• International Journal of Oral Biology
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• v.40 no.3
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• pp.143-146
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• 2015

The purpose of this study was to compare the effect of different methods of hand washing by counting the number of bacteria on the hand surface. Eighteen clinicians were chosen and divided into three groups, consisting of six clinicians each. Culturing of the right raw palms of all individuals was performed. Individuals in the control group washed hands for 5 seconds with antimicrobial soap. Group 1 washed their hands for 10 seconds with antimicrobial soap. Group 2 washed with an instant alcohol-based hand sanitizer. After the respective washes, re-culturing of the right raw palm was done for each member of all groups. The colony-forming units (CFU) were calculated at each time point, and the reduction rate of CFU among the three groups were statistically evaluated using student t-test. All groups showed a significant decrease in CFU, according to the time applied (P<0.01). In addition, the reduction rate of CFU between the groups were statistically evaluated with ANOVA (P<0.01). It showed statistically difference between the control group and group 1, control group and group 2. The present study confirmed that the hand washing method with antimicrobial soap for 10 seconds and hand sanitizer, including alcohol, were excellent for decreasing the number of bacteria on the hand surface.

• Journal of Korean Society of Rural Planning
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• v.26 no.2
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• pp.13-24
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• 2020

This study analyzed the management efficiency of local food stores that are increasing recently. The analysis targeted 25 local food outlets in Jeonbuk area, and the analysis method analyzed the efficiency by CCR model. The input variables used to analyze the input-oriented efficiency of local food stores are business expenses, employees, organizational number of participating farms, and number of items, and sales are used as output variables. The main contents of the analysis are as follows. First, local food outlets increased due to support projects such as the government, local governments, and agricultural cooperatives, but their dependence was high. Second, the management efficiency of 25 local food stores in Jeonbuk is 28.0% when the efficiency is 1.000, and 72.0% of inefficient local food stores. Third, considering the projection point and the reference group, there was room for improvement in input variables. Therefore, it was determined that improvement efforts are needed to secure the continuity of local food outlets in the future. However, this study will require review of variable selection and analysis methods for further analysis.

• Nuclear Engineering and Technology
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• v.32 no.5
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• pp.433-445
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• 2000

The interfacial area concentration (IAC) is one of the most important parameters in the two-fluid model for two-phase flow analysis. The IAC can be measured by a local conductivity probe method that uses the difference of conductivity between water and air/steam. The number of sensors in the conductivity probe may be differently chosen by considering the flow regime of two-phase flow. The four sensor conductivity probe method predicts the IAC without any assumptions of the bubble shape. The local IAC can be obtained by measuring the three dimensional velocity vector elements at the measuring point, and the directional cosines of the sensors. The five sensor conductivity probe method proposed in this study is based on the four sensor probe method. With the five sensor probe, the local IAC for a given referred measuring area of the probe can be predicted more exactly than the four sensor probe. In this paper, the mathematical approach of the five sensor probe method for measuring the IAC is described, and a numerical simulation is carried out for ideal cap bubbles of which the sizes and locations are determined by a random number generator.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.866-870
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• 2008

In this study, we designed cold gas propulsion system with minimum 0.25 mm nozzle and micro-thrust measurement system to analyze flow characteristic of micro propulsion system in ambient and vacuum condition. Argon and Nitrogen are used for propellant and the result of experiments is compared with CFD analysis and theory. But there is a point where reduced scale versions of conventional propulsion systems will no longer be practical. Therefore, a fundamentally different approach to propulsion systems was taken. That is thermal transpiration based micro propulsion system. It has no moving parts such as lubricants, pressurizing system and can pump the gaseous propellant by temperature gradient only(cold to hot). We are advancing basic research of propulsion system based on thermal transpiration in vacuum conditions and had tried experiment process and theoretical access in advance. To characterize membrane of Knudsen pump, we select Polyimide material that has low thermal conductivity(0.29 W/mK) and can stand high temperature($300^{\circ}C$) for long time. And we fabricated hole diameter 1, 0.5, 0.2, 0.1 mm using precision manufacturing. Experimental results show that pressure gradient efficiency of Knudsen pump is increased to maximum 82% according to Knudsen number and thick membranes are more effective than thin membranes in transition flow regime.

• Nuclear Engineering and Technology
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• v.51 no.2
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• pp.533-538
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• 2019

The mechanical-collimation imaging is the most mature technology in prompt gamma (PG) imaging which is considered the most promising technology for beam range verification in proton therapy. The purpose of the present study is to compare the performances of two mechanical-collimation PG cameras, knife-edge (KE) camera and multi-slit (MS) camera. For this, the PG cameras were modeled by Geant4 Monte Carlo code, and the performances of the cameras were compared for imaginary point and line sources and for proton beams incident on a cylindrical PMMA phantom. From the simulation results, the KE camera was found to show higher counting efficiency than the MS camera, being able to estimate the beam range even for $10^7$ protons. Our results, however, confirmed that in order to estimate the beam range correctly, the KE camera should be aligned, at least approximately, to the location of the proton beam range. The MS camera was found to show lower efficiency, being able to estimate the beam range correctly only when the number of the protons is at least $10^8$. For enough number of protons, however, the MS camera estimated the beam range correctly, errors being less than 1.2 mm, regardless of the location of the camera.

• Geomechanics and Engineering
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• v.36 no.1
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• pp.71-81
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• 2024

This study analyzes the pull-out behavior of tunnel-type anchorage under various joint conditions, including joint direction, spacing, and position, using a finite element analysis. The validity of the numerical model was evaluated by comparing the results with a small-scaled model test, and the results of the numerical analysis and the small-scaled model test agree very well. The parametric study evaluated the quantitative effects of each influencing factor, such as joint direction, spacing, and position, on the behavior of tunnel-type anchorage using pull-out resistance-displacement curves. The study found that joint direction had a significant effect on the behavior of tunnel-type anchorage, and the pull-out resistance decreased as the displacement level increased from 0.002L to 0.006L (L: anchorage length). It was confirmed that the reduction in pull-out resistance increased as the number of joints in contact with the anchorage body increased and the spacing between the joints decreased. The pull-out behavior of tunnel-type anchorage was thus shown to be significantly influenced by the position and spacing of the rock joints. In addition, it is found that the number of joints through which the anchorage passes, the wider the area where the plastic point occurs, which leads to a decrease in the resistance of the anchorage.

• School Mathematics
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• v.17 no.2
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• pp.241-255
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• 2015

The purpose of this study is to analyze teachers' understanding on generating random number in Monte Carlo simulation and to provide educational implications in school practice. The results showed that the 70% of the teachers selected wrong ideas from three types for random-number as strategies for problem solving a probability problem and also they make some errors to justify their opinion. The first kind of the errors was that the probability of a point or boundary was equal to the value of the probability density function in the continuous probability distribution. The second kind of the errors was that the teachers failed to recognize that the sample space has been changed by conditional probability. The third kind of the errors was that when two random variables X, Y are independence of each other, then only, joint probability distribution is satisfied $P(X=x,\;Y=y)=p(X=x){\times}P(Y=y{\mid}X=x)$.

• Journal of the Korean Institute of Navigation
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• v.9 no.1
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• pp.1-40
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• 1985

The transport of cargoes carried by coastal and ocean-going vessels has increased with the rapid growth of the Korean economy these days. This increase of the sea-borne cargoes has made the Korean coastal traffic so congested that this can be a cause of large pollution as well as great marine casualties such as loss of human lives and properties. Marine casualties generally result from the complicated interaction of natural and human factors; the former being the topographic, marine traffic volume and meteorological conditions, and the latter being the quality of seafares. In this paper, the authors analyse the trend of marine casualties in the Korean coastal and clear up the cause of accidents and examine closely the mutual relations among sea accidents, weather conditions, and marine traffic volume. These accidents are classified into several patterns on hte point of view of ship's size, ship's type and ship's age and its characteristics of each pattern are described in detail. Also, the authors estimate the amount of economical losses resulting from marine casualties which are classified into the accident patterns, and clarify the effects of those losses on B/B(Balance Sheet) and P/L(Profit & Loss) of Korean shipping companies and Korean national economy. The analyzed results of marine casualties are summarized as follows: 1) The average number of sea accidents is 248 cases per year with the loss of 107 persons during last 13 years. 2) Collision is the top of causes of sea accidents (approx. 36.4%), shipwreck the second (approx. 20.3%), agroung the third rank (approx. 18.2%). 3) The ship's number under 1, 000G/T is approx. 74% of total ship's number of accidents. 4) 80% of total number of marine accidents is taken plact at the coastal waters. (involved ports & narrow channels) 5) Marine casualties are occur likely to in the night, the winter and the summer. 6) The average amount of economical losses is approx. 18.5 billion won. (approx. 0.14% of GNP) 7) Shipwreck is the top of the amount of economical losses (approx. 60.4%), collision the second (aprox. 24.5%), aground the third (approx. 9.9%). 8) The amount of economical losses is approx. 5.24% of gross capital of shipping co., 1.24% of shipping revenue, 1.38% of shipping total income in 1983.

• Journal of Acupuncture Research
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• v.27 no.2
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• pp.115-121
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• 2010

Objectives : Based on a national sample survey, we present an analysis of the current situation in the use of moxibustion therapeutics by qualified medical practitioners in Korea. Methods : The survey population of 11,737 hospitals is stratified by administrative regions, and 331 of them are randomly selected from the list of hospitals. The same number of Korean medical doctors is interviewed under the computer-assisted telephone interviewing(CATI) system. The bound on the error of estimation is ${\pm}\;5.0%$ point. Results : Of the 331 Korean medical doctors surveyed, 69% have used moxibustion therapy for remedial treatment. About half of those doctors have employed the therapy for their patients over 30%. The average number of acupuncture points per treatment using the therapy mostly ranges 1 between 5. The percent of practitioners, who have the number of average minutes less than 20 in treatment, is 74%. The number of practitioners who primarily use modified moxibustion is 4 times as many as that of those using traditional moxibustion. Conclusions : Considering the survey results, if the laser heater, alternative to conventional moxibustion, which not only gives high thermal effect but also reduces both the users inconvenience and side effects, are developed, it may benefit more patients as well as Korean medical doctors.

• Journal of Communications and Networks
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• v.11 no.5
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• pp.518-528
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• 2009

IEEE 802.11 wireless local area network (WLAN) has become the prevailing solution for wireless Internet access while transport control protocol (TCP) is the dominant transport-layer protocol in the Internet. It is known that, in an infrastructure-based WLAN with multiple stations carrying long-lived TCP flows, the number of TCP stations that are actively contending to access the wireless channel remains very small. Hence, the aggregate TCP throughput is basically independent of the total number of TCP stations. This phenomenon is due to the closed-loop nature of TCP flow control and the bottleneck downlink (i.e., access point-to-station) transmissions in infrastructure-based WLANs. In this paper, we develop a comprehensive analytical model to study TCP dynamics in infrastructure-based 802.11 WLANs. We calculate the average number of active TCP stations and the aggregate TCP throughput using our model for given total number of TCP stations and the maximum TCP receive window size. We find out that the default minimum contention window sizes specified in the standards (i.e., 31 and 15 for 802.11b and 802.11a, respectively) are not optimal in terms of TCP throughput maximization. Via ns-2 simulation, we verify the correctness of our analytical model and study the effects of some of the simplifying assumptions employed in the model. Simulation results show that our model is reasonably accurate, particularly when the wireline delay is small and/or the packet loss rate is low.