• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2002년도 추계학술대회 논문집
• /
• pp.250-253
• /
• 2002

The operation of surface and edge finishing is the last and essential process of parts machining, because a product is completed as an assembly. Therefore, the quality of the finished parts has a direct effect upon the performance of the product. Especially, the edge quality depending on the burr control process is very important. A number of deburring processes have been developed for macro burrs such as barreling, brushing, chemical methods, etc. However, micro burr removal when piercing a very thin plate is very difficult, because this badly deteriorates the surface quality of the processed part. When ultrasonic wave is propagated in liquids, it forms an infinitude of micro bubbles. These bubbles generate extremely strong force, which removes micro burrs. In ultrasonic micro deburring, the problem is that burrs are not removed completely, because only components of the explosive force directly act on the burrs, which is not enough. An attempt was made to remove the burrs using ultrasonic vibration in water with SiC as an abrasive agent. Because of the abrasive, smoother edges have been achieved. There are many control parameters in ultrasonic deburring such as abrasive size, ultrasonic frequency and amplitude, distance between tool and workpiece, tilt angle of workpiece etc. This study focuses on how distance and tilt angle influence deburring effect. A number of experiments for these parameters have been carried out, and then the effect of each parameter analyzed.

• 화약ㆍ발파
• /
• 제34권3호
• /
• pp.1-9
• /
• 2016

성형폭약의 조절발파 효과를 확인하기 위하여 정밀폭약에 금속라이너의 재질과 두께를 달리하여 상대적으로 폭속이 작은 암석 절단용 성형폭약을 제작하였다. 성형폭약이 암반 내부에서 기폭될 때 방향성 절단을 유도하기 위하여 폭약 양쪽으로 금속라이너를 부착하였다. 또한 콘크리트 부재 실험을 통하여 성형폭약의 성능을 확인하였고 성형폭약과 공벽과의 적정 이격거리를 유지하기 위한 센터 가이더를 제작하였다. 실험결과 0.8mm 두께의 Fe 라이너가 장착된 성형폭약을 사용할 때 가장 깊은 노치가 형성되었고, 콘크리트 부재의 방향성 절단을 확인할 수 있었다.

• 인터넷정보학회논문지
• /
• 제8권4호
• /
• pp.11-16
• /
• 2007

인터넷 서비스에 대한 수요의 폭발적인 증가로 인한 IP 주소 부족 문제가 대두되면서 인터넷 통신규약 표준 기관인 IETF에서는 사용자들이 가상의 사설 IP 주소 영역을 지정하여 사용할 수 있는 NAT 및 NAPT기능을 규정하였다. 본 논문에서는 ADSL을 통하여 서비스되는 하나의 공인 IP주소를 이용하여 여러 대의 PC 및 다수의 인터넷 접속 단말기 사용자가 동시에 인터넷 서비스를 이용할 수 있도록 NAPT기능을 사용하여 ATMOS 기반의 ADSL-IP 공유기 통합용 네트워크 모듈을 설계 및 구현하였으며 또한 구현된 ADSL-IP 공유기 통합용 네트워크 모듈의 성능 테스트 및 분석을 실시하였다.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2005년도 춘계학술대회 논문집
• /
• pp.175-179
• /
• 2005

The main objective of this paper is to module design and pressure relief test a new type of polymer gapless surge arrester for power distribution line. Metal oxide surge arrester for most electric power system applications, power distribution line and electric train are now being used extensively to protect overvoltage due to lightning. Surge arresters with porcelain housing must not have explosive breakage of the housing to minimize damage to other equipment when subjected to internal high short circuit current. When breakdown of gapless elements in a surge arrester occurs due to flashover, fault short current flows through the arrester and internal pressure of the arrester rises. The pressure rise can usually be limited by fitting a pressure relief diaphragm and transferring the arc from the inside to the outside of the housing. However, there is possibility of porcelain fragmentation caused by the thermal shock, pressure rise, etc. Non-fragmenting of the housing is the most desired way to prevent damage to other equipment. The pressure change which is occurred by flashover become discharge energy. This discharge energy raises to damage arrester housing and arrester housing is dispersed as small fragment. Therefore, the pressure relief design is requested to obstruct housing dispersion.

• 한국추진공학회지
• /
• 제22권3호
• /
• pp.8-13
• /
• 2018

ZPP(Zirconium Potassium Perchlorate)는 산화제 potassium perchlorate, 금속원료 zirconium, 결합제 Viton 조성의 점화제이다. ZPP는 항공우주산업, 추진제 점화원, 자동화 산업에 사용되고 있다. 본 연구에서는 PMD(Pyrotechnic Mechanical Device)에 사용되는 ZPP의 제조공정 및 형상/열량/압력값과 같은 특성을 연구하였다. ZPP 제작 시, 원료들을 고속으로 교반하여 ZPP가 균일한 입자크기 및 형상으로 제작될 수 있도록 혼화공정을 설계하였다.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
• /
• pp.445-450
• /
• 2017

ZPP(Zirconium Potassium Perchlorate)는 산화제 potassium perchlorate, 금속원료 zirconium, 결합제 Viton 조성의 점화제이다. ZPP는 항공우주산업, 추진제 점화원, 자동화 산업에 사용되고 있다. 본 연구에서는 PMD(Pyrotechnic Mechanical Device)에 사용되는 ZPP의 제조공정 및 형상/열량/압력값과 같은 특성을 연구하였다. ZPP 제작 시, 원료들을 고속으로 교반하여 ZPP가 균일한 입자크기 및 형상으로 제작될 수 있도록 혼화공정을 설계하였다.

• 한국정보통신학회논문지
• /
• 제11권7호
• /
• pp.1311-1317
• /
• 2007

최근 인터넷의 폭발적인 성장과 인기로 인하여, 인터넷상에서 정보의 교환이 매우 빠르게 증가하고 있다. 또한 XML은 인터넷상에서 정보교환의 수단인 동시에 표준으로서 자리를 잡아 가고 있다. 따라서 본 논문에서는 경로-지향 질의어를 평가하기 위한 새로운 인덱싱 기법과 사용자들에게 편리한 XML문서 검색 결과를 제공하기 위한 경로-지향 질의 처리 시스템의 설계 및 구현을 제공한다. 제안된 인덱싱 기법은 XML문서의 검색 성능을 향상시키기 위하여 이진 트라이 구조와 경로서명 파일을 결합하였다.

• Steel and Composite Structures
• /
• 제13권6호
• /
• pp.521-537
• /
• 2012

In this study, an experimental study is performed to understand the effect of spalling on the structural behavior of fire damaged steel reinforced high strength concrete (SRHSC) columns, and the test results of temperature distributions and the displacements at elevated temperature are analyzed. Toward this goal, three long columns are tested to investigate the effect of various test parameters on structural behavior during the fire, and twelve short columns are tested to investigate residual strength and stiffness after the fire. The test parameters are mixture ratios of polypropylene fiber (0 and 0.1 vol.%), magnitudes of applied loads (concentric loads and eccentric loads), and the time period of exposure to fire (0, 30, 60 and 90 minutes). The experimental results show that there is significant effect of loading on the structural behaviors of columns under fire. The loaded concrete columns result more explosive spalling than the unloaded columns under fire. In particular, eccentrically loaded columns are severely spalled. The temperature distributions of the concrete are not affected by the loading state if there is no spalling. However, the loading state affects the temperature distributions when there is spalling occurred. In addition, it is found that polypropylene fiber prevents spalling of both loaded and unloaded columns under fire. From these experimental findings, an equation of predicting residual load capacity of the fire damaged column is proposed.

• Advances in concrete construction
• /
• 제7권1호
• /
• pp.31-37
• /
• 2019

This paper evaluates the workability and hardened properties of self-compacting concrete (SCC) containing silica fume as the partial replacement of cement. SCC mixtures with 0, 2, 4, 6, 8 and 10% silica fume were tested for fresh and hardened properties. Slump flow with $T_{500}$ time, L-box and V-funnel tests were performed for evaluating the workability properties of SCC mixtures. Compressive strength, splitting tensile strength and modulus of rupture were performed on hardened SCC mixtures. Experiments revealed that replacement of cement by silica fume equal to and more than 4% reduced the slump flow diameter and increased the $T_{500}$ and V-funnel time linearly. Compressive strength, splitting tensile strength and modulus of rupture increased with increasing the replacement level of cement by silica fume and were found to be maximum for SCC mixture with 10% silica fume. Further, residual hardened properties of SCC mixture yielding maximum strengths (i.e., SCC with 10% silica fume) were determined experimentally after heating the concrete samples up to 200, 400, 600 and $800^{\circ}C$. Reductions in hardened properties up to $200^{\circ}C$ were found to be very close to normal vibrated concrete (NVC). For 400 and $600^{\circ}C$ reductions in hardened properties of SCC were found to be more than NVC of the same strength. Explosive spalling occurred in concrete specimens before reaching $800^{\circ}C$.

• 소성∙가공
• /
• 제30권1호
• /
• pp.16-21
• /
• 2021

A new concept of ammunition without the use of explosive gunpowder has been recently studied, which achieves performance equal to or higher than that of high explosives. Frangible Armor Piercing (FAP) is one of the concepts, which utilizes a tungsten alloy penetrator specialized for fragmentation. To investigate the fracture behavior of the tungsten alloy penetrator, Taylor impact tests were conducted at various impact velocities. Additionally, finite element analysis was performed to predict the fracture behavior of the tungsten alloy. Compression tests were also carried out at six strain rates for dynamic material properties and the dynamic hardening behavior was successfully predicted with the Lim-Huh model. Finally, the Mohr-Coulomb fracture model based on the mean stress was adopted to predict impact failure in Taylor impact simulation. The analysis predicts the deformation and fracture behaviors of the tungsten alloy successfully.