Impact of height control on constant volume simple shear testing on sand

Liquefaction is a failure behavior of saturated sand under undrained condition experiencing transient, usually seismic, loading. Current laboratory procedures for evaluating liquefaction behaviors and potentials include using simple shear tests to simulate a vertical propagating seismic wave or a monotonic load. To better simulate field conditions, the sand specimens are tested at saturation under undrained conditions. However, undrained condition can be simulated by keeping the volume of the specimen constant during the test. When performing simple shear tests under constant volume condition, ASTM Standard D6528 allows up to 0.05% volume change of the specimen to be considered a valid equivalent undrained test. Volumetric change of the specimen during constant volume shear impacts the changes in the normal stresses caused by the contractive or dilative behaviors of sand under constant volume condition. This impact on the change in the normal stress, even while the vertical deformations are within the allowed range, can be significant and is a function of the specimen properties. For this research, simple shear tests were run on different sand specimens using the modified UT Cyclic Simple Shear device. The previous version of the device tested saturated sand specimens under truly undrained conditions, while the modifications allowed dry sand specimens to be tested under constant volume conditions to simulate undrained condition. The modifications to the device were to increase the rigidity of the system and overall quality of the results. Monotonic and cyclic loading test results were obtained from the modified testing device. Analyzing the monotonic test results found that even small height changes to the specimen will affect the contractive and dilative behaviors of the specimen. Contractive height change of loose specimens decreased the amount of generated positive change in the axial stress during contraction, while the dilative height change to the dense specimens increased the dilative stress changes at high shear strains. Cyclic test results were compared to the results from corresponding tests obtained from the previous version of the testing device to verify the effect of the modification, as well as comparing the results of constant volume and undrained conditions.The results show that specimens tested under constant volume condition displayed lower strength than the specimen under undrained condition. The dense specimens showed a more significant reduced strength with the difference increasing with the amplitude of vertical movement of the top platen during cyclic loading. Finally, methods of remediating the stress change were proposed. These methods, while experimental, could be modified and used to improve the quality of the simple shear test results under constant volume condition.Civil, Architectural, and Environmental Engineerin

Effects of Aspect Ratio and Distance between Two Square Cylinders in a Tandem Arrangement on In-Line Oscillation Characteristics

When multiple structures, such as the main towers for a bridge, heat exchangers and offshore structures, are placed adjacently in fluid, structures placed in the downstream side are exposed to complicated flow regions, because the separated shear layer reattaches to the downstream structures or interferes with the flow. For this reason, the distance between structures greatly influences changes in flow patterns around the downstream cylinder structures, so that the response characteristics of structures can be altered correspondingly. The purpose of this study is to identify the basic in-line oscillation characteristics of two square cylinders in a tandem arrangement. Based on the supposition of actual structures, spring-supported tests, with both square cylinders elastically suspended, were conducted. Not only the distance between the two cylinders but also the aspect ratio, was also chosen as the parameters. Because it was found by past researches that the in-line oscillation characteristics of single cylinder depends on the aspect ratio, it was thought to be important to confirm it by two cylinders. Furthermore, flow visualization tests were performed by forced-oscillating two cylinders for consideration from the results of the spring-supported test.9th International Symposium on Fluid-Structure Interactions, Flow-Sound Interactions, Flow-Induced Vibration & Noise (FIV2018: FSI2 & FIV+N.), July 8-11, 2018, Toronto, Ontario, Canad

Study of Response Latencies of Interval Bisection Task in Rats

Interval timing, whose range is from a second to several minutes among the sense with respect to time, is related with feeding behavior, decision making and time estimation of animals. In this study, we used interval bisection task, which is a method for examining this interval timing quantitatively. First, rats learned left and right lever pressing associated with the tone stimuli of 2 seconds and 8 seconds for each. Second, probe stimulus tones (e. g. 2.5, 3.2, 4, 5, 6.4 seconds) were presented, and we observed which lever rats selected. When the proportion of the lever pressing associated with the 8 seconds tone is 50%, the point of subjective equality (PSE) can be obtained. The PSE is an indicator of decision making in time perception. In order to investigate whether the difference in the physical properties of the stimulus affects the time perception, we used two kinds of tones, a continuous tone and a 4 Hz pulse tone. The results suggest that the difference in physical properties between continuous tone and 4 Hz pulse tone does not affect time perception. As another index, response latency of lever pressing for each tone presented in the task was calculated. As a result, at the testing stage, a peak in a distribution of response latency was around 3.2 seconds or 4 seconds of probe stimulus. The durations of the peak was similar to PSE. From these results, it was suggested that response latency is an important indicator in decision making of which lever selected

Control of STING Agonistic/Antagonistic Activity Using Amine-Skeleton-Based c-di-GMP Analogues

Stimulator of Interferon Genes (STING) is a type of endoplasmic reticulum (ER)-membrane receptor. STING is activated by a ligand binding, which leads to an enhancement of the immune-system response. Therefore, a STING ligand can be used to regulate the immune system in therapeutic strategies. However, the natural (or native) STING ligand, cyclic-di-nucleotide (CDN), is unsuitable for pharmaceutical use because of its susceptibility to degradation by enzymes and its low cell-membrane permeability. In this study, we designed and synthesized CDN derivatives by replacing the sugar-phosphodiester moiety, which is responsible for various problems of natural CDNs, with an amine skeleton. As a result, we identified novel STING ligands that activate or inhibit STING. The cyclic ligand 7, with a cyclic amine structure containing two guanines, was found to have agonistic activity, whereas the linear ligand 12 showed antagonistic activity. In addition, these synthetic ligands were more chemically stable than the natural ligands

Mechanism of oxygen release from Li-rich cathode material for lithium ion batteries

For further wide spread of high energy density batteries, one of the most important technological challenges is preventing thermal runaway. For that, a key phenomenon is the oxygen release from cathode active materials, because released oxygen may react with the organic solvent and generate heat. Therefore, it is important to understand the mechanism of oxygen release to ensure safe battery operation. While the reaction of charged cathode material and organic solvent was investigated well [1], the mechanism of oxygen release from cathode material is not understood so far [2]. In this study, oxygen release behavior of Li-rich cathode material Li1.2Mn0.6Ni0.2O2-d was investigated, and the mechanism of oxygen release was discussed based on defect chemistry and thermodynamics. Please click Additional Files below to see the full abstract