检索结果-南通市图书馆

A lightweight DDoS detection scheme under SDN context

Cybersecurity 2023年第1期6卷 75-89页

作者： Kun Jia Chaoge Liu Qixu Liu Junnan Wang Jiazhi Liu Feng Liu State Key Laboratory of Information Security Institute of Information EngineeringBeijingChina School of Cyber Security University of Chinese Acad emy of SciencesBeijing 100049China The Sixth Research Offce Institute of Information EngineeringChinese Academy of SciencesBeijing 100093China

Software-defined networking(SDN),a novel network paradigm,separates the control plane and data plane into dif-ferent network equipment to realize the flexible control of network traffic.Its excellent programmability and global view present many new opportunities.DDoS detection under the SDN context is an important and challenging research field.Some previous works attempted to collect and analyze statistics related to flows,usually recorded in switches,to address DDoS threats.In contrast,other works applied machine learning-based solutions to identify DDos and achieved promising results.Generally,most previous works need to periodically request flow rules or packets to obtain flow statistics or features to detect stealthy exceptions.Nevertheless,the request for flow rules is very time-consuming and CPU-consuming;moreover may congest the communication channel between the controller and the switches.Therefore,we present FORT,a lightweight DDoS detection scheme,which spreads the rule-based detection algorithm at edge switches and determines whether to start it by periodically retrieving the ports state.A time-series algorithm,ARIMA,is utilized to determine the port statistics adaptively,and an SVM algorithm is applied to detect whether a DDoS attack does occur.Representative experiments demonstrate that FORT can significantly reduce the controller load and provide a reliable detection accuracy.Referring to the false alarm rate of 1.24%in the comparison scheme,the false alarm rate of this scheme is only 0.039%,which significantly reduces the probability of false alarm.Besides,by introducing the alarm mechanism,this scheme can reduce the load of the southbound chan-nel by more than 60%in the normal state.

关键词： DDoS Port monitoring Flow rule Software defined network MiniNet RYU controller Detection

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Microstructure refinement of AZ31 alloy solidified with pulsed magnetic field

引用

Transactions of Nonferrous Metals Society of China 2010年第9期20卷 1685-1690页

作者：汪彬杨院生孙明礼 College of Engineering Zhejiang Normal University Institute of Metal Research Chinese Acad emy of Sciences

The effects of a pulsed magnetic field on the solidified microstructure of an AZ31 magnesium alloy were investigated.The experimental results show that the remarkable microstructural refinement is achieved when the pulsed magnetic field is applied to the solidification of the AZ31 alloy.The average grain size of the as-cast microstructure of the AZ31 alloy is refined to 107 μm.By quenching the AZ31 alloy, the different primary α-Mg microstructures are preserved during the course of solidification.The microstructure evolution reveals that the primary α-Mg generates and grows in globular shape with pulsed magnetic field, contrast with the dendritic shape without pulsed magnetic field.The pulsed magnetic field causes melt convection during solidification, which makes the temperature of the whole melt homogenized, and produces an undercooling zone in front of the liquid/solid interface, which makes the nucleation rate increased and big dendrites prohibited.In addition, the Joule heat effect induced in the melt also strengthens the grain refinement effect and spheroidization of dendrite arms.

关键词： AZ31镁合金脉冲磁场组织细化合金凝固平均晶粒尺寸凝固过程高温熔体液/固界面

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Isotopic Tracing of Trophication Processes over the Last Millennia on Lake Chenghai

引用

chinese Journal Of Geochemistry 2003年第3期22卷 271-279页

作者：吴敬禄王苏民夏威岚 Nanjing Institute of Geography & Limnology Chinese Acad emy of Sciences

Multi-parameter studies (stable isotopes in carbonate and or ganic matter, pigment, organic carbon and nitrogen contents) from a 660-yr cont inuous sediment core from Lake Chenghai, a closed, eutropic lake in southern Chi na, provide information on lake historical eutrophication. During the last 660 y ears, great changes have taken place in productivity and eutrophication of Lake Chenghai in response to human activities. In 1690, the productivity of the lake began to increase as Lake Chenghai became closed from agriculture in the lake’s watershed. In 1942, Lake Chenghai evolved to eutrophic state, marked by an incr ease in organic carbon, nitrogen, CaCO\-3, pigment contents and obvious negative values of stable isotopes, which is more or less simultaneous with the large-s cale population immigration during the period. In 1984, intensive human activiti es induced modern lacustrine productivity and eutrophic level. Human-induced tr ophic changes during the past few decades have affected the Lake Chenghai ecosys tem to such an extent that it has never experienced before in the last 660 years .

关键词：稳定同位素 Chenghai湖超营养作用同位素地质学营养过程湖泊沉积

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Climate Change Impacts on Agroecosystems in China:Processes,Mechanisms and Prospects

引用

chinese Geographical Science 2023年第4期33卷 583-600页

作者： BAO Lun YU Lingxue LI Ying YAN Fengqin LYNE Vincent REN Chunying State Key Laboratory of Black Soils Conservation and Utilization Northeast Institute of Geography and AgroecologyChinese Acad emy of SciencesChangchun 130012China University of chinese academy of sciences Beijing 100049China Institute of Geographic sciences and Natural Resources Research CASBeijing 100101China IMAS-Hobart University of TasmaniaTasmania 7004Australia

Building a more resilient response system to climate change for sustainable development and reducing uncertainty in China’s food markets,requires access to historical research gaps and mapping future research progress for decision making.However,the lack of quantitative and objective analyses to ensure the stability and development of agroecosystems increases the complexity of agro-climatic mechanisms,which leads to uncertainty and undesirable consequences.In this paper,we review the characteristics of climate change in China(1951–2020),reveal the mechanisms of agroecosystem structure in response to climate,and identify challenges and opportunities for future efforts in the context of research progress.The aim is to improve the scientific validity and relevance of future research by clarifying agro-climatic response mechanisms.The results show that surface temperature,precipitation,and frequency of extreme weather events have increased to varying degrees in major agricultural regions of China in 1951–2020.And they have strong geographic variation,which has resulted in droughts in the north and floods in the south.Moreover,climate change has complicated the mechanisms of soil moisture,Net Primary Productivity(NPP),soil carbon pool,and crop pest structure in agroecosystems.This lends to a reduction in soil water holding capacity,NPP,soil carbon content,and the number of natural enemies of diseases and insects,which in turn affects crop yields.However,human interventions can mitigate the deterioration of these factors.We have also realized that the methodology and theory of historical research poses a great challenge to future agroecosystem.Historical and projected climate trends identified current gaps in interdisciplinary integration and multidisciplinary research required to manage diverse spatio-temporal climate change impacts on agroecosystems.Future efforts should highlight integrated management and decision making,multidisciplinary big data coupling,and numerical simulations to ensure sustainable agricultural

关键词： climate change agroecosystem Net Primary Productivity(NPP) soil carbon pool risk management crop yield

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Microdefects and electron densities in NiTi shape memory alloys studied by positron annihilation

引用

Transactions of Nonferrous Metals Society of China 2006年第6期7卷 1259-1262页

作者：胡益丰邓文郝文博岳丽黄乐黄宇阳熊良钺 College of Physics Science and Technology Guangxi University Institute of Metal Research Chinese Acad emy of Sciences

The microdefects and free electron densities in B2,R and B19’ phases of Ni50.78Ti49.22 alloy were studied by positron lifetime measurements.Comparing the lifetime parameters of the Ni50.78Ti49.22 alloy measured at 295 K and 225 K,it is found that the free electron density of the R phase is lower than that of the B2 phase;the open volume of the defects of the R phase is larger,while the concentration of these defects is lower than that of the B2 phase.The Ni50.78Ti49.22 alloy exhibits B19’ phase at 115 K.In comparison with the R phase,the free electron density of the B19’ phase increases,the open volume of the defects of the B19’ phase reduces,and the concentration of these defects increases.The microdefects and the free electron density play an important role during the multi-step transformations(B2→R→B19’ phase transformations)in Ni50.78Ti49.22 alloy with the decrease of temperature.

关键词： NiTi alloy microdefect electron density martensite transformation

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Spectra of sodium aluminate solutions

引用

中国有色金属学会会刊：英文版 2007年第4期17卷 853-857页

作者：马淑花郑诗礼徐红彬张懿 Laboratory of Green Process and Engineering Institute of Process Engineering Chinese Academy of Sciences Graduate University of chinese acad emy of sciences Beijing 100039 China

The UV spectra of sodium aluminate solutions were obtained in the sodium oxide concentration range from 59 to 409 g/L and the caustic ratio range from 1.5 to 4.0 to reveal the structure characteristics of them. It is found that a new peak appears at about 370 nm besides peaks at about 220 and 266 nm in all solutions. The new peak is strongly favored by high hydroxide concentration and high caustic ratio. And it only appears when the solutions are prepared by dissolving sodium hydroxide and aluminum hydroxide. In addition, the IR and Raman spectra of sodium aluminate solutions with high alkali concentration and high caustic ratio were measured, and the UV spectra of aqueous solutions of Al( H2O )36+and AlF 36?were measured as well. According to the crystal field theory in coordination chemistry as well as the above spectra characteristics, this new peak at about 370 nm is determined as the evidence of a new species of aluminate ion with a coordination number of 6.

关键词：铝酸钠溶液紫外光谱红外吸收光谱喇曼光谱铝酸盐离子

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Effect of Zn on mechanical property and corrosion property of extruded Mg-Zn-Mn alloy

引用

中国有色金属学会会刊：英文版 2008年第4期18卷 763-768页

作者：尹冬松张二林曾松岩 School of Materials Science and Technology Harbin Institute of TechnologyHarbin 150001China Institute of Metal Research Chinese Acad emy of SciencesShenyang 110016China

The effect of Zn on the microstructure, the mechanical property and the corrosion property in simulated body fluid(SBF) of an extruded Mg-Mn alloy was studied. The results indicate that the addition of Zn element can significantly refine the grain size of the extruded Mg-Mn alloy. When Zn content is increased from 0% to 3%, the grain size decreases from 12 μm to 4 μm. Meanwhile, the mechanical properties also increase remarkably with increasing Zn content. When Zn content is 3%, the ultimate tensile strength and the yield strength are increased by 54.7 MPa and 69.7 MPa, respectively. Zn can also improve the anti-corrosion property of the alloy. The best anti-corrosion property is obtained with 1% Zn. However, further increase of Zn content up to 3% deteriorates the corrosion property. Finally, the influence mechanism of Zn on the microstructure, the mechanical property and the corrosion property was discussed.

关键词：镁锌锰合金热挤出微观结构机械性能腐蚀行为模拟体液

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Effect of Tangweian Jianji on upper gastrointestinal remodeling in streptozotocin-induced diabetic rats

引用

World Journal of Gastroenterology 2012年第35期18卷 4875-4884页

作者： Gui-Fang Liu Jing-Bo Zhao Zhong Zhen Hong Sha Peng-Min Chen Min Li Jia-Cheng Zhang Ming-Ze Yuan Wen Gao Hans Gregersen Xiao-Lin Tong Guang'anmen Hospital China acad-emy of chinese Medical sciences Beijing 100053 China DK 9000 Aalborg and Instituteof Clinical Medicine Aarhus University DK8200 Aarhus NDenmark

AIM:To investigate the effect of Tangweian Jianji(TWAJJ) on the biomechanical and morphometrical remodeling of the upper gastrointestinal tract in diabetic rats.METHODS:Diabetes was induced in 27 rats by injecting streptozotocin(40 mg/kg body weight),the animals were then divided into three groups(n = 9 in each group),i.e.,diabetic control(DM);high dose(10 g/kg,T1) and low dose(5 g/kg,T2).Another 10 rats acted as normal controls(Control).TWAJJ was administered by gavage once daily.Blood glucose and serum insulin levels were measured.Circumferential length,wall thickness and opening angle were measured from esophageal,duodenal,jejunal and ileal ring segments.The residual strain was calculated from the morphometric data.Step-wise distension was carried out on esophageal and jejunal segments.The obtained data on the length,diameter and pressure changes were then used to calculate the circumferential and longitudinal stresses and strains.Real-time reverse transcription polymerase chain reaction was used to detect the receptor of advanced glycation end-products(RAGE) mRNA level in jejunal tissues.RESULTS:At the end of the experiment,the blood glucose level was significantly higher and the serum insulin level was significantly lower in DM,T1 and T2 groups than in the control group(Glucose:30.23 ± 0.41 mmol/L,27.48 ± 0.27 mmol/L and 27.84 ± 0.29 mmol/L vs 5.05 ± 0.04 mmol/L,P = 1.65 × 10-16,P = 5.89 × 10-19 and P = 1.63 × 10-18,respectively;Insulin:1.47 ± 0.32 g/L,2.66 ± 0.44 g/L,2.03 ± 0.29 g/L and 4.17 ± 0.54 g/L,P = 0.0001,P = 0.029 and P = 0.025,respectively).However,these levels did not differ among the DM,T1 and T2 groups.The wet weight per unit length,wall thickness and opening angle of esophageal and intestinal segments in the DM group were significantly higher than those in the control group(from P = 0.009 to P = 0.004).These parameters in the T1 group were significantly lower than those in the DM group(wet weight,duodenum:0.147 ± 0.003 g/cm vs 0.158 ± 0.001 g/cm,P = 0.047;jejunum,0.127 ± 0.003 g/cm vs 0.151 ±

关键词：糖尿病大鼠链脲佐菌素消化道 mRNA水平反转录聚合酶链反应十二指肠形态计量学诱导

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Influence of recrystallization and environment on tensile behavior of cold-rolled Ni_3Al(Zr) alloys

引用

中国有色金属学会会刊：英文版 2006年第2期16卷 368-375页

作者：李玉芳郭建亭沈以赴 College of Materials Science and Technology Nanjing University of Aeronautics and Astronautics Nanjing 210016 China Institute of Metal Research Chinese Acad emy of Sciences Shenyang 110016 China

The effects of recrystallization and environment (vacuum versus air) on tensile properties of B-free Ni3Al (Zr) alloys were investigated. The results indicate that the incompletely recrystallized and stress-relieved specimens show the most desirable ductility and ultimate tensile strength, and that the recrystallization treatment promotes susceptibility to the test environment of the alloys. It is found that the amount of ductile fracture is reduced by air for completely recrystallized specimens. The Auger analyses show that Zr atoms do not segregate to the grain boundaries(GBs) for specimens heat-treated at 1 100 ℃, however Zr atoms segregate to the GBs for specimens heat-treated at 900 ℃. These results imply that Zr-doping cannot suppress environmental embrittlement.

关键词： Ni3Al 锆镍合金再结晶拉伸性能冷轧

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Status and distribution of ungulates in Xinjiang,China

引用

Journal of Arid Land 2011年第1期3卷 49-60页

作者： XingYi GAO WenXuan XU WeiKang YANG David A BLANK JianFang QIAO KeFen XU Key Laboratory of Biogeography and Bioresource in Arid Land Xinjiang Institute of Ecology and Geography Chinese Acad- emy of Sciences Urumqi 830011 China Graduate University of chinese academy of sciences Beijing 100049 China Institute of Zoology Kazakhstan Academy of Sciences Almaty 050010 Kazakhstan

Based on a long-term field investigation and other research results, we reviewed the status and distribution of ungulates in Xinjiang, China. The ungulates in Xinjiang included 19 ungulate species （30 subspecies） from 6 families and 2 orders. Among them, 3 species （2 subspecies） relate to Equidae （Per- risodactyla）, and 16 species （28 subspecies） are from 5 families of Artiodactyla. In this paper, we analyzed the conservation status of most rare and important 13 ungulate species. Firstly, we proposed the protec- tion of genetic diversity of Camelus ferus and the distribution areas of Moschus sifanicus, Procapra przewalskii and Saiga tatarica in Xinjiang. We found that Moschus sifanicus but not Procapra przewalskii distributed in Xinjiang. It was not clear whether the remnant populations of Saiga tatarica existed in Xinjiang and China-Kazakhstan border or not. We discussed that the protection level and rational use of Capra si- birica and enhancing protection level and enlarging monitoring and research projects for Pantholops hodgsoni and Gazella subgutturosa. And we would like to suggest Forestry Department to develop the captive breeding of Tibetan antelope for rational use. In addition, the captive breeding of Cervus elaphus in Xinjiang was reviewed. Local government should lessen strong control to Cervus elaphus because of many breeding centers＇ establishment.

关键词： Xinjiang of China ungulate species and distribution status

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：