Negative phase time for Scattering at Quantum Wells: A Microwave Analogy Experiment

If a quantum mechanical particle is scattered by a potential well, the wave function of the particle can propagate with negative phase time. Due to the analogy of the Schr\"odinger and the Helmholtz equation this phenomenon is expected to be observable for electromagnetic wave propagation. Experimental data of electromagnetic wells realized by wave guides filled with different dielectrics confirm this conjecture now.Comment: 10 pages, 6 figure

Investigating the influence of professor characteristics on student satisfaction and dissatisfaction: a comparative study

This research uses the Kano model of satisfaction to investigate professor characteristics that create student satisfaction as well as those attributes that can cause their dissatisfaction. Kano questionnaires were handed out to 104 undergraduate students at a university in the Southwest and to 147 undergraduate students at a university in the Midwest of the United States. The two resulting Kano maps show the same delighting attributes although other satisfaction attributes are also similar. The findings reveal the importance of the personality of professors and the characteristics of professors that (a) are desired by students, (b) are not desired by students, (c) affect student satisfaction the most, and (d) affect satisfaction the least. The results also demonstrate how professors and universities can focus attention on those attributes most likely to influence satisfaction. No attributes of professors are classified as basic or taken for granted factors by students, although three attributes are excitement factors that have the potential to delight students. The findings illustrate that there is a set of multiple attributes that professors need to possess for satisfying student–professor classroom service encounters. Student populations appear to show strong similarities in their preferences for characteristics of professors that lead to satisfaction and dissatisfaction outcomes

Measurement of Superluminal optical tunneling times in double-barrier photonic bandgaps

Tunneling of optical pulses at 1.5 micron wavelength through double-barrier periodic fiber Bragg gratings is experimentally investigated. Tunneling time measurements as a function of barrier distance show that, far from the resonances of the structure, the transit time is paradoxically short, implying Superluminal propagation, and almost independent of the distance between the barriers. These results are in agreement with theoretical predictions based on phase time analysis and also provide an experimental evidence, in the optical context, of the analogous phenomenon expected in Quantum Mechanics for non-resonant superluminal tunneling of particles across two successive potential barriers. [Attention is called, in particular, to our last Figure]. PACS nos.: 42.50.Wm, 03.65.Xp, 42.70.Qs, 03.50.De, 03.65.-w, 73.40.GkComment: LaTeX file (8 pages), plus 5 figure

Phase Separation in Rapid Solidified Ag-rich Ag-Cu-Zr Alloys

The microstructure and phase formation of rapid solidified Ag-rich Ag-Cu-Zr alloys were investigated. Two types of structure; interconnected- and droplet-type structures, were obtained due to phase separation mechanisms. The former was spinodal decomposition and the later was nucleation and growth mechanism. Depending on the alloy compositions, three crystalline phases; FCC-Ag, AgZr and Cu10Zr7 phases were observed along with an in-situ nanocrystalline/amorphous composite. Vickers hardness testing indicated a significant increase of hardness in the nanocrystalline/amorphous-composite alloy

Interactive stratospheric aerosol models' response to different amounts and altitudes of SO2 injection during the 1991 Pinatubo eruption

A previous model intercomparison of the Tambora aerosol cloud has highlighted substantial differences among simulated volcanic aerosol properties in the pre-industrial stratosphere and has led to questions about the applicability of global aerosol models for large-magnitude explosive eruptions prior to the observational period. Here, we compare the evolution of the stratospheric aerosol cloud following the well-observed June 1991 Mt. Pinatubo eruption simulated with six interactive stratospheric aerosol microphysics models to a range of observational data sets. Our primary focus is on the uncertainties regarding initial SO2 emission following the Pinatubo eruption, as prescribed in the Historical Eruptions SO2 Emission Assessment experiments (HErSEA), in the framework of the Interactive Stratospheric Aerosol Model Intercomparison Project (ISA-MIP). Six global models with interactive aerosol microphysics took part in this study: ECHAM6-SALSA, EMAC, ECHAM5-HAM, SOCOL-AERv2, ULAQ-CCM, and UM-UKCA. Model simulations are performed by varying the SO2 injection amount (ranging between 5 and 10TgS) and the altitude of injection (between 18-25km). The comparisons show that all models consistently demonstrate faster reduction from the peak in sulfate mass burden in the tropical stratosphere. Most models also show a stronger transport towards the extratropics in the Northern Hemisphere, at the expense of the observed tropical confinement, suggesting a much weaker subtropical barrier in all the models, which results in a shorter e-folding time compared to the observations. Furthermore, simulations in which more than 5TgS in the form of SO2 is injected show an initial overestimation of the sulfate burden in the tropics and, in some models, in the Northern Hemisphere and a large surface area density a few months after the eruption compared to the values measured in the tropics and the in situ measurements over Laramie. This draws attention to the importance of including processes such as the ash injection for the removal of the initial SO2 and aerosol lofting through local heating

Dynamic Mechanical Thermal and Thermomechanical Characterizations of Rice Husk and Saw Dust Filled Polyolefin Composites

The composites based on bio-fillers and polymers have attracted great interest due to increasing environmental concern, their low cost and renewable resource. In this study, the dynamic mechanical thermal and thermomechanical characterizations of polyolefin (Polypropylene – PP and polyethylene - PE) as well as three composite systems including the rice husk (RH) filled polypropylene composite, rice husk filled polyethylene composite and saw dust (SD) filled polyethylene composite were investigated. The effect of two types of compatibilizers, maleic anhydride grafted polypropylene (2 wt% MAPP) for polypropylene matrix composite and maleic anhydride grafted polyethylene (4 wt% MAPE) for polyethylene matrix composites on dynamic mechanical thermal properties (Storage modulus - E', loss modulus - E”,damping factor - Tan δ)of three composite systems were studied. Moreover, the coefficient of thermal expansion and dimension change of neat matrices (PP, PE) and three composite systems (PP/RH, PE/RH and PE/SD) with compatibilizers were also investigated by Thermo Mechanical Analysis