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Functional brain imaging has tremendous applications. The existing methods for functional brain imaging include functional Magnetic Resonant Imaging (fMRI), scalp electroencephalography (EEG), implanted EEG, magnetoencephalography (MEG) and Positron Emission Tomography (PET), which have been widely and successfully applied to various brain imaging studies. To develop a new method for functional brain imaging, here we show that the dielectric at a brain functional site has a dynamic nature, varying with local neuronal activation as the permittivity of the dielectric varies with the ion concentration of the extracellular fluid surrounding neurons in activation. Therefore, the neuronal activation can be sensed by a radiofrequency (RF) electromagnetic (EM) wave propagating through the site as the phase change of the EM wave varies with the permittivity. Such a dynamic nature of the dielectric at a brain functional site provides the basis for an RF EM wave approach to detecting and imaging neuronal activation at brain functional sites, leading to an RF EM wave approach to functional brain imaging.

The effect of the magnetic field on the magnetic properties of NiFe/Cu composite wires electroplated under a longitudinal magnetic controlling field is presented. Composite wire samples of 20-μm-diameter Cu electroplated with a layer of Permalloy™ (Ni80Fe20) under the influence of a longitudinal magnetic field of intensities ranging from 0 to 400 Oe were produced, and the microstructure and magnetic properties were measured. The results showed that the longitudinal magnetic field in the composite wire plating makes the packing of the crystals in the plated layer more orderly, and thus increases the uniformity and magnetic softness of the plated material. It also shifts the magnetic anisotropy of the plated layer from circumferential to longitudinal, and increases the critical frequency of the plated composite wire in magnetoimpedance effect testing, at which the magnetoimpedance ratio reaches the maximum.

In this study, for developing microsensors for weak magnetic field, methods for developing high permeability nanocrystalline permalloy by electrodeposition and the relationship between the grain size and magnetic properties of the nanocrystalline permalloy are investigated. By dc plating with and without saccharin added and pulse plating with saccharin added, permalloy samples of grain sizes from 52 nm to 11 nm are obtained. The coercivity and magnetoimpedance (MI) ratio of the samples are tested against the grain size variation. Results show that the coercivity decreases rapidly and MI ratio increases greatly with grain size decrease from 52 nm to 11 nm.

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In this study, ductile mode chip formation in conventional cutting and ultrasonic vibration assisted cutting of tungsten carbide workpiece material has been investigated through experimental grooving tests using CBN tools on a CNC lathe. The experimental results show that as the depth of cut was increased there was a transition from ductile mode to brittle mode chip formation in grooving both with and without ultrasonic vibration assistance. However, the critical value of the depth of cut for ductile mode cutting with ultrasonic vibration assistance was much larger than that without ultrasonic vibration assistance. The ratio of the volume of removed material to the volume of the machined groove, f ab , was used to identify the ductile mode and brittle mode of chip formation in the grooving tests, in which f ab <1 indicates ductile mode chip formation and f ab >1 indicates brittle mode chip formation. For the same radius of tool cutting edge, the value of f ab at the ductile-brittle transition region either with or without ultrasonic vibration was less than 1. However, the f ab value with ultrasonic vibration assistance was close to 1. The experimental results demonstrate that ultrasonic vibration assisted cutting can be used to improve the ductile mode cutting performance of tungsten carbide work material.

In nanoscale ductile mode cutting of the monocrystalline silicon wafer, micro-, or nanogrooves on the diamond cutting tool flank face are often observed, which is beyond the understanding based on conventional cutting processes because the silicon workpiece material is monocrystalline and the hardness is lower than that of the diamond cutting tool at room temperature. In this study, the mechanism of the groove wear in nanoscale ductile mode cutting of monocrystalline silicon by diamond is investigated by molecular dynamics simulation of the cutting process. The results show that the temperature rise in the chip formation zone could soften the material at the flank face of the diamond cutting tool. Also, the high hydrostatic pressure in the chip formation region could result in the workpiece material phase transformation from monocrystalline to amorphous, in which the material interatomic bond length varies, yielding atom groups of much shorter bond lengths. Such atom groups could be many times harder than that of the original monocrystalline silicon and could act as “dynamic hard particles” in the material. Having the dynamic hard particles ploughing on the softened flank face of the diamond tool, the micro-/nanogrooves could be formed, yielding the micro-/nanogroove wear as observed.