An 8-Gb multi-level NAND Flash memory with 4-level programmed cells has been developed successfully. The cost-effective small chip has been fabricated in 70-nm CMOS technology. To decrease the chip size, a one-sided pad arrangement with compacted core architecture and a block address expansion scheme without block redundancy replacement have been introduced. With these methods, the chip size has been reduced to 146 mm/sup 2/, which is 4.9% smaller than the conventional chip. In terms of performance, the program throughput reaches 6 MB/s at 4-KB page operation, which is significantly faster than previously reported and very competitive with binary Flash memories. This high performance has been achieved by the combination of the multi-level cell (MLC) programming with write caches and with the program voltage compensation technique for neighboring select transistors. The read throughput reaches 60 MB/s using 16I/O configuration. 相似文献
In this study, the Al-1.9 wt.% Fe alloy was directionally solidified at different growth velocities under various high magnetic fields. The effect of high magnetic fields on microstructural evolution of the alloys during directional solidification and their dependence on the growth velocity were investigated. The microstructures near the transition growth regions of the alloys between two different growth velocities were observed. With increasing growth velocity, the microstructure exhibited a eutectic to cellular eutectic to hypoeutectic structure transformation. Applying high magnetic fields increased the spacing of the eutectic Al3Fe phase and decreased the alignment degree of the eutectic Al3Fe phase at 1 µm/s, decreased the size of the eutectic cells at 10 µm/s, and promoted development and branching of the primary Al dendrites at 100 µm/s. Near the transition growth region, applying high magnetic fields stopped the growth of existing eutectic Al3Fe and promoted nucleation of the new eutectic Al3Fe phase for 1–10 μm/s, and accelerated transformation of the growth behavior from cellular eutectic to hypoeutectic for 10–100 μm/s. The evolution of the eutectic growth behavior caused by the high magnetic fields can be attributed to suppression of convection and the corresponding decrease in solute migration owing to the Lorentz force.
The purpose of this paper is to propose an effective solution scheme of simultaneous optimization design of layup configuration and fiber distribution for maximum stiffness design of laminated plates. Firstly, a numerical analysis of the lamination parameters feasible region for a laminated plate consisting of various given number of ply groups (each ply group may have different thickness and all the fibers in one ply group are orientated in an identical direction) is carried out, and it is found that the feasible region based on only a few ply groups is very close to the overall one determined by infinite plies. Therefore, it is suggested that the feasible region of lamination parameters of a laminated plate could be approximately determined by the layup configuration of least ply groups. Secondly, a two-step simultaneous optimization scheme of layup configuration and fiber distribution for maximum stiffness design of laminated plates is proposed. Accordingly, by using ply thickness, fiber orientation angle and fiber volume fraction in a laminated plate of least ply groups as design variables, the optimal lamination parameters for maximum stiffness is obtained. Then, taking the optimal lamination parameters as the design objective, a detailed layup design optimization is implemented by considering some limitations on manufacturing, such as preset ply thickness, and specific fiber orientation angle and a limited maximum number of consecutive plies in the same fiber orientation. Numerical examples are also presented to validate the proposed two-step optimization scheme. 相似文献
Uniformity of change in catalyst activity during a multi-pulse TAP experiment with porous catalyst was theoretically analyzed for a TAP reactor with the ratio of the catalyst bed thickness to the reactor length of 1/30. The analysis was performed by simulation of an irreversible adsorption process. The catalyst change is described by the change in the occupied/unoccupied fractional surface coverages. The intraparticle uniformity is indicated by a small magnitude of Δθp,max, the maximum difference between the occupied fractional surface coverages at the outermost and the innermost of the catalyst pellet during the multi-pulse experiment. In the interparticle region, the indicating quantity is Δθb,max, the maximum difference between the pellet-outermost fractional surface coverages at the inlet and the outlet of the catalyst bed. It was found that Δθp,max generally depends only on the effectiveness factor in the first pulse experiment, η. For η ≥ 0.94, Δθp,max ≤ 0.05. In addition, Δθb,max depends only on the gas conversion in the first pulse experiment, X. For X ≤ 0.7, Δθb,max ≤ 0.05. 相似文献