Assessing Engineering Resilience for Systems with Multiple Performance Measures

Recently, efforts to model and assess a system's resilience to disruptions due to environmental and adversarial threats have increased substantially. Researchers have investigated resilience in many disciplines, including sociology, psychology, computer networks, and engineering systems, to name a few. When assessing engineering system resilience, the resilience assessment typically considers a single performance measure, a disruption, a loss of performance, the time required to recover, or a combination of these elements. We define and use a resilient engineered system definition that separates system resilience into platform and mission resilience. Most complex systems have multiple performance measures; this research proposes using multiple objective decision analysis to assess system resilience for systems with multiple performance measures using two distinct methods. The first method quantifies platform resilience and includes resilience and other “ilities” directly in the value hierarchy, while the second method quantifies mission resilience and uses the “ilities” in the calculation of the expected mission performance for every performance measure in the value hierarchy. We illustrate the mission resilience method using a transportation systems‐of‐systems network with varying levels of resilience due to the level of connectivity and autonomy of the vehicles and platform resilience by using a notional military example. Our analysis found that it is necessary to quantify performance in context with specific mission(s) and scenario(s) under specific threat(s) and then use modeling and simulation to help determine the resilience of a system for a given set of conditions. The example demonstrates how incorporating system mission resilience can improve performance for some performance measures while negatively affecting others.     

Residential Building Codes,Affordability, and Health Protection: A Risk-Tradeoff Approach

Residential building codes intended to promote health and safety may produce unintended countervailing risks by adding to the cost of construction. Higher construction costs increase the price of new homes and may increase health and safety risks through income and stock effects. The income effect arises because households that purchase a new home have less income remaining for spending on other goods that contribute to health and safety. The stock effect arises because suppression of new-home construction leads to slower replacement of less safe housing units. These countervailing risks are not presently considered in code debates. We demonstrate the feasibility of estimating the approximate magnitude of countervailing risks by combining the income effect with three relatively well understood and significant home-health risks. We estimate that a code change that increases the nationwide cost of constructing and maintaining homes by $150 (0.1% of the average cost to build a single-family home) would induce offsetting risks yielding between 2 and 60 premature fatalities or, including morbidity effects, between 20 and 800 lost quality-adjusted life years (both discounted at 3%) each year the code provision remains in effect. To provide a net health benefit, the code change would need to reduce risk by at least this amount. Future research should refine these estimates, incorporate quantitative uncertainty analysis, and apply a full risk-tradeoff approach to real-world case studies of proposed code changes.     

Bandwidth selection for local linear regression smoothers

Summary. The paper presents a general strategy for selecting the bandwidth of nonparametric regression estimators and specializes it to local linear regression smoothers. The procedure requires the sample to be divided into a training sample and a testing sample. Using the training sample we first compute a family of regression smoothers indexed by their bandwidths. Next we select the bandwidth by minimizing the empirical quadratic prediction error on the testing sample. The resulting bandwidth satisfies a finite sample oracle inequality which holds for all bounded regression functions. This permits asymptotically optimal estimation for nearly any regression function. The practical performance of the method is illustrated by a simulation study which shows good finite sample behaviour of our method compared with other bandwidth selection procedures.     

Methods for the analysis of mortality risks across heterogeneous small populations: examination of space-time gradients in cancer mortality in North Carolina counties 1970–75

A method of analyzing mortality rates in heterogeneous populations is presented. This method, appropriate for the investigation of mortality rates in small geographic areas (e.g., counties) where the forces of mobility operate to selectively “package” persons, is applied to the determination of whether a spatial west-east gradient in cancer mortality rates existed in North Carolina over the period 1970 to 1975. A significant gradient (as well as a significant temporal trend) is determined to exist in the data, though only for particular race, age and sex-specific demographic groups. Several alternate hypotheses are presented to explain the existence of the spatial gradient in these particular demographic groups.     

Cognitive-behavioral therapy for obsessive-compulsive disorder: review of treatment techniques

Obsessive-compulsive disorder (OCD) is a chronic, impairing condition with an estimated lifetime prevalence in adults of 2.5%. Controlled treatment trials have demonstrated that cognitive-behavioral therapy (CBT) is an effective intervention for OCD. However, many individuals diagnosed with OCD do not receive appropriate, empirically validated interventions, perhaps due to limited knowledge of CBT among mental health practitioners. This article provides a review of CBT for OCD. Issues related to treatment delivery and assessment are presented and highlighted by an individual example.     

How Much Is Leisure Worth? Direct Measurement with Contingent Valuation

This paper uses a contingent value survey in a Rocky Mountain city to measure the national income accounting value of leisure activities. Such direct measurement avoids shortcomings of the previously used labor value approach and individually values various types of leisure, e.g., napping and socializing. The results of the study indicate promise for this measurement approach but also raise some issues that require further research. Included are suggestions for overcoming problems discovered with this method and for future research.The authors wish to thank two anonymous referees of this journal who provided insightful comments and suggestions which improved the paper significantly.     

Effectiveness of couples treatment for spouse abuse

Despite its controversy, carefully conceptualized and delivered couples treatment appears to be at least as effective as traditional treatment for domestic violence, and preliminary data suggests that it does not place women at greater risk for injury. However, the body of research on which these conclusions rest is sparse. Only six experimental studies have been done, each using different eligibility criteria, outcome measures, and treatment approaches. Thus, further study of this modality is warranted. Marriage and family therapists have an important part to play in continuing to develop and test innovative ways of helping couples end violence and improve their relationships--an endeavor that promises to improve the quality of the partners' lives as well as those of their children.     

Use of Markov Chain Monte Carlo Analysis with a Physiologically-Based Pharmacokinetic Model of Methylmercury to Estimate Exposures in U.S. Women of Childbearing Age

A Bayesian approach, implemented using Markov Chain Monte Carlo (MCMC) analysis, was applied with a physiologically‐based pharmacokinetic (PBPK) model of methylmercury (MeHg) to evaluate the variability of MeHg exposure in women of childbearing age in the U.S. population. The analysis made use of the newly available National Health and Nutrition Survey (NHANES) blood and hair mercury concentration data for women of age 16–49 years (sample size, 1,582). Bayesian analysis was performed to estimate the population variability in MeHg exposure (daily ingestion rate) implied by the variation in blood and hair concentrations of mercury in the NHANES database. The measured variability in the NHANES blood and hair data represents the result of a process that includes interindividual variation in exposure to MeHg and interindividual variation in the pharmacokinetics (distribution, clearance) of MeHg. The PBPK model includes a number of pharmacokinetic parameters (e.g., tissue volumes, partition coefficients, rate constants for metabolism and elimination) that can vary from individual to individual within the subpopulation of interest. Using MCMC analysis, it was possible to combine prior distributions of the PBPK model parameters with the NHANES blood and hair data, as well as with kinetic data from controlled human exposures to MeHg, to derive posterior distributions that refine the estimates of both the population exposure distribution and the pharmacokinetic parameters. In general, based on the populations surveyed by NHANES, the results of the MCMC analysis indicate that a small fraction, less than 1%, of the U.S. population of women of childbearing age may have mercury exposures greater than the EPA RfD for MeHg of 0.1 μg/kgg/day, and that there are few, if any, exposures greater than the ATSDR MRL of 0.3 μgg/kgg/day. The analysis also indicates that typical exposures may be greater than previously estimated from food consumption surveys, but that the variability in exposure within the population of U.S. women of childbearing age may be less than previously assumed.     

Sharing genetic origins information in third party assisted conception: a case for Victorian family values?

In the United Kingdom (UK) approximately 2500 children are born each year as a result of third party assisted conception. Since formal record keeping by the statutory regulatory body, the Human Fertilisation and Embryology Authority, began in 1991, the total number of children known to have been born from all forms of third party assisted conception exceeds 13 500. Although the records contain information about these children's genetic origins, including the identity of the donor, current legislation severely circumscribes their ability to access this information and, save in very exceptional circumstances, they are not permitted to learn the identity of the donor. Consequently, they are the only individuals in the UK whose inability to learn the identity of both their genetic parents is formally endorsed by statute. This paper identifies different approaches to exchanging genetic origins information in third party assisted conception. It provides a critique of the model currently in force in the UK and advocates its replacement by a system that more closely resembles that introduced in Victoria (Australia) in 1998. Copyright © 2000 John Wiley & Sons, Ltd.