• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2000년도 유체기계 연구개발 발표회 논문집
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• pp.359-365
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• 2000

Port facilities and marine structures used in marine environment were encountered to corrosion damages because of the influence of $Cl^-$. Generally, to protect these accidents, mainly applied anti-corrosion paint and epoxy coating. But it was still remained erosion-corrosion damage such as impingement erosion, cavitation erosion, deposit attack. There was needs to develope the new coating materials to protective those corrosion damages. This paper, polyester glass flake, vinylester glass flake lining and epoxy coating for SS were investigated electrochemical tests and cavitation erosion test for corrosion behaviour under sea water. The main results obtained are as follows, 1) Surface of epoxy coating appear erosion pin hole but surface of polyester glass flake and vinylester glass flake lining do not appear erosion pin hole after impingement-cavitation erosion test in sea water. 2) Weight loss of polyester glass flake and vinylester glass flake lining do not occur after impingement-cavitation erosion test in sea water. 3) Corrosion current density of polyester glass flake lining less drained than epoxy coating and substrate under corrosion potential.. 4) Corrosion current density of vinylester glass flake lining with three coating less drained than that of polyester glass flake lining with two coating.

• 한국염색가공학회지
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• 제34권4호
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• pp.241-249
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• 2022

As for military backpacks in Korea, utility backpack products equipped with various functions along with comfort and convenience are being developed. As a result, the volume and weight of the backpack increase, and many lightweight studies of the materials forming the backpack are being conducted. This study is a basic study on frame lightweight using fiber-reinforced composites to deal with aluminum, a back frame that maintains the shape of a backpack and provides stability when worn by combatants. As is known, only fiber-reinforced composites have sufficient light weight and mechanical properties, but the mechanical properties were reviewed by drilling holes to maximize the light weight. Tensile strength and flexural strength were measured by drilling 6mm, 12mm, 18mm, and 24mm holes, and the tensile strength and flexural strength were measured when 1, 3, 5, and 7 holes of 12mm were increased. As a result, even when the number of holes was increased, tensile strength did not change significantly, and the flexural strength showed to be higher in the case of 3 holes and 5 holes than in the case of 1 hole.

• Biomolecules & Therapeutics
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• 제15권3호
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• pp.175-181
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• 2007

Zizyphi Spinosi Semen (ZSS), a traditional Chinese folk medicine, has been used for treatment of insomnia and anxiety. This experiment was performed to investigate the anxiolytic-like effect of methanol extract of ZSS (MEZSS) in mice by using the experimental paradigms of anxiety and compared with that of a known anxiolytic, diazepam. In the elevated plus-maze test, it showed that MEZSS (100 mg/kg, p.o.) and diazepam (2.0 mg/kg, p.o.) increased the percentage of time spent on the open arms and the number of open arms entries. MEZSS (50, 100 and 200 mg/kg, p.o.) and diazepam (0.5 mg/kg, p.o.) significantly increased the number of head dips compared with that of control group in the hole-board test. However, MEZSS has no effect on decreasing the locomotor activity, while diazepam (2.0 mg/kg, p.o.) significantly inhibited locomotor activity. MEZSS did not decrease the strength force in the grip strength test, either. In addition, GABAergic involvements were also investigated to understand the possible mechanisms. $GABA_{A}$ receptors subunits and glutamic acid decarboxylase (GAD) were not over expressed, compared with that of the saline group. We also found that MEZSS did not increase chloride influx in cultured cerebellar granule cells. It is concluded that MEZSS might have anxiolytic-like effects, but these effects might not be mediated by GABAergic transmission.

• 항공우주시스템공학회지
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• 제3권1호
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• pp.12-16
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• 2009

The laminated sequence and thickness of a composite structure is an important design parameter which affect the strength and impact damage. In this study, it was investigated the residual strength of carbon fiber laminate after impact damage by the experimental investigation. The tensile strength test and compressive strength test were used to find the mechanical properties, previously. Impact test was performed using low-velocity drop-weight test equipment. The impact damages were finally assessed by the compressive strength test. The investigation results revealed the residual strength of the damaged specimens due to the impact damage.

• 지질공학
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• 제28권1호
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• pp.1-9
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• 2018

We propose a borehole test technique to estimate permeability of rocks in borehole. The borehole tests are hydraulic injection tests such as leak-off test and hydraulic fracturing tests, which are originally conducted for stress or casing integrity assessment and not for permeability measurement. We use one-dimensional radial diffusion equation to interpret fluid injection test results in terms of permeability. We apply this technique to a leak-off test conducted at a depth of 700 m in a wellbore, where rock formation is mudstone. The estimated permeability is at an order of $10^{-16}m^2$, which is somewhat high but within the range reported for mudstones previously. Quantitative rick assessment suggests that an accurate measurement of open hole section length is important to improve reliability of results. More data may be needed to ensure the reliability of this technique. If validated, however, this technique can provide cost-effective estimation of in situ permeability without conducting independent permeability tests in borehole.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 추계학술발표대회 논문집
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• pp.88-91
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• 2002

The two dimensional size effect of specimen gauge section (length x width) was investigated on the compressive behavior of a T300/924 [45/-45/0/90]3s, carbon fiber-epoxy laminate. A modified ICSTM compression test fixture was used together with an anti-buckling device to test 3mm thick specimens with a 30$\times$30, 50$\times$50, 70$\times$70, and 90mm$\times$90mm gauge length by width section. In all cases failure was sudden and occurred mainly within the gauge length. Post failure examination suggests that $0^{\circ}$ fiber microbuckling is the critical damage mechanism that causes final failure. This is the matrix dominated failure mode and its triggering depends very much on initial fiber waviness. It is suggested that manufacturing process and quality may play a significant role in determining the compressive strength. When the anti-buckling device was used on specimens, it was showed that the compressive strength with the device was slightly greater than that without the device due to surface friction between the specimen and the device by pretoque in bolts of the device. In the analysis result on influence of the anti-buckling device using the finite element method, it was found that the compressive strength with the anti-buckling device by loaded bolts was about 7% higher than actual compressive strength. Additionally, compressive tests on specimen with an open hole were performed. The local stress concentration arising from the hole dominates the strength of the laminate rather than the stresses in the bulk of the material. It is observed that the remote failure stress decreases with increasing hole size and specimen width but is generally well above the value one might predict from the elastic stress concentration factor. This suggests that the material is not ideally brittle and some stress relief occurs around the hole. X-ray radiography reveals that damage in the form of fiber microbuckling and delamination initiates at the edge of the hole at approximately 80% of the failure load and extends stably under increasing load before becoming unstable at a critical length of 2-3mm (depends on specimen geometry). This damage growth and failure are analysed by a linear cohesive zone model. Using the independently measured laminate parameters of unnotched compressive strength and in-plane fracture toughness the model predicts successfully the notched strength as a function of hole size and width.

• 터널과지하공간
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• 제19권3호
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• pp.248-260
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• 2009

직접 개발 형식의 해외자원개발과 관련하여 단순 자본 투자에서 직접 개발로 변화하고 있다. 대규모 노천 석탄광산에서의 사면 안정성과 관련하여 지하수 유동 체계 분석과 사면 보강공으로서의 수평 배수공 타당성을 인도네시아 Pasir 탄광을 대상으로 검토하였다. 본 연구에서는 지하수 체계를 특징짓기 위해 지하수 수위 분석, 현장 투수 시험, 추적자 실험 등 다양한 현장 실험 및 계측을 수행하였다. 특히, 중부 지역의 상부에 위치한 SM강과의 연계성을 분석에 중점을 두었다. Guelph 투수계수를 활용하여 투수계수를 측정하였으며, 사암이 이암이나 탄층보다 투수성이 매우 높은 것으로 나타났다. 지하수 수위 분석 결과 사암층과 협재되어 많은 균열을 포함한 얇은 탄층이 주된 지하수 유동 경로 역할을 히는 것으로 나타났다. 추적자 시험 결과 SM강이 인근 지하수계에 미치는 영향은 강 바닥의 지층구조에 따라 다른 것으로 파악되었다. 수평 배수공의 효과를 파악하기 위한 2차원 지하수 유동 해석 결과는 폭이 좁은 탄층이 협재되어 있는 지층과 사암층이 주된 지하수 유동 경로이며, 충분한 심도로 수평 배수공 시공시 사면 안정화에 효과가 있는 것으로 파악되었다. 따라서 수평 배수공의 시공 위치와 시공 심도의 결정을 위해서는 지층 구조의 파악이 선행되어야 한다.

• 한국지반환경공학회 논문집
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• 제10권2호
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• pp.61-68
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• 2009

본 논문은 수리학적 현장 주입시험 기간 동안 고려될 필요가 있는 수리역학적 상호작용에 따른 균열암반매질의 수리학적 거동에 대한 수치적 연구이다. 이러한 주입시험은 굴착정 내에 설치된 개구간(open hole section)을 따라 높은 압력을 가진 유량을 주입하며, 이를 통해 굴착정을 가로지르는 균열로부터 유량을 측정하는 것이다. 시간에 따라 변화되는 유량측정결과는 수리역학적 상호작용에 대한 분석 및 예측을 위해 개발된 수치모형의 현장 적용성을 평가하기 위해 사용되었다. 유량측정결과 전도성이 있는 균열들은 상호의존적인 균열망을 형성하며, 이로 인해 균열망을 구성하는 개별적인 균열요소들은 독립적인 시스템으로서 적절하게 모형화 될 수 없음을 보여주었다. 또한 간극수압이 굴착정 주위에 작용하는 최소주응력을 초과할 때 새로운 유체유입영역이 발생되며, 이러한 최소주응력보다 훨씬 큰 간극수압은 굴착정 주위의 균열들에 의해 유지될 수 있다는 것을 보여주었다. 본 연구에서 이러한 특성들이 자연 상태의 균열망의 구성형태에 따라 어떻게 영향을 미치게 되는지 이산 균열망 모형을 통해 수치적으로 분석되었다.

• 한국식품저장유통학회지
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• 제8권4호
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• pp.356-361
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• 2001

양파 간이저장시 노지야적에 의해 발생하는 부패를 감소시켜 망과의 안전저장을 위하여 조립식 간이하우스를 이용하여 통풍조건 및 통풍구 재료의 크기에 따른 저장성을 조사한 결과는 다음과 같다. 평균온도는 노지야적에 비해 강제통풍에서 0.3~3.6$^{\circ}C$높았고, 무통풍에 비해서는 1.4~8.2$^{\circ}C$가 낮았다. 그러나 처리간 유의차는 없었다. 상대습도는 통풍처리구에서 무통풍 및 노지야적에 비해 약간 높았다. 구중감소율은 노지야적에서는 2.5%, 무통풍에서는 2.9%, 자연통풍 2단에서는 3%, 강제통풍 2단에서는 4.3%였다. 8월 하순까지의 부패율은 자연통풍 2단 27.7%, 강제통풍 2단 25.4%,인데 비해 무통풍 34.6%, 노지야적 37.8%로 통풍처리구에서 부패가 적었다. 통붕구 재료의 크기가 클수록 평균기온은 조금 낮았고, 상대습도는 7월에 조금 높은 경향을 보이다가 8월 이후에는 차이가 거의 없었다. 통풍 파이프 표면의 풍속은 통풍구의 크기가 작을수록 강했으며, 부위별로는 중간부위가 양끝쪽보다 낮았다. 부패율은 75mm통풍구 17.9%, 100mm통풍구 15.3%, 125mm통풍구 14.1%로 통풍구 크기가 클수록 부패는 적었다.

• The Journal of Advanced Prosthodontics
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• 제11권6호
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• pp.341-349
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• 2019

PURPOSE. A novel retentive type of implant prosthesis that does not require the use of cement or screw holes has been introduced; however, there are few reports examining the biomechanical aspects of this novel implant. This study aimed to evaluate the biomechanical features of cementless fixation (CLF) implant prostheses. MATERIALS AND METHODS. The test groups of three variations of CLF implant prostheses and a control group of conventional cement-retained (CR) prosthesis were designed three-dimensionally for finite element analysis. The test groups were divided according to the abutment shape and the relining strategy on the inner surface of the implant crown as follows; resin-air hole-full (RAF), resin-air hole (RA), and resin-no air hole (RNA). The von Mises stress and principal stress were used to evaluate the stress values and distributions of the implant components. Contact open values were calculated to analyze the gap formation of the contact surfaces at the abutment-resin and abutment-implant interfaces. The micro-strain values were evaluated for the surrounding bone. RESULTS. Values reflecting the maximum stress on the abutment were as follows (in MPa): RAF, 25.6; RA, 23.4; RNA, 20.0; and CR, 15.8. The value of gap formation was measured from 0.88 to 1.19 ㎛ at the abutment-resin interface and 24.4 to 24.7 ㎛ at the abutment-implant interface. The strain distribution was similar in all cases. CONCLUSION. CLF had no disadvantages in terms of the biomechanical features compared with conventional CR implant prosthesis and could be successfully applied for implant prosthesis.