Radio resource management across multiple protocol layers in satellite networks: a tutorial overview

Satellite transmissions have an important role in telephone communications, television broadcasting, computer communications, maritime navigation, and military command and control. Moreover, in many situations they may be the only possible communication set‐up. Trends in telecommunications indicate that four major growth market/service areas are messaging and navigation services (wireless and satellite), mobility services (wireless and satellite), video delivery services (cable and satellite), and interactive multimedia services (fibre/cable, satellite). When using geostationary satellites (GEO), the long propagation delay may have great impact, given the end‐to‐end delay user's requirements of relevant applications; moreover, atmospheric conditions may seriously affect data transmission. Since satellite bandwidth is a relatively scarce resource compared to the terrestrial one (e.g. in optical transport networks), and the environment is harsher, resource management of the radio segment plays an important role in the system's efficiency and economy. The radio resource management (RMM) entity is responsible for the utilization of the air interface resources, and covers power control, handover, admission control, congestion control, bandwidth allocation, and packet scheduling. RRM functions are crucial for the best possible utilization of the capacity. RRM functions can be implemented in different ways, thus having an impact on the overall system efficiency. This tutorial aims to provide an overview of satellite transmission aspects at various OSI layers, with emphasis on the MAC layer; some cross‐layer solutions for bandwidth allocation are also indicated. Far from being an exhaustive survey (mainly due to the extensive nature of the subject), it offers the readers an extensive bibliography, which could be used for further research on specific aspects. Copyright © 2005 John Wiley & Sons, Ltd.     

Hydride transfer to some initiators of cationic polymerization

Summary The hydride transfer from xanthene to stable carbenium salts with different cation electrophilities: 2,4,4'-trichlorotriphenylmethylhexachloroantimonate, triphenylmethylhexafluoroarsenate, triphenylmethylhexachloroantimonate, 4,4,4'-trimethyltriphenylmethylhexachloroantimonate and tropylium hexachloroantimonate is investigated. The reaction is controlled by the absorption of the carbenium ions in the visible region of their electronic spectra. The formation of the product of the reaction — triphenylmethane — is detected by gas chromatography and NMR spectroscopy. The rate constants and the reaction order are determined. The acceleration of the hydride transfer on UV-irradiation of the reaction mixture is shown.Paper presented at VII International Symposium Polymers '80, Varna, Bulgaria     

Photoabbau von copolymeren aus styrol,methylmethacrylat und acrylnitril mit 2-naphthylmethacrylat

Copolymers of styrene, methylmethacrylate (MMA), and acrylonitrile with increasing amounts of 2-naphthylmethacrylate (2-NMA) were photooxidized in order to investigate the influence of this comonomer as internal modifier during the photodegradation. It could be shown that amounts up to 15 wt.-% of 2-NMA in the copolymers with styrene lead to stabilizing of these copolymers. This stabilizing influence of 2-NMA was also verified in the copolymers with acrylonitrile. In case of the copolymers with MMA ^j+ was not possible to determine undoubtedly the influence of 2-NMA due to the depolymerisation tendency of MMA, although during the photooxidation of a copolymer with about 16 wt.-% 2-NMA the molecular weight distribution became smaller.     

Estimation of the Genetic Diversity in Tetraploid Alfalfa Populations Based on RAPD Markers for Breeding Purposes

Alfalfa is an autotetraploid, allogamous and heterozygous forage legume, whose varieties are synthetic populations. Due to the complex nature of the species, information about genetic diversity of germplasm used in any alfalfa breeding program is most beneficial. The genetic diversity of five alfalfa varieties, involved in progeny tests at Institute of Field and Vegetable Crops, was characterized based on RAPD markers. A total of 60 primers were screened, out of which 17 were selected for the analysis of genetic diversity. A total of 156 polymorphic bands were generated, with 10.6 bands per primer. Number and percentage of polymorphic loci, effective number of alleles, expected heterozygosity and Shannon's information index were used to estimate genetic variation. Variety Zuzana had the highest values for all tested parameters, exhibiting the highest level of variation, whereas variety RSI 20 exhibited the lowest. Analysis of molecular variance (AMOVA) showed that 88.39% of the total genetic variation was attributed to intra-varietal variance. The cluster analysis for individual samples and varieties revealed differences in their population structures: variety Zuzana showed a very high level of genetic variation, Banat and Ghareh were divided in subpopulations, while Pecy and RSI 20 were relatively uniform. Ways of exploiting the investigated germplasm in the breeding programs are suggested in this paper, depending on their population structure and diversity. The RAPD analysis shows potential to be applied in analysis of parental populations in semi-hybrid alfalfa breeding program in both, development of new homogenous germplasm, and identification of promising, complementary germplasm.     

Composite core-double sheath fibers based on some biodegradable polyesters obtained by self-organization during electrospinning

Obtaining core-sheath fibers by single-spinneret electrospinning is a recent and straightforward approach to prepare composite fibers. Fibers of more complex architecture consisting of poly(ethylene oxide) (PEO) core, inner poly(l -lactide) sheath sd and outer beeswax (BW) sheath may also be obtained using this method. In the present study we report its applicability for a large series of (bio)degradable polyesters such as poly(ε-caprolactone), poly(d ,l -lactide-co-glycolide), poly(butylene succinate), poly(3-hydroxybutyrate), and poly(l -lactide-co-d ,l -lactide). The fibers have a well-differentiated PEO core, polyester inner sheath and BW outer sheath. The possibility for targeted location of hydrophilic or hydrophobic substances in the core or in the sheaths of the PEO/polyester/BW fibers has been demonstrated using nanosized zinc oxide with unmodified (hydrophilic) or silanized (hydrophobic) surface. PEO/polyester/BW fibrous materials loaded with a model drug (5-nitro-8-hydroxyquinoline) exhibit antimicrobial activity. The obtained results show that single-spinneret electrospinning is a novel and versatile method to prepare core-double sheath composite fibers prospective for various applications such as biomedicine, cosmetics, and food packaging.     

Quality Characteristics and Antioxidant Properties of Breads Supplemented with Sugar Beet Molasses-Based Ingredients

Osmotic dehydration in sugar beet molasses as hypertonic medium was used to treat apples, plums, carrots and cabbage. Following the treatment, the fruits/vegetables were dried and ground. The obtained powders or pure beet molasses were incorporated into white wheat bread at 5 and 10% levels (flour basis). The results showed that the mineral content (K, Mg, Ca) and antioxidant potential of breads were significantly improved. The most marked was the increase in K content: 89.1% (bread with molasses)-94.1% (bread with plum), at 5% level. The highest increase in antioxidant potential was measured in the breads made with plum (62.5–81.6% for 5 and 10% levels, respectively).     

Application of the molière multiple scattering angle-lateral displacement function in Monte Carlo calculations

A two-dimensional approximation is found for the multiple scattering angle-lateral displacement correlation formula which satisfies two conditions: first, that it be close to the Molière one (better than 10^?3) and, second, that it be suitable for Monte Carlo calculations. These Monte Carlo calculations are made for relativistic particles.     

ATM‐based multimedia communication via NGSO‐satellites

Future broadband satellite networks for multimedia will be seamlessly integrated into terrestrial broadband networks which often use asynchronous transfer mode (ATM) and recently also the less complex multi protocol label switching (MPLS) technique as transmission and switching protocol. In light of this, future broadband satellite networks may adopt the ATM transmission scheme and implement ATM or ATM‐like switches on board the satellites. However, as compared to communication in fixed networks, satellite communication is characterized by special constraints (e.g. signal delay, channel quality, dynamic network topology) that require novel ATM‐based communication technology for satellite systems. This paper presents results from the ATM‐Sat project that aims to complete this technically challenging and important R&D task in the cooperation between DLR, Fraunhofer Gesellschaft and Tesat‐Spacecom. In brief the following aspects have been addressed in the ATM‐Sat project:

• development of the concept and communication technology for a multimedia satellite system with,
  • non‐geostationary orbit (NGSO) satellites;
  • inter satellite links (ISLs);
  • on‐board ATM switching;
  • fixed and mobile terminals;
• verification of the developed communication technology with a demonstrator.

In particular the ATM‐Sat R&D tasks cover the system and protocol architecture, on‐board processing, ISL routing, up/downlink and on board ATM resource management (including medium access control), error control, IP over satellite‐ATM, and active intelligent antennas. Copyright © 2005 John Wiley & Sons, Ltd.     

Pumpkin seed oil cake/polyethylene film as new food packaging material,with perspective for packing under modified atmosphere

Biopolymer packaging materials show increasing perspective in food packaging. Main limitation remains their high water sensitivity and poor water vapour barrier properties, compared to non polar materials of synthetic origin like polyethylene. In this paper, biopolymer layer obtained from by‐product of oil industry (pumpkin seed oil cake) was laminated on polyethylene in order to obtain new packaging material that would preferably combine water barrier properties of polyethylene and oxygen barrier properties of biopolymer composite material and perform satisfactory mechanical properties. Obtained two‐layer material showed good barrier properties for water vapour (7–8 g/m² 24h), as well as oxygen (12–45 cm³/m² 24h) and light. In addition, mechanical and water sensitivity tests were performed and results showed that new material inherited biopolymer film water sensitivity and mechanical properties with slight improvement. Measured tensile strength and elongation at break was 2–4 MPa and 150–250% in transversal direction and 6–8 MPa and 100–150% in longitudinal direction. Packing in modified atmosphere assay showed that new material can be used for this purpose with good control of oxygen concentration, while packing under increased concentration of CO₂ could be performed for shorter storage period. New two layer material shows promising properties for sensitive food packing under modified atmosphere conditions with reduced use of synthetic, oil‐based materials.     

Plasma effects on the bacteria Escherichia coil via two evaluation methods

The degradation of Escherichia coli bacteria by treatment with cold,weakly ionised,highly dissociated oxygen plasma,with an electron temperature of 3 eV,a plasma density of 8 × 1015 m-3 and a neutral oxygen atom density of 3.5 × 1021 m-3 was studied.To determine the 'real' plasma effects,two methods were used for evaluation and determination,as well as a comparison of the number of bacteria that had survived:the standard plate count technique (PCT) and advanced fluorescence-activated cell sorting (FACS).Bacteria were deposited onto glass substrates and kept below 50 ℃ during the experiments with oxygen plasma.The results showed that the bacteria had fully degraded after about 2 min of plasma treatment,depending slightly on the amount of bacteria that had been deposited on the substrates.The very precise determination of the O flux on the substrates and the two-method comparison allowed for the determination of the critical dose of oxygen atoms required for the destruction of a bacterial cell wall-about 6 × 1024 m-2-as well as deactivation of the substrates-about 8 × 1025 m-2.These results were taken in order to discuss other results obtained by comparable studies and scientific method evaluations in the determination of plasma effects on bacteria.