scholarly journals Properties of the fixed ring of a preprojective algebra

2019 ◽  
Vol 517 ◽  
pp. 276-319 ◽  
Author(s):  
Stephan Weispfenning
Keyword(s):  
Preprojective Algebra ◽  
Fixed Ring

scholarly journals Impact-Rubbing Dynamic Behavior of Magnetic-Liquid Double Suspension Bearing under Different Protective Bearing Forms

Processes ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 1105
Author(s):  
Jianhua Zhao ◽  
Lanchun Xing ◽  
Sheng Li ◽  
Weidong Yan ◽  
Dianrong Gao ◽  
...  
Keyword(s):  
Dynamic Behavior ◽  
Ball Bearing ◽  
Magnetic Liquid ◽  
Electromagnetic System ◽  
Fixed Ring ◽  
Deep Groove ◽  
Deep Groove Ball Bearing ◽  
Protection Devices ◽  
Hydrostatic System ◽  
The Impact

The magnetic-liquid double suspension bearing (MLDSB) is a new type of suspension bearing, with electromagnetic suspension as the main part and hydrostatic supports as the auxiliary part. It can greatly improve the bearing capacity and stiffness of rotor-bearing systems and is suitable for a medium speed, heavy load, and frequent starting occasions. Compared with the active electromagnetic bearing system, the traditional protective bearing device is replaced by the hydrostatic system in MLDSB, and the impact-rubbing phenomenon can be restrained and buffered. Thus, the probability and degree of friction and wear between the rotor and the magnetic pole are reduced drastically when the electromagnetic system fails. In order to explore the difference in the dynamic behavior law of the impact-rubbing phenomenon between the traditional protection device and hydrostatic system, the dynamic equations of the rotor impact-rubbing in three kinds of protection devices (fixed ring/deep groove ball bearing/hydrostatic system) under electromagnetic failure mode are established, and the axial trajectory and motion law of the rotor are numerically simulated. Finally, the dynamic behavior characteristics of the rotor are compared and analyzed. The results show that: Among the three kinds of protection devices (fixed ring/deep groove ball bearing/hydrostatic system), the hydrostatic system has the least influence on bouncing time, impact-rubbing force, and impact-rubbing degree, and the maximum impact-rubbing force of MLDSB is greatly reduced. Therefore, the protective bear is not required to be installed in the MLDSB. This study provides the basis for the theory of the “gap impact-rubbing” of MLDSB under electromagnetic failure, and helps to identify electromagnetic faults.

scholarly journals ON INTEGRALITY AND GOING-DOWN INSIDE THE FIXED RING OF A MONOID RING

2016 ◽  
Vol 19 (19) ◽  
pp. 132-132
Author(s):  
David E. Dobbs ◽  
Jay Shapiro
Keyword(s):  
Monoid Ring ◽  
Fixed Ring

Generalized Casimir Operators

1969 ◽  
Vol 21 ◽  
pp. 1496-1505
Author(s):  
A. J. Douglas
Keyword(s):  
Finite Group ◽  
Casimir Operator ◽  
Identity Element ◽  
Ring Homomorphism ◽  
Fixed Ring ◽  
Injective Modules ◽  
Casimir Operators ◽  
Maschke’S Theorem ◽  
A Finite Group ◽  
Special Case

Throughout this paper, S will be a ring (not necessarily commutative) with an identity element ls ≠ 0s. We shall use R to denote a second ring, and ϕ: S→ R will be a fixed ring homomorphism for which ϕ1S = 1R.In (7), Higman generalized the Casimir operator of classical theory and used his generalization to characterize relatively projective and injective modules. As a special case, he obtained a theorem which contains results of Eckmann (3) and of Higman himself (5), and which also includes Gaschütz's generalization (4) of Maschke's theorem. (For a discussion of some of the developments of Maschke's idea of averaging over a finite group, we refer the reader to (2, Chapter IX).) In the present paper, we define the Casimir operator of a family of S-homomorphisms of one R-module into another, and we again use this operator to characterize relatively projective and injective modules.

scholarly journals Inertial subalgebras of algebras possessing finite automorphism groups

1979 ◽  
Vol 28 (3) ◽  
pp. 335-345 ◽  
Author(s):  
Nicholas S. Ford
Keyword(s):  
Finite Group ◽  
Commutative Ring ◽  
Jacobson Radical ◽  
Automorphism Groups ◽  
Sufficient Conditions ◽  
Necessary And Sufficient Conditions ◽  
Finitely Generated ◽  
Fixed Ring ◽  
A Finite Group ◽  
Necessary And Sufficient

AbstractLet R be a commutative ring with identity, and let A be a finitely generated R-algebra with Jacobson radical N and center C. An R-inertial subalgebra of A is a R-separable subalgebra B with the property that B+N=A. Suppose A is separable over C and possesses a finite group G of R-automorphisms whose restriction to C is faithful with fixed ring R. If R is an inertial subalgebra of C, necessary and sufficient conditions for the existence of an R-inertial subalgebra of A are found when the order of G is a unit in R. Under these conditions, an R-inertial subalgebra B of A is characterized as being the fixed subring of a group of R-automorphisms of A. Moreover, A ⋍ B ⊗R C. Analogous results are obtained when C has an R-inertial subalgebra S ⊃ R.

scholarly journals Analysis on the Force and Life of Gearbox in Double-Rotor Wind Turbine

Energies ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 4220 ◽  
Author(s):  
Yaru Yang ◽  
Hua Li ◽  
Jin Yao ◽  
Wenxiang Gao ◽  
Haiyan Peng
Keyword(s):  
Renewable Energy ◽  
Life Span ◽  
Wind Turbine ◽  
Structural Parameters ◽  
Total Power ◽  
National Renewable Energy Laboratory ◽  
Ring Gear ◽  
Fixed Ring ◽  
Planet Gear ◽  
Planetary Transmission

In order to study the force and life of the key components in the gearbox of an existing double-rotor wind turbine, the design and structural parameters of the gearbox in the traditional National Renewable Energy Laboratory (NREL) 5 MW single-rotor wind turbine are adopted, and the fixed ring gear of the first planetary stage transmission is released to form a differential gearbox suitable for a double-rotor wind turbine with two inputs. The double input is used to connect the double rotor. Subsequently, the characteristics of the gearbox in a double-rotor wind turbine are discussed. On the basis of the constant rated power of the whole wind turbine, the total power is divided into two parts, which are allocated to the double rotors, then two rotational speeds of the two inputs are given according to different power ratios by complying with the matching principle of force and moment. Furthermore, the force acting on the pitch circle of the planet gear, as well as the force and life of the planet bearing of the two-stage planetary transmission are calculated and compared with a single-rotor wind turbine. The results show that the structural advantages of a double-rotor wind turbine can reduce the stress of key components of the gearbox and increase the life span of the planet bearing, thereby the life of the whole gearbox is improved and the downtime of the whole wind turbine is reduced.

Definability problems for modules and rings

1971 ◽  
Vol 36 (4) ◽  
pp. 623-649 ◽  
Author(s):  
Gabriel Sabbagh ◽  
Paul Eklof
Keyword(s):  
Ring Theory ◽  
Noetherian Rings ◽  
Fixed Ring ◽  
Injective Modules ◽  
Free Left ◽  
Right Noetherian Rings ◽  
The Right

This paper is concerned with questions of the following kind: let L be a language of the form Lαω and let be a class of modules over a fixed ring or a class of rings; is it possible to define in L? We will be mainly interested in the cases where L is Lωω or L∞ω and is a familiar class in homologic algebra or ring theory.In Part I we characterize the rings Λ such that the class of free (respectively projective, respectively flat) left Λ-modules is elementary. In [12] we solved the corresponding problems for injective modules; here we show that the class of injective Λ-modules is definable in L∞ω if and only if it is elementary. Moreover we identify the right noetherian rings Λ such that the class of projective (respectively free) left Λ-modules is definable in L∞ω.

Effects of gear type, entrance size and soak time on trap efficiency for freshwater crayfish Cherax destructor and C. albidus

2015 ◽  
Vol 66 (11) ◽  
pp. 989
Author(s):  
Paul Brown ◽  
Taylor L. Hunt ◽  
Khageswor Giri
Keyword(s):  
Field Experiments ◽  
Freshwater Crayfish ◽  
Recreational Fisheries ◽  
Air Breathing ◽  
Fixed Ring ◽  
Cherax Destructor ◽  
Fishing Gears ◽  
Opera House ◽  
By Catch ◽  
Aquatic Mammals

Freshwater crayfish support significant commercial and recreational fisheries worldwide. The genus Cherax is fished in Australia with a variety of fishing gears, yet little is known of the relative efficiency of the different fishing gears and methods. Additionally, freshwater-crayfish traps can pose a risk to air breathing by-catch such as aquatic mammals, reptiles and birds, so by-catch mitigation is important. We sought to understand whether freshwater-crayfish fishing can be undertaken efficiently, using passive traps and nets, without undue risk to air-breathing by-catch species. In field-experiments, we compared the efficiency of six gear types and tested the effect of five exclusion rings on catch performance over three soak times. The efficiency of gear types varied significantly by soak times. In productive locations, catch can be maximised by repeatedly deploying open-topped gear for short soak times. Opera-house traps fitted with fixed entrance rings (45–85-mm diameter) were not size-selective for yabbies. Encouragingly, open-topped gear and opera-house traps fitted with fixed ring entrances much smaller than many commercially available (45-mm diameter) still fish effectively for yabbies. We believe that smaller fixed ring-entrance size is likely to be correlated with a reduced risk of by-catch for air-breathing fauna.

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