沈阳地区砂浆强度新旧试验方法换算系数的比对总结

2009年6月1日,JGJ/T70—2009《建筑砂浆基本性能试验方法标准》(以下简称新标准)正式实施,原JGJ/T70—90《建筑砂浆基本性能试验方法标准》(以下简称旧标准)同时废止。在立方体抗压强度试验的规定中新标准与旧标准相比较有了较大的变化,为了使验收结果达到一致并偏于安全,新标准选择了系数K=1.35。为了验证系数K在本地区的安全性,沈阳地区进行了砂浆新旧试验方法的比对试验,对新标准的换算系数进行了回归统计得出K=1.28,并提出了相关思考。

新型高强度玻璃纤维制备与性能研究

研究了一种新的高强度玻璃纤维(NEWHS),其主成分为SiO2、Al2O3、MgO,总含量>96%(质量分数),其余为助熔剂、澄清剂和不可避免的杂质;经过熔制得到玻璃实验样品,对各试验样品进行高温粘度、析晶上限、新生态强度、软化点、耐酸性等性能检测,得到新型高强度玻璃纤维的各性能数据:新生态强度为4600～4800MPa、软化点温度为965～970℃、耐酸性质量损失率<5.25%;新型高强度玻璃纤维的力学性能、耐温性能、耐酸性能皆高于现有高强度玻璃纤维产品(HS2、HS4),也高于AdvantexTM、Hiper-texTM玻璃纤维,接近美国S-2TM,可以投入生产。

基于关联的自适应新生目标强度CPHD滤波

量测驱动的自适应新生目标强度基数概率假设密度(adaptive target birth intensity cardinalized probability hypothesis density,ATBI-CPHD)滤波器可以在新生目标强度未知的情况下进行多目标跟踪,然而该方法利用所有量测产生新生目标,没有考虑关联问题。为此,本文提出了一种基于数据关联的改进算法。首先,给出了ATBI-CPHD在高斯混合CPHD(Gaussian mixture CPHD,GMCPHD)框架下的实现。其次,在GMCPHD滤波框架下采用一种基于量测标签的方法进行量测-估计关联,并引入高斯元标签进行航迹保持,在此基础上提出了一种航迹管理方法。最后采用量测波门进行量测-量测关联,利用关联后的量测产生新生目标。仿真结果表明,该算法可以在提高跟踪效果的同时提升计算效率。

汕头市新旧暴雨强度公式对比分析

采用汕头国家气象站1980—2014年的年最大雨量资料对汕头市暴雨强度公式进行了修编,并与旧公式对比,结果表明:(1)新公式计算的暴雨强度值总体上大于旧公式,降雨历时越长,重现期越大,则偏大越明显,2~20年重现期平均增大了5.0%。(2)在年平均降雨量变化较平稳的气候背景下,新公式采用的资料年限的最大降水平均值大于旧公式对应资料年限的最大降水平均值,且资料中出现了强降雨样本,导致新公式比旧公式总体上偏大是合理的。(3)汕头市新暴雨强度公式可作为汕头市区室外排水设计的依据。

基于谱聚类的自适应新生目标强度状态提取

由于K均值算法易受噪声干扰且对初始粒子的选取较为敏感,在进行PHD状态提取时,难以获得稳定可靠的状态估计结果。对此,提出基于谱聚类的自适应新生目标强度状态提取方法,运用核密度估计理论和mean-shift算法二次估计PHD,提取滤波分布的峰值位置作为各个目标状态的估计值进行目标状态的提取。实验结果表明,改进后的算法相比原始算法在精度上有了明显提高。

CCNBD断裂韧度试样的SIF新公式和在尺度律分析中的应用

根据国际岩石力学学会于1995年推荐的一种测试岩石断裂韧度的新型试样-人字形切槽巴西圆盘试样,对其断裂韧度计算公式中的关键参数即无量纲应力强度因子(SIF)提出了一个改进的计算公式。采用分片合成方法结合有限元法对CCNBD试样的应力强度因子进行了宽范围标定,结果以表格的形式给出;并采用数据线性回归的方法,将标定结果以一个指数函数的形式给出。结果表明,与标定值相比,无量纲应力强度因子新公式的误差较小,并且囊括了CCNBD试样的较宽范围的尺寸,且查表使用方便,也为理论分析提供了条件。在此基础上,对岩石断裂韧度测试的尺度律进行了更进一步的探索,结果表明,利用新公式进行的尺度律分析是有效的。

新冠肺炎疫情是否激发了康养旅游意愿?——一个条件过程模型的检验

新冠肺炎疫情的暴发与蔓延对大众身心健康造成了影响,康养旅游则是缓解大众身心健康的重要方式。探讨疫情影响下大众康养旅游意愿,对旅游业提振恢复具有重要意义。文章基于刺激-机体-反应(S-O-R)理论,通过网络问卷对313名大众进行调查,并以风险感知为中介变量,以风险传播为调节变量,重点探讨大众新冠肺炎疫情的事件强度认知(新颖性认知、颠覆性认知和关键性认知)对其康养旅游意愿的影响机理。结果显示:(1)大众对新冠肺炎疫情的新颖性认知会抑制其康养旅游意愿,颠覆性认知并不影响大众康养旅游意愿,而事件的关键性认知能够唤起大众康养旅游意愿;(2)新冠肺炎疫情事件的新颖性认知对大众风险感知产生负向影响,而事件的关键性认知和颠覆性认知能够正向提升大众风险感知水平;(3)风险感知在事件的新颖性认知、关键性认知对康养旅游意愿的影响过程中起部分中介作用,而在事件的颠覆性认知对康养旅游意愿的影响过程中起完全中介作用;(4)风险传播并不能直接催生大众产生康养旅游意愿,而能够强化风险感知对康养旅游意愿的影响作用,即当外界发布更多风险信息时,其使得大众更加关注健康,从而增强了康养旅游意愿。

采用统计线性回归的改进ATBI-GMPHD滤波

提出一种改进的自适应新生目标GM-PHD算法。该算法以存活目标的量测更新权值构建“似然函数”,通过该函数确定量测来源并对新生目标权值做重分配,有效解决了归一化失衡问题。在量测方程高度非线性情况下,引入统计线性回归方法对量测方程进行线性化近似,求解新生目标预测均值和协方差。仿真结果表明,在新生目标信息先验缺失时,改进后的算法具有良好的跟踪精度和较低的计算量。

纤维素醚对无砂自流平材料物理力学性能的影响

将自流平砂浆中的细骨料换成粉料,制成无砂自流平材料,可以减少离析并充分利用废弃粉料。试验研究了2种不同黏度的纤维素醚对无砂自流平材料流动度和力学性能的影响,结果表明:随低黏纤维素醚掺量的增加,自流平材料的初始流动度和30min流动度都先增加,后逐渐减少,抗新和抗压强度大体上呈先增加后减少,再趋于稳定的趋势;随中黏纤维素醚掺量的增加,自流平材料的流动度先下降,后略有提升并保持稳定,抗新和抗压强度大体上呈先下降较快,后有所增加且总体上保持稳定的趋势。中黏纤维素醚不适合用于自流平材料,应该选择使用低黏的纤维素醚,且掺量小于0.2‰。

Mechanical performance of the mixed post-installed connection in low-strength concrete

Due to inadequate bearing capacity of the chemically-planted steel bar in low-strength concrete, a new mixed post-installed connection is proposed using small diameter anchoring steel bars and grouting materials together to anchor the main steel bar. To investigate the feasibility of the proposed post-installed connections, a series of pull-out tests with different anchors were conducted for comparison,including fully adhesive anchors, partially adhesive anchors,grouting material anchoring connection and the new mixed post-installed connection. The experimental results of the single steel bar pull-out test show that the mixed post-installed connection can effectively enhance the bearing capacity of post-installed steel bars in low-strength concrete. The bearing capacity is increased by nearly two times with no cone-type concrete failure compared with the fully adhesive anchor. The results show that adopting the new mixed post-installed connection can ensure that joint performance meets the requirements if the space dimension is available.

Seismic behavior and mechanism analysis of innovative precast shear wall involving vertical joints

To study the seismic performance and load-transferring mechanism of an innovative precast shear wall(IPSW) involving vertical joints, an experimental investigation and theoretical analysis were successively conducted on two test walls. The test results confirm the feasibility of the novel joints as well as the favorable seismic performance of the walls, even though certain optimization measures should be taken to improve the ductility. The load-transferring mechanism subsequently is theoretically investigated based on the experimental study. The theoretical results show the load-transferring route of the novel joints is concise and definite. During the elastic stage, the vertical shear stress in the connecting steel frame(CSF) distributes uniformly; and each high-strength bolt(HSB)primarily delivers vertical shear force. However, the stress in the CSF redistributes when the walls develop into the elastic-plastic stage. At the ultimate state, the vertical shear stress and horizontal normal stress in the CSF distribute linearly; and the HSBs at both ends of the CSF transfer the maximum shear forces.

Ultra-High Strength Concrete Mixtures Using Local Materials

This paper presents the development of ultra high strength concrete （UHSC） using local materials. UHSC mixture proportions were developed using local materials so that UHSC may be made more affordable to a wider variety of applications. Specifically, local sand with a top size of 600 um, and locally available Type I/II cement and silica fume were used in this research. Each of these material selections is seen as an improvement in sustainability for UHSC. Two mixtures （one with and one without fibers） were recommended as the UHSC mixtures. The greatest compressive strengths obtained in this study were 165.6 MPa for UHSC with steel fibers and 161.9 MPa for UHSC without fibers. The compressive and flexural strengths obtained from the UHSC mixtures developed in this work are comparable to UHSC strengths presented in the literature. Producing this innovative material with local materials reduces the cost of the material, improves sustainability, and produces mechanical performance similar to prepackaged, commercially available products.

新冠肺炎疫情事件强度对环卫工工作绩效的影响

新冠肺炎疫情爆发给人们的生活和工作造成巨大冲击。为了城市正常运行,许多从业者坚守在疫情防控一线,这其中就有承担了最脏最累工作的环卫工。然而,这群默默坚守的抗疫英雄却较少受到关注,特别是他们在这种特殊情况下的工作心理和结果表现。基于压力认知激活理论,从事件属性角度,考察环卫工感知的新冠肺炎疫情事件强度对工作绩效的影响及其作用机制。首先,检验新冠肺炎疫情事件强度对工作绩效的主效应;其次,分别检验工作意义和额外努力在二者关系中的中介效应;最后,构建链式中介模型检验新冠肺炎疫情事件强度通过工作意义和额外努力对工作绩效的链式中介效应。通过多时段、多来源的问卷调研,以四川省3个地级市578名环卫工为研究样本,借助Mplus 7.0统计软件和Bootstrap方法检验链式中介效应。研究结果表明,新冠肺炎疫情事件强度对环卫工工作绩效有显著正向影响;工作意义在新冠肺炎疫情事件强度与环卫工工作绩效关系中具有显著的中介作用;工作意义和额外努力在新冠肺炎疫情事件强度与环卫工工作绩效的关系之间具有链式中介作用,即新冠肺炎疫情事件强度越大,环卫工可以体验到更多的工作意义,进而付出额外努力的意愿就越强,相应的其工作绩效就越高。研究结果为组织正确认识事件及其相关主体之间的关系提供了重要的理论价值和实践启示,不仅丰富了组织行为学领域量化事件属性的实证研究,还扩展了压力认知激活理论的现有解释机制,为如何从消极的压力事件中获得积极效应增添了新的解读视角。在实践方面为组织管理中如何引导管理者和员工从逆境中变被动为主动提供了参考依据,倡导社会大众摒弃职业偏见,正确认识环卫工的劳动价值。

Major Mid-Late Holocene Cooling in the East China Sea Revealed by an Alkenone Sea Surface Temperature Record

Although the mid-late Holocene cold and dry event about 4000years ago （the 4ka event） has been observed almost globally, it was most prominent in terrestrial climate proxies from the lower latitudes. Here we evaluate the oceanic response to this event in terms of a Holocene sea surface temperature （SST） record reconstructed using the U^7 index for Core B3 on the continen- tal shelf of the East China Sea. The record reveals a large temperature drop of about 5~C from the mid-Holocene （24.7~C at 5.6ka） to the 4ka event （19.2~C at 3.8ka）. This mid-late Holocene cooling period in Core B3 correlated with （i） decreases in the East Asia summer monsoon intensity and （ii） the transition period with increased E1 Nifio/Southern Oscillation activities in the Equatorial Pa- cific. Our SST record provides oceanic evidence for a more global nature of the mid-late Holocene climate change, which was most likely caused by a southward migration of the Intertropical Converge Zone in response to the decreasing summer solar insolation in the Northern Hemisphere. However, the large SST drop around Core B3 indicates that the mid-late Holocene cooling was regionally amplified by the initiation/strengthening of eddy circulation/cold front which caused upwelling and resulted in additional SST de- crease. Upwelling during the mid-late Holocene also enhanced with surface productivity in the East China Sea as reflected by higher alkenone content around Core B3.

Influence of moisture content on shearing strength of unsaturated undisturbed quaternary system middle pleistocene

The unsaturated undisturbed quaternary system middle pleistocene loess,a typical unsaturated soil,often occurs in the implementation of western development strategy.To obtain the shearing strength characteristics of this unsaturated undisturbed loess,based on the analysis of mineral composition,the triaxial shear test of undisturbed quaternary system middle pleistocene loess under different moisture contents is conducted with the specialized triaxial instrument for unsaturated soil.The test results show that the mainly mineral composition of undisturbed quaternary system middle pleistocene loess is quartz and albite.Under the same confining pressure,the matric suction increases with the decrease of moisture content.The smaller the moisture content,the larger the matric suction;the higher the moisture content,the lower the matric suction.Under the same moisture content,the matric suction increases with the confining pressure and reaches a maximum when the confining pressure is 100 kPa,and then decreases with the increase of confining pressure.This phenomenon is closely related to the grain contact tightness of soil mass under high confining pressure.According to the triaxial test of loess,the sample of loess experiences 4 stages from loading to failure:1) compaction stage;2) compression stage;3) microcrack developing stage;4) shear failure stage.The test sample is of brittle failure(weak softening)under low moisture content and confining pressure.With the decrease of matric suction and the increase of consolidated confining pressure,the stress-strain curve changes from softening type to ideal plastic type.In the shearing strength parameters of unsaturated undisturbed loess,the influence of moisture content on internal friction angle is small,but that on cohesive force is obvious.Therefore,the shearing strength of unsaturated undisturbed loess is higher than that of saturated undisturbed loess and varies with the moisture content.

A Discussion on Seismic Intensity—Taking the Xinjiang Area As an Example

The intensity of an earthquake is an important criterion and index for earthquake resistance, and disaster relief and for antiseismic engineering in large and medium sized cities. The earthquake data in Xinjiang are abundant and have been widely applied to the statistic relationship of seismic intensity of western China. However, there exists some unreasonable and man_made factors in them. We put forward the idea of area A_ 0-1 to express the effect of seismic intensity, studied the questions and influencing factors arising from uncertainty of intensity zoning and finally, proposed some solutions.

Innovative Application of Scrap-Tire Steel Cords in Concrete Mixes

Many researchers have investigated the use of recycled tire products in several traditional civil engineering materials. This research is exploring the use of steel cords, a by-product of the tire recycling process, in concrete mixes. Different concrete specimens were fabricated and tested in uniaxial compression and splitting tensile strength. The steel cords were substituted into the concrete mix in volumetric percentages of various ratios. Results show that mechanical properties of concrete made with steel cords are improved compared with concrete mix made with the traditional scrap-tires recycled material. Also, results show that even though the compressive strength is reduced when using steel cords, this reduction is minimal. When 2% of steel cords are used there is 18% increase in ductility. Moreover, splitting tensile tests show that concrete mixtures with any steel cords content have much greater toughness than control mixture. This mechanical property mix indicates an excellent potential application of modified concrete mix in structures that absorb large amount of energy.

Energy Intensity and Fitness Cost of Cotton aphid Exposure to Neonicotinoids

Three populations of Aphis gossypii of distinct susceptibility to neonicotinoids show differences in the accumulation and mobilization of energy reserves, what may allow the production of their defensive tools against two neonicotinoid insecticides without impairing their reproductive performance. Bioassays were also carried out for these aphid populations. According to the results obtained, the Ag-R population showed resistant rate significantly higher than the other two populations. Levels of some biochemical characteristics were determined in the resistant, susceptible and semi susceptible populations of cotton aphid. The results obtained in the assays with biochemical parameters indicated significant differences in activity among the populations, with higher activity in using glycogen in the Ag-R population. The inverse activity trends oft （generation time） and DT （doubling time） in both resistant and susceptible populations, one showing fitness disadvantage without insecticide exposure and the other not showing it, may underlay the mitigation of insecticide resistance physiological costs observed in the Ag-R population.

Variation Characteristics of Focal Mechanisms of Small Earthquakes before Four Strong Earthquakes in Xinjiang

With the point source dislocation model and the velocity structure of a layered medium,focal mechanisms of small earthquakes are calculated using the maximum amplitude of the direct P- and S-waves in the vertical component. By system clustering,and using the vector synthesis method,the average focal mechanism solution is obtained. Using the above method,this paper analyzes the variation characteristics of the source ruptures and the P-axis azimuths of small earthquakes around the seismic zones before four strong earthquakes occurring since 2003 in the western part of north Tianshan and the middle part of Tianshan. The result shows that 2 ~ 3 years before the strong earthquakes,the focal mechanism types of small earthquakes are distributed randomly, and obvious dominant distributions are observed one year before the strong earthquakes. There are obvious changes in the P-axis azimuth.