Common operation scheduling with general processing times: A branch-and-cut algorithm to minimize the weighted number of tardy jobs

Common operation scheduling (COS) problems arise in real-world applications, such as industrial processes of material cutting or component dismantling. In COS, distinct jobs may share operations, and when an operation is done, it is done for all the jobs that share it. We here propose a 0-1 LP formulation with exponentially many inequalities to minimize the weighted number of tardy jobs. Separation of inequalities is in NP, provided that an ordinary min Lmax scheduling problem is in P. We develop a branch-and-cut algorithm for two cases: one machine with precedence relation; identical parallel machines with unit operation times. In these cases separation is the constrained maximization of a submodular set function. A previous method is modified to tackle the two cases, and compared to our algorithm. We report on tests conducted on both industrial and artificial instances. For single machine and general processing times the new method definitely outperforms the other, extending in this way the range of COS applications

A Realistic Model to Support Rescue Operations after an Earthquake via UAVs

In this paper, we consider the problem of completely flying over an area just hit by an earthquake with a fleet of Unmanned Aerial Vehicles (UAVs) to opportunely direct rescue teams. The cooperation between UAVs ensures that the search for possible survivors can be faster and more effective than the solutions currently implemented by civil protection. To study this scenario, we introduce the Cover by Multitrips with Priorities (CMP) problem, which tries to keep into account all the main real-life issues connected to the flight and coordination of the UAVs. We conduct a theoretical study to estimate the best number of UAVs and additional batteries, to give indications to the organization that leads the rescue teams to be able to guarantee rapid and effective rescue. Finally, based on some theoretical considerations, we propose some heuristics that tackle the problem of flying over the whole area with a fleet of UAVs in the shortest possible time. Simulations show that they work efficiently in both the proposed scenarios and provide better performance than previous solutions once they are arranged to work in our scenarios. The main advantages of our approach w.r.t. the current drone-based solutions used by the civil defense are that UAVs do not need drivers so the time of all available rescue workers can be invested in doing something else. In our model, we take into account that some sites (e.g. buildings with a high fire risk or schools and hospitals) have a higher priority and must be inspected first, and the possibility that UAVs can make a decision based on what they detect. Finally, our approach allows UAVs to collaborate so that the same sites will be flown over exactly once in order to speed up the rescue mission

Maximum Likelihood and the Bootstrap for Nonlinear Dynamic Models

We provide a unified framework for analyzing bootstrapped extremum estimators of nonlinear dynamic models for heterogeneous dependent stochastic processes. We apply our results to the moving blocks bootstrap of Künsch (1989) and Liu and Singh (1992) and prove the first order asymptotic validity of the bootstrap approximation to the true distribution of quasi-maximum likelihood estimators. We also consider bootstrap testing. In particular, we prove the first order asymptotic validity of the bootstrap distribution of suitable bootstrap analogs of Wald and Lagrange Multiplier statistics for testing hypotheses. Nous proposons une approche unifiée pour analyser la méthode de bootstrap appliquée aux estimateurs de pseudo-maximum de vraisemblance dans le contexte de modèles non linéaires dynamiques où les données sont caractérisées par une dépendance d'époque proche. Nous appliquons nos résultats à la méthode de bootstrap de blocs mouvants de Künsch (1989) et Liu et Singh (1992) et nous démontrons la validité asymptotique de premier ordre de l'approximation du bootstrap à la distribution asymptotique de l'estimateur de pseudo-maximum de vraisemblance. Nous considérons aussi l'application du bootstrap à la réalisation de tests d'hypothèses. En particulier, nous démontrons la validité asymptotique des versions de bootstrap des tests de Wald et du multiplicateur de Lagrange.Block bootstrap, quasi-maximum likelihood estimator, nonlinear dynamic model, near epoch dependence, Wald test, Bootstrap en bloc, pseudo-maximum de vraisemblance, modèle non linéaire dynamique, dépendance d'époque proche, test de Wald

A reliability/availability simulation model for evaluating network systems.

A project report submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Engineering.The simulator uses the Monte Carlo technique to quickly and accurately estimate the reliability and availability of complex network systems, Non-exponential failure and repair distributions are included in the model, as is standby redundancy and K out of N active redundancy. The program is easy to use and will work on a large variety of computers and FORTRAN compilers. Some knowledge of FORTRAN is required to program the simulator for each reliability network, The simulator is limited to the analysis of network systems, i.e, those systems whose logic can be fully represented by a reliability block diagram. The applicability of the model was demonstrated by the analysis of numerous systems in the aerospace and industrial environments. Validation of the model was accomplished by comparing these results with analytically determined values, or those from AMIR and SPAR where an analytic solution was impossible.Andrew Chakane 201

Civil service reform and the World Bank

The emphasis placed by the World Bank in recent years on the major overhaul of developing country economies has accentuated the importance of adequate public sector administrative capacity, especially within the central core of government, that is, the civil service. This paper surveys recent Bank experience in civil service reform, and begins to assess the progress made. The paper focuses on two separate but related aspects of civil service reform work. One deals with the shorter term, emergency steps to reform public pay and employment policies. These reforms usually focus on measures to contain the cost and size of the civil service, mostly in the context of structural adjustment lending. The other set of reforms are those dealing with longer range civil service strengthening efforts, some of which may support various nearer term cost containment measures, but most of which are directed toward ongoing, sustained management improvements. Many of these reforms have been included in technical assistance projects, either those that stand alone as"development management"operations or those that constitute direct institutional support for specific actions taken in SALs.Banks&Banking Reform,Municipal Financial Management,Health Monitoring&Evaluation,Labor Management and Relations,National Governance

Construction of a rapid soil quality measurement framework and its use at the Alabama A&M bioenergy reserach site

This thesis evaluated multiple possible soil quality indicators in order to choose a small set for inclusion in a rapid soil quality measurement scheme. The scheme was developed to be used for examining soil quality changes caused by land use differences. A more rapid, albeit less detailed, assessment of soil quality will be valuable to researchers studying the effects of land use change where evaluation of multiple widely scattered sites is necessary in order to understand soil quality changes over a-wide range of treatments and site conditions. Research projects sponsored by the United States Department of Energy are examining the environmental changes that occur when agricultural land is converted to bioenergy production. A small number of these sites are heavily instrumented and sampled in order document environmental changes on site. This work would be greatly enhanced if many more locations and treatments could be sampled rapidly and cheaply. The goal of this thesis was to determine which measurements should be included in a rapid soil quality measurement scheme and to develop the scoring structure to accurately reflect changes in soil quality as measured by a larger suite of indicators. The experimental design utilized for indicator evaluation included four treatments: agricultural control, switchgrass, sweetgum trees with fescue cover, and sweetgum trees maintained with no cover crop. These treatments were replicated twice on severely degraded agricultural land near Huntsville, Alabama in 1995. The soil was sampled at planting and again in the fall of 2002 for each of the replicated treatments. The erosion rate was modeled based on the characteristics of the crops using the Revised Universal Soil Loss Equation (RUSLE). After careful consideration of each indicator, the measurement framework was fashioned with only two simple parameters in order to make it easy to use, and thus widely employable by researchers and land managers. Soil organic matter level and erosion rate were chosen due to their direct links to the health of the land, widespread use, ease of measurement or estimation, correlation to other important soil attributes, and sensitivity over the correct time frame. In order to make the soil quality measurement more site-specific, the organic matter and erosion indicators were scaled between one and zero based on the values measured for a ~50 year old forest (1) and an extremely eroded agricultural plot (0) nearby. Multiplying the erosion score by the organic matter score yielded the overall site health score. In this way, both indicators must be fairly high in order for the site to be deemed healthy. The treatments scored as follows: tilled agricultural (.05), sweetgum (.21), switchgrass (.15), and sweetgum with fescue cover (.34). The bioenergy treatments scored significantly higher than the tilled agricultural treatment, but the site will clearly take many more years to approach the health of a forest The other measured values of soil and plant characteristics yielded little information or were closely correlated to the chosen measurements and were thus not included in the scheme