• Journal of Welding and Joining
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• 제35권3호
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• pp.68-74
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• 2017

Characteristics of dissimilar metal welds between alloy steel ASTM A387 Gr. 91 and carbon steel ASTM A516 Gr.70 made with Flux cored arc welding(FCAW) have been evaluated in terms of microstructure, mechanical strength, chemical analysis by EDS as well as corrosion test. Three heat inputs of 15.0, 22.5, 30.0kJ/cm were employed to make joints of dissimilar metals with E71T-1C wire. Post-weld heat treatment was carried out at $750^{\circ}C$ for 2.5 h. Based on microstructural examination, Intragranular polygonal ferrite and grainboundary ferrite were formed only in first layer of weld metal. Another layers consisted of acicular ferrite and $Widmannst{\ddot{a}}tten$ ferrite. The amount of acicular ferrite was increased with decreasing heat input and layer. Heat affected zone of alloy steel showed the highest hardness due to the formation of tempered martensite and lower bainite. Lower and upper bainite were formed in heat affected zone of carbon steel. Tensile strengths of dissimilar metal welds decreased with increasing heat inputs. Dissimilar metal welds showed a good hot cracking resistance due to the low HCS index below 4. The salt spray test of dissimilar metals welds showed that the weight loss rate by corrosion below 170 hours was decreased with increasing heat inputs due to the increase of the amount of acicular ferrite.

• 생명과학회지
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• 제15권1호
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• pp.112-117
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• 2005

하천변에 사는 식물들은 침수 저항성을 갖추고 있는데 그중 Ranunculus속이나 Rumex속에 속하는 일부 반수생 식물들에서 볼 수 있는 것처럼, 엽병이 급격한 생장을 일으켜 잎이 수표면에 이르게 함으로써 호흡할 수 있는 조건을 확보하는 현상은 식물체내에 축적된 에틸렌에 의하여 매개되는 현상이다. 침수 조건에서는 식물 조직 내에 에틸렌이 축적되며, 축적된 에틸렌은 옥신 등 다른 식물호르몬에 대한 조직의 감수성을 증가시켜 생장을 촉진한다. 증가된 생장으로 잎이 수표면에 이르게 되면 다시 공기를 접촉하여 호흡할 수 있게 되고, 식물체내에 축적되었던 에틸렌은 대기 중으로 확산하여 나가게 되므로 체내 에틸렌 농도가 감소하여 생장률이 침수 이전 수준으로 되돌아간다. 에틸렌에 의한 옥신의 감수성 증가는 선량 반응 곡선에 비추어 수용체의 친화도 증가가 수반되는 것으로 생각되는데, 아직 옥신 수용체가 밝혀지지 않아 분자생물학적 기작은 연구되어야 할 과제로 남아있다. 최근 옥신 수용체 발견의 가능성이 높아지고 있으며, 따라서 에틸렌에 의한 옥신 수용체의 옥신에 대한 감수성 조절기작을 탐구할 수 있는 길이 열릴 것으로 기대된다.

• 한국자원식물학회지
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• 제13권3호
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• pp.208-212
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• 2000

보온 피복재 종류가 자옥 포도 유목의 월동시 동해방지, 노동력 절감 및 병해 발생 억제에 미치는 영향을 구명하기 위하여 11월 하순에 짚을 덮은 다음 보온덮개B, 킬딩, 칼라부직A 및 백색니들펀칭부직포 등을 피복하여 시험한 결과를 요약하면 다음과 같다. 1. 보온력은 백색니들펀칭부직포가 가장 불량하였고, 다른 보온재간에는 차이가 미미하였다. 2. 발아는 보온덮개B에서 빨리 시작되었으며, 발아 9일 후에도 발아율이 79.7%로 타 보온재 보다 2.3∼12.5% 높았다. 3. 생육은 보온재간에 차이가 없었으며, 병해 발생은 킬딩과 보온덮개B에서 뿌리혹병이 지수 3.0∼3.2로 다소 많이 발생되었을 뿐 기타 병해는 처리간에 차이가 없거나 미미 하였다. 4. 작업 단계별 소요노력은 보온덮개B에 비하여 킬딩은 6% 많았으나, 칼라부직A는 6%, 백색니들펀칭 부직포는 15%적었다.

• 한국전기전자재료학회논문지
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• 제23권8호
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• pp.651-654
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• 2010

This paper describes the thermal and mechanical properties of doped thin film 3C-SiC and porous 3C-SiC. In this work, the in-situ doped thin film 3C-SiC was deposited by using atmospheric pressure chemical vapor deposition (APCVD) method at $120^{\circ}C$ using single-precursor hexamethyildisilane: $Si_2(CH_3)_6$ (HMDS) as Si and C precursors. 0~40 sccm $N_2$ gas was used as doping source. After growing of doped thin film 3C-SiC, porous structure was achieved by anodization process with 380 nm UV-LED. Anodization time and current density were fixed at 60 sec and 7.1 mA/$cm^2$, respectively. The thermal and mechanical properties of the $N_2$ doped porous 3C-SiC was measured by temperature coefficient of resistance (TCR) and nano-indentation, respectively. In the case of 0 sccm, the variations of TCR of thin film and porous 3C-SiC are similar, but TCR conversely changed with increase of $N_2$ flow rate. Maximum young's modulus and hardness of porous 3C-SiC films were measured to be 276 GPa and 32 Gpa at 0 sccm $N_2$, respectively.

• Journal of Welding and Joining
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• 제34권3호
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• pp.61-68
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• 2016

Characteristics of dissimilar metal welds between alloy steel ASTM A387 Gr. 91 and carbon steel ASTM A516 Gr.70 made with Flux cored arc welding(FCAW) have been evaluated in terms of microstructure, mechanical strength, chemical analysis by EDS as well as corrosion test. Three heat inputs of 15.0, 22.5, 30.0kJ/cm were employed to make joints of dissimilar metals with E91T1-B9C wire. Post-weld heat treatment was carried out at $750^{\circ}C$ for 2.5 h. Based on microstructural examination, tempered martensite and lower bainite were formed in first layer of weld metal. The amount of tempered martensite was decreased and the amount of lower bainite was increased with increasing heat input and layer. Heat affected zone of alloy steel showed the highest hardness due to the formation of tempered Martensite and lower Bainite. Tensile strengths of dissimilar welds decreased with increasing heat inputs. Dissimilar welds seemed to have a good hot cracking resistance due to the low HCS index below 4. The salt spray test of dissimilar metals showed that the corrosion rate increased with increasing heat inputs due to the increase of the amount of lower Bainite.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 추계학술대회 논문집
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• pp.138-144
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• 2003

Rencentely, the request for the light weight is more incresed in the area of industrial environment and machinery and consistent effort is needed to accomplish high strength of material for the direction of light weight. we got the following characteristic from crack growth test carried out in the range of stress ration of 0.1, 0.3 and 0.6 by means of opening mode displacement. At the content stress ratio, the threshold stress intensity factor crack range ${\Delta}K_{th}$in the early stage of fatigue crack growth (Region I) and dtress intensity factor range ${\Delta}K$ in the stable of fatigue crack growth (Region II) with an increase in ${\Delta}K$. Fatigue life shows more improvement in the Shot-peened material than in the Un-peening material. And compressive residual stress of surface on the Shot peening processed operate resistance force of fatigue. So we can obtain fallowings. (1) The fatigue crack growth rate on stage II is conspicuous with the size of compressive residual stress and is depend on Paris equation. (2) Although the maxium compressive residual stress is deeply and widely formed from surface, fatigue life does not improve than when maxium compressive residual stress is formed in surface. (3) The threshold stress intensity factor range is increased with increasing compressive residual stress.

• Asian Pacific Journal of Cancer Prevention
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• 제16권13호
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• pp.5191-5197
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• 2015

A partial response or resistance to chemotherapeutic agents is considered as a main obstacle in treatment of patients with cancer, including breast cancer. Refining taxane-based treatment procedures using adjuvant or combination treatment is a novel strategy to increase the efficiency of chemotherapy. PPM1D is a molecule activated by reactive oxygen species. whose expression is reported to modulate the recruitment of DNA repair molecules. In this study we examined the impact of arsenic trioxide on efficacy of paclitaxel-induced apoptosis in paclitaxel-resistant MCF-7 cells. We also investigated the expression of PPM1D and TP53 genes in response to this combination treatment. Resistant cells were developed from the parent MCF-7 cell line by applying increasing concentrations of paclitaxel. MTT assays were applied to determine the rate of cell survival. DAPI staining using fluorescent microscopy was employed to study apoptotic bodies. Real-time RT-PCR analysis was also applied to determine PPM1D mRNA levels. Our results revealed that combination of arsenic trioxide and paclitaxel elevates the efficacy of the latter in induction of apoptosis in MCF-7/PAC resistant cells. Applying arsenic trioxide also caused significant decreases in PPM1D mRNA levels (p<0.05). Our findings suggest that arsenic trioxide increases paclitaxel-induced apoptosis by down regulation of PPM1D expression. PPM1D dependent signaling can be considered as a novel target to improve the efficacy of chemotherapeutic agents in resistant breast cancer cells.

• Archives of Plastic Surgery
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• 제35권2호
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• pp.159-164
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• 2008

Purpose: Microvascular free tissue transfer has become a reliable technique for the reconstruction of complex wounds. Occasionally, unexpected intraoperative thrombosis and/or spasm of recipient artery might be annoying problems even for the technically competent microvascular surgeons. If such problems are not treated properly, they will inevitably cause to flap failure. Methods: From January 2006 to February 2007, soft tissue reconstructions by free tissue transfers were performed on 21 patients having complex defects in the lower extremity. Although segmental revision and various pharmacologic agents were repeatedly applied, arterial occlusions were not managed in 6 cases. For removal of thrombi and release of spasm, Fogarty No. 2 or No. 3 catheters were inserted into the lumen to the proximal recipient artery. Its balloon was then inflated after passing through a resistant area. Next, the catheter was gently withdrawn backward. Results: After the Fogarty catheter was inserted two or three times, the pulsatile arterial flow was restored. When the catheter was inserted into the lumen, a feeling of resistance existed in a 5-10cm more proximal portion that could not be easily accessed from the vascular end. After the reestablishment of blood flow, successful anastomoses were achieved and immediate rethrombosis or spasm did not occur. No long-term sequelae associated with balloon trauma to the arterial wall were observed. Conclusion: The use of the Fogarty catheter can be an effective method in treating pedicle thrombosis and spasm. This is a very simple and rapid technique that offers microvascular surgeons another option to increase the success rate of microvascular anastomosis in free tissue transfers.

• 열처리공학회지
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• 제4권3호
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• pp.13-20
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• 1991

The present work was aimed to examine the variation of precipitations and mechanical properties by thermomechanical treatments (TMT) in Al-2.19 wt%Li and Al-2.0 wt%Li-0.11 wt%Zr alloys. This study was performed by TEM, SEM observation, DSC, electrical resistance measurement, hardness and tensile strength measurement. First peak of resistivity aged at $90^{\circ}C$ was caused by precipitation of ${\delta}^{\prime}$-precursor phase, and second peak was caused by precipitation of ${\delta}^{\prime}$ phase. According to this result, the precipitation process of Al-2.19 wt%Li alloy was as follow : $SSSS{\rightarrow}{\delta}^{\prime}$-precursor phase ${\rightarrow}{\delta}^{\prime}$ (Coherent ${\rightarrow}$ Semi-coherent) ${\rightarrow}{\delta}$. In a Al-2.0 wt%Li-0.11 wt%Zr ternary alloy, the first peak of resistivity was appeared at initial aging heat-treatment. It is result from exsistant of ${\delta}^{\prime}$-precursor phase. The effect acceleration in a binary alloy was not appeared and the over-aging ternary alloy was accelerated with increase of the reduction rate. It is caused by combination effect of ${\delta}^{\prime}$ and composite phase.

• 한국임상수의학회지
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• 제21권3호
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• pp.270-275
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• 2004

Anesthetic machines may be equipped with either a precision or nonprecision vaporizer. A precision vaporizer is designed to deliver an exact concentration of anesthetic agent. Goldman vaporizer is a low-flow, closed-circle circuit with a low resistance vaporizer, in circuit. Vaporizers used within circle system(VIC) are not usually temperature compensated and this is generally thought to be a disadvantage. As the volatile agent is vaporized, heat is extracted from the liquid and temperature decreases. This cooling of the liquid leads to a decrease in concentration of the anaesthetic agent delivered by the vaporizer. The purpose of this study is to examine the mechanical consistency of the delivery of isoflurane from Goldman vaporizer and precision vaporizer at various gas flow rates and temperatures. And we first studied isoflurane concentration according to room temperature changes delivered by a Goldman vaporizer and precision vaporizer using different gas flow. The room temperature of $15^{\circ}C,$ $20^{\circ}C,$ $28^{\circ}C$ and fresh gas flow rates of 0.5, 1.0, 1.5, 2.0, 3.0 l/min were used. The inspired agent concentration was measured using a Datex-Ohmeda multigas analyzer. As rose in room temperature, the isoflurane concentration of precision vaporizer approximated the dial setting. On the other hand, at a dial setting concentration of 5.0 percent the delivered isoflurane concentration of precision vaporizer was more than the dial setting in high temperature. The isoflurane concentration of precision vaporizer remained constant despite the increase in temperature. The isoflurane concentration of Goldman vaporizer was increased with rise in room temperature and decreased with rise in gas flow.