Showing papers by "Toyota published in 2012"

Optically tunable amino-functionalized graphene quantum dots

Abstract: Amino-functionalized graphene quantum dots (af-GQDs) with discrete molecular weights and specific edges were self-limitedly extracted from oxidized graphene sheet. Their optical properties can be precisely controlled only by the selective and quantitative functionalization at the edge sites. The af-GQDS exhibit bright colorful fluorescence under a single-wavelength excitation.

Electrolyte roadblocks to a magnesium rechargeable battery

Abstract: Low cost, non-dendritic magnesium metal is an ideal anode for a post lithium ion battery. Currently, development of magnesium electrolytes governs the rate of progress in this field, because electrolyte properties determine the class of cathodes utilized. A review of the latest progress in the area of magnesium battery electrolyte and a perspective on mitigating present challenges is presented herein. Firstly, density functional theory has been shown to predict the potential window of magnesium electrolytes on inert electrodes. Secondly, we report initial efforts aimed to overcome the corrosive property of these magnesium organohaloaluminates towards less noble metals such as stainless steel. This is a major challenge in developing high voltage magnesium electrolytes essential for batteries which operate above 3V. We lastly touch on cathode candidates including the insertion and conversion classes. One conversion cathode we pay particular attention to is electrophilic sulfur which can be married with magnesium metal anodes by utilizing non-nucleophilic electrolytes obtained by simple crystallization of in situ generated magnesium organohaloaluminates. Effectively, non-nucleophilic electrolytes open the door to research on magnesium/sulfur batteries.

Magnesium Borohydride: From Hydrogen Storage to Magnesium Battery

Abstract: Beyond hydrogen storage: The first example of reversible magnesium deposition/stripping onto/from an inorganic salt was seen for a magnesium borohydride electrolyte. High coulombic efficiency of up to 94 % was achieved in dimethoxyethane solvent. This Mg(BH_4)_2 electrolyte was utilized in a rechargeable magnesium battery.

Highly stable Pt monolayer on PdAu nanoparticle electrocatalysts for the oxygen reduction reaction

Abstract: Platinum is used as a cathode in fuel cells but undergoes dissolution during potential changes, hindering commercial application in electric vehicles. Sasaki et al. report a new class of stable electrocatalysts that consist of platinum monolayers on palladium–gold alloy nanoparticles.

Distributed Receding Horizon Control of Vehicle Platoons: Stability and String Stability

Abstract: This paper considers the problem of distributed control of a platoon of vehicles with nonlinear dynamics. We present distributed receding horizon control algorithms and derive sufficient conditions that guarantee asymptotic stability, leader-follower string stability, and predecessor-follower string stability, following a step speed change in the platoon. Vehicles compute their own control in parallel, and receive communicated position and velocity error trajectories from their immediate predecessor. Leader-follower string stability requires additional communication from the lead car at each update, in the form of a position error trajectory. Predecessor-follower string stability, as we define it, implies leader-follower string stability. Predecessor-follower string stability requires stricter constraints in the local optimal control problems than the leader-follower formulation, but communication from the lead car is required only once at initialization. Provided an initially feasible solution can be found, subsequent feasibility of the algorithms are guaranteed at every update. The theory is generalized for nonlinear decoupled dynamics, and is thus applicable to fleets of planes, robots, or boats, in addition to cars. A simple seven-car simulation examines parametric tradeoffs that affect stability and string stability. Analysis on platoon formation, heterogeneity and size (length) is also considered, resulting in intuitive tradeoffs between lead car and following car control flexibility.

Li-O2 battery with a dimethylformamide electrolyte

Abstract: Stability of the electrolyte toward reduced oxygen species generated at the cathode is a crucial challenge for the rechargeable nonaqueous Li–O2 battery. Here, we investigate dimethylformamide as the basis of an electrolyte. Although reactions at the O2 cathode on the first discharge–charge cycle are dominated by reversible Li2O2 formation/decomposition, there is also electrolyte decomposition, which increases on cycling. The products of decomposition at the cathode on discharge are Li2O2, Li2CO3, HCO2Li, CH3CO2Li, NO, H2O, and CO2. Li2CO3 accumulates in the electrode with cycling. The stability of dimethylformamide toward reduced oxygen species is insufficient for its use in the rechargeable nonaqueous Li–O2 battery.

Rapid traffic information dissemination using named data

Abstract: This paper applies the Named Data Networking (NDN) concept to vehicle-to-vehicle (V2V) communications. Specifically, we develop a simple traffic information dissemination application based on the data naming design from our previous work and evaluate its performance through simulations. Our simulation results show that data names can greatly facilitate the forwarding process for Interest and data packets. With adequate vehicle density, data can propagate over long distances robustly at tens of kilometers per second, and a requester can retrieve the desired traffic information 10km away in a matter of seconds.

Motor-driven compressor

Abstract: A motor-driven compressor includes a compression unit, an electric motor, a housing, a cover, wherein the cover includes a main body and a connector coupler, and the cover and the housing define an accommodating chamber, a motor driving circuit that is accommodated in the accommodating chamber and includes a circuit board, and a metal terminal held in the connector coupler, wherein the metal terminal includes first and second end portions. The cover has a shield including a first shield portion, which blocks electromagnetic noise and forms at least part of the connector coupler, and a second shield portion, which blocks electromagnetic noise and forms at least part of the main body. The first and second shield portions are coupled to each other. The second shield portion includes an insertion hole into which one of the first and second end portions of the metal terminal is insertable.

Data naming in Vehicle-to-Vehicle communications

Abstract: Vehicular networking is becoming reality. Today vehicles use TCP/IP to communicate with centralized servers through cellular networks. However many vehicular applications, such as information sharing for safety and real time traffic purposes, desire direct V2V communications which is difficult to achieve using the existing solutions. This paper explores the named-data approach to address this challenge. We use case studies to identify the design requirements and put forth a strawman proposal for the data name design to understand its advantages and limitations.

Mild Traumatic Brain Injury Predictors Based on Angular Accelerations During Impacts

Abstract: Although Head Injury Criterion (HIC) is an effective criterion for head injuries caused by linear acceleration such as skull fractures, no criteria for head injuries caused by rotational kinematics has been accepted as effective so far. This study proposed two criteria based on angular accelerations for Traumatic Brain Injury (TBI), which we call Rotational Injury Criterion (RIC) and Power Rotational Head Injury Criterion (PRHIC). Concussive and non-concussive head acceleration data obtained from football head impacts were utilized to develop new injury criteria. A well-validated human brain Finite Element (FE) model was employed to find out effective injury criteria for TBI. Correlation analyses were performed between the proposed criteria and FE-based brain injury predictors such as Cumulative Strain Damage Measure (CSDM), which is defined as the percent volume of the brain that exceeds a specified first principal strain threshold, proposed to predict Diffuse Axonal Injury (DAI) which is one of TBI. The RIC was significantly correlated with the CSDMs with the strain thresholds of less than 15% (R > 0.89), which might predict mild TBI. In addition, PRHIC was also strongly correlated with the CSDMs with the strain thresholds equal to or greater than 20% (R > 0.90), which might predict more severe TBI.

Innovation by in-wheel-motor drive unit

Abstract: The in-wheel-motor (IWM) will be the most important key technology in the near future to be used by electric vehicles (including fuel cell vehicles). In the past 100 years of the internal combustion engine, several kinds of vehicle packages have been developed, for example, front-engine front-wheel drive, front-engine rear-wheel drive, mid-engine rear-wheel drive, and rear-engine rear-wheel drive. However, a conclusive solution for the best package has not been found. Combining electric drive and IWM enables both good vehicle dynamics and a roomy interior. In addition, the responsiveness of IWM raises the performance of the dynamic control to an even higher level.

Li1.20Mn0.54Co0.13Ni0.13O2 with Different Particle Sizes as Attractive Positive Electrode Materials for Lithium-Ion Batteries: Insights into Their Structure

Abstract: The effect of the synthesis temperature on the chemical composition of “Li1.20Mn0.54Co0.13Ni0.13O2” was considered using thermogravimetric analyses (TGA) and in situ X-ray diffraction (XRD) during thermal treatment. A continuous and small weight loss is observed above 800 °C because of Li evaporation, and the lamellar phase disappears to the benefit of a spinel-type phase formed above 940 °C. The layered structure is recovered upon cooling under air. “Li1.20Mn0.54Co0.13Ni0.13O2” materials synthesized at 800, 900, and 1000 °C show very similar compositions, structures, and electrochemical properties despite very different crystallization states. Their average structure is α-NaFeO2-type and described in the R3m space group, with less than 0.02 Ni2+ ions in the Li site. This peculiar composition “Li1.20Mn0.54Co0.13Ni0.13O2”, with one-third of large cations (Li+, Ni2+) and two-thirds of small cations (Mn4+, Co3+) promotes the extension of the cation ordering in the slabs as revealed by the √3ahex. × √3ahex. ...

On-Road Multivehicle Tracking Using Deformable Object Model and Particle Filter With Improved Likelihood Estimation

Abstract: This paper proposes a novel method for multivehicle detection and tracking using a vehicle-mounted monocular camera. In the proposed method, the features of vehicles are learned as a deformable object model through the combination of a latent support vector machine (LSVM) and histograms of oriented gradients (HOGs). The detection algorithm combines both global and local features of the vehicle as a deformable object model. Detected vehicles are tracked through a particle filter, which estimates the particles' likelihood by using a detection scores map and template compatibility for both root and parts of the vehicle while considering the deformation cost caused by the movement of vehicle parts. Tracking likelihoods are iteratively used as a priori probability to generate vehicle hypothesis regions and update the detection threshold to reduce false negatives of the algorithm presented before. Extensive experiments in urban scenarios showed that the proposed method can achieve an average vehicle detection rate of 97% and an average vehicle-tracking rate of 86% with a false positive rate of less than 0.26%.

Design and characterization of a 256x64-pixel single-photon imager in CMOS for a MEMS-based laser scanning time-of-flight sensor

Abstract: We introduce an optical time-of-flight image sensor taking advantage of a MEMS-based laser scanning device. Unlike previous approaches, our concept benefits from the high timing resolution and the digital signal flexibility of single-photon pixels in CMOS to allow for a nearly ideal cooperation between the image sensor and the scanning device. This technique enables a high signal-to-background light ratio to be obtained, while simultaneously relaxing the constraint on size of the MEMS mirror. These conditions are critical for devising practical and low-cost depth sensors intended to operate in uncontrolled environments, such as outdoors. A proof-of-concept prototype capable of operating in real-time was implemented. This paper focuses on the design and characterization of a 256 x 64-pixel image sensor, which also comprises an event-driven readout circuit, an array of 64 row-level high-throughput time-to-digital converters, and a 16 Gbit/s global readout circuit. Quantitative evaluation of the sensor under 2 klux of background light revealed a repeatability error of 13.5 cm throughout the distance range of 20 meters.

A system for real-time detection and tracking of vehicles from a single car-mounted camera

Abstract: A novel system for detection and tracking of vehicles from a single car-mounted camera is presented. The core of the system are high-performance vision algorithms: the WaldBoost detector [1] and the TLD tracker [2] that are scheduled so that a real-time performance is achieved. The vehicle monitoring system is evaluated on a new dataset collected on Italian motorways which is provided with approximate ground truth (GT0) obtained from laser scans. For a wide range of distances, the recall and precision of detection for cars are excellent. Statistics for trucks are also reported. The dataset with the ground truth is made public.

Isothermally reversible fluorescence switching of a mechanochromic perylene bisimide dye.

Abstract: Isothermally rewritable fluorescence mechanochromism has been realized for a perylene bisimide dye with bulky and flexible substituents. Fluorescent patterns drawn by mechanical stimuli can be erased by thermal stimuli, treatment with solvent vapors, or spontaneous structural transition from orange-fluorescent to green-fluorescent states. The isothermal fluorescence switching of solid dye films is applicable to displays and sensory materials.

A new one-pot method for the synthesis of Cu nanoparticles for low temperature bonding

Abstract: We developed a new one-pot method for the synthesis of Cu nanoparticles capped with fatty acids and amines from an insoluble salt, such as Cu carbonate and Cu hydroxide, in ethylene glycol. This method could be completed within a short period of time and provides a high collection rate from inexpensive raw materials without impurities. The mean diameter of the Cu nanoparticles was controlled from 93 to 13 nm as the alkyl carbon number increased from C10 to C22. The same fraction of fatty acids and amines used for capping agents was suitable to obtain the minimum size of Cu nanoparticles. The thermal decomposition temperature of the capping layer was lower than 300 °C even in an inert atmosphere. Higher strengths of the Cu plates bonded by the Cu nanoparticles were achieved owing to the more densely packed sintered structures by the smaller Cu nanoparticles. The shear strength of the Cu plates bonded by the Cu nanoparticles was higher than 30 MPa which was the same level as for ordinary solders even though the process temperature of 300 °C was much lower than high-temperature solders. The minimum electrical resistivity of the sintered Cu nanoparticle film was 13 μΩ cm which was obtained after annealing at 300 °C.

Reductions between Expansion Problems

Abstract: The Small-Set Expansion Hypothesis (Raghavendra, Steurer, STOC 2010) is a natural hardness assumption concerning the problem of approximating the edge expansion of small sets in graphs. This hardness assumption is closely connected to the Unique Games Conjecture (Khot, STOC 2002). In particular, the Small-Set Expansion Hypothesis implies the Unique Games Conjecture (Raghavendra, Steurer, STOC 2010). Our main result is that the Small-Set Expansion Hypothesis is in fact equivalent to a variant of the Unique Games Conjecture. More precisely, the hypothesis is equivalent to the Unique Games Conjecture restricted to instance with a fairly mild condition on the expansion of small sets. Alongside, we obtain the first strong hardness of approximation results for the Balanced Separator and Minimum Linear Arrangement problems. Before, no such hardness was known for these problems even assuming the Unique Games Conjecture. These results not only establish the Small-Set Expansion Hypothesis as a natural unifying hypothesis that implies the Unique Games Conjecture, all its consequences and, in addition, hardness results for other problems like Balanced Separator and Minimum Linear Arrangement, but our results also show that the Small-Set Expansion Hypothesis problem lies at the combinatorial heart of the Unique Games Conjecture. The key technical ingredient is a new way of exploiting the structure of the Unique Games instances obtained from the Small-Set Expansion Hypothesis via (Raghavendra, Steurer, 2010). This additional structure allows us to modify standard reductions in a way that essentially destroys their local-gadget nature. Using this modification, we can argue about the expansion in the graphs produced by the reduction without relying on expansion properties of the underlying Unique Games instance (which would be impossible for a local-gadget reduction).

Continuous markov random fields for robust stereo estimation

Abstract: In this paper we present a novel slanted-plane model which reasons jointly about occlusion boundaries as well as depth. We formulate the problem as one of inference in a hybrid MRF composed of both continuous (i.e., slanted 3D planes) and discrete (i.e., occlusion boundaries) random variables. This allows us to define potentials encoding the ownership of the pixels that compose the boundary between segments, as well as potentials encoding which junctions are physically possible. Our approach outperforms the state-of-the-art on Middlebury high resolution imagery [1] as well as in the more challenging KITTI dataset [2], while being more efficient than existing slanted plane MRF methods, taking on average 2 minutes to perform inference on high resolution imagery.

Photoconductivity of PbSe quantum-dot solids: dependence on ligand anchor group and length.

Abstract: The assembly of quantum dots is an essential step toward many of their potential applications. To form conductive solids from colloidal quantum dots, ligand exchange is required. Here we study the influence of ligand replacement on the photoconductivity of PbSe quantum-dot solids, using the time-resolved microwave conductivity technique. Bifunctional replacing ligands with amine, thiol, or carboxylic acid anchor groups of various lengths are used to assemble quantum solids via a layer-by-layer dip-coating method. We find that when the ligand lengths are the same, the charge carrier mobility is higher in quantum-dot solids with amine ligands, while in quantum-dot solids with thiol ligands the charge carrier lifetime is longer. If the anchor group is the same, the charge carrier mobility is ligand length dependent. The results show that the diffusion length of charge carriers can reach several hundred nanometers.

6% Efficiency Cu2ZnSnS4-based thin film solar cells using oxide precursors by open atmosphere type CVD

Abstract: An open atmosphere type chemical vapor deposition (OA-CVD) method is one of the most effective methods for producing functional thin films. Especially, the OA-CVD method is a unique technique which is able to deposit metal oxide thin films by decomposition of vaporized raw materials released through a nozzle onto substrates in the air. Cu2ZnSnS4 (CZTS)-based thin films as absorber layers of thin film solar cells were fabricated by sulfurizing oxide precursor thin films synthesized by the OA-CVD method. Cu(C5H7O2)2, Zn(C5H7O2)2 and Sn(C5H7O2)2 were used as raw materials. The oxide precursor thin films were sulfurized at 520–560 °C in 5 vol% H2S balanced with N2. The formed CZTS-based thin films included oxygen with the composition ratio of O/(S + O) = 0.17–0.27 according to energy dispersive X-ray spectroscopy. The thin film solar cells using the CZTS-based thin films including oxygen [CZT(S,O) films] as the absorber layers were fabricated. The CZT(S,O) thin film solar cell had a stack structure of Al/Al-doped-ZnO/CdS/CZT(S,O)/Mo/soda-lime glass substrate. The efficiency of the CZT(S,O) thin film solar cells was 6.03%, which was the high efficiency in the reported value for CZTS-based thin film solar cells using oxide thin film precursors. It was found that the OA-CVD method is suited to fabricate the absorber layers of thin film solar cells.

Discharge Performance of All-Solid-State Battery Using a Lithium Superionic Conductor Li10GeP2S12

Abstract: A solid electrolyte, Li10GeP2S12, exhibits a high lithium ionic conductivity of 12mS/cm at room temperature. Because of its high ionic conductivity, high charge-discharge performance would be expected for the all-solid-state batteries using the Li10GeP2S12 electrolytes. In this study, all-solid-state batteries using Li10GeP2S12, were constructed and their battery performances were examined. The batteries using the Li10GeP2S12 electrolyte showed higher discharge capacities than those with glass electrolyte, 75Li2S·25P2S5, particularly under the high-rate current discharge. © The Electrochemical Society of Japan, All rights reserved.