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Junpil Park,Sunho Choi,Seoung ho Baek,Sang-Hu Park,Yu-Hsi Huang,Jaesun Lee 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.24 No.6
3-Dimension (3D) printers are increasingly being used in high-tech industrial applications technology, because they can produce sophisticated products by laminating materials with less time and cost compared to cutting processing, such as conventional machine tools. However, since the reliability evaluation criteria and method for laminated manufacturing products are not clear, accidents cannot be prevented when 3D printed laminates are used as structures and machined parts. In this paper, ultrasonic wave propagation characteristics were evaluated on the specimens manufactured by laminating acrylonitrile butadiene styrene resin materials with a stereo lithography apparatus 3D printer using the ultrasonic inspection method among non-destructive techniques. Specimens were laminated in units of 0.1 mm, and thicknesses of 1, 2, 4, 6 and 8 mm were applied as variables. In addition, the ultrasonic characteristics according to laminating direction were analyzed by laminating diagonally and vertically, including laminating in the horizontal direction, and defect specimens were produced to check whether defects were read. It was found that the ultrasonic velocity of the horizontally laminated specimen having a thickness of less than 4 mm was slower than the ultrasonic reference velocity, and that the ultrasonic velocity was affected according to the laminated direction. In addition, by arranging the defect location of the specimen differently, it was determined whether the defect was detected, and whether it was possible to check the location. Based on the results of this study, it will be possible to broadly apply this technique to advanced industrial technologies through evaluation of the condition and reliability of laminated manufacturing products manufactured with 3D printers.
Kim Kwang Yoon,Park Jaesun,Yang Sungwon,Shin Junghwa,Park Ji Hyun,Park Bumhee,Kim Bom Taeck 대한의학회 2023 Journal of Korean medical science Vol.38 No.42
Background: Age-adjusted bone mineral density (BMD) in postmenopausal women decreases in developed countries whereas incidence of osteoporotic fracture decreases or remains stable. We investigated secular trends of bone density from 2008 to 2017 among different age groups of postmenopausal women. Methods: We analyzed BMD data obtained from health check-ups of 4,905 postmenopausal women during three survey cycles from 2008 to 2017. We divided them into 3 groups by age (50–59 years, 60–69 years, and 70 years or more) and observed the transition of lumbar and femoral BMD in each group, before and after adjusting for variables that may affect BMD. Results: Age-adjusted BMD, bone mineral content (BMC), and T-score demonstrated a declining trend over the survey period at lumbar spine (−2.8%), femur neck (−3.5%) and total femur (−4.3%), respectively. In the analysis for the age groups, the BMD, BMC, and T-score presented linear declining trend (−6.1%) in younger postmenopausal women while women aged over 70 or more showed linear increasing trends (+6.3%) at lumbar spine during the survey period. Femoral neck and total femur BMD demonstrated a declining linear trend only in the 50–59 and 60–69 years groups (−5.5%, −5.2%, respectively), but not in the 70 years or more group. Conclusion: BMD in younger postmenopausal women has decreased considerably but has increased or plateaued in elderly women. This discordance of BMD trends among different age groups may contribute to decreased incidence of osteoporotic fracture despite a recent declining BMD trend in postmenopausal women.
Template-engineered epitaxial BiVO<sub>4</sub> photoanodes for efficient solar water splitting
Song, Jaesun,Cha, Jaeseong,Lee, Mi Gyoung,Jeong, Hye Won,Seo, Sehun,Yoo, Ji Ae,Kim, Taemin Ludvic,Lee, Jongmin,No, Heesung,Kim, Do Hyun,Jeong, Sang Yun,An, Hyunji,Lee, Byoung Hun,Bark, Chung Wung,Park Royal Society of Chemistry 2017 Journal of Materials Chemistry A Vol.5 No.35
<▼1><P>The photoelectrochemical properties of template-engineered epitaxial BiVO4 photoanodes have been enhanced approximately 10 times that of bare BiVO4.</P></▼1><▼2><P>Bismuth vanadate (BiVO4) has attracted significant attention as a promising photoanode material for hydrogen production <I>via</I> photoelectrochemical (PEC) water splitting because of its narrow optical band gap and suitable band edge positions for water oxidation. However, the actual photoactivity of BiVO4 is considerably limited by its poor electron transport and slow water oxidation kinetics. Although several studies have been carried out to improve its photo-efficiency <I>via</I> the enhancement of electron transport and water oxidation kinetics, only a few studies have reported the growth of epitaxial BiVO4 to explore the fundamental properties of BiVO4 for PEC water splitting because extremely flat epitaxial films exhibit poor photo-efficiency because of their low surface-active area. However, studies of epitaxial BiVO4 still have the potential to provide new routes for improving its photo-efficiency. In this study, the growth of epitaxial BiVO4 is investigated using a thin γ-WO3 template layer deposited on a SrTiO3(001) substrate covered by a SrRuO3 (SRO) bottom electrode using pulsed laser deposition. Consequently, at 1.23 V <I>vs.</I> the RHE (reversible hydrogen electrode), the photocurrent density of epitaxial BiVO4 on the γ-WO3 template layer (2.20 mA cm<SUP>−2</SUP>) is approximately 10 times that of bare BiVO4, related to the effective charge transfer by the γ-WO3 intermediate layers and the subsequent increase in the surface-active area of epitaxial BiVO4. These results strongly suggest that epitaxial BiVO4 grown using a template layer can be a cornerstone for the in-depth understanding of the fundamental properties of BiVO4 for PEC water splitting.</P></▼2>
황혼부부의 갈등 개선을 위한 해방감 경험 서비스 연구 - 모바일 애플리케이션 중심으로 -
박선하 ( Park Seonha ),송원경 ( Song Wonkyoung ),유다희 ( Yu Dahee ),이재선 ( Yi Jaesun ) 디자인융복합학회(구.한국인포디자인학회) 2021 디자인융복합연구 Vol.20 No.2
최근 이혼건수가 감소하고 있는 반면 황혼이혼은 꾸준히 증가하고 있으며, 50대 이상 남녀의 이혼법률상담 증가 및 졸혼이라는 신조어 등장 등 황혼 이혼에 관한 논의가 활발히 이루어지고 있다. 현재 황혼부부의 이혼 절차에서 황혼부부는 미성년 자녀가 있는 부부와 비교하여 숙려기간이 짧고 의무 상담이 부재하다. 현재 황혼부부의 협의이혼절차는 미성년 자녀가 있는 부부와 달리 의무상담이 부재하고, 숙려기간이 2개월 더 짧은 1개월만 진행되고 있다. 이는 충동적인 이혼예방이 목적인 숙려기간이 제대로 이루어질 수 없다는 점에서 현 절차에 한계가 있음을 파악하였다. 황혼이혼에 대한 논의와 요구가 커지는 상황에서 본 연구는 황혼부부의 특성과 장년기의 특성을 고려하여 황혼이혼을 예방하는 서비스를 제안하고자 한다. While the overall number of divorces has recently decreased, the number of gray divorce has been steadily increasing, and discussions on gray divorces are actively taking place with the rise of divorce legal counseling in the elderly and the advent of the term ‘Jolhon’, graduation from marriage. In the current divorce process for couples, the elderly couples have a shorter cooling-off period and no mandatory counseling system compared to couples with underage children. It was recognized that there is a limitation of the current system in that there is a possibility that the prevention of impulsive divorce, which is the purpose of establishing the cooling-off period, cannot be properly performed. Therefore, in the context of growing discussions and demands for gray divorce, this study attempts to propose a service to prevent gray divorce by considering the characteristics of the couple in their middle and old age.