Axisymmetric particle-element coupled method for deformation problems of geomaterial

Although grid-based particle methods are widely used for engineering deformation problems, due to their robustness in large deformation analyses, the computational cost of these methods is quite high compared with mesh-based methods. In 3D problems, the computational cost becomes even higher, whereas some mechanical systems can be regarded as axisymmetric, allowing them to be modeled as two-dimensional axisymmetric entities, resulting in a reduced computation cost. In order to decrease the computational cost further, arbitrary spatial discretization has been introduced to reduce the degrees of freedom in the system. The Particle-Element Coupled Method (PEM), the coupled method of the Material Point Method (MPM) and the Arbitrary Particle Domain Interpolation (APDI) method, enables a system to be discretized in arbitrary spatial resolutions. In this paper, PEM is extended to axisymmetric problems, whose formulation and applicability to geomaterial deformation are presented. Firstly, the axisymmetric MPM simulation of a granular column collapse experiment and its efficiency in computation are reported. Secondly, in the simulation of footing penetration, it is shown that the axisymmetric MPM and the axisymmetric PEM can be used to analyze large deformations that cannot be analyzed by mesh-based methods, such as the Finite Difference Method (FDM). The axisymmetric PEM yields equivalent average pressure–displacement relationships and shear strain distributions, realizing a reduction in the computation cost by half as much

Microscopic characteristics of partially saturated dense sand and their link to macroscopic responses under triaxial compression conditions

This paper presents a set of triaxial compression tests on partially saturated dense sands to clarify the microscopic characteristics and their link to the macroscopic responses. Constant suction tests (CS tests) and constant water content tests (CW tests) are conducted under low confining pressure to observe microscopic and macroscopic behaviors of the sands associated with dilative shear bands. X-ray micro-tomography and image analysis techniques are applied to investigate the continuity as a defined index to evaluate the morphology of the pore water, the number of liquid bridges and the principal curvature of the air–water interface. The number of liquid bridges decreases for both the CS and CW tests, particularly during the strain softening process, while it decreases greater in the CW test than in the CS test. The curvature of the air–water interface remains at almost the same value under the CS test, while it tends to decrease under the CW test. The tendency of decreasing curvature corresponds to that of decreasing suction in the CW test. The peak deviator stress is higher in the CS test than in the CW test when the pore water is initially discontinuous, whereas it is identical between the two tests when the pore water is initially continuous. The residual stress is lower in the CW test than in the CS test, independent of the initial water retention states. The macroscopic responses at the different initial water retention states are qualitatively identical between poorly graded sand and well-graded sand

Investigation of localized deformation in partially saturated sand under triaxial compression using microfocus X-ray CT with digital image correlation

AbstractIn this paper, localized deformation in partially saturated sand was investigated quantitatively using microfocus X-ray computed tomography (CT) and an image analysis of the CT images. Triaxial compression tests on a partially saturated dense Toyoura sand specimen were carried out under a low confining pressure and under drained conditions for both air and water. The development of localized deformation was observed macroscopically using microfocus X-ray CT, and the displacement field over the entire specimen was quantified by an image analysis of the CT images with the digital image correlation (DIC) technique. The progressive development of shear bands is discussed with reference to these images. In addition, the region of localization was observed microscopically by partial CT scanning on a micron scale with high spatial resolution. Changes in the particulate structures are also discussed herein. The DIC image analysis of the partial CT images provided a microscopic displacement field and indicated that very fine localized shear deformation developed before the shear bands had become visible in the macroscopic investigation

Morphological transitions for pore water and pore air during drying and wetting processes in partially saturated sand

Water retention characteristics are important for modeling the mechanical and hydraulic behavior of partially saturated sand. It is well known that the soil water characteristic curve shows hysteresis during drying and wetting processes. For a better understanding of the water retention characteristics of partially saturated soil, a microscopic investigation of the morphological transitions for the pore water phase and the pore air phase, such as volume distribution, spatial distribution and continuity during drying and wetting processes, is crucial. In the present study, different water retention states of a partially saturated sand were visualized during water retention tests using microfocus X-ray computed tomography (CT). The CT images obtained from the tests were segmented into the soil particle phase, the pore water phase and the pore air phase. Then, a series of image processing, erosion, dilation and cluster labeling was applied to the images in this order to quantify the cluster volume distributions, the number of clusters and the continuity of both the pore water phase and the pore air phase. The morphological transitions for the pore air phase and the pore water phase, subjected to decreasing and increasing degrees of saturation, were revealed using the results of the image processing, and then, the water retention states were characterized based on the morphologies for the two phases. The influence of the morphologies on the hysteresis was discussed

Host selection of hematophagous leeches (Haemadipsa japonica): Implications for iDNA studies

The development of an efficient and cost‐effective method for monitoring animal populations or biodiversity is urgently needed, and invertebrate‐derived DNA (iDNA) may offer a promising tool for assessing the diversity and other ecological information of vertebrates. We studied the host species of a hematophagous leech (Haemadipsa japonica) in Yakushima by genetic barcoding and compared the results with those for mammal composition revealed by camera trapping. We analyzed 119 samples using two sets of primers by Sanger sequencing and one set of primer by next generation sequencing. The proportion of the samples that were successfully sequenced and identified to at least one species was 11.8–24.3%, depending on the three different methods. In all of these three methods, most of the samples were identified as sika deer (18/20, 6/15 and 16/29) or human (2/20, 7/15 and 21/29). The nonhuman mammal host species composition was significantly different from that estimated by camera trapping. Sika deer was the main host, which may be related with their high abundance, large body size and terrestriality. Ten samples included DNA derived from multiple species of vertebrates. This may be due to the contamination of human DNA, but we also found DNA from deer, Japanese macaque and a frog in the same samples, suggesting the mixture of the two meals in the gut of the leech. Using H. japonica‐derived iDNA would not be suitable to make an inventory of species, but it may be useful to collect genetic information on the targeted species, due to their high host selectivity

Variation in in-hospital mortality and its association with percutaneous coronary intervention-related bleeding complications : A report from nationwide registry in Japan.

Large-scale registries have demonstrated that in-hospital mortality after percutaneous coronary intervention (PCI) varies widely across institutions. However, whether this variation is related to major procedural complications (e.g., bleeding) is unclear. In this study, institutional variation in in-hospital mortality and its association with PCI-related bleeding complications were investigated. We analyzed 388,866 procedures at 718 hospitals performed from 2017 to 2018, using data from a nationwide PCI registry in Japan. Hospitals were stratified into quintiles according to risk-adjusted in-hospital mortality (very low, low, medium, high, and very high). Incidence of bleeding complications, defined as procedure-related bleeding events that required a blood transfusion, and in-hospital mortality in patients who developed bleeding complications were calculated for each quintile. Overall, 4,048 (1.04%) in-hospital deaths and 1,535 (0.39%) bleeding complications occurred. Among patients with bleeding complications, 270 (17.6%) died during hospitalization. In-hospital mortality ranged from 0.22% to 2.46% in very low to very high mortality hospitals. The rate of bleeding complications varied modestly from 0.27% to 0.57% (odds ratio, 1.95; 95% confidence interval, 1.58–2.39). However, mortality after bleeding complications markedly increased by quintile and was 6-fold higher in very high mortality hospitals than very low mortality hospitals (29.0% vs. 4.8%; odds ratio, 12.2; 95% confidence interval, 6.90–21.7). In conclusion, institutional variation in in-hospital mortality after PCI was associated with procedure-related bleeding complications, and this variation was largely driven by differences in mortality after bleeding complications rather than difference in their incidence. These findings underscore the importance of efforts toward reducing not only bleeding complications but also, even more importantly, subsequent mortality once they have occurred

Neural Substrates for the Motivational Regulation of Motor Recovery after Spinal-Cord Injury

It is believed that depression impedes and motivation enhances functional recovery after neuronal damage such as spinal-cord injury and stroke. However, the neuronal substrate underlying such psychological effects on functional recovery remains unclear. A longitudinal study of brain activation in the non-human primate model of partial spinal-cord injury using positron emission tomography (PET) revealed a contribution of the primary motor cortex (M1) to the recovery of finger dexterity through the rehabilitative training. Here, we show that activity of the ventral striatum, including the nucleus accumbens (NAc), which plays a critical role in processing of motivation, increased and its functional connectivity with M1 emerged and was progressively strengthened during the recovery. In addition, functional connectivities among M1, the ventral striatum and other structures belonging to neural circuits for processing motivation, such as the orbitofrontal cortex, anterior cingulate cortex and pedunculopontine tegmental nucleus were also strengthened during the recovery. These results give clues to the neuronal substrate for motivational regulation of motor learning required for functional recovery after spinal-cord injury

Insights into Land Plant Evolution Garnered from the Marchantia polymorpha Genome.

The evolution of land flora transformed the terrestrial environment. Land plants evolved from an ancestral charophycean alga from which they inherited developmental, biochemical, and cell biological attributes. Additional biochemical and physiological adaptations to land, and a life cycle with an alternation between multicellular haploid and diploid generations that facilitated efficient dispersal of desiccation tolerant spores, evolved in the ancestral land plant. We analyzed the genome of the liverwort Marchantia polymorpha, a member of a basal land plant lineage. Relative to charophycean algae, land plant genomes are characterized by genes encoding novel biochemical pathways, new phytohormone signaling pathways (notably auxin), expanded repertoires of signaling pathways, and increased diversity in some transcription factor families. Compared with other sequenced land plants, M. polymorpha exhibits low genetic redundancy in most regulatory pathways, with this portion of its genome resembling that predicted for the ancestral land plant. PAPERCLIP

ダンネンソセイ コウセイシキ ニ ヨル ホウワ ネンド ノ フアンテイセイ ト ヒズミ ノ キョクショカ カイセキ

京都大学0048新制・課程博士博士(工学)甲第10813号工博第2344号新制||工||1304(附属図書館)UT51-2004-G660京都大学大学院工学研究科土木工学専攻(主査)教授 岡 二三生, 教授 田村 武, 教授 松岡 俊文学位規則第4条第1項該当Doctor of EngineeringKyoto UniversityDFA

Trinarization of μX-ray CT images of partially saturated sand at different water-retention states using a region growing method

The trinarization of micro-computed tomography (CT) images for partially saturated soils at different water-retention states has been performed to clearly identify the three phases, i.e., the soil particles, the pore water and the pore air. We have proposed a trinarization technique for partially saturated soils whose histograms of the gray values for the three phases overlap each other. The segmentation method used in this study is the region growing method that ensures the spatial continuity of the phases extracted by the segmentation. Micro CT images of a dense sand specimen during the wetting process in a water retention test have been obtained. It has been found that the trinarization of the CT images in a high pore saturation regime provides reasonable results, while that in a low pore saturation regime overestimates the local void ratio. This is because the gray values of the mixels of the soil particle phase and the air phase, due to the partial volume effect, are similar to those of the water phase. It is necessary, therefore, to validate the trinarization results, by a comparison with the test results, because it is difficult to theoretically evaluate the partial volume effect. The correction of the tolerance value for the low pore saturation case with validation has provided better trinarization results. Through the trinarized CT images, the form of the existing pore water at different water-retention states has been discussed