• Journal of IKEEE
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• v.8 no.1 s.14
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• pp.12-21
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• 2004

Error control is one of major concerns in many electronic systems. Experience shows that most malfunctions during system operation are caused by transient faults, which often mean abnormal signal delays that may result in violations of circuit element timing constraints. This paper presents a novel CMOS-based concurrent timing error detector that makes a flip-flop to sense and then signal whether its data has been potentially corrupted or not by a setup or hold timing violation. Designed circuit performs a quiescent supply current evaluation to determine timing violation from the input changes in relation to a clock edge. If the input is too close to the clock time, the resulting switching transient current in the detection circuit exceeds a reference threshold at the instant of the clock transition and an error is flagged. The circuit is designed with a $0.25{\mu}m$ standard CMOS technology at a 2.5 V supply voltage. The validity and effectiveness are verified through the HSPICE simulation. The simulation results in this paper shows that designed circuit can be used to detect setup and hold time violations effectively in clocked circuit element.

• Journal of the Korean Society of Safety
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• v.25 no.6
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• pp.86-91
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• 2010

The purpose of this study is to analyze the damage patterns and metal structure of 3 phase mold transformers collected from places where accidents have occurred. Compared to an oil-immersed transformer, a mold transformer has the advantage of requiring a smaller installation area and can be kept clean, while its disadvantages include the fact that abnormal symptoms of an accident are difficult to discover and its repair is impossible. The capacity of the mold transformers collected from places where accidents have occurred was 200kVA with primary voltages being F23,900V, R22,900V, 21,900V, 20,900V, 19,900V, etc., as well as secondary voltages being 380V, 220V, etc. It was found from the analysis on the diffusion of combustion in the damaged mold transformers that fire occurred first inside the U-phase primary winding and that carbonization and heat were diffused to V-phase and W-phase in V-pattern. In addition, from the analysis on the cross-sectional structure of the metal of the melted high voltage winding using a metallurgical microscope, it was found that the boundary surface, voids, and columnar structure were formed when an interlayer short-circuit had occurred Therefore, even though it is not possible to find the cause for the occurrence of an interlayer short-circuit at the inner side of the primary winding, it is thought that, due to the thermal energy generated when the short-circuit occurred, the heat source was diffused to the upper side and outside, causing a secondary accident.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.610-613
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• 2009

New rod-disc liquid crystal (LC) molecule RD12 (12 is the number of carbon atoms between the rod and disc mesogenic liquid crystals) was synthesized via the chemical attachment of six cyanobiphenly calamitic mesogens linked to the triphenyl discotic mesogen with six alkyl chain linkage. Aligning characteristics associated with homogenous alignment is investigated at first and then field-dependent molecular reorientation under a vertical electric field is studied. Interestingly, they show abnormal slow molecular transition from initiate state (no electric field condition) to certain voltage. In this condition, we observe the molecular competition during reorientation. However, once a tilting direction of disk molecules are defined, the frustration is not observed anymore. The origin of this phenomenon is explained with a suggested model for the first time.

• Proceedings of the KIEE Conference
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• 1998.07c
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• pp.1220-1223
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• 1998

High Power Laboratory is the facility for building to simulate the various phenomena generated from electric systems of the real world and to test making and breaking capability, switching capability and durability of circuit breaker, switchgear and other electric utilities, moreover, load equipments which contain capacitor bank is installed for studying the diverse effects originated from the constituent of load through entire systems or receiving end. Such factors, abnormal voltage or current, can be serious in electrical systems, especially, in the case caused by capacitive components such as overvoltage or inrushcurrent, the problems may be more fatal to the systems. In this paper, the optimal design of capacitor bank which will be equipped in High Power Laboratory, which is for simulating as closely as the practical phenomena resulted from the capacitive currents, and the verification aided by computer simulations are presented. For this, analysis of the circuit characteristics according to the standards which can be criteria of the capacitive current tests and the test circuit configuration in accordance with the analysis are proposed in prelude. In the body of the paper the optimal design of capacitor bank has been obtained on the basis of all conditions mentioned above and the test circuit configuration with LGIS test requirements. furthermore, analysis and verification for the design are derived by EMTP. finally, evaluation for the capacitor bank design and further study plan are concluded.

• Korean Journal of Clinical Laboratory Science
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• v.37 no.3
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• pp.220-227
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• 2005

Recently, the use of an electrical apparatus has brought up concerns of health risks from exposure to electromagnetic fields. EMF is composed of electric fields and magnetic fields. Heavy exposure to EMF can occur only in the vicinity of high-voltage overhead transmission lines, close to transformers and underground cables, and also close to large electrical machinery. In this thesis I have investigated the hypothesis of the correlation between occupational exposure to ELF-EMF and the risks of leukemia, anemia, cancer. Therefore, the aim of this study is to investigate whether or not ELF-EMF emitted from electric power stations and transformer substations affect some hematological parameters and tumor markers of electric utility workers. The hematological test results and tumor markers under investigation were similar in the two groups but some of parameters such as RBC, AFP, LDH showed significant difference between the two groups from two sample t-test (p<0.05). The exposure group showed increased LDH level compared to the control group by two sample t-tests. In addition, the abnormal LDH level in the exposure group was observed to be clinically significant by ${\chi}^2$-test. However, the levels of RBC, AFP observed were not clinically significant by ${\chi}^2$-test (p>0.05). These results suggested that ELF-EMF does not affect most blood test parameters except LDH of electric utility workers.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.9
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• pp.78-84
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• 2022

An air circuit breaker (ACB) is an electrical protection device that interrupts abnormal fault currents that result from overloads or short circuits in a low-voltage power distribution line. The ACB consists of a main circuit part for current flow, mechanism part for the opening and closing operation of movable conductors, and arc-extinguishing part for arc extinction during the breaking operation. The driving mechanism of the ACB is a spring energy charging type. The faster the contact opening speed of the movable conductors during the opening process, the better the breaking performance. However, there is a disadvantage that the durability of mechanism decreases in inverse proportion to the use of a spring capable of accumulating high energy to configure the breaking speed faster. Therefore, to simultaneously satisfy the breaking performance and mechanical endurance of the ACB, its driving mechanism must be optimized. In this study, a dynamic model of the ACB was developed using the MDO(Mechanism Dynamics Option) module of CREO, which is widely used in multibody dynamics analysis. To improve the opening velocity, the Taguchi design method was applied to optimize the design parameters of an ACB with many linkages. In addition, to evaluate the improvement in the operating characteristics, the simulation and experimental results were compared with the MDO model and improved prototype sample, respectively.

• Journal of Korean Society of Forest Science
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• v.23 no.1
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• pp.1-8
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• 1974

The seed quality testing for Korean white pine (Pinus koraiensis), their pre-germination and embryo growing process were investigated and the abnormal embryo groups were discriminated by the use of soft X-ray photograph. The study results were as follows ; 1. The embryo reflection was clearly observed for air dried seeds (moisture content was 6.3%) at 30 sec, stratificated seeds at 60 sec (moisture content 24.0-36.0%) and immature seed (moisture content 41.0-64.0%) at 90sec., then the photographing variation for soft X-ray was the radiographing distance at 42cm focus M, voltage 19.5 K.V.P. and Ampere 8 mA. By the above result, the radiographing time for discriminating the embryo reflection was increased by the increase of moisture content in the seeds. 2. The embryo reflection could be clearly observed from the last ten days of June and the embryo length ratio to endosperm length was growing to 65% at the first ten days of September. By the result obtained the soft X-ray photograph was thought to be effective method for the study of inner morphology of seeds. 3. The clear reflection seeds for embryo and endorsperm were observed to 69.7% and the seeds were practically germinated to 75.2% The difference in number between the discriminated seeds by the soft X-ray photograph and the practically germinated seeds was only 6%. According to this results, the soft X-ray photograph was thought to be a effective methods for the germination diagnosis in the shortest time and with the exactness comparatively. 4. Because of the possibility of clearness for observation of pre-germination process, the soft X-ray photograph could be used for the study on the physiology of seed germination. 5. The frequency of abnormal embryos was observed of total 4.4% and their types and subtypes could be classified into twenty groups. Among these groups, single abnormal embryo type was divided into eight subtypes and observed of 2.0 percent, twin embryo was six subtypes and 1.8 percent, triple embryo was five subtypes and 0.5 percent, and inverse type was 0.12 percent.

• Clinical and Experimental Pediatrics
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• v.52 no.12
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• pp.1364-1369
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• 2009

Purpose : To analyze abnormal ventricular activation in childhood congenital heart disease induced by postoperative changes in ventricular volume and pressure and ventricular scar formation using signal-averaged electrocardiography (SAECG). Methods : Fifty-two patients who had undergone open heart surgery (OHS) were enrolled. Patients were divided into the following 3 groups: right ventricular volume overload (atrial septal defect, group1), left ventricular volume overload (ventricular septal defect, group2), and right ventricular pressure overload (tetralogy of Fallot, group 3). The patients were monitored by standard 12-lead ECG and SAECG before and 2 months after the operation. QRS duration, QT and QTc intervals, filtered QRS (f-QRS), high frequency low amplitude potential (HFLA), and root mean square (RMS) voltage in the terminal 40 ms of SAECG were determined. Results : In the preoperative period, group1 showed significant increase in QRS (P=0.011) compared to those of the other 2 groups. In the postoperative period, group3 showed significant increase in the QTc interval (P=0.004) compared to those in the other 2 groups. SAECG parameters showed no significant differences among the groups in the pre- or postoperative period. Of the 52 patients, 12 (23%) in the preoperative period and 21 (40%) in the postoperative period had at least 1 SAECG abnormality. The prevalence of SAECG abnormalities was significantly higher in the postoperative group 2 and group 3 (preoperative: 20% versus postoperative: 28%, P<0.001, preoperative: 14% versus postoperative: 64%, P<0.001, respectively). Conclusion : Abnormal SAECG patterns may be attributed to postoperative scars, OHS itself, and/or ventricular overload.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.39 no.2
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• pp.104-115
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• 2002

Core is the main component of inductor. This core should be classified into around 10 classes according to the value of inductance and Q. The coil should be winded with the outer-boundary of this core by different number of turns. Theses kind of precise inductors would be required in the future environment which PCs and communication devices demand more high speed and lower voltage level. It would be quite unefficient that only one core is classified once a time. There, it will be developed so that 10 cores are classified simultaneously. For the operation of classifying 10 cores once in a time, suppose 10 test instruments could be used. In this case, it would take much cost since a test instrument Is expensive. So, by using only one test instrument, it is really more desirable that this system is developed. Each core classified by 10 different classes is to be stored into the corresponding box through the corresponding rubber hose. 10 cores are passed on a serial line and are placed on each testing slot. Here, each core located at each slot is tested, and then the bowl located on the top of a step motor is moved into the corresponding spot by rotating step motor with some angles. Each bowl connected with the corresponding box through rubber hose. Actually 100 hoses are connected, 10 step motors are rotated at 10 different angles, so the size is really so big, the shape of connecting 100 hoses is so complicated. Therefore it is anticipated that the system would be going to be easily out of ordered. In this paper the main purpose is to make several suggestions to be able to work well in these kinds of being affected by the abnormal operation of motors and the flow of cores.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.5
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• pp.132-139
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• 2004

Unsymmetrical faults are classified into single line-to-ground faults, line-to-line faults, or double line-to-ground faults in receiving and distribution power systems. Many of overhead distribution-line faults are single line-to-ground faults, and lightning surge arresters are stressed by system frequency overvoltages due to unsymmetrical faults. In this work, the unsymmetrical faults in receiving and distribution systems were experimentally simulated, and the characteristics of total leakage current flowing through lightning surge arresters due to various unsymmetrical faults were investigated. As a result, a little variations of the leakage current flowing through Zinc oxide (ZnO) surge arresters in the range of $\pm$10[%] voltage regulations were observed. It could be concluded that the unsymmetrical faults have no effect on the long-term life performance of ZnO surge arresters in effective grounding systems. On the other hand, the magnitude of the leakage current flowing through ZnO surge arrester elements under single line-to-ground faults was more than 140 times as compared with that under normal operating voltages in ineffective grounding systems. But abnormal voltages caused by line-to-line faults and double line-to-ground faults have a little effect on total leakage current of ZnO surge arrester elements.