摘要：In this work,we have performed density functional theory(DFT)calculations to investigate the methanol electro‐oxidation reaction(MOR)catalyzed by the Pt,PtCu alloy and *** complex reaction networks,including the intermediate dehydrogenation,water dissociation and anti‐poison reaction steps,are systematically investigated to explore the *** the standard condition of pH=0 and zero potential,for Cu,most dehydrogenation steps along the favorable pathway are endergonic,making it less active in *** the Pt and PtCu alloy,their dehydrogenation steps are mainly exergonic,but the formed CO intermediate binds too tightly on Pt,that can accumulate on active sites to poison the electro‐*** CO can be consumed by the thermodynamic reaction with OH*,which comes from water *** calculation shows alloying the Pt with Cu could not only reduce the free energy barrier for binding between CO*and OH*,but also assist the water dissociation to produce more OH*for that anti‐poison *** makes the PtCu alloy more active than the pure Pt electrode in *** results reveal the importance of anti‐poison reaction and water dissociation in MOR,which could be applied to the rational design of more active alloy electro‐catalysts in future.

摘要：Single-atom catalysts(SACs),including metalmetal-bonded bimetallic ones named single-atom alloys(SAAs),have aroused significant interest in *** this article,the catalytic mechanism and bonding analysis of CO oxidation reaction on bimetallic gold–palladium(Au–Pd)model of single atom alloy Au37Pd1 are investigated by using quantum chemical *** molecular geometries and adsorbate/substrate binding energies of CO@Au–Pd,O2@Au–Pd and CO/O2@Au–Pd configurations are *** core-shell structure is confirmed to be the most stable structure for Au–Pd SAA,where the Pd atom prefers to situate at the core *** transfer from the Pd atom to the Au atoms has been confirmed to stabilize the *** to the binding energy and chemical bonding analysis,both CO and O2 prefer to bind to the Pd atom at the hex site with low coordination *** formation of new co-adsorption species is identified,in which vertical and parallel bridging adsorptions of CO and O2 on the Au–Pd bonds are *** oxidation on Au–Pd SAA is found to be feasible with low energy barriers and follows the Langmuir-Hinshewood(L-H)*** work offers insights into the significant role of single atom of the SAAs in catalytic reactions and can provide evidence for designing new SAAs with high-performance catalytic activities.

摘要：Low-temperature CO oxidation has attracted extensive interest in heterogeneous catalysis because of the potential applications in fuel cells,air cleaning,and automotive emission *** the present study,theoretical investigations have been performed using density functional theory to elucidate the crystal plane effect and structure sensitivity of Co3O4 nano-catalysts toward catalyzing CO *** is shown that the surface Co–O ion pairs are the active site for CO oxidation on the Co3O4 *** of stronger CO adsorption and easier removal of lattice oxygen ions,the Co3O4（011）surface is shown to be more reactive for CO oxidation than the Co3O4（001）surface,which is consistent with previous experimental *** comparing the reaction pathways at different sites on each surface,we have further elucidated the nature of the crystal plane effect on Co3O4 surfaces and attributed the reactivity to the surface *** results suggest that CO oxidation catalyzed by Co3O4 nanocrystals has a strong crystal plane effect and structure *** the vacancy formation energy of the oxide surface is key for high CO oxidation reactivity.

摘要：Surface tailoring of Pt-based nanocatalysts is an effective pathway to promote their electrocatalytic performance and ***,we report two kinds of one-dimensional(1D)ultrafine PtCu nanowires(smooth surface&rugged surface)synthesized via a wet chemical method and their distinct catalytic performances in electro-oxidation of *** alloyed PtCu nanowires having rough surfaces with atomic steps exhibit superior catalytic activity toward multiple electrochemical reactions compared with the smooth *** functional theory simulations show the excellent reactivity of rugged PtCu na-nowires and attribute it to the surface synergetic Pt-Cu site which accounts for the promotion of water dissociation and the dehydrogenation of the carboxyl *** current study provides an insight into reasonable design of alloy nanocatalysts in energy-related electrocatalytic systems.

摘要：单点金刚石超精密加工能够获得纳米级的低粗糙度表面。进一步的实验表明,采用该工艺进行退火态无氧铜切削,已加工表面在刀痕基础上还会出现清晰的晶界浮凸现象。传统的粗糙度概念无法有效表征与区分含有晶界浮凸信息的超精加工表面微观形貌。引入分形维数概念,采用该理论中尺码法对无氧铜超精加工表面的微观形貌进行分形维数计算;为降低切削刀痕信号干扰、突出晶界浮凸信息,设计表面信号带阻滤波方法。计算结果表明,超精加工后的表面分形维数包含了加工刀痕与晶界浮凸信息,由于两者尺度相近,传统的粗糙度测量无法区分其差异;采用带阻滤波与尺码法耦合方式,能够有效识别晶界浮凸特点,定量地反映微观尺度下超精加工表面的形貌特征信息。

摘要：电感耦合等离子体质谱仪(ICP-MS)以其灵敏度高、检出限低等优点,是痕量元素强有力的分析手段之一。在ICP-MS仪器设计中,如何将待分析物的离子束有效引入后级质量分析器系统是一大难点。为了实现离子束的高效传输,离子束进入偏转透镜后应有较小的角度发散和能量发散,并尽可能平行射出,即在垂直方向的速度尽量为0;同时为了最大程度去除中性粒子和光子,降低背景噪声,应使垂直方向的偏转位移较大。借鉴电子光学中的静电场理论,从离子在静电场中的运动过程出发,对离子在一种偏振悬挂式离轴偏转透镜中的运动过程进行理论推导并建立模型;通过SIMION仿真软件,分别对代表低、中、高质量数的Li、In、U离子束在此偏转透镜系统中的运动进行模拟仿真,考察了电场参数加速电压U_(a)、偏转电压U_(1)、偏转电压U_(2)和机械参数L2对离子束传输的影响,该影响包括离子偏转位移s y、垂直方向速度V′y和离子通过率;结合仿真结果和设计要求给出该离轴偏转透镜的关键电场参数值和机械参数优化设计方案;根据优化设计方案,将三种设计尺寸的偏转透镜系统应用于ICP-MS仪器中,进行了背景噪声和灵敏度的对比测试以验证模拟仿真可靠性。实验结果表明,借助仿真优化后的透镜结构,背景噪声和灵敏度有明显提升,尤其是低质量数提升更为明显,背景噪声降低了约2倍,灵敏度提升了约4倍。虽然模拟仿真与实际结果有一定的误差,而整体的趋势正确,能够为实际偏转透镜系统的结构设计和电气参数优化提供指导。

摘要：石泉水电站已投入运行近50年,原设计中泄洪表孔工作弧门前无检修闸门,因随梯级开发水位抬高失去旱地检修条件,需对该部位金属结构进行改造。对此,采用数字化手段和BIM技术,对工程泄洪表孔坝段进行数字化建模,重现原设计方案,在此基础上完成了施工阶段的金属结构设备布置、检修闸门的设计,并利用ANSYS实现了检修闸门结构数值仿真,形成了从CAD建模、CAE数值仿真、软件二次开发及三维制图的全面数字化应用成果。可视化改造方案有利于指导施工和运维,也为同类工程在方法和经验上提供借鉴。

摘要：针对农村偏远地区通信不畅的临时突发性问题,该文提出一种自适应的多无人机(UAV)辅助通感一体化(ISAC)机制,在地面用户和感测目标呈簇状随机分布的情况下,通过合理调度多无人机实现覆盖式通信保障,为无人机使能的通感一体系统提供了一种新的解决思路和方案。该文主要研究了无人机空间部署及其对地面设备的波束成形等问题,在空地关联约束条件下,系统可通过优化无人机的通信和感知波束成形变量组,最大限度地提高用户传输可达速率的下限,同时保证基本的通感需求。为了有效解决所考虑的非凸优化问题,该文借助基于高斯核的均值漂移算法(MS),用以处理关联策略中的混合整型线性问题,此外,结合2次变换与连续凸逼近(SCA)的相关技巧,采用块坐标下降(BCD)的方式优化波束成形,以获取次优解。数值结果验证了自适应机制的有效性。

摘要：恒功率电源是开关电源中的一种特殊电源,因其具有恒功率输出特性而得名。传统的恒功率电源存在着稳态性能差、设备利用率低和效率低等问题。研究表明,恒功率输出的Boost变换器是一个微分平坦系统。基于微分平坦理论设计的反馈控制系统有效地将非线性系统转化为线性系统,从而简化了设计过程,并且具有良好的动态性能和静态指标。本文以Boost变换器为例,基于微分平坦理论设计出控制策略。最后,研制了一台300W的Boost PFC电源样机,该恒功率电源的各项性能满足设计要求,具有较好的稳态和动态性能,实现了恒功率输出且功率可调功能。实验结果验证了控制策略的可行性与正确性。

摘要：针对某地18层椭圆形框架-核心筒结构楼房爆破拆除工况,通过系统分析楼房受力特征发现:椭圆形框筒结构楼房高宽比小、跨度长等特点,易发生后座甚至塌而不倒现象,核心筒内部剪力墙分布不规则,倒塌时易出现应力分布不均现象,导致楼体偏移设计方向。针对上述工程难点,设计时采用延期爆破、辅助弱化方式进行爆破拆除,首先通过拆分切割、化筒为墙等预处理方式破坏楼房抗侧移结构属性,避免楼体倒塌时发生偏移,再将爆破切口细致划分成4个爆破分区并逐步增大各区延期时间,尤其是将最后两分区延期时间提高至1 s,实现余留区域支撑点前移,避免塌而不倒现象,同时适当增大最末段起爆区域的支撑面积以控制后座,设计中选用上下双切口折叠爆破方法,控制楼房触地振动幅度,提高楼房整体解离效果。现场爆破拆除时,椭圆形楼房倒塌过程历时约5 s,基本沿设计方向倒塌,存在轻微后座,支柱失效明显,各层楼板依次折叠,爆堆集中,拆除爆破效果良好,为类似工程提供了借鉴。