bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the capacity optimization in multicarrier channel operation
Authors: Pujante‐Cuadrupani Antonio , de Haro‐Ariet Leandro 
Published: December 2003

AbstractThe transmission plan for a communications channel exploited in multicarrier mode involves the operational parameters and the prediction of the channel impairments with special consideration for the intermodulation noise generated by beating among carriers. The intermodulation noise is a driving factor in the design phase of a transmission plan as it seriously affects the C/N + 1 ratio of the carriers in the channel, being often the dominant factor.The transmission plan of a channel operated in multicarrier mode can be represented as an injective application between two sets: the carriers and the frequency slots of the channel. Classical combinatory laws allow for the prediction of the number of configurations that can be established with sets of unidimensional elements. However, if one of the sets has elements with non‐unidimensional attributes, the classical combinatory laws fail to predict the number of possible configurations. This is the case in multicarrier transmission plans, where the carriers have an associated bandwidth (attribute of the carrier) that typically occupy several frequency slots. In this paper, an expression for the prediction of the number of possible configurations in a transmission plan is derived. This expression permits to select the most appropriate method to achieve transmission plan optimization, as a function of the associated computational resources.The higher the number of configurations, the higher the options for the optimization of the transmission plan. Subsequently, the C/N + I ratio of the carriers can be increased and therefore the quality of the service and the use of the channels resources are improved. Investigation of the space of configurations show that the maximum number of possible configurations is achieved in the range of 70–90% of channel occupation, which converges with the typical operational use of satellite transponders in multicarrier operation.This discussion is applicable not only to the frequency domain but also to any other system where sets of elements with non‐unidimensional attributes have to be considered (time domain, space domain, etc.). Copyright © 2003 John Wiley & Sons, Ltd.
Performance limitation of laser satellite communication due to vibrations and atmospheric turbulence: down‐link scenario
Authors: Arnon S. , Kopeika N. S. , Kedar D. , Zilberman A. , Arbel Dan , Livne A. , Guelman M. , Orenstain M. , Michalik H. , Ginati A. 
Published: December 2003

AbstractIn this paper, we analyse the effects of vibrations and the atmosphere on the performance of a broadband laser inter‐satellite link (BLISL) which was studied within the framework of the BLISL joint Israeli–German applied research project. The use of optical radiation as a carrier between satellites and in satellite‐to‐ground links enables transmission using very narrow beam divergence angles. Due to the narrow beam divergence angle and the large distance between the satellite and the ground station or airplane the pointing is a complicated process. Further complication results from vibration of the pointing system caused by two fundamental mechanisms of a stochastic nature: (1) tracking noise created by the electro‐optic tracker and (2) vibrations caused by internal satellite mechanical mechanisms. Additionally an inhomogeneity in the temperature and pressure of the atmosphere leads to variations of the refractive index along the transmission path. These variations of refractive index as well as pointing vibrations can cause fluctuations in the intensity and the phase of the received signal leading to an increase in link error probability. In this paper, we develop a bit error probability (BEP) model that takes into account both pointing vibrations and turbulence‐induced log amplitude fluctuations (i.e. signal intensity fading) in a regime in which the receiver aperture D0 is smaller than the turbulence coherence diameter d0. Our results indicate that BLISL can achieve a BEP of 10−9 and data rate of 1Gbps with normalized pointing vibration of GT*σθ2=0.05 and turbulence of σX=0.3. Copyright © 2003 John Wiley & Sons, Ltd.
Analysis of growth curves via mixtures
Authors: Rosen Ori , Cohen Ayala 
Published: December 2003

AbstractWe present a method for analysing growth curves using the mixtures‐of‐experts (ME) approach, which enables flexible estimation of the dependence of height on age. Individual growth curves are first fitted and the resulting estimates are then pooled to facilitate the estimation of mean growth curves, velocity and acceleration of growth and centile curves. The method allows for comparisons between males and females. We illustrate our methodology with data on growth of male and female children (0–4 years old). Copyright © 2003 John Wiley & Sons, Ltd.
Simple procedures for blinded sample size adjustment that do not affect the type I error rate
Authors: Kieser Meinhard , Friede Tim 
Published: December 2003

AbstractFor normally distributed data, determination of the appropriate sample size requires a knowledge of the variance. Because of the uncertainty in the planning phase, two‐stage procedures are attractive where the variance is reestimated from a subsample and the sample size is adjusted if necessary. From a regulatory viewpoint, preserving blindness and maintaining the ability to calculate or control the type I error rate are essential. Recently, a number of proposals have been made for sample size adjustment procedures in the t‐test situation. Unfortunately, none of these methods satisfy both these requirements. We show through analytical computations that the type I error rate of the t‐test is not affected if simple blind variance estimators are used for sample size recalculation. Furthermore, the results for the expected power of the procedures demonstrate that the methods are effective in ensuring the desired power even under initial misspecification of the variance. A method is discussed that can be applied in a more general setting and that assumes analysis with a permutation test. This procedure maintains the significance level for any design situation and arbitrary blind sample size recalculation strategy. Copyright © 2003 John Wiley & Sons, Ltd.
Use of incomplete post‐treatment data in the analysis of viral eradication studies
Authors: Cheng Debbie M. , Lagakos Stephen W. 
Published: December 2003

AbstractIn some studies of chronic viral infections where the objective is to estimate the distributions of time until viral eradication and viral resistance to treatment, patients must have treatment terminated in order to assess eradication status. Such patients then have their viral load continually monitored during a post‐treatment period. If no virus is detected during this period, viral eradication is presumed to have occurred whereas detection of virus is interpreted to mean that the virus had been suppressed but not eradicated prior to treatment interruption. If the post‐treatment period is long, as would be the case with diseases such as hepatitis C and HIV, there will be patients who have not completed the post‐treatment period by the time the data are analysed. This paper proposes non‐parametric and semi‐parametric methods to incorporate partial post‐treatment data in the estimation of the subdistributions of the time until eradication and resistance. The new methods extend previous methods for the analysis of eradication studies that do not account for incomplete post‐treatment information, and are illustrated with data from a recent hepatitis C clinical trial. Copyright © 2003 John Wiley & Sons, Ltd.
Qualitative simulation of models of software evolution
Authors: Ramil Juan F. , Smith Neil 
Published: December 2003

AbstractLehman's laws and the quantitative models based on them seek to encapsulate empirical generalizations about E‐type program evolution. Such modelling is hampered by insufficient knowledge about the mechanisms at work and their parameters. Qualitative reasoning is a body of work that handles a lack of precise knowledge by reasoning at a more abstract level than with quantitative models. This paper describes the introduction of qualitative reasoning to the study of software evolution. It reports on the derivation of qualitative versions of two existing quantitative models of the software evolution process, leading to identification of previously unrecognized behaviours. A third qualitative model is also discussed. The paper also shows how qualitative trend abstraction enables a high level of abstraction analysis of empirical data and that, at this level, the empirical patterns observed in several different software systems display similarities. Finally, we compare the qualitative simulation outputs of the three systems to the abstracted empirical trends. Copyright © 2003 John Wiley & Sons, Ltd.
Evaluating the sustained performance of COTS‐based messaging systems
Authors: Tran Phong , Gosper Jeffrey , Gorton Ian 
Published: December 2003

AbstractMessaging systems, which include message brokers built on top of message‐oriented middleware, have been used as middleware components in many enterprise application integration projects. There are many COTS‐based messaging systems on the market, but there is little concrete understanding in the software industry on the performance of these different technologies. The authors have carried out a scenario‐based evaluation of three leading messaging systems to provide insight into performance issues. The evaluation process includes a study of the sustained performance of the system under load. The result of this study is used to derive a generic metric for quantifying a messaging system's performance. The paper describes a synthetic transactional scenario, which is used for load tests and performance measurement. The results from executing this test scenario with three messaging systems are then presented and explained. Copyright © 2003 John Wiley & Sons, Ltd.
Evaluating online control of goal‐directed arm movement while standing in virtual visual environment
Authors: Martin Olivier , Julian Benjamin , Boissieux Laurence , Gascuel Jean‐Dominique , Prablanc Claude 
Published: December 2003

AbstractIt has been shown that an inaccurate motor planning of a fast goal‐directed movement could be amended through an online comparison between the goal and the instantaneous representation of the (unseen) moving hand. The aim of this study was to test whether such an optimum processing was still efficient in a virtual visual environment (VE), by exploring the effect of immersion on the online visuomotor control of goal‐directed arm movement. Six subjects participated in the experiment, in which hand reaching toward either a stationary or a moving virtual visual target (double‐step paradigm) was executed in an upright posture. The analysis of the hand kinematics and postural adjustments showed an accurate control of movement and balance in both reaching conditions. This indicates that immersion does not affect the online control processes used by the CNS to adjust movement in interactive VE. Copyright © 2003 John Wiley & Sons, Ltd.
Third generation WCDMA radio evolution
Authors: Holma Harri , Toskala Antti 
Published: December 2003

AbstractThird Generation Partnership Project (3GPP) produced the first full version of the WCDMA standard at the end of 1999. This release, called Release'99, contains all the necessary elements to meet the requirements for IMT‐2000 technologies, including 2 Mbps data rate with variable bit‐rate capability, support of multi‐service, QoS differentiation and efficient packet data. The Release 5 specifications were created in March 2002 and they contain downlink packet data operation enhancement, under the title high speed downlink packet access (HSDPA). HSDPA utilizes Hybrid ARQ and higher order modulation for improving data‐spectral efficiency and for pushing bit rates beyond 10 Mbps. The further 3GPP releases will study the enhancements of packet‐data performance in uplink. Other important features in future 3GPP releases include advanced antenna technologies and WCDMA standard for new spectrum allocations. The paper describes the main solutions of 3GPP WCDMA standard in more detail. Copyright © 2003 John Wiley & Sons, Ltd.
Pilot pollution interference cancellation in CDMA systems
Authors: El‐Said Mostafa M. , Kumar Anup , Elmaghraby Adel S. 
Published: December 2003

AbstractIn CDMA systems, existence of large number of equally strong pilot signals is not desirable. As a consequence, this would create pilot pollution interference (PPI). Additionally, the limited number of fingers in the RAKE receiver adds a different dimension to the problem. The PPI has the influence of overloading the mobile station's RAKE receiver with excessive amount of signaling on the dedicated control channels. Therefore, the pilot signal's orthogonality erodes dramatically, and the system suffers from dropping of ongoing calls, blocking of originating fresh calls and decrease in the system capacity. In this paper, we demonstrate the power of using a novel multi‐carrier chip shaping to alleviate the impact of the PPI. Consequently, the mobile's RAKE receiver will have the capability to perform frequency diversity rather than multipath diversity. This will make efficient use of the received signal energy in the frequency domain and boost the performance of the system. Simulation studies have been carried out to verify the appropriateness of the proposed approach and we have obtained very promising results. Copyright © 2003 John Wiley & Sons, Ltd.
UMTS architecture extension to adapt multimedia services and manage their flow properties
Authors: Sfar Safouane , Choukair Zièd 
Published: December 2003

AbstractOur approach exposed in this paper consists of providing an end‐to‐end adaptation frame to UMTS REL.99 (UMTS Release 1999, first phase of UMTS) commercial services, according to a virtual home environment (VHE) context. A commercial service provided to the user should be adapted during its selection as well as during its transfer through the different parts of the network. These adaptations are due to the fluctuation of the parameters of the network and the need to adapt the quality of service (QoS) parameters. The four steps of adaptation we will develop in our model will be guaranteed by ‘adaptation bearer service (ABS)’. An ABS will provide, for example, data encoding or data compression. ABS differs according to the localization and the adaptation mode. In this paper, we present also our adaptation strategy and associated policies. The purpose of this strategy is to classify and then select service flows which are to be adapted in priority. Policies are specified according to factors that we defined. Fuzzy logic is used for the implementation of this strategy as it represents a natural reasoning mode useful to decide which commercial service adaptation policy is to be carried out according to resource use context. Copyright © 2003 John Wiley & Sons, Ltd.
A throughput‐efficient and channel‐adaptive scheduling scheme in voice/data DS‐CDMA networks with transmission power constraints
Authors: Shu Tao , Niu Zhisheng 
Published: December 2003

AbstractIn a practical voice/data CDMA network, the constraint of transmission powers makes it necessary to transmit multiple data users in parallel in order to fully utilize system resource (power). How to choose those data users that should be transmitted simultaneously and allocate appropriate powers among them remains an open issue. In this paper, we prove that it is optimal in the sense of maximum data throughput to select data users and allocate powers according to the descending order of their indexes of received power capability (IRPC). Here, IRPC is defined as the product of the transmission power upper bound and the channel gain. based on this principle, a channel‐adaptive scheduling scheme, partially descending IRPC (PDI) scheduling, is proposed to achieve efficient throughput performance for data traffic while maintaining certain fairness among different users. The efficiency and fairness of the PDI scheduling are verified by comparing with the conventional fair‐sharing scheme and round‐robin scheme through computer simulations. Numerical results also reveal the robustness of the new scheme to the channel estimation errors. Copyright © 2003 John Wiley & Sons, Ltd.
Sampling Bias on Cup Anemometer Mean Winds
Authors: Kristensen L. , Hansen O. F. , Højstrup J. 
Published: December 2003

AbstractThe cup anemometer signal can be sampled in several ways to obtain the mean wind speed. Here we discuss the sampling of series of mean wind speeds from consecutive rotor rotations, followed by unweighted and weighted averaging. It is shown that the unweighted averaging creates a positive bias on the long‐term mean wind speed, which is at least one order of magnitude larger than the positive bias from the weighted averaging, also known as the sample‐and‐hold method. For a homogeneous, neutrally stratified flow the first biases are 1%–2%. For comparison the biases due to fluctuations of the three wind velocity components and due to calibration non‐linearity are determined under the same conditions. The largest of these is the v‐bias from direction fluctuations. The calculations pertain to the Risø P2546A model cup anemometer. Copyright © 2003 John Wiley & Sons, Ltd.
Nitrogen Rich Materials: Salts of N, N′‐Bistetrazolatohydrazine
Authors: Hammerl Anton , Holl Gerhard , Kaiser Manfred , Klapötke Thomas M. , Piotrowski Holger 
Published: December 2003

AbstractSolutions of N, N′‐azobistetrazolate salts in anhydrous hydrazine were reduced to salts of N, N′‐bistetrazolatohydrazine. Several salts of this highly energetic, nitrogen rich anion were prepared this way and characterized by elemental analysis, vibrational (IR, Raman) and multinuclear NMR spectroscopy (1H, 13C, 14N). The crystal structure of the barium and hydrazinium salt were determined.
Funktionalisierte β‐Hydroxydithiozimtsäurederivate als Liganden. Kristallstrukturanalyse von 4′‐Hydroxy‐β‐hydroxydithiozimtsäuremethylester
Authors: Schubert Karsten , Saumweber Rupert , Görls Helmar , Weigand Wolfgang 
Published: December 2003

AbstractAus silylgeschütztem 4′‐Hydroxyacetophenon (1) entsteht durch Umsetzung mit Schwefelkohlenstoff und Iodmethan in Gegenwart von Kalium‐tert‐butylat der silylsubstituierte 4′‐Hydroxy‐β‐hydroxydithiozimtsäuremethylester (2). Die Molekülstruktur des nach Abspaltung der Schutzgruppe entstehenden Esters 3 wurde durch Röntgenstrukturanalyse bestimmt. Die phenolische OH‐Gruppe wird mit DL‐α‐Liponsäure (4) verestert. Der so zugängliche 4′‐(1, 2‐Dithiolan‐3‐pentanoyl)‐β‐hydroxydithiozimtsäuremethylester (5) bildet mit NiII, PdII und PtII Komplexe.
Strukturelle Modellierung der Alkoholdehydrogenase: Zinkkomplexe von Acetyl‐ und Benzoylpyridin
Authors: Schneider Astrid , Vahrenkamp Heinrich 
Published: December 2003

AbstractDie N, O‐Chelatliganden Acetyl‐ und Benzoylpyridin (L) bilden mit Zinkchlorid fünf‐ und sechsfach koordinierte Komplexe der Zusammensetzungen L2ZnCl2 und [L2ZnCl]+. Mit den Zinkthiolaten des Pentafluorthiophenols und 2, 4, 6‐triisopropylthiophenols entstehen dagegen tetraedrische Komplexe der Zusammensetzung L˙Zn(SR)2. Diese sind strukturelle Modelle der Zn(NOS2)‐Bindungssituation bei Anbindung eines Aldehyds im aktiven Zentrum des Enzyms Alkoholdehydrogenase.
Zur Synthese von Na3FeO3, einem ternären Oxoferrat(III) mit Kettenstruktur
Authors: Sobotka Bettina M. , Möller Angela 
Published: December 2003

AbstractSynthesis of Na3FeO3, a Ternary Oxoferrate(III) with a Chain StructureNa3FeO3 has been obtained from a redox reaction between CdO and iron metal in the presence of Na2O and Na2CO3 at 650 °C as amber colored transparent single crystals. The crystal structure determination (IPDS data: P21/n, a = 579.9(1) pm, b = 1265.9(2) pm, c = 582.8(1) pm, β = 116.02(2)°, Z = 4, Rall = 0.0576) reveals the presence of [FeO2O2/2] zig‐zag‐chains.
Zwei Cer(III)‐Chlorid‐Oxoborate im Vergleich: Ce3Cl3[BO3]2 und CeCl(BO2)2
Authors: Nikelski Tanja , Schleid Thomas 
Published: December 2003

AbstractKristalle der Zusammensetzung Ce3Cl3[BO3]2 werden durch Umsetzung von CeO2, elementarem Cer, CeCl3 und B2O3 mit einem Überschuß an CeCl3 als Flußmittel bei 550 °C in gasdicht verschweißten Platinampullen innerhalb von drei Wochen erhalten. Einkristallines CeCl(BO2)2 entsteht ebenfalls bei der Umsetzung von CeO2, elementarem Cer, CeCl3 und B2O3, allerdings im Überschuß von B2O3 als Flußmittel, in einer verschlossenen Platinampulle nach zwei Wochen bei 900 °C. Beide Verbindungen kristallisieren in Form von langen, dünnen, transparenten, farblosen, luft‐ und wasserbeständigen Nadeln. Die Kristallstruktur von Ce3Cl3[BO3]2 (hexagonal, P63/m; a = 920, 08(6); c = 580, 79(4) pm; Z = 2) zeigt strukturelle Ähnlichkeiten mit CeCl3 (UCl3‐Ty p), indem man Cl‐‐Anionen partiell gegen [BO3]3‐‐Gruppen austauscht. Ce3Cl3[BO3]2 ist aus planaren Schichten, die aus isolierten Oxoborat‐Einheiten [BO3]3‐ einerseits und aus Ce3+‐Kationen sowie Cl‐‐Anionen andererseits bestehen, aufgebaut. Das Ce3+‐Kation weist eine Koordinationszahl von zehn auf, wobei es sich mit sechs O2‐‐ und vier Cl‐‐Anionen vierfach‐überkappt trigonal‐prismatisch umgibt. CeCl(BO2)2 kristallisiert analog MCl(BO2)2 (M = La, Pr) triklin in der Raumgruppe P1¯ (a = 421, 74(5); b = 657, 63(7); c = 812, 21(9) pm; α = 82, 152(6); β = 89, 206(7); γ = 72, 048(6)°; Z = 2). Die charakteristische Baueinheit besteht aus unendlichen Ketten {[(B1)O1/1tO2/2e(B2)O1/1tO2/2e]2‐} (≡ {[BO2]‐}) eckenverknüpfter [BO3]3‐‐Dreiecke. Diese Einheiten sind derart verknüpft, daß zickzack‐förmige Stränge entstehen, die entlang [100] verlaufen. Das Ce3+‐Kation ist ebenfalls von zehn Anionen (sieben O2‐ und drei Cl‐) in Form eines Edshammar‐Polyeders koordiniert.
Synthesis, Crystallographic Studies, and Characterization of K2Bi8Se13—xSx Solid Solutions
Authors: Kyratsi Theodora , Kanatzidis Mercouri G. 
Published: December 2003

AbstractThe detailed crystal structures of selected members of solid solutions of the thermoelectric compounds K2Bi8Se13—xSx with x = 4, x = 6 and x = 10 were determined. The purpose of this study was to understand the nature of Se/S mass fluctuations introduced when β‐K2Bi8Se13 is alloyed with isostructural K2Bi8S13. The details of the K/Bi disorder and Se/S distribution are examined. Lattice parameters, semiconducting band gaps and melting points are reported as function of x.
La4Br2Al5 and Ce4Br2Ga5: Three‐dimensional Metal Networks Embedded in Condensed Ln6 Trigonal Prisms
Authors: Zheng Chong , Mattausch Hansjürgen , Oeckler Oliver , Nuss Jürgen , Simon Arndt 
Published: December 2003

AbstractLa4Br2Al5 and Ce4Br2Ga5 are metal‐rich and feature Al or Ga centered Ln6 (Ln = La, Ce) trigonal prisms. The packing of these prisms is unique and characterizes a new variation in reduced rare‐earth halides. The prisms fuse into dimeric units which in turn form rectangles parallel to the a‐b plane. They then stack in the [0 0 1] direction, creating channels along the c‐axis. The halides occupy these channels, while Al or Ga atoms join to a three‐connected, three‐dimensional network encircling these channels. The title compounds represent a new structure type, crystallizing in the space group Cmmm (No. 65) with lattice constants a = 16.115(3) and 15.796(3)Å, b = 17.206(3) and 16.795(3), c = 4.3280(9) and 4.2344(8)Å, respectively for La4Br2Al5 and Ce4Br2Ga5. An isostructural, however nonstoichiometric and disordered phase La4.15Br2Ga4.69 also exists with a = 15.902(1)Å, b = 17.034(1)Å, and 4.2612(3)Å. Computational analysis reveals that they belong to the class of reduced valence rare‐earth halides. However, because of the extended interaction between Ln and M, the conduction band of these compounds is partially occupied. Conductivity and magnetic susceptibility measurements confirm the metallic nature of these compounds, and reveal Cerium to be trivalent as expected.