Physical properties of portland cement based concrete exposed at a depth of 3520 m in the Nankai Trough

Concrete is widely used in large-scale construction of submarine infrastructure because of its high strength, durability, and ease of handling. However, knowledge of its durability in deep seawater is lacking. In the deep sea, materials are exposed to high pressures and low temperatures, which may cause early deterioration of concrete over time. Concrete materials may also be affected by the chemical composition of seawater, which induces the leaching of calcium. In situ exposure tests are therefore important for understanding degradation processes in the deep sea. In this study, Portland cement based concrete specimens were placed at a depth of 3520 m on the northern edge of the Nankai Trough in 2018 and retrieved in 2019, in the deepest exposure testing conducted to date. Here we provide an outline of the tests, describe the physical properties of materials exposed to deep seawater, freshwater, and air, and discuss possible concrete degradation mechanisms

Characteristic Scales of Baryon Acoustic Oscillations from Perturbation Theory: Non-linearity and Redshift-Space Distortion Effects

An acoustic oscillation of the primeval photon-baryon fluid around the decoupling time imprints a characteristic scale in the galaxy distribution today, known as the baryon acoustic oscillation (BAO) scale. Several on-going and/or future galaxy surveys aim at detecting and precisely determining the BAO scale so as to trace the expansion history of the universe. We consider nonlinear and redshift-space distortion effects on the shifts of the BAO scale in $k$-space using perturbation theory. The resulting shifts are indeed sensitive to different choices of the definition of the BAO scale, which needs to be kept in mind in the data analysis. We present a toy model to explain the physical behavior of the shifts. We find that the BAO scale defined as in Percival et al. (2007) indeed shows very small shifts ($\lesssim$ 1%) relative to the prediction in {\it linear theory} in real space. The shifts can be predicted accurately for scales where the perturbation theory is reliable.Comment: 21 pages, 9 figures, references and supplementary sections added, accepted for publication in PAS

Spin-Hall effect: Back to the Beginning on a Higher Level

The phenomena of the spin-Hall effect, initially proposed over three decades ago in the context of asymmetric Mott skew scattering, was revived recently by the proposal of a possible intrinsic spin-Hall effect originating from a strongly spin-orbit coupled band structure. This new proposal has generated an extensive debate and controversy over the past two years. The purpose of this workshop, held at the Asian Pacific Center for Theoretical Physics, was to bring together many of the leading groups in this field to resolve such issues and identify future challenges. We offer this short summary to clarify the now settled issues on some of the more controversial aspects of the debate and help refocus the research efforts in new and important avenues.Comment: 4 pages, Summary of the APCTP Workshop on the Spin-Hall Effect and Related Issue

活断層のずれ速度を利用したBPT分布更新過程とベイズ推定論による長期地震予測

平成21年度研究報告会、統計数理研究所(広尾）、H22.3.18-19ポスター発

Spatial and temporal turbidity currents sediment deposition assessment

Flume experiments are conducted to model sediment-laden density currents with continuous suspension supply. The initial density covers 1008, 1016, and 1032 kg/m3 and the bottom slope at 5.0 %. Sediment deposition profiles along the experimental flume are measured using an electrical resistance-based depositometer (ERBD). The measurement technique is described, its calibration procedure is presented and results shown. The discussion highlights the influence of the initial turbidity currents density respectively suspension concentration as well as the flow dynamics of the currents. After head passage, the main deposition takes place in the body and linear deposition pattern along the flume axis is observed

Sediment mass movement of a particle-laden turbidity current based on ultrasound velocity profiling and the distribution of sediment concentration

Particle-laden flows or turbidity currents along the seafloor are important to the formation and erosion of submarine topography. To understand the mass-transport process, flume tests were carried out with a continuous supply of quartz-laden suspension. The vertical and horizontal velocities were extracted by two pairs of ultrasound Doppler velocity profilers installed at different angles with respect to the bed-normal direction. Due to the head intrusion into the ambient water, the sediment in the suspension was continuously lifted up and mixed, leaving lobes and clefts. The velocity-maximum layer acted as the main sediment conveyor and divided the body into wall and jet regions. The concentration distribution was also quantified based on the Relationship between the fluid density and the intensity of light attenuation obtained using a video recording. An area of high sediment concentration was observed just behind the head frontal area. Analysis of the velocity and concentration distribution demonstrated that sediment in the turbidity current was transported mainly by head movement and that continuous sedimentation took place in the wall region. The results indicate that a turbidity current proceeds while maintaining an ordered inner dynamic structure

Thorium-doping induced superconductivity up to 56 K in Gd1-xThxFeAsO

Following the discovery of superconductivity in an iron-based arsenide LaO1-xFxFeAs with a superconducting transition temperature (Tc) of 26 K[1], Tc was pushed up surprisingly to above 40 K by either applying pressure[2] or replacing La with Sm[3], Ce[4], Nd[5] and Pr[6]. The maximum Tc has climbed to 55 K, observed in SmO1-xFxFeAs[7, 8] and SmFeAsO1-x[9]. The value of Tc was found to increase with decreasing lattice parameters in LnFeAsO1-xFx (Ln stands for the lanthanide elements) at an apparently optimal doping level. However, the F- doping in GdFeAsO is particularly difficult[10,11] due to the lattice mismatch between the Gd2O2 layers and Fe2As2 layers. Here we report observation of superconductivity with Tc as high as 56 K by the Th4+ substitution for Gd3+ in GdFeAsO. The incorporation of relatively large Th4+ ions relaxes the lattice mismatch, hence induces the high temperature superconductivity.Comment: 4 pages, 3 figure

P‐13: Photosensitivity of Amorphous IGZO TFTs for Active‐Matrix Flat‐Panel Displays

We studied the optical and electrical properties of the amorphous indium gallium zinc oxide thin‐film transistors (a‐IGZO TFTs). To develop a‐IGZO density‐of‐states model, intrinsic a‐IGZO optical properties such as optical band gap and Urbach energy, and TFT characteristics under illumination are investigated. During the a‐IGZO TFTs illumination with the wavelengths ranging from 460 to 660 nm, the off‐state drain current only slightly increases while a large increase was observed for the wavelength below 400 nm. Threshold voltage and subthreshold swing are also only slightly modified between 460 to 660 nm, while field‐effect mobility is almost unchanged in the investigated photon energy range. The observed results are consistent with the a‐IGZO optical energy band gap of about 3.05 eV. This study suggest that the a‐IGZO TFTs are light sensitive above 3.0 eV and photogenerated electrons are more mobile than holes within device channel region.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/92030/1/1.3069354.pd

Non-Gaussian Error Contribution to Likelihood Analysis of the Matter Power Spectrum

We study the sample variance of the matter power spectrum for the standard Lambda Cold Dark Matter universe. We use a total of 5000 cosmological N-body simulations to study in detail the distribution of best-fit cosmological parameters and the baryon acoustic peak positions. The obtained distribution is compared with the results from the Fisher matrix analysis with and without including non-Gaussian errors. For the Fisher matrix analysis, we compute the derivatives of the matter power spectrum with respect to cosmological parameters using directly full nonlinear simulations. We show that the non-Gaussian errors increase the unmarginalized errors by up to a factor 5 for k_{max}=0.4h/Mpc if there is only one free parameter provided other parameters are well determined by external information. On the other hand, for multi-parameter fitting, the impact of the non-Gaussian errors is significantly mitigated due to severe parameter degeneracies in the power spectrum. The distribution of the acoustic peak positions is well described by a Gaussian distribution, with its width being consistent with the statistical interval predicted from the Fisher matrix. We also examine systematic bias in the best-fit parameter due to the non-Gaussian errors. The bias is found to be smaller than the 1 sigma statistical error for both the cosmological parameters and the acoustic scale positions.Comment: 12 pages, 10 figures, accepted for publication in ApJ, minor change