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RISS 인기검색어
- 검색키워드
- 저자 : M. Refaie (검색결과 4 건)
- 무료
- 기관 내 무료
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The Effect of Superplasticizers on Eco-friendly Low-Energy One-Part Alkali-Activated Slag
M. Refaie,Alaa Mohsen,El-Sayed A. R. Nasr,Mohamed Kohail 한국콘크리트학회 2023 International Journal of Concrete Structures and M Vol.17 No.6
One-part alkali-activated materials (OP-AAM) have become a promising binder with low carbon and energy requirements associated with superior mechanical and durability characteristics. This study aims to employ commercial superplasticizers (naphthalene-based “Nb-SP” and polycarboxylate-based “PCb-SP”), as well as laboratory-prepared one (phenol–formaldehyde sulfanilate “PFS-SP”) in enhancing the properties of OP-AAM. The main problem of superplasticizers (SPs) in the AAM is their hydrolysis in the alkaline activator (NaOH) used in the activation reactions. Therefore, the thermo-chemical treatment process was utilized to mitigate the high activator alkalinity by impeding the NaOH in the aluminosilicate precursor matrix. The OP-AAM was fabricated from thermo-chemical treatment powder (TCT-P) resulting from sintering blast furnace slag (GGBFS) with 10 wt% NaOH at 300 and 500 °C. The XRD-pattern showed that NaOH was impeded in the GGBFS via sodium aluminum silicate phase formation after sintering at 500 °C. The results showed that the admixed OP-AAM prepared from TCT-P at 500 °C greatly enhanced the workability and mechanical properties. The PFS-SP proved its efficiency in improving the properties of OP-AAM prepared TCT-P at 300 and 500 °C, referring to its high stability in an alkaline medium. While PCb-SP reinforced the properties of OP-AAM prepared from TCT-P at 500 °C only, proving that PCb-SP promotes high capability in TCT-P-500 as well as in Portland cement.
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Formulation and evaluation of taste-masked paracetamol-lipid sachets and chewable tablets
Wessam M. El-Refaie,Magda A. EL-Massik,Ossama Y. Abdallah,Nawal M. Khalafallah 한국약제학회 2014 Journal of Pharmaceutical Investigation Vol.44 No.6
The use of lipids as taste-masking excipients inparacetamol sachets and chewable tablets without compromisingdrug release was investigated. Twelve paracetamolgranule formulations were prepared by meltgranulation, using Precirol (glyceryl palmitostearate),cetyl alcohol and stearic acid, at different paracetamol-lipidratios. Based on efficient taste-masking results coupledwith minimum retardation of drug release, paracetamol-Precirol (1:1), paracetamol-cetyl alcohol (1:2) and paracetamol-stearic acid (1:2) granules were selected forpreparation of chewable tablets and sachets. Formulationswere evaluated for the effect of storage, at 40 C and 75 %RH for 6 months, on their performance. Results inferredthat paracetamol sachets, after reconstitution in 100 mlwater, showed efficient taste-masking compared to controlsachets (without lipids). The sachets released more than90 % of their drug content in 30 min, when tested in900 ml of phosphate buffered saline, pH 5.8. Chewabletablets exhibited comparable taste-masking effect to areference product, Tylenol 80 mg chewable tablets, andyielded similar drug dissolution profiles (similarity factorf2[50). Differential scanning calorimetry indicated theabsence of interaction between paracetamol and lipids. Scanning electron micrographs supported the obtainedresults. Upon storage at 40 C and 75 % RH for 6 months,all the prepared sachets and chewable tablets were found tobe stable except cetyl alcohol-based tablets that showeddecrease in the efficiency of taste masking with increase inrelease rate. In conclusion, selected lipids, Precirol, cetylalcohol and stearic acid, could be efficiently used in formulationof taste masked paracetamol sachets and chewabletablets without adversely delaying drug release.
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Patel. B. Reddy,Ayman. M. EL-Refaie,Kum-Kang Huh 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5
Interior PM machines equipped with fractional-slot concentrated-windings are good candidates for high-speed traction applications. This is mainly due to the higher power density and efficiency that can be achieved. The main challenge with this type of machines is the high rotor losses at high speeds/frequencies. This paper will thoroughly investigate the effect of number of winding layers on the performance of this type of machines. It will be shown that by going to higher number of layers, there can be significant improvement in efficiency especially at high speeds mainly due to the reduction of the winding factor/magnitude of the most dominant stator mmf sub-harmonic component. It will also be shown that there is significant improvement in torque density. Even though there is reduction in the winding factor of the stator synchronous torque-producing mmf component, this is more than offset by increase in machine saliency and reluctance torque. The paper will provide general guidelines regarding the optimum spp combinations based on torque density and efficiency. Sample designs of various slot/pole combinations are used to quantify the benefit of going to higher number of layers in terms of torque density, efficiency and torque ripple.
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Song, S. H.,Kim, S. E.,Agashe, M. V.,Lee, H.,Refai, M. A.,Park, Y. E.,Choi, H. J.,Park, J. H.,Song, H. R. British Editorial Society of Bone and Joint Surger 2012 The Bone & Joint Journal Vol.94 No.4
<P>This study evaluated the effect of limb lengthening on longitudinal growth in patients with achondroplasia. Growth of the lower extremity was assessed retrospectively by serial radiographs in 35 skeletally immature patients with achondroplasia who underwent bilateral limb lengthening (Group 1), and in 12 skeletally immature patients with achondroplasia who did not (Group 2). In Group 1, 23 patients underwent only tibial lengthening (Group 1a) and 12 patients underwent tibial and femoral lengthening sequentially (Group 1b). The mean lengthening in the tibia was 9.2 cm (59.5%) in Group 1a, and 9.0 cm (58.2%) in the tibia and 10.2 cm (54.3%) in the femur in Group 1b. The mean follow-up was 9.3 years (8.6 to 10.3). The final mean total length of lower extremity in Group 1a was 526.6 mm (501.3?to 552.9) at the time of skeletal maturity and 610.1 mm (577.6 to 638.6) in Group 1b, compared with 457.0 mm (411.7 to 502.3) in Group 2. However, the mean actual length, representing the length solely grown from the physis without the length of distraction, showed that there was a significant disturbance of growth after limb lengthening. In Group 1a, a mean decrease of 22.4 mm (21.3 to 23.1) (4.9%) was observed in the actual limb length when compared with Group 2, and a greater mean decrease of 38.9 mm (37.2 to 40.8) (8.5%) was observed in Group 1b when compared with Group 2 at skeletal maturity. In Group 1, the mean actual limb length was 16.5 mm (15.8 to 17.2) (3.6%) shorter in Group 1b when compared with Group 1a at the time of skeletal maturity. Premature physeal closure was seen mostly in the proximal tibia and the distal femur with relative preservation of proximal femur and distal tibia. We suggest that significant disturbance of growth can occur after extensive limb lengthening in patients with achondroplasia, and therefore, this should be included in pre-operative counselling of these patients and their parents.</P>
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