空间用紫外探测及AlGaN探测器的研究进展

文中介绍了与空间应用有关的紫外探测。首先,介绍了美、欧等西方国家在空间天文以及行星、卫星探测等方面多年来的紫外应用情况,包括卫星探测器上搭载的紫外有效载荷;然后,评述了目前在空间使用的紫外探测器状况,以及在未来的空间应用中极具发展潜力的AlGaN紫外探测器;最后,对AlGaN紫外焦平面探测器国内外近年来的研究进展进行了阐述。     

A Highly Parallel Joint VLSI Architecture for Transforms in H.264/AVC

In H.264/AVC, the concept of adapting the transform size to the block size of motion-compensated prediction residue has proven to be an important coding tool. This paper presents highly parallel joint circuit architecture for 8 × 8 and 4 × 4 adaptive block-size transforms in H.264/AVC. By decomposing the 8 × 8 transform to basic 4 × 4 transforms, a unified architecture is designed for both 8 × 8 and 4 × 4 transform and the transform data-path can be efficiently reused for six kinds of transforms. i.e., 8 × 8 forward, 8 × 8 inverse, 4 × 4 forward, 4 × 4 inverse, forward-Hadamard, inverse-Hadamard transforms. Linear shift mapping is applied on the memory buffer to support parallel access both in row and column directions which eliminates the need for a transpose circuit. For reusable and configurable transform data-path, a multiple-stage pipeline is designed to reduce the critical path length and increase throughput. The design is implemented under UMC 0.18 um technology at 200 MHz with 13.651 K logic gates, which can support 1,920 × 1,088 30 fps H.264/AVC HDTV decoder.

Fabrication of the flexible pentacene thin-film transistors on 304 and 430 stainless steel (SS) substrate

Flexible organic thin-film transistors (OTFT) were fabricated on 304 and 430 stainless steel (SS) substrate with aluminum oxide as a gate insulator and pentacene as an organic semiconductor. Chemical mechanical polishing (CMP) process was used to study the effect of the SS roughens on the dielectric properties of the gate insulator and OTFT characteristics. The surface roughness was decreased from 33.8 nm for 304 SS and 19.5 nm for 430 SS down to ～2.5 nm. The leakage current of the metal–insulator–metal (MIM) structure (Au/Al₂O₃/SS) was reduced with polishing. Mobility and on/off ratio of pentacene TFT with bare SS showed a wide range of values between 0.005 and 0.36 cm²/Vs and between 10³ and 10⁵ depending on the location in the substrate. Pentacene TFTs on polished SS showed an improved performance with a mobility of 0.24–0.42 cm²/Vs regardless of the location in the substrate and on/off ratio of ～10⁵. With self assembled monolayer formation of octadecyltrichlorosilane (OTS) on insulator surface, mobility and on/off ratio of pentacene TFT on polished SS was improved up to 0.85cm²/Vs and ～10⁶. I–V characteristics of pentacene TFT with OTS treated Al₂O₃/304 SS was also obtained in the bent state with a bending diameter (D) of 24, 45 or 70 mm and it was confirmed that the device performed well both in the linear regime and the saturation regime.     

An Integration of Source and Jammer for a Decode-and-Forward Two-way Scheme Under Physical Layer Security

In this paper, we propose and analyze the integration of source and jammer for a decode-and-forward two-way scheme under physical layer security where the source nodes not only transmit data signals, but also transmit jamming signals to degrade the quality of eavesdropping links, and a selected relay forwards the combined data signals using an XOR operation. In this proposed protocol, the best relay is chosen by the maximum end-to-end achievable secrecy rate, and the secrecy system performance is evaluated by the exact and asymptotic secrecy outage probability over flat and block Rayleigh fading channels. The Monte-Carlo results are presented to verify the theoretical analysis.     

Modeling Channel Access Delay and Jitter of IEEE 802.11 DCF

With the ever-increasing requirement of WLAN to support real-time services, it is becoming important to study the delay properties of WLAN protocols. This paper constructs a new model to analyze the channel access delay and delay jitter of IEEE 802.11 DCF in saturation traffic condition. Based on this analytical model, average channel access delay and delay jitter are derived for both basic access and RTS/CTS-based access scheme. The accuracy of the analytical model is validated by simulations and furthermore we discuss the impact of initial contention window, maximal backoff stage, and packet size on channel access delay and delay jitter of 802.11 DCF using the proposed model.

互补共形匹配层研究

在运用数值方法求解开域散射问题时,需采用虚拟边界截断分析区域,这不可避免会造成人工反射。比较已存在的吸收边界条件,介绍了一种新型的吸收边界条件。这种方法基于特性互补的两种边界。分别求解两种边界条件下的解然后取平均,可以完全消除人工边界的一次反射。数值结果表明与其它广泛使用的边界条件相比这种方法可以显著减小由反射造成的误差。     

Effects of annealing temperature of aqueous solution-processed ZnO electron-selective layers on inverted polymer solar cells

We investigate the effects of ZnO annealing temperature (T_A) on the performance of inverted polymer solar cells with ZnO electron-selective layers deposited by spin coating aqueous solutions of an ammine-hydroxo zinc complex. The inverted solar cells based on poly(3-hexylthiophene):[6,6]-phenyl-C₆₁-butyric acid methyl ester with T_A as low as 80 °C exhibit power-conversion efficiencies of 3.6%, which is equal to those of devices with higher T_A. Characterizations of the ZnO films using X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, grazing incidence wide-angle X-ray scattering, and optical transmittance measurements show that the abrupt improvement of device performance from T_A = 60 to 80 °C is due to the improvement of energy-level alignment arising from the increases in the relative amount and the crystallinity of ZnO.     

Adaptive Directional Lifting Wavelet Transform VLSI Architecture

Journal of Signal Processing Systems - This paper presents an efficient VLSI architecture of the 2-D wavelet transform for the adaptive directional lifting (ADL) scheme in image coding. To avoid...     

Varactor-tuned combline bandpass filter using step-impedance microstrip lines

In this paper, a varactor-tuned combline bandpass filter using step-impedance microstrip lines is considered so that the absolute passband bandwidth can be maintained nearly constant within the tuning range. The difference between the odd- and even-mode characteristics of the coupled microstrip line makes it difficult to design a tunable bandpass filter with minimum degradation in passband performance. By using step-impedance microstrip lines, couplings between resonators can be controlled so that the constant bandwidth requirement could be satisfied with reasonable design parameter values. Lumped inductors are used for input and output coupling networks. Design equations are derived, and experimental results are compared with theoretical ones based on these equations.     

Characterization of a new type HPV16 E7 variant isolated from cervical cancer highest incidence area in Hubei Province of China

AIM: To investigate the variation and biological properties of HPV16 E7 isolated from cervical cancer biopsy samples from highest incidence area in HuBei province of China. METHODS: HVP16 E7 sequences isolated from the cervical cancer biopsies of 10 local patients were amplified, sequenced and compared with prototype E7 gene. Then the variant gene was cloned into different vectors to study the antigenicity, expression and immunogenicity of its protein by Western blot, immunofluorescence and genetic immunization in vitro or in vivo. RESULTS: The results showed that 7 of 10 samples had the same mutations which led to a nonsense mutation at codon 43 of E7 sequence. The truncated E7 protein could be recognized by standard E7 monoclonal antibody in Western blot and expressed in NIH3T3 cells. In the blood sera of mice immunized intramuscularly by the plasmid DNA expressing the variant E7 gene specific E7 antibodies could be detected at week 2, 3, 5 and 6 after inoculation. However, no specific lymphoproliferation after E7 protein stimulation in vitro was detected by MTT colorimetric assay in comparison to the prototype E7 protein. CONCLUSION: HPV16 E7 gene may show variation in China and the variant protein could be expressed and induce host humoral immune response, but could not elicit special cellular-immune response against it. These data might hold the key for future development of HPV16 vaccine in HuBei province of China.