• Journal of Korean Society of Transportation
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• v.27 no.3
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• pp.39-47
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• 2009

Currently, the minimum breadth as a point available for U-turn setup is designated as "over 9m for one way" in the traffic safety facilities practical manuals, and vehicles allowed to make a U-turn are limited to passenger cars. However, as passenger cars have recently become larger and SUVs (Sports Utility Vehicles) are being popularized, they fail to make a U-turn in one attempt. This causes a traffic jam and a problem with traffic safety. This study proposed, compared, and tested the measured values of actual differences in the turning radius of U-turn by actual cars with estimated values by using PC-Crash, a car accident simulation program. Then, the study forecasted the turning radius of U-turns of Korean passenger cars by using PC-Crash, and proposed appropriate breadth for U-turn setup.

• Magazine of the Korean Society of Agricultural Engineers
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• v.18 no.2
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• pp.4096-4104
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• 1976

This experiment was carried out to investigate the efficient turning method which will be able to use every cutting methods, to calculate the width of the center field which must transpose from rotary cutting method to return cutting method, to investigate the effects of L/W and unit field on the operation efficiency. The results are summarized as follows: 1. In case of cutting in the outer field, the efficient turning method is the "$\alpha$" type turning method (half U-shaped turning method) at the first rotation, is the "$\beta$" type turning method (T-shaped turning method) at the second to fourth rotation. 2. In case of cutting in the inner field, the efficient turning method which takes the least turning time is the "a" type turning method ($\Delta$-shaped turning method). 3. The width of the center field (W') changes by the length-width ratio (L/W) and width (W), W' is 9.0m in case that L/W is 2.5 and W is 30m. 4. The larger L/W and area of unit field (A) become, the more operation efficiency (E) increases, and the limits that E is affected signicantly by L/W is 2 to 3.5 and A is within 5,000$m^2$. within 5,000$m^2$.

• Journal of Biosystems Engineering
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• v.43 no.4
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• pp.273-284
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• 2018

Purpose: Conventional headland turning typically requires repeated forward and backward movements to move the farming equipment to the next row. This research focuses on developing an upland agricultural robot with an optimized headland turning mechanism that enables a $180^{\circ}$ turning positioning to the next row in one steering motion designed for a two-wheel steering, four-wheel drive agricultural robot named the HADA-bot. The proposed steering mechanism allows for faster turnings at each headland compared to those of the conventional steering system. Methods: The HADA-bot was designed with 1.7-m wide wheel tracks to travel along the furrows of a garlic bed, and a look-ahead path following algorithm was applied using a real-time kinematic global positioning system signal. Pivot turning tests focused primarily on accuracy regarding the turning radius for the next path matching, saving headland turning time, area, and effort. Results: Several test cases were performed by evaluating right and left turns on two different surfaces: concrete and soil, at three speeds: 1, 2, and 3 km/h. From the left and right side pivot turning results, the percentage of lateral deviation is within the acceptable range of 10% even on the soil surface. This U-turn scheme reduces 67% and 54% of the headland turning time, and 36% and 32% of the required headland area compared to a 50 hp tractor (ISEKI, TA5240, Ehime, Japan) and a riding-type cultivator (CFM-1200, Asia Technology, Deagu, Rep. Korea), respectively. Conclusion: The pivot turning trajectory on both soil and concrete surfaces achieved similar results within the typical operating speed range. Overall, these results prove that the pivot turning mechanism is suitable for improving conventional headland turning by reducing both turning radius and turning time.

• Journal of Biosystems Engineering
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• v.38 no.4
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• pp.255-263
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• 2013

Purpose: It is not easy to drive a rice-transplanter avoiding underlapped or overlapped transplanting in paddy fields. An automated guidance system for the riding-type rice-transplanter would be necessary to operate the rice-transplanter autonomously or to assist the beginning drivers as a driving aid. Methods: A prototype of guidance system was composed of embedded computers, RTK-GPS, and a power-steering mechanism. Two Kalman filters were adopted to overcome sparse positioning data (1 Hz) from the RTK-GPS. A global Kalman filter estimated the posture of rice-transplanter every one second, and a local Kalman filter calculated the posture from every new estimation of the global Kalman filter with an interval of 200 ms. A PID controller was applied to the row-following mode control. A control method of U-turning mode was developed as well. A stepping motor with a reduction gear set was used to rotate the shaft of steering wheel. Results: Test trials for U-turning and row-following modes were done in a paddy field after some parameters have been tuned at the ground speed range of 0.3 ~ 1.2 m/s. The minimum RMS error of offset was 3.13 cm at the ground speed of 0.3 m/s while the maximum RMS error was 13.01 cm at 1.2 m/s. The offset RMS error tended to increase as the ground speed increased. The target point distance, LT also affected the system performance and PID controller parameters should be adjusted on different ground speeds. Conclusions: A target angle-based PID controller plus stationary steering angle controller made it possible for the rice-transplanter to steer autonomously by following a reference line accurately and even on U-turning mode. However, as condition in paddy fields is very complicated, the system should control the ground speed that prevents it from deviating too much due to ditch and slope.

• Journal of Korea Trade
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• v.26 no.1
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• pp.1-19
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• 2022

Purpose - This paper analyzes the economic and non-economic factors that contribute to environmental sustainability by reducing CO₂ emissions, based on G20 panel data. Design/methodology - We conduct a comparative analysis of advanced and developing economies during 1995-2016. To examine the impact, an environmental Kuznets curve (EKC) model was employed, incorporating additional explanatory variables such as internet use, renewable energy, and services trade. Findings - The empirical findings show the existence of an inverted U-shaped EKC phenomenon between GDP per capita and CO₂ emissions in G20 economies, with the turning point at a per capita GDP level of US$ 38,340. Moreover, an inverted U-shape relation exists between internet use and CO₂ emissions, with the turning point at a 44% internet use rate. The comparative analysis show that the inverted U-shape curve only exits in advanced economies, with turning points of US$ 42,356 per capita GDP and 27% internet use rate, respectively. Renewable energy and services trade have a greater negative impact on CO₂ emissions in advanced economies than in developing economies. Originality/value - Renewable energy and services trade have a greater negative impact on CO₂ emissions in advanced economies than in developing economies. Overall, the results suggest the role of internet use, renewable energy and services trade in sustainable development in G20 countries.

• Journal of Power System Engineering
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• v.4 no.4
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• pp.108-115
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• 2000

The continuous chip in turning operation deteriorates the precision of workpiece and can cause a hazardous condition to operator. Thus the chip form control becomes a very important task for reliable turning process. Using the difference of energy radiated from the chip, the chip form is identified using the neural network of supervised data. The feed mechanism is adjusted in order to break continuous chip according to the result of the chip form recognition and shows a good approach for precision turning operation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.8
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• pp.1077-1087
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• 2002

The heat (mass) transfer characteristics on the blade surface of a high-turning first-stage turbine rotor for power generation has been investigated by employing the naphthalene sublimation technique. A four-axis profile measurement system is developed successfully for the measurements of local sublimation depth on the curved surface In the leading edge region, there is a good agreement between the present heat (mass) transfer data and the previous result on a turbine blade with a moderate turning angle, but some discrepancies are found in the mid-chord heat (mass) transfer between the two results. The local heat (mass) transfer on the present suction surface is greatly enhanced due to an earlier boundary transition, compared with that on a turbine blade with a moderate turning angle, meanwhile there is only a slight change in the pressure-side heat (mass) transfer between the two different turbine rotors. In general, the heat (mass) transfer augmentation by the endwall vortices is found much higher on the suction surface than on the pressure surface.

• Journal of the Korean Institute of Navigation
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• v.10 no.2
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• pp.83-96
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• 1986

In the restricted sea way such as fair way in harbor, narrow channel etc, the safe ship-handling is a very important problem, which is greatly related with turning ability of ships. It is of great importance that ship-handlers can grasp the position of pivoting point varying with time increase at any moment for relevant steering activities. Mean while, in advanced ship-building countries they study and investigated pivoting point related with turning characteristics, hut their main interest lies in ship design, not in safe ship controlling and maneuvering. In this regards it is the purpose of this paper to provide ship-handlers better under standing of pivoting point location together with turning characteristics and then to help them in safe ship-handling by presenting fact that pivoting points vary according to configuration of ships. The author calculated the variation of pivoting point as per time increase for various type of vessels, based on the hydrodynamic derivatives obtained at test of Davidson Laboratory of Stevens Institutes of Technology , New Jersey, U.S.A. The results were classified and investigated according to the magnitude of block coefficient , length-beam ratio, length-draft ratio, rudder area ratio ete, and undermentioned results were obtained. (1) The trajectory of pivoting point due to variation of rudder angle are all the same at any time, though the magenitude of turning circle are changed variously. (2) The moving of pivoting point is affected by the magnitude of block coefficient, length-beam ratio, length-draft ratio, however the effect by rudder area ratio might be disregarded. (3) In controlling and maneuvering of vessels in harbor, ship-handlers might regard that the pivoting point would be placed on 0.2~0.3L forward from center of gravity at initial stage. (4) The pivoting point of VLCC or container feeder vessels which have block coefficient more than 0.8 and length-beam ratio less than 6.5 are located on or over bow in the steady turning. (5) When a vessel intends to avoid some floating obstruction such as buoy forward around her eourse, the ship-handler might consider that the pivoting point would be close by bow in ballast condition and cloase by center of gravity in full-loaded condition.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.1121-1122
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• 2013

• Journal of the Korean Society for Precision Engineering
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• v.17 no.12
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• pp.68-75
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• 2000

This paper presents the construction of an ultra-precision machining system and machining experiments using the developed system. The system is composed of air bearing system, granite bed, air pad, and linear feeding mechanism. The cutting conditions have great effect on the surface quality in ultra-precision machining. the ultra-precision machining is mainly processed by several ${\mu}{\textrm}{m}$ depth of cut and feed rate. For this, tools with sharper cutting edge and less tool wear are needed. To satisfy these requirement, diamond is generally used as a tool material for ultra-precision machining. In order to evaluate the cutting characteristics of the PCD and MCD tools on the aluminum alloy, the machining experiments performed using the developed system.