The water hammer problem is an important issue in the dynamics of liquid propulsion system.This paper aims to use the Lattice Boltzmann Method(LBM)with entropy limiter to study the water hammer problems in propellant ...The water hammer problem is an important issue in the dynamics of liquid propulsion system.This paper aims to use the Lattice Boltzmann Method(LBM)with entropy limiter to study the water hammer problems in propellant feedlines.The dynamic characteristics of valve-closing water hammer and filling water hammer are investigated by this method,and the sensitivity of filling water hammer is analyzed with a single factor sensitivity analysis with 8 factors and 9 levels and a multi-factor sensitivity analysis with L_(27)(3^(13))orthogonal experiment based on range method.It is found that the solving result of LBM with entropy limiter is basically in good agreement with finite volume method,and using the entropy limiter can eliminate numerical oscillations when solving valve-closing water hammer problems and solve the numerical"blow up"when solving filling water hammer problems.It can be seen that the dynamic characteristics of valve-closing water hammer are relatively simple,while there are many factors that affect the filling water hammer and the degree of these effects varies.The effects on the maximum water hammer pressure are relatively uniform,but those on the water hammer response time vary greatly through the skewness analysis.展开更多
Temperature is a key meteorological factor that affects tropospheric ozone(O_(3)),with both humid-heat(sauna days)and dry-heat(roast days)conditions leading to O_(3) exceedances.However,the mechanisms influencing O_(3...Temperature is a key meteorological factor that affects tropospheric ozone(O_(3)),with both humid-heat(sauna days)and dry-heat(roast days)conditions leading to O_(3) exceedances.However,the mechanisms influencing O_(3) formation and degradation under these two weather conditions remain unclear.Therefore,experiments were conducted in Beijing from 2019 to 2021 to observe O_(3),its precursors,and related meteorological elements.A total of 18 days with O_(3) exceedances were selected,including 10 sauna days and 8 roast days.The results of this study revealed that on roast days,the sensible heat flux was 143.5 W/m^(2) greater and the wind speed gradient was 0.018 s^(-1) greater than those on sauna days,indicating more intense thermal and dynamic turbulence.The strong turbulence enhanced the vertical cycle of nitrogen dioxide(NO_(2))and O_(3),resulting in a 58.2μg/(m^(2)·h)increase in NO_(2) upward transport rate and a 1034.4μg/(m^(2)·h)increase in O_(3) downward transport rate on roast days than sauna days.Subsequently,a box model analysis was used to examine O_(3) formation under the two types of weather conditions,revealing that the NO_(2)-O_(3) vertical cycling speed dominated the O_(3) sensitivity.The O_(3) sensitivity was synergistically controlled by nitrogen oxides(NO_(x))and volatile organic compounds on sauna days,while it tended to be NO_(x)-limited on roast days.The aim of this study was to provide a scientific theoretical basis for the control of O_(3) under different types of high temperature weather conditions.展开更多
The primary concern in stealth aircraft design is the very large electrical size objects.However,the computational and storage requirements of these objects present significant obstacles for current highfidelity desig...The primary concern in stealth aircraft design is the very large electrical size objects.However,the computational and storage requirements of these objects present significant obstacles for current highfidelity design methods,particularly when addressing high-dimensional complex engineering design problems.To address these challenges,we developed a surface sensitivity technique based on the multilevel fast multipole algorithm(MLFMA).An access and storage of sparse partial derivative tensor was improved to significantly enhanced the computation performance.The far-field interactions of the surface sensitivity equation were realized by differential the multipole expansion.In addition,we proposed a fast far-field multiplication method to accelerate the multiplication process.The surface mesh derivative with respect to the design variables was calculated by analytical and complex variable methods,substantially improving computational efficiency.These advancements enabled the MLFMAbased surface sensitivity method to millions meshes and large-scale gradients,extending gradientbased optimization for very large electrical size problems.Test cases have verified the effectiveness of this method in optimizing very large electrical objects in terms of both accuracy and efficiency.展开更多
Ozone production sensitivity is widely used to reveal the chemical dominant precursors of urban ozone rise.Here,we diagnose the impact of the decline in global human production activities level caused by the COVID-19 ...Ozone production sensitivity is widely used to reveal the chemical dominant precursors of urban ozone rise.Here,we diagnose the impact of the decline in global human production activities level caused by the COVID-19 on ozone sensitivity through the ratio of formaldehyde(HCHO)and NO_(2)(FNR=HCHO/NO_(2))observations from the TROPOspheric Monitoring Instrument.We use a relative uncertainty threshold to clean the satellite FNR,and our satellite FNR present a good correlation(R=0.6248)with U.S.Environmental Protection Agency observations.We found that the outbreak of the COVID-19 did not change the pattern of global ozone sensitivity,while the global regimes was transforming or strengthening to VOC-limited regimes due to the significant decline of human production activities levels.During the COVID-19,ozone sensitivity in Eastern China and East Africa continued to shift to VOC-limited regimes,while India,Western Europe and North America first moved to NOx-limited regimes,and then changed to VOC-limited regimes with the resumption of production and the increase in travel.The clustering results tell that urban ozone sensitivity tends to shift towards NOx-limited regimes as economic growing.The ozone formation in cities with lower FNR and per capita gross domestic product(GDP)are more sensitive to changes in VOCs,while cities with higher FNR and per capita GDP are more sensitive to variations in NOx.Cities with intermediate FNR and GDP are good evidence of the existence of transitional regimes.Our study identifies the driving role of urban economics in orienting the evolution of ozone sensitivity regimes.展开更多
[Objectives]This study aimed to evaluate the detection sensitivity of Staphylococcus aureus in dairy products utilizing the chip digital PCR(cdPCR)technique.[Methods]Specific primers and probes were designed and synth...[Objectives]This study aimed to evaluate the detection sensitivity of Staphylococcus aureus in dairy products utilizing the chip digital PCR(cdPCR)technique.[Methods]Specific primers and probes were designed and synthesized based on the conserved sequence of the heat-resistant nuclease gene nuc of S.aureus.cdPCR was employed to detect S.aureus,and the sensitivity of this technique was systematically assessed in samples exhibiting low levels of contamination.[Results]cdPCR demonstrated precise quantification when the initial concentration of the sample enrichment solution was equal to or greater than 50 CFU/mL.The detection dynamic range extended across at least five orders of magnitude,with a minimum DNA detection limit of 0.2304 pg/μL.In artificially contaminated cheese samples,the method s lower limit of quantification for detecting S.aureus was 8×10^(2) CFU/g.Regression analysis demonstrated that the gene copy number concentration measured by cdPCR exhibited a strong linear correlation with bacterial contamination concentration across a broad range.[Conclusions]The cdPCR method developed in this study demonstrates high sensitivity and robust quantitative capabilities,offering a reliable technical approach for the precise detection of low-level S.aureus contamination in dairy products.展开更多
Objectives:Loneliness among left-behind adolescents is the most frequently reported emotional problem because of parental neglect.The present study explored the relationship between maternal absence and adolescent lon...Objectives:Loneliness among left-behind adolescents is the most frequently reported emotional problem because of parental neglect.The present study explored the relationship between maternal absence and adolescent loneliness as well as its mechanisms.Methods:The study included 305 participants(Meanage=15.99±0.81,48.9%females)in southeast China,and constructed a chain mediation model to test the roles of rejection sensitivity and friendship quality.Parent absence types,rejection sensitivity,friendship quality,and adolescent loneliness were all assessed with questionnaires.Results:The results showed that adolescents with a mother absent(both-parent absent,mother-only absent)experienced higher levels of loneliness than those with a mother not absent(father-only absent,non-parent absent)(β=0.3137,95%CI[0.0849,0.5425],p<0.01).Besides,the mediating roles of rejection sensitivity(β=0.0344,95%CI[0.0020,0.0808])and friendship quality(β=0.1198,95%CI[0.0049,0.2428])and their chain mediating role were found significant between maternal absence and loneliness(β=0.0245,95%CI[0.0015,0.0575]).Conclusions:These findings have revealed the significant impact of maternal absence on adolescent loneliness and provide important practical implications for educators to reduce adolescent loneliness.展开更多
Conductive elastomers combining micromechanical sensitivity,lightweight adaptability,and environmental sustainability are critically needed for advanced flexible electronics requiring precise responsiveness and long-t...Conductive elastomers combining micromechanical sensitivity,lightweight adaptability,and environmental sustainability are critically needed for advanced flexible electronics requiring precise responsiveness and long-term wearability;however,the integration of these properties remains a significant challenge.Here,we present a biomass-derived conductive elastomer featuring a rationally engineered dynamic crosslinked network integrated with a tunable microporous architecture.This structural design imparts pronounced micromechanical sensitivity,an ultralow density(~0.25 g cm^(−3)),and superior mechanical compliance for adaptive deformation.Moreover,the unique micro-spring effect derived from the porous architecture ensures exceptional stretchability(>500%elongation at break)and superior resilience,delivering immediate and stable electrical response under both subtle(<1%)and large(>200%)mechanical stimuli.Intrinsic dynamic interactions endow the elastomer with efficient room temperature self-healing and complete recyclability without compromising performance.First-principles simulations clarify the mechanisms behind micropore formation and the resulting functionality.Beyond its facile and mild fabrication process,this work establishes a scalable route toward high-performance,sustainable conductive elastomers tailored for next-generation soft electronics.展开更多
The photoacoustic imaging of lipid is intrinsically constrained by the feeble nature of endogenous lipid signals,posing a persistent sensitivity challenge that demands innovative solutions.Although adopting high-effic...The photoacoustic imaging of lipid is intrinsically constrained by the feeble nature of endogenous lipid signals,posing a persistent sensitivity challenge that demands innovative solutions.Although adopting high-efficiency excitation and detection elements may improve the imaging sensitivity to a certain extent,the application of the elements is inevitably subject to various limitations in practical applications,particularly during in vivo imaging and endoscopic imaging.In this study,we propose a multi-combinatorial approach to enhance the sensitivity of lipid photoacoustic imaging.The approach involves wavelet transform processing of one-dimensional A-line signals,gradient-based denoising of two-dimensional B-scan images,and finally,threedimensional spatial weighted averaging of the data processed by the previous two steps.This method not only significantly improves the signal-to-noise ratio(SNR)in distinguished feature regions of the image by around 10 dB,but also efficiently extracts weak signals with no distinct features in the original image.After processing with this method,the images acquired under single scanning were compared with those obtained under multiple scanning.The results showed highly consistent image features,with the structural similarity index increasing from 0.2 to 0.8,confirming the accuracy and reliability of the multi-combinatorial approach.展开更多
基金supported by the Natural Science BasicResearch Program of Shaanxi,China(No.2021JC-14)。
文摘The water hammer problem is an important issue in the dynamics of liquid propulsion system.This paper aims to use the Lattice Boltzmann Method(LBM)with entropy limiter to study the water hammer problems in propellant feedlines.The dynamic characteristics of valve-closing water hammer and filling water hammer are investigated by this method,and the sensitivity of filling water hammer is analyzed with a single factor sensitivity analysis with 8 factors and 9 levels and a multi-factor sensitivity analysis with L_(27)(3^(13))orthogonal experiment based on range method.It is found that the solving result of LBM with entropy limiter is basically in good agreement with finite volume method,and using the entropy limiter can eliminate numerical oscillations when solving valve-closing water hammer problems and solve the numerical"blow up"when solving filling water hammer problems.It can be seen that the dynamic characteristics of valve-closing water hammer are relatively simple,while there are many factors that affect the filling water hammer and the degree of these effects varies.The effects on the maximum water hammer pressure are relatively uniform,but those on the water hammer response time vary greatly through the skewness analysis.
基金supported by the National Natural Science Foundation of China(No.42177081)the National Key R&D Program of China(No.2023YFC3706103)+1 种基金Beijing Municipal Natural Science Foundation(No.8222075)the Youth Cross Team Scientific Research Project of the Chinese Academy of Sciences(No.JCTD-2021–10).
文摘Temperature is a key meteorological factor that affects tropospheric ozone(O_(3)),with both humid-heat(sauna days)and dry-heat(roast days)conditions leading to O_(3) exceedances.However,the mechanisms influencing O_(3) formation and degradation under these two weather conditions remain unclear.Therefore,experiments were conducted in Beijing from 2019 to 2021 to observe O_(3),its precursors,and related meteorological elements.A total of 18 days with O_(3) exceedances were selected,including 10 sauna days and 8 roast days.The results of this study revealed that on roast days,the sensible heat flux was 143.5 W/m^(2) greater and the wind speed gradient was 0.018 s^(-1) greater than those on sauna days,indicating more intense thermal and dynamic turbulence.The strong turbulence enhanced the vertical cycle of nitrogen dioxide(NO_(2))and O_(3),resulting in a 58.2μg/(m^(2)·h)increase in NO_(2) upward transport rate and a 1034.4μg/(m^(2)·h)increase in O_(3) downward transport rate on roast days than sauna days.Subsequently,a box model analysis was used to examine O_(3) formation under the two types of weather conditions,revealing that the NO_(2)-O_(3) vertical cycling speed dominated the O_(3) sensitivity.The O_(3) sensitivity was synergistically controlled by nitrogen oxides(NO_(x))and volatile organic compounds on sauna days,while it tended to be NO_(x)-limited on roast days.The aim of this study was to provide a scientific theoretical basis for the control of O_(3) under different types of high temperature weather conditions.
基金supported by the National Key Research and Development Program of China(Grant No.2023YFB3002800).
文摘The primary concern in stealth aircraft design is the very large electrical size objects.However,the computational and storage requirements of these objects present significant obstacles for current highfidelity design methods,particularly when addressing high-dimensional complex engineering design problems.To address these challenges,we developed a surface sensitivity technique based on the multilevel fast multipole algorithm(MLFMA).An access and storage of sparse partial derivative tensor was improved to significantly enhanced the computation performance.The far-field interactions of the surface sensitivity equation were realized by differential the multipole expansion.In addition,we proposed a fast far-field multiplication method to accelerate the multiplication process.The surface mesh derivative with respect to the design variables was calculated by analytical and complex variable methods,substantially improving computational efficiency.These advancements enabled the MLFMAbased surface sensitivity method to millions meshes and large-scale gradients,extending gradientbased optimization for very large electrical size problems.Test cases have verified the effectiveness of this method in optimizing very large electrical objects in terms of both accuracy and efficiency.
基金supported by the National Key R&D Program(No.2021YFE0117300)the National Natural Science Foundation of China(No.42375090)+6 种基金Shenzhen Key Laboratory of Precision Measurement and Early Warning Technology for Urban Environmental Health Risks(No.ZDSYS20220606100604008)Guangdong Basic and Applied Basic Research Foundation(No.2021A1515110713)Guangdong University Research Project Science Team(No.2021KCXTD004)the Major Talent Project of Guangdong Province(No.2021QN020924)Shandong Provincial Natural Science Foundation,China(No.ZR2020QD012)Shenzhen Science and Technology Program(Nos.KQTD20210811090048025,JCYJ20210324104604012 and JCYJ20220530115404009)supported by the Center for Computational Science and Engineering at Southern University of Science and Technology.
文摘Ozone production sensitivity is widely used to reveal the chemical dominant precursors of urban ozone rise.Here,we diagnose the impact of the decline in global human production activities level caused by the COVID-19 on ozone sensitivity through the ratio of formaldehyde(HCHO)and NO_(2)(FNR=HCHO/NO_(2))observations from the TROPOspheric Monitoring Instrument.We use a relative uncertainty threshold to clean the satellite FNR,and our satellite FNR present a good correlation(R=0.6248)with U.S.Environmental Protection Agency observations.We found that the outbreak of the COVID-19 did not change the pattern of global ozone sensitivity,while the global regimes was transforming or strengthening to VOC-limited regimes due to the significant decline of human production activities levels.During the COVID-19,ozone sensitivity in Eastern China and East Africa continued to shift to VOC-limited regimes,while India,Western Europe and North America first moved to NOx-limited regimes,and then changed to VOC-limited regimes with the resumption of production and the increase in travel.The clustering results tell that urban ozone sensitivity tends to shift towards NOx-limited regimes as economic growing.The ozone formation in cities with lower FNR and per capita gross domestic product(GDP)are more sensitive to changes in VOCs,while cities with higher FNR and per capita GDP are more sensitive to variations in NOx.Cities with intermediate FNR and GDP are good evidence of the existence of transitional regimes.Our study identifies the driving role of urban economics in orienting the evolution of ozone sensitivity regimes.
基金Supported by Science and Technology Program of Inner Mongolia Autonomous Region"Research and Demonstration of Novel Molecular Biological Identification Technology for Multiple Source Components in Milk and Dairy Products"(2025YFSH0029).
文摘[Objectives]This study aimed to evaluate the detection sensitivity of Staphylococcus aureus in dairy products utilizing the chip digital PCR(cdPCR)technique.[Methods]Specific primers and probes were designed and synthesized based on the conserved sequence of the heat-resistant nuclease gene nuc of S.aureus.cdPCR was employed to detect S.aureus,and the sensitivity of this technique was systematically assessed in samples exhibiting low levels of contamination.[Results]cdPCR demonstrated precise quantification when the initial concentration of the sample enrichment solution was equal to or greater than 50 CFU/mL.The detection dynamic range extended across at least five orders of magnitude,with a minimum DNA detection limit of 0.2304 pg/μL.In artificially contaminated cheese samples,the method s lower limit of quantification for detecting S.aureus was 8×10^(2) CFU/g.Regression analysis demonstrated that the gene copy number concentration measured by cdPCR exhibited a strong linear correlation with bacterial contamination concentration across a broad range.[Conclusions]The cdPCR method developed in this study demonstrates high sensitivity and robust quantitative capabilities,offering a reliable technical approach for the precise detection of low-level S.aureus contamination in dairy products.
基金supported by the National Natural Science Foundation of China(32171069).
文摘Objectives:Loneliness among left-behind adolescents is the most frequently reported emotional problem because of parental neglect.The present study explored the relationship between maternal absence and adolescent loneliness as well as its mechanisms.Methods:The study included 305 participants(Meanage=15.99±0.81,48.9%females)in southeast China,and constructed a chain mediation model to test the roles of rejection sensitivity and friendship quality.Parent absence types,rejection sensitivity,friendship quality,and adolescent loneliness were all assessed with questionnaires.Results:The results showed that adolescents with a mother absent(both-parent absent,mother-only absent)experienced higher levels of loneliness than those with a mother not absent(father-only absent,non-parent absent)(β=0.3137,95%CI[0.0849,0.5425],p<0.01).Besides,the mediating roles of rejection sensitivity(β=0.0344,95%CI[0.0020,0.0808])and friendship quality(β=0.1198,95%CI[0.0049,0.2428])and their chain mediating role were found significant between maternal absence and loneliness(β=0.0245,95%CI[0.0015,0.0575]).Conclusions:These findings have revealed the significant impact of maternal absence on adolescent loneliness and provide important practical implications for educators to reduce adolescent loneliness.
基金supported by National Natural Science Foundation of China(No.52103044)Double First-Class Initiative University of Science and Technology of China(KY2400000037)the Young Talent Programme(GG2400007009).
文摘Conductive elastomers combining micromechanical sensitivity,lightweight adaptability,and environmental sustainability are critically needed for advanced flexible electronics requiring precise responsiveness and long-term wearability;however,the integration of these properties remains a significant challenge.Here,we present a biomass-derived conductive elastomer featuring a rationally engineered dynamic crosslinked network integrated with a tunable microporous architecture.This structural design imparts pronounced micromechanical sensitivity,an ultralow density(~0.25 g cm^(−3)),and superior mechanical compliance for adaptive deformation.Moreover,the unique micro-spring effect derived from the porous architecture ensures exceptional stretchability(>500%elongation at break)and superior resilience,delivering immediate and stable electrical response under both subtle(<1%)and large(>200%)mechanical stimuli.Intrinsic dynamic interactions endow the elastomer with efficient room temperature self-healing and complete recyclability without compromising performance.First-principles simulations clarify the mechanisms behind micropore formation and the resulting functionality.Beyond its facile and mild fabrication process,this work establishes a scalable route toward high-performance,sustainable conductive elastomers tailored for next-generation soft electronics.
基金supported by the National Key Research and Development Program of China(2022YFC2402400)the National Natural Science Foundation of China(82027803,62275062)+7 种基金the Guangdong Provincial Key Laboratory of Biomedical Optical Imaging Technology(2020B121201010)the Shenzhen Science and Technology Innovation Committee under Grant(JCYJ20220818101417039)the Shenzhen Key Laboratory for Molecular lmaging(ZDSY20130401165820357)the Shenzhen Medical Research Fund(D2404002)the Project of Shandong Innovation and Startup Community of High-end Medical Apparatus and Instruments(2023-SGTTXM-002 and 2024-SGTTXM-005)the Shandong Province Technology Innovation Guidance Plan(Central Leading Local Science and Technology Development Fund)(YDZX2023115)the Taishan Scholar Special Funding Project of Shandong Provinceand the Shandong Laboratory of Advanced Biomaterials and Medical Devices in Weihai(ZL202402).
文摘The photoacoustic imaging of lipid is intrinsically constrained by the feeble nature of endogenous lipid signals,posing a persistent sensitivity challenge that demands innovative solutions.Although adopting high-efficiency excitation and detection elements may improve the imaging sensitivity to a certain extent,the application of the elements is inevitably subject to various limitations in practical applications,particularly during in vivo imaging and endoscopic imaging.In this study,we propose a multi-combinatorial approach to enhance the sensitivity of lipid photoacoustic imaging.The approach involves wavelet transform processing of one-dimensional A-line signals,gradient-based denoising of two-dimensional B-scan images,and finally,threedimensional spatial weighted averaging of the data processed by the previous two steps.This method not only significantly improves the signal-to-noise ratio(SNR)in distinguished feature regions of the image by around 10 dB,but also efficiently extracts weak signals with no distinct features in the original image.After processing with this method,the images acquired under single scanning were compared with those obtained under multiple scanning.The results showed highly consistent image features,with the structural similarity index increasing from 0.2 to 0.8,confirming the accuracy and reliability of the multi-combinatorial approach.
