在线粒度监控系统在线切割用碳化硅粉生产中的应用

针对目前国内碳化硅微粉的生产均为半自动化控制,本文中对Insitec在线粒度监控系统的功能和应用领域进行介绍,并在线切割用碳化硅粉的生产过程用来对产品粒度进行监控。结果表明:中控系统能够根据Insitec反馈的测量信息对工艺参数自动进行调节,使粒度变化控制在设定范围之内,粒度变化趋势平稳,波动很小,产品质量得到保证。整个生产过程达到全自动化控制。     

Design of an in-line, digital holographic imaging system for airborne measurement of clouds

We discuss the design and performance of an airborne (underwing) in-line digital holographic imaging system developed for characterizing atmospheric cloud water droplets and ice particles in situ. The airborne environment constrained the design space to the simple optical layout that in-line non-beam-splitting holography affords. The desired measurement required the largest possible sample volume in which the smallest desired particle size (～5 μm) could still be resolved, and consequently the magnification requirement was driven by the pixel size of the camera and this particle size. The resulting design was a seven-element, double-telecentric, high-precision optical imaging system used to relay and magnify a hologram onto a CCD surface. The system was designed to preserve performance and high resolution over a wide temperature range. Details of the optical design and construction are given. Experimental results demonstrate that the system is capable of recording holograms that can be reconstructed with resolution of better than 6.5 μm within a 15 cm(3) sample volume.     

基于数字图像分析的颗粒生长监测技术

为了实现滚筒造粒过程中对球形颗粒生长的精确控制,提出基于数字图像分析技术的球形颗粒尺寸在线检测方法,使用工业数码相机搭建颗粒图像采集实验平台,开发图像分析软件。结果表明,该方法对单幅图像的分析时间为0.9 s;系统对粒度检测的可重复精度约为±1%,与千分尺测量的粒度相比,误差约为±3%;该方法可用于构造造粒机的视觉反馈控制系统,以实现颗粒生长过程的闭环控制。     

Control of chaos in nonlinear systems with time-periodic coefficients

In this study, some techniques for the control of chaotic nonlinear systems with periodic coefficients are presented. First, chaos is eliminated from a given range of the system parameters by driving the system to a desired periodic orbit or to a fixed point using a full-state feedback. One has to deal with the same mathematical problem in the event when an autonomous system exhibiting chaos is desired to be driven to a periodic orbit. This is achieved by employing either a linear or a nonlinear control technique. In the linear method, a linear full-state feedback controller is designed by symbolic computation. The nonlinear technique is based on the idea of feedback linearization. A set of coordinate transformation is introduced, which leads to an equivalent linear system that can be controlled by known methods. Our second idea is to delay the onset of chaos beyond a given parameter range by a purely nonlinear control strategy that employs local bifurcation analysis of time-periodic systems. In this method, nonlinear properties of post-bifurcation dynamics, such as stability or rate of growth of a limit set, are modified by a nonlinear state feedback control. The control strategies are illustrated through examples. All methods are general in the sense that they can be applied to systems with no restrictions on the size of the periodic terms.     

Solid Dispersion Controlled Release: Effect of Particle Size, Compression Force and Temperature

Solid dispersions are dynamic systems, a careful control of processing variables is required to produce desired physicochemical properties of these systems.

The influence of drug particle size, dispersion temperature and compression force on the release rate of theophylline from solid dispersed system tablets was studied. Theophylline base (micronized and granulate) were embedded into a polymeric mixture of PEG and acrylic/methacrylic esters at controlled temperature and shock cooled. Tablets were made at two compressional forces and drug release was measured spectrophotometrically over a period of fifteen hours.

The release rate of drug dispersed in these insoluble matrices was independent of particle size but not of hardness.

However, variations in ratios of polymeric mixture and dispersion temperature controls the drug release rate from inert matrix more effectively than such factors as drug particle size and lower range of tablet hardness. The fast cooling produced excellent reproducibility of drug content throughout the entire entrapment product. X-ray diffraction study demonstrated no changes in crystalline form of theophylline.     

Solid Dispersion Controlled Release: Effect of Particle Size,Compression Force and Temperature

Abstract

Solid dispersions are dynamic systems, a careful control of processing variables is required to produce desired physicochemical properties of these systems.

The influence of drug particle size, dispersion temperature and compression force on the release rate of theophylline from solid dispersed system tablets was studied. Theophylline base (micronized and granulate) were embedded into a polymeric mixture of PEG and acrylic/methacrylic esters at controlled temperature and shock cooled. Tablets were made at two compressional forces and drug release was measured spectrophotometrically over a period of fifteen hours.

The release rate of drug dispersed in these insoluble matrices was independent of particle size but not of hardness.

However, variations in ratios of polymeric mixture and dispersion temperature controls the drug release rate from inert matrix more effectively than such factors as drug particle size and lower range of tablet hardness. The fast cooling produced excellent reproducibility of drug content throughout the entire entrapment product. X-ray diffraction study demonstrated no changes in crystalline form of theophylline.     

Identification of intermittent control in man and machine

Regulation by negative feedback is fundamental to engineering and biological processes. Biological regulation is usually explained using continuous feedback models from both classical and modern control theory. An alternative control paradigm, intermittent control, has also been suggested as a model for biological control systems, particularly those involving the central nervous system. However, at present, there is no identification method explicitly formulated to distinguish intermittent from continuous control; here, we present such a method. The identification experiment uses a special paired-step set-point sequence. The corresponding data analysis use a conventional ARMA model to relate a theoretically derived equivalent set-point to control signal; the novelty lies in sequentially and iteratively adjusting the timing of the steps of this equivalent set-point to optimize the linear time-invariant fit. The method was verified using realistic simulation data and was found to robustly distinguish not only between continuous and intermittent control but also between event-driven intermittent and clock-driven intermittent control. When applied to human pursuit tracking, event-driven intermittent control was identified, with an intermittent interval of 260–310 ms (n = 6, p < 0.05). This new identification method is applicable for machine and biological applications.     

Simple method for frequency locking of an extended-cavity diode laser

We have developed an extended-cavity tunable diode laser system that has a small linewidth and a large output power (more than 90% of the free-running power) whose operating frequency can be conveniently locked to a transition line of Rb atoms. Based on flat-mirror feedback and frequency self-locking and with weak feedback, we have achieved a continuous frequency detuning range greater than 900 MHz and a short-time linewidth stability of better than 0.4%. By using a two-step locking procedure we not only can lock the laser frequency but also can detune the frequency to any desired value. The locking is quite sturdy and rugged.     

液压二自由度力反馈操纵杆设计

 开发了一种用于遥操作双向伺服系统力反馈工作的液压二自由度力反馈操纵杆.该操纵杆采用PID控制器控制的电液伺服系统进行驱动,可以有效地解决一般电机型力反馈操纵杆在刚度和响应速度方面不足的问题.介绍了系统的软硬件构成,并通过对系统运动性能的分析,设计了用于该系统的力反射型力反馈算法,最后通过实验验证了该算法的有效性.实验证明,该操纵杆具有较好的力反馈操作特性,能够满足遥操作系统力反馈工作的需要.     

Preparation and Evaluation of Sustained release Indomethacin Nonpareil Seeds

A controlled release oral drug delivery system of Indomethacin was developed using nonpareil seeds as a matrix system. These seeds were coated with different concentrations of drug release controlling materials viz Eudragit RL100 and Eudragit RS100, and bees wax. The particle size of the seeds and the concentration as well as the type of the drug release controlling Eudragits has a pronounced effect on the release rate profile of Indomethacin. All types of formulations showed release rate pattern which can be described by both first-order and diffusion controlled mechanism.     

含脆性界面相的颗粒增强金属基复合材料的损伤

通过引入双夹杂模型,将传统增量损伤理论扩展应用到三相复合材料颗粒尺寸效应问题,同时提出一个可以研究颗粒增强金属基复合材料的弹塑性变形及渐进式脱黏损伤模型,该模型还可以研究含脆性界面相的颗粒增强金属基复合材料弹塑性损伤变形行为的颗粒尺寸效应。研究发现,包含各种不同颗粒尺寸的颗粒增强金属基复合材料的脱黏损伤按照颗粒尺寸从大到小的顺序先后发生,并且该模型与SiC/Al复合材料的试验结果比较一致。     

Preparation and Evaluation of Sustained release Indomethacin Nonpareil Seeds

Abstract

A controlled release oral drug delivery system of Indomethacin was developed using nonpareil seeds as a matrix system. These seeds were coated with different concentrations of drug release controlling materials viz Eudragit RL100 and Eudragit RS100, and bees wax. The particle size of the seeds and the concentration as well as the type of the drug release controlling Eudragits has a pronounced effect on the release rate profile of Indomethacin. All types of formulations showed release rate pattern which can be described by both first-order and diffusion controlled mechanism.     

料球粒径的非接触检测方法

本文介绍一种基于计算机视觉技术的水泥生料球粒径非接触检测方法，该方法可以在线检测料球的平均粒径及粒径分布，并可作为现有预加水成球控制系统的反馈信号，从而实现预加水成球的闭环控制。实验结果表明，用该检测方法得到的料球粒径分布及平均粒径基本上能够反映料球的真实状况     

自适应线性反馈与自适应微分反馈控制混沌

构造自适应线性反馈控制混沌Chen系统到达平衡点.应用Lyapunov第二方法证明受控系统可渐近稳定收敛到三个平衡点.将控制参数p看作第4个变量构成与受控系统等价的自治系统,数值仿真结果验证了受控系统(2)对指定平衡点的稳定收敛.构造自适应微分反馈控制混沌Chen系统,应用Ruoth Hurwitz定理证明受控系统(4)可稳定收敛到平衡点S+,S-,而不能收敛到平衡点S0.自适应方法的优点是控制信号微小简单,可在任意时刻加入,可以迅速将混沌系统控制到系统的平衡点,且在系统收敛到平衡点时,控制扰动u(t)也迅速趋于0.     

Dissolution rates of limestones of different sources

The dissolution characteristics of limestones from six sources in Taiwan have been studied by using the pH-stat method in a stirred tank at 60 degrees C, pH values of 4 and 6, stirrer speeds of 500-1000 rpm, and a particle size of 75-125 microm aperture width. The dissolution rates of the limestones were found to be controlled by the mass transfer of hydrogen ions with chemical reactions in the liquid film surrounding the limestone particle. The measured value of mass transfer coefficient increases with an increasing pH value and stirrer speed and remains constant with particle size. For the six limestones at the same particle size, the measured dissolution rates per unit area are the same due to the mass-transfer control kinetics; however, the time taken to reach a certain fraction of dissolution is proportional to the molar concentration of the soluble species in the limestone and the initial particle size.     

Synthesis of ZnO nanopowder via an aqueous acetate-citrate gelation method

The synthesis of nanoparticulate ZnO via an aqueous carboxylate gelation route is presented. Starting from a solution of zinc acetate with citric acid as a complexing agent, a solid glassy gel is obtained after drying that is converted into a fine powder by calcination. It is found that a very homogeneous precursor is indispensable when preparing very fine particles with a narrow size distribution. Cryo-transmission electron microscopy (Cryo-TEM) investigation is used as a feedback tool to prevent early precipitation during gelation. Study of the thermal decomposition of the gel shows that ZnO is formed before the final decomposition step takes place. After removing the organic backbone, very small oxide particles are found. The influence of the thermal treatment parameters on the particle size is investigated and a particle growth process is found. By a proper adjustment of the final calcination temperature in dry air, the mean particle size can be controlled between ∼11 and 175 nm. It was also seen that even in inert atmosphere, ZnO is formed and that particle morphology is greatly influenced by the calcination atmosphere.     

Effects of particle size and structure of carbon blacks on the abrasion of filled elastomer compounds

The effects of the particle size and structure of various carbon blacks on friction and abrasion behavior of filled natural rubber (NR), styrene–butadiene rubber (SBR) and polybutadiene (BR) compounds were investigated using a modified blade abrader. The effect of particle size and structure on abrasion resistance should be considered for the optimum design of desired wear properties. Characteristic parameters were introduced from the particle size and the structure of carbon blacks, with a linear relationship between the Young’s modulus and these characteristic parameters. The frictional coefficient depended not only on the particle size, but also on the structure of carbon black. The rates of abrasion were decreased with increasing surface area and developing structure of carbon blacks. Abrasion rates of the compounds were found to be proportional to a power n of the applied frictional work input. It was also observed that BR compounds caused much slower wear than NR and SBR compounds. The worn surfaces of the rubber compounds filled with carbon black having smaller particle size and a more developed structure showed narrower spaced ridges and better abrasion resistance. It means that smaller particle size and better structure development of carbon black resulted in improved abrasion resistance.     

Development of particle size and shape measuring system for machine-made sand

Abstract

In recent years, the use of machine-made sand has gradually increased. Simultaneous monitoring of the particle size and shape of machine-made sand during its production is vital. Here, a machine-made sand size measuring methods were developed using vibration dispersion and high-speed video imaging and subsequently evaluated. Moreover, a software system for particle size and shape identification of machine-made sand was also developed using image processing algorithms. Experiment studies on this system were conducted, and the results show that the measurement results of particle size between the vibration screening method and imaging method are different. The measurement results of particle size obtained from the imaging method were affected by the degree of dispersion and particle shape of the machine-made sand. The particle shape parameter of the machine-made sand was modified to compensate for the measurement results of particle size. After compensation for measurement results of the sand size by the imaging method, the cumulative curve of the particle size distribution was in agreement with that obtained from the vibratory sieve method; the measurement error of sand size is less than 3%. Based on sphericity characterization of the particles, the particle shape measurement using the imaging method was accurate. Thus, the particle size and shape measuring system based on imaging method met the monitoring requirements for machine-made sand.     

Model-assisted feedback control for liquid composite molding

A model-assisted feedback control algorithm, a type of generic model control, is implemented to control cure in resin transfer molding. This control algorithm calculates an apparent temperature of reaction based on the cure data input form a sensor, and this temperature is used to compare the actual rate of reaction to the desired rate and to calculate the mold set-point temperature. The model input into the control algorithm is an empirical cure model of a pre-ceramic polymer with an Arrhenius temperature dependence from 55 to 95 °C. In this work, the effect of varying control parameters is evaluated through cure simulations and experiments. Also, the effect of noise on the controller robustness is evaluated through simulation and experiment. Control parameters are evaluated for 55 and 95 °C.     

pH effect on the aggregation of silver nanoparticles synthesized by chemical reduction

Silver colloidal nanoparticles were prepared according to the chemical reduction method in which the ascorbic acid was used as a reducing agent and sodium citrate as a stabilizing agent. The absorption spectra of all prepared samples obtained using the UV-Vis spectrophotometer showed a surface plasmon peak at a wavelength of about 420 nm. The size of the silver nanoparticles was controlled by changing the pH values of the reaction system. At high pH, smaller size silver nanoparticles were obtained compared to low pH values. This difference can be attributed to the difference in the reduction rate of the precursor. In addition to the inverse proportionality between the size and the pH value it is clear that increasing the pH value enables us to obtain spherical nanoparticles while at low pH, rods and triangular particle shapes were formed. Poor balance between nucleation and growth processes could be the cause of this result.