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In this study, an efficient numerical model for predicting ship waves was developed using Green's functions. Avoiding detailed description of the complex boundary conditions around a ship, this model simply used an inversion technique for estimating the wave source induced by a ship as a function of the navigation route and adjacent measured water level fluctuations. The Green's functions were determined as linear summations of the water level fluctuations generated from discrete points along the navigation route. At each point, a time-varying wave source was determined as a linear summation of Gaussian pulses introduced at segments along the longitudinal direction of the ship. The linear inversion was then applied for estimating the optimum combinations of the magnitudes of these Gaussian pulses. Linear dispersive wave theory was applied to compute the water level fluctuations generated by a single Gaussian pulse so that the model can reproduce the dispersive characteristics of ship waves. The developed model was tested against experimental data and showed satisfactorily predictive skills of water level fluctuations for cases not used in the inversion. The present model was also found to be robust in that the estimated best-fitted wave source was not sensitive to changes in the conditions of the measured data used for the inversion. [ABSTRACT FROM AUTHOR]

The extreme typhoon Lan caused devastating damage to the Seisho Coast of Japan in 2017. This study presents nearshore wave measurements conducted at different locations along the shore and numerical hindcasts to elucidate the extreme wave field during the typhoon focusing on infragravity wave dynamics, which was comparable in magnitude to incident short waves in shallow water. During the peak of the typhoon, there was a significant wave height of ~8 m, and the infragravity wave height exceeded 2 m at a 14 m depth. The measurement data suggest that infragravity waves developed as bound waves from incident wave groups and partially dissipated during the typhoon peak in the surf and swash zones through their energy transfer to high-frequency waves. Numerical wave hindcasting models successfully reproduced the measured extreme wave field and indicated that the wave refraction over Oiso Spur caused an incident wave concentration in the severely damaged area where high waves collapsed a seawall during the typhoon. Moreover, infragravity waves also exhibited significant alongshore variation, which was due to the different bottom slopes and incident short-wave properties. This study identifies several key features that may have caused the localization of significant damage along the Seisho Coast. [ABSTRACT FROM AUTHOR]

Countermeasures are investigated against coastal erosion and sediment invasion around a half-buried floodway through a series of small-scale physical model experimentations. Further, countermeasures are proposed to shorten the protruded length of the floodway across the shoreline to prevent interruption of longshore sediment transport and to excavate downdrift sediments at the mouth of the floodway to minimize the downdrift erosion as well as the sedimentation inside the floodway. Results of the study show that the shortened floodway is successful in mitigating downdrift erosion, while continuous downdrift excavation is proven to be significantly effective in reducing sedimentation inside the floodway when excavation is implemented with the same order-of-magnitude of the longshore sand transport rate. Attention must be paid, however, on the effect of wave randomness and floodway discharge during stormy waves as they further increase sedimentation inside the floodway apparently owing to onshore sediment movement enhanced by asymmetric horizontal acceleration and to a large skewness in the water particle velocity at the mouth of the floodway. [ABSTRACT FROM AUTHOR]

The mechanism of void development inside the backfill of a concrete riprapped seawall was investigated through laboratory experiments and numerical modeling. Laboratory experiments have been conducted in an oscillatory flow tunnel. The leakage of sand through a small gap from an acrylic container has been examined with and without a large void in the container. The leakage rate was found to increase with the total void volume inside the container, thus suggesting the accelerated expansion of the void in the seawalls. In order to understand the role of pressure transmission in the backfill medium, a numerical model has been proposed based on the quasi-static assumption on Biot's consolidation equation using finite difference method in the one-dimensional domain. Results from the developed model using appropriate permeability and compressibility values demonstrated that the accelerated expansion of void could be developed by the compression of air void due to the transmission of oscillatory pressure through a gap. [ABSTRACT FROM AUTHOR]

An imagery-based monitoring system was developed for nearshore topography. The system was based on the wave breaking density observed using a land-based camera and calculated the bathymetry using a depth-controlled breaking wave model. The system was applied to the Fukude-Asaba Coast, Shizuoka Prefecture, where rapid topography change was expected around the outlet of pipeline-based sand bypassing. The validity of the system was verified through comparisons with bathymetry survey data. It is observed that the system can successfully capture the nearshore bathymetry change owing to a typhoon. It is also suggested that the accuracy is sensitive to the incident wave properties and therefore can be improved by introducing selective averaging in which only appropriate imageries were used for the depth estimation depending on the target depth zones. [ABSTRACT FROM AUTHOR]

The present study develops a SAR-based shoreline monitoring system which consists of: (i) selection of SAR scenes suitable for shoreline detection; (ii) extraction of shoreline from the selected scenes; and (iii) estimation of the shoreline at arbitrary water level. The first model focused on ALOS-2 SAR scenes and determined fitting formulae for estimation of the backscattering coefficients at a sea and a beach surfaces. To quantify the suitability of scenes for shoreline detection, a parameter, P, was newly introduced. The value of P represents a probability at which a backscattering coefficient at a beach becomes higher than the one at a sea and it was confirmed that P reasonably indicates suitability of scenes for shoreline detection. A shoreline extraction technique was then developed based on the edge detection technique. Bilateral filter was applied to reduce the speckle noise of SAR images and wavelet transform was applied to detect the edge location. Validity of the proposed technique was confirmed through application of the present technique to Shimizu and Shonan coasts. Finally, a simple polynomial function was introduced to represent the shoreline location at arbitrary water level. Applicability of the proposed technique was also tested and validated against the detailed data obtained by image analysis. [ABSTRACT FROM AUTHOR]

Purpose: Our previous study revealed that the application of a magnetic field longitudinal to a carbon-ion beam of 0.1 ≤ B//≤ 0.6 T enhances the biological effectiveness of the radiation. The purpose of this study is to experimentally verify whether the application of a magnetic field perpendicular to the beam also alters the biological effectiveness. Methods and materials: Most experimental conditions other than the magnetic field direction were the same as those used in the previous study to allow comparison of their results. Human cancer and normal cells were exposed to low (12 keV/μm) and high (50 keV/μm) linear energy transfer (LET) carbon-ion beams under the perpendicular magnetic fields of = 0, 0.15, 0.3, or 0.6 T generated by a dipole magnet. The effects of the magnetic fields on the biological effectiveness were evaluated by clonogenic cell survival. Doses that would result in the survival of 10%, D10s, were determined for the exposures and analyzed using Student's t-tests. Results: For both cancer and normal cells treated by low- and high-LET carbon-ion beams, the D10s measured in the presence of the perpendicular magnetic fields of ≥ 0.15 T were not statistically different (p ≫.05) from the D10s measured in the absence of the magnetic fields, = 0 T. Conclusions: Exposure of human cancer and normal cells to the perpendicular magnetic fields of ≤ 0.6 T did not alter significantly the biological effectiveness of the carbon-ion beams, unlike the exposure to longitudinal magnetic fields of the same strength. Although the mechanisms underlying the observed results still require further exploration, these findings indicate that the influence of the magnetic field on biological effectiveness of the carbon-ion beam depends on the applied field direction with respect to the beam. [ABSTRACT FROM AUTHOR]

Beach erosion mechanisms were investigated for Kujukuri Beach, a 60-km-long sandy beach facing the Pacific Ocean, located in Chiba Prefecture, Japan. The longshore sediment transport rate was estimated using aerial photograph analysis, physical property measurements of beach sediment samples, and land subsidence estimation owing to paleo-groundwater pumping. Alongshore distribution of sediment grain size and thermoluminescence intensity revealed that the longshore sand transport from both ends would meet at x = 40 km, where x denotes the distance from the north end of the beach. Sediment loss caused by the land subsidence was estimated at 130,000 m3/year in the south, which was observed to play an essential role in the beach erosion, as compared with the relatively small amount of sediment transport in the south. An effective and comprehensive countermeasure was proposed in which the land subsidence could be mitigated through the restoration of pumped water in the coastal zone. The countermeasure was found effective in decreasing the sediment loss by 85,000 m3/year, thus changing the sediment budget of the whole Kujukuri Beach positive. [ABSTRACT FROM AUTHOR]

The aim of this study is to estimate how and what kinds of tsunamis are generated near shorelines in the Japan Sea, using earthquake tsunami sources proposed by the Japanese government. Tsunami propagation based on these sources was first simulated based on the linear Boussinesq theory for Miho Bay, where a historical tsunami inundated the shoreline. The results indicate that tsunami sources not only near the bay but also farther from the bay could generate significant tsunami fluctuations. Thus, the amplification of the latter tsunamis was examined using Fourier analysis. Tsunami waveforms in the bay periodically fluctuate with large amplitudes after the first wave. The Fourier analysis specified these periods to be 13–16 min, consistent with the estimated resonance periods of the bay. Therefore, it can be concluded that one of the factors responsible for the amplification of tsunamis in Miho Bay is the bay-scale resonance. To investigate why resonance occurs during tsunamis, a relationship between the tsunami source geometry and the generated tsunami was examined. This analysis indicates that specific tsunami sources located in critical areas could enhance the resonance in Miho Bay. [ABSTRACT FROM AUTHOR]

This study investigated how the synthetic aperture radar (SAR) parameters and natural conditions affect the spatial distribution of backscattering coefficient of SAR images around the shoreline. Primary findings of this study are summarized as follows: (i) the HH polarization mode is the best mode for shoreline detection; (ii) SAR scenes with incident angle ranging from 30° to 50° under sea-to-land observation direction are recommended for shoreline detection; (iii) clear contrast of the backscattering coefficient between the beach and sea is expected when the nearshore significant wave height is smaller than 0.5 m for L-band SAR scenes; and (iv) X-band SAR scenes may be preferred to L-band SAR scenes for shoreline detection especially where the grain size of the beach material is relatively fine. [ABSTRACT FROM AUTHOR]

Purpose: A magnetic field longitudinal to an ion beam will potentially affect the biological effectiveness of the radiation. The purpose of this study is to experimentally verify the significance of such effects. Methods and materials: Human cancer and normal cell lines were exposed to low (12 keV/μm) and high (50 keV/μm) linear energy transfer (LET) carbon-ion beams under the longitudinal magnetic fields of B// = 0, 0.1, 0.2, 0.3, or 0.6 T generated by a solenoid magnet. The effects of the magnetic fields on the biological effectiveness were evaluated by clonogenic cell survival. Doses that would result in a survival fraction of 10% (D10s) were determined for each cell line and magnetic field. Results: For cancer cells exposed to the low (high)-LET beams, D10 decreased from 5.2 (3.1) Gy at 0 T to 4.3 (2.4) Gy at 0.1 T, while no further decrease in D10 was observed for higher magnetic fields. For normal cells, decreases in D10 of comparable magnitudes were observed by applying the magnetic fields. Conclusions: Significant decreases in D10, i.e. significant enhancements of the biological effectiveness, were observed in both cancer and normal cells by applying longitudinal magnetic fields of B// ≥ 0.1 T. These effects were enhanced with LET. Further studies are required to figure out the mechanism underlying the observed results. [ABSTRACT FROM AUTHOR]

This paper investigates the collapse and recovery processes of the sand spit at the Tenryu River mouth on the Pacific Coast of Japan, when two characteristic typhoons, Man-Yi and Fitow, passed over the study site in the year 2007. Although these two typhoons caused equally high storm waves, these two events were different in principal wave directions and in the amount of river discharges. As a result, Man-Yi collapsed the sand spit, while Fitow rather enhanced the recovery of the sand spit. Successive still images recorded by six field cameras were analyzed to investigate the dynamic morphology change of the river mouth for 2 months during which these two events had occurred. Comparisons of obtained topography changes and various hydrodynamic characteristics yielded several findings: (i) the sand spit was breached approximately 6 h after the peak of flow velocity and 2 h after the peak of the water head difference across the sand spit; (ii) the breached part of the sand spit was refilled by wave-induced shoreward sediment transport; and (iii) a core sample showed three clear layers of graded sedimentary structures of gravel, which correspond to the number of observed high waves overtopping the sand spit. [ABSTRACT FROM AUTHOR]

Propagation and inundation characteristics of the 2011 Tohoku tsunami on the central Sanriku coast are investigated through field surveys and numerical simulations using offshore wave recordings as incident wave conditions. The numerical model successfully reproduces the extent of flood areas as well as the distribution of tsunami heights along the intricate coastline except for run-up of extreme heights over steep slopes. The survey and computed results suggest significant variations of tsunami heights along the coastline. Their positive dependency on topographic slopes implies that the incoming tsunami propagates in standing wave mode to precipitous sites while in progressive wave mode accompanied by wave breaking over gentle slopes. Temporal-spatial analysis of wave properties in different bays reveals that the inner bay topography provides a clear contrast to inundation characteristics. The impacting waves have extreme heights due to the funnel effect and local wave resonances causing highly transient flooding in narrow V-shaped bays whereas tsunami surges over longer periods across innermost shores of U-shaped bays to produce large horizontal velocities during both run-up and backwash phases. [ABSTRACT FROM AUTHOR]

Small-scale physical and numerical experiments were conducted to investigate the local concentration of waves (monochromatic and group) due to abrupt change of nearshore bathymetry in alongshore direction. Wave run-up motions along the shoreline were measured using an image analysis technique to compare localized concentration of wave energy, when waves propagate over a bathymetry composing rhythmic patterns of mild/steep slope bottom configurations. Measured alongshore variation of maximum wave run-up heights showed significant peak near the boundary, which has sudden alongshore change of depth, both under monochromatic and group wave trains. This phenomenon is found to be due to the interaction of waves with nearshore currents, which is further enhanced by excitation of long-wave components by breaking of group waves. Furthermore, this paper discusses results of preliminary experiments carried out to test the effectiveness of several shore protection structure layouts in mitigating such wave concentrations. Numerical simulations were performed using a model based on Boussinesq-type equations; coupled with a transport equation to model energy dissipation due to wave breaking. [ABSTRACT FROM AUTHOR]

The preventive effect of schisandrin B (Sch B), an antioxidant ingredient of Schisandra chinensis, was studied on scopolamine-induced dementia in mouse. Scopolamine developed oxidative stress in the brain with the decreased levels of antioxidant enzymes and increased nitrite level. At the same time, a significant impairment of learning and memory occurred when evaluated by passive avoidance task (PAT) and Morris water maze (MWM) with concomitant increase of acetylcholinesterase (AChE) activity and decreased acetylcholine levels. Pre-treatment by Sch B (10, 25, 50 mg/kg) effectively prevented scopolamine-induced oxidative stress and improved behavioural tasks. Further, the scopolamine-induced increase in AChE activity was significantly suppressed and the level of acetylcholine was maintained as normal by Sch B treatment. These results suggest that Sch B have protective function against cerebral functional defects such as dementia not only by antioxidant prevention but also exerting its potent cognitive-enhancing activity through modulation of acetylcholine level. [ABSTRACT FROM AUTHOR]

This article discusses the validity of the incorporation of online communication in language education classes as a practice free of power politics. By examining blog activities in an advanced-level Japanese-as-a-Foreign-Language classroom at a university in the USA, we show that the blog's postings and readers' comments evoke certain modes of governmentality - practices that shape one's conduct - and define the space of a particular blog. This article illustrates two kinds of space created in blogs: that of language education in which 'native speakers' dominate 'non-native speakers'; and that of information exchange with less fixed relations of dominance, although participants' behavior is regulated nonetheless. We suggest involving students in analyzing blog comments so that they can understand, and respond to, how the mode of governmentality works outside the classroom and how to transform relations of dominance that manifest themselves in online spaces. [ABSTRACT FROM AUTHOR]

Traditionally, the goal of foreign language education has been to teach learners linguistic and cultural knowledge so that they could function successfully in the target language and cultural environment. But does demonstrating knowledge always help learners accomplish their interactional goals? To explore this question, this study investigate when and how the learners of Japanese-as-Foreign-Language used their 'ignorance' as a rhetorical strategy to negotiate their subject positions and shift power relations to their benefit while living in Japan as exchange students. Among the nine students we interviewed, we focus on the experiences of two students. The study reveals that regardless of their language ability, their racial appearance played a major role in determining whether one could use 'ignorance' as a strategy to accomplish their goals. Through experiencing such race politics in Japan, the students learned to maneuver their subject positions. Implications to the foreign language education are also discussed. [ABSTRACT FROM AUTHOR]

A new model for nearshore nonlinear water wave is established through the Galerkin Chebyshev spectral approach on the vertical direction. The model is based on the spatial-temporal separation conception. The Galerkin Chebyshev spectral approach is applied to solve the Laplace equation, while the Zakharov's expression of the free surface boundary condition is considered as the evolution equation of the free surface and integrated temporally. The accuracy and efficiency of the model are confirmed by the results of simulation of water waves over even bottom, nonlinear wave shoaling and harmonic generation over a submerged bar. Finally, the model is used to study the wave blocking phenomenon due to strong opposing currents. Both the location of the blocking point and the wave structure near the point are well presented. [ABSTRACT FROM AUTHOR]

Small-scale physical model tests were conducted to investigate the morphodynamics of a sandy beach of uniform grain size in the lee of single impermeable submerged breakwater under oblique incident waves. The primary objective of the tests was to assess the performance of a submerged breakwater on a littoral drift environment. Different patterns and mechanism of the currents behind this structure were identified on fixed and movable beds using a particle tracking velocimetry (PTV) technique. The physical model tests showed consistent results for the beach morphology and the subsequent shoreline response with the geometry and the position of the submerged breakwater under the same wave condition. Submerged breakwaters were found to perform well under oblique waves if the volume enclosed behind these structures is filled artificially. Attempts were also made to establish a relationship between shoreline evolution and relevant parameters associated with waves and structures. These preliminary results are sufficient to develop practical design guidelines for submerged breakwaters under obliquely incident waves. [ABSTRACT FROM AUTHOR]

A two-phase flow model based on the mass and momentum conservation is presented, which can simulate the fluid and sediment movement on a flat bed under sheetflow conditions. The governing equation in the vertical direction is modified by considering the influence of static normal intergranular stress. Horizontal pressure gradient is modified in terms of sediment concentration. A criterion is introduced to decide the temporal variation of the still bed level during a one-wave cycle. Vertically parabolic eddy viscosity and corresponding sediment diffusion coefficient are assumed. Numerical results include initial validation comparisons with the existing experimental data from Horikawa et al. [1982]. All measured properties, such as the concentration, sediment velocity and sediment flux are reproduced quite well. Further investigations on the experimental data of Delft Hydraulics [Ribberink and Al-Salem, 1995; Dohmen-Janssen, 1999] cover a wide range of pure sinusoidal wave and combined wave/current flow conditions for different sediment sizes. The numerical results are satisfactory with respect to the measured time-varying and time-averaged concentration distributions both in the sheetflow layer and the suspended layer. Taking into account the various experimental measurements, the present two-phase flow model shows the significant superiority over an existing two-phase flow model [Mina and Sato, 2004]. Comparison between the measurement and the present simulation for sediment flux and net transport rate is also performed. [ABSTRACT FROM AUTHOR]

Laboratory experiments were conducted under sinusoidal sheetflow conditions. By using image analysis, which overcame the demerits introduced by intrusive measurements, the time-varying as well as maximum erosion depths for different flow conditions were estimated. The temporal variation of suspended sand concentration in the sheetflow layer showed high concentration during the deceleration phase and relatively low concentration during the acceleration phase. Rapid sand deposition was observed around flow reversals. The phase lag between the free stream velocity and the sand concentration increased with elevation. The temporal and the spatial distribution of suspended sand concentration revealed an asymmetry in the suspension process, namely relatively long suspension (erosion) and short sedimentation (deposition) reflecting the asymmetry in turbulence. The instantaneous sand particle velocities were estimated using a PIV technique. The mean particle horizontal velocity was found to decrease at the beginning of the acceleration phase, corresponding to the rapid deposition of sand. [ABSTRACT FROM AUTHOR]

This paper describes a model of the net sediment transport rate under linear and arbitrary nonlinear oscillatory flows in the sheetflow regime. The model is based on a two-phase flow description. The turbulent diffusivity was formulated to take into account phase-lag effects for different wave conditions and sediment properties. An introduction of a modifier to the turbulent diffusivity produced asymmetry in the concentration profiles, which qualitatively agrees with temporal and spatial distributions of the concentration profiles measured during laboratory visualization experiments. The model can predict transport rates in the sheetflow regime for combined waves and co-directional currents and for waves alone. The model is validated for a wide range of sediment median particle diameters, wave periods, and maximum flow velocities. Comparisons with experimental data on transport rates under linear and nonlinear waves, including velocity and acceleration asymmetric oscillations, were made and showed good agreement. Other comparisons encompassing combined waves and currents were conducted, also with good agreement. [ABSTRACT FROM AUTHOR]

A field investigation on sediment movement and beach evolution was performed in a fluvial system composed of the Samegawa River and the Nakoso coast, which experienced significant beach erosion recently. Analyses of regional sand volume in the system revealed that the rate of decrease in nearshore sand on the beach is of the same order as the rate of accumulation of sand in dam reservoirs. Dredging of the riverbed near the river mouth also influenced nearby shoreline retreat. Long-term changes in sand movement processes were estimated from the distribution of mineral composition included in the sediment samples collected in a wide area. [ABSTRACT FROM AUTHOR]

The behavior of the bottom boundary layer of a natural rippled bed and plane bed is investigated utilizing PIV technique. An enhanced approach of the PIV is developed on the basis of the Minimum Quadratic Difference (MQD), which is better compared with the conventional cross-correlation method. Information of pixels below the instantaneous unmoved level is expelled from the calculation process so that the velocity close to the bed is computed accurately. The flow field over the natural rippled bed is measured with the enhanced approach and comparison with the LDV measurements showed that the measurements of flow field by the enhanced PIV are in a good agreement with the LDV measurements. Having verified the technique, the technique is utilized to measure the net volume flux of sand transported in sheetflow under asymmetric oscillation. The net mass transport is measured to be compared with the PIV measurement. The sand concentration is estimated from brightness through a calibration relationship. The velocity is measured and then the volume flux is integrated. It was found that the technique predicted net onshore transport although it slightly underestimated the volume flux. [ABSTRACT FROM AUTHOR]

No abstract received. [ABSTRACT FROM AUTHOR]

Abstract The effects of a magnetic field longitudinal to the ion beam track on the generation of hydroxyl radicals (•OH) and hydrogen peroxide (H2O2) in water were investigated. A longitudinal magnetic field was reported to enhance the biological effects of the ion beam. However, the mechanism of the increased cell death by a longitudinal magnetic field has not been clarified. The local density of •OH generation was estimated by a method based on the EPR spin-trapping. A series of reaction mixtures containing varying concentrations (0.76‒2278 mM) of DMPO was irradiated by 16 Gy of carbon- or iron-ion beams at the Heavy-Ion Medical Accelerator in Chiba (HIMAC, NIRS/QST, Chiba, Japan) with or without a longitudinal magnetic field (0.0, 0.3, or 0.6 T). The DMPO-OH yield in the sample solutions was measured by X-band EPR and plotted versus DMPO density. O2-dependent and O2-independent H2O2 yields were measured. An aliquot of ultra-pure water was irradiated by carbon-ion beams with or without a longitudinal magnetic field. Irradiation experiments were performed under air or hypoxic conditions. H2O2 generation in irradiated water samples was quantified by an EPR spin-trapping, which measures •OH synthesized from H2O2 by UVB irradiation. Relatively sparse •OH generation caused by particle beams in water were not affected by loading a magnetic field on the beam track. O2-dependent H2O2 generation decreased and oxygen-independent H2O2 generation increased after loading a magnetic field parallel to the beam track. Loading a magnetic field to the beam track made •OH generation denser or made dense •OH more reactive. [ABSTRACT FROM AUTHOR]