• Explosives and Blasting
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• v.26 no.1
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• pp.39-48
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• 2008

Using Electronic Detonators which is well known for controlling vibration, we have been studying Orchestra Blasting Method, OBM, for many years to transform the unpleasant blasting sound to favorable sound in some job-sites such as tunneling and bench blasting which have to been taken place near some structures needed great care. In this study, we focus on rhythmical sense. First, we acquired individual wave from a shot. With the program named the Program Blasting Wave, PBW, it was analyzed and found that its best delay time was 34ms and 50ms was acceptable. Also, delay time was fitted into the music which was accepted after analyzing the rhythm. As a result, the blasting sound along with the music felt comfortable as if the music was played with base drum.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.12
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• pp.1577-1583
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• 2012

Penetrator with enhanced lateral effect (PELE) is a novel projectile that does not require dynamite and a fuse. It comprises a high-density jacket that is closed at its rear end and filled with a low-density filling material. To study the explosion characteristics of PELE using AUTODYN-3D code, the calculation models of the projectile body and the bullet target were developed and the process of penetrating an aluminum-2024 alloy target using PELE was simulated. The scattering characteristics after PELE penetrated the aluminum-2024 alloy target were studied for different filling materials. The explicit finite element analysis of PELE fragmentation was implemented with the stochastic failure criterion in AUTODYN-3D code. As the filling expanded, the fragments gained velocity and dispersed laterally, increasing the damage area considerably. The number and shape of PELE fragments differed depending on the impact pressure of the filling that fragmented during the penetration and lateral dispersion processes.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.1
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• pp.69-77
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• 2005

To optimize and limit the axial length of the baffle of the KSR-III engine, stability rating tests using pulse gun as one of artificial disturbance devices have been done. Generally a rocket engine can be considered to be dynamically stable if a certain imposed external perturbation or pressure oscillation in rocket combustion chamber could be suppressed within a short time period. Decay time and other parameters for the evaluation of stabilization ability of an engine to external perturbation have been analyzed to quantify stabilization capacity of engine, in other words, dynamic stability margin. Baffle not covering flame zone enough which can be considered as collision region of injector wasn't be able to suppress external perturbation sufficiently. The limit of combustion stability margin of engine is assumed to be 50 mm length baffle of the KSR-III engine.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.4
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• pp.269-275
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• 2020

An explosive bolt is one of many representative pyrotechnic release devices that separates two joined structures using explosives inside the bolt. In this study, a 1/2 inch ridge-cut explosive bolt with an EBW detonator was developed for usage in sled tests. The initial shape design was carried out based on the design method, and the performance test showed that the separation performance was outstanding but fragments occurred. Therefore, numerical analysis was performed to reduce the amount of debris by minimizing the amount of explosives. From the numerical analysis, the separation mechanism and characteristics of the ridge-cut explosive bolts were identified, and the minimum amount of explosives that does not generate debris was proposed. Verification tests revealed that the ridge-cut explosive bolts with the proposed explosive weight minimized fragments while maintaining the separation performance.

• Journal of Korea Game Society
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• v.17 no.2
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• pp.75-84
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• 2017

With the rapid growth of smartphone game in Korea, it is necessary to review the new monetization model. Especially, various contents supplied by smartphone did not find proper monetization model from business view. But smartphone game industry actively accepted market experience of arcade game industry and console, PC based package game industry, then have developed and applied various monetization models to induce billing such as monetization model and in-game advertising model, thereby forming a thick charging user group in a short time. The development and application of this monetization model is an important catalyst for the rapid growth and development of the smartphone game market. Therefore, we will examine the process of changing the monetization model of the entire game industry and the cultural characteristics of the micropayment model in Korea. To this end, we will compare the micropayment model of Japan which introduced the micropayment model and China which leads the world market.

• The Journal of the Korea Contents Association
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• v.18 no.6
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• pp.545-553
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• 2018

This study analyzes the animal symbolism shown in the novella by Hyoseok Lee and seeks to shed light on the consciousness of the author expressed through such symbolism. Lee used animal symbolism since 1933 which was a literary turning point for him. Animal symbolism in his novels are more than an analogical theme but is used as a core meaning and image. This has a clear intention of the author underneath. Novella which is seen as the starting point of pure literature for Lee, uses the animal pig as a key symbol. The pig serves as a symbol of the capital for poor farmers, while also serving as an amplifier for the desires of the protagonist. The death of the pig that appears at the closing of the novella stands for the tragic reality of the farmers of the time who could not seek growth in their capital or realization of their desires. As such, has characteristics of pure literature but also represents the consciousness of the author who brings attention to the tragic reality of farmers. That is, is a work that realized the unique writing style of Lee and his animal symbolism to bring to life a middle way appraoch to realism and romanticism.

• Convergence Security Journal
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• v.15 no.7
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• pp.119-124
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• 2015

The purpose of this study was to examine the current status and future prospects through the Classification of sports and ICT convergence technology for the health. Sports and ICT convergence technology could be classified into three types-sports and virtual reality, wearable devices, application and platforms. First, the application of virt ual reality technology gives a user the feeling of reality, fun, and flow through the sensing technology. And this was extended to 'Gamification' concept, gamification of the Nike Plus has become a catalyst in the spread of wea rable devices market. Second, the fastest growing sector in the wearable device area is the health and sports. Chin ese and start-up companies as well as global ICT companies is competing for expanding the pool by releasing the fitness-related wearable devices. Third, the building of platform that can utilize the health and exercise-related dat a collected through the application is expanding.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.2
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• pp.75-85
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• 2016

A pyrotechnic system consisting of donor/acceptor pair separated by a gap relies on shock attenuation characteristics of the gap material and shock sensitivity of the donor and acceptor charges. Despite of its common use, numerical study of such pyrotechnic train configuration is seldom reported because proper modeling of the full process requires precise capturing of the shock wave attenuation in the gap prior to triggering a full detonation of high explosive and accurate description of the high strain rate dynamics of the explosively loaded inert confinements. We apply a Eulerian level-set based multimaterial hydrocode with reactive flow models for pentolite donor and heavily aluminized RDX as acceptor charge. The complex shock interaction, critical gap thickness, acoustic impedance, and go/no-go characteristics of the gap test are quantitatively investigated.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.10
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• pp.1027-1037
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• 2009

The development of a combustion chamber for a 30-$ton_f$ regeneratively-cooled space liquid rocket engine is described. Starting from the development of bi-propellant swirl coaxial injectors, essential technologies were verified through subscale combustion chambers and afterwards applied to the full-scale combustion chambers. A total of 5 full-scale combustion chambers have been utilized to verify ignition, combustion efficiency and stability, cooling, and duration requirements. A total of 46 combustion tests were performed among which 23 tests were parallely performed with stability rating tests using a pulse gun device. The test results have revealed that the 30-$ton_f$ regeneratively-cooled combustion chamber fully complies to the performance and combustion stability requirements and thus concluded that the development is successfully completed.

• Journal of the Korean Magnetics Society
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• v.21 no.5
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• pp.167-173
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• 2011

Underwater static magnetic field signature for the naval ship has been widely used as the detonating source of the influence mine system because it is possible to make an accurate target detection in the near field although the magnetic field falls off relatively fast with distance in comparison with the underwater radiated noise signal. In this paper, we describe the prediction results about the underwater static magnetic field by the ferromagnetic hull, the internal structures and the main on-board equipment for the target vessel using the commercial FEM software. Also we analyze the degaussing effectiveness for the target vessel through the degaussing coils arrangement.