• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.4
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• pp.318-327
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• 2012

The operating sound radiated from a laser printer includes tonal noise components caused by the rotating mechanical parts such as gear, shaft, motor, fan, etc. The negative effects of the tonal noise components need to be considered in the process of developing a sound quality index for the quantitative evaluation of the emotional satisfaction in terms of psycho-acoustics. However, in a previous paper, it was confirmed that the Aures tonality did not have enough correlation with the results of jury evaluation. The sound quality index based on loudness, articulation index, fluctuation strength has a little problem in considering the effects of rotating mechanical parts on the sound quality. In this paper, to solve the tonality evaluation problem, the calculation algorithm of Aures tonality was investigated in detail to find the cause of decreasing the correlation. The new tonality evaluation model was proposed by modifying and optimizing the masking effect, loudness ratio, and shape of weighting curve based on the basic algorithm of Aures tonality, and applied to two kinds of operating sound groups in order to verify the usefulness of proposed model. As a result, it is confirmed that the proposed tonality evaluation model has enough correlation and usefulness for expressing the tonalness in the operating sounds of laser printers. In the following paper, this results will be used to model the sound quality index as the input data by using the classification algorithm.

• International Journal of Precision Engineering and Manufacturing
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• v.6 no.1
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• pp.51-58
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• 2005

The development of the high-efficiency machine-tools equipment and new cutting tool materials with high hardness, heat- and wear-resistance has opened the way to application of high-speed cutting process. The basic argument of using of high-speed cutting processes is the reduction of time and the respective increase of machining productivity. In this sense, the spindle units may be regarded as one of the most important units, directly affecting many parameters of high-speed machining efficiency. One of the possible types of spindle units for high-speed cutting is the air-bearing type. In this paper, we propose the mathematical model of the dynamic behavior of the air-bearing spindle. To provide the high-level of speed capacity and spindle rotation accuracy we need the adequate model of "spindle-bearings" system. This model should consider characteristics of the interactions between system components and environment. To find the working characteristics of spindle unit we should derive the equations of spindle axis movement under the affecting factors, and solve these equations together with equations which describe the behavior of lubricant layer in bearing (bearing stiffness equations). In this paper, the three influence coefficients are introduced, which describe the center of spindle mass displacement, angle of shaft rotation around the axes under the unit force application and that under the unit torque application. These coefficients are operated in the system of differential equations, which describes the spindle axis spatial movement. This system is solved by Runge-Kutta method. Obtained trajectories and amplitude-frequency characteristics were then compared to experimental ones. The analysis shows good agreement between theoretical and experimental results, which confirms that the proposed model of air-bearing spindle is correctis correct

• Journal of the Korean Geotechnical Society
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• v.20 no.4
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• pp.75-88
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• 2004

It is known that the earth pressure acting on the cylindrical retaining wall in cohesionless soils is small than that acting on the retaining wall in plane strain condition due to three dimensional arching effect. In this study, the earth pressure equation considering the earth pressure decrease by horizontal and vertical arching effects, overburden, wall friction, and failure surface slope is proposed. For the purpose of verifying the applicability of proposed equation, model test is performed with apparatuses that can control wall displacement, wall friction, and wall shape ratio. Influence of each factor on the active earth pressure acting on the cylindrical retaining wall is analyzed according to the model test in constant wall displacement condition. The comparison of calculated results with measured values shows that the proposed equations satisfactorily predict the earth pressure distribution on the cylindrical retaining wall.

• Journal of Biosystems Engineering
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• v.6 no.1
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• pp.1-14
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• 1981

A laboratory model test was carried out with a newly designed model to figure out the vibration characteristics of the vibratory tillage tool according to the method of forced vibration, i.e., horizontally and vertically forced vibrations. The results are summarized as follows: 1. The reduction ratios of the draft force of the vibratory blade were 14.2-42.6% for the case where the vibration was forced parallel to the travelling direction of the blade, and 15-54.5% for the vertically forced vibration. And it was thought that the method of vertically forced vibration was preferable to the reduction of the draft force. 2. The ratio of the draft force of a vibratory blade to that of a static one could be represented as a function of V/At. It was found to be possible to reduce the draft force by taking a lower value of (V/Af) and this meant that the effictiveness of tillage practice using the vibratory system would be limited. 3. The torque to the main rotating shaft to vibrate the model blade increased frequency and amplitude. This tendency varied according to the physical properties of tested soil. In case of horizontally forced vibration, the torque was 8~34% less than in case of vertically forced vibration. 4. With the increase of frequency, the total power requirement increased linearly, and also the portion of oscillating power requirement in the total power tended to increase. The magnitude of the total power requirement was 1.4-13 times greater than that of a static one for the case of horizontal vibration, and 1.5-15 times greater for the case of vertical vibration. It was thought that the horizontal vibration of the blade was preferable to the vertical vibration in view of the power requirement. 5. A linearity was found between the amplitude of moment oscillogram and magnitude of oscillating acceleration. Only positive values of moment occurred when the blade was forced to vibrate vertically, but negative values occurred in rarity in the case of amplitude A3 when the blade was forced to vibrate horizontally.

• Tunnel and Underground Space
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• v.22 no.6
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• pp.373-382
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• 2012

Cessation of dewatering usually results in groundwater rebound after closing an underground coal mine because the mine voids and surrounding strata flood up to the levels of decant points such as shafts and drifts. Several numerical models have been developed to predict the timing, magnitude and location of discharges resulting from groundwater rebound. This study reviews the numerical models such as VSS-NET, GRAM and MODFLOW, and compares their scopes of assessment at different spatial and time scales. In particular, the GRAM model was reviewed in details to implement it. This paper describes the implementation of GRAM model and its application to the Dongwon coal mine in Korea. The application showed that the groundwater level modeled at the shaft of Dongwon coal mine using the GRAM model is similar to the observed one in the field.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.7
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• pp.723-728
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• 2011

Since the performance of a vacuum circuit breaker (VCB) mainly depends on the spring operating mechanism, an analysis of the spring operating mechanism is required in order to improve the design of a VCB. In this study, the static stiffness of the spring was determined by using a material testing machine, and the test results were used to model the spring through computer simulation. The multi-body dynamic model of the spring was established by using the RecurDyn program. The dynamic model was verified by comparing the results of stem displacements and rotating angles of the brake shaft obtained from the simulation and from the experiments. After verification of the dynamic model of VCB, the cam profile of the VCB was optimized through multi-body dynamics simulation in order to improve the performance of the closing mechanism.

• Journal of Biosystems Engineering
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• v.27 no.6
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• pp.479-490
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• 2002

A dynamic model of a power shuttle transmission was developed and its validity was verified using the experimental data obtained from a transmission test bench. A 40㎾, 4WD tractor was also modeled using an application software EASY5 to investigate parameters and their effects on the power shifting performance. For a tractor model, the manual reverse gear was replaced by a power shuttle transmission. The tractor model also included an engine, main-gears for transmission, wheels, differentials and planet gears. Using the tractor model, the effects of the parameters such as modulating pressure and time, engine speed, tractor speed. tractor weight. reverse to forward speed ratio and torsional damper on the transient characteristics at starting and shuttle shifting were investigated by the computer simulation. The transient characteristics were represented by variations in clutch pressure, torque transmitted to input shaft and driving wheels, and power transmission capacity of the clutch. It was found that the modulating pressure and time affected most significantly the torque transmission and shifting time. The input torque, axle torque, power transmission capacity of the clutch and transmission time all increased with increase in engine speed, tractor speed. tractor weight and ratio of reverse to forward speeds. However, the axle torque decreased with tractor speed. Both the axle torque and power transmission capacity of the clutch also decreased with the ratio of reverse to forward speeds.

• Journal of the Society of Naval Architects of Korea
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• v.58 no.6
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• pp.391-399
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• 2021

In order to investigate force and cavitation characteristics for the flat & twisted rudders in the Large Cavitation Tunnel (LCT), the rudder dynamometer was designed and manufactured. The measuring capacities of lift, drag and moment are ±1000 N, ±2000 N, and ±150 N-m, respectively. The present dynamometer uses the actuator with a harmonic drive to control the rudder angle without backlash. As the target ship is a military ship with twin shaft, each dynamometer was installed above the port & starboard rudders. After the installation of the model ship with all appendages, the model test composed of rudder force measurement and cavitation observation was conducted for the existing flat rudder & the designed twisted rudder. While the flat rudder showed the big difference of lift & moment between port & starboard, the twisted rudder presented a similar trend. The cavitation of the twisted rudder showed better characteristics than that of the flat rudder. Another set of model tests were conducted to investigate rudder performance by the change of the design propeller. There was little difference in rudder performance for the design propellers with slight geometric change. Through the model test, the characteristics of the flat & twisted rudders were grasped. On the basis of the present study, it is thought that the rudder with better performance would be developed.

• Computers and Concrete
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• v.32 no.2
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• pp.217-232
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• 2023

Numerous studies have been performed on the behavior of pile foundations in cold regions. This study first attempted to employ artificial neural networks (ANN) to predict pile-bearing capacity focusing on pile data recorded primarily on cold regions. As the ANN technique has disadvantages such as finding global minima or slower convergence rates, this study in the second phase deals with the development of an ANN-based predictive model improved with an Elephant herding optimizer (EHO), Dragonfly Algorithm (DA), Genetic Algorithm (GA), and Evolution Strategy (ES) methods for predicting the piles' bearing capacity. The network inputs included the pile geometrical features, pile area (m²), pile length (m), internal friction angle along the pile body and pile tip (Ø°), and effective vertical stress. The MLP model pile's output was the ultimate bearing capacity. A sensitivity analysis was performed to determine the optimum parameters to select the best predictive model. A trial-and-error technique was also used to find the optimum network architecture and the number of hidden nodes. According to the results, there is a good consistency between the pile-bearing DA-MLP-predicted capacities and the measured bearing capacities. Based on the R2 and determination coefficient as 0.90364 and 0.8643 for testing and training datasets, respectively, it is suggested that the DA-MLP model can be effectively implemented with higher reliability, efficiency, and practicability to predict the bearing capacity of piles.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5C
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• pp.199-206
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• 2009

This paper presents full scale model tests on the various types of model piles carried out to estimate the behavior of laterally loaded steel-concrete composite piles. Subgrade-reaction spring system was developed to simulate the reaction of ground in laboratory condition. In addition, lateral behavior of piles under working load condition was estimated using composite loading system, which is available for independent loading in vertical and horizontal direction. Steel-concrete composite piles showed higher efficiency in lateral resistance rather than drilled shaft made of reinforced concrete. The lateral resistance of composite pile was larger than the summation of steel pile and concrete pile due to the composite effect by steel casing. The effect of shear key or strength of concrete on the behavior of composite pile was examined. The substitution of reinforcing bar by steel casing was also investigated.