Hokkaido University

About: Hokkaido University is a education organization based out in Sapporo, Hokkaidô, Japan. It is known for research contribution in the topics: Catalysis & Population. The organization has 53925 authors who have published 115403 publications receiving 2651647 citations. The organization is also known as: Hokudai & Hokkaidō daigaku.

Intrinsic reaction coordinate: Calculation, bifurcation, and automated search

Abstract: The intrinsic reaction coordinate (IRC) approach has been used extensively in quantum chemical analysis and prediction of the mechanism of chemical reactions. The IRC gives a unique connection from a given transition structure to local minima of the reactant and product sides. This allows for easy understanding of complicated multistep mechanisms as a set of simple elementary reaction steps. In this article, three topics concerning the IRC approach are discussed. In the first topic, the first ab initio study of the IRC and a recent development of an IRC calculation algorithm for enzyme reactions are introduced. In the second topic, cases are presented in which dynamical trajectories bifurcate and corresponding IRC connections can be inaccurate. In the third topic, a recent development of an automated reaction path search method and its application to systematic construction of IRC networks are described. Finally, combining these three topics, future perspectives are discussed. © 2014 Wiley Periodicals, Inc.

Observed Associations Among Storm Tracks, Jet Streams and Midlatitude Oceanic Fronts

Abstract: An association is discussed among a midlatitude storm track, a westerly polar-front jet stream and an underlying oceanic frontal zone. Their close association is observed when a subtropical jet stream is weak, as in the Southern Hemisphere summer or in the North Atlantic. Along a near-surface baroclinic zone that tends to be anchored around a frontal zone, storm track activity is enhanced within a well-defined polar-front jet with modest core velocity. This eddy-driven jet exhibits a deep structure with the strong surface westerlies maintained mainly through a poleward eddy heat flux. The westerly wind stress exerted along the frontal zone acts to maintain it by driving the oceanic current system, suggestive of a feedback loop via midlatitude atmosphere-ocean interaction. It is argued that the context of this feedback must be included in interpreting the tropospheric general circulation and its variability. In fact, decadal-scale sea-surface temperature anomalies observed in the North Pacific subarctic frontal zone controlled the anomalous heat release to the atmosphere. Seemingly, the local storm track responded consistently to the decadal-scale shift of the frontal axis, acting to reinforce basin-scale flow anomalies. Over the North and South Pacific, the association is disturbed in winter by an intensified subtropical jet that traps eddy activity into its sharp core. The trapping impairs baroclinic interaction of upper-level eddies with the surface baroclinicity along a midlatitude oceanic front, leading to the suppression of eddy activity as observed in midwinter over the North Pacific.

Application of Probe Vehicle Data for Real-Time Traffic State Estimation and Short-Term Travel Time Prediction on a Freeway

Abstract: Traffic information from probe vehicles has great potential for improving the estimation accuracy of traffic situations, especially where no traffic detector is installed. A method for dealing with probe data along with conventional detector data to estimate traffic states is proposed. The probe data were integrated into the observation equation of the Kalman filter, in which state equations are represented by a macroscopic traffic-flow model. Estimated states were updated with information from both stationary detectors and probe vehicles. The method was tested under several traffic conditions by using hypothetical data, giving considerably improved estimation results compared to those estimated without probe data. Finally, the application of the proposed method was extended to the estimation and short-term prediction of travel time. Travel times were obtained indirectly through the conversion of speeds estimated or predicted by the proposed method. Experimental results show that the performance of travel-time estimation or prediction is comparable to that of some existing methods.