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.     

Immigrant incorporation in the garment industry of Los Angeles

This study expands immigrant social network theory and examined employment patterns in the garment industry in Los Angeles, California, among Latino workers employed by Asian immigrant entrepreneurs. The study determined that a large percentage of immigrant employees found their jobs through the immigrant economy. Entrepreneurship increased the supply of local jobs and expanded the economy at destination at no expense to natives. Immigrant entrepreneurs bought firms from nonimmigrant owners or started new ones with an immigrant labor supply. Massey's index is flawed due to its exclusion of the role of entrepreneurs. Migration networks facilitate entrepreneurship, but some ethnic groups have fewer entrepreneurs, such as Mexicans and Central Americans. A 1993 Los Angeles survey identified 3642 garment factories in its county. Mean employment was 27.1 persons. The garment industry was the 4th largest industry in the area in 1996, with 98,700 employees. It represented 6% of all wage and salary employees in the City and 5.5% of the immigrant labor force in the County in 1990. 93% of garment workers in 1990 were immigrants. It is estimated that 51% of garment factory owners were Asians; most employees were Latinos. Census figures on sewing machine operators indicated 47.3% of owners were Whites and 42.45 were Asians. 53.3% of employees were other ethnic groups, 14.5% were Asians, and 32.2% were Whites. It is estimated that 47.2% of total employment was due to the immigration economy. 71.5% of the total employment in the garment industry was in the immigrant sector.     

A Comparison of Child-sex-abuse-related and Mental-disorder-related Suicide in a Six-year Cohort of Regional Suicides: The Importance of the Child Protection-Psychiatric Interface

Correspondence to: Professor Colin Pritchard, Department of Mental Health, School of Medicine, Southampton University, Royal South Hants Hospital, Southampton SO14 0YG, UK. E-mail: cp1{at}soton.ac.uk Summary The study compares Mental-Disorder-Related (MDR) suicide rateswith Child-Sex-Abuse-Related (CSAR) suicide of ‘Victims’and ‘Perpetrators’ of child sex abuse, based uponan examination of all Coroners’ inquest files over a six-yearperiod (n = 1,017). Census data, psychiatric case register andpolice records were used to calculate the potential MDR andCSAR populations. There were five main findings: (i) male andfemale CSAR victim suicide rates were 2.2. and 2.5 times theGeneral Population Suicide Rate (GPSR), respectively; (ii) everyfemale, and 80 per cent of male CSAR victim suicides, also hada mental disorder but none of the CSAR perpetrator suicides;(iii) male and female MDR suicide rates were 5 and 6 times theCSAR Victim rates; (iv) the sex abuser perpetrators’ suiciderate was more than 3 times the male MDR rate; (v) the intra-and extra-familial perpetrator suicide rates, were 25 and 78times the GPSR, respectively. Possible explanations for thesesurprising results are briefly discussed. They confirm the overrepresentationof people with mental disorder amongst suicides, and identifyan overrepresentation of CSAR suicides, particularly perpetrators.The results have implications for suicide prevention programmes,whilst highlighting the importance of the child protection-psychiatricinterface, and indicates the futility of simple explanationsin an area of practical and moral complexity.     

Lattices of choice functions and consensus problems

In this paper we consider the three classes of choice functions satisfying the three significant axioms called heredity (H), concordance (C) and outcast (O). We show that the set of choice functions satisfying any one of these axioms is a lattice, and we study the properties of these lattices. The lattice of choice functions satisfying (H) is distributive, whereas the lattice of choice functions verifying (C) is atomistic and lower bounded, and so has many properties. On the contrary, the lattice of choice functions satisfying (O) is not even ranked. Then using results of the axiomatic and metric latticial theories of consensus as well as the properties of our three lattices of choice functions, we get results to aggregate profiles of such choice functions into one (or several) collective choice function(s).The authors thank two anonymous referee for several useful remarks or corrections on the first version of the paper.     

Family Therapy with the Learning Disabled Child and His/Her Family

No therapist can come in contact with and treat children with minimal brain damage or specific learning disabilities without being struck by the fact that there are numerous intertwined factors that have contributed to and continue to perpetuate the problems. In addition to the helping approaches which have been utilized in recent years, such as tutoring, special education, and child therapy, this article elaborates the importance of utilizing family therapy as the treatment of choice sometime during the course of treating the child and helping the parents to understand and deal with their handicapped youngster.     

On edge orienting methods for graph coloring

We consider the problem of orienting the edges of a graph so that the length of a longest path in the resulting digraph is minimum. As shown by Gallai, Roy and Vitaver, this edge orienting problem is equivalent to finding the chromatic number of a graph. We study various properties of edge orienting methods in the context of local search for graph coloring. We then exploit these properties to derive four tabu search algorithms, each based on a different neighborhood. We compare these algorithms numerically to determine which are the most promising and to give potential research directions.     

Robustness evaluation of multisite distributed schedule with perturbed virtual jobshops

A method for evaluating the robustness of medium term multisite distributed schedule is presented. The method of robustness evaluation is based on steps and tools associated with the conceptual model of a MultiSite Reactive Production Activity Control (MSR-PAC). The MSR-PAC makes it possible to study the sensitivity of the scheduled plans in presence of perturbations. These must be evaluated before being dispatched to the shop-floors. At present, to the best of the authors' knowledge, there is no means to make this evaluation in the distributed systems such as extended enterprise. The monitoring of errors is based on the discrepancy between the two flow-shape functions that model respectively the dynamics of the scheduled manufacturing orders and the state of the perturbed production. The MSR-PAC is based on a multisite agent system and on the monitoring of the perturbed virtual jobshops. The method can also be used for controlling short term distributed production activities.