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Suppression of Magnetic Signal Error in Trigger Assembly by Simultaneous Sensing of Bipolar Magnets
Kisu Lee,Joon Mo Ahn,Je-Wook Chae 한국자기학회 2019 Journal of Magnetics Vol.24 No.1
A previous trigger assembly with a single embedded permanent magnet has malfunction problems such as the generation of a virtual trigger signal by an external magnetic field. In this study, we improved a trigger assembly, which can minimize the influence of external magnetic field. In order to improve the trigger assembly, two designs were considered. Through an M&S study for the optimal characteristics of Hall-effect sensor, we confirmed that the magnitude of the driving magnetic field of the Hall-effect sensor should be at least 50 gauss for the application of a trigger assembly. The second design was a magnetic bipolar simultaneous recognition system with a time-interval of 10 ms, which occurs when two embedded permanent magnets with different polarities are recognized simultaneously. As a result, the improved trigger assembly, which reflects the two design results, excluded the malfunction of small arms by the external magnetic field without magnetic shielding.
Highly Crystalline Perovskite-Based Photovoltaics via Two-Dimensional Liquid Cage Annealing Strategy
Lee, Jong Woo,Yu, Haejun,Lee, Kisu,Bae, Sohyeon,Kim, Jungwon,Han, Gi Rim,Hwang, Doyk,Kim, Seong Keun,Jang, Jyongsik American Chemical Society 2019 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.141 No.14
<P>Rendering a high crystalline perovskite film is integral to achieve superior performance of perovskite solar cells (PSCs). Here, we established a two-dimensional liquid cage annealing system, a unique methodology for remarkable enhancement in perovskite crystallinity. During thermal annealing for crystallization, wet-perovskite films were suffocated by perfluorodecalin with distinctively low polarity, nontoxic, and chemically inert characteristics. This annealing strategy facilitated enlargement of perovskite grain and diminution in the number of trap states. The simulation results, annealing time, and temperature experiments supported that the prolonged diffusion length of precursor ions attributed to the increase of perovskite grains. Consequently, without any complicated handling, the performance of perovskite photovoltaics was remarkably improved, and the monolithic grains which directly connected the lower and upper electrode attenuated hysteresis.</P> [FIG OMISSION]</BR>
Lee, Kisu The Korean Society of Mechanical Engineers 2002 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.16 No.10
The numerical techniques are presented to solve the static and dynamic contact problems of deformable bodies having large rotations of the contact surfaces. The contact conditions on the possible contact surfaces are enforced by using the contact error vector, and an iterative scheme similar to augmented Lagrange multiplier method is employed to reduce the contact error vector monotonically. For dynamic contact problems using implicit time integration, a contact error vector is also defined by combining the displacement, velocity, and acceleration on the contact surface. The suggested iterative technique is implemented to ABAQUS by using the UEL subroutine UEL. In this work, after the computing procedures to solve the frictional contact problems are explained, the numerical examples are presented to compare the present solutions with those obtained by ABAQUS.
The Limit of Detection of Giant Magnetoresistive (GMR) Sensors for Bio-applications
Kisu Lee,Seungkyo Lee,Kwang-Seok Kim,Byungchul Kim,조병기 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.1
For the detection of specific bio-molecules, such as cells, proteins and DNA, it is necessary to verify the limit of detection (LOD) of an investigated giant magnetoresistive (GMR) sensor. We measured voltage drops across a GMR sensor before and after spreading magnetic particles on the surface of the GMR sensor and compared them to find the LOD of the GMR sensor. Magnetic particles (DynabeadsR) of 2.8 μm in diameter were used. The threshold for the detection was approximately 6 beads. This result indicates that the GMR sensor studied in this study can be used to detect bio-molecules, such as micron-sized cells.
Kisu Lee 대한기계학회 2002 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.16 No.10
The numerical techniques are presented to solve the static and dynamic contact problems of deformable bodies having large rotations of the contact surfaces. The contact conditions on the possible contact surfaces are enforced by using the contact error vector, and an iterative scheme similar to augmented Lagrange multiplier method is employed to reduce the contact error vector monotonically. For dynamic contact problems using implicit time integration, a contact error vector is also defined by combining the displacement, velocity, and acceleration on the contact surface. The suggested iterative technique is implemented to ABAQUS by using the UEL subroutine UEL. In this work, after the computing procedures to solve the frictional contact problems are explained, the numerical examples are presented to compare the present solutions with those obtained by ABAQUS.<br/>
Lee, Kisu,Cho, Sunghun,Kim, Minkyu,Kim, Jihoo,Ryu, Jaehoon,Shin, Keun-Young,Jang, Jyongsik The Royal Society of Chemistry 2015 Journal of Materials Chemistry A Vol.3 No.37
<▼1><P>A novel method to synthesize highly porous polyaniline (PANI) using carbon nanodots (CNDs) is reported. PANI-CND nanocomposite films exhibited high electrical conductivity (774 S cm<SUP>−1</SUP>) and excellent performance as counter electrodes in dye-sensitized solar cells (<I>η</I> = 7.45%).</P></▼1><▼2><P>We report a novel method for synthesizing highly porous polyaniline (PANI) using carbon nanodots (CNDs) as a nucleating agent and demonstrate their use as counter electrodes (CEs) for dye-sensitized solar cells (DSSCs). CNDs surrounded with aniline act as efficient nuclei in the polymerization reaction. CNDs disrupt undesirable secondary growth reactions leading to the formation of an agglomerated structure, and organize the highly porous PANI structures with a large surface area (43.6 m<SUP>2</SUP> g<SUP>−1</SUP>). Moreover, the presence of CNDs in the polymerization mixture facilitates generation of head-to-tail dimers, and enhances the degree of <I>para</I>-coupling in the molecular structure of PANI. As a result of these nucleation effects, the fabricated PANI-CND films exhibit an increased electrical conductivity of <I>ca.</I> 774 S cm<SUP>−1</SUP>. When used as a CE in DSSCs, PANI-CND CEs exhibit a superior power conversion efficiency (<I>η</I> = 7.45%) to those of conventional platinum (<I>η</I> = 7.37%) and pristine PANI CEs (<I>η</I> = 5.60%).</P></▼2>
Lee, Kisu,Yu, Haejun,Lee, Jong Woo,Oh, Jungkyun,Bae, Sohyeon,Kim, Seong Keun,Jang, Jyongsik The Royal Society of Chemistry 2018 Journal of Materials Chemistry C Vol.6 No.23
<P>Inverted-structure perovskite solar cells (PSCs), with low-temperature processed poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) and perovskite-passivating phenyl-C61-butyric acid methyl ester (PCBM) employed as charge transport layers, have great potential as efficient, flexible, and hysteresis-free solar cells. However, PEDOT:PSS processed from an aqueous solution has a hygroscopic nature, and can degrade the ambient stability of moisture-vulnerable perovskite electronics. Furthermore, excess insulating PSS in the PEDOT:PSS complex can deteriorate the hole extraction and photovoltaic performance of the solar cell. In this work, polyaniline doped with camphorsulfonic acid (PANI-CSA) is introduced as a hole transport layer (HTL) to promote hole extraction ability and improve the efficiency and stability of inverted PSCs. The device fabricated with PANI-CSA exhibited superior photovoltaic performance, with a maximum efficiency of 15.42%, compared to 14.11% efficiency for the device fabricated with PEDOT:PSS. Most notably, the stability of the device fabricated with PANI-CSA was greatly improved due to a stable HTL/perovskite interface against exposure to ambient moisture.</P>