Sharif Digital Repository

One of the main issues of business world is competition and competitiveness, and this cannot be happened unless one company absorb new ideas and innovations. Based on what scholars mentioned, companies should utilize users instead of professionals in order to create new innovations, and this is due to that users have better understanding of what users want. As a result, in the mobile platforms, platform owners need to know how to invoke users to create more innovative apps. In this research we were into finding important matters that increase number of innovation of users. We saw that lead-userness, toolkit support, work method autonomy, knowledge sharing, and modularity have an impact on... 

Additive manufacturing (AM) has gained significant attention in recent years as a novel approach to fabricate three-dimensional parts. Its advantages, including high speed, low-cost production for small-scale batches, and greater design freedom, have made it a competitive alternative to traditional manufacturing methods. However, the application of AM for components subjected to fretting fatigue requires careful evaluation. Fretting fatigue is a major cause of failure in turbines, particularly at the contact interface between turbine blade roots and disk. In this study, the influence of AM and post-processing treatments on the fretting fatigue life of Ti-6Al-4V alloy was investigated. Five... 

Fatigue cracking has a major impact on the performance of flexible pavements. Many test methods have been established to evaluate and estimate the fatigue life of asphaltic materials. Most of these test methods cannot successfully examine the fatigue properties of asphaltic materials. Recent studies demonstrate that using a standardized composite, which consists of glass beads and asphalt binder, can simulate the stress states that binder experiences in the field. This research used standardized composite to investigate the effect of crumb rubber on the fracture properties of asphaltic materials. To validate the test results, the authors conducted fracture tests on the Fine Aggregate Matrix... 

Chip seal is one of the most economical pavement maintenance practice that extends pavement life. To ensure chip seal good performance several quality control methods have been developed. However, most of these methods are qualitative and only measure the stone loss under a certain number on loading. This research developed a new method for quality control of chip seal, based on the assumption that characteristics of the bond between chips and pavement surface play a key role in chip seal performance. To validate this test method, the authors used a wheel track loading test. The results from this research clearly showed that the characteristics of the bond between chips and pavement surface... 

Recently, a new method to investigate chip seal performance has developed by a research team at Sharif University of Technology. This study investigates the effect of various additives such as CRM, SBR Latex, Hydrated Lime and Ordinary Portland Cement (OPC), on the curing time of chip seal by this method. In addition, the chip seal treatments were investigated in different climate conditions like Wet and Wet-Freeze zones. The overall performance of mixture specimens evaluated using creep loading test. In fact, the bonding properties between aggregates and surface of Hot Mix Asphalt measured. The test results were analyzed by using of the work and time parameters. These parameters were... 

The objective of this research is evaluating the effect of filler type and content on the characteristics of asphaltic materials. The properties of the asphalt mixture are greatly influenced by its components. As asphalt mixtures are composed of two prominent components, aggregates and binder, the change in type and contents of these materials may lead to altering the performance of asphalt mixtures. Aggregates in the asphalt mixtures are categorized into three groups based on their particle sizes: coarse aggregate, fine aggregate and mineral filler. The effect of filler on the characteristics of asphalt mixtures can be examined by changing the type and content of filler and holding the... 

Cracks or construction joints in an overlayed pavement can propagate into the overlay over time due to various factors, the most important of which are traffic and temperature loading, and cause premature failure of pavement. This propagated cracks are called reflective cracks and the phenomenon of crack propagation into the overlay is called reflective cracking. Use of stress-absorbing membrane interlayers (SAMI) is one of the ways can reduce the occurrence of reflective cracking and/or delay it. One of the most common SAMIs is an asphalt mixture consists of bitumen and aggregate layed down between the old and the veneer layers. The function of the SAMI depends on several factors such as... 

Studies have shown that use of crumb rubber additive can improve the mechanical and performance properties of hot mix asphalts. Nowadays, different methods are used for adding crumb rubber to asphalt mixtures. However, no comprehensive research has been done to investigate the effects of these different methods in cold mix asphalts. In this research, different crumb rubber modification methods were evaluated to compare their effects on cold mix asphalts’ performance. In this regard, various crumb rubber modification methods, such as pre blending crumb rubber into the asphalt before emulsification, post blending crumb rubber into the prepared asphalt emulsion and blending crumb rubber with... 

Insider threat is a significant security risk for organizations and hard to detect. Most of introduced detection methods need contextual data entries about users, or preprocessed user activity logs to detect insider threats while it is costly and time-consuming. In this thesis, we introduce a behavior analysis method that learns its context and detects multiple types of insider threats from raw logs and network traffic in real-time. This method, named XABA, learns user roles and exclusive behaviors, through analyzing raw logs related to each network session of the user. Then it checks for some abnormal patterns, and if so, triggers the appropriate alert. XABA is implemented on the big-stream... 

Modern microwave and wireless communications systems are too complex today to permit the complete simulation of the nonlinear behavior at the transistor level of description. This problem presents a significant productivity bottleneck for design engineers. At the bridge between the transistor circuit and the multichip module or RF integrated circuit (RFIC) we use “behavioral models” to describe the nonlinear circuit blocks or ICs in the system. The behavioral models are simplified models of the essential nonlinear behavior of the complex sub-circuits; this simplification means that these models will execute more quickly, and use much less memory than if an entire complex subsystem was... 

During 1980s Additive Manufacturing technologies for the purpose of prototyping with fast and less expensive, under the name of Rapid Prototyping was invented. But nowadays under the vast progress made in this field, it possesses a notable place in different industries such as automobile manufacturing, aerospace, architecture, medicine and so on for part manufacturing. In all AM machines, the CAD model design part is manufactured by adding layered to each other. In this research, at first by explaining manufacturing process and current different technologies, the place of this manufacturing process in today and future industry, is analyzed. For discussing replacement of this method instead... 

Crumb Rubber is one of the main polymer modifiers of binders. This modifier can improve chip seal performance against ravelling (aggregate loss). The most concerning distress in chip seal is ravelling. Aggregate loss is not restricted to the early life of chip seal, but continues throughout the service life. Chip seal can be made with hot binders or emulsion binders. These two type of binder were modified with 7% and 15% of crumb rubber in applicable way. Then, two major environmental effect on chip seal performance, freeze-thaw and asphalt aging, were investigeted based on laboratory test. For this purpose, authors used chip seal bonding test. Chip seal bonding test is developed recently... 

Stress Absorbing Membrane Interlayer (SAMI) is a slightly thin layer made of bitumen and aggregate placed between a pavement with limited cracking and overlay in order to avoid reflective cracking in overlay. SAMI’s performance depends on many factors such as pavement layer’s materials and thickness and existing pavement’s condition. Numerical simulations are powerful tools to evaluate SAMI’s performance. Previous studies showed that construction of SAMI does not necessarily reduce reflective cracking. This research investigated the effect of different parameters on SAMI’s performance using numerical simulations. The focus of this study was on the performance of SAMIs used between asphalt... 

This study presents the best layout with optimal number of sensors for an arbitrary monitoring area based on reference free damage detection and localization. In recent years, damage detection approaches with the concept of instantaneous baseline measurements in Structural Health Monitoring (SHM) with lamb wave propagation are being developed. An array of spars transducers is obligatory in SHM with lamb wave propagation, so that designing the best one is a concern for many researchers. To obtain the best sensors layout, damage localization process should be done for all definable sensors layouts in many different crack positions. Obviously, doing this seems not practical as wave propagation... 

A Specific process centrifugal compressor is upgraded. The operating range and efficiency pattern are increased. A one-dimensional performance prognosis tool (CCPP) is developed. The tool uses mean streamline method as the analysis model. Since the working media has various components, a complete equation of state is utilized to model the thermodynamic behavior of the real gas in super critical pressures. The performance of the base-line compressor is deyermined. The performance prognosis tool is validated with available experimental data. Upgrade road map and methodology were introduced in accordance to domestic requirements. The performance of the upgraded compressor is investigated and... 

Due to the long physical distance between the users and the cloud data centers, the idea of considering fog layer was established to bring computations closer to the edge of the network, and provide a solution for latency-sensitive applications. In such applications, the tasks are offloaded, and assigned to the available virtual machines in the cloud or fog layers, which directly contribute to Quality of Service (QoS) requirements. Among various applications, the real-time applications require their tasks to finish before their deadlines. Therefore, an assignment or a scheduling algorithm is needed to assign incoming tasks to virtual machines in cloud or fog layer. Most of the research on... 

Capacitive deionization (CDI) is a suitable method for water desalination with low energy consumption and high efficiency, which does not have secondary pollution and is environmentally friendly. The hybrid capacitive deionization uses a faradaic electrode next to the carbonaceous electrode, taking advantage of both electrodes, and high capacities have also been reported. Titanium carbide Mxene is an important candidate in CDI due to its high electrical conductivity and tunable interlayer distance, but Mxene suffers from low oxidation resistance. Therefore, in this research, molybdenum disulfide (MoS2) that is an essential member of the 2D transition metal dichalcogenides family, was used as... 

Existing face forgery detection methods mainly focus on certain features of images, such as features related to image noise, local textures or frequency statistics of images for forgery detection. This makes the extracted representations and the final decision depend on the data in the database and makes it difficult to detect forgery with unknown manipulation methods. Solving this challenge, which is called the generalization challenge in artificial intelligence literature, has become the main goal of researchers in this field. In this thesis, the focus is on extracting effective features for success in forgery detection and preventing the performance of the forgery detection network from...