Sand production is a critical issue during the development of offshore oil and gas fields.Certain gas fields(e.g.the AB gas field)have high porosity and high permeability,and with water at the bottom of the reservoir,...Sand production is a critical issue during the development of offshore oil and gas fields.Certain gas fields(e.g.the AB gas field)have high porosity and high permeability,and with water at the bottom of the reservoir,the risk of sand production greatly increases at high differential pressures.Based on reservoir properties,geological conditions,production requirements,and well logging data,in this study an ultrasonic time difference method,a B index method,and a S index method are used together with a model of rock mass failure(accounting for water influx and pressure depletion)to qualitatively predict sand production.The results show that considered sample gas field has an overall high risk of sand production.The critical differential pressure(CDP)without water influx is in the range of 1.40 to 2.35 MPa,the CDP after water influx is from 0.60 to 1.41MPa.The CDP under pressure depletion is in the range of 1.20 to 1.92 MPa.The differential pressure charts of sand production are plotted,and the safe differential pressure windows with or without water influx are obtained.The model calculation results and the experimental results are consistent with the field production data,which indicates that the implemented prediction method could be taken as a reference for sand production prediction in similar deep water gas fields.展开更多
The multitrip pickup and delivery problem with time windows and manpower planning(MTPDPTW-MP)determines a set of ambulance routes and finds staff assignment for a hospital. It involves different stakeholders with dive...The multitrip pickup and delivery problem with time windows and manpower planning(MTPDPTW-MP)determines a set of ambulance routes and finds staff assignment for a hospital. It involves different stakeholders with diverse interests and objectives. This study firstly introduces a multiobjective MTPDPTW-MP(MO-MTPDPTWMP) with three objectives to better describe the real-world scenario. A multiobjective iterated local search algorithm with adaptive neighborhood selection(MOILS-ANS) is proposed to solve the problem. MOILS-ANS can generate a diverse set of alternative solutions for decision makers to meet their requirements. To better explore the search space, problem-specific neighborhood structures and an adaptive neighborhood selection strategy are carefully designed in MOILS-ANS. Experimental results show that the proposed MOILS-ANS significantly outperforms the other two multiobjective algorithms. Besides, the nature of objective functions and the properties of the problem are analyzed. Finally, the proposed MOILS-ANS is compared with the previous single-objective algorithm and the benefits of multiobjective optimization are discussed.展开更多
In this paper, a delayed nonresident computer virus model with graded infection rate is considered in which the following assumption is imposed: latent computers have lower infection ability than infectious computers....In this paper, a delayed nonresident computer virus model with graded infection rate is considered in which the following assumption is imposed: latent computers have lower infection ability than infectious computers. With the aid of the bifurcation theory, sufficient conditions for stability of the infected equilibrium of the model and existence of the Hopf bifurcation are established. In particular, explicit formulae which determine direction and stability of the Hopf bifurcation are derived by means of the normal form theory and the center manifold reduction for functional differential equations. Finally, a numerical example is given in order to show the feasibility of the obtained theoretical findings.展开更多
Neuropathic pain is a long term and common pain disorder in clinics that is refractory to treatment,however,the neural substrates and underlying mechanisms are poorly understood.Using the com bination of neuronal mapp...Neuropathic pain is a long term and common pain disorder in clinics that is refractory to treatment,however,the neural substrates and underlying mechanisms are poorly understood.Using the com bination of neuronal mapping,optogenetics,chemogenetics,eletrophysiological recording,in vivo fiber photometry and behavioral testing,we previously identified a new neural circuit of BLA-mPFC-vIPAG and its key role in encoding and modulation of the spared nerve injury(SNI)-induced neuropathic pain..Here we report that the V M-vlOFC-vIPAG circuit modulates neuropathic pain and dissects the underlying mechanisms at cellular and circuitry level.展开更多
In this study,we investigate a forest-based solution representation for split delivery vehicle routing problems(SDVRPs),which have several practical applications and are among the most difficult vehicle routing proble...In this study,we investigate a forest-based solution representation for split delivery vehicle routing problems(SDVRPs),which have several practical applications and are among the most difficult vehicle routing problems.The new solution representation fully reflects the nature of split delivery,and can help reduce the search space when used in heuristic algorithms.Based on the forest structure,we devise three neighborhood search operators.To highlight the effectiveness of this solution representation,we integrate these operators into a standard tabu search framework.We conduct extensive experiments on three main SDVRPs addressed in the literature:The basic SDVRP,the multidepot SDVRP,and the SDVRP with time windows.The experimental results show that the new forest-based solution representation is particularly effective in designing and implementing neighborhood operators,and that our new approach outperforms state-of-the-art algorithms on standard datasets.展开更多
Infrared lead chalcogenide quantum dots(QDs)suffer fast degradation due to the easy oxidation of surface chalcogen atoms.Here,we report a trioctylphosphine-mediated surface passivation method to improve the air stabil...Infrared lead chalcogenide quantum dots(QDs)suffer fast degradation due to the easy oxidation of surface chalcogen atoms.Here,we report a trioctylphosphine-mediated surface passivation method to improve the air stability of PbS QDs.Surface mechanism study reveals an in situ surface reaction,which leads to site-selective passivation of surface S atoms with lead mono-carboxylate.The surface capping motif sufficiently protects PbS QDs from oxygen and improves their stability as well as quantum efficiency regardless of the QD size and original ligands on surface cations.The modified PbS QDs display no obvious fluorescence quenching and surface oxidization after 30 days of air exposure.The robust surface capping also provides high compatibility of PbS QDs with polymers for optoelectronic device fabrication.The near-infrared LEDs based on the modified PbS QDs display a slight degradation of only 1.47%from the maximum intensity after continuous operation in air for 250 hours(lifetime>10,000 h)at 0.5 W/cm^(2) power density,indicating the surface passivation route is promising strategy for promoting practical optoelectronic application of PbS QDs.展开更多
基金This research is financially supported by the National Natural Science Foundation of China(Grant No.52174015)supported by the Program for Changjiang Scholars and Innovative Research Team in University(IRT_14R58).
文摘Sand production is a critical issue during the development of offshore oil and gas fields.Certain gas fields(e.g.the AB gas field)have high porosity and high permeability,and with water at the bottom of the reservoir,the risk of sand production greatly increases at high differential pressures.Based on reservoir properties,geological conditions,production requirements,and well logging data,in this study an ultrasonic time difference method,a B index method,and a S index method are used together with a model of rock mass failure(accounting for water influx and pressure depletion)to qualitatively predict sand production.The results show that considered sample gas field has an overall high risk of sand production.The critical differential pressure(CDP)without water influx is in the range of 1.40 to 2.35 MPa,the CDP after water influx is from 0.60 to 1.41MPa.The CDP under pressure depletion is in the range of 1.20 to 1.92 MPa.The differential pressure charts of sand production are plotted,and the safe differential pressure windows with or without water influx are obtained.The model calculation results and the experimental results are consistent with the field production data,which indicates that the implemented prediction method could be taken as a reference for sand production prediction in similar deep water gas fields.
基金supported by the National Key R&D Program of China(2018AAA0101203)the National Natural Science Foundation of China(61673403,71601191)the JSPS KAKENHI(JP17K12751)。
文摘The multitrip pickup and delivery problem with time windows and manpower planning(MTPDPTW-MP)determines a set of ambulance routes and finds staff assignment for a hospital. It involves different stakeholders with diverse interests and objectives. This study firstly introduces a multiobjective MTPDPTW-MP(MO-MTPDPTWMP) with three objectives to better describe the real-world scenario. A multiobjective iterated local search algorithm with adaptive neighborhood selection(MOILS-ANS) is proposed to solve the problem. MOILS-ANS can generate a diverse set of alternative solutions for decision makers to meet their requirements. To better explore the search space, problem-specific neighborhood structures and an adaptive neighborhood selection strategy are carefully designed in MOILS-ANS. Experimental results show that the proposed MOILS-ANS significantly outperforms the other two multiobjective algorithms. Besides, the nature of objective functions and the properties of the problem are analyzed. Finally, the proposed MOILS-ANS is compared with the previous single-objective algorithm and the benefits of multiobjective optimization are discussed.
基金supported by Natural Science Foundation of Anhui Province (Nos. 1608085QF145, 1608085QF151)Project of Support Program for Excellent Youth Talent in Colleges and Universities of Anhui Province (No. gxyqZD2018044)
文摘In this paper, a delayed nonresident computer virus model with graded infection rate is considered in which the following assumption is imposed: latent computers have lower infection ability than infectious computers. With the aid of the bifurcation theory, sufficient conditions for stability of the infected equilibrium of the model and existence of the Hopf bifurcation are established. In particular, explicit formulae which determine direction and stability of the Hopf bifurcation are derived by means of the normal form theory and the center manifold reduction for functional differential equations. Finally, a numerical example is given in order to show the feasibility of the obtained theoretical findings.
文摘Neuropathic pain is a long term and common pain disorder in clinics that is refractory to treatment,however,the neural substrates and underlying mechanisms are poorly understood.Using the com bination of neuronal mapping,optogenetics,chemogenetics,eletrophysiological recording,in vivo fiber photometry and behavioral testing,we previously identified a new neural circuit of BLA-mPFC-vIPAG and its key role in encoding and modulation of the spared nerve injury(SNI)-induced neuropathic pain..Here we report that the V M-vlOFC-vIPAG circuit modulates neuropathic pain and dissects the underlying mechanisms at cellular and circuitry level.
文摘In this study,we investigate a forest-based solution representation for split delivery vehicle routing problems(SDVRPs),which have several practical applications and are among the most difficult vehicle routing problems.The new solution representation fully reflects the nature of split delivery,and can help reduce the search space when used in heuristic algorithms.Based on the forest structure,we devise three neighborhood search operators.To highlight the effectiveness of this solution representation,we integrate these operators into a standard tabu search framework.We conduct extensive experiments on three main SDVRPs addressed in the literature:The basic SDVRP,the multidepot SDVRP,and the SDVRP with time windows.The experimental results show that the new forest-based solution representation is particularly effective in designing and implementing neighborhood operators,and that our new approach outperforms state-of-the-art algorithms on standard datasets.
基金supported by the National Natural Science Foundation of China(81972276,31771540,82173040,91740205,and 31620103911)Natural Science Foundation of Zhejiang Province(LYY19H310011)Fundamental Research Funds for the Central Universities(2021QNA7004)。
基金This work is financially supported by National Natural Science Foundation of China(Nos.51672068,61974052,and 51902082)Natural Science Foundation of Tianjin City(No.17JCYBJC41500)+2 种基金Natural Science Foundation of Hebei Province(Nos.B2020202049,E2020202083,and F2019202252)Hubei Provincial Natural Science Foundation of China(No.2017CFB417)Tianjin Key Laboratory of Imaging and Sensing Microelectronic Technology.
文摘Infrared lead chalcogenide quantum dots(QDs)suffer fast degradation due to the easy oxidation of surface chalcogen atoms.Here,we report a trioctylphosphine-mediated surface passivation method to improve the air stability of PbS QDs.Surface mechanism study reveals an in situ surface reaction,which leads to site-selective passivation of surface S atoms with lead mono-carboxylate.The surface capping motif sufficiently protects PbS QDs from oxygen and improves their stability as well as quantum efficiency regardless of the QD size and original ligands on surface cations.The modified PbS QDs display no obvious fluorescence quenching and surface oxidization after 30 days of air exposure.The robust surface capping also provides high compatibility of PbS QDs with polymers for optoelectronic device fabrication.The near-infrared LEDs based on the modified PbS QDs display a slight degradation of only 1.47%from the maximum intensity after continuous operation in air for 250 hours(lifetime>10,000 h)at 0.5 W/cm^(2) power density,indicating the surface passivation route is promising strategy for promoting practical optoelectronic application of PbS QDs.
