神舟飞船防热大底结构设计

简要介绍了神舟飞船返回舱上的主要防热部件——防热大底的结构设计特点。从受热、受力和结构合理布局多方考虑,确定防热大底采用大面积烧蚀层和背壁玻璃钢蜂窝夹层结构、整体玻璃钢环的复合结构形式。经过大面积烧蚀计算与温度场分析、局部突起物烧蚀计算与温度场分析、防热大底受气动外压计算分析、静力计算分析以及详细的结构设计,设计出的防热大底较联盟号防热大底轻,结构比“双子星座号”飞船的防热大底简单。经过一系列的地面试验和神舟飞船的三次成功飞行试验,防热大底设计的正确性、合理性得到了充分验证。

不同鞋底结构网球鞋的运动生物力学性能研究

基于网球技术动作特征,根据既有运动鞋生物力学研究成果,本文以止滑试验机、肌电仪、测力板对3种不同鞋底结构网球鞋(A、B、C)的运动生物力学性能差异进行了试验测试。结果发现,虽然不同鞋底结构的网球鞋止滑性与耐磨性不存在显著性差异,但A网球鞋最具止滑性,B网球鞋最具耐磨性;穿着不同鞋底结构的网球鞋时下肢肌肉在各个通道时的做功不存在显著性差异;稳定慢跑持续1 min时,穿着A网球鞋时总做功最大,穿着B网球鞋时次之,穿着C网球鞋时最小,说明C网球鞋可有效降低身体能量消耗,具备一定能量回归作用;穿着B网球鞋与C网球鞋时左右下肢肌肉总做功存在显著线性相关,且存在显著性差异;而穿着A、B、C 3款网球鞋时下肢肌肉总做功差异并不显著。

A Comparison of Macrofauna Communities in Different Mangrove Assemblages

The characteristics of macrofauna communities in three mangrove assemblages [Avicennia marina＋Acgiceras corniculatum （MC）community, A.corniculatum （C） community and Bruguiera gymnorrhiza＋A.corniculatum （GC） community] were studied in Zhanjiang Mangrove Nature Reserves during 2005 and 2006. Of the three mangrove assemblages, the macrofauna species number, density, biomass, Richness index and Shannon-Wiener index were the highest, and the Simpson dominance index was medial at MC community. However the Pielou Evenness index of MC community was slightly lower than that at C community. At C community, the number of macrofauna species obviously reduced, especially infaunal, caving and adhering life forms, and the biomass and density were the lowest. Because of the even distribution of individuals of different species, the Simpson dominance index was the lowest and the evenness index was the highest. Although the Richness index at C community was slightly lower than that at MC community, the Shannon-Wiener index was near to that at MC community. At GC community, the number of macrofauna species, especially infaunal and caving life forms, continued to decrease comparing C community, but the biomass and density increased slightly. As the distribution of individuals of different species was uneven, the Simpson dominance index was the highest and the Pielou Evenness index was the lowest. Furthermore, the Richness index dropped to the lowest. The Shannon-Wiener index also dropped accordingly to the lowest. The dominant life forms of MC were infaunal and caving, while those of C and GC community were both caving. The ratio of the GS/GSB of macrofauna communities in the three mangrove assemblages were 0.48, 0.63 and 0.80, respectively. The community structures at the same mangrove assemblages were all quite similar, with those at GC community being most similar. However, there were obvious differences among the community structures at the three different mangrove assemblages. These results implied that the different mangrove assemblages had different affects on the macrofauna communities and shed light on the macrofauna adaptation capability to specific habitats.

Macrobenthos Community Structure and Its Relations With Environmental Factors in Three Reservoirs in Tianjin

[Objective] The aim was to research macrobenthos community structure and its relations with environmental factors in three reservoirs. [Method] Benthic diversity and water quality of Yuqiao Reservoir, Beidagang Reservoir and Er- wangzhuang Reservoir were investigated in May, July and September 2011, respec- tively. []Result] Of all the 14 sampling sites, 22 species of macroinvertebrates were collected, totally, which included 6 species of aquatic insects, 7 species of Mollusca, 2 species of Crustacean, 7 species of Oligochaeta. The species of macroinverte- brates during May, July and September in Yuqiao reservoir were 11, 8 and 10, respectively. The dominant species were Chironomus sinicus, and Monopylephorus limosus. The average density and biomass of the macrobenthos were 132.43 ind./m2 and 50.09 g/m2. Yuqiao reservoir was mostly at status of premediate polluted, according to the Margalef index, Shannon index and Pielou index. The species of during May, July and September in Beidagang reservoir were 5 5 and 5, respectively. The dominant species were Chironomus sinicus, Penaeus vannamei. The average density and biomass of the macrobenthos were 218 ind./m2 and 2.70 g/m2. Beidagang reservoir was mostly at status of heavy polluted, accord- ing to the Margalef index, Shannon-wiener index, Pielou index. The species of during May, July and September in Erwangzhuang reservoir were 3, 5 and 5, respectively. The dominant species were Monopylephorus limosus, Chi- ronomus sinicus. The average density and biomass of the macrobenthos were 104 ind/m2 and 0.20 g/m2. Erwangzhuang reservoir was mostly at status of intermediate polluted, according to the Margalef index, Shannon index, Pielou index. The density of zoobenthos in Yuqiao Reservoir was positively significantly correlated with TP （P〉 0.05）, negatively correlated with NH4＋-N （P〉0.05）, positively correlated with COD （P〈 0.01）, not significantly correlated with other environment factors （P〉0.05）. There was no significant correlation between biomass of zoobenthos and environment factors. The density of zoobenthos in Beidagang Reservoir with NH4＋-N was positively signif- icantly correlated （P〈0.05）, not significantly correlated with other aquatic environment factors （P〉0.05）. There was no significant correlation between biomass of zoobenthos and environment factors. The density of zoobenthos in Erwangzhuang Reser- voir with NO3-N was positively significantly correlated （P〈0.05）, not significant cor- related with other aquatic environment factors （F〉0.05）. The biomass of zoobenthos in Erwangzhuang Reservoir with NH4＋-N was positively significantly correlated （P〈 0.05）, not significant correlated with other aquatic environment factors （P〉0.05）. [Conclusion] It is indicated that this three reservoirs were all eutrophied and polluted, and the eurephication extent change of water in three reservoirs is as follows： Beidagang reservoir〉Erwangzhuang reservoir〉Yuqiao reservoir.

A 12-Channel,30Gb/s,0.18μm CMOS Front-End Amplifier for Parallel Optic-Fiber Receivers

This paper presents a 12-channel,30Gb/s front-end amplifier realized in standard 0.18μm CMOS technology for parallel optlc-fiber receivers. In order to overcome the problem of inadequate bandwidth caused by the large parasitical capacitor of CMOS photo-detectors,a regulated-cascode structure and noise optimization are used in the design of the transimpedance amplifier. The experimental results indicate that, with a parasitical capacitance of 2pF,a single channel is able to work at bite rates of up to 2.5Gb/s,and a clear eye diagram is obtained with a 0. 8mVpp input. Furthermore, an isolation structure combined with a p^＋ guard.ring （PGR）, an n^＋ guard-ring （NGR）,and a deep-n-well （DNW） for parallel amplifier is also presented. Taking this combined structure, the crosstalk and the substrate noise coupling have been effectively reduced. Compared with the isolation of PGR or PGR ＋ NGR,the measured results show that the isolation degree of this structure is improved by 29.2 and 8. ldB at 1GHz,and by 8. 1 and 2. 5dB at 2GHz,respectively. With a 1.8V supply,each channel of the front-end amplifier consumes a DC power of 85mW,and the total power consumption of 12 channels is about 1W.

Summertime community structure of intertidal macrobenthos in Changdao Archipelago,Shandong Province,China

The community structure of intertidal macrobenthos in Changdao Archipelago(north of Shandong Peninsula,between Bohai Bay and the northern Yellow Sea) was examined based on samples collected from 14 stations in five transects in June 2007.Three stations corresponding to high,medium and low tidal areas were set up for each transect.A total of 68 macrobenthic species were found in the research region,most of which belonged to Mollusca and Crustacea.The average abundance and biomass of the macrobenthos was 1 383 ind./m2 and 372.41 g/m2,respectively.The use of an arbitrary similarity level of 20% resulted in identification of five groups among the 14 stations in the research region.There were remarkable differences in the biomass,abundance and Shannon-Wiener diversity index of the different sediments.Specifically,the order of biomass was rocky shores > gravel > mud-sand > coarse sand > stiff mud,while the order of abundance was rocky shores > coarse sand > mud-sand > gravel > stiff mud,and that of the diversity index was mud-sand > gravel > stiff mud > rocky shores > coarse sand.The above results revealed that the sediment type was the most important factor affecting the structure of the macrobenthic community of the intertidal zone.

Community structure changes of macrobenthos in the South Yellow Sea

The ecological environment in the Yellow Sea has changed greatly from the 1950s to 1990s and this has had significant impact on marine organisms. In this study, data on soft-sediment macrobenthos occurring in depths from 25 m to 81 m in the South Yellow Sea were used to compare changes in community structure. The agglomerative classification (CLUSTER) and multidimensional scaling (MDS) methods were applied. Five communities were recognized by cluster analysis: 1. The Yellow Sea Cold Water Mass community dominated by cold water species, which changed slightly in species composition since the 1950s; 2. The mixed community with the coexistence of cold water species and warm water species, as had been reported previously; 3. The polychaete-dominated eurythermal community in which the composition changed considerably as some dominant species disappeared or decreased; 4. The Changjiang (Yangtze) River Estuarine community, with some typical estuarine species; 5. The community affected by the Yellow Sea Warm Current. The greatest change occurred in the coastal area, which indicated that the change may be caused by human activities. Macrobenthos in the central region remained almost unchanged, particularly the cold water species shielded by the Yellow Sea Cold Water Mass. The depth, temperature and median grain size of sediments were important factors affecting the distributions of macrobenthos in the South Yellow Sea.

Macrobenthic community structure and species composition in the Yellow Sea and East China Sea in jellyfi sh bloom

To understand the characteristics of macrobenthic structures and the relationship between environment and benthic assemblages in jellyfish bloom, we studied the macrobenthos and related environmental factors in the coastal waters of the Yellow Sea and East China Sea. Data were collected during two seasonal cruises in April and August of 2011, and analyzed with multivariate statistical methods. Up to 306 macrobenthic species were registered from the research areas, including 115 species of Polychaeta, 78 of Crustacea, 61 of Mollusca, 30 of Echinodermata, and 22 of other groups. Nine polychaete species occurred at frequencies higher than 25% from the sampling stations： Lumbrineris longifolia, Notomastus latericeus, Nin6e palmata, Ophelina acuminata, Nephtys oligobranchia, Onuphis geophiliformis, Glycera chirori, Terebellides stroemii, and Aricidea fragilis. Both the average biomass and abundance of macrobenthos are higher in August （23.8 g/m^2 and 237.7 ind./m^2） than those in April （11.3 g/m^2 and 128 ind./m^2）; the dissimilarity ofmacrobenthic structures among stations is as high as 70%. In terms of the dissimilarity values, we divided the stations into four clusters in spring and eight in summer. The ABC curve shows that the macrofauna communities in high jellyfish abundance were not changed. Canonical correspondence analysis showed that depth, temperature, median grain size, total organic carbon of sediment and total nitrogen in sediment were important factors affecting the macrozoobenthic community in the study area.

An overview of studies on marine macrobenthic community structure and biodiversity in the Bohai Sea

Due to the further intense human urbanization and industrialization,the environmental problems and climate changes became global issues that we have to face today.Like increasing environmental pollutants,ocean eutrophication,red-tide and acidification are causing irrevocably damages to the marine ecological environment.As an important part of marine ecosystem,macrobenthos plays an essential role in energy flow and substance circulation in the marine ecosystem.Therefore,the study of macrobenthic community structures and diversities were necessary,meanwhile the protection of macrobenthic diversity was also a tough problem.In recent years,many researches were mainly focus on Jiaozhou Bay of the Yellow Sea,the Yangtze Estuary,the coastal of Zhejiang and Fujian Provinces,while seldom on benthic organisms in the Bohai Sea.In this paper,the community structures and diversities of the common macrobenthos in the Bohai Sea were introduced and the macrobenthic response to environmental changes and environmental pollution caused by the construction of the Bohai Sea were also mentioned.The results showed that the large benthic fauna in th Bohai Sea was relatively simple compared to other China seas.There were about 400 species of large benthic organisms.The dominant species were low temperature and wide salt warm water.In the last five years,the annual average biomass was 23.82 g/m^2 and the annual average density was 1498 ind/m^2.The seasonal variation of average habitat density was usually summer autumn spring winter,and the average biomass was usually autumn spring summer winter.Original communities were destroyed and the dominant species appeared to be miniaturized caused by abuse of marine resources.Since the 21st century,the number of crustacean arthropods,bivalve molluscs,and echinoderms have decreased rapidly,but the number of polychaetes and small molluscs increased gradually.With the development of the comprehensive ecological management of the Bohai Sea,the ecological environment and habitat status in the studied area were remedied and improved.Afterwards,the trend of miniaturization was also suppressed.The results of this study presented some existed problems about marine ecological survey and provided some reasonable suggestions for the rational utilization and protection of marine resources.

Effects of a patchy seagrass meadow on the macrobenthic community

Based on macrobenthos collected from intertidal seagrass bed in Guangrao,Shandong Province in May 2013,the macrobenthic structure and diversity were analyzed.A total of 41 macrobenthic species were identified,among which crustaceans were the most speciose macrobenthic taxa(16 species),followed by polychaetes(15 species)and mollusks(10 species).Seven dominant macrobenthic species were identified,including 3 species of polychaetes,2 species of crustaceans and 2 species of mollusks.The total abundance across the whole sampling area was 661.33 ind/m2.Total abundance and the abundance of Potamocorbula laevis and Heteromastus filiformis showed significant spatial variation,and the macrobenthic abundance distributed in seagrass meadows was higher than that in other areas.The results of cluster,nMDS ordination,SIMPER and IMS analyses all showed no linear correlation along the distance gradient from the seagrass meadow.Therefore,degraded seagrass can still provide detectable but limited ecological services.However,the rehabilitation of seagrass bed is essential and urgent to regain their full ecological function.