There is an urgent need for novel processes that can integrate different functional nanostructures onto specific substrates,so as to meet the fast-growing need for broad applications in nanoelectronics,nanophotonics,a...There is an urgent need for novel processes that can integrate different functional nanostructures onto specific substrates,so as to meet the fast-growing need for broad applications in nanoelectronics,nanophotonics,and fexible optoelectronics.Existing direct-lithography methods are difficult to use on fexible,nonplanar,and biocompatible surfaces.Therefore,this fabrication is usually accomplished by nanotransfer printing.However,large-scale integration of multiscale nanostructures with unconventional substrates remains challenging because fabrication yields and quality are often limited by the resolution,uniformity,adhesivity,and integrity of the nanostructures formed by direct transfer.Here,we proposed a resist-based transfer strategy enabled by near-zero adhesion,which was achieved by molecular modification to attain a critical surface energy interval.This approach enabled the intact transfer of wafer-scale,ultrathin-resist nanofilms onto arbitrary substrates with mitigated cracking and wrinkling,thereby facilitating the in situ fabrication of nanostructures for functional devices.Applying this approach,fabrication of three-dimensional-stacked multilayer structures with enhanced functionalities,nanoplasmonic structures with~10 nm resolution,and MoS2-based devices with excellent performance was demonstrated on specific substrates.These results collectively demonstrated the high stability,reliability,and throughput of our strategy for optical and electronic device applications.展开更多
The practical application of CaSmAlO_(4)microwave dielectric ceramics is limited by its low quality factor(Q×f)value and non-zero temperature coefficient resonant frequency(τ_(f))value.In this study,we introduce...The practical application of CaSmAlO_(4)microwave dielectric ceramics is limited by its low quality factor(Q×f)value and non-zero temperature coefficient resonant frequency(τ_(f))value.In this study,we introduced Mg^(2+)-Ti^(4+)ionic pairs into CaSmAlO_(4),along with an excess of 9%Sm_(2)O_(3).The Mg^(2+)-Ti^(4+)ionic pairs substituted Al^(3+),and two phases simultaneously coexisted in the ceramics:CaSmAlO_(4) and Sm_(2)O_(3).As the doping concentration of Mg^(2+)-Ti^(4+)ionic pairs increased,the relative permittivity exhibited an upward trend,while the quality factor and resonant frequency temperature coefficient first rose and then descended.Remarkably,0.09Sm_(2)O_(3)-0.91CaSmAl_(0.7)Mg_(0.15)-Ti_(0.15)O_(4) sintered at 1450℃ yielded excellent dielectric properties:ε_(r)=19.72,Q×f=72,936 GHz,and τ_(f)=-0.044 ppm·℃^(-1).The factors influencing the microwave dielectric properties of 0.09Sm_(2)O_(3)-0.91CaSmAlO_(4)ceramics were further examined by considering the crystal structure,grain size,Lichtenecker logarithmic rule,tolerance factor and packing fraction.展开更多
Coal is the dominant energy source in China,and coal-fired power accounts for about half of coal consumption.However,air pollutant emissions from coal-fired power plants cause severe ecological and environmental probl...Coal is the dominant energy source in China,and coal-fired power accounts for about half of coal consumption.However,air pollutant emissions from coal-fired power plants cause severe ecological and environmental problems.This paper focuses on near-zero emission technologies and applications for clean coal-fired power.The long-term operation states of near-zero emission units were evaluated,and synergistic and special mercury(Hg)control technologies were researched.The results show that the principle technical route of near-zero emission,which was applied to 101 of China’s coal-fired units,has good adaptability to coal properties.The emission concentrations of particulate matter(PM),SO2,and NOx were below the emission limits of gas-fired power plants and the compliance rates of the hourly average emission concentrations reaching near-zero emission in long-term operation exceeded 99%.With the application of near-zero emission technologies,the generating costs increased by about 0.01 CNY∙(kW∙h)-1.However,the total emissions of air pollutants decreased by about 90%,resulting in effective improvement of the ambient air quality.Furthermore,while the Hg emission concentrations of the near-zero emission units ranged from 0.51 to 2.89μg∙m^-3,after the modified fly ash(MFA)special Hg removal system was applied,Hg emission concentration reached as low as 0.29μg∙m^-3.The operating cost of this system was only 10%-15%of the cost of mainstream Hg removal technology using activated carbon injection.Based on experimental studies carried out in a 50000 m^3∙h^-1 coal-fired flue gas pollutant control pilot platform,the interaction relationships of multi-pollutant removal were obtained and solutions were developed for emissions reaching different limits.A combined demonstration application for clean coal-fired power,with the new“1123”eco-friendly emission limits of 1,10,20 mg∙m^-3,and 3μg∙m^-3,respectively,for PM,SO2,NOx,and Hg from near-zero emission coal-fired power were put forward and realized,providing engineering and technical support for the national enhanced pollution emission standards.展开更多
The geomagnetic field affects all living organisms on the Earth.In this study we investigated the developmental and behavioral effects of rearing Mythimna separata in a near-zero magnetic field(<500 n T)compared to...The geomagnetic field affects all living organisms on the Earth.In this study we investigated the developmental and behavioral effects of rearing Mythimna separata in a near-zero magnetic field(<500 n T)compared to the local geomagnetic field(approximately 50μT).The near-zero magnetic field produced by a Helmholtz coil system significantly lengthened larval and pupal development durations,increased male longevity,and reduced pupal weight,female reproduction,and the relative expression level of the vitellogenin(Vg)gene in newly emerged females.Moreover,the near-zero magnetic field had a considerable negative effect on the mating ratio of M.separata adults.In addition,the moths in the near-zero magnetic field displayed less flight activity late in the night than those in the Earth's normal geomagnetic field,indicating that the flight rhythm of M.separata may be affected by the near-zero magnetic field.Reduction in magnetic field intensity may have negative effects on the development and flight of oriental armyworm,with consequent additional effects on its migration.展开更多
The Zr（0.5）Hf（0.5）VPO7 is successfully synthesized by the solid-state method with near-zero thermal expansion. Powder x-ray diffraction（XRD）, Raman spectroscopy, thermal dilatometry, and scanning electron micros...The Zr（0.5）Hf（0.5）VPO7 is successfully synthesized by the solid-state method with near-zero thermal expansion. Powder x-ray diffraction（XRD）, Raman spectroscopy, thermal dilatometry, and scanning electron microscopy（SEM） are used to investigate the structure, the phase transition, and the coefficient of thermal expansion（CTE） of Zr（0.5）Hf（0.5）VPO7. The investigation results show that the samples are of the single cubic type with a space group of Pa3ˉ at room temperature（RT）.It can be inferred that the superstructure is transformed from the 3 × 3 × 3 superstructure to the 1 × 1 × 1 ideal crystal in a temperature range between 310 K and 323 K. The CTE is measured by a dilatometer to be 0.59 × 10^（-6） K^（-1）（310 K–673 K）. The values of intrinsic（XRD） and extrinsic（dilatometric） thermal expansion are both near zero. The results show that Zr（0.5）Hf（0.5）VPO7 has near-zero thermal expansion behavior over a wide temperature range.展开更多
Near-zero energy buildings( nZEBs) are considered as an effective solution to mitigating CO_2 emissions and reducing the energy usage in the building sector. A proper sizing of the nZEB systems( e. g. HVAC systems,ene...Near-zero energy buildings( nZEBs) are considered as an effective solution to mitigating CO_2 emissions and reducing the energy usage in the building sector. A proper sizing of the nZEB systems( e. g. HVAC systems,energy supply systems,energy storage systems, etc.) is essential for achieving the desired annual energy balance,thermal comfort,and grid independence. Two significant factors affecting the sizing of nZEB systems are the uncertainties confronted by the building usage condition and weather condition,and the degradation effects in nZEB system components. The former factor has been studied by many researchers; however,the impact of degradation is still neglected in most studies. Degradation is prevalent in energy components of nZEB and inevitably leads to the deterioration of nZEB life-cycle performance. As a result,neglecting the degradation effects may lead to a system design which can only achieve the desired performance at the beginning several years. This paper,therefore,proposes a life-cycle performance analysis( LCPA) method for investigating the impact of degradation on the longitudinal performance of the nZEBs. The method not only integrates the uncertainties in predicting building thermal load and weather condition,but also considers the degradation in the nZEB systems. Based on the proposed LCPA method,a two-stage method is proposed to improve the sizing of the nZEB systems.The study can improve the designers "understanding of the components"degradation impacts and the proposed method is effective in the life-cycle performance analysis and improvements of nZEBs. It is the first time that the impacts of degradation and uncertainties on nZEB LCP are analysed. Case studies showthat an nZEB might not fulfil its definition at all after some years due to component degradation,while the proposed two-stage design method can effectively alleviate this problem.展开更多
We investigate a one-dimensional acoustic metamaterial with a refractive index of near zero（RINZ） using an array of very thin elastic membranes located along a narrow waveguide pipe. The characteristics of the effec...We investigate a one-dimensional acoustic metamaterial with a refractive index of near zero（RINZ） using an array of very thin elastic membranes located along a narrow waveguide pipe. The characteristics of the effective density, refractive index, and phase velocity of the metamaterial indicate that, at the resonant frequency fm, the metamaterial has zero mass density and a phase transmission that is nearly uniform. We present a mechanism for dramatic acoustic energy squeezing and anomalous acoustic transmission by connecting the metamaterial to a normal waveguide with a larger cross-section. It is shown that at a specific frequency f1, transmission enhancement and energy squeezing are achieved despite the strong geometrical mismatch between the metamaterial and the normal waveguide. Moreover, to confirm the energy transfer properties, the acoustic pressure distribution, acoustic wave reflection coefficient, and energy transmission coefficient are also calculated. These results prove that the RINZ metamaterial provides a new design method for acoustic energy squeezing,super coupling, wave front transformation, and acoustic wave filtering.展开更多
Anisotropic metamaterial with only one component of the mass density tensor near zero （ADNZ） is proposed to control the sound wave propagation. We find that such an anisotropic metamaterial can be used to realize pe...Anisotropic metamaterial with only one component of the mass density tensor near zero （ADNZ） is proposed to control the sound wave propagation. We find that such an anisotropic metamaterial can be used to realize perfect bending waveguides. According to a coordinate transformation, the surface waves on the input and output interfaces of the ADNZ metamaterial induces the sound energy flow to be redistributed and match smoothly with the propagating modes inside the metamaterial waveguide. According to the theory of bending waveguide, we realize the ＂T＂-type sound shunting and convergence, as well as acoustic channel selection by embedding small-sized defects. Numerical calculations are performed to confirm the above effects.展开更多
INTRODUCTION Recent development has seen a drastic increase in energy use trends in Saudi Arabian buildings leading to a demand for an effective course of action for energy conservation and production.A case study-bas...INTRODUCTION Recent development has seen a drastic increase in energy use trends in Saudi Arabian buildings leading to a demand for an effective course of action for energy conservation and production.A case study-based research initiative explor-ing near-zero energy potential in Saudi Arabia was undertaken.A 4-bedroom detached single-family faculty residence at King Fahd University of Petroleum and Minerals(KFUPM)representing common regional housing design trends was utilized.A base case simulation model of the house was developed and val-idated using short-term and real-time energy consumption data.Three sets of strategies:passive design strategies,representative codes and standards,and renewable technology were employed in the new design of the house.Passive strategies com-prised a green roof,a ventilated wall system,a sloped roof,and insulation for thermal bridges.These alternatives helped reduce the annual energy consumption of the house by 17.2%.The most recent version of the International Energy Conserva-tion Code(IECC 2012)was also incorporated along with ASHRAE Standard 62.2 for ventilation.The code and standard together reduced the annual energy consumption by 31.1%.Solar PV was then utilized to reduce grid utilization for the remainder of the house energy loads.This strategy provided 24.7%of the total energy consumed annually.A combination of strategies showed a 70.7%energy consumption reduction,thereby decreasing the energy index of the house from 162.9 to 47.7 kWh/m^(2)/yr.The Zero Energy Building(ZEB)concepts and strategies utilized in this study demonstrate a socially responsible approach to achieving near-zero energy performance for an existing house.展开更多
In this paper,a novel SrEr_(2)O_(4)ceramic with relative densities exceeding 96% was synthesized by a conve ntional solid-state reaction method.Furthermo re,investigations of the correlations between its crystal struc...In this paper,a novel SrEr_(2)O_(4)ceramic with relative densities exceeding 96% was synthesized by a conve ntional solid-state reaction method.Furthermo re,investigations of the correlations between its crystal structure,microstructure,and microwave dielectric properties were carried out.Rietveld refinements show that the SrEr_(2)O_(4)ceramics crystallize in the orthorhombic with the space group Pnam.The SrEr_(2)O_(4)ceramic sintered at 1575℃ exhibits the good performance of permittivity(ε_(r))=14.44,quality factor(Q × f)=23271 GHz,and resonant temperature frequency coefficient(τ_(f))=-21.5 ppm/℃,which is attributed to its high lattice energy,packing fraction,and relative density.In addition,to satisfy the requirement of temperature stability for communication devices,near-zero τ_(f) value is obtained by adding CaTiO_(3) at the cost of a small quality factor loss.The SrEr_(2)O_(4)+1.25 wt% CaTiO_(3) composite exhibits decent properties with ε_(r)=18.57,Q×f=19940 GHz,and T_(f)=+3.99 ppm/℃,making it an ideal candidate for microwave band applications.展开更多
A series of high-entropy ceramics with the nominal composition(Mg_(0.5)Zn_(0.5))_(0.4+x)Li_(0.4)(Ca_(0.5)Sr_(0.5))_(0.4−x)TiO_(3)(0≤x≤0.4)has been successfully synthesized using the conventional solid-phase method.T...A series of high-entropy ceramics with the nominal composition(Mg_(0.5)Zn_(0.5))_(0.4+x)Li_(0.4)(Ca_(0.5)Sr_(0.5))_(0.4−x)TiO_(3)(0≤x≤0.4)has been successfully synthesized using the conventional solid-phase method.The(Mg_(0.5)Zn_(0.5))_(0.4+x)Li_(0.4)(Ca_(0.5)Sr_(0.5))_(0.4−x)TiO_(3)ceramics are confirmed to be composed of the main phase(Zn,Mg,Li)TiO_(3)and the secondary phase Ca_(0.5)Sr_(0.5)TiO_(3)by X-ray diffractometer,Rietveld refinement,and X-ray spectroscopy analysis.The quality factor(Q×f)of the samples is inversely proportional to the content of the Ca_(0.5)Sr_(0.5)TiO_(3)phase,and it is influenced by the density.The secondary phase and molecular polarizability(α_(T))have a significant impact on the dielectric constant(ε_(r))of the samples.Moreover,the temperature coefficient of resonant frequency(τ_(f))of the samples is determined by the distortion of[TiO_(6)]octahedra and the secondary phase.The results indicate tha(Mg_(0.5)Zn_(0.5))_(0.4+x)Li_(0.4)(Ca_(0.5)Sr_(0.5))_(0.4−x)TiO_(3)ceramics achieve ideal microwave dielectric properties(ε_(r)=17.6,Q×f=40900 GHz,τ_(f)=-8.6 ppm/℃)when x=0.35.(Mg_(0.5)Zn_(0.5))_(0.4+x)Li_(0.4)(Ca_(0.5)Sr_(0.5))_(0.4−x)TiO_(3)ceramics possess the potential for application in wireless communication,and a new approach has been provided to enhance the perform-ance of microwave dielectric ceramics.展开更多
基金supported by the National Key Research and Development Program of China(No.2022YFB4602600)the National Natural Science Foundation of China(No.52221001)Hunan Provincial Innovation Foundation for Postgraduate(No.CX20220406)。
文摘There is an urgent need for novel processes that can integrate different functional nanostructures onto specific substrates,so as to meet the fast-growing need for broad applications in nanoelectronics,nanophotonics,and fexible optoelectronics.Existing direct-lithography methods are difficult to use on fexible,nonplanar,and biocompatible surfaces.Therefore,this fabrication is usually accomplished by nanotransfer printing.However,large-scale integration of multiscale nanostructures with unconventional substrates remains challenging because fabrication yields and quality are often limited by the resolution,uniformity,adhesivity,and integrity of the nanostructures formed by direct transfer.Here,we proposed a resist-based transfer strategy enabled by near-zero adhesion,which was achieved by molecular modification to attain a critical surface energy interval.This approach enabled the intact transfer of wafer-scale,ultrathin-resist nanofilms onto arbitrary substrates with mitigated cracking and wrinkling,thereby facilitating the in situ fabrication of nanostructures for functional devices.Applying this approach,fabrication of three-dimensional-stacked multilayer structures with enhanced functionalities,nanoplasmonic structures with~10 nm resolution,and MoS2-based devices with excellent performance was demonstrated on specific substrates.These results collectively demonstrated the high stability,reliability,and throughput of our strategy for optical and electronic device applications.
基金financially supported by the National Key Research Program of China (No.2021YFB3800601)the Basic Science Center Project of the National Natural Science Foundation of China (No.52388201)the Fellowship of China Postdoctoral Science Foundation (No.2022M710073)。
文摘The practical application of CaSmAlO_(4)microwave dielectric ceramics is limited by its low quality factor(Q×f)value and non-zero temperature coefficient resonant frequency(τ_(f))value.In this study,we introduced Mg^(2+)-Ti^(4+)ionic pairs into CaSmAlO_(4),along with an excess of 9%Sm_(2)O_(3).The Mg^(2+)-Ti^(4+)ionic pairs substituted Al^(3+),and two phases simultaneously coexisted in the ceramics:CaSmAlO_(4) and Sm_(2)O_(3).As the doping concentration of Mg^(2+)-Ti^(4+)ionic pairs increased,the relative permittivity exhibited an upward trend,while the quality factor and resonant frequency temperature coefficient first rose and then descended.Remarkably,0.09Sm_(2)O_(3)-0.91CaSmAl_(0.7)Mg_(0.15)-Ti_(0.15)O_(4) sintered at 1450℃ yielded excellent dielectric properties:ε_(r)=19.72,Q×f=72,936 GHz,and τ_(f)=-0.044 ppm·℃^(-1).The factors influencing the microwave dielectric properties of 0.09Sm_(2)O_(3)-0.91CaSmAlO_(4)ceramics were further examined by considering the crystal structure,grain size,Lichtenecker logarithmic rule,tolerance factor and packing fraction.
基金the National Science and Technology Support Program of China(2015BAA05B02).
文摘Coal is the dominant energy source in China,and coal-fired power accounts for about half of coal consumption.However,air pollutant emissions from coal-fired power plants cause severe ecological and environmental problems.This paper focuses on near-zero emission technologies and applications for clean coal-fired power.The long-term operation states of near-zero emission units were evaluated,and synergistic and special mercury(Hg)control technologies were researched.The results show that the principle technical route of near-zero emission,which was applied to 101 of China’s coal-fired units,has good adaptability to coal properties.The emission concentrations of particulate matter(PM),SO2,and NOx were below the emission limits of gas-fired power plants and the compliance rates of the hourly average emission concentrations reaching near-zero emission in long-term operation exceeded 99%.With the application of near-zero emission technologies,the generating costs increased by about 0.01 CNY∙(kW∙h)-1.However,the total emissions of air pollutants decreased by about 90%,resulting in effective improvement of the ambient air quality.Furthermore,while the Hg emission concentrations of the near-zero emission units ranged from 0.51 to 2.89μg∙m^-3,after the modified fly ash(MFA)special Hg removal system was applied,Hg emission concentration reached as low as 0.29μg∙m^-3.The operating cost of this system was only 10%-15%of the cost of mainstream Hg removal technology using activated carbon injection.Based on experimental studies carried out in a 50000 m^3∙h^-1 coal-fired flue gas pollutant control pilot platform,the interaction relationships of multi-pollutant removal were obtained and solutions were developed for emissions reaching different limits.A combined demonstration application for clean coal-fired power,with the new“1123”eco-friendly emission limits of 1,10,20 mg∙m^-3,and 3μg∙m^-3,respectively,for PM,SO2,NOx,and Hg from near-zero emission coal-fired power were put forward and realized,providing engineering and technical support for the national enhanced pollution emission standards.
基金the earmarked fund for China Agriculture Research System(CARS-22)the National Key Research and Development Program of China(2017YFD0201802 and 2017YFD0201701)+1 种基金the National Natural Science Foundation of China(31672019,31870367 and 31871951)the Beijing Municipal Natural Science Foundation,China(6172030)。
文摘The geomagnetic field affects all living organisms on the Earth.In this study we investigated the developmental and behavioral effects of rearing Mythimna separata in a near-zero magnetic field(<500 n T)compared to the local geomagnetic field(approximately 50μT).The near-zero magnetic field produced by a Helmholtz coil system significantly lengthened larval and pupal development durations,increased male longevity,and reduced pupal weight,female reproduction,and the relative expression level of the vitellogenin(Vg)gene in newly emerged females.Moreover,the near-zero magnetic field had a considerable negative effect on the mating ratio of M.separata adults.In addition,the moths in the near-zero magnetic field displayed less flight activity late in the night than those in the Earth's normal geomagnetic field,indicating that the flight rhythm of M.separata may be affected by the near-zero magnetic field.Reduction in magnetic field intensity may have negative effects on the development and flight of oriental armyworm,with consequent additional effects on its migration.
基金supported by the National Natural Science Foundation of China(Grant Nos.11574276,U173112,and 41401384)the Project of Shandong Provincial Higher Educational Science and Technology Program,China(Grant No.J17KB127)+1 种基金the Science and Technology Development Plans of Binzhou City,China(Grant Nos.2014ZC0307 and 2015ZC0210)Binzhou University Research Fund Project,China(Grant Nos.BZXYG1513 and BZXYG1706)
文摘The Zr（0.5）Hf（0.5）VPO7 is successfully synthesized by the solid-state method with near-zero thermal expansion. Powder x-ray diffraction（XRD）, Raman spectroscopy, thermal dilatometry, and scanning electron microscopy（SEM） are used to investigate the structure, the phase transition, and the coefficient of thermal expansion（CTE） of Zr（0.5）Hf（0.5）VPO7. The investigation results show that the samples are of the single cubic type with a space group of Pa3ˉ at room temperature（RT）.It can be inferred that the superstructure is transformed from the 3 × 3 × 3 superstructure to the 1 × 1 × 1 ideal crystal in a temperature range between 310 K and 323 K. The CTE is measured by a dilatometer to be 0.59 × 10^（-6） K^（-1）（310 K–673 K）. The values of intrinsic（XRD） and extrinsic（dilatometric） thermal expansion are both near zero. The results show that Zr（0.5）Hf（0.5）VPO7 has near-zero thermal expansion behavior over a wide temperature range.
文摘Near-zero energy buildings( nZEBs) are considered as an effective solution to mitigating CO_2 emissions and reducing the energy usage in the building sector. A proper sizing of the nZEB systems( e. g. HVAC systems,energy supply systems,energy storage systems, etc.) is essential for achieving the desired annual energy balance,thermal comfort,and grid independence. Two significant factors affecting the sizing of nZEB systems are the uncertainties confronted by the building usage condition and weather condition,and the degradation effects in nZEB system components. The former factor has been studied by many researchers; however,the impact of degradation is still neglected in most studies. Degradation is prevalent in energy components of nZEB and inevitably leads to the deterioration of nZEB life-cycle performance. As a result,neglecting the degradation effects may lead to a system design which can only achieve the desired performance at the beginning several years. This paper,therefore,proposes a life-cycle performance analysis( LCPA) method for investigating the impact of degradation on the longitudinal performance of the nZEBs. The method not only integrates the uncertainties in predicting building thermal load and weather condition,but also considers the degradation in the nZEB systems. Based on the proposed LCPA method,a two-stage method is proposed to improve the sizing of the nZEB systems.The study can improve the designers "understanding of the components"degradation impacts and the proposed method is effective in the life-cycle performance analysis and improvements of nZEBs. It is the first time that the impacts of degradation and uncertainties on nZEB LCP are analysed. Case studies showthat an nZEB might not fulfil its definition at all after some years due to component degradation,while the proposed two-stage design method can effectively alleviate this problem.
基金supported by the National Natural Science Foundation of China(Grant Nos.61571222,11104142,and 11474160)the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20161009)+1 种基金the Qing Lan Project of Jiangsu Province,Chinathe Six Talent Peaks Project of Jiangsu Province,China
文摘We investigate a one-dimensional acoustic metamaterial with a refractive index of near zero（RINZ） using an array of very thin elastic membranes located along a narrow waveguide pipe. The characteristics of the effective density, refractive index, and phase velocity of the metamaterial indicate that, at the resonant frequency fm, the metamaterial has zero mass density and a phase transmission that is nearly uniform. We present a mechanism for dramatic acoustic energy squeezing and anomalous acoustic transmission by connecting the metamaterial to a normal waveguide with a larger cross-section. It is shown that at a specific frequency f1, transmission enhancement and energy squeezing are achieved despite the strong geometrical mismatch between the metamaterial and the normal waveguide. Moreover, to confirm the energy transfer properties, the acoustic pressure distribution, acoustic wave reflection coefficient, and energy transmission coefficient are also calculated. These results prove that the RINZ metamaterial provides a new design method for acoustic energy squeezing,super coupling, wave front transformation, and acoustic wave filtering.
基金Project supported by the National Basic Research Program of China(Grant No.2012CB921504)the National Natural Science Foundation of China(Grant No.11474160)+2 种基金the Fundamental Research Funds for the Central Universities,China(Grant No.020414380001)the State Key Laboratory of Acoustics,Chinese Academy of Sciences(Grant No.SKLA201609)the Priority Academic Program Development of Jiangsu Higher Education Institution,China
文摘Anisotropic metamaterial with only one component of the mass density tensor near zero （ADNZ） is proposed to control the sound wave propagation. We find that such an anisotropic metamaterial can be used to realize perfect bending waveguides. According to a coordinate transformation, the surface waves on the input and output interfaces of the ADNZ metamaterial induces the sound energy flow to be redistributed and match smoothly with the propagating modes inside the metamaterial waveguide. According to the theory of bending waveguide, we realize the ＂T＂-type sound shunting and convergence, as well as acoustic channel selection by embedding small-sized defects. Numerical calculations are performed to confirm the above effects.
文摘INTRODUCTION Recent development has seen a drastic increase in energy use trends in Saudi Arabian buildings leading to a demand for an effective course of action for energy conservation and production.A case study-based research initiative explor-ing near-zero energy potential in Saudi Arabia was undertaken.A 4-bedroom detached single-family faculty residence at King Fahd University of Petroleum and Minerals(KFUPM)representing common regional housing design trends was utilized.A base case simulation model of the house was developed and val-idated using short-term and real-time energy consumption data.Three sets of strategies:passive design strategies,representative codes and standards,and renewable technology were employed in the new design of the house.Passive strategies com-prised a green roof,a ventilated wall system,a sloped roof,and insulation for thermal bridges.These alternatives helped reduce the annual energy consumption of the house by 17.2%.The most recent version of the International Energy Conserva-tion Code(IECC 2012)was also incorporated along with ASHRAE Standard 62.2 for ventilation.The code and standard together reduced the annual energy consumption by 31.1%.Solar PV was then utilized to reduce grid utilization for the remainder of the house energy loads.This strategy provided 24.7%of the total energy consumed annually.A combination of strategies showed a 70.7%energy consumption reduction,thereby decreasing the energy index of the house from 162.9 to 47.7 kWh/m^(2)/yr.The Zero Energy Building(ZEB)concepts and strategies utilized in this study demonstrate a socially responsible approach to achieving near-zero energy performance for an existing house.
基金Porject supported by National Natural Science Foundation of China (61761015, 11664008)Guangxi Natural Science Foundation(2018GXNSFFA050001, 2024GXNSFDA010060)High-Level Innovation Team and Outstanding Scholar Program of Guangxi Institutes。
文摘In this paper,a novel SrEr_(2)O_(4)ceramic with relative densities exceeding 96% was synthesized by a conve ntional solid-state reaction method.Furthermo re,investigations of the correlations between its crystal structure,microstructure,and microwave dielectric properties were carried out.Rietveld refinements show that the SrEr_(2)O_(4)ceramics crystallize in the orthorhombic with the space group Pnam.The SrEr_(2)O_(4)ceramic sintered at 1575℃ exhibits the good performance of permittivity(ε_(r))=14.44,quality factor(Q × f)=23271 GHz,and resonant temperature frequency coefficient(τ_(f))=-21.5 ppm/℃,which is attributed to its high lattice energy,packing fraction,and relative density.In addition,to satisfy the requirement of temperature stability for communication devices,near-zero τ_(f) value is obtained by adding CaTiO_(3) at the cost of a small quality factor loss.The SrEr_(2)O_(4)+1.25 wt% CaTiO_(3) composite exhibits decent properties with ε_(r)=18.57,Q×f=19940 GHz,and T_(f)=+3.99 ppm/℃,making it an ideal candidate for microwave band applications.
基金supported by the Sichuan Science and Technology Program,China(No.2023YFQ0082)the Guangdong Provincial Key Laboratory of Electronic Functional Materials and Device,China(No.EFMD2022005Z)the State Key Laboratory of Advanced Technologies for Comprehensive Utilization of Platinum Metals,China(No.SKL-SPM-202021).
文摘A series of high-entropy ceramics with the nominal composition(Mg_(0.5)Zn_(0.5))_(0.4+x)Li_(0.4)(Ca_(0.5)Sr_(0.5))_(0.4−x)TiO_(3)(0≤x≤0.4)has been successfully synthesized using the conventional solid-phase method.The(Mg_(0.5)Zn_(0.5))_(0.4+x)Li_(0.4)(Ca_(0.5)Sr_(0.5))_(0.4−x)TiO_(3)ceramics are confirmed to be composed of the main phase(Zn,Mg,Li)TiO_(3)and the secondary phase Ca_(0.5)Sr_(0.5)TiO_(3)by X-ray diffractometer,Rietveld refinement,and X-ray spectroscopy analysis.The quality factor(Q×f)of the samples is inversely proportional to the content of the Ca_(0.5)Sr_(0.5)TiO_(3)phase,and it is influenced by the density.The secondary phase and molecular polarizability(α_(T))have a significant impact on the dielectric constant(ε_(r))of the samples.Moreover,the temperature coefficient of resonant frequency(τ_(f))of the samples is determined by the distortion of[TiO_(6)]octahedra and the secondary phase.The results indicate tha(Mg_(0.5)Zn_(0.5))_(0.4+x)Li_(0.4)(Ca_(0.5)Sr_(0.5))_(0.4−x)TiO_(3)ceramics achieve ideal microwave dielectric properties(ε_(r)=17.6,Q×f=40900 GHz,τ_(f)=-8.6 ppm/℃)when x=0.35.(Mg_(0.5)Zn_(0.5))_(0.4+x)Li_(0.4)(Ca_(0.5)Sr_(0.5))_(0.4−x)TiO_(3)ceramics possess the potential for application in wireless communication,and a new approach has been provided to enhance the perform-ance of microwave dielectric ceramics.
