arXiv subjects

Katsuhiro Nishinari

Publications and source records attributed to Katsuhiro Nishinari.

At least 37 records · Page 2Linked to original sources

arXiv2023

Asymmetry-induced delocalization transition in the integrable non-Hermitian spin chain

The emergence of quasiparticles is a universal property in integrable systems. String-type quasiparticles, which are characterized by the string solutions of Bethe equations, play fundamental roles in the analysis of their physics. Through an investigation of the Bethe equations in the asymmetric simple exclusion process, we reveal the existence of string solutions in the presence of non-Hermiticity resulting from asymmetrical hopping. Because of the non-Hermiticity, the string solutions exhibit exotic properties such as the complexification of the center of string solutions and the delocalization of Bethe quantum numbers. In addition, we find the picture of string-type quasiparticles collapses in the strong asymmetry regime. The collapse of string solutions characterizes the transition of eigenstates from bound states to scattering states.

cond-mat.stat-mech↗

arXiv2022

Optimization of transition behaviors in a two-lane system

Transitions between two lanes often have a significant impact on various forms of road traffic. To address this problem, we have developed a two-lane asymmetric simple exclusion process model and two hypothetical traffic control strategies, to simulate a futuristic scenario where the timing and location of transitions between two lanes are highly controlled. Various scenarios were proposed to study the effectiveness of these control strategies. An optimized control strategy, whose parameters were determined through an optimization algorithm, is confirmed to effectively maximize the average traffic flow. Consequently, we may identify suitable road sections and the corresponding timings of transitions to resolve congestion in this model.

physics.soc-ph↗

arXiv2022

A case study of the profit-maximizing multi-vehicle pickup and delivery selection problem for the road networks with the integratable nodes

This paper is a study of an application-based model in profit-maximizing multi-vehicle pickup and delivery selection problem (PPDSP). The graph-theoretic model proposed by existing studies of PPDSP is based on transport requests to define the corresponding nodes (i.e., each request corresponds to a pickup node and a delivery node). In practice, however, there are probably multiple requests coming from or going to an identical location. Considering the road networks with the integratable nodes as above, we define a new model based on the integrated nodes for the corresponding PPDSP and propose a novel mixed-integer formulation. In comparative experiments with the existing formulation, as the number of integratable nodes increases, our method has a clear advantage in terms of the number of variables as well as the number of constraints required in the generated instances, and the accuracy of the optimized solution obtained within a given time.

cs.DM↗

arXiv2022

Effect of congestion avoidance due to congestion information provision on optimizing agent dynamics on an endogenous star network topology

The importance of fundamental research on network topologies is widely acknowledged. This study aims to elucidate the effect of congestion avoidance of agents given congestion information on optimizing traffic in a network topology. We investigated stochastic traffic networks in a star topology with a central node connected to isolated secondary nodes with different preferences. Each agent at the central node selects a secondary node by referring to the declining preferences based on the congestion rate of the secondary nodes. We examined two scenarios: 1) Each agent can repeatedly visit the central and secondary nodes. 2) Each agent can access each secondary node only once. For 1), we investigated the uniformity of the agent distribution in a stationary state, and for 2), we measured the travel time for all agents visiting all nodes. When agents repeatedly visit central and other nodes, the uniformity of agent distribution has been found to show three types of nonlinear dependence on the increase in nodes. We found that multivariate statistics describe these characteristic dependences well, suggesting that the balance between the equalization of network usage by avoiding congestion and the covariance caused by mutual referral to congestion information determines the uniformity. We discovered that congestion-avoidance linearizes the travel time, which increases exponentially with the number of nodes, notwithstanding the degree of reference to the congestion information. Consequently, we successfully described the optimization effect of congestion-avoidance on the collective dynamics of agents in star topologies. Our findings are useful in many areas of network science.

physics.soc-ph↗

arXiv2022

Analysis and modelling of macroscopic and microscopic dynamics of a pedestrian cross-flow

In this work we investigate the behaviour of a human crowd in a cross-flow. We first analyse the results of a set of controlled experiments in which subjects were divided into two groups, in such a way to explore different density settings, and asked to walk through the crossing area. We study the results of the experiment by analysing, along with traditional indicators such as density and velocity, also walking and body orientation, studying how these microscopic observables are influenced by density. Furthermore, we report a preliminary but quantitative analysis on the emergence of self-organising stripes in the crossing area. We also try to reproduce the empirical results using a hierarchy of models, which differ in the details of the body shape (using a disk-shaped body vs a more realistic elliptical shape) and in how collision avoiding is performed (using only information regarding "centre of mass" distance and velocity, or actually introducing body shape information). We verified that the most detailed model (i.e., using body shape information and an elliptical body) outperforms in a significant way the simplest one (using only centre of mass distance and velocity, and disk-shaped bodies). Furthermore, we observed that if elliptical bodies are introduced without using such information in collision avoidance, the performance of the model is relatively poor. Nevertheless, the difference between the different models is relevant only in describing the "tails" of the observable distributions, suggesting that the more complex models could be of practical use only for describing high density settings. We also verified that "stripe formation" emerges in all models.

physics.soc-ph↗

arXiv2022

Towards understanding network topology and robustness of logistics systems

Advanced integration of logistics systems has been promoted for the sake of competitiveness and sustainability. Such efforts will enable more globally optimal and flexible operations by efficiently utilizing transportation capacity. At the same time, interconnection of transport operations increases complexity at a network level, which reduces the predictability of the response of the system to disruptions. However, our understanding of the behavior of such systems is still limited. In particular, the topology of the network, which changes as the systems are integrated, is an important factor that affects the performance of the entire system. Knowledge of such mechanisms would be useful in the design and evaluation of integrated logistics. Here, we developed a simple mathematical model that extracts the essence of the problem and performed extensive numerical experiments by Monte Carlo simulations for three scenarios that mimic changes in demand: (i) locally and temporally increased traffic demand, (ii) globally and temporally increased traffic demand, and (iii) permanent change in demand pattern, under various conditions on the type of route-finding algorithm, network structure, and transportation capacity. Adaptive route-finding algorithms were more effective in square lattice and random networks, which contained many bypass routes, than in hub-and-spoke networks. Furthermore, the square lattice and random networks were robust to the change in the demand pattern and temporal blockage of delivery paths (e.g., due to high demand). We suggest that such preferable properties are only present in networks with redundancy and that the bypass structure is an important criterion for designing network logistics.

physics.soc-ph↗

arXiv2022

Multi-Quantum Dark Solitons in One-Dimensional Bose Gas

Quantum and classical integrable systems share common mathematical structures, and the phenomena appearing in them are interrelated. Solitons, which universally appear in classical integrable systems, also appear in quantum integrable systems. Here, we consider quantum-classical correspondence in a one-dimensional Bose gas with repulsive delta-function interaction and present quantum states corresponding to multi-dark solitons. Using an exact method, we compute the time evolution of the density profile in the multi-quantum dark soliton states. Localized solitary waves that behave like classical dark solitons are observed in the density profile. We observe collisions of quantum dark solitons and show that they exhibit the properties of classical solitons: stability against scatterings and position shifts due to interactions.

cond-mat.quant-gas↗

arXiv2021

Arranging the order of passengers on the boarding bridge to reduce the boarding time for single-aisle aircraft

Reducing the aircraft boarding time is a common problem not only for airlines, but also for passengers and airports. Group boarding is a popular boarding strategy that separates the passengers into several groups and those groups, which are then called in a certain order. Group boarding can reduce the boarding time compared with that in random order boarding; however, it is insufficient in several real scenarios because the passengers are not separated strictly into groups. In this paper, we propose a boarding strategy that arranges the order of the boarding passengers at the boarding gate. Although this approach appears more time-consuming, we show that such a rearrangement can be applied efficiently to the waiting queue of a single-aisle aircraft. We quantitatively demonstrate the boarding times for various patterns of this approach and discuss the mechanism underlying the reduction of boarding time. This strategy is a promising approach to reduce boarding times and can replace the conventional boarding strategy.

physics.soc-ph↗

arXiv2021

Model retraining and information sharing in a supply chain with long-term fluctuating demands

Demand forecasting based on empirical data is a viable approach for optimizing a supply chain. However, in this approach, a model constructed from past data occasionally becomes outdated due to long-term changes in the environment, in which case the model should be updated (i.e., retrained) using the latest data. In this study, we examine the effects of updating models in a supply chain using a minimal setting. We demonstrate that when each party in the supply chain has its own forecasting model, uncoordinated model retraining causes the bullwhip effect even if a very simple replenishment policy is applied. Our results also indicate that sharing the forecasting model among the parties involved significantly reduces the bullwhip effect.

physics.soc-ph↗

arXiv2021

Two-lane totally asymmetric simple exclusion process with extended Langmuir kinetics

Multi-lane totally asymmetric simple exclusion processes with interactions between the lanes have recently been investigated actively. This paper proposes a two-lane model with extended Langmuir kinetics on a periodic lattice. Both bidirectional and unidirectional flows are investigated. In our model, the hopping, attachment, and detachment rates vary depending on the state of the corresponding site in the other lane. We obtain a theoretical expression for the global density of the system in the steady state from three kinds of mean-field analyses (1-, 2-, and 4-cluster cases). We verify that the 4-cluster mean-field analysis approximates well the results of computer simulations for the two directional flows and reproduces the differences between them. We expect these findings to contribute to a deeper understanding of the dynamic features of actual traffic systems.

nlin.CG↗

arXiv2020

Diffusion enhancement in a levitated droplet via oscillatory deformation

Recent experimental results indicate that mixing is enhanced by a reciprocal flow induced inside a levitated droplet with an oscillatory deformation [T. Watanabe et al. Sci. Rep. 8, 10221 (2018)]. Generally, reciprocal flow cannot convect the solutes in time average, and agitation cannot take place. In the present paper, we focus on the diffusion process coupled with the reciprocal flow. We theoretically derive that the diffusion process can be enhanced by the reciprocal flow, and the results are confirmed via numerical calculation of the over-damped Langevin equation with a reciprocal flow.

nlin.PS↗

arXiv2020

Burgers equation with finite particle correction of the asymmetric simple exclusion process derived from the derivative nonlinear Schrödinger equation

We investigate the dynamics of the asymmetric simple exclusion process (ASEP) on a ring. The ASEP is equivalent to the derivative nonlinear Schrödinger equation (DNLS), which is integrable quantum field theory, in the continuous limit. We derive the Burgers equation with finite particle correction from the DNLS and numerically confirm that the obtained Burgers equation describes the dynamics of the ASEP at small numbers of particles better than the conventional Burgers equation.

cond-mat.stat-mech↗

arXiv2020

Some considerations on crowd Congestion Level

The concept of (crowd) Congestion Level ($CL$) was introduced in Feliciani et al (Transportation Research, 2018) and presented at the PED 2018 conference by C. Feliciani. Following the PED presentation, along with appreciation for the novel contribution, a few interesting questions were raised, concerning the integral/differential nature of the definition of $CL$, and the possibility of defining a related pure number. In these short notes we are going, although with no attempt at rigour or formality, to present some considerations suggesting that the two problems are related, and providing a possible solution. Furthermore, using both theoretical arguments and analysis of simulated data in complex scenarios, we will try to shed further light on the meaning and applications of this concept. Finally, we analyse some results of an experiment performed with human participants in a ``crossing-flows'' scenario.

physics.soc-ph↗

arXiv2020

Throughput reduction on an air-ground transport system by the simultaneous effect of multiple traveling routes equipped with parking sites

This paper examines the traffic flows on a two-dimensional stochastic lattice model that comprises a junction of two traveling routes: the domestic route and the international route each of which has parking sites. In our model, the system distributes the arrived particles to either of the two routes and selects one of the parking sites in the route for each particle, which stops at the parking site once during its travel. Because each particle has antennas in the back and front directions to detect other approaching particles, the effect of the volume exclusion of each particle extends in the moving direction. The system displays interesting behavior; remarkably, the dependence of the throughput on the distribution ratio of particles to the domestic route reduces after reaching the maximum parking capacity of the domestic route. Our simulations and analysis with the queueing model describe this phenomenon and suggest the following fact: As the distribution ratio of particles to the international route decreases, the throughput of the international route reduces, and simultaneously, that of the domestic route saturates. The simultaneous effect of the decrease and saturation causes a reduction in the throughput of the entire system.

nlin.CG↗

arXiv2019

Dependence of the transportation time on the sequence in which particles with different hopping probabilities enter a lattice

Smooth transportation has drawn the attention of many researchers and practitioners in several fields. In the present paper, we propose a modified model of a totally asymmetric simple exclusion process (TASEP), which includes multiple species of particles and takes into account the sequence in which the particles enter a lattice. We investigate the dependence of the transportation time on this `entering sequence' and show that for a given collection of particles group sequence in some cases minimizes the transportation time better than a random sequence. We also introduce the `sorting cost' necessary to transform a random sequence into a group sequence and show that when this is included a random sequence can become advantageous in some conditions. We obtain these results not only from numerical simulations but also by theoretical analyses that generalize the simulation results for some special cases.

nlin.CG↗

arXiv2019

Auto-generation of a centerline graph from a geometrically complex roadmap of real-world traffic systems using a hierarchical quadtree for cellular automata simulations

This paper proposes a method of auto-generation of a centerline graph from a geometrically complex roadmap of real-world traffic systems by using a hierarchical quadtree for cellular automata simulations. Our method is summarized as follows. First, we store the binary values of the monochrome image of target roadmap (one and zero represent the road and the other areas, respectively) in the two-dimensional square map. Second, we recursively divide the square map into sub-leafs by a quadtree until the summed-up value of pixels included inside the leaf becomes equal to or less than one. Third, we gradually remove the distal leaves that are adjacent to the leaves whose depths are shallower than the distal leaf. After that, we trace the remaining distal leaves of the tree using Morton's space-filling curve, while selecting the leaves that keep a certain distance among the previously selected leaves as the nodes of the graph. Finally, each selected node searches the neighboring nodes and stores them as the edges of the graph. We demonstrate our method by generating a centerline graph from a complex roadmap of a real-world airport and by carrying out a typical network analysis using Dijkstra's method.

nlin.CG↗

arXiv2019

Decision-making with reference information

We often try to predict others' actions by obtaining supporting information that shows a preference index of surrounding people. In order to reproduce these situations, we propose a game named "One-sided Preference Game with Reference Information (OSPG-R)." We conducted experiments in which players who have similar preferences compete for objects in OSPG-R. In the experiment, we used three different types of objects: boxes, faces, and cars. Our results show that the most frequently selected object was not the most popular one. In order to gain deeper insights into the experiment's results, we constructed a decision-making model based on two assumptions: (1) players are rational and (2) are convinced that the other players' preference orders are equivalent to the preference index for the group. Compared to the choice behavior of the model, the experiment's results show that there was a tendency to take risks when the objects were faces, or the priority of that particular player was low.

cs.GT↗

arXiv2019

Experimental study on the evading behavior of individual pedestrians when confronting with an obstacle in a corridor

In this paper, controlled experiments have been conducted to make deep analysis on the obstacle evading behavior of individual pedestrians affected by one obstacle. Results of Fourier Transform show that with the increase of obstacle width, the frequency and amplitude of body sway would barely be affected while the lateral deviation of walking direction would largely increase. On the one hand, the relation among the extracted gait features including body sway, stride length, frequency and speed has been illustrated. On the other hand, the walking direction can be featured by three critical evading points where apparent change of walking direction could be observed. Gaussian function has been used to fit the walking direction, thus allowing to estimate the three critical points and examine their variation with the increase of obstacle size. Furthermore, the direct-indirect evading and left-right turning preference as well as the possible psychological motivations behind have been analyzed. It is indicated that direct-evading pedestrians have a higher walking efficiency and right-turning pedestrians have a stronger tendency to behave `direct'. Results of this paper are expected to provide practical evidence for the modeling of pedestrian dynamics affected by obstacles.

physics.soc-ph↗