Temperature effect on threshold voltage and optical property of twisted nematic liquid crystal with applied different voltages

In this paper, temperature-dependent birefringence theory of liquid crystal is used to investigate the temperature effect on the threshold voltage. An expression for describing the non-linear relationship between the threshold voltage and temperature is deduced. In addition, we theoretically discuss the temperature effect on the transmitted ratio of the namatic twisted liquid crystal without the applied voltage and with the applied voltage. It is found that the transmitted ratio is decreased linearly as temperature is increased when the liquid crystal is not applied with voltage, but the transmitted ratio is increased linearly as temperature is increased when the liquid crystal is applied with voltage. The threshold voltages and the transmitted ratio are measured at different temperatures. The experimental data are consistent with the theoretical calculated results.     

Wide range instantaneous temperature measurements of convective fluid flows by using a schlieren system based in color images

In the schlieren method, the deflection of light by the presence of an inhomogeneous medium is proportional to the gradient of its refractive index. Such deflection, in a schlieren system, is represented by light intensity variations on the observation plane. Then, for a digital camera, the intensity level registered by each pixel depends mainly on the variation of the medium refractive index and the status of the digital camera settings. Therefore, in this study, we regulate the intensity value of each pixel by controlling the camera settings such as exposure time, gamma and gain values in order to calibrate the image obtained to the actual temperature values of a particular medium. In our approach, we use a color digital camera. The images obtained with a color digital camera can be separated on three different color-channels. Each channel corresponds to red, green, and blue color, moreover, each one has its own sensitivity. The differences in sensitivity allow us to obtain a range of temperature values for each color channel. Thus, high, medium and low sensitivity correspond to green, blue, and red color channel respectively. Therefore, by adding up the temperature contribution of each color channel we obtain a wide range of temperature values. Hence, the basic idea in our approach to measure temperature, using a schlieren system, is to relate the intensity level of each pixel in a schlieren image to the corresponding knife-edge position measured at the exit focal plane of the system. Our approach was applied to the measurement of instantaneous temperature fields of the air convection caused by a heated rectangular metal plate and a candle flame. We found that for the metal plate temperature measurements only the green and blue color-channels were required to sense the entire phenomena. On the other hand, for the candle case, the three color-channels were needed to obtain a complete measurement of temperature. In our study, the candle temperature was took as reference and it was found that the maximum temperature value obtained for green, blue and red color-channel was ∼275.6, ∼412.9, and ∼501.3 °C, respectively.     

Macrokinetic study on ozone boundary concentration. Effect of temperature

The process of ozone production in pure oxygen using the tubular, high voltage pulse supplied ozonizer was studied. The unusual methodology of conducting kinetics measurements of the ozone synthesis process was presented. It was shown how the process rate changes along the discharge gap. The effect of power density and gas residence time in the discharge gap on the process rate was analysed. The temperature influence on the course of the process, particularly on the ozone boundary concentration and ozone decomposition rate constant, was discussed.     

高速PCB设计中的差分等长处理及仿真验证

在进行高速PCB(Printed Circuit Board)设计时,通常需要对差分信号线的相对时延进行控制,以满足信号完整性要求,因此,如何处理差分线的等长,是需要解决的一个问题。通过分析不同相对时延对差分及共模信号波形的影响,得出相对时延对信号的影响及与信号的上升/下降时间有关,并给出了确定信号上升/下降时间的方法,最后对DSP(Digital Signal Processor)和DDR3(Double Data Rate Tree)内存之间的信号进行了仿真分析,验证了前述分析结果的正确性。     

Synthesis of L-Lysine and L-Glutamic Acid Derivatives with Long Alkyl Chains and Polycondensation of Langmuir-Blodgett Films

Two esters of L-lysine and L-glutamic acid containing long alkyl groups were synthesized and their polycondensation in monolayers and multilayers was investigated. The pressure-area isotherms of the ester of L-lysine depend markedly on the time of residence at the air-water interface. The change of FT-IR spectra of the deposited film, which can be lifted as a Z-type film, indicates that polycondensation can occur in the monolayer at 10°C without any treatment. The spectrum of the film cast from chloroform hardly changed with time. These results lead to the conclusion that a regular arrangement of monomer molecules in the monolayer, where the amino and ester carbonyl groups are concentrated, is more suitable for the polycondensation. The ester of L-glutamic acid can also form stable monolayers which can be easily deposited on a hydrophobic plate as a Y-type film by the Blodgett technique. The polycondensation of multilayers under an atmosphere of triethylamine was investigated by IR spectroscopy. It indicates that the condensation in multilayers proceeds via intermolecular and intramolecular reactions, by which poly(L-glutamate) derivatives and 2-pyrrolidone derivatives are formed, respectively. The condensation in the bulk crystalline powder gives exclusively the 2-pyrrolidone derivative by intramolecular reaction. These results suggest that the monomer molecules in the multilayers are favorably aligned for the intermolecular reaction, in contrast to the situation in the bulk crystalline powder.     

Suppression of Photoinduced BBO Defects Generation on TIO2（110） by Water

We have investigated creation of variable concentrations of defects on TIO2（110）-（1×1） surface by 266 nm laser using temperature programmed desorption technique. Oxygen-vacancy defects can be easily induced by ultraviolet light, the defects concentration has a linear dependence on power density higher than 50 mW/cm2 for 90 s irradiation. No observation of O2 molecule and Ti atom desorption suggests that UV induced defects creation on TiO2（110）-（1×1） is an effective and gentle method. With pre-dosage of thin films of water, the rate of defects creation on TiO2（110）-（1×1） is slower at least by two orders of magnitude than bare TiO2（110）-（1×1） surface. Further investigations show that water can be more easily desorbed by UV light, and thus desorption of bridging oxygen is depressed.     

Contact Angle Determined by Spontaneous Imbibition in Porous Media: Experiment and Theory

In this paper, a theoretical model was established to determine the contact angle by introducing a new defined effective capillary radius into the Lucas–Washburn equation. Based on the theoretical model, capillary rise experiments of water imbibed by different glass beads were carried out to measure the contact angle; the results were similar to the available data published in the literature. In addition, the model was modified to take account of the dynamic contact angle, according to the experimental data. The influence of the dynamic contact angle on the movement of the spontaneous imbibition was studied.     

Synthesis and mesomorphic investigation of calamitic liquid crystalline system ethyl-[4-(4′-decyloxy)benzoyloxy]-benzoate (4-EDBB): A temperature dependent micro-Raman study and DFT calculations

A new liquid crystalline material containing diester linking group ethyl-[4-(4′-decyloxy)benzoyloxy]-benzoate (4-EDBB) was synthesized. The phase transition temperatures were noted by differential scanning calorimetry (DSC), the texture pattern were observed by polarizing optical microscopy (POM) and temperature dependent Raman study was employed to observe the transitions as well as to understand the molecular rearrangement during phase transition. The transitions were observed with all the three techniques but the Raman signature of crystal → smectic A transition is many fold and more precise and accurate. The correlation between intermolecular interaction and phase behaviour has been discussed using temperature dependence Raman data of CH in-plane bending and CO stretching vibrations. With the help of DFT method the possible dimers of 4-EDBB were optimized and the rotational isomers were also investigated. There exists weak hydrogen bonds at room temperature, which breaks as the temperature is increased causing the CH in-plane bending to shift lower and CO stretching vibrations to shift higher. The discussion of the temperature dependent Raman data reveals that at crystal → smectic A transition as a result of intra-molecular rotation the molecules transform from trans- to cis- conformer.     

基于改进极根学习机的回转窑煅烧带温度预测方法

针对传统算法预测回转窑煅烧带温度存在精度低、速度慢的问题,提出了基于改进极限学习机(ELM)的回转窑煅烧带温度预测方法。对ELM输入权值矩阵定义了变换系数,采用黄金分割法在给定区间内搜寻变换系数的最佳值,改进了ELM网络参数的确定方式,弥补了随机确定输入权值并且不作调整的缺陷,在保证ELM训练速度的前提下提高预测精度、减小模型随机性。实验结果表明,改进的ELM预测精度高、训练速度快、模型性能优,可满足工况恶劣的回转窑的生产需要。     

Fuzzy-PID分级控制变水量空调系统温度的研究

针对变水量空调系统温度控制的时变、大滞后、非线性特点,结合模糊控制和PID控制,设计了基于模糊规则切换的Fuzzy-PID分级控制器,并在Matlab/Simulink软件上进行了仿真。仿真结果表明,控制器同时具有模糊控制超调量小、鲁棒性好和PID控制精度高、响应速度快的优点。