Modification of wetting property of Inconel 718 surface by nanosecond laser texturing

Topographic and wetting properties of Inconel 718 (IN718) surfaces were modified via nanosecond laser treatment. In order to investigate surface wetting behavior without additional post treatment, three kinds of microstructures were created on IN718 surfaces, including line pattern, grid pattern and spot pattern. From the viewpoint of surface morphology, the results show that laser ablated grooves and debris significantly altered the surface topography as well as surface roughness compared with the non-treated surfaces. The effect of laser parameters (such as laser scanning speed and laser average power) on surface features was also discussed. We have observed the treated surface of IN718 showed very high hydrophilicity just after laser treatment under ambient air condistion.And this hydrophicility property has changed rapidly to the other extreme; very high hydrophobicity over just about 20 days. Further experiments and analyses have been carried out in order to investigate this phenomena. Based on the XPS analysis, the results indicate that the change of wetting property from hydrophilic to hydrophobic over time is due to the surface chemistry modifications, especially carbon content. After the contact angles reached steady state, the maximum water contact angle (WCA) for line-patterned and grid-patterned surfaces increased to 152.3 1.2° and 156.8 1.1° with the corresponding rolling angle (RA) of 8.8 1.1° and 6.5 0.8°, respectively. These treated IN718 surfaces exhibited superhydrophobic property. However, the maximum WCA for the spot-patterned surfaces just increased to 140.8 2.8° with RA above 10°. Therefore, it is deduced that laser-inscribed modification of surface wettability has high sensitivity to surface morphology and surface chemical compositions. This work can be utilized to optimize the laser processing parameters so as to fabricate desired IN718 surfaces with hydrophobic or even superhydrophobic property and thus extend the applications of IN718 material in various fields

Numerical modeling of the horizontal flow and concentration distribution of nitrogen within a stored-paddy bulk in a large warehouse: Poster

The insect population in grain stores can be kept under control by maintaining a high concentration of N<sub>2</sub> gas throughout the grain bed. The development of controlled atmosphere storage technology for insect control requires an accurate prediction of the distribution of introduced gases in bulk grain. In this paper, based on the convective-diffusion model, the horizontal flow of N<sub>2</sub>, which was introduced into the paddy bulk in a large warehouse by means of the horizontal ventilation system, are modeled as fluid flow in a porous medium. The experimental data for N<sub>2</sub> transfer and flow through ducts and bulk paddy were used to validate the model. The equations were solved using the finite difference method, and the predictions from the proposed model were in good agreement with the experimental results. The concentration distribution and flow uniformity of nitrogen in stored paddy were also analyzed during the nitrogen-filling procedure for CA storage. It was shown that it is feasible and practical to introduce nitrogen into stored bulk grain in a large warehouse by means of the horizontal ventilation system.The insect population in grain stores can be kept under control by maintaining a high concentration of N<sub>2</sub> gas throughout the grain bed. The development of controlled atmosphere storage technology for insect control requires an accurate prediction of the distribution of introduced gases in bulk grain. In this paper, based on the convective-diffusion model, the horizontal flow of N<sub>2</sub>, which was introduced into the paddy bulk in a large warehouse by means of the horizontal ventilation system, are modeled as fluid flow in a porous medium. The experimental data for N<sub>2</sub> transfer and flow through ducts and bulk paddy were used to validate the model. The equations were solved using the finite difference method, and the predictions from the proposed model were in good agreement with the experimental results. The concentration distribution and flow uniformity of nitrogen in stored paddy were also analyzed during the nitrogen-filling procedure for CA storage. It was shown that it is feasible and practical to introduce nitrogen into stored bulk grain in a large warehouse by means of the horizontal ventilation system

Distributed Coordination of Fractional Dynamical Systems with Exogenous Disturbances

Distributed coordination of fractional multiagent systems with external disturbances is studied. The state observer of fractional dynamical system is presented, and an adaptive pinning controller is designed for a little part of agents in multiagent systems without disturbances. This adaptive pinning controller with the state observer can ensure multiple agents' states reaching an expected reference tracking. Based on disturbance observers, the controllers are composited with the pinning controller and the state observer. By applying the stability theory of fractional order dynamical systems, the distributed coordination of fractional multiagent systems with external disturbances can be reached asymptotically

A toxin hunter in the microworld of bacteria: a project on novel inhibitors against bacterial AB5 toxins

[要旨] 病原性細菌が産生する蛋白性のAB5型トキシンは1個のAサブユニットと5個のBサブユニットから構成される外毒素である。両サブユニットはそれぞれ特徴的な役割を持ち，互いに巧妙に機能分担をして一つのトキシンを形成している。Aサブユニットは主に毒性に直接関与する特異的な酵素活性を有する。一方，Bサブユニットは標的細胞のレセプターに対する結合能を有し，AB5型トキシンを標的細胞に吸着させる。ここでは毒性が全く異なるAB5型トキシンとして，コレラ菌が産生するコレラトキシン（CT），腸管出血性大腸菌が産生する志賀様トキシン（Stx），及び志賀トキシン産生大腸菌が産生するサブチラーゼサイトトキシン（SubAB）の3種類に関して，その作用メカニズムに着目した毒性を抑制する阻害因子の探索などの研究を紹介する。これらの3種類のAB5型トキシンに着目した理由は，それぞれのトキシンを産生する病原菌による感染症が世界的に流行し，社会問題となっているからである。つまり，コレラ菌は依然として発展途上国で大きな問題であり，腸管出血性大腸菌のO157:H7による集団食中毒は我国でも依然として多い。さらに21世紀になり，血清型がO157:H7以外の腸管出血性大腸菌による集団食中毒が世界的に急増しているためである。いずれも抗生物質を使用した後の残留トキシンによる病態悪化が指摘されており，トキシンを効率よく無毒化する事が急務である。[SUMMARY] Bacterial AB5 toxins are proteins, produced by pathogenic bacteria including of Vibrio cholerae, Shigella dysenteriae, and enterohaemorrhagic Escherichia coli, which are usually released into the extracellular medium and cause disease by killing or altering the metabolism of target eukaryotic cells. The toxins are usually composed of one A subunit（a toxic domain） and five B subunits（a receptor-binding domain）. This article overviews the characteristics and mode of actions of AB5 toxins including cholera toxin, Shiga-like toxin, and subtilase cytotoxin, and highlights a project on the novel inhibitors against these bacterial AB5 toxins

Low-gap zinc porphyrin as an efficient dopant for photomultiplication type photodetectors

A new zinc porphyrin, named as Por4IC, was synthesized, which through extension of conjugation and an enhancement of planarity and donor-acceptor interactions exhibits a very low band gap. The molecule was able to efficiently facilitate a photomultiplication effect in blend with P3HT which was assisted by electron trapping followed by hole tunneling injection from the Al electrode giving rise to a high external quantum efficiency of 22 182% and a specific detectivity of 4.4 7 1012 Jones at 355 nm and at -15 V bias. This work introduces porphyrin derivatives as promising dopants for photomultiplication type photodetectors. This journal i

A unified element stiffness matrix model for variable cross-section flexure hinges in compliant mechanisms for micro/nano positioning

This paper presents a unified analytical model of element stiffness matrix for variable cross-section flexure hinges in plane deformation which is most frequently employed in planar-motion compliant mechanisms for micro/nano positioning. The unified analytical model is derived for flexure hinges in plane deformation based on the principle of virtual work. The derivation is generalized such that it can be applied to various geometries. To optimize and simplify element stiffness matrix model, four coefficients with curve integral are introduced. The results of the analysis were validated in part by modeling several previously investigated configurations, namely flexible beam hinge and right circular hinge. To further validate the proposed analytical model, finite element analysis and experimental testing were used. And the experimental testing shows the proposed unified model is more precise than pseudo-rigid-body method. The proposed model provides a concise and generalized solution to derive the element stiffness matrices of flexible hinges in plane deformation, which will have excellent applications in design and analysis of variable cross-section flexible hinges in compliant mechanisms