bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis and design of self‐limiting single‐OP‐AMPRC oscillators
Authors: Huertas José L. , Pérez‐Verdú Belén , Rodríguez‐Vázquez Angel 
Published: July 2007

AbstractThis paper considers the design of self‐limiting single‐op‐amp RC oscillators inside the frequency range where the slew rate is the dominant non‐linearity. It is first demonstrated that limitation by the slew rate yields zero first‐order frequency sensitivity with respect to changes in the op amp gain‐bandwidth product (GB). Design procedures are then outlined for each of the structures comprising the complete set of canonical RC oscillators. Sensitivity figures providing criteria for comparison between the different structures are also included. Finally, experimental results are shown illustrating the validity of the proposed techniques.
Design of recursive digital filters with variable characteristics
Authors: Mitra Sanjit K. , Neuvo Yrjö , Roivainen Hannu 
Published: July 2007

AbstractA new method for changing the cut‐off frequency of infinite impulse response (IIR) digital filters with a single parameter is derived. the method is based on the use of the Taylor series expansion of the lowpass‐to‐lowpass frequency transformation. the filter structure is a parallel connection of real or complex allpass sections. the tuning range is several octaves for narrowband filters. By taking also the complementary output, a power‐complementary filter pair with tunable crossover frequency is readily obtained. Tunable centre frequency and bandwidth are obtained by incorporating a special lowpass‐to‐bandpass transformation into the structure. Design examples and a description of a signal processor implementation are included.
Linear frequency networks with applications to ‘frequency set‐on oscillators’ and ‘self‐adaptive bandpass filters’
Authors: Rhodes J. D. 
Published: July 2007

AbstractA ‘linear frequency network’ is a network system which consists of an arbitrary connection of devices, each of which performs a linear transformation on the instantaneous frequency of a signal. Thus a transfer function may be defined relating the output to input instantaneous frequency.Particular networks are investigated. the first is a basic section, producing a ‘self‐adaptive bandpass filter’ which is then applied to a ‘frequency set‐on oscillator’. Such an oscillator is a multimode oscillator where any mode will be stable when excited by a sample of an RF pulse adjacent to the mode. Cascading these basic sections results in an nth‐degree ‘self‐adaptive bandpass filter’ producing a bandpass characteristic which tracks a carrier frequency.Experimental devices in the 400‐600 MHz band are shown to have excellent agreement with theory, and applications to digital RF memories, ESM receivers and frequency memory loops are discussed.
A pole‐zero pairing strategy for minimum‐gain‐sensitivity nth‐order biquadratic filter cascades
Authors: Hiltgen Alaln , Moschytz G. S. 
Published: July 2007

AbstractIn attempting to use the pole‐zero assignment for gain sensitivity minimization in biquadratic filter cascades, a new expression for the total gain error is derived. In this result the logarithmic gain slope appears as a weighting factor to a second term depending on the structure and the parameter or component inaccuracies. On the basis of this partitioning, a pairing method for minimum gain sensitivity is developed which uses the ‘modified bottleneck algorithm’. Additional investigations finally show that minimum gain sensitivity and optimum dynamic range lead to similar constraints which can be achieved simultaneously in most applications.
A method for finding bounds on the location of all the solutions of dc piecewise‐linear circuits
Authors: Tadeusiewicz Michal 
Published: July 2007

AbstractIn this paper a method is developed for rapidly finding bounds on the location of all the solutions of a broad class of DC piecewise‐linear circuits. the class includes diode‐transistor circuits as well as circuits containing locally active resistors and controlled sources. the method can be useful as a preliminary stage of the computation process in which the well‐known Chua‐Ying algorithm is used for finding all solutions. It improves the efficiency of the Chua‐Ying algorithm. the convergence of the computation process is discussed in detail and numerical examples are given.
An improved macromodel for operational amplifiers
Authors: Hu Chenmin , Leach Donald P. , Chan Shu‐Park 
Published: July 2007

AbstractThe proposed macromodel in this paper precisely simulates almost all performance characteristics of integrated circuit operational amplifiers. It is shown by an example that the model bears very strong resemblance to actual circuits, A detailed comparison with other existing models demonstrates the great advantages of the proposed model. the simplicity and accuracy together with the employment of the most popular circuit simulator SPICE2 enable design engineers to use the macromodel on CAE workstations for all general purpose applications.
Generating randomness from chaos and constructing chaos with desired randomness
Authors: Chua Leon O. , Yao Yong , Yang Qing 
Published: July 2007

AbstractWe have designed, built and tested a switched‐capacitor circuit for generating pseudo‐random signals. the circuit is an electronic implementation of a one‐dimensional discrete map, which has been fully understood mathematically. the time series of the circuit has extremely rich dynamics, e.g. aperiodicity, non‐asymptoticity, ergodicity and fractal dimension. That is, the circuit is indeed chaotic. Furthermore, a general method for designing chaotic circuits with prescribed random properties is proposed. Numerous examples are given to illustrate the theory and methods developed in this paper.
Chaos and fractals from third‐order digital filters
Authors: Chua L. O. , Lin T. 
Published: July 2007

AbstractIt is observed that the third‐order digital filter with an overflow non‐linearity has a much richer dynamics than the second‐order digital filter. Computer simulations show that the third‐order non‐linear system can exhibit incredibly complicated fractal geometrical patterns. A three‐dimensional trajectory of the non‐linear system always lies on several parallel planes, but reaches these planes at different points to create the chaotic behaviour and the fractal geometrical patterns. the number and location of the planes are determined by the parameters of the system and the starting point of the trajectory. In general, a seven‐value symbolic dynamics is developed to explain the complex dynamics observed in the non‐linear digital filter.
On the minimum hybrid rank of a graph relative to a partition of its edges and its application to electrical network analysis
Authors: Narayanan H. 
Published: July 2007

AbstractWe consider the following problem in this paper: given a partition of the set of edges of a graph such that the subgraphs on the blocks of the partition are connected, what is the minimum number of node fission (splitting a node into two) and node fusion (coalescing two nodes) operations that will destroy all circuits containing edges from more than one block of the partition? This problem can be seen to be a generalization of the problem of determining the minimum hybrid rank of a graph. We may therefore regard this minimum number as the minimum hybrid rank of the graph relative to a specified partition of the edge set of the graph. We give an efficient algorithm for the construction of a minimum length sequence of such operations. Our solution can be applied to the problem of analysing networks after first decomposing them into subnetworks‐the equations of the network can be displayed in a bordered block diagonal form where the blocks along the diagonal correspond to the subnetworks and the thickness of the border corresponds to the minimum hybrid rank relative to the partition of the sets of edges of the network into the sets of edges of the subnetworks.
A fast linear programming approach to the design of 1D IIR digital filters
Authors: Papamarkos N. , Vachtsevanos G. 
Published: July 2007

AbstractA general method is proposed for the design of optimal 1D IIR digital filters via linear programming. the method is based upon the formulation of an appropriate linear problem which assures satisfactory approximation error for the filter's magnitude frequency response. the linear problem does not require differential correction methods or other iterative techniques for its solution, thus resulting in a computationally efficient algorithm. Analytical examples are presented to illustrate the efficiency of the method for the design of stable 1D recursive digital filters.
On a family of new two‐op‐amp switched‐capacitor biquads for high‐frequency applications
Authors: Mulawka J. J. , Konczykowska A. D. , Bon M. L. 
Published: July 2007

AbstractThis paper presents three novel biquads derived by applying the concept of so‐called basic elements for switched‐capacitor (SC) circuits. These biquads are without continuous feedback and comprise two op‐amps. They were derived assuming a transfer function denominator of the same form as the Fleischer‐Laker type E circuit. It is shown that by a simple modification of the switching arrangement, i.e. by changing the type of the basic SC element, the effect of the amplifier finite gain on the performance of SC filters can be significantly reduced. the efficiency of this approach has been established by extensive simulation studies using the dedicated symbolic analysis program SCYMBAL. Design equations and comparison with already known biquads of this type are presented. Examples are provided to demonstrate that the proposed circuits require a low total capacitance while finite‐gain effects are considerably reduced.
Boundary surfaces in sequential circuits
Authors: Špány V. , Plvka L. 
Published: July 2007

AbstractOne of the most important tasks in the analysis of a non‐linear system is lo determine its global behaviour and, in particular, to delineate the domains of attraction for asymptotically stable solutions. Stable manifolds often act as boundary surfaces between such domains in the state space.In this paper the morphology of boundary surfaces is studied in a single member of Chua's circuit family, although the techniques used apply equally well to many other non‐linear circuits. On the way, an answer is given to a former question of Matsumoto et al. concerning boundary surfaces in a chaotic circuit.Dynamical properties of a sequential circuit can be investigated by means of switching between the system's attractors, and boundary surfaces play a crucial role in the process of switching. As an application of the boundary surface techniques, dynamical properties of two models for ternary logic are presented and analysed.
Transformerless synthesis of transistor and thyristor switching RLC 1‐ports
Authors: Kropacz W. S. , Mikolajuk K. , Tobola A. 
Published: July 2007

AbstractAs an extension of the synthesis method developed in a previous paper, the transformerless synthesis of reciprocal switched 1‐ports is presented in this paper. the transformerless structures of resistance switching n‐ports described by impedance, admittance or hybrid matrices have been proposed. These structures enable the synthesis of dynamical switching RC, RL and RLC 1‐ports. Using the state variables method, the realizability conditions and identification formulae for constant and sinusoidal input functions have been derived. Three numerical examples illustrate the developed methods. the present theory can be applied to create new thyristor and transistor arrangements, particularly compensators and auxiliary switching LC circuits facilitating the commutation of thyristors and transistors.
A new approach for automatic fault diagnosis in analogue circuits
Authors: Hatzopoulos A. A. , Kontoleon J. M. 
Published: July 2007

AbstractIn this paper the problem of fault diagnosis in analogue circuits is addressed by a method which can be regarded as an artificial intelligence approach. the topology of the circuit under test along with the nominal element values, the necessary element models and their possible failure modes are the basic tools used in the procedure. Fault location is accomplished using appropriate DC node voltage measurements under certain DC excitations on the nominal circuit and the faulty one. the detection of signal faults which have DC effects is the goal of the method; cases of faults with non‐DC effects are also examined. Demonstrative examples are given to show the applicability of the method on passive and active analogue circuits.
Geometric approach to VLSI layout compaction
Authors: Xiong Xiao‐Ming , Kuh Ernest S. 
Published: July 2007

AbstractWe present a new geometric approach to VLSI layout compaction in this paper. In contrast to existing compaction algorithms, we rely on the geometric method and bypass both compaction grids and constraint graphs during the entire compaction process.A systematic and efficient way is introduced to enumerate all possible jogs. For the given layout topology we prove that the geometric algorithm yields the minimum‐area layout in one‐dimensional compaction with automatic jog insertion. In the final output, only necessary jogs are inserted and the total wire length is minimized as a secondary goal. Furthermore, the integration of local compaction tools into a layout CAD system and the practical extensions of our algorithm are addressed.
Upper bound on the number of equivalent oscillator‐notch filter circuits: A group theoretic approach
Authors: Raadhakrishnan P. , Rao B. V. 
Published: July 2007

AbstractIt is shown that the problem of synthesizing RC oscillators and notch filters can be reduced to a group theoretic problem of finding isomorphisms. the required group is identified as the Klein group. From this it is also shown that there is a sharp upper bound on the number of new circuits that can be generated from the knowledge of a parent circuit. This bound is independent of the number of branches and internal nodes.
An efficient algorithm for analysis of piecewise‐linear resistive circuits: Driving‐point and transfer characteristic plots
Authors: Huang Qiu , Liu Ruey‐Wen 
Published: July 2007

AbstractA new efficient algorithm is presented for finding all driving‐point characteristic (DP) and transfer characteristic (TC) plots for a broad class of piecewise‐linear (PWL) resistive circuits without the need for initial points for each solution branch. the piecewise‐linear circuits to be considered need not be continuous nor need their linear regions be divided by grid‐like hyperplanes. the computation of the new algorithm is based on zone‐by‐zone instead of the conventional region‐by‐region. Since each zone includes several regions and only one matrix inversion is needed for each zone, a significant reduction of computation can be achieved. Furthermore, the computational complexity for finding all solution branches, i.e. finding the DC operating points over the entire range of input values u, is no more than for finding all DC operating points over a single value u as far as the number of matrices needed to be inverted is concerned.
A one‐dimensional model of dynamics for a class of third‐order systems
Authors: Ogorzalek Maciej J. 
Published: July 2007

AbstractFor a class of third‐order non‐linear systems whose dynamics is governed by a differential equation of the form

equation image
we propose a one‐dimensional model reflecting the dynamic properties of the original system. Construction of this model map has been based on analysis of the trajectory behaviour in the original third‐order system. Properties of the model map have been investigated. Experiments have proved that the proposed one‐dimensional map, termed a deformed spiral map, reproduces the qualitative behaviour (e.g. bifurcation sequences) of the original system with very good accuracy.
Compositional data analysis
Authors: Reyment Richard A. 
Published: July 2007

ABSTRACTCompositional data occur naturally in the geosciences — tables of chemical analyses, rock‐compositions, sedimentary proportions, pollen‐analytical tables, etc. The statistical analysis of such data requires special techniques and it is not possible to use standard methods of computing correlation coefficients and carry out multivariate statistical analyses without the risk of incurring grave mistakes. The special property of compositional data, to wit, the fact that the determinations on each specimen sum to a constant, means that the variables involved in the study occur in constrained space defined by the simplex, a restricted part of real space.
An Early Cretaceous fossil bird from Montsec Mountain (Lleida, Spain)
Authors: Lacasa‐Ruiz A. 
Published: July 2007

ABSTRACTFrom among fossil fauna and flora specimens discovered in the famous outcrop of lithographic limestone of Montsec Mountain (Lleida, Spain), from the Early Cretaceous, there is one specimen of a small incomplete bird skeleton. Only the bones of the left wing, the wish‐bone (furcula), feathers and some other fragmentary bones are preserved. It lacks the skull, backbone, pectoral region, pelvic girdle and hind legs.
Coesite in the Straumen kyanite‐eclogite pod, Norway
Authors: Smith David C. , Lappin Michael A. 
Published: July 2007

ABSTRACTThe occurrence of coesite in the Straumen kyaniteeclogite pod in the Western Gneiss Region (WGR), Norway, is described. Although the microtextures of coesite, and of its partial or complete transformation into quartz, are similar to those described at the first coesite occurrence in Norway (the Grytting dolomite‐eclogite pod) there are some significant differences at this second locality. These include the host mineral of the SiO2 inclusions being garnet, instead of clinopyroxene, and also occasionally kyanite. An initial coesite—eclogite (sub)facies paragenesis was followed by a quartz—eclogite (sub)facies paragenesis which, in addition to rutile and dolomite or calcite, contains the highest number (7) of silicate phases known in any Norwegian eclogite: garnet, clinopyroxene, kyanite, quartz, phengite, zoisite and clinoamphibole. This second occurrence of definite coesite:(i) consolidates the very high pressury estimates (about 30 kbar minimum) previously deduced for certain eclogite pods occurring in the WGR; and(ii) justifies the recognition of the ‘Norwegian coesite—eclogite province’ constituted of a nappe (terrane) of about 30 kbar parageneses now residing in the WGR.
Percolation in the Crust
Authors: Gavrilenko P. , Gueguen Y. 
Published: July 2007

ABSTRACTConsidering the Earth's Crust as a heterogeneous medium, we show here that the general features of the seismic, electrical, and mechanical properties of the Crust can be conveniently described with a unified model derived from percolation theory. The basic assumption is that fracture density is a variable parameter which decreases with depth and as a result there exists a critical threshold below which fractures are only connected within finite clusters. This threshold corresponds to a critical fracture density and to a critical depth. Fluids circulate through a connected network of fractures down to the critical depth Zc. Below Zc, anisotropic fracture clusters result in seismic reflectors and high electrical conductivity. Earthquakes are restricted to depths shallower than Zc, where friction controls the mechanical resistance to fluid infiltrated pre‐existing fractures.
Archosaurian reptiles with Gondwanan affinities in the Upper Cretaceous of Europe
Authors: Buffetaut Eric 
Published: July 2007

ABSTRACTThe Late Cretaceous (mainly Campanian and Maastrichtian) non‐marine vertebrate faunas of Europe contain archosaurian reptiles which belong to groups otherwise known mainly or only from the southern ('Gondwanan') continents. They include titanosaurid sauropods, abelisaurid theropods, and trematochampsid crocodilians. The occurrence of these forms together with others of ‘Asiamerican’ affinities gives the Late Cretaceous vertebrate faunas of Europe a peculiar composition, which makes them clearly different from the well‐known faunas from western North America and Central Asia. The Gondwanan dinosaurs and crocodilians from Europe provide evidence of faunal interchange across the Tethys Sea during the Cretaceous, possibly via the Alboran plate, or the Apulian plate, which may have functioned as ‘stepping‐stones', especially during periods of low sea level.
Recent explosive volcanic episodes on the Island of Kos (Greece): associated hydrothermal parageneses and geothermal area of Volcania
Authors: Bardintzeff Jacques‐Marie , Dalabakis Pascalis , Traineau Hervé , Brousse Robert 
Published: July 2007

ABSTRACTAltered xenoliths in the 0.25–0.12 Myr non‐welded ignimbrite deposits of the Island of Kos (Greece) provide evidence for a hydrothermal convective system in the basement complex. The conjunction of a potential heat source, high‐temperature hydrothermal parageneses, permeable and porous bedded formations, continuing tectonic phenomena and successive fracturing and possible access by sea‐waters, argues for a favourable geothermal potential. The hydrothermal area of Volcania, where mineralized and sometimes degassing waters circulate, could be regarded as a zone of lateral leakage from the hydrothermal convective system, which developed above the cooling magma chamber.
Confidence bounds on risk assessments for underground nuclear waste repositories
Authors: Woo Gordon 
Published: July 2007

ABSTRACTThe estimation of risk confidence bounds is an important element of a comprehensive probabilistic risk assessment for a radioactive waste repository. Normal distribution bounds may be used in the asymptotic limit of a very large number of Monte Carlo simulations, but sharp skewness of the risk distribution may severely retard the convergence process. The Tchebycheff bounds are parameter‐free and may be applied regardless of distribution, save for the finiteness of variance. These bounds may be generally applicable, but they are invariably very broad. Better parameter‐free bounds for mean risk are presented here, based on an inequality originally derived by Guttman.
GEO LOGIC
Authors: Browning Paul 
Published: July 2007

ABSTRACTLet me begin by outlining the role of this column. It is aimed at European geoscientists who use personal computers. Rather than duplicating what is already discussed in the hundreds of computer magazines that can be found at any newsagent, I will concentrate on those products and services that have a particular application in the Earth Sciences. This is not to say that only those products with a specific Earth Science application will be discussed. Instead, anything that a practising geoscientist might find useful will be a candidate for review; a software package for compiling reference lists in the many styles demanded by different journals would be an example. The column will devote itself to products for IBM‐PC and Mac users. I apologise in advance for the UK perspective offered in the first few articles; this reflects my ignorance of the European scene and the difficulties I have faced in overcoming it. I look forward to feedback from continental geoscientists who, I hope, will bring me up to date regarding the truly European picture.
TERRA abstracts
Authors: Muir‐Wood R. 
Published: July 2007

If you are involved in organizing a meeting, conference or symposium on any aspect of the Earth Sciences, contact the TERRA Abstracts editorial office in Oxford at the earliest stage of your planning. TERRA Abstracts will organize the preparation of high quality supplements containing all the abstracts of your meeting. The headings (titles and authors’ names) for the abstracts will be typeset in a standard format and the whole supplement will be bound into a cover designed according to your requirements.Included in the supplement and at no extra charge, will be two indexes—one for all the authors, the second for keywords.