• Information Display
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• v.4 no.4
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• pp.6-10
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• 2003

우리는 연-X-선 흡수 분광법(soft-X-ray Absorption Spectroscopy ; XAS)을 사용하여 실제 산화물 음극 전자 방출 물질 표면의 화학 구조에 대해 연구하였다. 바륨 3d 흡수단의 고-에너지 분해 스펙트럼은 활성화 과정(온도와 전압 인가) 후에 산화물 음극표면에서 수십 나노미터 깊이 아래까지 바륨 함량이 현저히 증가한다는 것을 보여주었다. 바륨과 산소의 XAS 데이터를 비교해보면 표면에서 과잉 바륨이 형성되는 것을 확실히 입증하고 있다. 게다가 우리는 표면에서의 과잉 바륨의 증가가 활성화 과정에서 열에너지에 의한 것이 아니라 인가된 전압에 의한 것임을 밝혀냈다. 이 결과로 우리는 표면의 과잉 바륨 형성 전체 과정을 규명하고 활성화 동안 표면의 바륨 증가가 분말 입자로부터 니켈 계면으로의 바륨 이온의 전해 이동 속도에 의해 제어된다는 것을 제안한다. 우리는 또한 표면 바륨 증가가 전해 이동에 의한 분말 입자 내의 바륨의 고갈에서 비롯되는 것으로 추정한다.

• Korean Journal of Optics and Photonics
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• v.10 no.5
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• pp.396-400
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• 1999

In the fiber-optic gyroscope employing a high-power erbium-doped fiber source, the source excess noise was subtracted from the gyro output through a single processing to improve the gyroscope sensitivity. As the result, we obtained the reduction of noise by 13.5 dB (electrical) which was measured from the noise floor spectrum when the gyro was modulated with the depth of 1.8 rad. In addition, the random walk coefficient of the gyro output was reduced by a factor of 4~5.

• Proceedings of the KIEE Conference
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• 2002.11b
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• pp.268-270
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• 2002

본 논문에서는 댐핑이 고려된 전력계통에서 동요시 안정도를 향상시킬 수 있는 확장된 PI제어를 이용한 조속기 제어기를 제안하였다. 전력계통에서의 동요는 대부분 고장기간 동안에 발전기에 저장된 과잉운동에너지에 의해 발생한다. 계통이 안정하도록 하기 위해서 과잉에너지를 효과적으로 다루려면 보통 직접법을 사용된다. 과잉에너지를 제어하기 위한 직접적인 방법으로는 LFC(Load Frequency Control)의 궤한이 활용된다. 확장된 PI제어 방식이 적용된 제어기는 지역내에서와 지역사이에서의 동요를 감쇄시키기 위한 조속기에 적용될 수 있다 또한 제안된 제어기는 조속기에 스팀밸브 제한 조건이나 발전율 제약조건(Generation Rate Constraint; GRC)과 같은 특이점이 존재할 때에도 우수한 성능을 보여주었다. 시뮬레이션은 두지역의 다기계통에서 부하를 변화시켜가며 실시하였다. 시뮬레이션 결과는 제안된 PI 제어기를 기존의 PI 제어기와 비교하여 매우 향상된 성능을 보여주었다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.76-80
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• 2012

Uni-element preburners using a oxidizer-rich triplex injector have been designed and tested. During combustion tests 1L mode high-frequency instability of 1100 Hz and low-frequency instability of 100 Hz were observed. High-frequency instability has been suppressed by reducing chamber diameter and applying turbulent rings in combustion chamber. Recently, research to reduce low-frequency instability is in progress.

• The Korean Journal of Applied Statistics
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• v.19 no.3
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• pp.505-519
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• 2006

We consider zero-inflated count data, which is discrete count data but has too many zeroes compared to the Poisson distribution. Zero-inflated data can be found in various areas. Despite its increasing importance in practice, appropriate statistical inference on zero-inflated data is limited. Classical inference based on a large number theory does not fit unless the sample size is very large. And regular Poisson model shows lack of St due to many zeroes. To handle the difficulties, a mixture of distributions are considered for the zero-inflated data. Specifically, a mixture of a point mass at zero and a Poisson distribution is employed for the data. In addition, when there exist meaningful covariates selected to the response variable, loglinear link is used between the mean of the response and the covariates in the Poisson distribution part. We propose a Bayesian inference for the zero-inflated Poisson regression model by using a Markov Chain Monte Carlo method. We applied the proposed method to a Korean oral hygienic data and compared the inference results with other models. We found that the proposed method is superior in that it gives small parameter estimation error and more accurate predictions.

• Journal of Korean Ophthalmic Optics Society
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• v.15 no.4
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• pp.398-404
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• 2010

Purpose: Concerns had been voiced about an oversupply of optometrists in Korea. So, this study aimed to forecast the supply and demand for opticians for policy implications. Methods: Baseline Projection model combined with demographic method was adopted as the supply forecasting method and so was a ratio method using the number of physician and population using weight of healthcare utilization. Results: Under the 'physician to optician ratio', there would be a surplus of 83~700 opticians in 2010 and an undersupply of 15 to surplus of 6,118 opticians in 2025. Under the 'population to optician ratio', there would be a surplus of 1,055 opticians in 2010 and surplus of 9,376 opticians in 2025. Conclusions: We concluded that there would be oversupply for opticians until 2025, although the shortage and surplus of opticians might depend on the ratio's criteria. Hence, policies would need to be developed that could solve the imbalance in requirements and supply for opticians.

• Journal of the korean academy of Pediatric Dentistry
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• v.48 no.2
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• pp.221-228
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• 2021

The aim of this study was to evaluate the use of easily accessible machine learning application to identify mesiodens, and to compare the ability to identify mesiodens between trained model and human. A total of 1604 panoramic images (805 images with mesiodens, 799 images without mesiodens) of patients aged 5 - 7 years were used for this study. The model used for machine learning was Google's teachable machine. Data set 1 was used to train model and to verify the model. Data set 2 was used to compare the ability between the learning model and human group. As a result of data set 1, the average accuracy of the model was 0.82. After testing data set 2, the accuracy of the model was 0.78. From the resident group and the student group, the accuracy was 0.82, 0.69. This study developed a model for identifying mesiodens using panoramic radiographs of children in primary and early mixed dentition. The classification accuracy of the model was lower than that of the resident group. However, the classification accuracy (0.78) was higher than that of dental students (0.69), so it could be used to assist the diagnosis of mesiodens for non-expert students or general dentists.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.7 no.1
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• pp.44-51
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• 1996

Objective : The authors investigated family environemtn of ADHD referred to child psychiatric clinics. Method : Seventy two patients were grouped into pure ADHD and comorbid ADHD. Patient's lither and mother conducted the Korean Form of the Family Environment Scale(K-FES). And then, scores were compared with that of 77 normal controls. Results : Among subscales of K-FES, expressiveness, achievement orientation and organization were scored significantly lower in ADHD mothers' reporting than ADHD fathers' And only organization subscale was scored significantly lower in ADHD fathers' reporting than controls' In post hoc comparison, subscales of expressiveness, moral-religious emphasis and organization were significantly lower in mothers' reporting of pure ADHD and comorbid ADHD than of controls, and only organization subscale was significantly lower in fathers' reporting of comorbid ADHD than of controls. Conclusion : Parents of ADHD patients agreed that their families were not well organized, and each perceived somewhat differently on the family environment. Further study is needed to eludicate whether specific family environment causes ADHD or is caused by behavior of ADITD patients.

• Management & Information Systems Review
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• v.36 no.1
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• pp.81-94
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• 2017

In the age of information overload such as Internet of Things(IoT), big data, and cloud computing, Data and informations are collected to processed regardless of the individual's will. The purpose of this paper presents a model related to personal information overlord, information privacy risk, information privacy concern (collection, control, awareness) and personal information privacy protective response. The results of this study is summarized as follows. First, personal information overload significantly affects information privacy risk. Second, personal information overload significantly affects information privacy concern(collection, control, awareness) Third, information privacy risk significantly affects collection and awareness among information privacy concern, but control does not significantly affects. This results shows that users are cognitively aware the information risk through collection and awareness of information. Users can not control information by self, control of information does not affects. Last, information privacy concern(collection and awareness significantly affect information privacy protective response, but information privacy concern (control) does not affect. Personal information users are concerned about information infringement due to excessive personal information, ability to protect private information became strong.

• Korean Journal of Biological Psychiatry
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• v.8 no.2
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• pp.271-275
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• 2001

Hyposexuality after stroke has been frequently observed, but hypersexuality as a sequela of stroke has not been commonly documented. We report a patient who exhibited hypersexuality and obsessive-compulsive behaviors after stroke in the region of the left mesial frontal cortex and both basal ganglia. At 2 months after stroke, he visited psychiatric unit due to these symptoms. His motor function was almost full recovered. He was treated with fluvoxamine and perphenazine. With two-month medication, his hypersexuality and obsessive-compulsive behavior disappeared. This case may indicate that basal ganglia-thalamocortical circuit plays an important role in the mediation of sexual behavior and obsessive-compulsive behavior. Since changes in sexual activity may not be spontaneously reported, a systemic inquiry into patient's sexual functioning after infarction in frontal lobe or basal ganglia is warranted.