A Construction of Characteristic Tilting Modules

Associated with each finite directed quiver Q is a quasi-hereditary algebra, the so-called twisted double of the path algebra kQ. Characteristic tilting modules over this class of quasi-hereditary algebras are constructed. Their endomorphism algebras are explicitly described. It turns out that this class of quasi-hereditary algebras is closed under taking the Ringel dual. Received November 15, 2000, Accepted March 5, 2001     

粒子入射角度对冷喷涂涂层形成的影响

采用有限元数值计算方法，研究冷喷涂材料改性过程中铜粒子与铜基体非垂直碰撞的变形行为。针对单个粒子相同入射速度不同入射角度的碰撞条件，探讨粒子与基体的结合强度、侵彻深度以及绝热剪切失稳的发生条件。结果表明:随着粒子入射角度的增大，侵彻深度逐渐减少，粒子与基体的结合强度逐渐减弱。发生绝热剪切失稳的条件是入射速度的法向分量大于碰撞过程的临界速度。     

四瓦可倾瓦径向滑动轴承动力特性的实验研究

采用在线分析方法考察了300MW汽轮发电机可倾瓦轴承的静、动力特性,探讨了载荷、轴颈转速以及动态激振力频率等参数变化对可倾瓦轴承的静、动态性能的影响,比较试验结果与理论计算结果发现,在不同频率激振力作用下,理论计算所得到的可倾瓦轴承动特性参数与试验结果有较大的差异。     

Ordered perovskites in the A(Li1/4Nb3/4)O3-A(Li2/5W3/5)O3 (A=Sr, Ca) systems

Single-phase 1:2 B-site ordered perovskites are formed in the (1−x)A²⁺(Li_1/4Nb_3/4)O₃-(x)A²⁺(Li_2/5W_3/5)O₃ systems, A²⁺=Sr and Ca, within the range 0.238?x?0.333. The X-ray and electron diffraction patterns are consistent with a P2₁/c monoclinic supercell, , , , β≈125°, where the 1:2 order is combined with b⁻b⁻c⁺ octahedral tilting. Rietveld refinements of the ordered A(B^I_1/3B^II_2/3)O₃ structures give a good fit to a model with B^I occupied by Li and Nb, B^II by W and Nb, and a general stoichiometry (Sr,Ca)(Li_3/4+y/2Nb_1/4−y/2)_1/3(Nb_1−yW_y)_2/3O₃, y=0.9x=0.21-0.30. The Sr system also includes regions of stability of a 1:3 ordered phase for 0.0?x?0.111, and a 1:1 ordered double perovskite for 0.833?x?1.0. The formation of the non-stoichiometric 1:2 ordered phases is associated with the large site charge/size differences that can be accessed in these systems, and restricted by local charge imbalances at the A-sites for W-rich compositions. These concepts are used to generate stability maps to rationalize the formation of the known 1:2 ordered oxide perovskites.     

Convergence of the Gram-Charier expansion after the normalizing Box-Cox transformation

Consider an exponential family such that the variance function is given by the power of the mean function. This family is denoted by ED if the variance function is given by ^(2-)/(1-), where is the mean function. When 0<1, it is known that the transformation of ED⁽⁾ to normality is given by the power transformationX ^(1-2)/(3-3), and conversely, the power transformation characterizes ED⁽⁾. Our principal concern will be to show that this power transformation has an another merit, i.e., the density of the transformed variate has an absolutely convergent Gram-Charier expansion.     

Cluster-tilted algebras

We introduce a new class of algebras, which we call cluster-tilted. They are by definition the endomorphism algebras of tilting objects in a cluster category. We show that their representation theory is very close to the representation theory of hereditary algebras. As an application of this, we prove a generalised version of so-called APR-tilting.

     

三角矩阵代数的倾斜模

设R=（^A 0 ^M B）是三角矩阵代数,关于倾斜A-模T1,倾斜B-模T2何时能扩充为倾斜R-模的问题已有讨论．本文考察了倾斜R-模在Cokernel函子下是否还是倾斜模的问题．得到了如下结论：如果（X,Y,f）是倾斜R-模,f是单射,则Cok（y）中倾斜B-模．从而给出了单点扩张代数的倾斜模的结构．     

具有性质(G'_k)的Wakamatsu倾斜模

本文引进了具有性质(G'k)的Wakamatsu倾斜模的概念,并用同调有限子范畴的性质对其进行了刻画．     

Hereditary noetherian categories with a tilting complex

We are characterizing the categories of coherent sheaves on a weighted projective line as the small hereditary noetherian categories without projectives and admitting a tilting complex. The paper is related to recent work with de la Peña (Math. Z., to appear) characterizing finite dimensional algebras with a sincere separating tubular family, and further gives a partial answer to a question of Happel, Reiten, Smalø (Mem. Amer. Math. Soc. 120 (1996), no. 575) regarding the characterization of hereditary categories with a tilting object.