Non-uniform Intervals Research Articles

New properties of sigma-delta modulators with DC inputs

New properties of single- and double-loop sigma-delta modulators with constant inputs are derived by exploiting the inherent structure os the output sequences or codewords that the modulators are capable of producing. Upper bounds are derived on the number of N-bit codewords for the single- and double-loop modulators. Analytical lower bounds on the mean squared error (MSE) obtainable by any decoder, linear or nonlinear, in approximating the constant input are also derived. Optimal nonlinear decoders for constant inputs based on a table lookup approach which operates directly on the nonuniform quantization intervals are considered. Using simulations is is found that the optimal nonlinear decoders perform better than linear decoders, by about 3 and 20 dB for the single- and double-loop modulators, respectively. A cascade structure specifically for constant inputs is introduced, and its corresponding decoding algorithm is derived. It is shown that for a fixed latency, the MSE performance of the cascade structure is 12 dB superior, and its throughput is twice that of the conventional two-stage MASH modulator. >

Study on in-cylinder flow of direct injection diesel engine by LDV measurements. Turbulence analysis at low sampling rate with non-uniform time intervals.

The authors have developed a method to analyze the turbulence scale accurately from the descrete data, which are usually obtained by LDV measurements, at low sampling rate with non-uniform time intervals. In this method, the turbulence correlation is calculated from the data of many engine cycles, and successively the turbulence spectrum is calculated from the inverse Fourier-transform of the turbulence correlation. The reliability of this method is confirmed by the model data sampled randomly on a sinusoidal process, and by the data measured in the cylinder of a motored diesel engine having a direct injection system. Furthermore, it is clearly shown that the spectrum in the frequency range higher than the Nyquist frequency defined by the mean data rate can be analyzed by this method, and that it is not necessary to change the range of frequency analysis despite a little variation of mean sampling rate.

Probabilistic behavior and reliability analysis for a multi-robot system by applying Petri net and Markov renewal process theory

The strategic importance of robots in the workplace has greatly increased in recent years as an ever wider variety have been introduced into a whole host of industrial production lines. However, when these robots are examined in the context of the entire production system a number of problems can be identified. Firstly, the slowness of the operating time and secondly the fall-off in efficiency and reliability of the system when a robot is integrated with other units. This paper seeks to carefully analyze the behavior of two robots in a combination of arrangements. The robots operate independently and in coordination with each other and then each of them operates in conjunction with a conveyer incorporated in the system. Operations are then represented in a Petri net model and analysis of probabilistic behavior and reliability is performed with introducing of Markov renewal process. In terms of numerical examples a comparison of uniform and non-uniform mean operating time intervals is made in order to determine the effect of irregularities in robot operations on the system as a whole.

Experience with Speech Communication in Packet Networks

The integration of digital voice with data in a common packet-switched network system offers a number of potential benefits, including reduced systems cost through sharing of switching and transmission resources, flexible internetworking among systems utilizing different transmission media, and enhanced services for users requiring access to both voice and data communications. Issues which it has been necessary to address in order to realize these benefits include reconstitution of speech from packets arriving at nonuniform intervals, maximization of packet speech multiplexing efficiency, and determination of the implementation requirements for terminals and switching in a large-scale packet voice/data system. A series of packet speech systems experiments to address these issues has been conducted under the sponsorship of the Defense Advanced Research Projects Agency (DARPA). In the initial experiments on the ARPANET, the basic feasibility of speech communication on a store-and-forward packet network was demonstrated. Techniques were developed for reconstitution of speech from packets, and protocols were developed for call setup and for speech transport. Later speech experiments utilizing the Atlantic packet satellite network (SATNET) led to the development of techniques for efficient voice conferencing in a broadcast environment, and for internetting speech between a store-and-forward net (ARPANEI) and a broadcast net (SATNET). Large-scale packet speech multiplexing experiments could not be carried out on ARPANET or SATNET where the network link capacities severely restrict the number of speech users that can be accommodated. However, experiments are currently being carried out using a wide-band satellite-based packet system designed to accommodate a sufficient number of simultaneous users to support realistic experiments in efficient statistical multiplexing. Key developments to date associated with the wide-band experiments have been 1) techniques for internetting via voice/data gateways from a variety of local access networks (packet cable, packet radio, and circuit-switched) to a long-haul broadcast satellite network and 2) compact implementations of packet voice terminals with full protocol and voice capabilities. Basic concepts and issues associated with packet speech systems are described. Requirements and techniques for speech processing, voice protocols, packetization and reconstitution, conferencing, and multiplexing are discussed in the context of a generic packet speech system configuration. Specific experimental configurations and key packet speech results on the ARPANET, SATNET, and wide-band system are reviewed.

Prediction of multiple-dose blood level curves of drugs administered four times daily at non-uniform dosing intervals

This paper describes a program which can predict multiple-dose blood level curves of drugs administered four times daily at non-uniform dosing intervals. The program is applicable to any drug in an individual, provided that the drug follows one-compartment pharmacokinetics after oral administration, while the fraction of the oral dose absorbed, the volume of distribution, the absorption rate constant and the elimination rate constant of the drug in this individual are known.

Intertrial intervals and kindled seizures

The effects of nonuniform intertrial intervals on the development and retention of kindled amygdaloid seizures in rats were evaluated. Six consecutive grouped trial sessions (GTSs) consisting of five stimulations with 1-h intertrial intervals each day significantly reduced the average afterdischarge duration and behavioral seizure response of rats previously kindled by single, daily stimulations. Another group was treated with 32 consecutive stimulations at 1-h intervals. The development of kindling in this group was disrupted and only half the group exhibited occasional rank 5 seizures during the hourly stimulations. When the hourly group was subsequently stimulated once daily, kindled seizures were elicited in all animals. These data demonstrate that hourly stimulations or short, massed-trial paradigms disrupt kindled seizures and produce a convulsive response that is different from that produced by a single daily stimulation, suggesting that the pattern of stimulations must be taken into account when interpreting neurophysiologic, biochemical, or pharmacologic data from animals presumably kindled by the stimulations.

Optimal nonuniform sampling interval and test-input design for identification of physiological systems from very limited data

Optimal design of test-inputs and sampling intervals in experiments for linear system identification is treated as a nonlinear integer optimization problem. The criterion is a function of the Fisher information matrix, the inverse of which gives a lower bound for the covariance matrix of the parameter estimates. Emphasis is placed on optimum design of nonuniform data sampling intervals when experimental constraints allow only a limited number of discrete-time measurements of the output. A solution algorithm based on a steepest descent strategy is developed and applied to the design of a biologic experiment for estimating the parameters of a model of the dynamics of thyroid hormone metabolism. The effects on parameter accuracy of different model representations are demonstrated numerically, a canonical representation yielding far poorer accuracies than the original process model for nonoptimal sampling schedules, but comparable accuracies when these schedules are optimized. Several objective functions for optimization are compared. The overall results indicate that sampling schedule optimization is a very fruitful approach to maximizing expected parameter estimation accuracies when the sample size is small.

Stagger period selection for moving-target radars

A moving-target-indication (m.t.i.) radar is used to reject signals from fixed, unwanted targets whilst retaining the Doppler shifted signals from moving targets. For a radar with a constant p.r.f., nulls in the m.t.i. response (‘blind speeds’) occur at multiples of the p.r.f. in addition to the desired null at zero frequency. The frequency at which the first blind speed occurs may be extended by the use of a nonuniform pulse-repetition interval, or staggered p.r.f. This paper presents the results of an investigation into methods of selecting these stagger periods to achieve acceptable passband performance.

Signal recovery from repetitive non-uniform sampling patterns

This paper describes a technique for using amplitude samples which have been taken at non-uniform intervals of time. The method is essentially indirect as the non-uniform samples are first converted into uniform samples, the conversion being based upon the impulse response of a practical realizable filter. The problems encountered in the process are analysed, and a procedure for determining the optimum parameters in any given case is suggested.

A simple finite-difference grid with non-constant intervals

A finite difference network with non-uniform grid intervals, h i , such that h i = h i-1 + O ( h 2 i-1 ) is presented. The use of the grid network for two specific choices of h i - h i-1 for a linear boundary layer problem shows that it has distinct advantages in computational efficiency and in accuracy of representation of the analytical solution. DOI: 10.1111/j.2153-3490.1970.tb01933.x

Basic concepts of multidimensional space filters

The conventional electric network, consisting of linear or one-dimensional RLC (resistance-inductance-capacitance) elements, may be generalized by adding to it planar-, cubic-, etc., up to k-dimensional RLC elements. The resultant geometrical configuration of 0-, 1-, 2-... to k-dimensional spatial networks interconnected into one structure is called, in combinatorial topology, a “polyhedron.” Its electric-network realization may be called a “wave model.” The electromagnetic structure formed by interconnecting two or more wave models into one network, will be called a “multidimensional space filter.” The latter is expected to be employed eventually for the theoretical and perhaps practical solution of such physical problems for which the conventional linear (one-dimensional) electric filter is used today, on a much more elaborate multidimensional scale, of course. A single polyhedron is expected to be used in the numerical solution of simpler multidimensional problems of the calculus of finite differences, having nonuniform space intervals.