• 물과 미래
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• 제28권6호
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• pp.169-181
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• 1995

1986년 이후 급격한 하상변동에도 불구하고 고안지점의 수위-유량 관계곡선에 대한 수정작업이 이루어지지 않아 '90년 홍수시 한강홍수통제소로 제보된 팔당댐 하류부 수위나 방류량 자료들이 고안지점에서 계측된 수위자료에 의한 유량자료와의 비교에서 서로 간의 신뢰도에 문제가 발생하였다. 따라서 본 연구에서는 댐하류부의 하상변동을 고려하여 팔당댐에서 고안지점 하류를 포함하는 약 2.2km 구간에 대해 1/100 축척의 수리모형실험을 실시하였으며, 이를 통해 새로이 작성된 팔당댐 방류량 산정공식에 의한 방류량자료와 고안지점에서의 수위자료를 이용하여 새로운 수위-유량 관계곡선을 작성하였다. 한편 수리모형 실험성과로 작성한 수위-유량 관계곡선을 RMA-2V모형에 의한 수치모형을 이용하여 기존의 수위-유량 관계 곡선 및 새로운 수위-유량 관계곡선을 비교, 검정하였다.

• 한국분말재료학회지
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• 제31권2호
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• pp.137-145
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• 2024

In order to predict the process window of laser powder bed fusion (LPBF) for printing metallic components, the calculation of volumetric energy density (VED) has been widely calculated for controlling process parameters. However, because it is assumed that the process parameters contribute equally to heat input, the VED still has limitation for predicting the process window of LPBF-processed materials. In this study, an explainable machine learning (xML) approach was adopted to predict and understand the contribution of each process parameter to defect evolution in Ti alloys in the LPBF process. Various ML models were trained, and the Shapley additive explanation method was adopted to quantify the importance of each process parameter. This study can offer effective guidelines for fine-tuning process parameters to fabricate high-quality products using LPBF.

• Environmental Engineering Research
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• 제10권1호
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• pp.31-37
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• 2005

The selective catalytic experiments using both sulfated/sulfur-free titania and V2O5/TiO2 catalysts have been conducted for NO reduction by NH3 in a packed-bed, down-flow reactor. The sulfated and vanadia loaded titania exhibited higher activity for NO removal than the sulfur-free catalysts, where > 90% NO removal was achieved over the sulfated V2O5/TiO2 catalyst between 280∼500 C. The surface structure of vanadia species on the catalyst surface played a critical role in the high performance of catalysts in which the existence of monomeric/polymeric vanadate is revealed by Raman spectra studies. Water vapor and SO2 were added to the reacting system for the catalyst deactivation tests. At higher temperatures (T ≥ 350 C), little deactivation was observed over the sulfated V2O5/TiO2 catalysts, showing good durability against SO2 and water vapor, which is compared with deactivation at lower temperatures.

• 전력전자학회논문지
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• 제12권5호
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• pp.424-431
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• 2007

본 논문은 발전소의 이차공기송풍기를 가변 회전수 제어하여 소내 소비 전력을 절감하고 전동기의 직입기동에 의한 스트레스를 줄이기 위하여 실증 적용된 200MW 석탄화력 발전소 순환 유동층 보일러 이차 공기 송풍기 구동용 H-브릿지 멀티레벨 인버터에 관한 것이다. H-브릿지 멀티레벨 인버터는 독립적으로 절연된 직류 부를 갖는 저전압의 단상 인버터(셀 인버터)를 다수 직렬 접속하여 고전압 3상 전압을 출력하는 Cascaded H-브릿지 전압형 인버터이다. 전력연구원은 6.6kV, 1MVA급 인버터 개발, 발전소에 설치, 보일러 점화 전/후 시험 및 계통 병입 후 부하 시험 등을 국내 최초로 성공적으로 완료하였다. 현재 200MW 석탄화력 발전소 이차 공기 송풍기 구동용 인버터는 상업 운전 중에 있다. 본 논문에서는 개발된 H-브릿지 멀티레벨 인버터, 기존 발전 설비와 신규 인버터 시스템의 인터페이스 부분에 해당하는 보일러 DCS(Distributed Control System : 분산 제어 시스템) 로직, 계통 병입 후 시운전 결과에 대하여 상세히 기술하였다.

• 전기학회논문지
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• 제56권2호
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• pp.436-441
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• 2007

Background: As patients are positioned at insulated bed and practitioner are positioned at insulated floor or shoes, it could be a cause of lessening effect in acupuncture practice. We investigated how Ground connection could influence on the electrical meridian potential between practitioner and patient during acupuncture practice. Method: We treated 30 normal healthy subjects with acupuncture and measured changes in the electrical potential between the stomach meridian points ST-39 and ST-37 in response to light touch after insertion of a needle at ST-36. At first, we stimulated needle and measured electrical potentials for non ground, patient ground only, practitioner ground only, all ground, respectively. Result: All ground subject elicited positive mean potential $44.6{\pm}19.2{\mu}V$ and showed $181.4{\pm}59.7{\mu}V$ peak to peak potential. practitioner ground only showed negative mean potential $-51.5{\pm}9.3{\mu}V\;and\;367.4{\pm}27.8{\mu}V$ of peak to peak potential. Patient ground only revealed no mean potential as $2.9{\pm}1.3{\mu}V,\;16.4{\pm}11.9{\mu}V$ of peak to peak potential. All ground showed no mean potential as $1.6{\pm}0.7{\mu}V,\;3.3{\pm}1.9{\mu}V$ of peak to peak potential. respectively.

• 유기물자원화
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• 제25권3호
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• pp.79-89
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• 2017

경기도 포천시 관내 하수 및 인분 처리장들에서 발생하는 유기성 슬러지를 지렁이 먹이로 공급하였을 때, 지렁이 사육상의 수용성 양이온, 음이온 농도 및 pH, 전기전도도 등의 이화학 성상 변화를 추적하였다. 먹이로 공급된 슬러지의 pH, 전기전도도, 유기물 함량 및 함수율은 지렁이의 단기적 섭식이 가능한 범위였으나, 슬러지의 공급량이 늘어감에 따라 섭식속도가 느려지고 결국 지렁이 사멸현상이 나타났다. 또한 슬러지 공급량이 늘어감에 따라 지렁이 사육상이 산성화되었고, 전기전도도가 높아지는 것으로 보아 염류집적 현상이 일어난 것을 알 수 있었으며, 동시에 사육상의 수용성 음이온 및 양이온 농도가 높아졌다. 특히 수용성 이온 중 ${NO_3}^-$의 농도 집적이 두드러졌다.

• Nuclear Engineering and Technology
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• 제56권9호
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• pp.3864-3871
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• 2024

In case of a hypothetical severe accident in a Sodium-cooled Fast Reactor (SFR), coolability of the debris bed in the post-accident phase plays a vital role in mitigating the accident and ensuring the structural integrity of the reactor vessel. Few numerical studies are reported in literature, in which the boiling heat transfer in debris bed is expressed as equivalent heat conduction using similarity law between heat conduction and two-phase heat transfer. However, these studies assumed steady state mass conservation for the boiling zone and neglected the gravity force. Hence, a detailed study has been carried out for various particle sizes and porosities of SFR debris to investigate the influence of above considerations. The effect of gravity on debris bed coolability is studied using steady state model of Lipinski, which showed that gravity has a non-negligible effect, for particle size of 0.3 mm and porosity of 0.5. However, the gravitation force was found to have a negligible effect in dryout heat flux estimation for the bottom cooled configuration. A transient numerical model is developed for simulating the boiling phenomena in debris beds and validated with the published experimental results. The assumption of steady state mass conservation is verified by carrying out transient analysis, which indicated early prediction of the dryout inception. For time dependent heat generation case, the unsteady mass conservation predicted higher DHF compared to constant heat generation.

• 환경영향평가
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• 제20권1호
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• pp.61-69
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• 2011

Integrated stream naturalness based on abiotic and biotic factors were developed. Abiotic factors considered in this study were types of land use in the riparian area, river bank and high water bed streamside, revetment, bed substrate and artificial construction of streamside. Biotic factors included types of vegetation, assemblages of fish, macroinvertebrate, bird and mammal(Otter) in streams. The presence/absence of legal species and biological assessment index were also weighted as important parameters in this study. Scoring criteria selected for each matrix was five rating system; 1=poor, 2=moderate, 3=fair, 4=good, 5=excellent. Numerical ratings for the matrix were then summed. This resulted in a minimum score of 13 if all matrix at a site were poor, and a maximum score of 65 if all matrix were excellent. Five grade system from poor(I) to excellent condition(V) was employed. To verify its validity in natural environment, the evaluation system was applied to the Gapchun stream which is a test bed selected. Our result showed that stream naturalness of each reach was clearly distinguished by biotic and abiotic characteristics. Determination of correlation coefficient between abiotic and biotic factors was also high ($R^2=0.96$, p<0.05). In conclusion, assessment for stream naturalness reflecting abiotic and biotic factors was useful method representing stream integrated.

• Biotechnology and Bioprocess Engineering:BBE
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• 제9권5호
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• pp.362-368
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• 2004

A new one-column chromatography process, analogous to a four-zone simulated moving bed (SMB), was presented. The basic principle of the process was identical to that of a four-zone SMB. The process consisted of one chromatographic column and four tanks, instead of the four columns in the four-zone SMB (1-1-1-1), and has been used for the separation of two amino acids, phenylalanine and tryptophan, using an ion exchange resin. The operating parameters for the one-column process and four-zone SMB were obtained from equilibrium theory. Computer simulations were used to compare the performances of the new one column process to that of the general four-zone SMB, using Aspen $Chromatography^{TM}$ v 11.1. The differences between the one-column and SMB processes in terms of the purities and yields of phenylalanine and tryptophan were less than 4 and about $6\%$, respectively. The lower purities of the one-column process were due to the loss of the developed concentration profiles in the column when the liquid was stored in tanks. The one-column process gave great flexibility, and would be useful for reconstructing an existing conventional chromatography process to one of a SMB.

• Membrane and Water Treatment
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• 제4권4호
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• pp.265-275
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• 2013

China is one of the countries with the highest reserves of coal bed methane (CBM) in the world. Likewise, the CBM industry is significantly growing in China. However, activities related to CBM development have led to more environmental problems, which include serious environmental damage and pollution caused by CBM-produced water. In this paper, the detailed characteristics of CBM-produced water in the southern Qinshui Basin were investigated and analyzed and compared with local surface water and coal mine drainage. Most of CBM-produced water samples are contaminated by higher concentration of total dissolved solids (TDS), K (Potassium), Na (Sodium) and $NH_4$. The alkalinity of the water from coalmines and CBM production was higher than that of the local surface water. The concentrations of some trace elements such as P (Phosphorus), Ti (Titanium), V (Vanadium), Cr (Chromium), Ni (Nickel), Zn (Zinc), Ge (Germanium), As (Arsenic), Rb (Rubidium), and Pd (Palladium) in water from the coalmines and CBM production are higher than the acceptable standard limits. The ${\delta}D$ and ${\delta}^{18}O$ values of the CBM-produced water are lower than those of the surface water. Similarly, the ${\delta}D$ values of the CBM-produced water decreased with increasing drainage time.