《nuclear energy》由会员分享，可在线阅读，更多相关《nuclear energy（9页珍藏版）》请在金锄头文库上搜索。
1、OUR MATERIAL world is composed of many substances distinguished by their chemical, mechanical, and electrical properties. They are found in nature in various physical statesthe familiar solid, liquid, and gas, along with the ionic “plasma.”However, the apparent diversity of kinds and forms of materi
2、al is reduced by the knowledge that there are only a little more than 100 distinct chemical elements and that the chemical and physical features of substances depend merely on the strength of force bonds between atoms.我们的物质世界由许多物质组成，这些物质由它们的化学性质、机械特性和电的性质区分开来。物质在自然界中以各种各样的状态被发现，有熟悉的固态，液态和气态，还有离子的等离子
3、体态。然而，由于人们已认识到目前仅仅存在100多种不同的化学元素，并且物质的化学性质和物理性质仅仅是由原子间力键的强度所决定，因此物质种类和形式的表面上的多样性可以被归纳简化。We recall that radiant energy may be released by heating of solids, as in the wire of a light bulb; by electrical oscillations, as in radio or television transmitters; or by atomic interactions, as in the sun. Th
4、e radiation can be viewed in either of two waysas a wave or asa particledepending on the process under study. In the wave view it is a combination of electric and magnetic vibrations moving through space. In the particle view it is a compact moving uncharged object, the photon, which is a bundle of
5、pure energy, having mass only by virtue of its motion. 我们知道，加热的固体可以释放出辐射能，例如在灯泡里的灯丝上，又比如在无线电或电视发射机中的电振荡，或太阳内部的原子相互作用都可以释放这种能量。依据研究的方法，可以用两种方式来看待辐射，即一束波或者一个粒子。从波的角度，辐射可以看作通过空间传输的电磁振荡的混合。从粒子的角度，辐射可以看作一个紧凑的不带电的物体光子。因为光子只有运动才具有质量，所以光子是一束纯能量。A COMPLETE understanding of the microscopic structure of matter
6、 and the exact nature of the forces acting is yet to be realized. However, excellent models have been developed to predict behavior to an adequate degree of accuracy for most practical purposes. These models are descriptive or mathematical, often based on analogy with large-scale processes, on exper
7、imental data, or on advanced theory.对物质的微观结构和作用力的准确性质的完全认识仍有待于实现。然而，为了实际的用途，能足够精确地预知物质在微观世界行为的模型已经被研究出来。这些模型是描述性的或数学的，基于对大尺度过程的类推、实验数据或先进的理论。An increase in the temperature of the gas as a result of heating causes greater molecular motion,which results in an increase of particle bombardment of a cont
8、ainer wall and thusof pressure on the wall.加热使得气体温度上升，温度上升又引起分子运动的加剧导致粒子对容器内壁碰撞的增加，使得气体对器壁压力增大。The electronic structure of the other elements is described by the shell model,in which a limited number of electrons can occupy a given orbit or shell. Theatomic number Z is unique for each chemical eleme
9、nt and represents both thenumber of positive charges on the central massive nucleus of the atom and thenumber of electrons in orbits around the nucleus.其他元素的电子结构用壳层模型来描述。在此模型中，占据给定能级或壳层的电子数目是有限的。对每一个化学元素，原子序数Z是唯一的。原子序数代表两个数目：一个是中心重的原子核上的正电荷数，另一个是核周围轨道上的电子数。The force of electrostatic repulsion betwee
10、n like charges, which varies inverselyas the square of their separation, would be expected to be so large that nucleicould not be formed. The fact that they do exist is evidence that there is an evenlarger force of attraction. 同种电荷之间的静电排斥力与他们距离的平方成反比，预期核内排斥力很大，以至于不能形成原子核。而原子核的确存在的事实，表明存在着一个甚至更大的吸引力。
11、To disrupt a nucleus and separate it into its component nucleons, energy must be supplied from the outside. Recalling Einsteins relation between mass and energy, this is the same as saying that a given nucleus is lighter than the sum of its separate nucleons, the difference being the binding mass-en
12、ergy. 要想分裂一个原子核，并将原子核分离成它的组成成分，就必须从外部供给能量。联系爱因斯坦的质能等价关系式，这也就是说，一个给定的原子核比其各个核子的总的质量要轻，它们之间质量只差，就是结合质能。MANY NATURALLY occurring and man-made isotopes have the property of radioactivity,which is the spontaneous disintegration (decay) of the nucleus with the emissionof a particle. The process takes plac
13、e in minerals of the ground, in fibers ofplants, in tissues of animals, and in the air and water, all of which contain tracesof radioactive elements.许多天然和人造同位素都具有放射性的特性，即原子核发射出粒子的自发衰变。这个过程发生在地表的矿物中、植物的纤维中、动物的组织中、空气和水中，所有的这些物质都存在着放射性元素的痕迹（放射性元素无处不在）。Whereas the electron (sometimes called negatron) is
14、 a normal part of any atom, the positron is not. It is an example of what is called an antiparticle, because its properties are opposite to those of the normal particle. Just as particles form matter, antiparticles form antimatter.然而，电子（有时称为阴电子）是任何原子一个正常的部分，正电子则不是。正电子是反粒子中的一个例子。反粒子的性质与正常的例子的性质相反，正如粒
15、子形成物质，反粒子形成反物质。The measurement of the activity of a radioactive substance is complicated by the presence of background radiation, which is due to cosmic rays from outside the earth or from the decay of minerals in materials of construction or in the earth. It is always necessary to measure the backg
16、round counts and subtract them from those observed in the experiment.放射性物质活度的测量因“本底辐射”的存在而变得复杂，本底辐射来自地球外的宇宙射线，建筑物材料中或地球中的矿物质的衰变。因此，总是必须测量本底计数，并从实验中所观察到的那些计数中扣除本底。 NUCLEAR REACTIONSthose in which atomic nuclei participatemay take placespontaneously, as in radioactivity or may be induced by bombardment with aparticle or ray. Nuclear reactions are much more energetic than chemical reactions,b
