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FINITE GROUPS WHOSE MINIMAL SUbGROUPS ARE WEAKLY H-SUbGROUPS

Acta Mathematica Scientia 2012年第6期32卷 2295-2301页

作者： M.M.Al-mosa.Al-Shomrani M.Ramadan A.A.Heliel Department of Mathematics Faculty of Science 80203King Abdulaziz UniversityJeddah 21589Saudi Arabia Department of Mathematics Faculty of ScienceCairo UniversityGiza 12613Egypt Department of Mathematics Beni-Suef UniversityFaculty of Science 62511Beni-SuefEgypt

Let G be a finite group. A subgroup H of G is called an H-subgroup in G if NG（H）∩ H^g ≤ H for all g C G. A subgroup H of G is called a weakly H-subgroup in G if there exists a normal subgroup K of G such that G = HK and H N K is an H-subgroup in G. In this paper, we investigate the structure of the finite group G under the assumption that every subgroup of G of prime order or of order 4 is a weakly H-subgroup in G. Our results improve and generalize several recent results in the literature.

关键词： c-normal subgroup H-subgroup p-nilpotent group supersolvable group generalized Fitting subgroupi saturated formation

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Failure Analysis of the Semi-permanent Coupler Used in Metro Rail

Failure Analysis of the Semi-permanent Coupler Used in Metro...

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作者： M A Morsy S Khafagy ES mosa Welding and NDT Dept. CMRDI TIMS Al-Azhar University Faculty of Engineering Mining and Petroleum Engineering Dept.

Failure analysis of the semi-permanent coupler which failed in service of Metro rail was conducted in order to know the reason for failure. The examinations include visual, photo detection, chemical analysis, hardness measurements, tensile and v-notch impact test, microstructure and SEM observation of fracture surface. Chemical analysis and tensile test shows that the coupler material can be classified as grade b cast steel in AAR M201 steel casting specification. Although the microstructure of the coupler material shows incomplete homogenization indicating the improper conduction of heat treatment, the v-notch impact results is accepted according to this specification. The fracture surface shows the existence of much porosity at the internal surface of the hollow like pipe-coupler and the fracture started at these sites showing beach marks. SEM observation of the fracture surface shows fatigue striations indicating the occurrence of fatigue started at the porosity defects. The cast defects act as a stress concentration site for fatigue crack initiation. Crack occurred, propagated, and connected the defects to each other. The occurrence of collision resulted in bending of the female part of the coupler（plastic deformation occurs） at the lower thin wall（～ 5.41 mm thickness）. Moreover, opening of the previously formed fatigue crack and accelerating the failure were occurred. Recommendations were explained to prevent the occurrence of this failure.

关键词： failure analysis coupler chemical analysis mechanical testing microstructure fracture surface fatigue porosity crack

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Postoperative Mechanical Axis Alignment and Components Position after Conventional and Patient-Specific Total Knee Arthroplasty

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Open Journal of Orthopedics 2016年第8期6卷 253-258页

作者： mohamed mosa.mohamed Maher A. El Assal Ahmed M. Abdel Aal Yaser E. Khalifa Mahmoud A. Hafez Orthopaedic Department Alazhar University (Assiut Branch) Assiut Egypt Orthopaedic Department Assiut University Assiut Egypt Orthopaedic Department October 6 University Cairo Egypt

Introduction: Accurate postoperative alignment and implant positioning are determinant factors for successful total knee arthroplasty (TKA). Patient-specific template (PST) is a technique that uses computer technology for the planning, deigning and production of cutting guides. This study aims to compare PST to conventional technique in terms of mechanical axis alignment and component positioning. Patients and method: 109 TKA were performed for 78 patients in 2 groups. Group A included 69 conventional TKA in 55 patients and Group b included 40 patient-specific TKA in 23 patient. Postoperative long-film X-rays were done for all patients to observe the mechanical axis, anatomical axis, lateral distal femoral mechanical angle and medial proximal tibial angle. Results: No statistically significant difference was found between the two groups regarding alignment or component positioning. Conclusion: both techniques have shown similar results in restoring the mechanical axis and alignment after TKA. However, PST had the advantages of reduced blood loss and shorter operative time.

关键词： Total Knee Arthroplasty Patient-Specific Templates Conventional TKA Mechanical Axis Limb Alignment Component Position

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