Sharif Digital Repository

Abstract: Surface-nanostructured TiO2 nanorods were synthesized hydrothermally at 180 °C. Such nanorods have ‘crack-like’ surfaces that resemble burnt charcoal. Compared to nanorods with relatively smoother surfaces, the charcoal-like nanorods have higher-specific surface areas. By using the nanorods as a light-scattering layer in double-layered dye-sensitized solar cells, the cells based on the charcoal-like nanorods have 20 % higher dye loading and also higher diffuse reflectance compared with cells utilizing ‘smooth’ nanorods. The efficiency of a screen-printed double-layer dye-sensitized solar cell based on the charcoal-like nanorods is higher at 7.29 %. Electrochemical... 

Morphology tailored TiO2 nano assemblies consisting of nanorods with and without nanoparticle attachments were hydrothermally synthesized and their characteristics and light scattering properties were determined by x-ray diffraction (XRD), nitrogen sorption analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), electrochemical impedance spectroscopy (EIS) and ultraviolet-visible spectroscopy (UV-Vis). The nanorod-nanoparticles (NR-NP) assemblies and smooth nanorod (NR) double layers were screen printed onto fluorine doped tin oxide coated glass underlayers to fabricate dye-sensitized solar cell (DSSC) photoanodes. The double layer heterogeneous... 

Abstract: Here, the synthesis of TiO2 rutile nanorod arrays (TiO2 NRs) decorated with bimetallic gold–palladium cocatalyst nanoparticles (AuPd NPs) is described. The modified photoelectrode was characterized by field-emission scanning electron microscopy, high-resolution transmission electron microscopy, energy-dispersive spectroscopy, X-ray diffraction analysis, X-ray photoelectron spectroscopy, UV–vis spectroscopy, and electrochemical impedance spectroscopy (EIS). AuPd–TiO2 NRs (AuPd–TiO2) demonstrate high photocatalytic activity for photoelectrochemical (PEC) water splitting. The tailored structure of AuPd–TiO2 depicts a boosted photocurrent of 3.36 mA cm−2 under AM 1.5 illumination... 

In this paper, we report a promising sunlight-driven screen-printed TiO2 porous nanorods (PNR) photoanode decorated with Au plasmonic nanostructures for photoelectrochemical (PEC) light-to-electricity conversion. Fabricated photoanodes were characterized using field emission scanning electron microscopy, high-resolution transmission electron microscopy, energy dispersive spectroscopy, X-Ray diffraction analysis, X-ray photoelectron spectroscopy, N2 adsorption-desorption isotherms, UV–vis spectroscopy and electrochemical impedance spectroscopy in detail. The Au-PNR-TiO2 photoanode demonstrates superior PEC activities both under simulated sunlight and visible light irradiation. Interestingly,... 

Brain-computer interface (BCI) systems enable individuals to control external devices through brain activity. Among the various paradigms in the BCI domain, steady-state visual evoked potentials (SSVEPs) are particularly dominant. One of the most effective methods for frequency detection in SSVEP-based BCIs is canonical correlation analysis (CCA). In standard CCA, a sine-cosine signal is used as a reference signal, which may not be optimal for SSVEP recognition. In this paper, we propose a novel graph reference signal that preserves a sinusoidal form, yet exhibits temporal smoothness on a graph learned from the reference signal. We employ an alternating optimization approach to obtain the... 

During construction of one of the Sahand cooling towers due to slip forming performance some imperfections were raised mostly between elevation of +30 and +40 meter. It was evaluated that some points of the shell should be repaired. In constructing the cooling tower from elevation +40 to +60 meter these imperfections were removed and the cooling tower was constructed with no problem until the elevation +130 meter. In this paper reasons of generation of geometric imperfections in Sahand cooling tower are clearly shown and possible ways for preventing them are discussed. Applied repairing method for Sahand cooling tower is explained in detail. Geometrical imperfections of the constructed... 

In this work, the parametric study of a vapor compression refrigeration system integrated with a PCM storage tank for increasing the condenser sub-cooled temperature has been conducted based on the hottest day in Tehran city. The effects of various parameters such as comfort zone temperature, condenser and evaporator temperatures, and changes in heat transfer coefficient relative to the thickness of the ice formation in the PCM tank have been considered for simulating the desired system in the EES software. The focus of this study is to figure out the system's performance according to the changes in the effective parameters of the PCM storage tank. The results indicate that adding the PCM... 

In this study, the combination of a vapor compression cycle with a phase change material (PCM) storage tank has been assessed experimentally during the hottest day based on Tehran city climatic conditions. The temperature conditions for outdoor (condenser, compressor, etc.) and indoor (evaporator) air conditioning (AC) units are provided with the help of two separate test chambers and a controller system. The desired system has been surveyed based on two scenarios. In each scenario, the system is evaluated for the conventional AC system (with no PCM involved) and the AC plus PCM unit (conventional AC + PCM storage tank). Based on scenario 1 operating strategy, the results show that adding... 

In this study, a vapor compression refrigeration cycle integrated with a phase change material (PCM) storage tank has been dynamically simulated over a 24-h period. The primary objective of this system is to reduce electric energy consumption during on-peak hours (12:00–19:00) and shift it to off-peak hours (1:00–10:00). During off-peak hours, the vapor compression refrigeration system stores cooling energy in the PCM storage tank. The stored cooling energy is then reused during on-peak hours to pre-cool the condenser inlet refrigerant, enhancing the cooling system's performance and reducing electric consumption during on-peak hours. Oleic acid, eutectic mixtures of 45 % capric acid and 55 %... 

Steady State Visual Evoked Potential (SSVEP)-based Brain Computer Interfaces (BCIs) is one of the most prevalent methods in BCIs. The main purpose of these systems is to detect the frequency of SSVEP to understand which visual stimulus a person is looking at. Various methods have been proposed to detect the frequency of SSVEP. One of the most widely used methods is the Canonical Correlation Analysis (CCA) algorithm. Despite the simplicity and efficiency of the CCA algorithm, none of the methods based on CCA have incorporated the graph structure presented in the EEG and reference signals into the CCA cost function. In this paper, we introduce a novel approach that considers the graph... 

Diagnosing and detecting internal short circuits in lithium-ion batteries is a key issue to prevent thermal runaway failures and ensure overall safety. This study focuses on utilizing an Equivalent Circuit Model (ECM) and machine learning techniques to detect ISC faults in lithium-ion batteries. The impact of battery aging is considered by adjusting capacity and resistance values in the battery simulation. First, an ECM of a lithium-ion battery pack is developed in the MATLAB/SIMULINK platform, incorporating faulty and normal battery cells with varying aging levels. Subsequently, the output data from the simulated model is utilized as input for the Random Forest (RF) model under different... 

Depending on the type of dopant metal, many kinds of zircon based pigments are produced and blue vanadium pigment is the most important one of them. In this study, blue zircon ceramic pigments were synthesized from intermediate product, resulting from decomposition of zircon sand with NaOH. In this regard, various amounts of sulfuric acid, water, NH4VO3 as colorant, NaF as mineralizer and extra quartz were added to the prepared Na 2ZrSiO5. Role of quartz was to omit the repercussions of presence of free zirconia in the composition. The main objective of this work is to assess various reactions at different temperatures during blue pigment synthesis. Phase analysis was done by X ray...