Ensemble analyses by Minkowski-operations for spatially resolved structural and optoelectronic features of Cu(In,Ga)(Se2,S2) absorbers

Polycrystalline chalcopyrite semiconductors like Cu(In,Ga)(Se₂,S₂) as physically and technologically promising thin film solar cell absorbers show a considerable degree of spatial inhomogeneity of structural, optical and optoelectronic properties above and below the length scale of grain sizes. The dilution of magnitudes such as splitting of quasi-Fermi levels with a certain distribution of lower energies, introduced e.g. by local fluctuations, introduce an additional reduction of the free energy of the photon field and drop thus the solar light conversion yield. For a comprehensive interpretation of the influence of such inhomogeneity effects on the solar cell efficiency we perform lateral scans of various magnitudes recorded with a confocal setup with high lateral resolution (≤ 1 µm), like splitting of quasi-Fermi levels, AFM-surface contours with different scan sizes and at different sample positions. We compare these sets of magnitudes by their respective Minkowski-opening-operations, extract correlation coefficients, determine average values and their respective statistical momenta (variances), and extrapolate minimum scan sizes for the collection of statistically representative data.     

Application‐level differentiated services for Web servers

The current World Wide Web service model treats all requests equivalently, both while being processed by servers and while being transmitted over the network. For some uses, such as Web prefetching or multiple priority schemes, different levels of service are desirable. This paper presents three simple, server‐side, application‐level mechanisms (limiting process pool size, lowering process priorities, limiting transmission rate) to provide two different levels of Web service (regular and low priority). We evaluated the performance of these mechanisms under combinations of two foreground workloads (light and heavy) and two levels of available network bandwidth (10 Mb/s and 100 Mb/s). Our experiments show that even with background traffic sufficient to saturate the network, foreground performance is reduced by at most 4–17%. Thus, our user‐level mechanisms can effectively provide different service classes even in the absence of operating system and network support. This revised version was published online in August 2006 with corrections to the Cover Date.     

Design and analysis of a propagation delay tolerant ALOHA protocol for underwater networks

Acoustic underwater wireless sensor networks (UWSN) have recently gained attention as a topic of research. Such networks are characterized by increased uncertainty in medium access due not only to when data is sent, but also due to significantly different propagation latencies from spatially diverse transmitters—together, we call these space-time uncertainty. We find that the throughput of slotted ALOHA degrades to pure ALOHA in such an environment with varying delay. We therefore propose handling this spatial uncertainty by adding guard times to slotted ALOHA, forming Propagation Delay Tolerant (PDT-)ALOHA. We show that PDT-ALOHA increases throughput by 17–100% compared to simple slotted ALOHA in underwater settings. We analyze the protocol’s performance both mathematically and via extensive simulations. We find that the throughput capacity decreases as the maximum propagation delay increases, and identify protocol parameter values that realize optimal throughput. Our results suggest that shorter hops improve throughput in UWSNs.     

10-Gb/s transmission and beyond

The authors outline obstacles encountered in the development of 10-Gb/s (STM-64, OC-192) systems. Technologies to overcome these obstacles are presented and compared, taking into account real field environments. A perspective on 40-Gb/s systems technologies is also given     

Influence of faults on alteration,mineralogy, and geotechnical behavior of granitic residual soils

Bulletin of Engineering Geology and the Environment - Contact metamorphism and metasomatism are imposed on granitic rocks by late intrusions. This study shows the consequences of this phenomenon on...     

Fruchttod beim Reh

Zusammenfassung Es wird über eine Beobachtung von Fruchtmazeration in der Vagina beim Reh berichtet.

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Summary A case of maceration of a fetus in the vagina of roe deer is reported.

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Résumé Il est décrit la maceration d'un fetus dans la vagine chez le chevreuil.