• The Journal of the Acoustical Society of Korea
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• v.32 no.6
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• pp.455-471
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• 2013

Active sonar has been commonly used to detect targets existing in the shallow water. When a signal is transmitted and returned back from a target, it has been distorted by various properties of acoustic channel such as multipath arrivals, scattering from rough sea surface and ocean bottom, and refraction by sound speed structure, which makes target detection difficult. It is therefore necessary to consider these channel properties in the target signal simulation in operational performance system of active sonar. In this paper, a monostatic active sonar system is considered, and the target echo, reverberation, and ambient noise are individually simulated as a function of time, and finally summed to simulate a total received signal. A 3-dimensional highlight model, which can reflect the target features including the shape, position, and azimuthal and elevation angles, has been applied to each multipath pair between source and target to simulate the target echo signal. The results are finally compared to those obtained by the algorithm in which only direct path is considered in target signal simulation.

• Journal of Ocean Engineering and Technology
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• v.18 no.6 s.61
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• pp.79-83
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• 2004

The curved blocks which compose the bow and stem of a ship contain many skewed joints that are inclined horizontally and vertically. Most of these joints have a large fitness error and are continuously changing their form and are not easily accessible. The welding position and parameter values should be appropriately set in correspondence to the shape and the inclination of the joints. The welding parameters such as current, voltage, travel speed, and melting rate, are related to each other and their values must be in a specific limited range for the sound welding. These correlations and the ranges are dependent up on the kind and size of wire, shielding gas, joint shape and fitness. To determine these relationships, extensive welding experiments were performed. The experimental data were processed using several information processing technologies. The regression method was used to determine the relationship between current voltage, and deposition rate. When a joint is inclined, the weld bead should be confined to a the limited size, inorder to avoid undercut as well as overlap due to flowing down of molten metal by gravity. The dependency of the limited weld size which is defined as the critical deposited area on various factors such as the horizontally and vertically inclined angle of the joint, skewed angle of the joint, up or down welding direction and weaving was investigated through a number of welding experiments. On the basis of this result, an ANN system was developed to estimate the critical deposited area. The ANN system consists of a 4 layer structure and uses an error back propagation learning algorithm. The estimated values of the ANN were validated using experimental values.

• Earthquakes and Structures
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• v.27 no.2
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• pp.127-142
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• 2024

The amount of wave propagation through a rubber concrete construction is the subject of the current investigation. Rubber tire waste was used to make two different types of cement mixtures. One type contains sand substitute in amounts ranging from 15% to 60% of the total volume, while the other has gravel with diameters of 3/8 and 8/15 and 15% sand in the same mixture. A wide variety of concrete forms and compositions were created, and their viscous and solid state characteristics were assessed, along with their short-, medium-, and long-term strengths. Diffusion, density, mechanical strength resistance to compressive force, and ultrasound wave propagation were also assessed. The water-to-cement ratio and plasticizer were used in this investigation. In the second part of the study, an analytical model is presented that simulates the experimental model in predicting the speed of waves and the frequencies accompanying them for this type of mixture. Higher order shear deformation beam theory for wave propagation in the rubberized concrete beam is developed, considering the bidirectional distribution, which is primarily expressed by the density, the Poisson coefficient, and Young's modulus. Hamilton's concept is used to determine the governing equations of the wave propagation in the rubberized concrete beam structure. When the analytical and experimental results for rubber concrete beams were compared, the outcomes were very comparable. The addition of rubber gravel and sandy rubber to the mixture both resulted in a discernible drop in velocities and frequencies, according to the data.

• Geophysics and Geophysical Exploration
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• v.14 no.1
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• pp.18-24
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• 2011

A multi-channel seismic reflection (MCS) survey was conducted in 2009 to explore the deep crustal structure of the Pacific Plate south of Hokkaido. The survey line happened to traverse a 250-km-wide Warm Core Ring (WCR), a current eddy that had been generated by the Kuroshio Extension. We attempted to use these MCS data to delineate the WCR fine structure. The survey line consists of two profiles: one with a shot interval of 200m and the other with a shot interval of 50 m. Records from the denser shot point line show much higher background noise than the records from the sparser shot point line. We identified the origin of this noise as acoustic reverberations between the sea surface, seafloor and subsurface discontinuities, from previous shots. Results showed that a prestack migration technique could enhance the signal buried in this background noise efficiently, if the sound speed information acquired from concurrent temperature measurements is available. The WCR is acoustically an assemblage of concave reflectors dipping inward, with steeper slopes (${\sim}2^{\circ}$) on th ocean side and gentler slopes (${\sim}1^{\circ}$) on the coastal side. Within the WCR, we recognised a 30-km-wide lens-shaped structure with reflectors on the perimeter.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.12
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• pp.1057-1064
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• 2014

Recently, there has been a growing interest in sustainable energy. One method that has been used is an organic Rankine cycle using conventional turbine technology with a low-temperature waste heat source. A 200-kW organic Rankine cycle (ORC) system was designed for a waste heat recovery application using R245fa as the working fluid. A radial turbine running at 15,000 rpm was employed to generate more than 200 kW with an expansion ratio of nine. Because an ORC turbine uses a refrigerant as the working fluid, the ideal gas law was not employed to design the turbine. In addition, the complexity of the molecular structure of R245fa made it difficult to design the turbine. Because R245fa has an Ma value of one at a low velocity for the working fluid (about 1/3 of the speed of sound in air) at about $100^{\circ}C$, it easily reaches a supersonic flow condition with a small pressure expansion. To increase the efficiency of the turbine, a dual stage radial-type turbine with a subsonic speed was suggested. This paper will describe the design procedure and performance evaluation of the ORC turbine using R245fa.

• The Journal of Korean Academy of Prosthodontics
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• v.42 no.5
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• pp.535-543
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• 2004

Purpose: The purpose of this study is to compare the effect of two fiber post systems and one metal cast post system on the fracture strength and fracture pattern of crowned, endodontically treated teeth with 2 mm-height of the reamining tooth structure. Materials and methods: A total of 36 recently extracted sound human mandibular premolars were selected Each tooth structure of the crown portion except 2mm-height of the one above the cementoenamel junction was removed. After being endodontically treated, they were randomly distributed into 3 groups: group 1, restored with quarts fiber post(D.T. Light-Post), group 2, with glass fiber post(FRC Postec), and group 3, metal cast post and core. All teeth were fully covered with nonprecious metal crowns. Each specimen was embedded in an acrylic resin block and then secured in a universal load-testing machine. A compressive load was applied at a 130 degree angle to the long axis of the tooth until fractured, at a crosshead speed 20mm/min. The highest fracture loads were measured and recorded as the fracture strength of each specimen. Fracture areas were measured on the mid-buccal and mid-lingual point from the crown margins. One-way analysis of variance and Turkey test were used to determine the statistic significance of the different fracture loads and areas among the groups (p<0.05). Results: The mean fracture loads were $1391{\pm}$425N(group 1), $1458{\pm}476N$(group 2) and $1301{\pm}319N$(group 3). The fracture loads among the three groups had no statistically signifiant difference (p>.05). The mean fracture area of the fiber post was closer to the crown margin than that of the metal cast post and core(p<.05). The metal cast post showed unrestorable and catastrophic fracture patterns. Conclusion: Within the limitations of this study, fracture loads with any statistically significant difference were not recorded for endodontically treated teeth restored with two fiber posts and the metal cast post. But teeth restored with the fiber posts typically showed the fracture pattern close to the crown margin, which was almost restorable.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.6
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• pp.538-544
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• 2000

A phased array ultrasonic nondestructive inspection system is being developed to obtain images of the interior of steel structures by modifying a medical ultrasound imaging system. The medical system consists of 64 individual transceiver channels that can drive 128 array elements. Several modifications of the system were required mainly due to the change of sound speed. It was necessary to fabricate array transducers for steel structure and to obtain A-scan signal that is necessary for the nondestructive testing. Boundary diffraction wave model was used for the prediction of radiation beam field from array transducers, which provided guidelines to design array transducers. And a RF data acquisition board was fabricated for the A-scan signal acquisition along a selected un line within an image. For the proper beam forming in the transmission and reception for steel structure, delay time was controlled. To demonstrate the performance of the developed system and fabricated transducers, images of artificial specimens and A-scan signals for selected scan lines were obtained in a real time fashion.

• Journal of Korean Medicine Rehabilitation
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• v.18 no.3
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• pp.147-156
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• 2008

Objectives : Oriental Medicine Music Therapy is a new way of treating and preventing various diseases and promoting health by means of music specially picked and designed to produce Qi(氣) fitting to an individual person in the areas of the structure of human body, physiological function, pathological change, diagnosis and treatment. Therefore, it can facilitate the efficiency of the treatment much better and faster than only with herb or acupuncture. Equilibrium between body and mind is its originality. Methods : A 38-year old man came to hospital suffering from left side weakness, dysarthria because of cerebral infarction. After one week's medication in the part of neurology, he was sent to the oriental medicine music therapy center, and he took ten times' medical treatments once a day. Before and after the treatments, implementing 'Ink foot print analysis', as for the movement capacity and walking of left side weakness, these results are acquired. Results and Conclusions : 1. Before the oriental medicine music therapy, except the acceleration and deceleration section, within three meters, a right foot's step was measured 30.55 cm and a left foot was measured 15.2 cm, and the step distance was 15.2 cm. After the 10 times treatments, the right foot's step was 112.6 cm, the left foot's step was 113 cm, and the step distance improved to 51.8 cm. 2. The normal person's average step is about 38 cm, and it could be decreased owing to a decreptitude, pain, fatigue, and the weakness of the legs. In spite of all, from the increased 50 cm step measurement with the patient's body condition, it means that his movement capacity is recovered. 3. In the measurement of walking time, before 10 times treatments, it took 46.35 seconds within 6M, but after the treatments, it increased to 7.47 seconds as same as a normal person's walking speed. 4. In insomnia, and the abnormality of a facial muscle, it shows lots of improvement, and even the accuracy of a pronunciation, but despite of the 10 times treatments, the 'ㄹ(r)' sound placed under a vowel is unclear. 5. Before the 10 times' treatments, he can move the left side shoulder with pain and cannot move below the left elbow. After the treatments, the pain was disappeared, and he was able to move over 60 cm without pain. And improving of the movement of fingers, he can beat over 8 times with a drumstick.

• (The) Research of the performance art and culture
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• no.20
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• pp.5-30
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• 2010

It has been diversified and serious attempt to establish the identity of Changgeuk, but it is still independent dramaturgy or the current unformed progressive art. In this situation, exploring works of the identity of changgeuk that is base on the performed individual and specific works in the title of Changgeuk is needed. The 80s and 90s Heo, Gyu was leading an active life as a director who was responsible for directing of Changgeuk. He dramatized Siljeon Pansori -which is a group of Pansori missing text- as well as 5-remained Songs in Pansori and he presented a number of creative Changgeuk works on stage. Especially, the completion of dramatizing 5-remained Songs in Pansori under the name of 'Wanpan Changgeuk -which means full version performance without omit-' is the one of his big achievement by performing "Heungbojeon" on the stage 1982 and "Jeokbyeokga" 1985. The purposes of this research are confirmation of Heo's direction of the formulation and considering its characteristics & significance through 'Wanpan Changgeuk' which written by Heo. Heo was a practical play who was interested in the subjective formulation of national culture and creative transmission for Korean traditional performance. He tried to formulate Changgeuk to a representative performance of Korea. In the process he pointed out those problems, (1) interpretation of a work problem, (2) actor's creative problems, (3) structure problem of theater for Changgeuk. He indicated that the other challenges are to use of the stage & device, to overcome sentimentalism, to stylize acting, to improve own quality, to control the speed and length of the song, to choose the suitable musical accompaniment, to create new repertories problems, and etc. Changgeuk is classified in 3 group by origin, (1)dramatizing of 5-remained Songs, (2)dramatizing of 7-missing Songs, (3)creative dramatizing. It contains all of 3 types that Heo's work. The dramatizing of remained 5 Songs are the great importance among those works. Heo hoped that Chaggeuk has become the most representative art work of Korea by performing 'Wanpan Changgeuk' compiled heritage of Korea's outstanding artistic achievement. The characteristics of 'Wanpan Changgeuk' can be summarized following four. (1) Directing attitudes that emphasizes tradition, (2) Accepting the elements of traditional performance actively, (3) Valuing the classy and ethic, (4) Emphasizing humor and active utilizing of the secondary characters. Heo's 'Wanpan Changgeuk' shows a peak of the artistic level which Changgeuk can be reached. He want to make Changgeuk a Korean representative artistic performance by compiling Pansori heritage and accommodating Korean traditional performance. Heo continued his effort to present Pansori's authenticity and to dramatize from beginning to end without missing. It shows very well that 'Wanpan Changgeuk' takes 4~5 hours for playing. It looks Heo's achievement in the 'Wanpan Changgeuk' influenced Changgeuk significantly since then. Heo's 'Wanpan Changgeuk' is matrix of 'Wanpan JangMak Changgeuk' attempted in the 1990s. Especially, their intent is consistent to synthesize texts and to show all the virtue of Pansori. But 90's 'Wanpan JangMak Changgeuk' aim for large stage, fancy device & costume and variety contents compared with 'Wanpan Changgeuk'. Recently, producers have tried not to make a impressive Changgeuk but to make a interesting one. They usually organize performance within 2 hours and prefer orchestral music to its unique sound. In those point of view, it seems that Heo's idle in 'Wanpan Changgeuk' has become one of target to conquer in these days.