• Bulletin of the Korean Chemical Society
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• 제26권3호
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• pp.393-398
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• 2005

The stability constants for the diaza-18-crown-6 ethers 2-6 and alkali metal cations ($Na^+,\;K^+,\;Rb^+\;and\;Cs^+$) were determined using potentiometry in 95% methanol. For each metal ion the stability constants of the partiallyfluorinated ligands 3-6 were larger than that of the non-fluorinated ligand 2, which might reflect an interaction between fluorine atoms and alkali metal cations. The stability constant of the ligand 4 was larger than that of the ligand 5 for each metal cation tested. This finding was also supported by the results of cation-induced chemical shifts in $^1H-,\;^{19}F$-NMR and extraction experiment. The potentiometry and NMR results as well as the X-ray crystal structures revealed that the position and number of fluorine atoms in the benzyl side arms was crucial for the enhanced interaction between a ligand and an alkali metal.

• 한국식품조리과학회지
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• 제5권2호
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• pp.51-62
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• 1989

In the present study, an attempt was made to investigate the oxidative stability of the various sesasme blended oils. Sesame blended oils were perpared by mixing sesame oil with various vegetalbe oils (soybean oil, corn oil, ricebran oil, rapeseed oil, cottonseed oil, and perilla oil) in a ratio of 3:7 (w/w). Fatty acid composition and some of physico-chemical characteristics of the sesame blended oils and vegetable oils including sesame oil were determined before the oxidation experiments. The fatty acid compositions and the physico-chemical characteristics of the vegetable oils changed by blending the oils with sesame oil and the extent of change varied with the type of oil. Particularly, the iodine value of the vegetable oils decreased significantly by sesame oil blending. The sesame blended oils and the vegetable oils including sesame oil were oxidized at $45^{\circ}C$ for 25 days in a dark place, and at $35^{\circ}C$ for 12 days under the irradiation of incandescent electric lamp (40 W). During the oxidation, some physico-chemical characteristics of the oils were determined to evaluate the oxidative stability. Based on the changes of peroxide values, the oxidative stability of the vegetable oils was improved by sesame oil blending.

• Geomechanics and Engineering
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• 제12권3호
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• pp.483-503
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• 2017

Uncertainty is a fact belonging to engineering practice. An important uncertainty that sets geotechnical engineering is the variability associated with the properties of soils or, more precisely, the characterization of soil profiles. The reason is due largely to the complex and varied natural processes associated with the formation of soil. Spatial variability analysis for the study of the stability of natural slopes, complementing conventional analyses, is able to incorporate these uncertainties. In this paper the characterization is performed in back-analysis for a case of landslide occurred to verify afterwards the presence of the conditions of shear strength at failure. This approach may support designers to make more accurate estimates regarding slope failure responding, more consciously, to the legislation dispositions about slope stability evaluation and future design. By applying different kriging techniques used for spatial analysis it has been possible to perform a 3D-slope reconstruction. The predictive analysis and the areal mapping of the soil mechanical characteristics would support the definition of priority interventions in the zones characterized by more critical values as well as slope potential instability. This tool of analysis aims to support decision-making by directing project planning through the efficient allocation of available resources.

• 한국응용과학기술학회지
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• 제14권1호
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• pp.45-52
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• 1997

It is the problem point of stability for this study to produce cosmetics and to occur in the circulation process, and specially in a case of alcoholic toilet water the precipitation materials to float on content materials has study on the solubility of perfume, and it has practiced in order to examine the problem point whether the raw materials of plastic vessel is or not harmful in content materials. In testing result, A study on stability of alcoholic toilet water is above all the precipitation materials which floats in content materials, and It is appeared by combination ratio to the raw materials of perfume, ethanol, solubilizer and refining water etcs, and in second the alkali degree which has gushed out of glass vessel can understand the thing that the change of PH is largely increased following to the passage of time, and in third the harmful component of content materials out of raw material in plastics vessel must certainly consider a stability and a safety in quality control of products.

• Current Photovoltaic Research
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• 제11권1호
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• pp.18-26
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• 2023

Tin perovskite solar cells have attracted a lot of attention due to their potential to address the toxicity of lead, which is the biggest barrier to commercialization of perovskite solar cells. Unlike other lead-free perovskite, tin perovskite have a direct bandgap, which is suitable for use as light harvesting, and relatively good stability, which has led to a lot of attention. Since the first tin perovskite solar cell was reported in 2014, it has achieved an impressive power conversion efficiency of 14.81%. However, this efficiency is still low compared to that of lead perovskite solar cells, and the stability of tin perovskite solar cells is also an issue that needs to be addressed. In this review, we will discuss the basic properties of the tin atom in comparison to the lead atom, and then discuss the crystal structure, phase transition, and basic properties of tin perovskite. We will then discuss the advantages, applications, challenges, and strategies of tin perovskite, In particular, we will focus on how to prevent the oxidation of tin, which is arguably the biggest challenge for using tin perovskite solar cells. At the end, we summarize the key factors that need to be addressed for higher efficiency and stability, emphasizing what is needed to commercialize tin perovskite solar cells.

• Bulletin of the Korean Chemical Society
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• 제32권2호
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• pp.424-430
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• 2011

A novel T-type polyurethane 7 containing 1-(2,5-dioxyphenyl)-2-(5-(1,2,2-tricyanovinyl)-2-thienyl)ethenes as NLO chromophores, which constitute part of the polymer backbone, was prepared. Polyurethane 7 is soluble in common organic solvents such as DMF and DMSO. It shows a thermal stability up to $270^{\circ}C$ from TGA thermogram with $T_g$ value obtained from DSC thermogram near $155^{\circ}C$. The second harmonic generation (SHG) coefficient ($d_{33}$) of poled polymer film at 1560 nm fundamental wavelength is $3.56{\times}10^{-9}$ esu. Polymer 7 exhibits a thermal stability even at $5^{\circ}C$ higher than $T_g$, and no significant SHG decay is observed below $160^{\circ}C$, which is acceptable for nonlinear optical device applications.

• Bulletin of the Korean Chemical Society
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• 제32권1호
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• pp.145-148
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• 2011

The thermal behavior of lithiated Si anodes has been investigated using differential scanning calorimetry (DSC). In particular, the effect of Si particle size on the thermal stability of a fully lithiated Si electrode was investigated. For DSC measurements, a lithiated Si anode was heated in a hermetically sealed high-pressure pan with a polyvinylidene fluoride (PVDF) binder and a 1 M $LiPF_6$ solution in an ethylene carbonate (EC)-diethyl carbonate (DEC) mixture. The thermal evolution around $140^{\circ}C$ increases with lithiation and with decreasing particle size; this phenomenon is attributed to the thermal decomposition of the solid electrolyte interface (SEI) film. Exothermic peaks, following a broad peak at around $140^{\circ}C$, shift to a lower temperature with a decrease in particle size, indicating that the thermal stability of the lithiated Si electrode strongly depends on the Si particle size.

• Steel and Composite Structures
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• 제50권1호
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• pp.45-61
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• 2024

This research explores the domain of organic solar cells, a photovoltaic technology employing organic electronics, which encompasses small organic molecules and conductive polymers for efficient light absorption and charge transport, leading to electricity generation from sunlight. A computer simulation is employed to scrutinize resonance and dynamic stability in OSCs, with a focus on size effects introduced by nonlocal strain gradient theory, incorporating additional terms in the governing equations related to displacement and time. Initially, the Navier method serves as an analytical solver to delve into the dynamics of design points. The accuracy of this initial step is verified through a meticulous comparison with high-quality literature. The findings underscore the substantial impact of viscoelastic foundations, size-dependent parameters, and geometric factors on the stability and dynamic deflection of OSCs, with a noteworthy emphasis on the amplified influence of size-dependent parameters in higher values of the different layers' thicknesses.

• 대한화학회지
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• 제41권6호
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• pp.324-328
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• 1997

• Korean Chemical Engineering Research
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• 제49권4호
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• pp.387-392
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• 2011

생촉매인 효소의 기질선택성은 다양한 분야에서 유용하게 이용되고 있다. 그 중에서도 효소결합면역흡착검사(enzyme-linked immunosorbent assay, ELISA)는 항원항체의 결합을 항체와 공유결합된 효소의 반응으로 나타냄으로써 다양한 항원들의 진단을 가능케 했다. 하지만 기존의 효소결합면역흡착검사는 하나의 항체당 하나의 효소가 결합된 형태이기 때문에 감도(sensitivity)의 증가 폭에 그 한계가 있으며, 이를 극복하기 위한 방안으로 하나의 항체당 결합된 효소의 수를 증가시킴으로써 혁신적인 감도의 향상을 가져오는 연구가 진행되었다. 최근 나노바이오촉매(nanobiocatalyst, NBC) 접근방식을 이용한 효소활성의 안정화는 효소결합면역흡착검사의 감도 향상뿐만 아니라 그 성능의 안정성을 확보할 수 있는 연구결과로 이어지고 있다. 본 총설에서는 일반적인 효소결합면역흡착검사의 기본적인 원리와 감도향상을 위한 연구, 그리고 성능안정성(performance stability)을 향상시키기 위한 나노바이오촉매-결합면역흡착검사(Nanobiocatalyst-Linked Immunosorbent Assay, NBC-LISA)에 대하여 살펴보고자 한다.