This paper proposes and analyzes a fully discrete scheme that discretizes space with an ultra-weak local discontinuous Galerkin scheme and time with the Crank--Nicolson method for the nonlinear biharmonic Schr\"odinger equation. We first rewrite the problem into a system with a second-order spatial derivative and then apply the ultra-weak discontinuous Galerkin method to the system. The proposed scheme is more computationally efficient compared with the local discontinuous Galerkin method because of fewer auxiliary variables, and unconditionally stable without any penalty terms; it also preserves the mass and Hamiltonian conservation that are important properties of the nonlinear biharmonic Schr\"odinger equation. We also derive optimal L2-error estimates of the semi-discrete scheme that measure both the solution and the auxiliary variable with general nonlinear terms. Several numerical studies demonstrate and support our theoretical findings.
We have studied the effect of top electrode materials on the switching behavior of TaOx based memristors with an identical switching oxide layer and bottom electrode stack. We found that the virgin resistance, electroforming and switching performance depend heavily on the chemical property of the top electrode materials. In addition, the electrical properties of metal oxides formed with the top electrodes also contribute to the overall memristor performance, including the nonlinearity of the current–voltage relationship. These results provide insights into understanding of memristor behavior as well as approaches for device property engineering.
Spin-transfer torque random access memory (STT-RAM) is a promising nonvolatile memory technology aiming on-chip or embedded applications. In recent years, many researches have been conducted to improve the storage density and enhance the scalability of STT-RAM, such as reducing the write current and switching time of magnetic tunneling junction (MTJ) devices. In parallel with these efforts, the continuous increasing of tunnel magneto-resistance(TMR) ratio of the MTJ inspires the development of multi-level cell (MLC) STT-RAM, which allows multiple data bits be stored in a single memory cell. Two types of MLC STT-RAM cells, namely, parallel MLC and series MLC, were also proposed. The storage margin of a MLC STT-RAM cell, i.e., the distinction between the lowest and highest resistance states, is partitioned into multiple segments for multi-level data representation. As a result, the performance and reliability of MLC STT-RAM cells become more sensitive to the MOS and MTJ device variations and the thermal-induced randomness of MTJ switching. In this work, we systematically analyze the variation sources of MLC STT-RAM designs and their impacts on the reliability of the read and write operations. On top of that, we also discuss the optimal device parameters of the MLC MTJ for the minimization of the operation error rate of the MLC STT-RAM cells from statistical design perspective. Our simulation results show that under the current available technology, series MLC STT-RAM demonstrates overwhelming benefits in the read and write reliability compared to parallel MLC STT-RAM and could potentially satisfy the requirement of commercial practices.
With the integration of large-scale renewable energy, the weak support of renewable energy power generation equipment makes the grid voltage support strength difficult to meet the needs of safe and stable operation. By configuring synchronous condensers, the voltage strength of the power grid can be effectively increased, but in power transmission channel planning and building, there is a lack of feasible synchronous condenser configuration methods. Based on the evaluation effect of multiple renewable energy stations short circuit ratio (MRSCR) on grid voltage support strength, considering the the limits of curtailment rate, this paper proposed a distributed hybrid optimal configuration method based on the quantitative index of grid voltage support strength. This method can significantly increase the grid voltage support strength after the renewable energy is connected by configuring synchronous condensers with a smaller total capacity. Combined with the calculation results of full electromagnetic simulation and electromechanical transient simulation of typical examples, it can be seen that the synchronous condenser configuration method proposed in this paper can effectively increase the grid voltage support strength and ensure the curtailment rate of the renewable energy transmission channel meeting the need of national requirement.
Metal-Insulator-Metal (MIM) capacitors with various thickness as (22 nm, 30 nm, 37 nm and 44 nm) of La (8%) doped HfO2 deposited using atomic layer deposition were fabricated. A high dielectric constant value of 38 can be obtained when 8% La doped HfO2 is crystallized into cubic structure. While amorphous HfLaO demonstrates a quadratic voltage linearity <1000 ppm/V2 up to a capacitance density of 9fF/µm2, both amorphous and crystallized HfLaO film shows good leakage current characteristics. The higher k value of HfLaO benefits MIM capacitor for RF ICs.
Spin-transfer torque random access memory (STT-RAM) has widely believed as a promising candidate for the post-silicon nonvolatile memory technology. In many recent researches, STT-RAM has demonstrated many attractive characteristics, such as nanosecond access time, high integration density, adjustable non-volatility, and good CMOS process compatibility. As the distinction between the two boundary resistance states of the magnetic tunnel junction (MTJ) device continues to improve, multi-level cell (MLC) STT-RAM emerges as an interesting technology to pursue. However, since the resistance margin is partitioned into multiple segments for multi-level data representation, the performance and reliability of MLC STT-RAM cells become more sensitive to the MOS and MTJ device variations, as well as the thermal-induced randomness of MTJ switching. In this work, we report our recent study on the reliability of the read/write operations of the stacking MLC STT-RAM cells by consider the different variability sources. Our simulation result shows that although the stacking MCL STT-RAM has not yet satisfy the requirement of commercial product under the realistic fabrication conditions, it has shown the great potentials under careful design optimizations.
Large-scale renewable energy in Jibei Grid is collected and sent out through the power transmission channel, and the installed capacity of renewable energy far exceeds the capacity of the channel.With the integration of large-scale renewable energy, the weak support of renewable energy power generation equipment makes the grid voltage support strength difficult to meet the needs of safe and stable operation. By configuring synchronous condensers, the voltage strength of the power grid can be effectively increased, but in power transmission channel planning and building, there is a lack of feasible synchronous condenser configuration methods. Based on the evaluation effect of multiple renewable energy stations short circuit ratio (MRSCR) on grid voltage support strength, considering the the limits of curtailment rate, this paper proposed a synchronous condenser optimized configuration scheme for renewable energy transmission channel.Combined with the calculation results of full electromagnetic simulation and electromechanical transient simulation of typical examples, it can be seen that the synchronous condenser configuration method proposed in this paper can effectively increase the grid voltage support strength and ensure the curtailment rate of the renewable energy transmission channel meeting the need of national requirement.
Sb2Se3 is an emerging material in recent years and past studies have shown that it has good optoelectronic properties when doped with metals. In this paper, pure Sb2Se3 films and Ni-Sb2Se3 films with different doping content (1 W, 2 W, 3 W) were prepared by magnetron sputtering technology. The nonlinear optics properties of the sample films were investigated using femtosecond(fs) Z-scan technology under 800 nm. The results showed that both pure Sb2Se3 and doped films exhibited reverse saturated absorption(RSA), and the occurrence of the reverse saturated absorption behaviour of the doped films was mainly due to two-photon absorption (TRA) and free carrier absorption (FCA)and the presence of defective energy levels. Compared with pure Sb2Se3 films, Ni-Sb2Se3 films exhibit significantly enhanced nonlinear absorption properties and nonlinear refractive properties. By increasing Ni sputtering power and incident laser energy, the nonlinear optic properties of Ni-Sb2Se3 films are enhanced. The crystallinity etc. of the films was also optimised by testing other representations.
Metal-insulator-metal (MIM) capacitors fabricated with (8%) La-doped HfO 2 single layer as well as HfLaO/ LaAlO 3 /HfLaO multilayer dielectric stack are demonstrated. While the La-doped HfO 2 single layer is crystallized at 420 ° C annealing, HfLaO/LaAlO 3 /HfLaO multilayer dielectric stack remains amorphous. A high dielectric-constant value of 38 can be obtained when 8% La-doped HfO 2 is crystallized into cubiclike structure. However, it is observed that the linearity of MIM capacitor is degraded upon crystallization. The multilayer film has lower average dielectric constant but shows low quadratic voltage linearity of less than 1000 ppm/V 2 up to a capacitance density of 9 fF/¿m 2 . It is observed that the HfLaO single-layer MIM is suitable for the applications with requirements of high capacitance density and robust reliability, while the multilayer MIM is suitable for a precision circuit.
To further extend the scaling trend of traditional CMOS technology, many hybrid architectures integrating emerging device technologies have been proposed recently. Among them, memristor based cross-point memory (MBCPM) demonstrates great potential in data storage and computation. However, accessing a cross-point memory inevitably induces currents flowing through those unselected cells, called as sneak paths. The existence of sneak paths severely limits the capacity growth of MBCPM. In this work, we proposes a pseudo-weight sensing scheme. The design minimizes the impact of sneak paths in read operations by forcing all the unselected rows and columns to the same potential. Moreover, we use an op-amp to sum up the weighted currents through multiple cells and retrieve their information at a time. Thus, the efficiency of read peripheral circuit is significantly enhanced.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)
'/%3e%3cuse xlink:href='%23a' transform='translate(288.889 -214.211)'/%3e%3cuse xlink:href='%23a' transform='translate(108 342.749)'/%3e%3cuse xlink:href='%23a' transform='translate(469.189 342.749)'/%3e%3c/svg%3e)