198 research outputs found

    Effects of Current Density and Deposition Time on Corrosion Behaviour of Nickel-based Alloy Coatings

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    Corrosion of fasteners is an on-going issue and stainless steel 304 (SS304) is prone to this destructive process. One method to mitigate corrosion is electrodeposition of Co-Ni-Fe nanoparticles.  This paper studied the effects of deposition time and current density on corrosion behaviour of Co-Ni-Fe coated SS304 bolt. Co-Ni-Fe ternary alloys were electrodeposited onto SS304 bolt in 15, 30, or 45 minutes by using current density of 28, 35, 42 mA/cm2. Combinations of these parameters produced 9 samples. These samples were electrochemically tested by a potentiostat using open circuit potential (OCP) and potentiodynamic polarization (PDP). The samples were also characterised in terms of surface roughness and thickness of the coatings by using 3D surface metrology system. The OCP value decreased when deposition time was increased. All sample synthesised in 30 minutes had a more stable OCP curve. PDP curves exhibited active behaviour without passivation region. The corrosion potential (Ecorr) of T15 samples was more anodic than T30 and T45 samples. The corrosion current density (Icorr) of all samples fluctuated. Sample synthesised in 30 minutes using 42 mA/cm2 had the lowest corrosion rate. It was found that the surface roughness influences the corrosion behaviour in which a lower surface roughness tends to produce coating with better corrosion performance. Current density had small effect on the thickness of coating, whereas the tendency of a thickness to increase was obvious for deposition time

    Effects of Current Density and Deposition Time on Corrosion Behaviour of Nickel-based Alloy Coatings

    Get PDF
    Corrosion of fasteners is an on-going issue and stainless steel 304 (SS304) is prone to this destructive process. One method to mitigate corrosion is electrodeposition of Co-Ni-Fe nanoparticles.  This paper studied the effects of deposition time and current density on corrosion behaviour of Co-Ni-Fe coated SS304 bolt. Co-Ni-Fe ternary alloys were electrodeposited onto SS304 bolt in 15, 30, or 45 minutes by using current density of 28, 35, 42 mA/cm2. Combinations of these parameters produced 9 samples. These samples were electrochemically tested by a potentiostat using open circuit potential (OCP) and potentiodynamic polarization (PDP). The samples were also characterised in terms of surface roughness and thickness of the coatings by using 3D surface metrology system. The OCP value decreased when deposition time was increased. All sample synthesised in 30 minutes had a more stable OCP curve. PDP curves exhibited active behaviour without passivation region. The corrosion potential (Ecorr) of T15 samples was more anodic than T30 and T45 samples. The corrosion current density (Icorr) of all samples fluctuated. Sample synthesised in 30 minutes using 42 mA/cm2 had the lowest corrosion rate. It was found that the surface roughness influences the corrosion behaviour in which a lower surface roughness tends to produce coating with better corrosion performance. Current density had small effect on the thickness of coating, whereas the tendency of a thickness to increase was obvious for deposition time

    Squirrel cage induction motor scalar control constant V/F analysis

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    In constant V/f control technique it is assume that the stator resistance and leakage inductance drops are negligible, especially at high speed and small load. In other words, the back emf is comparatively large at high speed and hence these voltage drops can be neglected. By maintaining constant V/f, constant Eg/f and hence constant air-gap flux is assumed. This assumption is however invalid at low speeds since a significant voltage drop appears across the stator impedance. The terminal voltage, V no longer approximates ag. By using MATLAB Simulink, the open-loop constant V/f is simulated. It is shown that the performance of the drive deteriorates at low speeds. The improvement in the performance by applying voltage boost is shown and discussed

    Impact damage resistance and post impact tolerance of optimum banana-pseudo stem fiber reinforced epoxy sandwich structures

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    Banana fiber has a high potential for use in fiber composite structures due to its promise as a polymer reinforcement. However, it has poor bonding characteristics with the matrixes due to hydrophobic-hydrophilic incompatibility, inconsistency in blending weight ratio, and fiber length instability. In this study, the optimal conditions for a banana/epoxy composite as determined previously were used to fabricate a sandwich structure where carbon/Kevlar twill plies acted as the skins. The structure was evaluated based on two experimental tests: low-velocity impact and compression after impact (CAI) tests. Here, the synthetic fiber including Kevlar, carbon, and glass sandwich structures were also tested for comparison purposes. In general, the results showed a low peak load and larger damage area in the optimal banana/epoxy structures. The impact damage area, as characterized by the dye penetration, increased with increasing impact energy. The optimal banana composite and synthetic fiber systems were proven to offer a similar residual strength and normalized strength when higher impact energies were applied. Delamination and fracture behavior were dominant in the optimal banana structures subjected to CAI testing. Finally, optimization of the compounding parameters of the optimal banana fibers improved the impact and CAI properties of the structure, making them comparable to those of synthetic sandwich composites

    Effects of feeding frequency on growth performance of endangered Temoleh, Peobarbus jullieni (Sauvage, 1880) juveniles

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    The experiment was designed to investigate the effects of feeding frequencies on the growth and feed utilization efficiencies of endangered Temoleh, Probarbus jullieni under captive rearing condition. The juvenile fish, weighing from 12.03g to 32.64g, were fed with an extruded commercial pellet for 60 days. Three restricted feeding regimes were tested in treatments viz., three meals per day (Teratment-1, T1), two meals per day (Teratment-2, T2) and one meal per day (Teratment-3, T3). The experiment was carried out in aquarium tanks on a recirculating water system. The fortnightly mean growth rate was 2.00 g in T1, 1.27 g in T2 and 0.57 g in T3, decreasing from T1 to T3 in that order. The percentage weight gain, specific growth rate (SGR), and daily growth rate (DGR) were significantly different (P < 0.05) among the treatments, which were highest in T1 as compared to those in T2 and T3, respectively. The best food conversion ratio (FCR) was also observed in T1. Among the tested treatments, three times a day feeding regime appeared to be the most suitable and could be recommended for rearing of P. jullieni under intensive culture systems

    Effects of deforestation on physicochemical properties and microbial population of soils in a South-East Asian tropical forest

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    The study was conducted in deforested land and adjacent natural forest in Chittagong Forest South Division, Bangladesh, to explore the effects of deforestation on physico-chemical properties of soil and the soil microbial population. Soil samples from surface (0-10 cm depth) or subsurface (10-20 cm depth) of two hill positions (top and bottom) of deforested land and an adjacent natural forest were collected and analysed for their physico-chemical properties and microbial population. The study reveals that there was no significant (p≤0.05) difference in soil texture for soil surfaces or hill positions between the deforested land and natural forest. However, significantly (p≤0.05) low moisture content and high pH was observed in both the surfaces and hill position in deforested land compared to the natural forest. The microbial community i.e., the fungal and bacterial population was also significantly (p≤0.05) lower in both surfaces (0-10 cm and 10-20 cm) of hill positions in the deforested land compared to natural forest. Fungal population ranged from 59 to 76 million g-1 and 78 to 153 million g-1 of dry soil in deforested land and in natural forest, respectively, whereas bacterial population ranged from 70 to 146 million g-1 in deforested land and from 127 to 218 million g-1 in natural forest. A total of seven genera of fungi were primarily identified from the soils of natural forest and six from the deforested land. The six common genera of identified fungi in both the land used were Mucor, Aspergillus, Rhizopus, Fusarium, Penicillium and Trichoderma and the different one was Colletotrichum from the natural forest. Three genera of bacteria coccus, Streptococcus and Basillus were noticed in natural forest and two genera (coccus and Streptococcus) were recorded from deforested land

    Physical fatigue assessment for intrastate bus driver

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    Fatigue is considered a psychological or mental fatigue type characterized by subjective feelings of a disinclination to continue driving, drowsiness, fatigue, and deduction motivation. Bus drivers in Malaysia have been facing physical fatigue from driving for many years. Therefore, investigating the psychophysiological factor that related to fatigue could improve understanding and management for fatigue in the transport industry. Physical factors are divided by two parts that is upper and lower body. The objective of this study is to identify the cause, determine the level and analyze the physical fatigue on bus driver. There were two methods applied in this study, which were Modified Nordic Questionnaires that represent subjective measurement and surface Electromyography (sEMG) the objective measurement. Results from sEMG showed neck and upper back muscle groups leads to fatigue as the muscle is running out of energy based from the graph. Through the sEMG data, it can determine the level of physical fatigue on bus driver and analyzed the physical fatigue. Findings of this study from the questionnaire data analysis using the Statistical Package Social Science software, it is proved that physical fatigue really occurred to the intrastate bus driver. Results also showed significant correlation relationship between physical and mental

    Terminal ileum herniation through the broad ligament as rare cause of small bowel perforation

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    INTRODUCTION: Obstruction and perforation of small bowel due to internal herniation into the broad ligament is a rare. To the best of our knowledge, this is the third case report in the literature. OBJECTIVE: We report a case of small bowel herniated through broad ligament causing obstruction and perforation. REPORT A 38-year-old female with history of recent lower segment caesarean section, presented with nausea, abdominal pain and distention for 11 days prior. Clinically she was dehydrated, the abdomen was distended and tender but there was no peritonism. Abdomen X-ray show dilated small bowel. Contrast enhanced CT abdomen showed generalized dilation of small bowel most likely due to adhesion band. Emergency laparotomy was performed and noted small bowel was herniated and strangulated into a broad ligament defect with 2cm perforation at the terminal ileum. The attachment of the broad ligament then was released from the lateral peritoneal wall and limited right hemicolectomy with primary anastomosis was performed. Patient was discharged well post operatively. CONCLUSION Strangulated Small bowel broad ligament hernias are rare and challenging to diagnose preoperatively. Despite history of abdominal surgery, internal herniation should be considered before opting conservative treatment

    An Improved DC Circuit Breaker Topology Capable of Efficient Current Breaking and Regeneration

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    The DC power system, due to its convenience of conversion, integration, and use, is getting immense attention in the field of power transmission and distribution. It is superior to traditional AC systems in terms of efficiency, reliability, and control simplicity as well. A DC circuit breaker is one of the important elements of any DC power system. It is a sophisticated technology designed to break DC current only. The breaking of a DC current is always challenging compared to the breaking of an AC current, as DC current does not have natural zero crossing points like AC current has. Moreover, DC current breaking becomes more critical when the current is inductive as energy stored in the network inductance opposes instantaneous current breaking. Hence, this energy needs to be absorbed and dissipated as heat during the current breaking operation, which is exactly what is done in the traditional DC circuit breaker topologies. This paper introduces a new topology for DC circuit breakers with a mechanism to reuse this stored energy instead of dissipating it. The mechanism is analogous to regenerative braking in electric drive systems and can enhance the overall system efficiency. The proposed scheme was analyzed through rigorous computer simulation and was experimentally validated
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