Design hardware constraints

Besides as a property of the hardware modules, time can come in as designer-specified constraints. These are added into the graph as sequence edges, labeled with the time constraints. A detailed coverage falls outside the scope of this chapter. 

The intended operating environment for the system (e.g., hardware platform, operating system, etc., if this is a design constraint)... 

Different heat transfer applications require different types of hardware and different configurations of heat transfer equipment. The attempt to match the lieat transfer hardware to the heat transfer requirements within the specified constraints has resulted in numerous types of innovative heat exchanger designs. 

Although it dominated the market with its DOS operating system and its add-on Windows interface, Microsoft found that the constraints of DOS were rapidly making it difficult to take full advantage of rapidly improving hardware and software developments. The future of computing was clearly a 32-bit, preemptively multitasked system such as IBM s OS/2, but many current users had DOS-based software or older hardware that was specifically designed for DOS and would not operate outside of its Windows 3.1, cooperatively multitasked environment. 

Our third constraint was the need to design a system that would run on a microcomputer with only the basic 640K of RAM. This need stems from two facts Most of EPA s microcomputers had that hardware configuration, and EPA wanted the maximum number of users to have access to CORA without incurring the high cost of option-laden microcomputer hardware or the connect-time costs and possible lack of access of a mainframe system. Finally, the fourth constraint was that the chosen software must not levy licensing fees on production copies. 

The concept of a highly automated scale-up process is enticing. One vision of such a process for homogeneous (liquid phase, non-catalytic) reactions starts with little more than a list of reactants, solvents, and desired products. Given this information as well as constraints imposed by economic, environmental, safety, and practical factors, a highly automated system could include both software and hardware components to generate an optimal reactor design. The necessary software components would ... 

Protection against component failure accidents is well understood in engineering. Principles for safe design of common hardware systems (including sensors and actuators) with standard safety constraints are often systematized and encoded in checklists for an industry, such as mechanical design or electrical design. In addition. 

Software need not be treated any differently than the other parts of the system. Most safety-related software problems stem from requirements flaws. The system requirements and system hazard analysis should be used to determine the behavioral safety constraints that must be enforced on software behavior and that the software must enforce on the controlled system. Once that is accomplished, those requirements and constraints are passed to the software developers (through the black-box requirements specifications), and they use them to generate and validate their designs just as the hardware developers do. 

Requirements for safety strategies and design constraints, such as external interfaces, partitioning requirements, testability, design methods and hardware architectures. 

The enterprise shall prepare a preliminary human/system interface specification for the interaction among humans and the hardware and software elements identified in the system design architecture. The qualification section of the specifications should identify the methods used to confirm that each hnman/system interaction requirement has been satisfied under normal and abnormal conditions. In addition, hnman/systran interface specifications inclnde interface requirements between humans and/or snbsystems or components. These interfaces include human-human, human-hardware, and human-software. The reqnirements may inclnde functional and performance requirement, and workload and design constraints. 

In order to avoid this loop scheme that, on one hand, does not imply the optimahty of the final solution and on the other hand may result in a great number of cycles, a linear process is proposed. It consists in providing a description of the physical system from which aU hardware architectures can be deduced indirectly and automatically, thanks to the structural analysis. Then, an optimization problem is obtained by integrating the constraints about the fault tolerant level and the cost criteria. Following this strategy, the designer obtains efficiently the hardware architectures that satisfy the dependabUity constraints with the lowest cost. 

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