On August 6,2023,a magnitude MW5.5 earthquake struck Pingyuan County,Dezhou City,Shandong Province,China.This event was significant as no large earthquakes had been recorded in the region for over a century,and no act...On August 6,2023,a magnitude MW5.5 earthquake struck Pingyuan County,Dezhou City,Shandong Province,China.This event was significant as no large earthquakes had been recorded in the region for over a century,and no active fault had been previously identified.This study collects 1309 P-wave arrival times and 866 S-wave arrival times from 74 seismic stations less than 200 km to the epicenter to constrain the spatial distribution of the mainshock and its 125 early aftershocks by the double difference earthquake relocation method,and selects 864 P-waveforms from 288 stations located within 800 km of the epicenter to constrain the focal mechanism solution of the mainshock through centroid moment tensor inversion.The relocation and the inversion indicate,the Pingyuan MW5.5 earthquake was caused by a rupture on a buried fault,likely an extensive segment of the Gaotang fault.This buried fault exhibited a dip of approximately 75°to the northwest,with a strike of 222°,similar to the Gaotang fault.The rupture initiated at the depth of 18.6 km and propagated upward and northeastward.However,the ground surface was not broken.The total duration of the rupture was~6.0 s,releasing the scalar moment of 2.5895×1017 N·m,equivalent to MW5.54.The moment rate reached the maximum only 1.4 seconds after the rupture initiation,and the 90%scalar moment was released in the first 4.6 s.In the first 1.4 seconds of the rupture process,the rupture velocity was estimated to be 2.6 km/s,slower than the local S-wave velocity.As the rupture neared its end,the rupture velocity decreased significantly.This study provides valuable insights into the seismic characteristics of the Pingyuan MW5.5 earthquake,shedding light on the previously unidentified buried fault responsible for the seismic activity in the region.Understanding the behavior of such faults is crucial for assessing seismic hazards and enhancing earthquake preparedness in the future.展开更多
CsPbI_(2)Br perovskite solar cells(PSCs)have drawn tremendous attention due to their suitable bandgap,excellent photothermal stability,and great potential as an ideal candidate for top cells in tandem solar cells.Howe...CsPbI_(2)Br perovskite solar cells(PSCs)have drawn tremendous attention due to their suitable bandgap,excellent photothermal stability,and great potential as an ideal candidate for top cells in tandem solar cells.However,the abundant defects at the buried interface and perovskite layer induce severe charge recombination,resulting in the open-circuit voltage(V_(oc))output and stability much lower than anticipated.Herein,a novel buried interface management strategy is developed to regulate interfacial carrier dynamics and CsPbI_(2)Br defects by introducing ammonium tetrafluoroborate(NH_(4)BF_(4)),thereby resulting in both high CsPbI_(2)Br crystallization and minimized interfacial energy losses.Specifically,NH_(4)^(+)ions could preferentially heal hydroxyl groups on the SnO_(2)surface and balance energy level alignment between SnO_(2)and CsPbI_(2)Br,enhancing charge transport efficiency,while BF_(4)^(-)anions as a quasi-halogen regulate crystal growth of CsPbI_(2)Br,thus reducing perovskite defects.Additionally,it is proved that eliminating hydroxyl groups at the buried interface enhances the iodide migration activation energy of CsPbI_(2)Br for strengthening the phase stability.As a result,the optimized CsPbI_(2)Br PSCs realize a remarkable efficiency of 17.09%and an ultrahigh V_(oc)output of 1.43 V,which is one of the highest values for CsPbI_(2)Br PSCs.展开更多
Imaging the wave velocity field surrounding a borehole while drilling is a promising and urgently needed approach for extending the exploration range of the borehole point.This paper develops a drilling process detect...Imaging the wave velocity field surrounding a borehole while drilling is a promising and urgently needed approach for extending the exploration range of the borehole point.This paper develops a drilling process detection(DPD)system consisting of a multifunctional sensor and a pilot geophone installed at the top of the drilling rod,geophones at the tunnel face,a laser rangefinder,and an onsite computer.A weighted adjoint-state first arrival travel time tomography method is used to invert the P-wave velocity field of rock mass while borehole drilling.A field experiment in the ongoing construction of a deep buried tunnel in southwestern China demonstrated the DPD system and the tomography method.Time-frequency analysis of typical borehole drilling detection data shows that the impact drilling source is a pulse-like seismic exploration wavelet.A velocity field of the rock mass in a triangular area defined by the borehole trajectory and geophone receiving line can be obtained.Both the borehole core and optical image validate the inverted P-wave velocity field.A numerical simulation of a checkerboard benchmark model is used to test the tomography method.The rapid convergence of the misfits and consistent agreement between the inverted and observed travel times validate the P-wave velocity imaging.展开更多
For the further improvement of the power conversion efficiency(PCE)and stability of perovskite solar cells(PSCs),the buried interface between the perovskite and the electron transport layer is crucial.However,it is ch...For the further improvement of the power conversion efficiency(PCE)and stability of perovskite solar cells(PSCs),the buried interface between the perovskite and the electron transport layer is crucial.However,it is challenging to effectively optimize this interface as it is buried beneath the perovskite film.Herein,we have designed and synthesized a series of multifunctional organic-inorganic(OI)complexes as buried interfacial material to promote electron extraction,as well as the crystal growth of the perovskite.The OI complex with BF4−group not only eliminates oxygen vacancies on the SnO_(2) surface but also balances energy level alignment between SnO_(2) and perovskite,providing a favorable environment for charge carrier extraction.Moreover,OI complex with amine(−NH_(2))functional group can regulate the crystallization of the perovskite film via interaction with PbI2,resulting in highly crystallized perovskite film with large grains and low defect density.Consequently,with rational molecular design,the PSCs with optimal OI complex buried interface layer which contains both BF4−and−NH_(2) functional groups yield a champion device efficiency of 23.69%.More importantly,the resulting unencapsulated device performs excellent ambient stability,maintaining over 90%of its initial efficiency after 2000 h storage,and excellent light stability of 91.5%remaining PCE in the maximum power point tracking measurement(under continuous 100 mW cm−2 light illumination in N2 atmosphere)after 500 h.展开更多
ABSTRACT Embedding submicrocavities is an effective approach to improve the light out-coupling efficiency(LOCE)for planar perovskite light-emitting diodes(PeLEDs).In this work,we employ phenethylammonium iodide(PEAI)t...ABSTRACT Embedding submicrocavities is an effective approach to improve the light out-coupling efficiency(LOCE)for planar perovskite light-emitting diodes(PeLEDs).In this work,we employ phenethylammonium iodide(PEAI)to trigger the Ostwald ripening for the downward recrystallization of perovskite,resulting in spontaneous formation of buried submicrocavities as light output coupler.The simulation suggests the buried submicrocavities can improve the LOCE from 26.8 to 36.2%for near-infrared light.Therefore,PeLED yields peak external quantum efficiency(EQE)increasing from 17.3%at current density of 114 mA cm^(−2)to 25.5%at current density of 109 mA cm^(−2)and a radiance increasing from 109 to 487 W sr^(−1)m^(−2)with low rolling-off.The turn-on voltage decreased from 1.25 to 1.15 V at 0.1 W sr^(−1)m^(−2).Besides,downward recrystallization process slightly reduces the trap density from 8.90×10^(15)to 7.27×10^(15)cm^(−3).This work provides a self-assembly method to integrate buried output coupler for boosting the performance of PeLEDs.展开更多
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...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.展开更多
Currently,accelerated aging tests are widely used to study the aging process of polyethylene pipelines.However,this approach can only simulate one or several main influencing factors in the natural environment,which a...Currently,accelerated aging tests are widely used to study the aging process of polyethylene pipelines.However,this approach can only simulate one or several main influencing factors in the natural environment,which are often quite different from the actual environment of the buried pipelines.In this study,five types of PE80 buried pipelines in service for 9e18 years were taken as the research object,while new PE80 pipelines were taken as the reference group.The aging process and mechanism of polyethylene buried pipelines were studied through mechanical and chemical property tests and microstructural analysis.The results showed that the pipeline exhibited cross-linking as the main aging mechanism after being in service for 0e18 years.The aging degree and law of the inner and outer surface of the pipeline were compared,and the observed mechanism of both surfaces was explained.After 18 years in service,the elongation at the break of the pipe decreased by 16.2%,and the toughness of the matrix in the main collapse area of the tensile sample was the fundamental reason responsible for changes in the mechanical properties.Finally,after 18 years in service,the oxidation induction time of the pipeline was 25.7 min,which was 28.5% higher than the national standard value.There were no potential safety hazards during continuous long-term service.The results of this paper provide reference data and theoretical guidance for the aging process study of buried polyethylene pipelines.展开更多
Failure of pipe networks due to blast loads resulting from terrorist attacks or construction facilities, may cause economic loss, environmental pollution, source of firing or even it may lead to a disaster. The presen...Failure of pipe networks due to blast loads resulting from terrorist attacks or construction facilities, may cause economic loss, environmental pollution, source of firing or even it may lead to a disaster. The present work develops a closed-form solution of buried pipe with barrier system subjected to subsurface detonation. The solution is derived based on the concept of double-beam system. Euler Bernoulli's beams are used to simulate the buried pipe and the barrier system. Soil is idealized as viscoelastic foundation along with shear interaction between discrete Winkler springs(advanced soil model). The finite SineFourier transform is employed to solve the coupled partial differential equations. The solution is validated with past studies. A parametric study is conducted to investigate the influence of TNT charge weight, pipe material, damping ratio and TNT offset on the response of buried pipe with and without barrier system. Further a statistical analysis is carried out to get the significant soil and pipe input parameters. It is perceived that peak pipe displacements for both the cases(with and without barrier) are increases with increasing the weight of TNT charge and decreases with increasing the damping ratio and TNT offset. The deformation of pipe also varies with pipe material. Pipe safety against blast loads can be ensured by providing suitable barrier layer. The present study can be utilized in preliminary design stage as an alternative to expensive numerical analysis or field study.展开更多
Deciphering hydrocarbon generation and accumulation stage is of significance to understand oil and gas evolution and seek exploration targets.Taking the Upper Paleozoic buried-hills in the Huanghua Depression,Bohai Ba...Deciphering hydrocarbon generation and accumulation stage is of significance to understand oil and gas evolution and seek exploration targets.Taking the Upper Paleozoic buried-hills in the Huanghua Depression,Bohai Bay Basin,as a case study,hydrocarbon generation environment and detailed accumulation process are revealed by fluid inclusions observations,Laser Raman spectroscopy,Fourier Infrared spectroscopy,and K-Ar isotope measurements.The results show that both oil and gas inclusion were captured in the quartz overgrowth,dissolved feldspar and calcite microfractures,showing blue to dark brown fluoresce.The grains containing oil inclusions index(GOI)of oil,oil&gas and gas being 25%,65%,and 10%and the inclusions with abundant methyl groups and short chains,both indicate high thermal maturity.One series of fluids inclusion is generally observed,evidenced by the concentrated homogenization temperature of 135-145℃ and salinity of 3%-15 w.t.%NaCl equiv,indicating one primary charging stage.The gas and gas&liquid inclusions mainly contain CH_(4),with also peaks indicating CO_(2) and N_(2.)The Carboniferous and Permian biomarkers show reducing environment with brackish water,with organic matter sources both from marine and continental.The relative content ofααα20RC_(27),ααα20RC_(28),andααα20RC_(29) exhibit source contributions both from algae and higher plants,and mainly of II2 to III kerogen.Both coal derived gas and oil associated hydrocarbons are identified from most of the buried-hills.Combining the fluid homogenization temperature and salinity,as well as the thermal evolution history,the hydrocarbon generated from the Upper Paleozoic was concentrated at the end of the Eocene(40 Ma±),while the beginning of charging is 60 Ma±.The Wumaying Buried-hill is of only coal derived gas and has potential for inner coal measure natural gas exploration.The results provide a detailed understanding of hydrocarbon accumulations in the study area,which can also be reference for improving petroleum exploration efficiency in similar basins.展开更多
A comprehensive study was undertaken at Jiaozi coal mine to investigate the development regularity of ground fissures in shallow buried coal seam mining with Karst landform,shedding light on the development type,geogr...A comprehensive study was undertaken at Jiaozi coal mine to investigate the development regularity of ground fissures in shallow buried coal seam mining with Karst landform,shedding light on the development type,geographical distribution,dynamic development process,and failure mechanism of these ground fissures by employing field monitoring,numerical simulation,and theoretical analysis.The findings demonstrate that ground fissure development has an obvious feature of subregion,and its geographical distribution is significantly affected by topography.Tensile type,open type,and stepped type are three different categories of ground fissure.Ground fissures emerge dynamically as the panel advances,and they typically develop with a distance of less than periodic weighting step distance in advance of panel advancing position.Ground fissures present the dynamic development feature,temporary fissure has the ability of self-healing.The dynamic development process of ground fissure with closed-distance coal seam repeated mining is expounded,and the development scale is a dynamic development stage of“closure→expansion→stabilized”on the basis of the original development scale.From the perspective of topsoil deformation,the computation model considering two points movement vectors towards two directions of the gob and the ground surface is established,the development criterion considering the critical deformation value of topsoil is obtained.The mechanical model of hinged structure of inclined body is proposed to clarify the ground fissure development,and the interaction between slope activity and ground fissure development is expounded.These research results fulfill the gap of ground fissures about development regularity and formation mechanism,and can contribute to ground fissure prevention and treatment with Karst landform.展开更多
Although ionic liquids(ILs)have been widely employed to heal the defects in perovskite solar cells(PSCs),the corresponding defect passivation mechanisms are not thoroughly understood up to now.Herein,we first reveal a...Although ionic liquids(ILs)have been widely employed to heal the defects in perovskite solar cells(PSCs),the corresponding defect passivation mechanisms are not thoroughly understood up to now.Herein,we first reveal an abnormal buried interface anion defect passivation mechanism depending on cationinduced steric hindrance.The IL molecules containing the same anion([BF4]^(-))and different sizes of imidazolium cations induced by substituent size are used to manipulate buried interface.It was revealed what passivated interfacial defects is mainly anions instead of cations.Theoretical and experimental results demonstrate that the large-sized cations can weaken the ionic bond strength between anions and cations,and facilitate the interaction between anions and SnO2as well as perovskites,which is conducive to interfacial defect passivation and ameliorating interfacial contact.It can be concluded that interfacial chemical interaction strength and defect passivation effect are positively correlated with the size of cations.The discovery breaks conventional thinking that large-sized modification molecules would weaken their chemical interaction with perovskite.Compared with the control device(21.54%),the device based on 1,3-Bis(1-adamantyl)-imidazolium tetrafluoroborate(BAIMBF4)with maximum size cations achieves a significantly enhanced efficiency of 23.61%along with much increased moisture,thermal and light stabilities.展开更多
The interfacial defects and energy barrier are main reasons for interfacial nonradiative recombination.In addition,poor perovskite crystallization and incomplete conversion of PbI_(2) to perovskite restrict further en...The interfacial defects and energy barrier are main reasons for interfacial nonradiative recombination.In addition,poor perovskite crystallization and incomplete conversion of PbI_(2) to perovskite restrict further enhancement of the photovoltaic performance of the devices using sequential deposition.Herein,a buried interface stabilization strategy that relies on the synergy of fluorine(F)and sulfonyl(S=O)functional groups is proposed.A series of potassium salts containing halide and non-halogen anions are employed to modify SnO_(2)/perovskite buried interface.Multiple chemical bonds including hydrogen bond,coordination bond and ionic bond are realized,which strengthens interfacial contact and defect passivation effect.The chemical interaction between modification molecules and perovskite along with SnO_(2) heightens incessantly as the number of S=O and F augments.The chemical interaction strength between modifiers and perovskite as well as SnO_(2) gradually increases with the increase in the number of S=O and F.The defect passivation effect is positively correlated with the chemical interaction strength.The crystallization kinetics is regulated through the compromise between chemical interaction strength and wettability of substrates.Compared with Cl−,all non-halogen anions perform better in crystallization optimization,energy band regulation and defect passivation.The device with potassium bis(fluorosulfonyl)imide achieves a tempting efficiency of 24.17%.展开更多
Buried bumper syndrome(BBS)is the situation in which the internal bumper of the gastrostomy tube,due to prolonged compression of the tissues between the external and the internal bumper,migrates from the gastric lumen...Buried bumper syndrome(BBS)is the situation in which the internal bumper of the gastrostomy tube,due to prolonged compression of the tissues between the external and the internal bumper,migrates from the gastric lumen into the gastric wall or further,into the tract outside the gastric lumen,ending up anywhere between the stomach mucosa and the surface of the skin.This restricts liquid food from entering the stomach,since the internal opening is obstructed by gastric mucosal overgrowth.We performed a comprehensive search of the PubMed literature to retrieve all the case-reports and case-series referring to BBS and its management,after which we focused on the endoscopic techniques for releasing the internal bumper to re-establish the functionality of the tube.From the“push”and the“push and pull T”techniques to the most sophisticated-using high tech instruments,all 10 published techniques have been critically analysed and the pros and cons presented,in an effort to optimize the criteria of choice based on maximum efficacy and safety.展开更多
BZ13-2 oil field is a deep submerged strongly volatile reservoir in Bohai Sea. This oil reservoir has the characteristics of high gas oil ratio and small difference in formation pressure and saturation point pressure....BZ13-2 oil field is a deep submerged strongly volatile reservoir in Bohai Sea. This oil reservoir has the characteristics of high gas oil ratio and small difference in formation pressure and saturation point pressure. It usually adopts gas injection development to avoid crude oil degassing and fast decreasing production capacity. However, the phase characteristics and miscibility mechanism of this high-temperature and high-pressure fluid after gas injection are not clear. Therefore, it is necessary to study the feasibility of CO<sub>2</sub> injection to improve oil recovery in near critical volatile oil reservoirs through CO<sub>2</sub> injection experiments. In the early stage of the depletion experiment, the content of heavy components in the remaining oil increased significantly, so the depletion method is not conducive to the development of such reservoirs. With the increase of CO<sub>2</sub> injection, the volumetric expansion coefficient of formation crude oil increases significantly, while the saturation pressure and formation crude oil viscosity remain basically unchanged. The minimum miscible pressure experiment shows that CO<sub>2</sub> injection under formation pressure conditions can achieve multiphase miscibility. Based on experimental research results, the BZ13-2 oilfield is suitable for early gas injection development and can significantly improve recovery.展开更多
The Bohai Bay Basin is a Meso-Cenozoic rifted basin where the Paleozoic buried hills with great hydrocarbon potentials are well developed. The reservoir space types are complex and diverse due to tectonic activities, ...The Bohai Bay Basin is a Meso-Cenozoic rifted basin where the Paleozoic buried hills with great hydrocarbon potentials are well developed. The reservoir space types are complex and diverse due to tectonic activities, making fracture distribution highly heterogeneous. Reservoir identification and mapping is challenging due to their large burial depth and poor resolution of seismic data. An integration of well-logging, seismic data interpretation and core observation is applied to identify three structural unit types in the study area, that is, fault breccia zone, fault cataclastic zone, and fault massive rock zone. A comprehensive well-logging identification template and a comprehensive discriminant function M for the reservoir are established based on the well-logging response characteristics. A M value greater than 0.12 indicates a fault breccia zone, that between 0.04 and 0.12 marks a fault cataclastic zone, and that in the range from 0.02 to 0.04 represents a fault massive rock zone. A seismic prediction method with multi-parameter fusion is proposed in the study. The large-scale fractures are mapped by coherence-clutter parameters, while small fractures are predicted via waveform indication inversion. The spatial distribution of “fault-fracture reservoirs” is precisely mapped by frequency fusion technology. It is found that the fault breccia zones usually occur close to the fault planes, while the fault cataclastic zones are slightly away from the fault planes. The hydrocarbon abundance of the breccia zones is greater than that of the fault cataclastic and fault massive rock zones.展开更多
Percutaneous endoscopic gastrostomy(PEG) is a widely used method of nutrition delivery for patients with longterm insufficiency of oral intake. The PEG complication rate varies from 0.4% to 22.5% of cases, with minor ...Percutaneous endoscopic gastrostomy(PEG) is a widely used method of nutrition delivery for patients with longterm insufficiency of oral intake. The PEG complication rate varies from 0.4% to 22.5% of cases, with minor complications being three times more frequent. Buried bumper syndrome(BBS) is a severe complication of this method, in which the internal fixation device migrates alongside the tract of the stoma outside the stomach. Excessive compression of tissue between the external and internal fixation device of the gastrostomy tube is considered the main etiological factor leading to BBS. Incidence of BBS is estimated at around 1%(0.3%-2.4%). Inability to insert, loss of patency and leakage around the PEG tube are considered to be a typical symptomatic triad. Gastroscopy is indicated in all cases in which BBS is suspected. The depth of disc migration in relation to the lamina muscularis propria of the stomach is critical for further therapy and can be estimated by endoscopic or transabdominal ultrasound. BBS can be complicated by gastrointestinal bleeding, perforation, peritonitis, intra-abdominal and abdominal wall abscesses, or phlegmon, and these complications can lead to fatal outcomes. The most important preventive measure is adequate positioning of the external bolster. A conservative approach should be applied only in patients with high operative risk and dismal prognosis. Choice of the method of release is based on the type of the PEG set and depth of disc migration. A disc retained inside the stomach and completely covered by the overgrowing tissue can be released using some type of endoscopic dissection technique(needle knife, argon plasma coagulation, or papillotome through the cannula). Proper patient selection and dissection of the overgrowing tissue are the major determinants for successful endoscopic therapy. A disc localized out of the stomach(lamina muscularis propria) should be treated by a surgeon.展开更多
Seismic ground faulting is the greatest hazard for continuous buried pipelines.Over the years,researchers have attempted to understand pipeline behavior mostly via numerical modeling such as the finite element method....Seismic ground faulting is the greatest hazard for continuous buried pipelines.Over the years,researchers have attempted to understand pipeline behavior mostly via numerical modeling such as the finite element method.The lack of well-documented field case histories of pipeline failure from seismic ground faulting and the cost and complicated facilities needed for full-scale experimental simulation mean that a centrifuge-based method to determine the behavior of pipelines subjected to faulting is best to verify numerical approaches.This paper presents results from three centrifuge tests designed to investigate continuous buried steel pipeline behavior subjected to normal faulting.The experimental setup and procedure are described and the recorded axial and bending strains induced in a pipeline are presented and compared to those obtained via analytical methods.The influence of factors such as faulting offset,burial depth and pipe diameter on the axial and bending strains of pipes and on ground soil failure and pipeline deformation patterns are also investigated.Finally,the tensile rupture of a pipeline due to normal faulting is investigated.展开更多
We compared the chemical components and essential oils of ancient buried Zhennan(Phoebe zhennan)wood with those in samples from living trees.After removal of the carbon layer the recovered Zhennan exhibited a dark g...We compared the chemical components and essential oils of ancient buried Zhennan(Phoebe zhennan)wood with those in samples from living trees.After removal of the carbon layer the recovered Zhennan exhibited a dark green color,which differed from the yellow color of the living samples.Low molecular weight components(including hot-water and toluene-alcohol extractives),hemicellulose,and 1 % Na OH solubility in the recovered wood were greatly degraded.Degradation of cellulose was minor.Moreover,the ancient wood had somewhat more klason lignin than the modern wood.Fourier transform infrared(FTIR) analysis gave further evidence on the differences in chemical components.According to the GC–MS results,naphthalene derivatives were detected in the essential oils from both the modern and recovered wood.The delicate fragrance of the modern and recovered wood may be attributed to the aromatic constituents as identified by GC–MS.展开更多
Salt stress has been increasingly constraining crop productivity in arid lands of the world. In our recent study, salt stress was aleviated and crop productivity was improved remarkably by straw layer burial plus plas...Salt stress has been increasingly constraining crop productivity in arid lands of the world. In our recent study, salt stress was aleviated and crop productivity was improved remarkably by straw layer burial plus plastic iflm mulching in a saline soil. However, its impact on the microlfora diversity is not wel documented. Field micro-plot experiments were conducted from 2010 to 2011 using four tilage methods: (i) deep tilage with plastic iflm mulching (CK), (i) straw layer burial at 40 cm (S), (ii) straw layer burial plus surface soil mulching with straw material (S+S), and (iv) plastic iflm mulching plus buried straw layer (P+S). Culturable microbes and predominant bacterial communities were studied; based on 16S rDNA, bacterial com-munity structure and abundance were characterized using denaturing gradient gel electrophoresis (DGGE) and polymerase chain reaction (PCR). Results showed that P+S was the most favorable for culturable bacteria, actinomyces and fungi and induced the most diverse genera of bacteria compared to other tilage methods. Soil temperature had signiifcant positive correlations with the number of bacteria, actinomyces and fungi (P〈0.01). However, soil water was poorly correlated with any of the microbes. Salt content had a signiifcant negative correlation with the number of microbers, especialy for bacteria and fungi (P〈0.01). DGGE analysis showed that the P+S exhibited the highest diversity of bacteria with 20 visible bands folowed by S+S, S and CK. Moreover, P+S had the highest similarity (68%) of bacterial communities with CK. The major bacterial genera in al soil samples wereFirmicutes,Proteobacteria andActinobacteria. Given the considerable increase in microbial growth, the combined use of straw layer burial and plastic iflm mulching could be a practical option for aleviating salt stress effects on soil microbial community and thereby improving crop production in arid saline soils.展开更多
This paper presents a method for analysis of stress and strain of gas pipelines under the effect of horizontal catastrophic landslides. A soil spring model was used to analyze the nonlinear characteristics concerning ...This paper presents a method for analysis of stress and strain of gas pipelines under the effect of horizontal catastrophic landslides. A soil spring model was used to analyze the nonlinear characteristics concerning the mutual effects between the pipeline and the soil. The Ramberg–Osgood model was used to describe the constitutive relations of pipeline materials. This paper also constructed a finite element analysis model using ABAQUS finite element software and studied the distribution of the maximum stress and strain of the pipeline and the axial stress and strain along the pipeline by referencing some typical accident cases. The calculation results indicated that the maximum stress and strain increased gradually with the displacement of landslide.The limit values of pipeline axial stress strain appeared at the junction of the landslide area and non-landslide area. The stress failure criterion was relatively more conservative than the strain failure criterion. The research results of this paper may be used as a technical reference concerning the design and safety management of large-diameter gas pipelines under the effects of catastrophic landslides.展开更多
基金support from the National Natural Science Foundation of China(Nos.42104043,42374081,and U2039208)the Fundamental Research Funds for the Institute of Geophysics,China Earthquake Administration(No.DQJB22R35).
文摘On August 6,2023,a magnitude MW5.5 earthquake struck Pingyuan County,Dezhou City,Shandong Province,China.This event was significant as no large earthquakes had been recorded in the region for over a century,and no active fault had been previously identified.This study collects 1309 P-wave arrival times and 866 S-wave arrival times from 74 seismic stations less than 200 km to the epicenter to constrain the spatial distribution of the mainshock and its 125 early aftershocks by the double difference earthquake relocation method,and selects 864 P-waveforms from 288 stations located within 800 km of the epicenter to constrain the focal mechanism solution of the mainshock through centroid moment tensor inversion.The relocation and the inversion indicate,the Pingyuan MW5.5 earthquake was caused by a rupture on a buried fault,likely an extensive segment of the Gaotang fault.This buried fault exhibited a dip of approximately 75°to the northwest,with a strike of 222°,similar to the Gaotang fault.The rupture initiated at the depth of 18.6 km and propagated upward and northeastward.However,the ground surface was not broken.The total duration of the rupture was~6.0 s,releasing the scalar moment of 2.5895×1017 N·m,equivalent to MW5.54.The moment rate reached the maximum only 1.4 seconds after the rupture initiation,and the 90%scalar moment was released in the first 4.6 s.In the first 1.4 seconds of the rupture process,the rupture velocity was estimated to be 2.6 km/s,slower than the local S-wave velocity.As the rupture neared its end,the rupture velocity decreased significantly.This study provides valuable insights into the seismic characteristics of the Pingyuan MW5.5 earthquake,shedding light on the previously unidentified buried fault responsible for the seismic activity in the region.Understanding the behavior of such faults is crucial for assessing seismic hazards and enhancing earthquake preparedness in the future.
基金supported by the National Natural Science Foundation of China(22379010,22109166,22309191)Chinese Academy of Sciences。
文摘CsPbI_(2)Br perovskite solar cells(PSCs)have drawn tremendous attention due to their suitable bandgap,excellent photothermal stability,and great potential as an ideal candidate for top cells in tandem solar cells.However,the abundant defects at the buried interface and perovskite layer induce severe charge recombination,resulting in the open-circuit voltage(V_(oc))output and stability much lower than anticipated.Herein,a novel buried interface management strategy is developed to regulate interfacial carrier dynamics and CsPbI_(2)Br defects by introducing ammonium tetrafluoroborate(NH_(4)BF_(4)),thereby resulting in both high CsPbI_(2)Br crystallization and minimized interfacial energy losses.Specifically,NH_(4)^(+)ions could preferentially heal hydroxyl groups on the SnO_(2)surface and balance energy level alignment between SnO_(2)and CsPbI_(2)Br,enhancing charge transport efficiency,while BF_(4)^(-)anions as a quasi-halogen regulate crystal growth of CsPbI_(2)Br,thus reducing perovskite defects.Additionally,it is proved that eliminating hydroxyl groups at the buried interface enhances the iodide migration activation energy of CsPbI_(2)Br for strengthening the phase stability.As a result,the optimized CsPbI_(2)Br PSCs realize a remarkable efficiency of 17.09%and an ultrahigh V_(oc)output of 1.43 V,which is one of the highest values for CsPbI_(2)Br PSCs.
基金the support of the National Natural Science Foundation of China(Nos.42207211,42202320 and 42172296)Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education,Tongji University(No.KLE-TJGE-G2304).
文摘Imaging the wave velocity field surrounding a borehole while drilling is a promising and urgently needed approach for extending the exploration range of the borehole point.This paper develops a drilling process detection(DPD)system consisting of a multifunctional sensor and a pilot geophone installed at the top of the drilling rod,geophones at the tunnel face,a laser rangefinder,and an onsite computer.A weighted adjoint-state first arrival travel time tomography method is used to invert the P-wave velocity field of rock mass while borehole drilling.A field experiment in the ongoing construction of a deep buried tunnel in southwestern China demonstrated the DPD system and the tomography method.Time-frequency analysis of typical borehole drilling detection data shows that the impact drilling source is a pulse-like seismic exploration wavelet.A velocity field of the rock mass in a triangular area defined by the borehole trajectory and geophone receiving line can be obtained.Both the borehole core and optical image validate the inverted P-wave velocity field.A numerical simulation of a checkerboard benchmark model is used to test the tomography method.The rapid convergence of the misfits and consistent agreement between the inverted and observed travel times validate the P-wave velocity imaging.
基金The authors acknowledge the financial support from the Natural Science Foundation of China(Nos.21931002 and 22101123)the National Key Research and Development Program of China(2018YFB0704100)+4 种基金the Shenzhen Science and Technology Innovation Committee(no.JCYJ20200109140812302)the Leading talents of Guangdong province program(2016LJ06N507)the Guangdong Provincial Key Laboratory of Energy Materials for Electric Power(no.2018B030322001)the Guangdong Provincial Key Laboratory of Catalysis(no.2020B121201002)Outstanding Talents Training Fund in Shenzhen.
文摘For the further improvement of the power conversion efficiency(PCE)and stability of perovskite solar cells(PSCs),the buried interface between the perovskite and the electron transport layer is crucial.However,it is challenging to effectively optimize this interface as it is buried beneath the perovskite film.Herein,we have designed and synthesized a series of multifunctional organic-inorganic(OI)complexes as buried interfacial material to promote electron extraction,as well as the crystal growth of the perovskite.The OI complex with BF4−group not only eliminates oxygen vacancies on the SnO_(2) surface but also balances energy level alignment between SnO_(2) and perovskite,providing a favorable environment for charge carrier extraction.Moreover,OI complex with amine(−NH_(2))functional group can regulate the crystallization of the perovskite film via interaction with PbI2,resulting in highly crystallized perovskite film with large grains and low defect density.Consequently,with rational molecular design,the PSCs with optimal OI complex buried interface layer which contains both BF4−and−NH_(2) functional groups yield a champion device efficiency of 23.69%.More importantly,the resulting unencapsulated device performs excellent ambient stability,maintaining over 90%of its initial efficiency after 2000 h storage,and excellent light stability of 91.5%remaining PCE in the maximum power point tracking measurement(under continuous 100 mW cm−2 light illumination in N2 atmosphere)after 500 h.
基金supported by Startup Funds from the Central Organization Department and the South China University of Technology(SCUT),as well as funds from the national natural science foundation of China(Grant No:U2001217)the Guangdong Science and Technology Program(2020B121201003,2019ZT08L075,2019QN01L118,2021A1515012545)the Fundamental Research Fund for the Central Universities,SCUT(2020ZYGXZR095).
文摘ABSTRACT Embedding submicrocavities is an effective approach to improve the light out-coupling efficiency(LOCE)for planar perovskite light-emitting diodes(PeLEDs).In this work,we employ phenethylammonium iodide(PEAI)to trigger the Ostwald ripening for the downward recrystallization of perovskite,resulting in spontaneous formation of buried submicrocavities as light output coupler.The simulation suggests the buried submicrocavities can improve the LOCE from 26.8 to 36.2%for near-infrared light.Therefore,PeLED yields peak external quantum efficiency(EQE)increasing from 17.3%at current density of 114 mA cm^(−2)to 25.5%at current density of 109 mA cm^(−2)and a radiance increasing from 109 to 487 W sr^(−1)m^(−2)with low rolling-off.The turn-on voltage decreased from 1.25 to 1.15 V at 0.1 W sr^(−1)m^(−2).Besides,downward recrystallization process slightly reduces the trap density from 8.90×10^(15)to 7.27×10^(15)cm^(−3).This work provides a self-assembly method to integrate buried output coupler for boosting the performance of PeLEDs.
基金the funding support provided by National Natural Science Foundation of China(Grant No.42177121)Thammasat University Research Unit in Structural and Foundation Engineering.
文摘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.
基金Special technical support program of the State Administration of Market Supervision(2021YJ021)Science and technology program of the State Administration of Market Supervision(2021MK118,2021MK119).
文摘Currently,accelerated aging tests are widely used to study the aging process of polyethylene pipelines.However,this approach can only simulate one or several main influencing factors in the natural environment,which are often quite different from the actual environment of the buried pipelines.In this study,five types of PE80 buried pipelines in service for 9e18 years were taken as the research object,while new PE80 pipelines were taken as the reference group.The aging process and mechanism of polyethylene buried pipelines were studied through mechanical and chemical property tests and microstructural analysis.The results showed that the pipeline exhibited cross-linking as the main aging mechanism after being in service for 0e18 years.The aging degree and law of the inner and outer surface of the pipeline were compared,and the observed mechanism of both surfaces was explained.After 18 years in service,the elongation at the break of the pipe decreased by 16.2%,and the toughness of the matrix in the main collapse area of the tensile sample was the fundamental reason responsible for changes in the mechanical properties.Finally,after 18 years in service,the oxidation induction time of the pipeline was 25.7 min,which was 28.5% higher than the national standard value.There were no potential safety hazards during continuous long-term service.The results of this paper provide reference data and theoretical guidance for the aging process study of buried polyethylene pipelines.
文摘Failure of pipe networks due to blast loads resulting from terrorist attacks or construction facilities, may cause economic loss, environmental pollution, source of firing or even it may lead to a disaster. The present work develops a closed-form solution of buried pipe with barrier system subjected to subsurface detonation. The solution is derived based on the concept of double-beam system. Euler Bernoulli's beams are used to simulate the buried pipe and the barrier system. Soil is idealized as viscoelastic foundation along with shear interaction between discrete Winkler springs(advanced soil model). The finite SineFourier transform is employed to solve the coupled partial differential equations. The solution is validated with past studies. A parametric study is conducted to investigate the influence of TNT charge weight, pipe material, damping ratio and TNT offset on the response of buried pipe with and without barrier system. Further a statistical analysis is carried out to get the significant soil and pipe input parameters. It is perceived that peak pipe displacements for both the cases(with and without barrier) are increases with increasing the weight of TNT charge and decreases with increasing the damping ratio and TNT offset. The deformation of pipe also varies with pipe material. Pipe safety against blast loads can be ensured by providing suitable barrier layer. The present study can be utilized in preliminary design stage as an alternative to expensive numerical analysis or field study.
基金This study was supported by the National Natural Science Foundation of China(Grant No.42072194,U1910205)the Fundamental Research Funds for the Central Universities(800015Z1190,2021YJSDC02).
文摘Deciphering hydrocarbon generation and accumulation stage is of significance to understand oil and gas evolution and seek exploration targets.Taking the Upper Paleozoic buried-hills in the Huanghua Depression,Bohai Bay Basin,as a case study,hydrocarbon generation environment and detailed accumulation process are revealed by fluid inclusions observations,Laser Raman spectroscopy,Fourier Infrared spectroscopy,and K-Ar isotope measurements.The results show that both oil and gas inclusion were captured in the quartz overgrowth,dissolved feldspar and calcite microfractures,showing blue to dark brown fluoresce.The grains containing oil inclusions index(GOI)of oil,oil&gas and gas being 25%,65%,and 10%and the inclusions with abundant methyl groups and short chains,both indicate high thermal maturity.One series of fluids inclusion is generally observed,evidenced by the concentrated homogenization temperature of 135-145℃ and salinity of 3%-15 w.t.%NaCl equiv,indicating one primary charging stage.The gas and gas&liquid inclusions mainly contain CH_(4),with also peaks indicating CO_(2) and N_(2.)The Carboniferous and Permian biomarkers show reducing environment with brackish water,with organic matter sources both from marine and continental.The relative content ofααα20RC_(27),ααα20RC_(28),andααα20RC_(29) exhibit source contributions both from algae and higher plants,and mainly of II2 to III kerogen.Both coal derived gas and oil associated hydrocarbons are identified from most of the buried-hills.Combining the fluid homogenization temperature and salinity,as well as the thermal evolution history,the hydrocarbon generated from the Upper Paleozoic was concentrated at the end of the Eocene(40 Ma±),while the beginning of charging is 60 Ma±.The Wumaying Buried-hill is of only coal derived gas and has potential for inner coal measure natural gas exploration.The results provide a detailed understanding of hydrocarbon accumulations in the study area,which can also be reference for improving petroleum exploration efficiency in similar basins.
基金funded by State Key Laboratory of Strata Intelligent Control and Green Mining Cofounded by Shandong Province and the Ministry of Science and Technology,Shandong University of Science and Technology(Grant No.MDPC2023ZR01)Open Fund of State Key Laboratory of Water Resource Protection and Utilization in Coal Mining(Grant No.WPUKFJJ2019-19)Major research project of Guizhou Provincial Department of Education on innovative groups(Grant No.Qianjiaohe KY[2019]070)。
文摘A comprehensive study was undertaken at Jiaozi coal mine to investigate the development regularity of ground fissures in shallow buried coal seam mining with Karst landform,shedding light on the development type,geographical distribution,dynamic development process,and failure mechanism of these ground fissures by employing field monitoring,numerical simulation,and theoretical analysis.The findings demonstrate that ground fissure development has an obvious feature of subregion,and its geographical distribution is significantly affected by topography.Tensile type,open type,and stepped type are three different categories of ground fissure.Ground fissures emerge dynamically as the panel advances,and they typically develop with a distance of less than periodic weighting step distance in advance of panel advancing position.Ground fissures present the dynamic development feature,temporary fissure has the ability of self-healing.The dynamic development process of ground fissure with closed-distance coal seam repeated mining is expounded,and the development scale is a dynamic development stage of“closure→expansion→stabilized”on the basis of the original development scale.From the perspective of topsoil deformation,the computation model considering two points movement vectors towards two directions of the gob and the ground surface is established,the development criterion considering the critical deformation value of topsoil is obtained.The mechanical model of hinged structure of inclined body is proposed to clarify the ground fissure development,and the interaction between slope activity and ground fissure development is expounded.These research results fulfill the gap of ground fissures about development regularity and formation mechanism,and can contribute to ground fissure prevention and treatment with Karst landform.
基金financially supported by the Support Plan for Overseas Students to Return to China for Entrepreneurship and Innovation(cx2020003)the Fundamental Research Funds for the Central Universities(2020CDJ-LHZZ-074 and 2021CDJQY-022)Natural Science Foundation of Chongqing(cstc2020jcyjmsxmX0629)。
文摘Although ionic liquids(ILs)have been widely employed to heal the defects in perovskite solar cells(PSCs),the corresponding defect passivation mechanisms are not thoroughly understood up to now.Herein,we first reveal an abnormal buried interface anion defect passivation mechanism depending on cationinduced steric hindrance.The IL molecules containing the same anion([BF4]^(-))and different sizes of imidazolium cations induced by substituent size are used to manipulate buried interface.It was revealed what passivated interfacial defects is mainly anions instead of cations.Theoretical and experimental results demonstrate that the large-sized cations can weaken the ionic bond strength between anions and cations,and facilitate the interaction between anions and SnO2as well as perovskites,which is conducive to interfacial defect passivation and ameliorating interfacial contact.It can be concluded that interfacial chemical interaction strength and defect passivation effect are positively correlated with the size of cations.The discovery breaks conventional thinking that large-sized modification molecules would weaken their chemical interaction with perovskite.Compared with the control device(21.54%),the device based on 1,3-Bis(1-adamantyl)-imidazolium tetrafluoroborate(BAIMBF4)with maximum size cations achieves a significantly enhanced efficiency of 23.61%along with much increased moisture,thermal and light stabilities.
基金supported by the Defense Industrial Technology Development Program(JCKY2017110C0654)National Natural Science Foundation of China(11974063,61904023,62274018)+1 种基金Chongqing Special Postdoctoral Science Foundation(cstc2019jcyj-bsh0026)Fundamental Research Funds for the Central Universities(2021CDJQY-022).
文摘The interfacial defects and energy barrier are main reasons for interfacial nonradiative recombination.In addition,poor perovskite crystallization and incomplete conversion of PbI_(2) to perovskite restrict further enhancement of the photovoltaic performance of the devices using sequential deposition.Herein,a buried interface stabilization strategy that relies on the synergy of fluorine(F)and sulfonyl(S=O)functional groups is proposed.A series of potassium salts containing halide and non-halogen anions are employed to modify SnO_(2)/perovskite buried interface.Multiple chemical bonds including hydrogen bond,coordination bond and ionic bond are realized,which strengthens interfacial contact and defect passivation effect.The chemical interaction between modification molecules and perovskite along with SnO_(2) heightens incessantly as the number of S=O and F augments.The chemical interaction strength between modifiers and perovskite as well as SnO_(2) gradually increases with the increase in the number of S=O and F.The defect passivation effect is positively correlated with the chemical interaction strength.The crystallization kinetics is regulated through the compromise between chemical interaction strength and wettability of substrates.Compared with Cl−,all non-halogen anions perform better in crystallization optimization,energy band regulation and defect passivation.The device with potassium bis(fluorosulfonyl)imide achieves a tempting efficiency of 24.17%.
文摘Buried bumper syndrome(BBS)is the situation in which the internal bumper of the gastrostomy tube,due to prolonged compression of the tissues between the external and the internal bumper,migrates from the gastric lumen into the gastric wall or further,into the tract outside the gastric lumen,ending up anywhere between the stomach mucosa and the surface of the skin.This restricts liquid food from entering the stomach,since the internal opening is obstructed by gastric mucosal overgrowth.We performed a comprehensive search of the PubMed literature to retrieve all the case-reports and case-series referring to BBS and its management,after which we focused on the endoscopic techniques for releasing the internal bumper to re-establish the functionality of the tube.From the“push”and the“push and pull T”techniques to the most sophisticated-using high tech instruments,all 10 published techniques have been critically analysed and the pros and cons presented,in an effort to optimize the criteria of choice based on maximum efficacy and safety.
文摘BZ13-2 oil field is a deep submerged strongly volatile reservoir in Bohai Sea. This oil reservoir has the characteristics of high gas oil ratio and small difference in formation pressure and saturation point pressure. It usually adopts gas injection development to avoid crude oil degassing and fast decreasing production capacity. However, the phase characteristics and miscibility mechanism of this high-temperature and high-pressure fluid after gas injection are not clear. Therefore, it is necessary to study the feasibility of CO<sub>2</sub> injection to improve oil recovery in near critical volatile oil reservoirs through CO<sub>2</sub> injection experiments. In the early stage of the depletion experiment, the content of heavy components in the remaining oil increased significantly, so the depletion method is not conducive to the development of such reservoirs. With the increase of CO<sub>2</sub> injection, the volumetric expansion coefficient of formation crude oil increases significantly, while the saturation pressure and formation crude oil viscosity remain basically unchanged. The minimum miscible pressure experiment shows that CO<sub>2</sub> injection under formation pressure conditions can achieve multiphase miscibility. Based on experimental research results, the BZ13-2 oilfield is suitable for early gas injection development and can significantly improve recovery.
文摘The Bohai Bay Basin is a Meso-Cenozoic rifted basin where the Paleozoic buried hills with great hydrocarbon potentials are well developed. The reservoir space types are complex and diverse due to tectonic activities, making fracture distribution highly heterogeneous. Reservoir identification and mapping is challenging due to their large burial depth and poor resolution of seismic data. An integration of well-logging, seismic data interpretation and core observation is applied to identify three structural unit types in the study area, that is, fault breccia zone, fault cataclastic zone, and fault massive rock zone. A comprehensive well-logging identification template and a comprehensive discriminant function M for the reservoir are established based on the well-logging response characteristics. A M value greater than 0.12 indicates a fault breccia zone, that between 0.04 and 0.12 marks a fault cataclastic zone, and that in the range from 0.02 to 0.04 represents a fault massive rock zone. A seismic prediction method with multi-parameter fusion is proposed in the study. The large-scale fractures are mapped by coherence-clutter parameters, while small fractures are predicted via waveform indication inversion. The spatial distribution of “fault-fracture reservoirs” is precisely mapped by frequency fusion technology. It is found that the fault breccia zones usually occur close to the fault planes, while the fault cataclastic zones are slightly away from the fault planes. The hydrocarbon abundance of the breccia zones is greater than that of the fault cataclastic and fault massive rock zones.
基金Supported by Project PRVOUK P37-08 from Charles University PragueCzech Republic
文摘Percutaneous endoscopic gastrostomy(PEG) is a widely used method of nutrition delivery for patients with longterm insufficiency of oral intake. The PEG complication rate varies from 0.4% to 22.5% of cases, with minor complications being three times more frequent. Buried bumper syndrome(BBS) is a severe complication of this method, in which the internal fixation device migrates alongside the tract of the stoma outside the stomach. Excessive compression of tissue between the external and internal fixation device of the gastrostomy tube is considered the main etiological factor leading to BBS. Incidence of BBS is estimated at around 1%(0.3%-2.4%). Inability to insert, loss of patency and leakage around the PEG tube are considered to be a typical symptomatic triad. Gastroscopy is indicated in all cases in which BBS is suspected. The depth of disc migration in relation to the lamina muscularis propria of the stomach is critical for further therapy and can be estimated by endoscopic or transabdominal ultrasound. BBS can be complicated by gastrointestinal bleeding, perforation, peritonitis, intra-abdominal and abdominal wall abscesses, or phlegmon, and these complications can lead to fatal outcomes. The most important preventive measure is adequate positioning of the external bolster. A conservative approach should be applied only in patients with high operative risk and dismal prognosis. Choice of the method of release is based on the type of the PEG set and depth of disc migration. A disc retained inside the stomach and completely covered by the overgrowing tissue can be released using some type of endoscopic dissection technique(needle knife, argon plasma coagulation, or papillotome through the cannula). Proper patient selection and dissection of the overgrowing tissue are the major determinants for successful endoscopic therapy. A disc localized out of the stomach(lamina muscularis propria) should be treated by a surgeon.
基金This work was conducted at the Physical Modeling and Centrifuge Laboratory of the Soil Mechanics and Foundation Engineering Department in the School of Civil Engineering,University of Tehran
文摘Seismic ground faulting is the greatest hazard for continuous buried pipelines.Over the years,researchers have attempted to understand pipeline behavior mostly via numerical modeling such as the finite element method.The lack of well-documented field case histories of pipeline failure from seismic ground faulting and the cost and complicated facilities needed for full-scale experimental simulation mean that a centrifuge-based method to determine the behavior of pipelines subjected to faulting is best to verify numerical approaches.This paper presents results from three centrifuge tests designed to investigate continuous buried steel pipeline behavior subjected to normal faulting.The experimental setup and procedure are described and the recorded axial and bending strains induced in a pipeline are presented and compared to those obtained via analytical methods.The influence of factors such as faulting offset,burial depth and pipe diameter on the axial and bending strains of pipes and on ground soil failure and pipeline deformation patterns are also investigated.Finally,the tensile rupture of a pipeline due to normal faulting is investigated.
基金supported by "Key Laboratory of Wood Industry and Furniture Engineering of Sichuan Provincial Colleges and Universities"
文摘We compared the chemical components and essential oils of ancient buried Zhennan(Phoebe zhennan)wood with those in samples from living trees.After removal of the carbon layer the recovered Zhennan exhibited a dark green color,which differed from the yellow color of the living samples.Low molecular weight components(including hot-water and toluene-alcohol extractives),hemicellulose,and 1 % Na OH solubility in the recovered wood were greatly degraded.Degradation of cellulose was minor.Moreover,the ancient wood had somewhat more klason lignin than the modern wood.Fourier transform infrared(FTIR) analysis gave further evidence on the differences in chemical components.According to the GC–MS results,naphthalene derivatives were detected in the essential oils from both the modern and recovered wood.The delicate fragrance of the modern and recovered wood may be attributed to the aromatic constituents as identified by GC–MS.
基金funded by the National Natural Science Foundation of China(31471455,31000692 and 31070002)the Fundamental Research Funds for National Public Research Institutions,China(ZYQHS2015-25)the Beijing Natural Science Foundation,China(5152017)
文摘Salt stress has been increasingly constraining crop productivity in arid lands of the world. In our recent study, salt stress was aleviated and crop productivity was improved remarkably by straw layer burial plus plastic iflm mulching in a saline soil. However, its impact on the microlfora diversity is not wel documented. Field micro-plot experiments were conducted from 2010 to 2011 using four tilage methods: (i) deep tilage with plastic iflm mulching (CK), (i) straw layer burial at 40 cm (S), (ii) straw layer burial plus surface soil mulching with straw material (S+S), and (iv) plastic iflm mulching plus buried straw layer (P+S). Culturable microbes and predominant bacterial communities were studied; based on 16S rDNA, bacterial com-munity structure and abundance were characterized using denaturing gradient gel electrophoresis (DGGE) and polymerase chain reaction (PCR). Results showed that P+S was the most favorable for culturable bacteria, actinomyces and fungi and induced the most diverse genera of bacteria compared to other tilage methods. Soil temperature had signiifcant positive correlations with the number of bacteria, actinomyces and fungi (P〈0.01). However, soil water was poorly correlated with any of the microbes. Salt content had a signiifcant negative correlation with the number of microbers, especialy for bacteria and fungi (P〈0.01). DGGE analysis showed that the P+S exhibited the highest diversity of bacteria with 20 visible bands folowed by S+S, S and CK. Moreover, P+S had the highest similarity (68%) of bacterial communities with CK. The major bacterial genera in al soil samples wereFirmicutes,Proteobacteria andActinobacteria. Given the considerable increase in microbial growth, the combined use of straw layer burial and plastic iflm mulching could be a practical option for aleviating salt stress effects on soil microbial community and thereby improving crop production in arid saline soils.
基金funded by the National Science and Technology Support Program (2015BAK16B02 and 2015BAK16B01)the Fundamental Research Funds of China Academy of Safety Science and Technology
文摘This paper presents a method for analysis of stress and strain of gas pipelines under the effect of horizontal catastrophic landslides. A soil spring model was used to analyze the nonlinear characteristics concerning the mutual effects between the pipeline and the soil. The Ramberg–Osgood model was used to describe the constitutive relations of pipeline materials. This paper also constructed a finite element analysis model using ABAQUS finite element software and studied the distribution of the maximum stress and strain of the pipeline and the axial stress and strain along the pipeline by referencing some typical accident cases. The calculation results indicated that the maximum stress and strain increased gradually with the displacement of landslide.The limit values of pipeline axial stress strain appeared at the junction of the landslide area and non-landslide area. The stress failure criterion was relatively more conservative than the strain failure criterion. The research results of this paper may be used as a technical reference concerning the design and safety management of large-diameter gas pipelines under the effects of catastrophic landslides.