Analysis of spherical indentation of materials with plastically graded surface layer

AbstractIn the present work, a comprehensive parametric study for establishing contact mechanics of instrumented normal spherical indentation on homogeneous materials and materials with plastically graded surface layer (PGSL) was undertaken by dimensional analysis and finite element modeling. The spherical indentation response for homogeneous materials can be described only by two dimensionless parameters: strain hardening exponent and a unified parameter that can describe effects of both the normalized yield strength and the normalized indentation depth. The influences of these two parameters were investigated for a wide range of engineering materials, and the results may be used as an estimate of loading response and pile-up/sink-in behavior when the material properties are known. In the materials with PGSL, a linear gradient in yield strength, and no variation in elastic modulus and strain hardening exponent were explored. The indentation response of the materials with PGSL can be described only by three dimensionless parameters: the normalized indentation depth, the dimensionless strength gradient parameter, and the normalized PGSL thickness. The effects of these three parameters were studied systematically. The normalized pile-up/sink-in parameter is found to be an increasing function of the strength gradient parameter. The normalized pile-up/sink-in parameter increases (decreases) with increasing PGSL thickness for a fixed positive (negative) gradient case at large indentation depth. The results also indicate that the materials with positive PGSL can bear more loads and have significantly more resistance to contact crack formation

MyoPS A Benchmark of Myocardial Pathology Segmentation Combining Three-Sequence Cardiac Magnetic Resonance Images

Assessment of myocardial viability is essential in diagnosis and treatment management of patients suffering from myocardial infarction, and classification of pathology on myocardium is the key to this assessment. This work defines a new task of medical image analysis, i.e., to perform myocardial pathology segmentation (MyoPS) combining three-sequence cardiac magnetic resonance (CMR) images, which was first proposed in the MyoPS challenge, in conjunction with MICCAI 2020. The challenge provided 45 paired and pre-aligned CMR images, allowing algorithms to combine the complementary information from the three CMR sequences for pathology segmentation. In this article, we provide details of the challenge, survey the works from fifteen participants and interpret their methods according to five aspects, i.e., preprocessing, data augmentation, learning strategy, model architecture and post-processing. In addition, we analyze the results with respect to different factors, in order to examine the key obstacles and explore potential of solutions, as well as to provide a benchmark for future research. We conclude that while promising results have been reported, the research is still in the early stage, and more in-depth exploration is needed before a successful application to the clinics. Note that MyoPS data and evaluation tool continue to be publicly available upon registration via its homepage (www.sdspeople.fudan.edu.cn/zhuangxiahai/0/myops20/)

A compendium of genetic regulatory effects across pig tissues

The Farm Animal Genotype-Tissue Expression (FarmGTEx) project has been established to develop a public resource of genetic regulatory variants in livestock, which is essential for linking genetic polymorphisms to variation in phenotypes, helping fundamental biological discovery and exploitation in animal breeding and human biomedicine. Here we show results from the pilot phase of PigGTEx by processing 5,457 RNA-sequencing and 1,602 whole-genome sequencing samples passing quality control from pigs. We build a pig genotype imputation panel and associate millions of genetic variants with five types of transcriptomic phenotypes in 34 tissues. We evaluate tissue specificity of regulatory effects and elucidate molecular mechanisms of their action using multi-omics data. Leveraging this resource, we decipher regulatory mechanisms underlying 207 pig complex phenotypes and demonstrate the similarity of pigs to humans in gene expression and the genetic regulation behind complex phenotypes, supporting the importance of pigs as a human biomedical model.</p

Ionization Equilibrium of Water Molecule Dominated Ethanol-water Binary Solution Self-assemble

Water and ethanol are conventional solvents, the anomalous physio-chemical properties of water ethanol binary solution have drawn intensive research. The unidirectional impedance evolution of ethanol-water binary solution in time domain was discovered through electrochemical impedance spectroscopy. Binary solution with different volume ratios has various self-assembly rates indicate ionization equilibrium of water molecule dominate the dynamic self-assembly process of water ethanol binary solution. Combined with molecular dynamics simulation and Raman Spectroscopy, we elucidated that this self-assembly behavior was driven by hydrogen bonding between water as proton donor and ethanol as proton receptor under water ionization, the bond length (162 pm). Different electrolytes addition in binary solution were applied to shift ionization equilibrium of water directionally, and subsequent specified self-assembly evolution was observed to prove the above hypothesis. We proposed the self-assembly mechanism of ethanol-water binary solution is relevant to ionization equilibrium of water for the first time, such perspective may provide some insight to understand the dynamic structural organization of ethanol-water and other binary solutions

Chemical medium-range order in a medium-entropy alloy

High-/medium-entropy alloys (H/MEA) have the inherent local chemical order. Yet, as a structural link between the incipient short-range order and mature long-range counterpart, the chemical medium-range order (CMRO) is conjectural and remains open questions as to if, and what kind of, CMRO would be produced and if CMRO is mechanically stable during plastic deformation. Here, we show compelling evidences for CMRO in an Al9.5CrCoNi MEA. Specifically, the electron diffraction under both [112] and [013] zone axis show the definite spots for CMRO of lattice periodicity. CMRO entities are seen directly of medium-ranged in sizes by using dark-field imaging, along with the tendency towards like-pair avoidance and unlike-pair preference based on atomic-resolution EDS mapping. These findings substantiate CMRO with a realistic structural picture in view of crystal periodicity and chemical species occupation, shedding light on understanding the microstructural link at an extended length scale beyond the short-range order

Enhanced tensile properties by heterogeneous grain structures and coherent precipitates in a CoCrNi-based medium entropy alloy

A dual heterogeneous structure with both heterogeneous grain structure and coherent L1(2) nanoprecipitates was obtained in a CoCrNi-based medium entropy alloy (MEA) with chemical composition of Co34.5Cr32-Ni27.5Al3Ti3 (in at%). The volume fraction of L1(2) phase is observed to become higher and the corresponding interspacing becomes smaller after aging, resulting in a more severe heterogeneity. The unaged samples are found to have better tensile properties as compared to those for the CoCrNi MEA with homogeneous and het-erogeneous grain structures. The aged samples display an even better synergy of strength and ductility than the corresponding unaged samples. The hetero-deformation-induced hardening plays a more important role in the aged samples than in the unaged samples, especially at the elasto-plastic transition stage, producing higher density of geometrically necessary dislocations for better tensile properties. Multiple deformation twins, stacking faults and Lomer-Cottrell locks are the dominant deformation mechanisms for the unaged samples, while in-teractions between these defects and L1(2) nanoprecipitates play important roles in the aged sample, the shearing hardening mechanism is observed for L1(2) nano-particles

China's gas market under new situations: Trends and countermeasures – Taking Sichuan and Chongqing gas provinces as an example

The world oil and gas market has entered a new period of low oil prices, which has inevitably affected the natural gas market in China. So, it is urgent to timely study the market trends and to actively seek for appropriate countermeasures. In this paper, the development trends of China's gas market under the situations of New Normal and low oil prices were analyzed from the perspective of sustainable development of the natural gas industrial chain and market, by taking the Sichuan and Chongqing gas provinces as an example, which are of representative and of great significance to China in its natural gas market. The following trends were identified. First, the gas market reform will be deepened. Second, the competition among major market players will be intensified. Third, supply will exceed demand. Fourth, export tasks will be difficult. Fifth, higher demand of “guarantees of the minimum GDP, tax and profit” will be raised for local government. And sixth, low-cost strategy will be indispensable to oil and gas enterprises. In order to cater to these trends, some countermeasures were presented during the 13th Five-Year Plan. First, to improve the natural gas market system, to strengthen the supply-side reform, to complete market development modes, and to promote the introduction of governmental policies for relevant industries. Second, to develop the efficient gas-consuming clusters such as industrial parks, LNG-fueled vehicles and vessels, and distributed energy sources system, to establish innovative marketing strategy systems, and to boost the localization of resource consumption, through the establishment of strategic alliances for natural gas terminal markets in partnership with local governments and competitive enterprises, while the Chinese government is intensifying efforts in promoting energy conservation and pollution reduction and haze control. Third, to improve the cobweb pipeline network system, and to establish the strategic reserve system. And fourth, to make greater efforts to deepen internal reforms, to cut costs in a sustainable way through technological and managerial innovation, so as to respond to any changes in the natural gas market as a result of low oil prices