Acoustic-Emission Analysis of the Accumulation of Bulk Damage to Solid Bodies

Using the proposed concept, we developed a model for quantitative evaluation of the bulk damage to solid bodies in a plastically deformed volume by acoustic-emission signals. This model takes into account the principle of linear summation of damages and the solution in displacements of the dynamic problem of the formation of an isolated normal tensile microcrack in the zone of intense plastic strains. The main scientific propositions of the model are corroborated by the results of experimental investigations and published data.     

Stagnation Points in Flows about Solid Bodies

A possible first step in determining the flow about a steadily advancing ship is to consider the ship plus its mirror image in the undisturbed free surface. If the ship has a bulbous bow, the question may be asked whether a stagnation point can be expected not only at the intersection of the stem and the undisturbed surface, but also at some point on the stem near the bulb. In analogous two-dimensional situations the latter could not happen. That it can happen in three dimensions is shown here by the example of two dipoles situated perpendicularly to an oncoming flow. Both two- and three dimensional versions are considered. The conditions under which these stagnation points can occur in three dimensions are determined and the reason why this does not happen in two dimensions is explained.     

几种典型凸轮裹包执行机构的从动系统运动规律的理论分析

详细分析了裹包执行机构的正弦型和正切型从动系统的运动规律,用数学方法对运动规律进行了详尽的理论分析。     

变频空调系统的理论分析及实验研究

变频空调器是由变频压缩机驱动的空调系统 ,压缩机通过变频调节其转速使压缩机单位时间内的排气量变化 ,从而达到调节制冷量的目的。本文提出了变频空调器制冷系统的原理和设计方法 ,具体给出了制冷量和压缩机频率的关系方程 ,并从理论和实验两方面对变频空调器制冷系统进行了分析 ,得到了频率曲线图 ,为变频空调器制冷系统的设计提供了依据。     

Evaluation of the Rate of Change of Transfer Potentials in Porous Solid Bodies

A formula for calculating the potential diffusivity of energy in porous solid bodies has been obtained, which made it possible to express the velocity of propagation of the energy field in the form of a relation of the type of an equation of heat conduction with a constant coefficient. Under the same boundary conditions, the velocity of propagation of the energy field is intermediate in value between the velocities of propagation of the temperature and concentration fields.     

New Discrete Model of Plastic Deformation of Solid Bodies

Materials Science - We compare the dislocation model with a new discrete model of plasticity. According to the previously proposed model, a crystal lattice with spherically symmetric potential of...     

户式变频冷水机组空调系统综合匹配分析及实验研究

本文把户式变频冷水机组空调系统复杂的综合匹配关系进行了简化，建立了综合匹配关系式，分析了综合匹配的关键因素，设计了匹配实验装置及方法，并进行了实例实验研究，为该类空调系统的优化设计提供理论分析方法及实验参考结果。     

Thermodynamic Analysis of Water Interaction with Excipient Films

The interaction of water with excipients that can form moisture-protective coatings was examined earlier by the application of theoretical models. In this study, thermodynamic analysis of water-excipient film systems has been performed to elucidate the mechanistic details of the water-excipient interaction. Partial molal free energies, enthalpies, and entropies were computed for films of lipidic (glyceryl behenate, GB) and polymeric (polyvinyl alcohol, PVA) coating excipients using the temperature dependence of the adsorption process. The analysis of free energy changes showed that excipient films were not inert participants in the water sorption process. The isoteric heats of adsorption confirmed that water formed hydrogen bonds with the excipient films and allowed estimation of number of hydrogen bonds per water molecule. This result also provided the reason for hysteresis during drying. A comparative evaluation of the application of theoretical models and thermodynamic analysis revealed that results obtained from both approaches were not always complementary. An exponential relationship was found to exist between sorption microrate constants and water activity for the PVA films at all temperatures.     

温度对金刚石刀具影响的理论模型和实验分析

为减小大型金属反射镜在金刚石车削中,刀具的热变形对加工精度的影响,研究了金刚石刀具在温度影响下的热变形规律,结合俄罗斯在热力学方面的研究成果,根据金刚石晶体和刀体的热膨胀系数和导温系数的不同,建立了刀具变形量随温度变化的理论计算模型,并采用高精度的热像仪和电感测微仪记录刀具的温度变化和变形量,发现当温度从23．4℃升高到32．1℃时,刀具变形量达到1．48μm．     

Studying the Mutual Influence of a Set of Strikers during Simultaneous High-Velocity Entry into Water

Technical Physics Letters - High-velocity motion of a set of supercavitating kinetic strikers during their simultaneous entry into water has been experimentally studied. A special experimental...     

Experimental Measurements and Theoretical Prediction of the Thermal Conductivity of Two- and Three-Phase Water/Olivine Systems

The thermal conductivity of olivine, dry and mixed with water, up to saturation, has been measured with a thermal probe, using the step heating method. The olivine is composed of solid particles with dimensions in the range from 0.8 to 1 mm. Dry olivine has been measured in the range of temperatures between –17° to +50°C. Olivine mixed with water has been measured at +50°C. The cubic cell model has been used to make predictions to compare with the measured data. Comparisons of the experimental thermal conductivities and the predicted values of dry and water-mixed olivine show good agreement. The cubic cell model can be used to evaluate the porosity of olivine and the thermal conductivity of the solid particles, from the values measured at dryness and saturation, with reasonably good agreement. In this way, it is not necessary to measure the mineral composition of the particles of the porous media. Also, the porosity of the medium is predicted with reasonable agreement, which takes into account the phenomenon of the porosity increase near the probe, since the diameter of the probe is smaller than that of the solid particles.     

Smart MEMS Flow Sensor: Theoretical Analysis and Experimental Characterization

This paper presents analytical and experimental studies of a new microelectromechanical system (MEMS) smart flow sensor for the measurement of gas flow. The flow sensor has an array of curved-up cantilever beams that are surface-micromachined with two layers of deposition under two sets of different process parameters. The differential residual stress between the two layers of the polysilicon deposition causes the beams to curve upward from the substrate surface when the sacrificial layer is released. Each beam of the array of beams of different lengths vibrates successively as the flow rate increases, enabling more accurate sensing and identification of range of flow rates based on the vibration characteristics, thus making this a smart sensor design. Design and fabrication of these sensors are discussed. Experiments were conducted on this MEMS flow sensors to characterize the deflection of the curved cantilever beams with respect to flow rates. In addition, backflow tests were also conducted separately. Results of the analytical study are presented to investigate the cause of vibration of beams when subjected to flow. Finite-element analyses of vibration of the sensors comply with the experimental observation. Based on the analysis of fundamental natural frequencies, possible arrangement for the distribution of lengths of the beams is proposed to enhance its functionality as a sensor. Future work and plan of the on-board capacitive metrology and other practical issues are discussed     

空气弹簧弹性特性理论分析与试验研究

刚度特性、频率特性直接影响空气弹簧的隔振性能.利用工程热力学理论推导空气弹簧刚度及频率的数学表达式,并进一步利用试验研究空气弹簧静、动态特性,研究结果表明:空气弹簧弹性特性为一族非线性曲线,充气压力越大,承载能力越强;空气弹簧的刚度随充气压力增大而增大,而频率基本保持不变;在激励频率为0.5-6.0Hz范围内,空气弹簧的动刚度随着激励频率的增加呈先缓慢减小然后迅速减少的趋势;动刚度基本不随激励振幅发生变化.     

对流干燥过程理论分析:水分活度

在收缩和非收缩条件下,对胡萝卜的对流干燥特征进行了理论分析.结果表明,干燥速率是试样几何形状、尺寸以及热空气温度、风速、相对湿度的函数.整个干燥过程应划分为外部干燥条件控制的第一干燥阶段和物料内部水分扩散控制的第二干燥阶段.而基于经典干燥理论的恒速干燥阶段和降速干燥阶段的划分,只是特定形状和材质的物料在一定干燥条件下才出现的干燥现象.物科外层单元水分活度可以作为判别物科干燥过程是处于第一干燥阶段还是第二干燥阶段的判断依据,是表征物料干燥特性的特征参数.