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The Estimation of Shear Stress in Uniform and Nonuniform Flow by the Entropy Concept (엔트로피 개념을 이용한 개수로에서 등류 및 부등류 흐름의 전단응력 산정)

  • Choo, Yeon Moon;Choo, Tai Ho;Yang, Da Un;Kim, Joong Hoon
    • Journal of Wetlands Research
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    • v.19 no.2
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    • pp.202-210
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    • 2017
  • Shear stress is one of the most important mechanical factors used in various fields and is important for the design of artificial channels. Current shear stresses have been used in the past, but there are factors that are difficult to actually measure or calculate, such as bed shear stress and energy slope in the equation used. In particular, the energy slope is a very difficult factor to estimate, and it is difficult to estimate the slope and flow velocity of the boundary layer although the energy slope can be used to obtain the shear stress distribution. In addition, the bed shear stress among the shear stress distribution is very difficult to measure directly, and the research is somewhat slower than the velocity. In this study, we have studied the simple calculation of the average flow velocity and the shear stress distribution using entropy M without reflecting the energy gradient, and we used existing laboratory data to demonstrate the utility of the applied equation. The stress distribution in the graphs was comparatively analyzed. In the case of the uniform flow and the non-uniform flow, the correlation coefficient was almost identical to 0.930-0.998.

A Chromosomal Study on the Genus Cobitis (Pisces : Cobitidae) in the Southern Part of Korea (한국 남부지방에 서식하는 기름종개속(Cobitis) 어류의 핵형 비교)

  • KIM Ik-Soo;LEE Ji-Hyun
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.19 no.3
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    • pp.257-264
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    • 1986
  • The Chromosomes of five cobitid fishes, Cobitis taenia taenia, C. taenia lutheri, C. taenia striata, C. longicorpus and C. koreensis were studied. The karyotypic studies were based on the observations from the flame-drying preparations. The results obtained such as the number of somatic chromosomes, the type of chromosomes according to the centromeric loci and the number of chromosomal arm(AN) were as follows: C. longicorpus, 2n=50, 12m-8sm-30a, AN=70; C. koreensis, 2n=50, 10m-12sm-28a, AN=72; C. taenia taenia, 2n=48, 14m-4sm-30a, AN=66: C. taenia lutheri, 2n=50, 10m-6sm-34a, AN=66; and C. taenia striata, 2n=50, 10m-6sm-34a, AN=66. Peculiarly, in the case of C. taenia lutheri the chromosome number of somatic diploid was found to be 48-51, however, the number of chromosomal arm was 66, irrespective of the difference in the numbers of each somatic genome. It was confirmed there exists the Robertsonian event, one of the chromosomal polymorphism in C.t. lutheri. It was remarked taxonomically that the karyotype of C. taenia taenia of Korea having 48 diploid chromosomes was not identical with that of Europe and Japan with 50 chromosomes. Based on the karyotype analysis the Korean cobitid fishes can be classified roughly into three species groups according to arm numbers and diploid numbers; 1) C. taenia taenia, C. taenia lutheri, C. taenia striata 2) C. koreensis, C. longicor pus, C. rotundicaudata and 3) C. granoei.

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A Practical standard Air Flow Generator System to Calibrate and Compare Performance of Two Different Respiratory Air Flow Measurement Modules (호흡기류 계측모듈의 교정과 성능 비교를 위한 실용적인 표준기류 생성 시스템)

  • Lee, In-Kwang;Park, Mi-Jung;Lee, Sang-Bong;Kim, Kyoung-Ok;Cha, Eun-Jong;Kim, Kyung-Ah
    • Journal of Biomedical Engineering Research
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    • v.36 no.4
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    • pp.115-122
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    • 2015
  • A standard air flow generator system was developed to generate air flows of various levels simultaneously applied to two different air flow transducer modules. Axes of two identical standard syringes for spirometer calibration were connected with each other and driven by a servo-motor. Linear displacement transducer was also connected to the syringe axis to accurately acquire the volume change signal. The user can select either sinusoidal or square waveform of volume change and manually input any volume as well as maximal flow rate levels ranging 0~3 l and 0~15 l/s, respectively. Various volume and flow levels were input to operate the system, then the volume signal was acquired followed by numerical differentiation to obtain the air flow signal. The measured volumes and maximal air flow rates were compared with the user input data. The relative errors between the user-input and the measured stroke volumes were all within 0.5%, demonstrating very accurate driving of the system. In case of the maximal flow rate, relatively large error was observed when the syringe was driven very fast within a very short time duration. However, except for these few data, most measured flow rates revealed relative errors of approximately 2%. When the measure and user-input stroke volume and maximal flow rate data were analyzed by linear regression analysis, respectively, the correlation coefficients were satisfactorily higher than 0.99 (p < 0.0001). These results demonstrate that the servo-motor controls the syringes with enough accuracy to generate standard air flows. Therefore, the present system would be very much practical for calibration process as well as performance evaluation and comparison of two different air flow transducer modules.

A Study on Problems and Improvement of Personal Protective Regulations in Security Industry Act (경비업법상 신변보호 관련 규정의 문제점과 개선방안)

  • Park, Jung-Sub
    • Korean Security Journal
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    • no.51
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    • pp.81-100
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    • 2017
  • Recently, Crime patterns in our society are diversifying as followed on the urbanization of population and the influx of immgrants. Existing murder, kidnap, sexual assault, etc. Especially, the crimes such as school violence, dating violence, domestic violence, violent abuse and even social hatred a crime, motiveless crime are spreading into every phase of national life. Due to the social situation, the sharp increase in demand for personal protection, the scale of private security industry has been constantly expanded. Following this trend, the personal protective regulations in Security Industry Act has been revised several times since the it was enacted in 1995. However, despite the fact that the legal and institutional aspects should have been amended and improved systematically according to the industrial development, the regulations adopted initially adopted has been maintained so far, which have resulted in various problems as they could not coincide with the purpose of private security, being divorced from the reality of private security industry and social changes. Especially, in the case of personal protection service and facility security service, the legal requirements of both services are identical with each other in terms. Such legal systems may cause confusion to security businesses and employees, or the police managing and supervising them, regarding the scope and duties of security services. In order to improve such problems, the regulations of permission requirement that the personal protective regulations in Security Industry Act should be revised system. In this study, relevant personal protection provisions prescribed in the Security Industry Act have been reviewed critically in this paper. And also the regulations were review of those personal protection provisions enacted in security industry Act, so that the improvement plan for the personal protection provisions that are apposite to the cases in this country could be suggested in order to amend the current laws and provide real grounds for the law enforcement.

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Precipitation of Rare Earth Chlorides in a LiC-KCl Eutectic Molten Salt (LiCl-KCl 공융염 내에서 희토류염화물들의 침전)

  • Cho, Yung-Zun;Yang, Hee-Chul;Eun, Hee-Chul;Kim, Eung-Ho;Kim, In-Tae
    • Applied Chemistry for Engineering
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    • v.18 no.4
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    • pp.361-365
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    • 2007
  • The precipitation reaction of some rare earth chlorides ($Ce/Nd/GdCl_3$) in a LiCl-KCl molten salt has been carried out by reaction with oxygen. Identification of rare earth precipitates by reaction with oxygen and effects of oxygen sparging time (max. 420 min) and molten salt temperature ($450{\sim}750^{\circ}C$) on conversion were investigated. In this study, regardless of the oxygen sparging time and the molten salt temperature, oxychlorides (REOCl) for $NdCl_3$ and $GdCl_3$, and an oxide ($REO_2$) for $CeCl_3$ are formed as a precipitate, which are identical with the estimation results of Gibbs free energy of reaction (${\Delta}G_r$). The conversion of rare-earth chlorides into insoluble precipitates was described by using a conversion ratio. The conversion ratio increased exponentially with the oxygen sparging time and finally showed asymptotic value, over 0.999 at $750^{\circ}C$ of the molten salt temperature and over 300 min of sparging time conditions. The conversion ratios were increased with the molten salt temperature. In case of $CeCl_3$, when the sparging time exceed 60 min, the values of the conversion ratio were nearly constant over 0.999 in all experimental temperature conditions.

Effect of Oriental Melon Vinegar Treatment on Growth and Disease Control of Oriental Melon (참외식초 처리가 참외 생육 및 병충해 방제에 미치는 영향)

  • 주길재;안성호;홍순보;박춘근;최원경;이기동
    • Journal of Life Science
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    • v.14 no.1
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    • pp.67-71
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    • 2004
  • Oriental melon vinegar was prepared by two stage fermentations of alcohol and acetic acid. In the alcohol fermentation using oriental melon residual products, alcohol content showed 7.43% in 17$^{\circ}$ brix of initial sugar concentration and 80 h of fermentation time. In the acetic acid fermentation using oriental melon alcohol, acidity showed 5.25% in 250rpm of agitation rate and 200 h of fermentation time. The cultivation esults of oriental melons using its vinegar are as follows. Quantity and quality of samples treated with 500, 1,000 and 2,000 times of oriental melon vinegar were higher than that of control : weight, quality, sugar content and goods production rate were higher to degree of 33∼42 g/piece, 370 ∼460kg/10a, 0.6∼.9$^{\circ}$ Brix, 2∼5%, respectively. Coods production yield of samples treated with 500, 1,000 and 2,000 times of oriental melon vinegar was higher (400∼610 kg/10a) than that of control. The results of control of powdery mildew on oriental melons using oriental melon vinegar as the diluted solution with 500 and 1000 times were identical for control value that used by agrochemical. Powdery mildew were exterminated by 2nd treatment of the diluted solution. In case of aphids, the diluted solution with 500, 1,000 and 2,000 times of oriental melon vinegar exterminated thoroughly by 2nd treatment.

Characteristics Testing of the ECT Bobbin Probe for Steam Generator Tube Inspection of Nuclear Power Plant (원전 증기발생기 전열관 와전류검사 보빈탐촉자의 특성 시험)

  • Nam, Min-Woo;Lee, Hee-Jong;Cho, Chan-Hee;Yoo, Hyun-Joo
    • Journal of the Korean Society for Nondestructive Testing
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    • v.30 no.4
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    • pp.386-395
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    • 2010
  • The steam generator management program(SGMP) has recently defined the procedures for the qualification of eddy current hardware and technique. These procedures provide two basic methods for qualification. The first way is to qualify the equipment or the probe by using the flaw mechanism and method of the pulled tubes from the heat exchangers or the artificial flawed tubes. The second way is to verify the equivalency with the characteristics of the qualified equipment or probe. In this case, the qualified equipment or probe may be modified to substitute or replace instruments or probes without re-qualification provided that the range of essential variables defined in the examination technique specification sheet are met. This study is to describe the result of the comparative performance evaluation of bobbin coil eddy current probes manufactured by KEPCO Research Institute and probes manufactured by a foreign manufacturer. As a result of this study, although there were minor differences between the two kinds of probes, it was evaluated that the two kinds of probes were almost identical in the significant performance characteristics described in the KEPCO Research Institute guideline.

Evaluation of the consistency and homogeneity of artificial latent fingerprint printed with artificial sweat (인공땀으로 출력한 인공지문의 균질성 평가)

  • Hong, Ingi;Hong, Sungwook
    • Analytical Science and Technology
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    • v.28 no.1
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    • pp.26-32
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    • 2015
  • The consistency and homogeneity of repetitive printing of artificial fingerprint were evaluated using a visual minutiae comparison method and an Automated Fingerprint Identification System (AFIS). The standard latent fingerprint pattern was prepared by the printing of a master digital fingerprint pattern with an inkjet printer cartridge case filled with artificial sweat. The master digital fingerprint pattern was prepared with a scanning of an inked fingerprint pattern of a living subject. The intensities of the master digital fingerprint pattern were adjusted by changing the 'output level' values of the Adobe Photoshop CS 5 software. Number of standard latent fingerprint patterns were printed and then developed with conventional latent fingerprint developing methods; ninhydrin treatment method and 1,2-indandion(1,2-IND)/$ZnCl_2$ treatment method. The ridge details of the latent fingerprint patterns developed with the reagents were visually compared with the inked fingerprint pattern and could confirm that the minutiae of both patterns are visually identical. The ridge detail of the inked fingerprint and reagent developed standard latent fingerprint patterns were compared with an AFIS. The average number of minutiae searched by the AFIS was $52.4{\pm}2.4$ (range = 48~56) for 50 ninhydrin developed latent fingerprint patterns, and $50.2{\pm}1.9$ (range = 47~53) for 50 1,2-IND/$ZnCl_2$ developed latent fingerprint patterns. These low standard deviation values over 50 repetitive printing demonstrated that the 50 standard latent patterns were printed with consistent and homogeneous manner.

Removal of VOCs and H2S from Waste Gas with Biotrickling Filter (생물살수여과법을 이용한 공기중 VOC 및 H2S 제거)

  • Kim, Kyoung-Ok;Kim, Yong-Je;Won, Yang-Soo
    • Applied Chemistry for Engineering
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    • v.19 no.5
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    • pp.519-525
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    • 2008
  • Biodegradation of toluene, styrene and hydrogen sulfide as model compounds of volatile organic compounds and odor from waste gas was investigated experimentally in a biotrickling filter. This study focussed on the description of experimental results with regard to operating conditions. The effect of varying $H_2S$ load rate and inlet concentration was investigated under autotropic and mixotropic environmental conditions. The $H_2S$ removal efficiencies of greater than 99% were achieved at $H_2S$ loads below $10g/m^3{\cdot}hr$ for each environment. It was observed that the maximum elimination capacity of mixotrophic filter was achieved a little greater than the one of autotrophic filter. The biofiltration of toluene and styrene in trickling bed was examined under different gas flow rates, load rates, and inlet concentrations. Below $40g/m^3{\cdot}hr$ of toluene loading, the elimination capacity and loading were identical and it was completely destroyed. In high loading of toluene, the biotrickling filter was operated at its maximum elimination capacity. In the inlet concentration of 0.2, 0.5, and $1.0g/m^3$, the maximum elimination capacity of toluene showed 40, 45, and $60g/m^3{\cdot}hr$, respectively. After a short adaptation period, it was demonstrated that the results of styrene in originally toluene adapted bioreactor was similar with the ones of toluene. However, the performance of filer for styrene is generally a little lower than for toluene. The operating conditions (including liquid flow rate etc.) allowing the highest removal efficiency should be determined experimentally for each specific case.

Silver nanowires and nanodendrites synthesized by plasma discharge in solution for the catalytic oxygen reduction in alkaline media

  • Kim, Hoe-Geun;Song, Myeon-Gyu;Kim, Dong-U;Lee, Sang-Yul
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2018.06a
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    • pp.62-62
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    • 2018
  • Pt is still considered as one of the most active electrocatalysts for ORR in alkaline fuel cells. However, the high cost and scarcity of Pt hamper the widespread commercialization of fuel cells. As a strong candidate for the replacement of Pt catalyst, silver (Ag) has been extensively studied due to its high activity, abundance, and low cost. Ag is more stable than Pt in the pH range of 8~14 as the equilibrium potential of Ag/Ag+ being ${\approx}200mV$ higher than that of Pt/PtO. However, Ag is the overall catalytic activity of Ag for oxygen reduction reaction(ORR) is still not comparable to Pt catalyst since the surface Ag atoms are approximately 10 times less active than Pt atoms. Therefore, further enhancement in the ORR activity of Ag catalysts is necessary to be competitive with current cutting-edge Pt-based catalysts. We demonstrate the architectural design of Ag catalysts, synthesized using plasma discharge in liquid phase, for enhanced ORR kinetics in alkaline media. An attractive feature of this work is that the plasma status controlled via electric-field could form the Ag nanowires or dendrites without any chemical agents. The plasma reactor was made of a Teflon vessel with an inner diameter of 80 mm and a height of 80 mm, where a pair of tungsten(W) electrodes with a diameter of 2 mm was placed horizontally. The stock solutions were made by dissolving the 5-mM AgNO3 in DI water. For the synthesis of Agnanowires, the electricfield of 3.6kVcm-1 in a 200-ml AgNO3 aqueous solution was applied across the electrodes using a bipolar pulsed power supply(Kurita, Seisakusyo Co. Ltd). The repetition rate and pulse width were fixed at 30kHz and 2.0 us, respectively. The plasma discharge was carried out for a fixed reaction time of 60 min. In case of Ag nanodendrites, the electric field of 32kVcm-1 in a 200-ml AgNO3 aqueous solution was applied and other conditions were identical to the plasma discharge in water in terms of electrode configuration, repetition rate and discharge time. Using SEM and STEM, morphology of Ag nanowires and dendrites were investigated. With 3.6 kV/cm, Ag nanowire was obtained, while Ag dendrite was constructed with 32 kV/cm. The average diameter and legth of Ag nanowireses were 50 nm and 3.5 um, and thoes values of Ag dendrites were 40 nm and 3.0 um. As a results of XPS analysis, the surface defects in the Ag nanowires facilitated O2 incorporation into the surface region via the interaction between the oxygen and the electron cloud of the adjacent Ag atoms. The catalytic activity of Ag for oxygen reduction reaction(ORR) showed that the catalytic ORR activity of Ag nanowires are much better than Ag nanodendrites, and electron transfer number of Ag nanowires is similar to that of Pt (${\approx}4$).

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