Geometric and algebraic errors in calculating a transducer'sspatial impulse response

Two types of errors resulting from the numerical evaluation of a transducer's spatial impulse response function have been identified, One is geometric and is due to the mismatch between the emulated piston surface (approximated using many small planar elements) and the true surface. The other error is algebraic and is due to the inexact formulation of the response of the emulated surface. The deviations from the true response were calculated for three different pistons. The results indicate that the shape and placement of the elements are important for the computational accuracy     

Computer processing of artifact and arrhythmias in heart rate variability analysis.

Analysis of heart rate variability (HRV) with Holter monitoring is often difficult due to excessive artifacts and arrhythmias. While short sudden surges are treated successfully by most methods, slow heart rate (HR) variations, nocturnal trapezoidally-shaped HR increases and special types of arrhythmias which are similar to normal HRV fluctuations may distort further time domain and spectral analysis. This paper examines the advantages and disadvantages of different methods for preprocessing of HR data. We have developed the following approach to the analysis of HRV. (1) A combination method based on the absolute difference between HR values and both the last normal HR value and an updated mean is used for removal of artifacts and arrhythmias. This method can detect both sudden surges in HR values as well as longer periods of noise combined with slow normal variations. An additional stage of wild point removal is then optionally applied. (2) Certain special problems such as large T-waves, bigeminal rhythm, slow HR variations and nocturnal trapezoidally-shaped HR increases are also identified. Although none of the algorithms can be applied successfully to all cases, the final computer analysis for preprocessing described in the present study has proved to be superior to the simplified methods which are usually used and provides more suitable data for HRV analysis.     

Adaptive nonlinear cancellation for high-speed fiber-optic systems

The authors propose techniques for adaptive nonlinear cancellation of intersymbol interference (ISI) in the electrical signal at the receiver in Gb/s lightwave systems and describe several demonstrations of these techniques. Techniques for adjustable nonlinear cancellations are discussed and demonstrations of these techniques using commercially available integrated circuits (ICs) at data rates as high as 1.7 Gb/s are described. Techniques for automatic adjustment are discussed, and a demonstration of adaptive nonlinear cancellation at 450 Mb/s is described. The authors discuss how these techniques can be integrated onto the detector IC for operations at 2.5 Gb/s and higher data rates. These techniques allow a single IC detector with adaptive nonlinear cancellation to be used in long-haul and undersea lightwave systems to optimize the detector threshold and compensate for the ISI     

Queueing analyses of traffic access control strategies withpreemptive and nonpreemptive disciplines in wideband integrated networks

A multiserver queueing model of access control strategies for a wideband integrated services digital network (ISDN) is considered. There are two types of service requests (SRs): Type 1 SR requires b servers (basic bandwidth units, BBUs) of the c available servers, while Type 2 SR requires a single server. Both types of SRs are queuable in two separate infinite-size buffers. A Type 1 SR is allowed to seize d(⩽b) servers at first and then acquire additional servers as they become available to meet the original requirement of b servers. The arrival processes of both types of SRs are Poisson and the service times are exponentially distributed with mean b/dμ₁ and 1/μ₂ for Type 1 SR and Type 2 SR, respectively. Preemptive and nonpreemptive priority disciplines with movable boundary are analyzed using the Neuts' matrix-analytic approach. Numerical examples of the queue length distribution and the mean waiting time of the SRs are presented     

A multilevel soliton communication system

A multilevel soliton communication system is proposed and assessed. In this system, at the transmitter end each channel transmits its data via fundamental solitons with a pre-specified amplitude (i.e., soliton width). At the receiver end we take advantage of the sensitive relationship between the amount or fundamental soliton self-wavelength shift and the width of the soliton in the subpicosecond region. We first compress the incoming soliton noises to the subpicosecond level and pass them through a short length of fiber at the end of which the pulses have become separated in the wavelength domain since each soliton, corresponding to a data channel, has experienced a different Raman self-wavelength shift. The channels are then easily separated by optical filters. We have derived the design constraint relations for such a system. We have then heuristically designed a 40 Gbs (four channels) system for a 1000 km propagation distance (total data-rate distance product of 40 Tb/km). Numerical simulations and noise analyses have verified the feasibility and practicality of the proposed system with very good design margins. The wavelength jitter is found to be much smaller than the desired filter spacing, and thus its contribution to the bit error rate is negligible. We also argue that the system is more tolerant to Gordon-Haus timing jitter than conventional TDM soliton systems. The system is all fiber and is, therefore very cost effective as it does not require sophisticated electro-optic and microwave circuits for demultiplexing. The system can potentially operate at much higher speeds than those achievable in conventional soliton systems and it can be used in parallel with WDM soliton system     

Charge comparison protection of transmission lines-relayingconcepts

The authors describe the relaying concepts of charge comparison. Charge comparison is a new transmission line protection system. It is a form of current differential relaying. Charge comparison largely resolves the traditional problems of current differential relaying of transmission lines, which are that protection is lost if a channel fails, a large channel capacity is required, and precise channel delay compensation is required. This technique is suitable for the protection of two- or three-terminal AC transmission lines, of all lengths and voltage levels, with or without series of shunt compensation, with three-hole or single-pole tripping