自平衡机器人的模糊-PD控制

由于自平衡机器人是一种两轮左右平行布置的机器人,像传统的倒立摆一样,它的本身是一个自然不稳定体,必须要施加强有力的控制手段才能使之稳定.为了提高两轮自平衡机器人设计的可靠性,针对不稳定、非线性、强耦合的两轮自平衡机器人系统,运用牛顿力学方法建立了转向运动的数学模型.在模型中建立了模糊控制器,并用模糊控制加比例控制的方法...     

MELTING OF ICE AROUND A HORIZONTAL ISOTHERMAL CYLINDRICAL HEAT SOURCE

Processes during melting from a horizontal cylindrical heat source of uniform surface temperature embedded in ice have been studied experimentally. The volume of the melt and its shape were photographed at different times for various constant temperatures of the heat source. At early times and under all conditions, the melt occupied a cylindrical annulus. At later times free convective motion caused pear-shaped melt contours which pointed downward when the temperatures of the heat source were below 7°C and upward when the temperatures were above 8°C. Instabilities in cellular natural convection motion resulted in waviness of the interface. The location and magnitude of these ripples were found to depend on the temperature of the heat source and the melt layer thickness. Shadowgraph techniques were used to determine local heat transfer coefficients at the heat source surface.     

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对国内外常用的几种流变模式进行了分析和评价，指出了它们的特点和不足之处。在总结和归纳的基础上，提出了一个带静切应力的三参数多项幂律模式（简称Ｌ—Ｍ模式）。研究还从该模式的本构方程出发，推导出流变参数及有关水力参数计算式，并应用大量的泥浆及水泥浆试验资料和计算数据，对比和分析了各流变模式的适应范围及精确程度，进而证明了Ｌ—Ｍ、Ｈ—Ｂ流变模式具有适应范围广、准确性高的特点。     

Three-Dimensional Nonisothermal Simulation of Multi-Layer Extrusion Processes of Polymer Melts

The three-dimensional, nonisothermal, generalized Newtonian polymeric fluid flow (LPDE/PS) in coextrusion dies was simulated using the finite element method with evolutionary technique. Simulation results, especially the interface predictions, velocity profiles, and temperature profiles were discussed. The simulated interface shape was compared with that obtained by the previous researchers, and the simulated results were confirmed. The effects of fluids' temperature and flow rate ratio on the interface of LDPE/PS are further examined. Increasing temperature of more viscous fluid (PS) can influence the interface location. It is also found that the flow rate affects the shape and location of the interface notably. The velocity of fluid flow mainly controls the shape and location of the interface.     

沥青黏度影响因素的研究

沥青黏度是沥青一个重要指标。在分析沥青黏度的原理及黏度计的原理之后,利用黏度计进行黏度影响因素分析,主要分析温度、时间、转速和转子对黏度的影响。试验结果表明黏度的对数与温度成较好的线性关系,转速对黏度的稳定时间有较大的影响,转速、转子对黏度都有一定的影响。     

Synthesis and rheological properties of nickel‐zinc ferrite polymer nanocomposites

In this work, the ferrimagnetic nickel‐zinc ferrite nanopowder was synthesized via citrate‐ethylene glycol processing, followed by the preparation of the epoxy‐based nanocomposite. The materials were characterized using X‐ray diffraction (XRD), simultaneous thermal analysis (STA), alternative gradient force magnetometer (AGFM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that the sample calcined at 1000°C for 1 h had the best crystallinity, and the calculated crystallite size of this sample was ～ 105 nm. The rheological properties and the magnetoviscous effect of the nanocomposites were studied by a standard rotating rheometer. The effects of the magnetic fields and shear rate with respect to time were investigated, and the results were discussed in terms of aggregates and magnetic field‐induced structures. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

流体动压润滑失效机理的研究

本文分析了温度对润滑剂流变特性的影响，揭示了温度变化使润滑剂表现出明显的非牛顿特性。进一步的数值计算表明润滑油膜存在有限承载能力，从而提出了一种由于温度影响而引起油膜破裂的润滑失效模型，为预测滑动轴承的润滑状态、改进设计提供了新的理论依据。     

基于IAPWS-IF97的3区T(p,h)、v(p,h)反推牛顿迭代计算

利用牛顿迭代法求解IAPWS-IF97的3区T（p，h）、v（p，h），并同时与IAPWS-IF97的3区T（p，h）、v（p，h）反推线性拟合公式从计算精度和计算效率作了比较说明。通过分析说明，其计算精度高于IAPWS-IF97的3区T（p，h）、v（p，h）反推公式，而计算效率稍逊于反推公式。     

MELTING OF ICE AROUND A HORIZONTAL ISOTHERMAL CYLINDRICAL HEAT SOURCE

Processes during melting from a horizontal cylindrical heat source of uniform surface temperature embedded in ice have been studied experimentally. The volume of the melt and its shape were photographed at different times for various constant temperatures of the heat source. At early times and under all conditions, the melt occupied a cylindrical annulus. At later times free convective motion caused pear-shaped melt contours which pointed downward when the temperatures of the heat source were below 7°C and upward when the temperatures were above 8°C. Instabilities in cellular natural convection motion resulted in waviness of the interface. The location and magnitude of these ripples were found to depend on the temperature of the heat source and the melt layer thickness. Shadowgraph techniques were used to determine local heat transfer coefficients at the heat source surface.