Engineering nanoporosity for Ti ion irradiated Mylar (PET) polymer by positron beam

The interconnected, molecular sized pores of microporous materials as well as of nonporous materials are of great interest for absorption, separation and catalytic applications because of their large accessible surface area. Swift heavy ion (SHI) irradiation is a useful technique for the physical and chemical modifications of the polymers. To obtain calibrated pores in cylindrical shape the etching rate along the tracks should be essentially higher than the etching rate of undamaged polymer. Multiple pores, due to overlapping of the pores and inhomogeneous pore distribution, may arise due to high pore density and non-uniform target thickness. The shape of the pores in the polymers is affected by the conditions of chemical etching used for enlarging the latent track. It is well-established that pore size is the determining parameter for hydrogen storage as well as for nanofiltration. Slow positron beam in addition to Doppler Broadening Spectroscopy (DBS) is a useful technique to evaluate the nanoporosity of polymers.     

Computation of frequency-dependent propagation characteristics ofmicrostriplike propagation structures with discontinuous layers

A general procedure based on the method of lines is presented for the full-wave analysis of propagation structures having layered substrates with step inhomogeneities in each layer. Examples of such structures include microslab lines and microstrip near a substrate edge. It is shown that with this extended method of lines technique the frequency-dependent characteristics, including the modal impedance, current distribution, and other properties of these structures, can be calculated. To illustrate the technique, typical structures such as microstrips on a finite-width dielectric slab and microstrips near a substrate edge are considered, and the effect of the proximity of the edge on the propagation characteristics of the microstrip is computed. For the case of a microstrip near a substrate edge, the numerical results obtained are compared with measured values of propagation constants, showing that the proximity effect is predicted to within 1%     

Effect of water depth on internal heat and mass transfer for active solar distillation

In this communication, an attempt has been made to find out the convective heat transfer coefficient for active solar distillation system. It is a well-known fact that the distillate output (the yield) decreases significantly with the increase of water depth in the basin of the solar still. It is also known that more yield is obtained in case of active solar distillation system as compared to passive solar still due to higher temperature difference between the water and inner glass cover temperatures in the active mode. For the present study, experiments have been conducted for 24 hours during winter months for different water depths in the basin (0.05, 0.1 and 0.15 m) for passive as well as active solar distillation system. The objective of the present paper is to study the effect of different water depths in the basin on the heat and mass transfer coefficients. It is inferred that the convective heat transfer coefficient between water and inner condensing cover depends significantly on the water depth in the basin. It is also observed that more yield is obtained during the off shine hours as compared to daytime for higher water depths in solar still (0.10 m and 0.15 m) due to storage effect.     

Effect of Alumina Reactivity on the Densification and Properties of Al2O3–Cr2O3 Refractories

Alumina‐chrome (Al₂O₃–Cr₂O₃) refractories with Al₂O₃:Cr₂O₃ molar ratio 1:1 were synthesized in the temperature range of 1400–1700°C by conventional solid–oxide reaction route. The effect of different aluminas (viz., hydrated and calcined) on the densification, microstructure, and properties of Al₂O₃–Cr₂O₃ refractories was investigated without changing the Cr₂O₃ source. The starting materials were analyzed to determine the chemical composition, mineralogy, density, surface area, and particle size. Sintered materials were characterized in terms of densification, phase assemblage, and mechanical strength at room temperature and at higher temperatures. Microstructural evolution at different sintering temperature was correlated with sintering characteristics. It can be concluded that the Al₂O₃–Cr₂O₃ refractories prepared with hydrated alumina as Al₂O₃ source show better densification and hot mechanical strength than corresponding calcined variety.     

Dual material gate junctionless tunnel field effect transistor

This paper proposes a junctionless tunnel field effect transistor (JLTFET) with dual material gate (DMG) structure and the performance was studied on the basis of energy band profile modulation. The two-dimensional simulation was carried out to show the effect of conduction band minima on the abruptness of transition between the ON and OFF states, which results in low subthreshold slope (SS). Appropriate selection of work function for source and drain side gate metal of a double metal gate JLTFET can also significantly reduce the subthreshold slope (SS), OFF state leakage and hence gives improved I _ON/I _OFF.     

Hot Ductility and Deformation Behavior of C-Mn/Nb-Microalloyed Steel Related to Cracking During Continuous Casting

Hot ductility studies have been performed on C-Mn and C-Mn-Nb steels with an approach to simulate the effect of cooling conditions experienced by steel in secondary cooling zone during continuous casting. Thermal oscillations prior to tensile straining deteriorate hot ductility of steel by deepening and widening the hot ductility trough. C-Mn steels are found to exhibit ductility troughs in three distinct zones whereas C-Mn-Nb steel shows drop in ductility only at low temperature in the vicinity of ferrite transformation temperatures. Start of ferrite transformation in steels causes yield ratio to increase while work hardening rates and strength coefficient decrease with decrease in test temperature in presence of thermal oscillation prior to tensile testing. Inhibition of recrystallization due to build-up of AlN particles along with the presence of MnS particles in structure and low work hardening rates causes embrittlement of steel in austenitic range. Alloying elements enhancing work hardening rates in austenitic range can be promoted to improve hot ductility. The presence of low melting phase saturated with impurities along the austenitic grain boundaries causes intergranular fracture at high temperature in C-Mn steels.     

Intradomain QoS routing in IP networks: a feasibility andcost/benefit analysis

Constraint-based routing gradually becomes an essential enabling mechanism for a variety of emerging network services such as virtual private networking and QoS support. A number of previous works have recognized its significance and investigated many aspects of the operation of constraint-based routing and in particular its variant concerned with determining paths for requests with specific QoS requirements, known as QoS routing. In this work we build on previous results on the cost of QoS routing and investigate the performance/cost trade-offs involved in the operation of a representative QoS routing architecture, elaborate on the constituents of this cost, and identify the main methods for containing the cost that QoS routing incurs on routers. Our results show that the cost of QoS routing is not excessive and that there indeed exist operational configurations, which can achieve reasonable performance gains with only a minimal increase in processing cost when compared to conventional best-effort routing     

Study of uranium sorption using D2EHPA‐impregnated polymeric beads

The extractant‐impregnated polymeric beads (EIPBs), containing Di(2‐ethylhexyl) phosphonic acid (D2EHPA) as an extractant and polyethersulfone as base polymer, were prepared by phase‐inversion method. These beads were characterized by fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscope (SEM) analysis to gain insight into the composition and morphology of beads. The beads exhibited good acid stability as no significant structural deformation or leaching out of the extractant was observed in 6M HNO₃ solution, up to the studied equilibration time of 15 days. The synthesized EIPBs were evaluated, for their ability to absorb uranium from aqueous solution, at different concentration and pH values. The kinetics measurement showed that about 90 min of equilibration time was enough to remove saturation amount of uranium from the solution. Kinetic modeling analysis of the extraction results was carried out using pseudo‐first‐order, pseudo‐second‐order, and intraparticle diffusion equations and the corresponding rate constants were determined. The equilibrium data were fitted into different isotherm models and were found to be represented well by the Freundlich isotherm equation. Reusability of the beads was also established by multiple sorption–desorption experiments. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3355–3364, 2013