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The microwave dielectric properties of perfluorosulfonic acid membranes are characterized by a two-port transmission line technique. Two dielectric relaxation modes are observed in the microwave region (0.045-26 GHz) at 25{degree sign}C. The higher frequency process observed is identified as the cooperative relaxation of bulk-like water, whose amount was found to increase linearly with water content in the polymer. The lower-frequency process, characterized by longer relaxation times (20-70 picoseconds), is attributed to water molecules that are loosely bound to sulfonate groups. The loosely bound water amount was found to increase with hydration level at low water content, and levels-off at higher water contents. Flemion SH150, which has an equivalent weight of 909 g/equiv, displays higher dielectric strengths for both of these water modes compared to Nafion 117 (equivalent weight of 1100 g/equiv).
We have characterized the optical modes present in a two-dimensional photonic crystal single defect cavity fabricated in an InP/In0.53Ga0.47As/InP double heterostructure thin film on a glass slide. The cavity resonance was tuned to different frequencies in the 1.55 μm spectral region. Radiation losses and material absorption influence the measured value of cavity quality factor Q. We separated these two loss mechanisms by performing a curve fit of the loss rate 1/Q versus the wavelength-dependent absorption coefficient of In0.53Ga0.47As. By extrapolating this curve to zero absorption, the radiation loss rate 1/Qrad is obtained.
Abstract Review: 120 refs.
Abstract Joint venture activity and internal corporate venturing represent two administrative innovations receiving increased attention in strategic management research. This study investigates a new hybrid form of administrative innovation: internal corporate joint ventures , which combine the equity involvement typically found in joint ventures with the internal staffing of a semiautonomous unit typical of internal corporate ventures. Drawing on both a process model and a variance model, the structuring, development and performance of 53 such ventures in an industry‐specific setting is examined.
In 1989, Goodrich and collaborators suggested that SN 1961V, a very peculiar Type II (Zwicky's "Type V") supernova, was not the final explosion of a star at the end of its life, but rather the giant eruption of a massive, luminous blue variable, like n Car. To test this hypothesis, we have used the Hubble Space Telescope to obtain optical images of the site of SN 1961V. There is a cluster of faint (V ~ 24-25 mag), blue [(V-I)_0_ = -0.4-0.5 mag] stars around the general location of the supernova. We also see a very faint (V = 25.6 +/- 0.3 mag), much redder [(V-I)_0_ = 1.7 mag] star barely resolved from one of the blue stars. Its brightness and colors are consistent with those of a highly reddened O-type star, as predicted by Goodrich et al. Moreover, it is the star formally closest to the known radio position of SN 1961V; the coordinates are identical, to within the uncertainties. Thus, we tentatively identify this as the post eruption star of SN 1961V; it survived the giant eruption, which was not a genuine supernova, and it is now red due to a substantial envelope of dust (A_V_ ~ 4.1 mag). However, the current data do not allow us to eliminate the possibility that this star is an unrelated red supergiant or a peculiar supernova remnant. Alternatively, the blue object adjacent to it may be the actual post- eruption star of SN 1961V. If so, the envelope of dust is not as thick: A_V_ ~ 2.2-3.2 mag, but perhaps somewhat larger if the object's colors are significantly affected by a blue light echo of SN 1961V.
Abstract not Available.
For maximal performance solar cells should resemble semiconductor lasers, i.e., they should be constructed in the form of a double heterostructure. We have found rather good performance in SIPOS-crystalline silicon-SIPOS double heterostructure solar cells, where SIPOS≡SiOx. The processing of these solar cells gives insights into the truly outstanding performance of the n+-SIPOS: p-Si heterojunction which has a forward saturation current coefficient J0=10−14 A/cm2, or equivalently an ‘‘emitter Gummel number’’ Ge=3.3×1015 s/cm4. This suggests that crystalline silicon solar cells can be much more efficient than had been suspected.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
The HTTP adaptive streaming technique opened the door to cope with the fluctuating network conditions during the streaming process by dynamically adjusting the volume of the future chunks to be downloaded. The bitrate selection in this adjustment inevitably involves the task of predicting the future throughput of a video session, owing to which various heuristic solutions have been explored. The ultimate goal of the present work is to explore the theoretical upper bounds of the QoE that any ABR algorithm can possibly reach, therefore providing an essential step to benchmarking the performance evaluation of ABR algorithms. In our setting, the QoE is defined in terms of a linear combination of the average perceptual quality and the buffering ratio. The optimization problem is proven to be NP-hard when the perceptual quality is defined by chunk size and conditions are given under which the problem becomes polynomially solvable. Enriched by a global lower bound, a pseudo-polynomial time algorithm along the dynamic programming approach is presented. When the minimum buffering is given higher priority over higher perceptual quality, the problem is shown to be also NP-hard, and the above algorithm is simplified and enhanced by a sequence of lower bounds on the completion time of chunk downloading, which, according to our experiment, brings a 36.0% performance improvement in terms of computation time. To handle large amounts of data more efficiently, a polynomial-time algorithm is also introduced to approximate the optimal values when minimum buffering is prioritized. Besides its performance guarantee, this algorithm is shown to reach 99.938% close to the optimal results, while taking only 0.024% of the computation time compared to the exact algorithm in dynamic programming.
