Influence of head structure on hydrodynamic characteristics of transonic motion projectiles

Wang, Rui,Yao, Zhong,Li, Daqin,Xu, Baocheng,Wang, Jiawen,Qi, Xiaobin The Society of Naval Architects of Korea 2020 International Journal of Naval Architecture and Oc Vol.12 No.-

The hydrodynamic characteristic of transonic motion projectiles with different head diameters are investigated by numerical simulation. Compressibility effect in liquid-phase water are modeled using the Tait state equation. The result shows that with increasing of velocity the compression waves transfer to shock waves, which cause the significant increasing of pressure and decreasing the dimensions of supercavities. While the increasing of head diameter, the thickness, the vapor volume fraction and the drag coefficient of supercavities are all enhanced, which is conducive to the stability of transonic-speed projectiles. The cavity dynamics of the different head projectiles are compared, and the results shows when Mach number is in high region, the truncated cone head projectile is enveloped by a cavity which results in less drag and better stability.

Influence of head structure on hydrodynamic characteristics of transonic motion projectiles

Wang, Rui,Yao, Zhong,Li, Daqin,Xu, Baocheng,Wang, Jiawen,Qi, Xiaobin The Society of Naval Architects of Korea 2020 International Journal of Naval Architecture and Oc Vol.12 No.1

The hydrodynamic characteristic of transonic motion projectiles with different head diameters are investigated by numerical simulation. Compressibility effect in liquid-phase water are modeled using the Tait state equation. The result shows that with increasing of velocity the compression waves transfer to shock waves, which cause the significant increasing of pressure and decreasing the dimensions of supercavities. While the increasing of head diameter, the thickness, the vapor volume fraction and the drag coefficient of supercavities are all enhanced, which is conducive to the stability of transonic-speed projectiles. The cavity dynamics of the different head projectiles are compared, and the results shows when Mach number is in high region, the truncated cone head projectile is enveloped by a cavity which results in less drag and better stability.

Wind Power Interval Prediction Based on Improved PSO and BP Neural Network

Wang, Jidong,Fang, Kaijie,Pang, Wenjie,Sun, Jiawen The Korean Institute of Electrical Engineers 2017 Journal of Electrical Engineering & Technology Vol.12 No.3

As is known to all that the output of wind power generation has a character of randomness and volatility because of the influence of natural environment conditions. At present, the research of wind power prediction mainly focuses on point forecasting, which can hardly describe its uncertainty, leading to the fact that its application in practice is low. In this paper, a wind power range prediction model based on the multiple output property of BP neural network is built, and the optimization criterion considering the information of predicted intervals is proposed. Then, improved Particle Swarm Optimization (PSO) algorithm is used to optimize the model. The simulation results of a practical example show that the proposed wind power range prediction model can effectively forecast the output power interval, and provide power grid dispatcher with decision.

Multiscale Prototyping Approach via In-situ Switching Electrohydrodynamics for Flexible Microfluidic Design

Jiawen Xu,Haodong Hong,Zhenyu Wang,Xinhu Sun,Yen Wei,Yu Liu 한국정밀공학회 2024 International Journal of Precision Engineering and Vol.11 No.2

Microfluidic devices are critical in lab-on-chip, drug delivery, flexible sensors, etc. However, a formidable challenge remains in fabricating microfluidic channels with complex shapes during design and verification. Herein, we present a facile approach for manufacturing polystyrene (PS) templates by in-suit combining microscale electrohydrodynamic (EHD) printing and mesoscale direct ink writing (DIW). The desired multiscale filament width from 20 μm to > 1 mm could be obtained through appropriate voltage and pressure with continuous printing. The further process parameters for adjusting line width including deposition speed, auxiliary heating for DIW/EHD printing mode were investigated detailly. And we prove the stability and feasibility for producing microfluidics via the method by AFM, EDS and filling test. Based on the solubility of PS in the organic solvent, we can readily reconfigure the existing template by erasing and printing part of the patterns for better remanufacturing. Finally, the LM-filling PDMS microfluidic is experimented to demonstrate the future potential and advantage of the printing technology for fabricating the flexible microfluidic device.

Numerical study of the run-up of a solitary wave after propagation over a saw-tooth-shaped submerged breakwater

Sun, Jiawen,Ma, Zhe,Wang, Dongxu,Dong, Sheng,Zhou, Ting The Society of Naval Architects of Korea 2020 International Journal of Naval Architecture and Oc Vol.12 No.1

A numerical model is established to investigate the run-up of a solitary wave after propagating over a triangular saw-tooth-shaped submerged breakwater. A rectangular-shaped submerged breakwater is simulated for comparison. Several factors, including the submerged depth, the lagoon length and the beach slope, are selected as independent variables. The free surface motions and velocity fields of the solitary wave interacting with the submerged breakwater are discussed. The results show that the submerged depth and lagoon length play significant roles in reducing the run-up. The influence of the beach slope is not significant. At the same submerged depth, the triangular saw-tooth-shaped submerged breakwater has only a slightly better effect than the rectangular-shaped submerged breakwater on the run-up reduction. However, a calmer reflected wave profile could be obtained with the rougher surface of the saw-tooth-shaped submerged breakwater. The study conclusions are expected to be useful for the conceptual design of saw-tooth-shaped submerged breakwaters.

Incentivizing Consensus Propagation in Proof-of-Stake Based Consortium Blockchain Networks

Kang, Jiawen,Xiong, Zehui,Niyato, Dusit,Wang, Ping,Ye, Dongdong,Kim, Dong In IEEE 2019 IEEE wireless communications letters Vol.8 No.1

<P>In proof-of-stake based consortium blockchain networks, pre-selected miners compete to solve a crypto-puzzle with a successfully mining probability proportional to the amount of their stakes. When the puzzle is solved, the miners are encouraged to take part in mined block propagation for verification to win a transaction fee from the blockchain user. The mined block should be propagated over wired or wireless networks, and be verified as quickly as possible to decrease consensus propagation delay. In this letter, we study incentivizing the consensus propagation considering the tradeoff between the network delay of block propagation process and offered transaction fee from the blockchain user. A Stackelberg game is then formulated to jointly maximize utility of the blockchain user and individual profit of the miners. The blockchain user acting as the leader sets the transaction fee for block verification. The miners acting as the followers decide on the number of recruited verifiers over wired or wireless networks. We apply the backward induction to analyze the existence and uniqueness of the Stackelberg equilibrium. Performance evaluation validates the feasibility and efficiency of the proposed game model in consensus propagation.</P>

Numerical study of the run-up of a solitary wave after propagation over a saw-tooth-shaped submerged breakwater

Sun, Jiawen,Ma, Zhe,Wang, Dongxu,Dong, Sheng,Zhou, Ting The Society of Naval Architects of Korea 2020 International Journal of Naval Architecture and Oc Vol.12 No.-

A numerical model is established to investigate the run-up of a solitary wave after propagating over a triangular saw-tooth-shaped submerged breakwater. A rectangular-shaped submerged breakwater is simulated for comparison. Several factors, including the submerged depth, the lagoon length and the beach slope, are selected as independent variables. The free surface motions and velocity fields of the solitary wave interacting with the submerged breakwater are discussed. The results show that the submerged depth and lagoon length play significant roles in reducing the run-up. The influence of the beach slope is not significant. At the same submerged depth, the triangular saw-tooth-shaped submerged breakwater has only a slightly better effect than the rectangular-shaped submerged breakwater on the run-up reduction. However, a calmer reflected wave profile could be obtained with the rougher surface of the saw-tooth-shaped submerged breakwater. The study conclusions are expected to be useful for the conceptual design of saw-tooth-shaped submerged breakwaters.

Wind Power Interval Prediction Based on Improved PSO and BP Neural Network

Jidong Wang,Kaijie Fang,Wenjie Pang,Jiawen Sun 대한전기학회 2017 Journal of Electrical Engineering & Technology Vol.12 No.3

As is known to all that the output of wind power generation has a character of randomness and volatility because of the influence of natural environment conditions. At present, the research of wind power prediction mainly focuses on point forecasting, which can hardly describe its uncertainty, leading to the fact that its application in practice is low. In this paper, a wind power range prediction model based on the multiple output property of BP neural network is built, and the optimization criterion considering the information of predicted intervals is proposed. Then, improved Particle Swarm Optimization (PSO) algorithm is used to optimize the model. The simulation results of a practical example show that the proposed wind power range prediction model can effectively forecast the output power interval, and provide power grid dispatcher with decision.

Short-Term Photovoltaic Power Generation Forecasting Based on Environmental Factors and GA-SVM

Jidong Wang,Ran Ran,Zhilin Song,Jiawen Sun 대한전기학회 2017 Journal of Electrical Engineering & Technology Vol.12 No.1

Considering the volatility, intermittent and random of photovoltaic (PV) generation systems, accurate forecasting of PV power output is important for the grid scheduling and energy management. In order to improve the accuracy of short-term power forecasting of PV systems, this paper proposes a prediction model based on environmental factors and support vector machine optimized by genetic algorithm (GA-SVM). In order to improve the prediction accuracy of this model, weather conditions are divided into three types, and the gray correlation coefficient algorithm is used to find out a similar day of the predicted day. To avoid parameters optimization into local optima, this paper uses genetic algorithm to optimize SVM parameters. Example verification shows that the prediction accuracy in three types of weather will remain at between 10% -15% and the short-term PV power forecasting model proposed is effective and promising.

Effect of Mn Modification on Microstructure and Mechanical Properties of Magnesium Alloy with Low Gd Content

Dongdong Gu,Jian Peng,Jiawen Wang,Fusheng Pan 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.6

The evolution of microstructure and mechanical properties of the dilute Mg–Gd alloy with Mn modification were investigatedsystematically in this paper. The results show that the combination of Mn and different processing states could adjust thesolid solubility of Gd in the Mg matrix, thereby changing the morphology of the second phases and improving the propertiesof the alloy. With the addition of 0.8 wt% Mn into the Mg–4Gd alloy, the atomic utilization ratio of Gd atoms decreasesfrom 61.5 to 51.8% during the water-cooling casting process, but it increases from 73.8 to 81.0% during homogenizationtreatment and increases from 72.3 to 84.1% during hot extrusion. Thus, the mean diameter of granular phases of the Mg–4Gd alloy is larger than that of Mg–4Gd–0.8Mn alloy after the isothermal heat treatment. The Mn addition has little effecton the Hall–Petch constant KYand KHof Mg–4Gd alloy, but improves the σ0 value significantly due to the increase of theatomic utilization ratio of Gd atoms. Mn element can improve the mechanical properties of Mg–4Gd alloy, and the increaseof yield strength and ductility of as-extruded Mg–4Gd–0.8Mn alloy is mainly attributed to grain refinement and the decreaseof the texture intensity.