Sharif Digital Repository

In this paper, a decentralized controller for trajectory tracking of modular and reconfigurable robot manipulators is developed. The proposed control scheme uses joint-torque sensory feedback; also sliding mode control is employed to make both position and velocity tracking errors of robot manipulators globally converging to zero. Proposed scheme also guarantees that all signals in closed-loop systems will be bounded. In contrast to some of prior works in this scheme, each controller uses a smooth law to achieve its purposes. In this method, each controller uses only local information for producing control law hence separated controller can be used to control each module of manipulator and... 

Rolling-element bearing (REB) failure is one of the general damages in rotating machinery. In this manner, the correct prediction of remaining useful life (RUL) of REB is a crucial challenge to move forward the unwavering quality of the machines. One of the main difficulties in implementing data-driven methods for RUL prediction is to choose proper features that represent real damage progression. In this article, by using the outcomes of frequency analysis through the Envelope method, the initiated/existed defects on the ball bearings are identified. Also, new features based on developing faults of ball bearings is recommended to estimate RUL. Early-stage faults in ball bearings usually... 

In this paper, we investigate optimal coding strategies for a class of linear deterministic relay networks. The network under study is a relay network, with one source, one destination, and two relay nodes. Additionally, there is a disturbing source of signals that causes interference with the information signals received by the relay nodes. Our model captures the effect of the interference of message signals and disturbing signals on a single relay network, or the interference of signals from multiple relay networks with each other in the linear deterministic framework. For several ranges of the network parameters we find upper bounds on the maximum achievable source-destination rate in the... 

Heavy damages on structures caused by near field earthquakes in recent years has brought serious attention to this problem. An examination of previous records has shown significant differences for near field earthquakes, including a large energy pulse, unlike far field earthquakes. But as a general rule, the effects of near field earthquakes have been ignored in most building codes. The purpose of this paper is to investigate the effect of near field earthquakes on reinforced concrete (RC) moment frames. To achieve this goal, the Erduran damage index, an efficient way to calculate damage, was employed to analyze two 4- and 8-story RC moment frame buildings. The buildings with moderate and... 

This paper develops a stochastic multi-period mixed-integer model for collection, production, storage, and distribution of platelet in Blood Transfusion Organizations ranging from blood collection centers to clinical points. In this model, the age of platelet and ABO-Rh priority matching rules are incorporated based on the type of patient to raise the quality and safety of platelet transfusion services. At first, a discrete Markov Chain Process is applied to predict the number of donors. Afterwards, the uncertain demand is captured using a two-stage stochastic programming. A challenging aspect of applying stochastic programming in a dynamic setting is to construct an appropriate set of... 

Rolling element bearing (REB) failure is one of the general damages in rotating machinery. In this manner, the correct prediction of remaining useful life (RUL) of REB is a crucial challenge to move forward the unwavering quality of the machines. One of the main difficulties in implementing data-driven methods for RUL prediction is to choose proper features that represent real damage progression. In this article, by using the outcomes of frequency analysis through the envelope method, the initiated/existed defects on the ball bearings are identified. Also, new features based on developing faults of ball bearings are recommended to estimate RUL. Early-stage faults in ball bearings usually... 

The COVID-19 pandemic cast doubts on governments' traditional crisis responses and sparked a surge in citizen-led, participatory, bottom-up responses. Iran's experience is worth investigating because it relied significantly on citizen groups to manage the crisis despite long-term sanctions and extremely restricted resources. The authors undertook an exploratory case study using the grounded theory (GT) method and an online survey to explore Iran's confrontation. The central notion discovered was referred to as 'faith-driven civic engagement.’ The response was characterized by adaptability, promptness, and comprehensiveness. The causes and strategic orientations included intrinsic motives,... 

Background: Newcastle disease virus (NDV) has shown noticeable oncolytic properties, especially against cervical cancer. However, in order to improve the spread rate and oncotoxicity of the virus, employment of other therapeutic reagents would be helpful. It has been shown that some viral fusogenic membrane glycoproteins (FMGs) could facilitate viral propagation and increase the infection rate of tumor cells by oncolytic viruses. Additionally, immune checkpoint blockade has widely been investigated for its anti-tumor effects against several types of cancers. Here, we investigated for the first time whether the incorporation of influenza hemagglutinin-2 (HA2) FMG could improve the oncolytic... 

Natural and synthetic anion receptors are extensively employed, but the structures of their bound complexes are difficult to determine in the liquid phase. Infrared spectroscopy is used in this work to characterize the solution structures of bound anion receptors for the first time, and surprisingly only two of three hydroxyl groups of the neutral aliphatic triols are found to directly interact with Cl-. The binding constants of these triols with zero to three CF3 groups were measured in a polar environment, and KCD3CN(Cl-) = 1.1 × 106 M-1 for the tris(trifluoromethyl) derivative. This is a remarkably large value, and high selectivity with respect to interfering anions such as, Br-, NO3 -... 

Sit to stand (STS) is one of the most important activities of daily living that is shown to be affected in low back pain (LBP) patients. It requires a fundamental coordination action among all segments (DOFs) of the body in order to control important performance variables such as body's center of mass (CM) within base of support (BOS). In this study, possible differences in joint coordination and variability patterns between chronic LBP and healthy control subjects were investigated during STS task. Eleven adults with nonspecific chronic LBP and 12 healthy controls were recruited in the study. The participants performed the task in 3 exerimental conditions including: rigid surface, open eyes... 

Uncertainty of kidney exchange programs (KEP) is one of the main challenges that cause failure in most planned transplants to proceed to surgery. Unfortunately, this challenge usually decreases KEP performance in the real world. To face this challenge, we develop an efficient approach, consisting of scheduling methodology and recourse actions, to recover failing pairs and improve the number of successful transplants in KEPs. The developed policy can be implemented in two different schemes. The first scheme receives an optimal matching as an input and determines recourse actions and the sequence of disjoint cycles and chains for the given optimal matching. However, the second scheme does not... 

The strengthening behavior of particle reinforced metal-matrix composites is primarily attributed to the dislocation strengthening effect and the load transfer effect. To account for these two effects in a unified way, a new multi-scale approach is developed in this paper incorporating the aspect ratio effect into the geometrically necessary dislocation strengthening relationships. By making use of this multi-scale approach, the deformation behavior of metal-matrix composites (MMCs) and metal-matrix nanocomposites (MMNCs) as a function of size, volume fraction, aspect ratio, etc. of the particles has been investigated. Comparison with the previously proposed models and the available... 

A supramolecular linear-dendritic copolymer consisting of a polystyrene backbone and hanging hyperbranched polyglycerols was prepared and characterized. Host-guest interactions between β-cyclodextrin incorporated in the core of polyglycerol as a host and aromatic rings of polystyrene as guests lead to the formation of a supramolecular linear-dendritic copolymer. Supramolecules formed micelles in aqueous solutions which were able to encapsulate and transfer paclitaxel with a high loading capacity  

In this paper a two level supply chain system is studied, in which the final demand is assumed to be fuzzy with triangular membership function. The inventory control policy of (r, Q) is followed for this system and unsatisfied demand is assumed to be back ordered. The objective is to minimize the total cost of the system, including ordering, holding and shortage costs. The model happens to be a nonlinear programming. Considering the complexity arising from the model, we also develop a genetic algorithm to obtain a near-optimal solution. The method is illustrated through some numerical examples  

This paper puts forward a new methodology for time-variant seismic risk analysis of transportation networks. Risk here denotes the probability of exceeding the sum of direct loss due to repair costs of bridges in the network and indirect loss due to the reduced capacity for traffic flow. The proposed methodology employs reliability methods and a host of probabilistic models for earthquake events, damage, repair cost, downtime, and travel time, while accounting for time-varying phenomena of aging and discounting. A comprehensive application on the transportation network of Isfahan, Iran, is presented that features 64 bridges subject to seismicity from seven sources. © 2018 Taylor & Francis... 

This paper puts forward a new methodology for time-variant seismic risk analysis of transportation networks. Risk here denotes the probability of exceeding the sum of direct loss due to repair costs of bridges in the network and indirect loss due to the reduced capacity for traffic flow. The proposed methodology employs reliability methods and a host of probabilistic models for earthquake events, damage, repair cost, downtime, and travel time, while accounting for time-varying phenomena of aging and discounting. A comprehensive application on the transportation network of Isfahan, Iran, is presented that features 64 bridges subject to seismicity from seven sources. © 2018, © 2018 Taylor &... 

In this study the extrudate swell of polymer solutions is estimated using the microstructure of polymer molecules. When a flexible polymer chain goes through a narrow die shear stress exerting on the chain will cause the polymer chain to be stretched along the flow direction. After emerging from die all external stresses vanish immediately and the chains tend to recover their previous state due to elastic recovery. This phenomenon will results in a gradual increase in extrudate diameter and this is used as the key idea for estimating swell ratio. A Giesekus based conformational model was used in order to predict polymer chains microstructure everywhere in the domain. The resulting PDE set... 

Utilizing ground-based measurements to obtain water budget components, especially in large scale basins, is challenging due to the limitation in the spatiotemporal availability of in-situ data. In this paper, we propose a probabilistic framework for estimating water budgets in low runoff regions using remote sensing products. By studying water budgets in the Central Basin of Iran (CBI) over 8 years period (2009–2016), we investigate the locations and time scales at which the water budget calculated from satellite products provides most closure. To this end, we use precipitation from the Tropical Rainfall Measuring Mission (TRMM), evapotranspiration from the Water Productivity Open Access... 

The spatiotemporal dynamic of salinity concentration (SC) in saline lakes is strongly dependent on the rate of water flow into the lake, water circulation, wind speed, evaporation rate, and the phenomenon of salt precipitation and dissolution. Although in-situ observations most reliably quantify water quality metrics, the spatiotemporal distribution of such data are typically limited and cannot be readily extrapolated for either long-term projections or extensive areas. Alternatively, remotely sensed imagery has facilitated less expensive and a stronger ability to estimate water quality over a wide range of spatiotemporal resolutions. This study introduces an adaptive learning model that... 

The interaction between a lake and groundwater has important implications to the quantity and quality of water in both environments. Quantification of lake-groundwater interaction (LGI) has been challenging in regions with limited in-situ data. LGI can be quantified by physically-based models, direct measurement of seepage, measurements of conservative chemical or isotopic tracers, and lake water balance. Despite the accuracy of the methods based on hydrochemical or isotopic measurements and analysis, they require extensive field data that are costly to collect in large lakes. Instead, the data required to quantify LGI by the lake water budget method can be obtained via typical ground...