调制解调法是一种常用的微弱信号检测方法,高精度、低复杂度的解调方法的实现对于调制解调法的应用具有重要的意义.传统坐标旋转数字计算(coordinate rotation digital computer,CORDIC)算法具有占用资源多,需要缩放因子补偿等问题.因...调制解调法是一种常用的微弱信号检测方法,高精度、低复杂度的解调方法的实现对于调制解调法的应用具有重要的意义.传统坐标旋转数字计算(coordinate rotation digital computer,CORDIC)算法具有占用资源多,需要缩放因子补偿等问题.因此设计并实现了一种基于改进CORDIC算法的离散傅里叶变换(discrete Fourier transform,DFT)解调方法用于微弱信号的检测.首先改进了传统的CORDIC算法用于正余弦函数值的计算,该方法不仅免除了缩放因子,而且不需要进行旋转角度的判断,降低了算法的资源占用;然后基于该CORDIC算法设计了DFT解调算法,避免了乘法器与大量查找表的使用.最终仿真结果表明,设计的DFT解调方法在整周期采样的情况下能够实现对调制信号的高精度解调,并且具备良好的抗噪声性能,能够满足微弱信号检测的要求.展开更多
基于正交频分复用(orthogonal frequency division multiplexing,OFDM)的高速电力线载波通信(high-speed power line communication,HPLC)在配电网及智能家居中得到了广泛应用。HPLC信道存在噪声复杂、多径传播、阻抗多变等问题,对信号...基于正交频分复用(orthogonal frequency division multiplexing,OFDM)的高速电力线载波通信(high-speed power line communication,HPLC)在配电网及智能家居中得到了广泛应用。HPLC信道存在噪声复杂、多径传播、阻抗多变等问题,对信号检测带来了不利影响。文章研究了HPLC系统的信道估计问题。首先,定义循环前缀内采样点噪声的近似功率,提出基于噪声功率的离散傅里叶变换(noise power based discrete Fourier transform,NPDFT)算法,对传统DFT算法得到的信道冲激响应进行修正。其次,在NPDFT基础上,提出一种基于深度神经网络(deep neural networks,DNN)和门控循环单元(gated recurrent unit,GRU)组合的轻量级深度神经门控网络(DnGRUNet),使用DNN提取和细化多径信道特征,利用GRU网络对OFDM符号之间的信道变化进行学习。仿真结果表明,NPDFT-DnGRUNet算法的信道估计误差远低于对比算法,能有效降低信号检测误码率。展开更多
A corrosion discoloration model for copper-nickel alloys in Cl^(−)environments was established using CIE-Lab,UV-VIS absorption spectroscopy,X-ray diffraction,and X-ray photoelectron spectroscopy.The corrosion discolor...A corrosion discoloration model for copper-nickel alloys in Cl^(−)environments was established using CIE-Lab,UV-VIS absorption spectroscopy,X-ray diffraction,and X-ray photoelectron spectroscopy.The corrosion discoloration process and the corresponding main corrosion products can be summarized as follows:silver-white(Cu+Ni)→green(NiO)→reddishbrown(NiO+Cu_(2)O)→black(NiO+Cu_(2)O+CuO).Density functional theory was employed to explain the corrosion process of copper-nickel alloys and the detrimental effect of Cl^(−).The results indicate that adsorbates preferentially bind to nickel,leading to the preferential formation of NiO,which imparts a green appearance to the surface.Furthermore,the difficulty in forming nickel cation vacancies and the higher diffusion barrier for nickel inhibit the migration of species within the oxide layer.Notably,nickel also suppresses carrier migration within the oxide layer,reducing the charge transfer rate.In contrast,the promotion of corrosion by Cl^(−)is primarily attributed to the reduction in surface work function and the formation energy of cation vacancies.展开更多
Organic semiconductor materials have demonstrated extensive potential in the field of gas sensors due to the advantages including designable chemical structure,tunable physical and chemical properties.Through density ...Organic semiconductor materials have demonstrated extensive potential in the field of gas sensors due to the advantages including designable chemical structure,tunable physical and chemical properties.Through density functional theory(DFT)calculations,researchers can investigate gas sensing mechanisms,optimize,and predict the electronic structures and response characteristics of these materials,and thereby identify candidate materials with promising gas sensing applications for targeted design.This review concentrates on three primary applications of DFT technology in the realm of organic semiconductor-based gas sensors:(1)Investigating the sensing mechanisms by analyzing the interactions between gas molecules and sensing materials through DFT,(2)simulating the dynamic responses of gas molecules,which involves the behavior on the sensing interface using DFT combined with other computational methods to explore adsorption and diffusion processes,and(3)exploring and designing sensitive materials by employing DFT for screening and predicting chemical structures,thereby developing new sensing materials with exceptional performance.Furthermore,this review examines current research outcomes and anticipates the extensive application prospects of DFT technology in the domain of organic semiconductor-based gas sensors.These efforts are expected to provide valuable insights for further indepth exploration of DFT applications in sensor technology,thereby fostering significant advancements and innovations in the field.展开更多
It is advisable to look into efficient and environmentally friendly materials that have the ability to turn lost energy into electricity in order to mitigate the rapid depletion of fossil fuels and the ensuing environ...It is advisable to look into efficient and environmentally friendly materials that have the ability to turn lost energy into electricity in order to mitigate the rapid depletion of fossil fuels and the ensuing environmental damage.In the present work density functional theory(DFT)was employed to analyze the structural,optical,electronic,and thermoelectric characteristics of novel half-Heusler AMnSb(A=La,Lu)materials.The structural stability of both compounds under consideration was verified by using the Birch-Murnaghan equations of states,which indicate that both compounds have structural stability due to ground-state energy levels being negative.Band structure and total density of state analysis display that LaMnSb has an energy band gap of 0.96 eV for spin-up(↑)and 0.21 eV for spin-down(↓)configurations.LuMnSb has band gap of 0.47 eV for spin-up and an indirect band gap of 0.3 eV for spin-down channel.In terms of its optical properties,LuMnSb exhibits maximal conductivity and absorption of electromagnetic radiation in the ultraviolet range(99-462 nm),which makes it a desirable material for optoelectronic applications.Moreover,the transport characteristics of the examined materials were computed by means of the Boltztrap code based on Boltzmann transport theory.The thermoelectric parameters,like the thermal conductivity,Seebeck coefficient,and electrical conductivity are computed in the 200-1200 K temperature range.These anticipated results suggest that AMnSb(A=La,Lu)compounds would be the best choice for thermoelectric and green energy applications.展开更多
The rational design of Ni-based catalysts is essential due to their abundance and low cost for advancing sustainable energy technologies,particularly for water splitting and fuel cells.This study employs spinpolarized...The rational design of Ni-based catalysts is essential due to their abundance and low cost for advancing sustainable energy technologies,particularly for water splitting and fuel cells.This study employs spinpolarized density functional theory(DFT)to examine the influence of anchoring rare-earth elements on the γ-NiOOH lattice surface,aiming to identify the optimal catalytic site for the oxygen evolution reaction(OER)and oxygen reduction reaction(ORR).Following the identification of an appropriate active site through Ni vacancy,a rare earth element(REE_(1))is introduced as a dopant for single-atom catalysis(SACs).The structural,thermodynamic,and catalytic characteristics of all newly designed REE_(1)/γ-NiOOH catalysts have been extensively studied.Among the newly developed catalysts,Tb_(1)/γ-NiOOH exhibits the lowest OER overpotential of(0.36 V),while Ce_(1)/γ-NiOOH and Pr_(1)/γ-NiOOH also demonstrate excellent OER performance(0.51 and 0.41 V),respectively.Notably,Nd_(1)/γ-NiOOH and Pm_(1)/γ-NiOOH exhibit efficient ORR activity,with low overpotentials of(0.63 and 0.61 V)due to their balanced adsorption and desorption energies of intermediates.Bader charge analysis reveals strong electron donation from doped REE1to the surface.This study identified Ce_(1),Pr_(1),Nd_(1),and Tb_(1) anchoring catalysts as highly promising for water-splitting applications.Moreover,Nd_(1) and Pm_(1) doping markedly improve ORR performance,underscoring their promise for enhanced electrochemical applications in metal-air batteries.The catalytic performance of all newly developed catalysts was further evaluated using electronic descriptors.The catalytic performance was further assessed using the volcano curve and scaling relationships for the adsorbed intermediates.This study offers an extensive theoretical foundation for designing cost-effective and high-performance REE_(1)/γ-NiOOH electrocatalysts.展开更多
Our study employed self-consistent ab-initio calculations using highly precise spin-polarized density functional theory with both GGA and GGA+U approaches,coupled with the Boltzmann transport scheme.This co mprehensiv...Our study employed self-consistent ab-initio calculations using highly precise spin-polarized density functional theory with both GGA and GGA+U approaches,coupled with the Boltzmann transport scheme.This co mprehensive approach investigated the structural stability,magneto-electronic behavior,thermophysical characteristics,and thermoelectric transport properties of Co_(2)TiRE(RE=Nd,Tb)Heusler alloys.Through structural optimizations,we confirm that these materials exhibit fe rromagnetic behavior.Analysis of band occupation and density of states using GGA and GGA+U methods reveals that both compounds are metallic in both spin configurations.We evaluated key transport properties such as the Seebeck coefficient,electrical and thermal conductivity and the figure of merit to understand their potential in thermoelectric applications.Conservative estimates of the Seebeck coefficient and the figure of merit suggest promising applications in thermoelectric energy harvesting technologies.Additionally,we provide a comprehensive analysis of the thermophysical behavior,including the Debye temperature,thermal expansion,and specific heat,to assess the alloys thermodynamic stability across varying temperature and pressure conditions.展开更多
To achieve selective leaching of ion adsorption rare earth,it is necessary to thoroughly reveal the differences in the adsorption mechanisms of aluminum and rare earth elements.In this study,we investigated the adsorp...To achieve selective leaching of ion adsorption rare earth,it is necessary to thoroughly reveal the differences in the adsorption mechanisms of aluminum and rare earth elements.In this study,we investigated the adsorption processes of Dy and Al on the surface of K–homoionic kaolinite using batch experiments and sequential chemical extractions.The results revealed that the adsorption of Dy and Al,as well as the desorption of K,followed the Langmuir model.The maximum ion-exchangeable capacity of Dy was higher(9.39 mmol.kg^(-1))than that of Al(6.30 mmol.kg^(-1)).The ion exchange stoichiometry ratios of Dy–K and Al–K derived from the Langmuir model were2.0 and 2.6.The analysis of X-ray absorption fine structure(XAFS)and density functional theory(DFT)revealed that Dy and Al were adsorbed onto kaolinite as outer-sphere hydrated complexes via hydrogen bonds.Dy was adsorbed as[Dy(H_(2)O)_(10)]^(3+),and Al was adsorbed as[Al(OH)_(2)(H_(2)O)_(4)]^(+).In particular,the adsorption of Al resulted in protonation of the hydroxyl groups on the surface of the kaolinite.Based on the above insights,the higher ion exchange stoichiometry ratios are attributed to closer adsorption distances(6.04 A for Dy and 3.69 A for Al)and lower adsorption energies(-223.72 kJ.mol^(-1)for Dy and-268.33 kJ.mol^(-1)for Al).The maximum ionexchangeable capacity is related to the change of the surface electrical properties of kaolinite.The zeta potential was increased to-7.3 mV as the protonation resulted from aluminum adsorption,while Dy adsorption had a minor effect,maintaining a value of-17.5 m V.展开更多
文摘基于正交频分复用(orthogonal frequency division multiplexing,OFDM)的高速电力线载波通信(high-speed power line communication,HPLC)在配电网及智能家居中得到了广泛应用。HPLC信道存在噪声复杂、多径传播、阻抗多变等问题,对信号检测带来了不利影响。文章研究了HPLC系统的信道估计问题。首先,定义循环前缀内采样点噪声的近似功率,提出基于噪声功率的离散傅里叶变换(noise power based discrete Fourier transform,NPDFT)算法,对传统DFT算法得到的信道冲激响应进行修正。其次,在NPDFT基础上,提出一种基于深度神经网络(deep neural networks,DNN)和门控循环单元(gated recurrent unit,GRU)组合的轻量级深度神经门控网络(DnGRUNet),使用DNN提取和细化多径信道特征,利用GRU网络对OFDM符号之间的信道变化进行学习。仿真结果表明,NPDFT-DnGRUNet算法的信道估计误差远低于对比算法,能有效降低信号检测误码率。
基金supported by the Key Program of the National Natural Science Foundation of China(Grant No.51131007)the National Key Research and Development Program of China(Grant No.2021YFC2803102).
文摘A corrosion discoloration model for copper-nickel alloys in Cl^(−)environments was established using CIE-Lab,UV-VIS absorption spectroscopy,X-ray diffraction,and X-ray photoelectron spectroscopy.The corrosion discoloration process and the corresponding main corrosion products can be summarized as follows:silver-white(Cu+Ni)→green(NiO)→reddishbrown(NiO+Cu_(2)O)→black(NiO+Cu_(2)O+CuO).Density functional theory was employed to explain the corrosion process of copper-nickel alloys and the detrimental effect of Cl^(−).The results indicate that adsorbates preferentially bind to nickel,leading to the preferential formation of NiO,which imparts a green appearance to the surface.Furthermore,the difficulty in forming nickel cation vacancies and the higher diffusion barrier for nickel inhibit the migration of species within the oxide layer.Notably,nickel also suppresses carrier migration within the oxide layer,reducing the charge transfer rate.In contrast,the promotion of corrosion by Cl^(−)is primarily attributed to the reduction in surface work function and the formation energy of cation vacancies.
基金supported by National Natural Science Foundation of China(Nos.92263109 and 61904188)the Shanghai Rising-Star Program(No.22QA1410400)。
文摘Organic semiconductor materials have demonstrated extensive potential in the field of gas sensors due to the advantages including designable chemical structure,tunable physical and chemical properties.Through density functional theory(DFT)calculations,researchers can investigate gas sensing mechanisms,optimize,and predict the electronic structures and response characteristics of these materials,and thereby identify candidate materials with promising gas sensing applications for targeted design.This review concentrates on three primary applications of DFT technology in the realm of organic semiconductor-based gas sensors:(1)Investigating the sensing mechanisms by analyzing the interactions between gas molecules and sensing materials through DFT,(2)simulating the dynamic responses of gas molecules,which involves the behavior on the sensing interface using DFT combined with other computational methods to explore adsorption and diffusion processes,and(3)exploring and designing sensitive materials by employing DFT for screening and predicting chemical structures,thereby developing new sensing materials with exceptional performance.Furthermore,this review examines current research outcomes and anticipates the extensive application prospects of DFT technology in the domain of organic semiconductor-based gas sensors.These efforts are expected to provide valuable insights for further indepth exploration of DFT applications in sensor technology,thereby fostering significant advancements and innovations in the field.
基金the Deanship of Research and Graduate studies at King Khalid University for funding this work through a large group research project under grant number RGP2/96/45。
文摘It is advisable to look into efficient and environmentally friendly materials that have the ability to turn lost energy into electricity in order to mitigate the rapid depletion of fossil fuels and the ensuing environmental damage.In the present work density functional theory(DFT)was employed to analyze the structural,optical,electronic,and thermoelectric characteristics of novel half-Heusler AMnSb(A=La,Lu)materials.The structural stability of both compounds under consideration was verified by using the Birch-Murnaghan equations of states,which indicate that both compounds have structural stability due to ground-state energy levels being negative.Band structure and total density of state analysis display that LaMnSb has an energy band gap of 0.96 eV for spin-up(↑)and 0.21 eV for spin-down(↓)configurations.LuMnSb has band gap of 0.47 eV for spin-up and an indirect band gap of 0.3 eV for spin-down channel.In terms of its optical properties,LuMnSb exhibits maximal conductivity and absorption of electromagnetic radiation in the ultraviolet range(99-462 nm),which makes it a desirable material for optoelectronic applications.Moreover,the transport characteristics of the examined materials were computed by means of the Boltztrap code based on Boltzmann transport theory.The thermoelectric parameters,like the thermal conductivity,Seebeck coefficient,and electrical conductivity are computed in the 200-1200 K temperature range.These anticipated results suggest that AMnSb(A=La,Lu)compounds would be the best choice for thermoelectric and green energy applications.
基金supported by the BRICS STI Framework Programme(No.52261145703)the Higher Education Discipline Innovation Project(National 111 Project,No.B16016)。
文摘The rational design of Ni-based catalysts is essential due to their abundance and low cost for advancing sustainable energy technologies,particularly for water splitting and fuel cells.This study employs spinpolarized density functional theory(DFT)to examine the influence of anchoring rare-earth elements on the γ-NiOOH lattice surface,aiming to identify the optimal catalytic site for the oxygen evolution reaction(OER)and oxygen reduction reaction(ORR).Following the identification of an appropriate active site through Ni vacancy,a rare earth element(REE_(1))is introduced as a dopant for single-atom catalysis(SACs).The structural,thermodynamic,and catalytic characteristics of all newly designed REE_(1)/γ-NiOOH catalysts have been extensively studied.Among the newly developed catalysts,Tb_(1)/γ-NiOOH exhibits the lowest OER overpotential of(0.36 V),while Ce_(1)/γ-NiOOH and Pr_(1)/γ-NiOOH also demonstrate excellent OER performance(0.51 and 0.41 V),respectively.Notably,Nd_(1)/γ-NiOOH and Pm_(1)/γ-NiOOH exhibit efficient ORR activity,with low overpotentials of(0.63 and 0.61 V)due to their balanced adsorption and desorption energies of intermediates.Bader charge analysis reveals strong electron donation from doped REE1to the surface.This study identified Ce_(1),Pr_(1),Nd_(1),and Tb_(1) anchoring catalysts as highly promising for water-splitting applications.Moreover,Nd_(1) and Pm_(1) doping markedly improve ORR performance,underscoring their promise for enhanced electrochemical applications in metal-air batteries.The catalytic performance of all newly developed catalysts was further evaluated using electronic descriptors.The catalytic performance was further assessed using the volcano curve and scaling relationships for the adsorbed intermediates.This study offers an extensive theoretical foundation for designing cost-effective and high-performance REE_(1)/γ-NiOOH electrocatalysts.
文摘Our study employed self-consistent ab-initio calculations using highly precise spin-polarized density functional theory with both GGA and GGA+U approaches,coupled with the Boltzmann transport scheme.This co mprehensive approach investigated the structural stability,magneto-electronic behavior,thermophysical characteristics,and thermoelectric transport properties of Co_(2)TiRE(RE=Nd,Tb)Heusler alloys.Through structural optimizations,we confirm that these materials exhibit fe rromagnetic behavior.Analysis of band occupation and density of states using GGA and GGA+U methods reveals that both compounds are metallic in both spin configurations.We evaluated key transport properties such as the Seebeck coefficient,electrical and thermal conductivity and the figure of merit to understand their potential in thermoelectric applications.Conservative estimates of the Seebeck coefficient and the figure of merit suggest promising applications in thermoelectric energy harvesting technologies.Additionally,we provide a comprehensive analysis of the thermophysical behavior,including the Debye temperature,thermal expansion,and specific heat,to assess the alloys thermodynamic stability across varying temperature and pressure conditions.
基金financially supported by the National Key Research and Development Program of China(No.2021YFC2902203)the Key Research and Development Program of Guangxi Province(No.Guike-AB22080056)+2 种基金Beijing Nova Program(No.20230484379)the Science and Technology Innovation Fund of GRINM(No.2022PD0102)the Central Government Guides Local Science and Technology Development Fund Project(No.246Z4005G)。
文摘To achieve selective leaching of ion adsorption rare earth,it is necessary to thoroughly reveal the differences in the adsorption mechanisms of aluminum and rare earth elements.In this study,we investigated the adsorption processes of Dy and Al on the surface of K–homoionic kaolinite using batch experiments and sequential chemical extractions.The results revealed that the adsorption of Dy and Al,as well as the desorption of K,followed the Langmuir model.The maximum ion-exchangeable capacity of Dy was higher(9.39 mmol.kg^(-1))than that of Al(6.30 mmol.kg^(-1)).The ion exchange stoichiometry ratios of Dy–K and Al–K derived from the Langmuir model were2.0 and 2.6.The analysis of X-ray absorption fine structure(XAFS)and density functional theory(DFT)revealed that Dy and Al were adsorbed onto kaolinite as outer-sphere hydrated complexes via hydrogen bonds.Dy was adsorbed as[Dy(H_(2)O)_(10)]^(3+),and Al was adsorbed as[Al(OH)_(2)(H_(2)O)_(4)]^(+).In particular,the adsorption of Al resulted in protonation of the hydroxyl groups on the surface of the kaolinite.Based on the above insights,the higher ion exchange stoichiometry ratios are attributed to closer adsorption distances(6.04 A for Dy and 3.69 A for Al)and lower adsorption energies(-223.72 kJ.mol^(-1)for Dy and-268.33 kJ.mol^(-1)for Al).The maximum ionexchangeable capacity is related to the change of the surface electrical properties of kaolinite.The zeta potential was increased to-7.3 mV as the protonation resulted from aluminum adsorption,while Dy adsorption had a minor effect,maintaining a value of-17.5 m V.
