• Journal of the Korea Society for Simulation
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• v.28 no.2
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• pp.1-14
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• 2019

A full scale hydrodynamic simulation that requires an accurate reproduction of shock-induced detonation was conducted for design of an energetic component system. A detailed hydrodynamic analysis SW was developed to validate the reactive flow model for predicting the shock propagation in a train configuration and to quantify the shock sensitivity of the energetic materials. The pyrotechnic device is composed of four main components, namely a donor unit (HNS+HMX), a bulkhead (STS), an acceptor explosive (RDX), and a propellant (BPN) for gas generation. The pressurized gases generated from the burning propellant were purged into a 10 cc release chamber for study of the inherent oscillatory flow induced by the interferences between shock and rarefaction waves. The pressure fluctuations measured from experiment and calculation were investigated to further validate the peculiar peak at specific characteristic frequency (${\omega}_c=8.3kHz$). In this paper, a step-by-step numerical description of detonation of high explosive components, deflagration of propellant component, and deformation of metal component is given in order to facilitate the proper implementation of the outlined formulation into a shock physics code for a full scale hydrodynamic simulation of the energetic component system.

• Solar Energy
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• v.12 no.3
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• pp.28-36
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• 1992

The performance of a latent heat storage system using a thermosyphon as the heat transfer device between the heat source and the phase change material was investigated experimentally. In order to increase the effective conductivity of the phase change material, layers of copper wire mesh were immersed in the paraffin wax(Sunoco P-116) in such a way that they also may be considered as fins of the thermosyphon. The important results are as follows : (1) The void space of the wire mesh allowed the convection to occur, thus enhanced the performance of the system : (2) The increase of the number of layer of wire mesh increased the conduction heat transfer. However, it also had adverse effect of subduing convective motion of liquid wax : and (3) Overall heat transfer coefficient and thermosyphon conductance increased with the increase of the number of layer of wire mesh, whereas the heat transfer coefficient between the thermosyphon and the wax decreased.

• KIPS Transactions on Computer and Communication Systems
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• v.11 no.7
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• pp.217-224
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• 2022

Today, with the development of technology and industry, fire accidents in special buildings are increasing as special buildings increase. However, despite the rapid development of information and communication technology, human casualties are steadily occurring due to the underdeveloped and ineffective indoor fire alarm system. In this study, we confirmed that the existing indoor fire alarm system using acoustic alarm could not deliver a sufficiently large alarm to the in-room personnel. To improve this, we designed and implemented a fire alarm system using edge computing and beacons. The proposed improved fire alarm system consists of terminal sensor nodes, edge nodes, a user application, and a server. The terminal sensor nodes collect indoor environment data and send it to the edge node, and the edge node monitors whether a fire occurs through the transmitted sensor value. In addition, the edge node continuously generate beacon signals to collect information of smart devices with user applications installed within the signal range, store them in a server database, and send application push-type fire alarms to all in-room personnel based on the collected user information. As a result of conducting a signal valid range measurement experiment in a university building with dense lecture rooms, it was confirmed that device information was normally collected within the beacon signal range of the edge node and a fire alarm was quickly sent to specific users. Through this, it was confirmed that the "blind spot problem of the alarm" was solved by flexibly collecting information of visitors that changes time to time and sending the alarm to a smart device very adjacent to the people. In addition, through the analysis of the experimental results, a plan to effectively apply the proposed fire alarm system according to the characteristics of the indoor space was proposed.

• Korean Chemical Engineering Research
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• v.56 no.1
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• pp.85-95
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• 2018

In this research, a biofilter system equipped with a biofilter process and a humidifier composed of a fluidized aerobic and an anoxic reactor, was constructed to treat odorous waste air containing hydrogen sulfide, ammonia and VOC, frequently generated from pig and poultry housing facilities, compost manufacturing factories and publicly owned facilities. Its optimum operating condition was revealed and discussed. In the experiment of complex feed, the ammonia of fed-waste air was removed by ca. 75% and more than 20% at the stage of the humidifier and the biofilter, respectively. The toluene of the fed-waste air was removed by ca. 20% and more than 70% at the stage of the humidifier and the biofilter, respectively. Therefore the water-soluble ammonia and the water-insoluble toluene were treated mainly at the stage of the humidifier and the biofilter, respectively. In addition, hydrogen sulfide was almost absorbed at the stage of the humidifier so that it was not detected at the biofilter process. In the experiment of ammonia-containing feed, the ammonia of fed-waste air was removed by ca. 65% and 35% at the stage of the humidifier and the biofilter, respectively. Its removal efficiency of ammonia at the stage of the humidifier was 10% less than that in the experiment of complex feed, due to no supply of such carbon source as toluene required in the process of denitrification. In the experiments of complex feed, ammonia-containing feed with and without (instead, glucose) the addition of yeast extract, the absorption rates of ammonia-nitrogen were ca. 0.28 mg/min, 0.23 mg/min and 0.27 mg/min, respectively. The corresponding denitrification rates in the anoxic reactor were 0.42 mg/min, 0.55 mg/min and 0.27 mg/min, respectively. In addition, in the modeling of bubble column(the fluidized aerobic reactor of the humidifier) process, the value of specific surface area(a) of bubbles multiplied by enhanced mass transfer coefficient (E $K_y$) was evaluated to be 0.12/hr.

• Polymer(Korea)
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• v.32 no.4
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• pp.328-333
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• 2008

The osmotic delivery systems are based on osmosis. The transverse diffusion of water through a porous membrane from a medium with a low osmotic pressure to a medium with a high osmotic pressure. Nifedipine tablet dosage forms of Procardia $XL^{(R)}$(Pfizer) and $Adalat^{(R)}$(Bayer) are commercialized systems of this type that push-pull osmotic tablet operates successfully in delivering water-insoluble drugs. We prepared osmotic pellet system by fluidized bed coating method, and model-drug used nifedipine. The osmotic pellet system was composed of the core material. the swelling and osmotic pressure layer, the drug coating layer, and the porous membrane. This work is performed to investigate the effect of different factors, such as composition and thickness of membrane. The osmotic pellet has been successfully prepared by fluidized bed coating technology. The drug release behavior depended on the increase of CA ratio and thickness in porous membrane. The morphology of the osmotic pellet before and after the dissolution test were observed by SEM. In conclusion, we found that the drug release of osmotic pellet depended on the composition and coating thickness of porous membrane.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.5
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• pp.831-838
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• 2016

The disaster preventing system using vegetation has been growing in the field of coastal engineering in recent years. To analyze wave and flow fields under nonlinear interactions between tsunami and vegetation, the purpose of this study is to evaluate newly-developed 3-D numerical wave tank including energy dissipation by tsunami-vegetation interaction based on existing N-S solver with porous body model. Comparing numerical results using mean drag coefficient and dynamic drag coefficient due to Reynolds number to existing experimental results it is revealed that computed results considering the dynamic drag coefficient are in good agreement with the laboratory test results for time-domain waveform. In addition, the calculated transmission coefficients of solitary waves in various vegetation densities and incident wave heights are also in good agreement with the experimental values. This confirms the validity and effectiveness of the developed 3-D numerical wave tank with the fluid resistance by vegetation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.6 no.3
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• pp.237-246
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• 1994

Experimental data are reported for charging and collection of NaCl aerosols in the 0.03- to $0.2{\mu}m$-geometric-mean-diameter range in 2-stage parallel-plate electrostatic precipitators. The NaCl aerosols are generated with geometric standard deviation of about 1.74 and particle generation rate of about 10^9 particles/see by the constant output atomizer and injected into the air flow in the clean wind-tunnel. The 2-stage parallel-plate electrostatic precipitator installed in the test section of the wind-tunnel is operated with a positive corona discharge. The NaCl aerosols in the channel flow are sampled and transported to the aerosol particle number concentration measurement system by using the isoaxial sampling and transport system constructed based on the Okazaki and Willeke design. The aerosol particle number concentration measurement system measures the size distribution of submicrometer aerosols by an electrical mobility detection technique. It is confirmed from comparing the measured collection efficiencies in this study and the predicted ones by our previous theoretical analysis that the predicted collection efficiencies agree well with the experimental ones. It is also found from the comparison that below about $0.02{\mu}m$ all particles are not charged and the uncharged particles are not collected, and consequently 2-stage parallel-plate electrostatic precipitators are not suitable for that particle size range.

• Journal of the Institute of Convergence Signal Processing
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• v.12 no.4
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• pp.286-290
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• 2011

LBS(Location Based System) is the essential technology of ubiquitous market and utilizes the GNSS(Global Navigation Satellite). GNSS includes GPS of USA, Galileo of Europe Union, QZSS of Japan, Compass of China, and IRNSS of India. Related researches have recently been conducted. Once the satellite is launched, the maintenance such as modification and verification of its function is difficult. Therefore, before the launch of satellites, more precise and concrete verification of performance and operations are needed. In order to do this, hardware testbed may be developed. but software simulators can provide more flexible and cost effective simulation results. These simulators should provide the essential function handling all kinds of error features experienced upon propagation of the GNSS signal. In this paper, we present a design and implementation results of a window-based simulator applying the modeling of various error features for several GNSS.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.11 no.6
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• pp.75-82
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• 2002

Design for a quiet operation of fluid power system requires the understanding of noise and vibration characteristics of the system. It's not easy to analyze noise problem in hydraulic cylinder used in typical actuator Because they've got complex fluid dynamics. One of the fundamental problems associated with the hydraulic system is the pulsating flow in pipe lines, which can be tackled by the analysis under simplifying assumptions. The present study focuses on theoretic analysis and experimental study on the dynamics of laminar pulsating flow in a circular pipe. We analyze the propagation characteristics of the pressure pulse within a hydraulic pipe line taking into account the pulsating flow frequency variation. We also measure instantaneous pressure pulses within pipe line to identify the transfer functions. We conduct series of experiments to investigate the propagation characteristics of pressure pulse for various pressure of pulsating flow. The working fluid of the present study is ISO VG46 and the temperature ranges from 20 to $60^{\circ}$ with normal pressure at 4000kPa. The flow rate is measured by using an ultrasonic flow meter. Pressures at fixed upstream and downstream positions are measured concurrently. The electric signals of the pressure sensor are stored and analyzed using a system analyzer(PKE 983 series). The frequency is varied in the range of 10~500Hz. The Reynolds number is kept below 2,000. In the present study, boundary condition was varied by installing a surge tank and an orifice at the end of pipe. Experimental and theoretical results were compared each other under various boundary conditions.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.15 no.2
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• pp.53-64
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• 2005

Previous secure routing protocols for wireless sensor networks assume that a sink is static. In many cases, however, a sink operated by man or vehicle is moving. A mobile sink creates a lot of technical problems such as reconfiguration of routing path exposure of sink location. and selection of secure access point node, which are not considered by many previous researches. In this paper, we propose a new secure routing scheme for solving such problems using hi-directional hash chain and delegation nodes of grid structure. This scheme provides a secure routing path and prevents attacker from recognizing the location of a mobile sink in sensor networks. This new method reduces the resource requirements compared to the cashed routing schemes. Simulation results also show that the system is secure and efficient enough.