Improvement of Formability by Oscillation of Internal Pressure in Pulsating Hydroforming of Tube

A new history of internal pressure in the hydroforming processes of tubes is developed to attain high formability. The effect of improvement of formability by the oscillation of internal pressure in a pulsating hydroforming process of tubes is examined using both finite element simulation and experiment. The deformation behaviour during the hydroforming is greatly affected by the oscillation of internal pressure. For a monotonic history of small internal pressure, the wrinkling was caused by insufficient bulging, whereas the necking and bursting occurred for a monotonic history of large internal pressure. The occurrence of these defects can be avoided by oscillating the internal pressure in the pulsating hydroforming. The improvement of formability in the pulsating hydroforming is due to both low pressure and oscillation of pressure. The effects of the amplitude and cycle number of pressure in the pulsating hydroforming on the deformation behaviour are investigated. It is found the oscillation of internal pressure is effective in preventing the occurrence of defects.     

High-Rate Uncorrelated Bit Extraction for Shared Secret Key Generation from Channel Measurements

Secret keys can be generated and shared between two wireless nodes by measuring and encoding radio channel characteristics without ever revealing the secret key to an eavesdropper at a third location. This paper addresses bit extraction, i.e., the extraction of secret key bits from noisy radio channel measurements at two nodes such that the two secret keys reliably agree. Problems include 1) nonsimultaneous directional measurements, 2) correlated bit streams, and 3) low bit rate of secret key generation. This paper introduces high-rate uncorrelated bit extraction (HRUBE), a framework for interpolating, transforming for decorrelation, and encoding channel measurements using a multibit adaptive quantization scheme which allows multiple bits per component. We present an analysis of the probability of bit disagreement in generated secret keys, and we use experimental data to demonstrate the HRUBE scheme and to quantify its experimental performance. As two examples, the implemented HRUBE system can achieve 22 bits per second at a bit disagreement rate of 2.2 percent, or 10 bits per second at a bit disagreement rate of 0.54 percent.     

Locating the nodes: cooperative localization in wireless sensor networks

Accurate and low-cost sensor localization is a critical requirement for the deployment of wireless sensor networks in a wide variety of applications. In cooperative localization, sensors work together in a peer-to-peer manner to make measurements and then forms a map of the network. Various application requirements influence the design of sensor localization systems. In this article, the authors describe the measurement-based statistical models useful to describe time-of-arrival (TOA), angle-of-arrival (AOA), and received-signal-strength (RSS) measurements in wireless sensor networks. Wideband and ultra-wideband (UWB) measurements, and RF and acoustic media are also discussed. Using the models, the authors have shown the calculation of a Cramer-Rao bound (CRB) on the location estimation precision possible for a given set of measurements. The article briefly surveys a large and growing body of sensor localization algorithms. This article is intended to emphasize the basic statistical signal processing background necessary to understand the state-of-the-art and to make progress in the new and largely open areas of sensor network localization research.     

Comment: Scattering by infinite cylinders of arbitrary cross-section by the method of finite differences [and reply]

A finite-difference method of computing the field scattered by conducting cylinders of arbitrary cross-section has recently been proposed by Patwari and Davies. The advantage claimed for their method?essentially that it overcomes the fundamental objection to the Rayleigh method?is shown to be unjustified and the two methods are, in fact, shown to be identical.     

Clinical profile of cholera in young children--a hospital based report

Clinical profile of cholera was studied in children attending Diarrhea Training and Treatment Unit from January-December 1993. Out of a total 8714 cases of acute watery diarrhea, 64 children (0.7%) were suspected to have cholera on the basis of acute onset loose water/rice watery stools, high purge rate with or without excessive vomiting and/or severe dehydration. Stool culture was positive for cholera in 33 cases (51.6%). All the isolates were V. cholerae 01 biotype El Tor serotype Ogawa. Sixty four per cent of stool culture positive cases were below 5 years of age. The results assume importance because out of 28 children < 2 years with clinical suspicion of cholera, 11 cases (39.3%) were culture positive for V. cholerae, youngest child being 3 months old. Comparison of various parameters revealed that presence of vomiting > 4 episodes/ day (p < 0.005), frequency of stools >12/24 hours (p <0.002), rice watery stools (p < 0.01) and presence of severe dehydration (p < 0.01) were significant parameters associated with positive stool culture. Beside examination of stool sample by hanging drop method was an excellent diagnostic tool (p < 0.001) with a sensitivity of 51.5%, specificity 100% and positive predictive value of 100%. The isolates of V. cholerae were susceptible to furazolidone, cephelexin, nalidixic acid, norfloxacin and gentamicin. Our observations indicate that cholera is not uncommon in infants and young children. Like children in the older age group, acute onset diarrhea with watery/rice watery stools and high purge rate with or without excessive vomiting and/or rapid development of severe dehydration should arouse suspicion of cholera in younger children also. They should be investigated for cholera even in non-endemic areas and in the absence of cholera outbreaks.     

Customer Stratification for an Industrial Distributor With a Service and Repair Business

Abstract

Customer purchasing behavior is not unique. Complex costs to serve make it difficult to manage customers, especially today, when businesses are offering more value-added services. This research study develops a methodology to allow companies with a service or repair component to segment customers, as well as manage relationships and growth. This methodology differs from existing ones by allowing companies to include the full profit contribution derived from billed labor into the customer profitability calculation. By accurately identifying profitability of individual customers, this methodology yields results that are more pragmatic for managers.     

Helicobacter pylori infection in recurrent abdominal pain

The superior and inferior gemellus muscles were examined as to their forms and the patterns of nerve supply in 13 human cadavers (20 specimens). The superior gemellus muscle (Gs) was absent in 3 specimens, but showed no accessory slip or fusion with the internal obturator muscle (Oi). The nerve to the Gs originated from the nerve to the Oi (OiN) in 7, the nerve to the quadratus femoris muscle (QfN) in 4, or both in 6 specimens. The inferior gemellus muscle (Gi) was present in all, but fused with the Oi in 3 specimens. In one specimen, an accessory muscle bundle was observed between the Gi and Oi. The Gi always received branches from the QfN at its anterior surface, but received an additional nerve supply at its posterior surface from the OiN or the pudendal nerve in one specimen each, and the accessory bundle was supplied by a branch from the OiN at its posterior surface. In a well preserved specimen, a branch to the Gi from the QfN entered the Oi and communicated with the OiN after supplying and leaving the Gi. The frequency of the dual innervation of Gs by the OiN and QfN was 29.3%, but that of the Gi and Oi could not be determined, because of the occurrence of the fused part, the accessory bundle and nerve communication. There existed some gross anatomical differences between both gemelli muscles; they are considered to be parts of the internal obturator muscle in a broad sense.     

Liquid circulation characteristics in jet loop reactors

Liquid-velocity profile measurements in the annular region of a jet-loop reactor for a gas liquid system are reported, which facilitate evaluation of local phenomena. The range of variables studied included superficial gas velocities of 0-16 cm · s^?1 and superficial liquid velocities of 0-0.6 cm · s^?1. The main observations made with respect to the radial profile of axial liquid velocity are: a) a trend reversal in the changeover from a liquid phase system to a gas-liquid system; b) at low gas loading rates of 1-3 cm · s^?1 it is insensitive to liquid injection rates; c) at high liquid injection rates it shows a minimum. A correlation has been proposed to predict the circulation Reynolds number for the two-phase system.     

Design and implementation of an automated secondary cooling system for the continuous casting of billets

This paper describes a heat transfer model based automatic secondary cooling system for a billet caster. The model aims to minimize the variation in surface temperature and excessive reheating of the billet strands. It is also used to avoid the low ductility trough of the solidifying steel, which aggravates the tendency of steel to crack. The system has been designed and implemented in an integrated steel plant. A Programmable Logic Controller (PLC) based automation system has been developed to control the water flow in the secondary cooling zones of the strand. The results obtained through field trials have shown complete elimination of internal and off-corner cracks for the fifty billet samples that were monitored.