The development of semiconductors is always accompanied by the progress in controllable doping techniques.Taking AlGaN-based ultraviolet(UV)emitters as an example,despite a peak wall-plug efficiency of 15.3%at the wav...The development of semiconductors is always accompanied by the progress in controllable doping techniques.Taking AlGaN-based ultraviolet(UV)emitters as an example,despite a peak wall-plug efficiency of 15.3%at the wavelength of 275 nm,there is still a huge gap in comparison with GaN-based visible light-emitting diodes(LEDs),mainly attributed to the inefficient doping of AlGaN with increase of the Al composition.First,p-doping of Al-rich AlGaN is a long-standing challenge and the low hole concentration seriously restricts the carrier injection efficiency.Although p-GaN cladding layers are widely adopted as a compromise,the high injection barrier of holes as well as the inevitable loss of light extraction cannot be neglected.While in terms of n-doping the main issue is the degradation of the electrical property when the Al composition exceeds 80%,resulting in a low electrical efficiency in sub-250 nm UV-LEDs.This review summarizes the recent advances and outlines the major challenges in the efficient doping of Al-rich AlGaN,meanwhile the corresponding approaches pursued to overcome the doping issues are discussed in detail.展开更多
The expansion chamber serves as the primary silencing structure within the exhaust pipeline.However,it can also act as a sound-emitting structure when subjected to airflow.This article presents a hybrid method for num...The expansion chamber serves as the primary silencing structure within the exhaust pipeline.However,it can also act as a sound-emitting structure when subjected to airflow.This article presents a hybrid method for numerically simulating and analyzing the unsteady flow and aerodynamic noise in an expansion chamber under the influence of airflow.A fluid simulation model is established,utilizing the Large Eddy Simulation(LES)method to calculate the unsteady flow within the expansion chamber.The simulation results effectively capture the development and changes of the unsteady flow and vorticity inside the cavity,exhibiting a high level of consistency with experimental observations.To calculate the aerodynamic noise sources within the cavity,the flow field results are integrated using the method of integral interpolation and inserted into the acoustic grid.The acoustic analogy method is then employed to determine the aerodynamic noise sources.An acoustic simulation model is established,and the flow noise source is imported into the sound field grid to calculate the sound pressure at the far-field response point.The calculated sound pressure levels and resonance frequencies show good agreement with the experimental results.To address the issue of airflow regeneration noise within the cavity,perforated tubes are selected as a means of noise suppression.An experimental platformfor airflow regeneration noise is constructed,and experimental samples are processed to analyze and verify the noise suppression effect of perforated tube expansion cavities under different airflow velocities.The research findings indicate that the perforated tube expansion cavity can effectively suppress low-frequency aerodynamic noise within the cavity by impeding the formation of strong shear layers.Moreover,the semi-perforated tube expansion cavity demonstrates the most effective suppression of aerodynamic noise.展开更多
Blockchain,known for its secure encrypted ledger,has garnered attention in financial and data transfer realms,including the field of energy trading.However,the decentralized nature and identity anonymity of user nodes...Blockchain,known for its secure encrypted ledger,has garnered attention in financial and data transfer realms,including the field of energy trading.However,the decentralized nature and identity anonymity of user nodes raise uncertainties in energy transactions.The broadcast consensus authentication slows transaction speeds,and frequent single-point transactions in multi-node settings pose key exposure risks without protective measures during user signing.To address these,an alliance blockchain scheme is proposed,reducing the resource-intensive identity verification among nodes.It integrates multi-signature functionality to fortify user resources and transac-tion security.A novel multi-signature process within this framework involves neutral nodes established through central nodes.These neutral nodes participate in multi-signature’s signing and verification,ensuring user identity and transaction content privacy.Reducing interactions among user nodes enhances transaction efficiency by minimizing communication overhead during verification and consensus stages.Rigorous assessments on reliability and operational speed highlight superior security performance,resilient against conventional attack vectors.Simulation shows that compared to traditional solutions,this scheme has advantages in terms of running speed.In conclusion,the alliance blockchain framework introduces a novel approach to tackle blockchain’s limitations in energy transactions.The integrated multi-signature process,involving neutral nodes,significantly enhances security and privacy.The scheme’s efficiency,validated through analytical assessments and simulations,indicates robustness against security threats and improved transactional speeds.This research underscores the potential for improved security and efficiency in blockchain-enabled energy trading systems.展开更多
A new catalyst of Co/La_(4)Ga_(2)O_(9) for CO_(2) hydrogenation to produce ethanol was prepared by reducing LaCo^(0).5 Ga0.5 O3,which showed excellent selectivity to ethanol(%35 C-mol%)at mild reaction conditions(270&...A new catalyst of Co/La_(4)Ga_(2)O_(9) for CO_(2) hydrogenation to produce ethanol was prepared by reducing LaCo^(0).5 Ga0.5 O3,which showed excellent selectivity to ethanol(%35 C-mol%)at mild reaction conditions(270°C,3.5 MPa,3000 m L g-1 h-1).The catalysts were characterized by N_(2) adsorption/desorption,XRD,XAFS,CO and CO_(2)-TPD,H2 chemisorption,XPS and TEM techniques.The interaction between Co nanoparticles(NPs)and La2+4 Ga_(2)O_(9) oxide resulted in Co^(0)-Coon the surface of Co NPs.It was proposed that La_(4)Ga_(2)O_(9) could catalyze reverse water gas shift reaction(r-WGS),which converted CO_(2) to CO.Then,the CO migrated to Co^(0)-Co^(2+)on Co NPs,where it was hydrogenated to form ethanol like higher alcohols synthesis from syngas.The results suggest that by controlling the oxidation state of cobalt,and combined with a kind of active site for activating CO_(2) to form CO,a catalyst with excellent selectivity to ethanol could be obtained for CO_(2) hydrogenation,which means that the complex reaction may be proceed with high selectivity using only one active metal component.展开更多
Coal-based H2 generation has abruptly increased in recent years.The PSA-VPSA-SC process is the matured and standard framework for H2 purification and CO_(2) capture in many existing plants,including normal and vacuum ...Coal-based H2 generation has abruptly increased in recent years.The PSA-VPSA-SC process is the matured and standard framework for H2 purification and CO_(2) capture in many existing plants,including normal and vacuum pressure swing adsorption units in series(PSA-VPSA),and shallow condensation unit(SC).However,this standard process is frequently subjected to low H2 recovery ratio and high purification cost.In this work,H2-selective and C02-selective membrane units,i.e.,HM and CO_(2) M,are attempted to support the standard process and ameliorate constraints.In the beginning,HM unit is arranged after VPSA to enhance H2 recovery from the decarbonized stream,i.e.,the PSA-VPSA-SC/HM process.As a result,H2 recovery ratio can be enhanced significantly from 83%to 98%.In the following,VPSA is replaced with CO_(2) M unit to reduce investment and operation cost,i.e.,the PSA-CO_(2) M-SC/HM process.Accordingly,the specific purification cost is diminished from 33.46 to 32.02 USD·(103 m^(3) H_(2))-1,saved by 4.3%,meanwhile the construction cost is falling back and just a little higher than that for the standard process.In the end,another CO_(2) M unit is launched before PSA,i.e.,the CO_(2) M-PSA-CO_(2) M-SC/HM process,which could unbundle CO_(2) enrichment partially from H2 purification,and then save more investment and operation cost.In comparison with the standard process,this ultimate retrofitted process can be superior in all the three crucial indices,i.e.,recovery ratio,investment,and specific purification cost.On the whole,coal-based H2 generation can be ameliorated significantly through high efficient H2-selective and CO_(2)-selective membrane units.展开更多
Passivity breakdown on 436 ferritic stainless steel(FSS) has been investigated in solutions containing different concentrations of chloride at 25?C and interpreted in terms of the point defect model(PDM). The measured...Passivity breakdown on 436 ferritic stainless steel(FSS) has been investigated in solutions containing different concentrations of chloride at 25?C and interpreted in terms of the point defect model(PDM). The measured near-normal distributions of passivity breakdown potentials for 436 FSS under experimental conditions are in good agreement with the calculated results according to the PDM. The linear dependence of breakdown potential on the square root of potential scanning rate, which was described by the PDM,provides the estimation of the critical concentration of condensed vacancies at the metal/film interface,which leads to the passivity breakdown. This value is in good agreement with that calculated from the microstructure properties of the alloy substrate and the barrier layer of the passive film. This study demonstrates the validity of the PDM in describing the passivity breakdown on 436 FSS in NaCl solutions.展开更多
Rational structure design and regulation are of paramount importance for obtaining electrode materials with desirable electrochemical performance.Here,a novel binder-free electrode with the hollow Co_(9)S_(8) core@mul...Rational structure design and regulation are of paramount importance for obtaining electrode materials with desirable electrochemical performance.Here,a novel binder-free electrode with the hollow Co_(9)S_(8) core@multi-shell structure(CS-x@MXene@Bi_(2)O_(3))derived from metal-organic frameworks(MOFs)precursor is well designed by the electrospinning,sulfuration,carbonization,and hydrothermal processes.In this architecture,the concentration of Co_(9)S_(8)(CS-x)is optimized for an ideal flexible substrate,which alleviates the dimensional variation for long cycle life.The unique cores and the MXene flakes engineered by Bi_(2)O_(3) multiple shells can be responsible for the superior characteristics,including a fast electronic pathway,large specific surface area,enhanced electrical conductivity,and improved electrochemical performance.As expected,the obtained CS-2@MXene@Bi_(2)O_(3) binder-free electrode exhibits a high discharge capacitance of 646.1 F g^(–1)(1 A g^(–1)).Two binder-free electrodes can be assembled into a solid-state supercapacitor with desirable energy and power density,and long-term cyclic stability is demonstrated through 5000 cycles.Given these advantages,the CS-2@MXene@Bi_(2)O_(3) is selected as the electrode in a foldable supercapacitor.More importantly,the specific capacitance is reserved after various deformations.Therefore,it is expected that binder-free electrode materials with the unique core@shell structure design could be applied in wearable and portable energy conversion devices.展开更多
HY-2 A(Haiyang-2 A),launched in 2011,is the first ocean dynamic environment satellite of China and is equipped with a radar altimeter as one of the primary payloads.HY-2 A shifted the drift orbit in March 2016 and has...HY-2 A(Haiyang-2 A),launched in 2011,is the first ocean dynamic environment satellite of China and is equipped with a radar altimeter as one of the primary payloads.HY-2 A shifted the drift orbit in March 2016 and has been accumulating geodetic mission(GM)data for more than three years with 168-day cycle.In this paper,we present the preliminary gravity field inverted by the HY-2 A/GM data from March 2016 to December 2017 near Taiwan(21°–26°N,119°–123°E).The gravity anomaly is computed by Inverse Vening Meinesz(IVM)formula with a onedimensional FFT method during remove-restore procedure with the EGM2008 gravity model as the reference field.For comparison,CryoSat-2 altimeter data are used to inverse the gravity field near Taiwan Island by the same method.Comparing with the gravity field derived from CryoSat-2,a good agreement between the two data sets is found.The global ocean gravity models and National Geophysical Data Center(NGDC)shipboard gravity data also are used to assess the performance of HY-2 A/GM data.The evaluations show that HY-2 A and CryoSat-2 are at the same level in terms of gravity field recovery and the HY-2 A/GM altimeter-derived gravity field has an accuracy of 2.922 mGal.Therefore,we can believe that HY-2 A will be a new reliable data source for marine gravity field inversion and has the potentiality to improve the accuracy and resolution of the global marine gravity field.展开更多
Due to the bird’s eye view of remote sensing sensors,the orientational information of an object is a key factor that has to be considered in object detection.To obtain rotating bounding boxes,existing studies either ...Due to the bird’s eye view of remote sensing sensors,the orientational information of an object is a key factor that has to be considered in object detection.To obtain rotating bounding boxes,existing studies either rely on rotated anchoring schemes or adding complex rotating ROI transfer layers,leading to increased computational demand and reduced detection speeds.In this study,we propose a novel internal-external optimized convolutional neural network for arbitrary orientated object detection in optical remote sensing images.For the internal opti-mization,we designed an anchor-based single-shot head detector that adopts the concept of coarse-to-fine detection for two-stage object detection networks.The refined rotating anchors are generated from the coarse detection head module and fed into the refining detection head module with a link of an embedded deformable convolutional layer.For the external optimiza-tion,we propose an IOU balanced loss that addresses the regression challenges related to arbitrary orientated bounding boxes.Experimental results on the DOTA and HRSC2016 bench-mark datasets show that our proposed method outperforms selected methods.展开更多
A new scheme for the preparation of highly dispersed precious metal catalysts is proposed in this work. Samples of LaCol-xPtxO3/SiO2 （x = 0.03, 0.05, 0.07, 0.09, and 0.10） were prepared through a simple method of ci...A new scheme for the preparation of highly dispersed precious metal catalysts is proposed in this work. Samples of LaCol-xPtxO3/SiO2 （x = 0.03, 0.05, 0.07, 0.09, and 0.10） were prepared through a simple method of citrate acid complexa-tion combined with impregnation. In a nanocrystallite of LaCOl-xPtxO3, ions of lanthanum, cobalt, and platinum are evenly mixed at the atomic level and confined within the nanocrystallite. In the reduction process, platinum ions were reduced and migrated onto the surface of the nanocrystallite, and the platinum should be highly dispersed owing to the even mixing of the platinum ions in the precursor. When x = 0.05 or lower, the highest dispersion of Pt could be achieved. The highly dispersed Pt is stable, because of the strong interaction between Pt atoms and the support. The catalysts were characterized by BET surface area, temperature-programmed reduction, X-ray diffraction, transmission electron microscopy, CO temperature-programmed desorption, and turnover frequency. Compared with general precious metal Pt catalysts, the LaCo0.95Pt0.05O3/ SiO2 catalyst exhibited better activity for CO oxidation, and it maintained stability at a high temperature of 400 ℃ for 250 h with complete CO conversion.展开更多
Dear Editor,In pansharpening task,the most existing deep-learning-based pansharpening methods fail to fully utilize the different level features,inevitably leading to spectral or spatial distortions.To address this ch...Dear Editor,In pansharpening task,the most existing deep-learning-based pansharpening methods fail to fully utilize the different level features,inevitably leading to spectral or spatial distortions.To address this challenge,in this letter,we propose a dual-branch multi-level feature aggregation network for pansharpening(DMFANet).展开更多
[Objectives] To determine the optimum conditions and antioxidant activity of Myrica ruba leaf pigment,and provide reference for further development and use of Myrica ruba leaves. [Methods]Pigment of Myrica ruba leaves...[Objectives] To determine the optimum conditions and antioxidant activity of Myrica ruba leaf pigment,and provide reference for further development and use of Myrica ruba leaves. [Methods]Pigment of Myrica ruba leaves was extracted by ethanol extraction method. Absorbance was measured at wavelength of 300 nm. Effects of ethanol volume fraction,solid-to-liquid ratio,temperature,and extraction time were studied. L_9( 3~3) orthogonal experiment was carried out to optimize the extraction process,and DPPH scavenging ability was measured.[Results]The optimum extraction process of Myrica ruba leaf pigment was as follows: the ethanol volume fraction was 50%; the solid-to-liquid ratio was 1: 60( w/v),extraction temperature 70℃; extraction time was 60 min; after the concentration of purified Myrica ruba leaf pigment reached 0. 4455 mg/mL,the DPPH scavenging ability was basically the same as the same concentration Vc.[Conclusions] The experiment indicates that the optimized extraction process has a high yield rate,and Myrica ruba leaf pigment has high anti-oxidant activity.展开更多
The process parameters of laser additive manufacturing have an important influence on the forming quality of the produced items or parts.In the present work,a finite element model for simulating transient heat transfe...The process parameters of laser additive manufacturing have an important influence on the forming quality of the produced items or parts.In the present work,a finite element model for simulating transient heat transfer in such processes has been implemented using the ANSYS software,and the temperature and stress distributions related to 316L stainless steel thin-walled ring parts have been simulated and analyzed.The effect of the laser power,scanning speed,and scanning mode on temperature distribution,molten pool structure,deformation,and stress field has been studied.The simulation results show that the peak temperature,weld pool size,deformation,and residual stress increase with an increase in laser power and a decrease in the scanning speed.The scanning mode has no obvious effect on temperature distribution,deformation,and residual stress.In addition,a forming experiment was carried out.The experimental results show that the samples prepared by laser power P=800 W,V=6 mm/s,and the normal scanning method display good quality,whereas the samples prepared under other parameters have obvious defects.The experimental findings are consistent with the simulation results.展开更多
There is a large amount of information in the network data that we canexploit. It is difficult for classical community detection algorithms to handle network data with sparse topology. Representation learning of netwo...There is a large amount of information in the network data that we canexploit. It is difficult for classical community detection algorithms to handle network data with sparse topology. Representation learning of network data is usually paired with clustering algorithms to solve the community detection problem.Meanwhile, there is always an unpredictable distribution of class clusters outputby graph representation learning. Therefore, we propose an improved densitypeak clustering algorithm (ILDPC) for the community detection problem, whichimproves the local density mechanism in the original algorithm and can betteraccommodate class clusters of different shapes. And we study the communitydetection in network data. The algorithm is paired with the benchmark modelGraph sample and aggregate (GraphSAGE) to show the adaptability of ILDPCfor community detection. The plotted decision diagram shows that the ILDPCalgorithm is more discriminative in selecting density peak points compared tothe original algorithm. Finally, the performance of K-means and other clusteringalgorithms on this benchmark model is compared, and the algorithm is proved tobe more suitable for community detection in sparse networks with the benchmarkmodel on the evaluation criterion F1-score. The sensitivity of the parameters ofthe ILDPC algorithm to the low-dimensional vector set output by the benchmarkmodel GraphSAGE is also analyzed.展开更多
[Objectives] To compare different extraction methods for total alkaloids from Abrus Cantoniensis Hance taking chloroform as solvent. [Methods] The ethanol extraction method,ultrasonic extraction method,acid water extr...[Objectives] To compare different extraction methods for total alkaloids from Abrus Cantoniensis Hance taking chloroform as solvent. [Methods] The ethanol extraction method,ultrasonic extraction method,acid water extraction method,and Soxhlet extraction method were used to extract total alkaloids,and the total alkaloids of Abrus Cantoniensis Hance were measured at 238 nm wavelength. [Results] The extraction rate of ethanol extraction method was 14. 76 mg/100 g; the extraction rate of ultrasonic extraction method was 56. 85 mg/100 g; the extraction rate of acid water extraction method was 56. 63 mg/100 g; the extraction rate of Soxhlet extraction method was 58. 19 mg/100 g.[Conclusions]Results indicate that Soxhlet extraction method can obtain the highest extraction rate.展开更多
Sensors are a crucial component in heating,ventilation,and air conditioning(HVAC)control systems,and the quality of them plays an important role in control accuracy.In the research of fault detection and control optim...Sensors are a crucial component in heating,ventilation,and air conditioning(HVAC)control systems,and the quality of them plays an important role in control accuracy.In the research of fault detection and control optimization,improving sensor data quality has inspiring potential in application.It has been largely limited to the application of signal processing methods in research focus,whereas a detailed analysis of the characteristics of signals from various sensors of the HVAC system has not been conducted.Therefore,this study analyzes the time-frequency domain characteristics of control sensors within HVAC systems through integrating the structural design and control logic of such systems.Additionally,the research examines the correlations between control sensors in HVAC systems.Based on statistical principles and the energy-mass dynamic laws of the equipment,this paper defines first-class(Ⅰ)correlated sensors and second-class(Ⅱ)correlated sensors.To sum up,the main contribution of this paper is conducting a fundamental study on the characteristics of control sensors within HVAC systems,providing theoretical reference for future research on HVAC system fault diagnosis and control optimization.展开更多
将界面太阳能水蒸发技术与光催化降解过程耦合被视为解决能源和环境问题的有效策略,但开发具有光热与催化协同效应的双功能蒸发器仍然具有挑战性.本文构建了MoS_(2)-g-C_(3)N_(4)(MG)异质结并将其负载于气凝胶上制备了一系列双功能的MoS...将界面太阳能水蒸发技术与光催化降解过程耦合被视为解决能源和环境问题的有效策略,但开发具有光热与催化协同效应的双功能蒸发器仍然具有挑战性.本文构建了MoS_(2)-g-C_(3)N_(4)(MG)异质结并将其负载于气凝胶上制备了一系列双功能的MoS_(2)-g-C_(3)N_(4)(MG)气凝胶蒸发器.这些MG气凝胶具有高比表面积、有效光吸收和高光催化活性,表现出优异的光热转换性能和光催化降解能力.MG气凝胶大的比表面积和丰富的孔隙结构不仅有利于水的渗透和蒸发焓的降低,还有利于有机污染物的吸附降解.其中,基于MG-0.4构筑的蒸发器具有1.72 kg m^(-2)h^(-1)的高水蒸发效率,同时表现出显著的罗丹明B降解效率(90.1%).这项工作为解决淡水短缺和水污染控制问题提供了一个新方法.展开更多
Utilizing renewable lignocellulosic resources for wastewater remediation is crucial to achieving sustainable social development.However,the resulting by-products and the synthetic process characterized by complexity,h...Utilizing renewable lignocellulosic resources for wastewater remediation is crucial to achieving sustainable social development.However,the resulting by-products and the synthetic process characterized by complexity,high cost,and environmental pollution limit the further development of lignocellulose-based materials.Here,we developed a sustainable strategy that involved a new functional deep eutectic solvent(DES)to deconstruct industrial xylose residue into cellulose-rich residue with carboxyl groups,lignin with carboxyl and quaternary ammonium salt groups,and DES effluent rich in lignin fragments.Subsequently,these fractions equipped with customized functionality were used to produce efficient wastewater remediation materials in cost-effective and environmentally sound manners,namely,photocatalyst prepared by carboxyl-modified cellulose residue,biochar-based adsorbent originated from modified lignin,and flocculant synthesized by self-catalytic in situ copolymerization of residual DES effluent at room temperature.Under the no-waste principle,this strategy upgraded the whole components of waste lignocellulose into high-value-added wastewater remediation materials with excellent universality.These materials in coordination with each other can stepwise purify high-hazardous mineral processing wastewater into drinkable water,including the removal of 99.81%of suspended solids,almost all various heavy metal ions,and 97.09%chemical oxygen demand,respectively.This work provided promising solutions and blueprints for lignocellulosic resources to alleviate water shortages while also advancing the global goal of carbon neutrality.展开更多
基金This work was supported by the National Key Research and Development Program of China(No.2022YFB3605100)the National Natural Science Foundation of China(Nos.62234001,61927806,61974002,62135013,and 62075081)+1 种基金the Key-Area Research and Development Program of Guangdong Province(No.2020B010172001)the Major Scientific and Technological Innovation Project(MSTIP)of Shandong Province(No.2019JZZY010209).
文摘The development of semiconductors is always accompanied by the progress in controllable doping techniques.Taking AlGaN-based ultraviolet(UV)emitters as an example,despite a peak wall-plug efficiency of 15.3%at the wavelength of 275 nm,there is still a huge gap in comparison with GaN-based visible light-emitting diodes(LEDs),mainly attributed to the inefficient doping of AlGaN with increase of the Al composition.First,p-doping of Al-rich AlGaN is a long-standing challenge and the low hole concentration seriously restricts the carrier injection efficiency.Although p-GaN cladding layers are widely adopted as a compromise,the high injection barrier of holes as well as the inevitable loss of light extraction cannot be neglected.While in terms of n-doping the main issue is the degradation of the electrical property when the Al composition exceeds 80%,resulting in a low electrical efficiency in sub-250 nm UV-LEDs.This review summarizes the recent advances and outlines the major challenges in the efficient doping of Al-rich AlGaN,meanwhile the corresponding approaches pursued to overcome the doping issues are discussed in detail.
基金supported by the National Natural Science Foundation of China(NSFC)(Grant Nos.12104153 and 51765017)China Postdoctoral Science Foundation(Grant No.2021M701963)Training Plan for Academic and Technical Leaders of Major Disciplines in Jiangxi Province,China(Grant No.20204BCJL23034).
文摘The expansion chamber serves as the primary silencing structure within the exhaust pipeline.However,it can also act as a sound-emitting structure when subjected to airflow.This article presents a hybrid method for numerically simulating and analyzing the unsteady flow and aerodynamic noise in an expansion chamber under the influence of airflow.A fluid simulation model is established,utilizing the Large Eddy Simulation(LES)method to calculate the unsteady flow within the expansion chamber.The simulation results effectively capture the development and changes of the unsteady flow and vorticity inside the cavity,exhibiting a high level of consistency with experimental observations.To calculate the aerodynamic noise sources within the cavity,the flow field results are integrated using the method of integral interpolation and inserted into the acoustic grid.The acoustic analogy method is then employed to determine the aerodynamic noise sources.An acoustic simulation model is established,and the flow noise source is imported into the sound field grid to calculate the sound pressure at the far-field response point.The calculated sound pressure levels and resonance frequencies show good agreement with the experimental results.To address the issue of airflow regeneration noise within the cavity,perforated tubes are selected as a means of noise suppression.An experimental platformfor airflow regeneration noise is constructed,and experimental samples are processed to analyze and verify the noise suppression effect of perforated tube expansion cavities under different airflow velocities.The research findings indicate that the perforated tube expansion cavity can effectively suppress low-frequency aerodynamic noise within the cavity by impeding the formation of strong shear layers.Moreover,the semi-perforated tube expansion cavity demonstrates the most effective suppression of aerodynamic noise.
文摘Blockchain,known for its secure encrypted ledger,has garnered attention in financial and data transfer realms,including the field of energy trading.However,the decentralized nature and identity anonymity of user nodes raise uncertainties in energy transactions.The broadcast consensus authentication slows transaction speeds,and frequent single-point transactions in multi-node settings pose key exposure risks without protective measures during user signing.To address these,an alliance blockchain scheme is proposed,reducing the resource-intensive identity verification among nodes.It integrates multi-signature functionality to fortify user resources and transac-tion security.A novel multi-signature process within this framework involves neutral nodes established through central nodes.These neutral nodes participate in multi-signature’s signing and verification,ensuring user identity and transaction content privacy.Reducing interactions among user nodes enhances transaction efficiency by minimizing communication overhead during verification and consensus stages.Rigorous assessments on reliability and operational speed highlight superior security performance,resilient against conventional attack vectors.Simulation shows that compared to traditional solutions,this scheme has advantages in terms of running speed.In conclusion,the alliance blockchain framework introduces a novel approach to tackle blockchain’s limitations in energy transactions.The integrated multi-signature process,involving neutral nodes,significantly enhances security and privacy.The scheme’s efficiency,validated through analytical assessments and simulations,indicates robustness against security threats and improved transactional speeds.This research underscores the potential for improved security and efficiency in blockchain-enabled energy trading systems.
基金the National Natural Science Foundation of China(Nos.21872101,21962014)Tianjin science and technology commission(No.18JCZDJC31300)Beijing Synchrotron Radiation Facility(BSRF)。
文摘A new catalyst of Co/La_(4)Ga_(2)O_(9) for CO_(2) hydrogenation to produce ethanol was prepared by reducing LaCo^(0).5 Ga0.5 O3,which showed excellent selectivity to ethanol(%35 C-mol%)at mild reaction conditions(270°C,3.5 MPa,3000 m L g-1 h-1).The catalysts were characterized by N_(2) adsorption/desorption,XRD,XAFS,CO and CO_(2)-TPD,H2 chemisorption,XPS and TEM techniques.The interaction between Co nanoparticles(NPs)and La2+4 Ga_(2)O_(9) oxide resulted in Co^(0)-Coon the surface of Co NPs.It was proposed that La_(4)Ga_(2)O_(9) could catalyze reverse water gas shift reaction(r-WGS),which converted CO_(2) to CO.Then,the CO migrated to Co^(0)-Co^(2+)on Co NPs,where it was hydrogenated to form ethanol like higher alcohols synthesis from syngas.The results suggest that by controlling the oxidation state of cobalt,and combined with a kind of active site for activating CO_(2) to form CO,a catalyst with excellent selectivity to ethanol could be obtained for CO_(2) hydrogenation,which means that the complex reaction may be proceed with high selectivity using only one active metal component.
基金financial supports from the National Natural Science Foundation of China(Grant No.21978033,U1663223&21978035)China Postdoctoral Science Foundation(2019M650055)+3 种基金Liaoning Province Funds(XLYC1907063)the Changjiang Scholars Program(T2012049)the Fundamental Research Funds for the Central Universities(DUT19TD33)the Opening Project of Guangxi Key Laboratory of Petrochemical Resource Processing&Process Intensification Technology(2018K009)。
文摘Coal-based H2 generation has abruptly increased in recent years.The PSA-VPSA-SC process is the matured and standard framework for H2 purification and CO_(2) capture in many existing plants,including normal and vacuum pressure swing adsorption units in series(PSA-VPSA),and shallow condensation unit(SC).However,this standard process is frequently subjected to low H2 recovery ratio and high purification cost.In this work,H2-selective and C02-selective membrane units,i.e.,HM and CO_(2) M,are attempted to support the standard process and ameliorate constraints.In the beginning,HM unit is arranged after VPSA to enhance H2 recovery from the decarbonized stream,i.e.,the PSA-VPSA-SC/HM process.As a result,H2 recovery ratio can be enhanced significantly from 83%to 98%.In the following,VPSA is replaced with CO_(2) M unit to reduce investment and operation cost,i.e.,the PSA-CO_(2) M-SC/HM process.Accordingly,the specific purification cost is diminished from 33.46 to 32.02 USD·(103 m^(3) H_(2))-1,saved by 4.3%,meanwhile the construction cost is falling back and just a little higher than that for the standard process.In the end,another CO_(2) M unit is launched before PSA,i.e.,the CO_(2) M-PSA-CO_(2) M-SC/HM process,which could unbundle CO_(2) enrichment partially from H2 purification,and then save more investment and operation cost.In comparison with the standard process,this ultimate retrofitted process can be superior in all the three crucial indices,i.e.,recovery ratio,investment,and specific purification cost.On the whole,coal-based H2 generation can be ameliorated significantly through high efficient H2-selective and CO_(2)-selective membrane units.
基金supported by the National Natural Science Foundation of China (Grants No.51501041 and No.51671059)
文摘Passivity breakdown on 436 ferritic stainless steel(FSS) has been investigated in solutions containing different concentrations of chloride at 25?C and interpreted in terms of the point defect model(PDM). The measured near-normal distributions of passivity breakdown potentials for 436 FSS under experimental conditions are in good agreement with the calculated results according to the PDM. The linear dependence of breakdown potential on the square root of potential scanning rate, which was described by the PDM,provides the estimation of the critical concentration of condensed vacancies at the metal/film interface,which leads to the passivity breakdown. This value is in good agreement with that calculated from the microstructure properties of the alloy substrate and the barrier layer of the passive film. This study demonstrates the validity of the PDM in describing the passivity breakdown on 436 FSS in NaCl solutions.
基金support from the National Natural Science Foundation of China(no.52072307)。
文摘Rational structure design and regulation are of paramount importance for obtaining electrode materials with desirable electrochemical performance.Here,a novel binder-free electrode with the hollow Co_(9)S_(8) core@multi-shell structure(CS-x@MXene@Bi_(2)O_(3))derived from metal-organic frameworks(MOFs)precursor is well designed by the electrospinning,sulfuration,carbonization,and hydrothermal processes.In this architecture,the concentration of Co_(9)S_(8)(CS-x)is optimized for an ideal flexible substrate,which alleviates the dimensional variation for long cycle life.The unique cores and the MXene flakes engineered by Bi_(2)O_(3) multiple shells can be responsible for the superior characteristics,including a fast electronic pathway,large specific surface area,enhanced electrical conductivity,and improved electrochemical performance.As expected,the obtained CS-2@MXene@Bi_(2)O_(3) binder-free electrode exhibits a high discharge capacitance of 646.1 F g^(–1)(1 A g^(–1)).Two binder-free electrodes can be assembled into a solid-state supercapacitor with desirable energy and power density,and long-term cyclic stability is demonstrated through 5000 cycles.Given these advantages,the CS-2@MXene@Bi_(2)O_(3) is selected as the electrode in a foldable supercapacitor.More importantly,the specific capacitance is reserved after various deformations.Therefore,it is expected that binder-free electrode materials with the unique core@shell structure design could be applied in wearable and portable energy conversion devices.
基金The National Natural Science Foundation of China under contract No.41906199the Youth Innovation Project of National Space Science Center of Chinese Academy of Sciences under contract No.E0PD40012S。
文摘HY-2 A(Haiyang-2 A),launched in 2011,is the first ocean dynamic environment satellite of China and is equipped with a radar altimeter as one of the primary payloads.HY-2 A shifted the drift orbit in March 2016 and has been accumulating geodetic mission(GM)data for more than three years with 168-day cycle.In this paper,we present the preliminary gravity field inverted by the HY-2 A/GM data from March 2016 to December 2017 near Taiwan(21°–26°N,119°–123°E).The gravity anomaly is computed by Inverse Vening Meinesz(IVM)formula with a onedimensional FFT method during remove-restore procedure with the EGM2008 gravity model as the reference field.For comparison,CryoSat-2 altimeter data are used to inverse the gravity field near Taiwan Island by the same method.Comparing with the gravity field derived from CryoSat-2,a good agreement between the two data sets is found.The global ocean gravity models and National Geophysical Data Center(NGDC)shipboard gravity data also are used to assess the performance of HY-2 A/GM data.The evaluations show that HY-2 A and CryoSat-2 are at the same level in terms of gravity field recovery and the HY-2 A/GM altimeter-derived gravity field has an accuracy of 2.922 mGal.Therefore,we can believe that HY-2 A will be a new reliable data source for marine gravity field inversion and has the potentiality to improve the accuracy and resolution of the global marine gravity field.
基金This work is supported by the National Natural Science Foundation of China[grant numbers 41890820,41771452,41771454,and 41901340]。
文摘Due to the bird’s eye view of remote sensing sensors,the orientational information of an object is a key factor that has to be considered in object detection.To obtain rotating bounding boxes,existing studies either rely on rotated anchoring schemes or adding complex rotating ROI transfer layers,leading to increased computational demand and reduced detection speeds.In this study,we propose a novel internal-external optimized convolutional neural network for arbitrary orientated object detection in optical remote sensing images.For the internal opti-mization,we designed an anchor-based single-shot head detector that adopts the concept of coarse-to-fine detection for two-stage object detection networks.The refined rotating anchors are generated from the coarse detection head module and fed into the refining detection head module with a link of an embedded deformable convolutional layer.For the external optimiza-tion,we propose an IOU balanced loss that addresses the regression challenges related to arbitrary orientated bounding boxes.Experimental results on the DOTA and HRSC2016 bench-mark datasets show that our proposed method outperforms selected methods.
基金supported by the National Natural Science Foundation of China(Nos.21576192,21776214)
文摘A new scheme for the preparation of highly dispersed precious metal catalysts is proposed in this work. Samples of LaCol-xPtxO3/SiO2 （x = 0.03, 0.05, 0.07, 0.09, and 0.10） were prepared through a simple method of citrate acid complexa-tion combined with impregnation. In a nanocrystallite of LaCOl-xPtxO3, ions of lanthanum, cobalt, and platinum are evenly mixed at the atomic level and confined within the nanocrystallite. In the reduction process, platinum ions were reduced and migrated onto the surface of the nanocrystallite, and the platinum should be highly dispersed owing to the even mixing of the platinum ions in the precursor. When x = 0.05 or lower, the highest dispersion of Pt could be achieved. The highly dispersed Pt is stable, because of the strong interaction between Pt atoms and the support. The catalysts were characterized by BET surface area, temperature-programmed reduction, X-ray diffraction, transmission electron microscopy, CO temperature-programmed desorption, and turnover frequency. Compared with general precious metal Pt catalysts, the LaCo0.95Pt0.05O3/ SiO2 catalyst exhibited better activity for CO oxidation, and it maintained stability at a high temperature of 400 ℃ for 250 h with complete CO conversion.
基金supported in part by the National Natural Science Foundation of China(42090012)03 Special Research and 5G Project of Jiangxi Province in China(20212ABC03A09)the Open Grants of the State Key Laboratory of Severe Weather(2021LASW-A17)。
文摘Dear Editor,In pansharpening task,the most existing deep-learning-based pansharpening methods fail to fully utilize the different level features,inevitably leading to spectral or spatial distortions.To address this challenge,in this letter,we propose a dual-branch multi-level feature aggregation network for pansharpening(DMFANet).
基金Supported by Student’s Platform for Innovation and Entrepreneurship Training Program of Guangxi Zhuang Autonomous Region,China in 2016(201610599033)Innovation and Entrepreneurship Ethnical Medicine Teaching Team Program of Guangxi Zhuang Autonomous Region,China(Gui Jiao Gao Jiao[2015]93&Gui Jiao Gao Jiao[2016]6)
文摘[Objectives] To determine the optimum conditions and antioxidant activity of Myrica ruba leaf pigment,and provide reference for further development and use of Myrica ruba leaves. [Methods]Pigment of Myrica ruba leaves was extracted by ethanol extraction method. Absorbance was measured at wavelength of 300 nm. Effects of ethanol volume fraction,solid-to-liquid ratio,temperature,and extraction time were studied. L_9( 3~3) orthogonal experiment was carried out to optimize the extraction process,and DPPH scavenging ability was measured.[Results]The optimum extraction process of Myrica ruba leaf pigment was as follows: the ethanol volume fraction was 50%; the solid-to-liquid ratio was 1: 60( w/v),extraction temperature 70℃; extraction time was 60 min; after the concentration of purified Myrica ruba leaf pigment reached 0. 4455 mg/mL,the DPPH scavenging ability was basically the same as the same concentration Vc.[Conclusions] The experiment indicates that the optimized extraction process has a high yield rate,and Myrica ruba leaf pigment has high anti-oxidant activity.
基金funded by the National Natural Science Foundation of China(Grant Nos.51975339,51605262)China Postdoctoral Science Foundation(Grant Nos.2019T120602,2017M610439)Youth Innovation and Technology Support Program for University in Shandong Province(Grant No.2019KJB003).
文摘The process parameters of laser additive manufacturing have an important influence on the forming quality of the produced items or parts.In the present work,a finite element model for simulating transient heat transfer in such processes has been implemented using the ANSYS software,and the temperature and stress distributions related to 316L stainless steel thin-walled ring parts have been simulated and analyzed.The effect of the laser power,scanning speed,and scanning mode on temperature distribution,molten pool structure,deformation,and stress field has been studied.The simulation results show that the peak temperature,weld pool size,deformation,and residual stress increase with an increase in laser power and a decrease in the scanning speed.The scanning mode has no obvious effect on temperature distribution,deformation,and residual stress.In addition,a forming experiment was carried out.The experimental results show that the samples prepared by laser power P=800 W,V=6 mm/s,and the normal scanning method display good quality,whereas the samples prepared under other parameters have obvious defects.The experimental findings are consistent with the simulation results.
基金The National Natural Science Foundation of China(No.61762031)The Science and Technology Major Project of Guangxi Province(NO.AA19046004)The Natural Science Foundation of Guangxi(No.2021JJA170130).
文摘There is a large amount of information in the network data that we canexploit. It is difficult for classical community detection algorithms to handle network data with sparse topology. Representation learning of network data is usually paired with clustering algorithms to solve the community detection problem.Meanwhile, there is always an unpredictable distribution of class clusters outputby graph representation learning. Therefore, we propose an improved densitypeak clustering algorithm (ILDPC) for the community detection problem, whichimproves the local density mechanism in the original algorithm and can betteraccommodate class clusters of different shapes. And we study the communitydetection in network data. The algorithm is paired with the benchmark modelGraph sample and aggregate (GraphSAGE) to show the adaptability of ILDPCfor community detection. The plotted decision diagram shows that the ILDPCalgorithm is more discriminative in selecting density peak points compared tothe original algorithm. Finally, the performance of K-means and other clusteringalgorithms on this benchmark model is compared, and the algorithm is proved tobe more suitable for community detection in sparse networks with the benchmarkmodel on the evaluation criterion F1-score. The sensitivity of the parameters ofthe ILDPC algorithm to the low-dimensional vector set output by the benchmarkmodel GraphSAGE is also analyzed.
基金Supported by the 12th Five-Year TCM Key Discipline Chinese Medicine Chemistry Construction Program of State Administration of Traditional Chinese Medicine,China(Guo Zhong Yi Yao Ren Jiao Fa[2012]32)Natural Science Foundation Project of Guangxi(2013GXNSFAA019240)+2 种基金Key Discipline Chinese Medicine Chemistry Construction Program of Guangxi,China(Gui Jiao Ke Yan[2013]16)Student’s Platform for Innovation and Entrepreneurship Training Program of Guangxi in 2015(201510599037)Innovation and Entrepreneurship Ethnical Medicine Teaching Team Program of Guangxi Zhuang Autonomous Region,China(Gui Jiao Gao Jiao[2015]93 & Gui Jiao Gao Jiao[2016]6)
文摘[Objectives] To compare different extraction methods for total alkaloids from Abrus Cantoniensis Hance taking chloroform as solvent. [Methods] The ethanol extraction method,ultrasonic extraction method,acid water extraction method,and Soxhlet extraction method were used to extract total alkaloids,and the total alkaloids of Abrus Cantoniensis Hance were measured at 238 nm wavelength. [Results] The extraction rate of ethanol extraction method was 14. 76 mg/100 g; the extraction rate of ultrasonic extraction method was 56. 85 mg/100 g; the extraction rate of acid water extraction method was 56. 63 mg/100 g; the extraction rate of Soxhlet extraction method was 58. 19 mg/100 g.[Conclusions]Results indicate that Soxhlet extraction method can obtain the highest extraction rate.
基金supported by the National Natural Science Foundation of China(Grant Nos.52478080,52408101,and 52078096)the Natural Science Foundation Joint Fund of Liaoning Province(Grant No.2023-MSBA-023)+2 种基金2023 Dalian University of Technology-Cardiff University Cooperation and Exchange Foundation Project2023 International Exchange Foundation Project of“Co-Creation of Excellence Program”from Dalian University of Technology(Grant No.DUTIO-ZG-202307)the Key Project of DUT for International Students Studying and Researching in China:Innovation and Practice of Talent Cultivation Model in the Field of Smart Buildings for the“Belt and Road”Initiative(Grant No.1103-82120001).
文摘Sensors are a crucial component in heating,ventilation,and air conditioning(HVAC)control systems,and the quality of them plays an important role in control accuracy.In the research of fault detection and control optimization,improving sensor data quality has inspiring potential in application.It has been largely limited to the application of signal processing methods in research focus,whereas a detailed analysis of the characteristics of signals from various sensors of the HVAC system has not been conducted.Therefore,this study analyzes the time-frequency domain characteristics of control sensors within HVAC systems through integrating the structural design and control logic of such systems.Additionally,the research examines the correlations between control sensors in HVAC systems.Based on statistical principles and the energy-mass dynamic laws of the equipment,this paper defines first-class(Ⅰ)correlated sensors and second-class(Ⅱ)correlated sensors.To sum up,the main contribution of this paper is conducting a fundamental study on the characteristics of control sensors within HVAC systems,providing theoretical reference for future research on HVAC system fault diagnosis and control optimization.
文摘将界面太阳能水蒸发技术与光催化降解过程耦合被视为解决能源和环境问题的有效策略,但开发具有光热与催化协同效应的双功能蒸发器仍然具有挑战性.本文构建了MoS_(2)-g-C_(3)N_(4)(MG)异质结并将其负载于气凝胶上制备了一系列双功能的MoS_(2)-g-C_(3)N_(4)(MG)气凝胶蒸发器.这些MG气凝胶具有高比表面积、有效光吸收和高光催化活性,表现出优异的光热转换性能和光催化降解能力.MG气凝胶大的比表面积和丰富的孔隙结构不仅有利于水的渗透和蒸发焓的降低,还有利于有机污染物的吸附降解.其中,基于MG-0.4构筑的蒸发器具有1.72 kg m^(-2)h^(-1)的高水蒸发效率,同时表现出显著的罗丹明B降解效率(90.1%).这项工作为解决淡水短缺和水污染控制问题提供了一个新方法.
基金supported by the Fundamental Research Funds for the Central Universities(200-BLX202234)the National Natural Science Foundation of China(31971613 and 22308029).
文摘Utilizing renewable lignocellulosic resources for wastewater remediation is crucial to achieving sustainable social development.However,the resulting by-products and the synthetic process characterized by complexity,high cost,and environmental pollution limit the further development of lignocellulose-based materials.Here,we developed a sustainable strategy that involved a new functional deep eutectic solvent(DES)to deconstruct industrial xylose residue into cellulose-rich residue with carboxyl groups,lignin with carboxyl and quaternary ammonium salt groups,and DES effluent rich in lignin fragments.Subsequently,these fractions equipped with customized functionality were used to produce efficient wastewater remediation materials in cost-effective and environmentally sound manners,namely,photocatalyst prepared by carboxyl-modified cellulose residue,biochar-based adsorbent originated from modified lignin,and flocculant synthesized by self-catalytic in situ copolymerization of residual DES effluent at room temperature.Under the no-waste principle,this strategy upgraded the whole components of waste lignocellulose into high-value-added wastewater remediation materials with excellent universality.These materials in coordination with each other can stepwise purify high-hazardous mineral processing wastewater into drinkable water,including the removal of 99.81%of suspended solids,almost all various heavy metal ions,and 97.09%chemical oxygen demand,respectively.This work provided promising solutions and blueprints for lignocellulosic resources to alleviate water shortages while also advancing the global goal of carbon neutrality.
