Effect of electromagnetic force on the pressure drop and coupling loss of a cable-in-conduit conductor

In the central solenoid (CS) insert experiment performed with the International Thermonuclear Experimental Reactor CS model coil, significant changes in the pressure drop and coupling losses were observed during coil energization. This phenomenon was quantitatively analyzed from the viewpoint of the deformation of the cable shape in the CS insert conductor due to an electromagnetic force acting on the cable. A new calculation model was proposed to provide the relation between the electromagnetic force and hydraulic characteristics of the conductor. Calculation results indicated that there seemed to be a gap of 1.3 mm between the cable and jacket created by the electromagnetic force when the CS insert was operated at 40 kA and 10 T, which can cause the decrease of the pressure drop by 12% and also the decrease of the local void fraction of the cable from 36.3% to approximately 34%. The latter well explained the increase of coupling losses. A local void fraction of 34.5% is suggested from the calculation in order both to reduce the amount of deformation and to maintain the coupling losses at acceptable level for this type of large current-carrying conductor.     

Direct growth of high-quality thick CdTe epilayers on Si (211) substrates by metalorganic vapor phase epitaxy for nuclear radiation detection and imaging

Direct growth of high-quality, thick CdTe (211) epilayers, with thickness up to 100 μm, on Si (211) substrates in a vertical metalorganic vapor phase epitaxy system is reported. In order to obtain homo-orientation growth on Si substrates, pretreatment of the substrates was carried out in a separate chamber by annealing them together with pieces of GaAs at 800–900°C in a hydrogen environment. Grown epilayers had very good substrate adhesion. The full-width at half-maximum (FWHM) value of the x-ray double-crystal rocking curve from the CdTe (422) reflection decreased rapidly with increasing layer thickness and remained between 140–200 arcsec for layers >18 μm. Photoluminescence measurement at 4.2 K showed high-intensity, bound excitonic emission and very small defect-related deep emissions, indicating the high crystalline quality of the grown layers. Furthermore, a CdTe/n⁺-Si heterojunction diode was fabricated that exhibited clear rectifying behavior.     

Simulation of a seawater MHD power generation system

MHD (magnetohydrodynamics) power generation systems are expected to become popular with the development of superconducting technology because of their low cost and high efficiency. MHD power generation directly utilizes electromotive force, which arises when seawater crosses a magnetic field. The helical-type MHD generator is composed mainly of a helical partition board and electrodes, which include a cathode pipe on the exterior of the generator and an anode rod in the interior. Elementary research on a helical-type MHD power generation system has started at Kobe University, and a numerical simulation of the system has been carried out by FEM (Finite Element Method) at the National Institute for Materials Science. By comparing the simulation results with the theoretical and experimental results, we found that the proposed method is valid for simulating the MHD power generation system.     

Effect of chopped Si–Al–C fiber addition on the mechanical properties of silicon carbide composite

Silicon carbide (SiC) composites containing 0–50 mass% of chopped Tyranno^® Si–Al–C (SA) fiber (mean length: 214 μm (SA(214)), 394 μm (SA(394)), and 706 μm (SA(706)) were fabricated using the hot-pressing technique at 1800 °C for 30 min under a uniaxial pressure of 31 MPa in Ar atmosphere. The maximum flexural strength of the SiC composite was 344 MPa for 30 mass% of SA(706) fiber addition, whilst the maximum fracture toughness was 4.7 MPa m^1/2 for 40 mass% of SA(706) fiber addition. Increasing the mean fiber length from 214 to 706 μm decreased the flexural strength from 380 to 281 MPa for 30 mass% of fiber addition, whilst the fracture toughness increased from 3.4 to 4.7 MPa m^1/2 for 40 mass% of fiber addition. Through use of a treated SA(706) fiber containing an approximately 100 nm surface layer of carbon, the fracture toughness further increased to 6.0 MPa m^1/2 for 40 mass% of fiber addition; this value was more than twice that of the monolithic SiC ceramic and is believed to be the highest so far achieved for this type of SiC/SiC composite containing chopped fibers.     

Molecular beam epitaxy of c-plane wurtzite GaN on nitridized a-plane β-Ga2O3

Epitaxial growth of GaN on β-Ga₂O₃ single crystal substrates by the molecular beam epitaxy technique is demonstrated for the first time. Standard and in-plane X-ray diffraction evidence the growth of c-plane wurtzite GaN on a-plane β-Ga₂O₃, the epitaxial relationship being 0 1 0_Ga2O3 1 1 2¯ 0_GaN and 0 0 1_Ga2O31¯ 1 0 0_GaN. Epitaxial growth without any buffer layer is achieved after an effective surface nitridation under NH₃ gas.     

Studies on the thermal degradation of phosphorus containing polymers: 7. Thermal degradation of phosphorylated poly(vinyl alcohol)

The thermal degradation of phosphorylated poly(vinyl alcohol) was investigated using thermogravimetric analysis, infra-red spectroscopy and gas chromatography. The introduction of phosphoric acid groups changed the course of the thermal degradation of the polymer. The dehydration was accelerated and the scission of the polymer chain was inhibited. The cis-β-elimination mechanism of the phosphorus ester group was proposed for the accelerated dehydration.     

The effect of frequency on fatigue crack propagation rate and striation spacing in 2024-T3 aluminium alloy and SM-50 steel

The effect of loading frequency on fatigue crack propagation rate and striation spacing in 2024-T3 aluminium alloy and SM-50 steel was studied at room temperature. The fatigue crack propagation rate is expressed experimentally by the equation: $\text{dc/dN = AΔK}{}^3\text{?}{}^{\mathrm{?\lambda }}$ and striation spacing, s by the following formula: $\text{s = BΔK}{}^5\text{s?}{}^{\mathrm{?\lambda }}$, where ?= loading frequency, λ = 0.08~0.14 and γ = 0'06~0?12.Fractographical studies were made.The ln dc/dN?lnΔK straight line and the ln s?lnΔK straight line intersect each other. That is, dc/dN < s below the stress intensity factor at the intersecting point, and dc/dN >s above the critical stress intensity factor. It is to be noted that dc/dN and s will not coincide except the very narrow region near the intersecting point.The formula of dc/dN experimentally obtained in this article has quite the same type as indicated by the dislocation dynamic theory of fatigue crack propagation.     

Tetramer formation from methacrylic acid metal salts in solid state

We have investigated the formation of tetramers of methacrylic acid via the thermal reaction of metallic salts of methacrylic acid salts in the solid state in the temperature range 300°–350°C. N.m.r. and mass spectra and gas chromatography were used in the characterization of the tetramers formed.