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Loveless, Telisa M., and Paul E. Bishop. "Identification of genes unique to Mo-independent nitrogenase systems in diverse diazotrophs." Canadian Journal of Microbiology 45, no. 4 (April 1, 1999): 312–17. http://dx.doi.org/10.1139/w99-007.
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A number of nitrogen-fixing bacteria were screened using PCR for genes (vnfG and anfG) unique to the V-containing nitrogenase (vnf) and the Fe-only nitrogenase (anf) systems. Products with sequences similar to that of vnfG were obtained from Azotobacter paspali and Azotobacter salinestris genomic DNAs, and products with sequences similar to that of anfG were obtained from Azomonas macrocytogenes, Rhodospirillum rubrum, and Azotobacter paspali DNAs. Phylogenetic analysis of the deduced amino acid sequences of anfG and vnfG genes shows that each gene product forms a distinct cluster. Furthermore, amplification of an internal 839-bp region in anfD and vnfD yielded a product similar to anfD from Heliobacterium gestii and a product similar to vnfD from Azotobacter paspali and Azotobacter salinestris. Phylogenetic analysis of NifD, VnfD, and AnfD amino acid sequences indicates that AnfD and VnfD sequences are more closely related to each other than either is to NifD. The results of this study suggest that Azotobacter salinestris possesses the potential to express the vanadium (V)-containing nitrogenase (nitrogenase 2) and that R. rubrum, Azomonas macrocytogenes, and H. gestii possess the potential to express the Fe-only nitrogenase (nitrogenase 3). Like Azotobacter vinelandii, Azotobacter paspali appears to have the potential to express both the V-containing nitrogenase and the Fe-only nitrogenase.Key words: Mo-independent nitrogenase systems, diverse diazotrophs, vnfG, anfG.
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Rüttimann-Johnson, Carmen, Luis M. Rubio, Dennis R. Dean, and Paul W. Ludden. "VnfY Is Required for Full Activity of the Vanadium-Containing Dinitrogenase in Azotobacter vinelandii." Journal of Bacteriology 185, no. 7 (April 1, 2003): 2383–86. http://dx.doi.org/10.1128/jb.185.7.2383-2386.2003.
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ABSTRACT A gene from Azotobacter vinelandii whose product exhibits primary sequence similarity to the NifY, NafY, NifX, and VnfX family of proteins, and which is required for effective V-dependent diazotrophic growth, was identified. Because this gene is located downstream from vnfK in an arrangement similar to the relative organization of the nifK and nifY genes, it was designated vnfY. A mutant strain having an insertion mutation in vnfY has 10-fold less vnf dinitrogenase activity and exhibits a greatly diminished level of 49V label incorporation into the V-dependent dinitrogenase when compared to the wild type. These results indicate that VnfY has a role in the maturation of the V-dependent dinitrogenase, with a specific role in the formation of the V-containing cofactor and/or its insertion into apodinitrogenase.
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Chien, Yueh-Tyng, Victoria Auerbuch, Andrew D. Brabban, and Stephen H. Zinder. "Analysis of Genes Encoding an Alternative Nitrogenase in the Archaeon Methanosarcina barkeri227." Journal of Bacteriology 182, no. 11 (June 1, 2000): 3247–53. http://dx.doi.org/10.1128/jb.182.11.3247-3253.2000.
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ABSTRACT Methanosarcina barkeri 227 possesses two clusters of genes potentially encoding nitrogenases. We have previously demonstrated that one cluster, called nif2, is expressed under molybdenum (Mo)-sufficient conditions, and the deduced amino acid sequences for nitrogenase structural genes in that cluster most closely resemble those for the Mo nitrogenase of the gram-positive eubacteriumClostridium pasteurianum. The previously clonednifH1 from M. barkeri shows phylogenetic relationships with genes encoding components of eubacterial Mo-independent eubacterial alternative nitrogenases and other methanogen nitrogenases. In this study, we cloned and sequencednifD1 and part of nifK1 from M. barkeri 227. The deduced amino acid sequence encoded bynifD1 from M. barkeri showed great similarity with vnfD gene products from vanadium (V) nitrogenases, with an 80% identity at the amino acid level with the vnfDgene product from Anabaena variabilis. Moreover, there was a small open reading frame located between nifD1 andnifK1 with clear homology to vnfG, a hallmark of eubacterial alternative nitrogenases. Stimulation of diazotrophic growth of M. barkeri 227 by V in the absence of Mo was demonstrated. The unusual complement of nifgenes in M. barkeri 227, with one cluster resembling that from a gram-positive eubacterium and the other resembling a eubacterial V nitrogenase gene cluster, suggests horizontal genetic transfer of those genes.
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Chatterjee, Ranjini, Paul W. Ludden, and Vinod K. Shah. "Characterization of VNFG, the δ Subunit of thevnf-Encoded Apodinitrogenase fromAzotobacter vinelandii." Journal of Biological Chemistry 272, no. 6 (February 7, 1997): 3758–65. http://dx.doi.org/10.1074/jbc.272.6.3758.
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Wang, Yixiang, Ping Lu, Wei Lu, and Zuqing Zhu. "Cost-Efficient Virtual Network Function Graph (vNFG) Provisioning in Multidomain Elastic Optical Networks." Journal of Lightwave Technology 35, no. 13 (July 1, 2017): 2712–23. http://dx.doi.org/10.1109/jlt.2017.2700229.
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Eramo, V., A. Tosti, and E. Miucci. "Server Resource Dimensioning and Routing of Service Function Chain in NFV Network Architectures." Journal of Electrical and Computer Engineering 2016 (2016): 1–12. http://dx.doi.org/10.1155/2016/7139852.
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The Network Function Virtualization (NFV) technology aims at virtualizing the network service with the execution of the single service components in Virtual Machines activated on Commercial-off-the-shelf (COTS) servers. Any service is represented by the Service Function Chain (SFC) that is a set of VNFs to be executed according to a given order. The running of VNFs needs the instantiation of VNF instances (VNFI) that in general are software components executed on Virtual Machines. In this paper we cope with the routing and resource dimensioning problem in NFV architectures. We formulate the optimization problem and due to its NP-hard complexity, heuristics are proposed for both cases of offline and online traffic demand. We show how the heuristics works correctly by guaranteeing a uniform occupancy of the server processing capacity and the network link bandwidth. A consolidation algorithm for the power consumption minimization is also proposed. The application of the consolidation algorithm allows for a high power consumption saving that however is to be paid with an increase in SFC blocking probability.
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Bageshwar, Umesh K., Ramesh Raina, Nirupam Roy Choudhury, and H. K. Das. "Analysis of upstream activation of thevnfHpromoter ofAzotobacter vinelandii." Canadian Journal of Microbiology 44, no. 5 (May 1, 1998): 405–15. http://dx.doi.org/10.1139/w98-011.
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BAL-31 deletion products of the DNA fragment containing the vnfH promoter and upstream region, when cloned in a transcriptional fusion vector and analyzed for vnfH expression in Azotobacter vinelandii, revealed that the upstream activator sequence of the vnfH promoter lies about 140 nucleotides upstream of the promoter. Subsequent substitution and deletion analysis by oligonucleotide-directed mutagenesis in the upstream region of the vnfH promoter showed that sequences 5'-GTACCATGCGGAAC-3' and 5'-GTACCTGCGGGTAC-3', located 170 and 140 nucleotides upstream of the vnfH promoter, respectively, are both required for vnfH expression. Addition of four nucleotides in the intervening sequence between the vnfH promoter and the putative VnfA (analog of NifA of the conventional molybdenum-dependent nitrogen-fixation pathway) binding site resulted in a drastic reduction of expression from the vnfH promoter in Azotobacter vinelandii, where as addition of 10 nucleotides in the intervening sequence did not affect the expression. Therefore, the face of the helix-dependent contact appeared to be important. DNA bending seemed to play a crucial role in expression from vnfH promoter. The intervening sequence exhibited characteristics of sequence-dependent intrinsically curved DNA, as shown by anomalous low gel mobility with polyacrylamide gel electrophoresis, electron microscopy, and computer simulated curvature analysis. Distamycin at very low concentrations significantly reduced the anomaly in electrophoretic mobility of the intervening DNA sequence.Key words: Azotobacter vinelandii, vnfA, vnfH, promoter-lacZ fusion, DNA bending.
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Xu, Yansen, and Ved P. Kafle. "An Availability-Enhanced Service Function Chain Placement Scheme in Network Function Virtualization." Journal of Sensor and Actuator Networks 8, no. 2 (June 14, 2019): 34. http://dx.doi.org/10.3390/jsan8020034.
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A service function chain (SFC) is an ordered virtual network function (VNF) chain for processing traffic flows to deliver end-to-end network services in a virtual networking environment. A challenging problem for an SFC in this context is to determine where to deploy VNFs and how to route traffic between VNFs of an SFC on a substrate network. In this paper, we formulate an SFC placement problem as an integer linear programing (ILP) model, and propose an availability-enhanced VNF placing scheme based on the layered graphs approach. To improve the availability of SFC deployment, our scheme distributes VNFs of an SFC to multiple substrate nodes to avoid a single point of failure. We conduct numerical analysis and computer simulation to validate the feasibility of our SFC scheme. The results show that the proposed scheme outperforms well in different network scenarios in terms of end-to-end delay of the SFC and computation time cost.
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Xuan, Hejun, Lei You, Zhenghui Liu, Yanling Li, and Xiaokai Yang. "HS-MOEA/D: An Oriented Algorithm for Delay and Reliability VNF-SC Deployment." Security and Communication Networks 2021 (August 24, 2021): 1–9. http://dx.doi.org/10.1155/2021/5538931.
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Network function virtualization (NFV) technology can realize on-demand distribution of network resources and improve network flexibility. It has become one of the key technologies for next-generation communications. Virtual network function service chain (VNF-SC) deployment is an important problem faced by network function virtualization technology. In this paper, the problem, VNF deployment for VNF-SC, is investigated. First, a two-objective mathematical model, which maximizes balancing and reliability of SFC, is established. In this model, VNFs are divided into two classes, i.e., part of required VNFs in each VNF-SC is dependent, others are independent. Second, harmony search-based MOEA/D (HS-MOEA/D) is proposed to solve the model effectively. In HS-MOEA/D, Chebyshev decomposition mechanism is used to transform multiobjective optimization problem into a series of single-objective optimization subproblems. A new evolutionary strategy is deeply studied in order to propose a new harmony search (HS) algorithm. Finally, to show high performance of the proposed algorithm, a large number of experiments are conducted. The simulation results show that the proposed algorithm enhances the reliability of SFC and reduces the end-to-end delay.
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Betancourt, Doris A., Telisa M. Loveless, James W. Brown, and Paul E. Bishop. "Characterization of Diazotrophs Containing Mo-Independent Nitrogenases, Isolated from Diverse Natural Environments." Applied and Environmental Microbiology 74, no. 11 (March 31, 2008): 3471–80. http://dx.doi.org/10.1128/aem.02694-07.
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ABSTRACT Molybdenum-independent nitrogenases were first described in the nitrogen-fixing bacterium Azotobacter vinelandii and have since been described in other diazotrophic bacteria. Previously, we reported the isolation of seven diazotrophs with Mo-independent nitrogenases from aquatic environments. In the present study, we extend these results to include diazotrophs isolated from wood chip mulch, soil, “paraffin dirt,” and sediments from mangrove swamps. Mo-deficient, N-free media under both aerobic and anaerobic conditions were used for the isolations. A total of 26 isolates were genetically and physiologically characterized. Their phylogenetic placement was determined using 16S rRNA gene sequence analysis. Most of the isolates are members of the gamma subdivision of the class Proteobacteria and appear to be specifically related to fluorescent pseudomonads and azotobacteria. Two other isolates, AN1 and LPF4, are closely related to Enterobacter spp. and Paenibacillus spp., respectively. PCR and/or Southern hybridization were used to detect the presence of nitrogenase genes in the isolates. PCR amplification of vnfG and anfG was used to detect the genetic potential for the expression of the vanadium-containing nitrogenase and the iron-only nitrogenase in the isolates. This study demonstrates that diazotrophs with Mo-independent nitrogenases can be readily isolated from diverse natural environments.
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Wang, Juan, Yang Yu, Yi Li, Chengyang Fan, and Shirong Hao. "Design and Implementation of Virtual Security Function Based on Multiple Enclaves." Future Internet 13, no. 1 (January 6, 2021): 12. http://dx.doi.org/10.3390/fi13010012.
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Network function virtualization (NFV) provides flexible and scalable network function for the emerging platform, such as the cloud computing, edge computing, and IoT platforms, while it faces more security challenges, such as tampering with network policies and leaking sensitive processing states, due to running in a shared open environment and lacking the protection of proprietary hardware. Currently, Intel® Software Guard Extensions (SGX) provides a promising way to build a secure and trusted VNF (virtual network function) by isolating VNF or sensitive data into an enclave. However, directly placing multiple VNFs in a single enclave will lose the scalability advantage of NFV. This paper combines SGX and click technology to design the virtual security function architecture based on multiple enclaves. In our design, the sensitive modules of a VNF are put into different enclaves and communicate by local attestation. The system can freely combine these modules according to user requirements, and increase the scalability of the system while protecting its running state security. In addition, we design a new hot-swapping scheme to enable the system to dynamically modify the configuration function at runtime, so that the original VNFs do not need to stop when the function of VNFs is modified. We implement an IDS (intrusion detection system) based on our architecture to verify the feasibility of our system and evaluate its performance. The results show that the overhead introduced by the system architecture is within an acceptable range.
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Marchetto, Guido, Riccardo Sisto, Matteo Virgilio, and Jaloliddin Yusupov. "A VNF modeling approach for verification purposes." International Journal of Electrical and Computer Engineering (IJECE) 9, no. 4 (August 1, 2019): 2627. http://dx.doi.org/10.11591/ijece.v9i4.pp2627-2636.
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<span lang="EN-US">Network Function Virtualization (NFV) architectures are emerging to increase networks flexibility. However, this renewed scenario poses new challenges, because virtualized networks, need to be carefully verified before being actually deployed in production environments in order to preserve network coherency (e.g., absence of forwarding loops, preservation of security on network traffic, etc.). Nowadays, model checking tools, SAT solvers, and Theorem Provers are available for formal verification of such properties in virtualized networks. Unfortunately, most of those verification tools accept input descriptions written in specification languages that are difficult to use for people not experienced in formal methods. Also, in order to enable the use of formal verification tools in real scenarios, vendors of Virtual Network Functions (VNFs) should provide abstract mathematical models of their functions, coded in the specific input languages of the verification tools. This process is error-prone, time-consuming, and often outside the VNF developers’ expertise. This paper presents a framework that we designed for automatically extracting verification models starting from a Java-based representation of a given VNF. It comprises a Java library of classes to define VNFs in a more developer-friendly way, and a tool to translate VNF definitions into formal verification models of different verification tools.</span>
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Dwiardhika, Dhanu, and Takuji Tachibana. "Virtual Network Embedding Based on Security Level with VNF Placement." Security and Communication Networks 2019 (February 3, 2019): 1–11. http://dx.doi.org/10.1155/2019/5640134.
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In this paper, in order to embed virtual networks by considering network security, we propose a virtual network embedding based on security level with VNF placement. In this method, virtual networks are embedded in a substrate network by considering security and some security VNFs are placed in order to increase the security level of substrate networks. By using our proposed method, many virtual networks can be embedded by considering security level. As a result, the reward can be increased and the cost of placing VNFs is not increased so much. We evaluate the performance of our proposed method with simulation. The performance of this method is compared with the performance of a method that places VNFs randomly and the performance of a method without placing VNFs. From numerical examples, we investigate the effectiveness of this method. In numerical examples, we show that the proposed method is effective in embedding virtual networks by considering network security.
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Berekashvili, Ketevan, Alicia M. Zha, Mohammed Abdel-Al, Xu Zhang, Jazba H. Soomro, Samuel J. Prater, and James C. Grotta. "Emergency Medicine Physicians Accurately Select Acute Stroke Patients for Tissue-Type Plasminogen Activator Treatment Using a Checklist." Stroke 51, no. 2 (February 2020): 663–65. http://dx.doi.org/10.1161/strokeaha.119.026948.
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Background and Purpose— There is uncertainty among many emergency medicine physicians about the decision to give intravenous tPA (tissue-type plasminogen activator), which limits its use. A checklist approach has been suggested as a solution. We compared agreement on tPA treatment in suspected acute ischemic stroke patients between emergency medicine residents (EMRs) using a checklist and vascular neurology fellows (VNFs). Methods— Every suspected acute stroke patient brought to our comprehensive stroke center emergency room within 4.5 hours from symptom onset was prospectively evaluated simultaneously and independently by VNFs and EMRs. The latter used a tPA screening checklist, which included guideline exclusion criteria to help with their treatment decision. Agreement was determined using kappa (k) statistics. Results— Over 6 months, 60 patients were enrolled; 10% large vessel atherosclerosis, 18% cardioembolism, 12% small vessel, 12% cryptogenic, and 47% mimic. Forty-two percent were deemed tPA eligible by the EMR, 30% by the VNF, and 37% by the vascular neurology faculty. There were no complications in any tPA-treated patients. Agreement was substantial between EMR and VNF (κ=0.68 [95% CI, 0.49–0.87]) and between EMR and vascular neurology faculty (κ=0.69 [95% CI, 0.50–0.87]). Stroke mimics were the main cause of disagreement between EMR and VNF (κ=0.24 [95% CI, −0.15 to 0.63]) and between EMR and vascular neurology faculty (κ=0.35 [95% CI, −0.08 to 0.78]). Conclusions— Our data suggest that with the aid of a checklist, EMRs can accurately treat stroke patients with tPA. Areas for improvement include recognition of stroke mimics. Further studies are warranted to evaluate checklist-enhanced tPA treatment to allay emergency medicine physician uncertainty and expand the use of tPA.
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Abdelaal, Marwa A., Gamal A. Ebrahim, and Wagdy R. Anis. "Efficient Placement of Service Function Chains in Cloud Computing Environments." Electronics 10, no. 3 (January 30, 2021): 323. http://dx.doi.org/10.3390/electronics10030323.
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The widespread adoption of network function virtualization (NFV) leads to providing network services through a chain of virtual network functions (VNFs). This architecture is called service function chain (SFC), which can be hosted on top of commodity servers and switches located at the cloud. Meanwhile, software-defined networking (SDN) can be utilized to manage VNFs to handle traffic flows through SFC. One of the most critical issues that needs to be addressed in NFV is VNF placement that optimizes physical link bandwidth consumption. Moreover, deploying SFCs enables service providers to consider different goals, such as minimizing the overall cost and service response time. In this paper, a novel approach for the VNF placement problem for SFCs, called virtual network functions and their replica placement (VNFRP), is introduced. It tries to achieve load balancing over the core links while considering multiple resource constraints. Hence, the VNF placement problem is first formulated as an integer linear programming (ILP) optimization problem, aiming to minimize link bandwidth consumption, energy consumption, and SFC placement cost. Then, a heuristic algorithm is proposed to find a near-optimal solution for this optimization problem. Simulation studies are conducted to evaluate the performance of the proposed approach. The simulation results show that VNFRP can significantly improve load balancing by 80% when the number of replicas is increased. Additionally, VNFRP provides more than a 54% reduction in network energy consumption. Furthermore, it can efficiently reduce the SFC placement cost by more than 67%. Moreover, with the advantages of a fast response time and rapid convergence, VNFRP can be considered as a scalable solution for large networking environments.
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Rafiq, Adeel, Asif Mehmood, Talha Ahmed Khan, Khizar Abbas, Muhammad Afaq, and Wang-Cheol Song. "Intent-Based End-to-End Network Service Orchestration System for Multi-Platforms." Sustainability 12, no. 7 (April 1, 2020): 2782. http://dx.doi.org/10.3390/su12072782.
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On-demand service is the main feature of the 5G network, and Network Function Virtualization (NFV) provides it by virtualizing the existing 5G network infrastructure. NFV crafts various virtual networks on a shared physical network, but one of the core challenges in future 5G networks is to automate the modeling of Virtualized Network Functions (VNFs) and end-to-end Network Service (NS) orchestration with less human interaction. Traditionally, the descriptor of VNF and NS is created manually, which requires expert-level skills. This manual approach has a big threat of human error, which can be avoided by using the Intent-Based Networking (IBN) approach. The IBN approach eliminates the requirement of expertise for designing VNFs and NS by taking users’ intentions as an input. In this paper, the proposed system presents the Intent Management System for VNF modeling and end-to-end NS orchestration for multi-platforms. This system takes the high-level information related to a specific service, configures it accordingly, and converts it into the selected platform. The proposed system is tested using Mobile Central Office Re-architected as Data Center (M-CORD) and Open-Source Management and Orchestration (OSM) orchestrators. The results section shows that the proposed system reduces the effort of the end-user in creating network slices and provides seamless end-to-end service orchestration.
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Xuan, Hejun, Xuelin Zhao, Zhenghui Liu, Jianwei Fan, and Yanling Li. "Energy Efficiency Opposition-Based Learning and Brain Storm Optimization for VNF-SC Deployment in IoT." Wireless Communications and Mobile Computing 2021 (February 13, 2021): 1–9. http://dx.doi.org/10.1155/2021/6651112.
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Network Function Virtualization (NFV) can provide the resource according to the request and can improve the flexibility of the network. It has become the key technology of the Internet of Things (IoT). Resource scheduling for the virtual network function service chain (VNF-SC) is the key issue of the NFV. Energy consumption is an important indicator for the IoT; we take the energy consumption into the objective and define a novel objective to satisfying different objectives of the decision-maker. Due to the complexity of VNF-SC deployment problem, through taking into consideration of the heterogeneity of nodes (each node only can provide some specific VNFs), and the limitation of resources in each node, a novel optimal model is constructed to define the problem of VNF-SC deployment problem. To solve the optimization model effectively, a weighted center opposition-based learning is introduced to brainstorm optimization to find the optimal solution (OBLBSO). To show the efficiency of the proposed algorithm, numerous of simulation experiments have been conducted. Experimental results indicate that OBLBSO can improve the accuracy of the solution than compared algorithm.
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Dinh, Ngoc-Thanh, and Younghan Kim. "An Efficient Availability Guaranteed Deployment Scheme for IoT Service Chains over Fog-Core Cloud Networks." Sensors 18, no. 11 (November 15, 2018): 3970. http://dx.doi.org/10.3390/s18113970.
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High availability is one of the important requirements of many end-to-end services in the Internet of Things (IoT). This is a critical issue in network function virtualization (NFV) and NFV-enabled service function chaining (SFC) due to hard- and soft-ware failures. Thus, merely mapping primary VNFs is not enough to ensure high availability, especially for SFCs deployed over fog - core cloud networks due to resource limitations of fogs. As a result, additional protection schemes, like VNF redundancy deployments, are required to improve the availability of SFCs to meet predefined requirements. With limited resources of fog instances, a cost-efficient protection scheme is required. This paper proposes a cost-efficient availability guaranteed deployment scheme for IoT services over fog-core cloud networks based on measuring the improvement potential of VNFs for improving the availability of SFCs. In addition, various techniques for redundancy placement for VNFs at the fog layer are also presented. Obtained analysis and simulation results show that the proposed scheme achieves a significant improvement in terms of the cost efficiency and scalability compared to the state-of-the-art approaches.
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Chetty, Swarna Bindu, Hamed Ahmadi, Sachin Sharma, and Avishek Nag. "Virtual Network Function Embedding under Nodal Outage Using Deep Q-Learning." Future Internet 13, no. 3 (March 23, 2021): 82. http://dx.doi.org/10.3390/fi13030082.
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With the emergence of various types of applications such as delay-sensitive applications, future communication networks are expected to be increasingly complex and dynamic. Network Function Virtualization (NFV) provides the necessary support towards efficient management of such complex networks, by virtualizing network functions and placing them on shared commodity servers. However, one of the critical issues in NFV is the resource allocation for the highly complex services; moreover, this problem is classified as an NP-Hard problem. To solve this problem, our work investigates the potential of Deep Reinforcement Learning (DRL) as a swift yet accurate approach (as compared to integer linear programming) for deploying Virtualized Network Functions (VNFs) under several Quality-of-Service (QoS) constraints such as latency, memory, CPU, and failure recovery requirements. More importantly, the failure recovery requirements are focused on the node-outage problem where outage can be either due to a disaster or unavailability of network topology information (e.g., due to proprietary and ownership issues). In DRL, we adopt a Deep Q-Learning (DQL) based algorithm where the primary network estimates the action-value function Q, as well as the predicted Q, highly causing divergence in Q-value’s updates. This divergence increases for the larger-scale action and state-space causing inconsistency in learning, resulting in an inaccurate output. Thus, to overcome this divergence, our work has adopted a well-known approach, i.e., introducing Target Neural Networks and Experience Replay algorithms in DQL. The constructed model is simulated for two real network topologies—Netrail Topology and BtEurope Topology—with various capacities of the nodes (e.g., CPU core, VNFs per Core), links (e.g., bandwidth and latency), several VNF Forwarding Graph (VNF-FG) complexities, and different degrees of the nodal outage from 0% to 50%. We can conclude from our work that, with the increase in network density or nodal capacity or VNF-FG’s complexity, the model took extremely high computation time to execute the desirable results. Moreover, with the rise in complexity of the VNF-FG, the resources decline much faster. In terms of the nodal outage, our model provided almost 70–90% Service Acceptance Rate (SAR) even with a 50% nodal outage for certain combinations of scenarios.
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Qu, Hua, Ke Wang, and Jihong Zhao. "Reliable Service Function Chain Deployment Method Based on Deep Reinforcement Learning." Sensors 21, no. 8 (April 13, 2021): 2733. http://dx.doi.org/10.3390/s21082733.
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Network function virtualization (NFV) is a key technology to decouple hardware device and software function. Several virtual network functions (VNFs) combine into a function sequence in a certain order, that is defined as service function chain (SFC). A significant challenge is guaranteeing reliability. First, deployment server is selected to place VNF, then, backup server is determined to place the VNF as a backup which is running when deployment server is failed. Moreover, how to determine the accurate locations dynamically with machine learning is challenging. This paper focuses on resource requirements of SFC to measure its priority meanwhile calculates node priority by current resource capacity and node degree, then, a novel priority-awareness deep reinforcement learning (PA-DRL) algorithm is proposed to implement reliable SFC dynamically. PA-DRL determines the backup scheme of each VNF, then, the model jointly utilizes delay, load balancing of network as feedback factors to optimize the quality of service. In the experimental results, resource efficient utilization, survival rate, and load balancing of PA-DRL were improved by 36.7%, 35.1%, and 78.9% on average compared with benchmark algorithm respectively, average delay was reduced by 14.9%. Therefore, PA-DRL can effectively improve reliability and optimization targets compared with other benchmark methods.
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Vladislavić, Đani, Darko Huljenić, and Julije Ožegović. "Virtual Network Resource Optimization Model for Network Function Virtualization." Wireless Communications and Mobile Computing 2021 (August 17, 2021): 1–21. http://dx.doi.org/10.1155/2021/9928210.
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Network function virtualization (NFV) is a concept aimed at achieving telecom grade cloud ecosystem for new-generation networks focusing on capital and operational expenditure (CAPEX and OPEX) savings. This study introduces empirical throughput prediction model for the virtual network function (VNF) and network function virtualization infrastructure (NFVI) architectures based on Linux kernel. The model arises from the methodology for performance evaluation and modeling based on execution area (EA) distribution by CPU core pinning. EA is defined as a software execution unit that can run isolated on a compute resource (CPU core). EAs are derived from the elements and packet processing principles in NFVIs and VNFs based on Linux kernel. Performing measurements and observing linearity of the measured results open the possibility to apply model calibration technique to achieve general VNF and NFVI architecture model with performance prediction and environment setup optimization. The modeling parameters are derived from the cumulative packet processing cost obtained by measurements for collocated EAs on the CPU core hosting the bottleneck EA. The VNF and NFVI architecture model with performance prediction is successfully validated against the measurement results obtained in emulated environment and used to predict optimal system configurations and maximal throughput results for different CPUs.
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Bruschi, Roberto, Alessandro Carrega, and Franco Davoli. "A Game for Energy-Aware Allocation of Virtualized Network Functions." Journal of Electrical and Computer Engineering 2016 (2016): 1–10. http://dx.doi.org/10.1155/2016/4067186.
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Network Functions Virtualization (NFV) is a network architecture concept where network functionality is virtualized and separated into multiple building blocks that may connect or be chained together to implement the required services. The main advantages consist of an increase in network flexibility and scalability. Indeed, each part of the service chain can be allocated and reallocated at runtime depending on demand. In this paper, we present and evaluate an energy-aware Game-Theory-based solution for resource allocation of Virtualized Network Functions (VNFs) within NFV environments. We consider each VNF as a player of the problem that competes for the physical network node capacity pool, seeking the minimization of individual cost functions. The physical network nodes dynamically adjust their processing capacity according to the incoming workload, by means of an Adaptive Rate (AR) strategy that aims at minimizing the product of energy consumption and processing delay. On the basis of the result of the nodes’ AR strategy, the VNFs’ resource sharing costs assume a polynomial form in the workflows, which admits a unique Nash Equilibrium (NE). We examine the effect of different (unconstrained and constrained) forms of the nodes’ optimization problem on the equilibrium and compare the power consumption and delay achieved with energy-aware and non-energy-aware strategy profiles.
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Vidal, Ivan, Borja Nogales, Diego Lopez, Juan Rodríguez, Francisco Valera, and Arturo Azcorra. "A Secure Link-Layer Connectivity Platform for Multi-Site NFV Services." Electronics 10, no. 15 (August 3, 2021): 1868. http://dx.doi.org/10.3390/electronics10151868.
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Network Functions Virtualization (NFV) is a key technology for network automation and has been instrumental to materialize the disruptive view of 5G and beyond mobile networks. In particular, 5G embraces NFV to support the automated and agile provision of telecommunication and vertical services as a composition of versatile virtualized components, referred to as Virtual Network Functions (VNFs). It provides a high degree of flexibility in placing these components on distributed NFV infrastructures (e.g., at the network edge, close to end users). Still, this flexibility creates new challenges in terms of VNF connectivity. To address these challenges, we introduce a novel secure link-layer connectivity platform, L2S. Our solution can automatically be deployed and configured as a regular multi-site NFV service, providing the abstraction of a layer-2 switch that offers link-layer connectivity to VNFs deployed on remote NFV sites. Inter-site communications are effectively protected using existing security solutions and protocols, such as IP security (IPsec). We have developed a functional prototype of L2S using open-source software technologies. Our evaluation results indicate that this prototype can perform IP tunneling and cryptographic operations at Gb/s data rates. Finally, we have validated L2S using a multi-site NFV ecosystem at the Telefonica Open Network Innovation Centre (5TONIC), using our solution to support a multicast-based IP television service.
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Khoshkholghi, Mohammad Ali, Michel Gokan Khan, Kyoomars Alizadeh Noghani, Javid Taheri, Deval Bhamare, Andreas Kassler, Zhengzhe Xiang, Shuiguang Deng, and Xiaoxian Yang. "Service Function Chain Placement for Joint Cost and Latency Optimization." Mobile Networks and Applications 25, no. 6 (November 21, 2020): 2191–205. http://dx.doi.org/10.1007/s11036-020-01661-w.
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AbstractNetwork Function Virtualization (NFV) is an emerging technology to consolidate network functions onto high volume storages, servers and switches located anywhere in the network. Virtual Network Functions (VNFs) are chained together to provide a specific network service, called Service Function Chains (SFCs). Regarding to Quality of Service (QoS) requirements and network features and states, SFCs are served through performing two tasks: VNF placement and link embedding on the substrate networks. Reducing deployment cost is a desired objective for all service providers in cloud/edge environments to increase their profit form demanded services. However, increasing resource utilization in order to decrease deployment cost may lead to increase the service latency and consequently increase SLA violation and decrease user satisfaction. To this end, we formulate a multi-objective optimization model to joint VNF placement and link embedding in order to reduce deployment cost and service latency with respect to a variety of constraints. We, then solve the optimization problem using two heuristic-based algorithms that perform close to optimum for large scale cloud/edge environments. Since the optimization model involves conflicting objectives, we also investigate pareto optimal solution so that it optimizes multiple objectives as much as possible. The efficiency of proposed algorithms is evaluated using both simulation and emulation. The evaluation results show that the proposed optimization approach succeed in minimizing both cost and latency while the results are as accurate as optimal solution obtained by Gurobi (5%).
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Chen, Ming, Geetika Babu Bangera, Dean Hildebrand, Farhaan Jalia, Geoff Kuenning, Henry Nelson, and Erez Zadok. "vNFS." ACM Transactions on Storage 13, no. 3 (October 27, 2017): 1–24. http://dx.doi.org/10.1145/3116213.
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Manzanares-Lopez, Pilar, Juan Pedro Muñoz-Gea, and Josemaria Malgosa-Sanahuja. "VNF Placement for Service Function Chains with Strong Low-Delay Restrictions in Edge Computing Networks." Applied Sciences 10, no. 18 (September 20, 2020): 6573. http://dx.doi.org/10.3390/app10186573.
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The edge computing paradigm, allowing the location of network services close to end users, defines new network scenarios. One of them considers the existence of micro data centers, with reduced resources but located closer to service requesters, to complement remote cloud data centers. This hierarchical and geo-distributed architecture allows the definition of different time constraints that can be taken into account when mapping services into data centers. This feature is especially useful in the Virtual Network Function (VNF) placement problem, where the network functions composing a Service Function Chain (SFC) may require more or less strong delay restrictions. We propose the ModPG (Modified Priority-based Greedy) heuristic, a VNF placement solution that weighs the latency, bandwidth, and resource restrictions, but also the instantiation cost of VNFs. ModPG is an improved solution of a previous proposal (called PG). Although both heuristics share the same optimization target, that is the reduction of the total substrate resource cost, the ModPG heuristic identifies and solves a limitation of the PG solution: the mapping of sets of SFCs that include a significant proportion of SFC requests with strong low-delay restrictions. Unlike PG heuristic performance evaluation, where the amount of SFC requests with strong low-delay restrictions is not considered as a factor to be analyzed, in this work, both solutions are compared considering the presence of 1%, 15%, and 25% of this type of SFC request. Results show that the ModPG heuristic optimizes the target cost similarly to the original proposal, and at the same time, it offers a better performance when a significant number of low-delay demanding SFC requests are present.
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Pratte, Brenda S., Kim Eplin, and Teresa Thiel. "Cross-Functionality of Nitrogenase Components NifH1 and VnfH in Anabaena variabilis." Journal of Bacteriology 188, no. 16 (August 15, 2006): 5806–11. http://dx.doi.org/10.1128/jb.00618-06.
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ABSTRACT Anabaena variabilis fixes nitrogen under aerobic growth conditions in differentiated cells called heterocysts using either a Mo nitrogenase or a V nitrogenase. The nifH1 gene, which encodes the dinitrogenase reductase of the Mo nitrogenase that is expressed only in heterocysts, is cotranscribed with nifD1 and nifK1, which together encode the Mo dinitrogenase. These genes were expressed in the presence or absence of molybdate or vanadate. The vnfH gene, which encodes the dinitrogenase reductase of the V nitrogenase, was located about 23 kb from vnfDGK, which encodes the V dinitrogenase; however, like vnfDGK, vnfH was expressed only in the absence of molybdate, with or without vanadate. Like nifH1, the vnfH gene was expressed exclusively in heterocysts under either aerobic or anaerobic growth conditions and thus is under the control of developmental factors. The vnfH mutant was able to grow diazotrophically using the V nitrogenase, because NifH1, which was also made in cells starved for molybdate, could substitute for VnfH. Under oxic conditions, the nifH1 mutant grew in the absence of molybdate but not in its presence, using VnfH, while the nifH1 vnfH double mutant did not grow diazotrophically with or without molybdate or vanadate. A nifH1 mutant that expressed nifDK and vnfH but not vnfDGK was able to grow and fix nitrogen normally, indicating that VnfH could substitute for NifH in the Mo nitrogenase and that these dinitrogenase reductases are not involved in determining the metal specificity of the Mo nitrogenase or the V nitrogenase.
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Molina Zarca, Alejandro, Dan Garcia-Carrillo, Jorge Bernal Bernabe, Jordi Ortiz, Rafael Marin-Perez, and Antonio Skarmeta. "Enabling Virtual AAA Management in SDN-Based IoT Networks †." Sensors 19, no. 2 (January 12, 2019): 295. http://dx.doi.org/10.3390/s19020295.
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The increase of Software Defined Networks (SDN) and Network Function Virtualization (NFV) technologies is bringing many security management benefits that can be exploited at the edge of Internet of Things (IoT) networks to deal with cyber-threats. In this sense, this paper presents and evaluates a novel policy-based and cyber-situational awareness security framework for continuous and dynamic management of Authentication, Authorization, Accounting (AAA) as well as Channel Protection virtual security functions in IoT networks enabled with SDN/NFV. The virtual AAA, including network authenticators, are deployed as VNF (Virtual Network Function) dynamically at the edge, in order to enable scalable device’s bootstrapping and managing the access control of IoT devices to the network. In addition, our solution allows distributing dynamically the necessary crypto-keys for IoT Machine to Machine (M2M) communications and deploy virtual Channel-protection proxys as VNFs, with the aim of establishing secure tunnels among IoT devices and services, according to the contextual decisions inferred by the cognitive framework. The solution has been implemented and evaluated, demonstrating its feasibility to manage dynamically AAA and channel protection in SDN/NFV-enabled IoT scenarios.
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Zhang, Dong, Xiang Lin, and Xiang Chen. "Multiple instances mapping of Service Function Chain with parallel Virtual Network Functions." Journal of Algorithms & Computational Technology 13 (January 2019): 174830261986853. http://dx.doi.org/10.1177/1748302619868537.
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Network Function Virtualization addresses the defect of traditional middleboxes and enables operators to implement new services through a process named Service Function Chain mapping. Service Function Chain is composed by a sequence of Virtual Network Functions (VNFs) which is deployed in shared platforms. Service Function Chain with parallel VNFs is proposed to reduce the delivery latency. In this paper, a multiple instances mapping scheme named MIM is proposed to resolve the performance bottleneck introduced by the imbalance of parallel VNFs. A integer programing model is established to describe the multiple instances mapping problem based on queuing theory, and a double layer Genetic Algorithm is used to allocate parallel VNFs with multiple instances. Simulation results show that the multiple instances mapping scheme can improve the performance of Service Function Chain with parallel VNFs effectively.
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Ramalingam, Senthilmurugan, Vidya Ramamurthy, Lalji Gediya, Francis Murigi, Puranik Purushottamachar, Weiliang Huang, Eun Choi, et al. "The Novel Mnk1/2 Degrader and Apoptosis Inducer VNLG-152 Potently Inhibits TNBC Tumor Growth and Metastasis." Cancers 11, no. 3 (March 3, 2019): 299. http://dx.doi.org/10.3390/cancers11030299.
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Currently, there are no effective therapies for patients with triple-negative breast cancer (TNBC), an aggressive and highly metastatic disease. Activation of eukaryotic initiation factor 4E (eIF4E) by mitogen-activated protein kinase (MAPK)-interacting kinases 1 and 2 (Mnk1/2) play a critical role in the development, progression and metastasis of TNBC. Herein, we undertook a comprehensive study to evaluate the activity of a first-in-class Mnk1/2 protein degraders, racemic VNLG-152R and its two enantiomers (VNLG-152E1 and VNLG-152E2) in in vitro and in vivo models of TNBC. These studies enabled us to identify racemic VNLG-152R as the most efficacious Mnk1/2 degrader, superior to its pure enantiomers. By targeting Mnk1/2 protein degradation (activity), VNLG-152R potently inhibited both Mnk-eIF4E and mTORC1 signaling pathways and strongly regulated downstream factors involved in cell cycle regulation, apoptosis, pro-inflammatory cytokines/chemokines secretion, epithelial-mesenchymal transition (EMT) and metastasis. Most importantly, orally bioavailable VNLG-152R exhibited remarkable antitumor (91 to 100% growth inhibition) and antimetastatic (~80% inhibition) activities against cell line and patient-derived TNBC xenograft models, with no apparent host toxicity. Collectively, these studies demonstrate that targeting Mnk-eIF4E/mTORC1 signaling with a potent Mnk1/2 degrader, VNLG-152R, is a novel therapeutic strategy that can be developed as monotherapy for the effective treatment of patients with primary/metastatic TNBC.
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Baldi, Mario, and Amedeo Sapio. "Network Function Modeling and Performance Estimation." International Journal of Electrical and Computer Engineering (IJECE) 8, no. 5 (October 1, 2018): 3021. http://dx.doi.org/10.11591/ijece.v8i5.pp3021-3037.
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<p>This work introduces a methodology for the modelization of network functions focused on the identification of recurring execution patterns as basic building blocks and aimed at providing a platform independent representation. By mapping each modeling building block on specific hardware, the performance of the network function can be estimated in termsof maximum throughput that the network function can achieve on the specific execution platform. The approach is such that once the basic modeling building blocks have been mapped, the estimate can be computed automatically for any modeled network function. Experimental results on several sample network functions show that although our approach cannot be very accurate without taking in consideration traffic characteristics, it is very valuable for those application where even loose estimates are key. One such example is orchestration in network functions virtualization (NFV) platforms, as well as in general virtualization platforms where virtual machine placement is based also on the performance<br />of network services offered to them. Being able to automatically estimate the performance of a virtualized network function (VNF) on different execution hardware, enables optimal placement of VNFs themselves as well as the virtual hosts they serve, while efficiently utilizing available resources.</p>
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Ungerer, Justin L., Brenda S. Pratte, and Teresa Thiel. "RNA Processing of Nitrogenase Transcripts in the Cyanobacterium Anabaena variabilis." Journal of Bacteriology 192, no. 13 (April 30, 2010): 3311–20. http://dx.doi.org/10.1128/jb.00278-10.
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ABSTRACT Little is known about the regulation of nitrogenase genes in cyanobacteria. Transcription of the nifH1 and vnfH genes, encoding dinitrogenase reductases for the heterocyst-specific Mo-nitrogenase and the alternative V-nitrogenase, respectively, was studied by using a lacZ reporter. Despite evidence for a transcription start site just upstream of nifH1 and vnfH, promoter fragments that included these start sites did not drive the transcription of lacZ and, for nifH1, did not drive the expression of nifHDK1. Further analysis using larger regions upstream of nifH1 indicated that a promoter within nifU1 and a promoter upstream of nifB1 both contributed to expression of nifHDK1, with the nifB1 promoter contributing to most of the expression. Similarly, while the region upstream of vnfH, containing the putative transcription start site, did not drive expression of lacZ, the region that included the promoter for the upstream gene, ava4055, did. Characterization of the previously reported nifH1 and vnfH transcriptional start sites by 5′RACE (5′ rapid amplification of cDNA ends) revealed that these 5′ ends resulted from processing of larger transcripts rather than by de novo transcription initiation. The 5′ positions of both the vnfH and nifH1 transcripts lie at the base of a stem-loop structure that may serve to stabilize the nifHDK1 and vnfH specific transcripts compared to the transcripts for other genes in the operons providing the proper stoichiometry for the Nif proteins for nitrogenase synthesis.
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Sharma, Gourav Prateek, Wouter Tavernier, Didier Colle, and Mario Pickavet. "VNF-AAPC: Accelerator-aware VNF placement and chaining." Computer Networks 177 (August 2020): 107329. http://dx.doi.org/10.1016/j.comnet.2020.107329.
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Soriano, Ronaldo G., Reylan B. David, and Norberto V. Martinez. "Diagnostic Value of Computerized Dynamic Posturography in the Assessment of Peripheral Vestibular Disorders." Philippine Journal of Otolaryngology-Head and Neck Surgery 30, no. 1 (June 30, 2015): 14–16. http://dx.doi.org/10.32412/pjohns.v30i1.373.
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Objective: This study aims to determine the sensitivity, specificity, positive predictive value and negative predictive value of Computerized Dynamic Posturography (CDP) in properly labeling patients with peripheral vestibular disorders by Videonystagmography (VNG) as having vestibular dysfunction.
Methods:
Study Design: Case - Control Study
Setting: Tertiary Private Hospital
Subjects: Twenty-three (23) patients aged 18 and above, with no history of hypertension or cardiovascular disease and no intake of anti-vertigo medications for at least 48 hours prior to testing, and with complete VNG and CDP results obtained on the same day or at least two days apart were included in the study. Cases were defined as those diagnosed with a peripheral vestibular disorder by VNG while controls were defined as those with normal VNG results. Sensitivity, specificity, positive predictive value and negative predictive value of CDP in labeling those with peripheral vestibular disorders as vestibular were determined using VNG as gold standard.
Results: There were 11 cases (4 males, 7 females) and 12 controls (8 males, 4 females). Using VNG as the gold standard for diagnosing peripheral vestibular disorders, CDP had a sensitivity of 45.45% and specificity of 66.67% with Positive Predictive Value(PPV) of 55.56% and Negative Predictive Value(NPV) of 57.14% in assessing peripheral vestibular disorders among the adults tested. Interestingly, 33.33% of patients with normal VNG may actually have had a vestibular dysfunction that could be detected by CDP.
Conclusion:
Prospective studies with larger sample sizes utilizing VNG and CDP are recommended in order to verify our findings.
Keywords: dizziness, posturography, vertigo
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Brody-Camp, Sabrina, John A. Risey, and Edward D. McCoul. "Vestibular Characteristics of Patients with Chronic Rhinosinusitis." OTO Open 2, no. 4 (October 2018): 2473974X1880499. http://dx.doi.org/10.1177/2473974x18804993.
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Chronic rhinosinusitis (CRS) is a common disease entity with symptoms that may extend beyond the sinonasal tract. Limited data exist regarding the relationship between CRS and the vestibular system, and no previous study has investigated the association between objective vestibular findings on videonystagmography (VNG) and the diagnosis of CRS. We analyzed a prospective database of 3078 patients who underwent VNG at our institution over an 8-year period, which included 70 subjects who had a diagnosis of CRS assigned by an otolaryngologist. Overall, the VNG findings for patients with CRS were similar to those of the general population, with 50% exhibiting normal vestibular function. Peripheral lesions were the most common abnormal VNG finding, with a wide range of subjective symptom descriptions. This preliminary report of the prevalence of objective vestibular findings in patients with CRS may form the basis for future study.
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Jahedi, Zahra, and Thomas Kunz. "The Value of Simple Heuristics for Virtualized Network Function Placement." Future Internet 12, no. 10 (September 25, 2020): 161. http://dx.doi.org/10.3390/fi12100161.
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Network Function Virtualization (NFV) can lower the CAPEX and/or OPEX for service providers and allow for quick deployment of services. Along with the advantages come some challenges. The main challenge in the use of Virtualized Network Functions (VNF) is the VNFs’ placement in the network. There is a wide range of mathematical models proposed to place the Network Functions (NF) optimally. However, the critical problem of mathematical models is that they are NP-hard, and consequently not applicable to larger networks. In wireless networks, we are considering the scarcity of Bandwidth (BW) as another constraint that is due to the presence of interference. While there exist many efforts in designing a heuristic model that can provide solutions in a timely manner, the primary focus with such heuristics was almost always whether they provide results almost as good as optimal solution. Consequently, the heuristics themselves become quite non-trivial, and solving the placement problem for larger networks still takes a significant amount of time. In this paper, in contrast, we focus on designing a simple and scalable heuristic. We propose four heuristics, which are gradually becoming more complex. We compare their performance with each other, a related heuristic proposed in the literature, and a mathematical optimization model. Our results demonstrate that while more complex placement heuristics do not improve the performance of the algorithm in terms of the number of accepted placement requests, they take longer to solve and therefore are not applicable to larger networks.In contrast, a very simple heuristic can find near-optimal solutions much faster than the other more complicated heuristics while keeping the number of accepted requests close to the results achieved with an NP-hard optimization model.
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CHEN, L., and Y.-D. GU. "An Experimental Study of Contralateral C7 Root Transfer with Vascularized Nerve Grafting to Treat Brachial Plexus Root Avulsion." Journal of Hand Surgery 19, no. 1 (February 1994): 60–66. http://dx.doi.org/10.1016/0266-7681(94)90051-5.
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Experimental rat models of simulated brachial plexus injuries were devised to compare the effect of contralateral C7 root transfer with phrenic neurotization. The effect of vascularized nerve grafting (VNG) was also compared with the use of conventional nerve grafts (CNG) in the treatment of root avulsion of the brachial plexus. 160 rats were randomly divided into four groups of 40 each; contralateral C7 root transfer with a vascularized ulnar nerve graft (C7-VNG), contralateral C7 root transfer with conventional ulnar nerve grafting (C7-CNG), ipsilateral phrenic nerve transfer with a vascularized ulnar nerve graft (P-VNG) and ipsilateral phrenic nerve transfer with conventional ulnar nerve grafting (P-CNG). Electrophysiological and histological examinations and functional evaluation were performed at different post-operative intervals. C7 root transfer was found to be superior to phrenic nerve transfer and VNG superior to CNG. Severance of the C7 nerve root was not found to affect limb function on the healthy side.
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Elvidge, Christopher, Mikhail Zhizhin, Kimberly Baugh, Feng Hsu, and Tilottama Ghosh. "Extending Nighttime Combustion Source Detection Limits with Short Wavelength VIIRS Data." Remote Sensing 11, no. 4 (February 15, 2019): 395. http://dx.doi.org/10.3390/rs11040395.
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The Visible Infrared Imaging Radiometer Suite (VIIRS) collects low light imaging data at night in five spectral bands. The best known of these is the day/night band (DNB) which uses light intensification for imaging of moonlit clouds in the visible and near-infrared (VNIR). The other four low light imaging bands are in the NIR and short-wave infrared (SWIR), designed for daytime imaging, which continue to collect data at night. VIIRS nightfire (VNF) tests each nighttime pixel for the presence of sub-pixel IR emitters across six spectral bands with two bands each in three spectral ranges: NIR, SWIR, and MWIR. In pixels with detection in two or more bands, Planck curve fitting leads to the calculation of temperature, source area, and radiant heat using physical laws. An analysis of January 2018 global VNF found that inclusion of the NIR and SWIR channels results in a doubling of the VNF pixels with temperature fits over the detection numbers involving the MWIR. The addition of the short wavelength channels extends detection limits to smaller source areas across a broad range of temperatures. The VIIRS DNB has even lower detection limits for combustion sources, reaching 0.001 m2 at 1800 K, a typical temperature for a natural gas flare. Comparison of VNF tallies and DNB fire detections in a 2015 study area in India found the DNB had 15 times more detections than VNF. The primary VNF error sources are false detections from high energy particle detections (HEPD) in space and radiance saturation on some of the most intense events. The HEPD false detections are largely eliminated in the VNF output by requiring multiband detections for the calculation of temperature and source size. Radiance saturation occurs in about 1% of the VNF detections and occurs primarily in the M12 spectral band. Inclusion of the radiances affected by saturation results in temperature and source area calculation errors. Saturation is addressed by identifying the presence of saturation and excluding those radiances from the Planck curve fitting. The extremely low detection limits for the DNB indicates that a DNB fire detection algorithm could reveal vast numbers of combustion sources that are undetectable in longer wavelength VIIRS data. The caveats with the DNB combustion source detection capability is that it should be restricted to pixels that are outside the zone of known VIIRS detected electric lighting.
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Bielińska, Marzena, Anna Polaczkiewicz, Piotr Pietkiewicz, Jarosław Miłoński, and Jurek Olszewski. "Concurrent ENG and VNG recording in healthy people – preliminary report." Otolaryngologia Polska 72, no. 2 (April 30, 2018): 45–49. http://dx.doi.org/10.5604/01.3001.0011.7251.
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Introduction. The aim of the study was to evaluate concurrent recording of ENG and VNG measurements in selected diagnostic tests in healthy subjects so as to explore potential sensitivity and applicability of this kind of testing in the diagnostics of vertigo. Material and methods. The study was carried out in 50 healthy subjects including 24 women and 26 men aged 20-22 (mean age of 20.5 years) reporting no otorhinolaryngological organ-related complaints and no history of any balance disorders or vertigo. Every patient underwent subjective and objective otoneurological tests, electronystagmographic (ENG) examination including calibration, head-tracking test, optokinetic nystagmus test, rotatory chair test, positional tests according to Cawthorne and Rosen, and Hallpike caloric test as well as videonystagmographic (VNG) examination which included calibration, spontaneous nystagmus evaluation, head-tracking test, positional tests according to Cawthorne and Rosen with neck rotation test, and Hallpike caloric test. At first, ENG and VNG examinations were carried out separately at a 24-hour interval. Concurrent ENG and VNG recording was carried out 48 hours following the last test, with calibration being performed again before both evaluations. The concurrent recording included the spontaneous nystagmus evaluation, positional tests according to Cawthrone and Rose with the neck rotation test, and Hallpike caloric test. Results. No negative mutual interference of the conducted tests has been observed. Both in the concurrent and in the separate recordings, the caloric test revealed lower values of the mean velocity of the nystagmus free phase in the ENG test as compared to the VNG test. No signs of spontaneous nystagmus, as well as no signs of optokinetic and positional nystagmus, were detected in any case. Conclusions. The conducted tests did not reveal any mutual excludability between the selected ENG and VNG diagnostic tests upon concurrent recording. However, the concurrent use of both examinations in the diagnostics of balance disorders and vertigo requires further studies.
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Ruiz, Lidia, Ramón Durán, Ignacio de Miguel, Pouria Khodashenas, Jose-Juan Pedreño-Manresa, Noemí Merayo, Juan Aguado, et al. "A Genetic Algorithm for VNF Provisioning in NFV-Enabled Cloud/MEC RAN Architectures." Applied Sciences 8, no. 12 (December 13, 2018): 2614. http://dx.doi.org/10.3390/app8122614.
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5G technologies promise to bring new network and service capacities and are expected to introduce significant architectural and service deployment transformations. The Cloud-Radio Access Networks (C-RAN) architecture, enabled by the combination of Software Defined Networking (SDN), Network Function Virtualization (NFV) and Mobile Edge Computing (MEC) technologies, play a key role in the development of 5G. In this context, this paper addresses the problems of Virtual Network Functions (VNF) provisioning (VNF-placement and service chain allocation) in a 5G network. In order to solve that problem, we propose a genetic algorithm that, considering both computing resources and optical network capacity, minimizes both the service blocking rate and CPU usage. In addition, we present an algorithm extension that adds a learning stage and evaluate the algorithm performance benefits in those scenarios where VNF allocations can be reconfigured. Results reveal and quantify the advantages of reconfiguring the VNF mapping depending on the current demands. Our methods outperform previous proposals in the literature, reducing the service blocking ratio while saving energy by reducing the number of active core CPUs.
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Wu, Xing, Jing Duan, Mingyu Zhong, Peng Li, and Jianjia Wang. "VNF Chain Placement for Large Scale IoT of Intelligent Transportation." Sensors 20, no. 14 (July 8, 2020): 3819. http://dx.doi.org/10.3390/s20143819.
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With the advent of the Internet of things (IoT), intelligent transportation has evolved over time to improve traffic safety and efficiency as well as to reduce congestion and environmental pollution. However, there are some challenging issues to be addressed so that it can be implemented to its full potential. The major challenge in intelligent transportation is that vehicles and pedestrians, as the main types of edge nodes in IoT infrastructure, are on the constant move. Hence, the topology of the large scale network is changing rapidly over time and the service chain may need reestablishment frequently. Existing Virtual Network Function (VNF) chain placement methods are mostly good at static network topology and any evolvement of the network requires global computation, which leads to the inefficiency in computing and the waste of resources. Mapping the network topology to a graph, we propose a novel VNF placement method called BVCP (Border VNF Chain Placement) to address this problem by elaborately dividing the graph into multiple subgraphs and fully exploiting border hypervisors. Experimental results show that BVCP outperforms the state-of-the-art method in VNF chain placement, which is highly efficient in large scale IoT of intelligent transportation.
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Gnanasekar, Subashini, Prashant Sonar, Sagar M. Jain, Soon Kwan Jeong, and Andrews Nirmala Grace. "Performance evaluation of a low-cost, novel vanadium nitride xerogel (VNXG) as a platinum-free electrocatalyst for dye-sensitized solar cells." RSC Advances 10, no. 67 (2020): 41177–86. http://dx.doi.org/10.1039/d0ra06984a.
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A vanadium nitride xerogel (VNXG) was synthesised by a simple and effective method of ammonialising a vanadium pentoxide xerogel at a higher temperature. The electrochemical and photo-current studies were performed towards a counter electrode for DSSC.
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Liu, Yanyang, Jing Ran, Hefei Hu, and Bihua Tang. "Energy-Efficient Virtual Network Function Reconfiguration Strategy Based on Short-Term Resources Requirement Prediction." Electronics 10, no. 18 (September 17, 2021): 2287. http://dx.doi.org/10.3390/electronics10182287.
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In Network Function Virtualization, the resource demand of the network service evolves with the change of network traffic. VNF dynamic migration has become an effective method to improve network performance. However, for the time-varying resource demand, how to minimize the long-term energy consumption of the network while guaranteeing the Service Level Agreement (SLA) is the key issue that lacks previous research. To tackle this dilemma, this paper proposes an energy-efficient reconfiguration algorithm for VNF based on short-term resource requirement prediction (RP-EDM). Our algorithm uses LSTM to predict VNF resource requirements in advance to eliminate the lag of dynamic migration and determines the timing of migration. RP-EDM eliminates SLA violations by performing VNF separation on potentially overloaded servers and consolidates low-load servers timely to save energy. Meanwhile, we consider the power consumption of servers when booting up, which is existing objectively, to avoid switching on/off the server frequently. The simulation results suggest that RP-EDM has a good performance and stability under machine learning models with different accuracy. Moreover, our algorithm increases the total service traffic by about 15% while ensuring a low SLA interruption rate. The total energy cost is reduced by more than 20% compared with the existing algorithms.
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Ben Hamed, Asma, Aris Leivadeas, Matthias Falkner, and Nikolai Pitaev. "VNF Chaining Performance Characterization under Multi-Feature and Oversubscription Using SR-IOV." Informatics 7, no. 3 (September 14, 2020): 33. http://dx.doi.org/10.3390/informatics7030033.
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Network Function Virtualization (NFV) has revolutionized the way network services are offered, leading Enterprise and Service Providers to increasingly adapt their portfolio of network products in order to reap the benefits of flexible network service deployment and cost reduction promises. With this method, network services are offered in the form of software images instead of dedicated hardware. However, NFV presents several challenges, including standard networking challenges (e.g., security, resilience, and availability), management and orchestration challenges, resource allocation challenges, and performance trade-off challenges of using standard x86 servers instead of dedicated and proprietary hardware. The first three challenges are typical challenges found in virtualization environments and have been extensively addressed in the literature. However, the performance trade-off challenge can be the most impactful when offering networking services, negatively affecting the throughput and delay performance achieved. Thus, in this paper, we investigate and propose several configurations on a virtualized system for increasing the performance in terms of throughput and delay while chaining multiple virtual network functions (VNFs) in case of an undersubscribed and oversubscribed system, where the resource demands exceeds the physical resource capacity. Specifically, we use the Single Root Input Output Virtualization (SR-IOV) as our Input/Output (I/O) technology, and analyze the attainable throughput and delay when running multiple chained VNFs in a standard x86 server under various resource footprints and network features configurations. We show that the system throughput and delay in a multi-chained environment, offering multiple features, and under oversubscription can affect the overall performance of VNFs.
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Gandor, Florin, Manfred Tesch, Hannelore Neuhauser, Doreen Gruber, Hans-Jochen Heinze, Georg Ebersbach, and Thomas Lempert. "Diagnostic accuracy of a smartphone bedside test to assess the fixation suppression of the vestibulo-ocular reflex: when nothing else matters." Journal of Neurology 267, no. 7 (July 2020): 2159–63. http://dx.doi.org/10.1007/s00415-020-09947-5.
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Abstract Objective Validation of a bedside test to objectify the fixation suppression of the vestibulo-ocular reflex (FS-VOR) in patients with a cerebellar syndrome and healthy controls. Methods The vestibulo-ocular reflex and its fixation suppression were assessed by video-nystagmography (VNG) in 20 healthy subjects (mean age 56 ± 15) and 19 patients with a cerebellar syndrome (mean age 70 ± 11). The statistical cutoff delineating normal from pathological FS-VOR was determined at the 2.5th percentile of the normal distribution of the healthy cohort. VNG was then compared to a bedside test, where eye movements were recorded with a smartphone while patients were rotated on a swivel chair at a defined speed and amplitude. These videos were rated as normal or pathological FS-VOR by six blinded raters, and results compared to VNG. Results VNG in healthy controls showed FS-VOR with a reduction of nystagmus beats by 95.0% ± 7.2 (mean ± SD). The statistical cutoff was set at 80.6%. Cerebellar patients reduced nystagmus beats by only 26.3% ± 25.1. Inter-rater agreement of the smartphone video ratings was 85%. The sensitivity of the video ratings to detect an impaired FS-VOR was 99%, its specificity 92%. Inter-test agreement was 91%. Conclusion The smartphone bedside test is an easily performed, reliable, sensitive, specific, and inexpensive alternative for assessing FS-VOR.
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Ben Slama, Amine, Hanene Sahli, Aymen Mouelhi, Jihene Marrakchi, Seif Boukriba, Hedi Trabelsi, and Mounir Sayadi. "Hybrid clustering system using Nystagmus parameters discrimination for vestibular disorder diagnosis." Journal of X-Ray Science and Technology 28, no. 5 (September 19, 2020): 923–38. http://dx.doi.org/10.3233/xst-200661.
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BACKGROUD AND OBJECTIVE: The control of clinical manifestation of vestibular system relies on an optimal diagnosis. This study aims to develop and test a new automated diagnostic scheme for vestibular disorder recognition. METHODS: In this study we stratify the Ellipse-fitting technique using the Video Nysta Gmographic (VNG) sequence to obtain the segmented pupil region. Furthermore, the proposed methodology enabled us to select the most optimum VNG features to effectively conduct quantitative evaluation of nystagmus signal. The proposed scheme using a multilayer neural network classifier (MNN) was tested using a dataset involving 98 patients affected by VD and 41 normal subjects. RESULTS: The new MNN scheme uses only five temporal and frequency parameters selected out of initial thirteen parameters. The scheme generated results reached 94% of classification accuracy. CONCLUSIONS: The developed expert system is promising in solving the problem of VNG analysis and achieving accurate results of vestibular disorder recognition or diagnosis comparing to other methods or classifiers.
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Velenovsky, David S. "Electronystagmography and Videonystagmography (ENG/VNG)." Ear and Hearing 36, no. 2 (2015): e61. http://dx.doi.org/10.1097/aud.0000000000000141.
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Nguyen, Tri-Hai, and Myungsik Yoo. "A VNF Placement Optimization Framework for Network Function Virtualization." Journal of Korean Institute of Communications and Information Sciences 44, no. 10 (October 31, 2019): 1956–60. http://dx.doi.org/10.7840/kics.2019.44.10.1956.
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Kim, Hak-Yun, Tae-Un Kim, and Ho-Yong Choi. "A Two-Channel High-Performance DC-DC Converter for Mobile AMOLED Display Based on the PWM–SPWM Dual-Mode Switching Method." Electronics 10, no. 17 (August 26, 2021): 2059. http://dx.doi.org/10.3390/electronics10172059.
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In this paper, we propose a design of a two-channel high-performance DC-DC converter that provides a positive voltage VPOS with a low ripple, and a negative voltage VNEG with high power efficiency, for the purpose of enhancing power efficiency and output ripple under light loads of 100 mA or less for mobile active-matrix organic light-emitting diode (AMOLED) displays. The VPOS was designed as a boost converter using a novel input voltage variation reduction circuit (IVVRC), which rapidly changes the pulse width for input voltage fluctuations, using a feed-forward path. The VNEG was designed as an inverting buck–boost converter based on the pulse width modulation–set time variable pulse width modulation (PWM–SPWM) dual-mode switching method to enhance power efficiency, especially under light loads, and to reduce the overhead of the circuit configuration using a voltage-controlled oscillator. In addition, an adaptive dead-time using voltage detection of switching node (ADTVS) circuit was proposed to enhance power efficiency, which detects the voltage of the switching node at every cycle, and keeps the dead-time constant irrespective of changes in driving conditions. The proposed converter was fabricated with a chip size of 1.67 mm × 2.44 mm, using a 0.35 μm BCD process. Measurement results showed that the power efficiency of our converter was 72.9%~90.4% at 5 mA–100 mA light load output current, which is 2.7%~5.8% higher than the output of the previous converter. Furthermore, the output voltage ripple of VPOS and VNEG at 5 mA light load output current was 3.0 mV and 5.3 mV, respectively, which improved by 19% and 25% as compared to those of the previous converter, respectively.
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DONG, CHUANFEI, XU MA, and BINGHONG WANG. "EFFECTS OF VEHICLE NUMBER FEEDBACK IN MULTI-ROUTE INTELLIGENT TRAFFIC SYSTEMS." International Journal of Modern Physics C 21, no. 08 (August 2010): 1081–93. http://dx.doi.org/10.1142/s0129183110015683.
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We first study dynamics of traffic flow with real-time information and the influence of a new feedback strategy named Vehicle Number Feedback Strategy (VNFS) in a multi-route scenario in which dynamic information can be generated and displayed on the board (the board refers to a variable message sign where information on the routes is displayed) to guide road users to make a choice. In a multi-route scenario, our model incorporates the effects of adaptability into the cellular automaton models of traffic flow and simulation results adopting vehicle number feedback strategy have demonstrated high efficiency in controlling spatial distribution of traffic patterns compared with the other three information feedback strategies, i.e. Travel Time Feedback Strategy (TTFS), Mean Velocity Feedback Strategy (MVFS) and Congestion Coefficient Feedback Strategy (CCFS). We also discuss the influence of expected arrival rate (Vp) at the entrance on the average flux of each route, and we find that the flux adopting VNFS is always the largest at each Vp value among these four feedback strategies.