Showing papers by "Nagoya Institute of Technology published in 2013"
09 Apr 2013
TL;DR: This paper gives a general overview of hidden Markov model (HMM)-based speech synthesis, which has recently been demonstrated to be very effective in synthesizing speech.
Abstract: This paper gives a general overview of hidden Markov model (HMM)-based speech synthesis, which has recently been demonstrated to be very effective in synthesizing speech. The main advantage of this approach is its flexibility in changing speaker identities, emotions, and speaking styles. This paper also discusses the relation between the HMM-based approach and the more conventional unit-selection approach that has dominated over the last decades. Finally, advanced techniques for future developments are described.
424 citations
TL;DR: It is discovered that the marine flavobacterium Krokinobacter eikastus possesses two rhodopsins, the first, KR1, being a prototypical proton pump, while the second, KR2, pumps sodium ions outward.
Abstract: Light-driven proton-pumping rhodopsins are widely distributed in many microorganisms. They convert sunlight energy into proton gradients that serve as energy source of the cell. Here we report a new functional class of a microbial rhodopsin, a light-driven sodium ion pump. We discover that the marine flavobacterium Krokinobacter eikastus possesses two rhodopsins, the first, KR1, being a prototypical proton pump, while the second, KR2, pumps sodium ions outward. Rhodopsin KR2 can also pump lithium ions, but converts to a proton pump when presented with potassium chloride or salts of larger cations. These data indicate that KR2 is a compatible sodium ion-proton pump, and spectroscopic analysis showed it binds sodium ions in its extracellular domain. These findings suggest that light-driven sodium pumps may be as important in situ as their proton-pumping counterparts.
326 citations
TL;DR: A novel electrophilic-type trifluoromethanesulfonyl hypervalent iodonium ylide reagent was designed and reacted well with various nucleophiles to afford the desired CF3S-substituted products.
Abstract: A novel electrophilic-type trifluoromethylthiolation reagent, a trifluoromethanesulfonyl hypervalent iodonium ylide, was designed and reacted well with various nucleophiles to afford the desired CF3S-substituted products. In situ reduction of the trifluoromethanesulfonyl group to give the trifluoromethylthio group, which is the key step in this process, was realized in the presence of copper(I) chloride.
274 citations
TL;DR: In this paper, the authors present the development of Pt-based catalysts and the uses of Ptbased bimetallic and multi-metallic nanoparticles with mixture, alloy and core-shell structures for nanocatalysis, energy conversion, catalytic nanomaterials and fuel cells (FCs).
249 citations
TL;DR: In this paper, large-scale computer simulations of the hard disk system at high densities in the region of the melting transition are presented, where the authors reproduce the equation of state, previously obtained using the event-chain Monte Carlo algorithm, with a massively parallel implementation of the local Monte Carlo method and with event-driven molecular dynamics.
Abstract: We report large-scale computer simulations of the hard-disk system at high densities in the region of the melting transition. Our simulations reproduce the equation of state, previously obtained using the event-chain Monte Carlo algorithm, with a massively parallel implementation of the local Monte Carlo method and with event-driven molecular dynamics. We analyze the relative performance of these simulation methods to sample configuration space and approach equilibrium. Our results confirm the first-order nature of the melting phase transition in hard disks. Phase coexistence is visualized for individual configurations via the orientational order parameter field. The analysis of positional order confirms the existence of the hexatic phase.
216 citations
TL;DR: In this paper, a toolbox of analytical relations is proposed to describe the effective thermal conductivity as a function of solid phase thermal conductivities, pore thermal properties, and pore volume fraction.
Abstract: Incorporation of porosity into a monolithic material decreases the effective thermal conductivity. Porous ceramics were prepared by different methods to achieve pore volume fractions from 4 to 95%. A toolbox of analytical relations is proposed to describe the effective thermal conductivity as a function of solid phase thermal conductivity, pore thermal conductivity, and pore volume fraction (νp). For νp 0.65, the thermal conductivity of kaolin-based foams and calcium aluminate foams was well described by the Hashin Shtrikman upper bound and Russell’s relation. Finally, numerical simulation on artificially generated microstructures yields accurate predictions of thermal conductivity when fine detail of the spatial distribution of the phases needs to be accounted for, as demonstrated with a bio-aggregate material.
205 citations
TL;DR: In this article, the diffusion coefficient and site occupancy of Li ions within the 3D network structure of the cubic LLZO framework have been investigated using ab initio molecular dynamics calculations, and the complex mechanism for self-diffusion was viewed as a concerted migration governed by two crucial features: (i) the restriction imposed for occupied site-to-site interatomic separation, and (ii) the unstable residence of Li ion at the 24d site, which can serve as the trigger for ion mobility and reconfiguration of surrounding Li neighbors to accommodate the initiated movement.
Abstract: The garnet-type Li7La3Zr2O12 (LLZO) belonging to cubic symmetry (space group Ia3d) is considered as one of the most promising solid electrolyte materials for all-solid state lithium ion batteries. In this study, the diffusion coefficient and site occupancy of Li ions within the 3D network structure of the cubic LLZO framework have been investigated using ab initio molecular dynamics calculations. The bulk conductivity at 300 K is estimated to be about 1.06 × 10–4 S cm–1 with an energy barrier of 0.331 eV, in reasonable agreement with experimental results. The complex mechanism for self-diffusion of Li ions can be viewed as a concerted migration governed by two crucial features: (i) the restriction imposed for occupied site-to-site interatomic separation, and (ii) the unstable residence of Li ion at the 24d site, which can serve as the trigger for ion mobility and reconfiguration of surrounding Li neighbors to accommodate the initiated movement. Evidence for Li ordering is also found at low temperature fo...
197 citations
TL;DR: High-resolution crystal structures of a bacterial POT family transporter, including its complex with a dipeptide analog, alafosfalin, revealed the key mechanistic and functional roles for a conserved glutamate residue (Glu310) in the peptide binding site.
Abstract: Proton-dependent oligopeptide transporters (POTs) are major facilitator superfamily (MFS) proteins that mediate the uptake of peptides and peptide-like molecules, using the inwardly directed H+ gradient across the membrane. The human POT family transporter peptide transporter 1 is present in the brush border membrane of the small intestine and is involved in the uptake of nutrient peptides and drug molecules such as β-lactam antibiotics. Although previous studies have provided insight into the overall structure of the POT family transporters, the question of how transport is coupled to both peptide and H+ binding remains unanswered. Here we report the high-resolution crystal structures of a bacterial POT family transporter, including its complex with a dipeptide analog, alafosfalin. These structures revealed the key mechanistic and functional roles for a conserved glutamate residue (Glu310) in the peptide binding site. Integrated structural, biochemical, and computational analyses suggested a mechanism for H+-coupled peptide symport in which protonated Glu310 first binds the carboxyl group of the peptide substrate. The deprotonation of Glu310 in the inward open state triggers the release of the bound peptide toward the intracellular space and salt bridge formation between Glu310 and Arg43 to induce the state transition to the occluded conformation.
174 citations
TL;DR: An in-depth analysis and the key insights gained from the Second International Automated Negotiating Agents Competition (ANAC 2011) show that the most adaptive negotiation strategies, while robust across different opponents, are not necessarily the ones that win the competition.
172 citations
06 May 2013
TL;DR: The primary application of the proposed mechanism is to provide robotic support during physical therapy at the hospital, but it could also be used at home as an assistive/therapeutic device to support activities of daily living.
Abstract: In this paper, a new hand exoskeleton device using a three-layered sliding spring mechanism is presented. In contrast to state of the art hand exoskeleton mechanisms (typically link, wire or pneumatically driven), the proposed mechanism is driven through large deformations of the compliant mechanism body. The mechanism can be made compact and lightweight by adequately positioning the compliant elements. In addition, the mechanism is designed to distribute 1-DOF actuated linear motion into three rotational motions of the finger joints, which translate into natural finger flexion/extension. The primary application of the proposed mechanism is to provide robotic support during physical therapy at the hospital (e.g. Continuous Passive Motion). However, thanks to its light and wearable structure, the proposed device could also be used at home as an assistive/therapeutic device to support activities of daily living. We introduce the mechanical structure of the three-layered sliding spring mechanism, present a prototype implementation as a hand exoskeleton device, and provide a preliminary evaluation.
129 citations
TL;DR: This article outlines some of the research that has been done to obtain accurate propagation models supporting the standardization of implant communication in BANs and current research to enhance the channel models of IEEE Std 802.15.6.
Abstract: A body area network is a radio communication protocol for short-range, low-power, and highly reliable wireless communication for use on the surface, inside, or in the peripheral proximity of the human body Combined with various biomedical sensors, BANs enable realtime collection and monitoring of physiological signals Therefore, it is regarded as an important technology for the treatment and prevention of chronic diseases, and health monitoring of the elderly The IEEE 802 LAN/MAN Standards Committee approved Task Group TG156 in December 2007 As a result of more than four years of effort, in February 2012, TG156 published the first international standard for BANs, IEEE Std 802156 Throughout the development of this standard, ample collaboration between the standardization group and the research community was required In particular, understanding the radio propagation mechanisms for BANs demanded the most research effort Technical challenges were magnified for the case of implant communication because of the impossibility of conducting in-body measurements with human subjects Therefore, research in this field had to make use of intricate computer simulations This article outlines some of the research that has been done to obtain accurate propagation models supporting the standardization of implant communication in BANs Current research to enhance the channel models of IEEE Std 802156 through the use of ultra wideband signals for implantable devices along with physical measurements in animals is also presented
TL;DR: The results provide strong evidence for the feasibility of using a quantitative time series of phase-contrast cellular morphology for non-invasive cell quality prediction in regenerative medicine.
Abstract: Human bone marrow mesenchymal stem cells (hBMSCs) are widely used cell source for clinical bone regeneration. Achieving the greatest therapeutic effect is dependent on the osteogenic differentiation potential of the stem cells to be implanted. However, there are still no practical methods to characterize such potential non-invasively or previously. Monitoring cellular morphology is a practical and non-invasive approach for evaluating osteogenic potential. Unfortunately, such image-based approaches had been historically qualitative and requiring experienced interpretation. By combining the non-invasive attributes of microscopy with the latest technology allowing higher throughput and quantitative imaging metrics, we studied the applicability of morphometric features to quantitatively predict cellular osteogenic potential. We applied computational machine learning, combining cell morphology features with their corresponding biochemical osteogenic assay results, to develop prediction model of osteogenic differentiation. Using a dataset of 9,990 images automatically acquired by BioStation CT during osteogenic differentiation culture of hBMSCs, 666 morphometric features were extracted as parameters. Two commonly used osteogenic markers, alkaline phosphatase (ALP) activity and calcium deposition were measured experimentally, and used as the true biological differentiation status to validate the prediction accuracy. Using time-course morphological features throughout differentiation culture, the prediction results highly correlated with the experimentally defined differentiation marker values (R>0.89 for both marker predictions). The clinical applicability of our morphology-based prediction was further examined with two scenarios: one using only historical cell images and the other using both historical images together with the patient's own cell images to predict a new patient's cellular potential. The prediction accuracy was found to be greatly enhanced by incorporation of patients' own cell features in the modeling, indicating the practical strategy for clinical usage. Consequently, our results provide strong evidence for the feasibility of using a quantitative time series of phase-contrast cellular morphology for non-invasive cell quality prediction in regenerative medicine.
Proceedings Article•
16 Jun 2013TL;DR: It is claimed that some of the nonsupport vectors (non-SVs) that have no influence on the SVM classifier can be screened out prior to the training phase in pathwise SVM computation scenario, in which one is asked to train a sequence of S VM classifiers for different regularization parameters.
Abstract: In this paper, we claim that some of the nonsupport vectors (non-SVs) that have no influence on the SVM classifier can be screened out prior to the training phase in pathwise SVM computation scenario, in which one is asked to train a sequence (or path) of SVM classifiers for different regularization parameters. Based on a recently proposed framework so-called safe screening rule, we derive a rule for screening out non-SVs in advance, and discuss how we can exploit the advantage of the rule in pathwise SVM computation scenario. Experiments indicate that our approach often substantially reduce the total pathwise computation cost.
TL;DR: Findings suggest that tDCS has a direct and/or indirect effect on the dopaminergic system in the rat basal ganglia.
Abstract: Background: Transcranial direct-current stimulation is a non-invasive procedure that achieves polarity-dependent modulation of neuronal membrane potentials. It has recently been used as a functional intervention technique for the treatment of psychiatric and neurological diseases; however, its neuronal mechanisms have not been fully investigated in vivo. Objective/Hypothesis: To investigate whether the application of cathodal or anodal transcranial direct-current stimulation affects extracellular dopamine and serotonin levels in the rat striatum. Methods: Stimulation and in vivo microdialysis were carried out under urethane anesthesia, and microdialysis probes were slowly inserted into the striatum. After the collection of baseline fractions in the rat striatum, cathodal or anodal transcranial direct-current stimulation was applied continuously for 10 min with a current intensity of 800 µA from an electrode placed on the skin of the scalp. Dialysis samples were collected every 10 min until at least 400 min after the onset of stimulation. Results: Following the application of cathodal, but not anodal, transcranial direct-current stimulation for 10 min, extracellular dopamine levels increased for more than 400 min in the striatum. There were no significant changes in extracellular serotonin levels. Conclusion: These findings suggest that transcranial direct-current stimulation has a direct and/or indirect effect on the dopaminergic system in the rat basal ganglia.
TL;DR: The methodology is shown to generally predict the pKa values for all the cases investigated to within 1 pH unit so long as the differential solvation error is larger than the systematic error in the gas-phase acidity calculations.
TL;DR: In this article, a solar thermoelectric cogenerator (STECG) was designed to supply electric power and heat simultaneously, by adding thermodelectric modules to the heat pipe in evacuated tubular solar collectors.
TL;DR: The computational results are used for analysing previous experimental data to investigate the sensitivity of the eye to electrical stimulation and show that phosphenes induced by tACS are retinal in origin.
Abstract: Objective. Transcranial alternating current stimulation (tACS), which is a novel technique for the manipulation of cortical oscillations, can generate subjective visual sensations (phosphenes). In this work, we computationally investigate the current that reaches the eyes from tACS electrodes in order to show that phosphenes induced by tACS are retinal in origin. Approach. The finite-element method is used for modelling the path of the current in an anatomically realistic model of the head for various electrode montages. The computational results are used for analysing previous experimental data to investigate the sensitivity of the eye to electrical stimulation. Main results. Depending on the locations of both the stimulating and reference electrodes, a small portion of the stimulation current chooses a path that goes through the eyes. Due to the sensitivity of the retina to electrical stimulation, even distant electrodes can produce a sufficiently strong current at the eyes for inducing retinal phosphenes. Significance. The interference from retinal phosphenes needs to be considered in the design of tACS experiments. The occurrence of phosphenes can be reduced by optimizing the locations of the electrodes, or potentially increasing the number of reference electrodes to two or more. Computational modelling is an effective tool for guiding the electrode positioning.
TL;DR: Results indicate that epigenetic regulation by PRC2 is a key mediator of tumor cell plasticity, which is required for the adaptation of glioblastoma cells to their microenvironment, andPRC2-targeted therapy may reduce tumor cell Plasticity and tumor heterogeneity, offering a new paradigm for glioma treatment.
Abstract: Tumor cell plasticity contributes to functional and morphologic heterogeneity. To uncover the underlying mechanisms of this plasticity, we examined glioma stem-like cells (GSC) where we found that the biologic interconversion between GSCs and differentiated non-GSCs is functionally plastic and accompanied by gain or loss of polycomb repressive complex 2 (PRC2), a complex that modifies chromatin structure. PRC2 mediates lysine 27 trimethylation on histone H3 and in GSC it affected pluripotency or development-associated genes (e.g., Nanog, Wnt1, and BMP5) together with alterations in the subcellular localization of EZH2, a catalytic component of PRC2. Intriguingly, exogenous expression of EZH2-dNLS, which lacks nuclear localization sequence, impaired the repression of Nanog expression under differentiation conditions. RNA interference (RNAi)-mediated attenuation or pharmacologic inhibition of EZH2 had little to no effect on apoptosis or bromodeoxyuridine incorporation in GSCs, but it disrupted morphologic interconversion and impaired GSC integration into the brain tissue, thereby improving survival of GSC-bearing mice. Pathologic analysis of human glioma specimens revealed that the number of tumor cells with nuclear EZH2 is larger around tumor vessels and the invasive front, suggesting that nuclear EZH2 may help reprogram tumor cells in close proximity to this microenvironment. Our results indicate that epigenetic regulation by PRC2 is a key mediator of tumor cell plasticity, which is required for the adaptation of glioblastoma cells to their microenvironment. Thus, PRC2-targeted therapy may reduce tumor cell plasticity and tumor heterogeneity, offering a new paradigm for glioma treatment.
TL;DR: Using chiral 1,3-bis(imidazolin-2-yl)benzene (Phebim)-Pd(II) complexes afforded products with good enantioselectivity and can be converted to homoallylic amines and a spirocyclic amine without the loss of enantiopurity.
Abstract: Get selective! Enantioselective allylation of ketimines derived from isatins by using chiral 1,3-bis(imidazolin-2-yl)benzene (Phebim)-Pd(II) complexes afforded products with good enantioselectivity (see scheme). The reaction was applied to a wide variety of ketimines. The obtained product can be converted to homoallylic amines and a spirocyclic amine without the loss of enantiopurity.
TL;DR: For the first time, the asymmetric title epoxidation was disclosed by discovery of an aerobic organocatalytic system as discussed by the authors, which is the first known discovery of a system with asymmetric OP.
Abstract: For the first time the asymmetric title epoxidation is disclosed by discovery of an aerobic organocatalytic system.
TL;DR: In this article, the turbulence structure and turbulence kinetic energy transport in multiscale/fractal-generated turbulence in a wind tunnel are investigated, where a low-blockage, space-filling square-type fractal grid is placed at the inlet of the test section.
Abstract: The turbulence structure and turbulence kinetic energy transport in multiscale/fractal-generated turbulence in a wind tunnel are investigated. A low-blockage, space-filling square-type (i.e., fractal elements with square shapes) fractal grid is placed at the inlet of the test section. On the basis of the thickness of the biggest grid bar, t0, and the inflow velocity U∞, the Reynolds numbers (Re0) are set to 5900 and 11 400; these values are the same as those considered in previous experiments [D. Hurst and J. C. Vassilicos, “Scalings and decay of fractal-generated turbulence,” Phys. Fluids 19, 035103 (2007)10.1063/1.2676448; N. Mazellier and J. C. Vassilicos, “Turbulence without Richardson-Kolmogorov cascade,” Phys. Fluids 22, 075101 (2010)10.1063/1.3453708]. The turbulence characteristics are measured using hot-wire anemometry with I- and X-type probes. Generally, good agreements are observed despite the difference in the size of the test sections used: The longitudinal integral length-scale Lu and the T...
TL;DR: In this article, the highly enantioselective conjugate addition of nitromethane to β-aryl-β-trifluoromethyl aryl enones in the presence of cinchona alkaloids as chiral catalyst is reported.
Abstract: The highly enantioselective conjugate addition of nitromethane to β-aryl-β-trifluoromethyl aryl enones in the presence of cinchona alkaloids as chiral catalyst is reported.
TL;DR: The direct non-metallic trifluoromethylation of carbonyl compounds using fluoroform in the presence of t-Bu-P4 base afforded triffluorometHyl alcohols in high yields.
Abstract: A simple strategy avoiding the decomposition of a naked trifluoromethyl anion to difluorocarbene by a sterically very demanding organo-superbase without the help of a trifluoromethyl anion reservoir such as DMF is reported. The direct non-metallic trifluoromethylation of carbonyl compounds using fluoroform in the presence of t-Bu-P4 base afforded trifluoromethyl alcohols in high yields.
TL;DR: In this article, a crack-free AlGaN/GaN high-electron-mobility transistors (HEMTs) are presented on a 200 mm Si substrate by metal-organic chemical vapor deposition (MOCVD).
Abstract: Crack-free AlGaN/GaN high-electron-mobility transistors (HEMTs) grown on a 200 mm Si substrate by metal–organic chemical vapor deposition (MOCVD) is presented. As grown epitaxial layers show good surface uniformity throughout the wafer. The AlGaN/GaN HEMT with the gate length of 1.5 µm exhibits a high drain current density of 856 mA/mm and a transconductance of 153 mS/mm. The 3.8-µm-thick device demonstrates a high breakdown voltage of 1.1 kV and a low specific on-resistance of 2.3 mΩ cm2 for the gate–drain spacing of 20 µm. The figure of merit of our device is calculated as 5.3×108 V2 Ω-1 cm-2.
TL;DR: A transition-metal-free direct oxidative trifluoromethylation of unsymmetrical biaryls has been achieved by the simple combination of trifLUorometHanesulfinate and phenyliodine bis(trifluoroacetate).
TL;DR: In this article, the effect of Pt dispersion on the catalytic performance of Pt/Al2O3 for CO and C3H6 oxidation was investigated and the intrinsic activity, expressed in terms of turnover frequency (TOF), was found to be almost identical irrespective of the dispersion.
Abstract: Effect of Pt dispersion on the catalytic performance of Pt/Al2O3 for CO and C3H6 oxidation was investigated. The intrinsic activity, expressed in terms of turnover frequency (TOF), for CO oxidation on Pt/Al2O3 catalysts was found to be almost identical irrespective of Pt dispersion. Pt dispersion is the most important factor to determine the CO oxidation activity. On the other hand, the TOF values for C3H6 oxidation on Pt/Al2O3 catalysts were found to increase with increasing the Pt dispersion to 0.20 and then remain almost invariable above DPt = 0.20. In situ FT-IR spectroscopy suggested that acrylate species participates as a reaction intermediate in C3H6 oxidation on Pt/Al2O3 and the formation and reaction behavior of the acrylate species is different depending on the Pt dispersion. The acrylate species formed on Pt/Al2O3 with higher Pt dispersion can readily react with oxygen to form CO2. On the other hand, the reaction of acrylate species is the slow step in the reaction over Pt/Al2O3 with DPt = 0.07. Low TOF values on Pt/Al2O3 with lower Pt dispersion were considered to be due to the inhibition of catalytically active site by accumulation of acrylate species.
TL;DR: A zebrafish model is used to show that the microRNA, miR-21, is crucial for regulation of heart valve formation and is a central component of a flow-controlled mechanotransduction system in a physicogenetic regulatory loop.
Abstract: Heartbeat is required for normal development of the heart, and perturbation of intracardiac flow leads to morphological defects resembling congenital heart diseases. These observations implicate intracardiac haemodynamics in cardiogenesis, but the signalling cascades connecting physical forces, gene expression and morphogenesis are largely unknown. Here we use a zebrafish model to show that the microRNA, miR-21, is crucial for regulation of heart valve formation. Expression of miR-21 is rapidly switched on and off by blood flow. Vasoconstriction and increasing shear stress induce ectopic expression of miR-21 in the head vasculature and heart. Flow-dependent expression of mir-21 governs valvulogenesis by regulating the expression of the same targets as mouse/human miR-21 (sprouty, pdcd4, ptenb) and induces cell proliferation in the valve-forming endocardium at constrictions in the heart tube where shear stress is highest. We conclude that miR-21 is a central component of a flow-controlled mechanotransduction system in a physicogenetic regulatory loop.
TL;DR: A simple condition is derived among the number of cells, the average and variance of NLOS range error distribution which can correctly predict whether the TDOA method outperforms the TOA method or not for the case of all NLOS channels.
Abstract: In cellular communication systems where non-line-of-sight (NLOS) channels are dominant as compared to line-of-sight (LOS) channels, a time difference of arrival (TDOA) localization method can outperform a time of arrival (TOA) localization method, although the TDOA method loses one degree of freedom in the number of usable range estimates when selecting a range estimate as the reference and doubles the variance of range sampling error when subtracting the reference range estimate. In this paper, we first show the computer simulation result on the localization performance of conventional TOA and TDOA methods in mixed LOS/NLOS environments, and then validate it by theoretical analysis. Here, we analyze the root mean square localization error by decomposing it into two factors; for one factor, which is the contribution from range sampling error, we evaluate it by the Cramer-Rao lower-bound, whereas for the other factor, which is the contribution from positively biased NLOS range error, we analyze it by perturbation method. We show that the theoretical result can well explain the localization performance by computer simulation for both the TOA and TDOA methods, and furthermore, we derive a simple condition among the number of cells, the average and variance of NLOS range error distribution which can correctly predict whether the TDOA method outperforms the TOA method or not for the case of all NLOS channels.
01 Jan 2013
TL;DR: In this article, the effect of wall material on chemical quenching behavior was investigated in a methane-air premixed flame formed in a 5-mm wide channel, where the wall material was chosen as the wall materials.
Abstract: In order to elucidate effect of wall material on chemical quenching behavior, a methane-air premixed flame formed in 5-mm-wide channel is investigated. In the present study, platinum, quartz, alumina and chromium are chosen as the wall materials. Platinum, chromium and alumina thin films ∼100 nm in thickness are deposited on quartz substrates using sputtering, vacuum arc plasma gun or atomic layer deposition techniques to establish equivalent thermal boundary condition with different wall chemical reactions. OH-PLIF/micro-OH-PLIF and numerical simulation with detailed reaction mechanisms are employed to examine interaction between the gas-phase and the wall surface reactions. It is clearly shown through the PLIF measurements that OH ∗ mole fraction in the vicinity of the wall is the highest for alumina, while it is decreased in order of quartz, chromium, and platinum. On the platinum surface, the gas-phase combustion is suppressed due to fast consumption of the reactants by the catalytic reaction. On the other hand, on the other surfaces, radical quenching cause the reduction of OH ∗ near the wall. By using a radical quenching model, the initial sticking coefficient associated with radical adsorption is evaluated. It is found that radical quenching does exist on the quartz wall, while the alumina surface works as an inert surface.
TL;DR: By defining the time interval between the relative speed and acceleration, the gap and speed observed from real traffic as driver–vehicle reaction delay, a neural network for instantaneous reaction delay is built and incorporated into a neural-network-based car-following model.
Abstract: Reaction delay of the driver–vehicle unit varies greatly according to driver–vehicle characteristics and traffic conditions, and is an indispensable factor for modeling vehicle movements. In this study, by defining the time interval between the relative speed and acceleration, the gap and speed observed from real traffic as driver–vehicle reaction delay, a neural network for instantaneous reaction delay is built. Incorporating the reaction delay network into a neural-network-based car-following model, movements of nine vehicles which follow each other are simulated. Simulation results show that the models with instantaneous reaction delay apparently outperform the models with fixed reaction delay. In addition, the model with short fixed reaction delay makes the vehicles follow each other more closely than the vehicles in real traffic do, and collisions occur in the model with long fixed reaction delay, which also illustrates the necessity of taking into account instantaneous reaction delay in microscopic traffic simulation. Besides, for future reference, the calibrated weights and biases in the proposed methodology are presented in Appendix.