• Journal of Ocean Engineering and Technology
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• v.14 no.4
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• pp.9-16
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• 2000

This paper deals with the numerical and experimental study on the characteristics of the flow around a sunken vessel. Numerical simulation of the two dimensional steady flow on the midship section are carried out by the CFD code which is developed by using finite volume method and which includes the standard $textsc{k}$-$\varepsilon$ model with standard wall function. A experimental study is also carried out for the 1/100 scale model in circulating water channel. A velocity fields around the ship are measuremed by using particle image velocimetry technique. And the fluid forces acting on the ship hull by uniform current are measured by two axis load cell. The computed and measured velocity fields on the midship section are compared with each other in the view point of velocity dstribution and reattachement length, which shows good agreement in quality. The drag force on the vessel also showed the same tendency in both computational and experimental results. However, the quantitative disagreements are shown due to the three dimensional effect of the experiment. The result are used to determine the functional efficiency and stability of the vessel as a artificial reef.

• The Journal of Korea Robotics Society
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• v.17 no.2
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• pp.152-158
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• 2022

As various mobile robots and manipulator robots have been commercialized, robots that can be used by individuals in their daily life have begun to appear. With the development of robots that support daily life, the interaction between robots and humans is becoming more important. Manipulator robots that support daily life must perform tasks such as pressing buttons or picking up objects safely. In many cases, this requires expensive multi-axis force/torque sensors to measure the interaction. In this study, we introduce a low-cost two-axis pressure sensor that can be applied to manipulators for education or research. The proposed system used three force sensitive resistor (FSR) sensors and the structure was fabricated by 3D printing. An experimental device using a load cell was constructed to measure the biaxial pressure. The manufactured prototype was able to distinguish the +-x-axis and the +-y-axis pressures.

• Korean Journal of Agricultural Science
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• v.27 no.1
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• pp.48-53
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• 2000

The various errors existing in a weight measurement system in most automatic egg sorting system available in Korean poultry farms have caused a large amount of economic losses to the egg producers. The object of this study was an importance of egg measurement system by changing both the number and the arrangements of load cells to reduce measuring errors. The results obtained were summarized as follow : 1. Four arrangements of load cells were selected as follows : layout I : Conventional one load cell method layout II : One load cell located as egg moving direction layout III : Two load cells located facing each other layout IV : Two load cells located as parallel with egg moving direction 2. The results of egg weight measurement according to four arrangements (Layout I, II, III, IV) showed that the average errors were 1.1218g, 0.5953g, 0.7786g, 0.2793g respectively. This indicated that the Layout IV (measuring by 2 load cells located parallel with the egg moving direction) caused the lowest average error and the best in precision. 3. The average vibration of axis X, y, Z were resulted as $5.1937{\times}10^{-3}G$, $9.3604{\times}10^{-3}G$, and $16.8657{\times}10^{-3}G$ respectively when sorting large sized egg. This indicated that the vibration of axis-Z was relatively higher than those of axis-X, and axis-Y.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.47 no.5
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• pp.52-61
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• 2010

The use of the friction coefficient is known to provide good discrimination ability in the classification of human constitutions, which are used in alternative medicine. In this study, a system that uses a multi-axis load cell and a hemi-circular probe is designed. The equipment consists of a sensor (load cell type, manufactured by the authors), an x-axis linear-bush guide motorized mobile stage that supports the hand being analyzed, and a signal conditioner. Using the proposed system, the friction coefficients from different constitutions were compared, and the relative repeatability error for the friction coefficient measurement was determined to be less than 2 %. The direction along the ring finger line was determined to be the optimum measurement region for a constitutional diagnosis between Tae-eumin and Soyangin types using the proposed system. There were some differences in the friction coefficient between the two constitutions, as reported in ancient literature. The proposed system is applicable to a quantitative constitutional diagnosis between Tae-eumin and Soyangin types within an acceptable level of uncertainty.

• Structural Engineering and Mechanics
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• v.60 no.6
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• pp.939-952
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• 2016

A compression to tensile load transforming (CTT) device was developed to determine indirect tensile strength of concrete material. Before CTT test, Particle flow code was used for the determination of the standard dimension of physical samples. Four numerical models with different dimensions were made and were subjected to tensile loading. The geometry of the model with ideal failure pattern was selected for physical sample preparation. A concrete slab with dimensions of $15{\times}19{\times}6cm$ and a hole at its center was prepared and subjected to tensile loading using this special loading device. The ratio of hole diameter to sample width was 0.5. The samples were made from a mixture of water, fine sand and cement with a ratio of 1-0.5-1, respectively. A 30-ton hydraulic jack with a load cell applied compressive loading to CTT with the compressive pressure rate of 0.02 MPa per second. The compressive loading was converted to tensile stress on the sample because of the overall test design. A numerical modeling was also done to analyze the effect of the hole diameter on stress concentrations of the hole side along its horizontal axis to provide a suitable criterion for determining the real tensile strength of concrete. Concurrent with indirect tensile test, the Brazilian test was performed to compare the results from two methods and also to perform numerical calibration. The numerical modeling shows that the models have tensile failure in the sides of the hole along the horizontal axis before any failure under shear loading. Also the stress concentration at the edge of the hole was 1.4 times more than the applied stress registered by the machine. Experimental Results showed that, the indirect tensile strength was clearly lower than the Brazilian test strength.

• Tunnel and Underground Space
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• v.19 no.6
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• pp.473-478
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• 2009

The accuracy of point load apparatus is depend on point to point coaxial fitting. Also, the estimation of applied point load using the pressure gauge frequently lead to erroneous results. An improved point load apparatus has been developed in this study by mounting linear bearing on polished support rod, and eccentric error of point to point axis has been sustained less than 0.1 mm even under series of extreme work load conditions. Two digital displacement gauges are attached to measure the distance from point to point with sample specimen. A load cell mounted at the end of upper conical platen measure the applied net load on sample instead of preassure gauge. Total of 107 point load tests has been achieved to assure the quality and performance of developed apparatus. This exercise turned out to be successful.

• Journal of Electrical Engineering and Technology
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• v.12 no.6
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• pp.2378-2387
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• 2017

Violinists learn to make better sounds by hearing and evaluating their own playing though numerous practice. This study proposes a new method of auditory feedback, which mimics this violinists' step and verifies its efficiency using experiments. Making the desired sound quality of a violin is difficult without auditory feedback even though an expert violinist plays. An algorithm for controlling a robot arm of violin playing robot is determined based on correlations with bowing speed, bowing force, and sound point that determine the sound quality of a violin. The bowing speed is estimated by the control command of the robot arm, where the bowing force and the sound point are recognized by using a two-axis load cell and a photo interrupter, respectively. To improve the sound quality of a violin playing robot, the sounds information is obtained by auditory feedback system applied Short Time Fourier Transform (STFT) to the sounds from a violin. This study suggests Gaussian-Harmonic-Quality (GHQ) uses sounds' clarity, accuracy, and harmonic structure in order to decide sound quality, objectively. Through the experiments, the auditory feedback system improved the performance quality by the robot accordingly, changing the bowing speed, bowing force, and sound point and determining the quality of robot sounds by GHQ sound quality evaluation system.

• Korean Journal of Applied Biomechanics
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• v.21 no.4
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• pp.437-447
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• 2011

In this study, the lower limbs joints were analyzed for features based on the biomechanical characteristics of landing techniques according to height and landing on the ground type (flats and downhill). In order to achieve the objectives of the study, changes were analyzed in detail contents such as the height and form of the first landing on the ground at different angles of joints, torso and legs, torso and legs of the difference in the range of angular motion of the joint, the maximum angular difference between joints, the lower limbs joints difference between the maximum moment and the difference between COM changes. The subjects in this study do not last six months did not experience joint injuries 10 males in 20 aged were tested. Experimental tools to analyze were the recording and video equipment. Samsung's SCH-650A model camera was used six units, and the 2 GRF-based AMTI were used BP400800 model. 6-unit-camera synchronized with LED (photo cell) and Line Lock system were used. the output from the camera and the ground reaction force based on the data to synchronize A/D Syc. box was used. To calculate the coordinates of three-dimensional space, $1m{\times}3m{\times}2m$ (X, Y, Z axis) to the size of the control points attached to the framework of 36 markers were used, and 29 where the body was taken by attaching a marker to the surface. Two kinds of land condition, 40cm and 60cm in height, and ground conditions in the form of two kinds of flat and downhill slopes ($10^{\circ}$) of the landing operation was performed and each subject's 3 mean two-way RM ANOVA in SPSS 18.0 was used and this time, all the significant level was set at a=.05. Consequently, analyzing the landing technique as land form and land on the ground, the changes of external environmental factors, and the lower limbs joints' function in the evaluation were significantly different from the slopes. Landing of the slop plane were more load on the joints than landing of plane. Especially, knee extensor moment compared to the two kinds of landing, slopes plane were approximately two times higher than flat plane, and it was statistical significance. Most of all not so much range of motion and angular velocity of the shock to reduce stress was important. In the further research, front landing as well as various direction of motion of kinetic, kinetic factors and EMG variables on lower limbs joints of the study in terms of injury-prevention-approach is going to be needed.