Failure with Strain Localization of Aluminum Alloy 7075 Sheets at Elevated Temperature and its Application to Two-Step Hybrid Forming

Jong‑Hwa Hong,Hyunki Kim,Wonjae Kim,Yong‑Nam Kwon,Daeyong Kim 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.4

In this work, the onset of failure induced by severe strain at elevated temperature was numerically estimated with crossformedempirical hardening law describing material softening. The hardening law can replicate the rate-sensitive behaviorof aluminum alloy 7075 sheets (thickness of 2.0 mm) with initial hardening and progressive material deterioration causedby dynamic recrystallization, dynamic recovery, and micro-void development. The characterized material was applied to thetwo-step hybrid forming process consisting of a drawing at 400 °C followed by a pneumatic forming at 470 °C to produce ashock absorber housing with an extremely complex shape. The user-defined subroutine codes, VUMAT (ABAQUS/Explicit)and UMAT (ABAQUS/Standard), were sequentially utilized for the drawing and the pneumatic forming, respectively. Theidentified hardening parameters based on uniaxial tensile tests were validated by simulating the two-step hybrid formingprocess and compared with the conventional Voce type law (converging function) and the combined Swift-Voce type law(ever-increasing function) since they play a key role in accurately predicting the onset of failure induced by severe strainlocalization. Finally, simulation results are reasonably well matched with experiments in terms of the moment of failureoccurrence, failure location, final blank shape, and thickness distribution.

Science and Marxism

Kim, Jong Hwa 덕성여자대학교 사회과학연구소 2004 사회과학연구 Vol.10 No.-

Scrutiny라는 계간 저널은 1932년에 창설되었는데, Cambridge 대학의 Leavis 등을 중심으로 지식인들의 토론 광장으로서의 역할을 수행하였다. 이 연구는 Scrutiny가 다른 주제와 관심사를 Scrutiny와 그에 대한 비판론자들(마르크스주의자들)의 관점에서 과학과 Marxism에 대한 명제를 중심으로 점검해 보았다. 과학과 마르크스주의 관계에 대한 주제는 Scrutiny에서 핵심적 과제로 다루어 졌는데, Scrutiny와 마르크스주의자들의 충돌은 그 저널이 마르크스주의에 개입하면서 시발되었고, 마르크스주의자들은 Scrutiny를 역사적·이념적 궤도 속으로 몰아넣으면서 비판하였다. 마르크스주의자들은 특히 Scrutiny의 정치적 요소 고려에 대한 소홀함이 여러 측면에서 불균형적 논리전개를 표출하고 현실성을 간과하였다고 지적하였다. Scrutiny는 문화의 중요성을 강조하면서 본질적으로 生의 질을 순전히 물질적 개념으로 접근하는 공리주의에 반대하는 입장이었다. 즉 Leavis 등 Scrutiny 편집자들은 생의 질을 논하는데 있어서 물질적 측면과 정신적 측면을 포괄적으로 고려하지 않으면 의미가 없다고 주장하였다. 한걸음 더 나아가, Scrutiny가 중시하는 문화란 사회변혁과 산업화로 파괴된다고 봄으로써 분명히 과학과 실용주의적 요소를 결여하게 되었고 결과적으로는 마르크스주의자들의 Scrutiny에 대한 비판도 여기에 초점이 맞추어져 있다. 생각건대 Scrutiny의 정치·사회적 문제에 대한 문화적·도덕적 관행설정으로 Scrutiny가 문화적 엘리트주의에 빠져 문화적 편중접근이라는 비난을 면하기 어렵지만, 도덕적 기준에서 보면 깊이 있게 과학과 마르크스주의를 통찰한 점은 높이 평가 되어야 할 것으로 보여진다.

CD34+ 조혈 모세포 이식 2례

김정아,정현식,김원석,윤성수,이홍기,박찬형,박성규,김동욱,이종욱,한치화,민우성,김춘추,김동집 대한조혈모세포이식학회 1996 대한조혈모세포이식학회지 Vol.1 No.1

Background: In most solid tumors, the CD34 antigen has not been detected, so positive selection of CD34+ cells may reduce tumor cell contamination and the CD34+ cells are capable of reconstituting hematopoiesis. We tried CD34+ cell transplantation in two patients. Method: CD34+ cells from chemotherapy + G-CSF mobilized PBPCs or bone marrow were positively selected with an avidin-biotin immunoadsorption column (CEPRATE SC system). Case 1. One course of chemotherapy using cyclophosphamide(200㎎/㎡) and etoposide (4.2g/㎡), combined with G-CSF(5㎍/㎏) S.C. was used in a relapsed lymphoma patient. This patient responded to the induction chemotherapy. CD34+ cells from harvested bone marrow were selected by the CellPro immunoadsorption column. The total number of mononuclear cells loaded onto the CellPro was 2.4×10^(8)/㎏, with 1.1% CD34+ cells. After column separation, the total number of positively selected cells was 5.16×10^(6)/㎏. The number of CFU-GM was 76.8×10⁴/㎏. This patient was treated with melphalan (140㎎/㎡) and TBI (1200cGy) and the positively selected CD34+ cells were infused. The time to neutrophil recovery greater than 0.5×10^(9)/L was 19 days and the time to platelet recovery greater than 50×10^(9)/L was 21 days. Case 2. Two courses of mobilizing chemotherapy were given 4 weeks apart using taxol(210㎎/m2) and adriamycin(60㎎/m2), combined with G-CSF(5㎍/㎏) S.C. in a breast cancer patients with 7 axillary node metastasis. CD34+ cells from each single leukapheresis product were selected by the CellPro immunoadsorption column. In the first collection, the total number of nucleated cells was 4.4×10^(8)/kg, with 0.42% CD34+ cells. In the second collection, the total number of nucleated cell was 2.8× 10^(8)/㎏ with 0.43% CD34+ cells. After colum separation, the total numbers of collected cells were 4.0×106/kg and 4.8×10^(6)/kg, the total number of CD34+ cells were 1.2×10^(6)/㎏ and 0.82×10^(6)/㎏. Colonogenic assays of positively selected CD34+ cells gave rise to myeloid erythroid, and multilineage colonies, with a median of 190 CFU-GM, 190 BFU-E, and 164 CFU-GEMM per 1×10³ adsorbed cells, respectively. High-dose chemotherapy with cumulative doses of 40mg/㎡ mitoxantrone, 750mg/㎡ thioptepa, and 1000mg/㎡ carboplatin was administered. Positively selected CD34+ cells were rapidly infused 24 hours after the end of high-dose chemotherapy. The time to neutrophil recovery greater than 0.5×10^(9)/L was 16 days and the time to platelet recovery greater than 50×10^(9)/L was 20 days.

해도 정보를 이용한 선박의 최적 항로 생성

김민규(Min-Kyu Kim),김종화(Jong-Hwa Kim),양현(Hyun Yang) 한국항해항만학회 2022 한국항해항만학회 학술대회논문집 Vol.2022 No.2

Min-Kyu Kim*․Jong-Hwa Kim**․†최근 자율 운항 선박에 대한 관심이 높아지고 있다. 특히, MUNIN (Maritime Unmanned Navigation through Intelligence in Networks) 프로젝트를 계기로 자율 운항 선박에 대한 개발과 연구가 활발히 진행되고 있다. 또한 국제해사기구 IMO는 자율 운항 선박 시대에대응하기 위해 자율 선박을 MASS (Maritime Autonomous Surface Ship)라 정의하고 선박 자율화 정도에 따라 4단계 등급을 제시하고 있다. 완전한 자율 운항 선박에 대한 요구조건을 만족하기 위해서는 항로 결정과 제어기술이 필수적이다. 본 연구에서는 여러 가지 기술 중 선박의최적경로를 생성하는 기법을 다룬다. 기존에 최적항로를 생성하기 위한 방법으로는   , Dijkstra와 같은 알고리즘들이 주로 사용되었다. 그러나 이와 같은 알고리즘은 섬이나 육지에 대한 충돌 회피는 고려하고 있지만 수심 및 연안 선박에 대한 규정들은 고려하지 않고 있어실제로 적용하기에는 한계점이 있다. 따라서 본 연구에서는 안전을 위해 선박의 선저 여유 수심과, 해도에 규정되어 있는 선박 운항에 대한여러 규정들을 반영하여 최적 항로를 생성하고자 한다. 최적 항로를 생성하기 위한 알고리즘으로는 강화학습 기반의 Q-learning 알고리즘을적용하였다.

뇌간의 부위별 Enkephalin 함량에 미치는 전기침의 영향

김화연,김중수,이종흔 대한구강생물학회 1987 International Journal of Oral Biology Vol.11 No.2

This study was performed to clarify the effect of stimulation of meridian or nonmeridian point on content of methionine-enkephalin (MENK), which was related with analgesia, in brainstem. Sprague-Dawley rats were anesthetized and a pair of stimulating electrode was inserted into palatal mucosa as nonmeridian point or Ha-gwan which was known as meridian point for control of oro-facial pain. Experimental animals were divided into control, meridian and nonmeridian group, which were subdivided as noxious stimuli group and innocuous stimuli group, respectively. Noxious stimuli were applied with rectangular pulse of 1 msec duration, 5mA and 45 Hz for 30 minutes, and intensity and duration of innocuous stimulation was 200㎂ and 5 msec, respectively. After stimulation of Ha-gwan or palatal mucosa, animals were sacrificed and brain was removed. Brain was separated into midbrain, pons and medulla oblongata immediately. The content of MENK was analyzed by radioimmunoassay. MENK content of midbrain, pons and medulla oblongata was not changed by innocuous stimulation of meridian point and decreased by noxious stimulation. Noxious and innocuous stimulation of palatal mucosa produced decrease of MENK in midbrain, pons and medulla oblongata. And content of MENK showed no difference between meridian and nonmeridian group. In summary, change of MENK content in brainstem was not influenced by position of peripheral stimulation and depended on intensity of stimulation. Decrease in MENK content of brainstem could be related to analgesic effect of peripheral conditioned-stimulation.

중유재로부터의 갈륨의 분리 ·회수에 관한 연구

김종화 國立 昌原大學校 産業技術硏究所 1992 産技硏論文集 Vol.6 No.-

The separation and recovery of gallium from petroleum fly ash has been investigated. This experiments were consist of leaching and extraction. As a first step, aqueous solution containing 2.3∼8.7g/l gallium ion concentration was obtained by leaching with water, hydrochloric acid and sulfuric acid, as a leachant. Next, the liquor of filtrate was treated to remove impurities by solvent extraction technique, employing various extractant. Using the experimental results, the overall process for recovery and purification of gallium from pertroleum fly ash was synthesized.

인터넷상에서 신뢰성있는 실시간 오디오 스트림 전송방안에 대한 연구

김화종,박상혁 강원대학교 정보통신연구소 1999 정보통신논문지 Vol.3 No.-

This article deals with the basic characteristics of RTP(Real-time Transport Protocol) which is approved by the IESG as a real-time transport protocol and presents the audio stream transmission techniques using RTP. On the packet networks like the Internet, packet size is important to transmit the data from the end-point to the other with reliable, and especially influences on the receiving side. The suitable packet size for audio stream transmission and the packet-loss recovery techniques are proposed. In order to find out the suitable packet size and verify the techniques, two hosts over the Ethernet are used, and speech quality with variable packet size, packet loss rate and packet-loss recovery techniques in the Linux environment are evaluated through simulation. Also, the audio stream speech quality is measured through the subjective assessment of multimedia application recommended by ITU-T.

객체 지향 제품데이터 관리시스템의 동적 모델링

김종화,박우근 건국대학교 산업기술연구원 2000 건국기술연구논문지 Vol.25 No.-

As the number of product variants in a company increases and the life cycles of those products decrease, an efficient management of product data has become an important issue. To cope with these situation effectively, the object-oriented approaches have been applied as an alternative to the traditional approaches. In this paper, conceptual modeling of an object-oriented product data management system is suggested by applying Rumbaugh's Object-Modeling Technique. In modeling the system, we focus on the dynamic modeling for the efficient management of frequent changes in engineering data and functional modeling to represent data flow between the objects identified.

ATM 망에서의 VDT 제공 방안

김영선,김화종,정명순 강원대학교 정보통신연구소 1997 정보통신논문지 Vol.1 No.-

VDT was proposed in order to provide residential multimedia services such as digital video, voice, data and so on, We studied a VDT network architecture and MPEG-2 transmission scheme over an ATM network. For this purpose, we studied the network architecture and communication protocols for MPEG-2 over AAL 5. In a hierarchical video coding, a picture can be seperated into the basic and the higher layers. The basic layer coding is the minimal information needed to reconstruct the video, and the higher layer coding is used to make better quality. By simulation, we obtained the cell loss probability caused by the overflow of video traffic, when subscribers received MPEG-2 video through an ATM network.

Rhizopus oryzae KCTC 11970을 이용한 푸마르산 생산조건의 최적화

김진남,양환승,이종일,류화원 全南大學校 觸媒硏究所 2002 觸媒硏究 論文集 Vol.23 No.-

This work was developed in several steps to find the optimum conditions of fumaric acid production by Rhizopus oryzae KCTC 11970 in flask culture. Six different carbon sources and eleven nitrogen sources were tested. CaCO_3 was used as a neutralizing agent to control pH of medium. The optimum carbon source and nitrogen source were glucose 70 g/L and ammonium sulfate 0.4 g/L, respectively. At this optimum condition, the fumaric acid concentration, yield, and volumetric productivity were 19.33 g/L, 52.8%, and 0.32 g/L/h, respectivity, after fermentation time of 60 hr.