• Title/Summary/Keyword: cyclic group

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FINITE GROUPS WITH A CYCLIC NORM QUOTIENT

  • Wang, Junxin
    • Bulletin of the Korean Mathematical Society
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    • v.53 no.2
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    • pp.479-486
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    • 2016
  • The norm N(G) of a group G is the intersection of the normalizers of all the subgroups of G. In this paper, the structure of finite groups with a cyclic norm quotient is determined. As an application of the result, an interesting characteristic of cyclic groups is given, which asserts that a finite group G is cyclic if and only if Aut(G)/P(G) is cyclic, where P(G) is the power automorphism group of G.

A STUDY ON THE CYCLIC AMP IN THE ALVEOLAR BONE OF RATS APPLIED BY ORTHODONTIC FORCES IN EXPERIMENTAL DIABETES AND INSULIN TREATMENT (실험적 당뇨 백서에서 교정력에 의한 치조골의 Cyclic AMP의 변화에 관한 연구)

  • Baek, Il-Soo;Sohn, Byung-Hwa
    • The korean journal of orthodontics
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    • v.16 no.2
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    • pp.53-67
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    • 1986
  • The physical tooth movement by orthodontic force is based upon alveolar bone resorption at compression site and new bone formation at tension site of the alveolar socket. The function of the cyclic AMP is to participate not only in initial action of bone cells by mechanical forces but also in the continuous cellular response leading to bone remodelling. This experiment was performed to clarify the role of cyclic AMP in bone remodelling by mechanical force in the NORMAL group, the DIABETES group and the INSULIN TREATED group. The 72 rats were divided into the NORMAL group, the DIABETES group and the INSULIN TREATED group. The same orthodontic forces were applied to the rats of 3 groups. These rats were treated for periods of time ranging from 1 hour, 1 day, 7 days, 14 days, 21 days and 28 days. The samples of alveolar bones were obtained from compression and tension sites surrounding the tipping teeth from NORMAL, DIABETE and INSULIN TREATED rats. The samples were assayed for cyclic AMP by the cyclic AMP RIA kit. The results were as follows: 1. The cyclic AMP levels of alveolar bone in compression and tension sites showed initial decrease, then increased and .remained elevated by the time consuming. 2. The highest cyclic AMP level showed in the DIABETES group and the lowest level was in the NORMAL group. 3. The cyclic AMP levels in the INSULIN TREATED group was similar with the NORMAL group in control and tension sites, but in the compression sites it was similar with the DIABETES group.

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CYCLIC PRESENTATIONS OF GROUPS AND CYCLIC BRANCHED COVERINGS OF (1, 1)-KNOTS

  • Mulazzani, Michele
    • Bulletin of the Korean Mathematical Society
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    • v.40 no.1
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    • pp.101-108
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    • 2003
  • In this paper we study the connections between cyclic presentations of groups and cyclic branched coverings of (1, 1)- knots. In particular, we prove that every π-fold strongly-cyclic branched covering of a (1, 1)-knot admits a cyclic presentation for the fundamental group encoded by a Heegaard diagram of genus π.

Effect of adaptive motion on cyclic fatigue resistance of a nickel titanium instrument designed for retreatment

  • Ozyurek, Taha;Yilmaz, Koray;Uslu, Gulsah
    • Restorative Dentistry and Endodontics
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    • v.42 no.1
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    • pp.34-38
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    • 2017
  • Objectives: The aim of this study was to evaluate the cyclic fatigue resistance of the ProTaper Universal D1 file (Dentsply Maillefer) under continuous and adaptive motion. Materials and Methods: Forty ProTaper Universal D1 files were included in this study. The cyclic fatigue tests were performed using a dynamic cyclic fatigue testing device, which had an artificial stainless steel canal with a $60^{\circ}$ angle of curvature and a 5 mm radius of curvature. The files were randomly divided into two groups (Group 1, Rotary motion; Group 2, Adaptive motion). The time to failure of the files were recorded in seconds. The number of cycles to failure (NCF) was calculated for each group. The data were statistically analyzed using Student's t-test. The statistical significant level was set at p < 0.05. Results: The cyclic fatigue resistance of the adaptive motion group was significantly higher than the rotary motion group (p < 0.05). Conclusion: Within the limitations of the present study, the 'Adaptive motion' significantly increased the resistance of the ProTaper Universal D1 file to cyclic facture.

Response of a laterally loaded pile group due to cyclic loading in clay

  • Shi, Jiangwei;Zhang, Yuting;Chen, Long;Fu, Zhongzhi
    • Geomechanics and Engineering
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    • v.16 no.5
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    • pp.463-469
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    • 2018
  • In offshore engineering, lateral cyclic loading may induce excessive lateral movement and bending strain in pile foundations. Previous studies mainly focused on deformation mechanisms of single piles due to lateral cyclic loading. In this paper, centrifuge model tests were conducted to investigate the response of a $2{\times}2$ pile group due to lateral cyclic loading in clay. After applying each loading-unloading cycle, the pile group cannot move back to its original location. It implies that residual movement and bending strain are induced in the pile group. This is because cyclic loading induces plastic deformation in the soil surrounding the piles. As the cyclic load increases from 62.5 to 375 kN, the ratio of the residual to the maximum pile head movements varies from 0.30 to 0.84. Moreover, the ratio of the residual to the maximum bending strains induced in the piles is in a range of 0.23 to 0.82. The bending strain induced in the front pile is up to 3.2 times as large as that in the rear pile. Thus, much more protection measures should be applied to the front piles to ensure the serviceability and safety of pile foundations.

THE INFLUENCE OF ABUTMENT SCREW TIGHTENING TIMING AND DLC COATING OF CONICAL CONNECTION IMPLANT SYSTEM (일체형 지대주의 Diamond Like Carbon 표면 처리와 나사 조임 시기가 풀림 현상에 미치는 영향)

  • Kim, Ki-Hong;Koak, Jai-Young;Heo, Seong-Joo
    • The Journal of Korean Academy of Prosthodontics
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    • v.46 no.2
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    • pp.209-216
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    • 2008
  • Statement of problem: It is difficult about assessing the loosening tendency of conical connection type implant after cyclic loading with diamond like carbon coating one-piece abutments, and also about the retightening effect. Purpose: This study was performed to investigate the influence of one-piece abutment screw retightening after $5.0{\times}10^{4}$ cyclic loading and Diamond like coating Material and methods: Thirty two ITI implant were divided to 4 groups. Group 1,3-titanium abutment, group 2,4 - diamond like carbon coated abutment. Group 1,2 - $20.0{\times}10^{4}$ cyclic loading after $5.0{\times}10^{4}$ cyclic loading, Group 3,4- after $20.0{\times}10^{4}$ Cyclic loading. After cyclic loading, periotest values were taken and removal torque values of abutments were measured with a digital torque gauge. Results: 1. The removal torque of group 2 after $5.0{\times}10^{4}$ cyclic loading is slightly greater than the other groups but not significantly higher than others (P>0.05). 2. The final removal torque values after $20.0{\times}10^{4}$ cyclic loading of group 1 is bigger than group 3, and group 2 is bigger than group 4, but not significantly higher (P>0.05). 3. The final removal torque values after $20.0{\times}10^{4}$ cyclic loading of all groups are not significantly different (P>0.05).

THE UNITS AND INEMPOTENTS IN THE GROUP RING OF A FINITE CYCLIC GROUP

  • Park, Won-Sun
    • Communications of the Korean Mathematical Society
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    • v.12 no.4
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    • pp.855-864
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    • 1997
  • Let K be a algebraically closed field of characteristic 0 and G a cyclic group of order n. We find the units and idempotent elements of the group ring KG by using the basic group table matrix of G.

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THE ASSESSMENT OF ABUTMENT SCREW STABILITY BETWEEN THE EXTERNAL AND INTERNAL HEXAGONAL JOINT UNDER CYCLIC LOADING

  • Lee, Tae-Sik;Han, Jung-Suk;Yang, Jae-Ho;Lee, Jae-Bong;Kim, Sung-Hun
    • The Journal of Korean Academy of Prosthodontics
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    • v.46 no.6
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    • pp.561-568
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    • 2008
  • STATEMENT OF PROBLEM: Currently, many implant systems are developed and divided into two types according to their joint connection: external or internal connection. Regardless of the connection type, screw loosening is the biggest problem in implant-supported restoration. PURPOSE: The purpose of this study is to assess the difference in stability of abutment screws between the external and internal hexagonal connection types under cyclic loading. MATERIAL AND METHODS: Each of the 15 samples of external implants and internal abutments were tightened to 30 N/cm with a digital torque gauge, and cemented with a hemispherical metal cap. Each unit was then mounted in a $30^{\circ}$ inclined jig. Then each group was divided into 2 sub-groups based on different periods of cyclic loading with the loading machine (30 N/ cm - 300 N/cm,14 Hz: first group $1{\times}10^6$, $5{\times}10^6$ cyclic loading; second group $3{\times}10^6$, $3{\times}10^6$ for a total cyclic loading of $6{\times}10^6$) The removal torque value of the screw before and after cyclic loading was checked. SPSS statistical software for Windows was used for statistical analysis. Group means were calculated and compared by ANOVA, independent t-test, and paired t-test with ${\alpha}$=0.05. RESULTS: In the external hexagonal connection, the difference between the removal torque value of the abutment screw before loading, the value after $1{\tims}10^6$ cyclic loading, and the value after $1{\times}10^6$, and additional $5{\times}10^6$ cyclic loading was not significant. The difference between the removal torque value after $3{\times}10^6$ cyclic loading and after $3{\times}10^6$, and additional $3{\times}10^6$ cyclic loading was not significant. In the internal hexagonal connection, the difference between the removal torque value before loading and the value after $1{\times}10^6$ cyclic loading was not significant, but the value after $1{\times}10^6$, and additional $5{\times}10^6$ cyclic loading was reduced and the difference was significant (P < .05). In addition, in the internal hexagonal connection, the difference between the removal torque value after $3{\times}10^6$ cyclic loading and the value after $3{\times}10^6$, and additional $3{\times}10^6$ cyclic loading was not significant. CONCLUSION: The external hexagonal connection was more stable than the internal hexagonal connection after $1{\times}10^6$, and additional $5{\times}10^6$ cyclic loading (t = 10.834, P < .001). There was no significant difference between the two systems after $3{\times}10^6$, and additional $3{\times}10^6$ cycles.

The effects of autoclave sterilization on the cyclic fatigue resistance of ProTaper Universal, ProTaper Next, and ProTaper Gold nickel-titanium instruments

  • Ozyurek, Taha;Yilmaz, Koray;Uslu, Gulsah
    • Restorative Dentistry and Endodontics
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    • v.42 no.4
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    • pp.301-308
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    • 2017
  • Objectives: It was aimed to compare the cyclic fatigue resistances of ProTaper Universal (PTU), ProTaper Next (PTN), and ProTaper Gold (PTG) and the effects of sterilization by autoclave on the cyclic fatigue life of nickel-titanium (NiTi) instruments. Materials and Methods: Eighty PTU, 80 PTN, and 80 PTG were included to the present study. Files were tested in a simulated canal. Each brand of the NiTi files were divided into 4 subgroups: group 1, as received condition; group 2, pre-sterilized instruments exposed to 10 times sterilization by autoclave; group 3, instruments tested were sterilized after being exposed to 25%, 50%, and 75% of the mean cycles to failure, then cycled fatigue test was performed; group 4, instruments exposed to the same experiment with group 3 without sterilization. The number of cycles to failure (NCF) was calculated. The data was statistically analyzed by using one-way analysis of variance and post hoc Tukey tests. Results: PTG showed significantly higher NCF than PTU and PTN in group 1 (p < 0.05). Sterilization significantly increased the NCF of PTN and PTG (p < 0.05) in group 2. PTN in group 3 had significantly higher cyclic fatigue resistance than PTN group 4 (p < 0.05). Also, significantly higher NCF was observed for PTG in group 2 than in groups 3 and 4 (p < 0.05). Conclusions: PTG instrument made of new gold alloy was more resistant to fatigue failure than PTN and PTU. Autoclaving increased the cyclic fatigue resistances of PTN and PTG.

Comparison of cyclic fatigue life of nickel-titanium files: an examination using high-speed camera

  • Ozyurek, Taha;Keskin, Neslihan Busra;Furuncuoglu, Fatma;Inan, Ugur
    • Restorative Dentistry and Endodontics
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    • v.42 no.3
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    • pp.224-231
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    • 2017
  • Objectives: To determine the actual revolutions per minute (rpm) values and compare the cyclic fatigue life of Reciproc (RPC, VDW GmbH), WaveOne (WO, Dentsply Maillefer), and TF Adaptive (TFA, Axis/SybronEndo) nickel-titanium (NiTi) file systems using high-speed camera. Materials and Methods: Twenty RPC R25 (25/0.08), 20 WO Primary (25/0.08), and 20 TFA ML 1 (25/0.08) files were employed in the present study. The cyclic fatigue tests were performed using a dynamic cyclic fatigue testing device, which has an artificial stainless steel canal with a $60^{\circ}$ angle of curvature and a 5-mm radius of curvature. The files were divided into 3 groups (group 1, RPC R25 [RPC]; group 2, WO Primary [WO]; group 3, TF Adaptive ML 1 [TFA]). All the instruments were rotated until fracture during the cyclic fatigue test and slow-motion videos were captured using high-speed camera. The number of cycles to failure (NCF) was calculated. The data were analyzed statistically using one-way analysis of variance (ANOVA, p < 0.05). Results: The slow-motion videos were indicated that rpm values of the RPC, WO, and TFA groups were 180, 210, and 425, respectively. RPC ($3,464.45{\pm}487.58$) and WO ($3,257.63{\pm}556.39$) groups had significantly longer cyclic fatigue life compared with TFA ($1,634.46{\pm}300.03$) group (p < 0.05). There was no significant difference in the mean length of the fractured fragments. Conclusions: Within the limitation of the present study, RPC and WO NiTi files showed significantly longer cyclic fatigue life than TFA NiTi file.