Sharif Digital Repository

Flooding algorithm is one of the most significant algorithms used in sensor networks. Although simple, this algorithm causes a large amount of energy and bandwidth to be wasted. The most important application of flooding is RREQ flooding in initial step of most routing algorithms. Although simple, this algorithm causes a large amount of energy and bandwidth to be wasted. Most previous efficient flooding algorithms use location information which is impossible for simple node in sensor network. Some others are not suitable for RREQ flooding due to eliminating redundant retransmissions. We present a modified flooding that simultaneously decreases energy consumption as well as network delay.... 

The bulk of the worldwide annual commercial production of ethylene is based on thermal cracking of petroleum hydrocarbons with steam. In this research, the effect of coil outlet temperature on the reactor yield has been studied. In order to investigate a reliable mathematical correlation, several data points were obtained by adjusting coil outlet temperature in a real plant. In order to investigate best coil outlet temperature, an objective function was represented. Based on the obtained mathematical correlation and the assumed objective function, it was found that best coil outlet temperature for investigating maximum income is 1,128 K  

Most of the energy efficient routing algorithms proposed for sensor networks are reactive routing algorithms. By definition, reactive algorithms are those in which routes are constructed whenever there is data transmission. In such algorithms, to transmit data packets from a certain transmitter to the corresponding receiver, efficient route will be constructed using RREQ delivery. This delivery is performed via flooding and modified flooding algorithms. One of the most important criteria of such flooding algorithm is not to miss the best final route during RREQ delivery. Most of major algorithms ignored this fact and instead tried to minimize energy consumption during flooding algorithm. But... 

In a SEnsor Network with Mobile Agents (SENMA) is an architecture proposed for large scale sensor networks. In sensor networks, a fraction of the packets generated by only part of the sensors is sufficient to provide a good estimation of all network information. SENMA uses this inherent redundancy. However, the performance of such system is limited by estimation errors and packet errors due to collision. Estimation error is a major problem in applications such as habitat monitoring in which information is a function of node position. In this paper, we first derive the equations of distortion in a general scenario and use this model to compare the estimation error for regular networks. Then... 

Efficient operation of urban water systems necessitates accurate water demand forecasting. We present daily, weekly, and monthly water demand forecasting using dynamic artificial neural network (DAN2), focused time-delay neural network (FTDNN), and K-nearest neighbor (KNN) models for the city of Tehran. The daily model investigates whether partitioning weekdays into weekends and non-weekends can improve forecast results; it did not. The weekly model yielded good results by using the summation of the daily forecast values into their corresponding weeks. The monthly results showed that partitioning the year into high and low seasons can improve forecast accuracy. All three models offer very... 

In this paper a modified neighbor aware medium-access control protocol is proposed designed for wireless sensor networks. Wireless sensor networks are generally comprised of battery powered nodes. These nodes are densely deployed in an ad-hoc structure. The main objective for sensor networks is low power consumption while latency is less important. This leads different MAC layer design for wireless sensor networks compared to conventional ad hoc protocols. In this paper we propose a neighbor aware medium access control to reduce power consumption. This protocol is derived from Modified Distributed mediation device (MDMD) protocol and uses useful properties of this protocol while improves the... 

A SEnsor Network with Mobile Agents (SENMA) is an architecture proposed for large scale sensor networks in which the access point moves above the network and gathers information from a limited number of nodes. However, the performance of such system is limited by estimation errors and packet errors due to collision. In this paper, we first derive the equations of distortion in a general scenario and use this model to obtain four best node positions in order to achieve min-max estimation error in a square. In addition, an opportunistic MAC is proposed that considers both collision effects and estimation error based on Channel State Information (CSI). As the simulation results show the... 

The purpose of the present paper is to develop light beam method to measurement of interfacial area in a rectangular gas-liquid bubble column. Total interfacial area can be determined in bubble column filled by transparent liquid by light transmission method. According to pervious researches, the fraction of parallel light is function of interfacial area and optical path length that these two parameters imply Transmission Number or N T. The drop diameters were measured in the range of 2.2 to 5 mm, and in this range, the specific area is found to depend only upon the light transmission. Three different systems with various liquid phases have been used in this work. It had been proved that... 

Using multiple antennas at the transmit and receive sides of a passive radar brings both the benefits of MIMO radar and passive radar. However one of the obstacles arisen in such configuration is the receive antennas placement in proper positions so that the radar performance is improved. Here we just consider the case of positioning one receiver among multiple illuminators of opportunity. Indeed it is a start for the solution of optimizing the geometry of the multiple receivers in a passive radar  

SbCl3 supported on montmorillonite K-10 is an efficient catalyst for the ring opening of epoxides with aromatic amines under solvent-free conditions and microwave irradiation to give the corresponding b-amino alcohols in high yields with high regioselectivity  

In this paper, we consider an integrated sensing and communication (ISAC) system with wireless power transfer (WPT) where an unmanned aerial vehicle (UAV)-based radar serves a group of energy-limited communication users in addition to its sensing functionality. In this architecture, the radar senses the environment in phase 1 (namely sensing phase) and mean-while, the communications users (nodes) harvest and store the energy from the radar transmit signal. The stored energy is then used for information transmission from the nodes to UAV in phase 2, i.e., uplink phase. Performance of the radar system depends on the transmit signal as well as the receive filter; the energy of the transmit... 

One of the important obstacles in MIMO (Multiple Input Multiple Output) radars is the issue of designing proper transmit signals. Indeed, the capability of signal design is a significant advantage in MIMO radars, through which, the system can achieve much better performance. Many different aspects of this performance improvement have been considered yet, and the transmit signals have been designed to attain such goal, e.g., getting higher SNR or better detector's performance at the receiver. However, an important tool for evaluating the radar's performance is its ambiguity function. In this paper, we consider the problem of transmit signal design, in order to optimize the ambiguity function... 

Two gains play key roles in recently developed MIMO wireless communication systems: "spatial diversity" gain and "spatial multiplexing" gain. The diversity gain refers to the capability to decrease the error rate of the MIMO channel, while the multiplexing gain implicitly refers to the amount of increase in the capacity of the MIMO channel. It has been shown that there is a fundamental tradeoff between these two types of gains, meaning interplay between increasing reliability (via an increase in the diversity gain) and increasing data rate (via an increase in the multiplexing gain). On the other hand, recently, MIMO radars have attracted much attention for their superior ability to enhance... 

It is a well known fact that using multiple antennas at transmit and receive sides improves the detection performance. However, in such multiple-input multiple-output (MIMO) configuration, proper positioning of transmitters and receivers is a big challenge that can have significant influence on the performance of the overall system. In addition, determining the power of each transmitter under a total power constraint is a problem that should be solved in order to enhance the performance and coverage of such a system. In this paper, we design the Neyman-Pearson detector under the Rayleigh scatter model and use it to introduce a criterion for the antenna placement at both transmit and receive... 

There has been much interest, recently, towards exploiting the Multiple-Input Multiple-Output (MIMO) technique in radar. It is shown that using multiple antennas at transmit and receive sides can improve the performance of the system. However, in order to analyze the system's performance, its ambiguity function, i.e. the ambiguity function of a MIMO radar, is needed to be defined. In this paper, beginning from the information theoretic definitions, we derive such function, specifically for a MIMO radar with widely separated antennas  

By combining the two ideas of MIMO (Multiple Input Multiple Output) and PCL (Passive Coherent Location) in radar, one can achieve the advantages of both recently developed techniques simultaneously. While using multiple antennas at the receive side provides a spatial diversity of the object to be detected, using multiple illuminators of opportunity, most importantly, makes the radar covert to the interceptors. One obstacle in such MIMO configuration is choosing the positions of the receive antennas. In this paper, after analyzing the Neyman-Pearson detector for the DVB-T based PCL, we introduce the probability of missed detection as a criterion to place the receive antenna. Here, we only... 

One of the most important obstacles in passive radar applications is removing the direct signal from the target channel. Otherwise, week echoes from the targets in the target channel would be ignored due to the limited dynamic range of the system. One of the most effective techniques in this field is using adaptive filters. In this paper various adaptive filters are introduced and their performances are shown and compared  

It has been shown that using multiple antennas in a radar system improves the performance considerably, since multiple target echoes are received from different aspect angles of the target. In this way, the target detection is improved. However, when using multiple antennas, some problems, such as designing the transmit signals, synchronization, etc. emerge that should be solved. One of such problems is the receiver placement. Receiver placement deals with choosing a proper position for the receive antenna in order to optimize the whole system's performance. In this paper, a receiver placement procedure based on improving the radar ambiguity function is proposed for the case of a multisite... 

By employing the MIMO (multiple-input-multiple-output) technology in radar, some new problems emerged, that, in order to benefit the MIMO gains in radar, it was necessary to solve them suitably. One of such obstacles is determining the positions of receive antennas in a MIMO radar system with widely separated antennas (WS MIMO radar), since it is shown that the antennas' positions affect the whole system's performance considerably. In this study, a proper receivers' positioning procedure is proposed. To do this end, four criteria are developed based on the proposed MIMO detector and the MIMO ambiguity function. The simulations verify that the proposed positioning procedure improves the...