SDNにおけるパケット損失とループを防止するネットワーク設定更新方式の検討

今のインターネットは世界を結ぶ情報社会の基盤となっている。様々なサービスやアプリケーションはインターネット上で増加しており、ネットワークはますます複雑になっている。このような状態を打破するため新たなネットワークアーキテクチャの設計が必要となる。ソフトウェア定義ネットワーク（SDN）は、コントロールプレーンとデータプレーンを分離するネットワークへの新しいアプローチである。SDNネットワークにおいて、新しいトポロジーおよびサービスを適合させるため、ネットワークの設定を更新することは一般的である。この新しい技術を実現するため、OpenFlowという新しい技術を標準として導入される。OpenFlowプロトコルはコントロールプレーンとデータプレーンの間の通信が可能にする。しかし、全てのネットワーク機器において設定の更新が整合性を持たなければ、不一致性による問題が生じる。この問題により、ネットワークにおけるパケット損失やループなど不正確な動作が起こる可能性がある。本稿では、SDNとOpenFlowに関する関連技術を紹介し、SDNにおける不一致性問題を定義し、先行研究を交えて議論する。そして、パケット損失とループを防止するネットワーク設定更新方式を提案する。具体的にはSDNコントロールはネットワーク設定の更新前と更新後の転送経路を分析し、開放ループと閉合ループの有無により二つの経路間の関係を分類する。この関係を基づいて、スイッチ設定の更新の順番を計算し、コントロールはこの順番によってネットワーク設定を更新する。提案の正確性を検証するため、コントロールPOXとネットワークエミュレータMininet上で実装しシミュレーションを行い、TCPとUDP二つのプロトコルでリンクのスループットやパケット損失を評価した。結果としては提案手法はリンクのスループットを保証し、パケット損失を抑制を実現した。また上記の提案手法を実装するためには、コントローラとスイッチ間の遅延が大きく作用するため、コントロールとスイッチの間に遅延の測定と設置の手法を提案し、評価を行った。最後に関連研究と比較して提案方式を議論した。電気通信大学201

A Study on Efficient Service Function Chain Placement in Network Function Virtualization Environment

電気通信大学202

Reciprocal polarization imaging of complex media

The vectorial evolution of polarized light interaction with a medium can reveal its microstructure and anisotropy beyond what can be obtained from scalar light interaction. Anisotropic properties (diattenuation, retardance, and depolarization) of a complex medium can be quantified by polarization imaging by measuring the Mueller matrix. However, polarization imaging in the reflection geometry, ubiquitous and often preferred in diverse applications, has suffered a poor recovery of the medium's anisotropic properties due to the lack of suitable decomposition of the Mueller matrices measured inside a backward geometry. Here, we present reciprocal polarization imaging of complex media after introducing reciprocal polar decomposition for backscattering Mueller matrices. Based on the reciprocity of the optical wave in its forward and backward scattering paths, the anisotropic diattenuation, retardance, and depolarization of a complex medium are determined by measuring the backscattering Mueller matrix. We demonstrate reciprocal polarization imaging in various applications for quantifying complex non-chiral and chiral media (birefringence resolution target, tissue sections, and glucose suspension), uncovering their anisotropic microstructures with remarkable clarity and accuracy. We also highlight types of complex media that Lu-Chipman and differential decompositions of backscattering Mueller matrices lead to erroneous medium polarization properties, whereas reciprocal polar decomposition recovers properly. Reciprocal polarization imaging will be instrumental in imaging complex media from remote sensing to biomedicine and will open new applications of polarization optics in reflection geometry

Effects of elevated ozone concentration and nitrogen addition on ammonia stomatal compensation point in a poplar clone

The stomatal compensation point of ammonia (χs) is a key factor controlling plant-atmosphere NH3 exchange, which is dependent on the nitrogen (N) supply and varies among plant species. However, knowledge gaps remain concerning the effects of elevated atmospheric N deposition and ozone (O3) on χs for forest species, resulting in large uncertainties in the parameterizations of NH3 incorporated into atmospheric chemistry and transport models (CTMs). Here, we present leaf-scale measurements of χs for hybrid poplar clone ‘546’ (Populusdeltoides cv. 55/56 x P. deltoides cv. Imperial) growing in two N treatments (N0, no N added; N50, 50 kg N ha−1 yr−1 urea fertilizer added) and two O3 treatments (CF, charcoal-filtered air; E-O3, non-filtered air plus 40 ppb) for 105 days. Our results showed that χs was significantly reduced by E-O3 (41%) and elevated N (19%). The interaction of N and O3 was significant, and N can mitigate the negative effects of O3 on χs. Elevated O3 significantly reduced the light-saturated photosynthetic rate (Asat) and chlorophyll (Chl) content and significantly increased intercellular CO2 concentrations (Ci), but had no significant effect on stomatal conductance (gs). By contrast, elevated N did not significantly affect all measured photosynthetic parameters. Overall, χs was significantly and positively correlated with Asat, gs and Chl, whereas a significant and negative relationship was observed between χs and Ci. Our results suggest that O3-induced changes in Asat, Ci and Chl may affect χs. Our findings provide a scientific basis for optimizing parameterizations of χs in CTMs in response to environmental change factors (i.e., elevated N deposition and/or O3) in the future

Implementation of trait-based ozone plant sensitivity in the Yale interactive terrestrial biosphere model v1.0 to assess global vegetation damage

A major limitation in modeling global ozone (O3) vegetation damage has long been the reliance on empiri- cal O3 sensitivity parameters derived from a limited num- ber of species and applied at the level of plant functional types (PFTs), which ignore the large interspecific variations within the same PFT. Here, we present a major advance in large-scale assessments of O3 plant injury by linking the trait leaf mass per area (LMA) and plant O3 sensitivity in a broad and global perspective. Application of the new ap- proach and a global LMA map in a dynamic global veg- etation model reasonably represents the observed interspe- cific responses to O3 with a unified sensitivity parameter for all plant species. Simulations suggest a contemporary global mean reduction of 4.8 % in gross primary productivity by O3, with a range of 1.1 %–12.6 % for varied PFTs. Hotspots with damage > 10 % are found in agricultural areas in the eastern US, western Europe, eastern China, and India, accompanied by moderate to high levels of surface O3. Furthermore, we simulate the distribution of plant sensitivity to O3, which is highly linked with the inherent leaf trait trade-off strategies of plants, revealing high risks for fast-growing species with low LMA, such as crops, grasses, and deciduous trees

Genome-Wide Analysis of DNA Methylation and Cigarette Smoking in a Chinese Population

Background: Smoking is a risk factor for many human diseases. DNA methylation has been related to smoking, but genome-wide methylation data for smoking in Chinese populations is limited. Objectives: We aimed to investigate epigenome-wide methylation in relation to smoking in a Chinese population. Methods: We measured the methylation levels at > 485,000 CpG sites (CpGs) in DNA from leukocytes using a methylation array and conducted a genome-wide meta-analysis of DNA methylation and smoking in a total of 596 Chinese participants. We further evaluated the associations of smoking-related CpGs with internal polycyclic aromatic hydrocarbon (PAH) biomarkers and their correlations with the expression of corresponding genes. Results: We identified 318 CpGs whose methylation levels were associated with smoking at a genome-wide significance level (false discovery rate < 0.05), among which 161 CpGs annotated to 123 genes were not associated with smoking in recent studies of Europeans and African Americans. Of these smoking-related CpGs, methylation levels at 80 CpGs showed significant correlations with the expression of corresponding genes (including RUNX3, IL6R, PTAFR, ANKRD11, CEP135 and CDH23), and methylation at 15 CpGs was significantly associated with urinary 2-hydroxynaphthalene, the most representative internal monohydroxy-PAH biomarker for smoking. Conclusion: We identified DNA methylation markers associated with smoking in a Chinese population, including some markers that were also correlated with gene expression. Exposure to naphthalene, a byproduct of tobacco smoke, may contribute to smoking-related methylation. Citation: Zhu X, Li J, Deng S, Yu K, Liu X, Deng Q, Sun H, Zhang X, He M, Guo H, Chen W, Yuan J, Zhang B, Kuang D, He X, Bai Y, Han X, Liu B, Li X, Yang L, Jiang H, Zhang Y, Hu J, Cheng L, Luo X, Mei W, Zhou Z, Sun S, Zhang L, Liu C, Guo Y, Zhang Z, Hu FB, Liang L, Wu T. 2016. Genome-wide analysis of DNA methylation and cigarette smoking in Chinese. Environ Health Perspect 124:966–973; http://dx.doi.org/10.1289/ehp.150983

Abnormal change in dynamic mechanical behavior of metallic glass by laser shock peening

Laser shock peening (LSP) has been shown to be an effective technique to improve the plasticity of metallic glasses (MGs) by inducing residual stress and structural rejuvenation. However, the microstructural evolution and viscoelastic properties of MGs after LSP remain largely unknown. In this paper, the dynamic mechanical properties of Zr-based MG before and after LSP treatment were investigated. An abnormal increase of storage modulus near the glass transition temperature (T-g) was observed after LSP. An increased deviation between the dynamic mechanical result and the quasi-point defect (QPD) theory prediction was also observed after the LSP treatment. A competing mechanism between the liquid-like region change and the pre-existing fringe-like precipitations is proposed to explain the unusual dynamic behaviors of MGs after LSP treatment. The results provide insightful information about the microstructural changes and viscoelastic properties of the MGs after LSP