Typical Construction Program of 600 MV Unit Supercritical Boiler Boiler

文章介绍了国产600 MW机组超临界直流锅炉的施工方案,重点论述了主要施工机械和布置、施工方案简介,前后炉膛的吊装顺序.     

黏土中倾斜螺旋桩的水平承载性能数值模拟及理论研究

为研究黏土中螺旋桩倾斜单桩的水平承载性能,基于非线性有限元软件ABAQUS建立有限元分析模型.通过数值模拟结果与已有螺旋桩软土地基抗拔试验及砂土地基水平承载试验的对比分析,验证了该数值模型的准确性与可行性.探讨了不同倾斜角度下叶片数量和首层叶片埋深对螺旋桩水平承载性能的影响规律.结果 表明:叶片数量对倾斜螺旋桩的水平承载性能影响不大;倾斜角度增大,首层叶片埋深影响逐渐变小,但总体上首层叶片埋深越深,倾斜螺旋桩的水平承载性能越差,当埋深达到4倍叶片直径的深度后,水平承载性能基本不再变化.基于数值模拟结果提出了不同倾斜角度下螺旋桩水平极限承载力计算中锚片所承担部分的计算公式.随着倾斜角度增加,叶片在螺旋桩中的抗倾覆作用逐渐向抗拔作用转变,所提出的水平极限承载力计算公式较为可靠.     

Business Environment and Resource Allocation Based on the Perspective of the National Value Chain

China is actively upgrading its industrial structure through industries transferring between developed and undeveloped areas; however, the overall level of the national value chain is still not high, and the asymmetric competition pattern between the upstream and the downstream has not been broken. Therefore, this paper establishes a competitive equilibrium model for the production of manufacturing enterprises, with factor price distortion, under the condition of constant returns to scale.The au...     

Nano-mechanical and tribological properties of copper matrix composites reinforced by graphene nanosheets

The impacts of graphene nanosheets content on microstructure, nano-mechanical and tribological properties of the copper matrix composites were investigated. The graphene nanosheets randomly distributed in copper matrix, which obviously hindered its grain growth. The elastic modulus and nano-hardness of the copper matrix composite with 0.2 wt% graphene nanosheets were enhanced 47.5% and 54.7% compared to these of pure copper, respectively. The average creep degree(5.1%) was lower than that(11.8%) of pure copper in holding stage. The creep rate(ca. 0.016 nm/s) decreased 10 times as that(ca. 0.16 nm/s) of pure copper in steady-state creep. The tribological performances were improved dramatically with increase of graphene nanosheets content.     

中国海洋鱼类单殖吸虫研究XXIV. 斧形虫科一新记录种

本文记述了采自海南三亚杜氏下鱵Hyporhamphus dussumieri鳃上的1种单殖吸虫低鱵斧形虫Axine depauperati Yamaguti, 1968。所获标本与Yamaguti（1968）的原始描述基本一致，但在吸铗形状、端钩数量、生殖腔刺和阴茎刺数量上略有差异。低鱵斧形虫为中国新记录，杜氏下鱵为宿主新记录。     

日光温室果蔬地大型土壤动物多样性及群落结构

研究延安市郊(县)果蔬地大型土壤动物多样性及群落结构,以指导果蔬地害虫及虫害的立体防治。通过手拣法对大型土壤动物进行标本采集,从土壤动物的多样性指数、均匀性指数、优势度指数以及丰富度指数方面对其进行多样性和群落结构的研究。通过调查研究共获得大型土壤动物标本280个,隶属于3门7纲14目。其中,正蚓目和膜翅目为其群落的优势类群,占其群落个体总数的53.93%,其他12个类群则均为常见类群。对不同种植类型果蔬地Shannon-Wiener多样性指数(H′)进行分析,结果表明:2号样地的多样性指数最高,5号样地的多样性指数最低。而优势度指数(C)最高的为6号样地,最低的为2号样地。对垂直分布的分析结果表明,果蔬地大型土壤动物具有明显的表聚性,即0~5cm5~10cm10~15cm15~20cm。研究表明不同种植类型果蔬地大型土壤动物多样性及群落结构均有不同,这反应了果蔬地大型土壤动物对不同土地利用方式的适应性有所不同。     

Effects of Ce-rich RE on microstructure and mechanical properties of as-cast Mg-8Li-3Al-2Zn-0.5Nd alloy with duplex structure

The effects of Ce-rich RE on the microstructure and mechanical properties of as-cast Mg-8Li-3Al-2Zn-0.5Nd-x RE(x = 0, 1, 2, 3 wt%) alloys were investigated. The results indicated that the as-cast Mg-8Li-3Al-2Zn-0.5Nd alloy mainly consisted of α-Mg, β-Li, AlLi, MgLi2 Al and Al2 Nd phases. With the addition of Ce-rich RE in the alloy,Al3 RE and Al2 RE phases generated and gradually grew into net-like or block-like structure. With the addition of RE, Al-RE phases generated by consuming Al element and, thus, less Al element was dissolved in the matrix and less AlLi phase formed. Furthermore, less AlLi phase means that more Li element released to cause the increase ofβ-Li phase and refine the α-Mg phase. Under the influence of these factors, adding more RE led to higher elongation and lower tensile strength and hardness. With the addition of Ce-rich RE, the yield strength and ultimate tensile strength of the as-cast Mg-8Li-3Al-2Zn-0.5Nd alloy gradually decreased from 180 to 152 MPa and from 215 to 193 MPa, respectively, while the elongation was remarkably improved from 21.1% to 40.2%.     

变频空调电气控制系统设计

介绍了空调系统的基本工作原理,对变频空调与定频空调的工作原理进行了比较,充分体现了变频空调的优越性,从室内外的硬件设计和软件设计介绍了家用一拖一变频空调,室外逆变电路部分由智能功率模块取代了分立的六路IGBT构成的逆变电路,有效地提高了系统的稳定性和可靠性,最后的整机测试波形论证了整个系统的可行性。     

民国时期的江西绅士——以魏元旷为中心的个案考察

清末民初,江两绅士的整体形象是"风气未开"、"习俗守旧",然而历史表象的背后,还有很多深层次的信息需要我们去钩沉索隐.作为清末民初南昌绅士的代表人物,魏元旷在这段时期的表现,无疑是体现近代江西社会及其变迁的一个重要缩影.本文重点分析以魏元旷为个案的江西末代绅士晚年的生活及其心境,以此为突破口,探讨江西绅士应对近代中国社会变革的行为与心态.     

基于玻璃化转变温度的沥青混合料低温性能研究

鉴于目前尚未有公认、合理的沥青和沥青混合料低温性能评价指标,提出采用玻璃化转变温度来进行评价.采用动态剪切流变仪AR-2000对不同沥青和沥青混合料在线粘弹范围内进行了动态频率扫描;应用时温等效原理对频率扫描结果分析得到不同材料的玻璃化转变温度,并用沥青混合料低温弯曲试验进行验证.结果表明,由动态频率扫描测试得到的玻璃化转变温度符合路面实际情况,且物理意义明确,沥青和沥青混合料的玻璃化转变温度与混合料低温弯曲破坏应变相关性良好.因此,玻璃化转变温度可用于评价沥青和沥青混合料的低温性能.