A low-power high-performance SiGe BiCMOS 802.11a/b/g transceiver IC for cellular and bluetooth Co-existence applications

This paper describes a high-performance WLAN 802.11a/b/g radio transceiver, optimized for low-power in mobile applications, and for co-existence with cellular and Bluetooth systems in the same terminal. The direct-conversion transceiver architecture is optimized in each mode for low-power operation without compromising the challenging RF performance targets. A key transceiver requirement is a sensitivity of -77 dBm (at the LNA input) in 54 Mb/s OFDM mode while in the presence of a GSM1900 transmitter interferer. The receiver chain achieves an overall noise figure of 2.8/3.2 dB, consuming 168/185 mW at 2.8 V for the 2.4/5GHz bands, respectively. Signal loopback and transmit power detection techniques are used in conjunction with the baseband modem processor to calibrate the transmitter LO leakage and the transceiver I/Q imbalances. Fabricated in a 70 GHz f/sub T/ 0.25-/spl mu/m SiGe BiCMOS technology for system-in-package (SiP) use, the dual-band, tri-mode transceiver occupies only 4.6 mm/sup 2/.     

A joint parametric prediction model for wireless internet traffic using Hidden Markov Model

Addressing performance related issues of networks and ensuring better Quality of Service (QoS) for end-users calls for simple, tractable and realistic traffic models. The work reported here focuses on modelling the Wireless Internet traffic using realistic traffic traces collected over wireless networks and forecasting the end-to-end QoS parameters for the networks. A measurement framework is set-up to collect the QoS parameters and a traffic model is designed based on Hidden Markov Model considering joint distribution of End to End Delay (E2ED or d), Inter-Packet Delay Variation (IPDV) and Packet Size. States are mapped to the four traffic classes namely conversational, streaming, interactive, and background. The model is validated by forecasting QoS parameters and the results are shown to be within the tolerance limit.     

New voltage and current-mode APS using current controlled conveyor

A first-order all-pass section (APS) is introduced employing a single second-generation current conveyor and three passive components. The translinear conveyor version of the circuit employing only two passive components is also proposed. A fully tunable version of the circuit employing two current controlled conveyors (CCCIIs) and a single capacitor is finally derived. All the three versions of APS can be operated both in voltage as well as current mode without changing the circuit configuration. As an application, a quadrature oscillator providing two quadrature currents and two phase-shifted voltage outputs simultaneously, is realized using the proposed APS. RSPICE simulation results for the translinear-C APS, and the translinear-C quadrature oscillator are included to verify the theory.     

An Approach to Tackle the Threat of Sympathy Trips in Directional Overcurrent Relay Coordination

This paper proposes to introduce additional constraints in the directional overcurrent relay coordination problem to tackle the sympathy trips. This paper attempts to tackle the sympathy trips in which other relay(s) in the system operate(s) earlier in the designated primary relay. The solution to this problem requires the inclusion of some additional constraints, making the coordination problem too complex. This paper proposes to solve the problem in two phases. In the first phase, the problem is solved by a normal coordination procedure and sympathy trips are identified. In the second phase, the proposed additional constraints are imposed only for the sympathy trips identified in the first phase. For the second phase, three approaches for including additional constraints were investigated. This paper includes results of the proposed algorithm for the IEEE 30-bus system. The results amply suggest that one of the three approaches of including additional constraints successfully tackled the problem of sympathy trip     

EFFECTS OF SAWDUST ON BIOGAS PRODUCTION FROM COWDUNG

The biogas generation was performed using cowdung and sawdust in the ratios of 4:1 and 2:1, respectively. The experiments were also conducted using cowdung alone for the comparison purpose. The increase in the amount of sawdust in the mixture of cowdung and sawdust decreases the quantity of gas production. The production of methane up to three weeks is also effected by the amount of sawdust. The nitrogen contents increase and volatile solids decrease with the digestion of waste materials. The thermogravimetric studies of the materials support the biogas generation as the decomposition of particular part of cowdung.     

Choice of sink for air conditioning systems

This Paper presents general correlations to estimate the power demand of different conventional air conditioning (A/C) systems operating under varied climatological conditions. The results have been applied to estimate the peak power demand and annual energy consumption. As a case study, the analysis is applied to Kuwaiti buildings for quantitative assessments using a unit peak cooling load (1 kW_c). Contrary to general understanding and practice the results strongly favour the use of water-cooled systems for both the residential and the non-residential types of buildings.     

ZnS:Sm and ZnS:Cu,Sm electroluminescent phosphors

Electroluminescent ZnS: Sm and ZnS: Cu, Sm phosphors have been prepared and their electroluminescent (el) characteristics have been studied. The time-averagedel brightness follows the Alfrey-Taylor relation over a wide range of frequencies. The constants of this relation have been determined. Theel emission shows one main and one auxiliary peak during each half cycle of the applied voltage. Variation of current with applied voltage has also been investigated.     

Profiling of phenolic compounds using UPLC–Q-TOF-MS/MS and nephroprotective activity of Indian green leafy vegetable Merremia emarginata (Burm. f.)

The present study aimed at optimization and identification of phenolic compounds from Merremia emarginata (Burm. f.) through RP-HPLC and UPLC–MS/MS. Further, to investigate nephroprotective effect of M. emarginata against gentamicin induced nephrotoxicity in albino Wistar rats phenolic compound identification was carried out using UPLC–MS/MS in both positive and negative modes of ionization. There are about 29 known and 19 unknown phenolic compounds that have been detected in M. emarginata based on MS/MS fragmentation pattern. The nephrotoxicity was induced by gentamicin in albino Wistar rats through i.p. injection (20 mg/kg of b.wt) and the rats were treated orally with ethanol extract of M. emarginata (150, 200 and 250 mg/kg of b.wt) for fifteen days. Serum biochemical parameters were analyzed and histopathological study was carried out to evaluate nephroprotective activity. The histopathology study shows that compared to the control group, the kidney of the diseased group was highly damaged and the plant extract treated group shows regeneration of glomerular and tubular epithelial cells of damaged kidney.     

Modified Stanley's approach for statistical analysis of compression strength test data of rock specimens

A very wide scatter is usually observed in laboratory compressive strength test (uniaxial and triaxial) data of rock specimens due to randomness in the number, orientation and distribution of micro-cracks. This leads to an uncertainty in choosing the representative design strength which leads to the need for a probabilistic approach to the analysis of test data. An attempt has been made in this paper to propose such an approach which is a modified version of Stanley's approach and employs Weibull's statistical strength theory. Uniaxial compressive strength (UCS) test data from three sources have been analyzed and results compared with those from Weibull's theory. As the proposed approach employs Weibull's parameters, goodness-of-fit tests have been performed to check the fitness of tests data to Weibull's distribution. Further, the proposed approach for uniaxial conditions has been extended to triaxial stress conditions. Corresponding cumulative distribution functions of the applied stress level have been obtained which have been subsequently invoked to correlate the applied stress level at failure with the associated risk of failure. For the UCS test data, the proposed approach yields higher design strengths than does Weibull's theory when Weibull's m parameter is greater than unity. Strength under triaxial stress condition can be predicted by employing the proposed approach even though triaxial tests cannot be conducted, provided the UCS test data are available.