• 대한의용생체공학회:의공학회지
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• 제35권3호
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• pp.68-74
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• 2014

Recent research on mild cognitive impairment (MCI) has shown that cognitive and memory decline in this disease is accompanied by disruptive changes in the brain functional network. However, there have been no graph-theoretical studies using $^{11}C$-PIB PET data of the Alzheimer's Disease or mild cognitive impairment. In this study, we acquired $^{18}F$-FDG PET and $^{11}C$-PIB PET images of twenty-four normal aging control participants and thirty individuals with MCI from ADNI (Alzheimer's Disease Neuroimaging Initiative) database. Brain networks were constructed by thresholding binary correlation matrices using graph theoretical approaches. Both normal control and MCI group showed small-world property in $^{11}C$-PIB PET images as well as $^{18}F$-FDG PET images. $^{11}C$-PIB PET images showed significant difference between NC (normal control) and MCI over large range of sparsity values. This result will enable us to further analyze the brain using established graph-theoretical approaches for $^{11}C$-PIB PET images.

• 한국전자통신학회논문지
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• 제9권5호
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• pp.595-600
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• 2014

요즘 우리 사회는 급속히 고령화 사회로 변화되고 있다. 고령화 사회에서는 치매에 대하여 잘 아는 것이 매우 중요한 일이다. 따라서 본 연구는 기본적으로 치매환자로부터 측정한 EEG 신호의 특성을 파악하는 것을 목표로 한다. 먼저 그것을 위하여 치매환자와 정상인의 EEG 특성을 구분하기 위하여 두 그룹의 자발 EEG 신호를 분석하였다. EEG 신호는 16개의 전극으로 계측하였고, 그 신호들은 주파수대역으로 분류하여 분석하였다. 보다 선명한 EEG 신호로 처리하기 위해서는 2개의 채널 간에 상호상관함수를 적용하였다. 그 결과, 치매환자와 정상인의 EEG 신호의 특성은 분명히 다르다는 사실을 확인할 수 있었다.

• 수산해양기술연구
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• 제20권1호
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• pp.23-29
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• 1984

고역알루미늄합금의 파괴특성에 미치는 시효열처리의 영향에 대하여 검토한 결과는 다음과 같다. 1. 현미경 조직의 관찰결과 $190^{\circ}C,$ 12hr로 시효열처리한 것이 시효강화된 양호한 조직과 미세한 석출분포를 나타내고 있음을 알 수 있었다. 2. 계단식시효열처리에 의하여 정상시효열처리보다 시효시간을 반정도로 단축시킬 수 있었고, 이들 조직도 유사하였다. 3. 인장파단면의 SEM 전자현미경 사진관찰결과는 $190^{\circ}C,$ 12hr으로 시효열처리한 것은 딤플형 입계 및 입내연성파괴를 나타내나, 이를 제외한 대부분은 시효열처리 시간과 온도에는 관계없이 입계연성파괴인 것이 관찰되었다.

• 대한예방한의학회지
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• 제8권2호
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• pp.65-80
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• 2004

Objectives : CRATAEGII FRUCTUS(山査) is known as the substance which delays aging by the antioxidant effects. The purpose of this study is to investigate the effects of CRATAEGII FRUCTUS(山査) on antioxidant enzyme activities such as Thiobarbituric acid reactive substance(TBARS), Superoxide dismutase(SOD), Catalase(CAT), Glutathione peroxidase (GSH-px) in rat erythrocytes and blood plasma. Methods : Sprague-Dawley rats were divided into 3 groups, Normal group (supplied enough water and feeds only, Normal Group), D-galatose administered group(injected D-galatose 50mg/kg, 1time/day for 6 weeks, Control Group) and CRATAEGII FRUCTUS(山査) administered group (D-galactose 50mg/kg and CRATAEGII FRUCTUS(山査) extracts 85.0mg/200g 1time/day for 6 weeks, SS Group). Rats were sacrificed and TBARS, SOD, CAT, GSH-px, neutral fat and cholesterol were measured in rat erythrocytes and blood plasma. Results : There was no significant difference in the level of TBARS in the blood plasma between each experimental group. Red blood cell SOD activities were significantly different in each group. They were significantly decreased in the Control group compared to those of Normal and there was an increasing phenomenon in the SS group compared to the Control group. There was a significant difference in the activities of the red blood cell - glutathione peroxides in each group. There was a significant increase in the SS group compared to the Control group. Red blood cell catalase activities was no significant difference in each group. Plasma total lipid concentration was significantly different in each group. It was significantly increased in the Control group compared with the Normal group and it was decreasing in the SS group compared to the control group. Plasma triglyceride was not significantly different in each group. Plasma total cholesterol and Plasma HDL -cholesterol concentrations in the blood plasma were not significantly different in each group. Conclusions : According to the above results, it is considered that CRATAEGII FRUCTUS(山査) is effective in inhibiting lipid peroxides and increasing the activities of antioxidative(anti aging) enzyme in D-galactose induced aging rat.

• 한국신뢰성학회지:신뢰성응용연구
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• 제12권3호
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• pp.177-186
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• 2012

This paper presents a comparison of the failure mechanism for high power converted white LEDs(3W) with the commercially available YAG:Ce and silicate phosphor. We carry out the normal aging life test for 10,000 hours, the high temperature aging test for 8,000 hours, the high temperature and humidity aging test for 8,000 hours and the current aging testing for 5,000 hours. The optical and electrical parameters of LEDs were monitored, such as lumen, correlated color temperature (CCT), chromaticity coordinates(x, y), thermal resistance, I -V curve and spectrum intensity. The stress induced a luminous flux decay on LED in all experiments and causes a failure. So we try to find out what's a main failure mechanism for a high power LED.

• 대한전기학회논문지
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• 제43권3호
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• pp.432-436
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• 1994

The aging characteristics of amorphous FeS178TBS113TSiS19T wound cores have been investigated as a function of aging temperature and time. The core losses(1.2T/60Hz) of amorphous wound cores dipped in transformer oil decrease in comparision with initial stage of aging test due to insulation of ribbon stacks by oil penetration. It is estimated that it takes 30 years or more for 10% increase in core losses (1.2T/60Hz) of amorphous wound cores aged at normal transformer running temperature(100$^{\circ}C$). So we condlude that the amorphous core is satisfactorily applicable to transformer.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.645-650
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• 2000

The discrete wavelet transform is utilized as processing of neural network(NN) to identifying aging state of internal partial discharge in transformer. The discrete wavelet transform is used to produce wavelet coefficients which are used for classification. The mean values of the wavelet coefficients are input into an back-propagation neural network. The networks, after training, can decide if the test signals is aging early state or aging last state, or normal state.

• KIEE International Transactions on Power Engineering
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• 제5A권1호
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• pp.40-45
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• 2005

Substation facilities have become extremely large and complex parts of electric power systems. The development of condition monitoring and diagnosis techniques has been a very significant factor in the improvement of substation transformer security. This paper presents a method to analyze the cause, the degree, and the aging process power transformers by the Self Organizing Map (SOM) method. Dissolved gas data were non-linearly transformed by the sigmoid function in SOM that works much the same way as the human decision making process. The potential for failure and the degree of aging of normal transformers are identified by using the proposed quantitative criterion. Furthermore, transformer aging is monitored by the proposed criterion for a set of transformers. To demonstrate the validity of the proposed method, a case study is performed and its results are presented.

• 대한약학회:학술대회논문집
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• 대한약학회 2003년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.2-1
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• pp.96-96
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• 2003

Telomerase activity is expressed in most types of cancer cells but not in normal somatic cells, suggesting that telomerase may be an important target for cancer chemotherapy. Inhibition of telomerase results in telomere erosion leading to the subsequent growth-arrest of cancer cells followed by senescence or cell death. In this study, we screened a chemical library for inhibition of human telomerase, identifying two groups of inhibitors. (omitted)

• 대한방사선기술학회지:방사선기술과학
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• 제30권4호
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• pp.407-417
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• 2007

과거로부터 사회 경제학적인 문제로 주목을 받고 있는 요통은 노화와 유의한 관계가 있음이 보고되고 있으며, 이러한 노화에 의해 추간판의 여러 형태 조직학적 변화도 이미 여러 연구를 통해 보고되었으나 노화에 따른 추간판의 크기 변화에 대한 연구와 이러한 추간판의 변화가 요통과 관련이 있는지에 대한 연구는 거의 이루어지고 있지 않고 있는 실정이다. 이에 본 연구는 노화에 의한 추간판 변인의 변화를 알아보고, 이런 요인들이 정상 피검자와 요통 환자 사이에 차이가 있는지를 MRI 실계측에 의해 알아보고자 수행하였다. 본 연구는 근골격계 질환이 없는 20대$\sim$60대의 정상 성인 50명과 $20{\sim}60$대 요통 환자 50명을 대상으로 L4-5, L5-S1 추간판의 가로 직경, 세로 직경 그리고 면적을 MRI 영상을 통해 실계측하여 노화에 따른 변화와 정상 피검자와 요통 환자 사이의 차이를 비교하는 방식으로 진행하였다. 본 연구 결과 L4-5와 L5-S1 추간판의 가로 및 세로 직경, 면적은 노화에 의해 의미 있는 증가 경향을 보였으며 정상 피검자에 비해 요통 환자의 추간판 변인들이 큰 것을 확인하였다. 따라서 추간판의 크기 변화는 노화에 의한 자발적인 변화이며, 요통 환자의 추간판 변인 증가를 요통 진단에 참조할 수 있는 자료로 사용할 수 있을 것으로 사료되나, 차후 광범위한 피검자를 대상으로 하는 보다 폭넓고 다각적인 연구가 필요한 것으로 사료된다.