The limited lifespan is the Achilles＇ heel of solid state drives （SSDs） based on NAND flash.. NAND flash has two drawbacks that degrade SSDs＇ lifespan. One is the out-of-place update. Another is the sequential wri...The limited lifespan is the Achilles＇ heel of solid state drives （SSDs） based on NAND flash.. NAND flash has two drawbacks that degrade SSDs＇ lifespan. One is the out-of-place update. Another is the sequential write constraint within a block. SSDs usually employ write buffer to extend their lifetime. However, existing write buffer schemes only pay attention to the first drawback, while neglect the second one. We propose a hetero-buffer architecture covering both aspects simultaneously. The hetero-buffer consists of two components, dynamic random access memory （DRAM） and the reorder area. DRAM endeavors to reduce write traffic as much as possible by pursuing a higher hit ratio （overcome the first drawback）. The reorder area focuses on reordering write sequence （overcome the second drawback）. Our hetero-buffer outperforms traditional write buffers because of two reasons. First, the DRAM can adopt existing superior cache replacement policy, thus achieves higher hit ratio. Second, the hetero-buffer reorders the write sequence, which has not been exploited by traditional write buffers. Besides the optimizations mentioned above, our hetero-buffer considers the work environment of write buffer, which is also neglected by traditional write buffers. By this way, the hetero-buffer is further improved. The performance is evaluated via trace-driven simulations. Experimental results show that, SSDs employing the hetero-buffer survive longer lifespan on most workloads.展开更多
In copper oxide (CuO) based solar cells, various buffer layers such as CdS, In<sub>2</sub>S<sub>3</sub>, WS<sub>2</sub> and IGZO have been investigated by solar cell capacitance sim...In copper oxide (CuO) based solar cells, various buffer layers such as CdS, In<sub>2</sub>S<sub>3</sub>, WS<sub>2</sub> and IGZO have been investigated by solar cell capacitance simulator (SCAPS) in this work. By varying absorber and buffer layer thickness, photovoltaic parameters (open circuit voltage, fill factor, short-circuit current density and efficiency) are determined. The highest efficiency achieved is 19.6% with WS<sub>2</sub> buffer layer. The impact of temperature on all CuO-based solar cells is also investigated.展开更多
Copper indium gallium selenium （CIGS） thin film solar cells have become one of the hottest topics in solar energy due to their high photoelectric transformation efficiency. To real applications, CIGS thin film is co...Copper indium gallium selenium （CIGS） thin film solar cells have become one of the hottest topics in solar energy due to their high photoelectric transformation efficiency. To real applications, CIGS thin film is covered by the buffer layer and absorption layer. Traditionally, cadmium sulfide （CdS） is inserted into the middle of the window layer （ZnO） and absorption layer （CIGS） as a buffer layer. However, the application of the GIGS/CdS thin film solar cells has been limited because of the environmental pollution resulting from the toxic cadmium atom. Although zinc sulfide （ZnS） has been proposed to be one of the candidates, the performance of such battery cells has not been investigated. Here, in this paper, we systematically study the possibility of using zinc sulfide （ZnS） as a buffer layer. By including the effects of thickness, concentration of a buffer layer, intrinsic layer and the absorbing layer, we find that photoelectric transformation efficiency of ZnO/ZnS（n）/CIGS（i）/CIGS（p） solar cell is about 17.22%, which is qualified as a commercial solar cell. Moreover, we also find that the open-circuit voltage is -0.60 V, the short-circuit current is -36.99 mA/cm2 and the filled factor is -77.44%. Therefore, our results suggest that zinc sulfide may be the potential candidate of CdS as a buffer layer.展开更多
基金Supported by the National High Technology Research and Development 863 Program of China under Grant No.2013AA013201the National Natural Science Foundation of China under Grant Nos.61025009,61232003,61120106005,61170288
文摘The limited lifespan is the Achilles＇ heel of solid state drives （SSDs） based on NAND flash.. NAND flash has two drawbacks that degrade SSDs＇ lifespan. One is the out-of-place update. Another is the sequential write constraint within a block. SSDs usually employ write buffer to extend their lifetime. However, existing write buffer schemes only pay attention to the first drawback, while neglect the second one. We propose a hetero-buffer architecture covering both aspects simultaneously. The hetero-buffer consists of two components, dynamic random access memory （DRAM） and the reorder area. DRAM endeavors to reduce write traffic as much as possible by pursuing a higher hit ratio （overcome the first drawback）. The reorder area focuses on reordering write sequence （overcome the second drawback）. Our hetero-buffer outperforms traditional write buffers because of two reasons. First, the DRAM can adopt existing superior cache replacement policy, thus achieves higher hit ratio. Second, the hetero-buffer reorders the write sequence, which has not been exploited by traditional write buffers. Besides the optimizations mentioned above, our hetero-buffer considers the work environment of write buffer, which is also neglected by traditional write buffers. By this way, the hetero-buffer is further improved. The performance is evaluated via trace-driven simulations. Experimental results show that, SSDs employing the hetero-buffer survive longer lifespan on most workloads.
文摘In copper oxide (CuO) based solar cells, various buffer layers such as CdS, In<sub>2</sub>S<sub>3</sub>, WS<sub>2</sub> and IGZO have been investigated by solar cell capacitance simulator (SCAPS) in this work. By varying absorber and buffer layer thickness, photovoltaic parameters (open circuit voltage, fill factor, short-circuit current density and efficiency) are determined. The highest efficiency achieved is 19.6% with WS<sub>2</sub> buffer layer. The impact of temperature on all CuO-based solar cells is also investigated.
基金supported by the NSF of Jiangsu Province(No.BK.20131420)the Postgraduate Innovation Project of Jiangsu Province(No.KYLX15_0926)the NJFU Outstanding Young Scholars Funding
文摘Copper indium gallium selenium （CIGS） thin film solar cells have become one of the hottest topics in solar energy due to their high photoelectric transformation efficiency. To real applications, CIGS thin film is covered by the buffer layer and absorption layer. Traditionally, cadmium sulfide （CdS） is inserted into the middle of the window layer （ZnO） and absorption layer （CIGS） as a buffer layer. However, the application of the GIGS/CdS thin film solar cells has been limited because of the environmental pollution resulting from the toxic cadmium atom. Although zinc sulfide （ZnS） has been proposed to be one of the candidates, the performance of such battery cells has not been investigated. Here, in this paper, we systematically study the possibility of using zinc sulfide （ZnS） as a buffer layer. By including the effects of thickness, concentration of a buffer layer, intrinsic layer and the absorbing layer, we find that photoelectric transformation efficiency of ZnO/ZnS（n）/CIGS（i）/CIGS（p） solar cell is about 17.22%, which is qualified as a commercial solar cell. Moreover, we also find that the open-circuit voltage is -0.60 V, the short-circuit current is -36.99 mA/cm2 and the filled factor is -77.44%. Therefore, our results suggest that zinc sulfide may be the potential candidate of CdS as a buffer layer.
