• Korean Journal of Materials Research
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• v.18 no.6
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• pp.318-325
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• 2008

Single crystal $ZnIn_2S_4$ layers were grown on thoroughly etched semi-insulating GaAs(100) substrate at $450^{\circ}C$ with hot wall epitaxy (HWE) system by evaporating $ZnIn_2S_4$ source at $610^{\circ}C$. The crystalline structure of the single crystal thin films was investigated by the photoluminescence (PL) and double crystal X-ray rocking curve (DCRC). The temperature dependence of the energy band gap of the $ZnIn_2S_4$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)=2.9514\;eV-(7.24{\times}10^{-4}\;eV/K)T^2/(T＋489\;K)$. After the as-grown $ZnIn_2S_4$ single crystal thin films were annealed in Zn-, S-, and In-atmospheres, the origin of point defects of $ZnIn_2S_4$ single crystal thin films has been investigated by the photoluminescence (PL) at 10 K. The native defects of $V_{Zn}$, $V_S$, $Zn_{int}$, and $S_{int}$ obtained by PL measurements were classified as a donors or acceptors type. And we concluded that the heat-treatment in the S-atmosphere converted $ZnIn_2S_4$ single crystal thin films to an optical p-type. Also, we confirmed that In in $ZnIn_2S_4$/GaAs did not form the native defects because In in $ZnIn_2S_4$ single crystal thin films existed in the form of stable bonds.

• Proceedings of the Korea Crystallographic Association Conference
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• 2003.05a
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• pp.23-23
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• 2003

Cu 단결정과 다결정 Cu 막대(rod)를 시료로 하여 구부린 완전결정(bent perfect crystal, BPC)을 이용한 중성자 단색기의 특성을 평가함으로써 단결정 회절 및 집합조직 측정장치인 4축 단결정 회절장치(FCD)에 BPC 단색기를 적용할 수 있는지 시험하였다. 측정은 한국원자력연구소의 연구용 원자로인 하나로의 571 수평공에 구성된 test station에서 수행하였다. 단색기와 시료 사이의 거리는 3000mm, 시료와 검출기 사이는 600mm, 단색화빔 인출각도(2θ/sub M/)는 44.6°로 고정하여 FCD와 거의 같은 배치를 구현하였다 직사빔의 단면분포와 강도는 저효율 2차원 위치민감형 검출기(2-D PSD)를 이용하여 확인하였다. 이 검출기는 검출면적 90x90㎟, 공간 분해능 1.2mm, 검출효율 약 1%인 저효율 검출기이다. 회절빔은 검출면적 190x190㎟, 검출효율은 1Å에서 60%인 고효율 2-D PSD를 이용하여 측정하였다. Cu 단결정 측정에 사용한 ePC 단색화 결정은 200×40×3.4㎣ 크기의 Si(220) 슬랩이며, 비대칭 기하로 Si(331)면을 사용하여 파장 λ=0.954Å으로 중성자빔을 단색화시켰다. BPC-Si를 구부려 슬랩의 곡률반경을 변화시키면서 단색기-시료-검출기가 평행배치일 때 Cu(200), (220), (400), (420)면의 rocking curve를 측정하여 각 조건에서의 분해능과 강도를 평가하였다. BPC 단색기를 집합조직 측정에 적용할 수 있는지 시험하기 위하여 다결정 Cu 막대(직경 4.5mm, 길이 18mm)를 시료로 선택하였다. 207x30x3.0㎣ 크기의 Si 슬랩을 단색화 결정으로 사용하였다. 이 슬랩은 다양한 결정면을 이용한 특별한 기하를 구현할 수 있도록 Si(111)면에서 10° 벗어난 면을 절단한 것이다. 비대칭 기하로 Si(311)면을 사용하여 파장 λ=1.253Å의 단색화된 중성자빔으로 측정하였다 BPC-Si를 구부려 슬랩의 곡률반경을 변화시키면서 단색기-시료-검출기가 평행파 반평행배치일 때 Cu(111), (200), (220), (311), (331), (420)면의 회절선을 측정하여 각 조건에서 분해능과 강도를 평가하였다.

• Journal of the Korean Magnetics Society
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• v.13 no.6
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• pp.221-225
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• 2003

Effects of annealing temperature on the crystalline and magnetic properties of YIG films grown by solid phase epitaxy. The eptiaxy films were made by annealing Fe-Y-O amorphous films in the air at 550-1050 $^{\circ}C$ which were sputtered on GGG (111) substrates in a conventional rf sputtering system. Crystallization temperature of Fe-Y-O amorphous films on GGG (111) substrate was between 600 and 650 $^{\circ}C$ which is much lower than that Fe-Y-O powder prepared by sol-gel method. Excellent epitaxial growth of YIG films could be conformed by the facts that the diffraction intensity of YIG (888) plane was comparable with that of GGG (888) plane and full width at half maximum of YIG (888) rocking curve was smaller than 0.14$^{\circ}$ when films were annealed at 1050 $^{\circ}C$. It could be seen that it is necessary to anneal the films at higher temperature for an excellent epitaxy because lattice parameter of YIG films were smaller and the peak of YIG (888) plane is higher and narrower with increasing annealing temperature. Films annealed at higher temperature shows M-H loop with perpendicular anisotropy which was due to 0.15％ lattice mismatch between YIG and GGG.

• Clinical and Experimental Pediatrics
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• v.63 no.1
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• pp.25-29
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• 2020

Background: Pain during the developmental period may adversely affect developing neuronal pathways and result in adverse neurodevelopmental, cognitive, and behavioral effects in later life. Immunizations, e.g., hepatitis B vaccine (HBV), administered at birth are painful experiences to which neonates are universally subjected. Purpose: Here we aimed to study and compare the effectiveness of various nonpharmacological pain management methods in newborns to enable the development of safe and effective analgesic methods for newborns. Methods: This prospective study was conducted at a tertiary care hospital in the Himalayan region. Three hundred term healthy neonates were divided into 6 groups of 50 each. Groups 1-5 were intervention groups, patients of which received a nonpharmacological intervention (breastfeeding, nonnutritive sucking, rocking, 25% sucrose, or distilled water) before the intramuscular HBV, while patients in group 6 received no intervention. The pain response in each group after the HBV injection was assessed and compared using cry duration and Douleur Aigue Nveau-ne (DAN) score, a behavioral acute pain rating scale for newborns. Results: Cry duration was decreased in all intervention groups, significantly so in the sucrose (19.90 seconds), breastfeeding (31.57 seconds), and nonnutritive sucking (36.93 seconds) groups compared with controls (52.86 seconds). DAN scores decreased significantly (P<0.05) at one or more points i.e. 30, 60, or 120 seconds in the breastfeeding and 25% sucrose intervention groups compared with controls. Conclusion: Oral sucrose and nonnutritive sucking are simple yet underutilized nonpharmacological interventions that effectively reduce pain in newborns.

• Journal of the Earthquake Engineering Society of Korea
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• v.20 no.5
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• pp.285-293
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• 2016

Soil-foundation-structure interaction (SFSI) is one of the important issues in the seismic design for evaluating the exact behavior of the system. A seismic design of a structure can be more precise and economical, provided that the effect of SFSI is properly taken into account. In this study, a series of the dynamic centrifuge tests were performed to compare the seismic response of the single degree of freedom(SDOF) structure on the various types of the foundation. The shallow and pile foundations were made up of diverse mass and different conjunctive condition, respectively. The test specimen consisted of dry sand deposit, foundation, and SDOF structure in a centrifuge box. Several types of earthquake motions were sequentially applied to the test specimen from weak to strong intensity of them, which is known as a stage test. Results from the centrifuge tests showed that the seismic responses of the SDOF structure on the shallow foundation and disconnected pile foundation decreased by the foundation rocking. On the other hand, those on the connected pile foundation gradually increased with intensity of input motion. The allowable displacement of the foundation under the strong earthquake, the shallow and the disconnected pile foundation, have an advantage in dissipating the earthquake energy for the seismic design.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.99-99
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• 2008

To grow the large diameter GaN with high structure and optical quality has been obtained by hydride vapor phase epitaxy(HVPE) method. In addition to the nitridation of $Al_2O_3$ substrate, we also developed a "step-growth process" to reduce or to eliminate the bowing of the GaN substrate caused by thermal mismatch during cool down after growth. The as-grown 380um thickness and 75mm diameter GaN layer was separated from the sapphire substrate by laser-induced lift-off process at $600^{\circ}C$. A problem with the free-standing wafer is the typically large bowing of such a wafer, due to the built in the defect concentration near GaN-sapphire interface. A polished G-surface of the GaN substrate were characterized by room temperature Double crystal X-ray diffraction (DCXRD), photoluminescence(PL) measurement, giving rise to the full-width at half maximum(FWHM) of the rocking curve of about 107 arcsec and dislocation density of $6.2\times10^6/cm^2$.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.5
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• pp.41-51
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• 2010

For safe seismic evaluation and design, it is necessary to predict the plastic deformation demands of members. In the present study, a quick and reasonable method for the evaluation of member plastic deformations of dual systems was developed on the basis of results of elastic analysis, without using nonlinear analysis. Plastic deformations of beams, columns, and walls are functions of member stiffness, story drift ratio, and moment redistribution determined from elastic analysis. For dual systems with rigid connections between walls and beams, an increase in the plastic deformations of beams due to the rocking effect was considered. The proposed method was applied to 8-story dual systems and the predicted plastic deformations were compared with the results of nonlinear analysis. The results showed that the proposed method accurately predicted the member plastic deformations with simple calculations, but that for the accurate evaluation of member plastic deformations, the inelastic story drift ratio must also be predicted with accuracy. The proposed method can be applied to both the performance-based seismic design of new structures and the seismic evaluation of existing structures.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.4
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• pp.113-118
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• 2019

In this study, we investigated the growth of single-crystallinity α-Ga₂O₃ thin films on c-plane sapphire substrates using halide vapor pressure epitaxy. We also found the optimal growth conditions to suppress the phase transition of α-Ga₂O₃. Our results confirmed that the growth temperature and partial pressure of the reactive gas greatly influenced the crystallinity. The optimal growth temperature range was about 460~510℃, and the α-Ga₂O₃ thin films with the highest crystallinity were obtained at a III/VI ratio of 4. The thickness and surface morphology of the thin films was observed by scanning electron microscopy. The film thickness was 6.938 ㎛, and the full width at half maximum of the ω-2θ scan rocking curve was as small as 178 arcsec. The optical band gap energy obtained was 5.21 eV, and the films were almost completely transparent in the near-ultraviolet and visible regions. The etch pit density was found to be as low as about 6.0 × 10⁴ cm^-2.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.15 no.2
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• pp.86-96
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• 2003

A fracture or breakage of the concrete armor units in the primary cover layer of breakwaters is studied by using the reliability analysis which may be defined as the structural stability. The reliability function can be derived as a function of the angle of rotation that represents the rocking of armor units quantitatively. The relative influences of all of random variables related to the material and geometric properties on the fracture of armor units is analyzed in detail. In addition, the probability of failure for the fracture of individual armor unit can be evaluated as a function of the incident wave height. Finally, Bernoulli random process and the allowable fracture ratio may be introduced together in this paper, by which the probability of failure of a breakwater due to the fracture of armer units can be obtained straightforwardly. It is found that the probability of failure of a breakwater due to the fracture of armor units may be varied with the several allowable fracture ratios. Therefore, it should be necessary to consider the structural stability as well as the hydraulic stability for the design of breakwaters with multi-leg slender concrete armor units of large size under wave action in deep water.

• Korean Journal of Materials Research
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• v.16 no.6
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• pp.360-366
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• 2006

A series of ZnO thin films were grown by radio-frequency (RF) magnetron sputtering with various RF powers on $SiO_2/Si$(100) substrates at $500^{\circ}C$. Thicknesses of the investigated ZnO films were fixed to about 250nm by changing the growth time based on the changes of growth rates with RF powers. All the ZnO thin films were grown with <0001> preferred orientation. Average grain sizes of about 250nm-thick ZnO films evaluated by FE-SEM, AFM, and TEM were increased by decreasing the RF power. Structural properties addressed by FWHM values of XRD (0002) omega rocking curves and their intensities were better for the smaller grain sized ZnO films grown with high RF powers, which implies small values of tilt for smaller grain sized ZnO films. However, optical properties addressed by intensities of band edge emissions from room temperature and low temperature photoluminescence were better for the larger grain sized ZnO films with low RF power, which implies grain boundaries acted as nonradiation recombination centers.