| 1. |
- Azam, Asad Muhammad, et al.
(författare)
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Analysis of degradation in UHMWPE a comparative study among the various commercial and laboratory grades UHMWPE
- 2016
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Ingår i: 14TH INTERNATIONAL SYMPOSIUM ON ADVANCED MATERIALS (ISAM 2015). - : IOP PUBLISHING LTD.
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Konferensbidrag (refereegranskat)abstract
- Oxidative degradation of the ultra-high molecular weight polyethylene ( UHMWPE) limits the life of implants. This degradation can be monitored to estimate the service life of UHMWPE following the standard protocols as defined by American Standards for Testing Materials ( ASTM). In this work, a comparative study has been carried on two commercially available UHMWPE grades i. e. GUR 1020 and GUR 1050 and one laboratory grade UHMWPE which was purchased from Sigma Aldrich. These powder samples were pressed while using hot press with controlled heating and cooling setup in open air under 200 bar of external pressure. These sheets were then subjected to accelerated aging in an oven at 80 degrees C for three weeks. The degradation of the UHMWPE was monitored by ATR-FTIR techniquefor three weeks. The oxidation index ( OI) measurement showed that the commercial grade UHMWPE i. e. GUR-1020 and GUR-1050 degrade more as compared to laboratory grade UHMWPE. The values of OI after three weeks of accelerating aging were found 0.18, 0.14, and 0.09 for GUR-1020, GUR-1050, and Sigma Aldrich, respectively. In addition to this, it was found that commercial grades of UHMWPE suffer more structural alterations as compared to laboratory grade one. We hope that these results will be of particular and fundamental importance for the researchers and orthopaedic industry.
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| 2. |
- Naeem, Rehan, et al.
(författare)
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Impact of DC Grid Topology on Transient Stability of HVDC-Segmented Power System
- 2016
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Ingår i: 2016 International Conference on Intelligent Systems Engineering, ICISE 2016. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781467387538 ; , s. 51-54
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Konferensbidrag (refereegranskat)abstract
- This paper compares the effects of ring, radial and interconnected DC grid topologies on the transient stability of a segmented 15 - bus electric grid for different HVDC schemes. For this purpose, three HVDC convertor technologies and four HVDC station configurations are considered. A three phase AC bus fault is applied and the rotor angle disturbance is analyzed. The results show that the transient stability is dependent on the topology for bipolar configuration of line commutated current source and capacitor commutated convertor technologies. For rest of the HVDC schemes, transient stability is independent of the topology used.
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| 3. |
- Smith, Gregory N., et al.
(författare)
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The effects of counterion exchange on charge stabilization for anionic surfactants in nonpolar solvents
- 2016
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 465, s. 316-322
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Tidskriftsartikel (refereegranskat)abstract
- Hypothesis: Sodium dioctylsulfosuccinate (Aerosol OT or NaAOT) is a well-studied charging agent for model poly(methyl methacrylate) (PMMA) latexes dispersed in nonpolar alkane solvents. Despite this,few controlled variations have been made to the molecular structure. A series of counterion exchanged analogs of NaAOT with other alkali metals (lithium, potassium, rubidium, and cesium) were prepared, and it was expected that this should influence the stabilization of charge on PMMA latexes and the properties of the inverse micelles. Experiments: The electrophoretic mobilities of PMMA latexes were measured for all the counterion exchanged AOT analogs, and these values were used to calculate the electrokinetic or f potentials. This enabled a comparison of the efficacy of the different surfactants as charging agents. Small-angle scattering measurements (using neutrons and X-rays) were performed to determine the structure of the inverse micelles, and electrical conductivity measurements were performed to determine the ionized fractions and Debye lengths.
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