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A vertical InGaN-based blue light emitting diode (LED) with a reflective metal electrode and thick gold plated base free from insulating sapphire is demonstrated. A 50 μm-thick gold plated layer on a highly reflective platinum p-side ohmic contact is formed on the InGaN-based LED epi-structure, followed by irradiation with high power ultra-violet pulsed laser from the backside of the original sapphire substrate. The laser processing, so called laser lift-off technique, enables the separation of sapphire by decomposition of interfacial GaN layer. No transparent electrode is necessary for the LED because the current can spread well through the highly conductive n-GaN layer so that uniform blue light is emitted through the n-GaN layer. The electroluminescence (EL) spectra show small multi peaks due to the resonance within the formed vertical cavity. In addition, the measured thermal resistance of the vertical LED is smaller than that of the conventional LED on poor heat-conductive sapphire. The vertical LED would increase the brightness together with smaller chip size and lower series resistance. This would be advantageous espacially for high power and highly efficient LEDs applicable to future solid state lighting. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A very thin 1 μm-thick Al 0.11 Ga 0.89 N film is successfully separated from a sapphire substrate by thermal decomposition of interfacial region using high power laser, so-called laser lift-off technique. The used layer structure prior to the separation is 1.0 μm Al 0.11 Ga 0.89 N/0.3 μm GaN on sapphire grown by metal organic chemical vapor deposition (MOCVD), and third harmonic Q-switched Nd:YAG laser ( λ =355 nm) is irradiated from the backside of the sapphire. Absorption of the laser light occurs only at the GaN interlayer and the decomposed thickness is limited up to the interlayer thickness. As a result, a crack-free thin AlGaN film is separated from sapphire with metal Ga underneath through the optimization of the process parameters. In contrast, removal of 2 μm-thick GaN single layer from sapphire is also tested, where peeling-off of the film with cracks is seen. In addition, slight red shift of the peak energy in the cathodoluminescence (CL) spectra of the AlGaN film is observed after the lift-off process, which is due to the relaxation of compressive stress in the film. Thus, separated AlGaN film is free from the disadvantages of using sapphire substrates such as the thermal mismatch, higher series resistance and poor heat dissipation so that it would enable high performance AlGaN-based ultraviolet (UV) light emitters.

In order to reduce NOx and smoke simultaneously and also to improve markedly the trade-off between smoke and NOx without deteriorating fuel consumption, natural gas was charged homogeneously into the intake air and was burned igniting by a small amount of gas oil injection in a four cylinder naturally-aspirated DI diesel engine. Combustion tests were carried out by changing the ratio of the amount of natural gas and the amount of gas oil first, secondarily the intake preheating temperature, and thirdly the EGR rate respectively. Effects of the respective parameter on the ignition and the burning rate of natural gas, exhaust emissions and specific fuel consumption were clarified experimentally. It is found that significant improvement of smoke-NOx trade-off can be obtained without deteriorating fuel consumption by the suitable combination between the natural gas charge rate, the intake preheating temperature and the EGR rate for each engine load condition.

This paper presents a new method for measuring random timing jitter or sinusoidal timing jitter in signals of telecommunication devices. The method uses a divide-by-M circuit to reduce the frequency and the number of clock samples, and applies the Hilbert transform to measure the timing jitter. This new frequency division method is validated with experimental data from a serializer-deserializer device and a modulated signal source generating a 2.5 GHz FM signal.

Purpose : Because of the shape of mandibular complete dentures, stress is the greatest along the midline. These dentures frequently fracture at or near this area. In order to contribute to the database of information available to dental professionals, the present study was undertaken to evaluate the distribution of stress and the fracture strength of denture bases, both before and after repair of a midline fracture.Materials and Methods : Twelve denture bases (each 3 mm thick) were constructed of polymethyl methacrylate acrylic resin. The stress pattern of each base was characterized by measuring changes in thermal emission from the surface of the denture base. The fracture strength of six of the bases was measured by bending them with a compression-bending tester until they fractured.Results : Stress concentration along the midline of the denture bases was observed. The mean fracture strengths of unbroken bases, repaired bases, and bases repaired with both resin and wire were 9.36, 2.28, and 4.34 N, respectively.Conclusion : Greater stress was observed along the midline in bases repaired with autopolymerizing resin only than in unbroken bases. In addition, the fracture strength of the repaired bases was only about 1/4 that of unbroken bases. It was observed that stress was less concentrated along the midline of bases repaired with autopolymerizing resin and a reinforcement wire compared to either repaired bases or unbroken bases.

A normally-off AlGaN/GaN MOS heterojunction field-effect transistor (MOS-HFET) with a recessed gate structure formed by selective area regrowth is demonstrated. The fabricated MOS-HFET exhibits a threshold voltage of 1.7 V with an improved hysteresis of 0.5 V as compared with a device fabricated by a conventional dry etching process. An analysis of capacitance–voltage (C–V) characteristics reveals that the dry etching process increases interface state density and introduces an additional discrete trap. The use of the selective area regrowth technique effectively suppresses such degradation, avoiding the MOS interface from being exposed to dry etching. The results presented in this paper indicate that the selective area regrowth technique is promising for the fabrication of normally-off AlGaN/GaN MOS-HFETs.

Important clues for achieving well-behaved AlGaN/GaN metal-oxide-semiconductor (MOS) devices with Al-based gate dielectrics were systematically investigated on the basis of electrical and physical characterizations. We found that low-temperature deposition of alumina insulators on AlGaN surfaces is crucial to improve the interface quality, thermal stability, and variability of MOS devices by suppressing Ga diffusion into the gate oxides. Moreover, aluminum oxynitride grown in a reactive nitric atmosphere was proven to expand the optimal process window that would improve the interface quality and to enhance immunity against charge injection into the gate dielectrics. The results constitute common guidelines for achieving high-performance and reliable AlGaN/GaN MOS devices.

The existing non-destructive inspection method employed for concrete structures uses high energy X-rays to detect internal flaws in concrete structures and iron reinforcing rods. In addition to this conventional method, the authors are developing an innovative inspection system that uses a mobile compact linac-driven neutron source that utilizes neutron backscattering, to measure the moisture distribution in concrete structures and estimate the corrosion probability distribution of iron reinforcing rods.

The previously reported carbonyl allylation of isatin derivatives with β-amido-functionalized allylstannanes is extended towards the challenging utilization of α-ketoesters as acyclic 1,2-dicarbonyl substrates.

GaN-based Gate Injection Transistors (GITs) with p-type gate over AlGaN/GaN heterojunction serve normally-off operations with low on-state resistances owing to the conductivity modulation by injection of holes. Established basic technologies on the GIT have shown promising features for switching applications. Further improvement of the performances would extend the applications and lead to the widespread use. In this paper, recent technologies on the GITs to improve the performances and extract the full potential are described. These include extension of the wafer diameter of Si up to 8 inch, InAlGaN quaternary alloy to reduce the series resistances, shortening the gate length to improve the device performances, integration of the gate driver and flip-chip assembly for faster switching.

Magnesium alloys containing rare earth elements are attractive as lightweight structural materials due to their low density, high-specific strength and recycling efficiency. Mg-Zn-Gd system is one of promising systems because of their high creep-resistant property[1]. It is reported that the coherent precipitation formation of the 14H long period stacking ordered structure (LPSO) in Mg-Zn-Gd system at temperatures higher than 623 K[2,3]. In this study, the 14H LPSO phase formed in Mg-Zn-Gd alloys were investigated by multi-scale characterization with X-ray computer tomography (X-CT), focused ion beam (FIB) tomography and aberration-corrected STEM observation for further understanding of the LPSO formation mechanism.The Mg89.5 Zn4.5 Gd6 alloy ingots were cast using high-frequency induction heating in argon atmosphere. The specimens were aged at 753 K for 24 h in air. The aged specimen were cut and polished mechanically for microstructural analysis. The micrometer resolution X-CT observation was performed by conventional scaner (Bruker SKY- SCAN1172) at 80 kV. The FIB tomography and energy dispersive x-ray spectroscopy (EDS) were carried out by a dual beam FIB-SEM system (Hitachi MI-4000L) with silicon drift detector (SDD) (Oxford X-Max(N)). The electron acceleration voltages were used with 3 kV for SEM observation and 10 kV for EDX spectroscopy. The 3D reconstruction from image series was performed by Avizo Fire 8.0 software (FEI). TEM/STEM observations were also performed by transmission electron microscopes (JEOL JEM 2100, JEM-ARM 200F) at the acceleration voltage of 200 keV.The LPSO phase was observed clearly in SEM image of the Mg89.5Zn4.5Gd6 alloy at 753 K for 2h (Fig.1 (a)). The atomic structure of LPSO phase observed as white gray region of SEM image was also confirmed as 14H LPSO structure by using selected electron diffraction patterns and high-resolution STEM observations. The elemental composition of LPSO phase was determined as Mg97Zn1Gd2 by EDS analyses. The 3D representation of the LPSO phase shown in Fig.1 (b) reveals that the shape of LPSO phase was disk-like. The calculated volume fraction of LPSO was about 20%, which is consistent with estimated value from initial composition. The stacked LPSO disks were distributed along 3D network. It is suggested that this 3D structure is concerned with the distribution of Mg3Gd compounds observed in as-cast specimens.jmicro;63/suppl_1/i25-a/DFU068F1F1DFU068F1Fig. 1.(a) SEM image of the Mg89.5Zn4.5Gd6 alloy aged at 753 K for 2h. (b) 3D representation of the tomographic reconstruction from SEM images. The soiled parts of the 3D volume are 14 H LPSO phase.

This paper demonstrates our dynamic power integrity control for eliminating the overkills/underkills due to the difference of power supply impedance between an automatic test equipment (ATE) and a practical operating environment of the device under test (DUT). It injects compensation currents into the power supply nodes on the ATE system in a feed-forward manner such that the ATE power supply waveform matches with the one on the customer's operating environment of the DUT. Experimental results of delay fault testing with 105 real silicon chips show that 48% of overkills/underkills due to the different power supply characteristics can be eliminated by our dynamic power integrity control. Furthermore, it was found that adjusting the magnitude of the power integrity control based on the chip-to-chip active power variation improves the correlation of the test results between the ATE and the customer environment, resulting in 95% of the overkills/underkills can be eliminated.

In radial compressors or blowers, a low solidity circular cascade diffuser (LSD) is one of the effective devices to improve the pressure recovery at design flow rate while guaranteeing a wide operating range. The improvement is mainly attributed to the so called secondary flow effect, which reduces the flow separation on the LSD blade at small flow rates. However, it is very difficult to find out the effective shape of the blade in order to promote this secondary flow effect. In this paper, a multipoint and multi-objective optimization technique is applied to design the LSD blade of a centrifugal blower. The optimization method has been developed at the von Karman Institute for Fluid Dynamics (VKI), which makes use of an evolutionary algorithm, a metamodel as a rapid exploration tool, and a high fidelity 3D Navier-Stokes solver. The optimization is aiming at improving the static pressure coefficient at design point and at low flow rate condition while constraining the slope of the lift coefficient curve. Seven detailed design parameters describing the shape and position of the LSD vane were introduced, e.g. the radial spacing between impeller exit and the LSD leading edge, the radial chord length and the mean camber angle distribution of the LSD blade with five control points. Moreover, a small tip clearance of the LSD blade was applied in order to activate and to stabilize the secondary flow effect at small flow rate condition. The optimized LSD blade has an extended operating range of 114 % towards smaller flow rate as compared to the baseline design without deteriorating the diffuser pressure recovery at design point. The diffuser pressure rise and operating flow range of the optimized LSD blade are experimentally verified. It is found that the optimized LSD blade shows good improvement of the blade loading in the whole operating range, while at small flow rate the flow separation on the LSD blade has been successfully suppressed by the secondary flow effect. This is fully corresponding to the CFD predictions and demonstrates the effectiveness of the optimization methodology, by limiting the experimental testing to only two geometries.

A new isolated Drive-by-Microwave (DBM) gate driver with a high-speed voltage monitoring for over current detection is proposed, which is composed of a 2.4GHz GaN/Si DBM transmitter, DBM receiver chip and compact isolated couplers in a low-cost printed circuit board. The fabricated DBM gate driver demonstrates a 200 Mbps isolated data transmission and a GaN power switching device's driving with a turn-on skew rate of 4.2kV/us. Furthermore, it successfully detects the isolated 1.0Mbps monitoring signal at the secondary side without any isolated voltage source by means of detecting the 2.4GHz return power changing that results from the impedance miss matching of the varicap diode at a receiver.

In this paper, we present a novel compact DC-DC converter IC in which normally-off GaN-GITs (Gate Injection Transistors) and gate drivers are integrated into one chip. The DC-DC converter IC can achieve higher efficiency and smaller chip size by reducing parasitic inductances between switching power devices and gate drivers. The gate driver, having a DCFL (Direct Coupled FET Logic) with a buffer amplifier which is consisted of a GaN-HFET (Hetero-junction FET) and GaN-GITs can operate with higher speed and lower power consumption. The fabricated DC-DC converter IC exhibits a peak efficiency as high as 86.6% at 2MHz for the 12V-1.8V conversion.

A low cost and compact isolated gate driver with Drive-by-Microwave technology is developed, which consists of 2.4 GHz GaN/Si transmitter and receiver chips and the butterfly isolation coupler that integrated in a printed circuit board based package. The fabricated DBM gate driver successfully demonstrated that it drove a GaN power switching device with a very fast switching. The fabricated DBM gate driver was implemented the multi-level output function, which has the potential to realize the gate voltage profile control of a power switching device for a waveform shaping. And this function can also contribute the power consumption saving of the gate driver itself by low power output at on-state and off-state other than turn-on and turn-off.

By positioning the completely rough wall locally on the hub side diffuser wall alone in the vaneless diffuser, the flow rate of rotating stall inception was decreased by 42 percent at a small pressure drop of less than 1 percent. This is based on the fact that the local reverse flow occurs first in the hub side in most centrifugal blowers with a backswept blade impeller. The three-dimensional boundary layer calculation shows that the increase in wall shear component normal to the main-flow direction markedly decreases the skewed angle of the three-dimensional boundary layer, and results in suppression of the three-dimensional separation. It is also clarified theoretically that the diffuser pressure recovery is hardly deteriorated by the rough wall positioned downstream of R = l.2 because the increase in the radial momentum change, resulting from reduction in the skewed angle of the three-dimensional boundary layer, supports the adverse pressure gradient.

The authors have proposed a new technique to suppress successfully the rotating stall in the vaneless diffuser. By positioning the completely rough wall between R=1.2 and 1.6 on the hub side diffuser wall alone, the flow rate of rotating stall inception was decreased by 42% at a small pressure drop less than 1% of the blower pressure rise. This is based on that the local reverse flow occurs firstly at the hub side in most centrifugal blowers with backswept blade impeller mainly depending on the distortion of tangential component of inlet main-flow velocity. The 3-D boundary layer calculation shows that the local reverse flow is decreased remarkably by an increase in wall friction, and it disappears if the friction coefficient is 0.01 about twice of the smooth wall. By analyzing the effect of wall friction and turbulence induced by the rough wall, it is clearly shown that the rough wall positioned in the limited region, where the wall-limiting streamline flow angle shows the negative maximum, is quite effective to suppress the rotating stall at a small drop of the diffuser pressure recovery.

The three-dimensional flow behavior in a low pressure steam turbine under the low load operation was analyzed numerically by applying the Modified FLIC (Fluid In Cell) method to the quasi three-dimensional flow computation. And it was also measured by using the five-hole Pitot probe in the scale-model turbine with the last stage. By comparing the calculated flow angles with the measured ones at the inlet and exit of the rotor, it is shown that the present computation method is a useful skill to predict an occurrence of the reverse flow in the last stage under the low load operation. Both calculated and experimental results show that the reverse flow occurs at the root of the rotor, if the axial exhaust Mach number becomes smaller than 0.3 even though the stator works well.

Luminescence properties of nanosized zinc oxide (ZnO) colloids greatly depend on their surface properties. These surface properties in turn are largely determined by the method of preparation. The procedure for producing ZnO colloids consists of two major steps: (1) preparing the precursor by reacting zinc acetate with ethanol and (2) hydrolyzing the precursor to form the colloid by using lithium hydroxide. The sample colloids in this study were prepared by hydrolyzing zinc acetate precursors containing various concentrations of Zn2+ with different concentrations of lithium hydroxide. The luminescence properties were evaluated by the energy difference, ΔE, between the band gap and the emission energy which were obtained from the onset of the absorption spectrum and the peak wavelength of the emission spectrum, respectively. The surface properties of ZnO particles were studied using thermal gravimetric and infrared techniques. ZnO particles produced via these procedures are not pure but have acetate (CH3C...

Various theories of organizational behaviors suggest that there should be significant relationships between the work-related variables and commitment to an organization. This study shows that, for a sample of 203 Japanese industrial workers, four components (attachment, internalization, normative, and continuance) of organizational commitment are predicted by organizational climate, supervisory behavior, organizational tenure, and role clarity. Implications for future research are discussed.

Nitridation process of a sapphire surface was investigated with atomic force microscopy (AFM), reflection high-energy electron diffraction (RHEED), and X-ray photoelectron spectroscopy (XPS) in order to reveal a general nitridation mechanism. It was found that the nitridation process consists of two steps. First, inter-mixing between nitrogen-related species and sapphire surface occurs forming hydrogenated Al oxynitride. This step does not change the surface morphology significantly. Second, crystalline AlN islands are gradually formed by further nitridation of hydrogenated Al oxynitride, resulting in a very rough surface.

In order to clarify the characteristics of combustion fluctuation in diesel engines quantitatively, the fluctuations of pressure and flame temperature were measured, and the root mean square value, the autocorrelation coefficient and the power spectrum density of the measured fluctuations were analyzed by comparing the cases with and without pilot injection. The following concluding remarks are obtained. (1) The frequency power spectrum of the in-cylinder pressure history is reduced markedly by pilot injection in two frequency ranges from 0.2 to 2.0 kHz and from 2 to 5 kHz. (2) The fluctuation of combustion pressure is dependent on the maximum rate of pressure rise, which is dependent on the ignition delay. (3) The maximum rms of the flame temperature fluctuation during diffusion combustion has a clear correlation with that of the pressure fluctuation in the initial combustion. (4) The fluctuation of the flame temperature during diffusion combustion has the characteristics of isotropic turbulence.

In this paper, we describe a GaN 3x3 matrix converter chipset, which are composed of a GaN integrated bidirectional switching chip and a GaN integrated gate drive transmitter chip using 5.0GHz Drive-by-Microwave technology. The extremely compact three phase AC-AC matrix converter such as a 25x18mm2 is realized by these GaN/Si integrated chips and novel isolated dividing couplers, which duplicate the gate signal with different references for dual-gate bidirectional switches and reduce gate lines and gate drive components by half. The proposed GaN 3x3 matrix converter is significantly more compact than the conventional one that requires numerous power switches, flywheel diodes, photo-couplers, isolated power supplies and gate drivers.

The effect of port water-injection on the exhaust NOx reduction was examined experimentally as well as theoretically. In the experiment, water was injected into each suction port of a 4 cylinder turbocharged DI diesel engine using gasoline injectors. The exhaust NOx was reduced significantly by port water-injection, and about 50% reduction in NOx concentration was obtained by injecting an amount of 0.035kg of water/kg of air under various engine operation conditions. By comparing between the experiment and the analysis based on the authors' two-zone model, it is shown that the NOx reduction is mainly caused by a decrease in the temperature of the burned gas resulting from an increase in the specific heat due to humidification.

To examine the retinal displacement following successful macular hole (MH) surgery with internal limiting membrane (ILM) peeling and gas tamponade, and to determine the correlation between the extent of displacement and the basal MH size.Retrospective, interventional, observational case series.The medical records of consecutive patients with an idiopathic MH that had undergone vitrectomy with ILM peeling and gas tamponade were studied. The distances between the optic disc and the intersection of 2 retinal vessels located nasal or temporal to the fovea were measured manually preoperatively (A), and 2 weeks and 1, 3, 6, and 12 months postoperatively (B), on the fundus autofluorescence or near-infrared images. The basal and minimum diameters of the MHs were measured in the spectral-domain optical coherence tomographic images. The correlations between the ratio of the retinal displacement (A - B/A) and basal diameters of the MHs were determined.Twenty-one eyes of 21 patients (9 men, mean age: 64.6 ± 8.4 years) were studied. Ten eyes (47.6%) had stage 2 MH, 9 eyes (42.9%) had stage 3 MH, and 2 eyes (9.5%) had stage 4 MH. The temporal retinal vessels were displaced 260.8 ± 145.8 μm toward the optic disc at 2 weeks postoperatively, which was significantly greater than the 91.1 ± 89.7 μm of the nasal retinal vessels (paired t test, P.001). The ratio of retinal displacement in the temporal field at 2 weeks was significantly correlated with the basal diameter of the MH (Spearman's rank correlation coeffieient = -0.476, P = .033.The greater displacement of the temporal retina than the nasal retina toward the optic disc postoperatively suggests that the temporal retina is more flexible and can be retracted toward the optic disc during the MH closure.

This paper reports enhancement effect of N2/O2 gas addition in thermal plasma irradiation on the spallation phenomena from polyamide-66 (PA66) specimens with water absorption. The polyamide materials are widely used, for example, in low-voltage circuit breakers and arcing horns as ablation material. In such devices, the polymer is often contacted with arc discharges to be ablated, which increases the arc current interruption ability of the circuit breakers. In our previous experiments, not only ablation but also spallation phenomena had been found to occur from PA66 specimens with water absorption by Ar thermal plasma irradiation. The present work was conducted to investigate effect of N2/O2 inclusion in the irradiating thermal plasma on the occurrence of spallation phenomena because the air circuit breaker was used in air. Relative oxygen admixture ratio to N2 was changed from 0% to 100% with a fixed heat flux irradiated to PA66 specimens. Results indicated that O2 inclusion effectively promotes the frequency of spallation particle ejection from PA66 specimen with 3 wt% water absorption.

Recently, there is an increasing need for methods of functionally testing RF devices to provide lower cost alternatives to testing RF communication systems. In this paper, a real-time functional testing method of RF-ICs using a digital tester is proposed as an alternative to conventional RF testing. The method is based on a concept of direct modulation. By employing the proposed method, the QPSK and 16-QAM signals can be generated with digital tester drivers. The method can directly compare the baseband data with its expected data through digital tester comparators without demodulation. Therefore, the proposed method does not require any modulator or demodulator. Moreover, the method can perform both a stress test of RF receivers by injecting modulation error and a margin test of RF transmitters by using a dual-threshold comparator.

Si submonolayer-by-submonolayer epitaxy or subatomic-layer epitaxy (SALE) from Si 2 H 6 on Si(001) has been carried out by repeating Si 2 H 6 exposure and surface excitation induced by the combination of substrate resistive heating and Ar + laser irradiation. As the average substrate temperature or the laser irradiation power increases, the surface morphology of a grown film changes from a convex shape to a concave shape through a trapezoid shape. The roughness of a flat area of the trapezoid film is within ±2A˚per growth thickness of 100A˚, and a substrate temperature window of∼ 15°C and a laser power window of∼ 0.25W, where such a flat growth surface and a constant growth rate are obtained, has been observed. The ranges of these windows have been estimated to correspond to the same variation of the surface temperature in the laser irradiation area during the laser irradiation. This result together with the result of the analyses on growth thickness distribution profiles suggests that the laser irradiation works as a thermal effect. Thus, in the Ar + -laser-assisted SALE method, the growth surface morphology then the growth mode is controlled by the surface temperature during the laser irradiation. An Ar + laser is a useful tool to control the surface temperature.

GaN has been grown on 3CSiCSi(001) at temperatures from 600 to 800°C by low pressure MOCVD using TMGa and NH3. The grown films were characterized by X-ray diffraction signals from the zinc-blende GaN(002) and the wurtzite GaN(0002) planes. An X-ray diffraction signal detected at 36.8° indicated the wurtzite GaN(1011) plane. The growth of the wurtzite GaN was suppressed by increasing the growth temperature. The annealing of the thick polycrystalline GaN in NH3 ambient at 800°C was found to cause the atomic displacement and sublimation. Zinc-blende GaN with suppressed wurtzite domain was obtained on 3CSiCSi(001) at 800°C by inserting a thin polycrystalline GaN buffer layer deposited at 600°C.

This paper reports the investigation of microdroplet sample preparation for phosphate, strontium and rubidium using X-ray fluorescence. Sample filter papers were prepared by drying under several different conditions and the front and the back sides of the filter papers were measured using X-ray fluorescence (XRF), scanning electron microscopy (SEM), X-ray diffraction (XRD), and electron-probe microanalysis (EPMA). It was reported by Murata and Murokado that the elemental distribution difference between the front and the back sides after drying the filter paper led to erratic data.1 It has been found that the intensity difference between the front and the back sides was due to the condensation of the material of interest on the surface of the filter papers and the amount of the condensed material on the filter paper was related to the temperature at which the filter paper was dried. Optimum temperature at which a filter paper is dried and an appropriate internal standard are essential to reproduci...

This paper reports the development of a simple method for measuring titanium dioxide in cosmetic products using X-ray fluorescence. A sample is prepared by stirring in a dispersion medium and then filtering with a 0.1 μm pore size membrane filter. The titanium dioxide particles trapped on the dried membrane filter are then measured with a wave-length dispersive X-ray fluorescence spectrometer. This sample preparation procedure was investigated using scanning electron microscopy (SEM), energy dispersive X-ray fluorescence (EDX) mapping, inductively coupled plasma atomic emission spectrometry (ICP-AES) and turbidimetry. Interferences can be separated from the titanium dioxide layer on the membrane filter with this preparation procedure. The relative standard deviation for the analysis is less than 0.4%, the recovery is more than 99.0%, and the calibration curve gives a correlation coefficient of R = 1.000. The detection limit for titanium dioxide using this procedure is 0.02% by weight in product. ...

The burned zone excess air ratio λ_d in the diffusion combustion process was analyzed using the two-zone model, and it was compared with the excess air ratio λ_f estimated using a steady diffusion flame model of the fuel spray. It is found that λ_d is dependent on the fuel spray penetration and ignition delay. If the premixed combustion fraction is less than 50%, the NO formation is minimally influenced by the excess air ratio during premixed combustion and is dependent on the excess air ratio λ_d which determines the maximum temperature during diffusion combustion. It is clarified by analysis of the two-zone model that the large reduction in NO_x due to timing retard is mainly caused by decreases in both combustion temperature and combustion pressure, and the small reduction in NO_x occurring when the nozzle-hole diameter is decreased, is due to a small decrease in combustion pressure resulting from a decrease in the heat release rate during premixed combustion., JSME international journal. Ser. B, Fluids and thermal engineering. 1996, 39(3), p.632-639

The proposed two-zone model of diesel combustion consists of a burned zone and an unburned zone, and the thermodynamic process is independent and adiabatic in each zone except that the air is entrained from the unburned zone to the burned zone under a specified condition of the excess air ratio during the combustion period. The excess air ratio in the diffusion combustion period is assumed to be constant in the present model. The calculated time histories of the burned-zone gas temperature and the cumulative soot formation were compared with the measured time histories of the flame temperature and the KL value based on the infrared two-color method. The calculated results agree qualitatively and partly quantitatively with the experimental results except for the swirl effect. As a result, it is shown that the present two-zone model analysis is very useful and effective in evaluating the combustion process in a DI diesel engine., JSME international journal. Ser. B, Fluids and thermal engineering. 1996, 39(1), p.185-192

Initial oxidation of gallium nitride (GaN) (0001) epilayers and subsequent growth of thermal oxides in dry oxygen ambient were investigated by means of x-ray photoelectron spectroscopy, spectroscopic ellipsometry, atomic force microscopy, and x-ray diffraction measurements. It was found that initial oxide formation tends to saturate at temperatures below 800 °C, whereas the selective growth of small oxide grains proceeds at dislocations in the epilayers, followed by noticeable grain growth, leading to a rough surface morphology at higher oxidation temperatures. This indicates that oxide growth and its morphology are crucially dependent on the defect density in the GaN epilayers. Structural characterizations also reveal that polycrystalline α- and β-phase Ga2O3 grains in an epitaxial relation with the GaN substrate are formed from the initial stage of the oxide growth. We propose a comprehensive model for GaN oxidation mediated by nitrogen removal and mass transport and discuss the model on the basis of ex...

Interface reactions between Ti-based electrodes and n-type GaN epilayers were investigated by synchrotron radiation X-ray photoelectron spectroscopy. Metallic Ga and thin TiN alloys were formed at the interface by subsequently depositing Al capping layers on ultrathin Ti layers even at room temperature. By comparing results from stacked Ti/Al and single Ti electrodes, the essential role of Al capping layers serving as an oxygen-scavenging element to produce reactive Ti underlayers was demonstrated. Further growth of the metallic interlayer during annealing was observed. A strategy for achieving low-resistance ohmic contacts to n-GaN with low-thermal-budget processing is discussed.