Cryogenic helium gas circulation system for advanced characterization of superconducting cables and other devices

A versatile cryogenic test bed, based on circulating cryogenic helium gas, has been designed, fabricated, and installed at the Florida State University Center for Advanced Power Systems (FSU-CAPS). The test bed is being used to understand the benefits of integrating the cryogenic systems of multiple superconducting power devices. The helium circulation system operates with four sets of cryocooler and heat exchanger combinations. The maximum operating pressure of the system is 2.1 MPa. The efficacy of helium circulation systems in cooling superconducting power devices is evaluated using a 30-m-long simulated superconducting cable in a flexible cryostat. Experiments were conducted at various mass flow rates and a variety of heat load profiles. A 1-D thermal model was developed to understand the effect of the gas flow parameters on the thermal gradients along the cable. Experimental results are in close agreement with the results from the thermal model.     

Nanostructural investigation of frontalis sling biomaterial surfaces

This study examined the nanostructural surface of three frontalis sling biomaterials: autogenous fascia lata, preserved fascia lata and silicone rod. The morphological characteristics of the sling biomaterial surfaces were examined qualitatively and quantitatively by scanning electron microscopy and atomic force microscopy, respectively. The autogenous fascia lata showed well‐arranged nanostructures of parallel fascia collagen fibrils with clear 67 nm axial periodicity, whereas the preserved fascia lata showed tangled nanostructures of damaged collagen fibril bundles. The silicone rod showed a substantial amount of debris with some scratches and the smoothest roughness compared with the other sling biomaterials, followed by preserved fascia lata. Autogenous fascia lata showed the highest surface roughness. The association between the roughness and cell adhesion suggests that the nanostructure of autogenous fascia lata biomaterials is the best for frontalis sling and that of the silicone rod biomaterials is the worst. SCANNING 33:419–425, 2011. © 2011 Wiley Periodicals, Inc.     

Enhanced Cycle Stability of Low-Cost Na-Rich Metallic NaCl Electrode for Advanced Na-Ion Batteries

Sodium-rich metallic Na_x+z has received significant attention as a low-cost alternative to the conventional electrode materials used in Li-ion batteries. However, the poor cyclability of Na_xCl remains a major challenge to its practical application. Here, a simple method is developed for improving the electrochemical performance of Na_xCl by controlling the upper limit of cut-off voltage. It is demonstrated that additional Na-vacancy defects can be introduced in the NaCl structure during the high-voltage activation process at 4.5 V. The structure then accommodates more sodium ions during the next discharge, resulting in increased capacity. At the same time, Cl-ions released by NaCl decomposition are oxidized to form Cl-based organic species at the active material interfaces. This plays a crucial role in protecting the NaCl electrode from undesired side reactions at high voltage. In short, this control of the charging protocol helps to induce more vacancies in the NaCl structure, as well as form stable interphases on the electrode surface, contributing to the increased capacity and enhanced cycle stability. This study will help in exploring a new approach for developing low-cost and high-capacity electrode material, which can potentially be applied in future energy-storage systems.     

Fabrication of carbon nanotube AFM probes using the Langmuir-Blodgett technique

Carbon nanotube (CNT)-tipped atomic force microscopy (AFM) probes have shown a significant potential for obtaining high-resolution imaging of nanostructure and biological materials. In this paper, we report a simple method to fabricate single-walled carbon nanotube (SWNT) nanoprobes for AFM using the Langmuir-Blodgett (LB) technique. Thiophenyl-modified SWNTs (SWNT-SHs) through amidation of SWNTs in chloroform allowed to be spread and form a stable Langmuir monolayer at the water/air interface. A simple two-step transfer process was used: (1) dipping conventional AFM probes into the Langmuir monolayer and (2) lifting the probes from the water surface. This results in the attachment of SWNTs onto the tips of AFM nanoprobes. We found that the SWNTs assembled on the nanoprobes were well-oriented and robust enough to maintain their shape and direction even after successive scans. AFM measurements of a nano-porous alumina substrate and deoxyribonucleic acid using SWNT-modified nanoprobes revealed that the curvature diameter of the nanoprobes was less than 3nm and a fine resolution was obtained than that from conventional AFM probes. We also demonstrate that the LB method is a scalable process capable of simultaneously fabricating a large number of SWNT-modified nanoprobes.     

Learning and assimilation vs. M&A and innovation: Japan at the crossroads

Historically, Japan constructed its socio-cultural system so that it introduced, adopted, assimilated, and developed Western technology selectively without spoiling its own indigenous culture. And until recently, Japan learned and assimilated global best practices without being dependent on mergers and acquisitions (M&A). M&As in Japan were the lowest in the world until 2000, suggesting a low dependence on acquiring technology in this way. Recently, the number of M&As has increased dramatically among certain Japanese manufacturing firms. Prior to 2004, these firms were less profitable than their counterparts that did not depend on M&A. Today Japan's corporate technology and innovation strategy is at a crucial inflection point of maintaining the indigenous learning/assimilation function while also becoming more dependent on M&As. This paper explores the changing role of M&As in Japanese firms, and also considers the role of Web 2.0 and Enterprise 2.0 in the innovation process. Using an empirical analysis of the trajectories of Japan's leading electrical machinery firms, this paper explores the changing role of M&A in the context of business innovation in Japan, and the ongoing dialectic between indigenous strengths and global best practices.     

Experimental studies of 1 ton/day coal slurry feed type oxygen blown, entrained flow gasifier

Experimental Studies of a 1 Ton/Day coal slurry feed type oxygen blown, entrained flow gasifier have been performed with the slurry concentration and gasifier temperature at 65% and above 1,300 ‡C, respectively. The characteristics of ash fusion temperature with addition of CaO as a flux were investigated to maintain the proper slag tapping condition in the range of reaction temperature. As the flux addition increased, ash fusion temperature showed a eutectic effect with the eutectic at around 20–30% CaO. In order to analyze the gasification characteristics, the effects of O₂/coal feed ratio on the product gas composition, heating value, gasifier temperature and cold gas efficiency were evaluated. From the results, it was shown in the case of Kideco coal that the cold gas efficiency was 44–60% and the heating value was 1,700-2,200 kcal/Nm³, while Drayton coal showed a cold gas efficiency of 55–62% and a heating value of 1,800-2,200 kcal/Nm³. In the case of Datong coal, the cold gas efficiency was 38–65%, and the heating value was 2,000-2,300 kcal/Nm³. Also, the results showed that the optimal operating condition of O₂/coal ratio for the three different coals was 0.9. Presented at the Int’/Symp. on Chem. Eng. (Cheju, Feb. 8–10, 2001), dedicated to Prof. H. S. Chun on the occasion of his retirement from Korea University.     

Preparation and Microstructure of a Si-Mo Fused Slurry Coating on Carbon/Carbon Composites for Oxidation Protection

A coating of composition Si-40Mo (wt pct) was prepared by fused slurry coating method on the two-dimensional carbon/carbon (2D-C/C) composite to improve oxidation resistance. In the procedure of the fabrication, pure St slurry inner layer in the pre-coating was necessary to apply because of infiltration of liquid Si into the substrate during the sintering. The coating consists of Si continuous phase and MoSi2 particles. In addition, the infiltration of Si into the substrate and the SiC reaction layer between the coating and the C/C composite were observed. Oxidation resistance and the thermal shock resistance of the Si-Mo fused sluury coating were quite excellent at 1730℃     

Examination of selectivity of templates for the textured potassium sodium niobate ceramics

To achieve the surface-orientation-controlled microstructure of K_0.5Na_0.5NbO₃, not only the template must exhibit the high anisotropy like a plate-shape but the reactive stability as well as the crystallographic coherency between the template and the K_0.5Na_0.5NbO₃ must be carefully considered. In this work, we focused on what kinds of ceramics are suitable for the fabrication of the surface-orientation-controlled K_0.5Na_0.5NbO₃. First of all, BaTiO₃, SrTiO₃, Ba(Zr_0.1Ti_0.9)O₃, KNbO₃, NaNbO₃, KTaO₃ and NaTaO₃ were chosen as the candidates in the regard of the crystallographic coherency. To verify the chemical stability between candidate ceramics and K_0.5Na_0.5NbO₃, the prepared candidate ceramic bulks were embedded by the K_0.5Na_0.5NbO₃ powder, they were annealed at 1100 °C, and then the interface regions between candidate ceramics and K_0.5Na_0.5NbO₃ were investigated using Secondary Electron Microscopy (SEM) equipped with Energy Dispersive Spectrometer (EDS). From these experimental results, BaTiO₃, SrTiO₃, Ba(Zr_0.1Ti_0.9)O₃, KNbO₃ and NaTaO₃ were found to be not appropriate for the templates for the tailoring of K_0.5Na_0.5NbO₃, while the NaNbO₃ and KTaO₃ showed a good crystallographic coherency and a chemical stability with K_0.5Na_0.5NbO₃.