The buildings structures around the world suffer from terrorist attacks and bombings. This justifies the need to study the effect of blast loading on structures and the methods to prevent collapse of structures in order to save human lives and minimize financial losses. In this study, effects of the passive viscous dampers and BASE ISOLATORs on structures which are subjected to blast loading are separately investigated. Blast load is applied on the structures with a pressure wave. This pressure wave has many uncertainties specified in different codes. For the sake of simplicity, this pressure wave is applied on different faces of the structure. Herein, only loading on the fa\c{c}ade or the structure is considered and the loading on the other faces of the structure are neglected as the structure doesn't have any severe irregularities. In the 1st case, viscous dampers are added to the structure adding damping of the structure between 5 to 25\% and the effect of this added damping is studied through the paper. For the 2nd case, BASE ISOLATORs are designed according to UBC-1997 code. Numerical simulations are carried out in the SAP environment using nonlinear time-history analysis. Moreover, they are studied with different stiffness coefficients and the uncertainties in yielding force of these tools have been considered in numerical simulations. These passive control devices are mainly designed such that they can perform well under earthquake loads. Viscous dampers conform to the first mode of vibration of the structure and BASE ISOLATORs are designed according to seismic codes. Numerical simulations show that BASE shear in the optimum specifications of viscous dampers and BASE ISOLATORs compared to bare frame showed 60\% increase and 50\% decrease, respectively. However, drifts are minimized to 1. 7\% for added damping values of 25\%. This value is hard to reach with BASE ISOLATORs as the values of drifts in this case have a minimum value of 2\%.

Today, BASE isolation of buildings is a conventional approach to earthquake resistance. The prominent goal is to reduce displacement of structure by movement of elastomeric bearings installed on the BASE of structures on the ground. Considering widespread construction of asymmetric buildings well as the intensity of damages to such types of structures resulting from earthquake, the present research covers study of interaction mechanics of asymmetric BASE-isolated structures, where motion equations are presented in two coordinates, one fixed on the building BASE (global coordinate) and the other on the torsional isolation level (local coordinate). In this conventional approach, the motion equations are calculated on linear form in the initial coordinate system, whereas in the new approach proposed in this research, motion mechanics analysis in the secondary coordinate system will lead to non-linear equations. Three types of structures are proposed with ratio of torsional-lateral correlated natural frequency on asymmetric natural frequency. Responses of both linear and nonlinear methods for the three types of structures under harmonic effects and earthquake are compared while analyzing time history and frequency. Some differences are observed between the linear and nonlinear methods. Then, some non-linear phenomena such as saturation, energy transfer between modes, and rigid displacement in such structures are also analyzed.

Background: The application of ventilation systems in industries and workplaces is with the aim of improving environmental conditions for employees. The lack of appropriate ventilation system components design and control methods result in the production of sound and vibration in most components. The purpose of this study was to determine the role of the pad ISOLATOR in controlling vibration and reducing noise in ventilation systems.Methods: This analytical study was performed on the heating, ventilation and air-conditioning (HVAC) system that had a galvanized duct and axial fan. Vibration measurements were carried out on the body of the channel and the fan BASE and reduction of the amount of transmitted vibrations was assessed after installation and application of the ISOLATOR.Findings: A 61% reduction in fan vibration velocity at 2580 rpm was observed and maximum effect of the vibration ISOLATOR was observed in 2580 rpm. Moreover, the ISOLATOR had a much greater effect on reducing the rate of vibration at high speeds. At a speed of 2200 rpm and below, vibration velocity was decreased noticeably.Conclusion: Our study indicates that the performance of the rubber ISOLATOR is efficient in small machines such as fans in air conditioning systems. BASEd on the load, static deflection, and compression level of the materials used, ISOLATORs can be used as an effective means of reducing vibration.

Esthetic is a natural necessity among all human beings, and the reconstruction of the natural features of prosthesis is considered an important aspect in dentistry. Reconstruction of the natural features in removable prosthesis by characterization of denture BASE is one of the most important factors. In this regard esthetic, in removable prostheses, is achieved through different techniques such as: tooth selection and arrangement, designing the denture BASE and acrylic BASE color. The final goal for all these effects is to achieve a natural appearance for denture. However, other factors such as treatment limitations, different personal needs and general health principles, should be taken into consideration. This article not only reviews the natural appearance of oral mucosa that is replaced by the denture BASE, but also discusses about the materials used in tinting acrylic denture BASE and their application techniques.

This paper presents a new elastomeric sliding seismic ISOLATOR system. This ISOLATOR is made of a rubber core which is confined by sliding steel rings. In this system, the vertical load is applied directly on the rubber core. The friction mechanism existing in the mentioned system controls the lateral force due to winds, ambient vibrations and mild earthquakes, and also decreases transfer of lateral force to the superstructure during severe earthquakes. At the end of vibraion, the elasticity of rubber creates a restoring force and decreases residual deformation of the bearing device. Features of the proposed system are assessed by means of the finite element software ANSYS and the stress distribution of various components is obtained under compression and compression-shear loading. Contact elements were used to model the contact surfaces, and Solid185 elements were used to simulate the rubber. The studies show that an appropriate vertical and lateral stiffness is created by interaction of the steel rings and the elastomeric core. In addition, under vertical loading, all the stress components are far less than the allowable limit. Due to lateral movement, a part of the vertical load is transferred to the steel rings which not only de-escalates the stress at the rubber core, but also increases damping due to friction in the system. Steel rings effectively enhance the vertical stiffness of the system by controlling the lateral strains experienced by the rubber material. In the specific sample being examined, a vertical load of 100 kN leads to a vertical stiffness value of 131 kN/mm in the system. Under a vertical load of 100 kN, the stress values sx (along lateral displacement), sz, and sy in the rubber core, subjected to a 200% shear strain, were reduced by 25%, 50%, and 51%, respectively, compared to the scenario without lateral displacement.