A multi-objective optimization model for green demand responsive airport shuttle scheduling with a stop location problem

We proposed a multi-objective optimization framework for green demand responsive airport shuttle scheduling, which simultaneously aims at assigning demand points to selected stops and routing airport shuttles to visit these stops in their overlapping time windows to transport all passengers from their homes or workplaces to the airport. Our objectives were to minimize total travel time for passengers, the punishment expense of violating the time-window as well as carbon emissions for all shuttles. Since such issues belongs to the NP-problem, a two-stage Multi-objective ant lion optimizer (MOALO)-based algorithm incorporating dynamic programming search method was developed to acquire the optimal scheduling schemes. Finally, a case study of airport shuttle service in Tianjin Airport, China, was used to demonstrate the validity of the model and algorithm

Growth/differentiation factor 1 alleviates pressure overload-induced cardiac hypertrophy and dysfunction

AbstractPathological cardiac hypertrophy is a major risk factor for developing heart failure, the leading cause of death in the world. Growth/differentiation factor 1 (GDF1), a transforming growth factor-β family member, is a regulator of cell growth and differentiation in both embryonic and adult tissues. Evidence from human and animal studies suggests that GDF1 may play an important role in cardiac physiology and pathology. However, a critical role for GDF1 in cardiac remodelling has not been investigated. Here, we performed gain-of-function and loss-of-function studies using cardiac-specific GDF1 knockout mice and transgenic mice to determine the role of GDF1 in pathological cardiac hypertrophy, which was induced by aortic banding (AB). The extent of cardiac hypertrophy was evaluated by echocardiographic, hemodynamic, pathological, and molecular analyses. Our results demonstrated that cardiac specific GDF1 overexpression in the heart markedly attenuated cardiac hypertrophy, fibrosis, and cardiac dysfunction, whereas loss of GDF1 in cardiomyocytes exaggerated the pathological cardiac hypertrophy and dysfunction in response to pressure overload. Mechanistically, we revealed that the cardioprotective effect of GDF1 on cardiac remodeling was associated with the inhibition of the MEK–ERK1/2 and Smad signaling cascades. Collectively, our data suggest that GDF1 plays a protective role in cardiac remodeling via the negative regulation of the MEK–ERK1/2 and Smad signaling pathways

The serum matrix metalloproteinase-9 level is an independent predictor of recurrence after ablation of persistent atrial fibrillation

OBJECTIVES: This study investigated whether the serum matrix metalloproteinase-9 level is an independent predictor of recurrence after catheter ablation for persistent atrial fibrillation. METHODS: Fifty-eight consecutive patients with persistent atrial fibrillation were enrolled and underwent catheter ablation. The serum matrix metalloproteinase-9 level was detected before ablation and its relationship with recurrent arrhythmia was analyzed at the end of the follow-up. RESULTS: After a mean follow-up of 12.1±7.2 months, 21 (36.2%) patients had a recurrence of their arrhythmia after catheter ablation. At baseline, the matrix metalloproteinase-9 level was higher in the patients with recurrence than in the non-recurrent group (305.77±88.90 vs 234.41±93.36 ng/ml, respectively, p=0.006). A multivariate analysis showed that the matrix metalloproteinase-9 level was an independent predictor of arrhythmia recurrence, as was a history of atrial fibrillation and the diameter of the left atrium. CONCLUSION: The serum matrix metalloproteinase-9 level is an independent predictor of recurrent arrhythmia after catheter ablation in patients with persistent atrial fibrillation

Influence of the Heights of Low-Level Jets on Power and Aerodynamic Loads of a Horizontal Axis Wind Turbine Rotor

The influence of the heights of low-level jets (LLJs) on the rotor power and aerodynamic loads of a horizontal axis wind turbine were investigated using the fatigue, aerodynamics, structures, and turbulence code. The LLJ and shear inflow wind fields were generated using an existing wind speed spectral model. We found that the rotor power predicted by the average wind speed of the hub height is higher than the actual power in relatively weak and shallow LLJ inflow conditions, especially when the LLJ height is located inside the rotor-swept area. In terms of aerodynamic loads, when the LLJ height is located inside the rotor-swept area, the root mean square (RMS) rotor thrust coefficient and torque coefficient increase, while the RMS rotor unbalanced aerodynamic load coefficients, including lateral force, longitudinal force, tilt moment, and yaw moment, decreased. This means that the presence of both positive and negative wind shear in the rotor-swept area not only increases the rotor power but also reduces the unbalanced aerodynamic loads, which is beneficial to the operation of wind turbine. Power spectrum analysis shows no obvious difference in the power spectrum characteristics of the rotor torque and thrust in LLJ inflow conditions with different heights

Reduced vibration and Model validation of DFIG for wind turbine

The vibration system of wind turbine doubly-fed induction generator (DFIG) includes generator, elastic support and frame. The work in this paper was conceived to test whether the elastic support change could change the vibration severity. So establish the Simpack simulation model and modified theoretical model to research the vibration of 4 elastic support and 5 kinds rotor mass unbalanced condition. At the same time, the experiment was carried out on the drive train test rig, experimental results are basically consistent to simulation results, and it is proved that the research in the paper is correct. Meanwhile, it proved that modified theoretical analysis model can be use to vibration analysis in frequency domain and the Simpack simulation model can be use to vibration analysis in time domain(such as trend analysis) for the rotor unbalance

Influence of Low-Level Jet intensity on aerodynamic loads of horizontal axis wind turbine rotor

High wind speeds associated with Low-Level Jet (LLJ) make wind resources more favorable for wind energy production. However, the aerodynamic loads of large-scale horizontal axis wind turbine (HAWT) rotor under different LLJ inflow conditions have not been thoroughly studied. To gain insight into the aerodynamic loads of rotor under LLJ inflow conditions with different LLJ intensities, a method to establish an engineering LLJ inflow model was proposed according to the plane wall jet theory and Von Karman spectra model with user-defined scaling. The parameters in the engineering LLJ inflow model were determined by comparing the wind speed distribution obtained from the GP_LLJ spectral model, which was summarized from field measurements in the real atmosphere. The LLJ fluctuating wind fields with different intensities generated by the engineering LLJ inflow model were used as the inflow conditions of Fatigue, Aerodynamics, Structures, and Turbulence (FAST) open source code to calculate and analyze the aerodynamic loads of the HAWT. It was found that the engineering LLJ inflow model can be used to establish the LLJ inflow condition of HAWT. When the LLJ height is located at the hub height and LLJ intensity increases from 8 to 16 m/s, the RMS rotor unbalanced aerodynamic load coefficients, including ones of lateral force, longitudinal force, tilt moment and yaw moment are increased by 2.2, 2.13, 1.02 and 0.95 times, respectively

Reduced vibration and Model validation of DFIG for wind turbine

The vibration system of wind turbine doubly-fed induction generator (DFIG) includes generator, elastic support and frame. The work in this paper was conceived to test whether the elastic support change could change the vibration severity. So establish the Simpack simulation model and modified theoretical model to research the vibration of 4 elastic support and 5 kinds rotor mass unbalanced condition. At the same time, the experiment was carried out on the drive train test rig, experimental results are basically consistent to simulation results, and it is proved that the research in the paper is correct. Meanwhile, it proved that modified theoretical analysis model can be use to vibration analysis in frequency domain and the Simpack simulation model can be use to vibration analysis in time domain(such as trend analysis) for the rotor unbalance

Numerical Investigation the Effect of the Different Tip Vanes on the Loading of an H-VAWT

In this paper, the effect of the three typical tip vanes on the loading of an H-VAWT is investigated by employing the three-dimensional unsteady numerical simulation method. The results show that the both transient tangential force coefficient (CT) and normal force coefficient (Cn) have obvious change when the winglet and the V type vane is used at the blade's tip, respectively. However, in three tip vanes, the CT average value is the lowest and the CT fluctuation characteristic is the highest when the winglet is used. Although the winglet and V type vane contribute to change the transient CT and Cn, the normal force is increased too, it results in increasing fatigue loading and decreasing lifetime for H-VAWT. By comparison, the effect of the plate vane on the loading is weaker. Additionally, the winglet is advantage to improve power coefficient in the low tip speed ratio

A Review of Corrosion Behavior of Structural Steel in Liquid Lead–Bismuth Eutectic

Liquid lead–bismuth eutectic alloy is one of the candidate coolants for fourth-generation nuclear power systems because of its good physical and chemical properties, neutron economic performance, and safety. However, the compatibility between the coolant and structural steel is still the main factor restricting its large-scale industrial application in the nuclear energy field. Structural steel in a liquid lead–bismuth eutectic alloy for a long time would cause severe corrosion. The erosion of structural steel by high-flow-rate liquid lead–bismuth alloy will lead to a more complex corrosion process. This paper mainly reviews the corrosion characteristics of liquid lead–bismuth and the corrosion behavior of structural steel in liquid lead-bismuth eutectic. The main methods of inhibiting liquid lead–bismuth corrosion are summarized, and future research directions are suggested