scholarly journals Free manipulation system for nanorobot cluster based on complicated multi-coil electromagnetic actuator

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yun Kim ◽  
Jun Keun Chae ◽  
Jong-Hwan Lee ◽  
Eunpyo Choi ◽  
Yoon Koo Lee ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Degrees Of Freedom ◽  
Three Dimensions ◽  
Actuation System ◽  
Large Numbers ◽  
Electromagnetic Actuation System ◽  
Manipulation System ◽  
Actuation Systems ◽  
The Magnetic Field ◽  
Simple Parameter

AbstractChemotherapy is an important method in the field of cancer treatment and often follows surgery and/or radiotherapy to remove as many tumor cells as possible. In particular, among the chemotherapy methods, treatment using electromagnetic-based actuation systems is considered an effective method owing to the remote control of nanorobots. The existing electromagnetic-based actuation systems, however, have certain disadvantages such as the lack of degrees of freedom and the difficulty of manipulating large numbers of nanorobots (i.e., nanorobot clusters). Herein, we report that nanorobot clusters can be manipulated with high degrees of freedom through a simple parameter alpha that easily controls the gradient of the magnetic field of a multi-coil electromagnetic actuation system. The simulation results show that the gradient of the magnetic field is controlled using an introduced parameter, alpha, and the corresponding velocity is also controlled. Not only the velocity of the nanorobot cluster but also the unrestricted spatial control is enabled in two- and three-dimensions. We believe this study highlights an efficient method of electromagnetic control for cluster-based drug delivery.

Position-based compensation of electromagnetic fields interference for electromagnetic locomotive microrobot

2012 ◽  
Vol 227 (9) ◽  
pp. 1915-1926 ◽  
Author(s):  
Jongho Choi ◽  
Hyunchul Choi ◽  
Semi Jeong ◽  
Bang Ju Park ◽  
Seong Young Ko ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Field ◽  
Electromagnetic Fields ◽  
Electromagnetic Actuation ◽  
Helmholtz Coils ◽  
Compensation Algorithm ◽  
Actuation System ◽  
Electromagnetic Actuation System ◽  
Propulsion Force ◽  
The Magnetic Field

Recently, the locomotion of a microrobot wirelessly actuated by electromagnetic actuation systems has been studied in many ways. Because of the inherent characteristics of an electromagnetic field, however, the magnetic field of each coil in the electromagnetic actuation system induces magnetic field interferences, which can distort the desired electromagnetic field, preventing the microrobot from following the desired path. In this article, we used two pairs of Helmholtz coils and two pairs of Maxwell coils in a two-dimensional electromagnetic actuation system. Generally, the two pairs of Helmholtz coils generate the torque for the rotation of the microrobot and the two pairs of Maxwell coils generate the propulsion force of the microrobot. Both pairs of Helmholtz and Maxwell coils have to work to simultaneously align and propel the microrobot in a desired direction. In this situation, however, the electromagnetic fields produced by the Helmholtz coils can interfere with those produced by the Maxwell coils. This interference is closely dependent on the position of the microrobot in the region of interest inside the electromagnetic coils system. This means that the alignment direction and propulsion force of the microrobot can be distorted according to the position of the microrobot. Therefore, we propose a compensation algorithm for the electromagnetic field interference using the position information of the microrobot to correct the magnetic field interferences. First, the interference of an electromagnetic field obeying the Biot–Savart law is analyzed by numerical analysis. Second, a position-based compensation algorithm for the locomotion of a microrobot is proposed. Various locomotion tests of a microrobot verified that the proposed compensation algorithm could reduce the normalized average tracking error from 5.25% to 1.92%.

V.—Dissymmetrical Separations in the Zeeman Effect in Tungsten and Molybdenum

1909 ◽  
Vol 29 ◽  
pp. 75-83 ◽  
Author(s):  
Robert Jack
Keyword(s):  
Magnetic Field ◽  
Wave Length ◽  
Zeeman Effect ◽  
Normal Type ◽  
Single Spectrum ◽  
Large Numbers ◽  
Middle Component ◽  
The Absolute ◽  
The Difference ◽  
The Magnetic Field

It has been mentioned by Professor Voigt of Göttingen in his newly published book and by Professor Zeeman of Amsterdam in the Physikalische Zeitschrift, that I have found examples of strongly marked dissymmetry in studying the Zeeman Effect in tungsten and molybdenum. Professor Zeeman has also discovered and published such cases of dissymmetry in other elements. Not only have many examples of normal dissymmetry been found, but almost as many cases of abnormal dissymmetry. To explain those terms, normal and abnormal, let us consider that the single spectrum line is broken up, when the light is in the magnetic field, into the three components, 1, 2, 3, where the numbers begin from the component which has the shortest wave-length. In the normal dissymmetrical triplet the middle component is nearer the component on the red side than that on the violet one, i.e. for the normal type the interval 1–2 is greater than the interval 2–3, but in the abnormal dissymmetrical triplet 2 is nearer to 1 than to 3. These observations of Professor Zeeman and myself, which were made at the same time in the Universities of Amsterdam and Göttingen, having been communicated to Professor Voigt, he wrote and published in the above-mentioned book an extension to his and Professor H. A. Lorentz's theories of the Zeeman Effect. In his original theory Professor Voigt had shown that, considering the electrons as uncoupled, cases of normal dissymmetry might arise among the Zeeman triplets, this dissymmetry being accompanied by a greater intensity of the red component than the violet one. He pointed out also that the ‘absolute’ dissymmetry or the difference between the absolute displacements of the red and violet components should be independent of the magnetic field strength used to produce the Zeeman Effect. To explain the large numbers of complicated types of Zeeman Effect which have been found —in the study of the Zeeman Effect in tungsten I discovered lines with no fewer than 17 to 19 components, the largest numbers hitherto found—Professors Voigt and Lorentz made use in their theories of couplings between electrons of the same vibration frequencies.

RESPONSE OF DYKE TO OSCILLATING DIPOLE

Geophysics ◽  
1958 ◽  
Vol 23 (1) ◽  
pp. 128-133 ◽  
Author(s):  
James Paul Wesley
Keyword(s):  
Magnetic Field ◽  
Closed Form ◽  
Scalar Potential ◽  
Three Dimensions ◽  
Electromagnetic Response ◽  
Dipole Source ◽  
First Approximation ◽  
Sulfide Ore ◽  
Infinite Conductivity ◽  
The Magnetic Field

A dyke of sulfide ore may be geophysically prospected by observing its electromagnetic response to a slowly oscillating magnetic dipole source. An excellent first approximation of the fields generated is obtained by considering the idealized case of a dyke of infinite conductivity and vanishing thickness in a vacuum. Surprisingly, this idealized problem can be solved exactly in terms of a newly discovered Green’s function for Laplace’s equation (in three dimensions) which is simply expressed in closed form. The magnetic scalar potential and the magnetic field are given for final results.

Compressible magnetoconvection in three dimensions: planforms and nonlinear behaviour

1995 ◽  
Vol 305 ◽  
pp. 281-305 ◽  
Author(s):  
P. C. Matthews ◽  
M. R. E. Proctor ◽  
N. O. Weiss
Keyword(s):  
Magnetic Field ◽  
Shear Flow ◽  
Three Dimensional ◽  
Two Dimensions ◽  
Three Dimensions ◽  
Nonlinear Behaviour ◽  
Two Dimensional ◽  
Horizontal Shear ◽  
Mean Flow ◽  
The Magnetic Field

Convection in a compressible fiuid with an imposed vertical magnetic field is studied numerically in a three-dimensional Cartesian geometry with periodic lateral boundary conditions. Attention is restricted to the mildly nonlinear regime, with parameters chosen first so that convection at onset is steady, and then so that it is oscillatory.Steady convection occurs in the form of two-dimensional rolls when the magnetic field is weak. These rolls can become unstable to a mean horizontal shear flow, which in two dimensions leads to a pulsating wave in which the direction of the mean flow reverses. In three dimensions a new pattern is found in which the alignment of the rolls and the shear flow alternates.If the magnetic field is sufficiently strong, squares or hexagons are stable at the onset of convection. Both the squares and the hexagons have an asymmetrical topology, with upflow in plumes and downflow in sheets. For the squares this involves a resonance between rolls aligned with the box and rolls aligned digonally to the box. The preference for three-dimensional flow when the field is strong is a consequence of the compressibility of the layer- for Boussinesq magnetoconvection rolls are always preferred over squares at onset.In the regime where convection is oscillatory, the preferred planform for moderate fields is found to be alternating rolls - standing waves in both horizontal directions which are out of phase. For stronger fields, both alternating rolls and two-dimensional travelling rolls are stable. As the amplitude of convection is increased, either by dcereasing the magnetic field strength or by increasing the temperature contrast, the regular planform structure seen at onset is soon destroyed by secondary instabilities.

Small-scale magnetic fields in turbulence: Saffman's approximation revisited

1980 ◽  
Vol 99 (3) ◽  
pp. 481-493
Author(s):  
Ralph Baierlein
Keyword(s):  
Magnetic Field ◽  
Numerical Evaluation ◽  
Two Dimensions ◽  
Three Dimensions ◽  
Small Scale ◽  
Fluid Element ◽  
Relative Time ◽  
Fourier Decomposition ◽  
The Subject ◽  
The Magnetic Field

The subject is the small-scale structure of a magnetic field in a turbulent conducting fluid, ‘small scale’ meaning lengths much smaller than the characteristic dissipative length of the turbulence. Philip Saffman developed an approximation to describe this structure and its evolution in time. Its usefulness invites a closer examination of the approximation itself and an attempt to place sharper limits on the numerical parameters that appear in the approximate correlation functions, topics to which the present paper is addressed.A Lagrangian approach is taken, wherein one makes a Fourier decomposition of the magnetic field in a neighbourhood that follows a fluid element. If one construes the viscous-convective range narrowly, by ignoring magnetic dissipation entirely, then results for a magnetic field in two dimensions are consistent with Saffman's approximation, but in three dimensions no steady state could be found. Thus, in three dimensions, turbulent amplification seems to be more effective than Saffman's approximation implies. The cause seems to be a matter of geometry, not of correlation times or relative time scales.Strictly-outward spectral transfer is a characteristic of Saffman's approximation, and this may be an accurate description only when dissipation suppresses the contributions from inwardly directed spectral transfer. In the spectral region where dominance passes from convection to dissipation, one can generate expressions for the parameters that arise in Saffman's approximation. Their numerical evaluation by computer simulation may enable one to sharpen the limits that Saffman had already set for those parameters.

A Magnetorheological Actuation System: Part I — Testing

2007 ◽  
Author(s):  
Shaju John ◽  
Jin-Hyeong Yoo ◽  
Norman M. Wereley
Keyword(s):  
Magnetic Field ◽  
Active Vibration Control ◽  
Active Material ◽  
Wheatstone Bridge ◽  
Mr Fluids ◽  
Actuation System ◽  
Hybrid Devices ◽  
Actuation Systems ◽  
Frequency Rectification ◽  
Moving Parts

There is a demand for compact hybrid actuation systems which combines actuation and valving systems in a compact package. Such self-contained actuation systems have potential applications in the field of rotorcraft (as active pitch links) and automotive engineering (as active vibration control devices). Hybrid hydraulic actuation systems, based on frequency rectification of the high frequency motion of an active material, can be used to exploit the high bandwidth of smart material to design devices with high force and stroke. Magnetorheological (MR) fluids are active fluids whose viscosity can be changed through the application of a magnetic field. By using MR fluids as the hydraulic fluid in such hybrid devices, a valving system with no moving parts can be implemented. Such a system will be attractive in rotorcraft applications with large centrifugal force loading. Thus, MR fluids can be used to control the motion of an output cylinder. The MR fluid based valves can be configured in the form of a Wheatstone bridge to produce bi-directional motion in an output cylinder by alternately applying a magnetic field in the two arms of the bridge. In this study, the actuation is performed using a compact Terfenol-D stack driven actuator. The frequency rectification of the stack motion is done using reed valves. This actuator and valve configuration form a compact hydraulic system with fluidic valves. The advantages of such systems are that part count is low, absence of moving parts and the possibility of continuous controllability of the output cylinder. By applying varying magnetic fields in the arms of the bridge (by applying different currents to the coils), the differential pressure acting on the output cylinder can be controlled. The description of the experimental setup, the tests performed and the experimental results are presented in this paper.

Numerical modelling of MHD waves in the solar chromosphere

2005 ◽  
Vol 364 (1839) ◽  
pp. 395-404 ◽  
Author(s):  
Mats Carlsson ◽  
Thomas J Bogdan
Keyword(s):  
Magnetic Field ◽  
Acoustic Waves ◽  
Mode Conversion ◽  
Three Dimensions ◽  
Mhd Waves ◽  
Solar Chromosphere ◽  
Fast Mode ◽  
Reflected Waves ◽  
The Waves ◽  
The Magnetic Field

Acoustic waves are generated by the convective motions in the solar convection zone. When propagating upwards into the chromosphere they reach the height where the sound speed equals the Alfvén speed and they undergo mode conversion, refraction and reflection. We use numerical simulations to study these processes in realistic configurations where the wavelength of the waves is similar to the length scales of the magnetic field. Even though this regime is outside the validity of previous analytic studies or studies using ray-tracing theory, we show that some of their basic results remain valid: the critical quantity for mode conversion is the angle between the magnetic field and the k-vector: the attack angle. At angles smaller than 30° much of the acoustic, fast mode from the photosphere is transmitted as an acoustic, slow mode propagating along the field lines. At larger angles, most of the energy is refracted/reflected and returns as a fast mode creating an interference pattern between the upward and downward propagating waves. In three-dimensions, this interference between waves at small angles creates patterns with large horizontal phase speeds, especially close to magnetic field concentrations. When damping from shock dissipation and radiation is taken into account, the waves in the low–mid chromosphere have mostly the character of upward propagating acoustic waves and it is only close to the reflecting layer we get similar amplitudes for the upward propagating and refracted/reflected waves. The oscillatory power is suppressed in magnetic field concentrations and enhanced in ring-formed patterns around them. The complex interference patterns caused by mode-conversion, refraction and reflection, even with simple incident waves and in simple magnetic field geometries, make direct inversion of observables exceedingly difficult. In a dynamic chromosphere it is doubtful if the determination of mean quantities is even meaningful.

Magnetostrictive Alloy Actuator for a Bone Transport Device

2008 ◽  
Author(s):  
Parsaoran Hutapea
Keyword(s):  
Magnetic Field ◽  
Experimental Work ◽  
Magnetic Moment ◽  
Longitudinal Direction ◽  
Bone Transport ◽  
Constitutive Behavior ◽  
Actuation System ◽  
Periosteal Surface ◽  
The Magnetic Field ◽  
Transport Device

The ultimate goal of our research is to develop a bone transport device using a magnetostrictive alloy actuation system. The device is designed to be subcutaneously mounted on the periosteal surface of the tibia. The magnetomechanical behavior of Terfenol-D smart magnetostrictive material has been well investigated in the literature when a magnetic field is applied along the longitudinal direction of the Terfenol-D material (perpendicular to the material’s magnetic moment). However, the requirement of our device is to have the magnetic field transversely applied on the Terfenol-D material (along the material’s magnetic moment). Therefore, the objective of this work was to study the magnetomechanical behavior of Terfenol-D under a transversely applied magnetic field. Experimental work was performed and a Terfenol-D material constitutive behavior was investigated.

scholarly journals Theory of magnetic reconnection in solar and astrophysical plasmas

2012 ◽  
Vol 370 (1970) ◽  
pp. 3169-3192 ◽  
Author(s):  
David I. Pontin
Keyword(s):  
Magnetic Field ◽  
Magnetic Reconnection ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Astrophysical Plasmas ◽  
Current State ◽  
Fundamental Process ◽  
Recent Developments ◽  
The Magnetic Field ◽  
Theoretical Results

Magnetic reconnection is a fundamental process in a plasma that facilitates the release of energy stored in the magnetic field by permitting a change in the magnetic topology. In this paper, we present a review of the current state of understanding of magnetic reconnection. We discuss theoretical results regarding the formation of current sheets in complex three-dimensional magnetic fields and describe the fundamental differences between reconnection in two and three dimensions. We go on to outline recent developments in modelling of reconnection with kinetic theory, as well as in the magnetohydrodynamic framework where a number of new three-dimensional reconnection regimes have been identified. We discuss evidence from observations and simulations of Solar System plasmas that support this theory and summarize some prominent locations in which this new reconnection theory is relevant in astrophysical plasmas.

ALTERNATIVE VARIABLES FOR THE DYNAMICS OF GENERAL RELATIVITY

2008 ◽  
Vol 23 (06) ◽  
pp. 895-908 ◽  
Author(s):  
R. ROSAS-RODRÍGUEZ
Keyword(s):  
Magnetic Field ◽  
General Relativity ◽  
Electric Field ◽  
Degrees Of Freedom ◽  
Hamiltonian Structure ◽  
Dynamical Equations ◽  
Canonical Gravity ◽  
Constraint Algebra ◽  
New Form ◽  
The Magnetic Field

A new form of the dynamical equations of vacuum general relativity is proposed. This form involves the canonical Hamiltonian structure but noncanonical variables. The new field variables are the electric field [Formula: see text] and the magnetic field [Formula: see text] which emerge from the Ashtekar's representation for canonical gravity. The constraint algebra is studied in terms of the new field variables and the counting of the degrees of freedom is done. The quantization is briefly outlined.

Sign in / Sign up

Export Citation Format

Share Document