Heavy metal concentrations in fish,shellfish and fish products from internal markets of India vis-a-vis international standards

Heavy metals are an important group of chemical contaminants and food is the major vehicle for entry into the system. Fish constitute a major source of heavy metals in food. Concentration of heavy metals in commercially important species of fish, shellfish and fish products from fish markets in and around the Cochin area was evaluated using an atomic absorption spectrometer. The concentration ranges of Cd, Pb, Hg, Cr, As, Zn, Cu, Co, Mn, Ni, and Se in the samples were <0.07–1, <0.07–1.32, <0.05–2.31, <0.05 to 3.65, <0.1–4.14, 0.6 to 165, 0.15 to 24, <0.02 to 0.85, <0.08 to 9.2, <0.032–1.38 and; <0.03–1.35 mg/kg, respectively. The present study showed that different metals were present in the samples at different levels but within the maximum residual levels prescribed by the EU and USFDA and the fish and shellfish from these areas, in general, are safe for human consumption.     

Nonparametric Receiver for FH-MFSK Mobile Radio

Various parametric receivers such as the maximum likelihood and the hard-limiter have been analyzed for their performance in decoding the frequency hopped multilevel FSK (FH-MFSK) messages in mobile environment. Here, some nonparametric receivers such as the maximum rank sum receiver (MRSR) and the reduced rank sum receiver (RRR) are considered. RRR and MRSR are nearly identical in performance but the former is much simpler to implement. The results indicate that RRR is a competing alternative to the parametric receivers.     

Impact of Channel Errors on Decentralized Detection Performance of Wireless Sensor Networks: A Study of Binary Modulations, Rayleigh-Fading and Nonfading Channels, and Fusion-Combiners

We provide new results on the performance of wireless sensor networks in which a number of identical sensor nodes transmit their binary decisions, regarding a binary hypothesis, to a fusion center (FC) by means of a modulation scheme. Each link between a sensor and the fusion center is modeled independent and identically distibuted (i.i.d.) either as slow Rayleigh-fading or as nonfading. The FC employs a counting rule (CR) or another combining scheme to make a final decision. Main results obtained are the following: 1) in slow fading, a) the correctness of using an average bit error rate of a link, averaged with respect to the fading distribution, for assessing the performance of a CR and b) with proper choice of threshold, on/off keying (OOK), in addition to energy saving, exhibits asymptotic (large number of sensors) performance comparable to that of FSK; and 2) for a large number of sensors, a) for slow fading and a counting rule, given a minimum sensor-to-fusion link SNR, we determine a minimum sensor decision quality, in order to achieve zero asymptotic errors and b) for Rayleigh-fading and nonfading channels and PSK (FSK) modulation, using a large deviation theory, we derive asymptotic error exponents of counting rule, maximal ratio (square law), and equal gain combiners.     

Dual-mode control of tri-state boost converter for improved performance

A tri-state boost converter with an additional boost-inductor free-wheeling interval was proposed earlier to eliminate the right-half-plane (RHP) zero that occurs in the control-to-output transfer function of a classical boost converter under continuous-conduction mode of operation. A "constant-D/sub o/" control scheme, in which the "capacitor-charging" interval of the converter was kept constant, was employed. This resulted in a relatively large inductor current, especially under high line and load conditions, thereby causing high circuit losses. This paper proposes two variations of a novel dual-mode control (DMC) scheme that vary both the "boost" and the "capacitor-charging" intervals. Control analysis, design, and limitations of the proposed DMC schemes are presented. Through computer simulations and hardware experiments the performance of the tri-state boost converter with DMC schemes are compared with those of the tri-state boost converter with "constant-D/sub o/" control scheme, and the classical PI-controlled boost converter. The DMC schemes achieve a significant (about 10%) improvement in converter's efficiency for a wide load range over the "constant-D/sub o/" control scheme.     

Surface studies on activated and hydrided CaNi5 alloy

X-ray photoelectron spectroscopic studies on the activated pure CaNi₅ alloy as well as the hydride formed at 1 atm pressure and room temperature, CaNi₅H_4.8, showed that on activation calcium segregates to the surface and forms the oxide, whereas most of the nickel on the surface is present in the metallic form. This indicates that the coexistance of the oxide phase and the metal phase is essential for the facile hydriding behaviour of CaNi₅.     

Laterally supported sandwich panels subjected to large deflections: Part 2: FE analyses and model validation

Finite element (FE) models are used for predicting the global behavior of simply supported sandwich panels fixed by bolts on the two longitudinal edges or on all their four edges. The panels are subjected to transversal distributed loads and develop large deflections. Two finite element techniques are employed: (a) utilizing effective (equivalent) continuum solid elements for the core and plate elements for the face sheets and (b) utilizing plate elements of an equivalent three-layer laminate. In the first part of this project, discussed in a companion paper, the test set-up details were presented along with the experimental results. This second part of the work presents the procedure for estimating the panel–bolt bearing stiffness, the FE analysis procedure developed to simulate the behavior of the tested panels and the validation of the numerical models. A good correlation was observed between experimental and numerical results for the displacements of the panels and the shear loads at the attachment points. The results obtained demonstrated that the proposed two-dimensional FE approach yields a good trade off between the level of accuracy and computational efficiency.     

Compliant cryptologic protocols

Literally, the word compliance suggests conformity in fulfilling official requirements. This paper presents the results of the analysis and design of a class of protocols called compliant cryptologic protocols (CCPs). The paper presents a notion for compliance in cryptosystems that is conducive as a cryptologic goal. CCPs are employed in security systems used by at least two mutually mistrusting sets of entities. The individuals in the sets of entities only trust the design of the security system and any trusted third party the security system may include. Such a security system can be thought of as a broker between the mistrusting sets of entities. Published online: 15 November 2002