• Geomechanics and Engineering
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• 제13권4호
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• pp.585-600
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• 2017

This study deals with simple solutions for a spherical or circular opening excavated in elastic-brittle plastic rock mass compatible with a linear Mohr-Coulomb (M-C) or a nonlinear Hoek-Brown (H-B) yield criterion. Based on total strain approach, the closed-form solutions of stresses and displacement are derived simultaneously for circular and spherical openings using original H-B and M-C yield criteria. Two simple numerical procedures are proposed for the solution of generalized H-B and M-C yield criteria. Based on incremental approach, the similarity solution is derived for circular and spherical openings using generalized H-B and M-C yield criteria. The classical Runge-Kutta method is used to integrate the first-order ordinary differential equations. Using three data sets for M-C and H-B models, the results of the radial displacements, the spreading of the plastic radius with decreasing pressure, and the radial and circumferential stresses in the plastic region are compared. Excellent agreement among the solutions is obtained for all cases of spherical and circular openings. The importance of the use of proper initial values in the similarity solution is discussed.

• 한국환경과학회지
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• 제26권1호
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• pp.109-118
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• 2017

This study was conducted to investigate the effects of intermittent plasma and electrolysis treatments on lettuce (Lactuca sativa var. oak-leaf.), nutrient solution components ($NO_3{^-}-N$, $NH_4{^+}-N$, $PO{_4}^{3-}-P$, $K^+$, $Ca^{2+}$ and $Mg^{2+}$) and environmental parameters (electrical conductivity, total dissolved solids and pH). The recirculating hydroponic cultivation system consisted of planting port, LED lamp, water reservoir and circulating pump. Nutrient solution was circulated in the following order: reservoir ${\rightarrow}$ filtration-plasma or filtration-electrolysis ${\rightarrow}$ planting port ${\rightarrow}$ reservoir. The results showed that nutrient solution components and environmental parameters were changed by plasma or electrolysis treatment. Lettuce growth was not affected by the intermittent plasma or electrolysis treatment with 30 minutes or 90 minutes, respectively. The roots of the lettuce was damaged by excessive plasma and electrolysis treatment. Electrolysis treatment had greater effect on than plasma treatment because of the accumulation of high levels of TRO (Total Residual Oxidants).

• Journal of Ship and Ocean Technology
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• 제8권1호
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• pp.1-9
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• 2004

Experiments on friction drag reduction by injecting polymer (Polyethylene oxide) solution or micro-bubbles were carried out in the cavitation tunnel of KRISO. Two different drag reduction mechanisms were applied to a slender axi-symmetric body to measure the total drag reduction. And then the amount of friction drag reduction was estimated under the assumption that the reduction mechanisms were effective only to the friction drag component. As the result of the tests, polymer solution drag reduction up to 23％ of the total drag was observed and it corresponds to about 35％ of the estimated friction drag of the axi-symmetric body. This result matched reasonably well to that of the flat plate test "(Kim et al, 2003)". The normalization of the controlling parameters was tried at the end of this paper. Micro-bubble drag reduction was within 1％ of its total drag. This unexpected result was quite different from that of the flat plate case "(Kim et at, 2003)" The possible reasons were discussed in this paper.

• 한국대기환경학회지
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• 제21권4호
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• pp.431-438
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• 2005

In order to apply the photocatalytic decomposition of aromatic VOCs, adsorbent prepared from MSWI fly ash was coated by $TiO_2$ solution to endow with photo-catalytic function. The effects of coating number, existence of light source and the type of $TiO_2$ solution used for coating were examined. Adsorbent coated with amorphous $TiO_2$ solution showed higher adsorptivity than adsorbent coated with crystal $TiO_2$ solution. Without light source, breakthrough curve of photo -catalyst absorbent for VOCs removal was similar to that of absorbent made from MSWI fly ash. On the other hand, breakthrough time was enlarged with light source and total removal efficiency of benzene and toluene was also increased. It can be explained as photo-decomposition effect of $TiO_2$ photo-catalyst. Total removal efficiency of benzene and toluene was increased according to the increase of coating number with light source. It was due to the effect of adsorption and photo reaction of photo-catalytic adsorbent. But total removal efficiency of benzene was lower than that of toluene. Because benzene was removed more effectively than toluene by adsorption, but photo - decomposition effect oi toluene was more high than benzene.

• Journal of applied mathematics & informatics
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• 제19권1_2호
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• pp.151-164
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• 2005

The regularized structured total least norm (RSTLN) method finds an approximate solution x and error matrix E to the overdetermined linear system (H + E)x $\approx$ b, preserving structure of H. A new separation scheme by parts of variables for the regularized structured total least norm on blind deconvolution problem is suggested. A method combining the regularized structured total least norm method with a separation by parts of variables can be obtain a better approximated solution and a smaller residual. Computational results for the practical problem with Block Toeplitz with Toeplitz Block structure show the new method ensures more efficiency on image restoration.

• 생물환경조절학회지
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• 제22권4호
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• pp.385-391
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• 2013

본 실험은 SCB(slurry composting and biofiltration) 액비의 방울 토마토(Solanum lycopersicum L. 'Unicon') 수경재배 이용가능성을 알아보기 위해 실시 되었다. 배양액처리 대조구로는 방울 토마토 전용 배양액(Control 1N)을 사용하였고, 이 배양액의 질소량($218.32mg{\cdot}L^{-1}$)을 기준으로 시판양액 1N(CNS 1N), SCB 1/2N, SCB 1N, SCB 2N을 타이머 제어에 의해 하루에 440~520mL을 공급하였다. 31일 동안 재배한 후 지상부 생체중과 건물중, 엽면적, 초장, 줄기직경, SPAD값, 마디수를 조사하였으며, 그 후 주 1회 총 7번의 과실을 수확하여 총 생산량과 상품성 과실 비율, 과실중, 당도와 산도, 과실의 총 페놀 농도 및 항산화도, 배꼽썩음병 발생률을 조사하였다. 그 결과 SCB처리 중에는 SCB 1/2N은 지상부 생체중 건물중, 엽면적, 줄기직경, 마디수 및 SPAD값에서 Control 1N 및 CNS 1N과 유의적 차이를 보이지 않으면서 우수한 생육을 유도하였다. SCB는 질소 농도가 증가하면서 점차로 생육의 저해현상을 보였다. 과실의 총 생산량은 Control 1N에서 가장 높았으며, SCB 처리중 생장이 가장 좋았던 SCB 1/2N 처리구는 Control 1N 총 생산량의 47%를 기록하였다. 상품성 과실 비율도 SCB 1N과 SCB 1/2N 처리구는 약 57~58%로 낮게 나타났다. 당도와 산도, 총 페놀 농도와 항산화도에서는 SCB 2N에서 가장 높은 수치를 보였고, 나머지 처리구와 대조구에서는 유의적으로 차이를 보이지 않았다. 배꼽썩음병은 Control 1N, CNS 1N에서는 발생하지 않았지만, SCB 2N, 1N, 1/2N 처리구는 각각 약 7, 13, 19%의 발생률을 나타내었다. 결론적으로 SCB 1/2N 처리는 Control 1N와 CNS 1N과 비교해서 방울 토마토의 영양생장에는 양호한 결과를 보였지만, 과실의 수량과 품질을 유지하지는 못했다. 따라서 SCB 액비는 방울토마토 시설 수경 재배에서 배양액으로의 가능성은 확인하였지만, 과실의 생산량과 상품성을 고려한다면 개화기 및 과실 비대기에 추가적인 무기 양분의 공급이 필요할 것으로 판단되었다.

• 대한기계학회논문집B
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• 제20권10호
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• pp.3293-3303
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• 1996

Numerical analyses have been performed to estimate the absorption heat and mass transfer coefficients in absorption process of the LiBr aqueous solution and the total heat and mass transfer rates in a vertical tube absorber which is coolING ed by air. Axisymmetric cylindrical coordinate system was adopted to model the circular tube and the transport equations were solved by the finite volume method. Absorption behaviors of heat and mass transfer were analyzed through falling film of the LiBr aqueous solution contacted by water vapor in tube. Effects of film Reynolds number on heat and mass transfer coefficients have been also investigated. Especially, effects of tube diameter have been considered to observe the total heat and mass transfer rates through falling film along the tube. Based on the analysis it has been found that the total mass transfer rate increases rapidly in a region with low film Reynolds number(10 ~ 40) as the film Reynolds number increases, while decreases beyond that region. The total heat and mass transfer rates increase with increasing the tube diameter.

• 한국환경보건학회지
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• 제13권1호
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• pp.47-57
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• 1987

Owing to the modification of testing methods of disinfectants or antiseptics, variations of bacteria according to characteristics of regions and resistance changes of bacteria, it is necessary that the bactericidal activities of disinfectants or antiscptics should be reevaluated nowadays. This study was carried out to reevaluate in the vitro bactericidal activity of Chlorhexidine gluconate solution. The results of experiment were summarized as follows. 1. For Chlorhexidine gluconate solution, minimal inhibitory concentrations of total bacteria taken from sewage water and Legionella bozemanii were $2.0\times 10^{-3}$%, $1.0\times 10^{-2}$%, respectively and were comparatively high. Minimal inhibitory concentration of Shigella flexneri was $1.6\times 10^{-4}$%, and was comparatively low. 2. For total bacteria taken from sewage water, it was killed within 15 minute in 0.1% Chlorhexidine gluconate solution when number of cells was $1.6\times 10^7$/ml. 3. For 0.0125% Chlorhexidine gluconate solution, decimal reduction times of Ps. aeruginosa, S. typhi, E. Coli were 45 sec, 25 sec, 18 sec repectively. For 1%, 0.125% Chlorhexidine gluconate solution, decimal reduction times of Legionella bozemanii were 10 sec, 45 sec respectively. 4. There was significant difference in the bactericidal activity of Chlorhexidine gluconate solution according to temperattire. Phenol coefficient of Chlorhexidine gluconate solution as using Staph. aureus was 100 and comparatively higher than that of other disinfectants. In comparison with other disinfectants, Legionella bozemanii was killed within 5 minutes in 0.02% KMnO$_4$ and 0.125% Chlorhexidine giuconate solution but was not killed within 3 minutes in 1% 0-cresol, 1% Phenol.

• 멤브레인
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• 제23권1호
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• pp.92-99
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• 2013

본 연구는 인쇄회로기판(PCB) 제조 시 에칭공정에서 발생되는 구리이온($Cu^{+2}$)을 고농도로 함유한 황산 폐에칭액을 NF 막분리법을 사용하여 에칭액 회수와 구리이온 처리를 효율적으로 수행하기 위한 NF 막여과 공정의 운전 조건을 설정하기 위한 기본 자료를 확보하는데 있다. 이를 위해 미국 Koch사의 SelRO MPS-34 4040 NF 막을 대상으로 구리이온을 고농도(5~25 g/L)로 함유한 모의 황산 폐에칭액의 회분식(dead-end) 나노여과 실험을 수행하여 투과 플럭스와 구리이온의 총괄 배제도를 측정하였다. 이 결과 황산용액에의 막 보관기간이 길수록, 황산용액의 pH가 낮을수록 황산에 의한 NF 막의 손상이 더 크게 발생하여 순수 투과 플러스가 증가하였다. 황산 폐에칭액의 투과 플럭스는 황산용액 내 구리이온의 농도가 증가할수록 막 표면에의 구리이온 농축(농도분극)의 증가에 따라 감소하였으며, 구리이온의 배제도는 구리이온의 농도가 높을수록, pH가 낮을수록, 황산용액 내의 막 보관기간이 길수록 낮아져 초기 37%에서 최소 15% 수준으로까지 감소하였다.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2013년도 추계학술대회
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• pp.65-66
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• 2013

NFC 센싱 기술과 스마트폰 기술을 활용하여 어린이 집 등하원 토탈 솔루션 시스템을 개발하고 있다. 이를 이용하면 저비용으로 별도의 GPS 수신장치 및 하드웨어가 없어도 등하원 버스의 위치 및 시간 정보를 확인할 수 있다. 개발된 시스템은 어린이 집 등하원에 특화된 서비스에 적용될 예정이다.