ISSN:0253-3839    

DOI:10.1080/02533839.1990.9677291

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

This work analyzes the problem of interfacial resistance to heat and mass transfer for a gas absorption system with first order reaction when the solubility, the diffusivity, and the reaction rate constant are dependent upon temperature. A film theory model is applied. Two different types of temperature‐dependent solubility relationships, the linear and the exponential approximations, are employed. The temperature‐dependent diffusivity and reaction rate constant are expressed in exponential form. Three cases of different solute concentrations are compared to study the influence of solubility on the system performance. One of these cases with the exponential temperature‐dependent solubility is further examined for the effects of diffusivity coefficient and of surface resistance on the enhancement factor, the temperature rise, and the solubility. The results indicate that the form of the temperature‐dependent solubility relationship plays an important role in the estimation of the surface temperature rise and hence the enhancement factor. The linear approximation predicts slightly higher values in the intermediate region of√Mo, while the exponential approximation results in dramatically higher values at very large√Mo.The surface resistance significantly affects the absorption rate, the interfacial temperature rise, and the solubility at small values of√Mo.The effect of the variation of diffusivity on the system performance is of secondary importance, especially when the values of√Moare not large.

ISSN:0253-3839    

DOI:10.1080/02533839.1990.9677292

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A new hybrid token‐CSMA/CD protocol is proposed and analyzed in this paper. The new hybrid protocol is suitable for bus‐structured local area networks. Basically, the new hybrid protocol is a modification of the one proposed by Gopal and Wong [3]. In our new hybrid protocol, the first time slot after the channel changes state from busy to idle, is reserved for the exclusive use of the priority user who possesses the token. Results show that, by this simple modification, our new hybrid protocol has a better performance than the one proposed in [3], especially when the time wasted in detecting a collision is large. The reason is that most of the packet collisions will be avoided by reserving one time slot for the exclusive use of the priority user.

ISSN:0253-3839    

DOI:10.1080/02533839.1990.9677293

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A textual database deals with retrieval and manipulation of documents. It allows a user to search on‐line complete documents or parts of documents rather than attributes of documents. Resembling a formatted database which uses a data model as its underlying structure, a textual database has to base its development upon a document model. In this paper, a document model, called the ECHO model, is proposed. The ECHO model provides a document representation, called the ECHO structure, for expressing documents and operations on the representation that serve to express queries and manipulations on documents. It has the ability to provide multiple document structures for a document, a flexible search unit for retrieving textual information, and a subrange search on a textual database. In addition, the ECHO structure is relatively easy to maintain. An architecture of a textual database based on the ECHO model is also proposed. In order to improve the query performance, a refined character inversion method, called ARCIM, is proposed as the text‐access method of the Chinese textual database. The ARCIM can retrieve texts faster than a simple inversion method and requires less space overhead.

ISSN:0253-3839    

DOI:10.1080/02533839.1990.9677294

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

An efficient sub‐band coding method for encoding images is presented in this paper. In this method a frequency band decomposition of the image is carried out by means of two‐dimensional separable quadrature mirror filters (QMF's), which split the image spectrum into sixteen uniform sub‐bands. In the coding process, we employ special quantizers and encoding algorithms which are designed according to the characteristics (including the visual perceptual property) of the sub‐bands to quantize and to encode these subimages, separately. The simulation results are presented in terms of average bit rates and the quality (in subjective as well as mean squared senses) of the reconstructed images. These results indicate that a good quality reproduction can be achieved at high compression rates. The paper also shows that a seven‐band decomposition has very high performance in quality, compression rate, and economy.

ISSN:0253-3839    

DOI:10.1080/02533839.1990.9677295

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

This paper presents a generalized Cauer third continued‐fraction expansion abouts = aands = 8.A new algorithm is derived obtain this new form of continued‐fraction expansion from the coefficients of the power series of a transfer function expanded abouts= 8. Two Cauer third CFE canonical state‐space models are introduced, and their connections to a general state‐space model and a phase variable canonical state‐space model are also developed. Application of the generalized Cauer third CFE method to the problem of model reduction is demonstrated.

ISSN:0253-3839    

DOI:10.1080/02533839.1990.9677296

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The throughput efficiency of a set of continuous ARQ strategies for Markov channels is analyzed in this paper based on regenerative theorems. The operation of the investigated ARQ strategies can be described as follows. For each data block, a chunk ofnor less copies are transmitted contiguously to the receiver. Whenever a repeat request is received, the transmitter goes back to that data block and retransmits the same data block continuously until an ACK is received. Results show that the throughput efficiency depends heavily on the value ofn.Therefore, an optimal value ofncan be selected to maximize the throughput efficiency. We also compare the throughput performance of the investigated ARQ strategies for Markov systems and systems under the independent error model. It is found that using the independent error model to describe Markov channels may result in significant deviation.

ISSN:0253-3839    

DOI:10.1080/02533839.1990.9677297

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A new type of decoder for double‐error‐correcting binary BCH codes is presented. The simple and regular control clock signals of the decoder can be directly extracted from the line signals. The decoder needs onlynclock cycles to decode one received word, wherenis the block length of the code. A (31, 21, 5) BCH decoder is used as a hardware implementation example to illustrate the operation principle. The decoder can work at a data rate of up to 3.4Mbits/sec when it is implemented in a programmable Logic Cell Array (LCA) chip.

ISSN:0253-3839    

DOI:10.1080/02533839.1990.9677298

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Three‐layer channel routing is an important problem in VLSI layout. In this paper, we present a topological sorting algorithm to determine the topological order on nets depending on the operations of the vertical constraint graph (VCG) and the horizontal constraint graph (HCG). According to the order, the base router can finish the connections of all nets. In the algorithm, the HVH mode is assumed, and some examples including Deutsch's difficult example are used as test problems.

ISSN:0253-3839    

DOI:10.1080/02533839.1990.9677299

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Based on the matrix fraction description (MFD) consideration and polynomial matrix algebra, interesting results for the multivariable discrete linear quadratic regulator and optimal estimator are derived. The solutions are obtained by the spectral factorization of polynomial matrices in concise forms. The difficulties of solving the discrete algebraic Riccati equation can thus be avoided. In the derivation, some connections between the state space approach and the frequency domain approach are further investigated.

ISSN:0253-3839    

DOI:10.1080/02533839.1990.9677300

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor