In order to start up the brushless DC motor （BLDCM） without reverse rotation and smoothly switch the running state of the motor, a novel startup and smoothly switching method for a sensodess BLDCM is presented. Base...In order to start up the brushless DC motor （BLDCM） without reverse rotation and smoothly switch the running state of the motor, a novel startup and smoothly switching method for a sensodess BLDCM is presented. Based on the saturation effect of the stator iron, six short voltage pulses are applied to determine the initial rotor position and the rotor can be found within 60°. After that, a series of short and long voltage pulses are used to accelerate the motor and the variation of the response current is utilized to detect the rotor position dynamically. When the motor reaches a certain speed at which the back-electromotive force （EMF） method can be applied, all the power devices are turned off and the running state of the motor is smoothly switched at the moment determined by the relationship between the terminal voltage waveform and the commutation phases. The experimental results verify the feasibility and validity of the proposed method.展开更多
Android OS provides such security mechanisms as application signature, privilege limit and sandbox to protect the security of operational system. However, these methods are unable to protect the applications of Androi...Android OS provides such security mechanisms as application signature, privilege limit and sandbox to protect the security of operational system. However, these methods are unable to protect the applications of Android against anti-reverse engineering and the codes of such applications face the risk of being obtained or modified, which are always the first step for further attacks. In this paper, a security enhancement system with online authentication （SeSoa） for Android APK is proposed, in which the code of Android application package （APK） can be automatically encrypted. The encrypted code is loaded and run in the Android system after being successfully decrypted. Compared with the exiting software protecting systems, SeSoa uses online authentication mechanism to ensure the improvementof the APK security and good balance between security and usability.展开更多
Natural rubber(NR)is not only the main compounding ingredient used to make the majority of components of tires as well as other rubber products,as it plays a significant role in ensuring that they operate well and com...Natural rubber(NR)is not only the main compounding ingredient used to make the majority of components of tires as well as other rubber products,as it plays a significant role in ensuring that they operate well and complies with environmental standards.The applications of NR products are lim-ited to high temperatures due to the revision tendency of NR vulcanizate.To address these issues,the potential engagement of a carbon black(CB)coupling agent(CA)in the presence of metal oxide i.e.Zinc Oxide(ZnO)was investigated in an NR-based system.This CA has dual functionality on physicomechanical properties.CA has the ability to reduce hysteresis loss as well as improve anti-reversion properties and these properties thorough-ly depend on the presence of ZnO.While ZnO was added to the master formulation,a 65%improvement in reversion properties was observed.On the other hand,while ZnO fully transferred to the final formulation,bound rubber(BR)content increased by 19%,the difference in storage modulus(ΔG’)is reduced by 22%,cure rate index(CRI)improved by 14%,loss tangent(tanδ)reduced by 18%and slightly improve in elongation at break compared to control compound.Thermo-gravimetric analysis(TGA)was engaged to understand the thermal stability and degree of purity of CA.A differential Scanning Calorimeter(DSC)was used to detect the phase tran-sition of CA.Fourier Transform Infrared Spectrum(FTIR)was adopted to detect the presence of carboxyl and amine groups in the CA moiety.Payne effect,BR content and Transmission Electron Microscope(TEM)were em-ployed to investigate the micro-level dispersion of CB in the natural rubber(NR)matrix.展开更多
文摘In order to start up the brushless DC motor （BLDCM） without reverse rotation and smoothly switch the running state of the motor, a novel startup and smoothly switching method for a sensodess BLDCM is presented. Based on the saturation effect of the stator iron, six short voltage pulses are applied to determine the initial rotor position and the rotor can be found within 60°. After that, a series of short and long voltage pulses are used to accelerate the motor and the variation of the response current is utilized to detect the rotor position dynamically. When the motor reaches a certain speed at which the back-electromotive force （EMF） method can be applied, all the power devices are turned off and the running state of the motor is smoothly switched at the moment determined by the relationship between the terminal voltage waveform and the commutation phases. The experimental results verify the feasibility and validity of the proposed method.
基金supported by National Natural Science Foundation of China(61370195)ZTE Industry-Academia-Research Cooperation Funds
文摘Android OS provides such security mechanisms as application signature, privilege limit and sandbox to protect the security of operational system. However, these methods are unable to protect the applications of Android against anti-reverse engineering and the codes of such applications face the risk of being obtained or modified, which are always the first step for further attacks. In this paper, a security enhancement system with online authentication （SeSoa） for Android APK is proposed, in which the code of Android application package （APK） can be automatically encrypted. The encrypted code is loaded and run in the Android system after being successfully decrypted. Compared with the exiting software protecting systems, SeSoa uses online authentication mechanism to ensure the improvementof the APK security and good balance between security and usability.
文摘Natural rubber(NR)is not only the main compounding ingredient used to make the majority of components of tires as well as other rubber products,as it plays a significant role in ensuring that they operate well and complies with environmental standards.The applications of NR products are lim-ited to high temperatures due to the revision tendency of NR vulcanizate.To address these issues,the potential engagement of a carbon black(CB)coupling agent(CA)in the presence of metal oxide i.e.Zinc Oxide(ZnO)was investigated in an NR-based system.This CA has dual functionality on physicomechanical properties.CA has the ability to reduce hysteresis loss as well as improve anti-reversion properties and these properties thorough-ly depend on the presence of ZnO.While ZnO was added to the master formulation,a 65%improvement in reversion properties was observed.On the other hand,while ZnO fully transferred to the final formulation,bound rubber(BR)content increased by 19%,the difference in storage modulus(ΔG’)is reduced by 22%,cure rate index(CRI)improved by 14%,loss tangent(tanδ)reduced by 18%and slightly improve in elongation at break compared to control compound.Thermo-gravimetric analysis(TGA)was engaged to understand the thermal stability and degree of purity of CA.A differential Scanning Calorimeter(DSC)was used to detect the phase tran-sition of CA.Fourier Transform Infrared Spectrum(FTIR)was adopted to detect the presence of carboxyl and amine groups in the CA moiety.Payne effect,BR content and Transmission Electron Microscope(TEM)were em-ployed to investigate the micro-level dispersion of CB in the natural rubber(NR)matrix.
