Prediction of rate-independent constitutive behavior of Pb-free solders based on first principles

This paper presents a methodology for the theoretical estimation of rate-independent plastic constitutive properties of Pb-free solders using three approaches. The first approach is based on a nonlinear effective medium theory (NEMT) that is scale independent. The second approach is based on the micromechanics and physics of plastic slip in heterogeneous alloys (henceforth called the physical model). This approach explicitly includes microstructural features such as grain size, particle size etc. The third approach is a combination of NEMT and the physical model. Our estimates involve no adjustable calibration parameters and are based on first principles and constituent properties. Parametric studies are conducted to show that the physical model is more effective for small particles sizes (nanoscale <100 nm), small particle spacing (/spl sim/ nm range) and low volume fractions (<2.5%); while NEMT performs well for large volume fractions (>5%), large particle sizes (micron size) and large particle spacing (micron scale). The proposed hybrid approach, however, appears to be valid for a wider range of particle sizes and volume fractions. Limited comparison with experimental data is also made and implications of our work in the economical design of novel Pb-free solders is discussed.     

Polyarteritis nodosa and the antiphospholipid syndrome

We describe a case of classical polyarteritis nodosa (PAN) with visceral aneurysms presenting with renal infarction and hypertension. The female patient also had all the laboratory features of the antiphospholipid syndrome (APS) and 2 months into her illness developed a large iliofemoral thrombosis. She responded well to immunosuppressive therapy and anti-coagulation. Repeat arteriogram showed regression of the visceral aneurysms. The link between PAN and APS, and the therapeutic dilemma posed by this association, are discussed.     

An exercise in plausibility-driven design

The authors describe an evolutionary model of the computer design process and introduce the concept of plausibility of a design, which depends on the history of the design, where history refers to the recorded sequences of design decisions and the cause-effect relationships between design decisions, and the nature of the evidence used by the designer to justify design decisions and/or establish the fact that a design feature satisfies a particular set of requirements. The approach was used to design a special-purpose multiprocessor intended to serve as a computer architecture simulation engine (CASE). The authors present some of the main features of CASEs design as it evolved and, in the process, illustrate the practical application of the theory of plausible design     

Double wavelength operation of a grazing incidence tunable dye laser

Simultaneous operation at two or more wavelengths of a nitrogen laser pumped dye laser using gratings at grazing incidence is described. The output beams are independently tunable, collinear, and with variable linewidths. Output powers at the two wavelengths are smoothly varied when a variable loss is introduced in one of the resonators.     

Role of the stimulated-emission rate in the photostability of solid-state dye lasers

The lasing and photostability characteristics of Rhodamine 6G and Pyrromethene 567 dyes dispersed in polymeric host materials have been investigated as a function of the intensities of incident pump and signal beams in a longitudinally pumped dye laser in an oscillator-amplifier configuration. A substantial reduction in the rate of photodegradation was observed under lasing conditions and with increasing signal intensity in a dye amplifier, establishing that the service lives of these materials improve with an increase in the rate of stimulated emission. We observed approximately 62% amplifier efficiency at 2 Hz operation and 10% reduction in amplifier efficiency at 10 Hz operation after exposure of 72,000 pulses by use of a Pyrromethene disk.     

Continuous collection of soluble atmospheric particles with a wetted hydrophilic filter

Approximately one-third of the area (14-mm diameter of a 25-mm diameter) of a 5-microm uniform pore size polycarbonate filter is continuously wetted by a 0.25 mL/min water mist. The water forms a continuous thin film on the filter and percolates through it. The flowing water substantially reduces the effective pore size of the filter. At the operational air sampling flow rate of 1.5 standard liters per minute, such a particle collector (PC) efficiently captures particles down to very small size. As determined by fluorescein-tagged NaCl aerosol generated by a vibrating orifice aerosol generator, the capture efficiency was 97.7+% for particle aerodynamic diameters ranging from 0.28 to 3.88 microm. Further, 55.3 and 80.3% of 25- and 100-nm (NH4)2SO4 particles generated by size classification with a differential mobility analyzer were respectively collected by the device. The PC is integrally coupled with a liquid collection reservoir. The liquid effluent from the wetted filter collector, bearing the soluble components of the aerosol, can be continuously collected or periodically withdrawn. The latter strategy permits the use of a robust syringe pump for the purpose. Coupled with a PM2.5 cyclone inlet and a membrane-based parallel plate denuder at the front end and an ion chromatograph at the back end, the PC readily operated for at least 4-week periods without filter replacement or any other maintenance.     

Modeling and analysis of an extrinsic Fabry-Perot interferometer cavity

A schematic representation of optical feedback between two resonator mirrors undergoing a phase shift each round trip as a function of the separation of the mirrors is studied. A transfer function modeling of the extrinsic Fabry-Perot interferometer (EFPI) is presented. Nyquist analysis has been used to forecast the operational stability and possibility of interference in an EFPI. The analysis with two perfectly parallel surfaces of the cavity shows efficient interference. The performance when there is some tilt between the two mirrors in the cavity is also studied and is presented. In this case some restricted interference is found.     

Self-consistent solution of two-dimensional poisson and Schrödinger wave equations for nanoscale MOSFET approaching ballistic limit

A numerical solution of the potential distribution of two-dimensional Poisson equation and Schr?dinger wave equation under a set of boundary conditions has been obtained for a deep submicron and nanoscale MOSFET. The output characteristics can be found out by simply solving the two-dimensional Poisson equation under specific boundary conditions governed by the physics of the device. The channel potential profile has been presented. It is seen that the classical model underestimates the channel voltage and hence the longitudinal electric field in the channel as compared to that obtained through the quantum mechanical approach. For the purpose of validation, the results obtained on the basis of our model have been compared and contrasted with reported experimental result.