Frequency Of Electromagnetic Vibration Research Articles

Electromagnetically-vibrated solid-phase microextraction for analysis of aqueous-miscible organic compound transport in soil columns

Current methods of sampling pore water from soil columns to determine solute concentrations are slow and require relatively large volumes. Accordingly, an electromagnetically-vibrated (EMV) solid-phase microextraction (SPME) device was evaluated for determining temporal and spatial distributions of solute pore-water concentrations (solute concentration profiles) for four organic compounds, two polar (2-hexanone, 2,4-dimethyl phenol) and two nonpolar (toluene, 1,4-dichlorobenzene), in columns packed with simulated aquifer sands with different fractions of organic carbon. In batch equilibrium extraction tests, the equilibrium extraction time of the organic compounds in aqueous mixtures decreased from 30 to less than 10 min as the frequency of electromagnetic vibration increased from zero to 250 Hz. Mixture effects were not statistically significant (p > 0.05) in the extraction process using EMV SPME. Comparisons of the solute concentration profiles within the soil columns at different elapsed times measured by pore-water samples and in situ EMV SPME extractions revealed both methods were equally effective. However, EMV SPME extraction removed no solution volume and only 0.6–14% of the solute mass removed by the pore-water sample collections, substantially minimizing disturbances to solute transport and fate. Thus, the equilibrium extraction-based calibration method using EMV SPME offers an effective approach for rapidly and accurately determining solute concentration profiles in column tests with negligible solute mass loss and minimal solution flow disturbance.

The Effect of Frequency of Electromagnetic Vibrations on Vibrational Motion in Fe-Co-B-Si-Nb Bulk Metallic Glasses

The method for producing Fe-Co-B-Si-Nb bulk metallic glasses using electromagnetic vibrations is effective in forming the metallic glass phase. The purpose of this study was to investigate the effects of the frequency of electromagnetic vibrations on the vibrational motion in Fe-CoB-Si-Nb bulk metallic glasses. The amplitudes of the electromagnetic vibrations at 5 kHz were calculated to be on the order of micrometers, but those at higher frequencies were on the order of nanometers. It was found that the nanometer-sized amplitudes resulted in the disappearance of the increased cooling rate caused by electromagnetic vibrations observed at lower frequencies. When particles in the sample have lower electric resistance than the molten sample, these particles are considered to vibrate vigorously in the molten sample by Lorentz force because the electric current concentrates in those. It is suggested that this phenomenon is the reason electromagnetic vibrations decrease the number of crystal nuclei. [doi:10.2320/matertrans.48.234]

The Effect of Frequency of Electromagnetic Vibration on the Primary Silicon Size in Hypereutectic Al-Si Alloy

The structural control of Al-Si alloy, which was not studied among various electromagnetic processing of materials, was considered applying the alternating current and direct current magnetic flux density. The main aim of the present study is to investigate the effects of electromagnetic vibration on the control of the size of primary Si phase in order to develop a new process of structural control in Al-Si alloy. If the current density conducted for making high frequency electromagnetic vibration (EMV) (≥ 500Hz), the size of primary Si phase goes to small. If it conducted for making low frequency EMV (≤ 200Hz), the size of primary Si phase goes to large. This phenomenon considered to be related the collision, agglomeration and diffusion of silicon atoms.

The Effect of Electromagnetic Vibration on the Silicon Size at Hypoeutectic Al-Si Alloy

In this study, the electromagnetic vibration process is adopted for modifying the eutectic Si phase and reducing its size. The higher the current density and frequency of electromagnetic vibration (EMV), the finer the size of the eutectic Si phase. The tensile strength and elongation of EMVed alloys were highly improved. Measured twin probability of EMVed alloy at a frequency of 1000Hz was approximately six times as high as that of the normal alloy and half of that of Sr modified alloy. The mechanism for the increase in twin density due to EMV during solidification could be suggested from the fact that the preferential growth along <112> in silicon was suppressed by preventing the Si atom from attaching to the growing interface of the Si phase and by changing the solid/liquid interfacial energy of silicon.

The Effect of Frequency of Electromagnetic Vibration on the Primary Silicon Size in Hypereutectic Al-Si Alloy

In this study, the electromagnetic vibration is adopted for control of the size of primary Si phase. The higher the current density and frequency of electromagnetic vibration (EMV), the finer the size of primary Si phase. The higher the current density but the lower frequency of EMV, the bigger the size of primary Si phase. This phenomenon considered to be related the collision, agglomeration and diffusion of silicon atoms.

Effects of the Intensity and Frequency of Electromagnetic Vibrations on Glass-Forming Ability in Mg–Cu–Y Bulk Metallic Glasses

The present authors reported that a new method for producing Mg–Cu–Y bulk metallic glasses by using electromagnetic vibrations is effective in forming the metallic glass phase, and disappearance or decrement of clusters by the electromagnetic vibrations applied to a liquid state is presumed to cause suppression of crystal nucleation [Nature Materials 4 (2005) 289]. This paper aims to investigate the effects of the intensity and frequency of electromagnetic vibrations on apparent glass-forming ability in the Mg–Cu–Y bulk metallic glasses. It was found that the apparent glass-forming ability of Mg65Cu25Y10 alloys increases with increasing the frequency of electromagnetic vibrations up to 5000 Hz. The effects of frequency more than 5000 Hz could not be investigated because of alternating current power devices. Moreover, it was found that the apparent glass-forming ability of Mg65Cu25Y10 alloys increases with increasing the intensity of electromagnetic vibrations by an electric current or a magnetic flux density. However, increasing excessively the electric current was found to weaken the enhancement of the apparent glass-forming ability by using the electromagnetic vibration process because the crystalline particles grow larger by the Joule heat.

Effect of the frequency of electromagnetic vibrations on microstructural refinement of AZ91D magnesium alloy

The static magnetic field and the alternating electric field were simultaneously imposed on AZ91D magnesium alloy melt, and α-dendrite particles were refined by the electromagnetic vibrations. The effect of the frequency of electromagnetic vibrations on microstructural refinement was quantitatively investigated. In the frequency range from 60 to 1000 Hz, the vibration frequency near 200 Hz was the most effective for the refinement of α-dendrite particles, and α-dendrite particles were refined up to approximately 100 μm from 1800 μm at this frequency. However, the effect of refinement by the electromagnetic vibrations became weak at frequencies above 400 Hz. Although the degree of refinement of the primary particles differed with the frequency of the electromagnetic vibrations, the dendrite arm spacing was almost constant, 30–40 μm, in our experiment. Therefore, the refinement of primary α-dendrite particles is likely to be caused by collapse of dendrite arms due to the cavitation phenomenon and the stirring of the melt.

Effect of Electromagnetic Force on the Silicon Size in Hypoeutectic Al-Si Alloy

In general, the element (Sr, Na, Sb, etc.) is used as a modifier of eutectic Si phase in the hypoeutectic Al-Si system. When these elements are added into the hypoeutectic Al-Si melt, the flake shaped Si phase transforms to fibrous shape and the size of Si phase is also decreased. In this study, the electromagnetic vibration is adopted for modifying eutectic Si phase and reducing its size. The higher the current density and frequency of electromagnetic vibration(EMV), the finer the size of eutectic Si phase. The tensile strength and elongation of EMVed alloy were highly improved. Measured twin probability of EMVed alloy at a frequency of 1000Hz was approximately six times as high as that of the normal alloy and a half of that of Sr modified alloy. The mechanism for the increase in twin density due to EMV during solidification could be supposed from the fact that the preferential growth along <112> in silicon was suppressed by preventing Si atom from attaching to the growing interface of Si phase and by changing the solid/liquid interfacial energy of silicon.

Effect of the Intensity and Frequency of Electromagnetic Vibrations on Refinement of Primary Silicon in Al-17%Si Alloy

Electromagnetic vibrations, which are the interaction between a static magnetic field and an alternating electric field, were applied to the structural refinement of Al-17%Si hyper-eutectic alloy. The relationship between the intensity and frequency of the electromagnetic vibrations and the refinement of primary silicon particles is quantitatively investigated. In the frequency range from 10 Hz to 30 kHz, the vibration frequency near 1 kHz was most effective for the refinement of silicon particles, and silicon particles of sizes up to approximately 5 mm were refined at that frequency. The level of refinement increased with increasing the intensity of electromagnetic vibrations. A primary silicon particle was sufficiently refined with a magnetic field intensity of only approximately 1.6 Tesla (T).

Effects of the intensity and frequency of electromagnetic vibrations on the microstructural refinement of hypoeutectic Al-Si alloys

An experimental apparatus that uses a superconducting magnet and enables the simultaneous application of an alternating electric field with a frequency of up to 50 kHz and a magnetic field of up to 10 T was designed and assembled. Electromagnetic vibrations were induced in Al-7 wt pct Si alloy during solidification by simultaneous application of the two fields. The thorough investigation, which was carried out over wide ranges of intensity (an electromagnetic pressure range of 0 to 2.25×105 Pa) and frequency (0 to 50 kHz), clarified the effects of the two main parameters on the microstructural refinement brought about by electromagnetic vibrations. Low-intensity vibrations changed the highly columnar dendritic structure into one composed of large, equiaxed dendrites. As the intensity, and consequently, the magnetic pressure were increased, at about 0.93×105 Pa, fine isolated grains started to appear and dominated the structure as the pressure was increased further. At low frequencies, the structure was one with large, equiaxed dendrites, which disintegrated to form a fine and homogeneous structure as the frequency was increased. At about 1.5 kHz, the trend reversed and the structure gradually became a completely columnar dendritic one at frequencies higher than 10 kHz. Metallographic observations showed that the cavitation phenomenon has been a main factor behind the observed microstructural refinement. The effects of mechanical vibrations of the experimental apparatus were also investigated and found to have no contribution to the observed effects.

Light in the Sea—Correlations with Behaviors of Fishes and Invertebrates

SYNOPSIS. Light is characterized by three basic properties: intensity, the frequency of electromagnetic vibration, and polarization. Beneath the surface of the sea each of these properties of light is modified in ways that could affect the behaviors and the underlying physiological and biochemical mechanisms that control the behavior of organisms. How light changes under water in several time domains, such as seasonal, daily, and even shorter periods of time, is described. The correlation between diel shifts in the activity of fishes and marine invertebrates and the daily changes in light under water is described. It is concluded that exactly how light influences these daily shifts in animal activity, and whether or not circadian rhythms also influence the shifts, is, for most species, not known