Hasil untuk "Transportation and communications"

Zilin Huang, Zihao Sheng, Chengyuan Ma et al.

Junwei You, Rui Gan, Weizhe Tang et al.

Szabolcs Duleba, Bálint Farkas, Sarbast Moslem et al.

Rail freight policy should reflect both the current and foreseen situations of the certain national rail freight market. The situation analysis is often based on expert evaluations, in many cases with the participation of the market players themselves, and their synthesized group opinion is the basis of policy-making. However, the creation of opinion synthesis has not considered the market power of the players so far, and a clear research gap exists on how to properly addressing weights to the respondent experts in the group of evaluators to gain a realistic image on the present and future of the rail freight market. The objective of this paper is to identify problems, risks, and development potential in an EU national rail freight market by an expert survey based new methodology (Sectoral Group Analytic Hierarchy Process, SGAHP) that assigns different decision-maker weights in the respondent group based on the different market power of the players to gain a clear and overall image on the examined market. As a case study, a survey has been conducted in Hungary involving the significant representatives of the national rail freight. Results show that the recruitment and training of human resource is a common problem, while supporting single wagon traffic is meaningless for all players. However, big companies prioritise the reduction of locomotive maintenance time, while small ones strive to have own maintenance facilities. As an implication, the proposed model might help state decision-makers in customizing financial or other support to efficiently increase the competitiveness of the sector, as well as the rail companies to better adopt to the situation. The proposed new model has been proven successful not only from the aspect of robustness and sensitivity, but also of recommending practical modifications in rail freight to transport planners both on national and EU levels.

H. A. Elhamy, A. B. Eltawil

<i>Background</i>: Defining the optimal fleet portfolio is a crucial process in airline planning. The published efforts in literature provide ways to anticipate the disruption effects on the passenger demand; however, the proposed solution in this paper provides visibility on the impact of sustainable disruption and the way an airline can resist it. <i>Methods</i>: This paper proposes a two-stage methodology to find the best portfolio for airline operational requirements under the impact of disruption. The first stage considers optimization for normal airline operations under a specific fleet portfolio using an Integer Linear Programming (ILP) model. The second stage of the analysis is a mapping for the scenario-based methodology to find a way out for an airline subjected to some given disruption in operations. <i>Results</i>: The result of the two-stage analysis shall define the best fleet portfolio to withstand sustained disruptions by mapping the results in a disruption funnel and showing the impact of the supply and demand gap on the airline’s sustainable profitability. <i>Conclusions</i>: This paper provides a novel, practical way of evaluating strategic decisions to choose the best fleet portfolio and make airlines rely on the mapping of the disruption funnel to modify their network while increasing supply chain resilience.

Anis Elgabli, Wessam Mesbah

In this paper, we start with a comprehensive evaluation of the effect of adding differential privacy (DP) to federated learning (FL) approaches, focusing on methodologies employing global (stochastic) gradient descent (SGD/GD), and local SGD/GD techniques. These global and local techniques are commonly referred to as FedSGD/FedGD and FedAvg, respectively. Our analysis reveals that, as far as only one local iteration is performed by each client before transmitting to the parameter server (PS) for FedGD, both FedGD and FedAvg achieve the same accuracy/loss for the same privacy guarantees, despite requiring different perturbation noise power. Furthermore, we propose a novel DP mechanism, which is shown to ensure privacy without compromising performance. In particular, we propose the sharing of a random seed (or a specified sequence of random seeds) among collaborative clients, where each client uses this seed to introduces perturbations to its updates prior to transmission to the PS. Importantly, due to the random seed sharing, clients possess the capability to negate the noise effects and recover their original global model. This mechanism preserves privacy both at a &#x201C;curious&#x201D; PS or at external eavesdroppers without compromising the performance of the final model at each client, thus mitigating the risk of inversion attacks aimed at retrieving (partially or fully) the clients&#x2019; data. Furthermore, the importance and effect of clipping in the practical implementation of DP mechanisms, in order to upper bound the perturbation noise, is discussed. Moreover, owing to the ability to cancel noise at individual clients, our proposed approach enables the introduction of arbitrarily high perturbation levels, and hence, clipping can be totally avoided, resulting in the same performance of noise-free standard FL approaches.

ZHENG Junqiu, MA Hui, QIAO Yuelai et al.

To accurately assess the impact of structural cracks on the strength of pavement structures and establish corresponding evaluation indicators based on deflection response, field tests were conducted on multiple sections of expressways in Jiangsu Province. A falling weight deflectometer was used to test a total of 15 measurement points within a 3-meter range on both sides of each crack. The center deflection values at each measurement point were plotted into curves, and three evaluation indicators for cracks, namely deflection range, maximum influence distance on one side of the crack, and influence area, were proposed based on the characteristics of the curves. Core samples were taken directly above the selected cracks within the test sections to verify the crack types and development layers. According to the distribution and cracking conditions of the cracks in the core samples, six types of structural cracks were classified. The results show that the proposed indicators can effectively distinguish fatigue cracks from structural cracks. The coefficient of determination (R2) between deflection range and influence area is 0.75, and the Pearson correlation coefficient is 0.88. Both indicators have a good correspondence with the various stages of crack development and can be used in combination to evaluate the severity of cracks, providing practical guidance for pavement maintenance and construction.

Bile Peng, Musa Furkan Keskin, Balázs Kulcsár et al.

Keke Long, Zhaohui Liang, Haotian Shi et al.

Fangting Zhou, Ala Arvidsson, Jiaming Wu et al.

Felix Wilhelm Siebert, Christoffer Riis, Kira Hyldekær Janstrup et al.

Bicycle helmets are a main measure for injury prevention in case of a crash and are a central variable in transport safety studies. Despite this, helmet use data is only collected sporadically, as the observation of helmet use in traffic by human observers is costly and time-consuming. An automated method for the accurate registration of bicycle helmet use would enable the broad and precise registration of cyclists’ helmet use. In this paper, we develop and test a computer vision-based detection method that can be applied to traffic video data. We record bicycle traffic at two observation sites in Copenhagen, Denmark, and annotate a dataset of 4000 cyclists, registering their helmet use. We then train a state-of-the-art object detection algorithm on the detection of cyclists and helmet use. The developed model has good accuracy in registering active cyclists. For helmet use registration on the test data set, there was an underestimation of 0.52% (algorithm registered helmet use: 50.23%; actual helmet use: 50.75%). Cross-testing the algorithm, i.e., training on one observation site and applying it to another, results in a larger underestimation of bicycle helmet use between 5.28% and 6.31%. Finally, we apply the algorithm to a week of video data from two Copenhagen sites, identifying commuting-related peaks of cyclists and registering helmet use differences between the observation sites. This study shows that computer vision algorithms are a feasible method for the automated detection of bicycle helmet use. Further research needs to be conducted to make the site transfer more robust and to increase accuracy levels.

Alireza Mahpour, Iman Farzin, Arash Rasa Izadi et al.

The growth of the car fleet has caused many problems, such as environmental problems, uncontrolled energy consumption, and traffic congestion. To resolve the issues caused by transport-related activities, transportation planners should implement policies that reduce car use and move forward to sustainable transportation. The prerequisite of the efficiency of the policies that reduce car use is the acceptance of them by the entire community members. Previously a few studies have tested individuals’ environmental attitudes using the Value-Belief-Norm (VBN) theory. This research aims to analyze and examine car use reduction policy using a comprehensive VBN and Norm-Activation-model (NAM) theories to consider more variables and provide a model with more analytical capability. To address this issue, 500 questionnaires were filled by travelers’ in Tehran, Iran, in the restricted traffic area to describe their behavior. The result shows that the biospheric value significantly affects car use reduction policy, associated with considerable environmental concerns. Besides, it was found that a high ascription of responsibility (A.R.) appeared as the strongest predictor of the policy. The findings have represented initial support for the VBN theory and revealed that the theory could explain the car use reduction policy’s Intention, according to Tehran’s respondents’ environmental behavior. This study’s findings can assist policymakers in adopting appropriate policies to reduce car use based on environmental advantages and could target biospheric values and ascription of responsibilities.

Adebola Olutayo, Yanjie Dong, Julian Cheng et al.

Performance of wireless powered wireless systems is analyzed. The wireless devices in such systems scavenge energy from sources in downlinks and use the energy to communicate in uplinks. We introduce two new models for these energy harvesters to consider their nonlinear circuitry and their functioning over multiple line-of-sight and non-line-of-sight channels. The newly proposed Beaulieu-Xie fading model is used to characterize this manifold of channels. Performance analyses of average harvested energy and transmission outage probability show good fit between the proposed models and measured data.

Jing Qin, Feixiong Liao

Yuquan Du, Yanyu Chen, Xiaohe Li et al.

Jacob Larsson, Musa Furkan Keskin, Bile Peng et al.

Yuan Wang, Xiaopeng Li

Kai Li Lim, Jake Whitehead, Dongyao Jia et al.

Jeroen Pruyn, Jelle Willeijns

Abstract Cold ironing has the potential to reduce the impact of ship exhausts in densely populated areas. However, especially for tankers, the implementation of this concept is almost non-existent. Still, these vessels have a relatively high port energy use, despite relatively short port visits, as they provide power to both pumps and inert gas systems during unloading and loading. A key factor in the reluctance, besides the fact that a sparkless connection is required, is the lack of a standard and the uncertainty from both tanker owners visiting a berth and terminal owners on which shore power systems to apply. This paper investigates the interdependency between ship and terminal owner choices for systems and establishes the overall most economical solution. Cold ironing was reviewed to identify existing systems and solutions and analyse the tanker fleet and terminals. The insights were combined in an integrated economic model consisting of two sub-models; one relating terminal decisions to a cold ironing price and one establishing the vessel side costs and savings. By using fuel price as an input and acceptance rates (for both terminals and vessels) for cold ironing systems as key variables to determine. The models have been used to identify the potential of cold ironing for shortsea and parcel tankers against different fuel prices and % of fleet and terminals that have shore power equipment. In all cases, shore power was not economical, which was caused by the high costs of the fixed costs of electricity, due to the high powers required. Interesting avenues for further research would be to increase the individuality of the model using e.g. an agent based model. Also extending the model with a battery pack on the terminal to allow for peak-shaving could lead to much lower costs and higher economic potential.

Ran Yi, Yang Zhou, Xin Wang et al.

This paper presents a constrained connected automated vehicles (CAVs) trajectory optimization method on curved roads with infrastructure assistance. Specifically, this paper systematically formulates trajectory optimization problems in a spatial domain and a curvilinear coordinate. As an alternative of temporal domain and Cartesian coordinate formulation, our formulation provides the constrained trajectory optimization flexibility to describe complex road geometries, traffic regulations, and road obstacles, which are usually spatially varying rather than temporal varying, with assistances vehicle to infrastructure (V2I) communication. Based on the formulation, we first conducted a mathematical proof on the controllability of our system, to show that our system can be controlled in the spatial domain and curvilinear coordinate. Further, a multiobjective model predictive control (MPC) approach is designed to optimize the trajectories in a rolling horizon fashion and satisfy the collision avoidances, traffic regulations, and vehicle kinematics constraints simultaneously. To verify the control efficiency of our method, multiscenario numerical simulations are conducted. Suggested by the results, our proposed method can provide smooth vehicular trajectories, avoid road obstacles, and simultaneously follow traffic regulations in different scenarios. Moreover, our method is robust to the spatial change of road geometries and other potential disturbances by the road curvature, work zone, and speed limit change.

Mila Malekolkalami, Atefeh Sharif

<p class="Subjectcodes">Considering the essential role of knowledge management in organizations and the importance of knowledge auditing as one of its most vital processes, the purpose of this paper is to reveal the insights and thoughts of authors about knowledge auditing in the articles during 2016-2020 by using the systematic review method. In these articles, the progress and differences in the proposed models and frameworks of knowledge auditing are also examined. In this review, 20 articles out of 50 retrieved articles related to knowledge auditing were reviewed and analysed. The study of the obtained results shows the progress and changes of authors 'attitudes toward knowledge auditing and their attention and focus on the knowledge management process, making suggestions, and continues re-auditing in organizations.</p><p class="Subjectcodes"><a href="https://dorl.net/dor/20.1001.1.20088302.2022.20.3.13.0">https://dorl.net/dor/20.1001.1.20088302.2022.20.3.13.0</a>   </p>