Yun-Hap Song

Network reconfiguration for loss reduction in distribution systems is a very important way to save energy. However, due to its nature it is an inherently difficult optimisation problem. A new type of evolutionary search technique, evolutionary programming (EP), has been adopted and improved for this particular application. To improve the performance of EP, a fuzzy controlled EP (FCEP), based on heuristic information, is first proposed. The mutation fuzzy controller adaptively adjusts the mutatio

ABSTRACT This paper presents a new genetic approach for solving combined heat and power (CHP) economic dispatch problems. The complication of CHP dispatch lies in the constraints imposed by the multi-demand and heat-power capacity mutual dependencies. The paper proposes improved penalty function formulation for Genetic Algorithms (GAs) to effectively handle constraints. The method has been tested and compared to demonstrate its effectiveness

Computational efficiency and reliability are the major concerns in the application of genetic algorithms (GAS) to practical problems. Effort has been made in two directions to improve the performance of GAs: the investigation of advanced genetic operators and the development of genetic algorithm hybrids. In this paper, an advanced engineered-conditioning genetic algorithm hybrid (AEC-GA) is proposed, which is a combination strategy involving local search algorithms and genetic algorithms. Moreov

The paper presents a neural network based method for the identification of voltage-weak buses/areas. By using power flow analysis and the singular value decomposition method, a Kohonen neural network is trained to cluster/rank buses in terms of voltage stability. Special emphasis is placed on the selection of input information and analysis of the neural network output results. The generalisation capability of the Kohonen network under various operating conditions has been tested on a number of s

We propose a bilateral switching poly-Si junction device to realize a crossbar array with a perpendicular spin-transfer torque (STT) magnetic random access memory (MRAM). An N <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> /P/N <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> bilateral junction device with two bias terminals provides bidirectional current flow enough to write STT MRAM by

We present an investigation of the program and erase speed characteristics of three-dimensional (3D) gate-all-around (GAA) metal–oxide–SiN X –oxide–silicon (MONOS) cells. The effect of the tunneling oxide layer thickness in 3D GAA MONOS cells has been experimentally investigated and studied by 3D technology computer-aided design (TCAD) simulation. In particular, we considered physical parameters such as trap density, capture cross section, and trap level in order to analyze the physical properti

The effects of residual stress on a tungsten gate in a polysilicon channel in scaled 3D NAND flash memories were investigated using a technology computer-aided design simulation. The NAND strings, with respect to the distance from the tungsten slit, were also analyzed. The scaling of the spacer thickness and hole diameter induced compressive stress on the polysilicon channel. Moreover, the residual stress of polysilicon channel in the string near the tungsten slit had greater compressive stress

In this paper, we investigated the cell-to-cell interference in scaled-down 3D NAND flash memory by using a Technology Computer-Aided Design (TCAD) simulation. The fundamental cause of cell-to-cell interference is that the electric field crowding point is changed by the programmed adjacent cell so that the electric field is not sufficiently directed to the channel surface. Therefore, the channel concentration of the selected cell is changed, leading to a Vth shift. Furthermore, this phenomenon o

In this work, we present the results of an investigation of the impact of the stress on a poly-silicon channel induced by the neighboring layers in three-dimensional vertical NAND (3D V-NAND) flash memories. Using 3D process simulations, we confirmed the distributions of the residual stress after each process step in the cross-section of a NAND flash unit cell. To investigate the impact of the stress on the poly-silicon channel, we also studied the residual stress after changing the intrinsic st

We investigated the program and reliability characteristics of convex and concave structures for advanced 3-D NAND flash memory. The program characteristics of the convex structure included confined trapped charge distribution due to the concentration of the electric field in the word line (WL) region, leading to better characteristics than the conventional structure. On the other hand, the electric field of the concave structure was dispersed, and intercell trapped charge in the spacer region o

Temperature dependence of the reliability characteristics of magnetic tunnel junctions (MTJs) with a thin (∼1 nm thick) MgO dielectric film were investigated by numerical analyses based on the E-model, 1/E-model, and power-law voltage V-model, as well as by measuring time-dependent dielectric breakdown (TDDB) degradation. Although the tunneling process giving rise to TDDB is still under debate, the temperature dependence of TDDB was much weaker using the 1/E model than the E-model or power-law m

Time-dependent dielectric breakdown (TDDB), which is used to measure reliability, depends on both the thickness of the tunnel barrier and bias voltage. In addition, the heat generated by self-heating in a magnetic tunneling junction (MTJ) affects TDDB. Therefore, we investigated TDDB with the self-heating effect for a MgO tunnel barrier with thicknesses of 1.1 and 1.2 nm by the constant voltage stress (CVS) method. Using the results of this experiment, we predicted a TDDB of 1.0 nm for the tunne

The stress‐induced resistance drift in MgO‐based magnetic tunnel junctions (MTJs) with Mg insertion layer above and below a MgO tunnel barrier is investigated. Mg insertion suppresses the resistance drift. Resistance drift characteristics are improved when electrons tunnel into the Mg‐inserted barrier–electrode interface, indicating that Mg insertion significantly suppresses trap site formation at the anode‐side barrier–electrode interface. However, transmission electron microscopy images confir