• International Journal of Fluid Machinery and Systems
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• v.8 no.4
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• pp.264-273
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• 2015

This presentation describes an experimental approach for the detection of cavitation in hydraulic machines by use of ultrasonic signal analysis. Instead of using the high frequency pulses (typically 1MHz) only for transit time measurement different other signal characteristics are extracted from the individual signals and its correlation function with reference signals in order to gain knowledge of the water conditions. As the pulse repetition rate is high (typically 100Hz), statistical parameters can be extracted of the signals. The idea is to find patterns in the parameters by a classifier that can distinguish between the different water states. This classification scheme has been applied to different cavitation sections: a sphere in a water flow in circular tube at the HSLU in Lucerne, a NACA profile in a cavitation tunnel and two Francis model test turbines all at LMH in Lausanne. From the signal raw data several statistical parameters in the time and frequency domain as well as from the correlation function with reference signals have been determined. As classifiers two methods were used: neural feed forward networks and decision trees. For both classification methods realizations with lowest complexity as possible are of special interest. It is shown that two to three signal characteristics, two from the signal itself and one from the correlation function are in many cases sufficient for the detection capability. The final goal is to combine these results with operating point, vibration, acoustic emission and dynamic pressure information such that a distinction between dangerous and not dangerous cavitation is possible.

• Journal of the Korea Society of Computer and Information
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• v.12 no.3
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• pp.9-17
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• 2007

This paper introduces a Petri Net-based multimedia programming method. For this purpose, we are proposing MPN(Multimedia Petri Net) which can be used for representing a multimedia scenario. We are also introducing methods to analyze a MPN with which we can detect some kinds of design faults in the scenario. A multimedia program replays the scenario by interpreting the MPN. A method to implement such a multimedia program is also discussed. Our multimedia program provides the manipulation functions of stop, play, fast forward. rewind, and fast rewind. There are many varieties of Petri Net. Several of them are for modeling multimedia scenarios. They all have been used for synchronization analysis. But none of them were used for replaying multimedia scenario. We have extended these nets to MPN. A MPN model contains not only the flow of a scenario but also all the information associated with the data units. Therefore, our player can play the multimedia scenario by interpreting the MPN.

• Journal of the Society of Naval Architects of Korea
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• v.36 no.2
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• pp.50-60
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• 1999

In order to design a safe and economic catamaran, it is of clime importance to rigorously estimate the dynamic loads on the catamaran in waves. In this paper, the 2-D strip method by Lee et al.[3] is. extended to a 3-D method which can estimate the dynamic loads(horizontal and vertical shear forses, and bending and torsional moments) acting on the center of the cross deck of the catamaran travelling in an arbitrary wave heading angle. The computational results are compared with Wahab et al's experimental data[2], and also 2-D and 3-D numerical results published. It is found that in general, the 3-D method give much improved correlations with the experimental data compared with 2-D methods, but there are some discrcrepancy between the same 3-D results used by the same theory. In order to improve the accuracy, the effect of the viscous flow and the rigid consideration of the forward speed effect seem to be necessary.

• Journal of the Korea Society of Computer and Information
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• v.1 no.1
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• pp.7-24
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• 1996

In the emerging information society. a well-established national Information network plays a crucial role In enhancing economic efficiency and creating national wealth. Most of the advanced nations In the world are putting forward government-driven projects for the construction of their national Information Infrastructures. strategically focusing on the development of key technologies and Industrial essential for their Infrastructures. Development of the NII (National Infrastructure) can help unleash an Information revolution that will change forever the way people 1ive, work. and interact with each other. Nonetheless. the present Information Infrastructure In Korea loaves a lot to be Improved In order to realize the vision of Information society. The establishment of the KII (korea Information Infrastructure) does not merely mean the construction of physical network that enables the transmission of various modes of information such as voice, data, and image. It further implies the creation of a new kind of social overhead capital, ranging from the establishment of social and cultural which are conductive to seamless flow of information. For the successful implementation of the KII, it is critical to build the public consensus on the importance and necessity of informatization. At the same time, careful consideration should be given to the institutional factors such as timely and adequate supply of specialized personnel, the updating of policy and regulations, and the strengthening of interntional cooperation.

• Journal of the Korea Fashion and Costume Design Association
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• v.14 no.4
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• pp.29-42
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• 2012

Historically, the pattern and technology of Copts' textiles, who were a minority in Egypt, have been studied a lot in the textile sector due to its unique characteristics. Unlike ones in other regions that appeared around the same time, the overall configuration ratio of the patterns looks exaggerated or distorted because they expressed it plainly by interpreting the world with ordinary people's eyes. Also, because it had used mixed linen and woolen yarns, harsh expression way and the use of various colors have been one of the features in Coptic textiles. Coptic textiles, which have been developed along with the historical development of continued domination from neighboring countries, have expressed the effects of the Roman Empire, Christ, Christianity, and Islam on the pattern of its fabric. This study analyzed its characteristics which make people smile by the way of expressing a simple and humorous representation of the textiles and categorized them as Humoristic Beauty - the aesthetic category of humorous feature. In this study, the Humoristic Beauty in Coptic textiles has been analyzed in terms of the following three smiles; the smiles coincidental with the flow of time, the smiles made by the shaping of distorted proportions and appearance, and the smiles like folk-paintings made by a rustic expression way. This study shows the possibility of the further studies on the textile patterns history from a different angle. I look forward to more detailed analysis in the follow-up studies in the future.

• Wind and Structures
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• v.25 no.3
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• pp.283-299
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• 2017

Two types of aerodynamic admittance function (AAF) that have been adopted in bridge aerodynamics are addressed. The first type is based on a group of supposed relations between flutter derivatives and AAFs. In so doing, the aero-elastic properties of a section could be used to determine AAFs. It is found that the supposed relations hold only for cases when the gust frequencies are within a very low range. Predominant frequencies of long-span bridges are, however, far away from this range. In this sense, the AAFs determined this way are of little practical significance. Another type of AAFs is based on the relation between the Theodorsen circulation function and the Sears function, which holds for thin airfoil theories. It is found, however, that an obvious illogicality exists in this methodology either. In this article, a viewpoint is put forward that AAFs of bluff bridge deck sections are inherently dependent on oncoming turbulent properties. This kind of dependence is investigated with a thin plate and a double-girder bluff section via computational fluid dynamics method. Two types of wind fluctuations are used for identification of AAFs. One is turbulent wind flow while the other is harmonic. The numerical results indicate that AAFs of the thin plate agree well with the Sears AAF, and show no obvious dependence on the oncoming wind fields. In contrast, for the case of bluff double-girder section, AAFs identified from the turbulent and harmonic flows of different amplitudes differ among each other, exhibiting obvious dependence on the oncoming wind field properties.

• Wind and Structures
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• v.25 no.3
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• pp.233-259
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• 2017

Investigations on simulated near-surface atmospheric boundary layer (ABL) in an open-jet facility are carried out by conducting experimental tests on small-scale models of low-rise buildings. The objectives of the current study are: (1) to determine the optimal location of test buildings from the exit of the open-jet facility, and (2) to investigate the scale effect on the aerodynamic pressure characteristics. Based on the results, the newly built open-jet facility is well capable of producing mean wind speed and turbulence profiles representing open-terrain conditions. The results show that the proximity of the test model to the open-jet governs the length of the separation bubble as well as the peak roof pressures. However, test models placed at a horizontal distance of 2.5H (H is height of the wind field) from the exit of the open-jet, with a width that is half the width of the wind field and a length of 1H, have consistent mean and peak pressure coefficients when compared with available results from wind tunnel testing. In addition, testing models with as large as 16% blockage ratio is feasible within the open-jet facility. This reveals the importance of open-jet facilities as a robust tool to alleviate the scale restrictions involved in physical investigations of flow pattern around civil engineering structures. The results and findings of this study are useful for putting forward recommendations and guidelines for testing protocols at open-jet facilities, eventually helping the progress of enhanced standard provisions on the design of low-rise buildings for wind.

• Korean Journal of Food Science and Technology
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• v.41 no.4
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• pp.369-373
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• 2009

${\alpha}$-Waxy corn starch was used as a feed for twin-screw extrusion in order to enhance starch liquefaction with added thermostable ${\alpha}$-amylase (derived from Bacillus licheniformis). The residence time distribution and starch liquefaction were investigated. The starch liquefaction was analyzed in terms of reducing sugar contents, molecular size from gel permeation chromatography (GPC), and microstructure from scanning electron microscopy (SEM). The use of ${\alpha}$-starch contributed to the production of more reducing sugar than the use of raw starch use alone. From GPC, the effect of ${\alpha}$- starch on the molecular size reduction was shown to be small. From SEM, irregular and damaged surface were observed on the extrudate from ${\alpha}$-starch, as compared to those from raw starch. The spread of residence time distribution curves was greater with feed of ${\alpha}$-starch than raw starch, indicating that ${\alpha}$-starch was hard to flow forward during extrusion. This could be improved by increasing the feed moisture content and barrel temperature of extruder.

• Journal of Technologic Dentistry
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• v.16 no.1
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• pp.12-42
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• 1994

The study objected to the 36persons out of 55 persons who have registered under the association of the professor of department of Dental Laboratory Technology to grasp contents of May, 1992, and objected to the 74persons out of 100persons who have registered under the association of an a lumni of Department of dental Laboratory Technology, Jisan Junior college to grasp contents about improvement of dental laboratory technology, Jisan Junior College to grasp contents about improvement of the national practical examination in the dental technician of the present day of May, 1994 and its results which we have acquired by this study were as follows : There are lots of opinions who have required the necessities to enforce for a national practical examination in the dental technician. A sense of satisfaction forward the system of a national practical examination in the dental technician appeared as unsatisfaction and it's unsatisfaction decreased from evaluation me operation method, the makes of questions, selection of a markers, distribution of marks of a practical examination. The operation method of a practical examination have appeared the opinions which they wished the present system. A date of operation a practical examination have appeared the opinion of which they preferred late in February. The distribution of marks of a practical examination have appeared the opinions which they wished the present system. The problem of the makes of questions of carving test which derived by an out flow of cast appeared which 52.7 percent(58 persons), lack of objectivity and lack of a standard evaluation appeared which 40 percent(44 persons), and lastly appeared. 5.5 percent(6 persons) with partiality of a questions. The problem of the makes of question of Q-test which derived by lack of a standard evaluation appeared which 44.5 percent(49 persons), lack of objectivity appeared which 39.1 percent(43 persons).

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.5
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• pp.952-964
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• 1992

The interaction of natural convection and radiation heat transfer in a two dimensional square enclosure containing absorbing, emitting and linear anisotropically scattering gray medium is numerically analyzed. P-1 and P-3 approximation is introduced to calculate radiation heat transfer. The effects of scattering albedo, wall emissivity, scattering anisotropy, and optical thickness on the characteristics of the flow and temperature field and heat transfer are investigated. Temperature and velocity profiles depend a great deal on the scattering albedo, and the importance of this effect increases with decrease in albelo. Planck number is another important parameter in radiation heat transfer. The increase in scattering albedo increases convection heat transfer and decreases radiation heat transfer at hot wall. However, the increase in scattering albedo decreases both convection and radiation heat transfer at cold wall. The increase in optical thickness decreases radiation heat transfer. The scattering anisotropy has important effects on the radiation heat transfer only. The highly forward scattering leads to an increase of radiation heat transfer whereas the highly backward scattering leads to an decrease of radiation heat transfer. The effect of scattering anisotropy decreases when reducing the wall emissivity.