Sharif Digital Repository

Bitumen ageing is one of the principal factors causing the deterioration of asphalt pavements. Ageing is a complex process that is affected by different parameters.With the rapid growth of modified binders in road paving applications over the past twodecades, it is important to study the ageing properties of these binders. A number of laboratory methods are used tosimulatethe bitumenageing at various stages of the production and service of hot mix asphalt.Recent studies have shown that Superpave testing protocol does not fully address the ageing of modified binders. To study the ageing properties of modified binders, three different types of binder modifiers, plastomer, elastomer, and ground... 

In this study nanostructured composite from Al1050 and Al2024 were manufactured via accumulative roll bonding (ARB). Process was conducted in two different ways. In one approach the Al2024 sheets were annealed and in the other they were solution treated (ST). The sheets were degreased by acetone and wire-brushed, and then one Al2024 was placed between two sheets of Al1050, so three pieces of sheets were stacked to be 3 mm in thickness. The stacked sheets were rollbonded to produce the primary composite sandwich with thickness of 1 mm. Then, this sandwich was cut in the half and the two halves were degreased and wire-brushed and stacked to be 2 mm in thickness. Roll-bonding was conducted... 

In this research the effects of addition of clay in phenolic glass fiber reinforced composite has been investigated. Layered clay/phenolic nanocomposite resin systems were first prepared with 0.5, 1.5 and 2.5 wt% of Cloisite Na+ (CN) and Cloisite 30B (CB). After that the suspension was hold in an ultrasonic bath for 30 min in order to enhance nanodispersion of the clay platelet within the resin. The phenolic/clay solution was used to impregnate the glass fabric using the solvent impregnation method. After suspension for 2 days in the room with natural condition, the impregnated fabrics were pre-cured at 135 ˚C in an oven for 3.5 min to obtain B-stage prepregs. Seven layers of prepregs (150... 

Combined cycle power plants consist of three main sections, namely gas turbine, Heat Recovery Steam Generator (HRSG) and steam turbine. Occurring failure in HRSG causes the steam turbine trip, so the reliability assessment of HRSG has a great importance for forecasting the probability of occurring failure and also reducing failure causes. In this project, the reliability of HRSG considering effects of aging phenomenon, maintenance and, environmental and operational conditions on reliability is modeled. Afterward a method to estimate the model parameters is introduced. Using present method, failure data of six HRSGs of a plant each with a capacity of 50 MW is analyzed and the model parameters... 

Currently, the relatively long time of the turbine life passes and their parts and equipment damage are different, that loss optimum performance and thus reducing their efficiency and may lead to faults and other unexpected stops in their production cycle. Process used to estimate the remaining life of the various components of this turbine is an important tool for improving the efficiency of these units to perform preventive maintenance. In the present thesis, the types of damages in different parts of gas turbines and various methods for detection of critical points, particularly finite element method, high cycle fatigue, modal analysis, methods to estimate the lifetime of a gas turbine... 

Negative Bias Temperature Instability (NBTI) in CMOS devices is known as the major source of aging effect leading to performance and reliability degradation in modern processors. Instruction-cache (I-cache), which has a decisive role in performance and reliability of the processor, is one of the most affected modules by NBTI. Variations in duty Cycles and long-time residency of data blocks in I-cache lines (stress condition) are the two major causes of NBTI acceleration. This paper proposes a novel I-cache management technique to minimize the aging effect in the I-cache SRAM cells. The proposed technique consists of a smart controller that monitors the cache lines behavior and distributes... 

Combining the concept of Network-on-Chip (NoC) with three dimensional integrated circuits technology on 3D NoC enables reduction of propagation delay, interconnect power consumption, and die area, as well as increase in system operational bandwidth. Nevertheless, reducing the feature size of semiconductor technologies has raised certain aging mechanisms, like Negative Bias Temperature Instability (NBTI) and Electromigration, as the main reasons for reduction in reliability and lifetime of NoCs. Reduction in die area results in an increase in power density of the chip, which exacerbates temperature-related concerns of 3D NoCs compared to 2D NoCs. Thus, the aging mechanisms that are directly... 

The water-gas shift reaction, as a vital reaction in industry especially as a source of hydrogen for the manufacture of ammonia, is influential for all of the scientists and researchers in chemical engineering all around the world. In this research, high temperature water-gas shift (HTS) catalysts were investigated in order to study synthesis parameters and improvement of their performance and catalytic activity. The two catalyst categories; non pre-active and pre-active (magnetite-based samples, not requiring a reduction step prior to use) were prepared by co-precipitation method, using chloride, sulfate and nitrate metal (Fe, Cr, Cu) precursors and NaOH as precipitating agent (the aging... 

Signifcant downscaling of CMOS technology to provide high performance along with low power consumption has been accompanied by reliability degradations such as increased noise sensitivity and reliability concern due to aging phenomena (transient and permanent failuers). In this regard, with huge number of configuration bits, Field-Programmable Gate Arrays (FPGAs) are more susceptible to aging since aging not only degrades the performance, but also it may additionally result in corrupting the configuration cells and thus causing permanent circuit malfunctioning. While several works have investigated the aging effects in Look-Up Tables (LUTs), the routing fabric of these devices is seldom... 

Water-gas shift reaction (CO(g) + H2O(g) ↔ CO2(g) + H2(g)) is performed as the key step in the hydrogen and ammonia industrial plant. In this work, Fe/Cr/Cu high temperature water gas shift catalysts were synthesized by coprecipitation method, using sulfate precursors, in order to improve the catalytic performance and particular emphasis is placed on the catalytic activity affected by aging time, precipitating agent and ways of increasing the mechanical strength. Finally the prepared and industrial catalysts were compared when they were situated in the operating conditions (at 360oC and 2 bar) and were characterized by BET, XRD, TPR, TEM and crushing strength analysis. Catalysts being made... 

Today's latest technology integrated circuits are manufactured for a wide range of applications. With the constant increase in the usage rate of integrated circuits, designing a high reliable system is of utmost importance. The avoidance of counterfeit components is a major challenge of hardware security and trust. Counterfeit components cause lower performance and reduced life span. They are of great concern to the manufacturers and consumers of electronic systems, impacting the security and reliability of these systems. If these parts end up in critical applications like medical systems, satellites, aerospace, or power plants, the results could be catastrophic. So far, there are different... 

Reducing the size of transistors has dramatically increased the impacts of NBTI, HCI, and EM phenomena in comparison with decade ago. These phenomena are able to have influence on properties of different parts of a chip to make it changed gradually; including threshold voltage of a transistor and electrical conductivity of interconnections. These changes are known as the aging of a transistors that diminish the performance and reliability of a chip. A common reason that plays a significant role in all these phenomena is temperature. The temperature becomes more important when the power density increases per unit area due to decreased size of transistors, which is a trend in multi-core... 

In This thesis the properties of a compatible rubber compound for a specific chemical environment (acidic media) with high temperature and high pressure (HTHP) is studied. After primary studies, six formulations are designed on the basis of Nitrile rubber. after tensile and hardness tests at ambient temperature and 120 °C, samples putted in aging reservoir for aging tests. After that, tensile and hardness tests were performed again. Finally, by analyzing the results, the best formulation have chosen. Test results show that the NBR / PVC compound with higher filler load, has the best chemical resistance  

In this study, the aging of the LiFePO4/graphite cell was investigated in two different types of 18650 Li-ion batteries during cycling at various C-rates (0.5, 1, 2, 3, 4C) and high temperature under long-term cycling. An amount of 20% Capacity loss was considered as the end of the cycling. Batteries with a capacity of 1500 mAh after this capacity drop, experience 60, 120, 1502, and 2155 cycles, at the rates of 4, 3, 2, and 1C , and batteries with capacity of 1400 mAh was also 60, 360, 1100, 1000, and 805 cycles at a rate of 0.5C. Capacity decrease of the cell is in linear relationship with cycle number and the slope of the capacity-fading line increases with elevating current rate. Aging... 

Aging of rubber compounds at high temperature and pressure acidic gas is a challenge for using them for a long time. Therefore, in this thesis aging of NBR/PVC compounds against H¬2S and CO2 has been investigated. The main method have been used is Full Factorial Design of Experiment. The parameters have been examined are content of zinc oxide, plasticizer RPO ASTM 290 and antioxidant 4010 NA. The content have been set in tow levels and effect of each have investigated in ambient and 120 degree of centigrad temperature. The results show that the effect of antioxidant 4010 NA on aging of compounds is negative and zinc oxide and plasticizer RPO ASTM 290 are positive  

Despite the advantages of shrinking transistors’ dimensions, e.g. decrease in power consumption and fabrication cost and increase in their switching speed, it has an adverse impact on some characteristics of nano-scale (less than 130nm) transistors that can reduce the system lifetime. Bias Temperature Instability (BTI) and Hot Carrier Injection (HCI) are amongst the most important adverse effects of transistor shrinkage. These two effects, are known as transistor aging, decrease the switching speed of the transistors by increasing the threshold voltage and decreasing the charge carriers’ mobility in the channel of transistors. Temperature, operating voltage, and the size of transistors have... 

Due to outstanding advantages of polymeric insulators such as: hydrophobicity, impact resistance and lower weight, their application in the high voltage transmission and distribution lines is increased significantly, in recent years. The most important feature of these insulators is their hydrophobicity. Contamination and aging are some of the factors that weaken this important feature and reduce the reliability of these insulators. Due to aging effects partial discharges start on the surface of the composite insulators and increase by impact of external factors. This thesis examines the occurrence of partial discharge signals on polymeric insulators under: varying amounts of contamination,... 

Al-4.5% Cu alloy, an age-hardenable alloy, is an important alloy in industry due to such unique characteristics as high strength-to-weight ratio and considerable strength at elevated temperatures. In this study, the aim was to evaluate the combined effect of cooling rate and heat treatment on an A206 alloy having more impurities—especially iron—than the nominal specifications. To this end, the melt was poured in a five-step mold. Afterwards, each step was subjected to T4 and T6 treatments in order to study the changes compared to the as-cast samples. Ultimate tensile strength, yield strength, elongation, and grain size were determined by using tensile tests and optical microscopy,... 

Asphalt binders are known to exhibit an inherent ability to repair damage. Such selfhealing potentially affects the fatigue damage performance of bituminous materials. There is no consensus about the effect of aging and polymer modification on cohesive healing. Also, the effectiveness of rejuvenating agents have not been addressed in previous studies. In the current study, three healing indices are presented to precisely quantify the healing capacity of various binders. These indices have been defined using the damage characteristic curves derived from interrupted linear amplitude sweep (LAS) tests. Instantaneous healing (IH) describes immediate reduction in accumulated damage after the rest... 

Shrinking the dimensions of transistors in recent fabrication technologies has led to an increase in the aging rate of chips, as the most important challenge in reliability of new processors. Bias Temperature Instability (BTI) and Hot Carrier Injection (HCI) are amongst the most important adverse effect of transistor shrinkage. These two effects decrease the switching speed of transistors by increasing its threshold voltage over time. Threshold voltage shift causes timing violation in combinational parts of circuit and decreases the robustness of sequential parts against soft errors. Between different units of a processor, Arithmetic and Logic Unit (ALU) is one of the most susceptible units...