Climate change risk and the value of cash holdings

Sanghak Choi,Hail Jung,Daejin Kim 한국재무학회 2021 한국재무학회 학술대회 Vol.2021 No.11

In this paper, we investigate the effects of the firm-level climate change risk on the marginal value of corporate cash holdings. The underlying idea is that climate change risks would induce firms to increase their demand for capital, which may also lead to an increase in the value of the cash holdings. As the climate change risk is an uncertainty for firms, investors would also positively evaluate the firm’s excess cash. A regression analysis finds a positive association between the firm-level climate change risk and the value of cash holdings. Furthermore, we also test how the green swan and financial constraint level affect the relationship. Subsample analysis shows that the market positively values the cash holdings of firms that are more sensitive to climate change and that are more financially constrained. Various robustness tests confirm that the baseline regression results are not necessarily driven by endogeneity.

Age face simulation using aging functions on global and local features with residual images

Choi, Sung Eun,Jo, Jaeik,Lee, Sanghak,Choi, Heeseung,Kim, Ig-Jae,Kim, Jaihie Elsevier 2017 expert systems with applications Vol.80 No.-

<P><B>Abstract</B></P> <P>In many previous methods for facial age simulation, the shape and appearance features of Active Appearance Models (AAM) are widely used to model the global facial characteristics. However, they cannot sufficiently represent facial details such as spots, scars, fine wrinkles, and skin blemishes, because many of them are removed from the AAM features during the dimension reduction process. Therefore, previous methods are not suitable for real-world applications, such as forensics, face recognition, and entertainment production systems, which require more accurate and realistic age simulation. To overcome the limitation, this paper proposes an automatic age simulation method based on a synergetic combination of the residual image, local features, and AAM global features. The residual image, which is the difference between a facial image and its reconstructed image by using AAM features, contains facial details of the input image that are not included in the AAM features. Representation of facial details in the age simulation process is achieved by generating and adding a targeted age-weighted residual image to the facial image synthesized by the AAM features. Further, facial details such as wrinkles and skin blemishes that have not yet appeared at the current age but normally appear as aging proceeds, are supplemented, and represented by local features that show locally different aging characteristics. The experimental results show that the proposed method simulates a face more accurately and realistically than previous methods, thereby confirming that it is more suitable for the real-world applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Age simulation method using global, local features and residual image is proposed. </LI> <LI> The residual image represents the personal characteristics of the input image. </LI> <LI> Local features represent the local aging characteristics of wrinkle and skin. </LI> </UL> </P>

Pilot-scale evaluation of FO-RO osmotic dilution process for treating wastewater from coal-fired power plant integrated with seawater desalination

Choi, Byeong Gyu,Zhan, Min,Shin, Kyungyong,Lee, Sanghak,Hong, Seungkwan Elsevier 2017 Journal of membrane science Vol.540 No.-

<P><B>Abstract</B></P> <P>An osmotic dilution process of forward osmosis (FO) and reverse osmosis (RO) was applied at pilot-scale to integrate wastewater treatment with seawater desalination in a coal-fired power plant. FO was osmotically driven by seawater used as cooling water. FO-treated wastewater was diluted with seawater and then further processed by RO. Seasonal variation in water flux, fouling behavior and reversibility, and energy consumption in both FO and RO were systematically evaluated during 5 months of pilot operation. The FO water flux, which declined due to the organic fouling induced by the wastewater from the coal-fired power plant, was readily recovered by physical cleaning. The integrated FO-RO dilution process was able to reduce the RO fouling potential through FO treatment of wastewater, significantly decreasing SDI value to 1.5 ± 0.1. This study also reported energy consumption data, to our knowledge for the first time, at pilot scale operation of FO-RO dilution process, and showed that total energy consumption for desalinating the diluted feed, including wastewater reclamation by FO, was 15% less than that of typical seawater desalination by RO. The results of this FO-RO pilot study demonstrated that sustainable FO-RO operation can be achieved in the treatment of power plant wastewater owing to easy fouling control, low energy consumption, and superior final water quality.</P> <P><B>Highlights</B></P> <P> <UL> <LI> FO-RO osmotic dilution process was investigated at pilot-scale. </LI> <LI> Wastewater from coal-fired power plant was successfully treated by FO. </LI> <LI> FO was driven by seawater used as cooling water in the power plant. </LI> <LI> FO was less fouled with high reversibility and reduced fouling in RO. </LI> <LI> Pilot-scale energy consumption was first reported to be lower than SWRO. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Investigation of Protein Adsorption Using Plasma Treatment for Protein Chips

Sanghak Yeo,정동근,Changrok Choi,박헌용 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.48 No.6

For reliable protein chip performance, a sufficient level of proteins must be immobilized in a specific area on the surface of the chip. In this research, a plasma-polymerized hexamethyldisiloxane (PPHMDSO) thin film was deposited on the surface of a glass slide. The PPHMDSO-coated glass slide was modified by an additional oxygen plasma treatment with the patterned mask placed on the PPHMDSO-coated glass slide. The deposited PPHMDSO was hydrophobic and did not show adsorbed proteins, and the O2-plasma-treated areas of PPHMDSO were hydrophilic. The proteins were strictly adsorbed and immobilized on the patterned O2-plasma-treated areas of PPHMDSO, providing a more efficient way of fabricating high-density protein chips. The change in the O2-plasma-treated PPHMDSO surface was analyzed, and a possible reason for selective protein adsorption is suggested. For reliable protein chip performance, a sufficient level of proteins must be immobilized in a specific area on the surface of the chip. In this research, a plasma-polymerized hexamethyldisiloxane (PPHMDSO) thin film was deposited on the surface of a glass slide. The PPHMDSO-coated glass slide was modified by an additional oxygen plasma treatment with the patterned mask placed on the PPHMDSO-coated glass slide. The deposited PPHMDSO was hydrophobic and did not show adsorbed proteins, and the O2-plasma-treated areas of PPHMDSO were hydrophilic. The proteins were strictly adsorbed and immobilized on the patterned O2-plasma-treated areas of PPHMDSO, providing a more efficient way of fabricating high-density protein chips. The change in the O2-plasma-treated PPHMDSO surface was analyzed, and a possible reason for selective protein adsorption is suggested.

Patterned Amine Surfaces with Reduced Background Nonspecific Protein Adsorption Fabricated by Using Inductively Coupled Plasma Chemical Vapor Deposition

Sanghak Yeo,박헌용,Jaeyoung Yang,부진효,정동근,Changrok Choi 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.3

Nonspecific adsorption to the surface of slides decreases the sensitivity for chip-based biological assays. To solve this problem, we constructed novel patterned slides of plasma polymerized ethylenediamine (PPEDA) with protein-binding amine functional groups and a hydrophilic surface and of plasma polymerized cyclohexane (PPCHex) with a hydrophobic surface and a reduced nonspecific protein adsorption. PPEDA and PPCHex were deposited by using inductively coupled plasma chemical vapor deposition (ICP-CVD) with ethylenediamine (EDA) and cyclohexane (CHex) as precursors. PPEDA was deposited in a patterned manner on a PPCHex slide by using plasma polymerization with a patterned mask. Comparing the sample of the PPEDA/PPCHex pattern with the sample of PPEDA only, i.e., the sample with only PPEDA spots formed on bare glass slides, the average signal to noise ratio, defined as the ratio of the fluorescence intensity of the PPEDA-deposited circular spots to the fluorescence intensity of the surrounding areas, was higher for the sample with the PPEDA/PPCHex pattern, indicating that the nonspecific adsorption was reduced at the surface of PPCHex. It is thought that on the surface of PPCHex films, the reduction in the protein adsorption was more influenced by the chemical groups of the films, such as -OH groups, rather than by the physical properties of the surfaces, such as the roughness.s Nonspecific adsorption to the surface of slides decreases the sensitivity for chip-based biological assays. To solve this problem, we constructed novel patterned slides of plasma polymerized ethylenediamine (PPEDA) with protein-binding amine functional groups and a hydrophilic surface and of plasma polymerized cyclohexane (PPCHex) with a hydrophobic surface and a reduced nonspecific protein adsorption. PPEDA and PPCHex were deposited by using inductively coupled plasma chemical vapor deposition (ICP-CVD) with ethylenediamine (EDA) and cyclohexane (CHex) as precursors. PPEDA was deposited in a patterned manner on a PPCHex slide by using plasma polymerization with a patterned mask. Comparing the sample of the PPEDA/PPCHex pattern with the sample of PPEDA only, i.e., the sample with only PPEDA spots formed on bare glass slides, the average signal to noise ratio, defined as the ratio of the fluorescence intensity of the PPEDA-deposited circular spots to the fluorescence intensity of the surrounding areas, was higher for the sample with the PPEDA/PPCHex pattern, indicating that the nonspecific adsorption was reduced at the surface of PPCHex. It is thought that on the surface of PPCHex films, the reduction in the protein adsorption was more influenced by the chemical groups of the films, such as -OH groups, rather than by the physical properties of the surfaces, such as the roughness.s

The patterned hydrophilic surfaces of glass slides to be applicable for the construction of protein chips

Sanghak Yeo,Taeheon Kwon,Changrok Choi,박헌용,현준원,정동근 한국물리학회 2006 Current Applied Physics Vol.6 No.2

For protein chip construction, the chemical properties for the surface of glass slides have to be elaborately modified for protein immobilization. To immobilize proteins, plasma polymerized hexamethyldisiloxane (PPHMDSO) thin film was deposited onto the surface of glass slide. Previously, it was reported that proteins were immobilized onto PPHMDSO thin film [H. Miyachi, A. Hiratsuka, K. Ikebukuro, K. Yano, H. Muguruma, I. Karube, Biotechnol. Bioeng. 69 (3) (2000) 323–329]. Here, we modified PPHMDSO-coated glass slide by an additional oxygen plasma treatment with placing the patterned mask on the HMDSO-coated glass slide. Hydrophilic surfaces were detected by measuring the contact angle of water. Of great interest, proteins were strictly immobilized on the patterned O2 plasma treated areas, providing more efficient ways for fabricating the protein chips. For protein chip construction, the chemical properties for the surface of glass slides have to be elaborately modified for protein immobilization. To immobilize proteins, plasma polymerized hexamethyldisiloxane (PPHMDSO) thin film was deposited onto the surface of glass slide. Previously, it was reported that proteins were immobilized onto PPHMDSO thin film [H. Miyachi, A. Hiratsuka, K. Ikebukuro, K. Yano, H. Muguruma, I. Karube, Biotechnol. Bioeng. 69 (3) (2000) 323–329]. Here, we modified PPHMDSO-coated glass slide by an additional oxygen plasma treatment with placing the patterned mask on the HMDSO-coated glass slide. Hydrophilic surfaces were detected by measuring the contact angle of water. Of great interest, proteins were strictly immobilized on the patterned O2 plasma treated areas, providing more efficient ways for fabricating the protein chips.

교대 측방유동에 대한 원인 분석

최광복 ( Choi Gwangbok ),윤영내 ( Yoon Youngnae ),이상학 ( Lee Sanghak ),이상무 ( Lee Sangmoo ) 한국구조물진단유지관리공학회 2021 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.25 No.2

공용연수 15년인 PSCI형 교량의 역T형 교대에 측방유동과 같은 손상이 발생되어 원인분석을 실시하였다. 측방유동의 발생 원인과 영향 요소에 대해 분석하였다. 기초 보강 현황, 손상 진행 상황을 분석하고, 측방유동 평가 방법인 원호활동에 의한 방법, 측방유동지수 F에 의한 방법, 측방유동 판정지수 I_L에 의한 방법, 수정 측방유동 판정지수 M_IL에 의한 방법, 지반보강 고려시 측방유동 검토 등을 분석하였다.

오층석탑 정밀안전진단 결과에 대한 분석

최광복 ( Choi Gwangbok ),이상학 ( Lee Sanghak ),채선우 ( Chae Sunwoo ),이태준 ( Lee Taejoon ) 한국구조물진단유지관리공학회 2021 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.25 No.1

「국보·보물 건조물 문화재의 보존·관리 규정」에 따라 실시하는 정밀안전진단 용역으로 정밀조사 결과 지대석이 탑 안쪽으로 약간씩 기울어 있으며, 각 층의 탑신석에 부분적인 마모, 탈락 등이 있고, 각 상부 모서리가 부분적으로 탈락되어 있는 등 전반적인 보수 정비가 필요한 실정으로, 안전진단을 실시하여 변형으로 인한 구조적 불안정성의 요인을 규명한 후, 대책(안)을 수립함으로써 향후 귀중한 건조물 문화재가 더 이상 훼손되지 않도록 보존관리 지침을 마련하는데 목적이 있다.

수문학적 검토 및 물리탐사를 이용한 저수지 안정성 분석

최광복 ( Choi Gwangbok ),이상무 ( Lee Sangmoo ),이상학 ( Lee Sanghak ),김주희 ( Kim Juhee ),박기범 ( Park Kibum ),안승섭 ( Ahn Seungseop ) 한국구조물진단유지관리공학회 2019 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.23 No.1

In this investigation, the reservoir stability was reviewed using hydrological and physical examination. The results of the review showed that, Both sites were analyzed to lack embankment height and sidewall height in the event of flooding, and it was considered that measures to increase stability should be established in the future by adding more dam cest and increasing side wall of a spill way. In addition, analysis and research will be necessary for other reservoir deteriorated in the future.

준공후 40년 이상 경과된 OO시 소규모 교육시설의 정밀안전점검 결과에 대한 분석

최광복 ( Choi Gwangbok ),이상무 ( Lee Sangmoo ),이상학 ( Lee Sanghak ) 한국구조물진단유지관리공학회 2019 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.23 No.2

최근 지진 및 자연재해의 영향으로 인한 노후 건축물의 위험도가 높아지고 있으며, 이러한 시설물에 대한 정기적인 안전점검 및 유지관리의 필요성이 더욱 대두되고 있다. 특히나 소규모 노후시설물의 경우 정기적인 안전점검이 이루어지지 않는 경우가 많고, 내진성능평가가 이루어지지 않은 시설물도 많다. 본 연구에서는 준공 후 40년 이상 된 소규모 교육시설의 정밀안전점검 결과를 분석하여, 향후 유지관리 방안을 모색하고자 한다.