Hydrodynamic parameters in a flood impacted boulder block ramp: Krzczonówka mountain stream,Polish Carpathians

Boulder block ramps are river engineering structures used to stabilise river beds. Block ramps provide a semi-natural and aesthetically pleasing solution to certain river engineering problems in mountain streams. When constructing block ramps,one can use the dissipative behaviour of large macroroughness elements randomly placed on the river bed to enhance fish migration in an upstream direction thus, in this sense, meeting the requirements of the EU Water Framework Directive. Block ramps are often designed and constructed to replace damaged drop hydraulic structures in the channels of mountain streams. This paper investigates the resilience of a particular block ramp placed in the Krzczonówka stream(Polish Carpathians) in terms of the engineering design function and its durability against damaging. A hydrodynamic analysis of a block ramp is presented before and after a flood event that changed the configuration of the blocks. The seminatural unstructured hydraulic structure was built on the Krzczonowka stream to protect gas pipes which are located beneath it. As a result of several floods, the boulder block chute described in this paper was damaged, and some boulders were dislodged and transported downstream. Our post-flood investigations of bathymetry and velocity revealed that even damaged boulder blocks, removed from the chute and displaced downstream of the structure, still provide significant energy dissipation of the flowing water. The novel of our paper is for the first time showing very detailed analysis of unstructured block ramp hydrodynamics parameters done in the field.Also the novel finding of our investigations shows that before and after the flood event the unstructured block ramp structure, is still fish friendly in terms of hydrodynamics.     

High-Reflectivity Coatings for a Vacuum Ultraviolet Spectropolarimeter

Precise polarization measurements in the vacuum ultraviolet (VUV) region are expected to be a new tool for inferring the magnetic fields in the upper atmosphere of the Sun. High-reflectivity coatings are key elements to achieving high-throughput optics for precise polarization measurements. We fabricated three types of high-reflectivity coatings for a solar spectropolarimeter in the hydrogen Lyman-\(\upalpha \) (Ly\(\upalpha \); 121.567 nm) region and evaluated their performance. The first high-reflectivity mirror coating offers a reflectivity of more than 80 % in Ly\(\upalpha \) optics. The second is a reflective narrow-band filter coating that has a peak reflectivity of 57 % in Ly\(\upalpha \), whereas its reflectivity in the visible light range is lower than 1/10 of the peak reflectivity (\(\sim 5~\%\) on average). This coating can be used to easily realize a visible light rejection system, which is indispensable for a solar telescope, while maintaining high throughput in the Ly\(\upalpha \) line. The third is a high-efficiency reflective polarizing coating that almost exclusively reflects an s-polarized beam at its Brewster angle of 68° with a reflectivity of 55 %. This coating achieves both high polarizing power and high throughput. These coatings contributed to the high-throughput solar VUV spectropolarimeter called the Chromospheric Lyman-Alpha SpectroPolarimeter (CLASP), which was launched on 3 September, 2015.     

Seasonal and spatial variations in the partial pressure of carbon dioxide in a eutrophic brackish lake,Lake Hamana,Japan

The dissolved inorganic carbon and total alkalinity in the surface brackish waters of Lake Hamana were investigated monthly from October 2017 to September 2019 at 14 stations. The partial pressure of carbon dioxide (pCO₂) in the surface water ranged from 29 to 1476 μatm and was undersaturated for atmospheric CO₂ during the observation periods, although most coastal waters were net source areas because of the large amount of terrestrial organic and inorganic carbon input. Since there was a strong negative correlation between pCO₂ and the dissolved oxygen, seasonal and temporal variations in pCO₂ were mainly derived from phytoplankton activity. The high phytoplankton activity induced by the effluents from sewage treatment plants, which was low in carbon and high in nitrogen. Therefore, in urbanized coastal waters with sewage treatment plants, such as the coastal waters of Japan, there is a possibility of shifting from weaker carbon dioxide source areas to sink areas. However, pCO₂ was oversaturated at the polluted river mouth, especially after high precipitation events due to the large carbon supply.

     

Application of an earthquake early warning system and a real-time strong motion monitoring system in emergency response in a high-rise building

We apply a combination of earthquake early warning system (EEWS) and real-time strong motion monitoring system (RSMS) to emergency response for a high-rise building; The Kogakuin University has a 29-story high-rise building in Shinjuku Ward, Tokyo. The proposed strategy is based on the Plan, Do, Check, Action (PDCA) Cycle to brush up the systems and the users: in the “Plan” stage, we apply EEWS and RSMS to the building, where EEWS predicts not only short-period strong ground motions but also long-period ground motions [1]. The system is built into a building announcement system, an emergency elevator control system, and an email message system, which quickly send emails to the emergency response team. Meanwhile, RSMS provides information on seismic intensities at each floor of the building via the web browser in real time using the existing network in the building. In addition, the building response and structural damage can be estimated based on this information. The network system is impervious to the earthquake damage, because the network cable has extra length, there is, however, possible that a network system does not work due to power outage. Thus, we develop the network system that has uninterruptible power-supply system (UPS) and apply it to EEWS and RSMS. The high-rise building has the emergency call units to the security control center in the building on every floor. The emergency call line, however, will be busy promptly, because it is able to use only one line. Therefore, we installed IP telephone which uses the network system on main floors. UPS will work about 30 min after a major earthquake, it is supposed to be enough time for gathering the damage information about the building during initial response. In the “Do” stage, we prepare emergency response instruction manuals and educate the faculty members and students to carry out promptly emergency response. In the “Check” stage, the validity of the proposed systems are verified by carrying out an earthquake drill in an actual high-rise building. The earthquake drill confirmed that our proposed approach is valid. In the final “Action” stage, we improve these systems and emergency response manual and educate people in the building how to use effectively these systems.     

Statistical Models for the Solar Flare Interval Distribution in Individual Active Regions

This article discusses statistical models for the solar flare interval distribution in individual active regions. We analyzed solar flare data in 55 active regions that are listed in the Geosynchronous Operational Environmental Satellite (GOES) soft X-ray flare catalog for the years from 1981 to 2005. We discuss some problems with a conventional procedure to derive probability density functions from any data set and propose a new procedure, which uses the maximum likelihood method and Akaike Information Criterion (AIC) to objectively compare some competing probability density functions. Previous studies of the solar flare interval distribution in individual active regions only dealt with constant or time-dependent Poisson process models, and no other models were discussed. We examine three models – exponential, lognormal, and inverse Gaussian – as competing models for probability density functions in this study. We found that lognormal and inverse Gaussian models are more likely models than the exponential model for the solar flare interval distribution in individual active regions. The possible solar flare mechanisms for the distribution models are briefly mentioned. We also briefly investigated the time dependence of probability density functions of the solar flare interval distribution and found that some active regions show time dependence for lognormal and inverse Gaussian distribution functions. The results suggest that solar flares do not occur randomly in time; rather, solar flare intervals appear to be regulated by solar flare mechanisms. Determining a solar flare interval distribution is an essential step in probabilistic solar flare forecasting methods in space weather research. We briefly mention a probabilistic solar flare forecasting method as an application of a solar flare interval distribution analysis. The application of our distribution analysis to a probabilistic solar flare forecasting method is one of the main objectives of this study.     

The Solar Optical Telescope of Solar-B (Hinode): The Optical Telescope Assembly

The Solar Optical Telescope (SOT) aboard the Solar-B satellite (Hinode) is designed to perform high-precision photometric and polarimetric observations of the Sun in visible light spectra (388 – 668 nm) with a spatial resolution of 0.2 – 0.3 arcsec. The SOT consists of two optically separable components: the Optical Telescope Assembly (OTA), consisting of a 50-cm aperture Gregorian with a collimating lens unit and an active tip-tilt mirror, and an accompanying Focal Plane Package (FPP), housing two filtergraphs and a spectro-polarimeter. The optomechanical and optothermal performance of the OTA is crucial to attain unprecedented high-quality solar observations. We describe in detail the instrument design and expected stable diffraction-limited on-orbit performance of the OTA, the largest state-of-the-art solar telescope yet flown in space.     

Balloon-Borne Hard X-Ray Spectrometer Using CdTe Detectors

Spectroscopic observation of solar flares in the hard X-ray energy range, particularly the 20 ∼ 100 keV region, is an invaluable tool for investigating the flare mechanism. This paper describes the design and performance of a balloon-borne hard X-ray spectrometer using CdTe detectors developed for solar flare observation. The instrument is a small balloon payload (gondola weight 70 kg) with sixteen 10×10×0.5 mm CdTe detectors, designed for a 1-day flight at 41 km altitude. It observes in an energy range of 20−120 keV and has an energy resolution of 3 keV at 60 keV. The second flight on 24 May 2002 succeeded in observing a class M1.1 flare.     

Analysis of three-dimensional strong ground motions along principal axes,San Fernando earthquake

An orthogonal set of principal axes is defined for earthquake ground motions. These principal axes are obtained such that the corresponding variances of motion have maximum, minimum and intermediate values and the covariances equal zero. This indicates that the corresponding components of motion along the principal axes are uncorrelated with respect to each other. Since real earthquake accelerograms are assumed to be reasonably well represented by Gaussian random processes, the three components of motion along the principal axes are statistically independent of each other. Using these principal axes and applying the moving-window technique to the ground accelerograms recorded during the San Fernando earthquake of 9 February 1971, time-dependent characteristics of three-dimensional ground motions along principal axes are determined. Results of the analysis indicate significant correlation between directions of principal axes and directions from the recording stations to the fault slip zone. It is concluded that three components of ground motion can be generated stochastically with statistical independence being maintained, provided they are assumed to be directed along principal axes.     

On Presence of Seismic Anisotropy in the Asthenosphere beneath Continents and its Dependence on Plate Velocity: Significance of Reference Frame Selection

—We examine the possibility of seismic anisotropy in the asthenosphere due to present plate motion using SKS splitting results. The fast directions of anisotropy correlate weakly with the directions of the absolute plate motion (APM) for all APM models. Weak correlation indicates the possibility of asthenospheric anisotropy as well as frozen anisotropy in the lithosphere. Detection of strain rate dependence of anisotropy is helpful to further conclusion of the problem. The selection of reference frame is important to describe shear deformation in the asthenosphere beneath continent due to plate motion. The behavior of hot spots to the mesosphere, fixed or drifted by mantle return flow, is a key of the selection of the reference frame. For the NNR-NUVEL1 model, APM correlated anisotropy appears only at plate velocity faster than 1.4 cm/yr. It suggests the new possibility of the formation of asthenospheric anisotropy in addition to frozen anisotropy in the lithosphere. A critical plate velocity for the formation of anisotropy can be caused by the dislocation-diffusion transition as a function of strain rate on a deformation mechanism map of the upper mantle olivine.