Papers by Keyword: Temperature

Abstract: The thermochromic properties (color change with temperature) of n type doped SiC wafers of different polytypes (3C, 4H and 6H) have been investigated up to 500°C under air. It was found that 3C-SiC color passes from bright yellow at room temperature to deep orangeat 500°C leading to a color contrast (ΔE) as high as 64. The hexagonal polytypes undergo also a color change upon heating but far less pronounced, with ΔE values <20. All these semiconductors undergo band gap shrinkage upon heating which effect largely participated to the observed color change. This effect is very sensitive for 3C polytypesince its bandgap is already in the visible energy range at room temperature. The thermochromicity of 3C-SiC was found to be reversible thanks to its thermal stability and its resistance towards oxidation.

Abstract: Hot mix asphalt consists of a mixture of coarse aggregate and fine aggregate with asphalt binder that has certain requirements and is heated to a certain temperature. In the process of delivering hot mix asphalt, there is a temperature drop of hot mix asphalt when it arrives at the overlay site. The purpose of this study was to determine the characteristics of the temperature drop on hot mix asphalt during the trip to the overlay site. The research method is experimental method will be used on a hot mix asphalt transport truck. The temperature measurement was carried out 5 minutes after the asphalt was poured into the truck and while on the way to the overlay site with a measurement time span of 0, 30, 60, 90 and 120 minutes. The results of the study showed that a very significant drop in the temperature of hot mix asphalt occurred in transport trucks 2 at points T4 and T6, namely the initial temperature of each 150°C to the final temperature of 139°C. The transport of truck 1 the temperature drop of hot mix asphalt that occurs is 10 °C the largest and on transport truck 2 the maximum temperature decrease for hot mix asphalt that occurs is 11 °C. Before shipping the hot mix asphalt, the weather should be considered in order to minimize temperature drop of hot mix asphalt that occurs.

Abstract: This study analyse the effects of different wire drawing experimental tests on the die and product properties. Drawing load, temperature, and wear rate are main die factors, that concerned with the interaction effects of drawing speed variation, wire angle alignment and lubrication. For the product, two factors; tensile strength and hardness are taken. A copper wire is drawing from (4.3 mm) into (3.5 mm) diameter with an area reduction of 1.65, 34% ratio.Six dies were employed in various alignments at three different angles (0°, 1°, and 2°), each has two different drawing speeds of (20 mm/min and 40 mm/min). Results show, the highest drawing load and temperature values in die no.5. The effect of using grease on the die wear rate found that the die wear decreases compared to without. But, when using mixed gradients under the same working conditions, the wear rate changed into coating layer on the die surface. The interaction effect of wire alignment on the product strength showing very small when dealing with low or higher speed, but elongation and ductility are significantly reduced with increasing the angle. The wire produced from die no.1, gives the highest micro hardness.

Abstract: The combustion engines are widely used in the daily life of people, in cars, we find them with greater emphasis, and currently hybrid engines and electric motors are being used. In this analysis, one of the important factors for the failure of combustion engines is the temperature, for which cars have cooling systems, through the use of radiators and coolant-based systems. In this work we present a methodology for the analysis of the state of the components of the combustion engine system in cars, through the use and analysis of thermal images, for which it is necessary to identify the zones or control points depending on the model and type of engine and car, The analysis procedure requires a thermal camera, the results presented are related to the comparison of an optical and thermal image, in order to locate the control point, the method can be applied by mechanics, maintenance personnel and car drivers themselves, to analyze the condition of their car.

Abstract: High-performance computing equipment uses graphic processors, known as GPUs, as a mechanism for high computational capacity. To increase the computational capacity, additional graphics processors are added in the configurations. This strategy increases the computational capacity as well as considerably increases the temperature generated by the entire system, normally the GPUs have cooling systems, which help to cool as much as they are required, the operating systems have automatic mechanisms to access the GPUs, these functions are activated when it is required to use them, in the event of a need for high computing capacity requirement. In this work we demonstrate a method to analyze the operation of computing equipment when working on high-performance functions, such as video games, which require high computational capacity to be able to play in real time and perform the tasks. Necessary renderings, the method can be applied to other applications that are necessary to ensure the continued operation of the computing equipment.

Abstract: CO₂ levels in the world are constantly increasing and have generated a great impact on reinforced concrete structures causing increased carbonation. The phenomenon of carbonation causes corrosion of the reinforcing steel, therefore, reinforced concrete structures present a high risk of corrosion of its reinforcing steel causing the reduction of the useful life of the structure, or in extreme cases, a demolition must be carried out. The objective of the present study is to propose a prediction model for carbonation depth in pure concretes which are not designed for durability (w/c<0.50), but when they are designed for resistance (w/c>0.55). CEB-FIP model presents the limit of serving only for concrete with w/c<0.50, due to this, the present study proposes a model that will help as a reference to estimate the useful life of structures that are built and designed in cities where they do not are exposed to these durability conditions. The modified model for predicting the carbonation depth based on CEB-FIP in pure concrete with high w/c (0.60 and 0.72) uses the parameters of temperature, relative humidity, CO₂ concentration, and water/cement ratio. The objective is to obtain the accuracy of the modified model for predicting the carbonation depth in concrete over the years. For the results, the theoretical data obtained from the modified model was used and a comparison was made with the experimental results obtained from concrete specimens tested inside an accelerated carbonation chamber to find the model's accuracy.

Abstract: Space heating and cooling using geothermal heat exchangers is a promising environmentally friendly green energy solution. Modeling these energy storage systems is crucial for optimizing their design and operation. In this context, the present study consists of numerically investigating the effects of various physical properties, including thermal conductivity, density, and specific heat capacity of each material, as well as flow velocity, on the process of heat transfer in vertical geothermal heat exchangers using coaxial pipes to optimize their energy performance. Numerical simulations were carried out using Gambit-Fluent software. Different materials that make up the coaxial heat exchanger structure studied were tested to highlight their effects on the progress of heat flux and temperature. Thermal and fluid mechanics aspects were also studied. At the end of this study, a comparative analysis was carried out using the U-tube geothermal heat exchanger. The results indicate that the heat exchanger using a coaxial tube demonstrates superior thermal efficiency compared to the U-tube configuration. It has been found that using a low velocity with an appropriate selection of tube, grout, and soil materials results in enhanced dynamic exchanges, thereby enhancing the thermal efficiency of the geothermal exchanger.

Abstract: In order to have a good workspace design, it takes a series of activities consisting of several stages. Starting from the design planning stage, design testing/ experimentation, design analysis, selection of the best design, to design implementation. This research was conducted to evaluate workspace designs using the Taguchi method. In this study, four factors were determined as elements of the workspace environment: the level of lighting, noise, temperature, and aroma of the room. Taguchi orthogonal array design produces 8 experiments obtained from a combination of 4 factors and 2 levels. Experimental activities in the form of the influence of the physical work environment on the resulting typing speed. The research sample in each experiment was 30 responses. The experimental results were analyzed using the Taguchi method with the help of Minitab software. In the analysis of the larger the better factor, based on the ranking, it is found that three factors have amajor influence on typing speed: lighting using room lights, not adding sound (noise), and regulating the room temperature to keep it cool. The ANOVA results show that lighting, noise, and temperature factors significantly affect typing speed. It is known that the calculated F value of the lighting factor is 42.10, noise is 12.22 and temperature is 14.45, all of which are greater than the F table of 4.07. The results of this study can be used as managerial evaluation material for companies to design workspaces by prioritizing bright lighting, not too noisy, and cool temperature of room.

Abstract: The crack initiation and propagation in an aluminium alloy in a corrosive environment are complex because of the loading parameters and material properties, which may result in a sudden failure in real-time applications. This paper investigates the fracture toughness of aluminium alloy under varying environmental and corrosion conditions. The main objective of the work is to link the interdependencies of humidity and temperature for an AL6082-T651 alloy in a corrosive environment. This study investigates AL6082-T651alloy's fracture behaviour and mechanism through microstructure and fractographic studies. The results show that a non-corroded sample, at room conditions, provided more load-carrying capacity than a corroded sample. Additionally, an increase in temperature improves fracture toughness, while an increase in humidity results in a decrease in fracture toughness.

Abstract: The tensile behavior of an injection mold glass fiber reinforced polyamide matrix composite was determined between 10^-6-10^-1 s^-1 strain rates at 25, 65 and 90°C for the loading axis 0^o, 30^o and 90^o to the fiber plane. Microscopic studies were conducted to identify typical fracture mechanism involved at different temperatures. The composite exhibited the highest flow stress and elastic moduli sensitivities on the strain rate in the 0^o specimens, followed by the 30^o and 90^o specimens. The highest rate sensitivity was detected in the specimens tested at 25°C and the rate sensitivity declined as the test temperature increased from 25°C to 65 and 90°C. The observed rate sensitivity of the composite was ascribed to the rate sensitivity of the matrix while the elevated temperatures enhanced the fiber-matrix bonding.