The effects of three different typical resistivity models（Spitzer, Z＆L and M＆G） on the performance of pulsed inductive acceleration plasma are studied. Numerical results show that their influences decrease with th...The effects of three different typical resistivity models（Spitzer, Z＆L and M＆G） on the performance of pulsed inductive acceleration plasma are studied. Numerical results show that their influences decrease with the increase of the plasma temperature. The significant discriminations among them appear at the plasma temperature lower than 2.5 eV, and the maximum gap of the pulsed inductive plasma accelerated efficiency is approximately 2.5%.Moreover, the pulsed inductive plasma accelerated efficiency is absolutely related to the dynamic impedance parameters, such as voltage, inductance, capacitance and flow rate. However, the distribution of the efficiency as a function of plasma temperature with three resistivity models has nothing to do with the dynamic impedance parameter.展开更多
We highlighted the flexibility of using unstructured mesh together with the local refinement by a resistivity model with complicated topography. The effect of topography is emphasized. Based on this, we calculated a s...We highlighted the flexibility of using unstructured mesh together with the local refinement by a resistivity model with complicated topography. The effect of topography is emphasized. Based on this, we calculated a specific class of layered models and found that the accuracy is not always satisfactory by utilizing the standard approach. As an improvement, we employed the layered earth as the reference model to calculate the wavenumbers. The comparison demonstrates that the accuracy is considerably improved by using this enhanced approach.展开更多
Al/Ni reactive multilayer foil(RMF)possesses excellent comprehensive properties as a promising substitute for traditional Cu bridge.A theoretical resistivity model of Al/Ni RMF was developed to guide the optimization ...Al/Ni reactive multilayer foil(RMF)possesses excellent comprehensive properties as a promising substitute for traditional Cu bridge.A theoretical resistivity model of Al/Ni RMF was developed to guide the optimization of EFIs.Al/Ni RMF with different bilayer thicknesses and bridge dimensions were prepared by MEMS technology and electrical explosion tests were carried out.According to physical and chemical reactions in bridge,the electrical explosion process was divided into 5 stages:heating of condensed bridge,vaporization and diffusion of Al layers,intermetallic combination reaction,intrinsic explosion,ionization of metal gases,which are obviously shown in measured voltage curve.Effects of interface and grain boundary scattering on the resistivity of film metal were considered.Focusing on variations of substance and state,the resistivity was developed as a function of temperature at each stage.Electrical explosion curves were calculated by this model at different bilayer thicknesses,bridge dimensions and capacitor voltages,which showed an excellent agreement with experimental ones.展开更多
A novel simulation program with an integrated circuit emphasis（SPICE） model developed for trench-gate metal-oxide-semiconductor field-effect transistor（M OSFET）devices is proposed. The drift region resistance was ...A novel simulation program with an integrated circuit emphasis（SPICE） model developed for trench-gate metal-oxide-semiconductor field-effect transistor（M OSFET）devices is proposed. The drift region resistance was modeled according to the physical characteristics and the specific structure of the trench-gate MOSFET device. For the accurate simulation of dynamic characteristics, three important capacitances, gate-to-drain capacitance Cgd, gate-to-source capacitance Cgsand drain-to-source capacitance Cds, were modeled, respectively, in the proposed model. Furthermore,the self-heating effect, temperature effect and breakdown characteristic were taken into account; the self-heating model and breakdown model were built in the proposed model; and the temperature parameters of the model were revised. The proposed model is verified by experimental results, and the errors between measured data and simulation results of the novel model are less than 5%. Therefore, the model can give an accurate description for both the static and dynamic characteristics of the trench-gate MOSFET device.展开更多
Enhancing the spatio-temporal connectivity of dynamic landscapes is crucial for species to adapt to climate change.However,the spatio-temporal connectivity network approach considering climate change and species movem...Enhancing the spatio-temporal connectivity of dynamic landscapes is crucial for species to adapt to climate change.However,the spatio-temporal connectivity network approach considering climate change and species movement is often overlooked.Taking Tibetan wild ass on the Qinghai-Xizang Plateau as an example,we simulated species distribution under current(2019)and future scenarios(2100),constructed spatio-temporal connectivity networks,and assessed the spatio-temporal connectivity.The results show that under the current,SSP2–4.5 and SSP3–7.0 scenarios,suitable habitats for the Tibetan wild ass account for 21.11%,21.34%,and 20.95%of the total area,respectively,with increased fragmentation projected by 2100.78.35%of the habitats which are predicted to be suitable under current conditions will remain suitable in the future,which can be regarded as stable climate refuges.With the increase in future emission intensity,the percentage of auxiliary connectivity corridors increases from 27.65%to 33.57%.This indicates that more patches will function as temporary refuges and the auxiliary connectivity corridors will gradually weaken the dominance of direct connectivity corridors.Under different SSP-RCP scenarios,the internal spatio-temporal connectivity is always higher than direct connectivity and auxiliary connectivity,accounting for 42%–43%.Compared with the spatio-temporal perspective,the purely spatial perspective overestimates network connectivity by about 28%considering all current and future patches,and underestimates network connectivity by 16%–21%when only considering all current or future patches.In this study,a new approach of spatio-temporal connectivity network is proposed to bridge climate refuges,which contributes to the long-term effectiveness of conservation networks for species’adaptation to climate change.展开更多
Objective This study aimed to explore the interplay between the life-course body mass index(BMI)trajectories and insulin resistance(IR)on incident diabetes.Methods This longitudinal cohort included 2,336 participants ...Objective This study aimed to explore the interplay between the life-course body mass index(BMI)trajectories and insulin resistance(IR)on incident diabetes.Methods This longitudinal cohort included 2,336 participants who had BMI repeatedly measured 3–8times between 1989 and 2009,as well as glucose and insulin measured in 2009.BMI trajectories were identified using a latent class growth mixed model.The interplay between BMI trajectories and IR on diabetes was explored using the four-way effect decomposition method.Logistic regression and mediation models were used to estimate the interaction and mediation effects,respectively.Results Three distinct BMI trajectory groups were identified:low-stable(n=1,625),mediumincreasing(n=613),and high-increasing(n=98).Both interaction and mediation effects of BMI trajectories and IR on incident diabetes were significant(P<0.05).The proportion of incident diabetes was higher in the IR-obesity than in the insulin-sensitivity(IS)obesity group(18.9%vs.5.8%,P<0.001).After adjusting for covariates,the odds ratios(95%confidence intervals)of the IR,IS-obesity,and IRobesity groups vs.the normal group were 3.22(2.05,5.16),2.05(1.00,3.97),and 7.98(5.19,12.62),respectively.IR mediated 10.7%of the total effect of BMI trajectories on incident diabetes(P<0.001).Conclusion We found strong interactions and weak mediation effects of IR on the relationship between life-course BMI trajectories and incident diabetes.IS-obesity is associated with a lower risk of incident diabetes than IR-obesity.展开更多
Insulin resistance(IR)is widely recognized as a key contributor to metabolic disorders,and various surrogate indices have been developed to estimate IR in clinical and research settings.The hyperinsulinemic-euglycemic...Insulin resistance(IR)is widely recognized as a key contributor to metabolic disorders,and various surrogate indices have been developed to estimate IR in clinical and research settings.The hyperinsulinemic-euglycemic clamp is considered the gold standard method for assessing insulin resistance due to its precision;however,its complexity limits its widespread clinical application.Consequently,surrogate indices derived from fasting and post-load glucose and insulin levels have been developed to estimate IR,facilitating early detection and risk stratification in metabolic disorders.This mini-review discusses the clinical utility,strengths,and limitations of key IR indices,including the homeostasis model assessment of IR,quantitative insulin sensitivity check index,Matsuda index,and triglyceride-glucose index.Overall,the evidence presented to date suggests that these indices provide valuable estimates of IR in various popula-tions.Yet,their applicability varies depending on ethnic background,disease status,and clinical setting.Integrating these indices into routine clinical practice and research could improve metabolic risk assessment and guide preventive interventions.Further investigations are necessary to refine their accuracy and determine optimal cut-off values for various populations.展开更多
The development of fissures in expansive soils has a great effect on the stability of slope. Of the three phases of soils,the gas phase and solid phase are relatively insulated,so the average resistivity of soils can ...The development of fissures in expansive soils has a great effect on the stability of slope. Of the three phases of soils,the gas phase and solid phase are relatively insulated,so the average resistivity of soils can be calculated from the resistivity of the liquid phase. On this basis,the two-part model of resistivity changing with the water saturation of the expansive soil can be deduced. A 2-D resistance grid model is established based on simulating the resistance of ver-tically developed fissures. Variation in measured resistance of vertically developed fissures at different positions can be calculated from this model. Fissure development can be inversely determined from the variation in the measured resis-tance. Finally,the model is verified by an indoor resistivity test for remolded soil samples,indicating that the test result agrees well with that of the model established.展开更多
As an important and typical arid inland region in China,Shiyang River Basin plays an important role in maintaining the sustainable development of eco-environment,whose ecological land suitability restricts the develop...As an important and typical arid inland region in China,Shiyang River Basin plays an important role in maintaining the sustainable development of eco-environment,whose ecological land suitability restricts the development of the local human activities.Therefore,Shiyang River Basin was selected as the case study,the minimum cumulative resistance(MCR)model and GIS technique were integrated to create land suitability evaluation map.We calculated the MCR value of ecological source and living source,and divided the whole basin into five partitions according to the difference between ecological source and living source,and analyzed the patterns and characteristics of the ecological land suitability evaluation(ELSE)regions,respectively.The results showed that:1)The suitable ecological land includes prohibited development region and restricted development region,which accounts for 15.45%and 23.35%of the total land area of the Shiyang River Basin,respectively.These two regions mainly distributed high altitude region in the southern Qilian Mountain and low altitude region where had high density of rivers.2)The protection of ecological land requires not only conserving existing ecological land but also focusing on ecological buffer belts around ecological sources and improving ecological land service ability.3)Ecological networks should be constructed through artificial planting trees around the boundary of oasis and ecological restoration region.Buffer greenbelts should also be established between optimized development region and ecological restoration region.展开更多
The presence of natural voids and cavities in subsurface karstic limestones causes severe problem for civil engineering and environmental management. The presence of such features hinders the extension of urbanization...The presence of natural voids and cavities in subsurface karstic limestones causes severe problem for civil engineering and environmental management. The presence of such features hinders the extension of urbanizations particularly in the new metropolitan. The eastern part of Saudi Arabia contains various types of karstic limestone, sinkholes, solution cavities and voids. In this context, geophysical methods particularly electrical resistivity technique is used as a cost-effective solution for investigating subsurface caves, voids, and shallow weathered zones. 2-D electrical resistivity data sets have been acquired along seven profiles in the new urbanization at AI Hassa area. Data processing has been carried out taking into consideration the response of synthetic models, which simulates physical models of the most common karstic features in the area. The results are very useful to determine the extension of shallow weathered zones and to locate different cavities underneath them. The hard limestone bedrock can also be detected and traced along the surveyed profiles.展开更多
The aphid quantity ratio（AQR） is defined as the number of aphids on each cultivar divided by the number of aphids on all cultivars. AQR is based on the correlation between aphid populations and their host plants and...The aphid quantity ratio（AQR） is defined as the number of aphids on each cultivar divided by the number of aphids on all cultivars. AQR is based on the correlation between aphid populations and their host plants and is an important tool that has been utilized in evaluating Medicago sativa（alfalfa） cultivar resistance to aphids. However, assessment of alfalfa resistance to aphids can be confused by the presence of aphid predators, causing the assessment of plant resistance to aphids to be based on incorrect aphid population data. To refine the AQR and account for the effect of predators on aphid population assessments, we introduced a parameter ‘α＇, corresponding to the predator quantity ratio, and used αAQR as the ratio to quantify aphid populations. Populations of both aphids（4 species） and their predators（12 species） occurring in 28 M. sativa cultivars were sampled over two years at a research station near Cangzhou, Hebei Province, China. Results showed that the most suitable evaluation period was from May to June, as the aphid population was stable during this period. Compared with the AQR method, the predator population numbers based on the αAQR had a significant inverse relationship with aphid population numbers and the 28 cultivars were clustered into three classes： the resistant class, tolerant class, and susceptible class. In addition, 17 cultivars were reassigned when evaluated using αAQR. All numerical values calculated by αAQR were displayed as a Gaussian distribution, which showed that the 28 cultivars could be clustered into nine groups using a median value（±SE） of 1±0.1. Hence, ongoing alfalfa breeding trials will be assessed using the αAQR to establish a robust system that includes agronomic performance parameters in order to generalize the new method for further studies.展开更多
A model of deformation resistance during hot strip rolling was established based on generalized additive model.Firstly,a data modeling method based on generalized additive model was given.It included the selection of ...A model of deformation resistance during hot strip rolling was established based on generalized additive model.Firstly,a data modeling method based on generalized additive model was given.It included the selection of dependent variable and independent variables of the model,the link function of dependent variable and smoothing functional form of each independent variable,estimating process of the link function and smooth functions,and the last model modification.Then,the practical modeling test was carried out based on a large amount of hot rolling process data.An integrated variable was proposed to reflect the effects of different chemical compositions such as carbon,silicon,manganese,nickel,chromium,niobium,etc.The integrated chemical composition,strain,strain rate and rolling temperature were selected as independent variables and the cubic spline as the smooth function for them.The modeling process of deformation resistance was realized by SAS software,and the influence curves of the independent variables on deformation resistance were obtained by local scoring algorithm.Some interesting phenomena were found,for example,there is a critical value of strain rate,and the deformation resistance increases before this value and then decreases.The results confirm that the new model has higher prediction accuracy than traditional ones and is suitable for carbon steel,microalloyed steel,alloyed steel and other steel grades.展开更多
Accurate source apportionment of volatile organic compounds(VOCs)in soil nearby petrochemical industries prevailing globally,is critical for preventing pollution.However,in the process,seasonal effect on contamination...Accurate source apportionment of volatile organic compounds(VOCs)in soil nearby petrochemical industries prevailing globally,is critical for preventing pollution.However,in the process,seasonal effect on contamination pathways and accumulation of soil VOCs is often neglected.Herein,Yanshan Refining-Chemical Integration Park,including a carpet,refining,synthetic rubber,and two synthetic resin zones,was selected for traceability.Season variations resulted in a gradual decrease of 31 VOCs in soil from winter to summer.A method of dry deposition resistance model coupling partitioning coefficient model was created,revealing that dry deposition by gas phase was the primary pathway for VOCs to enter soil in winter and spring,with 100 times higher fux than by particle phase.Source profiles for five zones were built by gas sampling with distinct substance indicators screened,which were used for positive matrix factorization factors determination.Contributions of the five zones were 14.9%,20.8%,13.6%,22.1%,and 28.6%in winter and 33.4%,12.5%,10.7%,24.9%,and 18.5%in spring,respectively.The variation in the soil sorption capacity of VOCs causes inter-seasonal differences in contribution.The better correlation between dry deposition capacity and soil storage of VOCs made root mean square and mean absolute errors decrease averagely by 8.8%and 5.5%in winter compared to spring.This study provides new perspectives and methods for the source apportionment of soil VOCs contamination in industrial sites.展开更多
Clothing plays a crucial role in determining human thermal comfort.However,most existing models of clothing thermal resistance primarily focus on predicting the overall and local thermal resistance in a standing postu...Clothing plays a crucial role in determining human thermal comfort.However,most existing models of clothing thermal resistance primarily focus on predicting the overall and local thermal resistance in a standing posture.A few models can predict the overall thermal resistance in a sitting posture,but they do not account for local thermal resistance.Therefore,in this study,a mathematical model to predict the overall and local thermal resistance of clothing under various body postures is presented.The geometric models of the human body and clothing were constructed using three-dimensional virtual simulation technology to determine the geometric parameters.The predicted overall and local thermal resistances of 19 ensembles in different postures were compared with experimental data from previous studies.The ensembles validated in this study included single-layer and double-layer clothing for daily wear.The results demonstrated that the predicted values agreed well with the experimental data.The errors of predicted overall and most local thermal resistance were within 15%and 20%,respectively.Furthermore,the model exhibited higher accuracy and resolution compared to previous models.Finally,the effect of posture on clothing thermal resistance was analyzed,providing reliable guidance for the design of clothing thermal performance.This study has significant implications for clothing design and thermal comfort prediction,contributing to improving human thermal comfort.展开更多
To evaluate the geotechnical properties of coarse-grained soil affected by cyclic freeze-thaw,the electrical resistivity and mechanical tests are conducted.The soil specimens are prepared under different water content...To evaluate the geotechnical properties of coarse-grained soil affected by cyclic freeze-thaw,the electrical resistivity and mechanical tests are conducted.The soil specimens are prepared under different water contents,dry densities and exposed to 0?20 freeze-thaw cycles.As a result,the stress?strain behavior of the specimen(w=14.0%andρd=1.90 g/cm^3)changes from strain-hardening into strain-softening due to the freeze-thaw effect.The electrical resistivity of test specimen increases with the freeze-thaw cycles change,but the mechanical parameters(the unconfined compressive strength qu and the deformation modulus E)and brittleness index decrease considerably at the same conditions.All of them tend to be stable after 7?9 cycles.Moreover,both the dry density and the water content have reciprocal effects on the freeze-thaw actions.The failure and pore characteristics of specimens affected by freeze-thaw cycles are discussed by using the image analysis method.Then,an exponential function equation is developed to assess the electrical resistivity of specimens affected by the cyclic freeze-thaw.Linear relations between the mechanical parameters and the electrical resistivity of specimens are established to evaluate the geotechnical properties of the soil exposed to freeze-thaw actions through the corresponding electrical resistivity.展开更多
High-density resistivity imaging method is widely used in landslide monitoring.The resistivity of rock and soil is closely related to factors,such as porosity,moisture content,saturation and temperature.In this study,...High-density resistivity imaging method is widely used in landslide monitoring.The resistivity of rock and soil is closely related to factors,such as porosity,moisture content,saturation and temperature.In this study,the resistivity test was designed to investigate the influence of physical factors and pore solution components on the resistivity of landslide soil.Experimental and analytical results find that both moisture content and volumetric water content varies greatly under the same resistivity.At different temperatures,soil resistivity exhibits great changes.Under the same temperature,the ion concentration and species in pore solutions have great influence on soil resistivity.Based on the test results and grey correlation analysis,this study established a resistivity model by considering porosity,saturation,temperature and ion concentration.The study lays a foundation for the high-density resistivity method to measure the moisture content of landslides.展开更多
The subduction of the Indian continental lithosphere under the Asian continent caused the uplift of the Tibet Plateau,resulting in the formation of a thickened continental crust twice of the normal value and the crust...The subduction of the Indian continental lithosphere under the Asian continent caused the uplift of the Tibet Plateau,resulting in the formation of a thickened continental crust twice of the normal value and the crustal shortening of at least 1500 km.Therefore,many models have been proposed to explain the shortening and material transportation mechanism of the Tibetan Plateau.展开更多
Discrete element method(DEM)has been intensively used to study the constitutive behaviour of granular materials.However,to what extent a real granular material can be reproduced by virtual DEM simulations remains uncl...Discrete element method(DEM)has been intensively used to study the constitutive behaviour of granular materials.However,to what extent a real granular material can be reproduced by virtual DEM simulations remains unclear.This study attempts to answer this question by comparing DEM simulations with typical features of experimental granular materials.Three groups of models with spherical and clumped particles are investigated from four perspectives:(i)deviatoric stress and volumetric behaviour;(ii)critical state behaviour;(iii)stress-dilatancy relationship;and(iv)the evolution of principal stress ratio against axial strain.The results demonstrate that DEM with spherical or clumped particles is capable of qualitatively describing macroscopic deviatoric stress responses,volumetric behaviour,and critical state behaviour observed in experiments for granular materials.On the other hand,some qualitative deviations between experiments and the investigated DEM simulations are also observed,in terms of the stress-dilatancy behaviour and principal stress ratio against axial strain,which are proven to be critical for constitutive modelling.The results demonstrate that DEM with spherical or clumped particles may not necessarily fully capture experimental features of granular materials even from a qualitative perspective.It is thus encouraged to thoroughly validate DEM with experiments when developing constitutive models based on DEM observations.展开更多
The agro-pastoral ecotone has been recognized as the main distribution area of reserved land resource for cultivation. Accordingly, clarifying this assumption, as well as concerting land reclamation and ecological res...The agro-pastoral ecotone has been recognized as the main distribution area of reserved land resource for cultivation. Accordingly, clarifying this assumption, as well as concerting land reclamation and ecological restoration, is important to ensure food security and environmental improvement in the agro-pastoral ecotone. We selected Horqin Left Back Banner(HLBB) as the subject of our case study. The landscape ecological security pattern of this area was determined using the minimum cumulative resistance model. Over-cultivation, quantity of reserved land resource for cultivation, and changes in landscape indexes before and after land use adjustment were then analyzed. Over-cultivation is a serious problem in the agro-pastoral ecotone. Reserved land resource for cultivation is less than that considered previously, and the area of reserved land resource for cultivation in HLBB only accounts for 11.50% of total uncultivated land. With regard to changes in landscape indexes, the adjusted land use pattern is effective for anti-desertification. The compensation standard for abandoned cultivated land should be improved and the comprehensive results of ‘Grain for Green' should be evaluated to further implement ecological restoration in the agro-pastoral ecotone.展开更多
In this study of temperature rising in vehicular twin-tube hydraulic gas-precharged shock absorbers,thermodynamic analyses were conducted via simulations.Equations on heat conduction,heat convection as well as radiati...In this study of temperature rising in vehicular twin-tube hydraulic gas-precharged shock absorbers,thermodynamic analyses were conducted via simulations.Equations on heat conduction,heat convection as well as radiation were derived by applying certain laws governing heat transfer;an equivalent thermal resistance network model of a shock absorber undergoing heat transfer was established innovatively;moreover,the shock absorber’s thermodynamic model of control volume system was built by using the first law of thermodynamics;and finally,time required for shock absorber to reach thermal equilibrium and corresponding value of steady temperature were calculated by programming.In this way,a lower thermal equilibrium temperature will be achieved,hence help to improve reliability of shock absorbers in work by offering low ambient temperature,by reducing amplitudes and frequencies of external incentives exerted on them and by increasing flow rate of ambient air passing around them.展开更多
基金Supported by the Fund of Science and Technology on Vacuum Technology and Physics Laboratory of Lanzhou Institute of Physics under Grant No YSC0715the National Natural Science Foundation of China under Grant No 62601210the Civil Aerospace Technology Research Project under Grant No D010509
文摘The effects of three different typical resistivity models（Spitzer, Z＆L and M＆G） on the performance of pulsed inductive acceleration plasma are studied. Numerical results show that their influences decrease with the increase of the plasma temperature. The significant discriminations among them appear at the plasma temperature lower than 2.5 eV, and the maximum gap of the pulsed inductive plasma accelerated efficiency is approximately 2.5%.Moreover, the pulsed inductive plasma accelerated efficiency is absolutely related to the dynamic impedance parameters, such as voltage, inductance, capacitance and flow rate. However, the distribution of the efficiency as a function of plasma temperature with three resistivity models has nothing to do with the dynamic impedance parameter.
基金supported by the National High Technology Research and Development Program of China (863 Program) (No. 2007AA06Z134)the National Natural Science Foundation of China (No. 40874072)
文摘We highlighted the flexibility of using unstructured mesh together with the local refinement by a resistivity model with complicated topography. The effect of topography is emphasized. Based on this, we calculated a specific class of layered models and found that the accuracy is not always satisfactory by utilizing the standard approach. As an improvement, we employed the layered earth as the reference model to calculate the wavenumbers. The comparison demonstrates that the accuracy is considerably improved by using this enhanced approach.
基金National Natural Science Foundation of China(Grant No.11872013)for supporting this project.
文摘Al/Ni reactive multilayer foil(RMF)possesses excellent comprehensive properties as a promising substitute for traditional Cu bridge.A theoretical resistivity model of Al/Ni RMF was developed to guide the optimization of EFIs.Al/Ni RMF with different bilayer thicknesses and bridge dimensions were prepared by MEMS technology and electrical explosion tests were carried out.According to physical and chemical reactions in bridge,the electrical explosion process was divided into 5 stages:heating of condensed bridge,vaporization and diffusion of Al layers,intermetallic combination reaction,intrinsic explosion,ionization of metal gases,which are obviously shown in measured voltage curve.Effects of interface and grain boundary scattering on the resistivity of film metal were considered.Focusing on variations of substance and state,the resistivity was developed as a function of temperature at each stage.Electrical explosion curves were calculated by this model at different bilayer thicknesses,bridge dimensions and capacitor voltages,which showed an excellent agreement with experimental ones.
基金The National Natural Science Foundation of China(No.61604038)China Postdoctoral Science Foundation(No.2015M580376)+1 种基金the Natural Science Foundation of Jiangsu Province(No.BK20160691)Jiangsu Postdoctoral Science Foundation(No.1501010A)
文摘A novel simulation program with an integrated circuit emphasis（SPICE） model developed for trench-gate metal-oxide-semiconductor field-effect transistor（M OSFET）devices is proposed. The drift region resistance was modeled according to the physical characteristics and the specific structure of the trench-gate MOSFET device. For the accurate simulation of dynamic characteristics, three important capacitances, gate-to-drain capacitance Cgd, gate-to-source capacitance Cgsand drain-to-source capacitance Cds, were modeled, respectively, in the proposed model. Furthermore,the self-heating effect, temperature effect and breakdown characteristic were taken into account; the self-heating model and breakdown model were built in the proposed model; and the temperature parameters of the model were revised. The proposed model is verified by experimental results, and the errors between measured data and simulation results of the novel model are less than 5%. Therefore, the model can give an accurate description for both the static and dynamic characteristics of the trench-gate MOSFET device.
基金financially supported by the National Key Research and Development Program of China(Grant No.2022YFF1303201).
文摘Enhancing the spatio-temporal connectivity of dynamic landscapes is crucial for species to adapt to climate change.However,the spatio-temporal connectivity network approach considering climate change and species movement is often overlooked.Taking Tibetan wild ass on the Qinghai-Xizang Plateau as an example,we simulated species distribution under current(2019)and future scenarios(2100),constructed spatio-temporal connectivity networks,and assessed the spatio-temporal connectivity.The results show that under the current,SSP2–4.5 and SSP3–7.0 scenarios,suitable habitats for the Tibetan wild ass account for 21.11%,21.34%,and 20.95%of the total area,respectively,with increased fragmentation projected by 2100.78.35%of the habitats which are predicted to be suitable under current conditions will remain suitable in the future,which can be regarded as stable climate refuges.With the increase in future emission intensity,the percentage of auxiliary connectivity corridors increases from 27.65%to 33.57%.This indicates that more patches will function as temporary refuges and the auxiliary connectivity corridors will gradually weaken the dominance of direct connectivity corridors.Under different SSP-RCP scenarios,the internal spatio-temporal connectivity is always higher than direct connectivity and auxiliary connectivity,accounting for 42%–43%.Compared with the spatio-temporal perspective,the purely spatial perspective overestimates network connectivity by about 28%considering all current and future patches,and underestimates network connectivity by 16%–21%when only considering all current or future patches.In this study,a new approach of spatio-temporal connectivity network is proposed to bridge climate refuges,which contributes to the long-term effectiveness of conservation networks for species’adaptation to climate change.
基金supported by Grant 82222064 from the National Natural Science Foundation of Chinathe Shandong University Distinguished Young Scholars。
文摘Objective This study aimed to explore the interplay between the life-course body mass index(BMI)trajectories and insulin resistance(IR)on incident diabetes.Methods This longitudinal cohort included 2,336 participants who had BMI repeatedly measured 3–8times between 1989 and 2009,as well as glucose and insulin measured in 2009.BMI trajectories were identified using a latent class growth mixed model.The interplay between BMI trajectories and IR on diabetes was explored using the four-way effect decomposition method.Logistic regression and mediation models were used to estimate the interaction and mediation effects,respectively.Results Three distinct BMI trajectory groups were identified:low-stable(n=1,625),mediumincreasing(n=613),and high-increasing(n=98).Both interaction and mediation effects of BMI trajectories and IR on incident diabetes were significant(P<0.05).The proportion of incident diabetes was higher in the IR-obesity than in the insulin-sensitivity(IS)obesity group(18.9%vs.5.8%,P<0.001).After adjusting for covariates,the odds ratios(95%confidence intervals)of the IR,IS-obesity,and IRobesity groups vs.the normal group were 3.22(2.05,5.16),2.05(1.00,3.97),and 7.98(5.19,12.62),respectively.IR mediated 10.7%of the total effect of BMI trajectories on incident diabetes(P<0.001).Conclusion We found strong interactions and weak mediation effects of IR on the relationship between life-course BMI trajectories and incident diabetes.IS-obesity is associated with a lower risk of incident diabetes than IR-obesity.
文摘Insulin resistance(IR)is widely recognized as a key contributor to metabolic disorders,and various surrogate indices have been developed to estimate IR in clinical and research settings.The hyperinsulinemic-euglycemic clamp is considered the gold standard method for assessing insulin resistance due to its precision;however,its complexity limits its widespread clinical application.Consequently,surrogate indices derived from fasting and post-load glucose and insulin levels have been developed to estimate IR,facilitating early detection and risk stratification in metabolic disorders.This mini-review discusses the clinical utility,strengths,and limitations of key IR indices,including the homeostasis model assessment of IR,quantitative insulin sensitivity check index,Matsuda index,and triglyceride-glucose index.Overall,the evidence presented to date suggests that these indices provide valuable estimates of IR in various popula-tions.Yet,their applicability varies depending on ethnic background,disease status,and clinical setting.Integrating these indices into routine clinical practice and research could improve metabolic risk assessment and guide preventive interventions.Further investigations are necessary to refine their accuracy and determine optimal cut-off values for various populations.
基金Project 50579017 supported by the National Natural Science Foundation of China
文摘The development of fissures in expansive soils has a great effect on the stability of slope. Of the three phases of soils,the gas phase and solid phase are relatively insulated,so the average resistivity of soils can be calculated from the resistivity of the liquid phase. On this basis,the two-part model of resistivity changing with the water saturation of the expansive soil can be deduced. A 2-D resistance grid model is established based on simulating the resistance of ver-tically developed fissures. Variation in measured resistance of vertically developed fissures at different positions can be calculated from this model. Fissure development can be inversely determined from the variation in the measured resis-tance. Finally,the model is verified by an indoor resistivity test for remolded soil samples,indicating that the test result agrees well with that of the model established.
基金Under the auspices of National Natural Science Foundation of China(No.41861040,41761047)。
文摘As an important and typical arid inland region in China,Shiyang River Basin plays an important role in maintaining the sustainable development of eco-environment,whose ecological land suitability restricts the development of the local human activities.Therefore,Shiyang River Basin was selected as the case study,the minimum cumulative resistance(MCR)model and GIS technique were integrated to create land suitability evaluation map.We calculated the MCR value of ecological source and living source,and divided the whole basin into five partitions according to the difference between ecological source and living source,and analyzed the patterns and characteristics of the ecological land suitability evaluation(ELSE)regions,respectively.The results showed that:1)The suitable ecological land includes prohibited development region and restricted development region,which accounts for 15.45%and 23.35%of the total land area of the Shiyang River Basin,respectively.These two regions mainly distributed high altitude region in the southern Qilian Mountain and low altitude region where had high density of rivers.2)The protection of ecological land requires not only conserving existing ecological land but also focusing on ecological buffer belts around ecological sources and improving ecological land service ability.3)Ecological networks should be constructed through artificial planting trees around the boundary of oasis and ecological restoration region.Buffer greenbelts should also be established between optimized development region and ecological restoration region.
基金The second author thanks and appreciates KACST for their help and support during this study
文摘The presence of natural voids and cavities in subsurface karstic limestones causes severe problem for civil engineering and environmental management. The presence of such features hinders the extension of urbanizations particularly in the new metropolitan. The eastern part of Saudi Arabia contains various types of karstic limestone, sinkholes, solution cavities and voids. In this context, geophysical methods particularly electrical resistivity technique is used as a cost-effective solution for investigating subsurface caves, voids, and shallow weathered zones. 2-D electrical resistivity data sets have been acquired along seven profiles in the new urbanization at AI Hassa area. Data processing has been carried out taking into consideration the response of synthetic models, which simulates physical models of the most common karstic features in the area. The results are very useful to determine the extension of shallow weathered zones and to locate different cavities underneath them. The hard limestone bedrock can also be detected and traced along the surveyed profiles.
基金funded by the earmarked fund for China Agriculture Research System (CARS-34-07)the National Department of Public Benefit Research Foundation, China (201303057)
文摘The aphid quantity ratio（AQR） is defined as the number of aphids on each cultivar divided by the number of aphids on all cultivars. AQR is based on the correlation between aphid populations and their host plants and is an important tool that has been utilized in evaluating Medicago sativa（alfalfa） cultivar resistance to aphids. However, assessment of alfalfa resistance to aphids can be confused by the presence of aphid predators, causing the assessment of plant resistance to aphids to be based on incorrect aphid population data. To refine the AQR and account for the effect of predators on aphid population assessments, we introduced a parameter ‘α＇, corresponding to the predator quantity ratio, and used αAQR as the ratio to quantify aphid populations. Populations of both aphids（4 species） and their predators（12 species） occurring in 28 M. sativa cultivars were sampled over two years at a research station near Cangzhou, Hebei Province, China. Results showed that the most suitable evaluation period was from May to June, as the aphid population was stable during this period. Compared with the AQR method, the predator population numbers based on the αAQR had a significant inverse relationship with aphid population numbers and the 28 cultivars were clustered into three classes： the resistant class, tolerant class, and susceptible class. In addition, 17 cultivars were reassigned when evaluated using αAQR. All numerical values calculated by αAQR were displayed as a Gaussian distribution, which showed that the 28 cultivars could be clustered into nine groups using a median value（±SE） of 1±0.1. Hence, ongoing alfalfa breeding trials will be assessed using the αAQR to establish a robust system that includes agronomic performance parameters in order to generalize the new method for further studies.
基金supported by National Natural Science Foundation of China (51774219)Science and Technology Research Program of Hubei Ministry of Education(D20161103)Youth Science and technology Program of Wuhan(2016070204010099)
文摘A model of deformation resistance during hot strip rolling was established based on generalized additive model.Firstly,a data modeling method based on generalized additive model was given.It included the selection of dependent variable and independent variables of the model,the link function of dependent variable and smoothing functional form of each independent variable,estimating process of the link function and smooth functions,and the last model modification.Then,the practical modeling test was carried out based on a large amount of hot rolling process data.An integrated variable was proposed to reflect the effects of different chemical compositions such as carbon,silicon,manganese,nickel,chromium,niobium,etc.The integrated chemical composition,strain,strain rate and rolling temperature were selected as independent variables and the cubic spline as the smooth function for them.The modeling process of deformation resistance was realized by SAS software,and the influence curves of the independent variables on deformation resistance were obtained by local scoring algorithm.Some interesting phenomena were found,for example,there is a critical value of strain rate,and the deformation resistance increases before this value and then decreases.The results confirm that the new model has higher prediction accuracy than traditional ones and is suitable for carbon steel,microalloyed steel,alloyed steel and other steel grades.
基金supported by the National Key R&D Program of China (No.2018YFC1800300)the National Natural Science Foundation of China (Nos.41807493,22006156 and 21876193)。
文摘Accurate source apportionment of volatile organic compounds(VOCs)in soil nearby petrochemical industries prevailing globally,is critical for preventing pollution.However,in the process,seasonal effect on contamination pathways and accumulation of soil VOCs is often neglected.Herein,Yanshan Refining-Chemical Integration Park,including a carpet,refining,synthetic rubber,and two synthetic resin zones,was selected for traceability.Season variations resulted in a gradual decrease of 31 VOCs in soil from winter to summer.A method of dry deposition resistance model coupling partitioning coefficient model was created,revealing that dry deposition by gas phase was the primary pathway for VOCs to enter soil in winter and spring,with 100 times higher fux than by particle phase.Source profiles for five zones were built by gas sampling with distinct substance indicators screened,which were used for positive matrix factorization factors determination.Contributions of the five zones were 14.9%,20.8%,13.6%,22.1%,and 28.6%in winter and 33.4%,12.5%,10.7%,24.9%,and 18.5%in spring,respectively.The variation in the soil sorption capacity of VOCs causes inter-seasonal differences in contribution.The better correlation between dry deposition capacity and soil storage of VOCs made root mean square and mean absolute errors decrease averagely by 8.8%and 5.5%in winter compared to spring.This study provides new perspectives and methods for the source apportionment of soil VOCs contamination in industrial sites.
文摘Clothing plays a crucial role in determining human thermal comfort.However,most existing models of clothing thermal resistance primarily focus on predicting the overall and local thermal resistance in a standing posture.A few models can predict the overall thermal resistance in a sitting posture,but they do not account for local thermal resistance.Therefore,in this study,a mathematical model to predict the overall and local thermal resistance of clothing under various body postures is presented.The geometric models of the human body and clothing were constructed using three-dimensional virtual simulation technology to determine the geometric parameters.The predicted overall and local thermal resistances of 19 ensembles in different postures were compared with experimental data from previous studies.The ensembles validated in this study included single-layer and double-layer clothing for daily wear.The results demonstrated that the predicted values agreed well with the experimental data.The errors of predicted overall and most local thermal resistance were within 15%and 20%,respectively.Furthermore,the model exhibited higher accuracy and resolution compared to previous models.Finally,the effect of posture on clothing thermal resistance was analyzed,providing reliable guidance for the design of clothing thermal performance.This study has significant implications for clothing design and thermal comfort prediction,contributing to improving human thermal comfort.
基金Project(2016ZGHJ/XZHTL-YQSC-26)supported by the Key Scientific Research Project of China Gold GroupProject(SQ2019QZKK2806)supported by the Second Tibetan Plateau Scientific Expedition and Research(STEP)Program,China+1 种基金Project(300102268716)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(LHKA-G201701)supported by the Science and Technology Project of Yalong River Hydropower Development Company,China。
文摘To evaluate the geotechnical properties of coarse-grained soil affected by cyclic freeze-thaw,the electrical resistivity and mechanical tests are conducted.The soil specimens are prepared under different water contents,dry densities and exposed to 0?20 freeze-thaw cycles.As a result,the stress?strain behavior of the specimen(w=14.0%andρd=1.90 g/cm^3)changes from strain-hardening into strain-softening due to the freeze-thaw effect.The electrical resistivity of test specimen increases with the freeze-thaw cycles change,but the mechanical parameters(the unconfined compressive strength qu and the deformation modulus E)and brittleness index decrease considerably at the same conditions.All of them tend to be stable after 7?9 cycles.Moreover,both the dry density and the water content have reciprocal effects on the freeze-thaw actions.The failure and pore characteristics of specimens affected by freeze-thaw cycles are discussed by using the image analysis method.Then,an exponential function equation is developed to assess the electrical resistivity of specimens affected by the cyclic freeze-thaw.Linear relations between the mechanical parameters and the electrical resistivity of specimens are established to evaluate the geotechnical properties of the soil exposed to freeze-thaw actions through the corresponding electrical resistivity.
基金supported by Hubei Provincial Engineering Research Center of Slope Habitat Construction Technique Using Cement-based Materials(China Three Gorges University)No.2022SNJ15。
文摘High-density resistivity imaging method is widely used in landslide monitoring.The resistivity of rock and soil is closely related to factors,such as porosity,moisture content,saturation and temperature.In this study,the resistivity test was designed to investigate the influence of physical factors and pore solution components on the resistivity of landslide soil.Experimental and analytical results find that both moisture content and volumetric water content varies greatly under the same resistivity.At different temperatures,soil resistivity exhibits great changes.Under the same temperature,the ion concentration and species in pore solutions have great influence on soil resistivity.Based on the test results and grey correlation analysis,this study established a resistivity model by considering porosity,saturation,temperature and ion concentration.The study lays a foundation for the high-density resistivity method to measure the moisture content of landslides.
基金funded by the Sino Probe project(Sinoprobe-02-04)
文摘The subduction of the Indian continental lithosphere under the Asian continent caused the uplift of the Tibet Plateau,resulting in the formation of a thickened continental crust twice of the normal value and the crustal shortening of at least 1500 km.Therefore,many models have been proposed to explain the shortening and material transportation mechanism of the Tibetan Plateau.
文摘Discrete element method(DEM)has been intensively used to study the constitutive behaviour of granular materials.However,to what extent a real granular material can be reproduced by virtual DEM simulations remains unclear.This study attempts to answer this question by comparing DEM simulations with typical features of experimental granular materials.Three groups of models with spherical and clumped particles are investigated from four perspectives:(i)deviatoric stress and volumetric behaviour;(ii)critical state behaviour;(iii)stress-dilatancy relationship;and(iv)the evolution of principal stress ratio against axial strain.The results demonstrate that DEM with spherical or clumped particles is capable of qualitatively describing macroscopic deviatoric stress responses,volumetric behaviour,and critical state behaviour observed in experiments for granular materials.On the other hand,some qualitative deviations between experiments and the investigated DEM simulations are also observed,in terms of the stress-dilatancy behaviour and principal stress ratio against axial strain,which are proven to be critical for constitutive modelling.The results demonstrate that DEM with spherical or clumped particles may not necessarily fully capture experimental features of granular materials even from a qualitative perspective.It is thus encouraged to thoroughly validate DEM with experiments when developing constitutive models based on DEM observations.
基金Foundation item:Under the auspices of the Special Scientific Research of the Ministry of Land and Resources of China(No.201411009)
文摘The agro-pastoral ecotone has been recognized as the main distribution area of reserved land resource for cultivation. Accordingly, clarifying this assumption, as well as concerting land reclamation and ecological restoration, is important to ensure food security and environmental improvement in the agro-pastoral ecotone. We selected Horqin Left Back Banner(HLBB) as the subject of our case study. The landscape ecological security pattern of this area was determined using the minimum cumulative resistance model. Over-cultivation, quantity of reserved land resource for cultivation, and changes in landscape indexes before and after land use adjustment were then analyzed. Over-cultivation is a serious problem in the agro-pastoral ecotone. Reserved land resource for cultivation is less than that considered previously, and the area of reserved land resource for cultivation in HLBB only accounts for 11.50% of total uncultivated land. With regard to changes in landscape indexes, the adjusted land use pattern is effective for anti-desertification. The compensation standard for abandoned cultivated land should be improved and the comprehensive results of ‘Grain for Green' should be evaluated to further implement ecological restoration in the agro-pastoral ecotone.
基金Sponsored by the Ministerial Level Advanced Research Foundation (0020707)
文摘In this study of temperature rising in vehicular twin-tube hydraulic gas-precharged shock absorbers,thermodynamic analyses were conducted via simulations.Equations on heat conduction,heat convection as well as radiation were derived by applying certain laws governing heat transfer;an equivalent thermal resistance network model of a shock absorber undergoing heat transfer was established innovatively;moreover,the shock absorber’s thermodynamic model of control volume system was built by using the first law of thermodynamics;and finally,time required for shock absorber to reach thermal equilibrium and corresponding value of steady temperature were calculated by programming.In this way,a lower thermal equilibrium temperature will be achieved,hence help to improve reliability of shock absorbers in work by offering low ambient temperature,by reducing amplitudes and frequencies of external incentives exerted on them and by increasing flow rate of ambient air passing around them.
