Numerical analysis on mechanical difference of sandstone under in-situ stress,pore pressure preserved environment at depth

Deep in-situ rock mechanics considers the influence of the in-situ environment on mechanical properties,differentiating it from traditional rock mechanics.To investigate the effect of in-situ stress,pore pressure preserved environment on the mechanical difference of sandstone,four tests are numerically modeled by COMSOL:conventional triaxial test,conventional pore pressure test,in-situ stress restoration and reconstruction test,and in-situ pore pressure-preserved test(not yet realized in the laboratory).The in-situ stress restoration parameter is introduced to characterize the recovery effect of in-situ stress on elastic modulus and heterogeneous distribution of sandstone at different depths.A random function and nonuniform pore pressure coefficient are employed to describe the non-uniform distribution of pore pressure in the in-situ environment.Numerical results are compared with existing experimental data to validate the models and calibrate the numerical parameters.By extracting mechanical parameters from numerical cores,the stress-strain curves of the four tests under different depths,in-situ stress and pore pressure are compared.The influence of non-uniform pore pressure coefficient and depth on the peak strength of sandstone is analyzed.The results show a strong linear relationship between the in-situ stress restoration parameter and depth,effectively characterizing the enhanced effect of stress restoration and reconstruction methods on the elastic modulus of conventional cores at different depths.The in-situ pore pressurepreserved test exhibits lower peak stress and peak strain compared to the other three tests,and sandstone subjected to non-uniform pore pressure is more prone to plastic damage and failure.Moreover,the influence of non-uniform pore pressure on peak strength gradually diminished with increasing depth.

Impact of work environment on job satisfaction and stress among hemodialysis staff in Klang Valley

Objective:To investigate the factors contributing to satisfaction with the work environment,job satisfaction(JS),and stress among hemodialysis(HD)staff in the central region of Malaysia.Methods:A quantitative cross-sectional study was conducted on 215 HD staff working at private and non-government(NGO)dialysis centers using self-administered questionnaires.The chi-square test was used to determine factors associated with HD staff's JS,stress,and working environment.Results:The scientific proof was apparent that the working environment had an effect on JS and stress among employees at HD centers.Conclusions:This research offers useful insights into the essence and complexities of HD staff's work and will help nurses,dialysis managers,other dialysis personnel,and organizations to better understand the benefits and stresses faced by these workers.

Stress verification of a TLP under extreme wave environment

Stress response of a tension leg platform （TLP） in extreme environments was investigated in this paper. A location on one of the gussets was selected as the object point, where directional stresses were numerically simulated and also experimentally verified by a strain gage. Environmental loading and the platform＇s structural strength were analyzed in accordance with industrial standards, utilizing linear wave theory and the finite element method （FEM）. The fast Fourier transform technique was used to calculate the stress response amplitude operators （RAO） from the records of measurements. A comparison was performed between the stress RAO of the numerical simulation and that of the actual measurements. The results indicated that the stress RAO of the numerical simulation fitted well with measured data at specified wave headings with different periods.

Stress environment of entry driven along gob-side through numerical simulation incorporating the angle of break

Angle of break(AOB)is the acute angle created by the coal seam bedding plane and caving line formed by roof strata movement after extraction of a longwall panel.It has a significant influence on stress redistribution both in the gob and abutment.Throughout numerical simulation investigations up to now,little attention has been paid to it or an AOB of 90°was used,which however,is not realistic.This paper presents a detailed numerical modelling incorporating the AOB against Zhenchengdi Coal Mine.The AOB was obtained through cross-measure boreholes.Hoek-Brown constitutive model was used to simulate the rock masses.Double-yield constitutive model,which was best fitted by Salamon's model,was used to simulate the gob.The results show that a‘‘/\shape"shear failure zone develops around the gob.The shear failure in the floor along the panel edge is due to opposite shear of rock mass on two sides of the caving line,and the number of yielded zones within the gob floor close to the gob edge is smaller.According to the research,the entry was determined to be driven under the gob edge employing splitlevel longwall panel layout(SLPL).The other numerical simulation for SLPL shows that stress around the god-side entry is much smaller than pre-mining stress,and the area of intact rock mass at the elevating section is larger than conventional layout.Numerical modelling was then validated by field observation.

Effect of deteriorated microstructures on stress corrosion cracking of X70 pipeline steel in acidic soil environment

In order to investigate stress corrosion cracking （SCC） of X70 pipeline steel and its weld joint area in acidic soil environ- ment in China, two simulating methods were used： one was to obtain bad microstructures in heat affected zone by annealing at 1300 ℃ for 10 min and then, quenching in water; the other was to get different simulating solutions of acidic soil in Yingtan in south- east China. The SCC susceptibilities of X70 pipeline steel before and after quenching in the simulating solutions were analyzed using slow stain rate test （SSRT） and potentiodynamic polarization technique to investigate the SCC electrochemical mechanism of different microstructures further. The results show that SCC appears in the original microstructure and the quenched microstructure as the polarization potential decreases. Hydrogen revolution accelerates SCC of the two tested materials within the range of-850 mV to -1200 mV vs. SCE. Microstructural hardening and grain coarsening also increase SCC. The SCC mechanisms are different, anodic dissolution is the key of causing SCC as the polarization potential is higher than the null current potential, and hydrogen embrittlement will play a more important role to SCC as the polarization potential lower than the null current potential.

Performance and yield stability of maize hybrids in stress-prone environments in eastern Africa

Identification and deployment of high-yielding and stress-tolerant maize hybrids adapted to stress-prone agro-ecologies is important for improving the food security and livelihoods of smallholder farmers in eastern Africa.The objectives of this study were to(i)assess the performance of maize hybrids under well-watered and drought stress conditions;(ii)evaluate grain yield stability of 65 intermediate-maturing and 55 early-maturing hybrids in 24 well-watered locations and seven drought stress locations;and(iii)identify representative and/or discriminative testing locations for increasing genetic gains for the target traits.There were significant differences for grain yield among early-and intermediatematuring hybrids tested under well-watered and drought stress environments.Among the early-maturing hybrids,the top 10 hybrids produced 46.8%–73.9%and 31.2%–42.1%higher mean grain yields than the best commercial check under drought and well-watered conditions,respectively.Among the intermediate-maturing hybrids,the top 10 hybrids produced 25.2%–47.7%and 8.5%–13.5%higher grain yield than commercial checks under drought stress and well-watered conditions,respectively,suggesting improvement in the levels of drought tolerance in both early-and intermediate-maturing hybrids.GGE biplot analysis and a bi-segmented regression linear method identified specific early-maturing and intermediate-maturing hybrids that performed well under both well-watered and drought stress conditions.These hybrids could be recommended for commercial production in eastern Africa.Kakamega in Kenya was found to be the most representative and highly discriminating site among well-watered testing locations,while Kabuku in Tanzania was the least representative of test locations.For testing under drought stress conditions,Kiboko in Kenya was identified as the most representative location.This information could be useful for allocating resources and streamlining CIMMYT maize hybrid testing in eastern Africa.

Influence factors on stress corrosion cracking of P 110 tubing steel under CO2 injection well annulus environment

Stress corrosion cracking （SCC） behavior of P 110 tubing steel in simulated C02 injection well annulus environments was investigated through three-point bent tests, potentiodynamic polarization and EIS measurements. The results demonstrate that SCC of P110 tubing steel could occur in acidulous simulated environment, and the sensitivity of SCC increases with the decrease ofpH, as well as increase of sulfide concentration and total environmental pressure. Both anodic dissolution and hydrogen embrittlement make contributions to the SCC. Adequate concentration of corrosion inhibitor can inhibit the occurrence of SCC on account of the inhibition of localized anodic dissolution and cathodic hydrogen evolution.

Stress field evolution law of mining environment reconstructing structure with change of filling height

For improving global stability of mining environment reconstructing structure,the stress field evolution law of the structure with the filling height change of low-grade backfill was studied by ADINA finite element analysis code.Three kinds of filling schemes were designed and calculated,in which the filling heights were 2,4,and 7 m,separately.The results show that there are some rules in the stress field with the increase of the filling height as follows:(1) the maximum value of tension stress of the roof decreases gradually,and stress conditions are improved gradually;(2) the tension stress status in the vertical pillar is transformed into the compressive stress status,and the carrying capacity is improved gradually;however,when the filling height is beyond 2.8 m,the carrying capacity of the vertical pillar grows very slowly,so,there is little significance to continue to fill the low-grade backfill;(3) the bottom pillar suffers the squeezing action from the vertical pillars at first and then the gravity action of the low-grade backfill,and the maximum value of tension stress of the bottom pillar firstly increases and then decreases.Considering the economic factor,security and other factors,the low-grade backfill has the most reasonable height(2.8 m) in the scope of all filling height.

Specific Enthalpy Based Heat Stress Index for Indoor Environments without Radiation Effect

Over 100 human thermal indices have been developed to predict the combined thermal impact on the body.In principle,these indices based on energy thermal budget equations should not only be the most complex but also be the most accurate.However,the simple indices based on algebraic or statistical models[e.g.,the wet-bulb globe temperature(WBGT)]continue to be the most popular.A new heat stress index,the enthalpy dry-bulb temperature(EnD)for indoor environments is developed and validated in this study.The EnD index is unique in that it uses the air specific enthalpy,not the wet-bulb temperature,to measure the latent heat transfer from the skin to the surrounding environment.Theoretically,the EnD index can be treated as the equivalent temperature based on the convective heat transfer coefficient h_(c).Comparison is made between the EnD index and the widely used WBGT index based on the experimental data taken from three independent studies available in the scientific literature.The results show that the EnD index can reduce the overestimation of the dry-bulb air temperature and thus reduce heat stress in most cases,especially for hot and humid environments.It can be concluded that the EnD index has the potential to replace the WBGT index as the standard heat stress index in the future.

Reliability assessment considering stress drift and shock damage caused by stress transition shocks in a dynamic environment

Products are often subject to dynamic environmental conditions in field use.When stress transition occurs,products may be exposed to instantaneous shocks that result in shock damages to the products,causing a permanent change of the degradation signals.Meanwhile,under some conditions,instantaneous shocks also lead to stress drift,causing a temporary change of the degradation signals.In this paper,a degradation model is proposed to assess the reliability and predict the residual lifetime of products operating in a dynamic environment considering shock damage and stress drift.The model is established based on a Wiener process which combines a stress-dependent degradation rate function,a shock damage function and a stress drift function in response to the dynamic environment.The shock damage function is established as a linear function of the stress transition start level and the stress level increment.The stress drift function is established as the difference value of a specified function at the stress transition start and end levels.A simulation study is presented to demonstrate the application of the model,and a case study for miniature light bulbs is used to validate the effectiveness of the proposed model.

Influence of environmental enrichment on hippocampal synapses in adolescent offspring of mothers exposed to prenatal stress

Environmental enrichment attenuates hippocampal synaptic injury induced by prenatal stress in offspring. However, the influence of hippocampal synaptic changes and regional differences in prenatal stress remains poorly understood. The present study induced stress in Sprague Dawley rats, which were at gestational age 13-19 days. Following weaning, the offspring were raised in an enriched environment to establish models of stress ＋ enriched environment. Dendritic spine density and synaptophysin expression were detected in hippocampal neurons using Golgi staining and western blot analysis, respectively. Results showed that enriched environment increased dendritic spine density of apical dendrites in CA1 pyramidal cells and basal dendrites of granular cells in the outer layer of the dentate gyrus. In addition, hippocampal synaptophysin expression increased and the effects of prenatal stress on neuronal dendritic spines were reversed in adolescence.

On the minimum cost of an evolutionary strategy response to environment stress

Two revised drafts about a simple evolution trade off function studied by Mitchell(Mitchell, 2000) were put up first. Considering the complex of the environment, or the nonlinear interaction of the environment and species, we put up two new cost functions:c(u,z)=c 0+c 1u+k(z+az 2)u,u>0;c(u,z)=c 0+c 1u+kz du,u>0,d>0. In the first case, if the environment is adverse to species ( a >0), the region of low stress which is more suitable for the intolerant species is very small, and at the same environment stress z , the tolerant species will pay the more cost than it will paid in the normal environment. However the tolerant species will pay more cost but low strategies in the environment of a <0 than that it will paid in the environment of a =0 or a >0. In the second case, the results showed that the greater the stress of the environment is, or the more complex the environment is, the lower cost the intolerant species will pay in the region of z <1. In order to exist or to evolve from an environment of high stress, the organisms must possess a higher u , or a better means of mitigating of the stress of environment. Meanwhile in the region d >1, when d decrease, the intolerant species will pays more lower cost of exploiting a habitat in the low stress environment while the tolerant one will pays more lower cost in the high stress environment. This means that scale d describes the selection character of the species system in the evolution process, the smaller the d(d <1) is, the better the selection or the mitigation the system will possesses.

Stress Corrosion Cracking of Pressure Vessel Steel and Countermeasures by Titanium-Based & Cerium-Based Inhibitors in Subcritical Aqueous Environment

An overview of a severe kind of environmentally-assisted cracking-stress corrosion cracking (SCC) of pressure vessel steel (PVS),such as stainless steel 304, alloy 600,690 and other nickel-based alloys in subcritical (～300 ℃) aqueous environment was given. The mechanisms of SCC of metals under this inclement surrounding were briefly generalized. Herein,some pragmatic solutions to mitigate the SCC susceptibility and retard its propagation were presented. The titanium and cerium-based inhibitors addition countermeasure was highlighted.

Bioethanol Production from Molasses by Yeasts with Stress-Tolerance Isolated from Aquatic Environments in Japan

Bioethanol is a safe and renewable source of energy that continues to be a research focus, since fossil fuels have been linked to global warming and nuclear energy sources are affected by the increased safety concerns following the 2011 nuclear power plant accident in Japan. In general, bioethanol is converted from a biomass by yeast fermentation. The production efficiency of this bioethanol is not sufficiently high, and its practical use as a substitute for fossil fuels and nuclear energy is thus limited. For the industrial production of bioethanol, the yeast fermentation of biomass cultures containing high concentration sugar, NaCl, and ethanol is necessary, but this might induce phenomena in which the stresses arising in the yeasts weaken their cells during fermentation. As described herein, we isolated 1028 strains of yeasts from natural aquatic environments: Japan’s Tama River and Lake Kasumigaura. Among them, 412 strains were fermentative yeasts and 31 strains showed high fermentation ability under a 30% sorbitol + 10% ethanol condition. These strains were identified as Torulaspola delbrueckii, Wickerhamomyces anomalus, Candida glabrata, Pichia kudriavzevii, Saccharomyces cf. cerevisiae/paradoxus, and Lachancea kluyveri. The strains T. delbrueckii, W. anomalus, and C. glabrata also showed tolerance against 15% NaCl. Most importantly, S. cf. cerevisiae/paradoxus H28 and L. kluyveri F2-67 produced 57.4 g/L and 53.9 g/L ethanol from molasses (sucrose 104.0 g/L, fructose 33.4 g/L, and glucose 24.8 g/L) within 48 hrs at 25°C, respectively.

Season, Environment Stress and Refrigerated Storage Affect Genomic DNA Isolation of Tung Tree

Many metabolites in leaf tissue disturbed plant genomic DNA isolation and always varied when leaves was harvested from different environments. Objective of this study was to investigate whether season, environment stress and refrigerated storage affect genomic DNA isolation of tung tree leaves. Five types of young leaves and two DNA isolation protocols, the recycling CTAB protocol I and II, were adopted to carry out the experiment. Our results showed that both leaf type and protocol affected DNA isolation of tung tree. Using the recycling CTAB protocol II, though little DNA were obtained from three types of young leaves, the other two have satisfying results. Whereas the recycling CTAB protocol I could produce high yield genomic DNA from all the five types of young leaves. All the detectable DNA samples in agarose gel electrophoresis were good templates for PCR reaction. Season, environment stress and refrigerated storage had a big effect on genomic DNA isolation of tung tree. The recycling CTAB protocol I was proved to be an effective and universal protocol for DNA isolation of tung tree. Five types of young leaves could all act as the tissue for isolation of genomic DNA, but the summer healthy young leaves without long-time refrigerated storage are the best. The optimal leaf tissue will benefit DNA isolation of plant species.

Effect of Work Environment on Level of Work Stress and Burnout among Nurses in a Teaching Hospital in Nigeria

Nurses’ roles expose them to a lot of stress based upon the physical labour, exposure to human suffering, lengthy work hours, poor staffing, and interpersonal relationships that are central to the work they do. Nurses are expected to deliver humane, empathetic, culturally-sensitive and proficient care in working environments with limited resources and increasing responsibilities. Such imbalance between providing high quality care with limited resources leads to physical and mental stress. This stressful nature of nursing can ultimately lead to job dissatisfaction and burnout which among health care providers are important issues since they affect turnover rates, staff retention and ultimately the quality of patient care. A thoroughly validated self developed questionnaire with a reliability coefficient of 0.78 was used to explore the effect of work environment on the level of work stress and burnout among nurses. A purposive sampling technique was utilized to select 100 participants from the medical unit of the hospital. Three hypotheses were tested at a significant level of 0.05. Data were analyzed using ANOVA and Pearson’s Correlation. The study revealed that level of stress was higher among the staff nurses who had worked for only between 0 and 3 years, with mean stress score 46.0000. Findings further revealed that as the cadre rose, the nurses assumed that managerial roles were accountable for increased subordinates and oversee health related and administrative responsibilities and they experienced more stress. Also there is a significant relationship among work environment, stress and burnout among the nurses in the selected unit. In conclusion, though work conditions and environment are not favourable, there are job security and good interpersonal relationship among the nurses which cushion the stressful situations. It is therefore recommended that the management of the hospitals should provide a conducive work environment, providing necessary resources and adequate break periods to ensure staff welfare.

The environment shear stress field for the 1976 Tangshan earthquake sequence

The environment shear stress of Tangshan main earthquake and 38 great aftershocks have been calculated by the acceleration data of Tangshan earthquake sequence. The environment shear stress for 52 smaller aftershocks from July of 1982 to July of 1984 have also been calculated by use of the digital data of the Sino-American cooperation recorded by the instrumental arrays in Tangshan. The results represent that the environment shear stress τ0 values have a weak dependence on the seismic moment, only the small and moderate earthquakes will be able to occur in the region with smaller τ0 value and the large earthquakes are only in the region with greater τ0 value. The peak acceleration, velocity and displacement will be larger for the earthquakes occurred in the region with greater τ0 value, Therefore, the measurement of environment shear stress τ0 value for the significant region will play an important role in earthquske prediction and engineering shock-proof. The environment shear stress values for the great aftershocks occurred in the two ends of the main fault are often higher than that for the main shock. This case may represent the stress concentration in the two ends of the fault. This phenomenon provides the references for the place where the great aftershock will occur.

Effect of mechanical stresses on degradation behavior of high-purity magnesium in bone environments

High-purity(HP)magnesium(Mg)has emerged as a promising biomaterial for supporting functional bone tissue.Our previous study found that mechanical stresses and the surrounding fibrotic tissue(subcuta-neous)both play crucial roles in the degradation of HP Mg.However,due to challenges in the degradation and regeneration process in vivo,it remains unclear how stress affects HP Mg degradation in bone en-vironments,limiting its further application.In this study,novel loading devices were designed and the effects of tensile and compressive stresses on HP Mg degradation in vivo and in vitro bone environments were quantitatively analyzed.In addition,bone osteointegration around HP Mg was explored preliminar-ily.Tensile stress increases the degradation rate of HP Mg in vivo and in vitro.HP Mg degradation in vivo is more sensitive to stress factors than in vitro,but the sensitivity decreases with corrosion time.The volume loss rate of HP Mg is multilinear with the applied stress and degradation time.The volume of bone tissue surrounding HP Mg is larger in the no-stress group compared to the stressed groups,which is more pronounced with increasing implantation time.These results provide valuable insights for optimiz-ing the design of HP Mg-based implants considering load conditions.This will help to achieve a balance between the degradation rate of the implant and the regeneration rate of the surrounding bone.

Experimental investigation of stress unloading effects on rock damage and confining pressure-dependent crack initiation stress of porous sandstone under true triaxial stress environments

This study investigates the impact of intermediate(σ_(2))and minimum(σ_(3))principal stress unloading on damage behavior and the confining pressure influence on crack initiation stress(σci)in true triaxial stress conditions,utilizing large-scale cubic samples.Two distinct true triaxial tests were executed,examining the effects of confining stress(σ_(2)andσ_(3))unloading on porous sandstone damage and the correlation between confining stress andσci.Acoustic emission(AE)parameters,signal characteristics,and wave velocity variations were utilized to elucidate cracking mechanisms and damage development in the samples.Unloading tests reveal consistent ve-locities in three orthogonal directions(V_(11),V_(22),and V_(33))during the initial two unloading stages.In the subse-quent three stages,confining stress unloading leads to a decrease in wave velocity in the corresponding direction,while velocities in the other two directions remain nearly constant.Notably,σ_(2)unloading generates higher amplitude AE signals compared toσ_(3)unloading,with over 70%of the micro-cracks categorized as tensile.In the incremental loading tests,σ_(ci) is found to be contingent on confining pressure,withσ_(2)playing a crucial role.Duringσ_(1) loading,V_(33) decreases,indicating additional crack formation;conversely,σ_(3)loading results in V33 increase,signifying the continuous closure of existing cracks.Limitations of the experiments are summarized and prospects in this domain are outlined.

Identification of Light-Harvesting Chlorophyll a/b-Binding Protein Genes of Zostera marina L.and Their Expression Under Different Environmental Conditions

Photosynthesis includes the collection of light and a/b-binding （LHC） proteins. In high plants, the LHC gene family constituting the light-harvesting complex ofphotosystems I and II. the transfer of solar energy using light-harvesting chlorophyll includes LHCA and LHCB sub-families, which encode proteins Zostera marina L. is a monocotyledonous angiosperm and inhab- its submerged marine environments rather than land environments. We characterized the Lhca and Lhcb gene families of Z. marina from the expressed sequence tags （EST） database. In total, 13 unigenes were annotated as ZmLhc, 6 in Lhca family and 7 in ZmLhcb family. ZmLHCA and ZmLHCB contained the conservative LHC motifs and amino acid residues binding chlorophyll. The average similarity among mature ZmLHCA and ZmLHCB was 48.91% and 48.66%, respectively, which indicated a high degree of diver- gence within ZmLHChc gene family. The reconstructed phylogenetic tree showed that the tree topology and phylogenetic relation- ship were similar to those reported in other high plants, suggesting that the Lhc genes were highly conservative and the classification of ZmLhc genes was consistent with the evolutionary position of Z. marina. Real-time reverse transcription （RT） PCR analysis showed that different members of ZmLhca and ZmLhcb responded to a stress in different expression patterns. Salinity, temperature, light intensity and light quality may affect the expression of most ZmLhca and ZmLhcb genes. Inorganic carbon concentration and acidity had no obvious effect on ZmLhca and ZmLhcb gene expression, except for ZmLhca6.