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中国科学:技术科学（英文版）
中国科学:技术科学（英文版）

周光召

月刊

1674-7321

sales@scichina.org

010-64019820

100717

北京东黄城根北街16号

中国科学:技术科学（英文版）/Journal Science China Technological SciencesCSCDCSTPCDEISCI
查看更多>>《中国科学》是中国科学院主办、中国科学杂志社出版的自然科学专业性学术刊物。《中国科学》任务是反映中国自然科学各学科中的最新科研成果，以促进国内外的学术交流。《中国科学》以论文形式报道中国基础研究和应用研究方面具有创造性的、高水平的和有重要意义的科研成果。在国际学术界，《中国科学》作为代表中国最高水平的学术刊物也受到高度重视。国际上最具有权威的检索刊物SCI，多年来一直收录《中国科学》的论文。1999年《中国科学》夺得国家期刊奖的第一名。
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    A hybrid attention model based on first-order statistical features for smoke recognition

    GUO NanLIU JiaHuiDI KeXinGU Ke...
    809-822页
    查看更多>>摘要：Smoke and fire recognition are of great importance on foreseeing fire disasters and preventing environmental pollution by moni-toring the burning process of objects(e.g.,straw,fuels).However,since fire images suffer from problems like the variability of the features,complexity of scenarios,interference from background,changeable weather conditions as well as image quality prob-lems,identifying smoke and fire accurately and promptly from a given image still remains a substantial challenge.Automatically learning the features of smoke images by CNNs has improved the target recognition ability compared to traditional approaches,nonetheless,convolutions and pooling operations in CNNs may cause severe information loss which may lead to misjudgment.To tackle the above problems,this paper proposed a hybrid attention model based on the characteristics of smoke images.This model adopted multiple optimized attention mechanism in several stages to quickly and precisely capture the important features,achieving state-of-the-art performance on smoke and fire recognition in terms of accuracy and speed.Our proposed module mainly consists of two stages:pooling and attention.In the first stage,we conducted several newly proposed first-order pooling methods.Through traversing the data space in a larger scope,features are better reserved,thus constructing a more intact feature space of smoke and fire in an image.In the second stage,feature maps are aggregated together to perform channel and spatial attention.The channel and spatial dependencies allow us to quickly catch the important features presented in an image.By fully exploring the feature space and prominent salient features,characteristics of smoke and fire are better presented so as to obtain better smoke and fire detection results.Experiments have been conducted on public smoke detection dataset and new proposed fine-grained smoke and fire detection database.Experimental results revealed that the proposed method outperformed popular deep CNNs and existing prevalent attention models for smoke and fire detection problems.
      原文链接:
    • 万方数据
    • 维普

    Flexible assistance strategy of lower limb rehabilitation exoskeleton based on admittance model

    KOU JianGeWANG YiXuanCHEN ZhenLeiSHI Yan...
    823-834页
    查看更多>>摘要：Exercise training based on exoskeleton is an effective rehabilitation method for stroke patients.However,some rehabilitation exoskeletons still have poor wearable performance and obvious human-robot impedance during training,which easily cause secondary injuries to the patients.In this study,a variable admittance control strategy is proposed to improve the operator's wearable comfort,which can adapt to different operators by regulating admittance parameters.The admittance controller has two feedback loops:the position inner-loop and the admittance outer-loop.Meanwhile,the exoskeleton Lagrange model is constructed with unknown friction disturbance.By using Lyapunov technique and backstepping with state observer,the joint position error of exoskeleton is convergence into a zero neighborhood.The effectiveness of the proposed admittance controller is verified by both simulation and experiment.The tracking error of hip and knee joint is less than 4 degrees while the human-robot interaction torque is constrained in a tolerable range of the operator.
      原文链接:
    • 万方数据
    • 维普

    Modeling wave propagation across rock masses using an enriched 3D numerical manifold method

    YANG YongTaoLI JunFengWU WenAn
    835-852页
    查看更多>>摘要：The three-dimensional numerical manifold method(3DNMM)method is further enriched to simulate wave propagation across homogeneous/jointed rock masses.For the purpose of minimizing negative effects from artificial boundaries,a viscous non-reflecting boundary,which can effectively absorb the energy of a wave,is firstly adopted to enrich 3DNMM.Then,to simulate the elastic recovery property of an infinite problem domain,a viscoelastic boundary,which is developed from the viscous nonreflecting boundary,is further adopted to enrich 3DNMM.Finally,to eliminate the noise caused by scattered waves,a force input method which can input the incident wave correctly is incorporated into 3DNMM.Five typical numerical tests on P/S-wave propagation across jointed/homogeneous rock masses are conducted to validate the enriched 3DNMM.Numerical results indicate that wave propagation problems within homogeneous and jointed rock masses can be correctly and reliably modeled with the enriched 3DNMM.
      原文链接:
    • 万方数据
    • 维普

    Increasing operational stability of journal bearing in hydraulic suspension micro-pump by herringbone grooved structure

    HONG TaoXING GuanYingZUO HuaiYuXUE Song...
    853-862页
    查看更多>>摘要：The operational stability of radial journal bearings is the bottleneck that limits the reliability of hydraulic suspension micro-pump.Due to self-excited vibrations,the whirl amplitude of the plain journal bearing(PJB)is large at high rotational speeds,which will accelerate wear failure.It has been proven that employing herringbone grooved journal bearing(HGJB)is an effective method to reduce the whirl amplitude and improve operational stability.However,enhancing the stability of journal bearings in micro-pumps by herringbone grooved structures has rarely been studied,and its effect needs to be verified.We validated the mechanism of the stability improvement with the CFD method and compared the dynamic characteristics of HGJB and PJB by rotor dynamics evaluation and experiment.The experimental results show that under the same conditions the whirl amplitude of the HGJB decreases by 29.61％in the x direction and by 24.09％in the y direction compared with that of the PJB.This study reveals the effect of the herringbone grooved structure on the operational stability of bearings and may provide guidance for the reliability improvement of hydraulic suspension micro-pump.
      原文链接:
    • 万方数据
    • 维普

    A unified stochastic damage model for concrete based on multi-scale energy dissipation analysis

    GUO ChengGongLI Jie
    863-877页
    查看更多>>摘要：This work proposes a unified damage model for concrete within the framework of stochastic damage mechanics.Based on the micro-meso stochastic fracture model(MMSF),the nonlinear energy dissipation process of the microspring from nanoscale to microscale is investigated.In nanoscale,the rate process theory is adopted to describe the crack growth rate;therefore,the corresponding energy dissipation caused by a representative crack propagation can be obtained.The scale gap from nanoscale to microscale is bridged by a crack hierarchy model.Thus,the total energy dissipated by all cracks from the nanoscale to the microscale is gained.It is found that the fracture strain of the microspring can be derived from the above multi-scale energy dissipation analysis.When energy dissipation is regarded as some microdamage to the microspring,the constitutive law of the microspring is no longer linearly elastic,as previously assumed.By changing the expression of the damage evolution law from fracture strain to energy dissipation threshold,the new damage evolution model is derived.The proposed model can not only replicate the original static model but also extend to cases of rate dependence.By deriving the fracture strain under different strain rates,the rate sensitivity of concrete materials can be reflected.The model parameters can be conveniently obtained by identifying them with experimental data.Finally,several numerical examples are presented to verify the proposed model.
      原文链接:
    • 万方数据
    • 维普

    Triboelectric nanogenerator hybrid array driven by multiform natural energies and its applications in self-powered cathodic protection

    SUN WeiXiangYANG DiLUO NingLI Hao...
    878-890页
    查看更多>>摘要：In view of the increasing energy shortage and environmental pollution,the collection of friction charges to achieve the conversion of various natural energies and provide in-situ cathodic protection for metals is a significant challenge.Here,we designed a dual device-structure TENG composite array with the triboelectric layer of linear siloxane-modified polyurethane(PU)coating.This array could achieve a comprehensive collection for multiple forms of nature energy and cathodic protection of metals in multi-weather conditions.For one thing,the wave-mode TENG based on tanker structure could collect wave energy and showed the output performance with a short-circuit current of 15.5 μA.For another thing,the droplet-mode TENG based on arc-shaped surface structure could collect raindrop kinetic energy and showed the output performance with a short-circuit current of 16.3 μA.Notably,the parallel array of wave-mode TENG(W-TENG)and droplet-mode TENG(D-TENG)could simulta-neously collect wave energy and raindrop kinetic energy,which showed a short-circuit current of 30.7 μA.Besides,a self-powered a cathodic protection system powered by the dual structure TENG array is assembled and the open-circuit potential drop of the carbon steel connected with the TENG array is about 450 mV.Compared with cathodic protection system powered by single structure TENG,the composite array could provide more effective corrosion resistance for marine equipment in rainy weather.Due to the characteristic for comprehensive collection of nature energy,the anti-corrosion system supplied by TENG parallel array possesses great application potential in the all-weather corrosion protection of metal machinery under complex marine conditions.
      原文链接:
    • 万方数据
    • 维普

    Injectable chitosan hydrogels loaded with antioxidant agent as first-aid dressings for second-degree burn wounds

    REN HuiZHANG ZhenLU KaiLunSHEN YuanYuan...
    891-901页
    查看更多>>摘要：Bum wounds are destructive skin traumas typically of irregular shape and large area.Prone to infection,they require frequent dressing replacement,and painless removal of dressings from bum wounds remains a major challenge.This study focuses on the dynamic characteristics and treatment difficulty of burn wounds.Hydrogel dressings based on glycol chitosan and propio-naldehyde-or benzaldehyde-terminated 4-arm poly(ethylene glycol)were designed on the basis of Schiff base cross-linking networks.The hydrogels exhibited shape-adaptability,self-healing and fast-degradation properties,which makes these hydrogels suitable for burn wounds.Salvianolic acid B(SaB)-loaded hydrogel exhibited good antioxidant properties in vitro.In a rat model of deep second-degree bum wounds,the SaB-loaded hydrogel could quickly reduce wound temperature,regulate wound oxidant microenvironment,promote angiogenesis,and accelerate wound healing.Thus,the drug-loaded hydrogel shows significant potential as a first-aid dressing for treatment of bum wounds.
      原文链接:
    • 万方数据
    • 维普

    Design and performance investigation of modified dual reflector parabolic trough collector with double planar mirrors

    LI PeiJingLIU TaiXiuQIN YuanLongLI JiChao...
    902-918页
    查看更多>>摘要：In a typical parabolic trough collector(PTC),sunlight is concentrated at the bottom of the absorber tube.This concentrated solar flux leads to uneven heat distribution,resulting in high local temperatures and significant thermal stress on the absorber tube.These limitations have restricted the application of PTCs in solar thermochemistry and other fields and have impacted their safe operation.In this study,a new PTC with dual planar mirrors(DPMS)is proposed to homogenize the circumferential solar flux distribution of the absorber tube.A design method and single-objective optimization of the new PTC with a DPMS are proposed,and an uncertainty analysis of the operational and structural parameters is performed.A coupled light-heat-structure numerical model was developed to study the heat transfer performance and structural mechanical properties.The thermodynamic properties of the PTC with DPMS under different boundary conditions were analyzed.The results show that the circumferential tem-perature difference of the new PTC is within 2.6 K,and the circumferential thermal deformation is within 0.9 mm under typical working conditions(the inlet velocity of the heat transfer fluid is 3 m/s,inlet temperature is 573.15 K,and the direct normal irradiance is 1000 W/m2).Compared with conventional PTCs,the circumferential temperature difference is reduced by 74％-90％,and the maximum thermal deformation along the y-axis is reduced by more than 95％under all working conditions(1-5 m/s,373.5-675.15 K,200-1000 W/m2).The new PTC maintains the uniformity of the circumferential solar flux dis-tribution for different operating parameters(sun incident angle of 0°-3°)and installation errors(±3 mm),is suitable for solar energy applications in various fields,and has the potential for large-scale applications.
      原文链接:
    • 万方数据
    • 维普

    Constructal design of a rectangular porous fin considering minimization of maximum temperature difference and pumping power consumption

    LIU XiaoYeFENG HuiJunCHEN LinGenGE YanLin...
    919-929页
    查看更多>>摘要：A heat dissipation model of a rectangular porous fin is established based on constructal theory.First,the constructal design of rectangular porous fin is conducted by selecting a complex function minimization,which composed of linear weighting sum of maximum temperature difference and pumping power consumption,as optimization objective.Effects of gap height,air inlet velocity,total porous fin volume and porosity on the optimal constructs are investigated,respectively.The findings show that the complex function can attain its double minimum at a value of 0.802 when the fin length and number are optimized,and the corresponding optimal fin length and number are 8.01 mm and 10,respectively.In comparison to original design,the complex function and maximum temperature difference after twice optimization are decreased by 19.80％and 66.31％,respectively.Second,the comprehensive performance of porous fin is improved by simultaneously optimizing the fin length and number.The artificial neural network is applied to predict the fin performances,which is used to conduct multi-objective optimization based on NSGA-Ⅱ algorithm.Optimal structure of porous fin for multiple requirements is gained by LINMAP and TOPSIS decision-making strategies.The findings in this study can serve as theoretical guides for fin thermal designs of electronic devices.
      原文链接:
    • 万方数据
    • 维普

    Coupled interactive effects of ammonia and hydrogen additions on ethylene diffusion flames:A detailed kinetic study

    XIAO JiaYiXU TingTingSHU ZhiMeiDENG QiGe...
    930-948页
    查看更多>>摘要：In order to create effective combustion technologies and fuels with low or no carbon emissions,the research was conducted to assess the coupled interactive effects of NH3 and H2 additions on ethylene counterflow diffusion flames from a kinetic per-spective.The effects of the NH3/H2 combination on flame temperatures,major species,key radicals,important intermediate species,representative oxygenated species and NOx were examined.The results of the study utilizing fictitious inert NH3 and/or H2 revealed the chemical effects of the two components.It was found that the NH3/H2 coupled effects had a more effective inhibitory effect on soot precursors than the effects of corresponding sum of single NH3 or H2 addition.The production of soot precursors was promoted by the coupled chemical effects of NH3 and H2,but the coupled dilution and thermal effects were observed to have a greater impact,resulting in a decrease of the mole fractions of soot precursors.As for the interaction of NH3 and H2 effects,the presence of H2 decreased the chemical effects of NH3 on the augmentation of C2H2,Al,A2,and CH3CHO mole fractions.The NH3 addition alleviated the H2 chemical effects on increasing C2H2,C3H3,Al and A2 concentrations.Conversely,the NH3 chemical effects on C3H3,OH and CH3CHO were enhanced when H2 was added.The presence of NH3 augmented the chemical effects of H2 on the growth of OH mole fraction.Moreover,the H2 chemical effects hindered the production of NO and NO2 in the presence of NH3.
      原文链接:
    • 万方数据