Double Links Research Articles

Amphiphilic polymer Co-networks based on cross-linked tetra-PEG-b-PCL star block copolymers

A new class of AB4-type amphiphilic polymer co-networks (ACN) was prepared by hetero-complementary 2-(4-nitrophenyl)-benzoxazinone/amine end group cross-linking chemistry in dimethyl sulfoxide (DMSO). For this purpose, a well-defined star block copolymer (tetra-PEG-b-PCL) consisting of a hydrophilic tetra-arm PEG core (Mn ∼ 5 kg mol−1) and hydrophobic PCL wings with a total molar mass of Mn ∼ 10 kg mol−1 was synthesized by ring-opening polymerization (ROP). This tetra-PEG-b-PCL star block copolymer was functionalized either with 2-(4-nitrophenyl)-benzoxazinone or with amino terminal groups. The ACN synthesis was carried out by conversion of these two star block copolymers. The overlap concentration of c* ∼76 g L−1 determined by viscosity measurements of both stars showed no significant temperature dependence. The network syntheses carried out at different concentrations (0.5 c* to 2.5 c*) resulted in conversion degrees in the range of p ≈ 95 % or higher as detected by HR MAS NMR spectroscopy. As in previous work on the synthesis of A4B4 networks using the same cross-linking chemistry, deviations from the expected network structure (increased proportion of double links between two stars) were detected also here by multi quantum NMR spectroscopy. The expected environmentally sensitive behavior of the ACNs was confirmed in terms of their equilibrium swelling in solvents of different quality to PEG and PCL. The scaling of the swelling and viscoelasticity data as a function of preparation concentration showed deviations from the expectations of a perfectly cross-linked star polymer network. Finally, a two-step gelation process was observed by rheology at 30 °C in DMSO, which is related to associations between the 2-(4-nitrophenyl)-benzoxazinone groups surrounded by PCL blocks that become apparent on the time scale of rheology when the molar mass is increased as a result of cross-linking.

Orthogonal Space-Time Block Coding for Double Scattering V2V Links with LOS and Ground Reflections

This work presents the performance analysis of space-time block codes (STBCs) for vehicle-to-vehicle (V2V) fast-fading channels in scenarios with modified line-of-sight (LOS). The objective is to investigate how the V2V MIMO (multiple-input multiple-output) system performance is influenced by two important impairments: deterministic ground reflections and an increased Doppler frequency (time-variant channels). STBCs of various coding rates (using an approximation model) are evaluated by assuming antenna elements distributed over the surface of two contiguous vehicles. A multi-ray model is used to study the multiple constructive/destructive interference patterns of the transmitted/received signals by all pairs of Tx–Rx antenna links considering ground reflections. A double scattering model is used to include the effects of stochastic channel components that depend on the Doppler frequency. The results show that STBCs are capable of counteracting fades produced by destructive self-interference components across a range of inter-vehicle distances and for a range of Doppler frequency values. Notably, the effectiveness of STBCs in deep fades is shown to outperform schemes with exclusive receive diversity, despite the interference created by the loss of orthogonality in time-varying channels with a moderate increase of Doppler frequency (mainly due to higher vehicle speeds, higher frequency or shorter time slots). Higher-order STBCs with rate losses are also evaluated using an approximation model, showing interesting gains even for low coding rate performance, particularly when accompanied by a multiple antenna receiver. Overall, these results can shed light on how to exploit transmit diversity in time-varying vehicular channels with modified LOS.

Shear induced polarization: collisional contributions

It has been realized that thermal shear plays a similar role as thermal vorticity in polarizing spin of particles in heavy ion collisions. We point out that shear has a funda- mental difference that it leads to particle redistribution in the medium. The redistribution gives rise to an additional contribution to spin polarization through the self-energy, which is parametrically the same order as the one considered so far in the literature. The self-energy contribution is in general gauge dependent. We introduce double gauge links stretching along the Schwinger-Keldysh contour to restore gauge invariance. We also generalize the straight path to adapt to the Schwinger-Keldysh contour. We find another contribution associated with the gauge link, which is also parametrically the same order. We illustrate the two contributions with a massive probe fermion in massless QED plasma with shear. A modest suppression of spin polarization is found from the combined contributions when the probe fermion has momentum much greater than the temperature.

The experimental study of eccentrically braced frames with double vertical links

This study proposes a new detail of vertical links for eccentrically braced frames. The research was conducted with two full-scale tests of double vertical links specimens under quasi-static cyclic loading. The first specimen was tested out of frame to study the overall stability and to determine seismic parameters. The second test utilized links on a single-story single-bay frame. The first specimen yielded at 200 kN with the displacement assumed to be δy = 1 mm. In the 30th to 31st cycle, a significant strength decay occurred. By the last cycle (about 300 kN), the specimen webs at the displacement of 25δy were ruptured. The second specimen yielded at the approximate force of 180 kN with an average displacement of 1.5 mm. By the displacement of 16δy, a significant strength decay occurred. In the 22nd cycle, with the same displacement, the web rupture. As a result, both specimens experienced their plasticity simultaneously and without time lag. The detail configuration causes small axial force and consequently the development of maximum shear strength in the links with a significant decrease in the moments at the ends of the beam. Therefore, the beams in the both specimens remained essentially elastic. The overall stability without providing lateral supports has been confirmed. The results of the proposed detail suggest stable and symmetric hysteresis loops, appropriate seismic behavior, and adequate ductility as required by design codes compared to single vertical links. In seismic rehabilitation, as ductile fuses develop out of framing, repalcing links after an earthquake is not concern.

FACT: An Air-Ground Communication Framework for Seeding Quality Control of Aircraft

A new type of air-ground communication application framework named FACT (framework for air-ground communication technology with weather-modification aircraft) is presented to track and command weather-modification aircraft to perform ideal cloud seeding. FACT provides a set of solutions from three perspectives, namely, onboard, onground and air-to-ground, with the core purpose of solving the problems of the rapid exchange of information, contract analysis and identifying potential seeding areas when flight plans and meteorological conditions change. On board, the observed data are processed centrally and transmitted downward through air-to-ground communication. The real-time application and sharing of aircraft detection data are strengthened on the ground, and potential areas of operation are automatically identified based on ground data. The communication between the air and the ground achieves a technical breakthrough by realizing double satellite links, adaptive data transmission and VPN channel encryption. Additionally, an application based on FACT is designed and implemented for the real-time command of weather-modified aircraft. This approach has become the key air-to-ground communication system support for more than 40 Chinese aircraft and the big data service support center of airborne data to ensure improved operation of weather-modification aircraft in China.

Cooperative beamforming for a double-IRS-assisted wireless communication system

Intelligent reflecting surface (IRS) has emerged as an innovative and disruptive solution to boost the spectral and energy efficiency and enlarge the coverage of wireless communication systems. However, the existing literature on IRS mainly concentrates on wireless communication systems assisted by single or multiple distributed IRSs, which are not always effective. In view of this issue, this paper considers a special double-IRS-assisted wireless communication system, where IRS1 and IRS2 are deployed near the base station (BS) and the user, respectively, and the transmitted signals reach the user via the cascaded BS-IRS1-IRS2-user channel only. We cooperatively optimize transmit and passive beamforming on the two IRSs based on the particle swarm optimization (PSO) algorithm to maximize the received signal power. Simulation indicates that despite no direct line-of-sight (LoS) path from the BS to the user, an excellent signal-to-noise ratio (SNR) is available at the receiver with the aid of two IRSs, which demonstrates that it is feasible to assist communication by double reflection links composed of two IRSs. Additionally, we unexpectedly find that when the positions of the two IRSs are fixed, by exchanging the positions of the BS and the user, the obtainable SNRs are similar.

Seismic behavior of a two-level control system with double vertical shear links in series

To improve seismic behavior of structures, a two-level control system is proposed in this paper where by combining two vertical shear panels in series in a chevron bracing configuration, Double-Vertical Shear Panel, D-VSP is introduced. Utilizing two-levels of energy absorption for two different earthquake intensity levels, D-VSP is expected to beneficially change dynamic behavior parameters like strength, stiffness and damping ratio through increasing ductility. To validate research, a VSP is modeled in ABAQUS and related numerical results are compared to those of a previous experimental work. Pushover, quasistatic cyclic and seismic analyses are conducted on two models. The hysteresis curves show symmetric two-level behavior with stable strength and stiffness leading to increase ductility ratio up to 29.4%. Maximum displacement and maximum base shear under seismic loading decrease 5.91 and 11.18% respectively under moderate earthquakes when D-VSP system uses only first fuse, saving second fuse for severe earthquakes. However, in a strong earthquake, both of the shear panels absorb seismic energy and can control vibration better than conventional systems with one level control mechanism. The proposed system using a weaker panel can better control an extensive range of earthquakes as well as the earthquake with foreshocks.

Double Recurrent Perturbation Fuzzy Neural Network Fractional-Order Sliding Mode Control of Micro Gyroscope

In this paper, a fractional-order sliding mode control method based on a double recurrent perturbation fuzzy neural network (DRPFNN) is proposed for a micro gyroscope system with parameter uncertainty and external disturbance. The DRPFNN is used to realize the adaptive estimation of the unknown part, which ensures that the controller is independent of the accurate mathematical model. The sine-cosine perturbation membership function is used to deal with the uncertainty of rules in neural network, increasing the accuracy, reduce the calculation load, and simplifying computational complexity. In addition, double recurrent links are added to transmit more information with superior dynamic ability. Then, the proposed control system is composed of a DRPFNN estimator and a fractional-order sliding mode controller (FSMC). The fractional calculus operator is introduced into the sliding surface to improve the controller flexibility. The parameter adaptive laws in the neural network are designed to be adaptively stabilized to the optimal value. Finally, simulation studies verify the effectiveness of the proposed control method, showing it can obtain higher control accuracy and enhance robustness than the traditional sliding mode control method.

Global migration topology analysis and modeling of directed flow network 2006–2010

We applied the network theory to the global world migration phenomenon, seen as a directed network (flow of migrants between world countries from 2006 to 2010) and measured different centralities statistics: in and out-degree, in and out-closeness, and clustering coefficient. One of the important findings is that distributions of out-degree and in-degree for immigration and emigration are completely different aspects of the same phenomenon. The out-degree distribution is uniform with a Gaussian distribution when the in-degree distribution is compound by several groups depending on the in-degree and the in-weight. The receptor countries-nodes, which have large values of in-weight, can be divided into two groups: the developed countries (with low clustering coefficient but large values of the in-degree) and a small group of countries (with high clustering coefficient and small in-degree values). The countries-nodes with large out-weight can be divided into two subgroups with a high clustering coefficient. One of these groups is well connected and forms with the group of the developed countries an in-subgroup of diameter 2 thanks to the double links between them. The second group is characterized by low values of the in-degree (some with null value) and is connected to the rest of the network mainly by out-degrees. Finally, the Latin American countries may be seen as a homogeneous fifth group.

Double exceptional links in a three-dimensional dissipative cold atomic gas

We explore the topological properties of non-Hermitian nodal-link semimetals with dissipative cold atoms in a three-dimensional optical lattice. We construct a two-band continuum model in three dimensions with a spin-dependent gain and loss, where the exceptional points in the energy spectrum can comprise a double Hopf link. The topology of the bulk band is characterized by a winding number defined for a one-dimensional loop in the momentum space and a topological transition of the nodal structures emerges as the change of the non-Hermiticity strength. A non-Bloch theory is built to describe the corresponding lattice model which has anomalous bulk-boundary correspondence. Furthermore, we propose that the model can be realized using ultracold fermionic atoms in an optical lattice and the exceptional nodal links as well as the topological properties can be detected by measuring the atomic spin textures.

The braid index of DNA double crossover polyhedral links.

In this paper, the authors study the mathematical properties of a class of alternating links called polyhedral links which have been used to model DNA polyhedra. The motivation of such studies is to provide guidance and aid in the research of the properties of certain DNA molecules. For example, such studies can provide characterizations of the structural complexity of DNA molecules. In an earlier work, Cheng and Jin studied the mathematical properties of such polyhedral links and were able to determine the braid index of a double crossover polyhedral link with 4 turn. However, the braid index of a double crossover polyhedral link with 4.5 turn remained an unsolved problem to this date, even though the graphs that admit the double crossover polyhedral links with 4.5 turn have been synthesized. In this paper, we provide a complete formulation of the braid index of a double crossover polyhedral link with an arbitrary turn number. Our approach is more general and it allows us to completely determine the braid indices for a much larger class of links. In the case of the double crossover polyhedral links, our formulation of the braid index is a simple formula based on a simpler graph used as a template to build the double crossover polyhedral links.

MinDFul: Using double links for stabilizing mmWave wireless channels for application to autonomous vehicles and augmented reality

Abstract Applications that require short-range ultra-high bitrate communication, such as cable removal in virtual reality games and communication between autonomous vehicles, are examining solutions such as millimetre wave wireless (mmWave). When using mmWave, steerable directional antennas are used to mitigate the severe signal power attenuation common with high frequencies. Nonetheless, even small movements in the user device can cause a sudden drop in data-rate down (even to 0 bits/s) making mmWave channels unstable and unusable. To make the channel more stable for the aforementioned applications, which are vulnerable due to frequent blockages and fast movement, we designed and developed a robust solution based on a double link mmWave system. We duplicate the radio transceivers (RT) of a user device (UD) to increase the probability of finding line of sight to an access point (AP) representing the other side of the communication channel. The AP selects one RT of the UD for communication, based on continuous measurement of quality compared to the channel of the other RT. This concept was implemented in a laboratory environment and evaluated using a series of controlled experiments. The experiments serve to validate that using double links is feasible, and is considerably more robust and it can double the link utilization, compared to only using one mmWave link. These results show great promise for the concept, by demonstrating that using multiple mmWave links yields ultra-high bit-rate wireless communication with no disruption, even in the presence of blockages and mobility.

Movable Payload on Various Conditions of Two-Wheeled Double Links Wheelchair Stability Control Using Enhanced Interval Type-2 Fuzzy Logic

This paper presents investigations of control strategies for a two-wheeled wheelchair with a movable payload on various conditions using a double-link inverted pendulum concept. The wheelchair system is modeled in the SimWise 4D (SW4D) with its optimized control parameters determined using the Spiral Dynamic Algorithm (SDA) while being controlled by the proposed Interval Type-2 Fuzzy Logic Controller (IT2FLC). The robustness of the proposed controller in terms of maintaining the system’s stability while the wheelchair is standing in an upright position is tested under multiple circumstances. These included utilizing varying directions and applying magnitudes of external disturbances to the developed system with a movable payload (upward and downward) and testing the system’s forward and backward motions on a flat surface and the motions on an inclined surface. Ultimately, the two-wheeled wheelchair which adopts the proposed controller had shown a 68% and 77% reduction in the angular positions of Link1 and Link2, a 94% reduction in torques for both Link1 and Link2, and more than 98% reduction in traveling distance compared to the Fuzzy Logic Control Type-1 (FLCT1) controller which was used in the previous design. Moreover, the current work has taken into consideration the heightened nonlinearities and complexity of an additional moving payload on various conditions to represent more degree of freedom (DOF), compared to the fixed payload in the previous design with less DOF. This further rectifies that the enhanced IT2FLC had outperformed FLCT1 in handling nonlinearities and uncertainties, for the case of a two-wheeled wheelchair system with a movable payload.

IMPORTÂNCIA DO ÁCIDO LINOLEICO CONJUGADO (CLA) EM PRODUTOS DE ORIGEM ANIMAL

O termo CLA descreve um conjunto de isômeros geométricos do ácido linoleico com propriedades bioativas distintas, que têm duas duplas ligações separadas por apenas uma ligação simples. Assim, este trabalho trata-se de uma revisão bibliográfica baseada na literatura especializada, fundamentado através de consulta a artigos científicos selecionados em diferentes bases de dados com o objetivo de dar enfoque à importância do ácido linoleico conjugado (CLA) em produtos de origem animal e seus benefícios à saúde humana. Nesse contexto, em alimentos de origem animal é possível encontrar esse composto natural, principalmente na gordura do leite, carne e em alimentos naturalmente enriquecidos com este ácido e seus isômeros. O CLA tem propriedades bioativas distintas e é originário da biohidrogenação incompleta dos ácidos linoleico e linolênico realizada pelas bactérias ruminais ou da desaturação do trans-11 na glândula mamária e no intestino delgado. Os benefícios biológicos do CLA e dos isômeros cis-9 e trans-11, como um componente natural da gordura do leite, tem efeito anticarcinogênico, incluindo carcinomas na epiderme, tecido mamário e gastrintestinal. Dietas suplementadas com gorduras e a relação concentrado: volumoso, assim como a efetividade da fibra do volumoso podem aumentar a produção de leite, diminuir a produção de gordura e alterar seu perfil em ácidos graxos. Pesquisas avaliando os níveis de CLA nos produtos de origem animal e o seu efeito benéfico sobre a saúde e qualidade de vida do homem têm apresentado resultados satisfatórios, embora muitas vezes controversos, sendo necessários novos estudos para comprovar os resultados e a segurança na utilização desse composto, para que possa se determinar a sua real eficácia.

Murine Double Minute-2 Links Cell Cycle Control and Inflammation in Homeostasis and Disease

This commentary highlights the article by Fan etal that provides mechanistic insights into murine double minute-2's anti-inflammatory role in intraocular inflammation.

Coherent attacking continuous-variable quantum key distribution with entanglement in the middle

We suggest an approach on the coherent attack of continuous-variable quantum key distribution (CVQKD) with an untrusted entangled source in the middle. The coherent attack strategy can be performed on the double links of quantum system, enabling the eavesdropper to steal more information from the proposed scheme using the entanglement correlation. Numeric simulation results show the improved performance of the attacked CVQKD system in terms of the derived secret key rate with the controllable parameters maximizing the stolen information.

Inband Full-Duplex Radio Transceivers: A Paradigm Shift in Tactical Communications and Electronic Warfare?

Inband FD operation has great potential in civilian/commercial wireless communications, because it can as much as double transmission links� spectral efficiency by exploiting the newfound capability for STAR that is facilitated by advanced SIC techniques. This article surveys the prospects of exploiting the emerging FD radio technology in military communication applications as well. In addition to enabling high-rate twoway tactical communications, the STAR capability could give a major technical advantage to armed forces by allowing their radio transceivers to conduct electronic warfare at the same time that they are also receiving or transmitting other signals at the same frequency bands. After comprehensively introducing FD transceiver architectures and SIC requirements in military communications, this article outlines and analyzes all the most promising defensive and offensive applications of the STAR capability. It is not out of the question that this disruptive technology could even bring about a paradigm shift in operations at the cyber-electromagnetic battleground. At least, forward-looking innovators in the military communications community would right now have a window of opportunity to engage in original, potentially high-impact scientific research on FD military radio systems, which we would like to spur on by this speculative tutorial article.

Predetermined Ferromagnetic Coupling via Strict Control of M-O-M Angles.

An imidazolidine-phenolate ligand HL yields quadruple-bridged (μ-NCNimidazolidine)2(μ-Ophenolate)2 ferromagnetic dinuclear nickel and cobalt complexes. Both kinds of bridges contribute to the ferromagnetic coupling, but the ferromagnetism of these samples is mainly ascribed to the double μ-Ophenolate links, on the basis of density functional theory calculations. These studies demonstrate not only that the short M-O-M angles of the M2O2 cores favors the parallel alignment of the electrons but also that these angles are the optimal ones for maximizing the ferromagnetic contribution in these complexes. And these acute angles, close to 90°, are predetermined by the geometrical constrictions imposed by the ligand itself. Thus, HL is an uncommon polydentate donor that induces ferromagnetism per se in its metal complexes by strict control of one geometric parameter, the M-O-M angle.

Character varieties of double twist links

We compute both natural and smooth models for the $SL_2(\mathbb C)$ character varieties of the two component double twist links, an infinite family of two-bridge links indexed as $J(k,l)$. For each $J(k,l)$, the component(s) of the character variety containing characters of irreducible representations are birational to a surface of the form $C\times \mathbb C$ where $C$ is a curve. The same is true of the canonical component. We compute the genus of this curve, and the degree of irrationality of the canonical component. We realize the natural model of the canonical component of the $SL_2(\mathbb C)$ character variety of the $J(3,2m+1)$ links as the surface obtained from $\mathbb{P}^1\times \mathbb{P}^1$ as a series of blow-ups.

Topological chirality of a type of DNA and protein polyhedral links

Polyhedral links, interlinked and interlocked architectures, have been proposed for the description and characterization of DNA and protein polyhedra. In this paper, we study the topological chirality of a type of DNA polyhedral links constructed by the strategy of “n-point stars” and a type of protein polyhedral links constructed by “three-cross curves and untwisted double-line” covering. Furthermore, we prove that links corresponding to bipartite plane graphs have antiparallel orientations, and under these orientations, their writhes are not zero. As a result, the type of double crossover DNA polyhedral links are topologically chiral. We also prove that the unoriented link corresponding to a connected, even, bipartite plane graph always has self-writhe 0. Using the Jones polynomial for unoriented links we derive two simple criteria for chirality of unoriented alternating links with self-writhe 0. By applying this criterion we show that 3-regular protein polyhedral links are also topologically chiral. Topological chirality always implies chemical chirality, hence the corresponding DNA and protein polyhedra are all chemically chiral. Our chiral criteria may be used to detect the topological chirality of more complicated DNA and protein polyhedral links that may be synthesized by chemists and biologists in the future.