In the troposphere, ozone is a harmful gas compound to both human health and vegetation. Ozone is produced from the reaction of NO_x(@NO + NO_2) and VOCs(volatile organic compounds) with light. Due to the highly nonli...In the troposphere, ozone is a harmful gas compound to both human health and vegetation. Ozone is produced from the reaction of NO_x(@NO + NO_2) and VOCs(volatile organic compounds) with light. Due to the highly nonlinear relationships between ozone and its precursors, proper ozone mitigation relies on the knowledge of chemical mechanisms. In this study, an observation-based method is used to simulate ozone formation and elucidate its controlling factors for a rural site on the North China Plain. The instantaneous ozone production rate is calculated utilizing a box model using the dataset obtained from the Wangdu campaign. First, the model was operated in a time-dependent mode to calculate the ozone production rate at each time stamp. The calculated ozone formation rate showed a diurnal average maximum value of 17 ppbv/h(1-h diurnal averaged). The contribution of individual peroxy radicals to ozone production was analyzed. In addition, the functional dependence of calculated P(O_3) reveals that ozone production was in a NO_x-limited regime during the campaign. Furthermore, the missing peroxy radical source will further extend NO_x-limited conditions to earlier in the day, making NO_xlimitation dominate more of a day than the current chemical model predicts. Finally, a multiple scenarios mode,also known as EKMA(empirical kinetic modeling approach), was used to simulate the response of P(O_3) to the imaginary change in precursor concentrations. We found that ozone production was in the NO_x-limited region. However, the use of NO_2 measured by the molybdenum converter and/or the absence of a peroxy radical source in the current chemical model could over-emphasize the VOC-limited effect on ozone production.展开更多
Many problems in rock engineering are limited by our imperfect knowledge of the material properties and failure mechanics of rock masses. Mining problems are somewhat unique, however, in that plenty of real world expe...Many problems in rock engineering are limited by our imperfect knowledge of the material properties and failure mechanics of rock masses. Mining problems are somewhat unique, however, in that plenty of real world experience is generally available and can be turned into valuable experimental data.Every pillar that is developed, or stope that is mined, represents a full-scale test of a rock mechanics design. By harvesting these data, and then using the appropriate statistical techniques to interpret them,mining engineers have developed powerful design techniques that are widely used around the world.Successful empirical methods are readily accepted because they are simple, transparent, practical, and firmly tethered to reality. The author has been intimately associated with empirical design for his entire career, but his previous publications have described the application of individual techniques to specific problems. The focus of this paper is the process used to develop a successful empirical method. A sixstage process is described: identification of the problem, and of the end users of the final product; development of a conceptual rock mechanics model, and identification of the key parameters in that model;identification of measures for each of the key parameters, and the development of new measures(such as rating scales) where necessary; data sources and data collection; statistical analysis; and packaging of the final product. Each of these stages has its own potential rewards and pitfalls, which will be illustrated by incidents from the author's own experience. The ultimate goal of this paper is to provide a new and deeper appreciation for empirical techniques, as well as some guidelines and opportunities for future developers.展开更多
The infiltration process is a critical link between surface water and groundwater. In this research, a specific device to observe infiltration processes in homogeneous and heterogeneous soils with triangular and inver...The infiltration process is a critical link between surface water and groundwater. In this research, a specific device to observe infiltration processes in homogeneous and heterogeneous soils with triangular and inverted triangular profiles was designed, and the Green-Ampt model was employed for the process simulation. The results indicate that(1) the wetting front in coarse texture soils transports faster than in fine texture soils;(2) for the homogeneous case, the wetting front in triangularshaped soils transports faster than the inverted triangular type, but the triangular-shaped soils show a lower infiltration rate;(3) in the initial step, the wetting front in triangular-shaped soils shows higher transport speed, but depicts lower speed with increase in the time;(4) both the wetting front and infiltration rate show a significant exponential relation with the time. From these findings, an empirical model was developed which agrees well with the observed data and provides a useful method for this field of soil research.展开更多
The aim of this work is to model the drying kinetics of Safou pulp with or without endocarp using a phenomenological approach. Oven-drying kinetics at 70˚C, 90˚C and 105˚C were monitored using the curves given by the ...The aim of this work is to model the drying kinetics of Safou pulp with or without endocarp using a phenomenological approach. Oven-drying kinetics at 70˚C, 90˚C and 105˚C were monitored using the curves given by the reduced mass as a function of time, which are modeled according to the Avrami/page, Fick and Peleg models using OringinPro 2018 software. The results showed that parameters k and n of the Avrami/Page model vary very little with fruit size and drying temperature (0.0018 ± 0.0002 k n k (Avrami model/page) were virtually identical, while b (Fick model) and n (Avrami model/page) were virtually identical for the same sample. For the Peleg model, the parameter a, varies from 0.0018 ± 0.0002 to 0.03328 ± 0.0079, with a ratio of 18.6 for all experimental conditions studied. However, with 0.977 R2 χ2 < 0.00002, we have a good fit of the model to the experimental data. The same applies to parameter b, which ranges from 0.82 ± 0.05 to 1.21 ± 0.02. Thus, drying modeling by these three models can be used to describe and predict the progress of oven-drying of safou pulp.展开更多
情景感知(context aware)的应用是当前的一个研究热点,但是,由于情景的复杂性和不确定性,如何获取这些应用的需求面临着巨大挑战,需求工程领域出现了大量的研究来解决这一挑战.使用系统文献综述(systematic literature review)的方法首...情景感知(context aware)的应用是当前的一个研究热点,但是,由于情景的复杂性和不确定性,如何获取这些应用的需求面临着巨大挑战,需求工程领域出现了大量的研究来解决这一挑战.使用系统文献综述(systematic literature review)的方法首先分析了不同情景维度对需求获取与建模的支持,统计并深入分析情景感知的需求获取与建模中常用的方法,评估了不同经验方法的技术转移成熟度.最后,基于上述结论,给出了情景感知的需求获取与建模下一步的研究方向.展开更多
The hourly values of the ionospheric F2 layer critical frequency, foF2, recorded at Wakkanai ionosonde station （45.4°N, 141.7°E） have been collected to construct a middle-latitude single-station model for ...The hourly values of the ionospheric F2 layer critical frequency, foF2, recorded at Wakkanai ionosonde station （45.4°N, 141.7°E） have been collected to construct a middle-latitude single-station model for forecasting foF2 under geomagnetic quiet and disturbed conditions. The module for the geomagnetic quiet conditions incorporates local time, seasonal, and solar vari- ability of climatological foF2 and its upper and lower quartiles. It is the first attempt to predict the upper and lower quartiles of foF2 to account for the notable day-to-day variability in ionospheric foF2. The validation statistically verifies that the model captures the climatological variations of foF2 with higher accuracy than IRI does. The storm-time module is built to capture the geomagnetic storm induced relative deviations of foF2 from the quiet time references. In the geomagnetically disturbed module, the storm-induced deviations are described by diumal and semidiumal waves, which are modulated by a modified magnetic activity index, the Kf index, reflecting the delayed responses of foF2 to geomagnetic activity forcing. The coeffi- cients of the model in each month are determined by fitting the model formula to the observation in a least-squares way. We provide two options for the geomagnetic disturbed module, including or not including Kalman filter algorithm. The Kalman filter algorithm is introduced to optimize these coefficients in real time. Our results demonstrate that the introduction of the Kalman filter algorithm in the storm time module is promising for improving the accuracy of predication. In addition, comparisons indicate that the IRI model prediction of the F2 layer can be improved to provide better performances over this region.展开更多
In this study, systematic physical model tests were performed to investigate the wave forces on the twin-plate breakwater under irregular waves. Based on the experimental results, the effects of the relative plate wid...In this study, systematic physical model tests were performed to investigate the wave forces on the twin-plate breakwater under irregular waves. Based on the experimental results, the effects of the relative plate width B/L,wave height Hs/D and incident angle θ0 on the wave forces were analyzed and discussed. The results showed that:(1) The envelopes of the total wave pressure were generally symmetrical along the direction of plate width under the incident angles(θ0) being 0°, 15°, 30°, 45° and 60°. In particular, the envelopes of wave pressure atθ0=30° were larger than all other cases.(2) The synchronous pressure distribution of the breakwater under oblique wave action was more complicated comparing to the normal incident waves.(3) Based on data analysis, an empirical formula was obtained to estimate the total vertical force of the twin-plate breakwater.This empirical formula can be a good reference for the design basis of engineering applications under specified wave conditions.展开更多
Velocity of debris flow is one of the most important characteristics for the protective construction design. Since debris flows are rare events, and observations are conducted only on stations in Russia, Ukraine, Ital...Velocity of debris flow is one of the most important characteristics for the protective construction design. Since debris flows are rare events, and observations are conducted only on stations in Russia, Ukraine, Italy, Switzerland, USA, China, Japan and New Zealand, the velocity is calculated rather than measured. Nowadays, a large number of videos with passing debris flows have appeared on the Internet. Scientists can use such video materials to obtain qualitative and quantitative characteristics of the debris flow. Therefore, the aim of our research is an attempt to measure the debris flow velocity using video materials and compare the obtained results with the calculated values using various methods. The debris flow that came down in Firgen, Austria on August 4, 2012 was chosen as the object of our study. The video was carried out from several angles, so it was possible to select a section of the channel, through which we could measure the debris flows waves velocity. In addition, we calculated the velocities of waves by formulas adopted in the regulatory documents and compared with the measured by video values. During the video analysis, debris flow velocities at different sites were observed: minimum—7.2 m/s and maximum—10 m/s. The calculated values varied from 4.5 m/s to 11.4 m/s. Moreover, we applied model of the transport-shear process of debris flow formation developed by Yu. B. Vinogradov. When we were comparing the obtained debris flow discharges with results from Austrian colleagues, we found out that the values were similar to each other. However, internal scatter in the model changed from 151 to 190 m3/s, while in the report of Austrian colleagues the discharges were from 80 to 250 m3/s.展开更多
Soft robotics,compared with their rigid counterparts,are able to adapt to uncharted environments,are superior in safe human-robot interactions,and have low cost,owing to the native compliance of the soft materials.How...Soft robotics,compared with their rigid counterparts,are able to adapt to uncharted environments,are superior in safe human-robot interactions,and have low cost,owing to the native compliance of the soft materials.However,customized complex structures,as well as the nonlinear and viscoelastic soft materials,pose a great challenge to accurate modeling and control of soft robotics,and impose restrictions on further applications.In this study,a unified modeling strategy is proposed to establish a complete dynamic model of the most widely used pneumatic soft bending actuator.First,a novel empirical nonlinear model with parametric and nonlinear uncertainties is identified to describe the nonlinear behaviors of pneumatic soft bending actuators.Second,an inner pressure dynamic model of a pneumatic soft bending actuator is established by introducing a modified valve flow rate model of the unbalanced pneumatic proportional valves.Third,an adaptive robust controller is designed using a backstepping method to handle and update the nonlinear and uncertain system.Finally,the experimental results of comparative trajectory tracking control indicate the validity of the proposed modeling and control method.展开更多
A physical-based particle system is employed for cloth modeling supported by two basic algorithms, between which one is the construction of the internal and external forces acting on the particle system in terms of KE...A physical-based particle system is employed for cloth modeling supported by two basic algorithms, between which one is the construction of the internal and external forces acting on the particle system in terms of KES-F bending and shearing tests, and the other is the collision algorithm of which the collision detection is carried by means of bi-section of time step and the collision response is handled according to the empirical law for frictionless collision With these algorithms. the geometric state of parcles can be expressed as ordinary differential equationswhich is numerically solved by fourth order Runge- Kutta integration. Different draping figures of cotton fabric and wool fabric prove that such a particle system is suitable for 3D cloth modeling and simulation.展开更多
This paper investigates the average dielectric permittivity （^-ε） in the Maier-Meier theory for calculating the dielectric anisotropy （△ε） of nematic liquid crystals.For the reason that ^-ε of nematics has the...This paper investigates the average dielectric permittivity （^-ε） in the Maier-Meier theory for calculating the dielectric anisotropy （△ε） of nematic liquid crystals.For the reason that ^-ε of nematics has the same expression as the dielectric permittivity of the isotropic state,the Onsager equation for isotropic dielectric was used to calculate it.The computed ^-ε shows reasonable agreement with the results of the numerical methods used in the literature.Molecular parameters,such as the polarizability and its anisotropy,the dipole moment and its angle with the molecular long axis,were taken from semi-empirical quantum chemistry （MOCPAC/AM1） modeling.The calculated values of △ε according to the Maier-Meier equation are in good agreement with the experimental results for the investigated compounds having different core structures and polar substituents.展开更多
Rice-glucose-lysine blend was extruded using a co-rotating twin-screw extruder.The effects of different extrusion conditions on the browning properties of extrudates were analyzed and compared using the CIE Lab system...Rice-glucose-lysine blend was extruded using a co-rotating twin-screw extruder.The effects of different extrusion conditions on the browning properties of extrudates were analyzed and compared using the CIE Lab system of measurement.Extrusion process variables included moisture content,screw speed,barrel temperature,and screw geometry.The influence of product temperature on the browning property of extrudates was significant(P<0.05).The color parameters were related to product temperature by a 4th degree polynomial(P<0.05).Hunter color scale values(L*,a*,b*,-L*a*/b*,Whiteness Index,and Yellowness Index)from extruded samples were analyzed to relate to extrusion process variables.Product temperature and browning properties were modeled and tested at various screw configurations and extrusion conditions.Product temperature and browning property models were verified using different screw geometries and other processing conditions with reasonable accuracy.展开更多
This work is devoted to stochastic systems arising from empirical measures of random sequences(termed primary sequences) that are modulated by another Markov chain. The Markov chain is used to model random discrete ev...This work is devoted to stochastic systems arising from empirical measures of random sequences(termed primary sequences) that are modulated by another Markov chain. The Markov chain is used to model random discrete events that are not represented in the primary sequences. One novel feature is that in lieu of the usual scaling in empirical measure sequences, the authors consider scaling in both space and time, which leads to new limit results. Under broad conditions, it is shown that a scaled sequence of the empirical measure converges weakly to a number of Brownian bridges modulated by a continuous-time Markov chain. Ramifications and special cases are also considered.展开更多
Conventional spouted beds have been extensively used in many real-life applications but are not suited for all types of materials, especially fine particles, which require internal devices to improve their motion in t...Conventional spouted beds have been extensively used in many real-life applications but are not suited for all types of materials, especially fine particles, which require internal devices to improve their motion in the spouted bed. However, unlike conventional spouted beds, there are almost no mechanistic or empirical models available for the design of spouted beds with internals. Given the availability of an extensive but not experimentally designed database, the main purpose of this study is to present an analysis of neural networks and empirical models in terms of their suitability to fit and predict average cycle times in conical spouted beds with and without draft tubes. The parameters investigated are particle size, density, contactor angle, gas inlet diameter, static bed height, and draft tube features. Although the amount of information is always a key factor when fitting models, the size of the database used in this study strongly affects the fitting performance of empirical models, whereas artificial neural networks are more influenced by how the data are scaled. Results of model verification show that both techniques are suitable for predicting average cycle times for data outside the range covered by the database.展开更多
基金supported from the research projects of the Environmental Public Welfare Industry in China (201509001,201409005)the National Science and Technology Support Program of China (2014BAC21B01)+2 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB05010500)the Special Fund of State Key Joint Laboratory of Environment Simulation and Pollution Control (18K03ESPCP)the EU-project AMIS (Fate and Impact of Atmospheric Pollutants,PIRSES-GA-2011295132)
文摘In the troposphere, ozone is a harmful gas compound to both human health and vegetation. Ozone is produced from the reaction of NO_x(@NO + NO_2) and VOCs(volatile organic compounds) with light. Due to the highly nonlinear relationships between ozone and its precursors, proper ozone mitigation relies on the knowledge of chemical mechanisms. In this study, an observation-based method is used to simulate ozone formation and elucidate its controlling factors for a rural site on the North China Plain. The instantaneous ozone production rate is calculated utilizing a box model using the dataset obtained from the Wangdu campaign. First, the model was operated in a time-dependent mode to calculate the ozone production rate at each time stamp. The calculated ozone formation rate showed a diurnal average maximum value of 17 ppbv/h(1-h diurnal averaged). The contribution of individual peroxy radicals to ozone production was analyzed. In addition, the functional dependence of calculated P(O_3) reveals that ozone production was in a NO_x-limited regime during the campaign. Furthermore, the missing peroxy radical source will further extend NO_x-limited conditions to earlier in the day, making NO_xlimitation dominate more of a day than the current chemical model predicts. Finally, a multiple scenarios mode,also known as EKMA(empirical kinetic modeling approach), was used to simulate the response of P(O_3) to the imaginary change in precursor concentrations. We found that ozone production was in the NO_x-limited region. However, the use of NO_2 measured by the molybdenum converter and/or the absence of a peroxy radical source in the current chemical model could over-emphasize the VOC-limited effect on ozone production.
文摘Many problems in rock engineering are limited by our imperfect knowledge of the material properties and failure mechanics of rock masses. Mining problems are somewhat unique, however, in that plenty of real world experience is generally available and can be turned into valuable experimental data.Every pillar that is developed, or stope that is mined, represents a full-scale test of a rock mechanics design. By harvesting these data, and then using the appropriate statistical techniques to interpret them,mining engineers have developed powerful design techniques that are widely used around the world.Successful empirical methods are readily accepted because they are simple, transparent, practical, and firmly tethered to reality. The author has been intimately associated with empirical design for his entire career, but his previous publications have described the application of individual techniques to specific problems. The focus of this paper is the process used to develop a successful empirical method. A sixstage process is described: identification of the problem, and of the end users of the final product; development of a conceptual rock mechanics model, and identification of the key parameters in that model;identification of measures for each of the key parameters, and the development of new measures(such as rating scales) where necessary; data sources and data collection; statistical analysis; and packaging of the final product. Each of these stages has its own potential rewards and pitfalls, which will be illustrated by incidents from the author's own experience. The ultimate goal of this paper is to provide a new and deeper appreciation for empirical techniques, as well as some guidelines and opportunities for future developers.
基金supported by the National Natural Science Foundation of China (Grant No. 41201268)
文摘The infiltration process is a critical link between surface water and groundwater. In this research, a specific device to observe infiltration processes in homogeneous and heterogeneous soils with triangular and inverted triangular profiles was designed, and the Green-Ampt model was employed for the process simulation. The results indicate that(1) the wetting front in coarse texture soils transports faster than in fine texture soils;(2) for the homogeneous case, the wetting front in triangularshaped soils transports faster than the inverted triangular type, but the triangular-shaped soils show a lower infiltration rate;(3) in the initial step, the wetting front in triangular-shaped soils shows higher transport speed, but depicts lower speed with increase in the time;(4) both the wetting front and infiltration rate show a significant exponential relation with the time. From these findings, an empirical model was developed which agrees well with the observed data and provides a useful method for this field of soil research.
文摘The aim of this work is to model the drying kinetics of Safou pulp with or without endocarp using a phenomenological approach. Oven-drying kinetics at 70˚C, 90˚C and 105˚C were monitored using the curves given by the reduced mass as a function of time, which are modeled according to the Avrami/page, Fick and Peleg models using OringinPro 2018 software. The results showed that parameters k and n of the Avrami/Page model vary very little with fruit size and drying temperature (0.0018 ± 0.0002 k n k (Avrami model/page) were virtually identical, while b (Fick model) and n (Avrami model/page) were virtually identical for the same sample. For the Peleg model, the parameter a, varies from 0.0018 ± 0.0002 to 0.03328 ± 0.0079, with a ratio of 18.6 for all experimental conditions studied. However, with 0.977 R2 χ2 < 0.00002, we have a good fit of the model to the experimental data. The same applies to parameter b, which ranges from 0.82 ± 0.05 to 1.21 ± 0.02. Thus, drying modeling by these three models can be used to describe and predict the progress of oven-drying of safou pulp.
文摘情景感知(context aware)的应用是当前的一个研究热点,但是,由于情景的复杂性和不确定性,如何获取这些应用的需求面临着巨大挑战,需求工程领域出现了大量的研究来解决这一挑战.使用系统文献综述(systematic literature review)的方法首先分析了不同情景维度对需求获取与建模的支持,统计并深入分析情景感知的需求获取与建模中常用的方法,评估了不同经验方法的技术转移成熟度.最后,基于上述结论,给出了情景感知的需求获取与建模下一步的研究方向.
基金supported by the CMA (Grant No. GYHY201106011)the National Basic Research Program of China ("973" Project) (Grant No. 2012CB- 825604)+1 种基金the National Natural Science Foundation of China (Grant Nos. 41074112, 41174137, 41174138)the Specialized Research Fund for State Key Laboratories
文摘The hourly values of the ionospheric F2 layer critical frequency, foF2, recorded at Wakkanai ionosonde station （45.4°N, 141.7°E） have been collected to construct a middle-latitude single-station model for forecasting foF2 under geomagnetic quiet and disturbed conditions. The module for the geomagnetic quiet conditions incorporates local time, seasonal, and solar vari- ability of climatological foF2 and its upper and lower quartiles. It is the first attempt to predict the upper and lower quartiles of foF2 to account for the notable day-to-day variability in ionospheric foF2. The validation statistically verifies that the model captures the climatological variations of foF2 with higher accuracy than IRI does. The storm-time module is built to capture the geomagnetic storm induced relative deviations of foF2 from the quiet time references. In the geomagnetically disturbed module, the storm-induced deviations are described by diumal and semidiumal waves, which are modulated by a modified magnetic activity index, the Kf index, reflecting the delayed responses of foF2 to geomagnetic activity forcing. The coeffi- cients of the model in each month are determined by fitting the model formula to the observation in a least-squares way. We provide two options for the geomagnetic disturbed module, including or not including Kalman filter algorithm. The Kalman filter algorithm is introduced to optimize these coefficients in real time. Our results demonstrate that the introduction of the Kalman filter algorithm in the storm time module is promising for improving the accuracy of predication. In addition, comparisons indicate that the IRI model prediction of the F2 layer can be improved to provide better performances over this region.
基金The National Natural Science Foundation of China under contract Nos 51079025 and 11272079the Research Funds from State Key Laboratory of Coastal and Offshore Engineering under contract No.LY1602
文摘In this study, systematic physical model tests were performed to investigate the wave forces on the twin-plate breakwater under irregular waves. Based on the experimental results, the effects of the relative plate width B/L,wave height Hs/D and incident angle θ0 on the wave forces were analyzed and discussed. The results showed that:(1) The envelopes of the total wave pressure were generally symmetrical along the direction of plate width under the incident angles(θ0) being 0°, 15°, 30°, 45° and 60°. In particular, the envelopes of wave pressure atθ0=30° were larger than all other cases.(2) The synchronous pressure distribution of the breakwater under oblique wave action was more complicated comparing to the normal incident waves.(3) Based on data analysis, an empirical formula was obtained to estimate the total vertical force of the twin-plate breakwater.This empirical formula can be a good reference for the design basis of engineering applications under specified wave conditions.
文摘Velocity of debris flow is one of the most important characteristics for the protective construction design. Since debris flows are rare events, and observations are conducted only on stations in Russia, Ukraine, Italy, Switzerland, USA, China, Japan and New Zealand, the velocity is calculated rather than measured. Nowadays, a large number of videos with passing debris flows have appeared on the Internet. Scientists can use such video materials to obtain qualitative and quantitative characteristics of the debris flow. Therefore, the aim of our research is an attempt to measure the debris flow velocity using video materials and compare the obtained results with the calculated values using various methods. The debris flow that came down in Firgen, Austria on August 4, 2012 was chosen as the object of our study. The video was carried out from several angles, so it was possible to select a section of the channel, through which we could measure the debris flows waves velocity. In addition, we calculated the velocities of waves by formulas adopted in the regulatory documents and compared with the measured by video values. During the video analysis, debris flow velocities at different sites were observed: minimum—7.2 m/s and maximum—10 m/s. The calculated values varied from 4.5 m/s to 11.4 m/s. Moreover, we applied model of the transport-shear process of debris flow formation developed by Yu. B. Vinogradov. When we were comparing the obtained debris flow discharges with results from Austrian colleagues, we found out that the values were similar to each other. However, internal scatter in the model changed from 151 to 190 m3/s, while in the report of Austrian colleagues the discharges were from 80 to 250 m3/s.
基金Project supported by the National Natural Science Foundation of China(Nos.51875507,51821093,and U1908228)。
文摘Soft robotics,compared with their rigid counterparts,are able to adapt to uncharted environments,are superior in safe human-robot interactions,and have low cost,owing to the native compliance of the soft materials.However,customized complex structures,as well as the nonlinear and viscoelastic soft materials,pose a great challenge to accurate modeling and control of soft robotics,and impose restrictions on further applications.In this study,a unified modeling strategy is proposed to establish a complete dynamic model of the most widely used pneumatic soft bending actuator.First,a novel empirical nonlinear model with parametric and nonlinear uncertainties is identified to describe the nonlinear behaviors of pneumatic soft bending actuators.Second,an inner pressure dynamic model of a pneumatic soft bending actuator is established by introducing a modified valve flow rate model of the unbalanced pneumatic proportional valves.Third,an adaptive robust controller is designed using a backstepping method to handle and update the nonlinear and uncertain system.Finally,the experimental results of comparative trajectory tracking control indicate the validity of the proposed modeling and control method.
文摘A physical-based particle system is employed for cloth modeling supported by two basic algorithms, between which one is the construction of the internal and external forces acting on the particle system in terms of KES-F bending and shearing tests, and the other is the collision algorithm of which the collision detection is carried by means of bi-section of time step and the collision response is handled according to the empirical law for frictionless collision With these algorithms. the geometric state of parcles can be expressed as ordinary differential equationswhich is numerically solved by fourth order Runge- Kutta integration. Different draping figures of cotton fabric and wool fabric prove that such a particle system is suitable for 3D cloth modeling and simulation.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 60578035 and 60736042)the Science Foundation of Jilin Province of China (Grant Nos 20050520 and 20050321-2)
文摘This paper investigates the average dielectric permittivity （^-ε） in the Maier-Meier theory for calculating the dielectric anisotropy （△ε） of nematic liquid crystals.For the reason that ^-ε of nematics has the same expression as the dielectric permittivity of the isotropic state,the Onsager equation for isotropic dielectric was used to calculate it.The computed ^-ε shows reasonable agreement with the results of the numerical methods used in the literature.Molecular parameters,such as the polarizability and its anisotropy,the dipole moment and its angle with the molecular long axis,were taken from semi-empirical quantum chemistry （MOCPAC/AM1） modeling.The calculated values of △ε according to the Maier-Meier equation are in good agreement with the experimental results for the investigated compounds having different core structures and polar substituents.
文摘Rice-glucose-lysine blend was extruded using a co-rotating twin-screw extruder.The effects of different extrusion conditions on the browning properties of extrudates were analyzed and compared using the CIE Lab system of measurement.Extrusion process variables included moisture content,screw speed,barrel temperature,and screw geometry.The influence of product temperature on the browning property of extrudates was significant(P<0.05).The color parameters were related to product temperature by a 4th degree polynomial(P<0.05).Hunter color scale values(L*,a*,b*,-L*a*/b*,Whiteness Index,and Yellowness Index)from extruded samples were analyzed to relate to extrusion process variables.Product temperature and browning properties were modeled and tested at various screw configurations and extrusion conditions.Product temperature and browning property models were verified using different screw geometries and other processing conditions with reasonable accuracy.
基金supported by the Air Force Office of Scientific Research under Grant No.FA9550-15-1-0131
文摘This work is devoted to stochastic systems arising from empirical measures of random sequences(termed primary sequences) that are modulated by another Markov chain. The Markov chain is used to model random discrete events that are not represented in the primary sequences. One novel feature is that in lieu of the usual scaling in empirical measure sequences, the authors consider scaling in both space and time, which leads to new limit results. Under broad conditions, it is shown that a scaled sequence of the empirical measure converges weakly to a number of Brownian bridges modulated by a continuous-time Markov chain. Ramifications and special cases are also considered.
文摘Conventional spouted beds have been extensively used in many real-life applications but are not suited for all types of materials, especially fine particles, which require internal devices to improve their motion in the spouted bed. However, unlike conventional spouted beds, there are almost no mechanistic or empirical models available for the design of spouted beds with internals. Given the availability of an extensive but not experimentally designed database, the main purpose of this study is to present an analysis of neural networks and empirical models in terms of their suitability to fit and predict average cycle times in conical spouted beds with and without draft tubes. The parameters investigated are particle size, density, contactor angle, gas inlet diameter, static bed height, and draft tube features. Although the amount of information is always a key factor when fitting models, the size of the database used in this study strongly affects the fitting performance of empirical models, whereas artificial neural networks are more influenced by how the data are scaled. Results of model verification show that both techniques are suitable for predicting average cycle times for data outside the range covered by the database.
