Periodica Polytechnica (Budapest University of Technology and Economics)
Not a member yet
22160 research outputs found
Sort by
Imperial Past, Neoliberal Present, Dependent Future: A Political-Economic Approach to Urban Development of Bursa
Get PDFUrban spaces, as the material representatives of past capital accumulation strategies, survive or get replaced on the basis of actors' strategies and partnerships. Periodization allows conceptualising these decisions and subsequent spatial change with respect to evolving local and national settings. The study focuses on expanding such approaches to Türkiye's experience beyond the two primate cities Istanbul and Ankara by the example of a secondary city, Bursa. The study uses maps, plans, official documents and newspapers corresponding to the periods and literature to form the connections between the actors' decisions and the spatial changes. The results highlight that while the previous periods' urban fabric and heritage is being replaced during the neoliberal era in parallel with the national experience, the problems faced as a secondary centre in close proximity to a primate city reduces local agency much more severely, leaving the urban space more vulnerable to exogenous influences
Crystallization Cycles in Masonry Walls: Experimental Technique to Develop Accelerated Aging on a Real Scale
Get PDFMoisture in historic built heritage is one of the main degenerative agents, because it supports or manifests itself through multiple pathologies. Current knowledge allows for the diagnosis and assessment of the problem, but there are deficiencies in the evaluation of corrective systems due to the time it takes for moisture to become significant. In response, this study proposes an experimental methodology that aims to reproduce the accelerated aging of real scale specimens under laboratory conditions. Thereby improving the understanding of the impact of moisture related deterioration on masonry structures. To achive this, eight masonry walls were constructed and subjected to eight cycles of sulfate crystallization. They were saturated with different sulfate concentrations (5% or 10%) and exposed to different drying conditions (outdoor or solar dehydrator) in order to identify the factors favoring sulfate crystallization and the resulting deterioration. The progress of the experiments was monitored using a hygrometer, a thermographic camera and photogrammetry. The results indicate that it is possible to induce efflorescence in real scale specimens. Temperature and moisture monitoring helped identify the solar dehydrator as a more effective drying treatment. While digital photogrammetry was considered inefficient for quantifying volumetric damage, since this technique can present errors greater than 2%, a value exceeding the observed wear. Reason why the weight of material detached at the end of the experiment was recorded and a positive correlation between the increase in sulfate concentration and the use of the dehydrator was observed. Finally, pertinent considerations are made to improve the experimental conditions
Numerical Study of the Influence of Using Semicircular Corrugated Collecting Plate and Inverted Semicircular Corrugated on the Electrostatic Precipitator
Get PDFElectrostatic precipitators (ESPs) play a crucial role in removing harmful particles in various industries. Ongoing studies continuously strive to improve their performance and efficiency, leveraging the inherent advantages of ESPs. Researchers are exploring various types of collecting and discharge electrodes to achieve this. This study specifically focuses on comparing two types of collecting electrodes, Semicircular Corrugated Plates (SCPs) and inverted Semicircular Corrugated Plates (InvSCPs), against Flat Plates (FPs) as a reference case. Three distinct forms of ESPs were simulated, and the SCP and InvSCP designs were evaluated against the FPs, specifically assessing the impact of modifying the collecting electrode design on key electrostatic precipitator characteristics, such as electrical field distribution, space charge density distribution, particle trajectories, and particle collection efficiency. Notably, the study found that using SCP resulted in the highest particle collection efficiency compared to InvSCP and FP for the same range of particles
Improving Reinforcement Learning Exploration by Autoencoders
Get PDFReinforcement learning is a field with massive potential related to solving engineering problems without field knowledge. However, the problem of exploration and exploitation emerges when one tries to balance a system between the learning phase and proper execution. In this paper, a new method is proposed that utilizes autoencoders to manage the exploration rate in an epsilon-greedy exploration algorithm. The error between the real state and the reconstructed state by the autoencoder becomes the base of the exploration-exploitation rate. The proposed method is then examined in two experiments: one benchmark is the cartpole experiment while the other is a gridworld example created for this paper to examine long-term exploration. Both experiments show results such that the proposed method performs better in these scenarios
Oscillatory Potential-based Characterization of the Human Light-adapted Electroretinogram Using Discrete Wavelet Transform
Get PDFPurpose: Our aim was to apply multiple discrete wavelet transformation (DWT) types to healthy light-adapted (cone) electroretinogram (ERG) signals in order to optimize DWT analysy in ERG. Oscillatory potentials (OP) were individually extracted from the signals and used to calculate an indicator for ERG analysis.Methods: Light-adapted (LA) 3.0 cd.s/m2 ISCEV standard ERGs were recorded from both eyes of 15 healthy volunteers (mean age: 36.9 ± 13.0 years old; 13 females). LA ERG signal components, such as b-wave and OPs, were analyzed using the discrete wavelet transformation (DWT). An index (%OPi) was proposed to estimate the individual oscillatory potentials (OP1-OP5) by calculating the coefficient ratio of the OP to b-wave. Multiple mother wavelet functions (i.e., Daubechies, Symlet, and Coiflet) with five orders were applied and compared statistically using Wilcoxon tests and paired t-test comparisons with Bonferroni posthoc analyses (p < 0.005). Results: OP4 shows the most energy at both low and high-frequency bands (80Hz and 160Hz), while OP2 has lower energy at the low-frequency band (80Hz) and higher energy at the high-frequency band (160Hz). The %OP2 is the largest among the five individual OPs. %OPs obtained with different wavelet functions differ from each other. Db2 and sym2 seem to be the optimal wavelets for analyzing light-adapted ERG components.Conclusion: Individual OPs of the light-adapted ERG obtained with the DWT analysis may characterize different levels of retinal dysfunction. The %OPi may serve as an indicator in ERG analysis
Analysis of Vibratory Stress Relief (VSR) Parameters on Mechanical and Metallurgical Properties of AISI 1008
Get PDFVibrational stress relief (VSR) treatment is a method of stress relief which is currently used for different alloys in different sizes. Since the effect of VSR has not been fully analyzed and compared versus thermal stress relief (TSR) process, its merits require wider investigations. In this paper VSR treatment has been performed with certain parameters to check and assure the advantages of the process in terms of mechanical and metallurgical improvements on AISI 1008 workpiece as a preparatory process. The chosen parameters consist frequency, time, and amplitude of vibration. Factorial design of the experiment using response surface methodology has been performed to obtain an optimal response in numerical and experimental tests. The testing coupons have been evaluated in terms of hardness, tensile strength, elasticity modulus, toughness, elongation before fracture, and micro-structure. Experimental results have been compared with finite element analysis (FEA) results and previous studies. FEA elastic-plastic model was used to extract mechanical properties, while hardening effect has been accounted for in the model. The study has demonstrated the influential performance of VSR on the mechanical properties of the samples i.e., yield strength, toughness, elongation, and elasticity modulus while hardness and microstructure have not been affected significantly
Heat Characteristics and Emission Effect of a Fuel-operated Auxiliary Air Heater Fed with Fuel E10, E30 and E100
Get PDFIn order to increase the comfort of vehicle passengers in specific vehicle categories, the heating of the passenger compartment is not provided by the heat from the engine driving the vehicle but by an additional heating device. The study examines the effect of auxiliary heaters that use liquid fuels to heat the passenger compartment of vehicles. The device was operated during the test with two different mixtures containing bioethanol (E30, E100) and the original motor gasoline (E10). It aimed to understand the effects of different fuels, particularly heating performance, operating time and emissions. Based on the results, as the ethanol content increases, the temperature of the device’s flame and heating air decreases. The experiments showed that in the case of E100 bioethanol, the average temperature measured in stable operating conditions was significantly lower than in the case of E10 motor gasoline. That suggests that an increase in the ethanol content reduces the heating performance. Another significant result of the study was that in the case of mixtures containing ethanol, a longer operating time is required to achieve the same amount of heat, which leads to additional fuel consumption. In addition, when using E100 bioethanol, the amount of harmful gases that are emitted increases significantly during the longer operating time. This observation can be important for evaluating the environmental impact and efficiency of vehicles
New Dimensionless Power Number Equation for Horizontal Agitated Drum
Get PDFIn dryers where mechanical mixing is applied, it is necessary to know the motor power requirement in order to design the dryer correctly. The power requirement of the motor can be traced back to the no-load power requirement and the mixing power requirement. In this study, a new dimensionless power number equation has been introduced to determine the mixing power requirement of horizontal agitated drums. A simplified form of the dimensionless power equation for the investigated agitated drum and granular material was created. The equation took into account the effect of the mixing Froude number. The values of the equation’s unknown parameters were determined by a nonlinear solver using laboratory measurements. A new dimensionless number was introduced which contains the mixing power requirement and was named cohesive power number. This dimensionless number determines the relationship between the mixing power requirement and the bulk cohesion by taking into account the typical size of the mixer and the rotational speed
Sono-hydrogen: a Theoretical Investigation of its Energy Intensity
Get PDFThe present paper investigates the energy efficiency of hydrogen production by a freely oscillating microbubble placed in an infinite domain of liquid water. The spherical bubble initially contains a mixture of argon and water vapour. The bubble is expanded from its equilibrium size to a specific maximum radius via an isothermal expansion. The work needed to expand the bubble is its potential energy calculated by the sum of the work done by the internal gas, the work needed to displace the mass of the surrounding liquid, and the work needed to increase the area of the bubble against the surface tension. During the radial pulsation of the freely oscillating bubble, the internal temperature can reach several thousands of degrees of Kelvin inducing chemical reactions. The chemical yield is computed by solving a set of ordinary differential equations describing the radial dynamics of the bubble (Keller—Miksis equations), the temporal evolution of the internal temperature (first law of thermodynamics), and the concentration of the chemical species (reaction mechanism). The control parameters during the simulations were the equilibrium bubble size, initial expansion ratio, ambient pressure and temperature, the accommodation coefficient of the evaporation/condensation and the surface tension. In the best-case scenario, the energy requirement is 4072.3 MJ/kg
The Characteristics of Road Crashes on Indonesian National Roads Based on Integrated Road Safety Management System Data
Get PDFThe issue of traffic crashes in Indonesia continues to be a significant concern. In 2019, a total of 116,441 crashes were reported, resulting in 30,568 fatalities. Access to accurate data is crucial in lowering the fatality rate. The data were analyzed descriptively, categorized by crash type, and evaluated based on road configuration, geometric type, and surface conditions. The most frequent types of crashes on Indonesian national roads are rear-end crashes (25.64%), head-on crashes (21.95%), crashes at intersections (20.50%), pedestrian hit-and-runs (12.65%), and head-to-side crashes (8.01%). Head-on crashes showed correlation with undivided road, meanwhile rear-end crashes is more likely to occur on multi-lane roads. Predominantly, the crashes occurred on 2-lane 2-way undivided roads (54.28%), straight-aligned roads (81.36%), and roads with good surface conditions (94.92%). This crash data can serve as a foundation for formulating policies and initiatives aimed at enhancing road safety