基于Polyak步长的加速临近随机方差缩减算法

针对大规模机器学习中随机复合优化问题,本文将加速临近随机方差缩减算法(Acc-Prox-SVRG)和Polyak步长方法相结合,提出了一种新的加速临近随机方差缩减算法(Acc-Prox-SVRG-Polyak)。相比于已有算法,新算法充分利用加速技术和Polyak步长的优越性,提高了准确率。在通常的假定下论证了算法的收敛性,并分析了复杂度。最后,数值实验验证了新算法的有效性。

Law of gas production during coal heating oxidation

Coal spontaneous combustion is a great threat to mine safety,and gas is the key index to describe coal spontaneous combustion.Taking the coal samples of different kinds of coal as research object,the temperature programmed oxidation experiment was carried out,and the gases produced by coal samples at different temperatures were collected and analyzed by gas chromatography.This research studied the variation characteristics of gas species and gas concentrations in different coal samples during heating oxidation.The experimental results show that different coal samples produce different kinds of gases in the process of heating and oxidation.The order of gas production is CO,C2H6,C2H4,C3H8,and the relationship between gas production and temperature is approximately exponential.With the increase of coal metamorphic degree,the turning point temperature of sharp rise in coal sample gas production rate become higher,the oxidation ability of coal sample decreases,and the quantity of gas production decreases during the same time period.

Variation in individual biomass decreases faster than mean biomass with increasing density of bamboo stands

The total biomass of a stand is an indicator of stand productivity and is closely related to the density of plants. According to the self-thinning law, mean individual biomass follows a negative power law with plant density. If the variance of individual biomass is constant, we can expect increased stand productivity with increasing plant density. However, Taylor's power law(TPL) that relates the variance and the mean of many biological measures(e.g. bilateral areal differences of a leaf, plant biomass atdifferent times, developmental rates at different temperatures, population densities on different spatial or temporal scales), affects the estimate of stand productivity when it is defined as the total biomass of large plants in a stand.Because the variance of individual biomass decreases faster than mean individual biomass, differences in individual biomass decline with increasing density, leading to more homogeneous timbers of greater economic value. We tested whether TPL in plant biomass holds for different species and whether the variance of individual biomass changes faster than the mean with increasing stand density.The height, ground diameter and fresh weight of 50 bamboo species were measured in 50 stands ranging from 1 m by 1 m to 30 m by 30 m to ensure more than 150 bamboos in every stand. We separately examined TPL in height,ground diameter, and weight, and found that TPL holds for all three biological measures, with the relationship strongest for weight. Using analysis of covariance to compare the regression slopes of logarithmic mean and variance against the logarithm of density, we found that the variance in individual biomass declined faster than the mean with increasing density. This suggests that dense planting reduced mean individual biomass but homogenized individual biomass. Thus, there exists a trade-off between effective stand productivity and stand density for optimal forest management. Sparse planting leads to large variation in individual biomass, whereas dense planting reduces mean individual biomass. Consequently, stand density for a plantation should be set based on this trade-off with reference to market demands.

Plasma discharge characteristics of segmented diverter strips subject to lightning strike

In order to research segmented diverters for aircraft lightning protection, a transient 2 D multiphysics model based on magnetohydrodynamics theory is proposed to predict the location of the arc plasma discharge and lightning channel, and to simulate the electrothermal behavior.Based on numerical calculation and preliminary analysis, factors that affect the breakdown voltage of the segmented diverter are discussed. The results show that the voltage increase rate of the voltage source, the width of the air gap between metal segments and the geometry of these segments influence the breakdown voltage of the strip. High-voltage tests of the segmented diverter are performed to reveal air breakdown of the strip and redirect the lightning current.Experimental and numerical results are compared to verify the correctness of the numerical model. The ionization of the air gap between metal segments and the breakdown voltage of the strip calculated by the model are qualitatively consistent with experimental results. The breakdown voltage of the segmented diverter is far lower than the lightning voltage. When a lightning strike occurs, the segmented diverter can be quickly ionized to form a plasma channel which can guide the lightning current well.

Evolution simulation of lightning discharge based on a magnetohydrodynamics method

In order to solve the load problem for aircraft lightning strikes, lightning channel evolution is simulated under the key physical parameters for aircraft lightning current component C. A numerical model of the discharge channel is established, based on magnetohydrodynamics （MHD） and performed by FLUENT software. With the aid of user-defined functions and a user- defined scalar, the Lorentz force, Joule heating and material parameters of an air thermal plasma are added. A three-dimensional lightning arc channel is simulated and the arc evolution in space is obtained. The results show that the temperature distribution of the lightning channel is symmetrical and that the hottest region occurs at the center of the lightning channel. The distributions of potential and current density are obtained, showing that the difference in electric potential or energy between two points tends to make the arc channel develop downwards. The arc channel comes into expansion on the anode surface due to stagnation of the thermal plasma and there exists impingement on the copper plate when the arc channel comes into contact with the anode plate.

基于血清学指标的联合模型诊断代偿期肝硬化轻微型肝性脑病的价值

目的探讨血清学指标对代偿期肝硬化轻微型肝性脑病(MHE)的诊断价值,构建基于血清学指标的联合模型并评估其对MHE的诊断价值。方法前瞻性、多中心研究。选取2021年10月至2022年8月来自我国15个省(自治区、直辖市)的23家医院就诊的代偿期肝硬化患者263例。收集患者临床资料及实验室检查结果,并计算终末期肝病模型(MELD)评分。使用基线血氨测量值/正常参考值上限(AMM-ULN)集中校正各中心血氨测量结果,以我国《肝硬化肝性脑病诊疗指南》标准,数字连接试验-A、数字符号试验均异常作为诊断MHE的标准。基于R语言caret包将患者随机(7∶3)分为训练集(n=185)和验证集(n=78)。通过Logistic回归构建诊断MHE的联合模型;受试者工作特征曲线下面积(AUC)、Hosmer-Lemeshow拟合优度检验及校准曲线图评估诊断性能,并用Bootstrap法(n=200)进行内部验证;Delong检验比较AUC之间的差异。结果训练集中,MHE占37.8%(70/185),MHE组AMM-ULN、白蛋白、血小板、碱性磷酸酶、国际标准化比值、终末期肝病模型评分以及教育年限与无MHE组比较,差异有统计学意义(P均<0.05)。多因素Logistic回归分析显示,AMM-ULN(OR=1.78,95%CI 1.05~3.14,P=0.038)和MELD评分(OR=1.11,95%CI 1.04~1.20,P=0.002)是MHE的独立危险因素,AUC分别为0.663和0.625。联合AMM-ULN、MELD评分和教育年限的联合模型诊断MHE的AUC为0.755,特异度和敏感度分别为85.2%和55.7%。Hosmer-Lemeshow拟合优度检验表明模型具有较好的校准度(P=0.733),联合模型内部验证AUC为0.752。Delong检验显示联合模型诊断效能优于单独使用血氨(P=0.020)和MELD评分(P=0.003)。验证集中,联合模型诊断MHE的AUC为0.794,Hosmer-Lemeshow拟合优度检验显示有较好的校准度(P=0.841)。结论基于AMM-ULN、MELD评分和教育年限的联合模型可提高对MHE的诊断价值。

Guidelines for the Prevention and Treatment of Chronic Hepatitis B(version 2022)

To facilitate the achieving of the goal of“eliminating viral hepatitis as a major public health threat by 2030”set by the World Health Organization,the Chinese Society of Hepatology together with the Chinese Society of Infectious Diseases(both are branches of the Chinese Medical Association)organized a panel of experts and updated the guidelines for prevention and treatment of chronic hepatitis B in China(version 2022).With the support of available evidence,this revision of the guidelines focuses on active prevention,large scale testing,and expansion of therapeutic indication of chronic hepatitis B with the aim of reducing the hepatitis B related disease burden.

Prevalence and risk factors for minimal hepatic encephalopathy in cirrhotic patients with different etiologies

Aims:Minimal hepatic encephalopathy(MHE)significantly affects the prognosis of patients with cirrhosis.This study was performed to determine whether there is a difference in the prevalence of MHE among patients with cirrhosis of different etiologies and whether the etiology directly influences the occurrence of MHE.Methods:This multicenter,cross-sectional study enrolled 1879 patients with confirmed cirrhosis at 40 hospitals from October 25,2021,to January 10,2023(Trial registration:https://clinicaltrials.gov/[NCT05140837]).The patients'demographics,etiologies of cirrhosis,and laboratory test results were collected.The psychometric hepatic encephalopathy score(PHES)was determined in all patients to screen for MHE.Multivariate logistic analyses were performed to identify the risk factors for MHE.Results:In total,736 patients with cirrhosis were analyzed.The prevalence of MHE was 42.0%(n=309).The primary etiology among all patients was hepatitis B virus(HBV)-related cirrhosis(71.9%[529/736]).The prevalence of MHE was significantly higher in patients with alcoholic cirrhosis(57.1%[40/70])than in those with HBV-related cirrhosis(40.6%[215/529],p=0.009)or hepatitis C virus(HCV)-related cirrhosis(38.2%[26/68],p=0.026).Age(odds ratio[OR],1.042;95%confidence interval[CI],1.024-1.059;p<0.001),duration of education(OR,0.935;95%CI,0.899-0.971;p=0.001),etiology(OR,1.740;95%CI,1.028-2.945;p=0.039),and high MELD-Na scores(OR,1.038;95%CI,1.009-1.067;p=0.009)were independent risk factors for MHE.When patients with cirrhosis of different etiologies were analyzed separately,the results showed that age(OR,1.035;95%CI,1.014-1.057;p=0.001)and duration of education(OR,0.924;95%CI,0.883-0.966;p=0.001)were risk factors for MHE among patients with HBV-related cirrhosis,whereas age(OR,1.138;95%CI,1.033-1.254;p=0.009)and creatinine concentration(OR,16.487;95%CI,1.113-244.160;p=0.042)were risk factors for MHE in patients with HCV-related cirrhosis.No risk factors for MHE were found in patients with autoimmune cirrhosis.For patients with alcoholic cirrhosis,the platelet count(OR,1.014;95%CI,1.000-1.027;p=0.045)was a risk factor for MHE.The PHES subtest results were inconsistent among patients who had MHE with cirrhosis of different etiologies.Patients with HBV-related cirrhosis performed better on Number Connection Test B and the serial dotting test than those with alcoholic cirrhosis(p=0.007 and p<0.001),better on Number Connection Test B than those with HCV-related cirrhosis(p=0.020),and better on the line tracing test than those with autoimmune cirrhosis(p=0.037).Conclusion:The etiology of cirrhosis affected the prevalence of MHE and risk factors for MHE.The domains of major cognitive impairment varied among patients with cirrhosis of different etiologies.Further studies are required to verify these findings.

高校继续教育转型:组织变革理论视域下的阶段、方向与关系

以美国社会心理学家库尔特·勒温提出的组织变革理论三阶段模型为指导,借鉴物理学中"矢量"概念,界定了普通高校继续教育转型的"阶段矢量""方向矢量""关系矢量",建立了"矢量三角形"分析框架。阶段矢量上经历解冻以发现问题并明确发展方向、变革以推进模式创新和结构优化、再冻结以确立基于课程为单元的学分银行三个阶段的叠加式发展。方向矢量上进行战略性变革要克服熵增原理,体现在办学定位上从补偿教育向服务全民终身学习转变、节奏上从系统性向"短快新"转变、时效上从滞后性向前瞻性转变、内容上从理论性向实战性转变、模式上从单一性向灵活性转变五个方面。关系矢量上要抵制二律背反现象,要正确处理好市场规律和教育规律、社会效益和经济效益、线上和线下、学历和非学历、管理和服务之间的关系。组织变革推进矢量三角形进入一个新的平衡状态,从而实现普通高校继续教育转型发展。

Current advances in the elimination of hepatitis B in China by 2030

With its 78 million chronic carriers, hepatitis B virus （HBV） infection is still one of the leading public health challenges in China. Over the last two decades, China has made great progress on the prevention of HBV transmission through national vaccination programs. Zero transmission from mother to infant has been proposed as the current goal. Available anti-HBV therapy is efficacious in suppressing HBV replication; however, it fails to completely cure patients with chronic hepatitis B and even requires Hfelong treatment. To reduce the costs and improve the efficacy, several trials have been recently conducted in China to optimize the current anti-HBV managements. Novel biomarkers were identified to predict treatment outcomes, and new promising treatment strategies were developed. Reports also indicate that coinfections of HBV with other hepatotropic viruses and human immunodeficiency virus are common in China and cause severe liver diseases, which should be recognized early and treated properly. Work is still needed to eliminate hepatitis B in China by 2030.

Guideline of Prevention and Treatment for Chronic Hepatitis B (2nd Version)

This guideline is established to standardize the prevention,diagnosis and antiviral therapy of chronic hepatitis B(CHB).For other treatment regimens and methods involving CHB,please refer to relevant guidelines and consensuses.The Chinese Society of Hepatology,Chinese Medical Association(CMA)and the Society of Infectious Diseases,CMA organized relevant native experts to establish this Guideline of Prevention and Treatment for Chronic Hepatitis B(1st version)in 2005,and made the first revision in 2010.In the past 5 years,great progress has been made in the native and foreign fundamental and clinical research with respect to CHB,necessitating additional revision of this guideline.

Efficacy and Safety of All-oral,12-week Ravidasvir Plus Ritonavir-boosted Danoprevir and Ribavirin in Treatment-naive Noncirrhotic HCV Genotype 1 Patients:Results from a Phase 2/3 Clinical Trial in China

Background and Aims:Ravidasvir(RDV)is a new generation pangenotypic hepatitis C virus(HCV)NS5A inhibitor,with high barrier to baseline resistance-associated species.This is the first phase 2/3 study conducted in China's Mainland confirming the efficacy and safety of RDV+ritonavir-boosted danoprevir+ribavirin for 12 weeks in treatment-naive noncirrhotic patients with genotype 1 infection in a large population.Methods:In this multicenter,randomized,doubleblinded,placebo-controlled phase 2/3 trial(NCT03362814),we enrolled 424 treatment-nafve,noncirrhotic adult HCV genotype 1 patients.All patients were randomized at 3∶1 ratio to receive a combination of RDV 200mg once daily plus ritonavir-boosted danoprevir 100mg/100mg twice daily and oral ribavirin 1000/1200mg/day(body weight<75/≥75 kg)(n=318)or placebo(n=106)for 12 weeks.The primary end-point was the rate of sustained virologic response 12 weeks after the end of treatment,and the safety was evaluated and compared between treatment and placebo groups.Results:The overall rate of sustained virological response at 12 weeks after treatment is 99%(306/309,95%,CI:97%-100%)under per protocol set analysis.All patients harboring baseline NS5A resistance-associated species in the treatment group(76/76,per protocol set)achieved sustained virological response at 12 weeks after treatment.No treatment-related serious adverse events were reported.Laboratory abnormalities showed mild or moderate severity(grade 1 and grade 2)in liver function tests.Conclusions:In treatment-na(i)ve,noncirrhotic HCV Chinese patients infected with HCV genotype 1,all-oral regimen of RDV+ritonavir-boosted danoprevir+ribavirin for 12 weeks was highly efficacious,safe,and well tolerated.

Thermal damage analysis of aircraft composite laminate suffered from lightning swept stroke and arc propagation

Lightning strike is a complicated process involving multi-field coupling.In order to investigate the thermal damage mechanism of carbon fiber reinforced composites subject to lightning swept stroke,a complete numerical method is presented.Numerical model of lightning discharge is established based on Magneto Hydro Dynamics(MHD)and calculated by FLUENT secondary development technology.Considering aerodynamic flow effect,channel formation and evolution process during lightning discharge is analyzed for lightning current waveform A.Thermal-electric Coupling model is presented according to Radial Basis Function(RBF)interpolation theory,which is implemented by compiling program to make lightning current and heat energy inject into composite laminate.Consequently,damage mechanism of composite laminate under lightning swept stroke is studied based on the coupled numerical model and element deletion method.Ablation damage morphology of composite laminate is analyzed to understand plasma expansion and reattachment in arc root.The results show that aerodynamic flow makes the lightning channel move fast and composite laminate is deteriorated due to thermal damage.

Comparative study on virus shedding patterns in nasopharyngeal and fecal specimens of COVID-19 patients

Dear Editor,An acute viral pneumonia(COVID-19),caused by the novel coronavirus known as SARS-CoV-2,was first identified during December 2019 in China(Zhu et al.,2020).SARSCoV-2 was found to be highly transmissible in humans(Wang et al.,2020)and is now a pandemic spreading to over 140 countries and causing over 150,000 infections and 6,000 deaths as of March 15,2020.Diagnosis is critical for confirmation and treatment of COVID-19.Currently the primary criterion for diagnosis of COVID-19 is viral RNA detection for respiratory samples.Recently,two studies on virus loads in clinical samples reported that viral loads in nasal and throat swabs and sputum specimens peaked at 3–7 days after illness onset(d.a.o.)and virtually disappeared before 15 d.a.o.(Pan et al.,2020;Zou et al.,2020).Another study showed that the median duration of virus shedding in throat swabs was 20 d.a.o.in survivors and was detectable until death in non-survivors(Zhou et al.,2020).Additionally,live viruses have been isolated in the feces and urine samples of COVID-19 patients.However,the viral dynamics in these types of specimens has not yet been clearly elucidated,as well as comparative studies on virus shedding in the upper respiratory,intestinal,and urinary tracts.

A NEW TRUST-REGION ALGORITHM FOR FINITE MINIMAX PROBLEM

In this paper, a new trust region algorithm for minimax optimization problems is proposed, which solves only one quadratic subproblem based on a new approximation model at each iteration. The approach is different with the traditional algorithms that usually require to solve two quadratic subproblems. Moreover, to avoid Maratos effect, the nonmonotone strategy is employed. The analysis shows that, under standard conditions, the algorithm has global and superlinear convergence. Preliminary numerical experiments are conducted to show the effiency of the new method.

NORMAL CONTACT STIFFNESS OF THE ELLIPTIC AREA BETWEEN TWO ASPERITIES

A new expression for contact deformation is given, and the normal contact stiff- ness between single asperities is derived according to Hooke＇s law. A contact model between two ellipsoidal asperities is simulated by the FE method, the result compared with the theoretical solution. It is found that the curves of the normal contact stiffness versus the included angle in the principal curvature direction show similar trends and evolve as a cosine feature. The effects of the parameters on normal contact stiffness are found to show that normal contact stiffness increases and reaches the upper limit gradually with an increase in these parameters.

Olfactory and gustatory dysfunctions of COVID-19 patients in China:A multicenter study

Introduction:With the spread of the epidemic worldwide,an increasing number of doctors abroad have observed the following atypical symptoms of coronavirus disease 2019(COVID-19):olfactory or taste disorders.Therefore,clarifying the incidence and clinical characteristics of olfactory and taste disorders in Chinese COVID-19 patients is of great significance and urgency.Materials and Methods:A retrospective study was conducted,which included 229 severe acute respiratory syndrome coronavirus 2 confirmed patients,through face-to-face interviews and telephone follow-up.Following the completion of questionnaires,the patients participating in the study,were categorized according to the degree of olfactory and taste disorders experienced,and the proportion of each clinical type of patient with olfactory and taste disorders and the time when symptoms appeared were recorded.Results:Among the 229 patients,31(13.54%)had olfactory dysfunction,and 44(19.21%)had gustatory dysfunction.For the patients with olfactory dysfunction,6(19.35%)developed severe disease and became critically ill.Olfactory dysfunction appeared before the other symptoms in 21.43%of cases.The proportion of females with olfactory and gustatory dysfunction was higher than that of males(P<0.001).Conclusions:The incidence of olfactory and gustatory dysfunction was much lower than that reported abroad;the prognosis of patients with olfactory dysfunction is relatively favorable;olfactory and gustatory dysfunction can be used as a sign for early screening;females are more prone to olfactory and gustatory dysfunction.

Past climate change and recent anthropogenic activities affect genetic structure and population demography of the greater longtailed hamster in northern China

The genetic diversity and the spatial structure of a species are likely consequences of both past and recent evolutionary processes,but relevant studies are still rare in East Asia where the Pleistocene climate has unique influences.In this study,we examined the impact of past climate change and recent anthropogenic activities on the genetic structure and population size of the greater long-tailed hamster(Tscherskia triton),an agricultural rodent pest species in northern China.DNA sequence data of 2 mitochondrial genes and genotypic data of 11 microsatellite DNA loci from 41 populations(545 individuals)were gathered.Phylogenetic and population genetic analyses,as well as species distribution modeling and coalescent simulations,were conducted to infer its historical and demographic patterns and processes.Two deeply diverged mitochondrial clades were recovered.A small one was restricted to the Shandong Peninsula while the main clade was further divided into 3 geographic clusters by their microsatellite DNA genotypes:Northwest,North-center and Northeast.Divergence dating indicated a Middle-to-Late Pleistocene divergence between the 2 clades.Demographic analysis indicated that all 3 and pooled populations showed consistent long-period expansions during last glacial period;but not during the Holocene,probably due to the impact of climate warming and human disturbances.Conflicting patterns between mtDNA and microsatellite markers imply an anthropogenic impact on North-center populations due to intensified agricultural cultivation in this region.Our study demonstrated that the impact of past glaciation on organisms in East Asia significantly differs from that of Europe and North America,and human activity is an important factor in determining the genetic diversity of a species,as well as its spatial structure.

Preface

Cloud computing and big data have become increasingly popular and are changing our way of thinking about the world by providing new insights and creating new forms of value. The research of cloud data management is to address the challenges in managing large collections of data in the cloud computing environment, and identifying information of value to business, science, government, and society. The huge volumes of data in cloud computing environments pose major infrastructure challenges, including data storage at Petabyte scale, massively parallel query execution, facilities for analytical processing, online query processing, resource optimization, data privacy and security.