• Polymer(Korea)
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• v.38 no.2
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• pp.138-143
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• 2014

${\alpha},{\omega}$-Hydroxypropyl polydimethylsiloxane (HO-PDMS) was prepared by hydrosilylation of hydrogen terminated polydimethylsiloxane with allyl alcohol. Polydimethylsiloxane modified urethane with isocyanate group (PSU) was prepared from cyclic trimer of hexamethylenediisocyanate with HO-PDMS. PDMS modified urethane base resin with acrylic group (PSUA) was prepared from the urethane reaction of PSU with isocyanate group and 2-hydroxyethylmethacrylate. Their structures were characterized using FTIR and NMR. Coating materials were prepared by mixing PSUA, acrylic hardner, photo-initiator, and solvent and coated on PET film to obtain flexible and hard coating film by UV irradiation. Transparency of coating film was 89.7%, contact angle, $88^{\circ}$, and pencil hardness, 3H.

• Korean Chemical Engineering Research
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• v.45 no.5
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• pp.442-447
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• 2007

In order to improve the surface hardness of transparent plastic films, organic-inorganic hybrid coating solutions were synthesized by the sol-gel method. The coating solutions were prepared by adding GPTMS (glycidoxypropyl trimethoxysilane) to a colloidal silica (12 nm) suspension. PC(polycarbonate) substrates were dipped into the coating solutions and dried at room temperature for 10 min before being cured at $80^{\circ}C$ for 30 min. The effect of the solution pH and GPTMS content was investigated on the properties of coating films. The pencil hardness and adhesion to substrates of the coating films, prepared at acidic condition (pH 4), showed better properties than those at neutral or basic conditions. Also, the pencil hardness and adhesion to substrates of the coating films increased with increasing GPTMS content.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.9C
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• pp.778-785
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• 2010

This paper proposes a high-precision ranging scheme based on channel estimation technique and multipath delay analysis in IR-UWB systems. When the IR-UWB signal is transmitted and received, the high-precision ranging is estimated with the time-of-arrival information of the signal. In the proposed scheme, the channel estimation process with the minimum mean square error technique or zero forcing technique is performed and the overlapped multipath within the pulse is analyzed with matrix pencil (MP) algorithm to achieve the ranging accuracy of centimeters. The performance of proposed scheme is evaluated with various IEEE 802.15.4a channel models and the relationship between the ranging performance and the computational complexity is analyzed in terms of the MP parameter values.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.6
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• pp.989-996
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• 2017

The proposed directional pencil beam antenna consists of a waveguide feeder with bended elliptical conductor plate feed and a parabolic curved reflector. Two rectangular apertures located at the broad wall near the end of the feed waveguide inserted from behind the reflector are located at the focus of the reflector and emit electromagnetic energy with bended elliptical conductor plate. This plate is designed to reflect electromagnetic energy primarily and to face the main reflector. The two rectangular apertures located at the waveguide end have inwardly protruding tabs for impedance matching of the antenna system, the shape of the tabs is a truncated oval. The proposed parabolic reflector antenna has a diameter of 400 mm and a focal length of 134.23 mm. The antenna gain is 33.68 dBi at the center frequency of 16.5 GHz, the beam width is $3.3^{\circ}$ and the reflection loss is -15 dB. Using the HFSS-IE, simulation results are performed to validate the proposed antennas.

• Korean Chemical Engineering Research
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• v.45 no.4
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• pp.335-339
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• 2007

In order to overcome the problem of poor hardness of transparent polycarbonate (PC) sheets, organic-inorganic hybrid hard coating solutions, which show a high refractive index above 1.58, were made by the sol-gel method. These hybrid coating solutions were obtained from mixture of titanium tetraisopropoxide (TTIP), and (3-glycidoxypropyl)trimethoxysilane (GPTMS). The PC sheets were spin-coated, and cured at $120^{\circ}C$ for 2 hr. Change of refractive index in the range of 1.53-1.61 was obtained by varying the GPTMS content. The refractive index of the coated film decreased with increasing the GPTMS content, while the pencil hardness of the coated film was found to increase with increasing the GPTMS content.

• Polymer(Korea)
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• v.33 no.6
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• pp.569-574
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• 2009

Organic- inorganic hybrid waterborne polyurethane (PUD) is synthesized by using hybrid polyol consist of carbonate (PCD), ester (PCL), and siloxane (PDSBP) in order to enhance anti-scratch property of PUD film. The diameter of graft type PUD emulsion is bigger than that of linear type PUD due to the graft structure of hydrophobic siloxane chain. The glass transition temperature of linear type PUD increase and the decomposition temperature of linear type PUD decrease with the content of PCD polyol. While, the decomposition temperature of graft type PUD almost same with increasing PDSBP content. The anti-scratch property and pencil hardness of graft type PUD improves as adding PDSBP polyol in the hybrid polyol system. When 9 wt% of PDSBP polyol is mixed, PUD films shows excellent anti-scratch property (~3.3 N), and pencil hardness (> 9 H).

• School Mathematics
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• v.9 no.3
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• pp.409-426
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• 2007

The relevance of secondary school algebra focused on paper and pencil manipulation has been reconsidered along with the expansion of universal education and the development of ICT such as computer or calculators. This study was designed to investigate the issues and trends of the recent algebra so as to provide implementations for algebra curriculum in Korea. The focus of algebra education has being shifted from paper pencil manipulation to algebraic thinking. The early algebra or informal algebra is one of the important traits of revolution, and the role of ICT is integrated in newly developed curricula. In Korea, algebra education has been retaining the traditional line even though the national curriculum documents allows ICT for instruction. The reasons of these discrepancies were analyzed and the tasks for the new curriculum in accordance with the current trends were suggested in this paper.

• Progress in Medical Physics
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• v.10 no.3
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• pp.133-140
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• 1999

In this paper, as a preliminary study for developing a full 3D electron dose calculation algorithm, We developed 2.5D electron dose calculation algorithm by extending 2D pencil-beam model to consider three dimensional geometry such as air-gap and obliquity appropriately. The dose calculation algorithm was implemented using the IDL5.2(Research Systems Inc., USA), For calculation of the Hogstrom's pencil-beam algorithm, the measured data of the central-axis depth-dose for 12 MeV(Siemens M6740) and the linear stopping power and the linear scattering power of water and air from ICRU report 35 was used. To evaluate the accuracy of the implemented program, we compared the calculated dose distribution with the film measurements in the three situations; the normal incident beam, the 45$^{\circ}$ oblique incident beam, and the beam incident on the pit-shaped phantom. As results, about 120 seconds had been required on the PC (Pentium III 450MHz) to calculate dose distribution of a single beam. It needs some optimizing methods to speed up the dose calculation. For the accuracy of dose calculation, in the case of the normal incident beam of the regular and irregular shaped field, at the rapid dose gradient region of penumbra, the errors were within $\pm$3 mm and the dose profiles were agreed within 5%. However, the discrepancy between the calculation and the measurement were about 10% for the oblique incident beam and the beam incident on the pit-shaped phantom. In conclusions, we expended 2D pencil-beam algorithm to take into account the three dimensional geometry of the patient. And also, as well as the dose calculation of irregular field, the irregular shaped body contour and the air-gap could be considered appropriately in the implemented program. In the near future, the more accurate algorithm will be implemented considering inhomogeneity correction using CT, and at that time, the program can be used as a tool for educational and research purpose. This study was supported by a grant (＃HMP-98-G-1-016) of the HAN(Highly Advanced National) Project, Ministry of Health & Welfare, R.O.K.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.425-430
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• 2002

The needs of the times, a cement plays an important roll in the materials field. So, in this research we would like to study on the properties of Photocatalytic Cement for waste gas reduction. The fundamental phenomena of the Photocatalytic Cement were observed by the NOx Analyzer, Bonding strength, SEM, Flow and Surface hardness(Pencil tester). As a result of this study, the Photocatalytic Cement used Photocatalytic powder, admixture and other materials can obtain its physical properties, also photocatalytic efficiency. If we have added a various experiment, we could have to develop the Photocatalytic Cement.

• 한국정보교육학회:학술대회논문집
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• 2004.08a
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• pp.236-241
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• 2004

Algorithms is defined "step-by-step procedure for accomplishing a task that we wish to complete." Algorithms has much educational values. Already many scholar is making researches about paper-and-pencil algorithms in mathematic education. The purpose of this paper is to propose a study on the direction of teaching algorithms with analysis of algorithms