• 한국구조물진단유지관리공학회 논문집
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• 제21권5호
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• pp.21-29
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• 2017

시공지연 등으로 발생한 콜드조인트는 전단력에 취약하며 염화물 침투 및 확산을 촉진시킨다. 본 연구는 압축 및 인장하중과 콜드조인트 조건을 고려한 1년 양생된 콘크리트의 염화물 확산계수를 분석하였으며 선행연구인 91일 재령의 결과와 비교하였다. 91일 재령결과와 비교할 때, 하중을 재하하지 않은 일반적인 경우에는 건전부에서는 10.7%, 콜드조인트에서는 10.5%로 낮게 평가 되었다. 건전부와 콜드조인트의 감소율의 차이는 비슷하지만 염화물 확산계수는 콜드조인트에서 크게 발생하였다. 압축력 30%의 경우 건전부는 하중재하시 발생된 공극압밀로 인하여 확산계수가 감소하였다. 콜드조인트 콘크리트의 경우 365일 재령은 91일 재령보다 압축력 30%일 경우 10.9%, 압축력 60%일 경우 5.8% 확산계수가 낮게 평가되었는데, 이는 장기간 수중양생에 따른 지속적인 수화반응에 의해 확산계수가 낮게 평가되었기 때문이다. 인장력의 경우 압축부와는 다르게 동일 수준의 인장하중과 재령, 콜드조인트 유 무에 따른 확산계수의 차이가 비교적 크지 않았다. 이는 콘크리트가 1년 재령임에도 불구하고 인장력에 취약한 재료적 특성인 미세균열이 지배적인 영향으로 작용하였기 때문이다.

• 한국도로학회논문집
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• 제20권3호
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• pp.1-9
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• 2018

PURPOSES : In order to evaluate a crack resistance at cold joint, sealing tape was adopted to apply at cold joint instead of typical tack coat material(RSC-4). The sealing tape was made by hot sealing material. The crack resistance as function of environmental and traffic loading was measured with visual observation. METHODS : In this study, the crack resistance was evaluated as function of environmental and traffic loading. The freeze-thaw method was adopted for environmental loading of asphalt pavement. condition. The damage of cold joint under freeze-thaw action is initiated by ice expansion load and accelerated by the interfacial damage between new and old asphalt pavement. The traffic loading was applied with wheel tracking machine on the cold joint area of the asphalt pavement for 3 hours at $25^{\circ}C$. The evaluation of crack resistance was measured with visual observation. The freeze-thaw results shows that the sealing tape was significantly increased the crack resistance based on. RESULTS : To estimate the crack resistance at cold joint area due to the environmental loading, the Freeze-thaw test was conducted by exposing the product to freezing temperature(approximately $-18^{\circ}C$) for 24 hours, and then allowing it to thaw at $60^{\circ}C$ for 24 hours. The tack coat material(RSC-4) was debonded after 21 cycles of the Freeze-thaw test. The first crack was observed after 14 freeze-thaw cycle with RSC-4 material. But, the sealing tape was not debonded after 24 cycle test. Also, the sealing tape shows the better performance of the crack resistance under the traffic loading with wheel track test. The crack was generated the under traffic loading with RSC-4(tack coating), however, the crack was not shown with sealing tape. It indicates that the sealing tape has a strong resistance of tensile stress due to traffic loading. CONCLUSIONS :Based on limited laboratory test result, a performance of crack resistance using the sealing tape is better than that of general tack coat material(RSC-4). It means that the sealing tape is possible to extend a pavement service life because the crack, one of the main pavement distresses, will be delayed.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2005년도 창립60주년 기념 추계 학술대회
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• pp.230.1-230.1
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• 2005

• 대한기계학회논문집A
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• 제41권9호
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• pp.809-815
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• 2017

압력용기 재료로 사용되는 STS 304강은 저온에서 기계적 특성이 우수하지만, 다른 합금과 비교하여 중량이 무겁다. 이러한 문제를 해결하는 방안으로 STS 304강에 콜드 스트레칭(Cold stretching)공법을 사용하는 방법이 있다. 본 연구에서는 ASME 규정에 따라 제작된 콜드 스트레칭 압력용기에서 직접 채취한 콜드 스트레칭부 및 용접부 시험편을 이용하여, 상온 및 $-170^{\circ}C$에서 응력비 0.1과 0.5에 대하여 컴플라이언스법을 이용하여 피로균열진전시험을 수행하였다. 시험결과, 용접부의 피로균열진전속도는 콜드 스트레칭부에 비해 동일 응력확대계수범위에서 빠른 것을 확인하였다. 이러한 결과는 콜드스트레칭 공법을 사용하여 제작한 STS강 압력용기 개발을 위한 기초자료로 활용될 수 있을 것이다.

• 소성∙가공
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• 제23권4호
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• pp.211-220
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• 2014

The outer race of a constant velocity (CV) joint having six inner ball grooves has traditionally been manufactured by multi-stage warm forging, which includes forward extrusion, upsetting, backward extrusions, necking, ironing and sizing, and machining. In the current study, a multi-stage cold forging process is examined and an assessment for replacing and modifying the conventional multi-stage warm forging is made. The proposed procedure is simplified to the backward extrusion of the conventional process, and the sizing and necking are combined into a single sizing-necking step. Thus, the forging surface of the six ball grooves can be obtained without additional machining. To verify the suitability of the proposed process, a 3-dimensional numerical simulation on each operation was performed. The forging loads were also predicted. In addition, a structural integrity evaluation for the tools was carried out. Based on the results, it is shown that the dimensional requirements of the outer race can be well met.

• 한국안전학회지
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• 제29권3호
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• pp.1-7
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• 2014

In this study, for the evaluation of the static and fatigue joining strength of the joint, the geometry of the cross-tension specimen was adopted. The specimens were produced with optimal joining force and fatigue life of the clinch joint specimens was evaluated. The material selected for use in this study was cold rolled mild steel (SPCC) with a thickness of 0.8 mm. The maximum tensile load was 708 N for the specimen with single point. The fatigue endurance limit (=42.6 N) per point approached to 6% of the maximum tensile strength at a load ratio of 0.1, suggesting that the joints are vulnerable to cross-tension loading during fatigue. Compared to equivalent stress and maximum principal stress, the SWT fatigue parameter and equivalent strain can properly predict the current experimental fatigue life. The SWT parameter can be expressed as $SWT=2497.5N^{-0.552)_f$.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2007년도 정기총회 및 학술발표대회
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• pp.353-356
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• 2007

공항에 신규 활주로 및 유도로를 시공하기 위하여 공용중인 공항의 아스팔트 포장부를 모니터링한 결과, 종방향 균열이 관찰되었다. 종방향 균열의 원인은 아스팔트 포장 시공시 발생되는 종방향 시공조인트부의 낮은 밀도와 비행기의 높은 하중으로 판단되었다. 이에 따라 종방향 균열의 최소화 시공을 위해 공항의 연성 포장 구간에 12m폭의 스크리드를 가진 아스팔트 피니셔를 이용하여 편대포장을 실시하였다. 편대포장을 사용하면 첫 번째 차선의 비구속 단면부가 두 번째 차선과 같이 다짐되므로, 종방향 조인트부가 개선된다. 결과적으로 편대 포장 시공법을 사용하여 종방향 조인트부의 밀도와 인근의 일반 포장부의 밀도를 같게 하는 결과를 얻을 수 있었다.

• 대한임상전기생리학회지
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• 제5권2호
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• pp.85-93
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• 2007

Summary of background data: It is researched until now and the researches against the effect of position cold treatment the effect which pain threshold, change of skin temperature, researches the effective stiffness, the coldness in the patient it applied and relax an inflammation do the researches against were insufficient. Purpose: This project was to see how much it gives effect by using the cold air therapy an inflammation relief of rheumatoid arthritis patient. Methods: The medical subjects were 10 people from standard to diagnosis category of American College of Rheumatology(ACR) who had rheumatoid arthritis and to inspect informations about inflammation relief, have inspected ESR(erythrocyte sedimentation rate) and WBC(white blood cells). The experiment method was to let the patient bend the joint and lay down flat and treat with cold air from 10 cm away from joint line repeating 5 minutes treatment 1 minute rest and 3 minutes treatment. ESR and WBC cold air therapy reported with 5 days gap and each patient has been applied for 3 times. Result: The 5th day and 10th days ESR and WBC value shows when using cold air therapy, there was a reduction on rejected group but didn't last long, but 15th day it showed only on WBC it had its attention. Conclusions: So the cold air therapy shows it has positive effects on inflammation relief of rheumatoid arthritis patient.

• Journal of Welding and Joining
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• 제7권1호
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• pp.59-66
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• 1989

The weldability and joint performance were evaluated for newly developed 60kg/mm$\^$2/ steel which had low cold cracking susceptibility. The main results obtained were as follows; In case of quenched and tempered 60kg/mm$\^$2/ steels, it was very effective to improve weldability and joint performance by lowering carbon and Pcm level. Very small addition of about 0.001 to 0.002wt% boron exhibited an appreciable compensation effect on strength which was decreased by lowering carbon and Pcm level. As a result, the newly developed steel was able to be welded without preheating and exhibited superior joint performance to conventional steels.

• 한국임상수의학회지
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• 제16권2호
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• pp.300-308
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• 1999

Arthroscopy is a valuable diagnostic and operative tool in equine and human orthopedics. The arthroscope is a difficult instrument to use and requires patience, practice, and persistence in order to obtain good results. This technique was found to be less traumatic than arthrotomy, invasiveness, rapid recovery and the feasibility of surgically correcting many arthropathies. The use of the arthroscope in the dog provides a new dimension in the study and diagnosis of joint derangements. The purpose of this report is to introduce the use of the arthroscope in the dog-more specifically, in the stifle of the dog. A diameter 2.7 mm fore-oblique viewing arthroscope, cold light source, video and video printer are used. With the fore-oblique viewing type it is possible to view directly as well as slightly to the side and the range of viewing can be increased by rotating the arthroscope around the object The scope is connected with a cold light source by means of a fiber-optic light guide. The stifle joint was flexed to 20~30$^{\circ}$. The joint were lavaged with lactated Ringer's solution during arthroscopic examination. Arthroscopy of the stifle was performed prior to arthrotomy in 1 dead dog and 4 healthy dogs, and other 3 dogs was performed only arthroscopic examination. In this study only the conventional approaches were used and in most cases it was possible to view all the intra-articular structures via the lateral infrapatellar approach. In the stifle joint, endoscopic observation was performed to find lateral femoral condyle, patella, medial femoral condyle, trochlear groove, tibia, fat, cranial cruciate ligament, caudal cruciate ligament lateral meniscus, tendon of long digital extensor muscle, medial meniscus, and medial collateral ligament Post-arthroscopic examination, the lameness had disappeared within 12~24 hours. Pain and swelling in the stifle joint had disappeared within 24~36 hours. Post-arthroscopic secondary infection was never encountered in the dogs. In conclusion, arthroscopic insertion technique in canine stifle joint using a diameter 2.7 mm 30$^{\circ}$ arthroscope was established and arthroscopical views of all anatomical structures in the normal stilfe joint were obtained through lateral infrapatellar portal.