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RISS 인기검색어
- 검색키워드
- 저자 : El Baiomy, M (검색결과 2 건)
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Effect of perforation patterns on the fundamental natural frequency of microsatellite structure
Ahmad M. Baiomy,M. Kassab,B.M. El-Sehily,R.M. El-Kady Techno-Press 2023 Advances in aircraft and spacecraft science Vol.10 No.3
There is a burgeoning demand for minimizing the mass of satellites because of its direct impact on reducing launch-to-orbit cost. This must be done without compromising the structure's efficiency. The present paper introduces a relatively low-cost and easily implementable approach for optimizing structural mass to a maximum natural frequency. The natural frequencies of the satellite are of utmost pertinence to the application requirements, as the sensitive electronic instrumentation and onboard computers should not be affected by the vibrations of the satellite structure. This methodology is applied to a realistic model of Al-Azhar University micro-satellite in partnership with the Egyptian Space Agency. The procedure used in structural design can be summarized in two steps. The first step is to select the most favorable primary structural configuration among several different candidate variants. The nominated variant is selected as the one scoring maximum relative dynamic stiffness. The second step is to use perforation patterns reduce the overall mass of structural elements in the selected variant without changing the weight. The results of the presented procedure demonstrate that the mass reduction percentage was found to be 39% when compared to the unperforated configuration that had the same plate thickness. The findings of this study challenge the commonly accepted notion that isogrid perforations are the most effective means of achieving the goal of reducing mass while maintaining stiffness. Rather, the study highlights the potential benefits of exploring a wider range of perforation unit cells during the design process. The study revealed that rectangular perforation patterns had the lowest efficiency in terms of modal stiffness, while triangular patterns resulted in the highest efficiency. These results suggest that there may be significant gains to be made by considering a broader range of perforation shapes and configurations in the design of lightweight structures.
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Rasmy, A,Abozeed, W,Elsamany, S,El Baiomy, M,Nashwa, A,Amrallah, A,Hasaan, E,Alzahrani, A,Faris, M,Alsaleh, K,AlFaraj, A Asian Pacific Journal of Cancer Prevention 2016 Asian Pacific journal of cancer prevention Vol.17 No.7
Background: To investigate the association between preoperative pathological Ki-67 labeling index and serum tumor marker cancer antigen 15-3 (CA 15-3) with clinic-pathological parameters and treatment outcomes in early breast cancer. Materials and Methods: A retrospective study at 4 cancer centers in Saudi Arabia and Egypt was performed. Data were collected for female patients diagnosed with unilateral early breast cancer between March 2010 and October 2013. Cases treated with neoadjuvant chemotherapy (NACT) followed by surgery and radiotherapy were included. NACT included 6-8 cycles of anthracycline and taxane based regimens. Trastuzumab and hormonal treatments were added according to HER2 and hormone receptor status. Baseline serum CA15.3 and pathological Ki67 levels were evaluated and correlated with disease free survival (DFS) and overall survival (OS). Results: A total of 280 pts was included. The median age was 49 years (38-66 y) and median overall survival was 35 (20-38) months (mo). Estrogen receptors (ER), progesterone receptors (PR) and HER 2 receptors were positive in 233 (83.2%), 198 (70%) and 65 cases (23.2%), respectively. High preoperative Ki67 and CA15.3 were noted in 177 (63.2%) and 131 (46.8%). A total of 45 (16%) patients had distal or local recurrence and 24 (8.6%) died of their disease. Most of the relapsed cases had high preoperative Ki-67 (n=41, 91%) and CA15.3 (n=28, 62%) values. All of the patients who died had a high Ki-67 but CA15.3 was high in 9 (37%) only. Mean DFS/OS in patients with high preoperative Ki-67 was 32 months /32 months as compared to 37 months/35 months in those with normal Ki-67 (p<0.001). Correlation of preoperative CA15.3 and survival was statistically not significant. Conclusions:Preoperative Ki-67 can be a predictive and prognostic marker. Higher levels are associated with poor DFS and OS in patients with early BC.
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