检索结果-南通市图书馆

A low-melting-point metal doping strategy for the synthesis of small-sized intermetallic Pt_(5)Ce fuel cell catalysts

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Nano Research 2024年第9期17卷 8112-8118页

作者： zi-Jun Zou Shi-yi yin Yao Tang Sheng-Liang zhong Lei Wang Shi-Long Xu Hai-Wei Liang College of Chemistry and Chemical Engineering Jiangxi Normal UniversityNanchang 330022China Department of Chemistry University of Science and Technology of ChinaHefei 230026China School of Materials and Chemical Engineering Anhui Jianzhu UniversityHefei 230601China

Carbon-supported platinum-lanthanum(Pt-Ln)intermetallic compound(IMC)nanoparticles with high activity and robust stability have been demonstrated as promising cathode catalysts for proton-exchange membrane fuel ***,the preparation of Pt-Ln IMC catalysts needs high-temperature annealing treatment that inevitably causes nanoparticle sintering,resulting in significant reduction of the electrochemical surface area and mass-based ***,we prepare small-sized M-doped Pt_(5)Ce(M=Ga,Cd,and Sb)IMCs catalysts via a low-melting-point metal doping *** speculate that the doping of low-melting-point metals can facilitate the generation of vacancies in the crystal lattice through thermal activation and thus reduce the kinetic barriers for the formation of intermetallic Pt_(5)Ce *** prepared Ga-doped Pt_(5)Ce catalyst exhibits a higher electrochemical active surface area(81 m^(2)·gPt^(-1))and a larger mass activity(0.45 A·mgPt^(-1)at 0.9 V)over the undoped Pt_(5)Ce and commercial Pt/C *** the membrane electrode assembly test,the Ga-doped Pt_(5)Ce cathode delivers a power density of 0.98 W·cm^(-2)at 0.67 V,along with a voltage loss of only 27 mV at 0.8 A·cm^(-2)at the end of accelerated stability test.

关键词： P5Ce low-melting-point metal small-sized intermetallic compound catalysis fuel cells

More than just aligning the teeth:Clear aligners with multifunctional prowess

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Nano Research 2024年第8期17卷 7665-7674页

作者： Yang Chen Lei-Ming Cao Nian-Nian zhong zi-Zhan Li Lin-Lin Bu Fang-yi Huo Hong He State Key Laboratory of Oral and Maxillofacial Reconstruction and Regeneration Key Laboratory of Oral Biomedicine Ministry of EducationHubei Key Laboratory of StomatologySchool and Hospital of StomatologyWuhan UniversityWuhan 430079China Department of Oral and Maxillofacial-Head Neck Oncology School and Hospital of StomatologyWuhan UniversityWuhan 430079China Department of Zhuankou Clinical Branches School and Hospital of StomatologyWuhan UniversityWuhan 430000China Department of Orthodontics School and Hospital of StomatologyWuhan UniversityWuhan 430079China

With the increasing demand for beauty and health,clear aligners(CAs)have been widely applied among patients with ***,patients treated with CAs also face some potential complications,such as demineralization,dental caries,and periodontal *** addition,some patients have additional needs to improve their quality of life,such as bleaching *** order to prevent or solve these problems,the modification of CAs is a promising method because their extensive long-term contact with tooth surfaces makes them ideal devices for implementing adjuvant medical *** this review,we discuss various advanced CAs with medical functions based on the clinical needs of *** far as we know,the additional functions of CAs mainly include antibacterial,remineralization,whitening,and accelerating tooth *** functions are achieved by two major pathways,the combination of CAs with drugs/biomaterials and increasing the capacity or affinity of *** addition,we discuss the current limitations of in vitro experiments which are designed to explore the effectiveness and properties of novel CAs,and the challenges of bringing a multifunctional appliance from proposal to clinical *** the end of this review,we provide insights into the broader prospects for the improvement of CAs.

关键词： advanced clear aligners medical device modification drug delivery system personalized medicine

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

军事职业人员高尿酸血症患病情况研究现状

中国疗养医学 2025年第1期34卷 96-100页

作者：吴逸桑殷子斐海军军医大学基础医学院上海200433 海军军医大学中医系上海200433

作为国家战斗的有生力量,军事职业人员的健康对于国家安全保障、军队战斗力生成具有重要意义。高尿酸血症作为一种常见的代谢性疾病,是众多疾病的危险因素,近年来患病情况呈现上升与年轻化趋势。我军部队官兵高尿酸血症患病率显著高于... 详细信息

作为国家战斗的有生力量,军事职业人员的健康对于国家安全保障、军队战斗力生成具有重要意义。高尿酸血症作为一种常见的代谢性疾病,是众多疾病的危险因素,近年来患病情况呈现上升与年轻化趋势。我军部队官兵高尿酸血症患病率显著高于地方人群,严重影响官兵健康,已有许多文献对此进行报道。本文主要综述了高原、沿海岛礁环境下的部队官兵,航海、航空人员与火箭军官兵以及军队院校学员、机关干部、离退休干部等其他军队人员的高尿酸血症患病情况,分析了一些可能的原因,旨在为军队对该病的预防控制提供帮助,为军队卫生安全保障、军队战斗力维护提供理论依据,同时指出了军事职业人员高尿酸血症患病情况调查研究中可能存在的不足与问题,并提出了一定的解决措施。

关键词：部队官兵高尿酸血症患病情况研究进展综述

Multiband fitting to three long GRBs with Fermi/LAT data:structured ejecta sweeping up a density-jump medium

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2011年第9期11卷 1046-1066页

作者： Si-yi Feng zi-Gao Dai Department of Astronomy Nanjing University Nanjing 210093 China Key Laboratory of Modern Astronomy and Astrophysics （Nanjing University） Ministry of Education Nanjing 210093 China

We present broadband （radio, optical, X-ray and GeV） fits to the afterglow light curves and spectra of three long-duration gamma-ray bursts （GRBs 080916C, 090902B, and 090926A） detected by the Gamma-Ray Burst Monitor and Large Area Telescope （LAT） instruments on the Fermi satellite. Using the observed broadband data, we study the origin of the high energy emission, and suggest that the early-time GeV emission and the late-time radio, optical, and X-ray afterglows can be under- stood as being due to synchrotron emission from an external forward shock caused by structured ejecta propagating in a wind bubble jumping to a homogeneous density medium. If the ceasing time for a majority of the energy injection is assumed to be close to the deceleration time of the forward shock, the structured ejecta with con- tinuous energy injection towards the forward shock can well explain the early rising feature of the GeV mission from these bursts, and the density-jump medium can ac- count for some particular plateaus or flares in the late afterglows. From our fits, we find that, on one hand, the external shock origin of the GeV photons will make the optical depth not have a significant contribution to the early LAT rising part, which will loosen the strong constraint of lower limits of the Lorentz factor. On the other hand, these Fermi-LAT events preferentially occur in a low-density circumburst environment, in which case the Klein-Nishina cutoff will significantly suppress the Self- Synchrotron Compton radiation. Such an environment might result from superbubbles or low-metallicity progenitor stars （which have a low mass-loss rate at late times of stellar evolution） of type Ib/c supernovae.

关键词： gamma-rays: bursts -- gamma-rays: theory

Bayesian networks modeling for thermal error of numerical control machine tools

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第11期9卷 1524-1530页

作者： Xin-hua YAO Jian-zhong FU zi-chen CHEN College of Mechanical and Energy Engineering Zhejiang University Hangzhou 310027 China Zhejiang Provincial Key Lab of Advanced Manufacturing Technology Hangzhou 310027 China

The interaction between the heat source location, its intensity, thermal expansion coefficient, the machine system configuration and the running environment creates complex thermal behavior of a machine tool, and also makes thermal error prediction difficult. To address this issue, a novel prediction method for machine tool thermal error based on Bayesian networks (BNs) was presented. The method described causal relationships of factors inducing thermal deformation by graph theory and estimated the thermal error by Bayesian statistical techniques. Due to the effective combination of domain knowledge and sampled data, the BN method could adapt to the change of running state of machine, and obtain satisfactory prediction accuracy. Ex- periments on spindle thermal deformation were conducted to evaluate the modeling performance. Experimental results indicate that the BN method performs far better than the least squares (LS) analysis in terms of modeling estimation accuracy.

关键词： Bayesian networks (BNs) Thermal error model Numerical control (NC) machine tool

Optical Flash of GRB 990123: Constraints on the Physical Parameters of the Reverse Shock

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Astronomy and Astrophysics 2002年第5期2卷 449-453页

作者： yi-zhong Fan, zi-Gao Dai, Yong-Feng Huang and Tan Lu Department of Astronomy, Nanjing University, Nanjing 210093 Department of Astronomy Nanjing University Nanjing 210093

The optical flash accompanying GRB 990123 is believed to be powered by the reverse shock of a thin shell. With the best-fit physical parameters for GRB 990123 and the assumption that the parameters in the optical flash are the same as in the afterglow, we show that: 1) the shell is thick rather than thin, and we have provided the light curve for the thick shell case which coincides with the observation; 2) the theoretical peak flux of the optical flash accounts for only 3×10-4 of the observed. In order to remove this discrepancy, the physical parameters, the electron energy and magnetic ratios, εe and εB, should be 0.61 and 0.39, which are very different from their values for the late afterglow.

关键词： gamma rays: bursts - gamma rays: theory

Portable Dynamic Positioning Control System on A Barge in Short-Crested Waves Using the Neural Network Algorithm

在线全文

学校读者我要写书评

暂无评论

China Ocean Engineering 2013年第4期27卷 469-480页

作者： FANG Ming-chung LEE zi-yi Department of Systems and Naval Mechatronic Engineering National Cheng Kung University

This paper develops a nonlinear mathematical model to simulate the dynamic motion behavior of the barge equipped with the portable outboard Dynamic Positioning （DP） system in short-crested waves. The self-tuning Proportional- Derivative （PD） controller based on the neural network algorithm is applied to control the thrusters for optimal adjustment of the barge position in waves. In addition to the wave, the current, the wind and the nonlinear drift force are also considered in the calculations. The time domain simulations for the six-degree-of-freedom motions of the barge with the DP system are solved by the 4th order Runge-Kutta method which can compromise the efficiency and the accuracy of the simulations. The technique of the portable alternative DP system developed here can serve as a practical tool to assist those ships without being equipped with the DP facility while the dynamic positioning missions are needed.

关键词： neural network PD controller dynamic positioning short-crested wave

Effects of lead stress on Vg expression in the beet armyworm over five successive generations

在线全文

学校读者我要写书评

暂无评论

Journal of Integrative Agriculture 2019年第1期18卷 134-142页

作者： SU Hong-hua YANG Yong QIAN Yuan-yuan YE zi-bo CHEN Yu-qing YANG yi-zhong School of Horticulture and Plant Protection Yangzhou University

Heavy metals have been found to be endocrine disruptors in *** is one of the most widespread elements of contamination,but there has been no research about the effects of lead stress on vitellogenin(Vg) gene expression in insects exposed to lead over multiple *** this paper,the effects of different concentrations of lead(0,0.3,4.8 and 76.8 mg kg^(–1)) on the expression of Vg in the beet armyworm over five successive generations were *** results showed that lead stress had significant effects on Vg expression in a dose-dependent *** females at the larval and adult stages,as lead concentration increased,Vg expression was significantly inhibited; for males at these two developmental stages,Vg expression was induced and increased as lead concentration *** addition,with the increase over stressed generations,inhibited effects for females and induced effects for males at the larval and adult stages became increasingly more ***,at the pupal stage,Vg expression in the two genders was different from that at the larval and adult *** results indicate that lead stress can upregulate Vg expression in males which should be a useful indicator for environmental risk assessment.

关键词： Spodoptera exigua lead stress vitellogenin gene expression females males

A parameter formula connecting PID and ADRC

在线全文

学校读者我要写书评

暂无评论

Science China(Information Sciences) 2020年第9期63卷 175-187页

作者： Sheng zhong yi HUANG Lei GUO Key Laboratory of Systems and Control Academy of Mathematics and Systems ScienceChinese Academy of Sciences School of Mathematical Sciences University of Chinese Academy of Sciences

This paper presents a parameter formula connecting the well-known proportional-integralderivative(PID) control and the active disturbance rejection control(ADRC). On the one hand, this formula gives a quantitative lower bound to the bandwidth of the extended state observer(ESO) used in ADRC,implying that the ESO is not necessarily of high gain. On the other hand, enlightened by the design of ADRC, a new PID tuning rule is provided, which can guarantee both strong robustness and nice tracking performance of the closed-loop systems under the PID control. Moreover, it is proved that the ESO can be rewritten as a suitable linear combination of the three terms in PID, which can give a better estimate for the system uncertainty than the single integral term in the PID controller. Theoretical results are verified also by simulations in the paper.

关键词： nonlinear uncertain systems proportional-integral-derivative PID active disturbance rejection control ADRC extended state observer ESO