Effect of chitosan/carbon nanotube fillers on vibration behaviors of drilled composite plates

Ersin Demir,Hasan Çallıoğlu,Metin Sayer,Furkan Kavla 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.35 No.6

The effect of Chitosan (CS), Carbon Nanotube (CNT) and hybrid (CS-CNT) fillers on the natural frequency of drilled composite plate is investigated by experimentally in this study. The numerical validation is also made with a program based on Finite Element Method (SolidWorks). Nine types filled and one neat composite plates are used in the study. The fillers ratios are 1% CS, 2% CS, 3% CS, 0.1% CNT, 0.2% CNT, 0.3% CNT, 1% CS+0.3% CNT, 2% CS+0.3% CNT, 3% CS+0.3% CNT. The specimens cut to certain sizes by water jet from the plates 400 mm x 400 mm in dimensions. Some of them are drilled in certain dimensions with drill. The natural frequency of each specimen is measured by the vibration test set up to determine the vibration characteristic. The vibration test set up includes an accelerometer, a current source power unit, a data acquisition card and a computer. A code is written in Matlab program for the signal processing. The study are investigated and discussed in four main points to understand the effect of the fillers on the natural frequency of the composite plate. These are the effect of fillers contents and amounts, orientation angles of fibers, holes numbers and holes sizes. As results, the natural frequency of the plate with 1% CS and 0.1% CNT hybrid filler is lower than those of the plates with other fillers ratios for 45 orientation angle. Besides, in the composite plate with 0 orientation angle, the natural frequency increases with increasing the filler ratio. Moreover, the natural frequency increases until a certain hole number and then it decreases. Furthermore, the natural frequency is not affected until a certain hole diameter but then it decreases.

A study on natural frequencies and damping ratios of composite beams with holes

Ersin Demir 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.21 No.6

In this study, free vibration and damping characteristics of composite beams with holes are investigated, experimentally and numerically. Two types of samples with different fabrics are used: unidirectional and woven. The effects of diameter, number and location of circular holes on the vibration characteristics of composite beams are examined. The effects of rotation angle and minor to major diameter ratio of the elliptical hole are also investigated numerically. Moreover, the mode shapes of all types of beams are obtained numerically. According to the results, the natural frequency decreases with increasing hole diameter but increases very little with increasing the distance between the hole center and the clamped end. Damping ratio decreases by increasing the diameter of hole. But it fluctuates by increasing the diameters of holes of beam having three holes. Furthermore it decreases by increasing the distance between hole center and clamped end except for the range 50 mm to 100 mm.

Elasto-plastic thermal stress analysis of functionally graded hyperbolic discs

Ersin Demir,Hasan Çallıoğlu,Metin Sayer 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.62 No.5

The objective of this analytical study is to calculate the elasto-plastic stresses of Functionally Graded (FG) hyperbolic disc subjected to uniform temperature. The material properties (elastic modulus, thermal expansion coefficient and yield strength) and the geometry (thickness) of the disc are assumed to vary radially with a power law function, but Poisson’s ratio does not vary. FG disc material is assumed to be non-work hardening. Radial and tangential stresses are obtained for various thickness profile, temperature and material properties. The results indicate that thickness profile and volume fractions of constituent materials play very important role on the thermal stresses of the FG hyperbolic discs. It is seen that thermal stresses in a disc with variable thickness are lower than those with constant thickness at the same temperature. As a result of this, variations in the thickness profile increase the operation temperature. Moreover, thickness variation in the discs provides a significant weight reduction. A disc with lower rigidity at the inner surface according to the outer surface should be selected to obtain almost homogenous stress distribution and to increase resistance to temperature. So, discs, which have more rigid region at the outer surface, are more useful in terms of resistance to temperature.

Vibration and damping behaviors of symmetric layered functional graded sandwich beams

Ersin Demir 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.62 No.6

In this study, free vibration and damping behaviors of multilayered symmetric sandwich beams and single layered beams made of Functionally Graded Materials were investigated, experimentally and numerically. The beams were composed of Aluminum and Silicon Carbide powders and they were produced by powder metallurgy. Three beam models were used in the experiments. The first model was isotropic, homogeneous beams produced by using different mixing ratios. In the second model, the pure metal layers were taken in the middle of the beam and the weight fraction of the ceramic powder of each layer was increased towards to the surfaces of the beam in the thickness direction. In the third model, the pure metal layers were taken in the surfaces of the beam and the weight fraction of the ceramic powder of each layer was increased towards to middle of the beam. Then the vibration tests were performed. Consequently, the effects of stacking sequence and mixing ratio on the natural frequencies and damping responses of functionally graded beams were discussed from the results obtained. Furthermore, the results obtained from the tests were supported with a finite-element-based commercial program, and it was found to be in harmony.

Clinical and Prognostic Features of Erionite-Induced Malignant Mesothelioma

Ersin Demirer,Elamin M. Elamin,Christian F. Ghattas,Mohamed O. Radwan 연세대학교의과대학 2015 Yonsei medical journal Vol.56 No.2

This review analytically examines the published data for erionite-related malignantpleural mesothelioma (E-MPM) and any data to support a genetically predisposedmechanism to erionite fiber carcinogenesis. Adult patients of age ≥18 years with erionite-related pleural diseases and genetically predisposed mechanisms to erionite carcinogenesis were included, while exclusion criteria included asbestos- or tremolite-related pleural diseases. The search was limited to human studies though not limited to a specific timeframe. A total of 33 studies (31042 patients) including 22 retrospective studies, 6 prospective studies, and 5 case reports were reviewed. E-MPM developed in some subjects with high exposures to erionite, though not all. Chest CT was more reliable in detecting various pleural changes in E-MPM than chest X-ray, and pleural effusion was the most common finding in E-MPM cases, by both tests. Bronchoalveolar lavage remains a reliable and relatively less invasivetechnique. Chemotherapy with cisplatin and mitomycin can be administered either alone or following surgery. Erionite has been the culprit of numerous malignantmesothelioma cases in Europe and even in North America. Erionite has a higher degree of carcinogenicity with possible genetic transmission of erionite susceptibilityin an autosomal dominant fashion. Therapeutic management for E-MPM remains very limited, and cure of the disease is extremely rare.

Evaluation of Quality of Life with the Chronic Obstructive Pulmonary Disease Assessment Test in Chronic Obstructive Pulmonary Disease and the Effect of Dyspnea on Disease-Specific Quality of Life in These Patients

OguzhanOkutan,Dilaver Tas,Ersin Demirer,ZaferKartaloglu 연세대학교의과대학 2013 Yonsei medical journal Vol.54 No.5

Purpose: The chronic obstructive pulmonary disease (COPD) assessment test (CAT) was recently introduced for use in assessing disease-specific quality of life and follow-up of patients with COPD. The purpose of this study was to evaluate the effect of the dyspnea on disease-specific quality of life detected by CAT score in patients with COPD. Materials and Methods: In this study, 90 stable patients with COPD as defined by the Global Initiative for Chronic Obstructive Lung Disease (GOLD) criteria were included. The level of dyspnea was assessed with the Medical Research Council (MRC) dyspnea scale, and disease-specific quality of life was assessed with CAT score. Results: The mean±SD age was 68.5±10.9 (range 41-97) years. A significant relationship was established between CAT score, MRC dyspnea scale score and GOLD stage in patients with COPD. There was also a positive correlation between dyspnea scale scores and GOLD stage in the patients (p<0.001), as well as positive correlation between CAT score and dyspnea scale score (p<0.001). CAT score showed a significant correlation with hospitalization and exacerbations (p<0.05). Conclusion: Dyspnea is an important symptom that may impact quality of life in patients with COPD. CAT was shown to be a simple, fast and intelligible measurement of disease-specific quality of life, and was correlated with levels of dyspnea in patients with COPD.

Assessment of Proportion of Hidden Patients Having Symptoms of Overactive Bladder and Why Has It Been Hidden in Female Outpatients Admitted to Hospital

Oktay Üçer,Ömer Demir,Mehmet Fatih Zeren,Yasin Ceylan,İlker Çelen,Ali Ersin Zümrütbaş,Gökhan Temeltaş,Ozan Bozkurt,Bülent Günlüsoy,Orçun Çelik,Gökhan Ekin,Oğuz Mertoğlu,Aegean Study Group of Society o 대한배뇨장애요실금학회 2016 International Neurourology Journal Vol.20 No.1

Purpose: To determine the proportion of patients with undetected symptoms of overactive bladder by using the overactive bladder-validated 8 (OAB-V8) screening questionnaire and investigate these symptoms were undetected in female patients who were hospitalized. Methods: We invited 2,250 female patients hospitalized in the Aegean region of Turkey to answer a self-administered questionnaire. The questionnaire included questions on evidence of lower urinary tract symptoms (OAB-V8), relevant medical history, and demographic data. Patients with a total OAB-V8 score≥8 were defined as having OAB symptoms. Results: The proportion of patients with OAB symptoms in this study was 40.6%. Nearly 57% of the patients with OAB symptoms had not been previously admitted to any hospital for lower urinary tract symptoms (LUTS). The two most common reasons why women with OAB symptoms did not admit themselves to a hospital because of LUTS were as follows: “I did not think I had a disease” and “The symptoms did not bother me,” with a response rate of 74.7%. The mean OAB-V8 scores of the patients with these two responses were significantly lower than those of the other patients (P<0.001). Conclusions: This is the first study to demonstrate a significant proportion of women with undetected OAB symptoms. The main reasons the women did not admit themselves to a hospital were their unawareness of the disease and because the LUTS were not bothersome. Public awareness programs on this disease may resolve this problem.

Distinctive Features of Hepatic Steatosis in Children: Is It Primary or Secondary to Inborn Errors of Metabolism?

Karhan, Asuman Nur,Hizarcioglu-Gulsen, Hayriye,Gumus, Ersin,Akcoren, Zuhal,Demir, Hulya,Saltik-Temizel, Inci Nur,Orhan, Diclehan,Ozen, Hasan The Korean Society of Pediatric Gastroenterology 2021 Pediatric gastroenterology, hepatology & nutrition Vol.24 No.6

Purpose: The incidence of hepatic steatosis among children has been increasing; however, data distinguishing simple steatosis from a more complex disorder are lacking. Methods: This study identified the etiologies resulting in hepatic steatosis through a retrospective review of pediatric liver biopsies performed in the last 10 years. A total of 158 patients with hepatic steatosis proven by histopathological evaluation were enrolled in the study, and baseline demographic features, anthropometric measurements, physical examination findings, laboratory data, ultrasonographic findings, and liver histopathologies were noted. Results: The two most common diagnoses were inborn errors of metabolism (IEM) (52.5%) and nonalcoholic fatty liver disease/steatohepatitis (NAFLD/NASH) (29.7%). The three most common diseases in the IEM group were glycogen storage disorders, Wilson's disease, and mitochondrial disease. The rates of consanguineous marriage (75.6%; odds ratio [OR], 26.040) and positive family history (26.5%; OR, 8.115) were significantly higher (p=0.002, p<0.001, respectively) in the IEM group than those in the NAFLD/NASH group. Younger age (p=0.001), normal anthropometric measurements (p=0.03), increased aspartate aminotransferase levels (p<0.001), triglyceride levels (p=0.001), and cholestatic biochemical parameters with disrupted liver function tests, as well as severe liver destruction of hepatic architecture, cholestasis, fibrosis, and nodule formation, were also common in the IEM group. Conclusion: Parents with consanguinity and positive family history, together with clinical and biochemical findings, may provide a high index of suspicion for IEM to distinguish primary steatosis from the consequence of a more complex disorder.