• Title/Summary/Keyword: Mid ring

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ON Φ-FLAT MODULES AND Φ-PRÜFER RINGS

  • Zhao, Wei
    • Journal of the Korean Mathematical Society
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    • v.55 no.5
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    • pp.1221-1233
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    • 2018
  • Let R be a commutative ring with non-zero identity and let NN(R) = {I | I is a nonnil ideal of R}. Let M be an R-module and let ${\phi}-tor(M)=\{x{\in}M{\mid}Ix=0\text{ for some }I{\in}NN(R)\}$. If ${\phi}or(M)=M$, then M is called a ${\phi}$-torsion module. An R-module M is said to be ${\phi}$-flat, if $0{\rightarrow}{A{\otimes}_R}\;{M{\rightarrow}B{\otimes}_R}\;{M{\rightarrow}C{\otimes}_R}\;M{\rightarrow}0$ is an exact R-sequence, for any exact sequence of R-modules $0{\rightarrow}A{\rightarrow}B{\rightarrow}C{\rightarrow}0$, where C is ${\phi}$-torsion. In this paper, the concepts of NRD-submodules and NP-submodules are introduced, and the ${\phi}$-flat modules over a ${\phi}-Pr{\ddot{u}}fer$ ring are investigated.

Friction Characteristics of Piston Assembly (II) -Experiment- (피스톤계 마찰 특성 (II) -실험적 연구-)

  • Cho, Myung-Rae;Ha, Kyoung-Pyo;Kim, Joong-Soo;Oh, Dae-Yoon;Han, Dong-Chul
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.27 no.1
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    • pp.88-93
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    • 2003
  • The aim of this paper is to investigate the friction characteristics of piston assembly, which composed of ring pack and piston skirt. The friction force of piston assembly was measured by using the movable liner in the single cylinder engine, and the various parameters were tested. The friction force was suddenly increased at the expansion stroke due to higher cylinder pressure. The viscous friction was dominant at the mid stroke, but the boundary friction was dominant at the top and bottom dead centers. Through the experiment, we could validate previous theoretical study, and confirm that th e radial clearance and ring tension were very effective to reduce friction loss of piston assembly.

ON THE ANNIHILATOR GRAPH OF GROUP RINGS

  • Afkhami, Mojgan;Khashyarmanesh, Kazem;Salehifar, Sepideh
    • Bulletin of the Korean Mathematical Society
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    • v.54 no.1
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    • pp.331-342
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    • 2017
  • Let R be a commutative ring with nonzero identity and G be a nontrivial finite group. Also, let Z(R) be the set of zero-divisors of R and, for $a{\in}Z(R)$, let $ann(a)=\{r{\in}R{\mid}ra=0\}$. The annihilator graph of the group ring RG is defined as the graph AG(RG), whose vertex set consists of the set of nonzero zero-divisors, and two distinct vertices x and y are adjacent if and only if $ann(xy){\neq}ann(x){\cup}ann(y)$. In this paper, we study the annihilator graph associated to a group ring RG.

A Case of Congenital Esophageal Stricture due to Ectopic Tracheal Cartilagenous Ring Complicated by Peptic Esophageal Stricture after Esophagogastrostomy (식도.위문합술후 소화성 식도협착이 합병된 이소성 연골환에 의한 선천성 식도협착증 1례 보고)

  • 유회성;이호일
    • Journal of Chest Surgery
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    • v.8 no.1
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    • pp.57-60
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    • 1975
  • Congenital esophageal stricture is infrequent disease entity and usually occurs in the mid esophagus. Tracheobronchial remnants in the esophagus causing esophageal stricture are extremely rare, and only few cases were reported in the literature. During last 17 years the authors experienced a case of congenital esophageal stricture due to ectopic tracheal cartilaginous ring who was complicated by peptic esophageal stricture 11 years after esophagogastrostomy. During thoracotomy we thought that the patient had unual achalasia of the esophagus, and couldn`t perform cardiomyotomy because of firm ring encircling the lower esophagus just above the hiatus. The patient was operated on lower esophagectomy including cardia and esophagogastrostomy at his age of two and a half years. Postoperatively the patient did well for 11 years but later he developed intermittent regurgitation without substernal burning, and reoperated under the diagnosis of peptic esophageal stricture-lower esophagectomy, proximal gastrectomy, esophagogastrostomy and Heineke-Mikulicz pyloroplasty with good operative result.

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MATRIX RINGS AND ITS TOTAL RINGS OF FRACTIONS

  • Lee, Sang-Cheol
    • Honam Mathematical Journal
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    • v.31 no.4
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    • pp.515-527
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    • 2009
  • Let R be a commutative ring with identity. Then we prove $M_n(R)=GL_n(R)$ ${\cup}${$A{\in}M_n(R)\;{\mid}\;detA{\neq}0$ and det $A{\neq}U(R)$}${\cup}Z(M-n(R))$ where U(R) denotes the set of all units of R. In particular, it will be proved that the full matrix ring $M_n(F)$ over a field F is the disjoint union of the general linear group $GL_n(F)$ of degree n over the field F and the set $Z(M_n(F))$ of all zero-divisors of $M_n(F)$. Using the result and universal mapping property we prove that $M_n(F)$ is its total ring of fractions.

FLOW ANALYSIS AND PERFORMANCE EVALUATION OF HIGH PRESSURE DOUBLE STAGE RING BLOWER (고압 이단 링블로워의 삼차원 유동해석 및 성능평가)

  • Lee, K.D.;Kim, K.Y.
    • Journal of computational fluids engineering
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    • v.12 no.4
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    • pp.85-89
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    • 2007
  • In the present work, flow analysis has been performed for side channel type double stage ring blower by solving three-dimensional Reynolds-averaged Navier-Stokes equation. Shear stress transport model is used as turbulent closure. The commercial CFD code CFX 11.0 is used for the calculations. Each of two stage is calculated separately and the second stage inlet flow is same as the first stage outlet flow so that consecutive calculation is possible. Velocity and pressure fields have been analyzed at the mid-plane between blades. The numerical results are validated with experimental data for head coefficients at different flow coefficients.

Band-like Annular Pericardial Calcification -A case report - (띠 모양의 윤상 심막 석회화)

  • 조양현;류세민;조종호;손영상;최영호;김요한;김학제
    • Journal of Chest Surgery
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    • v.37 no.5
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    • pp.452-455
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    • 2004
  • We report a case of a 40-year-old woman whose right ventricular out-flow tract was moderately obstructed by a heavily calcified pericardial ring. It was passing over the base of pulmonary artery and mid-portion of left ventricle but the other parts of the pericardium was mildly fibrotic. The pericardium and calcified ring were completely removed under cardiopulmonary bypass. The patient was recovered uneventfully and we could not find the specific cause of calcified pericardial ring.

Sound Intensity Control in a Duct Using Smart Foam (스마트 폼을 이용한 덕트 내의 음향 인텐시티 제어)

  • 한제헌;강연준
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2001.11b
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    • pp.1132-1137
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    • 2001
  • The smart foam that is first proposed by Fuller(2) is not applicable to active noise control in a duct having flow. Thus. this paper presents the ring-type smart foam as an alternative. The ring-type smart foam consists of polyurethane acoustic foam of lining shape and PVDF film embedded along the mid-surface of the foam lining. A feedforward adaptive filtered-x LMS controller is used to minimize the signal from the error microphone. To enlarge quiet sound region. two error microphones are used to update system modeling filter (SIMO method). Sound intensity control using the ring-type smart foam is also discussed

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Inelastic general instability of ring-stiffened circular cylinders and cones under uniform external pressure

  • Ross, C.T.F.
    • Structural Engineering and Mechanics
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    • v.5 no.2
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    • pp.193-207
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    • 1997
  • Experimental tests are described on three ring stiffened machined circular cylinders and three ring stiffened machined circular cones, which were tested to destruction under uniform external pressure. All six vessels failed by inelastic general instability. The experiments showed that the vessels initially deformed plastically at mid-bay in the circumferential direction, and this caused the circumferential tangent modulus to become much less than the elastic Young's modulus, causing the vessels to fail through plastic general instability at pressures much less than that predicted by elastic theory. Based on a thinness ratio, two semi-empirical design charts are provided, which are intended to be used for design purposes in conjunction with the finite element method and a plastic reduction factor.

ON RINGS WHOSE ANNIHILATING-IDEAL GRAPHS ARE BLOW-UPS OF A CLASS OF BOOLEAN GRAPHS

  • Guo, Jin;Wu, Tongsuo;Yu, Houyi
    • Journal of the Korean Mathematical Society
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    • v.54 no.3
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    • pp.847-865
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    • 2017
  • For a finite or an infinite set X, let $2^X$ be the power set of X. A class of simple graph, called strong Boolean graph, is defined on the vertex set $2^X{\setminus}\{X,{\emptyset}\}$, with M adjacent to N if $M{\cap}N={\emptyset}$. In this paper, we characterize the annihilating-ideal graphs $\mathbb{AG}(R)$ that are blow-ups of strong Boolean graphs, complemented graphs and preatomic graphs respectively. In particular, for a commutative ring R such that AG(R) has a maximum clique S with $3{\leq}{\mid}V(S){\mid}{\leq}{\infty}$, we prove that $\mathbb{AG}(R)$ is a blow-up of a strong Boolean graph if and only if it is a complemented graph, if and only if R is a reduced ring. If assume further that R is decomposable, then we prove that $\mathbb{AG}(R)$ is a blow-up of a strong Boolean graph if and only if it is a blow-up of a pre-atomic graph. We also study the clique number and chromatic number of the graph $\mathbb{AG}(R)$.