Two equal symmetric circular arc cracks in an elastic medium – the Dugdale approach

The Dugdale model for two equal, symmetrically situated coplanar circular arc cracks contained in an infinite elastic perfectly-plastic plate is proposed. Biaxial loads are applied at the infinite boundary of the plate. Consequently, the rims of the cracks open in Mode I and develop a plastic zone ahead of each of the cracks. These plastic zones are then closed by the distribution of uniform normal closing stresses over the rims of the plastic zones. Based on the complex-variable technique and the superposition principle, the solution for the above problem is obtained. Closed-form analytic expressions are obtained for the determination of the sizes of the plastic zones and the crack-opening displacement (COD) at the tip of the crack. Numerical studies are carried out to calculate the load ratio (load applied at infinity/yield point stress applied at the rims of the plastic zones) required for the closure of the plastic zones, for various radii of arc cracks and for various angles subtended by them at the centre. The crack-opening displacement is also investigated with respect to these parameters.     

Tamoxifen increases the proliferation of human endometrial stromal cells in in vitro. A model for evaluation of endometrial hyperplasia

Tamoxifen given for breast cancer therapy, has a complex and an unclear action on the endometrium. A large number of literatures has attributed the proliferous changes in the endometrium caused by tamoxifen (Tam). No report has appeared on the endometrial cellular changes induced by Tam. The present study shows a significant (P < 0.001) increase in the proliferative activity due to Tam in endometrial stromal cells over control and estradiol (E2). This in vitro model is useful for the study of the hyperplasic effect of Tam at the cellular level.     

Repeated convolutional codes for high-error-rate channels

An error-correction scheme for an M-ary symmetric channel (MSC) characterized by a large error probability p_e is considered. The value of p_e can be near, but smaller than, 1-1/M, for which the channel capacity is zero, such as may occur in a jamming environment. The coding scheme consists of an outer convolutional code and an inner repetition code of length m that is used for each convolutional code symbol. At the receiving end, the m inner code symbols are used to form a soft-decision metric, which is passed to a soft-decision decoder for the convolutional code. The effect of finite quantization and methods to generate binary metrics for M>2 are investigated. Monte Carlo simulation results are presented. For the binary symmetric channel (BSC), it is shown that the overall code rate is larger than 0.6R₀, where R₀ is the cutoff rate of the channel. New union bounds on the bit error probability for systems with a binary convolutional code on 4-ary and 8-ary orthogonal channels are presented. For a BSC and a large m, a method is presented for BER approximation based on the central limit theorem     

Optimised power allocation for mixed rate traffic in DS-CDMAcellular system

An approach for determining the optimum power allocation for different types of traffic in a CDMA cellular system is presented. The system capacity can be improved significantly by simply employing suitable transmission power for different types of traffic     

Enforcement of data consistency in database systems

The absolute correctness of a database is an ideal goal and can not be guaranteed. Only a lower level of database consistency can be enforced in practice. We discuss the issue of database consistency beginning with identification of correctness criteria for database systems. A taxonomy of methods for verification and restoration of database consistency is used to identify classes of methods with a practical significance. We discuss how fault tolerance (using both general and application-specific system properties) allows us to maintain database consistency in the presence of faults and errors in a database system and how database consistency can be restored after site crashes and network partitionings. A database system can ensure the semantic integrity of a database via verification of a set of integrity assertions. We show how to efficiently verify the integrity of a database state. Finally, batch verification of integrity assertions is presented as one of the promising approaches that use parallelism to speed up the verification.     

Closed form and infinite series solutions for the MGF of a dual-diversity selection combiner output in bivariate Nakagami fading

Using a circular contour integral representation for the generalized Marcum-Q function, Q/sub m/(a,b), we derive a new closed-form formula for the moment generating function (MGF) of the output signal power of a dual-diversity selection combiner (SC) in bivariate (correlated) Nakagami-m fading with positive integer fading severity index. This result involves only elementary functions and holds for any value of the ratio a/b in Q/sub m/(a,b). As an aside, we show that previous integral representations for Q/sub m/(a,b) can be obtained from a contour integral and also derive a new, single finite-range integral representation for Q/sub m/(a,b). A new infinite series expression for the MGF with arbitrary m is also derived. These MGFs can be readily used to unify the evaluation of average error performance of the dual-branch SC for coherent, differentially coherent, and noncoherent communications systems.     

A model for adaptable systems for transaction processing

Adaptability is an essential tool for managing escalating software costs and to build high-reliability, high-performance systems. Algorithmic adaptability, which supports techniques for switching between classes of schedulers in distributed transaction systems, is modeled. RAID, an experimental system implemented to support experimentation in adaptability, is discussed. Adaptability features in RAID, including algorithmic adaptability, fault tolerance, and implementation techniques for an adaptable server-based design, are modeled     

A robust rate-adaptive hybrid ARQ scheme for frequency-hoppedspread-spectrum multiple-access communication systems

This paper considers the application of rate-adaptive coding (RAC) to a spread spectrum multiple access (SSMA) communication system. Specifically, RAC using a variable rate Reed-Solomon (RS) code with a single decoder is applied to frequency-hopped SSMA. We show that this combination can accommodate a larger number of users compared to that with conventional fixed-rate coding. This increase is a result of a reduction in the channel interference from other users. The penalty for this improvement in most cases is a slight increase in the delay (composed of propagation and decoding delay). The throughput and the undetected error probability for a M-ary symmetric channel are analyzed, and performance results are presented     

Kinetics and Mechanism of Drug Release From Calcium Alginate Membrane Coated Tablets

Compressed tablets containing guaifenesin (model drug), calcium acetate (reactant) and pharmaceutical excipients were prepared. The tablets were coated with calcium alginate hydrogel using a novel, self-correcting membrane coating technique. Effects of coating time, the type of alginate polymer and pH of the dissolution medium on the rate of drug release were evaluated. In distilled water, zero order drug release profiles were obtained from the coated tablets. The release rate decreased with an increase in the coating time (increased coat thickness) and molecular weight of alginate polymer. The release rate constants correlated with model for spherical reservoir system and, were used to calculate permeability of guaifenesin in the calcium alginate coatings. Alginate polymer with higher guluronic acid content provided acid stable coating and higher molecular weight polymer produced membrane with lower permeability for guaifenesin.     

Uniform amplification of a mixture of deoxyribonucleic acids with varying GC content

A PCR method for uniform amplification of a mixture of DNA templates differing in GC content is described using the two enzyme approach (Klentaq1 and Pfu DNA polymerase) and a combination of DMSO and betaine. This method was applied to amplify the CGG repeat region from the fragile X region.