摘要: The threading dislocation density (TDD) of thick GaN films grown by hydride vapor phase epitaxy (HVPE) was estimated through counting etch pit density (EPD) and calculating full width at half maximum(FWHM)of double crystal X-Ray diffraction (DCXRD). TDD was about 108 through counting EPD, while it was about 109 through calculating the FWHMs of (0002) and (10î2). The experiment results show that the two methods are both suited to estimating the TDD of the thick HVPE-GaN films with 350um thickness. But they have some difference: EPD method is fitter in evaluating the dislocation density of the surface of thick GaN film, but FWHM method can gain the total dislocation density of thick GaN film. The method calculating the FWHMs possesses more general statistical significance.
摘要: Automatic transmission may produce busy shifting on uphill and downhill. This article analyzes three algorithms about the estimation of road ramp: the first using a longitudinal acceleration, the second using estimated output torque, and the third using the difference between two accelerations. The first method is more accurate than the other two, but it is more expensive because an additional acceleration sensor is needed. The second is more complicated and in some driving conditions, it could not estimate the output torque. The third is based on simple theory and inexpensive since no additional sensor is needed. Some simulation results of avoiding unnecessary gear-shifting are also presented in the paper.
摘要: An experimental paltform for simulating the starting process of a PFI engine was set up. The contrastive analysis of prototype engine between conventional start with starting motor and high-speed cranking start with ISG (Integrate Starter/Generator) was carried out. Variation regulation of the transient engine speed, the cylinder pressure, the fuel compensation factor, the intake manifold pressure and the transient HC emission were elaborated. The results show that, with the increase of cranking speed, the intake air pressure dropped, and the intake air quantity reduced as well. The duration of fuel evaporation was shortened, so the fuel atomization was insufficient. The possibility of misfire was increased and the transient HC emission was prominent. All these phenomena had a close relationship with ECT (Engine Coolant Temperature). Fuel compensation in the first few working cycles during starting process could make the original lean mixture more preferable in order to improve the combustion environment.
摘要: The mode matching method is applied to analyze generalized ridged waveguides. The tangential fields in each region are expressed in terms of the product of several matrices, i.e., a functional matrix about x-F(x), a functional matrix about y-G(y) and a column vector of amplitudes. The boundary conditions are transformed into a set of linear equations by taking the inner products of each element of G(y) with weight functions. Two types of ridged waveguide are calculated to validate the theory. Several new modes not reported in previous analysis are presented.
摘要: On many occasions, gas phase and liquid phase of original mixture needed to be measured in the processes of petroleum, chemical, natural gas and other industry. A system of gas-liquid separation and metering were studied deeply in this paper. Kingview was taken as the software of the system. It realized dynamic show of the system state and generated various reports. Three of the functional modules were mainly introduced in the software design. The nucleus part of the system was the PID module. Its function was to regulate the aperture of the valve properly. The interface design of supervisory and report management is also described in detail. The testing on the spot has proved that system function and accuracy can meet the needs completely. The system has the characteristics of reasonable structure and stable performance. It provided a better solution to the means of gas-liquid separation.
摘要: For the purpose of measuring the micro changes of morphological parameters of melon organ, this paper put forth a new algorithm based on mathematical morphology and spline interpolation to obtain the phenotype information of melon such as area and horizontal and vertical diameter and developed a high-resolution non-destructive and contactless measuring system based on vision processing to get the projection area of melon and its diameter. The algorithm is easy to carry out, and can get more ideal edge information than some traditional algorithms. It supplies theoretical basis for revealing the combined response relationship and temporal and spatial variation character between melon morphologies and key environmental factors.
摘要: It’s very difficult to get high precision measuring result using contact torquemeter because of very low signal-to-noise ratio. To overcome this defect, a wireless torque measuring system is designed based on CC2500. This system uses strain gauge torque sensor to measure the surface principal stress of the transmission shaft, and get the maximum shearing stress, and then the torque that the transmission shaft bears. The weak output signal of torque sensor is magnified by the instrumentation amplifier AD623, and sent to the analog-to-digital convertor. These digital data are transmited to the portable receiving terminal by the wireless transceiver chip CC2500. The dynamic wireless torque measurement is realized by this system.
摘要: A new method, triboelectricity and ultrasonic, for the soot mass flow measurement is developed. The direct rod-shaped sensor is used to measuring the triboelectricity charge and the ring sensor is used to measuring the electrostatic induction charge. The pure-triboelectricity can be figured out and the pure-triboelectricity is eliminated the influence of the electrostatic induction. Through the numerical simulation, the proportion between the electrostatic induction charge and the electrostatic induction charge is presented. The gas flowrate is measured by the ultrasonic. The soot mass flow can be figured out through the pure-triboelectricity and the gas velocity. Additionally, the sample calibration equipment based on the pure-triboelectricity and ultrasonic method is also introduced. Experimental results show the method can on-line measure the soot mass flow.
摘要: Based on the theory of Fabry-Perot interference, we analyzed the inherent relationship between single-wavelength and the spectrometry, established the mathematical model of transformation from angular spectrum measurement to spectral measurement,realized the data conversion between angular spectrum measurement and spectrum measurement; build the experimental platform and got the laser's transmittance by changing the incidence angle of the laser, and given the comparison experiment by using spectrophotometer, measured the spectral transmittance of filters. Comparison of the two measurement, the results show that:it is a feasible scheme that the angular spectrum measurement replace spectral measurement for filter transmittance .
摘要: In vibration measure the signal processing system of Gaussian model was abnormal for the pulse noise environment. So it was necessary to find other model and transform the traditional signal processing method. Studies showed that the Alpha stable distribution was better to describe these non-Gaussian signals. After studying the property of Alpha stable distribution and the fractional lower order statistics theory, we altered the wavelet transform. The method was that the fractional lower order statistics replaced the 2-order statistics in the traditional wavelet algorithm. Experimental vibration measure system including some sensors on the spindle or other measure points collected the vibration signals and sent to computer. The results show that the alteration wavelet transform system can effectively restrain the pulse noise and reduce the signal distortion. The new signal processing system can achieve the generalized de-noising function including re-Gaussian distribution.