Magnetic force

Laplace transform plays very important role in the field of science and engineering. It is particularly useful in solving initial value problems involving linear ordinary differential equation with constant coefficient. This paper will discuss the advantage of unit step function in solving initial value problems having discontinuous functions in the area of electric circuit theory, biological modeling and atomic control and servomechanism. Also it will discuss the application of delta function in the area of mechanics.

Vibration of a BLDC motor is a coupled phenomenon between mechanical characteristics and magnetic origins which takes place through the motor airgap. When relative misalignment of a rotor in the airgap is introduced during assembly, the dynamic characteristics of the motor system are affected. The rotor-motor system used in a washing machine is modeled using FETM and magnetic forces in

In this work the effects of the electromechanical interaction on rotordynamics and vibration characteristics of cage rotor electrical machines were considered. An eccentric rotor motion distorts the electromagnetic field in the air-gap between the stator and rotor inducing a total force, the unbalanced magnetic pull, exerted on the rotor. In this paper a low-order parametric model for the unbalanced magnetic pull is coupled with a three-dimensional finite element structural model of the electrical machine. The main contribution of the work is to present a computationally efficient electromechanical model for vibration analysis of cage rotor machines. In this model, the interaction between the mechanical and electromagnetic systems is distributed over the air gap of the machine. This enables the inclusion of rotor and stator deflections into the analysis and, thus, yields more realistic prediction for the effects of electromechanical interaction. The model was tested by implementing ...

Single-crystal silicon triple-torsional micro-oscillators have been fabricated, characterized, and modeled primarily for use in a magnetic resonance force microscope. These structures exploit a high-Q triple-torsional mode of oscillation while providing added stability. Fabrication involves lithography, reactive ion etch, and a final KOH wet-etch, with the final oscillator material being single-crystal boron-doped silicon. Typical oscillators were 250 nm thick and 10 -200 microns in lateral dimensions. Finite element modeling provided the sequence and structure of the ten lowest-frequency modes and indicated that the upper torsional mode best isolates the motion from losses to the base. The oscillators were excited piezoelectrically and the resulting frequency-dependent motion was detected with fiber-optic interferometry, with a 0.002 nm/Hz 1/2 resolution. Phase-sensitive motion detection at various points on the oscillator facilitated the assignment of the principle modes. Magnetic...

Two different methods for calculating magnetic force distributions in magnetised material - a classical and a novel one - are studied and are compared by means of numerical simulations of electrical machines and transformer cores. The methods are evaluated and compared with respect to the resulting magnetic force distributions and the ensuing elastic deformations and vibrations. The magnetic and elastic equations are solved utilising a 2D finite element space discretisation. Both static and dynamic simulations are considered.

During curative cancer surgery, magnetic retraction could offer advantages over retraction by graspers because of reduced tissue trauma and with the potential for noncontact retraction. To realize magnetic retraction, magnetic fluid was injected into harvested porcine stomachs and an external permanent magnet was used to retract the ferromagnetized tissue. The magnetic forces of four ferrofluids were measured. The results of these experiments showed that iron-oxide-nanoparticle-based ferrofluids do not provide the required retraction force. However, sufficient retraction force is obtained by ferromagnetic microparticles fluids (stainless steel 410, denoted MP-SS410) by virtue of their high magnetization and saturation. In ex vivo surgical retraction experiments, MP-SS410 powder was dispersed in phosphate-buffered saline and other fluids. These ferrofluids were injected into the submucosal layer of harvested porcine stomachs at different concentrations and volumes. The inoculum generated a magnetic retraction force linearly proportional to the concentration and injected volume. Ex vivo surgical retraction, and dissection and resection were possible with a simple magnetic probe. The results of this study indicate that ferromagnetization of tissue can be used to facilitate localized tissue retraction and resection.

Layered nanoparticles have the potential to deliver any number of substances to cells both in vitro and in vivo. The purpose of this study was to develop and test a relatively simple alternative to custom synthesized nanoparticles for use in multiple biological systems, with special focus on the eye. The biotin-labeled transcriptionally active PCR products (TAP) were conjugated to gold, semiconductor nanocrystals, and magnetic nanoparticles (MNP) coated with streptavidin. The process of nanoparticle construction was monitored with gel electrophoresis. Fluorescence microscopy followed by image analysis was used to examine gene expression levels from DNA alone and tethered MNP in human hepatoma derived Huh-7 cells. Adult retinal endothelial cells from both dog (ADREC) and human (HREC) sources were transfected with nanoparticles and reporter gene expression evaluated with confocal and fluorescent microscopy. Transmission electron microscopy was used to quantify the concentration of nan...

Page 1. Magnetic Force Aided Compliant Needle Navigation and Needle Performance Analysis * Libo Tang, Yonghua Chen and Xuejian He Department of Mechanical Engineering The University of Hong Kong Pokfulam Road, Hong Kong, China yhchen@hku.hk ...

mplicated human body is a very challenging procedure, especially for cases where obstacle avoidance is required. In this paper, a compliant needle is designed to achieve the purpose of obstacle avoidance and path planning task. The compliant needle head can be deflected by a magnetic force aided method which helps to achieve a more flexible turning angle in 3D space navigation. The buckling effect of needle during insertion is investigated as well. By choosing an appropriate length and radius combination of a needle, the buckling effect can be avoided to achieve a more stable insertion.

Single-crystal silicon triple-torsional micro-oscillators have been fabricated, characterized, and modeled primarily for use in a magnetic resonance force microscope. These structures exploit a high-Q triple-torsional mode of oscillation while providing added stability. Fabrication involves lithography, reactive ion etch, and a final KOH wet-etch, with the final oscillator material being single-crystal boron-doped silicon. Typical oscillators were 250 nm thick and 10 - 200 microns in lateral dimensions. Finite element modeling provided the sequence and structure of the ten lowest-frequency modes and indicated that the upper torsional mode best isolates the motion from losses to the base. The oscillators were excited piezoelectrically and the resulting frequency-dependent motion was detected with fiber-optic interferometry, with a 0.002 nm/Hz1/2 resolution. Phase-sensitive motion detection at various points on the oscillator facilitated the assignment of the principle modes. Magnetic excitation was also investigated in order to best excite the torsional resonances. Cobalt micromagnets with moments below 10-12 J/T were electron-beam deposited onto oscillators, and the magnetic forces were measured. MRFM, the primary intended application of these novel structures, is discussed; in particular, an overview is given of an experiment which uses a double-torsional micro-oscillator for the force detection of nuclear magnetic resonance. All topics discussed in this work are being combined in order to achieve a NMRFM single-sweep sensitivity as low as 10-16 N/Hz1/2 at room temperature.

Single-crystal silicon triple-torsional micro-oscillators have been fabricated, characterized, and modeled primarily for use in a magnetic resonance force microscope. These structures exploit a high-Q triple-torsional mode of oscillation while providing added stability. Fabrication involves lithography, reactive ion etch, and a final KOH wet-etch, with the final oscillator material being single-crystal boron-doped silicon. Typical oscillators were 250 nm thick and 10 - 200 microns in lateral dimensions. Finite element modeling provided the sequence and structure of the ten lowest-frequency modes and indicated that the upper torsional mode best isolates the motion from losses to the base. The oscillators were excited piezoelectrically and the resulting frequency-dependent motion was detected with fiber-optic interferometry, with a 0.002 nm/Hz1/2 resolution. Phase-sensitive motion detection at various points on the oscillator facilitated the assignment of the principle modes. Magnetic excitation was also investigated in order to best excite the torsional resonances. Cobalt micromagnets with moments below 10-12 J/T were electron-beam deposited onto oscillators, and the magnetic forces were measured. MRFM, the primary intended application of these novel structures, is discussed; in particular, an overview is given of an experiment which uses a double-torsional micro-oscillator for the force detection of nuclear magnetic resonance. All topics discussed in this work are being combined in order to achieve a NMRFM single-sweep sensitivity as low as 10-16 N/Hz1/2 at room temperature.

This paper presents results on the development and application of a three-dimensional (3-D) microstructure assembly technique-Plastic deformation magnetic assembly (PDMA). In PDMA, certain part of the microstructure to be assembled is plastically deformed by the magnetic force generated from the interaction between a magnetic material piece deposited on the microstructure and an external magnetic field. As a result, the entire

Layered nanoparticles have the potential to deliver any number of substances to cells both in vitro and in vivo. The purpose of this study was to develop and test a relatively simple alternative to custom synthesized nanoparticles for use in multiple biological systems, with special focus on the eye. The biotin-labeled transcriptionally active PCR products (TAP) were conjugated to gold, semiconductor nanocrystals, and magnetic nanoparticles (MNP) coated with streptavidin. The process of nanoparticle construction was monitored with gel electrophoresis. Fluorescence microscopy followed by image analysis was used to examine gene expression levels from DNA alone and tethered MNP in human hepatoma derived Huh-7 cells. Adult retinal endothelial cells from both dog (ADREC) and human (HREC) sources were transfected with nanoparticles and reporter gene expression evaluated with confocal and fluorescent microscopy. Transmission electron microscopy was used to quantify the concentration of nan...