Showing 5 results for haghgoo
Volume 6, Issue 3 (Summer 2021)
Abstract
Aims: MusculoSkeletal Disorders (MSDs) are one of the most common problems of students which if not prevented and treated can lead to physical and psychosocial disorders.The aim of this study was to compare MSDs in two groups of students with special needs who suffering from low vision and hearing impairment.
Method and Materials: A cross-sectional study was conducted with of 62 students aged between 10-15 years old in Hamadan in 2019-2020 . Of these participants, 32 students living with hearing impairment and 30 students living with low visions. Demographic questionnaires and Nordic musculoskeletal disorders were used to collect data. SPSS software version 23 was used to analyse data through two-sample independent t-test, chi- square test and logestic regression.
Finding: Tottaly 62 students took part in the study. The mean age of Low Vision Students( LVS) and Hearing Impairment Students (HIS) was 12.101.47± and 12.47± 1.64 years respectively. Of all students with low vision 10 individual (33.3%) and of all students with hearing impaiement 10 individuals (31.3%) were suffering from MSDs. The most MSD affected areas in HIS was lumbar (15.6%) and in LVS was shoulder (16.7%). The results showed that MSDs did not differ significantly between the two groups of LVS and HIS (P> 0.05).
Conclusion: This study showed that at least one-third of LVS and HIS suffered from MSDs. The need for therapeutic and educational strategies in the field of ergonomics interventional program for health promoting of these students with special needs should be considered.
Volume 7, Issue 4 (Winter 2023)
Abstract
Given the ever-increasing demand for energy and the limited nature of fossil fuel resources, improving energy efficiency and storage has become one of the most significant challenges facing humanity. Phase Change Materials (PCMs), substances capable of absorbing and releasing thermal energy at a constant temperature, have emerged as an innovative solution in the field of energy storage. With their high latent heat capacity, ability to maintain a stable temperature, and environmental friendliness, PCMs have great potential for applications in various industries. However, their low thermal conductivity, especially in organic PCMs, has hindered their widespread use. To address this challenge, researchers have been exploring various methods to enhance the thermal properties of PCMs. One of the most effective approaches involves incorporating high thermal conductivity nanoparticles into the PCM matrix. This research comprehensively reviews recent advancements in the preparation and applications of nanoparticle-enhanced phase change materials. It delves into various types of nanoparticles used, production methods for nanocomposites, the impact of nanoparticles on the thermal and mechanical properties of PCMs, the stabilization of nanocomposites with surfactants and surface modification, and also their potential applications in diverse industries. The results of this study indicate that the use of nanoparticles can significantly improve the thermal conductivity of PCMs, with carbon-based nanofillers showing the highest impact. Additionally, nanoparticles have led to a relative reduction in the phenomenon of supercooling in PCMs. Based on the results of numerous studies, nanoparticle-enhanced phase change materials hold great promise for improving the performance of energy storage systems, reducing energy consumption in various industries, and fostering the development of sustainable technologies. These nanocomposites can be employed in the construction, automotive, electronics, and textile industries to create more comfortable environments, enhance energy efficiency, and reduce greenhouse gas emissions. Continued research in this field is expected to lead to the development of even more efficient PCMs with a broader range of applications.
Mojtaba haghgoo, Reza Ansari, Abolfazl Darvizeh, Mohammad Kazem Hassanzadeh-Aghdam,
Volume 18, Issue 4 (8-2018)
Abstract
In this research, an analytical method is presented for predicting the viscoelastic and dynamic behavior of polymer nanocomposite. The analytical model is achieved by coupling the SUC micromechanical model with standard linear solid model. Boltzmann superposition principle is used to develop the constitutive equations. First, the strain associated with a relaxation experiment is considered, and then by using the idea of linearity as embodied in the Boltzmann superposition principle, the resulting stress history is predicted. Eventually, the creep function corresponding to the relaxation modulus is obtained and the hysteresis loop for nanocomposite material is represented. Creep response is sinusoidal in time and a function of stress history. Loss and storage modulus and material behavior in Laplace domain are obtained using standard linear solid model and SUC micromechanical model, respectively. Standard linear solid model is achieved by paralleling the Kelvin model with Maxwell model. The model is validated with experimental results. Effects of different interphase thickness, CNT volume fraction and phase angle on hysteresis loop is studied. Obtained results reveal that increasing the CNT volume fraction and phase angle leads to decreasing and increasing the nanocomposite hysteresis loop area, respectively. Also, Interphase thickness contains considerable effects on the nanocomposite dynamic behavior.
Mojtaba haghgoo, Hashem Babaei, Tohid Mirzababaie Mostofi,
Volume 21, Issue 11 (November 2021)
Abstract
Numerical simulation of Eulerian fluid Lagrangian solid interaction incorporating H2-O2 mixture gas detonation plate forming by employing conservative element and solution element immersed boundary method in LS-DYNA software is proposed in this paper. The detonation mechanism includes 7 species and 16 reactions. The chemical reaction mechanism and detonation wave propagation of Eulerian solver and dynamic plastic response of mild steel thin plate of Lagrangian solver are discussed thoroughly. The Johnson-Cook phenomenological material model with failure criterion is used to provide accurate predictions of dynamic response and failure state of detonation loaded steel plates taking into account material strain-rate sensitivity and non-linearities. The 2D numerical model is validated by comparing the simulation results with experimental data for thickness strain. The simulated pressure-time history of combustion cylinder, von Mises stress and deflection pattern of plate are also represented. Furthermore, a series of numerical simulation was carried out to determine the effect of the magnitude of internal detonation pressure on plate, taking into account different combustion cylinder longitudinal capacities, pre-detonation pressures and ignition point locations. Results show that an increase of pre-detonation pressure is conducive to increase the value of maximum detonation pressure while decreasing the combustion duration. Moreover, combustion cylinder with higher longitudinal capacity is more powerful to deform the plate.
Seyed Mahmood Farmani, Majid Alitavoli, Hashem Babaei, Mojtaba haghgoo,
Volume 23, Issue 12 (December 2023)
Abstract
In this research, the deformation of circular metal sandwich panels with vertical tube cores under blast load has been investigated numerically and experimentally. The relationship of energy balance in different components of the structure has been considered. The core tubes are installed in a cross arrangement and vertically with the same height between the upper and lower sheets of the sandwich structure. The amount of energy absorbed by the cores is determined according to their location in the structure and the effect of their number and diameter. The grouping of the desired tests for this research has been done according to the thickness of the sheet 1.2 and 2 mm and with aluminum cores with diameters of 12 and 16 (mm). Numerical simulation has been done in the form of free explosion and by defining the pressure function using the Conwep method in Abaqus software. To validate the numerical results, experimental tests have been carried out with the construction of sandwich structure. In both methods, the maximum lateral displacement of the structure at its center and the displacement in terms of distance from the center of the structure, at cores location have been measured. Increased number of tubes in the core of the structure decreased the maximum rise in the upper layer and decreased the transverse displacement of the lower sheet. Structures with fewer cores and less sheet thickness showed more energy absorption. The average difference between the results of numerical and experimental methods was approximately 11%.
