Nanoscale Analysis of Black Carbon Particles with Applications to Optical Calculations

Weijun Li,Yuanyuan Wang 한국대기환경학회 2023 한국대기환경학회 학술대회논문집 Vol.2023 No.10

Bimodal-Structured Al–Mg Alloy with High Strength and Ductility Processed by High Strain Rate Rolling at Medium Temperature

Xinyu Li,Weijun Xia,Jihua Chen,Hongge Yan,Zhenzhen Li,Bin Su,Min Song 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.12

A bimodal grain distribution is generated in the Al-6.5Mg alloy deformed by high strain rate rolling (HSRR) at 320 °C, inwhich the fine grains with the average size of 2.1 μm and the coarse grains with the size of hundreds of microns containingultrafine sub-grains are developed. The deformed microstructures are detected by transmission electron microscopy, X-raydiffraction and electron backscattered diffraction. High strength and considerable ductility are achieved in the HSRRed alloyand the high strength is ascribed to solution strengthening, grain (sub-grain) strengthening and dislocation strengthening. The grain (sub-grain) strengthening is the dominant contributor (~ 146 ± 6 MPa) for yield strength. The generation of newfine grains is primarily observed along the deformation bands related to the high Mg solid content and the high strain rate at320 °C. The dynamic recrystallization related to the deformation bands is proposed to build the bimodal grain distributionfor achieving high strength and considerable ductility.

Exogenous Glycinebetaine Application Contributes to Abiotic Stress Tolerance in Maize

Pei Laming,Li Hongmei,Zhou Yuanyuan,Li Weijun,Jiang Yuhang,Li Hui 한국식물학회 2022 Journal of Plant Biology Vol.65 No.6

Plant growth and development are adversely affected by various environmental stresses. In this study, we investigated the possible function of glycinebetaine (GB) in improving abiotic stress tolerance in maize plants by exogenous application. Results indicated that GB application could effectively improve maize germination percentages, biomass weights and grain yield per plant under abiotic stresses. Moreover, GB-treated plants showed higher reactive oxygen species (ROS)-scavenging capacities, therefore less oxidative destruction than control plants under stresses. In addition, abscisic acid (ABA) levels were increased in GB-treated plants compared to control plants. The comparison of transcriptome profile was performed to analyze the possible mechanism underlying the enhanced tolerance mediated by GB. Many differentially expressed genes (DEGs) between GB-treated and control plants were found to be involved in responses to oxidative stress, abiotic stress and ABA. Taken together, these results indicated that GB might enhance abiotic stress tolerance in maize by regulating ROS-scavenging capacities and ABA-mediated stress-responsive pathways.

Mineralogical and geochemical study of hydrothermal dolomite from the Daliang zinc deposit in Guizhou, Southwest China: new evidence for the genesis

Weijun He,Youguo Li,Sigen Ma 한국지질과학협의회 2023 Geosciences Journal Vol.27 No.2

The Daliang zinc deposit occurs in the southwestern Xiangxi–Qiandong Zn-Pb metallogenic belt and is located on the southeastern margin of the upper Yangtze block. In this study, we present results from petrographic observations, rare earth elements, C-H-O isotopes, and fluid inclusions. The zinc deposit is hosted by middle Cambrian dolomite. The ore-forming process is divided into three stages from early to late: pyrite-galena, sphalerite-pyrite-dolomite, and dolomite. The characteristics of the REEs suggest that multiple fluids were involved in hydrothermal dolomite precipitation under low-temperature conditions. Two types of hydrothermal dolomite fluid inclusions were identified: pure liquid phase inclusions and liquid-rich phase inclusions. The fluid inclusions of hydrothermal dolomite yield homogenization temperatures of 108–192℃ (average 153℃), with salinities of 12.3–26.4 wt% (average 23.0 wt%) NaCl equiv. The δ13Cfluid, δDfluid and δ18Ofluid values for ore-forming fluids range from −4.2 to −3.5‰ (mean −3.8‰), −38.8 to −34.3‰ (mean −36.0‰), and 6.2–6.4‰ (mean 6.3‰), respectively. This study demonstrates that ore-forming fluid was sourced from a moderate- to high-salinity basinal brine and leached metals from metasedimentary rocks of the basement in the Yangtze block. The main transportation of ore-forming fluid occurred in the form of chlorine complexes along well-developed faults, and sulfides precipitated with decreases in pressure and temperature, as well as pH changes. Studies of the Daliang zinc deposit suggest that it is a mediumto low-temperature MVT-like deposit.

Block Compressed Sensing of Self-adaptive Measurement and Combinatorial Optimization

Li Mingxing,Chen Xiuxin,Su Weijun,Yu Chongchong 보안공학연구지원센터 2015 International Journal of Hybrid Information Techno Vol.8 No.5

The block compressed sensing has brought forth the problem that the reconstructed image is of lower quality compared with that of the compressed sensing. A new method is proposed in this paper, named as Block Compressed Sensing of Self-adaptive Measurement and Combinatorial Optimization, which capably solves the problem. According to different sparsity of each image block, we firstly measure the blocks by using different projections; then, we choose measurement with the optimal reconstruction as the final measurement. Eventually, reconstruct the original image using the optimal measurement we got. The proposed method outperforms the compressed sensing in terms of real-time and better reconstruction quality is achieved than the block compressed sensing. Our experimental results verify the superiority of the proposed method.

In Situ Synthesis and Strengthening of Powder Metallurgy High Speed Steel in Addition of LaB6

Weijun Shen,Linping Yu,Zhi Li,Yuehui He,Qiankun Zhang,Huibin Zhang,Yao Jiang,Nan Lin 대한금속·재료학회 2017 METALS AND MATERIALS International Vol.23 No.6

A novel technology which was characterized by the vacuum solid state sintering was developed for powder metallurgyhigh speed steels production. During sintering, both the WC and Mo2C reacted with Fe and transformed toW and Mo rich M6C carbides which were the common hard phases in high speed steels. Also, a high number of W,Mo and Fe were dissolved in VC, forming the MC carbides. The densification of the material mainly relied on thesolubility effect during the M6C and MC carbides formation. By alloying with a 0.1 wt% of LaB6 to the steel, thebending strength and the fracture toughness were improved from 3290 MPa and 25.6 MPam1/2to 4018 MPa and29.4 MPam1/2, respectively. The TEM analysis demonstrated three types of reaction products by the LaB6 addition:the amorphous phase, the core-shell structure and the La2O3 phase. The impurity elements such as the Mg, Al,Si, S, Ca, and O were absorbed following the LaB6 addition. Moreover, the deoxidization effect caused by the LaB6addition promoted the sintering at a high-temperature period which contributed to the bending strength and fracturetoughness improvement.

Preparation, Structure and Performance of Poly(lactic acid)/Poly(lactic acid)-γ -Cyclodextrin Inclusion Complex-Poly(glycidyl methacrylate) Composites

Ya Li,Weijun Zhen 한국고분자학회 2018 Macromolecular Research Vol.26 No.3

Poly(lactic acid)-γ-cyclodextrin inclusion complex-poly(glycidyl methacrylate) (PLA-IC-PGMA) was synthesized with poly(lactic acid) (PLA) and γ-cyclodextrin inclusion complex via surface initiated atom transfer radical polymerization. Then, the PLA/PLA-IC-PGMA composite was prepared by melt blending using PLA-IC-PGMA as additive. Structure and properties of PLA-IC-PGMA and PLA/PLA-IC-PGMA composites were confirmed by X-ray diffraction patterns, 1H nuclear magnetic resonance spectroscopy, Fourier transform infrared spectra, X-ray photoelectron spectroscopy, thermogravimetric analysis, differential scanning calorimetry (DSC), polarized optical microscopy, rheological analysis, etc. Mechanical testing analysis showed that the tensile strength, elongation at break, and impact strength of PLA/ (1 wt%) PLAIC- PGMA composites were improved by 2.3%, 10.8%, and 52.5%, respectively, compared with pure PLA. Scanning electron microscopy analysis demonstrated that the toughness of PLA/PLA-IC-PGMA composite was improved. The results of DSC and TG showed that the cold crystallization peak of PLA composites after the addition of PLA-IC-PGMA disappeared, and its crystallinity was increased by 25% compared with PLA. Furthermore, the thermal stability of PLA/PLA-IC-PGMA composite was improved. Dynamic mechanical analysis showed that the glass transition temperature of PLA/PLA-IC-PGMA composites decreased by 8 oC, which indicated that the flexibility of the chain of PLA was greatly improved. Therefore, the addition of PLA-IC-PGMA improved the comprehensive performance of PLA.

Effect of Mg Content on the Damping Behavior of Al–Mg Alloys

Zhenzhen Li,Hongge Yan,Jihua Chen,Weijun Xia,Bin Su,Lu Zhao,Min Song 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.9

This article investigated the effect of Mg content (4.5, 6.5 and 9.2, in wt%) on the damping capacities of Al–Mg alloys. The results indicate that the damping behavior can be divided into three regions. Region I refers to the low strain amplituderegion (ε < 5 × 10−5), where the damping capacity decreases with increasing the Mg content and has almost no relation withthe strain amplitude. Region II is the middle strain amplitude region (5 × 10−5 < ε < 8 × 10−4), where the damping capacityincreases rapidly with the strain. Region III refers to the high strain amplitude region (8 × 10−4 < ε < 2 × 10−3), where thedamping capacity remains constant and is independent of the strain when the strain is high enough, but increases with the Mgcontent. The damping values Q−1 of Al–4.5Mg, Al–6.5Mg and Al–9.2Mg alloys are 0.01501 ± 0.00032, 0.01633 ± 0.00032and 0.01862 ± 0.00119 at the strain of 1 × 10−3, respectively. The damping capacity in Region I is mainly determined bythe lattice distortion caused by Mg addition and the restoring force caused by pinning points and Suzuki segregation. Theextended dislocations break away from the pinning effect of Mg atoms and become moveable in Region II, and the movementof extended dislocations is the dominant damping mechanism in Region III.

Effect of Heat Treatment on the Microstructure and Properties of High Strain Rate Rolled 7050 Aluminum Alloy

Yang Liao,Hongge Yan,Weijun Xia,Jihua Chen,Bin Su,Xinyu Li,Lu Zhao 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.4

High strain rate rolling (HSRR) is developed to improve the strength, plasticity and stress corrosion resistance of 7050 aluminumalloy simultaneously. The volume fraction of the small-angle grain boundary in the HSRRed alloy sheet is 89.9%. TEM shows that the presence of dislocations and sub-grains promotes the precipitation of the second phase. The alloy inthe T6 state has the highest strength (622 MPa) and the biggest elongation to rupture (20.6%), but poor corrosion resistance. The over-aged state shows the best corrosion resistance. The RRA state can achieve the tensile strength equivalent to T6 of614 MPa, the highest yield strength of 561 MPa and corrosion resistance comparable to the over-aged state. TEM observationshows the existence of sub-grains and dislocations plays an important role in the nucleation of the second phase. Thehigh strength can be attributed to the higher volume fraction of the precipitates, and the high plasticity can be attributed tothe higher work hardening rate. The better corrosion resistance can be ascribe to the wider precipitate-free zones at the grainboundary and the presence of the larger size second phase particles.

Comparison of Urologist Satisfaction for Different Types of Prostate MRI Reports: A Large Sample Investigation

Zhong Jinman,Qin Weijun,Li Yu,Wang Yang,Huan Yi,Ren Jing 대한영상의학회 2020 Korean Journal of Radiology Vol.21 No.12

Objective: To evaluate urologist satisfaction on structured prostate MRI reports, including report with tumor-node-metastasis (TNM) staging (report B) and with Prostate Imaging Reporting and Data System (PI-RADS) score with/without TNM staging (report C, report with PI-RADS score only [report C-a] and report with PI-RADS score and TNM staging [C-b]) compared with conventional free-text report (report A). Materials and Methods: This was a prospective comparative study. Altogether, 3015 prostate MRI reports including reports A, B, C-a, and C-b were rated by 13 urologists using a 5-point Likert Scale. A questionnaire was used to assess urologist satisfaction based on the following parameters: correctness, practicality, and urologist subjectivity. Kruskal-Wallis H-test followed by Nemenyi test was used to compare urologists’ satisfaction parameters for each report type. The rate of urologist-radiologist recalls for each report type was calculated. Results: Reports B and C including its subtypes had higher ratings of satisfaction than report A for overall satisfaction degree, and parameters of correctness, practicality, and subjectivity (p < 0.05). There was a significant difference between report B and C (p < 0.05) in practicality score, but no statistical difference was found in overall satisfaction degree, and correctness and subjectivity scores (p > 0.05). Compared with report C-b (p > 0.05), report B and C-a (p < 0.05) showed a significant difference in overall satisfaction degree and parameters of practicality and subjectivity. In terms of correctness score, neither report C-a nor C-b had a significant difference with report B (p > 0.05). No statistical difference was found between report C-a and C-b in overall satisfaction degree and all three parameters (p > 0.05). The rate of urologist-radiologist recalls for reports A, B, C-a and C-b were 29.1%, 10.8%, 18.1% and 11.2%, respectively. Conclusion: Structured reports, either using TNM or PI-RADS are highly preferred over conventional free-text reports and lead to fewer report-related post-hoc inquiries from urologists.