• Journal of Microbiology and Biotechnology
• /
• 제20권2호
• /
• pp.363-369
• /
• 2010

This study was conducted to investigate the effects of different sanitizers and contact times on storage quality and microbial growth in fresh-cut broccoli. Fresh broccoli samples were cut into small pieces, washed each for 90 s and 180 s in normal tap water (TW), $100\;{\mu}/l$ chlorinated water (CL, pH 7), electrolyzed water (EW, pH 7.2) containing $100\;{\mu}/l$ free chlorine, or $2\;{\mu}/l$ ozonated water ($O_3$). Then, samples were packaged in 30-${\mu}m$ polyethylene bags and stored at $5^{\circ}C$ for 9 days. No significant differences were observed in gas composition and color parameters ($L^*$, $a^*$, $b^*$, and hue angle) among different sanitizers with contact times. No off-odor was detected during the storage. A longer contact time was not effective in reducing microbial population, except with $O_3$ washing. $O_3$ with 90 s was not much effective in reducing microbial population compared with Cl or EW. However, samples washed with $O_3$ for 180 s observed the lowest numbers of total aerobic and coliform plate counts. The result suggested that, a longer contact time of ozone can be used as a potential sanitizer to maintain the microbial quality and safety of fresh-cut broccoli.

• Journal of Communications and Networks
• /
• 제15권5호
• /
• pp.504-513
• /
• 2013

Communication in delay tolerant networks (DTNs) relies on message transport by mobile nodes, and a correct understanding of the node mobility characteristics is therefore crucial to the design of an efficient DTN routing protocol. However, previous work has mainly focused on uncovering all behaviors of node movement, which is not conducive to accurately detecting the specific movement characteristics of a different node. In this paper, we seek to address this problem based on a consideration of social relationships. We first consider social ties from both static and dynamic perspectives. For a static perspective, in addition to certain accidental events, social relations are considered for a long time granularity and tend to be stable over time. For a dynamic perspective, social relations are analyzed in a relatively short time granularity and are likely to change over time. Based on these perspectives, we adopted different efficient approaches to dividing node pairs into two classes, i.e., familiar and unfamiliar pairs. A threshold approach is used for static social ties whereas a density-based aggregation method is used for dynamic social relationships. Extensive experimental results show that both familiar and unfamiliar node pairs have the same inter-contact time distribution, which closely follows a power-law decay up to a certain point, beyond which it begins to exponentially decay. The results also demonstrate that the inter-contact time distribution of familiar pairs decays faster than that of unfamiliar pairs, whether from a static or dynamic perspective. In addition, we also analyze the reason for the difference between the inter-contact time distributions of both unfamiliar and familiar pairs.

• Tribology and Lubricants
• /
• 제36권5호
• /
• pp.262-266
• /
• 2020

Herein, we present a numerical investigation of wear analysis of sliding systems with a constant speed subjected to Archard's wear law. For this investigation, we compared two methods: eigen-wear analysis and adaptive meshing technique. The eigen-wear analysis is advantageous to predict the evolution of contact pressure due to wear using the initial contact pressure and contact stiffness. The adaptive meshing technique in finite element analysis is employed to obtain transient wear behavior, which needs significant computational resources. From the eigen-wear analysis, we can determine the appropriate element size required for finite element analysis and the time increment required for wear evolution by a dimensionless variable above a certain value. Since the prediction of wear depends on the maximum contact pressure, the finite element model should have a reasonable representation of the maximum contact pressure. The maximum contact pressure and wear amount according to this dimensionless variable shows that the number of fine meshes in the contact area contributes more to the accuracy of the wear analysis, and the time increment is less sensitive when the number of contact nodes is significantly larger. The results derived from a two-dimensional wear model can be applied to a three-dimensional wear model.

• 구강회복응용과학지
• /
• 제26권2호
• /
• pp.197-204
• /
• 2010

본 실험의 목적은 인공 치관의 수복을 통해 인접치간 접촉강도의 경시적 변화를 관찰하는 것이다. 인공 치관을 통한 단일 치관 수복이 필요한 12명의 성인에서 치아 삭제 전과 인공치관 적합 후의 시간 경과에 따른 접촉강도를 측정하였다. 그 결과 적합 직후의 인접치간 접촉강도는 처음 삭제 전의 접촉강도보다 컸으며 1-2주 이내에 치아삭제 전의 접촉강도와 유사한 양으로 변화하였고 2-4주 후까지 인접치간 접촉강도는 거의 변화가 없고 일정한 접촉강도를 유지하였다.

• 한국안광학회지
• /
• 제17권1호
• /
• pp.27-35
• /
• 2012

목적: 본 연구에서는 동일 재질 및 렌즈 파라미터를 가진 일반 소프트 콘택트렌즈와 써클 콘택트렌즈의 각막에서 중심안정위치와 움직임 양상을 비교하여 착색 여부에 따른 차이를 알아보고자 하였다. 방법: 눈물양이 정상인 20안을 대상으로 동일한 재질 및 파라미터의 일반 소프트 콘택트렌즈와 써클 콘택트렌즈를 각각 1일에 3시간씩 5일 동안 착용시키면서 각막에서의 중심안정위치와 반복적인 순목 후 콘택트렌즈의 이동거리 및 회전량을 측정하고 비교하였다. 결과: 일반 소프트 콘택트렌즈와 써클 콘택트렌즈 모두 착용 초기의 중심안정위치는 피팅 기준에서 벗어나는 경우가 있었으나 일반 소프트 콘택트렌즈의 경우는 착용 시간이 증가함에 따라 동공 중심으로 모이면서 모든 경우에도 피팅 기준에서 벗어나지 않는 적합한 중심안정위치로 변화되었다. 하지만, 써클 콘택트렌즈는 착용 시간이 증가하여도 수평 방향으로의 중심이탈이 여전히 존재하였다. 일반 소프트 콘택트렌즈와 써클 콘택트렌즈 모두 반복적인 순목 후 각막에서의 이동거리는 착용기간이 증가할수록 감소하였으나 두 콘택트렌즈 간에는 총 착용 기간이나 일일 착용 시간의 증가에 따른 차이는 통계적으로 유의하지 않았다. 반복적인 순목에 의한 써클 콘택트렌즈의 회전양은 착용기간이 증가하였을 때 일반 소프트 콘택트렌즈를 착용한 경우와 비교하여 통계적으로 유의한 차이가 있었다. 결론: 써클 콘택트렌즈의 각막에서의 위치 및 움직임은 일반 소프트 콘택트렌즈와 달라지며 이러한 차이는 착용기간이 증가하면 더 커짐을 밝혔다.

• 한국소음진동공학회논문집
• /
• 제22권3호
• /
• pp.253-263
• /
• 2012

With the local Hertz deformation on the contact point, the dynamic contact between a high-speed wheel and an elastic beam having a gap is numerically analyzed by solving the whole equations of motion of the wheel and the beam subjected to the contact condition. For the stability of the time integration the velocity and acceleration constraints as well as the displacement constraint are imposed on the contact point. Especially the acceleration contact condition on the gap is formulated, and it is demonstrated that the contact force variation computed by the velocity contact constraint or by the acceleration contact constraint agrees well with that computed by the displacement contact constraint. The numerical examples show that, when the wheel passes on the gap, the solution is governed by the stiffness of the local Hertzian deformation.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2010년도 하계학술대회 논문집
• /
• pp.115-115
• /
• 2010

This paper introduces a measurement system that measures behavior and electrical characteristics of overhead contact line irregular sections in real-time. For verification, we developed a prototype of the real-time overhead contact line irregular section behavior measurement system and a monitoring system for field tests. The current and temperature of contact wires and messenger wires were measured real-time by applying the system at KTX a commercial line. Therefore, acquiring data is possible with the developed system and this system that measures one of the fundamental and key factors, the catenary current, should be applicable to various areas such as detecting characteristics for designing overhead contact lines, enhancing speed, and enhancing energy.

• 한국전기전자재료학회논문지
• /
• 제20권3호
• /
• pp.281-285
• /
• 2007

Facilities of electric railway should be maintained only at night and it is necessary to maintain by human power because facilities are installed at a high place. This paper presents the development and application of a real-time data acquisition system for the characteristics measurement of overhead contact wires in electric railway. The system is designed to perform in the telemetry environments that developed to store data by wireless in a live wire state of 25 kV power source. The field test results show that the proposed technique and the developed system can be practically applied to measure characteristics of temperature, displacement, and strain on overhead contact lines.

• 상하수도학회지
• /
• 제31권4호
• /
• pp.321-328
• /
• 2017

Recently EC-MBR (Elctrocoagulation - Membrane Bio Reactor) has been suggested as one of alternative processes to overcome membrane fouling problems. Most important operational parameters in the EC-MBR are known to current density and contact time. Their effect on membrane filtration performances has been reported well, however, quantitative interrelationship between both parameters not been investigated yet. The purpose of this study is to give a kinetic model suggesting the current density and the contact time required to reduce the membrane fouling. The 4 different set of current densities (2.5, 6, 12 and $24A/m^2$) and contact times (0, 2, 6 and 12 hr) were selected as operational parameters. After each electro-coagulation under the 16 different conditions, a series of membrane filtration was carried out. The membrane fouling decreased as the current density and contact time increased, Total fouling resistances under different conditions, $R_t(=R_c+R_f)$ were calculated and compared to those of the controls ($R_0$), which were calculated from the data of experiments without electro-coagulation. A kinetic approach for the fouling reduction rate ($R_t/R_0$) was carried out and the equation ${\rho}^{0.46}_it=7.0$ was obtained, which means that the product of current density and the contact time needed to reduce the fouling in certain amounts (in this study, 10% of fouling reduction) is always constant.

• 한국안광학회지
• /
• 제13권4호
• /
• pp.43-49
• /
• 2008

목적: 본 연구에서는 UV-A 차단 콘택트렌즈의 UV-A 차단효과를 일반 콘택트렌즈의 효과와 비교하여 보고자 하였다. 방법: RNase A, catalase 및 superoxide dismutase(SOD)를 일반 콘택트렌즈(UV-A 차단율 20%) 및 자외선 차단 콘택트렌즈(UV-A 차단율 85%)로 차단하였을 때의 UV-A에 의한 변성을 아크릴아미드 겔 전기영동법으로 확인하였다. 효소의 용액은 각각 1, 3, 6, 24 및 96시간 동안 365 nm의 UV-A에 노출시켰으며, 콘택트렌즈에 의한 UVA차단 범위는 전안구를 덮는 RGP 렌즈, 소프트 콘택트렌즈, 안경의 크기를 계산하여 각각 50%, 70% 및 100%로 변화를 주었다. 결과: RNase A, catalase 및 SOD의 변성은 UV-A에 노출된 시간이 길어질수록 심하여졌다. 자외선차단 콘택트렌즈의 자외선 차단 효과는 일반 콘택트렌즈와 비교하여 보았을 때 모든 효소에서 차단 효과가 있음을 확인하였다. 콘택트렌즈로 차단된 범위가 줄어들수록 또한 UV-A에 노출된 시간이 길어질수록 자외선 차단 콘택트렌즈의 차단 효과는 감소됨을 알 수 있었다. 결론: 이상의 결과로 미루어 UV-A에 장시간 노출되었을 경우 자외선 차단 콘택트렌즈는 안구 내의 존재하는 효소를 보호하는 효과가 미흡할 것으로 생각되며, 따라서 햇볕 아래에서의 장시간 콘택트렌즈 착용은 충분한 고려를 하여야 할 것으로 제안할 수 있다.