Magnetic-Pole Flip by Millimeter Wave

In the era of Big Data and the Internet of Things, data archiving is a key technology. From this viewpoint, magnetic recordings are drawing attention because they guarantee long-term data storage. To archive an enormous amount of data, further increase of the recording density is necessary. Herein a new magnetic recording methodology, “focused-millimeter-wave-assisted magnetic recording (F-MIMR),” is proposed. To test this methodology, magnetic films based on epsilon iron oxide nanoparticles are prepared and a focused-millimeter-wave generator is constructed using terahertz (THz) light. Irradiating the focused millimeter wave to epsilon iron oxide instantly switches its magnetic pole direction. The spin dynamics of F-MIMR are also calculated using the stochastic Landau–Lifshitz–Gilbert model considering all of the spins in an epsilon iron oxide nanoparticle. In F-MIMR, the heat-up effect of the recording media is expected to be suppressed. Thus, F-MIMR can be applied to high-density magnetic recordings.     

Comparison between theory and experiment of nonlinear propagationfor a-few-cycle and ultrabroadband optical pulses in a fused-silicafiber

Wave-propagation equations, including effectively the second derivative in time under the condition of a small difference between the group and phase velocities and the first derivative in position ξ in the group velocity coordinate, are derived based on the slowly evolving wave approximation. These can describe ultrabroadband optical pulse propagation with not only self-phase modulation (SPM), but also induced-phase modulation (IPM) in the monocycle regime in a fiber. It is shown that linear dispersion effects can be rigorously included in the numerical calculations. Calculations including SPM in a single-mode fused-silica fiber with the Raman effect are performed and compared with experimental results. Also, calculations including IPM in the fused-silica fiber are compared with experimental results. The effects of each term in the calculations on spectra are analyzed and it is shown that inclusion of the Raman effect and the dispersion of the effective core area is important for obtaining better agreement with experiments. It is shown that inclusion of more than third-order dispersion terms is necessary for calculations of monocycle pulse propagation     

A 1/3-in 410000-pixel CCD image sensor with feedback field-plateamplifier

The design considerations and performance of a 1/3-in format 410000-pixel interline transfer charge coupled device (CCD) (IL-CCD) image sensor are described. Some techniques have been introduced in order to shrink the pixel size to 6.4(H)×7.5(V) μm without any deterioration in dynamic range and, signal-to-noise (S/N) ratio. The photodiode structure is designed to reduce the knee effect so as to avoid an overflow of the vertical CCD (V-CCD) register up to 500 times the saturating illumination. A depleted-well CCD structure is introduced to maintain the maximum charge-handling capability of 92000 electrons/packet in the V-CCD register, and high enough transfer efficiency of the horizontal CCD (H-CCD) registers with 5-V_p-p pulse driving. A feedback field-plate amplifier (FFPA) is introduced to raise the sensitivity of the output amplifier to 16.2 μV/electron in order to obtain a large enough S/N ratio to the background noise of the peripheral circuits in a video camera     

2 Gb/s operation of an optical-clock-driven monolithicallyintegrated GaAs D-flip-flop with metal-semiconductor-metalphotodetectors for high-speed synchronous circuits

Two Gb/s operation of an optical-clock-driven GaAs D-flip-flop is demonstrated which is monolithically integrated with metal-semiconductor-metal photodetectors. Optical-clock pulses of 100-ps pulsewidth generated from a semiconductor laser were used for the optical clock input. The relationship between optical clock input power and output signal waveform is determined     

Oxygen-Saturated Strong Metal-Support Interactions Triggered by Water on Titania Supported Catalysts

Strong metal-support interaction (SMSI) greatly improves the performances of various supported metal nanoparticle catalysts. Classical SMSI relies on the oxide species with substoichiometric oxygen concentration, which prefers to retreat off in humid and oxidative atmospheres. A SMSI is reported with oxygen-saturated overlayers on Au/TiO₂ catalyst achieved by steaming treatment, an opposite condition to the classical SMSI formation. Through a combination of experimental and theoretical methods, this study demonstrates that the strong interactions between the TiO_xH_y (x≥2) species and Au surface cause the support migration to encapsulate Au nanoparticles. The oxygen-saturated oxide overlayers are stable in oxidative, reductive, and humid atmospheres, providing great vitality to stabilize metal nanoparticle catalysts under varied and complex reaction conditions to outperform the classical SMSI.     

PreRAKE diversity combining in time-division duplex CDMA mobilecommunications

A preRAKE system is proposed for the time-division duplex (TDD) code-division multiple-access (CDMA) systems for portable communications. Since the up and down links are time slots on the same carrier frequency, they have the same channel impulse response during a short period of time. Instead of building a RAKE receiver in the portable unit, the base station (BS) can preRAKE the signal before transmission in the down link using the channel impulse response estimated from the up link. When the preRAKED signal is convolved with the channel impulse response, the function of the RAKE receiver is automatically performed. The mobile or portable unit uses a conventional receiver and still achieves the diversity gain of a RAKE receiver     

Measurement of cold neutron-beam focusing effect of a permanent sextupole magnet

The magnetic focus effect of cold neutron beam was measured using a permanent sextupole magnet and a gain of more than 35 was observed. The result was analyzed with a numerical simulation.     

Preparation and characterization of carbon-coated ZnO and CaO powders by pyrolysis of PVA

Carbon-coated ZnO and CaO powders were prepared by Poly(vinyl alcohol) (PVA) pyrolysis at 700 °C in inert atmosphere and characterized for their potential utilization in the field of antibacterial ceramics. No peaks corresponding to carbon were detected after XRD measurements of as-coated powders; that is, carbon coating is amorphous. Certain increase in specific surface area was observed after coating in all powders. Based on additional characterizations supported by SEM observations and particle size distributions, it is concluded that the formation of nanoporous structure of coated carbon layer resulted in an increase in the surface area. Some agglomeration also observed after treating powders that decreased with increasing polymerization degree of PVA used as a carbon precursor.     

An implantable power supply with an optically rechargeable lithiumbattery

A novel power supply for medical implants has been developed. A wireless near-infrared power transmission recharges a lithium secondary battery in the power supply. A photovoltaic cell array embedded under skin receives near-infrared light through the skin and charges the battery directly powering an implanted device. We have shown that, for a photodiode area of 2.1 cm2, 17 min of near-infrared irradiation at a 810-nm wavelength with a power density of 22 mW/cm2 can send enough energy to allow regular commercial cardiac pacemakers to run for 24 h. The temperature rise of the skin during the light irradiation was 1.4 degrees C.