Sharif Digital Repository

This research evaluates the effect of filler type and content on rutting resistance of asphaltic materials by using laboratory experiments. To examine the effect of filler type, two traditional fillers (Silica sandstone powder and Portland cement) and a new recycled lime powder (Eggshell) were considered. To investigate the effect of filler content, three different filler contents were used. Marshall Stability test was performed on full mixes in order to determine the optimum binder content of the mixtures. Then, the static creep test was performed on Fine Aggregate Matrix (FAM) samples. The permanent strain after 10 minutes of recovery (PS-660) was considered as the indicator of potential... 

In this study, the optimal sizing and performance analysis of a standalone integrated solar power system equipped with different storage scenarios to supply the power demand of a household is presented. One of the main purposes when applying solar energy resource is to face the increasing environmental pollutions resulting from fossil fuel based electricity sector. To this end, and to compare and examine two energy storage technologies (battery and hydrogen storage technology), three storage scenarios including battery only, hydrogen storage technology only and hybrid storage options are evaluated. An optimization framework based on Energy Hub concept is used to determine the optimum sizes... 

The techno-economic and environmental performance of hybrid solar hydrogen energy systems was investigated to provide combined cooling, heating and power (CCHP) demands of a standalone greenhouse in Iran to achieve sustainable agriculture based on an optimization procedure. From the environmental point of view, by deploying hybrid energy systems, 83%, to 100% of emissions can be avoided. Also a sensitivity analysis was performed on the hybrid energy systems in order to study the effect of major parameter variation on the systems justification. It was concluded that hybrid solar systems are economically competitive with conventional systems, for high solar intensity locations with high diesel... 

In this paper, hydrogen management in refineries is examined considering a new perspective to optimize refinery costs. In order to minimize the total annual cost in refineries a mixed-integer non-linear programming (MINLP) model has been developed. Retrofitting the hydrogen network and determining the hydrogen surplus capacity of refineries are the main outputs of the proposed model. Then, to utilize this surplus capacity and increase the profitability of refineries, surplus hydrogen is used to produce electricity and ammonia. The results of a case study showed that retrofitting of the hydrogen network can save 12% in the consumption of fresh hydrogen from hydrogen plants. After retrofitting... 

Common rail diesel engines with electronic fuel injection can accurately meter the fuel injection quantity with more accurate fuel injection control capability. In this work a common rail fuel injection system of a single cylinder diesel engine has been proposed and the important parameters like injection pressure, energizing time and high pressure pipes diameter and length are designed such that to be compatible with the engine basic design in case of pressure waves and injected mass variations. A one-dimensional approach has been used to model the injector using AMESim code in which Adiabatic models have been used to model injector system. Injected mass quantity has been calculated for... 

The sand–bentonite mixture is used as the buffer layer in nuclear waste disposals. The buffer layer, as a non-permeable protective layer, is generally exposed to temperature gradients and the long-term subjection to temperature results in creep and more intact structure for the layer. In the present study, thermally induced structure and its effects on the isotropic compression behavior and volume change behavior of buffer layer are evaluated. Thermal consolidation tests were conducted using a modified triaxial cell capable of handling temperatures up to 90 °C. In order to investigate the effects of thermal gradients on the behavior of the mixture, saturated specimens were cured at constant... 

With all the improvement in wave and hydrodynamics numerical models, the question rises in our mind that how the accuracy of the forcing functions and their input can affect the results. In this paper, a commonly used numerical third-generation wave model, SWAN is applied to predict waves in Lake Michigan. Wind data are analyzed to determine wind variation frequency over Lake Michigan. Wave predictions uncertainty due to wind local effects are compared during a period where wind has a fairly constant speed and direction over the northern and southern basins. The study shows that despite model calibration in Lake Michigan area, the model deficiency arises from ignoring wind effects in small... 

Aseismic base isolation is an effective method used to protect structures and their contents against earthquakes. An isolated structure may be designed to remain elastic throughout major ground motions as a result of the efficiency of the isolation systems. In this paper, the equations of motion of two-dimensional elastic structures supported on a new base isolation system called the Sliding Concave Foundation (SCF) are presented and a procedure for their solution is suggested. The responses of a number of structures subjected to different earthquake records are evaluated and the results are compared with those of the same structures supported on two other famous isolation systems and also a... 

In this work, a method for increasing the storage capability of a solar thermal energy system has been discussed. The system includes two tanks with the flexibility in choosing the best storage medium on the basis of the solar collector's outlet temperature. The results show that using such a hybrid storage system, the storable energy can be increased. Comparing the results with those for simple common storage systems, the extent of improvement was calculated. For verification of the results, a small pilot system was assembled. The test apparatus operated during 2008-2009 cold months and the parameters were recorded. Comparison of the theoretical and experimental results showed a good... 

In this work we used the vacuum distillation residue from an Iranian heavy crude oil refinery in a solvent deasphalting (SDA) process using different temperatures (60-120°C), pressures (5-9 bar), solvents (n-pentane and ethyl acetate), and solvent to feed ratios (3 to 1, 5 to 1, and 7 to 1). The resulting products included deasphalted oil (DAO) and residue (PITCH). The DAO yields in SDA when n-pentane was used as solvent were significantly higher than those when ethyl acetate was used as solvent. The DAO was subsequently processed by thermal cracking at 500°C and atmospheric pressure to investigate the effect of solvent deasphalting processing conditions on the yield of coke and liquid... 

Hydrolysis kinetics of the lead silicate glass (LSG) with 40 mol% PbO in 0.5 N HNO3 aqueous acid solution was investigated. The surface morphology and the gel layer thickness were studied by scanning electron microscopy (SEM) micrographs. Energy dispersive X-ray spectroscopy (EDS) and inductively coupled plasma spectroscopy (ICP) were used to determine the composition of the gel layer and the aqueous solution, respectively. The silicon content of the dissolution products was determined by using weight-loss data and compositions of the gel layer and the solution. The kinetic parameters were determined using the shrinking-core-model (SCM) for rate controlling step. The activation energy... 

In this paper, a new base isolation system, namely the sliding concave foundation (SCF), is introduced and the behaviour of the buildings using such a system is theoretically investigated. A building supported on the new system behaves like a compound pendulum during seismic excitation. The pendulum behaviour accompanied by the large radius of foundation curvature shifts the fundamental period of the system to a high value (e.g. more than 8 sec), in a frequency range where none of the previously recorded earthquakes had considerable energy. This results in a large decrease in the structural responses. Since small friction forces are essential on the contact surfaces, PTFE sheets can be used... 

This article describes the hydrogen storage capacity in different carbon nanotubes. The hydrogen storage capacities in the armchair, zigzag, and chiral nanotubes are investigated. The hydrogen storing capacities as a function of the carbon nanotube (CNT) diameter are investigated for the single-walled (SWNT), multi-walled (MWNT), and CNT bundles and results are compared. Hydrogen storage capacity in SWNTs is increased by increasing the nanotube diameter. For diameter d=0.3887 nm of (5,0) CNT the hydrogen capacity is 0.99%, while for the (17,17) SWNT with a diameter d=2.289 nm the capacity is increased to 5.06%. In comparison of different MWNTs for a common external diameter d=1.6064 nm the... 

The single-photon strong coupling in the deep-resolved sideband of the optomechanical system induces photon blockade (PB) effect. For the PB cavity, an initial mechanical coherent state evolves into superposition of phonon cat states entangled with the cavity Fock states. Measurement of the cavity photon number states produces phonon even and odd cat states. The information leakage effect of two photon states on the fidelity of cat states is calculated, it is shown that for low average phonon number this effect is negligible and decreases by increasing the two photon cavity state. The Lindblad equation is solved numerically to obtain the environmental effects on the fidelity of cat states  

Gait training is a critical rehabilitation procedure for patients suffering from walking problems. It, however, puts the therapist in high orthopedic risk since he should prevent the patient from possible falling. Body weight support system is a new technology helping such patients and the involved therapist by unloading a percent of the patient's weight. A new over-ground body weight support is introduced in this article. The system is composed of two main modules namely unloading and traction. The unloading module is capable of suspending an individual's weight up to 1000N dynamically. The whole system is attached to an overhead rail, moving over the head of the patient by the traction... 

Wireless mesh networks (WMNs) are well-promising future networks especially for ubiquitous connection to Internet. In this paper, we propose an analytical model in order to evaluate the maximum stable throughput of a WMN based on a simplified version of IEEE 802.11s MAC protocol. Our modeling approach is based on a multi-class open queueing network. In this respect, we map some of the important features of IEEE 802.11s MAC protocol, esp., its contention-based and contention-free periods onto different parameters of the proposed queueing network. By solving the related traffic equations and applying the stability condition, we determine the maximum stable throughput, i.e., the maximum packet... 

The shear behavior of a cemented gravely sand that can be considered as the representative of Tehran alluvium has been studied using triaxial equipment. Artificially cemented samples were prepared using gypsum plaster as the cementing agent. The plaster was mixed with the base soil at the weight percentages between 1.5 and 6. The critical state concepts were used to illustrate the mechanical behavior of tested soil. © 2005 ejge