• Structural Engineering and Mechanics
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• v.20 no.4
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• pp.435-450
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• 2005

Here, the dynamic instability characteristics of aero-thermo-mechanically stressed functionally graded plates are investigated using finite element procedure. Temperature field is assumed to be a uniform distribution over the plate surface and varied in thickness direction only. Material properties are assumed to be temperature dependent and graded in the thickness direction according to simple power law distribution. For the numerical illustrations, silicon nitride/stainless steel is considered as functionally graded material. The aerodynamic pressure is evaluated based on first-order high Mach number approximation to the linear potential flow theory. The boundaries of the instability region are obtained using the principle of Bolotin's method and are conveniently represented in the non-dimensional excitation frequency-load amplitude plane. The variation dynamic instability width is highlighted considering various parameters such as gradient index, temperature, aerodynamic and mechanical loads, thickness and aspect ratios, and boundary condition.

• Journal of architectural history
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• v.25 no.5
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• pp.27-40
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• 2016

The purpose of this study was to comprehend the procurement system of iron materials and the production process of ironwork in royal tombs constructions in the later Joseon period. For this purpose, sixteen Sanneung-uigwes were analyzed. The following conclusions have been reached through the study. First, it was procuring five types of iron materials in constructions of royal tombs. Sincheol had been supplied up to the mid-18th century. On the other hand, the amount of jeongcheol was increased rapidly. Because of the procurement system of initial tools was changed from bokjeong(a kind of tribute) to self-production in the Noyaso. Second, the government stockpiles were utilized as much as possible than bokjeong to manage the limited construction period and sudden construction start. Third, before moving the site of tombs, the melting furnace was installed in the Gungisi(armament factory). The amount of the melting furnace was increased from 5 to 8 since producing the initial tools in the Noyaso. Fourth, six kinds of master artisans were worked in the field of producing ironwork. Metal worker was assigned to one person per melting furnace. Fifth, the quality of final iron materials was controlled by use. Since the 19th century, it had been produced enhanced ironwork.

• Journal of the military operations research society of Korea
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• v.1 no.1
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• pp.131-135
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• 1975

One of the pending issues of the Ministry of Defense is the efficient management of space parts for the weapon systems. It has been known that more than 000 million dollars are needed for spare parts for the weapon systems annually. Though the problem demands a serious consideration, there has not been any systematic study on the problem as far as the author knows. One way to approach the problem is through an investigation of the system reliability under constraints. A measure of how well a system performs or meets its design objectives is provided by the concept of system reliability. If successful operation is desired for a specified period of time, reliability is defined as the probability that the system will perform satisfactorily for the required time period. This interpretation of reliability is normally applied to devices which are subject to random failures such as electrical or mechanical systems. It has been found necessary to express system reliability in terms of the reliability of the components or subsystems which comprise the system. The major subsystems of an aircraft, for example, include the electronics, powerplant, airframe and armament subsystems. Therefore, the optimal spare part kit can be found by maximizing the system reliability subject to cost or other constraints.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.4
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• pp.296-309
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• 2009

Thick-walled cylinder with high pressure have had wide application in the armament industry. In the thick-walled cylinder, fatigue crack is generated at inner radius and developed toward the outer radius. To prevent generation of fatigue crack, the autofrettage process had been used. The compressive residual stress induced by the autofrettage process extends loading pressure and fatigue life of the thick-walled cylinder. In this study, the residual stress of single and compound cylinder by the autofrettage process was evaluated. The analytical compressive residual stress of single cylinder was good agreement with experimental result at inner radius. The analysis on the residual stress of compound cylinder was conducted. The compressive residual stress at inner radius was increased with the overstrain level. And fatigue life of the compound cylinder with initial crack was evaluated. The considered initial crack shape was straight and semi-elliptical. The fatigue life was extended with the overstrain level. The fatigue life of the compound cylinder with semi-elliptical crack was longer than straight crack. The suitable way to extend fatigue life of the compound cylinder was proposed.

• Journal of the Korea Institute of Military Science and Technology
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• v.9 no.1 s.24
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• pp.50-59
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• 2006

Lately, there exist growing demands for the use of CTAs(Cased Telescoped Ammunitions) to increase the firepower of mid-calibre automatic guns despite spatial limitations of armament. In this paper, for automatic CTA guns a rotating chamber mechanism is designed based on parallel index concept. Via dynamic simulations it proves capable of smooth operation even at as high a firing rate as 200spm. Subsequently, motor controllers are synthesized to drive the chamber at any constant speed and also to control positions in the presence of large disturbances caused by the intermittently-rotating load. It is remarkable that we successfully adopted a disturbance observer to treat disturbances only with a moderate bandwidth of the closed-loop system.

• Journal of the Korea Institute of Military Science and Technology
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• v.10 no.2
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• pp.126-133
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• 2007

Lately, there exist growing demands to increase the firepower of mid-calibre automatic guns despite spatial limitations of armament. In this context, ammunitions of simple cylindrical shape are considered so advantageous that associated automatic guns are under development incorporating an intermittently rotating chamber mechanism. In this paper, relevant subsystems for such guns are to be described, and a digital controller to automate the entire system as well. Via dynamic simulations it proves to function well being able to drive the chamber at any constant speed up to 200spm, which is merely limited by the recoil performance. It is remarkable that the system synchronization idea in use is applicable to any other multi-actuator systems that should operate on the basis of event rather than time.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.05a
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• pp.371-372
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• 2017

The United States has built a missile defense system from the Cold War era, but since the end of the Cold War era, there have been many changes in international situation and threats. The forces of power divided between the United States and the Soviet Union have become increasingly threatened by China's willingness to expand its external influence, declaration of strong Russia and North Korea and Iran's nuclear armament and advanced ballistic missile technology. In response to this threat change, the Missile Defense Agency(MDA) has established strategies and policies, but its parent law has not been revised. United States changed to the FY2017 National Defense Authorization Act (FY2017 NDAA) including changed missile defense strategy. In this paper, I check US ballistic missile defense strategies included in the FY2017 NDAA and compare what changes have been made in existing strategies.

• Journal of the Society of Naval Architects of Korea
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• v.44 no.5
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• pp.526-533
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• 2007

It should be primarily aimed to increase survivability consisting of susceptibility, vulnerability and recoverability of naval vessels including ship hull, armament system as well as crews from the design stage to practical operations. With this in mind, swift and efficient actions should be executed on the basis of accurate calculations for the recoverability of damaged vessels. In this paper, it is established how the damage control system of naval vessels is embodied through step-by-step processes intending to cope with various damaged situations that may possibly occur during real operations. It is validated that this system has the applicability to naval vessels through the case study of the battle ship which has been damaged during the operation.

• Journal of the Korea Institute of Military Science and Technology
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• v.20 no.6
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• pp.788-793
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• 2017

This military aircraft requires the compatibility evaluation of armed installations in accordance with guidelines and standards. In order to ensure the influence of gas-air mixtures caused by gunfire of the supersonic aircraft, CFD analysis of internal and external flows was performed and the results carried out and discussed. The low velocity vortex was formed due to the shape of the Gun Port, after firing the gas-air mixture was evacuated to the outside flow, where it moved to the front of the aircraft and soon merged with the aircraft flow field.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.1
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• pp.17-24
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• 2011

It is reported that an intermittently rotating chamber system will improve the ratio of firepower to armament space in the case of mid-calibre automatic guns. However, the parallel index, which is a main component of the system, tends to be torsionally flexible due to the low lateral stiffness of cam followers on the index turret. This may cause the shaft system connecting the turret with the chamber prone to considerable residual torsional vibration so that serious misalignment problems occur during ammunition loading and firing processes. Herein, an electrorhelogical (ER) fluid actuator that can suppress such vibrations and the associated semiactive control algorithm are proposed. By mathematical modeling and computer simulations, the performance of the entire system is proved satisfactory.