Zugl.: Frankfurt (Oder), Europa-Univ., Diss., 2006

The focus of the current study was to investigate dephosphorization of ferromanganese to produce a low P containing alloy that could effectively be used for the production of AHSS. The study involved conducting laboratory scale testwork to investigate dephosphorization of of FeMn (HCFeMn and MCFeMn) alloys by CaO-based slag systems. Addition of Na2O, BaO, and CaF2 to MnO-CaO-SiO2 slag was investigated to study the influence on dephosphorization. The effect of MnO-BaO-BaF2 slag system without CaO was also investigated in a preliminary way. The testwork was carried out in a 25 kVA induction furnace at temperatures of 1350°C, 1400°C, and 1450°C at different retention times of 5 minutes, 30 minutes and 60 minutes. The analytical results of the product samples were used to evaluate the P-partition ratio. In general, analysing the low P contents of the slags and alloys proved to be a challenge and at the lowest concentrations the uncertainty was large. The analytical results of the slags generally reported higher MnO-contents than was anticipated. This resulted in dilution of the other major slag components, i.e. SiO2 and CaO. Low P2O5 contents were found in the slags, suggesting that the removal of P from the alloys was minimal. The alloy results reported C-pickup after the tests due to the dissolution of the graphite from the crucible. Loss of Mn from the alloys was also observed. The P-content of the alloys were generally higher than in the feed alloy. The results generally showed the 〖 L〗_p remained small at <1 which is an indication that dephosphorization had not been achieved. The baseline slag comprising of 40%CaO-40%SiO2-20%MnO reported relatively higher 〖 L〗_p values. Addition of Na2O and CaF2 did not show any added benefit. Substituting half of CaO by BaO, resulted in similar L_p values to those of the baseline slag under a few conditions, namely 1350°C and 1450°C at 30 minutes. The baseline slag was however not outperformed by the BaO-bearing slag under any of the other conditions. Increasing the temperature generally resulted in lower 〖 L〗_p values. This may be attributed to the exothermic nature of the phosphorus removal reaction which should be favourable at lower temperatures. Increasing the basicity (%CaO/%SiO2 ratio) of the baseline slag showed an initial increase in 〖 L〗_p value for basicities of 0.7 to 0.9, thereafter a slight reduction in the 〖 L〗_p value was obtained. The latter results were not expected as higher basicity is anticipated to improve the P capacity of the slag. Increasing the basicity resulted in increased slag liquidus temperature of about 1500°C which negatively affected dephosphorization. In summary, based on the 〖 L〗_p obtained, the conditions investigated with the CaO-based slags appeared to have been unfavourable for dephosphorization of FeMn alloys, as most of this impurity element remained in the alloy. The BaO-BaF2-MnO slag showed potential to dephosphorise HCFeMn alloy, however the slag posed numerous challenges and the slag should be investigated further / Dissertation (MEng)--University of Pretoria, 2020. / Mintek / Materials Science and Metallurgical Engineering / MEng / Unrestricted

The apparent effect of superior semicircular canal dehiscence (SSCD) on middle ear- and cochlear impedance has led researchers to investigate the use of wideband acoustic immittance as a screening tool when SSCD is suspected. The purpose of the study was to describe the absorbance characteristics and tympanometric values of ears with confirmed SSCD measured at tympanometric peak pressure (TPP) and at ambient pressure. Wideband Acoustic Immittance was performed at ambient pressure and at TPP on ten participants (12 ears) with confirmed SSCD, as well as on an age- and gender matched control group (12 ears). Inferential statistics were used to determine whether statistical differences existed for the absorbance values at each of the averaged frequencies, the resonance frequency (RF) and tympanometric data between the SSCD and control groups. The mean absorbance of the SSCD group reached a maximum at 890.9 Hz and a minimum at 6349.6 Hz. When testing absorbance at TPP, a statistically significant increase/peak in the absorbance values of the SSCD group (compared to those of the control group) was found from 630 to 890.9 Hz and a decrease from 4489.8 to 6349.6 Hz. Similar patterns were observed for absorbance at ambient pressure. A lower mean RF for ears with SSCD as well as an increased mean admittance magnitude (AM) value at RF was found compared to those of the control group. The peak in absorbance around 890 Hz that was found on SSCD ears in the current study is similar to findings from earlier studies that found a peak in absorbance/notch in reflectance around 1000 Hz, reiterating its use as a screening tool when SSCD is suspected. No significant difference was found between absorbance measured at ambient pressure and at TPP in the current study; however, the stringent inclusion criteria with regard to TPP most likely affected this outcome. As a result of the significant difference in RF of SSCD ears compared to the RF of the control group, the potential value of measuring the RF of the middle ear as well as AM at the RF, to differentiate between mass-and stiffness dominated pathologies, was also illustrated. Further research measuring the AM at RF in normal and pathological ears was suggested for comparison to the current study and to determine its clinical value. / Dissertation (MA (Audiology))--University of Pretoria, 2020. / Speech-Language Pathology and Audiology / MA (Audiology) / Unrestricted

Dissertation submitted to the Faculty of Arts in fulfillment of the requirements for the degree of Master of Arts, in the Department of Communication Science, University of Zululand, 2006. / Ubiquitous access to digital networks and the Internet have revolutionised the way multimedia information is being stored, accessed and disseminated by information services. New technologies have played an important role in redefining preferred information and communication models to facilitate the efficient dissemination and retrieval of information. So has the emergence of electronic publishing and the global trend towards accessing and sharing digital content on the World Wide Web (WWW) led to a greater electronic dissemination of postgraduate academic Theses and Dissertations (TDs). These electronic theses and dissertations (ETDs) provide a reservoir of knowledge that can easily be accessed by the international research community and diffused across all fields of research. Some 73 per cent of the study’s e-survey participants found obtaining research material online more efficient than using paperbound sources; 51 per cent were familiar with the concept of ETDs; 87 per cent agreed that adding TDs to an online database would improve the accessibility and use of this research; 65 per cent indicated that they would not have any reservations with adding their TD to an online database; and 48 per cent felt that ETDs should be introduced into their tertiary institutions.

Pontificia Univ. Católica, Diss. 2005--Zugl.: São Paulo, 2005.

University, Diss.--Tilburg, 2006.

Diss.--Zugl.: Univ. Federal do Rio Grande do Sul, 2006. / Zsfassung in engl. Sprache.

Univ., Diss. 2005--Zugl.: São Paulo, 2005. / Zsfassung in engl. Sprache.

Calif., Univ. of California, Diss.--Berkeley, 2004. / Kopie, ersch. im Verl. UMI, Ann Arbor, Mich.

Univ., Diss.--Regensburg, 2007.