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유입부하 변동에 따른 Bio-Sac 생물반응조의 최적 송풍량 결정에 관한 연구
정호종(Jung, Hojong),정민재(Jung, Minjae),최한영(Choi, Hanyong) 한국방재학회 2017 한국방재학회논문집 Vol.17 No.4
설계인구보다 증가된 인구에 따라서 하수처리장에서는 설계수질과 유입수질간에는 많은 차이가 있으며, 설계 유입수 농도보다 초과로 유입이 된 하수처리장은 적정운전에 많은 곤란함을 겪고 있다. 그런데 Bio-Sac공법은 설계대비 초과된 유입 BOD, SS, T-N에 의해 하수처리장에 대해서는 국⋅내외 선행 연구가 많이 부족하고, 미흡한 실정이다. 본 연구의 목적은 성남판교수질복원센터를 대상으로 설계초과되는 유입 BOD, SS, T-N 변동에 따른 생물반응조의 송풍량 조절을 통해 질산화, 탈질화 반응의 의한 최적의 송풍량을 선정하기 위한 연구이다. 생물반응조 호기조 송풍량 40, 50 및 60 Nm3/min으로 변경하여 실험한 결과50 Nm3/min일 때 질소제거율 92.8% 질산화율 96.9% 탈질화율 94.3%로 나타났다. 질소제거율과, 탈질율을 고려할 때 최적의 송풍량은 50 Nm3/min일 때 처리효율이 효과적이라는 결과를 얻었다. There are many differences between the design water quality and the influent water quality at the sewage treatment plant, depending on the population that is larger than the design population, and the sewage treatment plant which has flowed in excess of the design influent concentration suffers from the problem of proper operation. However, in the Bio-Sac construction method, there are insufficient prior researches on the sewage treatment plant due to excess BOD, SS, and T-N compared to the design. The purpose of this study is to select the optimal amount of ventilation by nitrification and denitrification through controlling the amount of blowing of bioreactor according to fluctuating influent BOD, SS, and T-N exceeding the design for Seongnam Pangyo water quality restoration center. Experiments were conducted at 40, 50 and 60 Nm3 / min ventilation rate of the bioreactor. The nitrogen removal rate was 92.8%, the nitrification rate was 96.9%, and the denitrification rate was 94.3% at 50 Nm3 / min. Considering the nitrogen removal rate and denitrification rate, the optimum treatment efficiency was 50 Nm3 / min.
A Cost-effective Light Emitting Diode-acoustic System for Preclinical Ocular Applications
Hojong Choi,Jaemyung Ryu,Jung-Yeol Yeom 한국광학회 2018 Current Optics and Photonics Vol.2 No.1
Opto-acoustic systems provide structural and functional information regarding biological tissues. Conventional opto-acoustic systems typically employ continuous or pulsed lasers as transmission sources. Compared to lasers, light emitting diodes (LEDs) are cost-effective and relatively portable excitation sources but are non, coherent. Therefore, in this study, a relatively low cost lens - a type of Ramsden eyepiece - was specially designed to theoretically calculate the illumination and achieve a constant brightness across the pupil of an eye. In order to verify the capability of the developed light-emitting diode-acoustic (LEDA) systems, we carried out experiments on bovine and bigeye tuna eyeball samples, which are of similar size to the human eye, using low frequency (10 MHz) and high frequency (25 MHz) ultrasound transducers. High frequency ultrasound transducers are able to provide higher spatial resolution compared to low frequency ultrasound transducers at the expense of penetration depth. Using the 10 MHz and 25 MHz ultrasound transducers, acceptable echo signals (3.82, 3.94, and 5.84 mV at 10 MHz and 282, 1557, 2356 mV at 25 MHz) from depth greater than 3 cm and 6 cm from the anterior surface of the eye were obtained. We thereby confirmed that the LEDA system using a pulsed LED with the designed Ramsden eyepiece lens, used in conjunction with low and high frequency ultrasound transducers, has the potential to be a cost-effective alternative method, while providing adequate acoustic signals from bovine and bigeye tuna ocular areas.
GOTHIC-3D APPLICABILITY TO HYDROGEN COMBUSTION ANALYSIS
LEE JUNG-JAE,LEE JIN-YONG,PARK GOON-CHERL,LEE BYUNG-CHUL,YOO HOJONG,KIM HYEONG-TAEK,OH SEUNG-JONG Korean Nuclear Society 2005 Nuclear Engineering and Technology Vol.37 No.3
Severe accidents in nuclear power plants can cause hydrogen-generating chemical reactions, which create the danger of hydrogen combustion and thus threaten containment integrity. For containment analyses, a three-dimensional mechanistic code, GOTHIC-3D has been applied near source compartments to predict whether or not highly reactive gas mixtures can form during an accident with the hydrogen mitigation system working. To assess the code applicability to hydrogen combustion analysis, this paper presents the numerical calculation results of GOTHIC-3D for various hydrogen combustion experiments, including FLAME, LSVCTF, and SNU-2D. In this study, a technical base for the modeling oflarge- and small-scale facilities was introduced through sensitivity studies on cell size and bum modeling parameters. Use of a turbulent bum option of the eddy dissipation concept enabled scale-free applications. Lowering the bum parameter values for the flame thickness and the bum temperature limit resulted in a larger flame velocity. When applied to hydrogen combustion analysis, this study revealed that the GOTHIC-3D code is generally able to predict the combustion phenomena with its default bum modeling parameters for large-scale facilities. However, the code needs further modifications of its bum modeling parameters to be applied to either small-scale facilities or extremely fast transients.
Bong-Kwang Jung,Taehee Chang,Hyejoo Shin,Seungwan Ryoo,Sooji Hong,Jeonggyu Lee,Hyemi Song,Jaeeun Cho,Deok-Gyu Kim,Hojong Jun,Min-Jae Kim,Eun Jeong Won,Eun-Taek Han,Eun-Hee Shin,Jong-Yil Chai 대한기생충학열대의학회 2021 The Korean Journal of Parasitology Vol.59 No.1
Life cycle stages, including daughter sporocysts, cercariae, and metacercariae, of Parvatrema duboisi (Dollfus, 1923) Bartoli, 1974 (Digenea: Gymnophallidae) have been found in the Manila clam Ruditapes philippinarum from Aphae-do (Island), Shinan-gun, Jeollanam-do, Korea. The daughter sporocysts were elongated sac-like and 307-570 (av. 395) μm long and 101-213 (av. 157) μm wide. Most of the daughter sporocysts contained 15-20 furcocercous cercariae each. The cercariae measured 112-146 (av. 134) μm in total length and 35-46 (av. 40) μm in width, with 69-92 (av. 85) μm long body and 39-54 (av. 49) μm long tail. The metacercariae were 210-250 (av. 231) μm in length and 170-195 (av. 185) μm in width, and characterized by having a large oral sucker, genital pore some distance anterior to the ventral sucker, no ventral pit, and 1 compact or slightly lobed vitellarium, strongly suggesting P. duboisi. The metacercariae were experimentally infected to ICR mice, and adults were recovered at day 7 post-infection. The adult flukes were morphologically similar to the metacercariae except in the presence of up to 20 eggs in the uterus. The daughter sporocysts and metacercariae were molecularly (ITS1-5.8S rDNA-ITS2) analyzed to confirm the species, and the results showed 99.8-99.9% identity with P. duboisi reported from Kyushu, Japan and Gochang, Korea. These results confirmed the presence of various life cycle stages of P. duboisi in the Manila clam, R. philippinarum, playing the role of the first as well as the second intermediate host, on Aphae-do (Island), Shinan-gun, Korea.
Four Year Surveillance of the Vector Hard Ticks for SFTS, Ganghwa-do, Republic of Korea
Myung-Deok Kim-Jeon,Seung Jegal,Hojong Jun,Haneul Jung,Seo Hye Park,Seong Kyu Ahn,Jinyoung Lee,Young Woo Gong,Kwangsig Joo,Mun Ju Kwon,Jong Yul Roh,Wook-Gyo Lee,Young Yil Bahk,Tong-Soo Kim 대한기생충학열대의학회 2019 The Korean Journal of Parasitology Vol.57 No.6
The Effect of ESG-motivated Turnover on Firm Financial Risk
( Daewoung Choi ),( Yong Kyu Gam ),( Min Jung Kang ),( Hojong Shin ) 한국금융연구원 2022 금융연구 working paper Vol.2022 No.13
This study investigates how effectively a forced CEO turnover mitigates firm’s financial distress that s triggered by a bad reputation for its Environmental, Social, and Governance (ESG) practices. We find that a firm’s CEO dismissal decision significantly reduces the level of its financial distress―measured by Altman’s Z-Score―subsequent to negative media coverage of the firm’s ESG practices. This suggests that the forced CEO turnover may be taken as an ex-post damage instrument. Additional results show that the moderating effect of the CEO dismissal is stronger in firms under greater market scrutiny conditioned on various mechanisms: market competition, sin stock industry, and analyst coverage.