Effects of Different Ti Content in Zn-30Al Filler Metals on the Microstructure and Mechanical Properties of Mg-Al Butt Joints

Liming Liu,Fei Liu,Disheng Fang,Hongyang Wang 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.

Based on the idea of alloying welding seam, a series of Zn-30Al-xTi filler metal was used to join Mg/Al dissimilar metals by tungsten inert gas welding, where the x was 0, 0.05, 0.1, 0.5, and 1, respectively. The effect of various Ti content on the microstructure and the mechanical property of Mg-Al butt joints was investigated. Results indicated that the fusion zones of the joints were mainly composed of α-Al, MgZn2 and Al-Zn eutectics when the Ti content was 0.05, 0.1 and 0.5 wt.%, and Al3Ti compounds could precipitate first and act as nucleuses during solidification process when the Ti content was appropriate. The mechanical property of the weld joints improved consistently to the increasing content of Ti. The optimum average tensile strength of the joints reached 148 MPa when Zn-30Al-0.5Ti was used, but the average tensile strength decreased again when Zn-30Al-1Ti was used.

Noun Phrase Complexity in EFL Academic Writing : A Corpus-based Study of Postgraduate Academic Writing

Liming Liu,Lan Li 아시아영어교육학회 2016 The Journal of Asia TEFL Vol.13 No.1

Noun phrase (NP) centered structures are distinctive syntactic devices in academic discourse. The commonly employed subordination-based complexity measures cannot adequately capture the development of syntactic complexity of noun phrases expected of advanced student academic writing (Biber, Gray, & Poonpon, 2011). Following the call for more research in this area (e.g. Lu, 2011, p. 57), the current study compared noun phrase complexity in two corpora: one is a corpus of MA dissertations written by Chinese EFL students and the other comprises published research articles in applied linguistics journals. The study examined overall noun phrase complexity using an automatic syntactic complexity analyzer and specifically identified features of one aspect of NP complexity: NP postmodification. The quantitative results were further contextualized in a textual analysis of excerpts from the two corpora for demonstrating the significance of NP complexity to the establishment of discourse coherence. Results of the analyses showed significant underdevelopment of NP postmodification complexity in student writing relative to published texts, meanwhile explicating the circumstances under which the difference is meaningful. Implications of the findings for the teaching of EFL academic writing were also discussed.

Power Converters Based Advanced Experimental Platform for Integrated Study of Power and Controls

Liu, Wenxin,Kim, Jang-Mok,Wang, Cheng,Im, Won-Sang,Liu, Liming,Xu, Hao IEEE 2018 IEEE TRANSACTIONS ON INDUSTRIAL INFORMATICS - Vol.14 No.11

<P>With increasing interest in smart grid and renewable energy, significant investments have been allocated to promote related studies. Since there is a wide spectrum of topics to study, it is necessary to have an advanced experimental platform that can accommodate both system- and component-level studies, both hardware and algorithm designs, and both teaching and research. Unfortunately, such experimental platform is not commercially available. In this paper, an advanced power electronics based experimental platform is introduced. The system is consisted of one OPAL-RT real-time simulator, two one-bus microgrid testbeds, and two modular multilevel converters. The subsystems can form a multiple-bus microgrid testbed if connected through emulated power lines. The system can provide real-time simulation, controller hardware-in-the-loop (HIL) simulation, and power HIL simulation for power systems study. Various converter topologies can be configured with the modular converters for power electronics study. Both real-time simulator and DSP control boards can be used to implement advanced control algorithms. The designs and experiences shared in the paper will benefit many researchers that are in need of such system and promote power and energy related studies.</P>

Effect of cooking methods on bioaccessibility of Zn, Se, Cd, Cu in sea cucumber (Apostichopus japonicus)

Liu, Chune,Wu, Lele,Xue, Ying,Liu, Feng,Sun, Shan,Wang, Liming 한국식품과학회 2018 Food Science and Biotechnology Vol.27 No.3

In this study, the total concentration and bioaccessibility of four metals (Zn, Se, Cd, Cu) in sea cucumbers (Apostichopus japonicus) before and after cooking were measured. The concentration of Zn, Se, Cd, and Cu were $22.24{\pm}0.75$, $0.75{\pm}0.06$, $0.32{\pm}0.07$, and $1.88{\pm}0.09mg/kg$ in raw cucumber, respectively. The contents of Zn, Se, and Cu in high-pressured samples were significantly higher than that in the raw sea cumber (p < 0.01). The levels of Cd were all decreased after three thermal treatments. The intake of Zn and Cu increased in sea cucumber cooked by all thermal processes. While the bioaccessibility of Se and Cd decreased after cooking. A significant correlation was observed between the concentration and bioaccessibility of minerals. These data provide useful information for dietary risk assessments of minerals in sea cucumbers.

Conformational Transitions of Polymer Brushes for Reversibly Switching Graphene Transistors

Liu, Song,Jamali, Safa,Liu, Qingfeng,Maia, Joao,Baek, Jong-Beom,Jiang, Naisheng,Xu, Ming,Dai, Liming American Chemical Society 2016 Macromolecules Vol.49 No.19

<P>We developed a facile, but efficient, approach to graphene field-effect transistors (FET) functionalized with polymer brushes, in which the conductance can be reversibly switched by solvent-induced polymer conformational changes. Our experimental and stimulation results demonstrated that the solvent-induced conformational transition of the polymer brush could affect the carrier concentration by changing the number of,scattering sites associated with the graphene-polymer contact areas, leading to reversible electrical switching for the graphene FET device. Both end-adsorbed diblock and triblock copolymers showed similar switching effect through the solvent-induced chain stretching-collapse and tail-to-loop conformational changes, respectively. This work provides new platform technologies for developing novel electronic devices with tunable electrical properties and for studying macromolecular conformations and conformational transitions.</P>

Effect of cooking methods on bioaccessibility of Zn, Se, Cd, Cu in sea cucumber (Apostichopus japonicus)

Chune Liu,Lele Wu,Ying Xue,Feng Liu,Shan Sun,Liming Wang 한국식품과학회 2018 Food Science and Biotechnology Vol.27 No.3

In this study, the total concentration and bioaccessibility of four metals (Zn, Se, Cd, Cu) in sea cucumbers (Apostichopus japonicus) before and after cooking were measured. The concentration of Zn, Se, Cd, and Cu were 22.24 ± 0.75, 0.75 ± 0.06, 0.32 ± 0.07, and 1.88 ± 0.09 mg/kg in raw cucumber, respectively. The contents of Zn, Se, and Cu in high-pressured samples were significantly higher than that in the raw sea cumber (p\0.01). The levels of Cd were all decreased after three thermal treatments. The intake of Zn and Cu increased in sea cucumber cooked by all thermal processes. While the bioaccessibility of Se and Cd decreased after cooking. A significant correlation was observed between the concentration and bioaccessibility of minerals. These data provide useful information for dietary risk assessments of minerals in sea cucumbers.

Study on Calcium Phosphate Cement for Bone Reconstruction

Liming, Hu,Changsheng, Liu,Wei, Shen,Yanfang, Gu 한국재료학회 1995 Fabrication and Characterization of Advanced Mater Vol.1 No.2

In this paper the prepartation of calcium phosphate salts, the setting technology, the mechanism of hydration and hardening and the biocompatibility of CPC are studied systematically. The results show that using ultrafine HAP and CaCo$_{3}$ as starting materials can greatly shorten the reaction time for the prepartation of pure TECP(only 9 hour needed) : the existence of HAP seed may cut down the setting time, bu lower the compressive strength ; the proper powder-to-liquid ratio is 4 : 1 ; the rate of hydration is comparatively rapid initially, controlled by dissolution of the reactants surfaces, however, eventually becomes diffusion nally controlled ; during the hydration and hardening process of CPC, the paste changes from viscoplasticity to viscoelasticity and to elasticity ; the initial structure is net-work fromed by Van der Waals' forces, which gradually strengthens, eventually connected by chemical bondings. The final product of CPC is acicular HAP, which has high biocompatibility including no toxicity, no carcinogenicity, no mutagenicity and no deformity. When CPC is implanted, it is highly compatible with soft tissue, and close connection between CPC and adjacent bone will occur one month later.

Highly Crystalline and Low Bandgap Donor Polymers for Efficient Polymer Solar Cells

Liu, Jun,Choi, Hyosung,Kim, Jin Young,Bailey, Chris,Durstock, Michael,Dai, Liming WILEY‐VCH Verlag 2012 Advanced Materials Vol.24 No.4

<P><B>A highly crystalline and low bandgap donor polymer</B>, EI‐PFDTBT, is developed by inserting ethylene bridging units to ensure a coplanar configuration between the side chains and the main chain. Polymer solar cells based on the EI‐PFDTBT and PC<SUB>71</SUB>BM blends spincoated at elevated temperatures exhibit a power conversion efficiency of 5.1%.</P>

Preparation and Oxidation resistance of Nanometre-sized Copper Powders

Liu, Zhijie,Zhao, Bin,Zhang, Zongtao,Hu, Liming 한국재료학회 1995 Fabrication and Characterization of Advanced Mater Vol.2 No.4

Using chemical reduction emthod in aqueous solutions, ultrafine copper powders with mean diameter about 50nm were prepared and the stability of nanometre-sized copper powders stored in deionic water was studied. The oxidation resistance of nanometre-sized copper powders was greatly improved by using silver-coating method and surface phosphazition. The oxidizing temperatures were beyond 25$0^{\circ}C$.

Hydrothermal Synthesis of Hierarchical Hollow Li(Ni0.8Co0.15Al0.05)O2 Microspheres for Lithium Ion Batteries

Liu Wenlong,Jiang Weiwei,Yan Chenran,Feng Wei,Wang Dongxia,Zhao Liming,Feng Tingting,Gong Feng 대한화학회 2017 Bulletin of the Korean Chemical Society Vol.38 No.11

Li(Ni0.8Co0.15Al0.05)O2 (NCA) cathode material for lithium ion batteries is synthesized by calcining Ni–Co–Al hydroxide or carbonate hydroxide hydrate precursor, which is obtained by hydrothermal method, and the NCA cathode material is hierarchical hollow microspheres with the diameter in the range of 3–5 µm and composed of nanoflakes and/or nanowires. The effect of hydrothermal reaction time on the morphologies and the crystalline quality of the NCA cathode material is investigated on the basis of scanning electron microscopy, X-ray diffraction, and tunneling electron microscopy. The NCA cathode material shows smooth and monotonous charge/discharge characteristics, delivers a reversible capacity as 144.4 mAh/g and retains 90.4% after 50 cycles at a current density of 0.1 C between 2.5 and 4.3 V.