Multimode Mechanism Research Articles

Chiral microporous organic network/covalent organic framework/silica composites: Powerful and versatile chromatographic separation materials

Nowadays, covalent organic framework (COF) has shown great potential in chromatographic separation, and enriching the design of novel COF based stationary phases and broadening their application prospects remains of great significance. Microporous organic network (MON) is a novel type of porous material with large specific surface area and excellent stability connected by covalent bonding, which is extremely similar to COF. Especially, nano-sized MON has the characteristics of easy binding with silica matrix and superior chromatographic separation performance. In this work, the combination of MON and COF as the surface modification materials of silica gel was first explored. The conjugated network structure of MON and COF can improve the permeability of silica stationary phase, and the presence of abundant functional groups in COF and MON can enhance the separation ability for a series of aromatic compounds. Moreover, hydrophilic L-cysteine containing thiol group was cleverly introduced into MON/COF@SiO2via thiol-ene/yne click reactions to balance the hydrophilicity and hydrophobicity of stationary phase. The L-cysteine modified chiral MON/COF@SiO2 (CMON/CCOF@SiO2) was used for effective separation of various chiral/hydrophilic/hydrophobic analytes, and the CMON/CCOF@SiO2 was observed to exhibit superior separation ability to the CCOF@SiO2. Multi-mode chromatographic separation mechanisms were explored, demonstrating that multiple interactions were involved in the separation process. Finally, the CMON/CCOF@SiO2 was applied to detect the environmental endocrine disruptors in the water sample and pyridoxine in the tablet sample, respectively, indicating a great potential for application in actual sample detection.

Application of finite screw method for multi-mode mechanism classification and determination

To enrich the theoretical system of multi-mode mechanisms, a classification method and a determination method are proposed in this paper. From the perspective of configuration transformation, the multi-mode mechanisms are divided into two types: one based on lockable joints and the other based on the principle of bifurcated motion. Furthermore, the mechanisms based on the principle of bifurcated motion are categorized into two types: one based on the variable mobility branch and the other based on constraint singularity generated by branches. The principles of classification are expounded and the determination method is developed. The proposed classification and the determination methods of the multi-mode mechanism provide new insights for their analysis.

Sextuplet luminescence with dynamically variable color/brightness in chromium activated gallium-silicate solid solution in R3 space group

The development of dynamic multi-color luminescence is a tremendous challenge for anti-counterfeiting. Herein, we have successfully synthesized Cr3+ activated gallium-silicate base material systems as the effective luminescent materials responsive to multiple field stimulation, exhibiting sextuplet luminescence including photoluminescence, strong red persistent luminescence (PersL), photo/thermo stimulated luminescence (PSL/TSL), photo-stimulated PersL and up-conversion luminescence (UCL). The luminescence quenching temperature is also improved in Cr3+,Yb3+,Er3+ co-doping sample relatives to Cr3+ single-doping phosphor. Especially, when Er3+ and Yb3+ are co-doped into Cr3+ activated phosphor system, UV preirradiated phosphor not only demonstrates an additional UCL from Er3+ ions accompanied with red PSL from the Cr3+ under NIR laser irradiation, but also leads to a dynamic change in color/brightness under the extension of NIR laser irradiation time. The multimode luminescence mechanisms are also proposed. Based on excellent luminescence characteristics, multi-color and multi-mode anti-counterfeiting patterns have been designed, especially appearing of dynamic anti-counterfeiting on luminescent color/brightness, which provides new dimensions for anti-counterfeiting technologies.

Multi-color and multi-mode luminescence tuning in persistent phosphors by trap engineering

Conventional persistent luminescent phosphors face a significant challenge in developing a single material for multi-color anti-counterfeiting. In this study, a wide range of Cr3+ activated gallium germanate-based persistent phosphors are successfully synthesized using high-temperature solid phase approach. By incorporating Cr3+ and Er3+ as dual emitting centers, and utilizing Yb3+ as a sensitizer and electron traps, the resulting phosphors exhibit an exceptional combination of photoluminescence, up-conversion luminescence, persistent luminescence, photo/thermo-stimulated luminescence, followed by photo-stimulated persistent luminescence in a single material system. Beyond its multi-mode emissions, the luminescence color output can be conveniently controlled by adjusting annealing time, Yb3+ ion doping concentration, excitation wavelength, or excitation power. A systematic study of trap distribution related to PersL has been conducted by regulating annealing temperature, time, doping concentration and type. The responding multi-mode luminescent mechanisms are also proposed. Particularly, these phosphors demonstrated outstanding performance as security labels in advanced anti-counterfeiting applications. This research holds the potential to inspire the design and development of more intricate luminescence anti-counterfeiting materials and technologies.

Oncolytic Viruses in Cancer Immunotherapy

AbstractOncolytic viruses are novel and promising therapeutic regimens that promote antitumor efficacy through multimode mechanisms, including direct lysis of tumor cells, release of the tumor antigens and danger signals, induction of immunological cell death, activation of innate, and adaptive immune response. In addition, oncolytic viruses can be engineered to express virus‐centered and immune‐centered therapeutic transgenes, further transforming the “cold” tumor into “hot” and enhancing the oncolytic efficacy. Several oncolytic viruses are engineered and widely used as potential therapeutic agents for many cancers and the therapeutic strategies and effectiveness vary among different types of oncolytic viruses. Finally, oncolytic viruses‐based combination immunotherapy is practiced in preclinical and clinical studies, and indicates that combination of oncolytic viruses with conventional therapy or immunomodulatory agents exerts favorable antitumor efficacy.

A replaceable-component method to construct single-degree-of-freedom multi-mode planar mechanisms with up to eight links

Abstract. The multi-mode planar mechanisms (MMPMs) are excellent-performance reconfigurable mechanisms, which not only inherit structural characteristics of planar mechanisms but also have the multi-task, multi-working-condition application advantages of multi-mode mechanisms. However, lacking common bifurcation analysis and construction methods, their industrial application and development are seriously hindered. This paper presents a replaceable-component method to construct a set of single-degree-of-freedom (single-DOF) MMPMs based on the branch graphs of the corresponding planar mechanisms and the proposed multi-mode modules (MMMs). First, according to the established loop equations, all the kinematic information of the original planar mechanism is obtained by the branch graphs and singularity points using Maple. Then, compared to the relationship between the concepts of the branch and motion mode, the number and continuity of branches are taken as the index to identify the potential bifurcation and mode conversion ability for the corresponding planar mechanisms. Subsequently, the MMM is presented to help the planar mechanisms break the singularity positions to form the corresponding MMPMs, and the steps of constructing single-DOF MMPMs are summarized. Finally, a single-DOF Stephenson six-bar three-mode planar mechanism, a Watt six-bar three-mode planar mechanism, and an eight-bar four-mode planar mechanism are constructed for the first time, and the corresponding multi-mode motion analyses are made. The results can give the available configuration for the design of corresponding MMPMs. The proposed method will provide strong guidance for the configuration design of MMPMs.

Design and Reconfiguration Analysis of the Trunk Mechanism for a Reconfigurable Wheeled Mobile Platform

Abstract This paper proposes a reconfigurable wheeled mobile platform (RWMP) consisting of two two-wheeled mobile robots and a reconfigurable trunk. The reconfigurable trunk is a 6R multi-mode single-loop mechanism (SLM) that is obtained by inserting two revolute (R) joints with intersected axes into a planar rhombus 4R mechanism. The 6R mechanism has reconfigurable characteristics owing to changes in the wrench system. All six motion modes and their constraint equations of the 6R mechanism are obtained by solving the closed-loop equation based on the D-H transformation matrix. The analysis shows that the mechanism has six single-DOF motion modes, including a planar rhombus 4R mode, two overconstrained spatial 6R modes, and three coaxial 1R modes. The motion characteristics of the six motion modes are identified using screw theory. The six transition configurations among different modes are identified by combining the constraint equations of each mode. The locomotion modes of the RWMP are designed based on the reconfiguration analysis of the trunk mechanism. The locomotion effect of the RWMP under two confined spaces is verified by simulation analysis and prototype experiment.

Construction and Multi-Mode Motion Analysis of Single-Degree-of-Freedom Four-Bar Multi-Mode Planar Mechanisms Based on Singular Configuration

Abstract The traditional four-bar mechanism is renowned for its simple structure, dependable performance, and wide range of applications. The single-degree-of-freedom (DOF) four-bar multi-mode planar mechanism (MMPM) is a type of four-bar mechanism that not only has the structural characteristics of the traditional four-bar mechanisms but also can achieve multiple motion modes by changing its structure. It has the advantage of performing diverse functions while conserving resources, which opens up new possibilities for research and application of the four-bar mechanism. However, due to the lack of a systematic configuration construction method, the design and application of single-DOF four-bar MMPMs are seriously limited. This paper presents a systematic method to construct a set of single-DOF four-bar MMPMs based on the loop equations and the proposed multi-mode modules (MMMs). First, depending on the loop equations, the four-bar planar mechanism containing two branches is identified by the corresponding branch graphs. Then, three kinds of MMMs are systematically proposed for the first time, helping the identified mechanism realize multiple motion modes. Subsequently, single-DOF four-bar MMPMs are constructed by replacing the specific component of the planar mechanism with the MMMs. Furthermore, the replacement rules of MMMs and the corresponding construction steps are summarized. Finally, 14 kinds of single-DOF four-bar MMPMs are listed, and the corresponding multi-mode motion analysis is discussed at the end of this paper. The proposed method is a straightforward one, which will provide great convenience for the configuration design of single-DOF four-bar MMPMs and promote the development and application of MMPMs.

Broadband Linear Polarization Converter Based on Slot-Line Loaded Structure for Pre-Determined Notched Band

This brief proposes a broadband linear polarization converter with pre-determined notched band. By loading a H-shaped slot line on the basis of the rectangular resonator, a pair of resonator modes as well as pre-determined polarization conversion zeros can be additionally allocated inside the band, thereby realizing broadband and band-notch characteristics, simultaneously. The multi-mode resonant mechanism to realize broadband and the conversion zero control principle for notched band are analyzed in detail. Finally, a notch-band broadband linear polarization converter is designed and fabricated, and the simulated and measured results are agreed well with each other. As the main advantage, the proposed multi-mode resonant structure realizing the notched band can achieve flexible isolation band design while hardly affecting the broadband filtering characteristics, and is especially suitable for pre-determined spectrum windows of broadband electromagnetic control devices.

Configuration Synthesis Method of Multi-Mode Parallel Mechanism Based on Variable Mobility Branch

Abstract In order to obtain more configurations of multi-mode parallel mechanism with the expected motion modes, a new configuration synthesis method of multi-mode parallel mechanism is proposed in this paper. The generation principle of parallel mechanism with multiple motion modes is analyzed. The relation between the motion of moving platform and the motion of branch is obtained. The finite motion and instantaneous motion of existing variable mobility branches are analyzed, and variable mobility branches are decomposed into variable mobility generators. By using variable mobility generators to construct variable mobility branches, a configuration synthesis method of multi-mode parallel mechanism based on variable mobility branch is proposed. Taking the multi-mode parallel mechanism with 2T1R and 2R1T motion modes as an example, a new class of multi-mode parallel mechanisms is obtained. The proposed method enriches the configuration synthesis theory of multi-mode parallel mechanism and the synthesis results enrich the configurations of multi-mode parallel mechanism.

Design of a Multi-Mode Mechanical Finger Based on Linkage and Tendon Fusion Transmission.

Today, most humanoid mechanical fingers use an underactuated mechanism driven by linkages or tendons, with only a single and fixed grasping trajectory. This paper proposes a new multi-mode humanoid finger mechanism based on linkage and tendon fusion transmission, which is embedded with an adjustable-length tendon mechanism to achieve three types of grasping mode. The structural parameters of the mechanism are optimized according to the kinematic and static models. Furthermore, a discussion was conducted on how to set the speed ratio of the linkage driving motor and the tendon driving motor to adjust the length and tension of the tendon, in order to achieve the switching of the shape-adaptive, coupled-adaptive, and variable coupling-adaptive grasping modes. Finally, the multi-mode functionality of the proposed finger mechanism was verified through multiple grasping experiments.

Research on configuration synthesis method of multi-mode parallel mechanism based on lockable joints

Research on configuration synthesis method of multi-mode parallel mechanism based on lockable joints

A multi-mode super-fano mechanism for enhanced third harmonic generation in silicon metasurfaces

We present strong enhancement of third harmonic generation in an amorphous silicon metasurface consisting of elliptical nano resonators. We show that this enhancement originates from a new type of multi-mode Fano mechanism. These ‘Super-Fano’ resonances are investigated numerically in great detail using full-wave simulations. The theoretically predicted behavior of the metasurface is experimentally verified by linear and nonlinear transmission spectroscopy. Moreover, quantitative nonlinear measurements are performed, in which an absolute conversion efficiency as high as ηmax ≈ 2.8 × 10−7 a peak power intensity of 1.2 GW cm−2 is found. Compared to an unpatterned silicon film of the same thickness amplification factors of up to ~900 are demonstrated. Our results pave the way to exploiting a strong Fano-type multi-mode coupling in metasurfaces for high THG in potential applications.

A multi-mode super-fano mechanism for enhanced third harmonic generation in silicon metasurfaces

A multi-mode super-fano mechanism for enhanced third harmonic generation in silicon metasurfaces

Stability of internal gravity wave modes: from triad resonance to broadband instability

A theoretical study is made of the stability of propagating internal gravity wave modes along a horizontal stratified fluid layer bounded by rigid walls. The analysis is based on the Floquet eigenvalue problem for infinitesimal perturbations to a wave mode of small amplitude. The appropriate instability mechanism hinges on how the perturbation spatial scale relative to the basic-state wavelength, controlled by a parameter $\mu$ , compares to the basic-state amplitude parameter, $\epsilon \ll 1$ . For $\mu ={O}(1)$ , the onset of instability arises due to perturbations that form resonant triads with the underlying wave mode. For short-scale perturbations such that $\mu \ll 1$ but $\alpha =\mu /\epsilon \gg 1$ , this triad resonance instability reduces to the familiar parametric subharmonic instability (PSI), where triads comprise fine-scale perturbations with half the basic-wave frequency. However, as $\mu$ is further decreased holding $\epsilon$ fixed, higher-frequency perturbations than these two subharmonics come into play, and when $\alpha ={O}(1)$ Floquet modes feature broadband spectrum. This broadening phenomenon is a manifestation of the advection of small-scale perturbations by the basic-wave velocity field. By working with a set of ‘streamline coordinates’ in the frame of the basic wave, this advection can be ‘factored out’. Importantly, when $\alpha ={O}(1)$ PSI is replaced by a novel, multi-mode resonance mechanism which has a stabilising effect that provides an inviscid short-scale cut-off to PSI. The theoretical predictions are supported by numerical results from solving the Floquet eigenvalue problem for a mode-1 basic state.

Game-Theory-Based Multimode Routing Protocol for Internet of Things

Various routing protocols have been proposed for ad hoc networks such as the Internet of Things (IoT). Most of the routing protocols introduced for IoT are specific to applications and networks. In the current literature, it is essential to configure all the network nodes with a single proposed protocol. Moreover, it is also possible for a single IoT network to consist of different kinds of nodes. Two or more IoT networks can also be connected to create a bigger heterogeneous network. Such networks may need various routing protocols with some gateway nodes installed. The role of gateway nodes should not be limited to the interconnection of different nodes. In this paper, a multi-mode hybrid routing mechanism is proposed that can be installed on all or a limited number of nodes in a heterogenous IoT network. The nodes configured with the proposed protocols are termed smart nodes. These nodes can be used to connect multiple IoT networks into one. Furthermore, a game-theory-based model is proposed that is used for intercommunication among the smart nodes to gain optimal efficiency. Various performance matrices are assessed under different network scenarios. The simulation results show that the proposed mechanism outperforms in broader heterogeneous IoT networks with diverse nodes.

Modeling and simulation of a multistage heat recovery steam generator

As the share of renewable energy increases in modern power grids, their inherent intermittency compels existing thermal power plants to become more agile and flexible in their operation. To achieve such flexibility, understanding the transient behavior of thermal power plants is key. In this regard, physics-based dynamic models are useful tools. They help in predicting performance and in exploring various operating conditions in a risk-free, cost-effective manner. To this end, this paper presents a multi-stage Heat Recovery Steam Generator (HRSG) model. Fast simulations are demonstrated for this three pressure-stage system with interconnected thermodynamic and mass transfer phenomena. The HRSG’s multi-physics behavior is captured through mathematically modeled and numerically simulated phase change, fluid dynamics, and thermal coupling. Heat exchange elements such as economizers and superheaters are modeled by directly solving the Unsteady Flow Energy Equation (UFEE). The phase change dynamics of the boiler are modeled using a multi-mode switching mechanism, where each mode is characterized by boiling/evaporation/condensation and heating/cooling phenomena. A judicious combination of spatially discretized or lumped and dynamic or quasi-static models is used to achieve reasonably accurate transient response while lowering the computational burden. In collaboration with Siemens Energy Inc., steady-state prediction capability and transient pressure behavior are validated with plant startup data from an operational HRSG.

Rayleigh–Taylor instability under multi-mode perturbation: Discrete Boltzmann modeling with tracers

The two-dimensional Rayleigh–Taylor Instability (RTI) under multi-mode perturbation in compressible flow is probed via the Discrete Boltzmann Modeling (DBM) with tracers. The distribution of tracers provides clear boundaries between light and heavy fluids in the position space. Besides, the position-velocity phase space offers a new perspective for understanding the flow behavior of RTI with intuitive geometrical correspondence. The effects of viscosity, acceleration, compressibility, and Atwood number on the mixing of material and momentum and the mean non-equilibrium strength at the interfaces are investigated separately based on both the mixedness defined by the tracers and the non-equilibrium strength defined by the DBM. The mixedness increases with viscosity during early stage but decreases with viscosity at the later stage. Acceleration, compressibility, and Atwood number show enhancement effects on mixing based on different mechanisms. After the system relaxes from the initial state, the mean non-equilibrium strength at the interfaces presents an initially increasing and then declining trend, which is jointly determined by the interface length and the macroscopic physical quantity gradient. We conclude that the four factors investigated all significantly affect early evolution behavior of an RTI system, such as the competition between interface length and macroscopic physical quantity gradient. The results contribute to the understanding of the multi-mode RTI evolutionary mechanism and the accompanied kinetic effects.

Tunable Microwave Pulse Generation Based on an Actively Mode-Locked Optoelectronic Oscillator

A tunable microwave-pulse-generation scheme is proposed and demonstrated by employing an actively mode-locked optoelectronic oscillator (OEO) based on a microwave photonic filter (MPF). The MPF mainly consists of a phase-shifted fiber Bragg grating (PS-FBG) and a phase modulator. The microwave pulse trains with variable repetition rates are achieved by injecting an external signal, of which the frequencies are equal to an integer multiple of the free spectrum range (FSR) of the OEO. The multi-mode oscillation mechanism is discussed in detail theoretically and experimentally. A microwave pulse train with a central frequency of 9.25 GHz and repetition rate of 1.68 MHz is demonstrated by setting the injecting signal frequency to be the same with the FSR of the OEO. A tunable center frequency of the microwave pulses from 5.47 GHz to 18.91 GHz can be easily generated by tuning the laser frequency benefit from adopting the MPF. Furthermore, the microwave pulses with different pulse periods of 297.62 ns, 198.69 ns, and 148.81 ns are also realized by harmonic mode-locking. The proposed tunable microwave-pulse-generation method has potential applications in the pulse Doppler radar and communications.

A Numerical Study on the Influence of Strain Rate in Finite-Discrete Element Simulation of the Perforation Behaviour of Woven Composites.

Predicting the perforation limit of composite laminates is an important design aspect and is a complex task due to the multi-mode failure mechanism and complex material constitutive behaviour required. This requires high-fidelity numerical models for a better understanding of the physics of the perforation event. This work presents a numerical study on the perforation behaviour of a satin-weave S2-glass/epoxy composite subjected to low-velocity impact. A novel strain-rate-dependent finite-discrete element model (FDEM) is presented and validated by comparison with experimental data for impacts at several energies higher and lower than their perforation limit. The strain rate sensitivity was included in the model by developing a novel user-defined material model, which had a rate-dependent bilinear traction separation cohesive behaviour, implemented using a VUSDFLD subroutine in Abaqus/Explicit. The capability of the model in predicting the perforation limit of the composite was investigated by developing rate-sensitive and insensitive models. The results showed that taking the strain rate into account leads to more accurate predictions of the perforation limit and damage morphology of the laminate subjected to impacts at different energies. The experimental penetration threshold of 89 J was estimated as 79 J by the strain-rate-sensitive models, which was more accurate compared to 52 J predicted by the strain-rate-insensitive model. Additionally, the coupling between interlaminar and intralaminar failure modes in the models led to a more accurate prediction of the delamination area when considering the rate sensitivity.