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Variable projection algorithms with sparse constraint for separable nonlinear models

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Control Theory and Technology 2024年第1期22卷 135-146页

作者： Hui-Lang xu guang-Yong chen Si-Qing cheng Min Gan Jing chen College of Computer and Data Science Fuzhou UniversityFuzhou350116FujianChina Fujian Key Laboratory of Network Computing and Intelligent Information Processing Fuzhou UniversityFuzhou350116FujianChina Key Laboratory of Intelligent Metro of Universities in Fujian Fuzhou UniversityFuzhou350116FujianChina Engineering Research Center of Big Data Intelligence Ministry of EducationFuzhou UniversityFuzhou350116FujianChina School of Science Jiangnan UniversityWuxi214122JiangsuChina

Separable nonlinear models are widely used in various fields such as time series analysis, system modeling, and machine learning, due to their flexible structures and ability to capture nonlinear behavior of data. However, identifying the parameters of these models is challenging, especially when sparse models with better interpretability are desired by practitioners. Previous theoretical and practical studies have shown that variable projection (VP) is an efficient method for identifying separable nonlinear models, but these are based on \(L_2\) penalty of model parameters, which cannot be directly extended to deal with sparse constraint. Based on the exploration of the structural characteristics of separable models, this paper proposes gradient-based and trust-region-based variable projection algorithms, which mainly solve two key problems: how to eliminate linear parameters under sparse constraint;and how to deal with the coupling relationship between linear and nonlinear parameters in the model. Finally, numerical experiments on synthetic data and real time series data are conducted to verify the effectiveness of the proposed algorithms.

关键词： Variable projection(VP) Non-smooth constraint Separable nonlinear models

Research on shell-side heat and mass transfer with multi-component in LNG spiral-wound heat exchanger under sloshing conditions

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Petroleum Science 2024年第2期21卷 1333-1345页

作者： xue-Ping Du guang-Lei Yu Ya-cheng xu Zhi-Jie chen Nai-Liang Li Huan-guang Wang School of Low-carbon Energy and Power Engineering China University of Mining and TechnologyXuzhou221116JiangsuChina Key Laboratory of Thermo-Fluid Science and Engineering MOEXi'an Jiaotong UniversityXi'an710049ShaanxiChina Xi'an Aerospace Propulsion Test Technology Institute Xi'an710100ShaanxiChina

The spiral-wound heat exchanger(SWHE) is the primary low-temperature heat exchanger for large-scale LNG plants due to its high-pressure resistance, compact structure, and high heat exchange efficiency. This paper studied the shell-side heat and mass transfer characteristics of vapor-liquid two-phase mixed refrigerants in an SWHE by combining a multi-component model in FLUENT software with a customized multicomponent mass transfer model. Besides, the mathematical model under the sloshing condition was obtained through mathematical derivation, and the corresponding UDF code was loaded into FLUENT as the momentum source term. The results under the sloshing conditions were compared with the relevant parameters under the steady-state condition. The shell-side heat and mass transfer characteristics of the SWHE were investigated by adjusting the component ratio and other working conditions. It was found that the sloshing conditions enhance the heat transfer performance and sometimes have insignificant effects. The sloshing condition is beneficial to reduce the flow resistance. The comprehensive performance of multi-component refrigerants has been improved and the improvement is more significant under sloshing conditions, considering both the heat transfer and pressure *** results will provide theoretical support for the research and design of multi-component heat and mass transfer enhancement of LNG SWHE under ocean sloshing conditions.

关键词： Spiral-wound heat exchanger Sloshing conditions Two-phase flow Multi-component Heat and mass transfer

Enhancing reversible hydrogen storage performance of 2LiBH_(4)–MgH_(2)via in-situ building heterogeneous nucleation sites

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Rare Metals 2024年第9期43卷 4367-4376页

作者： Wei chen Ya-Hui Sun Tian xu xue-Bin Yu guang-Lin Xia Department of Materials Science Fudan UniversityShanghai 200433China

2LiBH_(4)-MgH_(2)composite is one of the most attractive reactive hydride composites with a theoretic hydrogen capacity of 10.8 wt%.However,the large nucleation restriction of MgB_(2)during the second step of dehydrogenation results in sluggish hydrogen storage kinetics and high operating temperature,which hinders its practical application as on-board hydrogen storage ***,Al3Ti doped Al nanoparticles(AT NPs)are prepared by a facile chemical reduction reaction to improve the hydrogen storage performance of 2LiBH_(4)-MgH_(2)*** the initial H_(2)desorption process,MgAlB_(4)and TiB_(2)that have identical crystal structure and low d-value mismatch with MgB_(2)resulting from the reaction between AT NPs and 2LiBH_(4)-MgH_(2)composite serve as effective nucleation sites for the formation of MgB_(2).As a result,the apparent activation energy of the two-step H_(2)desorption of AT NPs doped 2LiBH_(4)-MgH_(2)composite are notably decreased to(110.0±5.9)and(119.6±1.4)kJ·mol^(-1),which is 55.5 and 33.5 kJ·mol^(-1)lower than that of the undoped *** importantly,a reversible hydrogen storage capacity of 9.2 wt%after 10cycles of H_(2)desorption and adsorption could be achieved,corresponding to a capacity retention rate of 99%.The building of reactive bimetallic catalyst towards in situ formation of heterogeneous nucleation sites provides a new strategy for improving the hydrogen storage performance of reactive hydride composites.

关键词： Reversible hydrogen storage Reactive hydride composites Catalytic effects Heterogeneous nucleation

Concurrent Design Study of the Petroleum Equipment CAD System

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厦门大学学报（自然科学版） 2002年第S1期41卷 269-270页

作者： chen Yong-guang, chen xu, WANG Jiang (Mechanical Engineering Institute, Chongqing University,Chongqing 4000 44, China)

Military petroleum equipment, as the special device a nd tool for petroleum storage, transportation, filling, chemical analysis, detec tion and maintenance for the army, is an important means and basis of petroleum indemnificatory. To adapt to modern war in high-tech conditions, the petroleum equipment have to develop towards higher reliability, adaptability, maneuverabil ity, standardization, container and cell type with versatile multi-functions. As a new design theory and design process, concurrent engineering may prod uce remarkable benefit when applying to product development. With the aid of the state-of-the-art modeling and simulation technology, it foresees the future or even the whole life cycle of the products designed. Based on wide statistics and survey, the product design period is reduced by 1/2～1/3 with concurrent des i gn process. The application of concurrent design process in new petroleum equi pment development shall greatly accelerate the petroleum equipment updating an d promote their indemnificatory.

关键词： petroleum equipment concurrent engineering CAD

Precipitating thermally reinforcement phase in aluminum alloys for enhanced strength at 400℃

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Journal of Materials Science & Technology 2024年第5期172卷 71-82页

作者： Xiang Su Yuan Lei Yang chen Hongjie Qu Zhixiang Qi Gong Zheng xu Liu Henggao Xiang guang chen National Key Laboratory of Advanced Casting Technologies MIIT Key Laboratory of Advanced Metallic and Intermetallic Materials TechnologyEngineering Research Center of Materials Behavior and DesignMinistry of EducationNanjing University of Science and TechnologyNanjing 210094China School of Aviation and Mechanical Engineering Changzhou Institute of TechnologyChangzhou 213032China

Heat-resistant aluminum alloys are widely used in aerospace and automotive fields for manufacturing hot components due to their advantages in lightweight design and energy ***,the high-temperature strength of existing cast aluminum alloys is always limited to about 100 MPa at 350℃due to coarsening and transformation of strengthening ***,we reveal that the yield strength and ultimate tensile strength of the T6 state Al-8.4Cu-2.3Ce-1.0Mn-0.5Ni-0.2Zr alloy at 400◦C increase by 34%and 44%after re-aging at 300℃for 100 h,and its thermal strength exhibits distinguished ad-vantage over traditional heat-resistant aluminum *** enhanced elevated-temperature strength is attributed to the reprecipitation of the Ni-bearing T-Al_(20)Cu_(2)Mn_(3)phase,whose number density increases over one *** significant segregation of Ni,Ce,and Zr elements at the interfaces helps improve the thermal stability of the T *** thermostable T phase effectively strengthens the matrix by in-hibiting dislocation ***,a highly interconnected 3D intermetallic network along the grain boundaries can still remain after long-term re-aging at 300℃,which is conducive to imposing a drag on the grain boundaries at high *** finding offers a viable route for enhancing the elevated-temperature strength of heat-resistant aluminum alloys,which could provide expanded opportunities for higher-temperature applications.

关键词： Aluminum alloys Precipitation Thermally reinforcement phase Re-aging treatment High-temperature strength

Spatiotemporal dynamics of the social structure of Indo-Pacific humpback dolphins(Sousa chinensis)in Xiamen waters from 2007 to 2019

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Zoological Research 2024年第2期45卷 439-450页

作者： Yi Lu Xin-Rong xu Bing-Yao chen Thomas A Jefferson Holly Fearnbach guang Yang Jiangsu Key Laboratory for Biodiversity and Biotechnology College of Life SciencesNanjing Normal UniversityNanjingJiangsu 210023China Clymene Enterprises LakesideCalifornia 92040USA Marine Mammal Research SR3SeaLife ResponseRehabilitation and ResearchWA 98275USA Southern Marine Science and Engineering guangdong Laboratory(guangzhou) No.1119Haibin RoadNansha DistrictGuangzhouGuangdong 511458China

As highly social animals,Indo-Pacific humpback dolphins(Sousa chinensis)exhibit community ***,our understanding of the external and internal factors influencing these dynamics,as well as their spatiotemporal variations,is still *** the present study,variations in the social structure of an endangered Indo-Pacific humpback dolphin population in Xiamen Bay,China,were monitored over two distinct periods(2007–2010 and 2017–2019)to analyze the effects of habitat utilization and the composition of individuals within the *** both periods,the population demonstrated a strikingly similar pattern of social differentiation,characterized by the division of individuals into two main clusters and one small ***,the two primary clusters occupied the eastern and western waters,respectively,although the core distribution area of the eastern cluster shifted further eastward between the two *** this distribution shift,the temporal stability of the social structure and inter-associations within the eastern cluster remained unaffected.A subset of 16individuals observed in both periods,comprising 51.6%and 43.2%of the population in each respective period,emerged as a foundational element of the social structure and may be responsible for sustaining social structure stability,especially during the 2007–2010 *** observations suggest that the composition of dominant individuals,an internal factor,had a more substantial influence on the formation of the social network than changes in habitat use,an external ***,the study proposes distinct conservation measures tailored to each of the two main clusters.

关键词： Social differentiation Social structure Sousa chinensis Dynamics Conservation

Influences of Earth Incidence Angle on FY-3/MWRI SST Retrieval and Evaluation of Reprocessed SST

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Journal of Tropical Meteorology 2024年第3期30卷 230-240页

作者： ZHANG Miao chen Lin xu Na CAO guang-zhen Key Laboratory of Radiometric Calibration and Validation for Environmental Satellites National Satellite Meteorological CenterChina Meteorological AdministrationBeijing 100081 China Innovation Center for FengYun Meteorological Satellite(FYSIC) Beijing 100081 China

Sea surface temperature(SST)is a crucial physical parameter in meteorology and *** study demonstrates that the influence of earth incidence angle(EIA)on the SST retrieved from the microwave radiation imager(MWRI)onboard FengYun-3(FY-3)meteorological satellites should not be *** with algorithms that do not consider the influence of EIA in the regression,those that integrate the EIA into the regression can enhance the accuracy of SST ***,based on the recalibrated Level 1B data from the FY-3/MWRI,a long-term SST dataset was reprocessed by employing the algorithm that integrates the EIA into the *** reprocessed SST data,including FY-3B/MWRI SST during 2010-2019,FY-3C/MWRI SST during 2013-2019,and FY-3D/MWRI SST during 2018-2020,were compared with the in-situ SST and the SST dataset from the Operational Sea Surface Temperature and Ice Analysis(OSTIA).The results show that the FY-3/MWRI SST data were consistent with both the in-situ SST and the OSTIA SST *** with the Copernicus Climate Change Service V2.0 SST,the absolute deviation of the reprocessed SST,with a quality flag of 50,was less than 1.5℃.The root mean square errors of the FY-3/MWRI orbital,daily,and monthly SSTs,with a quality flag of 50,were approximately 0.82℃,0.69℃,and 0.37℃,*** primary discrepancies between the FY-3/MWRI SST and the OSTIA SST were found mainly in the regions of the western boundary current and the Antarctic Circumpolar ***,this reprocessed SST product is recommended for El Niño and La Niña events monitoring.

关键词： FengYun-3 satellites sea surface temperature microwave radiation imager earth incidence angle reprocessing

Regulations of m^(6)A and other RNA modifications and their roles in cancer

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Frontiers of Medicine 2024年第4期18卷 622-648页

作者： Xin-Hui chen Kun-Xiong Guo Jing Li Shu-Hui xu Huifang Zhu guang-Rong Yan Biomedicine Research Center Guangdong Provincial Key Laboratory of Major Obstetric DiseaseGuangdong Provincial Clinical Research Center for Obstetrics and GynecologyState Key Laboratory of Respiratory Diseasethe Third Affiliated Hospital of Guangzhou Medical UniversityGuangzhou510150China

RNA modification is an essential component of the epitranscriptome,regulating RNA metabolism and cellular *** types of RNA modifications have been identified to date;they include N^(6)-methyladenosine(m^(6)A),N^(1)-methyladenosine(m1A),5-methylcytosine(m5C),N^(7)-methylguanosine(m^(7)G),N^(6),2′-O-dimethyladenosine(m^(6)Am),N4-acetylcytidine(ac^(4)C),*** modifications,mediated by regulators including writers,erasers,and readers,are associated with carcinogenesis,tumor microenvironment,metabolic reprogramming,immunosuppression,immunotherapy,chemotherapy,etc.A novel perspective indicates that regulatory subunits and post-translational modifications(PTMs)are involved in the regulation of writer,eraser,and reader functions in mediating RNA modifications,tumorigenesis,and anticancer *** this review,we summarize the advances made in the knowledge of different RNA modifications(especially m^(6)A)and focus on RNA modification regulators with functions modulated by a series of factors in cancer,including regulatory subunits(proteins,noncoding RNA or peptides encoded by long noncoding RNA)and PTMs(acetylation,SUMOylation,lactylation,phosphorylation,etc.).We also delineate the relationship between RNA modification regulator functions and carcinogenesis or cancer ***,inhibitors that target RNA modification regulators for anticancer therapy and their synergistic effect combined with immunotherapy or chemotherapy are discussed.

关键词： RNA modification writers erasers readers regulatory subunits PTMs cancer

SYNTHESIS OF cis-1, 4-POLYBUTADIENE WITH NICKEL CATALYST INVESTIGATIONS ON INTERACTIONS BETWEEN THE CATALYTIC COMPONENTS BY USING UV-VIS SPECTRUM

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Chinese Journal of Polymer Science 1987年第1期5卷 45-52页

作者：陈滇宝许光唐学明 Qingdao College of Chemical Technology Qingdao

Ni（Ⅱ） naphthenate in hydrogenated gasoline or toluene will appear light green, which is the result of absorption in the red and blue bands of the spectrum. The three peaks caused by the spin-allowed d-d transitions are 403, 680, and 1170nm respectively, and are similar to those of Ni（H2O）6+2. The configuration of Ni（Ⅱ） complex is *** a two-component system of Ni（naph）2-Al（i-Bu）3, the naphthenate ligand attached to Ni（Ⅱ） can be exchanged for the alkyl group on tri-isobutylaluminium, if Al（i-Bu）3/Ni（naph）2 in a system. containing metalalkyl and naphthenate does not exceed the value of 0.53. At a higher ratio, Al（i-Bu）3/Ni（naph）2>0.53, Ni（Ⅱ） is reduced to Ni（Ⅰ） and Ni（O）.In a two-component system Ni（naph）2-BF3·OEt2, a part of the naphthenate can be exchanged for halogen. A new Ni（Ⅱ） complex is formed, which consists of three new d-d bands in the region 360-1660 nm.

关键词： cis-1, 4-polybutadiene Nickel catalyst Ziegler-Natta catalyst UV-VIS spectrum