On a large-gain theorem

The aim of this paper is to give a general quantitative requirement which the loop gain must satisfy in order to stabilize a given unstable (possibly nonlinear and time-varying) plant, namely that the gain must exceed one.     

Conceptual damage-sensitive features for structural health monitoring: Laboratory and field demonstrations

The use of damage-sensitive features to evaluate structural condition or health is a very critical aspect of structural health monitoring. The purpose of this paper is to investigate the potential of two different damage-sensitive features for detecting damage. Different damage scenarios are simulated on a large-scale laboratory structure and a three-span highway bridge for demonstration. The features presented in this paper are the modal flexibility-based deflection and curvature both of which are obtained directly from dynamic properties. In the literature, flexibility associated with mode shapes and mode shapes curvatures have been mostly explored. In this study, multi-input–multi-output dynamic data are used to obtain modal flexibility, which is a close approximation to the actual flexibility. A main novelty is that the curvature is calculated from the deflected shapes using the modal flexibility as opposed to using modal vectors. In this paper, the theory of the methodology is explained and then experimental studies and results are presented. For the experimental studies, the laboratory specimen and the three-span bridge were gradually damaged. It is shown that both deflection and curvature are conceptual and physically meaningful features for damage detection and localization. The issues and the requirements for these features to perform successfully are also presented.     

CMV infection and cytomegalovirus disease in immunodepressed patients

An active entomologic survey was conducted by a team of trained health workers in a rural area endemic for Chagas' disease in central Brazil. They used pyrethrum as a flushing agent and 4,232 houses were inspected for triatomine bugs both inside and in the immediate environs. Houses with Triatoma infestans or evidence of an established colony were identified and defined as infested houses (cases). The building and environmental characteristics of 161 randomly selected infested houses were compared with 161 matched, noninfested houses (controls) that were the shortest distance from the infested house. Domestic and peridomestic potential risk factors associated with house infestation by Triatoma infestans were assessed by logistic regression analysis. Incomplete house construction (odds ratio [OR] = 2.5, 95% confidence interval [CI] = 1.5-4.1) was confirmed as a risk factor related to the presence or evidence of Triatoma infestans in the dwellings. The study also disclosed a statistically significant association between the presence of rats (OR = 1.6, 95% CI = 1.1-2.6) and indoor crop storage (OR = 2.3, 95% CI = 1.1-5.2) and house infestation. Further experimental field studies using tagged rodents should be conducted to assess their epidemiologic role in the domestic chain of Trypanosoma cruzi transmission.     

Synthesis and characterization of poly(N‐vinyl‐2‐pyrrolidone) grafted sodium alginate hydrogel beads for the controlled release of indomethacin

Graft copolymers of sodium alginate (NaAlg) with N‐vinyl‐2‐pyrrolidone were prepared using azobisisobutyronitrile as initiator. The graft copolymers (NaAlg‐g‐PVP) were characterized with Fourier transform infrared spectroscopy, elemental analysis, and differential scanning calorimetry. Polymeric hydrogel beads of NaAlg and NaAlg‐g‐PVP were prepared by crosslinking method using glutaraldehyde (GA) as a crosslinker in the hydrochloric acid catalyst (HCl) and these beads were used to deliver anti‐inflammatory drug, indomethacin (IM). Chemical stability of the IM after encapsulation into beads was confirmed by FTIR. Preparation conditions of the NaAlg‐g‐PVP beads were optimized by considering the percentage entrapment efficiency, particle size, swelling capacity and their release data. In vitro release studies were performed in simulated gastric fluid (pH 1.2) for the initial 2 h, followed by simulated intestinal fluid (pH 7.4) for 4 h. Effects of GA concentration, exposure time to GA, drug/polymer (d/p) ratio, and concentration of HCl on the release of IM were discussed. It was observed that IM release from the beads decreased with increasing GA concentration and exposure time. IM release also decreases with increasing d/p ratio and HCl concentration. The highest IM release was obtained to be 77% for beads crosslinked with 0.027M GA. Swelling experiments were also performed to compute molecular mass between crosslinks of the beads. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Accurate and simple synthesis formulas for coplanar waveguides

Simple and accurate closed‐form formulas obtained by using a differential evolution algorithm are presented for the synthesis of coplanar waveguides (CPW). The results of the synthesis formulas proposed in this article are compared with those of the quasi‐static analysis, the synthesis formulas reported by the other researchers and also the experimental works available in the literature. The accuracy of the proposed synthesis formulas is found to be better than 0.75% for 9256 CPWs samples. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.     

Ultrasonic study of molecular association of poly(vinyl chloride) solution in tetrahydrofuran

Ultrasonic absorption, velocity, adiabatic compressibility, relaxation time and relaxation amplitude measurements are reported on poly(vinyl chloride) (PVC) solution in tetrahydrofuran (THF) using pulsed ultrasonic apparatus operating at 2 MHz and 313 K. Results show a linear increase of velocity. density, viscosity, absorption coefficient, relaxation time and relaxation amplitude values with the increase of PVC concentration in THF. In contrast the compressibility decreases with increasing PVC concentration. This suggests interaction between PVC and THF molecules.     

Cloning SIM Cards Usability Reduction in Mobile Networks

This paper studies the probability of using cloning subscriber identity module (SIM) cards in Universal Mobile Telecommunications Systems. It also explores how the mobile system can discover the cloning SIM cards as soon as possible and how to reduce the probability of using cloning SIM cards in mobile networks. The illegal mobile station attached to mobile networks can be detected by a Normal Location Area Update, a periodic area location update, and by outgoing calls that are issued from genuine mobiles. An analytical model is developed to investigate the effects of a location area update and outgoing calls issued by genuine mobiles on the use of illegal mobiles. Mobility management, such as registration, cancellation, and outgoing and incoming procedures for legal and illegal users are investigated and analysed. An analytical model to investigate the effect of outgoing call arrival rates, and location area residence time on the detected illegal user has been presented. This paper seeks to increase the security of communication by avoiding fraud of cloned mobile phones by proposing a solution to speed up the detection of cloning SIM cards.