Continuous efforts are underway to reduce carbon emissions worldwide in response to global climate change.Water electrolysis technology,in conjunction with renewable energy,is considered the most feasible hydrogen pro...Continuous efforts are underway to reduce carbon emissions worldwide in response to global climate change.Water electrolysis technology,in conjunction with renewable energy,is considered the most feasible hydrogen production technology based on the viable possibility of large-scale hydrogen production and the zero-carbon-emission nature of the process.However,for hydrogen produced via water electrolysis systems to be utilized in various fields in practice,the unit cost of hydrogen production must be reduced to$1/kg H_(2).To achieve this unit cost,technical targets for water electrolysis have been suggested regarding components in the system.In this paper,the types of water electrolysis systems and the limitations of water electrolysis system components are explained.We suggest guideline with recent trend for achieving this technical target and insights for the potential utilization of water electrolysis technology.展开更多
Herein,incremental capacity-differential voltage (IC-DV) at a high C-rate (HC) is used as a non-invasive diagnostic tool in lithium-ion batteries,which inevitably exhibit capacity fading caused by multiple mechanisms ...Herein,incremental capacity-differential voltage (IC-DV) at a high C-rate (HC) is used as a non-invasive diagnostic tool in lithium-ion batteries,which inevitably exhibit capacity fading caused by multiple mechanisms during charge/discharge cycling.Because battery degradation modes are complex,the simple output of capacity fading does not yield any useful data in that respect.Although IC and DV curves obtained under restricted conditions (<0.1C,25℃) were applied in non-invasive analysis for accurate observation of degradation symptoms,a facile,rapid diagnostic approach without intricate,complex calculations is critical in on-board applications.Herein,Li Ni_(0.5)Mn_(0.3)Co_(0.2)O_(2)(NMC532)/graphite pouch cells were cycled at 4 and 6C and the degradation characteristics,i.e.,loss of active materials (LAM) and loss of lithium inventory (LLI),were parameterized using the IC-DV curves.During the incremental current cycling,the initial steep LAM and LLI slopes underwent gradual transitions to gentle states and revealed the gap between low-and high-current measurements.A quantitative comparison of LAM at high and low C-rate showed that a IC;revealed the relative amount of available reaction region limited by cell polarization.However,this did not provide a direct relationship for estimating the LAM at a low C-rate.Conversely,the limiting LLI,which is calculated at a C-rate approaching 0,was obtained by extrapolating the LLI through more than two points measured at high C-rate,and therefore,the LLI at 0.1C was accurately determined using rapid cycling.展开更多
In this study, we first attempted to discover the optimal configuration of membrane-electrode assemblies(MEAs) used to achieve a high performance of direct hydrazine fuel cells(DHFCs). We have investigated the effect ...In this study, we first attempted to discover the optimal configuration of membrane-electrode assemblies(MEAs) used to achieve a high performance of direct hydrazine fuel cells(DHFCs). We have investigated the effect of water management and the electrode thickness on the performance of DHFCs, depending on the hydrophobicity of the gas diffusion layers in the cathode and the catalyst loading in the anode with the carbon-supported Ni, synthesized by a polyol process. With the optimal water management and electrode thickness, the MEA constructed using the as-prepared Ni/C anode catalyst containing the metallic and low oxidative state and ultra-low Pt loading cathode reduced the ohmic resistance and mass transfer limitation in the current-voltage curves observed for the alkaline DHFC, achieving an impressive power performance over 500 mW cm^(–2).展开更多
Despite the scarcity and cost of iridium oxide,it is still the material of choice in numerous fields of science and applications,including capacitors,electrochromism,sensors,and various oxidation electrocatalysis(e.g....Despite the scarcity and cost of iridium oxide,it is still the material of choice in numerous fields of science and applications,including capacitors,electrochromism,sensors,and various oxidation electrocatalysis(e.g.,chlorine evolution reaction,detoxification,and oxygen evolution reaction).Such versatility is attributed to the distinct features of iridium oxides,such as their activity,biocompatibility,conductivity,and durability.The features and properties of iridium oxides are strongly dependent on the fabrication method.In this review,methodologies relating to the synthesis and fabrication of solid-state iridium oxides have been thoroughly collected and discussed.Structuring and crystallization techniques for iridium oxides are also noted.At the end of the review,the effects of utilizing a certain fabrication method on the characteristics of the iridium oxide product are recapitulated,together with the recommended application of the product in various fields.展开更多
Electrochemical water treatment is an attractive technology for water desalination and softening due to its low energy consumption. Especially, capacitive Deionization(CDI) is promising as a future technology for wate...Electrochemical water treatment is an attractive technology for water desalination and softening due to its low energy consumption. Especially, capacitive Deionization(CDI) is promising as a future technology for water treatment. Graphene(rGO) has been intensively studied for CDI electrode because of its advantages such as excellent electrical conductivity and high specific surface area. However, its 2D dimensional structure with small specific capacitance, high resistance between layers and hydrophobicity degrades ion adsorption efficiency. In this work, we successfully prepared uniformly dispersed Fe3O4/rGO nanocomposite by simple thermal reactions and applied it as effective electrodes for CDI. Iron oxides play a role in uniting graphene sheets, and specific capacitance and wettability of electrodes are improved significantly;hence CDI performances are enhanced. The hardness removal of Fe3O4/rGO nanocomposite electrodes can reach 4.3 mg/g at applied voltage of 1.5V, which is 3 times higher than that of separate r GO electrodes.Thus this material is a promising candidate for water softening technology.展开更多
Ammonia (NH_(3)) plays a key role in the agricultural fertilizer and commodity chemical industries and is useful for exploring hydrogen storage carriers.The electrochemical nitrogen reduction reaction (NRR) is receivi...Ammonia (NH_(3)) plays a key role in the agricultural fertilizer and commodity chemical industries and is useful for exploring hydrogen storage carriers.The electrochemical nitrogen reduction reaction (NRR) is receiving attention as an environmentally sustainable NH_(3) synthesis replacement for the traditional Haber–Bosch process owing to its near ambient reaction conditions (<100℃ and 1 atm).However,its NH_(3) yield and faradaic efficiency are extremely low because of the sluggish kinetics of N≡N bond dissociation and the hindrance from competitive hydrogen evolution.To overcome these challenges,we herein introduce a dual-functionalized ionic liquid (1-(4-hydroxybutyl)-3-methylimidazolium hydroxide[HOBIM]OH) for a highly dispersed ruthenium oxide electrocatalyst to achieve a biased NRR.The observed uniform distribution of RuO_(2) on the carbon fiber and increase in the surface area for N_(2) adsorption by limiting proton access can be attributed to the presence of imidazolium ions.Moreover,extensive N_(2) adsorption contributes to enhanced NRR selectivity with an NH_(3) yield of 3.0×10^(-10)mol cm^(-2)s^(-1)(91.8μg h^(-1)mg^(-1)) and a faradaic efficiency of 2.2%at-0.20 V_(RHE).We expect our observations to provide new insights into the design of effective electrode structures for electrochemical NH;synthesis.展开更多
In this paper, we propose a new algorithm for temporally consistent depth map estimation to generate three-dimensional video. The proposed algorithm adaptively computes the matching cost using a temporal weighting fun...In this paper, we propose a new algorithm for temporally consistent depth map estimation to generate three-dimensional video. The proposed algorithm adaptively computes the matching cost using a temporal weighting function, which is obtained by block-based moving object detection and motion estimation with variable block sizes. Experimental results show that the proposed algorithm improves the temporal consistency of the depth video and reduces by about 38% both the flickering artefact in the synthesized view and the number of coding bits for depth video coding.展开更多
Electrochemical water splitting is one of the most reliable approaches for environmental-friendly hydrogen production.Because of their stability and abundance,Mn-based materials have been studied as electrocatalysts f...Electrochemical water splitting is one of the most reliable approaches for environmental-friendly hydrogen production.Because of their stability and abundance,Mn-based materials have been studied as electrocatalysts for the oxygen evolution reaction(OER),which is a more sluggish reaction in the water splitting system.To increase the OER activity of Mn,it is imperative to facilitate the structural change of Mn oxide to the active phase with Mn_(3)+species,known as the active site.Here,we present the relationship between the electronic conductivity in the catalyst layer and the formation of the Mn active phase,δ-MnO_(2),from wrinkled Mn(OH)_(2).Mn(OH)_(2) has poor conductivity,and it disrupts the oxidation reaction toward MnOOH orδ-MnO_(2).Adjacent conductive carbon to Mn(OH)_(2) enabled Mn(OH)_(2) to be oxidized toδ-MnO_(2).Furthermore,after repetitive cyclic voltammetry activation,the more conductive environment resulted in a higher density ofδ-MnO_(2) through the irreversible phase transition,and thus it contributes to the improvement of the OER activity.展开更多
In this study,efficient spectral line selection and wcightcd-avcraging-bascd processing schemes are proposed for the classification of laser-induced breakdown spectroscopy(UBS)measurements.For fast on-line classificat...In this study,efficient spectral line selection and wcightcd-avcraging-bascd processing schemes are proposed for the classification of laser-induced breakdown spectroscopy(UBS)measurements.For fast on-line classification,a set of representative spectral lines arc selected ami processed relying on the information metric,instead of the time consuming full spectrum based analysis.I he most informative spectral line sets arc investigated by the joint mutual information estimation(MIR)evaluated with the Gaussian kernel density,where dominant intensity peaks associated with the concentrated components arc not necessarily most valuable for classification.In order to further distinguish the characteristic patterns of die LIBS measured spectrum,two-dimensional spectral images are synthesized through column-wise concatenation of the peaks along with their neighbors.For fast classification while preserv ing die effect of distinctive peak patterns,column-wise Gaussian weighted averaging is applied to die synthesized images,yielding a favorable trade off between classification performance and computational complexity.To explore the applicability of the proposed schemes,two applications of alloy classification and skin cancer detection arc investigated with the multi-class and binary support vector machines classifiers,respectively.Ihc MIE measures associated with selected spectral lines in bodi applications show a strong correlation to the actual classification or detection accuracy,which enables to find out meaningful combinations of spectral lines.In addition,the peak patterns of the selected lines and their Gaussian weighted averaging with nciehbors of the selected peaks efficiently distineuish different classes of LIBS measured spectrum.展开更多
Ammonia allows storage and transport of hydrogen over long distances and is an attractive potential hydrogen carrier.Electrochemical decomposition has recently been used for the conversion of ammonia to hydrogen and i...Ammonia allows storage and transport of hydrogen over long distances and is an attractive potential hydrogen carrier.Electrochemical decomposition has recently been used for the conversion of ammonia to hydrogen and is regarded as a future technology for production of CO_(2)-free pure hydrogen.Herein,a heterostructural Pt-Ir dual-layer electrode is developed and shown to achieve successful long-term operation in an ammonia electrolyzer with an anion exchange membrane(AEM).This electrolyzer consisted of eight membra ne electrode assemblies(MEAs)with a total geometric area of 200 cm~2 on the anode side,which resulted in a hydrogen production rate of 25 L h~(-1).We observed the degradation in MEA performance attributed to changes in the anode catalyst layer during hydrogen production via ammonia electrolysis.Furthermore,we demonstrated the relationship between the ammonia oxidation reaction(AOR)and the oxygen evolution reaction(OER).展开更多
The functionalities and diverse metastable phases of multiferroic BiFeO_(3)(BFO)thin films depend on the misfit strain.Although mixed phase-induced strain relaxation in multiphase BFO thin films is well known,it is un...The functionalities and diverse metastable phases of multiferroic BiFeO_(3)(BFO)thin films depend on the misfit strain.Although mixed phase-induced strain relaxation in multiphase BFO thin films is well known,it is unclear whether a singlecrystalline BFO thin film can accommodate misfit strain without the involvement of its polymorphs.Thus,understanding the strain relaxation behavior is key to elucidating the lattice strain–property relationship.In this study,a correlative strain analysis based on dark-field inline electron holography(DIH)and quantitative scanning transmission electron microscopy(STEM)was performed to reveal the structural mechanism for strain accommodation of a single-crystalline BFO thin film.The nanoscale DIH strain analysis results indicated a random combination of multiple strain states that acted as a primary strain relief,forming irregularly strained nanodomains.The STEM-based bond length measurement of the corresponding strained nanodomains revealed a unique strain accommodation behavior achieved by a statistical combination of multiple modes of distorted structures on the unit-cell scale.The globally integrated strain for each nanodomain was estimated to be close to1.5%,irrespective of the nanoscale strain states,which was consistent with the fully strained BFO film on the SrTiO_(3) substrate.Density functional theory calculations suggested that strain accommodation by the combination of metastable phases was energetically favored compared to single-phase-mediated relaxation.This discovery allows a comprehensive understanding of strain accommodation behavior in ferroelectric oxide films,such as BFO,with various low-symmetry polymorphs.展开更多
We observe the influence of AI occupancies in Li sites on the formation process of the garnet solid elec- trolyte of Li_7La_3Zr_2O_12 （LLZO）. A direct incorporation of AI is first promoted in a Li-insufficient garne...We observe the influence of AI occupancies in Li sites on the formation process of the garnet solid elec- trolyte of Li_7La_3Zr_2O_12 （LLZO）. A direct incorporation of AI is first promoted in a Li-insufficient garnet solid electrolyte during the calcination process of 850 ℃ and then the cubic phase of LLZO is obtained after successive annealing step of 1000 ℃. Comparing to pristine LLZO, AI incorporated LLZO shows less formation of Li_2CO_3, keeping crystallographic and physicochemical properties. This AI incorporation im- proves both the ionic conductivity and interfacial resistance to poisoning procedure.展开更多
Nonnegative matrix factorization(NMF)has shown good performances on blind audio source separation(BASS).While the NMF analysis is a non-convex optimization problem when both the basis and encoding matrices need to be ...Nonnegative matrix factorization(NMF)has shown good performances on blind audio source separation(BASS).While the NMF analysis is a non-convex optimization problem when both the basis and encoding matrices need to be estimated simultaneously,the source separation step of the NMF-based BASS with a fixed basis matrix has been considered convex.However,because the basis matrix for the BASS is typically constructed by concatenating the basis matrices trained with individual source signals,the subspace spanned by the basis vectors for one source may overlap with that for other sources.In this paper,we have shown that the resulting encoding vector is not unique when the subspaces spanned by basis vectors for the sources overlap,which implies that the initialization of the encoding vector in the source separation stage is not trivial.Furthermore,we propose a novel method to initialize the encoding vector for the separation step based on the prior model of the encoding vector.Experimental results showed that the proposed method outperformed the uniform random initialization by 1.09 and 2.21dB in the source-to-distortion ratio,and 0.20 and 0.23 in PESQ scores for supervised and semi-supervised cases,respectively.展开更多
Photoelectrochemical(PEC)H_(2)O_(2)production through water oxidation reaction(WOR)is a promising strategy,however,designing highly efficient and selective photoanode materials remains challenging due to competitive r...Photoelectrochemical(PEC)H_(2)O_(2)production through water oxidation reaction(WOR)is a promising strategy,however,designing highly efficient and selective photoanode materials remains challenging due to competitive reaction pathways.Here,for highly enhanced PEC H_(2)O_(2)production,we present a conformal amorphous titanyl phosphate(a-TP)overlayer on nanoparticulate TiO_(2)surfaces,achieved via lysozyme-molded in-situ surface reforming.The a-TP overlayer modulates surface adsorption energies for reaction intermediates,favoring WOR for H_(2)O_(2)production over the competing O_(2)evolution reaction.Our density functional theory calculations reveal that a-TP/TiO_(2)exhibits a substantial energy uphill for the O·*formation pathway,which disfavors O_(2)evolution but promotes H_(2)O_(2)production.Additionally,the a-TP overlayer strengthens the built-in electric field,resulting in favorable kinetics.Consequently,a-TP/TiO_(2)exhibits 3.7-fold higher Faraday efficiency(FE)of 63%at 1.76 V vs.reversible hydrogen electrode(RHE)under 1 sun illumination,compared to bare TiO_(2)(17%),representing the highest FE among TiO_(2)-based WOR H_(2)O_(2)production systems.Employing the a-TP overlayer constitutes a promising strategy for controlling reaction pathways and achieving efficient solar-to-chemical energy conversion.展开更多
基金supported by the Korea Institute of Energy Technology Evaluation and Planning(KETEP)grant from the Ministry of Trade,Industry&Energy,Republic of Korea(No.20213030040590)the National R&D Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Science and ICT(NRF-2021K1A4A8A01079455)。
文摘Continuous efforts are underway to reduce carbon emissions worldwide in response to global climate change.Water electrolysis technology,in conjunction with renewable energy,is considered the most feasible hydrogen production technology based on the viable possibility of large-scale hydrogen production and the zero-carbon-emission nature of the process.However,for hydrogen produced via water electrolysis systems to be utilized in various fields in practice,the unit cost of hydrogen production must be reduced to$1/kg H_(2).To achieve this unit cost,technical targets for water electrolysis have been suggested regarding components in the system.In this paper,the types of water electrolysis systems and the limitations of water electrolysis system components are explained.We suggest guideline with recent trend for achieving this technical target and insights for the potential utilization of water electrolysis technology.
基金supported by the projects of the Korea Electric Power Corporation(R19TA05)。
文摘Herein,incremental capacity-differential voltage (IC-DV) at a high C-rate (HC) is used as a non-invasive diagnostic tool in lithium-ion batteries,which inevitably exhibit capacity fading caused by multiple mechanisms during charge/discharge cycling.Because battery degradation modes are complex,the simple output of capacity fading does not yield any useful data in that respect.Although IC and DV curves obtained under restricted conditions (<0.1C,25℃) were applied in non-invasive analysis for accurate observation of degradation symptoms,a facile,rapid diagnostic approach without intricate,complex calculations is critical in on-board applications.Herein,Li Ni_(0.5)Mn_(0.3)Co_(0.2)O_(2)(NMC532)/graphite pouch cells were cycled at 4 and 6C and the degradation characteristics,i.e.,loss of active materials (LAM) and loss of lithium inventory (LLI),were parameterized using the IC-DV curves.During the incremental current cycling,the initial steep LAM and LLI slopes underwent gradual transitions to gentle states and revealed the gap between low-and high-current measurements.A quantitative comparison of LAM at high and low C-rate showed that a IC;revealed the relative amount of available reaction region limited by cell polarization.However,this did not provide a direct relationship for estimating the LAM at a low C-rate.Conversely,the limiting LLI,which is calculated at a C-rate approaching 0,was obtained by extrapolating the LLI through more than two points measured at high C-rate,and therefore,the LLI at 0.1C was accurately determined using rapid cycling.
基金supported by Technology Development Program to Solve Climate Changes through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT (2018M1A2A2063861)。
文摘In this study, we first attempted to discover the optimal configuration of membrane-electrode assemblies(MEAs) used to achieve a high performance of direct hydrazine fuel cells(DHFCs). We have investigated the effect of water management and the electrode thickness on the performance of DHFCs, depending on the hydrophobicity of the gas diffusion layers in the cathode and the catalyst loading in the anode with the carbon-supported Ni, synthesized by a polyol process. With the optimal water management and electrode thickness, the MEA constructed using the as-prepared Ni/C anode catalyst containing the metallic and low oxidative state and ultra-low Pt loading cathode reduced the ohmic resistance and mass transfer limitation in the current-voltage curves observed for the alkaline DHFC, achieving an impressive power performance over 500 mW cm^(–2).
基金supported by the Technology Development Program to Solve Climate Change through the National Research Foundation of Korea(NRF)funded by the Ministry of Science,ICT(2018M1A2A2063861)supported by the GIST Research Institute(GRI)grant funded by the GIST in 2019。
文摘Despite the scarcity and cost of iridium oxide,it is still the material of choice in numerous fields of science and applications,including capacitors,electrochromism,sensors,and various oxidation electrocatalysis(e.g.,chlorine evolution reaction,detoxification,and oxygen evolution reaction).Such versatility is attributed to the distinct features of iridium oxides,such as their activity,biocompatibility,conductivity,and durability.The features and properties of iridium oxides are strongly dependent on the fabrication method.In this review,methodologies relating to the synthesis and fabrication of solid-state iridium oxides have been thoroughly collected and discussed.Structuring and crystallization techniques for iridium oxides are also noted.At the end of the review,the effects of utilizing a certain fabrication method on the characteristics of the iridium oxide product are recapitulated,together with the recommended application of the product in various fields.
基金supported by international cooperation program for science and technology funded by the Ministry of Science,ICT&Future Planning(NRF-2014K1A3A1A09063208)
文摘Electrochemical water treatment is an attractive technology for water desalination and softening due to its low energy consumption. Especially, capacitive Deionization(CDI) is promising as a future technology for water treatment. Graphene(rGO) has been intensively studied for CDI electrode because of its advantages such as excellent electrical conductivity and high specific surface area. However, its 2D dimensional structure with small specific capacitance, high resistance between layers and hydrophobicity degrades ion adsorption efficiency. In this work, we successfully prepared uniformly dispersed Fe3O4/rGO nanocomposite by simple thermal reactions and applied it as effective electrodes for CDI. Iron oxides play a role in uniting graphene sheets, and specific capacitance and wettability of electrodes are improved significantly;hence CDI performances are enhanced. The hardness removal of Fe3O4/rGO nanocomposite electrodes can reach 4.3 mg/g at applied voltage of 1.5V, which is 3 times higher than that of separate r GO electrodes.Thus this material is a promising candidate for water softening technology.
基金supported by the National R&D Program through the National Research Foundation of Korea(NRF)funded by Ministry of Science and ICT(2021K1A4A8A01079455)。
文摘Ammonia (NH_(3)) plays a key role in the agricultural fertilizer and commodity chemical industries and is useful for exploring hydrogen storage carriers.The electrochemical nitrogen reduction reaction (NRR) is receiving attention as an environmentally sustainable NH_(3) synthesis replacement for the traditional Haber–Bosch process owing to its near ambient reaction conditions (<100℃ and 1 atm).However,its NH_(3) yield and faradaic efficiency are extremely low because of the sluggish kinetics of N≡N bond dissociation and the hindrance from competitive hydrogen evolution.To overcome these challenges,we herein introduce a dual-functionalized ionic liquid (1-(4-hydroxybutyl)-3-methylimidazolium hydroxide[HOBIM]OH) for a highly dispersed ruthenium oxide electrocatalyst to achieve a biased NRR.The observed uniform distribution of RuO_(2) on the carbon fiber and increase in the surface area for N_(2) adsorption by limiting proton access can be attributed to the presence of imidazolium ions.Moreover,extensive N_(2) adsorption contributes to enhanced NRR selectivity with an NH_(3) yield of 3.0×10^(-10)mol cm^(-2)s^(-1)(91.8μg h^(-1)mg^(-1)) and a faradaic efficiency of 2.2%at-0.20 V_(RHE).We expect our observations to provide new insights into the design of effective electrode structures for electrochemical NH;synthesis.
基金supported by the National Research Foundation of Korea Grant funded by the Korea Ministry of Science and Technology under Grant No. 2012-0009228
文摘In this paper, we propose a new algorithm for temporally consistent depth map estimation to generate three-dimensional video. The proposed algorithm adaptively computes the matching cost using a temporal weighting function, which is obtained by block-based moving object detection and motion estimation with variable block sizes. Experimental results show that the proposed algorithm improves the temporal consistency of the depth video and reduces by about 38% both the flickering artefact in the synthesized view and the number of coding bits for depth video coding.
基金supported by the National R&D Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Science and ICT(NRF-2021K1A4A8A01079455)supported by the Korea Institute of Energy Technology Evaluation and Planning(KETEP)granted financial resource from the Ministry of Trade,Industry&Energy,Republic of Korea(No.20213030040590)。
文摘Electrochemical water splitting is one of the most reliable approaches for environmental-friendly hydrogen production.Because of their stability and abundance,Mn-based materials have been studied as electrocatalysts for the oxygen evolution reaction(OER),which is a more sluggish reaction in the water splitting system.To increase the OER activity of Mn,it is imperative to facilitate the structural change of Mn oxide to the active phase with Mn_(3)+species,known as the active site.Here,we present the relationship between the electronic conductivity in the catalyst layer and the formation of the Mn active phase,δ-MnO_(2),from wrinkled Mn(OH)_(2).Mn(OH)_(2) has poor conductivity,and it disrupts the oxidation reaction toward MnOOH orδ-MnO_(2).Adjacent conductive carbon to Mn(OH)_(2) enabled Mn(OH)_(2) to be oxidized toδ-MnO_(2).Furthermore,after repetitive cyclic voltammetry activation,the more conductive environment resulted in a higher density ofδ-MnO_(2) through the irreversible phase transition,and thus it contributes to the improvement of the OER activity.
文摘In this study,efficient spectral line selection and wcightcd-avcraging-bascd processing schemes are proposed for the classification of laser-induced breakdown spectroscopy(UBS)measurements.For fast on-line classification,a set of representative spectral lines arc selected ami processed relying on the information metric,instead of the time consuming full spectrum based analysis.I he most informative spectral line sets arc investigated by the joint mutual information estimation(MIR)evaluated with the Gaussian kernel density,where dominant intensity peaks associated with the concentrated components arc not necessarily most valuable for classification.In order to further distinguish the characteristic patterns of die LIBS measured spectrum,two-dimensional spectral images are synthesized through column-wise concatenation of the peaks along with their neighbors.For fast classification while preserv ing die effect of distinctive peak patterns,column-wise Gaussian weighted averaging is applied to die synthesized images,yielding a favorable trade off between classification performance and computational complexity.To explore the applicability of the proposed schemes,two applications of alloy classification and skin cancer detection arc investigated with the multi-class and binary support vector machines classifiers,respectively.Ihc MIE measures associated with selected spectral lines in bodi applications show a strong correlation to the actual classification or detection accuracy,which enables to find out meaningful combinations of spectral lines.In addition,the peak patterns of the selected lines and their Gaussian weighted averaging with nciehbors of the selected peaks efficiently distineuish different classes of LIBS measured spectrum.
基金supported by the research program funded by the TKG Huchemssupported by the Korea Institute of Energy Technology Evaluation and Planning(KETEP)granted financial resources from the Ministry of Trade,Industry&Energy,Republic of Korea(20213030040590)supported by a National Research Foundation of Korea(NRF)grant funded by the Korean government(MSIT)(2021R1A5A1028138)。
文摘Ammonia allows storage and transport of hydrogen over long distances and is an attractive potential hydrogen carrier.Electrochemical decomposition has recently been used for the conversion of ammonia to hydrogen and is regarded as a future technology for production of CO_(2)-free pure hydrogen.Herein,a heterostructural Pt-Ir dual-layer electrode is developed and shown to achieve successful long-term operation in an ammonia electrolyzer with an anion exchange membrane(AEM).This electrolyzer consisted of eight membra ne electrode assemblies(MEAs)with a total geometric area of 200 cm~2 on the anode side,which resulted in a hydrogen production rate of 25 L h~(-1).We observed the degradation in MEA performance attributed to changes in the anode catalyst layer during hydrogen production via ammonia electrolysis.Furthermore,we demonstrated the relationship between the ammonia oxidation reaction(AOR)and the oxygen evolution reaction(OER).
基金Samsung Research Fundings&Incubation Center of Samsung Electronics(Grant No.SRFCMA1702-01)Y.-M.K acknowledges partial support from the National Research Foundation of Korea(NRF)(Grant No.2023R1A2C2002403)funded by the Korean government in KoreaA.Borisevich acknowledges support from FaCT,an Energy Frontier Research Center funded by the U.S.Department of Energy,Office of Science,Office of Basic Energy Science,Collaboratives Research Division.
文摘The functionalities and diverse metastable phases of multiferroic BiFeO_(3)(BFO)thin films depend on the misfit strain.Although mixed phase-induced strain relaxation in multiphase BFO thin films is well known,it is unclear whether a singlecrystalline BFO thin film can accommodate misfit strain without the involvement of its polymorphs.Thus,understanding the strain relaxation behavior is key to elucidating the lattice strain–property relationship.In this study,a correlative strain analysis based on dark-field inline electron holography(DIH)and quantitative scanning transmission electron microscopy(STEM)was performed to reveal the structural mechanism for strain accommodation of a single-crystalline BFO thin film.The nanoscale DIH strain analysis results indicated a random combination of multiple strain states that acted as a primary strain relief,forming irregularly strained nanodomains.The STEM-based bond length measurement of the corresponding strained nanodomains revealed a unique strain accommodation behavior achieved by a statistical combination of multiple modes of distorted structures on the unit-cell scale.The globally integrated strain for each nanodomain was estimated to be close to1.5%,irrespective of the nanoscale strain states,which was consistent with the fully strained BFO film on the SrTiO_(3) substrate.Density functional theory calculations suggested that strain accommodation by the combination of metastable phases was energetically favored compared to single-phase-mediated relaxation.This discovery allows a comprehensive understanding of strain accommodation behavior in ferroelectric oxide films,such as BFO,with various low-symmetry polymorphs.
基金financial support from the R&D Convergence Program (CAP-14-02-KITECH)the National Research Council of Science & Technology of the Republic of Korea
文摘We observe the influence of AI occupancies in Li sites on the formation process of the garnet solid elec- trolyte of Li_7La_3Zr_2O_12 （LLZO）. A direct incorporation of AI is first promoted in a Li-insufficient garnet solid electrolyte during the calcination process of 850 ℃ and then the cubic phase of LLZO is obtained after successive annealing step of 1000 ℃. Comparing to pristine LLZO, AI incorporated LLZO shows less formation of Li_2CO_3, keeping crystallographic and physicochemical properties. This AI incorporation im- proves both the ionic conductivity and interfacial resistance to poisoning procedure.
基金supported by the research fund of Signal Intelligence Research Center supervised by the Defense Acquisition Program Administration and Agency for Defense Development of Korea
文摘Nonnegative matrix factorization(NMF)has shown good performances on blind audio source separation(BASS).While the NMF analysis is a non-convex optimization problem when both the basis and encoding matrices need to be estimated simultaneously,the source separation step of the NMF-based BASS with a fixed basis matrix has been considered convex.However,because the basis matrix for the BASS is typically constructed by concatenating the basis matrices trained with individual source signals,the subspace spanned by the basis vectors for one source may overlap with that for other sources.In this paper,we have shown that the resulting encoding vector is not unique when the subspaces spanned by basis vectors for the sources overlap,which implies that the initialization of the encoding vector in the source separation stage is not trivial.Furthermore,we propose a novel method to initialize the encoding vector for the separation step based on the prior model of the encoding vector.Experimental results showed that the proposed method outperformed the uniform random initialization by 1.09 and 2.21dB in the source-to-distortion ratio,and 0.20 and 0.23 in PESQ scores for supervised and semi-supervised cases,respectively.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government,Ministry of Science and ICT(MSIT)(NRF-2020M3D1A2102837)the Korea Institute of Energy Technology Evaluation and Planning(KETEP)grant funded by the Korea government(MOTIE)(20214000000500,training program of CCUS for the green growth)。
文摘Photoelectrochemical(PEC)H_(2)O_(2)production through water oxidation reaction(WOR)is a promising strategy,however,designing highly efficient and selective photoanode materials remains challenging due to competitive reaction pathways.Here,for highly enhanced PEC H_(2)O_(2)production,we present a conformal amorphous titanyl phosphate(a-TP)overlayer on nanoparticulate TiO_(2)surfaces,achieved via lysozyme-molded in-situ surface reforming.The a-TP overlayer modulates surface adsorption energies for reaction intermediates,favoring WOR for H_(2)O_(2)production over the competing O_(2)evolution reaction.Our density functional theory calculations reveal that a-TP/TiO_(2)exhibits a substantial energy uphill for the O·*formation pathway,which disfavors O_(2)evolution but promotes H_(2)O_(2)production.Additionally,the a-TP overlayer strengthens the built-in electric field,resulting in favorable kinetics.Consequently,a-TP/TiO_(2)exhibits 3.7-fold higher Faraday efficiency(FE)of 63%at 1.76 V vs.reversible hydrogen electrode(RHE)under 1 sun illumination,compared to bare TiO_(2)(17%),representing the highest FE among TiO_(2)-based WOR H_(2)O_(2)production systems.Employing the a-TP overlayer constitutes a promising strategy for controlling reaction pathways and achieving efficient solar-to-chemical energy conversion.
