Application and optimal design of the bionic guide vane to improve the safety serve performances of the reactor coolant pump

Liu Haoran,Wang Xiaofang,Lu Yeming,Yan Yongqi,Zhao Wei,Wu Xiaocui,Zhang Zhigang 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.7

As an important device in the nuclear island, the nuclear coolant pump can continuously provide power for medium circulation. The vane is one of the stationary parts in the nuclear coolant pump, which is installed between the impeller and the casing. The shape of the vane plays a significant role in the pump's overall performance and stability which are the important indicators during the safety serve process. Hence, the bionic concept is firstly applied into the design process of the vane to improve the performance of the nuclear coolant pump. Taking the scaled high-performance hydraulic model (on a scale of 1:2.5) of the coolant pump as the reference, a united bionic design approach is proposed for the unique structure of the guide vane of the nuclear coolant pump. Then, a new optimization design platform is established to output the optimal bionic vane. Finally, the comparative results and the corresponding mechanism are analyzed. The conclusions can be gotten as: (1) four parameters are introduced to configure the shape of the bionic blade, the significance of each parameter is herein demonstrated; (2) the optimal bionic vane is successfully obtained by the optimization design platform, the efficiency performance and the head performance of which can be improved by 1.6% and 1.27% respectively; (3) when compared to the original vane, the optimized bionic vane can improve the inner flow characteristics, namely, it can reduce the flow loss and decrease the pressure pulsation amplitude; (4) through the mechanism analysis, it can be found out that the bionic structure can induce the spanwise velocity and the vortices, which can reduce drag and suppress the boundary layer separation.

Mesocarbon microbead densified matrix graphite A3-3 for fuel elements in molten salt reactors

Wang, Haoran,Xu, Liujun,Zhong, Yajuan,Li, Xiaoyun,Tang, Hui,Zhang, Feng,Yang, Xu,Lin, Jun,Zhu, Zhiyong,You, Yan,Lu, Junqiang,Zhu, Libing Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.5

This study aims to provide microstructural characterization for the matrix graphite which molten salt reactors (MSRs) use, and improve resistance to molten salt infiltration of the matrix graphite for fuel elements. Mesocarbon microbeads (MCMB) densified matrix graphite A3-3 (MDG) was prepared by a quasi-isostatic pressure process. After densification by MCMBs with average particle sizes of 2, 10, and 16 ㎛, the pore diameter of A3-3 decreased from 924 nm to 484 nm, 532 nm, and 778 nm, respectively. Through scanning electron microscopy, the cross-section energy spectrum and time-of-flight secondary ion mass spectrometry, resistance levels of the matrix graphite to molten salt infiltration were analyzed. The results demonstrate that adding a certain proportion of MCMB powders can improve the anti-infiltration ability of A3-3. Meanwhile, the closer the particle size of MCMB is to the pore diameter of A3-3, the smaller the average pore diameter of MDG and the greater the densification. As a matrix graphite of fuel elements in MSR was involved, the thermal and mechanical properties of matrix graphite MDG were also studied. When densified by the MCMB matrix graphite, MDGs can meet the molten salt anti-infiltration requirements for MSR operation.

Assembly of micro/nanomaterials into complex, three-dimensional architectures by compressive buckling

Xu, Sheng,Yan, Zheng,Jang, Kyung-In,Huang, Wen,Fu, Haoran,Kim, Jeonghyun,Wei, Zijun,Flavin, Matthew,McCracken, Joselle,Wang, Renhan,Badea, Adina,Liu, Yuhao,Xiao, Dongqing,Zhou, Guoyan,Lee, Jungwoo,Chu American Association for the Advancement of Scienc 2015 Science Vol.347 No.6218

<P><B>Popping materials and devices from 2D into 3D</B></P><P>Curved, thin, flexible complex three-dimensional (3D) structures can be very hard to manufacture at small length scales. Xu <I>et al.</I> develop an ingenious design strategy for the microfabrication of complex geometric 3D mesostructures that derive from the out-of-plane buckling of an originally planar structural layout (see the Perspective by Ye and Tsukruk). Finite element analysis of the mechanics makes it possible to design the two 2D patterns, which is then attached to a previously strained substrate at a number of points. Relaxing of the substrate causes the patterned material to bend and buckle, leading to its 3D shape.</P><P><I>Science</I>, this issue p. 154; see also p. 130</P><P>Complex three-dimensional (3D) structures in biology (e.g., cytoskeletal webs, neural circuits, and vasculature networks) form naturally to provide essential functions in even the most basic forms of life. Compelling opportunities exist for analogous 3D architectures in human-made devices, but design options are constrained by existing capabilities in materials growth and assembly. We report routes to previously inaccessible classes of 3D constructs in advanced materials, including device-grade silicon. The schemes involve geometric transformation of 2D micro/nanostructures into extended 3D layouts by compressive buckling. Demonstrations include experimental and theoretical studies of more than 40 representative geometries, from single and multiple helices, toroids, and conical spirals to structures that resemble spherical baskets, cuboid cages, starbursts, flowers, scaffolds, fences, and frameworks, each with single- and/or multiple-level configurations.</P>

The preliminary study of exosomes derived from thymosin beta 4-treated adipose-derived stem cells in fat grafting

Li Wandi,Yang Yan,Zhang Xiaoyu,Lin Yan,Li Haoran,Yao Yu,Mu Dali 한국유전학회 2023 Genes & Genomics Vol.45 No.4

Background The retention rate in autologous fat grafting is an increasing concern for surgeons and patients. Our previous research verified that thymosin beta 4 (Tβ4) positively affected fat survival, while the mechanism was unknown. The endothelial cells (ECs) and exosomes derived from adipose-derived stem cells (ADSCs) were regarded to play a critical role in fat transplantation. Objective This study aimed to evaluate the effect of exosomes derived from Tβ4-treated ADSCs on EC proliferation and to identify the exosomal microRNA (miRNA) profile compared with the Tβ4-untreated group. Additionally, this research intended to recognize the related molecules and signaling pathways in the Tβ4-treated group with potential roles in fat transplants. Methods ADSCs were collected from patients who underwent liposuction surgery. Depending on whether the medium was supplemented with exogenous Tβ4 or not, exosomes derived from cultured ADSCs were divided into the Tβ4-Exos group and Con-Exos group. Exosome uptake and cell counting kit-8 (CCK-8) assays assessed the influence of Tβ4-Exos on EC proliferation. The exosomal miRNAs of the two groups were analyzed by next-generation sequencing. With the criteria at the |log2 (fold change)| ≥ 1 and p-value < 0.05, up-regulated and down-regulated differentially expressed miRNAs (DEMs) were obtained. Prediction databases were used to predict the downstream mRNAs for DEMs. And then, overlapping genes for the up-regulated DEMs and the down-regulated were screened out, followed by enrichment analysis, protein–protein interaction network construction, and the gene cluster and hub gene identification. Results ADSCs were obtained from four female patients. The exosome uptake and CCK-8 assays showed that the Tβ4-Exos could increase cell growth rate compared with the control group (DMEM-H + PBS). In Tβ4-Exos and Con-Exos groups, 2651 exosomal miRNAs were recognized, with 80 up-regulated and 99 down-regulated DEMs according to the criteria. After the prediction, 621 overlapping genes for the up-regulated and 572 for the down-regulated DEMs were screened. The subsequent bioinformatics analysis found specific molecules and pathways related to the positive effect on fat survival. Conclusions The exosomes derived from Tβ4-treated ADSCs probably positively affect EC proliferation. Compared with the Con-Exos group, several exosomal DEMs, genes, and pathways were distinguished. These findings of this exploratory study provide the potential direction for future in-depth research on fat grafting.

Optimization Mechanisms of Microstructure and Mechanical Properties of SiC Fiber Reinforced Ti/Al3Ti Laminated Composite Synthesized Using Titanium Barrier

Chunfa Lin,Siyu Wang,Haoran Yan,Yuqiang Han,Junyi Zhu,Hao Shi 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.2

A novel structure-optimized SiC fiber reinforced metal-intermetallic-laminated composite (SiCf-Ti/Al3Ti) without intermetalliccenterline defect has been fabricated by vacuum hot pressing using stacked fibers and foils as well as Ti barrierlayer. Through microstructure characterization by SEM and EBSD, the mechanisms of centerline formation and structuraloptimization were investigated detailedly. The mechanical properties and fracture behaviors of the optimized and nonoptimizedSiCf-Ti/Al3Ti composites were studied via quasi-static compression tests. The experimental results indicatedthat the intermetallic centerline region existing at the mid-plane of Al3Tilayer in non-optimized composite mainly containsnewly-formed Kirkendall voids and gathered metallic oxides. Additionally, owing to the similar moving trails of fibers,oxides and voids in molten Al during hot pressing, SiC fiber is always accompanied with centerline, which causes the poorbonding of SiCf/Al3Ti interface. Unlike that, due to the adding of Ti barrier layer, SiC fibers are separated from centerlineand metallurgically bonded with Al3Tiintermetallic in the optimized composite. The compression testing results proved thatthe optimized SiCf-Ti/Al3Ti composite possesses superior strength and toughness compared with those of the non-optimizedcomposite. Besides, the extending of cracks along centerline often leads to large-scale centerline splitting and untimelySiCf/Al3Ti interface debonding in non-optimized composite. Nevertheless, cracks formed in optimized composite tend topropagate at the interfacial zone between layers instead of cutting off Al3Tilayer along its mid-plane. Moreover, ascribedto the well-bonded SiCf/Al3Ti interface, SiC fibers play an important role in strengthening and toughening the optimizedSiCf-Ti/Al3Ti composite by fiber bridging mechanism.

Load Forecasting Based on LSTM Neural Network and Applicable to Loads of “Replacement of Coal with Electricity”

Chen Zexi,Zhang Delong,Jiang Haoran,Wang Longze,Chen Yongcong,Xiao Yang,Liu Jinxin,Zhang Yan,Li Meicheng 대한전기학회 2021 Journal of Electrical Engineering & Technology Vol.16 No.5

With the complete implementation of the “Replacement of Coal with Electricity” policy, electric loads borne by urban power systems have achieved explosive growth. The traditional load forecasting method based on “similar days” only applies to the power systems with stable load levels and fails to show adequate accuracy. Therefore, a novel load forecasting approach based on long short-term memory (LSTM) was proposed in this paper. The structure of LSTM and the procedure are introduced firstly. The following factors have been fully considered in this model: time-series characteristics of electric loads; weather, temperature, and wind force. In addition, an experimental verification was performed for “Replacement of Coal with Electricity” data. The accuracy of load forecasting was elevated from 83.2 to 95%. The results indicate that the model promptly and accurately reveals the load capacity of grid power systems in the real application, which has proved instrumental to early warning and emergency management of power system faults. With the complete implementation of the “Replacement of Coal with Electricity” policy, electric loads borne by urban power systems have achieved explosive growth. The traditional load forecasting method based on “similar days” only applies to the power systems with stable load levels and fails to show adequate accuracy. Therefore, a novel load forecasting approach based on long short-term memory (LSTM) was proposed in this paper. The structure of LSTM and the procedure are introduced fi rstly. The following factors have been fully considered in this model: time-series characteristics of electric loads; weather, temperature, and wind force. In addition, an experimental verifi cation was performed for “Replacement of Coal with Electricity” data. The accuracy of load forecasting was elevated from 83.2 to 95%. The results indicate that the model promptly and accurately reveals the load capacity of grid power systems in the real application, which has proved instrumental to early warning and emergency management of power system faults.

SiC IGBT degradation mechanism investigation under HV‑H3TRB tests

Ziming Wu,Zongbei Dai,Jian Zhou,Huafeng Dong,Wencan Wang,Feiwan Xie,Haoran Wang,Jiahui Yan,Xiyu Chen,Shaohua Yang,Fugen Wu 전력전자학회 2024 JOURNAL OF POWER ELECTRONICS Vol.24 No.2

The high voltage-high humidity-high temperature reverse bias (HV-H3TRB) test was utilized to evaluate the reliability of silicon carbide insulated gate bipolar transistors (SiC IGBTs). Moisture invasion often induces termination/passivation and metal corrosion. Therefore, the HV-H3TRB test is generally used to assess termination / passivation robustness. However, under the HV-H3TRB test conditions, gate quality degradation may occur. In this study, the dominant degradation mechanism of SiC IGBTs was investigated. The changes of the most sensitive static characteristics (e.g., threshold voltage, breakdown voltage, and leakage current) were recorded. The threshold voltage decreased and leakage current increased substantially after > 1000 h of HV-H3TRB tests under 85 ℃/85% RH climate conditions. Capacitance-voltage (C-V) curve measurements indicated that the mobile ions at the SiC/SiO2 interface or in the gate oxide likely caused the threshold-voltage instability in the SiC IGBTs after the HV-H3TRB tests. This instability can be recovered by applying a negative gate bias. Subsequent failure analysis confirmed no corrosion of metals or termination/passivation in the device, which indicates the robustness of the passivation (consisting of phosphor-silicate glass and Si3N4). Therefore, the gate quality appears to be a significant reliability risk for SiC IGBTs under high humidity, high temperature, and high voltage conditions.

Structural Damage Detection using Deep Convolutional Neural Network and Transfer Learning

Chuncheng Feng,Hua Zhang,Shuang Wang,Yonglong Li,Haoran Wang,Fei Yan 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.10

During the long-term operation of hydro-junction infrastructure, water flow erosion causes concrete surfaces to crack, resulting in seepage, spalling, and rebar exposure. To ensure infrastructure safety, detecting such damage is critical. We propose a highly accurate damage detection method using a deep convolutional neural network with transfer learning. First, we collectedimages from hydro-junction infrastructure using a high-definition camera. Second, we preprocessed the images using an imageexpansion method. Finally, we modified the structure of Inception-v3 and trained the network using transfer learning to detectdamage. The experiments show that the accuracy of the proposed damage detection method is 96.8%, considerably higher thanthe accuracy of a support vector machine. The results demonstrate that our damage detection method achieves better damagedetection performance.

Microstructure Evolution and Mechanical Performances of SiCf Reinforced (Al3Ti + Al3Ni)-Based Metallic–Intermetallic Laminate Composite

Yuqiang Han,Qinghua Que,Ran Cheng,Ran Cheng,Chunfa Lin,Wenqing Han,Enhao Wang,Junyi Zhu,Haoran Yan 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.10

In present work, a novel SiCfreinforced (Al3Ti + Al3Ni)-based metallic–intermetallic laminate (Ti–(Al3Ti + Al3Ni)/SiCf-MIL) composite without centerline defect was prepared using Ti, Al foils, NiTi wires and SiC fibers by vacuum hot pressingsintering method. Electron backscatter diffraction was employed to characterize the microstructure and phase constituents ofTi–(Al3Ti + Al3Ni)/SiCf-MIL composite during various stages of preparation process. The elimination mechanism of intermetalliccenterline was discussed. Besides, quasi-static compressive performance and fracture toughness of the synthesizedcomposite were investigated. The experimental results indicated that as reaction time increasing, the NiTi/Al interfacialreaction occurred prior to the Ti/Al interfacial reaction to form an Al3Ti/Al3Ni zone. Then, the oxides gathered at the frontof Ti/Al interfacial reaction layer were dispersed in the intermetallic layer rather than being pushed together to generate thecenterline due to the Al3Ti/Al3Ni zone. After reaction, there were no residual NiTi phases and intermetallic layers mainlyconsisting of Al3Tiand Al3Niphases were obtained in this composite. In addition, high angle grain boundaries in Al3Tigrains occupied a large proportion, conversely, low angle grain boundaries dominated in Al3Nigrains. Furthermore, stressconcentration appears at the interface between layers instead of along the middle plane of intermetallic layer. Moreover,both compressive strength and fracture toughness of the composite are superior in comparison with SiCfreinforced Ti–Al3Timetallic–intermetallic laminate composite (Ti–Al3Ti/SiCf-MIL) ascribed to the elimination of centerline.