Synthesis of Pb(Ni1/3Nb2/3)0.72Ti0.28O3 perovskite ceramics by a reaction-sintering process

Pb(Ni_1/3Nb_2/3)_0.72Ti_0.28O₃ (PNNT) perovskite ceramics produced by a reaction-sintering process were investigated. Without any calcination, the mixture of PbO, Ni(NO₃)₂, Nb₂O₅ and TiO₂ was pressed and sintered directly into PNNT ceramics. PNNT ceramics of 100% perovskite phase were obtained. For PNNT sintered for 2 h in PbO compensated atmosphere, maximum density reaches a value 8.49 g/cm³ (99.8% of the theoretical value) at 1250^∘C. A maximum dielectric constant 20600 occurred around 37^∘C at 1 kHz in PNNT sintered at 1250^∘C for 2 h.     

钢坯连续加热炉计算机在线控制数学模型

在离线模型的基础上.开发了加热炉在线计算机控制数学模型;这种模型系统不仅能够最大程度地节能,而且保证了出钢温度的准确控制,结果表明:出炉钢坯温度与目标出炉温度偏差小于15℃.     

Synthesis and dielectric properties of polystyrene‐clay nanocomposite materials

Polystyrene‐clay nanocomposite (PsCN) materials were synthesized and their properties of crystallinity, thermal behavior, and dielectric characteristics were investigated. A polymerizable cationic surfactant, [2‐(dimethylamino)ethyl]triphenylphonium bromide, was used for the intercalation of montmorillonite (MMT). The organophilic MMT was prepared by Na⁺‐exchanged MMT and ammonium cations of a cationic surfactant in an aqueous medium. Organophilic styrene monomers were intercalated into the interlayer regions of organophilic clay hosts followed by a free‐radical polymerization. Exfoliation to 2 wt % MMT in the polystyrene (PS) matrix was achieved as revealed by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Thermal properties by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were also studied. The dielectric properties of PsCNs in the form of film with clay loading from 1.0 to 5.0 wt % were measured under frequencies of 100 Hz–1 MHz at 25–70°C. A decreased dielectric constant and low dielectric loss were observed for PsCN materials. The dielectric response at low frequency that originated from dipole orientation was suppressed due to the intercalation of clay materials. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1368–1373, 2004     

Design of micro-electromagnetic drive on reciprocally rotating disc used for micro-gyroscopes

For micro-gyroscopes, the angular rate detection components have to oscillate forwards and backwards alternatively. An innovative design of micro-electromagnetic drive module is proposed to make a Π-type thin disc reciprocally and efficiently rotate within a certain of angular interval. Twelve EM (Electromagnetic) poles, with iron cores at the center and wound by electroplated copper wires, enclosing the thin disc are designed to provide the magnetic drive power. Isotropic etching technique is employed to fabricate the high-aspect-ratio trench, housing of the follow-up electroplated copper, so that the contact angle of wire against trench can be increased and the potential defect of cavities and pores within the wire can be prevented. On the other hand, a Π-type thin disc, with a central bearing and a set of auxiliary bushing, is designed to conduct the pitch motion as an angular excitation, in addition to spinning, is exerted on the gyroscope. That is, the angular motion of the disc is two-dimensional: spinning, driven by the EM poles, and tilting, to respond to the exerted angular rate due to Coriolis effect.The efficacy of the micro-magnetic drive module is verified by theoretical analysis and computer simulations by the commercial software, Ansoft Maxewll. In comparison with the conventional planar windings in micro-scale systems, the magnetic drive force is increased by 150%.     

微量调速阀抗污染机理研究

本文分析和证明了微量调速阀在实现2-100ml/min 的微量控制时,其压力补偿器的结构性自动抗污染机理和阀具有的综合抗污染性能、其抗污染的机理和性能对设计和研究低污染敏感度的液压元件有实际的指导意义.     

An integrated method for finding key suppliers in SCM

Association rule is a widely used data mining technique that searches through an entire data set for rules revealing the nature and frequency of relationships or associations between data entities. Supplier selection is a significant work in supply chain management. Often, there will be thousands of potential suppliers and identifying a subset of these suppliers can be a complex process of determining a satisfactory subset based on a number of factors. In this paper, the supplier selection can be viewed as the problem of mining a large database of shipment. The proposed method incorporates the extended association rule algorithm of data mining with that of set theory to find key suppliers. This research has employed a numerical example for the integrated method to develop suitable supplier clusters. The results show that the method is effective and applicable.     

Assessment of drivers' visual perception of information displayed in LED traffic signs at road construction sites

This study investigated drivers' visual perception of information displayed in LED traffic signs under different levels of environmental luminance. Concerning the information displayed, the environmental luminance comprised four luminance contrasts, two arrow types, and three environmental luminances, which were used to identify the visibility of traffic signs at the reading distance. Regarding visible distance, visibility involved reading starting and end points, extent of glare, comfortable distance, and glare distance. According to the study results obtained by using a highly reliable glare assessment method and studying the LED traffic signs, the lower the luminance contrast of traffic signs was the higher glare the participants perceived. A luminance contrast of 6200:2066 cd/m² provided the farthest comfortable and glare distances, enabling drivers to notice the signs comparatively earlier and have sufficient time to react accordingly. Overall, arrow type “<<<” outperformed “←” because the former was easier for drivers to read and created less glare. Regarding environmental luminance, traffic signs displayed in high and medium luminance environments (i.e., extremely sunny and cloudy days, respectively) each featured their own advantage, whereas those displayed in low luminance environments (nights) have to be further improved.     

Electrical conductivity of ferroelectric sodium vanadate,rubidium vanadate,cesium vanadate and their solid solutions

The d.c. electrical conductivity of sodium vanadate, rubidium vanadate, cesium vanadate and their solid solutions sodium-rubidium vanadate and sodium-cesium vanadate were studied by a two-probe method in the temperature range covering their transition points. The electrical conductivity shows sharp change at the phase transition temperature of these materials. In NaVO₃, RbVO₃ and CsVO₃, increase in d.c. conductivity is observed in the ferroelectric region while nonlinearities are observed above transition temperatures. In solid solutions, the activation energy in the paraelectric state is higher than that in the ferroelectric state and depends upon sodium concentration.     

Output regulation of two-time-scale hyperbolic PDE systems

This paper addresses the output regulation of flow systems described by a class of two-time-scale nonlinear PDE systems. Within the framework of singular perturbation, the reduced-order slow model comprised of first-order PDEs coupled with ODEs is obtained. Based on the numerical approximation technique and the solvability of an inertial manifold, the finite-dimensional nonlinear model with nonlinear input is developed in this paper. Extending from the geometric control method, the non-distributed nonlinear controller can be synthesized. A combination of the state-space internal model control scheme, the reduced observer-based controller can asymptotically attenuate the effect of external disturbances. Finally, the developed methodologies are successfully applied to the development of a PFR system asscociated with the cooling coil apparatus.