• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.36.2-36.2
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• 2016

In mm-VLBI, the quality of observation data is largely affected by atmospheric effect. The most challenging matter is that the phase of correlator output fluctuates rapidly resulting from a variation of atmospheric propagation delay. Consequently, it is demanding to achieve high Signal-to-Noise ratio by integrating data in time domain before calibrating atmospheric delay. However, Korean VLBI Network (KVN) has a unique system to make a 4-frequency (22/43/86/129 GHz) simultaneous observation in mm-wavelength and Frequency Phase Transfer (FPT) calibration technique has effectively removed atmospheric delay in the simultaneous multi-frequency observation of the KVN. For astrometric and astrophysical studies, we evaluated the FPT performance of KVN in various observing conditions. Using the total 38 bright AGNs, we have compared atmospheric conditions such as ground-based weather information, system temperature, atmospheric delay with the calibration results of FPT at 22/43/86/129 GHz during the five experiments in 2013, and quantified its performance in terms of coherence function and Allan variance. We present the analysis result of the relation between the FPT performance and observing conditions.

• Journal of Information Technology Applications and Management
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• v.15 no.1
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• pp.99-116
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• 2008

This study explores the impacts of e-learning system characteristics on learner committment and satisfaction by surveying the firms utilizing e-learning systems for learning. In the study, we have, first, drawn the key factors and instruments to measure e-learning system characteristics through intensive literature review. Second, we have investigated whether the characteristics contribute to increasing learner's commitment and satisfaction. Finally, we have examined the mediating effect of learner's commitment between the characteristics of e-learning system and learner satisfaction. We have conducted a survey on the employees having experience in using e-learning systems for learning, and collected a total of 93 responses. The results of a statistical analysis show the following: First, expression and interaction affect the learner's commitment. The results indicate that a learner should engage in e-learning and ultimately be more committed on it when there is a coherence in design and organization of learning contents, and when the system offers various multimedia options including audio, sound, image, graphics, etc. Second, leaner's commitment leads to higher learning satisfaction. Finally, our results show that the commitment plays a mediating role between learner characteristics (expression, control, and trust) and learner satisfaction.

• Journal of Technologic Dentistry
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• v.23 no.2
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• pp.95-103
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• 2002

For this study, self curing resin and heat curing resin used for existing usual resin denture base in the denture industry were chosen by manufacturer. Curing tests for 30-minute, I-hour, 2-hour and 3-hour were conducted to know the strength of the resins and conduct analysis to get other necessary information. The results obtained are as follows: 1. Heat curing resins show a little differences among the manufacturers. However 30-minute curing resin shows great difference as shown in the fracture strength test. 2. The effect from the granularity of the resins on the fracture strength was found insignificant which means there is no difference between coherence and strength. 3. To summarize the results from each time level, the longer the time is, the more the minute cracks on the surface, which is the cause of reduced strength. From this test, it was identified that in making the denture base for patients in dental clinics, 30-minute curing is most efficient and effective in reducing discoloration and monomers, although long-time curing has been considered to be the principal.

• Annual Conference on Human and Language Technology
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• 2001.10d
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• pp.226-232
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• 2001

본 연구는 결속장치(cohesive devices)가 과학텍스트의 읽기 속도와 내용 이해에 끼치는 영향에 대해 연구하였다. 연구의 목적을 위한 실험을 통해서 먼저, 텍스트의 문단별 읽기 시간을 측정하여 온라인 처리 과정을 검토하였고, 둘째, 회상과 재인 검사를 실시하여 오프라인 상태에서의 이해도를 조사하였다. 이 연구의 재료로 사용된 텍스트는 번개 생성과정에 대한 과학텍스트로서, 반복, 지시사, 정박(anchoring), 인과적 접속사 등의 결속장치를 이용하여 응집성(coherence)의 강도를 높고, 낮게 조작하였다. 실험 결과, 결속장치가 길속장치의 종류와 지엽적 응집성의 강도에 따라 과학텍스트 읽기와 이해에 선택적으로 영향을 끼친다는 것을 발견하였다. 첫째, 인과적 접속사는 읽기 시간에는 영향을 주지 않는 반면, 이해를 촉진했는데, 이 긍정적 효과는 과제의 종류에 따라 다르게 나타났다. 즉, 회상 검사 결과에서는 인과적 접속사가 쓰인 모든 문단에서 유의한 차이가 나타났으나, 재인 검사에서는 유의한 차이가 부분적으로만 나타났다. 둘째, 반복 결속장치는 다른 결속장치와 같이 발생할 경우에만 읽기 시간과 이해를 부분적으로 촉진하는 것으로 나타났다. 셋째. 정박 결속장치의 영향은 읽기와 이해 두 처리 과정에 모두 선택적으로 영향을 준 것으로 나타났다. 인과적 접속사와 함께 쓰인 문단의 경우에는 회상 검사에서만, 반복 결속장치가 함께 쓰인 문단에서는 회상, 재인 검사에서 모두 긍정적 영향을 준 것으로 관찰되었다.

• Proceedings of the KSRS Conference
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• 2008.10a
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• pp.188-191
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• 2008

The Tonle Sap, Cambodia, is a huge lake and periodically flooded due to monsoon climate. The incoming water causes intensive flooding that expands the lake over vast floodplain and wetland consisting mainly of forests and shrubs. Monitoring the water-level change over the floodplain is essential for flood prediction and water resource management. A main objective of this study is flood monitoring over Tonle Sap area using ALOS PALSAR. To study double-bounce effects in the lake, backscattering effect using ALOS PALSAR dual-polarization (HH, HV) data was examined. InSAR technique was applied for detection of water-level change. HH-polarization interferometric pairs between wet and dry seasons were best to measure water level change around northwestern parts of Tonle Sap. The seasonal pattern of water-level variations in Tonle Sap studied by InSAR method is similar to the past and altimeter data. However, water level variation measured by SAR was much smaller than that by altimeter because the DInSAR measurement only represents water level change at a given region of floodplain while altimeter provides water level variation at the central parts of the lake.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.356-361
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• 2003

The objective of this study is a qualitative comparison between line-integrated OH chemiluminescence ($OH{\ast}$) image and its Abel inversion image at different phase of the oscillating pressure field. PIV(Particle Image Velocimetry) measurements were conducted under non-reacting conditions to see the global flow structure. Also NOx emission was measured to investigate the effect of fuel-air premixing on combustion instability and emission characteristics. Experiments were carried out in an atmospheric pressure, laboratory-scale dump combustor operating on natural gas. Combustion instabilities in present study exhibited a longitudinal mode with a dominant frequency of ${\sim}341.8$ Hz, which corresponded to a quarter wave mode of combustor. Heat release and pressure waves were in-phase when instability occurred. Results gave an insight about the location where the strong coherence of pressure and heat release existed. Also an additional information on active control to suppress the combustion instabilities was obtained. For lean premixed combustion, strong correlation between $OH{\ast}$ and NOx emissions was expected largely due to the exponential dependence of thermal NOx mechanism on flame temperature.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.2
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• pp.16-29
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• 1995

In this study a tracked vehicle is idealized as a 2-dimensional 9-degrees-of-freedom model which takes into account the effects of HSU units, torsion bars, and track. For the model equations of motion are derived using Kane's method. By using the equations of motion, a numerical example is solved and results are compared to those obtained by using a general purpose multi body dynamic analysis program. The comparison study shows the reasonable coherence between the two results. which confirms the effectiveness of the model. With the model, dynamic response optimization is carried out. The objective function is the peak value of the vertical acceleration of the vehicle at the driver's seat, and the constraints are the wheel travel limits, the ground clearance. and the limits of other design variables. Three different sets of design variables are chosen and used for the optimization. The results show the attenuation of the acceleration peak value. Thus the procedure presented in this study can be utilized for the design improvement of the real system.

• Journal of the Korean Society of Costume
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• v.65 no.2
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• pp.144-156
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• 2015

This research aims to develop textile patterns using mythical motives based on Buldoje in the Jeju myth. this textile design is not only decoration effect by filling the space, but also plays the original role of a pattern by expressing its symbolic meaning. The research methods are as follows: 1) Using integral analysis on materials related to the myth of Jeju and Gime used in Buldoje Gut, where Halmangbonpuli story is performed to set formative elements for textile design and their meanings; 2) Designing motive by composing formative elements; 3) Coloring properly; and 4) Layout motives. Adobe CS5 (Photoshop, Illustrator) and TexPro, a design CAD program, were used for textile design. Motives were combined in a various ways. Two-directional, four-directional, set, rotating, toss layout techniques, which are frequently used in apparel design and able to reduce cloth use, were used in developing patterns. Coloring methods including tone-in-tone and Faux camaieu were used to deliver coherence and soft effects. Developed textile design symbolizes the desire for the conception of a child, birth, and health, so it is made on baby clothes. In doing so, the plan for development of a fashion-cultural product applying Jeju myth symbol is suggested.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.390-390
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• 2010

Superconducting proximity effects of Nb/Si(111) were investigated with scanning tunneling microscopy(STM) and scanning tunneling spectroscopy(STS). A highly-doped($0.002\;{\omega}{\diamondsuit}cm$) Si wafer pieces were used as substrate and Nb source was thermally evaporated onto the atomically clean silicon substrate. The temperature of the silicon sample was held at $600^{\circ}C$ during the niobium deposition. And the sample was annealed at $600^{\circ}C$ for 30 minutes additionally. Volmer-Weber growth mode is preferred in Nb/Si(111) at the sample temperature of $600^{\circ}C$. With proper temperature and annealing time, we can obtain Nb islands of lateral size larger than Nb coherence length(~38nm). And outside of the islands, bare Si($7{\times}7$) reconstructed surface is exposed due to the Volmer-Weber Growth mode. STS measurement at 5.6K showed that Nb island have BCS-like superconducting gap of about 2mV around the Fermi level and the critical temperature is calculated to be as low as 6.1K, which is lower than that of bulk niobium, 9.5K. This reduced value of superconducting energy gap indicates suppression of superconductivity in nanostructures. Moreover, the superconducting state is extended out of the Nb island, over to bare Si surface, due to the superconducting proximity effect. Spatially-resolved scanning tunneling spectroscopy(SR-STS) data taken over the inside and outside of the niobium island shows gradually reduced superconducting gap.

• Transactions of Materials Processing
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• v.25 no.6
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• pp.402-408
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• 2016

A manufacturing technology of carbon fiber composites with thermoplastic polymer pellets and continuous woven fiber was investigated using a compression molding process. To secure the impregnation of resin into the porosity of fabric the composite specimens were prepared with general injection-molding grade polypropylene pellets and low viscosity polycarbonate pellets. Tensile tests of polypropylene and polycarbonate composites were performed. Polycarbonate composites showed higher fracture strength than that of polypropylene composites because of the difference of matrix properties. However, the increase rate of strength was lower than that of polypropylene composites due to the difference of coherence between matrix and reinforcement. To investigate the effect of carbon fiber volume fraction on the fracture strength variation polypropylene composites with different volume fraction were compression molded and tensile tests were performed together. It was shown that the fracture strength of the polypropylene composites increased by 3.2, 5.4 and 6.9 times with the increase of carbon fabric volume fraction of 0.256, 0.367, and 0.480, respectively.