Modified slant and modified slant Haar transforms for image data compression

Transform image processing is done in nonoverlapping blocks and a block of (4 × 4) or a (8 × 8) subpicture size is reasonable in terms of both mean-square error and subjective picture quality. It is therefore desirable to search for a fast transform which is efficient for data of small sequence length. This paper presents a modified slant and a modified slant Haar transform. Computational operations are increased by 2 additions and 4 multiplications only as compared to conventional slant and slant Haar transforms. Performance evaluation based on a first-order stationary Markov process signal such as variance distribution, mean-square error estimate due to scalar Wiener filtering of signal corrupted by white noise and decorrelation property establish the superiority of the transforms. Comparative study of results on a monochrome picture are encouraging.     

M/G/I queue analysis for Huffman coded english text decoding system

The queueing model with limited waiting room, i.e. buffer size for messages of arbitrary lengths and Poisson arrival, at a demultiplexing terminal using a HP 2100A computer has been studied. The data have been constructed using Huffman code to English text. Storage capacity for an ergodic system has been estimated by M/G/I analysis with practically no loss of information. This analysis may be used as a guide-line for buffer size estimation in computer communication networks when data are being constructed with the use of Huffman code and due consideration to the frequencies of alphabets and word size.     

Buffer Behavior for Mixed Arrivals and Single Server with Random Interruptions

A queueing model with finite buffer size, mixed input traffic (Poisson and burst Poisson arrivals), synchronous transmission and server interruptions through a Bernoulli sequence of independent random variables is studied. Using average burst length, traffic intensity and input traffic mixture ratio as parameters, the relationships among buffer size, overflow probability and expected message queueing delay are obtained. An integrated digital voice-data system with synchronous time division multiplexing (STDM) for a large number of voice sources and mixed arrival process for data messages is considered as an application for this model. The results of this study are portrayed on graphs and may be used as guidelines in buffer design problems in digital voice-data systems. The queueing model developed is quite general in a sense that it covers pure Poisson and burst Poisson arrival processes and the mixture of the two as well.     

Fast algorithm for the solution of banded linear systems

Linear systems can be solved by converting the coefficient matrix into a triangular matrix. If it is known, apriori, that the coefficient matrix is a banded matrix having only few non zero diagonals, then a substantial saving in both the time and the storage on the computer can be achieved. In this paper a new algorithm has been developed for triangularisation of the banded matrix. The algorithm is computationally economical and advantageous as compared to the existing known algorithms. The advantage decreases with the increase in bandwidth and the break even point being approximately N/√3 where N is the size of the square matrix.     

Lotsizing in Multi-Item Multi- Machine Job Shops

A great many manufacturing facilities can be described as closed job shops which process multiple items through multiple work centers for stock or for assembly. The performance of these shops is strongly dependent on the batching policies employed for work in the shop. In particular, waiting time in queue and total manufacturing lead time for batches are functions of lotsizes. In turn these affect work-in-process costs, safety stock requirements, schedule performance and part coordination for assembly. The relationship between lot-sizing and shop performance is represented using a queueing network model which is then embedded in an optimization routine that searches for optimal lot sizes.     

Integrated pretreatment with capacitive deionization for reverse osmosis reject recovery from water reclamation plant

Reverse osmosis (RO) reject recovery from the water reclamation process was demonstrated feasible using an integrated pretreatment scheme followed by the Capacitive Deionization (CDI) process. The RO reject had an average total dissolved solids (TDS) of 1276 ± 166 mg/L. Water recovery of 85% with water quality comparable with the RO feed was achieved. Pretreatments using biological activated carbon (BAC) and BAC–ultrafiltration (UF) attained total organic carbon (TOC) removal efficiencies of 23.5 ± 6.0% and 39.9 ± 9.0%, respectively. Organics removal of RO reject was attributed to simultaneous adsorption and biodegradation in the BAC pretreatment, while further biodegradation in the submerged UF membrane tank provided additional organics removal. Membrane and CDI fouling was reduced by pH adjustment of the pretreated RO reject to approximately 6.5, which prolonged the CDI operation time by at least two times. The CDI process was able to achieve more than 88 and 87% TDS and ion removals, respectively, while PO₄³⁻ and TOC removals were at 52–81% and 50–63%, respectively.     

Membrane bioreactors for water reclamation.

Singapore has been using dual membrane technology (MF/UF RO) to produce high-grade water (NEWater) from secondary treated sewage. Membrane bioreactor (MBR) has very high potential and will lead to the further improvement of the productivity and quality of high-grade water. This study was focused on the technical feasibility of MBR system for water reclamation in Singapore, making a comparison between various membrane systems available and to get operational experience in terms of membrane cleaning and other issues. Three MBR plants were built at Bedok Water Reclamation Plant with a design flow of 300 m3/day each. They were commissioned in March 2003. Three different types of submerged membranes were tested. They are Membrane A, plate sheet membrane with pore size of 0.4 microm; Membrane B, hollow fibre membrane with pore size of 0.4 microm; and Membrane C, hollow fibre membrane with pore size of 0.035 microm. The permeate quality of all the three MBR Systems were found equivalent to or better than that of the conventional tertiary treatment by ultrafiltration. MBR permeate TOC was about 2 mg/l lower than UF permeate TOC. GC-MS, GC-ECD and HPLC scan results show that trace organic contaminants in MBR permeate and UF permeate were in the same range. MBR power consumption can be less than 1 kwh/m3. Gel layer or dynamic membrane generated on the submerged membrane surface played an important role for the lower MBR permeate TOC than the supernatant TOC in the membrane tank. Intensive chemical cleaning can temporarily remove this layer. During normal operation conditions, the formation of dynamic membrane may need one day to obtain the steady low TOC levels in MBR permeate.     

Linear and nonlinear filtering for image enhancement

The modified slant and modified slant Haar transforms are proved to be efficient for image bandwidth compression. At times, it may be desirable use the existing hardware and software facilities for different purposes. This paper investigates the utility of the modified slant and modified slant Haar transforms for dynamic range reduction and enhancement of image. Both, the linear and nonlinear filtering techniques are used and the results are interpreted.     

An estimate of the distribution of message lengths in overseas communications

This paper presents three mathematical models for the distribution of message lengths in overseas communications. The results and conclusions presented in this paper are based on the outcome of a random experiment performed at Overseas Communication Service Centre, Bombay, India. A sample of sufficiently large size (about 21,000 messages) was selected so that the sample mean does not deviate more than 5% of the population mean at a level of confidence more than 95%. Three different models namely (1) Geometrical distribution with a constant of 7 words, (2) Compound distribution obtained as a weighted sum of a geometrical distribution with a constant of 7 words and an impulse function with impulse at 22 words, and (3) Compound distribution obtained as a weighted sum of two geometrical distributions with constants of 7 and 22 words respectively, were assumed to be the representatives of experimental distribution of message lengths. Model parameters were estimated using the method of least squares. Box method was used to solve the minimization problem. Chi-square and Kolmogorov-Smirnov tests were then applied to test for goodness-of-fit of the three assumed models. The K-S test results revealed that all three models are acceptable whereas chi-square test results revealed that the first two models are not supported by the experimental data and hence are rejected but the last model is supported by the data and is an acceptable probability model of message lengths in overseas communications.The developed models are useful in optimal design of computer communication systems such as data multiplexing and voice-data systems.     

An on-off single server queueing model with finite waiting room and its application to computer communications

A queueing model with finite waiting room, Poisson arrivals, constant service time, synchronous transmission and a single server interrupted through a first-order Markov process is studied. The buffer's access to a channel, transmitting data at a field rate is controlled by a switch which in turn is controlled through a first-order Markov process. The relationships among overflow probabilities, buffer size and expected queueing delay due to buffering are obtained. A recursive method for computation of steady-state probabilities of the buffer states is developed. The system of multiplexing data in analog speech signals on telephone lines is considered as an application of the model studied. The results of this study are portrayed on graphs and may be used as the guide lines for the buffer design in digital systems. The system of multiplexing data in analog speech signals using this model, is simulated on the EC-1030 computer to check the validity of the analytical results. Simulation results are also portrayed on the graphs for comparison. Although this study arose in the buffer design required for multiplexing the data in analog speech, the queueing model developed is quite general and may be useful for other industrial applications.