Studies on the requirements of the power supply system for the resistive-wall-mode control in JT-60SA

The JT-60SA satellite tokamak will be built in Naka, Japan. One of the main aims of this machine is to achieve steady-state high-beta plasmas. To reach this result, passive stabilizing plate (SP) and resistive wall modes (RWM) active control system based on 18 in-vessel coils will be installed. In the present design, these coils are placed on the plasma side of the SP, behind the first wall. This solution maximizes the efficiency in producing fast magnetic fields into the plasma by minimizing the shielding effect of the passive structures. Then, if the power supply (PS) and the control system have sufficient dynamic performance, it is possible to control the RWM with very low magnetic fields. This allows minimizing the Ampere-turns and the power requested to control the RWM. Conversely, the very fast dynamics required represents one of the main issues for the design of the RWM control system. This paper, after having recalled the main specification data for the RWM control system deriving from the physics studies, describes the analyses performed to complete the set of requirements necessary for the PS design. The characterization of coils and feeders is shown and the voltage necessary to produce the required current and bandwidth is quantified. Possible connections among PS and coils are analyzed in order to achieve the highest possible flexibility in controlling the RWM with a reduced set of independent PS. Finally, considerations on reasonable voltage margins to cope with load uncertainties are given.     

High-temperature oxidation of ceramic matrix composites dispersed with metallic particles

Oxidation behavior of ceramic matrix composites dispersed with metallic particles is discussed to establish materials design for high-temperature applications. Oxidation kinetics of ceramic matrix composites dispersed with metallic particles is understood from the viewpoint of the diffusion properties and defect chemistry of matrix oxides. High-temperature oxidation of Ni(p)/partially stabilized zirconia, Ni(p)/Al₂O₃ and Ni(p)/MgO was described as examples.     

Bayesian hemodynamic parameter estimation by bolus tracking perfusion weighted imaging

A delay-insensitive probabilistic method for estimating hemodynamic parameters, delays, theoretical residue functions, and concentration time curves by computed tomography (CT) and magnetic resonance (MR) perfusion weighted imaging is presented. Only a mild stationarity hypothesis is made beyond the standard perfusion model. New microvascular parameters with simple hemodynamic interpretation are naturally introduced. Simulations on standard digital phantoms show that the method outperforms the oscillating singular value decomposition (oSVD) method in terms of goodness-of-fit, linearity, statistical and systematic errors on all parameters, especially at low signal-to-noise ratios (SNRs). Delay is always estimated sharply with user-supplied resolution and is purely arterial, by contrast to oSVD time-to-maximum TMAX that is very noisy and biased by mean transit time (MTT), blood volume, and SNR. Residue functions and signals estimates do not suffer overfitting anymore. One CT acute stroke case confirms simulation results and highlights the ability of the method to reliably estimate MTT when SNR is low. Delays look promising for delineating the arterial occlusion territory and collateral circulation.     

High range resolution ultrasonographic vascular imaging using frequency domain interferometry with the Capon method

For high range resolution ultrasonographic vascular imaging, we apply frequency domain interferometry with the Capon method to a single frame of in-phase and quadrature (IQ) data acquired using a commercial ultrasonographic device with a 7.5 MHz linear array probe. In order to tailor the adaptive beam forming algorithm for ultrasonography we employ four techniques: frequency averaging, whitening, radio-frequency data oversampling, and the moving average. The proposed method had a range resolution of 0.05 mm in an ideal condition, and experimentally detected the boundary couple 0.17 mm apart, where the boundary couple was indistinguishable from a single boundary utilizing a B-mode image. Further, this algorithm could depict a swine femoral artery with a range beam width of 0.054 mm and an estimation error for the vessel wall thickness of 0.009 mm, whereas using a conventional method the range beam width and estimation error were 0.182 and 0.021 mm, respectively. The proposed method requires 7.7 s on a mobile PC with a single CPU for a 1×3 cm region of interest. These findings indicate the potential of the proposed method for the improvement of range resolution in ultrasonography without deterioration in temporal resolution, resulting in enhanced detection of vessel stenosis.     

Motion planning of a golf swing robot

We report our studies of a new motion planning method for a two-link golf swing robot. We introduce two fundamental properties of manipulator dynamics: the time-reversal symmetry property and the pendulum property. The former is used to reverse the rest-to-point pre-impact swing (backswing and downswing) into a symmetric point-to-rest swing in time, and the latter is used to design a proportional-derivative plus gravity, joint and coupling torque compensation control algorithm to plan the reversed pre-impact swing and the point-to-rest follow-through swing. By using this method, accurate impact position and hitting speed control of the golf swing and low computational cost are achieved. The introduced properties hold true for general multi-revolute-joint planar manipulators and the proposed motion planning algorithm can be implemented on them too.     

Comparative study of large-scale hydrogen storage technologies: Is hydrate-based storage at advantage over existing technologies?

Different technologies possibly applicable for large-scale hydrogen storage in urban or industrial-complex areas have been comparatively evaluated, focusing on the facility-construction costs, the utility expense, and the ground area required for the facility for each technology. The specific technologies examined in this study are the storage in the form of compressed or liquefied gas, the storage using a metal hydride, and the storage using a clathrate hydrate. The common requirements for these technologies are the function of loading or unloading hydrogen gas at a rate up to 3000 Nm³/h and also the storage capacity of 6.48 × 10⁶ Nm³ that enables continuous 90-day loading or unloading at the rate of 3000 Nm³/h. The storage using a clathrate hydrate is found to require the minimum ground area and, if the cool energy necessary for hydrate production is available from adjacent LNG facilities, the minimum annual depreciation + utility expense.     

Failure behavior of adhesively bonded joints with a rubber modified epoxy adhesive under tensile-shear combined cyclic loading

Rubber-modified epoxy adhesives are used widely as structural adhesive owing to their properties of high fracture toughness. In many cases, these adhesively bonded joints are exposed to cyclic loading. Generally, the rubber modification decreases the static and fatigue strength of bulk adhesive without flaw. Hence, it is necessary to investigate the effect of rubber-modification on the fatigue strength of adhesively bonded joints, where industrial adhesively bonded joints usually have combined stress condition of normal and shear stresses in the adhesive layer. Therefore, it is necessary to investigate the effect of rubber-modification on the fatigue strength under combined cyclic stress conditions. Adhesively bonded butt and scarf joints provide considerably uniform normal and shear stresses in the adhesive layer except in the vicinity of the free end, where normal to shear stress ratio of these joints can cover the stress combination ratio in the adhesive layers of most adhesively bonded joints in industrial applications.

In this study, to investigate the effect of rubber modification on fatigue strength with various combined stress conditions in the adhesive layers, fatigue tests were conducted for adhesively bonded butt and scarf joints bonded with rubber modified and unmodified epoxy adhesives, wherein damage evolution in the adhesive layer was evaluated by monitoring strain the adhesive layer and the stress triaxiality parameter was used for evaluating combined stress conditions in the adhesive layer. The main experimental results are as follows: S–N characteristics of these joints showed that the maximum principal stress at the endurance limit indicated nearly constant values independent of combined stress conditions, furthermore the maximum principal stress at the endurance limit for the unmodified adhesive were nearly equal to that for the rubber modified adhesive. From the damage evolution behavior, it was observed that the initiation of the damage evolution shifted to early stage of the fatigue life with decreasing stress triaxiality in the adhesive layer, and the rubber modification accelerated the damage evolution under low stress triaxiality conditions in the adhesive layer.     

Preparation and Characterization of Amphiphilic Lignin Derivatives as Surfactants

Abstract

Acetic acid lignin (AL), one of the organosolv lignins, was modified by polyoxyethylation using commercially available polyethylene glycol diglycidylethers (PEGDE) having various chain lengths in order to generate novel nonionic polymeric surfactants. AL could be converted to the amphiphile by modifying with PEGDE (PEGDE-AL) having more than 9 of the ethylene oxide (EO) repeating units. Although the surface activities of PEG and AL were very limited, PEGDE-AL did strongly depress surface tension of water, and showed clear critical micelle concentrations (CMC). The CMC value of PEGDE-AL could be comparable to a commercial anionic lignin surfactant, lignosulfonate. The surface activity of AL amphiphile was further improved by modification with monoepoxides, ethoxy-(2-hydroxy)-propoxy-polyethylene glycol glycidylether (EPEGGE). The surface tension of water was depressed by the addition of the EPEGGE-AL to the same level as Triton® X-100, which is a commercial PEG-based nonionic surfactant, although there is still room for improvement in CMC value. The hydrophile–lipophile balance (HLB) of these AL amphiphiles was in the range of 11–14, and significant biodegradation was observed. These results suggest that the AL amphiphiles can be used as emulsifier and detergent.     

Viscoelastic and thermal decomposition behaviors of polytetrahydrofuran binder prepared using glycerin as a crosslinking modifier

Polytetrahydrofuran (PTHF) is an effective binder ingredient used for improving the performance of propellants. PTHF becomes sufficiently rubbery for use as a binder with the addition of an adequate crosslinking modifier. This study investigated the viscoelastic and thermal decomposition behaviors of the PTHF binder prepared using glycerin as a crosslinking modifier, as well as the influence of the molecular weight of PTHF on the characteristics of the PTHF binder. The curing behavior of the PTHF binder was suitable for the manufacture of propellants, and the superior tensile properties of the PTHF binder made it suitable for use as a propellant binder. The degree of crosslinking of the samples decreased as the molecular weight of the PTHF increased. The PTHF binder has unique dynamic mechanical properties owing to its melting and chemical structure, and these properties were dependent on the molecular weight of PTHF. The glass transition temperature (T_g) and the loss tangent at T_g decreased as the molecular weight of the PTHF increased. The temperature and frequency dependence of the PTHF binder were influenced by the melting point of PTHF. The viscoelastic properties of the binder prepared using PTHF with a molecular weight of 650 followed the time–temperature superposition principle. The activation energy for the relaxation of this binder varied remarkably at the melting point of PTHF. The thermal decomposition behavior indicated that at low temperatures, the consumption rate of the binder with low‐molecular‐weight PTHF was slightly larger than that of the binder with high‐molecular‐weight PTHF. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013