In this paper, an alternative approach in operational MODAL analysis is presented, utilizing image processing technique and transmissibility functions. Imaging sensors do not impose additional mass on the structure due to their non-contact nature, while transmissibility functions, independent of excitation type, can directly extract mode shapes. The innovation of this research lies in combining these two techniques to record dynamic responses and identify MODAL PROPERTIES. To capture the temporal response history from video signals, the block-matching method with sub-pixel accuracy was employed. Validation was conducted by recording the response of the tip of a cantilevered steel beam subjected to impact excitation, using a high-speed camera and a laser vibrometer, simultaneously. The RMSE plots in the time domain and the PSD in the frequency domain indicate high accuracy of this method. Using this approach, the displacement time histories of various points on the structure were extracted from the video signals, and the MODAL PROPERTIES, including natural frequencies, damping ratios, and mode shapes, were identified using the transmissibility matrix method. The results obtained from the proposed method were compared with the stochastic subspace identification (SSI) method and analytical solutions. The findings reveal the accuracy of the MODAL identification approach introduced in this article. The highest relative error in estimating the natural frequencies of the first and second modes, compared to the values from the laser method, are 0.19% and 0.13%, respectively, and in comparison to the analytical values, they are 0.34% and 1.5%, respectively.

In performing vibration analysis of the car engine on the engine support, it is necessary to know the mass PROPERTIES of the engine including mass, position of the center of mass and mass inertia moments. Because the car engine has a relatively complex geometric shape and is composed of different components with different densities, determining its mass PROPERTIES faces many challenges. There are various methods to determine the mass PROPERTIES of a car engine, one of the most common of which is the use of MODAL analysis (mass line method). In this paper, the mass line method is presented in order to finding the mass PROPERTIES of rigid bodies. In order to evaluate the efficiency and accuracy of the method, dynamic modeling of a rigid body with known mass PROPERTIES is performed in MSC Adams software. So according to the theory of mass line, the rigid body is hung from a soft suspension and a force is applied to it in different locations. Then, by performing Adams simulations, the corresponding acceleration values are extracted at various points. After that, the mass line method is coded in MATLAB software and the applied forces and accelerations obtained from Adams in the time domain are entered as input to the MATLAB code and by executing the MATLAB code, the mass PROPERTIES of the rigid body are calculated. Finally, the values of the mass characteristics obtained from the MATLAB code are compared with the actual values of the rigid body simulated in Adams, and the accuracy of the mass line method in finding the mass PROPERTIES is evaluated.

During MODAL testing, the test structure is connected to its surroundings by a suspension system. Cable suspension system is one of the most common suspension systems which is used to simulate the free-free condition, due to its low stiffness. In this condition, the measured MODAL PROPERTIES are assumed to be free-free dynamic PROPERTIES of the test structure. But in situations in which the test structure is big and flexible, the stiffness of the suspension system is comparable with the stiffness of the test structure and cannot be neglected. In this paper, the suspension effects are eliminated from measured MODAL frequencies of a flexible structure which is suspended by a cable suspension system. The eigenvalue sensitivity analysis is done and then, the effective stiffness of the cable suspension system is derived. Based on the eigenvalue sensitivity and the effective stiffness of the suspension system, an iterative procedure is proposed to eliminate the suspension effects from measured MODAL frequencies of the test structure. The proposed iterative procedure is verified using a finite element model. Finally, the proposed iterative procedure is used to eliminate the suspension effects from measured MODAL frequencies of a real flexible structure.

Interest in the ability to monitor a structure and detect damage at the earliest possible stage is pervasive throughout civil, mechanical, and aerospace engineering communities. Research in vibration-based damage identification has been rapidly expanding over the past few years. The basic idea behind this technology is that MODAL parameters (frequencies and mode shapes) are functions of the physical PROPERTIES (mass and stiffness) of the structure. Therefore, changes in the physical PROPERTIES will cause detectable changes in MODAL PROPERTIES.The purpose of this research is to review some existing method and define a new method to predict location and severity of damage in structures using changes in MODAL characteristics. This new method is a combination of existing methods. Based on this method, a computer software is developed that can perform the damage detection process.

There is a famous idea in MODAL epistemology according to which conceivability of a proposition is a good guide for its possibility. Yablo (1993) persents a model for justification of MODAL beliefs, based on which Conceivability of a proposition is evidence for its possibility. Van Inwagen (1998) believes that if we accept Yablo’s model, we have to accept MODAL skepticism. To argue for this, Van Inwagen examines the MODAL status of the proposition that transparent iron exists on Yablo’s model. Van Inwagen claims that this proposition is undecidable on Yablo’s model. So we cannot have a justified belief that it is possible that transparent iron exists. If van Inwagen’s claim about the MODAL status of the proposition that transparent iron exists is correct, Yablo’s model, one might think, faces a serious problem. For if we generalize van Inwagen’s analysis of the proposition that transparent iron exists, we have to count intuitively possible propositions, propositions the MODAL status of which can be intuitively known as possible, as undecidable. But it is quite plausible that our beliefs about the possibility of some intuitively possible propositions are justified, so these propositions are not undecidable. I will, however, argue that van Inwagen’s analysis of MODAL status of the proposition that transparent iron exists cannot be generalized to all (or most) intuitively possible propositions. And therefore it is possible to accept at the same time both Yablo’s justification model and van Inwagen’s analysis about the MODAL status of propositions like transparent iron exist.

Sluggish Cognitive Tempo is used to describe a particular type of attention deficit, concentration, and slowness in information processing. The aim of this study was to investigate the psychometric PROPERTIES of the Sluggish Cognitive Tempo Scale (SCTS) of the parent form among Iranian children. The present study is a descriptive study. A sample of 1700 people was selected from the provinces of Tehran, East Azerbaijan, West Azerbaijan, Kurdistan, Fars and Khorasan using cluster sampling method. 122 subjects were excluded from statistical analysis due to incomplete answers to the questionnaires and thus the final sample was reduced to 1578 parents. The confirmatory factor analysis method and internal consistency were used to compute the Sluggish Cognitive Tempo Scale factorial validity and reliability, respectively. Also, in order to examine the construct validity of the Sluggish Cognitive Tempo Scale, we computed correlations between different dimensions of Sluggish Cognitive Tempo Scale with Attention Deficit Subscale of Mental Health Assessment Questionnaire for Children and Adolescents. The results of statistical results showed that this scale has structural validity, criterion and convergence in Iranian society. The results indicate that the scale is three factors and also the validity of the scale using Cronbach's alpha method and retest test after Approved two weeks. According to the findings of the present study, the parent form of the Sluggish Cognitive Tempo Scale (SCTS) has a good validity and reliability and it can be used in research related to slow cognitive multiplication in Iranian society.

This paper investigates the accuracy and convergence rate of different metaheuristic algorithms in determining the stiffness of structural elements using structural MODAL parameters and defining a suitable objective function. To achieve this purpose, three different structures, including a three-story one-dimensional frame, a six-story one-dimensional frame and a two-dimensional truss, were investigated. The metaheuristic algorithms, employed in this study, were Genetic Algorithm, Particle Swarm Optimization, and Teaching–learning-based Optimization. The objective function utilized in this study consists of two terms; the first part involves the squared difference between the first frequency of the structure obtained from the responses of the investigated structure and the first frequency obtained from the hypothetical stiffness matrix in each generation of algorithms. The second part measures the norm of the difference between the first mode shape of the structure obtained from the responses of the investigated structure and the first mode shape obtained from the hypothetical stiffness matrix in each generation of algorithms. By minimizing the objective function, the Genetic Algorithm, Particle Swarm Optimization, and Teaching–learning-based Optimization determined the element stiffness of the three-story, six-story and truss structures, thus demonstrating the high efficiency of metaheuristic algorithms in resolving unknown parameters of structures. The average run time for the Genetic Algorithm was 3.38 seconds, 4.47 seconds, and 15.73 seconds for the three respective problems. For Particle Swarm Optimization, the times were 3.76 seconds, 6.47 seconds, and 16.76 seconds. The Teaching–learning-based Optimization achieved times of 1.92 seconds, 4.51 seconds, and 12.76 seconds. The Teaching–learning-based Optimization exhibited the highest convergence rate and the lowest error compared to the Genetic Algorithm and Particle Swarm Optimization. For example, in the two-dimensional truss, the values of the objective function in the last iteration of the Genetic Algorithm, Particle Swarm Optimization, and Teaching–learning-based Optimization were , and , respectively. The Particle Swarm Optimization demonstrated an acceptable convergence rate and error compared to the Genetic algorithm. The Genetic Algorithm, however, displayed a significant error rate in determining the stiffness of structural elements compared to the other two algorithms.

One of the factors that can be the link between our intentions and actions and their external consequences is human agency, which indicates the conscious design and intentional execution of actions by the individual in order to influence future events.Objective and Method: This research with a developmental approach of psychometric method and method 1, examines the psychometric indices of the Human Factor Characteristics Scale using the classical theory of test score measurement and the graduated question-answer theory. The purpose of this study, which included high school students in Tehran, was selected by cluster sampling of 500 people as a sample size and statistical analysis was performed on 481 data. To collect the data, the ion Human Agent Characteristics Scale (2011) was used and the research questions were evaluated using IRTPRO and SPSS software.Results:The assumption of local independence based on Pearson x2 index was established by applying Simjima's calibrated question-answer theory and the assumption of being one-dimensional based on the analysis of multidimensional question-answer theory. Diagnosis parameters with question-answer approach and classical approach Test score Both item 25 approach had the lowest and item 2 had the highest diagnosis parameter. The answer thresholds for all the questions were so far apart that no option was covered by the other option, and the options were independently selected by individuals at intervals of theta. The total scale was calculated with Cronbach's alpha of 0.945, intentionality of 0.894, foresight of 0.780, self-reactivity of 0.871 and rethinking of 0.762. Also, the role of each item in internal consistency was investigated by the loop method, which all questions had a favorable role in internal consistency of this scale. The value of the validity coefficient obtained from the question-answer theory was obtained by marginal method for intentionality 0.92, forethought 0.85, self-reaction 0.91, rethinking 0.83..

This paper is concerned with the finite element analysis and MODAL testing of an industrial radial flow impeller. The goal is to determine and verify the vibration characteristics of the impeller using both experimental and analytical techniques.The finite element model of the impeller with tapered blades was built using a 3D solid element. The convergence PROPERTIES of the FE model was then verified by mesh refinement and mass distribution methods. Next, a pre-test plan was performed before conducting a MODAL test in order to select the proper suspension points, driving point(s) and response points on the  impeller.Impact testing using hammer excitation and laser Doppler vibrometer (LDV) response measuring techniques were used to measure the vibration PROPERTIES of the impeller. Using a scanning laser Doppler vibrometer enabled the backplate modes to be described in terms of their nodal diameter components. The nodal diameters versus natural frequencies graph was then compared with the same results obtained from FE and hammer testing and showed good agreement. Finally, a parametric study was conducted on disc thickness, blade thickness, blade trailing, leading edge profiles and blade mistuning. It was found that the effect of varying disc thickness on the lower modes of the impeller was not significant. However, significant natural frequency shifts were observed for the higher modes. It was also concluded that varying the blade leading edge position had a marked effect on the natural frequencies while the lower modes were somehow insensitive to the variation of trailing edge position.