Prediction of hole expansion ratio of titanium alloys using R programming

The hole expansion ratio (HER) is an important material property which defines the extent of edge formability of sheet metals. The stress states observed at the hole edge after the hole expansion test are similar to those seen during traditional uniaxial tensile deformation. This observation has provoked research, directed at ascertaining a correlation between the HER and tensile properties. In order to account for the forming behaviour of complex materials like titanium, a highly robust model that takes into account the material formability in all sheet-processing directions must be considered. The R programming language was used in this research to build a model fitting expression capable of predicting the HER as well as generating a regression model equation for titanium alloys, based on their thickness and Erichsen index number. The proposed regression model equation for predicting HER of titanium alloys exhibited an excellent statistical significance (p= 0.00076), indicating the robustness of the model fitting expression to predict HER values of titanium alloys. An accompanying adjusted R squared value of 0.9987 for the generated regression model equation also shows how well the regression line fits the data for accurate prediction of the HER of titanium alloys. A numerical validation analysis of the strength of the relationship derived between the predicted and the experimental HERs gave a correlation coefficient of 0.9884. This result shows a strong linear relationship between the experimental and predicted HER values of the titanium alloys with an average absolute error of 8.8%

Impact of machining induced surface defects on the edge formability of commercially pure titanium sheet at room temperature

Despite the good properties of titanium which have drawn the interest of various industries over the years, one of the major drawbacks of this material is its poor machinability. This has largely been attributed to its low thermal conductivity and elastic modulus. The ability to attain optimum sheet edge performance during forming is dependent on the quality of the edges produced. Also, the demanding nature of aerospace part design has provoked the interest of both industry and academia to continually explore avenues tailored at enhancing part performance. The sort of edge surface integrity produced for aerospace part fabrication thus becomes a vital consideration in the quest to ensuring prime performance of components. This work seeks to study the influence of different machining induced surface defects on the sheet edge performance of CP-Ti (Grade 2) at room temperature. Hole expansion test was used to assess the edge surface formability of CP-Ti with different machining induced edge defects. The research found that, machining induced surface defects act as stress concentration sites during the hole expansion test and have a major impact on the material flow. Electro-discharge machined edges were observed to exhibit high edge formability compared to laser and abrasive water jet cut edges due to the impact of machining induced microstructural changes

PROSPECTS AND CHALLENGES OF EDUCATING A DEAF-BLIND STUDENT IN A UNIVERSITY IN GHANA

This study explored the challenges and prospects of educating a deaf-blind student in a public university in Ghana. The study utilised an exploratory qualitative research design based on interviews and observation to explore how the deaf-blind learner navigated university life. The study found that the challenges experienced by all stakeholders included a lack of knowledge and understanding about deaf-blindness, communication challenges, inadequate preparation of educators/teachers and resource persons, lack of support structures for all stakeholders, and the time-consuming nature needed to educate the deaf-blind learner. The study recommends continuous in-service training on basic knowledge of deaf-blindness, instructional and socially inclusive strategies, and communication modes for deaf-blind learners for all stakeholders. A collaborative team approach to delivering training and inclusive education that involves all stakeholders is necessary. The study concludes that if lecturers of learners who are deaf-blind are provided with the necessary training on the skills and knowledge of facilitating communication with their students, this would, in turn, contribute positively towards teaching and learning.  Article visualizations

On Behaviour of a Host-vector Epidemic Model with Non-linear Incidence

In this paper we find the possible phase portraits and bifurcations for a general class of host-vector epidemic models with non-linear incidence function generalizing the Ross model.Key words: Epidemics; Non-linear incidence; Global analysis; BifurcationsMSC2010: 34C05, 34C23, 34D23, 92D3

Investigating the edge forming performance of DP600 and FV 607

This paper scrutinises the effect of varying test parameters on two grades of advanced high strength steels (AHSSs) prepared with abrasive water jet (AWJ) machining during hole expansion test (HET). The main objective was to understand the effect of the forming speed and the bottom die geometry on the hole edge forming performance of DP600 and FV 607 AHSSs. The results showed an optimum forming speed exists between 1 and 1.6mm/s and the FV 607 displayed better hole-expansion performance at 2mm/s. This was explained by correlation between the hole expansion ratio (HER) and the flange height. The results showed that the geometry of the bottom die have an influence on the hole-edge forming capability. The sheet thinning tendency was observed more in the bulge die, and particularly at speeds above 1 mm/s which was argued by requirement for larger HER values for more excessive thinning to account for an enhanced deformation. The FV 607 grade exhibited more thinning under all test conditions

Blind Algorithm Development for Peak to Average Power Ratio Reduction in OFDM Systems under Frequency Selective Channels

One major drawback of orthogonal frequency division multiplexing (OFDM) system is peak to average power ratio (PAPR). This effect causes high power amplifier (HPA) to introduce intermodulation and out of band radiation as the signal goes through, thus degrades the performance of OFDM systems. This paper proposes blind algorithms which takes advantage of signal transformation technique and signal distortion technique. Simulation results show that at complementary cumulative distribution function (CCDF) level of 10-3 , the proposed algorithm achieved 3.2 dB PAPR improvement compared to discrete Fourier transform with interleaved frequency division multiple access (DFT-IFDMA) based algorithm. The bit error rate (BER) performance has degraded by 2 dB compared to the original OFDM signal with no distortion under frequency selective channel (FCS) at BER of 10-4 . These presented results, mark this algorithm as a better candidate for PAPR reduction algorithm in long term evolution (LTE) network. Under AWGN channels, the proposed algorithm performs better both in low and high signal power values. Under frequency selective channels, the existing and proposed algorithm converges after 10 dB of signal to noise power values. The low BER transmissions at low signal power values signify energy efficiency, ideal for portable wireless devices with limited battery power

ATTITUDES OF NON-DISABLED STUDENTS TOWARDS THEIR PEERS WITH DISABILITIES IN AN INCLUSIVE SETTING IN GHANA

This study measured the attitudes of non-disabled students towards their peers with disabilities. A cross-sectional survey was employed for the study. The Chedoke-McMaster Attitudes Towards Children with “Handicaps” (CATCH) scale was used to collect data from n=119 respondents. Descriptive statistics analysis was employed in analysing the data. Results indicated that students without disabilities generally held neutral attitudes towards their peers with disabilities (M=2.12; SD=0.687) with no significant difference in gender, age, having a close friend or relative with a disability. Teachers in inclusive education schools were encouraged to measure the attitudes of students towards their peers with disabilities and other related variables. This would enable them to plan, design, develop, implement and evaluate effective interventions that would change non-disabled students’ negative and/or neutral attitudes, thereby ensuring the full social participation of students with disabilities in inclusive settings.   Article visualizations