논문 : Al - Li 다원계 합금에 있어서 δ' 상과 제3석출상과의 상호관계에 대한 조직학적인 해석

조현기,정동석 ( Hyun Kee Cho,Dong Seok Chung ) 대한금속재료학회 ( 구 대한금속학회 ) 1990 상변태 심포지엄 Vol.2 No.-

응력제거 열처리한 Mg-AX31B합금 TIG 용접부의 기계적 특성과 미세조직 변화에 미치는 용접조건의 영향

김용길 ( Yong Gir Kim ),정동석 ( Dong Seok Chung ),배차헌 ( Cha Hurn Bae ) 한국열처리공학회 2004 熱處理工學會誌 Vol.17 No.4

N/A Present work was carried out to investigate the influence of welded conditions, such as welding cur-rent, diameter of welding wire on the microstructural change and mechanical properties of TIG welded joint in AZ31B Mg alloy. It was found that good and sound welded joint was achieved in all welding conditions. The grain size decreased with increasing welding current and decreasing diameter of welding wire. Also, the second phases were homogeneously distributed in the grain and grain boundary as decreasing welding current and diameter of welding wire. The β discontinuos precipitates were observed in the welded joint, but this microstructure has not been reported by previous researchs in AZ31B Mg alloy. The hardness value is affected by the existence state of the second phase and the hardness of the welded joint region is lower than the other regions in welded AZ31B Mg alloy. The strength of the welded joint region was influenced by the grain size and has more than 90%, compared to that of ASTM standard specification.

자전고온반응에 의한 금속간화합물/금속 적층복합재료의 제조공정변수가 미세조직에 미치는 영향

김희연 ( Hee Yeoun Kim ),정동석 ( Dong Seok Chung ),홍순형 ( Soon Hyung Hong ) 한국복합재료학회 2003 Composites research Vol.16 No.3

본 논문에서는 Ni과 A1 금속박판 사이의 자전고온반응을 이용한 금속간화합물/금속 적충복합재료의 제조 시 제조공정 조건이 최종 미세조직에 미치는 영향을 연구하였다. 열분석을 통하여 Ni과 A1 사이의 반응은 먼저 NiA1₃가 핵생성-성장기구에 의해 생성된 후 다시 Ni₂A1₃로 확산변태됨을 확인하였다. 자전고온반응을 열역학적으로 해석하여 금속박판의 두께비(NiA1) 및 반응 전 열처리와 반응 후 미세조직에서 잔류한 A1의 부피분율과의 관계를 정립하였다. 후열처리 공정에 의해 Ni/Ni₃A1/NiA1의 적충구조와 각 두께비에서82%(1:1), 59.5%(2:1), 40%(4:1)의 부피분율을 가지는 금속간화합물/금속 적충재료를 얻을 수 있었다. In this paper, intermetallic/metal laminated composites have been successfully produced that utilizes SHS reactions between Ni and Al elemental metal foils. The reaction between Ni and Al started from the nucleation and growth of NiAl₃and was followed by the diffusional growth of Ni₂A1₃between Ni and NiAl₃. The SHS reaction was thermodynamically analyzed through the final volume fraction of the non-reacted Al related with the initial thickness ratio of Ni:Al and prior heat treatment. Thermally aging these laminates resulted in formation of a functionally gradient series of intermetallic phases. Microstructure showed that the intermetallic volume percent was 82, 59.5, 40% in the 1:1, 2:1, 4:1 thickness ratio specimen. Main phases of the intermetallic were NiAl and Ni₃AI having higher strength at room and high temperatures.

Mg-Ca 합금의 전기화학적 특성에 미치는 Ca 첨가량 및 열처리의 영향

이상희 ( S. H. Lee ),정동석 ( Dong Seok Chung ),박병옥 ( B. O. Park ),김용길 ( Y. G. Kim ),정하국 ( Ha Guk Jeong ),김혜성 ( Hye Sung Kim ) 한국열처리공학회 2004 熱處理工學會誌 Vol.17 No.3

N/A In this study, the influence of heat treatment and Ca contents on the electrochemical behavior was investigated. Mg-Ca alloys, i.e., Mg-0.22wt%Ca, Mg-0.56wt%Ca, Mg-1.31wt%Ca are prepared by ingot metallurgy. As-cast Mg-Ca alloys exhibited better electrochemical properties than pure Mg. Especially, Mg-0.22wt%Ca alloy improves its anode efficiency up to 62% and lowers the OCP up to -1.72VSCE. Microstructure and XRD patterns of Mg-Ca alloys show that additive Ca element is mainly solid-solutioned. While, the others show the microstructure and XRD pattern with large Mg₂Ca at grain boundary. To assess the effect of heat treatment on the as-cast Mg-alloy, the specimens were heat treated at 200℃ for 2 hours under CO2 gas atmosphere. Although corrosion properties of Mg-Ca alloys are somewhat deteriorated by heat treatment at 200℃ Mg-0.22wt%Ca alloy with uniformly distributed nano-sized Mg,Ca phase in a-Mg matrix show still better corrosion properties than pure Mg specimen.

IBDV (SH/92)의 인공감염에 의한 닭 면역장기의 병리조직학적 연구

엄성심 ( Sung Shim Eum ),김범석 ( Bum Seok Kim ),임채웅 ( Chae Woong Lim ),임병무 ( Byung Moo Rim ),이호일 ( Ho Il Lee ),정동석 ( Dong Suk Chung ) 한국동물위생학회 1999 한국동물위생학회지 (KOJVS) Vol.22 No.3

Sequential morphologic changes in the lymphoid organs were examined after ocular and cloacal inoculation in 3weekold chicks with a highly virulent strain (SH/92) of infectious bursal disease virus (IBDV). The infected chickens were sacrificed at 6, 12, 24, 48, 72, and 96 hrs post inoculation (P1), and thymus, harderian gland, ceacal tonsil, and spleen were observed. Histologically, the significant lesions were characterized by lymphocyte depletion and the earliest detectable changes were evident at 12 hrs PI. In thymic cortex, lymphoid depletion with apoptosis and prominent tingible body macrophages were observed. As the infection advanced, the lesions showed more severe changes. Dying cells were characterized either by capping of nuclear chromatin (apoptosis) or by cytoplasmic swelling (necrosis). In situ staining for apoptosis, some lymphoid cells revealed typical positive reaction, even the stainability was variable depend on every lymphoid organs. These results suggest that IBDV (SH/92) cause severe damage both primary and secondary lymphoid organs, and both T and B lymphocytes. Also the lymphoid depletion of these organs is caused by necrosis and apoptosis induced by IBDV.

분자동력학적 방법에 의한 저 에너지 As 이온 주입에 따른 Si 기판의 결함 형성 거동에 대한 컴퓨터 모사 실험

정동석,박병도 한국열처리공학회 2000 熱處理工學會誌 Vol.13 No.4

In this study, we quantitatively measure the ion ranges of arsenic with energies ranging from 10 KeV to 100 KeV, implanted at 3°, 9° 15°the (100) plane, and the damage created during ion implantation. To obtain detailed information of ion range and damage distributions in low energy region where elastic collisions dominate the slowing down process, molecular dynamics computer simulation was performed and compared to the existing results. The effects of implant energy and degree on damage generation are present. The number of vacancy were calculated from the deposited energy using Kinchin-Pease equation. In the energy range 10 keV-100 keV, simulations show that the number of Frenckel pairs produced by As-ion bimbardment is 9 and incident angle dependence of the vacancy was the same but defects were distributed at different depth.

Al-Zn-Mg-Cu-Zr 합금의 집합조직 발달과 기계적 특성에 미치는 Sc 첨가의 영향

제창웅,진승준,정동석,임성택,이용연,박노진 대한금속재료학회 2004 대한금속·재료학회지 Vol.42 No.10

The texture and mechanical properties during fabrication processes - extrusion, cold rolling and aging treatment - of plate in the 7050 Al alloys without/with 0.1%Sc were investigated. In both the cross section(CS) and longitudinal section(LS) of the specimen without Sc, after cold rolling, texture of R-fiber was predominant. In the Sc added alloy after cold rolling, {112}<111>(Cu)+weak (123)<634>(S) texture components developed in the CS of the specimen while strong (3-fiber+(110)<001>(Goss) components developed in the LS of the specimen. After solution treatment and aging treatment, the alloy (CS and LS) without Sc had random texture, but by the alloys with the 0.1%Sc, the components of the rolling texture are not changed. After the aging treatment, hardness and tensile strength of the alloy with 0.1%Sc increased about 15% and 17%, respectively, than those without Sc. Tensile strength of the Sc added specimen was the highest along the rolling direction where the <111> texture was strongly developed. On the other hand, in the specimen without Sc, the mechanical properties were not dependent on the direction of the sample. (Received May 3, 2004)

마취유도 중 Lidocaine 정주가 Propofol 유도 용량과 수면효과에 미치는 영향

이병호,정동석,김창재,정미영,주진덕,채준석 대한마취과학회 1999 Korean Journal of Anesthesiology Vol.37 No.3

Background : Recently, it was reported that bupivacaine-induced spinal block significantly reduced the hypnotic requirements for thiopentone, midazolam and propofol. We evaluated the hypnotic effect and requirements for intravenous propofol when pretreated with intravenous lidocaine. Methods : Fifty patients, ASA I or II, undergoing minor surgical procedures were randomly divided into five groups according to anesthetic pretreatment (group N: 0.9% normal saline; group 0.5: lidocaine 0.5 mg/kg; group 1.0: lidocaine 1.0 mg/kg; group 1.5: lidocaine 1.5 mg/kg; group 2.0 lidocaine 2.0 mg/kg). Ninty seconds after the administration of normal saline or lidocaine, propofol was administered intravenously over 5 sec in bolus doses of 0.2 mg/kg every 30 sec. The inability of patients respond to a simple command ($quot;Open your eyes,$quot; said twice) was used as the end point for hypnosis. Responses to verbal commands were evaluated 25 sec after each bolus. The total dose required to achieve complete loss of response in each patient was recorded in mg/kg. The time of the loss of response was from the adminstration of propofol to the loss of response. Mean arterial pressures and heart rates were measured before induction, after loss of response, and immediately after induction. Results: The time and total dose required to achieve loss of response was significantly reduced in groups 1.0, 1.5 and 2.0. Heart rates in groups 2.0 and mean arterial pressure in groups 0.5, 1.0, 1.5, 2.0 were significantly decreased after the loss of response. Conclusions : We suggest that lidocaine pretreatment significantly enhances the hypnotic effect and reduces the dose requirement for propofol during the induction period. (Korean J Anesthesiol 1999; 37: 382∼386)

흰쥐의 절개 통증모델에서 척수강내로 투여한 Gabapentin의 진통효과

송호경,권오경,조은정,정동석,장연,문동언,박수석,지승은 대한마취과학회 1999 Korean Journal of Anesthesiology Vol.37 No.4

Background: Gabapentin, an anticonvulsant structurally related to gamma-aminobutyric acid (GABA), was recently reported to be effective in pain associated with reflex sympathetic dystrophy and neuropathy. However, the effects of intrathecal (IT) gabapentin in postoperative pain are unclear. This study was designed to evaluate the analgesic action of IT gabapentin in a rat model of postoperative pain which was similar to human postoperative pain states. Methods: Rats were prepared with chronic intrathecal catheter. Under halothane anesthesia, a 1 cm incision was made in the plantar aspect of the hind paw and closed. Rats were divided into 7 groups, a control group (saline 20 μl intrathecally n = 6); a GP 30 group (gabapentin 30 μg intrathecally, n = 6); a GP 100 group (gabapentin 100 μg intrathecally, n = 6); a GP 300 group (gabapentin 300 μg intrathecally, n = 6); a GP 1000 group (gabapentin 1,000 μg intrathecally, n = 6); a NS-GP group (saline 10 μl and gabapentin 300 μg intrathecally, n = 6)-GP group (D-serine 100 μg and gabapentin 300 μg intrathecally, n = 6). The rats were placed on an elevated plastic mesh floor, and withdrawal threshold was determined using calibrated von Frey filaments applied from beneath the test cage to an area adjacent to the wound. A cumulative pain score based on the weight bearing behavior of the rats, and motor deficit score, were also assessed. Results: In all group, the median withdrawal threshold for punctate hyperalgesia decreased from 148.4 mN before surgery to 1.5 mN-14.5 mN 2 hours after surgery-inducing hyperalgesia and remained unchanged during the 2hr testing period. The IT administration of gabapentin (30 300 μg) increased the median withdrawal threshold toward preincision values dose-dependently and the nonevoked pain scores were also decreased. But the effects of intrathecal gabapentin were reversed by IT D-serine. The Analgegic effects of gabapentin were observed at doses that had no significant effect on motor function or spontaneous activ. Conclusions: These observations suggest that intrathecal gabapentin can modulate the facilitation of spinal nociceptive processing by tissue injury and may offer a therapeutic agent for the treatment of postoperative pain. (Korean J Anesthesiol 1999; 37: 704∼710)

Ti, Ni 및 Al 박판을 이용한 Ni/Ni-Aluminide//Ti/Ti-Aluminide 다층재료의 in-situ 제조 및 기계적 특성

조성우,조현기,강형구,정동석 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.7

Ni/Ni-aluminidel/Ti/Ti-aluminide laminate material, considered as a functionally gradient material, was manufactured by hot-press and Ti, Ni and Al foils. Thick intermetallic layers of NiAl and TiAl₃ were formed by self-propagating, high temperature synthesis (SHS) reaction, and thin layers of Ni₃Al and TiAl were formed by diffusion in the solid state at the interface between metal and aluminide layers. Bending strength in metal-intermetallic composite depended on loading direction in bending test. As a result of fracture toughness measurements crack arrester had greater fracture resistance than crack divider due to interruption of crack growth in metal layers. Pure metal Ni and Ti layers showed ductile rupture. Also Ni₃Al and NiAl in Ni-aluminide layers revealed cleavage fracture and intergranular fracture, respectively, while Ti-aluminide layers showed typical cleavage fracture.