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Recrystallization behaviour of fine-grained magnesium alloy after hot deformation

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中国有色金属学会会刊：英文版 2007年第6期17卷 1139-1142页

作者：杨续跃 H. Miura T. sakai School of Materials Science and Engineering Central South University Department of Mechanical Engineering and Intell igent Systems UEC Tokyo Tokyo 182-8585 Japan Department of Mechanical Engineering and Intell igent Systems UEC Tokyo Tokyo 182-8585 JapanYANGXu-yue

Annealing behaviors of hot-deformed magnesium alloy AZ31 were studied at temperatures from 300 to 673 K by optical and SEM/EBSD metallographic observation. Temperature dependence of the average grain size(D) is categorized into three temperature regions, i.e. an incubation period for grain growth, rapid grain coarsening, and normal grain growth. The number of fine grains per unit area, however, is reduced remarkably even in incubation period. This leads to grain coarsening taking place continuously in the whole temperature regions. In contrast, the deformation texture scarcely changes even after full annealing at high temperatures. It is concluded that the annealing processes operating in hot-deformed magnesium alloy with continuous dynamic recrystallized grain structures can be mainly controlled by grain coarsening accompanied with no texture change, that is, continuous static recrystallization.

关键词：镁合金退火连续再结晶晶体生长纹理

Effect of DOPO-containing Flame Retardants on Poly（lactic acid）： Non-flammability, Mechanical Properties and Thermal Behaviors

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Chemical Research in Chinese Universities 2017年第1期33卷 143-149页

作者： GU Liqiang QIU Jianhui sakai Eiichi Department of Machine Intelligence and Systems Engineering Faculty of Systems Science and Technology Akita Prefectural University Yurihonjo 015-0055 Japan

The flame retardancies of three kinds of 9,10-dihydro-9-oxa-10-phosphaphenan-threne 10-oxide（DOPO）- containing flame retardant（A1, A2, A3）/poly（lactic acid）（PLA） composites[PA-n/（Ax-y）, n= 1--12; x= l, 2, 3, denoting three kinds of flame retardants; y= 10%, 20%, 30%, 40%, denoting the mass fraction of Ax] were greatly enhanced by melt blending of flame retardant Ax with PLA, including twin-screw extrusion and injection-molding processes. With only 10%（mass fraction） of Ax added to PLA, good flame retardancy with limiting oxygen index（LOI） values of more than 33% was achieved. As the Ax mass fraction was further increased to 20%, PA-n/（Ax-20%） composites showed much better flame retardancy（LOI~〉35% and UL-94 V-0 rating）. Moreover, the thermal degradation behaviors and mechanical properties of PA-n/（Ax-y） composites were investigated via thermogravimetric analysis（TGA）, differen- tial thermal analysis（DTA）, tensile testing, notched impact-bar testing, and dynamic mechanical analysis（DMA）. TGA results show that PA-n/（Ax-y） composites have slower rate of mass loss and much higher char yield, compared to neat PLA. With the addition of Ax to PLA, the DTA and DMA results indicate slight variations in glass transition tcmpe- ratures（Tg） of PA-n/（Ax-y） composites. Based on TGA results under nonisothermal conditions, the thermal degrada- tion kinetics of PA-n/（Ax-y） composites were studied by KAssinger＇s and Ozawa＇s methods. These thermal degrada- tion dynamic analyses show lower activation energies（EK or Eo） for PA-n/（Ax-y） composites, corresponding to higher mass fractions of Ax（from 10% to 40%）. The PA-n/（Ax-y） composites with good flame retardancy and good mecha- nical properties obtained in this study could be potential candidates for fire- and heat-resistant applications in auto- motive engineering and building fields with more safety and excellent performance.

关键词： Poly(lactic acid) composite Flame retardancy Thermal degradation kinetics

Carbonation of low heat portland cement paste precured in water for different time

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Journal of University of Science and Technology Beijing 2007年第2期14卷 178-184页

作者： Deping Chen Etsuo sakai Masaki Daimon Yoko Ohba Civil and Environmental Engineering School University of Science and Technology Beijing Beijing 100083 China Graduate School of Science and Engineering Tokyo Institute of Technology Tokyo 152-8552 Japan

The carbonation technique was applied to accelerate the hydration of low heat portland cement （LHC）. Before carbonation, the demoulded pastes were precured in water for 0, 2, 7, and 21 d, respectively. The results show that precuring time in water strongly influences the carbonation process. The phenolphthalein test indicates that the paste precured in water for a shorter time is more quickly carbonated than that for a longer time. The content of calcium hydroxide increases with increasing the precuring time in water, whereas, the amount of absorbed carbon dioxide changes contrarily. Scanning electron microscope （SEM） observation shows that portlandite always fills up big air bubbles in the paste during precuring in water, and the mercury intrusion porosimetry （MIP） results show that there are less large capillary pores in the paste precured in water for a longer time. It is found that the paste without precuring in water has more carbon dioxide absorption during curing in carbon dioxide atmosphere, and its total pore volume decreases remarkably with an increase in the carbonation time than that precured in water. X-ray diffraction （XRD） and Brunauer-Emmett-Teller （BET） surface area analyses indicate that the carbonate products are vaterite and calcite; CxSHy formed from carbonation has low BET surface area in comparison with that of C-S-H formed from curing in water.

关键词： carbonation carbon dioxide absorption vaterite BET surface area pore size distribution

A method for estimating the errors in many-light rendering with supersampling

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Computational Visual Media 2019年第2期5卷 151-160页

作者： Hirokazu sakai Kosuke Nabata Shinya Yasuaki Kei Iwasaki Wakayama University WakayamaWakayama640-8510Japan Dwango CG Research KADOKAWA Hongo Bldg.5245 HongoBunkyo-kuTokyo1130033Japan

In many-light rendering, a variety of visual and illumination effects, including anti-aliasing,depth of field, volumetric scattering, and subsurface scattering, are combined to create a number of virtual point lights(VPLs). This is done in order to simplify computation of the resulting illumination. Naive approaches that sum the direct illumination from many VPLs are computationally expensive;scalable methods can be computed more efficiently by clustering VPLs, and then estimating their sum by sampling a small number of VPLs. Although significant speed-up has been achieved using scalable methods, clustering leads to uncontrollable errors, resulting in noise in the rendered images. In this paper, we propose a method to improve the estimation accuracy of manylight rendering involving such visual and illumination effects. We demonstrate that our method can improve the estimation accuracy by a factor of 2.3 over the previous method.

关键词： anti-aliasing depth of field many-light rendering participating media

Dynamics and geometry of developing planar jets based on the invariants of the velocity gradient tensor

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Journal of Hydrodynamics 2015年第6期27卷 894-906页

作者：吴楠楠 sakai Yasuhiko NAGATA Kouji ITO Yasumasa School of Electric Power Engineering China University of Mining and Technology Department of Mechanical Science and Engineering Nagoya University

Based on the direct numerical simulation （DNS）, the developing planar jets under different initial conditions, e.g., the con- ditions of the exit Reynolds number and the exit mean velocity profile, are investigated. We mainly focus on the characteristics of the invariants of the velocity gradient tensor, which provides insights into the evolution of the dynamics and the geometry of the planar jets along with the flow transition. The results show that the initial flow near the jet exit is strongly predominated by the dissipation over the enstrophy, the flow transition is accompanied by a severe rotation and straining of the flow elements, where the vortex structure evolves faster than the fluid element deformation, in the fully-developed state, the irrotational dissipation is dominant and the most probable geometry of the fluid elements should remain between the biaxial stretching and the axisymmetric stretching. In addition, with a small exit Re and a parabolic profile for the exit mean streamwise velocity, the decay of the mean flow field and the magnitude of the turbulent variables will be strengthened in the process of the flow transition, however, a large exit Re will promote the flow transition to the fully-developed state. The cross-impact between the exit Re and the exit mean velocity profile is also observed in the present study.

关键词： planar jet direct numerical simulation (DNS) velocity gradient tensor flow transition joint probability density function(joint pdf)

Mapping spatial variation in acorn production from airborne hyperspectral imagery

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Forestry Studies in China 2010年第2期12卷 49-54页

作者： Kenshi sakai Institute of Symbiotic Science and Technology Department of Ecoregion ScienceFaculty of AgricultureTokyo University of Agri-culture and TechnologyTokyo 183-8509Japan

Masting is a well-marked variation in yields of oak forests. In Japan, this phenomenon is also related to wildlife management and oak regeneration practices. This study demonstrates the capability of integrating remote sensing techniques into map- ping spatial variation of acorn production. The hyperspectral images in 72 wavelengths （407-898 nm） were acquired over the study area ten times over a period of three years （2003-2005） during the early growing season of Quercus serrata using the Airborne Im- aging Spectrometer Application （AISA） Eagle System. With the canopy spectral reflectance values of 22 sample trees extracted from the images, yield estimation models were developed via multiple linear regression （MLR） analyses. Using the object-oriented classi- fication approach in eCognition, canopies representative of individual oak trees （Q. serrata） were identified from the corresponding hyperspectral imagery and combined with the fitted estimation models developed, acorn yield over the entire forest were estimated and visualized into maps. Three estimation models, obtained for June 27 in 2003, July 13 in 2004 and June 21 in 2005, showed good performance in acorn yield estimation both for the training and validation datasets, all with R2 〉 0.4, p 〈 0.05 and RRMSE 〈 1 （the relative root mean square of error）. The present study shows the potential of airborne hyperspectral imagery not only in estimating acorn yields during early growing seasons, but also in identifying Q. serrata from other image objects, based on which of the spatial distribution patterns of acorn production over large areas could be mapped. The yield map can provide within-stand abundance and valuable information for the size and spatial synchrony of acorn production.

关键词： yield map estimation model classification map acorn spatial synchrony hyperspectral imagery masting

Application of Tungsten as a De-NO_x Catalyst

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Rare Metals 1994年第3期13卷 229-235页

作者： Nakatsuji T.(sakai Chemical Industry, Co. , LId. 5-I, Ebisujimacho sakai Osako 590, Japan) sakai Chemical Industry Co 日本

Abstract A catalyst for removal of nitrogen oxides, in stationary Sources, requires many kinds of characteristicsfor commercial application. At first, a vanadium pentaoxide based catalyst was used for the NO-NH3-OZreaction because of its high activity at lower temperatures. But it was`later found that this catalyst had *** like a low thermal durability and a high conversion rate of SO: to SO3. On the other hand, tungstentrioxide was well known as a catalyst that has a high thermal durability and a low conversion rate of SOZto SO3 but showed a low activity at appropriate temperature. For these reasons, tungsten trioxide basedcatalysts have not been used in the reaction in most actual plants except for special cases. Further *** on this catalyst revealed that a catalyst comprising of titania f80 wt%￣ 90 wt%j- tungsten trioxide(5 wt% ￣ 15 wt%j, and vanadium pentaoxide (0,l wt%￣ 5 wt%j, showed a high thermal durability and alow conversion rate of SOZ to SO3 as well as high activity towards the NO-NHrOz reaction.

关键词： NO De

Effect of fiber-reinforcement on the mechanical behavior of sand approaching the critical state

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Journal of Rock Mechanics and Geotechnical Engineering 2022年第4期14卷 1241-1252页

作者： Jakhongirbek Ganiev Shotaro Yamada Masaki Nakano Takayuki sakai Department of Civil Engineering Nagoya UniversityNagoya464-8603Japan Department of Civil Engineering Tohoku UniversitySendai980-8579Japan

Several types of ground improvement methods that employ fiber-reinforcement have been developed in recent years.A series of consolidated drained triaxial compression tests has been conducted here to examine the effect of short fibers on the mechanical properties of Toyoura *** with 0%,0.2%,0.4%,and 1%fiber contents,prepared to yield random distribution,was sheared under several confining pressures and controlled via their initial relative *** test results showed that the maximum and residual deviatoric stresses increased,whereas the volumetric expansion decreased with an increase in fiber *** the stress ratio h(=q/p′)and specific volume changed depending on the fiber content and confining pressure with shear progression,they each reached the same values for a definite fiber content at the end of shearing,independent of initial relative *** other words,the unique critical state line can be found for a definite fiber ***,the greater the fiber content,the larger the slope of the critical state line at the end of ***,as the length of fibers shortened with the same percentage of fiber inclusions in sand,the deviatoric stress and the stress ratio decreased,approaching the shear-strain-volumetric response of unreinforced sand.

关键词： Fiber-reinforced sand Triaxial compression Stress ratio Critical state Relative density

Accumulation of aberrant DNA methylation during colorectal cancer development

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World Journal of Gastroenterology 2014年第4期20卷 978-987页

作者： Eiji sakai Atsushi Nakajima Atsushi Kaneda Department of Gastroenterology Yokohama City University School of Medicine Genome Science Division Research Center for Advanced Science and Technology The University of Tokyo Department of Molecular Oncology Graduate School of Medicine Chiba University CREST Japan Science and Technology Agency

Despite the recent advances in the therapeutic modalities,colorectal cancer(CRC)remains to be one of the most common causes of cancer-related *** arises through accumulation of multiple genetic and epigenetic alterations that transform normal colonic epithelium into *** crucial roles of epigenetic alterations,gene silencing by aberrant DNA methylation of promoter regions is one of the most important epigenetic *** comprehensive methylation analyses on genome-wide scale revealed that sporadic CRC can be classified into distinct *** epigenotype cooperates with specific genetic alterations,suggesting that they represent different molecular carcinogenic *** lesions of CRC,such as conventional and serrated adenomas,already show similar methylation accumulation to CRC,and can therefore be classified into those epigenotypes of *** addition,specific DNA methylation already occurs in the normal colonic mucosa,which might be utilized for prediction of the personal CRC *** methylation is suggested to occur at an earlier stage than carcinoma formation,and may predict the molecular basis for future development of ***,we review DNA methylation and CRC classification,and discuss the possible clinical usefulness of DNA methylation as biomarkers for the diagnosis,prediction of the prognosis and the response to therapy of CRC.

关键词： Colorectal cancer Colorectal adenoma Aberrant crypt foci Genetic mutation Epigenotype DNA methylation Colorectal carcinogenesis