Additive effect of cobalt-exchanged coal on the liquefaction of subbituminous coal

In comparison with the liquefaction (420 °C, with tetralin and elemental sulfur) of the proton-exchanged Adaro subbituminous coal with complex (metallocene or metal carbonyl) of cobalt, nickel or iron, the coal liquefaction was enhanced significantly on the liquefaction of cation (Co²⁺, Ni²⁺ or Fe²⁺) exchanged Adaro coal. However, for several kinds of subbituminous coal, metal cations hardly exchange due to the small content of carboxyl group in coal. Therefore, the simultaneous liquefaction of subbituminous coal and cobalt-exchanged coal were carried out in this study. Further, the simultaneous liquefaction of lower rank and subbituminous coals with Co₂(CO)₈ was carried out to compare the catalytic effect of cobalt derived from either the exchanged coal or Co₂(CO)₈. The catalytic effect of cobalt in the exchanged Morwell brown coal was appeared as the decrease of residue yield on the liquefaction with Yilan subbituminous coal. On the other hand, there was little enhancement on the simultaneous liquefaction of cobalt-exchanged Adaro and Yilan subbituminous coals. Accordingly, it is clarified that the hydroliquefaction of subbituminous coal, which was exchanged cation hardly, was enhanced by the addition of cobalt-exchanged brown coal.     

Low-Temperature Synthesis of Aluminum Silicon Carbide Using Ultrafine Aluminum Carbide and Silicon Carbide Powders

The conditions for preparing α-aluminum silicon carbide (α-Al₄SiC₄) were examined by heating stoichiometric mixtures of ultrafine A1₄C₃ and SiC powders with sizes of <0.1 μm at and below 1600°C. The starting A1₄C₃ powder was obtained by the pyrolysis of trimiethylaluminum; the starting SiC powders were obtained by the pyrolyses of triethylsilane (3ES), tetraethylsilane (4ES), and hexamethyldisilane (6MDS). The reactivity of SiC with Al₄C₃ to form α-Al₄SiC₄ varies according to the kind of starting alkylsilane: 3ES > 4ES > 6MDS. The reaction of 3ES-derived SiC with A1₄C₃ produced α-Al₄SiC₄ at temperatures as low as 1400°C for 240 min, regardless of the presence of A1₄C₃ (trace). Only α-Al₄SiC₄ was formed at and above 1500°C for 60 min; the crystal growth was appreciable.     

Effect of Divalent Cation Additives on the γ-Al2O3-to-α-Al2O3 Phase Transition

The effect on the γ-Al₂O₃-to-α-Al₂O₃ phase transition of adding divalent cations was investigated by differential thermal analysis, X-ray diffractometry, and surface-area measurements. The cations, Cu²⁺, Mn²⁺, Co²⁺, Ni²⁺, Mg²⁺, Ca²⁺, Sr²⁺, and Ba²⁺, were added by impregnation, using the appropriate nitrate solution. These additives were classified into three groups, according to their effect: (1) those with an accelerating effect (Cu²⁺ and Mn²⁺), (2) those with little or no effect (Co²⁺, Ni²⁺, and Mg²⁺), and (3) those with a retarding effect (Ca²⁺, Sr²⁺, and Ba²⁺). The crystalline phase formed by reaction of the additive with γ-Al₂O₃ at high temperature was a spinel-type structure in groups (1) and (2) and a magnetoplumbite-type structure in group (3). In groups (2) and (3), a clear relationship was found between the transition temperature and the difference in ionic radius of Al³⁺ and the additive (Δ r ): The transition temperature increased as Δ r increased. This result indicates that additives with larger ionic radii are more effective in suppressing the diffusion of Al³⁺ and O²⁻ in γ-Al₂O₃, suppressing the grain growth of γ-Al₂O₃, and retarding the transformation into α-Al₂O₃.     

Compact thermosyphon using refrigerant flow control

In a compact closed two-phase thermosyphon which consists of a multitube radiator and a refrigerant bath, it is observed that the heat radiation performance drops as the refrigerant bath becomes thin. We have found that this is due to vapor–liquid interaction and dryness in the upper side of the boiling area. We have also improved that heat radiation performance with a new refrigerant flow controller. ©1999 Scripta Technica, Heat Trans Asian Res, 28(8): 627–639, 1999     

Proteolytic degradation of myofibrillar components by carp cathepsin L

Carp cathepsin L, which is the best candidate to produce textural change in the arai-treated carp fillet, exhibited maximum hydrolytic activity for Z-Phe-Arg-MCA and soluble casein at pH 5·0–5·5. The proteolytic action of the enzyme was evaluated by complete degradation of various carp myofibrils at pH 5·0 over 30 min and by potent degradation of the same proteins at pH 5·5–6·0 over 20 h. All myofibrillar components were partially degraded by the enzyme at pH 6·5–7·0, but varying amounts of them remained undegraded after 20 h. These findings indicate that carp cathepsin L degrades not only carp myofibrillar components but also their resultant products between pH 5·0 and 7·0 and that it markedly acts on myosin heavy chain, α-actinin and troponin-T and -I. Carp cathepsin L likely contributes to postmortem muscle tenderisation of carp fillet over an extensive pH range during storage. © 1998 SCI.     

Design progress of the ITER blanket remote handling equipment

The ITER blanket (BL) is composed of about 400 modules in the vacuum vessel (VV). The BL has to be maintained by remote handling means due to high radiation levels in the VV after D-T operation. The remote handling (RH) equipment for BL maintenance consists of articulated rail, supports, a rail-mounted vehicle, a telescopic arm, an end-effecter, tools and related systems such as transfer casks and umbilical system.Towards the construction, the BL RH equipment design has been improved and developed in more detail, based on the 2001 FDR design. The overview of design results is introduced in this paper. The design of rail deployment system of the BL RH has been updated to enable the rail connection in the transfer cask in order to minimize occupation space at storage area. For this purpose, design work has been performed for concept, sequence and typical simulation of BL replacement in the VV and rail deployment/storage of the RH equipment in the cask, including cask docking. In particular, the technical issues of the rail connection in the cask are (1) tight tolerance of a pin at a hinge, (2) limited space for the connection inside a cask and (3) tight positioning accuracy. This paper summarizes the idea to solve these issues and the results of the design work. The paper also introduces new cable handling equipment, rail support equipment and BL module transporter.     

Control and protection scheme of HVDC system with self‐commutated converter in system fault conditions

For extending self‐commutated converter application to future trunk power systems, it is important to develop a stable operation scheme as well as to realize substantial cost reduction through coordinated system and control design. Suppression controls of converter overcurrent and dc overvoltage in various system fault conditions are essential in order to ensure stable operation and cost reduction of HVDC systems with voltage source type self‐commutated converters. Converter control and protection schemes which include such suppression controls have been developed, employing CRIEPI's ac/dc Power System Simulator test and EMTP analysis. This paper first discusses the cause of converter overcurrent at ac system faults, considering the effect of PWM pulse number and converter control speed. Continued operation has been achieved by adding a new overcurrent suppression scheme to the converter control. In the case of a dc line grounding fault, the selection of the grounding circuit constant and the adoption of a high‐speed converter control practically ensure the reduction of dc overvoltage while suppressing converter overcurrent. The converter block and restart sequence after a dc fault, which is coordinated with dc circuit breaker operation, enables stable recovery of HVDC transmission as fast as the usual line‐commutated HVDC system. © 2000 Scripta Technica, Electr Eng Jpn, 132(2): 6–18, 2000     

Polymerization of methyl methacrylate with Ni(acac)2–methylaluminoxane catalyst

Polymerization of methyl methacrylate (MMA) with nickel(II) acetylacetonate [Ni(acac)₂] in combination with methylaluminoxane (MAO) was investigated. Ni(acac)₂ was found to be an effective catalyst for the polymerization of MMA. From a kinetic study of the polymerization of MMA with the Ni(acac)₂–MAO catalyst, the overall activation energy was estimated to be 15 kJmol⁻¹. The polymerization rate (R_p) was expressed as follows: R_p = k [MMA]^1.0[Ni(acac)₂–MAO]^0.6 (the MAO/Ni mole ratio was kept constant). The mechanism for the polymerization of vinyl monomers with the Ni(acac)₂–MAO catalyst is discussed. © 2000 Society of Chemical Industry     

Thermosyphon by refrigerant self‐excited oscillation

In a compact closed two‐phase thermosyphon, the boiling area is adjacent to the condensation area, and the condensation area is provided with innerfins different from conventional thermosyphons. We clarified that the combination of condensation and self‐excited oscillation convection resulted in a good heat release. To intensify this self‐excited oscillation, we made the innerfin unsymmetrical, and consequently an improvement was realized. © 2000 Scripta Technica, Heat Trans Asian Res, 29(6): 523–534, 2000