2023 Cilt 28 Sayı 1

Permanent URI for this collectionhttps://hdl.handle.net/11452/32900

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Design of hardware in the loop (HIL) simulator board for power electronic systems and its implementation for active power filters
(Bursa Uludağ Üniversitesi, 2023-01-11) Tekçe, Ferzende; Vardar, Kadir
In this study, firstly, a general-purpose test simulator circuit was developed that could test the response of the circuits used in power electronic systems on hardware under various operating conditions (hardware in the loop). In the next step, a control board to be used for Shunt Active Power Filters (SAPF) was designed. The control software for SAPF was prepared using CubeMX IDE compiler for two different harmonic extraction methods using instantaneous reactive power theory (IRPT) and synchronous rotating reference frame (SRF) methods. Finally, before connecting the prototype SAPF control board and software to the real system, it had been verified to work safely using the designed test system. With this study, both the SAPF prototype circuit was prepared and a cost-effective system that could be found in the market was designed.
Detection of alzheimer's disease from electroencephalography (EEG) signals using multitaper and ensemble learning methods
(Bursa Uludağ Üniversitesi, 2023-02-28) Göker, Hanife
Alzheimer's disease is a complex brain disease and is also the most common form of dementia that leads to impaired social and intellectual abilities. The disease only manifests itself with a simple forgetfulness, as the disease progresses, the patient forgets the recent events, cannot recognize his family members and close environment, and becomes in need of care in the last stage. Early detection is therefore crucial for medical intervention to prevent brain injury and prolong everyday functioning. In this study is aimed to detection of Alzheimer’s disease from EEG signals using the multitaper and ensemble learning methods. The dataset comprises of 24 healthy people and 24 Alzheimer's patients' EEG signals. 49 features were extracted by calculating the power spectral density (PSD) of the frequencies of the EEG signals between 1-49 Hz using the multitaper method. Then, the performances of AdaboostM1, Total Boost, Gentle Boost, Logit Boost, Robust Boost, and Bagging ensemble learning algorithms were compared. As a result of experiments, the Logit Boost algorithm has the highest performance. The algorithm has achieved a promising performance of 93.04% accuracy, 93.09% f1-score, 92.75% sensitivity, 93.43% precision, and 93.33% specificity.
Developing a low cost electronic nose for spoilage analysis of ground beef
(Bursa Uludağ Üniversitesi, 2023-02-11) Kızıl, Kemal Eren; Özalp, Simge
A low-cost, easy-to-use e-nose is developed to detect the spoilage of ground meat. E-nose consists of hardware, software and data processing components. The main elements of hardware component are gas sensors sensitive to hydrogen sulfide (H2S) and ammonia (NH3). Using MIT App Inventor 2 an Android application is developed to run the hardware component, retrieve the data, preprocess and send it to Google Sheets. Classification model is developed, and data management is carried out in Google Colab and Google Script. Logistic regression method is used to develop classification models from the collected signals. The model classified the samples as "spoiled" and "fresh" based on the gas concentrations. The Nessler solution is used to determine the actual spoilage state. Ground beef samples stored in the refrigerator and at room temperature are used to obtain spoiled and fresh samples to develop a logistic regression model. A total of 36 samples are used to develop model. Another set of 24 samples is used to test model and prototype device performance. It is observed that all samples used in the testing phase were classified correctly. The cost of the system has been determined as approximately $100 considering January 2021 exchange rates.
Dibenzo-18-crown-6/polycaprolactone composite nanofibers for selective adsorption of cations
(Bursa Uludağ Üniversitesi, 2023-03-14) Altan, Özlem İpek Kalaoğlu
Electrospun nanofibers are attractive alternatives to traditional adsorbents due to their high surface-to-volume ratio, porosity, and loading capacity. Functionalization of nanofibers with macrocycles can contribute to further enhancement in selective adsorption of ions. In this study, polycaprolactone (PCL) nanofibers were functionalized with a crown ether, namely dibenzo-18-crown-6 (DB18C6), and the potential of the resultant electrospun PCL/DB18C6 nanofibers for selective ion adsorption, particularly the selective recovery for K+ , was investigated. The morphology, chemical structure and thermal properties of PCL/DB18C6 nanofibers were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The average diameter of PCL/DB18C6 nanofibers was 529±196 nm. Single-ion adsorption experiments indicated that the adsorption capacity for K+ ion was 137 mg·g−1 and the selectivity sequence was found as K+>Ca2+>Na+ . The adsorption selectivity coefficients of K+ /Ca2+ and K+ /Na+ were calculated respectively as 1.37 and 4.28 for single ion experiments and as 1.13 and 5.11 for mixed ion adsorptions which illustrate that the difference between the adsorption capacities of K+ and Ca2+ decreased in mixed ion adsorption experiments. Overall results demonstrate that the electrospun PCL/DB18C6 nanofibers are amenable for use as polymer adsorbents for the selective ion recovery.
Effect of cavitation process on thermal comfort properties of denim fabrics
(Bursa Uludağ Üniversitesi, 2023-03-29) Özkan, Esra Taştan; Kaplangiray, Binnaz Meriç; 0000-0002-1296-9092
The process, which is defined as ultrasonic treatment or cavitation, ensures that the dirt is removed from the surfaces without damaging the fabric surface. There are studies on the ultrasonic washing processes of denim fabrics in the literature, but there is no study on the effect of the cavitation process on the thermal comfort of denim fabrics. For this purpose, denim fabrics were treated at three different times, 15, 30, and 45 minutes, and at two different frequencies 8khz and 16khz in the ultrasonic homogenizer test device. It was observed that the applied cavitation process reduces the air permeability, thermal conductivity, and thermal absorptivity values. On the other hand, the cavitation process increased the water vapour permeability value by cleaning the materials such as dirt and oil on the surface. It can be concluded that the applied cavitation process provides comfort by enabling quick throwing of the sweat to the outer surface, provides less heat conduction from the fabric, and the denim fabric felt warmer after the cavitation process.
The effect of mesa dimensions on mems diaphragms for fabry-perot interferometerbased fiber optic sensors
(Bursa Uludağ Üniversitesi, 2023-02-13) Atıf 4.0 Uluslararası; Durmaz, Ahmet; Hayber, Şekip Esat; Aydemir, Umut; Mühendislik Fakültesi; Elektrik Elektronik Mühendisliği; 0000-0002-8928-2563; 0000-0003-0062-3817; 0000-0001-5396-4610
In this study, the effects of mesa dimensions on sensor response in diaphragm-based FabryPerot fiber optic sensors (FOSs) were investigated in detail. Mesa diaphragms, also called centerembossed diaphragms, have been discussed sufficiently in the literature, but the effect of mesa thickness on sensor performance has not been discussed in detail. Moreover, there is no precise analytical solution for such diaphragms. For this reason, diaphragms with different thicknesses and radii were selected, and the deflection and frequency responses of the diaphragm according to the applied acoustic pressure were analyzed using the ANSYS software, depending on whether the mesa is thinner or thicker than the diaphragm. If the thickness of the mesa is smaller than the thickness of the diaphragm, the center deflection changes drastically. However, if the thickness of the mesa is two times greater than the thickness of the diaphragm, there is no significant change in the deflection results. Similarly, if the mesa thickness is thinner than the diaphragm, the sensor’s frequency response changes drastically with increasing mesa radius. In cases where the mesa thickness is larger than the diaphragm thickness, the frequency response changes less. According to the results, mesa dimensions should be considered when designing a mesa diaphragm-based Fabry-Perot FOS.
Gamma ray effect on Op-Amp 741 and timer 555 IC
(Bursa Uludağ Üniversitesi, 2023-03-30) Tekgül, Esra Kendir; Yaltkaya, Şerafettin
The commercial used the 555 single timer and the 741 operational amplifiers (op-amp) were investigated under the gamma-ray radiation of the Co-60 source. The maximum total doses were used 2 kGy and 4 kGy to irradiate. The abnormal behavior in the 555 single timer circuit frequency was observed, which decreased from 202 to 195 Hz at 744 Gy gamma-ray radiations. In the results of 741 opamp circuit, the amplitude signal of the 741 op-amp shows a maximum value of -0.054 dB at 4 kGy gamma dose and its slew rate decreases from 4 to 0.65 V/µs. The 555 single timer has two pn junctions and these cause that the 555 single timer is easily affected by the gamma radiation. Consequently, the integrated circuits must be tested to determine their resistance limits in the radiation environments.
A MAP/PH/1 production inventory model
(Bursa Uludağ Üniversitesi, 2023-03-11) Özkar, Şerife
In this study, a production inventory model with phase type service times where customers join the system occur according to a Markovian arrival process is discussed. When the inventory level is positive, if an arriving customer finds the server idle gets into service immediately. Served customer leaves the system and the on-hand inventory is decreased one unit of item at service completion epoch. Otherwise, the customer enters into a waiting space (queue) of infinite capacity and waits for get served. The production facility produces items according to an (𝑠𝑠, 𝑆𝑆) policy. The production is switched on when the inventory level depletes to 𝑠𝑠 and the production remains on until the inventory level reaches to the maximum level 𝑆𝑆. Once the inventory level becomes 𝑆𝑆, the production process is switched off. Applying the matrix-geometric method, we carry out the steady-state analysis of the production inventory model and perform a few illustrative numerical examples includes the effect of parameters on the system performance measures and an optimization study for the inventory policy.
A numerical investigation on the stress-balanced spur gear pairs
(Bursa Uludağ Üniversitesi, 2023-02-27) Yılmaz, Tufan Gürkan; Karadere, Gültekin; Karpat, Fatih; Mühendislik Fakültesi; Ali Durmaz Makine Mühendisliği Bölümü; 0000-0003-3772-7871; 0000-0002-9280-0982; 0000-0001-8474-7328
Involute spur gears are key machine elements for power transmission in various industrial sectors. During power transmission, the teeth are subjected to high stresses. Many design modifications are used to reduce these stresses, such as increasing the drive side pressure angle and profile shifting factor. These modifications change the contact ratio and center distance of the gear pair. Changing the tooth thickness is another solution to reduce stress. Because there is a difference in the number of teeth between the pinion and the gear, the pinion stress levels are higher than the gear for the same gear parameters. The tooth thickness value in the tooth thickness on the pitch circle is equal to 0.5xπm for both pinion and gear as standard. Stress compensation can be achieved by increasing this thickness at the pinion and decreasing it at the same rate at the gear. In this study, first of all, 3D designs of gears with non-standard thickness were created in CATIA and finite element analyzes were performed to obtain tooth thickness values that create equal root stresses for pinion and gear with various tooth numbers. According to preliminary results, tooth deformation and stress has a linear relationship with tooth thickness value, nearly.

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