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991.
Summary The synthesis of new high optical abrasion resistance coating materials has been undertaken by functionalizing melamine and
tris(m-aminophenyl)phosphine oxide with a triethoxysilane containing reagent. These highly functionalized compounds have been
used for coating a bis-phenol-A polycarbonate substrate by the sol-gel method. Preliminary data shows the abrasion resistance
of the polymer substrate is considerably improved when it is coated by these optically clear materials. 相似文献
992.
Tajiri A. Minakuchi K. Komeda K. Bessho Y. Inoue Y. Yodoshi K. Yamaguchi T. 《Electronics letters》1993,29(4):369-370
A highly reliable 200 mW AlGaAs laser diode with a fundamental transverse mode has been developed, by optimising its structure with a 0.8 mu m thick p-cladding layer, a 1200 mu m long cavity length, and a front facet coating with a low reflectivity of 2%. The maximum output power was 500 mW, and stable fundamental transverse mode operation was obtained up to 350 mW. Stable operation under 200 mW and 50 degrees C was confirmed for more than 1200 h. Optical feedback noise was below 3*10/sup -14/ Hz/sup -1/.<> 相似文献
993.
The noise characteristics of semiconductor laser amplifiers (SLAs) in the Ga1-xInxAs/GaInAsP/InP strained quantum well (QW) system are theoretically calculated and analyzed using density-matrix theory and taking into account the effects of band mixing on both the valence subbands and the transition dipole moments. The numerical results show that a reduced noise figure can be obtained in both tensile and compressively strained QW structures due to the increase in differential gain and the decrease in transparent carrier density. From a comparison among compressively strained (x=0.70), unstrained (x=0.53), and tensile strained (x=0.40) QW SLAs at a fixed carrier density and optical confinement factor, it is found that the noise figure of the tensile strained QW reaches its lowest value of 3.4 dB at average input optical power of -20 dB 相似文献
994.
R.N. ARNOLD K.K. SCHELLER S.C. ARP S.N. WILLIAMS D.M. SCHAEFER 《Journal of food science》1993,58(1):28-33
The effect of long-term feeding (252 days) of three supplemental levels of α-tocopheryl acetate (actual 0, 360 and 1290 IU/head/day) on meat quality was evaluated in Holstein and beef breed steers. Tissue vitamin E concentrations were increased by each increment of supplementation. The color display life of fresh beef under simulated retail conditions was extended 2 to 5 days by vitamin E and lipid oxidation was markedly reduced. Microbial population was not affected by level of supplementation. No deterioration in sensory quality occurred for steaks from supplemented steers that were displayed until the time steaks from unsupplemented steers discolored. 相似文献
995.
R. Borkowska J. Laskowski J. Płocharski J. Przyłuski W. Wieczorek 《Journal of Applied Electrochemistry》1993,23(10):991-995
Results for the performance of lithium/Mn02 batteries containing solid polymer electrolytes based on poly(ethylene oxide) blends with some acrylic derivatives are presented. The ionic conductivities of the electrolytes are promising for battery application. It was found, however, that interfacial phenomena impair the battery efficiency. Impedance spectroscopy shows resistive limitations at the anode interface of the batteries, caused either by formation of an electrically distinguishable resistive layer or by chemical interaction between the polymer and lithium, influencing, most probably, the kinetics of the lithium oxidation reaction. 相似文献
996.
R Labonte 《Canadian Metallurgical Quarterly》1994,21(2):253-268
Recent reformulations of health promotion focus on empowerment as both a means and an end in health promotion practice. Both concepts, however, are rarely examined for their assumptions about social change processes or the potential of community groups, professionals, and institutions to create healthier living situations. This article attends to some of these assumptions, expressing ideas generated during 6 years of professional training workshops with over 2,500 community health practitioners in Canada, New Zealand, and Australia. The article first argues that health promotion is not a social movement but a professional and bureaucratic response to the new knowledge challenges of social movements. As such, it has both empowering and disempowering aspects. The article analyzes empowerment as a dialectical relation in which power is simultaneously given and taken, and illustrates this in the context of health promotion programs. A model of an empowering professional (institutional) health promotion practice is presented, in which linkages among personal services, small group supports, community organizing, coalition advocacy, and political action are made explicit. Practice examples are provided to illustrate each level of the empowering relation, and the article concludes with a brief discussion of the model's educational and organizational utility. 相似文献
997.
Optoelectronic buses for high-performance computing 总被引:2,自引:0,他引:2
Chiarulli D.M. Levitan S.P. Melhem R.G. Bidnurkar M. Ditmore R. Gravenstreter G. Zicheng Guo Chungming Qiao Sakr M.F. Teza J.P. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1994,82(11):1701-1710
Modern computer buses are typically organized by the three functions of data transfer, addressing, and arbitration/control. In this paper we present a fiber-based bus design which provides optical solutions for each of these functions. The design includes an all-optical addressing system, based on coincident pulse addressing, which eliminates the latency contribution and bandwidth limitation associated with electronic address decoding. The control system uses time-of-flight relationships between a priority chain and a feedback waveguide to implement fully distributed asynchronous and self-timed bus arbitration 相似文献
998.
999.
GaAs MESFETs were fabricated using a spin-on platinum source as the gate material. They were subsequently aged at 200°C for up to 1000 h. DC electrical characterisation of the MESFETs was carried out during various stages of annealing. The aging behaviour of these MESFETs was compared with those fabricated using conventionally evaporated platinum sources. The results show that the performance of the MESFETs fabricated using a spin-on platinum source is comparable to those of MESFETs fabricated using a conventionally evaporated platinum source 相似文献
1000.
Fractal error for detecting man-made features in aerial images 总被引:3,自引:0,他引:3
A technique is proposed for aiding photointerpreters in detecting man-made features in aerial reconnaissance images. The technique, which uses a metric called fractal error, is based on the observed propensity of natural image features to fit a fractional Brownian motion model. Man-made features usually do not fit this model well, and consequently the fractal error metric may be used as a discriminant function for detecting man-made scene features 相似文献