Partial Differential Equation(PDE)is among the most fundamental tools employed to model dynamic systems.Existing PDE modeling methods are typically derived from established knowledge and known phenomena,which are time...Partial Differential Equation(PDE)is among the most fundamental tools employed to model dynamic systems.Existing PDE modeling methods are typically derived from established knowledge and known phenomena,which are time-consuming and labor-intensive.Recently,discovering governing PDEs from collected actual data via Physics Informed Neural Networks(PINNs)provides a more efficient way to analyze fresh dynamic systems and establish PEDmodels.This study proposes Sequentially Threshold Least Squares-Lasso(STLasso),a module constructed by incorporating Lasso regression into the Sequentially Threshold Least Squares(STLS)algorithm,which can complete sparse regression of PDE coefficients with the constraints of l0 norm.It further introduces PINN-STLasso,a physics informed neural network combined with Lasso sparse regression,able to find underlying PDEs from data with reduced data requirements and better interpretability.In addition,this research conducts experiments on canonical inverse PDE problems and compares the results to several recent methods.The results demonstrated that the proposed PINN-STLasso outperforms other methods,achieving lower error rates even with less data.展开更多
Sodium-and potassium-ion batteries have exhibited great application potential in grid-scale energy storage due to the abundant natural resources of Na and K.Conversion-alloying anodes with high theoretical capacity an...Sodium-and potassium-ion batteries have exhibited great application potential in grid-scale energy storage due to the abundant natural resources of Na and K.Conversion-alloying anodes with high theoretical capacity and low-operating voltage are ideal option for SIBs and PIBs but suffer the tremendous volume variations.Herein,a hierarchically structural design and sp^(2)N-doping assist a conversion-alloying material,Sb_(2)Se_(3),to achieve superior life span more than 1000 cycles.It is confirmed that the Sb_(2)Se_(3)evolves into nano grains that absorb on the sp^(2)N sites and in situ form chemical bonding of C-N-Sb after initial discharge.Simulation results indicate that sp^(2)N has more robust interaction with Sb and stronger adsorption capacities to Na^(+)and K^(+)than that of sp3 N,which contributes to the durable cycling ability and high electrochemical activity,respectively.The ex situ transmission electron microscopy and X-ray photoelectron spectroscopy results suggest that the Sb_(2)Se_(3)electrode experiences conversion-alloying dual mechanisms based on 12-electron transfer per formula unit.展开更多
Co-frequency and co-time full duplex(CCFD) is an attractive technology for the future wireless communication because of its high spectral efficiency.However,applications of CCFD to mobile network can suffer from stron...Co-frequency and co-time full duplex(CCFD) is an attractive technology for the future wireless communication because of its high spectral efficiency.However,applications of CCFD to mobile network can suffer from strong base station to base station(B2B)interference.In this paper,the authors proposed a design that uses centralized base station(BS)transmit antenna and distributed BS receive antennas,each of which consists of an antennary to perform beamforming that can nullify the B2 B interference.In addition,we proposed a combination algorithm that uses the zero forcing method to cascade the recursive least square(RLS) method for reducing the necessary number of the bits taken to the digital processor.This enables the faster convergence and,thus,allows the transmission of more information bits,compared to the conventional method,for mobile communication.The simulation results confirm this approach for practical application.展开更多
Prognosis of bearing is critical to improve the safety,reliability,and availability of machinery systems,which provides the health condition assessment and determines how long the machine would work before failure occ...Prognosis of bearing is critical to improve the safety,reliability,and availability of machinery systems,which provides the health condition assessment and determines how long the machine would work before failure occurs by predicting the remaining useful life(RUL).In order to overcome the drawback of pure data-driven methods and predict RUL accurately,a novel physics-informed deep neural network,named degradation consistency recurrent neural network,is proposed for RUL prediction by integrating the natural degradation knowledge of mechanical components.The degradation is monotonic over the whole life of bearings,which is characterized by temperature signals.To incorporate the knowledge of monotonic degradation,a positive increment recurrence relationship is introduced to keep the monotonicity.Thus,the proposed model is relatively well understood and capable to keep the learning process consistent with physical degradation.The effectiveness and merit of the RUL prediction using the proposed method are demonstrated through vibration signals collected from a set of run-to-failure tests.展开更多
A new three-dimensional(3D)cellular model based on hinging open-cell Kelvin structure is proposed for its negative compressibility property.It is shown that this model has adjustable compressibility and does exhibit n...A new three-dimensional(3D)cellular model based on hinging open-cell Kelvin structure is proposed for its negative compressibility property.It is shown that this model has adjustable compressibility and does exhibit negative compressibility for some certain conformations.And further study shows that the images of compressibility are symmetrical about the certain lines,which indicates that the mechanical properties of the model in the three axial directions are interchangeable and the model itself has a certain geometric symmetry.A comparison of the Kelvin model with its anisotropic form with the dodecahedron model shows that the Kelvin model has stronger negative compressibility property in all three directions.Therefore,a new and potential method to improve negative compressibility property can be derived by selecting the system type with lower symmetry and increasing the number of geometric parameters.展开更多
Co-thermal chemical conversion of coal and biomass is one of the important ways to realize efficient and clean utilization of coal.In this study,a typical Ningdong coal-Yangchangwan bituminous coal and cow manure were...Co-thermal chemical conversion of coal and biomass is one of the important ways to realize efficient and clean utilization of coal.In this study,a typical Ningdong coal-Yangchangwan bituminous coal and cow manure were used to study the synergistic effect of intrinsic alkali,alkaline earth metals(AAEM)and organic matter on the co-gasification of coal and biomass by thermogravimetry analyzer(TG).The results showed that AAEM had obvious synergistic promotion effect on the gasification of a bituminous coal-cow manure mixture in the isothermal gasification(1000℃),whereas the organic matter will show the opposite effect on the process.To further investigate the effect of organic matter on the gasification process,the influence of organic matter on non-isothermal(25-1000℃)gasification reaction was investigated with heating rate of 10℃/min,the kinetic parameters of the gasification reaction were obtained by Coats-Redfern method.The increase of biomass mass fraction in the sample facilitates the migration of alkali metals from the material to the solid phase.The possible mechanism of the synergistic effect of intrinsic AAEM/organic matter on the co-gasification process was proposed.展开更多
The increasingly serious electromagnetic(EM)radiation and related pollution effects have gradually attracted people's attention in the information age.Hence,it's crucial to develop adaptive shielding materials...The increasingly serious electromagnetic(EM)radiation and related pollution effects have gradually attracted people's attention in the information age.Hence,it's crucial to develop adaptive shielding materials with minimum EM waves(EMW)reflection.In this paper,Ag nanoparticles loaded mesoporous carbon hollow spheres(MCHS@Ag)were synthesized by chemical reduction method,and cellulose nanofibers(CNF)/MXene/MCHS@Ag homogeneous composites were prepared.The total EM interference shielding efficiency(SET)of CNF/MXene/MCHS@Ag composite film was 32.83 dB(at 12.4 GHz),and the absorption effectiveness(SEA)was improved to 26.6 dB,which was 63.1%and 195.5%higher than that of CNF/MXene/MCHS composite film.The low dielectric property of MCHS effectively optimized the impedance matching between the composites and air.The hollow porous structure prolonged the transmission path of EMW and increased the absorption loss of the composites.At the same time,Ag nanoparticles located the MCHS were helpful to construct the internal conductive path overcoming the damage of the conductive property caused by the low dielectric of MCHS.This research adopts a straightforward method to construct a lightweight,pliable,and mesoporous composites for EMI shielding,which serves a crucial role in the current era of severe EM pollution.展开更多
The alternating copolymer of CO_(2) with epoxide is a green plastic that can efficiently transform CO_(2) into valuable chemicals. Despite the significant advances made, the restricted practical application of CO_(2)-...The alternating copolymer of CO_(2) with epoxide is a green plastic that can efficiently transform CO_(2) into valuable chemicals. Despite the significant advances made, the restricted practical application of CO_(2)-sourced polycarbonates due to their lack of functionality has hindered field development. We successfully demonstrated the flame retardancy of poly(chloropropylene carbonate) (PCPC), a perfectly alternating copolymer of epichlorohydrin (ECH) and CO_(2). This was prepared at a 200-gram scale using a high-efficacy tetranuclear organoborane catalyst. PCPC’s excellent flame-retardant performance has been proven by both the vertical combustion test (UL94 V-0) and the limiting oxygen index (LOI) value (29.1%). The underlaid flame-retardant mechanism of PCPC was clearly elucidated. As a result, we confirmed that the generated cyclic carbonates and concurrently released flame-retardant chlorine radicals, hydrogen chloride, and CO_(2) during combustion render PCPC an excellent flame retardant. Furthermore, we investigated the practicability of PCPC as a halogen-rich polymeric flame retardant by blending it with commercial bisphenol A polycarbonate (BPA-PC). PCPC upgraded the flame retardancy rating of BPA polycarbonate from V-2 to V-0 even with a mere 1 wt% addition. It is our hope that this result will prove useful in future developments of advanced CO_(2)-sourced polymeric materials.展开更多
This work investigated the formation of carbonaceous and nitrogenous disinfection by-products （C-DBPs, N-DBPs） upon chlorination of water samples collected from a surface water and a ground water treatment plant （S...This work investigated the formation of carbonaceous and nitrogenous disinfection by-products （C-DBPs, N-DBPs） upon chlorination of water samples collected from a surface water and a ground water treatment plant （SWTP and GWTP） where the conventional treatment processes, i.e., coagulation, sedimentation, and filtration were employed. Twenty DBPs, including four trihalomethanes, nine haloacetic acids, seven N-DBPs （dichloroacetamide, trichloroacetamide, dichloroacetonitrile, trichloroacetonitrile, bromochloroace- tonitrile, dibromoacetonitrile and trichloronitromethane）, and eight volatile chlorinated compounds （dichloromethane （DCM）, 1,2-dichloroethane, tetrachloroethylene, chlorobenzene, 1,2-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene and 1,2,4- trichlorobenzene） were detected in the two WTPs. The concentrations of these contaminants were all below their corresponding maximum contamination levels （MCLs） regulated by the Standards for Drinking Water Quality of China （GB5749-2006） except for DCM （17.1 ~tg/L detected vs. 20 μg/L MCL）. The SWTP had much higher concentrations of DBPs detected in the treated water as well as the DBP formation potentials tested in the filtered water than the GWTP, probably because more precursors （e.g., dissolved organic carbon, dissolved organic nitrogen） were present in the water source of the SWTE展开更多
The complexity of the epigenome landscape and transcriptional regulation is significantly increased during plant polyploidization,which drives genome evolution and contributes to the increased adaptability to diverse ...The complexity of the epigenome landscape and transcriptional regulation is significantly increased during plant polyploidization,which drives genome evolution and contributes to the increased adaptability to diverse environments.However,a comprehensive epigenome map of Brassica napus is still unavailable.In this study,we performed integrative analysis of five histone modifications,RNA polymerase Ⅱ CCU-pancy,DNA methylation,and transcriptomes in two B.napus lines(2063A and B409),and established global maps of regulatory elements,chromatin states,and their dynamics for the whole genome(including the An and Cn subgenomes)in four tissue types(young leaf,flower bud,silique,and root)of these two lines.Approximately 65.8% of the genome was annotated with different epigenomic signals.Compared with the Cn subgenome,the An subgenome possesses a higher level of active epigenetic marks and lower level of repressive epigenetic marks.Genes from subgenome-unique regions contribute to the major differences between the An and Cn subgenomes.Asymmetric histone modifications between homeologous gene pairs reflect their biased expression patterns.We identified a novel bivalent chromatin state(with H3K4me1 and H3K27me3)in B.napus that is associated with tissue-specific gene expression.Furthermore,we observed that different types of duplicated genes have discrepant patterns of histone modification and DNA methylation levels.Collectively,our findings provide a valuable epigenetic resource for allopolyploid plants.展开更多
This study was designed to explore the regulatory effects of male germ cell secreting factor NODAL on Sertoli cell fate decisions from obstructive azoospermia （OA） and nonobstructive azoospermia （NOA） patients. Hu...This study was designed to explore the regulatory effects of male germ cell secreting factor NODAL on Sertoli cell fate decisions from obstructive azoospermia （OA） and nonobstructive azoospermia （NOA） patients. Human Sertoli cells and male germ cells were isolated using two-step enzymatic digestion and SATPUT from testes of azoospermia patients. Expression of NODAL and its multiple receptors in human Sertoli cells and male germ cells were characterized by reverse transcription-polymerase chain reaction （RT-PCRI and immunochemistry. Human recombinant NODAL and its receptor inhibitor SB431542 were employed to probe their effect on the proliferation of Sertoli cells using the CCK-8 assay. Quantitative PCR and Western blots were utilized to assess the expression of Sertoli cell functional genes and proteins. NODAL was found to be expressed in male germ cells but not in Sertoli cells, whereas its receptors ALK4, ALK7, and ACTR-IIB were detected in Sertoli cells and germ cells, suggesting that NODAL plays a regulatory role in Sertoli cells and germ cells via a paracrine and autocrine pathway, respectively. Human recombinant NODAL could promote the proliferation of human Sertoli cells. The expression of cell cycle regulators, including CYCLIN A, CYCLIN D1 and CYCLIN E, was not remarkably affected by NODAL signaling. NODAL enhanced the expression of essential growth factors, including GDNF, SCF, and BMP4, whereas SB431542 decreased their levels. There was not homogeneity of genes changes by NODAL treatment in Sertoli cells from OA and Sertoli cell-only syndrome （SCO） patients. Collectively, this study demonstrates that NODAL produced by human male germ cells regulates proliferation and numerous gene expression of Sertoli cells.展开更多
Developing excellent absorption-dominant electromagnetic interference(EMI)shielding composites is an urgent demand for the rapid development of 5 G technology and electronic equipment.Herein,a simple strategy is emplo...Developing excellent absorption-dominant electromagnetic interference(EMI)shielding composites is an urgent demand for the rapid development of 5 G technology and electronic equipment.Herein,a simple strategy is employed to fabricate carbon nanotubes-polypropylene fibers(CP)/polypropylene-glass fibers felt(PGFF)/Fe 3 O 4 composites with superior EMI shielding effectiveness and low reflection due to the magnetic-conductive bi-gradient structure which is naturally formed by deposition during the vacuum-assisted filtration process.The difference in dimensionality between one-dimensional CNT with outstand-ing electrical conductivity and zero-dimensional magnetic Fe 3 O 4 nanoparticles is the theoretical basis for the successful construction of the magnetic-conductive bi-gradient structure in a gap-rich PGFF matrix that endows the composites with“absorb-reflect-reabsorb”EMI shieldingmechanism.Whentheelectro-magnetic waves are incident from the magnetic layer,the EMI shielding effectiveness(SE)reaches 48.9 dB as the weight percentage of the conductive layer increases,more importantly,the reflection coefficients are reduced by more than 0.32 compared with that of another incident pattern.What’s more,the re-sultant composites exhibit an outstanding signal shielding function in the application.This work paves a convenient pathway for designing a magnetic-conductive bi-gradient structure and efficient absorbing EMI shielding composites applied in the next-generated electronic information and communication field.展开更多
Telluride tin(SnTe)is a promising conversion-alloying anode for potassium-ion batteries(PIBs)due to its high theoretical specific capacity induced by multi-electron transport reaction and low operating voltage,whereas...Telluride tin(SnTe)is a promising conversion-alloying anode for potassium-ion batteries(PIBs)due to its high theoretical specific capacity induced by multi-electron transport reaction and low operating voltage,whereas huge volume expansion and poor kinetics behavior become key scientific bottleneck limiting the battery performances.Herein,SnTe nanoparticles physicochemically wrapped by graphene and nitrogen-doped carbon(SnTe@rGO@NC)are proposed as anode materials for PIBs.The pre-electrostatic interaction urges the formation of Sn-C and Te-C chemical bonds between SnTe and double carbon to strengthen the interfacial stability and electron transfer,and the conductive architecture with hierarchical encapsulation effect is beneficial to maintaining the electrode integrity and electrochemical dynamics.It is demon-strated from first principles calculations and experimental results that SnTe@rGO@NC contributes fast electron transmission,strong K-ion adsorption,and superior K-ion diffusion capability.Ex-situ characteri-zations uncover that SnTe undergoes conversion-alloying dual-mechanism with the products of K_(2)Te and K_(4)Sn_(23)replied on Sn redox site(23SnTe+50K^(+)+50e^(-)↔K_(4)Sn_(23)+23K_(2)Te).Thus,the SnTe@rGO@NC electrode delivers a high initial charge specific capacity of 243.9 mAh g^(-1)at 50 mA g^(-1),superior rate performance(112.6 mAh g^(-1)at 1.0 A g^(-1)),and outstanding cyclic stability at various current densities.展开更多
High efficiency microwave absorption(MA)materials with tunable electromagnetic(EM)features have been highly sought.However,it is still a challenge to achieve multi-bands absorption performance by simple optimizing the...High efficiency microwave absorption(MA)materials with tunable electromagnetic(EM)features have been highly sought.However,it is still a challenge to achieve multi-bands absorption performance by simple optimizing the chemical composition of MA materials.Herein,a simple solvothermal method was used to embed magnetic Fe_(3)O_(4) nanodusters on MoS2 nanosheets,in which magnetic nanodusters weme quantitatively customized More importantly,the MA frequency and MA properties of the material are highly tailored,and multi-bands absorption is achieved.The minimum reflection loss(RL)of Fe_(3)O_(4)/MoS_(2) composite reaches-87.24 dB and is about 4 times more than pure MoS_(2) nanosheets.The effective ab-sorption bandwidth reaches 5.52 GHz(≤-10 dB).These desirable properties result from the introduction of appropriate magnetic Fe_(3)O_(4) nanoclusters,which provide optimal synegistic effect of dielectric and magnetic losses.This result provides a feasible idea for designing high efficiency MA materials with tunable EM features in the future.展开更多
In this paper, the vibration influence on a monument caused by Chengdu Subway Line 2 is analyzed. Due to its elaborate and unique design, both structural and architectural damages should be avoided. First, the allowab...In this paper, the vibration influence on a monument caused by Chengdu Subway Line 2 is analyzed. Due to its elaborate and unique design, both structural and architectural damages should be avoided. First, the allowable root mean square （RMS） velocity at the foundation of the monument is derived and a site measurement is performed to obtain the background vibrations induced by road traffic. In addition, a train-track coupled model and 3D tunnel-soil-structure coupled finite element models are built to predict the dynamic response of the monument. Prediction models are checked by site measurement in Beijing Subway Line 5. Different kinds of fasteners and train speeds are compared and discussed as well. Results show that： （1） At a train speed of 72 km/h, all the traffic vibrations exceed the low limit no matter what kind of fastener is used, which is mainly due to the contribution of road traffic. Slowing down train speeds can cause effective vibration attenuation; （2） Vibrations drop dramatically with the train speed from 65 to 58 km/h. When the train speed is lower than 58 krn/h, vibrations are lower than allowable value even if the contribution of road traffic is considered.展开更多
Testicular prostheses have been used to deal with anorchia for nearly 80 years. Here, we evaluated a novel testicular prosthesis that can controllably release hormones to maintain physiological levels of testosterone ...Testicular prostheses have been used to deal with anorchia for nearly 80 years. Here, we evaluated a novel testicular prosthesis that can controllably release hormones to maintain physiological levels of testosterone in vivo for a long time. Silastic testicular prostheses with controlled release of testosterone （STPT） with different dosages of testosterone undecanoate （TU） were prepared and implanted into castrated Sprague-Dawley rats. TU oil was applied by oral administration to a separate group of castrated rats. Castrated untreated and sham-operated groups were used as controls. Serum samples from every group were collected to measure the levels of testosterone （T）, follicle-stimulating hormone and luteinizing hormone （LH）. Maximum intracavernous penile pressure （ICPmax） was recorded. The prostates and seminal vesicles were weighed and subjected to histology, and a terminal dexynucleotidyl transferase-mediated UTP nick end labeling （TUNEL） assay was used to evaluate apoptosis. Our results revealed that the weights of these tissues and the levels of T and LH showed significant statistical differences in the oral administration and TU replacement groups compared with the castrated group （P 〈 0.05）. Compared with the sham-operated group, the ICPmax, histology and TUNEL staining for apoptosis, showed no significant differences in the hormone replacement groups implanted with medium and high doses of STPT. Our results suggested that this new STPT could release TU stably through its double semi-permeable membranes with excellent biocompatibility. The study provides a new approach for testosterone replacement therapy.展开更多
转换-合金基材料被认为是低成本钠离子电池最有价值的负极之一,然而大的体积变化、差的电化学动力学行为成为了阻碍其应用的关键科学问题.在本文中,超薄纳米片自组装Bi_(2)Se_(3)纳米花通过强健的C-O-Bi化学键合作用被锚定在还原氧化石...转换-合金基材料被认为是低成本钠离子电池最有价值的负极之一,然而大的体积变化、差的电化学动力学行为成为了阻碍其应用的关键科学问题.在本文中,超薄纳米片自组装Bi_(2)Se_(3)纳米花通过强健的C-O-Bi化学键合作用被锚定在还原氧化石墨烯(rGO)上,并被氮掺杂碳纳米层(NC)紧密地包裹,构筑出的Bi_(2)Se_(3)@rGO@NC复合材料被用于钠离子电池负极.物理化学限域几何有助于通过容纳大的晶格应变而获得优异的电极完整性,同时通过消除带隙并降低钠离子扩散势垒促进良好的动力学过程.钠离子的插入/脱出是通过以铋离子为氧化还原位点的转换-合金双重反应机制进行的,其中每个分子式单元可实现12个电子的传输(Bi_(2)Se_(3)+12Na^(+)+12e^(−)↔2Na_(3)Bi+3Na_(2)Se).因此Bi_(2)Se_(3)@rGO@NC电极在50 mA g^(-1)电流密度下呈现出高达288.4 mA h g^(-1)的首次充电容量,同时具有超过1000次的超长循环寿命与优异的倍率性能(在5.0 A g^(-1)电流密度下容量为119.9 mA h g^(-1)).本工作为转换-合金负极的系统研究奠定了基础,为钠离子电池电化学反应机理的阐明提供了新的思路.展开更多
文摘Partial Differential Equation(PDE)is among the most fundamental tools employed to model dynamic systems.Existing PDE modeling methods are typically derived from established knowledge and known phenomena,which are time-consuming and labor-intensive.Recently,discovering governing PDEs from collected actual data via Physics Informed Neural Networks(PINNs)provides a more efficient way to analyze fresh dynamic systems and establish PEDmodels.This study proposes Sequentially Threshold Least Squares-Lasso(STLasso),a module constructed by incorporating Lasso regression into the Sequentially Threshold Least Squares(STLS)algorithm,which can complete sparse regression of PDE coefficients with the constraints of l0 norm.It further introduces PINN-STLasso,a physics informed neural network combined with Lasso sparse regression,able to find underlying PDEs from data with reduced data requirements and better interpretability.In addition,this research conducts experiments on canonical inverse PDE problems and compares the results to several recent methods.The results demonstrated that the proposed PINN-STLasso outperforms other methods,achieving lower error rates even with less data.
基金supported by the Natural Science Basic Research Program of Shaanxi(2022JQ-113)Guangdong Basic and Applied Basic Research Foundation(2021A1515110164 and 2022A1515010208)+1 种基金project funded by China Postdoctoral Science Foundation(2021TQ0266)the Fundamental Research Funds for the Central Universities(G2020KY0534).
文摘Sodium-and potassium-ion batteries have exhibited great application potential in grid-scale energy storage due to the abundant natural resources of Na and K.Conversion-alloying anodes with high theoretical capacity and low-operating voltage are ideal option for SIBs and PIBs but suffer the tremendous volume variations.Herein,a hierarchically structural design and sp^(2)N-doping assist a conversion-alloying material,Sb_(2)Se_(3),to achieve superior life span more than 1000 cycles.It is confirmed that the Sb_(2)Se_(3)evolves into nano grains that absorb on the sp^(2)N sites and in situ form chemical bonding of C-N-Sb after initial discharge.Simulation results indicate that sp^(2)N has more robust interaction with Sb and stronger adsorption capacities to Na^(+)and K^(+)than that of sp3 N,which contributes to the durable cycling ability and high electrochemical activity,respectively.The ex situ transmission electron microscopy and X-ray photoelectron spectroscopy results suggest that the Sb_(2)Se_(3)electrode experiences conversion-alloying dual mechanisms based on 12-electron transfer per formula unit.
基金supported by the National High Technology Research and Development Program of China(Grant No.2014AA01A704)National Natural Science Foundation of China(Grant No.61271203)
文摘Co-frequency and co-time full duplex(CCFD) is an attractive technology for the future wireless communication because of its high spectral efficiency.However,applications of CCFD to mobile network can suffer from strong base station to base station(B2B)interference.In this paper,the authors proposed a design that uses centralized base station(BS)transmit antenna and distributed BS receive antennas,each of which consists of an antennary to perform beamforming that can nullify the B2 B interference.In addition,we proposed a combination algorithm that uses the zero forcing method to cascade the recursive least square(RLS) method for reducing the necessary number of the bits taken to the digital processor.This enables the faster convergence and,thus,allows the transmission of more information bits,compared to the conventional method,for mobile communication.The simulation results confirm this approach for practical application.
基金support in part by China Postdoctoral Science Foundation (No.2021M702634)National Science Foundation of China (No.52175116).
文摘Prognosis of bearing is critical to improve the safety,reliability,and availability of machinery systems,which provides the health condition assessment and determines how long the machine would work before failure occurs by predicting the remaining useful life(RUL).In order to overcome the drawback of pure data-driven methods and predict RUL accurately,a novel physics-informed deep neural network,named degradation consistency recurrent neural network,is proposed for RUL prediction by integrating the natural degradation knowledge of mechanical components.The degradation is monotonic over the whole life of bearings,which is characterized by temperature signals.To incorporate the knowledge of monotonic degradation,a positive increment recurrence relationship is introduced to keep the monotonicity.Thus,the proposed model is relatively well understood and capable to keep the learning process consistent with physical degradation.The effectiveness and merit of the RUL prediction using the proposed method are demonstrated through vibration signals collected from a set of run-to-failure tests.
基金the National Natural Science Foundation of China(Grant Nos.U1601203 and U19A20104)the Jilin Provincial Science and Technology Development Program,China(Grant Nos.20180101321JC and 20190302099GX)+2 种基金the Jilin Provincial Industrial Technology of Research and Development,China(Grant No.2019C037-3)the Science and Technology Project of Jilin Provincial Department of Education,China(Grant No.JJKH20200955KJ)the Graduate Innovation Fund of Jilin University,China(Grant No.101832018C191).
文摘A new three-dimensional(3D)cellular model based on hinging open-cell Kelvin structure is proposed for its negative compressibility property.It is shown that this model has adjustable compressibility and does exhibit negative compressibility for some certain conformations.And further study shows that the images of compressibility are symmetrical about the certain lines,which indicates that the mechanical properties of the model in the three axial directions are interchangeable and the model itself has a certain geometric symmetry.A comparison of the Kelvin model with its anisotropic form with the dodecahedron model shows that the Kelvin model has stronger negative compressibility property in all three directions.Therefore,a new and potential method to improve negative compressibility property can be derived by selecting the system type with lower symmetry and increasing the number of geometric parameters.
基金The work was supported by the Outstanding Youth Science Foundation of Ningxia(2022AAC05016).
文摘Co-thermal chemical conversion of coal and biomass is one of the important ways to realize efficient and clean utilization of coal.In this study,a typical Ningdong coal-Yangchangwan bituminous coal and cow manure were used to study the synergistic effect of intrinsic alkali,alkaline earth metals(AAEM)and organic matter on the co-gasification of coal and biomass by thermogravimetry analyzer(TG).The results showed that AAEM had obvious synergistic promotion effect on the gasification of a bituminous coal-cow manure mixture in the isothermal gasification(1000℃),whereas the organic matter will show the opposite effect on the process.To further investigate the effect of organic matter on the gasification process,the influence of organic matter on non-isothermal(25-1000℃)gasification reaction was investigated with heating rate of 10℃/min,the kinetic parameters of the gasification reaction were obtained by Coats-Redfern method.The increase of biomass mass fraction in the sample facilitates the migration of alkali metals from the material to the solid phase.The possible mechanism of the synergistic effect of intrinsic AAEM/organic matter on the co-gasification process was proposed.
基金supported by the National Natural Science Foundation of China(grant no.52273044,52373092)the Opening Project of State Key Laboratory of Polymer Materials Engineering(Sichuan University)(grant no.sklpme2023-3-4)+1 种基金the Key Research Program of Zhejiang Province(grant no.2023C01101,2023C01210,2022C01049,2022C01205)the Natural Science Foundation of Zhejiang Province(grant no.LY20E030008).
文摘The increasingly serious electromagnetic(EM)radiation and related pollution effects have gradually attracted people's attention in the information age.Hence,it's crucial to develop adaptive shielding materials with minimum EM waves(EMW)reflection.In this paper,Ag nanoparticles loaded mesoporous carbon hollow spheres(MCHS@Ag)were synthesized by chemical reduction method,and cellulose nanofibers(CNF)/MXene/MCHS@Ag homogeneous composites were prepared.The total EM interference shielding efficiency(SET)of CNF/MXene/MCHS@Ag composite film was 32.83 dB(at 12.4 GHz),and the absorption effectiveness(SEA)was improved to 26.6 dB,which was 63.1%and 195.5%higher than that of CNF/MXene/MCHS composite film.The low dielectric property of MCHS effectively optimized the impedance matching between the composites and air.The hollow porous structure prolonged the transmission path of EMW and increased the absorption loss of the composites.At the same time,Ag nanoparticles located the MCHS were helpful to construct the internal conductive path overcoming the damage of the conductive property caused by the low dielectric of MCHS.This research adopts a straightforward method to construct a lightweight,pliable,and mesoporous composites for EMI shielding,which serves a crucial role in the current era of severe EM pollution.
基金supported by the National Science Fund for Distinguished Young Scholars(No.T2225004)National Natural Science Foundation of China(No.52373092)Shccig-Qinling Program.
文摘The alternating copolymer of CO_(2) with epoxide is a green plastic that can efficiently transform CO_(2) into valuable chemicals. Despite the significant advances made, the restricted practical application of CO_(2)-sourced polycarbonates due to their lack of functionality has hindered field development. We successfully demonstrated the flame retardancy of poly(chloropropylene carbonate) (PCPC), a perfectly alternating copolymer of epichlorohydrin (ECH) and CO_(2). This was prepared at a 200-gram scale using a high-efficacy tetranuclear organoborane catalyst. PCPC’s excellent flame-retardant performance has been proven by both the vertical combustion test (UL94 V-0) and the limiting oxygen index (LOI) value (29.1%). The underlaid flame-retardant mechanism of PCPC was clearly elucidated. As a result, we confirmed that the generated cyclic carbonates and concurrently released flame-retardant chlorine radicals, hydrogen chloride, and CO_(2) during combustion render PCPC an excellent flame retardant. Furthermore, we investigated the practicability of PCPC as a halogen-rich polymeric flame retardant by blending it with commercial bisphenol A polycarbonate (BPA-PC). PCPC upgraded the flame retardancy rating of BPA polycarbonate from V-2 to V-0 even with a mere 1 wt% addition. It is our hope that this result will prove useful in future developments of advanced CO_(2)-sourced polymeric materials.
基金supported by the National Major Science and Technology Project on Water Pollution Control and Management of China (No. 2009ZX07424-003)the National Natural Science Foundation of China (No.51108327)the State Key Laboratory of Pollution Control and Resource Reuse Foundation (No. PCRRY11015)
文摘This work investigated the formation of carbonaceous and nitrogenous disinfection by-products （C-DBPs, N-DBPs） upon chlorination of water samples collected from a surface water and a ground water treatment plant （SWTP and GWTP） where the conventional treatment processes, i.e., coagulation, sedimentation, and filtration were employed. Twenty DBPs, including four trihalomethanes, nine haloacetic acids, seven N-DBPs （dichloroacetamide, trichloroacetamide, dichloroacetonitrile, trichloroacetonitrile, bromochloroace- tonitrile, dibromoacetonitrile and trichloronitromethane）, and eight volatile chlorinated compounds （dichloromethane （DCM）, 1,2-dichloroethane, tetrachloroethylene, chlorobenzene, 1,2-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene and 1,2,4- trichlorobenzene） were detected in the two WTPs. The concentrations of these contaminants were all below their corresponding maximum contamination levels （MCLs） regulated by the Standards for Drinking Water Quality of China （GB5749-2006） except for DCM （17.1 ~tg/L detected vs. 20 μg/L MCL）. The SWTP had much higher concentrations of DBPs detected in the treated water as well as the DBP formation potentials tested in the filtered water than the GWTP, probably because more precursors （e.g., dissolved organic carbon, dissolved organic nitrogen） were present in the water source of the SWTE
基金This work was financially supported by the National Natural Science Foundation of China(31930032,31701163,31771422,and 31771402)the National Key Research and Development Program of China(2016YFD0101300 and 2018YFC1604000)+3 种基金the China Postdoctoral Science Foundation(2017M612479)the Fundamental Research Funds for the Central Universities(2662018py033)the open funds of the National Key Laboratory of Crop Genetic Improvement(ZK201906)the Program for Modern Agricultural Industrial Technology System of China(grant no.CARS-12).
文摘The complexity of the epigenome landscape and transcriptional regulation is significantly increased during plant polyploidization,which drives genome evolution and contributes to the increased adaptability to diverse environments.However,a comprehensive epigenome map of Brassica napus is still unavailable.In this study,we performed integrative analysis of five histone modifications,RNA polymerase Ⅱ CCU-pancy,DNA methylation,and transcriptomes in two B.napus lines(2063A and B409),and established global maps of regulatory elements,chromatin states,and their dynamics for the whole genome(including the An and Cn subgenomes)in four tissue types(young leaf,flower bud,silique,and root)of these two lines.Approximately 65.8% of the genome was annotated with different epigenomic signals.Compared with the Cn subgenome,the An subgenome possesses a higher level of active epigenetic marks and lower level of repressive epigenetic marks.Genes from subgenome-unique regions contribute to the major differences between the An and Cn subgenomes.Asymmetric histone modifications between homeologous gene pairs reflect their biased expression patterns.We identified a novel bivalent chromatin state(with H3K4me1 and H3K27me3)in B.napus that is associated with tissue-specific gene expression.Furthermore,we observed that different types of duplicated genes have discrepant patterns of histone modification and DNA methylation levels.Collectively,our findings provide a valuable epigenetic resource for allopolyploid plants.
文摘This study was designed to explore the regulatory effects of male germ cell secreting factor NODAL on Sertoli cell fate decisions from obstructive azoospermia （OA） and nonobstructive azoospermia （NOA） patients. Human Sertoli cells and male germ cells were isolated using two-step enzymatic digestion and SATPUT from testes of azoospermia patients. Expression of NODAL and its multiple receptors in human Sertoli cells and male germ cells were characterized by reverse transcription-polymerase chain reaction （RT-PCRI and immunochemistry. Human recombinant NODAL and its receptor inhibitor SB431542 were employed to probe their effect on the proliferation of Sertoli cells using the CCK-8 assay. Quantitative PCR and Western blots were utilized to assess the expression of Sertoli cell functional genes and proteins. NODAL was found to be expressed in male germ cells but not in Sertoli cells, whereas its receptors ALK4, ALK7, and ACTR-IIB were detected in Sertoli cells and germ cells, suggesting that NODAL plays a regulatory role in Sertoli cells and germ cells via a paracrine and autocrine pathway, respectively. Human recombinant NODAL could promote the proliferation of human Sertoli cells. The expression of cell cycle regulators, including CYCLIN A, CYCLIN D1 and CYCLIN E, was not remarkably affected by NODAL signaling. NODAL enhanced the expression of essential growth factors, including GDNF, SCF, and BMP4, whereas SB431542 decreased their levels. There was not homogeneity of genes changes by NODAL treatment in Sertoli cells from OA and Sertoli cell-only syndrome （SCO） patients. Collectively, this study demonstrates that NODAL produced by human male germ cells regulates proliferation and numerous gene expression of Sertoli cells.
基金supported by the Key Research Pro-gram of Zhejiang Province(No.2020C01010)the Natural Science Foundation of Zhejiang Province(No.LY20E030008)the Na-tional Natural Science Foundation of China(No.21504078).
文摘Developing excellent absorption-dominant electromagnetic interference(EMI)shielding composites is an urgent demand for the rapid development of 5 G technology and electronic equipment.Herein,a simple strategy is employed to fabricate carbon nanotubes-polypropylene fibers(CP)/polypropylene-glass fibers felt(PGFF)/Fe 3 O 4 composites with superior EMI shielding effectiveness and low reflection due to the magnetic-conductive bi-gradient structure which is naturally formed by deposition during the vacuum-assisted filtration process.The difference in dimensionality between one-dimensional CNT with outstand-ing electrical conductivity and zero-dimensional magnetic Fe 3 O 4 nanoparticles is the theoretical basis for the successful construction of the magnetic-conductive bi-gradient structure in a gap-rich PGFF matrix that endows the composites with“absorb-reflect-reabsorb”EMI shieldingmechanism.Whentheelectro-magnetic waves are incident from the magnetic layer,the EMI shielding effectiveness(SE)reaches 48.9 dB as the weight percentage of the conductive layer increases,more importantly,the reflection coefficients are reduced by more than 0.32 compared with that of another incident pattern.What’s more,the re-sultant composites exhibit an outstanding signal shielding function in the application.This work paves a convenient pathway for designing a magnetic-conductive bi-gradient structure and efficient absorbing EMI shielding composites applied in the next-generated electronic information and communication field.
基金supported by the National Natural Science Foun-dation of China(No.52207248)China Postdoctoral Science Foun-dation(Nos.2022M722606,2021TQ0266)+2 种基金Natural Science Basic Research Program of Shaanxi(No.2022JQ-113)Guangdong Basic and Applied Basic Research Foundation(Nos.2021A1515110164 and 2022A1515010208)the Fundamental Research Funds for the Central Universities(No.G2020KY0534)。
文摘Telluride tin(SnTe)is a promising conversion-alloying anode for potassium-ion batteries(PIBs)due to its high theoretical specific capacity induced by multi-electron transport reaction and low operating voltage,whereas huge volume expansion and poor kinetics behavior become key scientific bottleneck limiting the battery performances.Herein,SnTe nanoparticles physicochemically wrapped by graphene and nitrogen-doped carbon(SnTe@rGO@NC)are proposed as anode materials for PIBs.The pre-electrostatic interaction urges the formation of Sn-C and Te-C chemical bonds between SnTe and double carbon to strengthen the interfacial stability and electron transfer,and the conductive architecture with hierarchical encapsulation effect is beneficial to maintaining the electrode integrity and electrochemical dynamics.It is demon-strated from first principles calculations and experimental results that SnTe@rGO@NC contributes fast electron transmission,strong K-ion adsorption,and superior K-ion diffusion capability.Ex-situ characteri-zations uncover that SnTe undergoes conversion-alloying dual-mechanism with the products of K_(2)Te and K_(4)Sn_(23)replied on Sn redox site(23SnTe+50K^(+)+50e^(-)↔K_(4)Sn_(23)+23K_(2)Te).Thus,the SnTe@rGO@NC electrode delivers a high initial charge specific capacity of 243.9 mAh g^(-1)at 50 mA g^(-1),superior rate performance(112.6 mAh g^(-1)at 1.0 A g^(-1)),and outstanding cyclic stability at various current densities.
基金The financial support comes from the National Natural Science Foundation of China(Nos.12074095,52177014,51977009,11774027)The 2020 Central Government's plan to support the Talent Training Project of the Reform and Development Fund of Local Universities(Grant No.2020YQ02).
文摘High efficiency microwave absorption(MA)materials with tunable electromagnetic(EM)features have been highly sought.However,it is still a challenge to achieve multi-bands absorption performance by simple optimizing the chemical composition of MA materials.Herein,a simple solvothermal method was used to embed magnetic Fe_(3)O_(4) nanodusters on MoS2 nanosheets,in which magnetic nanodusters weme quantitatively customized More importantly,the MA frequency and MA properties of the material are highly tailored,and multi-bands absorption is achieved.The minimum reflection loss(RL)of Fe_(3)O_(4)/MoS_(2) composite reaches-87.24 dB and is about 4 times more than pure MoS_(2) nanosheets.The effective ab-sorption bandwidth reaches 5.52 GHz(≤-10 dB).These desirable properties result from the introduction of appropriate magnetic Fe_(3)O_(4) nanoclusters,which provide optimal synegistic effect of dielectric and magnetic losses.This result provides a feasible idea for designing high efficiency MA materials with tunable EM features in the future.
基金Project supported by the National Natural Science Foundation of China (No. 51008017)the Fundamental Research Funds for the Central Universities (Nos. 2009JBM074 and 2009JBM075), China
文摘In this paper, the vibration influence on a monument caused by Chengdu Subway Line 2 is analyzed. Due to its elaborate and unique design, both structural and architectural damages should be avoided. First, the allowable root mean square （RMS） velocity at the foundation of the monument is derived and a site measurement is performed to obtain the background vibrations induced by road traffic. In addition, a train-track coupled model and 3D tunnel-soil-structure coupled finite element models are built to predict the dynamic response of the monument. Prediction models are checked by site measurement in Beijing Subway Line 5. Different kinds of fasteners and train speeds are compared and discussed as well. Results show that： （1） At a train speed of 72 km/h, all the traffic vibrations exceed the low limit no matter what kind of fastener is used, which is mainly due to the contribution of road traffic. Slowing down train speeds can cause effective vibration attenuation; （2） Vibrations drop dramatically with the train speed from 65 to 58 km/h. When the train speed is lower than 58 krn/h, vibrations are lower than allowable value even if the contribution of road traffic is considered.
文摘Testicular prostheses have been used to deal with anorchia for nearly 80 years. Here, we evaluated a novel testicular prosthesis that can controllably release hormones to maintain physiological levels of testosterone in vivo for a long time. Silastic testicular prostheses with controlled release of testosterone （STPT） with different dosages of testosterone undecanoate （TU） were prepared and implanted into castrated Sprague-Dawley rats. TU oil was applied by oral administration to a separate group of castrated rats. Castrated untreated and sham-operated groups were used as controls. Serum samples from every group were collected to measure the levels of testosterone （T）, follicle-stimulating hormone and luteinizing hormone （LH）. Maximum intracavernous penile pressure （ICPmax） was recorded. The prostates and seminal vesicles were weighed and subjected to histology, and a terminal dexynucleotidyl transferase-mediated UTP nick end labeling （TUNEL） assay was used to evaluate apoptosis. Our results revealed that the weights of these tissues and the levels of T and LH showed significant statistical differences in the oral administration and TU replacement groups compared with the castrated group （P 〈 0.05）. Compared with the sham-operated group, the ICPmax, histology and TUNEL staining for apoptosis, showed no significant differences in the hormone replacement groups implanted with medium and high doses of STPT. Our results suggested that this new STPT could release TU stably through its double semi-permeable membranes with excellent biocompatibility. The study provides a new approach for testosterone replacement therapy.
基金supported by the Natural Science Basic Research Program of Shaanxi(2022JQ-113)Guangdong Basic and Applied Basic Research Foundation(2021A1515110164 and 2022A1515010208)+1 种基金China Postdoctoral Science Foundation(2021TQ0266 and 2022M722606)the Fundamental Research Funds for the Central Universities(G2020KY0534)。
文摘转换-合金基材料被认为是低成本钠离子电池最有价值的负极之一,然而大的体积变化、差的电化学动力学行为成为了阻碍其应用的关键科学问题.在本文中,超薄纳米片自组装Bi_(2)Se_(3)纳米花通过强健的C-O-Bi化学键合作用被锚定在还原氧化石墨烯(rGO)上,并被氮掺杂碳纳米层(NC)紧密地包裹,构筑出的Bi_(2)Se_(3)@rGO@NC复合材料被用于钠离子电池负极.物理化学限域几何有助于通过容纳大的晶格应变而获得优异的电极完整性,同时通过消除带隙并降低钠离子扩散势垒促进良好的动力学过程.钠离子的插入/脱出是通过以铋离子为氧化还原位点的转换-合金双重反应机制进行的,其中每个分子式单元可实现12个电子的传输(Bi_(2)Se_(3)+12Na^(+)+12e^(−)↔2Na_(3)Bi+3Na_(2)Se).因此Bi_(2)Se_(3)@rGO@NC电极在50 mA g^(-1)电流密度下呈现出高达288.4 mA h g^(-1)的首次充电容量,同时具有超过1000次的超长循环寿命与优异的倍率性能(在5.0 A g^(-1)电流密度下容量为119.9 mA h g^(-1)).本工作为转换-合金负极的系统研究奠定了基础,为钠离子电池电化学反应机理的阐明提供了新的思路.
