Modeling and simulation of joint clearance effects on mechanisms having rigid and flexible links

Selçuk Erkaya,İbrahim Uzmay 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.8

In this study, kinematic and dynamic characteristics of a planar four-bar mechanism having joint clearance and link flexibility are investigated. Assuming that joint clearance as a virtual massless link, artificial clearances are developed at crank-coupler and couplerfollowerjoints. Contact model in joints with clearance is established using the nonlinear spring-damper model and the friction effect isconsidered using the Coulomb friction model. Then the simulation is implemented and the kinematic and dynamic characteristics ofmodel mechanism are investigated. The computational methodology can predict the effects of clearance on planar mechanism havingrigid and flexible links. The results are evaluated for the case of stationary phase, and naturally show that extreme values occur in outputof the mechanism with clearances. Due primarily to the suspension effect of the flexible link, values of these peaks in the flexible mechanismdecrease relative to that of the rigid mechanism. In addition, the flexibility has a significant effect on the vibration response of themechanism with joint clearance.

Prediction of vibration characteristics of a planar mechanism having imperfect joints using neural network

Selçuk Erkaya 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.5

"Clearance is inevitable in the joints of mechanisms due primarily to the design, manufacturing and assembly processes or a wear effect. Excessive value of joint clearance plays a crucial role and has a significant effect on the kinematic and dynamic performances of the mechanism. In this study, effects of joint clearances on bearing vibrations of mechanism are investigated. An experimental test rig is set up, and a planar slider-crank mechanism having two imperfect joints with radial clearance is used as a model mechanism. Three accelerometers are positioned at different points to measure the bearing vibrations during the mechanism motion. For the different running speeds and clearance sizes, this work provides a neural model to predict and estimate the bearing vibrations of the mechanical systems having imperfect joints. The results show that radial basis function (RBF) neural network has a superior performance for predicting and estimating the vibration characteristics of the mechanical system."

Investigation of balancing problem for a planar mechanism using genetic algorithm

Selçuk Erkaya 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.7

In this study, optimal balancing of a planar articulated mechanism is investigated to minimize the shaking force and moment fluctuations. Balancing of a four-bar mechanism is formulated as an optimization problem. On the other hand, an objective function based on the sub-components of shaking force and moment is constituted, and design variables consisting of kinematic and dynamic parameters are defined. Genetic algorithm is used to solve the optimization problem under the appropriate constraints. By using commercial simulation software, optimized values of design variables are also tested to evaluate the effectiveness of the proposed optimization process. This work provides a practical method for reducing the shaking force and moment fluctuations. The results show that both the structure of objective function and particularly the selection of weighting factors have a crucial role to obtain the optimum values of design parameters. By adjusting the value of weighting factor according to the relative sensitivity of the related term, there is a certain decrease at the shaking force and moment fluctuations. Moreover, these arrangements also decrease the initiative of mechanism designer on choosing the values of weighting factors.

Immobilization of Candida rugosa Lipase on Magnetic Biosilica Particles: Hydrolysis and Transesterification Studies

Ilkay Acıkgoz-Erkaya,Gulay Bayramoglu,Aydin Akbulut,Mehmet Yakup Arica 한국생물공학회 2021 Biotechnology and Bioprocess Engineering Vol.26 No.5

Biodiesel is a renewable fuel used mainly in diesel engines. At the present time, biodiesel is largely produced by acid or alkali transesterification reactions. A hot spring water algae isolate "Kamptonema formosum" was cultivated at three different temperatures, and the algae oil was extracted using chloroform and methanol (v/v, 1/1 ratio) as the solvent. The maximum amount of algal biomass (1.86 g/L) was obtained at 25°C, and the extracted oil was found to be 48.7% of the total dry biomass. Diatomic earth particles (Biosilica) were magnetized via thermal coprecipitation reaction, and then it was grafted with polydopamine (MBioSi@PDA). The lipase was covalently immobilized on the surface of the MBioSi@PDA via Schiff’s base reaction. The immobilization conditions were optimized and 3.0 mg/mL as the initial lipase concentration in the immobilization medium was found to be the most favorable. At this lipase concentration, the amount of the immobilized lipase on the MBioSi@PDA particles and immobilization yield were found to be 81.9 mg/g and 67.9%, respectively. The MBioSi@PDA@lipase particles were used for conversion of K. formosum oil into biodiesel, and the conversion yield was found as 91.2% under optimum conditions. The fatty acid methyl ester (FAME) compositions of the alga oil were identified using a gas chromatography-mass spectrometry (GC-MS). K. formosum oil mainly composed of the required fatty acids (i.e., 16 and 18 carbon long-saturated and unsaturated fatty acids) for biodiesel synthesis, and these were advantageous for synthesis of biodiesel from the algal oil.

Design of Neural Networks Model for Transmission Angle of a Modified Mechanism

Yildirim Sahin,Erkaya Selcuk,Su Siikrii,Uzmay ibrahim The Korean Society of Mechanical Engineers 2005 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.19 No.10

This paper discusses Neural Networks as predictor for analyzing of transmission angle of slider-crank mechanism. There are different types of neural network algorithms obtained by using chain rules. The neural network is a feedforward neural network. On the other hand, the slider-crank mechanism is a modified mechanism by using an additional link between connecting rod and crank pin. Through extensive simulations, these neural network models are shown to be effective for prediction and analyzing of a modified slider-crank mechanism's transmission angle.

Risk Factors for Endometrial Hyperplasia Concomitant Endometrial Polyps in Pre- and Post-menopausal Women

Topcu, Hasan Onur,Erkaya, Salim,Guzel, Ali Irfan,Kokanali, Mahmut Kuntay,Sarıkaya, Esma,Muftuoglu, Kamil Hakan,Doganay, Melike Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.13

Purpose: To evaluate the risk factors for endometrial hyperplasia concomitant endometrial polyps in pre- and post-menopausal women. Materials and Methods: A total of 203 patients undergoing endometrial sampling before hysterectomy were evaluated in this retrospective study. Data recorded were age, gravidity, parity, body mass index (BMI: weight(kg)/$height(m)^2$), endometrial thickness (ET), menopausal status, presence of adenomyosis and diabetes mellitus. Results: Endometrial hyperplasia and polyps were detected in 13 patients. There were statistically significant differences in terms of age, menopausal status, morbid obesity and diabetes mellitus (p<0.005). Logistic regression demonstrated that menopausal status and presence of diabetes mellitus were independent risk factors. Conclusions: According to the current study; menopause and diabetes mellitus are strong risk factors for the presence of concomitant endometrial polyps and endometrial hyperplasia.

Design of Neural Networks Model for Transmission Angle of a Modified Mechanism

Sukru Su,Sahin Yildirim,Ibrahim Uzmay,Selcuk Erkaya 대한기계학회 2005 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.19 No.10

Design of Neural Networks Model for Transmission Angle of a Modified Mechanism

Şahin Yildirim,Selçuk Erkaya,Şükrü Su,íbrabim Uzmay 대한기계학회 2005 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.19 No.10

This paper discusses Neural Networks as predictor for analyzing of transmission angle of slider-crank mechanism. There are different types of neural network algorithms obtained by using chain rules. The neural network is a feedforward neural network. On the other hand, the slider-crank mechanism is a modified mechanism by using an additional link between connecting rod and crank pin. Through extensive simulations, these neural network models are shown to be effective for prediction and analyzing of a modified slider-crank mechanism’s transmission angle.

Effects of metal surface grinding at the porcelain try-in stage of fixed dental prostheses

Mehmet Dincel,Hasan Onder Gumus,Selcuk Erkaya,Bulent Kesim,Halil İbrahim Kılınc 대한치과보철학회 2014 The Journal of Advanced Prosthodontics Vol.6 No.4

PURPOSE This study was to evaluate the effect of grinding of the inner metal surface during the porcelain try-in stage on metal-porcelain bonding considering the maximum temperature and the vibration of samples. MATERIALS AND METHODS Ninety-one square prism-shaped (1 × 1 × 1.5 mm) nickel-chrome cast frameworks 0.3 mm thick were prepared. Porcelain was applied on two opposite outer axial surfaces of the frameworks. The grinding was performed from the opposite axial sides of the inner metal surfaces with a low-speed handpiece with two types of burs (diamond, tungsten-carbide) under three grinding forces (3.5 N, 7 N, 14 N) and at two durations (5 seconds, 10 seconds). The shear bond strength (SBS) test was performed with universal testing machine. Statistical analyzes were performed at 5% significance level. RESULTS The samples subjected to grinding under 3.5 N showed higher SBS values than those exposed to grinding under 7 N and 14 N (P<.05). SBS values of none of the groups differed from those of the control group (P>.05). The types of bur (P=.965) and the duration (P=.679) did not affect the SBS values. On the other hand, type of bur, force applied, and duration of the grinding affected the maximum temperatures of the samples, whereas the maximum vibration was affected only by the type of bur (P<.05). CONCLUSION Grinding the inner metal surface did not affect the metal-porcelain bond strength. Although the grinding affected the maximum temperature and the vibration values of the samples, these did not influence the bonding strength.

Prevalence and Comparing of Some Microbiological Properties, Somatic Cell Count and Antibiotic Residue of Organic and Conventional Raw Milk Produced in Turkey

Bayram Urkek,Mustafa Sengul,Tuba Erkaya,Vecihi Aksakal 한국축산식품학회 2017 한국축산식품학회지 Vol.37 No.2

The aim of this study was to investigate the effects of production systems and milk collection periods on the somatic cell count (SCC), some microbiological properties, total aerobic mesophilic bacteria (TAMB), coliform, Staphylococcus aureus (S. aureus), yeast and mould) and antibiotic residue of milk; in Turkey. Milk samples were collected from 9 conventional farms and 9 organic farms during one year time, at six different months (December 2013 to October 2014), and all farms were selected from the same geographical locations. All organically managed farms had organic production certificates given by the Republic of Turkey Ministry of Food, Agriculture and Livestock. The count of TAMB, coliform, and coagulase positive S. aureus were affected by production systems at the level of p<0.01; yeast and mold, and somatic cell count (SCC) were affected at the level of p<0.05. But, differences according to months were statistically significant only on TAMB (p<0.01) and coliform (p<0.05) counts. The general means of TAMB, coliform and yeast and mould counts of the organic milk (OM) were significantly lower (p<0.05), while the general means of SCC and coagulase positive S. aureus count of the OM was significantly higher (p<0.05) compared to conventional milk (CM). Antibiotic residue was determined in one of the CM sample and in two of the OM samples. Our study is the first research that compared conventional and organic milk in Turkey. This study indicated that the microbiological quality of OM was the higher in terms of TAMB, coliform and yeast and mould, whereas was the lower in relation to SCC and coagulase positive S. aureus counts. But, the quality of both milk types should be improved.