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Haiyan Chen Jizhi Dai Yongzhi Liu 《Journal of Infrared, Millimeter and Terahertz Waves》2004,25(5):749-757
The effect of fog and clouds in millimeter communication is discussed, and the attenuation caused by fog and clouds is reviewed. Signal-to-noise ratio (SNR) of image is derived using relating models of fog and clouds attenuation. According to the relation of image quality and its signal-to-noise ratio, the system behavior is forecasted theoretically. It is shown that the signal-to-noise ratio of receiver at certain transmitter power is inverse with radio wave frequency, from about 70dB at 10GHz to 48dB for fog and 49dB for clouds. The image quality of received signal at certain transmitter power is inverse with radio wave frequency, from about 7 grade at 10GHz to 5.27 grade for fog and 5.37 grade for clouds. The above calculated results are consistent with experimental results. 相似文献
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本文介绍了Windows环境下基于消息的DDE和基于动态链接库的DDEML的区别,并详细叙述了如何使用DDEML编制Windows应用程序。 相似文献
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利用引进的制造技术和设备,制作出了 APT(STLRI)—1.78型系列化光纤连接器。 相似文献
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Enhanced light output in nitride-based light-emitting diodes by roughening the mesa sidewall 总被引:1,自引:0,他引:1
Chia-Feng Lin Zhong-Jie Yang Jing-Hui Zheng Jing-Jie Dai 《Photonics Technology Letters, IEEE》2005,17(10):2038-2040
In this letter, we will report on a nitride-based light emitting diode with a mesa sidewall roughening process that increases light output power. The fabricated GaN-based light-emitting diode (LED) wafers were first treated through a photoelectrochemical (PEC) process. The Ga/sub 2/O/sub 3/ layers then formed around the GaN : Si n-type mesa sidewalls and the bottoms mesa etching regions. Selective wet oxidation occurred at the mesa sidewall between the p- and the n-type GaN interface. The light output power of the PEC treated LED was seen to increase by about 82% which was caused by a reduced index reflectance of GaN-Ga/sub 2/O/sub 3/-air layers, by a rough Ga/sub 2/O/sub 3/ surface, by a microroughening of the GaN sidewall surface, and by a selective oxidation step profile of the mesa sidewall that increases the light-extraction efficiency from the mesa sidewall direction. Consequently, this wet PEC treated process is suitable for high powered nitride-based LEDs lighting applications. 相似文献
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Out-of-plane microlenses and microoptical fiber holder are two of the most important components for building an integrated
microoptic system with a precise alignment accuracy. In this paper, a simple and convenient method to fabricate these components
from SU-8 by using inclined UV lithography in water is proposed. It consists of two perpendicular exposures in SU-8 at ±45°.
DI water possesses a low absorption coefficient and a moderate and stable value of refractive index in near UV. Using water,
the exposure angle in SU-8 can be increased to 50° from 35° in air necessary to pattern the desired 45° slope of the sidewalls.
The principle of the proposed technique and the detailed fabrication process of the microoptic components will be presented.
The integratability of the fabricated components was demonstrated by the fabrication of the microoptical fiber holder with
a pre-aligned out-of-plane microlens. 相似文献
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A high‐melt‐strength polypropylene (HMSPP) was prepared using a twin‐screw reactive extruder from a commercial isotactic polypropylene through two stages, first, maleic anhydride is grafted to polypropylene to obtain a maleic anhydride‐grafted polypropylene (PP‐g‐MA), and then the grafted polymer is reacted with epoxy to extend the branched chain. Fourier transformed infrared spectroscopy indicated that maleic anhydride was grafted on polypropylene and reacted with epoxy. Melt flow rate and sag resistance test showed that the melt strength of the HMSPP improved considerably. Differential scanning calorimetry test showed that the long chain branches (LCBs) act as a nucleating agent in the crystallization of the HMSPP, which leads to a high crystallization temperature and crystallinity. Furthermore, the LCB efficiency of the HMSPP can also be calculated by analyzing its rheological property. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers 相似文献
10.
Local residence time,residence revolution,and residence volume distributions in twin‐screw extruders
Xian‐Ming Zhang Lian‐Fang Feng Sandrine Hoppe Guo‐Hua Hu 《Polymer Engineering and Science》2008,48(1):19-28
This work was aimed at studying the overall, partial, and local residence time distributions (RTD); overall, partial and local residence revolution distributions (RRD) and overall, partial and local residence volume distributions (RVD) in a co‐rotating twin screw extruder, on the one hand; and establishing the relationships among them, on the other hand. Emphasis was placed on the effects of the type and geometry of mixing elements (a gear block and various types of kneading elements differing in staggering angle) and process parameters on the RTD, RRD and RVD. The overall and partial RTD were directly measured in‐line during the extrusion process and the local ones were calculated by deconvolution based on a statistical theory. The local RTD allowed comparing the mixing performance of mixing elements. Also it was confirmed both experimentally and theoretically that specific throughput, defined as a ratio of throughput (Q) over screw speed (N), controlled all the above three types of residence distributions, be they local, partial or overall. The RRD and RVD do not provide more information on an extrusion process than the corresponding RTD. Rather they are different ways of representing the same phenomena. POLYM. ENG. SCI., 48:19–28, 2008. © 2007 Society of Plastics Engineers 相似文献