A field study was set up to compare dry matter accumulation and grain yield of 3 different types of film mulching, namely FFC(full film muched on tiny ridges covered with soil), PFC(full film muched covered with soil)...A field study was set up to compare dry matter accumulation and grain yield of 3 different types of film mulching, namely FFC(full film muched on tiny ridges covered with soil), PFC(full film muched covered with soil), and PF(full film muched with no cover). The experiment was laid out in a complete random design with 3 replications at northwest(34°40′N, 105°06′E) of China. This study determined that(1) film mulching treatment increased leaf area and dry matter accumulation of oil flax in semi-arid areas;(2) accumulation of dry matter under PFC treatment was markedly higher than other treatments except anthesis stage;(3) average grain yield of oil flax under film mulching treatment was 52.67%-60.33% higher than flat plot without mulched or ridge(CK) treatment;(4) grain yield of oil flax was substantially correlated with plant height, grain number and 1,000 kernels weight. This study demonstrated that film mulching has significant effects on crop grain yield improvement in the northwest of China.展开更多
A melilite Ba2CuGe2O7 ceramic was characterized by low sintering temperature and moderate microwave dielectric properties.Sintered at 960℃,the Ba2CuGe2O7 ceramic had a high relative density 97%,a low relative permitt...A melilite Ba2CuGe2O7 ceramic was characterized by low sintering temperature and moderate microwave dielectric properties.Sintered at 960℃,the Ba2CuGe2O7 ceramic had a high relative density 97%,a low relative permittivity(εr)9.43,a quality factor(Q×f)of 20,000 GHz,and a temperature coefficient of resonance frequency(τf)-76 ppm/℃.To get a deep understanding of the relationship between composition,structure,and dielectric performances,magnesium substitution for copper in Ba2CuGe2O7 was conducted.Influences of magnesium doping on the sintering behavior,crystal structure,and microwave dielectric properties were studied.Mg doping in Ba2CuGe2O7 caused negligible changes in the macroscopic crystal structure,grain morphology,and size distribution,while induced visible variation in the local structure as revealed by Raman analysis.Microwave dielectric properties exhibit a remarkable dependence on composition.On increasing the magnesium content,the relative permittivity featured a continuous decrease,while both the quality factor and the temperature coefficient of resonance frequency increased monotonously.Such variations in dielectric performances were clarified in terms of the polarizability,packing fraction,and band valence theory.展开更多
Single phase Li_(2)W_(2)O_(7) with anorthic structure was prepared by the conventional solid-state reaction method at 550℃ and the anorthic structure was stable up to 660℃.The dielectric properties at radio frequenc...Single phase Li_(2)W_(2)O_(7) with anorthic structure was prepared by the conventional solid-state reaction method at 550℃ and the anorthic structure was stable up to 660℃.The dielectric properties at radio frequency(RF)and microwave frequency range were characterized.The sample sintered at 640℃ exhibited the optimum microwave dielectric properties with a relative permittivity of 12.2,a quality factor value of 17,700 GHz(at 9.8 GHz),and a temperature coefficient of the resonant frequency of232 ppm/℃ as well as a high relative density~94.1%.Chemical compatibility measurement indicated Li_(2)W_(2)O_(7) did not react with aluminum electrodes when sintered at 640℃ for 4 h.展开更多
The Asian longhorn beetle (ALB) Anoplophora glabripennis is one of the most successful and most feared invasive insect species worldwide. This review covers recent research concerning the distribution of and damage ca...The Asian longhorn beetle (ALB) Anoplophora glabripennis is one of the most successful and most feared invasive insect species worldwide. This review covers recent research concerning the distribution of and damage caused by ALB, as well as major efforts to control and manage ALB in China. The distribution and destruction range of ALB have continued to expand over the past decade worldwide, and the number of interceptions has remained high. Detection and monitoring methods for the early discovery of ALB have diversified, with advances in semiochemical research and using satellite remote sensing in China. Ecological control of ALB in China involves planting mixtures of preferred and resistant tree species, and this practice can prevent outbreaks. In addition, strategies for chemical and biological control of ALB have achieved promising results during the last decade in China, especially the development of insecticides targeting different stages of ALB, and applying Dastarcus helophoroides and Dendrocopos major as biocontrol agents. Finally, we analyze recommendations for ALB prevention and management strategies based on native range and invasive area research. This information will hopefully help some invaded areas where the target is containment of ALB.展开更多
High-entropy effect is a novel design strategy to optimize properties and explore novel materials.In this work,(La_(1/5)Nd_(1/5)Sm_(1/5)Ho_(1/5)Y_(1/5))NbO_(4)(5RNO)high-entropy microwave dielectric ceramics were succ...High-entropy effect is a novel design strategy to optimize properties and explore novel materials.In this work,(La_(1/5)Nd_(1/5)Sm_(1/5)Ho_(1/5)Y_(1/5))NbO_(4)(5RNO)high-entropy microwave dielectric ceramics were successfully prepared in the sintering temperature(S.T.)range of 1210–1290℃via a solid-phase reaction route,and medium-entropy(La_(1/3)Nd_(1/3)Sm_(1/3))NbO_(4) and(La_(1/4)Nd_(1/4)Sm_(1/4)Ho_(1/4))NbO_(4)(3RNO and 4RNO)ceramics were compared.The effects of the entropy(S)on crystal structure,phase transition,and dielectric performance were evaluated.The entropy increase yields a significant increase in a phase transition temperature(from monoclinic fergusonite to tetragonal scheelite structure).Optimal microwave dielectric properties were achieved in the high-entropy ceramics(5RNO)at the sintering temperature of 1270℃for 4 h with a relative density of 98.2%and microwave dielectric properties of dielectric permittirity(ε_(r))=19.48,quality factor(Q×f)=47,770 GHz,and resonant frequency temperature coefficient(τ_(f))=–13.50 ppm/℃.This work opens an avenue for the exploration of novel microwave dielectric material and property optimization via entropy engineering.展开更多
AB_(2)O_(4)-type spinels with low relative permittivity(ε_(τ))and high quality factor(Q×f)are crucial to high-speed signal propagation systems.In this work,Zn^(2+)/Ge^(4+) co-doping to substitute Ga in ZnGa_(2)...AB_(2)O_(4)-type spinels with low relative permittivity(ε_(τ))and high quality factor(Q×f)are crucial to high-speed signal propagation systems.In this work,Zn^(2+)/Ge^(4+) co-doping to substitute Ga in ZnGa_(2)O_(4) was designed to lower the sintering temperature and adjust the thermal stability of resonance frequency simultaneously.Zn_(1+2)Ga_(2-2x)Ge_(x)O_(4)(0.1≤x≤0.5)ceramics were synthesised by the conventional solid state method.Zn^(2+)/Ge^(4+) co-substitution induced minimal variation in the macroscopical spinel structure,which effectively lowered the sintering temperature from 1385 to 1250℃.All compositions crystallized in a normal spinel structure and exhibited dense microstructures and excellent microwave dielectric properties.The compositional dependent quality factor was related to the microstructural variation,being confirmed by Raman features.A composition with x=0.3 shows the best dielectric properties with ε_(τ) ≈10.09,Q×f≈112,700 THz,and ε_(τ) ≈-75.6 ppm/℃.The negative τf value was further adjusted to be near-zero through the formation of composite ceramics with TiO_(2).展开更多
Ca_(5)Nb_(4)TiO_(17) ceramics with 0≤x≤0.4 were prepared through a solid-state reaction method.Effects of zinc substitution on sintering behavior and microwave dielectric properties of Ca_(5)Nb_(4)TiO_(17) ceramics ...Ca_(5)Nb_(4)TiO_(17) ceramics with 0≤x≤0.4 were prepared through a solid-state reaction method.Effects of zinc substitution on sintering behavior and microwave dielectric properties of Ca_(5)Nb_(4)TiO_(17) ceramics were investigated.The sintering temperature was significantly lowered from 1480℃for pure Ca_(5)Nb_(4)TiO_(17) to 1260℃ for x=0.4.The microwave dielectric properties are strongly correlated with the composition.It is worth noting that the temperature cofficient of resonant frequency(τf)displays a tendency toward positive value,ranging from-126.4 ppm/℃ to-8.6 ppm/℃.A temperature stable microwave ceramic with dielectric constant of 52 and Q×f value of 9937GHz is achieved at x=0.4 and is a potential candidate for application as cores in dielectrically loaded antennas.展开更多
Barium-doped Ca_(2)Nb_(2)O_(7)ceramics were prepared in the form of Ca_(2-x)Ba_(x)Nb_(2)O_(7)(0≤x≤0.6)by solid-state reaction.The solubility limit of barium in Ca_(2)Nb_(2)O_(7)was found to be x=0.4 based on X-ray d...Barium-doped Ca_(2)Nb_(2)O_(7)ceramics were prepared in the form of Ca_(2-x)Ba_(x)Nb_(2)O_(7)(0≤x≤0.6)by solid-state reaction.The solubility limit of barium in Ca_(2)Nb_(2)O_(7)was found to be x=0.4 based on X-ray diffraction and Raman spectroscopy analysis.When x≤0.4,Ca_(2-x)Ba_(x)Nb_(2)O_(7)solid solutions with a monoclinic perovskites-like layered structure(PLS)were formed,whereas beyond x=0.4,a secondary phase CaNb_(2)O_(6) was detected.The dielectric properties obviously depended on the barium substitution.With increasing barium amount,the dielectric constant increased from 33.5 for pure Ca_(2)Nb_(2)O_(7)to 38.6 for x=0.4(f=1 MHz).The Curie temperature(T_(c)) of the x=0.1 sample was 1280±5℃.The phase transition was confirmed to be the second order.展开更多
A series of ceramics with a general formula,La_(2)Ti_(2-x)Ta_(x)O_(7),in which x=0.05;0.1;0.2;and 0.3,were prepared by Spark Plasma Sintering(SPS).Effects of tantalum substitution for titanium on the structure,dielect...A series of ceramics with a general formula,La_(2)Ti_(2-x)Ta_(x)O_(7),in which x=0.05;0.1;0.2;and 0.3,were prepared by Spark Plasma Sintering(SPS).Effects of tantalum substitution for titanium on the structure,dielectric,and piezoelectric properties were studied.Results revealed that the structure changed gradually from 4-layer to 3-layer due to the higher valence of Ta.The solid solution limit of tantalum in La_(2)Ti_(2)O_(7)lattice was in the proximity of x=0.2.The ferroelectric Curie temperature(Tc)decreased with increasing tantalum doping content.dc resistivity reached a maximum value at x=0.2 with a value of~1.0×10^(8)Ωcm at 600℃.The influence of texture on the piezoelectric properties of La_(2)Ti_(2-x)Ta_(x)O_(7)ceramics was also investigated.A maximum d_(33)value~2:1 pC/N was obtained at x=0.2.展开更多
Two series of B-site deficient perovskites Ba_(5+m)Ti_(m)Nb_(4)O_(15+3m)(m=1,2,3)and Sr_(3+m)LaTi_(m)Nb_(3)O_(12+3m)(m=0,1,2)with the general formula A_(n)B_(n-1)O_(3n)(n=4-8;A=Ba,Sr,La;B=Nb,Ti)have been synthesized,a...Two series of B-site deficient perovskites Ba_(5+m)Ti_(m)Nb_(4)O_(15+3m)(m=1,2,3)and Sr_(3+m)LaTi_(m)Nb_(3)O_(12+3m)(m=0,1,2)with the general formula A_(n)B_(n-1)O_(3n)(n=4-8;A=Ba,Sr,La;B=Nb,Ti)have been synthesized,and their structure and microwave dielectric properties have been investigated.The effects of n(number of octahedra layers within a perovskite blocks)on structure and properties are investigated.The values of dielectric constantε_(r)and temperature coe±cient of resonant frequencyτ_(f)gradually increase,but quality factors Q×f values significantly decreases as the values of n increase.展开更多
基金financial support provided by China Agriculture Research System of Construct Special (CARS-14-116)the National Natural Science Programs of China (31360315, 31460331)Fuxi Outstanding Talent Cultivation Plan of Gansu Agricultural University (Gaufx-02J05)
文摘A field study was set up to compare dry matter accumulation and grain yield of 3 different types of film mulching, namely FFC(full film muched on tiny ridges covered with soil), PFC(full film muched covered with soil), and PF(full film muched with no cover). The experiment was laid out in a complete random design with 3 replications at northwest(34°40′N, 105°06′E) of China. This study determined that(1) film mulching treatment increased leaf area and dry matter accumulation of oil flax in semi-arid areas;(2) accumulation of dry matter under PFC treatment was markedly higher than other treatments except anthesis stage;(3) average grain yield of oil flax under film mulching treatment was 52.67%-60.33% higher than flat plot without mulched or ridge(CK) treatment;(4) grain yield of oil flax was substantially correlated with plant height, grain number and 1,000 kernels weight. This study demonstrated that film mulching has significant effects on crop grain yield improvement in the northwest of China.
基金National Natural Science Foundation of China(No.62061011)National Key R&D Program of China(No.2017YFB0406300)+1 种基金Natural Science Foundation of Guangxi Zhuang Autonomous Region(No.2018GXNSFAA281253)high-level innovation team and outstanding scholar program of Guangxi institutes.
文摘A melilite Ba2CuGe2O7 ceramic was characterized by low sintering temperature and moderate microwave dielectric properties.Sintered at 960℃,the Ba2CuGe2O7 ceramic had a high relative density 97%,a low relative permittivity(εr)9.43,a quality factor(Q×f)of 20,000 GHz,and a temperature coefficient of resonance frequency(τf)-76 ppm/℃.To get a deep understanding of the relationship between composition,structure,and dielectric performances,magnesium substitution for copper in Ba2CuGe2O7 was conducted.Influences of magnesium doping on the sintering behavior,crystal structure,and microwave dielectric properties were studied.Mg doping in Ba2CuGe2O7 caused negligible changes in the macroscopic crystal structure,grain morphology,and size distribution,while induced visible variation in the local structure as revealed by Raman analysis.Microwave dielectric properties exhibit a remarkable dependence on composition.On increasing the magnesium content,the relative permittivity featured a continuous decrease,while both the quality factor and the temperature coefficient of resonance frequency increased monotonously.Such variations in dielectric performances were clarified in terms of the polarizability,packing fraction,and band valence theory.
基金This work was supported by Natural Science Foundation of China(Nos.21261007,21561008 and 51502047)the Natural Science Foundation of Guangxi Zhuang Autonomous Region(Nos.2015GXNSFBA139234,2015GXNSFFA139003,2016GXNSFBA380134 and 2016GXNSFAA380018)+2 种基金Project of Scientific Research and Technical Exploitation Program of Guilin(2016010702-2)Projects of Education Department of Guangxi Zhuang Autonomous Region(Nos.YB2014160,KY2015YB341 and KY2015YB122)the talent cultivation project for innovation and entrepreneurship of Beibu Gulf of Guangxi Zhuang Autonomous Region(2015-09).
文摘Single phase Li_(2)W_(2)O_(7) with anorthic structure was prepared by the conventional solid-state reaction method at 550℃ and the anorthic structure was stable up to 660℃.The dielectric properties at radio frequency(RF)and microwave frequency range were characterized.The sample sintered at 640℃ exhibited the optimum microwave dielectric properties with a relative permittivity of 12.2,a quality factor value of 17,700 GHz(at 9.8 GHz),and a temperature coefficient of the resonant frequency of232 ppm/℃ as well as a high relative density~94.1%.Chemical compatibility measurement indicated Li_(2)W_(2)O_(7) did not react with aluminum electrodes when sintered at 640℃ for 4 h.
基金supported by the Chinese National Natural Science Foundation(32160379)the Fundamental Research Funds for the Central Universities(BFUKF202104)+1 种基金the Gansu Provincial Natural Science Foundation(20JR10R526)the Fuxi young talents training program of Gansu Agricultural University(Gaufx-04Y08).
文摘The Asian longhorn beetle (ALB) Anoplophora glabripennis is one of the most successful and most feared invasive insect species worldwide. This review covers recent research concerning the distribution of and damage caused by ALB, as well as major efforts to control and manage ALB in China. The distribution and destruction range of ALB have continued to expand over the past decade worldwide, and the number of interceptions has remained high. Detection and monitoring methods for the early discovery of ALB have diversified, with advances in semiochemical research and using satellite remote sensing in China. Ecological control of ALB in China involves planting mixtures of preferred and resistant tree species, and this practice can prevent outbreaks. In addition, strategies for chemical and biological control of ALB have achieved promising results during the last decade in China, especially the development of insecticides targeting different stages of ALB, and applying Dastarcus helophoroides and Dendrocopos major as biocontrol agents. Finally, we analyze recommendations for ALB prevention and management strategies based on native range and invasive area research. This information will hopefully help some invaded areas where the target is containment of ALB.
基金Fundamental Research Funds of Shaanxi Key Laboratory of Artificially-Structured Functional Materials and Devices(No.AFMD-KFJJ-21210)the financial support from the National Natural Science Foundation of China(No.62061011)Guangxi Key Laboratory Fund of Embedded Technology and Intelligent System(No.2020-1-6).
文摘High-entropy effect is a novel design strategy to optimize properties and explore novel materials.In this work,(La_(1/5)Nd_(1/5)Sm_(1/5)Ho_(1/5)Y_(1/5))NbO_(4)(5RNO)high-entropy microwave dielectric ceramics were successfully prepared in the sintering temperature(S.T.)range of 1210–1290℃via a solid-phase reaction route,and medium-entropy(La_(1/3)Nd_(1/3)Sm_(1/3))NbO_(4) and(La_(1/4)Nd_(1/4)Sm_(1/4)Ho_(1/4))NbO_(4)(3RNO and 4RNO)ceramics were compared.The effects of the entropy(S)on crystal structure,phase transition,and dielectric performance were evaluated.The entropy increase yields a significant increase in a phase transition temperature(from monoclinic fergusonite to tetragonal scheelite structure).Optimal microwave dielectric properties were achieved in the high-entropy ceramics(5RNO)at the sintering temperature of 1270℃for 4 h with a relative density of 98.2%and microwave dielectric properties of dielectric permittirity(ε_(r))=19.48,quality factor(Q×f)=47,770 GHz,and resonant frequency temperature coefficient(τ_(f))=–13.50 ppm/℃.This work opens an avenue for the exploration of novel microwave dielectric material and property optimization via entropy engineering.
基金support from the National Natural Science Foundation of China(No.62061011)the Guangxi Zhuang Autonomous Region(Nos.2018GXNSFAA281253 and 2019GXNSFGA245006)the High-Level Innovation Team and Outstanding Scholar Program of Guangxi Institutes.
文摘AB_(2)O_(4)-type spinels with low relative permittivity(ε_(τ))and high quality factor(Q×f)are crucial to high-speed signal propagation systems.In this work,Zn^(2+)/Ge^(4+) co-doping to substitute Ga in ZnGa_(2)O_(4) was designed to lower the sintering temperature and adjust the thermal stability of resonance frequency simultaneously.Zn_(1+2)Ga_(2-2x)Ge_(x)O_(4)(0.1≤x≤0.5)ceramics were synthesised by the conventional solid state method.Zn^(2+)/Ge^(4+) co-substitution induced minimal variation in the macroscopical spinel structure,which effectively lowered the sintering temperature from 1385 to 1250℃.All compositions crystallized in a normal spinel structure and exhibited dense microstructures and excellent microwave dielectric properties.The compositional dependent quality factor was related to the microstructural variation,being confirmed by Raman features.A composition with x=0.3 shows the best dielectric properties with ε_(τ) ≈10.09,Q×f≈112,700 THz,and ε_(τ) ≈-75.6 ppm/℃.The negative τf value was further adjusted to be near-zero through the formation of composite ceramics with TiO_(2).
基金supported by the National Basic Research Program of China(2009CB623306)International Science&Technology Cooperation Program of China(2013DFR50470).
文摘Ca_(5)Nb_(4)TiO_(17) ceramics with 0≤x≤0.4 were prepared through a solid-state reaction method.Effects of zinc substitution on sintering behavior and microwave dielectric properties of Ca_(5)Nb_(4)TiO_(17) ceramics were investigated.The sintering temperature was significantly lowered from 1480℃for pure Ca_(5)Nb_(4)TiO_(17) to 1260℃ for x=0.4.The microwave dielectric properties are strongly correlated with the composition.It is worth noting that the temperature cofficient of resonant frequency(τf)displays a tendency toward positive value,ranging from-126.4 ppm/℃ to-8.6 ppm/℃.A temperature stable microwave ceramic with dielectric constant of 52 and Q×f value of 9937GHz is achieved at x=0.4 and is a potential candidate for application as cores in dielectrically loaded antennas.
基金Natural Science Foundation of China(Nos.21561008 and 51502047)Natural Science Foundation of Guangxi Zhuang Autonomous Region(Nos.2015GXNSFBA139234 and 2015GXNSFFA139003,2016GXNSFBA380134,and 2016GXNSFAA380018)+1 种基金Project of Scientific Research and Technical Exploitation Program of Guilin(2016010702-2)talent cultivation project for innovation and entrepreneurship of Beibu Gulf of Guangxi Zhuang Autonomous Region(2015-09).
文摘Barium-doped Ca_(2)Nb_(2)O_(7)ceramics were prepared in the form of Ca_(2-x)Ba_(x)Nb_(2)O_(7)(0≤x≤0.6)by solid-state reaction.The solubility limit of barium in Ca_(2)Nb_(2)O_(7)was found to be x=0.4 based on X-ray diffraction and Raman spectroscopy analysis.When x≤0.4,Ca_(2-x)Ba_(x)Nb_(2)O_(7)solid solutions with a monoclinic perovskites-like layered structure(PLS)were formed,whereas beyond x=0.4,a secondary phase CaNb_(2)O_(6) was detected.The dielectric properties obviously depended on the barium substitution.With increasing barium amount,the dielectric constant increased from 33.5 for pure Ca_(2)Nb_(2)O_(7)to 38.6 for x=0.4(f=1 MHz).The Curie temperature(T_(c)) of the x=0.1 sample was 1280±5℃.The phase transition was confirmed to be the second order.
基金supported by the National Basic Research Program of China(2009CB623306)International Science&Technology Cooperation Program of China(2013DFR50470)China Scholarship Council。
文摘A series of ceramics with a general formula,La_(2)Ti_(2-x)Ta_(x)O_(7),in which x=0.05;0.1;0.2;and 0.3,were prepared by Spark Plasma Sintering(SPS).Effects of tantalum substitution for titanium on the structure,dielectric,and piezoelectric properties were studied.Results revealed that the structure changed gradually from 4-layer to 3-layer due to the higher valence of Ta.The solid solution limit of tantalum in La_(2)Ti_(2)O_(7)lattice was in the proximity of x=0.2.The ferroelectric Curie temperature(Tc)decreased with increasing tantalum doping content.dc resistivity reached a maximum value at x=0.2 with a value of~1.0×10^(8)Ωcm at 600℃.The influence of texture on the piezoelectric properties of La_(2)Ti_(2-x)Ta_(x)O_(7)ceramics was also investigated.A maximum d_(33)value~2:1 pC/N was obtained at x=0.2.
基金This work was supported by Natural Science Foundation of China(No.50962004,and No.21061004)Natural Science Foundation of Guangxi(No.0832003Z and No.0832001),and Programs for New Century Excellent Talents in Guangxi(No.2006202).
文摘Two series of B-site deficient perovskites Ba_(5+m)Ti_(m)Nb_(4)O_(15+3m)(m=1,2,3)and Sr_(3+m)LaTi_(m)Nb_(3)O_(12+3m)(m=0,1,2)with the general formula A_(n)B_(n-1)O_(3n)(n=4-8;A=Ba,Sr,La;B=Nb,Ti)have been synthesized,and their structure and microwave dielectric properties have been investigated.The effects of n(number of octahedra layers within a perovskite blocks)on structure and properties are investigated.The values of dielectric constantε_(r)and temperature coe±cient of resonant frequencyτ_(f)gradually increase,but quality factors Q×f values significantly decreases as the values of n increase.
