Dynamic response of railway vehicles under unsteady aerodynamic forces caused by local landforms

Zhengwei Chen,Tanghong Liu,Ming Li,Miao Yu,Zhaijun Lu,Dongrun Liu 한국풍공학회 2019 Wind and Structures, An International Journal (WAS Vol.29 No.3

When a railway vehicle runs in crosswinds, the unsteady aerodynamic forces acting on the train induced by the vehicle speed, crosswind velocity and local landforms are a common problem. To investigate the dynamic performance of a railway vehicle due to the influence of unsteady aerodynamic forces caused by local landforms, a vehicle aerodynamic model and vehicle dynamic model were established. Then, a wind-loaded vehicle system model was presented and validated. Based on the wind-loaded vehicle system model, the dynamic response performance of the vehicle, including safety indexes and vibration characteristics, was examined in detail. Finally, the effects of the crosswind velocity and vehicle speed on the dynamic response performance of the vehicle system were analyzed and compared.

Green and Efficient Synthesis of an Adsorbent Fiber by Plasma-induced Grafting of Glycidyl Methacrylate and Its Cd(II) Adsorption Performance

Haonan Chen,Mulin Guo,Xiaohong Yao,Zhengwei Luo,Kai Dong,Zhouyang Lian,Wuji Wei 한국섬유공학회 2018 Fibers and polymers Vol.19 No.4

A new chelating adsorbent for the removal of Cd(II) from aqueous solution, PP-g-GMA-DETA fibers, is prepared by plasma induced grafting of glycidyl methacrylate (GMA) onto the surface of polypropylene (PP) fibers, followed by modification with diethylenetriamine (DETA). The effects of grafting parameters on the grafting degree are investigated. Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy prove the successful grafting of GMA onto the surfaces of PP fibers and the subsequent conversion of epoxy groups of grafted GMA to amine groups, on reaction with DETA. The adsorption performances of Cd(II) by the chelating fibers are evaluated in detail. Kinetic and isothermal parameters are also evaluated. The data fit well with the pseudo-second order and Langmuir isotherm model, respectively. The maximum adsorption capacity of Cd(II) is 46.47 mg g-1 and the prepared fibers show selective adsorbability towards target Cd(II) in presence of competing Mg(II) ions.

A Load Balancing Algorithm Based on Fair Scheduler

Shengjun Xue,Zhengwei Chen,Jingyi Chen 보안공학연구지원센터 2016 International Journal of Grid and Distributed Comp Vol.9 No.10

With Hadoop been widely used, job scheduling technology, as a key technology in Hadoop, has been developed rapidly. However, Hadoop's default scheduling algorithm Fair Scheduler when performing the task scheduler does not consider load balancing status of each node cluster system, leading to low efficiency great job. For defect fair share scheduling algorithm, and combined LATE scheduling algorithm, load balancing scheduling algorithm based on a fair share. Experimental results show that the fair share scheduling algorithm can be improved in the scheduling task when taking into account the situation of each node load balancing, improve the efficiency of large jobs.

Comparison study of the effect of bridge-tunnel transition on train aerodynamic performance with or without crosswind

Lei Zhou,Tanghong Liu,Zhengwei Chen,Wenhui Li,Zijian Guo,Xuhui He,You-Wu Wang 한국풍공학회 2021 Wind and Structures, An International Journal (WAS Vol.32 No.6

This paper studied the case of high-speed train running from flat ground to bridges and into/out of tunnels, with or without crosswind based on the Computational Fluid Dynamics (CFD) method. First, the flow structure was analyzed to explain the influence mechanisms of different infrastructures on the aerodynamic characteristics of the train. Then, the evolution of aerodynamic forces of the train during the entire process was analyzed and compared. Additionally, the pressure variation on the train body and the tunnel wall was examined in detail. The results showed that the pressure coefficient and the flow structure on both sides of the high-speed train were symmetrical for no crosswind case. By contrast, under crosswind, there was a tremendous and immediate change in the pressure mapping and flow structure when the train passing through the bridge-tunnel section. The influence of the ground-bridge transition on the aerodynamic forces was much smaller than that of the bridge-tunnel section. Moreover, the variation of aerodynamic load during the process of entering and exiting the bridge-tunnel sections was both significant. In addition, in the case without crosswind, the change in the pressure change in the tunnel conformed to the law of pressure wave propagation, while under crosswind, the variation in pressure was comprehensively affected by both the train and crosswind in the tunnel.

Sensitivity Analysis of Laser Quenching Parameters of ASTM 1045 of Disk Laser Based on Response Surface Method

Zhibin Yu,Chang Li,Zhengwei Chen,Yunfei Li,Xing Han 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.5

Laser hardening is an important branch of laser surface hardening technology, which is widely used in metallurgy, transportation,machinery manufacturing, aerospace and other fields. At present, relying entirely on experience or process trial-anderrormethod, it can not effectively reveal the transient mechanism of laser quenching of disk laser, which is not conduciveto shortening the research and development cycle and saving costs. The numerical simulation provides an effective way toobtain the dynamic evolution law of multi-field coupling in laser quenching process. In this paper, a thermo-mechanicalcoupling model of ASTM 1045 laser quenching process by disk laser is established. In the model, the temperature-dependentphysical parameters were calculated by CALPHAD method. The transient law of temperature and microstructural transformationduring quenching was obtained by solving the model. The formation and transformation degree of martensite werecharacterized by the dynamic changes of the depth and width of quenched transformation layer. The quenching structure andtransformation hardening law were observed by Axioskop 2 SEM and Zeiss-IGMA HD FE-SEM to verify the accuracy ofthe simulation results. On this basis, the process parameters of laser quenching were sampled by Monte-Carlo method basedon response surface methodology. The sensitivity effects of different process parameters on the temperature field and phasechange field of laser quenching were analyzed, which laid a theoretical foundation for the optimization of process parameters.

Yaw effects on train aerodynamics on a double-track viaduct: A wind tunnel study

Wenhui Li,Tanghong Liu,Pedro Martinez-Vazquez,Zhengwei Chen,Xiaoshuai Huo,Zijian Guo,Yutao Xia 한국풍공학회 2021 Wind and Structures, An International Journal (WAS Vol.33 No.3

The aerodynamic performance of a scaled high-speed train model mounted on a double-track viaduct was studied through a wind tunnel test. The pressure distribution of different loops and the centerline on the streamlined nose region, as well as the aerodynamic load coefficients of the leading car were explored under yaw effects ranging from β=-30° to β=30°. Results showed that Reynolds effects became independent when the wind speed surpassed 40 m/s, the corresponding Re of which equals 6.51 × 105 . The pressures recorded along the centerline of train nose for the upstream scenario, was more sensitive to the yaw effects as the largest pressure difference gradually broadened against yaw angles. In addition, the pressure coefficients along the centerline and symmetrical taps of the loops, approximately fit a quadratic relationship with respect to yaw angles. The presence of the tracks and viaduct decks somehow mitigated the intensity of the airflow at downstream side. The experimental test also revealed that, the upstream configuration provided higher mean side force, yawing, and rolling moments up to β=20° whereas over that angle the force and moments exhibited the opposite performance.

Nondestructive Early Detection of Bruising in Pear Fruit Using Optical Coherence Tomography

Yang Zhou,Jianwei Mao,Di Wu,Tiebing Liu,Yun Zhao,Wujie Zhou,Zhengwei Chen,Fangni Chen 한국원예학회 2019 원예과학기술지 Vol.37 No.1

Pear fruit is susceptible to mechanical injury during harvesting, packaging, and transportation. Optical coherence tomography (OCT) can provide information concerning chemical and microstructural changes of fruit tissues. Therefore, using OCT to evaluate fruit quality is of great significance. In this study, OCT was used for early detection of subtle bruise symptoms underneath the pear peel. First, the signal intensity versus depth in relation to the OCT images of fruit tissue was determined, which was derived from the values of the OCT signal slope (OCTSS) and 1/e light penetration depth (D1/e). Furthermore, shaping (α) and scaling (β) indices were estimated by fitting a gamma distribution function to the signal intensity profile. After mechanical injury, OCTSS, α, and β decreased and the D1/e value increased. Distribution analysis of the relationship between α versus β served as an effective method to identify tissue bruising at an early stage. In conclusion, the results suggest that OCTSS, D1/e, and the α versus β distribution are closely correlated with bruise injury in pear fruit tissues. Thus, OCT is a promising technology for early and nondestructive bruise detection.

An automated longquan celadon glaze thickness measurement method based on optical coherence tomography

Yang Zhou,Longjie Shi,Gang Ceng,Tiebing Liu,Yang Shi,Zhengwei Chen,Fenglin Wang,Yuefeng Ceng 한양대학교 세라믹연구소 2020 Journal of Ceramic Processing Research Vol.21 No.3

The thickness of glaze is one of the important indicators in the quality evaluation of Longquan celadon. But till now, there isno automatic and non-destructive method to measure it. In order to satisfy this demand, an automated method has beenproposed to measure the glaze thickness based on optical coherence tomography (OCT) technique. According to themorphological characteristics of celadon glaze in OCT image, the proposed method locates the upper and lower boundariesof the glaze layer, then the glaze thickness is automatically calculated after the axial resolution calibration of the OCT imagesfor different categories of Longquan celadon. In the experiment, the glaze OCT images of 6 different categories of Longquanceladon were applied in the glaze thickness estimation. By comparing with the physical measuring result, this method is provedto be able to measure the glaze thickness rapidly and non-destructively and the performance is enough to meet the demandof the industrial application.

Metabolomes and transcriptomes revealed the saponin distribution in root tissues of Panax quinquefolius and Panax notoginseng

Wei, Guangfei,Yang, Feng,Wei, Fugang,Zhang, Lianjuan,Gao, Ying,Qian, Jun,Chen, Zhongjian,Jia, Zhengwei,Wang, Yong,Su, He,Dong, Linlin,Xu, Jiang,Chen, Shilin The Korean Society of Ginseng 2020 Journal of Ginseng Research Vol.44 No.6

Background: Panax quinquefolius and Panax notoginseng are widely used and well known for their pharmacological effects. As main pharmacological components, saponins have different distribution patterns in the root tissues of Panax plants. Methods: In this study, the representative ginsenosides were detected and quantified by desorption electrospray ionization mass spectrometry and high-performance liquid chromatography analysis to demonstrate saponin distribution in the root tissues of P. quinquefolius and P. notoginseng, and saponin metabolite profiles were analyzed by metabolomes to obtain the biomarkers of different root tissues. Finally, the transcriptome analysis was performed to demonstrate the molecular mechanisms of saponin distribution by gene profiles. Results: There was saponin distribution in the root tissues differed between P. quinquefolius and P. notoginseng. Eight-eight and 24 potential biomarkers were detected by metabolome analysis, and a total of 340 and 122 transcripts involved in saponin synthesis that were positively correlated with the saponin contents (R > 0.6, P < 0.05) in the root tissues of P. quinquefolius and P. notoginseng, respectively. Among them, GDPS1, CYP51, CYP64, and UGT11 were significantly correlated with the contents of Rg1, Re, Rc, Rb2, and Rd in P. quinquefolius. UGT255 was markedly related to the content of R1; CYP74, CYP89, CYP100, CYP103, CYP109, and UGT190 were markedly correlated with the Rd content in P. notoginseng.