• Journal of Bio-Environment Control
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• v.20 no.2
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• pp.150-155
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• 2011

The aim of this study was investigated long distance export condition of paprika from Korea to Canada, and evaluated the effect of non-perforated breathable films on the storability of paprika during MA storage in the simulated long distance export condition. The long distance export condition of paprika from Korea to Canada was $7{\pm}1^{\circ}C$ and RH 90% during shipping for 20 days, and then the temperature of that was increased to $13^{\circ}C$ for 3 hours during transferring from refrigerated container to storage room in Canada, and decreased $3{\sim}4^{\circ}C$ for 3 days before distributing to local markets. The temperature and relative humidity of local markets was $16^{\circ}C$ and 60%, respectively. The packing material treatments were non-packing, as control, perforated film (6 mm diameter hole, $18holes/m^2$), and 3 kind of laser treated non-perforated films (oxygen transmission rate was 5,000, 20,000 and 100,000 $cc/m^2{\cdot}day{\cdot}atm$). Under the simulated long distance export condition; $7^{\circ}C$ and RH 90% for 15 days and then $20^{\circ}C$ and RH 55% for 7 days, the fresh weight loss of paprika was less than 1% in 3 kind of laser treated non-perforated film treatments but was more than 4% in control and perforated film treatment that showed severe deterioration of visual quality after 20 days of storage. The atmosphere of paprika packages was changed 5% oxygen and 15% carbon dioxide in 5,000 $cc/m^2{\cdot}day{\cdot}atm$ treatment, and 16% oxygen and 4~5% carbon dioxide in 20,000 $cc/m^2{\cdot}day{\cdot}atm$ treatment during room temperature storage after cold storage for 15 days. A carbon dioxide concentration of these 2 treatments was exceeded the optimal MA and CA condition. There was no significant difference in ethylene concentration among 3 kind of laser treated non-perforated film treatments. A paprika packed with 100,000 $cc/m^2{\cdot}day{\cdot}atm$ non-perforated film showed the highest visual quality under the simulated long distance export condition. However, the firmness and soluble solids did not show any significant difference among 3 kind of laser treated non-perforated film treatments. Therefore, we may suggest that 100,000 $cc/m^2{\cdot}day{\cdot}atm$ laser treated non-perforated film was the proper film for MAP of paprika under long distance export condition that was $7{\pm}1^{\circ}C$ and RH 90% for 15 days, and then $20^{\circ}C$ and RH 55% for 7 days.

• Ecology and Resilient Infrastructure
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• v.2 no.4
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• pp.284-290
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• 2015

In this study, two hypotheses were examined to preliminarily verify for the vegetation recruitment and establishment on riparian bars in unregulated rivers; hydrologic regime change and nutrients influx into streams. In order to preliminarily verify the first hypothesis, precipitation patterns were analyzed during a period from March through to May when reeds, the most common riparian vegetation in Korea, germinate and start to grow in riparian areas. The results show that during the last 35 years, the total precipitation during the three-month period decreased by about 15 %, while the total annual one increased by about 15% in Korea. In order to verify the second hypothesis, a preliminary experiment was conducted with a set of two-vegetative flumes for one year. In this experiment, a stream flow with reeds on the riparian sand bars was simulated with a flume with reeds planted on the sand bed and water with a concentration of 3.5 mg of N flowing in the flume for four hours. For comparison, clean water was circulated in the same way in another flume for simulating a stream flow without N. The experimental results show that the growth rate of reeds in N-mixed flow exceeds that in clean water flow by about 30%. The above two results could explain the phenomenon of change in unregulated rivers from white river to green river in Korea, although they were obtained through limited extents of analysis and experiment.

• Journal of Digital Convergence
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• v.20 no.3
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• pp.251-264
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• 2022

The purpose of this study is to present factors and strategies for successful rewarded-crowdfunding of companies. For this, rewarded-crowdfunding based on the extended theory of planned behavior(E-TPB) by adding individual innovation and risk preference as extended variables, in addition to the basic variables of the theory of planned behavior(TPB), including attitude, subjective norm, and perceived behavior control. In addition, the moderating effect of rewarded-crowdfunding experience was confirmed. In addition, the moderating effect of the rewarded-crowdfunding experience was confirmed, and exploratory factor analysis and multiple regression analysis were conducted for questionnaires who were aware of the concept of rewarded-crowdfunding. As a result of testing the hypothesis, it was found that attitude, subjective norm, perceived behavioral control, and risk preference affect the intention to invest in rewarded-crowdfunding. Also, we could find that perceived behavior control and risk preference were moderately influenced by investor who had experience in rewarded-crowdfunding. Based on the research results, it has academic and practical value by presenting the direction of enhancing the success of rewarded-crowdfunding that companies can use as a way to raise funds and boost sales.

• Korean Journal of Environment and Ecology
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• v.22 no.6
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• pp.658-665
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• 2008

One of the characteristics of fluvial river channel with sand bed-material is the existence of movable sand bars not occupied with vegetation. However, sand bars at the Hahoe's reach of the Nakdong River showing a double-meandering channel has been changed into expanding vegetation area. Moreover, sand material, in recent years, has stopped moving to downstream in channel and the number and area of bare bars which did not occupied by vegetation have been decreased. In order to find out the mechanism, we carried out the channel characteristics surveys such as hydro-geomorphologic, soil physio-chemical and vegetation surveys were conducted twice on autumn season in 2005,2006. The results so far achieved showed that the reduced discharge of transported sediment and duration of dry season might be critical factors for the spread of luxuriant vegetation. The vegetation area was significantly expanded by floods exceeding the subsequent dominant flow discharge. Furthermore, the expansion of vegetation area was highly correlated with the supply of organic matter, nutrients and alteration of soil texture by sediment deposition during the flooding event.

• Composites Research
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• v.30 no.2
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• pp.116-125
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• 2017

The purpose of this study is to develop silicon carbide fiber showing an excellent mechanical properties under highly oxidative conditions at high temperature. Polycarbosilane(PCS) as a preceramic precursor was used for making the SiC fiber. PCS fiber was taken by melt spinning method followed by melting the PCS at $300{\sim}350^{\circ}C$ in N2 gas. The Curing of PCS fiber was carried out in air oxygen chamber, prior to high temperature pyrolysis. Degree of cure was calculated by characteristic peak's ratio of Si-H to $Si-CH_3$ in FT-IR spectra before and after curing of PCS fiber. The properties of SiC fiber was affected greatly by the degree of cure. The SiC fiber produced by controlling fiber tension during heat treatment showed good properties. The SiC fiber exposed to $1000^{\circ}C$ at air from 1 min. up to maximum 50 hrs showed around 60% reduction in tensile strength. We found that large amount of carbon content on the fiber surface after long-term exposure has resulted in lower tensile strength.

• Composites Research
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• v.24 no.4
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• pp.23-28
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• 2011

Recently CFRP laminate joints process by bolts and nets are developed rapidly in aircraft industries. However, there are serious drawback during jointing process. Many hole processes are needed for the manufacturing and structural applications using composite materials. Generally, very durable polycrystalline crystalline diamond (PCD) drill has been used for the CFRP hole process. However, due to the expensive price and slow process speed, chemical vapor deposition (CVD) diamond drill has been used increasingly which are relatively-low durability but easily-adjustable process speed via drill shape change and price is much lower. In this study, the comparison of hole process between PCD and CVD diamond coated drills was done. First of all, CFRP hole processbility was evaluated using the equations of hole processing conditions (feed amount per blade, feed speed). The comparison on thermal damage occurring from the CFRP specimen was also studied during drilling process. Empirical equation was made from the temperature photo profile being taken during hole process by infrared thermal camera. In addition, hole processability was compared by checking hole inside condition upon chip exhausting state for two drills. Generally, although the PCD can exhibit better hole processability, hole processing speed of CVD diamond drill exhibited faster than PCD case.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1073-1077
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• 2006

급속한 산업화로 인한 오염물질의 증가와 생물서식처의 감소는 수자원과 생태계를 위협하고 있다. 국내의 경우 수자원의 질을 개선하기 위해 '90년대 초부터 하수처리시설 등의 저감시설을 대폭 확충하였으나 현재까지 팔당호 등 주요상수원이 목표수질에 못 미치고 있으며 그 원인은 유입오염물질의 $22{\sim}37%$를 차지하는 비점오염원으로 지목되고 있다. 또한 생태.경관적 가치가 높은 수변지역은 각종 개발로 생물서식처가 급속도로 감소하여 종 다양성 보전 측면에서 대책마련이 시급한 실정이다. 이와 유사한 상황에 직면한 선진외국에서는 '하천회랑(river corridor)' 또는 '토양 및 생태시스템을 포함하는 수역과 육역의 점이(漸移)지대'를 의미하는 이른바 '수변완충지대(Riparian Buffer Zones)'의 오염정화 및 생태조성 효과 등의 연구를 통해 효율적 조성방안을 제시하고 있으며 다양한 형태로 현장에 적용하고 있다. RBZs의 일반적인 기능으로는, 유사나 오염물질의 여과 및 차단(필터링 효과), 영양염류의 저감, 하천변 식생을 통한 수자원의 정화 및 강턱의 안정화, 홍수로 인한 하천침식의 방지, 수변 생물 서식처 제공, 수변 그늘 제공에 의한 수온상승 방지, 심미 교육 위락 공간 제공 등이다. 본 연구에서는 외국의 RBZs(Riparian Buffer Zones)가이드라인을 참고하여 국내실정에 맞는 파일럿 규모의 시험완충지를 설계 및 조성하였다. 시험완충지는 남한강 연안에 초본류, 갈대류, 관목류, 자연식생, 혼합식생 등 5가지 'dry biotope'형태로 설치하여 1년간 계절별로 운영하였다. 또한 실험의 정량화와 다양한 조건변화를 위해 차수막, 위어, 유량.농도 조절장치, 라이시미터 등 보조시설을 설치하였고, 정기적인 모니터링을 실시하였다. 조사결과 외국사례를 살펴보면 RBZs의 적정 폭은 수질정화기능의 경우 $15{\sim}30m$, 생태서식처 기능은 최소 90m이상으로 제시되며, 시험완충지의 수질정화효과는 SS, T-N, T-P, TOC의 평균저감율이 각각 50%이상으로 나타났다. 식생모니터링 결과, 환삼덩굴 등 우점종의 잠식속도는 약 15일이며 갈대와 갯버들의 경우 우기시 인공목책호안과 동일한 침식방지 효과를 보이는 것으로 관찰되어 식생의 주기적인 모니터링과 지역 특성에 적합한 우점종 선정이 매우 중요한 것으로 판단된다.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.1637-1641
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• 2009

본 연구는 막공정을 이용하는 수처리기술에 있어서 최대 난점 중의 하나인 fouling 현상을 억제하기 위하여 여과방향의 반대방향에서 여과수를 지속적으로 분사하여 줌으로써 여과와 세정이 동시에 일어나는 동시세정방식을 평가하기 위한 것이다. 실험은 성균관대학교 환경플랜트 내에 pilot 실험지를 조성하여 실시하였으며, 실험원수는 오수처리방류수를 저류하는 연못수와 오수원수를 혼합하여 농도를 조절한 후에 저농도와 고농도 조건에서 실험을 실시하였다. 저농도 조건(SS 10$\sim$20 mg/L)에서는 연못의 HRT를 고려하여 일일 5시간 씩 8일간 가동하였고, 고농도 조건(SS 200 mg/L 이상)에서는 8시간씩 가동하였다. 저농도의 경우에는 가동기간 중 배수가 일어나지 않았고, 일일 운전 종료 후 유지관리를 위한 강제배수만 실시하였다. 고농도에서는 초기에 배수가 짧은 term으로 자주 일어났지만, 20분 이상의 비교적 긴 여과지속시간을 유지하였고 유입수 농도가 낮아지면서 배수타임이 점점 늘어나는 경향을 보였다. 이러한 결과는 동시세정방식에 의한 여과기술에 있어 유입수 농도가 fouling 발생빈도에 크게 영향을 미친다는 것을 의미하며, $5\;{\mu}m$의 미세막에서도 고농도 운전이 가능하다는 사실을 보여준다. 동시세정방식은 Rum Filter의 fouling을 억제하고 지속적인 운전을 가능하게 해주는 핵심기술이다. 세정 시 세정압력설정은 매우 중요한 운전인자 중 하나인데, 세정압력이 너무 클 경우에는 소요되는 동력이 많아져 효율적인 설계 및 운전에 장애요인이 될 수 있고, 너무 낮을 경우에는 세정이 제대로 되지 않고 여과막 내부와 외부의 압력차를 크게 가져와 배수타임이 빨라지는 결과를 초래한다. 따라서 적절한 세정압력을 파악하고 설정하기 위하여 세정압력을 변화시켜가면서 이에 따른 차압의 변화를 관측하여 보았다. 여과막의 공극과 세정압력에 변화를 주면서 실험을 한 결과, 세정압력이 커지면 여과막에 작용하는 부하가 약간 증가하는 것으로 나타났지만, 그 차이가 $0.02\;kg_f/cm^2$으로 나타나, $4.0\;kg_f/cm^2$ 이상의 세정압력에서 적용이 가능한 것으로 나타났다. 또한, 유입유량을 설정하기 위하여 $4.5\;kg_f/cm^2$의 세정압력을 유지한 상태로 유입유량을 점진적으로 증가시키면서 압력의 변화를 관측하였다. $5\;{\mu}m$에서는 180 LPM 및 200 LPM에서, $8\;{\mu}m$에서는 200 LPM에서 자체적으로 설정한 배수차압 상승분인 $0.1\;kg_f/cm^2$를 초과한 것으로 나타났고, $10\;{\mu}m$ 이상에서는 모두 200 LPM이상 처리해도 배수압력에 걸리지 않는 것으로 나타났다. 이러한 결과는 현재 본 시스템에 적용하고 있는 유입유량 기준치를 2배 이상 상회하는 결과로서 추가적인 실험을 통하여 기존 여과기술보다 여과지속시간이길고, 여과 flux가 높은 기술을 개발할 수 있을 것으로 판단된다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.10
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• pp.3626-3632
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• 2010

Some design changes were made to enhance the uniformity of temperature distribution inside the chamber of semiconductor test equipment. The design changes include the installation of adjustable airflow controller inside the chamber, the alignment of the centers of heater and match plate, the change in the size and the shape of holes in match plate base, and the addition of new holes of 2 mm diameter in order to allow airflow directly to the temperature sensors. In order to verify their effects, the temperature distributions inside the chambers were measured using 32 RTD sensors before and after the design changes. The temperature distributions were in the ranges of 87.1 to $91.5^{\circ}C$ ($90{\pm}2.9^{\circ}C$) and 89.5 to $90.8^{\circ}C$ ($90{\pm}0.8^{\circ}C$) before and after the design changes, respectively. The above temperature distribution after design changes was maintained for longer than 15 minutes, which satisfied the target temperature range of $90{\pm}1^{\circ}C$ for longer than 10 minutes.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.5
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• pp.590-597
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• 1985

A recursive geometric adaptive control method to compensate for machining straightness error in the finished surface due to tool deflection and guideway error generated by end milling process is developed. The relationship between the tool deflection and the feedrate is modeled by a modified Taylor's tool life equation. Without a priori knowledge on the variations off cutting parameters, time varying parameters are then estimated by an exponentially windowed recursive least squares method with only post-process measurements of the straightness error. The location error is controlled by shifting the milling bed in the direction perpendicular to the finished surface and adding a certain amount of feedrate with respect to the tool deflection model before cutting. The waviness error is compensated by adjusting the feedrate during machining. Experimental results show that location error is controlled within a range of fixturing error of the bed on the guideway and that about 60% reduction in the waviness error can be achieved within a few steps of parameter adaption under wide operating ranges of cutting conditions even if the parameters do not converge to fixed values.