Nonlinear empirical failure criterion for rocks under triaxial compression

Based on existing triaxial compression experimental data,a new empirical failure criterion with wide applicability was proposed considering hydrostatic pressure,second stress invariance,and maximum shear stress.Four fitting evaluation indicators were used to verify the consistency of the new failure criterion,and the differences with the other 6 failure criteria were discussed.The characteristics of the new failure criteria in the principal stress space were finally analyzed.The results indicate that(1)the new failure criterion exhibits strong predictive ability for triaxial experiments and has good applicability for both intact and jointed rocks;(2)the influence of hydrostatic pressure on the failure surface exhibits a non-linear trend,and different hydrostatic pressure also exhibits different distribution patterns on the deviatoric stress plane,with a distribution characteristic pattern of hexagonal snowflake-regular hexagon.The maximum shear stress has a torsional effect on the new criterion,in the three-dimensional failure surface.The parameters a and b of the rock have an impact on the failure surface morphology of the new criterion function on the offset surface.

Repurposing Loperamide as an Anti-Infection Drug for the Treatment of Intracellular Bacterial Pathogens

Infections caused by intracellular bacterial pathogens are difficult to treat since most antibiotics have low cell permeability and undergo rapid degradation within cells.The rapid development and dissemination of antimicrobial–resistant strains have exacerbated this dilemma.With the increasing knowledge of host–pathogen interactions,especially bacterial strategies for survival and proliferation within host cells,host-directed therapy(HDT)has attracted increased interest and has emerged as a promising antiinfection method for treating intracellular infection.Herein,we applied a cell-based screening approach to a US Food and Drug Administration(FDA)-approved drug library to identify compounds that can inhibit the intracellular replication of Salmonella Typhimurium(S.Typhimurium).This screening allowed us to identify the antidiarrheal agent loperamide(LPD)as a potent inhibitor of S.Typhimurium intracellular proliferation.LPD treatment of infected cells markedly promoted the host autophagic response and lysosomal activity.A mechanistic study revealed that the increase in host autophagy and elimination of intracellular bacteria were dependent on the high expression of glycoprotein nonmetastatic melanoma protein B(GPNMB)induced by LPD.In addition,LPD treatment effectively protected against S.Typhimurium infection in Galleria mellonella and mouse models.Thus,our study suggested that LPD may be useful for the treatment of diseases caused by intracellular bacterial pathogens.Moreover,LPD may serve as a promising lead compound for the development of anti-infection drugs based on the HDT strategy.

Structural characterization and prebiotic potential of polysaccharides from Polygonatum sibiricum

Polygonatum sibiricum has been widely used due to its excellent biological activities.We prepared a novel polysaccharide from P.sibiricum(PSP)in this study.According a monosaccharide composition analysis,PSP was mainly composed of fructose and glucose with a molar percentage of 93.81:5.12.The main linkage types were identified asα-D-Glcp-1→and→2-β-D-Fruf-1→.The molecular weight of PSP showed no significant change after simulated salivary and gastrointestinal digestion.However,PSP could be broken down by intestinal bacteria.Our findings revealed that PSP administration increased the abundance of probiotics such as Bifidobacterium.Furthermore,the results showed that gut microbes could utilize PSP to produce short-chain fatty acids including acetic acid,propionic acid,and butyric acid.Also,the PSP fermentation broth displayed an excellent scavenging effect on free radicals,including 2,2-diphenyl-1-picrylhydrazyl radical,superoxide radical,and hydroxyl radical.In summary,this study will help to promote the application of PSP as prebiotics in functional food and the medical industry.

豁痰化瘀利水方对创伤性脑损伤的疗效观察

目的探讨豁痰化瘀利水方对创伤性脑损伤的疗效。方法收集我院2015年7月~2017年10月收治的急性创伤性脑损伤患者110例。均进行头颅CT扫描检查,根据格拉斯哥昏迷计分法(GCS)分级进行系统评估,将患者分为治疗组和对照组,各55例。在常规治疗的基础上,对照组给予单纯西药常规治疗,治疗组采用豁痰化瘀利水方治疗。观察两组治疗的疗效差别。结果治疗组总有效率为93.4%,对照组总有率为64.7%,差异有统计学意义(P<0.05)。结论豁痰化瘀利水方能明显减轻减轻脑损伤的继发性脑改变,明显改善脑损伤预后,降低再出血的危险。

Effect of Carburization on the Mechanical Properties of Biomedical Grade Titanium Alloys

Titanium cermets were successfully synthesized on the surface of biomedical grade titanium alloys by using sequential carburization method. The mechanical properties such as hardness, fracture toughness and plasticity were measured to estimate the potential application of titanium cermets. The results show that after carburization the surface hardness of titanium cermets was 778 HV, with a significant improvement of 128% compared with that of titanium alloys. In addition, the fracture toughness of titanium cermets was 21.5 × 10^6 Pa.m^1/2, much higher than that of other ceramics. Furthermore, the analysis of the loading-unloading curve in the nanoindentation test also indicates that the plasticity of titanium cermet reached 32.1%, a relatively high value which illustrates the combination of the metal and ceramics properties. The results suggest that sequential carburization should be an efficient way to produce titanium cermets with hard surface, high toughness and plasticity.

In-situ assembly of TiO2 with high exposure of(001)facets on three-dimensional porous graphene aerogel for lithium-sulfur battery

Resulting from the development of electric vehicles,high energy-density Li-S batteries have recently attracted ever-increasing attentions worldwide.However,continuous dissolution of cathodic sulfur and followed shuttle effect of polysulfides lead to very limited service lifetime for currently-applied Li-S batteries.Herein,a 3 D porous graphene aerogel(GA)decorated with high exposure of anatase TiO2(001)nanoplatelets is proposed as robust host to immobilize cathodic sulfur.Compared with commonly used TiO2(101)nanoparticles,the Ti O2(001)nanoplatelets have highly matched lattices with graphene(002)nanosheets,thus facilitating the electronic transfer.The in-site assembled TiO2@GA host exhibits superior sulfur-immobilized capability,which cannot only entrap sulfur by physical confinement,but also capture dissoluble sulfurous species by chemical bonding.The fabricated S@TiO2@GA cathode shows excellent electrochemical performance with high discharge capacity,superior rate capability,and durable cycling stability as well,supposed to be a promising cathode for high-performance Li-S battery applications.

Review of Budd-Chiari Syndrome

This study aims to report the Budd-Chiari syndrome clinical research status and progress that has occurred in over nearly 30 years in China, and emphasize the value of imaging in facilitating the diagnosis of Budd-Chiari syndrome based on more than 2500 cases. Findings on ultrasonography, computed tomography, magnetic resonance imaging, and digital subtraction angiography images are used to propose new Budd-Chiari syndrome types and subtypes. The new subtype classification presented here has important value for guiding interventional treatment.This study also proposes a new concept of anatomical and functional obstruction of hepatic vein that stresses the compensatory value of accessory hepatic vein and azygos vein and describes the risk of manipulation of the communication branch of inferior vena cava obstruction in interventional therapy.

Experimental Study on Rotation Resistance Coefficient of Motor Bogie for Type A Vehicle

Rotation resistance coefficient is an important operating parameter for vehicle bogies, which influences the dynamic behavior of vehicles directly. A research on the rotation resistance coefficient of type A vehicle motor bogies was conducted by means of theoretical calculation, dynamic simulation, test certification, and so on. Result of the simulation analysis shows that the rotation resistance coefficient relates to air springs stiffness and negotiated curve radii, and it varies proportionally with the change of air springs horizontal stiffness. The greater the rotation angle is, the greater the factor becomes. The certifications made under the operating conditions(e.g., different air spring status, different rotation speeds) indicate that the rotation resistance coefficient increases with the increase of the rotation speed. The anti-yaw dampers can contribute to the rotation resistance torque acted on bogie, and the greater the rotation speeds are, the greater the torque generated by the anti-yaw dampers is. The results suggest that the theoretical analysis and dynamics simulation are in accordance with the results from the bogie bench tests, which meet the requirements in EN14363 and the indicators in vehicles safe operation.

Scalable preparation of water-soluble ink of few-layered WSe2 nanosheets for large-area electronics

Few-layer two-dimensional(2D)semiconductor nanosheets with a layer-dependent band gap are attractive building blocks for large-area thin-film electronics.A general approach is developed to fast prepare uniform and phase-pure 2HWSe2 semiconducting nanosheets at a large scale,which involves the supercritical carbon dioxide(SC-CO2)treatment and a mild sonication-assisted exfoliation process in aqueous solution.The as-prepared 2H-WSe2 nanosheets preserve the intrinsic physical properties and intact crystal structures,as confirmed by Raman,x-ray photoelectron spectroscopy(XPS),and scanning transmission electron microscope(STEM).The uniform 2H-WSe2 nanosheets can disperse well in water for over six months.Such good dispersivity and uniformity enable these nanosheets to self-assembly into thickness-controlled thin films for scalable fabrication of large-area arrays of thin-film electronics.The electronic transport and photoelectronic properties of the field-effect transistor based on the self-assembly 2H-WSe2 thin film have also been explored.

A New Elastoplastic 3D Sand Production Model for Fractured Gas Fields

Reservoirs characterized by high temperature,high-pressure,medium high cementation strength,low porosity,and low permeability,in general,are not affected by sand production issues.Since 2009,however,it is known that cases exists where sand is present and may represent a significant technical problem(e.g.,the the Dina II condensate gas field).In the present study,the main factors affecting sand production in this type of reservoir are considered(mechanical properties,stress fields,production system,completion method and gas flow pattern changes during the production process).On this basis,a new liquid-solid coupled porous elasto-plastic 3D sand production model is introduced and validated through comparison with effective sand production data.The related prediction errors are found to be within 15%,which represents the necessary prerequisite for the utilization of such a model for the elaboration of sand prevention measures.

Research on the influence of grouted sleeves and assembled seams on the deformation and bearing capacity of compression-flexure member

Grouted sleeves can effectively connect precast elements,but the effect of grouted sleeves for increased stiffness and assembled seam for weakening stiffness on the precast column’s mechanical properties is unclear.Based on the full-scale test results of precast columns connected with grouted sleeves and the correctness of the numerical models,the influence analysis of the individual and coupling action of the grouted sleeves and assembled seam on the deformation and bearing capacity of the precast column is carried out.The research results show that grouted sleeves significantly affect the deformation and peak bearing capacity of precast columns;when precast columns are subjected to the action of high axial pressure,grouted sleeves significantly affect the bearing capacity.However,the influence of assembled seams on the peaking capacity of the precast column is more obvious when it was tested under low axial compression.It is recommended that the connection position should be 2 times the height of the grouted sleeve from the bottom of the foundation.

A Model for the Determination of Semi-Circular Spot Corrosion Damage and Residual Strength in Oil Pipes

Pitting corrosion often occurs due to the presence of various corrosive substances,such as CO_(2) and H_(2)S,in the pipe service environment.As a result of this process,the residual strength of oil pipes is reduced and this can compromise the integrity of the entire pipe string.In the present work,a model is introduced on the basis of the API579 standard to determine the so-called stress concentration coefficient.The model accounts for pitting corrosion shapes such as shallow semi-circles,semi-circles,and deep semi-circles.The relationship between the corrosion pit depth and opening diameter and the residual strength of the oil casing is obtained.The results show that the influence of the pit opening diameter on the stress concentration coefficient is smaller than that of the pit depth.For a constant pit opening diameter,the coefficient increases gradually with increasing the pit depth.The compressive strength and internal pressure strength of the carbon steel oil casing decrease accordingly.When the depth of the corrosion pit is relatively small,the growth of the coefficient is slower;when the depth of the corrosion pit increases to a certain value,the increase in stress concentration coefficient becomes obvious.

Classification and Visualization of Surrounding Rock Mass Stability Based on Multi-Dimensional Cloud Model

The classification of the stability of surrounding rock is an uncertain system with multiple indices.The Multidimensional Cloud Model provides an advanced solution through the use of an improved model of One-dimensional Cloud Model.Setting each index as a one-dimensional attribute,the Multi-dimensional Cloud Model can set the digital characteristics of each index according to the cloud theory.The Multi-dimensional cloud generator can calculate the certainty of each grade,and then determine the stability levels of the surrounding rock according to the principle of maximum certainty.Using this model to 5 coal mine roadway surrounding rock examples and comparing the results with those of One-dimensional and Two-dimensional Cloud Models,we find that the Multi-dimensional Cloud Model can provide a more accurate solution.Since the classification results of the Multidimensional Cloud Model are difficult to be presented intuitively and visually,we reduce the Multi-dimensional Cloud Model to One-dimensional and Two-dimensional Cloud Models in order to visualize the results achieved by the Multi-dimensional Cloud Model.This approach provides a more accurate and intuitive method for the classification of the surrounding rock stability,and it can also be applied to other types of classification problems.

Risk Based Technology Qualification Method for HPHT Well

With the increasing demand for new technologies in HPHT (high pressure high temperature) wells, more and more attention has been paid to the system of technical qualifications. Most established norms, standards and recommended practices are written in prescribed formats, setting out methods, procedures and acceptance criteria for product design, manufacture and testing. However, established norms, standards or recommended practices may not adequately cover new technologies or applications. The technical qualification system is established in this paper, which can identify the potential failure modes and some activities in order to control the uncertainties and increase confidence of using new technology. A risk-based technical qualification system is used to assess non-traditional operations. It includes following seven main steps: system breakdown, technology assessment and classification, technical novelty, failure model and risk analysis, risk-based qualification planning and participation level development. The core of technical qualification system is to understand the ways and causes of system failure, and to carry out corresponding activities to provide evidence that the system will not fail. Through the technical identification process, the detailed equipment/operation specifications and identification requirements have been formulated. Different levels of participation are assigned for each eligibility activity, depending on the hazard and risk. It is proved that the application of the technical qualification principle in the systematic evaluation and control of the risks of new technologies or new applications is successful. In HPHT wells in particular, operators can move from a reactive approach to a proactive approach.

Reliability Analysis of Super 13Cr Tubing in Ultra-Deep Gas Well

Abnormal oil casing pressure appeared in the process of test production of multiple Ultra-Deep Gas Wells in Tarim Basin. The super 13Cr oil pipe string was used to analyze the causes of pipe string failure in view of the oil casing channeling well during the test and blowout period. The construction process of the well was analyzed in detail. Combined with the review of the operation flow and the detection of fracture string material and fracture morphology, the causes of pipe string fracture were analyzed and calculated in detail. Through field investigation, analysis and calculation, it was found that the main cause of cracking of super 13Cr tubing in this well is the decrease of vibration natural frequency caused by excessive fluid velocity in pipe and too long span of pipe string. At the same time, the mixed failure of stress corrosion cracking and stress load interaction occurred in Cl&#8722;1 environment and other corrosion environments.

Application of the “Accurate Control Groundwater Resources” Theory in Containment of Groundwater Resource Exhaustion Trend

The continued sustainable economic development of china depends in part,to the scientific management of China’s precious groundwater resources in the coming years.Groundwater resource scarcity is a common underlying problem across China,in addition,the large-scale groundwater exploitation for human consumption over recent decades has resulted in a series of environmental geological problems.As a result of these problems,the national economics in china have been seriously affected.In order to prevent groundwater resource exhaustion and environmental geology deterioration,“accurate control of groundwater resources(ACGR)”theory and its support system were established in this article,and the related prevention measures of the ACGR theory,such as accurate irrigation,accurate supply water,and accurate subsidies,were proposed.This paper highlights the ACGR theory as an efficient and essential way to achieve the sustainable groundwater resource management,which can be applied to countries such as China.

Fish Skin-Inspired Janus Hydrogel Coating for Drag Reduction

Comprehensive Summary,In nature,fishes have evolved functional skins with effective hydrodynamic performance and anti-fouling,facilitating predation and escaping from predators.Although a large number of fish scale-inspired structured surfaces have been explored,the incorporation of mucus on the structured surfaces has been largely ignored.Inspired by the skin of Osteichthyes fishes,a Janus hydrogel coating(JHC)is successfully prepared by a two-step UV light irradiation at room temperature.The bottom side of JHC(STH)achieves a shear adhesive strength of 103.3±17.5 kPa and can strongly adhere to a large variety of surfaces,including metals,ceramic and polymers.The top surface of JHC(SLH)replicates the structure of cycloid scales,while the nature of hydrogel mimics the mucus on fish skin.SLH possesses prominent mechanical,anti-swelling,anti-fouling and drag reduction properties.The design strategy for JHC has potential applications in numerous fields,like,pipeline transportation,bioengineering,and shipping industry.

Plant photobiology: From basic theoretical research to crop production improvement

As one of the most important environmental signals for plants,light plays a profound role in regulating virtually every aspect of plant growth and development.Light signals are perceived by plants via several families of photoreceptors,among which phytochromes are responsible for absorbing the red(R)and far-red(FR)wavelengths(600–750 nm),cryptochromes(CRYs)perceive the blue(B)/ultraviolet-A(UV-A)wavelengths(320–500 nm),and UV RESISTANCE LOCUS 8(UVR8)is a recently-characterized UV-B(280–320 nm)photoreceptor.

Biological nitrogen fixation in paddy soils is driven by multiple edaphic factors and available phosphorus is the greatest contributor

Biological nitrogen(N)fixation(BNF)is important for sustainable rice cultivation.Various edaphic factors have been individually evaluated for their effects on BNF in paddy soils.However,no single factor could fully explain the different soil outcomes.Paddy BNF is more likely to be simultaneously influenced to various degrees by combinations of several edaphic factors;however,the relative importance of the interaction of multiple edaphic factors on the regulation of BNF in paddy soils is still unclear.Twenty-seven paddy soil samples with different soil properties were collected from the major rice cropping areas in Southwest and Northeast China to determine the edaphic factors affecting paddy BNF amount.Rice was transplanted into pots filled with paddy soils and grown in a^(15)N_2-enriched airtight chamber.Estimation of BNF was based on the measurements of^(15)N enrichment in the paddy soils and rice plants at the end of a 77-d incubation period.The BNF amounts ranged from 0.66 to 12.3 kg ha^(-1),with a significant positive relationship with available phosphorus(AP)and significant quadratic relationships with available molybdenum(AMo)and total N(TN).Available P explained 42%of the observed variation in BNF,TN explained 17%,and AMo explained 13%.The specific interaction between soil cation exchange capacity and available soil N(as determined by rice N uptake)accounted for 28%of the variation in BNF.The BNF amount was decreased when AP was<14 mg kg^(-1),AMo<0.09 mg kg^(-1),or TN was>3.2 g kg^(-1).These results provide valuable benchmarks that could be used to guide farmers in managing paddy soils to improve the potential contribution of paddy BNF to soil fertility.

校企联动引领“产品工程学”课程创新实践

对传统课堂教育模式中面临的主要问题进行剖析,指出“校企联动”教育改革的必要性。以北京化工大学“产品工程学”课程为案例,邀请企业专家加盟,构建校企联动授课新模式,并从课程设计、教学团队组建和课程教学三方面介绍课程内涵。这种创新教学模式将有助于提高学生综合能力,提升教育教学质量,提升企业创新能力。