• Nuclear Engineering and Technology
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• 제34권5호
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• pp.421-432
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• 2002

As one of the advanced design features of the APR1400, direct vessel injection (DVI) system is being considered instead of conventional cold leg injection (CLI) system. It is known that the DVI system greatly enhances the reliability of the emergency core cooling (ECC) system. However, there is still a dispute on its performance in terms of water delivery to the reactor core during the reflood phase of a large-break loss-of-coolant accident (LOCA). Thus, experimental validation is under progress. In this paper, test results of direct ECC bypass performed in the steam-water test facility tailed MIDAS (Multi-dimensional Investigation in Downcomer Annulus Simulation) are presented. The test condition is determined, based on the preliminary analysis of TRAC code, by applying the ‘modified linear scaling method’with the l/4.93 length scale . From the tests, ECC direct bypass fraction, steam condensation rate and information on the flow distribution in the upper annulus downcomer region are obtained.

• Steel and Composite Structures
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• 제29권4호
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• pp.509-526
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• 2018

The direct strength method adopted by the AISI Standard and AS/NZS 4600 is an advanced design method meant to substitute the effective width method for the design of cold-formed steel structural members accounting for local instability of thin plate elements. It was proven that the design strength formula for the direct strength method could predict the ultimate strength of medium strength steel welded section compressive and flexural members with local buckling reasonably. This paper focuses on the modification of the direct strength formula for the application to high strength and high performance steel welded section columns which have the nominal yield stress higher than 460 MPa and undergo local buckling, overall buckling or their interaction. The resistance of high strength steel welded H and Box section columns calculated by the proposed direct strength formulae were validated by comparison with various compression test results, FE results, and predictions by existing specifications.

• Geomechanics and Engineering
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• 제12권6호
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• pp.883-898
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• 2017

To eliminate the holding and gluing problems making the direct tensile strength test hard to be applied, a new method of testing specimens prepared using lathe machine to make the dog bone shape is assessed whether it could be applied to determine accurate direct tensile strength values of rock materials. A series of numerical modelling analyses was performed using finite element method to investigate the effect of different specimen and steel holder geometries. In addition to numerical modelling study, a series of direct tensile strength tests was performed on three different groups of rock materials and a rock-like cemented material to compare the results with those obtained from the finite element analyses. A proper physical property of the lathed specimens was suggested and ideal failure of the dog bone shaped specimens was determined according to the results obtained from this study.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.262-267
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• 2004

The unloading compliance method is the most commonly used method to evaluate the fracture resistance characteristics of a material. In dynamic loading condition, the direct current potential drop(DCPD) method has been used because the unloading compliance method can not be applied due to the discontinuity of loading. However, even in the dynamic test using DCPD method, there is a problem that the voltage drops sharply on the initiation of crack. For the reason metioned above, the normalization method was suggested on ASTM E 1820 which is revised recently, as a new method to evaluate the dynamic fracture resistance characteristic. The nomalization method can be used to obtain a fracture resistance curve directly from a load-load line displacement. In this study, we obtained two fracture resistance curves from static test of welding part of nuclear piping both by unloading compliance and nomalization method. The two curves were almost same each other, so the adaptability of the nomalization method has been proved. We conducted a dynamic fracture resistance test for the same material. The fracture resistance curve from the dynamic test was obtained by normalization method and compared to that of the static test result.

• 복식문화연구
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• 제11권1호
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• pp.11-19
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• 2003

This study suggests the new 2D anthropometric method using digital camera. It is used MK2001 program that can convert 2D measurements to 3D measurements. To improve that it is measured 100 college students with direct and indirect anthropometric method. The measurements were processed by the SPSS ver10 Statistical Package. The average, standard deviation, and t-test were calculated for each category. Most measurements by 2D measurements are higher than direct measurements but degree. The difference between direct and indirect measurements is less than 2cm. In the results of t-test, height measurements including other 16 measurements which is easy to measure have no meaningful difference within 1cm. The depth measurements are most high difference. The result of each measurement proves that MK2001 program (2D anthropometry method using digital camera) is available for measuring the human body.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2008년도 추계 학술논문 발표대회
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• pp.13-16
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• 2008

This paper is to present the performance data for improved direct setting method using tile bond for application of porcelain tile under 1 percent absorptance. For this purpose, improved direct setting method type 1 & 2(tile bond curing time 0, 24H) were compared with the conventional setting methods(including direct setting method and improved pressure setting method) in the sight of the adhesive stability of porcelain tile. It tested for tiles after 14, 28days under standard condition and severe conditions. The severe conditions were water immersion, heat ageing(70℃) and freeze-thaw cycle. On the basis of test results, the adhesive strength of direct setting method was lowest for the conventional setting methods. But improved direct setting method using tile bonds(A, B) came close to the result of improved pressure setting method using tile bonds.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.529-536
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• 2005

Based on an estimating method for post-cyclic strength and stiffness with cyclic triaxial tests, Direct Simple Shear (DSS) tests were carried out to confirm whether the method can be adapted to DSS test on fine-grained soils: silty clay, plastic silt, and non-plastic silt. Results from post-cyclic DSS tests were interpreted by a modified method as adopted for post-cyclic triaxial tests. In particular, influence of plasticity index for fine-grained soils was emphasised. Findings obtained from the present study are: (i) the higher the plasticity index of fine-grained soils is, the less not stiffness ratio but strength ratio decreases with increment of a normalised excess pore water pressure; and (ii) post-cyclic strength and stiffness results from DSS tests agree well with those predicted by the method modified from a procedure used for triaxial test results.

• 지질공학
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• 제29권4호
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• pp.565-578
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• 2019

황등 화강암, Berea 사암, 정선 대리암, 홍천 편마암, 풍암 셰일 및 음성 사질 셰일의 여섯 종류의 암석에 대하여 직접전단시험, 기울임시험 그리고 당김시험을 이용하여 기본마찰각을 측정하고, 암종에 따른 기본마찰각의 특성, 시험방법의 정확성을 비교, 검토하여 기본마찰각 측정에 가장 정확하고 효율적인 시험방법을 제시하였다. 기본마찰각은 직접전단시험을 이용하면 정확하게 측정되지만, 비싼 장비와 복잡한 시험절차가 필요하다. 국제암반역학회에서 표준시험법으로 제안한 기울임시험은 직접전단시험에서 측정된 기본마찰각과 유사한 값을 제시하나, 동일한 암석으로 제작된 3개의 시료에서 측정된 기본마찰각은 최대 7° 이상의 오차를 보이고, 1개의 시료에서 5회 측정된 미끄러짐 각 또한 시료에 따라서 증가하거나, 감소하거나, 유사한 값을 보이는 등 일정한 패턴을 보이지 않고 변할 뿐만 아니라, 편마암에서는 최대 12°의 오차를 보여 시험의 신뢰성에 상당한 의문이 든다. 간단한 시험장비와 비교적 낮은 수직응력하에서 실시되는 당김시험은 직접전단시험에서 구한 기본마찰각과 매우 유사한 값을 제공하고, 측정된 값들이 일관성을 보이고 시험절차 또한 매우 간단하여 기본마찰각 측정에 가장 유용한 시험 방법으로 판단된다.

• Structural Engineering and Mechanics
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• 제12권6호
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• pp.633-656
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• 2001

In this paper, modal control with direct output feedback is formulated in a systematic manner for easy implementation. Its application to the seismic protection of structural systems is verified by a shaking table test, which involves a full-scale building model and an active bracing system as the control device. Two modal control cases, namely, one full-state feedback and one direct output feedback control were tested and compared. The experimental result shows that in mitigating the seismic response of building structures, modal control with direct output feedback can be as effective and efficient as that with full-state feedback control. For practical concerns, the control performance of the proposed method in the presence of sensor noise and stiffness modeling error was also investigated. The numerical result shows that although the control force may be increased, the maximum floor displacements of the controlled structure are very insensitive to sensor noise and modeling error.

• 터널과지하공간
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• 제21권3호
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• pp.181-191
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• 2011

단층대, 파쇄대 또는 풍화대가 발달한 암반은 실내시험을 위한 시료 성형이 어렵다. 기존에 현장에서 수행된 직접전단시험은 갱도 내벽의 수직반력을 이용하여 수행되었다. 이 연구에서 개발된 현장직접전단시험기는 터널내부 또는 노천의 현장상태 암반에서 시험을 수행할 수 있다. 현장직접전단시험기의 주요 구성은 전단하중 반력판 및 하중전달판, 유압실린더 시스템, 로드셀, 다단계 전단상자, 전단상자 고정장치, 수직하중 반력판 및 하중전달판, 마찰저항 감소용 롤러 등이다. 공시체는 각주형의 블록으로 최대 크기는 $400{\times}400{\times}460$ mm이며 현장에서 형성하는 방법 및 절차가 제시되었다. 개발된 시험기의 현장적용성 평가를 위하여 연구지역에 대한 지질공학적 조사 분석 연구를 통하여 성능시험을 위한 공시체 형성에 적합한 위치가 선정되었다. 현장적용 결과 개발된 현장용 시험기는 암석의 강도 및 변형과 관련하여 필요한 대부분의 정보를 제공할 수 있는 성능을 확보하였음을 확인하였다.