Transition layer thickness in microlaminar deposits

A theoretical analysis was carried out on the change of composition of a deposit obtained by the dual pulse method of forming laminar metal foils, with transition from a low current to a high current pulse, both in the galvanostatic and the potentiostatic mode of deposition. It was shown that the existence of a transition layer of varying composition between a layer of pure metal 1 and a layer consisting predominantly of the metal 2 is an inherent consequence of the electrochemical process, primarily because of an induction period in the concentration polarization with respect to ions of metal 1. The importance of this transition layer increases as the thickness of the layers of the two metals decreases. Eventually this limits the possibility of obtaining a sharp boundary between the layers, when the nanometre region of layer thickness is reached. Equations are given for calculating the deposition current density and rate of stirring of the electrolyte which provide a deposit of a required level of metal 1 in the layer of metal 2, as well as a required sharpness of the boundary between two layers. Experimental proof of the correctness of the analysis was sought. It was found that significant changes in the properties of the deposit occur in the same range of layer thickness in which the transition of the composition takes places.Nomenclature _c,1, a_c,2 transfer coefficient of the cathodic processes - C interfacial capacitance - C₁, C₂ concentration of the ions of metals 1 and 2 at the interface r - C ₀ ¹ , C ₀ ² concentration of ions of the metals 1 and 2 in solution - D ₁ diffusion coefficient for the diffusion of ions of the metal 1 - E _r,1,E _r,2 reversible potentials of metals 1 and 2, respectively - F the Faraday constant - J ₀ ¹ ,J ₀ ² exchange current density of the metals 1 and 2, respectively - M ₁,M ₂ atomic weights of the metals 1 and 2, respectively - kinematic viscosity of solution - ₁, ₂ densities of the metals 1 and 2 respectively - rotation speed (r.p.s.) - z number of electrons exchanged in the deposition process This paper is dedicated to Professor Brian E. Conway on the occasion of his 65th birthday, and in recognition of his outstanding contribution to electrochemistry.     

Synthesis of ZnO-based varistor precursor powders by means of the reaction spray process

High-purity, fine-grained oxide ceramic powders that are commonly used for ZnO-based varistors were synthesized by means of the reaction spray process. Processing steps included formation of the solutions of zinc nitrate and/or certain metal additives and spraying of the solution into a heated reaction column using a two-phase nozzle. After water evaporation from the droplets, the precursor salts were decomposed at elevated temperatures (up to 1473 K) in order to obtain homogeneous oxide powders with complex compositions corresponding to the final multicomponent varistor system. The decomposition behaviour of the precursors, as well as the characteristics of the resulting powders: crystallinity, phase composition, particle shape, morphology and particle-size distribution, were examined. It was shown that the characteristics of the reaction spray-derived powders can be controlled by adjusting the system and the solutions parameters.     

Unusual behavior of superconductors near the tricritical Lifshitz point

The properties of superconductors near the tricritical Lifshitz(TL) point are studied. Unusual behavior ofH _c2(T) near the TL point in three-dimensional (3D) systems is found, as well as an oscillatory character ofH _c2(T) in quasi-2D systems. The oscillatory character of the critical currentj _c of the S-S-S junction as a function of thickness and temperature is also studied. Predictions are compared to experimental data in such quasi-2D systems as T_aS₂(pyridine).     

Generation of sum-frequency sideband using 964 GHz HCN laser and 70 GHz klystron radiation

Continuosly tunable submillimeter radiation above 1 THz has been generated by sum-frequency mixing of HCN laser radiation (second strongest transition at 964.3 GHz) with that of klystron (70 GHz) in the Schottky barrier diode used as the non-linear element. Generated radiation was sufficiently strong to allow the high resolution frequency measurement of 9_9,1 ← 8_8,0 transition in³²S¹⁶O.     

Globally Synchronized Frames for guaranteed quality-of-service in on-chip networks

Future chip multiprocessors (CMPs) may have hundreds to thousands of threads competing to access shared resources, and will require quality-of-service (QoS) support to improve system utilization. This paper introduces Globally-Synchronized Frames (GSF), a framework for providing guaranteed QoS in on-chip networks in terms of minimum bandwidth and maximum delay bound. The GSF framework can be easily integrated in a conventional virtual channel (VC) router without significantly increasing the hardware complexity. We exploit a fast on-chip barrier network to efficiently implement GSF. Performance guarantees are verified by analysis and simulation. According to our simulations, all concurrent flows receive their guaranteed minimum share of bandwidth in compliance with a given bandwidth allocation. The average throughput degradation of GSF on an 8×8 mesh network is within 10% compared to the conventional best-effort VC router.     

Subsumptive general solutions and parametric general solutions of Post equations

In this paper we generalize Rudeanu’s results from [13] to Post algebras. We give a necessary and sufficient condition for the existence of a Post function f such that the set of solutions of equation f(x) = 0 is a given interval. We also prove that every Post transformation is the parametric solution of some consistent Post equation.     

Request redirection paradigm in medical image archive implementation

It is widely recognized that the JPEG2000 facilitates issues in medical imaging: storage, communication, sharing, remote access, interoperability, and presentation scalability. Therefore, JPEG2000 support was added to the DICOM standard Supplement 61. Two approaches to support JPEG2000 medical image are explicitly defined by the DICOM standard: replacing the DICOM image format with corresponding JPEG2000 codestream, or by the Pixel Data Provider service, DICOM supplement 106. The latest one supposes two-step retrieval of medical image: DICOM request and response from a DICOM server, and then JPIP request and response from a JPEG2000 server. We propose a novel strategy for transmission of scalable JPEG2000 images extracted from a single codestream over DICOM network using the DICOM Private Data Element without sacrificing system interoperability. It employs the request redirection paradigm: DICOM request and response from JPEG2000 server through DICOM server. The paper presents programming solution for implementation of request redirection paradigm in a DICOM transparent manner.     

Analysis for a class of singularly perturbed hybrid systems via averaging

A class of singularly perturbed hybrid dynamical systems is analyzed. The fast states are restricted to a compact set a priori. The continuous-time boundary layer dynamics produce solutions that are assumed to generate a well-defined average vector field for the slow dynamics. This average, the projection of the jump map in the direction of the slow states, and flow and jump sets from the original dynamics define the reduced, or average, hybrid dynamical system. Assumptions about the average system lead to conclusions about the original, higher-dimensional system. For example, forward pre-completeness for the average system leads to a result on closeness of solutions between the original and average system on compact time domains. In addition, global asymptotic stability for the average system implies semiglobal, practical asymptotic stability for the original system. We give examples to illustrate the averaging concept and to relate it to classical singular perturbation results as well as to other singular perturbation results that have appeared recently for hybrid systems. We also use an example to show that our results can be used as an analysis tool to design hybrid feedbacks for continuous-time plants implemented by fast but continuous actuators.     

The investigation of metastable ζ-hcp phase in the Ag-rich f c c region of Ag-In alloys rapidly quenched from the melt

Stacking faults, which were detected in the Ag-In system, have been examined by transmission electron microscopy and electron diffraction. An enhanced concentration of stacking faults in splat cooled specimens as well as the formation of a metastable hexagonal phase in the f c c region of the alloy was observed. As far as we know this is the first case of the terminal solid solubility being reduced by rapid quenching. Terminal solid solubility is reduced because of the high concentration of structural defects introduced by quenching, e.g. dislocations and stacking faults, which serve as the nuclei for the transformation from the f c c to the h c p structure. Our measurements and calculations show that the stacking fault energy minimum is shifted to lower electron concentrations with respect to the stacking fault energy minimum corresponding to the equilibrium phase boundary for the f c c-h c p transformation. The new metastable phase boundary for this transformation was confirmed by X-ray examinations. We explain this earlier h c p phase appearance in rapid quenched specimens as the consequence of enhanced interaction of the Fermi surface and contracted Brillouin zone. The Brillouin zone contraction we attributed to quenched-in vacancies.