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In order to achieve a high-quality SiC crystal in solution growth, one of the most difficult issues is to grow a thick layer on Si face avoiding polytype transformation. In this case, two-dimensional nucleation, which leads to the polytype transformation, is frequently induced because a density of threading screw dislocations acting as a source of spiral step decreases and wide terraces form by step...
The relationship between surface morphology and spatial distribution of basal plane dislocations in 4H-SiC crystal grown by top-seeded solution growth on the C face was investigated by the differential interference microscopy as well as X-ray topography. Basal plane dislocations were generated at the boundaries of the domains with the different macrosteps advance directions. On the other hand, at...
Electromagnetic time-reversal enabling potential super-resolution in telecommunication systems when operated within complex media — imaging is left aside from now — has been much studied, in particular since [1]. Yet it remains a controversial issue [2]. Here, one illustrates what could be the behavior of a radiating broad-frequency device when operated in a properly-structured, finitely-extended...
Delivering electric pulses to brain tissues has been done by Transcranial Magnetic Stimulation, but the resolution and penetration depth are limited. We use picosecond electric pulses to stimulate neurons (activation or inhibition). The delivery of such short pulses was simulated by CST Microwave Studio. Pulses were delivered to a shallow, subcranial target using a conical dielectric antenna. Results...
Continuing areal-density growth is critical for the hard disk drive industry to meet the increasing demand in data storage, and to improve costs. Heat-assisted magnetic recording (HAMR) is expected to be introduced in products as perpendicular magnetic recording (PMR) approaches its limitations in areal density growth. Beyond this, bit patterned media (BPM) recording is considered to provide a path...
Bubbles induced by blast waves or shocks are speculated to be the major cause of damages in the cells. We have studied the impact of the bubbles and shock waves generated by underwater discharges [1]. Microbubbles were found indeed to induce noticeable cell detachment from the cell substrate, changes in focal adhesion and biomechanics [2]. To better understand the bubble mechanism, we would like to...
In the research of bioelectrics, bipolar pulses appear to enhance the membrane effects by creating anode on both sides of the cell sequentially. On the other hand, the membrane charging resulted from the first part of the pulse may be removed by the following pulse of opposite polarity. To explore the biological effects of bipolar pusles on cells, we have constructed several types of nanosecond bipolar...
Delivery of subnanosecond pulses into biological tissue can be undertaken by an impulse radiating antenna (IRA). Previous analysis shows that it is important to add a dielectric lens, which reduces the abrupt change of dielectric constant from air to tissue and therefore increases the transmission of the pulses. As a proof of concept, we have simulated subnanosecond pulsed radiation focused into a...
For doubly-fed induction generator (DFIG)-based wind power systems, when a grid voltage dip happens, a large electromotive force (EMF) will be induced in the rotor circuit. Without proper control for protection, over-current will appear in the rotor circuit, and it may lead to the destruction of the rotor-side converter (RSC). To mitigate this problem, a new low voltage ride-through (LVRT) control...
Subnanosecond electric pulses (200 ps) at an electric field intensity of 25 kV/cm induce the death of B16 skin melanoma cells. We have observed 20% cell death after the exposure to 1.8 million pulses. The cytotoxic effect is due to the electric field effect coupled with temperature rise. A higher number of pulses, 2.4 million, causes 90% cell death, which is largely due to hyperthermia. When exposed...
HVDC (High Voltage Direct Current) transmission is considered as a mature technology to meet the demand for the bulk power transmission over long distances and provide flexibility for the network interconnections. For ultra-high voltage HVDC applications, the significant effects of the stray capacitance on the voltage imbalance for thyristor converters have to be considered during the transient conditions...
We use THz time-domain spectroscopy to investigate transmission and reflection properties of metallic fractal metamaterial structures. We observe loss of free-space energy at certain resonance frequencies, indicating excitation of surface modes of the metamaterial.
Detection of special nuclear material (SNM) hidden in cargo containers is considered to be one of the major challenges for homeland security. SNM impose a significant threat for public safety since they can be converted into nuclear weaponry and used for potential terrorist attacks. In this paper we present who we can fill the existing gap in quickly but accurately detecting hidden SNM. Synergism...
Focusing Impulse Radiating Antennas allow the application of intense electric fields to biological tissue with centimeter spatial resolution. At low electric field strength, the scattered electromagnetic waves from the focal volume can be used to obtain information on the complex permittivity of the tissue at this location. Since the permittivity of tumor tissue varies considerably from that of healthy...
Intense, subnanosecond electric fields can be used either to stimulate bioelectric effects, such as calcium release in cells (which can lead to various secondary physiological effects), or to generate local hyperthermia. High power wideband antennas radiating electromagnetic waves in the subnanosecond range allows us to treat deep lesions non-invasively. Electromagnetic waves launched at the first...
We have explored the use of a focusing antenna for imaging of targets based on their dielectric properties. At the focal point of the antenna, metal targets with various sizes were placed. A sensor behind the target was used to detect the forward scattered signal. With this system, the minimum dimensions of a target that can be detected are 7 cm, which is on the order of the product of the pulse duration...
The graphics processing unit (GPU) has emerged as a computational accelerator that dramatically reduces the time to discovery in high-end computing (HEC). However, while today's state-of-the-art GPU can easily reduce the execution time of a parallel code by many orders of magnitude, it arguably comes at the expense of significant power and energy consumption. For example, the NVIDIA GTX 280 video...
Modern power systems require that power delivery components operating at very high voltages use the minimum amount of insulation necessary for reliable operation in view of economic considerations. The insulation is subject to a high electrical stress, so that partial discharge (PD) activity may initiate under normal working conditions in high voltage equipment that is aging or has flawed insulation,...
We review recent progress in optical metamaterials and demonstrate our sample with negative index behavior at the shortest wavelength so far (710 nm). We discuss the impact of fabrication limitations on the performance of metamaterials.
32 nm Si and Si1-xGex SOI Coplanar N Channel Vertical Dual Carrier Field Effect Transistors for mixed signal and communication applications are presented.
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