• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.32 no.1
• /
• pp.1-5
• /
• 2019

In this paper, the experimental study and finite elements analysis were conducted on homogeneous and dissimilar metals single lap-shear bonded joints to investigate the factor that affect the joint failure load. It was found that factors which have the significant effects on the failure load of the joint was stiffness of the adherends. And from experimental results, it can be confirmed that the failure load increases linearly with overlap length increases. And the failure load of dissimilar metal joints is approximately 1KN(10~17%) larger than homogeneous metal joints. In order to confirm this phenomenon, the stress distribution and strain distribution of the specimens were analyzed through the finite element analysis. The difference between homogeneous metals joints and dissimilar metals joints is that stress and strain in adhesive are concentrated at the end of the overlap zone close to aluminium which has lower rigidity than aluminium in case of dissimilar metals joints. From high rigidity of steel, the stress concentration in bonds are decreased and it cause increase of the failure strength at dissimilar metal joints.

• Journal of Advanced Marine Engineering and Technology
• /
• v.35 no.1
• /
• pp.68-74
• /
• 2011

This papers investigated the mechanical characteristics and the weldability of identical as well as dissimilar welding by GTAW for STS 304 and STS 316L. It is applied to double wall gas pipe of duel fuel engine for LNG carrier. Consequently, the weldability of dissimilar and identical welded zone of STS 304 decreased compared to base metal significantly. The result of microstructure observation for welded zone, a degree of acicular ferrite in welding zone for STS 304 presented more than STS 316L. The hardness of welding zone for STS 304 presented higher value than that for STS 316L by this effect.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 1999.11a
• /
• pp.86-86
• /
• 1999

• Journal of the Korean Arthroscopy Society
• /
• v.12 no.1
• /
• pp.7-11
• /
• 2008

Purpose: The purpose of this study was to compare the clinical outcomes of ACL reconstruction using autogenous hamstring tendon and allo-tibialis tendon. Materials and Methods: Between March 2002 and March 2005, We performed 30 ACL reconstuructions using hamstring autograft and 20 ACL reconstuructions using tibialis tendon allograft. The average follow up period was 22 months in auto-hamstring tendon and 18 months in allo-tibialis tendon. For the clinical evaluation, we measured the Lysholm score, International Knee Documentation Committee(IKDC) score and anterior laxity by KT-2000 arthrometer at final follow up and compare the results between two groups. Results: The Lysholm score improved from 69.5 preoperatively, to 95.3 at final follow-up in the hamstring autograft groups and from 69.0 to 90.4 in the tibialis allograft groups. According to the IKDC evaluation form, 80% of autogenous hamstring tendon group and 73% of allograft group were good results, higher than B(almost normal)(p>0.05). The average KT-2000 arthrometer side-to-side difference, decreased from 7.1mm preoperatively, to 1.8mm at final follow-up in the hamstring autograft groups and from 7.4 mm to 2.4mm in the tibialis allograft groups. Conclusion: The clinical results of ACL reconstruction using auto-hamstring tendon and allo-tibialis tendon showed no significant differences. The allo-tibialis tendon is an acceptable substitute for auto-hamstring tendon in ACL reconstruction.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.12 no.2
• /
• pp.182-189
• /
• 2004

The application of adhesively bonded components is increasing in various industries such as automobile, aircraft, IC packages, and soldering techniques. In spite of such wide application in adhesively bonded components, nondestructive test techniques applying to adhesively bonded components have not been clearly established yet. In this paper, characteristics of ultrasonic test on interfaces of adhesively bonded components have been investigated by calculating transmission coefficient theoretically and experimentally. From the experimental results, the optimum conditions to establish frequencies for adhesively bonded homogeneous and dissimilar components are 4∼6 MHz and 2∼4 MHz, respectively.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2012.05a
• /
• pp.87.1-87.1
• /
• 2012

넓은 밴드갭 (3.37eV)과 높은 엑시톤 결합에너지 (60meV)를 가지는 ZnO 물질은 ultra violet light 센서 및 light emitting diode (LED)의 재료로써 많은 연구가 진행되고 있다. 특히 나노와이어 구조를 이용하여 소자를 만들 경우 양자효과와 1차원적 캐리어 수송경로 효과로 인하여 그 특성을 보다 향상 시킬 수 있다. 나노와이어를 이용한 이종접합 p-n 다이오드를 제작하기 위하여 ZnO와 격자상수가 비슷한 GaN, NiO, CoO와 같은 물질들이 나노구조 접합에 많이 쓰이고 있지만, 격자상수 차이로 인해서 접합부분 캐리어 수송효율이 떨어지는 단점을 가지고 있다. n-type과 p-type ZnO를 만들어 동종 접합을 만들 경우 이러한 문제점을 극복할 수 있지만, 도핑되지 않은 ZnO가 n-type을 특성을 나타내기 때문에 안정적인 p-type ZnO 합성에 대한 연구가 필수적이다. 본 연구에서는 안정적인 p-type ZnO 합성을 위해서 수열합성법을 이용하여 phosphorus (P) 도핑을 하였고, 나노와이어 diode 구조를 만들었다. P 도핑으로 인한 격자상수 변화는 x-ray diffraction (XRD)를 사용하여 확인하였고, x-ray photoelectron spectroscopy (XPS)를 통해 도핑 원소를 분석하였으며, 이때의 recification ratio, turn-on voltage 등의 전기적 특성을 평가하였다.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2011.05a
• /
• pp.17.2-17.2
• /
• 2011

모든 생물은 늙어가면서 그 생물체를 이루고 있는 생체조직들이 낡게 되고 약해지기 마련이며, 이외에도 자동차 사고 등 재해에 의해 생체 장기의 손상을 가져올 수도 있다. 또한 인간의 평균수명 연장과 함께 소득 수준이 높아지고 또한 'quality of life'를 추구하는 고령화 시대로 접어듦에 따라, 인공골, 인공치아 또는 인공 고/슬관절 등의 골조직 대체재료의 수요가 빠르게 증가하고 있다. 이와 같은 골조직 대체, 즉 골이식은 크게 자기골 이식(autografting), 동종이식(allografing), 인공재료(man-made materials)의 이식으로 구분된다. 현재 대체물질의 약 58%를 차지하고 있는 자기골 이식의 경우, 거부면역 반응이 없어 임상성공율이 80%에 달한다는 장점을 가지고 있으나, 비용이 비싸고 감염과 통증의 위험이 있다. 또한 시신으로부터 골을 이식하는 동종이식의 경우 대체물질의 약 34%를 차지하고 있는데, 성공률이 떨어지고 질병 감염의 위험이 있는 단점이 있다. 이외에 약 8%를 차지하고 있는 인공재료 이식의 경우, 파단, 독성반응, 마모, 골조직의 remodeling 등이 일어나는 단점이 있으나, 앞에서 언급한 바와 같이 그 필요성이 급격히 증가함에 따라 보다 나은 치료법과 골이식 대체물질의 개발에 많은 노력이 경주되고 있다. 2003년 6월 미국 Financial Times에 의하면, 인체내 식립형 생체재료의 세계시장 규모는 약 650억 달러에 이르며, 매년 200% 이상씩 신장하고 있다고 한다. 따라서 세계 각국의 의학, 약학, 임상학, 생명과학, 공학 등의 관련 연구 분야에서는 이 수요를 충족시키기 위한 활발한 연구활동을 펼치고 있다. 한편 인체내 식립용 임플란트의 국내 시장규모는 치과 임플란트의 경우 2006년 현재 2000억원 규모로, 정형외과, 악안면 성형외과, 이비인후과를 포함하면 소위 'bone-anchored metal implant' 영역의 시장 규모는 4~5조원에 이를 것으로 추산 되고 있다. 또한 소비 신장률 10~15%를 감안하면 향후 시장 규모는 폭발적으로 증가될 것으로 예상된다. 이에 발맞추어, 최근 들어 선진국은 물론, 국내에서도 인체내 식립을 목적으로 하는 생체재료에 관한 연구개발이 활발히 진행되고 있으며, 일부는 실용화 단계에 진입하고 있다. 본 강연에서는 금속 임플란트의 시장현황과 앞으로의 추세에 대하여 조망하고, Ti 임플란트를 중심으로 이의 생체활성을 부여하는 표면개질 필요성 및 최근의 연구개발 동행에 대해 소개하고자 한다.

• Journal of the Korean Orthopaedic Association
• /
• v.56 no.1
• /
• pp.14-25
• /
• 2021

Several factors need to be considered for a successful anterior cruciate ligament (ACL) reconstruction, such as preoperative planning, operation technique, and postoperative rehabilitation. Graft choice, fixation, preparation method, maturation, incorporation to host bone, and graft tension should also be considered to achieve a good outcome after an ACL reconstruction. Factors to consider when selecting a graft are the graft strength, graft fixation, fixation site healing, and donor site morbidity, as well as the effects of initial strength, size, surface area, and origin of the graft on its potential for weakening during healing. There are two types of graft for an ACL reconstruction, autograft or allograft. Several autografts have been introduced, including the bone-patellar tendon-bone, hamstring tendon, and quadriceps tendon-bone. On the other hand, each has its advantages and disadvantages. The recent increased use of allografts for an ACL reconstruction is the lack of donor site morbidity, decreased surgical time, diminished postoperative pain, and good availability of source. Despite this, there are no reports suggesting that an allograft may have a better long-term outcome than an autograft. Allografts have inherent disadvantages, including a longer and less complete course of incorporation, remodeling, biomechanically inferiority to autograft, the potential risk of an immunogenic reaction and disease transmission. Higher long-term failure rates and poorer graft maturation scores were reported for allografts compared to autografts. An autograft in an ACL reconstruction should remain the gold standard, although the allograft is a reasonable alternative. If adequate length and diameter of autograft can be obtained for an ACL reconstruction, an autograft with adequate graft fixation and postoperative rehabilitation should be chosen instead of an allograft to achieve better results.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• v.21 no.4
• /
• pp.360-365
• /
• 1999

This study was aimed to suggest to better treatment method of jaw cyst that the maximum diameter was wider than 3cm, using different treatment and clinical and radiographic result. We divided the 60 patients into three groups, group A(20 patients) were treated with cyst enucleation and Decalcified Freeze-Dried Allogeneic Bone(DFDB) graft, group B(20 patients) were treated with cyst enucleation and autogenous bone graft, group C(20 patients) were treated with only cyst enucleation. Each group was evaluated with panoramic radiograph and clinical sign & symptom at pre-op and post-op(immediate, 6, 12, 24, 36 month). Bone density was evaluated with disital densitometer. The result was as follows : 1. Post-Op infection was higher in group C(4 pts.) than in group A(1 pt.) and B(1 pt.) 2. Post-Op gingival recession was higher in group C(3 Pts.) than in group A(1 pt.) and B(1 pt.) 3. Anatomic distortion was higher in group C(3 Pt.) than in group A(1 Pt.), and B(1 pt.) 4. Reoperation was done in two patients who were in group C 5. There were donor site morbidity in two patients 6. There was no significant difference between group A and B in their bony density in their follow up period(p>0.05). 7. There were significant differences between group A, B and group C in their bony density until post-op 24 months but a little differences at post-op 36 months(P<0.01)

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.10 no.1
• /
• pp.5-12
• /
• 2000

As a semiconductor material for electronic devices operated under extreme environmental conditions, silicon carbides (SiCs) have been intensively studied because of their excellent electrical, thermal and other physical properties. The growth characteristics of single- crystalline 6H-SiC homoepitaxial layers grown by a thermal chemical vapor deposition (CVD) were investigated. Especially, the successful growth condition of 6H-SiC homoepitaxial layers using a SiC-uncoated graphite susceptor that utilized Mo-plates was obtained. The CVD growth was performed in an RF-induction heated atmospheric pressure chamber and carried out using off-oriented ($3.5^{\circ}$tilt) substrates from the (0001) basal plane in the <110> direction with the Si-face side of the wafer. In order to investigate the crystallinity of grown epilayers, Nomarski optical microscopy, transmittance spectra, Raman spectroscopy, XRD, Photoluninescence (PL) and transmission electron microscopy (TEM) were utilized. The best quality of 6H-SiC homoepitaxial layers was observed in conditions of growth temperature $1500^{\circ}C$ and C/Si flow ratio 2.0 of $C_3H_8$ 0.2 sccm & $SiH_4$ 0.3 sccm.