Vehicle Trajectory Prediction and Collision Warning via Fusion of Multisensors and Wireless Vehicular Communications

Driver inattention is one of the leading causes of traffic crashes worldwide. Providing the driver with an early warning prior to a potential collision can significantly reduce the fatalities and level of injuries associated with vehicle collisions. In order to monitor the vehicle surroundings and predict collisions, on-board sensors such as radar, lidar, and cameras are often used. However, the driving environment perception based on these sensors can be adversely affected by a number of factors such as weather and solar irradiance. In addition, potential dangers cannot be detected if the target is located outside the limited field-of-view of the sensors, or if the line of sight to the target is occluded. In this paper, we propose an approach for designing a vehicle collision warning system based on fusion of multisensors and wireless vehicular communications. A high-level fusion of radar, lidar, camera, and wireless vehicular communication data was performed to predict the trajectories of remote targets and generate an appropriate warning to the driver prior to a possible collision. We implemented and evaluated the proposed vehicle collision system in virtual driving environments, which consisted of a vehicle&ndash vehicle collision scenario and a vehicle&ndash pedestrian collision scenario. Document type: Articl

Metallicity-PAH Relation of MIR-selected Star-forming Galaxies in AKARI North Ecliptic Pole-wide Survey

We investigate the variation in the mid-infrared spectral energy distributions of 373 low-redshift ($z<0.4$) star-forming galaxies, which reflects a variety of polycyclic aromatic hydrocarbon (PAH) emission features. The relative strength of PAH emission is parameterized as $q_\mathrm{PAH}$, which is defined as the mass fraction of PAH particles in the total dust mass. With the aid of continuous mid-infrared photometric data points covering 7-24$\mu$m and far-infrared flux densities, $q_\mathrm{PAH}$ values are derived through spectral energy distribution fitting. The correlation between $q_\mathrm{PAH}$ and other physical properties of galaxies, i.e., gas-phase metallicity ($12+\mathrm{log(O/H)}$), stellar mass, and specific star-formation rate (sSFR) are explored. As in previous studies, $q_\mathrm{PAH}$ values of galaxies with high metallicity are found to be higher than those with low metallicity. The strength of PAH emission is also positively correlated with the stellar mass and negatively correlated with the sSFR. The correlation between $q_\mathrm{PAH}$ and each parameter still exists even after the other two parameters are fixed. In addition to the PAH strength, the application of metallicity-dependent gas-to-dust mass ratio appears to work well to estimate gas mass that matches the observed relationship between molecular gas and physical parameters. The result obtained will be used to calibrate the observed PAH luminosity-total infrared luminosity relation, based on the variation of MIR-FIR SED, which is used in the estimation of hidden star formation.Comment: 19 pages, 9 figures, AJ, in pres

<i>gzK</i>-colour-selected star-forming galaxies in the <i>AKARI</i> NEP-Deep Field

We study the clustering property and physical parameters of gzK-colour-selected star-forming galaxies (sgzKs) based on the Canada–France–Hawaii Telescope surveys over 0.55 deg2 in the AKARI North Ecliptic Pole-Deep Field. Two-point correlation functions for two magnitude-limited cases, Ks &amp;lt; 21.1 (N = 234) and Ks &amp;lt; 21.5 (N = 428), are estimated using a single power-law function with the fixed slope of 0.8. The bias factors of sgzKs with Ks &amp;lt; 21.1 and 21.5 are 5.79 ± 1.07 and 4.00 ± 0.67, respectively, representing that sgzKs with z ∼ 1.7 reside in dark matter haloes more massive than $10^{13} ~\rm M_{\odot }$. We find that haloes hosting sgzKs with Ks &amp;lt; 21.5 evolve into haloes that host local massive galaxies with ∼6 L*. This suggests that sgzKs with Ks &amp;lt; 21.5 are likely to be predecessors of local massive galaxies. The evolutionary track of bias factor for host haloes of the bright sgzKs is similar to that of the bright passive extremely red objects, implying a possible connection between the two populations of galaxies. From the spectral energy distribution fitting, we estimate physical parameters and active galactic nucleus (AGN) contribution for 75 mid-infrared (MIR)-detected sgzKs with Ks &amp;lt; 21.5. The median values of stellar mass and star formation rate are 9.5 × 1010$\rm M_{\odot }$ and 162 $\rm M_{\odot }$ yr−1, respectively. MIR-detected sgzKs have a variety of AGN contributions ranging from 0 to 80 per cent. The number ratio of sgzKs with larger AGN contribution than 10 per cent is 30 per cent

Photometric Selection of Unobscured QSOs in the Ecliptic Poles: KMTNet in the South Field and Pan-STARRS in the North Field

We search for quasi-stellar objects (QSOs) in a wide area of the south ecliptic pole (SEP) field, which has been and will continue to be intensively explored through various space missions. For this purpose, we obtain deep broadband optical images of the SEP field covering an area of $\sim$$14.5\times14.5$ deg$^2$ with the Korea Microlensing Telescope Network. The 5$\sigma$ detection limits for point sources in the $BVRI$ bands are estimated to be $\sim$22.59, 22.60, 22.98, and 21.85 mag, respectively. Utilizing data from Wide-field Infrared Survey Explorer, unobscured QSO candidates are selected among the optically point-like sources using the mid-infrared (MIR) and optical-MIR colors. To further refine our selection and eliminate any contamination not adequately removed by the color-based selection, we perform the spectral energy distribution fitting with archival photometric data ranging from optical to MIR. As a result, we identify a total of 2,383 unobscured QSO candidates in the SEP field. We also apply a similar method to the north ecliptic pole field using the Pan-STARRS data and obtain a similar result of identifying 2,427 candidates. The differential number count per area of our QSO candidates is in good agreement with those measured from spectroscopically confirmed ones in other fields. Finally, we compare the results with the literature and discuss how this work will be implicated in future studies, especially with the upcoming space missions.Comment: 14 pages, 9 figures, accepted for publication in ApJ

Characteristics of mid-infrared PAH emission from star-forming galaxies selected at 250 μm in the North Ecliptic Pole field

Evolutionary properties of infrared (IR) luminous galaxies are important keys to understand dust-obscured star formation history and galaxy evolution. Based on near- to mid-IR imaging with nine continuous filters of the AKARI space telescope, we present the characteristics of dusty star-forming (SF) galaxies showing polycyclic aromatic hydrocarbon (PAH) features observed by the North Ecliptic Pole (NEP) wide field survey of AKARI and Herschel. All the sample galaxies from the AKARI/NEP-Wide data are selected based both on the Herschel/SPIRE 250 μm detection and optical spectroscopic redshift data. The physical modeling of spectral energy distribution (SED) using all available data points from u* to sub-mm 500 μm band, including WISE and PACS data where available, takes unique advantages of the continuous near- to mid-IR coverage, the reliable constraint on the far-IR peak, and spectroscopically determined accurate redshifts, as well as the energy balance principle by MAGPHYS. This enables us to derive physically meaningful and accurate total infrared luminosity and 8 μm (or PAH) luminosity consistently. Our sample galaxies are in the redshift range z < 1, and the majority of them appear to be normal SF/spiral populations showing PAH features near 8 μm. These SF galaxies showing PAHs in the mid-IR include various types, from quiescent to starbursts. Some of our sample show shortage of 8 μm luminosity compared to the total IR luminosity and this PAH deficit gets severe in more-luminous IR galaxies, suggesting PAH molecules in these galaxies are destroyed by a strong radiation field from the SF region or a large amount of cold dust in the interstellar medium. The specific SFR of our sample shows mass-dependent time evolution which is consistent with a downsizing evolutionary pattern