• 한국안전학회지
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• 제21권3호
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• pp.107-113
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• 2006

Speeding is one of major causes of frequent and severe traffic accidents in school zones. In this paper, the long-term effectiveness of speed monitoring displays (SMD) on speed variability was investigated through a field study in a school zone environment. The performance difference was discussed with several dependent variables including average speed, 85th percentile speed, and distribution of speed. Study results showed that the speed of vehicles began to reduce where the driver recognized the presence of an SMD, and about 12.4 percent (5.8km/h) of average speed was reduced at the SMD location. This speed reduction was observed throughout the day regardless of time of day. Statistical tests showed that the speed difference was statistically significant. In addition, analysis results of speed distribution showed that the number of speeding vehicle was greatly reduced after the SMD was installed, and 85th percentile speed also decreased from 54.3km1h to 45.0km/h. Therefore, it was concluded that the application of SMD produced a positive impact on the driver's behavior for a long period of times.

• Design & Manufacturing
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• 제16권1호
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• pp.9-14
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• 2022

A lot of research is being done on metal materials to improve the lifespan of molded parts. As a result, excellent mold materials have been developed that withstand high hardness at high temperatures and frictional heat generated from high-speed cutting. In this study, the press mold life of powder high-speed tool steel and general high-speed tool steel was compared. Powdered high-speed steel is composed of alloying elements such as tungsten, maldividene, cobalt, chromium, and vanadium in steel, which improves wear resistance compared to high-hardness and high-speed tool steels. The mold parts of both steel types were manufactured in the same way from heat treatment to machining, and the powder high-speed tool steel was 66HRC and the high-speed tool steel was 61HRC. As a result of the experiment, it was observed that the number of punching of powder high-speed tool steel was improved by 40-50%, and powder high-speed tool steel had fewer impurities, uniform texture, and excellent surface structure. It has a microscopic structure.

• Tribology and Lubricants
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• 제5권2호
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• pp.101-106
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• 1989

Various squeeze film dampers have been theoretically and experimentally studied for flexible rotors. A cylindrical bush damper among them was selected and applied in a test rotor supported with ball bearings. A quiet running of the rotor over a critical speed was observed.

• 오토저널
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• 제9권5호
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• pp.49-56
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• 1987

This paper is a study on the effect of the cutting speed on the tool wear in turning of the glass fiber reinforced plastics. The wear behavior of cutting tool is studied by means of turning, changing the cutting speed and feed in the wide range. Moreover, the theoretical model applicable to the cutting speed of wide range is analysed. The main results obtained are as follows: The relation between the tool wear and the cutting speed is divided into three range in case of the constant cutting distance. 1) At the low cutting speed, the tool wear is independent of the cutting speed, but dependent mainly on the contact length between tool and glass fiber(lst range). 2) At the high cutting speed, the tool wear is independent of the contact length, and dependent on the cutting speed only(2nd range). The tool wear increases in proportion to the cutting speed. 3) At the higher cutting speed than the speed in the 2nd range, the tool wear is independent both of the cutting speed and the contact length(3rd range). 4) In the 3rd range, tool flank wear is constant and is observed that only the wear of cutting edge increases.

• 열처리공학회지
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• 제22권6호
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• pp.339-344
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• 2009

Recently, Laser surface treatment technologies have been used to improve wear charactenitics and fatigue resistance of metal molding. When the laser beam is irradiated on the surface and laser speed is appropriate, the laser focal position is rapidly heated and the thermal energy of surface penetrates the material after irradiation, finally imbuing it with a new mechanical characteristic by the process of self-quenching. This research estimates the material characteristic after efficient and functional surface treatment using HPDL, which is more efficient than the existing CW Nd:YAG laser heat source. To estimate this, microstructural changes and hardness characteristics of three parts (the surface treatment part, heat affect zone, and parental material) are observed with the change of laser beam speed and surface temperature. Moreover, the depth of the hardened area is observed with the change of the laser beam speed and temperature. From the results of the experiments, it has been shown that the maximum hardness is approximately 788Hv when the heat treatment temperature and the travel speed are $1150^{\circ}$ and 2 mm/sec, respectively.

• Geomechanics and Engineering
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• 제32권1호
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• pp.35-47
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• 2023

Deformability of road pavements in the form of ruts represent a safety risk for road users. In the procedures for dimensioning the pavement structure, the requirement that such deformations do not occur is imperatively included, which results in the appropriate selection of elements (material, geometry) of the pavement structure. Deformability and functionality, will depend of the correct design of pavement structure during exploitation period. Nevertheless, there are many examples where deformations are observed on the pavement structure, in the form of rutting at parts of the road with relatively short length, realised in the same climatic and the same geoenvironmental conditions. The performed analysis of deformability led to the conclusion that the level of deformation is a function of the speed of traffic. This effect is observed on city roads, but also outside of urban areas at roads with speed limits are significant, due to the traffic management, traffic jams (intersections, etc.). Still, the lower speed cause greater deformations. The authors tried to describe the deformability of flexible pavement structures, from the aspects of geotechnical problems, as a function of driving speed. Outcome of the analysis is a traffic load correction coefficient, in terms of using the existing methods of flexible pavement structures design.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.237-239
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• 2002

The effect of particle sizes of the metal matrix composites containing 10 wt.%SiCp was investigated with using various tools. The results showed that tool life decreased considerably with increasing particle size and cutting speed. The wear resistance of TiC-coated tools was considerably higher than that of the other tools. It was observed that abrasive wear was the main responsible mechanism for wear of the tool thermal cracks were at high speed while a built-edge formation was also evident at lower speed.

• 대한음성언어의학회:학술대회논문집
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• 대한음성언어의학회 1998년도 제10회 학술대회 심포지움
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• pp.208-209
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• 1998

It is generally known that many cases of pathological rough voice are characterized not by simple random perturbations but by quasi-periodic perturbations in the speech wave. However, there are few studies on the characteristics of perturbations in vocal fold vibrations associated with this type of voice. We have been conducting studies of pathological vocal fold vibration using a high-speed digital image recording system developed by our institute, Compared to the ordinary high-speed-motion picture system, the present system is compact and simple to operate and thus, it suited for pathological data collection. (omitted)

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.161-164
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• 2001

This paper presents a digital speed sensorless control system for Reluctance Synchronous Motor (RSM) drives with direct torque control (DTC). The system consist of stator flux observer, rotor speed estimator, torque estimator two hysteresis band controllers, an optimal switching look-up table. IGBT voltage source inverter, and TMS320C31DSP controller by using fully integrated control software. The stator flux observer is based on the combined voltage and current model with stator flux feedback adaptive control that inputs are current and voltage sensing of motor terminal with estimated rotor angle for wide speed range. The rotor speed is estimated by the observed stator flux-linkage space vector. The estimated rotor speed can be determinated by differentiation of the rotor position used only in the current model part of the flux observer for a low speed operating area. In order to prove the suggested speed sensorless control algorithm. There are some simulation and testing at actual experimental system. The developed digitally high- performance speed sensorless control system are shown a good speed control response characteristic results and high Performance features using 1.0Kw RSM.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1017-1022
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• 2004

This paper presents the conversion speed drive of the cooling tower fans from constant to variable speed. The speed of fan is adjusted using variable speed drives. Since the ambient temperature of cooling tower is varied seasonally, an economic evaluation was performed to determine the potential annual savings. The performances of the proposed technique were observed using cooling tower fans of chemical plant in Thailand as an illustrative case study. The experimental results demonstrating the energy savings fork cooling process and some economic benefits are obtained.