利用混合激励线性预测(mixed excitation linear prediction,MELP)算法和码激励线性预测(code excitation linear prediction,CELP)算法的优点,提出了一种混合MELP/CELP语音编码模型。编码端对强浊音帧采用MELP编码,对弱浊音帧和清音帧...利用混合激励线性预测(mixed excitation linear prediction,MELP)算法和码激励线性预测(code excitation linear prediction,CELP)算法的优点,提出了一种混合MELP/CELP语音编码模型。编码端对强浊音帧采用MELP编码,对弱浊音帧和清音帧进行CELP编码。MELP编码器采用相位对齐技术提取强浊音帧的相位参数,解决了合成语音与原始语音在时间上不同步的问题。对实现的4 kbit/s混合MELP/CELP声码器进行客观MOS(mean opinion score)值和主观DRT(diagnostic rhythm test)清晰度测试,结果表明,该声码器的合成语音具有较高的可懂度和清晰度。展开更多
The stabilization of the formamidinium lead iodide(FAPbI_(3))structure is pivotal for the development of efficient photovoltaic devices.Employing two-dimensional(2D)layers to passivate the threedimensional(3D)perovski...The stabilization of the formamidinium lead iodide(FAPbI_(3))structure is pivotal for the development of efficient photovoltaic devices.Employing two-dimensional(2D)layers to passivate the threedimensional(3D)perovskite is essential for maintaining the a-phase of FAPbI_(3) and enhancing the power conversion efficiency(PCE)of perovskite solar cells(PSCs).However,the role of bulky ligands in the phase management of 2D perovskites,crucial for the stabilization of FAPbI_(3),has not yet been elucidated.In this study,we synthesized nanoscale 2D perovskite capping crusts with<n>=1 and 2 Ruddlesden-Popper(RP)perovskite layers,respectively,which form a type-Ⅱ 2D/3D heterostructure.This heterostructure stabilizes the a-phase of FAPbI_(3),and facilitates ultrafast carrier extraction from the 3D perovskite network to transport contact layer.We introduced tri-fluorinated ligands to mitigate defects caused by the halide vacancies and uncoordinated Pb^(2+)ions,thereby reducing nonradiative carrier recombination and extending carrier lifetime.The films produced were incorporated into PSCs that not only achieved a PCE of 25.39%but also maintained 95%of their initial efficiency after 2000 h of continuous light exposure without encapsulation.These findings underscore the effectiveness of a phase-pure 2D/3D heterostructure-terminated film in inhibiting phase transitions passivating the iodide anion vacancy defects,facilitating the charge carrier extraction,and boosting the performance of optoelectronic devices.展开更多
Heterostructures combined by different individual two-dimensional(2D)materials are essential building blocks to realize unique electronic,optoelectronic properties and multifunctional applications.To date,the direct g...Heterostructures combined by different individual two-dimensional(2D)materials are essential building blocks to realize unique electronic,optoelectronic properties and multifunctional applications.To date,the direct growth of 2D/2D atomic van der Waals heterostructures(vdWHs)have been extensively investigated.However,the heterostructures from 2D inorganic molecular crystals and atomic crystals have been rarely reported.Here we report two-step direct epitaxial growth of the inorganic molecular-atomic Sb2O3/WS2 vdWHs.The thickness of Sb2O3 nanosheets on WS2 nanosheets can be tuned by variable growth temperatures.Oriented growth behavior of Sb2O3 on WS2 was determined through statistics.Optical images,Raman spectra,Raman mappings and selected-area electron diffraction(SAED),etc.,reveal that Sb2O3/WS2 heterostructures are vertically stacked with high crystal quality.Electrical transport measurements demonstrate that the heterotransistors based on the heterostructures possess high current on/off ratio of 5 × 10^5,obvious gate-tunable and current rectification output characteristics.Optoelectronic characterizations show that the heterostructures have a clear photoresponse with high responsivity of 16.4 AW.The growth of vdWHs from 2D inorganic molecular-atomic crystals may open up new opportunities in 2D functional electronics and optoelectronics.展开更多
This study relates the gait asymmetry, residual limb comfort, and energy cost during walking and identifies a compensating pattern for the trans-tibial amputees when the prostheses are misaligned. One male subject wit...This study relates the gait asymmetry, residual limb comfort, and energy cost during walking and identifies a compensating pattern for the trans-tibial amputees when the prostheses are misaligned. One male subject with a trans-tibial amputation volunteered for the study. The knee joint moments at the prosthetic side, the phase symmetry index, and the interface pressures were discussed under three sagittal alignment settings. The results show that the subject changes the knee joint moment, gait symmetry, and interface pressure with a misaligned prosthesis to improve his comfort and movement during walking. A high-quality liner reduces the gait sensitivity to misalignment and enhances the amputee＇s ability to compensate for misalignment. Since different people have different compensation patterns, more cases will be studied in future work.展开更多
Al-Ni hypereutectic alloys with various compositions were solidified under various magnetic field con- ditions to investigate the alignment of primary Al3Ni phases. The results showed that the application of high magn...Al-Ni hypereutectic alloys with various compositions were solidified under various magnetic field con- ditions to investigate the alignment of primary Al3Ni phases. The results showed that the application of high magnetic fields could improve the homogeneity of the primary Al3Ni phase distribution and induce the alignment of primary Al3Ni phases in the direction perpendicular to the magnetic field direction to form chain-like structures. However, the alignment was different from the orientation of the Al3Ni phases. Furthermore, the degree of the alignment decreased with the increasing concentration of Ni element. This can be attributed to the combination effects of high magnetic field and alloy composition on the concentration field around the crystallized primary Al3Ni crystals.展开更多
Phase transition temperatures of p,n-alkyloxy benzoic acids (nOBA, n = 3 to 10 and 12) are investigated basing on the textural image analysis of liquid crystal. The analysis is carried out by the computation of Legend...Phase transition temperatures of p,n-alkyloxy benzoic acids (nOBA, n = 3 to 10 and 12) are investigated basing on the textural image analysis of liquid crystal. The analysis is carried out by the computation of Legendre moments. Textures of the homeotropically aligned compounds are recorded as a function of temperature using POM in arthroscopic mode attached to the hot stage and high resolution camera. A recurrence formula is used to compute the liquid crystal textures based on Legendre polynomial. The discontinuities and fluctuations in the values of Legendre moments as a function of temperature are related to the phase transition temperatures of the sample. This method is successful in conforming or detecting the phase transition temperatures and the present findings are comparable with literature.展开更多
基金the Science and Technology Development Fund,Macao SAR(FDCT-0082/2021/A2,0010/2022/AMJ,0060/2023/RIA1,0136/2022/A3,006/2022/ALC,and EF044/IAPME-HG/2022/MUST)UM’s research fund(MYRG2022-00241IAPME,MYRG-GRG2023-00065-IAPME-UMDF,and MYRGCRG2022-00009-FHS)+8 种基金the research fund from Wuyi University(EF38/IAPME-XGC/2022/WYU)Shaanxi Fundamental Science Research Project for Mathematics and Physics(22JSY015 and 23JSY005)Shaanxi Province science and technology activities for overseas students selected funding project(2023015)the State Key Laboratory for Strength and Vibration of Mechanical Structures(SV2023-KF-18)Guangdong Provincial Key Laboratory of Semiconductor Optoelectronic Materials and Intelligent Photonic Systems(2023B1212010003)the China Fundamental Research Funds for the Central Universities,Young Talent Fund of Xi’an Association for Science and Technology(959202313020)the project of Innovative Team of Shaanxi Province(2020TD-001)the Natural Science Research Start-up Foundation of Recruiting Talents of Nanjing University of Posts and Telecommunications(NY223053)the National Natural Science Foundation of China(61935017,62105292,62175268,62288102 and 62304111)。
文摘The stabilization of the formamidinium lead iodide(FAPbI_(3))structure is pivotal for the development of efficient photovoltaic devices.Employing two-dimensional(2D)layers to passivate the threedimensional(3D)perovskite is essential for maintaining the a-phase of FAPbI_(3) and enhancing the power conversion efficiency(PCE)of perovskite solar cells(PSCs).However,the role of bulky ligands in the phase management of 2D perovskites,crucial for the stabilization of FAPbI_(3),has not yet been elucidated.In this study,we synthesized nanoscale 2D perovskite capping crusts with<n>=1 and 2 Ruddlesden-Popper(RP)perovskite layers,respectively,which form a type-Ⅱ 2D/3D heterostructure.This heterostructure stabilizes the a-phase of FAPbI_(3),and facilitates ultrafast carrier extraction from the 3D perovskite network to transport contact layer.We introduced tri-fluorinated ligands to mitigate defects caused by the halide vacancies and uncoordinated Pb^(2+)ions,thereby reducing nonradiative carrier recombination and extending carrier lifetime.The films produced were incorporated into PSCs that not only achieved a PCE of 25.39%but also maintained 95%of their initial efficiency after 2000 h of continuous light exposure without encapsulation.These findings underscore the effectiveness of a phase-pure 2D/3D heterostructure-terminated film in inhibiting phase transitions passivating the iodide anion vacancy defects,facilitating the charge carrier extraction,and boosting the performance of optoelectronic devices.
基金We acknowledge the financial support from the Fundamental Research Funds of the Central Universities(No.531118010112)the Double First-Class University Initiative of Hunan University(No.531109100004)+2 种基金We also acknowledge the support from the National Natural Science Foundation of China(No.751214296)Hunan Key Laboratory of Two-Dimensional Materials(No.801200005)Strategic Priority Research Program of Chinese Academy of Science(No.XDB30000000).
文摘Heterostructures combined by different individual two-dimensional(2D)materials are essential building blocks to realize unique electronic,optoelectronic properties and multifunctional applications.To date,the direct growth of 2D/2D atomic van der Waals heterostructures(vdWHs)have been extensively investigated.However,the heterostructures from 2D inorganic molecular crystals and atomic crystals have been rarely reported.Here we report two-step direct epitaxial growth of the inorganic molecular-atomic Sb2O3/WS2 vdWHs.The thickness of Sb2O3 nanosheets on WS2 nanosheets can be tuned by variable growth temperatures.Oriented growth behavior of Sb2O3 on WS2 was determined through statistics.Optical images,Raman spectra,Raman mappings and selected-area electron diffraction(SAED),etc.,reveal that Sb2O3/WS2 heterostructures are vertically stacked with high crystal quality.Electrical transport measurements demonstrate that the heterotransistors based on the heterostructures possess high current on/off ratio of 5 × 10^5,obvious gate-tunable and current rectification output characteristics.Optoelectronic characterizations show that the heterostructures have a clear photoresponse with high responsivity of 16.4 AW.The growth of vdWHs from 2D inorganic molecular-atomic crystals may open up new opportunities in 2D functional electronics and optoelectronics.
基金the National Natural Science Foundation of China (No. 50305013)
文摘This study relates the gait asymmetry, residual limb comfort, and energy cost during walking and identifies a compensating pattern for the trans-tibial amputees when the prostheses are misaligned. One male subject with a trans-tibial amputation volunteered for the study. The knee joint moments at the prosthetic side, the phase symmetry index, and the interface pressures were discussed under three sagittal alignment settings. The results show that the subject changes the knee joint moment, gait symmetry, and interface pressure with a misaligned prosthesis to improve his comfort and movement during walking. A high-quality liner reduces the gait sensitivity to misalignment and enhances the amputee＇s ability to compensate for misalignment. Since different people have different compensation patterns, more cases will be studied in future work.
基金Supported by the National Natural Science Foundation of China (Grant No. 50374027)the Program for New Century Excellent Talents in University (Grant No. NECT-06-0289) the 111 Project (Grant No. B07015)
文摘Al-Ni hypereutectic alloys with various compositions were solidified under various magnetic field con- ditions to investigate the alignment of primary Al3Ni phases. The results showed that the application of high magnetic fields could improve the homogeneity of the primary Al3Ni phase distribution and induce the alignment of primary Al3Ni phases in the direction perpendicular to the magnetic field direction to form chain-like structures. However, the alignment was different from the orientation of the Al3Ni phases. Furthermore, the degree of the alignment decreased with the increasing concentration of Ni element. This can be attributed to the combination effects of high magnetic field and alloy composition on the concentration field around the crystallized primary Al3Ni crystals.
文摘Phase transition temperatures of p,n-alkyloxy benzoic acids (nOBA, n = 3 to 10 and 12) are investigated basing on the textural image analysis of liquid crystal. The analysis is carried out by the computation of Legendre moments. Textures of the homeotropically aligned compounds are recorded as a function of temperature using POM in arthroscopic mode attached to the hot stage and high resolution camera. A recurrence formula is used to compute the liquid crystal textures based on Legendre polynomial. The discontinuities and fluctuations in the values of Legendre moments as a function of temperature are related to the phase transition temperatures of the sample. This method is successful in conforming or detecting the phase transition temperatures and the present findings are comparable with literature.
