Showing 5 results for Ghanad
Volume 1, Issue 1 (Spring 2021)
Abstract
PPrior to approving the Islamic Penal Code Act 2013, the concept of repentance was accepted to some extent in the context of provisions related to Hudud (fixed religious penalties). In the latest efforts to revise the Islamic Penal Code, the lawmakers dedicated some articles to repentance which stipulated specific rules on the framework and other detailed provisions on applying this concept. This initiative of the legislators can be challenged on the one hand through the criminological analysis of the subject, and on the other hand, in the context of its implementation within the framework of the Code of Criminal Procedure. Due to its ignorance of modern criminological theories, particularly on victimology, the deviation of attention from offender’s personality to the criminal act, and the impossibility of realization of all repentance conditions, it appears that approving legislative provisions on repentance in the Islamic Penal Code will result in a serious crisis. Therefore, in order to reach an effective criminal policy, it is necessary that all aspects of the concept be duly scrutinized. Taking into account the substantive and procedural limits surrounding this topic, the gap between the bases of repentance in the Islamic Penal Code with the recent developments in criminal policy and also the absence of practical approaches to materialize this concept, it seems that its implementation will face challenges, thereby making the criminal policy far away from being effective.
Volume 13, Issue 50 (5-2016)
Abstract
Volume 17, Issue 10 (1-2018)
Abstract
Due to unique properties, lattice composite structure are used extensively in aviation, marine and automotive industry. In this research, experimental and numerical investigation of the free vibration of composite sandwich plates with triangular grid has been studied. For the fabrication of this plates, silicone mold, filament winding, and hand lay-up method were used. Stiffened plates and simple plates are fabricated, separately. Then, composite sandwich plates with triangular grid were created by attaching the two parts together. The modal test is done on the plates and natural frequencies have been extracted.The comparison of numerical and experimental results showed that there is a good agreement between them. By using Taguchi method, a parametric study was performed on the vibrational behavior of sandwich plates with triangular cores via three parameters that such as stiffeners’ number, stiffener thickness and skin thickness. The results show that the natural frequency of sandwich plates with triangular grid has a most sensitive to the stiffener thickness, and least sensitive to stiffeners’ number. The sensitivity of natural frequency is almost identical to stiffener thickness and skin thickness.To evaluate the efficiency of sandwich plates with triangular grid, the natural frequency of sandwich plates are compared with simple plates in the different boundary condition. The results show that the natural frequency of sandwich plates with the triangular grid is 133% and 138% higher than an equivalent simple shell at free and clamp boundary condition, respectively.
Volume 21, Issue 6 (12-2021)
Abstract
In stochastic subspace methods, the most important factor influencing the dynamic specifications is the dimensions of the Hankel matrix include the number of rows and columns. Using small matrix dimensions is unlikely to identify existing poles, and selecting very large dimensions not only increases the likelihood of virtual and bias poles but also increases computational costs. In this study, it is intended that the optimal dimensions of the Hankel matrix in the balanced stochastic subspace method be calculated in such a way that in addition to covering the existing poles, it also has a minimum computational cost. For this purpose, the condition number of the Hankel Matrix and Energy Indicator is used in two steps. The steps are as follows: First, calculate the optimal order of each cycle, and then use the optimal order to draw the condition number of the system matrix for different dimensions and calculate the desired dimension from its convergence. To verify the accuracy of the proposed method, the ambient vibration test of the Namin Entrance Bridge has been used. This bridge is located at the entrance of Namin city, 25 km from the center of Ardabil province, Iran, which includes two spans of 27.10m with a concrete deck. The deck of the bridge is located on beams with I sections, which are 2.5m away from each other, and the whole set of beams and deck is located on a system of foundations and piles with a diameter of 120cm. This bridge being the only entrance to the city and is exposed to various traffic loads, it was necessary to monitor the dynamic characteristics of the bridge as modal frequencies and damping ratios to evaluate the performance and ensure the health of the bridge structure. According to the numerical analysis and the length of the data (12000), the minimum order and the maximum number of cycles are 22 and 55, respectively. By diverging the curvature of the energy indicator graph, the optimal order is determined in the initial 5-12% of the singular values of cycles. For example, the maximum order of the 6th cycles was obtained, 28-62. Also, from the convergence of the maximum condition number of cycles from the 8th cycle, the optimal dimension was selected 352. In a general summary, it can be said that the use of the energy indicator concept in finding the effective order of the stability diagram has a significant effect on reducing the uncertainty of the extracted results. So that from the three identified stable poles, two poles have been extracted in the effective-order area. Also, using the concept of conditional number to find the optimal dimension of the system was effective, so that by drawing a stability diagram for the 15th cycle, it was found that the identified modal characteristics were not significantly different from the results of the optimal cycle (8th). Finally, the extracted modal properties have an acceptable agreement with the numerical model and frequency domain decomposition method (FDD). The modal frequencies of both methods (FDDand B-SSI) have a good correlation but the damping ratios were very different. In frequency domain methods the damping ratios being very sensitive to the quality of data collection, one can expect that the results of the subspace method are closer to reality.
Volume 23, Issue 5 (11-2023)
Abstract
Infrastructures such as bridges, buildings, pipelines, marine structures, etc., play an important role in human life. Since major disasters in these structures, such as the collapse of bridges or buildings, often result in many casualties, damages, and social and economic problems, most industrialized countries allocate significant funds to monitor their health. Failure detection strategies and continuous monitoring of the structure's condition, especially after natural and manufactured disasters, make necessary measures to be taken in the early stages of failure and can reduce the cost of maintenance and the possibility of collapse. Structural health monitoring methods often provide an opportunity to reduce maintenance, repair, and retrofit costs during the structure's life cycle. Most of the structural health monitoring methods proposed and implemented to identify possible damages depend on the structure's dynamic characteristics. One of the most practical methods, which uses the results of time domain system identification to detect failure, is the damage locating vector (DLV) method. The DLV method aims to identify load combinations that result in zero strain fields for damaged members in both healthy and damaged structures. To accomplish this, we find a vector in the null space of the difference between the plasticity matrices of the two structures. The singular value analysis method is used on the plasticity difference matrix to calculate this space. The method involves applying the space vectors to the healthy structure and recording the internal stresses of the members, which are then converted into weighted normal stress (WSI) using statistical tools. The member with a lower WSI is more likely to be damaged. Since truss structures are usually used in bridges, long-span structures, as well, as a wide range of steel buildings with simple and braced frames, this research uses the covariance-based random subspace optimal method in identifying the modal characteristics, which is very efficient in low excitations, has been taken into consideration to check and monitor health during operation. To investigate the capability of the DLV method in the damage detection of these structures, a 5-story residential building with a simple steel frame was subjected to the Centro earthquake. According to the desired damage scenario, the second and fifth floors were introduced as the damaged floors in this earthquake by applying a 30 and 50% reduction in the cross-section. To account for uncertainty in the data collection, we included the mean root square of the second sensor's data in the results for sensors 3 and 5. As a result of this uncertainty, the damping error between 5 and 10% has been shown in the damaged and healthy structure. Using the method (SSI_ORT), it was observed that two DLV vectors were extracted. Further, with the increasing uncertainty of the random vibration test results, it was observed that the extraction DLVs could extract the possible damaged elements with high accuracy. Next, the effect of input and output noises on the results obtained from the DLV method was investigated. This study found that by increasing the SNR of the outputs by 15% while increasing the error of the extracted modal characteristics, the extracted DlVs also lose sufficient accuracy in diagnosing structural damage.
