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| 1 | A Model to Predict Stall Inception of Transonic Axial Flow Fan/Compressors显示文摘A stall inception model for transonic fan/compressors is presented in this paper. It can be shown that under some assumptions the solution of unsteady flow field consists of pressure wave which propagates upstream or downstream, vortex wave and entropy wave convected with the mean flow speed. By further using the mode-matching technique and applying the conservation law and conditions reflecting the loss characteristics of a compressor in the inlet and outlet of the rotor or stator blade rows, a group of homogeneous equations can be obtained from which the stability equation can be derived. Based on the analysis of the unsteady phenomenon caused by casing treatments, the function of casing treatments has been modeled by a wall impedance condition which has been included in the stability model through the eigenvalues and the corresponding eigenfunctions of the system. Besides, the effect of shock waves in cascade channel on the stability prediction is also considered in the stall inception model. Finally, some numerical analysis and experimental investigation are also conducted with emphasis on the mutual comparison. | SUN Xiaofeng SUN Dakun YU Weiwei | 2011 | Chinese Journal of Aeronautics2011，24，6： | 20 |
| 2 | Recent development of casing treatments for aeroengine compressors显示文摘Casing treatment is a mature stabilization technique which has been widely applied on aero-engines for modern aircrafts and turbo-chargers for automobiles. After the investigations of half century since the 1960 s, this technique has been well developed for various configurations with different effectiveness. From the perspective of stabilization mechanism, this paper roughly categorizes the configurations of casing treatment into two types: traditional ones which work by affecting the flow structure of blade tip region; a novel one named as Stall Precursor-Suppressed(SPS) casing treatment. The effectiveness of both types will be demonstrated for their applications on axial compressors and centrifugal compressors with uniform or distorted inlet. And the stabilization mechanism of casing treatments for regular types and SPS one will also be explained respectively. In addition, this review will summarize the methodologies of casing treatments with the numerical simulations for regular grooved configurations and the eigenvalue approach for SPS casing treatment.Looking forward to the future of compressor stabilization, casing treatment technique will still exist as a general and inexpensive option, and the exploration for its effectiveness and mechanism will be deeper with the development of computational fluid dynamics and advanced measurement techniques. | Xiaofeng SUN Xu DONG Dakun SUN | 2019 | Chinese Journal of Aeronautics2019，32，1： | 16 |
| 3 | Flow Stability Model for Fan/Compressors with Annular Duct and Novel Casing Treatment显示文摘A three-dimensional compressible flow stability model is presented in this paper, which focuses on stall inception of multi-stage axial flow compressors with a finite large radius annular duct configuration for the first time. It is shown that under some assumptions, the stability equation can be obtained yielding from a group of homogeneous equations. The stability can be judged by the non-dimensional imaginary part of the resultant complex frequency eigenvalue. Further more, based on the analysis of the unsteady phenomenon caused by casing treatment, the function of casing treatment has been modeled by a wall impedance condition which is included in the stability model through the eigenvalues and the corresponding eigenfunctions of the system. Finally, some experimental investigation and two numerical evaluation cases are conducted to validate this model and emphasis is placed on numerically studying the sensitivity of the setup of different boundary conditions on the stall inception of axial flow fan/compressors. A novel casing treatment which consists of a backchamber and a perforated plate is suggested, and it is noted that the open area ratio of the casing treatment is less than 10%, and is far smaller than conventional casing treatment with open area ratio of over 50%, which could result in stall margin improvement without obvious efficiency loss of fan/compressors. | LIU Xiaohua SUN Dakun SUN Xiaofeng WANG Xiaoyu | 2012 | Chinese Journal of Aeronautics2012，25，2： | 12 |
| 4 | Influence of SPS casing treatment on axial flow compressor subjected to radial pressure distortion显示文摘The present work is about the stall margin enhancement ability of a kind of stall precursor-suppressed(SPS) casing treatment when fan/compressor suffers from a radial total pressure inlet distortion.Experimental researches are conducted on a low-speed compressor with and without SPS casing treatment under radial distorted inlet flow of different levels as well as uniform inlet flow.The distorted flow fields of different levels are generated by annular distortion flow generators of different heights.The characteristic curves under these conditions are measured and analyzed.The results show that the radial inlet distortion could cause a stall margin loss from 2%to30%under different distorted levels.The SPS casing treatment could remedy this stall margin loss under small distortion level and only partly make up the stall margin loss caused by distortion in large level without leading to perceptible additional efficiency loss and obvious change of characteristic curves.The pre-stall behavior of the compressor is investigated to reveal the mechanism of this stall margin improvement ability of the SPS casing treatment.The results do show that this casing treatment delays the occurrence of rotating stall by weakening the pressure perturbations and suppressing the nonlinear amplification of the stall precursor waves in the compression system. | Li Fanyu Li Jun Dong Xu Sun Dakun Sun Xiaofeng | 2017 | Chinese Journal of Aeronautics2017，30，2： | 8 |
| 5 | Umbilical cord-derived mesenchymal stem cells retain immunomodulatory and anti-oxidative activities after neural induction显示文摘The immunomodulatory and anti-oxidative activities of differentiated mesenchymal stem cells contribute to their therapeutic efficacy in cell-replacement therapy. Mesenchymal stem cells were isolated from human umbilical cord and induced to differentiate with basic fibroblast growth factor, nerve growth factor, epidermal growth factor, brain-derived neurotrophic factor and forskolin. The mesenchymal stem cells became rounded with long processes and expressed the neural markers, Tuj1, neurofilament 200, microtubule-associated protein-2 and neuron-specific enolase. Nestin expression was significantly reduced after neural induction. The expression of immunoregulatory and anti-oxidative genes was largely unchanged prior to and after neural induction in mesenchymal stem cells. There was no significant difference in the effects of control and induced mesenchymal stem cells on lymphocyte proliferation in co-culture experiments. However, the expression of human leukocyte antigen-G decreased significantly in induced neuron-like cells. These results suggest that growth factor-based methods enable the differentiation of mesenchymal stem cell toward immature neuronal-like cells, which retain their immunomodulatory and anti-oxidative activities. | Jianjun Li Dong Li Xiuli Ju Qing Shi Dakun Wang Fengcai Wei | 2012 | Neural Regeneration Research2012，7，34： | 5 |
| 6 | Experimental investigation on SPS casing treatment with bias flow显示文摘Generally, casing treatment(CT) is a passivity method to enhance the stall margin of fan/compressor. A novel casing treatment based on the small disturbance theory and vortex and wave interaction suggestion is a method combining passive control and active control, which has been proved effective at enhancing the stall margin of fan/compressor in experiment. In order to investigate the mechanism of this kind of casing treatment, an experimental investigation of a stall precursor-suppressed(SPS) casing treatment with air suction or blowing air is conducted in the present paper. The SPS casing treatment is designed to suppressing stall precursors to realize stall margin enhancement in turbomachinery. The experimental results show that the casing treatment with blowing air of small quantity can improve the stall margin by about 8% with about 1% efficiency loss. By contrast, the SPS casing treatment with micro-bias flow does not improve the stall margin much more than that without bias flow, even worse. Meanwhile, the present investigation has also attempted to reveal the mechanism of stall margin improvement with the casing treatment.It is found that the stall margin improvements vary with the modification of the unsteady shedding flow and the unsteady wall boundary impedance. The experimental results agree fairly well with the theoretical prediction using a flow stability model of rotating stall. | Dong Xu Liu Xiaohua Sun Dakun Sun Xiaofeng | 2014 | Chinese Journal of Aeronautics2014，27，6： | 5 |
| 7 | Extraordinary simultaneous enhancement of the coercivity and remanence of dual alloy HRE-free Nd-Fe-B sintered magnets by post-sinter annealing显示文摘Post-sinter annealing process plays an important role in the microstructures and magnetic properties of the Nd-Fe-B sintered magnets.In this paper,systematically investigated are the magnetic properties and microstructures of the as-sintered and post-sinter annealed Nd-Fe-B magnets with Pr-Fe-Ga boundary addition.Two choice consecutive annealing methods are adopted at high and low temperatures,namely the 1 st annealing at 880℃ for 2 h and then the 2^(nd) annealing at 440℃ for 3 h.It is exceptional to find out that both the remanence and coercivity are improved after 2^(nd) annealing process for this type of magnet.The coercivity is hugely increased from 10.09 kOe for the as-sintered sample to 17.19 kOe for the 2^(nd) annealed magnet,with a significant increment of 70.37%in coercivity.The extraordinary magnetic properties of B_(r)=14.44 kGs,H_(cj)=17.19 kOe and(BH)_(max)=51.08 MGOe are obtained for the designated Nd-Fe-B sintered magnets without heavy rare earth(HRE)elements manufactured by dual alloy method.The Curie temperature is monotonically decreased from 634 K to 602 K while the c-axis alignment degree is optimized after annealing.Microstructural observation and analysis indicate that the elemental distribution patterns are altered after the 2^(nd) annealing.The diffusion of the aggregate(Pr,Nd,Cu,Ga)-rich phase from triple junctions into the grain boundary regions is ascribed to the formation of thin and continuous grain boundary layer,which is critical to improve the microstructures and magnetic properties. | Qingfang Huang Qingzheng Jiang Jifan Hu Sajjad Ur Rehman Gang Fu Qichen Quan Jixiang Huang Deqin Xu Dakun Chen Zhenchen Zhong | 2022 | Journal of Materials Science & Technology2022，，11： | 3 |
| 8 | Prediction of stall inception in multi-stage compressors based on an eigenvalue approach显示文摘A stability model for multi-stage compressor is developed on the basis of the eigenvalue approach.This model assumes that the unsteady flow field can be decomposed into pressure,vortex and entropy waves.Besides,a linear cascade of blades is modeled by three-dimensional semi-actuator disk theory and the characteristics of steady flow field are also considered in the present model.The connection between the analytical solution for stator,rotor and gap can be established by applying mode matching approach,the relevant stability equation can be expressed in the form of matrix,while the compressor system stability can be judged by the imaginary part of the matrix eigenvalue.The capacity of the stall inception model to predict the stall inception point of multi-stage compressor is assessed against the experimental data of National Aeronautics and Space Administration(NASA) two stage fan.The theoretical results show that this model can predict the stall onset points of a two-stage fan at different operating speeds with a reasonable accuracy. | CHENG FanJie SUN DaKun DONG Xu SUN XiaoFeng | 2017 | Science China(Technological Sciences)2017，60，8： | 3 |
| 9 | Effect of system response on partial surge initiated instability in a transonic axial flow compressor显示文摘Partial surge is a type of instability inception in transonic compressors and occurs in the form of axisymmetric low-frequency disturbances localized in the hub region.Previous studies illustrate that the frequency of partial surge is set by the Helmholtz frequency of the entire system,which motivates to propose a hypothesis that the system response performs an important role in the formation of partial surge.For further verification,a series of experiments are conducted to explore the link between the propagating of the partial surge and the system feedback in this study.In the first case,an additional test point is set on the wall of the plenum to detect the system response.Combining the flow behaviors inside the plenum with the disturbances in the rotor tip and stator hub/tip regions,the effects of the system feedback on the occurrence of the continuous disturbances and the rotating stall cells are illustrated.In the second case,a screen is mounted at the compressor outlet to prevent positive feedback from the plenum.The experimental results demonstrate that in the absence of system feedback,it is the occurrence of spike-type stall inception that leads to the flow instability instead of that of partial surge.In addition,three flow phenomena in the second case are discussed,including the occurrence of the single pulse,the unstable process during the stall evolution and the switch of instability inception. | Tianyu PAN Zhaoqi YAN Dakun SUN Simin LI Mengzong ZHENG Qiushi LI | 2022 | Chinese Journal of Aeronautics2022，35，2： | 2 |
| 10 | A novel mapping algorithm for three-dimensional network on chip based on quantum-behaved particle swarm optimization显示文摘在芯片上三维的网络印射是在关于芯片的三维的网络的研究的一个关键问题。直接使用的印射的算法的质量影响在 IP 核心之间的通讯效率并且在电源消费的优化和整个薄片的产量起一个重要作用。在这篇论文,基本概念和薄片上的三维的网络的相关工作被介绍。表现量的粒子群优化算法第一次在薄片上被用于三维的网络的印射的问题。模拟结果证明印射的算法基于粒子群算法与印射的算法相比与好一些的优化性能基于表现量的粒子群算法有更快的集中速度。它能有效地也减少在薄片上三维的网络印射的电源消费。 | Cui HUANG Dakun ZHANG Guozhi SONG | 2017 | Frontiers of Computer Science2017，11，4： | 2 |
| 11 | Response and stabilization of a two-stage axial flow compressor restricted by rotating inlet distortion显示文摘This paper considers effects of Rotating Inlet Distortion(RID)on a two-stage axial compressor and the stabilization effects of a casing treatment subjected to the considered RID.In multispool engines,the downstream compressor suffers a RID when the upstream fan/compressor is in rotating stall.A controlled rotating sectional screen upstream of the compressor was adopted to generate the RID in different intensities,and co-or counter spinning direction compared with the rotor.The response of the compressor to inlet distortion was interpreted as the changes of stall margin.Results show that there are two peaks for the stall margin degradation where the distortion screen rotates near 20%and 70%of the rotor’s rotational frequency,respectively.Based on the measurements taken during the pre-stall process,it is suggested that the two frequencies are associated with the eigen frequencies of the compressor.Specifically,the first is associated with a stall precursor that is suspected as an initial disturbance existing in compressor and the second is related to a spike-type stall precursor.At last,a kind of Stall Precursor-Suppressed(SPS)casing treatment was applied to enhance the compressor stability in RID conditions.The result indicates that the stall margin is improved by 6%at an average level and there is nearly no efficiency loss caused by the application of such casing treatment. | Jia LI Xu DONG Dakun SUN Ruize XU Xiaofeng SUN | 2021 | Chinese Journal of Aeronautics2021，34，9： | 2 |
| 12 | Application of Stall Warning Approach with Stall Precursor-Suppressed Casing Treatment on a Two-Stage Compressor显示文摘A stall warning approach based on aero-acoustic theory is studied in this paper. For this stall warning approach, a parameter Rc is defined to measure the periodicity of the blade-passing signal. Signal simulation is used to investigate the mechanism of the stall warning approach. The results suggest that the value of Rc is influenced by the power of the perturbations. The experiments on a two-stage compressor indicate this stall warning approach can generate a warning signal several seconds before the stall. It is demonstrated in this paper that the stall warning approach can detect the distribution and evolution of stall precursors. According to the distribution of the stall precursors, the partial stall precursor-suppressed casing treatment is applied and realized a stabilization of compressor. | XU Ruize SUN Dakun DONG Xu LI Fanyu SUN Xiaofeng LI Jia | 2019 | Journal of Thermal Science2019，28，5： | 2 |
| 13 | Digitalization for supply chain resilience and robustness: The roles of collaboration and formal contracts显示文摘Black swan events such as the coronavirus (COVID-19) outbreak cause substantial supply chain disruption risks to modern companies. In today’s turbulent and complex business environment, supply chain resilience and robustness as two critical capabilities for firms to cope with disruptions have won substantial attention from both the academia and industry. Accordingly, this study intends to explore how digitalization helps build supply chain resilience and robustness. Adopting organizational information processing theory, it proposes the mediating effect of supply chain collaboration and the moderating effect of formal contracts. Using survey data of Chinese manufacturing firms, the study applied structural equation modelling to test the research model. Results show that digitalization has a direct effect on supply chain resilience, and supply chain collaboration can directly facilitate both resilience and robustness. Our study also indicates a complementary mediating effect of supply chain collaboration on the relationship between digitalization and supply chain resilience and an indirect-only mediation effect on the relationship between digitalization and supply chain robustness. Findings reveal the differential roles of digitalization as a technical factor and supply chain collaboration as an organizational factor in managing supply chain disruptions. Paradoxically, formal contracts enhance the relationship between digitalization and supply chain resilience but weaken the relationship between supply chain collaboration and supply chain resilience. The validation of moderating effects determines the boundary conditions of digitalization and supply chain collaboration and provides insights into governing supply chain partners’ behavior. Overall, this study enhances the understanding on how to build a resilient and robust supply chain. | Ying LI Dakun LI Yuyang LIU Yongyi SHOU | 2023 | Frontiers of Engineering Management2023，10，1： | 2 |
| 14 | Application of health risk assessment on environmental assessment of quality显示文摘 | WANG Dakun LI Jianxin | 1995 | Environmental Pollution and Control1995，17，6： | 1 |
| 15 | Multi-Canans and Acculturation显示文摘 | Wang Dakun | 1998 | Guidelines Vol 20 No 11998，1998，： | 1 |
| 16 | A Game Theoretic Approach for Inter-Network Interference Mitigation in Wireless Body Area Networks显示文摘Wireless Body Area Network(WBAN) is an emerging technology to provide real-time health monitoring and ubiquitous healthcare services. In many applications, multiple wireless body area networks have to coexist in a small area, resulting in serious inter-network interference. This not only reduces network reliability that is especially important in emergency medical applications, but also consumes more power of WBANs. In this paper, an inter-network interference mitigation approach based on a power control algorithm is proposed. Power control is modeled as a non-cooperative game, in which both inter-network interference and energy efficiency of WBANs are considered. The existence and uniqueness of Nash Equilibrium in the game are proved, and an optimal scheme based on best response is proposed to find its Nash Equilibrium. By coordinating the transmission power levels among networks under interference environment, the total system throughput can be increased with minimum power consumed. The effectiveness of the proposed method has been illustrated by simulation results, where the performance of the proposed approach is evaluated in terms of overall utility and power efficiency and convergence speed. | Du Dakun Hu Fengye Wang Feng Wang Zhijun Du Yu Wang Lu | 2015 | China Communications2015，12，9： | 1 |
| 17 | Forward scattering light ofdroplets containing different size Inclusions显示文摘 | Wu Dakun Zhou Yanping | 2009 | Appl Opt2009，48，： | 1 |
| 18 | Promoting Communicative Activities in Grammar Teaching in China显示文摘 | Wang Dakun | 1999 | Asian Englishes1999，，1： | 1 |
| 19 | Activation of Ras/Erk Pathway by a Novel MET-interacting Protein RanBPM显示文摘 | Dakun Wang Zaibo Li Edward M | 2002 | J Biol Chem2002，39，36： | 1 |
| 20 | Comparison of Acoustic Radiation Force Impulse Imaging and Transient Elastography for Non-invasive Assessment of Liver Fibrosis in Patients with Chronic Hepatitis B显示文摘 | Dakun Zhang Min Chen Ruifang Wang Yang Liu Dedong Zhang Liping Liu Guangde Zhou | 2014 | Ultrasound in Medicine & Biology2014，，： | 1 |
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