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침전법으로 합성된 알루미나 분말을 이용한 세라믹 분리막 제조에 관한 연구(I)
박신서,서규식,김철홍,신민철,이희수,엄우식,이재훈 한국결정성장학회 1999 韓國結晶成長學會誌 Vol.9 No.1
$AlCl_3{\cdot}6H_2O$를 출발원료로 침전법에 의해 알루미늄 수화물을 합성하였다. 용액의 pH에 따라 amorphous, boehimite, bayerite, nordstrandite 상을 얻었고, 수산화 알루미늄은 열처리 온도가 증가함에 따라 $\gamma$, $\delta$, $\theta$를 거쳐${\alpha}-Al_2O_3$로 전이되었으며, 입자크기도 증가하였다. ${\gamma}-Al_2O_3$ 를 담금피막법(dip-coating method)으로 중간층 위에 코팅하였고, 비교를 위해 비지지체 분리막도 준비하였다. 지지체 분리막은 작은 입자(grain)들로 구성된 다공질 구조(porous structure)를 나타내었지만, 비지지체 분리막에서는 상호 연결된 큰 입자(grain)들이 나타났다. 지지체 분리막에서 보다 비지지체 분리막에서 결정립 성장이 명백하게 나타났다. Aluminum hydrates were synthesized using $AlCl_3$.$6H_2O$as starting material by precipitation method. The phases of obtained powder were amorphous, boehmite, bayerite, nordstrandite depending on the pH of solutions. Aluminum hydrates transformed to $\alpha-Al_2O_3$via $\gamma$- $Al_2O_3$,$\delta$- $Al_2O_3$,and $\theta$-$Al_2O_3$,and particle sizes were grown by increment of heating temperature. The $\gamma$- $Al_2O_3$ powder was coated on intermediate layer of ceramic membrane by the dip-coating method, and unsupported membrane was also prepared for comparison. The supported layer showed porous structure with small grains, but the unsupported layer revealed interconnected larger grains. Grain growth is dominant in the unsupported layer than in the supported one.
EFG법에 의한 Sapphire Ribbon 단결정 성장
박신서,류두형,정재우,최종건,오근호,손선기,변영재,전형탁 한국세라믹학회 1990 한국세라믹학회지 Vol.27 No.6
Shaped crystal growth apparatus were made for sapphire ribbon single crystal growth. Sapphire ribbon single crystal are grown by EFG(Edge-defined Film-fed Growth) methdo for use as watch-glass and SOS(Silicon-On-Sapphire) devices. Sapphire ribbon crystals were grown to be 40min wide, 1.8mm thick, 96mm long. Therelationshiops between growth striation and surface roughness, with various growth rates, were investigated and compared. It was found that sapphire ribbon crystal is suitable for watch-glass by measuring the transmittance in the visible light region.
A BLESSING OR A CURSE? BEING A UNICORN FIRM IN THE IPO MARKET
신서원,박의성,Suresh Kotha 한국경영학회 2021 한국경영학회 통합학술발표논문집 Vol.2021 No.8
By examining a novel entrepreneurial phenomenon-the emergence of unicorn ventures-we investigate the discrepancies between theoretical assertions and empirical evidence in the initial public offering (IPO) underpricing of such ventures. Unicorn ventures are private new ventures valued at over $1 billion. Drawing on the “sociology of expectations” literature, we suggest that at IPO, unicorn ventures experience a greater level of IPO underpricing relative to other firms because of media uncertainty stemming from the high expectations surrounding the venture’s future performance. We tested our hypotheses using a unique hand-collected dataset that includes the entire population of unicorn IPOs between 2011 and 2018. We found that the media coverage (both the volume and tenor of such content) does not explain unicorn ventures’ significantly greater IPO underpricing relative to other ventures. However, the sentiment polarity of unicorn ventures in the media was positively associated with IPO underpricing. Also, pre-IPO profitability, and a legitimacy jolt experienced at a point in the study, moderated the relationship between sentimental polarity and IPO underpricing. We demonstrate how the sociology of expectations literature can provide a sound theoretical lens to explain the persistence of IPO underpricing beyond past explanations of this important phenomenon.
신서연 ( Seo Yeon Shin ),김하늘 ( Ha Neul Kim ),강세원 ( Se Won Kang ),조홍석 ( Hong Suk Cho ),김은지 ( Eun Ji Kim ),박선화 ( Sun Hwa Park ),박경 ( Kyung Mok Park ) 대한화장품학회 2016 대한화장품학회지 Vol.42 No.2
히솝(Hyssopus officinalis)은 통화식물목 꿀풀과의 여러해살이풀로 방부제, 기침, 거담제 등 일반적으로 방향족 허브와 약용식물로 사용되어왔다. 본 연구에서는 항산화 및 미백소재의 개발을 위해 히솝을 열수와 주정으로 추출하여 각 추출물의 in vitro 상에서의 항산화 효과 및 B16F10 melanoma 세포에서 멜라닌 생성 저해효과를 평가하였다. DPPH와 ABTS assay 시험법을 이용하여 항산화 효과를 측정한 결과, 히솝 추출물의 항산화 활성이 모두 농도 의존적으로 증가하였다. 또한 히솝 추출물은 tyrosianse 활성을 저해시켰으며, B16F10 세포에서 UVB로 증가된 활성산소와 α-MSH로 유도된 멜라닌 또한 감소시키는 효과를 보였다. 멜라닌 생합성에 관여하는 유전자의 발현에 미치는 영향을 알아보기 위해 RT-PCR을 실시한 결과 히솝 추출물에 의해 MITF, tyrosinase, TRP-2의 발현이 감소되는 것을 확인할 수 있었다. 이러한 결과에 따라 히솝 추출물은 미백개선을 위한 화장품 소재로서 이용 가능성이 높을 것으로 사료된다. Hyssopus officinalis is a herbaceous plant of the genus Hyssopus. Due to its properties as an antiseptic, cough reliever and expectorant, it is commonly used as an aromatic herb and medicinal plant. This study was performed to investigate the anti-oxidative and anti-melanogenic properties of Hyssopus officinalis extracts (HE) using in vitro assays and cell culture systems. As a result, HE showed higher DPPH and ABTS radicals scavenging activity in a dose-dependent manner. Also, HE inhibited the prodution of intracellular ROS and melanin contents in B16F10 melanoma cell as well as tyrosinase activity. We also found that HE inhibit mRNA expression of MITF, tyrosinase and TRP-2 gene. These findings suggest that HE may be beneficial for preventing oxidative damage and melanogenesis of skin.
가로등 제어용 다층패드형 압전 하베스터의 개발 및 평가
김창일,정영훈,박운익,조정호,장용호,최범진,박신서,백종후,Kim, Chang-Il,Jeong, Young-Hun,Park, Woon Ik,Cho, Jeong-Ho,Jang, Yong-Ho,Choi, Beom-Jin,Park, Shin-Seo,Paik, Jong-Hoo 한국전기전자재료학회 2016 전기전자재료학회논문지 Vol.29 No.11
In this study, to increase output of road piezoelectric energy harvester, it was made into rack type in which many piezoelectric materials can be installed and load transfer device of the leverage type to transfer vehicle load was made. By paving it in the road, the output characteristics depending on vehicle load and speed were evaluated. Changing vehicle load, harvester output characteristics depending on speed changes were evaluated at the interval of 10 km/h from 10 km/h to 100 km/h. Also, by making a wireless switch and sending wireless signal with output of rack type harvester, whether to receive it was evaluated by distance. It was checked that all switches work up to front-to-back 100 m from harvester.
매설방법과 차량하중에 따른 벤더형 압전에너지 하베스터의 설계 및 평가
김창일,정영훈,윤지선,조정호,백종후,장용호,최범진,박신서,조영봉,Kim, Chang-Il,Jeong, Young-Hun,Yun, Ji-Sun,Cho, Jeong-Ho,Paik, Jong-Hoo,Jang, Yong-Ho,Choi, Beom-Jin,Park, Shin-Seo,Cho, Young-Bong 한국전기전자재료학회 2016 전기전자재료학회논문지 Vol.29 No.5
A road energy harvester was designed and fabricated to convert mechanical energy from the vehicle load to electrical energy. The road energy harvester is composed of 20 piezoelectric materials. This study attempted to evaluate output depending on pavement materials when paving road piezoelectric energy harvester in the road. Harvester is the bender type and is the method of supporting the both ends of piezoelectric material and applying the load in the middle part. Harvester was paved in the type paved with asphalt, type paved with cement and in the exposed type not covering the top of harvester. The output characteristics were compared and evaluated depending on changes in vehicle load and vehicle speed changes. As vehicles, truck (11.9 ton), SUV(1.6 ton) and sedan (1.5 ton) were used and the output characteristics when driving at the interval of 10 km/h from 10 km/h to 100 km/h were evaluated.
압전 캔틸레버 구조를 이용한 도로용 에너지 하베스터의 개발 및 평가
김창일,김경범,전종학,정영훈,조정호,백종후,강인석,이무용,최범진,조영봉,박신서,남산,이영진,Kim, Chang-Il,Kim, Kyung-Bum,Jeon, Jong-Hac,Jeong, Young-Hun,Cho, Jeong-Ho,Paik, Jong-Hoo,Kang, In-Seok,Lee, Moo-Yong,Choi, Beom-Jin,Cho, Young-Bong 한국전기전자재료학회 2012 전기전자재료학회논문지 Vol.25 No.7
A road energy harvester was designed and fabricated to convert mechanical energy from the vehicle load to electrical energy. The road energy harvester is composed of 24 piezoelectric cantilevers and a vehicle load transfer mechanism. Applying a vehicle load transfer mechanism rather than directly installing energy harvesters under roads decreases the area of road construction and allows more energy harvesters to be installed on the side of the road. The power generation amount with respect to the vehicular velocity change was assessed by installing the vehicle load transfer mechanism and the energy harvester in the form of speed bumps and underground. The energy harvester installed in a speed bump form generated power of 7.61 mW at the vehicular velocity of 20 km/h. Also, power generation of the energy harvester installed in the underground form was 63.9 mW at the vehicular velocity of 28 km/h. Although the number of piezoelectric cantilevers was reduced by 1/3 to 24 in comparison to the previous research results with 72 piezoelectric cantilevers, similar power generation characteristic value was obtained within the vehicular velocity of 20 km/h by altering the vehicle load transfer mechanism and cantilever vibration method.
압전 캔틸레버 구조와 차량하중 전달방법에 따른 도로용 에너지 하베스터의 설계 및 평가
김창일,김경범,정영훈,이영진,조정호,백종후,강인석,이무용,최범진,박신서,조영봉,남산,Kim, Chang-Il,Kim, Kyung-Bum,Jeong, Young-Hun,Lee, Young-Jin,Cho, Jeong-Ho,Paik, Jong-Hoo,Kang, In-Seok,Lee, Moo-Yong,Choi, Beom-Jin,Park, Shin-Seo,Cho, 한국전기전자재료학회 2012 전기전자재료학회논문지 Vol.25 No.10
A road energy harvester was designed and fabricated to convert mechanical energy from the vehicle load to electrical energy. The road energy harvester is composed of 16 piezoelectric cantilevers. We fabricated prototypes using a vehicle load transfer mechanism. Applying a vehicle load transfer mechanism rather than directly installing energy harvesters under roads decreases the area of road construction and allows more energy harvesters to be installed on the side of the road. The power generation amount with respect to the vehicular velocity change was assessed by installing the vehicle load transfer mechanism form and underground form. The energy harvester installed in the underground form generated power of 4.52 mJ at the vehicular velocity of 50 km/h. Also, power generation of the energy harvester installed in the vehicle load transfer mechanism form was 48.65 mJ at the vehicular velocity of 50 km/h.
전력계통 구조물의 상태진단용 자가발전 무선 센서 노드 개발 및 평가
김창일 ( Chang Il Kim ),정영훈 ( Young-hun Jeong ),윤지선 ( Ji Sun Yun ),홍연우 ( Youn Woo Hong ),장용호 ( Yong-ho Jang ),최범진 ( Beom-jin Choi ),박신서 ( Shin-seo Park ),손천명 ( Chun Myung Son ),서덕기 ( Duck Ki Seo ),백종후 ( 한국센서학회 2016 센서학회지 Vol.25 No.5
A self-powered piezoelectric energy harvester was developed for the application in wireless sensor node. The energy harvester was evaluated with power generation characteristics for the wireless sensor node for structural diagnosis of the electric power system. The self-powered wireless sensor node was set to measure temperature, vibration frequency of the electric power system. A piezoelectric harvester composed of 7 uni-morph cantilevers (functionalized as 6 generators and 1 vibration sensor) was connected to be an array and revealed to produce significantly high output power of approximately 10 mW at 120 Hz under 3.4 g((1 g = 9.8 m/sec²). The wireless sensor node could work as the electric power generated by the developed piezoelectric harvester.