摘要：Electrocatalysis is a promising approach to clean energy conversion due to its high efficiency and low environmental pollution. Noble metal materials have been studied to show high activity toward electrocatalyltic reactions, although such applications remain restricted by the high cost and poor durability of the noble metals. By precisely adjusting the catalyst composition, size, and structure, electrocatalysts with excellent performance can be obtained. Atomic layer deposition(ALD) is a technique used to produce ultrathin films and ultrafine nanoparticles at the atomic level. It possesses unique advantages for the controllable design and synthesis of electrocatalysts. Furthermore, the homogenous composition and structure of the electrocatalysts prepared by ALD favor the exploration of structure-reactivity relationships and catalytic mechanisms. In this review, the mechanism, characteristics, and advantages of ALD in fabricating nanostructures are introduced first. Subsequently, the problems associated with existing electrocatalysts and a series of recently developed ALD strategies to enhance the activity and durability of electrocatalysts are presented. For example, the deposition of ultrafine Pt nanoparticles to increase the utilization and activity of Pt, fabrication of core–shell, overcoat, nanotrap, and other novel structures to protect the noble-metal nanoparticles and enhance the catalyst stability. In addition, ALD developments in synthesizing non-noble metallic electrocatalysts are summarized and discussed. Finally, based on the current studies, an outlook for the ALD application in the design and synthesis of electrocatalysts is presented.

摘要：An atomic layer deposition （ALD） method has been employed to synthesize Fe3O4/graphene and Ni/graphene composites. The structure and microwave absorbing properties of the as-prepared composites are investigated. The surfaces of graphene are densely covered by Fe3O4 or Ni nanoparticles with a narrow size distribution, and the magnetic nanoparticles are well distributed on each graphene sheet without significant conglomeration or large vacancies. The coated graphene materials exhibit remarkably improved electromagnetic （EM） absorption properties compared to the pristine graphene. The optimal reflection loss （RL） reaches -46.4 dB at 15.6 GHz with a thickness of only 1.4 mm for the Fe3O4/graphene composites obtained by applying 100 cycles of Fe2O3 deposition followed by a hydrogen reduction. The enhanced absorption ability arises from the effective impedance matching, multiple interfacial polarization and increased magnetic loss from the added magnetic constituents. Moreover, compared with other recently reported materials, the composites have a lower filling ratio and smaller coating thickness resulting in significantly increased EM absorption properties. This demonstrates that nanoscale surface modification of magnetic particles on graphene by ALD is a very promising way to design lightweight and high-efficiency microwave absorbers.

摘要：Impedance matching is important for achieving high-efficiency microwave absorbers. The high conductivity of dielectric loss materials such as pure metals and carbon nanomaterials generally results in poor absorption owing to the low impedance matching between the absorbers and air. Carbon nanostructures are very promising candidates for high-efficiency absorption because of their attractive features including low density, high surface area, and good stability. Herein, a new strategy is proposed to improve the impedance matching of dielectric loss materials using electrospun carbon nanofibers as an example. The carbon nanofibers are coated with specifically designed gradient multilayer nanofilms with gradually increasing electroconductibility synthesized by doping ZnO with different A1203 content （AZO） by atomic layer deposition. The gradient nanofilms are composed of five layers of dielectric films, namely, pure A1203, AZO （5：1, the pulse cycle ratio of ZnO to A1203）, pure ZnO, AZO （10：1）, and AZO （20：1）. The versatile gradient films serve as intermediate layers to tune the impedance matching between air and the carbon nanofiber surfaces. Therefore, the carbon nanofibers coated with gradient films of rationally selected thicknesses exhibit remarkably enhanced microwave absorption performance, and the optimal reflection loss reaches -58.5 dB at 16.2 GHz with a thickness of only 1.8 mm. This work can help further understand the contribution of impedance matching to microwave absorption. Our strategy is general and can be applied to improve the absorption properties of other dielectric loss materials and even for applications in other fields.

摘要：桉树是广西柳州市重要的经济林木之一,但其在生长过程中面临诸多病虫害的威胁。为有效减少病虫害影响,确保桉树健康生长,重点分析青枯病、焦枯病、灰霉病、茎腐病、白蚁及蛴螬等桉树主要病虫害及其防治措施。

摘要：针对倾转旋翼机特殊的气动构型、不同的飞行模式以及模式横航向通道控制的稳定性、快速性和耦合性等需求,首先以XV 15倾转旋翼机为研究对象,建立其横航向动力学线性模型;其次针对倾转旋翼机直升机模式横向通道操纵冗余的问题,从定性和定量2个角度分析横向通道的飞行特性以及不同操纵方式的差异,提出了一种将倾转旋翼左右螺旋桨的横向周期变距与差动总距相结合的横向操纵方式,用于解决横向飞行的稳定与机动控制之间的矛盾,并采用经典控制方法对不同操纵方式分别进行了相应的横向控制律设计;最后基于MATLAB/Simulink和X Plane视景软件搭建了倾转旋翼机飞行控制仿真系统,将所设计的横向控制律进行了仿真验证与对比分析。仿真结果表明,倾转旋翼机直升机模式飞行采用基于横向周期变距与差动总距相结合的横向控制律,能够有效克服常规单通道控制的缺点,具有更好的控制稳定性和动态响应特性。

摘要：Empirical likelihood （EL） ratio statistic on θ=g（x） is constructed based on the inverse probability weighted imputation approach in a nonparametric regression model Y = g（x） ＋ε （x ∈ [0, 1]p） with fixed designs and missing responses, which asymptotically has X1^2 distribution. This result is used to obtain a EL based confidence interval on θ.

摘要：Suppose that we have a partially linear model Yi = xiβ ＋ g（ti） ＋εi with independent zero mean errors εi, where （xi,ti, i = 1, ... ,n} are non-random and observed completely and （Yi, i = 1,...,n} are missing at random（MAR）. Two types of estimators of β and g（t） for fixed t are investigated： estimators based on semiparametric regression and inverse probability weighted imputations. Asymptotic normality of the estimators is established, which is used to construct normal approximation based confidence intervals on β and g（t）. Results are reported of a simulation study on the finite sample performance of the estimators and confidence intervals proposed in this paper.

摘要：在国家提出产业数字化转型以及城市轨道交通数字化发展的宏观背景下,文章聚焦于多层级运营管理模式下的城市轨道交通数字化平台设计研究,依托多年实践经验,深入探索并实施数字化平台的设计方案。该平台整体框架由1张感知网、3个核心平台及6大重点应用领域构成,逻辑功能架构实现系统目标层、全局管理层、项目管理层、支撑平台层、生产层与感知层之间的紧密协作与高效联动,形成“1+N”群集大脑为支撑的物理分布式架构。为验证数字化平台设计的可行性和合理性,以现有运营中的数字化平台原型为基础,结合台州和锡澄线路的实际应用案例进行实践检验,充分展示其在提升城市轨道交通运营效率和管理水平方面的显著成效。

摘要：AIM:To investigate a newly designed stent and its dilatation effect in a rabbit model of benign esophageal ***:Thirty-four New Zealand white rabbits underwent a corrosive injury in the middle esophagus for esophageal stricture *** rabbits with a successful formation of esophageal strictures were randomly allocated into two *** control group(n = 15) was implanted with a conventional stent,and the study group(n= 15) was implanted with a detachable "pieced" *** study stent(30 mm in length,10 mm in diameter) was composed of three covered metallic pieces connected by surgical suture *** stent was collapsed by pulling the suture lines out of the *** weeks after stricture formation,endoscopic placement of a conventional stent or the new stent was *** extraction was carried out four weeks *** extraction rate,ease of extraction,migration,complications,and survival were ***:Stent migration occurred in 3/15(20%)animals in the control group and 2/15(13%) animals in the study group;the difference between the two groups was not statistically *** the end of four weeks,the remaining stents were successfully extracted with the endoscope in 100%(11/11) of the animals in the study group,and 60%(6/10)of the animals in the control group;this difference was statistically significant(P < 0.05).There was no difference in the mean number of follow-up days between the control and study groups(25.33 vs25.85).Minor bleeding was reported in five cases in the study group and four in the control *** were no severe complications directly associated with stent implantation or extraction in either of the two ***:In this experimental protocol of benign esophageal strictures,the novel "pieced" stent demonstrated a superior removal rate with a similar migration rate compared to a conventional stent.

摘要：混合K边密度计作为一种用于核材料衡算的无损分析仪器,仪器测量部件的结构对测量结果影响较大。本文采用Geant4软件对混合K边密度计测量部件的结构参数及其样品测量进行蒙特卡罗模拟研究,模拟分析了X光管管压、滤片材料及厚度、X射线源-样品-探测器夹角及出射准直器材料、孔径、长度等因素对能谱的影响,确定了模拟装置的X光管管压为140 kV,滤片材料为Cd,滤片厚度1mm,X射线源-样品-探测器夹角为30°,出射准直器材料为W,孔径为2.5 mm,长度为1.5 cm;建立了纯U样品、纯Pu样品以及U/Pu混合样品的拟合曲线。模拟分析结果验证了模拟装置和建模模型的可靠性,为仪器实际结构设计提供了理论支撑。