bluuebunny/crossref_metadata_2025_split huggingface dataset:
Metric transformation for a turbo‐coded DPSK waveform
Authors: Wang Charles C. , Sklar Dean J. 
Published: August 2003

AbstractThe classical turbo‐decoding algorithm is based on the assumption that the input sequence to the decoder has been disturbed by a noise process that has a Gaussian distribution. For a differentially coherent phase shift keying (DPSK) waveform, the output statistics of a differentially coherent demodulator is nonGaussian. When this sequence is fed directly into the turbo decoder, particularly under a fading environment, the mismatch between decoder algorithm assumptions and actual input statistics can result in significant decoder performance degradation. This paper investigates the bit error performance for such a mismatch for the DPSK waveform. Techniques for forming enhanced turbo‐decoding metrics with biased channel side information (CSI) are proposed. Using these new metrics, error performance in fading conditions is shown to improve significantly. Copyright © 2003 John Wiley & Sons, Ltd.
Optimum design criterion and multilevel coding for radio systems over AWGN and Rayleigh fading channels
Authors: Yuan Dongfeng , Zhang Haixia , Wang Chengxiang , Yao Qi , Song Xiaofei , Huber J. B. 
Published: August 2003

AbstractFor the narrow band Wireless Code Division Multiple Access (WCDMA) system, there are some channel coding schemes proposed and applied like Turbo code and convolutional codes. But for the 4G Code Division Multiple Access (CDMA) wideband systems, we have to use new channel coding schemes with high bandwidth efficiency. In this case, multilevel coding (MLC) scheme is easy to map to Multiple Quardrature Amplitude Modulation (MQAM) modulation strategy to be used for 4G, and MLC+MQAM will be a potential channel coding scheme for the error correcting of next generation of mobile systems.A novel criterion, that is ‘capacity rule’ plus ‘mapping rule’, for the design of the optimum MLC scheme for radio systems over Rayleigh fading channels is proposed in this paper. Based on this theory, a few of key issues related to design an optimum MLC system are investigated. These include a novel optimum design criterion proposed, different mapping strategies, different decoding methods of MLC/MSD and MLC/Parallel Decoding on Levels (PDL) and their performance comparison over Additive White Gaussian Noise (AWGN) and Rayleigh fading channels respectively. Copyright © 2003 John Wiley & Sons, Ltd.
On a space time parallel iterative coding scheme and its performance evaluation
Authors: Hou Jia , Lee Moon Ho 
Published: August 2003

AbstractThis paper proposes a class of space time parallel (STP) iterative coding scheme to combat fading for wireless MIMO systems. In addition to the inner iterations, thesuper iterations(or outer iterations) and symbol interleaved space time coding are employed to achieve additional time diversity and coding gain in fading channel. The numerical and simulation results demonstrate that the STP iterative coding scheme may make use of all the advantages of transmit diversity and time diversity in wireless MIMO systems. In particular, in the case of STP turbo codes, about 1 dB BER enhancement and half calculation time reduction from conventional space time (ST) turbo codes designs are achieved; in the case of low density parity check (LDPC) codes, about 0.8 dB improvement from conventional ST LDPC designs is obtained. Copyright © 2003 John Wiley & Sons, Ltd.
On the performance of truncated type III hybrid ARQ scheme with code combining
Authors: Chen Qingchun , Fan Pingzhi 
Published: August 2003

AbstractThe hybrid automatic repeats request (ARQ) scheme, together with code combining, is an effective way to provide reliable transmission of data packets over noisy channel. In this paper, it is shown that the application of rate‐compatible punctured convolutional (RCPC) codes in truncated type III hybrid ARQ scheme leads to the so‐called composite code combining. In order to illuminate the effect of the involved composite code combining, a new concept, i.e. combined puncturing pattern, is introduced. By state‐diagram analysis, it is revealed that the overall performance of the truncated type III hybrid ARQ with code combining is dependent on both the maximum transmission number and the residual error probability after code combining. By extending the analysis to the convolutional codes whose symbols exhibit different effective signal‐to‐noise ratio owing to the composite code combining, a closed form of the residual error probability of the combined RCPC codes is derived. Based on the combined puncturing patterns, upper and lower bounds on the error performance are derived, together with an approximation method which is shown to be quite satisfactory by numerical and simulation results. Copyright © 2003 John Wiley & Sons, Ltd.
Specific effects and deconvolution in submicrometre EPMA: application to binary diffusion
Authors: Arnould Olivier , Hild François 
Published: August 2003

AbstractElectron probe (x‐ray) microanalysis (EPMA) is nowadays a classical and well‐established method for qualitative and (semi)quantitative evaluation of the elemental composition of the (near) surface of a sample on the micrometre scale. This technique can be used to determine concentration profiles due to (inter)diffusion in materials at submicrometre resolution if physical and geometrical effects that occur during the measurement process are accounted for. Standard phenomena are usually corrected by commercial software for a homogeneous elemental composition in the analysed area. However, in the case of a diffusion process on a small scale, the composition is no longer homogeneous and the effect of the hemispherical volume of the x‐ray emission on the spatial resolution of the concentration profiles, and consequently on the diffusion coefficients, has to be considered. A radial x‐ray distribution associated with the classical depth distribution, ϕ(z), allows for the definition of a 2D x‐ray emission function for medium to heavy materials. This enables one to study the effect of some geometrical parameters on the measured concentration profile and to propose a method of reconstructing the real weight fraction profile from the measured profile of the x‐ray intensities by using regularized deconvolution algorithms. Copyright © 2003 John Wiley & Sons, Ltd.
Measurement of diffusion coefficients of Ag in YBa2Cu3O7 by the EDXRF technique
Authors: Dogan O. , Ertuǧrul M. , Çevik U. , Bacaksız E. , Tıraşoǧlu E. , Kobya A. I. , Erdoǧan H. 
Published: August 2003

AbstractThe diffusion of Ag in superconducting YBa2Cu3O7 ceramic was studied over the temperature range 700–850 °C by the energy‐dispersive X‐ray fluorescence (EDXRF) technique. For the excitation of silver atoms, an annular Am‐241 radioisotope source (50 mCi) emitting 59.543 keV photons was used. The temperature dependences of Ag diffusion coefficients in grains (D1) and over the grain boundaries (D2) are described by the equations D1 = 1.4 × 10−2exp[−(1.18 ± 0.10)/kT] and D2 = 3.1 × 10−4exp[−(0.87 ± 0.10)/kT]. Copyright © 2003 John Wiley & Sons, Ltd.
Bremsstrahlung spectra produced by 89Sr beta particles in thick targets
Authors: Dhaliwal Amarjit S. 
Published: August 2003

AbstractExternal bremsstrahlung spectra produced by hard beta particles of 89Sr (1.463 MeV) in thick targets of Al, Cu, Sn and Pb were studied. After making the necessary corrections, the experimental results were compared with the theoretical external bremsstrahlung distributions obtained from Elwert corrected (non‐relativistic) Bethe–Heitler theory, Tseng and Pratt theory and modified Elwert factor (relativistic) Bethe–Heitler theory. It was found that for low‐Z elements all theories are equally suitable throughout the energy region studied. For medium‐Z elements, the Tseng and Pratt and modified Elwert factor (relativistic) Bethe–Heitler theories are more accurate, particularly in medium and higher energy regions. However, for high‐Z elements, the modified Elwert factor (relativistic) Bethe–Heitler theory shows better agreement with the experiment, particularly at the higher energy end. Copyright © 2003 John Wiley & Sons, Ltd.
Determination of the provenance of medieval silver coins: potential and limitations of x‐ray analysis using photons, electrons or protons
Authors: Linke R. , Schreiner M. , Demortier G. , Alram M. 
Published: August 2003

AbstractOne hundred and fifty seven ‘Tiroler Kreuzer’, a medieval currency from the county of Tyrol/Austria, were analysed in order to determine their place of mintage. The silver coins were produced during the 15th century in the mints of Merano (South Tyrol) and Hall (North Tyrol) but they have no marks or punches which would allow a clear distinction. Energy‐dispersive x‐ray fluorescence analysis (EDXRF) was applied without sampling in order to determine the silver contents and also minor (Cu, Pb, Bi) and trace elements (Fe, Au, Hg, Ni). Owing to corrosion processes, which changed the chemical composition of the surfaces of the coins, investigations of cross‐sections were necessary using energy‐dispersive x‐ray microanalysis in a scanning electron microscope (SEM/EDX) to determine the stage of corrosion and the Ag concentration of the core of the coins. The results showed differences of up to 50% between the composition of the core and the surface. Finally, proton‐induced x‐ray emission (PIXE) at an external proton beam was applied, in order to detect also Ni, an element which could not be measured by either EDXRF or SEM/EDX in the ppm range. The data show a clear difference in the Ni content between the coins from Merano (∼0.1% Ni) and Hall (∼0.01% Ni). Copyright © 2003 John Wiley & Sons, Ltd.
Energies of KαLN x‐ray satellite lines produced in Ca, Ti, Cr and Fe targets bombarded by fast heavy ions
Authors: Kavčič M. , Budnar M. , Dousse J.‐Cl. , Hoszowska J. 
Published: August 2003

AbstractHigh‐resolution measurements of the Kα x‐ray spectra of metallic Ca, Ti, Cr and Fe were performed with a von Hamos Bragg crystal spectrometer. The target x‐ray emission was induced by 34, 72 and 134 MeV C ions, 28, 64 and 230 MeV O ions and 43, 160 and 380 MeV Ne ions. The energies of the resolved KαLN x‐ray satellite lines were determined. The possible variation of the energy differences between neighboring KαLN lines with the projectile energy, projectile atomic number and number of target L shell spectator vacancies was probed. No significant dependence on the projectile characteristics was observed. In contrast, the absolute energies of the KαLN satellite lines were found to depend on the projectile velocity. This dependence was attributed to the additional M shell ionization of the target atoms. Copyright © 2003 John Wiley & Sons, Ltd.
Distribution and incorporation of zinc in biological calcium phosphates
Authors: Barrea Raul A. , Pérez Carlos A. , Ramos Aline Y. , Sánchez Héctor J. , Grenón Miriam 
Published: August 2003

AbstractHuman dental calculi are biological calcium phosphates, which consist of an organic phase and an inorganic or mineral phase. In the latter phase, spectrochemical analyses have revealed the presence of several different magnesium and calcium phosphates. As the crystalline structure of the calculus passes through several stages during its allocation in the mouth, special attention is paid to some elements, such as zinc, that can modify the mineralization process. Several in vitro studies relating to the dental calculus mineralization process have been performed so far, but there is a lack of data obtained from biologically synthesized samples. The knowledge of the zinc distribution and incorporation in biological calcium phosphates is of great interest in providing more information about the biological process of calculus formation. In this paper we present surveys of the elemental distribution and incorporation of zinc in human dental calculus, by using a combination of different techniques: x‐ray microfluorescence using synchrotron radiation, scanning electron microscopy and x‐ray absorption spectroscopy. One‐dimensional x‐ray microfluorescence of zinc and magnesium measurement shows that there is a high accumulation of both elements in the sub‐gingival region of the calculus and a strong correlation of their spatial distribution. Experimental Ca/P molar ratios were determined by energy‐dispersive spectroscopy to identify different calcium phosphate phases, the sub‐gingival region being composed of a mixture of highly and poorly calcified phosphates and the supra‐gingival region composed mainly of carbonated hydroxyapatite. Finally, x‐ray absorption measurements were carried out at the zinc K edge on synthetic and biological samples. The Zn—O distance and coordination number of the synthetic samples and the supra‐gingival calculus show that zinc is adsorbed on these structures, whereas in the sub‐gingival samples it is allocated in a cation site. The results are indicative of the active participation of zinc in the calcification process of sub‐gingival calculus. Copyright © 2003 John Wiley & Sons, Ltd.
Energy‐dispersive x‐ray fluorescence analysis of modern coloured glasses from Marinha Grande (Portugal)
Authors: Valério P. , Markowicz A. , Kregsamer P. , Araújo M. F. , de Matos A. Pires , Chinea‐Cano E. , Carvalho C. 
Published: August 2003

AbstractThe elemental composition (K, Ca, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Sr, Ba, Nd and Pb) of modern coloured glasses was obtained by energy‐dispersive x‐ray fluorescence (EDXRF) spectrometry. This non‐destructive technique is frequently used in the analysis of historical glass objects. Two reference glasses were also measured to assess the overall accuracy of the EDXRF method. Reference and unknown glasses were analysed without any preparation. The coloured glass samples studied belong to the Glass Museum of Marinha Grande and were chosen from two distinct collections, which were characterized by the different concentrations of some elements (K, Ti, Cr, Mn, Fe, Ba and Pb). The determined major elements allowed the identification of two raw materials used in glass manufacture, sand and lime. Multivariate statistical analysis, namely principal component extraction, simplified the identification of some of the colouring chemical elements, associating them with the different colours of the glass objects. Copyright © 2003 John Wiley & Sons, Ltd.
Micro‐synchrotron x‐ray fluorescence of the metal distribution in a black spruce tree stem: evidence for radial mobility
Authors: Martin R. R. , Naftel S. J. , Skinner W. , Jones K. W. , Feng H. 
Published: August 2003

AbstractMicro‐synchrotron radiation x‐ray fluorescence has been used to examine the metal distribution across an entire black spruce stem. The results show the individual elements to be transported and sequestered in different ways so that apparent elemental mobility within the stem changes from element to element. The results suggest that a detailed knowledge of the behavior of each element is required before pollution chronologies can be inferred from dendroanalysis. Copyright © 2003 John Wiley & Sons, Ltd.
Synthesis, Crystal Structure, and Electrochemical Behaviour of an Azido μ‐bridged Ni2+ Complex
Authors: Kurtaran Raif , Arici Cengiz , Emregül Kaan C. , Ülkü Dinçer , Atakol Orhan , Taştekin Mustafa 
Published: August 2003

AbstractA homo‐dinuclear NiII complex was prepared from 2, 6‐bis(3, 5‐dimethylpyrazolyl)pyridine (Me4‐bpp) and azide ions in nonaqueous media. It was characterized by single crystal X‐ray structural analysis, IR spectroscopy, and elemental analysis. In addition, the electrochemical properties of the compound were determined with cyclic voltammetry in DMF. The title compound crystallizes in the P21/n monoclinic space group, with unit cell parameters a = 8.978(1), b = 12.459(1), c = 17.764(1) Å, ß =100.603(3)°, V = 1953.0(3) Å3, Z = 2. The Ni2+ ion has a distorted octahedral environment involving three nitrogen atoms of the Me4‐bpp ligand, two nitrogen atoms from the bridged azide group, and one nitrogen atom from the terminal azide group. The Ni···Ni distance is 3.273(5) Å.
Crystal Structures of [Cu2(bpy)2(H2O)(OH)2(SO4)]·4H2O and [Cu(bpy)(H2O)2]SO4 with bpy = 2, 2′‐Bipyridine
Authors: Zheng Yue‐Qing , Lin Jian‐Li 
Published: August 2003

AbstractTwo sulfato CuII complexes [Cu2(bpy)2(H2O)(OH)2(SO4)]· 4H2O (1) and [Cu(bpy)(H2O)2]SO4 (2) were synthesized and structurally characterized by single crystal X—ray diffraction. Complex 1 consists of the asymmetric dinuclear [Cu2(bpy)2(H2O)(OH)2(SO4)] complex molecules and hydrogen bonded H2O molecules. Within the dinuclear molecules, the Cu atoms are in square pyramidal geometries, where the equatorial sites are occupied by two N atoms of one bpy ligand and two O atoms of different μ2—OH groups and the apical position by one aqua ligand or one sulfato group. Through intermolecular O—H···O and C—H···O hydrogen bonds and intermolecular π—π stacking interactions, the dinuclear complex molecules are assembled into layers, between which the hydrogen bonded H2O molecules are located. The Cu atoms in 2 are octahedrally coordinated by two N atoms of one bpy ligand and four O atoms of two H2O molecules and two sulfato groups with the sulfato O atoms at the trans positions and are bridged by sulfato groups into 1[Cu(bpy)(H2O)2(SO4)2/2] chains. Through the interchain π—π stacking interactions and interchain C—H···O hydrogen bonds, the resulting chains are assembled into bi—chains, which are further interlinked into layers by O—H···O hydrogen bonds between adjacent bichains.
LiE(SiMe3)2 (E = P, As) als Synthesebaustein zur Darstellung von Molybdänkomplexen mit EH funktionellen Liganden
Authors: Vogel Ulf , Scheer Manfred 
Published: August 2003

AbstractDer Komplex [{CpMo(CO)2}2(μ‐H)(μ‐PH2)] (1) wird in einer Eintopfreaktion aus [CpMo(CO)2]2, LiP(SiMe3)2, MeOH und HBF4 in guten Ausbeuten erhalten. In einer zur Darstellung von 1 analogen Reaktion ausgehend von LiAs(SiMe3)2 konnten die Verbindungen [{CpMo(CO)2}2(μ, η2‐As2)] und ‐[{CpMo(CO)2}2(μ‐H)(μ4‐As){CpMo(CO)2}2(μ4, η1:η1‐As2H){CpMo(CO)2}2(μ‐H)] (3) isoliert werden. Das deprotonierte Derivat von 1, K[{CpMo(CO)2}2(μ‐PH2)] (2), das mittels Metallierung mit KH gebildet wird, reagiert mit GaCl3 nicht wie erwartet unter KCl‐Eliminierung. Stattdessen bildet sich das Lewis Säure/Base‐Addukt K[{CpMo(CO)2}2(μ‐PH2)(GaCl3)] (4), das im Festkörper eine polymere Kettenstruktur ausbildet. Die spektroskopischen und strukturellen Daten der Produkte werden diskutiert.
Zinc(II), Cadmium(II), and Mercury(II) Complexes with the 2, 2′‐Diamino‐4, 4′‐bithiazole (DABTZ) Ligand — Syntheses and X‐Ray Crystal Structure of [Hg(DABTZ)(SCN)2]
Authors: Morsali Ali , Payheghader Mahmod , Reza Poorheravi Mohammad , Jamali Fahimeh 
Published: August 2003

AbstractReaction of the ligand 2, 2′‐diamino‐4, 4′‐bithiazole (DABTZ) with Zn(ClO4)2, CdCl2, and Hg(SCN)2 gives complexes with composition [Zn(DABTZ)2](ClO4)2, [Cd(DABTZ)2Cl2], and [Hg(DABTZ)(SCN)2]. The complexes were characterized by elemental analyses and infrared spectroscopy. The crystal structure of the [Hg(DABTZ)(SCN)2] was determined by X‐ray crystallography. The complex is built up of a monomeric Hg(SCN)2 unit with one 2, 2′‐diamino‐4, 4′‐bithiazole ligand coordinated to the Hg atom via the two N atoms giving rise to a five‐member chelate ring in a distorted tetrahedral environment. There is π‐π stacking interaction between the parallel aromatic rings belonging to adjacent chain as planar species in which the mean molecular planes are close to parallel and separated by a distance of ∼ 3.5Å, close to that of the planes in graphite. The coordinated 2, 2′‐diamino‐4, 4′‐bithiazole molecule is involved in hydrogen bonding acting as hydrogen‐bond donors with N atoms from the SCN ligand as potential hydrogen‐bond acceptors. The hydrogen bonding yields infinite chains parallel to the crystallographic vectors a and b. Each molecule is bonded to three neighbours. Both amine H atoms are hydrogen bonded to N atoms.
A Novel 3D Framework Coordination Polymer based on Succinato bridged Helical Chains Connected by 4, 4' ‐ Bipyridine: [Cu(bpy)(H2O)2(C4H4O4)]?2H2O
Authors: Zheng Yue‐Qing , Kong Zu‐Ping 
Published: August 2003

AbstractBlue needle—shaped crystals of [Cu(bpy)(H2O)2(C4H4O4)]· 2H2O were obtained by slow evaporation of a methanolic aqueous solution containing a fresh Cu(C4H4O4)· 2H2O precipitate, 4, 4′—bipyridine, and ammonia. Within the complex, the six—coordinated Cu atoms are linked by bis—monodentate gauche succinate anions into chains propagating helically around the [001] axis. The chains are interconnected by 4, 4′—bipyridine ligands into a 3D framework with the crystal H2O molecules located in the channels along the [100], [010] and [110] directions. The Cu2+ ions are in distorted octahedral coordination of two nitrogen and four oxygen atoms (equatorial bonds: Cu—N 1.986(5), 2.015(5)Å; Cu—O 1.950(6), 1.954(6)Å; axial bonds Cu—O: 2.524(9), 2.539(8)Å). Furthermore, the thermal and magnetic behavior of the compound will be discussed. Crystal data: hexagonal, P61 (no. 169), a = 11.066(2)Å, c = 24.965(5)Å, V = 2647.5(8)Å3, Z = 6, R = 0.0528 and wR2 = 0.1103 for 1426 observed reflections (Fo2 > 2σ(Fo2)) out of 2170 unique reflections.
The Combustion of SiCl4 in Hot O2/H2 Flames
Authors: Hannebauer Bernd , Menzel Frank 
Published: August 2003

AbstractA simple kinetic model describing the molecular gas phase reactions during the formation of fumed silica (AEROSIL®) was developed. The focus was on the formation of molecular SiO2, starting from SiCl4, hydrogen and oxygen. Wherever available, kinetic and thermodynamic parameters were taken from the literature. All other parameters are based on quantum chemical calculations. From these data, an adiabatic model for the combustion reaction has been developed. It was found that a significant amount of molecular SiO2 forms after about 0.1 and 0.6 ms at starting temperatures between 1000 and 2000 K. The initial reaction of the SiCl4 combustion in a hydrogen/oxygen flame was found to be different from the combustion in air: The high reactivity of SiCl4 towards water is favored over the SiCl4 dissociation, which is the initial and rate‐determining step during the combustion of SiCl4 in air.
Photolytically Induced Reaction of Monomeric AlCl with Dihydrogen in a Solid Ar Matrix at 12 K: Generation and Characterization of the Previously Unknown Monomeric Aluminium Hydride ClAlH2
Authors: Himmel Hans‐Jörg , Klaus Christina 
Published: August 2003

AbstractMonomeric AlCl is shown to react with H2 under photoactivation to yield the new monomeric aluminium hydride ClAlH2. The planar, C2v symmetric molecule is characterized by its IR spectra, taking in the effects of isotopic substitution (H2, D2 and HD), allied with detailed quantum chemical calculations. A normal coordinate analysis is performed to calculate accurate force constants. The properties of this species are compared to the ones of other related compounds featuring either an Al‐H or an Al‐Cl bond. Finally, the dimerization to give the D2h symmetric H2Al(μ‐Cl)2AlH2 is investigated theoretically. This dimer is of interest as a possible reagent to prepare dialane, Al2H6. The enthalpy for the reaction of H2Al(μ‐Cl)2AlH2 in the gas‐phase with solid LiAlH4 to give gaseous Al2H6 and solid LiCl is calculated.