Early design decisions

Synthesizing of process systems with multiple objectives Given the importance and potential impact of early design decisions in synthesis, it is highly desirable to develop computational frameworks that allow the evaluation and determination of trade-offs for a number of different attributes. Besides traditional economic measures, these include operability, safety, and environmental aspects. 

There were other limitations imposed on the reactor design. One early design decision was that the core should not exceed five feet in diameter. Another constraint was the supply of U — 80 kg were made available for the project, and further supplies would be hard to come by. (The Orange Herald device which was tested in the Pacific in 1957 used 120 kg of U, which went up in smoke.)... 

However, in the early stages of design, decisions that have important safety implications must be made based on an incomplete picture. Let us explore simple quantitative measures which can be used to assist decision making in the early stages of design. 

It is also possible to circumvent these mechanical design decisions at the early process design stage by rewriting the differential equations (4.9) in terms of V, the volume of the reactor, instead of in terms of the length /. This is our chosen approach here. In it the independent variable V will vary from V = 0 to V = Vr = Vend = 1.0 m3. 

The main conclusion from this simple example is that important design decisions can be taken at the Input/Output level. Material balance analysis must consider the reaction selectivity. Impurities present in raw materials or formed by reactions generate environmental problems that must be detected at very early stages. 

Useful in making accurate design decisions early in the usability life cycle without the need for a prototype or costly user testing. 

The CRM process should be implemented as early as possible in a project as this will allow key design decision to take potential controls into account at the outset rather than suffer unexpected rework costs later. Basically, the sooner CRM activities become business as usual, the more effective and cost-efficient the work will be. Developing this process should involve the consultation of all appropriate stakeholders ensuring that the various gives and gets align and avoid circular dependencies. The use of a RACl matrix (Responsible, Accountable, Consulted, Informed) [5] or similar tool can be helpful in deriving these relationships. 

The key to having a cost-effective safety effort is to embed it into a system engineering process starting from early concept development and then to design safety into the system as the design decisions are made. Costs are much less when safety is built into the system design from the beginning rather than added on or retrofitted later. 

To start safety engineering early enough to be cost-effective, safety must be considered from the early concept formation stages of development and continue throughout the life cycle of the system. Design decisions should be guided by safety... 

As design decisions are made, an STPA-based hazard analysis is used to inform these decisions. Early in the system design process, little information is available, so the hazard analysis will be very general at first and will be refined and augmented as additional information emerges through the system design activities. 

For the application of cathodic protection to structures to be protected, the initial considerations are best made at the early design and preconstruction phase of the structure. For underground structures, it may be necessary to visit the proposed site, or for pipelines the proposed route, to obtain additional information on low-resistivity areas, availability of electric power, and the existence of stray dc current or other possible interactions. Other considerations will include fundamental design decisions to select the type of system and the most suitable type of anode appropriate to that system. In addition, it will be a requirement to determine the size and number of the power sources or sacrificial anodes and their distribution on the structure. Other factors that must be considered to ensure that cathodic protection is applied in the most economic and reliable manner are given as follows. 

The mentioned ideas and methods provide an evaluation of the system impact factors and system reliability in early phases of development. The application of this approach makes both a smart system design decision during the system design phase and a comprehensive reliability-oriented feedback of the product development possible. 

The visible design rules ( visible information ) are basic decisions that affect subsequent design decisions. Ideally, the visible design rules are established early in a design process and communicated broadly to those involved. Visible design mles consist of tiiree categories ... 

Adaptive methodologies, such as sample size or outcome re-estimations and early stopping decision rules, could be specified in the statistical analysis plans for cardiovascular safety outcome trials, potentially to reduce study duration, increase the chances of success, and facilitate earlier submissions. Many different types of adaptive designs are in use. The most common adaptation is to increase the sample size if the rate at which outcomes are accruing is slow. This modification raises no statistical issues if done in a blinded manner. 

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