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大口径反射镜组件发射段环境的防振设计 被引量:4
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作者 宫辉 陈伟 周峰 《航天返回与遥感》 北大核心 2015年第3期40-47,共8页
主反射镜组件力学性能是相机结构设计的重点。文章介绍了反射镜组件的基本构型,分析了采用Bipod支撑结构的反射镜组件振动抑制的必要性。基于阻尼受迫振动模型微分方程,分析了频率比、阻尼比对随机振动传递率的影响,根据分析结果选择增... 主反射镜组件力学性能是相机结构设计的重点。文章介绍了反射镜组件的基本构型,分析了采用Bipod支撑结构的反射镜组件振动抑制的必要性。基于阻尼受迫振动模型微分方程,分析了频率比、阻尼比对随机振动传递率的影响,根据分析结果选择增大阻尼比作为反射镜组件振动抑制方案。对某1.8m口径反射镜组件进行了抑振设计,利用MSC Nastran软件进行了动力学分析,仿真结果显示,抑振后反射镜动力学响应值及振动应力有较大降低,证明抑振设计有效。文章设计的振动抑制解决方案也可为空间遥感器其他部组件的振动抑制设计提供借鉴。 展开更多
关键词 阻尼模型 大口径 反射镜组件 发射环境 振动抑制 航天遥感
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体外模拟发酵探究KGM和KOS与不同胃肠段微环境的影响 被引量:1
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作者 张琪 孙瑞 +2 位作者 贾晓倩 张阳 钟耕 《食品与发酵工业》 CAS CSCD 北大核心 2020年第6期25-32,共8页
不同胃肠段微环境对机体健康的影响及其与膳食纤维的相互作用是目前研究的热点。该文为探究魔芋葡甘聚糖(konjacglucomannan,KGM)和魔芋葡甘低聚糖(konjac oligosaccharides,KOS)与不同胃肠段微环境的影响,分别以KGM和KOS为碳源,采用YCF... 不同胃肠段微环境对机体健康的影响及其与膳食纤维的相互作用是目前研究的热点。该文为探究魔芋葡甘聚糖(konjacglucomannan,KGM)和魔芋葡甘低聚糖(konjac oligosaccharides,KOS)与不同胃肠段微环境的影响,分别以KGM和KOS为碳源,采用YCFA培养基培养不同胃肠段微生物,同时做葡萄糖(glucose)和不加碳源的空白对照,测定不同发酵液pH值、黏度、菌落总数、短链脂肪酸(short-chain datty acids,SCFAs)、总糖及还原糖含量。与对照相比,随着发酵时间的延长,添加KGM和KOS的发酵液pH降低,SCFAs含量增加,菌落总数增加;KGM显著增加胃及小肠发酵液黏度,总糖和还原糖含量略有降低,大肠发酵液中还原糖含量先增加后减少。KGM和KOS可调节不同胃肠段发酵液环境,增加微生物数量及代谢产物含量,从而更有利于机体健康,为KGM和KOS的应用提供新思路。 展开更多
关键词 不同胃肠环境 魔芋葡甘聚糖 魔芋葡甘低聚糖 体外模拟发酵
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基于舱段数据的整船冲击环境组合预报方法
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作者 吴静波 黄式璋 +1 位作者 郭君 温岩岩 《噪声与振动控制》 CSCD 2019年第3期113-117,121,共6页
随着舰载设备抗冲击研究的不断发展,能否准确预报水下圆柱壳的整体冲击环境对于设备的布置与安装具有重大意义。对圆柱壳进行水下爆炸试验是一种具有较高可信度的研究手段,但成本巨大,相对而言,舱段试验较为容易方便。对比舱段与整体水... 随着舰载设备抗冲击研究的不断发展,能否准确预报水下圆柱壳的整体冲击环境对于设备的布置与安装具有重大意义。对圆柱壳进行水下爆炸试验是一种具有较高可信度的研究手段,但成本巨大,相对而言,舱段试验较为容易方便。对比舱段与整体水下圆柱壳的冲击环境差异,发现水下圆柱壳与舱段的冲击环境差异主要集中于低频段,水下圆柱壳的低频响应以低阶振动模态为主,而舱段的低频响应以刚体运动为主。根据上述差异,结合经验模态分解法、船体梁理论,提出以舱段冲击环境数据来预报整个圆柱壳冲击环境的组合方法,得到较高的拟合精度。 展开更多
关键词 振动与波 冲击环境、预报、舱、冲击谱
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全球导航卫星系统体系化发展趋势探讨 被引量:19
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作者 曹冲 《导航定位学报》 2013年第1期72-77,共6页
本文对全球导航卫星系统(GNSS)发展的最新动向和演变的重大趋势,进行了全方位多层次的研究。GNSS的系统之系统和天地一体化系统集成,导航系统与通信系统的互补化组合渗透,多系统室内外应用与服务的体系化融合构建,均已成为大家关注的焦... 本文对全球导航卫星系统(GNSS)发展的最新动向和演变的重大趋势,进行了全方位多层次的研究。GNSS的系统之系统和天地一体化系统集成,导航系统与通信系统的互补化组合渗透,多系统室内外应用与服务的体系化融合构建,均已成为大家关注的焦点。许多事实表明,GNSS已经进入发展的重大转折期。确切地说,GNSS概念业已从全球导航卫星系统转变为全球导航卫星服务,进而步入时空智能服务发展新时期,实际上是从技术系统向产业服务体系的转变,应该在其本身进一步完善和总体创新的同时,需要脱胎换骨的转变,进入一个泛在服务导航系统与产业发展的新兴领域,关键是要构建全新的体系,这就是新时空服务体系,本文对此进行了简要的阐述和探讨。 展开更多
关键词 GNSS 环境段 室内定位 室内外无缝导航 泛在导航 协同定位 全源感知 普适传输 智能服务 新时空服务体系
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小卫星随机振动特性分析与试验验证方法探讨 被引量:9
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作者 杨新峰 赵志明 +1 位作者 邓卫华 扈永强 《航天器环境工程》 2014年第4期357-362,共6页
通过试验数据分析了小卫星随机振动响应特性,探讨了组件质量与小卫星随机响应的变化关系,并提出了地面随机振动响应与板面密度关系的一个经验公式。针对某小卫星发射过程中测量得到的主动段振动数据,分析总结了小卫星的主动段振动特性,... 通过试验数据分析了小卫星随机振动响应特性,探讨了组件质量与小卫星随机响应的变化关系,并提出了地面随机振动响应与板面密度关系的一个经验公式。针对某小卫星发射过程中测量得到的主动段振动数据,分析总结了小卫星的主动段振动特性,着重探讨了小卫星主动段振动特性与地面试验的振动特性差异,给出了修正地面试验验证的一些建议。 展开更多
关键词 小卫星 随机振动试验 噪声试验 主动振动环境
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Evaluation of Environmental Impacts of Traction Motor Production and Disposal 被引量:2
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作者 李书华 李君 +3 位作者 李楠楠 卢强 佟达夫 高莹 《Transactions of Tianjin University》 EI CAS 2013年第6期413-418,共6页
By the application of life cycle assessment(LCA) methodology, this paper estimates the environmental impacts of production and disposal of traction motors used in electric vehicles in China. The results show that the ... By the application of life cycle assessment(LCA) methodology, this paper estimates the environmental impacts of production and disposal of traction motors used in electric vehicles in China. The results show that the total energy use, the criteria emissions and the greenhouse gases(GHG) emissions of a traction motor production and disposal are about 2,899,MJ, 4.5,kg and 259.5,kg per motor, respectively. Among the regulated emissions, the SOxemission ranks first by total mass, followed by CO, PM10, NOx, PM2.5, and volatile organic compound(VOC). The motor material production stage accounts for most of the energy consumption and emissions, followed by the assembly stage and the end-of-life disposal stage. In this study, the environmental performance analysis is extended to the comparison between the use of secondary material and primary material for the material production stage. It is found that using 100% secondary material results in a 52.9% reduction in energy consumption, a 49.8% reduction in regulated emissions, and a 49.3% reduction in GHG emissions compared with the use of 100% primary material. 展开更多
关键词 environmental impact life cycle assessment traction motor secondary material
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Vertical patterns in plant diversity and their relations with environmental factors on the southern slope of the Tianshan Mountains(middle section)in Xinjiang(China) 被引量:17
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作者 LIU Bin 《Journal of Mountain Science》 SCIE CSCD 2017年第4期742-757,共16页
The investigation of distribution patterns of species diversity is significant for successful biodiversity conservation. The spatial patterns of vegetation and different life-forms species diversity along an elevation... The investigation of distribution patterns of species diversity is significant for successful biodiversity conservation. The spatial patterns of vegetation and different life-forms species diversity along an elevation gradient in the middle section of the southern slope of the Tianshan Mountains in Xinjiang, China were explored, using the detrended canonical correspondence analysis (DCCA) and the generalized additive model (GAM) methods based on a field survey of 53 sampling plots. In this work 158 species of seed plants were recorded, including 141 herbaceous, 14 shrub, and 2 tree species, in which the woody plants are very limited. 53 sampling plots were classified into 9 major plant communities. The results indicate that the herb communities were the most sensitive to changes in elevation gradient. The diversity indices of the community as a whole presented bimodal patterns. The peak values for the species diversities were found in the transition region between mountain steppe desert and mountain desert steppe (2,200-2,300m), and in the alpine grassland region (2,900-3,100m), while maximum species diversities were in the areas of intermediate environmental gradient. The main environmental factors on the distribution patterns in plant diversity were the elevation, soft water, total nitroeen, available nitrogen, organic matter, and total salt. The response tendency of the four diversity indices for the whole community to the soil environment was the same as that of the herb layers. 展开更多
关键词 Species diversity Distribution pattern Plant community Soil properties Tianshan Mountains
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Extended Active Contour Algorithm Based on Color Variance
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作者 Seung-tae LEE Young-jun HAN Hern-soo HAHN 《Journal of Measurement Science and Instrumentation》 CAS 2010年第1期50-53,共4页
General active contour algorithm, which uses the intensity of the image, has been used to actively segment objects. Because the objects have a similar intensity but different colors, it is difficult to segment any obj... General active contour algorithm, which uses the intensity of the image, has been used to actively segment objects. Because the objects have a similar intensity but different colors, it is difficult to segment any object from the others, Moreover, this algodthm can only be used in the simple environment since it is very sensitive to noise. In tinter to solve these problems. This paper proposes an extended active contour algorithm based on a color variance. In complex images, the color variance energy as the image energy is introduced into the general active contour algorithm. Experimental results show that the proposed active contour algorithm is very effective in various environments. 展开更多
关键词 extended active contour algorithm color variance segmentaion method
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Zooplankton community structure in relation to environmental factors and ecological assessment of water quality in the Harbin Section of the Songhua River 被引量:2
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作者 李晓钰 于洪贤 马成学 《Chinese Journal of Oceanology and Limnology》 SCIE CAS CSCD 2014年第6期1344-1351,共8页
To study the relationship between zooplankton community structure and environmental factors and water quality in the Harbin Section of the Songhua River,investigations were carried out in June,August,and October 2011.... To study the relationship between zooplankton community structure and environmental factors and water quality in the Harbin Section of the Songhua River,investigations were carried out in June,August,and October 2011.Canonical correspondence analysis(CCA) and saprobic indices were used to process and analyze the data.Seasonal variability was identified as a significant source of variation,which explains the fluctuation in zooplankton density.In autumn,the dry season,water residence time increased and zooplankton biomass and abundance accumulated in the slow flowing waters.Zooplankton abundance increased when food conditions improved.Therefore,the total zooplankton abundance in autumn is much higher than that in spring and summer.According to the saprobic indices,all the sample sites had mesosaprobic water and water quality was worse in autumn.CCA revealed that temperature accounted for most of the spatial variation in the zooplankton community.Moreover,pH,dissolved oxygen saturation,and turbidity were important factors affecting zooplankton community distribution. 展开更多
关键词 ZOOPLANKTON canonical correspondence analysis (CCA) Saprobic index HARBIN Songhua River
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Stone Columns and Tensioned Anchors to Completely Eliminate Tunnels Trough Settlements
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作者 Ampeglio Diego Garini 《Journal of Civil Engineering and Architecture》 2015年第10期1202-1209,共8页
The complex tunnelling constructive environment in urban area in similar green field situations is faced through analytical evaluations in order to control the design calculation process and subsequently manage the in... The complex tunnelling constructive environment in urban area in similar green field situations is faced through analytical evaluations in order to control the design calculation process and subsequently manage the interventions techniques with the aim of totally reducing the typical settlements trough above the tunnel either during the construction stage or during the serviceability stage. Recently, the author has proposed an operative and mathematical method by an opportune choice of tensioned anchors to control the tunnel lining settlements. In order to completely eliminate the remainder typical soft soil trough which is normal to the line of the tunnel, it is here proposed to use and properly calculate the interventions of stone columns by the SAVE (silent, advanced, vibration-erasing) Compozer method, in combination with the anchorages. 展开更多
关键词 ANCHORAGES SAVE Compozer method stone columns tunnel lining tunnel trough.
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