• Coupled systems mechanics
• /
• v.2 no.3
• /
• pp.231-253
• /
• 2013

The impact of spar-nacelle-blade coupling on edgewise dynamic responses of spar-type floating wind turbines (S-FOWT) is investigated in this paper. Currently, this coupling is not considered explicitly by researchers. First of all, a coupled model of edgewise vibration of the S-FOWT considering the aerodynamic properties of the blade, variable mass and stiffness per unit length, gravity, the interactions among the blades, nacelle, spar and mooring system, the hydrodynamic effects, the restoring moment and the buoyancy force is proposed. The aerodynamic loads are combined of a steady wind (including the wind shear) and turbulence. Each blade is modeled as a cantilever beam vibrating in its fundamental mode. The mooring cables are modeled using an extended quasi-static method. The hydrodynamic effects calculated by using Morison's equation and strip theory consist of added mass, fluid inertia and viscous drag forces. The random sea state is simulated by superimposing a number of linear regular waves. The model shows that the vibration of the blades, nacelle, tower, and spar are coupled in all degrees of freedom and in all inertial, dissipative and elastic components. An uncoupled model of the S-FOWT is then formulated in which the blades and the nacelle are not coupled with the spar vibration. A 5MW S-FOWT is analyzed by using the two proposed models. In the no-wave sea, the coupling is found to contribute to spar responses only. When the wave loading is considered, the coupling is significant for the responses of both the nacelle and the spar.

• Structural Engineering and Mechanics
• /
• v.69 no.3
• /
• pp.257-268
• /
• 2019

Infills are as important members in structural design as beams, columns and braces. They have significant effect on structural behavior. Because of lots of variables in infills like material non-linear behavior, the interaction between frames and infill, etc., the infills performance during an earthquake is complicated, so have led designers do not consider the effect of infills in designing the structure. However, the experimental studies revealed that the infills have the remarkable effect on structure behavior. As if these effects ignored, it might occur soft-story phenomena, torsion or short-column effects on the structures. One simple and appropriate method for considering the infills effects in analyzing, is replacing the infills with diagonal compression strut with the same performance of real infill, instead of designing the whole infill. Because of too many uncertainties, codes and researchers gave many expressions that were not as the same as the others. The major intent of this paper is calculation the width of this diagonal strut, which has the most characteristics of infill. This paper by comprehensive on different parameters like the modulus of young or moment of inertia of columns presents a new formula for achieving the equivalent strut width. In fact, this new formula is extracted from about 60 FEM analyses models. It can be said that this formula is very efficient and accurate in estimating the equivalent strut width, considering the large number of effective parameters relative to similar relationships provided by other researchers. In most cases, the results are so close to the values obtained by the FEM. In this formula, the effect of out of plane buckling is neglected and this formula is used just in steel structures. Also, the thickness of infill panel, and the lateral force applied to frame are constant. In addition, this new formula is just for modeling the lateral stiffness. Obtaining the nearest response in analyzing is important to the designers, so this new formula can help them to reach more accurate response among a lot of experimental equations proposed by researchers.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.54 no.4
• /
• pp.343-352
• /
• 2018

In this study, a motion control problem for the vessels towed by tugboats or towing ships on the sea is considered. The towed vessel looks like the barge ship, which is used for many purposes. In these vessels, basically, the power propulsion system is not installed but just towed by a towing vessel such as tugboats with ropes and wires. It means that the motions of towed vessel are basically dependent on the tracking route of towing boat. Therefore, in some cases, undesirable and unpredictable motions may be made by environmental factors such as wave, wind attack and so on. As a result, a collision accident with others may occur during maneuvering situation. Based on these facts, the authors try to encourage the steering performance of the towed vessel by using controllable rudders without any propulsion system. In this study, especially, a controllable vessel with three rudders is considered, and a mathematical model is induced for the future study. The model is described as surge, sway motion and inertia moment by following the general representation method for the surface ship.

• Journal of the Microelectronics and Packaging Society
• /
• v.25 no.4
• /
• pp.59-66
• /
• 2018

In this paper, we analyzed the usefulness of single-structured printed circuit board (PCB) modeling by using numerical analysis to model the PCB structure applied to a package for semiconductor purposes and applying modeling assuming a single structure. PCBs with circuit layer of 3rd and 4th were used for analysis. In addition, measurements were made on actual products to obtain material characteristics of a single structure PCB. The analysis results showed that if the PCB was modeled in a single structure compared to a multi-layered structure, the warpage analysis results resulting from modeling the PCB structure would increase and there would be a significant difference. In addition, as the circuit layer of the PCB increased, the mechanical properties of the PCB, the elastic coefficient and inertia moment of the PCB increased, decreasing the package's warpage.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.49 no.9
• /
• pp.749-757
• /
• 2021

In transportation missions using quadrotor, the payload may change the model parameters, such as mass, moment of inertia, and center of gravity. Moreover, if position of the payload is constantly changing during flight, the effect can adversely affect the control performances. To handle this issue, we suggest Model Reference Adaptive Control based on Linear Quadratic Regulator(LQR+MRAC) to compensate the uncertainty caused by payload. Firstly, the mathematical modeling with the fixed payload is derived. Second, Linear Quadratic Regulator (LQR) is used to design the reference model and baseline controller. Also, through the Stability method, Adaptive law is derived to estimate the model parameters. To verify the performance of proposed control scheme, we compared LQR and LQR+MRAC in situations where uncertainties exist. And, when the disturbance exist, the classic MRAC and proposed controller is compared to analyze the transient response and robustness.

• Journal of IKEEE
• /
• v.26 no.2
• /
• pp.150-159
• /
• 2022

In this paper, we propose a physics simulation for augmented reality (AR) billiards content. The characteristics of the physics simulation for the proposed AR billiards content are as follows. First, physical equations are derived by calculating the force and moment of inertia applied to the billiards ball to realize the motion of the billiards ball similar to the real one in the AR environment. Then, we determine the velocity and angular velocity of the virtual billiards ball associated with the rotation of the virtual billiards ball with respect to the impact point. Second, using some vectors such as incidnet vector, normal vector, reflection vector, the trajectory of the virtual billiards ball would be implement. these equations are applied to AR environment so that AR billiards content could be implement. This physics simulation allows users to feel like the real world using a virtual pool table and induce them to interact with the real environment. As a result of the experiment, the accuracy range between the path of the real billiards ball and the path of the virtual billiards ball was calculated to be 97.75% to 99.11%. Therefore, it was determined that the performance of the physics simulation for the AR billiards content proposed in this paper performs similarly to the path of the real billiards ball.

• Structural Engineering and Mechanics
• /
• v.85 no.4
• /
• pp.469-484
• /
• 2023

A deep recursive bidirectional Cuda Deep Neural Network Long Short Term Memory (Bi-CuDNNLSTM) layer is recruited in this paper to predict the entire force time histories, and the corresponding hysteresis and backbone curves of reinforced concrete (RC) bridge piers using experimental fast and slow cyclic tests. The proposed stacked Bi-CuDNNLSTM layers involve multiple uncertain input variables, including horizontal actuator displacements, vertical actuators axial loads, the effective height of the bridge pier, the moment of inertia, and mass. The functional application programming interface in the Keras Python library is utilized to develop a deep learning model considering all the above various input attributes. To have a robust and reliable prediction, the dataset for both the fast and slow cyclic tests is split into three mutually exclusive subsets of training, validation, and testing (unseen). The whole datasets include 17 RC bridge piers tested experimentally ten for fast and seven for slow cyclic tests. The results bring to light that the mean absolute error, as a loss function, is monotonically decreased to zero for both the training and validation datasets after 5000 epochs, and a high level of correlation is observed between the predicted and the experimentally measured values of the force time histories for all the datasets, more than 90%. It can be concluded that the maximum mean of the normalized error, obtained through Box-Whisker plot and Gaussian distribution of normalized error, associated with unseen data is about 10% and 3% for the fast and slow cyclic tests, respectively. In recapitulation, it brings to an end that the stacked Bi-CuDNNLSTM layer implemented in this study has a myriad of benefits in reducing the time and experimental costs for conducting new fast and slow cyclic tests in the future and results in a fast and accurate insight into hysteretic behavior of bridge piers.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.1A
• /
• pp.15-24
• /
• 2008

This paper presents the analytical method for the long-term behavior of simply supported composite beams with precast decks prestressed in the longitudinal direction. The objectives of time-dependent analysis are to estimate losses of prestress on the concrete slab and long-term deflection due to creep and shrinkage of concrete, relaxation of prestressing steel. Also, the time-dependent analysis was carried out using the presented analytical method to evaluate the effects of several parameters on the long-term behavior of composite bridge with precast deck, including geometrical shapes of composite beams, compressive strength of concrete and magnitude of initial prestress. The results of the analysis indicated that, in the effects of geometrical shapes of composite beams, the main parameters affecting the losses of prestress and the long-term deflection were the cross sectional area and the moment of inertia of steel beam, respectively. Finally, the determination method for the required initial prestress was proposed by evaluation of the loss characteristics due to shrinkage and creep of concrete.

• Journal of Korean Society of Steel Construction
• /
• v.16 no.6 s.73
• /
• pp.759-768
• /
• 2004

The parametric analysis of vertically braced steel pipe arch ribs was performed to evaluate their in-plane buckling strengths and ultimate load-carrying capacities. The elastic and plastic behavior of braced arch ribs, unlike those of the usual single arch ribs, are affected by such factors as the flexural rigidity of the brace member, brace and pipe ribs spacing, loading situation, and arch curvature. To analyze these effects, several parameters were included, such as the rise-to-span ratio, the second moment of the inertia ratio of the rib to the brace member, the space ratio of the brace, the space ratio of the upper and lower ribs, the initial crookedness, the slenderness ratios of the braced arch ribs, and the loading conditions were considered with live-load-to-dead-load ratios. Based on the results of the parametric analyses, a proper profile of the braced arch rib was proposed. A large-scale structural experiment was also performed to evaluate the ultimate strength of the braced arch rib. The test results were determined to reasonably coincide with the analytical ones.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.37 no.1
• /
• pp.78-85
• /
• 1992

This experiment was carried out to investigate the heritabilities, phenotypic correlation, genetic correlation and path-coefficients for desirable characters on the lodging related traits. Characters, that had high relation degree with field lodging degree, were rice-straw length, Wl /P, W/I, Wl /d, L, Wl / A, W/l, P, W $s^2$/ $l^4$ etc. Breaking strength appear negative correlation having an intention to field lodging. The second inertia moment of culm diameter trunk (branch), cross section area, rice-straw thickness and trunk cross section didn't appear negative coefficient with field lodging. It is considered that rice-straw length, leaf dry weight and lodging index, because of high heritability, become selection index of characters for breeding. In direct, indirect effect, and right rice-straw wall thickness appear largest( $P_{7y}$=0.6904), the next is the order of leaf dry weight( $P_{3y}$=0.2848), root dry weight ( $P_{1y}$=0.2658), culm diameter ( $P_{6y}$=-0.2280), and negative relation appear the order of rice-straw length ( $P_{5y}$=-0.9640) and stem dry weight( $P_{2y}$=-0.7072), therefore, the smaller culm length and stem dry weight, the stronger to lodging. to lodging.