• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.2
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• pp.234-242
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• 1999

Flow phenomena such as the pressure transients Inside a high-speed railway tunnel and the Impulsive waves at the exit of the tunnel are closely associated with the characteristics of the entry compression wave, which is generated by a train entering the tunnel. Tunnel entrance hood may be an effective means for alleviating the Impulsive waves and pressure transients. The objective of the current work is to explore the effects of the train nose shape and the entrance hood on the characteristics of the entry compression wave. Numerical calculations using the method of characteristics were applied to one-dimensional, unsteady, compressible flow field with respect to high-speed railway/tunnel systems. Two types of the entrance hoods and various train nose shapes were employed to reveal their influences on the entry compression wave for a wide range of train speeds. The results showed that the entry compression wave length increases as the train nose becomes longer and the train speed becomes lower. The entry compression wave length in the tunnel with hood becomes longer than that of no hood. Maximum pressure gradient in the compression wavefront reduces by the entrance hood. The results of the current work provide useful data for the design of tunnel entrance hood.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.6D
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• pp.637-643
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• 2012

This research collected work drilling report of TBM method site developed by WRITH company to TBM equipment company in Germany and analyzed work operating productivity. Based Oil the data analyzed TBM operating productivity, This research derived and presented excavation speed (m/day) by TBM diameter (3.0m, 3.5m, 3.8m) and rock. Also, based on the excavation speed (m/day) by TBM diameter, This research estimated a day direct construction cost and total direct construction costs by applying a direct construction cost which spent on per 1m. When we perform a similar geological construction in the future, excavation speed and direct construction cost which were derived by TBM diameter and rock is thinking the effective utilization data to estimate construction cost and plan schedule management before the start of construction.

• Journal of Welding and Joining
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• v.24 no.5
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• pp.62-66
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• 2006

Panel line is an important process occupying the largest work amount in shipbuilding. In this research product simulation has been carried out to establish the optimal production scheduling. For this purpose a web-based panel line simulator was developed using an object modeling technology and C# language. The balance of work-load and increase in the productivity by the improvement of production facilities and process are the key factors for a good scheduling. In this study SPRT(Shortest Remaining Process Time) rule was applied for the work-load balancing and a good result achieved. To increase the productivity in the stiffener welding stage which is a bottleneck; process, more welding heads and higher welding speed were tested using the developed simulator. The simulation results showed that either more welding head or higher welding speed decreased the total work time. Use of both, however, deteriorated the productivity because of the bottleneck in the following stage. This result points out that the improvement of production facilities and/or process should be evaluated with their influences on the leading and following processing stage.

• Korean Journal of Adult Nursing
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• v.29 no.2
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• pp.190-199
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• 2017

Purpose: The purpose of this study was to investigate the differences in sleep, fatigue, and neurocognitive function between shift nurses and non-shift nurses. Methods: A cross-sectional descriptive study design was used. A total of 100 nurses participated in the study. 50 were shift nurses and the remaining 50 were non-shift nurses. The Pittsburgh Sleep Quality Index, Fatigue Severity Scale, and a computerized neurocognitive function test (CNS Vital Signs-VS4) were administered to the subjects to assess verbal and visual memory, processing speed, reaction time, and simple attention. After the last night shift, the shift nurse conducted the study at around 8:00 am and the non-shift nurse participated after work. Results: Compared to non-shift nurses, shift nurses had a significantly lower sleep quality (p=.002) and higher fatigue (p=.001) and achieved significantly lower scores on verbal memory (p=.001), processing speed (p=.003), and reaction time (p=.018). There were significant correlations between sleep quality and processing speed (p=.042), and reaction time (p=.015) of shift nurses who were bad sleepers. Conclusion: This study findings suggest shift work could interfere with cognitive function. Personal and organizational programs should be developed to support their sleep and neurocognitive function.

• Journal of the Korean Society of Safety
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• v.17 no.3
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• pp.1-6
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• 2002

A dynamic characteristics of shock absorber in the various excitation is investigated experimentally. Work diagrams and characteristic curves are used as a experimental standard. The various excitation conditions temperature and noise are very important factors in associated with the reduction of damping force. It is found that the heat occurrence from shock absorber, the gas shock absorber is much higher than oil shock absorber and increased in high speed. As to the variation of damping force, there are no change when the speed is low but we fixed amount of variation by increasing speed and change of new and old decrease. The sound pressure of the swash noise from cycle of shock absorber, we compared with theory sound pressure by experiment.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1270-1276
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• 2003

This paper describes an analytical method for wheel wear prediction. The outputs from vehicle dynamic software are used to calculation the wheel wear. Two calculation examples are shown for a high-speed line and a conventional line. Through the comparison of two cases, we can see the wheel wear characteristics on the conventional line and the high-speed line. The conventional line has many curved tracks that cause severe wheel flange wear. The influences of curve radius on wheel wear are also described considering the operational performance of the high speed trainset. A method of calculation using contact patch work model is presented for determination of the evolution by wear railway wheels.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.7
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• pp.59-64
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• 2002

Laser lithography technique is useful for fabricating micro-patterns of silicon wafers. In this work, the laser lithography micromachining technique is optimized based on Taguchi method. Sensitivity analysis was performed using laser scanning speed, laser power level, developing time and mixture ratio between developer and Di-water as the parameters. The results show that for the photoresist used in this work, 70${\mu}m$/s scan speed, 50㎽ laser power, 60sec. developing time and 6: 1 mixture ratio gives the best result. This work shows the effectiveness of laser lithography technique in fabricating patterns with a flew micrometer in width.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.256-259
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• 2004

In the present study, AZ31B sheets has a bad formability in room temperature, but the formability is improved significantly as increasing the temperature because of rolled magnesium alloy sheet has a hexagonal closed packed structure (HCP) and a plastic anisotropy. In this paper, after tensile test in various temperatures, strain rate, show the tensile mechanical properties, yield and ultimate strength, K-value, work hardening exponent(n), strain rate sensitivity(m). As temperature increased, yield, ultimate strength and K-value, work hardening exponent(n) are decreased but strain rate sensitivity(m) is increased. As cross-head-speed increased, yield, ultimate strength and K-value, work hardening exponent(n) are increased. And according to the temperature, how change the plastic anisotropy factor R. In addition, we observed how temperatures and cross-head-speed effect on microstructure.

• International Journal of Computer Science & Network Security
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• v.21 no.11
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• pp.23-30
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• 2021

Sentiment Analysis has become very important field of research because posting of reviews is becoming a trend. Supervised, unsupervised and semi supervised machine learning methods done lot of work to mine this data. Feature engineering is complex and technical part of machine learning. Deep learning is a new trend, where this laborious work can be done automatically. Many researchers have done many works on Deep learning Convolutional Neural Network (CNN) and Long Shor Term Memory (LSTM) Neural Network. These requires high processing speed and memory. Here author suggested two models simple & bidirectional deep leaning, which can work on text data with normal processing speed. At end both models are compared and found bidirectional model is best, because simple model achieve 50% accuracy and bidirectional deep learning model achieve 99% accuracy on trained data while 78% accuracy on test data. But this is based on 10-epochs and 40-batch size. This accuracy can also be increased by making different attempts on epochs and batch size.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.14 no.2
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• pp.21-26
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• 2005

From on the machining center cutting work of 5534, the characteristics such as spindle speed and feed speed fir the third point height, average spacing of roughness peaks, bearing ratio, center line average, ten point height. experiments is roughness for sampling length determine to measuring length of cutting feed speed 200, 400, 600, 800mm/min and spindle speed 800, 1000, 1200, 1400rpm. Third point height is spindle speed with most suitable cutting condition 1000rpm. Third point height is feed speed with most suitable cutting condition 400mm/min. Average spacing of roughness peaks are spindle speed with most suitable cutting condition feed speed increased to average spacing of roughness Peaks are increased. Spindle speed increased to average spacing of roughness peaks are decreased. Bearing ratio is spindle speed with feed speed increased to bearing ratio decreased. Center line average is spindle speed with most suitable cutting condition at 1200rpm feed speed with most suitable cutting condition at 200mm/min to cutting foe roughness suddenly decreased. Ten point height is spindle speed with most suitable cutting condition 1200rpm at ten point height cutting face roughness to decreased and feed speed with most suitable cutting condition 800mm/min at ten point height cutting face roughness to decreased.