The growing demand for flexible,lightweight,and highly processable electronic devices makes high-functionality conducting polymers such as poly(3,4-ethylene dioxythiophene):polystyrene sulfonate(PEDOT:PSS)an attractiv...The growing demand for flexible,lightweight,and highly processable electronic devices makes high-functionality conducting polymers such as poly(3,4-ethylene dioxythiophene):polystyrene sulfonate(PEDOT:PSS)an attractive alternative to conventional inorganic materials for various applications including thermoelectrics.However,considerable improvements are necessary to make conducting polymers a commercially viable choice for thermoelectric applications.This study explores nanopatterning as an effective and unique strategy for enhancing polymer functionality to optimize thermoelectric parameters,such as electrical conductivity,Seebeck coefficient,and thermal conductivity.Introducing nanopatterning into thermoelectric polymers is challenging due to intricate technical hurdles and the necessity for individually manipulating the interdependent thermoelectric parameters.Here,array nanopatterns with different pattern spacings are imposed on free-standing PEDOT:PSS films using direct electron beam irradiation,thereby achieving selective control of electrical and thermal transport in PEDOT:PSS.Electron beam irradiation transformed PEDOT:PSS from a highly ordered quinoid to an amorphous benzoid structure.Optimized pattern spacing resulted in a remarkable 70%reduction in thermal conductivity and a 60%increase in thermoelectric figure of merit compared to non-patterned PEDOT:PSS.The proposed nanopatterning methodology demonstrates a skillful approach to precisely manipulate the thermoelectric parameters,thereby improving the thermoelectric performance of conducting polymers,and promising utilization in cutting-edge electronic applications.展开更多
Acoustic detection has many applications across science and technology from medicine to imaging and communications.However,most acoustic sensors have a common limitation in that the detection must be near the acoustic...Acoustic detection has many applications across science and technology from medicine to imaging and communications.However,most acoustic sensors have a common limitation in that the detection must be near the acoustic source.Alternatively,laser interferometry with picometer-scale motional displacement detection can rapidly and precisely measure sound-induced minute vibrations on remote surfaces.Here,we demonstrate the feasibility of sound detection up to 100 kHz at remote sites with≈60 m optical path length via laser homodyne interferometry.Based on our ultrastable hertz linewidth laser with 10-15 fractional stability,our laser interferometer achieves 0.5 pm/Hz1/2 displacement sensitivity near 10 kHz,bounded only by laser frequency noise over 10 kHz.Between 140 Hz and 15 kHz,we achieve a homodyne acoustic sensing sensitivity of subnanometer/Pascal across our conversational frequency overtones.The minimal sound pressure detectable over 60 m optical path length is≈2 mPa,with dynamic ranges over 100 dB.With the demonstrated standoff picometric distance metrology,we successfully detected and reconstructed musical scores of normal conversational volumes with high fidelity.The acoustic detection via this precision laser interferometer could be applied to selective area sound sensing for remote acoustic metrology,optomechanical vibrational motion sensing,and ultrasensitive optical microphones at the laser frequency noise limits.展开更多
Earthquakes can cause significant hazards,leading to loss of human life and property damage.In this study,we applied the masking empirical mode decomposition(EMD)to the Gyeongju earthquake(ML 5.8)in South Korea and th...Earthquakes can cause significant hazards,leading to loss of human life and property damage.In this study,we applied the masking empirical mode decomposition(EMD)to the Gyeongju earthquake(ML 5.8)in South Korea and the Abe Pura earthquake(ML 7.0)in Indonesia and then revealed that the 7th intrinsic mode function(IMF7),composed of waveforms with a period band of approximately 150 to 750 minutes.展开更多
The last decade has witnessed remarkable technological advances in mass spectrometry-based proteomics. The development of proteomics techniques has enabled the reliable analysis of complex proteomes, leading to the id...The last decade has witnessed remarkable technological advances in mass spectrometry-based proteomics. The development of proteomics techniques has enabled the reliable analysis of complex proteomes, leading to the identification and quantification of thousands of proteins in gastric cancer cells, tissues, and sera. This quantitative information has been used to profile the anomalies in gastric cancer and provide insights into the pathogenic mechanism of the disease. In this review, we mainly focus on the advances in mass spectrometry and quantitative proteomics that were achieved in the last five years and how these up-andcoming technologies are employed to track biochemical changes in gastric cancer cells. We conclude by presenting a perspective on quantitative proteomics and its future applications in the clinic and translational gastric cancer research.展开更多
A rapidly air-cooled ladle furnace slag(RA-LFS), which is a type of steelmaking slag discharged from a steel mill, was used to synthesize CaCO_3 film. The CaCO_3 film with 35 cm^2 of surface area was synthesized under...A rapidly air-cooled ladle furnace slag(RA-LFS), which is a type of steelmaking slag discharged from a steel mill, was used to synthesize CaCO_3 film. The CaCO_3 film with 35 cm^2 of surface area was synthesized under atmospheric conditions, and the surface morphology of the CaCO_3 films was changed by using additives(CaCl_2 and ethylene glycol). Especially, the addition of CaCl_2 changed the surface morphology of CaCO_3 film with pore and induced new material properties, such as water adsorption. The(012) face of CaCO_3 film(calcite) was rapidly decreased by the addition of CaCl_2. The major components of RA-LFS were calcium(type of CaO, 53.9 wt%) and aluminum(type of Al_2 O_3, 37.9 wt%), and the major crystal phases of RA-LFS were C_3 S, C_(12) A_7, and C_3 A. The calcium extraction efficiency of RA-LFS was significantly increased after the CaCO_3 film synthesis. The material properties(hardness and elastic modulus) and the thermal characteristics of the CaCO_3 films were analyzed by nano-indentation and thermogravimetry–differential thermal analysis. The synthesized CaCO_3 films from RA-LFS and Ca(OH)_2(reagent) showed similarities in terms of their material properties and the decomposition temperature.展开更多
Two-dimensional(2D)transition metal chalcogenides(TMC)and their heterostructures are appealing as building blocks in a wide range of electronic and optoelectronic devices,particularly futuristic memristive and synapti...Two-dimensional(2D)transition metal chalcogenides(TMC)and their heterostructures are appealing as building blocks in a wide range of electronic and optoelectronic devices,particularly futuristic memristive and synaptic devices for brain-inspired neuromorphic computing systems.The distinct properties such as high durability,electrical and optical tunability,clean surface,flexibility,and LEGO-staking capability enable simple fabrication with high integration density,energy-efficient operation,and high scalability.This review provides a thorough examination of high-performance memristors based on 2D TMCs for neuromorphic computing applications,including the promise of 2D TMC materials and heterostructures,as well as the state-of-the-art demonstration of memristive devices.The challenges and future prospects for the development of these emerging materials and devices are also discussed.The purpose of this review is to provide an outlook on the fabrication and characterization of neuromorphic memristors based on 2D TMCs.展开更多
In this study,plasma density measurements were performed near the plume region of the remote plasma source (RPS) in Ar/NF3 gas mixtures using a microwave cutoff probe.The measured plasma density is in the range of 101...In this study,plasma density measurements were performed near the plume region of the remote plasma source (RPS) in Ar/NF3 gas mixtures using a microwave cutoff probe.The measured plasma density is in the range of 1010-1011 cm-3 in the discharge conditions with RPS powers of 2-4 kW and gas pressures of 0.87-4 Torr.The plasma density decreased with increasing gas pressures and RPS powers under various Ar/NF3 mixing ratios.This decrease in the plasma density measured at the fixed measurement position (plume region) can be understood by the reduction of the electron energy relaxation length with increases in the gas pressures and mixing ratio of NF3/(Ar/NF3).We also performed downstream etching of silicon and silicon oxide films in this system.The etch rate of the silicon films significantly increases while the silicon oxide is slightly etched with the gas pressures and powers.It was also found that the etch rate strongly depends on the wafer position on the processing chamber electrode,and that the etch selectivity reached 96-131 in the discharge conditions of RF powers (3730-4180 W) and gas pressures (3.6-4 Torr).展开更多
Metallic Pd clusters were embedded into TiO2 nanoparticles that were synthesized within reverse micelle via a solution reduction of Pd(NO3)2 by hydrazine hydrate. The size of the particles can be controlled by manipul...Metallic Pd clusters were embedded into TiO2 nanoparticles that were synthesized within reverse micelle via a solution reduction of Pd(NO3)2 by hydrazine hydrate. The size of the particles can be controlled by manipulating the relative rates of the hydrolysis and condensation reactions of titanium tetra-isopropoxide within the micro-emulsion. The spherical equivalent size for the Pd clusters formed in TiO2 matrix was estimated to be around (3±1) nm. The presence of Pd in the matrix was demonstrated by EDS spectroscopy. The effects of synthesis parameters, such as the concentration of Pd solution, the molar ratio of water to TIP, and the molar ratio of water to surfactant, were discussed.展开更多
The increasing demand for hydrogen energy to address environmental issues and achieve carbon neutrality has elevated interest in green hydrogen production,which does not rely on fossil fuels.Among various hydrogen pro...The increasing demand for hydrogen energy to address environmental issues and achieve carbon neutrality has elevated interest in green hydrogen production,which does not rely on fossil fuels.Among various hydrogen production technologies,anion exchange membrane water electrolyzer(AEMWE)has emerged as a next-generation technology known for its high hydrogen production efficiency and its ability to use non-metal catalysts.However,this technology faces significant challenges,particularly in terms of the membrane durability and low ionic conductivity.To address these challenges,research efforts have focused on developing membranes with a new backbone structure and anion exchange groups to enhance durability and ionic conductivity.Notably,the super-acid-catalyzed condensation(SACC)synthesis method stands out due to its user convenience,the ability to create high molecular weight(MW)polymers,and the use of oxygen-tolerant organic catalysts.Although the synthesis of anion exchange membranes(AEMs)using the SACC method began in 2015,and despite growing interest in this synthesis approach,there remains a scarcity of review papers focusing on AEMs synthesized using the SACC method.The review covers the basics of SACC synthesis,presents various polymers synthesized using this method,and summarizes the development of these polymers,particularly their building blocks including aryl,ketone,and anion exchange groups.We systematically describe the effects of changes in the molecular structure of each polymer component,conducted by various research groups,on the mechanical properties,conductivity,and operational stability of the membrane.This review will provide insights into the development of AEMs with superior performance and operational stability suitable for water electrolysis applications.展开更多
The original version of this article,unfortunately,contained some mistakes and unintentional wrong description of Fig.6 and the caption of Figs.9,10.The correct version of Fig.6 is below.The mentioned figure name for ...The original version of this article,unfortunately,contained some mistakes and unintentional wrong description of Fig.6 and the caption of Figs.9,10.The correct version of Fig.6 is below.The mentioned figure name for the Fig.6 on the manuscript should be updated.In 2D vdW synaptic devices,the length of the tunneling barrier can be increased or decreased on the trapped or detrapped electrons.Kumar et al.reported memristive and neuromorphic devices composed of vertically grown WS2 layer and ZnO(Fig.6e)[149].The interlayer separation between WS2 and ZnO layers serves as an effective porous medium allowing the ZnO to grow with defects.The interfacial region of ZnO,the very contiguous to WS2 layer.展开更多
Four oxide nanoparticles,such as yttrium oxide,lanthanum oxide,cerium oxide and zirconium oxide were coated on rhenium filaments by an electrophoretic deposition method.The oxide coatings were examined by scanning ele...Four oxide nanoparticles,such as yttrium oxide,lanthanum oxide,cerium oxide and zirconium oxide were coated on rhenium filaments by an electrophoretic deposition method.The oxide coatings were examined by scanning electron microscopy,and electron emission characteristics of the oxide-coated rhenium were studied to find alternative oxide materials for replacing the hazardous thorium oxide.Among four oxides tested in this work,yttrium oxide and lanthanum oxide coated rhenium showed enhanced electron emission compared with an uncoated rhenium.However,lanthanum oxide coating evaporated too quickly in a vacuum chamber,and hence yttrium oxide was found to be the only alternative material for use in a routine mass spectrometry.An optimum coating thickness of the yttrium oxide and lanthanum oxide was around 20 μm.展开更多
The nanosized Ba(CoxNb1-x)O3(BCN) particles were prepared under high temperature and pressure conditions by precipitation from metal nitrates with aqueous potassium hydroxide. Ba(CoxNb1-x)O3 powders were obtained in t...The nanosized Ba(CoxNb1-x)O3(BCN) particles were prepared under high temperature and pressure conditions by precipitation from metal nitrates with aqueous potassium hydroxide. Ba(CoxNb1-x)O3 powders were obtained in the temperature range of 170-210 ℃ for 6 h. The results show that the average size of the synthesized particles increases with increasing reaction temperature. The average size of the synthesized particles is about 10 nm. The crystalline phase of the synthesized particles is found to be Ba(CoxNb1-x)O3. Ceramics derived from the nano BCN powders could achieve high sintering density at a relatively low sintering temperature.展开更多
Despite the fact that a radio frequency (RF) shielding box affects a coil inductance used in matching network,RF engineers have used a coil inductance measured in open space on designing matching networks since it is ...Despite the fact that a radio frequency (RF) shielding box affects a coil inductance used in matching network,RF engineers have used a coil inductance measured in open space on designing matching networks since it is difficult to precisely measure the coil inductance within the RF shielding box.In this work,we investigate the influences of the RF shielding box on the coil inductance via a 3D full electromagnetic wave simulation.Simulation results shows that the coil inductance decreases from-6.0% to-11.9% compared with its ideal inductance depending on coil positions within the RF shielding box.Both inductive and capacitive coupling between the coil and surfaces of the RF shielding box contribute to the reduction of the coil inductance.We expect that these results would be useful for those who design RF matching networks.展开更多
To attain the volumetric information of the optic radiation in normal human brains, we per- formed diffusion tensor imaging examination in 13 healthy volunteers. Simultaneously, we used a brain normalization method to...To attain the volumetric information of the optic radiation in normal human brains, we per- formed diffusion tensor imaging examination in 13 healthy volunteers. Simultaneously, we used a brain normalization method to reduce individual brain variation and increase the accuracy of volumetric information analysis. In addition, tractography-based group mapping method was also used to investigate the probability and distribution of the optic radiation pathways. Our results showed that the measured optic radiation fiber tract volume was a range of about 0.16% and that the fractional anisotropy value was about 0.53. Moreover, the optic radiation probability fiber pathway that was determined with diffusion tensor tractography-based group mapping was able to detect the location relatively accurately. We believe that our methods and results are help- ful in the study of optic radiation fiber tract information.展开更多
Laser ablation inductively coupled plasma mass spectrometry （LA-ICP-MS） has been widely adopted for the direct multi-elemental analysis with high sensitivity. Especially analysis of fine ceramics by LA-ICP-MS withou...Laser ablation inductively coupled plasma mass spectrometry （LA-ICP-MS） has been widely adopted for the direct multi-elemental analysis with high sensitivity. Especially analysis of fine ceramics by LA-ICP-MS without time-consuming sample decomposition process has been one of the most expecting application field. Small additive elements in MgO powders were analyzed by LA-ICP-MS. For precise and accurate analysis influence of carrier gas （Ar or He） was presented by the signal intensities of ICP-MS, relative standard deviation of signal intensities and ablated particle size distribution. Ablated particles were collected and analyzed by scanning electron microscopy （SEM） to investigate the particle size distribution, and the ablated sample surface was examined by camscope. In He gas atmosphere, the signal was more stable than in Ar gas atmosphere. The signal intensity was higher in Ar than in He. Examination of ablated particles and sample surface reveals that more particles were generated in Ar atmosphere and the distribution of particle size was larger.展开更多
In or Ga gradients in the Cu(In1-xGax)Se2(CIGS)absorbing layer lead to change the lattice parameters of the absorbing layer,giving rise to the bandgap grading in the absorbing layer which is directly associated with t...In or Ga gradients in the Cu(In1-xGax)Se2(CIGS)absorbing layer lead to change the lattice parameters of the absorbing layer,giving rise to the bandgap grading in the absorbing layer which is directly associated with the degree of absorbing ability of the CIGS solar cell.We tried to characterize the depth profile of the lattice parameters of the CIGS absorbing layer using a glancing incidence X-ray diffraction(GIXRD)technique,and then investigate the bandgap grading of the CIGS absorbing layer.When the glancing incident angle increased from 0.50 to 5.00°,the a and c lattice parameters of the CIGS absorbing layer gradually decreased from 5.7776(3)to 5.6905(2)?,and 11.3917(3)to 11.2114(2)?,respectively.The depth profile of the lattice parameters as a function of the incident angle was consistent with vertical variation in the compositionof In or Ga with depth in the absorbing layer.The variation of the lattice parameters was due to the difference between the ionic radius of In and Ga co-occupying at the same crystallographic site.According to the results of the depth profile of the refined parameters using GIXRD data,the bandgap of the CIGS absorber layer was graded over a range of 1.222-1.532 eV.This approach allows to determine the In or Ga gradients in the CIGS absorbing layer,and to nondestructively guess the bandgap depth profile through the refinement of the lattice parameters using GIXRD data on the assumption that the changes of the lattice parameters or unit-cell volume follow a good approximation to Vegard’s law.展开更多
Mg-Al-Zn-Ca-Y alloys with excellent ignition and corrosion resistances—termed SEN alloys(where the letters"S,""E,"and"N"stand for stainless,environmentally friendly,and non-flammable,res...Mg-Al-Zn-Ca-Y alloys with excellent ignition and corrosion resistances—termed SEN alloys(where the letters"S,""E,"and"N"stand for stainless,environmentally friendly,and non-flammable,respectively)—have been developed recently.In this study,the microstructure,tensile properties,and high-cycle fatigue properties of an extruded Mg-9.0Al-0.8Zn-0.1Mn-0.3Ca-0.2Y(SEN9)alloy are investigated and compared with those of a commercial Mg-9.0Al-0.8Zn-0.1Mn(AZ91)alloy extruded under the same conditions.Both the extruded SEN9 alloy and the extruded AZ91 alloy have a fully recrystallized structure comprising equiaxed grains,but the former has a smaller average grain size owing to the promoted dynamic recrystallization during extrusion.The extruded AZ91 alloy contains coarse Mg_(17)Al_(12) discontinuous precipitate(DP)bands parallel to the extrusion direction,which are formed during its cool down after extrusion.In contrast,the extruded SEN9 alloy contains relatively fine undissolved Al_(2)Ca,Al_(8)Mn_(4)Y,and Al_(2)Y second-phase particles,which are formed during the solidification stage of the casting process.The tensile strength of the extruded SEN9 alloy,which has finer grains and more abundant particles,is slightly higher than that of the extruded AZ91 alloy.However,the difference in their strengths is relatively small because the stronger solid-solution hardening and precipitation hardening effects in the extruded AZ91alloy offset the stronger grain-boundary hardening and dispersion hardening effects in the extruded SEN9alloy to some extent.The tensile elongation of the extruded AZ91 alloy is significantly lower than that of the extruded SEN9 alloy because the large cracks formed in the DP bands in the former cause its premature fracture.Although the extruded SEN9 alloy has higher tensile properties than the extruded AZ91alloy,the high-cycle fatigue life and fatigue strength of the former are shorter and lower,respectively,than those of the latter.The DP bands in the extruded AZ91 alloy do not act as fatigue crack initiation sites,and therefore,fatigue cracks initiate on the specimen surface at all stress amplitude levels.In contrast,in most of the fatigue-fractured specimens of the extruded SEN9 alloy,fatigue cracks initiate on the undissolved Al_(2)Ca and Al_(2)Y particles present on the surface or subsurface of the specimens because of the high local stress concentration on the particles during cyclic loading.This particle-initiated fatigue fracture eventually decreases the high-cycle fatigue resistance of the extruded SEN9 alloy.展开更多
To address climate change and promote environmental sustainability,electrochemical energy conversion and storage systems emerge as promising alternative to fossil fuels,catering to the escalating demand for energy.Ach...To address climate change and promote environmental sustainability,electrochemical energy conversion and storage systems emerge as promising alternative to fossil fuels,catering to the escalating demand for energy.Achieving optimal energy efficiency and cost competitiveness in these systems requires the strategic design of electrocatalysts,coupled with a thorough comprehension of the underlying mechanisms and degradation behavior occurring during the electrocatalysis processes.Scanning electrochemical microscopy(SECM),an analytical technique for studying surface electrochemically,stands out as a powerful tool offering electrochemical insights.It possesses remarkable spatiotemporal resolution,enabling the visualization of the localized electrochemical activity and surface topography.This review compiles crucial research findings and recent breakthroughs in electrocatalytic processes utilizing the SECM methodology,specifically focusing on applications in electrolysis,fuel cells,and metal–oxygen batteries within the realm of energy conversion and storage systems.Commencing with an overview of each energy system,the review introduces the fundamental principles of SECM,and aiming to provide new perspectives and broadening the scope of applied research by describing the major research categories within SECM.展开更多
BACKGROUND： Previous studies have analyzed cerebral activation and lateralization of cognitive functions, as well as cerebellar function with reference to high-level cognitive processing. However, there has been very...BACKGROUND： Previous studies have analyzed cerebral activation and lateralization of cognitive functions, as well as cerebellar function with reference to high-level cognitive processing. However, there has been very little research on systematization and diversification. In particular, there are no reports on cerebellar lateralization, although reliable results have been reported on cerebral lateralization. OBJECTIVE： This study analyzed cerebellar activation and lateralization in relation to verbal and visuospatial tasks using functional magnetic resonance imaging （fMRI）. DESIGN, TIME AND SETTING： A block design for fMRI observation was performed at the fMRI Laboratory, Brain Science Research Center, Korea Advanced Institute of Science and Technology from May 2006 to September 2008. PARTICIPANTS： Sixteen healthy, male, college students, aged （23.3 ± 0.5） years, and 16 healthy, male, college students, aged （21.5 ± 2.3） years, participated in the study, respectively. METHODS： Verbal and visuospatial tasks were presented while functional brain images were acquired using a 3T fMRI system. Verbal analogy testing required the subject to select the word with the same relationship as one of the given words. Verbal antonym testing required the subject to select the word with a different meaning among four words. Visuospatial tasks involved selecting a shape that corresponded to a given figure with four examples, as well as selecting a development figure of a diagram. MAIN OUTCOME MEASURES： Changes in cerebellar activation and lateralization between two cognition tasks. RESULTS： Bilateral hemisphere Iobules VI and IX, right hemisphere Iobule VIII, bilateral hemisphere Iobules Crus I, and vermis Iobule IV, V, and Vl were closely related to verbal tasks in comparison to visuospatial tasks. Conversely, bilateral hemisphere Iobules IV and V, as well as the right hemisphere Iobule VI, were closely related to visuospatial tasks compared to verbal tasks. There was no great difference between the number of activated voxels in the cerebellums during the tasks, and cerebellar lateralization was not observed. CONCLUSION： In the cerebellum, the activation region, but not lateralization, was different between verbal and visuospatial tasks.展开更多
基金supported by Characterization of Mechanical/Thermal/Chemical Properties of EUV Absorption/Transmission Materials through the National Research Foundation of Korea(NRF)funded by the Ministry of Science and ICT(Grant 2020-M3H4A3081882)by the Korea Institute of Energy Technology Evaluation and Planning(KETEP)grant funded by the Ministry of Trade,Industry and Energy(MOTIE)(No.2021202080023D)the Characterization Platform for Advanced Materials(KRISS-2022-GP2022-0013)funded by the Korea Research Institute of Standards and Science。
文摘The growing demand for flexible,lightweight,and highly processable electronic devices makes high-functionality conducting polymers such as poly(3,4-ethylene dioxythiophene):polystyrene sulfonate(PEDOT:PSS)an attractive alternative to conventional inorganic materials for various applications including thermoelectrics.However,considerable improvements are necessary to make conducting polymers a commercially viable choice for thermoelectric applications.This study explores nanopatterning as an effective and unique strategy for enhancing polymer functionality to optimize thermoelectric parameters,such as electrical conductivity,Seebeck coefficient,and thermal conductivity.Introducing nanopatterning into thermoelectric polymers is challenging due to intricate technical hurdles and the necessity for individually manipulating the interdependent thermoelectric parameters.Here,array nanopatterns with different pattern spacings are imposed on free-standing PEDOT:PSS films using direct electron beam irradiation,thereby achieving selective control of electrical and thermal transport in PEDOT:PSS.Electron beam irradiation transformed PEDOT:PSS from a highly ordered quinoid to an amorphous benzoid structure.Optimized pattern spacing resulted in a remarkable 70%reduction in thermal conductivity and a 60%increase in thermoelectric figure of merit compared to non-patterned PEDOT:PSS.The proposed nanopatterning methodology demonstrates a skillful approach to precisely manipulate the thermoelectric parameters,thereby improving the thermoelectric performance of conducting polymers,and promising utilization in cutting-edge electronic applications.
基金supported by the Office of Naval Research(Grant Nos.N00014-16-1-2094 and N00014-24-1-2547)the Lawrence Livermore National Laboratory(Grant No.B622827)the National Science Foundation.Y.-S.J.acknowledges support from KRISS(Grant Nos.25011026 and 25011211).
文摘Acoustic detection has many applications across science and technology from medicine to imaging and communications.However,most acoustic sensors have a common limitation in that the detection must be near the acoustic source.Alternatively,laser interferometry with picometer-scale motional displacement detection can rapidly and precisely measure sound-induced minute vibrations on remote surfaces.Here,we demonstrate the feasibility of sound detection up to 100 kHz at remote sites with≈60 m optical path length via laser homodyne interferometry.Based on our ultrastable hertz linewidth laser with 10-15 fractional stability,our laser interferometer achieves 0.5 pm/Hz1/2 displacement sensitivity near 10 kHz,bounded only by laser frequency noise over 10 kHz.Between 140 Hz and 15 kHz,we achieve a homodyne acoustic sensing sensitivity of subnanometer/Pascal across our conversational frequency overtones.The minimal sound pressure detectable over 60 m optical path length is≈2 mPa,with dynamic ranges over 100 dB.With the demonstrated standoff picometric distance metrology,we successfully detected and reconstructed musical scores of normal conversational volumes with high fidelity.The acoustic detection via this precision laser interferometer could be applied to selective area sound sensing for remote acoustic metrology,optomechanical vibrational motion sensing,and ultrasensitive optical microphones at the laser frequency noise limits.
基金supported as part of the"2024 Groundwater Basic Survey Project,"funded by the Ministry of Environment(Project No.20240123-001)。
文摘Earthquakes can cause significant hazards,leading to loss of human life and property damage.In this study,we applied the masking empirical mode decomposition(EMD)to the Gyeongju earthquake(ML 5.8)in South Korea and the Abe Pura earthquake(ML 7.0)in Indonesia and then revealed that the 7th intrinsic mode function(IMF7),composed of waveforms with a period band of approximately 150 to 750 minutes.
基金Supported by the National Research Council of Science and Technology,No.DRC-14-2-KRISSthe National Research Foundation of Korea,No.2013056334,No.2014044403 and No.2015052849
文摘The last decade has witnessed remarkable technological advances in mass spectrometry-based proteomics. The development of proteomics techniques has enabled the reliable analysis of complex proteomes, leading to the identification and quantification of thousands of proteins in gastric cancer cells, tissues, and sera. This quantitative information has been used to profile the anomalies in gastric cancer and provide insights into the pathogenic mechanism of the disease. In this review, we mainly focus on the advances in mass spectrometry and quantitative proteomics that were achieved in the last five years and how these up-andcoming technologies are employed to track biochemical changes in gastric cancer cells. We conclude by presenting a perspective on quantitative proteomics and its future applications in the clinic and translational gastric cancer research.
基金supported by the Basic Research Project of the Korea Institute of Geoscience and Mineral Resources funded by the Ministry of Science, Information & Communication Technology and Future Planning of Korea
文摘A rapidly air-cooled ladle furnace slag(RA-LFS), which is a type of steelmaking slag discharged from a steel mill, was used to synthesize CaCO_3 film. The CaCO_3 film with 35 cm^2 of surface area was synthesized under atmospheric conditions, and the surface morphology of the CaCO_3 films was changed by using additives(CaCl_2 and ethylene glycol). Especially, the addition of CaCl_2 changed the surface morphology of CaCO_3 film with pore and induced new material properties, such as water adsorption. The(012) face of CaCO_3 film(calcite) was rapidly decreased by the addition of CaCl_2. The major components of RA-LFS were calcium(type of CaO, 53.9 wt%) and aluminum(type of Al_2 O_3, 37.9 wt%), and the major crystal phases of RA-LFS were C_3 S, C_(12) A_7, and C_3 A. The calcium extraction efficiency of RA-LFS was significantly increased after the CaCO_3 film synthesis. The material properties(hardness and elastic modulus) and the thermal characteristics of the CaCO_3 films were analyzed by nano-indentation and thermogravimetry–differential thermal analysis. The synthesized CaCO_3 films from RA-LFS and Ca(OH)_2(reagent) showed similarities in terms of their material properties and the decomposition temperature.
基金supported by the Characterization platform for advanced materials funded by the Korea Research Institute of Standards and Science(KRISS-2021-GP2021-0011)supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government MSIT(2021M3D1A20396541).
文摘Two-dimensional(2D)transition metal chalcogenides(TMC)and their heterostructures are appealing as building blocks in a wide range of electronic and optoelectronic devices,particularly futuristic memristive and synaptic devices for brain-inspired neuromorphic computing systems.The distinct properties such as high durability,electrical and optical tunability,clean surface,flexibility,and LEGO-staking capability enable simple fabrication with high integration density,energy-efficient operation,and high scalability.This review provides a thorough examination of high-performance memristors based on 2D TMCs for neuromorphic computing applications,including the promise of 2D TMC materials and heterostructures,as well as the state-of-the-art demonstration of memristive devices.The challenges and future prospects for the development of these emerging materials and devices are also discussed.The purpose of this review is to provide an outlook on the fabrication and characterization of neuromorphic memristors based on 2D TMCs.
文摘In this study,plasma density measurements were performed near the plume region of the remote plasma source (RPS) in Ar/NF3 gas mixtures using a microwave cutoff probe.The measured plasma density is in the range of 1010-1011 cm-3 in the discharge conditions with RPS powers of 2-4 kW and gas pressures of 0.87-4 Torr.The plasma density decreased with increasing gas pressures and RPS powers under various Ar/NF3 mixing ratios.This decrease in the plasma density measured at the fixed measurement position (plume region) can be understood by the reduction of the electron energy relaxation length with increases in the gas pressures and mixing ratio of NF3/(Ar/NF3).We also performed downstream etching of silicon and silicon oxide films in this system.The etch rate of the silicon films significantly increases while the silicon oxide is slightly etched with the gas pressures and powers.It was also found that the etch rate strongly depends on the wafer position on the processing chamber electrode,and that the etch selectivity reached 96-131 in the discharge conditions of RF powers (3730-4180 W) and gas pressures (3.6-4 Torr).
基金supported by the Ministry of Education,Science Technology(MEST) and Korea Industrial Technology Foundation(KOTEF) through the Human Resource Training Project for Regional Innovation
文摘Metallic Pd clusters were embedded into TiO2 nanoparticles that were synthesized within reverse micelle via a solution reduction of Pd(NO3)2 by hydrazine hydrate. The size of the particles can be controlled by manipulating the relative rates of the hydrolysis and condensation reactions of titanium tetra-isopropoxide within the micro-emulsion. The spherical equivalent size for the Pd clusters formed in TiO2 matrix was estimated to be around (3±1) nm. The presence of Pd in the matrix was demonstrated by EDS spectroscopy. The effects of synthesis parameters, such as the concentration of Pd solution, the molar ratio of water to TIP, and the molar ratio of water to surfactant, were discussed.
基金supported by the KRISS(Korea Research Institute of Standards and Science)MPI Lab.program。
文摘The increasing demand for hydrogen energy to address environmental issues and achieve carbon neutrality has elevated interest in green hydrogen production,which does not rely on fossil fuels.Among various hydrogen production technologies,anion exchange membrane water electrolyzer(AEMWE)has emerged as a next-generation technology known for its high hydrogen production efficiency and its ability to use non-metal catalysts.However,this technology faces significant challenges,particularly in terms of the membrane durability and low ionic conductivity.To address these challenges,research efforts have focused on developing membranes with a new backbone structure and anion exchange groups to enhance durability and ionic conductivity.Notably,the super-acid-catalyzed condensation(SACC)synthesis method stands out due to its user convenience,the ability to create high molecular weight(MW)polymers,and the use of oxygen-tolerant organic catalysts.Although the synthesis of anion exchange membranes(AEMs)using the SACC method began in 2015,and despite growing interest in this synthesis approach,there remains a scarcity of review papers focusing on AEMs synthesized using the SACC method.The review covers the basics of SACC synthesis,presents various polymers synthesized using this method,and summarizes the development of these polymers,particularly their building blocks including aryl,ketone,and anion exchange groups.We systematically describe the effects of changes in the molecular structure of each polymer component,conducted by various research groups,on the mechanical properties,conductivity,and operational stability of the membrane.This review will provide insights into the development of AEMs with superior performance and operational stability suitable for water electrolysis applications.
文摘The original version of this article,unfortunately,contained some mistakes and unintentional wrong description of Fig.6 and the caption of Figs.9,10.The correct version of Fig.6 is below.The mentioned figure name for the Fig.6 on the manuscript should be updated.In 2D vdW synaptic devices,the length of the tunneling barrier can be increased or decreased on the trapped or detrapped electrons.Kumar et al.reported memristive and neuromorphic devices composed of vertically grown WS2 layer and ZnO(Fig.6e)[149].The interlayer separation between WS2 and ZnO layers serves as an effective porous medium allowing the ZnO to grow with defects.The interfacial region of ZnO,the very contiguous to WS2 layer.
文摘Four oxide nanoparticles,such as yttrium oxide,lanthanum oxide,cerium oxide and zirconium oxide were coated on rhenium filaments by an electrophoretic deposition method.The oxide coatings were examined by scanning electron microscopy,and electron emission characteristics of the oxide-coated rhenium were studied to find alternative oxide materials for replacing the hazardous thorium oxide.Among four oxides tested in this work,yttrium oxide and lanthanum oxide coated rhenium showed enhanced electron emission compared with an uncoated rhenium.However,lanthanum oxide coating evaporated too quickly in a vacuum chamber,and hence yttrium oxide was found to be the only alternative material for use in a routine mass spectrometry.An optimum coating thickness of the yttrium oxide and lanthanum oxide was around 20 μm.
基金supported by the Ministry of Education,Science Technology (MEST) and Korea Industrial Technology Foundation (KOTEF) through the Human Resource Training Project for Regional Innovation
文摘The nanosized Ba(CoxNb1-x)O3(BCN) particles were prepared under high temperature and pressure conditions by precipitation from metal nitrates with aqueous potassium hydroxide. Ba(CoxNb1-x)O3 powders were obtained in the temperature range of 170-210 ℃ for 6 h. The results show that the average size of the synthesized particles increases with increasing reaction temperature. The average size of the synthesized particles is about 10 nm. The crystalline phase of the synthesized particles is found to be Ba(CoxNb1-x)O3. Ceramics derived from the nano BCN powders could achieve high sintering density at a relatively low sintering temperature.
文摘Despite the fact that a radio frequency (RF) shielding box affects a coil inductance used in matching network,RF engineers have used a coil inductance measured in open space on designing matching networks since it is difficult to precisely measure the coil inductance within the RF shielding box.In this work,we investigate the influences of the RF shielding box on the coil inductance via a 3D full electromagnetic wave simulation.Simulation results shows that the coil inductance decreases from-6.0% to-11.9% compared with its ideal inductance depending on coil positions within the RF shielding box.Both inductive and capacitive coupling between the coil and surfaces of the RF shielding box contribute to the reduction of the coil inductance.We expect that these results would be useful for those who design RF matching networks.
文摘To attain the volumetric information of the optic radiation in normal human brains, we per- formed diffusion tensor imaging examination in 13 healthy volunteers. Simultaneously, we used a brain normalization method to reduce individual brain variation and increase the accuracy of volumetric information analysis. In addition, tractography-based group mapping method was also used to investigate the probability and distribution of the optic radiation pathways. Our results showed that the measured optic radiation fiber tract volume was a range of about 0.16% and that the fractional anisotropy value was about 0.53. Moreover, the optic radiation probability fiber pathway that was determined with diffusion tensor tractography-based group mapping was able to detect the location relatively accurately. We believe that our methods and results are help- ful in the study of optic radiation fiber tract information.
基金supported by grants-in-aid for the National Research Laboratory Program from MOST/KOSEF (No. R0A-2003-000-10320)partially supported by grants-in-aid for the National Core Research Center Program from MOST/KOSEF (No. R15-2006-022-01001-0)
文摘Laser ablation inductively coupled plasma mass spectrometry （LA-ICP-MS） has been widely adopted for the direct multi-elemental analysis with high sensitivity. Especially analysis of fine ceramics by LA-ICP-MS without time-consuming sample decomposition process has been one of the most expecting application field. Small additive elements in MgO powders were analyzed by LA-ICP-MS. For precise and accurate analysis influence of carrier gas （Ar or He） was presented by the signal intensities of ICP-MS, relative standard deviation of signal intensities and ablated particle size distribution. Ablated particles were collected and analyzed by scanning electron microscopy （SEM） to investigate the particle size distribution, and the ablated sample surface was examined by camscope. In He gas atmosphere, the signal was more stable than in Ar gas atmosphere. The signal intensity was higher in Ar than in He. Examination of ablated particles and sample surface reveals that more particles were generated in Ar atmosphere and the distribution of particle size was larger.
基金supported by Korea Research Institute of Standards and Science(KRISS–2019–GP2019-0014)。
文摘In or Ga gradients in the Cu(In1-xGax)Se2(CIGS)absorbing layer lead to change the lattice parameters of the absorbing layer,giving rise to the bandgap grading in the absorbing layer which is directly associated with the degree of absorbing ability of the CIGS solar cell.We tried to characterize the depth profile of the lattice parameters of the CIGS absorbing layer using a glancing incidence X-ray diffraction(GIXRD)technique,and then investigate the bandgap grading of the CIGS absorbing layer.When the glancing incident angle increased from 0.50 to 5.00°,the a and c lattice parameters of the CIGS absorbing layer gradually decreased from 5.7776(3)to 5.6905(2)?,and 11.3917(3)to 11.2114(2)?,respectively.The depth profile of the lattice parameters as a function of the incident angle was consistent with vertical variation in the compositionof In or Ga with depth in the absorbing layer.The variation of the lattice parameters was due to the difference between the ionic radius of In and Ga co-occupying at the same crystallographic site.According to the results of the depth profile of the refined parameters using GIXRD data,the bandgap of the CIGS absorber layer was graded over a range of 1.222-1.532 eV.This approach allows to determine the In or Ga gradients in the CIGS absorbing layer,and to nondestructively guess the bandgap depth profile through the refinement of the lattice parameters using GIXRD data on the assumption that the changes of the lattice parameters or unit-cell volume follow a good approximation to Vegard’s law.
基金supported by the National Research Council of Science&Technology(NST)grant(No.CRC-15-06-KIGAM)funded by the Korea government(MSIP)。
文摘Mg-Al-Zn-Ca-Y alloys with excellent ignition and corrosion resistances—termed SEN alloys(where the letters"S,""E,"and"N"stand for stainless,environmentally friendly,and non-flammable,respectively)—have been developed recently.In this study,the microstructure,tensile properties,and high-cycle fatigue properties of an extruded Mg-9.0Al-0.8Zn-0.1Mn-0.3Ca-0.2Y(SEN9)alloy are investigated and compared with those of a commercial Mg-9.0Al-0.8Zn-0.1Mn(AZ91)alloy extruded under the same conditions.Both the extruded SEN9 alloy and the extruded AZ91 alloy have a fully recrystallized structure comprising equiaxed grains,but the former has a smaller average grain size owing to the promoted dynamic recrystallization during extrusion.The extruded AZ91 alloy contains coarse Mg_(17)Al_(12) discontinuous precipitate(DP)bands parallel to the extrusion direction,which are formed during its cool down after extrusion.In contrast,the extruded SEN9 alloy contains relatively fine undissolved Al_(2)Ca,Al_(8)Mn_(4)Y,and Al_(2)Y second-phase particles,which are formed during the solidification stage of the casting process.The tensile strength of the extruded SEN9 alloy,which has finer grains and more abundant particles,is slightly higher than that of the extruded AZ91 alloy.However,the difference in their strengths is relatively small because the stronger solid-solution hardening and precipitation hardening effects in the extruded AZ91alloy offset the stronger grain-boundary hardening and dispersion hardening effects in the extruded SEN9alloy to some extent.The tensile elongation of the extruded AZ91 alloy is significantly lower than that of the extruded SEN9 alloy because the large cracks formed in the DP bands in the former cause its premature fracture.Although the extruded SEN9 alloy has higher tensile properties than the extruded AZ91alloy,the high-cycle fatigue life and fatigue strength of the former are shorter and lower,respectively,than those of the latter.The DP bands in the extruded AZ91 alloy do not act as fatigue crack initiation sites,and therefore,fatigue cracks initiate on the specimen surface at all stress amplitude levels.In contrast,in most of the fatigue-fractured specimens of the extruded SEN9 alloy,fatigue cracks initiate on the undissolved Al_(2)Ca and Al_(2)Y particles present on the surface or subsurface of the specimens because of the high local stress concentration on the particles during cyclic loading.This particle-initiated fatigue fracture eventually decreases the high-cycle fatigue resistance of the extruded SEN9 alloy.
基金supported by a characterization platform for advanced materials funded by the Korea Research Institute of Standards and Science(KRISS-2023-GP2023-0014)the KRISS(Korea Research Institute of Standards and Science)MPI Lab.program。
文摘To address climate change and promote environmental sustainability,electrochemical energy conversion and storage systems emerge as promising alternative to fossil fuels,catering to the escalating demand for energy.Achieving optimal energy efficiency and cost competitiveness in these systems requires the strategic design of electrocatalysts,coupled with a thorough comprehension of the underlying mechanisms and degradation behavior occurring during the electrocatalysis processes.Scanning electrochemical microscopy(SECM),an analytical technique for studying surface electrochemically,stands out as a powerful tool offering electrochemical insights.It possesses remarkable spatiotemporal resolution,enabling the visualization of the localized electrochemical activity and surface topography.This review compiles crucial research findings and recent breakthroughs in electrocatalytic processes utilizing the SECM methodology,specifically focusing on applications in electrolysis,fuel cells,and metal–oxygen batteries within the realm of energy conversion and storage systems.Commencing with an overview of each energy system,the review introduces the fundamental principles of SECM,and aiming to provide new perspectives and broadening the scope of applied research by describing the major research categories within SECM.
文摘BACKGROUND： Previous studies have analyzed cerebral activation and lateralization of cognitive functions, as well as cerebellar function with reference to high-level cognitive processing. However, there has been very little research on systematization and diversification. In particular, there are no reports on cerebellar lateralization, although reliable results have been reported on cerebral lateralization. OBJECTIVE： This study analyzed cerebellar activation and lateralization in relation to verbal and visuospatial tasks using functional magnetic resonance imaging （fMRI）. DESIGN, TIME AND SETTING： A block design for fMRI observation was performed at the fMRI Laboratory, Brain Science Research Center, Korea Advanced Institute of Science and Technology from May 2006 to September 2008. PARTICIPANTS： Sixteen healthy, male, college students, aged （23.3 ± 0.5） years, and 16 healthy, male, college students, aged （21.5 ± 2.3） years, participated in the study, respectively. METHODS： Verbal and visuospatial tasks were presented while functional brain images were acquired using a 3T fMRI system. Verbal analogy testing required the subject to select the word with the same relationship as one of the given words. Verbal antonym testing required the subject to select the word with a different meaning among four words. Visuospatial tasks involved selecting a shape that corresponded to a given figure with four examples, as well as selecting a development figure of a diagram. MAIN OUTCOME MEASURES： Changes in cerebellar activation and lateralization between two cognition tasks. RESULTS： Bilateral hemisphere Iobules VI and IX, right hemisphere Iobule VIII, bilateral hemisphere Iobules Crus I, and vermis Iobule IV, V, and Vl were closely related to verbal tasks in comparison to visuospatial tasks. Conversely, bilateral hemisphere Iobules IV and V, as well as the right hemisphere Iobule VI, were closely related to visuospatial tasks compared to verbal tasks. There was no great difference between the number of activated voxels in the cerebellums during the tasks, and cerebellar lateralization was not observed. CONCLUSION： In the cerebellum, the activation region, but not lateralization, was different between verbal and visuospatial tasks.
