Stress response characteristics of BFRP anchors on loess mudstone slope under rainfall conditions

To investigate the stress response characteristics and shear stress transfer mechanism of BFRP(basalt fiber reinforced plastics)anchors under rainfall conditions and to explore the reinforcement effect of BFRP anchors,a comparative indoor physical model test was conducted in this study using loess mudstone slope as a typical case,and multi-attribute response data,such as slope displacement,BFRP anchor strain and axial force,were obtained.Based on the variation law of slope displacement,it can be concluded that the deformation displacement of the slope on the side reinforced by BFRP anchors is smaller than that of slopes reinforced with steel anchors;the bearing capacity of BFRP anchor is given priority in time,and the anchoring effect of BFRP anchor at the top of the slope is given priority,and the axial force value of anchor is characterized by a surface amplification effect in space;the axial force is higher around the anchor head and tends to decay as a negative exponential function as the anchor extends in the direction of the interior of the slope;the shear stress of BFRP anchor and anchorage body are unevenly distributed along the axial direction,with the maximum value occurring in the free section near the slope surface and decreases as the BFRP anchor extends towards the interior of the slope.These results can provide a theoretical basis for the optimal design of BFRP anchors.

Variations of suction and suction stress of unsaturated loess due to changes in lignin content and sample preparation method

Unsaturated loess in natural sites loses stability as the overburden load continuously increases.Traditional soil modifiers such as cement and fly ash affect the surrounding environment.A new type of material,i.e.,lignin,is environmentally friendly and able to increase the strength of loess.However,the engineering characteristics of the improved loess under unsaturated conditions are not yet clear.In this study,the soil-water characteristic curves(SWCCs)of lignin-improved loess samples were determined from 0 kPa to 700 kPa using a pressure plate instrument,and then,they were fitted using the van Genuchten(VG)model and the Fredlund and Xing(FX)model.In addition,the effects of the lignin content and sample preparation methods on the SWCCs were investigated to determine the optimal lignin content and a suitable sample preparation method for loess foundations.As the lignin content increases,the matric suction and residual water content of the improved loess increase.The suction stress increases with the increasing lignin contents of 1%–2%.At lignin contents of 3%–4%,the suction stress begins to decrease and the samples prepared using the slurry method has a lower suction stress than that prepared using the wet mixing method.The air entry value(AEV)increases with increasing lignin content.In addition,scanning electron microscopy(SEM)was used to investigate the microstructural variations.It was found that after the addition of lignin,the entrapment of the loess particles by the lignin fibers created some larger particles and smaller pore diameters,which in turn led to poor connectivity of the loess pores.These changes cause the matric suction of the modified loess to increase.

Non-uniform Stress Field and Stress Concentration Induced by Grain Boundary and Triple Junction of Tricrystal

The stress characteristics in the anisotropic bicrystal and tricrystal specimens were analyzed using the anisotropic elastic model, orthotropic Hill's model and rate-dependent crystallographic model. The finite element analysis results show that non-uniform stresses are induced by the grain boundary. For bicrystal specimens in different crystallographic orientations, there exist stress concentrations and high stress gradients nearby the boundaries. The activation and slipping of the slip systems are dependent on the crystallographic orientations of the grains and also on the relative crystallographic orientations of the two adjoining grains. For the tricrystal specimens, there is not always any stress concentrations in the triple junction, and the concentration degree depends on the relative crystallographic orientations of the three grains. Different from the bicrystal specimens, there may be or no stress concentration in the vicinity of grain boundaries for the tricrystal specimens, which depends on the relative crystallographic orientations of the three grains. The stress concentration near to the grain boundaries and triple junction can be high enough for the local plastic deformation, damage and voiding or cracking even when the whole specimen is still under the elastic state. It can be further concluded that homogeneous assumption for polycrystalline materials is not suitable to study the detailed meso- or micro-mechanisms for damaging and fracturing.

The Challenges of the Engineering Inspection of Pipelines and Heat Engines by Temperature Deformation and Stress

Pipelines and engines are studied under the thermal stress during operation. With the calculated ratios obtained, it is possible to settle practical issues in operation in order to increase the reliability and safety of equipment. To this end, it is first necessary to investigate the thermal mode of the pipeline, the engine for the planned period by the operations control centre. At the same time, the equipment with the average temperature at a certain time of the year exceeding the design value should be identified. In addition, the equipment concerning the nature of jamming should be studied at the sections specified in such a way. In case of identifying the jammed sections based on the above calculated ratios by thermal deformation and stressing the necessary value of movement of the sections, it should be determined that the actual voltage does not exceed the permissible level.

重金属短期胁迫下5种观赏植物积累特性与生理抗性研究

采用盆栽试验研究不同处理浓度下铅镉胁迫对斑叶龟背竹、多花白鹤芋、麒麟叶、金钻、银叶合果芋5种观赏植物的积累特性与生理抗性的影响。结果表明:在高浓度处理下,5种观赏植物地上部与根系的Pb积累量为:麒麟叶>斑叶龟背竹>金钻>多花白鹤芋>银叶合果芋;Cd积累量为:斑叶龟背竹>麒麟叶>金钻>多花白鹤芋>银叶合果芋。斑叶龟背竹、多花白鹤芋、麒麟叶叶片中可溶性蛋白的含量随着铅处理浓度的增加而增加,而金钻、银叶合果芋含量减少,除了多花白鹤芋之外,其他4种植物可溶性蛋白含量随着镉处理浓度的增加而减少;随着铅镉处理浓度的增加,斑叶龟背竹、多花白鹤芋、麒麟叶、金钻叶片游离脯氨酸含量呈现上升趋势,而银叶合果芋呈现先递增后下降的趋势;在铅镉胁迫条件下,5种观赏植物叶片丙二醛含量和相对电导率均不同程度增加。5种观赏植物抗重金属铅能力为斑叶龟背竹>金钻>多花白鹤芋>麒麟叶>银叶合果芋;抗重金属镉能力为金钻>斑叶龟背竹>多花白鹤芋>麒麟叶>银叶合果芋。

Seismic bearing capacity of strip footings on rock masses using the Hoeke Brown failure criterion

In this paper,the bearing capacity of strip footings on rock masses has been studied in the seismic case.The stress characteristics or slip line method was used for analysis.The problem was analyzed in the plane strain condition using the Hoeke Brown failure criterion.First,the equilibrium equations along the stress characteristics were obtained and the rock failure criterion was applied.Then,the equations were solved using the finite difference method.A computer code has been provided for analysis.Given the footing and rock parameters,the code can calculate the stress characteristics network and obtain the stress distribution under the footing.The seismic effects have been applied as the horizontal and vertical pseudo-static coefficients.The results of this paper are very close to those of the other studies.The seismic bearing capacity of weightless rock masses can be obtained using the proposed equations and graphs without calculating the whole stress characteristics network.

茉莉酸甲酯处理的油用牡丹干旱下的光合及生理特性

以油用牡丹‘凤丹’为材料,整株喷施4种浓度(50、100、200、400μmol/L)的茉莉酸甲酯(MeJA),以喷施清水处理为对照(CK),连续喷施3 d后进行干旱处理再复水,在‘凤丹’到达中度、重度干旱2 d及复水2 d后取样,测定‘凤丹’叶片的渗透调节物质含量、丙二醛(MDA)含量、光合色素含量,同时对光合指标进行测定。结果表明:200μmol/L MeJA处理后,中度干旱的‘凤丹’幼苗的脯氨酸含量最高,较CK显著提高250.34%,净光合速率、气孔导度和蒸腾速率最大,较CK分别提高25.73%、68.0%、43.04%;‘凤丹’的叶绿素a、叶绿素b和类胡萝卜素含量在400μmol/L MeJA处理下达到最高,较CK分别提高了33.33%、26.09%、34.48%;喷施200μmol/L MeJA后,重度干旱的‘凤丹’幼苗可溶性糖含量达到最大值,净光合速率最大,较CK提高了41.73%;蒸腾速率和胞间CO;浓度在400μmol/L Me JA处理下最高,分别较CK提高了74.07%和13.44%;复水后,适宜浓度的MeJA处理使光合生理指标均得到不同程度的恢复。表明外源MeJA处理能增强‘凤丹’幼苗对干旱的抵抗能力,提高‘凤丹’幼苗的光合速率、光合色素和渗透调节物质含量,降低干旱对细胞膜的损伤,以200μmol/L MeJA处理效果最佳。

Research review on steel–concrete composite joint of railway hybrid girder cable-stayed bridges

Purpose–This study aims to research the development trend,research status,research results and existing problems of the steel–concrete composite joint of railway long-span hybrid girder cable-stayed bridge.Design/methodology/approach–Based on the investigation and analysis of the development history,structure form,structural parameters,stress characteristics,shear connector stress state,force transmission mechanism,and fatigue performance,aiming at the steel–concrete composite joint of railway long-span hybrid girder cable-stayed bridge,the development trend,research status,research results and existing problems are expounded.Findings–The shear-compression composite joint has become the main form in practice,featuring shortened length and simplified structure.The length of composite joints between 1.5 and 3.0 m has no significant effect on the stress and force transmission laws of the main girder.The reasonable thickness of the bearing plate is 40–70 mm.The calculation theory and simplified calculation formula of the overall bearing capacity,the nonuniformity and distribution laws of the shear connector,the force transferring ratio of steel and concrete components,the fatigue failure mechanism and structural parameters effects are the focus of the research study.Originality/value–This study puts forward some suggestions and prospects for the structural design and theoretical research of the steel–concrete composite joint of railway long-span hybrid girder cable-stayed bridge.

Hybridization between salt resistant and salt susceptible genotypes of mungbean(Vigna radiata L.Wilczek)and purity testing of the hybrids using SSRs markers

Six cultivated and two wild genotypes of mungbean（Vigna radiata L. Wilczek） possessing variation for phenotypic and genotypic response for salt tolerance were hybridized. Hybridization results showed successful pod set and significant variations in cross-compatibility of investigated genotypes. Genotypes PLM 380 and PLM 562 showed promising combining ability with all genotypes. Results revealed significant crossing compatibility between V. radiata and V. sublobata. The cross ability ranged from 1.99 to 5.12%（average 3.08%）. Molecular analysis confirmed the hybrids purity. All F_1 seeds were bold, green/shiny green and germinated between 3 to 5 days. Hybrid plants were normal, fertile and healthier over their respective progenitors. Uniform flowering and maturity of the hybrids showed absence of any defect or alteration in plant habit and life cycle of the hybrids. The hybrid plants showed increase in yield characteristics as no. of pods, pod length, 100 seeds weight, and yield per plant. Number of pods containing F_2 seeds ranged from 5–8 per cluster. The F_2 seeds were collected and stored for further research. Present study suggests that salt resistant wild relatives or cultivars of mungbean can be explored by breeding as a source of useful traits/genes providing salt tolerance. This may help in development of best mungbean variety for saline prone areas. Micro-satellite markers linked to the trait/genes may assist breeding by early selection of the genotypes compared to the phenotypic screening.

Dynamic Stresses in a Francis Turbine Runner Based on Fluid-Structure Interaction Analysis

Fatigue and cracks have occurred in many large hydraulic turbines after they were put into production. The cracks are thought to be due to dynamic stresses in the runner caused by hydraulic forces. Computational fluid dynamics （CFD） simulations that included the spiral case, stay vane, guide vane, runner vane, and draft tube were run at various operating points to analyze the pressure distribution on the runner surface and the stress characteristics in the runner due to the fluid-structure interactions （FSI）. The dynamic stresses in the Francis turbine runner at the most dangerous operating point were then analyzed. The results show that the dynamic stresses caused by the hydraulic forces during off-design operating points are one of the main reasons for the fatigue and cracks in the runner blade. The results can be used to optimize the runner and to analyze other critical components in the hydraulic turbine.