CEE597_Midterm-Soln09rr - CEE 597 Risk Analysis and...

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CEE 597 Risk Analysis and Management Evening Midterm Exam March 5, 2009 Test is open book and open notes. You have 90 minutes to complete this 90 point exam. Please show work. 1. (4 pts) How have the major causes of death changed in the United States over the last hundred years, and why? 2. (8 pts) Accidents are often imagined as simple linear chains of events: chemical reaction at Bhopol gets out of control, toxic gas escapes from plant, people die. Based upon our study of historic accidents, how should the causes and consequences of accidents best be understood ? <Remember Prof. Stedinger’s remarks about essays. Provide at least one good example to support your conclusion. Use words & concepts from 5970. Answer this question!> 3. (14 pts) The identification of new security breaches in critical software (Adobe Reader, mail programs, MS_Word …) is a continuing and critical concern. The occurrence of such events can be described by a Poisson process, wherein on average 1 such breach is identified every four months. a) What then is the probability of having at least two breaches in the 6 months between 1 Jan 2010 and 1 July 2010? What is the probability of exactly 4 breaches in a year? b) On average, how many months will pass until 10 of these events occur? What is the standard deviation of that waiting time? c) How can the Disaster Management Cycle be used to understand activities associated with software security breaches. 4. (12 pts) Consider the reliability of the system described by the network below: D G C J B F H A E K a) What are ALL the MINIMAL cut sets with 4 or fewer components? b) If all elements are 95% reliable, what approximately is reliability of entire system? c) What component is most critical to the reliability of the system? Why? What 2 components individually are least critical? Why? 5. (8 pts) a) Consider the network in problem 4. If components C and J failed, describe the remaining network as a fault tree so that its failure probability could be evaluated.
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CEE 597 Risk Analysis and Management – Midterm 2009 Page 2 of 3 b) Consider the fault tree below, if each component is 95% reliable, what is the reliability of this system? A C B D 6. (9 pts) Consider a system with two independent components in parallel . Assume component failures are independent Poisson processes with arrival rates of 0.002 /week and 0.010/week, respectively. (a) What is the reliability function for the system? (b) What is the mean time before failure? (c) For how long can one be 99.5 percent certain the system will still be operating? 7. (15 pts) A research laboratory handles a lot of very unpleasant chemicals and performs some tricky experiments. Still, accidents happen. Assume that the probability of an accident is 1 per thousand-employee-working-days (i.e. 0.001 per employee-day), and that 82 employees work at the laboratory 5 days a week.
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CEE597_Midterm-Soln09rr - CEE 597 Risk Analysis and...

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