一种用于逐次逼近ADC的高能效高线性度开关电容时序

提出了一种用于逐次逼近模数转换器的高能效高线性度开关电容时序。相较于典型的基于V_CM的开关原理,该开关时序可减少37%的开关能量,并具有更高的线性度。该开关时序已应用于1V,10位300kS/s的SAR ADC,并在0.18μm标准CMOS工艺下成功流片。测试结果表明,在1V电源电压下,此SAR ADC的SNDR为55.48dB,SFDR为66.98dB,功耗为2.13μW,品质因数到达14.66fJ/c-s。DNL和INL分别为0.52/-0.47 LSB和0.72/-0.79 LSB,并且与静态非线性模型一致,最大INL出现在 V_FS/4处和3V_FS/4处。     

基于分解法建模的泵送系统可靠性和可用性评估

为解决马尔科夫模型的状态空间爆炸问题,在状态空间分解法的基础上,建立单个部件(层次3)的SPN模型,然后根据子系统的组成结构建立单个子系统(层次2)的SPN模型.将子系统SPN模型集成为系统模型(层次1),得到系统模型的可达图及缩小的等效半马尔科夫图,按图建立系统模型的状态方程并求解,然后对系统进行可靠性和可用性评估.以泵送系统为例,验证分解法有助于解决状态空间爆炸问题,并使建模的难度和计算量减小,更易于操作.     

非旋波近似下薛定谔猫态光场与V型三能级原子相互作用系统的量子特性

在非旋波近似下,通过采用相干态正交展开的方法,对薛定谔猫态光场与V型三能级原子相互作用的量子特性进行了研究。首先,精确求解了V型三能级的能谱,并判断了系统的保真度。其次,演化问题的结果表明：当原子初态处于基态时,随着初始光场强度的增大,奇相干态和偶相干态的二阶相干度的振幅都减小,且表现出聚束效应与反聚束效应的临界状态。当原子初态处于叠加态时,随着初始光场强度的增大奇相,奇干态和偶相干态的二阶相干度的振幅都减小,且表现出聚束效应。最后,当系统耦合系数减小,光场二阶相干度的振荡幅度减小,光场呈现反聚束效应。     

Blind Source Separation of Instantaneous Mixture of Delayed Sources Using High‐Order Taylor Approximation

This paper deals with the problem of blind source separation (BSS), where observed signals are a mixture of delayed sources. In reference to a previous work, when the delay time is small such that the first‐order Taylor approximation holds, delayed observations are transformed into an instantaneous mixture of original sources and their derivatives, for which an extended second‐order blind identification (SOBI) approach is used to recover sources. Inspired by the results of this previous work, we propose to generalize its first‐order Taylor approximation to suit higher‐order approximations in the case of a large delay time based on a similar version of its extended SOBI. Compared to SOBI and its extended version for a first‐order Taylor approximation, our method is more efficient in terms of separation quality when the delay time is large. Simulation results verify the performance of our approach under different time delays and signal‐to‐noise ratio conditions, respectively.     

Coverage and Energy Modeling of HetNet Under Base Station On‐Off Model

Small cell networks, as an important evolution path for next‐generation cellular networks, have drawn much attention. Different from the traditional base stations (BSs) always‐on model, we proposed a BSs on‐off model, where a new, simple expression for the probabilities of active BSs in a heterogeneous network is derived. This model is more suitable for application in practical networks. Based on this, we develop an analytical framework for the performance evaluation of small cell networks, adopting stochastic geometry theory. We derive the system coverage probability; average energy efficiency (AEE) and average uplink power consumption (AUPC) for different association strategies; maximum biased received power (MaBRP); and minimum association distance (MiAD). It is analytically shown that MaBRP is beneficial for coverage but will have some loss in energy saving. On the contrary, MiAD is not advocated from the point of coverage but is more energy efficient. The simulation results show that the use of range expansion in MaBRP helps to save energy but that this is not so in MiAD. Furthermore, we can achieve an optimal AEE by establishing an appropriate density of small cells.     

Conservative Approximation–Based Full‐Search Block Matching Algorithm Architecture for QCIF Digital Video Employing Systolic Array Architecture

This paper presents a power‐efficient hardware realization for a motion estimation technique that is based on the full‐search block matching algorithm (FSBMA). The considered input is the quarter common intermediate format of digital video. The mean of absolute difference (MAD) is the distortion criteria employed for the block matching process. The conventional architecture considered for the hardware realization of FSBMA is that of the shift register–based 2‐D systolic array. For this architecture, a conservative approximation technique is adapted to eliminate unnecessary MAD computations involved in the block matching process. Upon introducing the technique to the conventional architecture, the power and complexity of its implantation is reduced, while the accuracy of the motion vector extracted from the block matching process is preserved. The proposed architecture is verified for its functional specifications. A performance evaluation of the proposed architecture is carried out using parameters such as power, area, operating frequency, and efficiency.     

一种社交网络群组间信息推荐的有效方法

群组间信息推荐是社交网络中人们传递和分享资讯的重要途径,然而获取精确的最优推荐方案需要指数级时间开销.为此,本文提出一种有效算法EAOORS(Efficient Algorithm for Obtaining Optimal Recommendation Solution),将该指数级时间开销问题等价归约为EST(Extended Steiner Tree,扩展Steiner树)问题,并在多项式时间复杂度内快速获取近似最优推荐方案.理论分析和仿真实验表明,本文所提的算法具有有效性和实用性.     

基于随机桥过程的窄带信道多径衰落仿真研究

将多径分量仿真为随机射线的传播,其轨迹描述为随机桥过程的样本。研究随机射线在渗流网格中扩散的物理规律,以改进物理散射约束,使之有足够样本用于场强时延分布建模。通过实验,模拟不同波长的波束在不同散射体密度的渗流网格内的扩散,得出信道的相干带宽、误码率和场强的统计特征,验证了信号的多径衰落统计特征与相应的随机射线扩散程度有关,随机射线模型能够较大概率地仿真信号多径衰落的特性。     

An efficient algorithm for low-order direct discrete-time implementation of fractional order transfer functions

Fractional order systems become increasingly popular due to their versatility in modelling and control applications across various disciplines. However, the bottleneck in deploying these tools in practice is related to their implementation on real-life systems. Numerical approximations are employed but their complexity no longer match the attractive simplicity of the original fractional order systems. This paper proposes a low-order, computationally stable and efficient method for direct approximation of general order (fractional order) systems in the form of discrete-time rational transfer functions, e.g. processes, controllers. A fair comparison to other direct discretization methods is presented, demonstrating its added value with respect to the state of art.     

Stochastic collocation-based nonlinear analysis of concrete bridges with uncertain parameters

This paper focuses on the stochastic response of concrete bridges considering uncertainty in bearing and abutment stiffness. A multi-span simply supported bridge with concrete girders is selected. A 3D-dimensional model is prepared, and nonlinear response history analyses are performed. For the numerical dynamic simulation, the non-sampling stochastic method based on generalized polynomial chaos (gPC) expansion is utilised. The uncertain parameters include the vertical and shear stiffness of bearings and the lateral stiffness of abutments are presented by the truncated gPC expansions. Furthermore, the system response such as base shear, acceleration, velocity and displacement in different columns is presented by gPC expansion with unknown deterministic coefficients. The stochastic Galerkin projection is employed to calculate a set of deterministic equations. A non-intrusive solution, as a set of collocation points, determines the unknown gPC coefficients of the system response and the results are compared with Monte Carlo simulations. The key advantage of spectral discretization is the combination of the mentioned method with the spatial discretization, e.g. finite element model. This study also emphasises the accuracy in results and time efficiency of the proposed non-sampling method for uncertainty quantification of stochastic systems comparing to sampling procedure (e.g. Monte Carlo simulation).