Successive multiuser detection and interference cancelation for contention based OFDMA ranging channel [transactions letters]

In this letter, we propose a successive multiuser detector (SMUD) for contention based OFDMA ranging channel compliant to the IEEE 802.16 (WiMAX) standard. A ranging channel consists of a set of subcarriers in specific time slots shared by multiple users, so the multiple access interference (MAI) limits the performance of ranging detectors. Different from existing methods that treat the MAI as noise, the proposed SMUD successively detects the channel paths of active ranging signals and cancels their interference for further detection. This approach significantly suppresses the MAI and improves both user detection and parameter estimation performance.     

Correlation investigation between contact approach speed of handheld metal rod and discharge parameters from charged human body

Characteristic measurement of contact discharge currents are made through a hand-held metal rod from charged human body. Correlation coefficients are obtained, through Statistic Package for Social Science （SPSS）, for various charge voltages, which is based on the effect test of electrode contact approach speeds on discharge current parameters of current peaks, maximum rising slope and spark lengths. Discharge parameters at charge voltage 300V are independent on approach speed. For charge voltages equal to and higher than 500V, the contact approach speed has strong positive correlation with discharge parameters of the peak current and the maximum rising slope, whereas has strong negative correlation with the spark length.     

High-sensitivity temperature sensor based on long-period fiber grating

Temperature sensitivity is greatly improved by taking the following three measures： proper long-period fiber grating （LPFG） whose strain coefficient of the core is larger than that of the cladding is employed, the LPFG is coated with a thin film of the material whose refractive index decreases with the temperature, and the sensor is encapsulated by metal material whose thermal expansion coefficient is large. By computer simulation, a measured temperature coefficient of 0.2375 nm/℃ and a temperature resolution less than 0.1 ℃ are obtained.     

GaN/metal/Si heterostructure fabricated by metal bonding and laser lift-off

A process methodology has been adopted to transfer GaN thin films grown on sapphire substrates to Si substrates using metal bonding and laser lift-off techniques. After bonding, a single KrF (248 nm) excimer laser pulse was directed through the transparent sapphire substrates followed by low-temperature heat treatment to remove the substrates. The influence of bonding temperature and energy density of the excimer laser on the structure and optical properties of GaN films were investigated systemically. Atomic force microscopy, X-ray diffraction and photolumi-nescence measurements showed that (1) the quality of the GaN film was higher at a lower bonding temperature and lower energy density; (2) the threshold of the energy density of the excimer laser lift-off GaN was 300 mJ/cm~2. The root-mean-square roughness of the transferred GaN surface was about 50 nm at a bonding temperature of 400 ℃.     

MOCVD于高温AlN模板上生长的AlGaN材料

A high temperature AlN template was grown on sapphire substrate by metalorganic chemical vapor deposition.AFM results showed that the root mean square of the surface roughness was just 0.11 nm.Optical transmission spectrum and high resolution X-ray diffraction（XRD）characterization both proved the high quality of the AlN template.The XRD（002）rocking curve full width at half maximum（FWHM）was about 53.7 arcsec and（102）FWHM was about 625 arcsec.The densities of screw threading dislocations（TDs）and edge TDs wereestimated to be - 6 × 10^6 cm^-2 and - 4.7 ×10^9 cm^-2. AlGaN of Al composition 80.2% was further grown on the AlN template. The RMS of the surface roughness was about 0.51 nm. XRD reciprocal space mapping was carried out to accurately determine the Al composition and relaxation status in the AlGaN epilayer. The XRD （002） rocking curve FWHM of the AIGaN epilayer was about 140 arcsec and （102） FWHM was about 537 arcsec. The density of screw TDs was estimated to be - 4 × 10^7 cm^-2 and that of edge TDs was - 3.3 × 10^9 cm^-2. These values all prove the high quality of the AlN template and AlGaN epilayer.     

Orthogonal-directional forward diffusion image inpainting and denoising model

In this paper, an orthogonal-directional forward diffusion Partial Differential Equation （PDE） image inpainting and denoising model which processes image based on variation problem is proposed. The novel model restores the damaged information and smoothes the noise in image simultaneously. The model is morphological invariant which processes image based on the geometrical property. The regularization item of it diffuses along and cross the isophote, and then the known image information is transported into the target region through two orthogonal directions. The cross isophote diffusion part is the TV （Total Variation） equation and the along isophote diffusion part is the inviscid Helmholtz vorticity equation. The equivalence between the Helmholtz equation and the inpainting PDEs is proved. The model with the fidelity item which is used in the whole image domain denoises while preserving edges. So the novel model could inpaint and denoise simultaneously. Both theoretical analysis and experiments have verified the validity of the novel model proposed in this paper.     

提高对抗复合末制导的质心干扰方案研究

质心干扰是水面舰艇抗击来袭导弹的一种有效手段。随着现代导弹技术的发展,末制导方式已趋于多样化,这对传统质心干扰作战使用提出了严峻的挑战。针对这一问题,在对新型反舰导弹末制导方式及其特点分析的基础上,叙述了传统质心干扰方式在对抗复合末制导过程中存在的不足,提出了一种能够有效对多制导方式进行干扰的质心干扰方案。并对此方案进行了定量和定性分析,建立了干扰空域和时域效能的数学模型,对干扰效果进行了仿真和评估。最后给出此干扰方案在作战使用中的几点建议和思考。     

透明导电GZO薄膜电学和光学性能的研究进展

ZnO因其价格便宜、无毒等优点,最有希望替代昂贵的掺锡氧化铟ITO,但未掺杂ZnO是高阻材料,如何提高其光电性能,制备出高质量的ZnO薄膜是实现其应用的关键。其中,Ga掺杂是提高ZnO性能的一种有效手段。从制备方法、掺杂浓度、生长条件等方面综述了Ga掺杂ZnO(GZO)薄膜光电性能的研究进展,归纳总结后发现:适当增加掺杂量、提高衬底温度等都有利于薄膜光学和电学性能的提高。目前,GZO薄膜电阻率最低可达10-3～10-4Ω.cm,透光率一般可达80%以上,光电性能可以满足透明导电膜的要求,但其性能的稳定性还不如广泛使用的ITO。因此,GZO薄膜要达到实际应用要求,尚需进一步优化工艺,提高其性能的稳定性。     

ANSYS在VLSI互连模拟中的应用

介绍了ＡＮＳＹＳ程序在ＶＬＳＩ互连几何最佳化设计中的初步应用,应用表明：ＡＮＳＹＳ的模拟精度高,图形显示功能强,应用ＡＮＳＹＳ自动寻优功能使延迟最佳化几何参数的寻找较为迅速和直观。