双线隧道暗挖法施工对既有地下管道影响的数值模拟研究

城市的快速发展导致地面交通拥挤,大量地下隧道被修建,修建过程中会遇到地下管线或者其他隧道等情况,如何安全的修建是重中之重。目前隧道修建的理论知识远远落后于工程实践,需发展隧道修建的相关研究。浅埋暗挖法是一个修建隧道的重要方法,施工过程中对地面扰动小,不影响地面交通和建筑物,需要的资金和设备相对较少,可以开挖多种不同的断面,本文基于北京地铁六号线西延段田村站~海淀五路居站区间隧道的开挖,利用FLAC3D建模,通过更换土压大小和衬砌参数来分析土压、衬砌参数等对地面沉降的影响以及浅埋暗挖法对管线的影响。

In-situ reduction of silver by surface DBD plasma:a novel method for preparing highly effective electromagnetic interference shielding Ag/PET

Electromagnetic interference(EMI)shielding composites with good flexibility and weatherability properties have attracted increased attention.In this study,we combined the surface modification method of sub-atmospheric pressure glow discharge plasma with in situ atmospheric pressure surface dielectric barrier discharge plasma(APSDBD)reduction to prepare polyethylene terephthalate supported silver(Ag/PET).Due to the prominent surface modification of PET film,mild plasma reduction,and effective control of the silver morphology by polyvinylpyrrolidone(PVP),a 3.32μm thick silver film with ultralow sliver loading(0.022 wt%)exhibited an EMI shielding efficiency(SE)of 39.45 d B at 0.01 GHz and 31.56 d B at 1.0 GHz(>30 d B in the range of 0.01–1.0 GHz).The SEM results and EMI shielding analysis indicated that the high performance originated from the synergistic effect of the formation of silver nanoparticles(Ag NPs)with preferentially oriented cell-like surface morphologies and layer-by-layer-like superimposed microstructures inside,which demonstrated strong microwave reflection properties.Fourier transform infrared spectrometer and x-ray diffractometer showed that the surface structures of the heat-sensitive substrate materials were not destroyed by plasma.Additionally,APSDBD technology for preparing Ag/PET had no special requirements on the thickness,dielectric constant,and conductivity of the substrate,which provides an effective strategy for manufacturing metal or alloy films on surfaces of heat-sensitive materials at a relatively low cost.

Somatic CDKN2A copy number variations are associated with the prognosis of esophageal squamous cell dysplasia

Background:Somatic copy number variations(SCNVs)in the CDKN2A gene are among the most frequent events in the dysplasia-carcinoma sequence of esophageal squamous cell carcinoma.However,whether CDKN2A SCNVs are useful biomarkers for the risk stratification and management of patients with esophageal squamous cell dysplasia(ESCdys)is unknown.This study aimed to investigate the characteristics and prognostic value of CDKN2A SCNVs in patients with mild or moderate(m/M)ESCdys.Methods:This study conducted a prospective multicenter study of 205 patients with a baseline diagnosis of m/M ESCdys in five high-risk regions of China(Ci County,Hebei Province;Yanting,Sichuan Province;Linzhou,Henan Province;Yangzhong,Jiangsu Province;and Feicheng,Shandong Province)from 2005 to 2019.Genomic DNA was extracted from paraffin biopsy samples and paired peripheral white blood cells from patients,and a quantitative polymerase chain reaction assay,P16-Light,was used to detect CDKN2A copy number.The cumulative regression and progression rates of ESCdys were evaluated using competing risk models.Results:A total of 205 patients with baseline m/M ESCdys were enrolled.The proportion of ESCdys regression was significantly lower in the CDKN2A deletion cohort than in the diploid and amplification cohorts(18.8%[13/69]vs.35.0%[28/80]vs.51.8%[29/56],P<0.001).In the univariable competing risk analysis,the cumulative regression rate was statistically significantly lower(P=0.008),while the cumulative progression rate was higher(P=0.017)in ESCdys patients with CDKN2A deletion than in those without CDKN2A deletion.CDKN2A deletion was also an independent predictor of prognosis in ESCdys(P=0.004)in the multivariable analysis.Conclusion:The results indicated that CDKN2A SCNVs are associated with the prognosis of ESCdys and may serve as potential biomarkers for risk stratification.

Microstructure and Mechanical Properties of the Ti_(62)Nb_(12)Mo_(12)Ta_(12)W_(2)Refractory High Entropy Alloy Prepared through Spark Plasma Sintering

A refractory high entropy alloy Ti_(62)Nb_(12)Mo_(12)Ta_(12)W_(2)was prepared by mechanical alloying and spark plasma sintering.The microstructure and mechanical properties of the Ti_(62)Nb_(12)Mo_(12)Ta_(12)W_(2)alloy were analyzed.The experimental results show that the microstructure of the alloy is composed of two BCC phases,an FCC precipitated phase,and the precipitated phase which is a mixture of TiC,TiN and TiO.The alloy exhibits good room temperature compressive properties.The plasticity of the sample sintered at 1550℃can reach 10.8%,and for the sample sintered at 1600℃,the yield strength can be up to 2032 MPa,in the meantime the plasticity is 9.4%.The alloy also shows high strength at elevated temperature.The yield strength of the alloy exceeds 420 MPa at 900℃,and value of which is still above 200 MPa when the test temperature reaches 1000℃.Finally,the compressive yield strength model at room temperature is constructed.The prediction error of the model ranges from−7.9%to−12.4%,expressing fair performance.

Microbial and epidemiological factors in early detection of esophageal squamous cell carcinoma and precancerous lesions

To the Editor:Esophageal cancer(EC)ranks ninth and fifth among the leading cause of global cancer-related morbidity and mortality,respectively.[1]Esophageal squamous cell carcinoma(ESCC)is the predominant histologic subtype of EC in China.Population screening effectively decreases the morbidity and mortality of ESCC,highlighting the necessity of early detection and early diagnosis.

Cell membrane coating for reducing nanoparticle-induced inflammatory responses to scaffold constructs

The controlled release of therapeutics from microparticles or nanoparticles （NPs） has been well-studied. Incorporation of these particles inside biomaterial scaffolds is promising for tissue regeneration and immune modulation. However, these particles may induce inflammatory and foreign body responses to scaffold constructs, limiting their applications. Here we show that widely used poly（lactic-co-glycolic acid） nanoparticles （PLGA NPs） formed by double emulsion dramatically increased neutrophil infiltration and pro-inflammatory cytokines in alginate scaffolds 1 day after the subcutaneous injection of the scaffolds into mice. The coating of red blood cell （RBC） membranes on PLGA NPs completely eliminated these short-term inflammatory responses. For a longer term of 10 days, neither PLGA NPs nor RBC membrane-coated NPs exerted a significant effect on the infiltration of neutrophils or macrophages in alginate scaffolds, possibly due to the degradation and/or clearance of NPs by infiltrating cells. Despite the extensive exploration of cell membrane-coated NPs, our study is the first to investigate the effects of cell membrane coating on foreign body reaction to NPs. By harnessing the natural biocompatibility of cell membranes, our strategy of anti-inflammatory protection for scaffolds may be pivotal for many applications such as those relying on the recruitment of stem cells and/or progenitor ceils to scaffolds.

Associations between cancer family history and esophageal cancer and precancerous lesions in high-risk areas of China

Background:Family clustering of esophageal cancer(EC)has been found in high-risk areas of China.However,the relationships between cancer family history and esophageal cancer and precancerous lesions(ECPL)have not been comprehensively reported in recent years.This study aimed to provide evidence for identification of high-risk populations.Methods:This study was conducted in five high-risk areas in China from 2017 to 2019,based on the National Cohort of Esophageal Cancer.The permanent residents aged 40 to 69 years were examined by endoscopy,and pathological examination was performed for suspicious lesions.Information on demographic characteristics,environmental factors,and cancer family history was collected.Unconditional logistic regression was applied to evaluate odds ratios between family history related factors and ECPL.Results:Among 33,008 participants,6143(18.61%)reported positive family history of EC.The proportion of positive family history varied significantly among high-risk areas.After adjusting for risk factors,participants with a family history of positive cancer,gastric and esophageal cancer or EC had 1.49-fold(95%confidence interval[CI]:1.36-1.62),1.52-fold(95%CI:1.38-1.67),or 1.66-fold(95%CI:1.50-1.84)higher risks of ECPL,respectively.Participants with single or multiple first-degree relatives(FDR)of positive EC history had 1.65-fold(95%CI:1.47-1.84)or 1.93-fold(95%CI:1.46-2.54)higher risks of ECPL.Participants with FDRs who developed EC before 35,45,and 50 years of age had 4.05-fold(95%CI:1.30-12.65),2.11-fold(95%CI:1.37-3.25),and 1.91-fold(95%CI:1.44-2.54)higher risks of ECPL,respectively.Conclusions:Participants with positive family history of EC had significantly higher risk of ECPL.This risk increased with the number of EC positive FDRs and EC family history of early onset.Distinctive genetic risk factors of the population in high-risk areas of China require further investigation.Trial registration:ChiCTR-EOC-17010553.

Photoinduced large polaron transport and dynamics in organic-inorganic hybrid lead halide perovskite with terahertz probes

Organic-inorganic hybrid metal halide perovskites(MHPs)have attracted tremendous attention for optoelectronic applications.The long photocarrier lifetime and moderate carrier mobility have been proposed as results of the large polaron formation in MHPs.However,it is challenging to measure the effective mass and carrier scattering parameters of the photogenerated large polarons in the ultrafast carrier recombination dynamics.Here,we show,in a one-step spectroscopic method,that the optical-pump and terahertz-electromagnetic probe(OPTP)technique allows us to access the nature of interplay of photoexcited unbound charge carriers and optical phonons in polycrystalline CH_(3)NH_(3)PbI_(3)(MAPbI_(3))of about 10μm grain size.Firstly,we demonstrate a direct spectral evidence of the large polarons in polycrystalline MAPbI_(3).Using the Drude-Smith-Lorentz model along with the Frӧhlich-type electron-phonon(e-ph)coupling,we determine the effective mass and scattering parameters of photogenerated polaronic carriers.We discover that the resulting moderate polaronic carrier mobility is mainly influenced by the enhanced carrier scattering,rather than the polaron mass enhancement.While,the formation of large polarons in MAPbI_(3)polycrystalline grains results in a long charge carrier lifetime at room temperature.Our results provide crucial information about the photo-physics of MAPbI3 and are indispensable for optoelectronic device development with better performance.

Probing into the Yield Plateau Phenomenon in Commercially Pure Titanium During Tensile Tests

To explain the intrinsic mechanism of the yield plateau phenomenon in commercially pure titanium,the tensile behaviors of commercially pure titanium specimens after 91.6%cryorolling and subsequent annealing at 280℃,335℃,450℃and 600℃have been studied.The results show that the yield plateau phenomenon is a result of dislocation behaviors controlled by grain size and thus only exists within a given range of mean grain size.αgrain boundaries are the main dislocation multiplication sources of commercially pure titanium.Fine-grained microstructure could offer numerous dislocation multiplication locations during deformation.Once the applied stress is above the yielding strength,dislocations multiply rapidly and the mobile dislocation density is high.To retrieve the imposed strain rate,the mean dislocation velocity is bound to be low.Therefore,it takes time for them to interact with each other.As a result,the movement of dislocations is hardly blocked and the deformation could continue at a nearly constant applied stress.Consequently,the so-called yield plateau behavior presents in the tensile curves.The disappearance of yield plateau phenomenon in coarse-grained and ultrafi ne-grained microstructures is attributed to the quick realization of the mutual interactions among dislocations at the initial stage of tensile test.

Geometric metasurface for polarization synthesis and multidimensional multiplexing of terahertz converged vortices

The investigation of converged twisted beams with a helical phase structure has a remarkable impact on both fundamental physics and practical applications.Geometric metasurfaces consisting of individually orientated metal/dielectric meta-atoms provide an ultracompact platform for generating converged vortices.However,it is still challenging to simultaneously focus left-handed and right-handed circularly polarized incident beams with pure geometric phase modulation,which hinders the independent operation on topological charges between these two helical components.Here we propose and experimentally demonstrate an approach to design terahertz geometric metasurfaces that can generate helicity-independent converged vortices with homogeneous polarization states by the superposition of two orthogonal helical vortices with identical topological charges.Furthermore,the multiplexing of polarization-rotatable multiple vortices in multiple dimensions,i.e.,in both longitudinal and transverse directions,and a vortex with an extended focal depth is confirmed by embedding polarization modulation into the geometric metasurfaces.The demonstrated approach provides a new way to simultaneously manipulate orthogonal helical components and expand the design dimension,enabling new applications of geometric metasurface devices in polarization optics,twisted-beam related image and edge detection,high capacity optical communication,and quantum information processing,to name a few.

Texture Evolution Behavior and Its Triggered Mechanical Anisotropy of CP Ti During Severe Cold Rolling and Subsequent Annealing

The texture evolution behavior and its triggered mechanical anisotropy of commercially pure titanium(CP Ti) during severe cold rolling and subsequent annealing are discussed based on the optical microscopy and the electron backscattered diffraction analyses. Some enlightening results are found. It is shown that planar textures exist under all treatments, namely the {11–29}<10–10> under rolling state, the {11–27}<10–10> under 300 °C annealing state and the {11–24}<10–10> under 500 °C annealing state. This indicates that the crystal plane indices of planar texture change toward {-12–10} with increasing annealing temperature, which is a result of crystal lattice rotation. Planar texture triggers anisotropy of the mechanical properties for CP Ti sheets under all treatments. In particular, CP Ti sheets exhibit severe and similar anisotropy behavior under rolling and 300 °C annealing states. Generally speaking, the rolling direction(RD) specimens get relatively low yield strength, high ultimate tensile strength and good plasticity, and RD + 45° specimens show relatively high yield strength, low ultimate tensile strength and good plasticity. The transverse direction specimens, however, usually exhibit high yield strength and low plasticity. It is proved that the above anisotropy behavior is mainly determined by the Schmid factor distribution of the(10–10)[11–20] prismatic slip system in different directions. Due to the non-negligible influence exerted by the(0001)[11–20] basal slip system after 500 °C annealing, the anisotropy behavior under this state is obviously different.

Crashworthiness Optimization of Steel-Magnesium Hybrid Double-Hat-Shaped Tubes

The double-hat-shaped magnesium tube was difficult to use in actual applications due to its frangible material property.Magnesium alloy and traditional steel were integrated into a new hybrid thin-walled double-hat-shaped tube to improve vehicle crashworthiness.Two classes of hybrid tubes were examined,namely Hybrid-I(steel top hat and magnesium alloy bottom hat)and Hybrid-II(magnesium alloy top hat and steel bottom hat).The energy absorption characteristics and crashworthiness optimization of the thin-walled hybrid structures were investigated under three-point bending conditions through experiments and simulations.Multi-objective optimization design for the two hybrid tubes was implemented to elucidate their lightweight properties.Results showed that the specific energy absorption of Hybrid-I tube and Hybrid-II tube was approximately 44.7%and 12.7%higher than that of the double-hat-shaped DC04 tube,respectively.The Hybrid-I tube had better crashworthiness and lightweight properties compared with Hybrid-II tube.Hybrid-I tube also had better lightweight properties than single-material steel tube and reduced wall thickness compared with magnesium alloy tube.