Construction Safety Risk Modeling and Simulation

By building on a genetic‐inspired attribute‐based conceptual framework for safety risk analysis, we propose a novel approach to define, model, and simulate univariate and bivariate construction safety risk at the situational level. Our fully data‐driven techniques provide construction practitioners and academicians with an easy and automated way of getting valuable empirical insights from attribute‐based data extracted from unstructured textual injury reports. By applying our methodology on a data set of 814 injury reports, we first show the frequency‐magnitude distribution of construction safety risk to be very similar to that of many natural phenomena such as precipitation or earthquakes. Motivated by this observation, and drawing on state‐of‐the‐art techniques in hydroclimatology and insurance, we then introduce univariate and bivariate nonparametric stochastic safety risk generators based on kernel density estimators and copulas. These generators enable the user to produce large numbers of synthetic safety risk values faithful to the original data, allowing safety‐related decision making under uncertainty to be grounded on extensive empirical evidence. One of the implications of our study is that like natural phenomena, construction safety may benefit from being studied quantitatively by leveraging empirical data rather than strictly being approached through a managerial perspective using subjective data, which is the current industry standard. Finally, a side but interesting finding is that in our data set, attributes related to high energy levels (e.g., machinery, hazardous substance) and to human error (e.g., improper security of tools) emerge as strong risk shapers.     

Von der Supervision zur Mediation und zurück

From supervision to mediation and vice versaMediation in organizations becomes more and more important because of increasing conflicts. The question is, which competencies of the counsellor are necessary, and above all, whether mediation is a particular method. The author explains the method of mediation and illustrates his concept of “patchwork-mediation”. This procedure allows to build a bridge between supervision and mediation.     

Decision Support by Interval SMART/SWING—Incorporating Imprecision in the SMART and SWING Methods

Interval judgments are a way of handling preferential and informational imprecision in multicriteria decision analysis (MCDA). In this article, we study the use of intervals in the simple multiattribute rating technique (SMART) and SWING weighting methods. We generalize the methods by allowing the reference attribute to be any attribute, not just the most or the least important one, and by allowing the decision maker to reply with intervals to the weight ratio questions to account for his/her judgmental imprecision. We also study the practical and procedural implications of using imprecision intervals in these methods. These include, for example, how to select the reference attribute to identify as many dominated alternatives as possible. Based on the results of a simulation study, we suggest guidelines for how to carry out the weighting process in practice. Computer support can be used to make the process visual and interactive. We describe the WINPRE software for interval SMART/SWING, preference assessment by imprecise ratio statements (PAIRS), and preference programming. The use of interval SMART/SWING is illustrated by a job selection example.     

Sequence Independent Lifting in Mixed Integer Programming

We investigate lifting, i.e., the process of taking a valid inequality for a polyhedron and extending it to a valid inequality in a higher dimensional space. Lifting is usually applied sequentially, that is, variables in a set are lifted one after the other. This may be computationally unattractive since it involves the solution of an optimization problem to compute a lifting coefficient for each variable. To relieve this computational burden, we study sequence independent lifting, which only involves the solution of one optimization problem. We show that if a certain lifting function is superadditive, then the lifting coefficients are independent of the lifting sequence. We introduce the idea of valid superadditive lifting functions to obtain good aproximations to maximum lifting. We apply these results to strengthen Balas' lifting theorem for cover inequalities and to produce lifted flow cover inequalities for a single node flow problem.     

Higher Education's Role in the Dialogue on Race

The university is a logical locus for discussionof the role race has played in our society. Perhaps noAmerican institution is more committed to free andopen dialogue than the university. Higher educationcan thus provide a context for the recognition ofissues as well as a forum for the resolution ofinitiatives. To date, however, university attempts atdiversity training have often imbued recipients withself-consciousness, usurping the unity implicit in theword `university' and evoking an even greater tendencytoward separatism. The university's traditional questfor truth has been subverted by a subtle and pervasivesense that some views are more correct than others,that openness is dangerous, and that some issues mighteven be taboo. At best, such an approach to diversityleads to a fragile stalemate among self-containedenclaves. By championing President Clinton's call fora dialogue on race, the university can restore itselfas an institution that puts honesty above all else.Not only is there a resonant rationale for theuniversity's central responsibility in this debate,but there is also a pedagogical means by which itsrole can be realized. This paper proposes a model forethnic dialogue relevant to either a text-based orissues-based class. Borrowing from pedagogy developedin professional schools, we believe that the tenets ofthe `case method' can create a climate conducive tothe substantive scrutiny of race, ethnicity, andprejudice in general. We argue that this dialogueshould not be a mere add-on to college life, butintegrated into existing curricula in the socialsciences, literature, and history. Heated debate canthen occur without anger, and race/ethnicity can bediscussed without fear of recrimination.Paradoxically, the very expression of ethnicity may bethe catalyst that eventually moves multiculturalismtoward interculturalism – where differences are nolonger articulated, measurable or even discernible.     

Don't fix it

Next to doing nothing, fixing a problem is often the worst thing you could do with it. Fix a problem but miss the context, and you still have the problem--only it's bigger, it's weirder, it costs more, and everybody's grumpy. When something comes at you with a "problem" label, use it as an opportunity to connect things up, to explore, to ask the bigger questions, to find the new possibilities. When we react to a problem, we put ourselves into a dilemma. To find fruitful and creative solutions, we need to be in a place of choice, with many possibilities. Real participation--giving people real choice--is the only way you can bring people's intelligence and life experiences to bear on the situation at hand.     

Optimal Contracts when Enforcement is a Decision Variable

This paper analyzes choice‐theoretic costly enforcement in an intertemporal contracting model with a differentially informed investor and entrepreneur. An intertemporal contract is modeled as a mechanism in which there is limited commitment to payment and enforcement decisions. The goal of the analysis is to characterize the effect of choice‐theoretic costly enforcement on the structure of optimal contracts. The paper shows that simple debt is the optimal contract when commitment is limited and costly enforcement is a decision variable (Theorem 1). In contrast, stochastic contracts are optimal when agents can commit to the ex‐ante optimal decisions (Theorem 2). The paper also shows that the costly state verification model can be viewed as a reduced form of an enforcement model in which agents choose payments and strategies as part of a perfect Bayesian Nash equilibrium.     

The Surgical Scheduling Problem: Current Research and Future Opportunities

This paper reviews the general problem of surgical scheduling. We organize the literature based on the time frame or planning horizon of the schedule into six categories: capacity planning, process reengineering/redesign, the surgical services portfolio, procedure duration estimation, schedule construction, and schedule execution, monitoring, and control. We survey past work and suggest topics for potential future research in each of those areas.     

Nonparametric Instrumental Regression

The focus of this paper is the nonparametric estimation of an instrumental regression function ϕ defined by conditional moment restrictions that stem from a structural econometric model E[Y−ϕ(Z)|W]=0, and involve endogenous variables Y and Z and instruments W. The function ϕ is the solution of an ill‐posed inverse problem and we propose an estimation procedure based on Tikhonov regularization. The paper analyzes identification and overidentification of this model, and presents asymptotic properties of the estimated nonparametric instrumental regression function.