A three-dimensional covalent organic framework (COF-505) constructed from helical organic threads, designed to be mutually weaving at regular intervals, has been synthesized by imine condensation reactions of aldehyde functionalized copper(I)- bisphenanthroline tetrafluoroborate, Cu(PDB)2(BF4), and benzidine (BZ). The copper centers are topologically independent of the weaving within the COF structure and serve as templates for bringing the threads into a woven pattern rather than the more commonly observed parallel arrangement. The copper(I) ions can be reversibly removed and added without loss of the COF structure, for which a ten-fold increase in elasticity accompanies its demetalation. The threads in COF-505 have many degrees of freedom for enormous deviations to take place between them, throughout the material, without undoing the weaving of the overall structure.
Scale formation in pipelines presents a serious problem in gas and oil industry. Our approach to tackle this issue relies on the use of real-time sensing of specific Ions in brine. In order to do so, electrochemical sensors based on Carbon Nanotubes (CNTs) were developed, taking advantage of their unique properties facilitated by various fabrication methods. One of these promising methods is inkjet printing of CNT films, which is relatively new. This method indeed seems to be a very promising. Overall, it offers unique advantages over other methods of depositing the CNT films. It does not require prefabrication of templates, and allows for rapid process at significantly lower cost. As scale sensors are exposed to hostile environment, the stability of the CNT films is of great importance, as it undergoes continuous exposure to brine. In this study, we present a comprehensive investigation of the stability of CNT surfaces upon exposure.
Commercially available Nylon? fabric and fibers are modified with non-destroyable and smooth graphene coating. The graphene coating induces electrical conductivity as well as piezo-resistivity in Nylon?. Due to its piezo-resistive functionality the modified Nylon? fibers sense both pressure and strain. When a Nylon? fiber is bent with a bend radius of 3mm, the resistance of the fiber changes about 300 kilo ohms relative to its original resistance. With the help of a read-out circuit it is also demonstrated that a grid of modified Nylon? fibers sense both position and pressure. Therefore, advanced force touch laptop trackpads can be made using these simple fibers.
This study develops a formula based on the viewpoint of Rule of Mixtures to identify the effective Young's and shear modulus of multi-walled carbon nanotubes (MWCNTs). The identified effective Young's modulus based on theoretical analysis is calculated and found a good agreement with that of other experimental studies. Results indicate that effective Young's modulus of MWCNTs is observed lower than that of single-walled carbon nanotubes (SWCNTs). Also, it is found only when the ratio of half CNT length to outermost radius is higher than 500, the effective Young's modulus of five-walled CNTs can reach the maximal value as equal as that of SWCNTs. The load transfer efficiency is also found to play a significant role to improve the Young's modulus of MWCNTs. The influence of layer number, aspect ratio and interlayer shear modulus on the MWCNT's Young's modulus is investigated in detail.
Graphene is a 2-D allotrope of carbon which has ultrahigh electron mobility and exceptional mechanical properties. Chemical Vapor Deposition (CVD) synthesis yields high quality (monolayer) and large size graphene used for multiple applications. This is synthesized to maintain uniform transparent nature of graphene which has less thermal resistance. Copper is an excellent conductor of heat, and since copper is hydrophilic and graphene hydrophobic keeping into account the hydrocarbon impurities present on it, the surface wetting nature can be changed. To reduce the surface energy of copper and bring about drop wise condensation, copper surface be coated with monolayer graphene which is mechanically/chemically stable compared to long chain fluorocarbons or fatty acids. This enables better heat transfer by allowing drop wise condensation as to film wise on copper. Graphene is synthesized on another substrate which is transferred onto a second roughened copper surface as a comparison to study the wettability.
This paper presents an analytical study concerning nanoscale networks operating at the THz frequency. Both the path loss and absorption coefficients of a simplified human body model are investigated. From the results, it has been concluded that with the rise of distance and frequency, the path loss increases. Actually, the path loss difference across the THz band ranging between 0.1THz and 10THz at a distance of 1mm is around 40dB for the various body parts. This value is acceptable especially in the context of in-vivo communication. At 1 THz, the path loss between 1mm and 1.5mm ranges between(36dB?40dB) for the different body parts. Thus, it can be seen that even though the distance is in the order of millimeters, it is enough for the electromagnetic communication among nano-devices since the path loss is not significantly high.
This paper presents a physics-based model for memristors with different active layer materials. The model predicts the effect of changing the active material on the electrical characteristics of the devices. It captures the essential characteristics of the memristor such as coupling between ion mobility and electron current in addition to the nonlinear effects of electric fields. The parameters in the model depend on material (metal-oxide) properties that have impact on the device behavior. In this work, the effect of each parameter is highlighted and explained. In addition, the physics-based Matlab model is used to analyze the electrical characteristics of simulated memristor device using the following oxide materials; ZnO, TiO2 and Ta2O5. The simulation results of the model are validated with experimental data reported in the literature. The value of this contribution is to enable the selection of suitable oxide materials for the target memristor using correlated mathematical models.
Multi-hop relaying technology is a promising technology for future wireless communication. It provides high data-rate coverage with low transmitting power. In this paper, novel analytic expression derived for the bit-error-rate (BER) in dual-hop system based amplify-and-forward (AaF) relaying strategy. The proposed system is considered over asymmetric Rayleigh-Weibull fading channel.
It is evident that increasing penetration of renewables has been the matter of interest in deregulated power industry. This is leading the world to clean and sustainable energy. However, the issues of power quality, control, and coordination is still challenging. The issues of voltage regulation, and frequency control is not satisfactorily achieved by conventional control techniques in the power system after the penetration. Thus, demand response (DR), a new control strategy for frequency regulation is studied in this paper. This paper presents the study of DR for frequency regulation in microgrids with distributed generation (DG). Simulation studies in Power Analysis Toolbox (PAT) in MATLAB is carried out on IEEE 13-bus standard industrial system. Simulation based results proved effectiveness of DR to regulate the system frequency at various conditions of frequency deviation. It is observed that on regulating frequency of the studied distribution system, voltage is also found to be regulated.
In response to the increased demand on high power electronics and more efficient energy storage devices, this article is dedicated to investigate the performance of a range of Lithium-ion batteries. The main scope of this work is to provide an insight about how much surface porosity and conductive additives could enhance electrodeelectrolyte interactions by means of AC electrochemical impedance spectroscopy (EIS) test. For this purpose, bare LiFePO4 as well as a range of LiFePO4/CNS porous composite films were fabricated and tested as a cathode electrodes. While porosity levels as well as LiFePO4 vs. CNS composition are sequentially changed, solution resistance, charge transfer resistance, Warburg resistance and double layer capacitance are recorded. This work suggests that electrodes with 73% porosity and 30% composition of the active material showed best performance and therefore could be witnessed as promising candidates for next generation power-hungry portable devices.
