National School of Management
Algiers, Algeria
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Gilman M.,Emory University | Hockenberry J.M.,National School of Management | Wilson I.B.,Brown University | Milstein A.S.,Stanford University
Health Affairs | Year: 2014

The Affordable Care Act includes provisions to increase th value obtained from health care spending. A growing concern among health policy experts is that new Medicare policies designed to improve the quality and efficiency of hospital care, such as value-based purchasing (VBP), the Hospital Readmissions Reduction Program (HRRP), and electronic health record (EHR) meaningful-use criteria, will disproportionately affect safety-net hospitals, which are already facing reduced disproportionate-share hospital (DSH) payments under both Medicare and Medicaid. We examined hospitals in California to determine whether safety-net institutions were more likely than others to incur penalties under these programs. To assess quality, we also examined whether mortality outcomes were different at these hospitals. Our study found that compared to non-safety-net hospitals, safety-net institutions had lower thirty-day risk-adjusted mortality rates in the period 2009-11 for acute myocardial infarction, heart failure, and pneumonia and marginally lower adjusted Medicare costs. Nonetheless, safety-net hospitals were more likely than others to be penalized under the VBP program and the HRRP and more likely not to meet EHR meaningful-use criteria. The combined effects of Medicare value-based payment policies on the financial viability of safety-net hospitals need to be considered along with DSH payment cuts as national policy makers further incorporate performance measures into the overall payment system. © 2014 by Project HOPE - The People-to-People Health Foundation.

Abdelkafi A.,National School of Management | Krichen L.,National School of Management
Energy | Year: 2011

In this paper, we are interested in a Wind Energy Conversion System (WECS) based on a Permanent Magnetic Synchronous Generator (PMSG). The studied WECS is made by the association of three aerogenerators. The objective of this work is to investigate a new strategy of pitch angle control to ensure a balance between the produced energy and the demanded one by the loads. The control strategy of the wind farm is composed of two parts: a local control according to the characteristics of each wind turbine « Pitch control » to protect the turbines against mechanical failure in the event of wind gust and a global control according to the total power demand and the available wind power. This strategy leads to achieving power objectives (active and reactive power targets) and system constraints. © 2011 Elsevier Ltd.

Masmoudi A.,National School of Management | Abdelkafi A.,National School of Management | Krichen L.,National School of Management
Energy | Year: 2011

This study was interested in the management of an energy production unit. A variable speed wind turbine (VSWT) was used as a principal source and a supercapacitor (SC) module was used as an energy storage system. Both were connected through a direct current bus. This unit was supplying a three-phase load using an inverter and an inductor and capacitor filter. In order to regulate the direct current bus voltage, the SC storage state was controlled by using a buck-boost converter according to load instructions and wind speed fluctuations. Then, a resonant controller was established to avoid any disturbances and to control the alternating line-to-line voltages of the load which may be unbalanced. This study has shown that the stability of the three-phase voltage source depends on the direct current bus power management and also on the line-to-line voltage control. Simulation results are presented to validate the efficiency of the control strategies used. © 2011 Elsevier Ltd.

Joo S.H.,National School of Management | Kim Y.,National School of Management
Scientometrics | Year: 2010

Intensified technology convergence, increasing relatedness between technological fields, is a mega-trend in 21st century science and technology. However, scientometrics has been unsuccessful in identifying this techno-economic paradigm change. To address the limitations and validity problems of conventional measures of technology convergence, we introduce a multi-dimensional contingency table representation of technological field co-occurrence and a relatedness measure based on the Mantel-Haenszel common log odds ratio. We used Korean patent data to compare previous and proposed methods. Results show that the proposed method can increase understanding of the technoeconomic paradigm change because it reveals significant changes in technological relatedness over time. © 2009 Akadémiai Kiadó, Budapest, Hungary.

Papanikolaou V.,National School of Management
Prehospital and disaster medicine | Year: 2013

Social and political instability have become common situations in many parts of the world. Exposure to different types of traumatic circumstances may differentially affect psychological status. The aim of this study was to compare the relationship between personal perceptions of control over the events happening in one's life and psychological distress in two groups who experienced physical trauma but differed as to whether the trauma was a result of political upheaval and violence. Views on the extent to which the state was interested in the individual were also assessed. The sample consisted of 120 patients who were injured in the Cairo epicenter and 120 matched controls from the greater Cairo area whose injuries were from other causes. The Brown Locus of Control Scale and the Symptom Checklist-90-Revised (SCL 90-R) were administered approximately three months after the January 2011 start of the demonstrations and subsequent overthrow of the government. The groups did not differ on locus of control. For both groups, externality was associated with greater distress, suggesting a relationship between perceived helplessness in controlling one's life and distress. The Cairo group scored significantly higher than the control group on the SCL 90-R Global Severity Index (GSI) and Positive Symptom Total (PST). Perceptions of state interest in the population were low; overall, 78% viewed the state as having little or no interest in them. Discussion The relationship between exposure intensity and psychological distress is examined. In addition, differences in findings in populations experiencing political chaos compared with other types of disasters are considered. Beliefs regarding personal control over one's life circumstances are more closely associated with psychological distress than the circumstances in which the trauma occurred.

Iverson K.M.,National School of Management | Pogoda T.K.,National School of Management
Medical care | Year: 2015

SUBJECTS: The sample comprised 176 New England Department of Veterans Affairs (VA) women Veteran patients.MEASURES: Self-reported IPV-related TBI was assessed with a modified VA TBI screening tool. The survey included validated measures of depression (Center for Epidemiologic Studies Depression Scale) and posttraumatic stress disorder (PTSD; Posttraumatic Disorder Checklist) symptoms, as well as overall mental and physical health (SF-12), and IPV (Conflict Tactics Scales-Revised-2). Questions assessed past-year VA and non-VA health care use.RESULTS: A total of 18.8% (n=33) met screening criteria for IPV-related TBI history. Women who experienced IPV-related TBI reported significantly higher depression (mean Center for Epidemiologic Studies Depression Scale scores: 26.6 vs. 20.7, P<0.0001) and PTSD (mean Posttraumatic Disorder Checklist scores: 53.2 vs. 34.1, P<0.0001) symptoms, and poorer perceptions of physical health (mean SF-12 34.6 vs. 42.3, P<0.01) than women who experienced IPV to the head without TBI. IPV-related TBI was also associated with poorer perceptions of mental health, as well as more frequent VA health care utilization and overall IPV.CONCLUSIONS: IPV-related TBI is associated with poorer mental and physical health in women Veterans. This invisible injury is associated with greater VA health care utilization and IPV exposure. Implications for VA practice and policy are discussed.BACKGROUND: Intimate partner violence (IPV) is prevalent among women Veterans and is known to increase women's risk for traumatic brain injury (TBI). IPV-related TBI has not been examined in the women Veteran population.OBJECTIVES: To identify the occurrence of IPV-related TBI in a sample of women Veterans and examine the associations of IPV-related TBI with sociodemographic characteristics, health symptoms, health care utilization, and IPV experiences.RESEARCH DESIGN: Cross-sectional mail survey conducted in 2013.

Rekik M.,National School of Management | Abdelkafi A.,National School of Management | Krichen L.,National School of Management
International Journal of Electrical Power and Energy Systems | Year: 2013

This study was interested in a renewable distributed generator (RDG) made up of a wind turbine used as a principal source and a supercapacitor (SC) considered as a storage system. The studied RDG is associated with loads to constitute a micro-grid (MG) which can operate in grid connected mode, stand alone mode or synchronization mode. The objective of this work is to investigate a novel control scheme for MG integrated into power electrical system in order to maintain the voltage and the frequency of the grid in an allowable range and to ensure the continuity of power supply in case of grid failure. This control strategy made up of two parts: the first one is the power management algorithm used to detect islanding in case of defect and to monitor the RDG into seven operating modes. The second one is the droop control used to control the exported or imported active and reactive powers transferred with the grid ensuring its stability by adjusting the frequency and amplitude of its output voltage. The system is simulated using MATLAB software and results are provided in order to show the feasibility of this control strategy. © 2012 Elsevier Ltd. All rights reserved.

Hachicha F.,National School of Management | Krichen L.,National School of Management
Energy | Year: 2012

This paper is interested in the control of a wind energy conversion system (WECS) based on the doubly fed induction generator (DFIG) under grid fault conditions. A single line to ground fault and a double line to ground fault are tested during the hyper-synchronous operation of the DFIG wind turbine. In order to manage the rotor power flow in case of fault, a control technique of the grid side converter (GSC) is proposed. It is found that, three controllers are necessary to control the line currents of the rotor side connection because of the power unbalance during the faults. Simulation results are presented to show some operating conditions of the DFIG wind turbine and to prove the effectiveness of the proposed control technique. © 2012 Elsevier Ltd.

Jallouli R.,National School of Management | Krichen L.,National School of Management
Energy | Year: 2012

Due to the mismatch between the load demand and the intermittent solar energy, a stand-alone photovoltaic-hydrogen system and an optimal control scheme are designed to maintain the high system efficiency. Based on meteorological and the load demand data, a system sizing technique is proposed to establish the minimum capacity of the system components, which are a photovoltaic (PV) panel, a proton exchange membrane fuel cell (PEMFC), a battery bank and an alkaline electrolyzer (Elz).An accurate energy management scheme that is utilized during power transfer is proposed to meet the economic requirements. Case studies are used to verify the efficiency of the energy management strategy and system sizing technique. Simulation results illustrate a simple solution to the design and processing of stand-alone PV-hydrogen (PV-H 2) systems. © 2012 Elsevier Ltd.

Abdelkafi A.,National School of Management | Masmoudi A.,National School of Management | Krichen L.,National School of Management
International Journal of Electrical Power and Energy Systems | Year: 2013

Distributed generation seems to be a very interesting solution to provide electricity especially for the remote areas far from the electrical grid. In this paper, an autonomous wind energy conversion system and the control strategies applied to feed an isolated site were presented. A test bench was achieved in order to emulate the behaviour of a variable speed wind turbine connected to isolated loads. This study shows that the use of resonant controllers ensures the stability of the three-phase source supplying the loads which may be unbalanced and subjected to abrupt variations. A comparison between simulation and experimental results proves the effectiveness of the test bench and the control strategies implemented in real time. © 2012 Elsevier Ltd. All rights reserved.

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