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Carbon nanotubes are one of the most extensively studied nanomaterials because of their remarkable mechanical and electrical properties. The Y-junction structures within carbon nanotubes have received significant attention in the field of nanotechnology, primarily due to their immense potential for powering the next generation of multi-terminal nanodevices. Topological indices play a crucial role in exploring the physicochemical properties and structural attributes of chemical compounds, as they are numerical values intricately linked to the molecular structure of these compounds. Moreover, graph-based entropies serve as essential thermophysical parameters used to quantify the heterogeneity and relative stabilities of molecular structures. In this article, we have utilized the NM-polynomial technique to calculate various neighborhood degree sum-based topological indices and graph-based entropies for carbon nanotube Y-junction graphs.

We investigate novel transport properties of chiral continuous-time quantum walks (CTQWs) on graphs. By employing a gauge transformation, we demonstrate that CTQWs on chiral chains are equivalent to those on non-chiral chains, but with additional momenta from initial wave packets. This explains the novel transport phenomenon numerically studied in (Khalique et al 2021 New J. Phys. 23 083005). Building on this, we delve deeper into the analysis of chiral CTQWs on the Y-junction graph, introducing phases to account for the chirality. The phase plays a key role in controlling both asymmetric transport and directed complete transport among the chains in the Y-junction graph. We systematically analyze these features through a comprehensive examination of the chiral CTQW on a Y-junction graph. Our analysis shows that the CTQW on Y-junction graph can be modeled as a combination of three wave functions, each of which evolves independently on three effective open chains. By constructing a lattice scattering theory, we calculate the phase shift of a wave packet after it interacts with the potential-shifted boundary. Our results demonstrate that the interplay of these phase shifts leads to the observed enhancement and suppression of quantum transport. The explicit condition for directed complete transport or 100 % efficiency is analytically derived. Our theory has applications in building quantum versions of binary tree search algorithms.

Carbon nanotube Y-shaped junctions (normally called as Y-junctions) are constructed by inserting heptagons into the graphene sheet. The design requires the inclusion of at least 6 heptagons at the junction where 3 carbon nanotubes joined. With the growing focus on carbon nanotubes, their junctions have garnered increased attention for their applications in various scientific fields. Chemical structures can be expressed in graphs, where atoms represent vertices, and the bonds between the atoms are called edges. To obtain the exact position of an atom, which is unique from all the atoms, several atoms are selected, this is called resolving set. The minimum number of atoms in the resolving set is called the metric dimension. In this paper, we have computed the metric dimension of carbon nanotube Y-junctions, assigning each atom a unique identifier to facilitate precise location. The metric dimension is constant for all the values of the 3 parameters included to develop a Y-junction. It resulted in 3 metric dimensions for the entire Y-junction. It means that whatever the order and quantity of nanotubes attached to it, the metric dimension will remain constant with number 3.

Recent research on nanostructures has demonstrated their importance and application in a variety of fields. Nanostructures are used directly or indirectly in drug delivery systems, medicine and pharmaceuticals, biological sensors, photodetectors, transistors, optical and electronic devices, and so on. The discovery of carbon nanotubes with Y-shaped junctions is motivated by the development of future advanced electronic devices. Because of their interaction with Y-junctions, electronic switches, amplifiers, and three-terminal transistors are of particular interest. Entropy is a concept that determines the uncertainty of a system or network. Entropy concepts are also used in biology, chemistry, and applied mathematics. Based on the requirements, entropy in the form of a graph can be classified into several types. In 1955, graph-based entropy was introduced. One of the types of entropy is edge-weighted entropy. We examined the abstract form of Y-shaped junctions in this study. Some edge-weight-based entropy formulas for the generic view of Y-shaped junctions were created, and some edge-weighted and topological index-based concepts for Y-shaped junctions were discussed in the present paper.

Multimode silicon photonics, leveraging mode-division multiplexing technologies, offers significant potential to increase capacity of large-scale multiprocessing systems for on-chip optical interconnects. These technologies have implications not only for telecom and datacom applications, but also for cutting-edge fields such as quantum and nonlinear photonics. Thus, the development of compact, low-loss and low-crosstalk multimode devices, in particular mode exchangers, is crucial for effective on-chip mode manipulation. This work introduces a novel mode exchanger that exploits the properties of subwavelength grating metamaterials and symmetric Y-junctions, achieving low losses and crosstalk over a broad bandwidth and a compact size of only 6.5 µm × 2.6 µm. The integration of SWG nanostructures in our design enables precise control of mode exchange through different propagation constants in the arms and metamaterial, and takes advantage of dispersion engineering to broaden the operating bandwidth. Experimental characterization demonstrates, to the best of our knowledge, the broadest operational bandwidth covering from 1,420 nm to 1,620 nm, with measured losses as low as 0.5 dB and extinction ratios higher than 10 dB. Enhanced performance is achieved within a 149 nm bandwidth (1,471–1,620 nm), showing measured losses below 0.4 dB and extinction ratios greater than 18 dB.

NRC publication: Yes

The results of experimental and computational studies for the coolant flows mixing at different temperatures for standard operational parameters of a nuclear power unit (NPU) are presented in this paper. Experiments were performed using an upgraded version of measurement model. This study defines a temperature filed in the mixing zone and offers the optimal set of operation parameters calculated from the condition of maximum temperature pulsation within the mixing zone. Simulation was performed using a software kit ANSYS Fluent. The grid model is based on the block structure in ANSYS ICEM code. Numerical simulation was performed for unsteady problem statement based on the LES WALE turbulence model. Analysis of simulation and experimental fields for flow velocity and temperature confirmed the validity of the developed numerical method. A qualitative compliance for the probability density distribution and the spectral-correlation characteristics for temperature signals in the mixing zone was observed. The spectral power density for calculated temperature and velocity distributions fits the case of 1D energy spectrum of developed isotropic turbulence.

This study numerically investigated the symmetric breakup of bubble within a heated microfluidic Y-junction. The established three-dimensional model was verified with the results in the literature. Two crucial variables, Reynolds number (Re) and heat flux (q), were considered. Numerical results demonstrated that the bubble breakup was significantly affected by phase change under the heated environment. The “breakup with tunnel” and “breakup with obstruction” modes respectively occurred at the low and high q. The breakup rate in pinch-off stage was much larger than that in squeezing stage. As Re increased, the bubble broke more rapidly, and the critical neck thickness tended to decrease. The bubble annihilated the vortices existing in the divergence region and made the fluid flow more uniform. The heat transfer was enhanced more drastically as Re was decreased or q was increased, where the maximum Nusselt number under two-phase case was 6.53 times larger than single-phase case. The present study not only helps understanding of the physical mechanisms of bubble behaviors and heat transfer within microfluidic Y-junction, but also informs design of microfluidic devices.

In this work, we propose a design in the proof-of-concept of a 1×3 two-mode selective silicon-photonics router/switch. The proposed device composes of a Y-junction coupler, two multimode interference (MMI) couplers, and two phase-shifters on the silicon-on-insulator (SOI) rib waveguides. The input modes of TE0 and TE1 can be arbitrarily and simultaneously routed to the yearning output ports by setting appropriate values (ON/OFF) for two tunable phase shifters (PSs). The structural optimization and efficient characterization processes are carried out by numerical simulation via three-dimensional beam propagation method. The proposed device exhibits the operation ability over the C-band with good optical performances in terms of insertion loss smaller than 1 dB, crosstalk under -19 dB, and relatively large geometry tolerances. Moreover, the proposed device can integrate into a footprint as compact as 5 μm ×475 μm. Such significant advantages are beneficial and promising potentials for very large-scale photonic integrated circuits, high-speed optical interconnects, and short-haul few-mode fiber communication systems.

Pseudo-spin and valley degrees of freedom engineered in photonic analogues of topological insulators provide potential approaches to optical encoding and robust signal transport. Here we observe a ballistic edge state whose spin–valley indices are locked to the direction of propagation along the interface between a valley photonic crystal and a metacrystal emulating the quantum spin–Hall effect. We demonstrate the inhibition of inter-valley scattering at a Y-junction formed at the interfaces between photonic topological insulators carrying different spin–valley Chern numbers. These results open up the possibility of using the valley degree of freedom to control the flow of optical signals in 2D structures. Valleys in the photonic band structure provide an additional degree of freedom to engineer topological photonic structures and devices. Here, Kang et al. demonstrate that inter-valley scattering is inhibited at a Y-junction between three sections with different valley topology.