Modularization of a Large-Scale Business Application: A Case Study

Large software systems, developed over several years, are the backbone of industries such as banking, retail, transportation, and telecommunications. With multiple bug fixes and feature enhancements, these systems gradually deviate from the intended architecture and deteriorate into unmanageable monoliths. This article presents a case study of a banking application besot with such problems and the modularization approach that the company adopted as a solution. It also highlights benefits unearthed as a result of this reengineering exercise.     

Enzymatic characteristics of recombinant medium isozyme of 2'-5' oligoadenylate synthetase

P69 is an isozyme of the medium size class of human 2'-5' oligoadenylate synthetases. In this study, recombinant P69 was expressed and used for enzymological and structural investigations. Bacterially expressed P69 was inactive whereas the same protein expressed in insect cells was highly active. Whether this difference could be due to differential post-translational modifications of the protein was investigated. Mutations of appropriate residues showed that myristoylation of the protein was not necessary for enzyme activity. In contrast, inhibition of glycosylation of P69, by tunicamycin treatment of the insect cells, produced an enzymatically inactive protein. Recombinant P69 produced in insect cells was purified by affinity chromatography. It was a dimeric glycoprotein, very stable and completely dependent on double stranded (ds) RNA for activity. The enzyme catalyzed the non-processive synthesis of 2'-5'-linked oligoadenylate products containing up to 30 residues. 2'-O-Methylated dsRNA was incapable of activating P69 and a 25-base pair dsRNA was as effective as larger dsRNA. This expression system will be useful for large scale production of P69 and its mutants for structural studies.     

Influence of Acidity on the Electrostatic Stability of Alumina Suspensions in Ethanol

Alumina (Al₂O₃) powders have been dispersed in ethanol (EtOH) solutions of different acidity. In aqueous media, acidity is defined by pH. This definition can be extended to nonaqueous media using ion-transfer functions. The electrical charge on the particle surfaces has been found to be acidity dependent. The electrostatic stability of Al₂O₃EtOH suspensions has been evaluated via electrophoresis and turbidity. An electrostatic stabilization mechanism is proposed and analyzed via Derjaguin–Landau–Verwey–Overbeek (DLVO) theory.     

Common-channel soft handoff in cdma2000. The paging channel

cdma2000 has been proposed as the standard in the US for next-generation (3G) mobile phones. This paper describes the proposed paging channel of the cdma2000. It provides both the physical layer details of operation, and the signaling and network issues required to support these new channels. The new paging channel significantly improves the standby times of the phones for the 3G systems. This paper looks at a way to put this common channel in soft handoff, thereby improving the reliability of call setup, and leading to a better standby time for the cdma2000 phones. It is shown that the method does not affect the call setup time, and causes no significant impact on the power budget of the base stations. Furthermore, it is completely backward compatible     

Radiological risk analysis of particle accelerators

Considering the growing use of high-current accelerators in medicine, industry and research, there is a need for evaluating the hazard potentials of new accelerator systems from the design stage itself. The present paper discusses the factors taken care of in a radiological safety analysis of accelerators. Possible hazards identified are beam loss, target rupture, faulty components and personnel being trapped in an active area. Human error is one of the major factors leading to accelerator hazard. How radiation dose to both occupational workers and general public is reduced and taken care of are discussed.     

Numerical method of reliability evaluation of a stand-by redundant system

This paper presents the probabilistic model of redundant system with common cause failure (ccf), logic failure and human error. The various states of the system are represented by Markov-model. As the number of states grows in size, it is tedious to solve the system state equations by Laplace inverse transform. This paper presents a new approach using standard numerical methods to solve such problems. The numerical results obtained in Ref. [1] B. S. Dhillon and S. N. Rayapati, Common cause failure and human error modelling of redundant systems with partially energized standby units, Reliab. Engng.19, 1–14 (1987) for redundant system with common cause failure and human error compare well with the results obtained with this new approach.     

A Call-Admission Control (CAC) Algorithm for Providing Guaranteed QoS in Cellular Networks

Future broadband wireless access systems are expected to integrate various classes of mobile terminals (MTs), each class with a different type of quality of service (QoS) requirement. When the load on a wireless network is high, the guarantee of QoS for each class of MTs is a challenging task. This study considers two classes of MTs—profiled MTs and nonprofiled or regular MTs. It is assumed that profiled users require a guaranteed QoS. The measure of QoS is the probability of forced termination of a call that was allowed to access the network. Two previous handoff prioritization schemes—(i) prerequest scheme and (ii) guard channel scheme—decrease handoff failure (and hence forced termination). In this work, we compare and contrast both the schemes through extensive simulation and we find that neither guard channel nor channel prerequest scheme can guarantee a desired level of QoS for the profiled MTs. We then propose a novel call-admission control (CAC) algorithm that can maintain any desired level of QoS, while the successful call completion rate is very high. In the proposed algorithm, the new call arrival rate is estimated continuously, and when the estimated arrival rate is higher than a predetermined level, some new calls are blocked irrespective of the availability of channels. The objective of this new call preblocking is to maintain a cell's observed new call arrival rate at no more than the predetermined rate. We show that the proposed method can guarantee any desired level of QoS for profiled users.     

Direction of arrival estimation based on temporal and spatial processing using a direct data domain (D/sup 3/) approach

The purpose of this paper is to estimate the direction of arrival (DOA) of the signal of interest (SOI) in the presence of both coherent and noncoherent interferences and multipath components utilizing a combined temporal and spatial processing technique based on a direct data domain approach. The concept of cyclostationarity, which deals with the temporal information of the SOI, is used to extract signals having the same cycle frequency and out the co-channel interferences and additive noise. Hence, the signal detection capability can be significantly increased over conventional filtering when the length of the data record is limited. The main contribution of the paper is that by combining temporal and spatial processing based on a direct data domain approach one can handle number of signals along with their various coherent and noncoherent multipaths and interferences which can exceed the number of antenna elements. Hence, this methodology may be advantageous over conventional spatial processing when the number of degrees of freedom can never exceed the number of antenna elements in the array. However, the number of multipaths and interferers at the same cycle frequency has to be less than approximately 66 % of the antenna elements. Since we do not form a covariance matrix of the data, this method is quite suitable for short data lengths or when the environment is quite dynamic. Hence, in the proposed algorithm, while the estimation of the cyclic array covariance matrix is avoided, we develop a new matrix form using extremely short data samples. As a result, the computational load in the proposed approach is relatively reduced and the robustness of the estimation of SOI is significantly improved when the number of available snapshots is extremely limited. Numerical results are presented to illustrate the efficiency and accuracy of this method.     

The effect of wall absorption on dispersion in annular flows

Summary The effect of the irreversible boundary reaction on the dispersion of tracers in annular flows is studied. The solution of the mathematical model, based on the generalized dispersion model, brings out the dispersive transport following the injection of a tracer in terms of the three effective transport coefficients, viz. the exchange, the convection and the dispersion coefficients. It is found that the exchange and the convection coefficients are enhanced while the dispersion coefficient is reduced with the increase in the value of the absorption parameter.The mathematical model is applied to a specific problem in clinical medicine: dispersion of solutes in blood flow in a catheterized artery. The model predicts that the insertion of a catheter in general and any further increase in its size will enhance the process of the dyes or other solutes getting out of the blood vessels, and this is found to be independent of the absorption parameter representing the absorption properties of the blood vessel wall.     

A framework for misuse detection in ad hoc networks- part II

We focus on detecting intrusions in ad hoc networks using the misuse detection technique. We allow for detection modules that periodically stop functioning due to operational failure or compromise by intruders. Combining theories of stochastic coverage processes and approximation algorithms, we develop a framework to counter failure of detection modules, while minimizing the resource consumption. We show that the selection of the optimal set of nodes for executing the detection modules is an NP-hard problem. We present a distributed polynomial complexity selection algorithm that attains the best possible approximation ratio. We next consider a simple heuristic selection strategy that allows for seamless operation in time varying topologies. We obtain analytical expressions to quantify the tradeoffs between the resource consumption and detection rates attained by these algorithms. Using analysis and simulation, we identify the appropriate algorithms for different failure rates, resource limitation, and required detection rates.