Duzce University
  • Düzce, Turkey
Recent publications
Operations and maintenance costs, and unplanned downtime accounts for a significant proportion of the total expenditure of windfarms. Therefore, reduction of these costs is essential, which requires a better understanding of the wind turbines' reliability in terms of failure rates and downtime with operational lifetime. Failure rates and downtime are generally logged using condition monitoring systems, which mainly focus on Supervisory Control and Data Acquisition (SCADA) alarm signals. The aim of this paper is to use SCADA alarm statistics to provide a new failure rate and downtime survey and thus to evaluate reliability performance of the major wind turbine components and subsystems. The paper focuses on a modern onshore windfarm located in Turkey with Type-III wind turbines over the course of the first two years of operations, which is the first time reliability data from Turkey has been published in literature. The presented data can help to provide a better understanding of early life operations, since all maintenance activities, as well as stoppages that caused the wind turbines not to generate electricity were considered in this paper. Furthermore, the evaluation and categorisation of the recorded SCADA alarms, their origins and whether they were associated with planned or unplanned downtime is presented. This analysis shows that early life modern wind turbines have the highest alarm rates and downtime associated with ‘safety’ factors, followed by the ‘electrical systems’, which was found to be the most critical (or unreliable) subsystem. The presented results therefore suggest that early life focus should be on the electrical systems of wind turbines for maximising their operating time and availability. Monthly distributions of both SCADA alarms and downtime rates are also presented to highlight the effects of environmental conditions.
Uniform resource locator (URL)‐based cyber‐attacks form a major part of security threats in cyberspace. Even though the experience and awareness of the end‐users help them protect themselves from these attacks, a software‐based solution is necessary for comprehensive protection. To this end, a novel robust URL classification model based on convolutional neural network is proposed in this study. The proposed model classifies given URLs into five classes, namely, (i$$ \mathrm{i} $$) benign$$ \mathrm{benign} $$, (ii$$ \mathrm{ii} $$) defacement$$ \mathrm{defacement} $$, (iii$$ \mathrm{iii} $$) phishing$$ \mathrm{phishing} $$, (iv$$ \mathrm{iv} $$) spam$$ \mathrm{spam} $$, and (v$$ \mathrm{v} $$) malware$$ \mathrm{malware} $$. The proposed model was trained and evaluated on a gold standard URL dataset comprising of 36,707$$ \mathrm{36,707} $$ samples. According to the experimental result, the proposed model obtained an accuracy as high as 98.1%$$ 98.1\% $$ which outperformed the state‐of‐the‐art. Based on the same architecture, we proposed another classifier, a binary classifier that detects malicious URLs without dealing with their types. This binary classifier obtained an accuracy as high as 99.3%$$ 99.3\% $$ which outperformed the state‐of‐the‐art as well. The experimental result demonstrates the feasibility of the proposed solution.
This study presents the affects of cryogenic treatment on flank wear (Vb) and surface roughness (Ra) in machining 41Cr4 steel with shallow (SCT (15 h at −80 °C)) and deep (DCT (15 h at −196 °C)) cryogenically treated carbide tools. The study revealed that the cryogenic treatment increases the hardness and wear resistance of coated carbide tools and improves the surface roughness, thanks to the changes in the microstructure. The η-phase is approximately 17.5 and 24.64% higher in the shallow and deep cryogenically treated tool's microstructure than in the untreated tool (U). The best machining performance was founded with the deep cryogenically treated cutting tool. Compared to the untreated tool, shallow and deep cryogenic treatment increased the hardness of the cutting tools by approximately 8.66 and 10.17%. Compared to the untreated cutting tool, the deep cryogenically treated tool was less worn at rates ranging from 13.04 to 18.60% and provided a lower average surface roughness between 2.49 and 20.15%. With increasing feed rate and cutting speed, the amount of cutting tool flank wear also increased. While the surface roughness values decreased slightly with increasing cutting speed, the increasing feed rate caused the surface roughness to increase significantly. The analysis of variance results showed that the most significant parameter on the cutting tool flank wear was heat treatment with a rate of 67.34%, and the most influential parameter on the surface roughness was the feed rate with a rate of 96.33%.
AimThe current study aimed to evaluate the effects of caspase-8 (CASP8) and mitogen-activated protein kinase 1 (MAPK1) gene expression levels and their products on preventing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection.MethodsA total of 40 patients (men, 15 [37.5%]; women, 25 [62.5%]) with COVID-19 infection were included in the current study. The patients were divided into four main groups based on disease severity: mild (n = 7), moderate (n = 10), severe (n = 14), and critical (n = 9). Individuals aged < 18 years and pregnant women were excluded. Patients were classified according to the World Health Organization (WHO) classification system (WHO/2019-nCoV/clinical/2021.1).ResultsConsidering all groups, statistically significant differences were detected among all groups for both CASP82−ΔΔCt (p = 0.006) and MAPK1 2−ΔΔCt values (p = 0.015). Moreover, statistically significant differences were detected between mild and moderate (p = 0.013), moderate and critical (p = 0.018), and severe and critical (p = 0.023) groups for lymphocytes.Conclusion The CASP8/MAPK1 expression levels and/or its products are essential in preventing injury caused by COVID-19 infection. They play crucial roles in maintaining cellular homeostasis and viability. Furthermore, CASP8/MAPK1 levels can provide information about disease severity.
At its peak period of the COVID-19 spread, this study investigates how transit-oriented sub-centered housing developments responded against the pandemic in line with the residents’ spatial experience and changing preferences. In this context, Batikent, a gated-community-based urban development and one of the successful urban residential projects realized in the 1980s in Ankara, Turkiye, was chosen as a case study. The four metro stations located on the same track in Batikent’s most densely populated areas were taken as reference points, and their surroundings, 1 km in diameter were spatially examined in terms of the housing types they host, and differences in their land coverages and building and population density, etc. A survey was carried out to examine the residents’ COVID-19 experience in line with spatial qualities. To match them against COVID-19 with the spatial patterns, both results were compared to the COVID-19 spread maps, collected for six months starting from October 2020 to March 2021. The spread risk was prominent in the places where the buildings are in closer proximity and increased interaction with the commercial networks. The results also suggest that perceived qualities of the residential environment are critical in dealing with extreme urban phenomena. Neither the spatial formation of the urban form nor the living habits change instantaneously but being aware of the capabilities of the spatial setting and properties which combat the pandemics helps with the spatial scale of the local adaptation process.
In this study, zinc oxide nanoparticles (ZnO-NPs) were synthesized by green and chemically using the sol–gel method. They compared in terms of current–voltage (I–V) characteristics. The synthesized plant-based (ZnO-NPs) were characterized via Fourier-transform infrared-spectroscopy, X-ray diffraction (XRD), and field-emission scanning electron microscopy. The XRD analysis determined the existence of pure-crystalline of (ZnO-NPs). Particle size distribution was routinely employed to characterize the green synthesized powders for size distribution, and the reactivity of green synthesized particles was found smaller than chemically synthesized particles. The I–V measurements of prepared thin films characteristics were compared both in the dark and ultraviolet spectrum (365 nm) under 100 mW/cm². While the reverse-saturation current (I0), ideality factor (n), and zero-bias barrier-height (Φbo) values were extracted from the I–V data as 1.68 × 10–6 A, 2.43, 0.61 eV in dark and 7.27 × 10–5 A, 5.64, 0.50 eV under illumination for Al/(Bio-ZnO)/pSi and 7.99 × 10–6 A, 3.75, 0.57 eV in dark and 3.09 × 10–5 A, 5.71, 0.53 eV under illumination for Al/(Chemical-ZnO)/pSi photodiodes. These photodiodes' energy-dependent profiles were also obtained using the Card-Rhoderick method.
Methoxy group enriched eight coumarin‐chalcone hybrid derivatives were synthesized. Antimicrobial/ antiproliferative activities were tested against eight human pathogenic microorganisms and four cancer cell lines (AGS, HepG2, MCF‐7 and PC‐3), respectively. Antimicrobial results showed that most of the compounds were almost more active than used standard antibiotics. Cytotoxicity results showed that 2,3,4‐trimethoxyphenyl and thiophene containing structures have promising antiproliferative effects against AGS gastric cell line with ~5µg/ml IC50 values. At the same time, 2,4‐dimethoxyphenyl bearing derivative exhibited the lowest IC50 values against HepG2 (~10µg/ml) and PC‐3 (~5µg/ml) cell lines. Particularly, the cell viabilities of MCF‐7 cell lines were remarkably inhibited by all the compounds with lower IC50 values. Therefore, molecular docking studies between hybrid ligands and quinone reductase‐2 enzyme (regulates in MCF‐7 cancer cells) were performed. The results demonstrated that all the derivatives can smoothly interact with interested enzyme in agreement with the experimental results. Finally, ADME parameters were studied to reveal drug‐likeness potentials of the coumarin‐chalcone hybrids.
Metastasis to the masticator space and mandible is very rare. The most common origin in women is breast cancer. Cystic metastases may radiologically mimic abscess. Definitive diagnosis can be made histopathologically. The prognosis of these patients is very poor and early diagnosis is important. Therefore, metastasis should be considered in the differential diagnosis of oral lesions.
Background There are limited studies on substance use in nurses. The importance of the role of nurse managers was emphasized in previous studies; however, there were no studies that revealed their experiences throughout the process. Methods A qualitative design was used. The data were collected using a snowball method with purposeful sampling methods. The inclusion criterion was being a nurse manager who had worked with nurses who had used psychoactive substances. Interviews were conducted with a total of seven participants using a semi-structured interview form. Qualitative content analysis was performed after the interviews. Results As a result of the analysis of reports of individual in-depth interviews conducted with a total of seven participants, and examination of the literature regarding the issue, experiences of nurse managers who had worked with nurses with substance use were examined in three main themes − 1) identifying substance-using nurses, 2) interventions, and 3) feelings and opinions of nurse managers Conclusions Nurse managers identifying the nurses with substance use and managing the process appropriately is the key point in ensuring that these nurses receive support and patient safety is provided without interruptions. Therefore it is important that the experience of nurse managers is investigated.
PurposeTo examine visual evoked potential (VEP) changes following botulinum toxin type A (BTA) administration in patients with blepharospasm.Methods Patients diagnosed with blepharospasm receiving BTA administration were included in the study. Three groups, a control group and two study groups (patients examined 14 days after BTA administration—Study Group 1, and patients examined 28 days after BTA administration—Study Group 2) were evaluated. Dilated fundus examinations were performed following detailed ophthalmological examinations and VEP tests. Keypoint (Dantec, Denmark) and ISCEV criteria were adopted for pattern VEP (PVEP) recording. BTA was applied in the form of local injections at a total 15–30 units, at 2.5–5 units per injection.ResultsA mean 19.4 ± 3.2 units of BTA was used for each eye. N70 (ms), P100 (ms), and P100 (uV) values were statistically significantly lower in both study groups following drug administrations compared to the control group (p < 0.001 for all). Significant positive correlation was observed between increased P100 amplitudes and age in the control group (p = 0.008, r = 0.200). Significant negative correlation was observed between the BTA units used and decreased P100 amplitudes in both study groups 1 and 2 following drug administrations (p = 0.017, r = − 0.180 and p = 0.043, r = − 0.153, respectively).ConclusionVEP may be an important method in the diagnosis and follow-up of blepharospasm and in determining the success of drug administration and additional therapeutic requirements.
In this study, fractional versions of Milne-type inequalities are investigated for differentiable convex functions. We present Milne-type inequalities for bounded functions, Lipschitz functions, functions of bounded variation, etc., found in the literature. New results are established in the area of inequalities. This article is the first to study Milne-type inequalities for fractional integrals.
Glass fiber reinforced concrete (GFRC) comprises of hydration products of cement or cement plus sand, and glass fibers which take part in the concrete as reinforcement characteristics. GFRC has been used for over 50 years in several construction elements, such as facade panels, decorative no recoverable formwork, and other products. However, various anchor elements and pad hooks are needed to attach large or small parts made of GFRC panels to the main structure of the buildings. The corrosion rate of embedded metal fasteners over time is related to the water impermeability properties of the GFRC elements. In this study, corrosion of an electro galvanized pad hook embedded in 10‐20 mm of the GFRC panel was investigated as a result of the salt spray test performed in accordance with ASTM B 117 standards. At the end of the experiment, the embedded pad hook was taken from the GFRC and analysed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) methods. The results showed that the embedded pad hook in the GFRC, which was examined in the test procedures comply with the TS EN 12467 standards, was not corroded by 120 h test carried out in accordance with ASTM B 117 standards. This article is protected by copyright. All rights reserved.
Synovial sarcoma is a soft tissue tumor originating from mesenchymal precursor stem cells. It is usually seen in young males and lower extremities. It is only seen in 10% of head and neck region and nasopharynx which is a very unexpected location. We report a rare case treated with radiotherapy and chemotherapy.
With the increase in industrialization and the number of people and buildings, the need for refrigeration systems has also increased. Maintenance of these systems, malfunctions and their late detection cause time and cost problems. Therefore, in this study, a machine learning application is recommended to diagnose the refrigerant undercharge and refrigerant overcharge faults that may occur in the refrigeration system by using infrared images. Firstly, infrared images obtained from normal charge, undercharge and overcharge situations in the refrigeration system, are passed through the two-dimensional discrete wavelet transform (2D-DWT) and the images are decomposed. Then, statistical texture features from the original input images are obtained by separating infrared images. The dimensionality of the extracted features is reduced using the principal component analysis (PCA) and the ReliefF (RF) algorithm. Finally, these selected features are applied to the K nearest neighbor (k-NN), naive Bayes algorithm (NBA), decision tree (DT), and cascade forward neural network (CFNN) classifiers. It has been found that RF-based feature selection is useful in obtaining the optimal feature vector. The classification results revealed that CFNN outperforms k-NN, NBA, and DT. Compared to traditional electrical measurements and fault detection methods, it has been shown that the recommended system is feasible due to its features such as ease of use, remote measurement, and self-adaptive recognition.
Objective Diabetes mellitus is a widespread endocrine disease in the world with accompanying chronic hyperglycemia. In this study, we investigated the effect of hydroxytyrosol which exerts an antioxidant effect on the expressions of insülin and Prdx6 that protects cells against oxidative injury in diabetic rat pancreas. Methods There were 4 groups in the study. These were control (nondiabetic) group (n:10), hydroxytyrosol group (were administered 10 mg/kg/day p.o. hydroxytyrosol for 30 days) (n:10), streptozotocin group (were administered single intraperitoneal (i.p) injection of 55 mg/kg streptozotocin) (n:10) and streptozotocin + hydroxytyrosol group (were administered single i.p. injection of streptozotocin, and were started on 10 mg/kg/day hydroxytyrosol p.o. 48 h later, and were continued for 30 days)(n:10). During the experiment, blood glucose levels were measured with regular intervals. Insulin expression was determined with immunohistochemistry and Prdx6 expression with immunohistochemistry and Western blot. Results Blood glucose levels on 21st and 28th-day measurements were significantly lower in the streptozotocin + hydroxytyrosol group compared to streptozotocin group. Insulin and Prdx6 expressions were lower in streptozotocin and streptozotocin + hydroxytyrosol group compared to control and hydroxytyrosol groups. Insulin and Prdx6 expressions in the streptozotocin + hydroxytyrosol group were higher compared to streptozotocin group. Immunohistochemistry findings of Prdx6 and Western blot were the same. Conclusion Hydroxytyrosol which is an antioxidant compound, increased Prdx6 and insulin expressions in diabetic rats. Hydroxytyrosol-induced increase in insulin lowered blood glucose levels in diabetic rats. Finally, hydroxytyrosol, by increasing Prdx6 expression, decreased chronic hyperglycemia which is observed in diabetes. Thus, hydroxytyrosol might decrease or prevent several hyperglycemia-dependent complications.
Medical detection dogs have potential to be used to screen asymptomatic patients in crowded areas at risk of epidemics such as the SARS-CoV-2 pandemic. However, the fact that SARS-CoV-2 detection dogs are in direct contact with infected people or materials raises important concerns due to the zoonotic potential of the virus. No study has yet recommended a safety protocol to ensure the health of SARS-CoV-2 detection dogs during training and working in public areas. This study sought to identify suitable decontamination methods to obtain non-pathogenic face mask samples while working with SARS-CoV-2 detection dogs and to investigate whether dogs were able to adapt themselves to other decontamination procedures once they were trained for a specific odor. The present study was designed as a four-phase study: (a) Method development, (b) Testing of decontamination methods, (c) Testing of training methodology, and (d) Real life scenario. Surgical face masks were used as scent samples. In total, 3 dogs were trained. The practical use of three different decontamination procedures, i.e., storage, heating, and UV-C light, while training SARS-CoV-2 detection dogs were tested. The dog trained for the task alerted to the samples inactivated by the storage method with a sensitivity of 100 % and specificity of 98.28 %. In the last phase of this study, one dog of 2 dogs trained, alerted to the samples inactivated by the UV-C light with a sensitivity of 91.30% and specificity of 97.16% while the other dog detected the sample with a sensitivity of 96.00% and specificity of 97.65 %. The storage method was found to be reliable for training as it did not affect the scent specific to the infection. Both dogs targeted the positive samples without any hesitation after UV-C light application. Thus, UV-C method may be the only decontamination method which can be used for public screening. To our knowledge, this is the first published study to suggest a reliable and safe protocol to train and use detection dogs for screening infectious diseases which have zoonotic potential.
Objectives: Dedouit et al., Kramer et al and Vieth et al defined different staging methods over different sequences in knee MRI for bone age determination. Our study aims to examine three different methods in which the maturation stages of the knee epiphyses are evaluated by MRI in the same population, to compare the methods and results and evaluate them for some age thresholds and to discuss their applicability in forensic age estimation. Methods: In this study, 597 knee images obtained using a 3.0T MR scanner were evaluated retrospectively. The T1-weighted and PD-weighted sequences were evaluated by two observers. Knee bone development was staged on the femur and tibia, and descriptive statistics were calculated for each stage according to age and sex. Descriptive statistics were presented according to the age and sex of the cases, and intra- and interobserver agreements were evaluated by the κ and κw statistics obtained by the Fleiss approach. Results: Significant changes were found in stages depending on age. The intra- and interobserver agreement levels were very good (κ > 0.80) for each method. The methods of Dedouit, Kramer and Vieth can be used as an additional criteria for forensic age estimation for 14, 15, 18 and 21 year thresholds. Conclusions: Knee MRI stands out as an alternative modality for age estimation and it is necessary to prefer the method intended for the investigated age range with an individual-specific approach. Advances in knowledge: Our study stands out as the first study in which current classification methods were applied and compared in the same population for age estimation with knee MRI.
Background To evaluate corneal topography and densitometry features in patients with polycystic ovary syndrome (PCOS) and compare them with healthy individuals. Methods 53 eyes of 53 female patients diagnosed with PCOS and 53 eyes of 53 age-matched female volunteers were analyzed in the study. In addition to the detailed ophthalmological and gynecological examination, anterior segment analysis was performed using Pentacam. A complete analysis of aberrometric, keratometric, topometric, and, densitometric values between the groups was performed, and the results were outlined. Results According to the results, although Kmax-front, Kmean-front, ISV, IVA, IHA, BAD_D and PI-Avg values were slightly higher in PCOS group along with a slight thinning in the thinnest location, there was no statistically significant difference between the groups. Moreover, correlation analysis between PCOS clinical parameters and keratometric/topometric/aberrometric data were found to be almost normal. Yet, when Pentacam tomography maps of all cases are examined in detail, mild ectatic changes were observed in 5 cases in PCOS group. Furthermore, a significant increase in thickness across all densitometry values except anterior (10–12 mm), central (10–12 mm), and total (10–12 mm) was found in PCOS group. Conclusions Our study showed that an intensification of corneal densitometry values and various changes in keratometry data implying ectasia can be observed in patients with PCOS. Prospective studies with larger patient series are needed to reveal any potential relationship between PCOS and corneal abnormalities.
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Yasar Selman Gultekin
  • Faculty of Forestry, Forest Economics Department
Serdar Aslan
  • Department of Forest Botany
Necmi Aksoy
  • Department of Forest Botany
Ismail Hamdi Kara
  • Department of Family Medicine
Salih Tunç Kaya
  • Department of Biology
Information
Address
Düzce University Main Campus Konuralp, 81620, Düzce, Turkey
Head of institution
Prof. Dr. Nigar DEMİRCAN ÇAKAR
Website
https://en.duzce.edu.tr/
Fax
+90 (380) 5421103