Triangular edge fairings are widely used and attached to the edges of rectangular box girder bridge decks to improve their aerodynamic responses. Bridge deck with edge fairing should be shaped efficiently to obtain optimum aerodynamic responses. In this paper, the shaping effect of a triangular edge fairing on aerodynamic behaviour of a bridge deck is presented. A wide range of top and bottom plate slopes is utilized to change the shape of the fairing. The unsteady RANS simulation with the k–ω-SST turbulence model is used to simulate the flow. The flow is discretized by the finite volume method with second-order accuracy in space and time. The mean and rms values of the force coefficients are evaluated and the after-body velocity fluctuations are plotted. The aerodynamic responses are tried to explain by means of pressure and velocity distributions around the bridge deck. A relative comparison of the aerodynamic responses of perforated and solid handrails is also presented. It is found that a lower aerodynamic response can be obtained by properly shaping the triangular edge fairing.
In order to prevent hydrofoil colliding with cetaceans, the underwater speaker (UWS) has been installed to repel cetaceans. Yamada et al. (2012) analyzed and devised the UWS sound as it fits the cetaceans' acoustic properties to prevent the collision furthermore. The new UWS sound was devised and synthesized by Yamada et al. (2015) with expectation of avoiding collision with large cetaceans (Patent applied for, JP2014-171411). In this research project, the new UWS sound was investigated by the playback experiment on humpback whale (Megaptera novaeangliae) and by sighting survey in the actual hydrofoil shipping service route. As a result, a physiological and behavioral change of the humpback whale was observed in the playback experiment of the new UWS sound, and the chance of hydrofoil encountering cetaceans of the new UWS sound was smaller than that of the previous UWS sound. Therefore, the improvement of the new UWS sound was confirmed. Lastly, we wish this research project would contribute toward the safer cruise of hydrofoil in the future.
The underwater speaker (UWS) has been installed on high speed vessels; hydrofoils (HF) with low-noise during their cruises, to avoid sudden collisions with large cetaceans, while its performance has remained uncertain because of the problem in quality of the produced sound. Thus, we developed a sound source for the UWS by modulating the sound based on the audible range of major large cetaceans so as to increase its utilities. To investigate the audible sound frequency range of cetacean, we tried two procedures, (1) indirect-estimation from relationship between cetaceans audibility and vocalization, and (2) indirect-estimation from measurements on the cochlear basal membrane. We also synthesized the two new sound sources which we can potentially expect an avoidance with large cetaceans. Through several field experiments with deploy the new sounds we reached a tentative conclusion that the new sound was effective in terms of inducing the cetaceans' avoidance reaction and would be also expected to be applied to other low-noise vessels.
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Recently, sudden collisions between large cetaceans and high-speed hydrofoils have become problematic to Japanese sea transport in some localities. We therefore initiated a project to investigate ap-proaches for minimizing risk to both ships and cetaceans. Under the present project, the following three sub-projects are underway: clarifying which whale species are found near sea routes and determining their season-al variations; identifying whale species that have a high collision risk; and determining the unique acoustic characteristics of high-collision-risk cetaceans for the improvement of underwater speakers (UWS). By con-ducting acoustic surveys using novel methods, including an anatomical approach based on characteristics of the inner ear, the aim of this project is to accurately estimate the audible range of species with a high collision risk and improve the sounds generated by the UWS. Thus far, we have identified the cetacean species at high-risk in two major sea routes. In the next phase of the study we plan to develop an imaging system that recog-nizes a cetacean's unique blow using an infrared camera, in an attempt to warn of the approach of high-collision-risk whale species at an early stage by sounding an alarm.
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To achieve safer navigation without sudden collisions with large cetaceans at high speed boats such as the hydrofoil, we examined its feasibility of an installation of the infrared camera. Because any ceta-ceans are of air-breathing animals, it is theoretically expected that they can be potentially detected through imaging of the infrared cameras. Thus, we examined the feasibility of detection with aiming at sperm whales in waters off Chichijima Islands (27°4'N, 142°13'E), Japan. Through the experiment, it was revealed that sperm whales could be detected stably within 200m, and detectable cue were blow, back body and fluke tails. However, boats and waves were also detected as noise images. Especially, waves greatly resemble the whale back bodies. Although potential of the infrared camera was confirmed, there are still necessities of further ex-periments including ones conducting at different temperate waters, to successfully install the infrared camera for earlier finding of large cetaceans.
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In order to avoid collisions between the hydrofoil (HF) and cetaceans, the Under Water Speaker (UWS) has been installed on the HF. Because of its potential in utility, we tried to improve the UWS to minimize the risk of the collisions. Under our project, we examined three subprojects; 1) Analyzing the characteristics of the HF underwater noise; 2) Assessing audibility of major large cetaceans by measuring their vocalizations and 3) An anatomical prediction of the audible range by examining the cochlear basal membrane. Through the analyses, it was identified that the noise produced by the HF was a broad-band noise with approximately 150dB re 1μPa-m.That noise level was lower than those of larger boats suggesting difficulties for cetaceans in sensing approach of the vessels. In addition, analysis of their vocalizations and anatomical obervation indicated that dominant frequency of their audible range was lower than signals produced by the existing UWS.
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We have proposed a sophisticated novel method of the SHPB experiment to measure the local strain-rate distributions on a surface of the specimen by using mechanoluminescent materials combined with a high-speed camera and an image intensi?er. The feasibility study was made for the aluminum specimens pasted by a typical mechanoluminescent material -Eu doped SrAl2O4 ?lm, in order to obtain the fundamental data for the method. Our results showed that SrAl2O4: Eu emitted lights as a response to the stress. Increase of the light intensity was swift enough to follow the strain change due to SHPB impact. The luminescence intensity was experimentally veri?ed and expressed as a product of strain and strain rate. Accordingly, it can be said that this method gives a good tool for measuring time variation of local strain distributions.
For an environmental-friendly sustainable society, the global environmental problems should be solved. Here we outline our recent results of environment purification materials with smart functions. For the effective adsorbent for remediation process, zeolite coated with layered double hydroxide (LDH) was prepared by the precipitation of LDH on zeolite-LTA under hydrothermal treatment. This multifunctional material has a possible application for simultaneous uptake of harmful cations and anions, and minimizes environmental pollution during municipal and industrial water management. For novel material for the nuclear waste management, zeolite with hydroxyapatite layers on its surface was obtained by a hydrothermal method on the basis of the cation exchange of Ca2+ in zeolite for NH4+ in solution. The novel nanocomposite is an ideal material for adsorbing and fixing radioactive elements for geological time-scale.
Methyl radicals generated by ă-irradiation in the proton form of synthetic rho zeolite exposed to CH4 have been investigated by electron paramagnetic resonance (EPR) in the temperature range 110-370 K. Depending on the methane adsorption temperature two EPR spectra of oCH3 radicals were recorded. The isotropic quartet observed after CH4 adsorption at room temperature was assigned to oCH3 radicals freely rotating in the middle of octagonal prism. After adsorption at 413 K, the isotropic quartet is overlapped with the second signal characterized with anisotropy of hyperfine splitting and g-value. It is postulated that anisotropic signal represents the oCH3 radicals located in á-cages and strongly interacting with silicaalumina framework. The mechanisms of radiolytic formation of methyl radicals and the possible stabilization sites are also discussed.
The formation and stabilization of reduced silver species in the regularly interstratified clay minerals, trioctahedral smectite/chlorite (tri-Sm/Ch) and dioctahedral smectite/mica (di-Sm/M), have been studied by electron paramagnetic resonance (EPR) spectroscopy. Both minerals loaded with Ag+ cations after degassing and dehydration were g-irradiated at 77 K and monitored by EPR as the temperature increased. Some samples were exposed to water or methanol vapor after dehydration. In both hydrated and dehydrated samples only the doublets assigned to Ag0 atoms were observed with no evidence of the formation of Ag clusters. However, the EPR parameters of silver atoms in both matrices are different. In tri-Sm/Ch the narrow anisotropic EPR lines overlap with the broader isotropic lines, whereas in di-Sm/M only broad lines are recorded. The hyperfine splitting - Aiso(Ag0) is larger in tri-Sm/Ch than in di-Sm/M. Also the stability of Ag0 in both clay minerals is distinctly different. Ag0 doublet in di-Sm/M disappears completely above 230 K, whereas in tri-Sm/Ch it is still recorded at 310 K. It is proposed, basing on the EPR results that Ag0 atoms appear at different sites in both matrices: - in tri-Sm/Ch in the middle of smectite interlayer and in hexagonal cavities in the silicate sheets of tetrahedron layer and in di-Sm/M in hexagonal cavities only. When samples had been exposed to methanol before irradiation, the silver clusters become stabilized in the interlayer sites. In tri- Sm/Ch matrix the silver dimer Ag2+ formed by g-irradiation at 77 K is transformed to tetrameric cluster, Ag43+ at 150 K. In di-Sm/M the radiation-induced silver agglomeration proceeds in a similar way, but with a slower rate and Ag tetramer is formed only above 190 K. In both clay minerals, Ag43+ clusters decay above 250 K.
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“Flameless combustion” of lean to ultra lean mixtures, supported by hightemperature burned gas, can resolve the dilemma between complete combustion versus ultralow NOx emissions in gas turbine combustors. The characteristic of NOx emissions and combustion in “leanlean” twostage combustion was investigated for premixedprevaporized keroseneair mixtures using a coaxial flow configuration. A circular jet of secondary keroseneair mixtures of lean to ultralean compositions were injected into the primary hot burned gas prepared by combustion of lean mixtures on an annular perforated flame holder The progress of reaction and NOx formation in the combustion tube were measured for nonswirled and swirled secondary jets. The conditions required for complete combustion of the secondary mixtures were defined for various ratios of secondary to primary air flow rates.
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