p-adic超几何函数与Dwork超曲面上的有理点

p-adic超几何函数是经典的Gauss超几何函数在有限域上的模拟,与许多数论问题都有联系.设Fq是q元有限域,λ∈Fq,n为正整数.本文研究了Dwork超曲面Dλ^n:x1^n+x2^n+…+xn^n=nλx1x2…xn及其推广形式上的Fq-有理点,并在n与q(q-1)互素时给出了由p-adic超几何函数表示的各种Fq-有理点个数的公式,从而修正和改进了Barman与Goodson等人的结论.     

压气机悬臂静叶流场非定常数值模拟

以现代高压压气机一排悬臂静叶与一排转叶组成的典型级为研究对象,采用非定常数值模拟方法,分析了非定常与定常数值模拟计算得出的级特性线以及峰值效率点气动参数在展向分布的差异,并对悬臂静叶内部流场结构进行了详细分析,结果表明:当悬臂静叶的轮毂设计间隙为2.5%叶高时,非定常计算的综合喘振裕度比定常大5.85%;在峰值效率点工况下,悬臂静叶总压损失和转子效率的非定常影响范围在10%以内,转叶进口相对气流角沿展向分布的影响在0.5°以内。悬臂静叶根部10%叶高以下区域出现了明显的泄漏流动,3.4%叶高压力系数变化最大,轮毂泄漏流起始于20%弦长附近,发展到70%弦长位置时泄漏损失最大,随后逐渐减弱.     

Palladium‐Catalyzed Electrophilic Functionalization of Pyridine Derivatives through Phosphonium Salts

Herein, we report a highly efficient and practical method for pyridine‐derived heterobiaryl synthesis through palladium‐catalyzed electrophilic functionalization of easily available pyridine‐derived quaternary phosphonium salts. The nice generality of this reaction was goes beyond arylation, enabling facile incorporation of diverse carbon‐based fragments, including alkenyl, alkynyl, and also allyl fragments, onto the pyridine core. Notably, the silver salt additive is revealed to be of vital importance for the success of this transformation and its pivotal role as transmetallation mediator, which guarantees a smooth transfer of pyridyl group to palladium intermediate, is also described.     

通过超宽139La固体核磁共振波谱研究层状La(OH)2NO3

层状稀土氢氧化物是一类新型的稀土功能材料，本文采用固体核磁共振（SSNMR）方法研究了同时具备离子交换能力和非线性光学特性的层状La（OH）₂NO₃化合物，探讨了通过四极核CPMG（QCPMG）脉冲序列和变频谱图采集获取超宽¹³⁹La SSNMR谱图的方法，并描述了适用于此类实验的滤波方程和谱图重建方法.重建谱图同时包含四极核中心跃迁和卫星跃迁信息，本文使用QUEST软件对超宽¹³⁹La NMR谱图进行了模拟，获取的四极耦合常数C_Q和非对称因子η_Q均与CASTEP密度泛函理论计算值高度吻合.SSNMR实验结果证实层状La（OH）₂NO₃化合物属于非中心对称结构（P2₁），解决了对其结构长期以来存在的争论.     

文化创意企业视角的长三角城市网络演变特征

运用社会网络与位序-规模法分析长江三角洲地区16市上市类文化创意企业的母-子公司数据信息, 揭示文化创意企业集聚视角长三角城市网络结构及其演变特征. 研究发现: (1) 2005~2015年, 长三角地区文化创意企业上市公司总部数量逐年增加, 公司总部多设立于上海、杭州、苏州以及南京4地; (2)传媒类和软件及计算机类企业多分布于传统区域, 设计咨询类企业生产网络中, 存在传统非核心城市跃升为区域核心城市的现象; (3)上市公司生产网络结构逐渐复杂, 多中心及新核心相继出现, 且生产网络中城市位序有变动趋势, 文化创意产业空间动态正形塑城市体系结构. 为此, 建议长三角文化创意企业发展中应加强企业母子间的联系强度, 促进城市创意流动网络化, 有望推进长三角创意源-流形塑创意城市群新体系.     

新型稀磁半导体Fe掺杂LiZnP的光电性质

采用基于密度泛函理论的第一性原理计算法研究了新型稀磁半导体Li_(1±)_y(Zn_(1-)_xFe_x)P (x=0, 0.0625;y=0, 0.0625)的电子结构、磁性及光学性质.结果表明,Fe的掺入使体系产生自旋极化杂质带,Fe的3d态与Li2s态,Zn4s态以及P3p态的态密度峰在费米能级处出现重叠,产生sp-d轨道杂化,此时体系净磁矩最大,材料表现出金属性,导电性增强.当Li空位时,导电性减弱,但杂质带宽度最大,居里温度最高.而Li填隙时,体系形成能最低,材料变为半金属性,表现为100%自旋注入,表明掺杂体系的磁性和电性可以分别通过Fe的掺入和Li的含量进行调控.对比光学性质发现,Li空位时,在介电函数虚部和复折射率函数的低能区出现新峰,扩大了对低频电磁波的吸收范围.能量损失函数表明掺杂体系具有明显的蓝移效应,且Li填隙时有更强的等离子共振频率.     

New lower bounds for partial k‐parallelisms

Due to the applications in network coding, subspace codes and designs have received many attentions. Suppose that $k\mid n$ and $V\left(n,q\right)$ is an $n$‐dimensional space over the finite field ${\mathbb{F}}_q$. A $k$‐spread is a $(q^n?1)/(q^k?1)$‐set of $k$‐dimensional subspaces of $V\left(n,q\right)$ such that each nonzero vector is contained in exactly one element of it. A partial $k$‐parallelism in $V\left(n,q\right)$ is a set of pairwise disjoint $k$‐spreads. As the number of $k$‐dimensional subspaces in $V\left(n,q\right)$ is ${\left[\genfrac{}{}{0ex}{}{n}{k}\right]}_q$, there are at most ${\left[\genfrac{}{}{0ex}{}{n?1}{k?1}\right]}_q$ spreads in a partial $k$‐parallelism. By studying the independence numbers of Cayley graphs associated to a special type of partial $k$‐parallelisms in $V\left(n,q\right)$, we obtain new lower bounds for partial $k$‐parallelisms. In particular, we show that there exist at least $\frac{q^k?1}{q^n?1}{\left[\genfrac{}{}{0ex}{}{n?1}{k?1}\right]}_q$ pairwise disjoint $k$‐spreads in $V\left(n,q\right)$.     

An improved evaluation of the neutron background in the PandaX-Ⅱ experiment

In dark matter direct detection experiments,neutron is a serious source of background,which can mimic the dark matter-nucleus scattering signals.In this paper,we present an improved evaluation of the neutron background in the PandaX-II dark matter experiment by a novel approach.Instead of fully relying on the Monte Carlo simulation,the overall neutron background is determined from the neutron-induced high energy signals in the data.In addition,the probability of producing a dark-matter-like background per neutron is evaluated with a complete Monte Carlo generator,where the correlated emission of neutron(s)andγ(s)in the(α,n)reactions and spontaneous fissions is taken into consideration.With this method,the neutron backgrounds in the Run 9(26-ton-day)and Run 10(28-ton-day)data sets of PandaX-II are estimated to be(0.66±0.24)and(0.47±0.25)events,respectively.     

Tuning the Reactivities of the Heteronuclear [AlnV3−nO7−n]+ (n=1, 2) Cluster Oxides towards Methane by Varying the Composition of the Metal Centers

The thermal gas-phase reactions of [Al₂VO₅]⁺ and [AlV₂O₆]⁺ with methane have been explored by using Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry complemented by high-level quantum chemical calculations. Both cluster ions chemisorbed methane as the major reaction channels at room temperature. [Al₂VO₅]⁺ could break only one C−H bond to liberate CH₃, whereas [AlV₂O₆]⁺ exhibited higher oxidizing ability such that it brings about the selective generation of formaldehyde. Mechanistic aspects are revealed and the crucial roles of the metal centers are discussed.