A method and procedure is presented to reconstruct three-dimensional(3D) positions of scattering centers from multiple synthetic aperture radar(SAR) images. Firstly, two-dimensional(2D) attribute scattering centers of...A method and procedure is presented to reconstruct three-dimensional(3D) positions of scattering centers from multiple synthetic aperture radar(SAR) images. Firstly, two-dimensional(2D) attribute scattering centers of targets are extracted from 2D SAR images. Secondly, similarity measure is developed based on 2D attributed scatter centers' location, type, and radargrammetry principle between multiple SAR images. By this similarity, we can associate 2D scatter centers and then obtain candidate 3D scattering centers. Thirdly, these candidate scattering centers are clustered in 3D space to reconstruct final 3D positions. Compared with presented methods, the proposed method has a capability of describing distributed scattering center, reduces false and missing 3D scattering centers, and has fewer restrictionson modeling data. Finally, results of experiments have demonstrated the effectiveness of the proposed method.展开更多
We present the experimental results of nitrogen-vacancy （NV） electron spin decoherence, which are linked to the coexistence of electron spin bath of nitrogen impurity （PI center） and 13C nuclear spin bath. In prev...We present the experimental results of nitrogen-vacancy （NV） electron spin decoherence, which are linked to the coexistence of electron spin bath of nitrogen impurity （PI center） and 13C nuclear spin bath. In previous works, only one dominant decoherence source is studied： P1 electron spin bath for type-Ⅰb diamond; or 13C nuclear spin bath for type-Ⅱa diamond. In general, the thermal fluctuation from both spin baths can be eliminated by the Hahn echo sequence, resulting in a long coherence time （T2 ） of about 400#8. However, in a high-purity type-Ⅱa diamond where 1℃ nuclear spin bath is the dominant decoherence source, dramatic decreases of NV electron spin T2 time caused by P1 electron spin bath are observed under certain magnetic field. We further apply the engineered Hahn echo sequence to confirm the decoherenee mechanism of multiple spin baths and quantitatively estimate the contribution of P1 electron spin bath. Our results are helpful to understand the NV decoherence mechanisms, which will benefit quantum computing and quantum metrology.展开更多
The China-Kazakhstan Horgos Frontier International Cooperation Center has been established for nearly 20 years,and its targeted policies have gone through the stages of initiative,negotiation and modification,official...The China-Kazakhstan Horgos Frontier International Cooperation Center has been established for nearly 20 years,and its targeted policies have gone through the stages of initiative,negotiation and modification,official operation,and optimization and enhancement.This paper explores the problems,policy,and political sources of policy changes since the establishment of the Horgos International Border Cooperation Center by applying the multi-source flow theory to find the opening of the problematic and political windows.It also constructs a model of policy change dynamics to provide suggestions on how the government should better promote the good development of China’s first transnational cooperation center.展开更多
As a kind of special acoustic field, the helical wavefront of an acoustic vortex（AV） beam is demonstrated to have a pressure zero with phase singularity at the center in the transverse plane. The orbital angular mom...As a kind of special acoustic field, the helical wavefront of an acoustic vortex（AV） beam is demonstrated to have a pressure zero with phase singularity at the center in the transverse plane. The orbital angular momentum of AVs can be applied to the field of particle manipulation, which attracts more and more attention in acoustic researches. In this paper,by using the simplified circular array of point sources, dual coaxial AV beams are excited by the even-and odd-numbered sources with the topological charges of l_E and l_O based on the phase-coded approach, and the composite acoustic field with an on-axis center-AV and multiple off-axis sub-AVs can be generated by the superimposition of the AV beams for｜l_E｜ ≠ ｜l_O｜. The generation of edge phase dislocation is theoretically derived and numerically analyzed for l_E=-l_O. The numbers and the topological charges as well as the locations of the center-AV and sub-AVs are demonstrated, which are proved to be determined by the topological charges of the coaxial AV beams. The proposed approach breaks through the limit of only one on-axis AV with a single topological charge along the beam axis, and also provides the feasibility of off-axis particle trapping with multiple AVs in object manipulation.展开更多
The expanded disability status scale (EDSS) is frequently used to classify the patients with multiple sclerosis (MS). We presented in this paper a novel method to automatically assess the EDSS score from posturologic ...The expanded disability status scale (EDSS) is frequently used to classify the patients with multiple sclerosis (MS). We presented in this paper a novel method to automatically assess the EDSS score from posturologic data (center of pres-sure signals) using a decision tree. Two groups of participants (one for learning and the other for test) with EDSS rang-ing from 0 to 4.5 performed our balance experiment with eyes closed. Two linear measures (the length and the surface) and twelve non-linear measures (the recurrence rate, the Shannon entropy, the averaged diagonal line length and the trapping time for the position, the instantaneous velocity and the instantaneous acceleration of the center of pressure respectively) were calculated for all the participants. Several decision trees were constructed with learning data and tested with test data. By comparing clinical and estimated EDSS scores in the test group, we selected one decision tree with five measures which revealed a 75% of agreement. The results have signified that our tree model is able to auto-matically assess the EDSS scores and that it is possible to distinguish the EDSS scores by using linear and non-linear postural sway measures.展开更多
合成氨(NH_(3))的发展是现代工业进程和人类生存的基石。受氮气(N_(2))化学惰性的限制,当前的合成氨工业能源消耗高并且排放大量的二氧化碳。电化学氮气还原反应(NRR),是有望取代高能耗的Haber-Bosch(HB)合成法的一种绿色可持续的合成...合成氨(NH_(3))的发展是现代工业进程和人类生存的基石。受氮气(N_(2))化学惰性的限制,当前的合成氨工业能源消耗高并且排放大量的二氧化碳。电化学氮气还原反应(NRR),是有望取代高能耗的Haber-Bosch(HB)合成法的一种绿色可持续的合成氨工艺。然而,因氮气以及析氢竞争富反应(HER)导致电催化氮气还原极低的NH_(3)产率和能量转换效率一直是目前人工固氮领域面临的挑战。在本文中,我们报道了一种具有丰富孔结构的磷掺杂碳(PC)负载Zn_(3)(PO_(4))_(2)/Zn_(2)P_(2)O_(7)纳米复合材料(h-PC/Zn_(3)(PO_(4))_(2)/Zn_(2)P_(2)O_(7)),在酸性和中性介质中将N_(2)高效催化转化为NH_(3)。其独特的分级多孔结构提高了表面粗糙度并加快了氮气在催化剂体相中的扩散,这有利于延长氮气在催化剂表面的停留时间以及提高活性位点的利用效率。而多组分的均匀分布可以调节电子结构并优化反应中间体的吸附行为,进而提高活性位点的本征活性。在0.1mol·L^(-1)HCI电解液中,h-PC/Zn_(3)(PO_(4))_(2)/Zn_(2)P_(2)O_(7)在-0.2 V vs.可逆氢电极(RHE)电位下NH_(3)的产率可以达到38.7±1.2μg·h^(-1)·mgcat^(-1),法拉第效率为19.8%±0.9%。此外;h-PC/Zn_(3)(PO_(4))_(2)/Zn_(2)P_(2)O_(7)在0.1 mol·L^(-1)Na_(2)SO_(4)溶液中同样展现出优异的电催化氮气还原合成氨性能,NH_(3)产率及法拉第效率分别为17.1±0.8μg·h^(-1)·mgcat^(-1)和15.g%±0.6%,明显优于PC/Zn_(3)P_(2)、C/ZnO和大多数报道的非贵金属电催化剂。这种优异的性能主要归因于多孔结构有利于传质及多组分活性位点协同效应。此外,我们采用非原位X射线光电子能谱(XPS)、透射电子显微镜(TEM)和X射线衍射(XRD)等表征手段对NRR测试前后h-PC/Zn_(3)(PO_(4))_(2)/Zn_(2)P_(2)O_(7)的组成和结构变化进行了剖析。在反应后检测到了新增的N物种信号,证明催化剂确实发生了氮气还原反应。本研究提供了一种通过同步构建传质通道并耦合不同的活性位点以协同增强NRR活性和选择性的新思路,这对加快绿色制氨工业化具有重大意义。展开更多
文摘A method and procedure is presented to reconstruct three-dimensional(3D) positions of scattering centers from multiple synthetic aperture radar(SAR) images. Firstly, two-dimensional(2D) attribute scattering centers of targets are extracted from 2D SAR images. Secondly, similarity measure is developed based on 2D attributed scatter centers' location, type, and radargrammetry principle between multiple SAR images. By this similarity, we can associate 2D scatter centers and then obtain candidate 3D scattering centers. Thirdly, these candidate scattering centers are clustered in 3D space to reconstruct final 3D positions. Compared with presented methods, the proposed method has a capability of describing distributed scattering center, reduces false and missing 3D scattering centers, and has fewer restrictionson modeling data. Finally, results of experiments have demonstrated the effectiveness of the proposed method.
基金Supported by the National Basic Research Program of China under Grant Nos 2014CB921402 and 2015CB921103the Strategic Priority Research Program of the Chinese Academy of Sciences under Grant No XDB07010300the National Natural Science Foundation of China under Grant No 11574386
文摘We present the experimental results of nitrogen-vacancy （NV） electron spin decoherence, which are linked to the coexistence of electron spin bath of nitrogen impurity （PI center） and 13C nuclear spin bath. In previous works, only one dominant decoherence source is studied： P1 electron spin bath for type-Ⅰb diamond; or 13C nuclear spin bath for type-Ⅱa diamond. In general, the thermal fluctuation from both spin baths can be eliminated by the Hahn echo sequence, resulting in a long coherence time （T2 ） of about 400#8. However, in a high-purity type-Ⅱa diamond where 1℃ nuclear spin bath is the dominant decoherence source, dramatic decreases of NV electron spin T2 time caused by P1 electron spin bath are observed under certain magnetic field. We further apply the engineered Hahn echo sequence to confirm the decoherenee mechanism of multiple spin baths and quantitatively estimate the contribution of P1 electron spin bath. Our results are helpful to understand the NV decoherence mechanisms, which will benefit quantum computing and quantum metrology.
文摘The China-Kazakhstan Horgos Frontier International Cooperation Center has been established for nearly 20 years,and its targeted policies have gone through the stages of initiative,negotiation and modification,official operation,and optimization and enhancement.This paper explores the problems,policy,and political sources of policy changes since the establishment of the Horgos International Border Cooperation Center by applying the multi-source flow theory to find the opening of the problematic and political windows.It also constructs a model of policy change dynamics to provide suggestions on how the government should better promote the good development of China’s first transnational cooperation center.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11474166 and 11604156)the Science and Technology Cooperation Projects of People’s Republic of China–Romania(Grant No.42-23)+2 种基金the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20161013)the Postdoctoral Science Foundation of China(Grant No.2016M591874)the Priority Academic Program Development of Jiangsu Higher Education Institutions,China
文摘As a kind of special acoustic field, the helical wavefront of an acoustic vortex（AV） beam is demonstrated to have a pressure zero with phase singularity at the center in the transverse plane. The orbital angular momentum of AVs can be applied to the field of particle manipulation, which attracts more and more attention in acoustic researches. In this paper,by using the simplified circular array of point sources, dual coaxial AV beams are excited by the even-and odd-numbered sources with the topological charges of l_E and l_O based on the phase-coded approach, and the composite acoustic field with an on-axis center-AV and multiple off-axis sub-AVs can be generated by the superimposition of the AV beams for｜l_E｜ ≠ ｜l_O｜. The generation of edge phase dislocation is theoretically derived and numerically analyzed for l_E=-l_O. The numbers and the topological charges as well as the locations of the center-AV and sub-AVs are demonstrated, which are proved to be determined by the topological charges of the coaxial AV beams. The proposed approach breaks through the limit of only one on-axis AV with a single topological charge along the beam axis, and also provides the feasibility of off-axis particle trapping with multiple AVs in object manipulation.
文摘The expanded disability status scale (EDSS) is frequently used to classify the patients with multiple sclerosis (MS). We presented in this paper a novel method to automatically assess the EDSS score from posturologic data (center of pres-sure signals) using a decision tree. Two groups of participants (one for learning and the other for test) with EDSS rang-ing from 0 to 4.5 performed our balance experiment with eyes closed. Two linear measures (the length and the surface) and twelve non-linear measures (the recurrence rate, the Shannon entropy, the averaged diagonal line length and the trapping time for the position, the instantaneous velocity and the instantaneous acceleration of the center of pressure respectively) were calculated for all the participants. Several decision trees were constructed with learning data and tested with test data. By comparing clinical and estimated EDSS scores in the test group, we selected one decision tree with five measures which revealed a 75% of agreement. The results have signified that our tree model is able to auto-matically assess the EDSS scores and that it is possible to distinguish the EDSS scores by using linear and non-linear postural sway measures.
文摘合成氨(NH_(3))的发展是现代工业进程和人类生存的基石。受氮气(N_(2))化学惰性的限制,当前的合成氨工业能源消耗高并且排放大量的二氧化碳。电化学氮气还原反应(NRR),是有望取代高能耗的Haber-Bosch(HB)合成法的一种绿色可持续的合成氨工艺。然而,因氮气以及析氢竞争富反应(HER)导致电催化氮气还原极低的NH_(3)产率和能量转换效率一直是目前人工固氮领域面临的挑战。在本文中,我们报道了一种具有丰富孔结构的磷掺杂碳(PC)负载Zn_(3)(PO_(4))_(2)/Zn_(2)P_(2)O_(7)纳米复合材料(h-PC/Zn_(3)(PO_(4))_(2)/Zn_(2)P_(2)O_(7)),在酸性和中性介质中将N_(2)高效催化转化为NH_(3)。其独特的分级多孔结构提高了表面粗糙度并加快了氮气在催化剂体相中的扩散,这有利于延长氮气在催化剂表面的停留时间以及提高活性位点的利用效率。而多组分的均匀分布可以调节电子结构并优化反应中间体的吸附行为,进而提高活性位点的本征活性。在0.1mol·L^(-1)HCI电解液中,h-PC/Zn_(3)(PO_(4))_(2)/Zn_(2)P_(2)O_(7)在-0.2 V vs.可逆氢电极(RHE)电位下NH_(3)的产率可以达到38.7±1.2μg·h^(-1)·mgcat^(-1),法拉第效率为19.8%±0.9%。此外;h-PC/Zn_(3)(PO_(4))_(2)/Zn_(2)P_(2)O_(7)在0.1 mol·L^(-1)Na_(2)SO_(4)溶液中同样展现出优异的电催化氮气还原合成氨性能,NH_(3)产率及法拉第效率分别为17.1±0.8μg·h^(-1)·mgcat^(-1)和15.g%±0.6%,明显优于PC/Zn_(3)P_(2)、C/ZnO和大多数报道的非贵金属电催化剂。这种优异的性能主要归因于多孔结构有利于传质及多组分活性位点协同效应。此外,我们采用非原位X射线光电子能谱(XPS)、透射电子显微镜(TEM)和X射线衍射(XRD)等表征手段对NRR测试前后h-PC/Zn_(3)(PO_(4))_(2)/Zn_(2)P_(2)O_(7)的组成和结构变化进行了剖析。在反应后检测到了新增的N物种信号,证明催化剂确实发生了氮气还原反应。本研究提供了一种通过同步构建传质通道并耦合不同的活性位点以协同增强NRR活性和选择性的新思路,这对加快绿色制氨工业化具有重大意义。
