Research on active flow control to reduce aerodynamic drag of mira notchback model

Yingchao Zhang,Ruizhuo Zhou,Jinji Li,Hui Zhu,Haipeng Liu,Zhe Zhang,Chengchun Zhang 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.11

The lattice Boltzmann method, combined with the boundary layer model and the very large eddy simulation method, was used to simulate the MIRA notchback model to obtain an accurate unsteady flow field and a more reliable mean flow field. Based on the analysis of the tail flow state, jet holes were set up at the model tail. To analyze the effects of different jet states on the aerodynamic performance, constant jet method was used to explore the optimal values of blowing and sucking conditions, jet hole diameters and jet velocities at each position. The numerical results indicate that setting up the jet scheme can reduce the drag coefficient by inhibiting the longitudinal vortex and improving the wake structure of the model. A case of single jet placing jet holes at the bottom of the rear windshield can achieve 10 % drag reduction.

Vibration mechanism and improved phenomenological model of the planetary gearbox with broken ring gear fault

Yingchao Luo,Lingli Cui,Jianyu Zhang,Jianfeng Ma 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.5

Accurate modeling of the vibration signal model of planetary gearboxes is essential for the subsequent fault diagnosis. According to the existing improved phenomenological model based on the meshing vibration, this paper conducts further investigations on the vibration mechanism of the gearbox. The time delay phenomenon of faulty ring gear tooth participating in meshing is theoretically analyzed, and the assisted phases for experimental verification are proposed and deduced. Based on the improved model, the vibration signal under the fault condition is simulated and compared with the results of traditional methods. Subsequently, the paper proposes to divide and reconstruct this signal and use the maximum correlation kurtosis deconvolution (MCKD) to enhance its impact characteristics. The results show that the phase between the fault impact and its adjacent meshing impact is consistent with the proposed assisted phase. Finally, the correctness of the vibration mechanism and the improved phenomenological model are verified experimentally.

AERODYNAMIC CHARACTERISTICS OF MIRA FASTBACK MODEL IN EXPERIMENT AND CFD

Yingchao Zhang,Jintao Zhang,Kaiguang Wu,Zijie Wang,Zhe Zhang 한국자동차공학회 2019 International journal of automotive technology Vol.20 No.4

The lasting high fuel cost has recently inspired the resurgence in drag reduction research for vehicles, which calls for a thorough understanding of the vehicle wake. The acknowledged MIRA fastback vehicle model is characterized by similar real vehicle geometry, thus it is especially suitable for the above purpose. In spite of a considerable number of previous investigations, our knowledge of flow around this model remains incomplete. This paper aims to visit turbulent flow structure behind this model. An investigation has been conducted to measure the near wake flow structure of the MIRA 1/8 scale mode, using both Particle Image Velocimetry (PIV) experimental method and Computational Fluid Dynamics (CFD) simulation method. In order to capture the flow structure accurately, PIV measurement was performed in different sections along three orthogonal directions, and the CFD method acquired additional simulation results to catch the better flow status. Through the maps of the time-averaged vorticity, the instantaneous vorticity and the handled velocity vector from the PIV and CFD methods, we found out the formation mechanism of the transient flow of fastback model and summed up the schematic of flow structure. This study not only analyzed the vortex shedding characteristics of turbulent near wake, but more importantly provided insight into the complex three-dimensional features of the flow structure in the wakes of MIRA fastback model.

문화적 거리, 흡수 능력과 중국 수출 무역 기술의 스필오버 효과 실증 연구

왕잉차오(Yingchao Wang),정응영(Yingrong Zheng) 한국콘텐츠학회 2023 한국콘텐츠학회논문지 Vol.23 No.3

문화적 거리는 국제 비즈니스 환경 중의 문화 차이, 즉 양국 간의 고객 선호도, 경쟁 유형 및 비즈니스 규칙방면 등의 차이를 평가할 수 있으며, 기술 이전 및 다국적 조직 간의 지식 공유에서 중요한 역할을 한다. 2002-2020년 패널 데이터를 기반으로 문화적 거리는 중국 수출 무역 기술의 스필오버 효과(spillover effect)에 영향을 미치는 메커니즘 및 흡수 능력의 조절 효과를 실증적으로 검증한다. 연구 결과에 따르면 문화적 거리는 중국의 수출 무역 기술 스필오버 효과에 뚜렷한 부정적 영향을 미치며, 아시아 샘플과 비아시아 샘플, 고소득 샘플과 저소득 샘플 간의 차이성이 존재한다. 혁신 능력, 인적 자본 수준 및 무역 개방도로 대표되는 흡수 능력은 문화적 거리의 수출 무역 기술 스필오버 효과에 긍정적인 조절 효과가 있다. 마지막으로 본 연구는 문화적 거리의 축소, 함축적 수출 지향식 업그레이드 전략 실시, 국가 혁신 시스템 개선, 혁신 인재 지원 강화 등의 방면에서 대책과 제안을 제시하였다. Cultural distance can measure cultural differences in the international business environment, that is, the differences between the two countries in terms of customer preferences, competition types, and business rules. It plays an important role in technical transfer and knowledge sharing between multinational organizations. Based on the transnational panel data from 2002 to 2020, this thesis studied the impact mechanism and adjustment effect of cultural distance on Chinas export trade technology overflow. The results show that the cultural distance has a significant negative impact on the overflow of Chinas export trade technology, and there are differences between Asian samples and non -Asian samples, high -income samples and low -income samples. The absorption capacity represented by innovation capabilities, human capital levels and trade openness has a positive adjustment effect on export trade technology overflowing effects. Finally, this study put forward countermeasures for reducing cultural distance, implementing connotative export -oriented upgrade strategies, improving national innovation systems, and strengthening innovative talent support.

Insect cytokine growth-blocking peptide may regulate density-dependent phase trait of cuticular melanization in the larval armyworm, Mythimna separata

Zhang Yingchao,He Juan,Zhang Yuxia,Li Yue,Yu Yang,Jiang Xingfu,Pan Weidong 한국응용곤충학회 2020 Journal of Asia-Pacific Entomology Vol.23 No.2

Growth-blocking peptide (GBP) is a 25 amino acid insect cytokine found in lepidopteran insects that has diverse biological activities such as larval growth regulation, paralysis induction, cell proliferation and stimulation of immune cells. Density-dependent phase polyphenism is a phenomenon of phenotypic plasticity in which the expression of a variety of traits can be affected by local population density. In the present study, the armyworm Mythimna separata larvae with four rearing densities (1 larva/vial, 2 larvae/vial, 4 larvae/vial and 6 larvae/vial) were tested for cuticular melanization and body weight throughout the third-fifth instar, and the functional role of GBP in regulating the changes was investigated. The results indicated that when reared at high densities, the larvae exhibited less body weight and more degree of cuticular melanization than larvae reared at low densities. The gene expression of GBP in armyworm larvae showed an initial rise and then decline trend with increased rearing densities in the third to fifth instar. Compared with control, more degree of cuticular melanization was observed in GBP-injected larvae (500 ng/larva in volume 50 μL) than that in Ringer’s solution-injected counterparts. Furthermore, the gene expression level of dopa decarboxylase and prophenoloxidase increased significantly in GBP-injected fifth instar larvae from 6 h to 12 h after injection, suggesting the role of GBP in modulating density-dependent phase trait of armyworm cuticular melanization.

Investigation of aerodynamic behaviour of a high-speed train on different railway infrastructure scenarios under crosswind

Jiqiang Niu,Yingchao Zhang,Zheng-Wei Chen,Rui Li,Huadong Yao 한국풍공학회 2022 Wind and Structures, An International Journal (WAS Vol.35 No.6

The aerodynamic behaviour of a CRH high-speed train under three infrastructure scenarios (flat ground, embankment, and viaduct) in the presence of a crosswind was simulated using a 1/8th scaled train model with three cars and the IDDES framework. The time-averaged and instantaneous flow field around the model were examined. The employed numerical algorithm was verified through a wind tunnel test, and the grid and timestep resolution analyses were conducted to ensure the reliability of the data. It was noted that the flow around the rail line was different under different infrastructure scenarios, especially in the case of the embankment, which degraded the aerodynamic performance of the train under the crosswind. The flow around the train on the flat ground and viaduct was different, although the aerodynamic performance of the train was similar in both cases. Moreover, the viaduct accidents were noted to have the most critical consequences, thereby requiring the most attention. The aerodynamic performance of the train on the windward track of the embankment under the crosswind was worse than that of the train on the leeward track. But for the other two infrastructure scenarios, the aerodynamic performance of the train on the windward track is relatively dangerous, which is mainly caused by the head car. These observations suggest that the aerodynamic behaviour of the train on an embankment under a crosswind must be carefully considered and that certain wind protection measures must be adopted around rail lines in windy areas.

A novel multistage approach for structural model updating based on sensitivity ranking

Yufeng Jiang,Yingchao Li,Shuqing Wang,Mingqiang Xu 국제구조공학회 2020 Smart Structures and Systems, An International Jou Vol.25 No.6

A novel multistage approach is developed for structural model updating based on sensitivity ranking of the selected updating parameters. Modal energy-based sensitivities are formulated, and maximum-normalized indices are designed for sensitivity ranking. Based on the ranking strategy, a multistage approach is proposed, where these parameters to be corrected with similar sensitivity levels are updated simultaneously at the same stage, and the complete procedure continues sequentially at several stages, from large to small, according to the predefined levels of the updating parameters. At every single stage, a previously developed cross model cross mode (CMCM) method is used for structural model updating. The effectiveness and robustness of the multistage approach are investigated by implementing it on an offshore structure, and the performances are compared with nonmultistage approach using numerical and experimental vibration information. These results demonstrate that the multistage approach is more effective for structural model updating of offshore platform structures even with limited information and measured noise. These findings serve as a preliminary strategy for structural model updating of an offshore platform in service.

Red Imported Fire Ant in China

Runzhi Zhang,Yingchao Li 한국응용곤충학회 2005 한국응용곤충학회 학술대회논문집 Vol.2005 No.05

Ethylene increases accumulation of compatible solutes and decreases oxidative stress to improve plant tolerance to water stress in Arabidopsis

Mengying Cui,Yingchao Lin,YUANGANG ZU,Thomas Efferth,Dewen Li,Zhonghua Tang 한국식물학회 2015 Journal of Plant Biology Vol.58 No.3

Ethylene (ET) plays an important role as signal transducer in plants in response to environmental stimuli. Under water deficient conditions, fine adjustment of osmosis and redox states through phytohormones is vital for plant resistance to drought. Here, physiological and cellular responses of ET insensitive mutants (ein2-5 and ein3-1) were analyzed under water deficiency stimulated by polyethylene glycol 6000 (PEG-6000), and compared with wild type plants (Col-0) as controls. The accumulation of compatible solutes was higher in Col-0 than in ein2-5 and ein3-1. In Col-0 plants, water stress also increased transcription of P5CS1, which encoded a key rate-limiting enzyme in proline biosynthesis. These results suggested that ET signaling is involved in increasing the up-regulation of soluble sugar and proline accumulation to adjust to osmotic stress. In addition, oxidative stress was higher in ET defective mutants than in Col-0 wild-type plants. Meanwhile, increased activities of the reactive oxygen species (ROS)-scavenging enzymes superoxide dismutase (SOD) and peroxidase (POD) were observed in ET insensitive mutants, indicating aggravated oxidative stress in ET-defective plants under drought. In conclusion, ET signaling is involved in modulating plant oxidative stress under drought conditions.

The Influence of Axial Compression Ratio on Seismic Behavior of SRUHSC Frame under Cyclic Loading

Dali Yao,Yingchao Ma,Jinqing Jia 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.2

In this paper, the seismic behavior of Steel Reinforced Ultra-High Strength Concrete (SRUHSC) frames is experimentally studied under cyclic loading. Three one story-one span frames are carried out, and the main parameter is axial compression ratio. The major purpose is to investigate the seismic behavior of frames with the increasing of axial compression ratio, meanwhile, analysis the hysteresis curve, skeleton curve, stiffness degradation, energy dissipation and residual displacements. The test results reveal that the seismic response of the frame is closely related to the failure process and failure mode of the columns, which indicates that as the axial compression ratio increases, the failure process of the entire structure and the weakening of the beam end are accelerated. Meanwhile, a change of the failure mode is also observed, accompanied by corresponding changes in the strength, stiffness andenergy dissipation capacity, and the seismic behavior of frame structure decreases.