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Flame retardant polyamide 6 by in situ polymerization of ε-caprolactam in the presence of melamine derivatives

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Chinese Chemical Letters 2008年第2期19卷 241-244页

作者： Zhi Yong Wu wei xu Jin Kui Xia Yao Chi Liu Qian Xin Wu wei jian xu College of Chemistry ＆ Chemical Engineering Hunan University Changsha 410082 China Research Institute of Yueyang General Petrochemical Works Yueyang 414000 China

An improved method for preparing melamine cyanurate （MCA） based flame retardant polyamide 6 （FRPA6） materials has been proposed. This processing method, i.e., improved in situ polymerization, was used to synthesize flame retardant PA6. In situ formed MCA nanoparticles were supposed to be linked to PA6 chains in the ε-caprolactam hydrolytic polymerization system to obtain startype polymers for the first time. Through TEM photographs, it can be found that the in situ formed MCA nanoparticles with diametric size of less than 50 nm, are nanoscaled, highly uniformly dispersed in the PA6 matrix. Synthesized flame retardant PA6 have good fire performance which can achieve UL-94 V-0 rating at 1.6 mm thickness with the presence of 7.34 wt.% MCA in the matrix.

关键词： Polyamide 6 In situ polymerization Melamine cyanurate Nanoparticles

Synthesis of Dendronized Aromatic Polyamides with Chloromethyl Groups in the Periphery by Macromonomer Approach

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Chinese Chemical Letters 2006年第11期17卷 1507-1510页

作者： Mei Hua LIU wei jian xu Xiao Cong xu Yah Bing LU Yah Ru MIAO College of Chemistry ＆ Chemical Engineering Hunan University Changsha 410082

The preliminary results for one-pot synthesis of dendronized aromatic polyamides with chloromethyl groups in the periphery by approach were reported first time. The GPC analysis of the resulting dendronized polymers h... 详细信息

关键词： Macromonomer dendronized functionalized polyamide.

Thermal-induced reversible ferroelastic phase transition in a new bromethyl-substituted molecular rotor

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Science China Chemistry 2015年第7期58卷 1137-1143页

作者： Bao-Ying Wang Chun-Ting He Bo Huang wei-jian xu wei xue Zi-Yi Du wei-Xiong Zhang Xiao-Ming Chen Key Laboratory of Bioinorganic and Synthetic Chemistry Ministry of Education School of Chemistry & Chemical Engineering Sun Yat-Sen University College of Chemistry & Chemical Engineering Gannan Normal University

A new bromethyl-substituted molecular rotor, [Cu（dabcoCH2Br）（H2O）Br3] （dabcoCH2Br＋=1-（2-bromethyl）-1,4-diazoniabi- cyclo[2.2.2]octane cation）, which belongs to a family of balomethyl-substituted molecular rotors, was synthesized and struc- turally characterized. The reversible phase transition at ca. 250 K was well established for this molecular rotor by thermal analyses, variable-temperature X-ray diffraction, and variable temperature dielectric measurements. The order-disorder trans- formation of the rotator part （dabco moiety） causes ferroelastic phase transition with an Aizu notation of mmmF2/m from high- temperature orthorhombic phase （Pbnm） to low-temperature monoclinic phase （P21/n）. More important, in reference to the density functional theory calculations and structural analyses, the key factors to tune the phase transition behaviors were dis- cussed in detail for this family of halomethyl-substituted molecular rotors.

关键词： ferroelastic phase transition molecular rotor confined space

Steady-state Voltage Security-constrained Optimal Frequency Control for Weak HVDC Sending-end AC Power Systems

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Journal of Modern Power Systems and Clean Energy 2024年第2期12卷 658-669页

作者： Qiangqiang Wang Liangzhong Yao jian xu Yuping Zheng wei Li wei Wang School of Electrical Engineering and Automation Wuhan UniversityWuhan 430072China Hubei Engineering and Technology Research Center for AC/DC Intelligent Distribution Network(Wuhan University) Wuhan 430072China State Key Laboratory of Smart Grid Protection and Control NARI Group Corporation(State Grid Electric Power Research Institute)Nanjing 211106China

Due to the fact that a high share of renewable energy sources(RESs)are connected to high-voltage direct current(HVDC)sending-end AC power systems,the voltage and frequency regulation capabilities of HVDC sending-end AC power systems have *** has resulted in potential system operating problems such as overvoltage and overfrequency,which occur simultaneously when block faults exist in the HVDC *** this study,a steady-state voltage security-constrained optimal frequency control method for weak HVDC sending-end AC power systems is *** integrated virtual inertia control of RESs is employed for system frequency *** dynamic reactive power compensation devices are utilized to control the voltage of all nodes meet voltage security ***,an optimization model that simultaneously considers the frequency and steady-state voltage security constraints for weak HVDC sending-end AC power systems is *** optimal control scheme with the minimum total cost of generation tripping and additional dynamic reactive power compensation required is obtained through the optimization *** are conducted on a modified IEEE 9-bus test system and practical Qing-Yu line commutated converter based HVDC(LCC-HVDC)sending-end AC power system to verify the effectiveness of the proposed method.

关键词： Renewable energy source(RES) high-voltage direct current(HVDC) AC power system optimal frequency control steady-state voltage security dynamic reactive power compensation

Charge-asymmetry Fe_(1)Cu single-atom alloy catalyst for efficient oxygen reduction reaction

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Nano Research 2024年第6期17卷 4702-4710页

作者： xudong Niu jian wei Dongyao xu Jiajing Pei Rui Sui School of Chemical&Environmental Engineering China University of Mining and TechnologyBeijing 100083China Institute of Water Ecology and Environment Chinese Research Academy of Environmental SciencesBeijing 100083China Beijing Synchrotron Radiation Facility Institute of High Energy PhysicsChinese Academy of SciencesBeijing 100049China Engineering Research Center of Advanced Rare Earth Materials Department of ChemistryTsinghua UniversityBeijing 100084China

The development of high-efficient and low-cost oxygen reduction reaction(ORR)electrocatalysts is crucial for the practical applications of metal-air *** promising way is to develop Fe single-atom ***,the single active center and inherent electronic structure of Fe single-atom catalysts lead to the undesirable adsorption of multiple ORR ***,a charge-asymmetry single-atom alloy(SAA)catalyst with Fe-Cu dual sites supported on nitrogen-doped carbon nanosheet(Fe_(1)Cu SAA/NC)was *** characterizations manifest the existence of electron interaction between Fe and Cu in Fe_(1)Cu SAA/NC,which facilitates the adsorption of ORR intermediate for fast ***,the charge-asymmetry Fe_(1)Cu SAA/NC exhibits much faster ORR kinetics with a half-wave potential of 0.917 V *** hydrogen electrode(RHE),outperforming its counterparts in the ***,Fe_(1)Cu SAA/NC still maintains a high half-wave potential with only a drop of 5 mV after 5000 cycles,indicating excellent *** work provides a new strategy to design highly active and non-noble metal ORR electrocatalysts,which hold great potential for various catalytic applications.

关键词： Fe_(1)Cu single-atom alloy(SAA) electrocatalysis oxygen reduction reaction charge-asymmetry

Coordinated Frequency Control for Isolated Power Systems with High Penetration of DFIG-Based Wind Power

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CSEE Journal of Power and Energy Systems 2024年第4期10卷 1399-1414页

作者： Xin Ding wei Lin jian xu Yuanzhang Sun Liangzhong Yao Beilin Mao School of Electrical Engineering and Automation Wuhan UniversityWuhan 430072China Department of Electrical Engineering and Computer Science Case Western Reserve UniversityClevelandOH 44106 USA

This paper proposes a coordinated frequency control scheme for emergency frequency regulation of isolated power systems with a high penetration of wind *** proposed frequency control strategy is based on the novel nonlinear regulator theory,which takes advantage of nonlinearity of doubly fed induction generators(DFIGs)and generators to regulate the frequency of the power *** deviations and power imbalances are used to design nonlinear feedback controllers that achieve the reserve power distribution between generators and DFIGs,in various wind speed *** effectiveness and dynamic performance of the proposed nonlinear coordinated frequency control method are validated through simulations in an actual isolated power grid.

关键词： Frequency control isolated power systems nonlinear feedback nonlinear regulator theory wind power

Carbon-based nanomaterials cause toxicity by oxidative stress to the liver and brain in Sprague-Dawley rats

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Nuclear Science and Techniques 2024年第6期35卷 54-64页

作者： Ying-Ying xu Chan Jin Meng Wu jian-Ye Zhou Hui-Ling wei Department of Gastroenterology China-Japan Friendship HospitalBeijing 100029China Shanghai Institute of Applied Physics Chinese Academy of SciencesShanghai 201800China Institute of Particle and Nuclear Physics College of PhysicsHenan Normal UniversityXinxiang 453007China

Carbon-based nanomaterials have important research significance in various disciplines,such as composite materials,nanoelectronic devices,biosensors,biological imaging,and drug ***,the human and ecological risks associated with carbon-based nanomaterials have received increasing ***,the biological safety of carbon based nanomaterials has not been systematically *** this study,we used different types of carbon materials,namely,graphene oxide(GO),single-walled carbon nanotubes(SWCNTs),and multiwalled carbon nanotubes(MWCNTs),as models to observe their distribution and oxidative damage in *** results of Histopathological and ultrastructural examinations indicated that the liver and lungs were the main accumulation targets of these ***-μ-XRF analysis revealed that SWCNTs and MWCNTs might be present in the *** shows that the three types of carbon-based nanomaterials could cross the gas-blood barrier and eventually reach the liver *** addition,SWCNTs and MWCNTs could cross the blood-brain barrier and accumulate in the cerebral *** increase in ROS and MDA levels and the decrease in GSH,SOD,and CAT levels indicated that the three types of nanomaterials might cause oxidative stress in the *** suggests that direct instillation of these carbon-based nanomaterials into rats could induce ROS *** addition,iron(Fe)contaminants in these nanomaterials were a definite source of free ***,these nanomaterials did not cause obvious damage to the rat brain *** deposition of selenoprotein in the rat brain was found to be related to oxidative stress and Fe *** information may support the development of secure and reasonable applications of the studied carbon-based nanomaterials.

关键词： Carbon-based nanomaterials Oxidative stress Trace element distribution TEM SR-μ-XRF

An Ultrasensitive, Durable and Stretchable Strain Sensor with Crack-wrinkle Structure for Human Motion Monitoring

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Chinese Journal of Polymer Science 2021年第3期39卷 316-326,I0005页

作者： Ze-Yu Li wei Zhai Yun-Fei Yu Guo-Jie Li Peng-Fei Zhan jian-wei xu Guo-Qiang Zheng Kun Dai Chun-Tai Liu Chang-Yu Shen Shen Key Laboratory of Materials Processing and Mold(Zhengzhou University) Ministry of EducationSchool of Materials Science and EngineeringZhengzhou UniversityZhengzhou 450001China

Flexible strain sensor has promising features in successful application of health monitoring, electronic skins and smart robotics, ***, we report an ultrasensitive strain sensor with a novel crack-wrinkle structure(CWS) based on graphite nanoplates(GNPs)/thermoplastic urethane(TPU)/polydimethylsiloxane(PDMS) nanocomposite. The CWS is constructed by pressing and dragging GNP layer on TPU substrate,followed by encapsulating with PDMS as a protective layer. On the basis of the area statistics, the ratio of the crack and wrinkle structures accounts for 31.8% and 9.5%, respectively. When the sensor is stretched, the cracks fracture, the wrinkles could reduce the unrecoverable destruction of cracks, resulting in an excellent recoverability and stability. Based on introduction of the designed CWS in the sensor, the hysteresis effect is limited effectively. The CWS sensor possesses a satisfactory sensitivity(GF=750 under 24% strain), an ultralow detectable limit(strain=0.1%) and a short respond time of 90 ms. For the sensing service behaviors, the CWS sensor exhibits an ultrahigh durability(high stability>2×10^(4) stretching-releasing cycles). The excellent practicality of CWS sensor is demonstrated through various human motion tests,including vigorous exercises of various joint bending, and subtle motions of phonation, facial movements and wrist pulse. The present CWS sensor shows great developing potential in the field of cost-effective, portable and high-performance electronic skins.

关键词： Polymer nanocomposites Microstructure Flexible strain sensor Human motion monitoring

Development of a novel staging classification for Siewert Ⅱ adenocarcinoma of the esophagogastric junction after neoadjuvant chemotherapy

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World Journal of Gastrointestinal Oncology 2024年第6期16卷 2541-2554页

作者： jian Zhang Hao Liu Hang Yu wei-Xiang xu Department of Gastrointestinal Surgery The First Affiliated HospitalZhejiang University School of MedicineHangzhou 310003Zhejiang ProvinceChina

BACKGROUND Stage classification for Siewert Ⅱ adenocarcinoma of the esophagogastric junction(AEG)treated with neoadjuvant chemotherapy(NAC)has not been *** To investigate the optimal stage classification for Siewert Ⅱ AEG with *** A nomogram was established based on Cox regression model that analyzed variables associated with overall survival(OS)and disease-specific survival(DSS).The nomogram performance in terms of discrimination and calibration ability was evaluated using the likelihood-ratio test,Akaike information criterion,Harrell concordance index,time-receiver operating characteristic curve,and decision curve *** Data from 725 patients with Siewert type Ⅱ AEG who underwent neoadjuvant therapy and gastrectomy were obtained from the Surveillance,Epidemiology,and End Results *** and multivariate analyses revealed that sex,marital status,race,ypT stage,and ypN stage were independent prognostic factors of OS,whereas sex,race,ypT stage,and ypN stage were independent prognostic factors for *** factors were incorporated into the OS and DSS *** novel nomogram model performed better in terms of OS and DSS prediction compared to the 8th American Joint Committee of Cancer pathological staging system for esophageal and gastric ***,a user-friendly web application was developed for clinical *** The nomogram established specifically for patients with Siewert type Ⅱ AEG receiving NAC demonstrated good prognostic *** using external data is warranted before its widespread clinical application.

关键词： Stage classification Prognosis Esophagogastric junction cancer Neoadjuvant chemotherapy Siewert type