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Jangmi Han,Lindsay P. Keller,Ichiro Ohnishi,Akira Yasuhara 대한지질학회 2021 대한지질학회 학술대회 Vol.2021 No.10
Refractory Ca-Al-rich inclusions (CAIs) in primitive meteorites consist of complex assemblages of high-temperature minerals [1], which are predicted to form by gas-solid condensation reactions in the early solar nebula [2]. Their mineralogy and petrography thus provide a window into events that occurred at the birth of our Solar System ~4.567 billion years ago [3]. Hibonite (CaAl12O19) is a common refractory mineral in CAIs [1], which is predicted as the second phase, after corundum, to condense from a cooling gas of solar composition [2]. Transmission electron microscope (TEM) studies have identified enigmatic planar defects in different occurrences of hibonite in the Allende meteorite that give rise to strong streaking along c* in electron diffraction patterns. Atomic resolution high-angle annular dark-field (HAADF) imaging and energy dispersive X-ray (EDX) analyses were used to determine the nature and origin of these planar features [4]. HAADF images of hibonite grains reveal lamellar intergrowths of common 1.6 nm spacing, and less commonly 2.0 nm and 2.5 nm spacings, interspersed in stoichiometric hibonite showing 1.1 nm (002) spacing. Stoichiometric hibonite consists of alternating Ca-containing (“R”) and spinel-structured (“S”) blocks stacked in a sequence RS [5]. In contrast, the 1.6 nm layers result from a doubled S block such that the stacking sequence is RSS, while in the widest defect observed, the stacking sequence is RSSSS. These intergrowths are epitaxial and have coherent, low-strain boundaries with the host hibonite. In addition, atomic resolution EDX maps of hibonite grains in the Allende CAI show that Mg is highly concentrated, but Ti is absent, in the planar defects where wider S blocks show Al-rich compositions compared to stoichiometric MgAl₂O₄ spinel. Therefore, Mg likely played the major role in the formation and metastability of planar defects in hibonite. The formation of planar defects in hibonite occurred during high-temperature condensation or melting/crystallization processes in the early solar nebula. The occurrence of non-stoichiometric hibonite intergrown with Al-rich spinel in the Allende CAI deviates from the mineral formation sequence predicted from equilibrium condensation models, suggesting that these phases formed metastably in place of thermodynamic equilibrium Ca-Al-oxide assemblages. Therefore, our atomic resolution TEM observations signify non-equilibrium, kinetic-controlled crystal growth during high-temperature formation of refractory solids in the early solar nebula [4,6].
A study on flow distribution for integrated hybrid actuator by analysis of reed valve
Jangmi Woo,Nam Seo Goo,Yong Zhe Li,Seung-Hwan Kang,Han Seo Ko 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.5
Many studies have been conducted recently on an integrated hybrid actuator due to the increasing need for unmanned aircraft and guided weapons. In this study, flow distribution was analyzed for a reed valve which was used for flow regulation to improve the performance of the actuator. By using a Fluid structural interaction (FSI) technique with Computational fluid dynamics (CFD) having a moving mesh, numerical analysis was performed according to the thickness, shape and driving frequency of the reed valve. From the calculated results, the maximum performance of the reed valve was found at the valve thickness of 0.15 mm and the driving frequency of 250 Hz for a no-load state. The optimum thickness and shape for the valve for each driving frequency were also realized.
피에조 구동기로 작동되는 멤브레인 펌프의 성능 해석에 관한 연구
우장미(Jangmi Woo),손동기(Dong Kee Sohn),고한서(Han Seo Ko) 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.11
As a demand for highly integrated mechanical systems such as precision robots increases, research on miniaturization as well as performance improvement of devices is getting more attention. Recently, development of smart materials such as a piezo has been accelerated for the miniaturization of the power source, and researches on the development and miniaturization of the driving device have been increased. In this study, the membrane pump using the piezoelectric actuator was analyzed. First, the pump was designed and fabricated to verify the performance, and the basic flow rate experiment was conducted. The body of the pump is made of a transparent material to measure the internal flow for precise analysis of the flow field. Numerical analysis for the performance was also performed using the FSI-2way method, which is suitable for simulating the movement of the membrane valves. Both the experimental and CFD results showed that the maximum flow rate was obtained at 30 Hz and the maximum flow velocity was 5.88 mm/s for the experiment and 5.33 mm/s for the numerical analysis, and the error was 9.35 %. The reliability of the numerical analysis could be obtained by the comparison with the experiment, and it is expected that the FSI-2way technique can be reliably used for the research on performance improvement of the pump.
Cross-Stacked Single-Crystal Organic Nanowire p–n Nanojunction Arrays by Nanotransfer Printing
Park, Kyung Sun,Lee, Ki Seok,Kang, Chan-mo,Baek, Jangmi,Han, Kyu Seok,Lee, Changhee,Koo Lee, Yong-Eun,Kang, Youngjong,Sung, Myung Mo American Chemical Society 2015 NANO LETTERS Vol.15 No.1
<P>We fabricated cross-stacked organic p–n nanojunction arrays made of single-crystal 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-PEN) and fullerene (C<SUB>60</SUB>) nanowires as p-type and n-type semiconductors, respectively, by using a nanotransfer printing technique. Single-crystal C<SUB>60</SUB> nanowires were synthesized inside nanoscale channels of a mold and directly transferred onto a desired position of a flexible substrate by a lubricant liquid layer. In the consecutive printing process, single-crystal TIPS-PEN nanowires were grown in the same way and then perpendicularly aligned and placed onto the C<SUB>60</SUB> nanowire arrays, resulting in a cross-stacked single-crystal organic p–n nanojunction array. The cross-stacked single-crystal TIPS-PEN/C<SUB>60</SUB> nanowire p–n nanojunction devices show rectifying behavior with on/off ratio of ∼13 as well as photodiode characteristic with photogain of ∼2 under a light intensity of 12.2 mW/cm<SUP>2</SUP>. Our study provides a facile, solution-processed approach to fabricate a large-area array of organic crystal nanojunction devices in a desired arrangement for future nanoscale electronics.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2015/nalefd.2015.15.issue-1/nl5035623/production/images/medium/nl-2014-035623_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl5035623'>ACS Electronic Supporting Info</A></P>
Experimental Study on the Performance of a Bidirectional Hybrid Piezoelectric-Hydraulic Actuator
Xiao Long Jin,Ngoc San Ha,Yong Zhe Li,Nam Seo Goo,Jangmi Woo,Han Seo Ko,Tae Heun Kim,Chang Seop Lee 한국항공우주학회 2015 International Journal of Aeronautical and Space Sc Vol.16 No.4
The piezoelectric-hydraulic actuator is a hybrid device that consists of a hydraulic pump driven by a piezo-stack coupled to a conventional hydraulic cylinder. The actuator is of compact size, but can produce a moderate energy output. Such hybrid actuators are currently being researched and developed in many industrialized countries due to the requirement for high performance and compact flight systems. In a previous study, we designed and manufactured a unidirectional hybrid actuator. However, the blocking force was not as high as expected. Therefore, in this study, we redesigned the pump chamber and hydraulic cylinder and also improved the system by removing the air bubbles. Two different types of piezo-stacks were used. In order to achieve bidirectional capabilities in the actuator, commercial solenoid valves were used to control the direction of the output cylinder. Experimental testing of the actuator in unidirectional and bidirectional modes was performed to examine performance issues related to driving frequency, bias pressure, reed valve thickness, etc. The results showed that the maximum blocking force was measured as 970.2N when the frequency was 185Hz.
Experimental Study on the Performance of a Bidirectional Hybrid Piezoelectric-Hydraulic Actuator
Jin, Xiao Long,Ha, Ngoc San,Li, Yong Zhe,Goo, Nam Seo,Woo, Jangmi,Ko, Han Seo,Kim, Tae Heun,Lee, Chang Seop The Korean Society for Aeronautical and Space Scie 2015 International Journal of Aeronautical and Space Sc Vol.16 No.4
The piezoelectric-hydraulic actuator is a hybrid device that consists of a hydraulic pump driven by a piezo-stack coupled to a conventional hydraulic cylinder. The actuator is of compact size, but can produce a moderate energy output. Such hybrid actuators are currently being researched and developed in many industrialized countries due to the requirement for high performance and compact flight systems. In a previous study, we designed and manufactured a unidirectional hybrid actuator. However, the blocking force was not as high as expected. Therefore, in this study, we redesigned the pump chamber and hydraulic cylinder and also improved the system by removing the air bubbles. Two different types of piezo-stacks were used. In order to achieve bidirectional capabilities in the actuator, commercial solenoid valves were used to control the direction of the output cylinder. Experimental testing of the actuator in unidirectional and bidirectional modes was performed to examine performance issues related to driving frequency, bias pressure, reed valve thickness, etc. The results showed that the maximum blocking force was measured as 970.2N when the frequency was 185Hz.