• Journal of the Korean institute of surface engineering
• /
• v.55 no.6
• /
• pp.448-459
• /
• 2022

Generally, steel is the most commonly used in the industry because of good strength, processability and cost-effectiveness. Steel can be surface-treated such as coating or used as an alloy by adding elements such as Cr, Ni, Zr, and Al to increase corrosion resistance. However, even if steel is used in same environment corrosion resistance is sharply lowered when it is exposed to a high temperature for a fixed or extended period of time due to an overload or other factors. In particular, the use of hot-dip aluminized plated steel, which is used in high-temperature atmospheres, is increasing due to the surface Al₂O₃ oxide film. This steel necessitates an urgent solution as issues of corrosion resistance limitations often appear. It is an important issue that not only cause analysis but also the research for the surface treatment method that can be solved. Thus, in this study, Cr in which it is expected to be effective in corrosion resistance and heat resistance attempted to deposit on hot dip aluminized plated steel with PVD sputtering. And it was possible to present the surface treatment application of various types of industrial equipment exposed to high temperature and basic design guidelines for use by confirming the corrosion resistance of hot dip Al-Si plated steel with Cr film deposited at high temperature.

• Journal of Ocean Engineering and Technology
• /
• v.34 no.6
• /
• pp.394-405
• /
• 2020

To assess the station-keeping performance of floating structures in the Arctic region, the ice load should be considered along with other environmental loads induced by waves, wind, and currents. However, present methods for performance evaluation in the time domain are not effective in terms of time and cost. An ice load generation module is proposed based on the experimental data measured at the KRISO ice model basin. The developed module was applied to a time domain simulation. Using the results of a captive model test conducted in multiple directions, the statistical characteristics of ice loads were analyzed and processed so that an ice load corresponding to an arbitrary angle of the structure could be generated. The developed module is connected to commercial dynamic analysis software (OrcaFlex) as an external force input. Station-keeping simulation in the time domain was conducted for the same floating structure used in the model test. The mooring system was modeled and included to reflect the designed operation scenario. Simulation results show the effectiveness of the proposed ice generation module and its application to station-keeping performance evaluation. Considering the generated ice load, the designed structure can maintain a heading angle relative to ice up to 4°. Station-keeping performance is enhanced as the heading angle conforms to the drift direction. It is expected that the developed module will be used as a platform to verify station-keeping algorithms for Arctic floating structures with a dynamic positioning system.

• Earthquakes and Structures
• /
• v.20 no.1
• /
• pp.109-122
• /
• 2021

Significant progress in the oil and gas industry advances the application of pipeline into an intelligent era, which poses rigorous requirements on pipeline safety, reliability, and maintainability, especially when crossing seismic zones. In general, strike-slip faults are prone to induce large deformation leading to local buckling and global rupture eventually. To evaluate the performance and safety of pipelines in this situation, numerical simulations are proved to be a relatively accurate and reliable technique based on the built-in physical models and advanced grid technology. However, the computational cost is prohibitive, so one has to wait for a long time to attain a calculation result for complex large-scale pipelines. In this manuscript, an efficient and accurate surrogate model based on machine learning is proposed for strain demand prediction of buried X80 pipelines subjected to strike-slip faults. Specifically, the support vector regression model serves as a surrogate model to learn the high-dimensional nonlinear relationship which maps multiple input variables, including pipe geometries, internal pressures, and strike-slip displacements, to output variables (namely tensile strains and compressive strains). The effectiveness and efficiency of the proposed method are validated by numerical studies considering different effects caused by structural sizes, internal pressure, and strike-slip movements.

• Journal of Korean Society on Water Environment
• /
• v.27 no.6
• /
• pp.877-884
• /
• 2011

In this paper, the removal characteristics of dissolved organic carbon (DOCs) by micro bubble ozonation process and $O_3/UV$ process were comparatively studied. In the point of DOC removing reaction coefficient, micro bubble ozonation system and $O_3/UV$ process had not significant difference, $0.0120sec^{-1}$ and $0.0141sec^{-1}$. Therefore micro bubble ozonation process is more suitable for tertiary treatment of sewage in the point of installation and maintenance cost-reducing. The optimum ozone injection rate was 2.0 g $O_3/g$ DOC and HRT was 3 min for the micro bubble ozonation process. The removal efficiency of DOC and SUVA in micro bubble ozonation system was 32.8% and 58.3% respective. Biological aerated filter (BAF) process was installed to remove soluble organic material increased by micro bubble ozonation system. And the effluent BOD of BAF was below 1.0 mg/L. In the view of cost-effectiveness, $O_3/BAF$ process was more profitable than $O_3/UV/BAF$ process for tertiary treatment of sewage. In order to nitrify ammonia in the BAF process completely, $NH_4{^+}-N$ concentration in the influent water of BAF should be designed considering low water temperature in the winter season.

• Archives of Craniofacial Surgery
• /
• v.21 no.6
• /
• pp.357-362
• /
• 2020

Background: Full-thickness skin grafts (FTSGs) have been widely used after facial skin cancer resection, for correcting defects that are too wide to be reconstructed using a local flap or if structural deformation is expected. The preauricular, posterior auricular, supraclavicular, conchal bowl, nasolabial fold, and upper eyelid skin areas are known as the main donor sites for facial FTSG. Herein, we aimed to describe the effectiveness of using infraclavicular skin as the donor site for specific cases. Methods: We performed FTSG using the infraclavicular skin as the donor site in older Asian adults following skin cancer resection. Outcomes were observed for > 6 months postoperatively. The Manchester Scar Scale was used for an objective evaluation of satisfaction following surgery and scarring. Results: We analyzed the data of 17 patients. During follow-up, the donor and recipient sites of all patients healed without complications. Upon evaluation, the average Manchester Scar Scale scores for the recipient and donor sites were 7.4 points and 5.7 points, respectively. Conclusion: In general, conventional donor sites, such as the preauricular, posterior auricular, and supraclavicular sites, are widely used for facial FTSG because they achieve good cosmetic results. However, the infraclavicular skin may be a useful donor for facial FTSG in cases where the duration of time spent under anesthesia must be minimized due to a patient's advanced age or underlying health conditions, or when the recipient site is relatively thick area, such as the nose, forehead, or cheek.

• Journal of the Korean Society of Safety
• /
• v.35 no.6
• /
• pp.78-84
• /
• 2020

The F&EI technique is one of the risk assessments with many advantages. It can save time and effort compared to quantitative risk assessment (QRA). By using the evaluation result of this technique, it is possible to check the effectiveness of the investment cost. In addition, a relative risk ranking can be created and used to establish the facility management cycle and to prioritize investment. However, evaluating the target process can be evaluated more than the actual risk since the LCCF, a loss prevention measure, is too limited. In addition, calculating premiums via this method can result in excessive premiums, making it difficult to evaluate the risk precisely. Therefore, new safety guard was added to the LCCF of the F&EI risk assessment with reference to HAZOP and LOPA techniques. Newly added LCCFs are Deflagration arrester, Check valve, SIS, and Vacuum beaker, etc. As a case study, F&EI risk assessment was performed on Acetone storage tank of a API (Active pharmaceutical ingredient) plant to compare actual MPPD. The estimated loss amount was 592,558$ for the existing technique and 563,571$ for the improved technique, which was reduced by about 5% compared to the previous one.This proved that a more precise evaluation is possible and that the efforts for safety at the workplace are reflected in the evaluation results.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.23 no.12
• /
• pp.1700-1709
• /
• 2019

Recently, many researches have been under way to develop systems (services) to support the safety navigation of ships, and in these studies, common difficulties have been encountered in assessing the usefulness and effectiveness of the developed system. To solve these problems, we propose the DEVS-based ship navigation modeling and simulation technique. Following the preceding study, we analyze the COLREG rules and reflected to officer and helmsman agent models for decision making. Also we propose estimation and interpolation techniques to adopt the motion characteristics of the actual vessel to simulation. In addition, we implement the navigation simulation system to reflect the designed proposed methods, and we present five-scenarios to verify the developed simulation system. And we conduct simulations according to each scenario and the results were reconstructed. The simulation results confirm that the components modelled in each scenario enable to operate according to the navigation relationships.

• International Journal of Advanced Culture Technology
• /
• v.9 no.1
• /
• pp.177-182
• /
• 2021

The fourth industrial revolution based on information and communication technology (ICT) becomes the center of society, and the overall industrial structure is also changing significantly. ICT refers to the hardware of information devices and the software technologies required for the operation and information management of these devices, and any means of collecting, producing, processing, preserving, communicating and utilizing them. ICT is integrated into industries and services or combined with new technologies in various fields such as robotics and nanotechnology to connect all products and services to the network. The development of ICT, which continuously creates new products and services, has spread to all sectors of the industry, affecting not only daily life but also the livestock sector recently. In agriculture, ICT technology can reduce production costs by efficiently managing labor and energy because it can improve quality and yield based on data on environmental and growth information such as temperature, humidity, light and soil. In particular, smart livestock is considered suitable for achieving livestock management goals because it can reduce labor force and improve productivity by remotely and automatically managing accurate information necessary for raising and breeding livestock with ICT devices. The purpose of this study is to propose the need for ICT technology by comparing farm productivity before and after ICT is introduced. The method of the study is to compare the productivity before and after the introduction of ICT in Korean beef farms, pig farms, and poultry farms. The effectiveness of the study proved the excellence of ICT technology through the production results before ICT introduction and the productivity improvement case of livestock farms that efficiently operated manpower management and reduced labor force after ICT introduction. The conclusion of this paper is to present the need for smart livestock through ICT adoption through case study results.

• Journal of Advanced Navigation Technology
• /
• v.24 no.6
• /
• pp.607-612
• /
• 2020

In this paper, we deal with the stability of linear discrete systems with time-varying delays and unstructured uncertainty. Stability conditions are derived based on Lyapunov stability theory, and can include the effect of uncertainty. The unstructured uncertainty in the papaer which can not be figured out its exact characteristics and only can be expreesed by its magnitude is considered. Compared with the previous results on the stability, the new results can expand the applicable systems and alleviate the stability conditions which are more effective and powerful. The proposed stability condition is expressed in the form of an simple inequality, and includes the both effects of the uncertainties and time-varying delay. We present the results comparing the new stability condition with the existing results, and verify the effectiveness and the superiority of the proposed results through numerical example.

• Journal of Advanced Navigation Technology
• /
• v.26 no.2
• /
• pp.72-77
• /
• 2022

Among the techniques of reinforcement learning, Q-Learning means learning optimal policies by learning Q functions that perform actionsin a given state and predict future efficient expectations. Q-Learning is widely used as a basic algorithm for reinforcement learning. In this paper, we studied the effectiveness of selecting and learning efficient paths by designing policies and rewards based on Q-Learning. In addition, the results of the existing algorithm and punishment compensation policy and the proposed punishment reinforcement policy were compared by applying the same number of times of learning to the 8x8 grid environment of the Frozen Lake game. Through this comparison, it was analyzed that the Q-Learning punishment reinforcement policy proposed in this paper can significantly increase the learning speed compared to the application of conventional algorithms.