Journal of Engineering and Technological Sciences
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Use of Systematic Approach in Accident Risk Analysis for Motorcyclists: A Conceptual Idea
Get PDFThus far, minimum stopping sight distance (SSD) is determined based on design speed, a minimum reaction time of 1.64 s and a deceleration rate of 3.4 m/s², whereas in certain situations the latter can be shorter than 1 s and higher than 4.5 m/s². Awareness of this can trigger speculative behavior, as can be seen from the choice of speed and/or the critical crossing gap, which is often smaller than the recommended minimum SSD. This study focused on the development of an appropriate minimum SSD model that is suited to risky conditions at an un-signalized intersection and its possible usage in accident risk evaluation, particularly for motorcyclists. The data were taken from direct measurements and related studies. Variables that potentially influence minimum SSD were tested. The results strongly suggest that the speed reduction achieved by downshifting significantly influences both the braking distance and the impact speed. Moreover, the minimum SSD obtained from the proposed model significantly differs from that obtained from a similar model recommended by AASHTO. Therefore, it is worthwhile to consider the application of the proposed minimum SSD as an accident probability indicator parameter
Axial Inlet Geometry Effects on the Flow Structures in a Cyclone Burner Related to the Combustion Performance of Biomass Particles
Get PDFSolid fuel combustion is always preceded by chemical decomposition. This process is largely determined by the flow structure and affected by the geometry and operating conditions of the combustion chamber. This study aimed to investigate the effect of relative axial inlet diameter (Dai//Dbc) on the flow structure in the proposed cyclone burner. The flow structure was determined with the standard k-e turbulent model using the Ansys-Fluent software. From the simulation results it was concluded that with all the axial inlet diameters used an integrated vortex formed in the center of the burner cylinder. The integrated vortex consisted of two vortices, namely a primary vortex and a secondary vortex. The primary vortex penetrated from the furnace box to the burner cylinder, while the secondary vortex was formed in the burner cylinder itself. There were two integration patterns from the primary vortex and the secondary vortex, namely a summation pattern and a multilayer pattern. The presence of a vortex in the center of the burner cylinder is allegedly responsible for an increase in the degree of mixing and pressure drop in that zone. The flow structure induced from the proposed burner had high symmetricity and was largely determined by the burner's axial inlet diameter
Development and Performance Evaluation of Coir Pith Ash as Supplementary Cementitious Material in Concrete
Get PDFIndia is the third largest producer of coconuts in the world after Indonesia and Brazil. The production of coconuts generates enormous volumes of by-products, which are dumped in landfills, causing issues like soil and air contamination, pollution of groundwater and other water bodies, with hazardous impacts on plant and animal life. Coir pith and short fibers are by-products from the coir industry obtained during the extraction of long fibers and account for approximately 70% of the mature coconut husk. Coir pith ash (CPA) was prepared by heating the dried coir pith in a metallic vessel at a temperature of 400 °C for 4 hours. The current paper shows an elaborate technical study on the material properties and performance of CPA in blended cements. The properties of concrete investigated were setting time, workability, compressive strength, splitting tensile strength, flexural strength and ultrasonic pulse velocity values. The specimens were tested at curing ages of 7, 28, 56 and 90 days. The test results indicated that CPA has moderate pozzolanic properties, with 10% as optimum replacement percentage
On-the-fly Computation Method in Field-Programmable Gate Array for Analog-to-Digital Converter Linearity Testing
Get PDFThis paper presents a new approach to linearity testing of analog-to-digital converters (ADCs) through on-the-fly computation in field-programmable gate array (FPGA) hardware. The proposed method computes the linearity while it is processing without compromising the accuracy of the measurement, so very little overhead time is required to compute the final linearity. The results will be displayed immediately after a single ramp is supplied to the device under test. This is a cost-effective chip testing solution for semiconductor companies, achieved by reducing computing time and utilization of low-cost and low-specification automatic test equipment (ATE). The experimental results showed that the on-the-fly computation method significantly reduced the computation time (up to 44.4%) compared to the conventional process. Thus, for every 100M 12-bit ADC tested with 32 hits per code, the company can save up to 139,972 Php on electricity consumption
Comparative Evaluation of Medical Thermal Image Enhancement Techniques for Breast Cancer Detection
Get PDFThermography is a potential medical imaging modality due to its capability in providing additional physiological information. Medical thermal images obtained from infrared thermography systems incorporate valuable temperature properties and profiles, which could indicate underlying abnormalities. The quality of thermal images is often degraded due to noise, which affects the measurement processes in medical imaging. Contrast stretching and image filtering techniques are normally adopted in medical image enhancement processes. In this study, a comparative evaluation of contrast stretching and image filtering on individual channels of true color thermal images was conducted. Their individual performances were quantitatively measured using mean square error (MSE) and peak signal to noise ratio (PSNR). The results obtained showed that contrast stretching altered the temperature profile of the original image while image filtering appeared to enhance the original image with no changes in its profile. Further measurement of both MSE and PSNR showed that the Wiener filtering method outperformed other filters with an average MSE value of 0.0045 and PSNR value of 78.739 dB. Various segmentation methods applied to both filtered and contrast stretched images proved that the filtering method is preferable for in-depth analysis
Novel Design of a Vertical Axis Hydrokinetic Turbine âStraight-Blade Cascaded (VAHTâSBC): Experimental and Numerical Simulation
Get PDFA promising technology to reduce dependency on fossil fuels is hydrokinetic energy conversion using either turbine and non-turbine technology. Hydrokinetic turbine technology is penalized by low efficiency and lack of self-starting. This study involved experimental testing and numerical simulation of a novel hydrokinetic turbine design, called a Vertical Axis Hydrokinetic Turbine â Straight-Blade Cascaded (VAHTâSBC). Three configurations of the design were tested. Model 1 had 3 passive-pitch blades, while Model 2 and Model 3 had 6 and 9 blades respectively, where the outer blades were passive-pitch and the others fixed-blade. Both in the experimental test and in the numerical simulation Model 3 outperformed the other two models. The Cp of Model 3 was 0.42, which is very close to the theoretical Cp for VAHTs (0.45). It worked properly at low TSR. A CFD simulation based on the RANS solver was performed to gain supplementary information for performance investigation. This simulation confirmed that the torque changes because of the change in angle of attack as the turbine rotates. Because they have different numbers of blades, each model has different periodical torque fluctuation patterns. This study verified that utilization of cascaded blades and a passive-pitch mechanism is able to improve turbine performance
Sliding Wear Properties of a Composite of Aluminum 2024 Powder Reinforced with Heat Treatment and Silicon Carbide
Get PDFWear behavior of aluminum alloy 2024 was investigated. Three patterns of specimens, namely, fabricated (compacted), reinforced with silicon carbide only and reinforced with silicon carbide followed by heat-treatment (quenching and aging processes) were selected. The effect of load on the specimen was studied for each type of pattern. Three values of load (10, 12.5 and 15N) were tested to investigate the wear behavior. The experimental results showed that the weight loss was 0.056 g for the specimen reinforced with silicon carbide and heat treatment, while it was 0.069 and 0.067 g for the as-fabricated specimen and the specimen reinforced with silicon carbide only, respectively. The increase of microhardness caused increased wear resistance and thus the weight loss was reduced. The microhardness increased with the increase of the ratio of silicon carbide, while, conversely, the density decreased with the increase of the ratio of silicon carbide. The maximum value of hardness was observed for the specimen reinforced with 5% of Sic followed with heat treatment at 284 Hv, while for the specimens reinforced with 4% and 3% Sic it was 255 and 227 Hv, respectively. It can be concluded that when heat treatment and reinforcement by Sic particles are performed, the microhardness value of aluminum 2024 will increase
