Sharif Digital Repository

Alaboratory testing program was conducted to investigate the effects of microstructure on the water retention curve (WRC) and wetting-drying induced volume change in loess. The axis translation and vapor equilibrium techniques were adopted to control suction in the range of 0-400 kPa and 4-140 MPa, respectively. Hysteresis in the WRC of loess was observed for the entire range of suction studied. Compared to re-compacted loess, intact loess exhibits a more pronounced hysteresis in the suction range below 20 kPa, which can be explained by the ink-bottle pore neck effect or constricted pores. The hypothesis is supported by microstructural evidence of mercury intrusion porosimetry and scanning... 

It is shown that a compact MOSFET-aging model for circuit simulation is possible by considering the dynamic trap-density increase, which is induced during circuit operation. The dynamic trap/detrap phenomenon, which influences the switching performance, is also considered on the basis of well-known previous results. Stress-dependent hot-carrier effect and NBTI effect, origins of the device aging, are modeled during the circuit simulation for each device by integrating the substrate current as well as by determining the oxide-field change due to the trapped carriers over the individual stress-duration periods. A self-consistent solution can be obtained only by iteratively solving the Poisson... 

Purpose: Many construction projects are implemented in open-environment job sites and can be significantly affected by various weather conditions. Evaluating the overall impacts of the weather conditions on a project can assist project managers to prepare effectively. Nevertheless, methods measuring the overall adverse impacts of the job sites’ weather condition on the project performance are still missing. This study aims to address this gap. Design/methodology/approach: In this investigation, a survey-based method was proposed to evaluate the overall impacts of the weather conditions on the construction project resources through a new indicator called job site weather index (JWI). The... 

Purpose: Motivated by the high cost of material movements in road construction projects, past studies have used analytical methods to optimize materials logistics plans. A key shortcoming of these methods is their inability to capture the uncertain, dynamic and complex characteristics of the road construction material logistics. Failure to incorporate these characteristics can lead to sub-optimal results. The purpose of this study is to propose the use of discrete event simulation (DES) to address the existing shortfall. Design/methodology/approach: Despite the powerful capabilities of DES models in capturing the operational complexities of construction projects, they have not been... 

Optimizing highway alignment requires a versatile set of cost functions and an efficient search method to achieve the best design. Because of numerous highway design considerations, this issue is classified as a constrained problem. Moreover, because of the infinite number of possible solutions for the problem and the continuous search space, highway alignment optimization is a complex problem. In this study, a customized particle swarm optimization algorithm was used to search for a near-optimal highway alignment, which is a compound of several tangents, consisting of circular (for horizontal design) and parabolic (for vertical alignment) curves. The selected highway alignment should meet... 

This paper presents a three-dimensional phenomenological constitutive model for magnetic shape memory alloys (MSMAs), developed within the framework of irreversible continuum thermodynamics. To this end, a proper set of internal variables is introduced to reflect the microstructural consequences on the material macroscopic behavior. Moreover, a stress-dependent thermodynamic force threshold for variant reorientation is introduced which improves the model accuracy. Preassumed kinetic equations for magnetic domain volume fractions, decoupled equations for magnetization unit vectors and appropriate presentation of the limit function for martensite variant reorientation lead to a simple... 

This study investigates the effect of stress magnitude and stress history on porosity and permeability values of anhydride and carbonate rocks. Porosity and permeability properties are measured for twelve anhydride and carbonate core samples under stress loading and unloading conditions. The results of permeability measurements show that tighter core samples are more stress dependent while the anhydride samples are generally more sensitive to the stress. The gap between stress loading and unloading (hysteresis) is more considerable at lower effective stress values. The results also indicate that the hysteresis is more noticeable in the anhydride core samples. The gas slippage factor is also... 

Preventive pavement maintenance methods such as slurry seals are cost-effective treatments that increase the longevity of pavements. The incorporation of recycled materials such as reclaimed asphalt pavement (RAP) into asphalt pavement helps to further reduce costs and energy consumption. The present research studied the feasibility of incorporating RAP into slurry seal mixtures or RAP slurry seals. Two slurry seal mixtures containing cement and hydrated lime as fillers were tested. The first mixture comprised slurry seal made with virgin aggregate and the second used RAP as the aggregate. The wet track abrasion test (WTAT) and loaded wheel test (LWT) were conducted to evaluate the...