• Journal of the Korean Physical Society
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• v.73 no.9
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• pp.1263-1268
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• 2018

Three different ice core samples from Antarctica were analyzed to identify activity concentrations of radioactive isotopes. Tracking migration of radioactive isotopes to Antarctica can provide a key clue to understand global environmental changes caused by radiation exposures because the Antarctic ice cores can preserve unique characteristics of various environmental conditions. We are particularly interested in the $^{137}Cs$ nucleus, because it is closely related to radiation exposure from nuclear power plant accidents and nuclear bomb tests. With its half life of $30.17{\pm}0.03$ years, $^{137}Cs$ can also be used to assess the age of sedimentation occurring after around the year 1945. We selected three ice core samples, called Tarn8, Styx27, and H25, from different time periods; the Tarn8 sample is known to be from earlier than ~ 1000 AD, the Styx27 sample is approximately from the year 1945, and the H25 sample is from the year 2012. Radioactive isotope measurements of the ice core samples were performed using a 100% HPGe detector at Cheongpyeong Underground Radiation Laboratory (CURL). We measured the activity of $^{137}Cs$ in the H25 sample to be $0.98{\pm}0.82mBq/kg$. Although the activity has a large uncertainty mainly due to the limited sample quantity, the $^{137}Cs$ isotopes in the Antarctic ice core were measured for the first time in Korea.

• Ceramist
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• v.21 no.4
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• pp.427-432
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• 2018

In this study, the aspherical lens for optical communications produced not with an one-step pneumatic type of external pressurization system (existed GMP process) but a constant weight of self-loaded mold put up to upper core. So the lens is molding with self-loaded weight molding and it calls Weight Molding process. In self-loaded molding process, we measured changes of center thickness molding lenses with each variable molding temperatures and time to find the effect of center of lens thickness to search key factors. As experimental results, the center thickness reach to targeted lenses step time value was changed drastically and it depends by molding temperature. If the molding temperature gets higher, the targeted lens that is reaching to the center thickness step time value was decreased. To find the effect of life improvement on mold core by imposing the self-loaded molding process we molded with GMP(Glass molding press) method and self-loaded molding method for 9,000 times and measured the lenses shape accuracy and surface roughness to evaluate the core life. As a result the self-loaded molding method core has 2,000 times longer that GMP (Glass molding press) method. If we adopt self-loaded molding method of the optical aspherical lens molding in the future, we expect that it would reduce the expense of changing the molds by molding core life improvements.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.467-467
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• 2011

Reflecting the growing importance of nanomaterials in science and technology, controlling the porosity combined with well-defined structural properties has been an ever-demanding pursuit in the related fields of frontier researches. A number of reports have focused on the synthesis of various nanoporous materials so far and, recently, the nanomaterials with multimodal porosity are getting an emerging importance due to their improved material properties compared with the mono porous materials. However, most of those materials are obtained in bulk phases while the spherical nanoparticles are one of the most practical platforms in a great number of applications. Here, we report on the synthesis of the core-shell silica nanoparticles with double mesoporous shells (DMSs). The DMS nsnoparticles are spherical and monodispersive and have two different mesoporous shells, i.e., the bimodal porosity. It is the first example of the core-shell silica nanoparticles with the different mesopores coexisting in the individual nanoparticles. Furthermore, the carbon and silica hollow capsules were also fabricated via a serial replication process.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.5
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• pp.82-86
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• 2013

The automotive weather strip has the functions isolating of dust, water, noise and vibration from outside. The core of weather strip is made of steel with stiffness. By using the wire formed as the core of weather strip, weight can be reduced as much as 35% by comparing with existing steel core. For this reason, forming wire is necessary to keep the zigzag shape as it is. The deformation which is occurred during forming process can be predicted and it can be used in case of manufacturing dies through CAE. In this paper, rolling process conditions are deduced and the springback amount is predicted after rolling process by using the simulation. The springback amount of product is measured by using optical microscope, and measurement result is compared with the simulation result of springback as the same condition. The suitable gap between dies to compensate springback after rolling process is predicted through simulation and it is used for manufacturing dies.

• Proceedings of the KIEE Conference
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• 2004.11b
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• pp.9-13
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• 2004

This paper proposes a modified current differential relay for Y-$\Delta$ transformer protection. The relay uses the same restraining current as a conventional relay, but the differential current is modified to compensate for the effects of the exciting current. A method to estimate the circulating component of the delta winding current is proposed. To cope with the remanent flux, before saturation, the core-loss current is calculated and used to modify the measured differential current. When the core then enters saturation, the initial value of the flux is obtained by inserting the modified differential current at the start of saturation into the magnetization cure. Thereafter, the core flux is then derived and used in conjunction with the magnetization curve to calculate the magnetizing current. A modified differential current is then derived that compensates for the core-loss and magnetizing currents. The performance of the proposed differential relay was compared against a conventional differential relay. Test results indicate that the modified relay remained stable during severe magnetic inrush and over-excitation because the exciting current was successfully compensated. The relay correctly discriminates magnetic inrush and over-excitation from an internal fault and is not affected by the level of remanent flux.

• Clinics in Shoulder and Elbow
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• v.26 no.2
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• pp.191-204
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• 2023

Avascular necrosis (AVN) of the humeral head is a rare, yet detrimental complication. Left untreated, humeral head AVN frequently progresses to subchondral fracturing and articular collapse. Cases of late-stage humeral head AVN commonly require invasive procedures including humeral head resurfacing, hemiarthroplasty, and total shoulder arthroplasty (TSA) to improve clinical outcomes. However, in cases of early-stage AVN, core decompression of the humeral head is a viable and efficacious short-term treatment option for patients with pre-collapse AVN of the humeral head to improve clinical outcomes and prevent disease progression. Several techniques have been described, however, a percutaneous, arthroscopic-assisted technique may allow for accurate staging and concomitant treatment of intraarticular pathology during surgery, although further long-term clinical studies are necessary to assess its overall outcomes compared with standard techniques. Biologic adjunctive treatments, including synthetic bone grafting, autologous mesenchymal stem cell/bone marrow grafts, and bone allografts are viable options for reducing the progression of AVN to further collapse in the short term, although long-term follow-up with sufficient study power is lacking in current clinical studies. Further long-term outcome studies are required to determine the longevity of core decompression as a conservative measure for early-stage AVN of the humeral head.

• Journal of Astronomy and Space Sciences
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• v.31 no.1
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• pp.67-72
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• 2014

The next generation small satellite-1 (NEXTSat-1) program has been kicked off in 2012, and it will be launched in 2016 for the science missions and the verification of space core technologies. The payloads for these science missions are the Instrument for the Study of Space Storms (ISSS) and NIR Imaging Spectrometer for Star formation history (NISS). The ISSS and the NISS have been developed by Korea Advanced Institute of Science and Technology (KAIST) and Korea Astronomy and Space science Institute (KASI) respectively. The ISSS detects plasma densities and particle fluxes of 10 MeV energy range near the Earth and the NISS uses spectrometer. In order to verify the spacecraft core technologies in the space, the total of 7 space core technologies (SCT) will be applied to the NEXTSat-1 for space verification and those are under development. Thus, the operation modes for the ISSS and the NISS for space science missions and 7 SCTs for technology missions are analyzed for the required operation time during the NEXTSat-1's mission life time of 2 years. In this paper, the operational concept of the NEXTSat-1's science missions as well as the verification of space core technologies are presented considering constraints of volume, mass, and power after launch.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.2
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• pp.106-110
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• 2017

This paper compared current limiting characteristics of superconducting fault current limiter (SFCL) using E-I core due to the location of windings. Since E-I core has three legs and two magnetic paths, the current limiting characteristics of SFCL were expected to be affected by the installation location of windings, either center leg or right/left leg. To analyze its characteristics, the electrical equivalent circuit of the SFCL were derived and the electromagnetic analysis for the SFCL with the designed structure were performed. From the short-circuit tests, the hysteresis curve and the voltage-current trajectory of the SFCL due to the installation location of windings were extracted and compared each other. The SFCL with windings in the center leg of E-I core was shown to be larger magnetizing inductance compared to the one with windings in the right or left leg of E-I, which was analyzed from the hysteresis curve. In addition, larger decreased fault current right after the fault occurrence in the SFCL with windings in the center leg of E-I core was confirmed than the SFCL with windings in the right or left leg of E-I.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.393-394
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• 2004

To get rid of cell assembly margin and have more process room of upper substrate, we developed truly COT (Color Filter On TFF Array) LCDs in that B/M (Black Matrix) as well as C/F (Color Filter) layer is located on TFT substrate. Novel B/M material is also developed for this COT structure. Difficulty in making contact hole through C/F layer was solved by making each C/F pattern isolated from others. We think this configuration will be core technology for prominent COT LCDs.

• Proceedings of the Korean Society of Plant Biotechnology Conference
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• 2005.11a
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• pp.338-338
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• 2005