Investigation of anisotropic strength criteria for layered rock mass

Layered rock mass is a type of engineering rock mass with sound mechanical anisotropy,which is generally unfavorable to the stability of underground works.To investigate the strength anisotropy of layered rock,the Mohr-Coulomb and Hoek-Brown criteria are introduced to establish the two transverse isotropic strength criteria based on Jaeger's single weak plane theory and maximum axial strain theory,and parameter determination methods.Furthermore,the sensitivity of strength parameters(K 1,K 2,and K 3)that are used to characterize the anisotropy strength of non-sliding failure involved in the strength criteria and confining pressure are investigated.The results demonstrate that strength parameters K 1 and K 2 affect the strength of layered rock samples at all bedding angles except for the bedding angle of 90°and the angle range that can cause the shear sliding failure along the bedding plane.The strength of samples at any bedding angle decreases with increasing K 1,whereas the opposite is for K 2.Except for bedding angles of 0°and 90°and the bedding angle range that can cause the shear sliding along the bedding plane,K 3 has an impact on the strength of rock samples with other bedding angles that the specimens'strength increases with increase of K 3.In addition,the strength of the rock sample increases as confining pressure rises.Furthermore,the uniaxial and triaxial tests of chlorite schist samples were carried out to verify and evaluate the strength criteria proposed in the paper.It shows that the predicted strength is in good agreement with the experimental results.To test the applicability of the strength criterion,the strength data of several types of rock in the literature are compared.Finally,a comparison is made between the fitting effects of the two strength criteria and other available criteria for layered rocks.

Determining role of heterogeneous microstructure in lowering yield ratio and enhancing impact toughness in high-strength low-alloy steel

Here we present a novel approach of intercritical heat treatment for microstructure tailoring,in which intercritical annealing is introduced between conventional quenching and tempering.This induced a heterogeneous microstructure consisting of soft intercritical ferrite and hard tempered martensite,resulting in a low yield ratio(YR)and high impact toughness in a high-strength low-alloy steel.The initial yielding and subsequent work hardening behavior of the steel during tensile deformation were modified by the presence of soft intercritical ferrite after intercritical annealing,in comparison to the steel with full martensitic microstructure.The increase in YR was related to the reduction in hardness difference between the soft and hard phases due to the precipitation of nano-carbides and the recovery of dislocations during tempering.The excellent low-temperature toughness was ascribed not only to the decrease in probability of microcrack initiation for the reduction of hardness difference between two phases,but also to the increase in resistance of microcrack propagation caused by the high density of high angle grain boundaries.

Characterizing large-scale weak interlayer shear zones using conditional random field theory

The shear behavior of large-scale weak intercalation shear zones(WISZs)often governs the stability of foundations,rock slopes,and underground structures.However,due to their wide distribution,undulating morphology,complex fabrics,and varying degrees of contact states,characterizing the shear behavior of natural and complex large-scale WISZs precisely is challenging.This study proposes an analytical method to address this issue,based on geological fieldwork and relevant experimental results.The analytical method utilizes the random field theory and Kriging interpolation technique to simplify the spatial uncertainties of the structural and fabric features for WISZs into the spatial correlation and variability of their mechanical parameters.The Kriging conditional random field of the friction angle of WISZs is embedded in the discrete element software 3DEC,enabling activation analysis of WISZ C2 in the underground caverns of the Baihetan hydropower station.The results indicate that the activation scope of WISZ C2 induced by the excavation of underground caverns is approximately 0.5e1 times the main powerhouse span,showing local activation.Furthermore,the overall safety factor of WISZ C2 follows a normal distribution with an average value of 3.697.

Research on Asymmetric Fault Location of Wind Farm Collection System Based on Compressed Sensing

Aiming at the problem that most of the cables in the power collection systemof offshore wind farms are buried deep in the seabed,whichmakes it difficult to detect faults,this paper proposes a two-step fault location method based on compressed sensing and ranging equation.The first step is to determine the fault zone through compressed sensing,and improve the datameasurement,dictionary design and algorithmreconstruction:Firstly,the phase-locked loop trigonometric functionmethod is used to suppress the spike phenomenon when extracting the fault voltage,so that the extracted voltage valuewillnot have a large error due to the voltage fluctuation.Secondly,theλ-NIM dictionary is designed by using the node impedancematrix and the fault location coefficient to further reduce the influence of pseudo-fault points.Finally,the CoSaMP algorithmis improved with the generalized Jaccard coefficient to improve the reconstruction accuracy.The second step is to use the ranging equation to accurately locate the asymmetric fault of the wind farm collection system on the basis of determining the fault interval.The simulation results show that the proposedmethod ismore accurate than the compressedsensingmethod andimpedancemethod in fault section location and fault location accuracy,the relative error is reduced from 0.75%to 0.4%,and has a certain anti-noise ability.

大庆油田修井工艺技术现状及发展方向

大庆油田在开发20年后的1979年,出现了一百口故障井,随着油水井生产年限的增长,加上地质条件和工程因素的影响,套管损坏速度明显加快,出现了成片套损区,出现了三次套损高峰期。套损井的出现,破坏了注采关系的完整性,严重影响了油田正常生产。为此,从1980年开始,采油工程系统根据油田不同时期的套损形式,研发了适应5-1/2″套管的解卡打捞、整形加固、取换套、侧斜及水平井修井等修井技术,达到年修复2000口井以上的施工能力,修复率不断提高,治理了成片套损区,提高了油水井利用率,"十二五"以来,修复率保持在85%左右,平均年恢复产油量24.96×10~4t,年恢复注水量805.85×10~4 m^3,完善了注采关系,为油田生产开发起到了保驾护航的重要作用,"十三五"及以后大修技术将面临新矛盾,提出其应向疑难复杂套损井修井、水平井套管密封加固、环保修井、智能可视化修井等方向发展。

Hippo/YAP signaling pathway is involved in osteosarcoma chemoresistance

Background:Osteosarcoma is the most common bone malignancy in children and adolescents,and 20%-30%of the patients suffer from poor prognosis because of individual chemoresistance.The Hippo/yes-associated protein(YAP) signaling pathway has been shown to play a role in tumor chemoresistance,but no previous report has focused on its involvement in osteosarcoma chemoresistance.This study aimed to investigate the role of the Hippo/YAP signaling pathway in osteosarcoma chemoresistance and to determine potential treatment targets.Methods:Using the Cell Titer-Glo Luminescent cell viability assay and flow cytometry analysis,we determined the proliferation and chemosensitivity of YAP-overexpressing and YAP-knockdown osteosarcoma cells.In addition,using western blotting and the real-time polymerase chain reaction technique,we investigated the alteration of the Hippo/YAP signaling pathway in osteosarcoma cells treated with chemotherapeutic agents.Results:Mammalian sterile 20-like kinase 1(MST1) degradation was increased,and large tumor suppressor kinase1/2(LAT51/2) total protein levels were decreased by methotrexate and doxorubicin,which increased activation and nuclear translocation of YAP.Moreover,YAP increased the proliferation and chemoresistance of MG63 cells.Conclusions:The Hippo/YAP signaling pathway plays a role in osteosarcoma chemoresistance,and YAP is a potential target for reducing chemoresistance.

Recent progress in third-generation low alloy steels developed under M^3 microstructure control

During the past thirty years, two generations of low alloy steels(ferrite/pearlite followed by bainite/martensite) have been developed and widely used in structural applications. The third-generation of low alloy steels is expected to achieve high strength and improved ductility and toughness, while satisfying the new demands for weight reduction, greenness, and safety. This paper reviews recent progress in the development of third-generation low alloy steels with an M^3 microstructure, namely, microstructures with multi-phase, meta-stable austenite, and multi-scale precipitates. The review summarizes the alloy designs and processing routes of microstructure control, and the mechanical properties of the alloys.The stabilization of retained austenite in low alloy steels is especially emphasized. Multi-scale nano-precipitates, including carbides of microalloying elements and Cu-rich precipitates obtained in third-generation low alloy steels, are then introduced. The structure–property relationships of third-generation alloys are also discussed. Finally, the promises and challenges to future applications are explored.

The Earliest Ascidiate Carpel and Its Implications for Angiosperm Evolution

According to the classic doctrine of angiosperm evolution,the archetype carpel in angiosperms is of plicate form.However,this concept is facing increasing challenges from the systematics based on molecular data,which now takes ascidiate carpel as ancestral.This reorientation in evolutionary thinking cannot be fully achieved unless there is supporting fossil evidence.Here a fruit, named Liaoningfructus,is reported from the famous Yixian Formation(Early Cretaceous,125 Ma), which yielded several pioneer angiosperms in the past decades.The configuration of the fruit suggests that the carpel giving rise to the fruit is most likely ascidiate,favoring the above reorientation.There are two seeds in the fruit,and at least one of them is served by a vascular bundle arising from the bottom of the fruit,implying a basal placentation in the former carpel,which again is different from the classic thinking.This discovery not only enhances the diversity of angiosperms in the Yixian Formation,but also accelerates the on-going switching of thinking on angiosperm evolution.

Fuzzy sliding mode control guidance law with terminal impact angle and acceleration constraints

In this paper, a novel fuzzy sliding mode control（FSMC） guidance law with terminal constraints of miss distance, impact angle and acceleration is presented for a constant speed missile against the stationary or slowly moving target. The proposed guidance law combines the sliding mode control algorithm with a fuzzy logic control scheme for the lag-free system and the first-order lag system. Through using Lyapunov stability theory, we prove the sliding surface converges to zero in finite time. Furthermore, considering the uncertain information and system disturbances, the guidance gains are on-line optimized by fuzzy logic technique. Numerical simulations are performed to demonstrate the performance of the FSMC guidance law and the results illustrate the validity and effectiveness of the proposed guidance law.

The regulatory impact of immune inhibitors on T cells of SD rats

Objective:To observe the regulatory impact of immune inhibitors on T cells in rats.Method:Forty SD rats were selected and randomly divided into experimental group and control group.Rapamycin(SRL)0.4 mg/d to fill the stomach of the former one,saline lavage was used with the latter one for two weeks.Using flow cytometry to detect the two groups of rats with spleen and thymus level of CD4+CD25+T cells;and the spleen cells FoxP3 mRNA expression;Using ELISA method to detect TGF-β,IL-10 levels.Results:The peripheral blood,spleen and thymus of CD4+CD25+T cells accounted for the proportion of mononuclear cells were significantly higher than that of control group(P<0.05);FoxP3 mRNA expression quantity also significantly higher than the control group(P<0.05);Experimental TGF-βin rats,IL-10 levels are significantly higher than control group(P<0.05).Conclusions:Immune inhibitors can regulatory CD4+CD25+foxp3+T cells in rats,a single nuclear cell proportion increase,shows that it can induce rat CD4+CD25+foxp3+regulatory T cells proliferation.

Polymorphism of heat shock protein 70-2 and enterocutaneous fistula in Chinese population

AIM:To investigate whether the heat shock protein 70-2(HSP70-2) polymorphism is associated with enterocutaneous fistulas in a Chinese population.METHODS:This study included 131 patients with enterocutaneous/enteroatmospheric fistulas.Patients with inflammatory bowel disease or other autoimmune diseases were excluded from this study.All patients with enterocutaneous/enteroatmospheric fistulas were followed up for three months to observe disease recurrence.In addition,a total of 140 healthy controls were also recruited from the Jinling Hospital,matched according to the sex and age of the patient population.Genomic DNA was extracted from peripheral blood from each participant.The HSP70-2 restriction fragment length polymorphism related to the polymorphic PstI site at position 1267 was characterized by polymerase chain reaction(PCR).First PCR amplification was carried out,and then PCR products were digested with PstI restriction enzyme.The DNA lacking the polymorphic PstI site within HSP70-2 generates a product of 1117 bp in size(allele A),whereas the HSP70-2 PstI polymorphism produces two fragments of 936 bp and 181 bp in size(allele B).RESULTS:The frequency of the HSP70-2 PstI polymorphism did not differ between patients and controls;however,the A allele was more predominant in patients with enterocutaneous fistulas than in controls(60.7% vs 51.4%,P = 0.038,OR = 1.425,95%CI:1.019-1.994).Sixty-one patients were cured by a definitive operation,drainage operation,or percutaneous drainage while 52 patients were cured by nonsurgical treatment.There was no significant difference in the frequency of the HSP70-2 PstI polymorphism between the patients who had surgery compared to those who did not(P = 0.437,OR = 1.237,95%CI:0.723-2.117).Moreover,11 patients refused any treatment for economic reasons or tumor burden,and 7 patients with enterocutaneous fistulas(5.8%) died during the followup period.However,there was no significant difference in the frequency of the HSP70-2 PstI polymorphism between the patients who survived compared to those who died(P = 0.403,OR = 0.604,95%CI:0.184-1.986).CONCLUSION:The A allele of the HSP70-2 PstI polymorphism was associated with enterocutaneous fistulas in this Chinese population.

CNT toughened aluminium and CFRP interface for strong adhesive bonding

This study presents a simple technique for strengthening the adhesive-bond strength between aluminium(Al)substrate and carbon fibre reinforced polymer(CFRP) utilising resin pre-coating(RPC) with carbon nanotubes(CNTs). The CNT-containing RPC solution with 90 wt% acetone and 10 wt% resin(without hardener) was applied onto Al substrates, where micro-/nano-vertical channels had been created by chemical or mechanical surface treatments to accommodate CNTs. RPC was able to fill all micro-/nano-cavities over the Al substrate surface, then CNTs were pulled into those vertical micro-channels by the capillary action generated from acetone evaporation.Normal epoxy adhesive(resin + hardener) was applied after the CNT-containing RPC treatment. CNTs bridging across the interface between the adhesive joint and Al substrate and sealing of micro-/nano-cavities by RPC effectively enhanced the interfacial shear bond strength between the Al substrate and CFRP by 30–100%depending on the Al substrate surface profiles. Al substrates with two different chemical treatments were compared in this study for the effectiveness of CNT interfacial reinforcement. Results from a steel substrate after sandblasting were also included for comparison.

Electrically Tunable Wafer-Sized Three-Dimensional Topological Insulator Thin Films Grown by Magnetron Sputtering

Three-dimensional(3 D)topological insulators(TIs)are candidate materials for various electronic and spintronic devices due to their strong spin-orbit coupling and unique surface electronic structure.Rapid,low-cost preparation of large-area TI thin films compatible with conventional semiconductor technology is the key to the practical applications of TIs.Here we show that wafer-sized Bi2Te3 family TI and magnetic TI films with decent quality and well-controlled composition and properties can be prepared on amorphous SiO2/Si substrates by magnetron cosputtering.The SiO2/Si substrates enable us to electrically tune(Bi1-xSbx)2Te3 and Cr-doped(Bi1-xSbx)2 Te3 TI films between p-type and n-type behavior and thus study the phenomena associated with topological surface states,such as the quantum anomalous Hall effect(QAHE).This work significantly facilitates the fabrication of TI-based devices for electronic and spintronic applications.

Dependence of domain wall structures on repetition n in[Pt(0.5 nm)/Co(0.4 nm)]_n/NiO(1.1 nm)/[Co(0.4 nm)/Pt(0.5 nm)]_n multilayers

The magnetic force microscopy and a sample vibrating magnetometer have been used to investigate the domain structure in two antiferromagnetically coupled Co/Pt multilayers.In the antiferromagnetic coupled[Pt（0.5 nm）/Co（0.4 nm）]n/NiO（1.1 nm）/[Co（0.4 nm）/Pt（0.5 nm）]n multilayers with perpendicular anisotropy,the antiferromagnetic interlayer coupling strength increases linearly with the repetition number n in Co/Pt multilayers.In demagnetized states,relatively shifted domain walls in the two Co/Pt multilayers are observed,with net ferromagnetic stripes formed between them for the repetition number n less than 5,and the stripe width decreases with the increase of n.The occurrence of these features can be attributed to the competition between the interlayer coupling and magnetostatic energies.

Correlation of serum Dickkopf-1 content with bone destruction, inflammatory response and oxidation reaction in patients with gouty arthritis

Objective:To study the correlation of serum Dickkopf-1 (DKK-1) content with bone destruction, inflammatory response and oxidation reaction in patients with gouty arthritis. Methods: A total of 40 patients with acute gouty arthritis who were treated in our hospital between 2013 and 2016 were selected as the group A of the study, 56 patients with asymptomatic hyperuricemia who were treated in our hospital during the same period were selected as the group B of the study, and 60 healthy volunteers who received physical examination in our hospital during the same period were selected as the control group of the study. The serum was collected to detect the contents of DKK-1, bone destruction indexes, inflammatory response indexes and oxidation reaction indexes.Results:Serum DKK-1, TRACP5b, RANKL,β-CTX, PGE2, sICAM-1, sVCAM-1, sCD14, MDA, 8-OHdG and 3-NT levels of group A and group B were significantly higher than those of control group while SOD and GSH-Px levels were significantly lower than those of control group;serum DKK-1, TRACP5b, RANKL,β-CTX, PGE2, sICAM-1, sVCAM-1, sCD14, MDA, 8-OHdG and 3-NT levels of group A were significantly higher than those of group B while SOD and GSH-Px levels were significantly lower than those of group B;serum DKK-1 level was positively correlated with TRACP5b, RANKL,β-CTX, PGE2, sICAM-1, sVCAM-1, sCD14, MDA, 8-OHdG and 3-NT levels, and negatively correlated with SOD and GSH-Px levels. Conclusion:Abnormally elevated DKK-1 in patients with gouty arthritis can induce articular bone destruction as well as inflammatory response and oxidative stress response activation.

水产品中嗜水气单胞菌耐药性研究进展

嗜水气单胞菌Aeromonas hydrophila具有广泛的致病性,是水生动物最常见的致病菌之一。由于抗生素不合理使用、质粒以及耐药基因的水平转移等因素,来自零售市场、超市和餐厅的即食海鲜产品中,均可分离出大量的嗜水气单胞菌耐药菌株及其耐药基因。因此,探明关键控制点、寻求有效缓解抗生素耐药性的防控策略至关重要。文中介绍了我国嗜水气单胞菌的耐药现状,嗜水气单胞菌的主要侵染及耐药机制,以及目前削减和防控耐药性的主要手段和策略,并对水产品耐药性研究方向和重点作出展望。

PMDA/ODA型聚酰亚胺薄膜的热氧化降解动力学研究

聚酰亚胺薄膜热氧化降解为多步反应过程,仅通过单一动力学三要素(表观降解活化能E、反应模型f(α)以及指前因子A)无法充分反映其降解行为特性.本研究基于均苯四甲酸二酐/4,4'-二氨基二苯醚(PMDA/ODA)型聚酰亚胺薄膜线性升温条件下的热氧化失重微分曲线,采用Fraser-Suzuki方程进行分峰拟合,将降解过程中每个反应步骤对应的失重行为区分开来,而后通过Friedman方法以及Master-plots理论对每个反应过程单独进行动力学分析,确定相应的E,f(α),以及A值.动力学分析结果表明聚酰亚胺薄膜热氧化降解过程包含2个主反应,两者的E值分别为154.00和139.27 kJ/mol,lnA值分别为18.55和16.74 s−1,且这2个主反应均符合理论Avrami-Erofeev模型.在此基础上,通过以上动力学参数重建并预测了动力学分析过程中所采用的升温程序以内以及之外的热失重曲线,验证了动力学参数的有效性.

Collaborative validation of GlobeLand30:Methodology and practices

30-m Global Land Cover(GLC)data products permit the detection of land cover changes at the scale of most human land activities,and are therefore used as fundamental information for sustainable development,environmental change studies,and many other societal benefit areas.In the past few years,increasing efforts have been devoted to the accuracy assessment of GlobeLand30 and other finer-resolution GLC data products.However,most of them were conducted either within a limited percentage of map sheets selected from a global scale or in some individual countries(areas),and there are still many areas where the uncertainty of 30-m resolution GLC data products remains to be validated and documented.In order to promote a comprehensive and collaborative validation of 30-m GLC data products,the GEO Global Land Cover Community Activity had organized a project from 2015 to 2017,to examine and explore its major problems,including the lack of international agreed validation guidelines and on-line tools for facilitating collaborative validation activities.With the joint effort of experts and users from 30 GEO member countries or participating organizations,a technical specification for 30-m GLC validation was developed based on the findings and experiences.An on-line validation tool,GLCVal,was developed by integrating land cover validation procedures with the service computing technologies.About 20 countries(regions)have completed the accuracy assessment of GlobeLand30 for their territories with the guidance of the technical specification and the support of GLCVal.

Near-infrared light activated persistent luminescence nanoparticles via upconversion

Persistent luminescence nanoparticles （PLNPs） and upconversion nanoparticles （UCNPs） are two special optical imaging nanoprobes. In this study, efficient upconverted persistent luminescence （UCPL） is realized by combining their unique features into polymethyl methacrylate, forming a film composed of both PLNPs and UCNPs. The red persistent luminescence （-640 nm） of the PLNPs （CaS：Eu,Tm, Ce） can be activated by upconverted green emission of UCNPs （-NaYF4：Yb, Er@NaYF4） excited by near-infrared light （NIR）. Using this strategy, both the unique optical properties of PLNPs and UCNPs can be optimally synergized, thus generating efficient upconversion, photoluminescence, and UCPL simultaneously. The UCPL system has potential applications in in vivo bioimaging by simply monitoring the biocompatible low power density of NIR-light-excited persistent luminescence. Due to its simplicity, we anticipate that this method for the preparation of UCPL composite can be easily adjusted using other available upconversion and persistent phosphor pairs for a number of biophotonic and photonic applications.

Finite Time Convergent Wavelet Neural Network Sliding Mode Control Guidance Law with Impact Angle Constraint

This paper presents a novel guidance law to intercept non-maneuvering targets with impact angle and lateral acceleration command constraints. Firstly, we formulate the impact angle control to track the desired line-of-sight(LOS) angle, which is achieved by selecting the missile s lateral acceleration to enforce the sliding mode on a sliding surface at impact time. Secondly, we use the Lyapunov stability theory to prove the stability and finite time convergence of the proposed nonlinear sliding surface. Thirdly, we introduce the wavelet neural network(WNN) to adaptively update the additional control command and reduce the high-frequency chattering of sliding mode control(SMC). The proposed guidance law, denoted WNNSMC guidance law with impact angle constraint,combines the SMC methodology with WNN to improve the robustness and reduce the chattering of the system. Finally, numerical simulations are performed to demonstrate the validity and effectiveness of the WNNSMC guidance law.