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Large oil-immersed transformers are an important part of the transmission and distribution network in power systems. Power transformers are the main noise source of substations. Because of the uneven manufacturing process, aging equipment, long-term operation, and close distance from sensitive points, the problem of transformer noise pollution has become increasingly prominent. In this paper, the transmission and analysis model is established for transformer sound waves on the interface between insulating oil and tank body according to the sound wave propagation rule in complicated medium, and the simplified acoustic simulation model is constructed for large oil-immersed transformers by simulating the vibration noise of transformer core with monopole sound source, with which, the sound field distribution rule inside and outside the transformer tank structure is obtained, and finally, the influence factors for noise distribution are given. The results of the study provide control basis for reducing transformer noise.

Pediatric skull deformity requires immediate surgery as indicated by increased cranial pressure, mental retardation, impaired or absent vision, cranial deformity, and mental and spiritual defects. This study explores the application value of computer aided simulation in treatment of pediatric skull deformity. The application of computer simulation surgery in the treatment of children with pediatric skull deformity allows surgeons to be familiar with the operation process in advance. The use of computer 3D digital technology for preoperative design planning and simulation can reduce surgical difficulty to a certain extent, improve surgical efficiency, significantly increase intraoperative accuracy, and also reduce the risk of intraoperative bleeding and postoperative complications.

This study explores the application value of computer aided simulation and biomechanical analysis in treatment of congenital sagittal synostosis. The traditional and proposed treatment methods were evaluated by comparing the operation time, blood loss, operation cost and postoperative complications. The application of computer simulation surgery and biomechanical analysis in the treatment of children with congenital sagittal synostosis allows surgeons to be familiar with the operation process and splicing scheme in advance. In particular, computer biomechanical analysis was proposed for the first time to determine the position and quantity of the joint materials, so as to achieve operation's objectives of stability, aesthetics, expansion, significantly improve the surgical efficiency, reduce the cost and postoperative complications.

The technological breakthrough of energy storage and the rapid decrease in cost make the application prospect of energy storage in power system more and more extensive, and will play an increasingly important role in the safe and efficient operation of power system. The optimal arrangement of energy storage load operation is conducive to the maximization of economic profit on the grid side, which is of great significance to the satisfaction of power demand of the distribution network.

China is promoting the construction of electric internet of things, and a large part of the fixed asset investment in the power grid is the investment in the upgrading of the distribution network. The economic benefits of investment are related to the sustainable development of power grid companies. At present, the Chinese government is reforming transmission and distribution tariff, and the economic benefits of power grid infrastructure investment are facing greater uncertainty. This paper studies the life cycle cost of the distribution network upgrading project from construction to decommissioning and the electricity revenue for the entire operation period. The dynamic input-output model of the distribution network upgrading project is established under the background of electric internet of things. An empirical analysis is conducted in combination with the case study. Through load forecasting and cost calculation, the input and output indicators of the project are obtained, which verifies the validity and accuracy of the model.

As a light-weight and ultra-thin artificial material, acoustic metamaterial have more different attributes than natural material. The study of sound insulation for acoustic metamaterial is hot, and the membrane-type acoustic metamaterials supplement the deficiency of linear sound insulation materials. The physical material parameters (young modulus and loss factors)of base material of membrane-type acoustic metamaterials (PVC) is obtained by cantilever beam dynamic measurement method. The acoustic metamaterial sound insulation analysis is simulated by CAE method based on the material parameters that measured. The configuration of the simulation accuracy is measured on impedance tube, and the design work of the acoustic metamaterial sound insulation for transformer is provided. The relationship between sound insulation and the mass on membrane-type acoustic metamaterial at the different frequencies (100Hz to 500Hz) provides the reference to set sound insulation frequency.

The push-bending process of stainless-steel tubes was investigated by using the experimental method and finite element (FE) analysis based on the commercial software MSC.MARC. The effects of the processing parameters and the lubricating condition on the forming quality of as-obtained ASTM304 tubes were discussed. The results demonstrated that the experiment results were consistent with the simulation both in deformation behaviour and the stress distribution during the push-bending process, which verified the reliability of the established FE-model. The results also show that the maximum residual stress concentrates in the middle of tubes, the residual strain on both the external side increases firstly, then decrease, and increase again with the increase of the location angel. After the push-bending, the interior wall thickness increases while the exterior wall thickness decreases. When the relative bending radius is larger, smaller variation of wall thickness will be obtained. With the increase of the friction coefficient, the wall thickness thinning rate will decrease. With the increase of the pushing speed, the wall thickness thinning rate decrease a little while the thickening rate increases slightly. When push-bending of the large radius tubes, a good lubricating condition can reduce the wall thickening problem at the intrados, which will ensure a better forming quality. Keyword. Bending, Quality control, Simulation

The evolution of the energy markets has been accelerating the use of distributed energy resources (DERs) all over the world. Virtual power plant (VPP) is a new method to management this increasing two-way complexity. In this paper, a bidding model for a VPP via robust optimization in the uncertain environment of the electricity market is presented. The flexible feature embedded in the model with respect to solution accuracy and computation burden would be advantageous to the VPP. Results of a case study are provided to show the applicability of the proposed bidding model.