Applied Mechanics and Materials Vols. 668-669

Abstract: The transient electromagnetic method (TEM), which is also called time domain electromagnetic method, is one of the common methods of geophysical disciplines of electrical prospecting. This paper, based on theory of the TEM, analysed the application of the embedded technology in TEM, and completed the design of the transient electromagnetic receiver system. The ARM processor is the core part of the system, combined with high precision A/D conversion chip, CPLD module, PC104 and other hardware parts.Through repeated field actual tests, the system works stably and reliably and data acquisition result is favourable.

Abstract: The surface centralized control system of belt transmission of coal mine is the main channel coal transmission in coal mine, whether or not to normally operate directly affect the safety of coal production and economic benefits. With the expansion of coal production, the original capacity and safety of the belt transport cannot meet the development needs of the current. In response to the problems above, this system will the surface belt transmission of coal mine factory. Focus on control, to realize centralized control of the system. And perfect testing and protecting of the most vital part of the system.

Abstract: The paper presents a design of rectangular waveguide-SIW transition, which provides a broadband and low insertion loss performance. The broadband transition is realized by using double-rhombus antenna probe inserted into rectangular metal waveguide. The transition is simulated and measured at 9-20GHz. The measured results show that a good agreement with simulation and an insertion loss less than 2.8 dB and a return loss better than 10 dB are obtained at 10–18.5 GHz for a back-to-back structure.

Abstract: The breakdown mechanism of the 4H-SiC metal-semiconductor field effect transistor (4H-SiC MESFET) at a large drain bias is explored and the dependence of breakdown voltage on the field-plate and the step-channel is investigated by simulation. The results revealed that the breakdown occurs at the corner of the gate near to the drain. The channel step and the field-plate length have sensitive effect on the breakdown voltage. The breakdown characteristics are improved since the electric field peak is lowered at breakdown point in the step-channel and field-plate structures. The largest breakdown voltage can be achieved by optimizing the field-plate length.

Abstract: The low frequency voltage controlled oscillator (VCO) is designed using integrated operational amplifier. The frequency of the output signal of VCO changes with the magnitude of the input signal voltage, and show a linear relationship within a certain range through the experimental test. Experiments show that, under the input of certain amplitude and frequency range of the square wave, triangle wave, saw-tooth wave, the output waveform of VCO respectively is ambulance, fire siren and other kinds of ambulance siren Signal. This innovative design’ cost is low, realized by analog circuit. It can be used in the practice of teaching case, electronic production or development of sound panels.

Abstract: This paper introduces a kind of monolithic emitter switched bipolar transistor (ESBT) for three-phase rectifier applications and other high voltage applications. This paper proposes an improved driving circuit, combining the soft switch circuit. We made a flyback circuit prototype which the rated power is 80W, and the maximum input voltage is 800V, and compared with the existing driving circuit.

Abstract: With the breakthrough of mobility in quantum dot electric field transistors (Q-EFTs), the potential application in these functional devices has revealed and been paid more attentions, due to flexibility in design, low cost, facility for processing and large area. One of the most important applications of FETs is the photoconductive detector. However, these functional FETs have less been reported. In this work, colloidal PbS Q-FETs were successfully fabricated by reasonable structure design and layer-by-layer depositon technique PbS quantum-dots. The bipolar property was demonstrated by the output and transfer characteristics, as devices work in I and III quadrants simultaneously. The mobilities of electron and hole are 0.16 cm²/(V⋅s) and 0.28 cm²/(V⋅s), respectively. Q-FETs work as photoconductive detectors at both positive and negative gate bias voltages. Under constant gate bias, photocurrent increase exponentially with the intensity of light. The responding region consisted with the absorption range of PbS quantum dots. A linearity was found in drain voltage and incidence of laser power, the ratio was attributing to 0.0019 (μW⋅V)^-1.

Abstract: The digital clock is the timing device by using of the digital circuit to implement the digital display for hours, minutes and seconds. Due to the development of the digital integrated circuit and the wide application of the quartz crystal oscillator, the accuracy of the digital clock is far more than the old clocks’. The control part of the design is SCM AT89C51, and the compiler environment is Keil. The software is developed with C language, and the simulation debugging is used Proteus. The digital clock is convenient to people’s production and life, and it expands the original time function of the clocks greatly. Development trend of electronic instrumentation, and has broad market prospects. The clock can be used in many fields, such as the timing automatic alarm, the automatic schedule bell, the time program automatic control, the regular radio, the automatic lights close, the oven timer switch, etc.

Abstract: With the rapid development of desktop computer, its motherboard power consumption has become an important factor. In this paper, experimental research under different conditions of the motherboard components is carried out. We select four kinds of load conditions of empty load, 100% load, one high-definition movie online display and two high-definition movies online display simultaneously. Through the temperature changing, its thermal effect is shown and so as to understand its heat transfer mechanism of desktop computer motherboard. From the experimental results, it is seen that, when working time more than forty minutes, the computer motherboard temperature will reach the maximum value in each operating state.

Abstract: Aiming at the problem of low accuracy and insufficient stability of master clock terminals frequency in Whole-view Test Systems, in this paper, a simple and effective method to Correct frequency of OCXO (Oven Controlled Crystal Oscillator) have been proposed. This approach based on the principle of establishing time system within FPGA, with TDC (Time to Digital Converter) measure the periodic deviation between OCXO and GPS, modifying the value of period within FPGA, reaching the purpose of frequency correction. To reduce the impact of GPS signal jitter, the moving average filter algorithm has been used to tame OCXO quickly. Through simulations and experiments, the clock frequency accuracy is higher than the average 5×10^-10, and the time accuracy is better than 1.8μ/h.