Explore the vast range of titles available.

This study examines the impact of the mother wavelet, sensor selection, and machine learning (ML) models for smart fault diagnosis of rotating machines via discrete wavelet transform (DWT). The ability of Daubechies, Haar, Biorthogonal (Bior), Symlets (Sym), and Coiflets (Coif) wavelets is measured in terms of distinguishing imbalance, horizontal/vertical misalignment, and overhang/underhang bearing ball, cage, and outer race faults. For this purpose, single-step and two-step fault monitoring (SSFM and TSFM) approaches are proposed. In SSFM, the ML models detect the fault type by the healthy and faulty signals. In TSFM, the built models first determined whether the machine is faulty or not. If it is, then the models detect the fault type. As ML models, Random Forest (RF), AdaBoost with C4.5 (AB-C4.5), and two artificial neural network algorithms are trained by the features of DWT. Besides, the effect of the sensor type on the fault diagnosis is measured by considering the tachometer, microphone, and two accelerometers individually and combined. The results are interpreted regarding the evaluation metrics such as accuracy, precision, recall, confusion matrix, and model built time. It is concluded that Bior3.1 and Haar wavelets distinguish the fault type more accurately than other wavelets. Besides, the RF-Bior3.1 give the best results for SSFM and TSFM by accuracy values of 99.80% and 99.98%, respectively. It is also found that the sensor type is correlated with the selected mother wavelet.

Purpose As the concept of Industry 4.0 is introduced, the significance of Smart Fault Diagnosis in the industry is increased. Therefore, it is essential to develop accurate, robust, and lightweight intelligent fault diagnosis approach that can be executed in real-time even with embedded systems. Additionally, it is preferable to use a single method for multi-purposes such as the fault detection, identification, and severity assessment. This study proposed a new approach called GaBoT for fault diagnosis of rotating machinery to satisfy those requirements. Method The proposed approach adopted the concept of the ensemble of ensembles by boosting random forest. The statistical features of discrete wavelet transform were considered since they are easy and fast to obtain. Model optimization was conducted by employing genetic algorithm to alleviate the computational load without decreasing the model performance. The proposed approach has been validated by unseen data from an experimental dataset including shaft, rotor, and bearing faults. Results The experimental results indicate that the proposed approach can effectively find the fault type with 99.85% accuracy. Besides, it successfully determines the fault severity by accuracy values between 96.45 and 99.72%. GABoT can also determine the imbalance severity in the presence of three bearing faults. Conclusion Employing GA eliminated most of the redundant features and reduced the model execution time consumption. The results yielded that GABoT is a highly accurate model, and can be utilized in real-time fault diagnosis of rotating machinery.

Localization of the delamination is an essential task that is conducted via various approaches, which may require time, experts, and cost. Various intelligent non-destructive techniques are utilized to reduce time consumption, the need for expertise, and expenditures. Yet, developing an accurate, robust, and low-cost intelligent delamination identification technique becomes a challenging task due to the anisotropy and the variation in the fiber orientation of the composites. Based on those issues, it is aimed to develop an effective intelligent model to localize delaminations in composite plates. This study measures the performance of the Bagging and Boosting techniques on delamination localization in thin composite plates. To validate the effectiveness of the proposed approaches; cross-ply, angle-ply, and quasi-isotropic composite plates having 2400 different delamination cases are considered. The bagging and boosting models are trained with the vibrational characteristics of the healthy and delaminated composite structures. The free vibration analysis is conducted for those structures to obtain the first five natural frequencies and the corresponding mode shapes. For this purpose, classical plate theory is employed by using finite element analysis. It is concluded that bagging and boosting techniques are robust, precise, and accurate in localizing delamination.

Frame structures are widely used in aerospace, maritime industries, construction, etc. These structures are subjected to static and dynamic loads, which may cause buckling, dynamic instability, or resonance. Hence, it is essential to determine the right material and understand the mechanic and dynamic properties of such structures. This thesis investigates the free vibration, buckling, and dynamic stability of isotropic and orthotropic curved beam and plate frame structures using the finite element method and beam or plate theory. The effects of the radius of curvature and stacking order of the single-bay and two-bay curved frame structures on the natural frequency, critical buckling load, and unstable regions are investigated. Similarly, the effects of the aspect ratio on the dynamic and buckling characteristics of the curved frame structures are examined. Besides, the effects of the thickness on the natural frequency and critical buckling load of the isotropic curved beam frame structure are investigated.Euler – Bernoulli Beam Theory and Classical Plate Theory is employed with the Finite Element Method to obtain isotropic and orthotropic beam frame structures. Curved plate frame structures are modeled considering Kirchhoff – Love Plate Theory for isotropic frames, whereas the Classical Plate Theory and First-Order Shear Deformation Theory for orthotropic frames. Results are validated with those of ANSYS and SolidWorks.Aluminum – potassium feldspar metal matrix composite materials are fabricated via the stir casting method. The mechanical properties of such materials are obtained by tensile testing. Free vibration, buckling, and dynamic stability analyses are performed considering a plate of such material.

Başta sosyal yaşam olmak üzere birçok alanda güç gerektiren hareket veya hareket kümesi mevcuttur. Bu hareketlerin bir kısmı uygulanabiliyor iken bir kısmı da güç yetersizliği ve sağlık sorunları nedeniyle gerçekleştirememektedir. Bu engeli ortadan kaldırmak ya da kısmi de olsa güç gerektiren bu harekeleri uygulamak için güçlendirilmiş dış iskelet sistemler ortaya çıkmıştır. Alt ekstremite dış iskelet sistemleri, bacaklar vasıtasıyla yapılan fakat bir rahatsızlık sebebiyle gerçekleştirilemeyen hareketlerin yapılmasını kolaylaştırmak veya tamamen yaptıracak gücü sağlamak, alt ekstremite bozukluğu olan hastaların rehabilitasyon sürecine de katkıda bulunması ve hayat kalitesini yükseltmek amacıyla tasarlanmış sistemlerdir. Bu çalışma kapsamında, 110M063 numaralı TÜBİTAK projesi kapsamında tamamlanmış olan 5000 serisi alüminyum çerçeveli alt ekstremite eksoskeleton (dış iskelet) sisteminin kütlesi hafifleştirilip mukavemetinin arttırılması hedeflenerek, tasarımın iyileştirilmesi ve geliştirilmesi yapılmıştır. Çalışmanın sonraki aşamalarından olan motor seçimi için gereken eklem tork ihtiyacı ve harcanan güç miktarının tespiti için SolidWorks programı aracılığıyla sanal yürüme simülasyonu gerçekleştirilmiş ve 110M063 numaralı TÜBİTAK projesinde elde edilen kritik durum verileri kullanılarak sistemin emniyet durumunu tespit etmek amacıyla statik analiz yapılmıştır. Bununla birlikte, daha ileride yapılacak olan çalışmalara bir zemin oluşturmak, bir fikir vermek amacıyla bir öngörü modeli tasarlanmış, sanal yürüme simülasyonları ile sistem emniyetini ölçmek amacıyla kritik durumlarda statik analizler yapılmıştır. Geliştirilen bu iki sistem birbiriyle ve 110M063 numaralı TÜBİTAK projesi kapsamında prototipi üretilen sistem ile karşılaştırılmıştır. Çalışmanın bir bölümü Yıldız Teknik Üniversitesi’nde düzenlenen Mekatro 15 isimli panelde de sunulmuştur.

It is useful to analyze the factors, polluting the livable environment, whose sustainability and protection are vital to all living things, and to take the necessary precautions promptly. Within this scope, the effects of foreign trade and investments on environmental pollution in BRICMT (Brazil, Russia, India, China, Mexico, and Turkey) countries were analyzed with the Fourier Kwiatkowski–Phillips–Schmidt–Shin (KPSS) stationarity test, Fourier Bootstrap augumented autoregressive distributive lag (AARDL) method, and Fourier Bootstrap Toda-Yamamoto causality test for the period 1980–2021 in this study. According to the findings, the pollution haven hypothesis is valid since increasing exports and foreign investment in China increased environmental pollution both in the short term and the long term. While environmental pollution increased in China, Brazil, Mexico, and Turkey with increasing imports, it decreased in Russia. The short-term impact of imports on rising environmental pollution is also valid for Brazil. Since foreign investment increases environmental pollution in Brazil and Mexico in the long run, the pollution haven hypothesis is valid in these countries. In Russia and Mexico, where there are findings that foreign investment reduces environmental pollution in the short term, the pollution halo hypothesis is valid in the short run. According to the Fourier Bootstrap Toda-Yamamoto causality test results, it was determined that there is causality from exports and imports to environmental pollution in China and India and from foreign investment to environmental pollution in Russia and Brazil.

In this study, the eggs of 30 wild Black Sea whiting ( Merlangius merlangus euxinus , Nordmann, 1840) and 30 farmed freshwater rainbow trout ( Oncorhynchus mykiss , Walbaum, 1792) collected from Samsun Province in Turkey were analyzed to determine the level of contamination by nine organochlorine pesticides (OCPs), namely α-hexachlorocyclohexane (α-HCH), β-HCH, γ-HCH (lindane), hexachlorobenzene (HCB), aldrin, 2,4′-dichlorodiphenyltrichloroethane (DDT), 4,4′-DDT, 2,4′-dichlorodiphenyldichloroethylene (DDE), 4,4′-DDE, and 15 polychlorinated biphenyls (PCBs) (PCB-28, -70, -74, -81, -99, -101, -118, -138, -153, -156, -170, -180, -183, -187, and -208), and their potential use as biomarkers to monitor levels of environmental contamination. OCPs and PCBs in the fat of fish eggs were extracted cryogenically and their concentrations were determined with a gas chromatography-electron capture detector (GC-ECD). The whiting eggs showed high OCP and PCB levels compared to the rainbow trout eggs. The median ∑ DDT values for whiting and rainbow trout eggs were 1601.62 ng g −1 fat (range 824.87–5049.81) and 406.49 ng g −1 fat (range 199.88–588.82); median ∑Indicator PCBs were 1264.24 ng g −1 fat (range 520.05–6140.32) and 82.11 ng g −1 fat (range 2.85–215.97); and median ∑ HCHs were 155.66 ng g −1 fat (range 35.45–330.40) and 13.48 ng g −1 fat (range 4.44–66.44), respectively. In the whiting eggs, the ∑Indicator PCB level was above the maximum residue limit (MRL) of 200 ng g −1 fat stated in the European Commission Regulation (EC) and Turkish Food Codex (TFC). In addition, there was a significant difference between the contamination levels of the eggs of the two species. In conclusion, it appears that fish eggs can serve as a valuable biomarker for the level of contamination of persistent organochlorine contaminants in different aquatic environments.

Forty-seven fish (24 endemic Alburnus tarichi, Güldenstädt, 1814; 8 Capoeta capoeta , Guldenstaedt, 1772; 15 mirror carp Cyprinus carpio, L., 1758) and 13 mussel ( Unio stevenianus, Krynicki, 1837) samples, with 10 specimens per sample, were collected from Van Lake, Turkey, and rivers flowing into it. Gamma-HCH was detected in 21 Alburnus tarichi samples (56.57 ng/g ± 22.18 ng/g) and in two Capoeta capoeta samples (27.6 ng/g and 36.45 ng/g). Beta-HCH was detected in 8 Alburnus tarichi samples (24.95 ng/g ± 4.42 ng/g) and in two mussel samples (101.25 ng/g and 129.44 ng/g). HCB was found in one Alburnus tarichi sample (14.4 ng/g) and one mussel sample (181.25 ng/g). The compound 4,4′-DDE was detected in 21 Alburnus tarichi samples (87.13 ng/g ± 32.23 ng/g), in 9 mirror carp samples (304.82 ng/g ± 100.76 ng/g) and one mussel sample (149.31 ng/g). PCB 28 was detected in one Alburnus tarichi (19.46 ng/g) sample and PCB 101 was found in one Capoeta capoeta (60.16 ng/g) sample. PCB 118 was detected in one mirror carp sample (277.5 ng/g) and in two Capoeta capoeta samples (43.77 and 54.38 ng/g). PCB 128 was detected in only one Capoeta capoeta sample (141.48 ng/g). It is concluded that (i) efforts should be made to reduce contamination of aquatic environments by these compounds and that (ii) their levels in fishery products from Van Lake and connected streams should be monitored and publicly reported on a regular basis.

In this study, 70 Wistar rats were randomly divided into seven equal groups (six experimental and one control), which consisted of animals belonging to both sexes. Different combinations of insecticides were administered daily to the experimental groups (group 1: cypermethrin + piperonyl butoxide (PBO); group 2: alphacypermethrin + PBO; group 3: deltamethrin + PBO; group 4: cypermethrin + PBO + tetramethrin; group 5: alphacypermethrin + PBO + tetramethrin; and group 6: deltamethrin + PBO + tetramethrin) for 28 days. During the study period, mortality and serious clinical findings were not observed in any animal. However, feed consumptions decreased in groups 1 and 3 (p < 0.05). Red blood cells, white blood cells, and hemoglobin levels, especially in cypermethrin and alphacypermethrin groups (groups 1, 2, and 4), were found to be higher than the control group (p < 0.05). Furthermore, biochemical changes related to liver, kidney functions, and protein metabolism occurred in males of almost all the groups. Relative liver and kidney weights of the male animals increased in the cypermethrin and alphacypermethrin groups (p < 0.05). The most common finding observed during the histopathological examination of all the experimental groups was centrilobular degeneration in the liver. It was concluded that although clinical symptoms were not observed, synthetic pyrethroid, synergist, and knockdown agent combinations might cause serious abnormalities when administered in certain doses in mammalians.

The concentrations of selected Organochlorine (OC) pesticides (α-HCH, β-HCH, γ-HCH, HCB, aldrin, 2,4′-DDE, 4,4′-DDE, 2,4′-DDT, 4,4′-DDT) and Polychlorinated Biphenyls (PCBs) (28, 70, 74, 81, 99, 101, 105, 118, 128, 138, 153, 156, 170, 180, 183, 187) were measured in two species of cultured freshwater fish (rainbow trout, Oncornhychus mykiss and catfish, Silurus glanis ) and two kinds of sea fish (mullet, Mugil cephalus and salmon, Salmo salar ) between March 2008 and June 2009 in order to evaluate the status, seasonal changes and potential sources of pollution in the Samsun region of Turkey. Concentrations of total PCBs ranged from 17.6 to 335 ng/g in rainbow trout, 1,063 to 3,234 ng/g in mullet, 21 to 1,887 ng/g in salmon and 108 to 1,172 ng/g lipid in catfish and total OC pesticide concentrations ranged from 303 to 473, 319 to 6,158, 101 to 249 and 34 to 6,069 ng/g lipid in rainbow trout, mullet, salmon and catfish, respectively. It is concluded that the levels of persistent organic pollutants should be monitored regularly and rigorously by the appropriate government agency, with mandatory public reporting.