• 한국지진공학회논문집
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• 제8권4호
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• pp.43-50
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• 2004

일반적으로 콘크리트댐은 비파괴 검사를 실시한 물성값을 이용하여 정적 및 동적 안전성 평가를 실시한다. 그러나 이런 값을 이용하여 수치해석을 할 경우 경험적인 물성값을 적용하기 때문에 안전성 평가에 대한 결과는 현실적 요소를 반영하기 어렵다. 또한 댐은 품질관리가 중요한 요소 중 하나이지만, 과거 건설된 몇몇 댐에 대해서 축조시기, 타설시기가 달라 재료적 특성에 따른 안전성 문제가 대두되어 관심이 되었다. 따라서, 본 연구에서는 오랜기간 동안 건설중단 된 후 완공된 콘크리트댐의 내부상태를 조사하고(BIPS), 시추코아에 대한 물리특성 실험을 실시하여 물성값 차이로 인해 발생되는 동적특성 결과를 비교분석하였다.

• Advances in concrete construction
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• 제6권4호
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• pp.363-373
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• 2018

Portland cement pervious concrete (PCPC) is an effective pavement material to solve or reduce the urban waterlogging problems. The Mechanical properties, the permeability, the abrasion resistance and the frost resistance of PCPC without fine aggregate were investigated. The increase of porosity was achieved by fixing the dosage of coarse aggregate and reducing the amount of cement paste. The results show that the compressive strength and the flexural strength of PCPC decrease with the increase of porosity. The permeability coefficient and the wear loss of PCPC increase with the increase of the porosity. The compressive strength and the flexural strength of PCPC subjected to 25 freeze-thaw cycles are reduced by 13.7%-17.8% and 10.6%-18.3%, respectively. For PCPC subjected to the same freeze-thaw cycles, the mass loss firstly increases and then decreases with the increase of the porosity. The relative dynamic modulus elasticity decreases with the increase of freeze-thaw cycles. And the lower the PCPC porosity is, the more obvious the dynamic modulus elasticity decreases.

• Computers and Concrete
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• 제13권2호
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• pp.209-220
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• 2014

Vibration based damage detection is very popular in the civil engineering area. Especially, special structures like dams, long-span bridges and high-rise buildings, need continues monitoring in terms of mechanical properties of material, static and dynamic behavior. It has been stated in the International Commission on Large Dams that more than half of the large concrete dams were constructed more than 50 years ago and the old dams have subjected to repeating loads such as earthquake, overflow, blast, etc.,. So, some unexpected failures may occur and catastrophic damages may be taken place because of theloss of strength, stiffness and other physical properties of concrete. Therefore, these dams need repairs provided with global damage evaluation in order to preserve structural integrity. The paper aims to show the effectiveness of the model updating method for global damage detection on a laboratory arch dam model. Ambient vibration test is used in order to determine the experimental dynamic characteristics. The initial finite element model is updated according to the experimentally determined natural frequencies and mode shapes. The web thickness is selected as updating parameter in the damage evaluation. It is observed from the study that the damage case is revealed with high accuracy and a good match is attained between the estimated and the real damage cases by model updating method.

• 터널과지하공간
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• 제17권2호
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• pp.83-89
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• 2007

충격반향기법은 특정 매질에 충격을 가하여 매질의 동적 불성을 측정할 수 있는 비파괴 시험법이다. 본 연구에서는 암석시편에 충격반향기법을 수행할 수 있는 시험장비를 설치하고, 동적 물성치를 측정할 수 있는 시스템을 구축하였다. 이를 통해 국내 5개 지역에서 채취한 암석 시료 및 시멘트 모르타르와 알루미늄 합금에 대해 시험을 수행하여 동적 물성치를 측정하고, 1회의 충격시험으로 종파 및 횡파의 공진주파수와 감쇠비를 결정하였다. 그 결과. 동탄성계수와 정탄성계수는 10%내외의 차이를 가진 결과치가 도출되었고, 동포아송비는 정포아송비에 비해 0.07 이상 높은 값이 측정되었다. 또한 풍화도가 높거나 절리가 발달한 암석일수록 감쇠비가 증가하는 현상을 관찰하였다.

• Computers and Concrete
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• 제14권5호
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• pp.563-575
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• 2014

Concrete which is a composite material is frequently used in construction works. Properties and behavior of concrete are significant under the effect of different loading cases. Impact loading which is a sudden dynamic one may have destructive effects on structures. Testing apparatuses are designed to investigate the impact effect on test members. Artificial Neural Network (ANN) is a computational model that is inspired by the structure or functional aspects of biological neural networks. It can be defined as an emulation of biological neural system. In this study, impact parameters as acceleration and impact force values of a reinforced concrete slab are obtained by using a testing apparatus and essential test devices. Afterwards, ANN analysis which is used to model different physical dynamic processes depending on several variables is performed in the numerical part of the study. Finally, test and predicted results are compared and it's seen that ANN analysis is an alternative way to predict the results successfully.

• 대한기계학회논문집A
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• 제28권8호
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• pp.1166-1173
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• 2004

In this paper, in order to apply magnetic fluid with superparamagnetic property as the substitute of ferromagnetic materials, physical properties of magnetic fluid are investigated. A targeted drug delivery system using a capsule filled magnetic fluid is proposed where a magnetic fluid capsule and cylinders are considered as a drug and vital organs, respectively. The dynamic governing equation of this system first is derived. Fluid viscosity, clearance between a cylinder and a magnetic fluid capsule, and levitation height with respect to different cylinder height are considered as major parameters to evaluate dynamic characteristics of the system. The experiments and simulations for the position control of the magnetic fluid capsule in various cylinders are conducted using PID controller. The results show that magnetic fluid with the superparamagnetic property can be applied to a targeted drug delivery system.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 춘계학술대회 논문집 유기절연재료 전자세라믹 방전플라즈마 일렉트렛트 및 응용기술
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• pp.71-74
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• 2002

In this study, resonant characteristics of $Pb_{0.88}(La_{0.6}Nd_{0.4})_{0.08}(Mn_{1/3}Sb_{2/3})_{0.02}Ti_{0.98}O_3$ ceramics were investigated with the variations of electrode radius size for manufacturing the best 30MHz SMD type ceramic resonator with the size of $3.7{\times}3.1{\times}0.255mm^3$. Physical properties were proper for appling for 30MHz SMD type ceramic resonator. In third overtone thickness vibration mode, with increasing electrode radius size, resonant resistant($Z_r$) was decreased gradually. Mechanical quality factor($Q_{mt3}$) and dynamic range(D.R) showed the maximum value of 2,283, 47.1dB respectively, at 0.74mm electrode radius size.

• 한국농공학회지
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• 제44권6호
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• pp.83-89
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• 2002

The purpose of this study is to obtain the basic data for the development of construction material products using non-active Hwangto and stone dust. The test result shows that the unit weight is in the range of 2,050~2,135 kg/m$^3$, the compressive strength is in the range of 107~451 kgf/cm$^2$, the bending strength is in the range of 23~81 kgf/cm$^2$ and the dynamic modulus is in the range of 137$\times$10$^3$~318$\times$10$^3$ kgf/cm$^2$. Also, it is decreased with increase using the non-active Hwangto and stone dust, respectively. The incorporation of non-active Hwangto for cement is possible to 40% in strength.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 B
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• pp.1200-1202
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• 1993

There are many methods to investigate the physical properties of monolayers formed at the air-water interface. Among them, the displacement current method is appropriate for the investigation of the dynamic behavior of monolayers. The measuring system of displacement current method was constructed at home-made Kuhn type LB deposition apparatus using aluminium plate electrode. The currents induced by the dynamic motion of molecules were measured when the molecules were pressed by barrier. To verify the measuring system, we used 4-octyl -4'-(5-carboxy-pentamethyleneoxy)-azobenzene molecules which has two remarkable variations of surface pressure of monolayer at the air-water interface. We can detect the two peaks of displacement currents which shows that the orientations of molecules are changed greatly at the state of these two remarkable changes of surface pressure.

• 멤브레인
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• 제4권2호
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• pp.85-95
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• 1994

이 논문은 막을 통한 전기적 여과시 동적이동현상을 연구하는데 있다. 액상에서의 전기적 대류는 막내에서의 전하고분자 물질의 속도를 증진시키는데, 이 문제의 해법은 액상과 교상의 직접적인 접촉을 통해 연구되었다. 연산자이론이 이 문제를 풀기 위해 적용되었고, 막에서의 물리적 변수들을 분석하는데 이용되었다. 이논문의 이론적 고찰은 분리조작 설계하는데 이용된다.