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Numerical study on the effective thermal conductivity and thermal tortuosity of porous media with different morphologies

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Science China(Technological Sciences) 2024年第6期67卷 1685-1694页

作者： du Shen LI Dong LI Meng-Jie HE ya-Ling Key Laboratory of Thermo-Fluid Science and Engineering of Ministry of Education School of Energy and Power EngineeringXi’an Jiaotong UniversityXi’an710049China

Effective thermal conductivity and thermal tortuosity are crucial parameters for evaluating the effectiveness of heat conduction within porous *** direct pore-scale numerical simulation method is applied to investigate the heat conduction processes inside porous structures with different *** thermal conduction performances of idealized porous structures are directly compared with real foams across a wide range of *** foam structures are reconstructed using X-ray computed tomography and image processing techniques,while Kelvin and Weaire-Phelan structures are generated through periodic unit cell *** detailed temperature fields inside the porous structures are determined by solving the heat conduction equation at the pore *** results present that the equivalent thermal conductivity of Kelvin and Weaire-Phelan structures is similar to and greater than that of the real foam structure with the same strut *** thermal tortuosity of real foam structure is relatively larger and the heat conduction path becomes straighter by adopting the anisotropic *** thermal tortuosity of the fluid channels for Kelvin,Weaire-Phelan,and real foam structures is close to *** thermal conductivity of porous structures with heat transfer fluid increases as the thermal conductivity ratio of fluid to solid becomes larger.A small porosity of porous media leads to a larger equivalent thermal conductivity due to the dominant contribution of porous skeleton in the heat conduction *** derived from parallel and series models,as well as the Maxwell-Eucken models,provide decent predictions of effective thermal conductivity,with an average error of less than 8%in the entire range of thermal conductivity ratio.

关键词： volumetric solar receiver porous morphology direct pore-scale simulation equivalent thermal conductivity thermal tortuosity empirical correlation

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Localization for mixed near-field and far-field sources under impulsive noise

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Journal of Systems Engineering and Electronics 2024年第2期35卷 302-315页

作者： gAO Hongyuan ZHANg Yuze du ya’nan CHENg Jianhua CHEN Menghan College of Information and Communication Engineering Harbin Engineering UniversityHarbin 150001China College of Intelligent Systems Science and Engineering Harbin Engineering UniversityHarbin 150001China

In order to solve the problem that the performance of traditional localization methods for mixed near-field sources(NFSs)and far-field sources(FFSs)degrades under impulsive noise,a robust and novel localization method is *** eliminating the impacts of impulsive noise by the weighted out-lier filter,the direction of arrivals(DOAs)of FFSs can be estimated by multiple signal classification(MUSIC)spectral peaks *** on the DOAs information of FFSs,the separation of mixed sources can be ***,the estimation of localizing parameters of NFSs can avoid two-dimension spectral peaks search by decomposing steering *** Cramer-Rao bounds(CRB)for the unbiased estimations of DOA and range under impulsive noise have been *** experiments verify that the proposed method has advantages in probability of successful estimation(PSE)and root mean square error(RMSE)compared with existing localization *** can be concluded that the proposed method is effective and reliable in the environment with low generalized signal to noise ratio(gSNR),few snapshots,and strong impulse.

关键词： source localization far-field source(NFS) near-field source(FFS) impulsive noise Cramer-Rao bound(CRB)

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Numerical analysis of the effects of subgrade settlement on top-down cracking in epoxy asphalt pavement

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Science China Technological Sciences 2024年第10期67卷 3308-3320页

作者： JIANg XiuJie HUANg Wei LUO Sang WEI ya KONg WeiYi du KaiJun School of Transportation Southeast University Intelligent Transportation System Research Center Southeast University Department of Civil Engineering Tsinghua University Nanjing Modern Multimodal Transportation Laboratory

Epoxy asphalt pavement cracking caused by subgrade settlement is detrimental to the long-term safe service of roads. A threedimensional finite element model of epoxy asphalt pavement is established to investigate the effects of subgrade settlement on the propagation of top-down cracking(TDC). The contour integral method is utilized to calculate the stress intensity factor(SIF)at the crack tip, and then the extended finite element method(XFEM) is used to analyze the propagation behavior of TDC under combined subgrade settlement and traffic loading. The results of these analyses indicate that increased subgrade settlement,stiffer surface layers, and softer bases will increase the SIF, resulting in a faster crack propagation rate. It is suggested that the use of epoxy asphalt materials in pavement structures can allow more subgrade settlement than conventional asphalt ***, when the base layer modulus is higher than 12500 MPa, the increase in surface modulus can decrease crack propagation length. Sensitivity analysis results demonstrate that subgrade settlement has the most significant impact on TDC propagation. The conclusions of this study are expected to provide a theoretical basis for crack prevention in the design and maintenance of pavement structures.

关键词： epoxy asphalt pavement subgrade settlement XFEM stress intensity factor crack propagation

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Insights into postural orthostatic tachycardia syndrome after COVID-19 in pediatric patients

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World Journal of Pediatrics 2024年第3期20卷 201-207页

作者： ya-Xi Cui Jun-Bao du Hong-Fang Jin Department of Pediatrics Peking University First HospitalNo.1 Xi-an Men StreetWest DistrictBeijing 100034China State Key Laboratory of Vascular Homeostasis and Remodeling Peking UniversityBeijing 100191China

The pandemic caused by the novel severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)profoundly threatened human health globally and greatly impacted the world economy[1].While most patients recovered,some suff... 详细信息

关键词： acute patients tachycardia

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Age and mean platelet volume-based nomogram for predicting the therapeutic efficacy of metoprolol in Chinese pediatric patients with vasovagal syncope

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World Journal of Pediatrics 2024年第9期20卷 957-965页

作者： Xiao-Juan du ya-Qian Huang Xue-Ying Li Ying Liao Hong-Fang Jin Jun-Bao du Department of Pediatrics Peking University First HospitalNo.1 Xi’anmen StreetWest DistrictBeijing100034China State Key Laboratory of Vascular Homeostasis and Remodeling Peking UniversityNo.38Xueyuan RoadHaidian DistrictBeijing100191China Department of Statistics Peking University First HospitalBeijing100034China

Background Vasovagal syncope(VVS)is the most common type of orthostatic intolerance in *** investigated whether platelet-related factors related to treatment efficacy in children suffering from VVS treated with *** Metoprolol-treated VVS patients were *** median duration of therapy was three *** were followed and divided into two groups,treament-effective group and treatment-ineffective *** and least absolute shrinkage selection operator regressions were used to examine treatment outcome ***-operating characteristic(ROC)curves,precision-recall(PR)curves,calibration plots,and decision curve analyses were used to evaluate the nomogram *** Among the 72 patients who complete the follow-up,treatment-effective group and treatment-ineffective group included 42(58.3%)and 30(41.7%)cases,*** patients in the treatment-effective group exhibited higher mean platelet volume(MPV)[(11.0±1.0)fl vs.(9.8±1.0)fl,Pgnificantly different(P=0.046).A fit model comprising age[odds ratio(OR)=0.766,95%confidence interval(CI)=0.594-0.987]and MPV(OR=5.613,95%CI=2.297-13.711)might predict therapeutic *** area under the curve of the ROC and PR curves was computed to be 0.85 and 0.9,*** P value of the Hosmer-Lemeshow test was *** decision curve analysis confirmed that managing children with VVS based on the predictive model led to a net advantage ranging from 0.01 to *** nomogram is convenient for clinical *** A novel nomogram based on age and MPV can predict the therapeutic benefits of metoprolol in children with VVS.

关键词： Metoprolol Nomogram Retrospective study Therapeutic effect Vasovagal syncope

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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

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The RFI Fast Mitigation Algorithm Based on Block LMS Filter

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Research in Astronomy and Astrophysics 2024年第1期24卷 265-272页

作者： Han Wu Hai-Long Zhang ya-Zhou Zhang Jie Wang Xu du Ting Zhang Xin-Chen Ye Xinjiang Astronomical Observatory Chinese Academy of SciencesUrumqi 830011China University of Chinese Academy of Sciences Beijing 100049China Key Laboratory of Radio Astronomy Chinese Academy of SciencesNanjing 210008China National Astronomical Data Center Beijing 100101China

The radio telescope possesses high sensitivity and strong signal collection *** receiving celestial radiation signals,it also captures Radio Frequency Interferences(RFIs)introduced by human ***,as signals originating from sources other than the astronomical targets,significantly impacts the quality of astronomical *** paper presents an RFI fast mitigation algorithm based on block Least Mean Square(LMS)*** enhances the traditional adaptive LMS filter by grouping L adjacent time-sampled points into one block and applying the same filter coefficients for filtering within each *** transformation reduces multiplication calculations and enhances algorithm efficiency by leveraging the time-domain convolution *** algorithm is tested using baseband data from the Parkes 64 m radio telescope's pulsar observations and simulated *** results confirm the algorithm's effectiveness,as the pulsar profile after RFI mitigation closely matches the original pulsar profile.

关键词： methods:data analysis techniques:interferometric (stars:)pulsars:individual(J0437-4715)

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Effects of different orthokeratology lens designs on slowing axial length elongation in children with myopia

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International Journal of Ophthalmology(English edition) 2024年第10期17卷 1843-1849页

作者： Hai-Long Ni Xiang Chen du-ya Chen Pei-Ke Hu Zhi-Yi Wu Eye Center the Second Affiliated Hospital of Zhejiang University School of MedicineHangzhou 310009Zhejiang ProvinceChina

AIM:To elucidate whether differences exist in the impact on retarding the elongation of axial length(AL)among children with myopia when utilizing orthokeratology(ortho-k)lenses employing the corneal refractive therapy(CRT)design versus those employing the vision shaping treatment(VST)***:This retrospective clinical trial aimed to collect and analyze AL data from individuals who wore ortho-k lenses for three years.A total of 654 subjects were enrolled and prescribed one of the three specific brands of ortho-k lenses:CRT,Euclid,and *** study’s primary focus was to compare the rates of AL elongation and myopic progression across these three brands of ortho-k ***:In the 3-year follow-up,the AL elongation exhibited variations of 0.73±0.36 mm in the CRT lens group,0.59±0.37 mm in the Euclid lens group,and 0.63±0.38 mm in the Mouldway lens group.A noteworthy disparity emerged between the CRT and Mouldway groups(Pgroups(Pgression of myopia,in contrast to 47.2%in the Euclid group and 44.4%in the Mouldway *** analyses revealed a statistically significant distinction between the CRT and Euclid groups(Pgroup demonstrated a statistically significant difference when compared to the Mouldway group(Pgmatic strategy for mitigating the advancement of *** contradistinction to ortho-k lenses utilizing the CRT design,those employing the VST design exhibited a more favorable impact regarding retarding AL elongation.

关键词： myopia orthokeratology design axial length

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Fast X-ray imaging beamline at SSRF

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Nuclear Science and Techniques 2024年第9期35卷 68-81页

作者： Ke Li Hong-Lan Xie ya-Nan Fu Fei-Xiang Wang guo-Hao du Jian-Feng ji Biao Deng Ti-Qiao Xiao Shanghai Synchrotron Radiation Facility Shanghai Advanced Research InstituteChinese Academy of SciencesShanghai 201204China

The fast X-ray imaging beamline(BL16U2)at Shanghai Synchrotron Radiation Facility(SSRF)is a new beamline that provides X-ray micro-imaging capabilities across a wide range of time scales,spanning from 100 ps toμs and *** beamline has been specifically designed to facilitate the investigation of a wide range of rapid phenomena,such as the deformation and failure of materials subjected to intense dynamic *** addition,it enables the study of high-pressure and high-speed fuel spray processes in automotive *** light source of this beamline is a cryogenic permanent magnet undulator(CPMU)that is cooled by liquid *** CPMU can generate X-ray photons within an energy range of 8.7-30 *** beamline offers two modes of operation:monochromatic beam mode with a liquid nitrogen-cooled double-crystal monochromator(DCM)and pink beam mode with the first crystal of the DCM out of the beam *** X-ray imaging methods were implemented in BL16U2:single-pulse ultrafast X-ray imaging,microsecond-resolved X-ray dynamic imaging,millisecond-resolved X-ray dynamic micro-CT,and high-resolution quantitative ***,BL16U2 is equipped with various in situ impact loading systems,such as a split Hopkinson bar system,light gas gun,and fuel spray *** the completion of the final commissioning in 2021 and subsequent trial operations in 2022,the beamline has been officially available to users from 2023.

关键词： Multiple time-scale X ray imaging Single-pulse X ray imaging Dynamic 2D imaging Dynamic micro-CT

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Predictive value of neutrophil-to-lymphocyte ratio in coronary chronic total occlusion patients

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Journal of geriatric Cardiology 2024年第5期21卷 542-549页

作者： Qian LI Yue YU ya-Qiong ZHOU Yi ZHAO Jin WU Yuan-Jing WU Bin du Pei-Jian WANg Tao ZHENg Department of Cardiovascular Medicine the First Affiliated Hospital of Xi’an Jiaotong UniversityXi’anChina Department of Cardiology First Affiliated Hospital of Chengdu Medical CollegeChengduChina Department of Neurology the First Affiliated Hospital of Xi’an Jiaotong UniversityXi’anChina

BACKgROUND The neutrophil to lymphocyte ratio(NLR)has been reported as a novel predictor for atherosclerosis and car-diovascular *** study aimed to determine the effects of NLR on long-term clinical outcomes of chronic total occlusion(CTO)*** A total of 670 patients with CTO who met the inclusion criteria were included at the end of the follow-up *** were divided into tertiles according to their baseline NLR levels at admission:low(n=223),intermediate(n=223),and high(n=224).The incidence of major adverse cardiac events(MACEs)during the follow-up period,including all-cause death,nonfatal myocardial infarction(MI),or ischemia-driven revascularization,were compared among the three *** Major adverse cardiac events were observed in 27 patients(12.1%)in the low tertile,40(17.9%)in the intermediate tertile,and 61(27.2%)in the high NLR tertile(Pgnificantly higher incidence of MACE,ischemia-driven coronary revascularization,non-fatal MI,and mortality in patients within the high tertile than those in the low and intermediate groups(all Pgression analysis showed that the high tertile of baseline NLR level showed a strong association with the risk of MACE(hazard ratio[HR]=2.21;95%confidence interval[CI]:1.21-4.03;P=0.009),ischemia-driven coronary revascularization(HR=3.19;95%CI:1.56-6.52;P=0.001),MI(HR=2.61;95%CI:1.35-5.03;P=0.043)and mortality(HR=3.78;95%CI:1.65-8.77;P=0.001).CONCLUSION Our findings suggest that NLR is an inexpensive and readily available biomarker that can independently pre-dict cardiovascular risk in patients with CTO.

关键词： patients coronary occlusion

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