19 research outputs found
Consonance of General Mathematics and Physics: The Learners’ Achievement Symmetry
No full textThe consonance and interrelatedness of mathematics and science Perdue in the parlance of scholars. Admittedly over the years, researchers have established mathematical components as germane in learning physics. The symmetry between these two subjects at the senior secondary school level may afford more answers than questions. This Ex post facto research traversed predictively, the consonance between students’ General Mathematics ability and their achievement in Physics. A purposive sampling technique was employed in the selection of 857 respondents in this study. Pro forma of students’ grade in General mathematics and Physics from West African Senior School Certificate Examinations (WASSCE) elicited data for the study. Pearson’s Product Moment Correlation and Multivariate Analysis of Variance tools inferenced four research hypotheses raised and succinctly answered. This study established symmetry in students’ General Mathematics ability and students’ achievement in Physics. Score levels, gender and school type were also pioneered to influence this predictio
Short communication: Hydrocarbon accumulation and discharge by the crayfish in some rivers of lagos, Nigeria
No full textCrayfishes exposed to 14C-naphthalene-5% of an aqueous fraction of crude oil in open non-aerated glass jars for 4 h at 25 0C showed no significant differences (P > 0.25) in the amount of naphthalene uptake. Different parts of the crayfishes were quantified for naphthalene uptake and cephalothorax containing hepatopancreas (a food absorption organ) was found to have greater uptake than the tail flesh or tail skeleton. Release of the oil from the crayfishes that were exposed for 1, 2, 3 or 4 h and later placed in open non-aerated jars containing oil-free water showed greater loss of most of the 14C activity during the first 24 h, there was little losses at 48, 72 and 96 h. There was significant volatilization (P 14C-naphthalene in a 5% of crude oil placed in open, non-aerated, oil-free glass jars for 24 h at 25 0C
Physico-Thermally Modified Chrysophyllum albidum Seed Shell Activated Carbon for Removal of Malachite Green Dye from Simulated Wastewater
No full textThe objective of this paper was to physico-thermally modify Chrysophyllum albidum seed shell (CASS) to Chrysophyllum albidum seed shell activated carbon (CASSAC) for removal of malachite green dye from simulated wastewater using isotherm, kinetic, and thermodynamic models after applying appropriate standard techniques. The result of physico-thermal treatment of CASS to CASSAC showed that the modification of CASS increases total pore volume to 0.522 cm³/g, average pore size to 24.22 Å and surface area to 1450.20 m²/g. The maximum dye removal efficiency was 80.12% at experimental conditions of (initial dye concentration - 50 mg/L, CASSAC dosage - 0.30g, pH 8, and agitation time - 60 min). The Temkin and pseudo-first-order models best fit the data, indicating homogeneous monolayer adsorption driven by physisorption. Thermodynamic study showed adsorption is feasible, spontaneous, and endothermic. On the other hand, the reusability study was carried out and the adsorbent was utilized in three cycles with a drop in the removal efficiencies from 80.0 to 58.9% after the third cycle usage. This study concludes that CASSAC effectively removes malachite green dye from wastewater through adsorption, offering a cost-effective, sustainable, and environmentally friendly solution for textile wastewater treatment
Physico-mechanical properties, tribological behaviour and metallurgical characteristics of aluminium metal matrix composites reinforced with agricultural residues: A Review: Physico-mechanical properties, tribological behaviour and metallurgical characteristics of aluminium metal matrix composites reinforced with agricultural residues: A Review
No full textAluminium Metal Matrix Composites (AMMCs) that are reinforced with agricultural residues (such as rice husk ash, coconut shell ash, sugarcane bagasse ash, maize/corn-cob ash, palm kernel and shell ash) have garnered increasing attention as environmentally friendly, low-cost, and lightweight alternatives to traditional ceramic reinforcements. This review gathers recent findings on (1) physico-mechanical properties (tensile strength, hardness, ductility, density), (2) tribological behaviour (wear rate, friction coefficient, wear mechanisms), and (3) metallurgical characteristics (microstructure, interfacial bonding, phase formation, porosity) of agro-reinforced AMMCs. The review describes common synthesis methods (stir casting and powder metallurgy), emphasises critical microstructure–property correlations, pinpoints persistent challenges (particle agglomeration, inadequate wettability, porosity, variable pre-treatment) and optimisation process. Key fabrication techniques are briefly outlined, and future research directions encompassing hybridisation techniques and surface modifications are provided
A Influência do pH e da dureza sobre a inibição do ciclo de vida do microcrustáceo moina micrura (Kurz, 1874) em um tanque de decantação
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Ambiental, Florianópolis, 2010Uma problemática encontrada pela empresa CLE Brasil, situada no litoral norte do estado de Santa Catarina, foi a presença do microcrustáceo Moina micrura (Kurz, 1874) no tanque decantador do sistema de tratamento de efluentes. Em grande densidade, esse organismo causa um aumento da concentração dos sólidos sedimentáveis em suspensão, necessitando de intervenções operacionais de limpeza no sistema para redução da população do microcrustáceo a fim de manter o efluente tratado dentro dos limites da legislação estadual. Na tentativa de solucionar o problema, nosso estudo avaliou a influência do pH e da dureza sobre a inibição do ciclo de vida do microcrustáceo Moina micrura, utilizando três variações para o pH (5,0; 7,0; 9,0) e quatro variações para a dureza (30; 65; 130; 260mg CaCO3/L), com dez repetições cada, com 1 indivíduo por unidade experimental. Verificou-se a influência sobre o total de indivíduos gerados por fêmea, sobre o número de desovas por fêmea e sobre a longevidade dos microcrustáceos para os diferentes tratamentos. Para as três variações de pH analisadas, não foi observada diferença significativa entre os tratamentos para o total de indivíduos gerados por fêmea e sobre o número de desovas por fêmea (p<0,05), porém para o tratamento pH = 5,0 houve maior mortalidade (menor longevidade). O tratamento dureza 30mg CaCO3/L apresentou o menor número de organismos gerados por fêmea e o menor número de desovas totais por fêmea (p<0,05); para os tratamentos de dureza 65 e 130mg CaCO3/L ocorreu um valor intermediário no número de organismos gerados por fêmea e, para o tratamento dureza 260mg CaCO3/L, ocorreu o maior número de organismos gerados por fêmea. Os tratamentos 65, 130 e 260mg CaCO3/L não apresentaram diferença significativa para o número de desovas totais por fêmea (p<0,05). Para o tratamento dureza 30mg CaCO3/L, houve maior mortalidade (menor longevidade). Assim, para controlar a proliferação dos microcrustáceos Moina micrura no tanque de decantação, a indústria deverá manter o pH do tanque de decantação próximo de 5,0, bem como dureza ao redor de 30mg CaCO3/L.A problem encountered by the company CLE Brazil, situated on the north coast of Santa Catarina, was the presence of microcrustacean Moina micrura (Kurz, 1874) in the settling tank of effluent treatment system. In great density, this organism causes an increase in turbidity and a lower deposition of the flakes, establishing a concentration of settleable solids in suspension above the acceptable, under state law, in the effluent released by this company. In an attempt to solve the problem, our study evaluated the influence of pH and hardness on the inhibition of the life cycle of Moina micrura, using three variations of pH (5.0, 7.0, 9.0) and four variations of hardness (30, 65, 130, 260mg CaCO3/L), using ten repetitions with one individual each. Was analyzed the influence on the total organisms generated per female, on the number of spawning per female and the longevity for the different treatments. For the three variations of pH examined, there was no significant difference between treatments for total organisms generated per female and the number of spawning per female (p <0.05), however for the treatment pH = 5,0 there was higher mortality (shorter lifetime). The treatment hardness 30 mg CaCO3/L showed the lowest number of organisms produced per female and a smaller number of spawning per female (p <0.05); the treatments hardness 65 and 130 mg CaCO3/L were an intermediate value in the number of organisms produced per female and for treatment hardness 260mg CaCO3/L was the highest number of organisms produced per female. Treatments 65, 130 and 260mg CaCO3/L showed no significant difference for number of spawning per female (p < 0.05). For treatment hardness 30mg CaCO3/L there was higher mortality (shorter lifetime). To control the proliferation of microcrustaceans Moina micrura in the settling tank, the company must maintain the pH of the settling tank near of 5,0 and hardness around 30 mg CaCO3/L
Tratamento de efluente agroindustrial contendo compostos persistentes por meio dos processos de coagulação-floculação, fenton, foto-fenton, foto-peroxidação e ozonização
No full textTese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia Química.Os efluentes gerados nos mais diversos segmentos de indústrias contêm uma série de compostos orgânicos e, dentre eles, substâncias químicas altamente perigosas, os chamados compostos persistentes de difícil degradação, também conhecidos como recalcitrantes, altamente prejudiciais ao meio-ambiente e que apresentam elevada toxicidade e bioacumulação. Esses compostos não são degradados nos sistemas de tratamento biológico normalmente aplicados nas indústrias, o que faz com que seja de fundamental importância que as indústrias busquem formas de melhorar a qualidade de seus efluentes por meio de modificações no processo ou nos sistemas de tratamento utilizados. Os processos de oxidação química e oxidação avançada têm se destacado como forte alternativa para o tratamento desses efluentes que contêm compostos persistentes. No presente trabalho, o efluente de estudo foi originário de um incubatório de aves e contém uma série de compostos persistentes. Numa primeira etapa, o efluente foi caracterizado e submetido a diferentes tipos de tratamento físico-químicos, como a coagulação-floculação, Fenton, foto-Fenton e foto-peroxidação. Dentre os processos investigados, o tratamento do efluente pelo processo foto-Fenton foi o que se mostrou mais adequado, resultando nas melhores eficiências de remoção de matéria orgânica, de aproximadamente 92% DQO. Posteriormente, o efluente foi submetido a análises de cromatografia líquida acoplada a espectrometria de massas (LC/MS), onde a presença de compostos persistentes foi investigada. Dentre os compostos detectados, confirmou-se a presença no efluente de um composto organoclorado, o pesticida imazalil, que é um fungicida utilizado nas atividades de limpeza da indústria, sobre o qual não há dados na literatura relacionados ao seu tratamento e degradação, sendo, portanto, definido como composto alvo desta etapa do trabalho. A cinética de degradação do pesticida imazalil pelo processo de oxidação avançada, foto-Fenton foi estudada. Paralelamente, investigou-se o tratamento do imazalil pelo processo de ozonização, em uma faixa de pH determinada, onde tert-butanol (t-BuOH) foi utilizado como agente seqüestrante de radicais hidroxilo, para que se pudesse avaliar a ação do ataque direto do ozônio molecular sobre o imazalil. Procederam-se, para ambos os processos, aos estudos de investigação, detecção e identificação dos produtos de degradação resultantes desses processos oxidativos, pelo emprego de LC/MSn (cromatografia líquida acoplada a espectrometria de massas tandem), bem como a avaliação da toxicidade causada por eles. Para cada processo detectou-se a presença de quatro produtos de degradação, antes desconhecidos, cujas estruturas foram elucidadas. As análises de toxicidade resultaram em um decréscimo na toxicidade no decorrer de ambos os tratamentos, indicando que os produtos de degradação formados não são mais tóxicos que sua molécula original, o imazalil. O presente trabalho resultou em uma importante contribuição por apresentar opções de tratamento para efluentes que contêm compostos persistentes, e em especial pelo estudo de degradação do pesticida imazalil, composto não estudado até então e, identificação de produtos de degradação originados nesses tratamentos, antes desconhecidos
Microstructure and mechanical properties of metal powder treated AISI- 430 FSS welds
No full textAbstract: An innovative yet simple technique for the inoculation of the weld pool of commercial AISI 430 Ferritic Stainless Steel (FSS) with metal powders for grain refinement is discussed. Aluminum or titanium powder in varying amounts introduced into the weld pool via powder preplacement technique was melted under a tungsten inert gas (TIG) torch. This strategy of inoculating the welds offers dual benefits of grain refinement and constriction in the weld geometry. The addition of the metal powders constricts the HAZ by as much as 50% of the conventional weld providing a grain refinement index (GRI) of about 0.8 in titanium powder treated welds. It equally emerged that weld property is not influenced by the grain size alone but equally by the amount of delta ferrite in the microstructure
Fatigue Behaviour of Medium Carbon Steel of Different Grain Structures
No full textThis paper investigated the effect of heat treatment operations on the fatigue resistance of low carbon steel. Specimens after preparation for fatigue testing were subjected to annealing, normalizing and quenching heat treatment. Results show that the annealed specimen had the largest number of cycles to failure, indicating a high fatigue resistance. The microstructure of the specimens was examined in other to corroborate the obtained property with the microstructure. When compared with the untreated specimen, the annealed specimen (with optimum fatigue resistance) shows a large grains size of pearlite which was distributed across the entire surface of the microstructure. Generally, it was found that the size and distribution of specimens’ grains affect the resistance of the low carbon steel to fatigue failure. Keywords: fatigue, low carbon steel, heat treatment, microstructur
Tracking local brittle zone in the heat affected zone of girth-welded API 5L x46 pipe
No full textIn this study, microhardness variation as well as macro and micro structural examination of the heat affected zone (HAZ) of a girth welded API 5L X46 pipeline material were conducted as a means of tracking local brittle zone (LBZ) in the HAZ region. The weldment analysed were built from heat input range of 695 J/mm – 2567 J/mm. Analysis of the results revealed that the HAZ profile changes with variation in the heat input and becomes shallow but wider as the heat input increases. Defects free welds were achieved under the heat input range of 1650 J/mm – 2017 J/mm welding condition. Localized high hardness values were obtained at certain locations within the HAZ of intermediate heat input welds produced at 1467 J/mm due to thermal stresses induced strains at this heat input in the resolidified weld. Other than this, non-equilibrium rapid heating/cooling that is common during welding as well as the magnitude of mechanical strain generated on cooling vary with heat input and was attributed to the development of high hardness value at localized region within the HAZ of the welds in low heat input welding condition. The macrographic profile at these locations, contrasted against that of a failed pipeline material of similar specification obtained from typical oil and gas infrastructure, established that crack initiation and propagation followed the trend of microhardness variations in the girth welded pipe. The crack initiates at specific location in the HAZ with very high hardness in the range 186-216 Hv within a radius of about 3-5 mm from the edge of the fusion zone.
Keywords: API 5L X46; Girth welding; Heat input; Heat affected zone; Local brittle zone
