Stability Analysis of Pneumatic Cabin Pressure Regulating System with Complex Nonlinear Characteristics

Stability of pneumatic cabin pressure regulating system with complex nonlinear characteristics is considered. The mathematical model of each component is obtained and given in detail. The governing equations of the considered system consist of 8 differential equations. In the circumstance, commonly used methods of nonlinear system analysis are not applicable. Therefore a new method is proposed to construct phase plane trajectories numerically. The calculation steps are given in detail. And convergence region of numerical calculation and limits on step size is defined. The method is applied constructing phase plane trajectories for considered cabin pressure regulating system. Phase plane analysis shows that there exists a limit cycle, which is responsible for pressure pulsating in aircraft cabin. After parameters adjustment, excellent stability characteristics are acquired. And the validity of this method is confirmed by the simulation

Influence of Carbon Dioxide Curing on the Corrosion Resistance of Reinforced Cement Mortar under the External Erosion of NaCl Freeze–Thaw Cycle

Carbon dioxide (CO2)-cured concrete is a novel material that can effectively reduce CO2 emissions in the atmosphere. However, limited research has been found to investigate the corrosion behavior of CO2-cured reinforced concrete. In this paper, the corrosion resistance of reinforced cement mortar is investigated. The mortars were cured in CO2 for 1 day~28 days. Water–cement ratios (w/c) of 0.3, 0.4 and 0.5 were designed. The corrosion resistance of inner steel bars was researched by the methods of ultrasonic velocity, electrical parameters (AC electrical resistance, Tafel curve method and AC impedance spectroscopy). Moreover, scanning electron microscope was selected for observing the micro-morphology of CO2-curing mortar. X-ray diffraction spectrum was used to characterize components of steel bars’ passive films. The results show that CO2 can effectively increase electrical resistivity and ultrasonic velocity, thus improving the corrosion resistance of reinforced cement mortar. The enhancement of carbon dioxide curing increases with the increasing w/c. The mass-loss rate, the electrical resistivity and the decreasing rate of ultrasonic velocity increase with the increasing sodium chloride freeze–thaw cycles, indicating the continuous increase in the corrosion degree of reinforcement. The corrosion deterioration degree of steel bars decreases with the increasing CO2-curing time. Specimens with w/c of 0.3 and 0.4 show the highest and lowest corrosion deterioration resistances after sodium chloride freeze–thaw cycles. Microscopic characterization found that CO2 curing could increase the corrosion resistance of the inner steel bars by improving the compactness of the cement matrix. Moreover, the iron oxides on the surface of the passivation film decreased after CO2 curing

Design and application of electric power communication network comprehensive simulation training system

To solve the problem that current communication network training tools have limited functions and can’t effectively support the electric power communication network training, a new communication network comprehensive training simulation system is designed and implemented. This paper introduces the architecture of the system and function of each part. Then the simulation model principle is explained. The paper introduces the key technologies of 3D modeling, mechanism modeling, communication network scenario automatic generation and network fault simulation. Finally, the system application is introduced and the results show that the system builds a multi-functional training tool to meet the requirements of training and assessment for electric power communication network personnels

Hopper discharge of cohesive powders using pulsated airflow

An aerated hopper with pulsated aeration was designed to study the effect of square‐wave pulsated airflow on the discharge characteristics of cohesive and non‐cohesive powders. Experiments were carried out with pulsation frequencies between 0 (continuous) and 50Hz. Two flow patterns were observed at different aeration rates and pulsation frequencies: intermittent and smooth. For non‐cohesive powders, pulsated aeration has a worsening effect on discharge flow. For cohesive powders, results revealed that pulsated aeration can reduce the minimum aeration necessary to allow continuous discharge. And the maximum discharge rate that can be attained applying pulsated aeration is higher than that of continuous aeration and it is significantly more uniform. The aggregates size of the powder was estimated and used to understand the stabilizing mechanism of pulsated aeration on the aggregative discharge. The model value of the minimum aeration rate and the discharge rate were obtained and compared with the experimental values

Research on the cost effectiveness of carbon emission reduction in the full life cycle of electric vehicles based on grey prediction

In order to research the carbon emission reduction potential of electric vehicles, a cost effectiveness model is used to calculate and compare the economic costs and carbon emissions of fuel vehicles and electric vehicles throughout the life cycle, and an improved grey prediction model is utilized to analyze the future trends of electric vehicle emission reduction benefits. The results show that electric vehicles play a positive role in carbon emission reduction, and the unit cost of carbon emission reduction is decreasing by years. Therefore, China should vigorously develop the electric vehicle industry and technology, and achieve the strategic goal of carbon emission reduction by promoting the electrification of vehicles

Optimal Effects of Combined Application of Nitrate and Ammonium Nitrogen Fertilizers with a Ratio of 3:1 on Grain Yield and Water Use Efficiency of Maize Sowed in Ridge–Furrow Plastic Film Mulching in Northwest China

Improving water use efficiency is essential for the advancement of agricultural production, particularly in arid and semiarid regions. Two-year field experiments were conducted to study the effects of ridge–furrow (RF) and flat planting (FP) plastic film mulching combined with five different nitrogen (N) fertilizers, N1 (KNO3), the nitrate (NO3−)/ammonium (NH4+) mixtures with different pure nitrogen ratios N2 (1:1), N3 (1:3), and N4 (3:1), and the control N5 (urea) on maize dry matter accumulation, soil water content, grain yield, water use efficiency (WUE), and N partial factor productivity. Our results showed that RF and N4 were more efficient than FP for increasing maize grain yield, WUE, and nitrogen partial factor productivity, and there was a significant interaction for cultivation practices × N formulation. RF and 3:1 NO3−/NH4+ significantly increased grain yield by 14.73% and 13.15%, and 20.07% and 24.14% in 2016 and 2017, respectively, compared to FP and nitrate only. RFN4 produced the highest grain yield in 2016 and 2017 due to the highest dry matter accumulation at filling and physiological maturity stage, ear rows per spike, and row grains per row. Over two growing seasons, the WUE and N partial factor productivity under RFN4 were 18.75% and 29.17% more on average than those of other treatments. Therefore, RFN4 is an effective planting system for increasing the simultaneity of grain yield and WUE for maize production in rain-fed agriculture