Topology Transformation Research Articles

Lagrangian method for deriving electrically dual power converters applicable to nonplanar circuit topologies

This paper proposes a novel method for deriving dual converters, namely deriving current‐source converters from voltage‐source counterparts, and vice versa. The conventional derivation method is based on the transformation of circuit topology, in which series connections are converted into parallel connections, and vice versa. However, this method cannot be directly applied to nonplanar circuits because they do not allow perfect topological transformation, although many of them are known to have duals. Lagrangian dynamics does not depend on the topological relation to transform a system into another equivalent system; therefore, it possibly avoids problems related to topological transformation and may provide a universal and systematic method that can be consistently applied to nonplanar circuits. This paper discusses the derivation of duals using Lagrangian dynamics. Along with the theory, this paper presents two examples of Lagrangian derivation of duals. One derives a dual of a planar circuit, to which the topological transformation is applicable. The other derives two duals of a nonplanar circuit. Consequently, these examples suggest that the proposed method is a prospective candidate for universal and systematic derivation of duals. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Synthesis and Star/Linear Topology Transformation of a Mechanically Linked ABC Terpolymer.

The synthesis of an ABC star terpolymer containing one polymer chain connected mechanically through a rotaxane linkage and its topology transformation to a linear structure are reported. Pseudo[2]rotaxane, which was designed as the key trifunctional species for the star polymer synthesis, comprised a sec-ammonium axle with ethynyl and hydroxy groups and a crown ether wheel with a trithiocarbonate group. Stepwise polymer connections to the pseudo[2]rotaxane using the three groups afforded a rotaxane-linked ABC star terpolymer. The topology transformation from star to linear by the removal of the attractive interaction between the axle and wheel components yielded a linear ABC terpolymer via the wheel shifting to the axle end. The spectroscopic and solution property changes clearly indicated the occurrence of the polymer topology change.

Efficient Synthesis of Cyclic Block Copolymers by Rotaxane Protocol by Linear/Cyclic Topology Transformation.

High-yielding synthesis of cyclic block copolymer (CBC) using the rotaxane protocol by linear-cyclic polymer topology transformation was first demonstrated. Initial complexation of OH-terminated sec-ammonium salt and a crown ether was followed by the successive living ring-opening polymerizations of two lactones to a linear block copolymer having a rotaxane structure by the final capping of the propagation end. CBC was obtained in a high yield by an exploitation of the mechanical linkage through the translational movement of the rotaxane component to transform polymer structure from linear to cyclic. Furthermore, the change of the polymer topology was translated into a macroscopic change in crystallinity of the block copolymer.

An improved local remeshing algorithm for moving boundary problems

ABSTRACTThree issues are tackled in this study to improve the robustness of local remeshing techniques. Firstly, the local remeshing region (hereafter referred to as ‘hole’) is initialized by removing low-quality elements and then continuously expanded until a certain element quality is reached after remeshing. The effect of the number of the expansion cycle on the hole size and element quality after remeshing is experimentally analyzed. Secondly, the grid sources for element size control are attached to moving bodies and will move along with their host bodies to ensure reasonable grid resolution inside the hole. Thirdly, the boundary recovery procedure of a Delaunay grid generation approach is enhanced by a new grid topology transformation technique (namely shell transformation) so that the new grid created inside the hole is therefore free of elements of extremely deformed/skewed shape, whilst also respecting the hole boundary. The proposed local remeshing algorithm has been integrated with an in-house unstructured grid-based simulation system for solving moving boundary problems. The robustness and accuracy of the developed local remeshing technique are successfully demonstrated via industry-scale applications for complex flow simulations.

Modified Cascaded Multilevel Grid-Connected Inverter to Enhance European Efficiency and Several Extended Topologies

This paper proposes a modified cascaded multilevel grid-connected inverter (MCM-GCI) suitable for photovoltaic grid-connected generation system, which considers wide operation range, low grid current total harmonics distortion (THD), and high European efficiency. In the proposed topology, a bidirectional power switch is added to the standard single-phase cascaded multilevel inverter (CMI) to implement the transformation between CMI mode and H-bridge inverter (HBI) mode. An online topology transformation approach of the MCM-GCI is proposed to guarantee the topology modes transformed safely and smoothly. The proposed MCM-GCI operates in CMI mode when the PV arrays’ output voltage and power are low, and transforms into HBI mode when the PV arrays’ output voltage and power are high. Experimental results of five-level MCM-GCI are represented to validate the feasibility of the proposed topology and it is also compared with other three classic grid-connected inverters to highlight its advantages. Furthermore, more structures based on hybrid CMI, which possess the topology transformation ability, are shown to further improve the generation range and obtain a higher efficiency of the system.

Star/Linear Polymer Topology Transformation Facilitated by Mechanical Linking of Polymer Chains

AbstractTopology transformation of a star polymer to a linear polymer is demonstrated for the first time. A three‐armed star polymer possessing a mechanical linking of two polymer chains was synthesized by the living ring‐opening polymerization of δ‐valerolactone initiated by a pseudo[2]rotaxane having three hydroxy groups as the initiator sites on the wheel component and at both axle termini. The polymerization was followed by the propagation end‐capping reaction with a bulky isocyanate not only to prevent the wheel component deslippage but also to introduce the urethane moiety at the axle terminal. The resulting rotaxane‐linked star polymer with a fixed rotaxane linkage based on the ammonium/crown ether interaction was subjected to N‐acetylation of the ammonium moiety, which liberated the components from the interaction to move the wheel component to the urethane terminal as the interaction site, eventually affording the linear polymer. The physical property change caused by the present topology transformation was confirmed by the hydrodynamic volume and viscosity.

Star/linear polymer topology transformation facilitated by mechanical linking of polymer chains.

Topology transformation of a star polymer to a linear polymer is demonstrated for the first time. A three-armed star polymer possessing a mechanical linking of two polymer chains was synthesized by the living ring-opening polymerization of δ-valerolactone initiated by a pseudo[2]rotaxane having three hydroxy groups as the initiator sites on the wheel component and at both axle termini. The polymerization was followed by the propagation end-capping reaction with a bulky isocyanate not only to prevent the wheel component deslippage but also to introduce the urethane moiety at the axle terminal. The resulting rotaxane-linked star polymer with a fixed rotaxane linkage based on the ammonium/crown ether interaction was subjected to N-acetylation of the ammonium moiety, which liberated the components from the interaction to move the wheel component to the urethane terminal as the interaction site, eventually affording the linear polymer. The physical property change caused by the present topology transformation was confirmed by the hydrodynamic volume and viscosity.

Bifurcations and eddy genesis of Stokes flow within a sectorial cavity PART II: Co-moving lids

This paper is a complementary study to earlier work (Gürcan, 2013), concerning eddy genesis and bifurcations in a sectorial driven cavity for Stokes flow, consisting of a pair of curved stationary side-walls and two straight translating lids moving in the same radial direction with speeds U1 and U2. The flow is governed by two physical control parameters: the cavity aspect ratio A=r2r1 where r1 and r2 are the radii of the inner and outer curved side-walls, respectively and the ratio of the upper and lower lid speeds (S=U1U2). In previous work (Gürcan, 2013), focus was on lids moving in the opposite direction or a single moving lid.By considering different A values for each S, the streamline patterns and their bifurcations are studied; occurrence of stagnation point bifurcations and transformation of the local flow topology are observed at critical values of A and S. The key results are shown in an (S,A) control space diagram which exhibits an intricate structure due to the intersection and confluence of eight bifurcation curves representing flow bifurcations at degenerate critical points. Six different eddy genesis mechanisms are observed for S∈(0,1] and A∈(1.45,20). In each case the flow structures and eddy genesis mechanisms are illustrated in detail with figures and bifurcation diagrams. The study also serves as a benchmark problem for testing new numerical algorithms.

DTA: Dynamic topology algorithms in content-based Publish/Subscribe

Publish/Subscribe (Pub/Sub) has been used in many large-scale distributed systems owing to its scalability and loose coupling, and most of the existing Pub/Sub systems are built on the basis of the acyclic topology because the routing algorithm can be simplified. However, the flexibility is limited and the robustness is also a big problem. This paper proposes a dynamic topology algorithm to facilitate the adaptation to the dynamic change of the network conditions, which is composed of two parts: Topology Generation Algorithm (TGA) and Topology Transformation Algorithm (TTA). The topology can switch between cyclic topology and acyclic topology automatically, and the advantages of both the cyclic topology and the acyclic topology can thus be exploited. In addition, the efficiency and scalability can also be guaranteed when the topology changes. The topology of a Pub/Sub system will be transformed into a cyclic one to enhance robustness when the network condition gets worse, while into the acyclic pattern when the network condition is getting better. Experiments show that average number of edges in the topology reduces by 12% and subscription notification delivery time improves by 20%.

Unified Synthesis of Tapped-Inductor DC-to-DC Converters

Tapped-inductor variations of single-switch, single-diode, dc-to-dc converters are categorized based on a new unified sequential circuit topology and mathematical transformation approach, all seeded from a basic buck–boost converter and its transfer function. Classification focuses on identifying two different ac circuit coupled inductor arrangements of the basic buck–boost dc-to-dc converter. Subsequent dc circuit sequential manipulation yields all 11 known, documented, in theory, in simulation and practically, tapped-inductor dc-to-dc converter topologies. The procedure not only generates sequences of topologies, but also generates the voltage transfer functions without recourse to analysis of the circuit internal operating mechanisms. Consequently, two converter classes group the 11 known tapped-inductor topologies, which is at least one fewer topology classes than universally accepted. The methodology yields two new classes of three and ten coupled inductor converter topologies, all with new transfer functions. The new analysis approach is adaptable to the analysis of all single-switch, single-diode, (noncoupled inductor), dc-to-dc converters (single and two inductor topologies), formulated from the basic buck–boost converter.

Principal resonance bifurcation of bending–torsion coupling of aero-engine compressor blade with assembled clearance under lateral displacement excitation of rotor shaft

The principal resonance of bending–torsion coupling of a compressor blade with an assembled clearance and a cubic structural nonlinearity, subjected to the lateral displacement excitation of rotor shaft and aerodynamic loads, is analyzed to explore the topology transformation of amplitude–frequency response along with the changes of the physical parameters. The bifurcation equation of the first-order principal resonance response is derived from using the averaging method. The transition set and the bifurcation figures of the response solution are obtained by the singularity theory. The effects of the main physical parameters of the system on the topology transformation of amplitude–frequency response are discussed.

Simultaneous transitions in cuprate momentum-space topology and electronic symmetry breaking.

The existence of electronic symmetry breaking in the underdoped cuprates and its disappearance with increased hole density p are now widely reported. However, the relation between this transition and the momentum-space (k-space) electronic structure underpinning the superconductivity has not yet been established. Here, we visualize the Q = 0 (intra-unit-cell) and Q ≠ 0 (density-wave) broken-symmetry states, simultaneously with the coherent k-space topology, for Bi₂Sr₂CaCu₂O(8+δ) samples spanning the phase diagram 0.06 ≤ p ≤ 0.23. We show that the electronic symmetry-breaking tendencies weaken with increasing p and disappear close to a critical doping p(c) = 0.19. Concomitantly, the coherent k-space topology undergoes an abrupt transition, from arcs to closed contours, at the same p(c). These data reveal that the k-space topology transformation in cuprates is linked intimately with the disappearance of the electronic symmetry breaking at a concealed critical point.

A highly miniaturized LTCC dual-band UWB filter using independent transmission zeros and lowpass filters

In this paper, a compact dual-band ultra-wideband (UWB) filter has been newly designed and fabricated for 3.1–4.75GHz and 6.0–8.5GHz UWB system applications by embedding all passive lumped elements into low temperature co-fired ceramic (LTCC) substrate. In order to reduce its size/volume and prevent parasitic electromagnetic (EM) coupling between the embedded passive elements, it was newly designed by using a modified 3rd order Chebyshev filter topology and J-inverter transformation technology. Moreover, in order to completely reject the wireless local area network (WLAN) bands of 2.4GHz and 5.15GHz, an independent transmission zeros technology was applied. For forming the higher passband, lowpass filters were also applied with two LC resonant circuits by using roll-off characteristics by independent transmission zeros. The measured insertion losses in the lower and upper passbands were better than 2.5 and 2.3dB, respectively. Return loss and group delay were better than 8dB and 0.61ns, respectively in all the passbands. Independent transmission zeros that occurred at 5.17 and 5.42GHz provided suppression of 22dB at the WLAN band. The size/volume of the fabricated LTCC dual-band UWB filter was 3.65×2.35×0.65 (H)mm3.

On Controllability Problems of High-Order Dynamical Multi-Agent Systems

Controllability problems of dynamical high-order multi-agent systems are concerned. A methodology on graph topology transformation is proposed, which can help to analyze the controllability. According to this methodology, a path can be regarded as controllability canonical form of graph, and any controllable graph can be transformed into an equivalent path. Besides, controllability of heterogeneous multi-agent systems is also discussed.

Access Points Planning in Urban Area for Data Dissemination to Drivers

Roadside infrastructure can greatly help disseminate data to drivers. In this paper, we study a fundamental problem, i.e., roadside infrastructure planning. We propose a class of algorithms named Tailor to select a minimum number of intersections to install the infrastructure. In the case when the traffic information is not available, we formulate the intersection selection problem, which formally proves its np-completeness, and provide novel heuristics, i.e., the adapted-bipartite-based heuristics (ABS), to solve it, whose worst-case approximation ratio is 4/3. ABS bridges the planar graph and the bipartite graph through topology transformation. With ABS, the approximate solution to all the problems that are NP-hard in a general planar graph but polynomially solvable in a bipartite graph can be efficiently obtained in the planar graph. We also prove that, even with traffic information, the intersection selection problem remains NP-hard. Greedy heuristics is employed to balance the tradeoff between the number of selected intersections and the percentage of reached vehicles.

Microstructural Evolution of As-cast 42CrMo Ring during Hot Rolling

In order to avoid traditional ring parts hot rolling process problems of many times heating and so on, the as-cast 42CrMo alloy ring short process flow blank-casting and rolling compound forming process is taken as the research object, a series of experiments are performed on the Gleeble-1500D machine and metallographic microscope, the flow stress curves under temperatures of 850-1 150 ℃ and strain rates of 0.05-5 s-1 are obtained. The dislocation density variation and the grain growth kinetics of each dynamically recrystallizing grain are calculated by transforming the flow stress curves. In addition, the nucleation and the growth kinetics of dynamically recrystallized grains are evaluated. The grain topology deformation technology is studied, and the grain topology structures are optimized by use of the principal component analysis. The results show that the Kock-Mecking(KM) dislocation density equation can be employed to calculate the dislocation evolution during dynamic recrystallisation of 42CrMo alloy. The KM dislocation density model coupled with cellular automata method and optimized grain topology transformation technology can simulate dislocation density during dynamic recrystallization process accurately.

A Controllable Gate Effect in Cobalt(II) Organic Frameworks by Reversible Structure Transformations

With H2 O or NH3 stimuli, the blue cobalt-based metal-organic framework (MOF) BP can reversibly transform to red RP. The removal/recovery of terephthalate ligands accompanied by the transformation leads to a gate effect, which allows the encapsulation and release of small solvent molecules under certain conditions. This is the first example of topology transformation from a self-penetrating to interpenetrating net in 3D MOFs.

A New Family of Cascaded Transformer Six Switches Sub-Multilevel Inverter with Several Advantages

This paper presents a novel topology for cascaded transformer sub-multilevel converter. Eachsub-multilevel converter consists of two DC voltage sources with six switches to achieve five-level voltage. The proposed topology results in reduction of DC voltage sources and switches number. Single phase low frequency transformers are used in proposed topology and voltage transformation and galvanic isolation between load and sources are given by transformers. This topology can operate as symmetric or asymmetric converter but in this paper we have focused on symmetric state. The operation and performance of the suggested multilevel converter has been verified by the simulation results of a single-phase nine-level multilevel converter using MATLAB/SIMULINK.

A Compact LTCC Dual-Band WLAN Filter using Two Notch Resonators

This paper presents compact dual-band WLAN filter and filter module. They were developed by embedding all of the passive lumped elements into a LTCC substrate. In order to reduce the size/volume of the filter and avoid EM parasitic couplings between the passive elements, the proposed filter was designed using a 3rd order Chebyshev circuit topology and J-inverter transformation technology. The 3rd order Chebyshev bandpass filter was firstly designed for the bandselection of the 802.11b and was then transformed using finite transmission zeros technologies. Finally, the dual-band filter was realized by adding two notch resonators to the 802.11b filter circuit for the band-selection of the 802.11a/g. The maximum insertion losses in the lower and higher passbands were better than 2.0 and 1.3 dB with minimum return losses of 15 and 14 dB, respectively. Furthermore, the filter was integrated with a diplexer to clearly split the signals between 2 and 5 GHz. The maximum insertion and minimum return losses of the fabricated module were 2.2 and 14 dB at 2.4 - 2.5 GHz, and 1.6 and 19 dB at 5.15 - 5.85 GHz, respectively. The overall volume of the fabricated filter was 2.7 × 2.3 × 0.59 mm3.

Straightforward synthesis of functionalized cyclic polymers in high yield via RAFT and thiolactone–disulfide chemistry

An efficient synthetic pathway toward cyclic polymers based on the combination of thiolactone and disulfide chemistry has been developed. First, heterotelechelic linear polystyrene (PS) containing an α-thiolactone (TLa) and an ω-dithiobenzoate group was synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization, employing a newly designed TLa-bearing chain transfer agent (CTA). The subsequent reaction of this heterotelechelic polymer with an amine, which acts as a nucleophile for both the TLa and dithiobenzoate units, generated the α,ω-thiol-telechelic PS under ambient conditions without the need for any catalyst or other additives. The arrangement of thiols under a high dilution afforded single cyclic PS (c-PS) through an oxidative disulfide linkage. The cyclic PS (c-PS) disulfide ring formation was evidenced by SEC, MALDI-TOF MS and 1H-NMR characterization. Moreover, we demonstrated a controlled ring opening via either disulfide reduction or thiol–disulfide exchange to enable easy and clean topology transformation. Furthermore, to illustrate the broad utility of this synthetic methodology, different amines including functional ones were employed, allowing for the one-step preparation of functionalized cyclic polymers with high yields.