• Journal of Sensor Science and Technology
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• v.15 no.4
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• pp.257-262
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• 2006

A Fe-C eutectic cell for thermocouple calibration was manufactured and tested to investigate its phase transition characteristics in the thermocouple thermometry. It was observed that the freezing plateaus were strongly affected by the freeze-inducing temperature $T_{f}$. In case of the melting process, the melting plateau was influenced by the previous thermal history. As $T_{f}$. in the previous freezing was lower, the melting plateau became lower with a temperature dependence as small as $-0.0015^{\circ}C/^{\circ}C$. Therefore, it was found that the freeze-inducing temperature should be fixed to obtain a reproducible phase transition temperature in the melting. After fixing $T_{f}$, the melting process was examined and it was found that long and flat melting plateau was obtained within a reproducibility of about ${\pm}0.01^{\circ}C$. Based on the observed results, it was recommended that Fe-C eutectic temperature be best realized for the melting process with a melt-inducing temperature of $+3^{\circ}C$ above the expected liquidus temperature after freezing at $-5^{\circ}C$ below the solidus temperature.

• Journal of the Korean Chemical Society
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• v.54 no.1
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• pp.105-109
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• 2010

HEMA (2-hydroxyethyl methacrylate), EGDMA (ethylene glycol dimethacrylate) and propylene glycol was copolymerized in the presence of AIBN (azobisisobutyronitrile) initiator in a mould. The physical properties of the contact lens were measured. The water content of 37.06~38.71%, refractive index of 1.492~1.432, visible transmittance of 89.4~91.5%, tensile strength of 0.1416~0.2302 kgf, and contact angle of $38.60{\sim}53.53^{\circ}$ were obtained. Therefore, the contact lens material produced using propylene glycol as an additive satisfied the basic physical properties required for contact lenses application. It is interesting to note that an increase in wettability and tensile strength while having no significant changes in water content.

• International Journal of Advanced Culture Technology
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• v.11 no.3
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• pp.18-25
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• 2023

The COVID-19 pandemic has had a significant impact on the educational landscape for students across the globe, leading to a shift towards long-term online learning. This study aims to examine the changes in the health status of college and university students before and after the transition to online classes. We conducted a survey questionnaire among 200 students enrolled at K University in Gangwon-do, including participants from both the Department of Visual Optics and the Department of Physical Therapy. The survey employed a 5-point Likert scale to evaluate a range of health-related factors, including physical and mental well-being, alterations in lifestyle, and academic performance. Both male and female students experienced a decline in physical strength and exercise during the online class period, while mental health and overall happiness showed improvement, particularly among female students. Notable shifts in lifestyle emerged, including an increased usage of electronic devices and enhanced familial connections. The study also shed light on intriguing trends related to academic accomplishments and adherence to official quarantine guidelines. In sum, the findings of this study offer valuable foundational information for the maintenance of students' well-being during online learning, as well as the development of effective strategies for online education in future academic settings.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.9
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• pp.979-986
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• 2010

This paper presents an algorithm for retrieving precise radar cross sections(RCS) of various trihedral corner reflectors (TCR) which are external calibrators of synthetic aperture radar(SAR) systems. The theoretical RCSs of the TCRs are computed based on the physical optics(PO), geometrical optics(GO), and physical theory of diffraction(PTD) techniques; that is, the RCS computation includes the single reflections(PO), double reflections(GO-PO), triple reflections(GO-GO-PO), and edge diffractions(PTD) from the TCR. At first, we acquire an SAR image of the area that five TCRs installed in, and then extract the RCS of the TCRs. The RCSs of the TCRs are extracted accurately from the SAR image by adding up the power spill, which is generated due to the radar IRF(Impulse Response Function), using a square window. We compare the extracted RCSs with the theoretical RCSs and analyze the difference between the theoretical and experimental RCSs of the TCR for various window sizes and various backscattering coefficient levels of the adjacent area. Finally, we propose the minimum size of the integration area and the maximum level of the backscattering coefficients for the adjacent area.

• Journal of Korean Ophthalmic Optics Society
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• v.6 no.1
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• pp.119-124
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• 2001

Dimethyl terephthalate (DMT). 1.4-butanediol (1.4-BD) and poly (tetramethylene ether) glycol (PTMG) in the molecular weight of 2000 (g/mol) were used to synthesize poly(ether-b-ester) thermoplastic elastomers (TPEEs). The final copolymers were annealed to improve thermal stability at elevated temperatures and mechanical properties. This study showed that as the proportion of soft segment increases melting temperature and degree of crystallinity of TPEEs decrease constantly. In case of mechanical properties like flexural strength and flexural elastic modulus. $35-PTMG^{2000}$ indicates the highest values due to more efficient physical interlock.

• Korean Journal of Optics and Photonics
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• v.24 no.4
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• pp.189-195
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• 2013

An F/1.2 infrared optical system that involves two aspheric BD-2 lenses and an aspheric diffractive surface was designed over $8-14{\mu}m$ with a field angle of $15.2^{\circ}$. The system may be used in uncooled cameras and is analyzed using beam synthesis propagation (BSP). The diffractive surface is modeled as a physical surface with a given thickness, and results are compared with those obtained by conventional methods, such as the exit-pupil method and a method which superposes diffraction orders.

• Journal of Korean Ophthalmic Optics Society
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• v.10 no.3
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• pp.215-220
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• 2005

On entering new millenium, there has been an important switchover in the divergent View and its cases on commercial marketing. This study is to focus on the related influence factors of the optician's marketing. Aiming to improve the relationship of the manager and the manager and the clients, this study tried to find out the influences of the marketing. We defined quality of relation as three element, trust, satisfaction, absorption. We investigated how it influenced optician's characters, goods, service, price, physical convenience and communication to the quality of relation. Moreover, we investigated how it influenced optician characters like knowledge information, good impression, contact and relation marketing of dissatisfaction solution, also quality of relation could or not influence about repurchase intension and Big Mouth marketing. Optician's characters affect on affirmative effect to trust and absorption, but little affirmative effect to satisfaction. Since optician's characters are trust and absorption rather than satisfaction influence, they actively should improve customer-oriented variety of goods, service, physical convenience, communication. As price and communication structure of optician was formed so not modernized, we realized these have not influenced their trust, satisfaction, absorption to customer. Optician's characters influenced more affirmative effect to satisfaction than thrust and absorption. quality of relations mostly provided affirmative effect to the result of relation. The opticians should make efforts to influence on customer satisfied with goods and service, also to have trust and absorption for customer, should maintain good partnership with customer.

• Proceedings of the KIEE Conference
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• 1984.07a
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• pp.287-291
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• 1984

The electromagnetic wave scattered by an arbitrary-angled dielectric wedge is constructed by physical optics solution and its corrected field. Two models of correction source are obtained; one is multipole line source at tip of wedge and the other is correction electric and magnetic currents distributed along the interfaces of dielectric wedge. Calculated far-field patterns are presented and compared each other.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.227-230
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• 1999

Rigorous formulation for solving the scattered fields by a lossy dielectric wedge is proposed. By employing the Kirchhoff's integrals in the physical domain and the extinction theorem in the mathematically complementary region, it is shown that the accurate solution is obtained by adding the numerically corrected fields generated by the multipole source expansions to the analytically approximated physical optics solution. Its accuracy is affirmed by the extinction behavior of the solution in the complementary region.

• Journal of the Korean Physical Society
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• v.73 no.10
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• pp.1506-1511
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• 2018

Spectral behaviors of lasing from semiconductor square ring microcavities with structures for unidirectional laser oscillation were investigated. When a tapered structure was introduced, the lasing envelope shifted to a shorter wavelength region. Statistical estimate of the additional loss caused by the tapered structure was carried out by analyzing spectral data from many sets of cavities with various sizes. When a saw-edged structure was introduced, the unidirectional lasing functioned well but no apparent spectral shift was observed due to negligible additional loss.