A two-level Structural Equation Model for evaluating the external effectiveness of PhD

In recent years the number of PhDs in Italy has significantly grown and purposes of PhD courses have expanded from the traditional ones. The analysis of the contribution of PhD title for job placement and employment condition of PhDs is an important tool for evaluating the quality and the effectiveness of PhD courses. For this reason, knowledge of the employment status and career of PhDs becomes essential and can help to reduce the gap between academia and labour market. The aim of this paper is to estimate a two-level structural equation model with latent variables to assess the external effectiveness of PhD. The analysis is performed using data from the research "Current situation and employment prospects of PhDs", commissioned by National Committee for the Evaluation of the University System (CNVSU) to the Department of Statistics "G. Parenti" of the University of Florence. The proposed measure of "external effectiveness" is a latent variable obtained by evaluating the level of satisfaction with the employment status of PhDs who achieved the title in 2008. The opinion was expressed one year after obtaining PhD on a ten ordered point scale. External effectiveness indicators used are Consistency with studies, Utilization of the acquired skills and Compliance with the cultural interests

Te-and Zn-Doped InSb Crystals Grown in Microgravity

In 2002, within the SUBSA (Solidification Using a Baffle in Sealed Ampoules) investigation, seven doped InSb crystals were grown in microgravity at the International Space Station. The key goals of the SUBSA investigation are: (a) to clarify the origin of the melt convection in space laboratories; (b) to reduce melt convection to the level which allows reproducible diffusion-controlled segregation; (e) to explore the submerged baffle process and liquid encapsulation in microgravity. 30 crystal growth experiments were conducted in the ground unit, to optimize the design of flight ampoules and to test the transparent SUBSA furnace developed by TecMasters Inc. The specially designed furnace, allowed observation of the crystal growth process (melting, seeding, motion of the solid-liquid interface, etc.). In the summer of 2002, eight crystal growth experiments were conducted in the Microgravity Science Glovebox (MSG) facility at the ISS. Four Te-doped (k = 0.5) and three Zn-doped (k2.9) crystals were grown on undoped seeds. In one experiment, we were not able to seed and grow. The seven grown crystals were sectioned and analyzed using SIMS. The design of the SUBSA ampoules, the segregation data and the video images obtained during the SUBSA flight experiments will be presented and discussed

Ostrogorsky)

Abstract Axial and radial segregation of (i) Ga in Ge and (ii) InSb in GaSb has been evaluated in crystals grown by the submerged heater method. The values of di!usion coe$cients obtained by "tting the Tiller's equation to the initial transients in composition are signi"cantly lower than the values in the literature, obtained by using shear cells with capillaries

Dewetting and Segregation of Zn-Doped InSb in Microgravity Experiments

In directional solidification, dewetting is characterized by the lack of contact between the crystal and the crucible walls, due to the existence of a liquid meniscus at the level of the solid-liquid interface. This creates a gap of a few tens of micrometers between the crystal and the crucible. One of the immediate consequences of this phenomenon is the dramatic improvement of the quality of the crystal. This improvement is partly due to the modification of the solid-liquid interface curvature and partly to the absence of sticking and spurious nucleation at the crystal-crucible interface. Dewetting has been, commonly observed during the growth of semiconductors in crucibles under microgravity conditions where it appears to be very stable: the gap between the crystal and the crucible remains constant along several centimetres of growth. The physical models of the phenomenon are well established and they predict that dewetting should not occur in microgravity, if sufficient static pressure is imposed on the melt, pushing it towards the crucible. We present the results of InSb(Zn) solidification experiments conducted at the International Space Station (ISS) where, in spite of a spring exerting a pressure on the liquid, partial dewetting did occur. This surprising result is discussed in terms of force exerted .by the spring on the liquid and of possibility that the spring did not work properly. Furthermore, it appears that the segregation of the Zn was not affected by the occurrence of the dewetting. The data suggest that there was no significant interference of convection with segregation of Zn in InSb

Heat Transfer Model of the SUBSA Furnace

No abstract availabl

TPV energy conversion: A review of material and cell related issues

This paper presents an overview of thermophotovoltaic (TPV) energy conversion using low band gap semiconductor photovoltaic cells. Physics of PN junctions related to TPV cells is described and the factors that affect overall cell efficiencies are outlined. Current status of bulk and epitaxial growth of TPV materials and cell fabrication issues are also described

Sb crystals through forced convection in the melt

Abstract It was demonstrated that forced convection or mixing in the melt during directional solidification of bulk In V Ga \V Sb (0(x(0.1) ternary alloys significantly reduces cracks in the crystals. In this study, the enhanced mixing in the melt was generated by a rotating submerged baffle. The resultant improvement in spatial compositional homogeneity lowers the strain gradient or chemical stresses; thus eliminating cracks. The results presented are generally beneficial and should also improve the crystalline quality of other mixed alloys