Sharif Digital Repository

Random Polytopes, the first occurrence of which dates back to the famous Sylvester’s four points problem in the 1860s, is a branch of geometric probability, typically concerning the convex hull of some random points chosen from a convex subset of Rd. In this thesis we have studied some special kind of random polytopes; the one that is the convex hull of some independent random points chosen from a convex body (a convex, compact set with interior point) according to the uniform distribution. It was a new approach from A. Rényi and R. Sulanke in 1963 to consider this type when the number of random points tends to infinity.This thesis consists of three main parts: The first part is devoted to... 

One of the major challenges in construction of rubber modified asphalt mixtures is determination of mixing and compaction temperature (MCT). In order to estimate MCT according to Superpave volumetric mix design procedure, a temperature-viscosity relationship for the binder should be developed using ASTM D2493. This approach provides reasonable temperatures for unmodified binders which are Newtonian fluids at high temperatures and their viscosity is independent of shear rate. However, this method often yields excessively high temperatures for modified binders which exhibit non-Newtonian pseudoplastic behavior. The reason is that viscosity of modified binders depend on not only temperature but... 

One of the applications of signal digitization is its use in nuclear spectroscopy and in particular gamma ray spectroscopy. Parameters such as pulse amplitude and formation, pulse shrinkage correction or reduction, and pulse sampling are performed by the amplifier circuit and MCA. Such algorithms have advantages such as real-time pulse height analysis, high flexibility and significant cost reduction.Therefore, in this project, an attempt has been made to design a pulse analyzer system using electronic circuits and a computer ADC sound card. Optimal system will detect, amplify and shape the detector input signal, reduce the effect of pulse accumulation, count the number of pulses, and so... 

Today, lots of vulnerabilities are discovered by researchers who are analyzing the software. Some researchers study these discovered vulnerabilities and find new ones that are similar to them. So they need to first characterize each previously discovered vulnerability and extract the vulnerable context of the program, then extract new vulnerabilities based on that. Some vulnerabilities are emerging because of developer mistakes in the implementation phase. Software developers use different function calls to do the goal of the program. Incorrect invocation for functions can lead to critical vulnerabilities. Our investigation shows that the root cause for some vulnerabilities is incorrect... 

Epidemiological studies have identified manual material handling and lifting as risk factors in occupational low back pain (LBP). There are many lifting analysis tools to estimate the risk of injury during a specific lifting task. One for using these tools, needs to know the limitations of each tool and be noticed where a tool cannot be used. The purpose of this study is to compare different biomechanical models of lumbar spine and find out their characteristics.Five models are chosen for this study which are: the University of Michigan’s Static Strength Prediction Program ( ) software, the revised Hand-Calculation Back Compressive Force (HCBCF) equation, the simple polynomial equation of... 

High performance concrete has a compressive strength of more than one hundred and twenty MPa. The effect of steel fibers on the flexural fracture of this type of concrete has been studied, but the mechanical behavior of fracture of this material has not been fully studied yet. In this research, the effect of different percentages of propylene fibers on the mechanical properties of reinforced concrete will be investigated experimentaly. For this purpose, beam samples with dimensions of 40*10*10 cm, which had an initial notch with a depth of 3 cm in the lower middle of it, have been tested to investigate the effect of fiber percentage on how the crack propegate and the sample breaks. It is... 

The seismic performance of a low-rise nonductile reinforced concrete (RC) building rehabilitated using eccentric steel bracing is investigated. At first three-story building was Modeled using sap 2000 computer program then analyzed and getting the results. The effectiveness of the eccentric steel bracing in rehabilitating the building was examined. The effect of distributing the steel bracing over the height of the RC frame on the seismic performance of the rehabilitated building was studied. The behavior of the nonductile RC frame members is represented by a beam–column element capable of modeling the strength deterioration and the effect of the axial force on the yield moment and the... 

Change detection involves comparing images of a specific area taken at different times to identify the key changes that have occurred over time. It is critically important in the field of remote sensing, with applications spanning urban planning, disaster monitoring, and environmental conservation. However, challenges such as varying weather conditions and lighting in satellite images taken at different times, as well as the presence of non-target changes, can make this task challenging. In this research, we will focus on changes in land-use, particularly in building infrastructure, which is crucial for urban development planning. Moreover, since change detection does not specify the type of... 

attacks have become such a serious problem that according to the recent security firms’ reports, more than five thousands attacks are launched per day, whichcould lead to lots of damage and loss of online businesses. When a P2P system has millions of concurrently active peers, there is the risk that an attacker misuses these clients, or diverts their generated traffic to launch DDoS attack.As we will see, since BitTorrent has gained more popularity among other P2P protocols,and ithas the most number of concurrent active users,it may lead to destructivedamagesif exploited by attackers for lunching DDoS attack. Thus, we have focused on DDoS detection over this protocol.In this study, first,we... 

AdS/CFT correspondence is a suitable framework for studying strongly coupled gauge theories. It corresponds a strongly coupled gauge theory to a classical gravity theory with an extra dimension. Quark-gluon plasma which is produced in accelerators is strongly coupled. We use AdS/CFT correspondence to calculate Meson thermalization time by approximating the collisions by a sudden change of baryon number chemical potential. On the gravity side, this is followed with an apparent horizon formation on probe-brane which is the signal of thermalization