The response of three-dimensional sample of Al, containing vacancy complex, under shear loading was simulated. The molecular dynamics method was used and interaction between atoms was described on the base of pseudopo...The response of three-dimensional sample of Al, containing vacancy complex, under shear loading was simulated. The molecular dynamics method was used and interaction between atoms was described on the base of pseudopotential theory Solitary waves were generated in the sample under mechanical loading. Their interaction with the vacancy complexes was shown to be able to initiate hot spot in that local region of the complexes. Some parameters of the hot spot as well as solitary waves were calculated. The initiation of the hot spot is accompanied with sufficient local structural relaxation.展开更多
Direct visualization of the structural defects in two-dimensional(2D)semiconductors at a large scale plays a significant role in understanding their electrical/optical/magnetic properties,but is challenging.Although t...Direct visualization of the structural defects in two-dimensional(2D)semiconductors at a large scale plays a significant role in understanding their electrical/optical/magnetic properties,but is challenging.Although traditional atomic resolution imaging techniques,such as transmission electron microscopy and scanning tunneling microscopy,can directly image the structural defects,they provide only local-scale information and require complex setups.Here,we develop a simple,non-invasive wet etching method to directly visualize the structural defects in 2D semiconductors at a large scale,including both point defects and grain boundaries.Utilizing this method,we extract successfully the defects density in several different types of monolayer molybdenum disulfide samples,providing key insights into the device functions.Furthermore,the etching method we developed is anisotropic and tunable,opening up opportunities to obtain exotic edge states on demand.展开更多
It is well known that for technological application,a great effort has been done to enchance Jvalue ofsuperconducting YBaCuO sintered bulk.Except oxygen content,the main problem for increasing critical cur-rent densit...It is well known that for technological application,a great effort has been done to enchance Jvalue ofsuperconducting YBaCuO sintered bulk.Except oxygen content,the main problem for increasing critical cur-rent density Jis to eliminate the weak link and to control crystallographic anisotropy.It is necessary tomake YBaCuO superconducting bulk have a strong texture with C-axis orientation.Since Jin et al.has suc-展开更多
We theoretically investigate the transmission spectra and the field distributions with different defects in the gold nanotube arrays by using the finite-difference time-domain method. It is found that the optical prop...We theoretically investigate the transmission spectra and the field distributions with different defects in the gold nanotube arrays by using the finite-difference time-domain method. It is found that the optical properties of the nanotube arrays are strongly influenced by different defects. When there are no defects in the central nanotube, the values of peaks located at both sides of the photonic band gap have their maxima. Based on the distributions of electric field component Ex and the total energy distribution of the electric and the magnetic field, we show that mainly a dipole field distribution is exhibited for the plasmon mode at the long-wavelength edge of the band gap but higher order modes of the composite are excited at the short-wavelength edge of the band gap. The plasmon resonant modes can also be controlled by introducing defects.展开更多
Structural development defects essentially refer to code structure that violates object-oriented design principles. They make program maintenance challenging and deteriorate software quality over time. Various detecti...Structural development defects essentially refer to code structure that violates object-oriented design principles. They make program maintenance challenging and deteriorate software quality over time. Various detection approaches, ranging from traditional heuristic algorithms to machine learning methods, are used to identify these defects. Ensemble learning methods have strengthened the detection of these defects. However, existing approaches do not simultaneously exploit the capabilities of extracting relevant features from pre-trained models and the performance of neural networks for the classification task. Therefore, our goal has been to design a model that combines a pre-trained model to extract relevant features from code excerpts through transfer learning and a bagging method with a base estimator, a dense neural network, for defect classification. To achieve this, we composed multiple samples of the same size with replacements from the imbalanced dataset MLCQ1. For all the samples, we used the CodeT5-small variant to extract features and trained a bagging method with the neural network Roberta Classification Head to classify defects based on these features. We then compared this model to RandomForest, one of the ensemble methods that yields good results. Our experiments showed that the number of base estimators to use for bagging depends on the defect to be detected. Next, we observed that it was not necessary to use a data balancing technique with our model when the imbalance rate was 23%. Finally, for blob detection, RandomForest had a median MCC value of 0.36 compared to 0.12 for our method. However, our method was predominant in Long Method detection with a median MCC value of 0.53 compared to 0.42 for RandomForest. These results suggest that the performance of ensemble methods in detecting structural development defects is dependent on specific defects.展开更多
In this paper, we present the finding that periodic structural defects(PSDs) along a Bragg grating can shift the Bragg wavelength. This effect is theoretically analyzed and confirmed by numerical calculation. We find ...In this paper, we present the finding that periodic structural defects(PSDs) along a Bragg grating can shift the Bragg wavelength. This effect is theoretically analyzed and confirmed by numerical calculation. We find that the Bragg wavelength shift is determined by the defect size and the period of the defects. The Bragg wavelength can be well tuned by properly designing the PSDs, and this may provide an alternative method to fabricate grating-based multiwavelength devices, including optical filter arrays and laser arrays. In regards to wavelength precision, the proposed method has an advantage over the traditional methods, where the Bragg wavelengths are changed directly by changing the grating period. In addition, the proposed method can maintain grating strength when tuning the wavelength since only the period of defects is changed. This will be a benefit for devices such as arrays.展开更多
We describe here a one-step method for the synthesis of Au/TiO2 nanosphere materials,which were formed by layered deposition of multiple anatase TiO2 nanosheets.The Au nanoparticles were stabilized by structural defec...We describe here a one-step method for the synthesis of Au/TiO2 nanosphere materials,which were formed by layered deposition of multiple anatase TiO2 nanosheets.The Au nanoparticles were stabilized by structural defects in each TiO2 nanosheet,including crystal steps and edges,thereby fixing the Au-TiO2 perimeter interface.Reactant transfer occurred along the gaps between these TiO2 nanosheet layers and in contact with catalytically active sites at the Au-TiO2 interface.The doped Au induced the formation of oxygen vacancies in the Au-TiO2 interface.Such vacancies are essential for generating active oxygen species(-*O^-) on the TiO2 surface and Ti^3+ ions in bulk TiO2.These ions can then form Ti^3+-O^--Ti^4+species,which are known to enhance the catalytic activity of formaldehyde(HCHO) oxidation.These studies on structural and oxygen vacancy defects in Au/TiO2 samples provide a theoretical foundation for the catalytic mechanism of HCHO oxidation on oxide-supported Au materials.展开更多
To understand the relation between different nanostructures and thermal properties, a simple yet effective model is in demand for characterizing the underlying phonons and electrons scattering mechanisms. Herein, we m...To understand the relation between different nanostructures and thermal properties, a simple yet effective model is in demand for characterizing the underlying phonons and electrons scattering mechanisms. Herein, we make a systematic review on the newly developed thermal reffusivity theory. Like electrical resistivity which has been historically used as a theory for analyzing structural domain size and defect levels of metals, the thermal reffusivity can also uncover phonon behavior, structure defects and domain size of materials. We highlight that this new theory can be used for not only metals, but also nonmetals, even for amorphous materials. From the thermal reffusivity against temperature curves, the Debye temperature of the material and the ideal thermal diffusivity of single perfect crystal can be evaluated. From the residual thermal reffusivity at the 0 K limit, the structural thermal domain (STD) size of crystalline and amorphous materials can be obtained. The difference of white hair and normal black hair from heat conduction perspective is reported for the first time. Loss of melanin results in a worse thermal protection and a larger STD size in the white hair. By reviewing the different variation of thermal reffusivity against decreasing temperature profiles, we conclude that they reflected the structural connection in the materials. Ultimately, the future application of thermal reffusivity theory in studying 2D materials and amorphous materials is discussed.展开更多
Ti_3AlC_2 samples are irradiated in advance by 3.5 MeV Fe-ion to the fluence of 1.0×10^(16) ion/cm^2,and then are implanted by 500 keV He-ion with the fluence of 1.0×10^(17) ion/cm^2 at room temperature....Ti_3AlC_2 samples are irradiated in advance by 3.5 MeV Fe-ion to the fluence of 1.0×10^(16) ion/cm^2,and then are implanted by 500 keV He-ion with the fluence of 1.0×10^(17) ion/cm^2 at room temperature.The irradiated samples are investigated by grazing incidence x-ray diffraction(GIXRD) and transmission electron microscopy(TEM).GIXRD results show serious structural distortion,but without amorphization in the irradiated samples.Fe-ion irradiation and He-ion implantation create much more serious structural distortion than single Fe-ion irradiation.TEM results reveal that there are a large number of defect clusters in the damage region,and dense spherical He bubbles appear in the He depositional region.It seems that the pre-damage does not influence the growth of He bubbles,but He-ion implantation influences the pre-created defect configurations.展开更多
Carbon-based metal-free nanomaterials are promising alternatives to precious metals as electrocatalysts of key energy storage and conversion technologies.Of paramount significance are the establishment of design princi...Carbon-based metal-free nanomaterials are promising alternatives to precious metals as electrocatalysts of key energy storage and conversion technologies.Of paramount significance are the establishment of design principles by understanding the catalytic mechanisms and identifying the active sites.Distinct from sp2-conjugated graphene and carbon nanotube,fullerene possesses unique characteristics that are growingly being discovered and exploited by the electrocatalysis community.For instance,the well-defined atomic and molecular structures,the good electron affinity to tune the electronic structures of other substances,the intermolecular self-assembly into superlattices,and the on-demand chemical modification have endowed fullerene with incomparable advantages as electrocatalysts that are otherwise not applicable to other carbon ma-terials.As increasing studies are being reported on this intriguing topic,it is necessary to provide a state-of-the-art overview of the recent progress.This review takes such an initiative by summarizing the promises and challenges in the electrocatalytic applications of fullerene and its derivatives.The content is structured according to the composition and structure of fullerene,including intact fullerene(e.g.,fullerene composite and superlattices)and fullerene derivatives(e.g.,doped,endohedral,and disintegrated fullerene).The synthesis,characterization,catalytic mechanisms,and deficiencies of these fullerene-based materials are explicitly elaborated.We conclude it by sharing our perspectives on the key aspects that future efforts shall consider.展开更多
NH_(2)-UIO66(NU)is a promising photocatalyst for the reduction of Cr(VI)to low-toxic Cr(III)driven by visible light under ambient conditions.However,the main limitation in this process is the ineffi cient ligand to me...NH_(2)-UIO66(NU)is a promising photocatalyst for the reduction of Cr(VI)to low-toxic Cr(III)driven by visible light under ambient conditions.However,the main limitation in this process is the ineffi cient ligand to metal charge transfer(LMCT)of photo-excited electrons,which is caused by inherent energy gap(ΔE_(LMCT)).This study synthesized the defective NU(NUXH,where X is the molar equivalent of the modulator)with reducedΔE_(LMCT)through linkers removal via acid treatment.The electronic structure of NUX-H was systematically investigated,and the results indicated that the structural defects in NUX-H strongly altered the environment of the Zr atoms.Furthermore,they substantially lowered the energy of the unoccupied d orbitals(LUMO),which was benefi cial to effi cient LMCT,resulting in an improved photocatalytic activity of NUX-H toward high-concentration(100 mg/L)Cr(VI)reduction.Compared to NU with defect-free structure,the reducing rate of Cr(VI)was increased by 47 times.This work introduced an alternative strategy in terms of designing effi cient photocatalysts for reducing Cr(VI)under ambient conditions.展开更多
Anti-structured defects bridge atom migration among heterogeneous sublattices facilitating diffusion but could also result in the collapse of ordered structure.Component distribution Ni(75)AlxV(25-x) alloys are in...Anti-structured defects bridge atom migration among heterogeneous sublattices facilitating diffusion but could also result in the collapse of ordered structure.Component distribution Ni(75)AlxV(25-x) alloys are investigated using a microscopic phase field model to illuminate relations between anti-structured defects and composition,precipitate order,precipitate type,and phase stability.The Ni(75)AlxV(25-x) alloys undergo single Ni3V(stage Ⅰ),dual Ni3Al and Ni3V(stage Ⅱ with Ni3V prior;and stage Ⅲ with Ni3Al prior),and single Ni3Al(stage Ⅳ) with enhanced aluminum level.For Ni3V phase,anti-structured defects(V(Ni1),Niy,except V(Ni2)) and substitution defects(Al(Ni1),Al(Ni2),Alv) exhibit a positive correlation to aluminum in stage I,the positive trend becomes to negative correlation or smooth during stage Ⅱ.For Ni3 Al phase,anti-structured defects(Al(Ni),Ni(Al)) and substitution defects(V(Ni),V(Al)) have a positive correlation to aluminum in stage Ⅱ,but Ni(Al) goes down since stage Ⅲ and lasts to stage Ⅳ.V(Ni) and V(Al) fluctuate when Ni3Al precipitates prior,but go down drastically in stageⅣ.Precipitate type conversion of single Ni3V/dual(Ni3V+Ni3Al) affects Ni3V defects,while dual(Ni3V+Ni3Al)/single Ni3 Al has little effect on Ni3Al defects.Precipitate order swap occurred in the dual phase region affects on Ni3Al defects but not on Ni3V.展开更多
This paper presents a compact Multiple Input Multiple Output(MIMO)antenna with WLAN band notch for Ultra-Wideband(UWB)applications.The antenna is designed on 0.8mmthick low-cost FR-4 substrate having a compact size of...This paper presents a compact Multiple Input Multiple Output(MIMO)antenna with WLAN band notch for Ultra-Wideband(UWB)applications.The antenna is designed on 0.8mmthick low-cost FR-4 substrate having a compact size of 22mm×30 mm.The proposed antenna comprises of two monopole patches on the top layer of substrate while having a shared ground on its bottom layer.The mutual coupling between adjacent patches has been reduced by using a novel stub with shared ground structure.The stub consists of complementary rectangular slots that disturb the surface current direction and thus result in reducing mutual coupling between two ports.A slot is etched in the radiating patch for WLAN band notch.The slot is used to suppress frequencies ranging from 5.1 to 5.9 GHz.The results show that the proposed antenna has a very good impedance bandwidth of|S11|<−10 dB within the frequency band from 3.1–14 GHz.A low mutual coupling of less than−23 dB is achieved within the entire UWB band.Furthermore,the antenna has a peak gain of 5.8 dB,low ECC<0.002 and high Diversity Gain(DG>9.98).展开更多
Mutual coupling reduction or isolation enhancement in antenna arrays is an important area of research as it severely affects the performance of an antenna.In this paper,a new type of compact and highly isolated Multip...Mutual coupling reduction or isolation enhancement in antenna arrays is an important area of research as it severely affects the performance of an antenna.In this paper,a new type of compact and highly isolated Multiple-Input-Multiple-Output(MIMO)antenna for ultra-wideband(UWB)applications is presented.The design consists of four radiators that are orthogonally positioned and confined to a compact 40×40×0.8 mm3 space.The final antenna design uses an inverted L shape partial ground to produce an acceptable reflection coefficient(S11<−10 dB)in an entire UWB band(3.1–10.6)giga hertz(GHz).Moreover,the inter-element isolation has also been enhanced to>20 db for majority of the UWB band.The antenna was fabricated and tested with the vector network analyzer(VNA)and in an anechoic chamber for scattering parameters and radiation patterns.Furthermore,different MIMO diversity performance metrics are also measured to validate the proposed model.The simulation results and the experimental results from the constructed model agree quite well.The proposed antenna is compared with similar designs in recently published literature for various performance metrics.Because of its low envelope correlation coefficient(ECC<0.1),high diversity gain(DG>9.99 dB),peak gain of 4.6 dB,reduced channel capacity loss(CCL<0.4 b/s/Hz),and average radiation efficiency of over 85%,the proposed MIMO antenna is ideally suited for practical UWB applications.展开更多
In this paper,the investigation of a novel compact 2×2,2×1,and 1×1 Ultra-Wide Band(UWB)based Multiple-Input Multiple-Output(MIMO)antenna with Defected Ground Structure(DGS)is employed.The proposed Elect...In this paper,the investigation of a novel compact 2×2,2×1,and 1×1 Ultra-Wide Band(UWB)based Multiple-Input Multiple-Output(MIMO)antenna with Defected Ground Structure(DGS)is employed.The proposed Electromagnetic Radiation Structures(ERS)is composed of multiple radiating elements.These MIMO antennas are designed and analyzed with and without DGS.The feeding is introduced by a microstrip-fed line to significantly moderate the radiating structure’s overall size,which is 60×40×1 mm.The high directivity and divergence characteristics are attained by introducing the microstripfed lines perpendicular to each other.And the projected MIMO antenna structures are compared with others by using parameters like Return Loss(RL),Voltage Standing Wave Ratio(VSWR),Radiation Pattern(RP),radiation efficiency,and directivity.The same MIMO set-up is redesigned with DGS,and the resultant parameters are compared.Finally,the Multiple Input and Multiple Output Radiating Structures with and without DGS are compared for result considerations like RL,VSWR,RP,radiation efficiency,and directivity.This projected antenna displays an omnidirectional RP with moderate gain,which is highly recommended for human healthcare applications.By introducing the defected ground structure in bottom layer the lower cut-off frequencies of 2.3,4.5 and 6.0 GHz are achieved with few biological effects on radio propagation in human body communications.The proposed design covers numerous well-known wireless standards,along with dual-function DGS slots,and it can be easily integrated into Wireless Body Area Networks(WBAN)in medical applications.This WBAN links the autonomous nodes that may be situated either in the clothes,on-body or beneath the skin of a person.This system typically advances the complete human body and the inter-connected nodes through a wireless communication channel.展开更多
In this study,a Ni-Fe metal-organic framework modified by-NH_(2)and-SH was synthesized using a sim-ple hydrothermal process for enhancing photocatalytic CO_(2)reduction.As expected,the N2S-NiFe(NH_(2)-BDC/H_(4)DSBDC,2...In this study,a Ni-Fe metal-organic framework modified by-NH_(2)and-SH was synthesized using a sim-ple hydrothermal process for enhancing photocatalytic CO_(2)reduction.As expected,the N2S-NiFe(NH_(2)-BDC/H_(4)DSBDC,2:1)displayed excellent photocatalytic CO_(2)reduction activity and high CO selectivity(12,412.23μmol g^(−1)h^(−1))under visible light irradiation(λ≥420 nm),which is 5 times that of NiFe-MOF.Notably,the excellent photocatalytic performance of N2S-NiFe can benefit from the rich defect trap site caused by the introduction of amino and sulfhydryl groups,accelerating charge transfer and promoting space charge separation,as supported by the photo-electrochemical properties.To better understand the CO_(2)adsorption mechanism,density functional theory calculations were performed,which revealed that the Niov site has more negative adsorption energy compared with the Feov site.This study provides a simple strategy to establish efficient photocatalysts for CO_(2)reduction through the modification of organic ligands.展开更多
Fluoride mediated nano-sized ZSM-5 (ZSM-5-F) with a high Si/AI ratio of 181 was fabricated using a seed-induction method and evaluated the catalysis of the methanol to propylene (MTP) reaction. High propylene sele...Fluoride mediated nano-sized ZSM-5 (ZSM-5-F) with a high Si/AI ratio of 181 was fabricated using a seed-induction method and evaluated the catalysis of the methanol to propylene (MTP) reaction. High propylene selectivity (45%) was similar to ZSM-5-OH synthesized via a hydroxide route. However, ZSM- 5-F showed much longer lifetime (305 h) compared with ZSM-5-OH (157 h) in spite of similar crystal size and aluminum content. Characterization by NH3-TPD. Py-IR, OH-IR, SEM, TG-DTA, XRD and 1H MAS NMR techniques indicated that the enhanced catalytic performance of ZSM-S-F is attributed to the fewer structural defects in the form of internal silanol groups and silanol nests.展开更多
This paper considers that the crystal grains of HDDR Pr2Fe14B permanent magnetic material are cubic, the size is 0.3 μm, and the crystal grains are in simple cubic accumulation. It is considered that there are bounda...This paper considers that the crystal grains of HDDR Pr2Fe14B permanent magnetic material are cubic, the size is 0.3 μm, and the crystal grains are in simple cubic accumulation. It is considered that there are boundary phases between grains. It is assumed that the boundary phases are non-magnetic phases with the thickness of d, and evenly distributed between grains. The anisotropy expression of single grain boundary is given considering structure defect and intergranular exchange coupling interaction. Based on micro-magnetic simulation calculation, the variation of the average anisotropy of a single grain with the structural defects and boundary phases was calculated. The results show that when the thickness of structural defects is constant, the average anisotropy of a single grain decreases with increasing of grain boundary phase thickness, and while the thickness of grain boundary phase is constant, it also decreases with increasing of structural defect thickness.展开更多
This article studies the application of the alternating current field measurement (ACFM) method in defect detection for underwater structures. Numerical model of the ACFM system is built for structure surface defect...This article studies the application of the alternating current field measurement (ACFM) method in defect detection for underwater structures. Numerical model of the ACFM system is built for structure surface defect detection in seawater environment. Finite element simulation is performed to investigate rules and characteristics of the electromagnetic signal distribution in the defected area. In respect of the simulation results, underwater artificial crack detection experiments are designed and conducted for the ACFM system. The experiment results show that the ACFM system can detect cracks in underwater structures and the detection accuracy is higher than 85%. This can meet the engineering requirement of underwater structure defect detection. The results in this article can be applied to establish technical foundation for the optimization and development of ACFM based underwater structure defects detection system.展开更多
Due to rapid growth in wireless communication technology,higher bandwidth requirement for advance telecommunication systems,capable of operating on two or higher bands with higher channel capacities and minimum distor...Due to rapid growth in wireless communication technology,higher bandwidth requirement for advance telecommunication systems,capable of operating on two or higher bands with higher channel capacities and minimum distortion losses is desired.In this paper,a compact Ultra-Wideband(UWB)V-shaped monopole antenna is presented.UWB response is achieved by modifying the ground plane with Chichen Itzia inspired rectangular staircase shape.The proposed V-shaped is designed by incorporating a rectangle,and an inverted isosceles triangle using FR4 substrate.The size of the antenna is 25 mm×26 mm×1.6 mm.The proposed V-shaped monopole antenna produces bandwidth response of 3 GHz Industrial,Scientific,and Medical(ISM),Worldwide Interoperability for Microwave Access(WiMAX),(IEEE 802.11/HIPERLAN band,5G sub 6 GHz)which with an additional square cut amplified the bandwidth response up to 8 GHz ranging from 3.1 GHz to 10.6 GHz attaining UWB defined by Federal Communications Commission(FCC)with a maximum gain of 3.83 dB.The antenna is designed in Ansys HFSS.Results for key performance parameters of the antenna are presented.The measured results are in good agreement with the simulated results.Due to flat gain,uniform group delay,omni directional radiation pattern characteristics and well-matched impedance,the proposed antenna is suitable for WiMAX,ISM and heterogeneous wireless systems.展开更多
文摘The response of three-dimensional sample of Al, containing vacancy complex, under shear loading was simulated. The molecular dynamics method was used and interaction between atoms was described on the base of pseudopotential theory Solitary waves were generated in the sample under mechanical loading. Their interaction with the vacancy complexes was shown to be able to initiate hot spot in that local region of the complexes. Some parameters of the hot spot as well as solitary waves were calculated. The initiation of the hot spot is accompanied with sufficient local structural relaxation.
基金the Key-Area Research and Development Program of Guangdong Province,China(Grant No.2020B0101340001)the Strategic Priority Research Program of Chinese Academy of Sciences(CAS)(Grant No.XDB30000000)the National Natural Science Foundation of China(Grant Nos.61888102 and 11834017)。
文摘Direct visualization of the structural defects in two-dimensional(2D)semiconductors at a large scale plays a significant role in understanding their electrical/optical/magnetic properties,but is challenging.Although traditional atomic resolution imaging techniques,such as transmission electron microscopy and scanning tunneling microscopy,can directly image the structural defects,they provide only local-scale information and require complex setups.Here,we develop a simple,non-invasive wet etching method to directly visualize the structural defects in 2D semiconductors at a large scale,including both point defects and grain boundaries.Utilizing this method,we extract successfully the defects density in several different types of monolayer molybdenum disulfide samples,providing key insights into the device functions.Furthermore,the etching method we developed is anisotropic and tunable,opening up opportunities to obtain exotic edge states on demand.
文摘It is well known that for technological application,a great effort has been done to enchance Jvalue ofsuperconducting YBaCuO sintered bulk.Except oxygen content,the main problem for increasing critical cur-rent density Jis to eliminate the weak link and to control crystallographic anisotropy.It is necessary tomake YBaCuO superconducting bulk have a strong texture with C-axis orientation.Since Jin et al.has suc-
基金Project supported by the Scientific Research Foundation of Hunan Provincial Education Department,China (Grant Nos. 11C0425 and 09C314)the Natural Science Foundation of Hunan Province,China (Grant No. 10JJ3088)+1 种基金the Major Program for the Research Foundation of Education Bureau of Hunan Province,China (Grant No. 10A026)the National Natural Science Foundation of China (Grant No. 11164007)
文摘We theoretically investigate the transmission spectra and the field distributions with different defects in the gold nanotube arrays by using the finite-difference time-domain method. It is found that the optical properties of the nanotube arrays are strongly influenced by different defects. When there are no defects in the central nanotube, the values of peaks located at both sides of the photonic band gap have their maxima. Based on the distributions of electric field component Ex and the total energy distribution of the electric and the magnetic field, we show that mainly a dipole field distribution is exhibited for the plasmon mode at the long-wavelength edge of the band gap but higher order modes of the composite are excited at the short-wavelength edge of the band gap. The plasmon resonant modes can also be controlled by introducing defects.
文摘Structural development defects essentially refer to code structure that violates object-oriented design principles. They make program maintenance challenging and deteriorate software quality over time. Various detection approaches, ranging from traditional heuristic algorithms to machine learning methods, are used to identify these defects. Ensemble learning methods have strengthened the detection of these defects. However, existing approaches do not simultaneously exploit the capabilities of extracting relevant features from pre-trained models and the performance of neural networks for the classification task. Therefore, our goal has been to design a model that combines a pre-trained model to extract relevant features from code excerpts through transfer learning and a bagging method with a base estimator, a dense neural network, for defect classification. To achieve this, we composed multiple samples of the same size with replacements from the imbalanced dataset MLCQ1. For all the samples, we used the CodeT5-small variant to extract features and trained a bagging method with the neural network Roberta Classification Head to classify defects based on these features. We then compared this model to RandomForest, one of the ensemble methods that yields good results. Our experiments showed that the number of base estimators to use for bagging depends on the defect to be detected. Next, we observed that it was not necessary to use a data balancing technique with our model when the imbalance rate was 23%. Finally, for blob detection, RandomForest had a median MCC value of 0.36 compared to 0.12 for our method. However, our method was predominant in Long Method detection with a median MCC value of 0.53 compared to 0.42 for RandomForest. These results suggest that the performance of ensemble methods in detecting structural development defects is dependent on specific defects.
基金supported by the National Natural Science Foundation of China(Youth)(61306068)the Natural Science Foundation of Jiangsu Province of China(BK20130585,BK20140414)+1 种基金the National Natural Science Foundation of China(61435014,61504170,61504058)the National 863 Program(2015AA016902)
文摘In this paper, we present the finding that periodic structural defects(PSDs) along a Bragg grating can shift the Bragg wavelength. This effect is theoretically analyzed and confirmed by numerical calculation. We find that the Bragg wavelength shift is determined by the defect size and the period of the defects. The Bragg wavelength can be well tuned by properly designing the PSDs, and this may provide an alternative method to fabricate grating-based multiwavelength devices, including optical filter arrays and laser arrays. In regards to wavelength precision, the proposed method has an advantage over the traditional methods, where the Bragg wavelengths are changed directly by changing the grating period. In addition, the proposed method can maintain grating strength when tuning the wavelength since only the period of defects is changed. This will be a benefit for devices such as arrays.
基金supported by the National Natural Science Foundation of China (21107124, 21337003)the Youth Innovation Promotion Association (2011037)Science Promotion Program of Research Center for Eco-Environmental Sciences, Chinese Academic Sciences (No. 121311RCEES-QN-20130046F)
文摘We describe here a one-step method for the synthesis of Au/TiO2 nanosphere materials,which were formed by layered deposition of multiple anatase TiO2 nanosheets.The Au nanoparticles were stabilized by structural defects in each TiO2 nanosheet,including crystal steps and edges,thereby fixing the Au-TiO2 perimeter interface.Reactant transfer occurred along the gaps between these TiO2 nanosheet layers and in contact with catalytically active sites at the Au-TiO2 interface.The doped Au induced the formation of oxygen vacancies in the Au-TiO2 interface.Such vacancies are essential for generating active oxygen species(-*O^-) on the TiO2 surface and Ti^3+ ions in bulk TiO2.These ions can then form Ti^3+-O^--Ti^4+species,which are known to enhance the catalytic activity of formaldehyde(HCHO) oxidation.These studies on structural and oxygen vacancy defects in Au/TiO2 samples provide a theoretical foundation for the catalytic mechanism of HCHO oxidation on oxide-supported Au materials.
文摘To understand the relation between different nanostructures and thermal properties, a simple yet effective model is in demand for characterizing the underlying phonons and electrons scattering mechanisms. Herein, we make a systematic review on the newly developed thermal reffusivity theory. Like electrical resistivity which has been historically used as a theory for analyzing structural domain size and defect levels of metals, the thermal reffusivity can also uncover phonon behavior, structure defects and domain size of materials. We highlight that this new theory can be used for not only metals, but also nonmetals, even for amorphous materials. From the thermal reffusivity against temperature curves, the Debye temperature of the material and the ideal thermal diffusivity of single perfect crystal can be evaluated. From the residual thermal reffusivity at the 0 K limit, the structural thermal domain (STD) size of crystalline and amorphous materials can be obtained. The difference of white hair and normal black hair from heat conduction perspective is reported for the first time. Loss of melanin results in a worse thermal protection and a larger STD size in the white hair. By reviewing the different variation of thermal reffusivity against decreasing temperature profiles, we conclude that they reflected the structural connection in the materials. Ultimately, the future application of thermal reffusivity theory in studying 2D materials and amorphous materials is discussed.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11405231 and 91426301
文摘Ti_3AlC_2 samples are irradiated in advance by 3.5 MeV Fe-ion to the fluence of 1.0×10^(16) ion/cm^2,and then are implanted by 500 keV He-ion with the fluence of 1.0×10^(17) ion/cm^2 at room temperature.The irradiated samples are investigated by grazing incidence x-ray diffraction(GIXRD) and transmission electron microscopy(TEM).GIXRD results show serious structural distortion,but without amorphization in the irradiated samples.Fe-ion irradiation and He-ion implantation create much more serious structural distortion than single Fe-ion irradiation.TEM results reveal that there are a large number of defect clusters in the damage region,and dense spherical He bubbles appear in the He depositional region.It seems that the pre-damage does not influence the growth of He bubbles,but He-ion implantation influences the pre-created defect configurations.
基金This study is supported by the National Natural Science Foundation of China(21925104)the Natural Science Foun-dation of Hubei Province(2021CFA020)the start-up funding of Huazhong University of Science and Technology(3004110178).
文摘Carbon-based metal-free nanomaterials are promising alternatives to precious metals as electrocatalysts of key energy storage and conversion technologies.Of paramount significance are the establishment of design principles by understanding the catalytic mechanisms and identifying the active sites.Distinct from sp2-conjugated graphene and carbon nanotube,fullerene possesses unique characteristics that are growingly being discovered and exploited by the electrocatalysis community.For instance,the well-defined atomic and molecular structures,the good electron affinity to tune the electronic structures of other substances,the intermolecular self-assembly into superlattices,and the on-demand chemical modification have endowed fullerene with incomparable advantages as electrocatalysts that are otherwise not applicable to other carbon ma-terials.As increasing studies are being reported on this intriguing topic,it is necessary to provide a state-of-the-art overview of the recent progress.This review takes such an initiative by summarizing the promises and challenges in the electrocatalytic applications of fullerene and its derivatives.The content is structured according to the composition and structure of fullerene,including intact fullerene(e.g.,fullerene composite and superlattices)and fullerene derivatives(e.g.,doped,endohedral,and disintegrated fullerene).The synthesis,characterization,catalytic mechanisms,and deficiencies of these fullerene-based materials are explicitly elaborated.We conclude it by sharing our perspectives on the key aspects that future efforts shall consider.
基金This work was supported by the National Key Research and Development Program of China(No.2020YFA0211000)the National Natural Science Foundation of China(Nos.21876114,21761142011,and 51572174)+3 种基金the Shanghai Government(Nos.19DZ1205102 and 19160712900)the International Joint Laboratory on Resource Chemistry(No.IJLRC)the Ministry of Education of China(No.PCSIRT_IRT_16R49)This research was also supported by The Program for Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learning,the Shuguang Research Program of Shanghai Education Committee,and the Shanghai Engineering Research Center of Green Energy Chemical Engineering(No.18DZ2254200).
文摘NH_(2)-UIO66(NU)is a promising photocatalyst for the reduction of Cr(VI)to low-toxic Cr(III)driven by visible light under ambient conditions.However,the main limitation in this process is the ineffi cient ligand to metal charge transfer(LMCT)of photo-excited electrons,which is caused by inherent energy gap(ΔE_(LMCT)).This study synthesized the defective NU(NUXH,where X is the molar equivalent of the modulator)with reducedΔE_(LMCT)through linkers removal via acid treatment.The electronic structure of NUX-H was systematically investigated,and the results indicated that the structural defects in NUX-H strongly altered the environment of the Zr atoms.Furthermore,they substantially lowered the energy of the unoccupied d orbitals(LUMO),which was benefi cial to effi cient LMCT,resulting in an improved photocatalytic activity of NUX-H toward high-concentration(100 mg/L)Cr(VI)reduction.Compared to NU with defect-free structure,the reducing rate of Cr(VI)was increased by 47 times.This work introduced an alternative strategy in terms of designing effi cient photocatalysts for reducing Cr(VI)under ambient conditions.
基金Project supported by the Natural Science Basic Research Plan in Shaanxi Province of China(Grant No.2016JQ5014)the Fundamental Research Funds for the Central Universities,China(Grant No.3102014JCQ01024)+2 种基金the Research Fund of the State Key Laboratory of Solidification Processing(NWPU),China(Grant No.114-QP-2014)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20136102120021)the National Natural Science Foundation of China(Grant Nos.51474716 and 51475378)
文摘Anti-structured defects bridge atom migration among heterogeneous sublattices facilitating diffusion but could also result in the collapse of ordered structure.Component distribution Ni(75)AlxV(25-x) alloys are investigated using a microscopic phase field model to illuminate relations between anti-structured defects and composition,precipitate order,precipitate type,and phase stability.The Ni(75)AlxV(25-x) alloys undergo single Ni3V(stage Ⅰ),dual Ni3Al and Ni3V(stage Ⅱ with Ni3V prior;and stage Ⅲ with Ni3Al prior),and single Ni3Al(stage Ⅳ) with enhanced aluminum level.For Ni3V phase,anti-structured defects(V(Ni1),Niy,except V(Ni2)) and substitution defects(Al(Ni1),Al(Ni2),Alv) exhibit a positive correlation to aluminum in stage I,the positive trend becomes to negative correlation or smooth during stage Ⅱ.For Ni3 Al phase,anti-structured defects(Al(Ni),Ni(Al)) and substitution defects(V(Ni),V(Al)) have a positive correlation to aluminum in stage Ⅱ,but Ni(Al) goes down since stage Ⅲ and lasts to stage Ⅳ.V(Ni) and V(Al) fluctuate when Ni3Al precipitates prior,but go down drastically in stageⅣ.Precipitate type conversion of single Ni3V/dual(Ni3V+Ni3Al) affects Ni3V defects,while dual(Ni3V+Ni3Al)/single Ni3 Al has little effect on Ni3Al defects.Precipitate order swap occurred in the dual phase region affects on Ni3Al defects but not on Ni3V.
基金The authors would like to acknowledge the support from Taif University Researchers Supporting Project Number (TURSP-2020/264),Taif University,。
文摘This paper presents a compact Multiple Input Multiple Output(MIMO)antenna with WLAN band notch for Ultra-Wideband(UWB)applications.The antenna is designed on 0.8mmthick low-cost FR-4 substrate having a compact size of 22mm×30 mm.The proposed antenna comprises of two monopole patches on the top layer of substrate while having a shared ground on its bottom layer.The mutual coupling between adjacent patches has been reduced by using a novel stub with shared ground structure.The stub consists of complementary rectangular slots that disturb the surface current direction and thus result in reducing mutual coupling between two ports.A slot is etched in the radiating patch for WLAN band notch.The slot is used to suppress frequencies ranging from 5.1 to 5.9 GHz.The results show that the proposed antenna has a very good impedance bandwidth of|S11|<−10 dB within the frequency band from 3.1–14 GHz.A low mutual coupling of less than−23 dB is achieved within the entire UWB band.Furthermore,the antenna has a peak gain of 5.8 dB,low ECC<0.002 and high Diversity Gain(DG>9.98).
基金Deanship of ScientificResearch,King Abdulaziz University for providing financial vide grant number (KEP-MSc-41-135-1443).
文摘Mutual coupling reduction or isolation enhancement in antenna arrays is an important area of research as it severely affects the performance of an antenna.In this paper,a new type of compact and highly isolated Multiple-Input-Multiple-Output(MIMO)antenna for ultra-wideband(UWB)applications is presented.The design consists of four radiators that are orthogonally positioned and confined to a compact 40×40×0.8 mm3 space.The final antenna design uses an inverted L shape partial ground to produce an acceptable reflection coefficient(S11<−10 dB)in an entire UWB band(3.1–10.6)giga hertz(GHz).Moreover,the inter-element isolation has also been enhanced to>20 db for majority of the UWB band.The antenna was fabricated and tested with the vector network analyzer(VNA)and in an anechoic chamber for scattering parameters and radiation patterns.Furthermore,different MIMO diversity performance metrics are also measured to validate the proposed model.The simulation results and the experimental results from the constructed model agree quite well.The proposed antenna is compared with similar designs in recently published literature for various performance metrics.Because of its low envelope correlation coefficient(ECC<0.1),high diversity gain(DG>9.99 dB),peak gain of 4.6 dB,reduced channel capacity loss(CCL<0.4 b/s/Hz),and average radiation efficiency of over 85%,the proposed MIMO antenna is ideally suited for practical UWB applications.
文摘In this paper,the investigation of a novel compact 2×2,2×1,and 1×1 Ultra-Wide Band(UWB)based Multiple-Input Multiple-Output(MIMO)antenna with Defected Ground Structure(DGS)is employed.The proposed Electromagnetic Radiation Structures(ERS)is composed of multiple radiating elements.These MIMO antennas are designed and analyzed with and without DGS.The feeding is introduced by a microstrip-fed line to significantly moderate the radiating structure’s overall size,which is 60×40×1 mm.The high directivity and divergence characteristics are attained by introducing the microstripfed lines perpendicular to each other.And the projected MIMO antenna structures are compared with others by using parameters like Return Loss(RL),Voltage Standing Wave Ratio(VSWR),Radiation Pattern(RP),radiation efficiency,and directivity.The same MIMO set-up is redesigned with DGS,and the resultant parameters are compared.Finally,the Multiple Input and Multiple Output Radiating Structures with and without DGS are compared for result considerations like RL,VSWR,RP,radiation efficiency,and directivity.This projected antenna displays an omnidirectional RP with moderate gain,which is highly recommended for human healthcare applications.By introducing the defected ground structure in bottom layer the lower cut-off frequencies of 2.3,4.5 and 6.0 GHz are achieved with few biological effects on radio propagation in human body communications.The proposed design covers numerous well-known wireless standards,along with dual-function DGS slots,and it can be easily integrated into Wireless Body Area Networks(WBAN)in medical applications.This WBAN links the autonomous nodes that may be situated either in the clothes,on-body or beneath the skin of a person.This system typically advances the complete human body and the inter-connected nodes through a wireless communication channel.
基金the National Natural Science Foundation of China(Nos.51278001,U22A20401)Anhui Province Major Science and Technology Projects(No.202003a0702014)+1 种基金Natural Science Foundation of Anhui Province(No.2018085QD172)Natural Science Key Project of Education Department of Anhui Province(No.KJ2020A0017)for supporting this work.We thank Letpub(www.letpub.com.cn)for its linguistic assistance during the preparation of this manuscript.Thanks to the University of Science and Technology of China for providing MATERIAL STUDIO software copyright support.
文摘In this study,a Ni-Fe metal-organic framework modified by-NH_(2)and-SH was synthesized using a sim-ple hydrothermal process for enhancing photocatalytic CO_(2)reduction.As expected,the N2S-NiFe(NH_(2)-BDC/H_(4)DSBDC,2:1)displayed excellent photocatalytic CO_(2)reduction activity and high CO selectivity(12,412.23μmol g^(−1)h^(−1))under visible light irradiation(λ≥420 nm),which is 5 times that of NiFe-MOF.Notably,the excellent photocatalytic performance of N2S-NiFe can benefit from the rich defect trap site caused by the introduction of amino and sulfhydryl groups,accelerating charge transfer and promoting space charge separation,as supported by the photo-electrochemical properties.To better understand the CO_(2)adsorption mechanism,density functional theory calculations were performed,which revealed that the Niov site has more negative adsorption energy compared with the Feov site.This study provides a simple strategy to establish efficient photocatalysts for CO_(2)reduction through the modification of organic ligands.
文摘Fluoride mediated nano-sized ZSM-5 (ZSM-5-F) with a high Si/AI ratio of 181 was fabricated using a seed-induction method and evaluated the catalysis of the methanol to propylene (MTP) reaction. High propylene selectivity (45%) was similar to ZSM-5-OH synthesized via a hydroxide route. However, ZSM- 5-F showed much longer lifetime (305 h) compared with ZSM-5-OH (157 h) in spite of similar crystal size and aluminum content. Characterization by NH3-TPD. Py-IR, OH-IR, SEM, TG-DTA, XRD and 1H MAS NMR techniques indicated that the enhanced catalytic performance of ZSM-S-F is attributed to the fewer structural defects in the form of internal silanol groups and silanol nests.
文摘This paper considers that the crystal grains of HDDR Pr2Fe14B permanent magnetic material are cubic, the size is 0.3 μm, and the crystal grains are in simple cubic accumulation. It is considered that there are boundary phases between grains. It is assumed that the boundary phases are non-magnetic phases with the thickness of d, and evenly distributed between grains. The anisotropy expression of single grain boundary is given considering structure defect and intergranular exchange coupling interaction. Based on micro-magnetic simulation calculation, the variation of the average anisotropy of a single grain with the structural defects and boundary phases was calculated. The results show that when the thickness of structural defects is constant, the average anisotropy of a single grain decreases with increasing of grain boundary phase thickness, and while the thickness of grain boundary phase is constant, it also decreases with increasing of structural defect thickness.
基金supported by the National Natural Science Foundation of China(Grant No.50905187)the Shandong Provincial Natural Science Foundation(Grant No.ZR2009FQ001)
文摘This article studies the application of the alternating current field measurement (ACFM) method in defect detection for underwater structures. Numerical model of the ACFM system is built for structure surface defect detection in seawater environment. Finite element simulation is performed to investigate rules and characteristics of the electromagnetic signal distribution in the defected area. In respect of the simulation results, underwater artificial crack detection experiments are designed and conducted for the ACFM system. The experiment results show that the ACFM system can detect cracks in underwater structures and the detection accuracy is higher than 85%. This can meet the engineering requirement of underwater structure defect detection. The results in this article can be applied to establish technical foundation for the optimization and development of ACFM based underwater structure defects detection system.
基金This work was supported by the Research Program through the National Research Foundation of Korea,NRF-2019R1A2C1005920,S.K.
文摘Due to rapid growth in wireless communication technology,higher bandwidth requirement for advance telecommunication systems,capable of operating on two or higher bands with higher channel capacities and minimum distortion losses is desired.In this paper,a compact Ultra-Wideband(UWB)V-shaped monopole antenna is presented.UWB response is achieved by modifying the ground plane with Chichen Itzia inspired rectangular staircase shape.The proposed V-shaped is designed by incorporating a rectangle,and an inverted isosceles triangle using FR4 substrate.The size of the antenna is 25 mm×26 mm×1.6 mm.The proposed V-shaped monopole antenna produces bandwidth response of 3 GHz Industrial,Scientific,and Medical(ISM),Worldwide Interoperability for Microwave Access(WiMAX),(IEEE 802.11/HIPERLAN band,5G sub 6 GHz)which with an additional square cut amplified the bandwidth response up to 8 GHz ranging from 3.1 GHz to 10.6 GHz attaining UWB defined by Federal Communications Commission(FCC)with a maximum gain of 3.83 dB.The antenna is designed in Ansys HFSS.Results for key performance parameters of the antenna are presented.The measured results are in good agreement with the simulated results.Due to flat gain,uniform group delay,omni directional radiation pattern characteristics and well-matched impedance,the proposed antenna is suitable for WiMAX,ISM and heterogeneous wireless systems.