• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.6
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• pp.692-696
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• 2017

The shape of press components is becoming increasingly complex due to customer demands, process shortening and cost savings. In addition, the stability of the pressing process frequently varies during mass production due to the influence of many factors. In order to ensure the process stability, it is necessary to establish a process in which reproducibility is realized in tolerance, which is sufficient for advance study of shape, material, press, mold and lubrication. However, unforeseen changes in process parameters cause disruptions in production line shutdowns and production planning. In this paper, we introduce a method to monitor a real time process by applying a sensor to a press mold. A non-contact type sensor for measuring the flow of a sheet material and an example of an experiment using the optical sensor which is highly applicable to mass production are presented. An optical sensor was installed in a cylindrical drawing mold to test its potential application while changing the material, blank holder force, and drawing ratio. We also quantitatively determined that the flow of other sheet materials was quantified locally using a square drawing die and that the measured value was always smaller than the drawing depth due to the material elongation. Finally, we propose a field that can be used by attaching the sensor to the press mold. We hope that the consequent cost reduction will contribute to increasing global mold competitiveness.

• Journal of the Korean Society of Combustion
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• v.18 no.4
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• pp.37-43
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• 2013

The effects of preferential diffusion of hydrogen in interacting counterflow $H_2$-air and CO-air premixed flames were investigated numerically. The global strain rate was varied in the range $30-5917s^{-1}$, where the upper bound of this range corresponds to the flame-stretch limit. Preferential diffusion of hydrogen was studied by comparing flame structures for a mixed average diffusivity with those where the diffusivities of H, $H_2$ and $N_2$ were assumed to be equal. Flame stability diagrams are presented, which show the mapping of the limits of the concentrations of $H_2$ and CO as a function of the strain rate. The main oxidation route for CO is $CO+O_2{\rightarrow}CO_2+O$, which is characterized by relatively slow chemical kinetics; however, a much faster route, namely $CO+OH{\rightarrow}CO_2+H$, can be significant, provided that hydrogen from the $H_2$-air flame is penetrated and then participates in the CO-oxidation. This modifies the flame characteristics in the downstream interaction between the $H_2$-air and CO-air flames, and can cause the interaction characteristics at the rich and lean extinction boundaries not to depend on the Lewis number of the deficient reactant, but rather to depend on chemical interaction between the two flames. Such anomalous behaviors include a partial opening of the upper lean extinction boundary in the interaction between a lean $H_2$-air flame and a lean CO-air flame, as well as the formation of two islands of flame sustainability in a partially premixed configuration with a rich $H_2$-air flame and a lean CO-air flame. At large strain rates, there are two islands where the flame can survive, depending on the nature of the interaction between the two flames. Furthermore, the preferential diffusion of hydrogen extends both the lean and the rich extinction boundaries.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.146-149
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• 2013

For in recently years, global cellular network service is changing rapidly to 4G. However, the fast introducing of 4G has been going with not enough research about security threat, it could be many kind of vulnerability. Therefore the research about security threat on 4G network is ongoing in external countries, but not sufficient in domestic. particularly in domestic situation of rapidly increased subscribers, The security threats which are hindering stability and usability could make a fatal effect on many users. 4G network should be considered about the feature of mobile network to protect 4G network stable. Mobile network has limited radio resources, it releases the radio resource which is not used in selected time and reallocate when detected the data transmission. Many signaling messages are transferred in the network entities to allocate or release the radio resource. In this paper, it will be introduced the technology to detect signaling DoS traffic hindering the stability and usability of network entities managing the radio resources by huge signaling message from the repetitive wireless connection/release message.

• Journal of Industrial Convergence
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• v.20 no.8
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• pp.127-136
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• 2022

This study was conducted using a multiple regression model to empirically analyze the impact of personal emotions and social change perceptions of pandemic experienced by Korean people in the COVID-19 situation on the perception of disaster response after the endemic. For this end, we used the survey data with 996 respondents on 「Daily Changes of the People After COVID-19」conducted by the Korea Press Promotion Foundation. The results showed that COVID-19 positive emotions and social change perception factors had a positive (+) effect on disaster response perception, while the sense of community had a moderating effect that alleviated COVID-19 negative emotions which had a negative (-) effect. The most influential factors on disaster response perception after the endemic were COVID-19 positive emotions and community sense that had pride and stability in Korean society during disaster situations. Therefore, this study suggests that systematic disaster response manuals and control towers that give the public pride and stability are more strongly requested for the government's prior and follow-up measures performed in the post-endemic disaster situation, and that the people are asked to have the community sense to overcome disasters together rather than to respond with personal actions and judgments.

• Tunnel and Underground Space
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• v.33 no.2
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• pp.95-107
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• 2023

In this study, the effect of repeated traffic vibration on the long-term stability of mine openings is analyzed for re-utilization of abandoned mine galleries. The research mine in this study is an underground limestone mine which is developed by room-and-pillar mining method, and a dynamic numerical analysis is performed assuming that the research mine will be utilized as a logistics warehouse. The actual traffic vibration generated by the mining vehicles is measured directly, and its waveform is used as input data for dynamic numerical analysis, As a results of dynamic numerical analysis, after 20,000 repetitions of traffic vibration, the mine openings is analyzed to be stable, but an increase in the maximum principal stress and an additional area of plastic zone are observed in the analysis section. As shown in the changes of displacement, volumetric strain, and maximum principal stress which are measured at the mine opening walls. It is confirmed that if the repeated traffic vibration is continuously applied, the instability of the mine openings can be increased. Authors expect that the results of this study can be used as a reference for basic study on utilization of abandoned mine.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.49 no.2
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• pp.97-106
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• 2023

In this study, we would like to study the stabilization of the high content of ceramide formulation by containing cyclodextrin. Ceramide, which constitutes the intercellular lipid, a human skin barrier, is a very important ingredient in moisturizing maintenance by protecting moisture in the skin and strengthening the skin barrier. However, since ceramide is poorly soluble, even if it is included in the cosmetic formulation, it has a problem that it is slowly gelled or crystallized and deposited over time, making it difficult to containing a high amount of ceramide. Cyclodextrin is a cyclic oligosaccharide connected with glucose molecules and has a cylindrical structure with hydrophilic outer surface and hydrophobic inner surface, which is known to improve the physicochemical properties of drugs such as improving solubility and absorption of poorly soluble drugs. We demonstrated the stability of the formulation containing high amount of ceramide by measuring hardness and observing emulsion drops with polarized microscope. This study also demonstrated that the high-content ceramide formulation containing cyclodextrin has the effect of preventing gelation or crystallization of ceramide, thus having excellent environmental conditions stability and skin moisturization.

• International conference on construction engineering and project management
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• 2024.07a
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• pp.1321-1321
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• 2024

Concrete arch dams, unlike conventional concrete gravity dams, have thin arch-shaped cross sections and must be designed considering a three-dimensional shape. In particular, double-curvature arch dams, which have arch-shaped vertical and horizontal sections, require careful consideration during design due to their unique shape. Although stress analysis is complex, and various factors need to be considered during the design, these dams offer economic advantages as they require less material. Consequently, numerous double-curvature arch dams have been constructed worldwide, and ongoing research focuses on optimizing their shapes. In this study, an efficient optimization algorithm was developed for the shape optimization of concrete arch dams with double-curvature using genetic algorithms and improved population initializing technique. The developed technique utilized domain knowledge in the field of arch dams to generate an excellent initial population. To assess the relevance of domain knowledge, an investigation was conducted on the accumulated knowledge and empirical formulas from literature. Two pieces of domain knowledge can be gleaned from the iterative structural design experiences associated with arch dams. First, it concerns the thickness of the central cantilever of an arch dam. For minimum tensile stress, it is best to make the thickness as thin as possible at the dam crest and gradually become thicker as it goes down. The second aspect concerns the sliding stability of the arch dam, which depends on the central angle of the horizontal section. This angel is important for stability because the plane arch serves to transfer the hydraulic load from the reservoir to both abutments. Also, preliminary design formulas for arch dams from a manual written by the United States Bureau of Reclamation (USBR) were used. On the other hand, since domain knowledge is based on engineering experiences and data from existing dams, its usability should be verified by comparing it with the results of design optimization performed by classic genetic algorithms. To validate the performance of the optimization algorithm with the improved population initialization technique, a test site with an existing dam was selected, and algorithmic application tests were conducted. Stress analysis is performed for each design iteration, evaluating constraints and calculating fitness as the objective function. The results confirmed that the algorithm developed in this study exhibits superior performance in terms of average fitness and convergence rate compared to classic genetic algorithms.

• Clean Technology
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• v.30 no.3
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• pp.159-174
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• 2024

The rapid increase in energy consumption based on fossil fuels is accelerating global warming. In particular, the road transportation sector has high carbon dioxide emissions, so transitioning towards electric vehicles is recommended. Thus, the importance of secondary batteries is increasing. Secondary batteries are reversible batteries that use energy and can be reused through a charging and discharging process. Currently, lithium-ion batteries are widely used. Secondary batteries place importance on six major factors: energy, output, lifespan, environmental friendliness, cost, and stability. Research is actively being conducted to satisfy all six factors by understanding the material characteristics of each component of the battery. As it is difficult to move away from lithium as a cathode material, researchers are investigating higher performance materials that mix materials such as cobalt, nickel, manganese, and aluminum with lithium and use graphite, silicon, and lithium metal to increase capacity. In the case of electrolytes, liquid electrolytes are still mainly used. However, solid electrolytes are being studied due to their stability, but additional research must be conducted to satisfy the energy and output factors. This review paper aims to provide an understanding of secondary batteries through an overview of secondary batteries, the materials and characteristics of their components, their technological trends, and their associated companies.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.6 s.52
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• pp.19-28
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• 2006

Most conventional model updating methods must use mathematical objective function with experimental modal matrices and analytical system matrices or must use information about the gradient or higher derivatives of modal properties with respect to each updating parameter. Therefore, most conventional methods are not appropriate for complex structural system such as bridge structures due to stability problem in inverse analysis with ill-conditions. Sometimes, moreover, the updated model may have no physical meaning. In this paper, a new FE model updating method based on a hybrid optimization technique using genetic algorithm (GA) and Holder-Mead simplex method (NMS) is proposed. The performance of hybrid optimization technique on the nonlinear problem is demonstrated by the Goldstein-Price function with three local minima and one global minimum. The influence of the objective function is evaluated by the case study of a simulated 10-dof spring-mass model. Through simulated case studies, finally, the objective function is proposed to update mass as well as stiffness at the same time. And so, the proposed hybrid optimization technique is proved to be an efficient method for FE model updating.

• Journal of the Korean Institute of Gas
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• v.14 no.1
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• pp.15-20
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• 2010

The interest on the utilization of landfill gases and biogases for energy production has been increasing due to environment concerns and global warming caused by burning fossil fuels, renewable nature of these gases. Using those synthesis gases to generate energy with engine encourages more efficient collection reducing emissions into the atmosphere and generates revenues for the operators. However the lower calorific value of synthesis gases than that of LPG or CNG affects the combustion stability and power output. Thus it becomes necessary to address disadvantages involved by studying synthesis gases in technological perspective. This paper discussed synthesis gas as a fuel for 60kW dual-fuel engine to produce power in an effective way. The methane diluted with $N_2$ was used as a fuel and developed ECU and injector driver facilitated the investigations with diesel fuel.