Design and Optimization for the Windowless Target of the China Nuclear Waste Transmutation Reactor

Cheng, Desheng,Wang, Weihua,Yang, Shijun,Deng, Haifei,Wang, Rongfei,Wang, Binjun Korean Nuclear Society 2016 Nuclear Engineering and Technology Vol.48 No.2

A windowless spallation target can provide a neutron source and maintain neutron chain reaction for a subcritical reactor, and is a key component of China's nuclear waste transmutation of coupling accelerator and subcritical reactor. The main issue of the windowless target design is to form a stable and controllable free surface that can ensure that energy spectrum distribution is acquired for the neutron physical design when the high energy proton beam beats the lead-bismuth eutectic in the spallation target area. In this study, morphology and flow characteristics of the free surface of the windowless target were analyzed through the volume of fluid model using computational fluid dynamics simulation, and the results show that the outlet cross section size of the target is the key to form a stable and controllable free surface, as well as the outlet with an arc transition. The optimization parameter of the target design, in which the radius of outlet cross section is $60{\pm}1mm$, is verified to form a stable and controllable free surface and to reduce the formation of air bubbles. This work can function as a reference for carrying out engineering design of windowless target and for verification experiments.

Experimental Study on the Thermal Performance of Rice Straw-Mortar Composite Materials

Rongfei Zhao,Yan Qin,Hongxu Guo,Huaqian Zhang,Wei Gao,Tieliang Wang 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.1

Thermal properties of mortar block can be improved through adding straw, which is related to the type, size, amount of the straw, and so on. In order to test the thermal insulation performance of rice straw-mortar composite materials, this paper adopted response surface methodology (RSM), which employed a four-factor, three-level Box-Behnken design regarding gypsum content (% mass fraction of gypsum), straw size (mm), straw content (% mass fraction of straw) and water content (g) of rice straw-mortar composite materials as independent variables. Thermal conductivity, thermal diffusivity and thermal resistance of composite materials were response variables. The straw content and water content extremely significantly affected all the responses; the straw size had extremely significant effect on the thermal resistance as well as significant effect on the thermal conductivity. According to the optimum solution of regression equations, the optimum values of thermal conductivity, thermal diffusivity and thermal resistance were 0.048 W (m K)−1, 0.163 mm2 s−1, and 12.743 K W−1, respectively. The optimization options of gypsum content, straw size, straw content and water content were 5.01%, 20 mm, 22.7% and 0.06 g, respectively. Due to the state change of pore water, thermal conductivity of rice straw-mortar composite materials containing free water decreased seriously after complete freezing and increased slightly after 15 times freeze-thaw. During first freezing process, the thermal conductivity increased obviously with the increasing of freezing time, then increased slowly. A theoretical basis was provided by the experimental results, which was essential for the study on the thermal performance of rice straw-mortar composite materials as well as the application of similar materials.

Effects of Frequency and Amplitude of Local Dynamic Hump and Inlet Turbulence Intensity on Flow Separation Control in Low-Pressure Turbine

Rongfei Yang,Hao Wang,Dongdong Zhong,Ning Ge 한국항공우주학회 2023 International Journal of Aeronautical and Space Sc Vol.24 No.3

Dynamic hump is an active control method, which has been proved to be able to suppress laminar flow separation on the suction surface of high-loaded low-pressure turbine (LPT) blades at low Reynolds number (Re). This paper further discusses the effectiveness of dynamic hump with different parameters for flow separation control. The Pak-B cascade working at Re = 25,000 was selected as the research object, and a small-sized two-dimensional dynamic hump designed in a half-sinusoidal configuration was placed just upstream of the peak velocity point on the suction surface. At inlet free-stream turbulence intensity (FSTI or Tu) of 1.5%, the controlled cascade loss and flow mechanism under different hump-oscillating frequency and amplitude was numerically analyzed in detail. The results show that the development characteristics of vortices/separation bubbles attached to the suction surface of the blade were significantly changed under the influence of the dynamic hump, which contributed to the variations of cascade loss accordingly. When the separation bubble at the trailing edge of the hump was forced to form shedding vortices, the large-sized separation bubble on suction surface of uncontrolled cascade was replaced by small-sized vortices with a certain spacing, thus inhibited the flow separation. The increase in amplitude and frequency of hump promote the formation of shedding vortices at the trailing edge of the hump. The optimal amplitude should be slightly less than the local boundary layer thickness at the position of hump on the uncontrolled cascade. Under the optimal hump amplitude, the effective hump-oscillating frequency is 50–250 Hz, which is approximately 0.5–2.7 times of the characteristic frequency defined by blade exit velocity and the distance between the hump trailing edge and the blade trailing edge. When inlet FSTI of the controlled cascade is reduced from 1.5 to 0.08%, the profile loss is approximately unchanged due to the same characteristics of the boundary layer in the hump region and upstream.

Review of the Preparation and Structures of Si Nanowires, Ge Quantum Dots and Their Composites

Xiaokang Weng,Jie Yang,Dongze Li,Rongfei Wang,Feng Qiu,Chong Wang,Yu Yang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.14 No.4

Because the motion of charge carriers in nanowires and quantum dots is restricted within nanoscale in two and three dimensions, respectively, both nanowires and quantum dots exhibit many excellent optoelectronic properties. Particularly, with the advantage of being compatible with Si integrated circuits, Silicon nanowires (SiNWs) and germanium quantum dots (GeQDs) have been extensively studied in the past few decades. In order to explore novel physical properties, the integration of SiNWs and GeQDs has attracted great attention recently. In this paper, recent researches on the preparation methods and structures of SiNWs, GeQDs and their composites are reviewed, respectively. The synthesis of SiNWs with random distribution and ordered arrays by using vapor–liquid–solid growth mechanism and metal-assisted chemical etching technique is firstly summarized. Some special structures of SiNWs are also discussed. Furthermore, the development of some novel structures of GeQDs for further improving their optical properties is reviewed. Finally, the growth mechanism and structure evolution of SiNWs/GeQDs composites are illustrated from the view of theory and experiment. The strain inGe shell layers and SiNWs, the relationship between Ge growth mode and SiNW diameter, and the distribution of GeQDs on the radial and axial directions of SiNWs are discussed in detail. The research about the growth of SiNWs/GeQDs composite structures is in its early stage, so there are many questions that need to be resolved in future.

Review of the Synthetic Techniques and Applications of the Quantum Dots/Graphene Composites

Yong Duan,Tianjian Zeng,Tao Sun,Ling Tong,Anran Chen,Jin Zhang,Rongfei Wang,Chong Wang,Yu Yang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2018 NANO Vol.13 No.5

The Quantum Dots/Graphene (QDs/GR) composites have attracted numerous interests caused by its unique physical and chemical properties in past few decades. The shortages of the single QD and graphene materials could be remedied by the synergistic effects from QDs/GR composite materials; meanwhile, some unique phenomena and superior physical properties were also produced. The QDs/GR composites processed better photocatalytic activities, higher photon capture abilities and excellent optical responsibilities. Therefore, they were widely applied in various techniques. Here, we reviewed and discussed recent research progresses about the QDs/GR composites and focused on their industrial preparation and commercial applications. Among these synthetic methods, ion beam sputtering deposition (IBSD) and molecular beam epitaxy (MBE) were discussed in detail because they could be directly applied in commercial industry for preparing size-tunable quantum dots. In another part, the applications of the QDs/GR composites were also discussed, the advanced physical and chemical properties promoted these composites to have numerous potential for being applied in photodetectors, lithium ion batteries, solar cells, supercapacitors and other devices. The appropriate synthetic method for QDs/GR materials is highly dependent on the requirements of its applications. We firmly believe that the direct synthesis technique of ideal QDs/GR composite for specific applications is a challenge and research emphasis for scientist and engineers in future.

Systemic Reactions to Dust Mite Subcutaneous Immunotherapy: A 3-Year Follow-up Study

Xiang Dong,Nan Huang,Wenjing Li,Lintao Hu,Xiaolong Wang,Yin Wang,Ning Xiang,Guanghui Liu,Rongfei Zhu 대한천식알레르기학회 2016 Allergy, Asthma & Immunology Research Vol.8 No.5

Purpose: The incidence of allergen specific immunotherapy-related systemic reactions (SRs) varies among different studies, and many factors are likely to contribute to SRs. This study aims to investigate the incidence, characteristics, and risk factors of SRs to standardize dust mite-specific subcutaneous immunotherapy (SCIT) in Central China. Methods: All patients receiving standardized dust mites (100-100,000 SQ-U/mL; Alutard SQ, Hørsholn, Denmark) immunotherapy were followed up. Recorded data included demographics, diagnosis, patient status, pulmonary function testing results before and after each injection, allergen dosage, and details of SRs. Results: From June 2011 to August 2014, a total of 208 patients received 4,369 injections; 27 (13.0%) patients experienced 48 (1.1%) systemic reactions. Most of the SRs were grade 2 reactions (n=30, 62.5%), followed by grade 1 (n=11, 22.9%), grade 3 (n=7, 14.6%), and no fatal reactions occurred. Forty-six SRs (95.8%) occurred within 30 minutes. Higher SR rates were associated with high concentration extracts (100,000 SQ-U/mL), injections with concomitant local reactions (LRs), children, asthma and high sensitivity (skin prick test 3+/4+ and/or sIgE≥17.5 kUA/L) (P<0.05). The estimated odds of SRs increased in children (OR=6.57; 95% CI: 1.88-22.97, P=0.003), asthmatic patients (OR=4.10; 95% CI: 1.72-9.80, P=0.002), and injections with LRs (OR=2.41; 95% CI: 1.33-4.36, P=0.004).Conclusions: The incidence of SRs to dust mite SCIT was low, and multiple factors were associated with the increased incidence of SRs. Children, asthmatics and patients with concomitant LR may be prone to develop SRs.