Nonlinear models of the flow control valves relate the control flows through the valve ports to the valve parameters. An integrated model covers thoroughly the critical-lapped, over-lapped and under-lapped valves. The non-equality of spool lands and incorrect null position of spools can also be simulated using this model. Moreover, the Simplified model can be used base on some assumptions for ease of analysis. In this paper, an accuracy analysis is performed to compare a fully nonlinear valve model to the conventional Simplified one. According to the second order linear model of a servohydraulic system, a non-dimensional analysis for the fully nonlinear model shows that the accuracy of the model is independent of the specific categories of its parameters. In fact, the model error for a certain amount of hydraulic damping coefficient does not depend on the model parameters, such that a combination of these parameters leads to a constant damping coefficient. Therefore, the accuracy of the model can already be determined using simulation. This point provides a high flexibility to the hydraulic control system designer to put up the possibility of using Simplified models without any need to determine the model errors. Because the hydraulic systems are barely driven beyond the scope of the desired frequency, it can be concluded that for some applications, the Simplified model of the valves can accurately express the valve dynamic.

Optimization of engine mounts has been investigated in several studies in which different models, a model of a single engine mount to an intricate full vehicle model, have been used for the optimization. In this paper two Simplified vehicle models and a simple full vehicle model are used in the optimization of the Hyadraulic Engine Mounts (HEMs) to determine whether optimization through the Simplified models can result in appropriate HEMs or the simple full vehicle model or even more intricate models has to be used in the optimization process. Hydraulic Engine Mounts (HEMs) are optimized through a global optimization method called Direceted Tabu Search (DTS) method in order that the best ride comfort is achieved for the vehicle system.

Numerical analysis of fluid sloshing in tank wagons is one of the updated matters focused by railway engineers. The free surface of fluid becomes unstable and turns into a dynamic complex non-linear problem for fluid-structure interaction (FSI). In this paper, first, the dynamic response of the tank, including lateral force analysis and pressure distribution during braking, is obtained using an explicit dynamic finite element model based on the Multi Material Arbitrary Lagrangian Eulerian method (MM-ALE); then, the Simplified model is developed for sloshing during turning.Numerical finite element model is validated using a test setup. Comparing these models during turning with parametric studies for tank filling, it is observed that frequency and sloshing amplitude, when filling is less than 25%, have less than 10% of difference; therefore, the Simplified model in the above conditions can be used with an acceptable accuracy because of a remarkable reduction in the time and cost of numerical calculations.

Automatic topic detection seems unavoidable in social media analysis due to big text data which their users generate. Clustering-based methods are one of the most important and up-to-date categories in topic detection. The goal of this research is to have a wide study on this category. Therefore, this paper aims to study the main components of clustering-based-topic-detection, which are embedding methods, distance metrics, and clustering algorithms. Transfer learning and consequently pretrained language models and word embeddings have been considered in recent years. Regarding the importance of embedding methods, the efficiency of five new embedding methods, from earlier to recent ones, are compared in this paper. To conduct our study, two commonly used distance metrics, in addition to five important clustering algorithms in the field of topic detection, are implemented by the authors. As COVID-19 has turned into a hot trending topic on social networks in recent years, a dataset including one-month tweets collected with COVID-19-related hashtags is used for this study. More than 7500 experiments are performed to determine tunable parameters. Then all combinations of embedding methods, distance metrics and clustering algorithms (50 combinations) are evaluated using Silhouette metric. Results show that T5 strongly outperforms other embedding methods, cosine distance is weakly better than other distance metrics, and DBSCAN is superior to other clustering algorithms.

Evaluating the cutting rate (CR) of stones is important in the cost estimation and the planning of the stone processing plants. This research used regression models to estimate the stones’ CR based on their physico-mechanical characteristics. Stone processing factories in Mahallat City (Markazi province, Iran) were visited, and the CR of diamond circular saws was recorded on six different travertine stones. Next, the stone block samples were collected from the quarries for laboratory tests. Stones’ porosity (n), uniaxial compressive strength (UCS), and Schmidt hammer hardness (SH) were determined in the laboratory as their physico-mechanical characteristics. Correlation relationships of CR with physico-mechanical characteristics were evaluated using simple and multiple regression analyses, and estimator models were developed. Results showed that multiple regression models are more reliable than simple regression for estimating the stones’ CR. The validity of the developed multiple regression models was verified with the published data of one researcher. The findings indicated that these models are accurate enough for estimating the CR of stones. Consequently, the multiple regression models provide practical advantages for estimating the CR and save time and cost during the planning and design of the stone processing factories.

Background & Aims: Different scoring systems are used in order to assess the functional quality of intensive care units (ICU) and to predict the required costs and facilities of intensive cares. Variety of scoring systems has been explained that each has advantages and disadvantages. In this study Simplified Acute Physiology Score-III (SAPS-III) and Mortality Probability Model-III (MPM-III) were compared. Materials & Methods: The current cross-sectional study was conducted on 240 non-traumatic patients admitted at ICU of Al-Zahra Hospital in 2016-17. Patients' information including demographics, mean of systolic, diastolic and arterial pressure, pulse rate, respiratory rate, temperature, Glasgow Coma Scale(GCS), WBC, hematocrit, bilirubin, creatinine, arterial blood gas, and the presence of underlying diseases was gathered from the records for measurement of MPM-III and SAPS-III scores and then they were compared. Results: This study was conducted on 240 non-traumatic patients. Discrimination of MPM-III in cutoff point of 0. 17 was 0. 83(P<0. 001; 95%CI: 0. 765-0. 898), sensitivity and specificity of this test in prediction of non-traumatic mortality was 82% and 73%, respectively. Discrimination of SAPS-III in cut-off of 48. 5 was 0. 78(P<0. 001; 95%CI: 0. 72-0. 84), while its sensitivity and specificity was 83% and 70%, respectively. Duration of ICU hospitalization (P=0. 028 and 0. 002) and duration of intubation (P=0. 001 and <0. 001) had direct association with mortality based on both scoring systems while total duration of hospitalization was only significant in SAPSIII (P=0. 002). Conclusion: Comparison of SAPS-III and MPM-III in non-traumatic patients presented a higher discrimination ability for MPM-III. In addition, findings showed that mortality in MPM-III was in association with duration of ICU admission and intubation while for SAPS-III, in addition to previous factors, total duration of hospitalization was associated as well.