• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.18 no.10
• /
• pp.960-964
• /
• 2005

In this paper, we dealt with a partial discharge(PD) measurement method that has been accepted as an effective and non-destructive technique to estimate insulation performance of low-voltage electric and electronic devices. The PD measurement system Is composed of a coupling network, a low noise amplifier, and associated electronics. h shielded box Is adopted to make a better measurement environment against around noise. A low cut-off frequency of the coupling network estimated by a sinusoidal wave input was 125 kHz (-3 dB). Calibration tests on laboratory set-up have shown that the PD measurement system has a stable sensitivity of 10 mV/pC. In an application test oil a low-voltage three phase Induction motor (5 HP), we could detect 0.53 pC level of partial discharge at the applied voltage of AC 650 $V_{peak}$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.21 no.1
• /
• pp.85-89
• /
• 2008

An objective of this paper is to develop a partial discharge (PD) measurement device for monitoring gas insulated switches installed in power distribution system. A capacitive voltage probe was studied and designed to detect PD pulse without an electrical connection. The PD measurement device consists of the capacitive voltage probe attached outside of a bushing, a coupling network which attenuates AC voltage by 270 dB, and a low noise amplifier with the gain of 40 dB in ranges of 500 kHz${\sim}$20 MHz. The sensitivity of the prototype device calculated by a calibrator was 1.98 m V /pc. An application experiment was carried out in a 25.8 kV gas insulated switch and the peak pulse of 76.7 pC was detected. From the experimental results, it is expected that the PD measurement device can be applied to online monitoring system of gas insulated switches.

• Biomolecules & Therapeutics
• /
• v.21 no.1
• /
• pp.1-9
• /
• 2013

Polyamines, putrescine, spermidine and spermine, are ubiquitous in living cells and are essential for eukaryotic cell growth. These polycations interact with negatively charged molecules such as DNA, RNA, acidic proteins and phospholipids and modulate various cellular functions including macromolecular synthesis. Dysregulation of the polyamine pathway leads to pathological conditions including cancer, inflammation, stroke, renal failure and diabetes. Increase in polyamines and polyamine synthesis enzymes is often associated with tumor growth, and urinary and plasma contents of polyamines and their metabolites have been investigated as diagnostic markers for cancers. Of these, diacetylated derivatives of spermidine and spermine are elevated in the urine of cancer patients and present potential markers for early detection. Enhanced catabolism of cellular polyamines by polyamine oxidases (PAO), spermine oxidase (SMO) or acetylpolyamine oxidase (AcPAO), increases cellular oxidative stress and generates hydrogen peroxide and a reactive toxic metabolite, acrolein, which covalently incorporates into lysine residues of cellular proteins. Levels of protein-conjuagated acrolein (PC-Acro) and polyamine oxidizing enzymes were increased in the locus of brain infarction and in plasma in a mouse model of stroke and also in the plasma of stroke patients. When the combined measurements of PC-Acro, interleukin 6 (IL-6), and C-reactive protein (CRP) were evaluated, even silent brain infarction (SBI) was detected with high sensitivity and specificity. Considering that there are no reliable biochemical markers for early stage of stroke, PC-Acro and PAOs present promising markers. Thus the polyamine metabolites in plasma or urine provide useful tools in early diagnosis of cancer and stroke.

• Journal of Magnetics
• /
• v.16 no.4
• /
• pp.398-402
• /
• 2011

A novel laminate composite of FeCuNbSiB/FeNi /PZT is proposed, where FeCuNbSiB has a permeability of around 100000, which is much larger than that of FeNi. The high-permeability FeCuNbSiB was laminated with piezomagnetic FeNi rather than attached to its ends. It is expected that the effect produced by the high permeability will act on the whole of the piezomagnetic layer. While a FeNi layer was laminated with a FeCuNbSiB layer, the strong demagnetization produced by the latter was expected to be imposed on the FeNi layer as well as the applied fields. The distribution of applied fields was altered by the high-permeability material (both bias and ac field) and the field variation positively contributed to the ME effect in piezomagnetic/piezoelectric composites. Thus the ME voltage coefficient along with the field sensitivity were improved.

• Proceedings of the KIEE Conference
• /
• 2007.10a
• /
• pp.129-130
• /
• 2007

Self servo track writing(SSTW)은 servo track writer(STW)를 이용하지 않고 hard disk drive의 내부 VCM을 이용하여 servo track을 기록하는 방식이다. SSTW는 이전 servo track을 상대적인 reference로 하여 기록하게 되므로 초기에 발생된 error와 외부의 disturbance의 영향으로 error는 급속하게 증가된다. 이것을 radial error propagation 이라 한다. 본 논문에서는 radial error propagation을 억제하기 위한 correction signal을 설계하고 servo writing 과정에서 발생하는 disturbance의 영향을 제거하기 위하여 disturbance observer(DOB)를 add-on type으로 구성하여 tracking 제어기를 설계하였다. 또한 DOB를 적용한 경우와 유사한 gain margin, phase margin과 sensitivity function을 갖는 제어기를 설계하여 그 성능을 비교하였다. 제안된 방식은 radial error propagation을 억제 하였을 뿐만 아니라 disturbance의 최소화하여 쓰여진 track의 DC track spacing과 AC track Squeeze가 개선된 것을 모의실험을 통하여 검증하였다.

• Journal of the Korean Solar Energy Society
• /
• v.33 no.6
• /
• pp.92-97
• /
• 2013

This paper proposes DC offset current compensation method of transformerless fuel cell/PV PCS. DC offset current is generated by the unbalanced internal resistance of the switching devices in full bridge topology. The other cause is the sensitivity of the current sensor, which is lower than DSP in resolution. If power converter system has these causes, the AC output current in the inverter will generate the DC offset. In case of transformerless grid-connected inverter system, DC offset current is fatal to grid-side, which results in saturating grid side transformer. Several simulation results show the difficulties of detecting DC offset current. Detecting DC offset current method consists of the differential amplifiers and PWM is compensated by the output of the Op amp circuit with integrator controller. PSIM simulation verifies that the proposed method is simpler and more effective than using low resolution current sensor alone.

• The Transactions of the Korean Institute of Electrical Engineers A
• /
• v.55 no.5
• /
• pp.202-213
• /
• 2006

This paper presents a new approach for optimal dispatch of energy and frequency regulation reserve considering contingency in a competitive electricity market. It is necessary to introduce the reserve market with the spot energy market for operating efficiently and obtaining the security of the electricity market. However, the reserve market is closely connected with the energy market since the energy and reserve are produced from the same resources. Thus, it is inevitable to co-optimize the energy and ancillary service for efficient operation of energy and ancillary service market. Therefore, this paper proposes a new method for optimal dispatch of energy and frequency regulation reserve considering n-1 contingency of generator and transmission line using constraints and sensitivity based on AC power flow To verify the effectiveness of the proposed method, the numerical studies have been performed for 5-bus sample system and modified IEEE 14-bus system.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• v.9 no.2
• /
• pp.208-211
• /
• 2005

This paper presents an ultra-low partial discharge(PD) measurement system that has been accepted as a non-destructive method to estimate electrical insulation of low-voltage electric devices. The PD measurement system is composed of a coupling network, a low noise amplifier, and associated electronics. A shielding box is used to make a better condition against electromagnetic interference. A low cut-off frequency of the coupling network was 1MHz(-3 dB). Calibration tests on laboratory set-up have shown that the PD measurement system has a stable sensitivity of 11.4mV/pC. In an application experiment on a low-voltage induction motor(5HP), we could detect 0.77pC level of partial discharge pulse at the applied voltage of AC 664 V$_{peak}$.

• Journal of the Korean Society for Precision Engineering
• /
• v.18 no.1
• /
• pp.89-97
• /
• 2001

A microgyroscope, which vibrates in two orthogonal axes on the substrate plane, is designed and fabricated. The shuttle mass of the vibrating gyroscope consists of two parts. The one is outer shuttle mass which vibrates in driving mode guided by four folded springs attached to anchors. And the other is inner shuttle mass which vibrates in driving mode as the outer frame does and also can vibrate in sensing mode guided by four folded springs attached to the outer shuttle mass. Due to the directions of vibrating mode, it is possible to fabricate the gyroscope with simplified process by using polysilicon on insulator structure. Fabrication processes of the microgyroscope are composed of anisotropic silicon etching by RIE, gas-phase etching (GPE) of the buried sacrificial oxide layer, metal electrode formation. An eletromechanical model of the vibrating microgyroscope was modeled and bandwidth characteristics of the gyroscope operates at DC 4V and AC 0.1V in a vacuum chamber of 100mtorr. The detection circuit consists of a discrete sense amplifier and a noise canceling circuit. Using the evaluated electromechanical model, an operating condition for high performance of the gyroscope is obtained.

• Journal of Radiation Industry
• /
• v.17 no.4
• /
• pp.471-479
• /
• 2023

In In-situ radioactivity measurement techniques, efficiency calibration models use predefined models to simulate a sample's geometry and radioactivity distribution. However, simplified efficiency calibration models lead to uncertainties in the efficiency curves, which in turn affect the radioactivity concentration results. This study aims to develop an efficiency calibration optimization methodology to improve the accuracy of in-situ gamma radiation measurements for byproducts from industrial facilities. To accomplish the objective, a drive mechanism for rotational measurement of an byproduct simulator and a sample was constructed. Using ISOCS, an efficiency calibration model of the designed object was generated. Then, the sensitivity analysis of the efficiency calibration model was performed, and the efficiency curve of the efficiency calibration model was optimized using the sensitivity analysis results. Finally, the radiation concentration of the simulated subject was estimated, compared, and evaluated with the designed certification value. For the sensitivity assessment of the influencing factors of the efficiency calibration model, the ISOCS Uncertainty Estimator was used for the horizontal and vertical size and density of the measured object. The standard deviation of the measurement efficiency as a function of the longitudinal size and density of the efficiency calibration model decreased with increasing energy region. When using the optimized efficiency calibration model, the measurement efficiency using IUE was improved compared to the measurement efficiency using ISOCS at the energy of ²²⁸Ac (911 keV) for the nuclide under analysis. Using the ISOCS efficiency calibration method, the difference between the measured radiation concentration and the design value for each simulated subject measurement direction was 4.1% (1% to 10%) on average. The difference between the estimated radioactivity concentration and the design value was 3.6% (1~8%) on average when using the ISOCS IUE efficiency calibration method, which was closer to the design value than the efficiency calibration method using ISOCS. In other words, the estimated radioactivity concentration using the optimized efficiency curve was similar to the designed radioactivity concentration. The results of this study can be utilized as the main basis for the development of regulatory technologies for the treatment and disposal of waste generated during the operation, maintenance, and facility replacement of domestic byproduct generation facilities.