m. hoseinzadeh

This paper discusses the nonlinear dynamic behavior of nanocomposite microplates reinforced with carbon nanotubes in contact with static fluids. Equations of motion are derived using the first-order shear deformation theory of plates and considering the size effects and large deformations. Effective mechanical properties are determined by applying the law of mixtures. By use of the Galerkin method, the nonlinear equations governing motion are discretized and the numerical solution is obtained. The results have been verified and the effect of micro-plate geometrical characteristics, small size parameter, fluid height and weight fraction of the carbon nanotubes studied on natural linear and nonlinear frequencies and the dynamic response has been evaluated. The results indicate that the natural frequency of the system decreases with increasing fluid height. The reinforcement of microplates by carbon nanotubes also results in a softening of the stiffening behavior of the spring and a substantial bending of the response curve. Depending on the excitation frequency, this bending may result in jump instability. By examining the time response, phase, and Poincaré map of the system, periodic, quasi-periodic, and chaotic vibration behavior can be observed.

In order to reduce the cost and time of seismic analyses, due to lack of correct understanding of structural characteristics and the forces acting on, usually simplified assumptions are applied in the structural modeling that could lead to unrealistic responses. One of these simplified assumptions in bridge modeling is ignoring the pounding phenomenon and soil-structure interaction. Nowadays, the bridges are considered as a vital component in urban and inter-urban transportation systems that the disruption in their operation due to partial or full collapses could lead to disruptions in the transportation system and heavy costs and consequences. One of the major factors, which is considered by the researchers after some earthquakes such as Northridge, Kobe and Chi Chi and their destructive effects on bridges in recent decades, is the pounding phenomenon. This phenomenon is a result of a collision
between two parts of the deck and/or deck and lateral piers (abutments) in the gaps during the earthquake. The pounding in bridges could cause damage in the deck and abutment or the dislocation of deck from the pier. In conventional bridge designs with a few centimeters gap, pounding in severe earthquakes will be unavoidable. Therefore, in this study, with modeling two- and three-span bridges with different periods and considering the gaps of 2.5, 5, 7.5, 10, 12.5 and 15 cm, the effects of the gap size on seismic parameters, including maximum absolute displacement of the deck, the maximum pier bending moment, the maximum pounding force, and the number of pounding, are analyzed. The bridges are subjected to 8 far-field and 8 near-field accelerograms. The results show that increasing the size of gap reduces the number of poundings and increases the maximum deck displacement. However, the trend of changes in maximum pounding force is subject to the bridge period and applied earthquake specifications. In addition, the near-field earthquakes lead to greater seismic responses than that of the far field ones.

Problem-based learning (PBL) is possibly one of the most innovative methods in medical education. In this training method, small groups of students work on a subject and learn the educational goals which include basic and clinical sciences. The aim of this study was comparing students’ and facilitators’ satisfaction in teaching pediatric course materials by two methods of large group PBL and lecture-based teaching.

In this analytic study, all pediatric theory course students (40 students) were divided into 5 groups. 6 PBL training sessions was added to regular conventional lectures of pediatric subjects. Students’ and facilitators’ satisfaction data for both methods of teaching were collected during the semester. Finally the data was analyzed using descriptive and inferential statistics.

The results of this study indicated that most students preferred PBL over the lecture-based traditional teaching in the most of the aspects (P<0.05). Tutors activity did not show any significant difference in both methods. Tutors managed this form of PBL effectively within time restraints and reported that they enjoyed the process.

Based on the findings of this study, the modified problem based learning methodology can be successfully used with larger groups of students.

Kawasaki disease is an acute febrile multisystem vasculitis syndrome. This study designed to assess clinical and laboratory findings of children diagnosed as Kawasaki disease hospitalized in two major pediatrics departments of Abuzar and Golestan hospitals affiliated to Ahvaz Jundishapur University of Medical Sciences.Subjects and

According to the criteria of Centers for Disease Control (CDC) for Kawasaki disease, all children who were diagnosed as Kawasaki from Oct 2001 to Apr 2004 were enrolled. History taking, physical examination and laboratory assessment were performed and standard treatment was carried out. Echocardiography was performed for all patients at the time of diagnosis and two weeks later.

Twenty five subjects had the definite diagnosis of Kawasaki. The mean age was 30 ±19.55 month; male/female ratio was 1.77: 1. Hospitalization was more frequent in winter season, especially in January. The most common presenting symptom (except fever) was maculopapular rash and the most common diagnostic criteria was bilateral non-purulent conjunctivitis. Leukocytosis with polymorphoneuclear predominance, high erythrocyte sedimentation rate and positive CRP were present in patients in acute phase of the disease. The mean serum hemoglobin level was 10.4 g/dl before treatment. The mean platelet count rose from 418000/mm2 in acute phase to 621000/mm2 in convalescence period (P0.05).

Clinical and laboratory findings of Kawasaki in this area is similar to other centers and were not affected with coronary artery involvement