Failure characterization of fully grouted rock bolts under triaxial testing

Confining stresses serve as a pivotal determinant in shaping the behavior of grouted rock bolts.Nonetheless,prior investigations have oversimplified the three-dimensional stress state,primarily assuming hydrostatic stress conditions.Under these conditions,it is assumed that the intermediate principal stress(σ_(2))equals the minimum principal stress(σ_(3)).This assumption overlooks the potential variations in magnitudes of in situ stress conditions along all three directions near an underground opening where a rock bolt is installed.In this study,a series of push tests was meticulously conducted under triaxial conditions.These tests involved applying non-uniform confining stresses(σ_(2)≠σ_(3))to cubic specimens,aiming to unveil the previously overlooked influence of intermediate principal stresses on the strength properties of rock bolts.The results show that as the confining stresses increase from zero to higher levels,the pre-failure behavior changes from linear to nonlinear forms,resulting in an increase in initial stiffness from 2.08 kN/mm to 32.51 kN/mm.The load-displacement curves further illuminate distinct post-failure behavior at elevated levels of confining stresses,characterized by enhanced stiffness.Notably,the peak load capacity ranged from 27.9 kN to 46.5 kN as confining stresses advanced from σ_(2)=σ_(3)=0 to σ_(2)=20 MPa and σ_(3)=10 MPa.Additionally,the outcomes highlight an influence of confining stress on the lateral deformation of samples.Lower levels of confinement prompt overall dilation in lateral deformation,while higher confinements maintain a state of shrinkage.Furthermore,diverse failure modes have been identified,intricately tied to the arrangement of confining stresses.Lower confinements tend to induce a splitting mode of failure,whereas higher loads bring about a shift towards a pure interfacial shear-off and shear-crushed failure mechanism.

Limit load and failure mechanisms of a vertical Hoek-Brown rock slope

The problem considered in this short note is the limit load determination of a vertical rock slope.The classical limit theorem is employed with the use of adaptive finite elements and nonlinear programming to determine upper and lower bound limit loads of a Hoek-Brown vertical rock slope.The objective function of the mathematical programming problem is such as to optimize a boundary load,which is known as the limit load,resembling the ultimate bearing capacity of a strip footing.While focusing on the vertical slope,parametric studies are carried out for several dimensionless ratios such as the dimensionless footing distance ratio,the dimensionless height ratio,and the dimensionless rock strength ratio.A comprehensive set of design charts is presented,and failure envelopes shown with the results explained in terms of three identified failure mechanisms,i.e.the face,the toe,and the Prandtl-type failures.These novel results can be used with great confidence in design practice,in particularly noting that the current industry-based design procedures for the presented problem are rarely found.

Fly Ash-based Geopolymers:Effect of Slag Addition on Efflorescence

Blended fly ash/blast-furnace slag geopolymers are focused on due to their excellent mechanical and chemical resistant properties. We investigated the effect of slag partial substitution for fly ash on the efflorescence of the resulting geopolymers. The efflorescence of geopolymer binders was inspected and evaluated through leaching tests. The efflorescence deposits on surface of the geopolymer binders were analyzed using XRD and SEM-EDS. The results showed that sodium and calcium cations leached from geopolymer binders reacted with the atmospheric CO2 and formed the crystal deposits, gaylussite and calcite, in the forms of granular and angular crystal particles. The slag addition led to a refinement of the pore structure of fly ash-based geopolymers, but an increment in the concentration of alkali leaching. The crystal deposits gradually developed in the pore volume of the binders, and finally exceeded the capacity of pore volume. The extent of efflorescence on the surface of specimens increased with the slag substitution. The visible efflorescence is therefore a result of available alkalis and pore sizes and volumes. Higher concentration of available alkalis and smaller pores （and volume） will lead to more intensive efflorescence.

Fundamental and progress of Bi_2Te_3-based thermoelectric materials

Thermoelectric materials,enabling the directing conversion between heat and electricity,are one of the promising candidates for overcoming environmental pollution and the upcoming energy shortage caused by the over-consumption of fossil fuels.Bi2Te3-based alloys are the classical thermoelectric materials working near room temperature.Due to the intensive theoretical investigations and experimental demonstrations,significant progress has been achieved to enhance the thermoelectric performance of Bi2Te3-based thermoelectric materials.In this review,we first explored the fundamentals of thermoelectric effect and derived the equations for thermoelectric properties.On this basis,we studied the effect of material parameters on thermoelectric properties.Then,we analyzed the features of Bi2Te3-based thermoelectric materials,including the lattice defects,anisotropic behavior and the strong bipolar conduction at relatively high temperature.Then we accordingly summarized the strategies for enhancing the thermoelectric performance,including point defect engineering,texture alignment,and band gap enlargement.Moreover,we highlighted the progress in decreasing thermal conductivity using nanostructures fabricated by solution grown method,ball milling,and melt spinning.Lastly,we employed modeling analysis to uncover the principles of anisotropy behavior and the achieved enhancement in Bi2Te3,which will enlighten the enhancement of thermoelectric performance in broader materials

Microstructure and wear characteristics of ATZ ceramic particle reinforced gray iron matrix surface composites

The alumina toughened zirconia(ATZ) ceramic particle reinforced gray iron matrix surface composite was successfully manufactured by pressureless infi ltration. The porous preform played a key role in the infi ltrating progress. The microstructure was observed by scanning electron microscopy(SEM); the phase constitutions was analyzed by X-ray diffraction(XRD); and the hardness and wear resistance of selected specimens were tested by hardness testing machine and abrasion testing machine, respectively. The addition of high carbon ferrochromium powders leads to the formation of white iron during solidifi cation. The wear volume loss rates of ATZ ceramic particle reinforced gray iron matrix surface composite decreases fi rst, and then tends to be stable. The wear resistance of the composite is 2.7 times higher than that of gray iron matrix. The reason is a combination of the surface hardness increase of gray iron matrix and ATZ ceramic particles and alloy carbides protecting effect on gray iron matrix.

Depth of anaesthesia monitors and the latest algorithms

This paper reviews the existing depth of anaesthesia(DoA) monitors and their algorithms and also proposes to improve their performance from four aspects.\n ideal DoA monitor should be able to suggest a personalised drug dosages,to predict and provide early warnings when dosages are inappropriate,to he porlalile and highty cost—effective.The limitations of the existing DoA monitors commonly include unsatisfied data filtering techniques.time delay for the monitoring responses,and inflexible and low noise immunity problems.The latest research results show that their performance can be improved using up—to—date computing technology and neurophysiology.The findings in Chinese market review show that neither the imported nor the Chinese domestic DoA monitors are widely utilised at hospitals.but the demand for DoA monitors is very high.Clearly there is a high demand which encourages the development of a better DoA monitor and its mass production in China.

A phase inversion polymer coating to prevent swelling and spalling of clay fines in coal seam gas wells

We report a phase inversion polymer coating as a novel concept with potential to prevent clay swelling and fines generation in coal seam gas, or other petroleum, wellbores. Our approach uses polyethersulfone （PES） with N-methyl-2- pyrrolidone （NMP） as a water-soluble solvent to form a dense, low-porosity film across the clay-rich interburden layers, but a porous and permeable membrane on coal seams. This contrasting behaviour occurs because the coal contains much more free water than the clay-rich interburden layers. We demonstrate the efficacy of the method to prevent clay spalling in immersion tests and under a flow of fresh water in a visual swell test apparatus. The clay-rich rocks studied were mudstone and siltstone, and these were dip coated in the PES/NMP solution. The uncoated mudstone swelled and broke apart quickly in the immersion test and visual flow test, but the PES coated rock samples were stable for 30 days. The coated rock and coal samples were characterised by X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. The morphology of coated mudstone and coated coal samples showed that the polymer formed a dense layer across the low-permeability mudstone, but an open porous structure on the coal surface. The effect of the coating on the permeability of KCl brine through coal was measured in a core-flood apparatus. Although the permeability of the coal showed some deterioration after coating, from （0.58 ± 0.12） mD to （0.3 ±0.03） mD, these results demonstrate the potential of a smart polymer coating to prevent clay swelling while remaining permeable to gas and water on coal layers.

Leaf photosynthesis and yield components of mung bean under fully open-air elevated[CO_2]

Mung bean（Vigna radiata L.） has the potential to establish symbiosis with rhizobia,and symbiotic association of soil micro flora may facilitate the photosynthesis and plant growth response to elevated[CO2].Mung bean was grown at either ambient CO2 400 μmol mol^（-1） or[CO2]（（550＋17） μmol mol^（-1）） under free air carbon dioxide enrichment（FACE） experimental facility in North China.Elevated[CO2]increased net photosynthetic rate（Pn）,water use efficiency（WUE） and the non-photochemical quenching（NPQ） of upper most fully-expanded leaves,but decreased stomatal conductance（Gs）,intrinsic efficiency of PSII（Fv ＇/Fm＇）,quantum yield of PSII（φ（PSll）） and proportion of open PSII reaction centers（qp）.At elevated[CO2],the decrease of Fv＇/Fm＇,φ（PSII）,qp at the bloom stage were smaller than that at the pod stage.On the other hand,Pn was increased at elevated[CO2]by 18.7 and 7.4%at full bloom（R2） and pod maturity stages（R4）,respectively.From these findings,we concluded that as a legume despite greater nutrient supply to the carbon assimilation at elevated[CO2],photosynthetic capacity of mung bean was still suppressed under elevated[CO2]particularly at pod maturity stage but plant biomass and yield was increased by 11.6 and 14.2%,respectively.Further,these findings suggest that even under higher nutrient acquisition systems such as legumes,nutrient assimilation does not match carbon assimilation under elevated[CO2]and leads photosynthesis down-regulation to elevated[CO2].

Sustainability of Transhumance Grazing Systems under Socio-economic Threats in Langtang,Nepal

The decline or loss of traditional social- ecological systems may induce adverse effects to the societies and ecosystems. Transhumance, the recurring and seasonal movement of grazing livestock, is increasingly constrained by a numbers of factors including policy, land use and soeio-economic changes in Nepal. To explore how these changes have affected the transhumance, this study investigated transhumance at the Langtang valley in central Nepal. The specific objectives of this study were to determine the herd size and composition, spatial-temporal patterns and to identify the major drivers of the system and the system changes. Data were collected from field study comprising semi-structured interviews with the herders, focus group discussions, key informants survey, and observations of rangeland and livestock management systems. The study revealed that the transhumanee system in the Langtang is influenced by two types of drivers. In one hand, traditional practices are contributing to the sustainability of the system. On the other hand, the grazing patterns and adaptive responses are strongly influenced by changes in government policies, socioeconomic and cultural transformation, livestock productivity, markets, rangeland conditions and climate change. The findings of this study help with the development and implementation of transhumance management policy for the sustainability.

Fusarium pseudograminearum and F.culmorum affect the root system architecture of bread wheat

Yield losses of bread wheat due to crown rot can be more severe when drought conditions occur during the grain-filling period.Root architecture characteristics are important for soil exploration and belowground resource acquisition and are essential for adaptation to water-limited environments.Traits such as root angle,length and density have been strongly associated with acquisition efficiency and contribute to yield stability of the crop.The impact of crown rot pathogens on wheat root architecture is poorly understood.We examined differences in root angle,length and number,as well as dry root weight of the crown rot-susceptible bread wheat cultivar,Livingston inoculated with one of two crown rot pathogens Fusarium culmorum or Fusarium pseudograminearum in a transparent-sided root observation chamber.Significant adverse impacts on plant health and growth were revealed by visual discolouration of the leaf sheaths;fresh and dry shoot weight;leaf area of the oldest and the youngest fully expanded leaf and leaf number.Values of most recorded root system measurements were reduced when inoculated with either F.culmorum or F.pseudograminearum.In contrast,root angle was increased in the presence of F.culmorum but was not significantly changed by F.pseudograminearum.The development of whiteheads and grain losses in bread wheat caused by crown rot have previously been associated with blockages of the vascular systems.The method employed here was able to identify differences in the pathogen impacts on roots,which were not detected using previous systems.This research indicates that in the presence of F.culmorum and F.pseudograminearum infection,not only reductions in the size and biomass of the shoot system but also changes in the length,biomass and architecture of the root system could play an important role in yield loss.

COVID‑19 pandemic risk and probability of loan default:evidence from marketplace lending market

As the COVID-19 pandemic adversely affects the financial markets,a better understanding of the lending dynamics of a successful marketplace is necessary under the conditions of financial distress.Using the loan book database of Mintos(Latvia)and employing logit regression method,we provide evidence of the pandemic-induced exposure to default risk in the marketplace lending market.Our analysis indicates that the probability of default increases from 0.056 in the pre-pandemic period to 0.079 in the post-pandemic period.COVID-19 pandemic has a significant impact on default risk during May and June of 2020.We also find that the magnitude of the impact of COVID-19 risk is higher for borrowers with lower credit ratings and in countries with low levels of FinTech adoption.Our main findings are robust to sample selection bias allowing for a better understanding of and quantifying risks related to FinTech loans during the pandemic and periods of overall economic distress.

Physics-based and data-driven modeling for stability evaluation of buried structures in natural clays

This study presents a hybrid framework to predict stability solutions of buried structures under active trapdoor conditions in natural clays with anisotropy and heterogeneity by combining physics-based and data-driven modeling.Finite-element limit analysis(FELA)with a newly developed anisotropic undrained shear(AUS)failure criterion is used to identify the underlying active failure mechanisms as well as to develop a numerical(physics-based)database of stability numbers for both planar and circular trapdoors.Practical considerations are given for natural clays to three linearly increasing shear strengths in compression,extension,and direct simple shear in the AUS material model.The obtained numerical solutions are compared and validated with published solutions in the literature.A multivariate adaptive regression splines(MARS)algorithm is further utilized to learn the numerical solutions to act as fast FELA data-driven surrogates for stability evaluation.The current MARS-based modeling provides both relative importance index and accurate design equations that can be used with confidence by practitioners.

Cellular automaton modeling of semisolid microstructure formation

Computer modeling of semi-solid structure formation is of significance in both understanding the mechanisms of globular structure formation and determining the effect of solidification conditions on final microstructure.A modified cellular automaton(mCA) model has been developed,which is coupled with macroscopic models for heat transfer calculation and microscopic models for nucleation and grain growth.The mCA model is applied to A356 Al alloy-one of the most widely used semi-solid alloys,to predict grain morphology and grain size during semi-solid solidification,and determines the effects of pouring temperature on the final microstructure.The modeling results show that the lower the initial temperature,the finer grain size will be obtained.In addition,the model can be used to predict the solutal micro-segregation.

Exploring the Potential Impacts of Climate Variability on Spring Wheat Yield with the APSIM Decision Support Tool

Assessing the impacts of climate variability on agricultural productivity at regional, national or global scale is essential for defining adaptation and mitigation strategies. We explore in this study the potential changes in spring wheat yields at Swift Current and Melfort, Canada, for different sowing windows under projected climate scenarios (i.e., the representative concentration pathways, RCP4.5 and RCP8.5). First, the APSIM model was calibrated and evaluated at the study sites using data from long term experimental field plots. Then, the impacts of change in sowing dates on final yield were assessed over the 2030-2099 period with a 1990-2009 baseline period of observed yield data, assuming that other crop management practices remained unchanged. Results showed that the performance of APSIM was quite satisfactory with an index of agreement of 0.80, R2 of 0.54, and mean absolute error (MAE) and root mean square error (RMSE) of 529 kg/ha and 1023 kg/ha, respectively (MAE = 476 kg/ha and RMSE = 684 kg/ha in calibration phase). Under the projected climate conditions, a general trend in yield loss was observed regardless of the sowing window, with a range from ?-24% to -94% depending on the site and the RCP, and noticeable losses during the 2060s and beyond (increasing CO2 effects being excluded). Smallest yield losses obtained through earlier possible sowing date (i.e., mid-April) under the projected future climate suggested that this option might be explored for mitigating possible adverse impacts of climate variability. Our findings could therefore serve as a basis for using APSIM as a decision support tool for adaptation/mitigation options under potential climate variability within Western Canada.

A Comparison of Libyan and Australian Students＇ Perceptions of Empowerment in Accounting Courses

The concept of empowerment was introduced into the accounting education research by Zraa, Imran, Kavanagh, and Morgan （2011）. The authors＇ purpose is to compare Libyan and Australian students＇ perceptions of empowerment in accounting courses and to investigate their relationships with classroom instruction. This study involves a survey of 409 students, who are studying the first-year business degree at institutions in Libya and Australia. Observations and interviews are also conducted. Data are analyzed using reliability tests, factor analysis, t-tests, and correlations. The results indicate that Australian students are more empowered than Libyan students. In addition, the result reveals that classroom instruction methods influence students＇ empowerment.

Significance Analysis of Flexural Behaviour of Hybrid Sandwich Panels

This paper presents the significance analysis of a new type of hybrid composite sandwich wall panel which can be manufactured as modular panelised system. Two different types of natural fibers reinforced plastics (NFRP) laminate were incorporated into the new sandwich panel as an intermediate layer. The significance analysis in this research has been carried out using analysis of variance (ANOVA). As the aim of the analysis is to select the most appropriate natural fiber composites for the intermediate layer, the experiments were arranged as a single factor experiment in which 3 levels of a factor have been examined. The factor refers to the type of intermediate layer used in the sandwich panel. The result of this study shows that the incorporation of intermediate layer has significantly enhanced the load carrying capacity of the sandwich panels.

Process of Security Assurance Technique for Application Functional Logic in E-Commerce Systems

Security practices such as Audits that often focus on penetration testing are performed to find flaws in some types of vulnerability & use tools, which have been tailored to resolve certain risks based on code errors, code conceptual assumptions bugs, etc. Most existing security practices in e-Commerce are dealt with as an auditing activity. They may have policies of security, which are enforced by auditors who enable a particular set of items to be reviewed, but also fail to find vulnerabilities, which have been established in compliance with application logic. In this paper, we will investigate the problem of business logic vulnerability in the component-based rapid development of e-commerce applications while reusing design specification of component. We propose secure application functional processing Logic Security technique for component-based e-commerce application, based on security requirement of e-business process and security assurance logical component behaviour specification approach to formulize and design a solution for business logic vulnerability phenomena.

Investigating Two Configurations of a Heat Exchanger in an Indirect Heating Integrated Collector Storage Solar Water Heating System

Due to the environmental impact of energy usage and increased price of fusel fuel, consumers need to be encouraged to use renewable energy sources. The IHICSSWHS （indirect heating integrated collector storage solar water heater system） is one of the most economical systems. It incorporates the collection of a solar energy component and a hot water storage component in one unit. The objective of this study was to investigate ways to enhance the thermal performance of the system. Two configurations of the system were studied： system with double row HX （heat exchanger） and tube length of 16.2 m, and system with single row HX and tube length of 8.1 m and 10.8 m. The service water tube inside diameter was also varied to 10.7 mm and 17.1 mm The steady state continuity, momentum and energy equations were numerically solved, using FLUENT software. A standard k-w turbulent model and surface-to-surface radiation model were used. The result showed that the system of 10.8 m tube length and single row HX provided higher outlet temperature than the system of 16.2 m and double row HX. Therefore, a significant reduction in cost and power usage can be achieved by using a single row HX.

Organisational Hierarchies and Decision Making Process of Chinese Multinational Enterprises in Vietnam

This paper examines the organisational hierarchies and decision making processes of two Chinese multinational enterprises operating in Vietnam—hina Luoyang Floating Glass Corp. （CLFG） and China TCL Holdings Co. Ltd. （TCL）. For this study, research data were obtained from in-depth interviews of more than 20 government officials in E R. China and Vietnam, and managers and staff of those two enterprises. Results indicate that the organisational structures of the two enterprises are still vertical but complex, although moderate changes made to them post the nationwide economic reform of China. Consequently, decision making process follows a ＂top-down＂ model, sometimes, with insufficient grassroots information. Findings are discussed in the light of political, social and cultural milieu, and implications are drawn for the management of Chinese multinational enterprises operating in overseas markets. Both CLFG and China TCL are structured on task specialisations. However, departmentalisation in TCL＇s overseas division in head office is not only based on products, but also on geographical regions of markets. The organisational structure of TCL in Vietnam is less complex than the international division, but it is more centralised. Decision making at TCL combines more traditional Chinese business philosophy with modern western organisational characteristics. TCL has a strong western influence in its management style. However, some traditional characteristics such as ＂hero＂ leadership influence and political influence are involved with decision making at TCL. Amongst others, the transitional economy, social culture, poor management system and political sensitivity have been major elements influencing decision making. In the case of CLFG. some decisions have been made before proper information has been gathered and analysed.

Water, land, and energy use efficiencies and financial evaluation of air conditioner cooled greenhouses based on field experiments

High temperature and humidity can be controlled in greenhouses by using mechanical refrigeration cooling system such as air conditioner(AC)in warm and humid regions.This study aims to evaluate the techno-financial aspects of the AC-cooled greenhouse as compared to the evaporative cooled(EV-cooled)greenhouse in winter and summer seasons.Two quonset single-span prototype greenhouses were built in the Agriculture Experiment Station of Sultan Qaboos University,Oman,with dimensions of 6.0 m long and 3.0 m wide.The AC-cooled greenhouse was covered by a rockwool insulated polyethylene plastic sheet and light emitting diodes(LED)lights were used as a source of light,while the EV-cooled greenhouse was covered by a transparent polyethylene sheet and sunlight was used as light source.Three cultivars of high-value lettuce were grown for experimentation.To evaluate the technical efficiency of greenhouse performance,we conducted measures on land use efficiency(LUE),water use efficiency(WUE),gross water use efficiency(GWUE)and energy use efficiency(EUE).Financial analysis was conducted to compare the profitability of both greenhouses.The results showed that the LUE in winter were 10.10 and 14.50 kg/m^(2) for the AC-and EV-cooled greenhouses,respectively.However,the values reduced near to 6.80 kg/m^(2) in both greenhouses in summer.The WUE of the AC-cooled greenhouse was higher than that of the EV-cooled greenhouse by 3.8%in winter and 26.8%in summer.The GWUE was used to measure the total yield to the total greenhouse water consumption including irrigation and cooling water;it was higher in the AC-cooled greenhouse than in the EV-cooled greenhouse in both summer and winter seasons by almost 98.0%–99.4%.The EUE in the EV-cooled greenhouse was higher in both seasons.Financial analysis showed that in winter,gross return,net return and benefit-to-cost ratio were better in the EVcooled greenhouse,while in summer,those were higher in the AC-cooled greenhouse.The values of internal rate of return in the AC-and EV-cooled greenhouses were 63.4%and 129.3%,respectively.In both greenhouses,lettuce investment was highly sensitive to changes in price,yield and energy cost.The financial performance of the AC-cooled greenhouse in summer was better than that of the EV-cooled greenhouse and the pattern was opposite in winter.Finally,more studies on the optimum LED light intensity for any particular crop have to be conducted over different growing seasons in order to enhance the yield quantity and quality of crop.