• 조명전기설비학회논문지
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• 제26권4호
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• pp.57-66
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• 2012

When typical Z-source DC/AC inverter(ZSI) is operated in high voltage gain area, because of its high duty ratio, voltage and current stress in Z-network of typical ZSI are increased. This paper proposes a new switched trans ZSI(STZSI) with two switched trans cells which consist of one trans and two diodes. To confirm the operation performance of the proposed system, the PSIM simulation is performed for typical ZSI, switched inductor ZSI and the proposed STZSI. Voltage / current stress and transient state characteristics of each method are compared under the condition of DC input voltage 100[V] and output phase voltage 66[Vrms]. As a result, we confirmed that transient state of the proposed STZSI is short compared with the conventional ZSI because the high voltage gain is obtained using the same duty ratio, also a low duty ratio is required for the same output voltage. Finally, we could know the proposed system have low voltage and current stress in Z-network compared with the conventional ZSI.

• 대한의용생체공학회:의공학회지
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• 제26권4호
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• pp.207-214
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• 2005

Breast cancer detection using electrical impedance techniques is based on numerous experimental findings that cancerous tissues have higher electrical conductivity values than normal tissues. Lately, by taking advantage of the structure of current flows underneath a planar probe of array electrodes, a mathematical formula to find lesions from a measured trans­admittance map has been derived. In order to experimentally validate its mathematical analysis and the suggested lesion estimation algorithm, we developed a 256-channel trans-admittance scanner (TAS) for probing anomalies underneath a planar array of electrodes. In this paper, we describe the design and implementation of the TAS. Its performance together with the lesion estimation algorithm was evaluated using saline phantoms. Further studies are proposed to validate the system on human subjects.

• 한국산학기술학회논문지
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• 제12권1호
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• pp.493-499
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• 2011

기존의 직교변조 (Orthogonal Modulation)는 그 효용성에 비해 대역폭 효율이 지나치게 떨어져 이를 개선하기 위한 다중부호 트랜스직교변조 (MCTO: Multi-Code Trans-Orthogonal Modulation)가 제안되었다. 그러나 MCTO 변조는 송신신호의 진폭이 일정하게 유지되지 않아 RF (Radio Frequency) 단에 포함되어 있는 전력 증폭기 (Power Amplifier)의 부담이 커지게 되는 문제점이 있다. 따라서 본 논문에서는 다중부호 신호를 정진폭으로 부호화하는 방식을 이용한 정진폭 다중부호 트랜스직교변조 (CAMCTO: Constant-Amplitude Multi-Code Trans-Orthogonal Modulation)를 제안한다. 또한 제안된 CAMCTO 변조의 성능을 실험을 통해 제시하고 기존의 직교변조 및 MCTO 변조와 비교한다. 실험 결과에 의하면 제안된 CAMCTO 변조는 기존의 직교변조에 비해 대역폭 효율은 매우 증가하며 MCTO 변조에 비해 RF의 부담을 매우 경감시킬 수 있음을 알 수 있다.

• Korean Journal of Radiology
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• 제22권1호
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• pp.118-130
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• 2021

Objective: This study aimed to investigate the blood-brain barrier (BBB) disruption in mild traumatic brain injury (mTBI) patients with post-concussion syndrome (PCS) using dynamic contrast-enhanced (DCE) magnetic resonance (MR) imaging and automatic whole brain segmentation. Materials and Methods: Forty-two consecutive mTBI patients with PCS who had undergone post-traumatic MR imaging, including DCE MR imaging, between October 2016 and April 2018, and 29 controls with DCE MR imaging were included in this retrospective study. After performing three-dimensional T1-based brain segmentation with FreeSurfer software (Laboratory for Computational Neuroimaging), the mean K^trans and v_p from DCE MR imaging (derived using the Patlak model and extended Tofts and Kermode model) were analyzed in the bilateral cerebral/cerebellar cortex, bilateral cerebral/cerebellar white matter (WM), and brainstem. K^trans values of the mTBI patients and controls were calculated using both models to identify the model that better reflected the increased permeability owing to mTBI (tendency toward higher K^trans values in mTBI patients than in controls). The Mann-Whitney U test and Spearman rank correlation test were performed to compare the mean K^trans and v_p between the two groups and correlate K^trans and v_p with neuropsychological tests for mTBI patients. Results: Increased permeability owing to mTBI was observed in the Patlak model but not in the extended Tofts and Kermode model. In the Patlak model, the mean K^trans in the bilateral cerebral cortex was significantly higher in mTBI patients than in controls (p = 0.042). The mean v_p values in the bilateral cerebellar WM and brainstem were significantly lower in mTBI patients than in controls (p = 0.009 and p = 0.011, respectively). The mean K^trans of the bilateral cerebral cortex was significantly higher in patients with atypical performance in the auditory continuous performance test (commission errors) than in average or good performers (p = 0.041). Conclusion: BBB disruption, as reflected by the increased K^trans and decreased v_p values from the Patlak model, was observed throughout the bilateral cerebral cortex, bilateral cerebellar WM, and brainstem in mTBI patients with PCS.

• Journal of Advanced Marine Engineering and Technology
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• 제31권6호
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• pp.723-728
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• 2007

In order to evaluate the performance of carbon dioxide cycle with a sub-cooling loop. a simulation system was developed to predict the steady state of $CO_2$ trans-critical cycle. Mathematical models are derived to describe the relationships between the system's coefficient of performance and other operating parameters The mathematical models are based entirely on the basic mass and energy conservation law and thermodynamic and transport properties of carbon dioxide A parametric study has been conducted in order to investigate the effect of sub-cooling loop and various operating conditions on the cycle performance. An optimal mass fraction of a refrigerant flowing through sub-cooling cycle existed for the given evaporating temperature, high pressure and air inlet temperature through gas cooler.

• 한국전기전자재료학회논문지
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• 제18권2호
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• pp.153-158
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• 2005

Recently, as the feasibility study shows that trans-Korea railway and trans-continental railway are advantageous, interest in high-speed railway system is increasing. Because railway vehicle is environment-friendly and safe compared with airplane and ship, its market-sharing increases gradually. KHST(Korean High Speed Train) has been developed by KRRI (Korea Railroad Research Institute) for last 6 years to satisfy the need. An electric railway system is composed of high-tech subsystems, among which main electric equipment such as transformers and converter are critical components determining the performance of rolling stock. We developed a measurement system for on-line test and evaluation of performances of KHST. The measurement system is composed of software part and hardware part. Perfect interface between multi-users is possible. A now method to measure temperature was applied to the measurement system. By using the system, fault diagnosis and performance evaluation of electric equipment in Korean High Speed Train was conducted during test running.

• 한국식품과학회지
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• 제35권5호
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• pp.764-768
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• 2003

본 연구는 생물학적, 비생물학적인 스트레스에 대한 방어물질중의 한가지인 trans-resveratrol를 포도와 포도가공품(포도주, 포도쥬스)으로부터 분석하는 방법을 확립하였다. trans-Resveratrol 기기분석 조건은 다음과 같다. 분석 column은 Nucleosil 100-5 C18을 사용하였으며 이동상은 acetonitrile: water(40:60, v/v)로서 UV검출기(306 nm)를 이용하여 0.3 mL/min의 유속으로 측정하였다. 분석한 결과, 재현성과 반복성의 CV%는 10%이하였으며, 회수율은 $90{\sim}110%$이었다. 또한, 포도, 포도주 그리고 포도쥬스의 최소검출한계는 14.5 ng/g, 3.62 ng/mL 그리고 4.02 ng/mL이고, 최소정량한계는 14.8 ng/g, 3.69 ng/mL 그리고 4.10 ng/mL이었다. 표준물질인 trans-resveratrol 농도가 $0.048{\sim}2.4\;{\mu}g/mL$일때 $R^2$ 값은 0.999이었다. 32품종의 포도, 9종류의 포도주 그리고 9종류의 포도쥬스 내의 trans-resveratrol 함량은 각각 $0.76{\sim}207.14\;{\mu}g/100\;g$, $5.41{\sim}275.66\;{\mu}g/L$ 그리고 $63.25{\sim}751.55\;{\mu}g/L$로 분석되었다.

• Safety and Health at Work
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• 제8권2호
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• pp.220-225
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• 2017

Background: Benzene is a known occupational and environmental pollutant. Its urinary metabolite trans, trans-muconic acid (tt-MA) has been introduced by some environmental and occupational health regulatory associations as a biological index for the assessment of benzene exposure; however, recently, doubts have been raised about the specificity of tt-MA for low-level benzene exposures. In the present study, we investigated the association between urinary levels of tt-MA and inhalational exposure to benzene in different exposure groups. Methods: Benzene exposure was assessed by personal air sampling. Collected benzene on charcoal tube was extracted by carbon disulfide and determined by a gas chromatograph (gas chromatography with a flame ionization detector). Urinary tt-MA was extracted by a strong anion-exchange column and determined with high-performance liquid chromatography-UV. Results: Urinary levels of tt-MA in intensive benzene exposure groups (chemical workers and police officers) were significantly higher than other groups (urban and rural residents), but its levels in the last two groups with significant different exposure levels (mean = 0.081 ppm and 0.019 ppm, respectively) showed no significant difference (mean = $388{\mu}g/g$ creatinine and $282{\mu}g/g$, respectively; p < 0.05). Before work shift, urine samples of workers and police officers showed a high amount of tt-MA and its levels in rural residents' samples were not zero. Conclusion: Our results suggest that tt-MA may not be a reliable biomarker for monitoring low-level (below 0.5 ppm) benzene exposures.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1989년도 추계학술대회 논문집 학회본부
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• pp.197-200
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• 1989

The corona interference of extra high voltage (EHV) transmission lines has to be considered as an important design factor for establishing an electrical environmental countermeasure at a basic line design stage. This paper describes the conductor selection procedure through both corona performance test result in corona cage and its evaluation by the design criterion. It is known that three conductor configurations including $6{\times}810mm^2$ (spacing: 40 cm) are the suitable conductor bundle for the environmental preservation around both 2-circuits and 1-circuit T/L.

• Journal of Ship and Ocean Technology
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• 제2권1호
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• pp.13-30
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• 1998

The design method for trans-cavitating propellers is considered as the combination of super-and sub-cavitating propellers. Especially the design method of the super-cavitating region of the propeller blade is elaborated. A design example is shown. Encouraging test results obtained in the Korea Research Institute of Ship and Ocean (KRISO) cavitation tunnel of a model designed by the present method are discussed.