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Base flow separation for soil erosion simulation in a granitic forested headwater catchment using a process-based model, GeoWEPP

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International Journal of Sediment Research 2023年第4期38卷 494-502页

作者： takuhei yamasaki Shoichiro Hamamoto Taku Nishimura The Graduate School of Agricultural and Life Sciences The University of Tokyo

Distributed erosion models, which simulate the physical processes of water flow and soil erosion, are effective for predicting soil erosion in forested catchments. Although subsurface flow through multiple pathways is dominant for runoff generation in forested headwater catchments, the process-based erosion model, Geo-spatial interface for Water Erosion Prediction Project(Geo WEPP), does not have an adequate subsurface component for the simulation of hillslope water flow. In the current study, the quick flow related to soil erosion during rainfall events is separated from the total hydrograph using base flow separation for Geo WEPP to use direct runoff to predict sediment discharge from a granitic-forested catchment in Japan. Water runoff and sediment discharge also are simulated using the conventional method that reproduces the total hydrograph, and the accuracy of the calculation and estimated erodibility parameters are evaluated. The proposed procedure reproduced the quick-flow runoff during rainfall and the cumulative sediment discharge from the catchment. Simultaneously, the proposed procedure overestimates water runoff during extreme weather events, such as typhoons. The estimated erodibility parameters for the hillslope soil were comparable to those of the surface soil in Japan using both the proposed procedure and the conventional one. Conversely, the channel erodibility obtained from the proposed procedure matched the observed sediment characteristics in the granitic forested catchment. The proposed procedure is a promising method to predict sediment discharge from forested catchments based on the geological features of the catchment.

关键词： Soil erosion Base flow separation GeoWEPP Headwater catchment Forest

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Active Control of Fan Noise

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Journal of Thermal Science 2008年第2期17卷 163-169页

作者： Nobuhiko yamasaki Hirotoshi TAJIMA Department of Aeronautics and Astronautics Kyushu University

In the wake-rotor interaction fan noise, a number of the interacting modes at the blade passing frequency （BPF） and its harmonics are generated which are prescribed by the number of stator and rotor blades etc. In the present study, the dominant mode is tried to be suppressed by the secondary sound from the loudspeaker actuators. One of the novel features of the present system is the adoption of the control board with the Field Programmable Gate Array （FP（3A） hardware and the LabVIEW software to synchronize the circumferentially installed loudspeaker actuators with the relative location of rotational blades under arbitrary fan rotational speeds. The experiments were conducted under the conditions of three rotational speeds of 2004, 3150, and 4002 [rpm]. The reduction in the sound pressure level （SPL） was observed for all three rotational speeds. The sound pressure level at the BPF was reduced approximately 13 [dB] for 2004 [rpm] case, but not so large reduction was attained for other cases probably due to the inefficiency of the loudspeaker actuators at high frequencies

关键词： Stator-Rotor Interaction Anti Noise Control (ANC) Cut-on Control

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Synthesis of bulk lanthanum polyphosphate and other rare earth phosphates through hydrothermal hot-pressing

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Journal of Advanced Ceramics 2013年第4期2卷 301-307页

作者： Hiroaki ONODA Taro yamasaki Department of Informatics and Environmental Sciences Faculty of Life and Environmental SciencesKyoto Prefectural University1-5Shimogamo Nakaragi-choSakyo-kuKyoto 606-8522Japan

Bulk samples of lanthanum polyphosphate were synthesized through a hydrothermal hot-pressing(HHP)*** this process,pressing temperature,pressure and volume of water were varied in order to improve the density and strength of the resulting *** strength of the bulk samples was estimated through drilling and ultrasonic *** order to improve the strength of the materials,the use of microwave irradiation was *** polyphosphate formed porous bulk samples with a filling factor of approximately 70%,which was calculated from real and theoretical *** respect to machinable strength,a drilled hole greater than 7.0 mm in diameter was obtained on some bulk samples,and the diameter of the samples was 14 *** HHP process is a useful method for obtaining bulk samples of lanthanum *** lanthanum polyphosphate containing water crumbled easily to a powder form upon ***,these bulk samples retained their shape upon ultrasonication,despite containing water,after exposure to microwave irradiation,and also experienced minimal weight ***,to study the effect of microwave heating,bulk lanthanum orthophosphate,yttrium orthophosphate and polyphosphate were also examined.

关键词： lanthanum polyphosphate hydrothermal hot-pressing(HHP)process machinable strength vibration strength microwave heating

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Large Eddy Simulation of Swirling Jet in a Bluff-Body Burner

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Journal of Thermal Science 2005年第1期14卷 28-33页

作者： Yohei FUJIMOTO Yuzo INOKUCHI Nobuhiko yamasaki Department of Aeronautics and Astronautics Kyushu-University 6-10-1HakozakiHigashikuFukuoka812-8581JapanDepartment of Aeronautics and Astronautics Kyushu-University 6-10-1HakozakiHigashikuFukuoka812-8581JapanDepartment of Aeronautics and Astronautics Kyushu-University 6-10-1HakozakiHigashikuFukuoka812-8581Japan

The large eddy simulation (LES) is applied to an unconfined swirling flow of an air surrounding a bluff-body having a central jet of air, and the complicated flowfield that involves the recirculation and vortex breakdown is investigated. The Smagorinsky model is used as the sub-grid scale model. The results of the present numerical simulation are compared with the experimental data of the mean and stochastic root mean square (RMS) variations of two velocity components. Although the inflow conditions are specified in a simple manner, the obtained numerical results are in reasonable agreement with the experiments, except for a part of RMS variation values near downstream of the bluff body. The present numerical calculations can successfully reproduce the two characteristics of the flow, i.e., an upstream recirculation zone established just downstream of the burner plane and the additional recirculation zone established at the more downstream location.

关键词： large eddy simulation swirl bluff-body recirculation.

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Large Eddy Simulation of Methane Non-premixed Flame Using the Laminar Flamelet Model

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Journal of Thermal Science 2011年第6期20卷 534-542页

作者： Mari Mitani Yuta Ito Nobuhiko yamasaki Department of Aeronautics and Astronautics Kyushu University

The large eddy simulation (LES) using the steady laminar flamelet model is applied to a simple turbulent jet flame with 33.2% H2,22.1% CH4 and 44.7% N2 at the Reynolds number of 15,200 in order to validate the numerical methods and to investigate the flame *** the validation,the detailed experimental data of DLR-A flame is *** numerical results are in reasonable agreement with experimental results except mass fractions of minor *** the flow field,the break-down of the potential core,the vortex structure and the mixing intensity are well *** the combustion field,mass fractions of major species (H2O,CO2,CO) are well predicted *** species are well predicted *** the present study,the simulations conducted on the Cartesian and cylindrical grids with approximately 6.6× 10 5 nodes are compared.

关键词： Cartesian grid cylindrical grid validation calculation

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Numerical Simulation for Fan Broadband Noise Prediction

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Journal of Thermal Science 2011年第1期20卷 58-63页

作者： Takaaki Hase Nobuhiko yamasaki Tsutomu Ooishi Kyushu University Fukuoka819-0395Japan IHI Corporation Nishitama-gunTokyo190-1297Japan

In order to elucidate the broadband noise of fan,the numerical simulation of fan operating at two different rotational speeds is carried out using the three-dimensional unsteady Reynolds-averaged Navier-Stokes (URANS) *** computed results are compared to experiment to estimate its accuracy and are found to show good agreement with experiment.A method is proposed to evaluate the turbulent kinetic energy in the framework of the Spalart-Allmaras one equation turbulence *** the calculation results,the turbulent kinetic energy is visualized as the turbulence of the flow which leads to generate the broadband noise,and its noise sources are identified.

关键词： Broadband Noise Fan Noise Rotor-Stator Interaction URANS

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Inherited multimodal microstructure evolution of high-fracture-toughness Mg-Zn-Y-Al alloys during extrusion for the consolidation of rapidly solidified ribbons

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Journal of Magnesium and Alloys 2022年第9期10卷 2433-2445页

作者： Soya Nishimoto Michiaki yamasaki Yoshihito Kawamura Department of Materials Science Graduate School of Science and TechnologyKumamoto University2-39-1 KurokamiChuo-kuKumamoto 860-8555Japan Magnesium Research Center Kumamoto University2-39-1 KurokamiChuo-kuKumamoto 860-8555Japan

The mechanisms of multimodal microstructure evolution and the effects of microstructural factors on mechanical properties must be elucidated to design new alloys with superior *** this study,high-fracture-toughness and ductile Mg_(96.75)Zn_(0.85)Y_(2.05)Al_(0.35) alloys were developed using rapidly solidified(RS)ribbon-consolidation technique,and the inherited multimodal microstructure evolution during plastic flow consolidation of the RS ribbons was *** use of extrusion for plastic flow consolidation of the heat-treated RS ribbons produced a multimodal microstructure consisting of the worked grains with high Kernel average misorientation(KAM)angles(Group1),the ultrafine dynamically recrystallized(DRXed)grains with intermediate KAM angles(Group 2),and the fine DRXed grains with low KAM angles(Group 3).Groups 1 and 2 contribute to the alloy strengthening,while Group 3 contributes to improving ductility with strainhardening,resulting in enhancement of the fracture *** form the multimodal microstructure,it was necessary to apply plastic flow with equivalent strains of>2.3 to the heat-treated RS ribbons possessing duplex microstructures with different dispersions of the long-period stacking ordered phase.

关键词： Magnesium alloy Long-period stacking ordered phase Multimodal microstructure Rapid solidification Extrusion Dynamic recrystallization

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Effect of a Curved Duct Upstream on Performance of Small Centrifugal Compressors for Automobile Turbochargers

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Journal of Thermal Science 2013年第1期22卷 92-96页

作者： Shigeta Kikuchi Nobuhiko yamasaki Akihiro Yamagata Department of Aeronautics and Astronautics Kyushu University Products Development Center IHI Corporation

Since the automobile turbochargers are installed in an engine compartment with limited space, the ducts upstream of the turbocharger compressor may be curved in a complex manner. In the present paper, the effect of a curved duct upstream on performance of small centrifugal compressors for automobile turbochargers is discussed. The computational fluid dynamics (CFD) analysis of a turbocharger compressor validated for the compressor model with the straight pipe applied to the compressor with the curved pipe are executed, and the deterioration of the performance for the curved pipe is confirmed. It is also found that the deterioration of compressor performance is caused by the interaction of the secondary flow and the impeller.

关键词： Cartesian grid cylindrical grid validation calculation

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Effects of multimodal microstructure on fracture toughness and its anisotropy of LPSO-type extruded Mg-1Zn-2Y alloys

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Journal of Magnesium and Alloys 2024年第7期12卷 2952-2966页

作者： Soya Nishimoto Taiga Yasuda Koji Hagihara Michiaki yamasaki Department of Materials Science Graduate School of Science and TechnologyKumamoto University2-39-1 KurokamiChuo-kuKumamoto 860-8555Japan Magnesium Research Center Kumamoto University2-39-1 KurokamiChuo-kuKumamoto 860-8555Japan Department of Physical Science and Engineering Nagoya Institute of technologyGokiso-choShowa-kuNagoya 466-8555Japan

The fracture toughness of extruded Mg-1Zn-2Y(at.%)alloys,featuring a multimodal microstructure containing fine dynamically recrystallized(DRXed)grains with random crystallographic orientation and coarse-worked grains with a strong fiber texture,was *** DRXed grains comprised randomly oriented equiaxedα-Mg *** contrast,the worked grains includedα-Mg and long-period stacking ordered(LPSO)phases that extended in the extrusion direction(ED).Both types displayed a strong texture,aligning the(10.10)direction parallel to the *** volume fractions of the DRXed and worked grains were controlled by adjusting the extrusion *** the longitudinal-transverse(L-T)orientation,where the loading direction was aligned parallel to the ED,there was a tendency for the conditional fracture toughness,KQ,tended to increase as the volume fraction of the worked grains ***,the KQ values in the T-L orientation,where the loading direction was perpendicular to the ED,decreased with an increase in the volume fraction of the worked *** suggests strong anisotropy in the fracture toughness of the specimen with a high volume fraction of the worked grains,relative to the test *** worked grains,which included the LPSO phase and were elongated perpendicular to the initial crack plane,suppressed the straight crack extension,causing crack deflection,and generating secondary ***,these worked grains significantly contributed to the fracture toughness of the extruded Mg-1Zn-2Y alloys in the L-T orientation.

关键词： Magnesium alloy Magnesium-zinc-yttrium Long-period stacking ordered phase Multimodal microstructure Fracture toughness

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Study on Rotational Frequency Noise in a Centrifugal Compressor for Automobile Turbochargers

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Journal of Thermal Science 2014年第1期23卷 53-59页

作者： Daichi Wakaki Yuta Sakuka Nobuhiko yamasaki Akihiro Yamagata Department of Aeronautics and Astronautics Kyushu University Products Development Center IHI Corporation

The rotational frequency noise(also known as the pulsation noise) due to the mistuning of impeller blade rows introduced at the manufacturing stage of the impellers is observed in the small-sized centrifugal compressor for automobile turbochargers. The present paper addresses the elucidation of the generating mechanism and parameter dependency such as the kind and degree of mistuning. In order to analyze numerically the rotational frequency noise due to mistuning, the unsteady computational fluid dynamics(CFD) of the whole compressor including volute is executed, and the resultant time history of the pressure is fed into the spectral analysis.

关键词： Centrifugal compressor Impeller Diffuser Volute Pulsation noise Mistuning

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