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X-band radar observations with a transmitting frequency of 9.4 GHz were conducted for over 10 h at the mouth of Tenryu River, Japan, to estimate surface velocity distributions during floods in 2010 and 2020 and analyse changes in the flow field caused by dredging in 2014. X-band radar is an imaging radar that can collect backscatter of floating objects flowing downstream with the flood flow every 2 s. The observation area extends approximately 1000 m × 1000 m. Particle image velocimetry is applied to the image sequences to guess the surface flow pattern. Flow direction in the main river channel changed smoothly, while surface flow speeds ranged from 1 to 3 m s–1 depending on the discharge. Water levels were computed using the estimated surface flow velocities, river cross-section from survey data, and observed discharge for indirect validation: it agreed within an error of 0.3 m with the observed water level. This paper highlights radar's potential for estimating surface velocity distribution during floods and harsh weather conditions. [ABSTRACT FROM AUTHOR]

The potential ability of VHF or UHF Doppler radars to measure turbulence kinetic energy (TKE) dissipation rate ε in the atmosphere is a major asset of these instruments because of the possibility to continuously monitor turbulence in the atmospheric column above the radars. Several models have been proposed over the past decades to relate ε to half the Doppler spectral width σ , corrected for non-turbulent contributions, but their relevance remains unclear. Recently, Luce et al. (2023) tested the performance of a new model expected to be valid for weakly stratified or strongly sheared conditions, i.e., for low Richardson (Ri) numbers. Its simplest expression is εS=CSσ2S , where CS∼0.64 and S=|dV/dz| is the vertical shear of the horizontal wind V. We assessed the relevance of this model with a UHF (1.357 GHz) wind profiler called WPR LQ-7, which is routinely operated at the Shigaraki Middle and Upper Atmosphere (MU) observatory (34.85 ∘ N, 136.10 ∘ E) in Japan. For this purpose, we selected turbulence events associated with Kelvin–Helmholtz (KH) billows, because their formation necessarily requires Ri<0.25 somewhere in the flow, a condition a priori favorable to the application of the model. Eleven years of WPR LQ-7 data were used for this objective. The assessment of εS was first based on its consistency with an empirical model εLout=σ3/Lout , where Lout has the dimension of an outer scale of turbulence. It was found to compare well in a KH layer with direct estimates of ε from in situ measurements for Lout≈70 m. Some degree of equivalence between εS and εLout was confirmed by statistical analysis of 192 KH layers found in the height range 0.3–5.0 km indicating that Lout≈LH/0.64 , where LH=σ/S is the Hunt scale defined for neutral turbulence. The degree of equivalence is even significantly improved if Lout is not treated as a constant but depends on the depth D of the layer. We found Lout≈0.0875D or equivalently LH∼0.056D , which also means that σ is proportional to the apparent variation in the horizontal velocity (S×D) over the depth of the KH layer. Consequently, εS=0.64σ2S and εLout=σ3/0.0875D would express the same model for KH layers when Ri remains low. For such a condition, we provide a physical interpretation of εLout , which would be qualitatively identical to that for neutral boundary layers. [ABSTRACT FROM AUTHOR]

• Moderate earthquake-induced HF radio propagation effects are detected in the ∼(1–2) × 103 km range from the epicenter. • Earthquake was associated with an increase of–(0.3–0.4) Hz in Doppler shift and in the number of rays up to 5. • Earthquake was associated with the 1–1.5 Hz Doppler spectrum broadening in the 5–9.8 MHz frequency range. • Moderate earthquake-induced geophysical effects were detected in the ∼(1–2) × 103 km range from the epicenter. The Harbin Engineering University HF software-defined radio system since 2018 continuously monitors dynamic processes launched in the ionosphere by energetic events in the Sun–interplanetary-medium–magnetosphere–ionosphere–subsystem coupling. The data collected during the submarine magnitude 6.0 earthquake that occurred off the East coast of Honshu, Japan, on April 11, 2019, have been analyzed with the specific objectives of determining the ionospheric response to the earthquake, the distortions of the radio-wave propagation channels, and identifying possible mechanisms for the transport of the disturbances at 845–2,260 km great-circle distances between the epicenter and the propagation path midpoints. Despite the ionospheric responses to powerful earthquakes have been studied since 1964, the problem of deriving global specifications of the disturbances remains pressing. The effects that the ionospheric disturbances from earthquakes have on radar, communications channels, radio navigation, radio astronomy, etc., are a matter of even greater urgency. The multiple path multifrequency radio system for sounding the ionosphere at oblique incidence provides a convenient tool for diagnosing such HF radio-wave propagation problems, acquiring a database containing the complex amplitudes of the signals and used to produce a sequence of Doppler spectra, for the first time, at a rate of 480 spectra per 1 h along 14 radio-wave propagation paths simultaneously with a 7.5-s temporal resolution and 0.02-Hz Doppler resolution over 20-s intervals. Analysis of the Doppler spectra, Doppler shift along the main ray, and signal amplitudes on the day when the earthquake occurred and on quiet time reference days showed that after the earthquake the Doppler spectra exhibit essential broadening, the Doppler shift along the main ray undergoes alternating sign Doppler variations, as well as quasi-sinusoidal variations with 3–5- and 10–20-min periods pertaining to the infrasound and atmospheric gravity wave frequency bands. The relative amplitudes of disturbances in the electron density are estimated to be ∼1% and 2–19% in the fields of infrasound of atmospheric gravity waves, respectively. [ABSTRACT FROM AUTHOR]

Interactions between near-inertial waves and the balanced eddy field modulate the intensity and location of turbulent dissipation and mixing. Two EM-APEX profiling floats measured near-inertial waves generated by Typhoons Mindulle, 22 August 2016, and Lionrock, 30 August 2016, near the radius of maximum velocity of a mesoscale anticyclonic eddy in the Kuroshio–Oyashio confluence east of Japan. High-vertical-wavenumber near-inertial waves exhibit energy fluxes inward toward eddy center, consistent with wave refraction/reflection at the eddy perimeter. Near-inertial kinetic energy tendencies are nearly two orders of magnitude greater than observed turbulent dissipation rates ε, indicating propagation/advection of wave packets in and out of the measurement windows. Between 50 and 150 m, ε ∼ O (10−10) W kg−1, more than an order of magnitude weaker than outside the eddy, pointing to near-inertial wave breaking at different depths or eddy radii. Between 150 and 300 m, small-scale inertial-period patches of intense turbulence with near-critical Ri occur where comparable near-inertial and eddy shears are superposed. Three-dimensional ray-tracing simulations show that wave dynamics at the eddy perimeter are controlled by radial gradients in vorticity and Doppler shifting with much weaker contributions from vertical gradients, stratification, and sloping isopycnals. Surface-forced waves are initially refracted downward and inward, consistent with the observed energy flux. A turning-point shadow zone is found in the upper pycnocline, consistent with weak observed dissipation rates. In summary, the geometry of wave–mean flow interaction creates a shadow zone of weaker near-inertial waves and turbulence in the upper part while turning-point reflections amplify wave shear leading to enhanced dissipation rates in the lower part of the eddy. [ABSTRACT FROM AUTHOR]

Summary: The use of zirconium carbide (ZrC) as a substitute for silicon carbide (SiC) has been proposed to improve the performance of coated particles for high‐temperature gas‐cooled reactor (HTGR) fuel. Irradiation test on ZrC has proved that it has excellent characteristics for HTGR fuel compared with SiC, such as fission product retention capabilities and better resistance on fission product corrosion. Neutronic analysis on 30 MWt HTGR using ZrC and SiC has been performed in many previous studies. The research presented in this paper was conducted as a further continuation of the aforementioned studies. The present study was directed to analyze tristructural isotropic (TRISO)‐coated particles with ZrC as a substitute for the SiC layer on an HTGR with different power rates. Here, we used high‐temperature test reactor design, an experimental scale prismatic HTGR built and operated in Japan. The power was varied at the range of 50‐100 MWt, while the reactor geometry was modified by applying an additional fuel layer in the axial and radial directions. Neutronic analysis of the reactor was investigated by calculating the k‐eff, k‐inf, power peaking factor, burn‐up level, neutron spectrum, and Doppler effect using ZrC and SiC layers for TRISO‐coated fuel particles. The result shows the coated fuel particle using the ZrC layer has the same performance as SiC with an insignificant difference in the values on neutronic aspects calculation. Neutronic calculations are performed using the SRAC code with the Japanese Evaluated Nuclear Data Library 4.0 nuclear data library. [ABSTRACT FROM AUTHOR]

Abstract The response of the ionosphere to the earthquake of a moderate magnitude (M ≈ 5.9) that occurred in Japan at 11:23:50 UT on 7 July 2018 has been studied using a newly developed coherent multi-frequency radio diagnostic system for remotely probing the ionosphere at oblique incidence. The seismic activity in Japan on 7 July 2018 was accompanied by aperiodic processes in the ionosphere at distances of no less than (1–2) × 103 km from the epicentre, with an enhancement in multiple-mode propagation, and a significant Doppler spectrum broadening. Three ways of transporting disturbances from the earthquake to the changes in the character of Doppler spectra variations have been identified by examination. First, the disturbances are generated by a surface Raleigh wave launched at the earthquake epicentre. They have been ascertained in the infrasonic range (a 3- to 4-min period) of oscillations. The relative amplitude of these quasi-periodic oscillations in the electron density is equal to 1.7–9%. The duration of the oscillation trains is found to be in the range of 24–55 min. The wave disturbance speed of propagation is approximately 3 km/s. Second, wave disturbances have also been ascertained in a 15- to 30-min period range. They could be generated in the vicinity of the epicentre and then propagated as atmospheric gravity waves modulating the electron density in the ionosphere. The relative amplitude of the quasi-periodic disturbances in the electron density is equal to 14 – 34%. The wave train attains a temporal duration of about 100 min and a speed of approximately 0.3 km/s. Third, the broadening of the Doppler spectra toward negative Doppler shifts with the time delay estimated to be 49–124 min, depending on the orientation of the propagation path, is the most pronounced Doppler signature of the disturbances caused by the earthquake. This time delay corresponds to a speed of about 0.3 km/s, and consequently, it suggests that this effect most likely is caused by the atmospheric gravity waves launched at the earthquake epicentre. Apparently, the rearrangement of the ionosphere acts to reverse the sign of the Doppler spectrum shift when the atmospheric gravity waves arrive at the reflection level. Highlights • Developed coherent multi-frequency multipath radio diagnostic system demonstrated high efficiency. • Seismic activity is accompanied by aperiodic processes in the ionosphere, with enhancement in multiple-mode propagation. • Seismic activity is accompanied by significant Doppler spectrum broadening. • Wave disturbances detected in infrasonic oscillation range are generated by surface Raleigh wave. • Wave disturbances generated at epicentre propagate as atmospheric gravity waves modulating electron density. [ABSTRACT FROM AUTHOR]

In the 2011 Tohoku tsunamigenic earthquake, ionospheric anomalies generated by tsunami-induced gravity waves were observed by many types of instruments. Three digisondes and one Doppler receiver located in East Asia were applied to investigate the far-field ionospheric response to the westward-propagating gravity waves generated by the earthquake. Based on time–period spectrum analysis, oscillations between 20 and 36 min on the fo\textF2 (critical frequency of F2 layer) curves and Doppler variations of each observation location were identified. The horizontal group speed, generation time, and source location estimated with the ray-tracing method all indicated that the periodic disturbances recorded by the four radio systems were gravity waves induced by the tsunami following the 2011 Tohoku earthquake. The plasma frequency variations at five fixed altitudes in the ionospheric F2 layer over I-Cheon were used to investigate the vertical propagation of the tsunami-associated gravity waves. The measured phase progression in the vertical direction was opposite that of the energy transport, which further confirmed that the recorded waves were atmospheric gravity waves. The use of multisite remote sensing for examining tsunami-induced waves in the ionosphere may open new perspectives in oceanic monitoring and future tsunami warning systems. [ABSTRACT FROM PUBLISHER]

A tornadic supercell and associated low-level mesocyclone (LMC) observed on the Kanto Plain, Japan, on 6 May 2012 were predicted with a nonhydrostatic mesoscale model with a horizontal resolution of 350 m through assimilation of surface meteorological data (horizontal wind, temperature, and relative humidity) of high spatial density and C-band Doppler radar data (radial velocity and rainwater estimated from reflectivity and specific differential phase) with a local ensemble transform Kalman filter. With assimilation of both surface and radar data, a strong LMC was successfully predicted near the path of the actual tornado. When either surface or radar data were not assimilated, however, the LMC was not predicted. Therefore, both surface and radar data were essential for successful LMC forecasts. The factors controlling the strength of the predicted LMC, defined as a low-level maximum vertical vorticity, were clarified by an ensemble-based sensitivity analysis (ESA), which is a new approach for analyzing LMC intensification. The ESA showed that the strength of the LMC was sensitive to low-level convergence forward of the storm and to low-level relative humidity in the rear of the storm. Therefore, the correction of these low-level variables by assimilation of dense observations was found to be particularly important for forecasting and monitoring the LMC in the present case. [ABSTRACT FROM AUTHOR]

Objective.—Symptoms consistent with neurological decompression sickness (DCS) in commercial breath-hold (Ama) divers has been reported from a few districts of Japan. The aim of this study was to detect circulating intravascular bubbles after repetitive breath-hold diving in a local area where DCS has been reported in Ama divers. Methods.—The participants were 12 partially assisted (descent using weights) male Ama divers. The equipment (AQUALAB system) consisted of continuous-wave Doppler with a 5-MHz frequency, and the Doppler probe was placed in the precordial site with the ultrasonic wave directed into the pulmonary infundibulum. We carried out continuous monitoring for 10 minutes at the end of the series of repetitive dives, and the recordings were made on numerical tracks and graded in a blind manner by 2 experienced investigators, according to the Spencer Doppler code. Results.—Depths and number of dives were 8 to 20 m and 75 to 131 times. Mean diving duration and surface interval were 64 ± 12 seconds and 48 ± 8 seconds, respectively (mean ± SD). We detected the lowest grade of intravascular bubbles (Spencer's grade I) in an Ama diver whose mean surface interval was only 35.2 ± 6.2 seconds. His mean descending, bottom, and ascending times were 10.4 ± 1.6 seconds, 39.2 ± 8 seconds, and 18.2 ± 3.0 seconds, respectively, over the course of 99 dives. Conclusions.—Jntravascular bubbles may be formed after repetitive breath-hold dives with short surface intervals or after a long breath-holding session in Ama divers. Symptoms consistent with neurological accidents in repetitive breath-hold diving may be caused in part by the intravascular presence of bubbles, indicating the need for safety procedures. [ABSTRACT FROM AUTHOR]

Recently Li et al. proposed an exactly-solvable one-dimensional quantum field theory of a dislocation for both edge as well as screw dislocations in an isotropic medium and, via the electron self-energy calculation, Li et al. claimed they can investigate directly the electron-dislocation relaxation time which is reducible to classical results obtained in [T. Ninomiya, J. Phys. Soc. Japan 25, 830 (1968)]. As the qualitative comparison is rather good thus Li et al. claimed the classical fluttering model prior to quantization has already obtained excellent agreement with experiments. However, as the present authors here point out, Ninomiya's approach and results are of doubt (violation of the principle of detailed balance; cf. V.I. Alshits and Yu. M. Sandler, Phys. Stat. Solidi (b) 64, K45 (1974) which performed the corrections: Doppler frequency shift effect included). In fact Ninomiya published a more complete paper latter on: Scr. Metal. 18, 669 (1984) which confirmed the critical remarks by Alshits and Sandier but Li et al. didn't notice or cite it. With above evidences Li et al. should seek quantitative. agreement with realistic materials so that the valid comparison with previous corrected theories considering the classical fluttering mechanism of dislocations can be confirmed. • Li et al.'s dynamic fluttering dislocation scattering process was reexamined. • Li et al.'s treatment of dislocation-phonon interaction was of doubt. • We illustrate Doppler frequency shift effect and violation of the principle of detailed balance. [ABSTRACT FROM AUTHOR]

We have developed an automated analysis scheme for meteor head echo observations by the 46.5MHz Middle and Upper atmosphere (MU) radar near Shigaraki, Japan (34.85° N, 136.10° E). The analysis procedure computes meteoroid range, velocity and deceleration as functions of time with unprecedented accuracy and precision. This is crucial for estimations of meteoroid mass and orbital parameters as well as investigations of the meteoroid-atmosphere interaction processes. In this paper we present this analysis procedure in detail. The algorithms use a combination of single-pulse- Doppler, time-of-flight and pulse-to-pulse phase correlation measurements to determine the radial velocity to within a few tens of metres per second with 3.12 ms time resolution. Equivalently, the precision improvement is at least a factor of 20 compared to previous single-pulse measurements. Such a precision reveals that the deceleration increases significantly during the intense part of a meteoroid's ablation process in the atmosphere. From each received pulse, the target range is determined to within a few tens of meters, or the order of a few hundredths of the 900m long range gates. This is achieved by transmitting a 13-bit Barker code oversampled by a factor of two at reception and using a novel range interpolation technique. The meteoroid velocity vector is determined from the estimated radial velocity by carefully taking the location of the meteor target and the angle from its trajectory to the radar beam into account. The latter is determined from target range and bore axis offset. We have identified and solved the signal processing issue giving rise to the peculiar signature in signal to noise ratio plots reported by Galindo et al. (2011), and show how to use the range interpolation technique to differentiate the effect of signal processing from physical processes. [ABSTRACT FROM AUTHOR]

The relationship between local meteorological fields and the behaviour of airborne Asian dust that arrived in the Tokyo metropolitan area on 1 April 2007 with the passage of a synoptic-scale cold front has been investigated through Doppler lidar observations, experiments using a regional atmospheric numerical model, and analyses of surface and upper-air meteorological observations. Results of the Doppler lidar observations showed that the Asian dust passed above the metropolitan area with strong south-westerly winds with speeds of 15–26 m s−1. Meteorological fields reproduced by the numerical experiments showed the development of a surface-based stable layer in the metropolitan area caused by nocturnal radiational cooling near the ground surface and south-westerly warm air advection at upper levels. The blocking effect of the mountainous region located to the west of the metropolitan area induced an area of stagnant air inside the metropolitan area and promoted the stable layer development. Although strong downdrafts prevailed in the upper air, the airborne Asian dust did not spread to the ground when the stable layer was formed. These results strongly indicate that the developed stable layer prevented strong downdrafts from spreading to the ground, acting as an obstacle to the transport of the Asian dust particles from the upper air towards the ground. This is considered to be one of the main causes of the low appearance frequency of Asian dust phenomena near the ground in the Tokyo metropolitan area and eastern Japan. [ABSTRACT FROM AUTHOR]

In 1842, an Austrian professor of mathematics and practical geometry, Christian Doppler, presented results of his investigations in the field of astronomy, without any clue that they would become important principles of modern ultrasound diagnostics. Almost a century later, at the University of Osaka, Japan, S. Satomura first applied these principles to measure the blood flow velocities in peripheral and extracranial brain-supplying vessels. The father of tissue Doppler imaging is Karl Isaaz, a French scientist, who was the first to realize the importance of clinical and diagnostic potentials of tissue Doppler imaging. Today, this noninvasive echocardiographic method is widely used in evaluation of myocardial function, especially in diagnosing of diastolic heart failure and early diagnosis of coronary artery disease, but also in diffrential diagnosis of restrictive cardiomyopathy and constrictive pericarditis and aberrant myocardial conduction. It is also an antecedent of "stain rate", a new sensitive method for diagnosing myocardial diseases.