• Smart Structures and Systems
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• v.22 no.1
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• pp.71-79
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• 2018

The nonlinear vibration analysis of a magneto-rheological elastomer (MRE) sandwich plate is conducted experimentally. Experiments have been performed in order to construct the frequency-response curves in the vicinity of the fundamental natural frequency of an MRE sandwich plate (plate A) in either the absence or presence of a localised external magnetic field at 3 different geometrical locations, for both small and medium magnetic fields. Furthermore, experiments have also been conducted on a pure aluminium plate (plate B) with an equal thickness to the MRE sandwich plate (plate A) in order to examine the influence of the MRE layer on the nonlinear dynamics of the system. An electrodynamic shaker was used to directly force each system and the displacement at the centre of the plate was measured. Meanwhile, permanent magnets were used to apply a localised magnetic field for the experiments where the MRE sandwich plate was subject to an external magnetic field. It was observed all the MRE systems displayed strong hardening-type nonlinear behaviour, however, with increasing magnetic field this behaviour transitioned to a weak hardening-type nonlinearity.

• Journal of Biosystems Engineering
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• v.29 no.2
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• pp.167-174
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• 2004

Density is a physical property which contains information relating to the internal quality of fruits and vegetables, and can be used as an index for nondestructive quality evaluation. Density sorting has been employed by farmers for some agricultural products since ancient times. In this study, an automatic density measuring system based on the platform scale or water displacement method was developed for density sorting of watermelon. It consisted of water tan, load cell, net tray, electric motor, limit switch, control system and its program. The resolution of density was 0.001 g/㎤. In order to calibrate and evaluate the accuracy, the density was measured using a balloon kept in cold water. It showed 1.002 g/㎤ which almost correspond to real density of water. Test results with 6 watermelons and 3 replications showed that the standard deviations of the dens were 0.001∼0.004 g/㎤. The relationship between density and internal quality of watermelon was investigated using the system. The densities of hollow watermelons were less than 0.950 g/㎤, it was apparent that the density of the watermelon was related to the degree of hollowness. But the soluble solid contents and internal defects could not be estimated from the density.

• Journal of Korea Multimedia Society
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• v.23 no.11
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• pp.1372-1382
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• 2020

This paper proposes a core technology for a micro river monitoring terminal device suitable for flood monitoring in small rivers and valleys. Our proposed device is basically equipped with a 77GHz radar, gyro and accelerometer sensors. To measure the flow velocity and water level, we proposed a signal processing technique that extracts pure water energy components from the observed Doppler velocity and reflection intensity from the radar. And to determine the stability of the river structure equipped with our device, we constantly monitor the displacement of the measured values of the gyro and accelerometer sensors. Experimental result verified that our method detects pure water energy in various river environments and distinguishes between flow velocity and water level well. And we verified that vibration and position change of structures can be determined through a gyro sensor. In future research, we will work to build a secure digital twin river network by lowering the cost of supplying RF-WAV devices. Also we expect our device to contribute to securing a preventive golden time in rivers.

• Structural Engineering and Mechanics
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• v.15 no.3
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• pp.299-314
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• 2003

This investigation presents an efficient method for identifying modal characteristics from the measured displacement, velocity and acceleration signals of multiple channels on structural systems. A Vector Backward Auto-Regressive model (VBAR) that describes the relationship between the output information in different time steps is used to establish a backward state equation. Generally, the accuracy of the identified dynamic characteristics can be improved by increasing the order of the Auto-Regressive model (AR) in cases of measurement of data under noisy circumstances. However, a higher-order AR model also induces more numerical modes, only some of which are the system modes. The proposed VBAR model provides a clear characteristic boundary to separate the system modes from the spurious modes. A numerical example of a lumped-mass model with three DOFs was established to verify the applicability and effectiveness of the proposed method. Finally, an offshore platform model was experimentally employed as an application case to confirm the proposed VBAR method can be applied to real-world structures.

• Steel and Composite Structures
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• v.27 no.5
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• pp.555-566
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• 2018

A 1/3 composite cylindrical shell with a central rectangular opening was axially compressed experimentally, and its critical buckling load and displacement, and strains were measured. A finite element model (FEM) of the shell with Hashin failure criteria was established to analyze its buckling and post-buckling behaviors by nonlinear Newton-Raphson method. The geometric imperfection sensitivity and the effect of side supported conditions of the shell were investigated. It was found that the Newton-Raphson method can be used to analyze the buckling and post-buckling behaviors of the shell. The shell is not sensitive to initial geometric imperfection. And the support design of the shell by side stiffeners is a good way to obtain the critical buckling load and simplify the experimental fixture.

• Geomechanics and Engineering
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• v.20 no.4
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• pp.333-343
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• 2020

Preventing or reducing the damage impact of lateral soil movements on piled foundations is highly dependent on understanding the behavior of passive piles. For this reason, a detailed experimental study is carried out, aimed to examine the influence of soil density, the depth of moving layer and pile spacing on the behavior of a 2×2 free-standing pile group subjected to a uniform profile of lateral soil movement. Results from 8 model tests comprise bending moment, shear force, soil reaction and deformations measured along the pile shaft using strain gauges and others probing tools were performed. It is found that soil density and the depth of moving layer have an opposite impact regarding the ultimate response of piles. A pile group embedded in dense sand requires less soil displacement to reach the ultimate soil reaction compared to those embedded in medium and loose sands. On the other hand, the larger the moving depth, the larger amount of lateral soil movement needs to develop the pile group its ultimate deformations. Furthermore, the group factor and the effect of pile spacing were highly related to the soil-structure interaction resulted from the transferring process of forces between pile rows with the existing of the rigid pile cap.

• Steel and Composite Structures
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• v.34 no.5
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• pp.657-670
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• 2020

In this paper, vibration analysis of functionally graded nanoshell is studied based on the sinusoidal higher-order shear and normal deformation theory to account thickness stretching effect. To account size-dependency, Eringen nonlocal elasticity theory is used. For more accurate modeling the problem and corresponding numerical results, sinusoidal higher-order shear and normal deformation theory including out of plane normal strain is employed in this paper. The radial displacement is decomposed into three terms to show variation along the thickness direction. Governing differential equations of motion are derived using Hamilton's principle. It is assumed that the cylindrical shell is made of an arbitrary composition of metal and ceramic in which the local material properties are measured based on power law distribution. To justify trueness and necessity of this work, a comprehensive comparison with some lower order and lower dimension works and also some 3D works is presented. After presentation of comparative study, full numerical results are presented in terms of significant parameters of the problem such as small scale parameter, length to radius ratio, thickness to radius ratio, and number of modes.

• The Korean Journal of Pharmacology
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• v.10 no.1 s.15
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• pp.47-52
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• 1974

The isolated rabbit gall bladder strips were prepared according to the technique described by Amer and Becvar (1969). The strips were placed in a bath containing 100 ml of Locke-Ringer solution maintained at $38^{\circ}C$. Oxygen was continuously bubbled through the solution. The tension of the muscle strip was initially adjusted to 0.7g. The contractile response was measured isometrically by a force-displacement transducer connected to a polygraph. The effect of a number of autonomic drugs were studied for their interaction with caerulein (Prof. V. Erspamer, F.I. 6934 Caerulein, Farmitalia, Italia), a gastrin or CCK.PZ like peptide, on isolated rabbit gall bladder strips. In this preparation caerulein produced contractions of CCK-PZ type, but the relative potency on a weight basis was 40 times that of CCK-PZ. The response of caerulein was not modified by either cholinergic or alpha or beta adrenergic blockade. However, the response of caerulein and of barium on the strips were prevented by papaverine or aminophylline. Isoproterenol, papaverine or aminophylline alone relaxed the preparation whereas caerulein, CCK-PZ, acetylcholine, serotonin, histamine or barium chloride contracted the preparation. In summary, it is concluded that caerulein on the gall bladder strip seems to act independently of the autonomic nervous system and mediated via mechanisms apparently similar to those involved in the action of barium chloride.

• Journal of Aerospace System Engineering
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• v.10 no.4
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• pp.50-58
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• 2016

In our preceding study, we reported that the use of light, composite-material wings in long-endurance Solar-Powered UAVs is a critical factor. Ribs are critical components of wings, which prevent buckling and torsion of the wing skin. This study was undertaken to design and manufacture optimal composite ribs. The ribs were manufactured by applying laminated-layer patterns and shapes, considering the anisotropic properties of the composite material. Through the finite element analysis using the MSC Patran/Nastran, the maximum load and the displacement shape were identified. Based on the study results measured by structural tests, we present an optimal design of ribs.

• Wind and Structures
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• v.18 no.6
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• pp.669-691
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• 2014

Since low-rise residential buildings are the most common and vulnerable structures in coastal areas, a reliable prediction of their performance under hurricanes is necessary. The present study focuses on developing a refined finite element model that is able to more rigorously represent the load distributions or redistributions when the building behaves as a unit or any portion is overloaded. A typical 5:12 sloped low-rise residential building is chosen as the prototype and analyzed under wind pressures measured in the wind tunnel. The structural connections, including the frame-to-frame connections and sheathing-to-frame connections, are modeled extensively to represent the critical structural details that secure the load paths for the entire building system as well as the boundary conditions provided to the building envelope. The nail withdrawal, the excessive displacement of sheathing, the nail head pull-through, the sheathing in-plane shear, and the nail load-slip are found to be responsible for the building envelope damage. The uses of the nail type with a high withdrawal capacity, a thicker sheathing panel, and an optimized nail edge distance are observed to efficiently enhance the building envelope performance based on the present numerical damage predictions.