In this paper, a new method is proposed to estimate coupling directions among neural networks with conditional mutual information that is estimated by Bayesian estimation. First, this method is applied to analyze the simulated EEG series generated by a nonlinear lumped-parameter model. In comparison with the conditional mutual information with Shannon entropy, it is found that this method is more successful in estimating the coupling direction, and is insensitive to the length of EEG series. Therefore, this method is suitable to analyze a short time series in practice. Second, we demonstrate how this method can be applied to the analysis of human intracranial epileptic electroencephalogram (EEG) recordings, and to indicate the coupling directions among neural networks. Therefore, this method helps to elucidate the epileptic focus localization.     

抗氧化剂——叶黄素

叶黄素是含紫罗酮环的二羟基类胡萝卜素,在自然界广泛存在。大量的流行病学证据表明,叶黄素在保护眼睛、预防癌症和心血管疾病等方面起着重要作用,是目前国际上功能性食品成分研究中的一个热点。介绍了叶黄素的性质、功能方面的最新研究进展。     

N—烯丙基—N′—(1—对苯磺酸钠偶氮萘—2)硫脲及N—烯丙基—N′—(间苯磺酸钠)硫脲的合成

我们用对苯磺酸钠偶氮β-萘胺和间氨基苯磺酸钠分别和烯丙基芥子油作用合成了两种新的硫脲化合物N—烯丙基—N′—(1—对苯磺酸钠偶氮萘—2)硫脲及N—烯丙基—N′—(间苯磺酸钠)硫脲,并对它们的一些性质作了初步研究。     

2——正则码

定义一类特殊码：２ ———正则码，在给出若干特征后，得到它的分类与构造。     

N—甲基-2-吡咯烷酮的电解合成

以丁二酸和甲胺水溶液为原料,先合成N—甲基丁二酰亚胺,再经电解还原得N—甲基—2—吡咯烷酮。经分离提纯,含量达99.5%以上,可满足液晶技术的使用要求。     

运动电荷周围的位移电流和磁场

相对于观察者来说,电荷运动时,周围空间各点的电场要发生变化。根据麦克斯韦电磁场理论可知,电场变化时,周围空间各点要产生磁场。因此,从产生磁场的角度上讲,变化的电场相当于一电流,这个电流叫做位移电流,由此可见,运动电荷周围是有位电流存在的。有位移电流存在的区域叫位移电流场,在位移电流场中,任一点的位移电流密度矢量的方向如何确定?大小如何确定?位移电流线是何形状?位移电流的磁场是如何分布的?本文想针对这些问题谈一谈自己的一些看法。     

关于cf-可膨胀空间和csf-可膨胀空间的注记

文章主要给出了关于cf-可膨胀空间类的映射性质,并证明了若X=Πσ∈ΣXσ是Σ-仿紧(遗传Σ-仿紧)的,则X是cf-可膨胀(遗传cf-可膨胀)的当且仅当对F∈[Σ]相似文献   

实践能力是大学生步入社会的有力资本——对培养大学生实践能力的思考

随着社会的发展，社会对人才质量要求不断提高，用人观念也由学历型逐渐向能力型、实践型转变，因此高校切实加强大学生实践能力的培养愈有其重要的意义。应从转变观念、完善实践教学体系、建立健全激励机制等方面进一步提高大学生实践能力的培养。     

HSDW——Ⅱ型杨氏模量实验仪

该型实验仪,是在Ⅰ型(1)的基础上改制而成的,它不但具备了Ⅰ型仪器的优点,而且克服了Ⅰ型不足之处。