Browsing by Author "Yildirim, MS"
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Item TRIP OPTIMIZATION FOR PUBLIC TRANSPORTATION SYSTEMS WITH LINEAR GOAL PROGRAMMING (LGP) METHODTekin, S; Köfteci, S; Aydin, MM; Yildirim, MSDetermination of the optimum trip schedules is an important problem for public transportation systems. It is complex task to assign optimum number of vehicles and determine the trip schedules for a public transport systems which consist of many routes. In the case of taking infrequent trip schedules, the existing passenger demand is not satisfied. Therefore waiting times are increased in the bus stops. In contrary, with more frequent intervals, unutilized capacity and higher operational costs are expected. Also, intense traffic density and environmental pollution are associated with the frequent trips. The optimum trip frequencies of the passenger demands varies during the hours of a day and is important for passenger satisfaction and operation efficiency of the system. Trip scheduling and vehicle assignment studies take attention in the current literature assisted with different optimization techniques and artificial intelligence method. In this study, only 10 different bus routes which is operated privately, were considered in the city center of Antalya and the Linear Goal Programming (LGP) was used to determine the optimum number of vehicles operated on the routes. The study results showed that the existing system performance can be preserved by reducing the frequency of specific trips and LGP is stated as an efficient algorithm for determining the optimum trip frequencies and number of vehicles in a public transportation systems.Item Multimethod simulation approach for capacity design of a truck parking area in city portsYildirim, MS; Aydin, MM; Gökkus, ÜThe port induced freight can cause traffic congestion problems in city ports if road freight transportation is used. The secondary congestion problem arises from the pooling of the trucks at the port gates because of the delays of the port operations. The absence of the truck parking areas inside the port causes additional truck trips between the port and auxiliary truck servicing areas around the port. For reducing the impacts of the associated problems of the port induced truck traffic, truck parking areas can be used as buffer zones between the port and city. The purpose of this study is to develop a Decision Support System (DSS) with using multimethod simulation and cost optimization model for the capacity design of a truck parking area for a city port. The preliminary design of the parking area is used to estimate the development cost and outputs of the simulation model is coupled for the capacity optimization for truck arrival scenarios. The methodology is implemented for a case study of the Izmir city port in Turkey. The results of the study indicated that significantly different parking area capacities are required for different truck dwell times for the time restricted and unrestricted truck arrivals.Item Station Capacity Analysis of a Metro Line with Discrete Event SimulationYildirim, MS; Aydin, MMThis paper demonstrates the utilization of discrete event simulation for the capacity assessment of an existing metro line using performance metrics of train utilization and passenger waiting queues at the stations. The metro line was modelled with using Arena Simulation model blocks of queues and train routing delays and the simulation model was executed with using the hourly passenger arrival schedules, an origin-destination matrix scenario and variable train time headways. The results indicated the significant deviations of the waiting passenger numbers prior to train boarding with failed train boarding resulted from system congestion. The study indicated that the train time headways can influence the system equilibrium and significant congestions are especially prominent for the intermediate stations with high passenger traffic. The characteristics of the O-D matrix was also a significant contributor to the individual station congestion since the train capacity is highly occupied with the passengers of the popular stations.Item Scheduling of the Shuttle Freight Train Services for Dry Ports Using Multimethod Simulation-Optimization ApproachYildirim, MS; Karasahin, M; Gökkus, ÜThis paper introduces a simulation-optimization method for addressing scheduling problems for shuttle freight trains (SFTs) in a shared railway corridor between a seaport and dry port. We use dispatching delays for scheduling the SFT trips so as to not disturb the existing scheduled regular train (SRT) paths. The method employs a multi-method microscopic simulation model and an optimization framework. A swarm-based optimization algorithm is used for finding the best dispatching delays to preserve SRT paths. The method is demonstrated for a railway corridor between the Alsancak seaport and a close-distance dry port. The railway corridor is modeled using a simulation model considering single and double railway tracks, stations, and schedules. By running the simulation-optimization, the SFT freight transport capacity and the quality of the SFT and SRT operations were compared using key performance indicators (number of completed trips and station stops, average trip delay, and average station delay) addressing the throughput and punctuality after the application of dispatching delays. The results show that, by preserving the existing SRT paths, freight transport capacity decreased by 11.1% (from 18 to 16 completed SFT trips) and 13.8% (from 36 to 31 completed SFT trips) for single and couple SFT scenarios, respectively. The methodology also decreased the average SFT station delays by 45.2% and 45.6% for the single and couple SFT scenarios comparing with the unoptimized SFT trips. However, the number of SFT station stops increased by 12.5% and 57.1% for the single and couple SFT scenarios for prioritizing the SRTs. Also after the optimization, the average SFT trip delays decreased by 30.7% and 0.58% for the single and couple SFT scenarios. This study successfully demonstrates that the proposed method can be used for scheduling the SFT trips inside a congested railway corridor and can be implemented as a capacity assessment tool for cyclic SFT service using a series of key performance indicators addressing throughput and punctuality.Item Simulation optimization of the berth allocation in a container terminal with flexible vessel priority managementYildirim, MS; Aydin, MM; Gökkus, ÜSolving the berth allocation problem (BAP) in ports is not trivial where the berth resources are limited and various sizes of vessels arrive with dramatically dissimilar loads. Especially in real scenarios, arriving vessels are accepted for a berth with the first come first served (FCFS) priority rule. This study proposes a decision support system coupled with a simulation optimization module based on the swarm-based Artificial Bee Colony optimization algorithm for solving the BAP. The proposed methodology was implemented for the Izmir port in Turkey. To investigate the influences of the vessel priorities on the BAP, four different experimental scenarios based on the single (SQM) and multiple queue models (MQM) were coupled with FCFS and proposed hybrid queue priority (HQP) rule. The results indicated that SQM scenarios were superior to MQM scenarios in a manner of minimizing the average vessel waiting times and the implementation of a dynamic berth allocation strategy for the MQM significantly decreases the vessel waiting times. Results of the SQM also imply that utilization of the HQP approach further minimizes the average vessel waiting times and increases the berth utilization and port throughput without yielding excessive waiting times for the larger vessels compared with the FCFS priority rule.Item Estimation of Container Traffic at Seaports by Using Several Soft Computing Methods: A Case of Turkish SeaportsGökkus, Ü; Yildirim, MS; Aydin, MMContainer traffic forecasting is important for the operations and the design steps of a seaport facility. In this study, performances of the novel soft computing models were compared for the container traffic forecasting of principal Turkish seaports (Istanbul, Izmir, and Mersin seaports) with excessive container traffic. Four forecasting models were implemented based on Artificial Neural Network with Artificial Bee Colony and Levenberg-Marquardt Algorithms (ANN-ABC and ANN-LM), Multiple Nonlinear Regression with Genetic Algorithm (MNR-GA), and Least Square Support Vector Machine (LSSVM). Forecasts were carried out by using the past records of the gross domestic product, exports, and population of the Turkey as indicators of socioeconomic and demographic status. Performances of the forecasting models were evaluated with several performance metrics. Considering the testing period, the LSSVM, ANN-ABC, and ANN-LM models performed better than the MNR-GA model considering overall fitting and prediction performances of the extreme values in the testing data. The LSSVM model was found to be more reliable compared to the ANN models. Forecasting part of the study suggested that container traffic of the seaports will be increased up to 60%, 67%, and 95% at the 2023 for the Izmir, Mersin, and Istanbul seaports considering official growth scenarios of Turkey.Item Quantifying the Operational Benefits of Dry Port Integrated Cooperation in Port Clusters: A Microsimulation StudyYildirim, MSAs marine cargo traffic continues to grow, ports are experiencing increasing problems with congestion. To address this issue without requiring significant capital investment, neighboring ports can share their capacity to meet the rising demand for cargo throughput. While there are many planning level studies on inter-port cooperation, there is a scarcity of operational-level studies, and there is currently no available dry port integrated cooperation scheme for port clusters that utilizes a microsimulation approach. This study aims to contribute to the existing literature by proposing a conceptual port integration scheme that includes a dry port for improved coordination between ports in clusters. The discrete event simulation (DES) approach was used to construct three representative microsimulation models with dry port integration considering vessel transfer policies and no-cooperation scenario. The outputs of the models were evaluated using performance metrics (vessel delays, storage capacities, and the number of serviced vessels) using t-test statistics. The results show that the cooperation scheme with the vessel transfer policy and the strategic management of vessel transfer can significantly reduce the vessel operation delay by over 39% for the no-cooperation scenario with an integrated dry port and this value is further improved to 62% if a simulation-based port selection module (PSM) is used for vessel transfer policy. Additionally, the mean number of containers of the average of two port storages decreased by 40% and further decreased by 69% with the PSM. In terms of decision-making performance for vessel transfer decisions with varying quay lengths, PSM was determined to be superior to the vessel transfer policy considering the number of vessels in port queues. The proposed conceptual port integration model and approach can assist decision-makers in evaluating the effectiveness of different cooperation schemes and vessel transfer policies for adjacent ports in port clusters.Item Investigating the Impact of Buffer Stacks with Truck Restriction Time Window Policy on Reducing Congestion and Emissions at Port of IzmirYildirim, MSUrban traffic congestion is a critical problem for port-city areas. The truck restriction time window (TRTW) aims to curb congestion by restricting truck use on city roads during peak hours. But TRTW can cause congestion at ports after the restriction ends, leading to economic losses and higher emissions. This paper proposed a buffer stack model to reduce truck delays and emissions from TRTW at port-city areas. The model was implemented for Port of Izmir with using Discrete Event SimulationF (DES). A cost model was used for evaluating DES results. The results showed that buffer stack reduced truck delays by 28.1-43.9% and gate queue lengths by 31.2-43.2% in high and low truck traffic scenarios. The congestion costs (NOX, CO2 PM2.5, emission, and truck delay costs) were also reduced by 35.8-43.9% and the total cost including the buffer stack operation was reduced by 25.6-36.3% for high and low truck traffic. The comparison between buffer stack and chassis exchange terminal (CET) system showed that both systems had comparable emission reduction values, however, CET had a higher reduction in truck delays (83.8% compared to 28.0%). Results showed buffer stacks are effective and affordable solution for ports to mitigate the impact of peak truck traffic resulted from TRTW, lower truck emissions, and reduce the logistics cost.Item A Management System for Autonomous Shuttle Freight Train Service in Shared Railway CorridorsYildirim, MSThis study proposes a train dispatching management algorithm for autonomous shuttle freight train (AST) service in a shared railway corridor with regular train traffic. The method operates the ASTs without disturbing the regular train paths and involves consecutive overtaking and waiting decisions at the intermediate stations. The developed methodology and algorithm were used for developing a real-time dispatching control module integrated with a multimethod railway microsimulation model capable of simulating the timetable and non-timetable-based regular trains and ASTs. The model was implemented for a railway corridor with regular train traffic and the efficiency of the control module was confirmed. The AST freight transport capacity was evaluated using several key performance indicators based on train throughput, punctuality, and delays. The main conclusions of the study are as follows: the control logic decreased the number of AST trips by 5.6% in favor of protecting the regular train paths for (1 + 1) locomotive couple (LC) and decreased down to 14.8% for (6 + 6) LC. The AST yard delay increased by 238.2% for (6 + 6) LC. The average number of station stops and total trip times increased up to 51.2% and 14.2% for the (6 + 6) LC. The slower AST speeds also triggered more dramatic capacity decreases, increased station stops and total trip times. The model was also evaluated for random regular train failures, and daily average of AST trips made per year decreased by 8.6% for (6 + 6) LC for the mean failure interval time of 5 days and a randomly selected regular train.Item Dry port integrated port development with microsimulation method for solving port-city conflict: a case of Alsancak PortYildirim, MS; Gökkus, ÜIn this research, we have developed a dry port integrated development scenario for a city port with a port-city conflict problem and evaluated the economic benefits of the integration compared with the 'port-only' development. Discrete event simulation was used for developing intermodal port simulation models with (IPSM-2) and without dry port (IPSM-1). A port development cost model was developed for economic comparison of the scenarios considering the port storage area requirement and traffic predictions in 20-foot equivalent units (TEU). The model results indicated that for the year of 2019, IPSM-2 decreased the port storage area up to 87% and IPSM-2 ($101/TEU) was 47% more economical compared to the IPSM-1 ($191/TEU) considering the handling rate. The study concludes that dry port integration can yield sustainable and more economic port development and can be used for solving port-city conflict for land usage.Item Wind Load Design of Hangar-Type Closed Steel Structures with Different Roof Pitches Using Abaqus CAE SoftwareÇiftçioglu, AO; Yildizel, SA; Yildirim, MS; Dogan, EStructures convert the kinetic energy available in the air into potential energy which is in the form of pressure and suction forces reducing or fully stopping its motion. The potential impact of the wind depends on the geometric properties and pertinacity of a building, the angle of the wind flow, its strength and velocity. Design gains importance for tall buildings against the impact of the resonance along with the force based on pressure. Relevant calculations are made in Turkey based on the TS 498 Wind Load Velocity Criterion and this standard is currently being updated. This study develops the wind load design of hangar-type closed steel structures with different roof pitches using Abaqus CAE software.Item Germline landscape of BRCAs by 7-site collaborations as a BRCA consortium in TurkeyBisgin, A; Sag, SO; Dogan, ME; Yildirim, MS; Gumus, AA; Akkus, N; Balasar, O; Durmaz, CD; Eroz, R; Altiner, S; Alemdar, A; Aliyeva, L; Boga, I; Cam, FS; Dorgan, B; Esbah, O; Hanta, A; Mujde, C; Ornek, C; Ozer, S; Rencuzogullari, C; Sonmezler, O; Bozdogan, ST; Dundar, M; Temel, SGBRCA1/2 mutations play a significant role in cancer pathogenesis and predisposition particularly in breast, ovarian and prostate cancers. Thus, germline analysis of BRCA1 and BRCA2 is essential for clinical management strategies aiming at the identification of recurrent and novel mutations that could be used as a first screening approach. We analyzed germline variants of BRCA1/2 genes for 2168 individuals who had cancer diagnosis or high risk assessment due to BRCAs related cancers, referred to 10 health care centers distributed across 7 regions covering the Turkish landscape. Overall, 68 and 157 distinct mutations were identified in BRCA1 and BRCA2, respectively. Twenty-two novel variants were reported from both genes while BRCA2 showed higher mutational heterogeneity. We herein report the collective data as BRCA Turkish consortium that confirm the molecular heterogeneity in BRCAs among Turkish population, and also as the first study presenting the both geographical, demographical and gene based landscape of all recurrent and novel mutations which some might be a founder effect in comparison to global databases. This wider perspective leads to the most accurate variant interpretations which pave the way for the more precise and efficient management affecting the clinical and molecular aspects.