Showing papers by "Osaka Institute of Technology published in 2019"

KAGRA: 2.5 Generation Interferometric Gravitational Wave Detector

Abstract: The recent detections of gravitational waves (GWs) reported by the LIGO and Virgo collaborations have made a significant impact on physics and astronomy. A global network of GW detectors will play a key role in uncovering the unknown nature of the sources in coordinated observations with astronomical telescopes and detectors. Here we introduce KAGRA, a new GW detector with two 3 km baseline arms arranged in an ‘L’ shape. KAGRA’s design is similar to the second generations of Advanced LIGO and Advanced Virgo, but it will be operating at cryogenic temperatures with sapphire mirrors. This low-temperature feature is advantageous for improving the sensitivity around 100 Hz and is considered to be an important feature for the third-generation GW detector concept (for example, the Einstein Telescope of Europe or the Cosmic Explorer of the United States). Hence, KAGRA is often called a 2.5-generation GW detector based on laser interferometry. KAGRA’s first observation run is scheduled in late 2019, aiming to join the third observation run of the advanced LIGO–Virgo network. When operating along with the existing GW detectors, KAGRA will be helpful in locating GW sources more accurately and determining the source parameters with higher precision, providing information for follow-up observations of GW trigger candidates.

Space gravitational-wave antennas DECIGO and B-DECIGO

Abstract: DECi-hertz Interferometer Gravitational-wave Observatory (DECIGO) is a future Japanese space gravitational-wave antenna. The most important objective of DECIGO, among various sciences to be aimed at, is to detect gravitational waves coming from the inflation of the universe. DECIGO consists of four clusters of spacecraft, and each cluster consists of three spacecraft with three Fabry–Perot Michelson interferometers. As a pathfinder mission of DECIGO, B-DECIGO will be launched, hopefully in the 2020s, to demonstrate technologies necessary for DECIGO as well as to lead to fruitful multimessenger astronomy. B-DECIGO is a small-scale or simpler version of DECIGO with the sensitivity slightly worse than that of DECIGO, yet good enough to provide frequent detection of gravitational waves.

Assembly Challenge: a robot competition of the Industrial Robotics Category, World Robot Summit – summary of the pre-competition in 2018*

Abstract: The World Robot Summit (WRS) is a robotic ‘challenge and exposition’ organized by the Japanese government to accelerate social implementation, research and development of robots working in realisti...

First cryogenic test operation of underground km-scale gravitational-wave observatory KAGRA

Abstract: KAGRA is a second-generation interferometric gravitational-wave detector with 3 km arms constructed at Kamioka, Gifu, Japan. It is now in its final installation phase, which we call bKAGRA (baseline KAGRA), with scientific observations expected to begin in late 2019. One of the advantages of KAGRA is its underground location of at least 200 m below the ground surface, which reduces seismic motion at low frequencies and increases the stability of the detector. Another advantage is that it cools down the sapphire test mass mirrors to cryogenic temperatures to reduce thermal noise. In April–May 2018, we operated a 3 km Michelson interferometer with a cryogenic test mass for 10 d, which was the first time that km-scale interferometer was operated at cryogenic temperatures. In this article, we report the results of this ‘bKAGRA Phase 1’ operation. We have demonstrated the feasibility of 3 km interferometer alignment and control with cryogenic mirrors.

What are the important technologies for bin picking? Technology analysis of robots in competitions based on a set of performance metrics

Abstract: Bin picking is still a challenge in robotics, as patent in recent robot competitions. These competitions are an excellent platform for technology comparisons since some participants may use state-o...

Visual Decoding of Hidden Watermark in Trained Deep Neural Network

Abstract: Deep neural network (DNN) is a kind of intellectual property considering its usefulness and cost to develop. This paper proposes watermarking to a trained DNN models to protect its copyright. The proposed method has a remarkable feature for watermark detection process, which can decode the embedded pattern cumulatively and visually. In the experiment, we can embed a specific visual pattern using 5,000 or 60,000 images on the pretrained image classification DNN model. Then the embedded pattern is decoded using 20 images out of the 5,000 or 60,000 images, while a performance degradation to the original image classification task is small. At the conference site, real time and animated visual decoding demonstration is performed.

Quantitative detection of near-infrared (NIR) light using organic layered composites

Abstract: Quantitative detection of external stimuli, such as light, heat, and force, is an important challenge for sensing materials. Near-infrared (NIR) light is used in a variety of fields, such as biological, physical, medical, and engineering applications. Visualization and quantitative detection of invisible NIR are significant for its safe use. Here we fabricate a paper-based device coated with polypyrrole (PPy) and layered polydiacetylene (PDA). As PPy induces evolution of heat with irradiation of NIR, the effective conjugation length of the layered PDA is changed by the dynamic structure changed through the heat conduction. The visible color change from blue to red proceeds on the paper device. The red-color intensity has a relationship with the irradiation power of NIR. These facts suggest that the irradiation time and power of NIR are quantified by the color. Moreover, the results indicate that layered PDA can be applied to the quantification of external stimuli through conversion from the desired stimulus to the detectable one.

Switchable Multi-Wavelength Thulium-Doped Fiber Laser Employing a Polarization-Maintaining Sampled Fiber Bragg Grating

Abstract: A continuous wave, switchable multi-wavelength, thulium-doped fiber laser (TDFL) with a polarization-maintaining sampled fiber Bragg grating (PM-SFBG) is proposed and demonstrated for the first time. A length of 150 m highly-nonlinear fiber (HNLF) was used to introduce the four-wave mixing effect for the efficient suppression of the wavelength competition existing in the gain medium of thulium-doped fiber. By adjusting the state of polarization (SOP) of light in the laser cavity, two six-wavelength operations at two orthogonal SOPs and a ten-wavelength operation were obtained. When the TDFL ran at the six-wavelength operation mode with a pump power of 4.11 W, there were at least four lasing wavelengths with an optical signal-to-noise ratio (OSNR) higher than 30 dB, and when it ran at the ten-wavelength operation mode with a pump power of 4.60 W, there were nine lasing wavelengths with an OSNR higher than 30 dB. Regardless of the operation mode, the TDFL exhibited high stability.

Liquid Marbles in Nature: Craft of Aphids for Survival.

Abstract: Some aphids that live in the leaf galls of the host plant are known to fabricate liquid marbles consisting of honeydew and wax particles as an inner liquid and a stabilizer, respectively. In this study, the liquid marbles fabricated by the galling aphids, Eriosoma moriokense, were extensively characterized with respect to size and size distribution, shape, nanomorphology, liquid/solid weight ratio, and chemical compositions. The stereo microscopy studies confirmed that the liquid marbles have a near-spherical morphology and that the number-average diameter was 368 ± 152 μm, which is 1 order of magnitude smaller than the capillary length of the honeydew. The field emission scanning electron microscopy studies indicated that micrometer-sized wax particles with fiber- and dumpling-like shapes coated the honeydew droplets, which rendered the liquid marbles hydrophobic and nonwetting. Furthermore, the highly magnified scanning electron microscopy images confirmed that the wax particles were formed with assembl...

Ellipsoidal Artificial Melanin Particles as Building Blocks for Biomimetic Structural Coloration.

Abstract: Inspired by the structural coloration of anisotropic materials in nature, we demonstrate the preparation of structural color materials by the assembly of anisotropic particles. Spherical artificial melanin particles consisting of a polystyrene core and polydopamine shell were stretched asymmetrically to form uniform-sized ellipsoidal particles with different aspect ratios. The aspect ratio and assembly method of the ellipsoidal particles influence the structural coloration, indicating that the particle shape is one of the important parameters for controlling the structural coloration. The discovery of a method to control the structural color using ellipsoidal particles is useful in basic research on structural colors in nature and provides flexibility in material design and extends the application range of structural color materials.

A hybrid small-diameter tube fabricated from decellularized aortic intima-media and electrospun fiber for artificial small-diameter blood vessel.

Abstract: Hybrid small-diameter tubes were fabricated by wrapping decellularized aortic intima-media sheets around a tubular stainless steel mandrel with diameter 4 mm, and then by coating with electrospun segmented polyurethane. The synthetic coat was deposited uniformly to a thickness of about 0.5-3.5 μm depending on the duration of electrospinning. Resistance to luminal pressure, burst strength, and stiffness increased with the thickness of the electrospun coat, suggesting that the synthetic fabric reinforces the reconstructed acellular aortic intima-media. Human umbilical vein endothelial cells seeded on the inner surface acquired flagstone morphology, while normal human dermal fibroblasts seeded on the outer surface proliferated well and partly migrated into deeper layers. Collectively, the data suggest that reinforcing decellularized aortic intima-media with electrospun fibers generates a small-diameter hybrid blood vessel with good biocompatibility and suitable mechanical properties. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1064-1070, 2019.

Virtual Reality Fire Disaster Training System for Improving Disaster Awareness

Abstract: The current state of disaster prevention education in schools involves people who are unaware of the necessity of education (i.e., people with no intrinsic motivation and disaster education away). To facilitate disaster prevention education, we propose a virtual reality (VR) disaster prevention training system focused on fire disasters. This system has three modes, namely, VR evacuation drills, VR firefighting training, and VR comprehensive training. First, VR evacuation drills can be learned by users by gaining experience of evacuation methods in cases of fire. Second, users can undergo VR firefighting training by gaining experience of extinguishing methods. Finally, in general training, the users can experience trial training in case of fires on the basis of the knowledge gained in the evacuation and fire drills. We conducted an experiment by dividing participants into two groups: one group was trained using existing methods employing teaching materials, whereas the other was trained using the proposed method. Subsequently, we conducted VR comprehensive training and an IMMS evaluation to investigate whether this system demonstrates an improvement over existing teaching methods. The results indicated that the proposed system achieved better results in terms of attention (+1.58), relevance (+0.7), confidence (+0.2), and user satisfaction (+2.16). Furthermore, for groups trained with the proposed system, the average evacuation risk of the player during VR comprehensive training was -6.45 p, the fire extinguishing start time was -10 s lower, and the user could act against disasters safely and rapidly.

Stimulus-responsive soft dispersed systems developed based on functional polymer particles: bubbles and liquid marbles

Abstract: There is increasing interest in solid particle-stabilized soft dispersed systems, including bubbles/foams (a gas-in-liquid dispersed system) and liquid marbles (a liquid-in-gas dispersed system) The studies on these dispersed systems have mainly been conducted utilizing inorganic particles and research using polymer particles has recently gained attention Synthetic colloidal polymer particles are attractive stabilizers, as their hydrophilic–hydrophobic character and surface chemistries can be designed and controlled on demand via polymerization with various functional monomers and post polymer reactions The successful synthesis of polymer particles would inspire the construction of well-defined and functionalized particle-stabilized gas–liquid soft dispersed systems In this review article, bubbles/foams and liquid marbles stabilized solely with stimulus-responsive polymer particles will be reviewed The stabilities, structures, and motions of these dispersed systems can be controlled by external stimuli There is increasing interest in solid particle-stabilized soft dispersed systems, including bubbles/foams (a gas-in-liquid dispersed system) and liquid marbles (a liquid-in-gas dispersed system) Synthetic colloidal polymer particles are attractive stabilizers, as their hydrophilic–hydrophobic character and surface chemistries can be designed and controlled on demand via polymerization with various functional monomers and post polymer reactions In this review article, bubbles/foams and liquid marbles stabilized solely with stimulus-responsive polymer particles will be reviewed The stabilities, structures, and motions of these dispersed systems can be controlled by external stimuli

Cooperative enhanced scatter search with opposition-based learning schemes for parameter estimation in high dimensional kinetic models of biological systems

Abstract: Industrial bioprocesses development nowadays is concerned with producing chemicals using yeast, bacteria and therapeutic proteins in mammalian cells. This involves the utilization of microorganism cells as factories and re-engineering them in silico. The tools that could facilitate this process are known as the kinetic models. Kinetic models of cellular metabolism are important in assisting researchers to understand the rational design of biological systems, predicting metabolites production, and improving bio-products development. However, the most challenging task in model development is parameter estimation, which is the process of identifying an unknown value of model parameters which provides the best fit between the model output and a set of experimental data. Due to the increased complexity and high dimensionality of the models, which are extremely nonlinear and contain large numbers of kinetic parameters, parameter estimation is known to be difficult and time-consuming. This study proposes a cooperative enhanced scatter search with opposition-based learning schemes (CeSSOL) for parameter estimation in large-scale biology models. The method was executed in parallel with the proposed cooperative mechanism in order to exchange information (kinetic parameters) between individual threads. Each thread consists of different parameters settings that enhance the systemic properties in obtaining the global minimum. The performance of the proposed method was assessed against two large-scale microorganisms models using mammalian and bacteria cells. The results revealed that the proposed method recorded faster computation time compared to other methods. The study has also demonstrated that the proposed method can be used to provide more accurate and faster estimation of kinetic models, indicating the potential benefits of utilizing this method for expert systems of industrial biotechnology.

Photoelectrochemical properties of copper oxide (CuO) influenced by work functions of conductive electrodes

Abstract: Copper (II) oxide (CuO) is a promising p-type semiconductor for water splitting to produce hydrogen under visible-light irradiation. The CuO photoelectrode was successfully fabricated on several conductive supports by an assist of electrochemical deposition methods. The electronic structures of CuO electrodes were characterized by FE-SEM, XRD, UV–Vis, Raman, electrochemical impedance spectroscopy, as well as photoelectrochemical properties. Cathodic photocurrent was observed on the CuO electrodes in 0.5 M Na2SO4 aqueous solution under AM1.5G solar irradiation. It was also found that the photocurrent densities significantly increased as an increase in work functions of conductive supports: carbon < FTO < gold < nickel < platinum plates. It was clearly demonstrated that Ohmic junction between CuO and conductive supports with large work function plays a significant role in the effective charge separations of holes and electrons.

Wavelength-tunable thulium-doped fiber laser with sampled fiber Bragg gratings

Abstract: A continuous wave (CW) wavelength-tunable Tm3+-doped fiber laser with two sampled fiber Bragg gratings (SFBGs) has been proposed and demonstrated. This proposed laser is stable operating with a significant 14.44 nm wavelength range from 1942.09 nm to 1956.53 nm due to the Vernier effect. The laser OSNRs of different wavelengths ranged from 45 dB to 58 dB at a launched pump power of 3.67 W. The wavelength shift and power fluctuation were less than 0.03 nm and 0.46 dB, respectively. An 8.62% slope efficiency was achieved using a grating for laser extracting. To the authors’ knowledge, this is the first time that a wavelength-tunable Tm3+-doped fiber laser with two SFBGs has been demonstrated.

Pressure dependency on a nanosecond pulsed dielectric barrier discharge plasma actuator

Abstract: The behavior of a nanosecond pulsed dielectric barrier discharge (ns-DBD) plasma actuator with the ambient pressure from 30 to 100 kPa was characterized with Schlieren images. Shock wave propagation speed and strength were recorded, showing clear trends with decreasing ambient pressure. Higher ambient pressures result in stronger shock waves; this has been observed irrespective of the actuator thickness. This might be explained with fewer air molecules to ionize at lower ambient pressures and hence a lower temperature from the exothermal recombination reactions. The thickness of the dielectric barrier also influences the shock strength. In accordance with previous findings, it was confirmed that a thinner dielectric barrier results in a greater shock strength. NS-DBD shock waves were modeled numerically using OpenFOAM through a source term added to the energy equation, which controls the amount of thermal energy added to the near-wall deposition region. The compressible, unsteady sonicFoam solver was used with second order schemes. A mesh sensitivity study gives confidence that the solution is grid independent. The overall shock wave structure and propagation speed match well with experimental data. The heat addition required to reproduce experimental results varied with ambient pressure. Less heating of the near-wall region was needed with lower ambient pressures.