Investigation on bubble snap-off in 3-D pore-throat micro-structures

Yining Wu,Sisi Fang,Caili Dai,Yongpeng Sun,Jichao Fang,Yifei Liu,Long He 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.54 No.-

Bubble behaviors in the single and cascaded three-dimensional (3-D) pore-throat micromodels were studied at the operating ranging from 0.0007 to 0.0249. It was found that the average size of daughter bubbles decreased with the rising of the pore-throat ratio, length of throat and mother bubble velocity. The variation of the average size of daughter bubbles with capillary number could be scaled with a power law. In addition, the bubble breakup mainly occurred in the first pore-throat structure and the size of the daughter bubbles maintained almost stable.

B, N-codoped 3D micro-/mesoporous carbon nanofibers web as efficient metal-free catalysts for oxygen reduction

Qi Shi,Yongpeng Lei,Yingde Wang,Huaping Wang,Lehua Jiang,Hongliang Yuan,Dong Fang,Bing Wang,Nan Wu,Yanzi Gou 한국물리학회 2015 Current Applied Physics Vol.15 No.12

B, N-codoped carbon nanofibers were massively prepared by heat treatment of electrospun carbon nanofibers with the mixture of boric acid/urea in N2 (BNCf-N) and subsequently activated in NH3 (BNCf- NA). The directly electrospun self-standing 3D non woven structure with void spaces between each fiber facilitates the mass transport of reactant and resulted molecules. Further NH3 activation gives BNCf-NA a high surface area of 306.3 m2 g-1 with micro/mesoporous structure, providing abundant passageway for proton transfer. Simultaneously, NH3 activation also realizes the optimization of surface functionalities, such as more BeNeC and pyridinic-N. These intriguing features render BNCf-NA excellent catalytic behavior with nearly four-electron oxygen reduction reaction (ORR) process in alkaline media, especially much better stability and methanol tolerance than the commercial Pt/C catalyst. Our work provides a large-scale preparation method for efficient metal-free catalysts toward ORR, thus further intensifying the commercial application of fuel cells.

Performance Optimization and Analysis on P2P Mobile Communication Systems Accelerated by MEC Servers

( Xuesong Liang ),( Yongpeng Wu ),( Yujin Huang ),( Derrick Wing Kwan Ng ),( Pei Li ),( Yingbiao Yao ) 한국인터넷정보학회 2022 KSII Transactions on Internet and Information Syst Vol.16 No.1

As a promising technique to support tremendous numbers of Internet of Things devices and a variety of applications efficiently, mobile edge computing (MEC) has attracted extensive studies recently. In this paper, we consider a MEC-assisted peer-to-peer (P2P) mobile communication system where MEC servers are deployed at access points to accelerate the communication process between mobile terminals. To capture the tradeoff between the time delay and the energy consumption of the system, a cost function is introduced to facilitate the optimization of the computation and communication resources. The formulated optimization problem is non-convex and is tackled by an iterative block coordinate descent algorithm that decouples the original optimization problem into two subproblems and alternately optimizes the computation and communication resources. Moreover, the MEC-assisted P2P communication system is compared with the conventional P2P communication system, then a condition is provided in closed-form expression when the MEC-assisted P2P communication system performs better. Simulation results show that the advantage of this system is enhanced when the computing capability of the receiver increases whereas it is reduced when the computing capability of the transmitter increases. In addition, the performance of this system is significantly improved when the signal-to-noise ratio of hop-1 exceeds that of hop-2.

MEDU-Net+: a novel improved U-Net based on multi-scale encoder-decoder for medical image segmentation

Zhenzhen Yang,Xue Sun,Yongpeng, Yang,Xinyi Wu Korean Society for Internet Information 2024 KSII Transactions on Internet and Information Syst Vol.18 No.7

The unique U-shaped structure of U-Net network makes it achieve good performance in image segmentation. This network is a lightweight network with a small number of parameters for small image segmentation datasets. However, when the medical image to be segmented contains a lot of detailed information, the segmentation results cannot fully meet the actual requirements. In order to achieve higher accuracy of medical image segmentation, a novel improved U-Net network architecture called multi-scale encoder-decoder U-Net+ (MEDU-Net+) is proposed in this paper. We design the GoogLeNet for achieving more information at the encoder of the proposed MEDU-Net+, and present the multi-scale feature extraction for fusing semantic information of different scales in the encoder and decoder. Meanwhile, we also introduce the layer-by-layer skip connection to connect the information of each layer, so that there is no need to encode the last layer and return the information. The proposed MEDU-Net+ divides the unknown depth network into each part of deconvolution layer to replace the direct connection of the encoder and decoder in U-Net. In addition, a new combined loss function is proposed to extract more edge information by combining the advantages of the generalized dice and the focal loss functions. Finally, we validate our proposed MEDU-Net+ MEDU-Net+ and other classic medical image segmentation networks on three medical image datasets. The experimental results show that our proposed MEDU-Net+ has prominent superior performance compared with other medical image segmentation networks.

Research on the reinforcement experiment of recycled aggregates based on particle shaping and vacuum cement coating

Shuai Wang,Aixun Wang,Xudong Fu,Keyang Wu,Xianwei Zhang,Yongpeng Tang 한양대학교 청정에너지연구소 2024 Journal of Ceramic Processing Research Vol.25 No.3

Reinforcement of recycled aggregates stands as a pivotal strategy to stimulate their resource utilization. This study proposesa strengthening method of recycled aggregate combined with particle molding and vacuum cement coating, and the keycontrol parameters in the reinforcement process, resultant reinforcement outcomes, failure modes, and water absorptionkinetics were discussed. Experimental findings suggest that diminutive surface particle sizes present amplified challenges forshaping. The particle strength within each size categories demonstrates an initial ascent followed by descent with prolongedshaping, underscoring an optimal reinforcement duration. Excessive shaping precipitates a decline in the property of recycledaggregates, manifested through fracture, crush, and local damage. The moisture content of recycled aggregates undergoesfluctuations throughout the shaping process. Notably, the application of vacuum cement coating markedly ameliorateswater absorption post-particle shaping, thereby augmenting failure mode resilience. Building upon these observations, theframework of “moderate shaping,” “moderate damage,” and “damage-repair integration” is introduced for both internaland external reinforcement. This paradigm aims to bolster the particle strength of recycled aggregates, thus facilitating waterconservation during the scale-up preparation phase. This study can guide the establishment of production facilities tailoredfor recycled concrete and furnish insights for the scaled-up preparation of recycled concrete materials.

Biomimetic functional hydrogel particles with enhanced adhesion characteristics for applications in fracture conformance control

Jiawei Liu,Lin Li,Zhongzheng Xu,Yongpeng Sun,Yining Wu,Caili Dai 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.106 No.-

Fracture conformance control in reservoir can effectively improve water channel to increase crude oil displacementefficiency of subsequent waterflooding. Inspired by the remarkable underwater wet adhesionof mussel byssus, hydrogel particles which can adhere stably on the fracture rock surface in reservoir conditionscould achieve long-lasting reservoir control effect. In this work, the size-controllable biomimeticfunctional hydrogel particles were prepared by mechanical shearing after bulk hydrogel was constructedby catechol-functionalized polyacrylamide and phenolic resin crosslinking agent. The influence of solutionsalinity on the aggregation and adhesion of hydrogel particles was investigated via scanning electronmicroscope (SEM), colloidal probe atomic force microscope (AFM) and quartz crystal microbalance withdissipation (QCM-D). The results showed that hydrogel particles maintained well-dispersed state in lowsalinitywater, while exhibited significant adhesion and adsorption capacity to the silica surface in simulatedreservoir salinity water. This is of great importance to the practical applications that the hydrogelparticles would not show enhanced adhesion to rock surfaces until the reservoir salinity water was met,which was beneficial to the in-depth migration of hydrogel particles to achieve effective deep reservoirprofile control. Furthermore, the visible micro-model was designed and applied to evaluate profile controleffect of hydrogel particles, and the results showed that hydrogel particles could withstand waterflushing and adhere stably to the fracture surface. The waterflooding sweep efficiency was increasedremarkably from 20.3% ± 2.0% to 38.8% ± 2.0%. This work would help better understand the functionmechanism of hydrogel particles in reservoir control and provide novel and efficient method for the practicalapplication in enhanced oil recovery.