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环脊式PDC钻头破岩机理实验研究 被引量:9
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作者 杨迎新 胡浩然 +2 位作者 黄奎林 谢宗亮 于洪波 《地下空间与工程学报》 CSCD 北大核心 2019年第5期1451-1460,共10页
环脊式PDC钻头是一种采用不连续布齿原理在井底形成易破碎岩石环脊的钻头技术新思想。在不同岩性、不同岩脊尺寸等条件下,开展了针对岩脊的牙轮牙齿的单齿静压和PDC齿刮切破岩单元实验,以及针对平整表面岩石的对比实验;设计制造了全尺... 环脊式PDC钻头是一种采用不连续布齿原理在井底形成易破碎岩石环脊的钻头技术新思想。在不同岩性、不同岩脊尺寸等条件下,开展了针对岩脊的牙轮牙齿的单齿静压和PDC齿刮切破岩单元实验,以及针对平整表面岩石的对比实验;设计制造了全尺寸可变参数实验钻头,并进行了环脊式PDC钻头与常规PDC钻头的室内钻岩对比实验。实验研究结果表明:与平整岩样的实验相比,牙轮牙齿和PDC齿在岩脊上的切削破碎载荷和破碎比功均显著降低;在全尺寸钻头钻岩实验中,与同等布齿密度条件下的常规PDC钻头相比,环脊式钻头的破岩比功显著降低,破岩效率明显提高;环脊式PDC钻头在钻进过程中有明显的体积性破碎现象,岩屑的尺寸或粒度显著增大,有利于地质录井。 展开更多
关键词 PDC钻头 井底岩石 环脊 破岩机理 岩屑
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脊加载环板行波管高频特性的研究 被引量:1
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作者 宫玉彬 王文祥 +2 位作者 魏彦玉 孙嘉鸿 刘盛纲 《电子学报》 EI CAS CSCD 北大核心 2000年第3期64-68,共5页
脊加载环板行波管是一种频带相对较宽的大功率行波管 ,本文用场匹配和变分原理相结合的方法 ,研究了脊加载环板慢波结构的导波特性及这种行波管的小信号、大信号特性 ,讨论了结构的几何尺寸及电子注参量对慢波的传播特性、小信号增益及... 脊加载环板行波管是一种频带相对较宽的大功率行波管 ,本文用场匹配和变分原理相结合的方法 ,研究了脊加载环板慢波结构的导波特性及这种行波管的小信号、大信号特性 ,讨论了结构的几何尺寸及电子注参量对慢波的传播特性、小信号增益及注 波互作用非线性效应的影响 .本文的结果将为脊加载环板行波管的设计提供理论基础 . 展开更多
关键词 加载 行波管 慢波系统 高频特性
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新型脊杆环撑索穹顶结构静力性能分析 被引量:17
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作者 张爱林 白羽 +1 位作者 刘学春 孙超 《空间结构》 CSCD 北大核心 2017年第3期11-20,共10页
索穹顶结构是一种结构效率极高的大跨预应力空间结构,适用于体育馆、展览会馆等大跨度场馆的屋盖结构.为解决传统索穹顶结构脊索易发生松弛、斜索数量多等不足,丰富索穹顶结构方案,提出一种新型预应力空间结构——脊杆环撑索穹顶结构,... 索穹顶结构是一种结构效率极高的大跨预应力空间结构,适用于体育馆、展览会馆等大跨度场馆的屋盖结构.为解决传统索穹顶结构脊索易发生松弛、斜索数量多等不足,丰富索穹顶结构方案,提出一种新型预应力空间结构——脊杆环撑索穹顶结构,具有无脊索松弛现象、承载能力提高、斜索数量少等优点.建立了脊杆环撑索穹顶的有限元模型,进行静力分析,研究结构在满跨、半跨均布活荷载的组合工况下弹性阶段的受力特点.进一步进行参数分析,探讨了结构基本参数对脊杆环撑索穹顶的杆件内力、节点位移及失效荷载的影响规律.分析结果表明,脊杆环撑索穹顶具有良好的静力性能,避免了脊索易松弛退出工作的缺点,结构整体刚度大于传统索穹顶,施工难度降低.结合初始预应力、矢跨比、斜索与水平夹角、构件截面及总截面面积等结构参数的影响规律,给出结构设计建议,为脊杆环撑索穹顶结构的工程应用提供依据. 展开更多
关键词 撑索穹顶 结构体系 预应力 静力性能 参数分析
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Sedimentary Environment Analysis of Ancient Sand Ridges from Zk23 Hole in the East China Sea
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作者 杜文博 叶银灿 庄振业 《Marine Science Bulletin》 CAS 2009年第2期72-80,共9页
Abstract: Based on the analysis of core samples from the hole of Zk23 in the East China Sea Continental Shelf and by means of sedimentary stratigraphy, biostratigraphy and chronostratigraphy, the authors consider tha... Abstract: Based on the analysis of core samples from the hole of Zk23 in the East China Sea Continental Shelf and by means of sedimentary stratigraphy, biostratigraphy and chronostratigraphy, the authors consider that the fine-sand deposition in borehole was part of buried ancient estuary sand ridges of the Yangtze River. The deposition history of study area around the hole before and after the glacial period as well as postglacial period is made clear after our research: (1) the estuarine sublayer -undersea delta facies strata was deposited under the fast sea level rise about 15 kaB.P; (2) sand ridges mostly consisting of fine-sand, were formed when the sea level was the fluctuant range of 60 - 80 m of isoba during the deglacial period around 15 - 12 kaB.P; (3) first silty clay and clay silt strata above the sand ridges were deposited during the period when the sea level rose fast from 12 to 7 kaB.P, and then it keeps stable to the present. 展开更多
关键词 ancient sand ridges sedimentary environment East China Sea Continental Shelf
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Single-stage Posterior Spondylectomy, Circumferential Decompression and Reconstruction Using Mesh Cage for Spinal Tumors 被引量:1
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作者 Yong Zhu Hong Zhao Giu-xing Qiu Jian-guo Zhang Ye Tian Shu-gang Li Suo-mao Yuan 《Chinese Medical Sciences Journal》 CAS CSCD 2009年第3期172-177,共6页
Objective To explore the feasibility and clinical results of circumferential decompression and three column reconstruction through single-stage posterior transpedicular approach for spinal tumor treatment. Methods Tot... Objective To explore the feasibility and clinical results of circumferential decompression and three column reconstruction through single-stage posterior transpedicular approach for spinal tumor treatment. Methods Totally, 24 patients with spinal tumor underwent tumor resection and spinal reconstruc tion through single-stage posterior transpedicular approach. Preoperatively, according to the Frankel classification, 12 patients were grade E, 9 grade D, and 3 grade C. Anterior column was reconstructed with non-expandable titanium cages. Posterior segmental instrumentation was used to maintain the stability of spine in all cases. Anterior and posterolateral fusion was performed with autograft and allogenic bone. The following data were followed up in these patients: deformity angle, local recurrence, neurological function, and spinal bony fusion. Results The average operating time and blood loss was 5.6 hours and 3 400 ml respectively. No intraoperative and postoperative complications were observed in this group. Postoperatively, 21 patients were Frankel grade E, 2 grade D, and 1 grade C. Four patients reported significant functional restoration and twenty patients reported complete resolution of pain. At follow-up (range, 6-42 months), implant failure or recurrent neurological symptoms was not found. Conclusions The tumor resection and spinal reconstruction through single-stage posterior transpedicular approach is a safe and effective technique for the treatment of spinal tumor. It can fully decompress the neurological structures, correct the kyphosis, and achieve early weight-bearing. This technique can improve life quality for the patients with spinal tumor. 展开更多
关键词 spinal tumor VERTEBRECTOMY spinal reconstruction
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某车辐式双层索系屋盖结构介绍
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作者 李东强 《建筑与设备》 2011年第2期46-48,共3页
通过对某商场大跨度圆伞型采光屋面结构的介绍,简要阐述了的车辐式双层索系结构的结构体系,供类似结构设计提供一定的参考。
关键词 车辐式双层索系 外桁架压(谷)索下索 内拉飞柱系统
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Major Accumulations of Life and Main "Pain Points" in the Seas and Oceans
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作者 Yuvenaly Zaitsev 《Journal of Environmental Science and Engineering(A)》 2012年第7期886-897,共12页
Because of permanent matter and energy accumulation in the sea marginal biotopes, communities of organisms adapted to these specific conditions are developed. Terms contour biotopes and contourobiont's communities we... Because of permanent matter and energy accumulation in the sea marginal biotopes, communities of organisms adapted to these specific conditions are developed. Terms contour biotopes and contourobiont's communities were proposed. These habitats are populated by a great variety of organisms with numerical superiority of early stages of development of hydrobionts. Therefore, contour biotopes are responsible for the reproduction of many species of plants and animals, including commercialiy ~rnportant species of invertebrate and fish. But as a result of natural physical and chemical processes, the same habitats accumulate many substances that are harmful to living organisms, especially for early ontogenetic stages. So here formed main hotspots, critical ecological zones in seas and oceans, which need to be monitored in the first place. Understanding of the key role of contour biotopes and communities in marine ecological processes development is an ecological imperative. Making of ecological diagnoses, prediction of possible departures from the ecological norm and prevention of serious negative events in the marine environment needs special consideration of contour biotopes and their inhabitants, which are underestimated in traditional marine biological and ecological investigations. 展开更多
关键词 Marine environment contour biotopes contourobionts HOTSPOTS ecological diagnosis.
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REE (Rare Earth Element) Geochemistry Signature of an Articulated Horse from Pleistocene Deposits of Fossil Lake, Oregon
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《Journal of Earth Science and Engineering》 2013年第6期401-410,共10页
REE (Rare Earth Element) signatures in fossil vertebrates from different stratigraphic units are sufficiently distinctive to allow identification of the original unit or location in which fossilization occurred. Our... REE (Rare Earth Element) signatures in fossil vertebrates from different stratigraphic units are sufficiently distinctive to allow identification of the original unit or location in which fossilization occurred. Our field studies at the classic Pleistocene site of Fossil Lake, Oregon, reveal at least nine exposed depositional packages, most separated by disconformities. Bones analyzed from eight of the defined packages have distinctly different REE signatures. By accruing an extensive REE data library, samples with nebulous origin can be compared to this data library to determine the best stratigraphic context of the fossil. The research involves an articulated horse from the Ferruginous Sandstone unit at Fossil Lake. This unit shows subtle lithological changes which may indicate differences in depositional environment. The recovered specimen transected these subtle variations of this unit. Since REE reflect depositional environment this specimen offers a unique opportunity to investigate the possible variations in a signature due to subtle changes in lithology. This was accomplished by collecting bone and sediment material from 1 cm increments. By relating subtle changes in lithology to possible variations in REE signature, this study will offer a better resolution for application of REE signatures to Paleoenvironmental interpretations, fossil provenience and stratigraphic correlation. 展开更多
关键词 PLEISTOCENE sediments Fossil Lake rare earth elements bioapatite.
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Effects of Electroacupuncture on Expression of COX-2 in the Dorsal Horn of Spinal Cord of Arthritic Rats 被引量:1
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作者 徐红 王彦青 +3 位作者 汪军 俞瑾 吴根诚 朱忠春(Translator) 《Journal of Acupuncture and Tuina Science》 2006年第5期264-266,共3页
Objective: The present study was to observe the expression of COX-2 protein in the dorsal horn of the spinal cord in rats with chronic inflammatory pain to investigate whether COX-2 is involved in the mechanism of el... Objective: The present study was to observe the expression of COX-2 protein in the dorsal horn of the spinal cord in rats with chronic inflammatory pain to investigate whether COX-2 is involved in the mechanism of electroacupuncture (EA) analgesia. Methods: After EA treatment, the pain score and expression of COX-2 protein in the dorsal horn of spinal cord in rats with complete Freund's adjuvant (CFA)-induced arthritis were measured by the behavioral test and immunohistochemistry technique, and compared with those of the normal group, model group and medicine group. Results: EA could decrease the pain score significantly and repeated EA treatments had the remarkable cumulative analgesic effect; and with the increase in EA treatments, the number of COX-2 immunoreactive cells was obviously decreased. Conclusion: EA at acupoints Yanglingquan (GB 34) and Kunlun (BL 60) had remarkable analgesic effect on adjuvant arthritis rats; and in the meantime, could inhibit the expression of COX-2 protein in the dorsal horn of spinal cord. 展开更多
关键词 ELECTROACUPUNCTURE Complete Freund's Adjuvant Arthritis Spinal Dorsal Horn
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Seasonal changes on two different spatial scales: response of aquatic invertebrates to water body and microhabitat
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作者 WILCO C.E.P. VERBERK HEIN H. VAN KLEEF +3 位作者 MARTIJN DIJKMAN PAUL VAN HOEK PETER SPIERENBURG HANS ESSELINK 《Insect Science》 SCIE CAS CSCD 2005年第4期263-280,共18页
Knowledge about the spatial and temporal scales of both habitat use and the functional significance of different adaptations is essential for an understanding of the population dynamics of invertebrate assemblages. Th... Knowledge about the spatial and temporal scales of both habitat use and the functional significance of different adaptations is essential for an understanding of the population dynamics of invertebrate assemblages. This fundamental knowledge is not only interesting from an academic point of view, but is sorely lacking and needed in the field of restoration ecology. Many species are threatened due to degradation. Knowing what environmental conditions are needed dtLring the life cycle of these species is important in the design of restoration measures which aim to lift existing bottlenecks for threatened species. To assess the relative importance of water type and microhabitat in structuring the invertebrate assemblage during different seasons, invertebrates were sampled in three water bodies differing in trophic level and acidity. Different parts within a water body (microhabitats) were sampled separately and each water body was sampled in all four seasons. Results show that water body is an important factor structuring the invertebrate assemblage early in the season, whereas microhabitat became more important later in the season. Structural complexity of microhabitats was related to the type of locomotion employed by invertebrates. Seasonal differences could be related to population dynamics (reproduction, mortality). Moreover, fluctuations in resource availability were expected to differ between the water bodies, with highest fluctuations in the eutrophic water body and with fluctuations becoming less predictable later in the season. This was confirmed by the data: species synchronization to pulses in food availability was strongest in the eutrophic water body. Moreover, synchronization was strongest in summer, while in autumn waters were invaded by dispersive species. Based on these results a synthesis is presented on the functioning of the different waters during the different seasons. 展开更多
关键词 dispersal fluctuations in resource availability FOOD SUBSTRATE SYNCHRONIZATION
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Environmental factors determining growth of salamander larvae: A field study
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作者 Laura LIMONGI Gentile Francesco FICETOLA +1 位作者 Giuseppe ROMEO Raoul MANENTI 《Current Zoology》 SCIE CAS CSCD 2015年第3期421-427,共7页
Larval growth and survival of organisms are strongly influenced by abiotic and biotic factors, as demonstrated by ex- perimental studies performed under controlled laboratory or semi-natural conditions. Even if they h... Larval growth and survival of organisms are strongly influenced by abiotic and biotic factors, as demonstrated by ex- perimental studies performed under controlled laboratory or semi-natural conditions. Even if they have many advantages, ex- periments cannot cover the full complexity of natural conditions and field studies are needed for a better understanding of how environmental variation determines growth and development rate. Fire salamander Salamandra salamandra females give birth to larvae in a variety of habitats, both epigean and subterranean. In caves, salamander larvae successfully grow and metamorphose, but their growth is more than three times longer than in epigean streams and factors determining these differences require inves- tigation. We performed a field study to understand the factors related to the growth of fire salamander larvae in different envi- ronmental conditions, evaluating the relationship between environmental features and larval growth and differences between caves and epigean spring habitats. Both caves and epigean larvae successfully grew. Capture-mark-recapture allowed to individu- ally track individuals along their whole development, and measure their performance. Growth rate was significantly affected by environmental variables: larvae grew faster in environments with abundant invertebrates and few conspeciflcs. Taking into ac- count the effect of environmental variables, larval growth was significantly lower in caves. Food availability plays a different ef- fect in the two environments. Larval growth was positively related to the availability of invertebrates in epigean sites only. The development rate of hypogeous populations of salamanders is slower because of multiple parameters, but biotic factors play a much stronger role than the abiotic ones 展开更多
关键词 Spring FRESHWATER CAVE AMPHIBIANS SALAMANDRA CANNIBALISM
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电真空器件
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《电子科技文摘》 2000年第10期17-17,共1页
001609835GHz 三次谐波低电压回旋管理论研究[刊]/黄勇//电子学报.—2000,28(3).—73~76(C)0016099脊加载环板行波管高频特性的研究[刊]/宫玉彬//电子学报.—2000,28(3).—64~68(C)脊加载环板行波管是一种频带相对较宽的大功率行波管... 001609835GHz 三次谐波低电压回旋管理论研究[刊]/黄勇//电子学报.—2000,28(3).—73~76(C)0016099脊加载环板行波管高频特性的研究[刊]/宫玉彬//电子学报.—2000,28(3).—64~68(C)脊加载环板行波管是一种频带相对较宽的大功率行波管,本文用场匹配和变分原理相结合的方法,研究了脊加载环板慢波结构的导波特性及这种行波管的小信号、大信号特性,讨论了结构的几何尺寸及电子注参量对慢波的传播特性、小信号增益及注-波互作用非线性效应的影响。本文的结果将为脊加载环板行波管的设计提供理论基础。 展开更多
关键词 加载板行波管 电真空器件 慢波结构 电子学报 大功率行波管 变分原理 三次谐波 相结合 大信号特性 非线性效应
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电真空器件
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《电子科技文摘》 2000年第7期13-13,共1页
Y2000-62094-77 0010847模糊控制金属卤素灯的高功率因数=High power fac-tor of metal halide lamp with dimming control[会,英]/Lin,B.-R.& Hsieh,Y.-C.//1999 IEEE Interna-tional Symposium on Circuits and Systems.Vol.6 of6... Y2000-62094-77 0010847模糊控制金属卤素灯的高功率因数=High power fac-tor of metal halide lamp with dimming control[会,英]/Lin,B.-R.& Hsieh,Y.-C.//1999 IEEE Interna-tional Symposium on Circuits and Systems.Vol.6 of6.—77~80(EZ) 展开更多
关键词 光电子技术 模糊控制 真空科学 高功率因数 电真空器件 功率行波管 毫米波 结构特点 加载板行波管 幅相一致行波管
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Functional study of hyperpolarization activated channel (I_h) in Drosophila behavior 被引量:1
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作者 CHEN ZiJing WANG ZuoRen 《Science China(Life Sciences)》 SCIE CAS 2012年第1期2-7,共6页
Hyperpolarization-activated, cyclic nucleotide-gated and cation-nonselective ion channels (lh channels, or HCN channels) are known to play important roles in mammals. Their physiological functions in invertebrate re... Hyperpolarization-activated, cyclic nucleotide-gated and cation-nonselective ion channels (lh channels, or HCN channels) are known to play important roles in mammals. Their physiological functions in invertebrate remain largely unclear. Here, we re- port our studies with lh channel in Drosophila melanogaster. Drosophila lh channel mutants are found with several defects by behavioral analyses. Their lifespan is reduced, and their chemical sensitivity is shifted. In addition, their length of sleep at light-dark condition is mildly reduced. We generated transgenic flies of lh promoter-driven Gal4 and examined its expression pattern in both larvae and adult flies. Our results suggest that Ih channel may play diverse roles in Drosophila and provide a basis to further expand our understanding of Drosophila Ih channel function in vivo. 展开更多
关键词 Ih channel Drosophila melanogaster HCN BEHAVIOR
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Genotoxicity biomarkers in aquatic bioindicators 被引量:1
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作者 Claudia BOLOGNESI Silvia CIRILLO 《Current Zoology》 SCIE CAS CSCD 2014年第2期273-284,共12页
Pollution of the aquatic environment is an ever-growing problem, as waters are the ultimate sink for the large number of xenobiotics from multiple sources. DNA damaging agents have a significant ecological relevance s... Pollution of the aquatic environment is an ever-growing problem, as waters are the ultimate sink for the large number of xenobiotics from multiple sources. DNA damaging agents have a significant ecological relevance since they are implicated in many pathological processes and exert effects beyond that of individual being active through following generations. A large number of methods have been applied to evaluate genotoxic damage in different aquatic species. Comet assay, as method for de- tecting DNA alterations, and micronucleus test, as an index of chromosomal damage are the most widely applied and validated methods in field studies. These methods were applied in different vertebrate and invertebrate aquatic species, but only mollusk and fish species have been employed in routine biomonitoring programs. Mussels, due to their widely geographical distribution and the suitability for caging represent the bioindicator of choice in field studies. Mytilus species is the most used marine mussel. The use of fish is limited to specific geographic areas. The present review mainly focuses on the application of comet assay and micronucleus test in mussels. A number of biomonitoring studies in mussels, using comet assay or micronucleus test, revealed exposure to different classes of genotoxic compounds with a good discrimination power. The different evidence from the two as- says, reflects different biological mechanisms for the two genetic endpoints, DNA damage and chromosomal damage, suggesting their combined application in the field. Different endogenous and exogenous factors have been shown to modulate the genotoxic responses in mussels, acting as confounding factors in environmental monitoring. The use of standardized protocol for caging, sampling and genotoxity evaluation is critical in biomonitoring studies. The use of a multimarker approach coupling genotoxicity biomarkers with physiological and biochemical factors allows to have a complete picture of the environmental pollution [Current Zoology 60 (2): 273-284, 2014]. 展开更多
关键词 Aquatic animals GENOTOXICITY BIOINDICATOR Biomarker Micronucleus test Comet assay BIVALVE MUSSEL
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