Analysis of diffused planar and channel waveguides

A simple analytical method is presented which improves upon the Hermite-Gauss field proposed by S.K. Korotky et al. (1982) for diffused waveguides by taking into account the evanescent field in the cover region. The method is used to analyze the propagation characteristics of diffused planar and channel waveguides     

Synthesis,characterization and corrosion performance evaluation of DDR membrane for H2 separation from HI decomposition reaction

An all silica DDR (deca dodecasil rhombohedral) zeolite membrane with dense, interlocked structure has been developed for separation of H₂ from HI/I₂ mixture of HI decomposition reaction. In this work, the DDR zeolite membrane was synthesized on the seeded clay-alumina substrate within 5 days. The seeds were synthesized by sonication mediated hydrothermal process within short crystallization time which enhanced the nucleation for the membrane growth. The synthesized membranes along with seed crystals were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), Field emission scanning electron microscope (FESEM) and energy dispersive X-ray spectroscopy (EDAX). The selectivity of hydrogen with respect to CO₂ and Ar was evaluated by single gas permeation studies at room temperature. The tests for corrosion resistance were carried out upto 120 h with both support and DDR membrane at 130 °C which confirmed the stability of membrane under the harsh HI/I₂ environment.     

An undergraduate system-on-chip (SoC) course for computer engineering students

The authors have developed a senior-level undergraduate system-on-chip (SoC) course at San Jose State University, San Jose, CA, that emphasizes SoC design methods and hardware-software codesign techniques. The course uses a "real world" design project as the teaching vehicle and implements an SoC platform to control a five-axis robotic arm using Altera's state-of-the-art Excalibur chip. The Excalibur chip contains both ARM Corporation's embedded processor and a programmable logic device (PLD) array. The course goes through a complete hardware-software codesign flow from implementing custom hardware devices on a PLD to developing an embedded algorithm in a state-of-the-art design environment for a complete SoC solution. Students learn the Quartus II design environment by examining the sample design files in Altera's EXPA1 development kit and following the step-by-step instructions toward creating a simple embedded application. After this familiarization process, students define the architectural specifications of a memory-mapped servo controller, implement it in the Excalibur's PLD array, and interface this device with the ARM processor's internal bus to control each robotic arm servo. Functional regression tests and post-synthesis timing verification steps are applied to the servo controller following the implementation phase. Subsequently, students integrate the servo controller with the rest of the system and perform board-level functional verification tests to observe whether the robotic arm can move an object from a source to a destination point accurately. Students also develop an embedded algorithm, which translates user inputs in Cartesian coordinates into robotic arm movements in spherical coordinates during laboratory sessions.     

Effect of ZrO2 on phase transformation of Al2O3

This study investigates the effect of ZrO₂ on phase transformation of alumina. Alumina and alumina–zirconia composite powders were produced by the precipitation method from aluminum sulfate and zirconium sulfate precursors. Precipitates obtained at 15 °C were dried at 80 °C for 72 h, and then calcinated at four different temperatures; 1000 °C, 1100 °C, 1200 °C and 1300 °C for 1 h. Powders calcinated at 1300 °C were pressed uniaxially and sintered at 1600 °C for 1 h. XRD and DSC analyses showed that the presence of zirconia retarded the transformation to α-alumina. SEM studies on the powders calcinated at 1300 °C revealed that both alumina and alumina–zirconia particles were 100–300 nm in size and of near spherical shape. Zirconia additions inhibited abnormal grain growth of alumina and provided homogeneous, equaxied grain structure.     

Characterization of cryogenic heat treated Vanadis 4 PM cold work tool steel

The amount of retained austenite in the quenched cold work tool steel sample is 17.7%, in the condition of sub-zero heat treated and double tempered samples following by quenching is 1.9% determined by XRD analysis. The types of carbides (MC, M₇C₃, M₂₃C₆) present in the structure was determined by XRD and SEM-EDS analysis. The hardness of test samples were 865 HV(0.1) for quenched sample and 785 HV(0.1) forth sample subjected to sub-zero treatment and double tempered after the quenching.     

Physical and tribological properties of diamond films grown in argoncarbon plasmas

Nanocrystalline diamond films have been deposited using a microwave plasma consisting of argon, 2–10% hydrogen and a carbon precursor such as C₆₀ or CH₄. It was found that it is possible to grow the diamond phase with both carbon precursors, although the hydrogen concentration in the plasma was 1–2 orders of magnitude lower than normally required in the absence of the argon. Auger electron spectroscopy, X-ray diffraction measurements and transmission electron microscopy indicate the films are predominantly composed of diamond. Surface roughness, as determined by atomic force microscopy and scanning electron microscopy indicate the nanocrystalline films grown in low hydrogen content plasmas are exceptionally smooth (30–50 nm rms) to thicknesses of 10 m. The smooth nanocrystalline films result in low friction coefficients (μ = 0.04–0.06) and low average wear rates as determined by ball-on-disk measurements.     

Modeling of Ti:LiNbO3 waveguide directional couplers

A simple and accurate method is presented for studying the coupling characteristics of 3D diffused channel waveguide directional couplers. The method is based on the scalar variational principle and differs from other methods as it does not require any assumption for the functional form of the trial field. The authors also propose an equivalent 2D directional coupler that also gives accurate results and, hence, saves considerable computational time, Comparison with experimental and other theoretical results is also presented     

Hard iron boride (Fe2B) on 99.97 wt% pure iron

Some properties such as hardness and fracture toughness of boride formed on the 99.97 wt% pure iron were investigated. Boronizing was carried out in a solid medium, consisting of Ekabor powders of 5% B₄C as donor, 5% KBF₄ as an activator and 90% SiC as diluent at 800 °C for 2, 4 and 8 h. The dominant phase formed on the substrate was found to be Fe₂B that had a finger-like shape morphology. The hardness of boride on the 99.97% pure iron was over 1700HVN, while the hardness of pure iron was about 130HVN. It was found that the fracture toughness of boride formed on surfaces of 99.97% pure iron, depending on the process time, ranged from 3.59 to 3.83 MPa m^1/2. Depending on process time and temperature, the depth of the boride layer ranges from 22 to 43 μm, leading to a diffusion-controlled process.     

Tribological characteristics of boronized niobium for biojoint applications

Boride coatings on corrosion-resistant refractory metals are potentially used as implanting materials. In this research, we investigated wear mechanisms of boride coatings on pure niobium using a pin-on-disk tribometer in two different conditions i.e. in dry and using a simulated body fluid (SBF). Surface morphology studied using a scanning electron microscope (SEM) shows the compressed boride layer with indistinguishable regions such as coating intermediate transition layer and the substrate. The surface analysis after wear tests was conducted using an atomic force microscope (AFM). It was found that, in dry condition, the boride coating underwent deformation wear, and debris formed and accumulated at both ends of the track due to adhesion. In presence of SBF, the coating shows different mode of failure. The tribo-chemical wear dominates the wear mode.     

Effect of phosphotungstic acid blending on properties of sulfonated poly(ether ether ketone)–poly(ethylene glycol) crosslinked membranes

This study shows the effect of phosphotungstic acid (PWA) blended into a sulfonated poly(ether ether ketone) (SPEEK) and poly(ethylene glycol) (PEG) crosslinked membrane on the membrane's electrochemical and mechanical properties. The PWA weight percentage was varied from 0 to 50%. All of the membranes were equilibrated with water at room temperature (27 °C) and elevated temperature (60 °C), and their properties were investigated. A scanning electron microscope with energy dispersive X‐ray was used to ascertain the tungsten concentration remaining in the membrane after water treatment. A systematic decrease in tungsten concentration was seen with the increase in the initial PWA percentage. The membrane blended with 10% PWA showed the best properties, having the highest conductivity (0.11 S cm^?1), mechanical strength, and chemical stability. Membranes with 10% PWA and without PWA were studied in a H₂/O₂ fuel cell. The membrane blended with 10% PWA gave 33% more power density than the membrane without PWA. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46667.