Narrowband-IoT (NB-IoT) is a low power wide area network technology introduced by the 3rd Generation Partnership Project (3GPP) in Release 13 specifications. The NB-IoT aims at providing cellular ...connectivity to low cost, low throughput, delay-tolerant devices, and hence, is a key technology for smart connected living. The NB-IoT specifications continue to evolve as part of 5G New Radio (NR), and the technology is expected to co-exist with 5G NR. A transmission bandwidth of 180 KHz is required to deploy the NB-IoT. In NB-IoT, the duration of the physical downlink control channel (NPDCCH) and the physical downlink shared channel (NPDSCH) changes dynamically. When the base station broadcasts the NPDCCH region, all the active NB-IoT devices try to decode it. Hence, to reduce the power consumption of the NB-IoT devices, more number of NB-IoT devices have to be scheduled in each scheduling attempt. For each payload in NPDCCH, there is a respective payload in NPDSCH. Thus, a base station should schedule the devices simultaneously in both NPDCCH and NPDSCH to reduce resource wastage. The time–frequency resources in NB-IoT are limited and valuable. Further, the NB-IoT devices have low battery power constraint. Thus, scheduling the devices by considering the above constraints has a significant impact on the NB-IoT system performance. Motivated by this, we propose a joint scheduling algorithm for both NPDCCH and NPDSCH. Further, we propose an adaptive repetition allocation algorithm and present a receiver design for NB-IoT. We also define performance metrics to evaluate the impact of the proposed scheduler and then present bounds on the performance gains with the proposed scheduler. With system-level and link-level simulations, we show that the proposed scheduler significantly outperforms the current state-of-the-art algorithms.
Cationic dendrimers are promising nanocarriers for gene delivery thanks to their ability to establish strong interactions with oppositely charged strands of DNA and siRNA and to promote their ...aggregation. The binding between dendrimers and nucleic acids is typically a complex process that involves various types of interactions at different scales. To design efficient dendrimer candidates for DNA and siRNA binding it is necessary to have a detailed understanding of their interactions with oligonucleotides in the solvent. Molecular simulation can support experimental work, providing a privileged point of view on the aggregation process. This Minireview discusses recent computational efforts to unravel dendrimer-oligonucleotide binding, and proposes a perspective of the multiscale aggregation process based on hierarchy and on the transformations of the interacting "molecular units" following intermolecular interactions.
Covalent organic frameworks (COFs) are commonly synthesized under harsh conditions yielding unprocessable powders. Control in their crystallization process and growth has been limited to studies ...conducted in hazardous organic solvents. Herein, we report a one-pot synthetic method that yields stable aqueous colloidal solutions of sub-20 nm crystalline imine-based COF particles at room temperature and ambient pressure. Additionally, through the combination of experimental and computational studies, we investigated the mechanisms and forces underlying the formation of such imine-based COF colloids in water. Further, we show that our method can be used to process the colloidal solution into 2D and 3D COF shapes as well as to generate a COF ink that can be directly printed onto surfaces. These findings should open new vistas in COF chemistry, enabling new application areas.
Polyurethane (PU) coatings were prepared using polyesteramide polyols based on different types of vegetable oils and itaconic acid. Long chain fatty diethanolamides were synthesized using the ...amidation of linseed/castor/karanja oils and the desired hydroxyl group was introduced via esterification reaction with itaconic acid to yield polyesteramide polyols. Its structural elucidation was carried out using Fourier-transform infrared spectroscopy (FT-IR) and proton nuclear magnetic resonance (1H NMR). The study of crosslinking these polyols with hexamethylene diisocyanate (HDI-trimer and HDI-biuret) shows that the isocyanate structure and functionality contribute to the final polyurethane coatings properties. Various optical, mechanical, and durability performance of the cured PU metal coating films were examined. The gel content method was used to compare the crosslink density of various PU films. The thermal properties of the PU coating, including stability and glass transition temperature (Tg), were assessed using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The corrosion resistance of PU coatings was analyzed by employing electrochemical impedance spectroscopy (EIS). PU metal coatings display superior gloss, adhesion, and chemical resistance properties. Differences in fatty acid compositions of linseed/castor/karanja oils were found to influence the air curing and mechanical and corrosion resistance properties of PU metal coatings. The use of itaconic acid and vegetable oils in the synthesis of these polyols contributes to their bio based characteristics and permits replacing the currently used petroleum-based polyols.
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•Use of vegetable oils and bio-based itaconic acid for synthesis of polyesteramide polyols.•Preparation of air cured polyurethane coatings from crosslinking of bio-based polyols with HDI-trimer and HDI-biuret.•Effect of hydroxyl functionalities and unsaturation on the performance of PU coatings.•Polyurethane metal coatings showed superior gloss, adhesion, chemical resistance and corrosion resistance properties.
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•Green synthesis of dimer fatty acid based polyurethane acrylate (PUA) oligomer.•Preparation of UV curable coatings from PUA with HDDA and TMPTA reactive diluents.•UV cured PUA ...coatings showed superior flexibility, impact, hydrophobicity and resistance to volume shrinkage.•Renewable dimer acid are excellent candidate for future polyurethane coatings.
A UV-curable polyurethane acrylate (PUA) oligomer was prepared from dimer acid (DA) based polyester polyol (DAPEP) with a monofunctional acrylate precursor which was developed upon isophorone diisocyanate (IPDI) reacted with 2-hydroxyethyl methacrylate (HEMA). The structural elucidation of synthesized dimer acid based PUA (DAPUA) oligomer was verified through Fourier-transform infrared spectroscopy (FT-IR) and Proton nuclear magnetic resonance (1H NMR). A series of UV cured coatings were prepared by adding trimethylolpropane triacrylate (TMPTA) and 1,6-hexanediol diacrylate (HDDA) reactive diluents in varying percentages (10−30 wt%) to PUA oligomer. The bio-coatings exhibited exceptional results, including the highest thermal degradation temperature of 382–422 °C, glass transition temperature (Tg) of 56.38–66.27 °C, the tensile strength of 17.3–30.6 MPa, volume shrinkage of 6.19–9.13 %, and surface roughness of 4.89–28.21 nm. Compared to vegetable oil based UV-curable coatings, long chain dimer acid based PUA oligomer coatings exhibited excellent flexibility, impact, hydrophobicity, and resistance to volume shrinkage.
Chemists have created molecular machines and switches with specific mechanical responses that were typically demonstrated in solution, where mechanically relevant motion is dissipated in the Brownian ...storm. The next challenge consists of designing specific mechanisms through which the action of individual molecules is transmitted to a supramolecular architecture, with a sense of directionality. Cellular microtubules are capable of meeting such a challenge. While their capacity to generate pushing forces by ratcheting growth is well known, conversely these versatile machines can also pull microscopic objects apart through a burst of their rigid tubular structure. One essential feature of this disassembling mechanism is the accumulation of strain in the tubules, which develops when tubulin dimers change shape, triggered by a hydrolysis event. We envision a strategy toward supramolecular machines generating directional pulling forces by harnessing the mechanically purposeful motion of molecular switches in supramolecular tubules. Here, we report on wholly synthetic, water-soluble, and chiral tubules that incorporate photoswitchable building blocks in their supramolecular architecture. Under illumination, these tubules display a nonlinear operation mode, by which light is transformed into units of strain by the shape changes of individual switches, until a threshold is reached and the tubules unleash the strain energy. The operation of this wholly synthetic and stripped-down system compares to the conformational wave by which cellular microtubules disassemble. Additionally, atomistic simulations provide molecular insight into how strain accumulates to induce destabilization. Our findings pave the way toward supramolecular machines that would photogenerate pulling forces, at the nanoscale and beyond.
Bio-based polyurethane (PU) coatings were prepared from novel branched isostearic acid (ISA) and long chains dimer fatty acid. Fatty amide was synthesized by the amidation of ISA with diethanolamine ...and the required hydroxyl functionality was developed via condensation polymerization with dimer fatty acid to produce polyesteramide polyol. The structure of the synthesized ISA based fatty amide (ISAFA) and polyesteramide polyol (ISAPEP) were identified using Fourier-transform infrared spectroscopy (FT-IR) and proton nuclear magnetic resonance (
1
HNMR). The number average molecular weight of prepared polyesteramide polyol was assessed by gel permeation chromatography (GPC), while the rheological behavior was examined by the rheometer. Polyurethane metal coatings were developed from polyesteramide polyol, which crosslinks with hexamethylene diisocyanate (PU-H) and toluene diisocyanate (PU-T) and studied the influence of isocyanate structure on final PU coatings. A comparison in the crosslinks density of PU films was investigated by the gel content method. Differential scanning calorimetry (DSC) and thermo gravimetric analysis (TGA) were performed to evaluate the glass transition temperature (T
g
) and thermal stability of the PU coatings. The surface roughness of prepared PU coatings was examined by Atomic force microscopy (AFM). The PU coated metal panels and films were examined for swelling resistance, hydrophobicity, mechanical, and coating properties. Results confirmed that bio-based long chain fatty acids provided hydrophobicity, flexibility and impact resistance to final PU coatings. It also noted that PU-T coating resulted in increasing thermal, mechanical, and coating properties compared to PU-H coating and this resulted from the structure of TDI, which contribute to higher crosslink density (i.e. presence of aromatic ring).
Graphical Abstract
The Spectrum is a scarce resource in wireless networks, hence these resources need to be perfectly channelized for their better utilization. By the study of the previous decades, it is found that the ...spectrum is colossally underutilized and the main reason for the underutilization found out to be the policies that are fixed and not dynamic. The dynamic spectrum allocation of frequency bands may overcome this problem. Cognitive radio provides an important concept that can used to solve the problem of underutilization of spectrum. Reinforcement learning is a key technique that is widely used to learn the spectrum allocation behaviour and maximize the system's efficiency. Therefore, in this work, we have designed and developed a Reinforcement learning-based model to allocate the channels among secondary users. Also, a Deep Reinforcement learning- based channel allocation algorithm (DRLCA) has been proposed. The proposed DRLCA is compared with existing JPCRL 1. In our algorithm, the Python libraries were used for simulation. From the simulation results and analysis, it is found that the DRLCA outperforms the JPCRL in terms of channel utilization by 5%.
While a great deal of knowledge on the roles of hydrogen bonding and hydrophobicity in proteins has resulted in the creation of rationally designed and functional peptidic structures, the roles of ...these forces on purely synthetic supramolecular architectures in water have proven difficult to ascertain. Focusing on a 1,3,5-benzenetricarboxamide (BTA)-based supramolecular polymer, we have designed a molecular modeling strategy to dissect the energetic contributions involved in the self-assembly (electrostatic, hydrophobic, etc.) upon growth of both ordered BTA stacks and random BTA aggregates. Utilizing this set of simulations, we have unraveled the cooperative mechanism for polymer growth, where a critical size must be reached in the aggregates before emergence and amplification of order into the experimentally observed fibers. Furthermore, we have found that the formation of ordered fibers is favored over disordered aggregates solely on the basis of electrostatic interactions. Detailed analysis of the simulation data suggests that H-bonding is a major source of this stabilization energy. Experimental and computational comparison with a newly synthesized 1,3,5-benzenetricarboxyester (BTE) derivative, lacking the ability to form the H-bonding network, demonstrated that this BTE variant is also capable of fiber formation, albeit at a reduced persistence length. This work provides unambiguous evidence for the key 1D driving force of hydrogen bonding in enhancing the persistency of monomer stacking and amplifying the level of order into the growing supramolecular polymer in water. Our computational approach provides an important relationship directly linking the structure of the monomer to the structure and properties of the supramolecular polymer.
Sunnhemp (Crotalaria juncea) is a valuable lignocellulosic biomass for both fodder and textile fibre. It exhibits an appealing specific tensile strength which make it a desirable reinforcement ...material for development of the green composites. However, to enhance its compatibility with hydrophobic polymers, a suitable chemical modification was desired. Hence, in the current study an attempted was made to modify the surface of the Sunnhemp fibre by sodium hydroxide and to optimize the operational protocol through hybrid Artificial Neural Network-Multi-Objective Genetic Algorithm (ANN-MOGA). The physical, chemical, mechanical, and surface morphological properties of raw and alkali-modified fibre were evaluated as per standard protocols. The optimized conditions are 5.01 g/L alkali concentration, 30 minutes of treatment time, and 1:20 material-to-liquor ratio. The optimized condition was validated, with less deviation between predicted and actual values, which confirmed the adequacy of the developed model. The alkali modified Sunnhemp fibre showed higher cellulose content, mechanical strength, and thermal stability than the raw fibre. SEM analysis revealed a distinct channel-like patterns in the alkali-treated fibres and affirmed the removal of surface impurities. Notably, the alkali-modified Sunnhemp fibre exhibited desirable antimicrobial properties against Staphylococcus aureus bacteria. It was concluded that AI based optimization could offer a sustainable approach for the surface modification of the natural fibre by identifying the effective processing condition with saving energy.
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•Optimization of alkali modification protocol on Crotalaria juncea fibre using hybrid ANN-MOGA approach•Alkali modification protocol has improved the physical, mechanical properties and surface morphology of C. juncea fibre•Developed AI model efficiently predicted the response variables•Alkali modified Crotalaria juncea fibre has potential applications in the development of technical textiles
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