Path Topology Research Articles

Low Power, Ring VCO with Pre-Charge and Pre-Discharge Circuit for 4 GHz–6.1 GHz Applications in 0.18 μm CMOS

The differential ring voltage controlled oscillator (VCO) is one of the critical devices in wireless communication system having excellent stability, controllability and noise rejection ability. A novel design of delay cell is proposed for the four staged CMOS differential ring VCO with high output frequency, low power consumption and low phase noise. The differential ring VCO utilizes multiloop dual delay path topology to acquire both high output frequency and low phase noise. Results have been achieved in TSMC 0.18-[Formula: see text]m CMOS process with a supply voltage ([Formula: see text]) 1.8[Formula: see text]V. The proposed design achieves an output frequency range of 4.029[Formula: see text]GHz to 6.122[Formula: see text]GHz and power of 4.475[Formula: see text]mW is consumed with control voltage variation from 1[Formula: see text]V to 2[Formula: see text]V. The proposed VCO exhibits [Formula: see text]89.7[Formula: see text]dBc/Hz phase noise at 1[Formula: see text]MHz offset frequency and the corresponding figure of merit (FoM) is [Formula: see text]155.9[Formula: see text]dBc/Hz. The design of differential ring VCO with novel delay stage has improved performance in terms of power consumption, output oscillation frequency and phase noise.

Ab initio studies of Ti2S3 as a new cathode material for magnesium secondary batteries

In this work, we use spin unpolarized van der Waals-corrected static for the comparative study of highly defective TiS2 with Ti2S3 stoichiometry and stoichiometric TiS2, a well-known compound studied experimentally. Our study predicts that Ti2S3 exhibits high theoretical capacity of up to 112 mA h/g, moderate stability, a high electronic conductivity (zero band gap for all magnesium contents), and 0.8–1.0 eV lower operating voltage due to less intense Ti3+/Ti2+ redox couple. The bond valence sum method analysis showed that Mg diffusion occurs through the hopping of Mg cations between the cavities in the form of cubes. In contrast, nudged elastic band method reveals the linear topology of the migration path. Although in Ti2S3 a huge contraction of the c parameter was found (up to 8.17% in comparison with TiS2), the migration barrier for Mg diffusion was found to be comparable to that of layered TiS2 (1.078–1.281 eV depending on Mg content). This can be explained by the lower partial atomic charge of Ti in Ti2S3, as well as rehybridization over higher amount of Ti atoms.

A Novel Adaptive Optimization of Intragrated Network Topology and Transmission Path for IoT System

The Internet of Things (IoT) is currently the emerging trend in network applications. The core component is the network layer in the IoT system. There are already some existing improvements, most of them are focused either on the transmission path or on the network topology. We have previously designed the Queen Honey Bee Migration (QHBM) algorithm which is a new method for solving routing and transmission path. In this paper, we further improve both the transmission path and the network topology at the same time. The authors designed two novel adaptive models to solve the optimization of networking. We employed the Adaptive Model of Network Topology (AMNT) based on the QHBM algorithm to optimize the repeater; moreover, we also used the probability model to design Adaptive Model of Transmission Path (AMTP) to optimize the end-device. It allows the access point (AP) in the network to perform transmission path transfer or network topology reorganization according to the specified conditions. We evaluated two network performance parameters: transmission time and packet loss rate. The control mode maintains a conventional mode and does not change the existing network topology or transmission path with any factors. The experimental mode performs according to the novel adaptive integrated network topology and the transmission path for the IoT system, thus this system will operate according to the setting of the environment with the signal interference source generated by a random process method. We found that in laboratory testing, compared to conventional mode, the network performance of the novel integrated network topology and the transmission path for the IoT system has been increased by AMNT and AMTP. The performance index of the transmission time increased by 70.6±11%, and the performance index of the packet loss rate increased by 84 ± 38%. We conclude that our novel adaptive optimization of integrated network topology and the transmission path for the IoT system is practically applicable and has achieved encouraging result in terms of IoT performance. We hope for a wide application of this novel design on the networking of the IoT in the future.

Quantitative Visualization of Topology and Morphing of Percolation Path in Nanoparticle Network Array Exhibiting Coulomb Blockade at Room Temperature

A network of one-dimensional (1D) necklaces of 10 nm Au nanoparticles was fabricated by a directed self-assembly to synthesize 1D necklaces followed by self-limiting monolayer deposition to form a two-dimensional (2D) network array. Scanning electron microscope (SEM) image analysis revealed a percolation threshold lower than random 2D arrays signifying the local 1D structure. The topology of (shortest) percolation paths (tortuosity) and the fraction of clusters isolated from the percolating array were quantified to relate the network morphology to the observed non-Ohmic (Coulomb blockade effect) behavior. Leveraging charge contrast in SEM, the morphing of the percolation path as a function of the kinetic energy of the conduction electron was visualized and quantified to understand the dynamic nature of the percolation behavior. The morphology can be systematically tailored by tuning the two self-assembly processes to obtain the same coverage of the array with significantly diverse non-Ohmic behavior. It w...

Sub-ppm-Level Ammonia Detection Using Photoacoustic Spectroscopy with an Optical Microphone Based on a Phase Interferometer

A sensitive optical microphone for photoacoustic spectroscopy based on the common path topology of a fibre laser Doppler vibrometer (FLDV) using phase-generated carrier demodulation and a slim diaphragm as an acoustic wave transducer was demonstrated. A resonant gas cell was adapted to enhance gas-detection performance and simultaneously provide efficient cancellation of the window background acoustic signal. Ammonia (NH3) was selected as the target gas. The absorption line was experimentally identified using a distributed feedback laser diode emitting at 1530 nm. The linearity and sensitivity of the gas sensor were measured using wavelength modulation spectroscopy with second harmonic detection. A Teflon diaphragm was used to implement the optical microphone, along with the FLDV, showing a minimum detectable pressure of 79.5 μPa/Hz1/2. The noise-equivalent absorption sensitivity for NH3 detection at the absorption line at 1531.7 nm was 1.85 × 10−8 W cm−1 Hz−1/2, and the limit of detection was 785 ppbv.

Reflection and Time Reversal Symmetry Enriched Topological Phases of Matter: Path Integrals, Non-orientable Manifolds, and Anomalies

We study symmetry-enriched topological (SET) phases in 2+1 space-time dimensions with spatial reflection and/or time-reversal symmetries. We provide a systematic construction of a wide class of reflection and time-reversal SET phases in terms of a topological path integral defined on general space-time manifolds. An important distinguishing feature of different topological phases with reflection and/or time-reversal symmetry is the value of the path integral on non-orientable space-time manifolds. We derive a simple general formula for the path integral on the manifold $\Sigma^2 \times S^1$, where $\Sigma^2$ is a two-dimensional non-orientable surface and $S^1$ is a circle. This also gives an expression for the ground state degeneracy of the SET on the surface $\Sigma^2$ that depends on the reflection symmetry fractionalization class, generalizing the Verlinde formula for ground state degeneracy on orientable surfaces. Consistency of the action of the mapping class group on non-orientable manifolds leads us to a constraint that can detect when a time-reversal or reflection SET phase is anomalous in (2+1)D and, thus, can only exist at the surface of a (3+1)D symmetry protected topological (SPT) state. Given a (2+1)D reflection and/or time-reversal SET phase, we further derive a general formula that determines which (3+1)D reflection and/or time-reversal SPT phase hosts the (2+1)D SET phase as its surface termination. A number of explicit examples are studied in detail.

Optimizing movement in convex and non-convex path-networks to establish connectivity

We solve a movement problem in which there are n sensors in path network in plane, where any sensor communicates only with its two immediate neighbors and only at a given maximum communication distance λ. Initially, some of the inter-sensor distances may be more than λ. We need to move sensors so that each sensor is in the communication range of its two neighbors, keeping the path topology intact. The problem is to minimize the maximum movement of any sensor. We present an O(n3)-time algorithm to compute the new positions of sensors to establish transmission connectivity, called λ-connectivity in the paper, in a convex path-network which minimizes the maximum movement among the sensors. We also generalize our algorithm for ring, non-convex path, tethered and heterogeneous networks.

Generalised Chebyshev function bandpass filters in box‐like topologies based on the properties of dual‐mode loop microstrip resonator

A new class of compact microstrip bandpass filters in doublet topology based on a dual-mode loop microstrip resonator with controllable locations of input/output feeding lines is presented and researched. Filters with up to five poles are proposed and researched. Diagonal cross-coupling path in box-like topology can be introduced to produce a finite transmission zero (TZ) with controllable position. Some design examples are provided to illustrate the performances of the proposed two-, three-, four- and five-pole filters with controllable TZs. A three-pole and a five-pole filters were fabricated and measured. Good agreement is achieved between the simulated and the measured results.

Development of R-Group Fingerprints Based on the Local Landscape from an Attachment Point of a Molecular Structure.

Molecular fingerprints are indispensable in medicinal chemistry for quantifying chemical structures. Fingerprints can be calculated for substructures with attachment points, which are positions where a substructure and a corresponding core structure connect. Because structures with attachment points can be crucial for understanding structure-activity relationships, fingerprints specialized for representing this structural feature are required. R-group fingerprints and R-group descriptors were proposed previously for this purpose; however, these molecular representations have limitations. Current R-group fingerprints do not emphasize information about attachment points, and R-group descriptors are too sensitive to changes in the topological path length from an attachment point. In the present work, we developed novel R-group fingerprints, termed R-path fingerprints, which contain substituent information from an attachment point without being sensitive to small differences in topological distances. The concept of the R-path fingerprints is to describe a chemical substructure from the viewpoint of an attachment point, to distinguish atomistic information around the attachment point and other parts of the substructure. This was achieved by considering all the paths on the shortest path between the attachment point and each atom in a substituent. Benchmark testing was conducted, including comparisons of similarity distributions and potency prediction for R-group substituents. The results showed that R-path fingerprints should be useful for classifying and comparing substructures with attachment points.

Space-time Singularities vs. Topologies in the Zeeman—Göbel Class

In this article we first observe that the Path topology of Hawking, King and MacCarthy is an analogue, in curved spacetimes, of a topology that was suggested by Zeeman as an alternative topology to his so-called Fine topology in Minkowski spacetime. We then review a result of a recent paper on spaces of paths and the Path topology, and see that there are at least five more topologies in the class $\mathfrak{Z}-\mathfrak{G}$ of Zeeman-G\"obel topologies which admit a countable basis, incorporate the causal and conformal structures, but the Limit Curve Theorem fails to hold. The "problem" that L.C.T. does not hold can be resolved by "adding back" the light-cones in the basic-open sets of these topologies, and create new basic open sets for new topologies. But, the main question is: do we really need the L.C.T. to hold, and why? Why is the manifold topology, under which the group of homeomorphisms of a spacetime is vast and of no physical significance (Zeeman), more preferable from an appropriate topology in the class $\mathfrak{Z}-\mathfrak{G}$ under which a homeomorphism is an isometry (G\"obel)? Since topological conditions that come as a result of a causality requirement are key in the existence of singularities in general relativity, the global topological conditions that one will supply the spacetime manifold might play an important role in describing the transition from the quantum non-local theory to a classical local theory.

SoftBV - a software tool for screening the materials genome of inorganic fast ion conductors.

The identification of materials for advanced energy-storage systems is still mostly based on experimental trial and error. Increasingly, computational tools are sought to accelerate materials discovery by computational predictions. Here are introduced a set of computationally inexpensive software tools that exploit the bond-valence-based empirical force field previously developed by the authors to enable high-throughput computational screening of experimental or simulated crystal-structure models of battery materials predicting a variety of properties of technological relevance, including a structure plausibility check, surface energies, an inventory of equilibrium and interstitial sites, the topology of ion-migration paths in between those sites, the respective migration barriers and the site-specific attempt frequencies. All of these can be predicted from CIF files of structure models at a minute fraction of the computational cost of density functional theory (DFT) simulations, and with the added advantage that all the relevant pathway segments are analysed instead of arbitrarily predetermined paths. The capabilities and limitations of the approach are evaluated for a wide range of ion-conducting solids. An integrated simple kinetic Monte Carlo simulation provides rough (but less reliable) predictions of the absolute conductivity at a given temperature. The automated adaptation of the force field to the composition and charge distribution in the simulated material allows for a high transferability of the force field within a wide range of Lewis acid-Lewis base-type ionic inorganic compounds as necessary for high-throughput screening. While the transferability and precision will not reach the same levels as in DFT simulations, the fact that the computational cost is several orders of magnitude lower allows the application of the approach not only to pre-screen databases of simple structure prototypes but also to structure models of complex disordered or amorphous phases, and provides a path to expand the analysis to charge transfer across interfaces that would be difficult to cover by ab initio methods.

The key mechanical problems of on-orbit construction

On-orbit construction is an space mission to construct spacecraft and modules on spatial orbits or objects outside the Earth, which would be manufactured and assembled with the local or carry-on materials. Since it is not necessary to undergo the severe mechanical environment during the rocket launching and not constrained by the limit room in rocket dome, on-orbit construction can reduce the weight of the spacecraft effectively and complete the construction of ultra-large space facility in hundreds or even thousands meters. It shows the tremendous potential for human space exploration. However, some challenging mechanical factors need to be considered for this exciting plan. In this paper some key mechanical problems were discussed about the concept and process of on-orbit construction with the complete concept on demand, material requirements, space environment, dynamics, and mechanical constrains. The technical advantages and the practical demand are introduced for the on-orbit construction in the aerospace engineering. And the methodology on material processing were proposed. Some unique chareacteristics of space enviroment were considered, e.g. microgravity, high vacuum and extrame temperature conditions, along with the change on physical properties. The material property is fundamental and challenging for the construction. Furthermore, the dynamic analysis and control strategy were analyzed in all fabricating process for ultra-lage structures. The possilbe exciters and source of fluctuation were discussed. At last, the mechanical constrains were clarified for large space sturcture in on-obrit construction. And a two steps optimization model was defined for structure topology and construction path. Some suggestions were given on the key mechanical problems in the field of on-orbit construction.

Simulating Transport Networks With a <italic>Physarum</italic> Foraging Model

Designing effective transport networks can be considered as one of the most debated problems in the area of computational intelligence. Some nature-inspired algorithms have shown excellent abilities in the adaptive network construction. In this aspect, a unique creature, called Physarum , has exhibited the computing capacity to optimize protoplasmic networks connecting distributed food sources. This inspires our work to design a Physarum foraging platform for constructing transport networks. Specifically, the traditional Physarum foraging model is adapted to construct transport networks in China. In order to get close to the real scenario, practical data are collected to build the environment of the Physarum foraging model and the structure of real transport networks. Some measurements in the domain of complex networks, such as average path length, network efficiency, topology robustness, and functional robustness, are used for performance comparison. The experimental results demonstrate that Physarum foraging models excel in constructing highly efficient and robust networks, which can be utilized for directing the design of transport networks in the real world.

Formation of the quasi-planar B50 boron cluster: topological path from B10 and disk aromaticity.

The lowest-lying isomer of the B50 boron cluster is confirmed to have a quasi-planar shape with two hexagonal holes. By applying a topological (leap-frog) dual operation followed by boron capping, we demonstrated that such a quasi-planar structure actually comes from the smallest elongated B102-, and its high thermodynamic stability is due to its inherent disk aromaticity arising from its 32 valent π electrons that fully occupy a disk configuration of [(1σ)2(1π)4(1δ)4(2σ)2(1φ)4(2π)4(1γ)4(2δ)4(1η)4]. The aromatic character of the quasi-planar B50 is further supported by a strong diatropic magnetic current flow. The sudden appearance of a quasi-planar B50 again points out that the growth pattern of pure boron clusters is still far from being completely understood.

Research on multi-load AGV path planning of weaving workshop based on time priority.

The multi-load AGV (Automatic Guided Vehicle) is a new kind of materials handling equipment used to load cloth automatically in an intelligent weaving workshop. It can transport multiple rolls of cloth and choose the correct, most effective path to improve the transportation efficiency without people engaged in. This paper creates a feasible path topology according to the layout of the workshop and the logistics environment, and uses the Warshall-Floyd algorithm to search for the optimal route between two arbitrary points. The aim of the path planning is to maximize the machine efficiency, which is constrained by environmental limits, load limits and work limits. This paper establishes the mathematical model of the path planning problem using the mixed genetic particle swarm optimization algorithm (GA-PSO) to solve the problem, and the particle iteration mechanism based on the time priority is proposed to make the evolution more directional and accelerate the convergence speed of the algorithm. The effectiveness and practicability of the model and methods are verified by simulation and benefit analysis.

Indoor Localization Method Based on Sequential Motion Tracking Using Topological Path Map

This paper proposes a novel indoor localization method based on sequential motion tracking (SMT) using a topological path map that can improve the shortcomings of traditional methods using range-only measurement sensors. The proposed method consists of map generation and location estimation. First, in the map preparation, we present the construction method of a radio fingerprint map and the topological path map. The radio fingerprint map contains radio signals moderated by a median filter, and the topological path map includes possible path motions in the form of nodes and edges using a floorplan drawing. Second, for location estimation, fingerprint analysis and SMT methods are developed. Fingerprint analysis finds the global region based on a histogram evaluation between the radio fingerprint map and online observations, which rely on Wi-Fi. The SMT determines the optimal position on the topological path map by considering the historical motion data and the fingerprint analysis result. Finally, the experimental results show that the proposed method is robust to the uncertainty of the fingerprint analysis using the range sensors and that it can accurately track global positions with efficient computations.

Inter-Network Crosstalk and Communication Solutions for Self-Adaptive Nodes Build Self-Organizing Network

When there are multiple ZigBee wireless sensor networks in the same area, in order to solve the problems such as mutual interference between the transmitted information of these subnetworks, abnormal parameters of coordinator network construction, and disorder of network access between nodes, an improved communication method between ZigBee sub-networks is proposed. Compared with other traditional algorithms that show in the simulation results, the improved algorithm mechanism is more reasonable in network topology and transmission path. Each node can evenly share the network energy consumption, making the network run longer. In practice tests, several sub-networks composed of several improved algorithms are used to verify the feasibility of this method.

Topochemical Path in High Lithiation of MoS2

Lithiation of MoS2/RGO (reduced graphite oxide) electrodes repeatedly reached experimental capacities larger than 1000 mA·g–1, corresponding to at least 6 lithium equivalents per gram of MoS2. At our best knowledge, a convincing explanation is still missing in literature. In most cases, phase separation into Li2S and elemental Mo was assumed to occur. However, this can only explain capacities up to 669 mA·g–1, corresponding to an exchange of four Li. Formation of LiMo alloys could resolve the problem but the Li/Mo system does not contain any binary phases. If signs for Li2S formation were found, indeed experimental capacities were below 700 mAh·g–1. Here we present a topochemical mechanism, which sustains multiple charge/discharge cycles at 1000 mAh·g–1, corresponding to an exchange of at least 6 Li per formula unit MoS2. This topochemical reaction route prevents decomposition into binary phases and thus avoids segregation of the components of MoS2. Throughout the whole lithiation/delithiation process, distinct layers of Mo are preserved but extended or shrunk by slight movements and reshuffling of sulfur and lithium atoms. On addition of 6 Li per formula unit to MoS2, all central sulfur atoms are hosted in mutual Mo–S layers such that formal S2– and Mo2– anions appear coordinated by lithium cations. Indeed, similar structures are known in the field of Zintl phases. Our first‐principles crystal structure prediction study describes this topological path through conversion reactions during the lithiation/delithiation processes. All optimized phases along the topological path exhibit a distinct Mo layering giving rise to a series of dominant scattering into pseudo 001 reflections perpendicular to these Mo planes. The mechanism we present here explains why such high capacities can be reached reversibly for MoS2/RGO nano composites

Observation of the Sub-100 Femtosecond Population of a Dark State in a Thiobase Mediating Intersystem Crossing.

We combined sub-30 fs broadband transient absorption spectroscopy in the ultraviolet with state-of-the-art quantum mechanics/molecular mechanics simulations to study the ultrafast excited-state dynamics of the sulfur-substituted nucleobase 4-thiouracil. We observed a clear mismatch between the time scales for the decay of the stimulated emission from the bright ππ* state (76 ± 16 fs, experimentally elusive until now) and the buildup of the photoinduced absorption of the triplet state (225 ± 30 fs). These data provide evidence that the intersystem crossing occurs via a dark state, which is intermediately populated on the sub-100 fs time scale. Nonlinear spectroscopy simulations, extrapolated from a detailed CASPT2/MM decay path topology of the solvated system together with an excited state mixed quantum-classical nonadiabatic dynamics, reproduce the experimental results and explain the experimentally observed vibrational coherences. The theoretical analysis rationalizes the observed different triplet buildup times of 4- and 2-thiouracil.

Can Combined Electrostatic and Polarization Effects Alone Explain the F···F Negative-Negative Bonding in Simple Fluoro-Substituted Benzene Derivatives? A First-Principles Perspective

The divergence of fluorine-based systems and significance of their nascent non-covalent chemistry in molecular assemblies are presented in a brief review of the field. Emphasis has been placed to show that type-I and -II halogen-centered F···F long-ranged intermolecular distances viable between the entirely negative fluorine atoms in some fluoro-substituted dimers of C6H6 can be regarded as the consequence of significant non-covalent attractive interactions. Such attractive interactions observed in the solid-state structures of C6F6 and other similar fluorine-substituted aromatic compounds have frequently been underappreciated. While these are often ascribed to crystal packing effects, we show using first-principles level calculations that these are much more fundamental in nature. The stability and reliability of these interactions are supported by their negative binding energies that emerge from a supermolecular procedure using MP2 (second-order Møller-Plesset perturbation theory), and from the Symmetry Adapted Perturbation Theory, in which the latter does not determine the interaction energy by computing the total energy of the monomers or dimer. Quantum Theory of Atoms in Molecules and Reduced Density Gradient Non-Covalent Index charge-density-based approaches confirm the F···F contacts are a consequence of attraction by their unified bond path (and bond critical point) and isosurface charge density topologies, respectively. These interactions can be explained neither by the so-called molecular electrostatic surface potential (MESP) model approach that often demonstrates attraction between sites of opposite electrostatic surface potential by means of Coulomb’s law of electrostatics, nor purely by the effect of electrostatic polarization. We provide evidence against the standalone use of this approach and the overlooking of other approaches, as the former does not allow for the calculation of the electrostatic potential on the surfaces of the overlapping atoms on the monomers as in the equilibrium geometry of a complex. This study thus provides unequivocal evidence of the limitation of the MESP approach for its use in gaining insight into the nature of reactivity of overlapped interacting atoms and the intermolecular interactions involved.