• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1999.05a
• /
• pp.669-672
• /
• 1999

In this paper, we studied the properties of small-size disk-type ultrasonic motor using travelling wave for the application to the precise control robotic joint motor and fabricated it. The diameter of the ultrasonic motor fabricated was 13mm. Also, the piezoelectric vibrator was constructed by piezoelectric ceramic and elastic material. The piezoelectric ceramic was composed to PZ-PT-PMN which was shown the high electromechanical stability under high vibration level and stainless steel was used as the elastic material in which configuration was disk-type. To conform the capability of application to robotic motor, we measured the change of rotational speed according to applied voltage and applied frequency. As the results, the small-size disk-type ultrasonic motor was able to fabricate, and the revolution speed was 350 (rpm) when input voltage was 55 (Vrms) and applied frequency 160.4 IkHz] under pre-load.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.19 no.4
• /
• pp.576-581
• /
• 2010

As a super high speed small-sized centrifugal separator which is operated by the center inputting method has solved two difficulty problems, it can be made use of developing the new composition through the making of Nano particle (50~100nm) by high speed revolution and alleviation of unbalanced shapes inside the disk continuously throwing slurry in the central part. Uses the air spindle and the centrifugal machine production will be able to manufacture the Roh class fine particle under boil.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1999.11a
• /
• pp.323-326
• /
• 1999

In this paper, a windmill type ultrasonic motor operated by single-Phase AC electric field was fabricated, and then torque characteristics were investigated. A metal-ceramic composite component was used as the stator\`s vibrator to generate ultrasonic vibrations. The windmill type ultrasonic motors has only three components; a stator element with two wind-mill shape slotted metal endcaps, a rotor and a bearing. In this parer we measured torque, when stator\`s slot was changed Iron 4, 6, 8. Brass metal was pressed with umbrella-type using metal molt then slot of 3 kind was manufactured. The maximum revolution speed was 388(rpm) in the case of a small ultrasonic motor of 11.35 mm diameter, 8 slot and 1.01 mm thickness. The maximum torque of 0.17 mNm was obtained at a speed of 131 rpm.

• Journal of Advanced Navigation Technology
• /
• v.14 no.1
• /
• pp.93-101
• /
• 2010

In this study, the performance characteristics of turbocharged engine is analyzed. The methods of engine performance improvements are suggested not only for full load characteristics of the engine but also for partial load characteristics of the engine, which is more frequently used in actual driving conditions. The compression ratio of the compressor is increased rapidly in a straight line pattern until 1260 engine rpm, and after that it is increased slowly to 2.5 ratio. Also the brake mean effective pressure increased until 1260 engine rpm and decreased rapidly after 1600 engine rpm. The higher the pressure ratio, the better the fuel consumption, air excess ratio and brake mean effective pressure. But those are higher in the rated revolution range than in the mid-low revolution range. The turbocharger is operated in a stable condition from 1260 rpm and its efficiency is low in the low speed range for the reason of its characteristics. The results of this study can be applied in the fundamental control methods of turbocharged engine for stable load and speed.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.30 no.11 s.158
• /
• pp.1589-1597
• /
• 2006

Nowadays, Korean consumers prefer drum-type washing machines to pulsator-type washers. Washing is a complex process involving the interaction of numerous physical and chemical influences. The main factors in the washing operations are the washing chemistry of the detergent along with the mechanical input, the wash temperature, and the time provided by the washing machine. Heavy-duty detergents that are used in drum-type washing machines contain different components from those used in vertical-axis washing machines. The bath ratio and the mechanical actions to which laundry is subjected are different between the drum-type and the vertical-axis washing machines. In this study we examined the effects of wash temperature, wash time, detergent concentration, and revolution speed on the removal of soils from artificially soiled cloths in a drum-type washing machine with heavy-duty commercial detergent. We used multiple regression analyses to find the relative importance of the factors and the optimum washing conditions. The results of these experiments showed that the washing temperature was the most important factor in the effective removal of most soils. This was followed by the washing time, the detergent concentration, and finally the revolution speed. In this study it was found that superfluous amounts of detergent did not sufficiently increase the soil removal rate. Koreans who are used to washing with cold water should increase the wash time to launder more efficiently.

• Journal of Internet Computing and Services
• /
• v.21 no.2
• /
• pp.27-37
• /
• 2020

Recently, big data is rapidly emerging as a core technology in the 4th industrial revolution. Further, the utilization and the demand of drones are continuously increasing with the development of the 4th industrial revolution. However, as the drones usage increases, the risk of drones falling increases. Drones always have a risk of being able to fall easily even with small problems due to its simple structure. In this paper, in order to predict the risk of drone fall and to prevent the fall, ESC (Electronic Speed Control) is attached integrally with the drone's driving motor and the acceleration sensor is stored to collect the vibration data in real time. By processing and monitoring the data in real time and analyzing the data through big data obtained in such a situation using a Fast Fourier Transform (FFT) algorithm, we proposed a prediction system that minimizes the risk of drone fall by analyzing big data collected from drones.

• The Journal of Engineering Geology
• /
• v.26 no.3
• /
• pp.315-324
• /
• 2016

Because of a fissility characteristics of shale in the Gyoungsang super-group, it breaks down to debris when daylighted by construction work and causes a slope unstability. To assess the durability property of shale, a series of slake durability tests was conducted by controlling test conditions such as shape of specimen, number of specimen, revolution speed, revolution number, drying temperature and pH of submerging liquid. For the specimen shape, cube one showed relatively lower durability index than cuboid and/or fan shape one. The test with the more number of specimens showed the less durability index because of a higher friction among specimens in the drum. The durability index is linearly decreased by increasing the total number of revolution, while the revolution velocity could not affect the index. And the durability index is also decreased by increasing the drying temperature of specimen and by decreasing the pH of submerging liquid. Because the durability index of shale is almost similar to that of crystalline rocks, the disintegration characteristics of shale could not be assessed by the slake durability test recommended by ISRM, and thus a new test method by changing the total revolution number may be required for the shale having fissility characteristics.

• Journal of the Korea Furniture Society
• /
• v.22 no.3
• /
• pp.160-173
• /
• 2011

Increased internet use under a ubiquitous environment may be called as a great human information space revolution followed by Industrial Revolution. This revolution is exerting its significant influence over all the industry as a whole with speed faster than that of any other times. Along with this trend, if furniture design field that leads living culture should fail to jump on this main stream without noticing it, it may be reduced to a unpopular field some day without any sign of recovery. Under this background, this study is intended to recognize a goal aiming at understanding our rapidly changing living environment and leading our way positively. Currently, our surrounding living environment is immersed in computers here and there and Mark Weiser once defined a system that moves in advance before an action as ubiquitous computing and in this respect, I am going to observe a detailed transformation process of space. First nature of the space may be defined as atoms, a physical space equivalent to a spatial element and Bits space that is untouchable is usually called as 2nd space and a combination of atoms and Bits is an intelligent space - 3rd space - that can be intelligible without touching it and finally, this space is called as a ubiquitous space. This spatial transformation is developed by several changes of living environment and we may call it as living trend or interior design trend. Transformation in terms of social perspective, space structural perspective and digital technique perspective may be enumerated. These transformations were surveyed based on its contents being implemented at a future housing exhibition hosted by 5 construction companies along with fusion of information furniture and furniture depending on each housing space. In conclusion, it could be realized that most of the companies were decorating future space by implementing ubiquitous environment as a success factor of future housing market. It may be meaningful to note once again that under an interior environment, a fusion of furniture and information furniture is required considering interior trend elements.

• Journal of the Society of Naval Architects of Korea
• /
• v.57 no.5
• /
• pp.262-270
• /
• 2020

An outdoor free-running model test system was designed for assessing ship maneuverability with test uncertainty. The test model was a surface combatant of tumblehome hull geometry. The straight forward tests were conducted first to obtain the relationship between the propeller revolution rate and advance speed. During the outdoor tests, the propeller revolution rate to achieve a certain Froude number condition was higher than that in the indoor free-running model tests. Turning circle and zigzag tests for evaluating ship maneuverability criteria were carried out at the propeller revolution rate determined by the straight forward test results. The random and systematic standard uncertainties of maneuvering criteria were obtained by repeated tests and comparison with the indoor free-running model test results, respectively. The test uncertainty was largely dominated by the systematic standard uncertainty, while the random standard uncertainty was small with good repeatability.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2005.05a
• /
• pp.925-934
• /
• 2005

The dynamic response due to the unbalance and crack and the quasi-static response due to gravity are analytically derived based on the complex transfer matrix. The additional slope is expressed as function of the bending moment at crack position based on the fracture mechanics concept, and inversely the bending moment is expressed as function of the additional slope at the crack position. At each angle step during the shaft revolution, the additional slope and bending moment are calculated by an iterative method. The transient behavior is considered by introducing Fourier series expansion concept for the additional slope. Simulation is carried out for a simple rotor similar to those available in the literature and comparison of the basic crack behavior is shown. Using the additional slope, the cracked rotor behavior is explained with the crack depth increased: the magnitude of the additional slope increases and the closed crack duration during a revolution decreases as the crack depth increases. The direction of unbalance is also shown as a factor to affect the crack breathing. Whirl orbits are shown near the sub-critical speed ranges of the rotor.