Peridynamic simulations of nanoindentation tests to determine elastic modulus of polymer thin films

This study combines atomic force microscope (AFM) nanoindentation tests and peridynamic (PD) simulations to extract the elastic moduli of polystyrene (PS) films with varying thicknesses. AFM nanoindentation tests are applied to relatively hard PS thin films deposited on soft polymer (polydimethylsiloxane (PDMS)) substrates. Linear force versus deformation response was observed in nanoindentation experiments and numerical simulations since the soft PDMS substrate under the stiff PS films allowed bending of thin PS films instead of penetration of AFM tip towards the PS films. The elastic moduli of PS thin films are found to be increasing with increasing film thickness. The validity of both the simulation and experimental results is established by comparison against those previously published in the literature

Thermomechanical analysis of porous solid oxide fuel cell by using peridynamics

Solid oxide fuel cell (SOFC) is widely used in hybrid marine propulsion systems due to its high power output, excellent emission control and wide fuel suitability. However, the operating temperature in SOFC will rise up to 800–1000 ℃ due to redox reaction among hydrogen and oxygen ions. This provides a suitable environment for ions transporting through ceramic materials. Under such operation temperatures, degradation may occur in the electrodes and electrolyte. As a result, unstable voltage, low capacity and cell failure may eventually occur. This study presents thermomechanical analysis of a porous SOFC cell plate which contains electrodes, electrolytes and pores. A microscale specimen in the shape of a plate is considered in order to maintain uniform temperature loading and increase the accuracy of estimation. A new computational technique, peridynamics, is utilized to calculate the deformations and stresses of the cell plate. Moreover, the crack formation and propagation are also obtained by using peridynamics. According to the numerical results, damage evolution depends on the electrolyte/electrode interface strength during the charging process. For weak interface strength case, damage emerges at the electrode/electrolyte interface. On the other hand, for stronger interface cases, damage emerges on pore boundaries especially with sharp corner

An assessment approach for non-governmental organizations in humanitarian relief logistics and an application in Turkey

The ever-increasing natural disasters have been causing the loss of lives, properties and resources. By the preparedness and response ability of non-governmental organizations, it is aimed to minimize these losses. In this paper, first, the critical success factors of humanitarian relief logistics management operations are determined and categorized. Then, by considering these factors, a hybrid method that consists of trapezoidal interval type-2 fuzzy sets, AHP and TOPSIS, is proposed to evaluate emergency preparedness and response ability performance of non-governmental relief organizations. The proposed hybrid method is applied for non-governmental relief organizations in Turkey to evaluate their performance, and to the factors need to be improved for each determined organization. First published online 11 September 2015

Usporedba performansi modela ARIMAX, ANN i hibridizacije ARIMAX-ANN u predviđanju prodaje za industriju namještaja

Manufacturing firms aim to increase their profits and reduce costs in a competitive and rapidly changing market. One of the most important ways to reach these goals is to forecast sales correctly. Furniture manufacturing, which is considered a prosperous and growing industry in Turkey, has an increasing trend related to the growth in construction and associated industries, increase in urban migration and increase in per capita income. Accuracy of sales forecasting in furniture industry is affected by external factors, such as consumer confidence index, producer price index, month of the year and number of vacation days as well as the time factor itself. This study aims to develop an Autoregressive Integrated Moving Average with external variables (ARIMAX) to forecast the total monthly sales of furniture products of a well-known manufacturer in Turkey. As a follow up study, a performance comparison between ARIMAX, artificial neural networks (ANNs) and ARIMAX-ANN hybridization is performed. In conclusion, results of performance measures demonstrate that hybrid model developed for each amount of product sales give better accuracy values than single methods. Overall, it is proved that using the ARIMAX and hybridization of this method with ANN are applicable for forecasting monthly sales of furniture products

Determining the instantaneous bruising pattern in a sample potato tuber subjected to pendulum bob impact through finite element analysis

Potato bruising resulting from mechanical impact during production operations including harvest and postharvest is a significant concern within the potato production sector, leading to consumer complaints and economic losses. The detection of instantaneous internal bruising poses a particular challenge as it can progress over time during storage or transportation, making it difficult to identify immediately after external impact. This study aims to investigate the progression of bruising and accurately represent the instantaneous dynamic deformation behavior of potato tubers under four pendulum bob impact cases (pendulum arm angles of 30°, 45°, 60°, and 90°). To analyze the dynamic impact deformation characteristics of the tubers, solid modeling based on a reverse engineering approach and explicit dynamic engineering simulations were employed. The simulation results yielded valuable numerical data and visual representation of the deformation progression. The loading conditions considered in this study indicated that the maximum stress values, reaching 0.818 MPa at a pendulum arm angle of 90°, remained below the bio-yield stress point of the tuber flesh (1.05 MPa) determined through experimental compression tests. Therefore, it was concluded that the impact did not cause permanent deformation (i.e., permanent bruising) in the tuber. However, the numerical analysis clearly demonstrated the sequence of stress occurrences, which is a key contributing factor to potential permanent bruising. In this regard, the bruising energy threshold of 318.314 mJ (R2: 0.96) was extrapolated. The numerical findings presented in this study can aid in evaluating the susceptibility of tuber samples to bruising. By employing nonlinear explicit dynamics simulations, this research contributes to the advancement of understanding complex deformation and bruising in solid agricultural products. Moreover, the application of these techniques holds significant industrial implications for enhancing the handling and transportation of agricultural produce. Practical applications: This research aims to tackle the challenge of accurately representing the immediate internal bruising pattern in potato tubers resulting from mechanical impact. Conventional methods, such as physical or analytical expressions, may not fully capture the distribution of bruising experienced by the tubers. To overcome this limitation, an engineering simulation approach is proposed to provide a more precise depiction of the instantaneous bruising pattern. By advancing the understanding of complex deformation and bruising in solid agricultural products, this research contributes to improving the efficiency and quality of agricultural production in the industry. Additionally, this study offers a step-by-step guide on how to conduct these simulations effectively

Assessment of human error contribution to container loss risk under fault tree analysis and interval type-2 fuzzy logic-based SLIM approach

Human is a key element of the safety of life on board ships and a significant contributing factor to most of the accidents and incidents in the maritime industry. At this point, risk analysis plays a critical role in ensuring operational safety and maritime transportation sustainability. This paper aims to systematically evaluate how human errors (HEs) contribute to operational risks. Based on this, Fault Tree Analysis (FTA) is combined under an Interval Type-2 Fuzzy Logic environment with Success Likelihood Index Method (SLIM). Whilst the FTA evaluates the criticality of the operational activities, the Interval Type-2 Fuzzy Sets (IT2FS) deals with vagueness and subjectivity in using experts’ judgments, and the SLIM estimates the probabilities for the human error-related basic events. Since container losses can lead to severe damage and catastrophic events in a container terminal, loading operation was investigated as a case study. Safety culture, experience, and fatigue were observed as highly effective factors in crew performance. The obtained results also indicate that this hybrid approach can effectively be applied to determine the operational vulnerabilities in high-risk industries. The paper intends to improve safety control levels and lower losses in the future of maritime container transport besides emphasizing the potential consequences of failures and crucial human errors in the operational process

Echocardiographic evaluation of diastolic functions in patients with polycystic ovary syndrome: A comperative study of diastolic functions in sub-phenotypes of polycystic ovary syndrome

Background: Polycystic ovary syndrome (PCOS) is a heterogeneous endocrine disorder among reproductive-aged women. It is known to be associated with cardiovascular diseases. The aim of this study was to determine and compare the echocardiographic data of patients according to the phenotypes of PCOS. Methods: This study included 113 patients with PCOS and 52 controls. Patients were classified into four potential PCOS phenotypes. Laboratory analyses and echocardiographic measurements were performed. Left ventricular mass was calculated by using Devereux formula and was indexed to body surface area. Results: Phenotype-1 PCOS patients had significantly higher homeostasis model assessment — insu­lin resistance (HOMA-IR) (p = 0.023), free testosterone (p < 0.001), LDL cholesterol levels (p < 0.001) and free androgen index (p < 0.001) compared with the control group. There were significant differences between groups regarding the septal thickness, posterior wall thickness, Left ventricular ejection frac­tion, E/A ratio and left ventricular mass index (for all, p < 0.05). PCOS patients with phenotype 1 and 2 had significantly higher left ventricular mass index than the control group (p < 0.001). In univariate and multivariate analyses, PCOS phenotype, modified Ferriman-Gallwey Score and estradiol were found as variables, which independently could affect the left ventricular mass index. Conclusions: This study showed that women in their twenties who specifically fulfilled criteria for PCOS phenotype-1 according to the Rotterdam criteria, had higher left ventricular mass index and decreased E/A ratio, which might be suggestive of early stage diastolic dysfunction. (Cariol J 2017; 24, 4: 364–373

Atherosclerosis burden and coronary artery lesion complexity in acute coronary syndrome patients

Background: Syntax score (SS) is a prognostic marker in patients with acute coronary sydromes (ACS). Carotid intima media thickness (CIMT) and cardio ankle vascular index (CAVI) are well known surrogate marker of atherosclerosis burden. But association between atherosclerosis burden and coronary artery disease (CAD) complexity in ACS patients has not been investigated yet. Methods and Results: Consecutive patients with first time diagnosis of ACS (n = 172) were enrolled. SS, a marker of CAD complexity, was assessed by dedicated computer software. CIMT was examined by B-mode ultrasound. CAVI was assessed by VaSera VS-1000 cavi instrument. SS for low, intermediate and high tertiles of CIMT value were 10.1 ± 8.2 vs 11.4 ± ± 7.9 and 15.2 ± 8.8; p = 0.02). SS for normal, borderline and abnormal CAVI values were 4 ± 3.7 vs 11.1 ± 7.2 and 14.1 ± 9.1, respectively p = 0.009). Also, there was independent association between SS and CIMT (95% coinfidence interval [CI] 2.1–19, p = 0.014) and CAVI (95% CI 15–29, p = 0.021]. Neither traditional cardiovascular risk factor nor thrombolysis in myocardial infarction (TIMI) risk score was independent determinant of SS. Conclusions: We have shown that patients with higher atherosclerosis burden have more complex coronary artery lesions. Also these patients may be identified early by using surrogate markers of atherosclerosis. Its clinical significance requires further research