• Korean Chemical Engineering Research
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• v.59 no.2
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• pp.209-218
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• 2021

First principle-based modeling studies have been performed to improve the heat exchange efficiency of ORV and optimize operation, but the heat transfer coefficient of ORV is an irregular system according to time and location, and it undergoes a complex modeling process. In this study, FNN, LSTM, and AutoML-based modeling were performed to confirm the effectiveness of data-based modeling for complex systems. The prediction accuracy indicated high performance in the order of LSTM > AutoML > FNN in MSE. The performance of AutoML, an automatic design method for machine learning models, was superior to developed FNN, and the total time required for model development was 1/15 compared to LSTM, showing the possibility of using AutoML. The prediction of NG and seawater discharged temperatures using LSTM and AutoML showed an error of less than 0.5K. Using the predictive model, real-time optimization of the amount of LNG vaporized that can be processed using ORV in winter is performed, confirming that up to 23.5% of LNG can be additionally processed, and an ORV optimal operation guideline based on the developed dynamic prediction model was presented.

• Journal of the Korean Geotechnical Society
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• v.37 no.12
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• pp.73-87
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• 2021

Pile-supported wharf is a structure that can transmit and receive cargo, and it is mainly installed on saturated inclined ground. In the seismic design of these structures, the codes suggest using the response spectrum analysis method as a preliminary design method. However, guideline on modeling method for pile-supported wharf installed in saturated soil is lacking. Therefore, in this study, the dynamic centrifuge model test and response spectrum analysis were performed to evaluate the seismic performance of pile-supported wharf installed into the saturated soil. For the test, some sections (3×3 pile group) among the pile-supported wharf were selected, and they were classified into two model (dry and saturated sand model). Then the response spectrum analysis was performed by using the soil spring method to the test model. As a result of test and analysis, the m om ent difference occurred within a m axim um of 51% in the dry sand m odel and the saturated sand model where liquefaction does not occur, and it was found that the pile moment by depth was properly simulated. Therefore, in the case of these models, it is appropriate to perform the modeling using the Terzaghi (1955) constant of horizontal subgrade reaction (n_h)

• Journal of Navigation and Port Research
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• v.47 no.4
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• pp.256-270
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• 2023

In this study, a sliding mode (SM) controller for dynamic positioning (DP) was specifically designed for a turret connection operation of a ship or an offshore structure in which an arbitrary point on the structure could be controlled as the motion center instead of the center of mass. The SM controller allows control of the arbitrary point and provides capability to manage uncertainties in the dynamics of ships and offshore structures, external forces caused by unknown changing marine environments, and transient performance of DP systems. The Jacobian matrix included in kinematic equations of the controlled object was modified to design the SM controller to control based on an arbitrary point of ships or offshore structures. To ensure robustness of the controller, the Lyapunov stability theory was applied in the design of the SM controller. In general, for robustness in DP control, gain scheduling based on a proportional-derivative (PD) control algorithm is employed. However, finding appropriate gains for gain scheduling complicates the application of DP systems. Therefore, in this study, the SM control algorithm was considered to mitigate the complexity of the DP controller for ships and offshore structures. To validate the proposed SM control algorithm, time-domain simulations were conducted and utilized to evaluate the performance of the control algorithm. The effectiveness of the proposed SM controller was assessed by comparing simulation results with results of a conventional PD control algorithm applied in DP control.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.7
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• pp.27-38
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• 2016

This work proposes a 12b 30MS/s 0.18um CMOS SAR ADC based on low-power composite switching with an active die area of $0.16mm^2$. The proposed composite switching employs the conventional $V_{CM}$-based switching and monotonic switching sequences while minimizing the switching power consumption of a DAC and the dynamic offset to constrain a linearity of the SAR ADC. Two equally-divided capacitors topology and the reference scaling are employed to implement the $V_{CM}$-based switching effectively and match an input signal range with a reference voltage range in the proposed C-R hybrid DAC. The techniques also simplify the overall circuits and reduce the total number of unit capacitors up to 64 in the fully differential version of the prototype 12b ADC. Meanwhile, the SAR logic block of the proposed SAR ADC employs a simple latch-type register rather than a D flip-flop-based register not only to improve the speed and stability of the SAR operation but also to reduce the area and power consumption by driving reference switches in the DAC directly without any decoder. The measured DNL and INL of the prototype ADC in a 0.18um CMOS are within 0.85LSB and 2.53LSB, respectively. The ADC shows a maximum SNDR of a 59.33dB and a maximum SFDR of 69.83dB at 30MS/s. The ADC consumes 2.25mW at a 1.8V supply voltage.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.7
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• pp.539-546
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• 2013

Surge phenomenon can be occurred in a compressor when compressor performance of turbofan engine for an aircraft is changed considerably in a short time on the cases like take-off phase and changing of RPM from idle to maximum, because performance of aircraft engine is changed suddenly. This study is aimed to avoid surge in a compressor. Dynamic simulation in a compressor is modeled by simulink in specific condition. Fuel flow is control input, rpm and air mass flow are expressed in terms of transfer function. Surge margin is obtained by using compressor performance map from NPSS. VIGV(Variable Inlet Guide Vane) is controlled by PD controller with difference between surge margin and reference. Finally this paper verifies IGV can prevent surge phenomenon in a compressor.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.48 no.6
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• pp.71-81
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• 2011

Unlike a typical internal combustion engine vehicle, the powertrain system of the pure electric vehicle, consisting of battery, inverter and motor, has direct effects on the vehicle performance and dynamics. Then, the specific modeling of such complex electro-mechanical components enables the insight into the longitudinal dynamic outputs of the vehicle and analysis of entire powertrain systems. This paper presents the dynamic model of electric vehicle powertrain systems based on theoretical approaches to predict and analyze the final output performance of electric vehicles. Additionally, the correlations between electric input signals and the final output of the mechanical system are mathematically derived. The proposed model for powertrain dynamics of electric vehicle systems are validated with a reference electric vehicle model using generic simulation platform based on Matlab/Simulink software. Consequently, the dynamic analysis results are compared with electric vehicle simulation model in some parameters such as vehicle speed/acceleration, and propulsion forces.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.3
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• pp.75-82
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• 2019

Slab panels are very important to develop asphalt concrete (AC) track for minimizing the roadbed stress due to the train load and reducing the plastic deformation of infrared-sensitive AC. In this study, the slab panel for AC track was developed through the shape design and the indoor performance test and its structural integrity has been investigated through the finite element analysis under the flexural tensile stress and the design moment according to various static load combination by KRL-2012 standard train load model and KR-C code. In order to verify the suitability of the slab panel for AC track, static bending strength test and dynamic bending strength test were performed according to EN 13230-2. Results show that the slab panel for AC track satisfies all the performance standards required by European standards such as crack loads and crack extension.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.37 no.1
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• pp.17-24
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• 2024

This paper assesses the structural performance of the Daeungbojeon Hall of Magoksa in Gongju, a representative multi-tiered roof traditional timber structure from the Joseon Dynasty, under vertical loads. Employing midas Gen, a structural analysis software, we developed a three-dimensional analysis model closely resembling the actual structure. Static analysis was employed to evaluate the safety and serviceability of the main vertical and horizontal members under vertical loads. While all members met the safety and serviceability criteria, structural weaknesses were identified in the Daelyang of the lower floor, particularly as a transitional beam, necessitating improvement. For the evaluation of dynamic behavior characteristics, eigenvalue analysis was conducted, assuming a relative rotational stiffness of 5% at the main joints. The natural period was determined to be 1.105 seconds, placing it within the category of a Hanok of similar size. The first mode manifested as a translational movement in the forward and backward direction of the building.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.4
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• pp.15-22
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• 2003

Seismic design codes developed taking into account the strong earthquakes may result in unnecessary economical loss in the low seismic area, and the importance of the performance based design considering the soil-structure interaction is recognized for the reasonable seismic design. In this study. elastic and inelastic seismic response analyses of a single degree of freedom system on the soft soil layer were performed considering the nonlinearity of the soil for the 1 weak earthquakes scaled to the nominal peak accelerations of 0.07g and 0.11g. The seismic response analyses were performed in one step applying the earthquake motions to the bedrock, utilizing a pseudo 3-D dynamic analysis software of the soil-structure system. The study results indicated that seismic response spectra of a system assuming the rigid base or the linear soil layer does not represent the true behavior of a structure-soil system, and it is necessary to take into account the nonlinear soil-structure interaction effects and to perform the performance based seismic design for the various soil layers, having different characteristics, rather than to follow the routine design procedures specified in the design codes for the reasonable seismic design. The nonlinearity of the soft soil excited with the weak seismic motions also affected significantly on the elastic and inelastic seismic response spectra of a system due to the nonlinear soil amplification of the earthquake motions, and it was pronounced especially for the elastic response spectra.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.10
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• pp.881-886
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• 2013

Even though a multi-view camera system is able to capture multiple images at different viewpoints, the color distributions of captured multi-view images can be inconsistent. This problem decreases the quality of multi-view images and the performance of post-image processes. In this paper, we propose an improved polynomial model for effectively correcting the color inconsistency problem. This algorithm is fully automatic without any pre-process and considers occlusion regions of the multi-view image. We use the 5th order polynomial model to define a relative mapping curve between reference and source views. Sometimes the estimated curve is seriously distorted if the dynamic range of extracted correspondences is quite low. Therefore we additionally estimate the first order polynomial model for the bottom and top regions of the dynamic range. Afterwards, colors of the source view are modified via these models. The proposed algorithm shows the good subjective results and has better objective quality than the conventional color correction algorithms.