Estimation of Magnetizing Characteristics of Pole Transformers in Islanding Area

For the detection of islanding, it is very important to choose the threshold value for the change in the harmonic voltage. In this paper, we propose an analytical model of a pole transformer using a Fourier series and clarify the nonlinear magnetizing characteristics of the pole transformer in an islanding area. After determining the proposed model coefficients from the tests of the pole transformer excited by a sinusoidal voltage, distorted wave voltage tests were performed under conditions in which the third harmonic voltage or the fifth harmonic voltage was superimposed. The results of the testing showed that the magnetic properties vary greatly upon increasing the harmonic component of the voltage. The analytical and measurement results were in good agreement. By using the proposed method, the distributed generators (DGs) can estimate the magnetizing characteristics of the pole transformer by monitoring the connected terminal voltage. Thus, as an active signal for islanding detection, DGs can inject a harmonic current synchronized to the excitation current harmonics of the pole transformer into the distribution network. In the case of DGs equipped with the above functions, there is no need to change the settings of the islanding detection threshold for changes in the harmonic voltage even when there is a change in the excitation voltage or an increase in the number of DGs.     

Examination of Eddy Current between Steel Sheets without Insulation and a Criterion for Determining the Necessity of Insulation

In the laminated core of transformers, motors, and so on, each electrical steel sheet is usually insulated in order to reduce the eddy current loss. It has been reported that insulation is not necessary in such a laminated core under some conditions. However, few studies have been performed in the form of a quantitative and systematic examination of the relationship between the insulation and eddy current. In this study, the eddy current losses of a core made of SPCC (cold rolled steel sheets) of different widths with and without insulation under various conditions are analyzed using the finite element method (FEM) and with the contact resistance taken into consideration. The equivalent circuit of a laminated core without insulation is presented, and can be used for determining the necessity of insulation. It is shown that the increase in the eddy current is affected by the ratio of the resistance of the steel to the contact resistance. An experimental investigation is also carried out.     

Phase decomposition of (Ti,Zr)(C,N) solid solutions prepared by spark plasma sintering

(Ti, Zr)(C, N) solid solutions with 10–90 mol% of ZrC were prepared by spark plasma sintering (SPS) using TiCN and ZrC powders as starting materials. The decomposition behavior of the (Ti, Zr)(C, N) solid solutions as a function of heat treatment temperature (1273–2173 K) was investigated. (Ti, Zr)(C, N) solid solutions with 20–80 mol% of ZrC were decomposed into TiCN-rich (Ti, Zr)(C, N) and ZrCN-rich (Zr, Ti)(C, N) phases when heat-treated in the temperature ranged from 1373 to 2173 K for 3.6 ks, respectively. After heat treatment, lamellar microstructure was formed with an orientation relationship of TiCN-rich (Ti, Zr)(C, N) {100} // ZrCN-rich (Zr, Ti)(C, N) {100}. The Vickers hardness and fracture toughness simultaneously increased with increasing heat-treatment temperature and showed the maximum values of 25.0 GPa and 2.5 MPa m^1/2, respectively, for Ti_0.5Zr_0.5C_0.75N_0.25 at the heat-treatment temperature of 1873 K.     

Measurement System for Flexed Shape of Flexibly Articulated Mobile Track

This paper proposes and validates a system for measuring the flexed posture of the flexible mono-tread mobile track (FMT) using a flexible displacement sensor (FDS). The FMT proposed previously has a single track and vertebral structure. The flexed posture of the FMT determines its turning radius and direction; thus, knowing its posture is important. However, it is impossible to measure the shape of flexible mobile systems using sensors located internally, such as a rotary potentiometer, or located externally, such as a laser scanner. To solve the problem, we introduce the FDS to measure the flexed FMT shape. The sensor consists of two fixed electrodes, a sliding electrode, and a nylon string coated with carbon (NSCC). It works as a flexible potentiometer by moving the sliding electrode along the NSCC while maintaining electrical contact. The measurement system is implemented in a prototype of the FMT called RT02-WORMY and is validated in a series of experiments.     

High hydrostatic pressure treatment impairs AcrAB-TolC pump resulting in differential loss of deoxycholate tolerance in Escherichia coli

We reported previously that high hydrostatic pressure-injured stationary phase cells of Escherichia coli K-12 lost their intrinsic deoxycholate tolerance. The AcrAB-TolC multi-drug resistance pump driven by proton motive force has been argued to be responsible for the tolerance to deoxycholate. In this report, we tested the sensitivity of the AcrAB-TolC (three components) pump to high hydrostatic pressure treatment (HPT). E. coli K-12 treated with HPT became sensitive to AcrAB-TolC-specific drugs such as ethidium bromide, but not to tetracycline which is pumped out by a one-component transporter, Tet. Only E. coli K-12 overproducing both AcrAB and TolC exhibited restored tolerance to deoxycholate after HPT but not E. coli overproducing either TolC or AcrAB. These observations strongly suggest that three-component pumps such as AcrAB-TolC are more susceptible to HPT than one-component pumps such as Tet, resulting in the differential loss of deoxycholate tolerance in high hydrostatic pressure-injured E. coli cells.     

Hydrogenolysis of sugar beet fiber by supported metal catalyst

Sugar beet fiber is an agricultural by-product in the sugar manufacturing and an available biomass source with a rich hemicellulose component. So far, there has been no report on the catalytic conversion of the beet fiber for the synthesis of chemicals. In this work, the hydrogenolysis of the beet fiber was studied by using supported metal catalysts under pressurized hydrogen conditions. Activated carbon supported Ru was found to show the highest catalytic activity to give arabitol as a major product in the hydrogenolysis of hemicellulose part of this material. The reuse ability of the catalyst was also investigated.     

Enhanced Superconductivity of the Pb-Based 1212 Cuprates in the (Pb0.75S0.25)(Sr2?xBax)(Y0.4Ca0.6)Cu2Oz System by High-Pressure O2 Annealing

We have already reported on substitution effects of Ba for Sr in the sulfur contained Pb-based 1212 compound with the composition of (Pb_0.75S_0.25)(Sr_2−x Ba _x ) (Y_0.4Ca_0.6)Cu₂O _z . It was found that each sample with x=0.3–0.6 showed a resistivity drop originating from superconductivity, and the highest onset temperature of the drop was about 32 K for a sample with x=0.5, but the volume fraction was very small. More recently, we have investigated effect of high-pressure O₂ annealing on superconductivity of the Ba-substituted samples with x=0.4–0.6. As a result, the sample with x=0.5 is found to show an onset of the resistivity drop at the highest temperature of about 41.7 K and it shows an onset of the diamagnetic signal at about 42.0 K. These transition temperatures are higher by ∼10 K than those of the previously reported sample with x=0.5. Moreover, the superconducting volume fraction is increasing more by the high-pressure O₂ annealing. These results indicate that the high-pressure O₂ annealing effectively promotes superconductivity of the present (Pb_0.75S_0.25)(Sr_2−x Ba _x )(Y_0.4Ca_0.6)Cu₂O _z system.     

Immobilization of leukemia inhibitory factor (LIF) to culture murine embryonic stem cells

Murine embryonic stem (ES) cells were cultured on a material containing immobilized leukemia inhibitory factor (LIF). To immobilize LIF, we synthesized photoreactive gelatin mixed with LIF and cast the mixture on a polystyrene plate, which was then dried. LIF was immobilized by photoirradiation in the presence or absence of a photo mask. The plate was washed until LIF was no longer released. Murine ES cells were cultured on the immobilized LIF. Activation of STAT3 was maintained on the immobilized LIF for 6 d even after removing soluble LIF. Oct-3/4 was also expressed in the cells cultured on the immobilized LIF. As a result, the mouse ES cells were cultured without differentiating on the immobilized LIF for 6 d. It was possible to culture murine ES cells without adding soluble LIF at each medium change. We conclude that our material containing immobilized LIF might be useful in the culture of murine ES cells.     

Effect of Time Lag in Response to Switching Signal in Interrupted Electric Circuit

In this study, we analyze the characteristics of an interrupted electric circuit. In particular, we focus on a special situation where the switching action of the circuit is delayed because of a time lag in the response to the switching signal. This situation is observed in switching circuits driven by a high-frequency switching signal. However, the fundamental characteristics of this type of circuit have not yet been clarified. To address this shortfall, we assume that a time lag of the response to the switching signal occurs in simple interrupted electric circuits, and investigate how this time lag affects circuit characteristics. First, we show the model of a circuit whose switching action is the same as that of a current-mode-controlled dc/dc converter. Here by using logic circuits, we impose an artificial time lag on the response to the switching signal. Next, we define a sampled data model (i.e., a return map) that we analyze in detail. Based on the return map, we derive one- and two-parameter bifurcation diagrams. Finally, we compare the bifurcation diagrams constructed with time lag to those constructed without time lag. The results clearly show that time lag is responsible for a new structure in the return map that does not occur in circuits with ideal switching. This new return map structure is a key to understanding the essential characteristics of circuits with time lag. Furthermore, the mathematical results are verified experimentally.