Observation of Hysteretic Transport Due to Dynamic Nuclear Spin Polarization in a GaAs Lateral Double Quantum Dot

We report a new transport feature in a GaAs lateral double quantum dot that emerges only for magnetic field sweeps and shows hysteresis due to dynamic nuclear spin polarization (DNP). This DNP signal appears in the Coulomb blockade regime by virtue of the finite inter-dot tunnel coupling and originates from the crossing between ground levels of the spin triplet and singlet extensively used for nuclear spin manipulations in pulsed gate experiments. The unexpectedly large signal intensity is suggestive of unbalanced DNP between the two dots, which opens up the possibility of controlling electron and nuclear spin states via DC transport.Comment: 5 pages, 4 figure

Coastal Marine Debris Mapping Using Multi-Modal Feature Extraction Pipeline

Marine debris in the ocean is becoming an increasing problem for the management of coastal oceans and seaside resort areas. This paper presents a method for coastal marine debris mapping using satellite images from multiple satellite platforms. We carry out a pilot project in association with a local government to collect in-situ measurements of debris deposited on beaches and download the coincident satellite images to identify the marine debris. We propose to study the detection of marine debris on land and in the coastal ocean with various sources of satellite imagery as a way to increase the revisit frequency. High temporal resolution data can provide an agile estimation of the resources required to mitigate the pollution accumulation on the shoreline. A major challenge of monitoring specific areas from optical satellite images is the obscuration by cloud cover, which makes it decrease the sampling frequency. To get a handle on this problem and establish high-fidelity model, we acquired the greatest number of satellite images from a variety of platforms including high temporal-resolution imagery provided by small satellite constellation programs. We first established our method using entropy of the segmentation model output on marine debris mapping in coastal areas using WorldView images provided by MAXAR corp. Then we extended the pipeline to other small satellite images using unsupervised domain adaptation techniques. We showed that the spatial representation of the segmentation map is greatly improved by the domain adaptation techniques. Whereas some dataset still requires more data samples and additional quantitative analysis, we confirmed the compatibility of the segmentation output to the established pipeline using entropy metrics to estimate the accumulation density of the debris. This analysis shows the robust capability to be able to apply the pipeline to different types of satellite images, which can be also applied in other remote sensing applications

Antena solution for future communication devices in mm-wave range

Different type of printed antennas for millimeter ranges like: high gain (narrow beam) with linear and circular polarization, sector antennas with azimuth angle of 600, 900 and 1800, omnidirectional antennas are proposed. All type suitable for integration with active microwave and millimeter wave like amplifiers, down and up convectors. Also, proposed sector and omnidirectional antennas are practically applicable for lower microwave range of 5 GHz that is included in new generation of communication systems for 60 GHz range

Stimulated emission from multilayer graphene

Monolayer graphene absorbs $\sim$ 2.3 percent of the incident visible light. This "small" absorption was used to emphasize visual transparency of graphene, but in fact it means that multilayer graphene absorbs sizable fraction of incident light, which causes non-negligible fluorescence. In this paper, we study the light emission properties of multilayer graphene composed of tens to hundreds of layers, because these are informative materials having interesting optical properties correlated closely with fluorescence. For example, it was recently predicted that 87-layer graphene absorbs infrared light at maximum efficiency and 20-layer graphene on silicon substrates exhibits zero reflectance (a total absence of backscattering) at a specific visible light wavelength. By modeling light emissions from multilayer graphene using a transfer matrix method, we could quantitatively explain the measured reflectivity from multilayer graphene on silicon substrates. We found sizable corrections, that cannot be classified as incoherent light emissions, to the reflectance of visible light. The new component originates from stimulated emission caused by absorption at each graphene layer, and it is a coherent sum over the amplitudes coming from all graphene layers with a common phase shift of $\pi$ relative to the incident light. The coherent corrections to the reflectance become dominant for samples thicker than 40-layers and thinner than 160-layers. Multilayer graphene thus functions as a partial coherent light source of various wavelengths and it may have surface-emitting laser applications.Comment: 9 pages, 9 figure

6U CubeSat for Ultraviolet Time-Domain Astronomy

A wide-field ultraviolet observatory for time-domain astronomy utilizing 6U CubeSat is presented. Ultraviolet waveband is one of the unexplored fields in astronomy. Potential targets are short duration transient sources in UV-band: early-phase emission from gravitational wave sources, supernovae shock-breakouts, tidal disruption events around super massive blackholes, etc. The telescope was designed for covering the large error circle of GW detectors, FoV~100 deg2. Thanks to the high quantum efficiency of “delta-doping” detector, the detection limit achieves 20 mag (AB) for 1800 s exposure in NUV band, which is sufficient to detect UV emission from a binary neutron star merger within 200 Mpc from the earth. The satellite has a high-performance on-board computer for on-orbit analysis to detect transient sources and measure the magnitude and the accurate position of the target. The obtained information is required to be transferred to the ground within 30 min from the detection to start multi-messenger follow-up observations utilizing ground-based observatories and astronomical satellites. In this presentation we show the mission overview and conceptual design of the satellite system

Development of Attitude Sensor using Deep Learning

A new method for attitude determination utilizing color earth images taken with COTS visible light camera is presented. The traditional earth camera has been used for coarse attitude determination by detecting the edge of the earth, and therefore it can only provide coarse and 2-axis information. In contrast, our method recognizes the ground pattern with an accuracy of sub-degrees and can provide 3-axis attitude information by comparing the detected ground pattern and the global map. Moreover, this method has advantages in the size, mass and cost of the detector system which consists of a cheap optical color camera and a single board computer. To demonstrate the method in space, we have developed a sensor system named “Deep Learning Attitude Sensor (DLAS)”. DLAS uses COTS camera modules and single board computers to reduce the cost. The obtained images are promptly analyzed with a newly developed real-time image recognition algorithms