Permanent Disc Research Articles

Ionic Liquid-Based Magnetic Needle Headspace Single-Drop Microextraction Combined with HPLC/UV for the Determination of Chlorophenols in Wastewater.

A magnetic needle headspace single-drop microextraction (MN-HS-SDME) method coupled to HPLC/UV has been developed. Trihexyl(tetradecyl)phosphonium chloride was employed as an ionic liquid (IL) solvent for the headspace extraction of some chlorophenol (CP) compounds from wastewater samples. Despite of the nonmagnetic character of the IL, a significant improvement in the extraction efficiency was obtained by the magnetization of the single-drop microextraction needle using a pair of permanent disk magnets. A simplex method for the fast optimization of the experimental conditions (e.g., stirring speed, ionic strength, pH, extraction time and temperature) was used. The coefficients of determination (R2) varied between 0.9932 and 0.9989, the limits of detection were from 0.004 to 0.007μgmL-1 and the relative recoveries were in the range of 88-120% for the studied analytes. The developed MN-HS-SDME HPLC/UV method was successfully applied to the determination of CPs in industrial wastewater.

Design of Axial Magnetic Coupling for Compressor

A mechanical device which raises the pressure of a gas by decreasing its volume is called as compressor. A coupling is a device which transmits the power from one end to another end. The purpose of coupling is to join two parts which allowing some degree of misalignment or end movement or both. But in conventional coupling, there are lots of losses like mechanical losses, noise and vibration losses etc. These losses have effects on the efficiency of the system. In mechanical seals, leakages are possible. So, leakage of hazardous chemicals polluting the environment has to prevent. The mechanical seal limits the speed of the compressor as the wear rates of the seal are proportional to speed. To improve the efficiency of coupling and to minimize the mechanical losses of coupling, magnetic coupling is introduced. It is contactless coupling which transfer the power from input shaft to output shaft. MATLAB software is used for analysis of magnetic coupling. This paper represents evaluation of force and torque transmitted by magnetic coupling. The theoretical analysis of magnetic coupling is carried out by using basic principle of electromagnetism. Magnetic coupling is designed to sustain the given load and torque. Permanent disc magnets of NdFeB material are selected for magnetic coupling for high strength of magnetic field. The brass plates are used to hold the magnets.

Magnetic fiber headspace solid-phase microextraction coupled to GC-MS for the extraction and quantitation of polycyclic aromatic hydrocarbons.

A technique was developed for magnetic fiber headspace-solid phase microextraction (MF-HS-SPME) of polycyclic aromatic hydrocarbons (PAHs). The efficiency of the extraction of a steel SPME fiber coated with an aminoethyl-functionalized SBA-15 (Santa Barbara Amorphous 15; a nanoporous sorbent) is substantially improved after its magnetization during HS-SPME. The effects of magnetic field strength, extraction temperature, extraction time, moisture content of the sample, desorption time and desorption temperature were optimized using a simplex method. The application of a moderately strong magnetic field to the fiber results in up to 135% increase in the extraction efficiency and wider linear dynamic ranges. The PAHs (specifically naphthalene, acenaphthene, fluorene, anthracene, phenanthrene, fluoranthene and pyrene) were then quantified by GC-MS analysis. Comparison of an electromagnet and a permanent magnet indicated the superior effect of the permanent magnet for the target analytes due to the Ohmic heating of the magnetic coil and its negative effect on the extraction of some of the PAHs. The limits of detections of the PAHs are between 0.17 to 0.57ngg-1 by using the electromagnet, and between 0.10 and 0.32ngg-1 for the permanent magnet. Relative standard deviations of 2.9 to 7.6% were obtained for six replicated analyses of the analytes. The method was applied to some polluted soil samples, and satisfactory results were obtained. Graphical abstract Schematic representation of the designed magnetic fiber headspace solid-phase microextraction (MF-HS-SPME) system using (a) an electromagnet, (b) a pair of permanent disc magnets.

Levitation and motion of a magnet partially immersed into a magnetic fluid

The levitation of a permanent disc magnet partially immersed into a magnetic fluid volume on a horizontal plane is studied theoretically and experimentally. Motion of the magnet along a thin magnetic fluid layer is investigated experimentally. A mathematical model of the magnet dynamics is proposed.

Stochastic reversal dynamics of two interacting magnetic dipoles: A simple model experiment.

We report an experimental study of the dynamics of two coupled magnetic dipoles. The experiment consists in two coplanar permanent disk magnets separated by a distance d, each allowed to rotate on a fixed parallel axis-each magnet's axis being perpendicular to its dipolar moment vector. A torque of adjustable strength can be externally applied to one of the magnets, the other magnet being free. The driving torque may be time-independent or temporally fluctuating. We study the influence of the parameters of the driving torque on the dynamics of the coupled system, in particular the emergence of dynamical regimes such as stochastic reversals. We report transitions between stationary and stochastic reversal regimes. All the observed features can be understood by a simple mechanical dynamical model. The transition between statistically stationary regimes and reversals is explained introducing an effective potential energy incorporating both the coupling between magnets and the external driving. Relations between this simple experimental model with macroscopic models of magnetic spin coupling, as well as with chaotic reversals of turbulent dynamos, are discussed.

A simple experiment showing the determination of the magnetic dipole moment of a permanent disc magnet

We propose a simple experiment to estimate the magnetic dipole moment of a neodymium disc magnet. The experiment employs a precision digital balance and a 1 m ruler to measure the force between two magnets. The magnetic dipole moment is determined from the slope of the magnetic force as a function of the inverse fourth power of the distance. The presented activity can be performed by teachers and students at college or university level to enhance their knowledge of the physics of magnetism.

Artificially Structured Boundary as a Charged Particle Beam Deflector Shield

The possibility of using a planar artificially structured boundary as a charged particle beam deflector shield is studied via classical trajectory Monte Carlo simulation. The artificially structured boundary (ASB) is formed by a planar array of permanent disk magnets with like poles facing out and creates a spatially periodic magnetostatic field. A mono-energetic beam of charged particles is incident on the ASB, and the conditions under which particles penetrate through the array are determined.

A QUASI-STATIC ELECTROMAGNETIC ANALYSIS FOR EXPERIMENTS WITH STRONG PERMANENT MAGNETS

An electromagnetic analysis is presented for experiments with strong permanent disc magnets. The analysis is based on the well known experiment that demonstrates the effect of circulating eddy currents by dropping a strong magnet through a vertically placed metal cylinder and observing how the magnet is slowly falling through the cylinder with a constant velocity. This experiment is quite spectacular with a super strong neodymium magnet and a thick metal cylinder made of copper or aluminum. A rigorous theory for this experiment is provided based on the quasi-static approximation of the Maxwell equations, an infinitely long cylinder (no edge effects) and a homogeneous magnetization of the disc magnet. The results are useful for teachers and students in electromagnetics who wish to obtain a deeper insight into the analysis and experiments regarding this phenomenon, or with industrial applications such as the grading and calibration of strong permanent magnets or with measurements of the conductivity of various metals, etc.. Several experiments and numerical computations are included to validate and to illustrate the theory.

Magnetic Levitation Over Large Translation and Rotation Ranges in All Directions

This paper describes a magnetic levitation system that uses a planar array of 16 cylindrical coils to levitate a platform containing two permanent disk magnets. Position and orientation feedback for closed-loop levitation control is provided by an optical rigid-body motion tracker and wireless LED markers. The actuation model for the levitation system across the full translation and rotation ranges was calculated using electromagnetic finite element analysis and validated with force and torque measurements between a single magnet and coil using motion stages and a six-axis force sensor. The transformation from the set of coil currents to the force and torque generated on the levitated body is recalculated in real time at each update of the levitated platform position and orientation obtained from the motion tracker using a precomputed single magnet and coil actuation model, and redundant kinematic control methods are used to find the least squares set of coil currents to generate the forces and torques needed to stabilize the levitated platform by proportional-derivative feedback control. The approximately 80 × 80 × 25 mm translation range of the implemented levitation system is comparable to the dimensions of the levitated magnet platform. The rotation ranges are ±40° in roll and ±15° in pitch, with unlimited yaw. The horizontal translation ranges can be extended by adding coils to the array, and the vertical translation and tilt rotation ranges are limited by heat dissipation in the coils. Analysis and control methods of the system are described, and large range translation and rotation trajectory following experimental results are given.

Calculation of Levitation Force Using a Critical-State Model

The interaction forces between a permanent disk and a superconductor disk are calculated for a cylindrical system by using the Anderson–Kim model. Model calculations show that both the vertical force and the stability exhibit a peak-like behavior in the repulsive branch. These peaks in the calculations are dependent on the model parameter and the ratio between the penetration and the applied fields, Hp/Hm. The features of hysteretic force and magnetic stiffness are discussed.

Size Effects on Levitation Force Between a Magnet and a Superconducting Thin Film in the Meissner State

The levitation force between a permanent magnetic disk and a thin superconducting disk in the Meissner state is calculated using the dipole–dipole interactions model. The levitation force as a function of the magnet and superconductor radii, the levitation height, and the superconductor thickness is studied under the assumption that the radius of the magnet is much smaller than the radius of the superconductor. Results showed an increase in the levitation force as a function of the radius of the superconducting disk. However, the levitation force decreases as the radius of the permanent magnetic disk increases. Demagnetizing effects are taken into account by considering the appropriate demagnetizing factor for the suggested system.

Noncontact Spinning Mechanism Using Rotary Permanent Magnets

This paper proposes a noncontact spinning mechanism that spins a levitated object (in this case, an iron ball) using four rotary permanent disk magnets. When the object was stably levitated in the vertical direction by a magnetic suspension system, the disk magnets spun the suspended object in the horizontal direction by means of the remanent magnetization on the surface of the suspended object. In this mechanism, the disk magnets are arranged around the levitated object, and the magnetic poles are arranged in a parallel configuration. In this paper, the noncontact spinning principle of the noncontact spinning mechanism is discussed. Second, a prototype and a control system of the spinning system are introduced. Third, the rotational torque of the iron ball is calculated using a mathematical model and IEM (integral element method) analysis. Finally, the spinning experiments of the iron ball's velocity step response to the disk magnets and the relationship between the input and output velocities are examined, and the results are shown and discussed. All results indicate that a suspended object can be spun using this noncontact spinning mechanism.

Analysis and Experimental Verification of a Three-Dimensional Noncontacting Angular Motion Sensor

A three-dimensional noncontacting angular motion sensor, based on magnetometry, has been developed for velocity feedback in the ball wheel mechanism, which serves as the drivetrain for a class of omnidirectional mobile platforms. More generally, this scheme tracks rigid-body rotation about a fixed point with an undefined axis of rotation. The approach involves tracking the time-varying magnetic field of a permanent disc magnet embedded at the center of the sphere. This data is then used to determine the absolute orientation of the magnet axis. Finally, an approach based on the natural invariants of rigid-body motion is used to determine the instantaneous axis of rotation and the angular speed of the sphere about this axis. In this paper, the sensing scheme is formulated, effects of geometric offsets within the tri-axial fluxgate magnetometer are addressed, and results from experimental verification are presented.

THE CLASSIC: Pyogenic Vertebral Osteomyelitis

THE CLASSIC: Pyogenic Vertebral Osteomyelitis

BSR: B-spline atomic R-matrix codes

BSR is a general program to calculate atomic continuum processes using the B-spline R-matrix method, including electron–atom and electron–ion scattering, and radiative processes such as bound–bound transitions, photoionization and polarizabilities. The calculations can be performed in LS-coupling or in an intermediate-coupling scheme by including terms of the Breit–Pauli Hamiltonian. New version program summary Title of program: BSR Catalogue identifier: ADWY Program summary URL: http://cpc.cs.qub.ac.uk/summaries/ADWY Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Computers on which the program has been tested: Microway Beowulf cluster; Compaq Beowulf cluster; DEC Alpha workstation; DELL PC Operating systems under which the new version has been tested: UNIX, Windows XP Programming language used: FORTRAN 95 Memory required to execute with typical data: Typically 256–512 Mwords. Since all the principal dimensions are allocatable, the available memory defines the maximum complexity of the problem No. of bits in a word: 8 No. of processors used: 1 Has the code been vectorized or parallelized?: no No. of lines in distributed program, including test data, etc.: 69 943 No. of bytes in distributed program, including test data, etc.: 746 450 Peripherals used: scratch disk store; permanent disk store Distribution format: tar.gz Nature of physical problem: This program uses the R-matrix method to calculate electron–atom and electron–ion collision processes, with options to calculate radiative data, photoionization, etc. The calculations can be performed in LS-coupling or in an intermediate-coupling scheme, with options to include Breit–Pauli terms in the Hamiltonian. Method of solution: The R-matrix method is used [P.G. Burke, K.A. Berrington, Atomic and Molecular Processes: An R-Matrix Approach, IOP Publishing, Bristol, 1993; P.G. Burke, W.D. Robb, Adv. At. Mol. Phys. 11 (1975) 143; K.A. Berrington, W.B. Eissner, P.H. Norrington, Comput. Phys. Comm. 92 (1995) 290].

Design synthesis of non-symmetrically loaded high-performance disc brakes: Part 2: Finite element modelling

The prediction of the behaviour of wheel-mounted disc brakes is particularly complex due to non-symmetrical heat input, making disc coning during braking inevitable. Furthermore, severe brake applications cause high local temperatures and stresses, resulting in disc material yielding and permanent disc coning. To ensure adequate brake operation, disc coning during braking and permanent disc coning must be kept within acceptable limits. Obviously, excessive hub stresses must also be avoided, to ensure structural integrity throughout expected brake life. In order to predict disc permanent coning, it is necessary to model macro thermal effects, i.e. thermoelastic instability. The paper deals with different finite element (FE) modelling techniques and measurements of disc material properties, establishing efficient methodology for the prediction of wheel-mounted disc performance. The procedure developed is widely based on a standard FE code, with subroutines developed for data preparation, processing and visualization. This approach, combined with the efficiency and robustness of the methodology, is very suitable for industrial use, reducing risks, costs and development time.

MOLED: Simulation of multilayer organic light emitting diodes

MOLED solves the dynamics of electrons and holes in multilayer Organic Light Emitting Diodes (OLED). The carriers are injected on the positive and negative electrodes of the device by tunneling through a potential barrier. Thermal excitation processes across the barrier are also included. In the interior of the device the electron–hole recombination occurs when the two carriers are close enough, according to a model inspired from the one of Langevin. A fraction of these recombined pairs gives photons. The charge transport inside the organic material occurs through hopping. Several choices of mobility formulae are available in the code. MOLED can be used for OLEDs with an arbitrary number of layers. The output consists of numerous fields that describe the device performance. For example, there are the current, the recombination and the charge density distributions, the electric field distribution, the current-voltage characteristics and the device internal quantum efficiency. Program summary Title of program: MOLED Catalogue identifier: ADSG Program summary URL: http://cpc.cs.qub.ac.uk/summaries/ADSG Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Operating systems under which the program has been tested: Unix, Linux Programming language used: FORTRAN 90 Memory required to execute with typical data: 2 MB No. of bytes in distributed program: 26 942 No. of bits in a word: 64 Peripherals used: permanent disk storage No. of lines in distributed program, including test data, etc.: 3695 Distribution format: tar gzip file Nature of the physical problem: Injection of electrons and holes into an organic electroluminescent material occurs through tunneling from metal electrodes. The transport of carriers inside the molecular medium proceeds by hopping from one molecule to another. The emission of light is a result of their radiative Langevin recombination (for a review see [Scott et al., Synthetic Metals 111–112 (2000) 289; Friend et al., Nature 397 (1999) 121]). Method of solution: The equations governing the time evolution of current, charge density and electric field in the device are solved after discretization in time. An implicit procedure is used to perform the time step. The nonlinear effects, originating from strong dependence of the hopping frequency on charge distribution, are treated within the first order in the implicit method [Press et al., Numerical Recipes, Cambridge Univ. Press, 1986, Ch. 17]. The molecular energy levels are updated at each time step to take into account the Coulomb interactions [Tutiš et al., J. Appl. Phys. 89 (2001) 430]. Typical running time: A typical calculation takes a few minutes on DEC Alpha 500 MHz or Pentium 4 1.8 GHz machines. The execution time may vary considerably, depending on the complexity of the problem. Unusual features of the program: This code has a GUI interface for input/output that can be obtained from the URL: http://lomm.epfl.ch/.

Arrays of ferromagnetic FeCo and FeCr binary nanocluster wires

We report fabrication of the arrays of ferromagnetic FeCo and FeCr binary nanocluster wires (NCWs) by thermally decomposing the Fe(CO)5/Co2(CO)8 and Fe(CO)5/Cr(CO)6 metal carbonyl vapors, respectively, with a resistive heater placed in the middle of a pair of permanent disc magnets. The NCWs are produced through the pileup of binary nanoclusters along the lines of magnetic flux, perpendicular to the substrates attached to a pair of permanent disc magnet surfaces. For both arrays of FeCo and FeCr binary NCWs, the diameter of individual NCWs ranges from 8 to 20 nm and the NCWs exist as bundles with their length up to 2–3 mm. We observed compositional dependence of structure.

Impulsive compression influences the viscous behavior of porcine temporomandibular joint disc.

Traumatic joint injury is known to produce osteoarthritic degeneration in the temporomandibular joint (TMJ). However, little information, is available on its possible effect on the dynamic viscoelastic behavior of the disc. In the present study, impulsive compression was applied to the disc as a model for traumatic joint injury. This was tested in 32 porcine discs. Prior to a dynamic tensile test, impulsive compression with strain rates of 0.01, 0.1 and 1 s(-1) to a final strain of 30% was applied to these discs. Tensile stress was applied in the antero-posterior direction with a wide range of frequencies (0.1-100 Hz). The dynamic E-moduli increased as the loading frequency increased. The dynamic viscosity and elasticity decreased with an increase of strain rate, although the effect on viscosity was greater than on elasticity. The results suggest that strain rate and subsequent peak stress of impulsive compression affect primarily the dynamic viscosity of the disc, and that impulsive compression at high strain rates reduces the resistance of the TMJ disc to stress, resulting in permanent disc deformation and perforation.

CoCr Binary Nanocluster Wires: Enhanced Magnetic Properties of the Co-rich Phase

We report fabrication of CoCr binary nanocluster wires (NCWs) by thermally decomposing Co 2 (CO) 8 /Cr(CO) 6 metal carbonyl vapors by using a resistive heater placed in the middle of a pair of permanent disk magnets. In general, NCWs grow through the pile-up of binary CoCr nanoclusters perpendicularly to the substrates attached to the magnet surfaces. NCWs, ranging from 10 to 20 nm in diameter and also branching out while they grow, exist as a bundle. The bundles with lengths up to 2-3 mm form a three-dimensional array. We observed much higher coercivities and larger remanences for arrays with magnetic field applied parallel to the NCWs than those with magnetic field applied perpendicular to the NCWs. Importantly, we observed that arrays of CoCr NCWs with a 0.8-2.2 mol % Cr in which only Co-rich phase exists showed enhanced magnetic properties, that is, nearly doubled coercivities compared to that of the array of pure Co NCWs. When the Cr mole percentage is above 2.2, however, coercivities decreased because the amount of nonmagnetic Cr-rich phase increased accordingly.