Effect of Sc Content on the Microstructure and Properties of Al–Mg–Sc Alloys Deposited by Wire Arc Additive Manufacturing

Lingling Ren,Huimin Gu,Wei Wang,Shuai Wang,Chengde Li,Zhenbiao Wang,Yuchun Zhai,Peihua Ma 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.1

Despite showing considerable potential, wire arc additive manufacturing (WAAM) has been limited to producing Al–Mgalloys. As the addition of Sc can improve the mechanical properties of Al–Mg alloys, in this study, Al–Mg–Sc alloy depositswith different Sc contents were prepared by a WAAM process. The porosity, microstructure, and mechanical properties ofthe deposits were studied. At Sc contents less than 0.15%, Sc was completely dissolved in the Al matrix without grain refinement,and the mechanical properties were slightly improved. At a Sc content of 0.3%, the primary Al3Scphase precipitatedout of the as-deposited body, resulting in an abrupt change in the microstructure, significant grain refinement, significantlyincreased tensile strength and yield strength, with a tensile strength, yield strength, and elongation of 372 MPa, 270 MPa,and 22.5%, respectively. Following heat treatment at 350 °C for 1 h, the grain boundaries were refined and the secondaryAl3Scphase was precipitated. Furthermore, the tensile strength and yield strength were significantly increased to 415 MPaand 279 MPa, respectively, and elongation decreased to 18.5%. At a Sc content of 0.45%, due to the aggregated precipitatedphase, the coarsened grain boundaries and the limited solid solution amount of Sc in the α(Al) matrix (~ 0.25%), themechanical properties were not further improved compared with the deposit with Sc content of 0.3%. Thus, based on economicconsiderations, the optimal Sc content was 0.3%. Owing to their enhanced mechanical properties, WAAM-producedAl–Mg–Sc alloys are expected to have a wide range of applications in aviation, aerospace.

Discrete Element Simulation Study on Particle Segregation Effect of a Hemispherical Shell Swing-Oscillating Trough Under Combination Swing-Oscillating

Lingling Li,Zhenghai Liu,Jiaye Xu,Xuedong Ma 한국전기전자재료학회 2020 Transactions on Electrical and Electronic Material Vol.21 No.3

In order to enhance the segregation eff ect of material particles in a hemispherical shell swing-oscillating trough under combination swing-oscillating, by means of three dimensional discrete element method, and by use of the two-dimensional dry granules of plastic ball and steel ball, the discrete element simulation study of particle segregation process is carried out in turn in three cases, which is composed of a single swing-oscillating in smooth trough, a combination swing-oscillating in smooth trough, and a combination swing-oscillating in adding bulge trough. The particle segregation eff ect was evaluated by particle volume concentration and combined with segregation cloud picture simulated. The result indicates that segregation effect of combination swing-oscillating is better than that in single swing-oscillating; layering eff ect of the trough added bulge is better than that in the smooth trough. And compared to single swing-oscillating in smooth trough, the degree of segregation of particles in added bulge trough can be increased by 10–15% when being combination swing-oscillating.

Microwave-Assisted Hydrothermal Preparation of SnO2/MoS2 Composites and Their Electrochemical Performance

Lin Ma,Xiaoping Zhou,Limei Xu,Xuyao Xu,Lingling Zhang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2016 NANO Vol.11 No.2

We introduce a two-step hydrothermal and microwave method to prepare novel SnO2/MoS2 composites. The as-prepared samples are well characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The experimental results indicate that the SnO2/MoS2 composites are composed of MoS2 nanosheets and ultrafine SnO2 nanoparticles with mean size of 3–4 nm which are well-distributed and anchored on the surface of MoS2 nanosheets. The resultant composites demonstrate prominently improved electrochemical performances, which could be attributed to the unique and robust microstructures and synergetic effect between MoS2 and SnO2.

One-Pot Hydrothermal Synthesis of Sulfur-Doped SnO2 Nanoparticles and their Enhanced Photocatalytic Properties

Lin Ma,Limei Xu,Xuyao Xu,Xiaoping Zhou,Lingling Zhang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2016 NANO Vol.11 No.3

Sulfur-doped SnO2 nanoparticles with ultrafine sizes have been successfully prepared by a one-pot hydrothermal method. The obtained samples are characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy (HRTEM), thermogravimetric (TG), analyzer UV-Vis spectroscopy, photoluminescence (PL) and electrochemical impedance spectroscopy (EIS). The experimental results indicate that the doping level of sulfur element as well as the bandgaps of SnO2 can be controlled to a certain extent by varying the amount of L-cysteine (L-cys). When evaluated as photocatalysts in the degradation of rhodamine B (RhB) and reduction of Cr(VI) under visible light region, the resultant sulfur-doped SnO2 nanoparticles demonstrate obviously enhanced photocatalytic activities due to the markedly improved visible light response and effective separation of the photo-generated electron–hole pairs.

Role of Organic Counterion in Lead- and Tin-Based Two-Dimensional Semiconducting Iodide Perovskites and Application in Planar Solar Cells

Mao, Lingling,Tsai, Hsinhan,Nie, Wanyi,Ma, Lin,Im, Jino,Stoumpos, Constantinos C.,Malliakas, Christos D.,Hao, Feng,Wasielewski, Michael R.,Mohite, Aditya D.,Kanatzidis, Mercouri G. American Chemical Society 2016 Chemistry of materials Vol.28 No.21

<P>Hybrid halide perovskites are emerging semiconducting materials, with a diverse set of remarkable optoelectronic properties. Besides the widely studied three-dimensional (3D) perovskites, two-dimensional (2D) perovskites show significant potential as photovoltaic (PV) active layers while exhibiting high moisture resistance. Here, we report two series of new 2D halide perovskite solid solutions: (HA)Pb1-xSnxI4 and (BZA)(2)Pb1-xSnxI4 (x = 1, 0.75, 0.5, 0.25, 0), where HA stands for the organic spacer histammonium and BZA stands for benzylammonium cations. These compounds are assembled by corner-sharing octahedral [MI6](4-) units stabilizing single-layered, anionic, inorganic perovskite sheets with organic cations filled in between. The optical band gaps are heavily affected by the M-I-M perovksite angles with the band gap steadily decreasing when the angle approaches 180 degrees, ranging from 2.18 eV for (BZA)(2)PbI4 to 2.05 eV for (HA)PbI4. We find an anomalous trend in electronic band gap in the mixed compositions (HA)Pb1-xSnxI4 and (BZA)(2)Pb1-xSnxI4. When Sn substitutes for Pb to form a solid solution, the band gap further decreases to 1.67 eV for (HA)SnI4. The minimum band gap is at x = 0.75 at 1.74 eV. For BZA, the irregular trend is more intense, as all the intermediate compounds (BZA)(2)Pb(1-x)SnxI(4) (x = 0.75, 0.5, 0.25) have even slightly lower band gaps than (BZA)(2)SnI4 (1.89 eV). DFT calculations confirm the pure Pb and Sn compounds are direct band gap semiconductors. Relatively shorter photoluminescence (PL) lifetime in (BZA)2PbI4 than (HA)PbI4 is observed, suggesting faster recombination rates of the carriers. Solution deposited thin films of (HA)PbI4 and (BZA)2PbI4 show drastically different orientations with (HA)PbI4 displaying a perpendicular rather than parallel growth orientation with respect to the substrate, which is more favorable for PV devices. The higher potential in PV applications of the HA system is indicated by device performance, as the champion air stable planar device with the structure ITO/PEDOT:PSS/2D-perovskite/PCBM/Al of (HA)PbI4 achieves a preliminary power conversion efficiency (PCE) of 1.13%, featuring an open-circuit voltage (VOC) of 0.91 V.</P>

Transcriptome analysis reveals sunflower cytochrome P450 CYP93A1 responses to high salinity treatment at the seedling stage

Peng Wang,Lingling Ma,Ya Li,Shu’an Wang,Linfang Li,Rutong Yang 한국유전학회 2017 Genes & Genomics Vol.39 No.6

Sunflower (Helianthus annuus) is an important global source of plant lipids and protein for food and other industries. Salinity is an abiotic stress that affects sunflower yield. Although recent studies have revealed that the cytochrome P450 (CYP) 93 family is involved in biotic and abiotic stresses, the relationship between the CYP93A gene and salt stress is not well understood in sunflower. In the present study, we performed transcriptome analysis of a relatively salt-tolerant sunflower variety ‘Xinkui 10’ at the seedling stage under high salinity treatment. Following de novo assembly, 66,426 unigenes were obtained, 45,724 (68.83%) of which were annotated. 5,852 differentially expressed genes (DEGs) were identified 11 distinct clusters in which three main clusters (K1–K3) accounted for 94.39% of DEGs. Mapman analysis showed that CYP450 genes were greatly enriched in cluster K3 and one continuously up-regulated gene, HaCYP93A1, was identified among 248 common DEGs in the transcriptome of ‘Xinkui 10’. Real-time quantitative RT-PCR (qRT-PCR) analysis indicated that transcript levels of HaCYP93A1 were induced by high salinity and jasmonic acid (JA) in roots. Meanwhile, three JA-biosynthesis genes (allene oxide cyclase 3 [AOC3], lipoxygenase 3 [LOX3], and allene oxide synthase [AOS]) in roots were up-regulated under salinity treatment. Moreover, correlation analysis indicated that the expression of HaCYP93A1 was markedly related with the JA-biosynthesis genes. Our results suggested that HaCYP93A1 might be involved in the salt tolerance pathway by regulating JA signaling in sunflower.

Multi-objective Fuzzy-optimization of Crowbar Resistances for the Low-Voltage Ride-through of Doubly Fed Induction Wind Turbine Generation Systems

Zhang, Wenjuan,Ma, Haomiao,Zhang, Junli,Chen, Lingling,Qu, Yang The Korean Institute of Power Electronics 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.4

This study investigates the multi-objective fuzzy optimization of crowbar resistance for the doubly fed induction generator (DFIG) low-voltage ride-through (LVRT). By integrating the crowbar resistance of the crowbar circuit as a decision variable, a multi-objective model for crowbar resistance value optimization has been established to minimize rotor overcurrent and to simultaneously reduce the DFIG reactive power absorbed from the grid during the process of LVRT. A multi-objective genetic algorithm (MOGA) is applied to solve this optimization problem. In the proposed GA, the value of the crowbar resistance is represented by floating-point numbers in the GA population. The MOGA emphasizes the non-dominated solutions and simultaneously maintains diversity in the non-dominated solutions. A fuzzy-set-theory-based is employed to obtain the best solution. The proposed approach has been evaluated on a 3 MW DFIG LVRT. Simulation results show the effectiveness of the proposed approach for solving the crowbar resistance multi-objective optimization problem in the DFIG LVRT.

Multi-objective Fuzzy-optimization of Crowbar Resistances for the Low-Voltage Ride-through of Doubly Fed Induction Wind Turbine Generation Systems

Wenjuan Zhang,Haomiao Ma,Junli Zhang,Lingling Chen,Yang Qu 전력전자학회 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.4

This study investigates the multi-objective fuzzy optimization of crowbar resistance for the doubly fed induction generator (DFIG) low-voltage ride-through (LVRT). By integrating the crowbar resistance of the crowbar circuit as a decision variable, a multi-objective model for crowbar resistance value optimization has been established to minimize rotor overcurrent and to simultaneously reduce the DFIG reactive power absorbed from the grid during the process of LVRT. A multi-objective genetic algorithm (MOGA) is applied to solve this optimization problem. In the proposed GA, the value of the crowbar resistance is represented by floating-point numbers in the GA population. The MOGA emphasizes the non-dominated solutions and simultaneously maintains diversity in the non-dominated solutions. A fuzzy-set-theory-based is employed to obtain the best solution. The proposed approach has been evaluated on a 3 MW DFIG LVRT. Simulation results show the effectiveness of the proposed approach for solving the crowbar resistance multi-objective optimization problem in the DFIG LVRT.

Experiment on the Behavior of a Self-Anchored Suspension and Cable-Stayed Hybrid Bridge during Structural Transformation

Yu Zhao,Yongjun Zhou,Lingling Wu,Changchang Li,Zhongguo John Ma 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.6

The Longgang Bridge in Shaanxi, China, is a complex continuous hybrid structure composed of two cable-stayed self-anchored suspension parts and one single-pylon cable-stayed part. A 1:20-scaled model was established due to the effect of multiple structural transformation, frequent internal force changes during the construction process, and differences between actual material parameters and theoretical calculation parameters. In this paper, the design, materials, counterweight, experimental instrumentation, and construction stages of the scaled model are introduced. Based on the experimental data, the nonlinear behavior of the self-anchored suspension and cable-stayed hybrid bridge during the structural transformation of the construction process is systematically and comprehensively studied. The evolutions of the hanger force and stayed cable force, the variation in the subcable and back-cable forces, the displacement characteristics of the suspension cable and the deflection of the stiffened girder are analyzed, and the relationships among these variables in different states of the structural system are discussed. This paper will serve as a technical reference for the construction of similar bridges in the future.

Over-expression of GmMYB39 leads to an inhibition of the isoflavonoid biosynthesis in soybean (Glycine max. L)

Jinxin Yi,Xiaoqing Liu,Lingling Yuan,Ling Xu,Zhaolong Xu,Yihong Huang,Xiaolan He,Hongxiang Ma,Dayong Zhang 한국식물생명공학회 2013 Plant biotechnology reports Vol.7 No.4

In this paper, we isolated and characterized a gene encoding the soybean MYB transcription factor, GmMYB39 (Accession No: XM_003538605). Analysis of the deduced amino acid sequence revealed that GmMYB39 contained N-terminal R2R3 repeats that corresponded to the DNA-binding domain of plant MYB-type proteins, which were highly conserved among the R2R3-MYB proteins. The detailed expression pattern of GmMYB39 in various tissues of soybean was investigated by quantitative RT-PCR. The transcript level was found to be higher in flowers than in other examined organs. In contrast, the GmMYB39 expression level was relatively weak in the pod. The GmMYB39–GFP fusion protein was found to localize in the nucleus of Arabidopsis mesophyll protoplasts. Over-expression of GmMYB39 in hairy roots resulted in a significant reduction of the transcript levels of PAL, C4H, CHS, 4CL, and CHR. Whereas, the IFS transcript level was slightly but not significantly increased, and no significant change in CHIexpression was observed between over-expression and control roots. The repressing effect on expression of CHS was further supported by the results from co-transfection assays of CHS promoter (reporter) and GmMYB39 (effector) in soybean. Compared to the control (only with the reporter construct), a significant decrease in the GUS activity was observed in soybean hairy roots with both effector and reporter constructs. Furthermore, an ultimate decrease in isoflavonoids contents coincided with the decrease in the transcript levels of PAL, C4H, CHS, 4CL, and CHR. Overall, the results suggest that GmMYB39 plays an inhibiting role in regulating the isoflavonoid biosynthesis in soybean.