• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.1
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• pp.1-10
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• 2020

The application of multiphase flows is increasingly being applied to analyze phenomena such as single phase flows where the fluid boundary changes continuously over time or the problem of mixing a liquid phase and a gas phase. In particular, multiphase flow models that take into account incompressible Newtonian fluids for liquid and gas are often applied to solve the problems of the free water surface such as wave fields. In general, multi-phase flow models require time-based the surface tracking of each fluid's phase boundary, which determines the accuracy of the final calculation of the model. This study evaluates the advection performance of representative VOF-type boundary tracking techniques applied to various CFD numerical codes. The effectiveness of the FCT method to control the numerical flux to minimize the numerical diffusion in the conventional VOF-type boundary tracking method and advection calculation was mainly evaluated. In addition, the possibility of tracking performance of free surface using CIP method (Yabe and Aoki, 1991) was also investigated. Numerical results show that the FCT-VOF method introducing an anti-diffusive flux to precent excessive diffusion is superior to other methods under the confined conditions in this study. The results from this study are expected to be used as an important basic data in selecting free surface tracking techniques applied to various numerical codes.

• Korean Journal of Agricultural and Forest Meteorology
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• v.19 no.4
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• pp.270-279
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• 2017

Regional assessment of crop productivity using a gridded simulation approach could aid policy making and crop management. Still, little effort has been made to develop the systems that allows gridded simulations of crop growth using ORYZA 2000 model, which has been used for predicting rice yield in Korea. The objectives of this study were to develop a series of data processing modules for creating input data files, running the crop model, and aggregating output files in a region of interest using gridded data files. These modules were implemented using C++ and R to make the best use of the features provided by these programming languages. In a case study, 13000 input files in a plain text format were prepared using daily gridded weather data that had spatial resolution of 1km and 12.5 km for the period of 2001-2010. Using the text files as inputs to ORYZA2000 model, crop yield simulations were performed for each grid cell using a scenario of crop management practices. After output files were created for grid cells that represent a paddy rice field in South Korea, each output file was aggregated into an output file in the netCDF format. It was found that the spatial pattern of crop yield was relatively similar to actual distribution of yields in Korea, although there were biases of crop yield depending on regions. It seemed that those differences resulted from uncertainties incurred in input data, e.g., transplanting date, cultivar in an area, as well as weather data. Our results indicated that a set of tools developed in this study would be useful for gridded simulation of different crop models. In the further study, it would be worthwhile to take into account compatibility to a modeling interface library for integrated simulation of an agricultural ecosystem.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.7
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• pp.2549-2558
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• 2010

A Remote Vital Sign Monitor is an in-home healthcare system designed to wirelessly monitor core-body temperature. The Remote Vital Sign Monitor provides accuracy and features which are comparable to hospital equipment while minimizing cost with ease-of-use. It has two parts, a bandage and a monitor. The bandage and the monitor both use the Chipcon2430(CC2430) which contains an integrated 2.4GHz Direct Sequence Spread Spectrum radio. The CC2430 allows Remote Vital Sign Monitor to operate at over a 100-foot indoor radius. A simple user interface allows the user to set an upper temperature and a lower temperature that is monitored with respect to the core-body temperature. If the core-body temperature exceeds the one of two defined temperatures, the alarm will sound. The alarm is powered by a low-voltage audio amplifier circuit which is connected to a speaker. In order to accurately calculate the core-body temperature, the Remote Vital Sign Monitor must utilize an accurate temperature sensing device. The thermistor selected from GE Sensing satisfies the need for a sensitive and accurate temperature reading. The LCD monitor has a screen size that measures 64.5mm long by 16.4mm wide and also contains back light, and this should allow the user to clearly view the monitor from at least 3 feet away in both light and dark situations.

• Journal of KIISE:Information Networking
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• v.37 no.5
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• pp.374-385
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• 2010

Wireless mesh networks can be deployed for various networks from home networking to last-mile broadband Internet access. Wireless mesh networks are composed of mesh routers and mesh clients. In these networks, static nodes form a multi-hop backbone of a large wireless access network that provides connectivity to end-users' mobile terminals. The network nodes cooperate with each other to relay data traffic to its destinations. In order to increase connectivity and better performance, researchers are getting interested in multi-channel and multi-interface wireless mesh networks. In these networks, non-overlapping multiple frequency channels are used simultaneously to increase the aggregate bandwidth available to end-users. Recently, researches have focused on finding suitable channel assignments for wireless network interfaces, equiped in a mesh node, together with efficient routing to improve overall system throughput in wireless mesh networks. This goal can be achieved by minimize channel interference. Less interference among using channels in a network guarantees more aggregated channel capacity and better connectivity of the networks. In this thesis, we propose interference aware channel assignment and routing algorithms for multi-channel multi-hop wireless mesh networks. We propose Channel Assignment and Routing algorithms using Traffic Profiles(CARTP) and Routing algorithms allowing detour routing(CARTP+2). Finally, we evaluate the performance of proposed algorithms in comparison to results from previous methods using ns-2 simulations. The simulation results show that our proposed algorithms can enhance the overall network performance in wireless mesh networks.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.11
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• pp.1021-1030
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• 2010

In the sensor network, many tiny nodes construct Ad-Hoc network using wireless interface. As this type of system consists of thousands of nodes, managing each sensor node in real world after deploying them is very difficult. In order to install the sensor network successfully, it is necessary to verify its software using a simulator beforehand. In fact Sensor network simulators require high fidelity and timing accuracy to be used as a design, implementation, and evaluation tool of wireless sensor networks. Cycle-accurate, instruction-level simulation is the known solution for those purposes. In this paper, we developed an instruction-level sensor network simulator for Telos sensor node as named TeloSlM. It consists of MSP430 and CC2420. Recently, Telos is the most popular mote because MSP430 can consume the minimum energy in recent motes and CC2420 can support Zigbee. So that TeloSlM can provide the easy way for the developers to verify software. It is cycle-accurate in instruction-level simulator that is indispensable for OS and the specific functions and can simulate scalable sensor network at the same time. In addition, TeloSlM provides the GUI Tool to show result easily.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.11
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• pp.1592-1597
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• 2015

In this study, we developed a fiber-optic temperature sensor (FOTS) based on a silicone oil and an optical time domain reflectometer (OTDR) to apply the measurement of a coolant leakage in the nuclear power plant. The sensing probe of the FOTS consists of a silicone oil, a stainless steel cap, a FC terminator, and a single mode optical fiber. Fresnel reflection arising at the interface between the silicone oil and the single mode optical fiber in the sensing probe is changed by varying the refractive index of the silicone oil according to the temperature. Therefore, we measured the optical power of the light signals reflected from the sensing probe. The measurable temperature range of the FOTS using a Cu-coated silica fiber is from $70^{\circ}C$ to $340^{\circ}C$ and the maximum operation temperature of the FOTS is sufficient for usage at the secondary system in the nuclear power plant.

• Journal of Wetlands Research
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• v.20 no.1
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• pp.63-71
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• 2018

The particle filtration mechanisms in an infiltration trench should be varying due to the different hydraulic conditions during stormwater runoff. The understanding of these variations associated with different filtration mechanisms and their effect on the particle removal efficiency is of vital importance. Therefore, a LID (Low Impact Development) system comprising of an infiltration trench packed with gravel and woodchip was investigated during the monitoring of several independent rainfall events. A typical rainfall event was divided into separate regimes and their corresponding flow conditions as well as filtration mechanisms in the trench were analyzed. According to hydraulic conditions, it was found out that filtration changes between vertical and horizontal flows as well as between unsaturated, saturated, and partially-saturated flows. Particle separation efficiency was high (55-76%) and was mainly governed by physical straining during the unsaturated period. It was then enhanced by diffusion during the saturated period (75-95%). When the trench became partially saturated at the end of the rainfall event, the efficiency decreased which was believed to be due to the existence of a negatively charged air-water interface which limited the removal to positively charged particles.

• Korean Journal of Materials Research
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• v.11 no.2
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• pp.88-93
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• 2001

The thermal behavior and the crystallographic characteristics of an epitaxial $C49-TiSi_2$ island formed in a Si (001) substrate by $N_2$, treatment were investigated by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). It was found from the analyzed results that the epitaxial $C49-TiSi_2$ was thermally stable even at high temperature of $1000^{\circ}C$ therefore did not transform into the C54-stable phase and did not deform morphologically. HRTEM results clearly showed that the epitaxial $TiSi_2$ phase and Si have the orientation relationship of (060)[001]$TiSi_2$//(002)[110]Si, and the lattice strain energy at the interface was mostly relaxed by the formation of misfit dislocations. Furthermore, the mechanism on the formation of the epitaxial $_C49-TiSi2$ in Si and stacking faults lying on the (020) plane of the C49 Phase were discussed through the analysis of the HRTEM image and the atomic modeling.

• Journal of KIISE:Software and Applications
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• v.30 no.11
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• pp.1080-1091
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• 2003

Recently, the distance education has been rapidly proliferated with the rapid growth of the Internet and high speed networks. There has been relatively much research with regard to online lecture (teaching and studying) tools for the distance education, compared to the virtual laboratory tools (for self-study and experiments). In this paper, we design and implement a web-based simulation tool, named as SimDraw, for the virtual laboratory in the distance education. To apply the web-based simulation technology into the distance education, some requirements should be met; firstly, the user interface of the simulation should be very easy for students. Secondly, the simulation should be very portable to be run on various computer systems of remote students. Finally, the simulation program on remote computers should be very thin so that students can easily install the program onto their computers. To meet these requirements, SimDraw adopts the client/server architecture; the client program contains only model development and animation functions so that no installation of a client program onto student's system is required, and it can be implemented by a Java applet in Web browsers. The server program supports client programs by offering the functions such as remote compiling, model storing, library management, and user management. For the evaluation of SimDraw, we show the simulation process using the example experimentation of the RIP(Routing Information Protocol) Internet routing protocol.

• Journal of KIISE:Computing Practices and Letters
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• v.7 no.4
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• pp.273-287
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• 2001

In this paper, we introduce our experience for designing and implementing a media manager in the Integrated Streaming Service Architecture (ISSA) developed by the authors. The media manager is regarded as a necessary module in the ISSA framework for the following reasons. It realizes that from which locations of the media source devices, the media streams are coming. Once it knows where the origin is, the media manager should recognizes what types of stream are. After that, it performs how to chose an appropriate CODEC to handle the recognized input streams efficiently, and what type of media playback device should be selected. In order to do such a job efficiently, the proposed media manager consists of two modules source module and sink module. The major role of a media source module is to make an abstraction for the media streams that are coming from various types of media device. This, in consequence, enables a media manager to consistently handle tlle media streams without considering wherever they come from. On the other hand, the media sink module distributes the input streams to an appropriate media device to playback. One of the remarkable virtues of the proposed media manager is an ability to supporting high value-added database services since it provides an interface between the ISSA and real-time multimedia database. Also, it provides the RTP!RTSP source filter and Winamp gateway modules which allow the flexibility to the system. Moreover, the media manager can adopt any types of new media which in fact will provide scalability to the ISSA.