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Underwater self-interference suppression method based on multistage delay estimation and transfer function fitting

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Chinese Journal of Acoustics 2024年第2期43卷 199-217页

作者： WANG Boheng ZHANG Qunfei SHI Wentao school of Marine Science and technology Northwestern Polytechnical UniversityXi'an 710072

In order to suppress strong self-interference signals in received signals, a selfinterference suppression method based on transfer function fitting and multistage delay estimation is proposed. Firstly, the transfer function of transmitting leakage is estimated by frequency domain deconvolution to construct the basic cancellation signal. Then, the multistage delay estimation based on the cross correlation method and the cross spectrum method is used to accurately compensate the cancelling signals to obtain a good selfinterference suppression effect. The processing results of the actual sea trial data indicate that the suppression ratio of the proposed method can reach 36 d B, and the signal-tointerference ratio of the detectable echo can be reduced from-30 d B to-55 d B when the unmanned undersea vehicle(UUV) integrated system is used to transmit multi-frame linear frequency modulated(LFM) signals in the working sector of the side array for active detection of the target ship. The same suppression effect is found for the subsequent selfinterference signals. The above results indicate that the method can suppress the strong self-interference signal, and presents stability, so that the echo signal submerged in the strong self-interference signal can be detected.

关键词： estimation delay function

Superior energy storage performance of BNT-based ferroelectric ceramics based on maintaining high polarization and breakdown strength

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Journal of Advanced Dielectrics 2024年第4期14卷 20-29页

作者： Mingjia Jiang Zhanhui Peng Qiyuan Zhou Di Wu Lingling Wei Pengfei Liang Xiaolian Chao Zupei Yang Key Laboratory for Macromolecular Science of Shaanxi Province Shaanxi Key Laboratory for Advanced Energy Devices Shaanxi Engineering Laboratory for Advanced Energy Technology School of Materials Science and EngineeringShaanxi Normal UniversityXi’an 710062ShaanxiP.R.China school of Chemistry and Chemical Engineering Shaanxi Normal university Xi’an 710062 ShaanxiP.R.China school of Physics and information technology Shaanxi Normal university Xi’an 710062 ShaanxiP.R.China

Bi_(0.5)Na_(0.5)TiO_(3)(BNT)-based lead-free ceramics with superior ferroelectric properties are considered to be extremely advantageous in energy storage capacitors for future green ***,we demonstrate an approach to achieve both ultrahigh energy density W_(rec)and efficiencyηby regulating the multiscale electropolar structures and microstructure.A satisfactory energy storage performance of a high W_(rec)of 4.02 J·cm^(-3),and a decentηof 80%under 415 kV·cm^(-1)are attained in the 0.5(BNT-CS)-0.5SB_(0.2)T ceramic(abbreviated as BNT-0.2SBT).Moreover,BNT-0.2SBT exhibits superior power density(P_(D)=107MW·cm^(-3)),ultrafast discharge time(t_(0.9)=116 ns)at 150 kV·cm^(-1),and good temperature *** findings in this work not only demonstrate that a valid candidate,but also provide a new idea of how to achieve both high-energy storage density and efficiency in lead-free ferroelectric materials.

关键词： Energy storage Bi_(0.5)Na_(0.5)TiO_(3)ceramics relaxor characteristics breakdown strength

Estimation and validation of characteristic length of internal solitary wave based on normal mode coupling

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Chinese Journal of Acoustics 2024年第1期43卷 82-97页

作者： FAN Lei YAO Pan AO Peiting WANG Huigang school of Marine Science and technology Northwestern Polytechnical UniversityXi'an 710072

For a fluid medium with density stratification, the internal wave is easily observed under disturbance of waves, and the acoustic transmission loss and the characteristic parameters of the internal solitary wave are related. The mathematical relationship between the horizontal wavenumber difference of normal modes and the characteristic length of internal wave is established according to the coupling theory of normal modes. Furthermore, a method for estimating the characteristic length of internal solitary wave based on active acoustic means is proposed. The numerical simulation results reveal that the internal solitary wave has a significant influence on the forward transmission of sound *** a specific frequency, the transmission loss of sound waves fluctuates significantly and is related to the wavenumber difference of the coupling between internal waves and normal modes. An experiment system for studying internal waves in a tank is established, and the forward scattering data of the internal waves are collected by using a developed broadband transient plasma sound source. The feasibility of estimating the characteristic parameters of the internal solitary wave based on the resonance phenomenon is verified through experimental data analysis.

关键词： stratification wave characteristic

Simulation of deuterium pellet ablation and deposition in the EAST tokamak with HPI2 code

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Chinese Physics B 2024年第4期33卷 561-569页

作者：李大正张洁侯吉磊李懋孙继忠 Key Laboratory of Materials Modification by Laser Ionand Electron BeamsSchool of PhysicsDalian University of TechnologyDalian 116024China Department of Plasma Physics and Fusion Engineering University of Science and Technology of ChinaHefei 230026China Institute of Plasma Physics Chinese Academy of SciencesHefei 230031China

Pellet injection is a primary method for fueling the plasma in magnetic confinement *** that goal the knowledges of pellet ablation and deposition profiles are *** the present study,the pellet fueling code HPI2 was used to predict the ablation and deposition profiles of deuterium pellets injected into a typical H-mode discharge on the EAST *** ablation and deposition profiles were evaluated for various pellet injection locations,with the aim at optimizing the pellet injection to obtain a deep fueling *** this study,we investigate the effect of the injection angle on the deposition depth of the pellet at different velocities and *** ablation and deposition of the injected pellet are mainly studied at each injection position for three different injection angles:0°,45°,and 60°.The pellet injection on the high field side(HFS)can achieve a more ideal deposition depth than on the low field side(LFS).Among these angles,horizontal injection on the middle plane is relatively better on either the HFS or the *** the injection location is 0.468 m below the middle plane on the HFS or 0.40 m above the middle plane of the LFS,it can achieve a similar deposition depth to the one of its corresponding *** the pre-cooling effect is taken into account,the deposition depth is predicted to increase only slightly when the pellet is launched from the *** findings of this study will serve as a reference for the update of pellet injection systems for the EAST tokamak.

关键词： pellet injection pellet ablation HPI2 pellet deposition

Analysis of photocatalytic degradation of polyamide microplastics in metal salt solution by high resolution mass spectrometry

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Journal of Environmental Sciences 2024年第5期139卷 473-482页

作者： Yunjin Zhong Lebing Zhuo Wangyang Lu National Engineering Lab for Textile Fiber Materials&Processing technology(Zhejiang) School of Materials Science&EngineeringZhejiang Sci-Tech UniversityHangzhou 310018China

Microplastic pollution has become one of the most concerned focuses in the *** many treatment methods,photocatalysis is considered to be one of the most environmentally friendly *** this work,the photodegradation behavior of polyamide microplastics is studied by using polyamide 6(PA6)as model microplastics and FeCl_(3) as *** is hoped that the PA6 fiber can be effectively degraded by utilizing the strong oxidizing active species that can be produced after FeCl_(3) is irradiated in *** results shows that PA6 fiber can be almost completely degraded after 10 days of irradiation in FeCl_(3) aqueous solution,indicating that it is promising to use this new method to solve the problem of PA6type *** addition,the chain scission mechanism and degradation process of PA6 are analyzed in detail by ultra-high performance liquid chromatography-tandem mass spectrometry(UPLC-MS),which provides a new insight for the study of polymer degradation mechanism.

关键词： FeCl_(3) Photocatalysis Polyamide 6 Chain scission

Comprehensive study on the spatial distribution of heavy metals and their environmental risks in high-sulfur coal gangue dumps in China

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Journal of Environmental Sciences 2024年第2期136卷 486-497页

作者： Yingbo Dong Huan Lu Hai Lin school of Energy and Environmental Engineering University of Science and Technology BeijingBeijing 100083China Beijing Key Laboratory on Resource-oriented Treatment of Industrial Pollutants Beijing 100083China

The accumulation of coal gangue(CG)from coal mining is an important source of heavy metals(HMs)in *** spatial distribution and environment risk assessment are extremely important for the management and remediation of *** soil samples were collected from the high-sulfur CG site in northern China and analyzed for six *** results showed that the soil was heavily contaminated by Mn,Cr and Ni based on the Nemerow index,and posed seriously ecological risk depended on the geo-accumulation index,potential ecological risk index and risk assessment *** semi-variogram model and ordinary kriging interpolation accurately portrayed the spatial distribution of ***,Mn,and Cr were distributed by band diffusion,Ni was distributed by core,the distribution of Cu had obvious patchiness and Zn was more *** spatial autocorrelation indicated that all HMs had strong spatial *** BCR sequential extraction was employed to qualify the geochemical fractions of *** data indicated that Fe and Cr were dominated by residual fraction;Cu,Ni and Zn were dominated by reducible and oxidizable fractions;Mn was dominated by reducible and acid-extractable(25.38%-44.67%)*** correlation analysis showed that pH was the main control factor affecting the non-residue fractions of ***,acid production from high sulfur CG reduced soil pH by 2-3,which indirectly promoted the activity of ***,the conceptual model of HMs contamination at the CG site was proposed,which can be useful for the development of ecological remediation strategies.

关键词： High-sulfur coal gangue Soil contamination Heavy metals Spatial distribution Geochemical fractions Risk assessment

Logit prototype learning with active multimodal representation for robust open-set recognition

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Science China(information Sciences) 2024年第6期67卷 297-312页

作者： Yimin FU Zhunga LIU Zicheng WANG school of Automation Northwestern Polytechnical University

Robust open-set recognition(OSR) performance has become a prerequisite for pattern recognition systems in real-world applications. However, the existing OSR methods are primarily implemented on the basis of single-modal perception, and their performance is limited when single-modal data fail to provide sufficient descriptions of the objects. Although multimodal data can provide more comprehensive information than single-modal data, the learning of decision boundaries can be affected by the feature representation gap between different modalities. To effectively integrate multimodal data for robust OSR performance, we propose logit prototype learning(LPL) with active multimodal representation. In LPL, the input multimodal data are transformed into the logit space, enabling a direct exploration of intermodal correlations without the impact of scale inconsistency. Then, the fusion weights of each modality are determined using an entropybased uncertainty estimation method. This approach realizes adaptive adjustment of the fusion strategy to provide comprehensive descriptions in the presence of external disturbances. Moreover, the single-modal and multimodal representations are jointly optimized interactively to learn discriminative decision ***, a stepwise recognition rule is employed to reduce the misclassification risk and facilitate the distinction between known and unknown classes. Extensive experiments on three multimodal datasets have been done to demonstrate the effectiveness of the proposed method.

关键词： logit prototype learning multimodal perception open-set recognition uncertainty estimation

Novel Model of Proton Exchange Membrane Fuel Cell with Predictive Control Using Hildreth Algorithm Based on Fractional-order Dynamic Model

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China Petroleum Processing & Petrochemical technology 2024年第3期26卷 122-135页

作者： Chu Kaihui Qi Zhidong Qin Hao Shan Liang school of Automation Nanjing University of Science and TechnologyNanjing 210094China

Considering the multivariable and fractional-order characteristics of proton exchange membrane fuel cells(PEMFCs),a fractional-order subspace identification method(FOSIM)is proposed in this paper to establish a fractionalorder state space(FOSS)model,which can be expressed as a multivariable configuration with two inputs,hydrogenflow rate and stack current,and two outputs,cell voltage and *** on this model,a novel constrained optimal control law named the Hildreth model predictive control(H-MPC)strategy is created,which employs a Hildreth quadratic programming algorithm to adjust the output power of fuel cells through adaptively regulating hydrogen flow and stack *** semi-physical simulation results demonstrate that,compared with proportional-integral-derivative and quadratic programming MPC(QP-MPC),the proposed H-MPC exhibits better tracking ability and strong robustness against variations of PEMFC power.

关键词： PEMFC fractional-order subspace identification method fractional-order state space H-MPC

Effect of Sintering Temperature on the Microstructure and Mechanical Properties of Nanocrystalline Cemented Carbide

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Journal of Wuhan university of technology(Materials Science) 2024年第3期39卷 664-672页

作者：陈先富刘颖 YE Jinwen WANG Lu school of Materials Science and Engineering Sichuan UniversityChengdu 610065China Key Laboratory of Advanced Special Ma-terial&technology Ministry of EducationChengdu 610065China

WC-Co nanocrystalline nitrogen-containing cemented carbides were prepared by vacuum sintering and low pressure *** sintering processes of Cr_(2)(C,N)doped nano WC-Co powders were studied by using thermogravimetric analysis(TGA)and differential scanning calorimetry(DSC).The effect of sintering temperature on the microstructure and mechanical properties of nanocrystalline cemented carbide was studied by scanning electron microscope(SEM),high resolution transmission electron microscope(HRTEM)and mechanical property *** results showed that the nano WC grains began to grow in the solid phase sintering stage.A high-performance nano-nitrogen-containing cemented carbide with uniform microstructure and good interfacial bonding can be obtained by increasing the sintering temperature to 1380℃.It has a transverse rupture strength(TRS)of 5057 MPa and a hardness of 1956 HV30.

关键词： nano nitrogen cemented carbide sintering temperature microstructure mechanical properties