The burst error of wireless channels and the two-state Markov wireless model are analyzed. Based on this model and the coding modes of the video encoder,the channel distortion of inter-coding and intra-coding due to b...The burst error of wireless channels and the two-state Markov wireless model are analyzed. Based on this model and the coding modes of the video encoder,the channel distortion of inter-coding and intra-coding due to burst error is deduced. Then we propose a novel intra refresh scheme in rate-distortion (R-D) framework. This scheme optimizes the error resilience and coding efficiency of wireless video transmission system. It can also stop error propagation and reduce channel distortion effectively. Simulations under different channel conditions verify the improvements of the proposed scheme with respect to error resilience for wireless video communication.展开更多
A dual-resolution（DR） version of a regional ensemble Kalman filter（EnKF）-3D ensemble variational（3DEnVar） coupled hybrid data assimilation system is implemented as a prototype for the operational Rapid Refresh f...A dual-resolution（DR） version of a regional ensemble Kalman filter（EnKF）-3D ensemble variational（3DEnVar） coupled hybrid data assimilation system is implemented as a prototype for the operational Rapid Refresh forecasting system. The DR 3DEnVar system combines a high-resolution（HR） deterministic background forecast with lower-resolution（LR） EnKF ensemble perturbations used for flow-dependent background error covariance to produce a HR analysis. The computational cost is substantially reduced by running the ensemble forecasts and EnKF analyses at LR. The DR 3DEnVar system is tested with 3-h cycles over a 9-day period using a 40/13-km grid spacing combination. The HR forecasts from the DR hybrid analyses are compared with forecasts launched from HR Gridpoint Statistical Interpolation（GSI） 3D variational（3DVar）analyses, and single LR hybrid analyses interpolated to the HR grid. With the DR 3DEnVar system, a 90% weight for the ensemble covariance yields the lowest forecast errors and the DR hybrid system clearly outperforms the HR GSI 3DVar.Humidity and wind forecasts are also better than those launched from interpolated LR hybrid analyses, but the temperature forecasts are slightly worse. The humidity forecasts are improved most. For precipitation forecasts, the DR 3DEnVar always outperforms HR GSI 3DVar. It also outperforms the LR 3DEnVar, except for the initial forecast period and lower thresholds.展开更多
The paper presents the research results of using an innovative method to reclaim the waste moulding sands containing water glass. Two of the examined processes are connected with "dry" or "wet" act...The paper presents the research results of using an innovative method to reclaim the waste moulding sands containing water glass. Two of the examined processes are connected with "dry" or "wet" activation of inorganic binder in waste moulding sand mixtures physically hardened by microwave radiation. The sand mixtures consisting of high-silica sand and water-glass with average molar module 2.5, were subjected to the following cyclical process: mixing the components, compacting, microwave heating, cooling-down, thermally loading the mould to 800 °C, cooling-down to ambient temperature, and knocking-out. After being knocked-out, the waste moulding sands were subjected to either dry or wet activation of the binder. To activate thermally treated inorganic binder, each of the examined processes employed the surface phenomenon usually associated to mechanical reclamation. The study also covered possible use of some elements of wet reclamation to rehydrate waste binder. To evaluate the effectiveness of the two proposed methods of waste binder activation, selected strength and technological parameters were measured. After each subsequent processing cycle, the permeability, tensile strength and bending strength were determined. In addition, the surface of activated sand grains was examined with a scanning electron microscope. Analysis of the results indicates that it is possible to re-activate the used binder such as sodium silicate, and to stabilize the strength parameters in both activation processes. Permeability of the refreshed moulding sands strongly depends on the surface condition of high-silica grains. The wet activation process by wetting and buffering knocked-out moulding sands in closed humid environment makes it possible to reduce the content of refreshing additive in water-glass. The moulding sands cyclically prepared in both processes do not require the addition of fresh high-silica sand. The relatively high quality achieved in the refreshed moulding sands allows them to be reused for manufacture of next moulds. Thus, the two proposed methods for cyclically processing used moulding sands containing sodium silicate, subject to microwave hardening, are suitable for economic and ecological circulation moulding mixtures.展开更多
The partial cycle(PC)strategy has been used in many rapid refresh cycle systems(RRC)for regional short-range weather forecasting.Since the strategy periodically reinitializes the regional model(RM)from the global mode...The partial cycle(PC)strategy has been used in many rapid refresh cycle systems(RRC)for regional short-range weather forecasting.Since the strategy periodically reinitializes the regional model(RM)from the global model(GM)forecasts to correct the large-scale drift,it has replaced the traditional full cycle(FC)strategy in many RRC systems.However,the extra spin-up in the PC strategy increases the computer burden on RRC and generates discontinuous smallscale systems among cycles.This study returns to the FC strategy but with initial fields generated by dynamic blending(DB)and data assimilation(DA).The DB ingests the time-varied large-scale information from the GM to the RM to generate less-biased background fields.Then the DA is performed.We applied the new FC strategy in a series of 7-day batch forecasts with the 3-hour cycle in July 2018,and February,April,and October 2019 over China using a Weather Research and Forecast(WRF)model-based RRC.A comparison shows that the new FC strategy results in less model bias than the PC strategy in most state variables and improves the forecast skills for moderate and light precipitation.The new FC strategy also allows the model to reach a balanced state earlier and gives favorable forecast continuity between adjacent cycles.Hence,this new FC strategy has potential to be applied in RRC forecast systems to replace the currently used PC strategy.展开更多
The recently reported quasi-nonvolatile memory based on semi-floating gate architecture has attracted extensive attention thanks to its potential to bridge the large gap between volatile and nonvolatile memory.However...The recently reported quasi-nonvolatile memory based on semi-floating gate architecture has attracted extensive attention thanks to its potential to bridge the large gap between volatile and nonvolatile memory.However,the further extension of the refresh time in quasi-nonvolatile memory is limited by the charge leakage through the p-n junction.Here,based on the density of states engineered van der Waals heterostructures,the leakage of electrons from the floating gate to the channel is greatly suppressed.As a result,the refresh time is effectively extended to more than 100 s,which is the longest among all previously reported quasi-nonvolatile memories.This work provides a new idea to enhance the refresh time of quasi-nonvolatile memory by the density of states engineering and demonstrates great application potential for high-speed and low-power memory technology.展开更多
For video streaming over lossy channels, intra refresh can mitigate the error-propagation effect caused by packet losses Besides some intra-mode macroblocks （MBs） generated by the ＂Lagrangian rate-distortion＂ or ...For video streaming over lossy channels, intra refresh can mitigate the error-propagation effect caused by packet losses Besides some intra-mode macroblocks （MBs） generated by the ＂Lagrangian rate-distortion＂ or ＂Sum of absolute difference＂ mode decision, the encoder or transcoder possibly needs to increase some ＂forced＂ intra-mode MBs for robust video streaming. Based on the error-propagation analysis in a group of pictures （GOP）, we propose an unequal Forced-Intra-Refresh （FIR） scheme to improve packet loss resilience of video streaming. According to a GOP-level error-propagation model, the proposed unequal FIR scheme can optimally increase the unequal number of forced intra-mode MBs for different frames in a GOP. Simulation results showed that the proposed scheme can effectively enhance the robustness of video streaming under different channel conditions, and achieve about 0. 1-0.9 dB gains over the average FIR scheme in H.264/AVC tools.展开更多
<正> Like most July days,it was hot. I stepped into a tiny ice-cream shop to cool off with a chocolate sundae. It was an old-time store, just recently restored—~* with white oak wood-work,little round tables an...<正> Like most July days,it was hot. I stepped into a tiny ice-cream shop to cool off with a chocolate sundae. It was an old-time store, just recently restored—~* with white oak wood-work,little round tables and curlicue chairs.As I entered, 1 caught a glimpse of a very old woman bentover a table near the door.~* Her back was so badly twisted展开更多
在第四代迅驰平台Sonta Rosa发布八个月之后,名为Sonta Rosa Refresh的平台正式于2008年1月8日发布。正如人们之前预料的那样,它在保持芯片组和无线模块等组件不变的基础上,将基于第五代迅驰平台(Montevina),代号为Penryn的45纳米处理...在第四代迅驰平台Sonta Rosa发布八个月之后,名为Sonta Rosa Refresh的平台正式于2008年1月8日发布。正如人们之前预料的那样,它在保持芯片组和无线模块等组件不变的基础上,将基于第五代迅驰平台(Montevina),代号为Penryn的45纳米处理器提前应用到现有平台当中。那么,新规格的Penryn处理器有哪些优化设计? Penryn处理器的加入能给迅驰平台带来多大的性能提升?Santa Rosa Refresh平台体现在游戏上又有怎么样的表现呢?展开更多
目的探讨以问题为基础的教学法(problem based learning,PBL)联合以案例为基础的教学法(case based learning,CBL)在儿童肺功能专科进修培训中的应用效果。方法以2020年1月—2022年12月25名在四川大学华西第二医院肺功能专科的进修人员...目的探讨以问题为基础的教学法(problem based learning,PBL)联合以案例为基础的教学法(case based learning,CBL)在儿童肺功能专科进修培训中的应用效果。方法以2020年1月—2022年12月25名在四川大学华西第二医院肺功能专科的进修人员为调查对象,应用PBL联合CBL教学法,比较进修前后的理论知识与实际操作水平、胜任力水平,并调查进修人员对培训的满意度。结果经过一段时间理论和实践的培训,进修人员理论知识和实践技能操作水平以及胜任力水平较进修前均得到较大提升,培训前理论知识水平、实际操作和胜任力水平评分分别为(22.48±9.52)分、(15.40±5.97)分和(21.04±6.47)分,培训后理论知识水平、实际操作和胜任力水平评分分别为(75.00±24.00)分、(58.84±19.44)分和(65.32±17.39)分,培训前后差异有统计学意义(P<0.05)。肺功能检测进修人员对肺功能检测室整体工作环境比较满意。结论在PBL联合CBL教学法模式下,进修人员的理论知识与实际操作水平均有不同程度的提高,胜任力水平有较大提升,PBL联合CBL教学法可有效提高肺功能专科进修培训效果,肺功能检测应不断规范培训流程,完善肺功能检测进修体系,提升肺功能检测进修人员综合素质与学习满意度。展开更多
文摘The burst error of wireless channels and the two-state Markov wireless model are analyzed. Based on this model and the coding modes of the video encoder,the channel distortion of inter-coding and intra-coding due to burst error is deduced. Then we propose a novel intra refresh scheme in rate-distortion (R-D) framework. This scheme optimizes the error resilience and coding efficiency of wireless video transmission system. It can also stop error propagation and reduce channel distortion effectively. Simulations under different channel conditions verify the improvements of the proposed scheme with respect to error resilience for wireless video communication.
基金supported by the National Natural Science Foundation of China (Grant Nos.41730965,41775099 and 2017YFC1502104)PAPD (the Priority Academic Program Development of Jiangsu Higher Education Institutions)
文摘A dual-resolution（DR） version of a regional ensemble Kalman filter（EnKF）-3D ensemble variational（3DEnVar） coupled hybrid data assimilation system is implemented as a prototype for the operational Rapid Refresh forecasting system. The DR 3DEnVar system combines a high-resolution（HR） deterministic background forecast with lower-resolution（LR） EnKF ensemble perturbations used for flow-dependent background error covariance to produce a HR analysis. The computational cost is substantially reduced by running the ensemble forecasts and EnKF analyses at LR. The DR 3DEnVar system is tested with 3-h cycles over a 9-day period using a 40/13-km grid spacing combination. The HR forecasts from the DR hybrid analyses are compared with forecasts launched from HR Gridpoint Statistical Interpolation（GSI） 3D variational（3DVar）analyses, and single LR hybrid analyses interpolated to the HR grid. With the DR 3DEnVar system, a 90% weight for the ensemble covariance yields the lowest forecast errors and the DR hybrid system clearly outperforms the HR GSI 3DVar.Humidity and wind forecasts are also better than those launched from interpolated LR hybrid analyses, but the temperature forecasts are slightly worse. The humidity forecasts are improved most. For precipitation forecasts, the DR 3DEnVar always outperforms HR GSI 3DVar. It also outperforms the LR 3DEnVar, except for the initial forecast period and lower thresholds.
基金co-financed by the European Union within the European Social Fund in the project"Mloda Kadra 2015+"
文摘The paper presents the research results of using an innovative method to reclaim the waste moulding sands containing water glass. Two of the examined processes are connected with "dry" or "wet" activation of inorganic binder in waste moulding sand mixtures physically hardened by microwave radiation. The sand mixtures consisting of high-silica sand and water-glass with average molar module 2.5, were subjected to the following cyclical process: mixing the components, compacting, microwave heating, cooling-down, thermally loading the mould to 800 °C, cooling-down to ambient temperature, and knocking-out. After being knocked-out, the waste moulding sands were subjected to either dry or wet activation of the binder. To activate thermally treated inorganic binder, each of the examined processes employed the surface phenomenon usually associated to mechanical reclamation. The study also covered possible use of some elements of wet reclamation to rehydrate waste binder. To evaluate the effectiveness of the two proposed methods of waste binder activation, selected strength and technological parameters were measured. After each subsequent processing cycle, the permeability, tensile strength and bending strength were determined. In addition, the surface of activated sand grains was examined with a scanning electron microscope. Analysis of the results indicates that it is possible to re-activate the used binder such as sodium silicate, and to stabilize the strength parameters in both activation processes. Permeability of the refreshed moulding sands strongly depends on the surface condition of high-silica grains. The wet activation process by wetting and buffering knocked-out moulding sands in closed humid environment makes it possible to reduce the content of refreshing additive in water-glass. The moulding sands cyclically prepared in both processes do not require the addition of fresh high-silica sand. The relatively high quality achieved in the refreshed moulding sands allows them to be reused for manufacture of next moulds. Thus, the two proposed methods for cyclically processing used moulding sands containing sodium silicate, subject to microwave hardening, are suitable for economic and ecological circulation moulding mixtures.
基金the two anonymous reviewers.This work is supported by the National Key R&D Program of China(2018YFC1506803,2019YFB2102901)National Natural Science Foundation of China(Grant 41705135,41790474).
文摘The partial cycle(PC)strategy has been used in many rapid refresh cycle systems(RRC)for regional short-range weather forecasting.Since the strategy periodically reinitializes the regional model(RM)from the global model(GM)forecasts to correct the large-scale drift,it has replaced the traditional full cycle(FC)strategy in many RRC systems.However,the extra spin-up in the PC strategy increases the computer burden on RRC and generates discontinuous smallscale systems among cycles.This study returns to the FC strategy but with initial fields generated by dynamic blending(DB)and data assimilation(DA).The DB ingests the time-varied large-scale information from the GM to the RM to generate less-biased background fields.Then the DA is performed.We applied the new FC strategy in a series of 7-day batch forecasts with the 3-hour cycle in July 2018,and February,April,and October 2019 over China using a Weather Research and Forecast(WRF)model-based RRC.A comparison shows that the new FC strategy results in less model bias than the PC strategy in most state variables and improves the forecast skills for moderate and light precipitation.The new FC strategy also allows the model to reach a balanced state earlier and gives favorable forecast continuity between adjacent cycles.Hence,this new FC strategy has potential to be applied in RRC forecast systems to replace the currently used PC strategy.
基金This work was supported by the National Natural Science Foundation of China(61925402,61851402 and 61734003)Science and Technology Commission of Shanghai Municipality(19JC1416600)+2 种基金National Key Research and Development Program(2017YFB0405600)Shanghai Education Development Foundation and Shanghai Municipal Education Commission Shuguang Program(18SG01)China Postdoctoral Science Foundation(2019M661358,2019TQ0065).
文摘The recently reported quasi-nonvolatile memory based on semi-floating gate architecture has attracted extensive attention thanks to its potential to bridge the large gap between volatile and nonvolatile memory.However,the further extension of the refresh time in quasi-nonvolatile memory is limited by the charge leakage through the p-n junction.Here,based on the density of states engineered van der Waals heterostructures,the leakage of electrons from the floating gate to the channel is greatly suppressed.As a result,the refresh time is effectively extended to more than 100 s,which is the longest among all previously reported quasi-nonvolatile memories.This work provides a new idea to enhance the refresh time of quasi-nonvolatile memory by the density of states engineering and demonstrates great application potential for high-speed and low-power memory technology.
基金Project (No. 60332030) supported by the National Natural ScienceFoundation of China
文摘For video streaming over lossy channels, intra refresh can mitigate the error-propagation effect caused by packet losses Besides some intra-mode macroblocks （MBs） generated by the ＂Lagrangian rate-distortion＂ or ＂Sum of absolute difference＂ mode decision, the encoder or transcoder possibly needs to increase some ＂forced＂ intra-mode MBs for robust video streaming. Based on the error-propagation analysis in a group of pictures （GOP）, we propose an unequal Forced-Intra-Refresh （FIR） scheme to improve packet loss resilience of video streaming. According to a GOP-level error-propagation model, the proposed unequal FIR scheme can optimally increase the unequal number of forced intra-mode MBs for different frames in a GOP. Simulation results showed that the proposed scheme can effectively enhance the robustness of video streaming under different channel conditions, and achieve about 0. 1-0.9 dB gains over the average FIR scheme in H.264/AVC tools.
文摘<正> Like most July days,it was hot. I stepped into a tiny ice-cream shop to cool off with a chocolate sundae. It was an old-time store, just recently restored—~* with white oak wood-work,little round tables and curlicue chairs.As I entered, 1 caught a glimpse of a very old woman bentover a table near the door.~* Her back was so badly twisted
文摘在第四代迅驰平台Sonta Rosa发布八个月之后,名为Sonta Rosa Refresh的平台正式于2008年1月8日发布。正如人们之前预料的那样,它在保持芯片组和无线模块等组件不变的基础上,将基于第五代迅驰平台(Montevina),代号为Penryn的45纳米处理器提前应用到现有平台当中。那么,新规格的Penryn处理器有哪些优化设计? Penryn处理器的加入能给迅驰平台带来多大的性能提升?Santa Rosa Refresh平台体现在游戏上又有怎么样的表现呢?
文摘目的探讨以问题为基础的教学法(problem based learning,PBL)联合以案例为基础的教学法(case based learning,CBL)在儿童肺功能专科进修培训中的应用效果。方法以2020年1月—2022年12月25名在四川大学华西第二医院肺功能专科的进修人员为调查对象,应用PBL联合CBL教学法,比较进修前后的理论知识与实际操作水平、胜任力水平,并调查进修人员对培训的满意度。结果经过一段时间理论和实践的培训,进修人员理论知识和实践技能操作水平以及胜任力水平较进修前均得到较大提升,培训前理论知识水平、实际操作和胜任力水平评分分别为(22.48±9.52)分、(15.40±5.97)分和(21.04±6.47)分,培训后理论知识水平、实际操作和胜任力水平评分分别为(75.00±24.00)分、(58.84±19.44)分和(65.32±17.39)分,培训前后差异有统计学意义(P<0.05)。肺功能检测进修人员对肺功能检测室整体工作环境比较满意。结论在PBL联合CBL教学法模式下,进修人员的理论知识与实际操作水平均有不同程度的提高,胜任力水平有较大提升,PBL联合CBL教学法可有效提高肺功能专科进修培训效果,肺功能检测应不断规范培训流程,完善肺功能检测进修体系,提升肺功能检测进修人员综合素质与学习满意度。
