表面纹路的评定

本文系统地阐述了表面纹路评定的各个方面,举例说明了表面纹路对摩擦、摩损和润滑作用以及对摩擦副承载能力,抗胶合能力的影响,指出了目前评定表面纹路国家标准所存在的问题,提出了能全面反映纹路特征的三个统计函数作为评定指标,即表面轮廓的中线平均值,概率分布函数和自相关函数。     

论投资项目评估中的市场风险

在社会主义市场经济条件下,客观、科学、公正的投资评估（包括可行性研究、项目评估等）,是项目决策的重要依据。投资评估的主要内容包括：项目投资主体评价、项目建设必要性分析、项目建设规模与市场分析预测、项目总投资及资金筹措评估、项目经济与社会效益评价、项目的不确定性分析等方面。项目市场分析预测的目的是为了准确预测产品的市场价格和销售量,分析产品市场能力,是投资评估的核心内容之一。投资项目的市场风险问题主要是指产品售价、销售量和产品竞争力问题。由于过去我国长期实行集中计划经济模式,结果造成一种“短缺”经…     

一种带微机的摩擦过程动态测试仪

本文介绍了一种新型的摩擦过程动态测试仪,该仪器与MHK-500型摩擦试验机联用时,在保留原试验机结构不变的情况下,改变原手工测试为自动测试,可连续给出摩擦过程摩擦力和摩擦系数的变化,并有三种输出方式;数字显示、数字打印、曲线图形,测量误差<1％。     

MMP-2、TIMP-2在小鼠原发性肝泡球蚴病中的表达及意义

为初步研究基质金属蛋白酶-2(MMP-2)及其抑制剂(TIMP-2)在小鼠原发性肝泡球蚴病血清中的表达及意义。将60只12周龄健康雌性昆明小鼠分为空白组(20只)和肝泡状棘球蚴组(40只)。建模100d后分别提取2组小鼠血清,用酶联免疫吸附试验(ELISA)检测2组小鼠血清中MMP-2和TIMP-2的浓度。结果显示:肝泡状棘球蚴组小鼠血清MMP-2、TIMP-2浓度均高于空白组(P<0.05),且MMP-2与TIMP的比例明显高于空白组。由此可知,小鼠血清MMP-2浓度的升高及MMP-2与TIMP-2比例的失衡可能和肝脏泡球蚴组织的侵润生长存在相关性。     

非系统性金融风险的产生机理及对策

安全性是企业在经营中为使资产收入信誉及所有经营生存发展条件免遭损失所应遵循的原则与安全性相对的是风险性即遭受损失的可能性货币是商品经济中使用最频繁地位最特殊的商品金融机构是经营货币的特殊企业其经营活动实际上牵动了社会经济生活的各个方面影响到了社会再生产过程的各个环节其经营风险所带来的损失往往远远超过一般生产企业对整个社会经济的破坏性影响力更大贯彻安全性方针尽可能减少经营风险是保证银行稳健经营的重要条件基于此种认识本文试就金融风险主要是非系统性风险的类别成因进行粗浅分析提出几种风险因素的分析方法并…     

Fragmentation of stable and neutron-rich 12-16C into boron fragments at approximately 240 MeV/nucleon

The elemental fragmentation cross sections of boron fragments produced by stable and neutron-rich^12-16C beams with a carbon target were systematically measured at an incident beam energy of approximately 240 MeV/nucleon.The measured cross sections were found to increase as the projectile mass number increases.The observed feature is explained qualitatively based on the abrasion-ablation two-stage reaction model and is compared quantitatively with predictions from various reaction models,including empirical and statistical models.All models agree with the measured cross sections within a factor of 2.     

兰州320kV高压平台低能核天体物理实验研究进展(英文)

在低温核天体物理环境下,如静态核稳定燃烧阶段的核反应都发生较低的能区,其伽莫夫窗口内的核反应截面非常小,这就需要加速器提供较强束流才能完成核反应截面的直接测量。最近在中国科学院近代物理的320 kV高压平台上建立了低能核天体物理实验室以及相应的研究平台。驱动该平台的是一个14.5 GHz的永磁铁型ECR离子源,它能够提供非常强的束流离子。对于质子和氦离子,离子源出口的最大流强可以达到100 eμA,在实验终端上可以获得大约30 eμA的流强。基于此强流加速器装置,我们建立了核天体物理实验测量装置,包括靶室以及带电粒子和伽玛射线探测器等设备。利用已知的核反应对探测器性能和实验方法进行了一系列测试。同时,展示了近年来取得的一些主要实验结果。最后,对该平台上开展工作的前景进行了展望,并指出基于该地面装置的低能核反应研究所积累的技术及经验对于我国锦屏深地核天体物理JUNA项目的重要意义。For the hydrostatic stable burning in stars, the Gamow window is well below the Coulomb barriers for the charged-particle-induced nuclear reaction involved. Such nuclear reaction occurs through the quantum-mechanics tunneling effect, and its cross section drops rapidly approaching the Gamow window. An accelerator which can provide intense beam current is thus required to directly measure the reactions at low energies. An experimental setup for low-energy nuclear astrophysics studies has been recently established at a 320 kV high-voltage platform of the Institute of Modern Physics (IMP), Lanzhou, China. The driver machine of this platform is a very strong ECR ion source employing all-permanent magnets, which can typically supply up to about 100 eμA proton, alpha and many other heavy ions, and ultimately about 30 eμA currents can be achieved at the experimental terminal. The experimental setup includes a target chamber, and the charged-particle and γ-ray HPGe detectors. This work describes the setup established, characteristics of detectors, methodologies, and test results of several reactions with known cross sections. Furthermore, some important results published are shown briefly. We believe that the experimental technologies developed and experiences accumulated at this above-ground platform will be extremely helpful for the Jinping Underground Nuclear Astrophysics laboratory (JUNA) project in China.     

低能加速器质子束流性质的测量(英文)

中国锦屏地下实验室（CJPL）坐落于四川省锦屏山中,利用水电站修建的隧道建成。由于其本底环境极低,非常适合开展低本底实验测量。一台基于ECR源的400 kV强流加速器将安装在CJPL中,其可以为核天体物理实验提供流强为12 emA的质子束流,6 emA的He+束流和2.5 emA的He2+束流。拟通过非共振反应12C（p,γ）13N以及一系列的共振反应27Al（p,γ）28Si等,对加速器的束流能量进行精确刻度,对束流的能量展宽以及长期稳定性进行测量。由于该加速器正在中国原子能科学研究院进行地面调试,我们利用中国科学院近代物理研究所的320 kV研究平台,进行了12C（p,γ）13N和27Al（p,γ）28Si反应的测试实验。测量结果表明,在质子束流能量为224 keV时,束流的能量展宽约为1.0 keV,束流能量在连续4小时的测量期间,其晃动幅度远小于±200 eV。China JinPing underground Laboratory (CJPL) was established inside the tunnels piercing Jinping Mountain in Sichuan Province, China, which can provide an ideal environment for low background experiment. A new 400 kV accelerator, with high current based on an ECR source, will be placed at this underground laboratory for nuclear astrophysics experiment. The beam characteristics of this accelerator, like absolute energy, energy spread, and long-term energy stability, will be determined by several wellknown resonance and non-resonance reactions. Due to the new accelerator still being under construction, the resonance reaction of 27Al(p, γ)28Si and non-resonance 12C(p, γ)13N were studied at the 320 kV highvoltage platform in Institute Modern Physics of CAS in Lanzhou. The energy spread of proton beam is about 1.0 keV at proton energy E_p=224 keV and the long-term energy stability of proton beam is much better than 200 eV during 4 hours measurement.     

Measurement of the ~2H(~7Be,~6Li)~3He reaction rate and its contribution to the primordial lithium abundance

In the standard Big Bang nucleosynthesis(SBBN) model, the lithium puzzle has attracted intense interest over the past few decades, but still has not been solved. Conventionally, the approach is to include more reactions flowing into or out of lithium, and study the potential effects of those reactions which were not previously considered.~7Be(d,~3He)~6Li is a reaction that not only produces~6Li but also destroys~7Be, which decays to~7Li, thereby affecting~7Li indirectly. Therefore, this reaction could alleviate the lithium discrepancy if its reaction rate is sufficiently high.However, there is not much information available about the~7Be(d,~3He)~6Li reaction rate. In this work, the angular distributions of the~7Be(d,~3He)~6Li reaction are measured at the center of mass energies Ecm = 4.0 Me V and 6.~7Me V with secondary~7Be beams for the first time. The excitation function of the~7Be(d,~3He)~6Li reaction is first calculated with the computer code TALYS and then normalized to the experimental data, then its reaction rate is deduced. A SBBN network calculation is performed to investigate its influence on the~6Li and~7Li abundances. The results show that the~7Be(d,~3He)~6Li reaction has a minimal effect on~6Li and~7Li because of its small reaction rate. Therefore,the~7Be(d,~3He)~6Li reaction is ruled out by this experiment as a means of alleviating the lithium discrepancy.     

锦屏深地核天体物理实验(JUNA)地面实验进展

锦屏深地核天体物理(JUNA)实验项目将利用中国锦屏深地实验室(CJPL)的良好条件,在天体物理伽莫夫能量窗口开展核天体关键反应$^{25}{\rm{Mg}}({\rm{p}},{\rm{\gamma}})^{26}{\rm{Al}}$、$^{19}{\rm{F}}({\rm{p}},\alpha)^{16}{\rm{O}}$、$^{13}{\rm{C}}(\alpha, {\rm{n}})^{16}{\rm{O}}$和$^{12}{\rm{C}}(\alpha,{\rm{\gamma}})^{16}{\rm{O}}$的直接测量,为理解恒星演化和元素起源提供新的数据。目前,已经在地面上对加速器装置、束流稳定性、靶、探测器以及电子学进行了系统的测试。地面实验内容包括高纯锗探测器效率刻度,$^{25}{\rm{Mg}}({\rm{p}}, {\rm{\gamma}})^{26}{\rm{Al}}$在304 keV的共振强度测量,$^{19}{\rm{F}}({\rm{p}}, \alpha)^{16}{\rm{O}}$的截面测量,聚乙烯作为慢化体的中子探测器的设计、加工和效率刻度,靶的设计和稳定性检测等。JUNA项目整体进展顺利,地面实验已取得一系列关键进展和初步成果。在不远的将来,JUNA项目将有序开展地下实验,完成设定目标,也将促进更广泛的国际合作,助力于天体演化中的若干重大科学问题的解决。