• Proceedings of the Korea Association of Crystal Growth Conference
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• 1998.06a
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• pp.39-43
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• 1998

Single crystals of{{{{ { Zn}_{ 1-x} {Mn }_{x }{Te} }}}} with x=0.3-0.6 were prepared by the standard Bridgeman method. Diffuse neutron diffraction intensities due to the short range magnetic ordering is found in the vicinities of 1 1/2 0 reciprocal point and its equivalent point, indicating that the magnetic correlation of the clusters is the type III antiferromangetic one do the F-type Bravais class crystals, being identical with that of {{{{{ Cd}_{ 1-x} {Mn }_{x }Te }}}}. Neutron inelastic scattering measure-ment has been performed for {{{{{ Zn}_{ 0.6} { Mn}_{ 0.4}Te }}}} sample using the cold neutron spectrometer. AGNES. High resolution measurement with the energy resolution of {{{{ TRIANGLE E= +- .01meV}}}} was carried out in the temperature range from 10K to the ambient. Critical scattering, closely related with the spin glass transition, has been observed for the first time in this semimagnetic semi-conductor. The critical scattering is observed at temperatures in the vicinity of the spin glass transition temperature, 17K. The scattering is observed as a kind of quasielastic scattering in the reciprocal range where the elastic magnetic diffuse scattering has been observed, e.g., 11/20 reciprocal point, indicating the spin fluctuation has dynamic components in this material. Photoconductivity has been discovered below 150K in {{{{{ Zn}_{ 0.4} {Mn }_{0.6 } Te}}}}. The electric AC conductivity has been increased dramatically under the laser light with the wave lengths of {{{{ lambda =6328,5145 and4880 }}}}$\AA$ ,respectively. After the light was darkened, the conductivity was reduced to the original level after about 2000 seconds at 50K, being above the spin glass transition temperature. This phenomenon is the typical persistent photoconductivity; PPC which was similarly found in {{{{ { Zn}_{ 1-x} { Mn}_{x} Te}}}}.

• Korean Journal of Optics and Photonics
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• v.15 no.6
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• pp.519-526
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• 2004

We developed a 2-D imaging system to detect ultra weak biophoton by using a high sensitive fast CCD camera. We installed an illumination apparatus to generate delayed luminescence from plant leaves. Shutters at the illumination system and detector were synchronized to each other. The lens system of the CCD camera was newly designed to accommodate the specific requirements to enhance the collection efficiency for biophoton. Based on the lens simulation, commercial lenses were chose for the lens system. All the equipment was installed in a multi-purpose dark box and the delayed luminescence of Euonymus japonica was successfully acquired.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.301-301
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• 2006

The physical properties of well-defined star-shape polystyrenes with high number of arms (6 to 57 arms) in good and theta solvents were studied using synchrotron X-ray scattering. The scattering profiles for multi-armed polystyrenes shown the molecular shape is changed according to increasing of number of arm. From various parameters which were obtained from scattering profiles, the molecular shape was determined more detail. As results, the molecular shape was changed from a fuzzy-ellipsoid for 6-armed PS to a fuzzy-sphere sphere for 57-armed PS according to increasing of number of arm.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.11
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• pp.5370-5393
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• 2019

In this paper, we consider a two-way relay non-orthogonal multiple access (TWR-NOMA) system with residual hardware impairments (RHIs) and channel estimation errors (CEEs), where two group users exchange their information via the decode-and-forward (DF) relay by using NOMA protocol. To evaluate the performance of the considered system, exact analytical expressions for the outage probability of the two groups users are derived in closed-form. Moreover, the asymptotic outage behavior in the high signal-to-noise ratio (SNR) regime is examined and the diversity order is derived and discussed. Numerical simulation results verify the accuracy of theoretical analyses, and show that: i) RHIs and CEEs have a deleterious effects on the outage probabilities; ii) CEEs have significant effects on the performance of the near user; iii) Due to the RHIs, CEEs, inter-group interference and intra-group interference, there exists error floors for the outage probability.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.180-180
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• 2012

Heteroepitaxial GaN nano- and micro-rods (NMRs) are one of the most promising structures for high performance optoelectronic devices such as light emitting diodes, lasers, solar cells integrated with Si-based electric circuits due to their low dislocation density and high surface to volume ratio. However, heteroepitaxial GaN NMRs growth using a metal-organic vapor phase epitaxy (MOVPE) machine is not easy due to their long surface diffusion length at high growth temperature of MOVPE above $1000^{\circ}C$. Recently some research groups reported the fabrication of the heteroepitaxial GaN NMRs by using MOVPE with vapor-liquid-solid (VLS) technique assisted by metal catalyst. However, in the case of the VLS technique, metal catalysts may act as impurities, and the GaN NMRs produced in this mathod have poor directionallity. We have successfully grown the vertically well aligned GaN NMRs on Si (111) substrate by means of self-catalystic growth methods with pulsed-flow injection of precursors. To grow the GaN NMRs with high aspect ratio, we veried the growth conditions such as the growth temperature, reactor pressure, and V/III molar ratio. We confirmed that the surface morphology of GaN was strongly influenced by the surface diffusion of Ga and N adatoms related to the surrounding environment during growth, and we carried out theoretical studies about the relation between the reactor pressure and the growth rate of GaN NMRs. From these results, we successfully explained the growth mechanism of catalyst-free and mask-free heteroepitaxial GaN NMRs on Si (111) substrates. Detailed experimental results will be discussed.

• Journal of Magnetics
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• v.13 no.1
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• pp.30-33
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• 2008

A highly sensitive, giant magnetoresistance-spin valve (GMR-SV) biosensing device with high linearity and very low hysteresis was fabricated by photolithography. The detection of magnetic nanoparticles and Fe-hemoglobin inside red blood cells using the GMR-SV biosensing device was investigated. When a sensing current of 1 mA was applied to the current electrode in the patterned active devices with an area of $2{\times}6{\mu}m^2$, the output signals were about 13.35 mV. The signal from even one drop of human blood and nanoparticles in distilled water was sufficient for their detection and analysis.

• Nuclear Engineering and Technology
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• v.52 no.8
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• pp.1777-1783
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• 2020

As a part of R&D work for the high intensity proton linac of China Accelerator Driven Sub-critical System project, a superconducting half-wave cavity with a frequency of 162.5 MHz and an optimal beta of 0.15 (HWR015) has been developed at Institute of Modern Physics (IMP), Chinese Academy of Sciences. In this paper, the design and test results will be described in detail. We introduced a new stiffening strategy for the HWR cavity, the simulation results show that the cavity has much lower frequency sensitivity coefficient (df/dp), Lorentz force detuning coefficient (KL), and can achieve more stable mechanical properties. The performance of the HWR cavity operated in cryostat will be also reported.

• Journal of Science Education
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• v.33 no.2
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• pp.165-172
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• 2009

Korean 7th national curriculum gave the right to elect the advanced subject such as physics II, chemistry II. Students could elect the subject by their aptitude and interest. But, actually, the choice was constrained by school circumstances such as the number of teacher and the number of class. high school students. We investigated the demand about school science and perception about scientifically specialized high school in which the students could have all advanced science subjects by the survey of 336 middle school students including 148 students in the science education center for the gifted, 220 high school students, and 70 science teachers in capital region. As results of this study, most of the high school opened chemistry and biology advanced subjects, but only 37.1% of them opend physics advanced subject. This constrained students' right of elect the subject by their interest. While most of middle school and high school students normally demanded the more experiment in the class and the easier science content, the students in the science education center for the gifted demanded more science class time. The students who wanted to have science career had very positive recognition of scientifically specialized high school and science teachers agreed to running the scientifically specialized high school.

• Korean Educational Research Journal
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• v.38 no.2
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• pp.109-125
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• 2017

The purpose of this study was to examine how group argumentations mediated individual arguments by analyzing physics teachers' group argumentation and individual follow-up written arguments. Five in-service physics teachers participated in this study, two middle school and three high school teachers. The topics of argumentation included physics topics and pedagogy of them. Findings showed that the teachers constructed much more elaborated individual written arguments than group argumentation, which seemed to be resulted from different perceptions of teachers' verbal and written argumentations. Also, in their written arguments the teachers selectively utilized their colleagues' ideas shared during group argumentation. Lastly, teachers' argumentation showed different features between topics of physics and physics pedagogy. These differences were related to their orientations toward argumentation about content knowledge and teaching. These findings shed light on a productive physics teacher professional development in argumentation.

• Nuclear Engineering and Technology
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• v.54 no.5
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• pp.1616-1622
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• 2022

Selenium has been identified as an element of interest for the safety assessment of a deep geological repository (DGR) for used nuclear fuel. In Canada, groundwaters at DGR depths in sedimentary rocks have been observed to have a high ionic strength. This paper examines the sorption behavior of Se(-II) onto illite, MX-80 bentonite, Queenston shale, and argillaceous limestone in Na-Ca-Cl solutions of varying ionic strength (0.1-6 mol/kgw (m)) and across a pH range of 4-9. Little ionic strength dependence for Se(-II) sorption onto all solids was observed except that sorption at high ionic strength (6 m) was generally slightly lower than sorption at low ionic strength (0.1 m). Illite and MX-80 exhibited the expected results for anion sorption, while shale and limestone exhibited more constant sorption across the pH range tested. A non-electrostatic surface complexation model successfully predicted sorption of Se(-II) onto illite and MX-80 using the formation of an inner-sphere surface complex and an outer-sphere surface complex. Optimized values for the formation reactions of these surface species were proposed.