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This paper proposes a compact high-voltage pulse electron gun power supply (EGPS) consisted of interleaved capacitor-charging power supply (CCPS) with a series-resonant converter (SRC) to drive the electron tube. Requirement specifications are −40 kV, −7 A (280 kW), and continuous output lower than ±1% ripple stability lasted few seconds with

In this study, the toughness under sharp cracks and blunt notches is investigated in terms of the prior austenite grain size (PAGS) and inclusion particles as a function of the austenitizing treatment in a Ti-added 13Co-8Ni secondary hardening steel. For the quantitative analyses of the inclusion and precipitate particles, small-angle neutron scattering analyses are conducted under austenitizing conditions of 1050 °C, 1200/1050 °C, and 1200/1200 °C; the impact toughness values are 32, 30, and 24 J for each austenitizing condition, respectively. In contrast, the fracture toughness values under the same conditions are 66, 78, and 103 MPa·m1/2. Thus, the fracture toughness significantly improves under 1200/1200 °C austenitizing conditions with coarse PAGS; however, the impact toughness deteriorates. The adverse effect of the grain size on the toughness under sharp cracks and blunt notches is elucidated in terms of the effective microstructural factors that control the fracture process inside the plastic zone, the size of which varies with the notch sharpness. In particular, through considering the density of the slip bands as a function of the grain size in the small confined plastic zone before the sharp crack, the complicated problem regarding an increase in the fracture toughness with an increasing grain size is described from micromechanical and microstructural perspectives.

This report discusses the structural and spectroscopic analysis of yttria-stabilized-zirconia (YSZ) thin films grown on Al 2 O 3 (0001) substrates. It is found that the changes of oxygen partial pressure during the growth are closely related to the surface chemical compositions and the surface crystal orientations of the thin films. The presence of oxygen partial pressure produces a polycrystalline structure on the thin film while a preferred orientation of crystal structures is formed under no oxygen partial pressure. Difficulty arises in identifying the structure of the thin films due to the broad characteristics of the x-ray diffraction (XRD) peaks; however, the XRD rocking scan suggests the existence of two lateral domain sizes. The chemical analysis of the thin films from x-ray photoelectron spectroscopy measurements indicates the enrichment of surface yttrium-oxide as the oxygen partial pressure increases. The detailed analysis of valence band spectra also suggests that the thin films undergo a surface structural phase transition, i.e., transforming from a single tetragonal structure to a mixed (cubic + monoclinic) structure. Furthermore, the optical data display the small increments of the band gap as the oxygen partial pressure increases, which reflects the presence of the structural phase transition of the thin films.

Top blow injection of a gas–solid jet through a circular lance is used in the Mitsubishi continuous smelting process. One of the problems associated with such injection is the severe erosion of the hearth refractory below the lances. A new configuration of the lance to form an annular gas–solid jet rather than the circular jet was designed in this laboratory. With this new configuration, solid particles, fed through the centre tube, leave the lance at a much lower velocity than the gas, and the penetration behaviour of jet is significantly different than that of circular lance where the solid particles leave the lance at the same high velocity as the gas. In an earlier cold model investigation, the effects of gas velocity, solid feedrate and lance height of the annular lance were studied and compared to the circular lance. This paper reports on experimental work that includes the effects of the size of the annular lance, which greatly expands the applicable range of the developed correlation. It h...

The effects of Ce addition on the microstructure, age hardening response and mechanical properties of an indirect-extruded Mg-5wt.%Sn-4Zn (TZ54) alloy were investigated. Addition of Ce accelerated the aging response with the peak aging time moving from 300 h in TZ54 to 30 h in Mg-5wt.%Sn-4Zn-1Ce (TZE541), while the peak harness was similar to each other. The addition of Ce also caused an increase in the precipitation stability during overageing. Though the tensile strength of extruded TZ54 was improved by the addition of Ce, the tensile strength of the TZE541 was reduced after T6-treatment. The combined mechanical properties of the present as-extruded alloys by solution heat-treatment and artificial aging (T6) were comparable to commercial wrought magnesium alloys.

A sand-cone method is commonly used to determine the density of compacted soils. The density of the compacted soil calculated from the sand-cone method could be correct, provided the calibration container has approximately the same size or volume and allows the sand to fall to approximately the same height as a test hole in the field. However, in most cases, the size or shape of the test hole is not exactly the same as that of the calibration container. This can result in a difference in the settlement or deposition of sand particles between the laboratory calibration and the field testing, which may cause an erroneous determination of the in-situ density. The sand-filling process is simulated in the laboratory and its effect on the determination of density is investigated. Artificially made holes with different depths and bottom shapes are prepared to simulate various shapes of the test hole in the field. Sands with different particle size distributions are used in the testing to examine how sand grain size influences the determination of density in the field. The error between the assumed and calculated densities is highly dependent on the types of sand used in the sand-cone method. This paper presents some guidelines for obtaining correct in-situ densities through the sand-cone method.

Luminescence experiments in magnetic fields up to 28 T on a freestanding gallium nitride ( GaN ) sample and a heteroepitaxial GaN layer lightly doped with silicon are presented. In these samples, the principal D0X recombination channel is accompanied by two electron satellites (TES), which involve the excited donor states as well as by the longitudinal-optic (LO) phonon replica of the principal transitions. When the internal donor excitations are magnetically tuned into resonance with the LO-phonon excitation, the intensity of TES is strongly enhanced and clear avoided-crossings between the LO-phonon replica of the principal D0X transition and TES involving highly excited states of oxygen and silicon are resolved. The observed behavior is explained in terms of resonant interaction between LO-phonons and donor-bound electrons. It is found that the resonant magnetopolaron interaction is stronger for the oxygen as compared to the silicon donor.

We have performed a detailed contactless electroreflectance study of the interband excitonic transitions on both the Ga and N faces of a 200-μm-thick freestanding hydride-vapor-phase-epitaxy grown wurtzite GaN sample with low defect concentration in the temperature range between 20 and 300 K. The transition energies of the A, B, and C excitons and broadening parameters of the A and B excitons have been determined by least-square fits to the first derivative of a Lorentzian line shape. The energy positions and separations of the excitonic transitions in the sample reveal the existence of residual strain. At 20 K the broadening parameter of A exciton deduced for the Ga (5×105 dislocation cm−2) and N (1×107 dislocation cm−2) faces are 3 and 7 meV, respectively, indicating a lower defect concentration on the former face. The parameters that describe the temperature dependence of the interband transition energies of the A, B, and C excitons as well as the broadening function of the A and B features are evaluated. The results from an analysis of the temperature dependence of the broadening function of excitons A and B indicate that GaN exhibits a very large exciton-phonon coupling.

An ultrasonic method is used to disperse iron oxide particles of two different sizes in an epoxy vinyl ester resin. The dispersion quality is assessed from sedimentation, density measurements, and scanning electron micrographs. By varying parameters such as power and duration of sonication, optimum dispersion conditions are suggested. Dispersion is most effective in the early stage of sonication and becomes more difficult to improve later. Once separated, however, the particles do not come into direct contact with one another because of the steric hindrance. The nano-size (29 nm) particles delay curing whereas the larger (200 nm) particles do not. The results indicate a strong interaction between nanoparticles and the resin.

The joining of titanium boride (TiB2) to aluminum oxide (AL2O3) was investigated using compositionally graded interlayers. For the joint each interlayer was stepwise stacked in a mold. The stacked samples were hot-pressed at 1470°C and 10 MPa for 0.5 h in a nitrogen atmosphere. Optical microscopy, x-ray diffractometry (XRD), wavelength dispersive spectroscopy (WDS), laser flash method and three point bend test were used to evaluate the joint material. It has been shown that the original stepwise distribution of Ti and Al constituents in the graded region prior to hot-pressing changes to continuous distribution after the sintering. The compositionally graded interlayers are shown to promote the formation of crack-free joints between TiB2 and AL2O3

In this paper, we present the results of an experimental study focused on understanding the strain concentrations arising due to nonlinear phenomena associated with polarization switching. A moire interferometry technique is used to measure the normal and shear strains of a PZT-5H piezoceramic undergoing 180 and 90 deg switching. These results include the strain concentrations measured between polarized regions oriented 180 and 90 deg apart. The results show that very large strain mismatches (e.g., as large as 4500 microstrains) occur along the boundary of dissimilar oriented domains, suggesting a source of microcrack initiation and fatigue degradation.

We investigate pattern formation in the immiscible displacement of foam from a confining geometry. The dominant length scales with the driving pressure gradient as for a Newtonian fluid, but depends surprisingly on the ratio of plate separation to bubble diameter. The pattern morphology exhibits a transition from a jagged, presumably elastic, character to a smooth, viscous character as the shear strain rate rises far above the natural internal relaxation time scale of the foam. These features may result from the two-dimensional nature of the flows and the unusual rheology of foams.

High-quality free-standing GaN was obtained by hydride vapor-phase epitaxy (HVPE) growth and the subsequent removal of the sapphire substrates. In the photoluminescence (PL) spectra of the as-grown HVPE-GaN, we observed a strong phonon replica peak for temperatures higher than 80 K. Both the near-band-edge emission and the yellow emission in the cathodoluminescence spectra were inhomogeneous, and correlated with the crystalline structure. With the homoepitaxial regrowth by metal–organic chemical-vapor deposition (MOCVD) in the GaN substrates, these unusual optical properties were no longer observed and the PL peak became sharper than GaN grown by MOCVD on sapphire substrates, indicating that the free-standing GaN is suitable as substrates for the growth of device structures.

The microwave heating process has shown potential for uniform material heating with rapid heating rates possible. The ceramic composite 80 wt % ZrO2 (+3 mol % Y2O3) 20 wt % Al2O3 was sintered in a Cober S6F microwave oven operating at 2.45 GHz even though it was considered to be microwave transparent at room temperature. The microwave-sintered sample was densified more rapidly and in a short time and lower temperature than the conventionally sintered sample. The fracture of the conventionally sintered sample was intergranular, but one of the microwave-sintered samples was transgranular. The fraction of the monoclinic-phase zirconia was different in the conventionally and microwave-sintered samples. The unusual microstructure of microwave-processed materials is explained by a microwave heating theory.

Summary form only given. A high voltage resonant pulser is designed by using an air core transformer. Triple resonant circuit is used to step up the primary voltage. The voltage step-up ratio is designed as about eleven at the charging stage. A distributed PFN is used to form a squre waveform. The output has an overvolted sparkgap switch that transfers energy to a matched resistive load with the PFN. The pulser is positioned in a cylindrical transformer oil tank. The height and diameter of the tank are respectively 1.06 m and 1.28 m. A dummy water load will be used to test the pulser. Design procedures and preliminary test results will be presented.

The neutral donor bound exciton recombination processes in freestanding GaN have been studied. The photoluminescence spectrum shows emission lines related to silicon and oxygen donors. Time-resolved luminescence allows us to correlate the principal donor bound exciton lines with their two-electron satellites. The magnetic field splitting of the two-electron lines is well described by the theory of the hydrogen atom in a magnetic field. For the oxygen donor a 1.5 meV chemical shift and a 30.8 meV effective Rydberg have been evaluated. Two-electron satellites involving excitations to the $2p$ and $2s$ donor states are separated by an energy of 1.0 and 1.3 meV for O and Si impurity, respectively. The temperature dependence of the two-electron emission clearly shows that this separation arises from a splitting of the ground state of the neutral donor bound exciton complex. The nature of this splitting is discussed and it is suggested that it is due to rotational states of donor bound excitons.

We have developed a synchronously switched cyclic capillary electrophoresis (CE) separator that is fabricated on a silicon substrate and glass containing reservoirs, Au electrode, and isolated channels. The advantage of a cyclic separator is the high resolution and ability to separate each sample to the designated reservoir from mixed samples. This approach makes it possible to reduce the supplied voltage and the total chip size. Another goal of this work is to introduce the methodology of electroosmosis flow (EOF) to silicon substrate and to separate DNA samples using a modified double-T injector.

After 14 years of successful operation, the Pohang Light Source (PLS) has completed PLS-II upgrade to meet the increasing demand from the growing user community. The PLS-II upgrade has increased the beam energy from 2.5 GeV to 3 GeV; the number of insertion devices has been increased by a factor of two (20 IDs); and the beam current has been increased to 400 mA from 200 mA. The beam emittance has been reduced to below 10 nm while retaining the existing PLS tunnel as well as the existing injection system. During the six months of commissioning in the latter half of 2011, we have successfully achieved 14 insertion device operations and top-up operations with 100 mA beam current and 5.8 nm beam emittance. In this paper, we report the experimental results obtained from the PLS-II commissioning.

A novel sol-gel technique was used to immobilize malachite green ions (MG{sup +}) in stable, optically transparent, porous silica gel films. A simple and sensitive method was developed for the detection of cyanides in solutions using spectrophotometry to measure changes caused by cyanide ions (CN{sup {minus}}) in the absorption spectra of the green-colored silica gel films. After reaction with cyanide ions, the absorption spectra of the films changed with a typical decrease in absorbance at 620 nm. On the basis of the absorption spectra of the films, a portable and easy to use fiber optic cyanide film sensor was fabricated. Decolorization undergone by the green-colored gel films, as they were exposed to cyanide ions, was detected through a fiber. Preliminary results indicate concentrations on the order of a few ppm are detected using the fiber optic sensor.

InGaAsP/InGaAsP multiple-quantum-well (MQW) double-channel planar-buried heterostructure (DCPBH) lasers emitting at λ∼ 1.57 μm were fabricated by optimizing the epitaxial growth with material characterization. At 25 °C (85 °C), a 1.8-μm-wide and 300-μm-long antireflectivity/high reflectivity coated laser exhibits a threshold current of 8 mA (23 mA) and a slope efficiency of 0.34 mW/mA (0.24 mW/mA) in continuous-wave mode (cw) as a result of the optimized thickness of the p-InP filling layer in the PBH structure with p-n-p-n current blocking layers. The maximum cw output power was approximately 20 mW at 25 °C, which was reduced to 17 mW at 85 °C. The peak wavelength varied from 1572 nm at 25 °C to 1602 nm at 100 °C for a fixed output power of 5 mW, indicating a temperature coefficient of ∼ 0.4 nm/K. The resonance frequency in the small-signal modulation response of devices depends on the etching depth of the U-shaped double channel; it increases from 0.4 GHz without channel etching to 4.3 GHz with 7-μm-thick etching. The full-width at half maximum values in the horizontal and vertical far-field patterns were approximately 24.5° (25.2°) and 29.4° (30.1°), respectively, at 25 °C (85 °C).

Rotational Maker fringes, scaled with respect to χ11(2) of crystalline quartz, were used to determine the second order susceptibilities χ31(2) and χ33(2) for samples of thin AlxGa1−xN films, a thicker GaN film, and a free-standing GaN platelets. The pump wavelength was 1064nm. The AlxGa1−xN samples, ranging in thickness from roughly 0.5to4.4μm, were grown by metalorganic chemical vapor deposition (MOCVD) and hydride vapor-phase epitaxy (HVPE) on (0001) sapphire substrates. The Al mole fractions x were 0, 0.419, 0.507, 0.618, 0.660, and 0.666, for the MOCVD-grown samples, and x=0, 0.279, 0.363, and 0.593 for the HVPE-grown samples. An additional HVPE-grown GaN sample ∼70μm thick was also examined. The free-standing bulk GaN platelets consisted of an HVPE grown film ∼226μm thick removed from its growth substrate, and a crystal ∼160μm thick grown by high-pressure techniques. For the AlxGa1−xN samples, the magnitudes of χ31(2) and χ33(2) decrease roughly linearly with increasing x and extrapolate to ∼0 for x=...

The measurement of temperature in a microwave field is critical to the understanding of many phenomena which occur in materials heated in such an environment. Researchers have employed many techniques [1–4] to measure temperature in an electromagnetic field. This work examined three approaches: the use of a thermocouple, an IR meter, and a d. c. resistance technique.

A series of sharp intense peaks was observed in the low-temperature photoluminescence spectrum of unintentionally doped GaN in the photon energy range between 3.0 and 3.46 eV. We attributed the majority of these peaks to excitons bound to unidentified structural and surface defects. Most of the structural- and surface-related peaks (at 3.21, 3.32, 3.34, 3.35, 3.38, and 3.42 eV) were observed in Ga polar films. In N polar GaN, we often observed the 3.45 eV peak attributed to excitons bound to the inversion domain interfaces.

A free-standing GaN template grown by hydride vapor phase epitaxy has been characterized by transmission electron microscopy ~TEM!. The TEM investigation was augmented by x-ray diffraction, defect delineation etching process followed by imaging with atomic force microscopy and variable temperature photoluminescence. The density of dislocations near the N face was determined to be, in order, 3613107, 4613107, and about 13107 cm22 by cross-sectional TEM, plan-view TEM, and a defect revealing etch, respectively. The same methods on the Ga face revealed the defect concentration to be, in order, less than 13107 cm22 by plan-view TEM, less than 53106 cm22 by cross-sectional TEM, and 53105 cm22 by defect revealing hot H3PO4 acid, respectively. The full width at half maximum of the symmetric ~0002! x-ray diffraction peak was 69 and 160 arc sec for the Ga and N faces, respectively. That for the asymmetric (101I4) peak was 103 and 140 arc sec for Ga and N faces, respectively. The donor bound exciton linewidth was about 1meV each at 10 K, and a green band centered at about 2.44 eV was observed.

Schottky barrier diodes, on both Ga and N faces of a ∼300-μm-thick free-standing GaN layer, grown by hydride vapor phase epitaxy (HVPE) on Al2O3 followed by laser separation, were studied by capacitance–voltage and deep level transient spectroscopy (DLTS) measurements. From a 1/C2 vs V analysis, the barrier heights of Ni/Au Schottky contacts were determined to be different for the two polar faces: 1.27 eV for the Ga face, and 0.75 eV for the N face. In addition to the four common DLTS traps observed previously in other epitaxial GaN including HVPE-grown GaN a new trap B′ with activation energy ET = 0.53 eV was found in the Ga-face sample. Also, trap E1 (ET = 0.18 eV), believed to be related to the N vacancy, was found in the N-face sample, and trap C (ET = 0.35 eV) was in the Ga-face sample. Trap C may have arisen from reactive-ion-etching damage.

Deep traps in a 300-m m-thick freestanding GaN sample were characterized by deep level transient spectroscopy (DLTS), using Schottky barrier diodes (SBDs) fabricated on the Ga polarity surface. Most of the SBDs show nearly ideal current-voltage characteristics, with both forward and reverse currents controlled by the thermionic emission mechanism. Five common traps, which include A1 (1.0 eV), A (0.66 eV), B (0.59 eV), C (0.35 eV), and D (0.25 eV), can be consistently observed in all SBDs. Two of them, A1 and C, are related to surface damage. Surprisingly, some new traps can be found in the DLTS spectra of some SBDs if higher reverse biases are used in the measurements. However, they cannot be fitted by DLTS simulations, and are likely associated with parasitic capacitance somewhere in the cryostat.

A free-standing 300-μm-thick GaN template grown by hydride vapor phase epitaxy has been characterized for its structural and optical properties using x-ray diffraction, defect delineation etch followed by imaging with atomic force microscopy, and variable temperature photoluminescence. The Ga face and the N face of the c-plane GaN exhibited a wide variation in terms of the defect density. The defect concentrations on Ga and N faces were about 5×105 cm−2 for the former and about 1×107 cm−2 for the latter. The full width at half maximum of the symmetric (0002) x-ray diffraction peak was 69 and 160 arc sec for the Ga and N faces, respectively. That for the asymmetric (10–14) peak was 103 and 140 arc sec for Ga and N faces, respectively. The donor bound exciton linewidth as measured on the Ga and N faces (after a chemical etching to remove the damage) is about 1 meV each at 10 K. Instead of the commonly observed yellow band, this sample displayed a green band, which is centered at about 2.44 eV.