Realistic closed ecosystems: a rebuttal

This paper rebuts Loehle's correspondence entitled ‘Hirata's stability analysis refuted’. His criticism is that the model and analysis of Hirata are void of meaning because materially-closed ecological systems are not ecologically realistic. This paper demonstrates that his criticism is irrelevant by showing several realistic materially-closed ecosystems and by pointing out the important tradition of research on such systems.     

Numerical Simulation of Solidification Process on Single Crystal Ni-Based Superalloy Investment Castings

Bridgman directional solidification of investment castings is a key technology for the production of reliable and highly efficient gas turbine blades. In this paper, a mathematical model for three-dimensional （3D） simulation of solidification process of single crystal investment castings was developed based on basic heat transfer equations. Complex heat radiation among the multiple blade castings and the furnace wall was considered in the model. Temperature distribution and temperature gradient in superalloy investment castings of single blade and multiple ones were investigated, respectively. The calculated cooling curves were compared with the experimental results and agreed well with the latter. It is indicated that the unsymmetrical temperature distribution and curved liquid-solid interface caused by the circle distribution of multiple turbine blades are probably main reasons why the stray grain and other casting defects occur in the turbine blade.     

ICRF Experiments and GAMMA 10 Potential Formation on the Tandem Mirror

Target plasmas, on which the formation of the electrostatic potentials and the improvement of the confinement are studied, are produced with ICRF in the GAMMA 10 tandem mirror. The ion temperature of more than 10 keV has been achieved in relatively low density plasmas. When the strong ICRF heating is applied, it is observed that the high frequency and the low frequency fluctuations are excited and suppress the increase of the plasma parameters. Recently, a new high power gyrotron system has been constructed and the ECRH power in plug extends up to 370 kW. The improvement of the confinement due to the formation of the potential in the axial direction and the strong radial electric field shear has been observed.     

A model of energy systems and its macro-properties

This paper proposes a new mathematical model of energy systems rooted in Odum and Odum's (1976) concepts of energy flows. Models of two types of energy systems have been studied: a composite system with energy supply and consumption sectors, and a competition system with two energy consumption sectors drawing in parallel on the same energy source. Interesting results were obtained as follows : feedback of high quality energy to pump in more energy, and voluntary energy supply are generally effective in stability and growth of the supply-consumption energy system ; saving energy plays an important role in coexistence in the competition system     

A Cooperative Control Algorithm for Multiple SVRs Using Correlation of Measurement Data of Distribution Line

In this paper, a cooperative control algorithm for multiple step voltage regulator (SVR) using correlation of measurement data of distribution line is proposed. Conventionally, the control time constant of a SVR placed on the feeder end side was set slower than a SVR placed on the substation side. The unnecessary tap movement of SVR was reduced by this setting. In this case, on the condition that “the photovoltaic power generation output of the feeder end fluctuates” and “only SVR of the end side works”, it is a problem that control of SVR becomes slow. By the proposed method, the SVR settled in end side of a feeder can change its tap rapidly only if the SVR settled in sending side of a feeder will not change its tap by using proposed method. The features of the method are followings: (1) to estimate tap change possibility of the sending side SVR using correlation model of both of the SVR, (2) only use local measurement data of the SVRs for tap change control. By the proposed method, unnecessary tap change operation and lag of tap control are reduced without communication networks.     

Coupled Analysis by Viscoelastic Body with Rigid Body for Design of MRE Soft Actuator

The magneto rheological elastomer (MRE) is composed of silicone elastomers and ferromagnetic powders that are responsible for its ferromagnetic and viscoelastic properties. The shape and the stiffness of the MRE change depending on the magnetic field. Therefore, it is expected to be used for artificial muscle or damping material. We developed a coupled analysis method by combining the moving particle semi‐implicit/simulation (MPS) method with the finite element method (FEM) for the design of the MRE actuator. However, this method does not take into account a rigid body. Therefore, when analyzing the coil embedded in the MRE, it was difficult to calculate parameters such as the coil rotation and position. Therefore, this paper presents a numerical method for MRE actuator analysis by coupling MPS method with FEM to arrive at a calculation method for a rigid body. The numerical algorithm is described and the calculated results are shown.     

Development of Control Method for Outer‐Rotor Spherical Actuator

Conventional multi‐degree‐of‐freedom drive systems need many single‐degree‐of‐freedom actuators, but this makes the structure larger and heavier. The development of a spherical actuator should reduce the number of actuators, but the low torque and narrow rotation range are still problems. We developed a 2‐degree‐of‐freedom spherical actuator with an outer rotor that can produce a higher torque and wider rotation angle. In this paper, we propose a control method; we confirmed its usefulness by performing dynamic analysis using the three‐dimensional finite element method and by taking measurements with a prototype.     

Local structure studies of Fe-Nb-B metallic glasses using electron diffraction

Local atomic structures in Fe₈₄Nb₇B₉ and Fe₇₀Nb₁₀B₂₀ amorphous alloys were examined by means of electron diffraction with the help of computer calculation. Electron diffraction patterns were taken by using energy‐filtered transmission electron microscopy (TEM) to eliminate inelastic scattering. We constructed structure models with 5000 atoms fitting to experimental interference functions. Voronoi polyhedral analyses were performed for the obtained final structure models. Local atomic structures of the alloys were closely related to those of the crystalline phases that appeared on annealing. A difference of stability of two amorphous phases was discussed on the basis of structure models.