【正文】 plete set of operations according to the precedence relationship on the stages, a function or task is acplished. Thus, 39。), and, conversely, the effects in which the system influences the environment are outputs. From this consideration 39。. Systems Defined ? (3) Transformational (or functional) definition. From the last attribute, the effects of the environment upon the system are inputs (including unforeseen 39。a system is a collection of recognizable units having relationships among the units39。business system39。manufacturing system39。set.39。group39。Systems Engineering Review 系統(tǒng)工程 Chapter 1 Introduction to Systems Engineering Characterizing Systems (1)Four Basic Attributes of the System (1) Assemblage(集合 ). A system consists of a number of distinguishable units (elements, ponents, factors, subsystems, etc.), which may be physical or conceptual, natural or artificial. For Example, Consider a university as a system for producing educated graduates. Some of the parts of the university system are structural or static ponents, such as university buildings. As the system is operating, these structural ponents usually do not change much. Operating ponents are dynamic and perform processing such as the professors in a university who teach students. Flow ponents are often material, energy, or information。 but in this example, students are the parts that flow or matriculate through the university system (2) Relationship. Several units assembled together are merely a 39。 or a 39。 For such a group to be admissible as a system, a relationship or an interaction must exist among the units. The systems point of view also recognizes that a problem and its solution have many elements or ponents, and there are many different relations among them. For example, grades are one mechanism（機(jī)制） for interaction between professors and students. Grades serve a purpose, intended or not. Basic Attributes of the System Basic Attributes of the System (3) Goalseeking. An actual system as a whole performs a certain function or aims at single or multiple objectives. Wherever these objectives are attained at their maximum/minimum levels, system optimization is said to have been performed. An objective that is measurable by any means is called a goal/target. For example ： A 39。 effectively converts resources of production into produced goods (products), attaining an objective that creates high utilities by adding values to the raw materials, resulting in superior quality, cost and delivery. Basic Attributes of the System (4) Adaptability to environment. A specific, factual system behaves so as to adapt to the change in its surroundings, or external environment. For example， A 39。 is a selfanizing system, in that it generates a diversified variety of activities, resulting in economies of scope. Systems Defined Four Definitions of Systems On the basis of the foregoing considerations, the four essential definitions of systems can now be given as follows (Hitomi, 1975). Systems Defined (1) Abstract (or basic) definition. On the basis of the first two attributes above, 39。. Under this definition, general system theory has been developed, wherein things are deliberated theoretically, logically, and speculatively. Systems Defined (2) Structural (or static) definition. On the basis of all four attributes, a system is a collection of recognizable units having relationships among the units, aiming at specified single or multiple objectives subject to its external environment39。disturbances39。a system receives inputs from its environment, transforms them to outputs, and releases the outputs to the environment, whilst seeking to maximize the productivity of the transformation39。a system is a procedurea series of chronological, logical steps by which all repetitive tasks are performed39。 Knowledge principles include a host of scientific theories. In a sense, these represent the why associated with the functioning of systems. SYSTEMS ENGINEERING KNOWLEDGE For example, one knowledge principle is that associated with Newton39。s law of mechanics, until we actually e up with a differential equation, SYSTEMS ENGINEERING KNOWLEDGE doubtlessly a very plicated one, that could be used to predict the motion of an automobile when subjected to various forcing functions due to different time histories of accelerator pedal movement and braking controls. Then we could use this differential equation to project the time that would be required to stop a fancy sports car traveling at 60 miles per hour under a certain type of braking action. We would be using knowledge principles to predict the braking effectiveness of this particular car. SYSTEMS ENGINEERING KNOWLEDGE ? Knowledge practices, which represent the accumulated wisdom and experiences that have led to the development of standard operating policies for wellstructured problems。 Knowledge perspectives are needed when we attempt to project various futures for the automobile. For example, we might envision a significant increase in gasoline prices due to an oil embargo. Or we might envision renewed concern for environmental preservation. Each of these SYSTEMS ENGINEERING KNOWLEDGE could lead to significant interest in smaller size engines, engines that would result in greater fuel use efficiency at the expense of lower power. This could increase the incentives for electric batterypowered automobiles. For these to be costeffective, there would have to be a technological revolution in battery storage capacities. There would have to be other changes, such as in societal willingness to accept lowpowercapacity automobiles. SYSTEMS ENGINEERING KNOWLED