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Calculating the Excitation Temperature for H2CO Absorption lines in Molecular Clouds

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Research in Astronomy and Astrophysics 2024年第7期24卷 271-274页

作者： Jia Bu Jarken Esimbek Jianjun zhou Toktarkhan Komesh Xindi tang Dalei li Yuxin He Kadirya Tursun Dongdong zhou Ernar Imanaly Serikbek Sailanbek Xinjiang Astronomical Observatory Chinese Academy of Sciences University of Chinese Academy of Sciences Key Laboratory of Radio Astronomy Chinese Academy of Sciences Xinjiang Key Laboratory of Radio Astrophysics Energetic Cosmos Laboratory Nazarbayev University Institute of Experimental and Theoretical Physics Al-Farabi Kazakh National University

The excitation temperature Texfor molecular emission and absorption lines is an essential parameter for interpreting the molecular *** temperature can be obtained by observing multiple molecular transitions or hyperfine structures of a single transition,but it remains unknown for a single transition without hyperfine structure *** H2CO absorption experiments for a single transition without hyperfine structures adopted a constant value of Tex,which is not correct for molecular regions with active star formation and H II *** H2CO,two equations with two unknowns may be used to determine the excitation temperature Texand the optical depthτ,if other parameters can be determined from *** observational data of the4.83 GHz （λ=6 cm） H2CO (110-111) absorption line for three star formation regions,W40,M17 and DR17,have been used to verify this *** distributions of Texin these sources are in good agreement with the contours of the H110α emission of the H II regions in M17 and DR17 and with the H2CO (110-111) absorption in *** distributions of Texin the three sources indicate that there can be significant variation in the excitation temperature across star formation and H II regions and that the use of a fixed （low） value results in misinterpretation.

关键词： (ISM:) HII regions ISM: clouds ISM: molecules

Bimetal MOF-derived NiFe-P nanocomposites coupled with Cu_(3)P nanoparticles to construct tandem electron transfer channels for photocatalytic hydrogen evolution

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Journal of Environmental Sciences 2024年第3期137卷 333-346页

作者： Haiyan Zhang Shitao Yang Peng Zhu Senpei tang Ming li College of Chemistry and Chemical Engineering Jishou UniversityJishou 416000China School of Account Hunan University of Technology and BusinessChangsha 410205China

Finely modulated light-induced charge separation and transfer is a central challenge to achieve efficient *** progress has been made in this field,most of the previous research works focused on the separation or migration of photogenerated carriers but did not build a bridge between the *** to realize the strong driving and precise migration of carriers has become the focus of our *** report an ingeniously designed ternary *** NiFe-MOF as the“parent material”,the FeP_(4)/Ni_(x)P_(y)heterojunction is derived in situ while maintaining the frame structure through gas-solid reaction,and finally the Z-type electron transfer is *** Cu_(3)P anchoring spindle matrix,an electron transport tunnel is opened up in Cu_(3)P/FeP_(4)/Ni_(x)P_(y)ternary heterojunction under the action of p-n heterojunction built-in electric field driving and accurate energy band *** strong driving force of the built-in electric field provides an inexhaustible power for the transmission of electrons,and the fine series of electron transmission channels realizes the precise transmission of *** above fine design makes the perfect fit between the built-in electric field and the electron transfer channel,which not only effectively improves the embarrassing situation of insufficient electron driving force of hydrogen evolution reaction in the previous research,but also makes up for the weakening of semi-conductor reduction ability caused by the construction of traditional p-n *** research work provides a new idea for the construction of multiple heterostructures and the design of fine interface engineering in the future.

关键词： Cu_(3)P/FeP_(4)/Ni_(x)P Built-in electric field Electron transfer channels Photocatalysis

Effective Ultra-High-Speed Identification Scheme of lightning Strikes Suitable for VSC-Based DC Grids

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CSEE Journal of Power and Energy Systems 2024年第2期10卷 548-561页

作者： Longlong Chen Xiangyu Pei Xiaoguang Wei Pengzhi li Guangfu tang North China Electric Power University(NCEPU) Beijing 102206China Changsha University of Science and Technology Changsha 410114China State Key Laboratory of Advanced Power Transmission Technology State Grid Smart Grid Research Institute Co.Ltd.Beijing 102209China

To ensure their sound and continuous operation to the greatest extent,VSC-based DC girds have extremely stringent requirements for transmission line relay *** terms of guaranteeing their reliability,accurate identification of lightning strikes on DC transmission lines is one of the urgent key problems to be *** effective ultra-high-speed identification scheme of lightning strikes suitable for the VSC-based DC grid is proposed in this ***,an 1-mode reverse voltage traveling wave(RVTW)is constructed applying the pole-mode transformation ***,fault traveling wave propagation characteristics along the DC transmission line are analyzed in depth utilizing Peterson's ***,differences of time-frequency electromagnetic transient characteristics of 1-mode RVTWs between disturbances and faults caused by lightning strikes are distinguished in detail by means of the classical wavelet transformation multi-resolution analysis ***,extensive simulations are carried out to evaluate the performance of the proposed identification scheme,and by which its excellent rapidity,reliability and robustness are *** Terms-lightning-strike identification,Multi-resolution analysis,Relay protection,Traveling-wave protection,VsC-based DC grid,Wavelet transformation.

关键词： lightning-strike identification Multi-resolution analysis Relay protection Traveling-wave protection VsC-based DC grid Wavelet transformation

Joint position optimization,user association,and resource allocation for load balancing in UAV-assisted wireless networks

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Digital Communications and Networks 2024年第1期10卷 25-37页

作者： Daosen Zhai Huan li Xiao tang Ruonan Zhang Haotong Cao School of Electronics and Information Northwestern Polytechnical UniversityXian710072China State Key Laboratory of Integrated Services Networks Xidian UniversityXian710071China Department of Computing Hong Kong Polytechnic UniversityHong Kong SARChina

Unbalanced traffic distribution in cellular networks results in congestion and degrades spectrum *** tackle this problem,we propose an Unmanned Aerial Vehicle(UAV)-assisted wireless network in which the UAV acts as an aerial relay to divert some traffic from the overloaded cell to its adjacent underloaded *** fully exploit its potential,we jointly optimize the UAV position,user association,spectrum allocation,and power allocation to maximize the sum-log-rate of all users in two adjacent *** tackle the complicated joint optimization problem,we first design a genetic-based algorithm to optimize the UAV ***,we simplify the problem by theoretical analysis and devise a low-complexity algorithm according to the branch-and-bound method,so as to obtain the optimal user association and spectrum allocation *** further propose an iterative power allocation algorithm based on the sequential convex approximation *** simulation results indicate that the proposed UAV-assisted wireless network is superior to the terrestrial network in both utility and throughput,and the proposed algorithms can substantially improve the network performance in comparison with the other schemes.

关键词： Load balance Unmanned aerial vehicle Userassociation Resource management

Time-varying parameters estimation with adaptive neural network EKF for missile-dual control system

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Journal of Systems Engineering and Electronics 2024年第2期35卷 451-462页

作者： YUAN Yuqi zhou Di li Junlong LOU Chaofei School of Astronautics Harbin Institute of TechnologyHarbin 150001China Beijing Institute of Electronic System Engineering Beijing 100854China

In this paper, a filtering method is presented to estimate time-varying parameters of a missile dual control system with tail fins and reaction jets as control variables. In this method, the long-short-term memory(LSTM) neural network is nested into the extended Kalman filter(EKF) to modify the Kalman gain such that the filtering performance is improved in the presence of large model uncertainties. To avoid the unstable network output caused by the abrupt changes of system states,an adaptive correction factor is introduced to correct the network output online. In the process of training the network, a multi-gradient descent learning mode is proposed to better fit the internal state of the system, and a rolling training is used to implement an online prediction logic. Based on the Lyapunov second method, we discuss the stability of the system, the result shows that when the training error of neural network is sufficiently small, the system is asymptotically stable. With its application to the estimation of time-varying parameters of a missile dual control system, the LSTM-EKF shows better filtering performance than the EKF and adaptive EKF(AEKF) when there exist large uncertainties in the system model.

关键词： long-short-term memory(LSTM)neural network extended Kalman filter(EKF) rolling training time-varying parameters estimation missile dual control system

Effects of Number of Bleed Holes on Shock-Wave/Boundary-Layer Interactions in a Transonic Compressor Stator

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Journal of Thermal Science 2024年第2期33卷 611-624页

作者： li Bai zhou Xun LUO Lei DU Wei School of Energy Science and Engineering Harbin Institute of TechnologyHarbin150001China

An extensive numerical investigation is conducted to characterize the flow separation control in a transonic compressor cascade with a porous *** bleed holes are arranged on the suction surface in a single row,two staggered rows and three staggered *** each bleed scheme,five bleed pressure ratios are examined at an inlet Mach number of *** results indicate that the aerodynamic performance of the cascade is significantly improved by the porous *** the single-row scheme,the maximum reduction in total pressure losses is 57%.For the two-staggered-row and three-staggered-row schemes,there is an optimal bleed pressure ratio of 1.0,and the maximum reductions in total pressure loss are 68% and 75%,*** low loss in the cascade is due to the well-controlled boundary *** new local supersonic region created by the bleed hole is the key reason for the improved boundary *** vortex induced by side bleeding provides another mechanism for delaying flow *** the bleed holes could create multiple local supersonic regions,which reduce the range of the adverse pressure gradient that the boundary layer needs to *** is the reason why cascades with more bleed holes perform better.

关键词： transonic compressor stator shock wave/boundary layer interaction porous bleed number of bleed holes

Experimental study on the size effect on the equation of state of concretes under shock loading

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Defence Technology（防务技术） 2024年第3期33卷 160-167页

作者： Mei li Jian Cui Yanchao Shi Baijian tang Xin Chen Key Laboratory of Coast Civil Structural Safety of the Ministry of Education Tianjin UniversityTianjin 300072China School of Civil Engineering Suzhou University of Science and Technology1701 Binhe RoadSuzhou 215011JiangsuChina School of Civil Engineering Tianjin UniversityTianjin 300072China

Adopting the classical theory of hydrocodes,the constitutive relations of concretes are separated into an equation of state(EoS)which describes the volumetric behavior of concrete material and a strength model which depicts the shear properties of *** experiments on the EoS of concrete is always challenging due to the technical difficulties and equipment limitations,especially for the specimen size effect on the *** some researchers investigate the shock properties of concretes by fly-plate impact tests,the specimens used in their tests are usually in one *** this paper,the fly-plate impact tests on concrete specimens with different sizes are performed to investigate the size effect on the shock properties of concrete *** mechanical background of the size effect on the shock properties are revealed,which is related to the lateral rarefaction effect and the deviatoric stress produced in the *** to the tests results,the modified EoS considering the size effect on the shock properties of concrete are proposed,which the bulk modulus of concrete is unpredicted by up to 20% if size effects are not accounted for.

关键词： Concrete Equation of state Size effect Shock wave Fly-plate impact test

Structural uncertainty quantification of Reynolds-Averaged Navier–Stokes closures for various shock-wave/boundary layer interaction flows

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Chinese Journal of Aeronautics 2024年第3期37卷 34-48页

作者： Fanzhi ZENG Tianxin ZHANG Denggao tang Jinping li Chao YAN School of Aeronautic Science and Engineering Beihang UniversityBeijing 100191China School of Aeronautical Engineering Air Force Engineering UniversityXi’an 710038China

Accurate prediction of Shock-Wave/Boundary Layer Interaction(SWBli)flows has been a persistent challenge for linear eddy viscosity models.A major limitation lies in the isotropic representation of the Reynolds stress,as assumed under the Boussinesq *** studies have shown promise in improving the prediction capability for incompressible separation flows by perturbing the Reynolds-stress anisotropy ***,it remains uncertain whether this approach is effective for SWBli flows,which involve compressibility and *** address this issue,this study systematically quantifies the structural uncertainty of the anisotropy for oblique SWBli *** eigenspace perturbation method is applied to perturb the anisotropy tensor predicted by the Menter Shear–Stress Transport(SST)model and reveal the impacts of anisotropy on the prediction of quantities of interest,such as separation and reattachment positions,wall static pressure,skin friction,and heat *** results demonstrate the potential and reveal the challenges of eigenspace perturbation in improving the SST ***,a detailed analysis of turbulent characteristics is performed to identify the source of *** findings indicate that eigenspace perturbation primarily affects turbulent shear stress,while the prediction error of the SST model is more related to turbulent kinetic energy.

关键词： Shock-wave/boundary layer interaction(SWBli) Turbulence models Uncertainty analysis Eigenspace perturbation Anisotropy

Optimal Planning of Hybrid AC/DC Low-voltage Distribution Networks Considering DC Conversion of Three-phase Four-wire Low-voltage AC Systems

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Journal of Modern Power Systems and Clean Energy 2024年第1期12卷 141-153页

作者： Bo Zhang Lu Zhang Wei tang Gen li Chen Wang the College of Information and Electrical Engineering China Agricultural UniversityBeijing 100083China the Electric Energy Group Department of Engineering TechnologyTechnical University of Denmark(DTU)2750 BallerupDenmark the Power Distribution Technology Center State Grid Beijing Electric Power Research InstituteBeijing 100075China

The increasing integration of distributed household photovoltaics(PVs)and electric vehicles(EVs)may further ag gravate voltage violations and unbalance of low-voltage distribu tion networks(LVDNs).DC distribution networks can increase the accommodation of PVs and EVs and mitigate mutilple pow er quality problems by the flexible power regulation capability of voltage source *** paper proposes schemes to es tablish hybrid AC/DC LVDNs considering the conversion of the existing three-phase four-wire low-voltage AC systems to DC op *** characteristics and DC conversion constraints of typical LVDNs are *** addition,converter configura tions for typical LVDNs are proposed based on the three-phase four-wire characteristics and quantitative analysis of various DC ***,an optimal planning method of hybrid AC/DC LVDNs is proposed,which is modeled as a bi-level programming model considering the annual investments and three-phase *** are conducted to verify the effectiveness of the proposed optimal planning *** ulation results show that the proposed optimal planning method can increase the integration of PVs while simultaneously reduc ing issues related to voltage violation and unbalance.

关键词： Optimal planning low-voltage distribution net work three-phase unbalance DC conversion