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Contact-Stress-Based Stress Recovery Methods for Discontinuous Deformation Analysis

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Acta Mechanica Solida Sinica 2020年第4期33卷 508-520页

作者： Ruoyu guan Shean Bie State Key Laboratory of Hydraulic Engineering Simulation and Safety School of Civil EngineeringTianjin UniversityTianjin 300072China

Discontinuous deformation analysis(DDA)has been widely applied for the simulation of block systems that have many discontinuous *** penalty method is utilized to ensure that there are no penetrations between blocks.A linear polynomial function for displacement leads to a constant stress for a block,which cannot precisely describe the stress field within the ***,a high-order polynomial displacement function and a flue mesh are always used to improve the precision of the stress ***,these means are not practical for simulating block systems that have many *** this paper,the contact-stress-based stress recovery methods are proposed for ***-precision solutions for the contact stresses on the boundaries of the blocks are *** first-order Gaussian point of a block is the block's centroid,where the constant stress obtained via DDA is of higher *** high-precision solutions for the stresses are utilized in the least squares method to recover a single block's inner stress *** proposed methods enhance the resolution of the stress field inside a single block without increasing the computational effort in the main iterative process for displacement in *** examples are simulated using both the finite element method(FEM)with a fine mesh and the proposed DDA *** recovered DDA results can accurately describe the distribution of the stresses in a single block and,in some areas,have the same precision as the FEM ***,the precision of the proposed methods improves as the gradient of the contact stress on the boundary decreases.

关键词： Contact stress Postprocessing Stress recovery method Discontinuous deformation analysis

A Novel PLL Structure for Dynamic Stability Improvement of DFIG-based Wind Energy Generation Systems During Asymmetric LVRT

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Journal of Modern Power Systems and Clean Energy 2023年第4期11卷 1149-1164页

作者： Lei guan Jun Yao State Key Laboratory of Power Transmission Equipment&System Security and New Technology School of Electrical EngineeringChongqing UniversityChongqing 400044China

The dynamic coupling effect,which is introduced by the dual-sequence phase-locked loops(PLLs)used in doublyfed induction generator(DFIG)based wind energy generation systems(WEGSs)during asymmetric low voltage ride-through(LVRT)in weak grid,needs *** order to study this new dynamic coupling effect,an equivalent two-degree-of-freedom(2-DOF)spring damper particle model is used in this paper to develop a small-signal model for the dual-sequence *** dynamic interaction between the positive-sequence(PS)and negative-sequence(NS)PLLs is ***,the impact of the dynamic coupling between the dual-sequence PLLs on the dynamic stability during the steady-state stage of an asymmetric fault is *** analysis results show that the dynamic coupling between the dual-sequence PLLs will cause drift in the frequency and damping for the PS and NS PLL *** will change the instability modal of the system and introduce the risk of dynamic ***,the effectiveness of existing control strategies for enhancing the dynamic stability will be ***,a novel PLL structure is designed to improve the dynamic stability of the system during the steady-state stage of an asymmetric *** effectiveness of the proposed strategy is verified by simulations and experiments.

关键词： Doubly-fed induction generator(DFIG) phaselocked loop(PLL) dynamic stability dynamic coupling weak grid asymmetric low-voltage ride through(LVRT)

TiP_2O_7-coated LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 cathode materials with improved thermal stability and superior cycle life

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Journal of Energy Chemistry 2019年第1期28卷 151-159页

作者： guan Wu Yingke Zhou The State Key Laboratory of Refractories and Metallurgy Institute of Advanced Materials and Nanotechnology College of Materials and Metallurgy Wuhan University of Science and Technology

The co-precipitation derived LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 cathode material was modified by a coating layer of TiP_2O_7 through an ethanol-based process. The TiP_2O_7-coated LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 is characterized by Xray diffraction analysis, scanning electron microscopy and transmission electron microscopy to investigate the microstructure and morphology. The differential scanning calorimetry was employed to confirm the improved thermal stability. The electrochemical properties were evaluated by the constant-current charge/discharge tests. The TiP_2O_7 coating layer is effectively suppressing the structural degradation and ameliorating the surface status of LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 particles, and the intrinsic rhombohedral layered structure of TiP_2O_7-coated LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 was well maintained during the long-term cycling process, while the surface structure of pristine LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 was degraded from rhombohedral R3 m layered structure to cubic rock-salt structure. The charged state Ni^(4+) ions will easily transform into Ni^(2+) when the electrolytes oxidized at the interface of cathode/electrolytes and formed the cubic rock-salt NiO type structure, and the cubic rock-salt structure without electrochemical activity on the surface of LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 particles will finally accelerate capacity fading. The thermal stability and cyclic performances of the LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 electrode were remarkably improved by TiP_2O_7 coating, the total amount of heat release corresponding to the intensity of thermal runaway were 1075.5 and 964.6 J/g for pristine LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 and TiP_2O_7-coated LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 respectively, the pouch shaped full cells that employed TiP 2 O7-coated LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 as cathode were able to perform more than 2200 cycles at 25 ℃ and more than 1000 cycles at 45 ℃ before the capacity retention fading to 80%.

关键词： LiNi0.8Co0.15Al0.05O2 Coating Thermal stability Cyclic performances Lithium-ion batteries

Applications of single-atom catalysts

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Nano Research 2022年第1期15卷 38-70页

作者： Qiaoqiao Zhang Jingqi guan Institute of Physical Chemistry College of ChemistryJilin UniversityChangchun 130012China

Owing to unsaturated coordination environment,quantum size effect and metal-support interaction,single-or dual-atom metal sites,such as Mn,Fe,Co,Ni,Cu,Zn,Mo,Ru,Rh,Pd,Ag,Sn,Ir,Pt,Au,Bi,and Er coordinated with nonmetallic elements such as O,N,P,and S,exhibit different electronic configurations,which endow them with high catalytic performances in multiple redox reactions and versatile applications in organic synthesis,environmental remediation,energy conversion,and *** intense research,the relation of structure-activity for single-atom catalysts(SACs)still bedazzles researchers,since diversified configurations of active sites would bring about difficulty in structural identification and theoretical ***,recent results on the applications of SACs are reviewed with an emphasis on identifying the active sites and discussing the relation between structure and property.

关键词： biomedicine energy conversion environmental remediation organic synthesis single-atom catalysis

Applications of Atomically Dispersed Oxygen Reduction Catalysts in Fuel Cells and Zinc–Air Batteries

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Energy & Environmental Materials 2021年第3期4卷 307-335页

作者： Qiaoqiao Zhang Jingqi guan Key Laboratory of Surface and Interface Chemistry of Jilin Province College of ChemistryJilin UniversityChangchun 130021China

Due to severe energy crisis and environmental problems,green and renewable electrochemical energy devices such as fuel cells and metal–air batteries have attracted great attention,where oxygen reduction reaction(ORR)plays a vital *** rational design of efficient and robust singleatom catalysts(SACs)is vital but challenging toward ***,recent developments of single-atom ORR catalysts in fuel cells and Zn–air batteries are systematically summarized,focusing on transition-metal-based electrocatalysts including single or dual Fe,Co,Ni,Cu,Zn,Pd,Ag,and Pt *** the atomic level,different synthesis methods and characterization techniques are *** studies of ORR mechanisms are *** active sites and structure–property relationships of SACs for ORR are highlighted,and the performances of proton exchange membrane fuel cells(PEMFCs),anion exchange membrane fuel cells(AEMFCs),and Zn–air batteries are *** great challenges and future directions of SACs in fuel cells and Zn–air batteries are presented.

关键词： fuel cells oxygen reduction single-atom catalysts theoretical calculations zinc-air batteries

Use of the UPOINT phenotype system in treating Chinese patients with chronic prostatitis/chronic pelvic pain syndrome： a prospective study

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Asian Journal of Andrology 2015年第1期17卷 120-123,I0010,I0011页

作者： Xiao guan Department of Urology Xiangya Hospital Central South University Changsha 410008 China

The urinary, psychosocial, organ-specific, infection, neurological/systemic and tenderness （UPOINT） phenotype system has been validated to be an effective phenotype system in classifying patients with chronic prostatitis/chronic pelvic pain syndrome （CP/CPPS） in western populations. To validate the utility of the UPOINT system and evaluate the effect of multimodal therapy based on the UPOINT system in Chinese patients with CPICPPS, we performed this study. Chinese patients with CP/CPPS were prospectively offered multimodal therapy using the UPOINT system and re-examined after 6 months. A minimum 6-point drop in National Institutes of Health-Chronic Prostatitis Symptoms Index （NIH-CPSI） was set to be the primary endpoint. Finally, 140 patients were enrolled in the study. The percentage of patients with each domain was 59.3%, 45.0%, 49.3%, 22.1%, 37.9%, and 56.4% for the UPOINT, respectively. The number of positive domains significantly correlated with symptom severity, which is measured by total NIH-CPSI scores （r = 0.796, P 〈 0.001）. Symptom duration was associated with a greater number of positive domains （r = 0.589, P〈 0.001）. With 6 months follow-up at least, 75.0% （105/140） had at least a 6-point improvement in NIH-CPSI after taking the therapy. All NIH-CPSI scores were significantly improved from original ones： pain 10.14 ± 4.26 to 6.60 ± 3.39, urinary 6.29 ± 2.42 to 3.63 ± 1.52, quality of life 6.56 ± 2.44 to 4.06 ± 1.98, and total 22.99 ± 7.28 to 14.29 ±5.70 （all P〈 0.0001）. Our study indicates that the UPOINT system is clinically feasible in classifying Chinese patients with CP/CPPS and directing therapy.

关键词： chronic pelvic pain syndrome chronic prostatitis drug therapy prospective study UPOINT

Multicomponent transition metal oxides and(oxy)hydroxides for oxygen evolution

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Nano Research 2023年第2期16卷 1913-1966页

作者： Jingyi Han Jingqi guan Institute of Physical Chemistry College of ChemistryJilin UniversityChangchun 130021China

Oxygen evolution reaction(OER)is the core electrode reaction in energy-related technologies,such as electrolytic water,electrocatalytic carbon dioxide reduction,rechargeable metal-air batteries,and renewable fuel *** of well-stocked,cost-effective,and high-performance OER electrocatalysts is the key to the improvement of energy efficiency and the large-scale commercial implementation of these *** transition metal oxides and(oxy)hydroxides are the most promising OER catalysts due to their low cost,adjustable structure,high electrocatalytic activity,and outstanding *** this review,a brief overview about the mechanisms of OER is first offered,accompanied with the theory and calculation ***,the latest advances in the rational design of the related OER electrocatalysts and the modulation of the electronic structure of active sites are comprehensively ***,various strategies(including element doping,defect engineering,and fabrication of binderless catalysts)used to improve the OER performance are detailedly discussed,emphasizing the structure–function ***,the challenges and perspectives on this promising field are proposed.

关键词： oxyhydroxide mixed oxide oxygen evolution reaction single-atom catalyst water splitting

Cancer metastases: challenges and opportunities

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Acta Pharmaceutica Sinica B 2015年第5期5卷 402-418页

作者： Xiangming guan Department of Pharmaceutical Sciences College of Pharmacy South Dakota State University

Cancer metastasis is the major cause of cancer morbidity and mortality, and accounts for about 90% of cancer deaths. Although cancer survival rate has been signi fi cantly improved over the years, the improvement is primarily due to early diagnosis and cancer growth inhibition. Limited progress has been made in the treatment of cancer metastasis due to various factors. Current treatments for cancer metastasis are mainly chemotherapy and radiotherapy, though the new generation anti-cancer drugs(predominantly neutralizing antibodies for growth factors and small molecule kinase inhibitors) do have the effects on cancer metastasis in addition to their effects on cancer growth. Cancer metastasis begins with detachment of metastatic cells from the primary tumor, travel of the cells to different sites through blood/lymphatic vessels, settlement and growth of the cells at a distal site. During the process, metastatic cells go through detachment, migration, invasion and adhesion. These four essential, metastatic steps are inter-related and affected by multi-biochemical events and parameters. Additionally, it is known that tumor microenvironment(such as extracellular matrix structure,growth factors, chemokines, matrix metalloproteinases) plays a signi fi cant role in cancer metastasis. The biochemical events and parameters involved in the metastatic process and tumor microenvironment have been targeted or can be potential targets for metastasis prevention and inhibition. This review provides an overview of these metastasis essential steps, related biochemical factors, and targets for intervention.

关键词： Metastasis Detachment Migration Invasion Adhesion Cancer

Fullerene Mechanochemistry:Serendipitous Discovery of Dumb-Bell-Shaped C_(120) and Beyond

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Chinese Journal of Chemistry 2021年第7期39卷 1797-1803页

作者： guan-Wu Wang Hefei National Laboratory for Physical Sciences at Microscale CAS Key Laboratory of Soft Matter Chemistryand Department of ChemistryUniversity of Science and Technology of ChinoHefeiAnhui 230026China State Key Laboratory of Applied Organic Chemistry Lanzhou UniversityLonzhouGansu 730000Chino

The serendipitous discovery of dumb-bell-shaped C_(120) under high-speed vibration milling conditions is *** mechanochemical protocol has been employed to synthesize the He-,H_(2)-or H_(2)O-encapsualted C_(120),the cross-dimer C_(130),trimer C_(180),bridged C_(60) dimers as well as products from many other reactions of fullerenes,carbon nanotubes and *** extended to various reactions of non-fullerene molecules is briefly discussed.

关键词： Fullerenes Solvent-state reactions 1 Green chemistry Mechanochemistry Fullerene chemistry