• Progress in Superconductivity
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• v.10 no.2
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• pp.74-78
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• 2009

Inter-grain nanobridges of the $MgB_2$ superconductor have been fabricated by focused-ion-beam(FIB) and their electrical transport properties were studied. The $MgB_2$ film was prepatterned into microbridges by a standard argon ion milling technique and then FIB-patterned into 100 nm$\times$100 nm bridges. Current-voltage characteristics showed a strong flux-flow type behavior at all temperatures with a trait of Josephson coupling near $T_c$. At low temperatures, the curves showed a two-step resistance-doubled transition with occasional hysteresis. The resistance-doubling transition is believed to be due to a two-channel flux-flow effect. The temperature-dependent critical current data showed $I_c(T){\propto}(1-T/T_c)^2$ near $T_c$, same as a normal barrier junction, and $I_c(T){\propto}(1-T/T_c)^{1.2}$ at low temperatures, similar to that of a film.

• Journal of Electrochemical Science and Technology
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• v.9 no.3
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• pp.212-219
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• 2018

Perovskite type ceramic membranes which exhibit dual ion conduction (proton and oxygen ion conduction) can permeate water and can aid solving operational problems such as temperature gradient and carbon deposition associated with a working solid oxide fuel cell. From this point of view, it is crucial to reveal water transport mechanism and especially the nature of the surface sites that is necessary for water incorporation and evolution. $BaCe_{0.8}Y_{0.2}O_{3-{\alpha}}$ (BCY20) was used as a model proton and oxygen ion conducting membrane in this work. Four different catalytically modified membrane configurations were used for the investigations and water flux was measured as a function of temperature. In addition, CO was introduced to the permeate side in order to test the stability of membrane against water and $CO/CO_2$ and post operation analysis of used membranes were carried out. The results revealed that water incorporation occurs on any exposed electrolyte surface. However, the magnitude of water permeation changes depending on which membrane surface is catalytically modified. The platinum increases the water flux on the feed side whilst it decreases the flux on the permeate side. Water flux measurements suggest that platinum can block water permeation on the permeate side by reducing the access to the lattice oxygen in the surface layer.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.4
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• pp.357-363
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• 2014

The electrolyte wetting phenomena in the electrode of lithium ion battery is studied numerically using a multiphase lattice Boltzmann method (LBM). When a porous electrode is compressed during roll-pressing process, the porosity and thickness of the compressed electrode are changed, which can affect its wettability. In this study, the change in electrolyte distribution and degree of saturation as a result of varying the compression ratio are investigated with two-dimensional LBM approach. We found that changes in the electrolyte transport path are caused by a reduction in through-plane pore size and result in a decrease in the wettability of the compressed electrode.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.6
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• pp.660-669
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• 2016

A fluorinated-sulfonated, hydrophobic-hydrophilic copolymer was planed subsequently synthesized using typical nucleophilic substitution polycondensation reaction. A novel AB and ABA (or BAB) block copolymers were synthesized using sBCPSBP (sulfonated 4,4'-bis[4-chlorophenyl)sulfonyl]-1,1'-biphenyl), DHN (1,5-dihydroxynaphthalene), DFBP (decafluorobiphenyl) and HFIP (4,4'-hexafluoroisopropylidenediphenol). All block copolymers were easily cast and made into clear films. The structure and synthesized copolymers and corresponding membranes were analyzed using GPC (gel permeation chromatography), $^1H$-NMR ($^1H$ nuclear magnetic resonance) and FT-IR (Fourier transform infrared). TGA (Thermogravimetric analysis) and DSC (differential scanning calorimetry) analysis showed that the prepared membranes were thermally stable, so that elevated temperature fuel cell operation would be possible. Hydrophobic/hydrophilic phase separation and clear ionic aggregate block morpology was confirmed in both triblock and diblock copolymer in AFM (atomic force microscopy), which may be highly related to their proton transport ability. A sulfonated BAB triblock copolymer membrane with an ion-exchange capacity (IEC) of 0.6 meq/g has a maximum ion conductivity of 40.3 mS/cm at $90^{\circ}C$ and 100% relative humidity.

• Journal of the Korean Ceramic Society
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• v.52 no.5
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• pp.331-337
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• 2015

$LaBO_3$ (B = Cr, Mn, Fe, Co, and Ni) perovskites, the most common perovskite-type mixed ionic-electronic conductors (MIECs), are promising candidates for intermediate-temperature solid oxide fuel cell (IT-SOFC) cathodes. The catalytic activity on MIEC-based cathodes is closely related to the bulk ionic conductivity. Doping B-site cations with other metals may be one way to enhance the ionic conductivity, which would also be sensitively influenced by the chemical composition of the dopants. Here, using density functional theory (DFT) calculations, we quantitatively assess the activation energies of bulk oxide ion diffusion in $LaBO_3$ perovskites with a wide range of combinations of B-site cations by calculating the oxygen vacancy formation and migration energies. Our results show that bulk oxide ion diffusion dominantly depends on oxygen vacancy formation energy rather than on the migration energy. As a result, we suggest that the late transition metal-based perovskites have relatively low oxygen vacancy formation energies, and thereby exhibit low activation energy barriers. Our results will provide useful insight into the design of new cathode materials with better performance.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2005.09a
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• pp.110-123
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• 2005

This paper proposes an intelligent method for the optimal load distribution of two cooperating robots(TCRs) using fuzzy logic. The proposed scheme requires the knowledge of the robots' dynamics, which in turn depend upon the characteristics of large flat panel displays(LFPDs) carried by the TCRs. However, the dynamic properties of the LFPD are not known exactly, so that the dynamics of the robots, and hence the required joint torque, must be calculated for nominal set of the LFPD characteristics. The force of the TCRs is an important factor in carrying the LFPD. It is divided into external force and internal force. In general , the effects of the internal force of the TCRs are not considered in performing the load distribution in terms of optimal time, but they are essential in optimal trajectory planning: if they are not taken into consideration, the optimal scheme is no longer fitting. To alleviate this deficiency, we present an algorithm for finding the internal-force factors for the TCRs in terms of optimal time. The effectiveness of the proposed system is demonstrated by computer simulations using two three-joint planner robot manipulators.

• Nuclear Engineering and Technology
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• v.55 no.1
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• pp.378-390
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• 2023

The SPES (Selective Production of Exotic Species) facility, currently under development at Legnaro National Laboratories of INFN, aims at the production of intense RIB (Radioactive Ion Beams) employing the Isotope Separation On-Line (ISOL) technique for interdisciplinary research. The radioactive isotopes of interest are produced by the interaction of a multi-foil uranium carbide target with a 40 MeV 200 μA proton beam generated by a cyclotron proton driver. The Target Ion Source (TIS) is the core of the SPES project, here the radioactive nuclei, mainly neutron-rich isotopes, are stopped, extracted, ionized, separated, accelerated and delivered to specific experimental areas. Due to efficiency reasons, the TIS unit needs to be replaced periodically during operation. In this highly radioactive environment, the employment of autonomous systems allows the manipulation, transport, and storage of the TIS unit without the need for human intervention. A dedicated remote handling infrastructure is therefore under development to fulfill the functional and safety requirement of the project. This contribution describes the layout of the SPES target area, where all the remote handling systems operate to grant the smooth operation of the facility avoiding personnel exposure to a high dose rate or contamination issues.

• Membrane Journal
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• v.8 no.3
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• pp.148-156
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• 1998

Diffusion dialysis is a membrane process driven by concentration difference using ion-exchange membranes and has been employed for many years for the acid recovery from acidic waste generated in steel, metal-refining and dectro-plating industries. Theoretically acid flux increases in propomon to the acid concentration difference. At acid concentrations higher than 3 N HCl, however, the acid flux had not increased linearly with the concentration difference. In this paper the effects of acid concentrations on diffusion dialysis for hydrochloric acid recovery and the acid transport mechanism in an anion exchange membrane were studied by membrane sorption tests and diffusion clialysis cell tests. The experimental results showed that the molecular diffusion was a major transport mechanism in a low acid concentration range and the proton leakage through an anion exchange membrane played an important role at higher acid concentrations. Also osmotic water transport and membrane dehydration retarded the transport of protons and caused the permeate flux to decrease.

• Journal of the Korean Electrochemical Society
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• v.22 no.1
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• pp.22-35
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• 2019

Development of low cost rechargeable batteries has been considered as a significant task for future large-scale energy storage units (i.e. electric vehicles, smart grids). Sodium-ion batteries (SIBs) have been recognized as a promising alternative to replace conventional lithium-ion batteries (LIBs) because of their abundancy and economic benign. Nevertheless, Na ions have larger ionic radius than that of Li ions, resulting in sluggish transport of Na ions in electrodes for cell operation. There have been efforts to seek suitable anode materials for the past years operated based on three different kinds of reaction mechanism (intercalation, alloy reaction, and conversion reaction). In this review, we introduce a class of conversion reaction anode materials for Na-ion batteries, which have been reported.

• Nuclear Engineering and Technology
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• v.54 no.7
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• pp.2586-2591
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• 2022

In the present work, we have irradiated the DI-BSCCO superconducting tapes with the 100 keV deuterium ions to investigate the effect of ion irradiation on their critical current (Ic). The damage simulations are carried out using the binary collision approximation method to get the spatial distribution and depth profile of the damage events in the high temperature superconducting (HTS) tape. The point defects are formed near the surface of the HTS tape. These point defects change the vortex profile in the superconducting tape. Due to the long-range interaction of vortices with each other, the Ic of the tape degrades at the 77 K and self magnetic field. The radiation dose of 2.90 MGy degrades the 44% critical current of the tape. The results of the displacement per atom (dpa) and dose deposited by the deuterium ions are used to fit an empirical relation for predicting the degradation of the Ic of the tape. We include the dpa, dose and columnar defect terms produced by the incident particles in the empirical relation. The fitted empirical relation predicts that light ion irradiation degrades the Ic in the DI-BSCCO tape at the self field. This empirical relation can also be used in neutron irradiation to predict the lifetime of the DI-BSCCO tape. The change in the Ic of the DI-BSCCO tape due to deuterium irradiation is compared with the other second-generation HTS tape irradiated with energetic radiation.