Advanced Materials Research Vols. 383-390

Abstract: The S band limits from 2 to 4 GHz, is part of the electromagnetic spectrum’s microwave band. It is used by radars, satellites and some communications. This paper is concerned with the theory and design of 3 GHz feedback type and negative resistance oscillators by using Aiglent ADS software simulator with GaAs ED02AH 0.2-μm technology, and comparison of their results. A lumped element resonator has used in the design of feedback type oscillator and a negative resistance oscillator has utilized a microstrip resonator. The negative resistance oscillator operates at 3.072 GHz with phase noise levels at -99.49 dBc/Hz and -119.6 dBc/Hz at 100KHz and 1 MHz offset frequencies respectively. The phase noise levels of feedback type oscillator are -83.30 dBc/Hz and -103.3 dBc/Hz at 100KHz and 1 MHz offset at oscillation frequency of 3 GHz. Furthermore, we compared the output power of these oscillators and negative resistance oscillator showed 7.124 dBm, and feedback type oscillator presented -10.707dBm.

Abstract: This paper is concerned with the investigation of the effect of magnesium to sulfur ratio on the graphite morphology and estimation of the ranges of this ratio use to produce graphite cast iron at different section sections. The main factors affecting shape of graphite cast iron are the metallurgical structures and the section thicknesses. Cast iron of different shapes of graphite particles directly affect its thermo-mechanical properties. The nodular shape of these graphite particles such as in ductile cast iron improve its mechanical properties, on the other hand, when the shape of these graphite particles become elongated such as in flake graphite cast iron results in improving its thermal conductivity. In between, the worm-like shape of these graphite particles such as in compacted graphite cast iron, make this type of cast iron to have thermo-mechanical properties in between those of ductile and flake graphite cast iron. The different types of ductile , compacted and flake graphite cast iron were produced by means of plunger method at different section thicknesses and the effect of Mg/S ratio on these types of graphite particles was investigated and its range was established.

Abstract: The influence of the real and simulated thermal cycles with different secondary peak temperatures on the properties of the reheated coarse grained heat affected zone (CGHAZ) in the X80 microalloyed steel has been investigated. The four wires tandem submerged arc welding process with different heat input values was used to generate real double passes thermal cycles. The simulated thermal cycles involved heating to the first peak temperature (TP1) of 1400 °C and then reheating to different secondary peak temperatures (TP2) of 700, 800 and 900 °C with cooling rates of 3.75 and 2 °C/s. The toughness of the simulated reheated CGHAZ with different peak temperature was assessed using Charpy impact testing at 0 °C and -50 °C. It is clear that the reheated CGHAZ thermal cycles with different second peak temperatures have a significant effect on morphology of the martensite/austenite (M/A) constituent. The blocky and connected M/A constituent along the prior-austenite grain boundaries as a brittle phase for crack initiation. The Charpy impact results indicated that intercritically reheated coarse grained heat affected zone had less absorbed energy with higher transition temperature and hardness. In the same prior-austenite grain size, cycles 2 and 4 with lower cooling rate (2 °C/s) have larger size of M/A constituents. The M/A constituent size such as mean diameter and length are important factors influencing Charpy impact properties of the simulated reheated CGHAZ.

Abstract: The stabilizer anti-roll bar can prevent the vehicle from rollover, so it is important to get the mechanical properties of it. To achieve it, the finite element technology is chosen and the parametric model was built in the first place. The von Mises stress distribution, reliability and the sensitivity were obtained after being analyzed respectively. Based on these, the fatigue life was estimated finally. The fatigue analysis results were contrasted with the life requirements of stabilizer bar’s endurance test.

Abstract: The converters connected to the power grid, including rectifier and inverter. The rectifier uses DC voltage outer loop control method and the input current inner loop control method, three-phase inverter output current uses SPWM modulation. With the capacity of the system increasing, the capacity of a single converter can no longer meet the requirements, for improving the system's power grid, reliability and efficiency, converters can be paralleled. Parallel operation generates loop current; one of the effective methods of suppressing the loop current is to connect limiting inductance in the inverter AC side. Through simulation, gets the suitable inductance value, and researches the dead zone time affecting on the loop current. When the dead zone times of two modules are not equal, the loop current increases.

Abstract: Appling a high voltage to the dielectric barrier discharge device in a coaxial geometry in flowing argon, a uniform plasma plume is generated at one atmospheric pressure. The waveforms of discharge current and the applied voltage are investigated and results indicate that both the intensity and duration width of the discharge current pulse increase with increasing the applied voltage. The gas temperature of the plasma plume is investigated by using an infrared thermometer. The gas temperature of the plasma plume are functions of gas flow rate, peak value and the frequency of the applied voltage. Results show that the gas temperature increases with increasing the applied voltage or its frequency, while it decreases with increasing the gas flow rate. A qualitative explanation is given for the variance of gas temperature as functions of the experimental parameters by analyzing the waveforms of the discharge current and the applied voltage.

Abstract: A set of experimental device is built，to research the air purification under high voltage and high frequency complex electric fields. The results show that the half time TH will drop while the initial concentration of the aerosol particles reduces in air conditioning room, under high voltage and high frequency complex electric fields only or under the joint action of high voltage and high frequency complex electric fields and the filter. Compared with high voltage and high frequency complex electric fields only，the half time TH is observably reduced when they work together. The time of indoor air purification of air conditioning is greatly shortened. While the initial concentration of the aerosol particles is same, the diameters of aerosol particles are larger; the half time TH is less. The aerosol particles easily removed and the time of air purification is shorter.

Abstract: Mining portable static resistance strain gauge based on ATmega16L is introduced in this paper. It is used to monitor stress of bolt support in coal mines. The strain gauge is high-precision, simple and Chinese-displaying. It offers a more portable testing method of bolt support in coal mines for the workers.

Abstract: To depend on the development platform of the smart car contest, a smart car servosystem, based on Freescale 16-bit HCS12 micro-controller MC9S12XS128, is designed in this paper. The system uses the low-power CMOS digital camera OV6620 to obtain the real-time track information, and extracts the black line on the contest lane with the edge detection method to calculate the position deviation between the car and the black line, with the purpose of distinguishing the different shape of the lane. The nonlinear PD control algorithm for the steering control was given in this paper. Through the photo electrical encoder named YZ30D4S-2NA-200 to attain the real-time car speed, the system uses the nonlinear P strategy to achieve the speed closed-loop control. It is proved that the servosystem can achieve the automatic line patrol control, so as to make the smart car drive stably and quickly.

Abstract: In this paper, based on the analysis of the basic electromagnetic relation for the doubly fed induction generator (DFIG), the fundamental and harmonic equivalent circuits are presented. The harmonic propagation from the stator to the rotor side and in sub-synchronous mode and super-synchronous mode is explained. The model of probabilistic harmonic load flow equivalent circuits for DFIG is presented. Then, the influence of the harmonic from DFIG to a small power system are analysed. Finally, according to the harmonic characteristics of wind turbine, the concept of the probability density function of total harmonic distortion (PDFTHD) is proposed. The impacts on power grid from harmonic propagated by DFIG are analysed by the PDFTHD of each node after the probabilistic harmonic load flow.