Checking of Radially Sawn Scots Pine and Norway Spruce Wood

In exterior use, wood is subjected to weathering that causes checking and other deterioration in the appearance and technical properties. We studied quantitatively the surface checking of radially and tangentially sawn specimens of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies Karst.) wood in a cyclic climate chamber test. The results strongly suggested that the sawing direction determines the checking performance of both Scots pine and Norway spruce wood. The radial surface of Scots pine specimens had 62% less checks than the tangential one, and the cumulative area of checks was 74% smaller. For Norway spruce, the respective figures were: 83% less in the check number and 91% less in the check area. Different from pine, in spruce specimens the checks of radial surface were significantly smaller. Thus, spruce timber gained clearly more about radial sawing pattern. The effect of annual ring width was similar for pine and spruce: the reduction in annual growth worsened the checking. The increase in density worsened the checking of spruce but did not change the performance of pine. In pine wood, the increase of heartwood proportion reduced the fluctuation of moisture content and the formation of checks.

Endomorphism Algebras of Support τ-Tilting Modules

Let A be a finite dimensional k-algebra and T be a supportτ-tilting right A-module.In this note,we give lower and upper bounds for the global dimension of the endomorphism algebra End_(A)(T)under some mild conditions.Finally,we give some examples to illustrate that both the upper and lower bounds can be reached.

Relative homological dimensions in recollements of triangulated categories

Let E be a proper class of triangles in a triangulated category C, and let (A, B, C) be a recollement of triangulated categories. Based on Beligiannis's work, we prove that A and C have enough E-projective objects whenever B does. Moreover, in this paper, we give the bounds for the E-global dimension of B in a recollement (A, B, C) by controlling the behavior of the E-global dimensions of the triangulated categories A and C: In particular, we show that the finiteness of the E-global dimensions of triangulated categories is invariant with respect to the recollements of triangulated categories.

Recollements arising from cotorsion pairs on extriangulated categories

This paper is devoted to constructing some recollements of additive categories associated to concentric twin cotorsion pairs on an extriangulated category.As an application,this result generalizes the work by W.J.Chen,Z.K.Liu,and X.Y.Yang in a triangulated case[J.Algebra Appl.,2018,17(5):1-15].Moreover,it highlights new phenomena when it applied to an exact category.Finally,we give some applications of our main results.In particular,we obtain Krause's recollement whose proofs are both elementary and very general.

幂等子代数上的支撑τ-倾斜模

设A是数域k上的有限维代数, e是A中的幂等元.本文证明了,如果A/AeA是左投射A-模,则有限生成右eAe-模T是支撑τ-倾斜模当且仅当T■eAe eA是A上的支撑τ-倾斜模.另一方面,如果A是遗传代数, T是支撑τ-倾斜A-模, A/AeA是右投射A-模,则Hom_(A)(eA, T)是支撑τ-倾斜eAe-模.作为应用,本文证明了,若代数A是τ-倾斜有限的,则幂等子代数eAe也是τ-倾斜有限的.