The oscillatory behavior of neutral differential equation with positive and negative coefficients is investigated by mathematics analysis technique and the fixed point principle. Some sufficient conditions for oscilla...The oscillatory behavior of neutral differential equation with positive and negative coefficients is investigated by mathematics analysis technique and the fixed point principle. Some sufficient conditions for oscillation of neutral differential equation with positive and negative coefficients are obtained.展开更多
Dense nano-grained Ni_(0.7)Mn_(2.3O4) negative temperature coefficient(NTC) thermistors were fabricated by a novel two-step sintering approach that combines rapid sintering and principle of conventional two-step sinte...Dense nano-grained Ni_(0.7)Mn_(2.3O4) negative temperature coefficient(NTC) thermistors were fabricated by a novel two-step sintering approach that combines rapid sintering and principle of conventional two-step sintering technique.Samples were sintered at 1042℃ for 30 s in the first rapid step and then at 850-950℃ for 20 h in the second soaking step.Crystal phase,microstructure and electrical properties of sintered samples were studied by X-ray diffraction(XRD),scanning electron microscopy(SEM),resistance temperature relationship and aging performance.Sintered samples show a single-phase cubic spinel structure and indicate a high relative density ranging from 84% to 91% of the theoretical density.Moreover,average grain sizes of sintered samples under SEM are distributed between 254 and 570 nm.Meanwhile,the resistivity and the aging coefficient significantly decrease when soaking sintering temperature rises.In addition,the obtained material constant(B) ranges from 3931 to 3981 K.Ni_(0.7)Mn_(2.3)O_(4)-3(soaking at 900℃) and Ni_(0.7)Mn_(2.3O4)-4(soaking at 950℃) present little aging behavior,implying great electrical stability.展开更多
A neutral difference equation with positive and negative coefficientsΔ(x n-c nx n-k )+p nx n-l -q nx n-r =0, n=0,1,2,...,is considered and a sufficient condition for the global attractivity of the ze...A neutral difference equation with positive and negative coefficientsΔ(x n-c nx n-k )+p nx n-l -q nx n-r =0, n=0,1,2,...,is considered and a sufficient condition for the global attractivity of the zero solution of this equation is obtained, which improves and extends the all known results in the literature.展开更多
In this paper the sufficient conditions for the existence of positive solutions of the neutral difference equations with positive and negative coefficients are established. The results improve some known conclusions i...In this paper the sufficient conditions for the existence of positive solutions of the neutral difference equations with positive and negative coefficients are established. The results improve some known conclusions in the literature.展开更多
The change of the temperature coefficient of resistivity (a) with the particle size, dp, and the grain size, dc, in the nanostructured Ag bulk samples was investigated. dp and dc were controlled by heating the nano-Ag...The change of the temperature coefficient of resistivity (a) with the particle size, dp, and the grain size, dc, in the nanostructured Ag bulk samples was investigated. dp and dc were controlled by heating the nano-Ag powders over the temperature range from 393 to 453 K. The electrical resistance measurements of the nanostructured Ag bulk samples obtained by compacting the Ag powders after heat treatments showed a change in the sign of a with dP and dc. When dp and dc are smaller or equal to 18 and 11 nm below room temperature or 20 and 12 nm above room temperature, respectively, the sign of the temperature coefficient of resistivity changes from positive to negative. The negative a arises mainly from the high resistivity induced by the particle interfaces with very lowly ordered or even disordered structure, a large volume fraction of interfaces and impurities existing in the interfaces, and the quantum size effect appearing in the nano-Ag grains.展开更多
In this paper we consider the class ∑^＊（p,α,β,k,c） consisting of analytic functions with negativecoefficients and fixed second coefficient. The object of the present paper is to give coefficient estimates, conve...In this paper we consider the class ∑^＊（p,α,β,k,c） consisting of analytic functions with negativecoefficients and fixed second coefficient. The object of the present paper is to give coefficient estimates, convex linear combinations, some distortion theorems and radii of starlikeness and convexity for f（z） in the class ∑^＊（p,α,β,k,c） .展开更多
This paper suggests a scheme of electromagnetic chirality-induced negative refraction utilizing magneto-lectric cross coupling in a four-level atomic system. The negative refraction can be achieved with the two chiral...This paper suggests a scheme of electromagnetic chirality-induced negative refraction utilizing magneto-lectric cross coupling in a four-level atomic system. The negative refraction can be achieved with the two chirality coefficients having the same amplitude but the opposite phase, without requiring the simultaneous presence of an electric-dipole and a magnetic-dipole transition near the same transition frequency.展开更多
The electrical properties of high-entropy ceramics(HECs)have been extensively studied in recent years due to their unique structural characteristics and fascinating functional properties induced by entropy engineering...The electrical properties of high-entropy ceramics(HECs)have been extensively studied in recent years due to their unique structural characteristics and fascinating functional properties induced by entropy engineering.Novel high-entropy(Sm_(0.2)Eu_(0.2)Gd_(0.2)Ho_(0.2)Yb_(0.2))CrO_(3)(HE-RECrO_(3))nanofibers were prepared by electro spinning.This work demonstrates that HE-RECrO_(3)nanofibe rs were successfully synthesized at a low temperature(800℃),which is approximately 400℃lower than the temperatures at which chromate ceramics were synthesized via the sol-gel method and the solid-state reaction method.The resistivity of HE-RECrO_(3)nanofibers decreases exponentially with increasing temperature from 25 to600℃.The logarithm of the resistivity is linearly related to the inverse of the temperature,confirming the negative temperature coefficient property of HE-RECrO_(3)nanofibers.The B_(25/50)value of the HERECrO_(3)nanofibers reaches 4072 K.In conclusion,HE-RECrO_(3)nanofibers are expected to be potential candidates for negative-temperature-coefficient(NTC)thermistors.展开更多
Negative thermal expansion （NTE） ZrW2O8 powders were prepared by step-by-step solid-state reaction with ZrO2 and WO3 powders. The coefficient of thermal expansion （CTE） of the as-prepared ZrW208 was around -5.08&#...Negative thermal expansion （NTE） ZrW2O8 powders were prepared by step-by-step solid-state reaction with ZrO2 and WO3 powders. The coefficient of thermal expansion （CTE） of the as-prepared ZrW208 was around -5.08×10^-6 K^-1 at 20-700℃. Different amounts of ZrW208 powders were added in BTDA-ODA polyamic acid to form polyimide/ZrW2O8 composites （PI/ZrW2O8）. With the increment of ZrW2O8, experimental results show that ZrW2O8 powders can significantly enhance the thermal stability of the composites, and reduce the thermal expansion. A 50 wt pct ZrW2O8 addition can give rise to a 31% reduction of CTE. It is suggested that the PI/ZrW2O8 composites have potential applications in high performance microelectronic devices.展开更多
Y^3＋-doped （Bi 1/2 Na 1/2） TiO 3-CaTiO 3-BaTiO 3 （BNCBT） positive temperature coefficient of resistivity （PTCR） ceramics sintered in air atmosphere were investigated in this study. （Bi 1/2 Na 1/2） TiO 3 （BNT...Y^3＋-doped （Bi 1/2 Na 1/2） TiO 3-CaTiO 3-BaTiO 3 （BNCBT） positive temperature coefficient of resistivity （PTCR） ceramics sintered in air atmosphere were investigated in this study. （Bi 1/2 Na 1/2） TiO 3 （BNT） component can remarkably increase the onset temperature T c of PTCR ceramics with the expense of the resistivity R 25 increase. CaTiO 3 （9–27 mol%） component can decrease the resistivity, and adjust the effects of BNT phase on the T c point. For the sample containing 3 mol% CaTiO 3 , T c raises from 122 ℃ to 153 ℃ when only 0.6 mol% BNT added, while for the ones with higher CaTiO 3 content （9–27 mol%）, T c is only increased by a rate of 8–9℃/1.0 mol% BNT. The effects of BNT and CaTiO 3 components on R25/Rmin （negative temperature coefficient effect） are also discussed.展开更多
We investigate oscillation of certain second order neutral dynamic equations of Emden-Fowler type with positive and negative coefficients. We use some different techniques and apply Riccati transformation to establish...We investigate oscillation of certain second order neutral dynamic equations of Emden-Fowler type with positive and negative coefficients. We use some different techniques and apply Riccati transformation to establish new oscillatory criteria which include two necessary and sufficient conditions. Moreover, we point out that how the power γ plays its role. Some interesting examples are given to illustrate the versatility of our results.展开更多
Negative temperature coefficient(NTC)thermistor plays a crucial role in science research and engineering applications for precise temperature monitoring.Although great progress has been achieved in NTC materials,enhan...Negative temperature coefficient(NTC)thermistor plays a crucial role in science research and engineering applications for precise temperature monitoring.Although great progress has been achieved in NTC materials,enhancing sensitivity and maintaining this high sensitivity along with linearity across extensive temperature ranges remain a significant challenge.In this study,we introduce a diamondbased thermistor(DT)characterized by its outstanding sensitivity,swift response time,and broad temperature monitoring capabilities.The temperature constant B for this DT,measured from 30 to 300°C(B30/300),achieves an exceptional value of 8012 K,which notably exceeds the temperature sensing capabilities of previously reported NTC thermistors within this extensive range.Moreover,diamond’s unique thermal conductivity and stability significantly boost the response speed and durability of the DT,offering substantial advantages over traditional ceramic thermistors.The enhanced temperature-sensitive properties of the DT are attributed to the presence of impurity elements in polycrystalline diamond.Impedance analysis indicates a hopping conduction mechanism,likely involving C-H or C-N dipoles at the diamond grain boundaries.This study marks a significant leap forward in diamond thermistor technology and sheds light on the mechanisms of thermal active conduction in diamond materials.展开更多
Friction force(f)usually increases with the normal load(N)macroscopically,according to the classic law of Da Vinci–Amontons(f=μN),with a positive and finite friction coefficient(μ).Herein near-zero and negative dif...Friction force(f)usually increases with the normal load(N)macroscopically,according to the classic law of Da Vinci–Amontons(f=μN),with a positive and finite friction coefficient(μ).Herein near-zero and negative differential friction(ZNDF)coefficients are discovered in two-dimensional(2D)van der Waals(vdW)magnetic CrI_(3)commensurate contacts.It is identified that the ferromagnetic–antiferromagnetic phase transition of the interlayer couplings of the bilayer CrI_(3)can significantly reduce the interfacial sliding energy barriers and thus contribute to ZNDF.Moreover,phase transition between the in-plane(p_(x)and p_(y))and out-of-plane(p_(z))wave-functions dominates the sliding barrier evolutions,which is attributed to the delicate interplays among the interlayer vdW,electrostatic interactions,and the intralayer deformation of the CrI_(3)layers under external load.The present findings may motivate a new concept of slide-spintronics and are expected to play an instrumental role in design of novel magnetic solid lubricants applied in various spintronic nano-devices.展开更多
This paper is concerned with the existence of eventually positive solutions and oscillatory solutions of first-order neutral differential equation with positive and negative coefficients. The 'sharp' condition...This paper is concerned with the existence of eventually positive solutions and oscillatory solutions of first-order neutral differential equation with positive and negative coefficients. The 'sharp' conditions of oscillation for the equation have been obtained, i.e., the conditions are sufficient and necessary when all of the coefficients are constants. These conditions are distinguished from the previous criteria in the literatures, and also weaker than those existing results.展开更多
In this paper, a new oscillating result is established for the first order neutral delay differential equation with positive and negative coefficients, which improves and generalizes several results in the literatures.
High-quality Mn-Co-Ni oxalate powder was prepared in a mixed solvent of water and ethanol by an improved oxalate coprecipitation approach.The as-prepared oxalate powder appears a controlled homogeneous morphology and ...High-quality Mn-Co-Ni oxalate powder was prepared in a mixed solvent of water and ethanol by an improved oxalate coprecipitation approach.The as-prepared oxalate powder appears a controlled homogeneous morphology and narrower particle size distribution by conveniently adjusing the ratio of water to ethanol.The ceramic,moulded with the high quality oxalate precursor,could be densified at a lower temperature of 1150 ℃;and also exhibits a higher density and the more homogeneous microstructurc with smaller grain sizes of 2-5 urn.Accordingly,the NTC thermistors fabricated from the ceramic have a better yield as compared to the traditional method.展开更多
Some comparison theorems of the non-existence of positive solutions are derived for a classof neutral type difference equations with positive and negative coefficients. These results extendand improve some comparison ...Some comparison theorems of the non-existence of positive solutions are derived for a classof neutral type difference equations with positive and negative coefficients. These results extendand improve some comparison criteria obtained in the literature [1] and [2].展开更多
Two-dimensional(2D)materials with tunable electronic transitions are vital for next-generation electronics and energy storage technologies.Here,we demonstrate a novel,thermally-driven,reversible modulation of electron...Two-dimensional(2D)materials with tunable electronic transitions are vital for next-generation electronics and energy storage technologies.Here,we demonstrate a novel,thermally-driven,reversible modulation of electronic conductivity in the quaternary heteroanionic 2D van der Waals superlattice Bi_(4)O_(4)SeCl_(2).Systematic thermal annealing of bulk Bi_(4)O_(4)SeCl_(2)induces a striking reversible transition from insulating to semiconducting behavior,accompanied by a 10~6 times magnitude enhancement in electrical conductivity.This dramatic transformation originates from thermally mediated defect annihilation and grain boundary elimination,substantially reducing carrier scattering barriers and enhancing intrinsic carrier concentration.Moreover,leveraging its intrinsic layered structure,we successfully exfoliated Bi_(4)O_(4)SeCl_(2)into nanosheets(~1.5 nm in thickness)and utilized these exfoliated layers as interfacial coatings on Zn electrodes,markedly improving dendrite suppression and extending the cycling stability of Zn-ion hybrid capacitors and Zn/MnO_(2)batteries.Our work elucidates crucial defect-driven micro s tructural mechanisms responsible for thermally-induced reversible electronic transitions,establishing heteroanionic Bi_(4)O_(4)SeCl_(2)as a promising platform for advanced electronic and energystorage materials engineering.展开更多
The water characteristic curve for aeolian sand in two processes of wetting and drying was obtained by the negative water column technique.The values of fitting parameters were calculated according to Van Genuchten fo...The water characteristic curve for aeolian sand in two processes of wetting and drying was obtained by the negative water column technique.The values of fitting parameters were calculated according to Van Genuchten formula and the parameters that characterized the prosperities of aeolian sand such as the unsaturated infiltration coefficient and specific water capacity were obtained.The results showed that the water characteristic curve for aeolian sand in wetting process had greater hysteresis quality than ...展开更多
文摘The oscillatory behavior of neutral differential equation with positive and negative coefficients is investigated by mathematics analysis technique and the fixed point principle. Some sufficient conditions for oscillation of neutral differential equation with positive and negative coefficients are obtained.
基金financially supported by the National Natural Science Foundation of China(Nos.51302138 and 21663001)the Western Light Talent Training Program of Chinese Academy of Sciences。
文摘Dense nano-grained Ni_(0.7)Mn_(2.3O4) negative temperature coefficient(NTC) thermistors were fabricated by a novel two-step sintering approach that combines rapid sintering and principle of conventional two-step sintering technique.Samples were sintered at 1042℃ for 30 s in the first rapid step and then at 850-950℃ for 20 h in the second soaking step.Crystal phase,microstructure and electrical properties of sintered samples were studied by X-ray diffraction(XRD),scanning electron microscopy(SEM),resistance temperature relationship and aging performance.Sintered samples show a single-phase cubic spinel structure and indicate a high relative density ranging from 84% to 91% of the theoretical density.Moreover,average grain sizes of sintered samples under SEM are distributed between 254 and 570 nm.Meanwhile,the resistivity and the aging coefficient significantly decrease when soaking sintering temperature rises.In addition,the obtained material constant(B) ranges from 3931 to 3981 K.Ni_(0.7)Mn_(2.3)O_(4)-3(soaking at 900℃) and Ni_(0.7)Mn_(2.3O4)-4(soaking at 950℃) present little aging behavior,implying great electrical stability.
基金the Science Foundation of Educational Committee of Hunan Provinc
文摘A neutral difference equation with positive and negative coefficientsΔ(x n-c nx n-k )+p nx n-l -q nx n-r =0, n=0,1,2,...,is considered and a sufficient condition for the global attractivity of the zero solution of this equation is obtained, which improves and extends the all known results in the literature.
基金the National Natural Science Foundation of China(1 0 0 71 0 1 8)
文摘In this paper the sufficient conditions for the existence of positive solutions of the neutral difference equations with positive and negative coefficients are established. The results improve some known conclusions in the literature.
基金the National Natural Science FOundation of China under grant! No.19974041the National Major Fundamental ResearCh Program-Nal
文摘The change of the temperature coefficient of resistivity (a) with the particle size, dp, and the grain size, dc, in the nanostructured Ag bulk samples was investigated. dp and dc were controlled by heating the nano-Ag powders over the temperature range from 393 to 453 K. The electrical resistance measurements of the nanostructured Ag bulk samples obtained by compacting the Ag powders after heat treatments showed a change in the sign of a with dP and dc. When dp and dc are smaller or equal to 18 and 11 nm below room temperature or 20 and 12 nm above room temperature, respectively, the sign of the temperature coefficient of resistivity changes from positive to negative. The negative a arises mainly from the high resistivity induced by the particle interfaces with very lowly ordered or even disordered structure, a large volume fraction of interfaces and impurities existing in the interfaces, and the quantum size effect appearing in the nano-Ag grains.
基金The work is supported by UKM grant ST-028-2003 IRPA grant 09-02-02-80 EA208, Malysia.
文摘In this paper we consider the class ∑^＊（p,α,β,k,c） consisting of analytic functions with negativecoefficients and fixed second coefficient. The object of the present paper is to give coefficient estimates, convex linear combinations, some distortion theorems and radii of starlikeness and convexity for f（z） in the class ∑^＊（p,α,β,k,c） .
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 60768001 and 10464002)
文摘This paper suggests a scheme of electromagnetic chirality-induced negative refraction utilizing magneto-lectric cross coupling in a four-level atomic system. The negative refraction can be achieved with the two chirality coefficients having the same amplitude but the opposite phase, without requiring the simultaneous presence of an electric-dipole and a magnetic-dipole transition near the same transition frequency.
基金Project supported by the National Key Research and Development Program of China(2019YFC0605000)the"Transformational Technologies for Clean Energy and Demonstration",Strategic Priority Research Program of the Chinese Academy of Sciences(XDA21000000)+4 种基金the Independent Deployment Project of Ganjiang Innovation Research Institute of Chinese Academy of Sciences(E055A002)the Independent Deployment Project of China Fujian Innovation Laboratory of Optoelectronic Information Technology(2021ZZ109)the Fujian Provincial Natural Fund(2021J05101)the National Natural Science Foundation of China(21771196,62275276)Advanced Energy Science and Technology Guangdong Laboratory(HND20TDGFDC00)。
文摘The electrical properties of high-entropy ceramics(HECs)have been extensively studied in recent years due to their unique structural characteristics and fascinating functional properties induced by entropy engineering.Novel high-entropy(Sm_(0.2)Eu_(0.2)Gd_(0.2)Ho_(0.2)Yb_(0.2))CrO_(3)(HE-RECrO_(3))nanofibers were prepared by electro spinning.This work demonstrates that HE-RECrO_(3)nanofibe rs were successfully synthesized at a low temperature(800℃),which is approximately 400℃lower than the temperatures at which chromate ceramics were synthesized via the sol-gel method and the solid-state reaction method.The resistivity of HE-RECrO_(3)nanofibers decreases exponentially with increasing temperature from 25 to600℃.The logarithm of the resistivity is linearly related to the inverse of the temperature,confirming the negative temperature coefficient property of HE-RECrO_(3)nanofibers.The B_(25/50)value of the HERECrO_(3)nanofibers reaches 4072 K.In conclusion,HE-RECrO_(3)nanofibers are expected to be potential candidates for negative-temperature-coefficient(NTC)thermistors.
基金supported by the National NaturalScience Foundation of China(No.50372027)the Natural Science Foundation of Jiangsu Province(No.BK2003404)
文摘Negative thermal expansion （NTE） ZrW2O8 powders were prepared by step-by-step solid-state reaction with ZrO2 and WO3 powders. The coefficient of thermal expansion （CTE） of the as-prepared ZrW208 was around -5.08×10^-6 K^-1 at 20-700℃. Different amounts of ZrW208 powders were added in BTDA-ODA polyamic acid to form polyimide/ZrW2O8 composites （PI/ZrW2O8）. With the increment of ZrW2O8, experimental results show that ZrW2O8 powders can significantly enhance the thermal stability of the composites, and reduce the thermal expansion. A 50 wt pct ZrW2O8 addition can give rise to a 31% reduction of CTE. It is suggested that the PI/ZrW2O8 composites have potential applications in high performance microelectronic devices.
基金Project supported by the SPAT of Shanghai Committee of Chinese People's Political Consultative Conference and Shanghai Education Development Foundation (Grant No.2008012)
文摘Y^3＋-doped （Bi 1/2 Na 1/2） TiO 3-CaTiO 3-BaTiO 3 （BNCBT） positive temperature coefficient of resistivity （PTCR） ceramics sintered in air atmosphere were investigated in this study. （Bi 1/2 Na 1/2） TiO 3 （BNT） component can remarkably increase the onset temperature T c of PTCR ceramics with the expense of the resistivity R 25 increase. CaTiO 3 （9–27 mol%） component can decrease the resistivity, and adjust the effects of BNT phase on the T c point. For the sample containing 3 mol% CaTiO 3 , T c raises from 122 ℃ to 153 ℃ when only 0.6 mol% BNT added, while for the ones with higher CaTiO 3 content （9–27 mol%）, T c is only increased by a rate of 8–9℃/1.0 mol% BNT. The effects of BNT and CaTiO 3 components on R25/Rmin （negative temperature coefficient effect） are also discussed.
基金supported by National Natural Science Foundation of China (Grant No. 11271379)Guangzhou Postdoctoral Science Research Foundation Project (Grant No. gdbsh2014003)
文摘We investigate oscillation of certain second order neutral dynamic equations of Emden-Fowler type with positive and negative coefficients. We use some different techniques and apply Riccati transformation to establish new oscillatory criteria which include two necessary and sufficient conditions. Moreover, we point out that how the power γ plays its role. Some interesting examples are given to illustrate the versatility of our results.
基金supported by the Fundamental Research Funds for the Central Universities(CUG2106117)Hubei Jewelry Engineering Technology Research Center(CIGTXM03202301)+1 种基金Hubei Provincial Natural Science Foundation(20241350053)GuangDong Basic and Applied Basic Research Foundation(2023A1515110043).
文摘Negative temperature coefficient(NTC)thermistor plays a crucial role in science research and engineering applications for precise temperature monitoring.Although great progress has been achieved in NTC materials,enhancing sensitivity and maintaining this high sensitivity along with linearity across extensive temperature ranges remain a significant challenge.In this study,we introduce a diamondbased thermistor(DT)characterized by its outstanding sensitivity,swift response time,and broad temperature monitoring capabilities.The temperature constant B for this DT,measured from 30 to 300°C(B30/300),achieves an exceptional value of 8012 K,which notably exceeds the temperature sensing capabilities of previously reported NTC thermistors within this extensive range.Moreover,diamond’s unique thermal conductivity and stability significantly boost the response speed and durability of the DT,offering substantial advantages over traditional ceramic thermistors.The enhanced temperature-sensitive properties of the DT are attributed to the presence of impurity elements in polycrystalline diamond.Impedance analysis indicates a hopping conduction mechanism,likely involving C-H or C-N dipoles at the diamond grain boundaries.This study marks a significant leap forward in diamond thermistor technology and sheds light on the mechanisms of thermal active conduction in diamond materials.
基金supported by the National Natural Science Foundation of China(Nos.12074345,12174349,11674289,11804306,11634011 and U2030120)Henan Provincial Key Science and Technology Research Projects(No.212102210130).
文摘Friction force(f)usually increases with the normal load(N)macroscopically,according to the classic law of Da Vinci–Amontons(f=μN),with a positive and finite friction coefficient(μ).Herein near-zero and negative differential friction(ZNDF)coefficients are discovered in two-dimensional(2D)van der Waals(vdW)magnetic CrI_(3)commensurate contacts.It is identified that the ferromagnetic–antiferromagnetic phase transition of the interlayer couplings of the bilayer CrI_(3)can significantly reduce the interfacial sliding energy barriers and thus contribute to ZNDF.Moreover,phase transition between the in-plane(p_(x)and p_(y))and out-of-plane(p_(z))wave-functions dominates the sliding barrier evolutions,which is attributed to the delicate interplays among the interlayer vdW,electrostatic interactions,and the intralayer deformation of the CrI_(3)layers under external load.The present findings may motivate a new concept of slide-spintronics and are expected to play an instrumental role in design of novel magnetic solid lubricants applied in various spintronic nano-devices.
基金Research supported by National Natural Science Foundation of P. R. China (10071016) by Foundation of the Education Department for Excellent Teacher of University.
文摘This paper is concerned with the existence of eventually positive solutions and oscillatory solutions of first-order neutral differential equation with positive and negative coefficients. The 'sharp' conditions of oscillation for the equation have been obtained, i.e., the conditions are sufficient and necessary when all of the coefficients are constants. These conditions are distinguished from the previous criteria in the literatures, and also weaker than those existing results.
基金Supported by the NSF Education Dept. (hjkj200317) and the NSF of Hainan Province (80403).
文摘In this paper, a new oscillating result is established for the first order neutral delay differential equation with positive and negative coefficients, which improves and generalizes several results in the literatures.
文摘High-quality Mn-Co-Ni oxalate powder was prepared in a mixed solvent of water and ethanol by an improved oxalate coprecipitation approach.The as-prepared oxalate powder appears a controlled homogeneous morphology and narrower particle size distribution by conveniently adjusing the ratio of water to ethanol.The ceramic,moulded with the high quality oxalate precursor,could be densified at a lower temperature of 1150 ℃;and also exhibits a higher density and the more homogeneous microstructurc with smaller grain sizes of 2-5 urn.Accordingly,the NTC thermistors fabricated from the ceramic have a better yield as compared to the traditional method.
文摘Some comparison theorems of the non-existence of positive solutions are derived for a classof neutral type difference equations with positive and negative coefficients. These results extendand improve some comparison criteria obtained in the literature [1] and [2].
基金supported by the National Key Research and Development Program of China(No.2021YFA1200903)National Natural Science Foundation of China(Nos.22175203,22006023,and 11974435)+1 种基金Natural Science Foundation of Guangdong Province(Nos.2022B1515020065 and 2020A1515110821,2023A1515010841,2025A1515010050)Guangzhou Science and Technology Project(No.202102020126)
文摘Two-dimensional(2D)materials with tunable electronic transitions are vital for next-generation electronics and energy storage technologies.Here,we demonstrate a novel,thermally-driven,reversible modulation of electronic conductivity in the quaternary heteroanionic 2D van der Waals superlattice Bi_(4)O_(4)SeCl_(2).Systematic thermal annealing of bulk Bi_(4)O_(4)SeCl_(2)induces a striking reversible transition from insulating to semiconducting behavior,accompanied by a 10~6 times magnitude enhancement in electrical conductivity.This dramatic transformation originates from thermally mediated defect annihilation and grain boundary elimination,substantially reducing carrier scattering barriers and enhancing intrinsic carrier concentration.Moreover,leveraging its intrinsic layered structure,we successfully exfoliated Bi_(4)O_(4)SeCl_(2)into nanosheets(~1.5 nm in thickness)and utilized these exfoliated layers as interfacial coatings on Zn electrodes,markedly improving dendrite suppression and extending the cycling stability of Zn-ion hybrid capacitors and Zn/MnO_(2)batteries.Our work elucidates crucial defect-driven micro s tructural mechanisms responsible for thermally-induced reversible electronic transitions,establishing heteroanionic Bi_(4)O_(4)SeCl_(2)as a promising platform for advanced electronic and energystorage materials engineering.
基金Supported by Key Project of Science and Technology Research of Ministry of Education(308021)Chang Jiang Scholars Innovation Team of Ministry of Education(IRT0811)Geological Survey Project of China Geological Survey(1212010331302)~~
文摘The water characteristic curve for aeolian sand in two processes of wetting and drying was obtained by the negative water column technique.The values of fitting parameters were calculated according to Van Genuchten formula and the parameters that characterized the prosperities of aeolian sand such as the unsaturated infiltration coefficient and specific water capacity were obtained.The results showed that the water characteristic curve for aeolian sand in wetting process had greater hysteresis quality than ...
