We demonstrate the fabrication of a single electron transistor device based on a single ultra-small silicon quantum dot connected to a gold break junction with a nanometer scale separation. The gold break junction is ...We demonstrate the fabrication of a single electron transistor device based on a single ultra-small silicon quantum dot connected to a gold break junction with a nanometer scale separation. The gold break junction is created through a controllable electromigration process and the individual silicon quantum dot in the junction is deter- mined to be a Si 170 cluster. Differential conductance as a function of the bias and gate voltage clearly shows the Coulomb diamond which confirms that the transport is dominated by a single silicon quantum dot. It is found that the charging energy can be as large as 300meV, which is a result of the large capacitance of a small silicon quantum dot （-1.8 nm）. This large Coulomb interaction can potentially enable a single electron transistor to work at room temperature. The level spacing of the excited state can be as large as 10meV, which enables us to manipulate individual spin via an external magnetic field. The resulting Zeeman splitting is measured and the g factor of 2.3 is obtained, suggesting relatively weak electron-electron interaction in the silicon quantum dot which is beneficial for spin coherence time.展开更多
For switched linear system with colored measurement noises,the identification difficulties of this system are that there exist unknown switching information,unknown middle variables and noise terms in the information ...For switched linear system with colored measurement noises,the identification difficulties of this system are that there exist unknown switching information,unknown middle variables and noise terms in the information vector.For the mentioned issues,the fuzzy clustering and the multi-innovation recursive identification algorithm are used to deal with these problems.Firstly,the mode detection is transformed into the detection of membership degree values confirmed by the fuzzy clustering method,and the problem of mode detection is solved by judgment and decision of the fuzzy membership values.Moreover,the multi-innovation recursive identification algorithm based on the generalized auxiliary model is proposed to estimate the parameters of the switched linear system with colored noises.Finally,the effectiveness of the proposed method is verified by the results of the simulation example.展开更多
One of the limitations of using OFDM technique is its higher PAPR in the time domain signal. The higher PAPR OFDM signal would cause the fatal degradation of BER performance and undesirable spectrum regrowth in the no...One of the limitations of using OFDM technique is its higher PAPR in the time domain signal. The higher PAPR OFDM signal would cause the fatal degradation of BER performance and undesirable spectrum regrowth in the nonlinear channel. One of the promising PAPR reduction methods for OFDM signal is the Partial Transmit Sequence (PTS) method which can achieve better PAPR performance with reasonable computation complexity. However the PTS method is required to inform the phase coefficients of PTS as the side information to the receiver for the correct demodulation of data information through the data or separate channels. To simplify the transceiver of OFDM system with the PTS method, the phase coefficients of PTS are usually embedded in the data information. However since the phase coefficients of PTS are obtained after the PTS processing only for the data information at each OFDM symbol, it is hard to embed the phase coefficients of PTS in the data information separately without degradation of PAPR performance. To solve this problem, this paper proposes a new PAPR reduction method based on the packet-switched transmission systems in which all the clusters within the certain number of OFDM symbols have the sequential cluster ID numbers embedded in the header of each cluster. The salient features of the proposed method are to reduce the PAPR performance by re-ordering of clusters (ROC) in the frequency domain at the transmitter and to reconstruct the original ordering of clusters by using the cluster ID number demodulated from each cluster at the receiver. This paper also proposes a reduction technique of computation complexity for the proposed ROC method by using the feature of IFFT processing. This paper presents various computer simulation results to verify the effectiveness of the proposed ROC method with the reduction technique of computation complexity.展开更多
随着现代科技的迅猛发展,时钟同步技术在通信领域的重要性日益凸显。在地铁公安PDT(Police Digital Trunking)集群通信系统中,为实现语音的无缝切换和可靠传输,时钟同步至关重要。首先阐述时钟同步的定义及对地铁公安PDT集群通信系统的...随着现代科技的迅猛发展,时钟同步技术在通信领域的重要性日益凸显。在地铁公安PDT(Police Digital Trunking)集群通信系统中,为实现语音的无缝切换和可靠传输,时钟同步至关重要。首先阐述时钟同步的定义及对地铁公安PDT集群通信系统的关键作用,接着详细剖析PDT和TETRA(Trans European Trunked Radio)标准对时钟同步的要求,深入探讨PDT系统中时钟同步对语音通信切换的多方面影响及配置NTP(Network Time Protocol)设备的重要意义,最后得出合理配置NTP设备对地铁公安PDT集群通信系统具有重要性的结论。展开更多
Web QoS 是当前 Web 计算中的重要研究内容,用于解决 Web 计算环境中端到端 QoS 保证问题。本文提出一种支持 QoS 的 Web 服务器集群系统方案以及实现技术,整个系统由支持 QoS 的集群交换机和 Web 服务器集群两级结构组成,通过集群交换...Web QoS 是当前 Web 计算中的重要研究内容,用于解决 Web 计算环境中端到端 QoS 保证问题。本文提出一种支持 QoS 的 Web 服务器集群系统方案以及实现技术,整个系统由支持 QoS 的集群交换机和 Web 服务器集群两级结构组成,通过集群交换机和 Web 服务器的协同工作,实现优先转发与优先服务相结合的分布式 QoS 保证体系,充分满足 Web 用户的服务质量需求。通过系统测试,原型系统的性能指标达到了设计要求。展开更多
基金Supported by the National Key Research and Development Program of China under Grant No 2017YFA0303200the National Natural Science Foundation of China under Grant Nos U1732273,U1732159,91421109,91622115,11522432,11574217 and 61774133the Natural Science Foundation of Jiangsu Province under Grant No BK20160659
文摘We demonstrate the fabrication of a single electron transistor device based on a single ultra-small silicon quantum dot connected to a gold break junction with a nanometer scale separation. The gold break junction is created through a controllable electromigration process and the individual silicon quantum dot in the junction is deter- mined to be a Si 170 cluster. Differential conductance as a function of the bias and gate voltage clearly shows the Coulomb diamond which confirms that the transport is dominated by a single silicon quantum dot. It is found that the charging energy can be as large as 300meV, which is a result of the large capacitance of a small silicon quantum dot （-1.8 nm）. This large Coulomb interaction can potentially enable a single electron transistor to work at room temperature. The level spacing of the excited state can be as large as 10meV, which enables us to manipulate individual spin via an external magnetic field. The resulting Zeeman splitting is measured and the g factor of 2.3 is obtained, suggesting relatively weak electron-electron interaction in the silicon quantum dot which is beneficial for spin coherence time.
基金supported by the National Natural Science Foundation of China(61863034)
文摘For switched linear system with colored measurement noises,the identification difficulties of this system are that there exist unknown switching information,unknown middle variables and noise terms in the information vector.For the mentioned issues,the fuzzy clustering and the multi-innovation recursive identification algorithm are used to deal with these problems.Firstly,the mode detection is transformed into the detection of membership degree values confirmed by the fuzzy clustering method,and the problem of mode detection is solved by judgment and decision of the fuzzy membership values.Moreover,the multi-innovation recursive identification algorithm based on the generalized auxiliary model is proposed to estimate the parameters of the switched linear system with colored noises.Finally,the effectiveness of the proposed method is verified by the results of the simulation example.
文摘One of the limitations of using OFDM technique is its higher PAPR in the time domain signal. The higher PAPR OFDM signal would cause the fatal degradation of BER performance and undesirable spectrum regrowth in the nonlinear channel. One of the promising PAPR reduction methods for OFDM signal is the Partial Transmit Sequence (PTS) method which can achieve better PAPR performance with reasonable computation complexity. However the PTS method is required to inform the phase coefficients of PTS as the side information to the receiver for the correct demodulation of data information through the data or separate channels. To simplify the transceiver of OFDM system with the PTS method, the phase coefficients of PTS are usually embedded in the data information. However since the phase coefficients of PTS are obtained after the PTS processing only for the data information at each OFDM symbol, it is hard to embed the phase coefficients of PTS in the data information separately without degradation of PAPR performance. To solve this problem, this paper proposes a new PAPR reduction method based on the packet-switched transmission systems in which all the clusters within the certain number of OFDM symbols have the sequential cluster ID numbers embedded in the header of each cluster. The salient features of the proposed method are to reduce the PAPR performance by re-ordering of clusters (ROC) in the frequency domain at the transmitter and to reconstruct the original ordering of clusters by using the cluster ID number demodulated from each cluster at the receiver. This paper also proposes a reduction technique of computation complexity for the proposed ROC method by using the feature of IFFT processing. This paper presents various computer simulation results to verify the effectiveness of the proposed ROC method with the reduction technique of computation complexity.
文摘随着现代科技的迅猛发展,时钟同步技术在通信领域的重要性日益凸显。在地铁公安PDT(Police Digital Trunking)集群通信系统中,为实现语音的无缝切换和可靠传输,时钟同步至关重要。首先阐述时钟同步的定义及对地铁公安PDT集群通信系统的关键作用,接着详细剖析PDT和TETRA(Trans European Trunked Radio)标准对时钟同步的要求,深入探讨PDT系统中时钟同步对语音通信切换的多方面影响及配置NTP(Network Time Protocol)设备的重要意义,最后得出合理配置NTP设备对地铁公安PDT集群通信系统具有重要性的结论。
文摘Web QoS 是当前 Web 计算中的重要研究内容,用于解决 Web 计算环境中端到端 QoS 保证问题。本文提出一种支持 QoS 的 Web 服务器集群系统方案以及实现技术,整个系统由支持 QoS 的集群交换机和 Web 服务器集群两级结构组成,通过集群交换机和 Web 服务器的协同工作,实现优先转发与优先服务相结合的分布式 QoS 保证体系,充分满足 Web 用户的服务质量需求。通过系统测试,原型系统的性能指标达到了设计要求。
