Vibration control for pneumatic isolation table with feedforward control input

In this paper, we consider a vibration suppression problem for a pneumatic isolation table with on–off valves using the feedforward control input profile. In this system, it is possible to enhance the vibration suppression performance by adjusting the flow rate of air into and from air springs. However, there is a significant problem that a steady‐state deviation, namely an offset, for displacement of the table occurs. Therefore, we propose an efficient search method of the optimal feedforward control input profile, which provides high vibration suppression performance without a steady‐state deviation. A key idea is to update the control input profile to belong to a space where velocity of the table does not change.     

Estimates of GHG emission reduction potential by country,sector, and cost

In this study, emission reduction potentials in greenhouse gases (GHG) are assessed by country, sector, and cost using a GHG emission reduction assessment model with high resolutions with respect to region and technology and high consistency in terms of assumptions, interrelationships, and solution principles. Model analyses show that large potential reductions can be achieved at low cost in developing countries and power sectors. In addition, cost-efficient emission reductions were evaluated for some international emission reduction targets that have been derived on the basis of the principle of common but differentiated responsibilities among developed and developing countries. If (1) emission reduction measures at negative costs and below 50 $/tCO₂ for developed countries, (2) intensity improvement measures for selected sectors at negative costs and below 20 $/tCO₂ for major developing countries, and (3) all emission reduction measures with negative costs for other developing countries in 2020 are adopted, then emission reductions of 8.9, 14.8, and 27.7 GtCO₂ eq./yr compared to the technology-frozen case can be expected in developed countries, major developing countries, and globally, corresponding to a 11% decrease, 40% increase, and 17% increase from 2005 levels, respectively. Large-scale emission reductions can be achieved even if CO₂-intensity targets for major sectors are assumed for major developing countries.     

Surface coating with a high resistance to hydrogen entry under high-pressure hydrogen-gas environment

Development of a surface coating with high resistance to hydrogen entry under a high-pressure hydrogen-gas environment is presented. Two aluminum-based coatings were developed on the basis of preliminary tests: two-layer (alumina/Fe–Al) and three-layer (alumina/aluminum/Fe–Al) coatings, deposited onto cylindrical and pipe (Type 304 austenitic stainless steel) surfaces by immersion into a specially blended molten aluminum alloy. The coated specimens were exposed to hydrogen gas at 10–100 MPa at 270 °C for 200 h. Specimen hydrogen content was measured by thermal desorption analysis; hydrogen distributions were analyzed by secondary ion mass spectroscopy. Both coatings showed high hydrogen-entry resistance at 10 MPa. However, resistance of the two-layer coating clearly decreased with an increase in pressure. In contrast, the three-layer coating showed excellent hydrogen-entry resistance at a wide pressure range (10–100 MPa), achieved by the combined effect of alumina, aluminum, and Fe–Al layers.     

Preparation of carbon-supported PtCo nanoparticle catalysts for the oxygen reduction reaction in polymer electrolyte fuel cells by an electron-beam irradiation reduction method

We prepared carbon-supported PtCo bimetallic nanoparticles (PtCo/C) as electrode catalysts for the oxygen reduction reaction (ORR) at the cathodes in polymer electrolyte membrane fuel cells (PEFCs) by an electron-beam irradiation reduction method (EBIRM). An EBIRM allows nanoparticles to be easily prepared by the reduction of precursor ions in an aqueous solution irradiated with a high-energy electron beam. The structures of PtCo/C were characterized by transmission electron microscopy, inductively coupled plasma atomic emission spectrometry, and the techniques of X-ray diffraction and X-ray absorption near edge structure. It found for the first time that both PtCo alloy and Co oxide were prepared simultaneously on the carbon support by an EBIRM. The catalytic activity and durability of PtCo/C were evaluated by linear-sweep voltammetry and cyclic voltammetry, respectively. The addition of Co to Pt/C not only enhanced the catalytic activity for the ORR but also improved the catalytic durability. As the Co concentration increased, both behaviors became pronounced. These improvements are explained by the effects of both PtCo alloy and Co oxide. We demonstrated that an EBIRM can not only synthesize the alloy and oxide simultaneously on the carbon support but also mass-produce the electrode catalysts for PEFC cathodes.     

Real-time observation of Brownian motion and cluster movement of ferro- and non-magnetic particles in magnetic fluids

Cluster movements of ferro- and non-magnetic particles in magnetic fluids were investigated using optical microscope system and image processing system. Real-time visualizations of the Brownian motion of particles and the chain-like cluster movement of both types of particle were performed under a magnetic field. The principal objectives of this study were to clarify the applicability of the optical microscope system and image processing system, and to analyze the growth process of the cluster under magnetic field. The analysis of particle image was done using Particle Tracking Velocimetry (PTV). The results clarified that the real-time observation of Brownian motion and cluster movement of ferro- and non-magnetic particles in magnetic fluids can be carried out using the optical microscope system and the PTV image measurement. Independent continuous measurements with changing positions and velocity of the minute particle were made possible. The study concluded that the system can obtain satisfactory results on growth process measurement of cluster under a magnetic field.     

Intracavity second-harmonic generation at 320 nm of an actively Q-switched Pr:LiYF4 laser

We demonstrate pulse laser operation of a Pr:LiYF(4) laser pumped by InGaN laser diodes (444 nm) using an acousto-optic modulator. We obtained a maximum laser peak power of 167 W (4 μJ/pulse) with a pulse width of 24 ns at an 11 kHz repetition rate for a 63 nm wavelength. Employing an 8 mm long lithium triborate nonlinear crystal in the laser cavity, we obtained a maximum peak power of 55 W (2.7 μJ/pulse) at 320 nm, which corresponds to a conversion efficiency of 69% with respect to the fundamental laser energy. The UV laser pulse width was 36 ns.     

Size Effect Analysis for Pullout Strength under Various Boundary Conditions

One of the goals of this research is to apply nonlinear fracture mechanics to design problems encountered by the engineering society. Nonlinear fracture mechanics makes it possible to study the size effect with respect to the pullout cone failure of headed anchors embedded in concrete under various boundary conditions. This investigation shows that the fictitious crack approach can be extended with two orthogonal rod elements to become a new technique that can successfully predict the size effect on the pullout tests. In this study the numerical investigation that describes the behavior of headed anchors under tension loading has been carried out by a computer simulation using our original program ANACS (Advanced Nonlinear Analysis of Concrete Structures). To judge the validity of the results, the numerical results were compared with Eligehausen and Sawade's empirical equation and test results of a report by the Reunion International des Laboratoire d'Essais et de Recherches sur les Materiaux et les Constructions.     

Simple Mathematical Model for the Electrical Conductivity of Highly Porous Ceramics

A novel approach has been proposed to describe the relationship between the conductivity and relative density of highly porous materials. As a first approximation, porous material was represented by a uniaxial string of spheres along the direction of the potential gradient. Then, a string of spheres was remodeled into a rotating body of sine-wave functions, f ( x ) = (1 + r ₀)/2 + [(1 – r ₀)/2] sin (π x / c ) for 0 ≤ x < c and f (π x ) = (1 + r ₀)/2 + [(1 – r ₀)/2] sin {π( x + 1 − 2 c )/(l − c )} for c ≤ x < 1, where the former represents the shape of a sphere, the latter that of the bottleneck between neighboring spheres, and r ₀ denotes the ratio of the minimum diameter at the bottleneck to the maximum diameter of the rotating body. It was shown that the calculated relationships reproduced the reported experimental results for the relationship between the porosity and conductivity of La_0.5Sr_0.5CoO₃, BaF₂, and (ZrO₂)_0.9(Y₂O₃)_0.1. The relative conductivity to the bulk material was close to zero at 45–60% relative density, which is the density of green wares. It steeply increased with an increase in the relative density and then gradually approached that of the bulk material.