Urchin-Like Ni Microspherical Structure with Enhanced Magnetic Loss for Thin Microwave Absorber at Gigahertz

Yuping Sun,Zhengwu Pan,Hongming Long,Siu Wing Or,S. L. Ho,Chao Feng,Xianguo Liu 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2017 NANO Vol.12 No.3

We describe in this report a wet chemical reduction synthetic strategy for synthesizing urchin-like Ni microspherical structures, in which the nanowires self-assembled by Ni nanoparticles with the size of 5–20 nm are assembled in a radial form from the center to the surface of the spherical oriented arrays. Urchin-like Ni microspherical structures exhibit the strong magnetic natural resonance peak at 7.0 GHz and superior magnetic loss at 2–18 GHz, originated from relatively high anisotropy energy of urchin-like shape. Electromagnetic absorption measurements show that the urchin-like Ni microspherical structures possess outstanding microwave absorption performance at 2–18 GHz. An optimal reflection loss of –21.98 dB can be observed at 17.4 GHz with a matching thickness of 1.4 mm and the effective absorption (below –10 dB, 90% absorption) bandwidth is 5 GHz (12–17 GHz) with a thickness of 1.7 mm. The excellent microwave absorption performance may be attributed to the good impedance, large attenuation constant and novel magnetic loss ability.

Damage-control technology of oil-based drilling fluid for Kuqa piedmont structure

Peng Xu,Zhengwu Tao,Xiao Liu,Zhihang Yan,Mingbiao Xu 한국자원공학회 2018 Geosystem engineering Vol.21 No.1

Oil-based drilling fluid is widely used in tight sandstone well and shale well in recent years, performance advantages of borehole stability and formation protection are the main reason to promote its use. According to the development and existing research, oil-based drilling fluid still existed serious damage, and could not catch the attention of developers. The study chose Keshen Block as the research object, analyzed reservoir characteristics, evaluated rock wettability, damage of oil-based drilling fluid and oil trapping, and analyzed damage mechanisms of oil-based drilling fluid. Based on the damage mechanisms and the characteristics of drilling fluid, the study analyzed the damage-control mechanisms, established optimization principle of oil-based drilling fluid, and optimized drilling fluid. Dynamic damage experiments and field application of drilling fluid showed that formation protection performance of optimized oil-based drilling fluid had improved significantly, and the formation damage caused by oil-based drilling fluid had been controlled effectively.

Micromechanical investigation for the probabilistic behavior of unsaturated concrete

Qing Chen,Zhiyuan Zhu,Fang Liu,Haoxin Li,Zhengwu Jiang 사단법인 한국계산역학회 2020 Computers and Concrete, An International Journal Vol.26 No.2

There is an inherent randomness for concrete microstructure even with the same manufacturing process. Meanwhile, the concrete material under the aqueous environment is usually not fully saturated by water. This study aimed to develop a stochastic micromechanical framework to investigate the probabilistic behavior of the unsaturated concrete from microscale level. The material is represented as a multiphase composite composed of the water, the pores and the intrinsic concrete (made up by the mortar, the coarse aggregates and their interfaces). The differential scheme based two-level micromechanical homogenization scheme is presented to quantitatively predict the concrete’s effective properties. By modeling the volume fractions and properties of the constituents as stochastic, we extend the deterministic framework to stochastic to incorporate the material’s inherent randomness. Monte Carlo simulations are adopted to reach the different order moments of the effective properties. A distribution-free method is employed to get the unbiased probability density function based on the maximum entropy principle. Numerical examples including limited experimental validations, comparisons with existing micromechanical models, commonly used probability density functions and the direct Monte Carlo simulations indicate that the proposed models provide an accurate and computationally efficient framework in characterizing the material’s effective properties. Finally, the effects of the saturation degrees and the pore shapes on the concrete macroscopic probabilistic behaviors are investigated based on our proposed stochastic micromechanical framework.

Study on softening behavior of laser welded joint in GH909 alloy

Fei Yan,Tao Zhan,Sang Liu,Zhengwu Zhu,Chunming Wang,Xiyuan Hu 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.11

Laser beam welding was conducted on GH909 alloy in a solution treatment and aging conditions. The microstructure, mechanical properties, and softening behavior of welded joints were carefully studied using scanning electron microscopy, energy diffraction spectroscopy, and other techniques. Results indicated that γ′-Ni 3 (TiAl)-precipitated phases were produced inside the matrix, and the presence of Laves at grain boundaries restricted grain growth. A sharp reduction in γ′-precipitated phases evidently weakened the average tensile strength and microhardness of the welded joints. Moreover, fractures occurred in the weld zone. Microcracks in the fracture of the joint mainly depended on the competition result between thermal stress and cohesion forces among the grains.

Locating QTLs controlling overwintering seedling rate in perennial glutinous rice 89-1 (Oryza sativa L.)

Xiaoshu Deng,Lu Gan,Yan Liu,Ancai Luo,Liang Jin,Jiao Chen,Ruyu Tang,Lixia Lei,Jianghong Tang,Jiani Zhang,Zhengwu Zhao 한국유전학회 2018 Genes & Genomics Vol.40 No.12

A new cold tolerant germplasm resource named glutinous rice 89-1 (Gr89-1, Oryza sativa L.) can overwinter using axillary buds, with these buds being ratooned the following year. The overwintering seedling rate (OSR) is an important factor for evaluating cold tolerance. Many quantitative trait loci (QTLs) controlling cold tolerance at different growth stages in rice have been identified, with some of these QTLs being successfully cloned. However, no QTLs conferring to the OSR trait have been located in the perennial O. sativa L. To identify QTLs associated with OSR and to evaluate cold tolerance. 286 F12 recombinant inbred lines (RILs) derived from a cross between the cold tolerant variety Gr89-1 and cold sensitive variety Shuhui527 (SH527) were used. A total of 198 polymorphic simple sequence repeat (SSR) markers that were distributed uniformly on 12 chromosomes were used to construct the linkage map. The gene ontology (GO) annotation of the major QTL was performed through the rice genome annotation project system. Three main-effect QTLs (qOSR2, qOSR3, and qOSR8) were detected and mapped on chromosomes 2, 3, and 8, respectively. These QTLs were located in the interval of RM14208 (35,160,202 base pairs (bp))–RM208 (35,520,147 bp), RM218 (8,375,236 bp)–RM232 (9,755,778 bp), and RM5891 (24,626,930 bp)–RM23608 (25,355,519 bp), and explained 19.6%, 9.3%, and 11.8% of the phenotypic variations, respectively. The qOSR2 QTL displayed the largest effect, with a logarithm of odds score (LOD) of 5.5. A total of 47 candidate genes on the qOSR2 locus were associated with 219 GO terms. Among these candidate genes, 11 were related to cell membrane, 7 were associated with cold stress, and 3 were involved in response to stress and biotic stimulus. OsPIP1;3 was the only one candidate gene related to stress, biotic stimulus, cold stress, and encoding a cell membrane protein. After QTL mapping, a total of three main-effect QTLs—qOSR2, qOSR3, and qOSR8—were detected on chromosomes 2, 3, and 8, respectively. Among these, qOSR2 explained the highest phenotypic variance. All the QTLs elite traits come from the cold resistance parent Gr89-1. OsPIP1;3 might be a candidate gene of qOSR2.

Influence of Heat Treatment on Microstructure and Mechanical Properties of TC4 Fabricated by Laser Melting Deposition

Qi Chaoqi,Du Yang,Yang Ping,Liu Zhengwu,Lyu Hongya,Zhao Kai,Guo Lijie 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.12

The phase composition, microstructure, tensile properties of TC4 samples produced by laser melting deposition (LMD)and LMD followed by solution-aging treatment were investigated to explore a simpler approach to improve the mechanicalperformances and eliminate negative influences by post treatment. The as-deposited TC4 microstructure showed a combinationof α΄martensite and α-colony with various shapes, such as acicular, rod-like and lamellar. As a synergistic result ofsolution and aging treatment, the dispersion strengthening of secondary-α as well as optimization on length-width ratio ofprimary-α and volume fraction of β-phase cause an increase in the ductility and strength. Meanwhile, there is a differencebetween microstructure of water-quenched specimens and air-cooled specimens, subsequently playing a key role in properties. The solution with air-cooling and aging is comparatively found to significantly reduce the anisotropy and improvecomprehensive performance.