查询词典 radioactive element

A radioactive transuranic metallic element produced by bombarding plutonium with neutrons.

一种放射性超铀元素，用中子轰击钚时产生。

A short - lived , radioactive synthetic transuranic element produced from californium and having

铹一种寿命期短的、人工合成的放射性超铀元素，从锎中生成，有质量从255到260的同位素，半衰期从几秒钟到三分钟；原子序数

Periodic Table Ⅶ B family silver or gray-black powder bulk solid metal transition element, atomic number Z = 35, the original of the amount of 186,207, the chemical symbol FRe, there are two natural isotopes, stable 18575Re and radioactive 18775Re.

元素周期表中ⅦB族银白色的块状或灰黑色粉末状固体金属过渡元素，原子序数Z＝35，原了量186207，化学符号FRe，天然同位素有两种，稳定的18575Re和放射性的18775Re。

Activity exceeds 75 becquerels of parent radioactive chemical element per gram of substance.

成的任何物质，或包含该等元素的任何物质，而其放射性比，以每克物质计算，超逾75贝克耳的源放射性化学元素。

Activity exceeds 75 becquerels of parent radioactive chemical element per gram of substance.

或包含该等元素的任何物质，而其放射性比，以每克物质计算，超逾75贝克耳的源放射性化学元素。

Radioactive heat-producing element abundance in the crust of continental China estimated from terrestrial heat flow and the helium isotopic composition of underground fluids

根据实测岩石热导率和测温资料计算了柴达木盆地的大地热流值并编制了热流分布图，对 47个测点的热流值进行了统计。

Libby discovered radioactive carbon element dating method and solved the puzzle of earth and human history.

利比发现的放射性碳14定年法，解答了地球与人类历史上的疑惑。

The basic approach of protecting people from being hurt or killed in an accident is to improve crashworthiness of vehicles. This paper starts with discussing theories and methods for vehicle passive safety design, which included experiential methods, analytic methods, multi-body dynamics methods, crash test methods and the finite element method. Emphasis will be paid to the basic FEM theories and algorithms of impact problems. Topics discussed include the governing equation, element discretization, hourglass control, time integration, material model, shell element algorithms and contact-impact algorithms. For more reliable simulation results, this paper then conducts study on how to accurately get material model parameters by combining the FEM method with experimental method, and develops relevant material test machine and parameter calculating software. Based on that, basic typical impact simulation and test validation study are conducted. On the basis of the above work, the paper studies the thin-shell structures'crashworthiness, which was affected by the following factors: spot-weld features, shell thickness, cross-section and pre-deformation. As to vehicle parts'crashworthiness, the paper conducts simulation study of designing energy-absorbing steering system and adaptive airbag system. A practical energy-absorbing steering wheel is designed as an example. In further depth research, the paper suggests several inverse quantificational methods for vehicle crashworthiness design based on the ideal crash characteristics. The above theories and methods are applied with good results through several practical vehicles' crashworthiness design and improvement.

文中对汽车碰撞安全性的设计理论和方法进行了归类和总结，其中包括经验法、解析法、多刚体动力学法、试验法以及有限元方法等；重点介绍了碰撞有限元法的基本理论和有关算法，涉及到有限元求解控制方程、单元离散、沙漏模态控制、时间积分、材料模型和应力修正、薄壳单元算法以及接触碰撞界面算法等，探讨了有限元计算中的材料模型参数获取技术，开发了相应的材料试验装置及材料模型参数反求软件，在此基础上进行了基本的碰撞仿真算例和试验对比研究；文中通过应用有限元方法研究了薄壁构件的碰撞吸能特性，指出了设计薄壁吸能构件时需要考虑的几个主要影响因素，即焊点、壁厚、横截面和预变形等；在关于车辆部件的碰撞安全性能设计中进行了吸能转向机构和自适应安全气囊的仿真研究，提出了吸能转向机构和自适应安全气囊的仿真研究方法；文中最后探讨了整车碰撞性能的设计与改进方法，提出了以理想碰撞特性为目标，采用分段加速度或者根据碰撞时间进行设计的反推设计法、部件吸能仿真优化设计法等量化设计方法，并通过综合应用文中所讨论的相关技术进行了整车碰撞性能的设计与改进实例研究，所选定的车型是大众化的普通轿车和碰撞安全性基础较差的微型面包车，研究结果表明，本文所提出的设计与改进方法是适用而有效的，具有重要的工程实用意义和价值。

Shadow effect can not be neglected for thermal analysis of spacecraft,Accroding to the angle between solar light and antenna orbit plane and its orbit location,analytical geometry method was used for accurately calculating solar radiation heat flux distribution of reflector surfaces.To analyze the temperature field under heat flux,the formulations of net radiation flux density between two gray elements and the net flux density of gray surface under external thermal flux were deduced.Based on the characteristic of space environment,the nonlinear temperature distribution in transverse direction of reflector shell self radiation were considered,the finite element formulations were given for orthogonal material layered shell by Galerkin method.A layered element including a inner heat source layer was proposed,and the finite element formulation expressed by DOF of the inner heat source layer were put forward with temperature and heat flux boundarys between adjacent layer.

单馈反射面赋形天线是未来星载天线发展的一个重要形式，分析了基于物理光学、几何光学和几何绕射理论的理想反射面辐射场；介绍了基于几何光学的反射面天线赋形方法；针对赋形过程中辐射场的快速分析要求，比较分析了基于物理光学的Fourier-Bessel和Jacobi-Bessel级数展开方法以及GB展开分析方法；利用GB展开快速分析方法在20GHz频率下对0.6m口径的天线进行赋形分析，实现中国大陆的30dB增益覆盖，通过数值计算研究了固定增益期望下的口径尺寸随频率的变化，以及频率为20GHz的不同尺寸天线赋形后的覆盖目标区域最大增益的变化情况。

In this paper we introduce a finite element program design method for solving 3 D thoracic electrical field distribution,based on Borland C++ for DOS and using isoparametric element of arbitrary hexahedron.In the process of solving final finite element equation,this paper uses the method of blocking and 'getting big number' to deal with total coefficient matrix and boundary conditions.

本文介绍了一种采用等参数8节点任意六面体单元来求解人体胸腔三维恒定电场分布的有限元程序设计方法，程序的编制基于BorlandC＋＋ForDOS的编程环境，在对最终形成的有限元代数方程的求解过程中采用了分块处理总系数矩阵及"取大数"处理边界条件的方法。

But GST= 0.156, Nm=1. 588. As a result, the foundation of Youyongchi Avicennia marina population was the result of the migration of hypocotyles and human factors.

这项工作可以为海岸防护林中新引进种类的判定以及为研究种群建立者效应方法的确定提供科学依据。

The two-dimensional CDRC-ADI-FDTD update equations for collision unmagnetized plasma are induced. The unconditional stability of the CDRC-ADI-FDTD formulation for collision unmagnetized plasma is obtained by the examples.

推导了碰撞非磁化等离子体中的二维CDRC-ADI-FDTD迭代公式，并用算例验证了碰撞非磁化等离子体CDRC-ADI-FDTD算法也是无条件稳定的。