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| 1 | Numerical and experimental investigation into hypersonic boundary layer transition induced by roughness elements显示文摘In this work, the Direct Numerical Simulation(DNS) and Oil-Film Interferometry(OFI)technique are used to investigate the hypersonic boundary layer transition induced by single and double roughness elements at Mach number 5. For single roughness, the DNS results showed that both horseshoe vortices and hairpin vortices caused by shear layer instability can affect the boundary layer instability. The generation of the near-wall unstable structure is the key point of boundary layer transition behind the roughness element. At the downstream of the roughness element, the interaction between horseshoe vortices and hairpin vortices will spread in the spanwise direction.For double roughness elements, the effect of the spacing between roughness elements on the transition is studied. It is found that the case of higher spacing between roughness elements is more effective for inducing transition than the lower one. The interaction between two adjacent roughness elements can suppress the evolution of horseshoe vortices in the downstream and trigger the instability of shear layer. Thus, the transition will be suppressed accordingly. | Hao DONG Shicheng LIU Xi GENG Song LIU Liming YANG Keming CHENG | 2019 | Chinese Journal of Aeronautics2019，32，3： | 6 |
| 2 | Experimental investigation of influence of strake wings on self-induced roll motion at high angles of attack显示文摘The modern high performance air vehicles are required to have extreme maneuverability,which includes the ability of controlled maneuvers at high angle of attack. However, the nonlinear and unsteady aerodynamic phenomena, such as flow separation, vortices interaction, and vortices breaking down, will occur during the flight at high angle of attack, which could induce the uncommanded motions for the air vehicles. For the high maneuverable and agile air missile, the nonlinear roll motions would occur at the high angle of attack. The present work is focused on the selfinduced nonlinear roll motion for a missile configuration and discusses the influence of the strake wings on the roll motion according to the results from free-to-roll test and PIV measurement using the models assembled with different strake wings at a = 60°. The free-to-roll results show that the model with whole strake wings(baseline), the model assembled with three strake wings(Case A)and the model assembled with two opposite strake wings(Case C) experience the spinning, while the model assembled with two adjacent strake wings(Case B), the model assembled with one strake wing(Case D) and the model with no strake wing(Case E) trim or slightly vibrate at a certain '×'rolling angle, which mean that the rolling stability can be improved by dismantling certain strake wings. The flow field results from PIV measurement show that the leeward asymmetric vortices are induced by the windward strake wings. The vortices would interact the strake wings and induce crossflow on the downstream fins to degrade the rolling stability of the model. This could be the main reason for the self-induced roll motion of the model at a = 60°. | Geng Xi Shi Zhiwei Cheng Keming | 2016 | Chinese Journal of Aeronautics2016，29，6： | 3 |
| 3 | Drag Reduction Effect for Hypersonic Lifting-Body Vehicle with Counterflowing Jet显示文摘This study takes the novel approach of using a counterflowing jet positioned on the nose of a lifting-body vehicle to explore its drag reduction effect at a range of angles of attack.Numerical studies are conducted at a freestream Mach number of 8 in standard atmospheric conditions corresponding to the altitude of 40 km.The effects of jet pressure ratio and flying angles of attack on drag reduction of the model are systematically investigated.Considering the reverse thrust generated from the counterflowing jet,the drag on the nose at hypersonic speeds could be reduced up to 66%.The maximum lift-to-drag ratio of the model is obtained at 6°;meanwhile,the counterflowing jet produces a drag reduction of 8.8%for the whole model.In addition to the nose,the counterflowing jet influences the drag by increasing the pressure drag of the model and reducing the skin friction drag of the first cone within 8°.The results show that the potential of the counterflowing jet as a means of active flow control for drag reduction is significant in the engineering application on hypersonic lifting-body vehicles. | Dong Hao Deng Fan Xie Feng Geng Xi Cheng Keming | 2018 | Transactions of Nanjing University of Aeronautics and Astronautics2018，35，5： | 2 |
| 4 | Development and application of molecular markers for TSW(thousand-seed weight)related gene BnaGRF7.C02 in Brassica napus显示文摘Brassica napus L(rapeseed)is one of the most important oil crops with large cultivated area in China.Seed size and seed weight play crucial roles for yield and harvest.In this study,a type of 15 bp-deletion in BnaGRF7.CO2 coding region was identified through sequence alignment of BnaGRF7.C02 in 42 rapeseed varieties,and associ-ation analysis indicated that the 15 bp-deletion was related to the rapeseed Thousand-Seed Weight(TSW)phenotype.Furthermore,we developed two InDel markers to identify this 15 bp InDel.The tissue-specific expression patterns showed that BnaGRF7.C02 prominently expressed in the late stage of seed development.These findings may assist in InDel markers-based breeding efforts to select higher TWS varieties and improve the crop yield of B.nqpus. | Jing Zhao Chanyu Jin Rui Geng Yixuan Xue Minqiang Tang Keming Zhu Yulong Li Duoduo Wang Shengyi Liu Xiaoli Tan | 2021 | Oil Crop Science2021，6，3： | 0 |
| 5 | Corrosion Resistance of Fused Cr_2O_3-Al_2O_3 Grains with Different Compositions显示文摘Six kinds of Cr2O3 Al2O3 fused grains ( the mass percent of Cr2O3 was 15% ,40% ,50% ,60% ,85% and 99% ,respectively) were prepared using chrome green and Al2O3 powder as starting materials by electrofusion,named as CR15,CR40,CR50,CR60,CR85, and CR99,respectively. The corrosion resistance of the six kinds of Cr2O3 Al2O3 fused grains ( 4 1 mm) was studied using rotary slag corrosion method. The results show that: ( 1) the corrosion resistance of the fused grains increases with the Cr2O3 content and the grain size increasing; ( 2) the grains of CR99 and CR85 with higher Cr2O3 content are corroded at the slag surface layer,because FeO and Al2O3 in the slag corrode the grains; FeO reacts with Cr2O3 in the aggregates forming ( Fe,Cr) 3O4 spinel firstly,and the spinel reacts with other phases forming composite spinel; when FeO is fully consumed,Al2O3 penetrated into the grains reacts with Cr2O3 forming Al2O3 Cr2O3 solid solution on the grains surface; ( 3) for CR60,the corrosion exists both in the slag surface layer and in the penetration layer; in the penetration layer,CaO and SiO2 react with Al2O3 in Al2O3 Cr2O3 solid solution forming anorthite, gehlenite, and glass phase; the grains of CR50,CR40 and CR15 have the same corrosion mechanism with CR60 in the penetration layer. | WANG Han LAN Heqing GENG Keming LV Shiping FANG Xu | 2012 | China's Refractories2012，21，2： | 0 |
| 6 | Clinical Report on Californium-252 Neutron Intraluminal Brachytherapy Combined with External Irradiation for Cervical Carcinoma Treatment显示文摘OBJECTIVE To observe the curative effects and complications of californium-252 (252Cf) neutron intraluminal brachytherapy (IBT) combined with external irradiation (El) for treatment of cervical carcinoma. METHODS From December 2000 to December 2004, 128 cases of cervical carcinoma staged intoⅡA-ⅢB according to the International Federation of Gynecology and Obstetrics (FIGO) standards were treated with 2S2Cf neutron IBT using 8-10 Gy per fraction, once a week. The total dose at reference A point was 36-40 Gy in 4-5 fractions. From the second day after 252Cf neutron IBT treatment, the whole pelvic cavity was treated with 60Coγ-ray El, applying 2 Gy per fraction, 4 times per week. After 20-25 Gy of El, the center of the whole pelvic field was blocked with 4 cm of lead in width. The total dose of El was 45-50 Gy. RESULTS The short-term therapeutic effects were CR 95.3% and PR 4.7%. The 3 and 5-year local control rates were 93.5% and 87.9%. The overall 3-year survival rate was 87.5% and for StagesⅡandⅢ, 90.9% and 81.5% respectively; the overall 5-year survival rate was 70% and for StagesⅡandⅢ, 76.2% and 61% respectively. The rate of radiation complications was 4.7% for radiation cystitis, 7.8% for radiation proctitis, 6.3% for vagina contracture and adhesion and 5.5% for protracted radiation proctitis. CONCLUSION An combination of 252Cf neutron IBT with El for treatment of cervical carcinoma can be well -tolerated by cervical carcinoma patients. The rate of local tumor control is high and radiation complications are few. | Huanyu Zhao Keming Wang Jian Sun Xin Geng Weiming Zhang | 2006 | Chinese Journal of Clinical Oncology2006，3，5： | 0 |
| 7 | Study on Microstructure and Slag Corrosion Mechanism of High Chrome Bricks for Gasifier显示文摘Research was focused on slag corrosion mechanism of high chrome bricks used for different types of gasifier by comparing the structure of high chrome bricks for petroleum coke gasifier and water-coal slurry gasifier with slag corroded test ing brick and water coal slurry gasifier through Scanning Electron Microscope (S EM) examination and X-ray diffraction. Results show that for high chrome brick used for petroleum coke gasifier, corrosion is mainly caused by Cr2O3 in the brick and V2O5 in molten slag and liquid phase generation at low temperatur e; for high chrome brick used for water-coal slurry gasifier, corrosion is caus ed by dissolution of Cr2O3 in molten slag and corrosion of ZrO2. For LIRR -HK95 brick, it performs better petroleum coke corrosion resistance than the ot hers due to the optimal composition and structure. | XU Yanqing GENG Keming LI Hongxia WANG Jinxiang RUAN Bo CHEN Renpin | 2006 | China's Refractories2006，15，1： | 0 |
| 8 | A Dynamic Memory Allocation Optimization Mechanism Based on Spark显示文摘Spark is a distributed data processing framework based on memory.Memory allocation is a focus question of Spark research.A good memory allocation scheme can effectively improve the efficiency of task execution and memory resource utilization of the Spark.Aiming at the memory allocation problem in the Spark2.x version,this paper optimizes the memory allocation strategy by analyzing the Spark memory model,the existing cache replacement algorithms and the memory allocation methods,which is on the basis of minimizing the storage area and allocating the execution area according to the demand.It mainly including two parts:cache replacement optimization and memory allocation optimization.Firstly,in the storage area,the cache replacement algorithm is optimized according to the characteristics of RDD Partition,which is combined with PCA dimension.In this section,the four features of RDD Partition are selected.When the RDD cache is replaced,only two most important features are selected by PCA dimension reduction method each time,thereby ensuring the generalization of the cache replacement strategy.Secondly,the memory allocation strategy of the execution area is optimized according to the memory requirement of Task and the memory space of storage area.In this paper,a series of experiments in Spark on Yarn mode are carried out to verify the effectiveness of the optimization algorithm and improve the cluster performance. | Suzhen Wang Shanshan Geng Zhanfeng Zhang Anshan Ye Keming Chen Zhaosheng Xu Huimin Luo Gangshan Wu Lina Xu Ning Cao | 2019 | Computers, Materials & Continua2019，，8： | 0 |
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