在新兴的软件定义网络(Software Defined Networking,SDN)、OpenFlow交换机中,为满足OpenFlow协议宽匹配域的需求,SDN交换设备需要更大的查找表存储容量.当流表溢出时,将导致控制报文数目爆炸性增长、数据包传输时延增大等危害网络正常...在新兴的软件定义网络(Software Defined Networking,SDN)、OpenFlow交换机中,为满足OpenFlow协议宽匹配域的需求,SDN交换设备需要更大的查找表存储容量.当流表溢出时,将导致控制报文数目爆炸性增长、数据包传输时延增大等危害网络正常运行的后果.然而考虑成本因素,高速查找表容量不可能无限增加.即使单纯地增加流表容量,并不能使溢出的概率降低为零,且极不经济.本文分析了网络流量的特征,提出了一种流表共享方法(Flow Table Sharing,FTS),针对流表溢出现象带来的危害,完善了Table-Miss处理机制,有效遏制了由于流表溢出而引发的危害网络正常运行的情况.相比目前的Table-Miss处理方式,FTS对流表溢出情况下控制消息数量和RTT时间的优化都达到两个数量级.此外,该文针对流表扩散方法设计了简单高效的基于OpenFlow组表的随机路由选择算法,系统结构实施简单,可以方便地降级为现行的通用Table-Miss处理模式.展开更多
A unitized regenerative fuel cell(URFC)is a device that may function reversibly as either a fuel cell(FC)or water elec-trolysis(WE).An important component of this device is the Membrane electrode assembly(MEA).Therefo...A unitized regenerative fuel cell(URFC)is a device that may function reversibly as either a fuel cell(FC)or water elec-trolysis(WE).An important component of this device is the Membrane electrode assembly(MEA).Therefore,this study aimed to compare the performance outcomes of MEA using electrodes with single and three catalyst layers.This study measured Electrochemical Surface Area(ECSA),Electrochemical Impedance Spectroscopy(EIS),X-ray Diffraction analysis(XRD),and X-ray Fluorescence(XRF).Furthermore,the round-trip efficiency(RTE)of the MEA,as w ell as the performance in FC and WE mode,was measured.In comparison,The ECSA values of Pt-Ru/C and Pt/C with three catalyst layers were higher than the single catalyst layer.This result was supported by electrode characterization data for XRD and XRF.The respective electrical conductivity values of Pt-Ru/C and Pt/C with three catalyst layers are also higher than the single cata-lyst layer,and the performance of URFC using MEA with three catalyst layers has the highest value of RTE among the MEA performances of URFC,which is 100%at a current density of 4 mA·cm-2.展开更多
Micro computed tomography (Micro-CT) was applied to obtain three-dimensional images of the microstructure of cement paste (water-to-cement mass ratio of 0.5) at different ages. By using the Amira software, component p...Micro computed tomography (Micro-CT) was applied to obtain three-dimensional images of the microstructure of cement paste (water-to-cement mass ratio of 0.5) at different ages. By using the Amira software, component phases of the cement paste such as pores, hydration products, and unhydrated clinker particles were segmented from each other based on their 3D image grey levels; their relative contents were also calculated with the software, and the data are 61.2%, 0% and 38.8% at the beginning of hydration and 11.8%, 78.5% and 9.7% at 28 d age, respectively. The hydration degree of cement paste at different ages was compared with the experimental data acquired by loss on ignition (LOI) tests. The results show that the calculated and measured data reasonably agree with each other, which indicates that micro-CT is a useful and reliable approach to characterize the micro structure evolution of hydrating cement paste.展开更多
The chemical fractions,i.e.,water soluble(WS),exchangeable(Ex),carbonate(Car),weakly organic(WO),Fe-Mn oxide(FMO),strongly organic(SO),residual(Res) fraction,of Pb in irrigated soils in South China were investigated b...The chemical fractions,i.e.,water soluble(WS),exchangeable(Ex),carbonate(Car),weakly organic(WO),Fe-Mn oxide(FMO),strongly organic(SO),residual(Res) fraction,of Pb in irrigated soils in South China were investigated by a modified Tessier sequential extraction technique.The results show that the chemical fraction of Pb in soil is mainly the Res fraction and followed by FMO fraction,and the WS,WO,FMO,and SO fractions in topsoils(0-10 cm) are higher than those in subsoils(30-40 cm).The sum of contents of WS and Ex fractions(SWE) in topsoils is significantly positively related with that in subsoils,indicating the strong mobility of Pb in WS and Ex fractions in soils,and the SWE in soils is higher than the German trigger value for the transfer path soil-plant,indicating the high bioavailability of Pb in soils of this area.Fortunately,SWE and the ratio of WS and Ex fractions(RWE) to the sum of all fractions generally decrease with the soil depth in soil profile and the RWE in soil profile is lower than 0.5%,indicating the low pollution risk for Pb in groundwater.In addition,soil particles,pH and Fe2O3 play an important role in the impact of mobility and chemical fractions of Pb in soils.展开更多
文摘在新兴的软件定义网络(Software Defined Networking,SDN)、OpenFlow交换机中,为满足OpenFlow协议宽匹配域的需求,SDN交换设备需要更大的查找表存储容量.当流表溢出时,将导致控制报文数目爆炸性增长、数据包传输时延增大等危害网络正常运行的后果.然而考虑成本因素,高速查找表容量不可能无限增加.即使单纯地增加流表容量,并不能使溢出的概率降低为零,且极不经济.本文分析了网络流量的特征,提出了一种流表共享方法(Flow Table Sharing,FTS),针对流表溢出现象带来的危害,完善了Table-Miss处理机制,有效遏制了由于流表溢出而引发的危害网络正常运行的情况.相比目前的Table-Miss处理方式,FTS对流表溢出情况下控制消息数量和RTT时间的优化都达到两个数量级.此外,该文针对流表扩散方法设计了简单高效的基于OpenFlow组表的随机路由选择算法,系统结构实施简单,可以方便地降级为现行的通用Table-Miss处理模式.
基金support from the Ministry of Higher Education Malaysia under grant HICOE-2023-005.
文摘A unitized regenerative fuel cell(URFC)is a device that may function reversibly as either a fuel cell(FC)or water elec-trolysis(WE).An important component of this device is the Membrane electrode assembly(MEA).Therefore,this study aimed to compare the performance outcomes of MEA using electrodes with single and three catalyst layers.This study measured Electrochemical Surface Area(ECSA),Electrochemical Impedance Spectroscopy(EIS),X-ray Diffraction analysis(XRD),and X-ray Fluorescence(XRF).Furthermore,the round-trip efficiency(RTE)of the MEA,as w ell as the performance in FC and WE mode,was measured.In comparison,The ECSA values of Pt-Ru/C and Pt/C with three catalyst layers were higher than the single catalyst layer.This result was supported by electrode characterization data for XRD and XRF.The respective electrical conductivity values of Pt-Ru/C and Pt/C with three catalyst layers are also higher than the single cata-lyst layer,and the performance of URFC using MEA with three catalyst layers has the highest value of RTE among the MEA performances of URFC,which is 100%at a current density of 4 mA·cm-2.
基金Project(2009CB623201) supported by the National Basic Research Program of ChinaProjects(50902106, 51272193) supported by the National Natural Science Foundation of ChinaProject(NCET-10-0660) supported by New Century Excellent Talents in Universities of China
文摘Micro computed tomography (Micro-CT) was applied to obtain three-dimensional images of the microstructure of cement paste (water-to-cement mass ratio of 0.5) at different ages. By using the Amira software, component phases of the cement paste such as pores, hydration products, and unhydrated clinker particles were segmented from each other based on their 3D image grey levels; their relative contents were also calculated with the software, and the data are 61.2%, 0% and 38.8% at the beginning of hydration and 11.8%, 78.5% and 9.7% at 28 d age, respectively. The hydration degree of cement paste at different ages was compared with the experimental data acquired by loss on ignition (LOI) tests. The results show that the calculated and measured data reasonably agree with each other, which indicates that micro-CT is a useful and reliable approach to characterize the micro structure evolution of hydrating cement paste.
基金Project(41103059) supported by the National Natural Science Foundation of ChinaProject(2010CB428806-2) supported by the National Basic Research Program of China
文摘The chemical fractions,i.e.,water soluble(WS),exchangeable(Ex),carbonate(Car),weakly organic(WO),Fe-Mn oxide(FMO),strongly organic(SO),residual(Res) fraction,of Pb in irrigated soils in South China were investigated by a modified Tessier sequential extraction technique.The results show that the chemical fraction of Pb in soil is mainly the Res fraction and followed by FMO fraction,and the WS,WO,FMO,and SO fractions in topsoils(0-10 cm) are higher than those in subsoils(30-40 cm).The sum of contents of WS and Ex fractions(SWE) in topsoils is significantly positively related with that in subsoils,indicating the strong mobility of Pb in WS and Ex fractions in soils,and the SWE in soils is higher than the German trigger value for the transfer path soil-plant,indicating the high bioavailability of Pb in soils of this area.Fortunately,SWE and the ratio of WS and Ex fractions(RWE) to the sum of all fractions generally decrease with the soil depth in soil profile and the RWE in soil profile is lower than 0.5%,indicating the low pollution risk for Pb in groundwater.In addition,soil particles,pH and Fe2O3 play an important role in the impact of mobility and chemical fractions of Pb in soils.
