Effect of NaCl Concentration on the Cumulative Strain and Pore Distribution of Clay under Cyclic Loading

Clay,as the most common soil used for foundationfill,is widely used in various infrastructure projects.The phy-sical and mechanical properties of clay are influenced by the pore solution environment.This study uses a GDS static/dynamic triaxial apparatus and nuclear magnetic resonance experiments to investigate the effects of cyclic loading on clay foundations.Moreover,the development of cumulative strain in clay is analyzed,and afitting model for cumulative plastic strain is introduced by considering factors such as NaCl solution concentration,con-solidation stress ratio,and cycle number.In particular,the effects of the NaCl solution concentration and con-solidation stress ratio on the pore distribution of the test samples before and after cyclic loading are examined,and the relationship between microscopic pore size and macroscopic cumulative strain is obtained accordingly.Our results show that as the consolidation stress ratio grows,an increasing number of large pores in the soil samples are transformed into small pores.As the NaCl solution concentration becomes higher,the number of small pores gradually decreases,while the number of large pores remains unchanged.Cyclic loading causes the disappearance of the large pores in the samples,and the average pore size before cyclic loading is posi-tively correlated with the axial cumulative strain after cyclic loading.The cumulative strain produced by the soil under cyclic loading is inversely proportional to the NaCl solution concentration and consolidation stress ratio.

A switchable high-sensitivity strain sensor based on piezotronic resonant tunneling junctions

Developing emerging technologies in Internet of Things and artificial intelligence requires high-speed, low-power, high-sensitivity, and switchable-functionality strain sensors capable of sensing subtle mechanical stimuli in complex ambience. Resonant tunneling diodes (RTDs) are the good candidate for such sensing applications due to the ultrafast transport process, lower tunneling current, and negative differential resistance. However, notably enhancing sensing sensitivity remains one of the greatest challenges for RTD-related strain sensors. Here, we use piezotronic effect to improve sensing performance of strain sensors in double-barrier ZnO nanowire RTDs. This strain sensor not only possesses an ultrahigh gauge factor (GF) 390 GPa^(−1), two orders of magnitude higher than these reported RTD-based strain sensors, but also can switch the sensitivity with a GF ratio of 160 by adjusting bias voltage in a small range of 0.2 V. By employing Landauer–Büttiker quantum transport theory, we uncover two primary factors governing piezotronic modulation of resonant tunneling transport, i.e., the strain-mediated polarization field for manipulation of quantized subband levels, and the interfacial polarization charges for adjustment of space charge region. These two mechanisms enable strain to induce the negative differential resistance, amplify the peak-valley current ratio, and diminish the resonant bias voltage. These performances can be engineered by the regulation of bias voltage, temperature, and device architectures. Moreover, a strain sensor capable of electrically switching sensing performance within sensitive and insensitive regimes is proposed. This study not only offers a deep insight into piezotronic modulation of resonant tunneling physics, but also advances the RTD towards highly sensitive and multifunctional sensor applications.

Effect of Strain Ratio on Fatigue Model of Ultra-fine Grained Pure Titanium

The ultra-fine grained(UFG)pure titanium was prepared by equal channel angular pressing(ECAP)and rotary swaging(RS).The strain controlled low cycle fatigue(LCF)test was carried out at room temperature.The fatigue life prediction model and mean stress relaxation model under asymmetrical stress load were discussed.The results show that the strain ratio has a significant effect on the low cycle fatigue performance of the UFG pure titanium,and the traditional Manson-coffin model can not accurately predict the fatigue life under asymmetric stress load.Therefore,the SWT mean stress correction model and three-parameter power curve model are proposed,and the test results are verified.The final research shows that the threeparameter power surface model has better representation.By studying the mean stress relaxation phenomenon under the condition of R≠-1,it is revealed that the stress ratio and the strain amplitude are the factors that significantly afiect the mean stress relaxation rate,and the mean stress relaxation model with the two variables is calculated to describe the mean stress relaxation phenomenon of the UFG pure titanium under different strain ratios.The fracture morphology of the samples was observed by SEM,and it was concluded that the final fracture zone of the fatigue fracture of the UFG pure titanium was a mixture of ductile fracture and quasi cleavage fracture.The toughness of the material increases with the increase of strain ratio at the same strain amplitude.

Influences of Nitrogen-phosphorus Ratio on the Growth and Competition of Chlorella vulga and Anabaena sp. strain PCC

This paper studied the effects of different ratios of nitrogen and phospho- rus on the growth and competition of Anabaena sp. strain PCC and chloralla vul- gads （low nitrogen-phosphorus ratio group： N/P=16：1; Medium low nitrogen-phospho- rus ratio group： N/P=32：1; Medium high nitrogen-phosphorus ratio group： N/P=64：1; High nitrogen-phosphorus ratio group： N/P=320：1）. Results suggested that the largest amount of anabaena sp.strain PCC survived in medium high nitrogen-phosphorus ratio group. The nitrogen-phosphorus ratio showed no significant influences on the growth of Chlorella vulgaris, but it exerted dramatic influences on the growth of Chlore/la vulgaris of the mixed cultivation system. The largest amount of Ch/orel/a vulgaris can be found in the medium-high nitrogen-phosphorus ratio group. The inhi- bition parameter of nitrogen-phosphorus on the algae was distinctive. Anabaena sp. strain PCC had advantages in the competition with the low nitrogen-phosphorus ra- tio and medium-low nitrogen-phosphorus ratio. Potential instability existed between anabaena sp.strain PCC and Chlorella vulgaris when the nitrogen to phosphorus ratio was medium-high and high.

Specimen aspect ratio and progressive field strain development of sandstone under uniaxial compression by three-dimensional digital image correlation

The complete stress-strain characteristics of sandstone specimens were investigated in a series of quasistatic monotonic uniaxial compression tests.Strain patterns development during pre-and post-peak behaviours in specimens with different aspect ratios was also examined.Peak stress,post-peak portion of stress-strain,brittleness,characteristics of progressive localisation and field strain patterns development were affected at different extents by specimen aspect ratio.Strain patterns of the rocks were obtained by applying three-dimensional(3D) digital image correlation(DIC) technique.Unlike conventional strain measurement using strain gauges attached to specimen,3D DIC allowed not only measuring large strains,but more importantly,mapping the development of field strain throughout the compression test,i.e.in pre-and post-peak regimes.Field strain development in the surface of rock specimen suggests that strain starts localising progressively and develops at a lower rate in pre-peak regime.However,in post-peak regime,strains increase at different rates as local deformations take place at different extents in the vicinity and outside the localised zone.The extent of localised strains together with the rate of strain localisation is associated with the increase in rate of strength degradation.Strain localisation and local inelastic unloading outside the localised zone both feature post-peak regime.

Real time endoscopic ultrasound elastography and strain ratio in the diagnosis of solid pancreatic lesions

AIM To evaluate the accuracy of the elastography score combined to the strain ratio in the diagnosis of solid pancreatic lesions(SPL). METHODS A total of 172 patients with SPL identified by endoscopic ultrasound were enrolled in the study to evaluate the efficacy of elastography and strain ratio in differentiating malignant from benign lesions. The semi quantitative score of elastography was represented by the strain ratio method. Two areas were selected, area(A) representing the region of interest and area(B) representing the normal area. Area(B) was then divided by area(A). Sensitivity, specificity, positive predictive value(PPV), negative predictive value(NPV), and accuracy were calculated by comparing diagnoses made by elastography, strain ratio and final diagnoses.RESULTS SPL were shown to be benign in 49 patients and malignant in 123 patients. Elastography alone had a sensitivity of 99%, a specificity of 63%, and an accuracy of 88%, a PPV of 87% and an NPV of 96%. The best cut-off level of strain ratio to obtain the maximal area under the curve was 7.8 with a sensitivity of 92%, specificity of 77%, PPV of 91%, NPV of 80% and an accuracy of 88%. Another estimated cut off strain ratio level of 3.8 had a higher sensitivity of 99% and NPV of 96%, but with less specificity, PPV and accuracy 53%, 84% and 86%, respectively. Adding both elastography to strain ratio resulted in a sensitivity of 98%, specificity of 77%, PPV of 91%, NPV of 95% and accuracy of 92% for the diagnosis of SPL. CONCLUSION Combining elastography to strain ratio increases the accuracy of the differentiation of benign from malignant SPL.

Effects of Strain Ratio on Fatigue Behavior of G20Mn5QT Cast Steel

Due to traffic and wave actions, cast steel joints are subjected to variable-amplitude fatigue loading, which may cause fatigue problems. The ratio of the minimum strain to the maximum strain(strain ratio)can be employed to analyze the influence of variable-amplitude fatigue both in the elastic and plastic ranges. To evaluate the effect of the strain ratio on G20Mn5 QT cast steel, the fatigue tests of smooth specimens were carried out at the strain ratio of 0.1. The cyclic deformation and the relationships between the strain amplitude, the stress amplitude, the Smith, Watson and Topper(SWT)parameter and fatigue life were studied and compared with those at the strain ratio of-1. Compared with other methods, Basquin formula and Solonberg formula provide reliable and appropriate ranges of S-N curve and fatigue limit at different strain ratios respectively. The SWT parameter can be used to predict the fatigue life at other strain ratios accurately.

Rockburst proneness considering energy characteristics and sample shape effects

Accurate prediction of rockburst proneness is one of challenges for assessing the rockburst risk and selecting effective control measures.This study aims to assess rockburst proneness by considering the energy characteristics and qualitative information during rock failure.Several representative rock types in cylindrical and cuboidal sample shapes were tested under uniaxial compression conditions and the failure progress was detected by a high-speed camera.The far-field ejection mass ratio(FEMR)was determined considering the qualitative failure information of the rock samples.The peak-strength energy impact index and the residual elastic energy index were used to quantitatively evaluate the rockburst proneness of both cylindrical and cuboidal samples.Further,the performance of these two indices was analyzed by comparing their estimates with the FEMR.The results show that the accuracy of the residual elastic energy index is significantly higher than that of the peak-strength energy impact index.The residual elastic energy index and the FEMR are in good agreement for both cylindrical and cuboidal rock materials.This is because these two indices can essentially reflect the common energy release mechanism characterized by the mass,ejection velocity,and ejection distance of rock fragments.It suggests that both the FEMR and the residual elastic energy index can be used to accurately measure the rockburst proneness of cylindrical and cuboidal samples based on uniaxial compression test.

IMPROVEMENT ON THE CALCULATION OF PLASTIC STRAIN RATIO IN BCC MONOCRYSTALS

Two improvements have been made on the calculation of plastic strain ratio (r value) in BCC monocrystals by considering the differences in the critical shear stresses among the three slip systems and the rotation of crystal lattice. It is found that the results calculated by the improved method are more rational.

STRAIN-DEPENDENCE OF PLASTIC STRAIN RATIO OF DEEP-DRAWING ALUMINIUM-KILLED STEEL SHEET

The change of width and length of an aluminium-killed(AK)steel sheet was measured in detail at various tensile strain levels.The effects of tensile strain on the conventional strain ratio,rc-value,and the instantaneous strain ratio,r^(1)-value,were analyzed.It was shown that the strain ratio of the AK steel sheet had obvious strain-dependency.The individual r^(c)-values for all tested directions tended to unity with increasing strain so that the planar anisotropy decreased with increasing strain.The r^(1)-value had overall straidenpendency similar to that of r^(c)-value,though it was overly sensitive to the experimental errors and showed significant variation with strain.In the representation of average strain ratio.the linear regression strain ratio,r^(r)-value,which was obtained by fitting a straight line to the εw vs εt curve,is preferable to the r^(c)-value measured at some specfic extension.

Research on the Distribution Features of the Benioff Strain Ratio in the North-South Seismic Belt after the Two Yutian M_S7.3 Earthquakes

In view of the correlation between tectonic activity and seismicity,the strong earthquake risk in the North-South Seismic Belt aroused wide concern after the 2014 Yutian M_S7.3 earthquake. Using the seismic catalog of the China Earthquake Networks Center,the Benioff strain ratio in the North-South Seismic Belt is calculated in 30 days before and after the March 21,2008 and February 12,2014 Yutian M_S7.3 earthquakes. Results show that in a year after the 2008 Yutian M_S7.3 earthquake,M > 5. 0 earthquakes all occurred near the high strain ratio area or the junction between the low and high strain ratio areas,the activity of strong earthquakes obviously coincides with the high strain ratio area,which indicates that these areas have a higher stress level. The Yutian earthquakes promoted the release of small earthquakes in the high stress areas. This research is of certain indicating significance to the study of subsequent strong earthquakes of this region.

Physical meaning and prediction efficiency of the load/unload response ratio of rocks in strain-weakening phase before failure

Rock experiment results indicate that the load/unload response ratio (LURR) of rocks expressed via strain energy may have singular or negative value after the stress in the rock reaches its maximum before rock failure or when the rock goes into the strain-weakening phase. The universality of this phenomenon is discussed. Expressed via strain or strain energy and the travel time of P wave, the variation form of the reciprocal of LURR during the process of rock failure preparation is derived. The results show that after a sharp decrease the reciprocal of LURR reaches its minimum when the main fracture of the rock is about to appear. This feature can be taken as an indication that the rock main fracture is impending.

The correlation between the ultrasonic elastic strain ratio of thyroid cancer and the malignant biological characteristics of cancer cells in the lesions

Objective:To study the correlation between the ultrasonic elastic strain ratio of thyroid cancer and the malignant biological characteristics of cancer cells in the lesions.Methods:A total of 90 patients with thyroid cancer who accepted surgical treatment in our hospital between March 2015 and September 2016 were selected as the observation group, and 50 patients who received surgery in our hospital during the same period and were with clear pathological diagnosis of thyroid adenoma were selected as the control group. According to the median of ultrasonic elastic strain ratio, the observing group were further divided into high elastic strain ratio group and low elastic strain ratio group (n=45). RT-PCR was used to determine the mRNA expression of proliferation genes, invasion genes and autophagy genes in lesions of all groups of patients.Results: The mean elastic strain ratio of observation group was significantly lower than that of control group. Proliferation gene FOXA1 mRNA expression in lesions of low elastic strain ratio group and high elastic strain ratio group were higher than those of control group while PP4R1 and Smac mRNA expression were lower than those of control group, and as the elastic strain ratio decreased, the FOXA1 mRNA expression increased while PP4R1 and Smac mRNA expression decreased;invasion genes BCORL1, SATB1, Twist1 and CXCR4 mRNA expression in lesions of low elastic strain ratio group and high elastic strain ratio group were higher than those of control group, and as the elastic strain ratio decreased, the BCORL1, SATB1, Twist1 and CXCR4 mRNA expression increased;autophagy genes ARHI, Beclin1, LC3 and PTEN mRNA expression in lesions of low elastic strain ratio group and high elastic strain ratio group were lower than those of control group, and as the elastic strain ratio decreased, the ARHI, Beclin1, LC3 and PTEN mRNA expression decreased.Conclusion:The ultrasonic elastic strain ratio of thyroid cancer is negatively correlated with tumor cell proliferation and invasion activity, and positively correlated with autophagy activity.

EFFECT OF THE POISSON RATIO ON THE PERFECTLY PLASTIC STRESS FIELD AT A STATIONARY PLANE-STRAIN CRACK TIP

Under the condition that all the perfectly plastic stress components at a crack tip are the functions of ? only, making use of equilibrium equations and Von-Mises yield condition containing Poisson ratio, in this paper, we derive the generally analytical expressions of perfectly plastic stress field at a stationary plane-strain crack tip. Applying these generally analytical expressions to the concrete cracks, the analytical expressions of perfectly plastic stress fields at the stationary tips of Mode I, Mode II and Mixed-Mode I-II plane-strain cracks are obtained. These analytical expressions contain Poisson ratio.

不同下壁导联室性早搏R/S波比值的慢性心力衰竭患者近期预后随访分析

目的对不同下壁导联室性早搏R/S波比值的慢性心力衰竭患者近期预后随访进行分析。方法选择2020年3月~2022年3月本院收治的93例动态心电图检查存在室性早搏的CHF患者93例。所有患者完善24h动态心电图检查,随访一年。依照近期预后进行分组,将出现急性心肌梗死、恶性心律失常等不良心脏事件纳入预后不良组(n=37),其余未出现心脏不良事件的患者纳入预后良好组(n=56)。比较两组不同下壁导联室性早搏R/S波比值的预后。结果两组在年龄、BMI、吸烟、高血压、糖尿病、LVEF、利尿剂、地高辛方面差异无统计学意义(P>0.05);两组在性别、NYHA分级上差异有统计学意义(P<0.05);预后良好组R/S比值≥1例数比率高于预后不良组,R/S比值<1例数比例低于预后不良组,差异有统计学意义(P<0.05)。Logistic回归分析显示,R/S比值<1与性别、NYHA分级均是CHF患者近期预后不良的独立危险因素(P<0.05)。结论不同下壁导联的室性早搏R/S比值与其预后具有相关性,R/S比值<1是其不良预后的预测因素。

Effects of rolling parameters of snake hot rolling on strain distribution of aluminum alloy 7075

The realization way of snake rolling was introduced. Flow velocity, strain and stress distribution of 7075 aluminum alloy plate during snake rolling and symmetrical rolling were analyzed in Deform 3D. Effects of velocity ratio, offset distance between two rolls and pass reduction on the distribution of equivalent strain and shear strain were analyzed. The results show that flow velocity and equivalent strain on the lower layer of the plate are larger than those of the upper layer because of the larger velocity of the lower roll and the gap is increased with the increase of velocity ratio and pass reduction. The shear strain of roiling direction in the center point is almost zero during symmetrical rolling, while it is much larger during snake rolling because of the existence of rub zone. The shear strain is increased with the increase of velocity ratio, offset distance and pass reduction. This additional shear strain is beneficial to improve the in_homogeneous strain distribution.

Isolation of High-virulence Strains and Antagonistic Bacteria of the Pathogen of Ginger Blast (Ralstonia solanacearum)

[ Objective] The paper was to screen Bacillus with strong antagonistic effect. [ Method] The diseased ginger and the surrounding soils were collected from Laiwu of Shandong Province, and the high-virulence strains of the pathogen of ginger blast （Ralstonia solanacearum） were isolated, Bacillus was used to carry out antagonistic test. [Result] Three strains LW-4, LW-7 and LW-32 had strong antagonistic effect against R. solanacearum, the area of their inhibition zone was larger than other strains. [ Conclusion] The study provided theoretical basis for the control of ginger blast.

BFRP筋混凝土深梁动态剪切破坏尺寸效应模拟

为研究玄武岩纤维增强聚合物(BFRP)筋混凝土深梁动态剪切破坏机制及其尺寸效应规律,考虑混凝土非均质性、混凝土/BFRP筋相互作用以及混凝土和BFRP筋在材料层面的应变率效应,建立了BFRP筋混凝土深梁细观尺度三维数值模型。利用已有的试验数据验证了该数值模拟方法的合理性和准确性,采用该方法研究了不同尺寸但几何相似的BFRP筋混凝土深梁在不同应变率下的剪切破坏模式及失效机制。分析了截面尺寸、配箍率、应变率对BFRP筋混凝土深梁剪切破坏及相应尺寸效应规律的影响。结果表明:动载下梁的破坏模式与静载时存在较大差异,但均表现出尺寸效应;增大应变率及配箍率均能有效提高梁承载力且削弱剪切尺寸效应,但应变率的作用程度明显大于配箍率。

BFRP-FRCM复合层弯曲性能试验研究

以玄武岩织物网格-纤维水泥基复合材料(BFRP-FRCM)为研究对象,通过四点弯曲试验探究水胶比、纤维种类、玄武岩网格层数对BFRP-FRCM复合层弯曲力学性能的影响规律。研究结果表明:外掺BFRP网格试件呈多裂缝的破坏模式,荷载-位移曲线呈应变硬化趋势,试件延性明显提高,弯曲韧性指标满足I30>30;掺入聚乙烯醇(PVA)纤维的BFRP-FRCM试件弯曲力学性能均优于掺入聚丙烯(PP)纤维试件;水胶比为0.30与0.35时,BFRP网格对试件抗弯强度的提升效果明显,存在BFRP网格最优配网率。

债务期限结构错配抑制了高科技企业R&D投入吗?——基于认证高新技术企业的经验证据

选取认证高新技术企业为样本,将债务水平与债务-资产期限结构配置纳入统一分析框架,并充分考虑两者的内生关系,考察债务期限结构错配对高科技企业R&D投入强度的影响。结果表明:债务杠杆对高科技企业后期R&D投入强度存在显著的负面影响,但影响呈减弱趋势;“短债长用”类错配对高科技企业R&D投入强度存在一定程度的正面促进作用,而“长债短用”类错配则抑制了R&D投入;债务杠杆与债务期限结构配置之间存在影响R&D投入的正面交互效应,交互效应的存在强化了债务杠杆的负面影响和债务期限错配的积极作用,采用“低杠杆”加“短债长用”错配组合,更有利于促进高科技企业R&D投入。