3D digital-image correlation insight into generalized relaxation behavior of sandstone under stress and pore pressure coupling

The occurrence of geological hazards and the instability of geotechnical engineering structures are closely related to the time-dependent behavior of rock.However,the idealization boundary condition for constant stress in creep or constant strain in relaxation is not usually attained in natural geological systems.Therefore,generalized relaxation tests that explore the simultaneous changes of stress and strain with time under different stress levels with constant pore-water pressure are conducted in this study.The results show that in area Ⅰ,area Ⅱ,and area Ⅲ,the stress and strain both change synchronously with time and show similar evolutionary laws as the strain-time curve for creep or the stress-time curve for relaxation.When the applied stress level surpasses the δ_(ci) or δ_(cd) threshold,the variations in stress and strain and their respective rates of change exhibit a significant increase.The radial deformation and its rate of change exhibit greater sensitivity in response to stress levels.The apparent strain deforms homogeneously at the primary stage,and subsequently,gradually localizes due to the microcrack development at the secondary stage.Ultimately,interconnection of the microcracks causes the formation of a shear-localization zone at the tertiary stage.The strain-time responses inside and outside the localization zone are characterized by local strain accumulation and inelastic unloading during the secondary and tertiary stages,respectively.The width of the shear-localization zone is found to range from 4.43 mm to 7.08 mm and increased with a longer time-to-failure.Scanning electron microscopy(SEM)reveals a dominant coalescence of intergranular cracks on the fracture surface,and the degree of physiochemical deterioration caused by water-rock interaction is more severe under a longer lifetime.The brittle sandstone’s time-dependent deformation is essentially controlled by microcrack development during generalized relaxation,and its expectancy-life is determined by its initial microstructural state and the rheological path.

Change in self-image pressure level before and after autologous fat breast augmentation and its effect on social adaptability

BACKGROUND There is an increasingly strong demand for appearance and physical beauty in social life,marriage,and other aspects with the development of society and the improvement of material living standards.An increasing number of people have improved their appearance and physical shape through aesthetic plastic surgery.The female breast plays a significant role in physical beauty,and droopy or atrophied breasts can frequently lead to psychological inferiority and lack of confidence in women.This,in turn,can affect their mental health and quality of life.AIM To analyze preoperative and postoperative self-image pressure-level changes of autologous fat breast augmentation patients and their impact on social adaptability.METHODS We selected 160 patients who underwent autologous fat breast augmentation at the First Affiliated Hospital of Xinxiang Medical University from January 2020 to December 2022 using random sampling method.The general information,selfimage pressure level,and social adaptability of the patients were investigated using a basic information survey,body image self-assessment scale,and social adaptability scale.The self-image pressure-level changes and their effects on the social adaptability of patients before and after autologous fat breast augmentation were analyzed.RESULTS We collected 142 valid questionnaires.The single-factor analysis results showed no statistically significant difference in the self-image pressure level and social adaptability score of patients with different ages,marital status,and monthly income.However,there were significant differences in social adaptability among patients with different education levels and employment statuses.The correlation analysis results revealed a significant correlation between the self-image pressure level and social adaptability score before and after surgery.Multiple factors analysis results showed that the degree of concern caused by appearance in selfimage pressure,the degree of possible behavioral intervention,the related distress caused by body image,and the influence of body image on social life influenced the social adaptability of autologous fat breast augmentation patients.CONCLUSION The self-image pressure on autologous fat breast augmentation patients is inversely proportional to their social adaptability.

Study on the Soil Moisture Stress Level in Regulated Deficit Irrigation Experiment

On the basis of discussing the influencing mode of plant moisture stress on plant physiological process and the division of soil moisture availability range, the water suction values partitioning soil moisture were put forward, and then the corresponding water moistures under water stress were obtained by conversing together with characteristic curve of water moisture.

Effect of stress level on fatigue behavior of 2D C/C composites

Laminated carbon fiber clothes were infiltrated to prepare carbon fiber reinforced pyrolytic carbon （C/C） using isothermal chemical vapor infiltration （CVI）. The bending fatigue behavior of the infiltrated C/C composites was tested under two different stress levels. The residual strength and modulus of all fatigued samples were tested to investigate the effect of maximum stress level on fatigue behavior of C/C composites. The microstructure and damage mechanism were also investigated. The results showed that the residual strength and modulus of fatigued samples were improved. High stress level is more effective to increase the modulus. And for the increase of flexural strength, high stress level is more effective only in low cycles. The fatigue loading weakens the bonding between the matrix and fiber, and then affects the damage propagation pathway, and increases the energy consumption. So the properties of C/C composites are improved.

Characteristics of microseismic b-value associated with rock mass large deformation in underground powerhouse caverns at different stress levels

Rock mass large deformation in underground powerhouse caverns has been a severe hazard in hydropower engineering in Southwest China.During the development of rock mass large deformation,a sequence of fractures was generated that can be monitored using microseismic(MS)monitoring techniques.Two MS monitoring systems were established in two typical underground powerhouse caverns featuring distinct geostress levels.The MS b-values associated with rock mass large deformation and their temporal variation are analysed.The results showed that the MS bvalue in course of rock mass deformation was less than 1.0 in the underground powerhouse caverns at a high stress level while larger than 1.5 at a low stress level.Prior to the rock mass deformation,the MS b-values derived from both the high-stress and low-stress underground powerhouse caverns show an incremental decrease over 10%within 10 d.The results contribute to understanding the fracturing characteristics of MS sources associated with rock mass large deformation and provide a reference for early warning of rock mass large deformation in underground powerhouse caverns.

Preliminary analysis on the tectonic stress level in the source region of Tangshan earthquake

The abundant data of focal mechanism solutions in Tangshan region, China, are inverted for the tectonic stress field. Combined with tectonophysical consideration, the magnitude of the three principal stresses, as well as their vertical variation under the average crustal rock property, in the source region of the 1976 Tangshan earthquake is estimated. The relationship between crustal stress and friction mc, pore pressure P0 and stress shape factor F is studied. The paper draws the conclusion that the vertical increasing rate of the maximum principal stress s is directly proportional to friction, and inversely to pore pressure P0 and stress shape factor F ; while the vertical increasing rate of the minimum principal tress s is directly proportional to pore pressure P0, inversely to friction mc and stress shape factor F. This study is a try to invert the data of focal mechanism solutions for the complete stress tensor.

Study on determination of stress level by seismic stress drops and the stress axis de-flections before and after large earthquakes

To obtain the stress level at the earthquake source, this paper sets forth the solution of the stress magnitude at the earthquake source by seismic stress drop and the stress axis deflections before and after large earthquakes. The pre-seismic and post-seismic stress direction can be statistically determined by a large collection of foreshock and aftershock focal mechanism data while the stress drop can be determined through the source fracture inversion from seismic wave data or crust deformation data. The paper attempts to make a fundamental contribution to seismic dynamics.

Estimation of the stress levels in the focal region before and after the 2001 M=8.1 Western Kunlun Mountain Pass earth-quake

A method estimating the stress level in the focal region of an earthquake is proposed here. Taking the 2001 M=8.1 Western Kunlun Mountain Pass earthquake as an example, we estimate its stress level in the focal region before and after it by this method. The results show that the stress level in the focal region just prior to the initiation of this event is approximately 6.3-8 MPa, and about 5-6.7 MPa remained in the focal region after its occurrence. The stress in the focal region decreased by roughly twenty percent after this event.

In situ stress measurement and analysis of the stress accumulation levels in coal mines in the northern Ordos Basin,China

For non-directional drilling cores,selection of samples and the test methods for in situ stress measurements to evaluate the Kaiser effect(KE)were proposed,and the magnitude and direction of the principal stresses were derived from first principles.Based on this approach,the KE for 423 samples in the Burtai and Baode coal mines in the northern Ordos Basin(NOB),China,have been investigated.The results show that the maximum horizontal principal stress(σ_(H)),the minimum horizontal principal stress(σ_(h))and the vertical stress(σ_(v))varied with depth and location,and the values increase with increasing depth.Generally,the horizontal stresses play a leading role.For the main stress regimes in the NOB,σ_(H)>σ_(h)>σ_(v)(Burtai Mine,<172 m;Baode Mine,<170 m)andσ_(H)>σ_(v)>σ_(h)(Burtai Mine,170-800 m;Baode Mine,170-400 m),and theσ_(v)>σ_(H)>σ_(h)stress regimes are mainly distributed in moderately deep to deep coal mines.For rock masses with a depth of 350 m,k((σ_(H)+σ_(h))/2σ_(v))tends to 1,indicating that a deep critical state will gradually emerge.The test results are compared with those for the overcoring(OC)method,the anelastic strain recovery(ASR)method and micro-hydraulic fracturing(HF).The relative errors forσ_(H),σ_(h)andσ_(v)were 14.90%,19.67%,15.47%(Burtai Mine)and 10.74%,22.76%,19.97%(Baode Mine),respectively,and the errors are all within an acceptable range,thus verifying the reliability of the KE method.The dominant orientation for theσ_(H)(Burtai mine,NE-NNE;Baode Mine,NEE)is obtained via paleomagnetic technology,and the data are consistent with those(NE-NEE)of the earthquake focal mechanism solutions for the area.Based on the Byerlee-Anderson theory,a discussion is given on the levels of stress accumulation in the rock mass of the mines.For dry rocks or hydrostatic pressure rocks,the friction coefficients of the faults are low for both locations,and the values are less than the lower limit(0.6)of the strike-slip faults slip,indicating that the stress fractures at a low level around the study areas are lower than the friction limit stress.The stress accumulation levels in the Baode Mine are slightly larger than those in the Burtai Mine.

Endogenous Levels of Polyamines under Water-Deficit Stress during Cotton’s Reproductive Development

Polyamines, putrescine (PUT), spermidine (SPD) and spermine (SPM) are implicated in plants’ responses under conditions of abiotic stress. Previous research in other crops has indicated that polyamines and changes in their concentrations are associated with drought tolerance under conditions of water-deficit stress;however, no information exists on cotton (Gossypium hirsutum L.). Growth chamber experiments were conducted with two cotton cultivars differing in drought tolerance, ST5288B2F (drought-sensitive) and Siokra L23 (drought-tolerant) in order to investigate the distribution of free polyamines, the effect of water-deficit stress on the polyamine metabolism of cotton reproductive units and their subtending leaves as well as the possible relationship between polyamines and drought tolerance in cotton. Our results showed that cotton ovaries contained significantly higher levels of total free polyamines compared to their subtending leaves under both control and water stress conditions. Water-deficit stress significantly increased PUT concentrations in ST5288B2F, while SPM levels significantly decreased in Siokra L23. The results indicated that water-deficit stress significantly affected cotton polyamine metabolism in reproductive structures and their subtending leaves;however, no clear relationship between drought-tolerance and changes in polyamine accumulation was established. Further research is needed to elucidate the mechanism according to which water-deficit stress affects polyamine metabolism.

Region Division and Stress Analysis for Plate Roller Leveling Process

The flatness of leveled plate is settled by residual stress. According to stress distribution simulated by FEM software ANSYS/LS-DYNA, the plate can be divided into non-steady region and steady region. The nonsteady region is composed of four zones, two of which are about half of leveling roller pitch at leading and end edges and other two are about 10% of the width at lateral edges. The steady region is the rest part enclosed by the non-steady regions. It is helpful to improve the leveling process by analyzing forming mechanism of each region and selecting suitable processes settings.

Exploring Work-Related Stress and Coping Strategies among Omani Nurses Working in Tertiary Governmental Hospitals at Muscat: A Cross-Sectional Study

Introduction: Work-related stress has become a global issue in the nursing workplace, with about 9.20% - 68.0% of nurses globally experiencing stress. Conversely, work-related stress ranges between 20% and 40% in nursing. Other researchers noted that 35.1% of nurses globally experienced elevated stress levels. Stress can damage well-being and lead to coping, which can, directly and indirectly, improve well-being through a perceived state. Nurses need coping mechanisms to manage their stress levels and maintain stability. Coping mechanisms can vary greatly depending on a nurse’s culture and background. Numerous findings indicate that managing stress is more critical than the cause of stress and that the more successful a stress-management approach, the less damage stress brings. Objective: In response to this, it is necessary to explore Omani nurses’ stress level and their coping strategies working in tertiary governmental hospitals in Muscat. Methods: The sample size for this study was 383 Omani nurses, with a 100% response rate. This study used a descriptive cross-sectional design from 15 October 2020 to 30 November 2020. Samples were selected through proportionate population sampling (PPS) from the five selected tertiary hospitals. Data were collected by self-administered questionnaires using a perceived stress scale and Ways of Coping. A simple random sample within a stratum (each hospital admitting ward) was done to identify the study participants. The sample size for this study was 383 Omani nurses, with a 100% response rate. Results: About 83.3% of participants had a moderate perceived level of stress with an overall mean perceived stress level of 18.46 ± 4.52. The most common sources of perceived stress are feeling nervous and “stressed” in the last month (2.30 ± 0.95). According to the ways of coping strategies, nurses seemed to be resorting to more “planful problem” (mean = 11.04) and least was seeking social support (mean = 9.67). Conclusion: This study highlighted the work-related stress level of staff nurses, explored their ways of coping and determined the relationship between work-related stress levels and methods of coping. The key finding of this study was that the frequency of stress reported by nurses was high enough to suggest that their stress levels were significant, given the demanding nature of their profession that requires maximum attention. Additionally, nurses seemed to resort to more planful problem-solving mechanisms to deal with their stressful situations than other coping strategies.

Relationship between changes of endogenous ABA level and resistance in hybrid rice under temperature stress

We studied the relationship between endogenous ABA and resistance to temperature stress in seedlings of hybrid rice. The hybrid rice Combinations Shanyou 63, Shanyou 287, Weiyou 63, and Weiyou 287 were treated under 2℃ and 42℃ respectively for 48 h. Endogenous ABA concentrations were obtained by gas chromatography with electron capture detector (GC-ECD) and a nickel labelled external standard. Leakage of electrolytes were determined. At optimal temperature (27℃), there was difference between the level of endogenous ABA and the leakage of electrolytes in hybrid rice combinations, which attributed to genetic difference. ABA level in Weiyou system was higher than that in Shanyou, and there were distinctions between Shanyou system itself (see table). At 2℃, the ABA content of rice seedling was increased. ABA level of Weiyou system maintained higher than Shanyou system at 27℃. The leakage quantities of

保乳术联合前哨淋巴结活检术对乳腺癌患者生活质量、应激水平及血清肿瘤标志物的影响

目的:探究保乳术联合前哨淋巴结活检术对乳腺癌患者生活质量、应激水平及血清肿瘤标志物的影响。方法:回顾性研究常熟市第五人民医院2017年2月—2021年12月收治的102例乳腺癌患者的病例资料。根据治疗方案将其分为对照组和观察组,其中对照组51例接受保乳术治疗,观察组51例接受保乳术联合前哨淋巴结活检术治疗。比较两组手术指标,生活质量的情况、应激水平血管紧张素Ⅱ(AngⅡ)、肾上腺素(AD)、检测血清肿瘤标志物水平。结果:观察组手术时间短于对照组,术后引流量少于对照组(P<0.05)。两组1年后生活质量评分(总体健康、生理职能、生理功能、活力、躯体疼痛、社会功能、情感职能、精神健康)比较,差异均有统计学意义(P<0.05)。术前0.5 h,两组应激反应相关指标对比,差异均无统计学意义(P>0.05);术后1 d,两组AD、AngⅡ水平均升高(P>0.05),观察组AD、AngⅡ水平均低于对照组(P<0.05)。术前0.5 h,两组血清癌胚抗原(CEA)和糖类抗原153(CA153)水平比较,差异均无统计学意义(P>0.05);术后1 d,两组血清CA153、CEA水平均低于术前0.5 h(P<0.05),观察组CA153、CEA水平均低于对照组(P<0.05)。结论:保乳术联合前哨淋巴结活检术应用于乳腺癌患者治疗中,更有助于缩短手术时间等手术指标,提高患者的生活质量,调节应激反应,且术后短期肿瘤标志物调节水平较低。

高围压状态下堆石料湿化变形特性

堆石料是土石坝的主要填筑材料,其湿化变形特性对土石坝蓄水期变形有显著影响。对两河口水电站的2种筑坝堆石料,采用单线法分别开展围压为0.5、1.0、2.0、3.0 MPa的大型三轴湿化变形试验。结果表明:随着应力水平和围压增加,堆石料轴向湿化变形和体积湿化变形都显著增大,与中低围压下的湿化变形规律相近。高围压下的各向等压湿化变形,堆石料体积湿化应变与围压在双对数坐标中仍服从直线关系,轴向湿化应变与围压不再满足直线关系。高围压下的偏压湿化变形,堆石料体积湿化应变与轴向湿化应变之比一般在0~2范围内,与围压呈现近似水平发展趋势,随应力水平的增加而逐渐降低。采用六参数湿化模型,仍能准确表达轴向湿化变形、体积湿化变形随应力水平、围压的变形规律。

胸腔镜下肺楔形切除术用于老年肺癌患者的效果及对呼吸功能、应激指标的影响

目的:探讨胸腔镜下肺楔形切除术用于老年肺癌的效果及对呼吸功能、应激指标的影响。方法:选取2020年1月—2023年1月无锡市第二人民医院收治的102例老年肺癌患者,按照随机数表法分为两组,研究组(n=51)采用胸腔镜下肺楔形切除术,对照组(n=51)采用胸腔镜下常规肺叶切除术,对比两组围手术期指标(手术时间、术中出血量、胸引流管留置时间、引流量、住院时间)、呼吸功能指标如第1秒用力呼气容积(FEV_(1))、一秒率[FEV_(1)/用力肺活量(FVC)%]、最大呼气流量(PEF)、应激指标[皮质醇(Cor)、去甲肾上腺素(NE)、血管紧张素Ⅱ(AT-Ⅱ)、淀粉样蛋白A(SAA)]、并发症(切口感染、肺漏气、乳糜胸)。结果:研究组胸引流管留置时间、住院时间均短于对照组,且术中出血量、引流量低于对照组,差异有统计学意义(P<0.05),两组手术时间对比,差异无统计学意义(P>0.05);术后3个月,两组FEV_(1)、FEV_(1)/FVC%、PEF较术前均降低,但研究组FEV_(1)、FEV_(1)/FVC%、PEF均高于对照组,差异有统计学意义(P<0.05);术后即刻,两组Cor、NE、AT-Ⅱ、SAA水平均升高,但研究组Cor、NE、AT-Ⅱ、SAA水平均低于对照组,差异有统计学意义(P<0.05);研究组并发症发生率低于对照组,差异有统计学意义(P<0.05)。结论:在老年肺癌患者中行胸腔镜下肺楔形切除术能够获得较好的疗效,且对应激水平的影响较小,减少术后肺功能损伤程度,术后并发症少。

受压混凝土中硫酸根离子的扩散与损伤机理分析

针对沿海、盐渍土环境下荷载和硫酸盐侵蚀的耦合作用对混凝土结构耐久性造成的损伤,提出了一种受压混凝土中硫酸根离子扩散的数值模型。首先,基于Fick第二定律,考虑应力和混凝土孔隙率之间的关系建立了荷载作用下混凝土内硫酸根离子的理论扩散模型;其次,通过自编程序构建包含水泥砂浆、界面过渡区和天然骨料的混凝土三相随机凸多边形骨料模型,从而实现了受压混凝土中硫酸根离子扩散的细观模拟;最后,通过与受压混凝土在硫酸盐溶液中全浸泡的实验结果对比分析,验证了理论模型和细观模型的有效性。进而对不同水灰比的受压混凝土试件在不同浓度硫酸盐溶液中的离子扩散与损伤过程进行了数值分析,分析结果表明:随着压应力水平的提高,同深度处硫酸根离子浓度逐渐减小;与压应力相比,侵蚀溶液浓度和水灰比对硫酸根离子扩散的影响更加明显;水灰比对压应力抑制离子扩散程度的影响要大于侵蚀溶液浓度;适当减小水灰比更有利于受压状态下的混凝土抵抗硫酸盐侵蚀。

不同应力水平下给定含水率混凝土低温有效预压性能试验研究

为评估低温储罐类预应力混凝土结构设计及安全性能,通过对混凝土施加各种初始预压应力水平(0.2、0.3、0.4、0.5、0.6及0.7)并在-160℃低温作用下的试验,系统地探讨其有效预压性能变化规律,同时比较较高和正常两种较为典型混凝土含水率情况对其影响差异。结果表明,随施加的初始预压应力水平提高,混凝土降温点和温均点时的有效预压应力损失率均呈下降的变化趋势,而其降温段和恒温段时的有效预压应力变化率的变化较为复杂;混凝土达其降温点后恒温阶段的有效预压应力损失均有所恢复,且随初始预压应力水平的提高其恢复程度更加明显;含水率对不同初始预压应力水平混凝土低温作用下降温点和恒温点时的有效预压应力损失率变化趋势未产生影响,仅使其变化程度有较明显的差异。

基于环境听觉管理的舒适化口腔治疗应用于儿童牙科畏惧症的效果观察

目的:探讨基于环境听觉管理的舒适化口腔治疗应用于儿童牙科畏惧症的效果。方法:选取2021年1月-2022年7月医院收治的122例儿童牙科畏惧症患儿作为研究对象,随机分为对照组与观察组,各61例。对照组实施常规口腔治疗,观察组实施基于环境听觉管理的舒适化口腔治疗。比较两组患儿治疗前后生理应激水平、牙科畏惧症状、临床焦虑水平及舒适度变化。结果:观察组患儿治疗后舒张压、心率低于对照组,收缩压高于对照组(P<0.05);观察组患儿治疗后“害怕牙医”“让不认识的人碰”“医生钻牙”“想象钻牙的场景”“医生把工具放到嘴巴里”及总分低于对照组(P<0.05);观察组患儿临床焦虑水平轻于对照组(P<0.05);观察组患儿治疗后舒适度各维度评分、总分均高于对照组(P<0.05)。结论:基于环境听觉管理的舒适化口腔治疗应用于儿童牙科畏惧症中可促使生理应激水平保持稳定,提高舒适度,减轻患儿畏惧症状及焦虑水平。

Heart Rate Variability as an Indicator of Stress in Students’ Athletes

Introduction: The wellbeing of student’s athletes has a paramount importance, a prolonged period of cognitive and physical performance that characterizes the life of student’s athletes often leads to fatigue, and a psychobiological state that increases the risk of injury and accidents. The use of Heart rate variability (HRV) has become increasingly popular as a non-invasive methodology that provides an indirect insight into the autonomic nervous system. HRV can be utilized as a diagnostic tool in detection of autonomic nervous system impairment and sympatho-vagal imbalance. HRV technology is employed to monitor the internal response of athletes to workload and identify athletes’s psychophysical stress to predict and therefore prevent injuries. Objective: The objective of the investigation is to establish whether the use of Polar H10 sensor heart rate monitors worn by athletes in a sitting position (inclination 60 degrees) during periods characterized by stress can provide a valid and non-invasive method to assess the psychophysiological state during sports competition and school exams. Method and Statistics: In the study, the HRV of 12 basketball students athletes and 4 students non-athletes was analyzed as a control group. The autonomic nervous system activity was assessed based on heart variability parameters (HRV): SDNN, rMSSD, LF, HF, and LF/HF. The measurements were made after establishing the baseline at rest, during the training phase (CT), competition phase (CC) and during the acute phase of stressors due to school exams coinciding with the competitive season (CC + E). Results: Compared to the respective values prior to the stress of the competitions and exams, a significant decrease in HRV indices was found: SDNN (P Conclusions: The analysis and examination of the data on the sample of the student population also showed a statistically significant correlation between decreased cardiac variability and injuries or indisposition to physical exertion.