• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 A
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• pp.82-84
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• 1998

The normal zone propagation velocity and minimum quench energy (MQE) of cable-in-conduit conductors (CICC) has been investigated at the different background magnetic fields and supercritical helium pressures. The sample CICC of 2 m in length was fabricated with triplet NbTi/Cu strands inserting into a round stainless-steel tube. The heat pulse disturbance with duration time about 400 ms was acted on the center region of the CICC to quench the strands. The normal zone propagation velocity increased with operating current of the CICC. The measured velocity with respect to operation current could be fitted with numerical results.

• 한국통신학회논문지
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• 제16권12호
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• pp.1324-1335
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• 1991

본 논문은 음절을 음소로 분리하고 각각의 특징을 추출하여 음소를 판별할 수 있는 패턴을 설정하는 실험에 관한 연구이다. 음소분리는 피치검출, 각 성문피크펄스의 폭, 포락실, 진폭의 바이어스, 발성시간 등의 파라메타를 적용한다. 최초의 피치는 성문펄스의 폭, 에너지, 정규화와 성문피크의 가변바이어스 등의 변화에 따라 모음 포라선의 봉우리 부분에서 검출, 이를 기준으로 전체의 피치구간을 추적한다. 모음은 포만트 패턴의 유동을 감소시키는 방법과 제2포만트만으로 모음의 판별이 가능함을 제시하며, 피치 고저에 무관한 압축파형을 추정한다. 자음은 포락실, 스펙트럼, 압추파형, 분석방법 등을 발음방법과 음소 상호 영향에서 패턴을 추출한다. 실험결과 모음음소 90%, 초성자음80%, 종성자음 60% 판별된다.

• Nuclear Engineering and Technology
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• 제56권4호
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• pp.1145-1152
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• 2024

To realize an initial objective of the negative ion-based neutral beam injection (N-NBI) at the Comprehensive Research Facility for Fusion Technology (CRAFT) test facility, which targets an H⁰ beam power of 2 MW at an energy of 200-400 keV and a pulse duration of 100 s, it is crucial to study the cesium dynamics of the negative ion source. Here a numerical simulation program CSFC3D is developed and applied to simulate the distribution and time dynamics of cesium during short pulses. The calculations show that most of the cesium on the plasma grid (PG) area originates from the release of cesium that is accumulated within the ion source in the plasma phase. Increasing the wall temperature reduces the loss of cesium on the wall of the ion source. Furthermore, the thickness of the cesium monolayer is directly influenced by the PG temperature. Both simulated and experimental results demonstrate that maintaining the PG temperature between 180 ℃ and 200 ℃ is essential for enhancing the performance of the ion source and optimizing the cesium behavior.

• The Korean Journal of Pain
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• 제12권1호
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• pp.16-20
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• 1999

Background: Tourniquet pain has important impacts on anesthesia. Tourniquet pain and accompanying cardiovascular changes are important factors that make patients in distress during anesthesia. As tourniquet pain may be modified by anesthesia, a study on the changes in the neural functions by tourniquet inflation in normal volunteers is important. Methods: Time-dependent changes in tourniquet pain, heart rate, phantom limb sensation, motor function, pain to pressure on upper extremity of 10 healthy and unpremedied volunteers were measured. Each parameter were measured every 5 minutes starting from 10 minutes before inflation to 15 minutes after deflation of tourniquet. Tourniquet was deflated when the subject felt unbearable pain (score 100 with visual analog scale). Results: Subjects manifested time-dependent pain responses to tourniquet inflation, characterized by increase in VAS, systolic and diastolic blood pressure. Mean duration of tourniquet inflation was 36.4 minutes, volunteers experienced motor paralysis at 27.6 minutes and sensory loss at 33.1 minutes. Pain to pressure decreased over time in both arms. The degree of decrease was greater in the arm on which tourniquet was applied than that in the non-applied arm. Phantom limb sensation occurred in 3 subjects. Conclusions: This study demonstrated dynamic changes in the neural functions during tourniquet inflation period. Tourniquet-induced pain and resultant hypertension occurred in all subjects. Appropriate anesthetic management is needed for the surgery using tourniquet.

• Transactions on Electrical and Electronic Materials
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• 제4권6호
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• pp.9-12
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• 2003

The electrical properties of stabilized amorphous selenium typical of the material used in direct conversion x-ray imaging devices are reported. Carrier mobility was measured using time-of-flight (TOF) measurements to investigate the transport properties of holes and electrons in stabilized a-Se film. A laser beam with pulse duration of 5 ns and wavelength of 350nm was illuminated on the surface of a-Se with thickness of 400 $\mu\textrm{m}$. The photo induced signals of a-Se film as a function of time were measured. The measured transit times of hole and electron were about 8.73${\mu}\textrm{s}$ and 229.17${\mu}\textrm{s}$, respectively. The hole and electron drift mobilities decreases with increase of electric field up to 4V/$\mu\textrm{m}$. Above 4V/$\mu\textrm{m}$, the measured drift mobilities exhibited no observable dependence with respect to electric field. The experimental results showed that the hole and electron drifting mobility were 0.04584 $\textrm{cm}^2$ V$\^$-1/s$\^$-1/ sand 0.00174 $\textrm{cm}^2$V$\^$-1/s$\^$-1/ at 10 V/$\mu\textrm{m}$.

• Journal of Korean Neurosurgical Society
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• 제52권6호
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• pp.509-512
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• 2012

Objective : The purpose of this study is to evaluate neuroprotective effect of sacral neuromodulation in rat spinal cord injury (SCI) model in the histological and functional aspects. Methods : Twenty-one female Sprague Dawley rats were randomly divided into 3 groups : the normal control group (CTL, n=7), the SCI with sham stimulation group (SCI, n=7), and the SCI with electrical stimulation (SCI+ES, n=7). Spinal cord was injured by dropping an impactor from 25 mm height. Sacral nerve electrical stimulation was performed by the following protocol : pulse duration, 0.1 ms; frequency, 20 Hz; stimulation time, 30 minutes; and stimulation duration, 4 weeks. Both locomotor function and histological examination were evaluated as scheduled. Results : The number of anterior horn cell was $12.3{\pm}5.7$ cells/high power field (HPF) in the CTL group, $7.8{\pm}4.9$ cells/HPF in the SCI group, and $6.9{\pm}5.5$ cells/HPF in the SCI+ES group, respectively. Both the SCI and the SCI+ES groups showed severe loss of anterior horn cells and myelin fibers compared with the CTL group. Cavitation and demyelinization of the nerve fibers has no significant difference between the SCI group and the SCI+ES group. Cavitation of dorsal column was more evident in only two rats of SCI group than the SCI+ES group. The locomotor function of all rats improved over time but there was no significant difference at any point in time between the SCI and the SCI+ES group. Conclusion : In a rat thoracic spinal cord contusion model, we observed that sacral neuromodulation did not prevent SCI-induced myelin loss and apoptosis.

• 한국식품과학회지
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• 제34권4호
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• pp.631-636
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• 2002

Lactobacillus plantarum, Lactbacillus brevis, Leuconostoc mesenteroids, Pediococcus pentosaceus를 대상으로 하여 광펄스 처리에 따른 미생물의 영향에 대하여 검토하였다. 광원에 인가하는 전압의 세기를 15-25 kV로 하고 $2500\;{\mu}s$ 이내의 처리시간으로 젖산균 세포를 광 펄스 처리하였을 경우 빛의 세기가 증가할수록 사멸 속도와 사멸율이 증가하였으며, $1500\;{\mu}s$ 처리후에는 빛의 세기에 상관없이 7 log 정도의 동일한 사멸율을 나타내었다. 빛의 세기 25 kV에서 광원과 시료 표면의 거리를 60, 85, 110, 135 mm으로 변화를 주어 처리한 결과 광원과 시료 표면과의 거리가 가까울수록 높은 살균율을 나타내었다. 광펄스 처리시 시료 표면의 온도 상승은 $5^{\circ}C$ 미만으로 거의 나타나지 않았다. 광펄스 처리후 투과 전자 현미경으로 형태적인 변화를 관찰한 결과 광펄스 처리를 한 세포는 처리하지 않은 세포에 비해 세포내 물질이 상당 부분 손실되었으며, 일부 세포막과 세포벽에 손상이 일어났음을 알 수 있었다.

• 한국세라믹학회지
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• 제41권3호
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• pp.183-189
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• 2004

음극전착법을 이용하여 전도성유리(ITO-glass)위에 Cu$_2$O 막을 제조하였다. Cu$_2$O 막의 특성을 향상시키기 위하여 전착방법, 시간, 전압, 전착 후 열처리 조건을 변화시켰다. 전착 후 열처리를 통해 얻어진 전극에 100mW/$ extrm{cm}^2$의 백색광을 조사하여 광전류밀도를 측정하고 XRD, SEM, UV-visible spectrophotometer를 통해 제조 조건변화에 따른 특성변화를 관찰하였다. 그리고 100mW/$\textrm{cm}^2$의 백색광하에서 bias 전압이 0V인 조건에서 전극의 안정성을 측정하였다 인가전압 -0.7V, 인가시간 300초 전착 조건에서 얻어진 막을 30$0^{\circ}C$에서 1시간 열처리하여 순수한 Cu$_2$O 막을 제조하였으며, 이 전극을 이용 광전류밀도를 측정한 결과 1048 $\mu$A/$\textrm{cm}^2$가 측정되었다. 또한 chemical deposition을 이용 TiO$_2$ 박막을 Cu$_2$O 막 위에 코팅하여 전극의 안정성을 향상시켰다.

• 한국산학기술학회논문지
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• 제12권10호
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• pp.4561-4568
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• 2011

본 논문에서는 비엔나 정류기의 전압제어를 위한 반송파 비교 PWM 방법에 대하여 논한다. 일반적으로 산업용 및 통신용 등 여러 응용분야에서 2레벨 정류기가 주로 사용되어 왔다. 하지만 2레벨 정류기는 효율을 높이고, THD를 낮추는데 한계가 있기 때문에 3레벨 정류기에 대한 연구가 진행 되어 왔다. 3레벨 정류기의 대표적인 회로가 비엔나 정류기이다. 기존의 비엔나 정류기는 대부분 전압 명령으로부터 인가 공간전압 벡터를 선택하고, 공간전압 벡터 인가시간을 직접 계산하여, 그 시간동안 전압 명령을 인가하는 공간 전압 변조 방식이 사용된다. 하지만 이 방법은 전압 명령 생성 및 전압 벡터의 인가시간 계산이 매우 복잡하여, 구현이 어려운 단점이 있다. 이 단점을 보완하기 위해 기존의 3레벨 인버터에 사용되던 반송파 비교 PWM 방법을 비엔나 정류기에 적용할 수 있도록 수정하여, 비엔나 정류기를 위한 간단한 전압제어를 위한 반송파 비교 PWM방식을 도출하고 시뮬레이션 및 실험을 통해 검증 한다.

• 한국정밀공학회지
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• 제27권10호
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• pp.29-33
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• 2010

UV laser micromachining of metallic materials has been used in microelectronic and other industries. This paper shows on experimental investigation of micromachining of copper using a 355nm UV laser with 50ns pulse duration. A finite element model with high strain rate effect is especially suggested to investigate the phenomena which are only dominated by mechanically pressure impact in disregard of thermally heat transfer. In order to consider the strain rate effect, Cowper-Symonds model was used. To analyze the dynamic deformation during a very short processing time, which is nearly about several tens nanoseconds, a commercial Finite Element Analysis (FEA) code, LS-DYNA 3D, was employed for the computational simulation of the UV laser micro machining behavior for thin copper material. From these computational results, depth of the dent (from one to six pulsed) were observed and compared with previous experimental results. This will help us to understand interaction between UV laser beam and material.