Compact Topology Research Articles

Highly miniaturized dual-band bandpass filter with wide bandwidth and large center frequency ratio

The design of a miniaturized dual-band bandpass filter featuring a broad bandwidth and a high center frequency ratio is demonstrated in this article. A novel symmetrically loaded shunt coupled line with dual stepped impedance stubs has been investigated for the first time and it is utilized to realize a dual-band bandpass filter with seven transmission zeros. The transmission zeros frequencies of the filter response have been theoretically verified using even-odd mode analysis. For experimental validation purposes, a dual-band filter with a center frequency ratio of 4.06 covering 5G applications is implemented using Rogers RT/duroid 5870 substrate and tested. The tested filter has wide 3 dB fractional bandwidths of 53.8% and 17.9% in the first and second passbands, respectively, and has a compact topology of 0.20 × 0.09 λg 2. The full-wave simulated and tested magnitude and group delay responses of the proposed filter are in good congruence.

Antigenic cartography using variant-specific hamster sera reveals substantial antigenic variation among Omicron subvariants

Severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2) has developed substantial antigenic variability. As the majority of the population now has pre-existing immunity due to infection or vaccination, the use of experimentally generated animal immune sera can be valuable for measuring antigenic differences between virus variants. Here, we immunized Syrian hamsters by two successive infections with one of nine SARS-CoV-2 variants. Their sera were titrated against 16 SARS-CoV-2 variants, and the resulting titers were visualized using antigenic cartography. The antigenic map shows a condensed cluster containing all pre-Omicron variants (D614G, Alpha, Delta, Beta, Mu, and an engineered B.1+E484K variant) and considerably more diversity among a selected panel of Omicron subvariants (BA.1, BA.2, BA.4/BA.5, the BA.5 descendants BF.7 and BQ.1.18, the BA.2.75 descendant BN.1.3.1, the BA.2-derived recombinants XBB.2 and EG.5.1, and the BA.2.86 descendant JN.1). Some Omicron subvariants were as antigenically distinct from each other as the wildtype is from the Omicron BA.1 variant. Compared to titers measured in human sera, titers in hamster sera are of higher magnitude, show less fold change, and result in a more compact antigenic map topology. The results highlight the potential of sera from hamsters for the continued antigenic characterization of SARS-CoV-2.

Information orientation-based modular Type-2 fuzzy neural network

Type-2 fuzzy neural networks (T2FNNs) have gained popularity due to their processing ability for high uncertainty. However, concerned with the high-dimensional problems of nonlinear systems, the interpretability of individual T2FNNs is weak due to the exponential growth of fuzzy rules. To deal with this problem, an information orientation-based modular T2FNN (IO-MT2FNN) is developed to improve its interpretability in this paper. First, an information entropy-based decomposition method is designed to divide the original input space into three sub-spaces, namely edge, local and global regions. Then, the information with different attributes is separated to provide an unambiguous interpretation. Second, the independent module describing these regions with type-2 fuzzy sets is embedded in the membership function layer of IO-MT2FNN to represent the coupling relationship between regional information in an interpretable way. Third, an information mapping strategy is introduced with low-order Gaussian kernel matrices, instead of a high-order mapping matrix, to extract the features from the allocated information in each module, which enables IO-MT2FNN to achieve a compact topology through dimensionality reduction. Finally, the simulations demonstrate that the proposed IO-MT2FNN can compete with the advanced approaches in terms of interpretability for the prediction of high-dimensional and complex systems.

The Hyperreals enlargement sets and its application on compact topology

This paper presents a study of hyperreal numbers and their relations to real numbers. The hyperreals are a number system extension of the real number system. With this system, simpler and more intuitively natural definition (topological notions of special points and compactness), proofs (Heine-Borel theorem), and new concepts (limited, unlimited numbers, enlargement sets, and halos) of mathematical interest are offered.

A Compact Dual-polarized Probe-fed UWB Antenna System for Breast Cancer Detection Applications

This article proposes an electrically small, probe-fed Ultra-Wideband (UWB) monopole antenna on a slotted truncated ground plane for breast cancer detection. The physical footprint of the proposed antenna element is 33 mm × 35 mm × 0.5 mm. This element is designed on the low-cost FR4 Epoxy substrate with a thickness of 0.5 mm. The proposed antenna has an electrical size of 0.33λ × 0.35λ × 0.005λ at the lowest frequency of operation; the radiator offers an impedance bandwidth of 8.34 GHz, which implies a fractional bandwidth of 115.5%. A compact dual-polarized antenna topology with two orthogonally placed probe-fed monopole antennas is proposed to achieve polarization diversity. The impedance characteristics of the individual radiating elements are maintained in spite of the electrical proximity of the radiators. The numerically computed and experimentally measured results of dual-polarized electrically small UWB antenna agree quite well. The proposed dual-polarized antenna topology is investigated for its utility in breast cancer detection in simulation.

On locally compact shift continuous topologies on the semigroup $\boldsymbol{B}_{[0,\infty)}$ with an adjoined compact ideal

Let $[0,\infty)$ be the set of all non-negative real numbers. The set $\boldsymbol{B}_{[0,\infty)}=[0,\infty)\times [0,\infty)$ with the following binary operation $(a,b)(c,d)=(a+c-\min\{b,c\},b+d-\min\{b,c\})$ is a bisimple inverse semigroup.In the paper we study Hausdorff locally compact shift-continuous topologies on the semigroup $\boldsymbol{B}_{[0,\infty)}$ with an adjoined compact ideal of the following tree types.The semigroup $\boldsymbol{B}_{[0,\infty)}$ with the induced usual topology $\tau_u$ from $\mathbb{R}^2$, with the topology $\tau_L$ which is generated by the natural partial order on the inverse semigroup $\boldsymbol{B}_{[0,\infty)}$, and the discrete topology are denoted by $\boldsymbol{B}^1_{[0,\infty)}$, $\boldsymbol{B}^2_{[0,\infty)}$, and $\boldsymbol{B}^{\mathfrak{d}}_{[0,\infty)}$, respectively. We show that if $S_1^I$ ($S_2^I$) is a Hausdorff locally compact semitopological semigroup $\boldsymbol{B}^1_{[0,\infty)}$ ($\boldsymbol{B}^2_{[0,\infty)}$) with an adjoined compact ideal $I$ then either $I$ is an open subset of $S_1^I$ ($S_2^I$) or the topological space $S_1^I$ ($S_2^I$) is compact. As a corollary we obtain that the topological space of a Hausdorff locally compact shift-continuous topology on $S^1_{\boldsymbol{0}}=\boldsymbol{B}^1_{[0,\infty)}\cup\{\boldsymbol{0}\}$ (resp. $S^2_{\boldsymbol{0}}=\boldsymbol{B}^2_{[0,\infty)}\cup\{\boldsymbol{0}\}$) with an adjoined zero $\boldsymbol{0}$ is either homeomorphic to the one-point Alexandroff compactification of the topological space $\boldsymbol{B}^1_{[0,\infty)}$ (resp. $\boldsymbol{B}^2_{[0,\infty)}$) or zero is an isolated point of $S^1_{\boldsymbol{0}}$ (resp. $S^2_{\boldsymbol{0}}$).Also, we proved that if $S_{\mathfrak{d}}^I$ is a Hausdorff locally compact semitopological semigroup $\boldsymbol{B}^{\mathfrak{d}}_{[0,\infty)}$ with an adjoined compact ideal $I$ then $I$ is an open subset of $S_{\mathfrak{d}}^I$.

Axial Flux Permanent Magnet Motor Topologies Magnetic Performance Comparison

Axial flux permanent magnet motors have attracted increasing attention due to their compact topology and high torque density. Many topological variations have arisen over time; however, limited research has directly compared the differences in magnetic performance of these topologies. This paper carries out a comprehensive investigation, employing both analytical and 3D finite element analyses, to compare the magnetic performance of three topologies: yokeless and segmented armature (YASA), axial flux internal rotor (AFIR), and offset AFIR. The findings reveal that each topology offers specific advantages for different applications. The YASA topology excels in minimizing core losses; the AFIR configuration achieves the highest torque density; and the offset AFIR topology shows the highest efficiency. The offset AFIR topology appears to offer advantages for a wide array of applications due to its higher power factor and lower permanent magnet loss, leading to reduced costs for converter design and cooling system design.

ON LOCALLY COMPACT SHIFT-CONTINUOUS TOPOLOGIES ON SEMIGROUPS C+(A;B) AND C

Let $\mathscr{C}_{+}(a,b)$ and $\mathscr{C}_{-}(a,b)$ be upper and down subsemigroups of the bicyclic semigroup defined in \cite{Makanjuola-Umar=1997}. Let $\mathscr{C}_{+}(p,q)^0$ and $\mathscr{C}_{-}(p,q)^0$ be the semigroups $\mathscr{C}_{+}(a,b)$ and $\mathscr{C}_{-}(a,b)$ with the adjoined zero. We show that the semigroups $\mathscr{C}_{+}(p,q)^0$ and $\mathscr{C}_{-}(p,q)^0$ admit continuum many different Hausdorff locally compact shift-continuous topologies up to topological isomorphism.

In silico protein dynamics in the human cytoplasm: Partial folding, misfolding, fold switching, and non-native interactions.

We examine the influence of cellular interactions in all-atom models of a section of the Homo sapiens cytoplasm on the early folding events of the three-helix bundle protein B (PB). While genetically engineered PB is known to fold in dilute water box simulations in three microseconds, the three initially unfolded PB copies in our two cytoplasm models using a similar force field did not reach the native state during 30-microsecond simulations. We did however capture the formation of all three helices in a compact native-like topology. Folding in vivo is delayed because intramolecular contact formation within PB is in direct competition with intermolecular contacts between PB and surrounding macromolecules. In extreme cases, intermolecular beta-sheets are formed. Interactions with other macromolecules are also observed to promote structure formation, for example when a PB helix in our simulations is shielded from solvent by macromolecular crowding. Sticking and crowding in our models initiate sampling of helix/sheet structural plasticity of PB. Relatedly, in past in vitro experiments, similar GA domains were shown to switch between two different folds. Finally, we also observed that stickiness between PB and the cellular environment can be modulated in our simulations through the reduction in protein hydrophobicity when we reversed PB back to the wild-type sequence. This study demonstrates that even fast-folding proteins can get stuck in non-native states in the cell, making them useful models for protein-chaperone interactions and early stages of aggregate formation relevant to cellular disease.

Real-valued measurable cardinals and sequentially continuous homomorphisms

A. V. Arkhangel'skiĭ asked in 1981 if the variety V of topological groups generated by free topological groups on metrizable spaces coincides with the class of all topological groups. We show that if there exists a real-valued measurable cardinal then the variety V is a proper subclass of the class of all topological groups. A topological group G is called g-sequential if for any topological group H any sequentially continuous homomorphism G→H is continuous. We introduce the concept of a g-sequential cardinal and prove that a locally compact group is g-sequential if and only if its local weight is not a g-sequential cardinal. The product of a family of non-trivial g-sequential topological groups is g-sequential if and only if the cardinal of this family is not g-sequential. Suppose G is either the unitary group of a Hilbert space or the group of all self-homeomorphisms of a Tikhonov cube. Then G is g-sequential if and only if its weight is not a g-sequential cardinal. Every compact group of Ulam-measurable cardinality admits a strictly finer countably compact group topology.

Capacity Assessment and Analysis of Vertiports Based on Simulation

City air traffic as a new transportation mode has gradually attracted attention in recent years which will bring endless vitality to future urban development. An objective and accurate assessment of the vertiport capacity for UAVs (Unmanned Aerial Vehicles) is the basis for implementing air traffic flow management for UAVs, which is also a prerequisite for improving the efficiency of urban airspace resources used. Firstly, new topology designs are proposed and named as connected and compact topology designs based on the existing central airport topology design. Subsequently, three modes of operation are summarized for vertiports with multiple TLOF pads: independent operation, dependent operation, and segregated operation. In the next place, the overall traffic flow of the vertiport model is established based on AnyLogic while analyzing the logic of UAV operation in three modes as mentioned above. Eventually, according to the simulation results, the vertiport operation capacity, the UAVs delay, and surface area utilization under different operation modes and topology designs are analyzed. The simulation result shows that the overall average delay time of UAVs for independent operation mode is about 100 s less than that of segregated operation and it also shows that the utilization rate of independent operation mode under central design is as high as 54.42% while the utilization rate of TLOF pads of other design is less than 50%, and its vertiport capacity is the largest, so the independent operational mode under central configuration is the optimal combination.

Compact and Scalable Active-Integrated Antenna System With Both Oscillation and Amplification Characteristics for High-Power Applications

An active-integrated antenna (AIA) system with a compact and scalable topology is proposed in this work. Two kinds of highly integrated AIA unit cells, i.e., the oscillating unit cell and the amplifying unit cell, are designed by integrating the active switching circuits into the modified monopole antennas. In each working cycle, the amplifying unit cell remains stable until it is triggered by the radiation wave from the oscillating unit cell for in-phase radiation, thereby amplifying the output power. In order to reduce the antenna spacing, the corners of the ground of the antennas are cut off and the threshold voltage of the amplifying unit cells is precisely controlled to offset the mutual coupling, consequently realizing a much compact system. The AIA systems with and without the amplifying unit cell are fabricated, and the measured results verify the power amplification characteristic of the compact and scalable system. Compared to the existing self-oscillating AIAs, this work provides one more degree of freedom for power enhancement with a compact topology.

Countably compact group topologies on arbitrarily large free Abelian groups

We prove that if there are c incomparable selective ultrafilters then, for every infinite cardinal κ such that κω=κ, there exists a group topology on the free Abelian group of cardinality κ without nontrivial convergent sequences and such that every finite power is countably compact. In particular, there are arbitrarily large countably compact groups. This answers a 1992 question of D. Dikranjan and D. Shakhmatov.

Analytical Design of Compact Multiband Bandpass Filters with Multiconductor Transmission Lines and Shunt Open Stubs

A compact topology for implementing compact multiband bandpass filters is presented in this paper. To achieve the desired frequency response, two identical short-circuited multiconductor transmission lines (MTLs) and properly connected shunt open stubs are interconnected. Using this configuration, it is possible to design multiband bandpass filters effortlessly. As both the MTLs and the stubs are distributed elements, spur-line band-stop filters are added to mitigate the first replica of the structure’s frequency response. To assess the behavior of the developed filter design procedure, a prototype consisting of a six fingers-MTL and two shunt open stubs has been designed, manufactured, and analyzed, showing excellent agreement between analytical and measured results, considering that no simulation or optimization process has been performed during the design process, just for result verification. Furthermore, it is possible to establish a design criterion that allows the fast and reliable synthesis of multiband responses by varying just a small number of geometrical parameters of the MTLs and the corresponding stubs.

On a semitopological semigroup $\boldsymbol{B}_{\omega}^{\mathscr{F}}$ when a family $\mathscr{F}$ consists of inductive non-empty subsets of $\omega$

Let $\boldsymbol{B}_{\omega}^{\mathscr{F}}$ be the bicyclic semigroup extension for the family $\mathscr{F}$ of ${\omega}$-closed subsets of $\omega$ which is introduced in \cite{Gutik-Mykhalenych=2020}.We study topologizations of the semigroup $\boldsymbol{B}_{\omega}^{\mathscr{F}}$ for the family $\mathscr{F}$ of inductive ${\omega}$-closed subsets of $\omega$. We generalize Eberhart-Selden and Bertman-West results about topologizations of the bicyclic semigroup \cite{Bertman-West-1976, Eberhart-Selden=1969} and show that every Hausdorff shift-continuous topology on the semigroup $\boldsymbol{B}_{\omega}^{\mathscr{F}}$ is discrete and if a Hausdorff semitopological semigroup $S$ contains $\boldsymbol{B}_{\omega}^{\mathscr{F}}$ as a proper dense subsemigroup then $S\setminus\boldsymbol{B}_{\omega}^{\mathscr{F}}$ is an ideal of $S$. Also, we prove the following dichotomy: every Hausdorff locally compact shift-continuous topology on $\boldsymbol{B}_{\omega}^{\mathscr{F}}$ with an adjoined zero is either compact or discrete. As a consequence of the last result we obtain that every Hausdorff locally compact semigroup topology on $\boldsymbol{B}_{\omega}^{\mathscr{F}}$ with an adjoined zero is discrete and every Hausdorff locally compact shift-continuous topology on the semigroup $\boldsymbol{B}_{\omega}^{\mathscr{F}}\sqcup I$ with an adjoined compact ideal $I$ is either compact or the ideal $I$ is open, which extent many results about locally compact topologizations of some classes of semigroups onto extensions of the semigroup $\boldsymbol{B}_{\omega}^{\mathscr{F}}$.

Dual-Band High-Efficiency Power Amplifier With Adjustable Transmission Zero

A methodology for designing a dual-band (DB) high-efficiency power amplifier (PA) with adjustable transmission zero (TZ) is proposed in this brief. For achieving a compact topology, the circuit for constructing the adjustable TZ is merged into the output matching network (OMN), and an open stub is shared by the harmonic control network (HCN) and the OMN. For verifying the proposed design method and structure, a prototype operating at 2.1 and 3.5 GHz is designed. The adjustability of the TZ is analyzed, and the frequency range of the TZ is between 2.3 and 3.2 GHz. For verification, the TZ is set to be 2.4 GHz and the DB PA is fabricated and measured. The result shows that the PA achieves the maximum power-added efficiency (PAE) of 68.5% and 64.8% with the output power of 41.0 and 40.4 dBm at 2.1 and 3.5 GHz, respectively. Moreover, the power gain at the TZ of 2.4 GHz is −26.9 dB, which shows a good suppression effect. Therefore, the proposed PA has a good application prospect in wireless communication systems.

Power Factor Corrector Control Strategies of a Bidirectional Wireless Battery Charger With an Unfolding Active Rectifier

In this article, two power factor corrector (PFC) control strategies for a bidirectional inductive power transfer (IPT) system are proposed. These control strategies are presented for a novel power circuit without input and output interfaces for a wireless electric vehicle battery charger application. This compact topology comprises: unfolding rectifier, primary resonant bridge, and secondary-side active rectification. Two PFC controls are described in detail: a primary-side PFC control, performed in the primary resonant bridge; and a secondary-side PFC control, implemented in the secondary-side active rectification stage. Both strategies are based on a duty-cycle control operating close to the resonance frequency, integrating different functionalities, i.e., PFC, current shaping (CS), and power control on a single control strategy. We analyze each control strategy, evaluating them for different operating points of the charging process. The performance of the wireless charger applying both control strategies is evaluated in terms of power losses, power factor, harmonic distortion, and bifurcation. Additionally, the theoretical results are validated using a GaN-based experimental prototype. The presented analysis and experimental results clearly identify the advantages and limitations of each control strategy leaving no doubt about their usefulness for the future IPT systems.

Design and analysis of a frequency division and duty cycle control circuit for on-chip signal synthesis

In this article, a complementary metal–oxide–semiconductor (CMOS) frequency and duty cycle controller (FDCC) is presented for on-chip signal synthesis. The circuit consists of a few logic gates and a voltage-controlled oscillator, and is functionally similar to a programmable divide-by-N frequency divider. It is designed for driving integrated sensor and actuator systems. Compared with other frequency dividers with the same control flexibility, the proposed circuit features a compact topology and allows the control over the output signal duty cycle. For the proof-of-concept, a prototype 1 × 4 array of identical FDCCs has been fabricated on a 0.35μm Austria Mikro Systeme (AMS) CMOS process. Each FDCC occupies an active area of 0.0051mm2, which is area-efficient. The array has been validated to generate 4 synchronized 4MHz∼64MHz outputs with a duty cycle tuning range of 3.125%∼96.875%. Although driven by a 5-V power supply, it still provides a relatively high power-efficiency of 1.26GHz/mW.

A low-cost current flow controlling interline hybrid circuit breaker combined with SCR and H-bridge sub-module

A massive number of DC circuit breaker is usually necessary to be installed to protect HVDC grids from DC faults, this will lead to high capital costs because large number of expensive IGBT-in-series are used. In this paper, an interline hybrid circuit breaker is proposed by the combination of SCR string and a small number of H-bridge modules (SCR-IHCB). The proposed SCR-IHCB has the capacity of blocking DC fault of two adjacent lines respectively by sharing only one main breaker branch (MB) mainly composed of low-cost SCR string and H-bridge module instead of IGBT-in-series string. The interline current flow control function is also integrated. Hence it has advantages of simple and compact topology, economical design compared with typical IGBT based HCB solutions. The operation process of the proposed SCR-IHCB is discussed in detail, and the performance is verified by MATLAB Simulink simulation and scale-down prototype experiment.

Toward Ultracompact Multi-Materials Rectangular Waveguide Terminations

A new multi-materials’ compact topology, allowed by multi-materials 3-D-printing, is proposed to design microwave terminations in rectangular waveguide technology. The concept is based on a Salisbury-like resonant absorber constituted of a 3-D-printed polylactic acid (PLA) dielectric spacer and a lossy dielectric in the form of a pad whose dimensions allow controlling the frequency of maximum absorption. The flange of the termination is also printed with a lossy dielectric to achieve a compact and low-weight component that can be directly connected to a standard metallic waveguide. The concept has been validated experimentally in K-band (18–26 GHz) and X-band (8–12 GHz) with relative bandwidths (RBWs) around 20% for both frequency bands. These components demonstrate a quite stable temperature behavior. The power-handling capability (PHC) has been investigated through simulations and experiments. It was demonstrated that the maximum power than can support the termination is around 4–5 times lower than a more standard and bulky termination made with the same materials.