氮化硼/石墨烯共混对环氧树脂复合材料导热性和形状记忆效应的影响

采用不同摩尔比的熔融氢氧化钠和氢氧化钾剥离六方氮化硼。分别利用原子力显微镜、扫描电子显微镜和透射电子显微镜观察剥离效果发现,氢氧化钠和氢氧化钾摩尔比为2∶1时,氮化硼被剥离成4个原子层的氮化硼纳米片,剥离效果较好。为了提高环氧树脂的导热性,研究了不同质量比的氮化硼纳米片(BNNS)和石墨烯(Gr)混合物对其导热性能的影响。实验结果表明,BNNS和Gr混合物对环氧树脂导热性的影响优于单一的BNNS和Gr。当m(BNNS)∶m(Gr)=1∶4时,环氧树脂的导热系数最高,从纯环氧树脂的0.22 W/(m·K)增加到0.42 W/(m·K)。同时,该混合物还改善了环氧树脂的形状记忆效果,当m(BNNS)∶m(Gr)=1∶4时,复合材料的形状回复率可达到100%;70℃时,纯环氧树脂的形状回复时间为30 s,复合材料的形状回复时间缩短为4 s。

激光显微拉曼光谱仪在本科实验教学中的应用

拉曼光谱作为一种无损检测的指纹光谱是科研中的主要表征手段。激光显微拉曼光谱实验教学通过测试科研中的样品让学生了解拉曼测试的重要性以及科研的分析方法,构建科学研究和实验教学的桥梁。本实验课程同时安排创新探索实验,培养学生的自主学习兴趣和科研创新能力。通过本实验的学习,让学生们了解目前先进的分析手段和先进的大型仪器,有利于学生综合实验素质及科研能力的培养,为以后从事科学研究及相关工作所需综合能力的培养打下坚实的基础。

Quasi-optimal complexity of adaptive finite element method for linear elasticity problems in two dimensions

This paper introduces an adaptive finite element method （AFEM） using the newest vertex bisection and marking exclusively according to the error estimator without special treatment of oscillation. By the combination of the global lower bound and the localized upper bound of the posteriori error estimator, perturbation of oscillation, and cardinality of the marked element set, it is proved that the AFEM is quasi-optimal for linear elasticity problems in two dimensions, and this conclusion is verified by the numerical examples.

Quantum Engineering of Helical Charge Migration in HCCI

Electronic charge of molecules can move on time scales when the nuclei stand practically still,from few hundreds of attoseconds to few femtoseconds.This ultrafast process is called“charge migration”.A typical consequence is rapid change of electronic dipole,which points to the center of charge.Corresponding linear(one-dimensional,1D)and planar(2D)dipolar motions have already been well documented.Here we construct the first case of charge migration which causes chiral 3D dipolar motion,specifically along a helix about oriented iodo-acetylene(HCCI).Quantum dynamics simulations show that this can be induced by well-designed laser pulses.

TLC Identification of Laggerae Alatae Herba and Extraction Process of Chlorogenic Acid

[Objectives]Taking chlorogenic acid as index component,TLC and content determination method of Laggerae Alatae Herba were established.[Methods]TLC identification used silica gel G thin-layer plate,and butyl acetate∶formic acid∶water(7∶2.5∶2.5)was taken as developing agent,and it was inspected under ultraviolet lamp(365 nm).The content was determined by chromatographic column Inertsil ODS-3 C_(18)(4.60 mm×250 mm,5μm).Mobile phase:methanol-0.1%phosphoric acid(28∶72);detection wavelength:329 nm;flow speed:1.0 mL/min;column temperature:25℃;injection volume:10μL.[Results]Chlorogenic acid can be detected by TLC,with clear spots and good specificity.When injection volume of chlorogenic acid was between 0.099 and 0.990μg(R^(2)=0.9999),there was good linear relationship.In low,medium and high sample adding groups of Laggerae Alatae Herba,average recovery rates of chlorogenic acids were 98.80%(RSD=2.09%),98.24%(RSD=1.96%)and 99.65%(RSD=2.15%).[Conclusions]The method could effectively identify medicinal material Laggerae Alatae Herba,and accurately measure the content of chlorogenic acid in Laggerae Alatae Herba,thereby providing a scientific basis for developing and using medicinal resources of Laggerae Alatae Herba.

Current Situation and Demand of Rural Endowment Security in Shaanxi Province

With intensification of population aging and rise in elderly dependency ratio,the demand for endowment security becomes higher and higher,particularly in rural areas.Taking Shaanxi Province as an example,the authors selected people older than 65 in 18 natural villages in north Shaanxi,south Shaanxi and Guanzhong.With the aid of survey data and related official statistical data,they made an evaluation of current situation of the rural endowment security in Shaanxi Province.Results indicate that home-based endowment is the major endowment method of rural elderly,but such method is influenced by family's economic support ability and children's support willingness,thus facing big demand gap.On the basis of analyzing gap problem,the authors recommended that government should increase financial and policy supports,optimize management and monitoring,actively develop non-government organizations,and promote socialization of rural endowment service.

Placenta Percreta with Bladder Invasion:Delayed Bladder Bleeding After Hysterectomy

Placenta percreta is a rare condition,which can lead to significant morbidity and potentially,mortality.This paper discusses two cases of complete placenta previa with placenta percreta invading the urinary bladder.Both patients underwent caesarean hysterectomy and experienced delayed bladder bleeding postoperatively.

超声O-RADS分类和临床特征对不同病理类型卵巢浆液性肿瘤的诊断价值

目的探讨卵巢浆液性肿瘤不同病理类型之间的卵巢-附件影像报告和数据系统(O-RADS)超声特征及临床特征的差异,并分析超声O-RADS分类和临床特征在诊断不同病理类型卵巢浆液性肿瘤方面的应用价值。方法回顾性分析2021年1月至2022年6月浙江大学医学院附属第二医院经病理证实为卵巢浆液性肿瘤的病例57例,共76个附件肿块,记录患者的临床资料及超声图像。依据组织病理学类型将卵巢浆液性肿瘤患者分为良性肿瘤组(20例)、交界性肿瘤组(16例)和恶性肿瘤组(21例)。采用单因素方差分析3组患者年龄、体质量指数及肿瘤最大径的差异;采用秩和检验对3组患者糖类抗原125(CA125)水平、病灶血流评分、病灶内乳头状突起数目及病灶O-RADS分类进行两两比较;采用χ^(2)检验分析3组患者主诉的差异;采用Bonferroniχ^(2)分割法对患者是否合并有腹水和(或)腹膜增厚/结节、病变发生部位、病灶性质、病灶内有无分隔进行两两比较;绘制受试者操作特征(ROC)曲线评价CA125、O-RADS分类对卵巢浆液性肿瘤的诊断效能。结果临床特征上,良性肿瘤组、交界性肿瘤组和恶性肿瘤组病变位于双侧[15.0%(3/20)vs 18.7%(3/16)vs 61.9%(13/21)]、合并出现腹水和(或)腹膜增厚/结节[0%(0/20)vs 0%(0/16)vs 57.1%(12/21)]及血清CA125水平[15.8(7.8,21.7)U/ml vs 43.3(29.4,105.6)U/ml vs 1229.2(142.9,2222.7)U/ml]比较,差异具有统计学意义(χ^(2)=12.271,P=0.003;χ^(2)=18.321,P<0.001;H=38.393,P<0.001),血清CA125水平截断值为293.0 U/ml(曲线下面积=0.917),诊断恶性肿瘤的敏感度为71.43%,特异度为100%。超声特征方面,良性肿瘤组、交界性肿瘤组和恶性肿瘤组病变呈多房囊性含实性成分及实性/实性样变[13.1%(3/23)vs 21.0%(4/19)vs 91.2%(31/34)]、病灶血流评分≥2分[0%(0/23)vs 68.4%(13/19)vs 82.4%(28/34)]、囊性病灶内含乳头状数目>3个[0%(0/23)vs 68.4%(13/19)vs 8.7%(2/23)]、囊性病灶呈多房[34.8%(8/23)vs 21.1%(4/19)vs 87.0%(20/23)]比较,差异具有统计学意义(χ^(2)=89.998,P<0.001;H=35.407,P<0.001;H=26.210,P<0.001;χ^(2)=19.477,P<0.001)。ROC曲线分析显示,O-RADS 4-5类诊断交界性肿瘤或恶性浆液性肿瘤的敏感度为92.45%,特异度为82.61%。结论不同病理类型的卵巢浆液性肿瘤具有不同的超声特征及临床特征,超声O-RADS分类(病灶性质、病灶内有无分隔、病灶血流评分、病灶内乳头状突起数目)和临床特征(患者CA125水平、病变部位)可有效区分不同病理类型的卵巢浆液性肿瘤。

一株兼性氧化亚氮还原菌的还原N2O能力

【目的】从水稻土中分离筛选出一株兼性氧化亚氮还原菌,并探索其在不同条件下还原N_2O的能力,为减少温室气体N_2O的排放提供重要依据。【方法】通过微生物富集培养分离技术从水稻土中分离得到纯菌;利用nosZ基因和16S rRNA的测序分析鉴定菌株;通过测定菌株在不同条件下N_2O的还原量,分析该菌株还原N_2O的能力及调控因子。【结果】经鉴定,该菌株含有nos Z基因,属于假单胞菌属,在温度30°C、厌氧条件下还原N_2O速率高达0.0219μmol/min以上,改变不同温度和氧气浓度后其能力相对减弱,但仍具备较强的还原N_2O作用。【结论】从水稻土中分离筛选得到的兼性氧化亚氮还原菌为假单胞菌,它在不同环境条件下都具备较强的还原N_2O能力,该菌株可能为减少土壤N_2O排放提供新途径,对保障生态环境安全具有重要的应用价值。

Cross-sectional deformation behavior of double-ridged rectangular tube with fillers in different stages of H-typed bending

The bent double-ridged rectangular tube(DRRT)with high forming quality is helpful to improve the microwave transmission accuracy.For reducing the cross-sectional deformation in the H-typed bending process,in addition to using rigid mandrel to support the inside of tube,ridge groove fillers are also added to restrict the deformation of ridge grooves.Because of the change of stress and strain state of bent tube in bending,rigid mandrel retracting and specially twicespringback stages,and the springback of fillers,the cross-sectional deformation of tube in each stage may be different.Therefore,based on the ABAQUS platform,the finite element models(FEM)for H-typed bending,mandrel retracting and twice-springback stages of H96 DRRT with fillers were established and validated.It is found that,for the height and width deformation of tube and spacing deformation of ridge grooves,retraction of mandrel can make the distribution of these deformations more uniform along the bending direction.The first springback can reduce these deformations significantly,which should be emphasized.But the second springback only increases them by less amount,which can be ignored.The smaller height deformation of ridge groove and filler can be neglected.

Improving biomethane yield by strengthening acidification of maize stover in two-phase anaerobic digestion

In this study,the acidification and two-phase anaerobic digestion(AD)were conducted in batch and continuous stirred tank reactors,respectively,to determine the effect of acidification on methane production in AD.The results showed that two-phase AD achieved an observable enhancement in the methane production under optimal acidification conditions(organic loading rate of 60 g TS/L,the ratio of raw material to inoculum(based on dry weight)of 2:1,the temperature of 45℃,urea concentration of 4%,and time of 6 d).Under these conditions,the daily biogas and biomethane productions were 0.48 L/g TS and 0.30 L/g TS,respectively,which were 26.32%and 57.89%higher than those of the untreated group,respectively.The ammonia nitrogen(AN),alkalinity,and pH value of the methanogenic phase of C4 continued to increase up to 956 mg/L,5680 mg/L,and 7.41,respectively,after 60 d,which might have destroyed the stability of the system.Therefore,for the purpose of reusing the nitrogen source,reducing AN,and maintaining the stability of the reaction system,another set of acidification and two-phase AD with water pretreatment using the discharge of the methanogenic phase of C4 as the inoculum was subsequently conducted.The results showed that the daily biogas productions of single-phase and two-phase AD were 5.26%and 15.79%higher than that of the untreated group,respectively;similarly,their daily methane yields were 10.42%and 21.05%higher than that of the untreated group.

Fully Discrete H^(1) -Galerkin Mixed Finite Element Methods for Parabolic Optimal Control Problems

In this paper,we investigate a priori and a posteriori error estimates of fully discrete H^(1)-Galerkin mixed finite element methods for parabolic optimal control prob-lems.The state variables and co-state variables are approximated by the lowest order Raviart-Thomas mixed finite element and linear finite element,and the control vari-able is approximated by piecewise constant functions.The time discretization of the state and co-state are based on finite difference methods.First,we derive a priori error estimates for the control variable,the state variables and the adjoint state variables.Second,by use of energy approach,we derive a posteriori error estimates for optimal control problems,assuming that only the underlying mesh is static.A numerical example is presented to verify the theoretical results on a priori error estimates.

An Iterative Two-Grid Method of A Finite Element PML Approximation for the Two Dimensional Maxwell Problem

In this paper,we propose an iterative two-grid method for the edge finite element discretizations(a saddle-point system)of Perfectly Matched Layer(PML)equations to the Maxwell scattering problem in two dimensions.Firstly,we use a fine space to solve a discrete saddle-point system of H(grad)variational problems,denoted by auxiliary system 1.Secondly,we use a coarse space to solve the original saddle-point system.Then,we use a fine space again to solve a discrete H(curl)-elliptic variational problems,denoted by auxiliary system 2.Furthermore,we develop a regularization diagonal block preconditioner for auxiliary system 1 and use H-X preconditioner for auxiliary system 2.Hence we essentially transform the original problem in a fine space to a corresponding(but much smaller)problem on a coarse space,due to the fact that the above two preconditioners are efficient and stable.Compared with some existing iterative methods for solving saddle-point systems,such as PMinres,numerical experiments show the competitive performance of our iterative two-grid method.

Mono-isotope Prediction for Mass Spectra Using Bayes Network

Mass spectrometry is one of the widely utilized important methods to study protein functions and components. The challenge of mono-isotope pattern recognition from large scale protein mass spectral data needs computational algorithms and tools to speed up the analysis and improve the analytic results. We utilized na¨？ve Bayes network as the classifier with the assumption that the selected features are independent to predict monoisotope pattern from mass spectrometry. Mono-isotopes detected from validated theoretical spectra were used as prior information in the Bayes method. Three main features extracted from the dataset were employed as independent variables in our model. The application of the proposed algorithm to public Mo dataset demonstrates that our na¨？ve Bayes classifier is advantageous over existing methods in both accuracy and sensitivity.

Influence of deformation zone length on bending radius of SS304 tubes with small diameters manufactured via free bending-based active motion

In three and six-axis free-bending equipment,the deformation zone length(A)is a fixed mechanical structure parameter modified when the relevant structure is redesigned and manufactured.In this study,a six degree of freedom(6-DOF)parallel mechanism was used as the control mechanism of the bending die,and a new method of changing the deformation zone length(A)was proposed.Firstly,an idealized geometric model of free bending-based active motion was established.Then,the influence of the deformation zone length(A)on the bending moment and the bending radius of the tube was analyzed.In addition,the finite element simulation and a kinematic model of free bending-based active motion controlled by the 6-DOF parallel mechanism were established,and bending processes of the SS304 tube with different deformation zone lengths were investigated.Afterwards,the impact of the deformation zone length(A)on the bending radius,bending moment,wall thickness,and motion of the parallel mechanism were analyzed.Finally,experiments were carried out on the free-bending equipment based on the 6-DOF parallel mechanism.Experiments verified the rules in the theoretical analysis,finite element simulation,and kinematic simulation.

Effects of punch size, magnetic field, and magnetorheological elastomers medium on forming T-shaped thin-walled Inconel 718 tubes

This study aims at investigating the impact of using the Magnetorheological Elastomers(MREs)medium to improve the formability of T-shaped Inconel 718 tubes during the bulging process.Besides,the influence of the punch size and the intensity of the magnetic field on the branch height and wall thickness distribution of the T-shaped Inconel 718 tubes are also explored.The results showed that the parts formed by the punch with a length of 5 mm in the pressurization zone have better forming quality.The external magnetic field can promote a high branch,and by increasing the intensity of the magnetic field,the branch height was increased and then decreased.At the same time,the magnetic field reduced the amount of material accumulation between the guiding zone and the bulging zone.Besides,it promotes the material in the guiding zone to enter the bulging zone and improve the bulging ability of the T-shaped tube.

TWO-GRID ALGORITHM OF H^(1)-GALERKIN MIXED FINITE ELEMENT METHODS FOR SEMILINEAR PARABOLIC INTEGRO-DIFFERENTIAL EQUATIONS

In this paper,we present a two-grid discretization scheme for semilinear parabolic integro-differential equations by H1-Galerkin mixed finite element methods.We use the lowest order Raviart-Thomas mixed finite elements and continuous linear finite element for spatial discretization,and backward Euler scheme for temporal discretization.Firstly,a priori error estimates and some superclose properties are derived.Secondly,a two-grid scheme is presented and its convergence is discussed.In the proposed two-grid scheme,the solution of the nonlinear system on a fine grid is reduced to the solution of the nonlinear system on a much coarser grid and the solution of two symmetric and positive definite linear algebraic equations on the fine grid and the resulting solution still maintains optimal accuracy.Finally,a numerical experiment is implemented to verify theoretical results of the proposed scheme.The theoretical and numerical results show that the two-grid method achieves the same convergence property as the one-grid method with the choice h=H^(2).

Accurate Identification of Mass Peaks for Tandem Mass Spectra Using MCMC Model

In proteomics, many methods for the identification of proteins have been developed. However, because of limited known genome sequences, noisy data, incomplete ion sequences, and the accuracy of protein identification,it is challenging to identify peptides using tandem mass spectral data. Noise filtering and removing thus play a key role in accurate peptide identification from tandem mass spectra. In this paper, we employ a Bayesian model to identify proteins based on the prior information of bond cleavages. A Markov Chain Monte Carlo（MCMC）algorithm is used to simulate candidate peptides from the posterior distribution and to estimate the parameters for the Bayesian model. Our simulation and computational experimental results show that the model can identify peptide with a higher accuracy.