Microstructure and Mechanical Properties of Mullite Prepared by the Sol-Gel Method

Mullite (3Al₂O₃·2SiO₂) of stoichiometric composition was prepared by mixing boehmite sol and silica dispersion and gelling at a pH of 3. Complete mullitization takes place at or above 1300°C. Ultrafine mullite powder prepared by calcining gel at 1400°C and attrition milling could be sintered to >98% (theoretical density) at 1650°C for 1.5 h. The flexural strength of the sintered body at room temperature was 405 MPa and 350 MPa at 1300°C. Only traces of a secondary phase were observed along the grain boundary.     

Efficient characterization for protein crystals using confocal Raman spectroscopy

Confocal Raman spectroscopy was applied to the characterization of various states emerging in the screening of protein crystallization. Four main characterized states, namely single crystals, microcrystals, precipitates, and clear drops without solid materials, appear in a droplet for crystallization; the first three states should be critically distinguished and characterized because of the limitations of visual observation under an optical microscope. Using lysozyme and other proteins, crystallization was performed by the hanging drop vapor diffusion technique and was monitored through an automated confocal Raman system. Prior to the spectroscopic analysis, an optical microscope with a charge-coupled device (CCD) camera and associated image processing software were used to rapidly identify the XY locations to be measured spectroscopically by focusing the laser beam on a test sample. Instead of the current image analysis by optical microscopy, confocal Raman spectroscopy with a high spatial resolution was used to identify the state of protein crystallization. Such real-time Raman monitoring also distinguished real protein crystals from pseudo-protein crystals emerging in a crystallization droplet.     

Energy storage system utilizing large‐capacity electric double‐layer capacitors for peak‐cut of power demand

Recently, due to a rapid increase of demand for air conditioning in summer, peak power demand is becoming increasingly acute. Therefore, the load factor has a tendency to drop every year. The drop of the load factor is leading to a drop in the utilization factor of the power facilities and an increase in the cost of installation. In this paper, we propose an energy storage system for peak‐cut of power demand, in which we use large‐capacity electric double‐layer capacitors. This energy storage system has some distinctive characteristics, including long life span, maintenance‐free operation, preservation of environment, high efficiency at charge/discharge, and so on. This paper deals with the circuit arrangement of the proposed energy storage system, the charge equalization method of the capacitors, and the control method of the converter at charge/discharge. Finally, the operating characteristics of this system are evaluated by simulation analysis. © 2000 Scripta Technica, Electr Eng Jpn, 133(3): 83‐92, 2000     

Fault current limiting system for 500‐kV power systems

Recently, expansion in the scale of power systems and development of localized power sources are leading to an increase in fault current of 500‐kV systems. In the future, it is quite likely that the fault current at the interconnection of such power systems may exceed the rated short‐time current of existing electric power facilities. As one of the solutions of this problem, a thyristor‐controlled series‐resonant‐type fault current limiter (FCL) is proposed to restrain the fault current. This paper deals with the FCL system configuration, the placement method of the FCL in power systems, the outline of the FCL's specification, and the operation method of the protective relay in the multimachine system. Finally, the effectiveness of the FCL is evaluated from the viewpoints of limiting the fault current by simulation analysis. The FCL is shown to be a useful protection device for large, high‐capacity power systems. © 1999 Scripta Technica, Electr Eng Jpn, 127(1): 11–22, 1999     

Analysis of the Microstructure of Mg2Si Thermoelectric Devices

High-performance Mg₂Si thermoelectric devices have been obtained by spark plasma sintering of high-purity, pre-synthesized, all-molten Mg₂Si powder. We studied the effects of source powder particle size on thermoelectric performance. To improve the performance, further investigation of the microstructure of the devices is needed. In this work we studied the microstructure of grain boundaries and interfaces between electrodes and Mg₂Si sintered bodies to increase understanding of Mg₂Si thermoelectric devices.     

A Generic Implementation of Tree Skeletons

In data-parallel skeleton libraries, the implementation of skeletons is usually tightly-coupled with that of data structures. However, loose coupling between them like C++ STL will improve modularity and flexibility of skeletons and data structures. This flexibility is particularly valuable for tree skeletons. To achieve such loose coupling, we present an iterator-based interface of trees for tree skeletons. We have implemented tree skeletons on the basis of our interface; we present their design and implementation. This paper also reports the results of preliminary experiments.     

Adsorption and reaction of cyclohexene and 1-hexene on nascent gold surface formed by friction

Adsorption and reaction of cyclohexene, 1-hexene and benzene on nascent gold surface formed by friction were investigated using an adsorption test apparatus in high vacuum at room temperature. Chemisorption of cyclohexene, 1-hexene and benzene was observed during the sliding processes by a quadrupole mass spectrometer. It is found that nascent gold surface has catalytic activity for hydrogenation of cyclohexene and 1-hexene, and for dehydrogenation of the olefins and benzene. The adsorbed cyclohexene and 1-hexene molecules were hydrogenated on the surface to form cyclohexane and hexane, respectively. As dehydrogenation products, hydrogen from all the sample gases, and benzene from cyclohexene desorbed. Adsorption rate of the olefins was higher than that of benzene, and hydrogenation activity of 1-hexene is higher than that of cyclohexene. However, on nascent Pd–Ag alloy surface, the desorption of hydrogenation products was not detected, although adsorption of the sample gases and desorption of the dehydrogenation products were also observed.     

Site-specific functionalization of proteins by organopalladium reactions

A new carbon-carbon bond has been regioselectively introduced into a target position (position 32 or 174) of the Ras protein by two types of organopalladium reactions (Mizoroki-Heck and Sonogashira reactions). Reaction conditions were screened by using a model peptide, and the stability of the Ras protein under the reaction conditions was examined by using the wild-type Ras protein. Finally, the iF-Ras proteins containing a 4-iodo-L-phenylalanine residue were subjected to organopalladium reactions with vinylated or propargylated biotin. Site-specific biotinylations of the Ras protein were confirmed by Western blot and LC-MS/MS.     

Effect of crystallization temperature of palm oil on its crystallization. IV. The influence of tripalmitoylglycerol (PPP) on the crystallization of 1,3-dipalmitoyl-2-oleoyl-glycerol (POP) and 1,2-dioleoyl-3-palmitoyl-glycerol (POO)

Triacylglycerin in Palm Oil contains POP (1,3-dipalmitoyl-2-oleoyl-glycerol) at 30%, POO (1,2-dioleoyl-3-palmitoyl-glycerol) at 20% and PPP (tripalmitoylglycerol) at 5%. The crystallization temperature of PPP is high and the rates of crystal nuclear formation and growth are fast. It is thus considered that PPP may have some effect on the manner or mode of Palm Oil. Examination was thus made to clarify how PPP may affect the crystallization of POP and POO by differential scanning calorimetry (DSC) and X ray diffractometry (XRD) conducted on PPP/POP and PPP/POO mixtures. High and low temperature peaks were noted to appear on the DSC crystallization curve for either of these mixtures. The high temperature peak was considered possibly due to PPP, and the low temperature peak, to POP or POO. DSC isothermal analysis indicated the rate of crystal growth of either mixture to exceed that of pure of POP or POO. Crystal mixture structure was also seen to be complicated than either compound in pure form. The present findings thus clearly indicate that clarification should be made of the effects of high melting point triacylglycerin, such as PPP, on the crystallization of Palm Oil.