Sharif Digital Repository

Ground Source Heat Pumps (GSHP), as a renewable source heating, ventilating, and air conditioning (HVAC) technology, has the highest energy efficiency among different heat pump types. One of the major drawbacks of GSHPs is the long-term ground temperature variations as a result of heat accumulation or depletion in the ground. This contribution puts forward a novel ground thermal recovery system for horizontal ground heat exchangers in a hot climate. The proposed recovery system consists of open-loop horizontal Ground-Air Heat Exchangers (GAHEs) that are buried between the horizontal Ground-Water Heat Exchangers (GWHEs). A fan supplies ambient air to the GAHE pipes when the soil around GWHE... 

Silver (0) nanoparticles supported on silica-coated ferrite were synthesized to be used as an efficient and recyclable heterogeneous catalyst for oxidant-free dehydrogenation of alcohols to the corresponding carbonyl compounds. The catalyst can be easily recovered and reused for 8 reaction cycles without considerable loss of activity. The facile recovery of the catalyst is carried out by applying an external magnetic device. The catalyst was fully characterized by the techniques of TEM, SEM, XRD, EDS, ICP-AES, and VSM. This journal is  

A molybdate-based heterogeneous magnetic catalyst was synthesized and used in direct oxidation of various primary and secondary organic halides to the corresponding aldehydes and ketones using 30% H2O2 as an oxidant in ethanol. Various organic halides were oxidized to their corresponding aldehydes and ketones in good to excellent yields. The catalyst system can be easily separated by applying an external magnetic field and reused for 6 runs without any significant loss of catalytic activity. The catalyst was fully characterized by FT-IR, SEM, TEM, EDS, XRD, VSM, ICP-AES techniques, and elemental analysis (CHN)  

Langmuir probes (LP) are the most common diagnostics for the local measurement of very important plasma parameters such as plasma density, electron temperature, plasma potential and the electron energy distribution function (EEDF). In this paper the applicability of the first derivative Langmuir probe method in processing the electron part of the current-voltage (I-V) characteristics in IR-T1 Tokamak is reported. The EEDF at different radial positions in the edge region and Scrape off Layer (SOL) are derived and the values of the plasma potential, electron temperature and electron density are estimated. Results comparison between the first derivative method and Stangeby method shows a... 

Fe3O4@SiO2-Ag catalyst was found to be highly active and selective in the N-alkylation of amines with a variety of aromatic and linear alcohols. The heterogeneous nature of the Fe3O4@SiO2-Ag catalyst allows easy recovery and regeneration by applying an external magnet for six subsequent reaction cycles. The prepared catalyst was characterized using electron microscopy techniques, X-ray diffraction, vibrating sample magnetometry and atomic absorption spectroscopy. Copyright © 2017 John Wiley & Sons, Ltd  

A heterogeneous and recyclable catalyst with a high loading of silver nanoparticles was synthesized via the silver nanoparticles being supported onto the surface of magnetic nanoparticles coated with poly(4-vinylpyridine). The synthesized catalyst was used in the dehydrogenation of alcohols to corresponding carbonyl compounds. A broad diversity of alcohols was converted into their corresponding carbonyl compounds in excellent yields. The catalyst was easily recovered by applying an external magnetic field and reused for seven reaction cycles without considerable loss of activity. The catalyst was fully characterized using various techniques. Copyright © 2017 John Wiley & Sons, Ltd  

In this paper, proper and safe planning of excavation method and design of support system in very weak rocks with case study of control room of Silveh dam are discussed. Silveh earth-storage dam, with 102 m height; is under construction in North-West of Iran. Due to numerous and various tectonic occurrences, the area of dam site is known as a high activity zone of Iran. In purposed location of control room, bedrock contains mostly weathered and crushed Shale and Schist. 60 m overburden and finite aquifers are another specific concern of this project. In this paper by using 3D finite element modeling, different stages of excavation and support system installation have been analyzed for the... 

This paper presents a new method to simultaneously optimize components' size, set points of the control system and slope of PV panels of standalone hybrid energy systems (HESs) using the Passive Congregation PSO (PSOPC) approach. New control set points are defined for the HES, and a new operation strategy is presented based on the defined set points. The optimization algorithm determines the optimal values of the set points to efficiently optimize the HES operation. The effectiveness of the proposed control set points is finally verified through some numerical analyses. In this regard, the proposed optimization method is employed to optimize various HES configurations and compared with other... 

This paper presents a new method to simultaneously optimize components' size, set points of the control system and slope of PV panels of standalone hybrid energy systems (HESs) using the Passive Congregation PSO (PSOPC) approach. New control set points are defined for the HES, and a new operation strategy is presented based on the defined set points. The optimization algorithm determines the optimal values of the set points to efficiently optimize the HES operation. The effectiveness of the proposed control set points is finally verified through some numerical analyses. In this regard, the proposed optimization method is employed to optimize various HES configurations and compared with other... 

Free vibration analysis of a transversely stiffened circular thin hollow cylinder made of functionally graded materials (FGMs) is analytically evaluated. Functionally graded materials are inhomogeneous composites which are usually made from a mixture of metal and ceramic. The gradient compositional variation of the constituents from one surface to the other provides an elegant solution to the problem of high transverse shear stresses induced when two dissimilar materials with large differences in material properties are bonded. In this paper, application of an FGM made of two different materials is investigated by applying Ritz method. While cylinder is assumed to be thin, strain energy... 

In the present density functional theory study, we have compared intrinsic properties of non-natural nucleobases (acA, acG, acC, and acT nucleobases) such as proton affinities, gas phase acidities, tautomerization, and hydrogen-bonding properties with those in normal Watson-Crick nucleobases (A, G, C, T nucleobases). The hydrogen-bonding interactions in non-natural and Watson-Crick base pairs were studied at B3LYP/6-311++G (d,p) level regarding their geometries, energies, and topological features of the electron density. The quantum theory of atoms-in-molecule (QTAIM) and natural bond orbital (NBO) analyses were employed to elucidate the interaction characteristics in base pairs. The... 

This paper investigates the optimal operation of distribution feeder reconfiguration (DFR) strategy in the smart grids with high penetration of plug-in electric vehicles (PEVs) and correlated wind power generation. The increased utilization of PEVs in the system with stochastic volatile behavior along with the high penetration of renewable power sources such as wind turbines (WTs) can create new challenges in the system that will affect the DFR strategy greatly. In order to reach the most efficiency from the PEVs, the idea of vehicle-to-grid (V2G) is employed in this paper to make a bidirectional power flow (either charging/discharging or idle mode) strategy when providing the main charging... 

Distribution feeder reconfiguration (DFR) is a precious operation strategy that can improve the system from different aspects including total cost, reliability, and power quality. Nevertheless, the high complexity of the new smart grids has resulted in much uncertainty in the DFR problem that necessities the use of a sufficient stochastic framework to deal with them. In this way, this paper proposes a new stochastic framework based on cloud theory to account the uncertainties associated with multiobjective DFR problem from the reliability point of view. Cloud theory is constructed based on fuzzy theory and probability idea. In comparison with the Monte Carlo simulation method, cloud models... 

Three-dimensional porous scaffolds are essential in tissue engineering applications. One of the most conventional methods to form porosity in scaffolds is freeze-drying, which is not energy efficient and cost effective. Therefore in this work, it was experimentally investigated whether gelatin, with its unique mechanical properties and cell binding applications, could be used as a comprising polymer of scaffolds with porous structure made by the freeze-gelation method. Chitosan, gelatin and chitosan/gelatin scaffolds were fabricated by the freeze-gelation method and their behaviors, determined by analysis of scanning electron microscopy images, Fourier transform infrared spectroscopy,... 

In this study, a year-round dynamic simulation of a Combined Cooling, Heating and Power generation (CCHP) system has been performed. The proposed system is composed of an ejector cooling system, an Organic Rankine Cycle (ORC), a solar collector field, heat exchangers and hot and cold storage tanks. It is considered that, a portion of the system input energy is provided by a solar collector field and an auxiliary heater supplies the extra required energy. The dynamic simulation of the introduced CCHP system is performed. The developed model is used to evaluate a year-round performance of the system for a residential building located in Tehran. The obtained results indicated that the proposed... 

High mountains and cold climate in the north-west of Iran are critical factors for the design of optimized District Heating (DH) systems and energy-efficient buildings. It is essential to consider the Life Cycle Cost (LCC) that includes all costs, such as initial investment and operating costs, for designing an optimum DH system. Moreover, considering climate change for accurately predicting the required heating load is also necessary. In this research, a general optimization is carried out for the first time with the aim of a new design concept of a DH system according to a LCC, while considering all-involved parameters. This optimized design is based on various parameters such as ceiling... 

High mountains and cold climate in the north-west of Iran are critical factors for the design of optimized District Heating (DH) systems and energy-efficient buildings. It is essential to consider the Life Cycle Cost (LCC) that includes all costs, such as initial investment and operating costs, for designing an optimum DH system. Moreover, considering climate change for accurately predicting the required heating load is also necessary. In this research, a general optimization is carried out for the first time with the aim of a new design concept of a DH system according to a LCC, while considering all-involved parameters. This optimized design is based on various parameters such as ceiling... 

The pool boiling is one of the heat transfer mechanisms used in cooling systems. Using an external force to improve the efficiency of thermo-fluid systems is among the most effective approaches, and also highly applicable in enhancing heat transfer. In this study, the pool boiling of water, as the working fluid, in the presence of a variable magnetic field, is studied. To this end, ferromagnetic beads were placed on the boiling surface, and the effect of their movements due to a variable magnetic field was observed and measured. The number of beads was selected such that they would cover 1/3, 1/2 and 2/3 of the surface in different cases and the magnetic field was controlled by altering... 

The application of incinerators for the municipal solid waste (MSW) is growing due to the ability of such instruments to produce energy and, more specifically, reduce waste volume. In this paper, a numerical simulation of the combustion process with the help of the computational fluid dynamics (CFD) inside a portable (mobile) incinerator has been proposed. Such work is done to investigate the most critical parameters for a reliable design of a domestic portable incinerator, which is suitable for the Iranian food and waste culture. An old design of a simple incinerator has been used to apply the natural gas (NG), one of the available cheap fossil fuels in Iran. After that, the waste height,... 

In this paper, we study the problem of secret communication over a Compound Multiple Access Channel (MAC). In this channel, we assume that one of the transmitted messages is confidential that is only decoded by its corresponding receiver and kept secret from the other receiver. For this proposed setting (compound MAC with confidential messages), we derive general inner and outer bounds on the secrecy capacity region. Also, as examples, we investigate 'Less noisy' and 'Gaussian' versions of this channel, and extend the results of the discrete memoryless version to these cases. Moreover, providing numerical examples for the Gaussian case, we illustrate the comparison between achievable rate...