Three kinds of oxide underlayers, namely Si02, ZnO and Al2O3, were deposited prior to the sputtering of Sr-ferrite films, respectively, in order to induce the optimum grain morphology and the texture of the films. A S...Three kinds of oxide underlayers, namely Si02, ZnO and Al2O3, were deposited prior to the sputtering of Sr-ferrite films, respectively, in order to induce the optimum grain morphology and the texture of the films. A Sr-ferrite film with an easy axis in-plane orientation was induced by SiO2 underlayer. In contrast, it prefers to be perpendicular to film plane for the cases of ZnO and Al2O3 underlayers. The optimum magnetic properties of the former film along film plane are: 4πMr=1.7 kG, iHc=5.35 kOe, and Sq=0.59, which are mainly dominated by the exchange coupling effect, determined by Wohlfarth's remanence analysis, among grains. While those for the films with an easy axis perpendicular to film plane can be as high as 4πMr=3.72 kG, iHc=6.42 kOe, and Sq=0.82, which are mainly dominated by the magnetostatic interaction among grains.展开更多
The γ＇-Fe4N films on Cu underlayers are deposited on the glass and Si substrates by dc magnetron reactive sputtering. The effects of Cu underlayer on the structure, morphology and magnetic properties of the γ＇-Fe4...The γ＇-Fe4N films on Cu underlayers are deposited on the glass and Si substrates by dc magnetron reactive sputtering. The effects of Cu underlayer on the structure, morphology and magnetic properties of the γ＇-Fe4N films are studied. The single-phase γ＇-Fe4N films with Cu underlayers on the glass substrate are obtained, while the mixture of Fe and γ＇-Fe4N is observed on the Si substrate. In comparison with the films without Cu underlayers, the grains of the films with Cu underlayers exhibit a non-uniform size distribution and give rise to a rougher surface. The magnetic measurements indicate that the γ＇-Fe4N films show a good soft ferromagnetic behavior. The enhanced coercivity in the films with Cu underlayers is observed due to the deterioration of the crystallographic structure as well as the rougher surface.展开更多
国家新型基础设施建设给各运营商带来了新的发展契机,纷纷布局以云网融合为特征的数据中心建设。本文重点分析运营商如何打造云网一体化网络服务提供点(Point of Presence,POP),满足不同客户差异化的入云或云间组网需求,实现云网能力端...国家新型基础设施建设给各运营商带来了新的发展契机,纷纷布局以云网融合为特征的数据中心建设。本文重点分析运营商如何打造云网一体化网络服务提供点(Point of Presence,POP),满足不同客户差异化的入云或云间组网需求,实现云网能力端到端快速贯通,云资源池快速规模化部署,缩短云资源池或数据中心接入网络的建设和开通周期。展开更多
针对underlay认知无线电中时频重叠正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)信号的信噪比(Signal to Noise Ratio,SNR)难以估计的问题,提出了一种基于循环自相关特性的时频重叠OFDM信噪比盲估计方法.该方法提取...针对underlay认知无线电中时频重叠正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)信号的信噪比(Signal to Noise Ratio,SNR)难以估计的问题,提出了一种基于循环自相关特性的时频重叠OFDM信噪比盲估计方法.该方法提取接收信号的循环自相关函数截面中的离散谱线估计出分量信号的总功率,并结合时延和循环频率均为零时的离散谱线估计出时频重叠OFDM信号的信噪比.仿真结果表明,在无需先验信息的情况下,当SNR大于-7d B时,所提方法估计的均方误差小于0.1,并且对分量信号的功率比和频谱重叠率具有稳健性.展开更多
认知无线电通过与MIMO(Multi-Input Multi-Output)、OFDM(Orthogonal Frequency Division Multiplexing)、超宽带、协作通信等技术融合来改善频谱利用率.而认知MIMO是认知无线电和MIMO技术的融合,虽然具有干扰抑制、抗多径衰落、空间分...认知无线电通过与MIMO(Multi-Input Multi-Output)、OFDM(Orthogonal Frequency Division Multiplexing)、超宽带、协作通信等技术融合来改善频谱利用率.而认知MIMO是认知无线电和MIMO技术的融合,虽然具有干扰抑制、抗多径衰落、空间分集和复用等优势,但是由于underlay共享方式中干扰温度约束的存在,导致发送预编码矩阵之间相互耦合,因此该技术在underlay干扰网络中难以获得最优的传输性能.针对该问题,通过交替迭代的方式,结合Rayleigh-Ritz定理和凸优化理论,推导了最优收发矩阵之间的迭代关系,提出一种最优干扰对齐算法.该算法利用Lagrange部分对偶方式来去除干扰温度约束,并采用次梯度投影法更新Lagrange变量,克服了已有半正定松弛算法因忽略矩阵秩约束而导致速率性能下降的缺陷.理论分析和数值仿真验证了算法的有效性,结果表明所提算法可实现网络可达速率和的最大化.展开更多
Heusler Co2FeSi films with a uniaxial magnetic anisotropy and high ferromagnetic resonance frequency fr were deposited by an oblique sputtering technique on Ru underlayers with various thicknesses tRufrom 0 nm to 5 nm...Heusler Co2FeSi films with a uniaxial magnetic anisotropy and high ferromagnetic resonance frequency fr were deposited by an oblique sputtering technique on Ru underlayers with various thicknesses tRufrom 0 nm to 5 nm.It is revealed that the Ru underlayers reduce the grain size of Co2FeSi,dramatically enhance the magnetic anisotropy field HK induced by the internal stress from 242 Oe(1 Oe=79.5775 A·m^-1)to 582 Oe with an increment ratio of 2.4,while a low damping coefficient remains.The result of damping implies that the continuous interface between Ru and Co2FeSi induces a large in-plane anisotropic field without introducing additional external damping.As a result,excellent high-frequency soft magnetic properties with fr up to 6.69 GHz are achieved.展开更多
Hematite is regarded as a promising photoanode for photoelectrochemical(PEC) water splitting.However,the charge recombination occurred at the interface of FTO/hematite strictly limits the PEC performance of hematite.H...Hematite is regarded as a promising photoanode for photoelectrochemical(PEC) water splitting.However,the charge recombination occurred at the interface of FTO/hematite strictly limits the PEC performance of hematite.Herein,we reported a Ti3C2 MXene underlayer modified hematite(Ti-Fe2O3) photoanode via a simple drop-casting followed by hydrothermal and annealing processes.Owing to the bifunctional role of Ti3C2 MXene underlayer in improving the interfacial properties of FTO/hematite and providing Ti source for the construction of Fe2 TiO5/Fe2O3 heterostructure in hematite nanostructure,the bulk and interfacial charge transfer dynamics of hematite are significantly enhanced,and consequently enhancing the PEC performance.Compared with the pristine hematite,the as-prepared Ti-Fe2O3 photoanode shows an increased photocurrent density from 0.80 mA/cm^(2) to 1.30 mA/cm^(2) at 1.23 V vs.RHE.Moreover,a further promoted PEC performance including a dramatically increased photocurrent density of 2.49 mA/cm^(2) at1.23 V vs.RHE and an obviously lowered onset potential is achieved for the Ti-Fe2O3 sample after the subsequent surface F-treatment and the loading of FeNiOOH cocatalyst.Such results suggest that the introduction of Ti3C2 MXene underlayer is a facile but effective approach to improve the PEC water splitting activity of hematite.展开更多
This paper focuses on potential issues related to the random selection of a sensing channel that occurs after the prediction phase in a Cognitive Radio Network (CRN).A novel approach (Approach-l)for improved selection...This paper focuses on potential issues related to the random selection of a sensing channel that occurs after the prediction phase in a Cognitive Radio Network (CRN).A novel approach (Approach-l)for improved selection is proposed,which relies on the probabilities of channels by which they are predicted idle.Further,closed-form expressions are derived for the throughput of Cognitive Users (CUs)in the conventional and proposed approaches. In addition to this,a fimdamental approach for computing the prediction probabilities is also proposed.Moreover, a new challenging issue named "sense and stuck"was observed in the conventional approach.The proposed approach is validated by comparing the results achieved with the results of the conventional approach.However, to achieve the prediction probabilities,the pre-channel-state-information is a prerequisite,but it may be unavailable for particular scenarios;therefore,a modified selection method is introduced to avoid the sense and stuck problem.An algorithm to evaluate the throughput using the random,improved,and modified selection methods is presented with its space and time complexities.Furthermore,for additional improvement in the throughput of the CU,a new frame structure is introduced,in which the spectrum prediction and sensing periods are exploited for simultaneous transmission of data via the underlay spectrtun access technique (Approach-2).The simulated results of Approach-2 are compared with our pre-obtalned results of Approach-I,which confirm significant improvement in the throughput.展开更多
文摘Three kinds of oxide underlayers, namely Si02, ZnO and Al2O3, were deposited prior to the sputtering of Sr-ferrite films, respectively, in order to induce the optimum grain morphology and the texture of the films. A Sr-ferrite film with an easy axis in-plane orientation was induced by SiO2 underlayer. In contrast, it prefers to be perpendicular to film plane for the cases of ZnO and Al2O3 underlayers. The optimum magnetic properties of the former film along film plane are: 4πMr=1.7 kG, iHc=5.35 kOe, and Sq=0.59, which are mainly dominated by the exchange coupling effect, determined by Wohlfarth's remanence analysis, among grains. While those for the films with an easy axis perpendicular to film plane can be as high as 4πMr=3.72 kG, iHc=6.42 kOe, and Sq=0.82, which are mainly dominated by the magnetostatic interaction among grains.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61434002,61204097,11274214 and 51301099the National High-Tech Research and Development Program of China under Grant No 2014AA032904+1 种基金the Chang Jiang Scholars and Innovative Team Development Plan by the Ministry of Education under Grant No IRT1156the Specialized Research Fund for the Doctoral Program of Higher Education of China under Grant Nos 20121404130001 and 20121404120003
文摘The γ＇-Fe4N films on Cu underlayers are deposited on the glass and Si substrates by dc magnetron reactive sputtering. The effects of Cu underlayer on the structure, morphology and magnetic properties of the γ＇-Fe4N films are studied. The single-phase γ＇-Fe4N films with Cu underlayers on the glass substrate are obtained, while the mixture of Fe and γ＇-Fe4N is observed on the Si substrate. In comparison with the films without Cu underlayers, the grains of the films with Cu underlayers exhibit a non-uniform size distribution and give rise to a rougher surface. The magnetic measurements indicate that the γ＇-Fe4N films show a good soft ferromagnetic behavior. The enhanced coercivity in the films with Cu underlayers is observed due to the deterioration of the crystallographic structure as well as the rougher surface.
文摘国家新型基础设施建设给各运营商带来了新的发展契机,纷纷布局以云网融合为特征的数据中心建设。本文重点分析运营商如何打造云网一体化网络服务提供点(Point of Presence,POP),满足不同客户差异化的入云或云间组网需求,实现云网能力端到端快速贯通,云资源池快速规模化部署,缩短云资源池或数据中心接入网络的建设和开通周期。
文摘针对underlay认知无线电中时频重叠正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)信号的信噪比(Signal to Noise Ratio,SNR)难以估计的问题,提出了一种基于循环自相关特性的时频重叠OFDM信噪比盲估计方法.该方法提取接收信号的循环自相关函数截面中的离散谱线估计出分量信号的总功率,并结合时延和循环频率均为零时的离散谱线估计出时频重叠OFDM信号的信噪比.仿真结果表明,在无需先验信息的情况下,当SNR大于-7d B时,所提方法估计的均方误差小于0.1,并且对分量信号的功率比和频谱重叠率具有稳健性.
文摘认知无线电通过与MIMO(Multi-Input Multi-Output)、OFDM(Orthogonal Frequency Division Multiplexing)、超宽带、协作通信等技术融合来改善频谱利用率.而认知MIMO是认知无线电和MIMO技术的融合,虽然具有干扰抑制、抗多径衰落、空间分集和复用等优势,但是由于underlay共享方式中干扰温度约束的存在,导致发送预编码矩阵之间相互耦合,因此该技术在underlay干扰网络中难以获得最优的传输性能.针对该问题,通过交替迭代的方式,结合Rayleigh-Ritz定理和凸优化理论,推导了最优收发矩阵之间的迭代关系,提出一种最优干扰对齐算法.该算法利用Lagrange部分对偶方式来去除干扰温度约束,并采用次梯度投影法更新Lagrange变量,克服了已有半正定松弛算法因忽略矩阵秩约束而导致速率性能下降的缺陷.理论分析和数值仿真验证了算法的有效性,结果表明所提算法可实现网络可达速率和的最大化.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11674187 and 51871127)the Fund from the Technology on Electronic Test&Measurement Laboratory(Grant No.6142001180103)。
文摘Heusler Co2FeSi films with a uniaxial magnetic anisotropy and high ferromagnetic resonance frequency fr were deposited by an oblique sputtering technique on Ru underlayers with various thicknesses tRufrom 0 nm to 5 nm.It is revealed that the Ru underlayers reduce the grain size of Co2FeSi,dramatically enhance the magnetic anisotropy field HK induced by the internal stress from 242 Oe(1 Oe=79.5775 A·m^-1)to 582 Oe with an increment ratio of 2.4,while a low damping coefficient remains.The result of damping implies that the continuous interface between Ru and Co2FeSi induces a large in-plane anisotropic field without introducing additional external damping.As a result,excellent high-frequency soft magnetic properties with fr up to 6.69 GHz are achieved.
基金the support from the high-performance computing platform of Jiangsu UniversityThe Jiangsu University Foundation (18JDG019)+3 种基金the Postdoctoral Foundation of Jiangsu Province (2018K072C)Six Talent Peak Project of Jiangsu Province (XLC-158)the China Postdoctoral Science Foundation (2019M651727, 2019M651719)the National Natural Science Foundation of China (21808090, 51902139, U1932211) financially supported this work。
文摘Hematite is regarded as a promising photoanode for photoelectrochemical(PEC) water splitting.However,the charge recombination occurred at the interface of FTO/hematite strictly limits the PEC performance of hematite.Herein,we reported a Ti3C2 MXene underlayer modified hematite(Ti-Fe2O3) photoanode via a simple drop-casting followed by hydrothermal and annealing processes.Owing to the bifunctional role of Ti3C2 MXene underlayer in improving the interfacial properties of FTO/hematite and providing Ti source for the construction of Fe2 TiO5/Fe2O3 heterostructure in hematite nanostructure,the bulk and interfacial charge transfer dynamics of hematite are significantly enhanced,and consequently enhancing the PEC performance.Compared with the pristine hematite,the as-prepared Ti-Fe2O3 photoanode shows an increased photocurrent density from 0.80 mA/cm^(2) to 1.30 mA/cm^(2) at 1.23 V vs.RHE.Moreover,a further promoted PEC performance including a dramatically increased photocurrent density of 2.49 mA/cm^(2) at1.23 V vs.RHE and an obviously lowered onset potential is achieved for the Ti-Fe2O3 sample after the subsequent surface F-treatment and the loading of FeNiOOH cocatalyst.Such results suggest that the introduction of Ti3C2 MXene underlayer is a facile but effective approach to improve the PEC water splitting activity of hematite.
文摘This paper focuses on potential issues related to the random selection of a sensing channel that occurs after the prediction phase in a Cognitive Radio Network (CRN).A novel approach (Approach-l)for improved selection is proposed,which relies on the probabilities of channels by which they are predicted idle.Further,closed-form expressions are derived for the throughput of Cognitive Users (CUs)in the conventional and proposed approaches. In addition to this,a fimdamental approach for computing the prediction probabilities is also proposed.Moreover, a new challenging issue named "sense and stuck"was observed in the conventional approach.The proposed approach is validated by comparing the results achieved with the results of the conventional approach.However, to achieve the prediction probabilities,the pre-channel-state-information is a prerequisite,but it may be unavailable for particular scenarios;therefore,a modified selection method is introduced to avoid the sense and stuck problem.An algorithm to evaluate the throughput using the random,improved,and modified selection methods is presented with its space and time complexities.Furthermore,for additional improvement in the throughput of the CU,a new frame structure is introduced,in which the spectrum prediction and sensing periods are exploited for simultaneous transmission of data via the underlay spectrtun access technique (Approach-2).The simulated results of Approach-2 are compared with our pre-obtalned results of Approach-I,which confirm significant improvement in the throughput.
