An application of recent developments of Data Envelopment Analysis to the evaluation of secondary schools in Portugal

This paper highlights the potentialities of Data Envelopment Analysis to evaluate the performance of organisations, using the concept of super-efficiency - an extension of DEA which increases its performance - and presents an example from the public sector to illustrate the method. The example selected is that of a school network where a place in a school can be seen as a perishable good, as places which are not occupied during an academic year are wasted. Results for the Portuguese Secondary school network show that the average efficiency of overcrowded schools, that is, those exceeding their capacity, is lower than that of schools which are less crowded. This shows clearly that overcrowded schools, on average, are less efficient in transforming their inputs into academic performance. It is this conviction, seldom proved scientifically, which leads governments and international organisations to recommend planning criteria for public facilities

Quasi-Equatorial Gravitational Lensing by Spinning Black Holes in the Strong Field Limit

Spherically symmetric black holes produce, by strong field lensing, two infinite series of relativistic images, formed by light rays winding around the black hole at distances comparable to the gravitational radius. In this paper, we address the relevance of the black hole spin for the strong field lensing phenomenology, focusing on trajectories close to the equatorial plane for simplicity. In this approximation, we derive a two-dimensional lens equation and formulae for the position and the magnification of the relativistic images in the strong field limit. The most outstanding effect is the generation of a non trivial caustic structure. Caustics drift away from the optical axis and acquire finite extension. For a high enough black hole spin, depending on the source extension, we can practically observe only one image rather than two infinite series of relativistic images. In this regime, additional non equatorial images may play an important role in the phenomenology.Comment: 13 pages, 9 figures. Improved version with detailed physical discussio

Thermal performance of loop heat pipes with smooth and rough porous copper fiber sintered sheets

Smooth and rough porous copper fiber sintered sheets, employed here as wicks for loop heat pipes for the first time, were fabricated using a low-temperature solid-phase sintering method. The capillary performance of these porous copper fiber sintered sheets were analyzed and discussed. The influence of the surface morphology, filling ratio, and working fluid on the thermal resistance, evaporator wall temperature, and start-up time of the loop heat pipes were investigated. The results showed that the capillary pumping amount of working fluid for both smooth and rough porous copper fiber sintered sheets initially increases rapidly, and then gradually attains a stable state. The curve of the capillary pumping amount of working fluid can be described as a function that increases exponentially over time. When rough porous copper fiber sintered sheets are used as wicks and deionized water is used as the working fluid, the capillary pumping amount is maximized. Compared to smooth porous copper fiber sintered sheets, loop heat pipes with rough porous copper fiber sintered sheets exhibit a shorter start-up time, lower thermal resistance, and lower evaporator wall temperature. For a filling ratio in the range of 15–45%, loop heat pipes with rough porous copper fiber sintered sheets and a 30% filling ratio show lower thermal resistance and a lower evaporator wall temperature. Ultimately, the use of deionized water as the working fluid with a 30% filling ratio enables loop heat pipes with rough porous copper fiber sintered sheets to be stably operated at a heat load of 200 W

Energy-Momentum Localization for a Space-Time Geometry Exterior to a Black Hole in the Brane World

In general relativity one of the most fundamental issues consists in defining a generally acceptable definition for the energy-momentum density. As a consequence, many coordinate-dependent definitions have been presented, whereby some of them utilize appropriate energy-momentum complexes. We investigate the energy-momentum distribution for a metric exterior to a spherically symmetric black hole in the brane world by applying the Landau-Lifshitz and Weinberg prescriptions. In both the aforesaid prescriptions, the energy thus obtained depends on the radial coordinate, the mass of the black hole and a parameter $\lambda_{0}$, while all the momenta are found to be zero. It is shown that for a special value of the parameter $\lambda_{0}$, the Schwarzschild space-time geometry is recovered. Some particular and limiting cases are also discussed.Comment: 10 pages, sections 1 and 3 slightly modified, references modified and adde

Research on the Assembly Pattern of MMC Bolted Flange Joint

AbstractIn a Metal-to-Metal Contact (MMC) bolted flange joint the stress of sealing surfaces is constant. It canwithstand higherbolt load. So, under the operating conditions of high temperature, high pressure or their fluctuations, the sealing effect of MMC bolted flange joints is better than of floating (FLT) bolted flange joints. According to the structure characteristics of MMC bolted flange joints, a new tightening method (SH-Method) was recommended in this work.The bolt forces during the tightening process of a MMC bolted flange joint with SH-Method were calculated and analyzed with the finite element analysis Software ANSYS. The calculating model and results were experimentally verified. Both calculating and experimentally results showed, the new tightening method ‘SH-Method’has the advantages of fewer steps, simpler operation, more uniform bolt force, and better sealing effect, compared to the star pattern and the alternative pattern #3 of ASME PCC-1, in which only the pattern methods for FLT flange joints are recommended

Hyperuricemia and severity of coronary artery disease: An observational study in adults 35 years of age and younger with acute coronary syndrome

Background: Coronary artery disease (CAD) in adults ≤ 35 years of age is rare, but the incidence is on the rise and the risk factors for this age group are largely uncertain. Previous studies have shown that hyperuricemia (HUA) is an independent risk factor for CAD in the general population, whereas the role in adults ≤ 35 years of age with acute coronary syndrome (ACS) is unclear. Methods: Patients, 18–35 years of age, diagnosed with ACS for the first time at the documented institu- tion between January 2005 and December 2015, were enrolled in the current study. The severity of CAD was assessed by the Gensini score. Patients were divided into two groups according to the definition of HUA. The relationship between HUA and CAD severity was assessed based on multi-variate analysis.  Results: Seven hundred seventy-one participants fulfilling the criteria were included in this study (mean age, 31.6 years; 94.4% male). HUA, which was defined as a serum uric acid level ≥ 7.0 mg/dL (420μmol/L) in males and ≥ 6.0 mg/dL (357 μmol/L) in females, accounted for 37% of the participants. Multivariate analysis identified that HUA is an independent risk factor of CAD severity, as assessed by the Gensini score, in very young adults with ACS (OR 8.28; 95% CI 1.96–14.59; p = 0.01), and the effect of HUA on CAD severity was second only to diabetes mellitus. Conclusions: Hyperuricemia was shown to be an independent risk factor for CAD severity in young adults with ACS (18–35 years of age)

Randall-Sundrum Brane Tensions

We show that the singular sources in the energy-momentum tensor for the Randall-Sundrum brane world, viewed as a solution of type IIB supergravity, are composed of two elements. One of these is a D3-brane source with tension opposite in sign to the RS tension in five dimensions; the other arises from patching two regions of flat ten-dimensional spacetime. This resolves an apparent discrepancy between supersymmetry and the sign and magnitude of the RS tension.Comment: Latex, 21 pages, 2 figure

D=5 M-theory radion supermultiplet dynamics

We show how the bosonic sector of the radion supermultiplet plus d=4, N=1 supergravity emerge from a consistent braneworld Kaluza-Klein reduction of D=5 M--theory. The radion and its associated pseudoscalar form an SL(2,R)/U(1) nonlinear sigma model. This braneworld system admits its own brane solution in the form of a 2-supercharge supersymmetric string. Requiring this to be free of singularities leads to an SL(2,Z) identification of the sigma model target space. The resulting radion mode has a minimum length; we suggest that this could be used to avoid the occurrence of singularities in brane-brane collisions. We discuss possible supersymmetric potentials for the radion supermultiplet and their relation to cosmological models such as the cyclic universe or hybrid inflation.Comment: 18 pages, 4 figures, plain Late

Supersymmetry of the Schrodinger and PP Wave Solutions in Einstein-Weyl Supergravities

We obtain the Schrodinger and general pp-wave solutions with or without the massive vector in Einstein-Weyl supergravity. The vector is an auxiliary field in the off-shell supermultiplet and it acquires a kinetic term in the Weyl-squared super invariant. We study the supersymmetry of these solutions and find that turning on the massive vector has a consequence of breaking all the supersymmetry. The Schrodinger and also the pp-wave solutions with the massive vector turned off on the other hand preserve 1/4 of the supersymmetry.Comment: 13 pages, no figur

Gravity and Electromagnetism with Y(R)F2Y(R)F^2-type Coupling and Magnetic Monopole Solutions

We investigate $Y(R) F^2$-type coupling of electromagnetic fields to gravity. After we derive field equations by a first order variational principle from the Lagrangian formulation of the non-minimally coupled theory, we look for static, spherically symmetric, magnetic monopole solutions. We point out that the solutions can provide possible geometries which may explain the flatness of the observed rotation curves of galaxies.Comment: 10 page