• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.10 s.241
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• pp.1416-1429
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• 2005

In order to meet the increasing competitive pressures coupled with higher demands for component quality, whirling machines have been at the cutting edge of the automobile industry for more than 25 years. The hard whirling process can save on machining time and operation elimination. Hard whirling is done dry, without coolant. The chips carry away nearly all of the heat during cutting, leaving the workpiece cool and minimizing any thermal geometry variations. The surface finish and profile accuracy are close to grinding quality. Whirling machines usually consist of four major parts; 1) loading system that requires the necessary axial speeds, 2) head stock that needs high precision clamping and positioning system at the chuck and tailstock, 3) whirling unit that demands the high cutting speeds and cutting power fer cutting deep thread profiles and 4) unloading system that requires an easy workpiece unloading. Also, capabilities of the whirling machine can be improved by attaching a vision system to the machine. Most of whirling machines in Korean automobile industry are imported from the Leistritz company, Germany and the Hasegawa company, Japan. Tn this paper, a basic research will be performed to improve and enhance the existing whirling machines. Finally, a new Korean whirling machine will be proposed and developed.

• Geomechanics and Engineering
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• v.37 no.1
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• pp.49-64
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• 2024

Rocks undergoing repeated loading and unloading over an extended period, such as due to earthquakes, human excavation, and blasting, may result in the gradual accumulation of stress and deformation within the rock mass, eventually reaching an unstable state. In this study, a CNN-CCM is proposed to address the mechanical behavior. The structure and hyperparameters of CNN-CCM include Conv2D layers × 5; Max pooling2D layers × 4; Dense layers × 4; learning rate=0.001; Epoch=50; Batch size=64; Dropout=0.5. Training and validation data for deep learning include 71 rock samples and 122,152 data points. The AI Rock Constitutive Model learned by CNN-CCM can predict strain values(ε₁) using Mass (M), Axial stress (σ₁), Density (ρ), Cyclic number (N), Confining pressure (σ₃), and Young's modulus (E). Five evaluation indicators R², MAPE, RMSE, MSE, and MAE yield respective values of 0.929, 16.44%, 0.954, 0.913, and 0.542, illustrating good predictive performance and generalization ability of model. Finally, interpreting the AI Rock Constitutive Model using the SHAP explaining method reveals that feature importance follows the order N > M > σ₁ > E > ρ > σ₃.Positive SHAP values indicate positive effects on predicting strain ε₁ for N, M, σ₁, and σ₃, while negative SHAP values have negative effects. For E, a positive value has a negative effect on predicting strain ε₁, consistent with the influence patterns of conventional physical rock constitutive equations. The present study offers a novel approach to the investigation of the mechanical constitutive model of rocks under cyclic loading and unloading conditions.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.4
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• pp.65-73
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• 2002

It has been recognized that the damage control must become a more explicit design consideration. In an effort to develop design methods based on performance it is clear that the evaluation of the nonlinear response is required. The methods available to the design engineer today are nonlinear time history analyses, monotonic static nonlinear analyses, or equivalent static analyses with simulated nonlinear influences. Some building codes propose the capacity spectrum method based on the nonlinear static analysis(pushover analysis) to determine the earthquake-induced demand given by the structure pushover curve. These procedures are conceptually simple but iterative and time consuming with some errors. This paper presents a nonlinear direct spectrum method(NDSM) to evaluate seismic performance of structures, without iterative computations, given by the structural initial elastic period and yield strength from the pushover analysis, especially for MDF(multi degree of freedom) systems. The purpose of this paper is to investigate the accuracy and confidence of this method from a point of view of various earthquakes and unloading stiffness degradation parameters. The conclusions of this study are as follows; 1) NDSM is considered as practical method because the peak deformations of nonlinear system of MDF by NDSM are almost equal to the results of nonlinear time history analysis(NTHA) for various ground motions. 2) When the results of NDSM are compared with those of NTHA. mean of errors is the smallest in case of post-yielding stiffness factor 0.1, static force by MAD(modal adaptive distribution) and unloading stiffness degradation factor 0.2~0.3.

• Transactions of the Society of Information Storage Systems
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• v.5 no.2
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• pp.70-75
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• 2009

Most hard disk drives uses load/unload technology because of benefits as like an increased areal density, a reduced power consumption and an improved shock resistance. However, ramp tilt induced by ramp manufacture and assembly causes mechanical problems such as unload fail in case of exceeding ramp tolerance. In this paper, we focus on experimental analysis for unloading characteristics affected by ramp tilt. We repeatedly perform load/unload test as 500,000 cycles for original model and ramp tilt model. This paper shows that it is possible to analyze unload characteristics through measuring scratch and wear of suspension lift-tab, ramp, suspension dimple-flexure and disk. We also identify structural relation between suspension lift-tab and ramp through scratch and wear of suspension lift-tab and ramp. As the result of measurement and analysis, we can investigate decrease of unloading performance in ramp tilt model.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.7
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• pp.542-549
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• 2002

Computer simulation is essential to design the suspension elements of railway vehicle. By computer simulation, engineers can assess the feasibility of given design variables and chance them to get a bettor design. Even though commercial simulation codes are used, the computational time and cost remains non-trivial. Therefore, malty researchers have used a mesa model made by sampling data through simulation. In this paper, four mesa-models for each index group such as ride comfort, derailment Quotient, unloading radio and stability index, are constructed by use of neural network. After these meta models are constructed, multi-objective optimization are achieved by using the differential evolution. This paper shows that the optimization of design variables using the neural network model is very efficient to solve the complex optimization Problem.

• Proceedings of the Korean Magnestics Society Conference
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• 2007.05a
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• pp.259.1-259.1
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• 2007

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.249-252
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• 1997

In this paper the sway-control problem of a container crane is investigated in the perspective of controlling an underactuated mechanical system. For fast loading/unloading of containers from the ship, quick suppression of the remaining swing motion of the container at the end of each trolley stroke is crucial. Known nonlinearities are fully incorporated by feedback linearization. Robustness is enhanced by variable structure control. Compared with the linear LQ control, much better performance can be obtained.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.05a
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• pp.570-571
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• 2010

• Proceedings of the KSR Conference
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• 2000.05a
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• pp.125-134
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• 2000

This paper presents the results of vehicle dynamics simulation for development of single axle bogie for freight vehicle. Those results consists of hunting stability, ride comfort and curving performance such as derailment ratio, unloading ratio. Dynamic behaviors of vehicle having single axle bogie is carried out using the multi-body dynamics simulation program(VAMPIRE). The results of analysis meet the criteria proposed by Korean National Railroad(KNR) and Korea Railroad Research Institute(KRRI).

• Proceedings of the Safety Management and Science Conference
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• 2006.11a
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• pp.287-292
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• 2006

Reducing the logistic cost may be accomplished by numbers of logistic management methods, but the most fundamental and essential one is the accomplishment of the consistent reverse logistics system that is the core of worker performance system, and the purpose of consistent reverse system is the treatment of logistic functions such as transportation, storage and unloading with consistent logistics, and increasing the turnover ratio is required for the improvement of the system. As the turnover ratios is increased, this paper make reverse worker performance evaluation system with lifetime value include of weight variables.