• The KSFM Journal of Fluid Machinery
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• v.14 no.3
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• pp.50-58
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• 2011

To utilize wind resources effectively around buildings in urban area, the magnitudes of wind velocity and turbulence intensity are important, which means the need of the information about the relationship between the magnitude of wind velocity and that of fluctuating wind velocity. In the paper, wind-tunnel experiments were performed to provide the information about Characteristic of Wind flow around buildings with the spanwise distance and the side ratio of buildings as variables. For a single building with the side ratios of one and two, the average velocity ratio was 1.4 and the velocity standard deviation ratio ranged from 1.4 to 2.6 at the height of 0.02m at the corner of the windward side, in which flow separation occurred. For twin buildings with the side ratios of one and two, the velocity ratio ranged from 2 to 2.5 as the spanwise distance varied at the height of 0.02m, and the velocity standard deviation ratio varied near 1.25. For twin buildings with the side ratios of one and two, the maximum velocity ratio was 1.75 at the height of 0.6m, and the maximum velocity standard deviation ratio was 2.1. It was also found from the results of CFD analysis and wind-tunnel experiments that for twin buildings with the side ratios of one and two, the difference between the velocity ratio of CFD analysis and that of wind-tunnel experiments at streamwise distances was near 0.75.

• Journal of Korean Physical Therapy Science
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• v.11 no.1
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• pp.14-19
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• 2004

Objective : This study obtained normative values for variable parameters of lumbar function with the isoinertial triaxial dynamometer in patients with chronic low back pain. Subjects and Methods : 30 patients(male 15, female 15) with chronic low back pain in this study. Variable parameters that were measured with the Isostation B-200 were lumbar range of motion, isometric maximum torques, and maximum velocities in three axis. Results : In patient male group mean R.O.M. was $82.9{\pm}12.5$ degrees in lumbar rotation, $76.5{\pm}17.1$ degrees in lumbar flexion/extension, and $64.3{\pm}14.5$ degrees in lumbar lateral flexion. In patient female group mean R.O.M. was $78.4{\pm}18.5$ degrees in lumbar rotation, $71.7{\pm}20.4$ degrees in lumbar flexion/extension, and $63.2{\pm}14.4$ degrees in lumbar lateral flexion. In patient male group mean isometric maximum torques was $64.7{\pm}23.8ft-lbs$ in lumbar rotation, $81.1{\pm}42.0ft-lbs$ in lumbar flexion, $122.2{\pm}43.6ft-lbs$ in lumbar extension, and $101.0{\pm}37.0ft-lbs$ in lumbar lateral flexion. In patient female group mean isometric maximum torques was $41.9{\pm}9.2ft-lbs$ in lumbar rotation, $49.9{\pm}23.9ft-lbs$ in lumbar flexion, $90.1{\pm}26.8ft-lbs$ in lumbar extension, and $62.0{\pm}16.7ft-lbs$ in lumbar lateral flexion. In patient male group mean maximum velocity of isoinertial exercise with low (25%) resistance was $102.4{\pm}28.8deg/sec$ in lumbar rotation, $108.9{\pm}32.2deg/sec$ in lumbar flexion/extension, and $103.5{\pm}30.4deg/sec$ in lumbar lateral flexion. In patient female group mean maximum velocity of isoinertial exercise with low (25%) resistance was $84.1{\pm}24.4deg/sec$ in lumbar rotation, $93.2{\pm}32.9deg/sec$ in lumbar flexion/extension, and $98.5{\pm}33.7deg/sec$ in lumbar lateral flexion. In patient male group mean maximum velocity of isoinertial exercise with high (50%) resistance was $74.0{\pm}20.9deg/sec$ in lumbar rotation, $98.7{\pm}32.8deg/sec$ in lumbar flexion/extension, and $85.0{\pm}25.8deg/sec$ in lumbar lateral flexion. In patient female group mean maximum velocity of isoinertial exercise with high (50%) resistance was $67.3{\pm}26.4deg/sec$ in lumbar rotation, $82.5{\pm}31.0deg/sec$ in lumbar flexion/extension, and $79.7{\pm}23.9deg/sec$ in lumbar lateral flexion. Conclusion : Maximum isoinertial velocities were more reliable and more significant than isometric maximum torque for the objective assessment of chronic low hack pain.

• Korean Journal of Applied Biomechanics
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• v.16 no.2
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• pp.75-83
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• 2006

The Purpose of this study was to compare the biomechanical difference of two soccer footwear. which will provide scientific data to coaches and players, to further prevent injuries and to improve each players skills. The result of this study can be summarized after testing the two types of soccer footwear with comparative transforming heel angles and also with a pressure distribution in running. When a player's foot first touched the ground, the average difference of in/eversion was between 1.2 and 3.1 degrees for the two soccer shoes. In regards to maximum inversion and eversion of foot, maximum tibial rotation, and maximum and total movement of foot, the condition of barefoot and the two soccer shoes showed a small difference from 1.5 to 3.5 degrees and the difference among the subjects of study wasn't constant. In regards to maximum velocity of inversion and eversion running in one's bare feet showed much lower inversion velocity in comparison to putting on two types of soccer shoes and comparison of the average. Among some of the subjects, after putting on the two types of soccer shoes exceeded $97^{\circ}/s$ in maximum velocity of eversion. In the maximum braking impulse(t=2774, p<.05) and propulsive impulse for antero-posterior direction, there was a statistically significant difference between the two soccer footwear at running. In the maximum braking force(t=3.270, p<.05) and propulsive force(t=4.956, p<.05) for antero-posterior direction, there was a statistically significant difference between the two soccer footwear at running.

• Journal of Ocean Engineering and Technology
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• v.24 no.5
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• pp.81-87
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• 2010

This study presents the results of collision and lift analyses of a cylinders-connected protector under stock anchor colliding and dragging. For the analyses, the terminal velocity of the stock anchor was obtained first, and, then, the velocity was used to calculate the falling distance of the stock anchor in air. In addition, two other falling distances were considered for purposes of comparison. From the finite element analyses, using ANSYS, the maximum responses obtained from the stock anchor colliding and dragging were obtained and compared for different collision distances (3, 5, and 8.83 m) and dragging angles (0, 30, 60, $90^{\circ}$). Then, the maximum displacements and stresses were discussed, along with the strength and dimensions of the protector. Finally, conclusions were made for the maximum responses.

• The Journal of Korea Robotics Society
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• v.5 no.1
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• pp.32-40
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• 2010

This paper proposes the technique of estimating the pipe thickness using the measured group velocity. To measure the group velocity from the accelerometer data in the frequency domain, Wigner-Ville distribution is utilized, which interprets the waveform of the shock wave. Using this measured group velocity, this paper proposes the technique to estimate the thickness of pipes with the impact on the pipe. The group velocity is estimated by the modeling correlation between the group velocity and the thickness of the pipe based on the propagation velocities. The correlation model between thickness and group velocity has been proved through the real experiments. The measured group velocity in the frequency-domain is the maximum at the center frequency of the bending waves in the modeling of the group velocity. In addition to these, a smoothing technique for analyzing lamb wave Wigner-Ville distribution has been introduced to improve the reliability of the data acquisition.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.3
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• pp.209-216
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• 2001

A numerical study is peformed to investigate the effect of circumferential velocity generated by the guide vane on the nozzle flow of a jet fan, s a way of increasing the penetration force of jet fan with nozzle of 175mm diameter. For the validation of numerical results. the velocity is measured by a 5-hole pitot tube and flow visualization is conducted by the tuft method. Under the inlet condition that the maximum circumferential velocity in the stator outlet of the present jet fan is 1.8m/s, the axial velocity in the nozzle outlet has the feature that the velocity at the axis is low and the velocity near the wall high. Therefore, to increase the throw length of the jet fan, the configuration of the fairing and nozzle needs to be developed and the precise revise of the stator angle is required, In addition, the bigger the circumferential velocity, the smaller the axial velocity at the axis and the bigger non-uniformity of the flow distribution.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.977-980
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• 1995

This paper proposes the look ahead algorithm with the trapezoidal velocity trajectory in each G-code block. The algorithm requires the information on the length of next trajectories and the connecting angle between each trajectiories. A method of generating the maximum corner velocity upon the connecting angle within the machining tolerance is developed and applied to the look ahead algorithm. Simulations and experiments witha machining center show the effectiveness of the methodology.

• Journal of Mechanical Science and Technology
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• v.17 no.6
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• pp.879-887
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• 2003

The flow in a parallel walled test channel, when obstructed with a geometry at the entrance, can be forward, reverse and stagnant depending on the position of the obstruction. This interesting flow phenomenon has potential benefit in the control of energy and various flows in the process industry In this experiment, the flat plate obstruction geometry was used as an obstruction at the entry of the test channel. The parameters that influence the flow inside and around the test channel were the gap (g) between the test channel and the obstruction geometry, the length (L) of the test channel and the Reynolds number (Re). The effect of the gap to channel width ratio (g/w) on the magnitude of the velocity ratio (V$\_$i/ / V$\_$o/ : velocity inside/ velocity outside the test channel) was investigated for a range of Reynolds numbers. The maximum reverse flow observed was nearly 20% to 60% of the outside velocity for Reynolds number ranging from 1000 to 9000 at g/w ratio of 1.5. The maximum forward velocity inside the test channel was found 80% of the outside velocity at higher g/w ratio of 8. The effect of the test channel length on the velocity ratio was investigated for different g/w ratios and a fixed Reynolds number of 4000. The influence of the Reynolds number on the velocity ratio is also discussed and presented for different gap to width ratio (g/w). The flow visualisation photographs showing fluid motion inside and around the test channel are also presented and discussed.

• Advances in materials Research
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• v.6 no.1
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• pp.65-78
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• 2017

A hat section was designed and developed for maximum impact energy absorption and/or transmission under low velocity impact. Towards this, different hat sections, having material properties of thermoplastic, were modeled and investigated numerically using finite element analysis (FEA) in the range of 20-50 J impact energy. In the study it was experienced that the design configuration of hat section with curvilinear profile (HSCP) was excellent in energy attenuation capacity and for even distribution of maximum impact force around and along the hat section under low velocity impact loading. To validate the numerical findings, polypropylene copolymer (Co-PP) HSCP and low density polyethylene (LDPE) HSCP were developed and evaluated experimentally in the said impact energy range. A correlation was established between FEA and experimental test results, thereby, validating a numerical model to predict results for other thermoplastic materials under given range of impact energy. The LDPE HSCP exhibited better performance as compared to Co-PP HSCP in the said range of impact energy. The findings of this study will enable the engineers and technologists to design and develop low velocity impact resistance devices for various applications including devices to protect bone joints.

• Journal of Biosystems Engineering
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• v.43 no.3
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• pp.194-201
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• 2018

Purpose: The objective of this study was to propose a formula for the theoretical grain mean transport velocities of an elliptically moving oscillator by modifying the grain mean transport velocity formula applied to linear motion and to compare the calculated values with the experimental values of grain mean transport velocity. Methods: The values of the throwing index ($K_v$) and the maximum horizontal velocities for various positions on the elliptical oscillator were obtained using kinematic analysis. To obtain the actual grain transport velocity, the mean transport velocities of perilla grains at six positions on the sieve surface were measured using a high-speed camera and compared with the theoretical values. The cam with an eccentric bearing on the oscillator was designed to be eccentric by 1.6 cm so that the lengths of the major axis of the elliptical motion were 3.2-3.6 cm. The material used in the experiments was perilla grain. Results: The experimental result was consistent with the theoretical value calculated using the proposed formula ($R^2$ is 0.80). It is considered that the angle difference between the maximum accelerations in the directions vertical and horizontal to the sieve has as much influence on the grain mean transport velocity as the value of Kv itself. Conclusions: It was possible to theoretically obtain the grain mean transport velocities through a screening device in elliptical motion by modifying the formula of the grain mean transport velocities used in linear motion.