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Interest in the highly efficient energy hub (EH) model has been growing despite the high computational requirements of planning for a multi-energy, multi-device operation. To address both the device size limitation and the multi-scenario issue, we propose a new solution methodology for solving the EH planning problem. In the method, the decision variables are device sizes. First, a dimension reduction technique is proposed to address the curse of dimensionality based on the correlation of unknown variables such as the capacities of different devices in an EH. Second, to avoid local convergence, a solution method called the variable-sized unimodal searching (VUS) approach is proposed to assure a global optimal planning scheme for the one-dimensional non-convex optimization model obtained from the preceding dimension reduction process. The case study indicates that the proposed approach has a higher computing efficiency than the Benders decomposition (BD) algorithm to deal with a scenario-based stochastic planning problem with a large number of scenarios. Thus, the effectiveness of the EH planning approach is verified.

At present, the in-situ testing equipment used for measuring the thermophysical properties of rock and soil is scarce. Based on the working principle of the pressuremeter and ground heat exchanger, a pre-drilling thermal probe in-situ testing equipment is developed. This novel developed pre-drilling thermal probe in-situ testing equipment includes thermal probe, pressure control system, temperature control system, integrated conversion control device, and coaxial pressure pipe connection pipeline. A three-dimensional heat transfer model was established to simulate the heat transfer between the thermal probe and surrounding ground. Based on the principle of the temperature dissipation and numerical simulation, a calculation method for the thermal conductivity of rock and soil with pre-drilling thermal probe is proposed. Laboratory model tests of the sand under dry and saturated conditions were conducted. The deviation values for the thermal conductivities of sand under dry and saturated conditions measured by the designed pre-drilling thermal probe and thermal conductivity tester are 0.037 and 0.026 W/m·°C, respectively. Thus, the reliability of utilizing the new pre-drilling thermal probe testing equipment to measure the thermal conductivity of the soil is confirmed. The field test of utilizing this new pre-drilling thermal probe testing equipment to measure the thermal properties of the soil was performed. The results show that because the soil layers are in undisturbed state during the test process, the pre-drilling thermal probe testing equipment can truly reflect the inherent thermal properties of different soil layers.

Aiming at the problem that the relative important degree of indexes will change, when urban rail power supply equipment is in different running state, this paper proposes a comprehensive degradation assessment model. The model uses the discrete degree of indexes' historical data to describe the relative importance of each indexes, and calculates the initial weights of each indexes by mean variance method (MVM). When the equipment is in normal operation state, the initial weight is corrected by the current detection data of the index, and the comprehensive degradation degree of the equipment is obtained. According to the principle of "more value punishment", when the equipment is in failure state, the weight of the index can be reassigned by the variable weight formula to realize the comprehensive assessment of the degradation degree of the equipment. Finally, the effectiveness of the comprehensive assessment method is verified by an example.

This paper proposes a multi-objective optimization algorithm based on the membrane computing. Inspired by the theory of membrane optimization, the membrane structure, multiple sets and reaction rules is employed to tackle multi-objective optimization issues. Aiming at adaptability of algorithm, the cross-over and mutation mechanism of the genetic algorithm are introduced to combine with membrane framework. Moreover, for the sake of improving the diversity of global search solution, the non-dominated sorting and crowding distance are used to update external archive. The experimental results demonstrate that the proposed algorithm is not only practicable and efficient but also capable of obtaining the approximate Pareto front in KUR and ZDT test function.

In order to improve the degree of renewable energy integration, the demand response resource, especially on the air conditioning load side, has received attention. Currently, most of the control modes for air conditioners are centralised control, which is difficult to be applied to widely distributed air conditioning. The current studies focus on central air conditioning, but there are few studies on split-type inverter air conditioning, even though inverter air conditioning has become the most common split air system on the market. With this background, this study designs a consensus control strategy on the basis of distributed control mode, which for inverter air conditioners. The strategy is used for renewable energy integration in the studied region. The test results of various cases reveal the following findings: (i) the strategy adapts to the widely distributed air conditioning, (ii) the strategy can guarantee a fair allocation of power imbalance and user comfort, (iii) the control strategy can adapt to the uncertainties of air conditioners and the urban microclimate while efficiently consuming renewable energy. Therefore, the proposed consensus control strategy has practical value.

Abstract A new conical-cylindrical top-discharge blow tank is designed, by introducing the pulsed gas to facilitate discharging, for stable transportation for kaolin powders. A series of experimental studies on pulsed gas characteristic parameters like pulsed gas flow rate Qpulsed (5 m3/h ≤ Qpulsed ≤ 25 m3/h), pulsed interval tpulsed (1 s ≤ tpulsed ≤ 5 s) and pulsed width τpulsed (50 ms ≤ τpulsed ≤ 250 ms) are conducted with the fluidized gas flow rate of 12 m3/h. The experiments mainly test the powder mass flow rate and solid-gas ratio in the conveying process. The results indicate that the mass flow rate and solid-gas ratio range 12.6–278.04 kg/h and 0.9–19.56 kg/m3, respectively. With the increase of the pulsed gas flow rate, the mass flow rate and solid gas ratio first increase and then decrease. When the ratio of fluidized gas flow rate to pulsed gas flow rate is within 0.8–1.2, its conveying capacity reaches the maximum. Meanwhile, the increase in the pulsed interval leads to the decrease of the mass flow rate and solid-gas ratio. Moreover, the increase in the pulsed width leads to the initial increase and then the stabilization of the mass flow rate and solid gas ratio. When the pulsed width is 50 ms, the improvement of discharge would small. Conversely, increasing the pulsed width can increase the discharge, and stabilize subsequently until over 200 ms. Besides, moisture content is one of the important factors affecting kaolin powders discharge. When the moisture content is 0.83%, the pulsed gas does not improve the discharge significantly. Meanwhile, pressure distribution at different locations in the tank is also measured. The results reveal that the introduction of pulsed gas changes the pressure distribution in the tank. A pressure zone is formed on the upper part of the tank, which promotes the powder discharge.

Abstract Mixing behavior of binary particles with different densities in a wet fluidized bed has been experimentally investigated in this work. Some important hydrodynamic characteristics during mixing, such as the minimum fluidization velocity, flow pattern, and flotsam particle distribution are measured. The differences between dry and wet particles are systematically compared. It is found that the minimum fluidization velocity Umf of wet particles is higher than that of dry particles due to the liquid bridge force between particles. Umf reaches its maximum when the liquid saturation S = 0.1, and then decreases, and does not change much when the liquid saturation in the region of S = 0.2–0.3. Liquid addition can bring two opposite effects on the mixing of a binary mixture of particles with different densities. First, the intensity of bubbling in the wet fluidized bed is lower than that in the dry fluidized bed at the same operation gas velocity Uf, which will weaken the mixing. Secondly, the liquid bridge forces between particles can restrain the density segregation, which is beneficial for mixing. A simple method is developed based on the analysis of forces on flotsam particles to evaluate the effect of liquid bridge force on mixing. A segregation index Se, defined as Se = Flift/Fresis, where Flift contains the drag force Fd and buoyancy force Fb, and Fresis contains the gravitation force Fg and liquid bridge force Flb, is used to indicate the segregation potential. The calculated results show that Se > 1 in the dry fluidized bed and Se

This study investigates the face stability of small curvature shield tunnels during excavation and its relationship with various excavation parameters. The stability of the excavation face is critical to the safety and efficiency of underground construction projects. Despite the increase in the use of small curvature shield tunnels in urban areas, research works on this type of tunnel are limited and the existing literature focuses only on straight shield tunnels. This study addresses this research gap through numerical simulations, analyzing the effects of different excavation parameters such as jacking force, cutting speed, and soil conditioning on face stability. The results of the study show that the excavation parameters significantly affect face stability. The findings can be used to optimize the performance of small curvature shield tunnels and support their continued development in urban areas.

This paper analyzes the effects of flow-through inrush on CTs, especially on transformer and its differential protection. The flow-through inrush can cause the transformer to produce series-type sympathetic inrush, when the series-type sympathetic inrush current is followed by heavy CT saturation in the secondary side of transformer, false operation may be introduced in the existing 2nd harmonic restraint relays. This paper discusses the reason of false operation and presents a restraint criterion based on 2nd and 3rd harmonic according to the characteristic of this kind of phenomena. The presented criterion is an extension of the traditional 2nd harmonic restraint criterion and is proved to be feasible by lots of simulation tests.