REIVM 모델링에 의한 엔드밀 시스템의 모드 분석

김종도(Jong-Do Kim),윤문철(Moon-Chul Yoon) 한국생산제조학회 2010 한국생산제조시스템학회 학술발표대회 논문집 Vol.2010 No.10

An mode analysis of end-milling system was introduced using recursive parametric modeling analysis. Also, the numerical mode analysis of end-milling system with different conditions was performed systematically. In this regard, a recursive extended instrumental variable method(REIVM) modeling algorithm and the natural mode for real part and imaginary one was discussed. This recursive approach (REIVM) can be adopted for the on-line system identification and monitoring of an end-milling for this purpose. After experimental practice of the end-milling, the end-milling force was obtained and it was used for the calculation of FRF(Frequency response function) and mode analysis. Also, the FRF was analysed for the prediction of a end-milling system and its mode shape was acquired by solving the eigen-problem using recursive algorithm. Thus, these algorithm for the detection of natural modes of end-milling was successful in each condition. After numerical analysis of the responses, which is cutting force was conducted for the calculation of FRF and mode analysis.

CO₂ 레이저용접시 용접조건에 따른 플라즈마 방사신호의 특성연구

김종도(Jong-Do Kim),이창제(Chang-Je Lee) 대한기계학회 2009 大韓機械學會論文集A Vol.33 No.11

Today, implementation of the defect detection in laser welding has been researched for a long time, but most studies have been made around thin plate within 1~3mm<SUP>t</SUP>. Therefore, this study was measured and analyzed light emission signals of the induced plasma in CO₂ laser lap welding of 6mm<SUP>t</SUP> Zn primer-coated steel, and based on this analysis, research made an investigation into possibility of monitoring in thick plate welding. It was been analyzing the measured signals by RMS and FFT processing, as a results, we were able to confirm definite difference of two signals between humping bead and sound bead. Thus, possibility of real time monitoring in CO₂ laser lap welding verified experimentally.

REIVM 모델링에 의한 엔드밀 시스템의 모드 분석

김종도(Jong-Do Kim),윤문철(Moon-Chul Yoon) 한국생산제조학회 2010 한국공작기계학회 추계학술대회논문집 Vol.2010 No.-

An mode analysis of end-milling system was introduced using recursive parametric modeling analysis. Also, the numerical mode analysis of end-milling system with different conditions was performed systematically. In this regard, a recursive extended instrumental variable method(REIVM) modeling algorithm and the natural mode for real part and imaginary one was discussed. This recursive approach (REIVM) can be adopted for the on-line system identification and monitoring of an end-milling for this purpose. After experimental practice of the end-milling, the end-milling force was obtained and it was used for the calculation of FRF(Frequency response function) and mode analysis. Also, the FRF was analysed for the prediction of a end-milling system and its mode shape was acquired by solving the eigen-problem using recursive algorithm. Thus, these algorithm for the detection of natural modes of end-milling was successful in each condition. After numerical analysis of the responses, which is cutting force was conducted for the calculation of FRF and mode analysis.

질화규소 세라믹의 레이저 예열선삭에 관한 연구 (I) - 공정변수에 따른 질화규소의 예열특성 및 산화거동 -

김종도,이수진,서정,이제훈,Kim, Jong-Do,Lee, Su-Jin,Shu, Jeong,Lee, Jae-Hoon 대한용접접합학회 2010 대한용접·접합학회지 Vol.28 No.4

Silicon nitride is widely used as an engineering ceramics because it has high strength, abrasion resistance and corrosion resistance even at high temperature. However, machining of silicon nitride is difficult due to its high hardness and brittleness. Laser assisted machining(LAM) allows effective cutting using CBN tool by locally heating the cutting part to the softening temperature of YSiAlON using the laser beam. The effect of preheating depending on process parameters were studied to find out the oxidation mechanism. If silicon nitride is sufficiently preheated, the surface is oxidized and $N_2$ gas is formed and escapes from the material, thereby making the cutting process more advantageous. During laser preheating process before machining, high temperature results in strong oxidation which makes the bloating, silicate layers and micro cracks. Using the results of these experiments, preheating characteristics and oxidation behavior were found out.

아연코팅 강판의 CO₂ 레이저용접시 인프로세스 모니터링을 위한 측정신호와 용접결함과의 관련성 연구

김종도(Jong-Do Kim),이창제(Chang-Je Lee) 대한기계학회 2010 大韓機械學會論文集A Vol.34 No.10

본 연구에서는 조선용 6㎜ 아연코팅강판의 CO₂ 레이저 겹치기 용접시 발생하는 유기 플라즈마를 마이크로폰과 포토다이오드로 측정하였다. 이때 겹치기 갭간극에 따른 용접조건을 RMS한 신호와 비교분석하였다. 이를 통해 아연증발량이 증가함에 따라 RMS값도 증가하였으며, 겹침부의 조건에 따라 결함 발생시 RMS의 급격한 변화도 확인할 수 있었다. 또한 용접조건에 따른 Raw signal의 FFT값을 구한 후, 이때 구해진 주파수값을 밴드폭으로 설정하여 Raw signal을 필터링한 뒤의 RMS값을 용접비드와 대응하여 필터링하지 않은 RMS와의 차이점도 비교 분석하였다. 이를 통해 기존의 방법들보다 신뢰성 높은 In-process 모니터링이 가능함을 확인하였다. In this study, the plasma induced by CO₂ laser lap welding of 6t Zn coated steel used for ship building was measured using photodiodes and a microphone. Then, the welding phenomenon with gap clearance of lap joint was compared with RMS-treated signal. Thus, we found that intensity of the RMS-treated signal increased with Zn vaporization; further, the presence of defects results in rapid variations with the RMS value as a function of lap-joint parameters. Besides, the FFT value of the raw signal with variations of changing welding parameters was calculated, and then the calculated FFT frequency value was set as the bandwidth of digital filter for a more accurate in-process monitoring. The RMS values were acquired by filtering the raw signal. By matching the weld beads and the calculated RMS values, we confirmed that there is a strong relationship between the signals and the defects.

수단 형법에 나타난 후두드(Hudud)고찰

김종도(Kim Jong do) 한국중동학회 2018 韓國 中東 學會 論叢 Vol.38 No.3

This paper aims to study on Hudud of the Criminal Law of the Sudan. In the early 16th century, Sudan adopted the Shari a partly with the appearance of the Funji kingdom of Islam. With the announcement of Sharia in September 1983, the Sudanese society became more infamous than the past and provided a reason for independence of the Southern Sudan in July 2011. The current Sudanese Criminal Law is a revision of the criminal law enacted in 1991, which was enacted again in 2009. It consists of 18 chapters and 192 articles. At the time of the 2009 amendment, it added 186-192, adding that the current President Bashir addressed anti-human crimes, genocide crimes, war crimes in order to avoid accusations of genocide in the Darfur incident. The traditional Sharia classifies Hudud crimes into five kinds, namely adultery, theft, apostasy, drinking, armed robbery but Sudanese criminal law added to defamation and sariqa haddiya. The hudud crime is a single-trial system and does not have a second trial or a third trial. Sariqa haddiya of Sudan is a unique concept that does not apply in the other Islamic countries and it means to take the property of others privately, which should be worth 4.25 grams of gold. The Sudanese Criminal Law is more serious than the supposed criminal offense of the same person. In relation to adultery, the Sudanese Criminal Law divides it into seven categories and gives it a heavy penalty. In relation to alcohol, the Sudanese Criminal Law refers to only two articles, but it is understood that the law related to alcohol is the whipping of 40 lashes or imprisonment for a term not exceeding one month, which is somewhat less strict than alcohol has. In apostasy, punishment is death penalty, but this applies only to Muslims. The Sudanese Criminal Law enlarges Shariah s category and applies hudud against defamation because it belongs to the seven avoidance items of the Prophet. It is important to note in the Sudanese Criminal Law that penalties imposed on criminals (whip-type, deportation, limb-cutting, dialysis-style execution, etc.) are all based on the Quran and Hadith.

소형 추력기의 성능 개선을 위한 액체 추진제 주입기 최적 설계 및 추진제 거동 연구

김기로(Kiro Kim),김수겸(Su-Kyum Kim),변도영(Do-Young Byun),이세민(Se-Min Lee),정강수(Kang-Su Jung),박수형(Soo-Hyung Park),김성균(Sung-Kyun Kim),유명종(Myoung-Jong Yu) 한국항공우주학회 2011 韓國航空宇宙學會誌 Vol.39 No.4

본 연구는 기존의 인젝터와 새로운 형태의 인젝터를 비교분석 함으로써 소형 추력기의 성농을 연구하였다. 기존의 인젝터는 볼록한 표면에 8개의 노즐로 구성되어 액체 추진제를 분사하는 형태로 제작되었다. 우리가 제안한 새로운 형태의 인젝터는 오목한 표면에 4, 5, 6, 8, 9개의 노즐로 구성된 충돌형 인젝터이다. 노즐의 구멍을 통해 분사되는 액체 추진제는 축 방향으로 한 점에서 부딪히게 설계되었으며, 이는 분사되는 액체 추진체의 입자를 더욱 세분화하여 사방으로 일정하게 분무할 수 있도록 하였다. 본 논문에서는 천산유체역학, 입자 유속계 및 고속 카메라를 이용하여 분무 가시화 및 인젝터의 성능을 연구하였다. This work studies the performance of an injector for a monopropellant thruster, comparing a conventional and new injector types. The conventional injector consists of 8 nozzles on a convex surface allowing the jet to be diverged. The new injector, we suggested, is an impinging type with nozzle holes on a concave surface. The fuel streams through the nozzle holes are collide at a point on an axial direction, which allow to atomize the liquid streams and to spray more uniformly along circular direction. The performance of the injectors is investigated by using computational fluid dynamics, particle image velocimetry and high speed camera visualization.

이산시간 불확실 특이시스템의 저차 강인 피동성 필터링

김종해(Jong-Hae Kim),오도창(Do-Cang Oh) 대한전기학회 2012 전기학회논문지 Vol.61 No.3

In this paper, we consider the problem of a robust passive filtering with low-order for discrete-time singular systems with polytopic uncertainties. A BRL(bounded real lemma) for robust passivity with a dissipativity of discrete-time uncertain singular systems is derived. A low-order robust passive filter design method is proposed by new reduced-order method and LMI(linear matrix inequality) technique on the basis of the obtained BRL. Finally, illustrative examples are presented to show the applicability of the proposed method.

질화규소 세라믹의 레이저 예열선삭에 관한 연구 (III) - SSN 및 HIPSN의 예열선삭시 절삭력 및 공구수명의 특성 -

김종도,이수진,강태영,서정,이제훈,Kim, Jong-Do,Lee, Su-Jin,Kang, Tae-Young,Suh, Jeong,Lee, Jae-Hoon 대한용접접합학회 2010 대한용접·접합학회지 Vol.28 No.6

Generally, ceramic material is very difficult to machine due to high strength and hardness. However, ceramic material can be machined at high temperature by plastic flow as metallic material due to the deterioration of the grain boundary glassy phase. Recently, a new method was developed to execute cutting process with CBN cutting tool by local heating of surface with laser. There are various parameters in LAM because it is a complex process with laser treatment and machining. During laser assisted machining, high power results in reducing of cutting force and increasing tool life, but excessive power brings oxidation of the surface. The effect of laser power, feed rate, cutting depth and etc. were investigated on the life of cutting tool. Chips were observed to find out suitable machining conditions. Chips of SSN had more flow-types than HIPSN. It means SSN is easier to machining. The life of cutting tool was increased with increasing laser power and decreasing feed rate and cutting depth.

질화규소 세라믹의 레이저 예열선삭에 관한 연구 (II) - 예열선삭된 SSN 및 HIPSN 질화규소 세라믹의 표면특성 -

김종도,이수진,강태영,서정,이제훈,Kim, Jong-Do,Lee, Su-Jin,Kang, Tae-Young,Suh, Jeong,Lee, Jae-Hoon 대한용접접합학회 2010 대한용접·접합학회지 Vol.28 No.5

This study focused on laser assisted machining (LAM) of silicon nitride ceramic that efficiently removes the material through machining of the softened zone by local heating. The effects of laser-assisted machining parameters were studied for cost reduction, and active application in processing of silicon nitride ceramics in this study. Laser assisted machining of silicon nitride allows effective cutting using CBN tool by local heating of the cutting part to the softening temperature of YSiAlON using by the laser beam. When silicon nitride is sufficiently preheated, the surface is oxidized and decomposed and then forms bloating, micro crack and silicate layer, thereby making the cutting process more advantageous. HIPSN and SSN specimens were used to study the machining characteristics. Higher laser power makes severer oxidation and decomposition of both materials. Therefore, HIPSN and SSN specimens were machined more effectively at higher power.