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Approximately 48 medical institutions in South Korea own and use blood irradiators; however, the quality control of blood irradiators is insufficient. This study was conducted to establish quality control procedures for blood irradiators using an alanine dosimeter and to ensure reliability of dosimetry. For dosimetry using alanine dosimeters, measurements were performed using an alanine dosimeter jig developed in this study to ensure dose delivery system reliability. Furthermore, the dose and dose distribution were verified, and the uncertainty was evaluated.

C), crystal structure became cleared accompanying achange of surface structure. In the temperature dependences of magnetization, phase transitions were observed at ~100 K for bothbefore and after post-growth treated samples which were not observed for the bulk. For both samples, ferromagnetic behaviors wereobserved above 100 K while it turned to ferrimagnetism at low temperature below 100 K. In particular, the ferrimagnetic behaviorbecame strong after the post-growth treatment. These results indicate that the post-growth annealing process plays an important role indetermining the physical properties of spinel CoMn

The flux distributions on the device in the solar reactor with the solar furnace were studied. This study aims to understand of characters of concentrated sun rays through KIER solar furnace and design of device shape for uniform heat distribution on the device surface. For the calculation of heat flux on the device with the KIER solar furnace, the optical modeling program Soltrace was used. At first, the KIER 45 kWth solar furnace and flat disk type device shape was simulated for understand of past experimental results. And then 3 cylinder shape device model and 1 conical shape device model was suggested and the heat flux intensity on the device was calculated. Finally, 5 models which is including flat disk type device shape, 3 cylinder shape, and 1 conical shape device models was calculated and compared. The results show that the concentrated sun rays from dish and heat flux intensity are has a directional characteristic concentrated to normal direction than perpendicular direction. The results will be applied to next solar demonstrations which are design of new solar reactor and new device shape.

In this study, the natural convection phenomenon of the air side and the forced convection phenomenon of the oil side were simulated in the radiator through a 3-D numerical analysis, and the total heat released by the oil side into the radiator heating plate and then to the air side was evaluated. Also, a quantitative analysis was carried out on the effect of each thermal resistance on the overall heat transfer coefficient through a 1-D thermal circuit analysis on the heat transfer mechanisms of the radiators considered in this study. In addition, for the diverse shapes of the heating plates considered in this study, the pressure drops of the oil side were quantitatively compared and evaluated. The temperatures at the air side and the oil side outlets of the radiators with 8 different fin shapes considered in this study had almost similar values showing a difference of +/-3% and, accordingly, the total heat transfer also showed similar heat dissipation performance in all the models. As a result of the 1-D thermal circuit analysis, in all the models considered in this study, while the thermal resistance of the air side accounted for 92% to 96% of the total, that of the oil side was 5 to 7%, and that of the heating plate showed a very small value of 0.02%.

Biomass is considered to be a major potential fuel and renewable resource for the future. In fact, there is high potential to produce the large amount of energy from biomass around the world. In this study, to obtain basic data for practical application of agricultural and forest by-products as fuel of heating system in agriculture, agricultural and forest biomass resources were surveyed, the pelletizer with capacity of was designed and manufactured and pellets were made by the pelletizer. High heating value, ash content, etc. of pellets made of agricultural and forest by-products were estimated. Straw of rice was the largest agricultural biomass in 2009 and the total amount of rice straw converted into energy of TOE. And in 2009, amount of forest by-product converted into energy of TOE. High heating values of pellets made of stem and seed of rape, stem of oat, rice straw and rice husk were 16,034, 16,026, 16,089, 15,650, respectively. High heating values of pellets made of agricultural by-products were average 83.6% compared to that of wood pellet. Average bulk density of pellets made of stem and seed of rape, stem of oat, rice straw and rice husk was (). Ash contents of the pellets were 6.6, 7, 6.2, 5.5, 33% respectively. Rice husk pellet produced the largest ash content compared to other kinds of pellets.

In this study, a reinforced silver-embedded silica matrix was designed by utilizing the interaction between the [AlO4]− tetrahedral and the Ag+ in sol–gel process using sodium silicate as a silica precursor. The Ag+ mole ratio in each sample was significantly varied to examine the influence of silver concentration on the properties of the final product. Aluminium ions were added to reinforce and improve the chemical durability of silver-embedded silica. A templated sample at Al/Ag = 1 atomic ratio was also synthesized to attempt a possibility of controlling porosity of the final product. Also, a sample neither embedded with silver nor templated was synthesized and characterized to serve as reference. The material at Al/Ag = 1 was found to have a desirable properties, compared to its counterparts, before and even after calcination up to 1000 °C. The results demonstrate that materials with desirable properties can be obtained by this unprecedented method while utilizing sodium silicate, which is relatively cheap, as a silica precursor. This may significantly boost the industrial production of the silver-embedded silicas for various applications.

Low resistance p-layers are achieved in this paper using a graphite cap to protect SiC surface from out-diffusion of Si during high temperature post-implantation annealing, which is carried out to maximize the activation of Al dopant in 4H-SiC. With a graphite layer converted from photoresist, as high as 1700 and 1800oC post-implantation annealing is able to be used. Low RMS roughness of surface after high temperature annealing shows the effectiveness of the graphite cap. Small sheet resistance and resistivity are also achieved from the high temperature annealing. At room temperature, sheet resistances of 9.8 and 1.3 k/□, and the corresponding resistivities of 235 and 31 m-cm are obtained from 1700 and 1800oC annealed samples, respectively. The Al ionization energy extracted from Arrhenius plot is also close to the typical reported values. Therefore, it can be concluded that, using graphite cap could help to activate the Al dopant effectively during high temperature annealing.

This present work investigated the influence of welding conditions, such as welding current, diameter of welding wire on the microstructural change, and mechanical properties of TIG welded joint in extruded AZ31B Mg plate. It was found that a good and sound welded joint was achieved in all welding conditions. The grain size decreased with increasing welding current and decreasing diameter of welding wire. In addition, the second phases were homogeneously distributed in the grain and grain boundary as the welding current and the diameter of the welding wire were decreased. β discontinuous precipitates were observed in the welded joint; this microstructure has not been reported by previous researches investigating AZ31B Mg alloy. The hardness value was affected by the existence state of the second phase and the hardness of the welded joint region was lower than the other regions in welded AZ31B Mg alloy. The strength of the welded joint region was influenced by the grain size and had more than 90 %, compared to that of ASTM standard specification.

A comparison of the volume conductivity measured by standard four-electrode (FE) and four-point probe (FPP) methods for graphite-based powdery polypropylene (PP) and poly(vinylidene fluoride) (PVDF) composite bar specimens was made in this study. Significant difference in the conductivity data obtained by standard FE and FPP methods was found for highly conductive PP and PVDF composites which were molded from hybrid carbon/polymer powders dry-blended in a high-speed mixer and jar ball mill. However, it was found that the conductivity values were approximately equal for moderately conductive PVDF/graphite and PP/graphite composites. It was also shown that polishing the specimens to remove 100–150 μm of the surface layer and decrease surface roughness did not bring about significant changes in conductivity values. Consequently, bulk non-uniformity and inhomogeneity of graphite-based polymer material were considered to be the most probable sources of the difference in the volume conductivity values measured by the FE and FPP methods.

The organic-inorganic hybrid nanocomposites were successfully obtained by the sol-gel process with tetraethylorthosilicate (TEOS) as an inorganic networking precursor and 2-hydroxyethylmethacrylate (HEMA) as the nonsurfactant template in the presence of benzil initiator. The characteristics of the obtained hybrid were examined by means of TGA, FTIR, SEM, and TEM. The synthesized HEMA/SiO2 hybrid was nearly transparent, monolithic, and monodispersed with the average size of 25 nm. It was found that the hybrid structure could be defined by intertwining organic and inorganic polymeric networks.

Thin foil hot press process was used to fabricate metal/intermetallic compound laminate composites to induce self-propagating high-temperature (SHS) reaction between different pure metal sheets. In the present study, Ni/Ni-aluminide and Ti/Ti-aluminide laminate composites were fabricated through diffusion bonding, reaction synthesis and post-heat treatment of alternatively stacked pure Ni/Al and Ti/Al foils, respectively. Thick intermetallic layers of NiAl and TiAl3 were formed by a self-propagating high-temperature synthesis (SHS) reaction, and thin continuous layers of Ni3Al and TiAl were formed by a solid-state diffusion. Also, Ni/Ni-aluminide//Ti/Ti-aluminide laminate composite, considered as a functionally gradient material, was manufactured from stacked foils of pure Ni, Ti and Al in order of Ni/Al/Ni/.../Ni/Al /Ti/.../Ti/Al/Ti. Nb/Nb-aluminide laminate composite was manufactured with pure Nb and Al multilayered foils, consisting of fine Nb/Nb3Al/Nb2Al/NbAl3 layer structure.

In this report, nanopatterns consisting of an organic polymer film were fabricated using a simple detachment method. The method used a patterned ultraviolet (UV) curable poly(urethane acrylate) (PUA) as a mold and an organic polymer layer as a template material. A thin film was prepared by spin coating and then annealed below the glass transient temperature while in physical contact with the PUA mold. The polymer layer in contact with the mold was detached due to the difference in adhesion force, resulting in a well-defined nanoarray of the polymer template. Nanopatterns as small as 70 nm lines were fabricated using this approach.

Non-aggregated nanoscale α-Al2O3 powders with average size ranging from 7 to 20 nm were prepared successfully at various conditions with the use of the hydrated aluminum sulfate extracted from kaolin by polyacrylamine (PAA) gel method. The calcination temperature was relatively lower about 100°C, compared to conventional solid-state reaction. It revealed that PAA worked as a chelating agent to disperse the Al3+ ions homogeneously, and the size of alumina nanoparticles could be controlled by varying the concentration of crosslinking agent.

Two composites of five plies of STS/Al/Al/Al/STS and STS/Al/STS/Al/STS were produced from ferritic stainless steel (STS 430) and aluminum alloy (AA 3003) sheets by roll-cladding at elevated temperature. In order to analyze the strain states during roll-cladding, the evolution of crystallographic textures at different through-thickness positions in the roll-clad composites was investigated. The finite element method (FEM) was employed to simulate the co-deformation of the different sheets and to determine the stresses and strains acting in the five-ply composites during roll-cladding. The strain states derived from the FEM simulations were used to model the texture evolution in the individual sheets of the roll-clad composites. Friction conditions were determined in a parametric study by fitting the overall thickness strains and modeled textures to the results obtained experimentally.

In this study, the microstructure and the texture development in Al–Zn–Mg–Cu–Zr alloys with/without 0.1%Sc has been investigated after extrusion, cold rolling, and aging treatment. After aging treatment, in Al alloy without Sc recrystallized equiaxed grains are obtained, while in Al alloy with Sc fine grains with an average size of 0.1~0.3 μm are obtained. After cold rolling, in case of the sample from the cross section (CS) to which Sc was added, texture with {112}(Cu) + weak {123}(S) component was developed while in case of the sample from longitudinal section (LS) to which Sc was added, texture with strong β-fiber + {110}(Goss) components was developed. In case of CS and LS without Sc, texture of β-fiber was developed. After solid solution treatment and aging treatment, Al alloys (LS and CS) with Sc had rolling texture while Al alloys without Sc had random texture. The role of these differently developed textures in the plastic behavior, such as the normal anisotropy r-value (the plastic strain ratio) and planar anisotropy r-values are discussed.

The mechanical properties of Al–5%Cu–1.3%Li–0.4%Mg–0.4%Ag–1.16%Zr alloys without Mn and with 0.3%, 0.6% and 1.2% Mn have been investigated after the aging at the temperatures of 90, 150, 180, and 230 oC. With Mn addition the alloys show a good work-hardening property, and the elongation of alloys increases. With the 0.6% Mn the best elongation can be obtained. The strength of alloys with 0.3% or 1.2% Mn is lower than that of the alloy without Mn, whereas the strength of alloy with 0.6% Mn is almost same as that of the alloy without Mn. In the alloy with 0.6% Mn aged at 180 oC for 12 hours the optimum properties – combination of tensile strength and elongation, 620 MPa and over 12 %, respectively – are obtained. These favorable effects by a proper Mn addition are considered to come mainly from the Mn-dispersoid to prevent strain localization normally associated with the shearable precipitates.

Liquid electrolyte volume is a key driver in the lifetime and overall size of microfabricated biodegradable batteries. Harnessing liquid from the body to serve as the battery electrolyte may, therefore, be desirable; however, for stable operation, maintaining a constant environment inside the electrochemical cell is required even in the presence of changing body conditions. We report a biodegradable battery featuring a solid electrolyte of sodium chloride (NaCl) and polycaprolactone (PCL). This approach harnesses the body fluid that diffuses into the cell as an element of the electrolyte; however, the large excess of ionic material suspended in the PCL holds intracellular conditions constant. A constant discharge profile can then be achieved even in the presence of varying external aqueous conditions, enabling compact, stably-performing cells.

This work focuses on the strain states of the mid AA 3003 strip sandwiched in between either AA 3003 sheets or STS 430 sheets. For that purpose, the strain states at various through-thickness layers were analyzed by measurements of crystallographic texture and by simulations with the finite element method (FEM). During sandwich rolling, the material property of outer sheets of sandwich samples played an important role in the evolution of the strain states and the corresponding texture formation. In the mid AA 3003 sheets, rolling with the harder outer sheets gave rise to pronounced through-thickness texture gradients, whereas fairly uniform strain states prevailed during rolling with the outer sheets of the same AA 3003.

Strain distribution on the cross-sectional area of the workpiece (X plane) normal to the pressing direction was examined based on the strain contours obtained in full 3D along various diameter directions. The largest inhomogeneous strain distribution developed along vertical direction of the cross-sectional area, while the strain distribution along the transverse direction was relatively uniform. Variation in magnitude and sign of shear and normal stress components during passage of the workpiece through the die was computed. Among the three shear components acting on the shear planes within the die corner region where ECAE deformation is confined to occur, the shear stress along the diagonal direction connecting the sharp and round corners is overwhelmingly dominant over the other shear components. Near pure shear condition is only observed on the plane that is in the middle of the die corner region where two channels are interconnected, being inclined by 45° to the pressing direction. As shear and normal components additionally considered in 3D is much smaller than the other components considered in 2D, stress state in 3D is can be approximated to be that in 2D.

Loose beds of hollow fly ash particles (cenospheres) were pressure infiltrated with A356 alloy melt to fabricate metal-matrix syntactic foam, using applied pressure up to 275 kPa. The volume fractions of cenospheres in the composites were in the range of 20–65%. The processing variables included melt temperature, gas pressure and particles size of fly ash. The effect of these processing variables on the microstructure and compressive properties of the synthesized composites is characterized. Compressive tests performed on these metal-matrix composites containing different volume fractions of hollow fly ash particles showed that their yield stress, Young's modulus, and plateau stress increase with an increase in the density. Variations in the compressive properties of the composites in the present study were compared with other foam materials.

Aluminium doped zinc oxide (ZnO:Al) films were deposited on glass substrate by DC magnetron sputtering from a ZnO target mixed with a various wt% Al2O3. The lowest resistivity of 8.54×10−4 Ω cm as well as over 90% of optical transmission of the ZnO:Al film was obtained with a 2 wt% Al2O3 doped ZnO target for the following processing conditions: substrate temperature of 400 ∘C; discharge power of 40 W; Ar pressure of 1 mtorr. In order to reduce the electrical resistivity, positive and negative biases (−60 V to +40 V) were applied to the substrate. We report the effects of substrate bias on the structure, deposition rate, electrical properties, and optical transmission of ZnO:Al thin films. Films deposited with either positive or negative bias have strong (002) preferred orientation. The electrical resistivity of the film decreases significantly as either the positive or negative bias increases. However, as the positive and the negative bias increases over 30 V and −40 V, the resistivity decreases. Films with electrical resistivity as low as 4.3×10−4 Ω cm and optical transmittance of 91.5% were obtained with a substrate bias of +30 V.

Effective strain distribution within a sample subjected to equal channel angular extrusion up to 4 passes was examined in full 3-D using a commercial FVM code. Strain uniformity was evaluated by using particle tracking method and measuring strain distribution on the transverse and longitudinal planes. Strain uniformity was achieved after 4 passes when BC route was used.

This study was designed to evaluate the effect of polyethylene glycol (PEG) and nonsteroidal anti-inflammatory drug (ibuprofen) on the prevention of postoperative tissue adhesion. For this, we synthesized poly(L-lactic acid)-PEG diblock copolymers and used them to prepare ibuprofen-loaded films as tissue adhesion barrier films. We also prepared lower critical solution temperature (LCST)-controllable Pluronic F127/F68 mixtures including mildly crosslinked alginate and ibuprofen as tissue adhesion barrier gels. The prepared films and gels with/without ibuprofen were evaluated by the observations of peritoneal tissue adhesion via animal study using a rat model.

The effect of beryllium (Be) on the precipitation behaviors and mechanical properties of Al–Cu–Li–Mg–Zr–(Ag) alloys was investigated. The results show that adding 0.02%Be to Al–Cu–Li–Mg–Zr–(Ag) alloys, the elongation of the alloy increased without significant decrease in strength and the aging response was accelerated. In a Al–Cu–Li–Mg–Zr–(Ag) alloy, G.P. zone was formed at early aging time (2 h) and T1 and q′ phases were formed at peak-aging and over-aging times, while in Al–Cu–Li–Mg–Zr–(Ag)–Be alloys T1 and q′ phases were formed at early aging time (2 h) and the density of q′ phase was very low and fine T1 phases were homogeneously distributed at peak-aging and over-aging times.

Ni/Ni-aluminide//Ti/Ti-aluminide laminate composite, considered as a functionally gradient material, was manufactured by thin foil hot press technique. Thick intermetallic layers of NiAl and TiAl3 were formed by a self-propagating high-temperature synthesis (SHS) reaction, and thin continuous layers of Ni3Al and TiAl were formed by a solid-state diffusion. Fracture resistance with loading along the crack arrester direction is higher than crack divider direction due to the interruption of crack growth in metal layers. The Ni3Al and NiAl intermetallic layer showed cleavage and intergranular fracture behavior, respectively, while the fracture mode of TiAl3 layer was found to be a intragranular cleavage. The debonding between metal and intermetallic layer and the pores were observed in the Ni/Ni-aluminide layers, resulting in the lower fracture resistance.

The synthesis of beta-alumina powder by microwave heating of the precipitate obtained through solution-precipitate techniques was described. A homogeneous mixture of Al2(SO4)3·18H2O and Na2SO4·10H2O was precipitated by dropping the mixed solution of kaolin-derived aluminum sulfate and sodium hydroxide into ethanol with agitation by stirring. The precipitates were calcined at various temperatures for 1 h under conventional and microwave heating process for obtaining the beta-alumina powder with the structure consisting of β- and β″-alumina phases with a larger amount of β″-alumina phase. The amount of β″-alumina phase in the microwave-calcined samples was larger than that in the conventionally calcined samples.

This letter reports wafer-bonded p-n heterojunction diodes, which consist of GaAs and chemomechanically polished N-polar GaN. The measured I-V and C-V show well-behaved p-n junction characteristics. The built-in voltage extrapolated from the C-V is 0.2 V less than the theoretical, suggesting the existence of interface states. However, this offset is much less than that (1.14 V) reported of wafer-bonded GaAs/Ga-polar GaN p-n diodes. The limited maximum current suggests pinning of the Fermi level at interface traps near the conduction band accessed under forward bias. Yet, this junction shows promise as a collector junction for wafer-bonded devices to achieve higher breakdown voltages.

Ductile iron castings with 2, 3, 4, 6, 8, and 25 mm thickness and various amount of rare earth elements (RE) (from 0 to 0.04%), were cast in sand molds to identify the effects of sample thickness and the content of RE% on microstructural formation and selected mechanical properties. The effects of RE content and sample thickness on microstructural formation, including on graphite nodule count, graphite nodule shape, spherodization, and ferrite amount, were observed. The yield strength of the samples with RE within the range investigated were lower than those of the specimens without RE. The elongation was improved with the addition of RE up to 0.03% in ductile iron castings. The additions of 0.02% RE caused a smaller graphite nodule size and a higher number of graphite nodules than those in the specimen without RE at all levels of RE addition; the nodule count decreased with increase in section size. The chill zones were observed in the 2 mm thick samples, but were absent in the samples from castings which were thicker than 2 mm, irrespective of the addition of RE. The nodularity of graphite nodules improved due to the addition of 0.02–0.04% RE. The specimens with RE content up to 0.03% had a lower tensile strength and hardness, higher elongation than that of the specimens without RE. The ferrite content in all castings increased with additions of 0.02% RE. The tensile strengths of the 2 and 3 mm thick samples were also estimated using the relationship between strength and hardness, obtained from the data on the tensile strength and hardness of the 25 mm thick samples.

In the presence of sodium sulfate as a flux, α-alumina particles, composed of highly aggregated platelets, were synthesized by conventional thermal and microwave heating of Al2(SO4)3 powders at 900–1100 °C for 1 h in an alumina crucible. The size of α-alumina platelets increased with increasing flux concentrations and temperatures in both conditions of conventional thermal and microwave heating. However, the sizes and size distributions of α-alumina platelets obtained by microwave heating were smaller and narrower, relatively, compared to those obtained by conventional thermal heating. It was assumed that microwaves had a significant non-thermal effect in the stage of nucleation and crystal growth of α-alumina.

The dependence on nickel oxide thickness in unidirectional and isotropic exchange-coupled NiO/NiFe bilayer films was investigated by magnetic force microscopy to better understand exchange biasing at microscopic length scales. As the NiO thickness increased, the domain structure of unidirectional biased films formed smaller and more complex in-plane domains. By contrast, for the isotropically coupled films, large domains generally formed with increasing NiO thickness including a new cross type domain with out-of-plane magnetization orientation. The density of the cross domain is proportional to exchange biasing field, and the fact that the domain mainly originated from the strongest exchange coupled region was confirmed by imaging in an applied external field during a magnetization cycle.

The wear behavior of new lead free metal matrix composite (MMC), centrifugally cast copper alloy graphite (C90300–10%graphite) composite (CG) is studied in comparison to a commonly used leaded copper (LC) alloy (18–22% Pb). Tribological tests were conducted with pins made from these materials and tested against a SAE 1045 steel counterface. The CG material showed higher wear resistance than the LC in the load range investigated (27–118 N). The CG and the LC showed similar friction coefficient (0.38) values at a low load of 27 N, where as at 118 N the CG had a slightly higher friction coefficient than the LC against the 1045 steel counterface. Transfer of material from the CG and the LC pins resulted in lowering the wear rate of the counterface as measured by the weight loss of the steel counterface. At the load of 27 N, the CG composite seems to be a viable substitute for the LC. For other loads modified versions of the CG are likely to provide optimum substitutes for the LC. Observations on structure, composition and morphology of surface, subsurface and wear debris was utilized in understanding the wear properties in each material.

Polypyrrole (PPy) was polymerized chemically and electrochemically in sequence on a polyester (PET) woven fabric, giving rise to PET fabric/PPy composite with high electrical conductivity. In the chemical polymerization, pyrrole dissolved in an aqueous solution without or with polyvinyl alcohol as a surfactant was first sprayed on the PET fabric and oxidized by spraying an aqueous solution of an oxidant and a dopant. Electrochemical polymerization was carried out in an aqueous electrolyte solution by applying a constant current density to the PET fabric coated with chemically polymerized PPy and a stainless steel plate as the working and the counter electrodes, respectively. We investigated the effects of the chemical or the electrochemical polymerization conditions on the properties of the resulting composite such as surface morphology, electrical conductivity, environmental stability, and electromagnetic interference shielding effectiveness (EMI SE). We found that the composite shielded EMI by absorption as well as reflection and that EMI shielding through reflection increased with the electrical conductivity. The specific volume resistivity of the composite prepared in this study was extremely low as 0.2 Ω cm and EMI SE was in the practically useful range of about 36 dB over a wide frequency range up to 1.5 GHz.

The morphology, composition and crystallinity of both precipitator (solid) and cenosphere (hollow) fly ash particles of different sizes were studied with scanning electron microscopy (SEM), EDX, and X-ray diffraction (XRD). Bulk density, tap density and real density of both precipitator and cenosphere particles of different sizes as well as the wall thickness to diameter ratio of cenosphere particles were measured. The microhardness of individual fly ash particles embedded in the matrix of aluminum alloy was also measured. The crystalline to amorphous ratio weight percentage in fly ash particles, and the weight or volume fraction of each crystalline component varies with the particle size. The crystallinity of precipitator particles increased as the particle size increases, whereas the crystallinity of cenosphere decreased as the particle size increases. The elastic modulus of fly ash was estimated from the crystallinity of fly ash and the volume fraction of each component, using the rule of mixtures. The calculated upper limits for Young's modulus of precipitator particles were 126 GPa for particles in the size range 150–250 μm and 98 GPa for particles in the size range 5–10 μm. Young's modulus of cenosphere particles was estimated to be approximately in the range of 13–17 GPa in all particle size ranges. The hardness of the larger precipitator fly ash particles (120 μm) exhibited a wide scatter in the range of 160–400 kg mm−2, while the hardness of the smaller size precipitator particles (20 μm) were in a narrow range from 250 to 270 kg mm−2.

The design space of conventional semiconductor devices - from the materials point of view - is currently set by heteroepitaxy, whose capability is strongly limited by lattice parameters and structures of materials of interest. Heterostructures of substantially different semiconductors may offer significant advantages in device design, but many of them are likely heteroepitaxy-incompatible. In such cases, direct wafer-bonding can be exploited, in which materials of interest are separately grown and then their heterostructures formed by thermo-compression. InGaAs, with its superior electron mobility and injection velocity, is considered as the best candidate material for achieving electronic devices in THz applications, whereas III-N has proven its promise in high-power applications. Thus, transistors consisting of InGaAs channel and III-N drain may potentially attain both the high-speed and high-power performances. The first bonded aperture vertical electron transistor (BAVET) with In 0.53 Ga 0.47 As channel and Ga-polar InGaN/GaN drain was demonstrated in 2009 [1], and further improvements on it have also been reported [2], [3]. Here, we demonstrate the first BAVET consisting of In 0.53 Ga 0.47 As channel and N-polar In 0.1 Ga 0.9 N/GaN drain, which has an inherent advantage over Ga-polar InGaN/GaN drain, as discussed below.

We review the design, fabrication, and characterization of 1.55-/spl mu/m lattice-matched vertical-cavity surface-emitting lasers, operating continuous wave up to 88/spl deg/C. For one embodiment, the threshold current is 800 /spl mu/A, the differential quantum efficiency is 23%, and the maximum output power is more than 1 mW at 20/spl deg/C and 110 /spl mu/W at 80/spl deg/C. The basic structure consists of AlAsSb-AlGaAsSb mirrors, which provide both high reflectivity and an InP-lattice-matched structure. The quaternary mirrors have poor electrical and thermal conductivities, which can raise the device temperature. However, a double-intracavity-contacted structure along with thick n-type InP cladding layers circumvents these drawbacks and finally leads to an excellent performance. The measured voltage and thermal impedances are much lower for the intracavity-contacted device than an air-post structure in which current is injected through the Sb-based quaternary mirror. The structure utilizes an undercut aperture for current and optical confinement. The aperture reduces scattering loss at the etched mirror and contributes to high differential efficiency and low threshold current density.

Plumbing components fabricated from copper base alloys containing lead, pose health and environmental problems, and there is a need to find suitable alternatives to lead which can impart comparable machinability to cast copper alloys. Bismuth and selenium are two potential substitutes for lead, but their cost is high and their toxicity is in question. In the present work, graphite particles have been substituted for lead in a cast copper alloy. Graphite is low in cost, non-toxic, and our previous work showed that it imparts machinability to cast copper alloys similar to lead. However, very limited information is available on the corrosion behavior of cast copper alloys containing graphite particles. In this study, C90300 copper alloy containing titanium as the wetting agent and graphite particles were cast using a stir casting technique. The cast microstructure of this alloy has α-dendrites with graphite and a titanium rich intermetallic phase in the interdendritic regions; the graphite is presumably changed to titanium carbide formed on the surface of graphite. The corrosion and dealloying of (a) the base C90300 copper alloy, (b) the base copper alloy containing only titanium, and (c) C90300 copper alloy containing graphite particles and titanium were studied in aggressive aqueous solutions. Two types of corrosion tests have been carried out: (1) 17-day Australian test, and (2) 1-year Rockwell test. In both the 17-day Australian test and the 1-year Rockwell test, the copper alloys containing both graphite and titanium, as well as the copper alloy containing only titanium gained weight. Dealloying penetration of the graphite containing copper alloy is observed to be only slightly higher than that of the base copper alloy, but microhardness at the dealloyed layer of the composite containing graphite and titanium is higher than the base alloy. Electrochemical measurements suggest that the addition of graphite to the copper base alloy may not significantly alter the corrosion characteristics of the base alloy.

Although quantum-dot (QD) lasers are yet to reach their promise of ultralow threshold and high characteristic temperature because of QD size nonuniformity, we have found that they can be used to effectively limit the lateral diffusion of carriers in the active region, enabling the scaling of lasers to small lateral dimensions. Although oxide apertures continue to enable improved performance in vertical-cavity surface-emitting lasers (VCSEL's) by reducing optical losses and current spreading, lateral carrier losses remain uncontrolled. We investigate QD active material in which lateral diffusion is intentionally reduced. Cathodoluminescence (CL) results demonstrate reduced lateral diffusion in the material with which we expect 50% reduction in the threshold current for 1-/spl mu/m-wide edge-emitters or 5-/spl mu/m-diameter VCSEL's. We have made QD stripe lasers with submicrometer widths that lase from the ground state and have quantified the lateral carrier reduction in the QD laser active region. We show empirically that the degree of lateral carrier confinement is dependent on the quantum state from which lasing occurs and demonstrate 63% reduction in lateral carrier leakage for the ground-state lasers. Finally, the scaling of threshold current in QD VCSEL's is compared with that of quantum-well (QW) VCSEL's by numerical modeling for future design considerations.

Superplasticity was investigated in powder-metallurgy (PM) processed 7475Al+0.7Zr alloy. Strain-rate-change (SRC) tests were carried out at various temperatures to examine the relationship between strain rate and flow stress. After the compensation by threshold stress, the superplastic flow was found to be well correlated with lattice diffusivity in aluminium, like that in the ingot-metallurgy (IM) processed 7475Al alloy having a coarser grain size. Large tensile elongations of up to 1000% could be obtained at a very high strain rate near 10 −1 s −1 and at 515°C. Short fibre formation was observed after the superplastic deformation. This formation seemed to be related to liquid formation on the grain boundaries and similar evidences were found over a wide range of temperature, not necessarily near the incipient melting point.

An experimental study was conducted on the mixing quality of two-phase slurries in the model SiC–water system using a gravimetric technique with a view to determining the influence of impeller geometry and baffles on the uniformity of distribution of SiC in the mixture. A three-blade paddle with different blade angles and a variable-pitch blade impeller (A-3) were used for stirring the mixture at various rotational speeds. The results show that SiC concentration variation during stirring in the absence of baffles was 7.5 vol.%, whereas in the presence of four vertical baffles the concentration variation was reduced to 2 vol.%. The power consumption for homogeneous mixing varied between 17.5 and 175 W vol.−1 depending upon the type of impeller and its rotational speed. A semi-empirical correlation for obtaining uniform mixing has been developed based on the Reynolds number, the power number and the Froude number for stirred SiC–water slurries. The results on inhomogeneity of silicon carbide in water concentration during mixing are in close agreement with the modeling studies by previous workers on the water–SiC system, and with limited experimental studies on the real molten aluminum–SiC system used to cast metal–matrix composites.

Particle pushing phenomena during solidification in the melt containing a particle lighter than the melt under the influence of centrifugal forces is described. This phenomena is observed in centrifugally cast copper alloys originally containing an average of 7 vol% graphite particles, cast in a 9.5-cm outer diameter mold rotating at 800 and 1900 rpm. A model to calculate the critical interface velocity, depending on the centrifugal force and the location of the cellular interface where the particle interacts with the interface, is proposed, and the particle pushing criterion is discussed. It is found that as the particle velocity increases with increasing the rotational speed of the mold, the effect of the particle velocity on the critical interface velocity increases; in addition the critical interface velocity is lowest at the tip of the cellular interface, and increases with distance from the tip of the interface. The critical interface velocity calculated in copper alloy containing 5 μm graphite cast in a 9.5-cm outer diameter mold rotating at 800 rpm (1.5×10 −3 m s −1 ) is higher than the interface velocity calculated for casting in a mold rotating at 1750 rpm (5×10 −4 m s −1 ) obtained numerically by Kang and Rohatgi (C.G. Kang, P.K. Rohatgi, Met. Trans. 27B (1996) 277). The fact that the actual interface velocity is lower than the critical interface velocity leads to pushing of particles by the growing dendrites in the last freezing interdendritic regions, as observed experimentally.

Interaction between moving solid/liquid interfaces and particles during solidification of alloys has been analyzed. A particle pushing criterion which incorporates the diffusion of the solute between the particle and the interface is proposed. In addition, the stability of the interface behind the particle is discussed. The shape of the interface behind the particle was obtained in terms of the ratio of the diffusion coefficient of the solute to the velocity of the interface (D/V). Based on this, the critical interface velocity was calculated under steady state conditions. It was found that the concentration of the solute behind the particle increases with increasing the interface velocity; in addition at high interface velocity the curvature of the interface is independent of interface velocities. It was found that the critical interface velocity under steady state conditions is one order lower than the critical interface velocity calculated numerically by Wu et al. in Al-Si alloy containing SiC particles.

This study aims to develop a facility that can irradiate subjects with a desired low dose, which can be used to assess the biological effects of low-dose radiation. We develop a single-occupancy mouse-cage and shelf system with adjustable geometric parameters, such as the distances and angles of the cages relative to the collimator. We assess the irradiation-level accuracy using two measurement methods. First, we calculate the angle and distance of each mouse cage relative to the irradiator. We employ a Monte Carlo n-particle simulation for all of the cages at a given distance from the radiation source to calculate the air kerma and the relative absorbed dose in the in-house designed shelving system; these are found to be approximately 0.108 and 0.109 Gy, respectively. Second, we measure the relative absorbed dose using glass dosimeters inserted directly into the heads and bodies of the mice. For a conventional irradiation system, the irradiation measurements show a maximum discrepancy of 42% between the absorbed and desired doses, whereas a discrepancy of only 6% from the desired dose is found for the designed mouse apartment system. In addition, multi-mouse cages are shown to yield to significantly greater differences in the mouse head and body relative absorbed doses, compared to the discrepancies found for single-occupancy cages in the conventional irradiation system. Our findings suggest that the in-house shelving system has greater reliability for the biological analysis of the effects of low-dose radiation.

Al2O3 films were grown in situ by metalorganic chemical vapor deposition at 900 °C on GaN of both Ga- and N-face polarities. High-resolution transmission electron microscopy revealed that the Al2O3 films were crystalline and primarily γ-phase. The Al2O3/Ga-GaN and Al2O3/N-GaN interfaces were both atomically sharp, and the latter further exhibited a biatomic step feature. The corresponding current-voltage (J-V) characteristics were measured on a metal-Al2O3-semiconductor capacitor (MOSCAP) structure. The leakage current was very high when the Al2O3 thickness was comparable with the size of the crystalline defects, but was suppressed to the order of 1 × 10−8 A/cm2 with larger Al2O3 thicknesses. The interface states densities (Dit) were measured on the same MOSCAPs by using combined ultraviolet (UV)-assisted capacitance-voltage (C-V), constant capacitance deep level transient spectroscopy (CC-DLTS), and constant capacitance deep level optical spectroscopy (CC-DLOS) techniques. The average Dit measured by CC-...

The effect of the profile of the hot coil on the flatness and the profile of cold-rolled strip has been studied by means of samples from a tandem cold mill of Pohang Iron and Steel Co., South Korea. Using geometrical relationships between the factors, measured values of the flatness and the profile were evaluated and theoretical correlation between the steepness values and the change in crown ratios were confirmed experimentally. As for coil build-up, it was established that a very small trace of a high spot in the hot-coil profile gave rise to a wavy shape in the uncoiled strip. Although the crown ratio of the cold strip became larger than that of the hot strip as the measurement point approached the strip edge, the influence of the profile of the mother strip remained even to a point 15 mm from the edge. Based on the results, the height limit of a high spot for good flatness and hot-strip crown values for uniform thickness over the width of the cold-rolled strip have been discussed.

We have shown that it is possible to make Ni/Mn superlattice-based spin valves that have high thermal stabilities. Ni/Mn superlattice was compared with Pt/Mn. The Ni/Mn superlattice after a thermal treatment at 240°C showed an FCT structure with the antiferromagnetic phase. The exchange coupling field ( H ex ) and the coercive field ( H c ) of [Ni(2 A)/Mn(3 A)] 40 /NiFe(60 A)/Cu(30 A)/NiFe(60 A) spin valves with 30 at% Ni [Ni/Mn] superlattice as the pinning layer are 305 and 245 Oe after thermal annealing for 12 h at 240°C, respectively. As-deposited Pt/Mn superlattice spin valves showed uniaxial anisotropy and exchange biasing without deposition field and post-annealing.