Diamond turning of contact lens polymers

Contact lens production requires high accuracy and good surface integrity. Surface roughness is generally used to measure the index quality of a turning process. It has been an important response because it has direct influence toward the part performance and the production cost. Hence, choosing optimal cutting parameters will not only improve the quality measure but also the productivity. In this study, an ONSI-56 (Onsifocon A) contact lens buttons were used to investigate the triboelectric phenomena and the effects of turning parameters on surface finish of the lens materials. ONSI-56 specimens are machined by Precitech Nanoform Ultra-grind 250 precision machine and the roughness values of the diamond turned surfaces are measured by Taylor Hopson PGI Profilometer. Electrostatics values were measured using electrostatic voltmeter. An artificial neural network (ANN) and response surface (RS) model were developed to predict surface roughness and electrostatic discharge (ESD) on the turned ONSI-56. In the development of predictive models, turning parameters of cutting speed, feed rate and depth of cut were considered as model variables. The required data for predictive models were obtained by conducting a series of turning test and measuring the surface roughness and ESD data. Good agreement is observed between the predictive models results and the experimental measurements. The ANN and RSM models for ONSI-56 are compared with each other using mean absolute percentage error (MAPE) for accuracy and computational cost

Impact of Climate Variability on Reservoir Based Hydro-Power Generation in Jebba Dam, Niger State, Nigeria

This study examined impact of climate variability on reservoir-based hydro-power-generation in Jebba dam, Niger State of Nigeria. Data of rainfall, temperature, evaporation, reservoir inflow and outflow and power output for thirty-one years were obtained from Jebba Hydropower Station [JHP]. The Man-Kendall and Pearson’s Product Moment Correlation Coefficient (PPMCC) were used to establish the influence of weather parameters on the reservoir inflow and outflow. Findings showed increased electricity generation during dry season than wet season. The highest annual mean amount of the electricity generated was in 2016 having mean of 689.12mwh, dry season (352.26mwh) and wet season (336.86mwh). Reservoir inflow showed negative trend with severe fluctuations in 1998 (1436.42M3/Sec), 1999 (1581.08M3/Sec) and 2010 (1641.08M3/Sec) with steady increase in 2016 (1556.0042M3/Sec), 2017 (1556.4242M3/Sec) and 2018 (1635.7542M3/Sec). The reservoir outflow pattern showed tremendous and negative trend in fluctuation with increase in 1998 (1421.75M3/Sec) 1999 (1581.58M3/Sec) and 2010 (1641.16M3/Sec) and a steady increase in 2016 (1535.00M3/Sec), 2017 1558.83M3/Sec and 2018 (1632.00M3/Sec). Thus, rainfall and reservoir inflow had strong relationships with the amount of power generated than temperature and evaporation. Therefore, the government should increase the water carrying capacity of the reservoir construction by storing water to be used during dry periods

Ultra-high precision diamond turning of advanced contact lens polymers

Contact lens polymer-based materials are extensively used in the optical industry owing to their excellent corrosion resistance, the possibility of mass production and their ability to be processed without external lubrication. Owing to the fast growth in optical industries, contact lens (CL) requires high accuracy and a high surface quality. The demand for high-accuracy and minimal surface roughness drives the development of ultra-high precision machining technology with regard to single point diamond turning (SPDT). Ultra-high precision diamond turning is an advanced manufacturing technique employed in the machining of CLs owing to its capability of producing high optical surfaces with complex shapes and nanometric accuracy. Yet, even with the advances in ultra-high precision machining (UHPM), it is not continuously easy to achieve a highquality surface finish during polymers machining as the adhesion of the tool chip around the tool dictates the presence of electrostatic charges. The electrostatic charges encountered by a cutting tool when turning advanced CLs are important as they reflect the quality and condition of the tool, machine, fixture, and sometimes even the finished surface, which is responsible for tool wear and poor surface quality. This study investigates the role of cutting parameters, namely cutting speed, feed rate and depth of cut on surface roughness (Ra), electrostatic charge (ESC) and material removal rate (MRR), which determines machine economics and the quality of machining contact lens polymers. The experiments were mainly conducted on two different advanced polymeric materials: polymethyl methacrylate (PMMA) and Optimum Extreme (Roflufocon E) CLs. Experimentation was carried out on the Nanoform 250 ultra-grind turning machine with a monocrystalline diamond-cutting tool for machining the PMMA and Roflufocon E CL polymers, covering a wide range of machining parameters. Before conducting the experiments, a design of experiment was conducted according to the response surface methodology (RSM) that is based on the Box-Behnken Design (BBD). In addition, the research study focused on the determination of the optimum cutting conditions leading to minimum Ra and ESC as well as maximum productivity in the SPDT of the PMMA and Roflufocon E CL polymers, using a monocrystalline diamondcutting tool. The optimization was based on RSM together with the desirability function approach. In addition, a mathematical model was developed for Ra, ESC and MRR using a RSM regression analysis for PMMA and Roflufocon E CL polymers by means of Design Expert software. RSM allowed for the optimization of the cutting conditions for minimal Ra and ESC as well as maximal MRR, which provides an effective knowledge base for process parameters to enhance process performance in the SPDT of CL polymers. Furthermore, this study also deals with the development of Ra, ESC and MRR prediction models for the diamond turning of PMMA and Roflufocon E CL polymers, using the fuzzy logic based artificial intelligence (AI) method. The fuzzy logic model has been developed in terms of machining parameters for the prediction of Ra, ESC and MRR. To judge the accuracy and ability of the fuzzy logic model, an average percentage error was used. The comparative evaluation of experiments and the fuzzy logic approach suggested that the obtained average errors of Ra, ESC and MRR using the fuzzy logic system were in agreement with the experimental results. Hence, the developed fuzzy logic rules can be effectively utilized to predict the ESC, Ra and MRR of PMMA and Roflufocon E CL polymers in automated optical manufacturing environments for high accuracy and a reduction of computational cost. Moreover, owing to the brittle nature of optical polymers, the Roflufocon E CL polymer requires ductile-mode machining for improved surface quality. Molecular Dynamics (MD) simulation methods are thus applied to investigate the atomistic reaction at the tool/workpiece surface to clearly study and observe conditions occurring at nanometric scale in polymer machining. This research study is particularly concerned with the comparative analysis of experiments and a MD study of the Roflufocon E optical polymer nano cutting approach to the atomistic visualization of the plastic material flow at the tool/workpiece interface during cutting. The simulated MD acting force, machine stresses, and the temperature at the cutting region were evaluated to access the accuracy of the model. Hence, the nanomachining simulations were found to have a correlation to the experimental machining results

Characterization and Modification of Activated Carbon Generated from Annogeissus Leiocarpus

Activated carbon (AC) is a versatile adsorbent that is used in the treatment of waste water, colour, odour removal and CO2 capture. Annogeissus leiocarpus is one of abundant agricultural precursor that can be used for the production of activated carbon. Characterization was done to investigate some proximate parameters. The modifications were made by soaking AC in 40% H2SO4 and 40% NaHCO3 for 24hours in the ration of 1:3 w/v. The FT-IR and SEM was conducted for surface functional group and morphology respectively. The result of this study revealed that the activated carbon produced possessed high yield, low Ash content, low Burnt off, low moisture content Average bulk density and large pore volume. The results from FT-IR analysis identified appearance and disappearance of carbonyl and hydroxyl groups which contributed in the creation of more adsorptive site for adsorption process. The results for SEM indicated the development of pores all over the surface of adsorbent with Acid modified activated carbon (AMAC/ H2SO4) having the highest pore distribution followed by Base Modified Activated Carbon (BMAC/NaHCO3) and finally ordinary (AC). The results suggest that the modification of AC using Acid and Base can significantly enhance the surface properties which improves adsorptive properties of the activated carbon produced and enhances it adsorption potentials for wastewater treatment

Physical and Chemical Quality of Corn Husks with Ammoniation, Biofermentation and Ammonia Fermentation Processing

This study aimed to evaluate the processing of ammoniated, biofermented and amorphous corn husks on physical quality, dry matter, ash content, crude protein (CP), ether extract (EE), crude fiber (CF), and nitrogen free extract (NFE). This study used a completely randomized design (CRD) which consisted of 4 treatments and 4 replications. The treatments given were P1: untreated corn husks (control), P2: ammoniated corn husks (2% urea), P3: fermented corn husks (5% Aspergillus niger), and P4: amofered corn husks (2% urea + 5% Aspergillus niger). The variables observed included physical quality and nutrient content (dry matter, ash, crude protein, ether extract, crude fiber, and nitrogen free extract). The data obtained  analyzed using Analysis of Variety and followed by Duncan's Multiple Range Test (DMRT). The results of the study had a significant effect on the physical quality, dry matter, ash, crude protein, ether extract, crude fiber and nitrogen free extract (P0,05) on the ash content. Amopheric processing has the best effect on physical quality, crude protein and crude fiber content of corn husks. Fermentation processing gives the best effect on ether extract and nitrogen free extract

Optimization of reaction variables in situ transesterification of Jatropha curcas seed oil for biodiesel production

Biodiesel was produced from seed oil of Jatropha curcas by in situ acid-catalyzed transesterification with methanol. Optimization of the reaction parameters was carried out using response surface methodology based on Box-Behnken design. All the four variables investigated were found to be significant. The empirical model obtained adequately expresses the relationship between the biodiesel yield and the statistically significant reaction variables (R2 = 96.97%). The optimization result predicted an optimal biodiesel yield of 84.07% at a reaction temperature of 48°C; a reaction time of 240 min; with 5 cm3 methanol/g of the seed and catalyst concentration of 0.88M. The validation result was in agreement with the predicted biodiesel yield. The fatty acid methyl profile of the biodiesel shows that it predominantly contains methyl esters of octadecenoic acid, octadecadienoic acid and hexadecanoic acid which make up about 87% the biodiesel. The fuel properties of the biodiesel were in agreement with the requirements of Worldwide Fuel Charter Committee Biodiesel Guidelines.Keywords: Jatropha curcas, Biodiesel, In situ transesterification, Optimization, Box-Behnke

Usable Privacy Mechanisms in Home Security Camera Systems

IoT is the interconnection of People and things. When our home is connected to IoT devices it is referred to as smart home. The idea behind smart home is to make life easier such that there is little human intervention. The IoT devices in our smart home exchange data for storage and processing. This exchange of data leads to users concerns on data security and privacy. In this work, we implemented home security camera systems in such a way that the data is encrypted first before being sent to the cloud in a very simplified and almost automatic encryption process. This implementation was done putting in mind usability. A questionnaire was used to gather results on users’ perception about the system. The user study conducted yielded positive result

Tracking professional conduct of graduates of Federal College of Education, Yola, Nigeria between 2000 and 2010

INTRODUCTION: The fundamental obligations of Colleges of Education is to breed fleet of teachers that are employed in primary and Junior Secondary Education levels to impart knowledge, moral and societal values for better change and stability, hence the need for institutions to have regular feedbacks from the adjoining societies so as to breed developmental policies and planning to ascertain development. PURPOSE: The study’s purpose was to survey the students’ experiences shortly after completing their NCE and to examine the impact of their academic training, social engagement and inter-personal relationship while they were at the College on their present professional conduct. METHOD: A multi-faceted methodological approach was engaged in this study. This made room for a wide range of data collection. Robust discourse questionnaires and interviews were employed. RESULTS: The results showed 35% of the graduates have gone for further studies, 58.2% still with NCE and 6.1% are currently pursuing additional qualification. Most of the alumni are fully engaged in teaching either at Primary or Secondary school levels for permanent and pensionable appointments and only a few are engaged by Parent Teacher Association (PTA). It also revealed that collection of statement of results after graduation was very difficult and that graduates’ relationship with staff and others was very pleasant. The training received from the college was also found to be impressive by most graduates. CONCLUSION: The study recommended that there should be room for quality in the teaching/learning environment and that lecturers should make maximum impact on the would-be teachers as they go through learning in the College