• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.537-540
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• 2006

Over the past few decades, a considerable number of studies on the durability of concrete have been carried out extensively. A lot of improvements have been achieved especially in modeling of ionic flows. However, the majority of these researches have not dealt with the chloride binding isotherm based on the mechanism, although chloride binding capacity can significantly impact on the total service life of concrete under marine environment. The purpose of this study is to develop the model of chloride binding isotherm based on the individual mechanism. It is well known that chlorides ions in concrete can be present; free chlorides dissolved in the pore solution, chemical bound chlorides reacted with the hydration compounds of cement, and physical bound attracted to the surface of C-S-H grains. First, sub-model for water soluble chloride content is suggested as a function of pore solution and degree of saturation. Second, chemical model is suggested separately to estimate the response of binding capacity due to C-S-H and Friedel's salt. Finally, physical bound chloride content is estimated to consider a surface area of C-S-H nano-grains and the distance limited by the Van der Waals force. The new model of chloride binding isotherm suggested in this study is based on their intrinsic binding mechanisms and hydration reaction of concrete. Accordingly, it is possible to characterize chloride binding isotherm at the arbitrary stage of hydration time and arbitrary location from the surface of concrete. Comparative study with experimental data of published literature is accomplished to validity this model.

• Environmental Analysis Health and Toxicology
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• 제22권3호
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• pp.189-196
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• 2007

[ $TiO_2$ ] is widely used because it is non-toxic. Recently, however, nanometer size $TiO_2$ particles (P-25) have been produced and used to increase the photo catalysis efficiency. Nanometer-sized $TiO_2$ is efficient, but due to its small size ($20{\sim}30\;nm$), it can flow into ecosystems and into cells. Thus, it may affect human health. Additionally, $TiO_2$ can produce a second contaminant, OH-radical, which is a health risk for all living organisms during photo degradation reaction. Hence, when nanometer-sized $TiO_2$ flows into natural streams and attaches to living organisms, it will create health risks. We investigated the biological toxicity of this condition in zebrafish embryos. We observed abnormal morphology, hatching rate, and measured the catalase activity to determine anti-oxidation at 100 post fertilization hours. Zebrafish were somewhat affected by $TiO_2$ nanometer sized particles under UV-A (a condition similar to sunlight). Powdered $TiO_2$ is toxic to the zebrafish fly. Even without light, $TiO_2$ particles attached to embryos and flies, having an effect on both.

• Advances in nano research
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• 제4권2호
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• pp.113-128
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• 2016

Luminescent metallic clusters have attracted great interest due to their unique optical, electronic and chemical features. Comparing with intensively studied Au and Ag Clusters, Cu clusters are superior in the aspects of cost and wide industrial demanding. However, tiny copper clusters are extremely prone to aggregate and undergo susceptibility of oxidation, thereby the synthesis of fluorescent zero valent copper clusters is rather challenging. In this review, synthetic strategies towards luminescent copper clusters, including macromolecule-protection and micro molecule-capping, have been systematically surveyed. Both "bottom-up" and "top-down" synthetic routes are found to be effective in fabricating luminescent copper clusters, some of which are quite stable and possess decent luminescence quantum yields. In general, the synthesis of fluorescent copper clusters remains at its infant stage. A great deal of effort on developing novel and economic synthetic routes to produce bright and stable copper clusters is highly expected in future.

• 한국분말재료학회지
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• 제26권2호
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• pp.107-111
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• 2019

The activation energy to create a phase transformation or for the reaction to move to the next stage in the milling process can be calculated from the slop of the DSC plot, obtained at the various heating rates for mechanically activated Al-Ni alloy systems by using Kissinger's equation. The mechanically activated material has been called "the driven material" as it creates new phases or intermetallic compounds of AlNi in Al-Ni alloy systems. The reaction time for phase transformation by milling can be calculated using the activation energy obtained from the above mentioned method and from the real required energy. The real required energy (activation energy) could be calculated by subtracting the loss energy from the total input energy (calculated input energy from electric motor). The loss energy and real required energy divided by the reaction time are considered the "metabolic energy" and "the effective input energy", respectively. The milling time for phase transformation at other Al-Co alloy systems from the calculated data of Al-Ni systems can be predicted accordingly.

• Advances in nano research
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• 제10권2호
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• pp.129-138
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• 2021

In present article, utilizing the Love shell theory with volume fraction laws for the cylindrical shells vibrations provides a governing equation for the distribution of material composition of material. Isotopic materials are the constituents of these rings. The position of a ring support has been taken along the radial direction. The Rayleigh-Ritz method with three different fraction laws gives birth to the shell frequency equation. Moreover, the effect of height- and length-to-radius ratio and angular speed is investigated. The results are depicted for circumferential wave number, length- and height-radius ratios with three laws. It is found that the backward and forward frequencies of exponential fraction law are sandwich between polynomial and trigonometric laws. It is examined that the backward and forward frequencies increase and decrease on increasing the ratio of height- and length-to-radius ratio. As the position of ring is enhanced for clamped simply supported and simply supported-simply supported boundary conditions, the frequencies go up. At mid-point, all the frequencies are higher and after that the frequencies decreases. The frequencies are same at initial and final stage and rust itself a bell shape. The shell is stabilized by ring supports to increase the stiffness and strength. Comparison is made for non-rotating and rotating cylindrical shell for the efficiency of the model. The results generated by computer software MATLAB.

• Clinical and Experimental Reproductive Medicine
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• 제47권4호
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• pp.245-262
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• 2020

In recent years, nanotechnology has revolutionized global healthcare and has been predicted to exert a remarkable effect on clinical medicine. In this context, the clinical use of nanomaterials for cancer diagnosis, fertility preservation, and the management of infertility and other pathologies linked to pubertal development, menopause, sexually transmitted infections, and HIV (human immunodeficiency virus) has substantial promise to fill the existing lacunae in reproductive healthcare. Of late, a number of clinical trials involving the use of nanoparticles for the early detection of reproductive tract infections and cancers, targeted drug delivery, and cellular therapeutics have been conducted. However, most of these trials of nanoengineering are still at a nascent stage, and better synergy between pharmaceutics, chemistry, and cutting-edge molecular sciences is needed for effective translation of these interventions from bench to bedside. To bridge the gap between translational outcome and product development, strategic partnerships with the insight and ability to anticipate challenges, as well as an indepth understanding of the molecular pathways involved, are highly essential. Such amalgamations would overcome the regulatory gauntlet and technical hurdles, thereby facilitating the effective clinical translation of these nano-based tools and technologies. The present review comprehensively focuses on emerging applications of nanotechnology, which holds enormous promise for improved therapeutics and early diagnosis of various human reproductive tract diseases and conditions.

• 한국가시화정보학회지
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• 제22권1호
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• pp.6-17
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• 2024

This study examined the natural convection heat flow characteristics of the melting process of PCM (palm oil) inside a liquid flexitank(bag) for a cargo container. A film heating element was installed on the bottom of the container, and numerical analysis was performed under heat flux conditions of 1,000 to 4,000 W/m². As a result, the melt interface of the PCM rises to a nearly horizontal state over time. In the initial stage, conduction heat transfer dominates, but gradually waves at the cell flow and melt interfaces are formed due to natural convection heat transfer. As melting progresses, the Ra number increases parabolically, and the Nu number increases linearly and has a constant value. The Nu number rises slowly under low heat flux conditions, whereas under high heat flux conditions, the Nu number rises rapidly. As the heat flux increases, the internal temperature oscillation of the liquid phase after melting increases. However, under high heat flux conditions, excess heat exceeding the latent heat is generated, and the temperature of the molten liquid is raised, so the increase in melting rate decreases. Therefore, the appropriate heating element specification applied to a 20-ton palm oil container is 2,000 W/m².

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.412-412
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• 2009

Carbon-based nano materials have a significant effect on various fields such as physics, chemistry and material science. Therefore carbon nano materials have been investigated by many scientists and engineers. Especially, since graphene, 2-dimemsonal carbon nanostructure, was experimentally discovered graphene has been tremendously attracted by both theoretical and experimental groups due to their extraordinary electrical, chemical and mechanical properties. Electrical conductivity of graphene is about ten times to that of silicon-based material and independent of temperature. At the same time silicon-based semiconductors encountered to limitation in size reduction, graphene is a strong candidate substituting for silicon-based semiconductor. But there are many limitations on fabricating large-scale graphene sheets (GS) without any defect and controlling chirality of edges. Many scientists applied micromechanical cleavage method from graphite and a SiC decomposition method to the fabrication of GS. However these methods are on the basic stage and have many drawbacks. Thereupon, our group fabricated GS through Thermo-electrical Pulse Induced Evaporation (TPIE) motivated by arc-discharge and field ion microscopy. This method is based on interaction of electrical pulse evaporation and thermal evaporation and is useful to produce not only graphene but also various carbon-based nanostructures with feeble pulse and at low temperature. On fabricating GS procedure, we could recognize distinguishable conditions (electrical pulse, temperature, etc.) to form a variety of carbon nanostructures. In this presentation, we will show the structural properties of OS by synthesized TPIE. Transmission Electron Microscopy (TEM) and Optical Microscopy (OM) observations were performed to view structural characteristics such as crystallinity. Moreover, we confirmed number of layers of GS by Atomic Force Microscopy (AFM) and Raman spectroscopy. Also, we used a probe station, in order to measure the electrical properties such as sheet resistance, resistivity, mobility of OS. We believe our method (TPIE) is a powerful bottom-up approach to synthesize and modify carbon-based nanostructures.

• 폴리머
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• 제29권2호
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• pp.146-150
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• 2005

본 연구는 수십 마이크로미터 크기의 임의의 3차원 형상제작을 위한 이광자 광중합에 의한 나노 입체 리소그래피(nano-stereolithography) 공정개발에 관한 것이다. 본 연구에서 제안한 공정은 3차원 CAD 파일을 이용하여 형상의 윤곽선을 고화시켜서 연속적으로 적층하여 구조물을 제작하는 공정으로 기존의 리소그래피 공정과 달리 복잡한 형상제작이 가능하다. 형상제작은 펨토초 레이저를 이용하여 이광자 흡수 색소가 첨가된 아크릴레이트 계열의 단량체에 이광자 중합반응으로 제작하였으며 선 폭 정밀도는 150 nm수준이었다. 이광자 광중합법으로 윤곽선을 고화시켜 쉘(shell) 형태로 3차원 형상을 제작할 때에는 기계적 강성이 약하여 고화 후에 용매로 중합반응이 일어나지 않는 부분을 제거할 때 변형이 쉽게 발생하게 된다. 본 연구에서는 이러한 문제점을 해결하고자 윤곽 쉘 두께를 증가시켜 윤곽선을 중첩으로 제작하는 이중 윤곽선 스캐닝 방법(double contour scanning)을 시도하였으며 이를 통하여 제작된 형상의 강도가 향상됨을 확인할 수 있었다.

• 한국환경보건학회지
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• 제36권6호
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• pp.480-495
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• 2010

This study evaluated the distribution of the concentrations of nano-particles and heavy metals (08-Pb, Cr, Zn, As, Fe, 09-Pb, Cr, Zn, Cu, Ni, Mn) in Seoul, Chungnam A and Gwangyang from August to December, in 2008 5 times each in the Seoul area, 5 times in and Chungnam A area and from August to November, in 2009 14 times in the Chungnam A area, 8 times in the Gwangyang area. The examined results showed high concentration level from $PM_1$ through $PM_{0.1}$ in all three areas. These results were obtained the concentration of particles by diameter and statistically significant in Stage5 (1.0-0.56 ${\mu}m$) from the result of conducting Kruskal-Wallis H test (p < 0.05). In the case of the heavy metal concentration included in 0.10-0.056 ${\mu}m$, 0.056 ${\mu}m$, the lead concentration of Chungnam Asan area was 6.49 ng/$m^3$ and 9.93 ng/$m^3$, which was higher than 3.05 ng/$m^3$ and 4.22 ng/$m^3$ of Seoul, respectively. The concentration of iron in Seoul was 9.28 ng/$m^3$ and 13.24 ng/$m^3$, that appeared higher than 2.38 ng/$m^3$ and 3.23 ng/$m^3$ of Chungnam A area, respectively. The concentration level was similar to other metals except lead and iron in Chungnam A area and Seoul. From the concentration of heavy metal included in 0.10-0.056 ${\mu}m$, 0.056 ${\mu}m$, the lead concentration of Chungnam A area was 0.31 ng/$m^3$ and 0.12 ng/$m^3$ while Gwangyang was 0.28 ng/$m^3$, 0.06 ng/$m^3$. Thus Chungnam A area showed higher lead concentration than Gwangyang. The manganese concentration of Chungnam A area was 0.12 ng/$m^3$ and 0.03 ng/$m^3$ while Gwangyang was 0.21 ng/$m^3$ and 0.08 ng/$m^3$. Therefore, the concentration of Gwangyang appeared higher than that of Chunnam A area. These two metals showed statistically significant in 0.056 ${\mu}m$ (p < 0.05, p < 0.01). Among the concentration of heavy metal in all regions, the result demonstrated that the order of higher concentration is arsenic > iron > zinc > chrome > lead > nickel > copper > manganese.