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燃气轮机的可靠性

燃气轮机技术 1991年第3期4卷 58-64页

作者： h.D.lenz h.w.hill jr. 程素玲南京燃气轮机研究所

确定部件可靠性的方法已经问世近40年了.然而,这些方法由于缺乏一致的定义和分类,迄今尚未用到燃气轮机的系统设计中去.本文阐述了控制系统可靠性计算的惯常步骤,它也适用于其它机械设备可靠性的计算.这些步骤均由计算机处理的模型来完... 详细信息

确定部件可靠性的方法已经问世近40年了.然而,这些方法由于缺乏一致的定义和分类,迄今尚未用到燃气轮机的系统设计中去.本文阐述了控制系统可靠性计算的惯常步骤,它也适用于其它机械设备可靠性的计算.这些步骤均由计算机处理的模型来完成.运用这个模型算出的一系列结果,就可对初步设计的系统的操作方法和配置是否合理进行讨论,进而达到改进燃气轮机可靠性的目的.例如,主要部件的冗余度;部件的质量;环境因素;传感装置与执行机构;电路与逻辑设计等.本文对这些方法进行了比较,并从可靠性的角度提出了在系统成本与系统复杂性之间的最佳选择.

关键词：燃气透平可靠性

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微创脊柱外科学

微创脊柱外科学

2016年

作者：（美）FRANK M.PhILLIPS （美）ISADOR h.LIEBERMAN （美）DAVID w.POLLY jr. 赵杰马辉主译

《微创脊柱外科》一书详细讨论了相关的研究进展、外科技术、特定疾病的手术方法,以及微创脊柱外科特有风险和并发症的处理策略。主要内容包括:脊柱微创手术的历史和发展、脊柱微创手术的理念和生物学基础等。

关键词：脊柱病-显微外科学

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固体燃料冲压发动机燃料燃速与推力调节

空天技术 1993年第5期 28-33+46页

作者： w. h. Campbell jr.龚建民

为了确定进气涡流和二次气体喷射能否有效地用于固体燃料冲压发动机燃料燃速的控制和推力调节,曾进行了一项实验研究.进气涡流的特性是在无反应流中测量的.试验是用当量比为0.5～1.8之间的三种燃料成分在高、低空气质量流量下进行的.发... 详细信息

为了确定进气涡流和二次气体喷射能否有效地用于固体燃料冲压发动机燃料燃速的控制和推力调节,曾进行了一项实验研究.进气涡流的特性是在无反应流中测量的.试验是用当量比为0.5～1.8之间的三种燃料成分在高、低空气质量流量下进行的.发现,在进气道下游引入涡流对实现燃料燃速的有限增长会产生影响,但影响的幅度与发动机的几何尺寸有很大关系.涡流与再附着进气道气流和大大增强的近壁混合之间的相互作用对有效燃烧不利.高能气体燃料（h2,C2h4）可以很容易地喷入,并在贫油条件下有效地燃烧,大大提高推力.

关键词：固体燃料冲压发动机燃烧速率可变推力

四相编码——一种具有独特性能的雷达脉冲压缩信号

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现代雷达 1988年第Z1期 142-149页

作者： J.w.Taylor jr. h.J.Blinchikoff 公毅

引言本文叙述独特的一类雷达信号,称作四相编码,它是又一种可以用于脉冲压缩的技术。这种编码信号由***.提出用于雷达,并在过去的十年中取得了成功的应用;其工作性能在三个重要领域,即辐射频谱、接收滤波器的失配损失和脉冲压缩用数字... 详细信息

引言本文叙述独特的一类雷达信号,称作四相编码,它是又一种可以用于脉冲压缩的技术。这种编码信号由***.提出用于雷达,并在过去的十年中取得了成功的应用;其工作性能在三个重要领域,即辐射频谱、接收滤波器的失配损失和脉冲压缩用数字硬件来实现时的距离采样损失方面,都胜过采用矩形子脉冲的相位编码。表1给出典型数据。并且,与线性调频相反,匹配接收机输出具有较低的距离旁瓣可满足恒虚警率处理;因此,不必为了利用加权解决旁瓣问题而牺牲灵敏度。

关键词：四相编码自相关函数脉冲压缩二相编码编码脉冲相位编码调相制PM 子脉冲距离旁瓣失配损失数字相关器

Early Mesoproterozoic evolution of midcontinental Laurentia: Defining the geon 14 Baraboo orogeny

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Geoscience Frontiers 2021年第5期12卷 37-53页

作者： L.Gordon Medaris jr.Brad S.Singer Brian R.Jicha David h.Malone Joshua J.Schwartz Esther K.Stewart Amanda Van Lankvelt Michael L.williams Peter w.Reiners Department of Geoscience University of Wisconsin-MadisonMadisonWI 53706USA Department of Geography Geology&EnvironmentIllinois State UniversityNormalIL 61790USA Department of Geological Sciences California State University-NorthridgeNorthridgeCA 91330USA wisconsin Geological&Natural history Survey MadisonWI 53705USA Cameca Instruments 5470 Nobel Dr.MadisonWI 54711USA Department of Geosciences University of Massachusetts-AmherstAmherstMA 01003USA Department of Geosciences University of ArizonaTucsonAZ 85721USA

New geochronologic data from midcontinental Laurentia demonstrate that emplacement of the 1476-1470 Ma wolf River granitic batholith was not an isolated igneous event,but was accompanied by regional metamorphism,deformation,and *** for such metamorphism and deformation is best seen in siliciclastic sedimentary rocks of the Baraboo Interval,which were deposited closely following the 1.65-1.63 Ga Mazatzal *** Baraboo Interval strata,muscovite parallel to slatey cleavage,in hydrothermal veins,in quartzite breccia,and in metamorphosed paleosol yielded ^(40)Ar/^(39)Ar plateau ages of 1493-1465 *** addition,U-Th-total Pb dating of neoblastic overgrowths on detrital monazite gave an age of 1488±20 Ma,and recrystallized hematite in folded metapelite gave a mean U/Th-he age of 1411±39 ***-Baraboo,arkosic polymictic conglomerate,which contains detrital zircon with a minimum peak age of 1493 Ma,was intruded by a 1470 Ma granite porphyry at the northeastern margin of the wolf River *** episode of magmatism,regional deformation and metamorphism,and sedimentation,which is designated herein as the Baraboo orogeny,provides a midcontinental link between the Picuris orogeny to the southwest and the Pinware orogeny to the northeast,completing the extent of early Mesoproterozoic(Calymmian)orogenesis for 5000 km along the southern margin of *** transcontinental orogen is unique among Precambrian orogenies for its great width(-1600 km),the predominance of ferroan granites derived from partial melting of lower continental crust,and the prevalence of regional high T-P metamorphism related to advective heating by granitic magmas emplaced in the middle to upper crust.

关键词： Mesoproterozoic orogeny Ferroan granite Detrital zircon ^(40)Ar/^(39)Ar geochronology U-Th-total Pb geochronology U/Th-he geochronology

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Improving the hard magnetic properties by intragrain pinning for Ta doped nanocrystalline Ce-Fe-B alloys

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Journal of Materials Science & Technology 2019年第9期35卷 1877-1885页

作者： J.S.Zhang w. Li X.F. Liao h.Y. Yu L.Z. Zhao h.X. Zeng D.R. Peng Z.w. Liu School of Materials Science and Engineering South China University of TechnologyGuangzhou510640China Innovative Center for Advanced Materials (ICAM) Hangzhou Dianzi UniversityHangzhou310012China

To develop Ce based permanent magnets with high performance/cost ratio, Ta doping is was employed to enhance the magnetic performance of Ce-Fe-B alloys. For melt spun Cei7Fe78-xTaxB6 (x = 0-1) alloys, the coercivity hc increases from 439 to 553 kA/m with increasing x value from 0 to 0.75. Microstructure characterizations indicate that Ta doping is helpful for grain refinement. A second phase of TaB2 is observed in Ce17Fe77.25Tao.75B6 alloy, which acts as the pinning center of the magnetic domains, resulting in the change of coercivity mechanism from nucleation type to nucleation +pinning type. The micromagnetic simulation confirms that non-magnetic particles within hard magnetic phase can increase the demagnetization field around them and it is crucial for preventing the further magnetization reverse by pinning effect. Take the advantage of Ta doping for enhancing the coercivity, Ce content of Ce-Fe-B alloy can be further cut down to increase the remanence jr.due to the reduced volume fraction of CeFe2 phase and increased Fe/Ce ratio. As a result, a good combination of magnetic properties with hc = 514 kA/m, jr.= 0.49 T, and the maximum energy product (Bh)max = 36 kJ/m^3 have been obtained in Ce15Fe79.25Tao.75B6 alloy. It is expected that the present work can serve as a useful reference for designing new permanent magnetic materials with low-cost.

关键词： Melt-spinning Permanent magnets Second phase Coercivity mechanism Thermal stability

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Effects of Land Use on Greenhouse Gas Flux in Playa wetlands and Associated watersheds in the high Plains, USA

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Agricultural Sciences 2019年第2期10卷 181-201页

作者： Dale w. Daniel Loren M. Smith Scott T. McMurry Brian A. Tangen Charles F. Dahl Ned h. Euliss jr. Ted LaGrange Department of Integrative Biology Oklahoma State University Stillwater OK USA U.S. Geological Survey Northern Prairie Wildlife Research Center Jamestown ND USA Nebraska Game & Parks Commission Wetlands Program Lincoln NE USA

In the high Plains, U.S., native prairie conversion to cropland agriculture has resulted in a loss of service delivery capabilities from most depressional wetlands as a result of sedimentation. Restoring historic hydrological conditions to affected wetlands may rejuvenate some services, however, there may be tradeoffs due to emissions of Ch4 and N2O. we evaluated the influence of two predominant conservation programs (wetlands Reserve Program, wRP and Conservation Reserve Program, CRP) on gas emissions (CO2, Ch4, N2O) from 42 playas and uplands in the high Plains of Nebraska. Because playa restoration through the wRP is most prevalent in the Rainwater Basin (RwB), we studied 27 playas/uplands among reference condition, cropland, and wRP land uses. we studied 15 playas/uplands within native grassland, cropland, and CRP land uses in the western high Plains (whP) of Nebraska. Emissions were collected bi-weekly from April-October of 2012 and 2013 from four landscape positions extending outward from the wetland center into upland. In RwB playas, Ch4 and N2O emissions were similar among land uses but CO2 was 28% higher in cropland than wRP wetlands. Cropland uplands emitted 648% more N2O than reference and wRP uplands. Overall, net CO2-equiv emissions were lower in playas/uplands in wRP, suggesting that benefits of playa restoration may include climate mitigation services as well as increased water storage capacity and biodiversity provisioning. In the whP, cropland and grassland playas emitted 46 and 23 times more Ch4, respectively, than CRP in 2013. Playas in CRP emitted 43% less N2O than cropland playas. In 2013, net emissions for cropland and native grassland playas were 75% and 39% greater, respectively, than CRP playas. In the whP, the benefits of lower gas emissions must be appropriately weighted against tradeoffs of ecosystem services related to shorter hydroperiods as a result of reduced runoff into playas in CRP.

关键词： Conservation Reserve Program Depressional wetlands Ecosystem Services Global Climate Change wetlands Reserve Program wetland Restoration