Simple Method to Evaluate the Ballistic Properties for Gas Generant Compositions

Combustion, Explosion, and Shock Waves - The study of the ballistic properties of energetic materials remains vital to ensure safety during their transportation, handling, storage, and processing....     

Phrase-based correction model for improving handwriting recognition accuracies

We propose a method for increasing word recognition accuracies by correcting the output of a handwriting recognition system. We treat the handwriting recognizer as a black box, such that there is no access to its internals. This enables us to keep our algorithm general and independent of any particular system. We use a novel method for correcting the output based on a “phrase-based” system in contrast to traditional source-channel models. We report the accuracies of two in-house handwritten word recognizers before and after the correction. We achieve highly encouraging results for a large synthetically generated dataset. We also report results for a commercially available OCR on real data.     

Treatment of non-extractable common bile duct stones with combination ursodeoxycholic acid plus endoprostheses

To assess the effect of timing of human chorionic gonadotrophin (HCG) administration in ovarian stimulation cycles, the serum oestradiol concentration and follicle profile were compared with the clinical pregnancy rate in 582 ovarian stimulation-intra-uterine insemination (OS-IUI) cycles and 3917 in-vitro fertilization-embryo transfer (IVF-ET) cycles. The pregnancy rates increased exponentially with increasing oestradiol in both OS-IUI and IVF-ET cycles (R2 = 0.720, P < 0.001) but then decreased in OS-IUI cycles when the oestradiol concentration exceeded 5000 pmol/l (R2 = 0.936, P < 0.004) at HCG administration. In OS-IUI cycles the percentages of cycles with three or more mature follicles (> or = 18 mm diameter) increased up to an oestradiol concentration of 5000 pmol/l then declined, mirroring the pregnancy rate (R2 = 0.900, P = 0.01). The exponential increase in pregnancy rate with increasing oestradiol concentration in IVF-ET cycles suggests that high oestradiol concentration does not have a deleterious effect on endometrial receptivity. The decrease in pregnancy rate in OS-IUI cycles when oestradiol concentration exceeded 5000 pmol/l reflected fewer mature follicles, resulting from premature administration of HCG to avoid severe ovarian hyperstimulation syndrome (OHSS). We recommend that HCG administration be delayed until multiple follicles have reached maturity, and reducing the risk of severe OHSS by converting high risk OS-IUI cycles to IVF-ET, or if funds or facilities are unavailable, transvaginally draining all but four or five mature follicles.     

Fatigue Growth Analysis of Pre Induced Surface Defects Using Piezoelectric Wafer Based Impedance Method and Digital Image Correlation System

Defects in real mechanical, industrial and aerospace structures frequently have complex shapes. Most real structures are typically prone to multiple fatigue cracks and their propagation can be monitored by observing changes in the structural stiffness resulting from strength reduction as a function of the number of loading cycles. In addition, strain variations on the structural surface can be captured using digital equipments. The present work monitors two specimens (AISI 4340 steel) with electrode sparked hemispherical defects on their surfaces. Multiple-cracks emanating from these defects, under fatigue cyclic loading were monitored using piezoelectric wafer based electromechanical impedance (EMI) technique, and digital image correlation (DIC) system. EMI technique uses signature comparison of healthy and damaged state of the structure to depict the occurrence of crack and its growth. Images of DIC system captures initial sightings of surface hair-line cracks from the corners of machined defects and their propagation till merging. Thus, a signature analysis based technique such as EMI and image processing technology such as DIC were found to complement each other to expedite the prediction of early crack and their appearance on the surface.     

Mass transfer correlation for phenol biodegradation in a fluidized bed bioreactor

Experiments have been carried out in a draft tube fluidized bed bioreactor to study biodegradation of synthetic wastewater containing phenol. The microorganism employed in the study Psuedomonas putida has been immobilized on solid support particles. Studies have been carried out at different feed concentrations of phenol, air flow rates and feed flow rates. The mass transfer coefficient for phenol transfer from bulk phase to the surface of the biofilm on the solid particle has been estimated from observed experimental data using the conservation equations. The mass transfer coefficient was found to be in the range of 0.0726 x 10(-5) to 0.2012 x 10(-5) m s(-1). It was found to increase with increase in feed concentration, air flow rate and feed flow rate. A dimensionless correlation has been developed for the mass transfer coefficient in terms of Sherwood, Reynolds and Schmidt numbers, and the same has been compared with correlations available in literature.     

Synthesis and characterization of bis(4‐cyanato 3,5‐dimethylphenyl) naphthyl methane/epoxy/glass fiber composites

Bis(4‐cyanato 3,5‐dimethylphenyl) naphthylmethane was prepared by treating CNBr with bis(4‐hydroxy 3,5‐dimethylphenyl) naphthylmethane in the presence of triethylamine at −5 to 5°C. The dicyanate was characterized by FT‐IR and NMR techniques. The prepared dicyanate was blended with commercial epoxy resin in different ratios and cured at 120°C for 1 hr, 180°C for 1 hr, and post cured at 220°C for 1 hr using diamino diphenyl methane (DDM) as curing agent. Castings of neat resin and blends were prepared and characterized by FT‐IR technique. The morphology of the blends was evaluated by SEM analysis. The composite laminates were also fabricated from the same composition using glass fiber. The mechanical properties like tensile strength, flexural strength, and fracture toughness were measured as per ASTMD 3039, D 790, and D 5528, respectively. The tensile strength increased with increase in cyanate content (3, 6, and 9%) from 322 to 355 MPa. The fracture toughness values also increased from 0.7671 kJ/m² for neat epoxy resin to 0.8615 kJ/m² for 9% cyanate ester epoxy modified system. The thermal properties were also studied. The 10% weight loss temperature of pure epoxy is 358°C and it increased to 398°C with incorporation of cyanate ester resin. The incorporation of cyanate ester up to 9% loading level does not affect the T_g to a very great extent. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Symmetric hash functions for secure fingerprint biometric systems

Securing biometrics databases from being compromised is an important research challenge that must be overcome in order to support widespread use of biometrics based authentication. In this paper we present a novel method for securing fingerprints by hashing the fingerprint minutia and performing matching in the hash space. Our approach uses a family of symmetric hash functions and does not depend on the location of the (usually unstable) singular points (core and delta) as is the case with other methods described in the literature. It also does not assume a pre-alignment between the test and the stored fingerprint templates. We argue that these assumptions, which are often made, are unrealistic given that fingerprints are very often only partially captured by the commercially available sensors. The Equal Error Rate (EER) achieved by our system is 3%. We also present the performance analysis of a hybrid system that has an EER of 1.96% which reflects almost no drop in performance when compared to straight matching with no security enhancements. The hybrid system involves matching using our secure algorithm but the final scoring reverts to that used by a straight matching system.     

Educating the Next Generation of Mobile Game Developers

Mobile gaming is one of the fastest growing segments in the video game industry. Through a partnership between Motorola Laboratories and GamePipe Laboratory at the University of Southern California, we are exploring Linux's capabilities for mobile gaming and to provide developers with an alternative to what is predominantly a Java-based medium. Moving beyond Java lets game developers fully leverage the hardware advances and software capabilities of high-end smart phones     

Reliability and availability analysis of an n-unit outdoor power system subject to adjustable repair facility

This paper presents a newly developed stochastic mathematical model to represent a system of n active redundant outdoor power equipment. The system considered is subject to common cause failure and adjustable repair facility. Laplace transforms of the state probabilities, system reliability and availability equations are developed. In addition, steady-state availability and mean-time-between-failures expressions are developed. The special case when n = 2 is discussed numerically.     

Performance Evaluation of a Multithreaded Fast Fourier Transform Algorithm for Derivative Pricing

Pricing of derivatives is one of the central problems in computational finance. Since the theory of derivative pricing is highly mathematical, numerical techniques such as lattice approach, finite-difference and finite-element among others have been employed. Recently fast Fourier transform (FFT) has been employed for derivative pricing in sequential computers. In this paper, we report development of a multithreaded FFT pricing algorithm and performance evaluation on a multithreaded platform. The focus of this study is on the effectiveness of using a parallel computer for financial problems and performance evaluation of a multithreaded algorithm for finance applications such as derivative pricing. In general, a parallel algorithm for FFT, with blocked data distribution of N elements on P processors, involves communication for log P iterations and terminates after log N iterations. The first (log N – log P) iterations therefore, require no communication and a sequential algorithm can be used in each processor. We call this a local algorithm. At the end of the (log N – log P) iterations, the processors switch to a multithreaded algorithm where sending and receiving of threads is through message passing. We call this a remote algorithm. The algorithm has been implemented on the EARTH (Efficient Architecture for Running THreads) multithreaded platform. Our results indicate that the FFT multithreaded algorithm for option pricing is very efficient giving a relative speedup of 50% on 64 processors. This study reveals an important commercial application for High Performance Computing.