• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.7
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• pp.2118-2133
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• 1996

A preform is designed by the backward tracing scheme of the rigid-plastic finite element method(FEM) for net-shape shell nosing components without machining after forming. The current process of the shell nosing requires cost-consuming machining to produce final products. Here, the backward tracing scheme of the rigid-plastic FEM, a novel method for preform design of metal forming processes, derives a sound preform for net-shape shell nosing product. The current process is simulated by the rigid-plastic finite element analysis to check the metal flow involved in the forming with a trial preform and its modified preform. The two preforms are found to be inadequate for net-shape shell nosing product. The first application of the back ward tracing scheme derives a preform producing a not-shape shell nosing product. The first application of the backward tracing scheme derives a preform producing a net-shape product numerically, but it is difficult to be formed economically as a preform. Thus an improved preform is designed by the badkward tracing scheme, which is suitable for net-shape manufacturing of the shell nosing components in view of economy of production and forming characteristics of the product. The preform in the current process and a modified preform are confirmed by a series of experiments and the results give the same deformation with the numerical ones. Finally the newly designed preform by the FEM was experimentally proved to be adequate in obtaining net-shape products.

• Magazine of the Korean Society of Agricultural Engineers
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• v.43 no.2
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• pp.59-68
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• 2001

A water balance analysis was performed for a paddy field neighboring the Dongchang stream, downstream of the Unmun reservoir, which is constructed for the urban water supply. Daily rainfall data were collected and irrigation water flow rate, drainage flow rate, evaportranspiration, infiltration, and piezometeric head were measured in the field. The flow rates were continuously observed by water level logger during the growing season. The evaportranspiration and the infiltration were measured by N-type depletion meter and cylindrical infiltrometer, respectively. PVC pipes with 12mm diameter were used for piezometric head measurement. Total Irrigation and drainage flows were 3,608mm and 1,170mm in 1999, and 3,971mm and 1,548mm in 2000, respectively. The mean and range of the daily infiltration rate were 4.4mm/d and 3.4mm/d to 5.5mm/d in 1999 and 5.1mm/d and 4.1mm/d to 6.5mm/d in 2000, respectively. The net ground water flow including the change of soil water storage was 2,855mm in 1999 and 2,540mm in 2000. The evapotranspiration was 458.3mm in 1999 and 553.5mm in 2000. The range of daily evapotranspiration rate was from 1.6 to 8.7mm/d. The return flow ratio was about 32% in 1999 and 39% in 2000 and three year average was 35% including previous study in 1997. The amount of irrigation water was much higher than design standards or references in this study, This was caused by the inadequate water management practice in the area where water was oversupplied on farmers’ request rather than following sound water management principles.

• Journal of Biosystems Engineering
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• v.31 no.4 s.117
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• pp.315-322
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• 2006

A torsional damper comprised of two stage pre-dampers was used to reduce the rattle noise generated in the PTO gear box of a direct engine-PTO driveline of agricultural tractors. It was designed and mounted to the engine flywheel to reduce the torque fluctuation-induced speed variations at the driving gears in the PTO gearbox, which were found to be main cause of the rattle noise. The effects of a hysteresis torque and a torsional stiffness of the damper on the speed variation were analyzed using an 11 degree of freedom non-linear model of the damped PTO driveline. The torsional damper was represented by a single degree of freedom model with 7 parameters. Under a constant hysteresis torque, velocity variation was reduced with decrease in the torsional stiffness of the damper. The velocity variation was also decreased with decrease in the hysteresis torque under a constant torsional stiffness. Optimum values of the torsional stiffness and hysteresis torque were obtained by the model simulation for the PTO driveline under the study. When the optimum values of the damper were used, the sound pressure level of the rattle noise was reduced by 81%, resulting in a reduction of 15dB(A). The optimum damper also reduced the engine speed variation, resulting in a reduction of 80% at the driving gears in the PTO gearbox. The torsional damper showed a good performance in reducing the rattle noise caused by the speed variation in the direct engine-PTO driveline.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.3
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• pp.238-243
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• 2008

Several experimental techniques for identifying the noise sources distributed over a moving vehicle have been developed recently and are used to design a low noise vehicle. The beamforming method, which uses phase information between several microphones to localize the source position, is proved to be one of the promising techniques applicable even under complicated test environments. In this study a beamforming algorithm is developed and applied to measure the dominant noise sources on a passenger car passing by. Unlike the acoustic signals from a stationary noise source, the sound generated from a moving source is distorted due to the Doppler effects. The information about the speed and relative position of the vehicle are used to eliminate the Doppler effects from the measured acoustic signal by using a de-Dopplerization algorithm. The noise generated from a moving vehicle can be grouped in many ways, however, tire noise and the noise generated from the engine are distinguishable at the speeds being tested.

• The Journal of the Korea Contents Association
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• v.20 no.5
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• pp.1-10
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• 2020

In this paper, we propose a new pornographic content detection scheme using bi-directional relationships between neighboring auditory signals in order to accurately detect sound-centered obscene contents that are rapidly spreading via the Internet. To capture the bi-directional relationships between neighboring signals, we design a multilayered bi-directional dilated-causal convolution network by stacking several dilated-causal convolution blocks each of which performs bi-directional dilated-causal convolution operations. To verify the performance of the proposed scheme, we compare its accuracy to those of the previous two schemes each of which uses simple auditory feature vectors with a support vector machine and uses only the forward relationships in audio signals by a previous stack of dilated-causal convolution layers. As the results, the proposed scheme produces an accuracy of up to 84.38% that is superior performance up to 25.80% than other two comparison schemes.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2005.11a
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• pp.235-239
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• 2005

A 30-tonf-class fullscale thrust chamber for the application to a LEO SLV has been combustion tested over the wide ranges of a mixture ratio and a chamber pressure. The thrust chamber designed for an open cycle engine with a turbopump was tested with a ablative combustion chamber instead of a regenerative chamber to first evaluate its performance and function. The test results revealed stable combustion characteristics. The hardware survived the harsh environment and showed very sound functional characteristics. The estimated combustion efficiency of the chamber turned out to be 95% and a specific impulse at sea level was estimated as 254sec, which are comparable to or above the predicted design values.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.4
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• pp.40-46
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• 2006

A 30-tonf-class fullscale thrust chamber for the application to a Low-Earth-Orbit Space Launch Vehicle has been combustion tested over the wide ranges of a mixture ratio and a chamber pressure. The thrust chamber designed for a pump-fed open cycle engine was tested with an ablative chamber instead of a regenerative one for the initial evaluation of its performance and function. The test results revealed stable combustion characteristics. The hardware survived the harsh environment and showed very sound functional characteristics. The measured combustion efficiency turned out to be 95% and a specific impulse at sea level was estimated as 254sec, which are comparable to or above the predetermined design values.

• THE INTERNATIONAL COMMERCE & LAW REVIEW
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• v.54
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• pp.235-260
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• 2012

The CMI Rules for Electronic Bills of Lading were based on sound principles that are now reflected in the provisions of the Rotterdam Rules, which provide for the use of electronic equivalents to bills of lading. Services involving bills of lading which exist in electronic form for at least part of their lives, and which use encryption to guarantee integrity and security of these electronic records, are already being offered by a number of carriers, among them APL. The relative success of APL's system demonstrates that the use of a system which embodies the basic ideas and processes underlying the CMI Rules could easily become a practical reality in the near future. The basic principles in the CMI Rules and the Rotterdam Rules adopt a minimum requirements approach and does not flesh out the details of procedures for the use of electronic bills. This is an improvement, as it allows adaptability to future technological developments. Successful electronic bill of lading systems can only be developed in response to customer demand, and carriers are in the best position to gauge this and design systems to cater for it. APL has demonstrated this by creating a system which is tailor-made to its customers' requirements. The CMI Rules were correct in their assumption that electronic bill of lading services should be provided by carriers. They also seem to have anticipated that the switch to the electronic medium would not be sudden and complete, but would require a gradual phasing out of paper documents over a long period of time.

• The Journal of the Korea Contents Association
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• v.7 no.10
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• pp.146-156
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• 2007

This study is possible because, first, "rammatology" and typography are connected by language. Second, I believe that language in typography should be comprehended in a relationship between peripheral studies such as history, philosophy, literature, and linguistics. Finally, "grammatology" is an excellent subject for experiments which attempt to rehabilitate the right of language, which is dependent on sound within the metaphysical boundary. This study is formed on the idea that the study of typography should be based on language, which is the basic foundation, and that this is possible in investigations related to peripheral studies. The main purpose of typography is an accurate delivery of meaning. However, the dynamics of creative thoughts towards advancement mainly depends on experiment, thus we cannot limit the purpose of typography as a means of communication to exchange meanings. For these reasons, I admit that interest in peripheral studies -which are not yet approached in the study on typography -take precedence.

• The Journal of the Korea Contents Association
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• v.8 no.1
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• pp.128-136
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• 2008

As Chinese characters occupies more than 70% of words we currently use, the education of Chinese characters is becoming important day by day to accurately deliver the meaning of words in our language life. In recent, there are increasing concerns on writing Chinese characters correctly, especially the order of stroke, as well as memorizing the meaning and the sound of a character. Books and Internet contents on Chinese character writing is emerging. However, currently available Internet media on the Chinese characters education only illuminates recitation and interpretation. Even though some books contain the chapter concerning the order of stroke of a character, those only force simple repetitions. In this paper, we propose a design and implementation of teaming system for writing of Chinese character based on web which enables the user-directed teaming. Using the system, a user can manage the status of learning by oneself. Additionally, we can enhance the efficiency of learning by making users understood the correct reading and writing in Chinese character education.