시화호 및 주변해역의 수질 특성

장정익,한인섭,김경태,나공태,Jang, Jeong-Ik,Han, Ihn-Sub,Kim, Kyung-Tae,Ra, Kong-Tae 해양환경안전학회 2011 해양환경안전학회지 Vol.17 No.2

본 연구에서는 시화호의 수질 관리 정책 연구를 위한 최근의 수질 자료 확보를 목적으로 2010년에 시화호 내 외측 해역에서 수질 조사를 수행하였다. 시화호 표층수 수질항목들의 수평적 농도분포는 하천을 통한 담수 유업과 배수갑문을 통한 외해수 유입의 영향으로 인하여 반윌 및 시화 산단 얀근 상류지역에서는 높고 배수갑문으로 갈수록 낮아지는 경향을 나타냈다. 시화호 외해에서는 TN 및 TP가 소래포구에 가까운 곳에서 높은 농도를 나타내었으며, 전체적으로 시화호 내해보다는 상대적으로 낮은 농도를 나타내었다. 시화호 내측의 경우, 여름철 성층 형성 및 저층의 활발한 유기물 분해로 빈산소층이 발달되고 있었다. 수질항목들의 수직적 농도분포의 경우, 용존영양염, TN 및 TP는 표층보다 저층에서 높았지만, COD, 클로로필-a 및 POC는 이와 반대로 저층보다 표층에서 높은 분포를 나타냈다. 시화호 표층수에서 염분은 용존영양염과 양호한 음의 상관성을 보여 담수 기원의 영양염 공급이 확인되었고, 이에 의한 식물플랑크톤의 대증식으로 COD 및 POC가 높게 나타났다. The operation of tidal power facility may induce severe changes of water quality in Shihwa Lake. Current water quality data are quite important to water quality management policy of Shihwa Lake. Thus, the water quality data of Shihwa Lake and its adjacent sea in 2010 were presented to characterize the temporal and spatial changes of water parameters such as pH, SS, DO, COD, dissolved nutrients, chlorophyll-a, TN and TP. Highest levels of water quality parameters were observed near the Shihwa and Banweol industrial complexes and the levels of water quality parameters were on a decreasing trend to those near the water gate. It suggests that the horizontal distributions of water quality levels are mainly controlled by the supply of fresh water from streams and the inflow of outer seawater by operation of water gate. Although the higher concentrations of TN and TP were observed in the location being affected by Sorae port, the levels of water quality parameters in outer sea of Shihwa Lake were lower than those in Lake. In summer season, hypoxic condition was well developed in bottom water by strong stratification and active decomposition of organic matter. Thus, the vertical distributions of dissolved nutrient, TN and TP concentrations showed the concentrations to be higher in bottom seawater than those in surface seawater whereas the vertical distributions of chlorophyll-a, COD and POC concentrations showed the concentrations to be higher in surface seawater than those in bottom water. Results of Pearson's correlation matrix for surface seawater demonstrated that salinity showed negatively good correlation with not only dissolved nutrients except for ammonium but chlorophyll-a, COD and POC This result indicates that the supply of dissolved nutrients through several streams might significantly affect phytoplankton bloom and increase of COD concentration in surface seawater.

마이크로중력 과학미션 수행용 초소형 위성의 구조설계 및 해석

장정익(Jeong-Ik Jang),김진혁(Jin-Hyuk Kim),박설현(Seul-Hyuk Park) 한국항공우주학회 2019 한국항공우주학회 학술발표회 논문집 Vol.2019 No.4

전원 불평형과 역률을 보상하는 직렬형 능동전력필터의 통합적 제어

張正翼(Jeong-Ik Jang),李東椿(Dong-Choon Lee),석줄기(Jul-Ki Seok) 대한전기학회 2006 전기학회논문지 B Vol.55 No.5

This paper presents an integrative control scheme for series-type active power filters combined with shunt passive filters not only to compensate for the source voltage unbalance and current harmonics but also to correct the power factor. To reduce the power capacity of the active filters, passive filters are connected in parallel. Diode rectifiers are replaced by the PWM converters in order to feed the real power back to the source. Power factor control is performed by changing the phase of the load voltage so that the phase of the source current coincides with that of the source voltage. The resultant voltage reference is the addition of the voltage component compensating for the source voltage unbalance and harmonic currents and the voltage component correcting the power factor. The validity of the proposed algorithm has been verified by experimental results.

시화호 유입하천의 수질오염물질 농도에 관한 연구

장정익(Jeong Ik Jang),한인섭(Ihn Sup Han),김경태(Kyung Tae Kim),나공태(Kong Tae Ra) 大韓環境工學會 2011 대한환경공학회지 Vol.33 No.4

본 연구에서는 시화호 연안오염총량관리제 도입시 과학적인 기초자료를 제공하기 위하여 하천을 통해 시화호로 유입되는 수질오염물질의 농도 특성을 조사하였다. 시화호 유역 하천수 내 부유물질(SS), 화학적 산소요구량(COD), 용존영양염(NO₂, NO₃, NH₄, PO₄, SiO₂), 총인(TP) 및 총질소(TN) 등을 분석하였으며 조사시기별 및 지역별(산업지역, 도시지역 및 농업지역) 하천수의 오염물질 농도 특성을 비교하였다. 12월 조사 결과가 다른 조사 시기에 비해 모든 수질항목에서 상대적으로 높은 농도를 나타냈다. 산업지역 내 하천수에서의 COD의 평균값은 12.6 mg/L로 도시지역(6.6 mg/L) 및 농업지역(5.9 mg/L)에 비해 약 2배 높은 농도를 나타냈다. 총인 농도는 COD와 유사하게 산업지역 내 하천수에서 가장 높았고 농업지역 내 하천에서 상대적으로 낮은 농도를 보였으며 용존 인산염(PO₄)이 약 21%를 차지하고 있었다. 총질소는 산업지역, 도시지역 및 농업지역에서의 평균농도가 각각 5.89 mg/L, 3.02 mg/L 및 5.27 mg/L로 산업지역과 더불어 질소계 비료의 사용의 영향으로 농업지역에서도 높은 농도를 보였다. 조사시기 및 지역에 따라 차이는 있으나 총질소 중 질소화합물의 평균비율은 NH₄ (35.1%) > NO₃ (30.0%) > DON (22.8%) > PON (8.9%) > NO₂ (3.2%)의 순으로 나타났고 약 70%가 용존무기질소(NH₄, NO₃, NO₂)의 형태로 존재하고 있었다. 하천수의 용존영양염, 총인 및 총질소 농도는 시화호 표층수에 비해 3.2~37.2배 높았으며 이는 많은 양의 오염물질이 처리과정 없이 하천을 통해 시화호로 유출되는 것을 시사하고 있다. 특히 시화산단을 관통하는 군자천 중류지역에서 상류 또는 하류지점에 비해 높은 농도를 나타내 산업단지에서 발생한 하수와 폐수 일부가 관로 오접 및 무단 방류되어 하수구를 통하여 유입되고 있어 하천수에 대한 하수처리시설로의 이송 및 환경기초시설 증대 등의 대책이 필요한 것으로 사료된다. 본 연구결과는 향후 시행 예정인 시화호 연안오염총량관리제의 기본계획 및 시행계획 수립시 오염부하량 산정과 삭감계획 수립에 유용한 정보로 사용될 수 있을 것이다. We studied the characteristics of pollutant concentrations in 9 streams that flow into Shihwa Lake in order to provide the scientific data for effective implementation of total pollution loads management system (TPLMS) of the Lake. Suspended solid (SS), chemical oxygen demand (COD), dissolved nutrients (NO₂, NO₃, NH₄, PO₄ and SiO₂), total phosphorus (TP) and total nitrogen (TN) in stream water from industrial complexes, urban and agricultural regions were determined. Pollutant concentrations in December were higher than that in other sampling periods. COD concentration from industrial complex region with average of 12.6 mg/L was 2 times higher those from urban region (6.6 mg/L) and agricultural region (5.9 mg/L). TP concentration from industrial region also showed higher concentration than other regions. TN concentration in stream water was 5.89 mg/L for industrial region, 3.02 mg/L for urban region and 5.27 mg/L for agricultural region, respectively, suggesting inflow of TN due to fertilizer usage in agricultural field. Relative percentage of nitrogen compounds in TN follows the sequence: NH₄ (35.1%) > NO₂ (20.0%) > DON (22.8%) > PON (8.9%) > NO₂ (3.2%). Concentrations of dissolved nutrients, TP and TN in stream water were 3.2~37.2 times higher than that in Shihwa Lake seawater, therefore large amount of pollutants may be directly entered into Shihwa Lake without any treatment. For Gunja stream of industrial region, pollutants at midstream showed relatively higher concentration compared to upstream and downstream. It is necessary to manage the illegal discharging of sewage and waste water. Our results provide valuable informations on the estimation and reduction of total pollutant loads in the process of establishing adequately strategic and implemental plan of Shihwa Lake TPLMS.

마이크로중력 과학미션 수행용 초소형위성의 구조체 설계와 해석

장정익(Jeong Ik Jang),박설현(Seul Hyun Park) 한국생산제조학회 2019 한국생산제조학회지 Vol.28 No.2

Recently, the use of nanosatellites in the space industry has been receiving increased attention. For the robust construction of a nanosatellite, the structure of the nanosatellite needs to be able to protect avionics and payloads from launch and space environments. In this study, we performed the structural design and analysis to build and implement a robust structure for the Korea Microgravity Science Laboratory nanosatellite. To this end, quasi-static and random vibration analyses were numerically conducted by applying a load of 18.75 G (specified by the GSFC-STD-7000 regulations) to the designed structure. The predicted natural frequency of the designed structure for the nanosatellite was greater than the resonance frequency of the launch vehicle. Additionally, the robustness of the structure was confirmed by the numerical results obtained from the quasi-static and random vibration analyses.

전원 불평형과 역률을 보상하는 직렬형 능동전력필터

장정익(Jeong-Ik Jang),이동춘(Dong-Choon Lee),석줄기(Jul-Ki Seok) 전력전자학회 2005 전력전자학술대회 논문집 Vol.- No.-

This paper presents a unified control scheme for series-type active power filters combined with shunt passive filters for the source voltage unbalance compensation and the power factor correction simultaneously. The power factor correction is achieved by controlling the amplitude of reactive power current in a series filter as zero in a synchronously rotating reference frame. The proposed algorithm successfully compensates the source voltage unbalance and the power factor. The validity of the proposed scheme has been verified by simulation for a 3-kVA hybrid active power filter system.

고체가연물의 열분해 전산모사에 관한 연구

장정익(Jeong-Ik Jang),박설현(Seul-Hyun Park) 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.11

전원전압 왜곡시 3상 AC/DC PWM 컨버터의 전류제어

장정익(Jeong-Ik Jang),김동억(Dong-Eok Kim),이동춘(Dong-Choon Lee),김흥근(Heung-Geun Kim) 전력전자학회 2006 전력전자학술대회 논문집 Vol.- No.-

본 논문에서는 전원전압 왜곡시 3상 PWM 컨버터의 새로운 전류제어 기법을 제시한다. 전원전압의 5, 7차 고조파성분에 의한 고조파 전류가 0이 되도록 각 성분에 대한 전류 제어루프를 구성한다. 그리고 전원전압이 불평형일 경우 직류링크에 나타나는 전압리플을 제거한다. 실험을 통해 제안한 전류제어기법의 타당성을 검증한다.

고 흡수성 수지 첨가가 증류수의 과냉각 및 열적 특성에 미치는 영향

이석준 ( Seok-joon Lee ),장정익 ( Jeong-ik Jang ),김진혁 ( Jin-hyuk Kim ),이명규 ( Myung-kyu Lee ),박설현 ( Seul-hyun Park ) 조선대학교 공학기술연구원 2018 공학기술논문지 Vol.11 No.3

This paper investigated the thermal properties of phase change materials (PCMs) prepared by adding a super absorbent polymer (SAP) to distilled water. The thermal properties of PCMs were investigated using differential scanning calorimeter (DSC) and T-history methods. It was found that 0.1 g SAP addition to distilled water resulted in the best PCM in terms of its thermal properties. The experimental results obtained from the DSC analysis showed that the addition of SAP to distilled water lowered the latent heat from 11.2 J/g to 17.2 J/g. However, the phase separation characteristics which are typically observed for water-based PCMs were found to be improved by adding the SAP. Similar behaviors were observed in results determined from the T-history method. Additionally, the T-history method clearly demonstrated that adding the SAP to distilled water improved the supercooling temperature, shortening the liquid retention time. Despite reductions in the latent heat of PCM with the SAP addition, it is expected that the operating cost of the cooling system can be further reduced due to its improved phase change characteristics such as phase separation and supercooling temperature when the PCM with the 0.1 g SAP added is applied.

SVR을 이용한 AC/DC/AC PWM 컨버터의 직류링크 커패시턴스 추정

아보칼릴 아메드(Ahmed. G. Abo-Khalil),張正翼(Jeong-Ik Jang),李東椿(Dong-Choon Lee) 대한전기학회 2007 전기학회논문지 Vol.56 No.1

This paper proposes a new capacitance estimation scheme for a DC-link capacitor in a three-phase AC/DC/AC PWM converter. A controlled AC voltage with a lower frequency than the line frequency is injected into the DC-link voltage, which then causes AC power ripples at the DC side. By extracting the AC voltage and power components on the DC output side using digital filters, the capacitance can then be calculated using the Support Vector Regression (SVR). By training of SVR, a function which relates a given input (capacitor's power) and its corresponding output (capacitance value) can be derived. This function is used to predict outputs for given inputs that are not included in the training set. The proposed method does not require the information of DC-link current and can be simply implemented with only software and no additional hardware. Experimental results confirm that the estimation error is less than 0.16%.