Sharif Digital Repository

The aim of the present study is to investigate the effects of using hybrid fibers on rheological, mechanical and durability properties of the high-strength Self-Consolidating Concrete (SCC). For this purpose, two types of fibers including hooked-end steel fibers and polypropylene fibers were used. In this study, a total of eleven mixtures were used: one as a control mix, one containing 0.5% steel fibers, four containing 0.5% hybrid fibers (steel and polypropylene), one containing 1.0% steel fibers and the four containing 1.0% hybrid fibers (steel and polypropylene). For investigating the rheological properties, slump flow, J-ring and V-funnel tests were performed. Mechanical properties were... 

In recent years we have witnessed a growth in handheld or wearable technologies among others, which have tested the limits of SRAM. The technological advancements of recent years and a persistent trend in reduced feature sizes have been testing the limits of SRAM for quite a while. It is becoming clear that because of high leakage the SRAM technology does not satisfy the ever increasing demand for reduced cost and dimensions, and, as a result Non-Volatile Memory with lower leakage property is a promising alternative to bridge the aforementioned gaps. But limited endurance is one of its weaknesses.In this paper we propose a novel method dubbed “online write-prevention coding” to incorporate... 

Fuel cell is a very attractive technology for clean electricity production and has a wide range of applications from industry to transportation and power generation. There are several issues that prevent the development of this technology widely. Rapid degradation of fuel cells during operation is one of them. Online monitoring of operational parameters in order to control and optimize the effective variables of power generation and life of the fuel cell considered as an important way to mitigate fuel cell’s degradation. In this research, a set of models were developed to calculate the voltage, current, corrosion, as well as the fuel cell system state variables instantaneously. Two robust... 

In the present study, the performance of fly ash-based geopolymer concrete blended with cement as an additional calcium source under exposure to marine, acidic and alkaline environments was evaluated. Three mixtures of fly ash-based geopolymer concrete with different cement ratios (0, 10 & 20%) were prepared and immersed in tap water, seawater, sulfuric acid, and sodium hydroxide solutions for up to one year. Change in the appearance, weight, compressive strength, splitting tensile strength, energy absorption and microstructure of the specimens were evaluated at 1, 3, 6, 9 and 12 months of exposure. Ultrasonic pulse velocity test was also used to determine its relationship with the... 

Polymer concrete is well-known for the quick repair of concrete structures and pavement. Many concrete structures such as bridges, offshore, and pavements are under cyclic loads when they are exposed to different environmental conditions during their lifespan. However, there are relatively few studies on the durability of Polymer concrete. The durability and fatigue performance of these structures are significant issues that should be considered. This study aims to investigate the long-term environmental effects on the mechanical properties of Polymer concrete. Therefore, polymer and ordinary cement concrete specimens were prepared and exposed to four chemical solutions with pH values of... 

Material durability is quite critical in corrosive environments. In this study, two hundred and seventy geopolymer concrete specimens with different mix designs were prepared and then wrapped with two different fiber reinforced polymer (FRP) materials. For 12960 hrs (eighteen months), the specimens were exposed to four different pHs (2.5, 7, 7.25, 12.5). The reliability and SEM analysis were performed after modeling the compressive strength over time. Based on the results, the reduction of the compressive strength was up to 22% in an acidic environment. The compressive strength of the specimens was increased up to 11 percent after alkaline solution exposure. The ductility of all specimens... 

As nuclear energy continues to be used as a useful energy resource, waste management, especially management of high-level nuclear waste (HLW), will always be a major concern, as the future generations should not be deprived of the valuable benefits of this energy. Vitrification of liquid high-level radioactive waste (HLW) has received greater attention, worldwide, than any other high-level waste solidification process. The high solubility of HLW in borosilicate glass, the controllable temperature of this type of glass and its low leaching rate in repository environment, have introduced borosilicate glass as a suitable host for HLW immobilization. In this project, the immobilization of the... 

The increasing growth of digital data and the use of data-intensive applications and cloud computing have made data storage systems the performance bottlenecks of computing systems. To improve the efficiency of data storage systems and enhance the quality of service, storage system manufacturers use high-performance storage devices such as solid-state drives (SSDs) in their designs, namely, all-flash storage systems. SSDs provide significant performance compared to hard disk drives and are used in the architecture of high-speed storage systems. Despite very high speed of SSDs, their high price and low endurance have limited their usage in data storage systems. The limited endurance of SSDs... 

The goal of this research is to study the effect of local microcracking due to step by step pressure loading on the durability properties of geopolymer concrete. To better understand the behavior of GGBS-based GPC under different pressure stress levels, some experiments such as water permeability and water absorption conducted on the samples at each state of damage. Also, non-destructive tests such as ultrasonic waveform and pulse velocity (UPV) was used to quantify the extent of damage at each step. GGBFS and a blend of sodium silicate solution and 10 molar sodium hydroxide solution with SSSH⁄ ratio of 2 were used for production of GPC samples. GPC, OGPC and OPC samples with water to binder...