By establishing the discrete iterative mapping model of a current mode controlled buck-boost converter, this paper studies the mechanism of mode shift and stability control of the buck-boost converter operating in dis...By establishing the discrete iterative mapping model of a current mode controlled buck-boost converter, this paper studies the mechanism of mode shift and stability control of the buck-boost converter operating in discontinuous conduction mode with a ramp compensation current. With the bifurcation diagrazn, Lyapunov exponent spectrum, time- domain waveform and parameter space map, the performance of the buck-boost converter circuit utilizing a compensating ramp current has been analysed. The obtained results indicate that the system trajectory is weakly chaotic and strongly intermittent under discontinuous conduction mode. By using ramp compensation, the buck-boost converter can shift from discontinuous conduction mode to continuous conduction mode, and effectively operates in the stable period-one region.展开更多
As per statistics,two-wheeler(TW)alone shares the highest number of vehicle registrations in India,which develops the various transportation-related issues such as traffic conflicts,congestions,and pollutions.Electric...As per statistics,two-wheeler(TW)alone shares the highest number of vehicle registrations in India,which develops the various transportation-related issues such as traffic conflicts,congestions,and pollutions.Electric two-wheelers(E-TW)are a better alternative to conventional two-wheelers because of their significant advantage in mitigating environmental impacts.But E-TWs are less attractive among road users due to unawareness of the benefits of E-TW.In addition,the traditional methods are less accurate in predicting users’mode choice behavior because of their limitations.Therefore,there is a need to conduct a study to understand the road user’s willingness to adopt E-TW and find a suitable method for predicting mode choice behavior accurately.This study analyzes the Indian road users encouraging and discouraging factors to adopt E-TW and investigates the application of non-traditional models for estimating mode shift behaviour towards E-TW.Based on the literature review and expert opinion,a detailed questionnaire form was framed,and a total of 522 samples were collected from four states of India.The data findings show that Indian road users prefer TW compared to public transport,private four-wheeler,paratransit,and non-motorized transport because of its easy to ride,low maintenance,fast and convenient travel nature.The environmental concern of reducing air pollution and lower vehicle operating costs are significant factors that encourage E-TW adoption.However,the non-availability of charging infrastructure,lower speed,higher initial purchase cost,and lack of awareness about EVs are the significant discouraging factors in adopting ETW in India.Further,Machine Learning(ML)methods were adopted to predict the mode shift behaviour from the fuel based TW to E-TW,and the results were compared with the Binary Logit(BL)method.The model results indicated that Support vector machine predicted the mode shift behavior with the highest accuracy rate compared with other methods such as Artificial Neural Network,K-Nearest Neighbor,Random Forest,and BL.The outcome of this study would help the transportation planner,EV manufacturers,researchers,and policymakers to understand the Indian user’s preference to adopt E-TW.展开更多
The properties of C-H vibration softening for CH2 and CHa radicals absorbed on Cun（n=1-6） clusters have been investigated, using the density functional theory with hybrid functional. The results indicate that the ab...The properties of C-H vibration softening for CH2 and CHa radicals absorbed on Cun（n=1-6） clusters have been investigated, using the density functional theory with hybrid functional. The results indicate that the absorption of CH2 on Cu clusters is stronger than the case of CH3. The vibrational frequencies of C-H bonding agree with the experimental results obtained for CH2 and CH3 absorbed on Cu（111）. With the increase of cluster size, the softening （Einstein shift） of C-H vibrational modes become stronger.展开更多
The analytical expression for the transmission spectra of coupled cavity waveguides （CCWs） in photonic crystals （PCs） is derived based on the coupled-mode theory （CMT）. Parameters in the analytical expression ca...The analytical expression for the transmission spectra of coupled cavity waveguides （CCWs） in photonic crystals （PCs） is derived based on the coupled-mode theory （CMT）. Parameters in the analytical expression can be extracted by simple numerical simulations. We reveal that it is the phase shift between the two adjacent PC defects that uniquely determines the flatness of the impurity bands of CCWs. In addition, it is found that the phase shift also greatly affects the bandwidth of CCWs. Thus, the engineering of the impurity bands of CCWs can be realized through the adjustment of the phase shift. Based on the theoretical results, an interesting phenomenon in which a CCW acts as a single PC defect and its impurity band possesses a Lorentz lineshape is predicted. Very good agreement between the analytical results and the numerical simulations based on transfer matrix method has been achieved.展开更多
In this study, two-section mode-locked semiconductor lasers with different numbers of quantum wells and different types of waveguide structures are made. Their ultrashort pulse features are presented. The spectral dyn...In this study, two-section mode-locked semiconductor lasers with different numbers of quantum wells and different types of waveguide structures are made. Their ultrashort pulse features are presented. The spectral dynamical behaviors in these lasers are studied in detail. In the simulation part, a two-band compressive-strained quantum well（QW） model is used to study thermally induced band-edge detuning in the amplifier and saturable absorber（SA）. A sudden blue shift in laser spectrum is expected by calculating the peak of the net gain. In the experiment part, the sudden blue shift in the emission spectrum is observed in triple QW samples under certain operating conditions but remains absent in single QW samples.Experimental results reveal that blue shift phenomenon is connected with the difference between currents in two sections.Additionally, a threshold current ratio for blue-shift is also demonstrated.展开更多
基金Project supported by the National Natural Science Foundations of China (Grant Nos 50677056 and 60472059)
文摘By establishing the discrete iterative mapping model of a current mode controlled buck-boost converter, this paper studies the mechanism of mode shift and stability control of the buck-boost converter operating in discontinuous conduction mode with a ramp compensation current. With the bifurcation diagrazn, Lyapunov exponent spectrum, time- domain waveform and parameter space map, the performance of the buck-boost converter circuit utilizing a compensating ramp current has been analysed. The obtained results indicate that the system trajectory is weakly chaotic and strongly intermittent under discontinuous conduction mode. By using ramp compensation, the buck-boost converter can shift from discontinuous conduction mode to continuous conduction mode, and effectively operates in the stable period-one region.
文摘As per statistics,two-wheeler(TW)alone shares the highest number of vehicle registrations in India,which develops the various transportation-related issues such as traffic conflicts,congestions,and pollutions.Electric two-wheelers(E-TW)are a better alternative to conventional two-wheelers because of their significant advantage in mitigating environmental impacts.But E-TWs are less attractive among road users due to unawareness of the benefits of E-TW.In addition,the traditional methods are less accurate in predicting users’mode choice behavior because of their limitations.Therefore,there is a need to conduct a study to understand the road user’s willingness to adopt E-TW and find a suitable method for predicting mode choice behavior accurately.This study analyzes the Indian road users encouraging and discouraging factors to adopt E-TW and investigates the application of non-traditional models for estimating mode shift behaviour towards E-TW.Based on the literature review and expert opinion,a detailed questionnaire form was framed,and a total of 522 samples were collected from four states of India.The data findings show that Indian road users prefer TW compared to public transport,private four-wheeler,paratransit,and non-motorized transport because of its easy to ride,low maintenance,fast and convenient travel nature.The environmental concern of reducing air pollution and lower vehicle operating costs are significant factors that encourage E-TW adoption.However,the non-availability of charging infrastructure,lower speed,higher initial purchase cost,and lack of awareness about EVs are the significant discouraging factors in adopting ETW in India.Further,Machine Learning(ML)methods were adopted to predict the mode shift behaviour from the fuel based TW to E-TW,and the results were compared with the Binary Logit(BL)method.The model results indicated that Support vector machine predicted the mode shift behavior with the highest accuracy rate compared with other methods such as Artificial Neural Network,K-Nearest Neighbor,Random Forest,and BL.The outcome of this study would help the transportation planner,EV manufacturers,researchers,and policymakers to understand the Indian user’s preference to adopt E-TW.
文摘The properties of C-H vibration softening for CH2 and CHa radicals absorbed on Cun（n=1-6） clusters have been investigated, using the density functional theory with hybrid functional. The results indicate that the absorption of CH2 on Cu clusters is stronger than the case of CH3. The vibrational frequencies of C-H bonding agree with the experimental results obtained for CH2 and CH3 absorbed on Cu（111）. With the increase of cluster size, the softening （Einstein shift） of C-H vibrational modes become stronger.
基金Project supported by the National Natural Science Foundation of China （Grant No 10374065）, the Natural Science Foundation of Guangdong Province of China （Grant No 32050）, the Ministry of Education of China （Grant No 204107）, and the Department of Education of Guangdong Province of China （Grant No Z03033）.
文摘The analytical expression for the transmission spectra of coupled cavity waveguides （CCWs） in photonic crystals （PCs） is derived based on the coupled-mode theory （CMT）. Parameters in the analytical expression can be extracted by simple numerical simulations. We reveal that it is the phase shift between the two adjacent PC defects that uniquely determines the flatness of the impurity bands of CCWs. In addition, it is found that the phase shift also greatly affects the bandwidth of CCWs. Thus, the engineering of the impurity bands of CCWs can be realized through the adjustment of the phase shift. Based on the theoretical results, an interesting phenomenon in which a CCW acts as a single PC defect and its impurity band possesses a Lorentz lineshape is predicted. Very good agreement between the analytical results and the numerical simulations based on transfer matrix method has been achieved.
基金Project supported by the National Basic Research Program of China(Grant Nos.2013CB933304 and 2012CB932701)the National Natural Science Foundation of China(Grant Nos.61274125 and 61435012)the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant No.XDB01010200)
文摘In this study, two-section mode-locked semiconductor lasers with different numbers of quantum wells and different types of waveguide structures are made. Their ultrashort pulse features are presented. The spectral dynamical behaviors in these lasers are studied in detail. In the simulation part, a two-band compressive-strained quantum well（QW） model is used to study thermally induced band-edge detuning in the amplifier and saturable absorber（SA）. A sudden blue shift in laser spectrum is expected by calculating the peak of the net gain. In the experiment part, the sudden blue shift in the emission spectrum is observed in triple QW samples under certain operating conditions but remains absent in single QW samples.Experimental results reveal that blue shift phenomenon is connected with the difference between currents in two sections.Additionally, a threshold current ratio for blue-shift is also demonstrated.
