摘要：Alloying and nanostructuring are two strategies used to facilitate the efficient electrocatalysis of the oxygen reduction reaction(ORR)by Pt,where the high index surfaces(HISs)of Pt exhibit superior activity for ***,we report the fabrication of PtCu3 nanodendrites possessing rich spiny branches exposing n(111)×(110)*** dendrites were formed through an etching‐modulated seeding and growing ***,an oxidative atmosphere was initially applied to form the concaved nanocubes of the Pt‐Cu seeds,which was then switched to an inert atmosphere to promote an explosive growth of ***,the oxidative or inert atmosphere failed to produce this hyperbranched *** dealloying of the PtCu3 nanodendrites produced Pt3Cu shells with Pt‐rich surfaces where HIS‐exposed dendrite structures were *** resulting PtCu_(3)@Pt_(3)Cu@Pt nanodendrites in 0.1 M HClO4 exhibited excellent mass and area specific activities for ORR,which were 14 and 24 times higher than that of commercial Pt/C,*** calculations revealed that Cu alloying and HISs both contributed to the significantly enhanced activity of Pt,and that the oxygen binding energy on the step sites of HISs on the PtCu_(3)@Pt_(3)Cu@Pt nanodendrites approached the optimal value to achieve a near peak‐top ORR activity.

摘要：The development of high‐performance nonprecious metal catalysts(NPMCs)to supersede Pt‐based catalysts for the oxygen reduction reaction(ORR)in polymer electrolyte membrane fuel cells is highly desirable but remains *** this paper,we present a pyrolysis strategy for spatial confinement and active‐site fixation using iron phthalocyanine(FePc),phthalocyanine(Pc)and Zn salts as *** the obtained carbon‐based NPMC with a hierarchically porous nanostructure of thin‐layered carbon nanosheets,nearly 100%of the total Fe species are Fe^(Ⅱ)‐N_(4) active *** contrast,pyrolyzing FePc alone forms Fe‐based nanoparticles embedded in amorphous carbon with only 5.9%Fe^(Ⅱ)‐N_(4) active *** experimental characterization and density functional theory calculations reveal that spatial confinement through the staggeredπ–πstacking of Pc macrocycles effectively prevents the demetallation of Fe atoms and the formation of Fe‐based nanoparticles via ***,Zn‐induced microporous defects allow the fixation of Fe^(Ⅱ)‐N_(4) active *** synergistic effect of staggered stacking confinement and microporous defect fixation results in a high density of atomic Fe^(Ⅱ)‐N_(4) active sites that can enhance the *** optimal Fe^(Ⅱ)‐N_(4)‐C electro‐catalyst outperforms a commercial Pt/C catalyst in terms of half‐wave potential,methanol toler‐ance,and long‐term stability in alkaline *** modulation strategy can greatly advance efforts to develop high‐performance NPMCs.

摘要：针对埋头弹药的闭气和抽壳问题,设计复合药筒方案,并对方案的闭气性能进行分析。分析结果表明:在最大380 MPa膛压下,药筒底座与筒体和闩体之间闭气性能良好,但端盖与身管之间闭气性较差,且筒体前端塑性变形较大,易出现抽壳后筒体破损。在此基础上,提出复合药筒改进方案,并与改进前方案进行对比分析。对比结果表明:端盖与身管之间有效接触面积增大,闭气效果明显改善,且筒体前端塑性变形明显变小,局部破损情况得到明显改善,膛压卸载后端盖与底座均与药室脱离,可实现几乎零抽壳力。

摘要：主动控制旋翼可用于减振、降噪、性能提升等,被称为下一代旋翼。经典的频域HHC算法常受限于作动器性能饱和,极大的降低了控制性能。在基于1-范数约束的二次规划(QP)法的基础上,提出了一种迭代-QP算法,进一步减小了控制信号的保守,提升了控制性能。采用一副装有主动控制后缘襟翼(ACF)旋翼的线性模型进行仿真,并与缩放、截断、自动权重、序列二次规划、1-范数-QP法进行比较,展现了迭代-QP法处理HHC中作动器饱和问题的优越性。

摘要：旋翼桨叶的一阶摆振后退型模态是影响直升机地面共振稳定性的主要模态。为了识别装机状态下桨叶一阶摆振模态阻尼,该研究发展了基于FFT分析的移动矩形窗法、基于Fourier级数的移动矩形窗法、基于希尔伯特变换法和基于Wavelet小波变换等四种方法的无轴承旋翼一阶摆振模态阻尼识别技术,针对试验中测得的信号出现的频率成分密集和信噪比差等情况在阻尼识别过程中增加了数字滤波器,数值仿真和基于装机试验数据的识别均表明,基于Fourier级数的移动矩形窗和基于Wavelet小波变换两种阻尼识别技术可有效分离无轴承旋翼摆振模态,数字滤波器可有效提高桨叶摆振阻尼识别精度。

摘要：低渗透油藏CO2驱开发过程中,面临的最大问题是容易发生气窜。针对目前尚无定量的气窜识别标准,以及现有的气窜通道体积计算方法实用性较差等问题,通过分析产出气中CO2含量的动态变化特征,将气窜类型划分为明显气窜和微弱气窜两大类,明确了见气时间确定方法,建立了气窜识别判断标准。在此基础上,利用物质守恒原理分别计算注入端和产出端的气窜通道体积,并借助气窜通道体积交会图实现对气窜通道体积的校正,从而消除单井产液比例系数或井网形状因子对气窜通道体积计算结果的影响。通过对实际气窜单井的分析和计算表明,该方法具有较强的操作性和实用性,一方面实现了对气窜类型和气窜程度的定性评价,另一方面实现了对气窜通道体积和气窜通道横截面积的定量计算,为后期合理设计封堵措施和堵剂用量提供理论依据。

摘要：针对鱼骨状分支水平井井形设计问题,应用分段耦合模型优化确定了不同参数的设计原则,并应用正交实验方法评价了各参数的敏感性。结果表明:影响鱼骨状分支水平井产能的参数主要为分支展布参数(分支点位置、同异侧和对称性)和分支形态参数(分支长度、数目、角度和间距),其中分支形态参数对产能影响的强弱顺序依次为:分支长度、分支数目、分支角度、分支间距。鱼骨状分支水平井形态设计原则是:异侧、非对称,分支点位置靠近主井筒两端,分支数不少于2支,分支角度不小于30°,实际应用时可结合工程技术能力综合确定。方法应用于胜利油田3口鱼骨状水平井产能计算,预测误差小于3%;设计的东海平湖油气田八角亭油藏BO2井,初期产能达350 m3/d。

摘要：页岩储层储集空间主要为纳米尺度孔隙,页岩油在纳米尺度孔隙中的赋存状态对其流动规律会产生重要影响。利用核磁共振冻融技术得到了东营凹陷页岩孔隙结构的全尺寸孔径分布及纳米尺度孔隙的主频孔隙直径,基于东营凹陷牛斜55井的井流物组成,采用分子动力学模拟方法建立东营凹陷典型纳米尺度孔隙模型,开展原油在有机质纳米尺度孔隙内赋存状态研究。研究结果表明:①东营凹陷页岩储层纳米尺度孔隙的主频孔隙直径为15 nm;②有机质纳米尺度孔隙内的原油密度从孔隙壁面到孔隙中央逐渐降低;③页岩油分子会在有机质纳米尺度孔隙的壁面处形成“类固体”层,其密度约为孔隙中央游离态原油密度的1.1~3.15倍;④页岩油分子在有机质纳米尺度孔隙内发生四层吸附,第1吸附层的厚度最大,计算得到东营凹陷页岩油吸附态比例为19.8%。

摘要：从隐蔽通道概念入手,阐述了隐蔽通道分析在Oracle中的设计思想,讨论了隐蔽通道分析的内容与层次、隐蔽通道的标识方法、隐蔽通道带宽的计算与测量、隐蔽通道的处理,就如何提高Oracle9i安全性能提供了一种途径。

摘要：为了提高液压立柱的抗冲击力学性能,增强冲击地压巷道支护效果.采用在常规液压立柱中加入具有恒定承载力的吸能防冲构件方法,设计了吸能防冲立柱,并采用ABAQUS有限元软件对吸能防冲立柱的抗冲击力学性能进行数值分析.结果表明:吸能防冲构件变形阶段吸收了部分冲击能量,有效改善了立柱受冲击载荷时的受力情况,减小了立柱变形,较大地提高了立柱抗冲击力学性能;在外界条件均相同情况下,吸能防冲立柱的抗冲击力学性能远好于常规立柱.在常规液压立柱中加入吸能防冲构件可有效增强立柱抗冲击性能.