• Journal of the Korean Wood Science and Technology
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• 제31권1호
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• pp.22-26
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• 2003

증량제로서 카제인과 콩을 첨가한 요소수지 접착제와 소나무 간벌재 파티클로 실험실 파티클보드를 제조하였다. 소나무 간벌재 파티클로 제조된 파티클보드를 성능 평가한 결과 소나무 간벌재는 파티클보드의 원료로서 적합하다. 증량된 요소수지로 접착된 파티클보드는 증량제의 첨가량이 증가함에 따라 기계적인 성능은 감소하는 경향이었다. 그러나 요소수지 접착제의 고형분량에 대해 카제인은 15%까지 콩은 20%까지 첨가하여 파티클보드 제조에 사용할 수 있다.

• Wind and Structures
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• 제34권1호
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• pp.91-100
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• 2022

Numerical simulations are conducted to investigate the uniform flow (UF) and sinusoidal streamwise flow (SSF) over an oscillating 5:1 rectangular cylinder with harmonic heaving motion at initial angles of attack of α = 0° and 3° using two-dimensional, unsteady Reynolds-averaged Navier-Stokes (URANS) equations. First, the aerodynamic parameters of a stationary 5:1 rectangular cylinder in UF are compared with the previous experimental and numerical data to validate the capability of the computationally efficient two-dimensional URANS simulations. Then, the unsteady flow field and aerodynamic forces of the oscillating 5:1 rectangular cylinder in SSF are analysed and compared with those in UF to explore the effect of SSF on the rectangular cylinder. Results show that the alternative vortex shedding is disturbed by SSF both at α = 0° and 3°, resulting in a considerable decrease in the vortex-induced force, whereas the unsteady lift component induced by cylinder motion remains almost unchanged in the SSF comparing with that in UF. Notably, the strong buffeting forces are observed at α = 3° and the energy associated with unsteady lift is primarily because of the oscillations of SSF. In addition, the components of unsteady lift induced by the coupling effects of SSF and cylinder motion are discussed in detail.

• Nuclear Engineering and Technology
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• 제56권4호
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• pp.1532-1537
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• 2024

Time-of-flight (TOF) PET detectors with fast-rise-time scintillators and fast-single photon time resolution silicon photomultiplier (SiPM) have been developed to improve the coincidence timing resolution (CTR) to sub-100 ps. The CTR can be further improved with an optimal bandwidth and minimized electronic noise in the readout circuit and this helps reduce the distortion of the fast signals generated from the TOF-PET detector. The purpose of this study was to develop an ultra-high frequency and fully-differential (UF-FD) readout circuit that minimizes distortion in the fast signals produced using TOF-PET detectors, and suppresses the impact of the electronic noise generated from the detector and front-end readout circuits. The proposed UF-FD readout circuit is composed of two differential amplifiers (time) and a current feedback operational amplifier (energy). The ultra-high frequency differential (7 GHz) amplifiers can reduce the common ground noise in the fully-differential mode and minimize the distortion in the fast signal. The CTR and energy resolution were measured to evaluate the performance of the UF-FD readout circuit. These results were compared with those obtained from a high-frequency and single ended readout circuit. The experiment results indicated that the UF-FD readout circuit proposed in this study could substantially improve the best achievable CTR of TOF-PET detectors.

• Membrane and Water Treatment
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• 제2권3호
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• pp.175-185
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• 2011

Ultrafiltration is an emerging technology for drinking water treatment because it produces better water quality as compared with conventional treatment systems. More recently, the combination of UF technology with other processes in order to improve its performance has been observed. These associations aim to maximize the contaminants removal and reduce membrane fouling. The operational performance of contaminants removal and water production of two UF pilot plants was compared. The first plant (Guarapiranga) was fed with raw water and the second plant (ABV) with pre-treated water by the coagulation, flocculation and sedimentation processes at Alto da Boa Vista WTP (Sao Paulo, Brazil). Both units operated continuously for approximately 2,500 hours, from September/2009 to January/2010. The results showed that the ABV UF pilot plant was able to operate at higher specific fluxes (6.2 $L.d^{-1}.m^{-2}.kPa^{-1}$ @ $25^{\circ}C$) than Guarapiranga (3.1 $L.d^{-1}.m^{-2}.kPa^{-1}$ @ $25^{\circ}C$). However, the number of chemical cleanings conducted in both pilot units during the considered operation period was the same (4 chemical cleanings for each plant), which shows that the pre-treatment reduced the membrane fouling. The water quality at ABV for all the variables analyzed was better, but the feed water quality was also better due to pretreatment. The rejection values for the different contaminants were higher at Guarapiranga mainly because of a pollution load reduction after pre-treatment at ABV. Even with the better performance of the ABV UF pilot plant, it is necessary to take into consideration the complexity of the complete treatment system, and also the costs involved in the construction and operation of a full-scale treatment unit.

• 한국잠사곤충학회지
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• 제27권2호
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• pp.47-53
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• 1985

요소-formaldehyde 수지를 여러 가지 조건에서 견직물에 처리하여 다음과 같은 결과를 얻었다. 1. 수명수지의 생성 조건은 요소 1mol에 대하여 formaline을 2mod 이상 사용하여 pH 4∼5로 수지욕을 만들어야 한다. 2. 수지농도가 증가하는데 비례적으로 수지부착율도 증가한다. 상대적으로 수분율을 감소하는 경향을 보였다. 3. wet pick 70%, 80%, 90%, 100% 중에서 70%일 경우가 수지잔존율이 가장 높았다. 4. curing 조건에 따른 수지의 부착율은 온도가 높을수록 탈락율은 감소하며 부착율은 증가된다. 5. 촉매의 양은 (NH4)2SO4 경우는 수지에 대하여 2.5%, HCI 경우는 1%, tataric acid 경우는 10%가 적당하였고 나머지 NaHCO3, Zn(NO3)2·6H2O인 경우는 분석이 곤란하였다. 6. 촉매의 종류에 따른 부착율은 산성 혹은 (NH4)2SO4와 같은 잠복성 촉매가 뛰어난 효과를 나타냈다. 7. 촉매에 따른 세탁견뢰성은 산성 촉매일수록 뛰어난 효과를 나타냈다.

• 대한환경공학회지
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• 제22권3호
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• pp.429-439
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• 2000

Lake Red C(바롬) 계열 및 Lithol Rubine(칼슘) 계열의 안료나 이들의 혼합물이 포함된 안료폐수에 대하여 여러 가지 폐수처리 및 탈색기법을 적용하였다. 우선, 오존처리법에서는 전체적으로 오존주입량 증가에 따른 폐수의 $COD_{Mn}$ 감소는 다소 있었지만 일부의 Lithol Rubine 계열을 제외하고는 탈색효과는 아주 미미하였다. Fenton 산화법 및 전기분해법의 적용에 있어서는 폐수시료 모두 좋은 $COD_{Mn}$ 감소효과가 있었고 일부의 Lithol Rubine 계열 안료폐수의 색깔제거 효과도 관찰되었다. UF와 RO를 이용한 막분리법의 적용에서는, UF 자체만 적용한 여기에 경우에도 상당한 $COD_{Mn}$ 제거효과가 있었고, 약간의 색깔 제거효과가 있었다. UF 적용후 여기에 RO를 적용하였더니 방류수 기준을 충분히 만족할 수 있을 정도로 아주 우수한 $COD_{Mn}$ 제거효과가 관찰되었다. 또한 색깔제거 측면에서도 거의 100%의 색도제거가 확인되었고, 처리수의 pH도 중성에 가까워서 이를 재활용할 수도 있을 것으로 판단된다.

• 한국의류학회지
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• 제9권2호
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• pp.13-26
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• 1985

In this study, when cotton fabrics dyed with Direct dyes are treated under various resin concentration 2, 4, 8, 12, $14\%$ with ureaformaldehyde(UF) and melamineformaldehyde(MF) resin which can be imparted the crease recovery to textiles, chang of properties on lightfastness, washfastness, crease recovery, breaking strength, etc. and color changes are investigated. the results are as follows 1) Color difference(${\Delta}$E) increased but K/S value decreased according to the increase of resin cone. such tendency showed that MF treated fabrics and soaping fabrics were evident than UF treated fabrics and non-soaping fabrics. 2) In lightfastness, ${\Delta}$E and K/S value of resin treated fabrics were reduced as compared with untreated fabrics according to the increase of resin cone. The lower ${\Delta}$E and K/S value of MF than ${\Delta}$E and K/S value of UF showed low lightfastness of MF. pH of resin treted fabrics was almost unaffected with lightfastness. 3) In washfastness, ${\Delta}$E and K/S value of resin treated fabrics decreased slightly as com-pared with untreated fabricsaccording tothe increase of resin cone. The ${\Delta}$E and K/S value of MF decreased lower than UF. But in the case of the higher resin cone. than about $8\%$, they were not almost differentiated. 4) As resin cone. increased, crease recovery considerably increased but breaking strength and elongation decreased. The fabrics treated with UF were good crease recovery, whereas the fabrics treated with MF were good breaking strength. 5) Soaping appeared to improve the lightfastness, washfastness, crease recovery but appeared to work adverse effect on breaking strength.

• 디지털콘텐츠학회 논문지
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• 제19권7호
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• pp.1333-1339
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• 2018

최근 집중호우 등 기상으로 인한 재해가 증가함에 따라 수문기상, 방재분야에서 레이더를 이용한 기상 및 재해예측에 대한 관심이 증대되고 관련연구가 활발히 이루어지고 있다. 환경부 등에서는 레이더 네트워크를 전국적으로 구축 운영함에 따라 레이더의 활용성이 강조되고 있지만, 레이더자료를 활용하고자 하는 실무자 및 연구자들은 레이더자료의 특성을 이해해야하고 레이더자료 형식(UF)의 변환과 보정에 시행착오를 경험하고 있다. 이에 본 연구에서는 UF형식의 레이더자료를 이미지 및 텍스트파일(ASCII file)로 생성할 수 있도록 JAVA 언어를 이용한 GUI방식의 레이더자료를 표출 및 분석 프로그램(RaDAP; Radar Display and Analysis Program)을 개발하였다. 본 프로그램을 이용하여 원하는 레이더강우 자료를 도출하고 이를 이용한 분석을 수행하는데 필요한 소요시간을 최소화 할 수 있어 다양한 분야에서 레이더자료의 활용성을 높이는데 기여할 것으로 예상된다.

• Membrane and Water Treatment
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• 제11권5호
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• pp.323-331
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• 2020

With the increasing demand on reverse osmosis (RO) membranes for water purification worldwide, the number of disposed membrane elements is expected to increase accordingly. Thus, recycling and reuse of end-of-life RO membranes should be a global environmental action. In this work, we aim to reuse the spent RO membrane for nanofiltration (NF) and ultrafiltration (UF) process by subjecting the spent membrane to solvent and oxidizing solution treatment, respectively. Our results showed that solvent-treated RO membrane could perform as good as commercial NF membrane by achieving similar separation efficiencies, but with reduced water permeability due to membrane surface fouling. By degrading the polyamide layer of RO membrane, the transformed membrane could achieve high water permeability (85.6 L/㎡.h.bar) and excellent rejection against macromolecules (at least 87.4%), suggesting its reuse potential as UF membrane. More importantly, our findings showed that in-situ transformation on the spent RO membrane using solvent and oxidizing solution could be safely conducted as the properties of the entire spiral wound element did not show significant changes upon prolonged exposure of these two solutions. Our findings are important to open up new possibilities for the discarded RO membranes for reuse in NF and UF process, prolonging the lifespan of spent membranes and promoting the sustainability of the membrane process.

• 한국지반환경공학회 논문집
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• 제12권2호
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• pp.55-61
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• 2011

NDMA(N-Nitrosodimethylamine)는 극저농도(10ng/L)에서도 암을 일으킬 수 있는 물질로 알려져 있지만, 기존의 NDMA 제거율 평가 연구는 고농도의 NDMA를 대상으로 한 것이 대부분이었다. 따라서 극저농도의 NDMA 제거효율 평가가 필요하며 그 기초연구로써 호기성/혐기성 조건에서의 분말활성탄, GS(Granular Sludge), MF(Microfiltration), UF(Ultrafiltration)를 이용한 제거효율과 Silica gel(MCM-41, Diatomite, Spherical silica gel)을 이용한 제거효율을 평가하였다. 그 결과 혐기성 조건에서 GS, PAC를 접촉한 후 UF membrane을 이용한 고액분리가 65%의 제거율로 가장 높았으며, Silica gel(MCM-41)이 6%의 제거율로 가장 낮았다. 본 연구는 극저농도의 NDMA 제거의 기초 연구로서 향후 관련 연구의 기초자료로써 활용을 기대한다.