This paper presents a new AC optimal power flow (AC OPF) model for sub-transmission networks. This model, which consists of sub-transmission and distribution Bus-bar switching actions, can avoid undesirable over-current (OC) status and subsequent actions of OC relays. The proposed AC OPF optimizes the Bus-bar switching actions along with optimizing sub-transmission control actions. Also, to consider the impact of OC relays’ actions in the proposed AC OPF, the cost of load shedding caused by these relay actions is included in the objective function and is minimized along with the sub-transmission operation cost. The Bus-bar switching actions are modeled using binary decision variables. Therefore, the proposed AC OPF model is formulated as a Mixed Integer Non-linear Programming (MINLP) optimization problem. The effectiveness of the proposed model is illustrated on a real-world sub-transmission network of Iran’ s power system.

This paper presents the application of automatic under voltage load tripping and switching of shunt reactors as counter measures for fault induced delayed voltage recovery (FIDVR). As dynamic behavior of loads has significant impact on simulating FIDVR, proper load modeling is also discussed in this paper. Simulations conducted on actual network show that the proposed load model is effectively able to simulate FIDVR. It also shown that automatic under voltage load shedding and switching of shunt reactors can be used as counter measures for reducing risk of voltage collapse or over voltage conditions that may take place following load tripping caused by FIDVR.

Cycloidal propellers constitute a specialized category of underwater propulsion devices, widely employed in vehicles requiring exceptional maneuverability. The parameters of the blade-driving mechanism directly impact the propeller performance. Hence, the effect of variations in the geometric parameters of the blade-driving mechanism on the hydrodynamic performance of cycloidal propellers must be investigated. In this study, a specific set of four-bar and mixed four-bar/five-bar mechanisms are taken as examples, and the effect of linkage-length variations on the hydrodynamic performance of cycloidal propellers was analyzed using numerical simulation methods. First, we established a physical model of the cycloidal propeller, and then derived the relationship between blade-rotation and revolution angles. Subsequently, by solving the Navier–Stokes equations and employing computational fluid dynamics simulations based on viscosity, an analysis is conducted to reveal the trends in the impact of different linkage-length combinations on the hydrodynamic performance of the cycloidal propeller. Finally, the outcomes of the numerical simulations are interpreted using the wing element theory. In similar blade-driving mechanisms, the effects of varying linkage lengths on propeller hydrodynamic performance are determined through alterations in the blade rotation angle range and equilibrium position. An increase in the range of the blade-rotation angle significantly enhances the hydrodynamic performance of the cycloidal propeller. This research employs a more realistic auto-propulsion mode for numerical simulations, establishing a mapping relationship between the blade-driving mechanism and hydrodynamic performance of the cycloidal propeller, while analyzing the underlying influencing mechanisms. Furthermore, crucial numerical simulations and theoretical foundations are employed for designing the four-bar and mixed four-bar/five-bar mechanism cycloidal propellers. The findings of this study could also be used in similar cycloidal propellers with multilinkage mechanism.

Bus accident is a major health problem for Bus drivers. To identify the risk factors involved in Bus accidents and to design a model showing the relation between the risk factors and Bus driver’s health status, 219 Bus drivers who worked for travel agencies in two areas of west and central Iran were enrolled into this study. We used a questionnaire to gather information regarding both the Bus drivers’ health status and Bus accident. The most prevalent health problems among Bus drivers were musculoskeletal disorders, ulcer, hyperacidity, obesity, hypertension and diabetes. There was a significant (p<0.05) correlation between the chance of Bus accidents and occurrence of low back pain, leg pain, neck pain, hypertension and migraine. Based on the results of this study we suggest a model that can be used to design a prevention plan in making Bus transportation safer. In light of this study, more comprehensive studies can be planned for the safety of traveling by Bus, in Iran. Bus driver’s health status is a determinant factor in the incidence of accidents.