Planning considerations for domestic replacement satellites

Several domestic satellite systems have been more than 10 years in operation. During this time, the world has experienced a dramatic growth in communication. While the demand for more telephony and data circuits and television channels is still on the rise, new methods of signal transmission and circuit compression have been developed which may balance or reduce the need for more satellite trunk capacity. And while whole national networks are converting to digital transmission, new transmission media like optical fibre, are finding application, and may take over some of the heavy traffic routes previously carried by satellite. On the other side, business data communication between roof-top terminals, thin route traffic to remote users, television distribution by direct satellite broadcasting are becoming more popular and satellite land mobile communication may soon be a reality. Thus the domestic satellite's role appears to be slowly changing towards thin route and mobile traffic and DBS-type distribution and perhaps even radio position determination. System planners are adapting to the new trends in satellite communication and are trying to accommodate the various service payloads on a single satellite. This article discusses some aspects of the emerging multi-purpose domestic satellite, which carries fixed and mobile services, TV direct broadcasting and radio position determination, in view of network digitalization, network expansion, circuit compression, synchronization. The discussion centres on transponder supply and demand, satellite replenishment, K_u-band vs. C-band for TV direct satellite broadcasting, choice of modulation/multiple access for mobile communication, and expected accuracy in radio position determination.     

UR: SMART–A tool for analyzing social media content

Information Systems and e-Business Management - The digital transformation, with its ongoing trend towards electronic business, confronts companies with increasingly growing amounts of data which...     

Television Sound Subcarrier Transmission in Space Communication

In a nonideal transmission enviromnent, the transmission of video sound in the form of an FM subcarrier above the video baseband causes interactions between video and sound subcarrier which result in signal distortion. The degree of distortion depends on the type of channel impairments and the selection of transmission parameters. While the fidelity of the video signal can be preserved by mainly limiting the subcarrier level, the quality of the audio channel can be optimized by choosing the right subcarrier frequency. It can be shown that for a given video-carrier-to-noise ratio, subcarrier power below video signal power, and for given system impairments, there exists an optimum subcarrier location which provides a maxinum audio-signal-to-noise ratio.     

Radio fluorination and positron emission tomography (PET) as a new approach to study the in vivo distribution and elimination of the advanced glycation endproducts N epsilon-carboxymethyllysine (CML) and N epsilon-carboxyethyllysine (CEL).

After synthesis of fluorine-18 labelled analogues by [18F]fluorobenzoylation at the alpha-amino group, biodistribution and elimination of individual advanced glycation endproducts, namely N epsilon-carboxymethyllysine and N epsilon-carboxyethyllysine, were studied in comparison to lysine in rats after intravenous injection using positron emission tomography (PET). The [18F]radiofluorinated amino acids were fast distributed via the blood, followed by a rapid excretion through the kidneys. Elimination kinetics were similar for both AGEs and lysine. For CML and CEL, but not for lysine, a temporary liver accumulation could be observed, which was not connected with any metabolisation or enterohepatic circulation. No further accumulation in any tissues was observable, indicating that increased tissue levels of CML or CEL, which have been described for certain disorders, are exclusively derived from endogenous origin and should not depend on a dietary intake. However, under uremic conditions, an impaired kidney function might result in a significant increase of the AGE-load of blood and tissues. PET based on 18F-labelled AGEs proved to be a promising tool to elucidate the physiological fate of post-translationally modified amino acids and to clarify the role of AGEs as possible "glycotoxins".     

TVRO Antenna Size, Ku Band Versus C Band

At this point in time, with the advent of high powered Ku band direct broadcast satellites (DBSs) and the ever increasing requirement for TV via satellite, it is safe to say that satellite rooftop receiving antennas will soon shrink in size. This will be true for DBS systems operating in the Ku DBS band, since Ku band EIRP has been increased considerably over C band EIRP. It will not necessarily be true for Ku band satellite systems operating in the broadcast satellite service band, where maximum power flux density, and therefore EIRP, is limited.     

Das Dekompositionsmodell nach Wand und Weber im Kontext der Prozessmodellierung

Whereas the benefits of decomposing process models are obvious, the question what actually characterizes a ??good?? decomposition of a business process model has been given little attention to date. In addition, the process of decomposition itself is considered as being an ??art?? in literature. Our approach for achieving a ??good?? decomposition is Wand and Weber??s decomposition model for information systems. As a first step in our investigation we aim to explore in how far the decomposition model can be adapted for business process modelling at all. The potential this model might bear for evaluating decompositions of process models has been promoted in literature quite often, while a corresponding investigation is still missing. We address this gap by the following research. In the long term, we intend to establish guidelines for decomposing business process models in a structured way.     

Novel rhenium complexes derived from alpha-tropanol as potential ligands for the dopamine transporter

A series of rhenium complexes was synthesized as model compounds for the corresponding radioactive technetium-99m complexes for preliminary biological investigations. In a '3 + 1' mixed-ligand approach the tropanol molecule was linked with the metal core through a omega-mercaptoester group as monodentate ligand. Bis(thioethyl)sulphide was used as the tridentate dithiol ligand to block the remaining free coordination sites. The omega-mercaptoesters were synthesized via the trityl-protected precursors. Binding tests on the cloned human dopamine transporter revealed moderate binding affinities for some of the prepared compounds. The complexes were characterised by X-ray and the lipophilicity as well as pKa values were determined.     

A study of FTP traffic: Estimation of the non-optimality

File retrieval constitutes a major component of the traffic in the Internet. In the Internet the same file is in general offered by several servers and this redundancy gives rise to a lot of avoidable non-optimality. In this work a study has been carried out to examine and estimate this non-optimality.     

Yeast flora of non-radurised and radurised minced beef — a taxonomic study

Yeast flora present in minced beef before and after radurisation were examined. No reduction in the number of yeast cells was observed after the meat was radurised at a dose of 2.5 kGy. A definite increase in the number of psychrotrophic yeast was observed in radurised meat after 14 days of storage at 4°C. The recovered yeast flora comprised representatives of the following species: Candida famata (9 isolates); C. lipolytica (4 isolates); C. parapsilosis (20 isolates); C. sake (27 isolates); C. zeylanoides (28 isolates); Cryptococcus albidus var. albidus (6 isolates); Cr. infirmo-miniatus (1 isolate); Cr. laurentii var. laurentii (31 isolates); Trichosporon cutaneum (1 isolate); Tr. pullulans (2 isolates); Rhodotorula minuta var. texensis (1 isolate); Rh. rubra (1 isolate).     

Combating sun outage in satellite television distribution systems

Two methods of sun outage avoidance in satellite television transmission are discussed. Each method requires two satellites and dual-beam antennas. The two C-band satellites transmit identical programs at the time when the sun outage period occurs. The separation of the spacecraft is dependent on the dual-feed earth station antenna size. For large television receive-only antennas, the separation must be small; for small antennas, or antennas with large beamwidths, the satellite separation can be large. If the separation is larger than 8° on the geosynchronous arc, only one transmit station is required to transmit program information. Scaling this system for Ku-band use is then considered. It is concluded that in a Ku-band direct-broadcasting system with earth station antenna diameters of 1-m and below, the rise in noise temperature due to sun outage is not significant and can be overcome by a modest amount of system margin, equivalent to that normally provided against rain fades