Analysis of emergency braking performance with particular consideration of temperature effects on brakes

During vehicle deceleration due to braking there is friction between the lining surface and the brake drum or disc. In this process the kinetic energy of vehicle is turned into thermal energy that raises temperature of the components. The heating of the brake system in the course of braking is a great problem, because besides damaging the system, it may also affect the wheel and tire, which can cause accidents. In search of the best configuration that considers the true conditions of use, without passing the safety limits, models and formulations are presented with respect to the brake system, considering different braking conditions and kinds of brakes. Some modeling was analyzed using well-known methods. The flat plate model considering energy conservation was applied to a bus, using for this a computer program. The vehicle is simulated to undergo an emergency braking, considering the change of temperature on the lining-drum. The results include deceleration, braking efficiency, wheel resistance, normal reaction on the tires and the coefficient of adhesion. Some of the results were compared with dynamometer tests made by FRAS-LE and others were compared with track tests made by Mercedes-Benz. The convergence between the results and the tests is sufficient to validate the mathematical model. The computer program makes it possible to simulate the brake system performance in the vehicle. It assists the designer during the development phase and reduces track tests.

Early detection of metabolic and energy disorders by thermal time series stochastic complexity analysis

Maintenance of thermal homeostasis in rats fed a high-fat diet (HFD) is associated with changes in their thermal balance. The thermodynamic relationship between heat dissipation and energy storage is altered by the ingestion of high-energy diet content. Observation of thermal registers of core temperature behavior, in humans and rodents, permits identification of some characteristics of time series, such as autoreference and stationarity that fit adequately to a stochastic analysis. To identify this change, we used, for the first time, a stochastic autoregressive model, the concepts of which match those associated with physiological systems involved and applied in male HFD rats compared with their appropriate standard food intake age-matched male controls (n=7 per group). By analyzing a recorded temperature time series, we were able to identify when thermal homeostasis would be affected by a new diet. The autoregressive time series model (AR model) was used to predict the occurrence of thermal homeostasis, and this model proved to be very effective in distinguishing such a physiological disorder. Thus, we infer from the results of our study that maximum entropy distribution as a means for stochastic characterization of temperature time series registers may be established as an important and early tool to aid in the diagnosis and prevention of metabolic diseases due to their ability to detect small variations in thermal profile.

Chemical, morphological, rheological and thermal properties of Solanum lycocarpum phosphorylated starches

The increasing need for starches with specific characteristics makes it important to study unconventional starches and their modifications in order to meet consumer demands. The aim of this work was to study physicochemical characteristics of native starch and phosphate starch of S. lycocarpum. Native starch was phosphated with sodium tripolyphosphate (5-11%) added with stirring. Chemical composition, morphology, density, binding ability to cold water, swelling power and solubility index, turbidity and syneresis, rheological and calorimetric properties were determined. Phosphorus was not detected in the native sample, but the phosphating process produced modified starches with phosphorus contents of 0.015, 0.092 and 0.397%, with the capacity of absorbing more water, either cold or hot. Rheological data showed the strong influence of phosphorus content on viscosity of phosphate starch, with lower pasting temperature and peak viscosity higher than those of native starch. Enthalpy was negatively correlated with the phosphorus content, requiring 9.7; 8.5; 8.1 and 6.4 kJ g-1 of energy for the transition from the amorphous to the crystalline state for the starch granules with phosphorus contents of 0; 0.015; 0.092 and 0.397%, respectively. Cluster analysis and principal component analysis showed that starches with 0.015 and 0.092% phosphorus have similar characteristics and are different from the others. Our results show that the characteristics of phosphate modified S. lycocarpum starch have optimal conditions to meet the demands of raw materials, which require greater consistency in stickiness, combined with low rates of retrogradation and syneresis.

A Theoretical investigation of a potential high energy density compound 3,6,7,8-tetranitro-3,6,7,8-tetraaza-tricyclo[3.1.1.1(2,4)]octane

The B3LYP/6-31G (d) density functional theory (DFT) method was used to study molecular geometry, electronic structure, infrared spectrum (IR) and thermodynamic properties. Heat of formation (HOF) and calculated density were estimated to evaluate detonation properties using Kamlet-Jacobs equations. Thermal stability of 3,6,7,8-tetranitro-3,6,7,8-tetraaza-tricyclo [3.1.1.1(2,4)]octane (TTTO) was investigated by calculating bond dissociation energy (BDE) at the unrestricted B3LYP/6-31G(d) level. Results showed the N-NO2 bond is a trigger bond during the thermolysis initiation process. The crystal structure obtained by molecular mechanics (MM) methods belongs to P2(1)/C space group, with cell parameters a = 8.239 Å, b = 8.079 Å, c = 16.860 Å, Z = 4 and r = 1.922 g cm-3. Both detonation velocity of 9.79 km s-1 and detonation pressure of 44.22 GPa performed similarly to CL-20. According to the quantitative standards of energetics and stability, TTTO essentially satisfies this requirement as a high energy density compound (HEDC).

Energy balance in the poultry-shed system and its influence on broiler performance

ABSTRACTThe objective of this study was to determine the energy balance of the poultry-shed system and its effect on broiler performance during the production cycle. The experimental design was completely random with sub-divided blocks. The blocks were composed of five different types of sheds and the sub-blocks of the evaluation times (00:00 h to 23:00 h), allowing an analysis of variance and a comparison between means with the Tukey test. There were no significant differences between the mean values of the exchanges of sensible, latent and total heat between the poultry sheds but the differences for the evaluation times were significant (P<0.05). There was no significant difference between sheds 1 and 4 for broiler productive performance regarding weight gain, feed consumption and feed conversion. Bird performance was significant (P<0.05) for the remaining poultry sheds. The productive indexes remained below the ranges considered ideal for broilers and values in the final weeks were characterized by the poor installation efficiency in controlling temperature variations and, consequently, the energy balance in the system, which adversely affected bird productive performance.

Analysis of heart rate control to assess thermal sensitivity responses in Brazilian toads

In anurans, changes in ambient temperature influence body temperature and, therefore, energy consumption. These changes ultimately affect energy supply and, consequently, heart rate (HR). Typically, anurans living in different thermal environments have different thermal sensitivities, and these cannot be distinguished by changes in HR. We hypothesized that Rhinella jimi (a toad from a xeric environment that lives in a wide range of temperatures) would have a lower thermal sensitivity regarding cardiac control than R. icterica (originally from a tropical forest environment with a more restricted range of ambient temperatures). Thermal sensitivity was assessed by comparing animals housed at 15° and 25°C. Cardiac control was estimated by heart rate variability (HRV) and heart rate complexity (HRC). Differences in HRV between the two temperatures were not significant (P=0.214 for R. icterica and P=0.328 for R. jimi), whereas HRC differences were. All specimens but one R. jimi had a lower HRC at 15°C (all P<0.01). These results indicate that R. jimi has a lower thermal sensitivity and that cardiac control is not completely dependent on the thermal environment because HRC was not consistently different between temperatures in all R. jimi specimens. This result indicates a lack of evolutive trade-offs among temperatures given that heart rate control at 25°C is potentially not a constraint to heart rate control at 15°C.

Processing of Brazil-nut flour: characterization, thermal and morphological analysis

The Brazil nut (Bertholletia excelsea H. B. K.) is noteworthy for its high content of lipids and proteins of elevated biological value and these factors justify the need for further research and incentives for the manufacturing of new trade products. In the present study we sought new forms of technological use of these nuts by the food industry, through their processing as flour, with no alteration in its energy content. The results after its elaboration showed a product with high energy value (431.48 kcal.100 g-1), protein content of 45.92 g.100 g-1, and fiber of 17.14%. The thermal analyses indicate that the introduction of another protein component, such as soy protein isolate, does not alter the reactions or thermal behavior. On the other hand, morphological analyses revealed granular structures similar to the structure of globular proteins. It was observed that after processing to obtain the flour, the product maintains its protein-energy content, as well as its characteristics when subjected to high temperatures.

Energy evaluation of an evaporative cooling system using water driven ejector

The search for efficient and accessible cooling systems has increased worldwide. This study aims to build and evaluate an evaporative cooling system using a water driven ejector, allowing it to be installed in places with plenty of water. The system was investigated varying the flow rate and temperature of the circulating water, temperature of the replacement water, and coefficient of performance. The best vacuum obtained was 8.5 kPa at nominal operating conditions of 4.1 ± 0.1 m³/h and 5 ± 0.5 ºC for the circulating water reaching the temperature of 9.7 ± 0.5 ºC. The pulse-like disturbance generated by replacing the cooling water at different periods of times did not result in significant affect vacuum destabilization and the temperature rise in the cooling tank. The coefficient of performance of the system at the highest thermal power of 92.27 W was 0.077, which was underestimated due to possible problems related to pump efficiency. The system evaluated under the conditions proposed can be very efficient for cooling fluids at higher temperatures, and it can be complementary to main refrigeration systems.

Energy efficiency and moisture diffusivity of apple slices during convective drying

Abstract The present study aimed at investigating the influences of drying air temperature and flow rate on energy parameters and dehydration behaviour of apple slices. For this purpose, apple slices were dried in a convective dryer at air temperatures of 50, 60 and 70 °C, and air velocities of 1, 1.5 and 2 m s–1. Dehydration rate increased as the air temperature and flow rate increased from 50 to 70 °C and 1 to 2 m s–1, respectively. The effective moisture diffusivity was determined to be in the range of 6.75×10–10-1.28×10–9 m2 s–1. Results of data analysis showed that the maximum energy consumption (23.94 kW h) belonged to 50 °C and 2 m s–1 and the minimum (13.89 kW h) belonged to 70 °C and 1 m s–1 treatment. Energy efficiency values were in the range of 2.87-9.11%. Moreover, the results indicated that any increment in the air temperature increases thermal and drying efficiencies while any increment in the air flow rate decreases both of them.