bluuebunny/crossref_metadata_2025_split huggingface dataset:
Funktionalisierte Dioxide (syn‐1,3) und Trioxide (syn,syn; syn,anti) des Tropilidens
Authors: Rücker Christoph , Seppelt Wolfgang , Fritz Hans , Prinzbach Horst 
Published: June 2007

AbstractVon Tropiliden ausgehende, präparativ brauchbare Synthesen für die C‐5‐funktionalisierten syn‐1,3‐Tropiliden‐dioxide (3 – 5) und für die C‐8‐funktionalisierten syn,anti (12 – 14) bzw. syn,syn‐Trioxide (17, 18, 37) werden entwickelt. Anders als bei analogen Cyclohexan‐Derivaten findet in anti‐1,2‐Epoxyalkoholen (z. B. 5a, 12a, 14a, 18a) intramolekulare Epoxidsubstitution („Epoxidwanderung”︁) – wenn überhaupt – nur unter massiven Bedingungen statt. Hingegen kann bei 1,4‐anti‐Epoxyalkoholen (z. B. 14a, 38) transannulare Epoxidsubstitution sehr rasch ablaufen. An Hand der syn,syn‐Trioxid‐Derivate 18a, d, 50 werden orientierende Versuche zur Regioselektivität bei nucleophiler Substitution (mit Phenylmethanthiol, Natriumazid, Hydrazin und Lithiumchlorid) angestellt.
Azodesilylierung — eine neue aprotische Diazotierungstechnik
Authors: Weiß Robert , Wagner Klaus‐Georg , Hertel Marion 
Published: June 2007

AbstractNitrosylverbindungen NOA (4a – e, A  Cl, Br, BF4, CF3SO3, I) – teilweise in situ hergestellt aus O  N – OR/(CH3)3SiA (7a, b, R  i‐C5H11, C2H5/8a, b, e, A  Cl, Br, I) – reagieren mit N,N‐bissilylierten Organylaminen RN[Si(CH3)3]2 (3b, R  C6H5; 15, R  CH3) in aprotischen organischen Medien unter Bildung von Diazonium‐Systemen R – N2+ A− und nicht‐nucleophilem Hexamethyldisiloxan (6b). Diese Methode repräsentiert die erste, Nucleophile ausschließende Diazotierungstechnik auf der Basis von 3fach koordiniertem Stickstoff und wird als „Azodesilylierung”︁ bezeichnet.
Notizen. Die Erzeugung von Nitrosylsalzen in wasserfreien organischen Medien
Authors: Weiß Robert , Wagner Klaus‐Georg 
Published: June 2007

Generation of Nitrosyl Salts in Dry Organic MediaTrimethylsilyl halides (CH3)3SiX (2a – c, X  Cl, Br, I) are sufficiently electrophilic to cleave, in an equilibrium reaction, alkyl nitrites O  NOR (1a, b, R  i‐C5H11, C2H5) with formation of O  NX (3a – c) and (CH3)3SiOR (4a, b). This reaction serves as a convenient in‐situ‐method to generate nitrosyl compounds NOX in chlorinated hydrocarbons as inert organic media.
Bestimmung der Lage der Wassermoleküle im Kieserit MgSO4 · H2O mit Hilfe der magnetischen Protonenresonanz
Authors: Schnabel B. , Jungnickel B. , Taplick T. , Heide K. 
Published: July 2007

AbstractEs werden Untersuchungen der magnetischen Protonenresonanz von Kieserit beschrieben. für die mehrere Kristalle mit wesentlich besserer Qualität zur Verfügung standen. Die Einkristallmessungen ergeben praktisch den gleichen, ziemlich hohen Wert des Proton‐Proton‐Abstandes der Kristallwassermoleküle wie früher, jedoch ergibt sich eine andere, aber infolge der hohen Qualität der verwendeten Einkristalle gut fundierte Angabe über die Orientierung der Proton‐Proton‐Verbindungslinie. Das zweite Moment des magnetischen Protonenresonanzsignals von Kieserit‐Kristallpulver erweist sich über einen Bereich von nahezu vierhundert Grad als unabhängig von der Temperatur, was zur Absicherung des oben angegebenen Wertes für den intramolekularen Proton‐Proton‐Abstand beiträgt. Die Ergebnisse beweisen das Vorliegen von „gegabelten”︁ Wasserstoffbrückenbindungen und passen gut zu anderen Eigenschaften des Kieserits. Die in den Spektren auftretende Feinstruktur wird als Auswirkung der intermolekularen magnetischen Dipol‐Dipol‐Wechselwirkung der Wasserprotonen gedeutet.
The Crystal Structure of Ca[Zn2(OH)6] · 2 H2O ‐ a Retarder in the Setting of Portland Cement
Authors: Liebau F. , Amel‐Zadeh A. 
Published: July 2007

AbstractWird das Abbinden von Ca3SiO5 durch Zugabe von Zinkverbindungen verzögert, dann entsteht intermediär das Calciumhydroxozinkat‐Hydrat Ca[Zn2(OH)6] · 2 H2O. Die Gitterkonstanten dieser Phase sind:

Die Kristallstruktur wurde mit zweidimensionalen Röntgendaten bestimmt. [Zn(OH)4]‐Tetraeder sind über Ecken zu Ketten parallel [001] verknüpft. Die Ketten werden durch [Ca(OH)4(H2O)2]‐Oktaeder zusammengehalten.
Derivation and Use of a Generalized Rate Equation for Crystallization and Precipitation
Authors: Konak A. R. 
Published: July 2007

AbstractA general rate equation is derived for crystallization and precipitation which takes into account the effects of initial supersaturation and particle density change during the process. Three special cases are distinguished, including those spontaneously initiated. Pitfalls are indicated in interpreting growth rate data for sparingly soluble salts.
Preparation of extremely pure silver iodide
Authors: Danew G. V. 
Published: July 2007

AbstractA method based on the direct interaction of crystalline silver and iodine at a temperature higher than the AgI melting point as well as a suitable apparatus permitting the obtaining of a granular product have been developed. Spectral analysis of 9 elements shows impurities content lower than 0.05 ppm. Two crystalline modifications – cubic (about 20%) and hexagonal (about 80%) are detected by X‐ray analysis.
Ionic conductivity of BaF2 crystals
Authors: Bollmann W. 
Published: July 2007

AbstractBy fitting theoretically calculated to experimentally found lg σT ÷ 1/T dependencies (σ conductivity) there were obtained: the free formation enthalpy of anti‐Frenkel defects gAF = 1.81 eV − 7.85 kT, and the mobilities vV and vi of F− ion vacancies and interstitials: vVT = 240 exp (−0.59 eV/kT) cm2 K/Vs, viT = (4080 + 610) exp (−0.79 eV/kT) cm2 K/Vs.The free association enthalpies were reestimated for complexes consisting of single foreign cations (Na+, K+, Y3+, La3+, Tm3+, Yb3+) and the corresponding charge‐compensating defects. At the melting point of BaF2 at least 5.7 per cent of the F− ions are disordered.
Synthesis of a nonlinear filter for fm demodulation
Authors: Mullick S. K. 
Published: June 2007

AbstractThe well‐known techniques of the so‐called high sensitivity FM demodulation namely the frequency feedback (FMFB) and the phase locked loop (PLL) systems can be considered as variations of FM detection system using tracking filters. The fact that FM signals can be demodulated by such systems shows that the energy of the FM wave is concentrated in a narrow band around the instantaneous frequency. The purpose of this paper is to show that such a system configuration for FM detection arises naturally from the phase‐plane study of the forced behaviour of a quasi‐linear second‐order differential equation to narrow band signals bearing amplitude and/or phase modulation. A nonlinear filter is synthesized which is designed to offer wide bandwidth to phase modulation vis‐a‐vis amplitude modulation. The filtering scheme is simulated on the digital computer and the desired behaviour verified by observing the response to a step change in phase and amplitude of the input sinusoidal signal.
Identification of the return difference matrix of a multivariable linear control system, in terms of its inverse closed‐loop transfer matrix
Authors: Arbel A. F. 
Published: June 2007

AbstractThe return difference matrix F(s) of a multivariable control system with respect to its gain elements is obtainable directly from the inverse transfer matrix T−1(s), which is in turn derived (by elimination of undriven node groups) from the coefficient matrix of the set of independent differential equations describing the system. Thus, no knowledge of the system's topology is required in order to obtain F(s). Furthermore, the inverse of one of the submatrices of T−1(s) yields the idealized response, if all gain elements are assumed to exhibit infinite gain.
Return ratio and sensitivity computation for multivariable control systems and feedback‐stabilized multiple amplifier active circuits
Authors: Arbel A. F. 
Published: June 2007

AbstractA method is presented for determining the sensitivities of multivariable control systems and feedback‐stabilized multiple‐amplifier active circuits. The derivation is based on the inverse transfer matrix, from which the return difference matrix with respect to a particular set of elements is obtainable directly for properly‐chosen variables. When the sensitivities are determined with respect to the gain elements and all local loop transmissions are high, the local return differences can be substituted by the corresponding negative return ratios, which simplifies the resulting relationships greatly if no interaction exists between the various gain elements. A related problem occurs with feedback circuits, for which the desirable stabilizing looptransmissions cannot be identified by inspection. In this case, the return difference matrix yields the formal answer. Two practical examples are given.
Inversion of the nodal admittance matrix by the use of state equations
Authors: Neill T. B. M. , Bond D. J. 
Published: June 2007

AbstractPrevious methods1–4 for inverting the nodal admittance matrix when the elements are rational functions of the Laplace transform variable s used pivotal techniques. Problems of numerical stability made this type of approach suitable only for quite small circuits.A new method based on diagonalizing the A‐matrix of a set of state equations defining the circuit has greatly improved stability. The state equations are derived directly from the nodal equations using a newly developed algorithm. These equations are then used to compute the inverse of the nodal admittance matrix as a matrix of rational functions of s.An example is presented of the application of these methods to a system of 21 degrees of freedom.
Digital filters with maximally flat amplitude and delay characteristics
Authors: Rhodes J. D. , Fahmy M. I. F. 
Published: June 2007

AbstractAn analytical solution is obtained for the transfer function of a digital filter which exhibits an optimum maximally flat amplitude characteristic and a maximally flat delay characteristic simultaneously. Explicit values for the multipliers are given for the direct realization in terms of the degree of the network and an arbitrary bandwidth scaling factor.Finally, it is concluded that this type of filter is useful in the area where the degree of a non‐recursive filter becomes excessive to fulfil an amplitude requirement (e.g. narrow bandwidth) and where recursive filters designed solely on an amplitude basis are too dispersive.
Active synthesis using the DVCCS/DVCVS
Authors: Bialko Michal , Sienko Wieslaw , Newcomb Robert W. 
Published: June 2007

AbstractIn the paper basic properties of a new versatile linear active element acting simultaneously as a Differential Voltage Controlled Current Source (DVCCS) and Differential Voltage Controlled Voltage Source (DVCVS) are described. This element called a DVCCS/DVCVS can be used for generation of all linear nondynamic elements and also can be applied directly in active RC synthesis models. The general synthesis model with one DVCCS/DVCVS element and two particular synthesis models derived from the general one are described. All synthesis models presented here allow for cascading the second degree sections without additional buffers.
Some considerations on state equations of linear active networks
Authors: Hirano Kotaro , Nishi Fumiaki , Tomiyama Shin‐Ichiro 
Published: June 2007

AbstractIt is shown that if there equivalently exist the virtual resistive elements in parallel with the inductive elements of the over‐normal tree of a given linear active network or in series with the capacitive elements of the corresponding co‐tree, an increase in the number of state variables arises. It is also shown that when a virtual resistor equivalently appears in parallel with the distinct resistor in a tree or in series with the distinct resistor in the co‐tree, a decrease in the number of state variables may arise. This is, however, a rare case in the usual types of network.Two algebraic methods for obtaining the state equation of linear active networks are presented. One is useful for the networks in which the decrease in the number of state variables does not arise. From the other, the output equation for the required variables is obtained at the same time as the state equation. Further, the initial values are simply determined without iteration in many cases.
The step responses for even degree equidistant linear phase filters
Authors: Dillon C. R. , Lind L. F. 
Published: June 2007

AbstractThe step response curves for the above class of filters are presented for degrees 4–12. The filters have been normalized so that their 3 dB point occurs at ω = 1 rad sec, to permit comparison with published step responses. The curves show that for n > 6 they closely approximate the ideal case.
Rectifier circuits for optimal frequency conversion
Authors: Belevitch V. , Genin Y. 
Published: June 2007

AbstractIt is proved that a circuit consisting of non‐linear passive resistances and of any linear invariant passive elements cannot convert power from frequencies ω1 and ω2 into power at frequency mω1 + nω2 with an efficiency better than 1/(|m| + |n|)2. Circuits attaining that efficiency are constructed for all m, n, so that the condition is both necessary and sufficient. For m = μt, n = vt, |μ| + |v| = 2s (all literals are integers), the optimal circuit consists of a finite number of rectifiers and tuned circuits. For values of m, n that are not of the above form an infinite number of tuned circuits is necessary, but an efficiency better than 93 per cent of the optimum is attainable by simple finite circuits in all cases.
The jaumann structure in wave‐digital filters
Authors: Nouta R. 
Published: June 2007

AbstractThis paper deals with an extension of the wave‐digital filter structures introduced by Fettweis.A new structure is introduced, viz, the digital translation of the Jaumann structure. The Jaumann structure is a well‐known canonical realization of analogue, symmetric, grounded lossless two‐port networks. With this structure, transfer functions with complex transmission zeros can be obtained in a wave‐digital realization, which is not possible by means of a wave‐digital ladder filter. Two examples are given, one of which has been implemented using TTL digital integrated circuits showing excellent properties.
Wave digital lattice filters
Authors: Fettweis A. , Levin H. , Sedlmeyer A. 
Published: June 2007

AbstractSymmetric wave digital filters derived from reference filters in lattice configuration require, in general, fewer multipliers. They can be designed with excellent pass‐band sensitivity properties. Their theory is easily established by using results from the scattering parameter theory of classical symmetric filters. Numerical results obtained by computer simulation are presented.
Designing monotonic low‐pass filters—comparison of some methods and criteria
Authors: Rakovich Branko D. 
Published: June 2007

AbstractA New Approach Has Been Presented To Find Characteristic Functions Of A Certain Class Of Monotonic Low‐Pass Filters Of Non‐Maximally Flat Type. The Well‐Known Legendre Filters, And The More Recently Introduced Class H Filters, Both Belonging To This Class, Are Derived As Special Cases Of The Application Of Least‐Squares Approximation Technique By Optimizing The Asymptotic Loss. It Is Shown That Class H Filters Provide Higher Stopband Attenuation Than The Legendre Filters But Have Less Favourable Passband Magnitude Response. On The Other Hand, If The Minimization Of The Passband Loss Is At A Premium Then The Unconstrained Least‐Squares Monotonic Approximants, Referred To As Lsm Filters, Yield The Best Results. Therefore, Among All Filters With Monotonic Magnitude Response, The Legendre Filters Have Neither Optimum Passband, Nor Optimum Stopband Performance, Though They Are Suitable For Some Applications.
A new synthesis procedure of lossless two‐port networks with reference to integrated circuits
Authors: Piekarski M. S. 
Published: June 2007

AbstractA new synthesis procedure of non‐reciprocal lossless two‐port networks employing grounded gyrators and minimal number of capacitors is presented. In particular, it is shown that by appropriate elementary extractions of capacitors in shunt and/or series with port 1 and/or 2, gyrators in cascade with port 1 and/or 2, capacitively terminated gyrators in shunt with port 1 and/or 2, gyrators in parallel with ports 1 and 2, the synthesis of any lossless two‐port network can be accomplished.The synthesis procedure described gives much freedom in the choice of realization structure and element values, and is very convenient for integrated circuits synthesis.
Nonlinear distortion cancellation in class a junction transistor amplifier stages
Authors: El‐Said M. A. , El‐Bayoumi F. , Talkhan E. A. 
Published: June 2007

AbstractVarious sources of distortion in class A junction transistor amplifier stages are investigated using a unified method of analysis. Expressions for simultaneous cancellation of second and third harmonic distortions at low frequencies are derived giving the design relations between the source and load resistances together with the transistor operating parameters. High frequency effects are considered and a simple compensating method is devised to extend the gain‐bandwidth product to the order of (1/2°CTCrb′b).
On the unambiguous generalization of kirchhoff's laws
Authors: Haas A. 
Published: June 2007

AbstractIn generalized linear networks the application of Kirchhoff's laws for through and across analogous quantitites, which do not possess the basic properties presumed by these laws, may lead to confusion.Using the proper extensive parameters and axioms of the irreversible thermodynamics however the muddle may be overcome. A third equation for entropy‐flux, having no resembalance with the first two, is also presented.
Fault identification in resistive and reactive networks
Authors: Gefferth L. 
Published: June 2007

AbstractIn this paper we present a method for identifying a faulty component in resistive and reactive networks. Our assumption is that the value of only one component may differ from the nominal value. This method is based on the fact that two network functions suitably chosen are in linear relation. One of them is plotted against the other. So we get a set of straight lines. The two functions of the faulty network will be measured. The measured values give a point on the set of loci from which the faulty component can be identified.
A new active rc configuration for realizing nonminimum phase transfer functions
Authors: Soliman Ahmed M. 
Published: June 2007

AbstractA new active RC configuration for realizing a second order nonminimum phase transfer function having a unity gain factor is given. The circuit has the advantages of being canonic, is always stable and is capable of realizing a high pole Q. The ω0 and the pole Q sensitivities to all passive and active circuit components are derived. The effect of the limited frequency response of the OA is examined.
On the existence of solutions to linear active networks: A state‐space approach
Authors: Chandrashekar M. , Kesavan H. K. 
Published: June 2007

AbstractIn recent literature, several alternative conditions for the existence of solutions to active networks are given. In this paper, yet another condition is given which is both necessary and sufficient for the existence of a unique solution to the network. Based on this new condition a precise upper bound for the order of complexity of an active network is established which differs from published results. A Fortran coded program is also available.
Design and predistortion of passive filters by optimization
Authors: Gaunholt Hans 
Published: June 2007

AbstractA method has been developed for design of passive filters based on optimization in the complex frequency domain. On the basis of the observation that a network response takes on very large values near the poles and very small values near the zeros it is possible to select an error function with the value zero when the network under consideration has the wanted pole‐zero positions. Application of the damped least square algorithm for minimization of that error function has produced excellent results in design and predistortion of passive ladder filters.
Computational aspects of the DC analysis of transistor networks
Authors: Stikvoort E. F. , Heins W. 
Published: June 2007

AbstractFor a general transistor‐resistor network a method is proposed to obtain, in some normed linear vector space Rn, the numerical solution of the dc equation G(U) = C for a given constant vector C = C*. At each step k, k = 0, 1,…, a vector Ck is chosen from a certain set Γk and the equation solved for C = Ck by a Newtonian iteration yielding the locally unique solution Uk. Convergence in a finite number of steps is proved for a sequence {Ck} on the straight line through C° and C*, provided this line does not contain a point C̄ between C° and C*, such that at the solution C̄ of G(U) = C̄, the derivative G'(Ū) is singular. Otherwise another initial point C° must be chosen, or the path of {Ck be altered to reach C*. The method is restricted to a closed and bounded subset of Rn, in which all the solutions of the dc equation have to lie. To find all the solutions, this bounded subset can be covered with balls.The method proposed in this paper is also useful in the analysis of a transistor‐resistor circuit, where often the important problem arises of whether the circuit will admit its correct dc bias, since this problem can be best understood by investigating the uniqueness of solutions of the dc equation.
New return difference matrix
Authors: Acar C. 
Published: June 2007

AbstractIn this paper, a new return difference matrix is defined. The partial loop difference and the signal‐flow graph determinant are extended to the partial loop difference matrix and to the matrix signal‐flow graph determinant. It is shown that the matrix signal‐flow graph determinant is invariant for any order of node numbering. Using this property, a general relation for system function is derived. Finally, it is shown that, the return difference matrix, the null return difference matrix and complementary return difference matrix are special values of the new return difference matrix.
Effect of rounding on the stability of two‐dimensional digital filters
Authors: Maria G. A. , Fahmy M. M. 
Published: June 2007

AbstractIt is well known that rounding the coefficients of digital filters may lead to instability. In this paper two approaches are used to obtain a lower bound for the word length to avoid such problems in two‐dimensional filters. The first bound is expressed in terms of the coefficients of the filter while the second bound is expressed in terms of the filter bandwidth. Both approaches were found to result in almost equal bounds.
A new approach to overcome the overflow problem in computer‐aided analysis of nonlinear resistive circuits
Authors: Chua Leon O. , Wang Niantsu N. 
Published: June 2007

AbstractThis paper is addressed to the so‐called overflow problem commonly encountered in the computer simulation of nonlinear resistive circuits containing rapidly varying nonlinearities—such as exponentials found in the models of diodes and transistors. A novel approach which makes use of the arc‐lengths of the nonlinear characteristic curves as the variables of iteration is proposed. It is proved, under rather mild conditions, that the arc‐length approach not only overcomes the overflow problem, but also leads to a more rapid rate of convergence. Moreover, it is proved that for most practical diode‐transistor circuits, the region of convergence associated with the arc‐length approach is larger and the convergence of the Newton‐Raphson algorithm is not sensitive to the initial guess. Since it is more difficult to make good initial guesses when the size of the network is large, in so far as choosing the initial guess is concerned, the advantage for using the arc‐length approach over the conventional approach increases with the size of the network. Extensive numerical experiments confirm the superior convergence property of this approach even for circuits which violate the sufficient conditions invoked by the rigorous mathematical proofs. Although the approach is applicable to a much wider class of nonlinear networks, particular emphasis is focused on diode‐transistor networks in this paper.