Increase of static electrification in an aged oil‐immersed transformer

Increase of static electrification activity and discharge generation was experienced during the service operation of an aged power transformer. The transformer oil had high sulfide and sulfoxide contents and was liable to show high ECT value after aging. However, there was no apparent increase in standard ECT (electrostatic charging tendency) measurement of the insulating oil and, therefore, deterioration of pressboard was suspected as the cause of the increase. The ECT tests with aged oil and pressboard sampled from the aged transformer were insufficient to demonstrate the increase in static electrification for the aged transformer. On the other hand, the results suggested a possibility that increase in static electrification can be caused by adsorption of some deterioration compound in the aged oil to the pressboard. In order to make more effective evaluation to the transformer insulation, potential measurement on the pressboard in the oil duct was carried out. The experimental results demonstrated strong increase of the accumulated charge by the aged pressboard, which suggested effectiveness of potential measurement for the assessment of static electrification in transformers. The device of potential measurement for practical use was designed by reducing the necessary amount of oil sampling. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(3): 10–19, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20789     

Formation of Continuous Pore Structures in Si–C–O Fibers by Adjusting the Melt Spinning Condition of a Polycarbosilane–Polysiloxane Polymer Blend

A polymer blend containing polycarbosilane (PCS) and 15 mass% of polyhydromethylsiloxane (H-oil) was prepared and the properties of the polymer melt were investigated in order to clarify the mechanisms of continuous pore formation. Melt viscosity decreased as the H-oil content increased. Moreover, the saturation of the plasticizer effect of H-oil on the viscosity and apparent turbidity of the melting polymer suggested that the compatibility of H-oil to PCS in melting was limited at 15 mass%. Gas chromatography data after heating showed that an amount of evolved hydrogen at 573 K was increased by 15 mass% of H-oil addition. The fibers formed by the melt-spun of the polymer blend at 578 K mainly possessed a single pore at the center of the fibers' cross section. On the other hand, the fibers melt-spun at 543 K usually included multiple pores, and the fibers melt-spun at 538 K included a number of tiny pores. It is proposed that the evolved hydrogen can be dissolved in the polymer melt, and the desaturation process of the dissolved gas during the fiber spinning with a sudden temperature reduction likely determined the size and location of pores in the fibers.     

Estimation of respiratory muscle endurance using an inspiratory threshold loading device in patients with chronic pulmonary emphysema and in elderly subjects

We studied respiratory muscle endurance with an inspiratory threshold loading (ITL) device using Martyn's method (2-min incremental loading test) in 9 patients with chronic pulmonary emphysema (CPE patients) and in 9 elderly subjects with no lung disease (NE subjects), and their endurance was compared with that of 9 normal young subjects (NY subjects). In 11 cases (8 CPE patients and 3 NE subjects) a treadmill exercise test was performed and cardiopulmonary parameters obtained from the ITL and treadmill tests were compared. The maximum weight tolerated for 2 minutes (Wmax) and the mean peak inspiratory mouth pressure/maximum inspiratory mouth pressure ratio at the maximum load (Ppk/MIP at Max Load) were used as indices of respiratory muscle endurance. CPE patients had significantly decreased Wmax compared with those of NE and NY subjects. Wmax in all cases positively correlated with Ppk/MIP at Max Load, and endurance time of both the ITL and treadmill tests. During both tests, SaO2 significantly decreased, and heart rate and mean blood pressure significantly increased. There was less change in SaO2 and heart rate during the ITL test than during the treadmill test, and neither arrhythmias nor ST changes on ECG were observed during the ITL test. These results indicate that the ITL test can be easily and safely employed in CPE patients and elderly subjects to estimate respiratory muscle endurance.     

Testing for EGARCH Against Stochastic Volatility Models

Abstract. It is shown that the EGARCH model is the degenerate case of Danielsson's [Journal of Econometrics (1994) Vol. 61, pp. 375–400] stochastic volatility model where the disturbance of the transition equation of conditional volatility has zero variance. The Lagrange multiplier test statistic is obtained for the EGARCH model against the stochastic volatility model by expressing the degenerate density under the null hypothesis by the Dirac delta function. The finite sample performance of the test is studied in a small Monte Carlo experiment.     

An experimental study of energy-saving pneumatic conveying system in a horizontal pipeline with dune model

In order to reduce power consumption and conveying velocity, a pneumatic conveying system where a dune model is mounted in a pipeline is proposed in this paper. The experimental study focuses on the effect of the mounted dune model in the horizontal pneumatic conveying system in terms of pressure drop, power consumption and conveying velocity. The test pipeline consisted of a horizontal smooth acrylic tube with an inside diameter of 80 mm and a length of about 5 m. Polyethylene spherical particles with a density of 952 kg/m³ and diameters of 2.3 and 3.3 mm are used as conveying materials. The mean air velocity is varied from 9 to 16 m/s, and the solid mass flow rate is from 0.25 to 0.45 kg/s. Firstly, the effect of the dune model location on pneumatic conveying is experimentally studied. It is found that in the lower air velocity range, the pressure drop of the pneumatic conveying with a mounted dune model is lower than that of a conventional pneumatic conveying system. A lower conveying velocity and energy-saving conveying can be realized by installing a dune model in the conveying pipe. Especially the case of fixing the dune model on the bottom of the pipe at the inlet of particle feed is more effective. The particle flow patterns also show that the dune model reduces the deposition of particles. Then, the effect of different surface materials of the dune model is examined. By using a surface material of the dune model with a large coefficient of restitution, the pressure drop of conveying large particles is the lowest. When conveying relatively small particles, however, the pressure drop becomes the lowest by a small coefficient of restitution. The maximum reduction rates of the minimum velocity and power consumption by the dune model are about 19% and 34%, respectively.     

An Interactive Data Language software package to calculate ionospheric conductivity by using numerical models

The Inter-university Upper atmosphere Global Observation NETwork (IUGONET) project focuses on handling ground-based observational data of the upper atmosphere. To this end, the project members have been developing a data analysis software package which is based on Interactive Data Language (IDL). Filling the spatial gaps in observational data requires the use of numerical models. In this paper, we discuss an IDL software package for global ionospheric conductivity by integration of 3rd party numerical models. The model can be used to create further derived models.     

Process design of chondrocyte cultures with monolayer growth for cell expansion and subsequent three-dimensional growth for production of cultured cartilage

The subculture of rabbit chondrocytes with serial passaging was carried out for cell expansion on a collagen-coated surface, and the morphological transition of round-shaped cells to spindle-shaped ones was examined. The observation of cytoskeletal formation by staining F-actin and vinculin supported the view that the round-shaped cells were in the process of differentiation with immature stress fibers relating to less cellular polarity. The cellular morphology was estimated in terms of the distribution of roundness, R(C), during the subculturing on the collagen substrate. The frequency of the number of round-shaped cells, which was defined as the ratio of the number of cells with R(C) >0.9 against the total cell number, was correlated in a logarithmic formula with the number of population doublings during the subcultures. Kinetic models were adopted for the process design of the combined culture of chondrocytes with monolayer growth on the collagen substrate and subsequent three-dimensional growth in Atelocollagen gel, employing the boundary conditions based on the population balance between differentiated and dedifferentiated cells. The combined culture was performed successfully according to the process design scheduled as monolayer growth for 240 h and three-dimensional growth for 264 h, the number of seed cells being 68% of that in the conventional culture for 504 h where monolayer growth for cell expansion was not included.