Sharif Digital Repository

Hydrogen is considered to be the fuel of the future. It is a cleaner alternative to the fossil fuels we consume every day. Of all the different hydrogen production pathways that exist, producing the gas by utilizing the power generated by renewable energy sources has been a topic of interest for many researchers across the world. The following work focuses on minimizing the energy loss by optimizing the size and the operating conditions of an electrolyzer directly connected to a photovoltaic (PV) module at different irradiance. The hydrogen, in the proposed system, is produced using a proton exchange membrane (PEM) electrolyzer. A nonlinear method is considered, because of the complexity of... 

We propose an all-optical arbitration architecture to resolve end-point contention in the optical networks-on-chip. The proposed architecture reduces on-chip optical power and energy losses by 37% and 21%, respectively, compared to Corona's token-based control plane  

One of the most prominent issues in fully adiabatic circuits is the breaking reversibility problem; i.e., non-adiabatic energy dissipation in the last stage adiabatic gates whose outputs are connected to external circuits. In this paper, we show that the breaking reversibility problem can result in significant energy dissipation. Subsequently, we propose an efficient technique to address the breaking reversibility problem, which is applicable to the usual fully adiabatic logic such as 2LAL, SCRL, and RERL. Detailed SPICE simulations are used to evaluate the proposed technique. The experimental results show that the proposed technique can considerably reduce (e.g., about 74% for RERL, 35% for... 

We propose a new optical reconfigurable Network-on-Chip (NoC), named ReFaT ONoC (Reconfigurable Flat and Tree Optical NoC). ReFaT is a dynamically reconfigurable architecture, which customizes the topology and routing paths based on the application characteristics. ReFaT, as an all-optical NoC, routes optical packets based on their wavelengths. For this purpose, we propose a novel architecture for the optical switch, which eliminates the need for optical resource reservation, and thus avoids the corresponding latency and area overheads. As a key idea for dynamic reconfiguration, each application is mapped to a specific set of wavelengths and utilizes its dedicated routing algorithm. We... 

Energy constraint is the most critical problem in wireless sensor networks (WSNs). To address this issue, clustering has been introduced as an efficient way for routing. However, the available clustering algorithms do not efficiently consider the geographical information of nodes in cluster-head election. This leads to uneven distribution of cluster-heads and unbalanced cluster sizes that brings about uneven energy dissipation in clusters. In this paper, an Efficient Distributed Cluster-head Election technique for Load balancing (EDCEL) is proposed. The main criterion of the algorithm, dispersal of cluster-heads, is achieved by increasing the Euclidian distance between cluster-heads.... 

Charge recovery is a promising concept to design (cryptographic) VLSI circuits with low energy dissipation. However, unsatisfactory designs of proposed logic cells degrade its theoretical efficiency significantly both in its energy consumption and the resistance against differential power analysis attacks (DPA-attacks). Short circuit dissipation and non-adiabatic discharging of capacitance loads are the two major sources of this degradation which are addressed in this paper. In order to reduce these dissipation significantly, we manipulate threshold voltage of circuits transistors by body biasing. To evaluate the efficiency of our method we select a common charge recovery logic called 2N2N2P... 

In this paper, the hysteresis in the tipsample interaction force in noncontact force microscopy (NC-AFM) is measured with the aid of atomistic dynamics simulations. The observed hysteresis in the interaction force and displacement of the system atoms leads to the loss of energy during imaging of the sample surface. Using molecular dynamics simulations it is shown that the mechanism of the energy dissipation occurs due to bistabilities caused by atomic jumps of the surface and tip atoms in the contact region. The conducted simulations demonstrate that when a gold coated nano-probe is brought close to the Au(0 0 1) surface, the tip apex atom jumps to the surface, and instantaneously, four... 

The effect of an intermediate standing baffle on the flow structure in a rectangular open channel has been investigated by a three-dimensional acoustic Doppler velocimeter. Investigation of time-averaged velocity profiles at different streamwise positions reveals that the approach flow is fully developed upstream of the baffle. By analysing the space-averaged power spectra of streamwise velocity, a peak structure was observed in the upstream baffle region. Downstream of the baffle this peak structure has been alleviated by the baffle. The same analysis for the vertical component indicates the existence of a peak structure both up- and downstream of the baffle. Consequently, a baffle affects... 

In this paper, we extract analytical models for data transmission delay, power consumption, and energy dissipation of optical and traditional NoCs. Utilizing extracted models, we compare optical NoC with electrical one for varying values of link length and degree of multiplexing and calculate lower bound limit on the optical link length below which optical on-chip network loses its efficiency. Based on this constraint, we propose a novel hierarchical on-chip network architecture, named as H2NoC, which benefits from optical transmissions in large scale SoCs and overcomes the scalability problem resulted from lower bound limit on the optical link length. Performing a series of simulation-based... 

A new structural connection with special unique features was developed. While under bending it showed very high rotational capacity, in shear, unlike other existing connections, it also demonstrated a large shear deformation capacity. The ductile response of this connection stems from its innovative geometry as well as the ductility of the elements embedded in it. Since the previous shear tests on the specimens of this connection were carried out under 'unrestricted' conditions, the tests reported here were all under 'restricted' conditions. These shear tests consisted of 'monotonie' as well as 'cyclic' tests on mild steel specimens. Due to the restrictions imposed on the specimens during... 

The paper presents a conceptual study on modification of the electric arc furnace (EAF) slag doors in order to allow removal of the excess slag from the EAF. The idea behind additional slag doors is to allow deslagging of the bath in certain unfavorable cases when the slag height is too great. Slags which exceed the optimal height cause unnecessary refractory corrosion and additional energy losses. The study proposes symmetric slag doors comprised of two hatches, i.e. upper and lower. The upper hatch is intended to decrease the slag height to the optimal level, while the lower hatch can be used to completely deslag the EAF at tapping. In this manner, tilting of the EAF is not necessary. A... 

Structural engineers have recognized unstiffened Steel Plate Shear Wall (SPSW) as an economical lateral resisting system due to the post-buckling capacity, energy dissipation, and deformability. This study investigates practical application of an added Energy Absorbent Element (EAE), subjoined to the SPSW in order to improve seismic behavior of the SPSW. The EAE is an aluminum shear panel with or without bracings and surrounding frame. Furthermore, a series of parametric studies are implemented to examine the effect of dimensions, position, and formation of the EAE. It is assumed that the lateral loading is applied as quasi-static loading. Further, nonlinearity of the material and the... 

Greenhouses are complex systems that require considerable amounts of energy. In order to optimize their performance, it is necessary to reduce the amount of energy per unit of crop produced. This requires a combined assessment of greenhouse energy balance and crop growth, as well as their interaction. In this work, more than 30 existing greenhouse models are reviewed and different algorithms are combined to propose an integrated energy-yield model. The physical model of greenhouse energy demand is based on the dynamic energy and mass balance while yield production is based on a physiological crop model. The integrated model is validated with observed energy demand and crop yield datasets... 

When a droplet impinges on a hot surface it is crucial to increase the contact time or decrease the rebounding distance if the heat transfer between the droplet and the surface is important. This will be more sensitive when the temperature regime is above the Leidenfrost values. The focus of the present experimental study is on the maximum height of drop bouncing after impinging on flat and semi-cylindrical concave surfaces, in particular in terms of surface temperature. It is shown that the behavior of the lamella during the spreading to its maximum diameter has a considerable impact on the maximum height of the drop bouncing. For different impact Weber numbers the map of thermal versus... 

When a droplet impinges on a hot surface it is crucial to increase the contact time or decrease the rebounding distance if the heat transfer between the droplet and the surface is important. This will be more sensitive when the temperature regime is above the Leidenfrost values. The focus of the present experimental study is on the maximum height of drop bouncing after impinging on flat and semi-cylindrical concave surfaces, in particular in terms of surface temperature. It is shown that the behavior of the lamella during the spreading to its maximum diameter has a considerable impact on the maximum height of the drop bouncing. For different impact Weber numbers the map of thermal versus... 

With the emergence of various battery operated technologies in different computing domains and the challenge of heating in such technologies, the issue of energy dissipation has become more critical than ever before. In such systems, energy constraints in one hand, and heat generation, on the other hand, necessitates the employment of energy efficient technologies in the fabrication of digital circuits. One possible solution for mitigating the energy dissipation in digital circuits is the use of adiabatic families in the process of designing computing devices. Adiabatic circuits are designed mainly based on the principles of thermodynamics and provide a paradigm shift in the design of... 

Nowadays, one of the biggest concerns in the world is increasing the CO2 emissions and global warming due to the over-consumption of fossil fuels. In addition, under the intense market competition, the demand for more efficient systems with higher performance and lower energy consumption has escalated. Since the drag force contributes to a considerable percentage of the energy loss and reducing the performance, a large number of studies have been conducted to improve the surface characteristics and, subsequently, declining the drag force. Making the surface superhydrophobic is one of the most effective ways for this purpose. In this work, two different superhydrophobic surfaces using SiO2... 

The interface behavior of rock and concrete and between layers of concrete highly affects the performance of concrete dam structures. In this investigation, a modified direct shear test was implemented in the laboratory to evaluate the interface behavior between (1) rock and conventional vibrated concrete (CVC), (2) rock and roller compacted concrete (RCC), (3) CVC and RCC and (4) two layers of RCC. Series of in situ shear tests were also performed between rock and concrete. The friction angle and cohesion for all tested interface were determined and analyzed. The effect of uniaxial compressive strength (UCS) of concrete on the interface behavior was determined. Additionally, the effect of...