【正文】 and the distribution of spinning electrons gives rise to magnetic properties.After World War Ⅱ, economic progress and national defense needs required the development of sophisticated materials, and it was soon apparent that an integration of the knowledge and methods of metallurgy, chemistry, and physics was essential for their development. The field of semiconductor electronics was a prime example of this. The basic work was done by physicists, who were oriented toward the analysis of electronic properties of pure, sample solids. But the successful production, of good semiconductor devices required a knowledge of defect structure, traditionally the province of the metallurgist, and the importance of impurity control was in many respects a problem of chemistry.By 1960 the integration of the three fields into a new activity was well under way. In the late 1950s the Advanced Research Projects Agency of the . Department of Defense, in cooperation with research universities, sponsored an open petition to establish governmentsupported research laboratories at a limited number of university to pursue the integrated study of materials and to educate graduate students in the new field. A dozen such facilities were set up in the United Sates.The methods of materials science have been extended to the study of polymers, glasses, ceramics, amorphous metals, and even biological materials such as bone. The simple concept of relating properties to structure has resulted in an astonishing variety of advanced materials of great utility.LESSON 16 Chemical Process SafetyIn 1978, Robert M. Solow, an economist at the Massachusetts Institute of Technology, received the Nobel Prize in economics for his work in determining the source of economic growth. Professor Solow concluded that the bulk of an economy’s growth is the result of technological advances.It is reasonable to conclude that the growth of an industry is also dependent on technological advances. This is especially true in the chemical industry, which is entering an era of more plex processes: higher pressure, more reactive chemicals, and exotic chemistry.More plex processes require more plex safety technology. Many industrialists even believe that the development and the application of safety technology is actually a constraint on the growth of the chemical industry. As chemical process technology bees more plex, chemical engineers will need a more detailed and fundamental understanding of safety. . Fawcett has said that to know is to survive and to ignore fundamentals id to court disaster.Since 1950, significant technological advances have been made in chemical process safety. Today, safety is equal in importance to production and has developed into a scientific discipline which includes many highly technical and plex theories and practices.Examples of the technology safety include:（a） Hydrodynamic models representing twophase flow through a vessel relief. （b） Dispersion models representing the spread of toxic vapor through a plant after a release.（c） Mathematical techniques to determine the various ways that processes can fail, and the probability of failure.Recent advances in chemical plant safety emphasize the use of appropriate technological tools to provide information for making safety to decision with respect to plant design and operation. The word safety used to means the older strategy of accident prevention through the used of hats, safety shoes, and a variety of rules and regulations. The main emphasis was on worker safety. Much more recently, safety has been replaced by loss prevention. This term includes hazard identification, technical evaluation, and the design of new engineering features to prevent loss. The words safety and loss prevention will be used synonymously throughout for convenience.Safety, hazard, and risk are frequentlyused terms in chemical process safety. Their definitions are:（a）Safety or loss prevention is the prevention of accidents by the use of appropriate technologies to identifiers the hazard of a chemical plant and to eliminate them before an accident occurs.（b）A hazard is anything with potential for producing an accident.（c）Risk is the probability of a hazard resulting in an accident.Chemical plants contain a large variety of hazards. Fires, there are the usual mechanical hazards that cause worker injuries from tripping failing, or moving equipment. Second, there are chemical hazards. These include fire and explosion hazards, reactivity hazards, and toxic hazards.As will be shown later, chemical plants are the safest of all manufacturing facilities. However, the potential always exists for an accident of catastrophe proportions. Despite substantial safety programs by the chemical industry, headlines of the type shown in Figure continue to appear in newspapers.A successful safety program requires several ingredients. These ingredients are a) Safety knowledge b) Safety experiencec) Technical petenced) Safety management supporte) CommitmentLESSON 17 Plant Design and General ConsiderationsThe general term plant design includes all engineering aspects involved in the development of either a new, modified, or expanded industrial plant. In this development, the chemical engineer will be making economic evaluations of new processes, designing individual pieces of equipment for the proposed new venture, or developing a plant layout for coordination of the overall operation. Because of these many design duties, the chemical engineer is many times referred to here as a design engineer. On the other hand, a chemical engineer specializing in the economic aspects of the design is often referred to as a cost engineer. In many instances, the process engineering is used in connection with economic evaluation and general economic analyses of industrial processes, while process design refers to the actual design of th