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Stobart B Teleki K Buckley R Downing N Callow M 《Philosophical transactions. Series A, Mathematical, physical, and engineering sciences》2005,363(1826):251-255
Changes in reef benthos were assessed at Aldabra Atoll following the mass coral bleaching event of 1998. Video transects were used to survey the benthos and analysed using the Australian Institute of Marine Science five-dot method. Comparison of coral cover data collected by the Cambridge Southern Seychelles Atoll Research Programme with data collected during this study revealed that mortality of coral at Aldabra following the bleaching event was approximately 66% at 10 m depth and 38% at 20 m depth. Five years on, there are signs of hard coral recovery at some locations, but in spite of several years of high coral recruitment (7-9 recruits per m2 at 10 m depth, 4-6 recruits per m2 at 20 m depth, where recruits are defined as any colony under 5 cm maximum diameter), recovery of hard coral has not occurred at a significant level. There has been a considerable increase in soft coral cover at some locations, which was dominated by the genus Rhytisma. Macro algal cover did not increase following the bleaching event, although, as would be expected, dead corals have been colonized by coralline algae. There have been no further events leading to large-scale coral mortality at Aldabra since 1998. 相似文献
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M Pan J Suárez de Lezo A Medina M Romero E Hernández J Segura F Melian F Wangüemert M Landin F Benítez M Amat F Velasco A Torres 《Canadian Metallurgical Quarterly》1997,80(10):1336-1338
Two hundred twenty-eight patients with successful coronary stent implantation were randomized either to protamine administration and femoral sheath removal (group I, n = 117) or no heparin neutralization and delayed sheath removal (group II, n = 111). The hospital stay after treatment was shorter in patients receiving protamine; therefore, protamine use for neutralizing circulating heparin may be safely administered immediately after stent implantation. 相似文献
85.
Ben Flood Brett Houlding Simon P. Wilson Sergiy Vilkomir 《Quality and Reliability Engineering International》2010,26(1):83-96
Traditional approaches toward modeling the availability of a system often do not formally take into account uncertainty over the parameter values of the model. Such models are then frequently criticized because the observed reliability of a system does not match that predicted by the model. This paper extends a recently published segregated failures model so that, rather than providing a single figure for the availability of a system, uncertainty over model parameter values is incorporated and a predictive probability distribution is given. This predictive distribution is generated in a practical way by displaying the uncertainties and dependencies of the parameters of the model through a Bayesian network (BN). Permitting uncertainty in the reliability model then allows the user to determine whether the predicted reliability was incorrect due to inherent variability in the system under study, or due to the use of an inappropriate model. Furthermore, it is demonstrated how the predictive distribution can be used when reliability predictions are employed within a formal decision‐theoretic framework. Use of the model is illustrated with the example of a high‐availability computer system with multiple recovery procedures. An BN is produced to display the relations between parameters of the model in this case and to generate a predictive probability distribution of the system's availability. This predictive distribution is then used to make two decisions under uncertainty concerning the offered warranty policies on the system: a qualitative decision and an optimization over a continuous decision space. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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在阐述直升机红外辐射特征和面临的威胁基础上,对直升机红外辐射特性抑制的原理进行了阐述。回顾了直升机红外辐射抑制技术的研究进展,详细分析了各种红外辐射抑制技术的特点和适用范围。直升机红外辐射特性抑制技术主要有红外抑制器抑制技术、红外诱饵弹等干扰技术、热红外隐身涂料涂层技术、地面停放伪装遮障隐蔽技术等。其中,红外抑制器抑制技术采取混流装置以降低热空气温度,采用耐高温隔热遮挡装置隔绝高温部位等。红外诱饵弹等干扰技术利用其中的烟火剂燃烧产生高温时释放出的大量红外特征信号,达到干扰红外侦察和红外制导武器打击的目的。热红外隐身涂料涂层技术通过涂层自身较低的红外发射率,有效降低直升机表面红外辐射特性,实现与空地背景的较好融合。地面停放伪装遮障隐蔽技术采用具有光学、红外、雷达等隐身性能的伪装器材,实现直升机多波段隐身和防风、防雨、防沙尘等性能。最后,对未来红外隐身技术的研究进行了展望。 相似文献
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Ben Leslie Peter Chubb Nicholas Fitzroy-Dale StefanGotz Charles Gray Luke Macpherson Daniel Potts Yue-Ting Shen and Kevin Elphinstone 《计算机科学技术学报》2005,20(5):654-664
Running device drivers as unprivileged user-level code, encapsulated into their own process, has often been proposed as a technique for increasing system robustness. However, in the past, systems based on user-level drivers have generally exhibited poor I/O performance. Consequently, user-level device drivers have never caught on to any significant degree. In this paper we demonstrate that it is possible to build systems which employ user-level device drivers, without significant performance degradation, even for high-bandwidth devices such as Gigabit Ethernet. 相似文献
89.
温度是影响半导体激光器(LD)寿命和输出特性的重要因素之一。为保证LD输出稳定的激光模式和功率,采用以ADC和DAC集成的微处理器芯片C8051F350和具有双极性输出电流的TEC驱动芯片MAX1968为控制核心,以积分分离和变速积分增量式相结合的数字PID算法为运算程序的自动温度控制系统(ATC)控制TEC驱动电流的方向和大小,实现对LD的加热或制冷,使其工作在恒定温度。实验证明,应用该系统,LD在0℃~40℃环境温度范围内能很快稳定在设定温度,且其不确定度为±0.03℃。 相似文献
90.
天然气水合物储运技术研究进展 总被引:8,自引:1,他引:8
近年来,天然气水合物储运技术引起了广泛的关注,并得到了快速发展。文章首先介绍了天然气运输的多种方式,进而分析了常见天然气储运方式的物理特性及其经济性,接着着重介绍了天然气水合物的基本特性、天然气水合物储运的基本原理和技术路线,分析了天然气水合物制备技术、储存技术和分解技术等的特点,最后概述了提高水合物储气效率的措施和相关研究进展等。此外,还对天然气水合物储运技术的应用前景进行了展望 相似文献