Sharif Digital Repository

This paper is concerned with a distributed model predictive control (DMPC) method that is based on a distributed optimisation method with two-level architecture for communication. Feasibility (constraints satisfaction by the approximated solution), convergence and optimality of this distributed optimisation method are mathematically proved. For an automated irrigation channel, the satisfactory performance of the proposed DMPC method in attenuation of the undesired upstream transient error propagation and amplification phenomenon is illustrated and compared with the performance of another DMPC method that exploits a single-level architecture for communication. It is illustrated that the DMPC... 

Users often have very specific visual content in mind that they are searching for. The most natural way to communicate this content to an image search engine is to use key-words that specify various properties or attributes of the content. A naive way of dealing with such multi-attribute queries is the following: train a classifier for each attribute independently, and then combine their scores on images to judge their fit to the query. We argue that this may not be the most effective or efficient approach. Conjunctions of attribute often correspond to very characteristic appearances. It would thus be beneficial to train classifiers that detect these conjunctions as a whole. But not all... 

This work presents results on the development of robust H∞ control strategy for Networked Control Systems (NCSs) by involving uncertainties in both communication and controlled plant subsystems. The network-induced delays in both communication links (to and from the controller) are assumed to behave as Markov chains. An analytical approach is presented to calculate the transition probabilities of the Markovian network-induced delays. By employing the augmentation method, the resultant system is converted into a delay-free uncertain singular Markovian jump system with bounded transition probabilities. New conditions are established to assure that the uncertain NCS satisfies an H∞ performance... 

This article is concerned with remote monitoring and control of the 2-degrees of freedom (DoF) robotic manipulators, which have nonlinear dynamics over the packet erasure channel, which is an abstract model for communication over the Internet, WiFi, or Zigbee modules. This type of communication is subject to imperfections, such as random packet dropout and rate distortion. These imperfections cause a significant challenge for monitoring and control of robotic manipulators in the industrial environments because sensitive data, such as sensor data and control commands may not ever reach to their destination resulting in significant performance degradation. Therefore, the effects of these... 

Nowadays, the salinisation of groundwaters causes a substantial reduction in the yield of agricultural lands. To reduce the impact of this problem on the profitability of the lands, farmers tend to use desalination processes. However, this transition is not simple and some technical, economic, and environmental issues should be considered. In this study, we highlight some key factors for the use of desalination processes in the agricultural sector. Also, we conduct a techno-economic evaluation of using reverse osmosis desalination in a pistachio orchard as a high-value crop. Moreover, because of the solar energy potential in the location of the case study, the use of solar panels is assessed... 

MEG regeneration and injection unit regenerates aqueous MEG. The main goal of this unit is approaching desired MEG concentration whereas MEG loss via removed water is a big issue. Circulating glycol is polluted with Ca++ and Mg++ which forms carbonate scale and causes plugging of pipe lines, filters, lean/rich exchanger, still column packings and reboiler tube bundle and decreases their efficiency, consequently increases MEG loss via top product. Different alternatives exist according to similar experiences around the world. Using specific criteria and AHP (Analytical Hierarchy Process) method priority of these alternatives has been found. Results are as following: 1. Increasing number of... 

In this study, maleic anhydride grafted polypropylene microporous flat-sheet membranes were prepared via a thermally induced phase separation method with a mixture of dibutyl phthalate and dioctyl phthalate as a diluent. The effects of the polymer composition and coagulation bath temperature on the morphology and performance of the fabricated membranes were investigated. The hydrophilicity results of the membranes demonstrated that membrane modification reduced the water contact angle by about 45°, whereas the pure water flux was enhanced about four times. The antifouling behavior of the fabricated membranes was also investigated in a membrane bioreactor. The results show that the pure water... 

In this paper, we address the stability problem of a noiseless linear time invariant control system over parallel Gaussian channels with feedback. It is shown that the eigenvalues-rate condition which has been proved as a necessary condition, is also sufficient for stability over parallel Gaussian channels. In fact, it is proved that for stabilizing a control system over the parallel Gaussian channels, it suffices that the Shannon channel capacity obtained by the water filling technique is greater than the sum of the logarithm of the unstable eigenvalues magnitude. In order to prove this sufficient condition, we propose a new nonlinear joint source channel coding for parallel Gaussian... 

In this study, three equations of state (EOS) in conjunction with computational fluid dynamics (CFD) modeling were used to predict the Joule – Thomson (JT) process behavior for natural gas and various pure gases. The JT effect is encountered in several industrial applications. The experimental determination of the JT coefficient (JTC) is complicated, and there is little gas pressure-volume-temperature (PVT) data available for estimating these JTC. Thus, the development of an efficient model to predict the JT effect in industrial processes is necessary. This study was carried out to attain a clear view of the single phase-flow of hydrocarbons and nitrogen in the JT process with CFD modeling.... 

The use of solar-powered reverse osmosis desalination systems is a sustainable and environmentally friendly solution in the desalination industry. However, there are some substantial technical and economic challenges due to the intermittency and fluctuation of solar energy. Recent technological improvement and feed-in tariff policies enable these systems to be competitive with conventional grid-connected reverse osmosis systems. In this paper, a feasibility study of the integration of solar panels with the grid to power small-scale reverse osmosis systems (namely up to 2000 m3/day) is conducted in Iran, as a country with a low price of electricity. For this purpose, a city located on the... 

The use of solar-powered reverse osmosis desalination systems is a sustainable and environmentally friendly solution in the desalination industry. However, there are some substantial technical and economic challenges due to the intermittency and fluctuation of solar energy. Recent technological improvement and feed-in tariff policies enable these systems to be competitive with conventional grid-connected reverse osmosis systems. In this paper, a feasibility study of the integration of solar panels with the grid to power small-scale reverse osmosis systems (namely up to 2000 m3/day) is conducted in Iran, as a country with a low price of electricity. For this purpose, a city located on the... 

This paper is concerned with tracking state trajectory at remote controller, stability and performance of linear time-invariant noiseless dynamic systems with multiple observations over the packet erasure network subject to random packet dropout and transmission delay that does not necessarily use feedback channel full time. Three cases are considered in this paper: (1) without feedback channel, (2) with feedback channel intermittently and (3) with full time availability of feedback channel. For all three cases, coding strategies that result in reliable tracking of state trajectory at remote controller with asymptotically zero mean absolute estimation error are presented. Asymptotic mean... 

This paper is concerned with the stability of linear time-invariant dynamic systems over the packet erasure channel subject to minimum bit rate constraint when an encoder and a decoder are unaware of the control signal. This assumption results in co-designing the encoder, decoder and controller. The encoder, decoder, controller and conditions relating transmission rate to packet erasure probability and eigenvalues of the system matrix A are presented for almost sure asymptotic stability of linear time-invariant dynamic systems over the packet erasure channel with feedback acknowledgment. When the eigenvalues of the system matrix A are real valued, it is shown that the obtained condition for... 

In this paper a sub-optimal control technique is proposed for a linear Gaussian system with a few distributed interacting sub-systems. Controller of each sub-system has only access to its own measurement and a noisy version of measurement and control vectors of other sub-systems that are communicated through an Additive White Gaussian Noise (AWGN) communication network. The power to be allocated to each transmitter antenna is calculated so that the received signal is the transmitted signal plus additive white Gaussian noise. Under some conditions it is shown that the proposed sub-optimal control technique results in bounded mean square stability. The satisfactory performance of the proposed... 

This paper is concerned with the stability of nonlinear Lipschitz systems subject to bounded process and measurement noises when transmission from sensor to controller is subject to distortion due to quantization. A stabilizing technique and a sufficient condition relating transmission rate to Lipschitz coefficients are presented for almost sure asymptotic bounded stability of nonlinear uncertain Lipschitz systems. In the absence of process and measurement noises, it is shown that the proposed stabilizing technique results in almost sure asymptotic stability. Computer simulations illustrate the satisfactory performance of the proposed technique for almost sure asymptotic bounded stability... 

In this research, surface modification of aromatic polyamide thin film composite (TFC) reverse osmosis (RO) membranes was carried out using dielectric barrier discharge (DBD) plasma treatment to improve the performance and fouling resistance of prepared RO membranes. First, polyamide TFC RO membranes were synthesized via interfacial polymerization of m-phenylenediamine and trimesoyl chloride monomers over microporous polysulfone support membrane. Next, the DBD plasma treatment with 15 s, 30 s, 60 s, and 90 s duration was used for surface modification. The surface properties of RO membranes were characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR),... 

In this research, surface modification of aromatic polyamide thin film composite (TFC) reverse osmosis (RO) membranes was carried out using dielectric barrier discharge (DBD) plasma treatment to improve the performance and fouling resistance of prepared RO membranes. First, polyamide TFC RO membranes were synthesized via interfacial polymerization of m-phenylenediamine and trimesoyl chloride monomers over microporous polysulfone support membrane. Next, the DBD plasma treatment with 15 s, 30 s, 60 s, and 90 s duration was used for surface modification. The surface properties of RO membranes were characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR),... 

The natural gas liquid recovery is an important process in a gas plant to correct hydrocarbon dew point and earn profit. In this study, a natural gas liquid recovery unit operated based on the Joule–Thomson process was investigated and its performance was optimized. To improve the system performance, the plant configuration and intermediate pressure ratio were defined as the variables and maximization of the natural gas liquid recovery rate and maximization of exergy efficiency were defined as the objective functions. To improve the plant performance, the amount of natural gas liquid recovery rate should be increased. To achieve this goal, several scenarios for the intermediate pressure... 

A thermodynamic analysis was conducted on the Joule-Thomson (JT) process to improve separation performance and exergy efficiency of a three-stage throttling process in a natural gas liquid (NGL) recovery plant. The JT inversion curve (JTIC) along with the phase envelope diagram (PED) were used to study phase transition during the throttling process. Three different objective functions—maximization of NGL recovery rate, improvement of cooling performance, and minimization of the exergy destruction—were investigated in this study to increase the NGL recovery rate with minimum energy consumption. It was observed that the improvement of cooling performance did not always increase the NGL... 

In this study, six cubic equations of state (CEoSs) were used to predict the Joule-Thomson coefficient (JTC), specific heat capacity (SHC), inversion curve (IC) and outlet temperature of the Joule-Thomson (JT) valve parameters. The accuracy of each CEoS was evaluated from the comparison of experimental data with obtained results. Of the six CEoSs, three-paramter CEoSs— Esmaeilzadeh and Roshanfekr (ER), Harmen and Knapp (HK), and Patel and Teja (PT)— were more accurate than two-paramter equations— Nasrifar and Moshfeghian (NM), Peng-Robinson (PR), and Soave-Redlich-Kwong (SRK). Ironically, original SRK showed the optimum accuracy in estimation of JTC. In addition, the Joule-Thomson inversion...