Preparation of ultrasmooth and defect-free 4H-SiC(0001) surfaces by elastic emission machining

In this work, elastic emission machining (EEM), which is a precise surface-preparation technique using chemical reactions between the surfaces of work and fine powder particles, is applied to the flattening 4H-SiC (0001) surface. Prepared surfaces are observed and characterized by optical interferometry, atomic force microscopy (AFM), and low-energy electron diffraction (LEED). The obtained images show that the processed surface has atomic-level flatness, and the subsurface damage and surface scratches of the preprocessed surface are almost entirely removed.     

Physically Asymmetric Star Network with CWDM Wavelength Router

We propose and demonstrate a CWDM full-mesh wavelength-routing system with an asymmetric physical star topology. We design a wavelength router to optimize this topology in which the node distances from the wavelength router are unequal. In addition, the router utilizes all the wavelengths making it possible to increase the maximum number of nodes in the system. The routing function is confirmed experimentally using transceivers with two different optical budgets     

Leaching of Lead and Connectivity of Plumbate Networks in Lead Silicate Glasses

The formation of a plumbate network in binary lead silicate glasses was examined based on the leaching behavior of Pb²⁺ in lead silicate glasses over a wide composition region. The effective diffusion coefficient of Pb²⁺ at 40°C was on the order of 10⁻¹⁷ m²/s for PbO<35 mol% glasses, and increased three orders of magnitude for 35–50 mol% PbO contents. Such a steep composition dependence is considered to be because of changes in the medium or longer range structure. That is, it is proposed that the plumbate network forms a percolative 3D network in the composition region to form diffusion paths for the lead ions. In addition, the present results indicate that the lead ion exists as a network former over the entire glass forming composition range of the binary silicate glasses.     

Development of atom probe specimen preparation techniques for specific regions in steel materials

More elaborated specimen preparation techniques for atom probe analysis were developed using a focused ion beam with a sample lift-out system so as to expand the application field in steel materials. The techniques enable atom probe analysis of sample steel at site-specific regions of interest. The preferable form of the needle specimen was provided by electrostatic field calculation using a finite element method. The new techniques were applied to the observation of a bainite-ferrite interface in a low carbon steel, and atomic-scale partitioning and segregation of alloying elements at the phase interface were directly observed in three dimensions.     

Piezoelectric properties of vinylidene fluoride oligomer for use in medical tactile sensor applications

The piezoelectric effect of vinylidene fluoride (VDF) oligomer was evaluated with respect to its medical use as a new tactile sensor. VDF oligomer is a new substance that has a smaller number of VDF units and a lower molecular weight than poly(vinylidene fluoride) (PVDF); among the organic ferroelectrics, it has the largest reported remanent polarization. In this work, the performance of a prototype sensor device based on this material was evaluated. The piezoelectric coefficient of VDF oligomer was found to be greater than that of P(VDF/TrFE) copolymer; a film composed of VDF oligomer was thin and uniform. Based on the experimental results, possible applications of VDF oligomer in medical tactile sensors are discussed. This study confirms that VDF oligomer is a promising ferroelectric material for use in tactile sensors.     

Coupled Building Control Using Acceleration Feedback

Connecting adjacent buildings for response reduction has been shown to be an effective method of structural control. Active coupled building control has been implemented in 2001 in the recently constructed Triton Square office complex in Tokyo, Japan. To date, active coupled building control using acceleration feedback has not been demonstrated. This paper reports on studies at the Structural Dynamics and Control/Earthquake Engineering Laboratory (SDC/EEL) at the University of Notre Dame to experimentally verify active coupled building control employing acceleration feedback for the seismic protection of structures. Herein, a pair of 2–dof flexible building models with a DC servo–motor/ball–screw control mechanism are employed. Feedback control is incorporated, using the acceleration, as well as relative displacement, measurements at the top stories of the building models. The proposed approach is shown to be effective for reduction of structural vibration due to seismic excitation.     

Characterization of the aramid/epoxy interfacial properties by means of pull-out test and influence of water absorption

Single fiber pull-out tests were carried out to investigate the influence of water absorption on the interfacial properties of aramid/epoxy composite. The fiber/matrix interfacial strength was severely decreased between 4 and 7 week immersion time in deionized water at 80 °C, and thereafter showed a plateau. This change with immersion time did not correspond with that of the water gain of the pull-out specimens, because the water gain did not reflect the one in the fiber/matrix interface. As a result of the degradation of the fiber/matrix interfacial strength, the pulled-out fiber surfaces of 7, 10 and 13 week wet specimen were smooth. In situ observations of interfacial crack propagation by a video microscope and an analysis of acoustic emission (AE) signals showed that AE signals obtained during the pull-out process were classified into four types according to fracture modes. AE signals detected at final unstable crack propagation and fiber breakage had high amplitude and long duration.     

Structural Study of PbO–B2O3 Glasses by X-ray Diffraction and 11B MAS NMR Techniques

The structure of PbO–B₂O₃ glasses has been investigated in the composition range of 25–80 mol% PbO by using X-ray diffraction and ¹¹B NMR techniques. The well-separated peaks due to Pb–O and Pb–Pb pairs were first observed in the radial distribution function, and peak deconvolution was performed by using a pair function method. The average coordination number of lead atoms was determined to be about 6 in the low-PbO-content region and about 3 in the high-PbO-content region. With an increase of PbO content, the peaks at 0.24 and 0.40 nm shifted to shorter distances, and especially the latter peak drastically increased in intensity in the composition range >50 mol% PbO. It was suggested that PbO is a main glass former in the high-PbO-content region. Based on the results obtained, we propose structural models of lead borate glasses.     

Demand–Supply Balancing Capability Analysis for a Future Power System

Under the anticipated high penetration of variable renewable energy generation such as photovoltaics and higher share of nuclear generation, the issue of supply–demand balancing capability should be evaluated and fixed in a future power system. Improvement of existing balancing measures and new technologies such as demand activation and energy storage are expected to solve the issue. In this situation, a long‐range power system supply–demand analysis should have the capability to evaluate the balancing capability and balancing countermeasures. This paper presents a new analysis methodology of activated demand model and evaluation of supply–demand balancing capability for a long‐range power system demand–supply analysis model, ESPRIT. Model analysis was made to verify the new methodology of the tool including day‐ahead scheduling of a heat pump water heater, an EV/PHEV, and a battery. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 186(2): 21–30, 2014; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.22488     

Structural, Mechanical and Erosion Properties of Yttrium Oxide Coatings by Axial Suspension Plasma Spraying for Electronics Applications

Yttrium oxide (Y₂O₃) coatings have been prepared by axial suspension plasma spraying with fine powders. It is clarified that the coatings have high hardness, low porosity, high erosion resistance against CF₄ -containing plasma and retention of smooth eroded surface. This suggests that the axial suspension plasma spraying of Y₂O₃ is applicable to fabricating equipment for electronic devices, such as dry etching. Surface morphologies of the slurry coatings with splats are similar to conventional plasma-sprayed Y₂O₃ coatings, identified from microstructural analysis. Dense coating structures with no lamellar boundaries have been seen, which is apparently different from the conventional coatings. It has also been found that crystal structure of the suspension coatings mainly composed of metastable monoclinic phase, whereas the powders and the conventional plasma spray coatings have stable cubic phase. Mechanism of coating formation by plasma spraying with fine powder slurries is discussed based on the results.