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For decades, synchrotron radiation facilities have provided powerful research tools for a variety of photon sciences, industrial use, and other purposes. In [[9]], we discussed the suppression of emittance variation in extremely low emittance light sources and demonstrated that the emittance variation could be reduced to less than 1% and passively maintained by carefully optimizing the operating condition of insertion devices. The electron energy was optimized at 6 GeV to reduce the natural electron emittance, while covering the same range of X-rays with shorter period undulators. There is no such magnet for NanoTerasu and, more importantly, the LGB magnets are expected to be made using a permanent magnet for SPring-8-II that does not exist for NanoTerasu. [Extracted from the article]

The 2011 Great East Japan Earthquake and Tsunami are one of the most catastrophic natural disasters that took place in Japan. The disaster caused widespread destruction to the estuarine and coastal areas along the northeastern region of Japan. The Abukuma River mouth, among many estuaries in Miyagi Prefecture, suffered major damage from the tsunami in which the sand spit and the sand terrace were severely eroded. The present study aims to provide a better comprehension of the morphology of the Abukuma River mouth within a decade after the 2011 tsunami based on the collected datasets of imagery and offshore bathymetry surveys. The consecutive changes of the sand terrace and sand spit indicate their connection influencing the morphological recovery in the Abukuma River mouth. About a year after the tsunami, the sand terrace re-appeared by a flood event and became the sediment source to recover the sand spit under the intrusion process. When the sand spit almost recovered and achieved a stable configuration, the sediment from the sand terrace into the river was restricted. As a result, more sediment from the sand terrace was expected to be transported to the downdrift area under the dominant wave condition in the Abukuma River mouth. [ABSTRACT FROM AUTHOR]

In most of the current conventional tsunami numerical models, the steady flow friction law has been widely used to access the tsunami-induced bottom shear stress. However, according to our previous theoretical investigation showed that in almost the entire model domain from the tsunami source to the nearshore area, the tsunami-induced bottom boundary layer behaves like a wave boundary layer, rather than a quasi-steady flow boundary layer. The present study aims to develop a numerical method for tsunami simulation that elaborates a wave friction factor by implementing a correction method proposed by authors' previous work into the conventional 1D shallow water equation. As a result, the new method provides similar results to the original Manning method regarding the water level and the tsunami-induced velocity. However, the bottom shear stress estimated by the new method is higher than that from the Manning method over the entire computational domain. The transition locations from the wave friction zone to the steady friction zone are found at the water depth around 5 m under the present computational condition. [ABSTRACT FROM AUTHOR]

This paper presents a detailed investigation on unsteady effects in bottom boundary layer beneath a tsunami. In numerical simulation of tsunami, bottom shear stress has commonly been evaluated by using steady flow friction laws such as Manning equation, simply assuming that long-period wave motion satisfies quasi-steady flow conditions. However, the present study found that the behavior of tsunami-induced bottom boundary layer has an unsteady characteristics and acts similar to that induced by wind-generated waves even under long-period wave motion. As a result, bottom shear stress under tsunami is much larger than the estimation using steady friction coefficient due to a steep velocity gradient in the bottom boundary layer. Surprisingly, the steady flow friction law is not valid in almost the entire computational domain, from the source area to shallow region. This result highly coincides with the field measurement data obtained by Lacy group during the 2010 Chilean Tsunami at the Monterey Bay mouth in U.S. A correction coefficient is proposed to take into account unsteady effects in the conventional estimation method using a steady friction factor; this approach is validated by comparing with numerical simulation results using k-ω turbulence model. [ABSTRACT FROM AUTHOR]

In the 2011 Tohoku Earthquake Tsunami, run-up of the tsunami along rivers expanded the damaged area into more inland areas far from the coast. High water level in rivers was kept for more than several times of the wave period in the 2011 event, while more simple periodical oscillations of the water level superposed on the tidal motion was observed in the 2010 Chile Tsunami event. The difference of behaviors of tsunami in rivers was discussed with related to the magnitude of tsunami and river mouth morphology through two numerical experiments in this paper. In the first numerical experiments, the run-up of historical tsunamis was simulated along Kitakami River. It was found that the discharge of tsunami flow across the river mouth was proportional to third power of water depth if overflow of the sand spit occurred, and that caused unbalance of water volume coming into and going out from the river channel. Through the second numerical experiment with simple model bathymetry and sinusoidal waves, it was found that discharge during both tsunami run-up and run-down across river mouths is reduced by sand spits at the river mouths and the reduction effect is more significant during flow rushing into the rivers than that during return flow. [ABSTRACT FROM AUTHOR]

Cua Dai beach, located in Hoi An town - Quang Nam province, has experienced serious erosion for the past few years with extremely high speed of shoreline retreat. Despite coastal erosion itself may not be that much problematic, it turns out to be serious problem since there is a large residential area right behind and a huge investment in tourism has been done. Generally, causes of erosion are among unbalance of sediment transport, storm surges and sea level rise. However, the rate of shoreline retreat in Cua Dai beach within the past decade is so aberrant and not likely to be explained by the above phenomenon alone. The goal of this study is to consider effective factors of this coastal erosion based on analysis of the recent progress of erosion using Empirical Orthogonal Function. As a result, the dominant factor for the long-term erosion is concerned to be the change of longshore sediment transport, which was caused by the decrease in sediment supply from Thu Bon River. Therefore, it is recommended to collect more data on sediment transport in the river system and study the relationship between coastal erosion and the change of sediment supply. [ABSTRACT FROM AUTHOR]

This study investigates the changes in coastal topography of the Rikuzen-Takata Coast in Iwate Prefecture, Japan before and after the 2011 off the Pacific coast of Tohoku Earthquake Tsunami and the effects of coastal structures on these changes. The changes in coastal topography were analyzed using bathymetry data and aerial photographs before and after the tsunami in addition to aerial video during the tsunami. The bathymetry data were obtained from 1989 to 2002 during the construction of three submerged breakwaters and from after the 2011 tsunami until 2013. The aerial photographs were acquired from 1947 to 2015, and the aerial videos were acquired during the tsunami run-up and backwash. The results demonstrated that the coast was eroded mainly due to the tsunami backwash, and the submerged breakwaters trapped the seaward transport of sediment from the coast. Erosion was partly prevented in locations where the seawall was not washed away. The coastal structures had significant effects on the behavior of the coastal tsunami and on sediment transport. We also found that the coast did not recover naturally at the desired speed after the tsunami because the coast had been stable before the tsunami. Coastal restoration five years after the 2011 tsunami are also summarized in the Appendix to illustrate the future reconstruction plan for the study coast. [ABSTRACT FROM AUTHOR]

This study proposes a new embankment reinforcement using steel sheet piles against tsunami overflow, which has been known as the main cause of the failures of the embankments by the 2011 Tohoku Earthquake Tsunami. Effectiveness of the proposed technique was discussed through a hydraulic experiment. A model of embankment was set in a horizontal open channel, and one or two steel plates are installed into the embankment from the top as vertical walls inside. Temporal variations of the shapes of the embankment and the sheet pile structures were obtained from video images. In most of the cases, the sheet pile structures started to rotate after the erosion of the landward slope of the embankment. However the rotation stopped at about and from the initial location with the single- and double-wall cases. Height of the embankment after overflow was less than 20% with no reinforcement, while more than 70% and 95% of the height were kept with the single- and double-wall structures, respectively. The performance of the embankment with the reinforcement was also discussed in terms of tsunami energy reduction with an additional fixed-bed experiment. [ABSTRACT FROM AUTHOR]

For many years, scientists around the world have sought an ultra-low-emittance ring-based light source that offers greater performance than existing third-generation light sources. Pioneering work on the seven-bend lattice for MAX IV [1] initiated these efforts. Another significant development was the scheme for nonlinearity control based on “phase-matched” sextupole pairs. This configuration, first introduced in a light source design by the ESRF design group [2], efficiently suppresses strong nonlinear resonances induced by sextupoles for chromaticity correction. Since a small dynamic aperture due to the strong nonlinearities mentioned earlier presents a great obstacle when we attempt to lower the beam emittance of a high-energy light source using individual bending magnets with small deflection angles, the ESRF scheme contributes significantly to the emittance reduction that can be practically achieved. [ABSTRACT FROM PUBLISHER]

Free radical polymerization of captodative substituted methyl 2-methoxyacrylate (MMOA) was carried out in bulk with or without azo initiators at 90–130 °C. At higher temperatures, bimodal molecular weight distribution polymer was obtained by the polymerization of MMOA irrespective of the presence of initiator in contrast to the polymerization at 90 °C where unimodal polymer was produced. In addition, block copolymers were conveniently obtained by heating the comonomers including vinyl acetate and acrylonitrile at 130 °C in the presence of poly(MMOA) without any initiator. These unique reactions were reasonably explained by the cleavage of captodative substituted carbon–carbon single bond at head-to-head structure in polymer chain, which was produced by recombination termination. [ABSTRACT FROM PUBLISHER]