Determination of Time Dependent Stress Distribution on Potato Tubers at Mechanical Collision

This study focuses on determining internal stress progression and the realistic representation of time dependent deformation behaviour of potato tubers under a sample mechanical collision case. A reverse engineering approach, physical material tests and finite element method (FEM)-based explicit dynamics simulations were utilised to investigate the collision based deformation characteristics of the potato tubers. Useful numerical data and deformation visuals were obtained from the simulation results. The numerical results are presented in a format that can be used for the determination of bruise susceptibility magnitude on solid-like agricultural products. The modulus of elasticity was calculated from experimental data as 3.12 [MPa] and simulation results showed that the maximum equivalent stress was 1.40 [MPa] and 3.13 [MPa] on the impacting and impacted tubers respectively. These stress values indicate that bruising is likely on the tubers. This study contributes to further research on the usage of numerical-methods-based nonlinear explicit dynamics simulation techniques in complicated deformation and bruising investigations and industrial applications related to solid-like agricultural products

Finite Element Analysis of a PTO Shaft Used in an Agricultural Tractor

This study describes a finite element method (FEM) based deformation simulation procedure for a power take off (PTO) shaft in an agricultural tractor. The agricultural tractor is a mobile power source in agricultural fields. The Agricultural tractor transmits power to the working implement through several systems independently. Most especially, rotary elements used in agricultural machinery take the required power and movement from the tractor take off (PTO) shaft. During this operation, the PTO shaft experiences a high dynamic loading condition such as excessive instant (impact) loading. This may cause an undesired failure case for the PTO shaft. In order to prevent such undesired failures, loading condition and stress distribution on the component should be described properly; however, an accurate description of the structural stress distribution on the shaft becomes an important problem. In this content, a case study was carried out on a failed PTO shaft, as described in this paper. The aim of this case study is to exhibit the stress distribution on the PTO shaft through finite element analysis under a torsional loading case which may be considered as the main cause of the failure. Visual outputs from the simulation results revealed a better understanding of the failure zone on the shaft. The maximum equivalent stress magnitude obtained from the simulation was 632.08 [MPa] (which was lower than the fracture point) on the shaft under maximum PTO torque, however, it was concluded that the main reason for the failure was excessive shock torsional loading. This work contributes to further research into usage of numerical method based deformation simulation studies for the transmission elements used in agricultural tractors/machinery

Determination of Time Dependent Stress Distribution on a Potato Tuber during Drop Case

Realistic representation of time-dependent internal stress progression and deformation behaviour of a potato tuber during a sample drop case has been studied in this paper. A reverse engineering approach, compressive tests, slow motion camera records and finite element analysis (FEA) were employed to analyse the drop case deformation behaviour of a sample potato tuber. Simulation results provided useful numerical data and stress distribution visuals. The numerical results are presented in a format that can be used for the determination of bruise susceptibility magnitude on solid-like agricultural products during drop case. The visual observations revealed that slow motion camera images and simulation printouts were in good correlation. The modulus of elasticity of the potato specimens was calculated from experimental data to be 3.12 [MPa] and simulation results showed that the maximum equivalent stress was 0.526 [MPa] on the tuber. This value for stress indicates that bruising is not likely on the tuber under a pre-defined drop height. In order to test the simulation accuracy, empirical and simulation-based estimates for total energy in this drop case were compared. The relative difference between empirical and simulation results was 1.27 %. This study provide a good “how to do” guide to further research on the utilisation of (FEM)-based time-dependent simulation approach in complex mechanical impact based damaging analyses and industry focused applications related to solid-like agricultural products such as potato

Determination of the Failure Susceptibility of a Flat Die used in Biomass Pelletizing Machines by means of FEA based Design Exploration

This paper focuses on a design analysis of a flat die used in an agricultural biomass pelletizing machine by considering its high pressure loading failure susceptibility. The pellet die is one of the key elements in a pelletizing machine, and the strength of the die plate has an important role on the pellet’s quality and producibility. In fact, higher compression ratio (CR - the ratio of effective length and the internal (press channel) diameter of a die orifice/hole) will provide denser pellets which is a desired phenomenon, however, if the compression pressure is too high or CR is not determined to compensate high pressures, the raw material may block the die and the die may experience deformation failure due to overloading. If the desire is to make high quality pellets with no die failure, optimum flat die hole/orifice design parameters should be used which can provide the best CR for a specific compression pressure. This is the core motivation of this research. In this study, Finite Element Analysis (FEA) based design exploration has been utilised for a sample single hole flat die with various die geometry parameters against various compression pressure values. Following the FEA design exploration undertaken, a response surface analysis (RSA) was carried out and then estimation models (empirical equations), which could be used to calculate parameters of the die hole/orifice against applied compression pressure and failure susceptibility based on structural stress and deformation, was described. The results gained from the RSA has indicated that the estimation models have high R2 values (higher than 98 %) which could be used for adequately predicting failure susceptibility indicators. In addition to this, FEM-based simulation print-outs have provided useful stress distribution visuals on the die against different compression pressure values. Most especially, the study has highlighted that a detailed structural optimisation study may be scheduled in order to obtain die geometry design parameters with a focus on the failure susceptibility

Clinical, Laboratory, and Radiological Evaluation of 32 Cases with Tuberculous Meningitis

Introduction: Tuberculous meningitis is an important central nervous system infection, and it is the most severe clinical form of tuberculosis. Mycobacterium tuberculosis is the frequently isolated microorganism, and it is associated with high morbidity and mortality among central nervous system infections. Despite all the advances in medicine, diagnosis of tuberculous meningitis is still a significant problem. In our study, we aimed to evaluate clinical, microbiological and radiological features of the patients with tuberculous meningitis in detail

Oxidative stress in acne vulgaris

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Quality of life and related factors among chronic hepatitis B-infected patients: a multi-center study, Turkey

Background: The aim of this study was to assess health-related quality of life (HRQOL) among chronic hepatitis B (CHB) patients in Turkey and to study related factors

Quality of life and related factors among chronic hepatitis B-infected patients: a multi-center study, Turkey

balkan, ilker inanc/0000-0002-8977-5931; Altindis, Mustafa/0000-0003-0411-9669; Sahin, Ahmet Ziyaettin/0000-0003-1060-6746; atilla, aynur/0000-0001-8027-1991WOS: 000386954300001PubMed: 27809934Background: The aim of this study was to assess health-related quality of life (HRQOL) among chronic hepatitis B (CHB) patients in Turkey and to study related factors. Methods: This multicenter study was carried out between January 01 and April 15, 2015 in Turkey in 57 centers. Adults were enrolled and studied in three groups. Group 1: Inactive HBsAg carriers, Group 2: CHB patients receiving antiviral therapy, Group 3: CHB patients who were neither receiving antiviral therapy nor were inactive HBsAg carriers. Study data was collected by face-to-face interviews using a standardized questionnaire, Short Form-36 (SF-36) and Hepatitis B Quality of Life (HBQOL). Values equivalent to p < 0.05 in analyses were accepted as statistically significant. Results: Four thousand two hundred fifty-seven patients with CHB were included in the study. Two thousand five hundred fifty-nine (60.1 %) of the patients were males. Groups 1, 2 and 3, consisted of 1529 (35.9 %), 1721 (40.4 %) and 1007 (23.7 %) patients, respectively. The highest value of HRQOL was found in inactive HBsAg carriers. We found that total HBQOL score increased when antiviral treatment was used. However, HRQOL of CHB patients varied according to their socio-demographic properties. Regarding total HBQOL score, a higher significant level of HRQOL was determined in inactive HBV patients when matched controls with the associated factors were provided. Conclusions: The HRQOL score of CHB patients was higher than expected and it can be worsen when the disease becomes active. Use of an antiviral therapy can contribute to increasing HRQOL of patients