不同浓度的尾砂胶结充填体破坏过程 声发射特性试验研究*

制备了3种不同质量浓度的充填体试件，进行了单轴压缩声发射试验，分析了不同浓度的充填体力学特性，重点研究了试件破坏过程中的声发射振铃计数、声发射累计撞击数与声发射累计能量的比值(r值)、主频及其相对高频信号激增响应系数特征。研究表明：随着浓度的增加，充填体的峰值强度与弹性模量呈增大趋势，充填体中出现的声发射累计振铃计数越多；r值先升高再持续减小到一个较低值，随着外载荷的增加，进入缓慢升高阶段，峰值前均保持在该阶段。充填体破裂前兆信息在声发射信号主频分布中呈现主频段增多现象，表现为由加载初期的1~2个主频段，在临界主破裂时增多到3~5个主频段；且随着浓度的增加，声发射信号主频频段分布越宽，声发射相对高频信号(160~180 kHz)的激增响应系数呈递减趋势。以上特征可为不同浓度的尾砂胶结充填体稳定性监测、预测提供依据。     

Change of grading,injective dimension and dualizing complexes

Let G,H be groups, φ:G→H a group morphism, and A a G-graded algebra. The morphism φ induces an H-grading on A, and on any G-graded A-module, which thus becomes an H-graded A-module. Given an injective G-graded A-module, we give bounds for its injective dimension when seen as H-graded A-module. Following ideas by Van den Bergh, we give an application of our results to the stability of dualizing complexes through change of grading.     

Gorenstein injective envelopes and covers over two sided noetherian rings

We prove that the class of Gorenstein injective modules is both enveloping and covering over a two sided noetherian ring such that the character modules of Gorenstein injective modules are Gorenstein flat. In the second part of the paper we consider the connection between the Gorenstein injective modules and the strongly cotorsion modules. We prove that when the ring R is commutative noetherian of finite Krull dimension, the class of Gorenstein injective modules coincides with that of strongly cotorsion modules if and only if the ring R is in fact Gorenstein.     

Hochster’s small MCM conjecture for three-dimensional weakly F-split rings

We prove Hochster’s small maximal Cohen–Macaulay conjecture for three-dimensional complete F-pure rings. We deduce this from a more general criterion, and show that only a weakening of the notion of F-purity is needed, to wit, being weakly F-split. We conjecture that any complete ring is weakly F-split.     

Simple-direct-modules

A right R-module M is called simple-direct-injective if, whenever, A and B are simple submodules of M with A?B, and B?^⊕M, then A?^⊕M. Dually, M is called simple-direct-projective if, whenever, A and B are submodules of M with M∕A?B?^⊕M and B simple, then A?^⊕M. In this paper, we continue our investigation of these classes of modules strengthening many of the established results on the subject. For example, we show that a ring R is uniserial (artinian serial) with J²(R) = 0 iff every simple-direct-projective right R-module is an SSP-module (SIP-module) iff every simple-direct-injective right R-module is an SIP-module (SSP-module).     

A tensor product of the Steinberg module and a certain simple kG(pr)-module

Let G be a connected, semisimple, and simply connected algebraic group defined and split over the finite field of order p, and let G(q) be the corresponding finite Chevalley or twisted group, where q = p^r. Recently, Anwar determines the direct sum decomposition of the tensor product of the rth Steinberg module and a simple G-module with a (p,r)-minuscule highest weight λ. In this paper, we determine that of the tensor product regarded as a module for G(q) under some weak assumptions for λ.     

Frontispiece: Cationic Tetrylene-Iron(0) Complexes: Access Points for Cooperative,Reversible Bond Activation and Open-Shell Iron(−I) Ferrato-Tetrylenes

The open-shell cationic stannylene-iron(0) complex 4 ( 4 =[^PhiPDippSn⋅Fe⋅IPr]⁺; ^PhiPDipp={[Ph₂PCH₂Si(ⁱPr)₂](Dipp)N}; Dipp=2,6-ⁱPr₂C₆H₃; IPr=[(Dipp)NC(H)]₂C:) cooperatively and reversibly cleaves dihydrogen at the Sn−Fe interface under mild conditions (1.5 bar, 298 K), in forming bridging hydrido-complex 6 . The One-electron oreduction of the related Ge^II−Fe⁰ complex 3 leads to oxidative addition of one C−P linkage of the ^PhiPDipp ligand in an intermediary Fe^−I complex, leading to Fe^I phosphide species 7 . One-electron reduction reaction of 4 gives access to the iron(−I) ferrato-stannylene, 8 , giving evidence for the transient formation of such a species in the reduction of 3 . The covalently bound tin(II)-iron(−I) compound 8 has been characterised through EPR spectroscopy, SQUID magnetometry, and supporting computational analysis, which strongly indicate a high localization of electron spin density at Fe^−I in this unique d⁹-iron complex.