基于Seed-PCG法的列车-轨道-地基土三维随机振动GPU并行计算方法

为了解决列车-轨道-地基土三维有限元模型随机多样本计算效率低的问题,本文提出了一种基于Seed-PCG法的高效并行计算方法。基于有限元法和虚拟激励法建立轨道不平顺激励下的三维列车-轨道-地基土耦合随机振动分析模型;针对车致地基土随机振动分析产生的多右端项线性方程组求解问题,采用Seed-PCG方法进行求解。通过PCG方法求解种子系统得到的Krylov子空间进行投影,以改进其余线性方程组的初始解和对应的初始残量,有效提高了PCG法的收敛速度,最后,在MATLABCUDA混合平台上开发了并行计算程序。数值算例表明:相同计算平台下的该方法相比多点同步算法获得了104.2倍的加速;相比PCG法逐个求解方案减少了18%的迭代次数,获得了1.21倍的加速。

Quantitative relationship between visibility and mass concentration of PM2.5 in Beijing

The pollution of particulate matter less than 2.5μm （PM2.5） is a serious environmental problem in Beijing. The annual average concentration of PM2.5 in 2001 from seasonal monitor results was more than 6 times that of the U,S, national ambient air quality standards proposed by U.S. EPA. The major contributors to mass of PM2.5 were organics, crustal elements and sulfate. The chemical composition of PM2.5 varied largely with season, but was similar at different monitor stations in the same season. The fine particles （PM2.5） cause atmospheric visibility deterioration through light extinction, The mass concentrations of PM2.5 were anti-correlated to the visibility, the best fits between atmospheric visibility and the mass concentrations of PM2.5 were somehow different： power in spring, exponential in summer, logarithmic in autumn, power or exponential in winter. As in each season the meteorological parameters such as air temperature and relative humidity change from day to day, probably the reason of above correlations between PM2.5 and visibility obtained at different seasons come from the differences in chemical compositions of PM2.5.

First-principles investigation on stability and electronic structure of Sc-dopedθ′/Al interface in Al−Cu alloys

The properties of Sc-dopedθ′(Al_(2)Cu)/Al interface in Al−Cu alloys were investigated by first-principles calculations.Sc-doped semi-coherent and coherentθ′(Al_(2)Cu)/Al interfaces(Sc doped in Al slab(S1 site),Sc doped inθ′slab(S2 site))were modeled based on calculated results and reported experiments.Through the analysis of interfacial bonding strength,it is revealed that the doping of Sc at S1 site can significantly decrease the interface energy and increase the work of adhesion.In particular,the doped coherent interface with Sc at S1 site which is occupied by interstitial Cu atoms has very good bonding strength.The electronic structure shows the strong Al—Cu bonds at the interfaces with Sc at S1 site,and the Al—Al bonds at the interfaces with Sc at S2 site are formed.The formation of strong Al—Cu and Al—Al bonds plays an important role in the enhancement of doped interface strength.

Evaluation of Precipitation in Multi-Generation Reanalyses with Land Observations over Zhejiang Province

Based on various statistical indices,the abilities of multi-generation reanalyses,namely the NCEP/NCAR Reanalysis 1(R1),the NCEP-DOE Reanalysis 2(R2)and the NCEP Climate Forecast System Reanalysis(CFSR),to reproduce the spatiotemporal characteristics of precipitation over Zhejiang Province are comprehensively compared.The mean absolute bias percentages for three reanalyses are 20%(R1),10%(R2)and 37%(CFSR).R2(R1)gives the best(worst)general depiction of the spatial characteristics of the observed precipitation climatology,whereas a significant wet bias is noticed in the CFSR.All reanalyses reasonably reproduce the interannual variability with the correlation coefficients of 0.72(R1),0.72(R2)and 0.84(CFSR).All reanalyses well represent the first two modes of the observed precipitation through Empirical Orthogonal Function analysis,with CFSR giving the best capture of the principal components.The root-mean-square error(RMSE)is the largest(smallest)in the CFSR(R2).The large RMSE of CFSR in summer(especially in June)contributes mostly to its systematic wet bias.After 2001,the wet bias of CFSR substantially weakens,probably attributed to increasing observations assimilated in the CFSR.On a monthly basis,the percentage of neutral bias cases are similar for all reanalyses,while the ratio of positive(negative)bias cases for CFSR is distinctly larger(smaller)than that of R1 and R2.The proportions of negative bias cases for R1 and R2 begin to increase after 2001 while keeping stable for CFSR.On a daily basis,all reanalyses give good performances of reproducing light rain;however,the reflection of moderate rain and heavier rain by the CFSR is better than R1 and R2.Overall,despite being a third-generation reanalysis product,the CRSR does not exhibit comprehensive superiorities over R1 and R2 in all aspects on a regional scale.

Effects of concurrent chemoradiotherapy on immune function and tumor markers SCC-Ag and CYFRA21-1 in patients with esophageal carcinoma

Objective: To investigate the effects of concurrent chemoradiotherapy and radiotherapy alone on immune function and tumor markers SCC-Ag and CYFRA21-1 in patients with esophageal carcinoma. Method: A total of 84 patients with esophageal cancer treated in our hospital from June 2015 to April 2017 were selected and randomly divided into the observation group and the control group with 42 cases each. The control group received radiotherapy only and irradiated by medical electron linear accelerator, radiotherapy for 6 weeks. The observation group was given radiotherapy and chemotherapy concurrently, 3 weeks for 1 courses, 2 cycles of chemotherapy. The fasting venous blood of patients in two groups were collected in the morning when patients were hospitalized and after chemotherapy, using flow cytometry to detect the immune function indexes of two groups of patients with esophageal cancer before and after treatment, including natural killer cells (NK), T suppressor cells (Ts), T helper cells (Th), Th/Ts and T lymphocytes (T total). The levels of serum SCC-Ag and CYFRA21-1 were detected by electrochemiluminescence assay. Results: There were no significant differences in the indexes of immune function between the two groups before treatment. Total T, the proportion of Th and Th/Ts in the two groups both increased significantly;the proportion of Ts decreased significantly;the difference was statistically significant. NK was higher than treatment before but not significantly. After treatment, the levels of T total, Th, Th/Ts in the observation group were significantly higher than the control group;the levels of NK and Ts were not significantly different. Before treatment, there was no significant difference in serum SCC-Ag and CYFRA21-1 between the two groups. After treatment, the serum SCC-Ag and CYFRA21-1 levels of the two groups were both significantly decreased;the serum levels of SCC-Ag and CYFRA21-1 in the observation group were significantly lower than the control group. Conclusion: Radiotherapy combined with chemotherapy of cisplatin and paclitaxel can improve the immune function and reduce serum SCC-Ag and CYFRA21-1 levels of esophageal cancer patients. This therapeutic schemes can be beneficial to increase the survival rate of patients with esophageal cancer.

列车-轨道-地基土耦合系统三维随机振动的多GPU并行计算方法

针对列车-轨道-地基土耦合系统随机计算效率低的问题,本文提出了基于多GPU的列车-轨道-地基土随机振动方程的高效并行计算方法。基于OpenMP-CUDA混编技术将虚拟激励法不同频点下的多个线性方程组求解任务分配给多个GPU并行执行;在每块GPU上,采用基于CUDA的预处理共轭梯度法(PCG)并行求解对称正定的等效静力平衡方程。针对耦合系统等效刚度矩阵的稀疏特性,采用行压缩(CSR)格式存储大型稀疏矩阵以节省内存空间。最终通过MATLAB-CUDA混合平台开发并行计算程序,解决了随机振动分析中多个线性方程组串行求解效率低的难题。数值算例表明,基于四GPU节点的多GPU并行算法和单GPU加速PCG算法的计算效率是串行多点同步算法(MPSA)计算效率的22.59倍和3.75倍。

Improved ant colony optimization algorithm for the traveling salesman problems

Ant colony optimization （ACO） is a new heuristic algo- rithm which has been proven a successful technique and applied to a number of combinatorial optimization problems. The traveling salesman problem （TSP） is among the most important combinato- rial problems. An ACO algorithm based on scout characteristic is proposed for solving the stagnation behavior and premature con- vergence problem of the basic ACO algorithm on TSP. The main idea is to partition artificial ants into two groups： scout ants and common ants. The common ants work according to the search manner of basic ant colony algorithm, but scout ants have some differences from common ants, they calculate each route＇s muta- tion probability of the current optimal solution using path evaluation model and search around the optimal solution according to the mutation probability. Simulation on TSP shows that the improved algorithm has high efficiency and robustness.

Network traffic classification based on ensemble learning and co-training

Classification of network traffic is the essential step for many network researches. However, with the rapid evolution of Internet applications the effectiveness of the port-based or payload-based identification approaches has been greatly diminished in recent years. And many researchers begin to turn their attentions to an alternative machine learning based method. This paper presents a novel machine learning-based classification model, which combines ensemble learning paradigm with co-training techniques. Compared to previous approaches, most of which only employed single classifier, multiple classifters and semi-supervised learning are applied in our method and it mainly helps to overcome three shortcomings： limited flow accuracy rate, weak adaptability and huge demand of labeled training set. In this paper, statistical characteristics of IP flows are extracted from the packet level traces to establish the feature set, then the classification model is crested and tested and the empirical results prove its feasibility and effectiveness.

Bifunctional sulfonated covalent polymers as the modulator for oriented and highly reversible zinc plating

The vast superiority in resource sustainability and volumetric energy density enables metallic zinc(Zn)to construct costeffective and environment-benign battery systems for the energy storage.However,the problems of Zn dendrites and poor Coulombic efficiency(CE)during cell’s whole life cycle stump its advancement as a rechargeable battery choice.The solution is to modulate the Zn^(2+) desolvation prior to electro-reduction and subsequent deposition.Herein,a transferred protection tactic via a bifunctional sulfonated covalent polymer interlayer is proposed to regulate the Zn2+desolvation,which affects the formation of solid-electrolyte interphase,and guides its plating along with preferable(002)crystal plane.Thus,the high initial CE of 96.3%and the long-term average CE of 99.8%for 310 cycles are achieved in Zn||Cu cells and 570-h circulation is also realized at 2 mA cm^(-2)/10 mAh cm^(-2)in Zn||Zn cells.Besides,Zn||hydrated vanadium oxide-based full batteries with the low-concentration organic electrolytes are also demonstrated with the high specific capacity of 173.8 mAh g^(-1)at 0.5 A g^(-1)and 64%capacity retention over 305 cycles and oriented Zn deposition.

A theoretical study of the effect and mechanism of FeN_(3)-doped biochar for greenhouse gas mitigation

Paddy fields are a major emission source of greenhouse gases(GHGs)[for instance,methane(CH_(4)),nitrous oxide(N_(2)O),and carbon dioxide(CO_(2))]among agricultural fields.Biochar has been deemed a potential candidate for the reduction of GHGs in paddy fields.However,there is no consistent conclusion that biochar can simultaneously reduce emissions of CH_(4),N_(2)O,and CO_(2).Herein,we proposed the FeN_(3)-doped biochar(FG)as an excellent material for GHGs restriction in paddy fields via the first-principles calculation.The computation results indicated that the FG exhibited satisfactory adsorption ability for CH_(4),CO_(2),and N_(2)O,which improved the adsorption energies to−1.37,−1.54,and−2.91 eV,respectively.Moreover,the density of state(DOS)analyses revealed that the factor responsible for FeN_(3)-doped biochar to exhibit excellent adsorption ability was the occurrence of drastic energy up-or down-shift of the electron for Fe d,C p,O p,or N p orbital upon adsorption of CH_(4),CO_(2),or N_(2)O.Our study suggested an advanced modified biochar material for reducing the GHGs emissions in paddy fields,in addition to exploring the adsorption properties and mechanisms of FeN_(3)-doped biochar for GHGs mitigation,which provided a strategy to explore biochar modification and efficient emission reduction materials.

Revealing proton-coupled exchange mechanism in aqueous ion-exchange synthesis of nickel-rich layered cathodes for lithium-ion batteries

Ion exchange is a promising synthetic method for alleviating severe cation mixing in traditional layered oxide materials for lithium-ion batteries,leading to enhanced structural stability.However,the underlying mechanisms of ion exchange are still not fully understood.Such a fundamental study of the ion-exchange mechanism is needed for achieving the controllable synthesis of layered oxides with a stable structure.Herein,we thoroughly unearth the underlying mechanism that triggers the ion exchange of Ni-rich materials in aqueous solutions by examining time-resolved structural evolution combined with theoretical calculations.Our results reveal that the reaction pathway of ion exchange can be divided into two steps:protonation and lithiation.The proton is the key to achieving charge balance in the ion exchange process,as revealed by X-ray adsorption spectroscopy and inductive coupled plasma analysis.In addition,the intermediate product shows high lattice distortion during ion exchange,but it ends up with a most stable product with high lattice energy.Such apparent discrepancies in lattice energy between materials before and after ion exchange emphasize the importance of synthetic design in structural stability.This work provides new insights into the ion-exchange synthesis of Ni-rich oxide materials,which advances the development of cathode materials for high-performance lithium-ion batteries.