다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

During the last few decades, magnetorheological (MR) elastomers have attracted a significant amount of attention for their enormous potential in engineering applications. Because they are a solid counterpart to MR fluids, MR elastomers exhibit a unique field-dependent material property when exposed to a magnetic field, and they overcome major issues faced in magnetorheological fluids, e.g. the deposition of iron particles, sealing problems and environmental contamination. Such advantages offer great potential for designing intelligent devices to be used in various engineering fields, especially in fields that involve vibration reduction and isolation. This paper presents a state of the art review on the recent progress of MR elastomer technology, with special emphasis on the research and development of MR elastomer devices and their applications. To keep the integrity of the knowledge, this review includes a brief introduction of MR elastomer materials and follows with a discussion of critical issues involved in designing magnetorheological elastomer devices, i.e. operation modes, coil placements and principle fundamentals. A comprehensive review has been presented on the research and development of MR elastomer devices, including vibration absorbers, vibration isolators, base isolators, sensing devices, and so on. A summary of the research on the modeling mechanical behavior for both the material and the devices is presented. Finally, the challenges and the potential facing magnetorheological elastomer technology are discussed, and suggestions have been made based on the authors’ knowledge and experience.

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A state-of-the-art review on magnetorheological elastomer devices

In this paper, the design of a contactless charger for the lithium-ion battery of a cellular phone is presented. In this charger, the primary core of the transformer is in the charger unit and the secondary core is in the telephone. The gap (3 mm) between them is the thickness of the two plastic cases. The transformer core design for the maximum coupling coefficient with the size constraint on the secondary side is presented. Analysis of the primary-side series resonant power converter with the loosely coupled transformer is performed, and the design optimization is presented. For the battery-charging control, a simple control circuit is presented and its performance is verified from the experimental results.

Design of a contactless battery charger for cellular phone

Magnetorheological (MR) materials are classified as smart materials due to their responsiveness to external magnetic stimuli. Intensive research on MR materials has led to broad applications in several potential fields. A solid carrier matrix state called MR elastomer with its exceptional magnetic responsive feature is obtained by merging magnetizable particles within an elastomeric polymer. This integration results in outstanding characteristics on the rheological performances. Special prominence is given to the understanding of the base materials and fabrication as well as the functional behavior through various characterization methods. Broad applications of MREs are also explored to provide a profound market picture and to motivate researchers to develop novel technology. The functional behavior of MREs is briefly explained. The art of the materials provides the current position and mapping of the matrix and filler particles. Types of matrix and particles are mentioned together with the level of the research interest on MREs. Description of the fabrication is provided in simple diagrams as summarized from previous works to enhance the MREs performance. The possible tests to reveal the characteristics of the MREs are delivered with the global experimental setup. The review also explains the applications of MREs as well as discussion on the MREs future promising applications.

Recent Progress on Magnetorheological Solids: Materials, Fabrication, Testing, and Applications†

Soft materials that can undergo rapid and large deformation through the remote and wireless action of external stimuli offer a range of tantalizing applications such as soft robots, flexible electronics, and biomedical devices. A natural and simple embodiment of such materials is to embed magnetic particles in soft polymers. Unfortunately, existing magnetically responsive soft materials such as magnetorheological elastomers and ferrogels typically use magnetically-soft particles such as iron and iron oxides, which are characterized by the low coercivity and hence lack the capability to retain remnant magnetism. Accordingly, their deformation is limited to simple elongation or shortening, rendering these materials substantially unsuited for the complex transformations required in many applications. To introduce shape-programmability, magnetically-hard particles with high coercivity have been incorporated in mechanically soft materials. In addition, recent works aimed at ameliorating this situation have developed fabrication techniques and facile routes to engineer rapid and complex transformations in a programmable manner by introducing intricate patterns of magnetic polarities in soft materials. The resulting structures, when properly designed, have been shown to exhibit a diverse and rich array of actuation behavior. In this work, we develop a suitable theoretical framework to analyze these so-called hard-magnetic soft materials to facilitate the rational design of magnetically activated functional structures and devices based on a quantitative prediction of complex shape changes. We adopt a nonlinear field theory to describe the finite deformation coupled with magnetic fields and argue that the macroscopic behavior of the fabricated materials requires a new constitutive classification — ideal hard-magnetic soft material — which assumes that (i) the material has a residual magnetic flux density, and (ii) the induced magnetic flux density exhibits a linear relation with the applied actuating magnetic field. We implement the theory and constitutive law in a finite-element framework and find remarkable agreement between the simulation and experimental results on various deformation modes of hard-magnetic soft materials. Using the developed (and validated) model, we present a set of illustrative examples to highlight the use of our model-based simulation to guide the design of experimentally realizable complex shape-morphing structures based on hard-magnetic soft materials.

Mechanics of hard-magnetic soft materials

This paper describes a novel soft actuator using a magnetorheological elastomer. First, the material characteristics in the magnetization process and major contributing factors to magnetization of the magnetic elastomer are shown. Second, an actuator using a magnetorheological elastomer combined with an embedded electromagnet is proposed. The magnetic circuit when a current is applied is described and its operating principle is explained. Finally, the static and dynamic motions and dynamic stress of the actuator are determined by an experimental prototype and measurement setup.

Novel Soft Actuator Using Magnetorheological Elastomer

This paper describes the harmonic spectra of the cogging torque of a magnetic gear. The operating principle of this gear is described, and the transmission torque under operation in accordance with the gear ratio is mathematically formulated. In particular, the harmonic order of the cogging torque is described in detail. Moreover, the orders of the cogging torque of both rotors are verified by employing 3-D finite element method. The computed results are also then further verified by carrying out measurements on a prototype. Other harmonic components are observed in the computed and measured results, but it is discussed why they are contained in the cogging torque.

Cogging Torque Analysis of Magnetic Gear

This paper describes the operating principle and the performance analysis of the surface-permanent-magnet-type vernier motor with concentrated windings using finite element method analysis. To satisfy the structural relationship of $Z_{2}=Z_{1}\pm p$ , the number of auxiliary teeth in the stator, pole pairs in the rotor and winding pole pairs are chosen as $Z_{1}=12$ , $Z_{2}=11$ and $p=1$ respectively. With this setup which operates at a gear ratio of 1/11, the cogging torque tends to be lower and therefore the output torque contains only smaller ripples. The iron loss computation and the efficiency calculation employing the two-frequency method are also investigated. Estimation of the iron loss has clarified that the hysteresis loss was dominant in the laminated core and that the magnet eddy current loss increased dramatically at higher speeds due to the rotating magnetic field.

Analysis of a Vernier Motor with Concentrated Windings

This paper proposes a dynamic analysis method of a 2-D linear oscillatory actuator. In this method, a magnetic field equation is coupled with motion equations of both linear and rotary motion of a mover employing the 3-D finite element method. The usefulness of the method is verified by comparing computational results with the measured resonant oscillation of the mover when it is operated at different frequencies for both motions

Dynamic Analysis Method of Two-Dimensional Linear Oscillatory Actuator Employing Finite Element Method

This paper describes the transmission torque characteristics of a novel magnetic planetary gear. A hybrid-type magnetic planetary gear is proposed, and the operational principle is shown when it is operated as a star-, planetary-, and solar-type magnetic planetary gear. The dynamic transmission torque characteristics are computed by employing 3-D finite-element method, and lastly verified by carrying out measurements on a prototype.

Katsuhiro Hirata

Papers

Novel Soft Actuator Using Magnetorheological Elastomer

Cogging Torque Analysis of Magnetic Gear

Analysis of a Vernier Motor with Concentrated Windings

Dynamic Analysis Method of Two-Dimensional Linear Oscillatory Actuator Employing Finite Element Method

Transmission Torque Analysis of a Novel Magnetic Planetary Gear Employing 3-D FEM