• Journal of Sensor Science and Technology
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• v.14 no.5
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• pp.350-356
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• 2005

We have developed a dual-channel type automatic measurement system to evaluate AC-DC current transfer difference of the thermal current converter(TCC) which is primary standard of AC current. The output drift effect of the TCC is minimized by measuring simultaneously the output voltages of two TCCs using voltmeter. Furthermore, the offset voltage of the voltmeter is cancelled nearly out by taking the average values of two outputs of TCCs measured with the forward-reverse directions using dual channel scanner. The uncertainties of the automatic system were 7 to $86{\mu}A/A$ for 3 mA to 10 A at 40 Hz to 20 kHz, which were evaluated by the comparisons between adjacent range of TCCs and inter-comparison with national measurement institute of Germany(PTB). The capability for ac-dc transfer difference measurement was improved by one order compared with that for the manual ac-dc measurement system.

• Journal of Electrical Engineering and Technology
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• v.1 no.3
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• pp.279-286
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• 2006

A method for estimating the instantaneous phasor of a fault current signal is proposed for high-speed distance protection that is immune to a DC-offset. The method uses a modified notch filter in order to eliminate the power frequency component from the fault current signal. Since the output of the modified notch filter is the delayed DC-offset, delay compensation results in the same waveform as the original DC-offset. Subtracting the obtained DC-offset from the fault current signal yields a sinusoidal waveform, which becomes the real part of the instantaneous phasor. The imaginary part of the instantaneous phasor is based on the first difference of the fault current signal. Since a DC-offset also appears in the first difference, the DC-offset is removed trom the first difference using the results of the delay compensation. The performance of the proposed method was evaluated for a-phase to ground faults on a 345kV 100km overhead transmission line. The Electromagnetic Transient Program was utilized to generate fault current signals for different fault locations and fault inception angles. The performance evaluation showed that the proposed method can estimate the instantaneous phasor of a fault current signal with high speed and high accuracy.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.2
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• pp.719-724
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• 2012

This study aimed to investigate the clinical significance of expression and amplification of decoy receptor 3 (DcR3) in pancreatic carcinomas (PC). mRNA expression was detected by PQ-PCR, and amplification was determined. DcR3 protein expression was detected by immunohistochemistry and ELISA. Correlations between DcR3 expression and clinical pathological factors were analyzed. The relative amount of DcR3 in PC tissues and non-cancerous tissues showed a statistically significant difference, 21 cases displaying more than two fold DcR3 amplification, while no such amplification was found in normal pancreatic tissues. DcR3 positive cell staining was located in the cytoplasm. The positive rate of DcR3 in PC and non-cancerous tissues showed a significant difference. DcR3 mRNA expression was correlated with clinical staging, size of the tumor, lymph node metastasis and histological staging, while protein expression was correlated with clinical data like tumor size. DcR3 gene amplification only correlated with tumor size. The level of DcR3 in serum of the PC resectable group before operation was $72.2{\pm}10.2$ pg/ml, showing a significant difference compared to gallbladder carcinoma group (GC) or pancreatic benign tumor (PBT) group (P < 0.01). In conclusion, DcR3 amplification is correlated with DcR3 expression in PC tissues, especially those clinical pathological factors which reflect tumor progression. Assessment of DcR3 level in sera of PC patients may be helpful for the early diagnosis and prognostic judgement.

• Journal of the East Asian Society of Dietary Life
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• v.15 no.1
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• pp.20-28
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• 2005

The dietary effect of water extracts of Liriopis tuber(WELT) in the diabetic SD-rats on the level of blood sugar and serum cholesterol was investigated. The experimental plots divided into normal group(N), diabetic control(DC), 5% WELT-group(WELT-I) and 10% WELT-group (WELT-II). Each group was fed for 6 weeks, then continuously fed for 1 more week after streptozotocin injection. The loss of the body weight fed for one week after induction of the diabetes was 2.2～6.3% in the WELT-I and -II groups, but it was 18.6% in the DC-group. There was no significant difference in the feed intakes after diabetes induction between N-group and WELT-group, while it was significantly increased in DC-group. The feed efficiency ratios before diabetes induction were 1.70 in WELT-I group, 1.53～1.59 in the N, DC and WELT-II group, while the ratios after diabetes induction were 0.92 in DC-group, 1.51～1.83 in the N, WELT-I and -II group. While the amounts of water intakes for one week after diabetes induction was 625.4 mL in the DC-group, and it were 364.3～371.1 mL in the WELT-groups showing no significant difference with N-group. The excretion amounts of urine were 431.96 mL in DC-group for one week after diabetes induction, and it was 182～192.84 mL in WELT-groups. The ratios of liver weight against body weight were 2.74% in N-group, 2.93～2.96% in WELT-groups, but it was 4.01% in DC-group. The level of blood glucose in WELT-groups fed for one week after diabetes induction were 136.8～138.6 mg/dL showing no significant difference with N-group, but it was 357.8 mg/dL in DC-group. The level of serum triacylglycerol and serum total cholesterol were 93.8 and 68.7 mg/dL in N-group, 120.1 and 101.6 mg/dL in DC-group, 97.4～100.6 and 60.8～67.7 mg/dL in WELT-groups, respectively, showing no significant difference between N-group and WELT-groups. HDL-cholesterol/total cholesterol ratio were 0.63 in N-group, 0.57～0.67 in WELT -groups, which was significantly higher than that of DC-group(p<0.05). Atherogenic index were 0.58 in N-group, 0.49～0.74 in WELT-groups, but it was 1.32 in DC-group. The above results suggest that the WELT diets may have both preventive and curing effects against the diabetes.

• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.5
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• pp.536-541
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• 1988

The push-pull current-fed DC-to-DC converter has only one energy storage reactor in series with the input for any number of outputs. It is considered that this property of the converter has considerable advantages over other multiple-output circuits. The steady state characteristics of the converter with two outputs is analyzed. It is known that the voltage difference between the two outputs appears by existing the 2nd winding resistance of transformer and there is a region of the duty ratio in which the voltage difference of the converter is smaller than that of the forward converter.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.3A
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• pp.319-323
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• 2007

In this paper, the automatic precision measurement of RF voltage has been done using the power and impedance standards [1] in the frequency range of 50 to 1000 MHz. A coaxial microcalorimeter and an automatic network analyzer were used for the determination of the RF-DC differences and the total uncertainty is about 1.0 %. A HP computer, a commodore computer and IEEE-488 interface bus were used for measuring the effective efficiency of thermistor mount and the RF-DC difference of thermal voltage converter, All processes of measurement were accomplished by self-developed program automatically.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.1
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• pp.57-62
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• 2013

Because of high torque and easiness of speed control, Direct Current(DC) motors have been used for a long time. But, its applications are limited in circumstance and performance, since they contained brush and commutator. The commutation characteristic gives effect to life and performance of the DC motor. Naturally, the commutation characteristic analysis is strongly required. In this paper, With the result of finite element analysis, The inductance is calculated each rotor position and applied to the voltage equations coupled with commutation equation. Also, contact resistances of brush/commutator assembly are considered using contact area and brush width converted with commutator segments. The time derivative term in the differential equation is solved in time difference method. This algorithm was applied to 2-pole shunt DC motor. We considered commutation characteristic by changing contact resistance between brush and commutator segment.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.7
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• pp.59-66
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• 2013

This paper proposes a new voltage reference generation method for Four-Switch Inverters(FSI) with compensation of the neutral DC-link voltage variation. Since FSIs have the split DC-link causing the inherent problem of voltage fluctuations in the upper and lower capacitors, it is required to take account the voltage difference between the top and bottom capacitors. In this paper, to reduce the effect by the voltage variation, reference voltages are modified by adding compensation voltages proportional to the voltage difference between upper and lower capacitors. Simulation results showing control performance of induction and permanent magnet motors demonstrate the validity of the proposed method.

• Journal of the Korean Solar Energy Society
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• v.32 no.spc3
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• pp.255-261
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• 2012

Since PV PCS uses output current sensor for ac output current control, the sensor's sensing value includes unnecessary offset inevitably. If PV inverter is controlled by the included offset value, it's output current will generate DC offset. The DC offset of output current for trans-less PV inverter is fatal to grid, which results in saturating grid side transformer. Usually DSP controller of PV inverter reads several times sensing value during initial operation and, finally, it's average value is used for offset calibration. However, if temperature changes, the offset changes, too. And also, the switch device is not ideal, both each switching element of the voltage drop difference and on & off time delay difference generate DC offset. Thus, to compensate for deadtime and the switch voltage drop, feedback control by output current DC offset should be provided to compensate additional distortion of the output current. The validity of the proposed method is confirmed through PSIM simulation.

• Journal of Electrical Engineering and Technology
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• v.12 no.2
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• pp.549-558
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• 2017

DC distribution has several differences compared to AC distribution. DC distribution has a higher efficiency than AC distribution when distributing electricity at the same voltage level. Accordingly, power can be transferred further with low-voltage DC. In addition, power flow in a DC grid system is produced by only a voltage difference in magnitude. Owing to these differences, operation of a DC grid system significantly differs from that of an AC system. In this paper, the power flow problem in a bipolar-type DC grid with unbalanced load conditions is organized and solved. Control strategy of energy storage system on a slow time scale with power references obtained by solving an optimization problem regarding the DC grid is then proposed. The proposed strategy is verified with computer simulations.