• International Journal of Fluid Machinery and Systems
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• v.5 no.1
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• pp.1-9
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• 2012

In the turbopump inducer of a liquid propellant rocket engine, cavitation is affected by acceleration that occurs during an actual launch sequence. Since cavitation instabilities such as rotating cavitations and cavitation surges are suppressed during launch, it is difficult to obtain data on the influence of acceleration on cavitation instabilities. Therefore, as a fundamental investigation, in the present study, a three-blade cyclic cascade is simulated numerically in order to investigate the influence of acceleration on time-averaged and unsteady characteristics of cavitation that arise in cascade. Several cases of acceleration in the axial direction of the cascade, including accelerations in the upstream and downstream directions, are considered. The numerical results reveal that cavity volume is suppressed in low cavitation number condition and cavitation performance increases as a result of high acceleration in the axial-downstream direction, also, the inverse tendency is observed in the axial-upstream acceleration. Then, the regions in which the individual cavitation instabilities occur shift slightly to a low-cavitation-number region as the acceleration increases downstream. In addition, in a downstream acceleration field, neither sub-synchronous rotating cavitation nor rotating-stall cavitation are observed. On the other hand, rotating-stall cavitation occurs in a relatively higher-cavitation-number region in an upstream acceleration field. Then, acceleration downstream is robust against cavitation instabilities, whereas cavitation instabilities easily occur in the case of acceleration upstream. Additionally, comparison with the Froude number under the actual launch conditions of a Japanese liquid propellant rocket reveals that the cavitation performance will not be affected by the acceleration under the current launch conditions.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.12
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• pp.2346-2351
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• 2011

This paper presents the intelligent external noise analysis method for nonlinear maneuvering target. After recognizing maneuvering pattern of the target by the proposed method, we track the state of the target. The external noise can be divided into mere noise and acceleration using only the measurement. divided noise passes through the filtering step and acceleration is punched into dynamic model to compensate expected states. The acceleration is the most deterministic factor to the maneuvering. By dividing, approximating, and compensating the acceleration, we can reduce the tracking error effectively. We use the fuzzy c-means (FCM) clustering as the method to divide external noise. FCM can separate the acceleration from the noise without criteria. It makes the criteria with the data made by measurement at every sampling time. So it can show the adaptive tracking result. The proposed method proceeds the tracking target simultaneously with the learning process. Thus it can apply to the online system. The proposed method shows the remarkable tracking result on the linear and nonlinear maneuvering. Finally, some examples are provided to show the feasibility of the proposed algorithm.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.1
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• pp.13-20
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• 1994

Determination of the number of modes to be included in the mode superposition method(MSM) is very important and difficult. Mode acceleration method(MAM) is recommended recently with the intention to overcome the problem. But the solution of the MAM is complex and complicate in frequency domain analysis. In this paper, advanced mode acceleration method(AMAM) is formulated and examined. The results from example analyses show that AMAM is a simple, accurate and reliable method compared with the MSM and the MAM.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.3
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• pp.215-223
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• 2007

When the propulsion shafting system of marine diesel engine is designed. the vibratory stresses on shafts should be reviewed and be satisfied with limits which are laid down by classification societies In addition. the torsional vibration aspects for crankshaft of main engine are requested to be checked by engine designers. Especially. for the 4, 5, and 6-cylinder engines. the 2nd order moment compensator(s) may be installed to compensate the external moments of engine and not to excite the hull girder vibration. This moment compensator which is mounted on fore and/or after-end of engine is driven by the roller chain drive for some of MAN 2-stroke diesel engines. While the engine is running, the roller chain Is worn down, which causes the extension of roller chain. The chain therefore should be checked and tightened by periods in order to keep its functionality. However. when the torsional angular acceleration of chain drive exceeds the certain limit. the chain will suffer the excessive slack and transverse vibration. This may cause fatigue, wear or damage on the chain and the chain ultimately may be broken. The research object of this thesis is to review factors which affect the angular acceleration of chain drive and to find out how to decrease the angular acceleration of driving chain by checking factors which have a major contribution to acceleration reduction using the statistical method of DOE(design of experiment), correlation analysis and regression analysis methods.

• 한국전산유체공학회:학술대회논문집
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• 1998.05a
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• pp.168-173
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• 1998

A numerical analysis of axisymetric backward facing step main nozzle flow in air jet loom has been accomplished. To obtain basic design data for an optimum main nozzle for an air-jet loom and to predict the transonic/supersonic flow, a characteristic based upwind flux difference splitting compressible Navier-Stokes method has been used. The wall static pressure of the main nozzle and the flow velocity changes in the nozzle tube were analyzed by changing air tank pressures and acceleration tube lengths. The flow inside the nozzle experiences double choking one at the needle tip and the other at the acceleration tube exit at tank pressures over $4kg_f/cm^2$. The tank pressure $P_t$ leading to the critical condition depends on the acceleration tube length; i.e, $P_t$ is higher for longer acceleration tubes. The $P_t$ value required to bring the acceleration tube exit to the critical condition is nearly constant regardless of acceleration tube length. The round needle tip shape might lead to less total pressure loss when compared with step shape.

• Physical Therapy Korea
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• v.25 no.3
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• pp.27-38
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• 2018

Background: At present time, smartphones have become very popular and powerful devices, and smartphone applications with the good validity have been designed to assess human balance ability. Objects: The purpose of this study is to evaluate the feasibility of smartphone acceleration in the assessment of postural control ability for six different conditions. Methods: Twenty healthy college-aged individuals volunteered. Static balance ability was measured twice with one-day interval using smartphone application and 3D motion capture system under the six different conditions. Results: Dominant frequencies for each test condition did not show significant differences except for two conditions. The intra-rater correlation coefficient between the first and second tests showed high correlations in six conditions(r>.70, p<.05). Smartphone acceleration and the acceleration calculated from the 3D marker position data showed high correlation coefficient(r>.80, p<.001). Conclusion: Acceleration recorded from a smartphone could be useful assessment variables for balance test in the clinical field.

• Journal of Ocean Engineering and Technology
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• v.30 no.6
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• pp.440-450
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• 2016

The capsizing and consequent sinking of a coastal car ferry was recently reported, with numerous human casualties. The primary cause was determined to be a sudden turn with improperly stowed and secured cargo. Part I of this study introduces how long term acceleration components are determined from seakeeping analyses. A carferry with a displacement of 1,633 tonf was selected as the target vessel. Sea data that included the significant wave heights and periods were collected at four observation buoys, some of which were far away from two main voyage routes: Incheon-Jeju and Pusan-Jeju. Frequency response analyses were performed to obtain the linearized radiation force coefficients, hydrostatic stiffnesses, and wave excitation forces. Time response analyses were sequentially performed to produce the motion-induced acceleration processes. The probabilistic distributions of the acceleration components were determined using a peak and valley counting method. Long term extreme acceleration components were proposed as a final result.

• Geomechanics and Engineering
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• v.36 no.2
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• pp.157-166
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• 2024

Generally, the rubble mound installed on the slope embankment of the open-type wharf is designed based on the impact of wave force, with no consideration for the impact of seismic force. Therefore, in this study, dynamic centrifuge model test results were analyzed to examine the acceleration amplification of embankment reinforced with rubble mound under seismic conditions. The experimental results show that when rubble mounds were installed on the ground surface of the embankment, acceleration response of embankment decreased by approximately 22%, and imbalance in ground settlement decreased significantly from eight to two times. Furthermore, based on the experimental results, one-dimensional site response (1DSR) analyses were conducted. The analysis results indicated that reinforcing the embankment with rubble mound can decrease the peak ground acceleration (PGA) and short period response (below 0.6 seconds) of the ground surface by approximately 28%. However, no significant impact on the long period response (above 0.6 seconds) was observed. Additionally, in ground with lower relative density, a significant decrease in response and wide range of reduced periods were observed. Considering that the reduced short period range corresponds to the critical periods in the design response spectrum, reinforcing the loose ground with rubble mound can effectively decrease the acceleration response of the ground surface.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.1550-1554
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• 2011

In this paper the effect of frequency domain on the estimation of acceleration of high-speed railway bridges was investigated. Field test was conducted for two bridges. One bridge has ballasted tracks, the other slab tracks. Acceleration and displacement were measured. Effect of filtering on acceleration and displacement was analyzed.

• Journal of Korean Association for Spatial Structures
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• v.5 no.1 s.15
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• pp.65-71
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• 2005

This research analyzed dynamic responses of the preflex railroad bridge. Vertical deflection and acceleration induced by operating train loads and test train loads were measured. Deflection of bridge by train traveling satisfies deflection limitation regulation (L/800) about the concrete bridge, but compare with UIC standard, vibration acceleration happened fairly greatly. Also test result show that acceleration receives greatly effect about the speed than deflection. It must discuss about vibration acceleration problems for speed elevation hereafter.