Modeling method of fast transient for unsymmetrical stray capacitance to ground

Transient characteristic of power system apparatus in a high‐frequency region should be modeled with stray capacitors. Pi‐type circuit is commonly used to represent the stray capacitors between terminals and those to the ground. A modeling method for the pi‐type circuit with unsymmetrical stray capacitances to ground is proposed in this paper. To obtain the unsymmetrical stray capacitances to ground, a couple of differential‐mode measurements are interchangeably applied. The parameters of the pi‐type circuit can be determined by the measurements with a common‐mode measurement. A nonlinear least‐squares method is used to estimate the capacitances. The method is applied to compose an equivalent circuit of a miniature circuit breaker (MCB), which has unsymmetrical stray capacitances to ground. The application is not only for the MCB but also for a scaled model of a high‐voltage circuit breaker. A gas‐filled arrester is used as a voltage sensor for the test because the voltage across the stray capacitor cannot be directly measured due to the input capacitance of a voltage probe. A transient response of the MCB with the gas‐filled arresters is numerically simulated to show the usefulness of the equivalent circuit. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

An impedance measurement of a small‐capacitance circuit using transient responses for lightning surge analysis

A method to measure a small capacitance with its loss resistance using a set of transient current waveforms is proposed in this paper. The parameters are obtained from the time constants in the time domain. The method has high resistance to extraneous noise, because a time‐to‐frequency transformation, which is sensitive to noise, is not required. The transient current waveforms are obtained by a voltage or current source, a current transformer, and a waveform recorder. The measured capacitance by the proposed method is not affected by the capacitance of the voltage probe, because it is obtained without any voltage information. The sheath surge impedance of the current injection cable, which is indispensable for the transient measurement, is corrected. The application of the method has the advantage in that it allows the modeling of a fast transient of a power apparatus, comparing it with the steady‐state measurement using an impedance measuring instrument. The proposed method is applied to create an equivalent circuit between electrodes implanted into a piece of wood, and its reliability is confirmed by comparison between the measured and calculated results. Stray capacitances of a miniature circuit breaker are also measured, and the results show that the proposed method is applicable to equipment in power systems. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Comparison of the morphology and structure of WO3 nanomaterials synthesized by a sol-gel method followed by calcination or hydrothermal treatment

Tungsten (VI) oxide (WO₃) nanomaterials were synthesized by a sol-gel method using WCl₆ and C₂H₅OH as precursors followed by calcination or hydrothermal treatment. X-Ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) equipped with energy dispersive X-ray spectroscopy (EDX) were used to characterize the structure and morphology of the materials. There were significant differences between the WO₃ materials that were calcinated and those that were subjected to a hydrothermal process. The XRD results revealed that calcination temperatures of 300°C and 400°C gave hexagonal structures and temperatures of 500°C and 600°C gave monoclinic structures. The SEM images showed that an increase in calcination temperature led to a decrease in the WO₃ powder particle size. The TEM analysis showed that several nanoparticles agglomerated to form bigger clusters. The hydrothermal process produced hexagonal structures for holding times of 12, 16, and 20 h and monoclinic structures for a holding time of 24 h. The SEM results showed transparent rectangular particles which according to the TEM results originated from the aggregation of several nanotubes.     

The role of personal dexterity and incentive gamification to enhance employee learning experience and performance

Cognition, Technology & Work - This paper aims to develop a concept of incentive gamification for organizations in the digital era. Incentive gamification is an incentive-based policy using the...     

WO3 nanomaterials synthesized via a sol-gel method and calcination for use as a CO gas sensor

Carbon monoxide is a poisonous and hazardous gas and sensitive sensor devices are needed to prevent humans from being poisoned by this gas. A CO gas sensor has been prepared from WO₃ synthesized by a sol-gel method. The sensor chip was prepared by a spin-coating technique which deposited a thin film of WO₃ on an alumina substrate. The chip samples were then calcined at 300, 400, 500 or 600 °C for 1 h. The sensitivities of the different sensor chips for CO gas were determined by comparing the changes in electrical resistance in the absence and presence of 50 ppm of CO gas at 200 °C. The WO₃ calcined at 500 °C had the highest sensitivity. The sensitivity of this sensor was also measured at CO concentrations of 100 ppm and 200 ppm and at operating temperatures of 30 and 100 °C. Thermogravimetric analysis of the WO₃ calcined at 500 °C indicated that this sample had the highest gas adsorption capacity. This preliminary research has shown that WO₃ can serve as a CO gas sensor and that is should be further explored and developed.     

Nitrogen balances and nitrogen use efficiency of intensive vegetable rotations in South East Asian tropical Andisols

Nitrogen fertilizer application rates in intensive vegetable production in (South) East Asia have increased exponentially over the past decades, including in the low income countries. While there have been reports of excessive N inputs from e.g. Vietnam, Thailand and Indonesia, very little quantitative knowledge exists on the real extent of the problem. We calculated N balances and agronomic N use efficiencies (ANUE) for a number of typical intensive vegetable rotations in the highlands of Central Java, Indonesia, on fertile Andisols, both for individual cropping cycles (short term) as for 6 consecutive cropping cycles (long term). This was done for farmers practice (FP) treatments, and improved practice (IP) treatments, where N fertilization was significantly reduced. Yields were in general similar in FP and IP, but tended to be slightly higher in IP, with some significant differences. Both the short and long term N balances were always positive and usually very high. Short term N balances ranged from 9 to 559 kg N ha⁻¹ and 219 to 885 kg N ha⁻¹ in IP and FP, respectively, while short term ANUE ranged from 8 to 67 and 4 to 39% in IP and FP, respectively. Long term N balances ranged from 627 to 1,885 kg N ha⁻¹ and 962 to 3,808 kg N ha⁻¹ in IP and FP, respectively, indicating a massive excess of N supply especially in FP. N balances can thus be drastically reduced with no negative impacts on yield, on the contrary. Soil mineral N in the 0–25 cm layer was in general not very high (6.5–38.8 mg N kg⁻¹ soil) and not systematically different between IP and FP, probably as a result of excessive NO₃ ⁻ leaching. Therefore, topsoil mineral N seems to have only limited indicator value under these conditions. Because denitrification losses in these soils are not very high, most N in excess of the crop requirements will be lost by leaching. Quantitative data on N balances as obtained here may be used to sensitize policy makers and farmers about the threat of current farming practices to the environment, and to improve economic performance.     

Sources identification of the atmospheric aerosol at urban and suburban sites in Indonesia by positive matrix factorization

Samples of fine and coarse fractions of airborne particulate matter were collected in Indonesia (west central Java) at an urban site in Bandung and in suburban Lembang from January 2002 to December 2004. The samples were collected using a Gent stacked filter sampler in two size fractions of <2.5 microm (fine) and 2.5 to 10 microm (coarse). The samples were analyzed for elemental concentrations by instrumental neutron activation analysis (INAA) and proton-induced X-ray emission (PIXE). Black carbon was determined using an EEL Smoke Stain Reflectometer. The data sets were then analyzed using positive matrix factorization to identify the possible sources of fine and coarse atmospheric aerosols in both areas. The best solutions were found to be seven factors and five factors for elemental compositions of fine and coarse particulate matter in the urban area of Bandung and six factors and five factors for elemental compositions of fine and coarse particulate matter in the suburban area of Lembang, respectively. The sources are soil dust, motor vehicles, biomass burning, sea salt, and road dust. The PMF results showed that more than 50% of the PM2.5-10 mass at both sites comes from soil dust and road dust. The biomass burning factor contributes about 40% of the PM2.5 mass in case of suburban Lembang and about 20% in urban Bandung.     

The effect of calcination temperature on the capacitive properties of WO3-based electrochemical capacitors synthesized via a sol-gel method

Electrochemical capacitor （EC） is a promising energy storage device which can be hybridized with other energy conversion or energy storage devices. One type of ECs is pseudocapacitor made of metal oxides. WO3 is an inexpensive semiconductor metal oxide which has many applications. However the application of WO3 as an EC material was rarely reported. Therefore in this research EC was prepared from WO3 nanomaterial synthesized by a sol-gel process. The WO3 gel was spin-coated on graphite substrates and calcined at various temperatures of 300~C, 400℃, 500℃ and 600℃ for 1 h. Cyclic voltammetry （CV） measurements were used to observe the capacitive property of the WO3 samples. SEM, XRD, FTIR and Brunauer-Emmett-Teller （BET） analyses were used to characterize the material structures. WO3 calcined at 400~C was proved to have the highest capacitance of 233.63 Fo g^-1 （1869 mFo cm-2） at a scan rate of 2 mVo s-1 in 1 mol/L H2SO4 between potentials -0.4 and 0.4 V vs. SCE. Moreover it also showed the most symmetric CV curves as the indication of a good EC. Hence WO3 calcined at 400℃ is a potential candidate for EC material of pseudocapacitor type.     

Coordinated action of glutathione S-transferases (GSTs) and multidrug resistance protein 1 (MRP1) in antineoplastic drug detoxification. Mechanism of GST A1-1- and MRP1-associated resistance to chlorambucil in MCF7 breast carcinoma cells

To examine the role of multidrug resistance protein 1 (MRP1) and glutathione S-transferases (GSTs) in cellular resistance to antineoplastic drugs, derivatives of MCF7 breast carcinoma cells were developed that express MRP1 in combination with one of three human cytosolic isozymes of GST. Expression of MRP1 alone confers resistance to several drugs representing the multidrug resistance phenotype, drugs including doxorubicin, vincristine, etoposide, and mitoxantrone. However, co-expression with MRP1 of any of the human GST isozymes A1-1, M1-1, or P1-1 failed to augment MRP1-associated resistance to these drugs. In contrast, combined expression of MRP1 and GST A1-1 conferred approximately 4-fold resistance to the anticancer drug chlorambucil. Expression of MRP1 alone failed to confer resistance to chlorambucil, showing that the observed protection from chlorambucil cytotoxicity was absolutely dependent upon GST A1-1 protein. Moreover, using inhibitors of GST (dicumarol) or MRP1 (sulfinpyrazone), it was shown that in MCF7 cells resistance to chlorambucil requires both intact MRP1-dependent efflux pump activity and, for full protection, GST A1-1 catalytic activity. These results are the first demonstration that GST A1-1 and MRP1 can act in synergy to protect cells from the cytotoxicity of a nitrogen mustard, chlorambucil.     

Absorption of cyclohexane on a poly(tetrafluoroethylene) surface

Heat transfer measurements made when cyclohexane condenses on poly(tetrafluoroethylene) provide further support to the theory that absorption can occur on this surface.