Dynamic Evaluation of Traffic Noise through Standard and Multifractal Models

Traffic microsimulation models use the movement of individual driver-vehicle-units (DVUs) and their interactions, which allows a detailed estimation of the traffic noise using Common Noise Assessment Methods (CNOSSOS). The Dynamic Traffic Noise Assessment (DTNA) methodology is applied to real traffic situations, then compared to on-field noise levels from measurement campaigns. This makes it possible to determine the influence of certain local traffic factors on the evaluation of noise. The pattern of distribution of vehicles along the avenue is related to the logic of traffic light control. The analysis of the inter-cycles noise variability during the simulation and measurement time shows no influence from local factors on the prediction of the dynamic traffic noise assessment tool based on CNOSSOS. A multifractal approach of acoustic waves propagation and the source behaviors in the traffic area are implemented. The novelty of the approach also comes from the multifractal model's freedom which allows the simulation, through the fractality degree, of various behaviors of the acoustic waves. The mathematical backbone of the model is developed on Cayley-Klein-type absolute geometries, implying harmonic mappings between the usual space and the Lobacevsky plane in a Poincare metric. The isomorphism of two groups of SL(2R) type showcases joint invariant functions that allow associations of pulsations-velocities manifolds typ

Experimental investigation of noise characteristics for HVAC silencers

Heating, ventilating and air-conditioning (HVAC) systems represent a major source of inside buildings noise with a negative effect on the acoustical environment. Therefore, it is necessary to add attenuation to the system. This is provided by sound attenuators or silencers manufactured in different geometrical configurations and with various absorptive lining materials. The paper deals with the insertion loss, as a performance criterion for in-duct noise, of some dissipative silencers types. The measured data are compared in order to establish the efficiency of every tested silencer type. Third-octave band analysis of random noise of an air handling unit (AHU) from a HVAC system is realized without and with silencers (ducts fitted). Insertion loss measurements are made in an anechoic room using a test facility that agrees the requirements of ISO 7235:2009. The results highlight the effects of the silencers geometry, pressure-air flow and loading relations upon the sound attenuation level. The silencers selection could be a difficult task for the designers which have to consider all these parameters

Experimental investigation of noise characteristics for HVAC silencers

Heating, ventilating and air-conditioning (HVAC) systems represent a major source of inside buildings noise with a negative effect on the acoustical environment. Therefore, it is necessary to add attenuation to the system. This is provided by sound attenuators or silencers manufactured in different geometrical configurations and with various absorptive lining materials. The paper deals with the insertion loss, as a performance criterion for in-duct noise, of some dissipative silencers types. The measured data are compared in order to establish the efficiency of every tested silencer type. Third-octave band analysis of random noise of an air handling unit (AHU) from a HVAC system is realized without and with silencers (ducts fitted). Insertion loss measurements are made in an anechoic room using a test facility that agrees the requirements of ISO 7235:2009. The results highlight the effects of the silencers geometry, pressure-air flow and loading relations upon the sound attenuation level. The silencers selection could be a difficult task for the designers which have to consider all these parameters

Analysis of Ball Check Valves with Conical and Spherical Seat Designs from Common-Rail Pumps

Common-rail fuel injection systems are still a good option for equipping new car models. The technology is well known, systems of this type are reliable and can be used on a wide variety of diesel and petrol engines. However, there is still room for improvement. The ball check valve, which is part of the common-rail pump, is designed to open and allow the compressed fluid to be sent to the high-pressure accumulator and close to not allow fuel to return to the compression chamber. The valves’ design directly influences the volumetric efficiency of the outlet flow and the robustness against high pressures that lead to low performance and short service life of the fuel injection systems. This paper aims to compare two ball check valves with conical and spherical seat designs. The analysis is based on theoretical calculations and CFD simulations, which will give more confidence in the results. Considering the comparative analysis results, the ball check valve with a spherical seat shows better flow dynamics than the ball check valve with a conical seat. In addition to the improved flow dynamics, the ball check valve with spherical seat seems to have a uniformly distributed fluid pressure inside the valve. In contrast, the conical seat ball check valve has high local fluid pressures, leading to fatigue

Analysis of Ball Check Valves with Conical and Spherical Seat Designs from Common-Rail Pumps

Common-rail fuel injection systems are still a good option for equipping new car models. The technology is well known, systems of this type are reliable and can be used on a wide variety of diesel and petrol engines. However, there is still room for improvement. The ball check valve, which is part of the common-rail pump, is designed to open and allow the compressed fluid to be sent to the high-pressure accumulator and close to not allow fuel to return to the compression chamber. The valves’ design directly influences the volumetric efficiency of the outlet flow and the robustness against high pressures that lead to low performance and short service life of the fuel injection systems. This paper aims to compare two ball check valves with conical and spherical seat designs. The analysis is based on theoretical calculations and CFD simulations, which will give more confidence in the results. Considering the comparative analysis results, the ball check valve with a spherical seat shows better flow dynamics than the ball check valve with a conical seat. In addition to the improved flow dynamics, the ball check valve with spherical seat seems to have a uniformly distributed fluid pressure inside the valve. In contrast, the conical seat ball check valve has high local fluid pressures, leading to fatigue

A Rapid and Inexpensive Method for Finding the Basic Parameters of Involute Helical Gears

The paper proposes a rapid, straightforward, and inexpensive method for finding the basic parameters of helical gears with an involute profile. The basic parameters envisaged are the normal module, normal profile shift coefficient, and the helix angle. The proposed method uses balls introduced between the teeth and, thus, the contact with the measuring device surfaces is of the point type, and the centres of the balls are positioned symmetrically with respect to the measuring direction. The condition that the centre of the ball occupies an imposed position is mandatory. Additionally, there is the condition of the positions of the contact points between the balls and the flanks of the teeth. Two sets of balls of different sizes are necessary for a measurement. The conditions of the balls’ positioning lead to a system of five unknowns. The methodology of solving the system is detailed and the method is exemplified for an actual helical gear. The new proposed method is based on the distance over pins but, using balls, presents the following advantages: It can be applied equally to all gears, regardless of the odd or even number of teeth. Furthermore, the dimension to be measured is singular compared to the dimension over pins when a maximum value must be found from several measurements

The Effect of Dry Friction upon the Dynamics of a Short Eccentric Rotor: An Analytical and Experimental Study

The paper proposes the study of dry friction by means of a short eccentric rotor. The rotor was designed and realised in the laboratory. In an ideal frictionless situation, a rotor actuated by gravity will have an angular velocity which increases indefinitely. The analytical model assumes dry friction in the bushing of the rotor and the main result reveals that the angular velocity either stabilizes around a certain value or drops to zero. Two situations of friction were considered for the theoretical model: first only dynamic friction and secondly, both static and dynamic friction are present. The analytical model of the dynamics of the rotor presents the advantage that it can be applied for diverse friction cases, from dry friction to complex dry friction and wet friction. Experimental tests were carried out on the designed and constructed device; they are in very good agreement with the results of the theoretical model

Basal Cell Carcinoma Perineural Invasion and Suggestive Signs of Perineural Invasion—Findings and Perspectives

Basal cell carcinoma (BCC) is a malignant tumor with a rising incidence and is the beneficiary of several innovative evaluation techniques. Histopathology remains the gold standard for assessment, having the possibility of addressing multiple high-risk factors such as perineural invasion (PNI). The current study included a number of 244 BCC patients and targeted the identification of positive PNI and its suggestive signs, and whether they correlated or not with other high-risk tumor signs. PNI was found in 20.1% of patients, with 30.7% of patients having perineural chronic inflammation (PCI), which is a suggestive sign of PNI. PNI was also found in larger tumors, with deeper Clark levels, in high-risk BCCs and high-grade tumors. PNI and PCI are both important for pathology reporting, aiding in treatment choice and further patient management, with possibly positive outcomes concerning morbidity and mortality