Development of solid state pulse power modulator using toroidal amorphous core

This paper discusses the experiments conducted for the development of 50 kV, 10 A, 10 μs duration, and rise time of 2 μs solid state pulse power modulator using toroidal amorphous steel core and low cost IGBT switches. The experiments revealed (i) the need for new design methodologies based on energy transfer between the electrical and magnetic systems and (ii) the success of low-cost switching circuit.     

Structural, Optical and Magnetic Properties of Multiferroic GdMnO3 Nanoparticles

The structural, optical, and magnetic properties of multiferroic GdMnO₃ nanoparticles synthesized by the modified sol–gel route have been investigated. Raman spectroscopy and X-ray diffraction along with Rietveld refinement confirm the pure phase of the GdMnO₃ nanoparticles having an orthorhombic perovskite (space group: Pnma) type structure. The morphology was examined by scanning electron microscopy. Energy dispersive spectroscopy confirms the stoichiometry of the composition. The room temperature UV-visible absorption spectrum using Tauc’s relation gives an optical band gap of ～2.9 eV. A magnetization study of the GdMnO₃ nanoparticles was performed over a temperature range of 2–300 K at an applied field of 0.05 T by using a vibrating sample magnetometer. An effective magnetic moment (μ _eff) of ～9.2μ _B was obtained. The system is paramagnetic at room temperature and shows a ferromagnetic-like nature at 2 K as the applied magnetic field aligns the Gd moments and the contribution of the net moment of Gd spins is larger than that of the anti-ferromagnetically canted state of the Mn spins.     

Integrated Routing Algorithms for Provisioning “Sub-Wavelength” Connections in IP-Over-WDM Networks

This work focuses on developing and implementing comprehensive unified constraint-based routing algorithms within the generalized multi-protocol label switching framework (GMPLS) to provision sub-wavelength circuits (low-rate traffic streams). Constraint-based routing is further augmented in this work by dynamically routing both an active and another alternate link/node-disjoint backup path at the same time in order to provision a given connection request. This new integrated approach combines both IP routing and optical resource allocation to setup end-to-end connections.     

Acidity, valency and third-ion effects on the precipitation of scorodite from mixed sulfate solutions under atmospheric-pressure conditions

The present study is focused on the precipitation of scorodite from mixed sulfate media at 95 °C under atmospheric pressure. In particular, this study explores the effects of acidity (pH), valency [Fe(II)/Fe(III), As(III)/As(V)], and solution composition (third cation/anion) on the yield, crystallinity, and stability (leachability) of scorodite precipitates. Thus, it was found that the precipitation of crystalline scorodite can be achieved without stringent pH control once the precipitation has started. Nonetheless, the selection of the initial pH is critical to avoid the formation of an amorphous precipitate. A leachability as low as 0.5 mg/L As at pH 5 and 22 °C (TCLP-like test) is obtained when the initial molar ratio Fe(III):As(V) is increased to 3:1, but the precipitation yield is very low. When Fe(II) is used as excess iron, the precipitate solubility drops to 0.2 mg/L As with a yield exceeding 80 pct in 2.5 hours. The stability of the product is not measurably affected by the presence of Cu²⁺, Zn²⁺, Ni²⁺, Co²⁺, Mn²⁺, SO ₄ ²⁻ , and NO ₃ ⁻ . The presence of PO ₄ ³⁻ , however, leads to the formation of crystalline phosphate-containing scorodite precipitates of somewhat reduced stability. In most cases, the TCLP leachability of the precipitate was found to be between 1 and 3 mg/L As, and never exceeded the regulatory limit of 5 mg/L As.     

A knowledge-based system for the prediction of surface roughness in turning process

In the present work, a knowledge-based system is developed for the prediction of surface roughness in turning process. Neural networks and fuzzy set theory are used for this purpose. Knowledge acquired from the shop floor is used to train the neural network. The trained network provides a number of data sets, which are fed to a fuzzy-set-based rule generation module. A large number of IF–THEN rules are generated, which can be reduced to a smaller set of rules by using Boolean operations. The developed rule base may be used for predicting surface roughness for given process variables as well as for the prediction of process variables for a given surface roughness. The concise set of rules helps the user in understanding the behavior of the cutting process and to assess the effectiveness of the model. The performance of the developed knowledge-based system is studied with the experimental data of dry and wet turning of mild steel with HSS and carbide tools.     

Fabrication of large-aperture lightweight diffractive lenses for use in space

We describe the advantages of using diffractive (Fresnel) lenses on thin membranes over conventional optics for, among others, future space telescope projects. Fabrication methods are presented for lenses on two types of freestanding membrane up to 50 cm in size. The first is a Fresnel lens etched into a thin (380-mum) glass sheet, and the second is an ~50-mum-thick polymer membrane containing a Fresnel lens made by replication process from a specially made fused-silica master. We show optical performance analysis of all the lenses that are fabricated, including a diffraction-limited Airy spot from a 20-m- focal-length membrane lens in a diffractive telescope system.     

Hybrid Wireless-Optical Broadband-Access Network (WOBAN): A Review of Relevant Challenges

The hybrid wireless-optical broadband-access network (WOBAN) is a promising architecture for future access networks. Recently, the wireless part of WOBAN has been gaining increasing attention, and early versions are being deployed as municipal access solutions to eliminate the wired drop to every wireless router at customer premises. This architecture saves on network deployment cost because the fiber need not penetrate each end-user, and it extends the reach of emerging optical-access solutions, such as passive optical networks. This paper first presents an architecture and a vision for the WOBAN and articulates why the combination of wireless and optical presents a compelling solution that optimizes the best of both worlds. While this discussion briefly touches upon the business drivers, the main arguments are based on technical and deployment considerations. Consequently, the rest of this paper reviews a variety of relevant research challenges, namely, network setup, network connectivity, and fault-tolerant behavior of the WOBAN. In the network setup, we review the design of a WOBAN where the back end is a wired optical network, the front end is managed by a wireless connectivity, and, in between, the tail ends of the optical part [known as optical network unit (ONU)] communicate directly with wireless base stations (known as ldquogateway routersrdquo). We outline algorithms to optimize the placement of ONUs in a WOBAN and report on a survey that we conducted on the distribution and types of wireless routers in the Wildhorse residential neighborhood of North Davis, CA. Then, we examine the WOBAN's routing properties (network connectivity), discuss the pros and cons of various routing algorithms, and summarize the idea behind fault-tolerant design of such hybrid networks.     

A third-generation SPARC V9 64-b microprocessor

This quad-issue processor achieves 1-GHz operation through improved dynamic circuit techniques in critical paths and a more extensive on-chip memory system which scales in both bandwidth and latency. Critical logic paths use domino, delayed clocked domino, and logic embedded in dynamic flip-flops for minimum delay. A 64-KB sum-addressed memory data cache combines the address offset add with the cache decode, allowing the average memory latency to scale by more than the clock ratio. Memory bandwidth is improved by using wave pipelined SRAM designs for on-chip caches and a write cache for store traffic. Memory power is controlled without increased latency by use of delayed-reset logic decoders. The chip operates at 1000 MHz and dissipates less than 80 W from a 1.6-V supply. It contains 23 million transistors (12 million in RAM cells) on a 244 mm² die     

Heat transfer characteristics and pressure variation in a nanoscale evaporating meniscus

A nanoscale evaporating meniscus is simulated in this work using molecular dynamics. The heat and mass transfer characteristics and pressure variation in the non-evaporating and interline regions are studied. Very high heat and evaporation flux rates of the order of 100 MW/m² and 1000 kg/m² s, respectively, are achieved. The disjoining pressure increased significantly after the formation of the non-evaporating film. High negative liquid pressure induced due to capillary and disjoining pressures are obtained. Cavitation cannot occur as the film thickness is smaller than the critical cavitation radius, and the meniscus can exist in metastable state. A curve-fitted meniscus boundary condition is developed; a force function of the form F_n = An^?3 ? Cn^?2 can be applied at the boundaries of a liquid film to create curvature and form a meniscus.