• International Journal of Highway Engineering
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• v.18 no.2
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• pp.103-110
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• 2016

PURPOSES: In this paper, the effectiveness of speed-maintained standardization in road geometry on environmental impact at a downward slope location, based on greenhouse gas (GHG) emission indicators, was studied. Specifically, the aim of this study was to ascertain whether speed-maintained standardization resulted in decreased $CO_2$ emissions as well as noise pollution, due to reduced vehicle speeds. METHODS : In this study, speed-maintained standardization in road geometry was proposed as a means to reduce vehicle speeds, with a view to reducing $CO_2$ emissions and noise pollution. This technique was applied at a downward slope location. The vehicle speeds, $CO_2$ emissions, and noise levels before and after application of speed-maintained standardization were compared. RESULTS: It was found that speed-maintained standardization was effective as a means to reduce speed, as well as $CO_2$ emissions and noise pollution. By applying speed-maintained standardization, it was confirmed that vehicle speeds were reduced consistently. As a result, $CO_2$ emissions and noise levels were decreased by 9% and 11%, respectively. CONCLUSIONS : This study confirmed that speed-maintained standardization in road geometry is effective in reducing vehicle speeds, $CO_2$ emissions, and noise levels. Moreover, there is further scope for the application of this method in the design of roads in urban and rural areas, as well as in the design of highways.

• Journal of The Korean Society of Agricultural Engineers
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• v.63 no.5
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• pp.39-47
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• 2021

With rising concerns about pesticide spray drifts, this study analyzed the drift patterns of two typically-used nozzles, XR nozzle and AI nozzle, concerning their working pressures and wind speeds by wind tunnel experiments. AI nozzle showed low drift potential with larger droplet sizes compared to XR nozzle. Airborne and deposition drifts of XR nozzle were two times higher than those of AI nozzle under high wind speeds (≥2 m s^-1). In all cases, higher working pressures decreased the droplet sizes, thereby increasing the airborne and deposition drifts. Higher wind speeds also resulted in more airborne drifts, while ground deposition was increased under lower wind speeds. These effects of working pressures and wind speeds on the airborne and deposition drifts were observed at leeward distances less than 4 m from the nozzles. However, the airborne and deposition drifts were barely affected by the working pressures and wind speeds at leeward distances more than 11 m. The measurements were fitted to regression models of the drift curve with acceptable R² values greater than 0.8, demonstrating that further studies will be useful to settle domestic issues of spray drifts.

• Tribology and Lubricants
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• v.35 no.3
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• pp.190-198
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• 2019

Gas foil bearings (GFBs) enable small- to medium-sized turbomachinery to operate at ultra-high speeds in a compact design by using ambient air or process gas as a lubricant. When using air or process gas, which have lower viscosity than lubricant oil, the turbomachinery has the advantage of reduced power loss from bearing friction drag. However, GFBs may have high Reynolds number, which causes turbulent flows due to process gas with low viscosity and high density. This paper analyzes gas foil journal bearings (GFJBs) with high Reynolds numbers and studies the effects of turbulent flows on the static and dynamic performance of bearings. For comparison purposes, air and R-134a gas lubricants are applied to the GFJBs. For the air lubricant, turbulence is dominant only at rotor speeds higher than 200 krpm. At those speeds, the journal eccentricity decreases, but the film thickness, power loss, and direct stiffness and damping coefficients increase. On the other hand, the R-134a gas lubricant, which that has much higher density than air, causes dominant turbulence at rotor speeds greater than 10 krpm. The turbulent flow model predicts decreased journal eccentricity but increased film thickness and power loss when compared with the lamina flow model predictions. The vertical direct stiffness and damping coefficients are lower at speeds below 100 krpm, but higher beyond that speeds for the turbulent model. The present results indicate that turbulent flow effects should be considered for accurate performance predictions of GFJBs with high Reynolds number.

• Journal of Life Science
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• v.13 no.1
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• pp.21-28
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• 2003

The purpose of this experiment was to compare the energy expenditure and the physiological response among two groups by percent body fat(group A: 30-35% body fat, B: 35-40% body fat) to walking and running at several equivalent speeds. Subjects in group A and B followed A group(mean$\pm$SD, age; 24.0$\pm$0.4yrs, body fat; 32.3$\pm$0.7) and B group (age; 25.2$\pm$0.7yrs, body fat; 36.7$\pm$0.9). The walking and running protocol consisted of treadmill speeds for five min at each of the following speeds: 5.0, 5.5, 6.0, 6.5, 7.0 km.$hr^{-1}$. The obtained data reveal in group A, the rate of oxygen consumption and energy expenditure was higher during walking compared to running ate treadmill speeds $\geq$ 6.6km.$hr^{-1}$. In group 5, the rate of oxygen consumption and energy expenditure was higher during walking compared to running ate treadmill speeds $\geq$ 6.8km.$hr^{-1}$. Heart rates and respiratory exchange ratio were higher at treadmill speeds $\geq$5.8 in group A and $\geq$5.5 in group B. these findings demonstrated that a difference of percent body fat in obese women have no large effect on energy efficiency of walking, but walking within speeds 6.5~7.0km/hr resulted in rates of energy expenditure that were as high or higher than jogging at the same speeds even though the relative stress was greater during walking.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.6
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• pp.1851-1861
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• 2014

This study aims to calculate reliable sectional travel speeds with the consideration of the characteristics of the probe data collected in the interrupted traffic flow. First, in order to analysis the characteristics of the probe data, we looked into the distribution of the sectional travel times of each probe vehicle and compared the difference in the sectional travel speeds of each probe vehicle collected by DSRC. As a result, it is shown that outliers should be removed for the distribution of the sectional travel times. However, The comparison results show that the sectional travel speeds from the DSRC probe vehicles are not significantly different. Finally, based on the distribution characteristics of the sectional travel speeds of each probe vehicle and the representative values counted during a collection period, we drew the optimal outlier removal procedure and evaluated the estimation errors. The evaluation results showed that the DSRC sectional travel speeds were found to be similar to the observed values from actually running vehicles. On the contrary, in the case of the sectional travel speeds of intra-city bus, it was analyzed that they were less accurate than the DSRC sectional travel speeds. In the future, it will be necessary to improve BIS process and make use of the travel information on intra-city buses collected in real time to find various ways of applying it as traffic information.

• Journal of Industrial Convergence
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• v.18 no.3
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• pp.53-61
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• 2020

Travel speed is an important parameter for measuring road traffic and incident detection system. In this paper I suggests a model developed for estimating reliable and accurate average roadway link travel speeds using image processing sensor. This method extracts the vehicles from the video image from CCTV, tracks the moving vehicles using deep neural network, and extracts traffic information such as link travel speeds and volume. The algorithm estimates link travel speeds using a robust data-fusion procedure to provide accurate link travel speeds and traffic information to the public. In the field tests, the new model performed better than existing methods.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.7
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• pp.2289-2297
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• 1996

Flows in the combustion chamber near the spark plug are measured using LDv.A single cylinder DOHC S.I. engine of compression ratio 9.5:1 with a transparent quartz window piston is used. Combustion chamber shape is semi-wedge type. Measured data are analyzed using the ensemble averaged analysis and the cycle resolved analysis which uses FFT Filtering. Turbulent intensity and mean velocity are studied in the main flow direction and the normal to main flow direction as a function of engine speeds. The results shows that the turbulent intensity obtained by the ensemble averaged analysis is greater than that calculated by the cycle resolved analysis. Especially, the ensemble averaged analysis shows increase in turbulence at the end of compression stroke although the cycle resolved analysis shows increase only in the cycle-by-cycle variation with no noticeable increase in turbulence. The mean velocity in the main flow direction increase as engine speed increase. But the mean velocity normal to the main flow does not show such increase. Turbulent intensity in both direction increase in proportion to engine speeds. The magnitude of turbulent intensity is about 0.3 ~ 0.4 times the mean piston speeds at the end of the compression stroke.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.4
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• pp.301-307
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• 2013

MRU(motor reduction unit) for KTX is a assembled complex structure that is equipped with a lot of parts at the express train KTX and that is the core power source operating variable speeds. This study is recorded the dynamic characteristics analysis results tested by EMA which is done through the parts and assembly test, transient analysis and stoped train test in order to design the online monitoring system for KTX MRU. And the mode shapes result from critical vibration frequency explain the relation with variable speeds of express train over 250 km/hr. Also these variable speeds make variable operational frequencies at pinion, axle gear mesh frequency and normal bearing fault frequencies. As the specified speed can make resonance with natural frequencies of the MRU, for the train operating stability, this study also presents the MRU's critical speeds calculated by the each train speed.

• Bulletin of the Korean Space Science Society
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• 2011.04a
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• pp.28.3-28.3
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• 2011

Halo coronal mass ejections (HCMEs) are mainly responsible for the most severe geomagnetic storms. To minimize the projection effect of the HCMEs observed by coronagraphs, several cone models have been suggested. These models allow us to determine the geometrical and kinematic parameters of HCMEs : radial speed, source location, angular width, and the angle between the central axis of the cone and the plane of the sky. In this study, we compare these parameters form two representative cone models (the ice-cream cone model and the asymmetric cone model) using well-observed HCMEs from 2001 to 2002. And we obtain the root mean square error (rms error) between observed projection speeds and calculated projection speeds for both cone models. It is found that the average rms speed error (89 km/s) of the asymmetric cone model is a little smaller than that (107 km/s) of the ice-cream cone models, implying that the radial speeds from both models are reasonably estimated. We also find that the radial speeds obtained from two models are similar to each other with the correlation coefficient of about 0.8.

• Journal of Biosystems Engineering
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• v.32 no.5
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• pp.324-331
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• 2007

The purpose of this study is to analysis effects of defect factors of combine header for cutting speed of combine header, feeding depth of straw, and cylinder speed of thresher. Measurement system for defect factors was consists of sensors to monitor the combine operation and I/O interface to convert the signals. Cutting speed of combine header, feeding depth of straw, cylinder speed of thresher were measured and analyzed. The data were collected from three paddy field during rice harvesting. The tests were conducted at different grounding speeds, lug troubles, and cutter condition. The one way ANOVA and the multiple comparison tests were performed. The results showed that the measured data were useful to monitor the defect factors of combine during harvesting. The faults conditions of grounding speeds, lug troubles, and cutter conditions affected cutting speeds, feeding depths and cylinder speeds of the combine. The data seem to be useful to analysis the faults conditions of combine header.