• 방사성폐기물학회지
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• 제4권4호
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• pp.345-352
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• 2006

붕산폐액을 함유한 시멘트 및 파라핀 고화체, 폐이온교환수지를 함유한 시멘트 고화체 그리고 잡고체중의 제염지에 대하여 Co-60을 조사선원으로 하여 $10^8$ rads까지 조사하여 발생되는 분해가스의 종류 및 그의 발생량을 분석하였다. 그 결과 분해가스로는 $H_2,\;CH_4,\;N_2,\;C_2H_6,\;O_2,\;CO$ 및 $CO_2$ 등이 발생하였으며, $H_2$가 대부분을 차지하였다. 가스발생량은 폐기물과 고화매질의 종류에 따라 $0.029{\sim}0.788\;cm^3.atm/1.1g$으로 상당한 차이를 보였으며, 폐이온교환수지를 함유한 고화체에서 가장 높은 분해가스 발생량을 보였다. 그리고 수소가스는 제염지 폐기물에서 가장 많이 발생하였다. 제염지의 $G(H_2)$는 0.12이었다.

• 대한화장품학회지
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• 제39권2호
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• pp.149-158
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• 2013

피부 미백, 콜라겐 합성 및 노화방지 등에 좋은 효능을 나타내는 대표적인 항산화제인 L-ascorbic acid를 사용하여 다양한 보관 조건(분말 상, 수용액 상, 온도 변화, 자외선 조사 및 외부공기 유입 등)에서 산화특성을 조사하였으며, 열에 의한 산화 및 분해특성을 조사하였다. 또한 이중 공간을 갖는 파우치를 사용하여 L-ascorbic acid를 분말 상태 및 에센스와 혼합한 상태에서 각각 보관 조건에 따른 산화특성을 분석하여 파우치의 유효성을 검증하였다. 열 특성조사를 위해서는 TGA, DSC 및 FT-IR을 사용하여 분석하였고, 산화특성 조사를 위해서는 UV-visible spectrophotometer와 산화환원 적정법을 병행 시행하였다. 실험 결과, L-ascorbic acid는 금속이온, 하이드록시이온 등이 많이 함유된 수용액 상에서 고온, 자외선 조사 및 외부공기가 유입되는 상태가 가장 빠른 산화조건인 것으로 나타났고, 순수한 분말 상으로 보관할 경우에는 가열, 자외선 조사 및 외부공기 유입 시에도 오랜 기간 동안 산화되지 않는 특성이 있었다. 이러한 결과를 바탕으로, L-ascorbic acid와 같은 산화 안정성이 떨어지는 활성 성분을 분리하여 보관할 수 있도록 설계 제작 중인, 진공포장이 가능한 이중 공간 구조의 파우치를 사용할 경우 화장품 보관기간을 획기적으로 증가시킬 수 있음을 확인하였다.

• 한국식품조리과학회지
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• 제13권2호
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• pp.92-98
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• 1997

본 연구에서는 식품내의 ethyl carbamate 전구체와 그 형성에 영향을 주는 인자들을 규명하고자 하였다. 일반적으로 제조조건 보다는 원료 메주가 간장의 ethyl carbamate 형성에 기여도가 크나, 같은 메주로 제조한 간장의 경우, 저장 기간에 따라 생성이 증가하며 빛에 의해 그 농도가 감소하는 것이 관찰되었다. 따라서, 가정에서 간장을 담을 경우 전통적인 방법 인 빛을 쪼여 주며 보관하는 주의가 필요하다고 사료된다. 원료 메주에 따른 차이는 원료 콩의 화학적 조성도 관여를 하겠으나, 발효에 관여하는 미생물의'종류와 그에 따른 대사과정, 대사량의 차이에 의한 영향도 무시할 수 없으리라 사료된다. 따라서 이러한 기전들을 밝혀내기 위하여 앞으로 연구가 계속 진행되어야 할 것으로 사료된다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 춘계학술대회 및 기술 세미나 논문집 디스플레이 광소자
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• pp.42-42
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• 2008

Considerable attention has been focused on the applications of flexible liquid crystal (LC)-based displays because of their many potential advantages, such as portability, durability, light weight, thin packaging, flexibility, and low power consumption. To develop flexible LCDs that are capable of delivering high-quality moving images, like conventional glass-substrate LCDs, the LC device structure must have a stable alignment layer of LC molecules, concurrently support uniform cell gaps, and tightly bind two flexible substrates under external tension. However, stable LC molecular alignment has not been achieved because of the layerless LC alignment, and consequently high-quality images cannot be guaranteed. To solve these critical problems, we have proposed a PDMS pixel-wall based bonding method via the IB irradiation was developed for fasten the two substrates together strongly and maintain uniform cell gaps. The effect of the IB irradiation on PDMS with PI surface was also evaluated by side structure configuration and a result of x-ray photoelectron spectroscopic analysis of PDMS interlayer as a function of binder with substrates. large number of PDMS pixel-walls are tightly fastened to the surface of each flexible substrate and could maintain a constant cell gap between the LC molecules without using any other epoxy or polymer. To enhance the electro-optical performance of the LC device, we applied an alignment method that creates pretilt angle on the PI surface via ion beam irradiation. Using this approach, our flexible LCDs have a contrast ratio of 132:1 and a response time of about 15 ms, resulting in highly reliable electro-optical performance in the bent state, comparable to that of glass-substrate LCDs.

• 대한기계학회논문집B
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• 제23권11호
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• pp.1379-1389
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• 1999

A new technique for control of size and shape of flame-made particles is Introduced. The characteristic sintering time can be controlled Independently of collision time by heating the particles with irradiation of laser because the sintering time strongly depends on temperature. A coflow oxy-hydrogen diffusion flame burner was used for $SiCl_4$ conversion to silica particle. Nanometer sized aggregates irradiated by a high power CW $CO_2$ laser beam were rapidly heated up to high temperatures and then were sintered to approach volume-equivalent spheres. The sphere collides much slower than the aggregate, which results in reduction of sizes of particles maintaining spherical shape. Light scattering of Ar ion laser and TEM observation using a local sampling device were used to confirm the above effects. When the $CO_2$ laser was irradiated at low position from the burner surface, particle generation due to gas absorption of laser beam occurred and thus scattering intensity increased with $CO_2$ laser power. At high irradiation position, scattering intensity decreased with $CO_2$ laser power and TEM image showed a clear mark of evaporation and recondensation of particles for high $CO_2$ laser power. When the laser was irradiated between the above two positions where small aggregates exist, average size of spherical particles obviously decreased to 58% of those without $CO_2$ laser irradiation with the spherical shape. Even for increased carrier gas flow rate by a factor of three, TEM photograph also revealed considerable reduction of particle size.

• BMB Reports
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• 제28권6호
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• pp.499-503
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• 1995

In our previous studies (Chae et al., 1990; Chae et a1., 1993), we found that a phytochrome signal was clearly connected with the change in cytosolic free $Ca^{2+}$ concentration ($[Ca^{2+}]_i$) in oat cells. It was determined that the $[Ca^{2+}]_i$ change occured both by mobilization out of the intracellular $Ca^{2+}$ store and by influx from the medium. The specific aim of this work is to elucidate the processes connecting $Ca^{2+}$ mobilization and influx. The cells treated with thapsigargin (increasing $[Ca^{2+}]_i$ by inhibition of the $Ca^{2+}$-ATPase in the calcium pool) in the presence of external $Ca^{2+}$ showed the same increasing pattern (sustained increasing shape) of $[Ca^{2+}]_i$ as that measured in animal cells. Red light irradiation after thapsigargin treatment did not increase $[Ca^{2+}]_i$ These results suggest that thapsigargin also acts specifically in the processes of mobilization and influx of $Ca^{2+}$ in oat cells. When the cells were treated with TEA ($K^+$ channel blocker), changes in $[Ca^{2+}]_i$ were drastically reduced in comparison with that measured in the absence of TEA. The results suggest that the change in $[Ca^{2+}]_i$ due to red light irradiation is somehow related with $K^+$ channel opening to change membrane potential. The membrane potential change due to $K^+$ influx might be the critical factor in opening a voltage-dependent calcium channel for $Ca^{2+}$ influx.

• 한국초전도ㆍ저온공학회논문지
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• 제24권4호
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• pp.1-5
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• 2022

We investigate the effect of surface disorder on the lower critical field (H_c1) of MgB₂ thin films with a thickness of 850 nm, where the disorder on the surface region is produced by the irradiation of 140 keV Co ions with the dose of 1 × 10¹⁴ ions/cm². The thickness of the damaged region by the irradiation is around 143 nm, corresponding to ~17% of the whole thickness of the film, thereby forming the disordered MgB₂ overlayer on the pure MgB₂ layer. The magnetic field dependence of magnetization, M(H), for the pristine MgB₂ thin film and the film with overlayer is measured at various temperatures, and H_c1 is determined from the difference (△M) between the Meissner line and magnetization signal with the criterion of △M = 10^-3 emu. Intriguingly, the film with the disordered overlayer shows a remarkably large H_c1(0) = 108 Oe compared to the H_c1(0) = 84 Oe of pristine film, indicating that the disordered MgB₂ overlayer on the pure MgB₂ layer serves to prevent the penetration of vortices into the sample. These results provide new ideas for improving the superheating field to design high-performance superconducting radio-frequency cavities.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 춘계학술대회 및 기술 세미나 논문집 디스플레이 광소자
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• pp.41-41
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• 2008

In general, polyimides (PIs) are used in alignment layers in liquid crystal displays (LCDs). The rubbing alignment technique has been widely used to align the LC molecules on the PI layer. Although this method is suitable for mass production of LCDs because of its simple process and high productivity, it has certain limitations. A rubbed PI surface includes debris left by the cloth, and the generation of electrostatic charges during the rubbing induces local defects, streaks, and a grating-like wavy surface due to nonuniform microgrooves that degrade the display resolution of computer displays and digital television. Additional washing and drying to remove the debris, and overwriting for multi-domain formation to improve the electro-optical characteristics such as the wide viewing angle, reduce the cost-effectiveness of the process. Therefore, an alternative to non-rubbing techniques without changing the LC alignment layer (i.e, PI) is proposed. The surface of LC alignment layers as a function of the ion beam (IE) energy was modified. Various pretilt angles were created on the IB-irradiated PI surfaces. After IB irradiation, the Ar ions did not change the morphology of the PI surface, indicating that the pretilt angle was not due to microgrooves. To verify the compositional behavior for the LC alignment, the chemical bonding states of the ill-irradiated PI surfaces were analyzed in detail by XPS. The chemical structure analysis showed that ability of LCs to align was due to the preferential orientation of the carbon network, which was caused by the breaking of C=O double bonds in the imide ring, parallel to the incident 18 direction. The potential of non-rubbing technology for fabricating display devices was further conformed by achieving the superior electro-optical characteristics, compared to rubbed PI.

• Journal of Astronomy and Space Sciences
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• 제22권4호
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• pp.441-450
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• 2005

유기재료(organic material)는 위성이나 우주비행체의 열을 조절하고 우주환경에 직접 노출되는 것을 차단하기 위하여 가장 흔하게 사용되는 재료 중 하나이다. 본 논문에서는 지상설비를 이용하여 모사한 우주환경에서 유기재료의 물성변화를 관찰하였다. 대표적인 위성용 유기 열조절 재료 중 하나인 2mil ITO(Indium Tin Oxide) coated aluminized KAPTON을 실험 대상으로 선택하였다. 양성자에 의한 단일 우주환경효과를 실험하기 위하여, 한국 원자력의학원의 MC-50 싸이클로트론(cyclotron)을 이용하여 양성자를 조사(irradiation)하였으며, 조사조건은 지구궤도 주변 최고의 양성자 발생기록인 1972년 8월의 최고치 상황을 적용하였다. 조사에너지는 평균 관측에너지인 30MeV으로 고정하였으며, 등가 조사량은 우주노출 시간 1년, 3년, 5년 및 10년을 기준으로 설정하였다. 분석과정은 인장강도를 측정하여 정량적 물성저하를 확인하였고, 전계방출 전자주사현미경 등으로 결정성변화와 노출표면의 손상을 분석하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.312-312
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• 2012

Magnesium oxide has become focus for research activities due to its use in magnetic tunnel junctions and for understanding of do ferromagnetism. Theoretical investigations on such type of system indicate that the presence of defects greater than a threshold value is responsible for the magnetic behaviour. It has also been shown experimentally that by decreasing the film thickness and size of nanoparticles, enhancement/increase in magnetization can be achieved. Apart from the change in dimension, swift heavy ions (SHI) are well known for creating defects and modifying the properties of the materials. In the present work, we have studied the irradiation induced effects in magnesium oxide thin film deposited on quartz substrate via X-ray absorption spectroscopy (XAS). Magnesium oxide thin films of thickness 50nm were deposited on quartz substrate by using e-beam evaporation method. These films were irradiated by 200 MeV Ag15+ ion beam at fluence of $1{\times}10^{11}$, $5{\times}10^{11}$, $1{\times}10^{12}$, $3{\times}10^{12}$ and $5{\times}10^{12}ions/cm^2$ at Nuclear Science Centre, IUAC, New Delhi (India). The grain size was observed (as studied by AFM) to be decreased from 37 nm (pristine film) to 23 nm ($1{\times}10^{12}ions/cm^2$) and thereafter it increases upto a fluence of $5{\times}10^{12}ions/cm^2$. The electronic structure of the system has been investigated by X-ray absorption spectroscopy (XAS) measurements performed at the high energy spherical grating monochromator 20A1 XAS (HSGM) beamline in the National Synchrotron Radiation Research Center (NSRRC), Taiwan. Oxides of light elements like MgO/ZnO possess many unique physical properties with potentials for novel application in various fields. These irradiated thin films are also studied with different polarization (left and right circularly polarized) of incident x-ray beam at 05B3 EPU- Soft x-ray scattering beamline of NSRRC. The detailed analysis of observed results in the wake of existing theories is discussed.