确定生成子空间基的一种方法

设P是任一个数域,V是P上的有限维线性空间,σ是V的一个线性变换,对于V中任意m个线性无关的向量α_1,α_2,…,α_m,由σ(α_1),σ(α_2),…,σ(α_m)生成的子空间L(σ(α_1),σ(α_2),…,σ(α_m))的基的一种确定方法被给定。     

模糊关系中算子σ、α、ε之间的关系

讨论了模糊集中算子σ、α、ε之间的关系,研究了它们之间的结合律与分配律,证明了ε算子对σ算子分配律成立.给出了σ算子、α算子以及ε算子结合律成立的条件,给出了σ算子对α算子、α算子对σ算子、σ算子对ε算子、ε算子对σ算子、ε算子对α算子以及α算子对ε算子分配律成立的条件.     

单元体斜截面上的应力不是其上质点平衡的应力

以直杆轴向拉伸为例说明：单元体斜截面上的平衡应力只是保证斜截单元体平衡的应力，不是保证其上质点平衡的应力；单元体平衡与质点平衡是不同的。推导出二向应力状态下质点的平衡应力为σ′α=(σ2x+σ2y+2τ2+2τ(σ2x+σ2y)1/2(sinα2+cosα2))1/2，质点平衡应力σ′α与x轴的夹角为αx=arctan(τ+(σ2x+σ2y)1/2sinarctan (σy/σx))/(τ+(σ2x+σ2y)1/2cosarctan(σy/σx))。推导出二向应力状态质点平衡应力的极值条件：σx=σy；     

遗传σ-meso紧空间

获得了如下结果:(1)对任何空间X,下列各条等价:(ⅰ)X是遗传σ-meso紧的;(ⅱ)X的每个散射分解有一个σ-紧有限的开膨胀;(ⅲ)X的每个单调递减的闭集族{Fα:α<γ}有一个σ-紧有限的开集族V=∪n∈ωVn使得α<γ,X-Fα=∪{V∈V:V∩Fα=Φ};(ⅳ)X的每个单调递增的开集族U={Uα:α<γ}有一个σ-紧有限的开加细V=∪n∈ωVn使得α<γ,Uα=∪{V∈V:VUα};(ⅴ)X的每个单调递增的开覆盖U={Uα:α<γ}有一个σ-紧有限的开加细V=∪n∈ωVn使得α<γ,Uα=∪{V∈V:VUα}.(2)设X是遗传σ-meso紧空间且Y有一个σ-紧有限的基,则X×Y是遗传σ-meso紧的.     

高阶中立型差分方程非振动解的存在性

得到了下列高阶中立型差分方程的一个非振动性理论,△[rn（△^m-1（xn＋αxn-τ））α]＋α]＋f（n,xn-σ1,xn-σ2,…,xn-σn）=0,n∈N,其中α为正奇数的商,m,u为大于等于2的整数,rn〉0,其中n∈N,α∈R,τ,σ1,σ2都为大于等于0的整数以及f∈C（[n0,∞]×R×R×…×R,R）。     

双交叉积A#σ上A及其辫化结构

设（Ａ,Ｈ,σ）是斜配对的,文章首先构造了双交叉积Ａ＃σＨ,特别地,Ｄｒｉｎｆｅｌ’ｄ偶Ｄ（Ｈ）就是这种双交叉积,即Ｄ（Ｈ）＝Ｈ＾＊ｃｏｐ＃σＨ,其中σ为赋值映射。其次,若一般双交叉积Ａα＃βＨ有辫子结构σ,则存在σ使得（Ａ,Ｈ,σ）是斜配对的,且Ａα＃βＨ＝Ａ＃αＨ。     

二元差分域上一阶差分方程的多项式解

本文研究了在二元域F(α,β)(α、β是域F上代数无关的超越元)上一阶线性差分方程aσ(f)+bf=g的多项式解f,式中a、b、g是二元域F(α,β)上的已知多项式,σ是域F(α,β)上满足σ(α)=β,σ(β)=uα+vβ的域同构,其中u,v≠0.通过多项式次数分解得到多项式解f存在的性质,然后根据待定系数法求得多项...     

关于H．W．Hethcote的一个猜想

H．W．Hethcote对SβSIEp(t)Iq(t)S型的不具免疫功能的传染病模型提出了猜想：当非零平衡态存在时，该平衡态是局部渐近稳定的。本文证明：在参数σ－α的平面内，其中：α＝β∫0^∞p(t)dt,σ=β∫0^∞q(t)dt的平面内除去区城U＝｛（σ，α），α＞σ，α＋1＞（σ－1）^2｝，猜想正确。     

一族解析函数的系数不等式和卷积性质

设σ∈R,0≤a,0≤β〈1,0〈μ,若函数f（z）∈A,满足条件｜arg[z（H^σf（z））＇/H^σf（z）＋（1-α）z/1-z -β]｜〈μπ/2,z∈D,则称f（z）属于A（σ,α,β,μ）,其中H^σf（z）=z＋Σ∞k-aαnz^n,文[1]讨论了函数族A（σ,α,β,μ）的极值问题,主要给出了该函数族的系数问题和其子类的卷积性质．     

Jackson整插值算子在Besov空间中的逼近

研究在Besov空间中,Jackson整插值算子的逼近和饱和问题,确定了逼近的饱和类与饱和阶.1)设f∈Hα∩Xp,则‖Iσ(f;x)-f(x)‖α=O1σ1-α当且仅当f绝对连续且f′∈Lp,(1相似文献   

TEM observation on nucleation of Ca α-Sialon

Ca α -Sialon compacts pressurelessly-sintered to the intermediate temperature (1 450℃) were investigated with TEM for an overall composition Ca_1.8Si_6.6Al_5.4O_1.8N_14.2. It was found that in most cases, the newly-formed α -Sialon grains had no epitaxial orientation relationship with the Si₃N₄ particles; only occasionally heteroepitaxial nucleation of α -Sialon on α -Si₃N₄ was detected. Further EDAX analysis revealed a much higher Ca concentration in the non-epi- taxially nucleated α -Sialon than in the heteroepitaxially nucleated α -Sialon. Thus a possible correlation between the concentration of metal cations in the α -Sialon structure and the nucleation mechanism has been proposed, i.e. α -Sialon compositions with higher Ca concentration show a stronger trend of non-epitaxial nucleation.     

Deformation mechanism of fine structure and its quantitative relationship with quasi-static mechanical properties in near β-type Ti-4.5Mo-5.1Al-1.8Zr-1.1Sn-2.5Cr −2.9Zn alloy

The deformation mechanism of the fine structure composed of primary α phase (α_p) and acicular secondary α phase (α_s) on quasi-static mechanical properties is still not very clear. The main controversy is focused on the role of α_p in the mechanical behavior. In this paper, the microstructure of the heat-treated near β-type Ti-4.5Mo-5.1Al-1.8Zr-1.1Sn-2.5Cr-2.9Zn alloy after tensile tests was observed by transmission electron microscopy (TEM). And the results showed that in the slight deformation region the dislocations were accumulated at the intersection of α_p and β matrix separated by α_s, while only a few dislocations nucleated in β matrix. In the severe deformation region, a large quantity of dislocations in both α_p and β matrix were observed. It can be inferred that α_p deformed firstly and then activated the deformation of β matrix, that is, the thickness of α_p and the inter-particle spacing of α_s played a dominant role in the deformation process. The quantitative relationship between the yield strength and the microstructure parameters is consistent with this inference. By adjusting the solution treatment parameters and the subsequent aging treatment, three fine structures were obtained, and the corresponding mechanical properties were determined. Furthermore, the yield strength can be described by the mathematical model σ_y ​= ​756.4 ​+ ​135.6/h_p^1/2 +32.2/d_s^1/2, where h_p and d_s are the thickness of α_p and the inter-particle spacing of α_s, respectively.     

Transition-metal-doped Fe2O3 nanoparticles for oxygen evolution reaction

Hematite(α-Fe_2O_3)has been extensively studied as a promising photocatalyst,with the capacity to split water under visible light.To tune its electronic structure and improve the performance for oxygen evolution reaction(OER),high-quality single crystals ofα-Fe_2O_3nanoparticles were synthesized and doped by various transition metals(M=V,Cr,Mn,Zn,Co,Ni,Cu,Nb,Mo,Ti)by a molten-salt flux method.Optical,electronic and catalytic properties of transition-metal-dopedα-Fe_2O_3(TM-dopedα-Fe_2O_3)have been systematically investigated.Cobalt has been identified as the best dopant forα-Fe_2O_3,reducing the OER overpotential by 0.16 V with respect to the undoped.     

The role of isotropic and anisotropic Hubbard corrections for the magnetic ordering and absolute band alignment of hematite α-Fe_2O_3(0001)surfaces

An isotropic (+U) and anisotropic [+(U-J)] corrected Density Functional Theory study for bulk hematite (α-Fe_2O_3) was carried out,and several competing terminations of its (0001) surface modeled via slabs of increasing thickness from twelve to thirty-six Fe-layers.In spite of small quantitative differences,the use of either U or (U-J)corrections showed not to qualitatively affect the results of the simulations both for bulkα-Fe_2O_3 and the lowestenergyα-Fe_2O_3(0001) surface studied,regardless of the thickness of the slab used.The energy favored antiferromagnetic ordering of bulkα-Fe_2O_3 was preserved in the relaxed slabs,with the largest surface-induced effects limited to the outermost three Fe-layers in the slabs.Mixed O-and Fe-terminations were found to be energetically favored and insulating.Conversely,fully O-or Fe-terminated surfaces were calculated to be energetically disfavored and metallic.Finally,the role of Fe-or O-termination for the semiconducting or metallic nature as well as absolute band alignment ofα-Fe_2O_3 (0001) surfaces was analyzed and discussed with respect to the challenges in enhancing the activity ofα-Fe_2O_3 samples as photo-electrode for water splitting.     

[[alpha]]-[[beta]]广义逆矩阵的一个表征及其反序性

该文讨论了[[alpha]]-[[beta]] 广义逆矩阵的一个表征,并给出了其反序性几个充分条件.     

嗜麦芽黄单胞菌催化生产α－熊果苷的菌种选育

利用硫酸二乙酯和紫外线对嗜麦芽黄单胞菌（Xanthomonas maltophilia ）复合诱变，初筛和复筛后，得到了转化率高且遗传性能稳定的α－熊果苷生产菌株BT-112。该菌株在以蔗糖为碳源、发酵液初始pH为7.5，温度为28℃，摇床转速为150r/min及发酵时间为48h的条件下,对苯二酚转化为α－熊果苷的转化率可达93.2％，比出发菌株转化率（73.0％）提高了27.7%。纯化产物经NMR鉴定，与标准品对比，确定为α－熊果苷。     

Spectroscopic properties of Er3+/Ho3+/Tm3+ doped α-SiAlON ceramics under 793 ​nm excitation

This paper reports the first demonstration of super broadband infrared downshifting emission extending from 1640 ​nm to 2200 ​nm with the full width at half maximum of ∼ 417 ​nm in lanthanides (Er³⁺, Ho³⁺, and Tm³⁺)-doped α-SiAlON ceramics upon 793 ​nm excitation. Using α-Si₃N₄ ceramic as a precursor the lanthanides-doped α-SiAlON ceramics were synthesized by the hot-press method. The lanthanides induced no significant secondary phases in the sintered α-SiAlON ceramics. Strong two-photon upconversion emission bands centered at 547, 671 and 694 ​nm have also been observed upon 793 ​nm excitation. The time-resolved measurements of the upconversion emissions confirm that the efficient energy transfer among the Er³⁺, Ho³⁺ and Tm³⁺ ions as well as the ground state absorption in Er³⁺ and Tm³⁺ are responsible for the observed spectroscopic properties.     

胶原Ⅳα1链NC1结构域基因的克隆及其在大肠杆菌中的表达

 胶原中多个成分如ⅩⅤ,ⅩⅤⅢ的NC结构域能抑制血管内皮细胞增殖和迁移,具有抑制肿瘤生长和转移的活性.从胎盘组织中提取总RNA,根据文献报道的胶原Ⅳα₁链cDNA序列,设计一对特异性引物,应用RT-PCR方法扩增出胶原Ⅳα₁链NC1结构域基因.DNA序列测定发现,扩增得到的基因与文献报道序列存在单个核苷酸变异(A132C),编码氨基酸(Gly)不变.将扩增得到的胶原Ⅳα₁链NC1结构域基因克隆到原核表达载体pPROEXHTb上,并在大肠杆菌BL21中进行体外表达.     

Epoxy/α-alumina nanocomposite with high electrical insulation performance

An experimental study was conducted to improve the electrical insulation of epoxy resin. The effects of boehmite, γ-alumina and α-alumina nanoparticles on the volume resistivity, dielectric strength and glass transition temperature of epoxy nanocomposites were investigated. The results showed that α-alumina nanoparticles displayed obvious advantages in enhancing electrical insulation performance of epoxy nanocomposites, compared to boehmite and γ-alumina nanoparticles. The direct current volume resistivity and breakdown strength of epoxy nanocomposite with 2.0 wt% α-alumina nanoparticles was improved to 2.2 × 10~(18)Ω cm and76.1 kV mm~(-1) respectively. And these improved values of electrical insulation properties are much higher than these of epoxy nanocomposites reported in previous studies. The main reason of these improvements may be that the epoxy/α-alumina interaction zone was enhanced by crosslink.     

螺旋槽端面干气密封的参数研究

螺旋槽干气密封试验分析了干气密封螺旋槽几何参数对开启力、功耗、泄漏率和气膜刚度的影响,并通过理论计算对试验数据给予了验证.理论计算和试验结果的对比表明了试验数据的可靠性.整体来讲,在其他参数固定的条件下,槽深比、螺旋角对密封性能的影响较为突出,而槽数、密封坝宽度比、槽台宽比、压力比对密封性能的影响相对较弱.最后给出密封结构和试验条件下的最优几何参数取值范围(12＜Ng＜18,14°＜β＜16°,0.4＜αg＜0.6,0.3＜l＜0.5,1.6＜δ＜1.8,10＜Pr＜20).