• 한국해양공학회:학술대회논문집
• /
• 한국해양공학회 2006년 창립20주년기념 정기학술대회 및 국제워크샵
• /
• pp.80-90
• /
• 2006

The influence of waves on the dynamic properties of bending moments at the root of blades of tidal stream vertical axis rotors is reported. Blade theory for wind turbine is combined with linear wave theory and used to analyse this influence. Experiments were carried out to validate the simulation and the comparison shows the usefulness of the theory in predicting the bending moments. The mathematical model is then used to study the importance of waves for the fatigue design of the blade-hub connection.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 2011년도 정기 학술대회
• /
• pp.282-284
• /
• 2011

Based on graphene oxide and multi-walled carbon nanotube layers, a wireless bi-layer actuator that can be remotely controlled with an electromagnetic induction system has been developed. The graphene-based bi-layer actuator exhibits a large one-way bending deformation under eddy current stimuli due to asymmetrical responses originating from the temperature difference of the two different carbon layers. In order to validate one-way bending actuation, the coefficients of thermal expansion of carbon nanotube and graphene oxide are mathematically formulated in this study based on the atomic bonding energy related to the bonding length. The newly designed graphene-based bi-layer actuator is highly sensitive to electromagnetic wave irradiation thus it can trigger a new actuation mode for the realization of remotely controllable actuators and is expected to have potential applications in various wireless systems.

• Journal of the Korean Wood Science and Technology
• /
• 제24권2호
• /
• pp.1-6
• /
• 1996

This study was performed to investigate the feasibility of using sonic stress-wave technique in the longitudinal direction for the assessment of incipient decay of radiata pine wood. Decayed bending specimens by Tyromyces palustris and Gloeophyllum trabeum for varoious periods were tested nondestructively using stress-wave technique in the longitudinal direction and destructively. Decay detection, quantitative assessment of decay, and the prediction of residual strength of decayed wood with less than five percent weight loss can be feasible using stress-wave parameters (wave velocity, wave impedance, stress-wave elasticity) measured by stress-wave technique in the longitudinal direction and their percent reduction due to decay.

• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
• /
• pp.65-68
• /
• 2007

FORMOSAT-3 was launched in April of 2006. It consists of six low earth orbit (LEO) satellites that will be eventually deployed to an orbit at 800 km height. Its scientific goal is to utilize the radio occultation (RO) signals to measure the bending angles when the GPS signals transect the atmosphere. The bending angle is then used to infer atmospheric parameters, including refractivity, temperature, pressure, and relative humidity fields of global distributions through inversion schemes and auxiliary information. The expected number of RO events is around 2500 per day, of which 200 events or so fall into the polar region. Consequently, the FORMOSAT-3 observations are expected to play a key role to improve our knowledge in the weather forecasting and space physics research in the polar region. In this paper, we use temperature profiles retrieved from FORMOSAT-3 RO observations to study the climatology of gravity wave activity in the polar region. FORMOSAT-3 can provide about 200 RO observations a day in the polar region, much more than previous GPS RO missions, and, hence, more detailed climatology of gravity wave activity can be obtained.

• International Journal of Naval Architecture and Ocean Engineering
• /
• 제12권1호
• /
• pp.226-240
• /
• 2020

This paper presents an experimental investigation of asymmetric impact effects on hydroelastic responses. A 1:64 scaled segmented ship model with U-shape open cross-section backbone was newly designed to meet elastic similarity conditions of vertical, horizontal and torsional stiffness simultaneously. Different wave heading angles and wavelengths were adopted in regular wave test. In head wave condition, parametric rolling phenomena happened along with asymmetric slamming forces, the relationship between them was disclosed at first time. The impact forces on starboard and port sides showed alternating asymmetric periodic changes. In oblique wave condition, nonlinear springing and whipping responses were found. Since slamming phenomena occurred, high-frequency bending moments became an important part in total bending moments and whipping responses were found in small wavelength. The wavelength and head angle are varied to elucidate the relationship of springing/whipping loads and asymmetric impact. The distributions of peaks of horizontal and torsional loads show highly asymmetric property.

• Coupled systems mechanics
• /
• 제2권1호
• /
• pp.111-126
• /
• 2013

The structural design requirements of an offshore platform subjected to wave induced forces and moments in the jacket can play a major role in the design of the offshore structures. For an economic and reliable design; good estimation of wave loadings are essential. A nonlinear response analysis of a fixed offshore platform under structural and wave loading is presented, the structure is discretized using the finite element method, wave plus current kinematics (velocity and acceleration fields) are generated using 5th order Stokes wave theory, the wave force acting on the member is calculated using Morison's equation. Hydrodynamic loading on horizontal and vertical tubular members and the dynamic response of fixed offshore structure together with the distribution of displacement, axial force and bending moment along the leg are investigated for regular and extreme conditions, where the structure should keep production capability in conditions of the 1-yr return period wave and must be able to survive the 100-yr return period storm conditions. The result of the study shows that the nonlinear response investigation is quite crucial for safe design and operation of offshore platform.

• 한국의류학회지
• /
• 제36권6호
• /
• pp.583-591
• /
• 2012

This study selected three model designs used for air injection type welding clothes designed for insulation purposes and analyzed the performance of each design. The bending characteristics were analyzed in order to identify the flexibility of the welded areas; subsequently, the seam breaking strength and water pressure resistance were analyzed to identify the bonding strength. In addition, two types of waterproof fabric, polyurethane (PU) coated 2 layer and PU laminated 2 layer fabrics, were used for a performance analysis, according to fabric processing specifications. The circle type showed the highest flexibility in the terms of bending characteristics that influence wearability and were followed by the wave and the straight type. In terms of breaking strength, the straight type showed the highest breaking strength, followed by the wave and the circle type. The water pressure resistance analysis found that the wave type was superior to the straight type in terms of water pressure resistance. The wave type is deemed to be a design type suitable for maximizing performance, provided that the issue of stabilization in the welding production process is addressed. Looking at the bending characteristics of waterproof fabric for each specification, the laminating waterproof cloth outperformed the coated waterproof cloth in terms of flexibility. However, in terms of seam breaking strength, the coated waterproof cloth outperformed the laminated cloth. In contrast, the water pressure resistance of the laminated waterproof fabric was found to be higher than the coated waterproof fabric, leading to the conclusion that the bonding strength of the laminated waterproof fabric is higher than that of the coated waterproof fabric based on the assumption of injecting air.

• 비파괴검사학회지
• /
• 제29권5호
• /
• pp.415-420
• /
• 2009

이 논문은 표면파의 비선형특성을 이용하여 재료 표면의 열화손상을 평가한 사례 연구의 결과를 보고한다. 이 연구에서는 3점 굽힘 피로시험에 의해 표면에 피로열화를 가한 알루미늄 T6 시편을 대상으로 표면파의 음향 비선형 파라미터를 측정하기 위한 실험장치를 구성하였으며, 피로시험 전후에서 측정된 비선형파라미터의 크기를 비교하였다. 특히 3점 굽힘 피로시험에 의한 표면피로손상은 시편의 중앙부 표면에 집중 될 것이 예상되므로 이 주변에서의 비선형 파라미터의 변화를 세밀히 관찰하였다. 실험결과 피로손상이 거의 없는 시편의 가장자리에서는 비선형 파라미터가 피로시험 전후에서 큰 변화가 없었지만, 표면 피로열화가 집중된 중앙부에서는 뚜렷하게 증가하는 것으로 나타났다.

• Journal of the Korean Wood Science and Technology
• /
• 제44권2호
• /
• pp.274-282
• /
• 2016

This aims of this study were to investigate the relationship between non-destructive evaluation (NDE) and actual bending properties of particleboard, and to predict the bending properties of three-layer particleboard. Three kinds of raw materials, i.e. Hinoki (Chamaecyparis obtusa Endl.) strand, knife-milled Douglas-fir (Pseudotsuga manziesii (Mirb) Franco), and hammer-milled matoa (Pometia spp.) obtained from wooden industry, were utilized as furnish for experimental panel with methylene diphenyl diisocyanate (MDI) resin as binder. The NDE test was conducted by hit sounds using an FFT analyzer according to the spectrum peak of wave frequency, while the static bending test was conducted according to JIS A-5908. The results reveal that the dynamic Young's modulus as an NDE test has a potential for being used to predict the elastic bending of particleboards by a specific equation for adjusting its proper values. The values of NDE and static test are significantly different with a deviation range at 3-20%. The bending stiffness of three-layer particleboards manufactured from different wood species is predictable by observing the bending stiffness of two elements based on the thickness of its layers. The predicted values of bending stiffness and static test are significantly different with a deviation range at 5-24%.

• Earthquakes and Structures
• /
• 제13권3호
• /
• pp.255-265
• /
• 2017

In this paper, an efficient shear deformation theory is developed for wave propagation analysis in a functionally graded beam. More particularly, porosities that may occur in Functionally Graded Materials (FGMs) during their manufacture are considered. The proposed shear deformation theory is efficient method because it permits us to show the effect of both bending and shear components and this is carried out by dividing the transverse displacement into the bending and shear parts. Material properties are assumed graded in the thickness direction according to a simple power law distribution in terms of the volume fractions of the constituents; but the rule of mixture is modified to describe and approximate material properties of the functionally graded beams with porosity phases. The governing equations of the wave propagation in the functionally graded beam are derived by employing the Hamilton's principle. The analytical dispersion relation of the functionally graded beam is obtained by solving an eigenvalue problem. The effects of the volume fraction distributions, the depth of beam, the number of wave and the porosity on wave propagation in functionally graded beam are discussed in details. It can be concluded that the present theory is not only accurate but also simple in predicting the wave propagation characteristics in the functionally graded beam.