• Journal of Engineering Education Research
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• v.15 no.3
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• pp.3-11
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• 2012

This paper discusses the effect that classroom demonstrations have on students' conceptual understanding in concepts in introductory physics. We used the same conceptual survey to probe the students' understanding on certain concepts before and after taking the course. We introduce Hake's , which is used to evaluate the effect of various kind of teaching methods, suggested by physics education research groups, on conceptual understanding of students who took the class. The effect of physics class using demonstration turned to be better than the traditional lecture, higher for students who graduated from science schools with higher prior knowledge and demonstration experience. Authors suggest to use to probe concepts which need more attention.

• Nuclear Engineering and Technology
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• v.48 no.3
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• pp.711-718
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• 2016

Steady-state operation of a fusion power plant requires external current drive to minimize the power requirements, and a high fraction of bootstrap current is required. One of the external sources for current drive is lower hybrid current drive, which has been widely applied in many tokamaks. Here, using lower hybrid simulation code, we calculate electron distribution function, electron currents and phase velocity changes for two options of demonstration reactor at the launched lower hybrid wave frequency 5 GHz. Two plasma scenarios pertaining to two different demonstration reactor options, known as pulsed (Option 1) and steady-state (Option 2) models, have been analyzed. We perceive that electron currents have major peaks near the edge of plasma for both options but with higher efficiency for Option 1, although we have access to wider, more peripheral regions for Option 2. Regarding the electron distribution function, major perturbations are at positive velocities for both options for flux surface 16 and at negative velocities for both options for flux surface 64.

• Korean Journal of Optics and Photonics
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• v.22 no.3
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• pp.151-158
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• 2011

This paper reports design and demonstration of optical systems for reflective-type remote optical displacement sensors. Optical systems for light illumination sources and a position sensitive detector (PSD) for the displacement sensor were developed to sense displacement of bridges and instability of skyscrapers in a distance range from 10 m to 250 m to an accuracy better than a few mm. Performance of the optical systems was verified by composing a displacement sensor and by using it in measurement of displacement of a remote target with proper reflective optics depending on distance. The displacement sensor was composed of two LED light sources, each with collimating optics, and a two-dimensional PSD with telescope-type optics. Its displacement resolutions was measured to be 0.1 mm at a distance of 10 m and less than 3 mm at a distance of 250 m.

• Korean Journal of Optics and Photonics
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• v.24 no.5
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• pp.245-250
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• 2013

The Wiener-Khinchin theorem, which means that the autocorrelation function of a signal corresponds to the power spectrum of the signal, is very important in signal processing, spectroscopy and telecommunications engineering. However, because of needs for some relatively expensive equipments such as a correlator and the signal processing system, its demonstration in most undergraduate class is not easy so far. Recently, digital oscilloscopes whose functions can be replaced foresaid equipments are marketed with development of digital engineering. In this paper, a simple demonstration of the theorem is given by a digital storage oscilloscope and a personal computer with its theoretical background. The reason that deals again with this theorem which has been introduced in 1930 is that it has been not well informed yet to us and theoretical background of the demonstration is directly introduced from its driving process. Through deriving process of the theorem, some extended physical meanings of the impedance, power, power factor, Wiener spectrum, linear system response and, furthermore, basic idea of the Planck's quantization in the black body theory reveal themselves naturally. Hence it can be referred to lectures in general physics, modern physics, spectroscopy and material characterization experiment.

• Journal of the Optical Society of Korea
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• v.14 no.2
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• pp.137-141
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• 2010

We report, for the first time to our knowledge, observation of polarization bistability from 1.55-${\mu}m$ wavelength single-mode VCSELs of a conventional cylinder-shape under control of their driving current, and demonstration of all-optical flip-flop (AOFF) operations based on the bistability with optical set and reset pulse injection at a 50 MHz switching frequency. The injection pulse energy was less than 14 fJ. The average on-off contrast ratio of the flip-flopped signals was about 7 dB. These properties of the VCSELs will be potentially useful for future high-speed all-optical signal processing applications.

• Journal of Science Education
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• v.34 no.1
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• pp.175-184
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• 2010

We agree with Hanna and Jahnke's assertion on the use of arguments from physics in mathematical proofs and analyze their educational example of the use of arguments from physics in the proof of the center of gravity of a triangle. Moreover, we suggest practical models for the center of gravity of a triangle for the demonstration in a classroom. Comparing with the traditional mathematical arguments, the role of concepts and models from physics in arguments from physics will be clearly pointed out. Also, the necessity for arguments from physics in the classroom will be discussed in this paper.

• Journal of The Korean Association For Science Education
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• v.23 no.4
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• pp.419-429
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• 2003

The developments of science education until the middle of the 20th century were often driven by personal ideas and achievements of some influential individual scientists (e.g. T. H. Huxley, H. E. Armstrong. L. Hogben, J. Conant). while that of the 2nd half of the 20th century can be characterized as collective efforts through various research grou ps of science educators (e.g. PSSC, HPP, Nuffield, SATIS). In this respect, John Tyndall(1820-1894), a physicist of the Victorian England best known as Tyndall's Effect, can be considered as one of the great scientists who made a big influence on science teaching and the popularization of science before science secured its place in school curricula. Tyndall worked as a research scientist at the Royal Institution of London, where various lectures and demonstrations of physical sciences were regularly performed for general public, and he was particularly famous for his fascinating physics demonstrations. In this study, we summarize his activities and achievements as a teacher as well as a popularizer of physics, illustrate some of his famous demonstrations and his ideas concerning physics teaching and discuss their implications to today's physics education.

• Current Optics and Photonics
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• v.4 no.5
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• pp.421-427
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• 2020

A novel privacy-protection device to prevent visual hacking is realized by using a directional backlight and facial recognition. The proposed method is able to overcome the limitations of previous privacy-protection methods that simply restrict the viewing angle to a narrow range. The accuracy of user tracking is accomplished by the combination of a time-of-flight sensor and facial recognition with no restriction of detection range. In addition, an experimental demonstration is provided to verify the proposed scheme.

• Nuclear Engineering and Technology
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• v.53 no.8
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• pp.2564-2569
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• 2021

The neutronic analysis of Helium Cooled Ceramic Reflector (HCCR) breeding blankets has been performed using the 3D Monte Carlo code MCNPX and ENDF nuclear data library. This study aims to reduce ⁶Li percentage in the breeder zones as much as possible ensuring tritium self-sufficiency. This work is devoted to investigating the effect of ⁶Li percentage on the HCCR breeding blanket's neutronic parameters, such as neutron flux and spectrum, Tritium Breeding Ratio (TBR), nuclear power density, and energy multiplication factor. In the ceramic breeders at the saturated thickness, increasing the enrichment of ⁶Li reduces its share in the tritium production. Therefore, ceramic breeders typically use lower enriched Li from 30% to 60%. The investigation of neutronic analysis in the suggested geometry shows that using 60% ⁶Li in Li₂TiO₃ can yield acceptable TBR and energy deposition results, which would be economically feasible.

• Journal of the Optical Society of Korea
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• v.16 no.3
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• pp.313-317
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• 2012

We have evaluated a 1.3 ${\mu}m$ vertical-cavity surface-emitting laser (VCSEL), whose bottom mirror and central active layer were grown by metal organic chemical vapor deposition (MOCVD) and whose top mirror was covered with a dielectric coating, for 10 Gb/s data transmission over single-mode fibers (SMFs). Successful demonstration of error-free transmission of the directly modulated VCSEL signals at data rate of 10 Gb/s over a 10 km-long SMF was achieved for operating temperatures from $20^{\circ}C$ to $60^{\circ}C$ up to bit-error-rate (BER) of $10^{-12}$. The DC bias current and modulation currents are only 7 mA and 6 mA, respectively. The results indicate that the VCSEL is a good low-power consuming optical signal source for 10 GBASE Ethernet applications under controlled environments.