查看更多>>摘要：The transmission properties of double-ring split ring rcsonator(SRR) arrays and closed ring resonator arrays are measured using terahertz(THz) time-domain spectroscopy. This technique allows for the simultaneous measurement of the amplitude and phase of the transmission coefficient as a function of frequency. The ability to directly measure the phase spectrum is expected to be important in characterizing potential negative index media. In the employed experimental geometry, THz pulses are normally incident on the arrays. Thus, the magnetic field lies in the plane of the arrays and cannot contribute to the magnetic resonance of the SRR. However, it is found that the electric field, when appropriately polarized, can couple to the magnetic resonance. Shifts in the resonance properties with changes in the SRR dimensions and the substrate medium are measured, the results of which are consistent with theory.
查看更多>>摘要：Magnesium oxide(MgO) nanowires were synthesized on the gold-coated Si(100) and MgO(100) substrates at lower temperature (600 ℃) by pulsed liquid injection metal organic chemical vapor deposition (MOCVD). The gold catalyst could be found on the tips of nanowires, which presents the vapor-liquid-solid (VLS) growth mechanism. Reactive species(oxygen or magnesium) have strong effects on the growth of nanowires. Abundant reactive species kill the vertically aligned nanowires to be randomly aligned ones or even change the vertical growth mode to the horizontal growth mode with surface-parallel nanowires. Usually, nanowires with larger aspect ratio (＞10, aspect ratio＝length/diameter), higher density (＞500/μm2 ) and smaller diameter(≤20 nm) can be easily synthesized with longer injection period (≥2 s), smaller injection mass/period(≤4.6 mg) and suitable oxygen partial pressure(2.4 Torr).
查看更多>>摘要：In order to decrease the consumption of reagents and silicon during removal of surface contamination before silicon texturing in solar cell manufacturing industry, a new low-cost surface treatment approach of electrochemical cleaning technique (ECT) is reported. In this technique, a powerful oxidizing electrolyte was obtained from the electrochemical reaction on Boron-doped Diamond(BDD) electrodes, and applied during removal of surface contaminations on silicon wafer surfaces. The slightly polished monocrystalline silicon surfaces after cleaning were compared with the ones of primal silicon wafers. The measurement results show that ECT is quite efficient in removing NaCl and organic contaminants. After cleaning, the contrast test was conducted for the textured silicon wafers with/without pre-treatment(polish) separately. The results show that the size of pyramids on the surface without traditional polishing process is homogeneous and smaller than 4 μm, and the average surface reflectance is much lower in the wavelength range from 400 nm to 800 nm. Therefore, the new technique can save silicon material, and effectively avoid optical losses for improving photoconversion effect of solar cells.
查看更多>>摘要：This paper introduces the basic kinetic and thermodynamic factors affecting step-bunching instability and derive the one-dimensional(1D) step motion equation based adatom diffusion equation for further analysis.The step-bunching instability is analyzed for different cases.
PAN YinsongZHANG ChengweiLIU FenglinYANG Shuaiju...
24-28页
查看更多>>摘要：According to the characteristics of neural signal,a low-voltage and high-speed operational transconductance amplifier has been realized as a direct readout circuit.To reduce the size and cost of this chip,the amplifier uses feedforward compensation technique without Miller capacitor.Using capacitors as a closed-loop feedback not only amplifies the neural signal,but also reduces chip power consumption by replacing the feedback resistor.Simulations were carried out with 0.18 m CMOS technology,and the simulation results satisfied the requirements of neural signal.
查看更多>>摘要：The wavelet transform has remarkable advantages and wide applications in denoising because of its characteristic of good time-frequency.Based on the analysis of traditional wavelet denoising methods,which are based on Fourier transform,an improved method is proposed.It overcomes the shortcomings of the traditional Fourier denoising method.In this paper,the denoising procedures are introduced respectively based on the wavelet transform and the method of connecting the wavelet threshold with the wavelet basis is adopted.Through Matlab simulation and concrete data,it arrives at the conclusion that the method of signal denoising based on the wavelet transform is obviously more effective and better than the traditional method based on Fourier transform.
查看更多>>摘要：In2O3 : SnO2(ITO)thin films were fabricated on the substrate of flexible polyethylene terephthalate(PET)by DC magnetron sputtering from a ceramic target of In2O3/SnO2(90:10).Properties of the thin films were characterized by X-ray diffraction(XRD),four-point probe,Hall-effect measurement,UVVis spectrophotometer,and scanning electron microscopy(SEM).The effects of sputtering pressure,oxygen partial pressure and deposition temperature on properties of microstructure and optoelectronics properties of PET/ITO thin films were investigated in detail.High-quality ITO thin films on PET substrates with the resistivity as low as 8.5×10-4Ω·cm and the optical transmittance over 80% in the visible spectrum range were obtained.
查看更多>>摘要：Based on the structure and bootloader principle of DSP system,a method for the remote updation,debugging and self-loading of DSP system is developed by Ethernet.Hardware circuit and DM9000 driven program are presented and TCP/IP protocol is embedded into DSP.Through the re-mapping of external memory address,it is easy to implement the load of program section selectively and DSP self-boot.The experimental results show that the problem of high cost in system maintenance by conventional field debugging by emulator and the limitation in chip-level boot are resolved.
查看更多>>摘要：Vehicle anti-collision technique is a hot topic in the research area of Intelligent Transport System. The research on preceding vehicles detection and the distance measurement, which are the key techniques, makes great contributions to safe-driving. This paper presents a method which can be used to detect preceding vehicles and get the distance between own car and the car ahead. Firstly, an adaptive threshold method is used to get shadow feature, and a shadow area merging approach is used to deal with the distortion of the shadow border. Region of interest(ROI) is obtained using shadow feature. Then in the ROI, symmetry feature is analyzed to verify whether there are vehicles and to locate the vehicles. Finally, using monocular vision distance measurement based on camera interior parameters and geometrical reasoning, we get the distance between own car and the preceding one. Experimental results show that the proposed method can detect the preceding vehicle effectively and get the distance between vehicles accurately.
查看更多>>摘要：AlSb polycrystalline thin films were prepared by magnetron sputtering with an improved geometric target, and their structural, electrical and optical properties were studied. The results of XRD measurements suggest that the annealed AlSb thin films are Zinc-blende structure with the average size of about 23～31 nm, and the higher temperature promotes the crystallization of the films. The morphology obtained from the AFM measurements reveals that the surfaces of the films are smooth and the particles are uniform with the average size of about 50 nm. Hall Effect measurements show that AlSb films are p-type semiconductors and the test of temperature dependence of dark conductivity in vacuum indicates the conductivity activation energys are 0.05 eV at low temperature and 0.13 eV at a higher temperature. The optical bandgap for a typical AlSb film is 1.52 eV, which is indicated from the optical absorption measurements.
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