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Operational Characteristics of Superconducting Amplifier using Vortex Flux Flow
Lim, Sung-Hun The Korean Institute of Electrical and Electronic 2008 Transactions on Electrical and Electronic Material Vol.9 No.6
The operational characteristics of superconducting amplifier using vortex flux flow were analyzed from an equivalent circuit in which its current-voltage characteristics for the vortex motion in YBCO microbridge were reflected. For the analysis of operation as an amplifier, dc bias operational point for the superconducting amplifier is determined and then ac operational characteristics for the designed superconducting amplifier were investigated. The variation of transresistance, which describes the operational characteristics of superconducting amplifier, was estimated with respect to conditions of dc bias. The current and the voltage gains, which can be derived from the circuit for small signal analysis, were calculated at each operational point and compared with the results obtained from the numerical analysis for the small signal circuit. From our paper, the characteristics of amplification for superconducting flux flow transistor (SFFT) could be confirmed. The development of the superconducting amplifier applicable to various devices is expected.
( Sang Eun Lee ),( Seung Joon Oh ),( Jung Min Lim ),( Yutaka Takagi ),( Seung Hun Lee ) 대한피부과학회 2015 대한피부과학회 학술발표대회집 Vol.67 No.2
Background: The effects of permeability barrier disruption on UV-induced skin responses are unclear. In keratinocytes, UVB induces endoplasmic reticulum(ER) stress. The ER stress-associated PERK/CHOP pathway mediates inflammation and apoptosis. Objectives: To investigate whether barrier disruption exacerbates UV-induced inflammation through alteration of the ER stress-associated pathway in human skin and whether topical pseudoceramide can prevent this response. Methods: Tape-stripping was done in the back skin of healthy volunteers 3 days prior to suberythemal UVB irradiation. In the pseudoceramide group, barrier disrupted skin was treated with 3 days of topical pseudoceramide prior to UVB irradiation. Erythema value was assessed. Skin samples were obtained 24 h after irradiation. Results: Compared to control, barrier disrupted skin showed a significant increment in erythema and the mRNA level of IL-1?, TNF-メ, IL-6, and iNOS inresponse to UVB. In barrier disrupted skin, CHOP gene expression was significantly increased following UVB irradiation compared to control. Topical pseudoceramide significantly decreased the degree of increment in erythema and gene expression of inflammatory mediators and CHOP in response to UVB. Conclusion: Damaged barrier increases UV sensitivity by promoting inflammation and ER stress-associated PERK/CHOP pathway activation. Topical pseudoceramide can protect the barrier-disrupted skin against UV-induced inflammation, partly by suppressing UV-induced ER stress.
Lim, Min-Hwa,Park, Mi-Jung,Kim, Sang-Chai,Roh, S. H.,Jung, Seung-Hun,Kim, Hee Tak,Jung, Ho-Young American Scientific Publishers 2017 Journal of Nanoscience and Nanotechnology Vol.17 No.8
<P>Durability test of commercial polymer electrolyte membranes investigated because longer performance of VRFB depends on the membrane's chemical stability. For hydrolytic stability test, distilled water and membrane was placed in the pressurized container, activated for 24 h at 200 degrees C to check the weight loss, and distilled water's pH change. To confirm the chemical degradation, the membrane was impregnated in 0.1 M V(V) solution for 72 h and concentration change was measured by UV-vis Spectrum. Through this experiment, anion exchange membrane in VRFB is considered in terms of chemical degradation.</P>
Fault Current Limiting Characteristics of Flux-lock Type SFCL with Several Secondary Windings
Sung-Hun Lim,한병성,조용선,최효상,박형민,Chung-Ryul Park 한국전기전자재료학회 2005 Transactions on Electrical and Electronic Material Vol.6 No.5
We investigated fault current limiting characteristics of the flux-lock type superconducting fault current limiter (SFCL), which consisted of a primary winding and several secondary windings connected in series between high-TC superconducting (HTSC) thin films. Each YBCO thin film has a 2 mm wide and 42 cm long meander line with 14 stripes of different length. The power imbalance due to the slight difference of IC between YBCO current limiting elements causes the significant power burden on YBCO element with lower IC. We confirmed from our experiments that the mutual coupling between the primary winding and secondary windings of the flux-lock type SFCL reduced the power imbalance between YBCO current limiting elements compared with the resistive type SFCL connected in series.
Operational Characteristics of Flux-lock Type SFCL using Series Resonance
Sung-Hun Lim,한병성,Hyo-Sang Choi 한국전기전자재료학회 2005 Transactions on Electrical and Electronic Material Vol.6 No.4
We analyzed the fault current limiting characteristics of a flux-lock type high-TC super-conducting fault current limiter (HTSC-FCL) using series resonance between capacitor for series resonance and magnetic field coil which was installed in coil 3. The capacitor for the series resonance in the flux-lock type HTSC-FCL was inserted in series with the magnetic field coil to apply enough magnetic field into HTSC element, which resulted in higher resistance of HTSC element. However, the impedance of the flux lock type HTSC-FCL has started to decrease since the current of coil 3 exceeded one of coil 2 after a fault accident. The decrease in the impedance of the FCL causes the line current to increase and, if continues, the capacitor for the series resonance to be destructed. To avoid this operation, the flux-lock type HTSC-FCL requires an additional device such as fault current interrupter or control circuit for magnetic field. From the experimental results, we investigated the parameter range where the operation as mentioned above for the designed flux-lock type HTSC-FCL using series resonance occurred.
Comparative Study of Current Limiting Characteristics for Hybrid Type and Flux-Lock Type SFCLs
Sung-Hun Lim 한국전기전자재료학회 2007 Transactions on Electrical and Electronic Material Vol.8 No.5
In this paper, we compared the current limiting characteristics of both the hybrid type and the flux-lock type superconducting fault current limiters (SFCLs), which have a magnetic coupling structure between a primary winding and several secondary windings. The limiting impedances of two SFCLs were derived from each equivalent circuit considering the design parameters of SFCL such as the self-inductance of secondary winding and the resistance of high-TC superconducting (HTSC) element. Through the comparison for the limiting impedances of two SFCLs considering the dependence of the HTSC element’s resistance on the applying voltage into the SFCL, the hybrid type SFCL was confirmed to have larger limiting impedance with smaller resistance of HTSC element than the flux-lock type SFCL. It was expected from the analysis that the hybrid type SFCL was more advantageous than the flux-lock type SFCL from the viewpoint of the fault current limiting level.
Sung-Hun Lim,Jin-Seok Kim,Myong-Hyon Kim,Jae-Chul Kim Institute of Electrical and Electronics Engineers 2012 IEEE transactions on applied superconductivity Vol.22 No.3
<P>The introduction of various dispersed generation (DG) in a power distribution system has caused the short-circuit current to increase, which can make the operation of the protective device deviate from its original set value. Especially, the increase of a short-circuit current in a power distribution system due to the increase of the DG is expected to be required for the related power utilities such as the circuit breaker to be replaced with a larger one. Among the countermeasures to solve the short-circuit problem in a power distribution system considering the increase of the DG, the superconducting fault current limiter (SFCL) has been noticed as one of the promising devices. In this paper, the protection coordination of the protective de- vices due to the application of a SFCL in a power distribution system where the DG was introduced into its bus line was analysed. The experimental circuit to simulate the DG and the protective de- vices was designed and realized by using power electronic switches. The short-circuit tests for the power distributed system assembled with the DG, the protective devices and the SFCL were carried out. Through the analysis on the results from the short-circuit tests, the application of the SFCL with its proper resistance amplitude in a power distribution system with the DG could be confirmed to be contributed to the improvement of the protection coordination of the protective devices.</P>
Lim, Mi-Sun,Chang, Mi-Yoon,Kim, Sang-Mi,Yi, Sang-Hoon,Suh-Kim, Haeyoung,Jung, Sung Jun,Kim, Min Jung,Kim, Jin Hyuk,Lee, Yong-Sung,Lee, Soo Young,Kim, Dong-Wook,Lee, Sang-Hun,Park, Chang-Hwan American Society for Biochemistry and Molecular Bi 2015 The Journal of biological chemistry Vol.290 No.28
<P>Recent groundbreaking work has demonstrated that combined expression of the transcription factors <I>Brn2</I>, <I>Ascl1</I>, and <I>Myt1L</I> (BAM; also known as Wernig factors) convert mouse fibroblasts into postmitotic neuronal cells. However, questions remain regarding whether trans-conversion is achieved directly or involves an intermediary precursor stage. Trans-conversion toward expandable neural precursor cells (NPCs) is more useful than direct one-step neuron formation with respect to yielding a sufficient number of cells and the feasibility of manipulating NPC differentiation toward certain neuron subtypes. Here, we show that co-expression of Wernig factors and <I>Bcl-xL</I> induces fibroblast conversion into NPCs (induced NPCs (iNPCs)) that are highly expandable for >100 passages. Gene expression analyses showed that the iNPCs exhibited high expression of common NPC genes but not genes specific to defined embryonic brain regions. This finding indicated that a regional identity of iNPCs was not established. Upon induction, iNPCs predominantly differentiated into astrocytes. However, the differentiation potential was not fixed and could be efficiently manipulated into general or specific subtypes of neurons by expression of additional genes. Specifically, overexpression of <I>Nurr1</I> and <I>Foxa2</I>, transcription factors specific for midbrain dopamine neuron development, drove iNPCs to yield mature midbrain dopamine neurons equipped with presynaptic DA neuronal functions. We further assessed the therapeutic potential of iNPCs in Parkinson disease model rats.</P>