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Actively tunable electromagnetically induced transparency in hybrid Dirac-VO2 metamaterials

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Optoelectronics Letters 2025年第1期21卷 13-20页

作者： DI Ke XIE Meng XIA Huarong CHENG Anyu liu yu DU Jiajia Department of Optoelectronic Engineering Chongqing University of Post and Telecommunications Chongqing Key Laboratory of Autonomous Navigation and Microsystem Chongqing University of Posts and Telecommunications Department of Automation Chongqing University of Post and Telecommunications

In this paper, we present a metamaterial structure of Dirac and vanadium dioxide（VO2） and investigate its optical properties using the finite-difference time-domain（FDTD） technique. Using the phase transition feature of VO2, the design can realize active tuning of the plasmon induced transparency（PIT） effect at terahertz frequency, thereby converting from a single PIT to a double-PIT. When VO2is in the insulating state, the structure is symmetric to obtain a single-band PIT effect. When VO2is in the metallic state, the structure turns asymmetric to realize a dual-band PIT effect. This design provides a reference direction for the design of actively tunable metamaterials. Additionally, it is discovered that the transparent window's resonant frequency and the Fermi level in this structure have a somewhat linear relationship. In addition, the structure achieves superior refractive index sensitivity in the terahertz band, surpassing 1 THz/RIU. Consequently, the design exhibits encouraging potential for application in refractive index sensors and optical switches.

关键词： Transparency

Cultivation of Chlorella *** in inland saline-alkaline water under different light qualities

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Frontiers of Environmental Science & Engineering 2022年第4期16卷 59-68页

作者： Xiaoya liu yu Hong yu liu Beijing Key Laboratory for Source Control Technology of Water Pollution College of Environmental Science and EngineeringBeijing Forestry UniversityBeijing 100083China

Inland saline-alkaline water can be used for the low-cost cultivation of microalgae,but whether algal biomass under various light sources has the potential to produce biodiesel remains to be ***,the influence of different light-emitting diode(LEDs)light colors(blue,red,white,mixed blue-red,and mixed blue-white LED)on the growth performance,lipid accumulation,and fatty acid composition of Chlorella *** cultivated in inland saline-alkaline water was *** highest algal density was obtained under blue LEDs at the end of cultivation,reaching 1.93±0.03 × 10^(7) cells/*** LEDs can improve biomass yield,total lipid yield,and triacylglycerol yield per algal *** main fatty acid components of Chlorella from inland saline-alkaline water were palmitic acid and linoleic *** Biodiesel Analyzer software was used to predict algal biodiesel quality by estimating different quality *** cetane number,kinematic viscosity,and density of Chlorella biodiesel were 51.714-67.69,3.583-3.845 mm^(2)/s,and 0.834-0.863 g/cm^(3),*** flirther proved that the Chlorella biomass obtained from inland saline-alkaline water has the potential to be used as a high-quality biodiesel feedstock.

关键词： Light quality Chlorella Inland saline-alkaline water Fatty acid Biodiesel property

Core or edge? Revisiting GIScience from the geography-discipline perspective

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Science China Earth Sciences 2022年第2期65卷 387-390页

作者： yu liu Institute of Remote Sensing and Geographical Information Systems School of Earth and Space SciencesPeking UniversityBeijing 100871China

As an inter-disciplinary area between geography and computer sciences, geographical information science(GIScience) inherits the spatial analysis tradition of the former. Together with other branches of information geography, it seeks the balance between universality and particularity of geographical laws by combining methods from neighboring disciplines(such as big data and artificial intelligence) with the special nature of geographical spaces. Meanwhile, at the core position of the geography discipline, GIScience makes geography stronger from two directions: "strengthening the theoretical foundation" and "improving technology and promoting the practical applications".

关键词： Geographical information science Information geography Geography Characteristics of geographical spaces

Robust segmentation of raw point clouds into consistent surfaces

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Science China(Technological Sciences) 2016年第8期59卷 1156-1166页

作者： liu yu School of Aerospace Engineering Xiamen University Xiamen 361005 China

This paper presents a region-based method for extraction of consistent surfaces from raw point clouds. The method uses a new robust estimation method of constructing seed regions and a new method of orientating regions or surfaces. The robust estima- tion method selects good seed regions from candidate regions generated randomly in a structured neighborhood. The orienta- tion method uses transition vectors from which include angles of adjacent normal vectors are not greater than 90~ and thus can be orientated correctly crossing sharp features or close-by opposite surfaces. The region-based method consists of two levels of segmentation： planar segmentation and quadric segmentation, both of which produce consistent surfaces. The quadric segmen- tation fits general quadrics by 3 L fitting algorithm in its region growing process and can take consistent planar surfaces as ini- tials. Experimental results show that the robust estimation method has higher probability of success than the traditional one and the orientation method works well. Experimental results also demonstrate the applicability of our method to various data.

关键词： raw point clouds robust estimation segmentation orientation surface reconstruction

Experimental and Theoretical Study on Thermal Stability of Mixture R1234ze(E)/R32 in Organic Rankine Cycle

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Journal of Thermal Science 2023年第4期32卷 1595-1613页

作者： liu Jinyu liu yu liu Chao XIN Liyong yu Wei Key Laboratory of Low-Grade Energy Utilization Technologies and Systems Ministry of EducationSchool of Energy and Power EngineeringChongqing UniversityChongqing400030China

The use of Organic Rankine Cycle(ORC)for renewable energy utilization and industrial waste heat recovery is currently attracting growing *** working fluids in ORC may face thermally decompose during the working *** thermal stability and pyrolysis mechanism of R1234ze(E)/R32 mixtures was studied by ReaxFF-MD simulations and DFT *** experimental results indicated that the pyrolysis temperature range is 230℃-250℃ for R1234ze(E),270℃-290℃ for R32 and 230℃-250℃ for R1234ze(E)/R32 *** cleavage of C-H,C-C bond is the main decomposition pathway of pure R32,R1234ze(E),*** decomposition rate of R32 is significantly slower than that of R1234ze(E).In the mixture R1234ze(E)/R32,R1234ze(E)can significantly promote the decomposition of R32,while R32 has a slight inhibitory effect on the decomposition of R1234ze(E).The CF3 radicals generated by the decomposition of R1234ze(E)significantly reduced the energy barrier of R32 decomposition and promoted the decomposition rate of *** H and F radical in the system is more inclined to react with R32 than R1234ze(E)due to their lower energy *** increase of the pressure and mass ratio of R1234ze(E)in the mixture system has a great promoting effect on the pyrolysis of the mixtures.

关键词： R1234ze(E)/R32 pyrolysis ReaxFF-MD DFT

Atomically precise nickel-sulfur clusters for efficient electrochemical 2,5-hydroxymethylfurfural oxidation

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Nano Research 2025年第1期18卷 140-148页

作者： Fen Wang Lu-yu liu Sha-Sha Cui Ting-Ting Li Xiao-Meng Yang Zhijuan liu Yanyong Wang Henan Key Laboratory of Crystalline Molecular Functional Materials Henan International Joint Laboratory of Tumor Theranostical Cluster MaterialsGreen Catalysis Centerand College of ChemistryZhengzhou UniversityZhengzhou 450001China State Key Laboratory of Chem/Bio-sensing and Chemometrics College of Chemistry and Chemical EngineeringHunan UniversityChangsha 410082China

Nickel sulfide exhibits excellent catalytic activity in the electrochemical 2,5-hydroxymethylfurfural oxidation reaction(HMFOR).However,due to the polydispersity of nanoparticles,it is difficult to establish a clear structure-activity relationship at the atomic *** this work,we have successfully synthesized atomically precise Ni_(6)(PET)_(12)and Ni_(4)(PET)_(8)clusters(PET:2-phenylethanethiol)for ***^(2+)and S_(2)-with atomic ratio of 1:2 was mainly existed in Ni_(6)(PET)_(12)and Ni_(4)(PET)_(8)to form Ni-S *** electrochemical test results have suggested both Ni_(6)(PET)_(12)and Ni_(4)(PET)_(8)displayed outstanding electrocatalytic ability for *** Ni_(6)(PET)_(12)exhibited better electrocatalytic ability than Ni_(4)(PET)_(8)with higher current density,lower overpotential and faster reaction *** superior electrochemical ability of Ni_(6)(PET)_(12)may be due to the enhanced adsorption towards HMF molecule with strong interaction towards hydroxyl group and furan ***,it found that the Ni^(2+)species in Ni_(6)(PET)_(12)could rapidly oxidized into Ni^(3+)species,which could spontaneously capture electron and proton from HMF for *** theoretical calculation demonstrated that the Ni_(6)(PET)_(12)process lower free energy barrier than Ni_(4)(PET)_(8)to display excellent electrocatalytic *** work is of great significance for designing efficient electrocatalysts for HMFOR.

关键词： atomically precise nickel nanoclusters 2 5-hydroxymethylfurfural electro-oxidation Ni3+species

Improved artificial bee colony algorithm with mutual learning

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Journal of Systems Engineering and Electronics 2012年第2期23卷 265-275页

作者： yu liu Xiaoxi Ling yu Liang Guanghao liu School of Software Dalian University of Technology Dalian 116024 P. R. China Civil Aviation Flight University of China Guanghan 618307 E R. China

The recently invented artificial bee colony （ABC） al- gorithm is an optimization algorithm based on swarm intelligence that has been used to solve many kinds of numerical function optimization problems. It performs well in most cases, however, there still exists an insufficiency in the ABC algorithm that ignores the fitness of related pairs of individuals in the mechanism of find- ing a neighboring food source. This paper presents an improved ABC algorithm with mutual learning （MutualABC） that adjusts the produced candidate food source with the higher fitness between two individuals selected by a mutual learning factor. The perfor- mance of the improved MutualABC algorithm is tested on a set of benchmark functions and compared with the basic ABC algo- rithm and some classical versions of improved ABC algorithms. The experimental results show that the MutualABC algorithm with appropriate parameters outperforms other ABC algorithms in most experiments.

关键词： artificial bee colony (ABC) algorithm numerical func- tion optimization swarm intelligence mutual learning.

Adaptive Leader-Follower Consensus Control of Multiple Flexible Manipulators With Actuator Failures and Parameter Uncertainties

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IEEE/CAA Journal of Automatica Sinica 2023年第4期10卷 1020-1031页

作者： yu liu Lin Li School of Automation Science and Engineering South China University of TechnologyGuangzhou 510640 Research and Development Center of Precision Electronic Manufacturing Technology Guangzhou Institute of Modern Industrial TechnologyGuangzhou 511458China

In this paper,the leader-follower consensus problem for a multiple flexible manipulator network with actuator failures,parameter uncertainties,and unknown time-varying boundary disturbances is *** purpose of this study is to develop distributed controllers utilizing local interactive protocols that not only suppress the vibration of each flexible manipulator but also achieve consensus on joint angle position between actual followers and the virtual *** the accomplishment of the reconstruction of the fault terms and parameter uncertainties,the adaptive neural network method and parameter estimation technique are employed to compensate for unknown items and bounded ***,the Lyapunov stability theory is used to demonstrate that followers’angle consensus errors and vibration deflections in closed-loop systems are uniformly ultimately ***,the numerical simulation results confirm the efficacy of the proposed controllers.

关键词： Actuator failures leader-follower consensus multiple flexible manipulators neural network parameter uncertainties

Half Exact Functors Associated with Cotorsion Pairs on Exact Categories

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Acta Mathematica Sinica,English Series 2019年第8期35卷 1334-1356页

作者： yu liu School of Mathematics Southwest Jiaotong University

In the previous article "Hearts of twin cotorsion pairs on exact categories. J. Algebra, 394,245–284(2013)", we introduced the notion of the heart for any cotorsion pair on an exact category with enough projectives and injectives, and showed that it is an abelian category. In this paper, we construct a half exact functor from the exact category to the heart. This is an analog of the construction of Abe and Nakaoka for triangulated categories. We will also use this half exact functor to find out a sufficient condition when two different hearts are equivalent.

关键词： Cotorsion pair heart half exact functor equivalence