Studies of elastic waves caused by corona discharges in oil

In order to diagnose the deterioration of insulation and evaluate its location in oil-filled pole transformers, measurements of elastic waves brought by corona discharges in oil were performed, based on an acoustic emission (AE) technique. The detected signals in these measurements were analyzed by means of a fast Fourier transform (FFT) and their properties were discussed theoretically. It was found that the AE signals due to the Lamb waves of symmetric mode caused in a thin steel tank could be recognized easily by the FFT analysis of initial stages of the detected AE signals. This suggests that the accuracy on location of the AE sources in the transformer would be improved. Also, it was shown that a low pass filter was effective in improving the location accuracy     

Influence of Culture Period on Osteoblast Differentiation of Tissue-Engineered Bone Constructed by Apatite-Fiber Scaffolds Using Radial-Flow Bioreactor

With the limitation of autografts, the development of alternative treatments for bone diseases to alleviate autograft-related complications is highly demanded. In this study, a tissue-engineered bone was formed by culturing rat bone marrow cells (RBMCs) onto porous apatite-fiber scaffolds (AFSs) with three-dimensional (3D) interconnected pores using a radial-flow bioreactor (RFB). Using the optimized flow rate, the effect of different culturing periods on the development of tissue-engineered bone was investigated. The 3D cell culture using RFB was performed for 0, 1 or 2 weeks in a standard medium followed by 0, 1 or 2 weeks in a differentiation medium. Osteoblast differentiation in the tissue-engineered bone was examined by alkaline phosphatase (ALP) and osteocalcin (OC) assays. Furthermore, the tissue-engineered bone was histologically examined by hematoxylin and eosin and alizarin red S stains. We found that the ALP activity and OC content of calcified cells tended to increase with the culture period, and the differentiation of tissue-engineered bone could be controlled by varying the culture period. In addition, the employment of RFB and AFSs provided a favorable 3D environment for cell growth and differentiation. Overall, these results provide valuable insights into the design of tissue-engineered bone for clinical applications.     

Tailoring Silicon Nitride Surface Chemistry for Facilitating Odontogenic Differentiation of Rat Dental Pulp Cells

Silicon nitride (Si₃N₄) can facilitate bone formation; hence, it is used as a biomaterial in orthopedics. Nevertheless, its usability for dentistry is unexplored. The aim of the present study was to investigate the effect of Si₃N₄ granules for the proliferation and odontogenic differentiation of rat dental pulp cells (rDPCs). Four different types of Si₃N₄ granules were prepared, which underwent different treatments to form pristine as-synthesized Si₃N₄, chemically treated Si₃N₄, thermally treated Si₃N₄, and Si₃N₄ sintered with 3 wt.% yttrium oxide (Y₂O₃). rDPCs were cultured on or around the Si₃N₄ granular beds. Compared with the other three types of Si₃N₄ granules, the sintered Si₃N₄ granules significantly promoted cellular attachment, upregulated the expression of odontogenic marker genes (Dentin Matrix Acidic Phosphoprotein 1 and Dentin Sialophosphoprotein) in the early phase, and enhanced the formation of mineralization nodules. Furthermore, the water contact angle of sintered Si₃N₄ was also greatly increased to 40°. These results suggest that the sintering process for Si₃N₄ with Y₂O₃ positively altered the surface properties of pristine as-synthesized Si₃N₄ granules, thereby facilitating the odontogenic differentiation of rDPCs. Thus, the introduction of a sintering treatment for Si₃N₄ granules is likely to facilitate their use in the clinical application of dentistry.     

Enhancement of cooling rate during rapid quenching of a thin wire by ultrasonic vibration

Experiments were conducted to study the effect of ultrasonic vibrations on heat transfer during the rapid quenching of thin horizontal platinum wires in subcooled water and ethanol. The frequency of ultrasonic vibration was 24 and 44 kHz. The power input to the transducer P ranged from 0 to 280 W. The measured boiling curve had two minimum-heat-flux points; the first (named the MI point) corresponded to the onset of significant liquid–solid contact. For P ≤ 20 W, the wall superheat at the MI point increased considerably with increasing P. The heat flux was not much affected by the ultrasonic vibrations until the MI point was reached. After the MI point, the heat flux increased significantly with increasing P. The effect was more significant for υ = 24 kHz. Distributions of the sound pressure and the cavitation intensity were also measured and their effects on the heat transfer characteristics are discussed. © 1998 Scripta Technica. Heat Trans Jpn Res, 27(1): 16–30, 1998     

Project scheduling using a genetic algorithm with adaptable changing genetic operators

Genetic algorithms (GA) have been widely used to solve planning problems. However, they require one to determine the optimal values of many genetic parameters, such as population sizes, crossover probability, mutation probability, and so on. To make matters worse, the most suitable combination of parameters for one problem is not always optimal for others. Therefore, these parameters should be tuned whenever the problem changes. In this paper, we propose an adaptable GA mechanism that has autonomic parameter tuning for the composition of generic operators. This mechanism raises questions concerning the probability of genetic operators that acted effectively, that is, the probability that one operator created better individuals than the other operators. It also successively adjusts the combinations of genetic parameters suitable for the target problem. We applied the adaptable GA mechanism to a project scheduling model (PSM) and evaluated it with manual tuning methods. © 1998 Scripta Technica, Electr Eng Jpn, 124(2): 36–42, 1998     

Theoretical analysis of the stability of vapor film in subcooled film boiling on a horizontal wire

Linear stability analysis of a thin vapor film in subcooled film boiling on a horizontal cylinder is reported. The effects of liquid inertia, vapor viscosity and compressibility, and heat transfer were taken into account. Theoretical predictions of the heat transfer coefficient at the neutral stability point were compared with experimental data at the minimum-heat-flux point that was obtained during rapid quenching of thin horizontal wires in water and ethanol. At high liquid subcooling, the experimental value was 60% of the theoretical prediction irrespective of the wire diameter and quenching liquid. This difference was considered to be due to the nonuniformity of the vapor film which was neglected in the theoretical analysis. © 1998 Scripta Technica. Heat Trans Jpn Res, 26(4): 219–235, 1997     

Efficient Suppression of Abdominal Aortic Aneurysm Expansion in Rats through Systemic Administration of Statin-Loaded Nanomedicine

Abdominal aortic aneurysm (AAA) is a life-threatening disease. However, no systemically injectable drug has been approved for AAA treatment due to low bioavailability. Polymeric micelles are nanomedicines that have the potential to improve therapeutic efficacy by selectively delivering drugs into disease sites, and research has mainly focused on cancer treatments. Here, we developed a statin-loaded polymeric micelle to treat AAAs in rat models. The micelle showed medicinal efficacy by preventing aortic aneurysm expansion in a dose-dependent manner. Furthermore, the micelle-injected group showed decreased macrophage infiltration and decreased matrix metalloproteinase-9 activity in cases of AAA.     

Improvement on characteristics of porous alumina from platelets using a TEOS treatment

A porous alumina body was synthesized from anisotropic alumina particles, namely platelets. When green compacts, which had been uniaxially pressed at 1 MPa, were heated at 1200 and 1500 °C for 1 h, the average porosity of the resulting alumina bodies was 75.5 and 71.0%, respectively. The thermal conductivity of the porous alumina fabricated at 1400 °C for 1 h with 72.3% in porosity was 0.8 W m^?1 K^?1. In an attempt to increase the compressive strength of the porous alumina bodies, TEOS (tetraethyl orthosilicate) solution treatment was carried out, followed by reheating to 1400 °C for 1 h. The compressive strength of the porous alumina body increased from 3.8 MPa (without TEOS solution treatment) to 10.2 MPa (with three rounds of TEOS treatment), with the porosity decreasing to 65.5% and the thermal conductivity increasing to1.2 W m^?1 K^?1.     

Photosynthetic bacteria production from food processing wastewater in sequencing batch and membrane photo-bioreactors

Application of photosynthetic process could be highly efficient and surpass anaerobic treatment in releasing less greenhouse gas and odor while the biomass produced can be utilized. The combination of photosynthetic process with membrane separation is possibly effective for water reclamation and biomass production. In this study, cultivation of mixed culture photosynthetic bacteria from food processing wastewater was investigated in a sequencing batch reactor (SBR) and a membrane bioreactor (MBR) supplied with infrared light. Both photo-bioreactors were operated at a hydraulic retention time (HRT) of 10 days. Higher MLSS concentration achieved in the MBR through complete retention of biomass resulted in a slightly improved performance. When the system was operated with MLSS controlled by occasional sludge withdrawal, total biomass production of MBR and SBR photo-bioreactor was almost equal. However, 64.5% of total biomass production was washed out with the effluent in SBR system. Consequently, the higher biomass could be recovered for utilization in MBR.