pejman kiani

In this Study, the necessary force of the isothermal forging process of disc piece of aluminum alloy AA7075 was analyzed and calculated by theoretical methods and finite elements method. In the simulation of the isothermal forging process in Deform software, were selected the temperature of 400 °C, the speed of top mold of 0.1 mm/s and the shear friction coefficient of 0.075 as process parameters. The necessary force of isothermal forging was obtained 80 tons in 6.18 mm Motion Course for disc piece by analyzing the simulation results of finite element method in DEFORM software. The axisymmetric slip line field method was used to estimate the forming force of the isothermal forging of the closed die before of the flash filling, which obtained 23.54 tons. The comparison forming force of isothermal forging of disc piece by theory method with the results obtained from finite element simulation showed that the forming force corresponds very well with the force-displacement diagram is compatible. The geometry of billet, the final top and bottom dies and assembly drawing of isothermal forging process of disc piece of aluminum 7075 dies were calculated by assuming a constant volume in plastic deformation.

Traumatic brain injury is believed to be a public health disorder with some complications. Post Traumatic Neurocognitive Disorders (PTND) received much attention among these complications because of the high prevalence of mild traumatic brain injuries. On the other hand, advanced neuroimaging is increasingly becoming an exciting modality in the field of traumatic brain injury. Magnetic resonance spectroscopy (MRS) provides a new window to understand the detailed biochemistry alterations following traumatic brain injury. Therefore, some researchers have addressed the relations between MRS data and PTND.

The research aimed to achieve the biochemistry alterations following TBI and find the relations between these alterations and PTND based on published literature in this field.

With this mind, a systematic search in MEDLINE and EMBASE databases performed to identify relevant published articles without date limitation. The systematic search keyword-targeted all MRS data relevant to the post traumatic neurocognitive disorders.

Of the search results, a total of 22 journal articles were reported relations between MRS data and neurocognitive disorders. A variety of questionnaires and computerized tests has been used to detect neurocognitive outcomes. Most studies focused on N-acetyl aspartate (NAA), Choline (Cho), Creatine (Cr), Myo-inositol (MI), and their ratios. As MRI scanners are becoming stranger detecting extra-metabolites such as glutamate, glutamine and glutathione are more reliable. In this regard a few studies reported significant relations between alterations in these metabolites and PTND.

MRS is a powerful tool that can provide important data to detect long-term neurocognitive disorders following TBI.

The ability of simultaneous treatment of critical-sized femoral defects (CSFDs) with photobiomodulation (PBM) and demineralized bone matrix (DBM) with or without seeded adipose-derived stem cells (ASCs) to induce bone reconstruction in ovariectomized induced osteoporotic (OVX) rats was investigated.

The OVX rats with CSFD were arbitrarily separated into 6 groups: control, scaffold (S, DBM), S + PBM, S + alendronate (ALN), S + ASCs, and S + PBM + ASCs. Each group was assessed by cone beam computed tomography (CBCT) and histological examinations.

In the fourth week, CBCT and histological analyses revealed that the largest volume of new bone formed in the S + PBM and S + PBM + ASC groups. The S + PBM treatment relative to the S and S + ALN treatments remarkably reduced the CSFD (Mann-Whitney test, P = 0.009 and P = 0.01). Furthermore, S + PBM + ASCs treatment compared to the S and S + ALN treatments significantly decreased CSFD (Mann Whitney test, P = 0.01). In the eighth week, CBCT analysis showed that extremely enhanced bone regeneration occurred in the CSFD of the S + PBM group. Moreover, the CSFD in the S + PBM group was substantially smaller than S, S + ALN and S + ASCs groups (Mann Whitney test, P = 0.01, P = 0.02 and P = 0.009). Histological observations showed more new bone formation in the treated CSFD of S + PBM + ASCs and S + PBM groups.

The PBM plus DBM with or without ASCs significantly enhanced bone healing in the CSFD in OVX rats compared to control, DBM alone, and ALN plus DBM groups. The PBM plus DBM with or without ASCs significantly decreased the CSFD area compared to either the solo DBM or ALN plus DBM treatments.

Laser welding is a significant method for welding all kinds of alloys. High speed welding, low distortion and easy automation are the advantages of this method. In this study, pulsed Nd:YAG laser butt joint welding was performed on 304 and 316 Austenitic stainless Steels workpieces. All the parameters were designed by Full Factorial Method which the center point was repeated for 10 times. Henceforth, the effect of power, pulse duration, laser velocity and chemical composition on width and depth of welding area, ultimate tensile strength, elongation and Ferrite Number were studied. The welding process was performed in 1.2 and 1.8 KW as power, 3 and 4.4 ms as pulse duration and 0.2 and 0.8 mm/s as velocity of welding. Thus, the upper level of input parameters were selected as the optimal case. This was done by surveying all the samples to achieve maximum UTS, size of the weld and Ferrite Number. In these conditions, output error for width of weld, depth of weld, U.T.S, elongation and Ferrite Number was 2, 5, 1.6, 25 and 2%.