bluuebunny/crossref_metadata_2025_split huggingface dataset:
Services and supporting architecture of the ESA OBP system
Authors: Barani B. , Tork H. J. 
Published: July 2007

AbstractThe ESA on‐board processing (OBP) satellite system using on‐board regeneration and baseband circuit switching has been designed to provide ISDN connectivity and services to users on a Pan‐European basis. It is thus seen at its periphery as a 2 Mb/s primary rate access, hence allowing for the interconnection of equipment and terminals compatible with this standard interface.Among the various possible network architectures that the system could support, the business‐oriented closed networks look most promising. It has therefore been retained as a prime design driver for OBP system developments. Optionally, connectivity can be offered in an optimized manner to pure data networks, e.g. for LAN‐to‐LAN interconnection at rates up to 1 Mb/s. In the paper, communication services and networking capabilities offered by the system are briefly reviewed. The internal characteristics of the satellite system allowing for such capabilities are then reviewed and the corresponding performance outlined. The system is shown to be compatible with critical CCITT performance criteria.
Hybrid satellite and terrestrial networks
Authors: Chitre D. M. , Shyy D.‐J. , Ephremides A. , Gupta S. 
Published: July 2007

AbstractThe role of satellite communications in networks that provide new services, such as frame relay and multimedia, is investigated. Both passive and active (on‐board switching/processing) satellite systems are considered. Novel techniques are developed for each system to demonstrate, via detailed analysis and simulation, how the communications bandwidth agility of multipoint/broadcast satellite channels, and the on‐board switching/processing, makes it feasible to provide these new services via hybrid satellite and terrestrial networks in a resource‐efficient manner.
A new method for the prediction of fade duration statistics in satellite links above 10 GHz
Authors: Paraboni Aldo , Riva Carlo 
Published: July 2007

AbstractA model for the statistical prediction of fade durations, applicable both to scintillation and rain‐induced effects, is presented in this paper. It assumes that durations longer than about 1 minute are lognormally distributed whereas shorter durations follow a power‐law distribution. The model is assessed using data contained in the CCIR data bank and from measurements performed with the SIRIO and Olympus satellites. The model is tested using the same data, and the results give multiplicative errors in the range from 0.6 to 1.8 (averages) and from 0.3 to 3.0 (r.m.s.) in the estimation of the fade durations exceeded for fixed probability.
Integrated GPS/GLONASS navigation: Algorithms and results
Authors: Raby Peter , Daly Peter 
Published: July 2007

AbstractThe presence of selective availability (SA) on GPS has led to a variety of proposals for mitigation of its effects, for example combining GPS with other sensors or by identifying and removing the SA using redundant information in the position solution. A further method for reducing the impact of SA is the combination of GPS and GLONASS measurements. GLONASS does not have any deliberate degradation.This paper describes several algorithms for combining GPS and GLONASS measurements in real time on a single receiver. There are two least squares solutions using the code phase measurements alone: one with the measurements from both systems weighted equally, and one with the measurements weighted by the covariance of the measurements. Kalman filters with no SA model, and first‐ and second‐order models, using both the code and carrier phase to estimate user position and velocity, are also implemented. Two different adaptive schemes are compared which attempt to identify SA model parameters in real time. The algorithms are compared in terms of their positioning accuracy, computational overhead and robustness. A ten‐channel GPS/GLONASS receiver developed at The University of Leeds is used to provide satellite data for the evaluation of the different methods.
RESULTS AND PERFORMANCE OF MULTI‐SITE REFERENCE STATION DIFFERENTIAL GPS
Authors: Johnston Gordon T. 
Published: July 2007

AbstractThis paper describes in some detail the infrastructure and concept of two multi‐site reference station differential GPS (DGPS) options being offered to marine users by Racal Survey. The infrastructure of the Racal SkyFix system is briefly outlined, followed by descriptions of Racals' internetting and network capabilities.Comparisons between the two systems are made, including infrastructure, differential data management, user coverage, datalinks and positioning performance in various parts of the world. The paper describes the design of the systems and the tests undertaken to assess their functionality, before going on to compare their performances under a variety of conditions.Emphasis is placed on the technical issues associated with multi‐reference‐station DGPS, including error sources, weighting observations and monitoring of the data. The paper sets out to describe the fundamental approach of the systems to achieve high data integrity which is necessary to develop the systems to their next phase.Having described the two options, the paper uses examples of various combinations of reference stations to illustrate the potential of the system.Real‐time operations with the internetting and network systems are then used to show the increased performance of the two options over ordinary single station DGPS and lead into the conclusions section. The conclusions summarize the paper's findings and make recommendations for the future development of the system.The object of the developments so far has been to improve the quality of real‐time offshore DGPS positioning. The internetting and network options have provided real‐time results to illustrate the benefits and, together with SkyFix, offer significant developments in the ability of DGPS to provide accurate and reliable positioning over vast areas of the world.The ability to compare two multi‐reference‐station DGPS systems over large areas using co‐sited reference stations is very unusual. The opportunity has been taken to compare and report on the performance of the two systems.
Investigation of signal variance, bit error rates and pulse dispersion for DSPN signalling in A mobile dense scatterer ray tracing model
Authors: Amoroso Frank 
Published: July 2007

AbstractThe canonical ray tracing model of R. H. Clarke is used to validate the concept of mitigation bandwidth as used to predict DSPN spread spectrum signal variability at a mobile receiving antenna in dense scatterers. Illustrative examples of chip pulse dispersion are presented, and bit error rate performance is explored under the assumption of slow fading. The pulse dispersion is seen to pose potential obstacles to any eventual chip timing extraction and radio‐location ranging functions. Serendipitously, the performance of a DSPN embodiment of a 180° DPSK data link is seen to approximate closely that of a corresponding narrowband Rician fading link, even though no specular signal component is available to the DSPN link. The parameters of the equivalent Rician link are easily predicted from those of the DSPN link.
Phase synchronization in a satellite‐mobile channel
Authors: Salis Jose M. Riera , Rio Luis Mercader Del 
Published: July 2007

AbstractThis paper studies several aspects relevant to the design of phase synchronization circuits for land mobile satellite systems (LMSS). First, the results of a propagation experiment are presented, with special focus on the effects of vehicle mobility on the signal phase. It is found that the changes of speed and direction cause frequency variations that can be modelled as linear. Bounds for the frequency derivative are given for different percentages of time. The use of third‐order PLLs is considered, as they are optimum for tracking a frequency ramp embedded in white Gaussian noise. The model of third‐order PLL employed is presented, as it is an original model, developed by the authors. Then the performances of second‐ and third‐order PLLs are compared. Theoretical, as well as simulation, results are given. It is shown that third‐order loops give better performance in the presence of frequency variations of the kind observed in this link, but they suffer from a higher sensitivity to oscillators' phase noise. Several conclusions regarding the use of third‐order loops in future systems are presented.
An efficient algorithm for generalized SS/TDMA scheduling with satellite cluster and intersatellite links
Authors: Kim Sehun , Kim Soo‐Hyun 
Published: July 2007

AbstractWe consider the satellite cluster scheduling problem, which is one of the most interesting problems in the satellite communication scheduling area. This problem is known to be NP‐complete, and a couple of heuristic algorithms have been developed. In this paper, we suggest another algorithm for this problem which has the same computational complexity as the best existing one and provides much better solution quality. Extensive computational simulation results are reported.
A comparative analysis of frequency scanning and multispot beam satellite systems for mobile communications
Authors: Cornacchini C. , Crescimbeni R. , D'Ippolito A. , Russo P. , Vernucci A. , Ruggieri M. , Jones T. 
Published: July 2007

AbstractA comparative analysis between frequency scanning and multispot satellite systems has been performed in the context of land mobile applications. The aim of the work has been to confirm the effectiveness of the frequency scanning approach, whose technical feasibility has already been proved by the authors in a previous study, also in a comparative investigation with a more conventional satellite configuration.A proper comparative methodology has been established to compare two baseline configurations of the two systems. The analysis has also been rendered parametric, varying some system characteristics such as bandwidth, traffic distributions and linearity requirement. The achieved results are provided and widely commented on in the paper.
Spectrum sharing considerations for the proposed ESA ‘archimedes’ satellite DAB service
Authors: Rudd Richard 
Published: July 2007

AbstractAt the 1992 World Administrative Radio Conference (WARC), spectrum was allocated, on a primary basis, to the broadcast satellite service (sound). The allocations were not, however, uniform worldwide, nor will the BSS(S) have sole use of these allocations. In addition, many countries have reserved primary use of the spectrum for existing services until 2007, with the BSS(S) permitted only on a noninterference basis.This situation will impose serious constraints on the proposed ESA S‐DAB service, to be radiated from the ‘Archimedes’ constellation of satellites. The launch date for this service may be before the end of the century, and sharing with other spectrum users will therefore be necessary. Such users include fixed telephony links, broadcast links and mobile aeronautical telemetry.This paper reviews current spectrum usage in Europe and elsewhere, and investigates the restrictions thus imposed on the ESA S‐DAB service. Numerical examples based on real‐world systems are given, and demonstrate the feasibility, in many cases, of spectrum sharing.
Mobile P‐service satellite system comparison
Authors: Johannsen Klaus G. 
Published: July 2007

AbstractSeveral future operators of the mobile handheld telephone (P‐service) satellite communications systems are gearing up for system implementation to compete for the mobile handheld telephone market of the future. While these companies are proceeding with system realization, they are also looking for partners to finance these huge satellite projects. Potential partners or bulk users are administrations of national communication systems and operators of national communication satellites. These future partners ask themselves which P‐service satellite communication system they should choose.There is not an easy answer because P‐service satellite systems come in many varieties. There are the low altitude earth orbiting satellites (LEOs), the medium altitude earth orbiting satellites (MEOs), and the geosynchronous altitude earth orbiting satellites (GEOs). Each system has a different type of satellite repeater: digital regenerative, transparent digital, and the bent‐pipe. And each satellite system uses its own modulation/multiple access system. The fact that satellites circle the earth at different altitudes has an impact on speech quality, and, because systems vary in satellite as well as constellation complexity, there are different price tags attached. All systems display ingenious features and will eventually work. Mobile users will decide which system will best serve their purposes.This article attempts to compare six P‐service satellite systems and find a method for system selection. By use of self‐established system criteria, it is possible to arrive at a P‐service system selection. By weighing the system criteria, the sensitivity of system selection can be tested. The results or the selection of a particular system should not be considered a recommendation; rather, the process of selection should be used as a possible guideline.
Marketing margin and determinants of net returns of beef marketing in southeast Nigeria
Authors: Eze CC 
Published: July 2007

AbstractThis study examined: the marketing costs, margins and returns of retailed beef meat in southeast Nigeria; factors influencing the traders' net returns; problems associated with marketing of beef; and the socio‐economic characteristics of respondent traders. Sixty respondents were selected at random, with 20 respondents from each of three purposively selected markets in the study area. A structured interview schedule and personal observations were sources of primary data. The field data were analysed using cost‐return principles, multiple regression analysis and descriptive statistics. The gross margin for trading was
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9,790 (=US$81.58) per 250 kg dressed meat, with a net return of
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8,605 (=US$71.71) and an average sales receipt of
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78,400 (= US$653.33). The cost of meat, transport costs, other costs (garage fees, storage, taxes), experience in the trade and level of education significantly (p < 0.05) affected the traders' net returns. Insufficient capital, inadequate stock supply, high transport cost and storage were identified as the major problems associated with meat trading in the study area. Copyright © 2007 John Wiley & Sons, Ltd
Studies on candelilla wax. II. Itsn‐paraffins
Authors: Schuette H. A. , Baldinus Joseph G. 
Published: July 2007

SummaryA simple, rapid adsorption method for the isolation of candelilla paraffins has been described. Use of the method as a quantitative procedure yielded 52.2% paraffins.X‐ray analysis and other physical data indicated that the principal candelilla paraffin was the C31 compound. The C29 and C33 homologues were also found to be present, C29 being reported for the first time.The presence of ketones could not be established.
Polymerization of drying oils. V. Further observations on the reaction of unsaturated dibasic anhydrides with methyl linoleate
Authors: Teeter H. M. , Kini U. S. , Myren R. A. , Cowan J. C. 
Published: July 2007

SummaryAdducts of methyl linoleate with itaconic and citraconic anhydrides have been prepared. Each adduct was separated into monomeric and polymeric components. With ethylene diamine, the itaconic and citraconic polymeric adducts gave gelled products at 170° in one hour and 3.5 hours, respectively. The adduct of citraconic anhydride and monomeric distillate gave a tough, tacky resin which did not gel during a reaction time of 20 hours at 170°–180°.The effect of dimethylaniline on the condensation of methyl linoleate and maleic anhydride was studied. Increasing amounts of dimethylaniline were found to promote the formation of a heteropolymer and to decrease the yield of liquid adduct.
Evaluation of peanut protein for industrial utilization. A review
Authors: Arthur Jett C. 
Published: July 2007

SummaryThe properties of peanut protein have been briefly reviewed, and procedures for the evaluation of this protein for different industrial uses have been indi cated. The determination of the solubility of the protein in different solvents, analysis of the isolated protein to determine its nitrogen and ash contents and its color when dispersed in sodium hydroxide solutions, determinaztion of the viscosity characteristics of concentrated peanut protein solutions, and specific product testing are used to evaluate peanut protein for industrial utilization.
Modified procedures for determination of gossypol pigments. II. Determination of free gossypol in low gossypol meals and of gossypol in oils
Authors: Deacon Benjamin D. 
Published: July 2007

AbstractMuch of the «free» gossypol in meals of low free gossypol content consists of «soluble‐bound» gossypol. Addition of dilute hydrochloric acid reduces the optical densities of gossypol blanks in free and total gossypol calibrations and assays. The reductions in these optical densities were lower than expected in free gossypol assays on meals of lower free gossypol content. The soluble‐bound gossypol in these can be converted into gossypol by heating the extracts with dilute acid at 100C. This does not affect the optical densities of the nongossypol pigments, nor does it affect the optical densities obtained on heating with aniline. The procedure affords more accurate analyses for these meals. A similar modification has been developed for gossypol in oils.
Perceived consequences among pregnant and non‐pregnant women of continuing or ceasing to smoke
Authors: Näsman P. , Ortendahl M. 
Published: July 2007

AbstractObjectiveTo examine the perception of risk of smoking‐related psychological and social outcomes, and the effect of pregnancy and intention to stop smoking on the perceived risk.MethodsEighty women were asked to make judgments about the probability of outcomes for smoking‐related consequences. Four subgroups were created using the variables of pregnancy (pregnant versus not pregnant) and cessation of smoking (intention to stop versus no intention to stop). Judgments were based on the decision to stop and not stop smoking.ResultIntention to stop smoking affected the estimated probabilities for the occurrence of consequences for both continuing and stopping smoking, whereas pregnancy did not affect the estimated probabilities. The estimated effect of stopping smoking was statistically significant.ConclusionHealth messages about smoking for all population groups should consider both future risk of mortality and immediate quality‐of‐life effects of smoking.
SEASON OF BIRTH AND CHESS EXPERTISE
Authors: GOBET FERNAND , CHASSY PHILIPPE 
Published: July 2007

SummaryThe origin of talent and expertise is currently the subject of intense debate, with explanations ranging from purely biological to purely environmental. This report shows that the population of expert chess players in the northern hemisphere shows a seasonal pattern, with an excess of births in late winter and early spring. This effect remains when taking into account the distribution of births in the population at large, using statistics from the European Union member countries. A similar pattern has been found with schizophrenia, and the possible link between these two phenomena is discussed.
A rewriting calculus for cyclic higher-order term graphs
Authors: BALDAN PAOLO , BERTOLISSI CLARA , CIRSTEA HORATIU , KIRCHNER CLAUDE 
Published: July 2007

The Rewriting Calculus (ρ-calculus, for short) was introduced at the end of the 1990s and fully integrates term-rewriting and λ-calculus. The rewrite rules, acting as elaborated abstractions, their application and the structured results obtained are first class objects of the calculus. The evaluation mechanism, which is a generalisation of beta-reduction, relies strongly on term matching in various theories.In this paper we propose an extension of the ρ-calculus, called ρg-calculus, that handles structures with cycles and sharing rather than simple terms. This is obtained by using recursion constraints in addition to the standard ρ-calculus matching constraints, which leads to a term-graph representation in an equational style. Like in the ρ-calculus, the transformations are performed by explicit application of rewrite rules as first-class entities. The possibility of expressing sharing and cycles allows one to represent and compute over regular infinite entities.We show that the ρg-calculus, under suitable linearity conditions, is confluent. The proof of this result is quite elaborate, due to the non-termination of the system and the fact that ρg-calculus-terms are considered modulo an equational theory. We also show that the ρg-calculus is expressive enough to simulate first-order (equational) left-linear term-graph rewriting and α-calculus with explicit recursion (modelled using a letrec-like construct).
Antibody against Bacillus thuringiensis phosphatidylinositol‐phospholipase C: Some examples of its potential uses
Authors: Théveniau M. A. , Malapert P. , Rougon G. N. 
Published: July 2007

SummaryWe have purified the phosphatidylinositol‐phospholipase C enzyme from the bacterium Bacillus thuringiensis. This enzyme is able to release in soluble form molecules which are anchored lo membranes via a glycan‐phosphatidylinositol group. It exhibits a molecular weight of 33–35 kDa. We raised polyclonal antisera against the molecule and used them in immunoblot as well as radioimmunoassays for enzyme detection. This last technique should facilitate monitoring of chromatographic steps during enzyme purification. We coupled antibodies to Sepharose beads in order to remove the enzyme from incubation media. This reagent also proved to be particularly useful in control experiments designed to ascertain that the observed release of molecules is due to the action of the phosphatidylinositol‐phospholipase C enzyme and not to spontaneous release or to cleavage by nonspecific hydrolases. A search for cross‐reactive molecules in other bacterial strains or mammalian tissues gave negative results. This leads to the conclusion that a great diversity exists between phosphatidylinositol‐phospholipases C, even among different bacterial strains.
Presentation of Salmonella antigens by peritoneal cells of normal and Salmonella‐infected mice
Authors: Vordermeier H. M. , Pope M. , Kotlarski I. 
Published: July 2007

SummaryA comparison of the ability of normal peritoneal cells (PC) and those harvested from mice 1–3 days after intraperitoneal immunization with live Salmonella enteritidis 11RX (11RX) to present antigen to 11RX‐primed T cells was made using formalin‐killed 11RX and a soluble 11RX antigen extract as antigens. Unfractionated PC and the adherent and non‐adherent PC populations were analysed separately and the effects of the lysosomal function‐impairing drug chloroquine and the fixative paraformaldehyde, used before or after antigen‐pulsing, were also determined. The results presented indicate that immunization with live 11RX did not induce any detectable modulation of APC function which could account for the ability of live 11RX to induce cell‐mediated immune responses involving Lyt 2+ T cells.