Tandem Connection Research Articles

Aortic and arterial aneurysms in behçet disease: management with stent-grafts--initial experience.

To assess the application of stent-grafts in the management of aortic and arterial aneurysms in patients with Behçet disease. Nine aneurysms in seven patients were managed with various types of stent-grafts. Diagnoses were based on clinical findings. The aortic aneurysms (n = 3) were thoracic (n = 1), suprarenal (n = 1), or infrarenal (n = 1). The arterial aneurysms (n = 6) were in the right and left subclavian (n = 2), right common carotid (n = 2), right brachiocephalic (n = 1), or left common iliac arteries (n = 1). A tandem connection of Gianturco stent covered with polytetrafluorethylene was placed in three aneurysms, and a balloon-expandable stent was placed in six. The stent-graft was successfully placed in all patients. Immediate follow-up angiography revealed complete exclusion of the aneurysm in all cases. Follow-up computed tomography performed 3 days to 2 weeks later revealed complete exclusion and thrombosis of the aneurysm and patency of the stent-graft in six patients. In one patient, total occlusion of the artery with a stent occurred due to flow disturbance caused by double lesions. During follow-up (range, 6-59 months; mean, 28 months), the aneurysm resolved and completely regressed in four patients. A recurrent aneurysm at the distal margin of previously inserted stent-graft was successfully managed with an additional stent-graft. The findings in this initial experience suggest that stent-graft insertion may be a safe and effective alternative to surgical treatment of aortic and arterial aneurysms in patients with Behçet disease.

Design of nonlinear inverse systems by means of adaptive Volterra filters

A conventional linear filter increases nonlinear distortion when it is applied to the elimination of linear distortion of a system. This paper proposes an off-line design method of an adaptive Volterra filter that eliminates linear and nonlinear distortions at the same time. This paper analyzes, by using the Volterra theory, the mechanism of increase of nonlinear distortion due to the elimination of linear distortion. This paper also analyzes, again using the Volterra theory, a signal component caused by the tandem connection of a nonlinear system and gives a design method for a nonlinear inverse system that eliminates nonlinear distortion. The proposed method reduces the nonlinear distortions by as much as 70 dB. The design time of the method is much shorter than that of existing conventional methods. © 1997 Scripta Technica, Inc. Electron Comm Jpn Pt 3, 80(8): 36–45, 1997

A version of Hautus' test for tandem connection of linear systems

In this note, we consider systems which can be decomposed as a cascade connection of linear subsystems. The second subsystem is assumed to have the controller canonical form. The main result is a version of Hautus' test, which allows us to check controllability and stabilizability properties of these systems by means of reduced-order rank computations. >

Modeling and analysis of a tandem link connection under the burst-error condition

Transmission errors are known to be bursty in nature. In block-oriented data communication, this bursty error behavior should be treated assuming that there are non-renewal correlations between the transmission conditions of data block. In this paper, using the stochastic sequential machine method the authors suggest a block-level burst error model of a digital tandem connection that consists of a set of segmented channels, and then investigate several end-to-end error performance characteristics under the burst-error condition. Also, they derive expressions that approximate the tandem connection model parameters by combining individual segment channel models into an equivalent combined error model. They show the proposed method is very useful in describing the error performance of tandem link connections.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

TLINE: Software for sinusoidal steady-state analysis of transmission lines

This article describes the use of the software package TLINE, which includes three programs for the sinusoidal steady-state analysis of transmission lines. The first program provides analysis of the tandem connection of several transmission lines with the possibility of including PI, T, or L lumped-element discontinuity junctions between the transmission lines. The other two programs are related to analysis of impedance matching using single and double stubs. All analysis procedures are graphically displayed on Smith charts. Output files that include numerical values of input impedances, values of time-average powers, and reflection coefficients at various sections of a tandem transmission line system are included. The TLINE software package is used to train students on the use of the Smith chart and also to help in the teaching and demonstration of various transmission line and impedance-matching concepts.

Synthetic studies on bryostatins, antineoplastic metabolites: Convergent synthesis of the C 1-C 16 fragment shared by all of the bryostatin family

The C 1-C 16 fragment of bryostatins could successfully be synthesized by tandem connection of the appropriate three fragments and effective introduction of the α,β-unsaturated esters at the C 13 position.

Asymmetric multipoint control by diastereo-differentiative assembly of three components with palladium catalyst

Palladium-catalyzed diastereodifferentiative tandem connection of cis-alkenyl iodide, norbornene and its homologues, and cyano nucleophile accompanying isomerization of the cis-olefin to trans was executed, where the diastereotopic face and olefinic carbons of norbornene were discriminated to give 2,3-disubstituted norbornanes.

Asymmetric multipoint control by palladium-catalyzed diastereoselective tandem carbon-carbon bond formation

Palladium-catalyzed diastereo-differentiative tandem connection of cis-alkenyl iodide, cyclic fragment, and terminal acetylene was executed. The discrimination of the diastereotopic face and olefinic carbons of norbornene was achieved with accompanying isomerization of the cis-geometry of the olefin to trans in good yields.

Novel dielectric waveguide components-microwave applications of new ceramic materials

Several dielectric-waveguide components utilizing appropriate metallized surface structures on dielectric ceramics are examined. Using magnetic walls, easily realized with ceramics, several dielectric components of a type quite different from conventional hollow waveguide components have been fabricated. Multistage bandpass filters (BPFs) with tandem connection of quarter-wave resonators have been realized on the same dielectric waveguide; multistage BPFs with coaxial resonators in the waveguide are also shown. Components similar to earlier dielectric waveguide components are made smaller by taking the image half-section. Coupling to waveguide can be realized by a probe, in the form of a metallized hole in a dielectric waveguide, or by means of the open surface corresponding to a magnetic wall loaded with the proper metallic surface patterns. These components are described, and experimental performance data are given.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Star wiring network for premises

AbstractIt is known by experience that a single‐layer star wiring network is suited for the design of premises distribution network with a small number of terminals. On the other hand, it is anticipated that the star wiring network with more than one layer will be better when there are a large number of terminals. In the design of the star wiring network with more than one layer, there are a number of parameters to be determined, e.g. the number of nodes, the placement of nodes, and the reduction of cables. However, no method has been presented by which the optimal distribution network configuration can be determined. This paper aims at the determination of the optimal configuration for the premises distribution network with two‐layer star structure. A model is presented for the modified two‐layer star wiring network, including anew the tandem connection. The cost function is derived, and the network configuration is determined to minimize the cost function. As a result, parameters which are important in the design can be determined for the practical rectangular area, where the important design parameters such as the number of nodes, the placement of nodes and the necessity for reducing the cable, are determined from the given area size and the number of terminals.

End-to-end performance models for variable bit rate voice over tandem links in packet networks

Analytical models are presented for computing the end-to-end voice call performance in a packet network that drops the less significant bits in voice packets during periods of congestion. These models provide information about the end-to-end quality likely to be experienced in future packet-switched integrated services networks. An existing single-node bit-dropping model is modified to include the situation resulting when the overall arrival process at an internal node consists of a mix of packets of different sizes due to bit dropping at previous nodes. A detailed model to capture bit-dropping effects in a tandem connection of nodes is presented. The model includes the effect of load fluctuations at each node, and also takes into account the dependencies in bit dropping experienced by a voice packet at successive nodes in a tandem connection. The model also incorporates the internodal dependence when reductions in packet service times occur at intermediate nodes due to bit dropping at previous nodes. Two approximation procedures are discussed that serve as upper and lower bounds. In particular, the upper bound is shown to be very tight for a practical range of loads, and hence serves as a good approximation with significant computational simplicity. >

Relaxations for the numerical solutions of some stochastic problems

This paper is concerned with the systematic design of efficient Jacobi and Gauss-Seidel relaxations, and their over-relaxed variants, for the computation of the stationary distributions of continuous-time Markov processes. An important factor in the design of Gauss-Seidel relaxations is the order in which the states of the Markov process is scanned in each iteration; proper designs outperform other relaxations many times over. The analysis shows that in essence each relaxation evolves identically in law with an explicitly identified discrete-time Markov chain, and its convergence rate is given by the ergodic coefficient of the chain. The ergodic coefficient is in turn determined by the connectivity of the graph of a random walk, which is considerably influenced by the ordering selected. Woven into the general theory is the specific analysis of a tandem connection of several machines with finite buffers in which each machine is subject to blocking. Examples of orderings for this system and their salient, c...

Impedance-Transforming 3-dB 90° Hybrids

Design techniques and performance results for impedance-transforming branch-line and coupled-line 3-dB 90° hybrids are discussed, and designs equations for a single-section impedance-transforming branch-Iine coupler are presented. Test results for a 50- to 25-Omega branch-line hybrid show approximately 20-percent bandwidth at a 5.4-GHz center frequency with 3.15+-0.25-dB amplitude balance. A. broad-band hybrid with 50- to 20-Omega impedance transformation has also been realized by tandem connection of coupled-line sections. Measured results show an amplitude balance of 3.7+-0.68 dB over the 3-5-GHz range for a section coupling of 11.44 dB. The amplitude balance is improved to +-0.2 dB for a design with section coupling of 12.1 dB. Test results for a 50-Omega tandem hybrid are also presented.

Adaptive echo canceller employing DM encoding

The letter presents an echo canceller employing both delta modulation (DM) and a least-mean-square (LMS) adaptive filter. An adaptive filter operating on a DM binary output sequence attempts to model the echo path. This tandem connection can significantly reduce the hardware complexity. The proposed scheme appears to have considerable potential in telecommunications as the results are comparable to those obtained from the classical echo canceller with PCM.

Simple model to calculate repeater spacings on analogue optical fibre video transmission routes

Analogue video transmission over a tandem connection of optical fibre systems is examined. A simple mathematical model is presented which relates section length and fibre attenuation to route length and video SNR at the final receiver. The model takes account of any analogue modulation format and applies to direct and coherent detection.

Synthesis and Realization of Multisection Tandem Stripline Bandpass Filters

A bandpass filter is described which is made up of two identical multi-element coupled symmetrical striplines in tandem connection. For the filter, a precise synthesis procedure is presented reducing the design to the synthesis of a directional coupler. The required equal-ripple polynomials are calculated by an iterative method. Relations for the polynomial extreme values are provided, derived from the attenuation requirements in passband and stopband. On the basis of this procedure the coupling factors of two 21-element filters are calculated and realized three-layer polyolefin. Measurements show good agreement with theoretical results.

Acoustic antialiasing filter having one resistive element for digitized microphone.

The synthetic method of electrical passive networks is successfully applied to the development of an acoustic antialiasing filter for an electret condenser microphone. The Butterworth type lowpass filter of order nine is realized as a tandem connection of an acoustic filter of order five and an electronic filter of order four which is imbeded in the microphone amplifier. The merit of this synthetic design is that the filter can be so realized with only one acoustic resistance that makes the adjustment at the production easy.

Delay Analysis of a Two-Queue, Nonuniform Message Channel

A Message Channel is defined as a tandem connection of single server queues in which the successive service times experienced by any particular customer are scaled versions of the same random variable, and thus it serves as a model for sparsely connected store-and-forward data communications networks (or network segments) where messages typically preserve their lengths as they traverse the system . A particular instance of sucha nonstandard queueing model is analyzed in this paper. The system consists of two single server queues in tandem subject tao Poisson arrival process (at the first queue) and providing service according to scaled versions of a sequence of two-level, discrete random variables. A set of recursive equations that can be used to solve the model for any given scaling factor at the second queue (normalized with respect to the first queue service) is explicitly derived. In addition, complete solutions are displayed for several cases of interest, and the equilibrium mean cumulative waiting times for these instances are compared as a method of indicating the impact of the scaling factor on the operation of the system. The extension of several results to systems with more general service time processes is discussed.

Message Delays in Repeated-Service Tandem Connections

One of the inherent complexities associated with queueing models for store and forward data communications networks arises from the fact that messages typically preserve their length as they traverse the system. The interarrival and service sequences at queues internal to the network are thus dependent, making standard methods of analysis realistically inappropriate (except in an approximate sense). In an effort to find methods of dealing with such nonstandard queueing systems, a model for sparsely-connected networks (or network segments) called a message channel has been studied. A message channel is defined as a tandem connection of single server queues in which the successive service times experienced by any particular customer are scaled versions of the same random variable. A number of recent results concerning the delay properties of such systems are presented. These include: ordering relations for the successive waiting times in the channel; characterizations of waiting time properties under extreme conditions (simultaneous arrival of all customers): and, simple bounds on performance parameters for systems with uniformly bounded service processes. A general integral equation for the distribution of the equilibrium cumulative waiting time in GI/(G/1)^{M} queueing systems (which are instances of uniform message channels) is also derived. The solution of this equation for systems with discrete service time distributions and Poisson arrivals is indicated and explicitly exhibited for the case of two discrete levels (corresponding to a message switching system with two packet classes).

Conditions for controllability and reconstructibility of discrete-time linear composite systems

In this paper necessary and sufficient controllability and reconstructibility conditions are given for the tandem connection of two discrete-time, linear, time-invariant systems. These conditions take into account the controllability and the reconstructibility of both systems. The same conditions can be applied to the feedback connection Conditions for the parallel connection are also derived.