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Nonlinear Extrapolation Estimates of π

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Acta Mathematicae Applicatae Sinica 2024年第1期40卷 91-108页

作者： Wen-qing Xu sha-sha Wang Da-chuan Xu Beijing Institute for Scientific and Engineering Computing Beijing University of TechnologyBeijing100124China Department of Mathematics and Statistics California State UniversityLong BeachCalifornia90840USA Department of Mathematics and Physics Shijiazhuang Tiedao UniversityShijiazhuang050043China

The classical Archimedean approximation of π uses the semiperimeter or area of regular polygons inscribed in or circumscribed about a unit circle in R~2 and it is well-known that by using linear combinations of these basic estimates,modern extrapolation techniques can greatly speed up the approximation process.Similarly,when n vertices are randomly selected on the circle,the semiperimeter and area of the corresponding random inscribed and circumscribing polygons are known to converge to π almost surely as n→∞,and by further applying extrapolation processes,faster convergence rates can also be achieved through similar linear combinations of the semiperimeter and area of these random polygons.In this paper,we further develop nonlinear extrapolation methods for approximating π through certain nonlinear functions of the semiperimeter and area of such polygons.We focus on two types of extrapolation estimates of the forms χ_n=S_n~αA_n~β and Y_n(p)=(αS_n~p+βA_n~p)~(1/p) where α+β=1,p≠0,and Sn and An respectively represents the semiperimeter and area of a random n-gon inscribed in the unit circle in R~2,and Xn may be viewed as the limit of Y_n(p) when p→0.By deriving probabilistic asymptotic expansions with carefully controlled error estimates for Xn and Y_n(p),we show that the choice α=4/3,β=-1/3 minimizes the approximation error in both cases,and their distributions are also asymptotically normal.

关键词： Archimedean polygons random polygons approximations ofπ extrapolation processes asymptotic convergence

Construction of Protograph LDPC Codes Based on the Convolution Neural Network

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China Communications 2023年第5期20卷 84-92页

作者： Zhiyuan Xiao Liguang Li jin Xu jin sha School of Electronic Science and Engineering Nanjing UniversityNanjing 210023China Institute of Wireless Research ZTE CorporationShenzhen 518055China

This paper presents an intelligent protograph construction algorithm.Protograph LDPC codes have shown excellent error correction performance and play an important role in wireless communications.Random search or manual construction are often used to obtain a good protograph,but the efficiency is not high enough and many experience and skills are needed.In this paper,a fast searching algorithm is proposed using the convolution neural network to predict the iterative decoding thresholds of protograph LDPC codes effectively.A special input data transformation rule is applied to provide stronger generalization ability.The proposed algorithm converges faster than other algorithms.The iterative decoding threshold of the constructed protograph surpasses greedy algorithm and random search by about 0.53 dB and 0.93 dB respectively under 100 times of density evolution.Simulation results show that quasi-cyclic LDPC(QC-LDPC)codes constructed from the proposed algorithm have competitive performance compared to other papers.

关键词： LDPC codes protograph codes iterative decoding threshold neural network

Relative contributions of temperature and salinity to steric sea level over the South China Sea

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Journal of Oceanology and Limnology 2022年第2期40卷 428-437页

作者： jin sha Xiaoming LI Xiaohai YAN Key Laboratory of Digital Earth Science Aerospace Information Research InstituteChinese Academy of SciencesBeijing 100094China Hainan Key Laboratory of Earth Observation Sanya 502022China Center for Remote Sensing College of EarthOcean and EnvironmentUniversity of DelawareNewark 19711DEUSA Joint Institute for Coastal Research and Management University of Delaware/Xiamen UniversityUSA/China

The relative contributions of surface temperature and salinity to steric sea-level variations are investigated using satellite observations and reanalysis datasets.By defi ning a contribution factor,the relative roles of thermal and haline steric height variations are quantifi ed over the South China Sea(SCS).The thermosteric height dominates the steric sea level variation in the northern SCS deep basin,while the contribution of the halosteric height increases southward.Further investigation reveals that this transition is related to the meridional imbalance of surface heat flux and precipitation variations.The revealed steric constitution distribution is not confi ned to the surface but extends within the upper layer to approximately 50m depth,and then the thermosteric component dominates from the depth underneath.The results of this study clarify the steric sea level constitution over the SCS,benefit the understanding of sea-level variations at the regional scale,and may further facilitate multisensor remote sensing data mining studies.

关键词： South China Sea(SCS) steric height steric constitution

Establishment of a three-dimensional particle library for graded crushed stone based on a new aggregate morphology characterization method

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Journal of Traffic and Transportation Engineering(English Edition) 2024年第1期11卷 117-130页

作者： Haitao Ge Aimin sha Zhenqiang Han School of Future Transportation Chang'an UniversityXi'an 710064China University of Strasbourg INSA StrasbourgCNRSICubeUMR 7357Strasbourg F-67000France School of Highway Chang'an UniversityXi'an 710064China Key Laboratory for Special Area Highway Engineering of Ministry of Education Chang'an UniversityXi'an 710064China

The morphology of graded crushed stone(GCS)particles has an essential influence on the performance of aggregate mixtures.The impact of particle shape is a comprehensive effect that cannot be considered separately,leading to difficulties in establishing the relationship between the mixture properties and the aggregate morphology by using laboratory methods.The discrete element method(DEM)is an effective way widely adopted to reconstruct the morphology of particles and simulate performance tests of granular materials.However,selecting limited particles characterizing a real particle-assembly for simulation is still a challenge in current research due to the inherent rich variability of particle shapes.In this study,based on the acquisition of three-dimensional(3D)aggregate shapes by using laser scanning,ellipsoid index(EDI)translating the particle shape as a function of surface area,volume,and contour length is proposed to comprehensively evaluate aggregate morphology.Further,a particle library capable of characterizing aggregate morphology distribution is established based on the statistics of the corresponding morphological characteristics of particle samples.The model reliability is validated by carrying out a series of experimental and numerical penetration tests with nine different gradations.The established particle library can be used to model aggregate mixtures and the proposed simulation framework is promising for optimizing the mixture gradation design numerically.

关键词： Particle library Discrete element method 3D laser scanning Coarse aggregate Morphology characterization Gradation design

Quantifying peripapillary vessel density and retinal nerve fibre layer in type 1 diabetic children without clinically detectable retinopathy using OCTA

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International Journal of Ophthalmology(English edition) 2024年第2期17卷 278-281页

作者： Ling Chen Yun Feng sha-sha Zhang Yan-Fang Liu Ping Lin Xi’an Children’s Hospital Affiliated to Xi’an Jiaotong University Xi’an 710002Shaanxi ProvinceChina

AIM:To quantify changes in radial peripapillary capillary vessel density(ppVD)and the peripapillary retinal nerve fiber layer(pRNFL)in children with type 1 diabetes without clinical diabetic retinopathy by optical coherence tomography angiography(OCTA),providing a basis for early retinopathy in children with type 1 diabetes.METHODS:This was a retrospective study.A total of 30 patients(3–14y)with type 1 diabetes without clinical diabetic retinopathy(NDR group)were included.A total of 30 age-matched healthy subjects were included as the normal control group(CON group).The HbA1c level in the last 3mo was measured once in the NDR group.The pRNFL thickness and ppVD were automatically measured,and the mean pRNFL and ppVD were calculated in the nasal,inferior,temporal,and superior quadrants.The changes in ppVD and pRNFL in the two groups were analyzed.RESULTS:Compared with CON group,the nasal and superior ppVDs decreased in the NDR group(all P0.05).Person and Spearman correlation analysis of ppVD and pRNFL thickness in each quadrant of the NDR group showed a positive correlation between nasal and superior(all P0.05).There was no significant correlation between the HbA1c level and ppVD and pRNFL in any quadrant(all P>0.05).There was no significant correlation between the course of diabetes mellitus and ppVD and pRNFL in any quadrant(all P>0.05).CONCLUSION:ppVD and pRNFL decrease in eyes of children with type 1 diabetes before clinically detectable retinopathy and OCTA is helpful for early monitoring.

关键词： diabetic retinopathy children peripapillary vessel density peripapillary retinal nerve fiber layer optical coherence tomography angiography

Laser powder bed fusion of NiTiFe shape memory alloy via premixed powder: microstructural evolution, mechanical and functional properties

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Rare Metals 2024年第5期43卷 2300-2316页

作者： Bo Yuan jin-Guo Ge Liang Zhang Hong-Jun Chen Long-sha Wei Yu-Duo Zhou Run-Hua Song Institute of Intelligent Manufacturing Technology Shenzhen Polytechnic School of Mechanical and Electrical Engineering Guilin University of Electronic Technology Guangdong Advanced Polymer Composite EngineeringTechnology Research Center Shenzhen Academy of Aerospace Technology Jihua Laboratory Testing Center Jihua Laboratory

High-cost pre-alloyed powder is the bottleneck problem that limits the widespread application of additivemanufactured shape memory alloys. In this work, the lowcost ternary NiTiFe shape memory alloy is fabricated by laser powder bed fusion (LPBF) technique via mechanically mixed pre-alloy NiTi powder and varying contents pure Fe powder (1, 2, 3 wt%). All NiTiFe alloys show a relative density of up to 99.8%by optimizing the LPBF processing parameters. Owing to the heterogeneous nucleation effect of micron-sized Fe particles, both grain refinement and texture weakening are generated in the NiTiFe alloys, accompanied by the reduction of dislocation density. For the room-temperature mechanical properties,the NiTi-3Fe alloy shows the highest microhardness of HV370, but the fracture strength and elongation reduce to1701 MPa and 23%simultaneously. The evolution of mechanical properties is attributed to the high internal defects, low dislocation density and the incoherent oxide.Moreover, the NiTi-3Fe alloy shows the quasi-linear superelasticity behavior; the superelastic recoverable strain of NiTi-1Fe and NiTi-2Fe decreased with the increase in Fe content. This study provided a new-fangled insight for the development of multi-component NiTi-based shape memory alloys by additive manufacturing.

关键词： Additive manufacturing shape memory alloy Metal matrix composite Microstructure Mechanical properties

Insight into the development of electrolytes for aqueous zinc metal batteries from alkaline to neutral

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Chinese Chemical Letters 2024年第2期35卷 232-241页

作者： An Duan sha Luo Wei Sun School of Materials and Energy University of Electronic Science and Technology of ChinaChengdu 611731China

Aqueous zinc metal batteries are considered as promising candidates for next-generation electrochemical energy storage devices,especially for large-scale energy storage,due to the advantages of high-safety,high energy density and low cost.As the bridge connecting cathode and anode,electrolyte provides a realistic operating environment.In alkaline and neutral aqueous zinc metal batteries,issues associated with electrolyte and anode are still intractable.In this review,we reveal the development and evolution of electrolytes for aqueous zinc metal batteries from alkaline to neutral via the description of fundamentals and challenges in terms of comparison and connection.We also elaborate the strategies in electrolytes regulation and highlight the basic roles and progresses in additives engineering.

关键词： Aqueous electrolytes Zinc metal batteries pH-dependent chemistry Electrolyte regulation Additives engineering

Lenvatinib combined with sintilimab plus transarterial chemoembolization as first-line treatment for advanced hepatocellular carcinoma

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World Journal of Clinical Cases 2024年第2期12卷 285-292页

作者： sha-sha Sun Xiao-Di Guo Wen-Dong Li jing-Long Chen Department of Oncology Capital Medical University Affiliated Beijing Ditan HospitalBeijing 100015China

BACKGROUND Recently,combination therapy has shown a better trend towards improved tumour response and survival outcomes than monotherapy in patients with hepatocellular carcinoma(HCC).However,research on triple therapy[lenvatinib+sintilimab+transarterial chemoembolization(TACE)]as a first-line treatment for advanced HCC is limited.AIM To evaluate the safety and efficacy of triple therapy as a first-line treatment for advanced HCC.METHODS HCC patients with Barcelona Clinic Liver Cancer stage C treated with triple therapy were enrolled.All patients were treated with lenvatinib every day and sintilimab once every 3 wk.Moreover,TACE was performed every 4-6 wk if necessary.The primary outcome of the study was overall survival(OS).The secondary outcomes were the objective response rate(ORR),disease control rate(DCR),and incidence of adverse events.RESULTS Forty HCC patients who underwent triple therapy were retrospectively analysed from January 2019 to January 2022.With a median follow-up of 8.5 months,the 3-,6-,and 12-mo OS rates were 100%,88.5%,and 22.5%,respectively.The ORR and DCR were 45%and 90%,respectively.The median progressive free survival and median OS were not reached.Common complications were observed in 76%of the patients(grade 3,15%;grade 4,2.5%).CONCLUSION Combination therapy comprising lenvatinib,sintilimab and TACE achieved promising outcomes in advanced HCC patients and had manageable effects.

关键词： Lenvatinib Sintilimab Advanced hepatocellular carcinoma Combination therapy Tumor response

Clinical study of different prediction models in predicting diabetic nephropathy in patients with type 2 diabetes mellitus

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World Journal of Diabetes 2024年第1期15卷 43-52页

作者： sha-sha Cai Teng-Ye Zheng Kang-Yao Wang Hui-Ping Zhu Department of Nephrology The First People’s Hospital of WenlingWenling 317500Zhejiang ProvinceChina

BACKGROUND Among older adults,type 2 diabetes mellitus(T2DM)is widely recognized as one of the most prevalent diseases.Diabetic nephropathy(DN)is a frequent com-plication of DM,mainly characterized by renal microvascular damage.Early detection,aggressive prevention,and cure of DN are key to improving prognosis.Establishing a diagnostic and predictive model for DN is crucial in auxiliary diagnosis.AIM To investigate the factors that impact T2DM complicated with DN and utilize this information to develop a predictive model.METHODS The clinical data of 210 patients diagnosed with T2DM and admitted to the First People’s Hospital of Wenling between August 2019 and August 2022 were retrospectively analyzed.According to whether the patients had DN,they were divided into the DN group(complicated with DN)and the non-DN group(without DN).Multivariate logistic regression analysis was used to explore factors affecting DN in patients with T2DM.The data were randomly split into a training set(n=147)and a test set(n=63)in a 7:3 ratio using a random function.The training set was used to construct the nomogram,decision tree,and random forest models,and the test set was used to evaluate the prediction performance of the model by comparing the sensitivity,specificity,accuracy,recall,precision,and area under the receiver operating characteristic curve.RESULTS Among the 210 patients with T2DM,74(35.34%)had DN.The validation dataset showed that the accuracies of the nomogram,decision tree,and random forest models in predicting DN in patients with T2DM were 0.746,0.714,and 0.730,respectively.The sensitivities were 0.710,0.710,and 0.806,respectively;the specificities were 0.844,0.875,and 0.844,respectively;the area under the receiver operating characteristic curve(AUC)of the patients were 0.811,0.735,and 0.850,respectively.The Delong test results revealed that the AUC values of the decision tree model were lower than those of the random forest and nomogram models(P<0.05),whereas the difference in AUC values of the random forest and colu

关键词： Type 2 diabetes mellitus Diabetic nephropathy Random forest Decision-making tree Nomogram Forecast