Hydrogen,as a zero-carbon secondary energy carrier,provides a unified pathway for low-carbon energy transformation.In electro–hydrogen coupling systems(EHCSs),surplus renewable power is stored via water electrolysis ...Hydrogen,as a zero-carbon secondary energy carrier,provides a unified pathway for low-carbon energy transformation.In electro–hydrogen coupling systems(EHCSs),surplus renewable power is stored via water electrolysis and later reconverted to electricity using fuel cells or gas turbines,enhancing the system’s flexibility and reliability in support of deep decarbonization.This study constructs an electricity–hydrogen energy-recycling model based on a coupling relationship considering the bidirectional conversion between electricity and hydrogen.A multistage carbon-emission-reduction indicator constraint is also established.Additionally,the green-certificate and carbon trading markets are introduced to optimize equipment investment and operation costs while achieving carbon-emission reduction.A case study reveals that the proposed EHCS planning model effectively allocates carbon emissions across different system stages,while mitigating economic repercussions,thus ensuring closer alignment with China’s emission-reduction policies.Incorporating diverse market mechanisms significantly enhances the system’s economy and decision-making flexibility,particularly in addressing future challenges in the energy market.展开更多
Inspired by nature's self-similar designs,novel honeycomb-spiderweb based self-similar hybrid cellular structures are proposed here for efficient energy absorption in impact applications.The energy absorption is e...Inspired by nature's self-similar designs,novel honeycomb-spiderweb based self-similar hybrid cellular structures are proposed here for efficient energy absorption in impact applications.The energy absorption is enhanced by optimizing the geometry and topology for a given mass.The proposed hybrid cellular structure is arrived after a thorough analysis of topologically enhanced self-similar structures.The optimized cell designs are rigorously tested considering dynamic loads involving crush and high-velocity bullet impact.Furthermore,the influence of thickness,radial connectivity,and order of patterning at the unit cell level are also investigated.The maximum crushing efficiency attained is found to be more than 95%,which is significantly higher than most existing traditional designs.Later on,the first and second-order hierarchical self-similar unit cell designs developed during crush analysis are used to prepare the cores for sandwich structures.Impact tests are performed on the developed sandwich structures using the standard 9-mm parabellum.The influence of multistaging on impact resistance is also investigated by maintaining a constant total thickness and mass of the sandwich structure.Moreover,in order to avoid layer-wise weak zones and hence,attain a uniform out-of-plane impact strength,off-setting the designs in each stage is proposed.The sandwich structures with first and second-order self-similar hybrid cores are observed to withstand impact velocities as high as 170 m/s and 270 m/s,respectively.展开更多
Ship outfitting is a key process in shipbuilding.Efficient and high-quality ship outfitting is a top priority for modern shipyards.These activities are conducted at different stations of shipyards.The outfitting plan ...Ship outfitting is a key process in shipbuilding.Efficient and high-quality ship outfitting is a top priority for modern shipyards.These activities are conducted at different stations of shipyards.The outfitting plan is one of the crucial issues in shipbuilding.In this paper,production scheduling and material ordering with endogenous uncertainty of the outfitting process are investigated.The uncertain factors in outfitting equipment production are usually decision-related,which leads to difficulties in addressing uncertainties in the outfitting production workshops before production is conducted according to plan.This uncertainty is regarded as endogenous uncertainty and can be treated as non-anticipativity constraints in the model.To address this problem,a stochastic two-stage programming model with endogenous uncertainty is established to optimize the outfitting job scheduling and raw material ordering process.A practical case of the shipyard of China Merchants Heavy Industry Co.,Ltd.is used to evaluate the performance of the proposed method.Satisfactory results are achieved at the lowest expected total cost as the complete kit rate of outfitting equipment is improved and emergency replenishment is reduced.展开更多
The leaching process of magnesiothermic self-propagating product generated during the multistage deep reduction process was investigated.The influence of magnesiothermic self-propagating product particle size,HCl solu...The leaching process of magnesiothermic self-propagating product generated during the multistage deep reduction process was investigated.The influence of magnesiothermic self-propagating product particle size,HCl solution concentration,and leaching solution temperature on the leaching behavior of elements Al and V was investigated.Results demonstrate that the leaching rate of Al and V is increased with the rise in leaching solution temperature,the increase in HCl solution concentration,and the enlargement of magnesiothermic self-propagating product particle size.The leaching processes of Al and V are consistent with the chemical reaction control model.When the magnesiothermic self-propagation product with D_(50) of 59.4μm is selected as the raw material,the leaching temperature is 40℃,and 1 mol/L HCl solution is employed,after leaching for 180 min,the leaching rates of Al and V are 24.8%and 12.6%,respectively.The acid-leached product exhibits a porous structure with a specific surface area of 3.5633 m^(2)/g.展开更多
Quantitative inversion is a major topic in remote sensing science.The development of visible light-based hyperspectral reconstruction techniques has opened novel prospects for low-cost,high-precision remote sensing in...Quantitative inversion is a major topic in remote sensing science.The development of visible light-based hyperspectral reconstruction techniques has opened novel prospects for low-cost,high-precision remote sensing inversion in agriculture.The aim of this study was to assess the effectiveness of hyperspectral reconstruction technology in agricultural remote sensing applications.Hyperspectral images were reconstructed using the MST++hyperspectral reconstruction model and compared with the original visible light images in terms of their correlations with physiological parameters,the accuracy of single-feature modeling,and the accuracy of combined feature modeling.The results showed that compared to the visible light image,the reconstructed data exhibited a stronger correlation with the measured physiological parameters,and the accuracy was improved for both the single feature and combined feature inversion modes.However,compared to multispectral sensors,hyperspectral reconstruction provided limited improvement of the inversion model accuracy.The results suggest that for physiological parameters that are not easy to observe directly,deep mining of features in visible light data through hyperspectral reconstruction technology can improve the accuracy of the inversion model.However,appropriate feature selection and simple models are more suitable for the remote sensing inversion task of traditional agronomic plot experiments.To strengthen the application of hyperspectral reconstruction technology in agricultural remote sensing,further development is necessary with broader wavelength ranges and more diverse agricultural scenarios.展开更多
Multistage fracturing technology has been used to enhance tight hydrocarbon resource recovery.Determining the proper well spacing and fracturing strategy is crucial for generating a complex fracture network that facil...Multistage fracturing technology has been used to enhance tight hydrocarbon resource recovery.Determining the proper well spacing and fracturing strategy is crucial for generating a complex fracture network that facilitates oil and gas flow in reservoirs.The stress-shadow effect that occurs between multiple wells significantly affects the development of fracture networks in reservoirs.However,the quantification of the stress-shadow effect and its influence on fracture networks has not been satisfactorily resolved because of the difficulties in detecting and identifying fracture propagation and reorientation in reservoirs.In this study,based on the geological information from the Shengli oilfield,we applied a hybrid finite element-discrete element method to analyze engineering-scale three-dimensional fracture propagation and reorientation by altering well spacings and fracturing strategies.The results indicate that the fracturing area generated by the synchronous fracturing scheme is much smaller than those generated by the sequential and alternative schemes.An alternative hydrofracturing scheme is optimal with respect to fracturing area.The stress-blind area was defined to quantify the mechanical disturbance between adjacent wells.Our study improves the understanding of the effect of fracturing schemes on fracture networks and the impact of independent factors contributing to stress-shadow effects.展开更多
The “well factory” mode's high-density well placement and multi-stage hydraulic fracturing technology enable efficient development of unconventional oil and gas resources.However,the deployment of platform wells...The “well factory” mode's high-density well placement and multi-stage hydraulic fracturing technology enable efficient development of unconventional oil and gas resources.However,the deployment of platform wells in the “well factory” model results in small wellbore spacing,and the stress disturbances caused by fracturing operations may affect neighboring wells,leading to inter-well interference phenomena that cause casing deformation.This study investigates the issue of inter-well interference causing casing deformation or even failure during multi-stage hydraulic fracturing in the “well factory”model,and predicts high-risk locations for casing failure.A flow-mechanics coupled geomechanical finite element model with retaining geological stratification characteristics was established.Based on the theory of hydraulic fracturing-induced rock fragmentation and fluid action leading to the degradation of rock mechanical properties,the model simulated the four-dimensional evolution of multi-well fracturing areas over time and space,calculating the disturbance in the regional stress field caused by fracturing operations.Subsequently,the stress distribution of multiple well casings at different time points was calculated to predict high-risk locations for casing failure.The research results show that the redistribution of the stress field in the fracturing area increases the stress on the casing.The overlapping fracturing zones between wells cause significant stress interference,greatly increasing the risk of deformation and failure.By analyzing the Mises stress distribution of multi-well casings,high-risk locations for casing failure can be identified.The conclusion is that the key to preventing casing failure in platform wells in the “well factory” model is to optimize the spatial distribution of fracturing zones between wells and reasonably arrange well spacing.The study provides new insights and methods for predicting casing failure in unconventional oil and gas reservoirs and offers references for optimizing drilling and fracturing designs.展开更多
Background Obsessive-compulsive disorder(OCD)is classified by the World Health Organization as 1 of the 10 most disabling conditions.However,nationally representative epidemiological data on OCD are not yet available ...Background Obsessive-compulsive disorder(OCD)is classified by the World Health Organization as 1 of the 10 most disabling conditions.However,nationally representative epidemiological data on OCD are not yet available in China.Aims To investigate the prevalence,comorbidity,role impairment and healthcare utilisation of OCD in China.Methods The present study used a multistage clustered area probability sample to obtain representative populationbased data of adults from 157 nationwide disease surveillance points across 31 provinces in China.Trained interviewers conducted face-to-face interviews with respondents to collect information based on the Composite International Diagnostic Interview 3.0.Data weighting was performed to account for differential selection probabilities and response rates,and to post-stratify the sample to ensure its representativeness of the population in China.Results A total of 28140 respondents(12537(44.55%)males and 15603(55.45%)females)completed the diagnostic interview.Two-thirds of the respondents with liftime OCD had comorbid mental disorders,with OCD typically emerging later than the comorbidities.The most common comorbidities were mood disorders(39.67%,odds ratio(OR):9.60,95%confidence interval(CI)7.35 to 12.53)and anxiety disorders(32.75%,OR:13.33,95%CI 10.14 to 17.52).Overall,588(weighted 58.19%)respondents with obsessions or compulsions experienced role impairment,which was most severe in those reporting unspecified symptoms.Only 46(6.74%)respondents with lifetime OCD and 28(6.48%)with 12-month OCD received any healthcare services for their conditions.Conclusions The weighted lifetime and 12-month prevalence of OCD were 2.43%and 1.63%,respectively.Most patients with OCD reported comorbid mental disorders and role impairment,but very few sought healthcare services.National programmes to expand service coverage and increase awareness of OCD are essential to meet healthcare needs in China.展开更多
This study reconstructed the paleo-uplift and depression pattern within the sequence stratigraphic framework of the Mid-Permian Maokou Formation,Sichuan Basin,investigated its tectono-sedimentary mechanisms and its co...This study reconstructed the paleo-uplift and depression pattern within the sequence stratigraphic framework of the Mid-Permian Maokou Formation,Sichuan Basin,investigated its tectono-sedimentary mechanisms and its control on paleogeomorphology and large-sale shoals based on analysis of outcrops,loggings and seismic data.The results show that the Maokou Formation comprises two third-order sequences,six fourth-order sequences(SSQ1-SSQ6),and four distinct slope-break zones developing progressively from north to south.Slope-break zones I-III in the northern basin,controlled by synsedimentary extensional faults,exhibited a NE-trending linear distribution with gradual southeastward migration.In contrast,slope-break zone IV in the southern basin displayed an arcuate distribution along the Emeishan Large Igneous Province(ELIP).The evolutions of these multistage slope-break zones governed the Mid-Permian paleogeomorphy in the Sichuan Basin transformations from a giant,north-dipping gentle slope(higher in the southwest than in the northeast)in the early-stage(SSQ1-SSQ2)to a platform(south)-basin(north)pattern in the middle-stage(SSQ3-SSQ5).Ultimately,a further depression zone developed in the southwestern basin during the late-stage(SSQ6),forming a paleo-uplift bounded by two depressions.The developments of the Mid-Permian paleogeomorphic configuration reflected the combined control by the rapid subduction of the Mianlüe Ocean and the episodic eruptions of the Emeishan mantle plume(or hot spots),which jointly facilitated the formation of extensive high-energy shoal facies belts along slope-break zones and around paleo-volcanic uplifts.展开更多
Background To investigate the relationship of age at first separation from parents(AFSP)with suicidal ideation(SI),suicide planning(SP)and suicide attempts(SA)among left-behind children(LBC)in China and the mediating ...Background To investigate the relationship of age at first separation from parents(AFSP)with suicidal ideation(SI),suicide planning(SP)and suicide attempts(SA)among left-behind children(LBC)in China and the mediating effect of traumatic events(TEs).Methods This cross-sectional study employed a multistage sampling method to conduct questionnaire surveys in six high-concentrated LBC provinces.Logistic regression and restricted cubic splines were performed to investigate the association of AFSP with SI,SP and SA,and meta-analysis(I2)was used to assess the heterogeneity.Causal mediation analysis(structural equation modelling)was used to evaluate the mediating effect of TEs,and bootstrap resampling was employed to assess the robustness of the causal mediation analysis.Results A total of 12162(6269 LBC)participants were included in this study;the prevalence rates of SI,SP and SA among LBC were 30.7%,18.6%and 11.9%;and LBC had a higher risk of SI(OR:1.32),SP(OR:1.40)and SA(OR:1.25)than non-LBC,all p<0.001.AFSP was negatively associated with SI,SP and SA,particularly peaking before 2 years old.LBC with AFSP<2 years old had a higher risk of SI(OR 2.65;95%CI 2.17 to 3.24;p<0.001),SP(OR 2.63;95%CI 3.36 to 4.29;p<0.001)and SA(OR 2.04;95%CI 2.73 to 3.63;p<0.001).TEs mediated the increased risk of SI(average causal mediation effect(ACME)0.03–0.07;proportion(Prop)40–54%;all p<0.001),SP(ACME 0.03–0.06;Prop 39–61%;all p<0.001)and SA(ACME 0.02–0.04;Prop 53–80%;all p<0.01).Conclusions We found that AFSP was associated with SI,SP and SA,mediated by TEs.Our findings supported the necessity of reducing SI,SP and SA risks among LBC and highlighted the need to consider AFSPs and TEs in intervention strategies.展开更多
The current portfolio model for property-liability insurance company is only single period that can not meet the practical demands of portfolio management, and the purpose of this paper is to develop a multiperiod mod...The current portfolio model for property-liability insurance company is only single period that can not meet the practical demands of portfolio management, and the purpose of this paper is to develop a multiperiod model for its portfolio problem. The model is a multistage stochastic programming which considers transaction costs, cash flow between time periods, and the matching of asset and liability; it does not depend on the assumption for normality of return distribution. Additionally, an investment constraint is added. The numerical example manifests that the multiperiod model can more effectively assist the property-liability insurer to determine the optimal composition of insurance and investment portfolio and outperforms the single period one.展开更多
This paper presents an efficient way to implement an interpolation filter in a 20bit ∑-△ DAC with an oversampling ratio of 128. A multistage structure is used to reduce the complexity of filter coefficients and the ...This paper presents an efficient way to implement an interpolation filter in a 20bit ∑-△ DAC with an oversampling ratio of 128. A multistage structure is used to reduce the complexity of filter coefficients and the fi- nite word length effect. A novel method based on mixed-radix number representation is proposed to realize a poly- phase multiplier-free half-band subfilter with a high resolution. This approach reduces the complexity of the con- trol system and saves chip area dramatically. The IC is realized in a standard 0.13μm CMOS process and the inter- polation filter occupies less than 0.63mm^2 . This realization has desirable properties of regularity with simple hard- ware devices which are suitable for VLSI and can be applied to many other high resolution data converters.展开更多
A new frequency compensation technique for low-power, area-efficient multistage amplifiers is introduced. Using nested active capacitors, our scheme achieves better bandwidth-to-power and slew-rate-to-power performanc...A new frequency compensation technique for low-power, area-efficient multistage amplifiers is introduced. Using nested active capacitors, our scheme achieves better bandwidth-to-power and slew-rate-to-power performances than previous works. Implemented in standard 0.35μm CMOS technology, our three-stage amplifier achieves 105dB DC gain, 3.3M GBW,68 phase margin, and 2.56V/μs average slew rate under a 150pF capacitive load. All of these are realized with only 40μW power consumption under a 2V power supply,with very small compensation capacitors.展开更多
Abstract There are two extensional systems in the Xiaoqinling metamorphic core complex (XMCC). One is the detachment fault system developed along the peripheries of the XMCC, which extended in an ESE-WNW direction and...Abstract There are two extensional systems in the Xiaoqinling metamorphic core complex (XMCC). One is the detachment fault system developed along the peripheries of the XMCC, which extended in an ESE-WNW direction and whose upper plate moved towards the WNW. The other extensional system includes the retrograde shear zones and normal faults developed within the XMCC, which represent the collapse of the XMCC. Ar-Ar and K-Ar dating shows that the extension of the detachment fault system continued from 135 to 123 Ma, i.e. in the late stage of its evolution at about 127 Ma. The collapse represented by the extensional system within the XMCC was operative during 120–106 Ma, and its main activity occurred about 116 Ma ago. These suggest that the XMCC experienced two extensional stages in its evolution, i.e., the syn-orogenic regional extension and post-orogenic collapse extension.展开更多
Rotor blades fault of aeroengine compressor is mostly caused by mechanical and aerodynamic excitation.And the excitation factor of high intensity sound wave to rotor blades should not be ignored.Experimental researche...Rotor blades fault of aeroengine compressor is mostly caused by mechanical and aerodynamic excitation.And the excitation factor of high intensity sound wave to rotor blades should not be ignored.Experimental researches are conducted on a multistage high pressure compressor.When high level vibration occurs on the first stage of rotor blades, the noise spectrum presents typical characteristic for discrete multi-tone in the compressor.The amplitude of blade vibration displacement and the sound pressure level of characteristic frequency noise increases and decreases simultaneously and reaches the maximum value at the same time.This frequency merely occur on a certain speed range and is locked in a specific range which presents no variation with the rotating speed.When high level vibration occurs on the first stage of rotor blades, the noise spectrum presents a sharp peak and the propagation state of the characteristic frequency is a helix structure in the compressor.It can be confirmed that acoustic resonance occurs in the multistage compressor.The acoustic resonance frequency and its side band frequencies are generated by modulation of a rotating noise source at the rotor speed which is the excitation source of the rotor blades vibration.展开更多
The Huangtuling hypersthene-garnet-biotite gneiss at Luotian County, Hubei Provine, is a typicalgranulite-facies rock of the Dabie Group Complex in the Dabie orogenic belt. Investigations on the morphology andoccurren...The Huangtuling hypersthene-garnet-biotite gneiss at Luotian County, Hubei Provine, is a typicalgranulite-facies rock of the Dabie Group Complex in the Dabie orogenic belt. Investigations on the morphology andoccurrence of zircons and their internal structures shown in the thin sections lead to the recognition of three types ofzircons, which are in good agreement with the types identified on the basis of morphology, colour and external fea-tures from the related zircon concentrates. The observation of zircons in the rock reveals that part of type 1 zirconsshow signs of a double-layered structure. The interval part existed in the protolith prior to the granulite-facies meta-morphism. Type 2, the prismatic zircons which mainly occur in garnet and hypersthene are metamorphic minerals ofthe granulite-facies metamorphism. Type 3, the round multifaceted zircons in felsic minerals and biotite, are proba-bly attributed to a later geological event related to migmatization. The ^(207)Pb/^(206)Pb zircon dating by direct evaporationon (thermal evaporation ion mass spectrometer) yields ages ranging from 2814 Ma to 1992 Ma. The age discrepancyamong these different zircon types is conspicuous. The yellow-brown(type 1) zircons give ages of 2814±29 Ma to2527±6 Ma, the prismatic euhedral zircons (type 2), 2456±7 Ma to 2254±4 Ma, and the round multifaceted zircons(type 3), 1992±10 Ma. The results are geologically interpreted in consideration of the complicated behaviours of zir-cons during Precambrian geological evolution of the Dabie area. (1) If the protolith of the gneiss is a sedimentaryrock, then type 1 zircons are clastic ones and the ages 2814±29 Ma and 2811±27 Ma may reflect the minimum age ofthe rocks of its source region. also the first geological event in the area. Sedimentation of the protolith occurred be-tween 2814 Ma and 2527 Ma, probably close to 2814 Ma. If the protolith is a volcanic rock, then the formation age ofthe supracrustal rocks of the Dabie Group Complex is around 2814 Ma. The age 2456±7 Ma reflects the time whenthe granulite-facies metamorphism took place. The later migmatization event is dated at aboat 1992±10 Ma, and isprobably the latest early Precambrian event in the area. The present work provides geochronological evidence for the existence of the Dabie Archaean craton, whichhad probably experienced 3 or 4 geological events during its early Precambrian evolution.展开更多
The upper Paleozoic natural gas reservoirs in the Ordos basin are generally characterized by a large gas-bearing area and low reserve abundance. On such a geological background, there still exist gas-enriched zones, w...The upper Paleozoic natural gas reservoirs in the Ordos basin are generally characterized by a large gas-bearing area and low reserve abundance. On such a geological background, there still exist gas-enriched zones, with relatively high outputs, high reserve abundance and stably distributed gas layers. The gas-enriched layers with relatively high permeability （the lower limit permeability is 0.5×10^-3μm^2） are key factors for the enrichment and high output of natural gas. Based on core observation, analytic results of inclusions, and a great deal of drilling data, we proposed the following four mechanisms for the formation of high-quality reservoirs： （1） in the source area the parent rocks are mainly metamorphic rocks and granites, which are favorable to keeping primary porosity; （2） under the condition of low A/S （accommodation/sediment supply） ratios, sandstone complex formed due to multistage fluvial stacking and filling are coarse in grain size with a high degree of sorting, low content of mud and good physical properties; （3） early-stage recharge of hydrocarbons restricted compaction and cementation, and thus are favorable to preservation of primary pores; （4） microfractures caused by the activity of basement faults during the Yanshan Movement stage can not only improve the permeability of tight sandstones, but also afford vertical pathways for hydrocarbon gas migration.展开更多
基金supported by State Grid Jiangsu Electric Power Co.,Ltd.Technology Project(Research on Planning and Operation Technology of Electric–Hydrogen Coupling System Driven by the Electric–Carbon–Green Certificate Market):J2024005.
文摘Hydrogen,as a zero-carbon secondary energy carrier,provides a unified pathway for low-carbon energy transformation.In electro–hydrogen coupling systems(EHCSs),surplus renewable power is stored via water electrolysis and later reconverted to electricity using fuel cells or gas turbines,enhancing the system’s flexibility and reliability in support of deep decarbonization.This study constructs an electricity–hydrogen energy-recycling model based on a coupling relationship considering the bidirectional conversion between electricity and hydrogen.A multistage carbon-emission-reduction indicator constraint is also established.Additionally,the green-certificate and carbon trading markets are introduced to optimize equipment investment and operation costs while achieving carbon-emission reduction.A case study reveals that the proposed EHCS planning model effectively allocates carbon emissions across different system stages,while mitigating economic repercussions,thus ensuring closer alignment with China’s emission-reduction policies.Incorporating diverse market mechanisms significantly enhances the system’s economy and decision-making flexibility,particularly in addressing future challenges in the energy market.
基金the Science and Engineering Research Board(SERB),Department of Science and Technology,India,for funding this research through grant number SRG/2019/001581。
文摘Inspired by nature's self-similar designs,novel honeycomb-spiderweb based self-similar hybrid cellular structures are proposed here for efficient energy absorption in impact applications.The energy absorption is enhanced by optimizing the geometry and topology for a given mass.The proposed hybrid cellular structure is arrived after a thorough analysis of topologically enhanced self-similar structures.The optimized cell designs are rigorously tested considering dynamic loads involving crush and high-velocity bullet impact.Furthermore,the influence of thickness,radial connectivity,and order of patterning at the unit cell level are also investigated.The maximum crushing efficiency attained is found to be more than 95%,which is significantly higher than most existing traditional designs.Later on,the first and second-order hierarchical self-similar unit cell designs developed during crush analysis are used to prepare the cores for sandwich structures.Impact tests are performed on the developed sandwich structures using the standard 9-mm parabellum.The influence of multistaging on impact resistance is also investigated by maintaining a constant total thickness and mass of the sandwich structure.Moreover,in order to avoid layer-wise weak zones and hence,attain a uniform out-of-plane impact strength,off-setting the designs in each stage is proposed.The sandwich structures with first and second-order self-similar hybrid cores are observed to withstand impact velocities as high as 170 m/s and 270 m/s,respectively.
基金supported in part by the High-tech ship scientific research project of the Ministry of Industry and Information Technology of the People’s Republic of China,and the National Nature Science Foundation of China(Grant No.71671113)the Science and Technology Department of Shaanxi Province(No.2020GY-219)the Ministry of Education Collaborative Project of Production,Learning and Research(No.201901024016).
文摘Ship outfitting is a key process in shipbuilding.Efficient and high-quality ship outfitting is a top priority for modern shipyards.These activities are conducted at different stations of shipyards.The outfitting plan is one of the crucial issues in shipbuilding.In this paper,production scheduling and material ordering with endogenous uncertainty of the outfitting process are investigated.The uncertain factors in outfitting equipment production are usually decision-related,which leads to difficulties in addressing uncertainties in the outfitting production workshops before production is conducted according to plan.This uncertainty is regarded as endogenous uncertainty and can be treated as non-anticipativity constraints in the model.To address this problem,a stochastic two-stage programming model with endogenous uncertainty is established to optimize the outfitting job scheduling and raw material ordering process.A practical case of the shipyard of China Merchants Heavy Industry Co.,Ltd.is used to evaluate the performance of the proposed method.Satisfactory results are achieved at the lowest expected total cost as the complete kit rate of outfitting equipment is improved and emergency replenishment is reduced.
基金Scientific and Technological Project of Nanyang(23KJGG017)Key Specialized Research&Development and Promotion Project(Scientific and Technological Project)of Henan Province(232102221022)+1 种基金College Students and Technology Innovation Fund Project of Nanyang Institute of Technology(2023139)Project of Doctoral Scientific Research Startup Fund of Nanyang Institute of Technology(NGBJ-2023-25)。
文摘The leaching process of magnesiothermic self-propagating product generated during the multistage deep reduction process was investigated.The influence of magnesiothermic self-propagating product particle size,HCl solution concentration,and leaching solution temperature on the leaching behavior of elements Al and V was investigated.Results demonstrate that the leaching rate of Al and V is increased with the rise in leaching solution temperature,the increase in HCl solution concentration,and the enlargement of magnesiothermic self-propagating product particle size.The leaching processes of Al and V are consistent with the chemical reaction control model.When the magnesiothermic self-propagation product with D_(50) of 59.4μm is selected as the raw material,the leaching temperature is 40℃,and 1 mol/L HCl solution is employed,after leaching for 180 min,the leaching rates of Al and V are 24.8%and 12.6%,respectively.The acid-leached product exhibits a porous structure with a specific surface area of 3.5633 m^(2)/g.
基金supported by the China Agriculture Research System(CARS-15-22)the Laboratory of Lingnan Modern Agriculture Project,China(NT2021009)+2 种基金the Key-Area Research and Development Program ofGuangdong Province,China(2019B020214003)the Guangdong Technical System of Peanut and Soybean Industry,China(2019KJ136-05)the 111 Project,China(D18019)。
文摘Quantitative inversion is a major topic in remote sensing science.The development of visible light-based hyperspectral reconstruction techniques has opened novel prospects for low-cost,high-precision remote sensing inversion in agriculture.The aim of this study was to assess the effectiveness of hyperspectral reconstruction technology in agricultural remote sensing applications.Hyperspectral images were reconstructed using the MST++hyperspectral reconstruction model and compared with the original visible light images in terms of their correlations with physiological parameters,the accuracy of single-feature modeling,and the accuracy of combined feature modeling.The results showed that compared to the visible light image,the reconstructed data exhibited a stronger correlation with the measured physiological parameters,and the accuracy was improved for both the single feature and combined feature inversion modes.However,compared to multispectral sensors,hyperspectral reconstruction provided limited improvement of the inversion model accuracy.The results suggest that for physiological parameters that are not easy to observe directly,deep mining of features in visible light data through hyperspectral reconstruction technology can improve the accuracy of the inversion model.However,appropriate feature selection and simple models are more suitable for the remote sensing inversion task of traditional agronomic plot experiments.To strengthen the application of hyperspectral reconstruction technology in agricultural remote sensing,further development is necessary with broader wavelength ranges and more diverse agricultural scenarios.
基金supported in part by the National Key Research and Development Project of China(No.2022YFC3004602)in part by the National Natural Science Foundation of China(Nos.52121003 and 52342403).
文摘Multistage fracturing technology has been used to enhance tight hydrocarbon resource recovery.Determining the proper well spacing and fracturing strategy is crucial for generating a complex fracture network that facilitates oil and gas flow in reservoirs.The stress-shadow effect that occurs between multiple wells significantly affects the development of fracture networks in reservoirs.However,the quantification of the stress-shadow effect and its influence on fracture networks has not been satisfactorily resolved because of the difficulties in detecting and identifying fracture propagation and reorientation in reservoirs.In this study,based on the geological information from the Shengli oilfield,we applied a hybrid finite element-discrete element method to analyze engineering-scale three-dimensional fracture propagation and reorientation by altering well spacings and fracturing strategies.The results indicate that the fracturing area generated by the synchronous fracturing scheme is much smaller than those generated by the sequential and alternative schemes.An alternative hydrofracturing scheme is optimal with respect to fracturing area.The stress-blind area was defined to quantify the mechanical disturbance between adjacent wells.Our study improves the understanding of the effect of fracturing schemes on fracture networks and the impact of independent factors contributing to stress-shadow effects.
基金supported by the National Natural Science Foundation of China (No.52104008&No.52274042)the Natural Science Foundation of Sichuan,China (No.2024NSFSC0963)。
文摘The “well factory” mode's high-density well placement and multi-stage hydraulic fracturing technology enable efficient development of unconventional oil and gas resources.However,the deployment of platform wells in the “well factory” model results in small wellbore spacing,and the stress disturbances caused by fracturing operations may affect neighboring wells,leading to inter-well interference phenomena that cause casing deformation.This study investigates the issue of inter-well interference causing casing deformation or even failure during multi-stage hydraulic fracturing in the “well factory”model,and predicts high-risk locations for casing failure.A flow-mechanics coupled geomechanical finite element model with retaining geological stratification characteristics was established.Based on the theory of hydraulic fracturing-induced rock fragmentation and fluid action leading to the degradation of rock mechanical properties,the model simulated the four-dimensional evolution of multi-well fracturing areas over time and space,calculating the disturbance in the regional stress field caused by fracturing operations.Subsequently,the stress distribution of multiple well casings at different time points was calculated to predict high-risk locations for casing failure.The research results show that the redistribution of the stress field in the fracturing area increases the stress on the casing.The overlapping fracturing zones between wells cause significant stress interference,greatly increasing the risk of deformation and failure.By analyzing the Mises stress distribution of multi-well casings,high-risk locations for casing failure can be identified.The conclusion is that the key to preventing casing failure in platform wells in the “well factory” model is to optimize the spatial distribution of fracturing zones between wells and reasonably arrange well spacing.The study provides new insights and methods for predicting casing failure in unconventional oil and gas reservoirs and offers references for optimizing drilling and fracturing designs.
基金funded by the special research project for non-profit public service of the Chinese Ministry of Health(grant number:201202022 to YH)the national twelfth five-year plan for science and technology support of the Chinese Ministry of Science and Technology(grant numbers:2012BAI01B01 to YH)+1 种基金the National Key R&D Program of China(grant numbers:2017YFC0907800 to YH and 2017YFC0907801 to GX)the Major Projects of the Health Commission of Hunan Province(grant number:W20241001 to YZ)。
文摘Background Obsessive-compulsive disorder(OCD)is classified by the World Health Organization as 1 of the 10 most disabling conditions.However,nationally representative epidemiological data on OCD are not yet available in China.Aims To investigate the prevalence,comorbidity,role impairment and healthcare utilisation of OCD in China.Methods The present study used a multistage clustered area probability sample to obtain representative populationbased data of adults from 157 nationwide disease surveillance points across 31 provinces in China.Trained interviewers conducted face-to-face interviews with respondents to collect information based on the Composite International Diagnostic Interview 3.0.Data weighting was performed to account for differential selection probabilities and response rates,and to post-stratify the sample to ensure its representativeness of the population in China.Results A total of 28140 respondents(12537(44.55%)males and 15603(55.45%)females)completed the diagnostic interview.Two-thirds of the respondents with liftime OCD had comorbid mental disorders,with OCD typically emerging later than the comorbidities.The most common comorbidities were mood disorders(39.67%,odds ratio(OR):9.60,95%confidence interval(CI)7.35 to 12.53)and anxiety disorders(32.75%,OR:13.33,95%CI 10.14 to 17.52).Overall,588(weighted 58.19%)respondents with obsessions or compulsions experienced role impairment,which was most severe in those reporting unspecified symptoms.Only 46(6.74%)respondents with lifetime OCD and 28(6.48%)with 12-month OCD received any healthcare services for their conditions.Conclusions The weighted lifetime and 12-month prevalence of OCD were 2.43%and 1.63%,respectively.Most patients with OCD reported comorbid mental disorders and role impairment,but very few sought healthcare services.National programmes to expand service coverage and increase awareness of OCD are essential to meet healthcare needs in China.
基金Supported by the Key projects of the PetroChina Joint Fund Under the National Natural Science Foundation of China(U23B20154,92255302)Science and Technology Cooperation Project of the Innovation Consortium between PetroChina and Southwest Petroleum University(2020CX010000)Open Fund of the Key Laboratory of Carbonate Reservoirs,China National Petroleum Corporation(RIPED-2024-JS-1804).
文摘This study reconstructed the paleo-uplift and depression pattern within the sequence stratigraphic framework of the Mid-Permian Maokou Formation,Sichuan Basin,investigated its tectono-sedimentary mechanisms and its control on paleogeomorphology and large-sale shoals based on analysis of outcrops,loggings and seismic data.The results show that the Maokou Formation comprises two third-order sequences,six fourth-order sequences(SSQ1-SSQ6),and four distinct slope-break zones developing progressively from north to south.Slope-break zones I-III in the northern basin,controlled by synsedimentary extensional faults,exhibited a NE-trending linear distribution with gradual southeastward migration.In contrast,slope-break zone IV in the southern basin displayed an arcuate distribution along the Emeishan Large Igneous Province(ELIP).The evolutions of these multistage slope-break zones governed the Mid-Permian paleogeomorphy in the Sichuan Basin transformations from a giant,north-dipping gentle slope(higher in the southwest than in the northeast)in the early-stage(SSQ1-SSQ2)to a platform(south)-basin(north)pattern in the middle-stage(SSQ3-SSQ5).Ultimately,a further depression zone developed in the southwestern basin during the late-stage(SSQ6),forming a paleo-uplift bounded by two depressions.The developments of the Mid-Permian paleogeomorphic configuration reflected the combined control by the rapid subduction of the Mianlüe Ocean and the episodic eruptions of the Emeishan mantle plume(or hot spots),which jointly facilitated the formation of extensive high-energy shoal facies belts along slope-break zones and around paleo-volcanic uplifts.
基金supported by the National Social Science Fund of China(NSSFC)(Grant No 20BSH066,JZ).
文摘Background To investigate the relationship of age at first separation from parents(AFSP)with suicidal ideation(SI),suicide planning(SP)and suicide attempts(SA)among left-behind children(LBC)in China and the mediating effect of traumatic events(TEs).Methods This cross-sectional study employed a multistage sampling method to conduct questionnaire surveys in six high-concentrated LBC provinces.Logistic regression and restricted cubic splines were performed to investigate the association of AFSP with SI,SP and SA,and meta-analysis(I2)was used to assess the heterogeneity.Causal mediation analysis(structural equation modelling)was used to evaluate the mediating effect of TEs,and bootstrap resampling was employed to assess the robustness of the causal mediation analysis.Results A total of 12162(6269 LBC)participants were included in this study;the prevalence rates of SI,SP and SA among LBC were 30.7%,18.6%and 11.9%;and LBC had a higher risk of SI(OR:1.32),SP(OR:1.40)and SA(OR:1.25)than non-LBC,all p<0.001.AFSP was negatively associated with SI,SP and SA,particularly peaking before 2 years old.LBC with AFSP<2 years old had a higher risk of SI(OR 2.65;95%CI 2.17 to 3.24;p<0.001),SP(OR 2.63;95%CI 3.36 to 4.29;p<0.001)and SA(OR 2.04;95%CI 2.73 to 3.63;p<0.001).TEs mediated the increased risk of SI(average causal mediation effect(ACME)0.03–0.07;proportion(Prop)40–54%;all p<0.001),SP(ACME 0.03–0.06;Prop 39–61%;all p<0.001)and SA(ACME 0.02–0.04;Prop 53–80%;all p<0.01).Conclusions We found that AFSP was associated with SI,SP and SA,mediated by TEs.Our findings supported the necessity of reducing SI,SP and SA risks among LBC and highlighted the need to consider AFSPs and TEs in intervention strategies.
文摘The current portfolio model for property-liability insurance company is only single period that can not meet the practical demands of portfolio management, and the purpose of this paper is to develop a multiperiod model for its portfolio problem. The model is a multistage stochastic programming which considers transaction costs, cash flow between time periods, and the matching of asset and liability; it does not depend on the assumption for normality of return distribution. Additionally, an investment constraint is added. The numerical example manifests that the multiperiod model can more effectively assist the property-liability insurer to determine the optimal composition of insurance and investment portfolio and outperforms the single period one.
文摘This paper presents an efficient way to implement an interpolation filter in a 20bit ∑-△ DAC with an oversampling ratio of 128. A multistage structure is used to reduce the complexity of filter coefficients and the fi- nite word length effect. A novel method based on mixed-radix number representation is proposed to realize a poly- phase multiplier-free half-band subfilter with a high resolution. This approach reduces the complexity of the con- trol system and saves chip area dramatically. The IC is realized in a standard 0.13μm CMOS process and the inter- polation filter occupies less than 0.63mm^2 . This realization has desirable properties of regularity with simple hard- ware devices which are suitable for VLSI and can be applied to many other high resolution data converters.
文摘A new frequency compensation technique for low-power, area-efficient multistage amplifiers is introduced. Using nested active capacitors, our scheme achieves better bandwidth-to-power and slew-rate-to-power performances than previous works. Implemented in standard 0.35μm CMOS technology, our three-stage amplifier achieves 105dB DC gain, 3.3M GBW,68 phase margin, and 2.56V/μs average slew rate under a 150pF capacitive load. All of these are realized with only 40μW power consumption under a 2V power supply,with very small compensation capacitors.
文摘Abstract There are two extensional systems in the Xiaoqinling metamorphic core complex (XMCC). One is the detachment fault system developed along the peripheries of the XMCC, which extended in an ESE-WNW direction and whose upper plate moved towards the WNW. The other extensional system includes the retrograde shear zones and normal faults developed within the XMCC, which represent the collapse of the XMCC. Ar-Ar and K-Ar dating shows that the extension of the detachment fault system continued from 135 to 123 Ma, i.e. in the late stage of its evolution at about 127 Ma. The collapse represented by the extensional system within the XMCC was operative during 120–106 Ma, and its main activity occurred about 116 Ma ago. These suggest that the XMCC experienced two extensional stages in its evolution, i.e., the syn-orogenic regional extension and post-orogenic collapse extension.
基金co-supported by the National Natural Science Foundation of China(Nos.51576009,11661141020 and 51711530036)the Aeronautical Science Foundation of China(No.20151554002)。
文摘Rotor blades fault of aeroengine compressor is mostly caused by mechanical and aerodynamic excitation.And the excitation factor of high intensity sound wave to rotor blades should not be ignored.Experimental researches are conducted on a multistage high pressure compressor.When high level vibration occurs on the first stage of rotor blades, the noise spectrum presents typical characteristic for discrete multi-tone in the compressor.The amplitude of blade vibration displacement and the sound pressure level of characteristic frequency noise increases and decreases simultaneously and reaches the maximum value at the same time.This frequency merely occur on a certain speed range and is locked in a specific range which presents no variation with the rotating speed.When high level vibration occurs on the first stage of rotor blades, the noise spectrum presents a sharp peak and the propagation state of the characteristic frequency is a helix structure in the compressor.It can be confirmed that acoustic resonance occurs in the multistage compressor.The acoustic resonance frequency and its side band frequencies are generated by modulation of a rotating noise source at the rotor speed which is the excitation source of the rotor blades vibration.
文摘The Huangtuling hypersthene-garnet-biotite gneiss at Luotian County, Hubei Provine, is a typicalgranulite-facies rock of the Dabie Group Complex in the Dabie orogenic belt. Investigations on the morphology andoccurrence of zircons and their internal structures shown in the thin sections lead to the recognition of three types ofzircons, which are in good agreement with the types identified on the basis of morphology, colour and external fea-tures from the related zircon concentrates. The observation of zircons in the rock reveals that part of type 1 zirconsshow signs of a double-layered structure. The interval part existed in the protolith prior to the granulite-facies meta-morphism. Type 2, the prismatic zircons which mainly occur in garnet and hypersthene are metamorphic minerals ofthe granulite-facies metamorphism. Type 3, the round multifaceted zircons in felsic minerals and biotite, are proba-bly attributed to a later geological event related to migmatization. The ^(207)Pb/^(206)Pb zircon dating by direct evaporationon (thermal evaporation ion mass spectrometer) yields ages ranging from 2814 Ma to 1992 Ma. The age discrepancyamong these different zircon types is conspicuous. The yellow-brown(type 1) zircons give ages of 2814±29 Ma to2527±6 Ma, the prismatic euhedral zircons (type 2), 2456±7 Ma to 2254±4 Ma, and the round multifaceted zircons(type 3), 1992±10 Ma. The results are geologically interpreted in consideration of the complicated behaviours of zir-cons during Precambrian geological evolution of the Dabie area. (1) If the protolith of the gneiss is a sedimentaryrock, then type 1 zircons are clastic ones and the ages 2814±29 Ma and 2811±27 Ma may reflect the minimum age ofthe rocks of its source region. also the first geological event in the area. Sedimentation of the protolith occurred be-tween 2814 Ma and 2527 Ma, probably close to 2814 Ma. If the protolith is a volcanic rock, then the formation age ofthe supracrustal rocks of the Dabie Group Complex is around 2814 Ma. The age 2456±7 Ma reflects the time whenthe granulite-facies metamorphism took place. The later migmatization event is dated at aboat 1992±10 Ma, and isprobably the latest early Precambrian event in the area. The present work provides geochronological evidence for the existence of the Dabie Archaean craton, whichhad probably experienced 3 or 4 geological events during its early Precambrian evolution.
基金This research is part of a project carried out during 2002-2004 and supported by the National Basic Research Program(Grant No.2001CB209100).
文摘The upper Paleozoic natural gas reservoirs in the Ordos basin are generally characterized by a large gas-bearing area and low reserve abundance. On such a geological background, there still exist gas-enriched zones, with relatively high outputs, high reserve abundance and stably distributed gas layers. The gas-enriched layers with relatively high permeability （the lower limit permeability is 0.5×10^-3μm^2） are key factors for the enrichment and high output of natural gas. Based on core observation, analytic results of inclusions, and a great deal of drilling data, we proposed the following four mechanisms for the formation of high-quality reservoirs： （1） in the source area the parent rocks are mainly metamorphic rocks and granites, which are favorable to keeping primary porosity; （2） under the condition of low A/S （accommodation/sediment supply） ratios, sandstone complex formed due to multistage fluvial stacking and filling are coarse in grain size with a high degree of sorting, low content of mud and good physical properties; （3） early-stage recharge of hydrocarbons restricted compaction and cementation, and thus are favorable to preservation of primary pores; （4） microfractures caused by the activity of basement faults during the Yanshan Movement stage can not only improve the permeability of tight sandstones, but also afford vertical pathways for hydrocarbon gas migration.
