• Restorative Dentistry and Endodontics
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• 제42권2호
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• pp.105-110
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• 2017

Objectives: This study investigated the cleaning ability of ultrasonically activated irrigation (UAI) and a novel activation system with reciprocating motion (EC, EasyClean, Easy Equipamentos $Odontol\acute{o}gicos$) when used with a relatively new chelating agent (QMix, Dentsply). In addition, the effect of QMix solution when used for a shorter (1 minute) and a longer application time (3 minutes) was investigated. Materials and Methods: Fifty permanent human teeth were prepared with K3 rotary system and 6% sodium hypochlorite. Samples were randomly assigned to five groups (n = 10) according to the final irrigation protocol: G1, negative control (distilled water); G2, positive control (QMix 1 minute); G3, QMix 1 minute/UAI; G4, QMix 1 minute/EC; G5, QMix 3 minutes. Subsequently the teeth were prepared and three photomicrographs were obtained in each root third of root walls, by scanning electron microscopy. Two blinded and pre-calibrated examiners evaluated the images using a four-category scoring system. Data were statistically analyzed using Kruskal-Wallis and Dunn tests (p < 0.05). Results: There were differences among groups (p < 0.05). UAI showed better cleaning ability than EC (p < 0.05). There were improvements when QMix was used with auxiliary devices in comparison with conventional irrigation (p < 0.05). Conventional irrigation for 3 minutes presented significantly better results than its use for 1 minute (p < 0.05). Conclusions: QMix should be used for 1 minute when it is used with UAI, since this final irrigation protocol showed the best performance and also allowed clinical optimization of this procedure.

• 정보처리학회논문지A
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• 제18A권2호
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• pp.75-80
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• 2011

최근 청소로봇을 위한 여러 가지 알고리즘들이 개발되면서 다양한 청소로봇들이 개발되고 있다. 그 중 청소로봇이 청소하는데 있어 청소시간의 제약이 있을 경우 효율적으로 청소할 수 있는 알고리즘인 DmaxCoverage 알고리즘이 있는데 이 알고리즘을 구현하는데 장애물이 존재하지 않는 비어있는 공간을 찾기 위해 Rectangle Tiling기법을 사용하고 있다. Map을 그리드 형태의 수많은 사각형으로 나타낼 경우 사각형을 찾는 기법 중 수학적 방법으로 Rectangle Tiling이 최적의 값을 찾아줄 수 있다. Rectangle Tiling 기법은 그리드 형식의 map에서 생성될 수 있는 사각형들의 모든 경우의 수를 찾는 것이다. 이때 그리드선의 간격이 촘촘하고 map의 크기가 클 경우 많은 사각형이 생성됨으로 많은 시간을 소모해야 하는 문제점이 있다. 본 논문에서는 Rectangle Tiling에 근접한 정확성과 보다 개선된 속도를 제공하는 Four Direction Rectangle Scanning(FDRS)기법을 제안한다. FDRS기법은 존재하는 모든 사각형을 찾는 것이 아니라 물체가 존재하는 셀의 상하좌우만을 검색하여 빈 공간을 찾는 기법이다. 이 두 알고리즘을 비교하여 FDRS의 효율이 뛰어남을 실험을 통해 보여준다.

• 한국농공학회논문집
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• 제61권4호
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• pp.63-73
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• 2019

Coastal and fishing facilities are gradually deteriorating in function due to the continual accumulation of soil sediments, which has affected local economic activities. Currently, there are many methods to remove soil sediments, but these methods are either a temporary solution or require a repetitive removal of the soil sediments, which is a huge financial burden for the maintenance of the facilities. To solve these problems, this study proposed a non-power soil cleaning system and evaluated field applicability by carrying out field model tests. The conditions for the evaluation focused on the drainage-elapsed time and drainage-outflow velocity according to the water level change in the water tank. In the field test, silty clay and sand were separately installed, and sedimentation soil removal test was practiced. As a result, the system was verified to have a sufficient outflow velocity for the removal of soil sediments. In addition, a generalization equation that can be used in different regions of the tide was suggested in this study. These results will greatly contribute to removing soil sediments in ports and dike gate facilities on the southwest coast. Since the system is an eco-friendly technology that does not require additional energy, thus it is expected to contribute to maintenance of sustainable facility performance as well as economic effect in the future.

• 청정기술
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• 제16권4호
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• pp.265-271
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• 2010

경유차 매연저감장치에서 비활성화된 디젤산화촉매(DOC)를 대상으로 여러 가지 조건에서 재제조한 후, 재제조된 DOC의 일산화탄소(CO)와 탄화수소화합물(THC)의 저감효율과 촉매물성 특성을 분석하여 비활성화된 DOC 촉매에 대한 재제조 효과를 관찰하였다. 재제조된 DOC촉매에 대한 오염물질 저감성능 평가는 디젤엔진 다이나모 장치를 이용, 배기가스를 일부 우회시켜 온도와 공간속도조절이 가능한 촉매반응장치로 수행하였으며, 촉매물성 분석은 광학현미경, EDX, ICP, TGA 그리고 porosimeter를 이용하였다. 연구수행 결과 비활성화된 DOC 촉매를 본 연구에서 적용된 고온배소세정, 산성/염기성용액에 의한 초음파세정, 세정 후 촉매활성성분 재함침에 의한 재제조를 수행할 경우, 재제조된 DOC 촉매의 성능이 신품 성능의 90% 이상으로 회복되는 것을 확인하였으며, 광학현미경, EDX, TGA와 ICP등의 분석을 통해 본 연구조건에서의 재제조 과정으로, 촉매의 활성 저하 원인이 되었던 각종 불순 성분 대부분이 비활성화된 DOC 촉매로부터 제거되는 것을 확인하였다.

• Bulletin of the Korean Chemical Society
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• 제30권10호
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• pp.2309-2317
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• 2009

Depurination, the release of purine bases from nucleic acids by hydrolysis of the N-glycosidic bond, gives rise to alterations of the cell genome. Though cells have evolved mechanisms to repair these lesions, unrepaired apurinic sites have been shown to have two biological consequences: lethality and base substitution errors. 2-Bromopropane (2-BP) is used as an intermediate in the synthesis of pharmaceuticals, dyes, and other organics. In addition, 2-BP has been used as a replacement for chloroflurocarbons and 1,1,1-trichloroethane as a cleaning solvent in electronics industry. However, 2-BP was found to cause reproductive and hematopoietic disorders in local workers exposed to it. Owing to the toxicity of 2-BP, there has been a tendency to use 1-BP as an alternative cleaning solvent to 2-BP. However, 1-BP has also been reported to be neurotoxic in rats. Though $N^7$-guanine adduct of 2-BP has been reported previously, massive depurination of the nucleosides and calf thymus DNA was observed in this study. We incubated the nucleosides (ddG, dG, guanosine, ddA, dA and adenosine) with excess amount 2-BP at the physiological condition (pH 7.4, $37\;{^{\circ}C}$), which were analyzed by HPLC and LC-MS/MS. In addition, the time and dose response relationship of depurination in nucleosides induced by 2-bromopropane at the physiological condition was investigated. Similarly, incubation of calf-thymus DNA with the excess amount 2-BP at the physiological condition was also performed. In addition, the time and dose response relationship of depurination in calf-thymus DNA induced by 2-BP at the physiological condition was investigated. Those results suggest that the toxic effect of 2-BP could be both from the depurination of nucleosides and DNA adduct formation.

• Journal of Radiation Protection and Research
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• 제40권2호
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• pp.101-109
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• 2015

대기 중에 존재하는 우라늄 동위원소 분석을 위해서 일반적으로 알파분광분석법(alpha spectrometry)이 사용되고 있으며, 정확한 분석을 위해서는 정밀한 방사화학 전처리가 요구된다. 보편적인 방사화학 전처리 방법으로는 회화법(ashing method) 및 알칼리 용융법(alkali fusion method)가 있다. 그러나 회화법의 경우 전처리 시간이 길어 빠른 분석이 어렵다는 단점이 있으며, 이와 달리 알칼리 용융법은 단시간 내에 전처리가 가능하다는 장점은 있으나 보편적으로 전처리 장비의 무게가 무겁고 분석 소요 비용 역시 상당히 높다는 단점이 있다. 이러한 단점들은 신속한 분석 결과가 요구되는 방사능 사고 분석 또는 IAEA 안전조치 물자재고 검사(Physical Inventory Verification, PIV) 수행시, 효율성을 저하시키는 원인이 된다. 이에 본 연구에서는 간편하면서도 주어진 짧은 시간 내에 공기 중 우라늄 동위원소 분석을 완료하는 것을 목적으로, 초음파 세척법(ultrasonic cleaning method)을 이용한 새로운 방사화학 전처리 방법을 개발하였다. 또한 초음파 세척법의 효율성 분석을 위해 전처리 소요시간, 편의성, 소요비용, 우라늄 동위원소 회수율의 측면에서 기존의 방법들과 비교 분석하였다. 동일 조건의 공기 포집시료에 대해 비교실험을 수행한 결과, 본 연구에서 개발한 초음파 세척법을 활용한 공정은 상대적으로 전처리 시간도 짧고, 이동이 간편하며, 저가이며, 단순함에도 불구하고 기존 방식과 비교하여 유사한 회수율을 보였다.

• 한국세라믹학회지
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• 제36권8호
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• pp.863-870
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• 1999

SOI(silicon on insulafor) was fabricated through the direct bonding using (100) Si wafer and 4$^{\circ}$off (100) Si wafer to investigate the stacking faults in silicon at the Si/SiO2 oxidized and bonded interface. The treatment time of wafer surface using MSC-1 solution was varied in order to observe the effect of cleaning on bonding characteristics. As the MSC-1 treating time increased surface hydrophilicity was saturated and surface microroughness increased. A comparison of surface hydrophilicity and microroughness with MSC-1 treating time indicates that optimum surface modified condition for time was immersed in MSC-1 for 2 min. The SOI structure directly bonded using (100) Si wafer and 4$^{\circ}$off (100) Si wafer at the room temperature were annealed at 110$0^{\circ}C$ for 30 min. Then the stacking faults at the bonding and oxidation interface were examined after the debonding. The results show that there were anomalies in the gettering of the stacking faults at the bonded region.

• 가정과삶의질연구
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• 제20권3호
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• pp.139-156
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• 2002

The purpose of this study is to compare the patterns of time use between Korean and USA families. The data for 353 Seoul-based Korean families with two children living in Seoul and 130 USA families with two children living in the State of Utah were collected using a structured questionnaire and time diary. The major findings were as the following: 1. The Korean couples spent more time at personal care, paid work, and travel than the USA couples did, while the USA couples spent more time at housework and social-cultural activities than the Korean couples did. 2. The Korean wives spent more time doing food and clothing related housework than the USA wives did. Compared with the Korean wives, however, the time spent at house cleaning and management, family care and shopping and home management were longer than USA wives. The time U.S. husbands engaged in housework was much greater than by the Korean husbands. 3. Regardless of sex and school level, the Korean children spent less time at sleeping/rest, housework and socio-cultural activities and more time at eating and learning than those of U.S. These time use patterns of the families in both countries may reflect the differences of the cultural contexts, social norms, life styles, and the degrees of urbanization. To fully explain the findings, further study on the differences in social and cultural factors between the two countries is needed.

• 한국CDE학회논문집
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• 제16권1호
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• pp.61-72
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• 2011

As the customer's needs for diverse colors, the process of bus painting shop is becoming more and more complex. In particular, frequent changes of paint colors in each spray process require the cleaning of the painting nozzles and setting them up for the new paints, which results in increased time and cost and reduced production. This also increases environmental influences. This paper proposes, as a solution to this issue, the use of color selection field (CSF). CSF is physically a system of conveyors that are used to rearrange objects in a flow line. CSF is proposed, in this paper, to be introduced right before the spray process so that buses are better grouped according to their desired colors. Various parameters of the CSF, such as the number of conveyors and algorithms to determine the rearranged sequence of buses, have been determined by running simulations using the digital manufacturing technology, and investigating the simulation results. As an outcome of the proposed solution, the CSF system is expected to reduce approximately 30% of the nozzle cleaning cost for a Korean motor company case, which will not only benefit the company economically, but will also benefit the environment.

• 동력기계공학회지
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• 제13권6호
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• pp.63-69
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• 2009

The experiment was performed to check operating characteristics of fouling auto removal apparatus for multi pass type heat exchanger using ejector. The results showed as following. The ejector suction flow rate increased with the head of operating pump of ejector. Proper suction flow rate showed $7.2{\sim}10.2m^3/h$ for ball collection in case of pump head 35~50m. The head of ejector outlet pipe is below 4.1m in case of 40m, the head of operating pump of ejector to confirm ejector suction flow rate 8.4m3/h. Lattice space of ball separator is allowed 6~10.3mm in ranges of ball diameter are 15~25mm and when mass flow of cooling water is 3.0m/sec. Average of passing time of balls is 1.2~2.8sec depend on the velocity of flow and the size of balls.