A Markov-Based Channel Model Algorithm for Wireless Networks

Techniques for modeling and simulating channel conditions play an essential role in understanding network protocol and application behavior. In [11], we demonstrated that inaccurate modeling using a traditional analytical model yielded suboptimal error control protocol parameters choices. In this paper, we demonstrate that time-varying effects on wireless channels result in wireless traces which exhibit non-stationary behavior over small window sizes. We then present an algorithm that extracts stationary components from a collected trace in order to provide analytical channel models that, relative to traditional approaches, more accurately represent characteristics such as burstiness, statistical distribution of errors, and packet loss processes. Our algorithm also generates artificial traces with the same statistical characteristics as actual collected network traces. For validation, we develop a channel model for the circuit-switched data service in GSM and show that it: (1) more closely approximates GSM channel characteristics than traditional Markov models and (2) generates artificial traces that closely match collected traces' statistics. Using these traces in a simulator environment enables future protocol and application testing under different controlled and repeatable conditions.     

The Weibull manifold in low-level image processing: An application to automatic image focusing

In this paper, we introduce a novel framework for low-level image processing and analysis. First, we process images with very simple, difference-based filter functions. Second, we fit the 2-parameter Weibull distribution to the filtered output. This maps each image to the 2D Weibull manifold. Third, we exploit the information geometry of this manifold and solve low-level image processing tasks as minimisation problems on point sets. For a proof-of-concept example, we examine the image autofocusing task. We propose appropriate cost functions together with a simple implicitly-constrained manifold optimisation algorithm and show that our framework compares very favourably against common autofocus methods from literature. In particular, our approach exhibits the best overall performance in terms of combined speed and accuracy.     

埃姆歇公园国际建筑展的社会思考

在鲁尔区的政策中,社会利益始终是一个重要的内容。该地区的大型煤炭和钢铁企业过去依靠这种政策,为本地吸引并保持了合格的劳动力。这样的经济政策环境历     

The theory of open-die forging in the course of historical change

The forging process – originating empirically – can nowadays be understood with the aid of a series of theoretical approaches within the field of metalforming technology. The classic methods (chiefly slip lines) have contributed to fundamental knowledge of the process. Parameters like force and energy requirement, performance and deformation resistance can be determined with sufficient accuracy by these means. Quantitative analyses of localised processes are, however, possible only with the aid of FE methods, though satisfactory solutions have not yet been found to the problems of applying 3 D FEM and taking into account the real boundary conditions.     

Identification and evaluation of volatile odor-active pollutants from different odor emission sources in the food industry

In order to elucidate the nature of different odor-emission sources in the food industry, odor-active pollutants of the exhaust air in the cooling gases from coffee bean roasting, the exhaust air of fish meal production, and the exhaust air of swine breeding were investigated. Knowledge of what pollutants are present in the odor emission and are responsible for the malodor is vital to the development of suitable adsorbers/absorbers and filters, and combinations of the same. Therefore, the objective of these investigations was to identify and evaluate the characteristic impact of compounds in the exhaust air of these odor-emission sources. The volatile compounds were collected by using a microprocessor-controlled gas sampler through sorbent tubes of Tenax TA. The adsorbed compounds were analyzed by thermal desorption into a cryotrap and subsequent gas chromatography separation, followed by simultaneous olfactometry and mass spectrometry. In cooling gases of the coffee bean roasting numerous compounds (up to 100) were identified of which only 22 were important for the characteristic odor. These compounds were aldehydes (2-methyl propanal, 2- and 3-methyl butanal, 2-furancarboxyaldehyde, 5-methyl-2-furancarboxyaldehyde), diketones (2,3-butandione, 2,3-pentandione), pyrazines, pyridine, acetic acid, and furanmethanol. Other compounds with low concentrations but with a very low odor threshold and, therefore, important for the total odor were 3-methyl butanoic acid and guaiacol. Up to 50 compounds were identified in the exhaust air of fish meal production, the most significant of these being trimethylamine. Trimethylamine, with a very low odor threshold (0.0025 g/l air) and the highest content (up to 60% in the total ion chromatogram, more than 100 g/l) in the exhaust air of fish meal production, was responsible for the characteristic fishy odor. Beside trimethylamine only a few compounds, e.g., sulfides (dimethyl sulfide, dimethyl disulfide, dimethyl trisulfide), aldehydes (2-methyl propanal, 2- and 3-methyl butanal), ethanol, and guaiacol, played a secondary role for the total odor. In the exhaust air of the pig house up to 50 compounds were identified. Beside ammonia, the most important odor-active compounds were various carboxylic acids (acetic acid, butanoic acid, 3-methyl butanoic acid), sulfides (dimethyl sulfide, dimethyl disulfide, dimethyl trisulfide), trimethylamine, and the intensive odor-active p-cresol and 4-ethylphenol.     

Relative frequency of a subclavian vs. a transverse cervical origin for the dorsal scapular artery in humans

Scanning electron microscopy of external ornamentation and internal armature of the pharynx was used to identify females of Sergentomyia sensu stricto. Five species from the eastern Mediterranean basin were compared; S. minuta clearly was separated from species of the fallax-group. Within the fallax-group, S. fallax was distinguished readily by its heart-shaped pharynx and the difference in armature between the dorsal and lateral plates.     

Berechnung und Meßmethode zur Bestimmung des Temperaturgefälles und des Wärmeübergangskoeffizienten bei der direkten Kühlung von Stahldraht

Direkte Wasserkühlung von Stahldraht nach dem Ziehvorgang. Berechnung des Temperaturgefälles in einem dem Ziehhol nachgeschalteten Kühlrohr. Messung der Drahttemperaturdifferenz zwischen Kühlrohrein- und -austritt mit der Infrarotthermometrie zur Bestimmung des Wärmeübergangskoeffizienten an der Drahtoberfläche. Ermittlung des Emissionsgrades.