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Ui Gyeong Hwang,Kyomin Kim,Woo Chul Kim,신원호,Won-Seon Seo,임영수 대한금속·재료학회 2019 ELECTRONIC MATERIALS LETTERS Vol.15 No.5
We report the thermoelectric transport properties of interface-controlled p-type bismuth antimony telluride (BST) compositesusing reduced graphene oxide (rGO). The composites were prepared by the spark plasma sintering (SPS) of BST–grapheneoxide (GO) hybrid powder, which could induce the in situ reduction of GO into rGO. Compared to the pristine BST, theinterface-controlled BST composites exhibited degraded electrical conductivities with similar Seebeck coefficients, consequentlyresulting in decreased power factors. However, thanks to the suppressed lattice thermal conductivity by the rGOnetwork at the grain boundaries, this disadvantage could be compensated in terms of ZT. Our results will be helpful forunderstanding thermoelectric transport properties of various graphene-hybrid thermoelectric materials.
Effect of a Facial Muscle Exercise Device on Facial Rejuvenation
Hwang, Ui-jae,Kwon, Oh-yun,Jung, Sung-hoon,Ahn, Sun-hee,Gwak, Gyeong-tae Oxford University Press 2018 Aesthetic surgery journal Vol.38 No.5
<P><B>Abstract</B></P><P><B>Background</B></P><P>The efficacy of facial muscle exercises (FMEs) for facial rejuvenation is controversial. In the majority of previous studies, nonquantitative assessment tools were used to assess the benefits of FMEs.</P><P><B>Objectives</B></P><P>This study examined the effectiveness of FMEs using a Pao (MTG, Nagoya, Japan) device to quantify facial rejuvenation.</P><P><B>Methods</B></P><P>Fifty females were asked to perform FMEs using a Pao device for 30 seconds twice a day for 8 weeks. Facial muscle thickness and cross-sectional area were measured sonographically. Facial surface distance, surface area, and volumes were determined using a laser scanning system before and after FME. Facial muscle thickness, cross-sectional area, midfacial surface distances, jawline surface distance, and lower facial surface area and volume were compared bilaterally before and after FME using a paired Student <I>t</I> test.</P><P><B>Results</B></P><P>The cross-sectional areas of the zygomaticus major and digastric muscles increased significantly (right: <I>P</I> < 0.001, left: <I>P</I> = 0.015), while the midfacial surface distances in the middle (right: <I>P</I> = 0.005, left: <I>P</I> = 0.047) and lower (right: <I>P</I> = 0.028, left: <I>P</I> = 0.019) planes as well as the jawline surface distances (right: <I>P</I> = 0.004, left: <I>P</I> = 0.003) decreased significantly after FME using the Pao device. The lower facial surface areas (right: <I>P</I> = 0.005, left: <I>P</I> = 0.006) and volumes (right: <I>P</I> = 0.001, left: <I>P</I> = 0.002) were also significantly reduced after FME using the Pao device.</P><P><B>Conclusions</B></P><P>FME using the Pao device can increase facial muscle thickness and cross-sectional area, thus contributing to facial rejuvenation.</P><P><B>Level of Evidence: 4</B></P><P>[GRAPHIC OMISSION]</P>
풀 화재의 열방출률 측정을 위한 판형 열유속계의 적용성 평가
모경의(Gyeong-Ui Mo),윤홍석(Hong-Seok Yun),황철홍(Cheol-Hong Hwang) 한국화재소방학회 2022 한국화재소방학회 학술대회 논문집 Vol.2022 No.추계
열방출률(Heat Release Rate, HRR)은 화재로부터 방출되는 단위시간 당 열에너지(kW)를 의미하며, 화재규모 및 위험성을 평가하기 위한 가장 기본적 물리량으로 인식된다. 열방출률은 연료의 질량감소율(Mass loss rate), 연소생성물의 엔탈피를 통해 측정될 수 있으나, 복합가연물에 대한 적용성 및 연소생성물이 겪는 열손실 정량화의 한계로 다양한 화재조건에 적용되는데 한계가 있다. 이에 따라 연소과정에서 생성 또는 소모되는 화학종의 농도를 고려하는 산소소모법(Oxygen consumption method)이 열방출률 측정에 널리 활용되고 있다. 산소소모법에 기반한 열방출률의 측정은 가연물의 종류 및 열손실의 영향을 받지 않는다는 장점이 있으나, 화재로부터 발생되는 연소생성물이 전량 포집되어야만 적절한 측정이 가능하다. 이로 인해 산소소모열량계는 포집후드 및 배기 fan의 성능에 따라 특정 규모 이상의 화재에 대한 열방출률 측정에 한계를 가지고 있다. 특히, 건축물 규모의 화재에 대한 열방출률 측정결과는 소방설계를 위한 유용한 참고자료가 될 수 있으나 산소소모열량계의 한계로 인해 충분한 화재 DB의 확보가 어려운 실정이다. 이러한 문제를 해결하기 위하여, 화재로부터 방출되는 열에너지의 종류 및 특성이 고려될 수 있다. 화재의 총 방출열량 중 일정 비율은 복사열에너지 형태로 방출된다. 또한 특정 거리 이상의 조건에서 화염으로부터 방출되는 복사열유속은 등방성 복사(isotropic radiation)로 간주될 수 있다. 이러한 특성들에 대한 고려를 통해 본 연구에서는 헵탄(heptane)풀 화재의 복사열유속에 기반한 열방출률의 측정이 시도되었다. 이 때 복사열유속의 측정에는 선행연구를 통해 응답성능 및 정확도가 검증된 Plate thermometer (PT)가 활용되었다. 매우 간단한 복사열유속 측정장치인 PT를 활용한 열방출률의 예측은 대형 화재의 규모평가 및 이를 고려한 화재안전설계에 유용한 정보를 제공할 것으로 기대된다.
Gwak Gyeong-tae,김준희,Hwang Ui-jae,정성훈,안선희 KEMA학회 2023 근골격계과학기술학회 Vol.7 No.2
Background Osteoporosis (OP) is a bone disease caused by a decrease in bone mineral density (BMD). OP is common in women because BMD gradually decreases after age 35. OP due to decreased BMD is highly likely to cause fatal traumatic injuries such as hip fracture. Purpose The purpose of this study was developed and evaluated a multi-layer perceptron neural network model that predicts OP using physical characteristics and activity factors of adult women over the age of 35 whose BMD begins to decline. Study design Cross-sectional study. Methods Data from KNHANES were used to develop a multi-layer perceptron model for predicting OP. Data preprocessing included variable selection and sample balancing, and LASSO was used for feature selection. The model used 5 hidden layers, dropout and batch normalization and was evaluated using evaluation scores such as accuracy and recall score calculated from a confusion matrix. Results Models were trained and evaluated to predict OP using selected features including age, quality of life index, weight, grip strength and average working hours per week. The model achieved 76.8% accuracy, 74.5% precision, 80.5% recall, 77.4% F1 score, and 74.8% ROC AUC. Conclusions A multi-layer perceptron neural network for predicting OP diagnosis using physical characteristics and activity factors in women aged 35 years or older showed relatively good performance. Since the selected variables can be easily measured through surveys, assessment tool, and digital hand dynamometer, this model will be useful for screening elderly women with OP or not in areas with poor medical facilities or difficult access.