• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.124-127
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• 2003

The stochiometric $AgGaSe_2$ polycrystalline mixture of evaporating materials for the $AgGaSe_2$ single crystal thin film was prepared from horizontal furnance. To obtain the single crystal thin films, $AgGaSe_2$ mixed crystal and semi-insulating GaAs(100) wafer were used as source material and substrate for the Hot Wall Epitaxy (HWE) system, respectively. The source and substrate temperature were fixed at $630^{\circ}C$ and $420^{\circ}C$, respectively. The thickness of grown single crystal thin films is $2.1{\mu}m$. The single crystal thin films were investigated by photoluminescence and double crystal X-ray diffraction(DCXD) measurement. From the photoluminescence measurement of $AgGaSe_2$ single crystal thin film, we observed free excition ($E_x$) observable only in high quality crystal and neutral bound excition ($D^{\circ}$,X) having very strong peak intensity. And, the full width at half maximum and binding energy of neutral donor bound excition were 8 meV and 14.1 meV, respectively. By Haynes rule, an activation energy of impurity was 141 meV.

• Geomechanics and Engineering
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• v.9 no.6
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• pp.729-742
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• 2015

The aim of the present work was the study of instability in a loose sand from Les Dunes beach in Ain Beninan, Algeria, where the Boumerdes earthquake occurred in 2003. This earthquake caused significant structural damages and claimed the lives of many people. Damages caused to infrastructures were strongly related to phenomena of liquefaction. The study was based on the results of two drained and six undrained triaxial tests over a local sand collected in a region where liquefaction occurred. All the tests hereby analyzed followed compression stress-paths in monotonic conditions and the specimens were isotropically consolidated, since the objective was to study the instability due to static loading as part of a more general project, which also included cyclic studies. The instability was modeled with the second-order work increment criterion. The definition of the instability line for Les Dunes sand and its relation with yield surfaces allowed the identification of the region of potential instability and helped in the evaluation of the susceptibility of soils to liquefy under undrained conditions and its modeling. The dilatancy rate was studied in the points where instability began. Some mixed tests were also simulated, starting with drained conditions and then changing to undrained conditions at different time steps.

• Steel and Composite Structures
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• v.30 no.6
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• pp.493-516
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• 2019

This paper is dedicated to nonlinear static and free vibration analysis of Uniform Distributed Carbon Nanotube Reinforced Composite (UD-CNTRC) structures under in-plane loading. The authors have suggested an efficient six-node triangular element. Mixed Interpolation of Tensorial Components (MITC) approach is employed to alleviate the membrane locking phenomena. Moreover, the behavior of the well-known LST element is considerably improved by applying an additional linear interpolation on the strain fields. Based on the rule of mixture, the properties of CNTRC are obtained. In this study, only the uniform distributed CNTs are employed through the thickness direction of element. To achieve the natural frequencies and shape modes, the eigenvalue problem is also solved. Using Total Lagrangian Principles, large amplitude free vibration is considered based on the first normalized mode shape of structure. Different well-known plane problem benchmarks and some proposed ones are studied to validate the accuracy and capability of authors' formulations. In addition, the effects of length to the height ratio of beam, CNT's characteristics, support conditions and normalized amplitude parameter on the linear and nonlinear vibration parameters are investigated.

• Steel and Composite Structures
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• v.39 no.5
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• pp.493-509
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• 2021

There is not enough mixed finite element method (MFEM) model developed for static and dynamic analysis of functionally graded material (FGM) beams in the literature. The main purpose of this study is to develop a reliable and efficient computational modeling using an efficient functional in MFEM for free vibration and static analysis of FGM composite beams subject to high order shear deformation effects. The modeling of material properties was performed using mixture rule and Mori-Tanaka scheme which are more realistic determination techniques. This method based on the assumption that a two phase composite material consisting of matrix reinforced by spherical particles, randomly distributed in the beam. To explain the displacement components of the shear deformation effects, it was accepted that the shear deformation effects change sinusoidal. Partial differential field equations were obtained with the help of variational methods and then these equations were transformed into a novel functional for FGM beams with the help of Gateaux differential derivative operator. Thanks to the Gateaux differential method, the compatibility of the field equations was checked, and the field equations and boundary conditions were reflected to the function. A MFEM model was developed with a total of 10 degrees of freedom to apply the obtained functional. In the numerical applications section, free vibration and flexure problems solutions of FGM composite beams were compared with those predicted by other theories to show the effects of shear deformation, thickness changing and boundary conditions.

• Korean Journal of Legislative Studies
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• v.26 no.2
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• pp.35-71
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• 2020

The purpose of this study is to verify the effect of electoral competition on voters deciding on strategic split-ticket voting under the mixed-member electoral system. As result, the more competitive the constituencies are, the more voters choose to vote for the major parties. The results of logistic regression analysis including interaction terms showed that the more competitive the constituencies are, the more voters choose for candidates from the major parties. Also, the finding shows that major party supporters are less affected by electoral competition than minor party supporters in choosing a candidate in the single-seat districts. In the case of minor party supporters, the more competitive the constituencies were, the more likely they were to choose the major party candidate instead of the minor party candidate. Based on these results, it can be inferred that voters are affected by the presence or behavior of other voters in local constituencies under the first-past-the-post rule. Because of the psychology of not wanting their votes to be useless, voters cast their ballots more strategically as the competition in constituencies intensifies, and as the competition in constituencies slackens, such tendencies weaken, and this trait is particularly evident among minor party supporters.

• Journal of Korean Ophthalmic Optics Society
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• v.1 no.1
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• pp.119-125
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• 1996

From 1995. 3. 20 to 1995. 4. 10 refractive errors were surveyed on the 1,197 middle and high school pupils in Dong-Du-Cuon area. On the basis of the power of the old glasses or newly examined power, we surveyed the distribution of the refractive errors according to their types, ages, heights, weights and differences between both eyes. Among 2,394 eyes examined, 1,125eyes(47%) were emmetropia, 967 eyes(40.4%) were myopic, and 302eyes(12.6%) were hyperopic. As to the distribution of refractive errors, simple myopia(42.9%) was most common, and mixed astigmatism and compound hyperopic astigmatism were below 1%, Among the types of astigmatism, 62% were with the rule, 23% were against the rule and 15% were oblique, Differences between both eyes, the left eye showed more myopic than those of right eye. The distribution of myopia according to their ages, 27.7 at age 11, 38.5% at age 12, 35.5% at age 41.5% at age 14, 37.7% at age 15, 48.3% at age 16 and 46.8% at age 17., there was a significant increase in the prevalence of the myopia but that or hyperopia decreases with increases of age.

• Journal of Korean Ophthalmic Optics Society
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• v.12 no.3
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• pp.105-110
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• 2007

To investigate the ametropia and refractive error of 222 ametropic eyes of the 111 high school students in Gwangju Metropolitan City, the visual acuity test was performed by the object and subject method. 85% of the eye types were positive for myopia, 14% for emmetropia, and 1% for hyperopia, respectively. 38% of the abnormal refraction eyes were positive for simple myopia, 4% for myopia simple astigmatism, 56% for myopia compound astigmatism, and 0% for simple hyperopia, 0% for hyperopia simple astigmatism, 2% for hyperopia compound astigmatism, 0% for mixed astigmatism, respectively. 92% of the axes fo astigmatism were for astigmatism with-the-rule, 6% for astigmatism against-the rule, 2% for astigmatism oblique, respectively. As for the astigmatic power, 0.50 < cylinder < 1.00D was 68%, 1.00 < cylinder < 2.00D was 25%, and anything over the 2.00 cylinder D was 7%. As for the equivalent spheric power of myopic abnormal refraction eyes, -0.50 < spheric equivalent < -2.00D was 26%, -2.00D < spheric equivalent < -6.00D was 55% and anything over the -6.00D was 19%. The rate of wearing glasses was 74%. It increases compared to 20 years ago. 91% of the eye test place was the optical shop, 9% the eye doctor hospital. 80% of the students need to change their optical lenses because spherical equivalent power was over 0.50D.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.1
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• pp.125-129
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• 2008

Purpose: To research the study of abnormal refraction eye on women population of university students in South - East Korea. Methods: Between March 2007 and October 2007, the refraction test of eye glasses wearer was evaluated on women population (367 students, aged 19~22 years) of university in living on Kyung-Nam and Pusan province. Data was analysed with T-test. Results: On the abnormal refraction status, Compound Myopic Astigmatism was 76.72%, simple myopia was 10.90%, mixed astigmatism was 6.27%, respectively. On the prevalence of myopic power, low was 59.57%, moderate was 24.93%, high was 15.49%, respectively. On the myopic equivalent power, the right eye had more increase to compare to left eye. but these was not a statically significant correlation (p<0.5) between the right and left eyes. On the anisometropia of spherical equivalents and cylinder power, most subjects was under 1.0 diopter. On the other hand, the type of astigmatic axis was with-the rule (70.79%), against -the rule (18.41%), and oblique (10.80%). Conclusions: This study identify that the refraction status of abnormal refraction eye on women population in university students in South-East Korea have been more increased prevalence the myopia and astigmatism.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.10
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• pp.51-59
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• 1998

($Na_{1/2}Ln_{1/2}$)$TiO_3$ceramics have a high relative dielectric constant and a positive temperature coefficient of resonant frequency ($\tau_f$)(where Ln represents a lanthanide: $La^{+3}$, $Pr^{+3}$, $Nd^{+3}$ and $Sm^{+3}$). On the other hand, $MgTiO_3$ ceramic has a high Qf value and a negative temperature coefficient. So We have investigated the microwave dielectric properties of $xMgTiO_3$-(1-x) ($Na_{1/2}Ln_{1/2}$)$TiO_3$. In these systems, there are no clues on solid-solution and secondary phase. There are mixed phases with $MgTiO_3$and ($Na_{1/2}Ln_{1/2}$)$TiO_3$ phases. Its dielectric characteristics (Qf, temperature coefficient and dielectric constant) are intermediate between ($Na_{1/2}Ln_{1/2}$)$TiO_3$ and $MgTiO_3$ and are predictable by the logarithmic mixing rule. The dielectric ceramic compositions temperature coefficient each approximates to zero at Ln=La, x=0.9, Ln=Pr, x=0.87, and Ln=Nd, x=0.84. At this time, there are Qf values in the range of 55,000 to 28,00GHz and relative dielectric constants in the range of 22 to 25.

• Korean Journal of Crystallography
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• v.12 no.3
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• pp.127-136
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• 2001

A stoichiometric mixture of evaporating materials for ZnGa₂Se₄single crystal thin films was prepared from horizontal furnace. To obtain the single crystal thin films, ZnGa₂Se₄mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperatures were 610℃ and 450℃, respectively. The crystalline structure of the single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of ZnGa₂Se₄single crystal thin films measured from Hall effect by von der Pauw method are 9.63×10/sup 17/㎤ and 296 ㎠/V·s at 293 K, respectively. From the photocurrent spectrum by illumination of perpendicular light on the c-axis of the ZnGa₂Se₄single crystal thin film, we have found that the values of spin orbit splitting △so and the crystal field splitting Δcr were 251.9meV and 183.2 meV at 10 K, respectively. From the photoluminescence measurement on th ZnGa₂Se₄single crystal thin film, we observed free excition (Ex) existing only high quality crystal and neutral bound exiciton (A°, X) having very strong peak intensity. Then, the full-width-at-half-maximum (FWHM) and binding energy of neutral acceptor bound excition were 11 meV and 24.4 meV, respectivity. By Haynes rule, an activation energy of impurity was 122 meV.