• Korean Journal of Remote Sensing
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• v.17 no.4
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• pp.285-295
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• 2001

We developed a CASE-II water model that will enable the simulation of remote sensing reflectance($R_{rs}$) at the coastal waters for the retrieval of suspended sediments (SS) concentrations from satellite imagery. The model has six components which are: water, chlorophyll, dissolved organic matter (DOM), non-chlorophyllous particles (NC), heterotrophic microorganisms and an unknown component, possibly represented by bubbles or other particulates unrelated to the five first components. We measured $R_{rs}$, concentration of SS and chlorophyll, and absorption of DOM during our field campaigns in Korea. In addition, we generated $R_{rs}$ from different concentrations of SS and chlorophyll, and various absorptions of DOM by random number functions to create a large database to test the model. We assimilated both the computer generated parameters as well as the in-situ measurements in order to reconstruct the reflectance spectra. We validated the model by comparing model-reconstructed spectra with observed spectra. The estimated $R_{rs}$ spectra were used to (1) evaluate the performance of four wavelengths and wavelengths ratios for accurate retrieval of SS. 2) identify the optimum band for SS retrieval, and 3) assess the influence of the SS on the chlorophyll algorithm. The results indicate that single bands at longer wavelengths in visible better results than commonly used channel ratios. The wavelength of 625nm is suggested as a new and optimal wavelength for SS retrieval. Because this wavelength is not available from SeaWiFS, 555nm is offered as an alternative. The presence of SS in coastal areas can lead to overestimation chlorophyll concentrations greater than 20-500%.

• Journal of the Korea Society of Computer and Information
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• v.25 no.4
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• pp.29-35
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• 2020

In this paper, we propose a new structured entity recognition DeNERT model. Recently, the field of natural language processing has been actively researched using pre-trained language representation models with a large amount of corpus. In particular, the named entity recognition, which is one of the fields of natural language processing, uses a supervised learning method, which requires a large amount of training dataset and computation. Reinforcement learning is a method that learns through trial and error experience without initial data and is closer to the process of human learning than other machine learning methodologies and is not much applied to the field of natural language processing yet. It is often used in simulation environments such as Atari games and AlphaGo. BERT is a general-purpose language model developed by Google that is pre-trained on large corpus and computational quantities. Recently, it is a language model that shows high performance in the field of natural language processing research and shows high accuracy in many downstream tasks of natural language processing. In this paper, we propose a new named entity recognition DeNERT model using two deep learning models, DQN and BERT. The proposed model is trained by creating a learning environment of reinforcement learning model based on language expression which is the advantage of the general language model. The DeNERT model trained in this way is a faster inference time and higher performance model with a small amount of training dataset. Also, we validate the performance of our model's named entity recognition performance through experiments.

• Ocean Systems Engineering
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• v.7 no.4
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• pp.435-460
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• 2017

The main objective of this study is to investigate the turning and zig-zag maneuvering performance of the well-known naval surface combatant DTMB (David Taylor Model Basin) 5415 hull with URANS (Unsteady Reynolds-averaged Navier-Stokes) method. Numerical simulations of static drift tests have been performed by a commercial RANS solver based on a finite volume method (FVM) in an unsteady manner. The fluid flow is considered as 3-D, incompressible and fully turbulent. Hydrodynamic analyses have been carried out for a fixed Froude number 0.28. During the analyses, the free surface effects have been taken into account using VOF (Volume of Fluid) method and the hull is considered as fixed. First, the code has been validated with the available experimental data in literature. After validation, static drift, static rudder and drift and rudder tests have been simulated. The forces and moments acting on the hull have been computed with URANS approach. Numerical results have been applied to determine the hydrodynamic maneuvering coefficients, such as, velocity terms and rudder terms. The acceleration, angular velocity and cross-coupled terms have been taken from the available experimental data. A computer program has been developed to apply a fast maneuvering simulation technique. Abkowitz's non-linear mathematical model has been used to calculate the forces and moment acting on the hull during the maneuvering motion. Euler method on the other hand has been applied to solve the simultaneous differential equations. Turning and zig-zag maneuvering simulations have been carried out and the maneuvering characteristics have been determined and the numerical simulation results have been compared with the available data in literature. In addition, viscous effects have been investigated using Eulerian approach for several static drift cases.

• International Journal of Control, Automation, and Systems
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• v.2 no.4
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• pp.463-474
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• 2004

Game theory is a method of mathematical analysis developed to study the decision making process. In 1928, Von Neumann mathematically proved that every two-person, zero-sum game with many pure finite strategies for each player is deterministic. In the early 50's, Nash presented another concept as the basis for a generalization of Von Neumann's theorem. Another central achievement of game theory is the introduction of evolutionary game theory, by which agents can play optimal strategies in the absence of rationality. Through the process of Darwinian selection, a population of agents can evolve to an Evolutionary Stable Strategy (ESS) as introduced by Maynard Smith in 1982. Keeping pace with these game theoretical studies, the first computer simulation of coevolution was tried out by Hillis. Moreover, Kauffman proposed the NK model to analyze coevolutionary dynamics between different species. He showed how coevolutionary phenomenon reaches static states and that these states are either Nash equilibrium or ESS in game theory. Since studies concerning coevolutionary phenomenon were initiated, there have been numerous other researchers who have developed coevolutionary algorithms. In this paper we propose a new coevolutionary algorithm named Game theory based Coevolutionary Algorithm (GCEA) and we confirm that this algorithm can be a solution of evolutionary problems by searching the ESS. To evaluate this newly designed approach, we solve several test Multiobjective Optimization Problems (MOPs). From the results of these evaluations, we confirm that evolutionary game can be embodied by the coevolutionary algorithm and analyze the optimization performance of our algorithm by comparing the performance of our algorithm with that of other evolutionary optimization algorithms.

• Journal of Energy Engineering
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• v.22 no.2
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• pp.226-236
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• 2013

The heat distribution and internal flow from the efficiency of actual reformer and specification variation, using the computer simulation and experiment about the steam methane reforming reaction which uses the high temperature reformer. Reaction model from steam refoemer uses the steam response model developed by Xu & Froment.As result we supposed the chemical react Steam Reforming(SR), Water Gas Shift(WGS), and Direct Steam Reforming(DSR) from the inner high temperature reformer dominates the response has dissimilar response. According to result of steam methane reforming reaction exam using high temperature reformer, we figured out when Steam Carbon Ratio(SCR) increase, number of hydrogen yield increases but methane decreases. When comparing and examining between design with one inlet and two inlet, result came out one inlet design is more outstanding at thermal distribution and internal flow, hydrogen yield in one inlet design than two inlet design.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.19 no.1
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• pp.93-101
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• 2009

This paper proposes the detection method of spreading mails which hacker injects malicious codes to steal the information. And I developed the 'Analysis model' which is decoding traffics when hacker's encoding them to steal the information. I researched 'Methodology of intrusion detection techniques' in the computer network monitoring. As a result of this simulation, I developed more efficient rules to detect the PCs which are infected malicious codes in the hacking mail. By proposing this security policy which can be applicable in the computer network environment including every government or company, I want to be helpful to minimize the damage by hacking mail with malicious codes.

• Nuclear Engineering and Technology
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• v.22 no.1
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• pp.1-11
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• 1990

Heavy water is used as a moderator and a coolant in the pressurized heavy water reactor Because of the high cost of heavy water, downgraded heavy water generated in the reactor system is recycled to the reactor after being concentrated up to 99.8% or more in heavy water upgraders. This study investigates the process of upgraders and then suggests a theoretical model. The relations between process variables are derived from tower packing characteristics, vapour-liquid equilibria, and mass-heat balance equations at a steady state operation of the upgrader h computer program UPGR is developed, using the algorithm that solves the nonlinear equations step by step. It shows that the results of computer simulation are in good agreement with the operating data of the Wolsung upgrader. Thus, this computer code offers the optimum operating guide and is now applied to manage the performance of upgraders for the effective operation of the heavy water upgraders.

• Journal of Intelligence and Information Systems
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• v.12 no.1
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• pp.125-137
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• 2006

One of the important tactical problems for the efficient operation of container terminals is to determine the usage of storage space There are two different strategies for stacking containers; mixing strategy, in which outbound containers and inbound containers are mixed in the same block, and segregating strategy, in which outbound containers and inbound containers are stacked in blocks different from each other The performance of space allocation strategies also depends on the types of handling equipment in the yard and the number of handling equipment allocated to each block. A simulation model is developed considering various handling characteristics of yard cranes. Performances of various space and equipment allocation strategies are evaluated by using the simulation model.

• Journal of Astronomy and Space Sciences
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• v.12 no.1
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• pp.78-89
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• 1995

We solved n-body problem about 9 planets, moon, and 4 minor planets with relativistic effect related to the basic equation of motion of the solar system. Perturbations including flgure potential of the earth and the moon and solid earth tidal effect were considered on this relativistic equation of motion. The orientations employed precession and nutation for the earth, and lunar libration model with Eckert's lunar libration model based on J2000.0 were used for the moon. Finally, we developed heliocentric ecliptic position and velocity of each planet using this software package named the SSEG (Solar System Ephemerides Generator) by long-term (more than 100 years) simulation on CRAY-2S super computer, through testing each subroutine on personal computer and short-time(within 800 dyas) running on SUN3/280 workstation. Epoch of input data JD2440400.5 were adopted in order to compare our results to the data archived from JPL's DE 200 by Standish and Newhall. Above equation of motion was integrated numerically having 1-day step-size interval through 40,000 days (about 110 years long) as total computing interval. We obtained high-precision ephemerides of the planets with maximum error, less $than\pm2\times10^{-8}AU(\approx\pm3km)$ compared with DE200 data (except for mars and moon).

• Journal of the Korea Society of Computer and Information
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• v.11 no.2 s.40
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• pp.159-167
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• 2006

Lipreading has been suggested as one of the methods to improve the performance of speech recognition in noisy environment. However, existing methods are developed and implemented only in software. This paper suggests a hardware design for real-time lipreading. For real-time processing and feasible implementation, we decompose the lipreading system into three parts; image acquisition module, feature vector extraction module, and recognition module. Image acquisition module capture input image by using CMOS image sensor. The feature vector extraction module extracts feature vector from the input image by using parallel block matching algorithm. The parallel block matching algorithm is coded and simulated for FPGA circuit. Recognition module uses HMM based recognition algorithm. The recognition algorithm is coded and simulated by using DSP chip. The simulation results show that a real-time lipreading system can be implemented in hardware.