• Bulletin of the Korean Chemical Society
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• 제34권5호
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• pp.1445-1453
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• 2013

$Zn_{(1-x)}Ni_xAl_2O_4$ (x = 0.0-1.0) spinels were prepared at $800^{\circ}C$ by co-precipitation method and characterized by infrared spectroscopy, X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy. The specific surface area was determined by BET. SEM image showed nano sized spherical particles. XPS confirmed the valence states of the metals, showing moderate Lewis character for the surface of materials. The powders were successfully used as new heterogeneous catalysts of Biginelli's reaction, a one-pot three-component reaction, leading to some dihydropyrimidinones (DHPMs). These new catalysts that produced good yields of DHPMs, were easily recovered by simple filtration and subsequently reused with persistent activity, and they are non-toxic and environmentally friendly. The optimum amount of catalyst is 20% by weight of benzaldehyde derivatives, while the doping amount has been found optimal for x = 0.1.

• Journal of the Korean Wood Science and Technology
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• 제45권6호
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• pp.836-845
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• 2017

Gravimetric method is usually used to evaluate air-dry density, which is governing physical or mechanical properties of wood. Although it had high evaluation accuracy, the method is time consuming process. Thus, this study was conducted to estimate air-dry density of wood with high accuracy by using polychromatic X-ray and digital detector as alternative of gravimetric method. To quantify polychromatic X-ray projection for evaluating air-dry density, Lambert-Beer's law with the integral value of probability function was used. The integral value was used as weighting factor in the law, and it was determined by conducting simple test at various penetration depths and tube voltage. Mass attenuation coefficient (MAC) of wood also calculated by investigating polychromatic X-ray projection according to species, penetration depth and tube voltage. The species had not an effect on change of MAC. Finally, an air-dry density of wood was estimated by applying the integral value, MAC and Lambert-Beer's law to polychromatic X-ray projection. As an example, the relation of the integral value (${\alpha}$) according to penetration depth (t, cm) at tube voltage of 35 kV was ${\alpha}=-0.00091t{\times}0.0184$ while the regression of the MAC (${\mu}$, $cm^2/g$) was ${\mu}=0.5414{\exp}(-0.0734t)$. When calculation of root mean squared error (RMSE) was performed to check the estimation accuracy, RMSE at 35, 45 and 55 kV was 0.010, 0.013 and $0.009g/cm^3$, respectively. However, partial RMSE in relation to air-dry density was varied according to tube voltage. The partial RMSE below air-dry density of $0.41g/cm^3$ was $0.008g/cm^3$ when tube voltage of 35 kV was used. Meanwhile, the partial RMSE above air-dry density of $0.41g/cm^3$ decreased as tube voltage increased. It was conclude that the accuracy of estimation with polychromatic X-ray and digital detector was quite high if the integral value and MAC of wood were determined precisely or a condition of examination was chosen properly. It was seemed that the estimation of air-dry density by using polychromatic X-ray system can supplant the gravimetric method.

• Bulletin of the Korean Chemical Society
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• 제31권5호
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• pp.1123-1127
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• 2010

We report a simple and quick route for the preparation of high-quality, nearly monodisperse $Bi_2Te_3$, $Sb_2Te_3$, and $Bi_xSb_{2-x}-Te_3$ nanocrystallites. The reactions of bismuth acetate or antimony acetate with Te in oleic acid result in pure phase of $Bi_2Te_3$ or $Sb_2Te_3$ nanoparticles, respectively. Also, ternary $Bi_xSb_{2-x}Te_3$ nanoparticles were successfully synthesized using the same method. The size and morphology of the nanoparticles were controlled by varying the stabilizing agents. The as-prepared nanoparticles are characterized by X-ray diffraction, scanning electron microscope, and high-resolution transmission electron microscope using an energy dispersive spectroscopy.

• 대한방사선기술학회지:방사선기술과학
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• 제1권1호
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• pp.31-35
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• 1978

X-rays contribute to electron emission from material surfaces primarily through photoelectric interaction. A simple model is described for predicting the yield and energy spectrum of photon and Auger electrons emitted from materials exposed to X-ray with low energy. In this paper, We have calculated the yield of primary, Auger, and secondary, electrons. The results of the photoelectric yield model developed here suggests that. I) The angular distribution of emitted electrons(Per unit angle) is proportional to $sin{\theta}\;cos{\theta}$ for all electron energies and all components(Primary, Auger, or Secondary) II) The shape of the energy spectrum of the photoelectric yield is independent of angle. III) For this targets the forward and backward photoelectric yields are indentical.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.442-443
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• 2006

Vacuum carbonization of nanometer tungsten powder was investigated in a simple designed apparatus. An X-Y recorder was used to plot differential thermal analysis (DTA) curves to determine starting temperature of carbonization of four samples with different specific surface area. The product was detected by X-ray Diffraction (XRD) and small angle X-ray scattering (SAXS). The results show that finer tungsten powder has lower starting temperature of carbonization. Tungsten powder, which BET surface area is $32.97m^2/g$, is completely carbonized to tungsten carbide at $1050^{\circ}C$, although the starting temperature is $865^{\circ}C$. Particle grows sharply before carbonization.

• Bulletin of the Korean Chemical Society
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• 제35권4호
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• pp.1182-1190
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• 2014

$Cd_{1-x}Zn_xS$-sensitized $K_4Nb_6O_{17}$ composite photocatalysts (designated $Cd_{1-x}Zn_xS/K_4Nb_6O_{17}$) were prepared via a simple deposition-precipitation method. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectrometry (EDS), $N_2$ sorption, ultraviolet-visible light diffuse reflectance spectroscopy (UV-Vis DRS), photoluminescence measurements (PL), and X-ray photoelectron spectroscopy (XPS). The $Cd_{0.8}Zn_{0.2}S$ particles were scattered on the surface of $K_4Nb_6O_{17}$, and had a relatively uniform size distribution around 50 nm. The absorption edge of $K_4Nb_6O_{17}$ was shifted to the visible light region and the recombination of photo-generated electrons and holes suppressed after $Cd_{0.8}Zn_{0.2}S$ loading. The $Cd_{0.8}Zn_{0.2}S$(25 wt %)/$K_4Nb_6O_{17}$ composite possessed the highest photocatalytic activity for hydrogen production under visible light irradiation, evolving 8.278 mmol/g in 3 h. Recyclability tests were performed, and the composite photocatalysts were found to be fairly stable. The mechanism of charge separation between the photogenerated electrons and holes at the $Cd_{0.8}Zn_{0.2}S/K_4Nb_6O_{17}$ composite was discussed.

• Journal of Radiation Protection and Research
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• 제9권1호
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• pp.33-42
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• 1984

핵분열(核分裂) 및 방사화생성물(放射化生成)物)에서 방출(放出)하는 여러가지 감마선들은 핵연료(核燃料)를 파괴(破壞)하지 않고도 추출(抽出)할 수 있는 많은 정보(情報)를 포함(包含)한다. 그러나 반도체(半導體) 검출기(檢出器)에서 얻은 복잡한 스펙트럼에서 이러한 정보를 추출(抽出)하기가 용역(容易)하지 않기 때문에 전산(電算)코드의 사용(使用)이 필요(必要)하게 된다. 본(本) 연구(硏究)에서는 그동안 국제적(國際的)으로 널리 보급(普及)되어 사용(使用)되는 감마선 분석(分析) 프로그램들의 장점(長點)을 취하여, 감마선은 물론 X-선(線)의 스펙트럼도 피팅 (fitting)하여 피이크의 중심과 면적을 정확(正確)히 계산(計算)할 수 있는 전산코드 CAERI를 개발(開發)하였다. CAERI는 FORTRAN으로 쓰여있고, 특히 고유복사선폭(固有輻射線幅)(natural line width) 을 무시할 수 없는 X-선(線)의 피이크 표현함수(表現函數)인 Voigt 함수(函數)에 대해서는, 다른 X-선(線) 분석(分析) 프로그램들이 사용(使用)한 간단한 근사식(近似式) 대신에, 더욱 정확(正確)한 무한급수근사식(無限級數近似式)을 사용하였다. 특히 CAERI 는 U이나 Pu과 같은 중원소(重元素)의 핵종분석시(核種分析時)에 직면(直面)하는 감마선과 U이나 Pu의 X-선(線)이 임의(任意)로 간섭(干涉)하며 공존(共存)하는 복잡한 스펙트럼까지도 취급(取扱)할 수 있다. $^{177m}Lu$감마선과 $^{235}U\;U_{\alpha}$X-선(線)의 시험(試驗)스펙트럼을 피팅하여, 다른 프로그램들의 피팅결과와 비교했을 때 좋은 일치(一致)를 보았다.

• Corrosion Science and Technology
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• 제21권4호
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• pp.250-257
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• 2022

Transition metal sulfide materials have emerged as a new anode material for Li secondary batteries owing to their high capacity and rate capability facilitated by fast Li-ion transport through the layered structure. Among these materials, niobium disulfide (NbS₂) has attracted much attention with its high electrical conductivity and high theoretical capacity (683 mAh g^-1). In this study, we propose a facile synthesis of Fe_xNbS₂/C composite via simple ball milling and heat treatment. The starting materials of FeS and Nb were reacted in the first milling step and transformed into an Fe-Nb-S composite. In the second milling step, activated carbon was incorporated and the sulfide was crystallized into Fe_xNbS₂ by heat treatment. The prepared materials were characterized by X-ray diffraction, electron spectroscopies, and X-ray photoelectron spectroscopy. The electrochemical test results reveal that the synthesized Fe_xNbS₂/C composite electrode demonstrates a high reversible capacity of more than 600 mAh g^-1, stable cycling stability, and excellent rate performance for Li-ion battery anodes.

• 대한두개안면성형외과학회지
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• 제13권2호
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• pp.111-118
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• 2012

Purpose: The nasal bone fracture is known as the most common facial fracture, with the postoperative results and the patient's satisfaction known to be lower than other facial fractures. The patient's satisfaction is firstly related to the accurate comprehension of the spatial relationship in the fractured nasal bone and secondly to the accurate reduction based on accurate comprehension. The aim of this study is to evaluate the objective usefulness of the three-dimensional (3D) imaging. Methods: The survey was conducted on 10 randomly selected cases of nasal bone fractures among the 46 cases with 3D computed tomography (CT) during the past one year. It was requested upon 4 plastic residents and 4 plastic surgeons to draw 3D aspect of fractured nasal bone directly on the printed photos of cadaver nasal bone, based on simple X-ray and two-dimensional (2D) CT. They were compared with the real fractured nasal bone aspects based on the 3D image and marked the difference in the 10-point scale of 0 to 10. Results: The average score of the 4 residents was 1.62 and that of the 4 surgeons was 4.47 out of 10 by simple X-ray. The average score of the 4 residents was 5.67 and that of the 4 surgeons was 7.25 out of 10 by 2D CT. Conclusion: It was surmised that the precise analysis and accurate comprehension of the spatial relationship of the fractured nasal bone using the 3D image, as based on the 2D CT images, can produce more favorable satisfaction levels in the patients.

• 로봇학회논문지
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• 제12권4호
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• pp.411-418
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• 2017

During the intramedullary nailing procedure, surgeons feel difficulty in manipulation of the X-ray device to align it to axes of nailing holes and suffer from the large radiation exposure from the X-ray device. These problems are caused by the fact the surgeon cannot see the hole's location directly and should use the X-ray device to find the hole's location and direction. In this paper, we proposed the robotic guidance of the distal screwing using an optical tracking system. To track the location of the hole for the distal screwing, the reference marker is attached to the proximal end of an intramedullary nail. To guide the drill's direction robustly, the 6-degree-of-freedom robotic arm is used. The robotic arm is controlled so as to align the drill guiding tool attached the robotic arm with the obtained the hole's location. For the safety, the robot's linear and angular velocities are restricted to the predefined values. The experimental results using the artificial bones showed that the position error and the orientation error were 0.91 mm and $1.64^{\circ}$, respectively. The proposed method is simple and easy to implement, thus it is expected to be adopted easily while reducing the radiation exposure significantly.