• Journal of Ocean Engineering and Technology
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• v.31 no.3
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• pp.189-195
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• 2017

A three-dimensional higher order boundary element method based on the B-spline is presented. The method accurately models piecewise continuous bodies and induced velocity potentials using B-spline tensor product representations, and it is capable of obtaining accurate pointwise values for the potential and its derivatives, especially in the trailing edge and tip region of the lift generating body, which may be difficult or impossible to evaluate with constant panel methods. In addition, we implement a wake roll-up and examine the tip vortex formation in the near wake region. The results are compared with existing numerical results and the results of experiments performed out at the cavitation tunnel of Chungnam National University.

• Structural Monitoring and Maintenance
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• v.10 no.4
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• pp.361-379
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• 2023

In cable structure maintenance, particularly for cable-stayed bridges, cable safety assessment relies on estimating cable tension. Conventionally, in Japan, cable tension is estimated from the natural frequencies of the cable using the higher-order vibration method. In recent years, dampers have been installed on cables to reduce cable vibrations. Because the higher-order vibration method is a method for damper-free cables, the damper must be removed to measure the natural frequencies of a cable without a damper. However, cables on some cable-stayed bridges have two dampers: one on the girder side and another on the tower side. Notably, removing and reinstalling the damper on the tower side are considerably more time- and labor-intensive. This paper introduces a tension estimation method for cables with two dampers, using natural frequencies. The proposed method was validated through numerical simulation and experiment. In the numerical tests, without measurement error in the natural frequencies, the maximum estimation error among 100 models was 3.3%. With measurement error of 2%, the average estimation error was within 5%, with a maximum error of 9%. The proposed method has high accuracy because the higher-order vibration method for a damper-free cable still has an estimation error of 5%. The experimental verification emphasizes the importance of accurate damper modeling, highlighting potential discrepancies between existing damper design formula and actual damper behavior. By revising the damper formula, the proposed method achieved accurate cable tension estimation, with a maximum estimation error of approximately 10%.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5B
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• pp.493-496
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• 2009

In this study, we derive the extended mild-slope equation in terms of the velocity potential using the Euler-Lagrange equation. First, we follow Kim and Bai (2004) who derive the complementary mild-slope equation in terms of the stream function using the Euler-Lagrange equation and we compare their equation to the existing extended mild-slope equations of the velocity potential. Second, we derive the extended mild-slope equation in terms of the velocity potential using the Euler-Lagrange equation. In the developed equation, the higher-order bottom variation terms are newly developed and found to be the same as those of Massel (1993) and Chamberlain and Porter (1995). The present study makes wide the area of coastal engineering by developing the extended mild-slope equation with a way which has never been used before.

• Korean Journal of Plant Resources
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• v.11 no.1
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• pp.93-100
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• 1998

This study was to investigate the dry weight, the amount of Na+ and K+ water potential and leaf photosynthesis rate in plants for determining the salt tolerance mechanism in rice cultivars on soil and solution culture with NaCl. The results obtained in this study are summarized as follows ; In general, rice cultivars, cv. Tetep and Jinbu, having high salt tolerance in ID(identified on dry matter production level) showed the higher salt tolerance in RGR (relative growth rate), compared with rice cultivars(cv. Nonglim 41ho, Dunraebyeo and Sobackbyeo) having low salt tolerance. The contents of Na in rice differed depending on culivars and plant parts. Tetep contained 2.9times higher amounts of Na+ than leaf blade and root part. High salt tolerance cultivar Obongbyeo showed a larger decrease in osmotic potential than low salt tolerance cultivar Dunraebyeo suggesting that osmotic adjustment was developed under salt stress conditions in a salt tolerant cultivar . In order to know the IY(identified on grain yeild level using rice cultivars having different salt tolerance the capacity of photosyntheiss was investigated. The capapcity of photosynthesis in cv. Tetep and Obongbyeo having high salt tolerance was much higher that in cv.Dunraebyeo and Nonglim 41 having low salt tolerance.

• Advances in aircraft and spacecraft science
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• v.5 no.1
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• pp.21-49
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• 2018

In this paper, geometric nonlinear bending characteristics of single wall carbon nanotube reinforced composite (SWCNTRC) doubly curved shell panels subjected to uniform transversely loadings are investigated. The nonlinear mathematical model is developed for doubly curved SWCNTRC shell panel on the basis of higher-order shear deformation theory and Green- Lagrange nonlinearity. All nonlinear higher order terms are included in the mathematical model. The effective material properties of SWCNTRC are estimated by using Eshelby-Mori-Tanaka micromechanical approach. The governing equation of the shell panel is obtained using the total potential energy principle and a Newton-Raphson iterative method is employed to compute the nonlinear displacement and stresses. The present results are compared with published literature. The effect of SWCNT volume fraction, width-to-thickness ratio, radius-to-width ratio (R/a), boundary condition, linear and nonlinear deflection, stresses and different types of shell geometry on nonlinear bending response is investigated.

• Steel and Composite Structures
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• v.35 no.4
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• pp.545-554
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• 2020

The present paper explores nonlinear dynamical properties of piezo-magnetic beams based on a nonlocal refined higher-order beam formulation and piezoelectric phase effect. The piezoelectric phase increment may lead to improved vibrational behaviors for the smart beams subjected to magnetic fields and external harmonic excitation. Nonlinear governing equations of a nonlocal intelligent beam have been achieved based upon the refined beam model and a numerical provided has been introduced to calculate nonlinear vibrational curves. The present study indicates that variation in the volume fraction of piezoelectric ingredient has a substantial impact on vibrational behaviors of intelligent nanobeam under electrical and magnetic fields. Also, it can be seen that nonlinear free/forced vibrational behaviors of intelligent nanobeam have dependency on the magnitudes of induced electrical voltages, magnetic potential, stiffening elastic substrate and shear deformation.

• Bulletin of the Korean Mathematical Society
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• v.58 no.1
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• pp.235-251
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• 2021

We consider the Schrödinger type operator ��k = (-∆)k+Vk on ℝn(n ≥ 2k + 1), where k = 1, 2 and the nonnegative potential V belongs to the reverse Hölder class RHs with n/2 < s < n. In this paper, we establish the (Lp, Lq)-boundedness of the higher order Riesz transform T��,�� = V2��∇2��-��2 (0 ≤ �� ≤ 1/2 < �� ≤ 1, �� - �� ≥ 1/2) and its adjoint operator T∗��,�� respectively. We show that T��,�� is bounded from Hardy type space $H^1_{\mathcal{L}_2}({\mathbb{R}}_n)$ into Lp2 (ℝn) and T∗��,�� is bounded from ��p1 (ℝn) into BMO type space $BMO_{\mathcal{L}_1}$ (ℝn) when �� - �� > 1/2, where $p_1={\frac{n}{4({\beta}-{\alpha})-2}}$, $p_2={\frac{n}{n-4({\beta}-{\alpha})+2}}$. Moreover, we prove that T��,�� is bounded from $BMO_{\mathcal{L}_1}({\mathbb{R}}_n)$ to itself when �� - �� = 1/2.

• Advances in nano research
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• v.16 no.5
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• pp.489-500
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• 2024

This paper studies the free vibration analysis of the piezo-magneto-thermo-elastic FG nanobeam submerged in a fluid environment. The problem governed by the partial differential equations is determined by refined higher-order State Space Strain Gradient Theory (SSSGT). Hamilton's principle is applied to discretize the differential equation and transform it into a coupled Euler-Lagrange equation. Furthermore, the equations are solved analytically using Navier's solution technique to form stiffness, damping, and mass matrices. Also, the effects of nonlocal ceramic and metal parts over various parameters such as temperature, Magnetic potential and electric voltage on the free vibration are interpreted graphically. A comparison with existing published findings is performed to showcase the precision of the results.

• The Journal of the Acoustical Society of Korea
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• v.19 no.1
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• pp.54-60
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• 2000

There are many works to analyze a simple expansion chamber involving higher order modes. These works are classified to mode matching method, velocity potential method and finite element method. Among these methods, mode matching method has good performance at analyzing a concentric expansion chamber. Generally inlet/outlet pipe cross section area is smaller than middle chamber cross section area. So the number of higher order modes of inlet/outlet pipe can be fewer than that of middle chamber. But mode matching method must use the same number of higher order modes at inlet pipe, middle chamber and outlet pipe. Therefore the redundant modes of inlet/outlet pipe makes the computation time of mode matching method longer. In this paper, the new method, which can select number of each higher order modes of inlet pipe, middle chamber and outlet pipe, was suggested. And this method was compared to conventional mode matching method and finite element method in order to demonstrate the accuracy of the new method and to show that the new method can reduce a calculating time.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.2
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• pp.57-62
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• 2008

This paper deals with a comparison of individual and connecting grounding electrode for potential rise. When a test current flowed through grounding electrode, potential rise was measured and analyzed for grounding method using a electrolytic tank in real time. In order to analyze the potential rise of grounding systems, a hemispherical water tank experimental apparatus was studied. Potential rise was measured and analyzed regarding the grounding method and distance by using this apparatus. The apparatus was composed of a hemispherical water tank, AC power supply, a movable potentiometer, and test grounding electrodes. The potential rise was measured by the horizontal moving probe of the potentiometer. The grounding electrodes were designed and fabricated with ground rods on a scale of one-eightieth. Potential rises of individual grounding electrode were higher than those of connecting grounding electrode. The distributions of surface potential are dependent on the distance from grounding electrode.