Resistivity Depends on Preferred Orientation for Transparent Conductive Thin Films

Ligang Ma,Xiaoqian Ai,Hanzhi Quan,Wei Yang,Xingxing Du 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.74 No.8

An Al-doped ZnO (AZO) thin film is an important and useful material for optoelectronic devices. In this paper, pure ZnO and AZO thin films were deposited on glass substrates by using pulsed laser deposition (PLD) at different substrate temperatures from room temperature to 650$^\circ$C. The effect of substrate temperature on the crystallization behavior and optoelectronic properties of the AZO thin films were studied using X-ray diffraction (XRD), atomic force microscopy (AFM), transmittance spectra and resistance measuring system, and so on. The XRD results indicated that all the samples were polycrystalline with a hexagonal wurtzite structure. As the substrate temperature was increased from RT to 650$^\circ$C, the preferred orientation of the AZO thin films undergone a gradual change that affect the resistivity of the thin film. The AFM morphology also showed the same growth pattern. The average optical transmittance of over 90\% in the visible range was obtained at a substrate temperature of 400$^\circ$C. In addition, with increasing substrate temperature, the optical band gap decreased first and then increased, reaching a minimum at 400$^\circ$C, which is the same trend as the resistivity. These results indicate that the atoms can easily diffuse from one position to another at the proper substrate temperature. The atoms trapped in non-equilibrium positions can shift to positions closer to equilibrium, which causes the Al atoms to be evenly disperse on the surface of the ZnO thin film to improve the transmittance and the conductivity.

Nonlocal atlas-guided multi-channel forest learning for human brain labeling : Nonlocal atlas-guided multi-channel forest learning

Ma, Guangkai,Gao, Yaozong,Wu, Guorong,Wu, Ligang,Shen, Dinggang Wiley Blackwell (John Wiley Sons) 2016 Medical physics Vol.43 No.2

Nanosponge membrane with 3D-macrocycle b-cyclodextrin as molecular cage to simultaneously enhance antifouling properties and efficient separation of dye/oil mixtures

Sisi Ma,Ligang Lin,Xinyang Li,Wenying Shi,Xiaofei Zhai,Jing Yang 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.112 No.-

Developing multifunctional, efficient and durable membrane for treating complex oily wastewater ishighly desirable but still a challenge due to the severe membrane fouling. Herein, nanosponge membranewith 3D-macrocycle b-cyclodextrin (b-CDs) as molecular cage was manufactured by azide-alkyne clickreaction for oil/water treatment and antifouling properties simultaneously. The macrocyclic ‘molecularcage’ geometry of b-CDs can induce various guest molecules into their cavities. When clickable b-CDN3was fixed onto a clickable EVAL- membrane surface, the hydrophilicity of the membrane was greatlyimproved. Furthermore, the molecular cage–grafted membrane (EVAL-g-CD) showed better antifoulingperformance than a pure EVAL membrane, with lower water flux decline (15%) and higher water fluxrecovery (91%). The flux and separation efficiency values of the EVAL-g-CD membrane were higher than120 Lm2h1 and 99%, respectively. The EVAL-g-CD membrane also exhibited good adsorption performancefor organic pollutants owing to its cavity structure. Furthermore, the membrane showed desirablestability and its rejection remained at 99% after filtration. This proposed 3D membrane strategy based onmolecular cages sheds light on the formation of hydrophilic membrane surfaces and shows great promisefor potential applications such as the separation of oil-in-water emulsions.

Coral stone-inspired superwetting membranes with anti-fouling and self-cleaning properties for highly efficient oil–water separation

Wensong Ma,Ligang Lin,Jing Yang,Zitian Liu,Xinyang Li,Meina Xu,Xiaopeng Li,Chunhong Wang,Qingping Xin,Kongyin Zhao 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.120 No.-

Nowadays, the use of separation membranes to deal with oil–water emulsions has gained popularity. However, oil fouling of membrane surfaces during the separation of oil–water emulsion is still a significantchallenge. In this study, inspired by the biological coral stone structure, the gel layer was firmlyattached to the surface of membrane using a simple co-blending and cross-linking strategy. A superwettingmembrane (PVDF/CD-SA) with a coral stone structure was obtained. The PVDF/CD-SA membranehad a high permeate flux that was 4.2 times higher than that of the original membrane and a high separationefficiency of about 99.2 % for the separation of oil–water emulsion. Furthermore, the membranehad outstanding chemical stability. The fluxes of several different oil-in-water emulsions significantlyimproved, and the separation efficiencies were as high as 98 %. Moreover, the separation efficienciesand contact angles of the membrane remained unchanged after numerous cycles of use. The membraneexhibited excellent superhydrophilicity in air (instantaneous water wetting in air) and superoleophobicityunder water (underwater oil contact angle > 156). Most importantly, the oil was able to automaticallydetach from the surface of membrane, resulting in self-cleaning performance. Therefore, this PVDF/CD-SAmembrane eliminated the problem of oil adhesion, exhibiting excellent potential for practical applicationsin oil–water separation.

A ‘‘micro-explosion” strategy for preparing membranes with high porosity, permeability, and dye/salt separation efficiency

Xinyang Li,Ligang Lin,Zitian Li,Jing Yang,Wensong Ma,Xu Yang,Xiaopeng Li,Chunhong Wang,Qingping Xin,Kongyin Zhao 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.119 No.-

In this study, inspired by ‘‘micro-explosion” strategies, a separation membrane with high porosity andpermeability, and highly efficient separation performance was prepared. With the use of polyvinylidenefluoride (Solvay6015) as membrane material, azodicarbonamide (AC) as an ‘‘explosion center point” tothe casting membrane solution, and NaOH as an ‘‘external stimulus” in the coagulation bath, the twochemicals undergo in-situ foaming reaction to form a loose nanofiltration membrane. FTIR, XPS, andTGA results demonstrated that the decomposition of AC was complete, which produced gases thatincreased the porosity of the membrane. The optimized membrane has a higher flux(101.72 L m2 h1 at 0.3 Mpa), higher negative surface charge, and better mechanical properties underthe premise of separating CR/NaCl. In the separation of pollutants with different molecular weights,the permeation flux of the optimized membrane increased by more than double. This foaming technologywas also applied to another membrane material, ethylene vinyl alcohol, from which we found that themembrane also had higher porosity and better permeability. Together, this paper presents an in-situfoaming method for preparing separation membranes and lays the foundation for solving the trade-offbetween membrane permeability and rejection in dye/salt separation.

Timoshenko beam-based stability and natural frequency analysis for heavy load mechanical spindles

Zhifeng Liu,Shiming Ma,Ligang Cai,Tieneng Guo,Yongsheng Zhao 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.11

The heavy load mechanical spindle is an important functional component in a 5-axis computer numerical control (CNC) machine tool,which is used to process large and complex free-form surfaces. It is necessary to obtain the natural frequency and analyze the spindle stability for improving the machining precision. In this paper, Timoshenko beam theory is introduced to model the mechanical spindle shaft, where the centrifugal force and gyroscopic effects are considered. Stability of the heavy load mechanical spindle shaft is analyzed,and the buckling load of the spindle shaft is obtained under different rotational speeds. The natural frequency of spindle is investigated in a freedom and restraint state, respectively. Comparing the proposed method with the simplified hollow cylinder and shaft prototype in the freedom state, the results show that they are highly correlated with experimental results. For the restraint state, the axial load, rotational speed, gyroscopic effect, and centrifugal force are discussed, and all of these parameters affect the natural frequency. The proposed modeling approach can be used for spindle design and optimization in a given machining process and can be easily extended to other spindle design.

Construction of Cubic Triangular Patches with $C^1$ Continuity around a Corner

Zhang, Renjiang,Liu, Ligang,Wang, Guojin,Ma, Weiyin Society for Computational Design and Engineering 2006 International Journal of CAD/CAM Vol.6 No.1

This paper presents a novel approach for constructing a piecewise triangular cubic polynomial surface with $C^1$ continuity around a common corner vertex. A $C^1$ continuity condition between two cubic triangular patches is first derived using mixed directional derivatives. An approach for constructing a surface with $C^1$ continuity around a corner is then developed. Our approach is easy and fast with the virtue of cubic reproduction, local shape controllability, $C^2$ continuous at the corner vertex. Some experimental results are presented to show the applicability and flexibility of the approach.

Security Cooperation Model Based on Topology Control and Time Synchronization for Wireless Sensor Networks

Zhaobin Liu,Wenzhi Liu,Qiang Ma,Gang Liu,Liang Zhang,Ligang Fang,Victor S. Sheng 한국통신학회 2019 Journal of communications and networks Vol.21 No.5

To address malicious attacks generated from wirelesssensor networks (WSNs), in this paper, we study the difficulty ofdetecting uncoordinated behavior by using a model that is unreliableand has uncontrollable accuracy, trustless control, and an inextensibleprotocol. A security collaboration model involving coupledstate vectors associated with topology control and time synchronizationis proposed. The networks achieve synchronizationusing weights and by controlling the number of goals. The simplecalculation of time synchronization values between neighboringnodes serves as the basis for judging the behavior of the nodetopology control. The coupling state vector calculation is the coreof the model. The topology coupling strength rate, signal intensityreduction, clock drift, and clock delay are combined to form a comprehensivemodel. The network energy consumption is reduced byupdating the coupling state vector regularly. The coupling cooperationthreshold is set to make security decisions and effectivelydistinguish between attack nodes and dead nodes. Thus, to ensurethe security and reliability of the network, we present a securitycooperation collection tree protocol (SC-CTP) scheme that maintainsa trusted environment and isolates misbehaving nodes. Thesimulation results show that the model can detect malicious nodeseffectively, has a high detection rate, and greatly reduces the energyconsumption of the whole network. In order to verify the effectivenessof the proposed model, a large-scale wireless sensor networkwith 200 nodes was deployed on a campus. The proposed modelwas applied to optimize the deployment of key nodes on the campus. Furthermore, a candidate set of these nodes were selected toachieve coupling cooperation of key goals. This test verified the reliabilityof the model, its customizable accuracy, and the reliabilityof the control.

The Characterization of Cu-Doped ZnO Thin Films Prepared by Using Radio-Frequency Reactive Magnetron Sputtering

Chaoqun Cai,Hongqiang Zhang,Jun Xie,Ligang Ma 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.70 No.9

Textured zinc-oxide (ZnO) thin films and Cu-doped ZnO (ZnO:Cu) thin films are deposited on glass substrates by using radio-frequency reactive magnetron sputtering. The effect of Cudoping concentration on the crystallization behavior, surface morphology, transmission spectrum, and luminescence properties of the ZnO thin films are systematically investigated by using X-ray diffraction, scanning probe microscopy and photoluminescence spectra. The results indicate that the crystallization quality, morphology, transmission, and luminescence of the ZnO films is affected by Cu-element doping. A stronger preferred orientation toward the c-axis is obtained after Cu doping at an appropriate concentration (3%). The transmittance rate gradually decreases with increasing Cu doping concentration. In the photoluminescence spectra of the samples measured at room temperature, four main emission peaks are observed: a violet peak located at about 390 nm, two blue peaks, one located at about 445 nm and the other at about 485 nm, and a green peak located at about 527 nm. The origins of these emissions are discussed in detail.