A derivative-free approach for a simulation-based optimization problem in healthcare

Hospitals have been challenged in recent years to deliver high quality care with limited resources. Given the pressure to contain costs,developing procedures for optimal resource allocation becomes more and more critical in this context. Indeed, under/overutilization of emergency room and ward resources can either compromise a hospital's ability to provide the best possible care, or result in precious funding going toward underutilized resources. Simulation--based optimization tools then help facilitating the planning and management of hospital services, by maximizing/minimizing some specific indices (e.g. net profit) subject to given clinical and economical constraints. In this work, we develop a simulation--based optimization approach for the resource planning of a specific hospital ward. At each step, we first consider a suitably chosen resource setting and evaluate both efficiency and satisfaction of the restrictions by means of a discrete--event simulation model. Then, taking into account the information obtained by the simulation process, we use a derivative--free optimization algorithm to modify the given setting. We report results for a real--world problem coming from the obstetrics ward of an Italian hospital showing both the effectiveness and the efficiency of the proposed approach

Effects of ownership, subsidization and teaching activities on hospital costs in Switzerland

This paper explores the cost structure of Swiss hospitals, focusing on differences due to teaching activities and those across different ownership and subsidization types. A stochastic total cost frontier with a Cobb-Douglas functional form has been estimated for a panel of 150 general hospitals over the six-year period from 1998 and 2003. Inpatient cases adjusted by DRG cost weights and ambulatory revenues are considered as two separate outputs. The adopted econometric specification allows for unobserved heterogeneity across hospitals. The results indicate that the time-invariant unobserved factors could account for considerable cost differences that could be only partly due to inefficiency. The results suggest that teaching activities are an important cost driving factor and hospitals that have a broader range of specialization are relatively more costly. The excess costs of university hospitals can be explained by more extensive teaching activities as well as the relatively high quality of medical units. However, even after controlling for such differences university hospitals have shown a relatively low cost-efficiency especially in the first two or three years of the sample period. The analysis does not provide any evidence of significant efficiency differences across ownership and subsidization categories.general hospitals, teaching hospitals, stochastic frontier, cost efficiency

A survey on pseudonym changing strategies for Vehicular Ad-Hoc Networks

The initial phase of the deployment of Vehicular Ad-Hoc Networks (VANETs) has begun and many research challenges still need to be addressed. Location privacy continues to be in the top of these challenges. Indeed, both of academia and industry agreed to apply the pseudonym changing approach as a solution to protect the location privacy of VANETs'users. However, due to the pseudonyms linking attack, a simple changing of pseudonym shown to be inefficient to provide the required protection. For this reason, many pseudonym changing strategies have been suggested to provide an effective pseudonym changing. Unfortunately, the development of an effective pseudonym changing strategy for VANETs is still an open issue. In this paper, we present a comprehensive survey and classification of pseudonym changing strategies. We then discuss and compare them with respect to some relevant criteria. Finally, we highlight some current researches, and open issues and give some future directions

Economies of Scope in European Railways: An Efficiency Analysis

In the course of railway reforms at the end of the last century, European na- tional governments, as well the EU Commission, decided to open markets and to separate railway networks from train operations. Vertically integrated railway com- panies argue that such a separation of infrastructure and operations would diminish the advantages of vertical integration and would therefore not be suitable to raise economic welfare. In this paper, we conduct a pan-European analysis to investi- gate the performance of European railways with a particular focus on economies of scope associated with vertical integration. We test the hypothesis that integrated railways realize economies of joint production and, thus, produce railway services on a higher level of efficiency. To determine whether joint or separate production is more efficient we apply an innovative Data Envelopment Analysis super-efficiency bootstrapping model which relates the efficiency for integrated production to a vir- tual reference set consisting of the separated production technology and which is applicable to other network industries as energy and telecommunication as well. Our findings are that for a majority of European Railway companies economies of scope exist.Efficiency, Vertical Integration, Railway Industry

Stress on the Ward – An Empirical Study of the Nonlinear Relationship between Organizational Workload and Service Quality

We discuss the impact of organizational workload on professional service outcomes, such as survival rates in hospitals. The prevailing view in the literature is that service quality deteriorates when organizational workload increases. In contrast, we argue that the relationship between workload and service outcomes is nonlinear and that there is a quality-optimal workload level. Whilst outcomes deteriorate with increasing workload when workload levels are already high, they will improve if workload increases from a low level. We reach this hypothesis by combining three perspectives: (i) the queuing theory perspective, with its focus on congestion, (ii) a discretionary choice perspective, with a focus on decisions made by professionals in response to changes in workload, and (iii) an endocrinological perspective, with a focus on the subconscious eff ects of workload on worker performance through the cognitive impact of stress hormones. Using a patient census of 1.4 million patients in 624 departments across 101 hospitals, we provide empirical support for the nonlinearity hypothesis in the context of hospital survival rates. We further discuss the implications for hospital capacity planning and the wider implications for service operations management.Service quality; service outcomes; organizational workload; hospital capacity planning; behavioral operations; stress

User-centered visual analysis using a hybrid reasoning architecture for intensive care units

One problem pertaining to Intensive Care Unit information systems is that, in some cases, a very dense display of data can result. To ensure the overview and readability of the increasing volumes of data, some special features are required (e.g., data prioritization, clustering, and selection mechanisms) with the application of analytical methods (e.g., temporal data abstraction, principal component analysis, and detection of events). This paper addresses the problem of improving the integration of the visual and analytical methods applied to medical monitoring systems. We present a knowledge- and machine learning-based approach to support the knowledge discovery process with appropriate analytical and visual methods. Its potential benefit to the development of user interfaces for intelligent monitors that can assist with the detection and explanation of new, potentially threatening medical events. The proposed hybrid reasoning architecture provides an interactive graphical user interface to adjust the parameters of the analytical methods based on the users' task at hand. The action sequences performed on the graphical user interface by the user are consolidated in a dynamic knowledge base with specific hybrid reasoning that integrates symbolic and connectionist approaches. These sequences of expert knowledge acquisition can be very efficient for making easier knowledge emergence during a similar experience and positively impact the monitoring of critical situations. The provided graphical user interface incorporating a user-centered visual analysis is exploited to facilitate the natural and effective representation of clinical information for patient care

A MERGE Model with Endogenous Technological Change and the Cost of Carbon Stabilization

Two stylized backstop systems with endogenous technological learning formulations (ETL) are introduced in MERGE: one for the electric and the other for the non-electric markets. Then the model is applied to analyze the impacts of ETL on carbon-mitigation policy, contrasting the resulting impacts with the situation without learning. As the model considers endogenous technological change in the energy sector only some exogenous key parameters defining the production function are varied together with the assumed learning rates to check the robustness of our results. Based on model estimations and the sensitivity analyses we conclude that increased commitments for the development of new technologies to advance along their learning curves has a potential for substantial reductions in the cost of climate mitigation helping to reach safe concentrations of carbon in the atmosphere.Climate change stabilization policies, Non-linear optimization, Induced technological change, Energy and macroeconomy

Induced Technological Change in a Limited Foresight Optimization Model

The threat of global warming calls for a major transformation of the energy system the coming century. Modeling technological change is an important factor in energy systems modeling. Technological change may be treated as induced by climate policy or as exogenous. We investigate the importance of induced technological change (ITC) in GET-LFL, an iterative optimization model with limited foresight that includes learning-by-doing. Scenarios for stabilization of atmospheric CO2 concentrations at 400, 450, 500 and 550 ppm are studied. We find that the introduction of ITC reduces the total net present value of the abatement cost over this century by 3-9% compared to a case where technological learning is exogenous. Technology specific polices which force the introduction of fuel cell cars and solar PV in combination with ITC reduce the costs further by 4-7% and lead to significantly different technological solutions in different sectors, primarily in the transport sector.Energy system model, Limited foresight, Climate policy, Endougenous learning, Technological lock-in

Testing for Economies of Scope in European Railways: An Efficiency Analysis

In this paper, we conduct a pan-European effciency analysis to investigate the performance of European railways with a particular focus on economies of vertical integration. We test the hypothesis that integrated railways realize economies of scope and, thus, produce railway services with a higher level of effciency. To determine whether joint or separate production is more effcient, we apply a Data Envelopment Analysis super-effciency bootstrapping model which relates the ef- ficiency for integrated production to a reference set consisting of separated firms which use a dierent production technology. We find that for a majority of European railways economies of scope exist.Efficiency, Vertical Integraton, Railway Industry