Virtual memory management is always a very essential issue of the modern microprocessor design. A memory management unit (MMU) is designed to implement a virtual machine for user programs, and provides a management me...Virtual memory management is always a very essential issue of the modern microprocessor design. A memory management unit (MMU) is designed to implement a virtual machine for user programs, and provides a management mechanism between the operating system and user programs. This paper analyzes the tradeoffs considered in the MMU design of Unity 11 CPU of Peking University, and introduces in detail the solution of pure hardware table walking with two level page table organization. The implementation takes care of required operations and high performances needed by modern operating systems and low costs needed by embedded systems. This solution has been silicon proven, and successfully porting the Linux 2.4.17 kernel, the XWindow system, GNOME and most application software onto the Unity platform.展开更多
In this study, we provided more theoretical method for estimation of dissolution amount and applied this method to enhanced coalbed methane recovery （ECBMR） simulator. Dissolution amount was measured by method of di...In this study, we provided more theoretical method for estimation of dissolution amount and applied this method to enhanced coalbed methane recovery （ECBMR） simulator. Dissolution amount was measured by method of differential heat of adsorption. Akabira coal, a Japanese bituminous coal, was used for the experiment. The results showed that CO2 was stored in coal by both adsorption and dissolution. Using this result the methane production was calculated by ECBMR-simulator, enhanced coalbed methane recovery simulator, the University of Tokyo （ECOMERS-UT）. Total stored CO2 was separated into adsorption component and dissolution component. Only the former component contributes to the competitive adsorption. Coalbed methane （CBM） production simulation considering the dissolution showed later and smaller peak production and prolonged methane production before the breakthrough than the conventional competitive adsorption.展开更多
The rapid consumption of fossil fuels has caused increasingly climatic issues and energy crisis,which leads to the urgent demand for developing sustainable and clean energies.Electrocatalysts play a key role in the de...The rapid consumption of fossil fuels has caused increasingly climatic issues and energy crisis,which leads to the urgent demand for developing sustainable and clean energies.Electrocatalysts play a key role in the development of electrochemical energy conversion and storage devices.Especially,developing efficient and cost-effective catalysts is important for the large-scale application of these devices.Among various electrocatalyst candidates,earth abundant transition metal compound(TMC)-based electrocatalysts are being widely and rapidly studied owing to their high electrocatalytic performances.This paper reviews the recent and representative advances in efficient TMC-based electrocatalysts(i.e.,oxides,sulfides,selenides,phosphides,carbides and nitrides)for energy electrocatalytic reactions,including hydrogen evolution reaction(HER),oxygen evolution reaction(OER)and oxygen reduction reaction(ORR).Different compounds with different applications are summarized and the relative mechanisms are also discussed.The strategies for developing earth-abundant and low-cost TMC-based electrocatalysts are introduced.In the end,the current challenges and future perspectives in the development of TMC research are briefly discussed.This review also provides the latest advance and outlines the frontiers in TMC-based electrocatalysts,which should provide inspirations for the further development of low-cost and high-efficiency catalysts for sustainable clean energy technologies.展开更多
Patterned ferromagnetic thin film shows promising applications in ultra-high density magnetic storage,magnetoresistive transducer,magnetic random access memory and many other devices.Since the performance of these dev...Patterned ferromagnetic thin film shows promising applications in ultra-high density magnetic storage,magnetoresistive transducer,magnetic random access memory and many other devices.Since the performance of these devices is closely associated with the magnetic properties of the etched patterns,it is necessary to study the effects of freshly etched surface oxidation on the magnetic properties of the patterned microstructures.In the current work,were carried out an X-ray Magnetic Circular Dichroism(XMCD) study on a 50 nm Co 0.9 Fe 0.1 continuous thin film and a related patterned Co 0.9 Fe 0.1 grating structure etched with a 2 μm period.Based on the sum rules,the spin and orbital moments were calculated for these two samples,respectively.The results indicated that the spin and orbital moments of grating structure(1.34μ B and 0.24μ B,respectively) decreased 17.3% compared with the corresponding continuous film(1.62μ B and 0.29μ B,respectively).We proposed that the moment decreasing of the patterned grating structure was mainly caused by the etched surface oxidation during the pattern manufacture process.The oxidation ratio of Co element in the patterned grating structure is 14.4% calculated from X-ray absorption spectroscopy(XAS) measurement.Considering the oxidation ratio,we amend the spin and orbital moment of Co and the amended result is basically in accordance with that of continuous film,demonstrating that the difference of the spin and orbital moments between the sub-micron grating unit and the continuous film is really caused by the oxidation.展开更多
文摘Virtual memory management is always a very essential issue of the modern microprocessor design. A memory management unit (MMU) is designed to implement a virtual machine for user programs, and provides a management mechanism between the operating system and user programs. This paper analyzes the tradeoffs considered in the MMU design of Unity 11 CPU of Peking University, and introduces in detail the solution of pure hardware table walking with two level page table organization. The implementation takes care of required operations and high performances needed by modern operating systems and low costs needed by embedded systems. This solution has been silicon proven, and successfully porting the Linux 2.4.17 kernel, the XWindow system, GNOME and most application software onto the Unity platform.
文摘In this study, we provided more theoretical method for estimation of dissolution amount and applied this method to enhanced coalbed methane recovery （ECBMR） simulator. Dissolution amount was measured by method of differential heat of adsorption. Akabira coal, a Japanese bituminous coal, was used for the experiment. The results showed that CO2 was stored in coal by both adsorption and dissolution. Using this result the methane production was calculated by ECBMR-simulator, enhanced coalbed methane recovery simulator, the University of Tokyo （ECOMERS-UT）. Total stored CO2 was separated into adsorption component and dissolution component. Only the former component contributes to the competitive adsorption. Coalbed methane （CBM） production simulation considering the dissolution showed later and smaller peak production and prolonged methane production before the breakthrough than the conventional competitive adsorption.
基金supported by the National Natural Science Foundation of China(51804216 and 51972224)the Young Elite Scientists Sponsorship Program by CAST(2018QNRC001)+1 种基金Tianjin Natural Science Foundation(17JCQNJC02100)support from China Postdoctoral Science Foundation(2019M661014)。
文摘The rapid consumption of fossil fuels has caused increasingly climatic issues and energy crisis,which leads to the urgent demand for developing sustainable and clean energies.Electrocatalysts play a key role in the development of electrochemical energy conversion and storage devices.Especially,developing efficient and cost-effective catalysts is important for the large-scale application of these devices.Among various electrocatalyst candidates,earth abundant transition metal compound(TMC)-based electrocatalysts are being widely and rapidly studied owing to their high electrocatalytic performances.This paper reviews the recent and representative advances in efficient TMC-based electrocatalysts(i.e.,oxides,sulfides,selenides,phosphides,carbides and nitrides)for energy electrocatalytic reactions,including hydrogen evolution reaction(HER),oxygen evolution reaction(OER)and oxygen reduction reaction(ORR).Different compounds with different applications are summarized and the relative mechanisms are also discussed.The strategies for developing earth-abundant and low-cost TMC-based electrocatalysts are introduced.In the end,the current challenges and future perspectives in the development of TMC research are briefly discussed.This review also provides the latest advance and outlines the frontiers in TMC-based electrocatalysts,which should provide inspirations for the further development of low-cost and high-efficiency catalysts for sustainable clean energy technologies.
基金supported by the National Natural Science Foundation of China (Grant No. 10274073)the Post-doctoral Research Start-up Funding of Anhui University of Architecture (Grant No. K02553)the Open Project of Building Energy Conservation Institute of Anhui University of Architecture (Grant No. K02592)
文摘Patterned ferromagnetic thin film shows promising applications in ultra-high density magnetic storage,magnetoresistive transducer,magnetic random access memory and many other devices.Since the performance of these devices is closely associated with the magnetic properties of the etched patterns,it is necessary to study the effects of freshly etched surface oxidation on the magnetic properties of the patterned microstructures.In the current work,were carried out an X-ray Magnetic Circular Dichroism(XMCD) study on a 50 nm Co 0.9 Fe 0.1 continuous thin film and a related patterned Co 0.9 Fe 0.1 grating structure etched with a 2 μm period.Based on the sum rules,the spin and orbital moments were calculated for these two samples,respectively.The results indicated that the spin and orbital moments of grating structure(1.34μ B and 0.24μ B,respectively) decreased 17.3% compared with the corresponding continuous film(1.62μ B and 0.29μ B,respectively).We proposed that the moment decreasing of the patterned grating structure was mainly caused by the etched surface oxidation during the pattern manufacture process.The oxidation ratio of Co element in the patterned grating structure is 14.4% calculated from X-ray absorption spectroscopy(XAS) measurement.Considering the oxidation ratio,we amend the spin and orbital moment of Co and the amended result is basically in accordance with that of continuous film,demonstrating that the difference of the spin and orbital moments between the sub-micron grating unit and the continuous film is really caused by the oxidation.
