Transformation of dissolved organic matter in a constructed wetland

Jongkwan Park,Mijin Choi,Jaeweon Cho,Kyongmi Chon 대한환경공학회 2018 Environmental Engineering Research Vol.23 No.4

This study investigated the transformation of dissolved organic matter (DOM) in a free-water surface flow constructed wetland. Pyrolysis gas chromatography-mass spectrometry (Py-GC/MS) coupled with preparative high-performance liquid chromatography (prep-HPLC) was used to analyze the compositions of biopolymers (polysaccharides, amino sugars, proteins, polyhydroxy aromatics, lipids and lignin) in DOM according to the molecular size at three sampling points of the water flow: inflow, midflow, and outflow. The prep-HPLC results verified the decomposition of DOM through the decrease in the number of peaks from three to one in the chromatograms of the sampling points. The Py-GC/MS results for the degradable peaks indicated that biopolymers relating to polysaccharides and proteins gradually biodegraded with the water flow. On the other hand, the recalcitrant organic fraction (the remaining peak) in the outflow showed a relatively high concentration of aromatic compounds. Therefore, the ecological processes in the constructed wetland caused DOM to become more aromatic and homogeneous. This indicated that the constructed wetland can be an effective buffer area for releasing biochemically stable DOM, which has less influence on biological water quality indicators, e.g., biochemical oxygen demand, into an aquatic ecosystem.

Design and Implementation of LED Driver Circuit for Vessel Lightings

Jongkwan Song,Jang-Sik Park,Hyun-Tae Kim,Byung-Woo Yoon 한국정보통신학회 2012 2016 INTERNATIONAL CONFERENCE Vol.5 No.1

[P4-09] Effect of Electron Beam Irradiation on the Microbial Safety and Qualities of Whole Black Pepper Powder and Commercial Sunsik

Jongkwan Ko,Yuhyun Ma,Heeyoung Shin,Kyung Bin Song 한국식품영양과학회 2005 한국식품영양과학회 학술대회발표집 Vol.2005 No.10

Mutual Friendly Force Identification Protocol based on Hash-Chain for Personal Combat Systems

( Jongkwan Lee ) 한국인터넷정보학회 2020 KSII Transactions on Internet and Information Syst Vol.14 No.9

In this paper, we propose a hash-chain based friendly force identification protocol for personal combatants equipped with a personal combat system in a tactical wireless network. It is imperative in military operations to effectively and quickly identify friendly forces. If the identification of friendly forces is not correct, this can cause friendly fire. In current ground operations, the identification of friendly forces by personal combatants is neither secure nor safe. To address this issue, the proposed protocol uses a hash-chain to determine if a detected person is friendly. Only friendly forces with the same materials that are assigned before they deploy can construct an initial hash-chain. Moreover, the hash-chain is changed at specific times. The performance of the proposed protocol is evaluated on the assumption that the secret key is leaked, which is the worst scenario in the security research field. We verify that the proposed protocol is secure for the various attack scenarios, such as message replay attack, fabrication attack, and Denial of Service attack.

Effect of Chlorine Dioxide Treatment on Microbial Growth and Qualities of Chicken Breast

Jongkwan Ko,Yuhyun Ma,Kyung Bin Song 한국식품영양과학회 2005 Preventive Nutrition and Food Science Vol.10 No.2

Chlorine dioxide (ClO₂) treatment was evaluated for microbial growth inhibition and its effects on the quality of vacuum-packaged chicken breasts. Chicken breast samples were treated with 3, 50, and 100 ppm of ClO₂ solution, respectively. After ClO₂ treatment, chicken breast samples were individually vacuumpackaged and stored at 4℃, a typical storage temperature for meat and meat product, for 7 days. The vacuum-packaged chicken breasts treated with ClO₂ had significantly lower total bacteria, yeast and mold, total coliform, and Salmonella spp. were significantly reduced by ClO₂ treatment. D_(10)-values of total bacteria count, yeast and mold, total coliform, and Salmonella spp. in vacuum-packaged chicken breasts was 93, 83, 85, and 50 ppm, respectively. The pH of vacuum-packaged chicken breasts decreased with increasing ClO₂ concentration. Thiobarbituric acid reacted substance (TBARS) values of vacuum-packaged chicken breasts increased during storage, regardless of ClO₂ concentration. ClO₂ treatment caused negligible changes in Hunter L, a, and b values in the vacuum-packaged chicken breasts. Sensory evaluation of the vacuumpackaged chicken breasts showed that there were no significant changes among the samples treated with various ClO₂ concentration. These results indicate that ClO₂ treatment could be useful in improving the microbial safety and quality of meat products.

Determining haloacetic acids formation potential of NOM fractionated based on molecular based on molecular size, using IC-ESI-MS

Jongkwan Park,Hojung Rho,Jaeweon Cho 대한환경공학회 2015 대한환경공학회 학술발표논문집 Vol.2015 No.10

Poster Session : PS 0970 ; Endoscopic Nested Y-Shaped Self-Expanding Metal Stent Placement for Advanced Hilar Cholangiocarcinoma: A Study of a Novel Stent with a Unique Mesh Structure

( Jongkwan Jung ),( Kyo Sang Yoo ),( Dongsoo Han ),( Changsoo Eun ),( Youngouk Ro ),( Sunmin Kim ),( Yeongjae Byeon ),( Jiyeon Kim ) 대한내과학회 2014 대한내과학회 추계학술대회 Vol.2014 No.1

Background: Hilar malignant biliary obstruction poses particular challenges for endoscopists. Although endoscopic placement of SEMS is generally accepted as a palliative treatment in unresectable hilar cholangiocarcinoma, endoscopic placement of SEMS has been considered very diffi cult and complex. The aim of this study was to evaluate the technical and clinical effi cacy of endoscopic placement of a newly designed SEMS with a nested Y-shaped confi guration for hilar malignant biliary obstruction. Methods: 39 patients were enrolled for this study. The used SEMS was a newly designed self-expandable nitinol stent with a nested Y-shaped configuration. Due to the unique mesh structure, it has superior widening center section with cross mesh structure between both end sections with hook and cross structure. The stents were placed with a nested technique. The 2nd uncoated SEMS was then deployed along the guidewire access through the interstices of the fi rst SEMS. Technical & functional success, early complications, and clinical outcome were evaluated. Results: Technical success was achieved in 32 patients. Mean procedure time was 26.6±10.0 minutes. All patients with successful placement of the stents showed a signifi cant decrease in serum bilirubin level. There was neither any early complication nor procedure-related mortality. Late complication occurred in 7 patients, and all of them were related to stent occlusion from tumor ingrowth. In case with stent occlusion, revision with additional metal stents in 2 cases, placement of plastic stents in 2 cases and PTBD in 4 cases. The mean stent patency period was 130 days. Conclusions: Endoscopic placement of a newly designed SEMS with a nested Y-shaped confi guration is easy, safe, and reasonably effective in achieving bilateral drainage of malignant biliary hilar obstruction.

WGT 가솔린 기관에서 내장형 WGV가 동력성능에 미치는 영향에 관한 연구

Jongkwan Jang(장종관) 한국자동차공학회 2016 한국자동차공학회 학술대회 및 전시회 Vol.2016 No.11

It was studied on the understanding of the operating characteristics of WGV which effected the power performance in a WGA gasoline engine. At first, according to engine operating conditions, the mechanical behavior of the WGV was established for this purpose. And the effects of the engine poser performance on WGA opening time, WGV duty control rate and the and the deterioration of WGV head were tested and experimented. To sum up the main results, the vibration of operating characteristics of WGV was rapidly iterated during the opening time. WGV started to open it`s head from over at least 45% throttle load through the whole engine RPM, And the load conditions of WGV`s opening time increased gradually up to 75% throttle load, Until about 5,0000rpm, maximum duty control rate was kept 100% duty rate. And it was gradually reduced down at the increased speed and load, but it dropped sharply at a very high speed of WOT. At these engine operating conditions, because of the decrease of volumetric charging efficiency, the engine torque was rapidly decreased. These were resulted from the increase of engine cooling loss and exhaust gas loss at a high combustion temperature. And the wear of WGV head and housing seat was observed during an endurance test of WGT engine. It led to result in cause of decrease of a boost pressure which directly caused the power output decrease of WGT gasoline engine.

미세조류를 이용한 바이오 에탄올 생산 연구에 관한 고찰

박종관(Jongkwan Park),문한솔(Hansol Mun),박민주(Min-Ju Park),장희원(Heewon Jang),정대운(Dae-Woon Jeong) 대한환경공학회 2020 대한환경공학회지 Vol.42 No.3

목적 : 바이오 에탄올은 식물체로부터 유래하고, 추가적인 시설 투자없이 기존의 에너지 인프라를 이용할 수 있다는 점에서 중요한 에너지원으로 알려져 있다. 또한 연소시에도 저농도의 오염물질을 매출하는 친환경 에너지 자원이다. 특히, 미세조류는 빠르게 성장하고 바이오에너지로 변환할 때 상대적으로 쉬운 전처리를 할 수 있다는 점에서 효과적인 바이오 에탄올을 위한 생물자원으로 보고되었다. 본 총설에서는 미세조류를 이용한 바이오 에탄올 생산에 대한 일반적인 내용과 다양한 생산 방식, 그리고 바이오 에탄올에 대한 경제적 전망에 대한 정보를 제공하는 것을 목적으로 한다. 방법 : 최근에 게제된 논문을 수집하고 분석하였으며, 연구 내용은 현재 바이오 에탄올과 미세조류 연구에 관한 소개, 바이오 에탄올 생산에 관한 일반적인 정보, 바이오 에탄올 생산 공정, 경제적 실효성, 마지막으로 한계점 및 앞으로의 전망의 순서로 구성되어 있다. 결과 및 토의 : 높은 수율의 바이오 에탄올을 얻기 위해서 적절한 미세조류의 선택과 배양 방법이 중요하다. 그리고 바이오 에탄올 생산을 위한 미세조류의 물리적, 화학적, 생물학적 전처리 방법과 다양한 생산 공정에 대한 장단점을 소개하였다. 결론 : 미세조류는 빠른 성장 주기, 높은 탄수화물 함량, 상대적으로 손쉬운 전처리 방법으로 인해 바이오 에탄올 생산을 위한 에너지원으로 기대가 된다. 그러나 경제성 향상을 위해 조류의 배양방법, 전처리 기술, 높은 수율의 바이오 에탄올을 생산하기 위한 적절한 발효 단계 등에 대한 추가적인 연구가 필요하다. Objectives : Bioethanol is known as an important energy source that comes from plants, uses existing energy infrastructure without additional investment, and emits a low concentration of pollutants during combustion as eco-friendly renewable energy. Microalgae is reported as an effective material for producing bioethanol because of rapid biomass growth and relatively easy pretreatment steps. The objectives of this study are 1) to introduce general information of bioethanol production, 2) to show various processes for bioethanol production from microalgae, and 3) to provide an economic perspective of bioethanol. Methods : Recent published peer-reviewed papers were collected and analyzed. The contents follow the order: 1) introduction, 2) general information about microalgae for bioethanol production, 3) bioethanol producing processes, 4) economic feasibility, and 5) conclusion. Results and Discussion : The selection of the microalgae species and growing method are important to obtain high yield bioethanol. Physical, chemical, biological pretreatment was introduced. Also, comparison of the bioethanol producing processes was provided. Conclusions : Bioethanol production from microalgae is a promising energy source because microalgae have lots of advantages as effective biomass such as rapid growth, high polysaccharide contents, and easy preparing step for bioethanol production. However, it has some limitations that need to overcome. Algae growing method, pretreatment technology, and fermentation steps still require advanced technology, which can improve economic feasibility.

Degradation of All-Solid-State Lithium-Sulfur Batteries with PEO-Based Composite Electrolyte

Lee, Jongkwan,Heo, Kookjin,Song, Young-Woong,Hwang, Dahee,Kim, Min-Young,Jeong, Hyejeong,Shin, Dong-Chan,Lim, Jinsub The Korean Electrochemical Society 2022 Journal of electrochemical science and technology Vol.13 No.2

Lithium-sulfur batteries (LSBs) have emerged as a promising alternative to lithium-ion batteries (LIBs) owing to their high energy density and economic viability. In addition, all-solid-state LSBs, which use solid-state electrolytes, have been proposed to overcome the polysulfide shuttle effect while improving safety. However, the high interfacial resistance and poor ionic conductivity exhibited by the electrode and solid-state electrolytes, respectively, are significant challenges in the development of these LSBs. Herein, we apply a poly (ethylene oxide) (PEO)-based composite solid-state electrolyte with oxide Li₇La₃Zr₂O₁₂ (LLZO) solid-state electrolyte in an all-solid-state LSB to overcome these challenges. We use an electrochemical method to evaluate the degradation of the all-solid-state LSB in accordance with the carbon content and loading weight within the cathode. The all-solid-state LSB, with sulfur-carbon content in a ratio of 3:3, exhibited a high initial discharge capacity (1386 mAh g^-1), poor C-rate performance, and capacity retention of less than 50%. The all-solid-state LSB with a high loading weight exhibited a poor overall electrochemical performance. The factors influencing the electrochemical performance degradation were revealed through systematic analysis.