University of Electro-Communications

About: University of Electro-Communications is a education organization based out in Tokyo, Japan. It is known for research contribution in the topics: Laser & Robot. The organization has 8041 authors who have published 16950 publications receiving 235832 citations. The organization is also known as: UEC & Denki-Tsūshin Daigaku.

A new mode of operation for arbiter PUF to improve uniqueness on FPGA

Abstract: Arbiter-based Physically Unclonable Function (PUF) is one kind of the delay-based PUFs that use the time difference of two delay-line signals. One of the previous work suggests that Arbiter PUFs implemented on Xilinx Virtex-5 FPGAs generate responses with almost no difference, i.e. with low uniqueness. In order to overcome this problem, Double Arbiter PUF was proposed, which is based on a novel technique for generating responses with high uniqueness from duplicated Arbiter PUFs on FPGAs. It needs the same costs as 2-XOR Arbiter PUF that XORs outputs of two Arbiter PUFs. Double Arbiter PUF is different from 2-XOR Arbiter PUF in terms of mode of operation for Arbiter PUF: the wire assignment between an arbiter and output signals from the final selectors located just before the arbiter. In this paper, we evaluate these PUFs as for uniqueness, randomness, and steadiness. We consider finding a new mode of operation for Arbiter PUF that can be realized on FPGA. In order to improve the uniqueness of responses, we propose 3−1 Double Arbiter PUF that has another duplicated Arbiter PUF, i.e. having 3 Arbiter PUFs and output 1-bit response. We compare 3−1 Double Arbiter PUF to 3-XOR Arbiter PUF according to the uniqueness, randomness, and steadiness, and show the difference between these PUFs by considering the mode of operation for Arbiter PUF. From our experimental results, the uniqueness of responses from 3−1 Double Arbiter PUF is approximately 50%, which is better than that from 3-XOR Arbiter PUF. We show that we can improve the uniqueness by using a new mode of operation for Arbiter PUF.

Slow hot carrier cooling in cesium lead iodide perovskites

Abstract: Lead halide perovskites are attracting a great deal of interest for optoelectronic applications such as solar cells, LEDs, and lasers because of their unique properties. In solar cells, heat dissipation by hot carriers results in a major energy loss channel responsible for the Shockley–Queisser efficiency limit. Hot carrier solar cells offer the possibility to overcome this limit and achieve energy conversion efficiency as high as 66% by extracting hot carriers. Therefore, fundamental studies on hot carrier relaxation dynamics in lead halide perovskites are important. Here, we elucidated the hot carrier cooling dynamics in all-inorganic cesium lead iodide (CsPbI3) perovskite using transient absorption spectroscopy. We observe that the hot carrier cooling rate in CsPbI3 decreases as the fluence of the pump light increases and the cooling is as slow as a few 10 ps when the photoexcited carrier density is 7 × 1018 cm−3, which is attributed to phonon bottleneck for high photoexcited carrier densities. Our findings suggest that CsPbI3 has a potential for hot carrier solar cell applications.

Efficient passively Q-switched Yb:LuAG microchip laser.

Abstract: An efficient passively Q-switched Yb:LuAG microchip laser with Cr4+:YAG as saturable absorber was demonstrated for the first time to our knowledge Slope efficiencies of 40% and 28% were measured for the initial transmission of Cr4+:YAG, T0=95% and 90%, respectively Laser pulses with a pulse energy of 19 μJ and a pulse width of 610 ps at the repetition rate of 128 kHz were achieved for T0=90%; the corresponding peak power of over 31 kW was obtained The lasers oscillated at two or three longitudinal modes owing to the broad emission spectra of Yb:LuAG and mode selection by Cr4+:YAG thin plate acting as an intracavity etalon

Communication using pheromone field for multiple robots

Abstract: In this paper, we consider a issue that the reliable and the inexpensive communication method in swarm robotics. The ants forage for preys by using pheromone trails. They lay down the pheromone trails between preys and a nest. By detecting the trail pheromone, they can find the preys. Though they do not have excellent intelligence, they can communicate with each other and cooperate by adding information to the environment, like a pheromone. This communication method has a merit that an agent does not need to memorize the place of the preys. We consider to answer the issue that ldquoHow do the swarm robots communicate using pheromone trail?rdquo. We construct a swarm behavior simulator and develop swarm robots that communicate using the pheromone trail. We demonstrate the effectiveness of the communication using the pheromone trail by computer simulations and experiments using swarm robots. To realize this purpose, we design a swarm behavior algorithm, based on 4 perceptual signs (stimuli) and 3 effector signs (actions). In the simulations, an experimental field is discretized by computational grids, and evaporation and diffusion are phenomena of the pheromone modeled by discretized equations. The proposed algorithm is demonstrated by the simulation. Simulation result shows that proposed algorithms act effectively. Based on the simulation results, we set three robots, one nest and one prey in the flat experimental field. We observe three robotspsila behavior and the state of the environment for 20 minutes. The robots laid down the pheromone trail between the nest and the prey, and reinforced the pheromone trail many times. This fact means that swarm robots can realize the function of the chemical, indirect, plastic and local communication like ants by using the pheromone trail.

Kinematic structure of massive star-forming regions - I. Accretion along filaments

Abstract: Context. The mid- and far-infrared view on high-mass star formation, in particular with the results from the Herschel space observatory, has shed light on many aspects of massive star formation. However, these continuum studies lack kinematic information. Aims: We study the kinematics of the molecular gas in high-mass star-forming regions. Methods: We complemented the PACS and SPIRE far-infrared data of 16 high-mass star-forming regions from the Herschel key project EPoS with N2H+ molecular line data from the MOPRA and Nobeyama 45 m telescope. Using the full N2H+ hyperfine structure, we produced column density, velocity, and linewidth maps. These were correlated with PACS 70 μm images and PACS point sources. In addition, we searched for velocity gradients. Results: For several regions, the data suggest that the linewidth on the scale of clumps is dominated by outflows or unresolved velocity gradients. IRDC 18454 and G11.11 show two velocity components along several lines of sight. We find that all regions with a diameter larger than 1 pc show either velocity gradients or fragment into independent structures with distinct velocities. The velocity profiles of three regions with a smooth gradient are consistent with gas flows along the filament, suggesting accretion flows onto the densest regions. Conclusions: We show that the kinematics of several regions have a significant and complex velocity structure. For three filaments, we suggest that gas flows toward the more massive clumps are present.