Oita National College of Technology

Oita, Japan
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Kotake N.,Japan National Institute of Advanced Industrial Science and Technology | Sano H.,Oita National College of Technology
Journal of Material Cycles and Waste Management | Year: 2017

For a prospective solution of effective recycling of gypsum board wastes, the present study was conducted to evaluate applicability of reclaimed gypsum as stabilizing agent for improvement of soft clayey ground. A series of unconfined compression tests and needle penetration tests were conducted to understand the fundamental properties of reclaimed gypsum and gypsum treated soils and the durability in water. An important finding was strength decrease in relation to mixing time of gypsum and soil. This may attribute to excessive mixing that caused breakage of the promptly hardened gypsum treated clay. In addition, from sounding and laboratory tests on the stabilized ground by shallow mixing method with different execution conditions, it was found that the strength of stabilized ground appeared in an early stage and that the hardening effect of cement that was used in combination with gypsum continued in a longer period. Regarding an environmental aspect, a specific amount of cement could have restrained leaching fluorine satisfactorily under the standard level in the field by adopting suitable mixing proportions based on the laboratory mixing test results. For practical application, the mixing procedure was a major factor of strength growth when hemihydrate gypsum was used to stabilize soft clayey ground. © 2017 Springer Japan KK

Higashino M.,Oita National College of Technology | Stefan H.G.,University of Minnesota
Environmental Fluid Mechanics | Year: 2012

The vertical diffusional mass (solute) transfer through a suspended sediment layer, e. g. at the bottom of a lake, reservoir or estuary, by the propagation of velocity fluctuations from above was investigated. The attenuation of the velocity fluctuations in the suspension layer and the associated effect on solute transfer through the suspension layer was simulated. To represent large eddies traveling downstream in water over a high-concentration suspended sediment layer, a streamwise velocity fluctuation moving in downstream direction was imposed along the upper boundary of the suspension layer. Velocity fluctuations and downstream velocity were normalized by the shearvelocity (U *) at the top of the suspension layer. Streamwise and vertical velocity components inside the suspension layer, were obtained from the 2-D continuity and the Navier-Stokes equations. The persistence of turbulence with depth-as it penetrates from the overlying water into the suspension layer-was found to depend on its amplitude, its period, and on the apparent viscosity of the suspension. The turbulence was found to propagate efficiently into the suspension layer when its frequency is low, and the apparent viscosity of the suspension is high. Effects on vertical mass transfer were parameterized by penetration depth and effective diffusion coefficient, and related to apparent viscosity of the suspension, Schmidt number and shear velocity on top of the suspension layer. The enhancement of turbulence penetration by viscosity is similar to the flow near an oscillating flat plate (Stokes' second problem), but is opposite to turbulence penetration into a stationary porous and permeable sediment bed. The information is applicable to water quality modeling mear the sediment/water interface of lakes, river impoundments and estuaries. © 2012 Springer Science+Business Media B.V.

Higashino M.,Oita National College of Technology | Stefan H.G.,University of Minnesota
Journal of Environmental Engineering | Year: 2011

A microbial dissolved oxygen (DO) uptake model was developed for a stream bed, including the effect of turbulence in the flow over the bed and pore water flow in the porous bed. The fine-grained sediment bed has hydraulic conductivities 0.01 ≤ k ≤ 1 cm/s, i.e., sediment particle diameter 0.006≤d s≤0.06 cm. The pore water flow is driven by pressure fluctuations at the sediment-water interface, mostly attributable to near-bed coherent motions in the turbulent boundary layer above the sediment bed. An effective mass transfer coefficient (D e) coupled to a pore water flow model was used in the DO transport and DO uptake model. DO flux across the sediment-water interface and into the sediment, i.e., sedimentary oxygen demand (SOD), was related to hydraulic conductivity and microbial oxygen uptake rate in the sediment and shear velocity at the sediment-water interface. Simulated SOD values were validated against experimental data. For hydraulic conductivities of the sediment bed up to k≈0.01 cm/s, the pore water flow effect on SOD was found negligible. Above this threshold, the effective mass (DO) transfer coefficient in the sediment bed (D e) becomes larger as the hydraulic conductivity (k) becomes larger as the interstitial flow velocities increase; consequently, DO penetration depth increases with larger hydraulic conductivity of the sediment bed (k), and SOD increases as well. The enhancement of vertical DO transport into the sediment bed is strongest near the sediment-water interface, and rapidly diminishes with depth into the sediment layer. An increase in shear velocity at the sediment-water interface also enhances DO transfer. Shear velocity increases at the sediment-water interface will raise SOD regardless of the maximum oxidation rate if the hydraulic conductivity is above the threshold of k≈1 cm/s. The relationship is nearly linear when U*lt;0.8 cm/s. At shear velocity U*=1.6 cm/s, SOD for oxidation rates μ=1000 and 2000 mg l -1 d -1 are almost five times larger than those with no pore water flow. When pore water transport of DO is not limiting, SOD is a linear function of oxygen demand rate μ in the sediment when 0≤ μ ≤200 mg l -1 d -1. © 2011 American Society of Civil Engineers.

Higashino M.,Oita National College of Technology | Stefan H.G.,University of Minnesota
Water Research | Year: 2011

A previously developed model of periodic pore water flow in space and time, and associated solute transport in a stream bed of fine sand is extended to coarse sand and fine gravel. The pore water flow immediately below the sediment/water interface becomes intermittently a non-Darcy flow. The periodic pressure and velocity fluctuations considered are induced by near-bed coherent turbulent motions in the stream flow; they penetrate from the sediment/water interface into the sediment pore system and are described by a wave number (χ) and a period (T) that are given as functions of the shear velocity (U *) between the flowing water and the sediment bed. The stream bed has a flat surface without bed forms. The flow field in the sediment pore system is described by the continuity equation and a resistance law that includes both viscous (Darcy) and non-linear (inertial) effects. Simulation results show that non-linear (inertial) effects near the sediment/water interface increase flow resistance and reduce mean flow velocities. Compared to pure Darcy flow, non-linear (inertial) effects reduce solute exchange rates between overlying water and the sediment bed but only by a moderate amount (less than 50%). Turbulent coherent flow structures in the stream flow enhance solute transfer in the pore system of a stream bed compared to pure molecular diffusion, but by much less than standing surface waves or bed forms. © 2011 Elsevier Ltd.

Furukawa T.,Oita National College of Technology | Suzuki Y.,University of Miyazaki
Microbes and Environments | Year: 2013

This study aimed to identify specific river sources of fecal contamination by applying pulsed-field gel electrophoresis (PFGE) to environmental water samples from a recreational beach in Japan. The genotypes of all Enterococcus faecium and Enterococcus faecalis strains used as indicators of fecal pollution on the recreational beach and rivers were analyzed by PFGE, and the PFGE profiles of the strains were classified at a 0.9 similarity level using dendrogram analysis. PFGE types of E. faecium isolated from Sakai River or urban drainage were classified in the same cluster. Therefore, the probable sources of fecal pollution on the recreational beach were Sakai River and urban drainage. The approaches for microbial source tracking employed in this study used PFGE with Enterococcus species as an indicator can be a potential tool to specify the source(s) of fecal pollution and contribute to improved public health in coastal environments.

Asano M.,Osaka University | Takahashi T.,Oita National College of Technology
Optics Express | Year: 2015

Many approaches for producing optical vortices have been developed both for fundamental interests of science and for engineering applications. In particular, the approach with direct excitation of several emitters has a potential to control the topological charges with a control of the source conditions without any modifications of structures of the system. In this paper, we investigate the propagation properties of the optical vortices emitted from a collectively polarized electric dipole array as a simple model of the several emitters. Using an analytical approach based on the Jacobi-Anger expansion, we derive a relationship between the topological charge of the optical vortices and the source conditions of the emitter, and clarify and report our new finding; there exists an intrinsic split of the singular points in the electric field due to the spin-orbit interaction of the dipole fields. © 2015 Optical Society of America.

Prochazka Z.,Oita National College of Technology
IPSJ Transactions on Computer Vision and Applications | Year: 2016

Vision based road recognition and tracking are crucial tasks in a field of autonomous driving. Road recognition methods based on shape analysis of road region have the potential to overcome the limitations of traditional boundary based approaches, but a robust method for road region segmentation is the challenging issue. In our work, we treat the problem of road region segmentation as a classification task, where road pixels are classified by statistical decision rule based on the probability density function (pdf) of road features. This paper presents a new algorithm for the estimation of the pdf, based on sequential Monte-Carlo (SMC) method. The proposed algorithm is evaluated on data sets of three different types of images, and the results of evaluation show the effectiveness of the proposed method. ©2016 Information Processing Society of Japan.

Yukawa H.,Nagoya University | Nambu T.,National College of Technology, Suzuka College | Matsumoto Y.,Oita National College of Technology
Journal of Alloys and Compounds | Year: 2011

The alloying effects of tungsten on the hydrogen solubility and the hydrogen permeability are investigated for V-based hydrogen permeable membranes. The hydrogen solubility is found to decrease by the addition of tungsten into vanadium or by increasing the temperature. It is shown that the ductile fracture occurs for V-5 mol%W alloy even in the hydrogen pressures of 0.3 MPa at 773 K. It is also found that the mechanical properties (i.e., strength and ductility) of V-based alloy are better than that of Nb-based alloy in hydrogen atmosphere at high temperature. It is demonstrated that the V-5 mol%W alloy possess excellent hydrogen permeability without showing any hydrogen embrittlement when used under appropriate permeation conditions, i.e., temperature and hydrogen pressures. © 2010 Elsevier B.V. All rights reserved.

Prochazka Z.,Oita National College of Technology
International Journal of Advanced Robotic Systems | Year: 2013

This paper deals with a problem of road tracking and vehicle positioning based on sequential images captured by a vehicle mounted monocular colour camera. The paper presents a new region-based road tracking method, which is suitable for both structured and unstructured roads. The proposed method is based on our original road segmentation algorithm and estimates road model parameters from measurements obtained by analysis of segmented road region. Although the proposed method is tested over a limited range, evaluation on real image sequences shows promising results for various types of road. © 2013 Procházka; licensee InTech.

Higashino M.,Oita National College of Technology
Water Research | Year: 2011

A model of sedimentary oxygen demand (SOD) for stagnant water in a lake or a reservoir is presented. For the purposes of this paper, stagnant water is defined as the bottom layer of stratified water columns in relatively unproductive systems that are underlain by silt and sand-dominated sediments with low-organic carbon (C) and nitrogen (N). The modeling results are compared to those with fluid flow to investigate how flow over the sediment surface raises SOD compared to stagnant water, depending on flow velocity and biochemical activity in the sediment. SOD is found to be substantially limited by oxygen transfer in the water column when water is stagnant. When flow over the sediment surface is present, SOD becomes larger than that for stagnant water, depending on flow velocity and the biochemical oxygen uptake rate in the sediment. Flow over the sediment surface causes an insignificant raise in SOD when the biochemical oxygen uptake rate is small. The difference between SOD with fluid flow and SOD for stagnant water becomes significant as the biochemical oxygen uptake rate becomes larger, i.e. SOD is 10-100 times larger when flow over the sediment surface is present. © 2011 Elsevier Ltd.

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