EFFECTS OF GAS FLOW RATE AND CATALYST LOADING ON POLYMER ELECTROLYTE MEMBRANE (PEM) FUEL CELL PERFORMANCE AND DEGRADATION

ABSTRACT In this paper, the effects of gas flow rates, and catalyst loading on polymer electrolyte membrane fuel cell (PEMFC) performance was investigated using a 50cm² active area fuel cell fixture with serpentine flow field channels machined into poco graphite blocks. Membrane Electrode Assemblies (MEAs) with catalyst and gas flow rates at two levels each (0.5mg/cm², 1mg/cm²; 0.3L/min, 0.5L/min respectively) were tested at 60°C without humidification. The cell performance was analyzed by taking AC Impedance, TAFEL plot, open circuit voltage, and area specific resistance measurements. It was observed that MEAs with lower gas flow rate had lesser cell resistance compared to MEAs with a higher gas flow rate. TAFEL plot shows the highest exchange current density value of -2.05 mAcm² for MEA with 0.5mg/cm² catalyst loading operated at reactant gas flow rate of 0.3L/min signifying it had the least activation loss and fastest reaction rate. Open circuit voltage curve shows a higher output voltage and lesser voltage decay rate for MEAs tested at higher gas flow rates

Evaluation of the Side Effects of Cisplatin Drug in a Nephrotoxicity Model of Wistar Rats

This study critically assessed the observable side effects of cisplatin (anti-tumor) drug in a Portulaca oleracea treated nephrotoxicized wistar rats. Twenty four albino female rats were grouped into four-groups A, B, C, & D. Group A served as the control group; group C and D were all nephrotoxicized using 2ml/kg cisplatin and treated with 400mg/kg and 800mg/kg doses of Portulaca oleracea methanolic extract respectively. Group B were nephrotoxicized but remained untreated. Significant Increase in serum creatinine (P<0.05) in group B rats showed presence of nephrotoxicity and results further showed recovery (significant decrease at P<0.05) in serum creatinine level of groups C &D rats due to the administration of portulaca oleracea. Physically observable features were examined in the rats at the 4th & 7th day of drug administration which showed the presence of side effects (ototoxicity, loss of appetite, black stool, dizziness, fever, etc) which were seen to be increasing with prolonged administration. This research posits seemingly untreatable side effect of cisplatin chemotherapy which increases with increased chemotherapy duration and decreased side effects in the combination of portulaca oleracea in cisplatin chemotherapy. Keywords: chemotherapy, cisplatin and nephrotoxicity

The Renoprotective Effect of Methanolic Extract of Portulaca Oleracea on Cisplatin-Induced Nephrotoxicity in Wistar Rats

This study was carried out to investigate the renoprotective effect of Portulaca oleracea on cisplatin-induced nephrotoxic wistar rats. Twenty four (24) female wistar rats were randomly divided into six (6) groups - Group A were given no treatment and served as the control group; Group B was given only a single dose of cisplatin (2ml/kg) and served as the cisplatin control group. Groups C and D were orally given 400mg/kg and 800mg/kg body weight of methanolic extract of portulaca oleracea (MEPO) respectively 6 hours after cisplatin injection (2ml/kg) . Groups E and F were orally given 400mg/kg and 800mg/kg body weight of MEPO respectively 6hours before cisplatin injection (2ml/kg) for 7 days. The effect of the treatment on relative kidney weight, serum creatinine level, serum uric acid and histoarchitecture of the rat kidney were accessed. Results showed significantly decreased serum creatinine levels (p<0.05) in rats treated with 400mg/kg b.wt. and 800mg/kg b.wt.  MEPO as compared with the cisplatin control group. Serum uric acid was significantly decreased  in groups C, D, E, and F when compared with control A. The relative average weight of the kidney increased significantly in all treated groups except group treated with 800mg/kg b.wt. MEPO 6hours before cisplatin. Kidney histological slides showed both recovery from and prevention of effects of induced toxicity at all treatment doses. Results suggest that Portulaca oleracea extract may be used to cure or prevent cisplatin-induced renal toxicity without any adverse effect; hence it can serve as a novel combination agent with cisplatin to limit renal injury. Keywords: Cisplatin, portulaca oleracea, renoprotection, nephrotoxicity

Structural Damage Detection in Beams by Wavelet Transforms

The use of a laser-based optical system and wavelet transforms is explored for the detection of changes in the properties of cantilevered aluminum beams as a result of damage. The beams were modeled using the ANSYS 5.3 finite-element method and the first six mode shapes for the damaged and the undamaged cases obtained. Damage was simulated by a reduction in the stiffness of one element. Gaussian white noise was added externally to simulate field conditions. The results show that a spatially-localized abnormality in the mode shape could be represented uniquely by a small set of wavelet coefficients while the white noise was uniformly spread throughout the wavelet space. It was observed that the damage clearly manifested in the sixth-order detail of certain modes only. A different finite-element model was used as a test beam to validate the proposed method. An actual aluminum beam, fabricated with dimensions similar to the test beam, was excited and the mode shapes recorded with the scanning laser vibrometer. Damage was created by machining a notch in the beam of the same dimensions as the finite-element test beam. An image of the damage location was obtained from the continuous wavelet transform coefficients. The magnitude of the wavelet coefficients at the damage location showed a close correlation to the severity of damage. It was observed to increase with increasing damage. The finite-element test beam results showed a close correlation to the corresponding experimental beam results. The method benefits from the fact that the undamaged mode shapes were not used to evaluate the condition of the beam, which in most field conditions is not feasible

Enhancement of Viscosity and Thermal Conductivity of Soybean Vegetable Oil using Nanoparticles to Form Nanofluids for Minimum Quantity Lubrication Machining of Difficult-To-Cut Metals

Sustainable use of vegetable oil as a base fluid in minimum quantity lubrication (MQL) strategy for machining advanced materials is promising but limited due to their low thermal conductivity and viscosity. This paper presents the results of experimental investigation for enhancing viscosity and thermal conductivity of high oleic soybean vegetable oil (HOSO) using Al2O3, MoS2, and TiO2 nanoparticles (30 nm particle size and 0.5-4.0% wt. concentration) inclusion to form nanofluids at temperature ranging from 25 to 70 °C for use in vegetable oil-based nanofluids-MQL machining of difficult-to-cut metals. The result shows that viscosity and thermal conductivity of HOSO increase with increase in nanoparticle weight concentration, but there is a decrease in suspension stability of the nanofluid. Also, viscosity of HOSO nanofluids decreases with increase in temperature, but thermal conductivity increases with increase in temperature, while for the base HOSO, it decreases with increase in temperature. This is a very significant positive observation especially for difficult-to-cut materials that generate high heat that need to be conducted away from the cutting zone. Thermal conductivity and viscosity were enhanced up to 55% (using MoS2 at 70 °C and 4% wt. concentration) and 11.5% (using TiO2 at 50 °C and 3.5% wt. concentration), respectively. The Brownian motion of the nanoparticles and liquid-solid interlayer interfaces are responsible for this behavior of the nanofluid thermal conductivity, while nanoparticle thickening and entangle mechanism were responsible for the behavior of the nanofluid viscosity. This implies that lower oil flow rate can be applied during machining of Inconel-718 due to increased viscosity and thermal conductivity to obtain optimal machining performance, lower power consumption, and reduce negative impact on the environment

An Approach for Development of Damage-Free Drilling of Carbon Fiber Reinforced Thermosets

A new comprehensive approach to select cutting parameters for damage-free drilling in carbon fiber reinforced epoxy composite material is presented. The approach is based on a combination of Taguchi\u27s experimental analysis technique and a multi-objective optimization criterion. The optimization objective includes the contributing effects of the drilling performance measures: delamination, damage width, surface roughness, and drilling thrust force. A hybrid process model based on a database of experimental results together with numerical methods for data interpolation are used to relate drilling parameters to the drilling performance measures. Case studies are presented to demonstrate the application of this method in the determination of optimum drilling conditions for damage-free drilling in BMS 8-256 composite laminate. A process map based on the results is presented as a tool for drilling process design and optimization for the investigated tool/material combination

Machinability Characterization in Drilling Graphite Fiber-Composites

Due to the inhomogeneous nature of the composite materials, the machinability of fiber reinforced composites is different from that of metals. In this paper, a method for characterization of the machinability of composite materials is presented. This method is based on parametric analysis of the drilling process using the Design of Experiments Approach. The project goal includes quantifying the effects of cutting speed, feed rate, tool material, and tool geometry on delamination, surface roughness, and thrust force during the drilling of carbon fiber-reinforced composites. Utilizing the aforementioned method, the optimum machinability characteristics of graphite fiber reinforced composites were predicted with 97% accuracy

Machinability Characterization in Drilling Graphite Fiber-Reinforced Composites

Due to the inhomogeneous nature of the composite materials, the machinability of fiber reinforced composites is different from that of metals. In this paper, a method for characterization of the machinability of composite materials is presented. This method is based on parametric analysis of the drilling process using the Design of Experiments Approach. The project goal includes quantifying the effects of cutting speed, feed rate, tool material, and tool geometry on delamination, surface roughness, and thrust force during the drilling of carbon fiber-reinforced composites. Utilizing the aforementioned method, the optimum machinability characteristics of graphite fiber reinforced composites were predicted with 97% accuracy

Detection and Characterization of Damage in Composite Plates Using Shearography and Wave-Based Acoustic Emission Techniques

This paper investigates the use of shearography and waveform- based acoustic emission (AE) techniques to detect and assess damage in composite plates due to high velocity impact. Five 48-ply [0/+45/90/-45]6s laminated AS4/PEEK composite plates donated by Boeing Company in St. Louis were used as test specimens. Shearography images of all five test specimens were taken before impact testing to detect any pre- existing internal damage from fabrication. Three broadband AE sensors were mounted on the surface of the composite plates to measure AE signals due to impact. High velocity impact tests of plates with all four edges clamped were conducted using a gas gun facility. The AE sensor signals were instantaneously acquired during the impact tests and stored in a Pentium computer. The digitized AE signals were processed in time and frequency domains. The raw AE signals were preprocessed to remove reflections from the plate boundaries that distort the wave form and cause errors. The resulting damage due to impact was evaluated using shearography fringe patterns and AE sensor signal features. The results show a correlation of AE parameters such as AE energy, AE amplitude, AE count, and shearography fringe patterns with impact energy and impact damage of the composite plates. The AE signals show the presence of both extensional and flexural wave modes with flexural wave the dominant mode. There is quite a distinctive difference between shearography fringe patterns of undamaged and damaged composite plates