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Search Results: 1 - 10 of 15053 matches for " Mohammad Hossein Jahangir "
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Evaluation of Unsaturated Layer Effect on Seismic Analysis of Unbraced Sheet Pile Wall  [PDF]
Mohammad Hossein Jahangir, Hadis Soleymani, Saeideh Sadeghi
Open Journal of Marine Science (OJMS) , 2017, DOI: 10.4236/ojms.2017.72022
Abstract: This paper is built upon the previous developments on lateral earth pressure by providing a series of analytical expressions that may be used to evaluate vertical profiles of the effective stress and the corresponding suction stress under steady-state flow conditions. Suction stress profile is modeled for one layer sand near the ground above the water level under hydrostatic conditions. By definition, the absolute magnitude of suction stress depends on both the magnitude of the effective stress parameter and matric suction itself. Thus, by developing the Rankine’s relations in seismic state, the composing method of active and passive surfaces in sides of unbraced sheet pile is examinated and the effects of soil parameter on those surfaces are evaluated by a similar process. The relations described the quantitative evaluation of lateral earth pressure on sheet pile and the effects of unsaturated layer on bending moment and embedded depth of sheet pile in soil.
RADIOLOGICAL ASSESSMENT OF 78 PATIENTS OF EWING SARCOMA INTRODUCTION OF INTERESTING & UNUSUAL PRESENTATIONS
MOHAMMAD JAHANGIR
Acta Medica Iranica , 1986,
Abstract: Ewing sarcoma is about 10 % of bone tumours, in the form of lytic, sclerotic and mixed type. The lytic type erodes the whole bone in such a way that the auther would like to name it 'Vanishing' type and recognition of this radiological type is of great importance from differential point of view in the study of primary and secondry tumours of bones.
The Simulation of Flood Hydrograph in Natural and Urban Basins  [PDF]
Seyyed Ahmadreza Torabi, Hossein Sedghi, Jahangir Porhemmat, Hossein Babazadeh
Open Journal of Geology (OJG) , 2018, DOI: 10.4236/ojg.2018.87037
Abstract: The exact estimation of the flood is one of the main concerns for designers of the water bodies. The significance of this issue in the catchment areas overlooking the cities is more and more visible. In this study, HEC-HMS model is used to simulate the catchment area of the Khoshk River in the Shiraz city. The simulation results and its comparison with the observations based on Nash-Sutcliffe coefficient confirm the validity of the model. The input data of the model includes Rainfall, Measured Discharge, Flood Peak Time, Curve Number (CN), and so on. These results indicate that although the shape of the simulated hydrograph is not exactly the same as the observed hydrograph, it has estimated the peak of flood discharge well with an error rate of two to five percent.
Information-Driven Collaborative Processing for Diffusive Source Estimation in Wireless Sensor Networks  [PDF]
Hossein Khonsari, Mohammad Hossein Kahaei
Wireless Sensor Network (WSN) , 2010, DOI: 10.4236/wsn.2010.27068
Abstract: This paper discusses an accurate distributed algorithm for diffusive source localization while maintaining the low energy consumption of sensor nodes in wireless sensor networks. In this algorithm, the sensor selection scheme based on the information utility measure is used. To update the estimation in each selected node, a neighborhood radius equal to the communication range of the sensor nodes is defined and all sensors located in the neighborhood circle, whose radius is equal to the neighborhood radius and the selected node is its centre, collaborate their information. To decrease the energy consumption, the neighborhood radius is reduced gradually based on the error covariance value of the estimation. In addition, this paper includes a new method for the initial point calculation which is important in the recursive methods used for distributed algorithms in wireless sensor networks. Numerical examples are used to study the performance of the algorithms. Simulation results show the accuracy of the new algorithm becomes better while its energy consumption is low enough.
Optimization of Fairhurst-Cook Model for 2-D Wing Cracks Using Ant Colony Optimization (ACO), Particle Swarm Intelligence (PSO), and Genetic Algorithm (GA)  [PDF]
Mohammad Najjarpour, Hossein Jalalifar
Journal of Applied Mathematics and Physics (JAMP) , 2018, DOI: 10.4236/jamp.2018.68134
Abstract:
The common failure mechanism for brittle rocks is known to be axial splitting which happens parallel to the direction of maximum compression. One of the mechanisms proposed for modelling of axial splitting is the sliding crack or so called, “wing crack” model. Fairhurst-Cook model explains this specific type of failure which starts by a pre-crack and finally breaks the rock by propagating 2-D cracks under uniaxial compression. In this paper, optimization of this model has been considered and the process has been done by a complete sensitivity analysis on the main parameters of the model and excluding the trends of their changes and also their limits and “peak points”. Later on this paper, three artificial intelligence algorithms including Particle Swarm Intelligence (PSO), Ant Colony Optimization (ACO) and genetic algorithm (GA) has been used and compared in order to achieve optimized sets of parameters resulting in near-maximum or near-minimum amounts of wedging forces creating a wing crack.
Evaluating the Efficacy of Remifentanil-Propofol versus Isoflurane in Reducing Blood Loss with Considering Depth of Anesthesia during Endoscopic Sinus Surgery  [PDF]
Mohammad Ali Haghbin, Hossein Hakimzadeh, Mohammad Shabani
Neuroscience & Medicine (NM) , 2013, DOI: 10.4236/nm.2013.42009
Abstract:

Several methods have been suggested to decrease bleeding during surgery, one of which is the usage of hypotensive anesthetic agents. Endoscopic Sinus Surgery (ESS) is one of the surgeries which need a clear field and the amount of bleeding profoundly impacts the ability of surgeons. Current study was designed to evaluate the effect of remifentanil combined with propofol versus Isoflurane on blood loss during ESS and its possible interaction with Depth of Anesthesia. Fifty one patients comprising 15 females and 36 males undergoing ESS were chosen for this study. One group received propofol and remifentanil to induce and maintain anesthesia and the second group received Isoflurane. Mean Arterial Blood Pressure (MAP), Depth of Anesthesia and total blood loss were recorded for the patients of both group. Data were analyzed using t-test, Repeated Measures ANOVA and Pearson’s correlation. P < 0.05 was considered statistically significant. Both agents induced hypotension during surgery. No significant difference was observed in total blood loss between two groups. DA was decreased in both groups, but no significant correlation was found between DA and MAP or DA and blood loss. There is no significant difference between remifentanil combined with propofol and Isoflurane in decreasing blood loss during ESS, thus we suggest usage of hypotensive anesthetic agent regardless of its type is ESS.

Numerical Simulation of Non-Newtonian Pseudo-Plastic Fluid in a Micro-Channel Using the Lattice Boltzmann Method  [PDF]
Hossein Hamedi, Mohammad Hassan Rahimian
World Journal of Mechanics (WJM) , 2011, DOI: 10.4236/wjm.2011.15029
Abstract: In this paper, the power-law model for a non-Newtonian (pseudo-plastic) flow is investigated numerically. The D2Q9 model of Lattice Boltzmann method is used to simulate the micro-channel flow with expansion geometries. This geometry is made by two squared or trapezoid cavities at the bottom and top of the channel which can simulate an artery with local expansion. The cavities are displaced along the channel and the effects of the displacements are investigated for inline structures and staggered ones (anti-symmetric expansion). The method is validated by a Poiseuille flow of the power-law fluid in a duct. Validation is performed for two cases: The Newtonian fluid and the shear thinning fluid (pseudo-plastic) with n = 0.5. The results are discussed in four parts: 1) Pressure drop; It is shown that the pressure drop along the channel for inline cavities is much more than the pressure drop along the staggered structures. 2) Velocity profiles; the velocity profiles are sketched at the centerline of the cavities. The effects of pseudo-plasticity are discussed. 3) Shear stress distribution; the shear stress is computed and shown in the domain. The Newtonian and non-Newto- nian fluids are discussed and the effect of the power n on shear stress is argued. 4) Generated vortices in the cavities are also presented. The shape of the vortices is depicted for various cases. The results for these cases are talked over and it is found that the vortices will be removed for flows with n smaller than 0.5.
Video Compression USING a New Active Mesh Based Motion Compensation Algorithm in Wavelet Sub-Bands  [PDF]
Mohammad Hossein Bisjerdi, Alireza Behrad
Journal of Signal and Information Processing (JSIP) , 2012, DOI: 10.4236/jsip.2012.33048
Abstract: In this paper, a new mesh based algorithm is applied for motion estimation and compensation in the wavelet domain. The first major contribution of this work is the introduction of a new active mesh based method for motion estimation and compensation. The proposed algorithm is based on the mesh energy minimization with novel sets of energy functions. The proposed energy functions have appropriate features, which improve the accuracy of motion estimation and compensation algorithm. We employ the proposed motion estimation algorithm in two different manners for video compression. In the first approach, the proposed algorithm is employed for motion estimation of consecutive frames. In the second approach, the algorithm is applied for motion estimation and compensation in the wavelet sub-bands. The experimental results reveal that the incorporation of active mesh based motion-compensated temporal filtering into wavelet sub-bands significantly improves the distortion performance rate of the video compression. We also use a new wavelet coder for the coding of the 3D volume of coefficients based on the retained energy criteria. This coder gives the maximum retained energy in all sub-bands. The proposed algorithm was tested with some video sequences and the results showed that the use of the proposed active mesh method for motion compensation and its implementation in sub-bands yields significant improvement in PSNR performance.
Management and Reduction of Chemical Nitrogen Consumption in Agriculture  [PDF]
Abedin Zafari, Mohammad Hossein Kianmehr
American Journal of Plant Sciences (AJPS) , 2012, DOI: 10.4236/ajps.2012.312A224
Abstract:

Nitrogen is an effective material for improving the crop production. There is a big concern about rising chemical nitrogen usage as fertilizer in soil, because some forms of nitrogen absorbs in soil and causes an increase of environment and water pollution and decrease fertilizer efficiency. Composted cow manure is an important resource of organic nitrogen which improves the soil conditions. However, low density of composted cow manure and inconstant nutrient content are two factors that limit the application of composted cow manure. The densification technology is an effective solution for both problems. In this research first the capability of single screw extruder for production of fertilizer pellets including composted cow manure and nitrogen fertilizer was studied and then the effect of fertilizer pellet on the reduction of chemical nitrogen consumption was evaluated. The response of basil plants was determined in three treatments: T1 control (no fertilizer), T2 (nitrogen fertilizer) and T3 (pellet). The results showed that pelletization can be used as a proper method for slow-release nitrogen fertilizer; enhance nitrogen uptake and reducing the chemical nitrogen consumption. The results also showed that all basil responses (chlorophyll content, total weight, leaves weight, root weight and leaf area) were significantly affected by application of N fertilizer and pellet. While maximum recorded parameters were observed with application pellet.

The Overload Reduction in SIP Servers through Exact Regulation of the Retransmission Timer of the Invite Message  [PDF]
Ahmadreza Montazerolghaem, Mohammad Hossein Yaghmaee
Journal of Computer and Communications (JCC) , 2013, DOI: 10.4236/jcc.2013.12002
Abstract:

To initiate voice, image, instant messaging and general multimedia communication, the Session communication must initiate between two participants. SIP (Session initiation protocol) is an application layer control, which task is creating management, and terminating this kind of Sessions. With regard to the independence of SIP from the Transport layer protocols, the SIP messages can be transferred on a variety of Transport layer protocols such as TCP or UDP. The mechanism of Retransmission, which has been embedded in SIP, is able to compensate the missing Packet loss, if needed. The application of this mechanism is when SIP messages are transmitted on an unreliable transmission layer protocol such as UDP. This mechanism, while facing with SIP proxy with overload, causes excessive filling of proxy queue, delays the increase of other contacts and adds the amount of the proxy overload. We in this article, while using UDP, as the Transport layer protocol, by regulating the Invite Retransmission Timer appropriately (T1), have improved the SIP functionality. Therefore, by proposing an Adaptive Timer of Invite message retransmission, we have tried to improve the time of Session initiation and as a result, improving the performance. The performance of the proposed SIP, by the SIPP software in a real network environment has been implemented and evaluated and its accuracy and performance has been demonstrated.

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