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101.
Qixian Xie Zhao Cai Pengsong Li Daojin Zhou Yongmin Bi Xuya Xiong Enyuan Hu Yaping Li Yun Kuang Xiaoming Sun 《Nano Research》2018,11(9):4524-4534
Atomic composition tuning and defect engineering are effective strategies toenhance the catalytic performance of multicomponent catalysts by improvingthe synergetic effect; however, it remains challenging to dramatically tune the active sites on multicomponent materials through simultaneous defect engineeringat the atomic scale because of the similarities of the local environment. Herein,using the oxygen evolution reaction (OER) as a probe reaction, we deliberatelyintroduced base-soluble Zn(II) or Al(III) sites into NiFe layered double hydroxides(LDHs), which are one of the best OER catalysts. Then, the Zn(II) or Al(III) siteswere selectively etched to create atomic M(II)/M(III) defects, which dramaticallyenhanced the OER activity. At a current density of 20 mA·cm?2, only 200 mV overpotential was required to generate M(II) defect-rich NiFe LDHs, which is the best NiFe-based OER catalyst reported to date. Density functional theory(DFT) calculations revealed that the creation of dangling Ni–Fe sites (i.e., unsaturated coordinated Ni–Fe sites) by defect engineering of a Ni–O–Fe site at the atomic scale efficiently lowers the Gibbs free energy of the oxygen evolutionprocess. This defect engineering strategy provides new insights into catalysts atthe atomic scale and should be beneficial for the design of a variety of catalysts. 相似文献
102.
Qingqing Xiong Gha Young Lee Jianxun Ding Wenliang Li Jinjun Shi 《Nano Research》2018,11(10):5281-5309
As an attractive alternative to plasmid DNA, messenger RNA (mRNA) has recently emerged as a promising class of nucleic acid therapeutics for biomedical applications. Advances in addressing the inherent shortcomings of mRNA and in the development of nanoparticle-based delivery systems have prompted the development and clinical translation of mRNA-based medicines. In this review, we discuss the chemical modification strategies of mRNA to improve its stability, minimize immune responses, and enhance translational efficacy. We also highlight recent progress in nanoparticle-based mRNA delivery. Considerable attention is given to the increasingly widespread applications of mRNA nanomedicine in the biomedical fields of vaccination, protein-replacement therapy, gene editing, and cellular reprogramming and engineering. 相似文献
103.
Fenfen Xiong Wei Chen Ying Xiong Shuxing Yang 《Structural and Multidisciplinary Optimization》2011,43(6):837-849
Conventional stochastic response surface methods (SRSM) based on polynomial chaos expansion (PCE) for uncertainty propagation
treat every sample point equally during the regression process and may produce inaccurate estimations of PCE coefficients.
To address this issue, a new weighted stochastic response surface method (WSRSM) that considers the sample probabilistic weights
in regression is studied in this work. Techniques for determining sample probabilistic weights for three sampling approaches
Gaussian Quadrature point (GQ), Monomial Cubature Rule (MCR), and Latin Hypercube Design (LHD) are developed. The advantage
of the proposed method is demonstrated through mathematical and engineering examples. It is shown that for various sampling
techniques WSRSM consistently achieves higher accuracy of uncertainty propagation without introducing extra computational
cost compared to the conventional SRSM. Insights into the relative accuracy and efficiency of various sampling techniques
in implementation are provided as well. 相似文献
104.
为减少高密度电路板的缺陷误报率,研究一种新型自动光学检测系统(AOI);系统采用自行研制的多色LED照明系统,利用机器视觉获取被测PCB的图像,通过图像处理软件系统快速准确地识别出各种缺陷;系统利用获取的彩色图像信息,根据各种缺陷的特征信息不同,采用OPENCV对各种缺陷的检测算法进行改进,使得系统性能有很大改进;对30块同类HDI型PCB的36300个检测点进行测试,测试结果证明,系统PCB缺陷的检出率高达99.87%,误报率只有0.32%。 相似文献
105.
106.
In this paper, optimum positioning of the conical cutter for five-axis flank milling of slender surfaces is addressed from the perspective of approximating the tool envelope surface to the data points on the design surface following the minimum zone criterion recommended by ANSI and ISO standards for tolerance evaluation. Based on the observation that a conical surface can be treated as a canal surface, i.e. envelope surface of one-parameter family of spheres, the swept envelope of a conical cutter is represented as a sphere-swept surface. Then, an approach is presented to efficiently compute the signed distance between a point in space and the swept surface without constructing the swept surface itself. The first order differential increment of the signed point-to-surface distance with respect to the differential deformation of the tool axis trajectory surface is derived. By using the distance function, tool path optimizations for semi-finish and finish millings are formulated as two constrained optimization problems in a unified framework, and a sequential approximation algorithm along with a hierarchical algorithmic structure is developed for the optimization. Numerical examples are given to confirm the validity and efficiency of the proposed approach. Comparing with the existing approaches, the present one improves the machining accuracy greatly. The rationale developed applies to general rotary cutters. 相似文献
107.
Different from reversible image data hiding, most reversible video data hiding schemes have the particular problem that the distortion due to hidden data will spread and accumulate. In this paper, the problem of distortion drift caused by reversible data hiding in compressed video is analyzed, and a lossless drift compensation scheme is proposed to restrain the distortion for the first time. In order to ensure the reversibility, drift compensation signals are merged in the quantized DCT (Discrete Cosine Transform) coefficients of P-frames and the corresponding recovery mechanism is presented as well. Experimental results demonstrate that the proposed lossless drift compensation scheme significantly improves the video quality, and the original compressed video can be recovered exactly after the hidden data and compensation signals are removed. In addition, the proposed scheme does not depend on specific reversible data hiding method. 相似文献
108.
Muzhou Xiong Michael Lees Wentong Cai Suiping Zhou Malcolm Yoke Hean Low 《The Visual computer》2010,26(5):367-383
This paper proposes a rule-based motion planning system for agent-based crowd simulation, consisting of sets of rules for
both collision avoidance and collision response. In order to avoid an oncoming collision, a set of rules for velocity sampling
and evaluation is proposed, which aims to choose a velocity with an expected time to collision larger than a predefined threshold.
In order to improve the efficiency over existing methods, the sampling procedure terminates upon finding an appropriate velocity.
Moreover, the proposed motion planning system does not guarantee a collision-free movement. In case of collision, another
set of rules is also defined to direct the agent to make a corresponding response. The experiment results show that the proposed
approach can be applied in different scenarios, while making the simulation execution efficient. 相似文献
109.
Longhua Liu Gang Liu Ying Xiong Jie Chen Wenjie Li Yangchao Tian 《Microsystem Technologies》2010,16(8-9):1315-1321
X-ray imaging and microscopy techniques have been developed in worldwide due to their capabilities of large penetration power and high spatial resolution. Fresnel zone plates is considered to be one of the most convenient optic devices for X-ray imaging and microscopy system. The zone plates with aspect ratio of 7 and 13 have been fabricated by e-beam lithography combined with X-ray lithography in this paper. Firstly, the X-ray lithography mask of zone plates with outermost zone width of 100 nm was fabricated by e-beam lithography and gold electroplating techniques. Secondly, the zone plates with gold profile thickness of 700 and 1,300 nm were replicated by X-ray lithography and gold electroplating techniques. X-ray imaging and microscopy techniques were introduced to characterize the high-aspect-ratio zone plates’ inner structures. At the X-ray energy of 7.5 keV, the first-order focusing efficiency of zone plates with gold profile thickness of 700 nm is about 8.63%. 相似文献
110.
本文阐述了辩论支持系统开发的背景和意义,介绍了基于J2EE的系统需求,分析了软件的结构和主要功能模块及所用的关键技术框架,并在J2EE平台上开发实现了系统。 相似文献