SIMULATION: Transactions of The Society for Modeling and Simulation International

Habaebi, Mohamed Hadi; Merrad, Yaçine; Islam, Md Rafiqul; Elsheikh, Elfatih A A; Sliman, F M; Mesri, Mokhtaria

doi: 10.1177/00375497221105530pmid: N/A

With the enormous growth of sensing devices tending to the use of Internet of everything, data aggregated by these devices are the biggest data streams generated in the history of IT. Thus, aggregating such data in the cloud for leveraging powerful cloud computing processing and storage is essential, and it eventually led to the emergence of Sensor-Cloud concept. This has allowed aggregation of the sensors’ data to the cloud for further processing, storage, and visualization. Furthermore, virtualization makes the sensors accessible to other end-user applications that require such data. All of these features are expected to be provided by the Sensor-Cloud invisibly, without the end-user application developer being aware of the sensor location or hardware specifications. For these reasons, a simulation platform where Sensor-Cloud infrastructure agents and components may be modeled, scheduling policies defined, and execution time assessed is essential to assure performance and quality of service. The aim of this study is to develop such a platform by enhancing CloudSim, the most well-known and powerful simulation tool for cloud computing. A user-friendly Java Script Swing-based graphical user interface (GUI) has been carefully designed and implemented for this purpose. The user can then utilize the specific interface to define the Cloudlet type as well as the scheduling on a single virtual machine. Finally, a simulation study is carried out on the platform to demonstrate its efficiency and accuracy. We were able to fully model the needed scenarios and acquire real-time results, displaying good accuracy in terms of application response time with a mean absolute percentage error (MAPE) of 3.37%, demonstrating the increased proposed platform’s proper operation.

Özkan, Emin Deniz; Koçer, Umay Uzunoğlu; Nas, Selçuk; İşlek, Özgür; Tüzgen, Emel; Doğan, Anıl

doi: 10.1177/00375497221107938pmid: N/A

Tanker ships arriving at liquid cargo terminals have to wait for getting service due to various operational restrictions in the terminal. Waiting time is the time passed until the tankers get service after the notice of readiness. The increase in the waiting times of tanker ships causes high demurrage costs. Reducing the waiting times of ships is of vital importance for the operational efficiency of the terminal. In this study, it is aimed to develop a simulation model in which alternative solutions in the cargo transfer operations can be tested to reduce the waiting times of tanker ships. The simulation model has several constraints that can be encountered in liquid cargo terminals, and it can be adapted to any liquid cargo terminal. The developed model was then applied to a liquid cargo terminal in Turkey.

Zhang, Shengwen; Lin, Hang; Chen, Yifan; Wang, Yixian; Zhao, Yanlin

doi: 10.1177/00375497221107935pmid: N/A

Frozen heaving failure of fractured rock mass is commonly encountered in engineering in cold regions, which is chiefly caused by the frost heaving pressure arising from the water–ice phase change in the crack. To explore the evolution of frost heaving pressure in penetrating elliptical crack considering water content and water migration, a new theoretical model embodying the frost heaving pressure evolutionary character was established by introducing freezing ratio function. The equivalent thermal expansion coefficient was used to analyze the evolution process of frost heaving pressure under the effect of water–ice phase change, which was then verified. It was found that the evolution process of frost heaving pressure can be divided into three stages: free expansion stage of water–ice phase change, rapid growth stage of frost heaving pressure, and stable stage of frost heaving pressure. Subsequently, the influences of rock thermal expansion effect, properties of rock and ice, and water content of crack on the frost heaving pressure were investigated. The results indicate that the impact of rock thermal expansion on frost heaving pressure is extremely slight, which is negligible. Comparing with the properties of rock, the properties of ice show significant effects on the frost heaving pressure, particularly the Poisson ratio of ice. In the case of identical water migration ratio, the peak frost heaving pressure increases linearly with the water content of crack.

Li, Zhengming; Smirnova, M N; Zhang, Yongliang; Smirnov, N N; Zhu, Zuojin

doi: 10.1177/00375497221109570pmid: N/A

To explore freeway tunnel effects on ring road traffic flow, a two-lane traffic model is put forward. The model adopts lane-changing time to describe the net lane-changing rate, assuming that the time is approximately equal to the relaxation time of traffic flow, but infinite when the absolute value of difference of traffic density between the two lanes is lower than 1 veh/km, as it is hard for car drivers to perceive such a small difference. Based on the two-lane traffic model, a simulation platform is built to predict traffic flow on a two-lane freeway ring with a tunnel of 0.3 km length having a speed limit of 80 km/h, and free flow speeds on lane I and II equal to 120 and 100 km/h, respectively. The platform uses a third-order Runge–Kutta scheme to handle the time derivative term, and a fifth-order weighted essentially non-oscillatory scheme to calculate numerical flux. Simulation results show that the freeway tunnel can trigger traffic shock originating at the entrance when the coming flow density is beyond a traffic density threshold that is dependent on the off-ramp flow just upstream the tunnel. The occurrence of traffic shock leads to the mean travel time through the tunnel is almost a constant when the initial density normalized by jam density is less than 0.5. When initial density is above the density threshold, generally vehicles need more fuel consumption to run through the ring road in comparison with the case without tunnel. But the situation is just the opposite for larger normalized initial density such as 0.5.

Meng, Wei; Yang, Yuanlin; Zang, Jiayao; Li, Hongyi; Lu, Renquan

doi: 10.1177/00375497221109575pmid: N/A

This paper is concerned with the first work on the integration of digital twin (DT), 5G, cloud platform, and virtual reality (VR) technologies for unmanned aerial vehicles (UAVs) autonomy development. DT focuses on connecting the virtual and physical world as an emerging strategic technology. Initially, it was implemented through mirror models of physical objects to realize the monitoring of their whole life cycle in the manufacturing area. In recent years, DT technologies have been applied in different fields, and some typical DT solutions have been proposed to solve complex system problems. In this paper, we study the problem of how to combine the DT and other emerging technologies for UAV autonomy development and supervision, aiming to propose a basic DT framework to integrate DT and UAVs as reference rules for building DT systems, which includes four parts, that is, Virtual Space, Real Space, Service Center, and Data and Model Processing Center. Based on the proposed basic DT framework, a cloud-based DT system is then further constructed in which cloud platform, 5G, and VR are integrated seamlessly. The running and implementation processes of each subsystem are introduced in detail. Multiple experiments are conducted to verify the usefulness of proposed DT system, that is, real-time system monitoring and cloud processing, VR connection, human–robot interaction through VR technology, and so on. The experimental results show that the proposed DTUAV system can be used in the interaction of virtual and physical systems, remote supervision, intelligence integration of swarm of unmanned vehicles, and so on. The development in our work introduces the DT into unmanned system applications and can promote relevant research in this direction. All implementation codes of the system will be shared in https://github.com/DTUAV.

Shahsavari-Pour, Nasser; Darabi, Leila; Zaer-Miri, Setareh

doi: 10.1177/00375497221113329pmid: N/A

The increasing young population of Iran and the subsequent increase in the unemployment rate in recent years make the government adopt temporary policies to solve the unemployment problem. Establishing private universities and increasing the capacity of university admissions in higher education are among these policies. Although these policies can reduce the youth unemployment problem temporarily, it leads to an influx of highly educated people in the labor market in the long term. Creating job opportunities for these young people will be more difficult, which requires the extensive cooperation of universities and higher education institutions to train student entrepreneurs. Hence, in this present study, the employment of university graduates is simulated through system dynamics approach. Then using the experimental design method, sensitivity analysis and optimization of variables are performed. In the following, identifying the variables influencing the employment of university graduates, scenarios are introduced regarding dynamic universities in youth employment.