Uniform gradient magnetic field and spatial localization method based on Maxwell coils for virtual surgery simulation

Effects of applying uniform and non-uniform external magnetic fields on the optimal design of microchannel heat sinks

The influence of the magnetic field on the convective heat transfer characteristics of Fe3O4/water nanofluids

view Abstract Citations (60) References (14) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Reflection and trapping of transient Alfven waves propagating in an isothermal atmosphere with constant gravity and uniform magnetic field An, C. -H. ; Musielak, Z. E. ; Moore, R. L. ; Suess, S. T. Abstract A time-dependent linear magnetohydrodynamic numerical model was used to investigate the propagation of Alfven waves in an isothermal and stratified atmosphere with constant gravity and uniform vertical magnetic field. Results show that the Alfven wave transit time for the wave source to infinity is finite and that the wave exhibits continuous partial reflection which becomes total reflection as the front approaches infinity. The total reflection causes the waves to be trapped in the cavity that extends from the wave source to infinity and in which the wave energy is stored. The results suggest that the reflection of Alfven waves (of sufficiently long period) from the outer corona is an intrinsic phenomenon for any stellar atmosphere stratified by gravity and an open magnetic field, and that, therefore, such waves may be trapped in the stellar atmosphere. Publication: The Astrophysical Journal Pub Date: October 1989 DOI: 10.1086/167933 Bibcode: 1989ApJ...345..597A Keywords: Computational Astrophysics; Magnetohydrodynamic Waves; Stellar Atmospheres; Stellar Magnetic Fields; Wave Propagation; Gravitational Effects; Kinetic Energy; Magnetic Field Configurations; Solar Wind; Stellar Coronas; Trapping; Wave Reflection; Astrophysics full text sources ADS |

With the development of computer technology, Virtual Surgery Simulation (VSS) becomes into reality. Virtual surgery is multi-disciplined and challenged. There have been some open source resources for VSS but they are all in progress. A new open source based VSS system is presented. An object oriented system analysis and design are described in detail including use case diagram, sequence diagrams, class diagram and a multi-level architecture that is multi platform. The system is a general framework that can be configured or customized by experts or developers resulting in a concrete XML scene file to prepare for another user - trainee training his/her surgical skills. The framework is based on open source libraries and existed VSS framework or codes. Some good ideas and good structures are integrated in this framework. It is extensible for developers or experts studying new algorithms and testing new methods. To test the framework lens capsule and liver simulator are configured. It is obvious that the presented framework needs further developing and perfecting.

Magnetic field-induced control of a compound ferrofluid droplet deformation and breakup in shear flow using a hybrid lattice Boltzmann-finite difference method

An intelligent tracking system for surgical instruments in complex surgical environment

We deduce the dissipative Alfven wave equation in a medium stratified in one direction, with a transverse magnetic field, in the presence of dissipation by fluid viscosity and electrical resistance; the dissipative Alfven wave equation generalizes earlier results for homogeneous (Cowling, 1960) and inhomogeneous (Campos, 1983a) media, and corrects an error in the literature (Heyvaerts and Priest, 1983). The wave equation is solved exactly in two cases: a uniform magnetic field, and a magnetic field decreasing with height. In both cases the mean state is assumed to be isothermal, with a constant rate of ionization, so that the magnetic diffusivity is constant, but the dynamic viscosity increases with height. There are therefore two regions, a low- (high-) altitude region where electrical resistance dominates fluid viscosity (or vice versa), and an asymptotic regime relevant to the uppermost (lowermost) layers. The two regions are separated by a transition layer, across which the wave field is cont...

Magneto-active elastomers (MAE) are a new branch of smart materials that consist of hard-magnetic particles such as barium ferrite in an elastomer matrix. Under the application of a uniform magnetic field, the MAE material undergoes large deformation as the material bends due to magnetic torques acting on the distribution of hard-magnetic particles. This behavior demonstrates the potential of MAEs to act as remote actuators. MAEs vary from magnetorheological elastomers (MRE) which use soft-magnetic iron particles in place of the hard-magnetic particles and they are driven by magnetic interactions between particles. In this work, MAEs were fabricated using 30% v/v 325 mesh M-type barium ferrite (BaM) particles in Dow Corning HS II silicone elastomers. Prior to curing, the samples were placed in a uniform (∼2 Tesla) magnetic field to align the magnetic particles and produce a magnetization oriented in the direction of the applied magnetic field. The specimens were bonded to a passive poldymethylsiloxane (PDMS) substrate to form a two-segment accordion structure where the MAEs with magnetization, M, were placed in opposing orientations a prescribed distance apart. The application of a uniform magnetic field perpendicular to the magnetization of the undeformed MAEs would result in a bend (on the PDMS) that is dependent upon the orientation of the magnetic particles and the direction of the applied field. This behavior of the composite structure highlights the ability of the MAE material to perform work. Experimental testing of the MAEs used a two-segment accordion structure with fixed boundary-conditions on both ends of the PDMS substrate and a uniform magnetic field was applied to the structure. The resulting deformation roughly represented either a mountain or valley fold (dependent upon the orientation of the applied field). The resulting axial force was observed and compared to computational simulations which utilized numerical techniques to develop approximate solutions. This procedure was repeated with a prescribed displacement on one of the two fixed boundary conditions to induce bending prior to the application of a uniform magnetic field. Results show a decrease in magnetic work potential with increases in the aforementioned prescribed displacement; results also show an increase in magnetic work potential with increases in the applied magnetic field.

Living organisms inspire the design of microrobots, buttheir functionalityis unmatched. Next-generation microrobots aim to leverage the sensingand communication abilities of organisms through magnetic hybridization,attaching magnetic particles to them for external control. However,the protocols used for magnetic hybridization are morphology specificand are not generalizable. We propose an alternative approach thatleverages the principles of negative magnetostatics and magnetophoresisto control nonmagnetic organisms with external magnetic fields. Todo this, we disperse model organisms in dispersions of Fe3O4 nanoparticles and expose them to either uniform orgradient magnetic fields. In uniform magnetic fields, living organismsalign with the field due to external torque, while gradient magneticfields generate a negative magnetophoretic force, pushing objectsaway from external magnets. The magnetic fields enable controllingthe position and orientation of Caenorhabditis elegans larvae and flagellated bacteria through directional interactionsand magnitude. This control is diminished in live spermatozoa andadult C. elegans due to stronger internalbiological activity, i.e., force/torque. Our study presents a methodfor spatiotemporal organization of living organisms without requiringmagnetic hybridization, opening the way for the development of controllableliving microbiorobots.

The macroscopic and microscopic behaviour of a plasma column with an extremely high initial plasma-beta in a uniform axial magnetic field has been studied by means of a “two-and-a-half-dimensional”, magnetostatic, collisionless particle simulation code. This study has been motivated by the results of laser-produced plasma experiments in magnetic fields. It includes not only a rapid initial plasma expansion but also subsequent complex phenomena such as the “re-thermalization” process, the formation of a high-beta sheath and the onset of flute-like plasma instability. The results found by the present simulation on the formation of “crater-wall-like” structures in both the plasma density and internal energy in the re-thermalization stage, the formation of the high-beta sheath with a thickness of the order of the “hybrid” Larmor radius (“Rosenbluth-sheath”) and a growth-rate of the instability nearly equal to that of the lower-hybrid-drift instability all appear to be consistent with the results of laser-produced plasma experiments hitherto performed by the present authors' group.

The motion of the electron in a uniform and constant magnetic field (about 900 Gauss) and in a transverse electromagnetic wave propagating along the magnetic field was studied experimentally. It was confirmed that the cyclotron resonance was maintained at a constant frequency due to the relativistic Doppler effect which canceled the reduction in the gyromagnetic frequency caused by the increase in kinetic energy. An application of this effect to a new type of dynamic energy analyzer, previously proposed by the author, was investigated experimentally. In the analyzer, a difference in the initial energy of about 24 eV was amplified to a difference in the final energy of about 9 keV.

In this paper, the effect of magnetic fields on the temperature and temperature profile of a diffusion flame obtained from a butane torch burner are investigated experimentally by using digital speckle pattern interferometry (DSPI). Experiments were conducted on a diffusion flame generated by a butane torch burner in the absence of a magnetic field and in the presence of uniform and nonuniform magnetic fields. A single DSPI fringe pattern was used to extract phase by using a Riesz transform and monogenic signal. Temperature inside the flame was determined experimentally both in the absence and in the presence of magnetic fields. Experimental results reveal that the maximum temperature of the flame is increased under the influence of an upward-decreasing magnetic gradient and decreased under an upward-increasing magnetic gradient while a negligible effect on temperature in a uniform magnetic field was observed.

The effect of the uniform vertical magnetic field acting opposite to gravity on the onset of steady Rayleigh-Benard-Marangoni convection in horizontal layer of an electrically conducting liquid is investigated, using the modified linear stability theory. The upper surface of liquid layer is free where surface tension gradients arise on account of variation of temperature and the lower boundary surface is rigid, each subject to the constant heat flux condition. Both mechanisms namely, surface tension and buoyancy causing instability are taken into account. The Galerkin method is used to obtain the eigenvalue equation which is then computed numerically. Results of this analysis indicate that the critical eigenvalues in the presence of a uniform magnetic field are greater in a relatively hotter layer of liquid than a cooler one under identical conditions otherwise. The asymptotic behaviour of both the Rayleigh and Marangoni numbers for large values of the Chandrasekhar number is also obtained. During the course of this analysis, we also correct the inaccuracies in the work of earlier authors.

Impact of sleep deprivation on medium-term psychomotor and cognitive performance of surgeons: Prospective cross-over study with a virtual surgery simulator and psychometric tests

Numerical investigation of falling ferrofluid droplets under magnetic fields