宇宙学上的里程碑：NASA发现宇宙时间表

通过测量大爆炸辐射的偏振模式，天文学家可以找出测量婴幼期宇宙的方法，最近他们报道了发现宇宙在最初百万兆分之一秒的时间内，曾经历过剧烈快速膨胀进发的证据。[编者按]     

地球与宇宙中心距离的测量

根据大爆炸理论,极早期的宇宙可看作是由微观粒子构成的均匀物质,温度极高,密度极大,并以很大的速度膨胀着。在1929年,天文学家哈勃也表明,宇宙正在膨胀,是一种全空间的膨胀。在任何一点的观测者都会看到完全一样的膨胀,任何星系都以它为中心四面散开,越远的星系间彼此散开的速度越大。有了这个认识前提,我们就可以测量地球与宇宙中心的距离了。测量地球离宇宙中心的距离,我们就要测出现如今的地球是以多大的速度在散开的(远离宇宙爆炸中心的瞬时速度)。我们可以假设这个速度数值是Vy(km/h),现在我们还不清楚它有多大。其次,我们还要知道宇…     

火星上的“麦田怪圈”

从地球上的南北极到遥远的火星,科学家们都发现了千奇百怪的图案,它们都是怎么形成的呢?难道真的与外星人有关?     

饱和潜水技术在深水海底管线膨胀弯安装中的应用

海洋石油的开发逐渐向更深水域发展,饱和潜水技术由于作业水深较深,持续作业时间长的特点正在被广泛采用,并将得到更大的发展。饱和潜水技术是人类对于潜水技术的又一个突破。在海管膨胀弯安装中,由于需要进行复杂的水下操作,饱和潜水技术被普遍用于海管膨胀弯的安装中。本文通过以平湖二期八角亭工程项目海管膨胀弯安装的实例,对饱和潜水技术进行简单介绍,并对膨胀弯安装中饱和潜水技术的应用进行重点叙述,对未来其他深水使用饱和潜水技术进行海管膨胀弯安装可以有借鉴作用。     

福建省明溪县老科协发现野生花魔芋群落

<正> 近日,福建省明溪县老科技工作者协会组织农、林等专业的科技工作者深入山场观察杉木林下套种红豆杉的生长情况,偶然在沙溪乡局上村附近的山地上发现一     

非饱和膨胀土卸载回弹特性经验模型研究

针对非饱和南宁膨胀土进行了一系列室内一维压缩卸栽回弹试验,得到相应的应力一应变曲线,探讨了该膨胀土的回弹变形特性。对不同含水率下的应变一时间关系曲线均可拟合成对数函数形式,可以得到拟合程度较高的经验方程,该方程为膨胀土的变形计算提供了依据。     

LaFe11.0 Co0.9 Si1.1 B0.2化合物负膨胀研究

利用电弧炉熔炼法制备了LaFe11Co0.9Si1.1B0.2化合物.扫描电镜和能量色散谱仪分析得该化合物主相为NaZn13相,还含有少量的富镧相和富铁相.X-射线衍射仪测量发现,该化合物在居里温度附近的衍射峰随着温度的升高向大角度偏移,分析软件分析并计算得到该化合物在居里温度附近具有明显的负膨胀现象.     

虚拟切片技术在实验教学中的应用

医学形态学是一门重要的医学基础课程,实验教学则是形态学教学的关键环节。传统形态学实验教学模式依赖于书本、玻璃切片和光学显微镜三者的结合,存在一定局限性。随着数字化技术和信息化技术在高校的普及,现代化的教学手段已被逐步运用于教学之中,为形态学实验教学寻求新的途径。阐述和分析了虚拟切片技术的优势、特点和功能,介绍其在教学、临床和学术交流等领域的广泛应用,旨在更大限度地利用和共享有限的教学资源,激发学生学习的积极性和主动性,从而提高实验教学质量,深化实验教学改革。     

关于地球

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Deformation mechanism of high-stress and broken-expansion surrounding rock and supporting optimization based on the gray correlation theory

Aiming at the large deformation and support problems of high-stress and broken-expansion surrounding rock, and taking 1 000 m level roadway of Mine II in Jinchuan as the research object, an investigation on the deformation and damage of roadway surrounding rock and an analysis of its mechanism were carried out. The gray correlation theory was used in support scheme optimization design. First, causes and mechanism of deformation of the 1 000 m horizontal transport channel were analyzed through field investigation, laboratory test and data processing methods. We arguued that poor engineering geological conditions and deep pressure increases were the main factors, and the deformation mechanism was mainly the ground deformation pressure. Second, the gray correlation theory was used to construct supporting optimization decision method in the deep roadway. This method more comprehensively considers various factors, including construction, costs, and supporting material functions. The combined support with pre-stressed anchor cables, shotcrete layer, bolt and metal net was put forward according to the actual roadway engineering characteristics. Finally, 4 support schemes were put forward for new roadways. The gray relational theory was applied to optimizing the supporting method, undertaking technical and economic comparison to obtain the correlation degree, and accordingly the schemes were evaluated. It was concluded as follows： the best was the flexible retaining scheme using the steel strand anchor; the second best was the one using plate anchors on the top and rigid common screw steel bolt on the two sides; the ttiird was; the rigid common screw steel bolt in full section of roadway; and the worst is the planished steel rigid support. The optimized scheme was applied to the 1000 m level of new excavation roadway. The results show that the roadway surrounding rock can reach a stable state after 5 to 6 months monitoring, with a convergence rate less than 1 mm/d.