• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.306-306
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• 2008

기계적 에너지를 전기적 에너지로 변환하는 에너지 변환소자인 압전 세라믹스는 액추에이터, 변압기, 초음파모터, 초음파 소자 및 각종 센서로 응용되고 있으며, 그 응용분야는 크게 증가하고 있다. 최근에는 이러한 압전 소자를 앞으로 도래하는 ubiquitous, 무선 모바일 시대의 휴대용 전자제품, robotics, MEMS 분야 등의 대체 에너지원으로 응용하기 위한 연구가 진행되고 있다. 특히 인간의 걷기 운동 등과 같은 일상적인 동작으로 필요한 전력을 얻을 수 있고, 세라믹 소자를 이용하기 때문에 전자노이즈가 발생되지 않을 뿐 아니라 반영구적으로 사용할 수 가 있어서, 기존 이차전지를 대체 또는 보완 할 수 있는 방안도 검토되고 있다. PZT계 세라믹스는 높은 유전상수와 우수한 압전특성으로 전자세라믹스 분야에서 가장 널리 사용되어지고 있지만 $1200^{\circ}C$ 이상의 높은 소결온도 때문에 $1000^{\circ}C$ 부근에서 급격히 휘발되는 PbO로 인한 환경오염과 기본조성의 변화로 인한 압전 특성의 저하가 문제시 되고 있다. 또한 적층 세라믹스의 제작 시 구조적 특성상 내부전극이 도포된 상태에서 동시 소결이 필요한데, 융점이 낮은 Ag전극 대신 값비싼 Pd나 Pt가 다량 함유된 Ag/Pd, Ag/Pt 전극이 사용되고 있어 경제성이 떨어지는 단점을 갖게 된다. 순수 Ag 전극을 사용하거나 Ag의 비율이 높은 내부전극을 사용하기 위해서는 $900^{\circ}C$ 이하에서 소결되고 우수한 전기적 특성을 보이는 압전 세라믹스를 개발 하는 것이 필요하다. 따라서 본 연구에서는 압전특성이 우수한 $(Pb_{1-x}Cd_x)(Ni_{1/3}/Nb_{2/3})_{0.25}(Zr_{0.35}/Ti_{0.4})O_3$ 계의 조성을 설계하고, 소걸온도를 낮추기 위해서 2 단계 하소법을 이용하였다. 또한 $MnCO_3$, $SiO_2$, $Pb_3O_4$ 등을 소량 첨가하여 액상 소결 특성을 부여하여 소결 온도를 감소시키려는 시도도 하였다. 분말을 볼 밀링 (ball milling)을 통해 24시간 동안 혼합하고, 혼합된 분말은 $800^{\circ}C$에서 2시간 동안 하소하였다. 하소한 분말을 다시 72시간 동안 볼 밀링 하여 최종 분말을 얻었다. 최종 분말에 PVB를 첨가하여 직경 15mm의 디스크 형태로 성형한 후, 850~$975^{\circ}C$ 범위에서 온도를 변화시키면서 소결을 하였다. 최종 분말 및 소결된 시편을 XRD분석을 통하여 상을 확인하였고, SEM을 이용하여 미세조직을 관찰 하였다. 전기적 특성을 평가하기 위하여 두께를 1mm로 연마한 시편에 Ag 전극을 도포하여 $650^{\circ}C$에서 열처리한 후, 분극처리 하였다. 압전특성은 $d_{33}$-meter로 측정하였고, impedance analyzer를 이용하여 압전 특성 (전기기계결합계수 및 기계적품질계수)을 측정 하였다. 또한 강유전체 특성 평가 장치 (Precision-LC)를 이용하여 분극-전계 특성을 평가하였다. 이상의 연구를 통하여 소결 온도가 $900^{\circ}C$인 경우에서도 양호한 압전 특성을 확보 할 수 있었다.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.14 no.1
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• pp.123-127
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• 2003

Cornelia de Lange syndrome is a dysmorphogenic disorder characterized by multiple congenital abnormalities, mental retardation, growth retardation and neurodevelopmental abnormalities. Diagnosis for the Cornelia de Lange syndrome is dependent on the clinical observation because neither definite biological marker nor definite chromosomal abnormality have been investigated. Clinical observation is important for the diagnosis, so we report a case of Corenelia de Lange syndrome with mental retardation and autistic disorder. The patient is a 6-year old girl. Her motor development and language development have been delayed. She could say no meaningful word and understood simple command partially. She showed poor eye contact and poor emotional interaction. Social interaction was impaired and she Showed stereotypic behaviors. Thus we diagnosed her as mental retardation with autistic disorder. She had vesicoureteral reflux, frequent upper respiratory infection and pneumonia. She had experienced febrile convulsions 4 times. She had short stature, confluent eyebrows, long eyelashes, and upturned nose with anteverted nostrils. She also showed low hairline and hypertrichosis in body and extremities. Her finger was short. In this case, we diagnosed Cornelia de Lange syndrome by her characteristic face, hypertrichosis and medical and behavioral problems that were frequently showed in this syndrome.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.1
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• pp.208-215
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• 2020

This study investigated the relationship among gait variables and physical fitness variables for Korean elderly people. Two hundred elderly people aged 65 to 85, (100 men and 100 women) participated in this study. They performed senior fitness test consisting of 6 tests, 3 additional physical tests (vertical jump, one leg stand, and grip force), body composition measures, and gait test. The gait test used shoes having an inertia measurement device in the outer-soles. The results indicated that the stride length, 6-min walking, lean body mass, and dumbbell curls were significantly affected by age (the above 75 group vs. the below 75 group). Among 33 measured parameters, the principal component analysis (PCA) revealed five PCs such as gait characteristics, physical features, gait variability, and fitness levels. In addition, the correlation analysis showed that the preferred walking speed was significantly, positively associated with stride length and single support time, whereas it was negatively associated with double support time and gait variability.(Ed note: please confirm my modification) In conclusion, sarcopenia should be avoided in elderly people, and resistance exercise is highly recommended to help elderly people maintain their gait ability.

• Journal of The Korean Society of Integrative Medicine
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• v.10 no.4
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• pp.241-250
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• 2022

Purpose : The purpose of this study was to investigate the effect of backward walking exercise on changes in the cervical angle and gait parameters in subjects with moderate forward head posture. Methods : Four subjects were selected for this study. In particular, subjects with an average of 43 subjects with moderate craniovertebral angles were selected as the criteria for subject selection. The exercise program consisted of a 5 minutes warm-up exercise, 20 minutes main exercise, and 5 minutes cool-down exercise. In the main exercise, the treadmill speed was 2.5 km/h for men, 2.0 km/h for women in the first week, from the 2nd week to the 4th week, it was increased by 0.5 km/h every week. Results : Craniovertebral angle increased by 2.06±2.46 ° before and after the backward walking exercise, and craniorotational angle decreased by -1.69±3.33 ° before and after exercise. As for the gait parameters, in the amount of change before and after the backward walking exercise, the left foot pressure was 4.58±5.70 % from front to back and the right foot pressure was 5.08±3.06 % from front to back. The left step length and right step length showed a change of -.33±4.43 cm and -2.08±7.26 cm, respectively. stride length showed a change of -2.59±11.18 cm. The left and right stance phase showed a change of -1.02±2.03 % and -1.23±1.54 %, respectively. The left and right swing phase showed changes of 1.02±2.03 % and 1.22±1.53 %, respectively. The left and right step times were -.01±.06 sec and -.02±.12 sec, respectively. The stride time showed a change of -.03±.18 sec. Conclusion : Changes in cervical angle and gait parameters were confirmed by performing backward walking exercise for subjects with moderate forward head posture for 4 weeks. Therefore, additional research should be conducted based on this case study.

• The Journal of Korean Society for School & Community Health Education
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• v.25 no.1
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• pp.1-15
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• 2024

Objectives: This study aims to examine the general characteristics and physical activity characteristics of young and middle-aged individuals with hypertension, with the goal of identifying key influencing factors and providing public health policy recommendations. Methods: Participants in this study used data from the 2021 Community Health Survey. The study participants include 5,511 individuals diagnosed with hypertension in the young and middle-aged group (aged 19 to 49). The collected data were analyzed using SPSS 26.0. Results: Model 1 is the influencing factors of young and middle-aged hypertensive patients according to general characteristics. The explanatory power is R²= .065. The influencing factors are as follows. Economic activity (𝛽= -.219, p<.001), breakfast per week (𝛽= .117, p<.001), gender (𝛽= .090, p<.001), subjective health status (𝛽= .073, p<.001), and education level (𝛽= .069, p<.001). Model 2 is the influencing factors of young and middle-aged hypertensive patients, including physical activity characteristics. The explanatory power is R²= .076. The influencing factors are as follows. Strength exercises (𝛽= -4.791, p<.001), the walking activity (𝛽= -2.694, p<.01), and the high-intensity physical activity (𝛽= -2.629, p<.01). Conclusion: The active management of young and middle-aged hypertension is essential to prevent progression to serious disease. To prevent hypertension in young and middle-aged people, health education is needed to develop and utilize health promotion programs that take into account general characteristics and physical activity characteristics.

• Journal of the Korean Dietetic Association
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• v.15 no.2
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• pp.97-112
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• 2009

The purpose of this study was to develop a nutrition education curriculum with teacher's guide which includes discretionary activities for obese children. A survey was carried out to investigate the recognition of body image and food behaviors according to the obesity index (mild, moderate, severe) in school children (4~6th grade, 158 boys and 60 girls) who were selected based on a physical examination in May, 2006 in the Gyeongnam province. Next, a nutrition education curriculum with teacher's guide was developed on the basis of the findings from the survey and from preceding researches. The results are summarized as follow. The results of this study showed the existence of some nutritional problems such as overeating, prejudice, skipping meals, snacking patterns, etc, which indicate the need for nutritional management for obese children. Most overweight children (80.3%) showed the most interest in the nutrition education program, particularly with regards to dieting for weight control (64.7%). The developed nutrition education curriculum consisted of 8 main subjects and 13 subtitles. The curriculum was prepared for 13 lessons and included songs and singing, making-up lyrics, games about nutrition, discussions of the experience of eating (satiety, thirst, hunger), debates on dietary habits, writing and others to promote the interest for learning. We aimed to develop this program in an attempt to improve the dietary habits of obese school children. This is very important because once a dietary habit is formed in adults, it is difficult to change and the best adjustable stage is during childhood. Therefore, early nutrition education during elementary school can change and build-up the awareness of health in young elementary school children.

• Journal of Nutrition and Health
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• v.46 no.4
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• pp.346-356
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• 2013

This study investigated the daily physical activity level, energy expenditure, energy balance, and body composition and their relationship with university students. The participants were 130 male students ($19.5{\pm}0.5$ yrs) and 139 female students ($19.5{\pm}0.3$ yrs) at a university in Chungnam province. Physical activity level was evaluated by an equation based on 24 hr-activity record and dietary nutrient intake was evaluated using the food record method during a three-day period consisting of two week days and one weekend. Body composition was measured using Inbody 430 (Biospace Co., Cheonan, Korea). As a result, mean body mass index (BMI) of subjects indicated that they had normal weight, however mean body fat ratio was $19.1{\pm}5.4%$ for males and $28.4{\pm}5.0%$ for females, indicating that they had higher than normal weight. Daily mean physical activity level was 1.55 for males and 1.47 for females, which was regarded as 'low active', respectively. Females had more light activity than males (p<0.01). Daily mean energy expenditure was $2,803.5{\pm}788.9$ kcal/d for males and $1,915.4{\pm}510.2$ kcal/d for females (p<0.001). Daily mean dietary energy intake was $2,327.0{\pm}562.5$ kcal/d for males and $1,802.1{\pm}523.6/d$ for females (p<0.001), and daily mean energy balance was $-476.5{\pm}955.9$ kcal/d for males and $-113.3{\pm}728.1$ kcal/d for females (p<0.01). Daily mean dietary intake of protein, vitamins, and minerals, except Ca, satisfied recommended nutrient intake. Daily energy expenditure was positively related to body weight (p<0.01), BMI (p<0.01), and fat free mass ratio (p<0.05), but was negatively related to body fat ratio (p<0.01). In conclusion, subjects had a negative energy balance and low physical activity. They had a normal weight by BMI but had a more fat than normal weight by body fat ratio. This appears to be related to their low physical activity. Thus, nutrition education should be provided for university students in order to increase their physical activity for maintenance of normal weight by body composition and health promotion.