• Journal of the Korean Chemical Society
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• v.54 no.3
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• pp.317-322
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• 2010

This study used 4-fluorostyrene with the cross-linker EGDMA (ethylene glycol dimethacrylate), HEMA (2-hydroxyethyl methacrylate) and the initiator AIBN (azobisisobutyronitrile) for copolymerization. Measurement of the physical properties of the copolymerized polymer showed that the water content was 19.98 ~ 31.08%, refractive index 1.443 ~ 1.475, visible transmittance 87 ~ 93% and tensile strength 0.246 ~ 0.311 kgf while the contact angle showed a distribution between $54.14^{\circ}$ and $66.95^{\circ}$. Therefore, the ophthalmic material produced using 4-fluorostyrene satisfied the basic physical properties required for contact lenses and also showed an increase in wettability and refractive index while having no significant change in water content with relation to styrene. Based on the results of this study, the produced copolymer is suitable for use as a material to high refractive index and wettability contact lenses.

• Applied Chemistry for Engineering
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• v.5 no.6
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• pp.990-997
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• 1994

The vulcanized NR and blend films were prepared with mixing of natural rubber latex (NRL) and methyl methacrylated grafted latex(MGL) with various additives by dipping process. It was investigated the basic properties of vulcanized NR films that is optimum condition of the mature time, swelling degree, cure time at $110^{\circ}C$, and measured the mechanical properties of tensile strength and elongation of its condition. In order to identify the surface structure and the slip properties of blend films contact angles and static and kinetic friction coefficient were measured. Contact angles were decreased with increment of blend ratio of MGL, and static and kinetic friction coefficient were decreased rapidly for the NR/MG and NR-d-MG films than for the NR films. From the results, NR/MG and NR-d-MG films has slip's reinforcement in skin contact surface with increased of blend ratio of MGL.

• Journal of the Korean Applied Science and Technology
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• v.35 no.2
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• pp.502-508
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• 2018

The acrylate copolymer having good coating, water-repellent and adhesion properties was designed and prepared. We prepared copolymers with high yield of > 95% using methyl methacrylate(MMA), 2,2,2-trifluoroethyl acrylate (FMA) and 2-hydroxyethyl methacrylate monomers(HEMA) by either bulk or emulsion polymerization techniques. The $^1H-NMR$ spectrum was used to identify chemical structure and DSC and DMA analysis were conducted. As a result, the glass transition temperature decreased by $3^{\circ}C$ as FMA content increased from 5% to 10%, and decreased by $2{\sim}8^{\circ}C$ when HEMA content increased from 5 % to 10 %. The physical properties were measured using Instron and TGA. As FMA or HEMA content increased by 10%, tensile strength decreased from 29 MPa to 22 MPa and Td decreased from $200^{\circ}C$ to $180^{\circ}C$ in both bulk and emulsion. The contact angle relatively decreased as hydrophilic HEMA content increased.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.12
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• pp.1511-1519
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• 2012

Pipe structures contain many welded zones, and ultrasonic tests are increasingly being performed by using automated testing devices in order to evaluate the weld integrity. An electromagnetic acoustic transducer (EMAT) is a noncontact transducer that can transmit or receive ultrasonic waves without a couplant. Furthermore, it can easily generate specific guided waves such as SH (shear horizontal) or Lamb waves by altering the design of the coil and magnet. Therefore, an EMAT should be useful for application to an automated ultrasonic inspection system. In this study, SH waves generated using an EMAT were applied to inspect the pipe-weld zone. To analyze the specific SH mode (SH0) from the SH wave signals, wavelet transform was applied. It was found that flaws could be detected precisely because the intensity of the $SH_0$ mode-frequency, which is analyzed by using wavelet transform, is proportional to the length of the flaw.

• Applied Chemistry for Engineering
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• v.3 no.4
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• pp.639-648
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• 1992

For recycling cement hydrate(CH) as waterproofers for mortar and concrete or a filler for rubber & plastics, the cement hydrates were treated with stearic acid(SA). And the bonding characteristics and the water repellency of the CH-SA compounds were investigated by using FT-IR, TGA, SEM, XRD, and contact angle measuring apparatus. Water tightness of the remitars used CH-SA compounds was also tested. The results are summarized as follows : 1) If the cement hydrates are treated with over 2.0% of stearic acid, the CH-SA compounds show very strong water repellency. 2) The stearic acids are solidified on the surfaces of cement hydrate in calcium stearate and aluminium stearate. 3) If CH-SA compounds which is cement hydrate treated with 5~10% of stearic acid are used 3%~6% in remitar, water absorption ratio and water permeatility ratio of remitar are decreased in below 30% of those of the ordinary remitar.

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.5
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• pp.687-695
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• 2007

Statement of problem: The proper contact relation between adjacent teeth in each arch plays an important role in the stability and maintenance of the integrity of the dental arches. Proximal contact has been defined as the area of a tooth that is in close association, connection, or touch with an adjacent tooth in the same arch. Purpose: The aim of this study was to develop a digital device for measuring the proximal tooth contact tightness by pulling a thin stainless steel strip (2mm wide, 0.03mm thick) inserted between proximal tooth contact. Material and method: This device consists of measuring part, sensor part, motor part and body part. The stainless steel strip was connected to a stain gauge. The strain gauge was designed to convert the frictional force into a compressive force. This compressive force was detected as a electrical signal and the electrical signal was digitalized by a A/D converter. The digital signals were displayed by a micro-processor. The pulling speed was 8mm/s. Results: For testing reliability of the device in vivo, two healthy young adults (A, B) participated in this experiment. The tightness of proximal tooth contact between the second premolar and the first molar of mandible (subject A) and maxilla (subject B) was measured fifteen times for three days at rest. We double-checked the accuracy of the device with a Universal Testing Machine. Output signals from the Universal Testing Machine and the measuring device were compared. Regression analysis showed high linearity between these two signals. In vivo test, no significant differences were found between measurements. Conclusion: This device has shown to he capable of producing reliable and reproducible results in measuring proximal tooth contact. Therefore, it was considered that this device was appropriate to apply clinically.

• Journal of the Korea Society of Computer and Information
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• v.13 no.3
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• pp.225-236
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• 2008

This study is to evaluate the influence of relationship marketing and identify empirically the important factors which affect relationship continuity between multimodal transport operators and shippers. The empirical findings of this research are, MTO's marketing activity factors which consist of customers' contact intensity, relationship-oriented factors, positively affects relationship continuity such as revisit intention and word-of-mouth communication. As a result, relationship marketing activities are essential to the market strategy of MTO for continuous and stable growth. Also, on condition of transactional types, On-line transaction has an effect of customer switching, but there is no different effect in case of service type. Accordingly, international MTO in domestic need to develop various relationship marketing programs such as a special program for enhancing the continuity, an event for long-term customers and training program should be implemented and enforced to elevate qualify of the service encounter.

• Membrane Journal
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• v.20 no.4
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• pp.335-341
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• 2010

This study focuses on the investigation of the anion exchange membrane through blending poly(ethylenimine) (PEI) and poly(vinyl alcohol) (PVA) varying the mixing ratio. To characterize the resulting membranes, the water content, contact angle, FT-IR, thermal gravimetric analysis, ion exchange capacity, ion conductivity and elastic modulus were measured. The PVA / PEI = 90 / 10 membrane showed the ion conductivity, $5.16{\times}10^{-2}S/cm$ and simultaneously the contact angle, $78.3^{\circ}$. According to TGA measurement, the resulting membranes seemed durable at room temperature. Through the modulus test, the mechanical properties increased with increasing PVA content and apparently the membranes looked very robust.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.245-248
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• 2008

Recently, much research has been conducted on FRP composite to replace steel. However, the concept of FRP girder filled with concrete has not been fully attempted. This study focuses on the analytical behavior of FRP girders filled with concrete. FRP girders usually have large deflection due to relatively low elastic modulus compared to steel members. However, in the previous experimental investigation on small sized modular beams, it has been verified that the displacement of FRP-girder filled with concrete is reduced and the strength is increased considerably. In this research, analytical investigations have conducted to verify the analytical method by comparing the results with tests. In addition, analyses on large girders assembled with small modules have been carried out to predict the feasibility before tests. The analytical results showed that the assembled FRP girders can be used as substitutes for steel girders.

• Journal of Adhesion and Interface
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• v.12 no.4
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• pp.144-150
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• 2011

The effect of low profile agent and release agent on the surface and mechanical properties of bulk mold compound were investigated. Atomic content and contact angle of surface were characterized using X-ray photoelectron spectroscopy and contact anglemeter. Surface morphology and surface roughness were obtained using field emission scanning electron microscope and atomic force microscope, respectively. As increasing the low profile agent from 0 to 9.2 wt%, the volume shrinkage and surface roughness decreased from 0.35% to 0.05%, and from $0.27{\mu}m$ to $0.12{\mu}m$, respectively. The increase of release agent from 1.8 wt% to 3.6 wt% resulted in the migration of release agent to sample surface and it increased the surface roughness. The flexural strength and impact strength were decreased approximately 30% as the low profile agent increasing from 5.0 wt% to 9.0 wt%.