Effect of Impact Velocity on Interface Characteristics of HT‑9 Steel Joints Fabricated by Magnetic Pulse Welding

Jun‑Woo Song,Jin‑Ju Park,Gyoung‑Ja Lee,Min‑Ku Lee,Kyu‑Hyun Park,Soon‑Jik Hong,Jung Gu Lee 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.3

The weldability window in magnetic pulse welding (MPW) is proposed for the end-closure joining of HT-9 steel tubularworkpieces. Based on both theoretical and experimental investigations, the impact velocity of the flyer tube at the momentof collision had a dominant effect on the bonding characteristics of the resultant joints and the optimal impact velocity wasestimated to be in the range of 265–290 m/s in this alloy system. Under the optimal process conditions, no leak was detectedduring helium leak testing. Moreover, the integrity of the joint interface was preserved until the tube section ruptured duringinternal pressure burst testing. For HT-9 steel, the ductile δ-ferrite phase produced by the localized interfacial melting duringMPW acted as an effective obstacle to crack propagation, thereby enhancing the fracture resistance of the joint interface. Allof the results demonstrated the high integrity and durability of the HT-9 steel tube assembly fabricated by the MPW process.

고속 주축 상태 모니터링용 광파이버 변위 센서 설계 제작 및 성능평가

홍준희,박찬규,신우철,이동주 한국공작기계학회 2004 한국공작기계학회 추계학술대회논문집 Vol.2004 No.-

This paper is focused on practical applicability of the optical fiber sensor considering the machine center which is going to use them. Optical fibers may be fluctuated because the machine center operates as column moving type. This causes distortion of the sensor output signal. To reduce this problem, we have improved the sensor structure and its bracket. And we evaluated performances of the sensor.

타타늄의 열처리 조건에 따른 동전위 양극분극특성 및 표면 미세구조 변화

주동현,이용렬,정영화,양홍서,박상원,이도재,송호준,박영준 大韓齒科器材學會 2002 대한치과재료학회지 Vol.29 No.2

The corrosion resistance of metallic implants is essential for successful implant osseointegration. Moreover, the implant surface should have appropriate surface roughness for the attachment of the osteoblast and collagen fibrils. When titanium is exposed to air a thermodynamically very stable oxide film is formed at once. This oxide is very thin and yet it protects the metal from corrosion instantaneously. However, the oxide would not be ideal, and it would be supposed that the state of oxide film would be various by the different conditions when it is formed. The objective of this study was to evaluate the electrochemical properties and surface microstructural changes of titanium after passivation treatment or exposure to high heat (in vacuum or in air). ASTM grade 2 commercially pure titanium (Ti) disks of 10㎜ diameter were wet ground and polished with 240 and 600 grit SiC, and then ultrasonically cleaned with distilled water and ethanol. Cleansed as-received samples (As-R group) were passivated with 30% nitric acid solution at 50℃ for 15 minutes to make the Pas group. The Std-V samples were made by treating the Ti disks in vacuum quartz tube (10^-8 Torr) at 530℃ for 40 min for stress relieving, followed by annealing at 700℃ for 90 min, and then slow cooling to room temperature. The Std-A samples undergo identical procedure as the Std-V group except that it is done in air. For 530℃-V samples, Ti disks were heated at 530℃ for 40 minutes and slow cooled to room temperature. The 1000℃-V samples were produced by heating Std-V specimens again at 1000℃ for 2 hr, followed by cooling to room temperature. 530℃-A and 1000℃-A samples were also prepared. Potentiodynamic anodic polarization measurement, SEM, AFM and XRD analysis were performed to evaluate the effects of the various treatments. The difference in the mean values of E_corr between groups showed statistically significant difference (P<0.05), but that of I_corr did not show significance (P>0.05). When Ti surface was passivated there was a shift of corrosion potential (E_corr) in the noble direction and a lower corrosion current density (I_corr) value. Std-A samples showed most noble E_corr value among the tested groups. 530℃-V samples showed more noble E-corr than other tested groups except Std-A group. 1000℃-V samples showed more noble E-corr than those of Std-V sample. In the case of Std-, 530℃- and 1000℃-groups, -A sub-groups showed better corrosion resistant characteristics than -V sub-groups in regard to E-corr and I_corr values. In the SEM observations, the surfaces of the As-R samples showed only scratch line on smooth surface. In Pas samples, thick oxide layer covered the surface under high magnification observation. 530℃-A samples were covered by oxide granules, and Std-A samples had 25~50 nm-thick acicular oxides. The 1000℃-A samples were covered by coarse oxide crystals with a granule diameter of 0.1~0.6 μm having a gross appearance of milky white color, which was identified by XRD as a rutile. On the other hand, 1000℃-V samples showed an Widmansta¨tten structrue of which the orientation of the lattice is formed along crystallographic planes of the parent crystals. On the AFM observation, 530℃-A samples showed RMS roughness of 79.38 nm which is 5 times rougher than those of the As-R samples. Std-A sample had a roughness of 330.47 nm which is about 20-times rougher than that of the As-R sample. 1000℃-A samples were covered by coarse granular oxides and the roughness were about 0.56 μm. Vacuum sub-group samples showed a more smooth surface than air sub-group samples, and the oxide film was more dense. Due to variability of the surface treatment and heat treatment conditions, the process of the oxide formation seems to be affected thereby making the corrosion properties and surface micro-morphology different. However, more various electrochemical analysis together with surface analysis, and an investigation for the effects of those on the osteoblast cell adhesion and calcium phosphate apposition are needed for the improvement of the osseointegration rates of the titanium implants.

중공 크랭크축의 비틀림 진동 해석 및 측정

金寬柱,文洪晙 弘益大學校 科學技術硏究所 1995 科學技術硏究論文集 Vol.6 No.-

In recent years, the problems of noise and vibration are critical issues in order to reduce the weight of internal combustion engine components. It is found that the bending, torsional and lateral vibration of crankshaft are the main causes of engine noise and vibration problems. Therefore it is necessary to identify the vibration behavior of crankshaft. In this paper, the vibration analysis of hollow crankshaft was carried out. The torsional vibration characteristics of hollow crankshaft were analyzed and compared with those of same size solid crankshaft in respect of equivalent mass and stiffness by using I-DEAS. The natural frequencies and mode shapes of both crankshafts are measured by impact hammer test using LMS CADA-X system.

좌측흉수로 발현된 Boerhaave 증후군 1예

이준,변유미,조민근,조주연,원경준,김영대,박찬국,김만우,유재근,서홍주,이석기 朝鮮大學校 附設 醫學硏究所 2008 The Medical Journal of Chosun University Vol.33 No.2

구토 후 발생한 토혈을 주소로 내원한 환자에서 좌측 늑막 삼출 동반 시 식도 파열의 가능성을 고려하여 흉수 천자 및 지속적인 흉부 단순 촬영의 추적관찰이 필요하며 식도 파열이 배제된 후 환자의 생체 징후 및 토혈 양을 파악하여 내시경 검사 시기를 신중히 결정하는 것이 좋을 것으로 생각된다. 본 증례는 토혈을 주소로 내원하여 Mallory-Weiss 증후군 의심 하에 내시경을 통한 치료 시행 후 추적 관찰에 의해 진단된 Boerhaave 증후군을 경험하였기에 보고하는 바이다. Boerhaave's syndrome is a spontaneous perforation of the esophagus most commonly resulting from a sudden increase in intraesophageal pressure combined with negative intrathoracic pressure caused by straining or vomiting. Surgery should generally be performed within 24 hours because mortality approached 30 to 50 percent in which surgery was delayed. Therefore, early diagnosis and prompt surgical repair are critical for survival. We have experienced a case of Boerhaave's syndrome in a patient presenting with hematemesis with left pleural effusion without any signs or symptoms of pneumomediastinum or pneumothorax.

노인여성의 유산소성 리듬운동이 신체구성 및 건강관련 체력에 미치는 영향

김주홍,이은희,홍명엽,안민호,김영준 한국스포츠리서치 2004 한국 스포츠 리서치 Vol.15 No.2

This study attempts to investigate whether 11 weeks' rhythmic exercise-three times a week, intensity at 50~70%HRmax-affects body composition, health-related fitness, and respiratory function in the elderly women. As for body composition, in excess body fat group/over 30% body fat), weight and %body fat were reduced, but, there was no significant difference, Under body fat group/under 30%body fat) showed a tendency to reduce in weight and %body fat significantly. As for health-related fitness, excess body fat group/over 30% body fat) showed a increase in the muscular strength of the lower limbs, but there were no significant differences in the muscular strength of the upper limbs. flexibility, quickness, balance, and endurance. However, the muscular strength of the lower(upper) limbs, quickness, and balance were significantly reduced in under body fat group. As for pulmonary ventilation in under body fat group, FVC and %FVC increased but there was no significant difference. In contrast, Fev1 was significantly increased. In conclusion, regularly rhythmic exercise may improve body composition and health-related fitness. Moreover, it could be one of the best ways for the elder to live actively.

유도형 변위 센서의 전기 노이즈 분석과 센서 성능에 미치는 영향 고찰

신우철,홍준희,이동주 한국공작기계학회 2003 한국공작기계학회 추계학술대회논문집 Vol.2003 No.-

Noise is a problem in many electronic circuits and active control system. Arising from spuriously coupled noise from other circuits, it corrupts the signal of interest and introduces an uncertainty into information it contains. In this paper, we have researched noise characteristics of the inductive displacement sensor which has been designed. we first present basic concept and characteristics of magnetic field-coupled noise in the sensor output signal. Then, we are present relation noise and sensor performances. Finally, we concentrate low noise design of a sensor driver and a signal detection circuit.

간 세포암에서 VEGF, TGF-β1, b-FGF 발현의 의의

김성용,남충현,주종우,채만규,백무준,이문수,김형철,안현철,김홍수,김창진,김창호 순천향의학연구소 2001 Journal of Soonchunhyang Medical Science Vol.7 No.1

Purpose: Angiogenesis is important for the proliferation and the metastasis of solid tumors. The growth of a solid tumor is widely recognized to depend on the process of neovascularrozation. Without angiogenesis, tumors cease to grow beyond even a few milimeters in diameter. It has been shown that tumor vascular density is an independent prognostic marker in several types of human tumors and is known to correlate with poor prognosis. To date, many angiogenic factors have been identified, such as transforming growth factor-α(TGF-α), transforming growth factor-β(TGF-β), fibroblast growth factor family(FGF), vascular endothelial growth factor(VEGF), platelet derived endothelial cell growth factor(PD-ECGF), tumor necrosis factor-α(TNF-α), and angiogenin. Hepatocellular carcinoma(HCC) is the second most common tumor in Korean males and is known as a typical hypervascular tumor with frequent portal vein invastion. The authors identified the expreesion of VEGF, TGF-β1, and b-FGF in HCC specimens and evaluated the relationship between these growth factors and the clinicopathologic characteristics of HCC. Method: We reviewed the medical records of 30 patients who were diagnosed as hepatocellular carinoma treated with hepatic resection between January 1994 and December 1998 in Soonchunhyang University Chunan Hospital. The selection of the cases was decided according to the condition of paraffin block fixation. The prognostic factors such as age, sex, tumor size, concentration of serum α-fetoprotein, presence of liver cirrhosis, presence of tumor emboli in portal vein, TMN stage, amount of transfusion during the operation, hepatitis B virus(HBV) infection, and Edmonson-Steiner(E-S) grade were investigated. Relationship between the prognostic factors and the immunopathologic expression of the TGF-β1, b-FGF, and VEGF was examined. Result: Thirty patients (24 males, 6 females) were included in the current study. The patient's mean age was 50.6 years and the age ranged from 36 to 65 years. The mean size of the tumor was found to be 5.2cm. All the patients were follewed up for 7 to 63 months. Child's classification A patients were 23(76.7%)cases, B patients were 7(23.3%)cases, and C was none. Immunohistochemical staining of HCC tumor mass in VEGF expression patients were 17(56.7%), b-FGF expression patients were 10(33.3%), and TGF-β1 expression patients were 10(33.3%). VEGF expression or more than one positive expression among the three factors correlated with tumor size and the stage of HCC but did not correlated with other clinicopathological characteristics. TGF-β1 and b-FGF did not correlate with any clinicopathological characteristics. Conclusion: The results suggest that the expression of VEGF or more than one positive expression among the three factors in HCC cells may be a significant prognostic factor of HCC.

유치원 적정 교육시간에 대한 교사의 인식

박은혜,박신영,전홍주 이화여자대학교 교육과학연구소 2015 교육과학연구 Vol.46 No.3

Providing activities with appropriate length is as important for young children’s learning as what is taught. In order to understand teachers' perceptions of the appropriate length of the school day, the study conducted a survey of 149 public and private kindergarten teachers in Korea. As for the length of the school day, kindergarten teachers perceived that 3 hours 16 minutes for 3 year olds, 3 hours 54 minutes for 4 year olds, and 4 hours 24 minutes for 5 year olds were appropriate. Public kindergarten teachers tended to perceive a shorter school day than private kindergarten teachers and teachers in mixed age group classes perceived a longer school day compared to the single age group teachers. Most teachers responded that 30 minutes is an appropriate length for a class period. As for the question regarding areas emphasized for each age group when organizing the curriculum according to the number of hours per lesson, the most frequent answer was to emphasize physical education and health for 3-year olds, social relationships for 4-year olds, and communication for 5-year olds. The findings of this study provide implications for including the appropriate length of the school day and hours of instruction in future curriculum revisions.

桔梗의 內部構造規格設定에 관한 硏究

金鍾旭,金弘寯,朱榮丞,陸相元,韓京植 대한본초학회 2000 大韓本草學會誌 Vol.15 No.2

In order to strengthen objectivity and availability of oriental herb medicine, the standard formula for herbs has been attempted to set up by experimenting and documentary testing original herbs which were recorded in authorized document. The object herb medicines are Platycodi Radix. The internal morphological standard in this study is expected to supply the search for several physiochemical reaction, biological reaction, determination of indicator material and identification of gene with basic sources in the future. The result of study is as follows; In the shape of real herbs, I compared current herbs in market with original herbs which were just collected or were on the course of drying. It was possible that the internal shape could be identified by using microscope after butanol series. In powder herbs, it was possible to purify the shape by microscope through maceration of natural and powder herbs. Despite such a useful character, it was difficult to deal with powder herbs because it was uncertain to make a standard for them on account of the crush of these tissue. Since powders shape of herbs in a few documents were regard not as the powder shapes of natural herbs but as the maceration state of them. It is suggested that we should inspect the original herbs which are not crushed yet with a microscope in order to identify crushed shape of powder herbs from now on. An Additional standard establishment including physiochemical reaction and gene research is required in order to supplement the fault of this search.