A wavelet collocation method with nonlinear auto companding is proposed for behavioral modeling of switched current circuits.The companding function is automatically constructed according to the initial error distri...A wavelet collocation method with nonlinear auto companding is proposed for behavioral modeling of switched current circuits.The companding function is automatically constructed according to the initial error distribution obtained through approximating the input output function of the SI circuit by conventional wavelet collocation method.In practical applications,the proposed method is a general purpose approach,by which both the small signal effect and the large signal effect are modeled in a unified formulation to ease the process of modeling and simulation.Compared with the published modeling approaches,the proposed nonlinear auto companding method works more efficiently not only in controlling the error distribution but also in reducing the modeling errors.To demonstrate the promising features of the proposed method,several SI circuits are employed as examples to be modeled and simulated.展开更多
Today’s air combat has reached a high level of uncertainty where continuous or discrete variables with crisp values cannot be properly represented using fuzzy sets. With a set of membership functions, fuzzy logic is ...Today’s air combat has reached a high level of uncertainty where continuous or discrete variables with crisp values cannot be properly represented using fuzzy sets. With a set of membership functions, fuzzy logic is well-suited to tackle such complex states and actions. However, it is not necessary to fuzzify the variables that have definite discrete semantics.Hence, the aim of this study is to improve the level of model abstraction by proposing multiple levels of cascaded hierarchical structures from the perspective of function, namely, the functional decision tree. This method is developed to represent behavioral modeling of air combat systems, and its metamodel,execution mechanism, and code generation can provide a sound basis for function-based behavioral modeling. As a proof of concept, an air combat simulation is developed to validate this method and the results show that the fighter Alpha built using the proposed framework provides better performance than that using default scripts.展开更多
The increasing architecture complexity of data converters makes it necessary to use behavioral models to simulate their electrical performance and to determine their relevant data features. For this purpose, a specifi...The increasing architecture complexity of data converters makes it necessary to use behavioral models to simulate their electrical performance and to determine their relevant data features. For this purpose, a specific data converter simulation environment has been developed which allows designers to perform time-domain behavioral simulations of pipelined analog to digital converters （ADCs）. All the necessary blocks of this specific simulation environment have been implemented using the popular Matlab simulink environment. The purpose of this paper is to present the behavioral models of these blocks taking into account most of the pipelined ADC non-idealities, such as sampling jitter, noise, and operational amplifier parameters （white noise, finite DC gain, finite bandwidth, slew rate, and saturation voltages）. Simulations, using a 10-bit pipelined ADC as a design example, show that in addition to the limits analysis and the electrical features extraction, designers can determine the specifications of the basic blocks in order to meet the given data converter requirements.展开更多
A novel behavioral model using three-layer time-delay feed-forward neural networks （TDFFNN）is adopted to model radio frequency （RF）power amplifiers exhibiting memory nonlinearities. In order to extract the paramet...A novel behavioral model using three-layer time-delay feed-forward neural networks （TDFFNN）is adopted to model radio frequency （RF）power amplifiers exhibiting memory nonlinearities. In order to extract the parameters, the back- propagation algorithm is applied to train the proposed neural networks. The proposed model is verified by the typical odd- order-only memory polynomial model in simulation, and the performance is compared with different numbers of taped delay lines（TDLs） and perceptrons of the hidden layer. For validating the TDFFNN model by experiments, a digital test bench is set up to collect input and output data of power amplifiers at a 60 × 10^6 sample/s sampling rate. The 3.75 MHz 16-QAM signal generated in the vector signal generator（VSG） is chosen as the input signal, when measuring the dynamic AM/AM and AM/PM characteristics of power amplifiers. By comparisons and analyses, the presented model provides a good performance in convergence, accuracy and efficiency, which is approved by simulation results and experimental results in the time domain and frequency domain.展开更多
An envelope domain multislice behavioral modeling is introduced. The tradition AM-AM and AM- PM characteristics of power amplifiers axe extended to envelope domain and base-band filter is applied to distortion complex...An envelope domain multislice behavioral modeling is introduced. The tradition AM-AM and AM- PM characteristics of power amplifiers axe extended to envelope domain and base-band filter is applied to distortion complex envelope signal for description of the envelope memory effect. Using traditional one and two-tone tests, the coefficients of nonlinear model and the FIR filter can be extracted. At last the model has been applied to a 10 W WCDMA Power amplifier to predict its output signal. And simulation results show that the model output conforms very well to the traditional transistor level simulation results.展开更多
A behavior model for the receiver of the Ethernet passive optical network（EPON） is presented. The model consists of a fiber, a photodetector, a transimpedance amplifier （TIA） followed by a limiting amplifier and a...A behavior model for the receiver of the Ethernet passive optical network（EPON） is presented. The model consists of a fiber, a photodetector, a transimpedance amplifier （TIA） followed by a limiting amplifier and a clock and data recovery＇ circuit （CDR）. Each sub-model is constructed based on the architecture of a circuit. The noise and jitter in each block such as shot noise, thermal noise, deterministic and random jitter are also considered. The performance of the whole receiver can be evaluated by the simulation of the behavior model, which is faster than the ordinary circuit model and more accurate than the analytical model. The whole model is implemented with C ＋＋ and simulated in Microsoft Visual C ＋＋ 6. 0. Using the Monte Carlo method, the EPON receiver is simulated. The simulation results show a good agreement with experimental ones.展开更多
Warm rotary draw bending provides a feasible method to form the large-diameter thin-walled（LDTW）TC4 bent tubes, which are widely used in the pneumatic system of aircrafts. An accurate prediction of flow behavior of ...Warm rotary draw bending provides a feasible method to form the large-diameter thin-walled（LDTW）TC4 bent tubes, which are widely used in the pneumatic system of aircrafts. An accurate prediction of flow behavior of TC4 tubes considering the couple effects of temperature,strain rate and strain is critical for understanding the deformation behavior of metals and optimizing the processing parameters in warm rotary draw bending of TC4 tubes. In this study, isothermal compression tests of TC4 tube alloy were performed from 573 to 873 K with an interval of 100 K and strain rates of 0.001, 0.010 and0.100 s^（-1）. The prediction of flow behavior was done using two constitutive models, namely modified Arrhenius model and artificial neural network（ANN） model. The predictions of these constitutive models were compared using statistical measures like correlation coefficient（R）, average absolute relative error（AARE） and its variation with the deformation parameters（temperature, strain rate and strain）. Analysis of statistical measures reveals that the two models show high predicted accuracy in terms of R and AARE. Comparatively speaking, the ANN model presents higher predicted accuracy than the modified Arrhenius model. In addition, the predicted accuracy of ANN model presents high stability at the whole deformation parameter ranges, whereas the predictability of the modified Arrhenius model has some fluctuation at different deformation conditions. It presents higher predicted accuracy at temperatures of 573-773 K, strain rates of 0.010-0.100 s^（-1）and strain of 0.04-0.32, while low accuracy at temperature of 873 K, strain rates of 0.001 s^（-1）and strain of 0.36-0.48.Thus, the application of modified Arrhenius model is limited by its relatively low predicted accuracy at some deformation conditions, while the ANN model presents very high predicted accuracy at all deformation conditions,which can be used to study the compression behavior of TC4 tube at the temperature range of 573-873 K and the strain rate of 0.001-0.100 s^（-1）. It can provide guideline for the design of processing parameters in warm rotary draw bending of LDTW TC4 tubes.展开更多
The flow behavior of delta-processed Inconel 718 was studied in temperature range of 900-1 060℃ and strain rate range of 0.001-0.5s-1.The effects of friction and temperature on the compressive deformation behavior we...The flow behavior of delta-processed Inconel 718 was studied in temperature range of 900-1 060℃ and strain rate range of 0.001-0.5s-1.The effects of friction and temperature on the compressive deformation behavior were investigated,and the flow stress-strain error caused by friction was revised.The results showed that the effect of the friction was obvious with increasing strain rate and decreasing deformation temperature.The revised flow stress is decreased by increasing temperature and decreasing strain rate and exhibits a typical dynamic recrystallization behavior.The constitutive model has been developed through a hyperbolic-sine Arrhenius type equation to relate the flow stress,strain rate and temperature.The influence of strain has also been incorporated by considering the variation of material constants as a function of strain.The prediction accuracy of developed constitutive model has been assessed using standard statistical formulae.According to the analysis results,the proposed deformation constitutive equation gives an accurate and precise estimate of flow stress of delta-processed Inconel 718 alloy.展开更多
The high-temperature creep behavior of asphalt mixture was investigated based on micromechanical modeling and virtual test by using three-dimensional discrete element method（DEM）. A user-defined micromechanical mode...The high-temperature creep behavior of asphalt mixture was investigated based on micromechanical modeling and virtual test by using three-dimensional discrete element method（DEM）. A user-defined micromechanical model of asphalt mixture was established after analyzing the irregular shape and gradation of coarse aggregates, the viscoelastic property of asphalt mastic, and the random distribution of air voids within the asphalt mixture. Virtual uniaxial static creep test at 60 ℃ was conducted by using Particle Flow Code in three dimensions（PFC3D） and was validated by laboratory test. Based on virtual creep test, the micromechanical characteristics between aggregates, within asphalt mastic, and between aggregate and asphalt mastic were analyzed for the asphalt mixture. It is proved that the virtual test based on the micromechanical model can efficiently predict the creep deformation of asphalt mixture. And the high-temperature behavior of asphalt mixture was characterized from micromechanical perspective.展开更多
Checking if the implementations conform to the requirement models is challenging. Most existing techniques for consistency checking either focus on requirement models（e.g., requirements consistency checking）, or on ...Checking if the implementations conform to the requirement models is challenging. Most existing techniques for consistency checking either focus on requirement models（e.g., requirements consistency checking）, or on the implementations（e.g., code-based testing） only. In this paper we propose an approach to checking behavioral consistency of implementations against requirement models directly to overcome these limitations. Our approach extracts two behavioral models represented by Labelled Transition Systems（LTS） from requirement models and implementations respectively, and checks the behavioral consistency between these two models based on behavioral simulation relation of LTS. The checking results of our approach provide evidence for behavioral inconsistency as well as inconsistent localization. A research prototype called BCCH and a case study are presented to give initial validation of this approach.展开更多
Objective Patients who experience knee osteoarthritis or chronic knee pain can alleviate their symptoms by performing self-knee massage.Understanding the readiness and types of determinants needed to facilitate self-k...Objective Patients who experience knee osteoarthritis or chronic knee pain can alleviate their symptoms by performing self-knee massage.Understanding the readiness and types of determinants needed to facilitate self-knee massage is needed to design effective,theory-informed interventions.The primary objective of this study was to apply the transtheoretical model of behavior change to identify how factors,which include the type of knee condition and pain level,predict an individual’s readiness to adopt self-knee massage.The secondary objective employed the capability,opportunity and motivation-behavior(COM-B)model to identify relevant determinants that are predictive of an individual’s readiness to undertake self-knee massage.Methods An observational study design was used to recruit individuals with knee osteoarthritis(n=270)and chronic knee pain(n=130).Participants completed an online survey that assessed the transtheoretical model of behavior change stages,COM-B determinants(capability,opportunity and motivation),along with self-administered massage behavior.Multivariate analysis of covariance and structural equation modeling were used to test the primary and secondary objective,respectively.Results Participants who had knee osteoarthritis scored higher on the action stage compared to those with chronic pain(P=0.003),and those who experienced greater level of pain scored higher in the contemplation(P<0.001)and action phases(P<0.001)of performing knee massage compared to those with milder pain.The COM-B structural equation model revealed self-administered knee massage to be predicted by capability(β=0.31,P=0.004)and motivation(β=0.29,P<0.001),but not opportunity(β=–0.10,P=0.39).Pain level predicted motivation(β=0.27,P<0.001),but not capability(β=0.09,P=0.07)or opportunity(β=0.01,P=0.83).Tests for mediating effects found that determinants of COM-B(motivation and capability)mediate between pain level and self-administered massage behavior(β=0.10,P=0.002).Conclusion Clinicians and researchers can expect that patients diagnosed with knee osteoarthritis or who have chronic knee pain are ready(action stage)or are considering the behavior(contemplation stage)of self-knee massage.Individuals who report having knee osteoarthritis or chronic knee pain should be coached to develop the skills to perform self-knee massage and helped to develop the motivation to carry out the therapy.展开更多
To linearize the multi.band PAs/transmitters, a serial of multi.band predistortion models based on multi.dimensional architecture have been proposed. However, most of these models work properly only for the signals wh...To linearize the multi.band PAs/transmitters, a serial of multi.band predistortion models based on multi.dimensional architecture have been proposed. However, most of these models work properly only for the signals whose harmonic and intermodulation products of carriers' non.overlap with the interested fundamental bands. In this paper, the non.overlapping conditions for dual.band and tri.band signals are derived and denoted in the form of closed.form expression. It can be used to verify whether a given dual.band/multi.band signals can be linearized properly by these multi.dimensional behavioral models. Also the conditions can be used to plan the frequency spacing and maximum bandwidth of a multi.band or non.continuous carrier aggregation signal. Several dual.band and triband signals were tested on the same PA, by employing 2.D DPD and 3.D DPD behavioral models. The measurement results show that the signals which don't satisfy the non.overlapping conditions cannot be linearized well by the multi.dimensional behavioral models which does not take the harmonic and intermodulation products of carriers' into account.展开更多
Symbolic circuit simulator is traditionally applied to the small-signal analysis of analog circuits. This paper establishes a symbolic behavioral macromodeling method applicable to both small-signal and large-signal a...Symbolic circuit simulator is traditionally applied to the small-signal analysis of analog circuits. This paper establishes a symbolic behavioral macromodeling method applicable to both small-signal and large-signal analysis of general two-stage operational amplifiers （op-amps）. The proposed method creates a two-pole parametric macromodel whose parameters are analytical functions of the circuit element parameters generated by a symbolic circuit simulator. A moment matching technique is used in deriving the analytical model parameter. The created parametric behavioral model can be used for op-amps performance simulation in both frequency and time domains. In particular, the parametric models are highly suited for fast statistical simulation of op-amps in the time-domain. Experiment results show that the statistical distributions of the op-amp slew and settling time characterized by the proposed model agree well with the transistor-level results in addition to achieving significant speedup.展开更多
The pathophysiology of tinnitus is poorly understood and treatments are often unsuccessful. A number of animal models have been developed in order to gain a better understanding of tinnitus. A great deal has been lear...The pathophysiology of tinnitus is poorly understood and treatments are often unsuccessful. A number of animal models have been developed in order to gain a better understanding of tinnitus. A great deal has been learned from these models re- garding the electrophysiological and neuroanatomical correlates of tinnitus following exposure to noise or ototoxic drugs. Re- liable behavioral data is important for determining whether such electrophysiological or neuroanatomical changes are indeed related to tinnitus. Of the many documented tinnitus animal behavioral paradigms, the acoustic startle reflex had been pro- posed as a simple method to identify the presence or absence of tinnitus. Several behavioral models based on conditioned re- sponse suppression paradigms have also been developed. In addition to determining the presence or absence of tinnitus, some of the behavioral paradigms have provided signs of the onset, frequency, and intensity of tinnitus in animals. Although none of these behavioral models have been proved to be a perfect model, these studies provide useful information on understanding the neural mechanisms underlying tinnitus.展开更多
With the advent of computing and communication technologies,it has become possible for a learner to expand his or her knowledge irrespective of the place and time.Web-based learning promotes active and independent lea...With the advent of computing and communication technologies,it has become possible for a learner to expand his or her knowledge irrespective of the place and time.Web-based learning promotes active and independent learning.Large scale e-learning platforms revolutionized the concept of studying and it also paved the way for innovative and effective teaching-learning process.This digital learning improves the quality of teaching and also promotes educational equity.However,the challenges in e-learning platforms include dissimilarities in learner’s ability and needs,lack of student motivation towards learning activities and provision for adaptive learning environment.The quality of learning can be enhanced by analyzing the online learner’s behavioral characteristics and their application of intelligent instructional strategy.It is not possible to identify the difficulties faced during the process through evaluation after the completion of e-learning course.It is thus essential for an e-learning system to include component offering adaptive control of learning and maintain user’s interest level.In this research work,a framework is proposed to analyze the behavior of online learners and motivate the students towards the learning process accordingly so as to increase the rate of learner’s objective attainment.Catering to the demands of e-learner,an intelligent model is presented in this study for e-learning system that apply supervised machine learning algorithm.An adaptive e-learning system suits every category of learner,improves the learner’s performance and paves way for offering personalized learning experiences.展开更多
Voherra series behavioral model for radio frequency （RF） power amplifier （PA） has been widely used in system-level simulation, however, high computational complexity makes this kind of model limited to ＂weak＂ no...Voherra series behavioral model for radio frequency （RF） power amplifier （PA） has been widely used in system-level simulation, however, high computational complexity makes this kind of model limited to ＂weak＂ nonlinearity. In order to reduce the computational complexity and the number of coefficients of Volterra series kernels, a Volterra series improved behavioral model based on Laguerre orthogonal polynomials function, namely Voherra-Laguerre behavioral model, is proposed. Mathematical expressions of Volterra-Laguerre behavioral model is derived, and accuracy of the model is verified through comparison of measured and simulation output data from a freescale PA using MRF21030 transistor. Mathematical analysis and simulation results show that Voherra-Laguerre behavioral model has a simple structure, much less coefficients and better modeling performance than general Volterra series model. The model can be used more correctly for system-level simulation of RF PA with wideband signal.展开更多
Phase locked loop(PLL) is a typical analog-digital mixed signal circuit and a method of conducting a top level system verification including PLL with standard digital simulator becomes especially significant.The behav...Phase locked loop(PLL) is a typical analog-digital mixed signal circuit and a method of conducting a top level system verification including PLL with standard digital simulator becomes especially significant.The behavioral level model(BLM) of the PLL in Verilog-HDL for pure digital simulator is innovated in this paper,and the design of PLL based clock and data recovery(CDR)circuit aided with jitter attenuation PLL for SerDes application is also presented.The CDR employs a dual-loop architecture where a frequency-locked loop acts as an acquisition aid to the phase-locked loop.To simultaneously meet jitter tolerance and jitter transfer specifications defined in G.8251 of optical transport network(ITU-T OTN),an additional jitter attenuation PLL is used.Simulation results show that the peak-to-peak jitter of the recovered clock and data is 5.17 ps and 2.3ps respectively.The core of the whole chip consumes 72 mA current from a 1.0V supply.展开更多
With the rapid growth of complexity and functionality of modern electronic systems, creating precise behavioral models of nonlinear circuits has become an attractive topic. Deep neural networks (DNNs) have been recogn...With the rapid growth of complexity and functionality of modern electronic systems, creating precise behavioral models of nonlinear circuits has become an attractive topic. Deep neural networks (DNNs) have been recognized as a powerful tool for nonlinear system modeling. To characterize the behavior of nonlinear circuits, a DNN based modeling approach is proposed in this paper. The procedure is illustrated by modeling a power amplifier (PA), which is a typical nonlinear circuit in electronic systems. The PA model is constructed based on a feedforward neural network with three hidden layers, and then Multisim circuit simulator is applied to generating the raw training data. Training and validation are carried out in Tensorflow deep learning framework. Compared with the commonly used polynomial model, the proposed DNN model exhibits a faster convergence rate and improves the mean squared error by 13 dB. The results demonstrate that the proposed DNN model can accurately depict the input-output characteristics of nonlinear circuits in both training and validation data sets.展开更多
In a multi-agent system, each agent must adapt itself to the environment and coordinate with other agents dynamically. TO predict or cooperate with the behavior of oiller agents. An agent should dynamically establish ...In a multi-agent system, each agent must adapt itself to the environment and coordinate with other agents dynamically. TO predict or cooperate with the behavior of oiller agents. An agent should dynamically establish and evolve the cooperative behavior model of itself. In this paper, we represent the behavior model of an agent as a f-mite state machine and propose a new method of dynamically evolving the behavior model of an agent by evolutionary programming.展开更多
This Special Issue of the Journal of Rock Mechanics and GeotechnicalEngineering （JRMGE） contains 13 papers prepared by internationalexperts on various general topics in geomechanics, rockmechanics and geotechnical e...This Special Issue of the Journal of Rock Mechanics and GeotechnicalEngineering （JRMGE） contains 13 papers prepared by internationalexperts on various general topics in geomechanics, rockmechanics and geotechnical engineering. It represents a usefulmix of theoretical developments, testing and practical applications.We present in the following brief details in the papers, alphabeticallyin accordance with the last name of the first author.Barla presents a review of tunneling techniques with emphasison the full-face method combining full-face excavation and facereinforcement by means of fiber-glass elements with a yieldcontrolsupport. This method has been used successfully in difficultgeologic conditions, and for a wide spectrum of ground situations.The validation of the method with respect to the Saint Martin LaPorte access adit along the LyoneTurin Base tunnel experiencingseverely squeezing conditions during excavation is also includedin the paper. The numerical modeling with consideration of therock mass time-dependent behavior showed a satisfactory agreementwith monitoring results.展开更多
文摘A wavelet collocation method with nonlinear auto companding is proposed for behavioral modeling of switched current circuits.The companding function is automatically constructed according to the initial error distribution obtained through approximating the input output function of the SI circuit by conventional wavelet collocation method.In practical applications,the proposed method is a general purpose approach,by which both the small signal effect and the large signal effect are modeled in a unified formulation to ease the process of modeling and simulation.Compared with the published modeling approaches,the proposed nonlinear auto companding method works more efficiently not only in controlling the error distribution but also in reducing the modeling errors.To demonstrate the promising features of the proposed method,several SI circuits are employed as examples to be modeled and simulated.
基金This work was supported by the National Natural Science Foundation of China(62003359).
文摘Today’s air combat has reached a high level of uncertainty where continuous or discrete variables with crisp values cannot be properly represented using fuzzy sets. With a set of membership functions, fuzzy logic is well-suited to tackle such complex states and actions. However, it is not necessary to fuzzify the variables that have definite discrete semantics.Hence, the aim of this study is to improve the level of model abstraction by proposing multiple levels of cascaded hierarchical structures from the perspective of function, namely, the functional decision tree. This method is developed to represent behavioral modeling of air combat systems, and its metamodel,execution mechanism, and code generation can provide a sound basis for function-based behavioral modeling. As a proof of concept, an air combat simulation is developed to validate this method and the results show that the fighter Alpha built using the proposed framework provides better performance than that using default scripts.
文摘The increasing architecture complexity of data converters makes it necessary to use behavioral models to simulate their electrical performance and to determine their relevant data features. For this purpose, a specific data converter simulation environment has been developed which allows designers to perform time-domain behavioral simulations of pipelined analog to digital converters （ADCs）. All the necessary blocks of this specific simulation environment have been implemented using the popular Matlab simulink environment. The purpose of this paper is to present the behavioral models of these blocks taking into account most of the pipelined ADC non-idealities, such as sampling jitter, noise, and operational amplifier parameters （white noise, finite DC gain, finite bandwidth, slew rate, and saturation voltages）. Simulations, using a 10-bit pipelined ADC as a design example, show that in addition to the limits analysis and the electrical features extraction, designers can determine the specifications of the basic blocks in order to meet the given data converter requirements.
基金The National Natural Science Foundation of China(No.60621002)the National High Technology Research and Development Pro-gram of China(863 Program)(No.2007AA01Z2B4).
文摘A novel behavioral model using three-layer time-delay feed-forward neural networks （TDFFNN）is adopted to model radio frequency （RF）power amplifiers exhibiting memory nonlinearities. In order to extract the parameters, the back- propagation algorithm is applied to train the proposed neural networks. The proposed model is verified by the typical odd- order-only memory polynomial model in simulation, and the performance is compared with different numbers of taped delay lines（TDLs） and perceptrons of the hidden layer. For validating the TDFFNN model by experiments, a digital test bench is set up to collect input and output data of power amplifiers at a 60 × 10^6 sample/s sampling rate. The 3.75 MHz 16-QAM signal generated in the vector signal generator（VSG） is chosen as the input signal, when measuring the dynamic AM/AM and AM/PM characteristics of power amplifiers. By comparisons and analyses, the presented model provides a good performance in convergence, accuracy and efficiency, which is approved by simulation results and experimental results in the time domain and frequency domain.
文摘An envelope domain multislice behavioral modeling is introduced. The tradition AM-AM and AM- PM characteristics of power amplifiers axe extended to envelope domain and base-band filter is applied to distortion complex envelope signal for description of the envelope memory effect. Using traditional one and two-tone tests, the coefficients of nonlinear model and the FIR filter can be extracted. At last the model has been applied to a 10 W WCDMA Power amplifier to predict its output signal. And simulation results show that the model output conforms very well to the traditional transistor level simulation results.
文摘A behavior model for the receiver of the Ethernet passive optical network（EPON） is presented. The model consists of a fiber, a photodetector, a transimpedance amplifier （TIA） followed by a limiting amplifier and a clock and data recovery＇ circuit （CDR）. Each sub-model is constructed based on the architecture of a circuit. The noise and jitter in each block such as shot noise, thermal noise, deterministic and random jitter are also considered. The performance of the whole receiver can be evaluated by the simulation of the behavior model, which is faster than the ordinary circuit model and more accurate than the analytical model. The whole model is implemented with C ＋＋ and simulated in Microsoft Visual C ＋＋ 6. 0. Using the Monte Carlo method, the EPON receiver is simulated. The simulation results show a good agreement with experimental ones.
基金financially supported by the National Natural Science Foundation of China(Nos.51275415 and50905144)the Natural Science Basic Research Plan in Shanxi Province(No.2011JQ6004)the Program of the Ministry of Education of China for Introducing Talents of Discipline to Universities(No.B08040)
文摘Warm rotary draw bending provides a feasible method to form the large-diameter thin-walled（LDTW）TC4 bent tubes, which are widely used in the pneumatic system of aircrafts. An accurate prediction of flow behavior of TC4 tubes considering the couple effects of temperature,strain rate and strain is critical for understanding the deformation behavior of metals and optimizing the processing parameters in warm rotary draw bending of TC4 tubes. In this study, isothermal compression tests of TC4 tube alloy were performed from 573 to 873 K with an interval of 100 K and strain rates of 0.001, 0.010 and0.100 s^（-1）. The prediction of flow behavior was done using two constitutive models, namely modified Arrhenius model and artificial neural network（ANN） model. The predictions of these constitutive models were compared using statistical measures like correlation coefficient（R）, average absolute relative error（AARE） and its variation with the deformation parameters（temperature, strain rate and strain）. Analysis of statistical measures reveals that the two models show high predicted accuracy in terms of R and AARE. Comparatively speaking, the ANN model presents higher predicted accuracy than the modified Arrhenius model. In addition, the predicted accuracy of ANN model presents high stability at the whole deformation parameter ranges, whereas the predictability of the modified Arrhenius model has some fluctuation at different deformation conditions. It presents higher predicted accuracy at temperatures of 573-773 K, strain rates of 0.010-0.100 s^（-1）and strain of 0.04-0.32, while low accuracy at temperature of 873 K, strain rates of 0.001 s^（-1）and strain of 0.36-0.48.Thus, the application of modified Arrhenius model is limited by its relatively low predicted accuracy at some deformation conditions, while the ANN model presents very high predicted accuracy at all deformation conditions,which can be used to study the compression behavior of TC4 tube at the temperature range of 573-873 K and the strain rate of 0.001-0.100 s^（-1）. It can provide guideline for the design of processing parameters in warm rotary draw bending of LDTW TC4 tubes.
基金Sponsored by National High Technology Research and Development Program of China(2012AA03A514)Youth Scientific Research Foundation of Central South University of Forestry and Technology of China(QJ2010001A)
文摘The flow behavior of delta-processed Inconel 718 was studied in temperature range of 900-1 060℃ and strain rate range of 0.001-0.5s-1.The effects of friction and temperature on the compressive deformation behavior were investigated,and the flow stress-strain error caused by friction was revised.The results showed that the effect of the friction was obvious with increasing strain rate and decreasing deformation temperature.The revised flow stress is decreased by increasing temperature and decreasing strain rate and exhibits a typical dynamic recrystallization behavior.The constitutive model has been developed through a hyperbolic-sine Arrhenius type equation to relate the flow stress,strain rate and temperature.The influence of strain has also been incorporated by considering the variation of material constants as a function of strain.The prediction accuracy of developed constitutive model has been assessed using standard statistical formulae.According to the analysis results,the proposed deformation constitutive equation gives an accurate and precise estimate of flow stress of delta-processed Inconel 718 alloy.
基金Funded by the National Natural Science Foundation of China(No.51378006)the Huoyingdong Foundation of China(No.141076)+1 种基金the Fundamental Research Funds for the Central Universities(No.2242015R30027)the Natural Science Foundation of Jiangsu Province(BK20161421 and BK20140109)
文摘The high-temperature creep behavior of asphalt mixture was investigated based on micromechanical modeling and virtual test by using three-dimensional discrete element method（DEM）. A user-defined micromechanical model of asphalt mixture was established after analyzing the irregular shape and gradation of coarse aggregates, the viscoelastic property of asphalt mastic, and the random distribution of air voids within the asphalt mixture. Virtual uniaxial static creep test at 60 ℃ was conducted by using Particle Flow Code in three dimensions（PFC3D） and was validated by laboratory test. Based on virtual creep test, the micromechanical characteristics between aggregates, within asphalt mastic, and between aggregate and asphalt mastic were analyzed for the asphalt mixture. It is proved that the virtual test based on the micromechanical model can efficiently predict the creep deformation of asphalt mixture. And the high-temperature behavior of asphalt mixture was characterized from micromechanical perspective.
基金Supported by the National Natural Science Foundation of China(91118003,61003071)the Fundamental Research Funds for the Central Universities(3101046,201121102020006)the Special Funds for Shenzhen Strategic New Industry Development(JCYJ20120616135936123)
文摘Checking if the implementations conform to the requirement models is challenging. Most existing techniques for consistency checking either focus on requirement models（e.g., requirements consistency checking）, or on the implementations（e.g., code-based testing） only. In this paper we propose an approach to checking behavioral consistency of implementations against requirement models directly to overcome these limitations. Our approach extracts two behavioral models represented by Labelled Transition Systems（LTS） from requirement models and implementations respectively, and checks the behavioral consistency between these two models based on behavioral simulation relation of LTS. The checking results of our approach provide evidence for behavioral inconsistency as well as inconsistent localization. A research prototype called BCCH and a case study are presented to give initial validation of this approach.
基金supported by Dr.Navin Kaushal's lab start-up funding from the School of Health and Human Sciences at Indiana University,Indianapolis.
文摘Objective Patients who experience knee osteoarthritis or chronic knee pain can alleviate their symptoms by performing self-knee massage.Understanding the readiness and types of determinants needed to facilitate self-knee massage is needed to design effective,theory-informed interventions.The primary objective of this study was to apply the transtheoretical model of behavior change to identify how factors,which include the type of knee condition and pain level,predict an individual’s readiness to adopt self-knee massage.The secondary objective employed the capability,opportunity and motivation-behavior(COM-B)model to identify relevant determinants that are predictive of an individual’s readiness to undertake self-knee massage.Methods An observational study design was used to recruit individuals with knee osteoarthritis(n=270)and chronic knee pain(n=130).Participants completed an online survey that assessed the transtheoretical model of behavior change stages,COM-B determinants(capability,opportunity and motivation),along with self-administered massage behavior.Multivariate analysis of covariance and structural equation modeling were used to test the primary and secondary objective,respectively.Results Participants who had knee osteoarthritis scored higher on the action stage compared to those with chronic pain(P=0.003),and those who experienced greater level of pain scored higher in the contemplation(P<0.001)and action phases(P<0.001)of performing knee massage compared to those with milder pain.The COM-B structural equation model revealed self-administered knee massage to be predicted by capability(β=0.31,P=0.004)and motivation(β=0.29,P<0.001),but not opportunity(β=–0.10,P=0.39).Pain level predicted motivation(β=0.27,P<0.001),but not capability(β=0.09,P=0.07)or opportunity(β=0.01,P=0.83).Tests for mediating effects found that determinants of COM-B(motivation and capability)mediate between pain level and self-administered massage behavior(β=0.10,P=0.002).Conclusion Clinicians and researchers can expect that patients diagnosed with knee osteoarthritis or who have chronic knee pain are ready(action stage)or are considering the behavior(contemplation stage)of self-knee massage.Individuals who report having knee osteoarthritis or chronic knee pain should be coached to develop the skills to perform self-knee massage and helped to develop the motivation to carry out the therapy.
基金supported by National Key Basic Research Program of China (973 Program) (No.2014CB339900)the National High Technology Research and Development Program of China (863 Program) (No. 2015AA016801)National Natural Science Foundations of China (No.61327806)
文摘To linearize the multi.band PAs/transmitters, a serial of multi.band predistortion models based on multi.dimensional architecture have been proposed. However, most of these models work properly only for the signals whose harmonic and intermodulation products of carriers' non.overlap with the interested fundamental bands. In this paper, the non.overlapping conditions for dual.band and tri.band signals are derived and denoted in the form of closed.form expression. It can be used to verify whether a given dual.band/multi.band signals can be linearized properly by these multi.dimensional behavioral models. Also the conditions can be used to plan the frequency spacing and maximum bandwidth of a multi.band or non.continuous carrier aggregation signal. Several dual.band and triband signals were tested on the same PA, by employing 2.D DPD and 3.D DPD behavioral models. The measurement results show that the signals which don't satisfy the non.overlapping conditions cannot be linearized well by the multi.dimensional behavioral models which does not take the harmonic and intermodulation products of carriers' into account.
文摘Symbolic circuit simulator is traditionally applied to the small-signal analysis of analog circuits. This paper establishes a symbolic behavioral macromodeling method applicable to both small-signal and large-signal analysis of general two-stage operational amplifiers （op-amps）. The proposed method creates a two-pole parametric macromodel whose parameters are analytical functions of the circuit element parameters generated by a symbolic circuit simulator. A moment matching technique is used in deriving the analytical model parameter. The created parametric behavioral model can be used for op-amps performance simulation in both frequency and time domains. In particular, the parametric models are highly suited for fast statistical simulation of op-amps in the time-domain. Experiment results show that the statistical distributions of the op-amp slew and settling time characterized by the proposed model agree well with the transistor-level results in addition to achieving significant speedup.
基金supported by the grants of the National Key Basic Research Program of China,No.2014CB943001the National Natural Science Foundation of China,Major Project,No.81120108009
文摘The pathophysiology of tinnitus is poorly understood and treatments are often unsuccessful. A number of animal models have been developed in order to gain a better understanding of tinnitus. A great deal has been learned from these models re- garding the electrophysiological and neuroanatomical correlates of tinnitus following exposure to noise or ototoxic drugs. Re- liable behavioral data is important for determining whether such electrophysiological or neuroanatomical changes are indeed related to tinnitus. Of the many documented tinnitus animal behavioral paradigms, the acoustic startle reflex had been pro- posed as a simple method to identify the presence or absence of tinnitus. Several behavioral models based on conditioned re- sponse suppression paradigms have also been developed. In addition to determining the presence or absence of tinnitus, some of the behavioral paradigms have provided signs of the onset, frequency, and intensity of tinnitus in animals. Although none of these behavioral models have been proved to be a perfect model, these studies provide useful information on understanding the neural mechanisms underlying tinnitus.
文摘With the advent of computing and communication technologies,it has become possible for a learner to expand his or her knowledge irrespective of the place and time.Web-based learning promotes active and independent learning.Large scale e-learning platforms revolutionized the concept of studying and it also paved the way for innovative and effective teaching-learning process.This digital learning improves the quality of teaching and also promotes educational equity.However,the challenges in e-learning platforms include dissimilarities in learner’s ability and needs,lack of student motivation towards learning activities and provision for adaptive learning environment.The quality of learning can be enhanced by analyzing the online learner’s behavioral characteristics and their application of intelligent instructional strategy.It is not possible to identify the difficulties faced during the process through evaluation after the completion of e-learning course.It is thus essential for an e-learning system to include component offering adaptive control of learning and maintain user’s interest level.In this research work,a framework is proposed to analyze the behavior of online learners and motivate the students towards the learning process accordingly so as to increase the rate of learner’s objective attainment.Catering to the demands of e-learner,an intelligent model is presented in this study for e-learning system that apply supervised machine learning algorithm.An adaptive e-learning system suits every category of learner,improves the learner’s performance and paves way for offering personalized learning experiences.
基金Supported by the National Natural Science Foundation of China （No. 60573111 ）
文摘Voherra series behavioral model for radio frequency （RF） power amplifier （PA） has been widely used in system-level simulation, however, high computational complexity makes this kind of model limited to ＂weak＂ nonlinearity. In order to reduce the computational complexity and the number of coefficients of Volterra series kernels, a Volterra series improved behavioral model based on Laguerre orthogonal polynomials function, namely Voherra-Laguerre behavioral model, is proposed. Mathematical expressions of Volterra-Laguerre behavioral model is derived, and accuracy of the model is verified through comparison of measured and simulation output data from a freescale PA using MRF21030 transistor. Mathematical analysis and simulation results show that Voherra-Laguerre behavioral model has a simple structure, much less coefficients and better modeling performance than general Volterra series model. The model can be used more correctly for system-level simulation of RF PA with wideband signal.
基金Supported by the National High Technology Research and Development Programme of China(No.2011AA010301)the Research Foundation of Zhongxing Telecom Equipment Corporation and the National Natural Science Foundation of China(No.60976029)
文摘Phase locked loop(PLL) is a typical analog-digital mixed signal circuit and a method of conducting a top level system verification including PLL with standard digital simulator becomes especially significant.The behavioral level model(BLM) of the PLL in Verilog-HDL for pure digital simulator is innovated in this paper,and the design of PLL based clock and data recovery(CDR)circuit aided with jitter attenuation PLL for SerDes application is also presented.The CDR employs a dual-loop architecture where a frequency-locked loop acts as an acquisition aid to the phase-locked loop.To simultaneously meet jitter tolerance and jitter transfer specifications defined in G.8251 of optical transport network(ITU-T OTN),an additional jitter attenuation PLL is used.Simulation results show that the peak-to-peak jitter of the recovered clock and data is 5.17 ps and 2.3ps respectively.The core of the whole chip consumes 72 mA current from a 1.0V supply.
文摘With the rapid growth of complexity and functionality of modern electronic systems, creating precise behavioral models of nonlinear circuits has become an attractive topic. Deep neural networks (DNNs) have been recognized as a powerful tool for nonlinear system modeling. To characterize the behavior of nonlinear circuits, a DNN based modeling approach is proposed in this paper. The procedure is illustrated by modeling a power amplifier (PA), which is a typical nonlinear circuit in electronic systems. The PA model is constructed based on a feedforward neural network with three hidden layers, and then Multisim circuit simulator is applied to generating the raw training data. Training and validation are carried out in Tensorflow deep learning framework. Compared with the commonly used polynomial model, the proposed DNN model exhibits a faster convergence rate and improves the mean squared error by 13 dB. The results demonstrate that the proposed DNN model can accurately depict the input-output characteristics of nonlinear circuits in both training and validation data sets.
文摘In a multi-agent system, each agent must adapt itself to the environment and coordinate with other agents dynamically. TO predict or cooperate with the behavior of oiller agents. An agent should dynamically establish and evolve the cooperative behavior model of itself. In this paper, we represent the behavior model of an agent as a f-mite state machine and propose a new method of dynamically evolving the behavior model of an agent by evolutionary programming.
文摘This Special Issue of the Journal of Rock Mechanics and GeotechnicalEngineering （JRMGE） contains 13 papers prepared by internationalexperts on various general topics in geomechanics, rockmechanics and geotechnical engineering. It represents a usefulmix of theoretical developments, testing and practical applications.We present in the following brief details in the papers, alphabeticallyin accordance with the last name of the first author.Barla presents a review of tunneling techniques with emphasison the full-face method combining full-face excavation and facereinforcement by means of fiber-glass elements with a yieldcontrolsupport. This method has been used successfully in difficultgeologic conditions, and for a wide spectrum of ground situations.The validation of the method with respect to the Saint Martin LaPorte access adit along the LyoneTurin Base tunnel experiencingseverely squeezing conditions during excavation is also includedin the paper. The numerical modeling with consideration of therock mass time-dependent behavior showed a satisfactory agreementwith monitoring results.
