The aqueous rechargeable Zn-ion batteries based on the safe,low cost and environmental benignity aqueous electrolytes are one of the most compelling candidates for large scale energy storage applications.However,pursu...The aqueous rechargeable Zn-ion batteries based on the safe,low cost and environmental benignity aqueous electrolytes are one of the most compelling candidates for large scale energy storage applications.However,pursuing suitable insertion materials may be a great challenge due to the strong electrostatic interaction between Zn^(^(2+))and cathode materials.Hence,a novel NaV_(6)O_(15)/V_(2)O_(5) skin-core heterostructure nanowire is reported via a one-step hydrothermal method and subsequent calcination for high-stable aqueous Zn-ion batteries(ZIBs).The NaV_(6)O_(15)/V_(2)O_(5) cathode delivers high specific capacity of 390 m Ah/g at 0.3 A/g and outstanding cycling stability of 267 m Ah/g at 5 A/g with high capacity retention over 92.3%after 3000 cycles.The superior electrochemical performances are attributed to the synergistic effect of skin-core heterostructured NaV_(6)O_(15)/V_(2)O_(5),in which the sheath of NaV_(6)O_(15) possesses high stability and conductivity,and the V_(2)O_(5) endows high specific capacity.Besides,the heterojunction structure not only accelerates intercalation kinetics of Zn^(2+)transport but also further consolidates the stability of the layers of V_(2)O_(5) during the cyclic process.This work provides a new perspective in developing feasible insertion materials for rechargeable aqueous ZIBs.展开更多
The alpha stable self-similar stochastic process has been proved an effective model for high variable data traffic. A deep insight into some special issues and considerations on use of the process to model aggregated ...The alpha stable self-similar stochastic process has been proved an effective model for high variable data traffic. A deep insight into some special issues and considerations on use of the process to model aggregated VBR video traffic is made. Different methods to estimate stability parameter a and self-similar parameter H are compared. Processes to generate the linear fractional stable noise （LFSN） and the alpha stable random variables are provided. Model construction and the quantitative comparisons with fractional Brown motion （FBM） and real traffic are also examined. Open problems and future directions are also given with thoughtful discussions.展开更多
To solve the problem of wide-baseline stereo image matching based on multiple cameras,the paper puts forward an image matching method of combining maximally stable extremal regions (MSER) with Scale Invariant Feature ...To solve the problem of wide-baseline stereo image matching based on multiple cameras,the paper puts forward an image matching method of combining maximally stable extremal regions (MSER) with Scale Invariant Feature Transform (SIFT) . It uses MSER to detect feature regions instead of difference of Gaussian. After fitted into elliptical regions,those regions will be normalized into unity circles and represented with SIFT descriptors. The method estimates fundamental matrix and removes outliers by auto-maximum a posteriori sample consensus after initial matching feature points. The experimental results indicate that the method is robust to viewpoint changes,can reduce computational complexity effectively and improve matching accuracy.展开更多
LoRa(Long Range radio)系统在当前不断发展的低功率广域网(LPWAN)中处于相对领先地位。它的MAC层采用的是基于ALOHA的接入协议。该接入机制虽然简单易实现,但同时也容易加剧冲突和碰撞的发生,降低整个系统的通信性能。因此,需要研究多...LoRa(Long Range radio)系统在当前不断发展的低功率广域网(LPWAN)中处于相对领先地位。它的MAC层采用的是基于ALOHA的接入协议。该接入机制虽然简单易实现,但同时也容易加剧冲突和碰撞的发生,降低整个系统的通信性能。因此,需要研究多个终端同时占用信道资源时的相互干扰情况,而LoRa信号的扩频因子(SF)将决定信号的通信覆盖范围。因此,分析了干扰信号的SF与发送信号的SF相同以及不同时,干扰信号对发送信号解调性能的影响。实验结果表明,相同SF信号间的干扰影响相对较大,而干扰信号使用的SF与发送信号不同时,干扰的影响相对较小。通过理论分析,获得了接收端正确解调时所要求的信干比(SIR)。可见,不同SF的LoRa信号可看作伪正交。展开更多
基金the financial support from the National Natural Science Foundation of China(Nos.21878231 and 51603145)the Tianjin Natural Science Foundation of China(Nos.17JC ZDJ38100 and 19JCZDJC37300)+2 种基金the Science and Technology Plans of Tianjin(Nos.17PT SYJC00040 and 18PTSY JC00180)the China National Textile and Apparel Council(J201406)the China Petroleum Chemical Co Technology Development Project(216090 and 218008-6)。
文摘The aqueous rechargeable Zn-ion batteries based on the safe,low cost and environmental benignity aqueous electrolytes are one of the most compelling candidates for large scale energy storage applications.However,pursuing suitable insertion materials may be a great challenge due to the strong electrostatic interaction between Zn^(^(2+))and cathode materials.Hence,a novel NaV_(6)O_(15)/V_(2)O_(5) skin-core heterostructure nanowire is reported via a one-step hydrothermal method and subsequent calcination for high-stable aqueous Zn-ion batteries(ZIBs).The NaV_(6)O_(15)/V_(2)O_(5) cathode delivers high specific capacity of 390 m Ah/g at 0.3 A/g and outstanding cycling stability of 267 m Ah/g at 5 A/g with high capacity retention over 92.3%after 3000 cycles.The superior electrochemical performances are attributed to the synergistic effect of skin-core heterostructured NaV_(6)O_(15)/V_(2)O_(5),in which the sheath of NaV_(6)O_(15) possesses high stability and conductivity,and the V_(2)O_(5) endows high specific capacity.Besides,the heterojunction structure not only accelerates intercalation kinetics of Zn^(2+)transport but also further consolidates the stability of the layers of V_(2)O_(5) during the cyclic process.This work provides a new perspective in developing feasible insertion materials for rechargeable aqueous ZIBs.
文摘The alpha stable self-similar stochastic process has been proved an effective model for high variable data traffic. A deep insight into some special issues and considerations on use of the process to model aggregated VBR video traffic is made. Different methods to estimate stability parameter a and self-similar parameter H are compared. Processes to generate the linear fractional stable noise （LFSN） and the alpha stable random variables are provided. Model construction and the quantitative comparisons with fractional Brown motion （FBM） and real traffic are also examined. Open problems and future directions are also given with thoughtful discussions.
基金Sponsored by the Scientific Research Common Program of Beijing Municipal Commission of Education(Grant No. KM201010772021the National High Technology Research and Development Program of China (863 Program) (Grant No. 2006AA74105)the National Natural Science Foundation of Chi-na(Grant No. 60803103)
文摘To solve the problem of wide-baseline stereo image matching based on multiple cameras,the paper puts forward an image matching method of combining maximally stable extremal regions (MSER) with Scale Invariant Feature Transform (SIFT) . It uses MSER to detect feature regions instead of difference of Gaussian. After fitted into elliptical regions,those regions will be normalized into unity circles and represented with SIFT descriptors. The method estimates fundamental matrix and removes outliers by auto-maximum a posteriori sample consensus after initial matching feature points. The experimental results indicate that the method is robust to viewpoint changes,can reduce computational complexity effectively and improve matching accuracy.
文摘LoRa(Long Range radio)系统在当前不断发展的低功率广域网(LPWAN)中处于相对领先地位。它的MAC层采用的是基于ALOHA的接入协议。该接入机制虽然简单易实现,但同时也容易加剧冲突和碰撞的发生,降低整个系统的通信性能。因此,需要研究多个终端同时占用信道资源时的相互干扰情况,而LoRa信号的扩频因子(SF)将决定信号的通信覆盖范围。因此,分析了干扰信号的SF与发送信号的SF相同以及不同时,干扰信号对发送信号解调性能的影响。实验结果表明,相同SF信号间的干扰影响相对较大,而干扰信号使用的SF与发送信号不同时,干扰的影响相对较小。通过理论分析,获得了接收端正确解调时所要求的信干比(SIR)。可见,不同SF的LoRa信号可看作伪正交。
