• Journal of Korean Society for Atmospheric Environment
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• v.13 no.5
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• pp.355-360
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• 1997

The atmospheric concentration of dimethylsulfide (DMS), known as the predominant volatile organic. sulfur compound, is determined at subnanogram level by a combined application of non-cryogenic preconcentration method and gas chromatography with flame photometric detection (GC/FPD). The volatile DMS in air is preconcentrated using a trapping tube containing adsorbent like Molecular Sieve 5A (or gold-coated sands). The tube is then connected to the GC/FPD system via a six-way rotary valve, thermally desorbed at 40$0^{\circ}C$, separated on OV101 column, and detected by a flame photometric detector. The DMS peak elutes at about 2.5 mins and is integrated electronically. The analytical precision, if expressed in terms of relative standard error, is around 5%. The detection limit of our GC/FPD system is ca 1 ng of DMS. Details of our analytical system are presented.

• Journal of Computational Design and Engineering
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• v.1 no.3
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• pp.187-193
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• 2014

One of the hottest challenges in automotive industry is related to weight reduction in sheet metal forming processes, in order to produce a high quality metal part with minimal material cost. Stamping is the most widely used sheet metal forming process; but its implementation comes with several fabrication flaws such as springback and failure. A global and simple approach to circumvent these unwanted process drawbacks consists in optimizing the initial blank shape with innovative methods. The aim of this paper is to introduce an efficient methodology to deal with complex, computationally expensive multicriteria optimization problems. Our approach is based on the combination of methods to capture the Pareto Front, approximate criteria (to save computational costs) and global optimizers. To illustrate the efficiency, we consider the stamping of an industrial workpiece as test-case. Our approach is applied to the springback and failure criteria. To optimize these two criteria, a global optimization algorithm was chosen. It is the Simulated Annealing algorithm hybridized with the Simultaneous Perturbation Stochastic Approximation in order to gain in time and in precision. The multicriteria problems amounts to the capture of the Pareto Front associated to the two criteria. Normal Boundary Intersection and Normalized Normal Constraint Method are considered for generating a set of Pareto-optimal solutions with the characteristic of uniform distribution of front points. The computational results are compared to those obtained with the well-known Non-dominated Sorting Genetic Algorithm II. The results show that our proposed approach is efficient to deal with the multicriteria shape optimization of highly non-linear mechanical systems.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.22 no.3
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• pp.15-23
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• 2014

There have been CFIT(Controlled Flight Into Terrain) accidents that can be prevented if the crew executed go-around. This study is to analyse the common factors of three typical CFIT accidents of Korea in TEM(threat and error management) frame, and the examples of go-around gate and the countermeasures of eight airlines through the survey facilitating go-around to prevent CFIT. The common factors found in three typical CFIT accidents occurred in Korea or by Korean carriers turned out to be in mountainous terrain, in bad weather while in non-precision approach or circling approach by captain as PF(Pilot Flying) when crew make monitoring errors and communication errors. It also turned out that the crew in all three typical tragic CFIT accidents did not execute go-around in unstabilized approaches. The captains did not respond immediately when first officers advised them to go-around until it is too late. Seven out of eight Airlines answered that they use stabilized approach height as 1,000 feet to be stabilized earlier to have more safety margin by enhancing go-around gate regardless of the weather to prevent CFIT in the survey.

• The Korean Journal of Physiology and Pharmacology
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• v.25 no.6
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• pp.545-553
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• 2021

Fixed-dose combinations development requires pharmacokinetic drugdrug interaction (DDI) studies between active ingredients. For some drugs, pharmacokinetic properties such as long half-life or delayed distribution, make it difficult to conduct such clinical trials and to estimate the exact magnitude of DDI. In this study, the conventional (non-compartmental analysis and bioequivalence [BE]) and model-based analyses were compared for their performance to evaluate DDI using amlodipine as an example. Raw data without DDI or simulated data using pharmacokinetic models were compared to the data obtained after concomitant administration. Regardless of the methodology, all the results fell within the classical BE limit. It was shown that the model-based approach may be valid as the conventional approach and reduce the possibility of DDI overestimation. Several advantages (i.e., quantitative changes in parameters and precision of confidence interval) of the model-based approach were demonstrated, and possible application methods were proposed. Therefore, it is expected that the model-based analysis is appropriately utilized according to the situation and purpose.

• International Journal of Internet, Broadcasting and Communication
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• v.14 no.1
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• pp.136-141
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• 2022

A very complex task in deep learning such as image classification must be solved with the help of neural networks and activation functions. The backpropagation algorithm advances backward from the output layer towards the input layer, the gradients often get smaller and smaller and approach zero which eventually leaves the weights of the initial or lower layers nearly unchanged, as a result, the gradient descent never converges to the optimum. We propose a two-factor non-saturating activation functions known as Bea-Mish for machine learning applications in deep neural networks. Our method uses two factors, beta (𝛽) and alpha (𝛼), to normalize the area below the boundary in the Mish activation function and we regard these elements as Bea. Bea-Mish provide a clear understanding of the behaviors and conditions governing this regularization term can lead to a more principled approach for constructing better performing activation functions. We evaluate Bea-Mish results against Mish and Swish activation functions in various models and data sets. Empirical results show that our approach (Bea-Mish) outperforms native Mish using SqueezeNet backbone with an average precision (AP50val) of 2.51% in CIFAR-10 and top-1accuracy in ResNet-50 on ImageNet-1k. shows an improvement of 1.20%.

• International Journal of Computer Science & Network Security
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• v.23 no.5
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• pp.1-6
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• 2023

Text mining (TM) is most widely used to process the various unstructured text documents and process the data present in the various domains. The other name for text mining is text classification. This domain is most popular in many domains such as movie reviews, product reviews on various E-commerce websites, sentiment analysis, topic modeling and cyber bullying on social media messages. Cyber-bullying is the type of abusing someone with the insulting language. Personal abusing, sexual harassment, other types of abusing come under cyber-bullying. Several existing systems are developed to detect the bullying words based on their situation in the social networking sites (SNS). SNS becomes platform for bully someone. In this paper, An Enhanced text mining approach is developed by using Ensemble Algorithm (ETMA) to solve several problems in traditional algorithms and improve the accuracy, processing time and quality of the result. ETMA is the algorithm used to analyze the bullying text within the social networking sites (SNS) such as facebook, twitter etc. The ETMA is applied on synthetic dataset collected from various data a source which consists of 5k messages belongs to bullying and non-bullying. The performance is analyzed by showing Precision, Recall, F1-Score and Accuracy.

• Journal of the Korean Society of Systems Engineering
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• v.17 no.1
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• pp.11-20
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• 2021

Decontamination of systems, structures and components (SSC) during the decommissioning of a Nuclear Power Plant (NPP) can be for a variety of reasons. The main reasons for decontamination are: to reduce the contamination of SSC to a reasonably low level, to reduce the potential for the spread of contaminants into the environment and to reduce the cost of disposal due to the reduced level of contamination in a particular SSC. The decontamination technique can be aggressive or non-aggressive depending on the intent after the decontamination process. Aggressive decontamination technique is used when the intent is not to reuse the SSC while a non-aggressive decontamination technique is used with the intent of SSC reuse. For different SSCs there are different decontamination techniques that can be used, each having its own advantages and drawbacks. Metal components such as pipes in the nuclear power plant account for a large amount of nuclear wastes generated. Some of these wastes can be reused if the contaminant level is reduced to an acceptable level. Laser ablation is a non-aggressive decontamination technique that can be used to reduce the contamination in pipes to an acceptable level with no secondary waste generated during the process. The operation and control of a laser ablation device must be precise to achieve a high decontamination factor. This precision can be achieved by a well-designed motion control system. For this purpose, a motion control system was developed consisting of two parts: the first part being the precise control of the laser ablation device inside the pipe and the second part is the control of the laser ablation device outside the pipe. This paper describes the Systems Engineering approach for the development process of a motion control system for the Laser decontamination system.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.6 s.183
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• pp.119-127
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• 2006

A non-destructive time domain approach to examine structural damage using parameterized partial differential equations and Galerkin approximation techniques is presented. The time domain analysis for damage detection is independent of modal parameters and analytical models unlike frequency domain methods which generally rely on analytical models. The time history of the vibration response of the structure was used to identify the presence of damage. Damage in a structure causes changes in the physical coefficients of mass density, elastic modulus and damping coefficients. This is a part of our ongoing effort on the general problem of modeling and parameter estimation for internal damping mechanisms in a composite beam. Namely, in detecting damage through time-domain or frequency-domain data from smart sensors, the common damages are changed in modal properties such as natural frequencies, mode shapes, and mode shape curvature. This paper examines the use of beam-like structures with piezoceramic sensors and actuators to perform identification of those physical parameters, and detect the damage. Experimental results are presented from tests on cantilevered composite beams damaged at different locations and different dimensions. It is demonstrated that the method can sense the presence of damage and obtain the position of a damage.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.3
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• pp.95-103
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• 2010

Roll to Roll (R2R) is one of the most promising production technologies in the printed electronics such as OLEDs, e-paper, backplanes, RFID because this technology can save production cost and increase production speed. Printed electronics includes various processes such as printing, drying, winding, unwinding, and so on. In printed electronics R2R system, air-flotation oven is employed for drying process. Therefore, it is essential to introduce efficient and fast drying process when printing is finished. This paper considers the analysis of drying process in R2R that involves hot air flow. Air-flotation oven consists of non-contact supports and drying of coated web materials such as plastic films and paper. In this paper, experimental results and numerical analysis of pressure-pad air bar are investigated. The aerodynamic characteristics of pressure-pad air bar are numerically calculated using computational fluid dynamics (CFD) approach. Then the measured values of the aerodynamic forces for air bars are compared with those of CFD analysis.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.497-500
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• 2002

When one is interested in the dynamics of a mechanical system with electric motors, the force generated by the motor is generally considered as only an applied torque or force independent of mechanical state variables such as velocity. For a system operated in non-steady dynamic conditions, however, the usual analysis approach may fail to predict some characteristics in the dynamic behaviors because of electromechanical coupling effects. In this paper, we propose dynamics analysis model in which dc motor dynamics with the electromechanical coupling effects are embedded to mechanical dynamics models. The do motor is modeled based on its equivalent circuit model and included in the dynamics solving algorithm which we developed before, called generalized recursive dynamics formula. The developed dynamic analysis model is effective and realistic for analysis of electromechanical dynamics of a system with do motors. The developed model is evaluated by constructing and simulating the flexible antennas of an artificial satellite driven by do motors.