The demand for high-performance embedded processors in multimedia mobile electronics is growing and their power consumption thus increasingly threatens battery lifetime. It is usually believed that the dynamic voltage...The demand for high-performance embedded processors in multimedia mobile electronics is growing and their power consumption thus increasingly threatens battery lifetime. It is usually believed that the dynamic voltage and frequency scaling （DVFS） feature saves significant energy by changing the performance levels of processors to match the performance demands of applications on the fly. However, because the energy efficiency of embedded processors is rapidly improving, the effectiveness of DVFS is expected to change. In this paper, we analyze the benefit of DVFS in state-of-the-art mobile embedded platforms in comparison to those in servers or PCs. To obtain a clearer view of the relationship between power and performance, we develop a measurement methodology that can synchronize time series for power consumption with those for processor utilization. The results show that DVFS hardly improves the energy efficiency of mobile multimedia electronics, and can even significantly worsen energy efficiency and performance in some cases. According to this observation, we suggest that power management for mobile electronics should concentrate on adaptive and intelligent power management for peripherM devices. As a preliminary design, we implement an adaptive network interface card （NIC） speed control that reduces power consumption by 1070 when NIC is not heavily used. Our results provide valuable insights into the design of power management schemes for future mobile embedded systems.展开更多
The light extraction efficiencies have been calculated for various InGaN/GaN multiple quantum well nanostructure light-emitting diodes including nanopillar, nanorough of P-CaN surface, coreshell and nano-interlayer st...The light extraction efficiencies have been calculated for various InGaN/GaN multiple quantum well nanostructure light-emitting diodes including nanopillar, nanorough of P-CaN surface, coreshell and nano-interlayer structure. From the calculated results we can see that the light extraction efficiency is remarkably improved in the nanostructures, especially those with an InGaN or AlCaN nano-interlayer. With a 420-nm luminescence wavelength, the light extraction efficiency can reach as high as 65% for the InGaN or AlGaN nano-interlayer structure with appropriate In or Al content while only 26% for the planar structure.展开更多
基金supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology under Grant Nos. 2009-0089491, 2010-0003453
文摘The demand for high-performance embedded processors in multimedia mobile electronics is growing and their power consumption thus increasingly threatens battery lifetime. It is usually believed that the dynamic voltage and frequency scaling （DVFS） feature saves significant energy by changing the performance levels of processors to match the performance demands of applications on the fly. However, because the energy efficiency of embedded processors is rapidly improving, the effectiveness of DVFS is expected to change. In this paper, we analyze the benefit of DVFS in state-of-the-art mobile embedded platforms in comparison to those in servers or PCs. To obtain a clearer view of the relationship between power and performance, we develop a measurement methodology that can synchronize time series for power consumption with those for processor utilization. The results show that DVFS hardly improves the energy efficiency of mobile multimedia electronics, and can even significantly worsen energy efficiency and performance in some cases. According to this observation, we suggest that power management for mobile electronics should concentrate on adaptive and intelligent power management for peripherM devices. As a preliminary design, we implement an adaptive network interface card （NIC） speed control that reduces power consumption by 1070 when NIC is not heavily used. Our results provide valuable insights into the design of power management schemes for future mobile embedded systems.
基金Project supported by the National Science Fund for Distinguished Young Scholars of China (Grant No.60925017)the National Natural Science Foundation of China (Grant Nos.10990100 and 60836003)+2 种基金the National Basic Research Program of China (Grant No.2007CB936700)the National High Technology Research and Development Program of China (Grant No.2007AA03Z401)the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No.ISCAS2009T05O9S4050000)
文摘The light extraction efficiencies have been calculated for various InGaN/GaN multiple quantum well nanostructure light-emitting diodes including nanopillar, nanorough of P-CaN surface, coreshell and nano-interlayer structure. From the calculated results we can see that the light extraction efficiency is remarkably improved in the nanostructures, especially those with an InGaN or AlCaN nano-interlayer. With a 420-nm luminescence wavelength, the light extraction efficiency can reach as high as 65% for the InGaN or AlGaN nano-interlayer structure with appropriate In or Al content while only 26% for the planar structure.
