• Journal of the Korean Data and Information Science Society
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• v.20 no.3
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• pp.527-539
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• 2009

The purpose of this study was to evaluate the influence of ankle joint mobilization on equilibrium ability of supinated foot. Both Joint mobilization group(n=20) and control group(n=20) were measured an equilibrium ability by Balance performance monitor at pre-test, post-test in 2 weeks, post-test in 4 weeks and follow-up test in 2 weeks. The sway area, sway path length and sway maximum velocity of the joint mobilization group were significantly reduced among the experimental period (p<.05). The reduction of sway area, sway path length and sway maximum velocity were significantly different between the joint mobilization group and the control group at in 2 weeks, 4 weeks and follow-up test(p<.05). In conclusion, we were found that ankle joint mobilization could reduce sway area, sway path length and sway max velocity and improve a balance for the individuals with supinated foot.

• Ocean and Polar Research
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• v.33 no.3
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• pp.309-319
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• 2011

This is a preliminary study of the feasibility of obtaining reliable tidal current harmonic constants, using one month of current observations, to verify the accuracy of a tidal model. An inference method is commonly used to separate out the tidal harmonic constituents when the available data spans less than a synodic period. In contrast to tidal constituents, studies of the separation of tidal-current harmonics are rare, basically due to a dearth of the long-term observation data needed for such experiments. We conducted concurrent and monthly harmonic analyses for tidal current velocities and heights, using 2 years (2006 and 2007) of current and sea-level records obtained from the Tidal Current Signal Station located in the narrow waterway in front of Incheon Lock, Korea. Firstly, the l-year harmonic analyses showed that, with the exception of $M_2$ and $S_2$ semidiurnal constituents, the major constituents were different for the tidal currents and heights. $K_1$, for instance, was found to be the 4th major tidal constituent but not an important tidal current constituent. Secondly, we examined monthly variation in the amplitudes and phase-lags of the $S_2$ and $K_1$ current-velocity and tide constituents over a 23-month period. The resultant patterns of variation in the amplitudes and phase-lags of the $S_2$ tidal currents and tides were similar, exhibiting a sine curve form with a 6-month period. Similarly, variation in the $K_1$ tidal constant and tidal current-velocity phase lags showed a sine curve pattern with a 6-month period. However, that of the $K_1$ tidal current-velocity amplitude showed a somewhat irregular sine curve pattern. Lastly, we investigated and tested the inference methods available for separating the $K_2$ and $S_2$ current-velocity constituents via monthly harmonic analysis. We compared the effects of reduction in monthly variability in tidal harmonic constants of the $S_2$ current-velocity constituent using three different inference methods and that of Schureman (1976). Specifically, to separate out the two constituents ($S_2$ and $K_2$), we used three different inference parameter (i.e. amplitude ratio and phase-lag diggerence) values derived from the 1-year harmonic analyses of current-velocities and tidal heights at (near) the short-term observation station and from tidal potential (TP), together with Schureman's (1976) inference (SI). Results from these four different methods reveal that TP and SI are satisfactorily applicable where results of long-term harmonic analysis are not available. We also discussed how to further reduce the monthly variability in $S_2$ tidal current-velocity constants.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.730-733
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• 2001

A computer aided design system for spur, helical, bevel and worm gears by using AutoCAD system and its AutoLISP computer language was newly developed in this study. Two methods are available for a designer to draw a gear. The first method needs the gear design parameters such as pressure, module, number of tooth, shaft angle, velocity, materials, etc. When the gear design parameters are inputted, a gear is drawn in AutoCAD system and maximum allowable power and shaft diameter are calculated additionally. The second method calculates all dimensions and gear design parameters to draw a gear when the information such as transmission, reduction ratio, rpm, materials and pressure are inputted. The system includes four programs. Each program is composed of a data input module, a database module, a strength calculation module, a drawing module, a text module and a drawing edit module. In conclusion, the CAD system would be widely used in companies to find the geometric data and manufacturing course.

• Journal of the Korea Institute of Military Science and Technology
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• v.10 no.2
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• pp.12-20
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• 2007

The aiming ability is a key to improve the accuracy performance of the gun pointing system in the ground military vehicle. This paper describes the new detection method of chatter vibration using disturbance acceleration in the pointing structure. In order to analysis the vibration trends of the pointing system occurred while the vehicle driving, acceleration data obtained from vehicle was processed by using data processing algorithm with moving average and Hilbert transform. The specific mode constants of acceleration were obtained from various disturbances. Vehicle velocity, road condition and property of pointing structure were considered as factors which make the change of vibration trend in vehicle dynamics. Finally, back propagation neural networks have been applied to the pattern recognition of the classification of vibration signal in various driving conditions. Results of signal processing were compared with other condition result and analysed.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.10
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• pp.1908-1914
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• 1992

A significant drag reduction in the turbulent flow of CWM(coal Water Mixture) adding minute amounts of high molecular weight polymer additives has been obtained and it was compared with pure CWM.However, the rate of drag reduction could come down with flow time, which is caused by polymer degradation, The rate of drag reduction and polymer degradation is affected by polymer type, concentration, molecular weight, and flow velocity. In the present investigation, these important parameters were evaluated for their influences on polymer degradation in order to find out stable conditions for CWM transportation with time. It was necessary to determine the more effective type of polymer additives to guarantee the optimum conditions for CWM transport. Experiments were undertaken with a test section of pipe diameter 9.8mm and pipe length 3500mm(L/D=357) in a closed loop, and polyacrylamide and polyetylene oxide were utilized as polymer additives. The tests were carried out under the conditions of 200, 400, 700ppm of polymer concentrations. CWM concentrations utilized were 5% and 10% with flow velocities of 4.9m/s and 6.1m/s. Experimental data show that polyehylene oxide degraded faster than polyacrylamide in CWM transport, and polyacryamide is considered to be a more effective candidate as additive for long time-CWM transport. Polymer degradation is also found to be more likely at lower polymer concentrations, at higher flow velocities, and higher CWM concentrations.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.8
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• pp.799-807
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• 2010

Direct numerical simulations (DNS) of turbulent channel flow for which the drag is reduced by using polymer additives have been performed by a pseudo-spectral method. The Reynolds number based on the friction velocity and half-channel height is 395, and the polymeric stresses due to the polymer additives are evaluated using the FENE-P (finitely extensible nonlinear elastic-Peterlin) model. The numerical results show that the drag reduction rate is significantly affected by the parameters used in the FENE-P model, such as the maximum extensibility and relaxation time of the polymer molecules. The turbulence data for both low- and high-drag reduction regimes are analyzed. In addition, the effects of FENE-P model parameters on the flow characteristics have been investigated for the same drag reduction rate due to the polymer additives. Finally, the present DNS results have been used to verify the correlation between rheological parameters and the extent of drag reduction, which was suggested by Li et al. (2006).

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.979-984
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• 2001

As a preceding process for developing design technology and establishing operation technology, the design procedure of the SCR(Selective Catalytic Reduction) pilot plant that can handle $1,000Nm^{3}/hr$ of flue gas was reported in this paper. And we also considered several factors that might cause abnormality of the plant in the designing process. The plant was designed and fabricated to test the $DeNO_{x}$ performances in variable operating conditions in the range of $3,000{\sim}36,000hr^{-1}/hr$ in space velocities, $1.67{\sim}6\;m/s$ in linear velocities, $200{\sim}500^{\circ}C$ temperatures, $300{\sim}1,000Nm^{3}/hr$ flow rates, and $0{\sim}1.4:1\;NH_{3}/NO$ ratios. In order to maintain the flow uniformity, the guide vanes and flow straightener were designed and constructed in the plant. The SCR pilot plant can be operated by the automatic control system, which enable to obtain performance data in real time and to set up the operating technology. The catalyst reactor consists of 4 catalyst layers and surface area of each layer can be adjusted to be of small size. Arrangement of catalysts per layer is $3{\times}6$ with the catalyst dimensions of $150{\times}150{\times}500mm(L{\times}W{\times}H)$.

• Journal of Korean Society for Atmospheric Environment
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• v.21 no.6
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• pp.573-583
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• 2005

Fugitive dust, which is emitted in the ambient air without first passing through a stack or duct designed to control flow, is frequently generated by means of wind erosion from storage yards at Pohang Steel Wokrs. The size distribution of fugitive dust is mostly in the range of coarse particulate which is deposited as soon as emitted and less harm to human health; however $20\%$ of fugitive dust contains PM 10 known as one of most harmful airborne pollutant. Consequently, effective control and reduction of fugitive dust is strongly requested by the local society, but it is not easy so far because the generation and dispersion of fugitive dust highly depends on meteorological conditions, and it being occurred for irregularity. This research presented a fugitive dust control system for each meteorological condition by providing statistical prediction data obtained from a statistical analysis on the probability of generating the threshold velocity at which the fugitive dust begins to occur, and the frequency occurring by season and by time of the wind direction that can generate atmospheric pollution when the dispersed dust spreads to adjacent residential areas. The research also built a fugitive dust detection system which monitors the weather conditions surrounding storage yards and the changes in air quality on a real-time basis and issues a warning message by identifying a situation where the fugitive dust disperses outside the site boundary line so that appropriate measures can be taken on a timely basis. Furthermore, in respect to the spraying of water to prevent the generation of fugitive dust from the storage piles at the storage yard, an advanced statistical meteorological analysis on the weather conditions in Pohang area and a case study of fugitive dust dispersion toward outside of working field during $2002\∼2003$ were carried out in order to decide an optimal water-spraying time and the number of spraying that can prevent the origin of fugitive dust emission. The results of this research are expected to create extremely significant effects in improving surrounding environment through actual reduction of the fugitive dust produced from the storage yard of Pohang Steel Works by providing a high-tech warning system capable of constantly monitoring the leakage of fugitive dust and water-spray guidance that can maximize the water-spraying effects.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.5
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• pp.13-19
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• 2014

Urea-SCR system is the selective catalytic reduction to reduce nitrogen oxides ($NO_x$) emitted from diesel vehicles. The objective of this study is numerical analysis of 3-dimensional unsteady melting problems of frozen urea by using an electric heater. It can be applied to determine capacity of power with respect to time and the location of the urea suction pipe in urea storage tank. The study includes the change of liquid volume fraction, temperature profiles and a influence of natural convection by using the commercial software STAR-CCM+(v7.06). The accuracy of the numerical analysis is estimated by comparisons with experimental data. After validation, a numerical analysis for freezing urea is conducted with four different heating power. From the results, it was found that relation of velocity of phase interface and amount of melting urea by increasing heating power in a container. There is also a difference in trend between velocity of phase interface and amounts of melting urea because of effect of natural convection.

• The KSFM Journal of Fluid Machinery
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• v.14 no.5
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• pp.5-11
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• 2011

In this study, the effect of cone angle of seven-hole probe on the accuracy of measured flow angle and velocity has been investigated. The seven-hole probe consisted of seven 1mm OD stainless inner tubes and one 3mm ID stainless tube. Six cone angles of $45^{\circ}$, $60^{\circ}$, $75^{\circ}$, $90^{\circ}$, $105^{\circ}$ and $120^{\circ}$ were tested. Calibrations of the seven-hole probes were conducted within ${\pm}60^{\circ}$ range with the interval of $5^{\circ}$. Analysis results show that the effect on the cone angle was not significant on the accuracy of the measured flow angle, pressure, and velocity. However, the data reduction method had more effect on the measurement accuracy.