• Structural Engineering and Mechanics
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• 제20권4호
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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.

• 건축역사연구
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• 제25권5호
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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.

• 한국국방경영분석학회지
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• 제1권1호
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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.

• 대한기계학회논문집A
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• 제33권4호
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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.

• 한국군사과학기술학회지
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• 제9권1호
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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.

• 한국군사과학기술학회지
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• 제10권2호
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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.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2017년도 춘계학술대회
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• pp.371-372
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• 2017

미국은 냉전시대부터 미사일방어체계를 구축해왔으나, 냉전시대 종식 이후 국제 정세와 위협 세력에 많은 변화가 있었다. 미국과 소련으로 양분되어있던 힘의 세력이 중국의 대외적 영향력 확장 의지, 강한 러시아의 표방, 북한과 이란의 핵 무장 및 탄도미사일 기술 고도화 등으로 인해 대응해야 할 위협이 다양해졌다. 이러한 위협 변화에 대해 미사일방어청(Missile Defense Agency : MDA)은 전략 및 정책을 수립하였으나, 이의 근간인 상위법은 개정되지 않다가 2017년 국방수권법(FY2017 National Defense Authorization Act : FY2017 NDAA)에 변화된 미국의 미사일방어 전략이 명문화되었다. 본 논문에서는 FY2017 NDAA에 반영된 미국의 탄도미사일방어 전략을 확인하고, 기존의 전략에서 어떤 부분이 변화하였는지 비교하였다.

• 대한조선학회논문집
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• 제44권5호
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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.

• 한국군사과학기술학회지
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• 제20권6호
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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.

• 대한기계학회논문집A
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• 제35권1호
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• pp.17-24
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• 2011

간헐 회전식 약실 계가 화력 대 무장 공간의 비율 관점에서 볼 때 중구경 자동포에 크게 유익하다고 보고되었다. 그러나 약실계의 핵심 부품인 평행 인덱스가 인덱스 터릿에 설치되는 캠종동절의 상대적으로 낮은 횡 강성으로 인하여 비틀림 방향으로 유연해지는 경향이 있으며, 이는 결국 터릿과 약실 사이의 연결 축이 상당한 크기의 비틀림 잔류 진동에 노출되어 탄 장전과 발사 시에 심각한 비정렬 문제를 야기시킬 수 있다. 이러한 맥락에서 본 논문에서는 상기 진동을 억제하는 ER 유체 작동기와 그에 적합한 반능동 제어 알고리듬을 제안하게 되었으며, 전체 계의 수학적 모델링과 컴퓨터 시뮬레이션을 통하여 그 성능이 만족스러움을 입증하였다.