Sufficient Number Of Channels Research Articles

Electron excitation processes in low energy collisions of hydrogen–helium atoms

The electron excitation processes of H(1s) + He(1s2) → H(2s/2p) + He(1s2) are studied in impact energy range of 20--2000 eV/u by using the quantum-mechanical molecular orbital close-coupling (QMOCC) method. Total and state-selective cross sections have been obtained and compared with the available theoretical and experimental results. The results agree well with available measurements in the overlapping energy regions overall. The comparison of our results with other theoretical calculations further demonstrates the importance of considering a sufficient number of channels. The datasets presented in this paper, including the excitation cross sections, are openly available at https://www.doi.org/10.57760/sciencedb.j00113.00083.

On Levenshtein’s Channel and List Size in Information Retrieval

The Levenshtein's channel model for substitution errors is relevant in information retrieval where information is received through many noisy channels. In each of the channels there can occur at most t errors and the decoder tries to recover the information with the aid of the channel outputs. Recently, Yaakobi and Bruck considered the problem where the decoder provides a list instead of a unique output. If the underlying code C ⊆ \mathbb F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sup> has error-correcting capability e, we write t=e+ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">l</i> , ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">l</i> ≥ 1). In this paper, we provide new (constant) bounds on the size of the list. In particular, we give using the Sauer-Shelah lemma the upper bound <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">l</i> +1 on the list size for large enough n provided that we have a sufficient number of channels. We also show that the bound <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">l</i> +1 is the best possible. Most of our other new results rely on constant weight codes.

STABILITY AND SIZE EFFECT ANALYSIS OF THIN MAGNESIUM NANOWIRES

The stability and size effect analysis of different isomeric structures of Mg n(n = 1–5) nanowires have been investigated by employing ab-initio approach. We have considered various geometrical structures up to five atoms to explore the minimum energy configuration. In the present study, we have calculated various physical properties in large energy interval for all structures. In particular, we have analyzed the effect of shape and size on these calculated values and investigated density of states (DOS) in four different ways to see the microscopic changes in their nature of peaks. We predict that five atom tetrahedral structure is stable having highest binding energy and DOS. The band structure calculations of all wires reflect the possibility of sufficient number of channels for quantum conduction and are metallic in character. In addition, we have also analyzed the effect of hydrogen adsorption on most stabilized geometrical structure of magnesium ( Mg ) nanowire which shows no evidence of better stability in comparison to pure Mg nanowires.

Ensemble-Averaged Flow Routing in Channel Networks: Kinematic Wave Equation

A new ensemble-averaged kinematic wave equation is derived for the flow routing problem in channel networks. This derivation is performed by ensemble averaging the second-order Taylor series expansion of the point scale kinematic wave equation around the mean value of the equation’s parameters. Utilizing this ensemble-averaged kinematic wave equation, the ensemble-averaged solution for the same ordered channels (according to the Strahler–Horton ordering) are obtained. Instead of solving the flow at each channel one by one, the ensemble-averaged solution is computed for the ensemble of channels that are of the same order within the channel network. Ensemble averaging is only applied to the channel orders that include a sufficient number of channels to form an ensemble of adequate size. Using this methodology, the computational load, parameter data requirements, and time/effort required to set up the model are reduced substantially. Besides the obtained economy in computations, data requirements and effort ...

Integrated Optimal Cell Site Selection and Frequency Allocation for Cellular Radio Networks

Two major planning problems are encountered when designing a cellular radio network. The initial question is where to locate the base transmitter stations such that full coverage is achieved at low interference. This is relevant for frequency division (FDMA) as well as code division multiple access (CDMA) technology. If the locations of base stations are given, then for an FDMA-system frequencies have to be assigned such that there is a sufficient number of channels per cell available at a low total interference level. Since cell site selection and frequency allocation have mutual influences on each other, the ultimate goal is to deal with both problems in a single design step. The main intention of this paper is to model the above planning issues as linear integer programs, and to discuss solution methods for the corresponding NP-hard problems. According to their increasing complexity we proceed from channel allocation via cell site selection to an integrated single setup.

Performance analysis of cellular mobile communication networks supporting multimedia services

This paper illustrates the development of an analytical model for a communication network providing integrated services to a population of mobile users, and presents performance results to both validate the analytical approach, and assess the quality of the services offered to the end users. The analytical model is based on continuous—time multidimensional birth–death processes, and is focused on just one of the cells in the network. The cellular system is assumed to provide three classes of service: the basic voice service, a data service with bit rate higher than the voice service, and a multimedia service with one voice and one data component. In order to improve the overall network performance, some channels can be reserved to handovers, and multimedia calls that cannot complete a handover are decoupled, by transferring to the target cell only the voice component and suspending the data connection until a sufficient number of channels become free. Numerical results demonstrate the accuracy of the approximate model, as well as the effectiveness of the newly proposed multimedia call decoupling approach.

Nucleated cell killing by complement: effects of C5b-9 channel size and extracellular Ca2+ on the lytic process.

For C5b-9 channels to mediate cytolysis of a nucleated cell, a sufficient number of channels must be formed in the plasma membrane to override the compensatory mechanisms that nucleated cells might employ to survive. It is well known that nucleated cells are relatively resistant to lysis by complement in comparison to erythrocytes, and it is now evident that this resistance is due, in part, to the ability of nucleated cells to rapidly eliminate C5b-9 from the cell surface. The ability of nucleated cells to eliminate complement complexes is related to physiochemical properties of the complex, such as channel diameter, which in turn affect Ca2+ fluxes that stimulate metabolic processes involved in the elimination process. Paradoxically, these same channel properties that stimulate the defense response may also be responsible for the lethal effects of complement. To further study the role of channel size on cytolysis of nucleated cells by C5b-9, we examined the lytic efficiency of larger C5b-9 channels containing several C9 molecules in comparison with smaller C5b-9 channels containing fewer C9. We have obtained data to indicate that although the larger channels were more cytolytically potent, the channel size had little influence on the rate of cell death. In contrast, the rate of lysis of erythrocytes was substantially slower when smaller C5b-9 channels were present. In evaluating the effect of the extracellular Ca2+ concentration, [Ca2+]o, on nucleated cell lysis in the presence of a lytic number of C5b-9 complexes, it was observed that when the [Ca2+]o was increased the rate of cell death also increased. These findings suggest that lysis of nucleated cells by C5b-9, unlike erythrocytes, may not be entirely due to colloid osmotic deregulation.

Cross sections for the rotationally inelastic scattering of Ne + N2: application of the exponential semi-classical distorted wave approximation

Exact quantum-mechanical close-coupling and approximate calculations are presented for Ne + N2 collisions using a model potential. The approximate calculations were performed using an exponential semi-classical distorted wave approximation (ESCDW) which is outlined in the paper. The ESCDW approximation involves the evaluation of the same integrals as the standard distorted wave approximation. The former method, however, in contrast to the latter, yields a unitary S matrix and therefore conserves particle flux. The exponentiation process is shown to lead to dramatic improvements in the calculated cross sections for the present system. Cross sections evaluated using the ESCDW approximation compare very well with exact ones over the entire range of thermally accessible energies. Total and differential rotationally inelastic cross sections are presented and their variation with energy is examined. The dependence of the cross sections on the number of coupled channels included in the calculations is also investigated and a sufficient number of channels are included to ensure convergence.

A quantitative study of asymmetric-sideband broadcasting

The major factor which hampers the progress of broadcasting is the lack of a sufficient number of channels in which to contain the increasing number of transmissions. In the present state of the art few, except local, stations can be received without interference from other broadcasting stations on frequency-contiguous channels Unless the upper frequencies of modulation of the wanted station are severely attenuated and unless, therefore, reproduction is lacking in intelligibility and naturalness. This inter-station interference can be eradicated or minimized, and quality improved as regards “top” reproduction, if all or part of one sideband of the transmitted spectrum is cut away. The cutting-away operation on the side-band, however, produces harmonic distortion in the received signals. It is the object of the asymmetricsideband system of transmission to cut away part of one sideband without introducing audible harmonic distortion.The paper gives a quantitative analysis which shows how asymmetry, either of phase or of magnitude, between two sideband components, created by any given modulation component, is related to harmonic distortion; and it is shown that this distortion is proportional, over a large range of values, to depth of modulation. The nature of the sound spectrum is such that the intensities in the upper register are much less than those in the lower middle register. Since the degree of asymmetry between counterpart sideband components is a measure of the attenuation of the cut-away sideband, this attenuation can be increased as the modulation frequency is made greater. This is tantamount to saying that, as the sideband frequency becomes more and more removed from the carrier frequency, it may be more and more attenuated while the distortion can be made to remain constant and small. Thus in asymmetric technique the outer parts of one sideband may be removed without the introduction of audible distortion.Curves are derived, based upon the evaluation of expressions given in the quantitative analysis, which show the required attenuation-constant of niters which cut away part of one sideband but produce no more than a constant distortion. It is proved that phase asymmetry between counterpart sidebands may give rise to more serious distortions than are created by magnitude asymmetry acting alone, and a network is described which keeps phase asymmetry to a minimum and yet gives a close approximation to the required attenuation.Accounts are given of practical tests wherein the quality of reproduction obtainable from an asymmetric transmitter is compared with that given by orthodox modulation. While it is true that a highly trained ear may, on rare occasions, be able to detect some slight differences between the two types of reproduction, when they are directly compared, the general public would be quite incapable of so doing, even if they possessed receiving apparatus so free from distortion itself as to give them an opportunity to do so. It is pointed out that it is better to face the occasional minute deteriorations in quality given by the asymmetric system than to suffer from the continuous hissing and splitting sounds brought about by existing inter-station interference.In the latter part of the paper an analysis is given which shows that the asymmetric system has three possible applications to space broadcasting as it is practised to-day, namely (1) It could be used to allow carrier difference frequencies of the order of 11–12 kc. without introducing any sideband overlap interference. (2) It could be applied to existing conditions, where carrier difference frequencies are of the order of 9 kc, and would reduce inter-station interference to the order of one-tenth its present value. (3) If existing interferences are considered to be tolerable, then carrier difference frequencies can be reduced to 6 kc. without increasing interference above its existing values; this implies that 11/2; times the number of stations workingin Europe to-day on exclusive waves could be accommodated in the existing waveband.It is suggested, finally, that a policy could be adopted such that the introduction of the asymmetric system would encourage receiver development along lines wherein, by an augmentation of only the carrier component at the detector, all distortion due to the use of an asymmetric spectrum would be eliminated. Thus an evolution might be envisaged which led to the introduction of the ideal carrier and single-sideband type of transmission when all receivers were adapted to reduce the resulting distortion to a tolerable amount.