Water-solid Suspension Grafting of Dual Monomers on Polypropylene to Prepare Ion-imprinted Fibers for Selective Adsorption of Cr(VI)

Zhengwei Luo,Lei Li,Mulin Guo,Hui Jiang,Wenhua Geng,Wuji Wei,Zhouyang Lian 한국섬유공학회 2020 Fibers and polymers Vol.21 No.12

In this work, a new strategy was developed to prepare Cr(VI)-imprinted polypropylene (PP) fibers-based materialsfor the adsorption of Cr(VI) from water. Granular PP was modified with dual monomers (glycidyl methacrylate (GMA) andacrylamide (AM)) by water-solid suspension grafting copolymerization. Then, this fibers morphology was obtained by meltblowing. Hence, the preparation steps of the fibrous Cr(VI)-imprinted adsorbent involved surface ion-imprinting andcrosslinking. The influence of the grafting conditions on the grafting percentage was investigated. The maxima graftingpercentages of GMA and AM were 16.4 and 10.6 %, respectively. The chemically modified products showed good mobilityand stability, thus meeting the requirements of melt-blowing method. The prepared Cr(VI)-imprinted polymers showed amaximum adsorption capacity to Cr(VI) of 43.2 mg/g at pH 3. The adsorption data were well fitted by the pseudo-secondorderand Langmuir adsorption models. The adsorbent showed good selectively toward Cr(VI) in a mixed solution containingCu(II) and SO42−. The X-ray photoelectron spectroscopy demonstrated that the adsorbed Cr(VI) was partly reduced to Cr(III).

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.

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.

로즈마리(Rosmarinus officinalis L.) 극성별 용매 추출물의 생리활성 검증

이커(Ke Li),양경희(Kyeong Hee Yang),궈루(Lu Guo),추이정웨이(Zhengwei Cui),손병구(Beung Gu Son),강점순(Jum Soon Kang),이용재(Yong Jae Lee),박영훈(Young Hoon Park),제병일(Beong Il Je),최영환(Young Whan Choi) 한국생명과학회 2019 생명과학회지 Vol.29 No.1

로즈마리(Rosmarinus officinalis L.)는 식품소재로서 널리 사용되고 있으며 다양한 생리활성이 보고되어 있다. 그러나 극성이 다른 용매 추출물의 상호작용과 생리활성에 관한 연구는 잘 정립되어서 보고되지 않았다. 따라서 본 연구에서는 로즈마리 분말을 hexane, EtOAc, MeOH 그리고 95%, 70%, 50% 또는 25% EtOH 및 물로 추출한 다음, 각각의 용매 추출물의 항산화, 항비만, 항 α-glucosidase 활성 및 미백효과 등을 조사하기 위해 수행되었다. 로즈마리 추출물의 항산화 및 tyrosinase 저해 효과는 비교적 극성이 높은 50% EtOH, 25% EtOH 및 증류수 추출물이 가장 효과가 좋았다. 그러나 α-glucosidase 활성억제는 EtOH의 농도가 높은 50~95%와 MeOH 추출물에서 효과가 가장 좋았다. 지방세포의 분화억제는 70% EtOH로 처리시에 가장 효과가 좋았으며, EtOH의 농도가 70%보다 증가하거나 감소하였을 경우에는 농도에 비례하여 감소하였다. 본 실험의 결과 최적의 추출용매는 항산화, tyrosinase 저해, α-glucosidase 활성억제 및 지방세포의 분화 억제 등의 질환에 따라서 차이가 있었다. 이러한 추출용매를 고려하면 추출용매에 따라서 최적의 생리활성 성분의 종류와 함량이 차이가 있고 이로 인하여 생리활성효과도 달라진 것으로 생각된다. Rosemary (Rosmarinus officinalis L.) is widely used as a food material. Although various physiological activities of rosemary have been reported, there have been no studies on the physiological activity of solvent extracts with different polarities. Rosemary extracts were obtained by extraction of dried powder using 0%, 25%, 50%, 70%, and 95% ethanol (EtOH) in distilled water, methanol, ethyl acetate, and hexane. As these ratios of EtOH are generally chosen by default and scarcely optimized, we investigated the impact of the composition of EtOH in distilled water on extract-related characteristics, such as DPPH free radical scavenging and α-glucosidase inhibition, on the differentiation of 3T3-L1 adipocytes and inhibition of tyrosinase. Adipogenesis inhibition was highest at 70% EtOH. DPPH scavenging activity and inhibition of tyrosinase activity were reduced with 50% EtOH in water. However, inhibition of α-glucosidase activity was higher in 50% EtOH in water. The best solvents in terms of DPPH scavenging activity, inhibition of tyrosinase and α-glucosidase, and differentiation of adipocytes obtained with different concentrations of EtOH, although a lower similar activities were found with 50% ethanol. Considering the extraction solvents, a ratio of EtOH in water gives different content and constituents of compounds. These differences will give activities inhibition of adipogenesis, tyrosinase, α-glucosidase activity, and DPPH scavenging activity.

Microstructure and Mechanical Properties of Friction Stir Lap Welded Mg/Al Joint Assisted by Stationary Shoulder

Shude Ji,Zhengwei Li 대한금속·재료학회 2017 METALS AND MATERIALS International Vol.23 No.6

Using magnesium alloy as upper sheet, 3 mm-thick AZ31 magnesium alloy and 6061 aluminum alloy were joinedusing friction stir lap welding assisted by stationary shoulder. The effects of tool rotating speed on cross-sections,microstructure and mechanical properties of Mg/Al lap joints were mainly discussed. Results showed thatstationary shoulder contributed to joint formation, by which stir zones (SZ) were characterized by big onionrings after welding. Because of the big forging force exerted by stationary shoulder, the upper region of hookwas well bonded. SZ showed much higher hardness because of intermetallic compounds (IMCs). The bondingconditions at the base material (BM)/SZ interface at advancing side and the hook region played important roleson joint lap shear properties. The X-ray diffraction pattern analysis revealed that the main IMCs were Al3Mg2and Al12Mg17.

Optical Polarization Characteristics of Low-Earth-Orbit Space Targets

Zhenduo Zhang,Yuanhao Wu,Zhengwei Li 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.76 No.4

This study investigates the optical polarization characteristics of low-earth-orbit (LEO) space targets at different operating attitudes for different surface materials by analyzing these characteristics using a microfacet analysis model. Subsequently, the polarization image of a typical LEO space target was simulated, and several laboratory and outfield polarization detection experiments were conducted. Simulated and experimental results validate the effectiveness of polarization in analyzing and evaluating the operating attitudes of the LEO space targets and in identifying their material properties. Results show that the polarization images can effectively determine the constituent structure of the LEO space targets.

Safety Ontology Modeling and Verification on MIS of Ship-Building and Repairing Enterprise

( Yumei Wu ),( Zhen Li ),( Lanjie Zhao ),( Zhengwei Yu ),( Hong Miao ) 한국인터넷정보학회 2021 KSII Transactions on Internet and Information Syst Vol.15 No.4

Shipbuilding and repairing enterprise has the characteristics of many hazards and accidents. Therefore, the safety management ability of shipbuilding and repairing MIS (management information system) must be effectively guaranteed. The verification on safety management is the necessary measure to ensure and improve the safety management ability of MIS. Safety verification can not only increase the safety of MIS, but also make early warning of potential risks in management to avoid the accidents. Based on the authoritative standards in the field of safety in shipbuilding and repairing enterprise, this paper applied modeling and verification method based on ontology to safety verification of MIS, extracted the concepts and associations from related safety standards to construct axiom set to support safety verification on MIS of shipbuilding and repairing enterprise. Then, this paper developed the corresponding safety ontology modeling and verification tool-SOMVT. By the application and comparison of two examples, this paper effectively verified the safety of MIS to prove the modeling method and the SOMVT can improve the safety of MIS in a much more effective and stable way to traditional manual analysis.

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.

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.

Study of a New Imaging Strategy Based on Compressed Sensing to Shorten the Imaging Time of a Fourier Telescope

Lei Dong,Zhenwu Lu,Xinyue Liu,Zhengwei Li,Liang Wang 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.74 No.12

A Fourier telescope (FT) is an imaging system based on laser illumination and optical aperture synthesis and is suitable for imaging distant targets with high resolution through the atmosphere. The imaging time of a conventional FT is so long (about two hours) as to limit its practical applications. In order to shorten the imaging time of a Fourier telescope, we propose a new imaging system called the compressed sensing Fourier telescope (CS-FT). The image quality, the imaging time and the effects of noise of the new system are studied in detail. Based on the analysis, we find that by reasonably choosing the total sampling rate (TSR), the imaging time of the CS-FT is obviously shorter than that of the conventional FT while the image quality of the CS-FT is near that of the conventional FT. Worth noting is that with the smaller values of the low-frequency sampling rate (LSR) and the order of the sampling probability density function (OPDF), the CS-FT can achieve a better image quality. The reconstruction results of the field data show that the CS-FT can reduce the imaging time of a FT in an actual noise environment.