Sharif Digital Repository

In the present study, a ratiometric fluorescent sensor array as an artificial tongue has been developed on a nanopaper platform for chemical discrimination applications. The bacterial cellulose (BC) nanopaper was utilized for the first time as a novel, flexible, and transparent substrate in the optical sensor arrays for developing high-performance artificial tongues. To fabricate this platform, the hydrophobic walls on the BC nanopaper substrates were successfully created using a laser printing technology. In addition, we have used the interesting photoluminescence (PL) properties of an immobilized ratiometric probe (carbon dot-Rhodamine B (CD-RhB) nanohybrids) on the nanopaper platform to... 

Nowadays, fluidized bed plays an important part in industry. The design of this kind of reactor requires knowing the interfacial area between two phases and this interfacial area leads to calculate the solid holdup in the bed. Consequently achieving interfacial area between gas and solid in the bed experimentally is so significant. On interfacial area measurement in fluidized bed with gas has been worked, but light transmission technique has been used less. Therefore, in the current research the possibility of using of this technique and its accuracy are investigated. Measuring, a fluidized bed was designed and the problems were averted as far as possible. By using fine solid with equal... 

One of the most important problems in teleoperation systems is time delay and packet loss in the communication channel, which can affect transparency and stability. One way to overcome the time delay effects in a teleoperation system is to predict the master-side motion. In this way, when data is received in the slave side, it will be considered as the current position of the master robot and, thus, complete transparency could be achieved. The majority of the previous works regarding operator position prediction have considered known and constant time delay in the system; however, in the real applications, time delay is unknown and variable. In this paper, an adaptive online prediction... 

Gold nanoparticles are widely used as high efficient photon-thermal energy converters in a broad range of applications. This paper presents a theoretical investigation on using the optothermal properties of gold nanoparticle arrays to generate nanoscale molten and rubbery regions on the surface of an amorphous polymeric film. Nanoparticles are assumed to be embedded in a transparent silica layer and illuminated with a 7.5 ns pulsed laser at 532 nm. Simulation results are presented for systems with single gold nanoparticles, dimers and chains. Both electromagnetic and thermal interaction between nanoparticles are found to be important factors in determining the result of surface processing.... 

In this research, response surface methodology (RSM) was applied to study the effects of Na-Montmorillonite (Na-MMT) and glycerol on some functional properties of corn starch films. Films were prepared by casting method according to central composite design (CCD). Originally image processing technique was used in order to estimate transparency of the films. It was found that Na-MMT absorbed UV light from 216 to 266. nm. No antimicrobial activities were observed against Escherichia coli and Staphylococcus aureus. Contact angle analysis revealed hydrophilicity of starch films decreased utilizing nanoparticles and increased with plasticizer content. Increase in glycerol content decreased... 

Design and operation of three different optical designs based on the light intensity modulation for investigation of the humidity effects on the air index of refraction are described. The measurement variable is the transmitted power, which depends on the refractive index of the medium in the path of a fiber-to-fiber optical design. Three different probes (probe #1, #2, and #3) are tested in which probe #1 and probe #2 can also check the presence of water or any other transparent liquid in the gap between the two axial fibers. Performances of the new systems are tested as a refractive index monitoring mean and experimental results are given. The variations of the modulated powers as... 

In this study operation of an optical design based on the intensity modulation for the refractive index change has been described. The reported instrument measures the transmitted output power depending up on the medium refractive index in the light path of a fiber-to-fiber design. A liquid cell is located between the fibers in the light path and power variations for different cold and hot water levels in the cell are measured. By using a reference humidity meter the calibration curve representing the relative humidity (%RH) as a function of the transmitted output power is obtained. For the hot water with the final temperature of T = 32.7°C the output power range of 255.0 -313.OnW is... 

Proper modeling of the human arm dynamic, as it interacts with telemanipulation and haptic systems, is important in enhancing the transparency of these systems. In this article, we introduced an adaptive identifier to estimate the impedance characteristic of a human operator as it interacts with a single translational degree of freedom mechanism. The five parameter model, including an extra spring and damper for a better approximation of the dynamic behavior of human arm, has been used. Since the impedance characteristic of human arm differs from one individual to another, it is important to estimate these parameters for each individual and update the controller to enhance the transparency... 

Conventionally, a film of TiO2 particles of 300 nm size is employed in Dye-sensitized solar cells (DSCs) as the back reflector film to enhance the light harvesting. Perfect reflectance of silver in visible and near infrared motivates to investigate its potential as the material for the light back reflector film in DSCs. In this study, light back reflector films consisting of 300 nm-sized silver particles, as well as vacuum evaporated silver flat film, were fabricated and compared to 300 nm-sized rutile-type TiO2 particulate reflector film to study their optical aspects. Conventional TiO2 rutile-type particulate film demonstrates slightly lower performance... 

Performance of a haptic device is evaluated based on the concept of transparency which indicates the match between the impedance transmitted to the user and the target virtual impedance. Stability of a haptic device prevalently has been evaluated based on the passivity criterion. Due to conservativeness of passivity, it appears as an obstacle to improve transparency. In this paper, passivity is suggested to be replaced by the complementary stability criterion which accounts for the robust stability of the interaction in the presence of uncertain user hand dynamics In this respect, an algorithm is proposed which guarantees transparency of the haptic device in a stable manner. Assuming that... 

The study of air-water, two-phase flows in hydraulic structures such as pressurized flow tunnels, culverts, sewer pipes, junctions, and similar conduits is of great importance for design purposes. Air can be provided by vortices at water intakes, pumping stations, aerators, steep channels, etc. Under certain conditions, air may also be introduced into pressurized intake systems, which may form large bubbles in portions of the pipe. The bubbles may, in turn, cause an unstable slug flow, or other flow patterns, that leads to sever periodic transient pressure. In this paper, an experimental model (a circular and transparent pipeline, 90 mm in ID and 10 m in length) is used to predict pressure... 

Transparency is a measure of performance in haptic devices. In order to improve transparency and reduce the difference between the impedance transmitted to the user and the target impedance it is necessary to compensate for the dynamics of the haptic device. Due to stability reasons improvement of transparency is limited. Passivity as a stability criterion has been used widely in design and analysis of haptic devices, Since passivity is a conservative criterion, it acts as an obstacle in improving transparency of the haptic interfaces. In this paper instead of passivity, robust stability of the interaction is studied in the presence of parametric uncertainties due to variations in user hand... 

Magnetic polyvinyl alcohol (M-PVA) films were prepared via solution casting filled with surface modified superparamagnetic nanoparticles (M-NPs). The M-NPs were coated with citric acid during synthesis. The chemical interaction between the citric acid and M-NPs was confirmed by Fourier transform infrared spectroscopy (FTIR). The average hydrodynamic diameter of M-NPs was 19.7 nm measured by dynamic light scattering DLS and appeared almost spherical in scanning electron microscopy (SEM). The M-NPs were uniformly dispersed in polyvinyl alcohol (PVA) matrix and showed high optical transparency with good mechanical properties. M-PVA hydrogels were synthesized using gamma irradiation. The... 

Carbon nanotubes (CNT) have unique electronic properties and remarkable optical properties. Despite of on layer thickness of CNTs, it has able to absorb photons from visible to far infrared and terahertz. These unique properties lets to create heterojunction devices by semiconductor/CNTs or metal/CNTs junctions e.g. photodiodes, sensor and heterojunction solar cell. The CNTs can play the role of a heterojunction component for charge separation as a high conductive network for charge transport and as a transparent electrode for light illumination and charge collection. The main objective of the present article is to establish a relation between interface recombination and the characteristics... 

Today’s the technology based on dye-sensitized solar cells (DSSCs) has an important role in all photovoltaic system technologies. DSSCs can generate electricity with various degrees of transparency; this makes it suitable for use in various industries, especially in construction industry as smart windows. In fact DSSC can produce electricity and having natural light, simultaneously. It is obvious that DSSCs need to absorb solar radiation as much as possible. Since, the effective use of all incident lights leads to an increase in cell efficiency and this increase in efficiency is related to the amount of dye adsorbed on the surface of nanostructured electrode, so higher amount of dye for... 

Nowadays, exoskeletons have been gaining popularity due to their potential use in rehabilitation and augmentation. These robots often utilize series elastic actuators to facilitate compliant interaction with the human. Numerous studies have been carried out with the purpose of identification and control of these type of actuators. The goal of this paper is to provide a method for dynamic modeling and identification of series elastic actuators. This model is then used in the control loop as a feed-forward term to eliminate the actuator's dynamics. Each series elastic actuator used in the Sharif wearable robot, uses a brushless DC motor, a torsional spring, a harmonic drive, a timing belt, a... 

Using low molecular weight polyethylenimine (PEI), transparent thin films of TiO2 nanoparticles were prepared by layer-by-layer self assembly method. UV-visible spectrophotometry was employed in a quantitative manner to monitor the adsorbed mass of TiO2 and PEI after each dip cycle. The adsorption of both TiO2 and PEI showed a saturation dip time of 10 min. The effect of dip time on the growth mode and surface morphology was investigated by scanning electron microscopy (SEM) and non-contact atomic force microscopy (AFM). It was found that growth proceeds in the form of laterally broad islands in case of short dip times, and taller but laterally smaller islands in case of longer dip times. A... 

Material design and input field properties limit high-harmonic excitation efficiency of surface-plasmon polaritons (SPPs) in a nanoscopic device. We remedy these limitations by developing a concept for a plasmonic waveguide that exploits spatiotemporal control of a weak surface polaritonic field to create efficient four-wave mixing (FWM) and periodic phase singularities. Our configuration comprises four-level double 3-type atomic medium (43 As) doped in a lossless dielectric situated above a negative-index metamaterial (NIMM) layer. We report the coherent excitation and propagation of the multiple surface polaritonic shock waves (SWs) and establish the highly efficient frequency combs by... 

A novel nanohybrid composite of TiO2, SiO2, γ-Fe2O3, and reduced graphene oxide (TiO2@Si:Fe:rGO) is fabricated by the sol-gel method. The properties of the coated film were examined by structural and self-cleaning analyses using simulated discoloration/soiling and roofing tests. The fabricated transparent TiO2@Si:Fe:rGO composite showed excellent photoactivity and wettability, behaving well in self-cleaning applications. The addition of SiO2 improved the crystalline structure and surface hydroxylation of TiO2 nanoparticles. γ-Fe2O3 decreased the recombination rate of e-/h+ pairs, and significantly improved photocatalytic activity under visible light. Moreover, rGO sheets as excellent...