Sharif Digital Repository

Soils are generally considered anisotropic with respect to hydraulic conductivity, while the evolution of anisotropy condition is unknown for bare and vegetated soils. Therefore, the main goal of this study is to compare the anisotropic hydraulic conductivity of as-compacted, bare, and vegetated specimens. Accordingly, a series of 54 hydraulic conductivity tests were conducted in a custom-made cube triaxial permeameter. The as-compacted specimens were revealed isotropic because the loosely packed preparation procedure resulted in a dominant flocculent structure. However, a fivefold increase in the anisotropy ratio of bare specimens was measured along the isotropic loading path because of the... 

The microscopic features of binary solvent systems formed by molecular solvents (methanol, ethanol, 2-methylpropan-2-ol, water, pyridine, acetonitrile, 1-propanol, 2-propanol, dimethylformamide) and the ionic liquid ([bmim]BF 4) as cosolvent were used to select mixed solvents with particular characteristics. Molecular-microscopic solvent parameters corresponding to these binary mixtures were utilised to study the kinetics of the nucleophilic substitution reaction between 2-chloro-3,5-dinitropyridine and aniline to investigate and compare the effects of the solvents on a model chemical reaction. For these mixtures, the solvation behaviour is dominated by both the dipolarity/ polarisability... 

Abstract Cu-15%NbC (volume fraction) powder was synthesized using the starting powders of Cu, Nb and graphite in a high energy vibratory disc mill for 7 h of milling under argon atmosphere. A composite sample and a Cu/NbC functionally graded material (FGM) sample were produced by using the two-step press and sintering at 900 °C for 1 h under vacuum. The microstructure and physical and mechanical properties of the specimens were investigated. The field emission scanning electron microscopy, energy dispersive X-ray and X-ray diffraction analysis confirmed the synthesis of the nanostructure matrix of 18-27 nm with the nanoparticles reinforcement of 42 nm after sintering, verifying the thermal... 

Shallow landslides can be mitigated through the hydro-mechanical reinforcement provided by vegetation. Several critical parameters, such as plant spacing and plant age, play a significant role in influencing bioengineered slope stability facilitated by vegetation. However, the coupling of these effects on the stability of vegetated slope has been ignored. The objective of this study is to investigate the hydro-mechanical impact of vegetation growth and spacing on the stability of bioengineered slopes based on the predictions of a calibrated numerical model against field measurements. The impact of vegetation is investigated, with specific attention given to different plant spacing and growth... 

Crashworthiness, energy absorption capacity, and safety are important factors in the design of lightweight vehicles made of fiber-reinforced polymer composite (FRP) components. The relatively recent emergence of the nanotechnology industry has presented a novel means to augment the mechanical properties of various materials. As a result, recent attempts have contemplated the use of nanoparticles to further improve the resiliency of resins, especially when resins are used for mating FRP components. Therefore, a comprehensive understanding of the response of nanoreinforced polymer composites, subjected to various rates of loading, is of paramount importance for developing reliable structures.... 

This paper presents a novel DLL-based frequency synthesizer architecture to generate fractional multiples of reference frequency and reduce the power consumption of the frequency synthesis block. The architecture is adopted for French VHF application as an example. The DLL architecture allows for minimal area, while consuming low power. The proposed circuit can operate at a substantially low supply voltage. The circuit level and system level designs are presented. It was shown that for the mentioned standard, a mere 27 delay stages for VCDL are sufficient to cover French VHF band. Simulation results confirm the analytical predictions. The proposed DLL-based frequency synthesizer is... 

Shallow landslides triggered by heavy rainfalls have caused casualties and economic losses to domestic infrastructures and industries worldwide. Rainfall mainly reduces the soil matric suction and the shear resistance, resulting in shallow landslides. Vegetation is an eco-friendly and cost-effective method for stabilizing slopes prone to shallow landslides. This research aims to investigate the hydrological and mechanical effects of vegetation on slope stability through a numerical study approach. Vegetated and bare slopes were subjected to a recorded climate condition and two rainfall scenarios of high intensity (HI) and low intensity (LI). Matric suction and factor of safety of vegetated... 

The microscopic features of binary solvent systems formed by molecular solvents (methanol, ethanol, 2-methylpropan-2-ol, water, pyridine, acetonitrile, 1-propanol, 2-propanol, dimethylformamide) and the ionic liquid ([bmim]BF4) as cosolvent were used to select mixed solvents with particular characteristics. Molecular-microscopic solvent parameters corresponding to these binary mixtures were utilised to study the kinetics of the nucleophilic substitution reaction between 2-chloro-3,5-dinitropyridine and aniline to investigate and compare the effects of the solvents on a model chemical reaction. For these mixtures, the solvation behaviour is dominated by both the dipolarity/ polarisability and... 

In this study, the effect of the geometrical parameters of the Lateral Flow Immunoassay (LFI) membrane on the performance of the pregnancy kits is investigated. Consequently, a new geometry for LFI membrane is proposed based on some theoretical, numerical and experimental observations in order to improve the performance of the related kits. A pregnancy kit (for the detection of hCG in urine samples) is developed and the effect of the relocation of the test and the control lines over the membrane was studied based on the variation of the sample fluid velocity. Using Lattice-Boltzmann simulation of the lateral flow within the porous media and the experimental results, the fluid flow within the... 

Background The cornea plays a role in the refractive power of the eye, and when its natural curvature and thickness are compromised by diseases such as keratoconus or high myopia, this results in loss of visual acuity. Intracorneal rings (ICRs) were developed as a treatment option to restore the natural corneal curvature by implanting rings into tunnels cut within the corneal stroma. However, selecting and placing the appropriate ring can be difficult, and predicting refractive outcomes is challenging. Objective The purpose of this study was to better understand the design parameters of the rings that determine postoperative refractive and mechanical outcomes. Methods We developed an... 

The Model Driven Architecture (MDA) is meant to facilitate system development by using models for representing both the "problem" and its "solution". In its ideal form, software development based on MDA would follow a development process that begins by producing models of the problem domain at a high level of abstraction, and then proceeds by gradually and automatically transforming them into executable code with the help of tools. However, MDA-based development has encountered several setbacks, the mitigation of which requires detailed scrutiny and analysis. In this research, MDA-based development is analyzed through applying SWOT (Strengths, Weaknesses, Opportunities, and Threats) analysis... 

The gas-phase kinetics of diallyl sulfide pyrolysis were studied experimentally and theoretically in a static system over the temperature range 433-463 K and a total pressure of 80 Torr in a glass vessel with the free radical inhibitor cyclohexene. The experimental results show that this reaction is homogeneous, unimolecular and follows a first-order rate law. Theoretical studies at the B3LYP/6-31G* computational level indicate that the elimination reaction proceeds through a six-centered cyclic transition state and the reaction mechanism is concerted and non-synchronous. Copyright © 2003 John Wiley & Sons, Ltd