• 대한청각학회지
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• 제23권2호
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• pp.112-117
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• 2019

Background and Objectives: The purpose of this study was to evaluate the efficacy of revision cochlear implant (CI) surgery for better speech comprehension targeting patients with low satisfaction after first CI surgery. Subjects and Methods: Eight patients who could not upgrade speech processors because of an too early CI model and who wanted to change the whole system were included. After revision CI surgery, we compared speech comprehension before and after revision CI surgery. Categoies of Auditory Performance (CAP) score, vowel and consonant confusion test, Ling 6 sounds, word and sentence identification test were done. Results: The interval between surgeries ranged from eight years to 19 years. Same manufacturer's latest product was used for revision surgery in six cases of eight cases. Full insertion of electrode was possible in most of cases (seven of eight). CAP score (p-value=0.01), vowel confusion test (p-value=0.041), one syllable word identification test (p-value=0.026), two syllable identification test (p-value=0.028), sentence identification test (p-value=0.028) had significant improvement. Consonant confusion test (p-value=0.063), Ling 6 sound test (p-value=0.066) had improvement but it is not significant. Conclusions: Although there are some limitations of our study design, we could identify the effect of revision (upgrade) CI surgery indirectly. So we concluded that if patient complain low functional gain or low satisfaction after first CI surgery, revision (device upgrade) CI surgery is meaningful even if there is no device failure.

• 대한기계학회논문집A
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• 제41권5호
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• pp.375-380
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• 2017

본 논문은 한국원자력연구원에서 개발 중인 소듐냉각 고속로 핵연료의 연료봉 하단 마개에 있는 관통구멍과 마운팅 레일의 원기둥 형상과의 접촉부에 발생하는 접촉 손상을 예측하기 위한 가속시험 방법을 연구한 것이다. 가속시험 조건으로서 연료봉의 유체유발진동수 및 진폭을 유한요소 해석을 통하여 구하였다. 약 35000 시간의 연료봉 수명기간을 고려한 가속시험 시간을 결정하기 위해 일반 기계부품류의 신뢰성 평가 방법을 적용하였으며, 이때 가장 보수적인 형상 모수와 원자로 내에서의 연료봉 파손허용 개수 기준 및 연료봉 피복관 재료인 HT-9강의 피로수명 데이터를 이용하였다. 시편의 개수를 5개로 하였을 때, 최종적으로 계산된 가속 시험시간은 각 시편 당 16.5시간이었다. 가속시험 후 전체 시편에 어떠한 접촉손상도 관찰되지 않을 때 연료봉의 수명기간 중 $B_{0.004}$ 수명이 신뢰수준 99%로 보장되는 것으로 평가하였다.

• 대한토목학회논문집
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• 제34권2호
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• pp.403-413
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• 2014

스트럿-타이 모델 방법을 이용한 콘크리트 구조부재의 설계 시 가장 중요한 요소 중 하나는 콘크리트 스트럿의 유효강도를 정확하게 결정하는 것이다. 콘크리트 스트럿의 유효강도를 결정하기 위한 많은 연구가 진행되어 왔으며, 여러 종류의 스트럿의 유효강도 값 및 산정식이 제안되었다. 그러나 이들은 2차원 콘크리트 구조부재의 스트럿-타이 모델 설계를 위한 것으로, 그 값을 3차원 콘크리트 구조부재의 설계에 적용하는 것은 적절하지 않다. 이 연구에서는 콘크리트 스트럿이 위치한 곳의 3축 응력 상태, 콘크리트의 3차원 파괴기준, 스트럿 길이의 영향, 스트럿과 압축 주응력 흐름과의 불일치의 영향, 콘크리트 압축강도의 영향, 그리고 철근에 의한 콘크리트 스트럿의 구속의 정도 등을 고려하여 3차원 콘크리트 스트럿의 유효강도를 일관성 있게 결정할 수 있는 방법을 제안하였다. 제안한 방법의 타당성을 검증하기 위해 기존 연구자들에 의해 파괴실험이 수행된 115개의 철근콘크리트 파일캡 시험체의 극한강도를 평가하였으며, 그 결과를 실험결과 및 현행 설계기준에서 제안한 스트럿의 유효강도 값을 이용하여 평가한 결과와 비교분석하였다.

• 한국지반신소재학회논문집
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• 제18권4호
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• pp.205-214
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• 2019

본 연구에서는 경사식 방파제의 원호활동에 대한 하중저항계수 설계법을 개발하였다. 이를 위하여 국내 8개의 경사식 방파제의 설계 자료를 수집하였으며, 지반의 강도 및 단위중량, 피복제와 상치구조물의 단위중량, 상치구조물 상부에 재하되는 하중의 불확실성을 결정하였다. 다양한 해석변수의 불확실성에 대해 가장 취약한 원호활동면을 찾는 과정을 재현하기 위하여 몬테카를로 시뮬레이션(Monte Carlo Simulation)을 수행하였다. 몬테카를로 시뮬레이션 결과는 신뢰성 분석을 위한 FORM(First-Order Reliability Method) 해석에 사용하였다. 신뢰성 분석 결과를 통해 목표신뢰도 지수에 따른 최적 하중 및 저항계수를 산정하였으며, 산정된 최적 하중 및 저항계수를 이용하여 본 연구에서 개발한 하중 및 저항 계수를 제시하였다.

• 한국작물학회:학술대회논문집
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• 한국작물학회 2017년도 9th Asian Crop Science Association conference
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• pp.281-281
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• 2017

Recently, global warming by greenhouse gas effect is getting danger and danger for human life and agriculture at present. In Indonesia, according to heavy rain in the agriculture land is often covered by excess water in result crop growth would be affected negative. This water stress triggers roots failure in anaerobic condition for upland crop because of limiting roots respiration. Chili pepper grows in upland sometimes in touch with waterlogging due to rainfall and /or over flow water from river in Indonesia. In this case, roots growing is inhibited by effect of shortage of oxygen at root cap. Therefore, the objective of this study is to observe the plant behavior in waterlogging using mahor local genotypes (Ferosa, Laris, Romario) in Sumatra. The experiment was kept by at 1cm depth water above the soil surface as a waterlogged treatment for ---days. As a result, waterlogging affected plant growth of chili negatively, especially for roots growth. Almost roots were getting bad and changed color for brown during waterlogging. A significant negative effect for nutrient absorption by roots was found in dry weight of all varieties during waterlogging. Dry weight of roots was decreased by 81.4% and 67.6%, and those of aerial part decreased by 74% and 67.2% compared with control in Ferosa and Romario at 1week after treatment. On the other hand, dry weight of roots was decreased only 35% in Laris. Therefore, Laris has a tolerance for waterlogging compared to with other varieties. Also, Laris in SPAD value was kept initial level during waterlogging however those of Ferosa and Romario decreased. Finally, due to impact of waterlogging, it may be the roots become failure because of less aerenchyma formation under anaerobic condition. We need confirm aerenchyma formation morphologically in the future.

• 한국전산구조공학회논문집
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• 제20권6호
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• pp.699-708
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• 2007

일반적으로 깊은 보의 개구부 보강을 할 경우 개구부 주변의 부족한 내력에 대해 수직, 수평, 대각, 혹은 혼합된 배근 형태를 사용하게 되는데, 경제성과 구조적 안전성을 고려하기 위해서는 각 배근 형태 및 방법에 따른 깊은 보의 거론 평가와 적절한 조합에 관한 연구가 절실히 필요하다. 이에 본 연구에서는 개구부 보강방법을 변수로 한 simulation 모델을 통해 수직, 수평 보강의 효과에 대해 해석적으로 검증을 한 후, 각 규준에서 제시하고 있는 개구부가 있는 깊은 보의 전단 내력식을 분석하고 해당 식을 보완하여 단순지지 1경간 및 연속 경간에 적용 가능한 전단 내력 산정식을 제안하고자 한다.

• 동력기계공학회지
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• 제15권4호
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• pp.19-24
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• 2011

The operational efficiency of domestic gas turbine is about 25% and it is now in the trend of the gradual growth in spite of the severe temperature, frequent starting and shutdown according to the environmental management and the energy-efficient use. Rotor bolts of gas turbine in power plants have been the cause of defects because these gas turbines have been operated for a long time under the high pressure and temperature environment experiencing the aging change and stress concentration of the bonded part. The connection parts of the bolt revealed various failure shape and these parts were elongated under very low pressure when operated in the relaxed condition. The cause is in the lack of the metal distribution in the bottle lack area and the cap screw of the bolt is broken totally in case that the nut is fastened in most cases. Gas turbine rotor bolts are connected to the rotor wheel and these bolts caused the vibration, the bulk accident of the rotor in the event that the coupling power among these bolts was relaxed. Therefore, we would like to evaluate the soundness of the main part of the gas turbine rotor bolt through the measurement of the inner condition change along with the mechanic deterioration and temperature, stress in the gas turbine rotor material.

• Earthquakes and Structures
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• 제12권1호
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• pp.55-65
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• 2017

Earthquake resilience of substations is essential for reliable and sustainable service of electrical grids. The majority of substation equipment consists of cylindrical porcelain components, which are vulnerable to earthquake shakings due to the brittleness of porcelain material. Failure of porcelain equipment has been repeatedly observed in recent earthquakes. Hence, proper seismic modelling of porcelain equipment is important for various limit state checks in both product manufacturing stage and detailed substation design stage. Sheds on porcelain core and cemented joint between porcelain component and metal cap have significant effects on the dynamic properties of the equipment, however, such effects have not been adequately parameterized in existing design guidelines. This paper addresses this critical issue by developing a method for taking these two effects into account in seismic modelling based on numerical and analytical approaches. Equations for estimating the effects of sheds and cemented joint on flexural stiffness are derived, respectively, by regression analyses based on the results of 12 pieces of full-scale equipment in 500kV class or higher. The proposed modelling technique has further been validated by shaking table tests.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 기초기술학술발표회
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• pp.11-29
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• 2002

Current design of pile group is based on the estimation of the overall bearing capacity of a pile group from that of a single pile using a group efficiency. However, the behaviors of a pile group are influenced by various factors such as method of pile installation, pile-soil-pile interaction, cap-soil-pile interaction, etc. Thus it is practically impossible to take into account these factors reasonably with the only group efficiency, In this paper, a new method for the design of pile groups is proposed, where the significant factors affecting the behavior of a pile group are considered separately by adopting several efficiencies. Furthermore, in the proposed method, the load transfer characteristics of piles and the difference of pile behaviors with respect to the pile locations in group can be taken into account. The efficiencies for the method are determined using the settlement failure criterion, which is consistent with the concept of allowable settlement for structures. The efficiencies calculated from the results of existing model tests are presented, and the bearing capacity of a pile group in the other model test is calculated and compared with that from the test result, to verify the validity of the proposed method.

• Structural Engineering and Mechanics
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• 제56권6호
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• pp.917-938
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• 2015

The nonlinear numerical analysis of the impact response of reinforced concrete/mortar beam incorporated with the updated Lagrangian method, namely the Smoothed Particle Hydrodynamics (SPH) is carried out in this study. The analysis includes the simulation of the effects of high mass low velocity impact load falling on beam structures. Three material models to describe the localized failure of structural elements are: (1) linear pressure-sensitive yield criteria (Drucker-Prager type) in the pre-peak regime for the concrete/mortar meanwhile, the shear strain energy criterion (Von Mises) is applied for the steel reinforcement (2) nonlinear hardening law by means of modified linear Drucker-Prager envelope by employing the plane cap surface to simulate the irreversible plastic behavior of concrete/mortar (3) implementation of linear and nonlinear softening in tension and compression regions, respectively, to express the complex behavior of concrete material during short time loading condition. Validation upon existing experimental test results is conducted, from which the impact behavior of concrete beams are best described using the SPH model adopting an average velocity and erosion algorithm, where instability in terms of numerical fragmentation is reduced considerably.