• 한국정밀공학회지
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• 제18권3호
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• pp.195-204
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• 2001

Virtual computer numerical control(VCNC) arises from the concept that one can experience pseudo-real machining with a computer-numerically-controlled(CNC) machine before actually cutting an object. To achieve accurate VCNC, it is important to determine abnormal behavior, such as chatter, before cutting. Detecting chatter requires an understanding of the dynamic cutting force model. In general, the cutting process is a closed loop system that consists of structural and cutting dynamics. Machining instability, namely chatter, results from the interaction between these two dynamics. Several previous reports have predicted stability for a single path, using a simple cutting force model without tool runout and penetration effects. This study considers both tool runout and penetration effects, using experimental modal analysis, to obtain more accurate predictions. The machining stability in the corner cut, which is a typical transient cut, was assessed from an evaluation of the cutting configurations at the corner.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1997년도 추계학술발표회논문집(1)
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• pp.645-650
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• 1997

An oxide fuel small size core (1200 MWt) was analyzed in comparison with a large size core (3600 MWt) in order to evaluate the size effects on transient safety performances of liquid-metal reactors (LMRs). in the first part of the study, main static safety parameters (i.e., Doppler coefficient, sodium void effect, etc.) of the two cores were characterized, and the second part of the study was focused on the dynamic behavior of the cores in two representative transient events: the unprotected loss-of-flow(ULOF) and the unprotected transient overpower (UTOP). Margins to fuel molting and sodium boiling have been evaluated for these representative transients. Results show that the small core has a generally better or equivalent level of safety performances during these events.

• 동의생리병리학회지
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• 제18권6호
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• pp.1777-1783
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• 2004

This study was conducted to determine the effects Wonjiseokchangpo-san on brain damage in transient focal cerebral ischemia. Rats were used for testing in the following three models: Morris Water Maze, Eight-Arm Radial Maze, and Histochemistry. In the Morris Water Maze Model, the Wonjiseokchangpo-san group showed significant decrease in the 3rd and 6th training session compared with the ischemia group. A retention test, in the Morris Water Maze Model, was performed on the 7th day without the escape platform. The Wonjiseokchangpo-san group showed significant increase compared to the ischemia group. In the Eight-Arm radial Maze model, the Wonjiseokchangpo-san group showed significant decrease in the error rate compared to the ischemia group. In the density of hippocampal CA1 cell of the cresyl violet-stained section, the Wonjiseokahangpo-san group showed significant increase compared to the ischemia group. These results suggest that Wonjiseokchangpo-san may have a significant protective effect on brain damage and cognitive dysfunction in transient focal cerebral ischemia.

• 대한한의학회지
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• 제26권2호
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• pp.52-62
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• 2005

Objectives: This study was conducted to determine the effects of Geupunggibodan on brain damage in transient focal cerebral ischemia in rats. Methods: Rats were used for testing in the following three models: Morris water maze, eight-ann radial maze, and histochemistry. Results: In the Morris water maze model, the Geupunggibodan group showed significant decrease in the 3rd, 4th and 6th training sessions compared with the ischemia, group. A retention test in the Morris water maze model was performed on the 7th day without the escape platform. The Geupunggibodan group showed significant increase compared to the ischemia group. In the eight-ann radial maze model, the Geupunggibodan group showed significant decrease in the error rate compared to the ischemia group. In the density of hippocampal CA1 cell of the cresyl violet-stained section, the Geupunggibodan group showed significant increase compared to the ischemia group. Conclusions: These results suggest that Geupunggibodan may have a significant protective effect on brain damage and cognitive dysfunction in transient focal cerebral ischemia.

• The Korean Journal of Physiology and Pharmacology
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• 제9권6호
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• pp.347-352
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• 2005

The effects of nitric oxide (NO) on inhibitory neurotransmitter receptors and some types of inhibitory receptors in dissociated rod bipolar cell (RBC) were investigated. In the whole cell voltage-clamping mode, the gamma-aminobutyric acid (GABA) activated current showed both sustained and transient components. GABA activated transient current was fully blocked by bicuculine, a $GABA_A$ receptor antagonist. The cis-4-aminocrotonic acid (CACA), a $GABA_C$ receptor agonist, evoked the sustained current that was not blocked by bicuculline (BIC). Glycine activated the transient current. These results indicate that the RBCs possess $GABA_A$, $GABA_C$, and glycine inhibitory receptors. Sodium nitroprusside (SNP), a NO analogue, reduced the currents activated by $GABA_A$ receptor only, however, did not reduce the currents activated by either $GABA_C$ or glycine receptors. This study signifies further that only NO depresses the fast inhibitory response activated by $GABA_A$ receptor in RBC. We, therefore, postulate that NO might depress the light-on/off transient inhibitory responses in RBCs in the rat retina.

• 대한기계학회논문집B
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• 제32권9호
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• pp.720-727
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• 2008

Time delay effects on near-wall turbulent structures are investigated by performing a large-eddy simulation of a transient turbulent flow in a pipe. To elucidate the time delay effects on the near-wall turbulence, we selected the dimensionless acceleration parameter which was used in the previous study. Various turbulent statistics revealed the distinctive features of the delay. It was shown that the dynamic Smagorinsky model is valid to capture the alterations of the turbulence physics well. A dimensionless time for the responses of the flow quantities was introduced to give the detailed information on the delay of the nearwall turbulence. The conditionally-averaged flow fields associated with Reynolds shear stress producing events show that sweep and ejections are closely related to the delays of the turbulence production and the turbulence propagation toward the pipe center. The present study suggested that the enhanced anisotropy of the turbulence in the initial and transient stages would be a challenging problem to standard turbulence models.

• 조명전기설비학회논문지
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• 제28권5호
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• pp.98-105
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• 2014

Soil discharges near the ground rod play an important role to reduce the ground potential rise and the ground impedance and to help the fault current to spread into the earth. This paper presents the effects of soil discharges on the transient and conventional ground impedances when the lightning impulse voltage was applied to a ground rod with radial needles. The current-voltage (I-V)curves and transient ground impedance curves were calculated based on the measured current and potential traces. Soil discharge behaviors related to I-V curves and transient ground impedance curves were analyzed as a function of the magnitude of lightning impulse voltages. As a result, the soil discharges occurred near the ground electrode contribute to the reduction of conventional ground impedance and limits the ground potential rise effectively under lightning impulse voltages.

• Journal of Preventive Medicine and Public Health
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• 제34권1호
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• pp.35-40
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• 2001

Objectives : To elucidate the transient effects on the risk of occupational injuries as acute events and establish so alternative proposal. Methods : The study population comprised a total of 302 workers randomly selected from applications for occupational injury compensation reported to the Inchon local labor office from January 1. 1999 to December 31. A case-crossover design, where each case serves its own control, was applied to this study. Through a telephone interview, workers provided useful data concerning five job related stressful events such as company transfer, work load change, overtime work, exchange duty, and work-part transfer. They were asked whether there were stressful events within a week of the occurrence of injury and the degree of stress. Exposure status from one year prior was used as control information. In the end, the data provided by 158 of selected persons was used for the analysis based on the quality of the data provided by the participants. A conditional logistic regression was used to discover the transient effects on the risk of occupational injuries as acute events. Results : The effects a company transfer and work load change on occupational injury was statistically significant on the risk of occupational Injuries as an acute event(RR=5.5, 95% CI=2.501-12.428; RR=3.1, 95% CI=1.963-5.017, respectively). Other stressful events were found to elevate the risk factor for the occurrence of occupational jujury, but were not significant. Conclusions : Our results suggested that transient stressful events elevated the risk factor for the occurrence of occupational injury.

• 한국항공우주학회지
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• 제49권3호
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• pp.251-262
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• 2021

최근 세계적으로 연구개발이 활발히 진행되고 있는 PAV(Personal Air Vehicle)에 대한 낙뢰 간접 영향성 인증 지침의 중요성이 부각되고 있다. 미래 교통수단으로서 소형화, 전기 엔진 사용, 복합재 사용 증가, 무인 항법 시스템 적용하는 추세인 PAV는 낙뢰에 취약할 수밖에 없다. 본 연구에서는 미연방항공청(FAA)에서 발행한 AC 20 136B에 나타난 낙뢰 간접 영향에 대한 적합성 인증절차를 확인하였다. 이와 함께 RTCA DO 160G Sec. 22에 수록된 장비 과도 설계 수준에 대한 인증 지침을 PAV에 적용하였다. 이어서 SAE ARP 5416A에 수록된 항공기 수준 시험을 전자기 해석 소프트웨어 EMA3D을 통해 수행하였다. 이를 통해 PAV에 대한 실제 과도 수준을 분석하였으며 이를 통해 적합성 인증에 필요한 자료를 도출하였다.

• Journal of Electrical Engineering and Technology
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• 제8권5호
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• pp.1182-1187
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• 2013

Transient radiation is emitted during a nuclear explosion and causes fatal errors as upset and latch-up in CMOS circuits. This paper proposes the transient radiation SPICE models of NMOS, PMOS, and INVERTER based on the transient radiation analysis using TCAD (Technology Computer Aided Design). To make the SPICE model of a CMOS circuit, the photocurrent in the PN junction of NMOS and PMOS was replaced as current source, and a latch-up phenomenon in the inverter was applied using a parasitic thyristor. As an example, the proposed transient radiation SPICE model was applied to a CMOS NAND circuit. The CMOS NAND circuit was simulated by SPICE and TCAD using the 0.18um CMOS process model parameter. The simulated results show that the SPICE results were similar to the TCAD simulation and the test results of commercial CMOS NAND IC. The simulation time was reduced by 120 times compared to the TCAD simulation.