Phase Transformation and Densification Behavior of Microwave-Sintered Si3N4–Y2O3–MgO–ZrO2 System

A 2.45 GHz microwave-sintered Si₃N₄–Y₂O₃–MgO system containing various amounts of ZrO₂ secondary additives have been studied with respect to phase transformation and densification behavior. The temperature dependent dielectric properties were measured from 25°C to 1400°C using a conventional cavity perturbation technique. Phase transformation behavior was studied using X-ray diffractometry. Microwave sintered results were compared with those of conventional sintered results. It has been found that α to β phase transformation was completed at a lower temperature in microwave-sintered samples than those of the conventionally sintered samples. Density of the microwave-sintered samples increased up to 2.5 wt% of ZrO₂ addition and thereafter it showed a tendency to decrease or remain constant. The decrease in density is attributed to the pore generation caused by decomposition due to the localized over heating.     

Signal design and system operation of GlobalstarTM versus IS‐95 CDMA – similarities and differences

The Globalstar^TM system provides telephone and data services to and from mobile and fixed users in the area between ±70 degrees latitude. Connection between user terminals and the PSTN is established through fixed terrestrial gateways via a constellation of low earth orbiting (LEO) satellites. Globalstar uses an extension of the IS‐95 CDMA standard that is used in terrestrial digital cellular systems. The LEO satellite link is sufficiently different from the terrestrial cellular link that certain departures from IS‐95 were needed both in signal design as well as in system operation. This paper describes some of the similarities and differences of Globalstar air interface versus IS‐95. This revised version was published online in August 2006 with corrections to the Cover Date.     

Cd2SnO4-its sol-gel preparation and materials properties

Cd₂SnO₄ powder has been synthesized through acrylamide sol-gel route for the first time. The gelation-calcination steps have been studied. Morphological examination of the network matrix and the calcined products has been done through SEM. XRD shows the orthorhombic structure of the Cd₂SnO₄ powder obtained. Arrhenius plots yield activation energies of 0·01 and 0·61 eV for the low and high slope regions, respectively. A semiconductor to metal transition is observed in the range 210–225°C.     

Minimality, stabilizability, and strong stabilizability ofuncertain plants

This paper considers a set of uncertain transfer functions whose numerator and denominators belong to independent polytopes. It shows that i) the members of this set are free from pole-zero cancellations iff all the ratios of numerator edges and denominator edges are free from pole-zero cancellations and the numerator and denominator corners evaluated at a finite number of points satisfy certain phase conditions, ii) the members of this set are free from pole zero cancellations in the closed right half plane, iff all the ratios of numerator edges and denominator edges are free from pole-zero cancellations in the closed right half plane, and the numerator and denominator corners evaluated at a finite number of points satisfy certain phase conditions, and iii) in the strictly proper case, all plants in the set are strongly stabilizable iff all plants avoid pole-zero cancellations in the closed right half plane and all the corner ratios are strongly stabilizable. A counter-example is presented to show that this last result does not extend to biproper plants     

Decision-making effects on compensation surveys: Implications for market wages.

Compensation specialists made 2 survey-sample decisions in a simulated wage survey. Policy-capturing analyses indicate that most specialists relied extensively on 2 of the available cues and consistently applied that policy across judgments. They were not able to accurately estimate their own decision-making policies, as demonstrated by the fact that rationally generated assessments of cue importance were significantly different from their actual policies. Finally, meta-analyses demonstrate that the variation in policies across decision makers could not be attributed to statistical artifacts or any moderators (e.g., salary-survey experience or industry) associated with the demographic data. Thus, different compensation specialists are likely to select a different sample of employers even for the same wage survey. Implications for the relevance of market wages obtained from surveys are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Toward secure and private service discovery anywhere anytime

With the advances in and convergence of Internet technologies, embedded computers, and wireless communication, computing devices have become part of our daily life. Hand-held devices and sensors with wireless connections create opportunities for many new nomadic applications. Service discovery is an essential component for cognitive science to discover existing network services just-in-time. Unlike many other approaches, we propose a service discovery model supporting nomadic users and services in public environments. Our model emphasizes secure and private service discovery in such environments. Location sensing is integrated for location dependent service discovery and is used to lessen service discovery network infrastructure requirements. We analyze the system performance and show our formal verification of the protocols. Our implementation shows that our model is feasible.     

An experimental study on single basin double slope simulation solar still with thin layer of water in the basin

Single basin solar still is a popular solar device used for converting available brackish or waste water into potable water. Because of its lower productivity, it is not popularly used. Numbers of works are under taken to improve the productivity of the still. The still productivity depends on parameters like solar radiation intensity, atmospheric temperature, basin water depth, glass cover material, thickness and its inclination, wind velocity and the heat capacity of the still. When compared with other parameters, the basin water depth is the main parameter that affects the performance of the still. For a particular still, the basin water temperature is the function of depth with day variation of solar radiation intensity. In this work a double slope single basin passive type still with basin area of 1.75 m² is fabricated and tested under laboratory conditions for a thin layer of water in the basin. For maintaining thin layer of water basin, it is necessary to spread the water through out the basin by some kinds of wick material or porous materials. In this work, performance of the still is compared by using wick materials like light cotton cloth, light jute cloth and sponge sheet of 2 mm thickness and porous materials like washed natural rock of average size 3/8" × 1/4" and quartzite rock of average size 3/8" as spread materials. The actual solar radiation condition is simulated by 2 kW electrical resistance heater placed below the inner basin. The results show that the still with black light cotton cloth as spread material is found to be more productive. At higher water and glass temperature region, for all basin materials, the production rate increases with the decrease of the difference between the water and glass temperatures for certain period and also the productivity decreases with the increase of water temperature for certain time during this period. Hence the production rate is a complex function of water, glass and the difference between the water and glass temperatures, basin volumetric heat capacity of the material and its porosity.     

Performance of TCP/RLP protocol stack on correlated fading DS-CDMAwireless links

In this paper, we present the throughput performance of the transport control protocol/radio link protocol (TCP/RLP) stack on correlated fading direct-sequence code-division multiple-access (DS-CDMA) wireless links. It is shown that because of significant burstiness in RLP frame errors in highly correlated Rayleigh fading, longer persistence at the RLP layer to recover lost RLP frames (more than the IS-99 specified three retransmission attempts at the RCP layer) is beneficial at low-link fading margins     

Throughput analysis of TCP on channels with memory

The focus of this paper is to analyze the relative sensitivity of the bulk throughput performance of different versions of TCP, viz., OldTahoe, Tahoe, Reno, and New Reno, to channel errors that are correlated. We investigate the performance of a single wireless TCP connection in a local environment by modeling the correlated packet loss/error process (e.g., as induced by a multipath fading channel) as a first-order Markov chain. A major contribution of the paper is a unified analytical approach which allows the evaluation of the throughput performance of various versions of TCP. The main findings of this study are that 1) error correlations significantly affect the performance of TCP, and in particular may result in considerably better performance for Tahoe and NewReno; and 2) over slowly fading channels which are characterized by significant channel memory, Tahoe performs as well as NewReno. This leads us to conclude that a clever design of the lower layers that preserve error correlations, naturally present on wireless links because of the fading behavior, could be an attractive alternative to the development or the use of more complex versions of TCP