• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 1996년도 춘계공동학술대회논문집; 공군사관학교, 청주; 26-27 Apr. 1996
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• pp.651-654
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• 1996

Although the tasks are being mechanized or automated today, many taks are still performed manually in serveral indeustrial settings and low back pain has been a social and economic problem. In this study, five machine repair tasks are selected from one manufacturing company in Pohang, which are accountable for relatively high complaints of low back pain. The purpose of this study is to quantitatively evaluate the hazards of the tasks, and finally to recommend the improved methods and guidelines for safe work practices. For most of the tasks under study, workers were found to be exposed to relatively high stresses in low back, mainly due to the heavy objects handled and the improper working postures.

• 설비공학논문집
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• 제15권5호
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• pp.346-351
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• 2003

This paper aims at suggesting design guidelines for a perimeter-less HVAC system that contributes energy savings. Perimeter-less HVAC system is one that relieves difficulties fuck as handling mixing loss, uneven radiative environment, and maintenance and repair. It prevents heat load gained through window and outdoor wall without modifying a previously equipped building skin system. In this paper, we performed several kinds of CFD (computational fluid dynamics) cases through numerical simulation to obtain an optimized perimeter-less design, and then we conducted a large-scale model experiment to see how the push-pull air flow would handle indoor heat to obtain an optimized perimeter-less design.

• 설비공학논문집
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• 제15권11호
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• pp.970-978
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• 2003

This paper aims at suggesting design guidelines for a perimeter-less HVAC system that contributes energy savings. Perimeter-less HVAC system is one that relieves difficulties such as handling mixing loss, uneven radiative environment, and maintenance and repair. It prevents heat load gained through window and outdoor wall without modifying a previously equipped building skin system. In this paper, we conducted a large-scale model experiment to see how the push-pull air flow would handle indoor heat to obtain an optimized perimeter-less design, and then we plan to perform several kinds of CFD (computational fluid dynamics) cases through numerical simulation

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.235-243
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• 2002

Ni-base superalloys are used extensively in industry, both in aeroengines and land based turbines. About 60% by weight of most modern gas turbine engine structural components are made of Ni-base superalloys. To satisfy practical demands, the efficiency of gas turbine engines has been steadily and systematically increased by design modifications to handle higher turbine inlet or firing temperatures. However, the increase in operating temperatures has lead to a decrease in the life of components and increase in costs of replacement. Moreover, around 80% of the large frame size industrial/utility gas turbines operating in the world today were installed in the mid-sixties to early seventies and are now 25 to 30 years old. Consequently, there are greater opportunities now to repair and refurbish the older models. Basically, there are two major factors influencing the weldability of the cast alloys: strain-age cracking and liquation cracking. Susceptibility to strain-age cracking is due to the total Ti plus AI content of the alloy; Liquation cracking is due either to the presence of low melting constituents or constitutional liquation of constituents. Though Rene 41 superalloy has 4.5wt.% total Ti and Al content and falls just below the safe limit proposed by Prager et al., controlled grain size and special heat treatments are needed to obtain crack-free welds. Varying heat treatments and filler materials were used in a laboratory study, then the actual welding of service parts was carried out to verity the possibility of crack-tree weld of components fabricated from Rene 41 superalloy. The microstructural observations indicated that there were two kinds of carbides in the FCC matrix. MC carbides were located along the grain boundaries, while M$_{23}$C$_{6}$ carbide was located both inter and intra granularly. Two kinds of filler materials, Rene 41 and Hastelloy X were used to gas tungsten arc weld a patch into the sheet metal, along with varying pre-weld heat treatments. The microstructure, hardness and tensile tests were determined. The service distressed parts were categorized into three classes: with large cracks, with medium cracks and with small or no visible cracks. No significant difference in microstructure among the specimens was observed. Specimens were cut from the corner and the straight edge of the patch repair, away from the corner. The only cracks present were found to be associated with inadequate surface preparation to remove oxidation. Guidelines for oxide removal and the welding procedures developed in the research enabled crack-free welds to be produced.d.

• 대한족부족관절학회지
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• 제26권1호
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• pp.22-29
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• 2022

Purpose: Despite continuous updates of standard treatment guidelines for acute ankle sprain and chronic ankle instability (CAI), in practice preferred treatment protocols vary widely. Based on a Korean Foot and Ankle Society (KFAS) member survey, this study reports current trends in the management of ankle ligament injuries. Materials and Methods: A web-based questionnaire containing 34 questions was sent to all KFAS members in September 2021. Questions mainly addressed clinical experience and preferences for the diagnosis and treatment of ankle ligament injuries. Answers with a prevalence of ≥50% among respondents were considered to reflect tendencies. Results: Eighty-four of the 550 members (15.3%) responded. Answers that showed a tendency were as follows: commonest additional image study (ultrasound), conservative treatment modality (immobilization, oral medication), frequency of surgical treatment (<5 cases per annum), most important factor when deciding on surgical treatment (activity level, e.g., occupation or sport), and commonest surgical procedure (open ligament repair). Answers that showed a tendency for CAI were as follows: most important symptom (repeated sprain, giving way), radiological factors (talar tilt, osteochondral lesion, anterior talar translation), and patient factors (occupation, sports activities, recurrent instability after surgery, etc.). For decision making regarding surgical treatment and method, the most preferred surgical procedure was the modified Broström procedure, and the most common repair technique was suture anchor technique. The following were considered poor prognostic factors; generalized laxity, failed previous surgery, cavovarus, severe mechanical instability, heavy work, obesity, and dissatisfaction after surgery because of residual pain. Conclusion: This study updates information regarding current trends in the management of ankle ligament injuries in Korea, and reveals consensus opinions and variations in approaches to patients with an acute or chronic injury. The divergence of approaches identified indicates the need for further studies to determine standard guidelines and long-term results.

• Journal of Chest Surgery
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• 제56권4호
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• pp.255-261
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• 2023

Background: The surgical threshold for bicuspid aortic valve (BAV)-related aortopathy is a matter of debate due to its uncertain etiology and prognosis. This study investigated the prognosis of unrepaired BAV aortopathy in patients undergoing surgical aortic valve replacement (SAVR). Methods: We retrospectively analyzed data from 720 patients (age, 60.8±11.5 years; 246 women) who underwent SAVR for BAV disease without aortic repair between 2005 and 2020 at Asan Medical Center. The clinical endpoints were defined as occurrences of sudden death, aortic dissection or rupture, and elective aortic repair. To estimate postoperative changes in the dimensions of the unrepaired aorta, the individual annual aortic expansion rate was calculated. Multiple linear regression models were used to evaluate the risk of aortic expansion. Results: The mean ascending aortic diameter was 39.5±4.6 mm, and 299 patients (41.5%) had a baseline ascending aorta diameter >40 mm. During 70.0±68.3 months of follow-up, the mean annual aortic expansion rate was 0.39±1.96 mm/yr, no aortic dissection or rupture was observed, and sudden deaths were reported in 12 patients (0.34% per person-year). Linear regression analysis revealed no significant correlation between the baseline ascending aortic diameter and postoperative aortic expansion (R²=0.004, β=-0.84, p=0.082). Conclusion: In selected patients undergoing SAVR for a BAV (<55 mm), the risk of adverse aortic events was very low. As this observation contradicts current practice guidelines advocating for proactive aortic replacement in dilated ascending aortas measuring >45 mm, the study results need further validation by studies involving larger populations or randomized controlled trials.

• 한국건축시공학회지
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• 제20권4호
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• pp.375-382
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• 2020

국내 국경 지역의 주요 도로에 낙석 장애물을 설치, 운영하여 적군의 이동을 방지하고 차단하고 있다. 그러나 접경지역의 개발로 인한 교통량 증가는 낙석으로 인한 도로 교통 혼잡, 교통 안전, 도시 미관 저하 등 많은 문제를 야기하고 있다. 따라서 본 연구는 단위별로 다르게 적용되는 낙석장해물 철거 및 교체 시설 설치 지침을 제공하고, 운영에 필요한 낙석 장해물 유지비에 대한 국방부의 정책 방향을 제시하고자 하였다. 본 연구에서는 낙석 장해물 제거 및 대체시설 설치에 관한 지침 연구의 일환으로 필수 낙하 장해물에 대한 표준 단가를 제시하여 암석 제거 여부를 판단 할때 판단 자료로 활용하고자 하였다.

• International Journal of Concrete Structures and Materials
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• 제11권1호
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• pp.171-183
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• 2017

Strengthening reinforced concrete (RC) beams with openings by using aramid fiber reinforcement polymers (AFRP) on the beams' surfaces offers a useful solution for upgrading concrete structures to carry heavy loads. This paper presents a repairing technique of the AFRP sheets that effectively strengthens RC beams, controls both the failure modes and the stress distribution around the beam chords and enhances the serviceability (deflection produced under working loads be sufficiently small and cracking be controlled) of pre-cracked RC beams with openings. To investigate the possible damage that was caused by the service load and to simulate the structure behavior in the site, a comprehensive experimental study was performed. Two unstrengthened control beams, four beams that were pre-cracked before the application of the AFRP sheets and one beam that was strengthened without pre-cracking were tested. Cracking was first induced, followed by repair using various orientations of AFRP sheets, and then the beams were tested to failure. This load was kept constant during the strengthening process. The results show that both the preexisting damage level and the FRP orientation have a significant effect on strengthening effectiveness and failure mode. All of the strengthened specimens exhibited higher capacities with capacity enhancements ranging from 21.8 to 66.4%, and the crack width reduced by 25.6-82.7% at failure load compared to the control beam. Finally, the authors present a comparison between the experimental results and the predictions using the ACI 440.2R-08 guidelines.

• 한국건설관리학회:학술대회논문집
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• 한국건설관리학회 2007년도 정기학술발표대회 논문집
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• pp.499-502
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• 2007

정부는 기존의 품셈에 의한 예정가격 산정 방식을 폐지하고, 실적계약 단가를 근거로 하는 실적공사비 적산제도를 도입하여 시행중에 있다. 그러나 현재 BTL 교육시설물 예정가격 산정방법의 경우 표준화된 작업분류체계(WBS : Work Breakdown Structure) 및 내역서 작성지침의 부족으로 인하여 단가 산정에 정확한 근거 마련이 힘든 실정이다. 따라서 본 연구에서는 BTL로 발주된 교육시설물의 내역서를 바탕으로 BTL 교육시설물의 실적공사비 적용을 위한 작업분류체계(WBS : Work Breakdown Structure) 구축을 목적으로 한다. 이를 통해 일반 시설물과는 다른 특징을 가지는 교육시설물 분류체계를 구축하고 이를 이용한 공사비 항목 및 유지보수비 항목의 체계화가 가능할 것으로 예상된다.

• 대한피부과학회지
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• 제56권10호
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• pp.581-593
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• 2018

Atopic dermatitis (AD) is a common, chronic, relapsing, inflammatory skin disease that affects both children and adults. AD is the cause of considerable morbidity including severe pruritus and impaired quality of life. Treatments for active disease include avoidance of triggering factors, barrier repair, topical medications including topical corticosteroids (TCs) and topical calcineurin inhibitors (TCIs), phototherapy, antibacterial agents, and systemic immunosuppressants including cyclosporine. Until recently, the only Food and Drug Administration (FDA)-approved systemic treatment options for patients with moderate-to-severe AD were steroids and cyclosporine. Systemic steroids are not recommended by current guidelines and are commonly associated with disease rebound. Instead, clinicians choose from several off-label immunosuppressants. In 2018, the Korean FDA approved dupilumab for adults with moderate-to-severe AD whose disease is not adequately controlled with topical therapies. The implementation of treatment guidelines for AD is challenging. Herein, we review the several treatment modalities for AD and recommend a treatment algorithm.