Dependence of Switching Current Distribution of a Current-Biased Josephson Junction on Microwave Frequency

We investigate the distribution of the switching current of a current-biased Josephson junction （CBJJ） and its dependence on the microwave frequency using two theoretical methods, one of which is the quantum trajectory method and the other is the master equation method. Both the methods show that the distribution of the switching current of CBJJ will exhibit double peaks in a certain range of microwave frequency if proper microwave power is given, and the gap between the two peaks will increase with the microwave frequency. The obtained results can be used to identify the energy difference of the ground and first excited states in a Josephson junction for any bias current.

Control synthesis of linear distributed parameter switched systems

The control synthesis for switched systems is extended to distributed parameter switched systems in Hilbert space. Based on semigroup and operator theory, by means of multiple Lyapunov method incorporated average dwell time approach, sufficient con- ditions are derived in terms of linear operator inequalities frame- work for distributed parameter switched systems. Being applied to one dimensional heat propagation switched systems, these lin- ear operator inequalities are reduced to linear matrix inequalities subsequently. In particular, the state feedback gain matrices and the switching law are designed, and the state decay estimate is explicitly given whose decay coefficient completely depends on the system＇s parameter and the boundary condition. Finally, two numerical examples are given to illustrate the proposed method.

考虑DG无功支撑和开关重构的主动配电网分布鲁棒无功优化模型

近年来,风光等分布式电源(distributed generation, DG)的大力发展给主动配电网无功优化带来了新的挑战。传统随机优化和鲁棒优化方法在处理清洁能源不确定性方面存在片面性或保守性等问题。基于此,该文构建以系统网损为优化目标,并考虑DG无功支撑和开关重构的主动配电网分布鲁棒无功优化模型。该模型除了包括传统无功优化中的开关、变电站有载调压变压器、离散与连续无功补偿装置等元素,重点对双馈风机和微型燃气轮机的容量曲线进行详细建模,从而融入DG的无功支撑能力,并设计有功无功出力耦合特性约束的线性化方法。结合风电和光伏的典型场景数据,以及决策变量的调节特性,构建基于数据驱动的分布鲁棒两阶段无功优化模型,其中不确定性概率分布置信集合同时受到1-范数和∞-范数约束。模型采用列与约束生成(columns and constraints generation,CCG)算法进行求解,并在IEEE33节点算例上验证模型对系统无功支撑能力的提升和分布鲁棒方法的有效性。

Investigation of L1_0 FePt-based soft/hard composite bit-patterned media by micromagnetic simulation

The soft/hard composite patterned media have potential to be the next generation of magnetic recording, but the composing modes of soft and hard materials have not been investigated systematically. L10 FePt-based soft/hard composite patterned media with an anisotropic constant distribution are studied by micromagnetic simulation. Square arrays and hexagonal arrays with various pitch sizes are simulated for two composing types： the soft layer that encloses the hard dots and the soft layer that covers the whole surface. It is found that the soft material can reduce the switching fields of bits effectively for all models. Compared with the first type, the second type of models possess low switching fields, narrow switching field distributions, and high gain factors due to the introduction of inter-bit exchange coupling. Furthermore, the readout waveforms of the second type are not deteriorated by the inter-bit soft layers. Since the recording density of hexagonal arrays are higher than that of square arrays with the same center-to-center distances, the readout waveforrns of hexagonal arrays are a little worse, although other simulation results are similar for these two arrays.

考虑开关重构与需求响应的配电网分布鲁棒优化运行

在高比例分布式光伏接入的背景下,给配电网运行的经济性与安全性带来了新的挑战。建立了考虑开关重构与需求响应的配电网分布鲁棒优化运行模型。首先,以配电网每日运行成本最小为优化目标,同时考虑开关重构与价格型需求响应,得到配电网拓扑结构优化方案与运行方案。其次,利用光伏历史出力数据,通过聚类获取典型场景与其概率分布,采用1-范数与∞-范数约束不确定性概率分布置信区间,建立数据驱动的分布鲁棒两阶段优化模型。最后,通过修改的IEEE 33节点系统,基于列与约束生产算法(column-and-constraint generation,CCG)利用Cplex求解器进行求解,验证了模型的可行性。