In recent years, Software-Defined Networks （SDNs） have become a promising technology to improve network utilization. However, limited flow table size and long deployment delays may result in low network performance ...In recent years, Software-Defined Networks （SDNs） have become a promising technology to improve network utilization. However, limited flow table size and long deployment delays may result in low network performance in large-scale networks and a poor user experience. While a typical solution to this issue is routing aggregation （i.e., wildcard routing）, the aggregation feasibility problem and reduced network performance may be encountered. To address this dilemma, we first design a novel wildcard routing scheme, called the Tag-based Rule Placement Scheme （TRPS）. We then formulate a Hybrid Routing by Joint optimization of Per-flow routing and Tag- based routing （HR-JPT） problem, and prove its NP-hardness. An algorithm with a bounded approximation factor is designed for this problem, and the proposed methods are implemented on a Mininet platform. Extensive simulation results show that our methods are efficient for wildcard/hybrid routing. For example, our proposed tag-based wildcard rule placement scheme can reduce the number of required rules by about 65% on average compared with previous wildcard routing methods. Our proposed hybrid routing algorithm can increase network throughput by about 43% compared with existing hybrid routing solutions.展开更多
A methodology is proposed to handle problem that under equiproble address of packet traffic at the input port, Generalized Shuffle-Exchange Network (GSEN) routes traffic unevenly because of the unbalanced routing tags...A methodology is proposed to handle problem that under equiproble address of packet traffic at the input port, Generalized Shuffle-Exchange Network (GSEN) routes traffic unevenly because of the unbalanced routing tags. The idea is to use routing tag according to probability, which can be evaluated by using Moore-Penrose inverse in matrix analysis. An instance is used to illustrate the idea, and the simulation is done to show the improvement in performance issues.展开更多
Natural products derived from bacterial sources have long been pivotal in the discovery of drug leads.However,the cultivation of only about 1%of bacteria in laboratory settings has left a significant portion of biosyn...Natural products derived from bacterial sources have long been pivotal in the discovery of drug leads.However,the cultivation of only about 1%of bacteria in laboratory settings has left a significant portion of biosynthetic diversity hidden within the genomes of uncultured bacteria.Advances in sequencing technologies now enable the exploration of genetic material from these metagenomes through culture-independent methods.This approach involves extracting genetic sequences from environmental DNA and applying a hybrid methodology that combines functional screening,sequence tag-based homology screening,and bioinformatic-assisted chemical synthesis.Through this process,numerous valuable natural products have been identified and synthesized from previously uncharted metagenomic territories.This paper provides an overview of the recent advancements in the utilization of culture-independent techniques for the discovery of novel biosynthetic gene clusters and bioactive small molecules within metagenomic libraries.展开更多
基金supported by the National Natural Science Foundation of China (Nos. 61472383, 61472385, and U1301256)the Natural Science Foundation of Jiangsu Province in China (No. BK20161257)
文摘In recent years, Software-Defined Networks （SDNs） have become a promising technology to improve network utilization. However, limited flow table size and long deployment delays may result in low network performance in large-scale networks and a poor user experience. While a typical solution to this issue is routing aggregation （i.e., wildcard routing）, the aggregation feasibility problem and reduced network performance may be encountered. To address this dilemma, we first design a novel wildcard routing scheme, called the Tag-based Rule Placement Scheme （TRPS）. We then formulate a Hybrid Routing by Joint optimization of Per-flow routing and Tag- based routing （HR-JPT） problem, and prove its NP-hardness. An algorithm with a bounded approximation factor is designed for this problem, and the proposed methods are implemented on a Mininet platform. Extensive simulation results show that our methods are efficient for wildcard/hybrid routing. For example, our proposed tag-based wildcard rule placement scheme can reduce the number of required rules by about 65% on average compared with previous wildcard routing methods. Our proposed hybrid routing algorithm can increase network throughput by about 43% compared with existing hybrid routing solutions.
基金Supported by the National High-Tech Programs(No.2002AA103062, No.2002AA121061 and No.2003AA103520) the Huawei Technologies Co. under contract number YBCN2002001.
文摘A methodology is proposed to handle problem that under equiproble address of packet traffic at the input port, Generalized Shuffle-Exchange Network (GSEN) routes traffic unevenly because of the unbalanced routing tags. The idea is to use routing tag according to probability, which can be evaluated by using Moore-Penrose inverse in matrix analysis. An instance is used to illustrate the idea, and the simulation is done to show the improvement in performance issues.
基金supported by the Start-Up Grant from China Pharmaceutical University(No.3154070046).
文摘Natural products derived from bacterial sources have long been pivotal in the discovery of drug leads.However,the cultivation of only about 1%of bacteria in laboratory settings has left a significant portion of biosynthetic diversity hidden within the genomes of uncultured bacteria.Advances in sequencing technologies now enable the exploration of genetic material from these metagenomes through culture-independent methods.This approach involves extracting genetic sequences from environmental DNA and applying a hybrid methodology that combines functional screening,sequence tag-based homology screening,and bioinformatic-assisted chemical synthesis.Through this process,numerous valuable natural products have been identified and synthesized from previously uncharted metagenomic territories.This paper provides an overview of the recent advancements in the utilization of culture-independent techniques for the discovery of novel biosynthetic gene clusters and bioactive small molecules within metagenomic libraries.
