Surface and catalytic properties of Cu–Ce–O composite oxides prepared by combustion method

Surface and catalytic properties of Cu–Ce–O composite materials prepared by solution combustion method have been investigated. The materials are characterized by X-ray diffraction (XRD), temperature programmed reduction (TPR) and electron paramagnetic resonance spectroscopy (EPR). The results of EPR and TPR show finely dispersed Cu²⁺ species on ceria matrix with low copper content. The Cu²⁺ species exists in the form of dimers and clusters which are not evident in XRD. In addition CuO is also present as small clusters which grow to larger size at higher Cu content. There is no evidence of CuO forming a solid solution with fluorite CeO₂ in combustion method. The Cu²⁺ species mostly appear on surface rather than in the bulk. Hydrogen peroxide decomposition kinetics has been carried out on Cu–Ce–O composite materials to investigate the effect of crystalline and well-dispersed copper oxide phases on CeO₂. From kinetic results, the catalyst materials can be grouped into highly dispersed as well as crystalline CuO phases present on CeO₂ matrix. Two parallel compensating lines for dispersed and crystalline CuO phases on CeO₂ are observed in ln A versus E_a plot indicating the compensation effect in H₂O₂ decomposition. This observation is consistent with XRD and EPR results.     

Conduction studies on electrodeposited indium selenide thin films

Indium Selenide thin films were electrodeposited on Indium Tin Oxide (ITO) coated glass substrates from a mixture of Indium trichloride (InCl₃) and selenium dioxide (SeO₂) in aqueous solution by the potentiostatic electrodeposition technique. The InSe films showed that Mott’s variable-range hopping conductivity (VRH) is dominant under low field (∼2×10⁵ Vcm⁻¹) condition. At high field the Current-Voltage studies (in the temperature range 300 – 380 K) revealed that the conductivity of Indium selenide thin films is of Poole-Frenkel type. The plot drawn between Ln (I/V) and tV showed a straight line and also the experimental data and the theoretical data closely matches. Hence Poole-Frenkel mechanism is confirmed and discussed in detail. Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, India, Nov. 28–30, 2003.     

Soft X-ray optimization studies on a dense plasma focus device operated in neon and argon in repetitive mode

This paper investigates the emission characteristics of a high-performance low-energy (3-kJ) repetitive dense plasma focus device, NX2, operated at up to 1-Hz repetition rate to develop it as an intense source of soft X-rays (SXR) for microlithography and micromachining. Various SXR yield optimization studies with argon and neon as filling gases were performed under different operating conditions (charging voltage, filling pressure, anode length, and insulator sleeve length). The SXR yield was computed using signals obtained from a PIN diode SXR spectrometer with appropriate filters. When operated in neon, the average optimum SXR (/spl lambda//spl sim/1 nm) yield in 4/spl pi/ steradians was found to be up to 140 J/shot, which corresponded to a wall plug efficiency of 5.6%. Operation in argon showed that optimized SXR (/spl lambda//spl sim/0.4 nm) yield was up to 1.3 J/shot. While operating with neon under optimized conditions with a water-cooled anode in repetitive mode, the NX2 device was used as a SXR source to imprint a test lithograph on a highly sensitive chemically-amplified resist SU-8. Test structures showing the effect of a stepper with aspect ratio 3:1 on 10-/spl mu/m-thick SU-8 resist film were obtained.     

Route optimization in mobile ATM networks

This paper presents an algorithm for optimizing the route of a connection that becomes suboptimal due to operations such as handoffs and location-based reroutes, and applies this algorithm to the handoff management problem in mobile ATM (Asynchronous Transfer Mode) networks based on the PNNI (Private Network-to-Network Interface) standard. The route optimization algorithm uses hierarchical route information of the connection and summarized topology and loading information of the network to determine a “crossover node” such that adjusting the connection from that crossover node results in an optimally routed connection. Handoff management schemes that perform local rerouting of connections have been proposed in order to support fast handoffs. These methods result in suboptimally routed connections. In this paper, we demonstrate how this route optimization algorithm can be used to optimize the route of a connection after such a handoff is executed, as the second phase of a two-phase handoff scheme. This route optimization procedure can also be executed as part of the handoff procedure resulting in a one-phase handoff scheme. Applying this route optimization algorithm, we propose two one-phase schemes, the one-phase optimal scheme and the one-phase minimal scheme. A comparative performance analysis of one- and two-phase handoff schemes is presented. Measures of comparison are handoff latency and the amount of network resources used by a connection. Handoff latency in the one-phase optimal scheme is greater than that in the two-phase schemes, and handoff latency in the one-phase minimal scheme is smaller than that in the two-phase schemes. The one-phase methods show a significant increase in efficiency of the connection compared to the two-phase methods. This revised version was published online in June 2006 with corrections to the Cover Date.     

Current sheet applicators for clinical microwave hyperthermia

Small lightweight applicators, intended to be operated in array configurations are described. Their radiative fields are induced by RF currents in a conducting sheet embedded a few millimeters below the dielectric covered aperture surface. In arrays, these elements can be used where conformity to body curvatures is necessary. The clinical prototypes are tuned to 434 MHZ and have a bandwidth of almost 20 MHZ, which accommodates the tuning and coupling changes due to different body movement, and tissue heterogeneities. They are relatively insensitive to air bubbles in bolus and scar tissue. Their inherent linear polarization allows easy visualization of the superposition of electric field vectors of each element of an array and provides deeper penetration on curved surfaces due to electric field vector addition in the medium. In the case of a large breast tumor, depth of heating of over 4 cm was achieved along the central axis of a 2×2 coherent array. Experimental evaluation of these elements, leading to clinical implementation, is described along with a clinical example     

A heuristic method for optimum redundancy allocation in non-coherent systems

This paper presents a heuristic method for optimum redundancy allocation in non-coherent systems. The method uses two forms of redundancy, namely parallel and series forms. System reliability of non-coherent systems cannot be generally improved by using only parallel redundancy. So use of series or parallel redundancy, whichever gives better system reliability, is recommended. The proposed method retains all the advantages of the most recommended [2,4,5] heuristic reliability optimization techniques. The method is general and can be used with linear or non-linear, separable or non-separable constraints.     

Elastic constants of sodium chlorate from 77 K to 350 K

The elastic constantsC ₁₁,C ₁₂ andC ₄₄ of sodium chlorate single crystal have been evaluated using 10 MHz ultrasonic pulse echo superposition technique. The values areC ₁₁=4.90,C ₁₂=1.39,C ₄₄=1.17 (× 10¹⁰ N/m ²) at 298 K and 6.15, 2.16, 1.32 (×10¹⁰ N/m ²) at 77 K. The data agree well with the values measured earlier up to 223 K. Brief mention is also made of the low temperature bonding problems in these soft crystals.