Railgun pellet injection system for fusion experimental devices

A railgun pellet injection system has been developed for fusion experimental devices. Using a low electric energy railgun system, hydrogen pellet acceleration tests have been conducted to investigate the application of the electromagnetic railgun system for high speed pellet injection into fusion plasmas. In the system, the pellet is pre-accelerated before railgun acceleration. A laser beam is used to induce plasma armature. The ignited plasma armature is accelerated by an electromagnetic force that accelerates the pellet. Under the same operational conditions, the energy conversion coefficient for the dummy pellets was around 0.4%, while that for the hydrogen pellets was around 0.12%. The highest hydrogen pellet velocity was 1.4 km s⁻¹ using a 1 m long railgun. Based on the findings, it is estimated that the hydrogen pellet has the potential to be accelerated to 5 km s⁻¹ using a 3 m long railgun.     

Switching characteristics of a triggered vacuum gap employing a trigger electrode in the respective main electrodes

Both switching time and minimum firing voltage of a triggered vacuum gap employing a trigger electrode in the cathode and anode (double triggered vacuum gap) were measured. The double triggered vacuum gap was operated below 100 V independent of the high voltage main electrode polarity (positive or negative). This minimum firing voltage was lower than that of the conventional triggered vacuum gap. The switching time is approximately 0.5 μs in the range 3 to 18 kV. The conventional triggered vacuum gap has a trigger electrode that is placed at the center of the grounded main electrode. The polarity of the main electrode affected switching time characteristics. A trigger electrode was added to the high voltage main electrode. The double triggered vacuum gap was only slightly influenced by the polarity of the high voltage main electrode when both main electrodes were triggered at the same time.     

Indene Compounds Synthetically Derived from Vitamin D Have Selective Antibacterial Action on Helicobacter pylori

Helicobacter pylori infects the human stomach and is closely linked with the development of gastric cancer. When detected, this pathogen can be eradicated from the human stomach using wide‐spectrum antibiotics. However, year by year, H. pylori strains resistant to the antibacterial action of antibiotics have been increasing. The development of new antibacterial substances effective against drug‐resistant H. pylori is urgently required. Our group has recently identified extremely selective bactericidal effects against H. pylori in (1R,3aR,7aR)‐1‐[(1R)‐1,5‐dimethylhexyl]octahydro‐7a‐methyl‐4H‐inden‐4‐one (VDP1) (otherwise known as Grundmann's ketone), an indene compound derived from the decomposition of vitamin D₃ and proposed the antibacterial mechanism whereby VDP1 induces the bacteriolysis by interacting at least with PtdEtn (dimyristoyl‐phosphatidylethanolamine [di‐14:0 PtdEtn]) retaining two 14:0 fatty acids of the membrane lipid constituents. In this study, we synthesized new indene compounds ((1R,3aR,7aR)‐1‐((2R,E)‐5,6‐dimethylhept‐3‐en‐2‐yl)‐7a‐methyloctahydro‐4H‐inden‐4‐one [VD2‐1], (1R,3aR,7aR)‐1‐((S)‐1‐hydroxypropan‐2‐yl)‐7a‐methyloctahydro‐1H‐inden‐4‐ol [VD2‐2], and (1R,3aR,7aR)‐7a‐methyl‐1‐((R)‐6‐methylheptan‐2‐yl)octahydro‐1H‐inden‐4‐ol [VD3‐1]) using either vitamin D₂ or vitamin D₃ as materials. VD2‐1 and VD3‐1 selectively disrupted the di‐14:0 PtdEtn vesicles without destructing the vesicles of PtdEtn (dipalmitoyl‐phosphatidylethanolamine) retaining two 16:0 fatty acids. In contrast, VD2‐2, an indene compound lacking an alkyl group, had no influence on the structural stability of both PtdEtn vesicles. In addition, VD2‐1 and VD3‐1 exerted extremely selective bactericidal action against H. pylori without affecting the viability of commonplace bacteria. Meanwhile, VD2‐2 almost forfeited the bactericidal effects on H. pylori. These results suggest that the alkyl group of the indene compounds has a crucial conformation to interact with di‐14:0 PtdEtn of H. pylori membrane lipid constituents whereby the bacteriolysis is ultimately induced.     

Virtual Society: Collaboration in 3D Spaces on the Internet

The Virtual Society (VS) project is a long term research initiativethat is investigating the evolution of the futureelectronic society. Our vision for this electronic societyis a shared 3D virtual world where users, from homes and offices, canexplore, interact and work. Our first implementation of aninfrastructure to support our investigation is known asCommunityPlace and has been developed to support large-scale shared 3D spaces onthe Internet using the Virtual Reality Modeling Language (VRML). Obviously, such an ambitious project cutsacross many different domains. In this paper we outline thegoals of the Virtual Society project, discuss the architecture andimplementation of CommunityPlace with particular emphasis on Internetrelated technologies such as VRML and present our views on the role ofVRML and the Internet to support large-scale shared 3D spaces.     

Cross-group secret sharing scheme for secure usage of cloud storage over different providers and regions

With the spread of the Internet, more and more data are being stored in the cloud. Here the technique of secret sharing can be naturally applied in order to provide both security and availability of the stored data, hereby reducing the risks of data leakage and data loss. The privacy property of secret sharing ensures protection against unauthorized access, while protection against data loss may be attained by distributing shares to the servers located in different regions. However, there is still a problem: If we naively employ the secret sharing technique without regarding to whom the cloud servers belong, a dishonest provider can obtain the secret data by collecting enough shares from its servers. In this scenario, there is a need to distribute shares over cloud services operated by different providers. In this paper, we propose a simple secret sharing technique, a cross-group secret sharing (CGSS), which is suitable for storing the data on cloud storage distributed over different groups—that is, different providers and regions. By combining an \(\ell \)-out-of-m threshold secret sharing scheme with a k-out-of-n threshold secret sharing scheme using a symmetric-key encryption scheme, we construct the CGSS scheme that forces k shares to be collected from \(\ell \) groups. Compared with the previous works, our scheme attains the functionality with reasonable computation. We also formalize the problem of allocating shares over different providers and regions as an optimization problem and show the design principles, which one must follow, when applying our proposal in practical settings. An experiment on real IaaS systems shows effectiveness of our proposed scheme, CGSS.     

DIFFUSION COEFFICIENTS OF CARBON DIOXIDE WITHIN TYPE 13X ZEOLITE PARTICLES

The self-diffusion processes of CO₂ in a single particle of commercial type 13X zeolite have been studied by a new sorption rate method using a constant volume, variable pressure system. Experiments were carried out at 303.2 and 343.2 K. An inverse analysis of experimental uptake curves based on a macropore and micropore series diffusion model was performed to determine effective diffusion coefficients for both macropore and micropore diffusion simultaneously. Knudsen diffusion occurs within the macropore and the micropore diffusion coefficients having values of the order 10^-15-10^-14 m²/s, which are slightly greater than the previously reported micropore diffusion coefficients of type 5A zeolite crystals.     

Acrylic/polyester hybrid powder coating system having excellent weather durability

There have been many attempts to improve weather durability in polyester powder coatings. However, no effective suggestion improves weather durability without sacrificing other properties, such as mechanical properties. A novel polyester powder coating system is described in this article, with especially excellent weather durability. This system was based on an acrylic/polyester hybrid curing system composed of polyester resin showing excellent weather durability and the new GMA-acrylic hardener which has a ‘soft segment' in its structure. The advanced acrylic/polyester hybrid curing system shows both excellent weather durability and good mechanical properties.     

Production of clean fuels by solvent skimming of coal at around 350 °C

The authors have recently presented a new coal extraction method by which various kinds of coals ranging from brown coals to bituminous coals could be extracted up to 80% of the parent coals in a flowing stream of tetralin or a coal derived oil, carbol oil, under 10 MPa at 350 °C. The extract obtained by this method was almost free from inorganic materials. In this study the effect of solvent recycling on the extraction behavior was examined to make the method practically applicable. The solvent recycling was found to be effective in enhancing the extraction yield and in decreasing further the inorganic fraction in the extract. The extract and residue obtained were characterized through various analyses. To examine how inorganic materials are removed by the extraction, the contents of inorganic elements, including harmful trace elements, in the extract were investigated. It was clarified that the presented method was effective in the removal of most of the inorganic elements including even harmful trace elements from coals, although the degree of removal was dependent on the kind of element.     

Local heating effect in point-contact spectroscopy for magnetic metals of Ni and α-Mn

The current-voltage characteristics at a homojunction point-contact of ferromagnetic Ni single crystal and antiferromagnetic -phase Mn polycrystalline metal have been measured at 4.2 K. Several singularities in the first and second derivative of I–V curves are observed at specific bias voltages for both metals. Taking into account the observed temperature dependence of the bulk electrical resistivity and thermal conductivity (and thus mean free path of electrons), we have performed computer simulations of these nonlinear I–V characteristics based on a modified local heating model and compared with the results by a traditional spherical spreading-out (SSO) model. When a constant additive correction to the bulk resistivity near a contact interface is incorporated, our calculated curves are in good agreement with the experimental results.     

Mechanical properties and microstructures of machinable silicon carbide

Mechanical properties and microstructures of machinable silicon carbide, fabricated by pressureless sintering of silicon carbide fine powder with the aid of polysilastyrene, have been examined. Drastic changes in microstrucyure and in mechanical properties between specimens sintered at below 1773 K and at above 1873 K were observed. By sintering at above 1883 K the macinable silicon carbide had a good strength of more than 200 Mpa with high reliability, which was maintained beyond 1773 K. Polysilastyrene was converted in -phase silicon carbide and ribbon carbon in the pores. The (001) plane of carbon is parallel to the (111) planes of -phase silicon carbide.