• Journal of Bio-Environment Control
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• v.29 no.3
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• pp.285-292
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• 2020

Because the inner environment of greenhouse has a direct impact on crop production, many studies have been performed to develop technologies for controlling the environment in the greenhouse. However, it is difficult to apply the technology developed to all greenhouses because those studies were conducted through empirical experiments in specific greenhouses. It takes a lot of time and cost to develop the models that can be applicable to all greenhouse in real situation. Therefore studies are underway to solve this problem using computer-based simulation techniques. In this study, a model was developed to predict the inner environment of glass greenhouse using CFD simulation method. The developed model was validated using primary and secondary heating experiment and daytime greenhouse inner temperature data. As a result of comparing the measured and predicted value, the mean temperature and uniformity were 2.62℃ and 2.92%p higher in the predicted value, respectively. R² was 0.9628, confirming that the measured and the predicted values showed similar tendency. In the future, the model needs to improve by applying the shape of the greenhouse and the position of the inner heat exchanger for efficient thermal energy management of the greenhouse.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.2
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• pp.151-157
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• 2005

A one-dimensional numerical model was developed to simulate vertical profiles of electron acceptors and their reduced species in benthic sediments. The model accounted for microbial degradation of organic matter and subsequent chemical reactions of interest using stoichiometric relationships. Depending on the dominant electron acceptors utilized by microorganisms, the benthic sediments were assumed to be vertically subdivided into six zones: (1) aerobic respiration, (2) denitrification, (3) manganese reduction, (4) iron reduction, (5) sulfate reduction, and (6) methanogenesis. The utilizations of electron acceptors in the biologically mediated oxidation of organic matter were represented by Monod-type expression. The mass balance equations formulated for the reactive transport of organic matter, electron acceptors, and their corresponding reduced species in the sediments were solved utilizing an iterative multistep numerical method. The ability of model to simulate a freshwater sediments system was tested by comparing simulation results against published data obtained from lake sediments. The simulation results reasonably agreed with field measurements for most species, except for ammonia. This result showed that the C/N ratio (106/16) in the sediments is lower than what the Redfield formula prescribes. Since accurate estimates of vertical profiles of electron acceptors and their reduced species are important to determine the mobility and bioavailability of trace metals in the sediments, the model has potential application to assess the stability of selected trace metals in the sediments.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.2
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• pp.71-78
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• 2014

There is a big risk of bullet impact because military rotorcraft is run in the battle environment. Due to the bullet impact, the rapid increase of the internal pressure can cause the internal explosion or fire of fuel cell. It can be a deadly damage on the survivability of crews. Then, fuel cell of military rotorcraft should be designed taking into account the extreme situation. As the design factor of fuel cell, the internal fluid pressure, structural stress and bullet kinetic energy can be considered. The verification test by real object is the best way to obtain these design data. But, it is a big burden due to huge cost and long-term preparation efforts and the failure of verification test can result in serious delay of a entire development plan. Thus, at the early design stage, the various numerical simulations test is needed to reduce the risk of trial-and-error together with prediction of the design data. In the present study, the bullet impact numerical simulation based on SPH(smoothed particle hydrodynamic) is conducted with the commercial package, LS-DYNA. Then, the resulting equivalent stress, internal pressure and bullet's kinetic energy are evaluated in detail to examine the possibility to obtain the configuration design data of the fuel cell.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.36C no.9
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• pp.54-65
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• 1999

As the integration ratio and operating speed increase, it has become an important problem to estimate the dissipated power during the design procedure to reduce th TTM(time to market). This paper proposed a prediction model for the maximum dissipated power of a CMOS logic gate. This model uses a calculating method. It was constructed by including the characteristics of MOSFETs, the operational characteristics of the gate, and the characteristics of the input signals. As the construction procedure, a maximum power estimation model for CMOS inverter was formed first, And then, a conversion model to convert a multiple input CMOS gate into a corresponding CMOS inverter was proposed. Finally, the power model for inverter was applied to the converted result so that the model could be applied to a general CMOS gate. We designed several CMOS gates in layout level with $0.6{\mu}m$ design rule to apply both to HSPICE simulation and to the proposed models. The comparison between the two results showed that the gate conversion model and the power estimation model had within 5% and 10% of the relative errors, respectively. Those values show that the proposed models have sufficient accuracies. Also in calculation time, the proposed models were more than 30 times faster than HSPICE simulation. Consequently, it can be said that the proposed model could be used efficiently to estimate the maximum dissipated power of a CMOS logic gate during the design procedure.

• Fire Science and Engineering
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• v.27 no.4
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• pp.27-34
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• 2013

The high prediction performance of fire detector models is essentially needed to assure the reliability of fire and evacuation modeling in the process of PBD (Performance Based fire safety Design). The main objective of the present study is to measure input information in order to predict the accurate activation time of smoke detector into a Large Eddy Simulation (LES) fire model such as FDS (Fire Dynamics Simulator). To end this, FDE (Fire Detector Evaluator) which can measure the device properties of detector was developed, and the input information of Heskestad and Cleary's models was measured for a ionization smoke detector. In addition, the activation times of smoke detectors predicted using default values into FDS and measured values in the present study were systematically compared. As a result, the device properties of smoke detector examined in the present study showed a significant difference compared to the default values used into FDS, which resulted in the considerable difference of up to 15 minutes or more in terms of the activation time of smoke detector. The database (DB) on device properties of various smoke and heat detectors will be built to improve the reliability of PBD in future studies.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.6
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• pp.408-417
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• 2016

The frequent regional torrential or heavy rain and typhoon mostly caused by climate change has resulted in sediment disasters particularly in mountainous or hilly areas. More than 65% of South Korea is mountainous and development and rapid urbanization has brought lots of steep sloping industrial complexes, which are adjacent to cities. Such continuous urbanization and industrialization can result in an increase in serious damage to those places. Korea has very high population density so sediment disaster could result in a tremendous loss of property and life. A recent 10-year (2001~2010) study of the average annual loss shows 68 casualties and property loss of 1.7044 trillion Won(?), which indicates a 20% and 25% decrease for both life and property, respectively, but urban areas are experiencing increasing damage. In this paper, a comprehensive simulator composed by references, analyses, and the recent technologies was applied to visualize the scale of the damaged Woomyeon-san (Mt.) and verify the performance of the simulator.

• Korean Journal of Remote Sensing
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• v.30 no.6
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• pp.777-786
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• 2014

Mt. Ontake is the second highest volcano in Japan. On 02:52 Universal Time Coordinated(UTC), 27th September 2014, Ontake volcano began on the large eruption without notice. Due to the recent eruption, 55 people were killed and around 70 people injured. Therefore, This paper performed numerical experiment to analyse damage effect of volcanic ash corresponding to Ontake volcano erupt. The forecast is based on the outputs of the HYSPLIT Model for volcanic ash. This model, which is based on the UM numerical weather prediction data. Also, a quantitative analysis of the ash dispersion area, it has been detected using satellite images from optical Communication, Ocean and Meterological Satellite-Geostationary Ocean Color Imager (COMS-GOCI) images. Then, the GOCI detected area and simulated ash dispersion area were compared and verified. As the result, the similarity showed the satisfactory result between the detected and simulated area. The concordance ratio between the numerical simulation results and the GOCI images was 38.72 % and 13.57 %, Also, the concordance ratio between the JMA results and the GOCI images was 9.05 % and 11.81 %. When the volcano eruptions, volcanic ash range of damages are wide more than other volcanic materials. Therefore, predicting ash dispersion studies are one of main way to reduce damages.

• Journal of Korea Water Resources Association
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• v.50 no.6
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• pp.373-386
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• 2017

This study simulated water quality item and flow rate of subbasin for Saemangeum watershed using Soil and Water Assessment Tool (SWAT) model and Environmental Fluid Dynamics Code (EFDC) model which simulate hydraulic and water quality in three-dimensions. The simulated values corresponded to observed value well. The result of simulation for floodgate operations at the M3 and M5 points, it exceeds water quality standard and at the M3 and D3 points, change of range for concentration is too wide, and upstream of Saemangeum reservoir is sensitive to inflow flow rate. Compared to the annual average concentration for observed station according to the discharge conditions, improvement of water quality for upstream was apparently compared to the downstream. Range of influence for change of water quality presented that maximum discharge condition, the influence range is 22 km in the direction of the Saemangeum downstream from the Mankyung bridge, and 15 km in the downstream direction of saemangeum in the Dongjin bridge. This study result demonstrated that floodgate operating at upstream has significant influence on water quality management of Saemangeum reservoir and it needs to be considered in plans of water quality management for Floodgate operation on Saemangeum reservoir.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.47 no.5
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• pp.153-164
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• 2010

A program consumes energy by executing its instructions. The amount of cosumed power is mainly proportional to algorithm complexity and it can be calculated by using complexity information. Generally, the complexity of a S/W is estimated by the microprocessor simulator. But, the simulation takes long time why the simulator is a software modeled the hardware and it only provides the information about computational complexity quantitatively. In this paper, we propose a complexity estimation method of analysis of S/W on source code level and produce the complexity metric mathematically. The function-wise complexity metrics give the detailed information about the calculation-concentrated location in function. The performance of the proposed method is compared with the result of the gate-level microprocessor simulator 'SimpleScalar'. The used softwares for performance test are $4{\times}4$ integer transform, intra-prediction and motion estimation in the latest video codec, H.264/AVC. The number of executed instructions are used to estimate quantitatively and it appears about 11.6%, 9.6% and 3.5% of error respectively in contradistinction to the result of SimpleScalar.

• Journal of the Korean Institute of Intelligent Systems
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• v.14 no.1
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• pp.9-14
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• 2004

Rational sense is affected by emotion. If we add the factor of estimated emotion by environment information into robots, we may get more intelligent and human-friendly robots. However, various sensory information and pattern classification are prescribed for robots to learn emotion so that the networks are suitable for the necessity of robots. Neural network has superior ability to extract character of system but neural network has defect of temporal cross talk and local minimum convergence. To solve the defects, many kinds of modular neural networks have been proposed because they divide a complex problem into simple several subproblems. The modular neural network, introduced by Jacobs and Jordan, shows an excellent ability of recomposition and recombination of complex work. On the other hand, the recurrent network acquires state representations and representations of state make the recurrent neural network suitable for diverse applications such as nonlinear prediction and modeling. In this paper, we applied recurrent network for the expert network in the modular neural network structure to learn data pattern based on emotional assessment. To show the performance of the proposed network, simulation of learning the environment and behavior pattern is proceeded with the real time implementation. The given problem is very complex and has too many cases to learn. The result will show the performance and good ability of the proposed network and will be compared with the result of other method, general modular neural network.