Applied Mechanics and Materials Vols. 130-134

Abstract: For the influence of the temperature and current, the power of semiconductor laser fluctuates constantly. So this paper comes up with a new method to solve this problem. The design of peripheral circuit contains two parts: temperature control and power control. The system of temperature control uses special laser temperature control chip, which realizes the accuracy of 0.01°C. The system of power control adopts hardware PI control, over-current protection, over-voltage protection, and temperature protection. Temperature compensation is added to the circuit, which realizes the accuracy of 0.01mW.

Abstract: In this paper, a YIG-tuned oscillator with low phase noise is designed successfully, the frequency range of 3 to 10 GHz, which is based on the theory of oscillation phase noise model and yttrium iron garnet (YIG) sphere’s characteristic. Its typical measure phase noise is-123.3 dBc at 100 kHz offset and-141.2 dBc/Hz at 1 MHz and-148 dBc/Hz at 10 MHz from carrier, and its minimum power output is more than 13 dBm across most of the band. The approach used to design the oscillator circuit will be discussed and test data will be presented.

Abstract: Nanocrystalline ZnS thin films were deposited on glass substrates at 300W and 0.6Pa by using radio frequency magnetron sputtering, and then annealed at different temperatures. This work investigated the influence of ZnS buffer layer on different annealing temperature, analysed structural, surface topography, and optical properties of ZnS films by using X-ray diffraction (XRD), UV-spectroscopy measurements and scanning electronic microscope (SEM) analysis techniques. Findings showed that the film annealed at 300°C was uniformity and compact, which was zinc blende cubic structure. The film exhibited the optical transparency as high as 85% in the visible region, and its optical band gap was calculated to be 3.56 eV.

Abstract: To study damage effectiveness of strong electro-magnetic pulse to components of equipments, the power density in area of MOS circuit, diodes and transistor of a computer is simulated, using the method of the finite-difference time-domain (FDTD). Coupling laws in different areas are achieved, and then judging the damage efficiency of components. Electromagnetic pulse reflects constantly in computer box, causing power density appears oscillations. Energy gradually declines to zero, for it radiates outward from slots. Field concentration around PCB board results in dissociation of field strength, and slows down the attenuation of energy. Finally, formula of power density at random field strength and rise time is also obtained.

Abstract: Aperture coupling is a main coupling mode through which strong electromagnetic pulse can disturb and even damage electronic equipments. The amount, offset and mixed shape of aperture arrays can affect the coupling effect, which is analyzed using finite-difference time-domain (FDTD) method. The field strength coupled increases with the decrease of the slot amount when the total area of aperture is unchanged. The shielding effectiveness is the smallest when the electromagnetic pulse reaches the resonant frequency, which is only affected by the actual structure size of the shielding cavity. Comparing to two direction offset, the single achieved much larger field strength, which is symmetrical about offset center. The coupled field strength is the smallest when the shape of aperture arrays contains round and rectangular.

Abstract: To eliminate errors of 3-axis magnetoresistive magnetometer, according to its offset errors, sensitivity errors and non-orthogonal errors which specialty was considered, an error compensation model of magnetoresistive magnetometer was established. And the calculation method of the error compensation model, which did not need accelerometers, was proposed to correct the magnetometer errors. The results show the algorithm of error compensation model decrease the root mean square error of the magnetometer from 413nT to 82nT. Thus the 3-axis magnetoresistive magnetometer could fast and accurately measure the geomagnetic field.

Abstract: Ca-substituted magnetic-dielectric composites were prepared by the conventional solid-state method. XRD and SEM techniques are employed to investigate the phase composition and microstructure of ferrite particles. The complex permeability, capacity and impedance were measured with HP4291B and 4572A instruments, respectively, in the frequency rage from 1MHz to 1.8GHz. The results showed that a improvement of resistivity and Q factor occurs with the increasing content of CaCO₃. The average grain size and dielectric loss decrease with increasing Ca-additions. It also found CaCO₃ can promote the sintering process.

Abstract: Numerical simulation and experimental analysis for a magnetic circuit model of a damper were carried out by adjusting the size of the auxiliary gap to obtain greater magnetic field strength and wider adjustable multiples of the damping force. Results of experiment indicate that there is a specific ratio of sizes between the auxiliary gap and the working gap; this gap ratio is 3:1. The adjustable multiple and gap ratio is validated by the results of the experiment. The largest value for the magnetic induction in the working gap can reach 80–90% of the maximum; the least value is close to zero, and the adjustable multiple of the magnetic induction is near about a factor of 7. Experimental data also indicate that the law of the magnetic flux leakage is affected by the size of auxiliary gap as well as the intensity and direction of the current. Performance testing of the real optimal damper reveals that the maximum damping force of the damper is 195.7 kN, which is ~92.7 percent of the theoretical maximum value, at a gap ratio of 1:2.5.

Abstract: In this paper, the levitation rigidity for the levitated crossbeam of the gantry numerical control machine tool which can eliminate friction and increase machining precision is discussed. The feedback linearization and sliding mode control methods are presented in this paper in order to achieve steady levitation. The nonlinear electromagnetic levitation system is transformed into linear system by using feedback linearization method. The sliding mode control method is adopted for improving the robustness of the levitation system. Simulation results show that the system has more powerful ability of suppressing disturbance and high rigidity compared with that using conventional PI control method.

Abstract: Processing chamber is important part of high-frequency electromagnetic, water processor, In order to determine what kind of processing chamber has better effect to the anti-scal, the paper simulates electromagnetic energy distribution in two common processing chambers by using the software Ansoft Maxwell, which is based on the finite element method. One processing chamber is set with coaxial electrodes and the other one is wrapped by spirals, both are composed by high-frequency electromagnetic pulses. According to the simulation data, electromagnetic energy of processing chamber with coaxial electrodes is much bigger than that of spiral wrapped process chamber. Meanwhile, a mini–circulating water system is built and water quality experiments are completed. Analysis results from experimental data illustrate that two kinds of processing chambers under high-frequency pulsed field have anti-scaling effects, but the processing chamber with coaxial electrodes is much better.