Effects of stiffening rings on the dynamic properties of hyperboloidal cooling towers

Jun-Feng Zhang,Huai Chen,Yao-Jun Ge,Lin Zhao,Shi-Tang Ke 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.49 No.5

As hyperboloidal cooling towers (HCTs) growing larger and slender, they become more sensitive to gust wind. To improve the dynamic properties of HCTs and to improve the wind resistance capability, stiffening rings have been studied and applied. Although there have been some findings, the influence mechanism of stiffening rings on the dynamic properties is still not fully understood. Based on some fundamental perceptions on the dynamic properties of HCTs and free ring structures, a concept named “participation degree” of stiffening rings was proposed and the influence mechanism on the dynamic properties was illustrated. The “participation degree” is determined by the modal deform amplitude and latitude wave number of stiffening rings. Larger modal deform amplitude and more latitude waves can both result in higher participation degree and more improvement to eigenfrequencies. Also, this concept can explain and associate the pre-existing independent findings.

AntagomiR-27a Targets FOXO3a in Glioblastoma and Suppresses U87 Cell Growth in Vitro and in Vivo

Ge, Yun-Fei,Sun, Jun,Jin, Chun-Jie,Cao, Bo-Qiang,Jiang, Zhi-Feng,Shao, Jun-Fei Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.2

Objective: To study the effect of the antagomiR-27a inhibitor on glioblastoma cells. Methods: The miR-27a expression level in specimens of human glioblastoma and normal human brain tissues excised during decompression for traumatic brain injury was assessed using qRT-PCR; The predicted target gene of miR-27a was screened out through bioinformatics databases, and the predicted gene was verified using genetic report assays; the effect of antagomiR-27a on the invasion and proliferation of glioma cells was analyzed using MTT assays and 5-ethynyl-2'-deoxyuridine (EdU) labeling. A xenograft glioblastoma model in BALB-c nude mice was established to detect the effect of antagomiR-27a on tumour growth. Results: qRT-PCR results showed that miR-27a significantly increased in specimens from glioblastoma comparing with normal human brain tissues. Th miR-27a inhibitor significantly suppressed invasion and proliferation of glioblastoma cells. FOXO3a was verified as a new target of miR-27a by Western blotting and reporter analyzes. Tumor growth in vivo was suppressed by administration of the miR-27a inhibitor. Conclusion: MiR-27a may be up-regulated in human glioblastoma, and antagomiR-27a could inhibit the proliferation and invasion ability of glioblastoma cells.

Influence of latitude wind pressure distribution on the responses of hyperbolodial cooling tower shell

Jun-Feng Zhang,Yao-Jun Ge,Lin Zhao 한국풍공학회 2013 Wind and Structures, An International Journal (WAS Vol.16 No.6

Interference effects are of considerable concern for group hyperboloidal cooling towers, but evaluation methods and results are different from each other because of the insufficient understanding on the structure behavior. Therefore, the mechanical performance of hyperboloidal cooling tower shell under wind loads was illustrated according to some basic properties drawn from horizontal rings and cantilever beams. The hyperboloidal cooling tower shell can be regarded as the coupling of horizontal rings and meridian cantilever beams, and this perception is beneficial for understanding the mechanical performance under wind loads. Afterwards, the mean external latitude wind pressure distribution, CP(θ), was artificially adjusted to pursue the relationship between different CP(θ) and wind-induced responses. It was found that the maximum responses in hyperboloidal cooling tower shell are primarily dominated by the non-uniformity of CP(θ) but not the local pressure amplitude CP or overall resistance/drag coefficient CD. In all the internal forces, the maximum amplitude of meridian axial tension shows remarkable sensitivity to the variation of CP(θ) and it’s also the controlling force in structure design, so it was selected as an indicator to evaluate the influence of CP(θ) on responses. Based on its sensitivity to different adjustment parameters of CP(θ), an comprehensive response influence factor, RIF, was deduced to assess the meridian axial tension for arbitrary CP(θ).

Performance of electrospun nanofibrous membranes for trapping of BTX aromatic hydrocarbons and heavy metal ions: Mechanisms, isotherms and kinetics

Ge, Jun Cong,Choi, Nag Jung Elsevier 2019 Journal of cleaner production Vol.217 No.-

<P><B>Abstract</B></P> <P>Fly ash (FA) was considered as an adsorbent for adsorbing some harmful substances because of its unique characteristics such as high specific surface area, porosity, functional groups, unburned carbon content in the ash, etc. In this study, FA powder with polyacrylonitrile (PAN) matrix was electrospun into a multi-functional nanofibrous membrane for trapping of BTX aromatic hydrocarbons (benzene, toluene, and xylene) and heavy metal ions. These obtained FA/PAN composites possessed the satisfactory adsorption capacity for BTX aromatic hydrocarbons and heavy metal ions including Co(II), Pb(II) and Cr(VI). The performance of electrospun PAN-based FA nanofibrous membranes for trapping of BTX compounds and heavy metal ions was investigated with emphasis on the mechanisms, isotherms and kinetics. The impact of specific surface area, pore structure, porosity and functional groups on the adsorption behavior as well as adsorbate-adsorbent physicochemical interactions (e.g., electrostatic attraction, nonpolar attraction) were discussed. The results showed that all the tested materials had the strongest adsorption capacity for trapping of xylene, followed by toluene and benzene, and for trapping of heavy metal ions followed the order: Pb(II) > Co(II) > Cr(VI). The most exciting result is that although the trapping of BTX aromatic hydrocarbons by FA/PAN nanofibrous membrane was slightly lower than that by activated carbon (AC) powder, it was about 1.48 and 5.04 times higher than that by AC powder for trapping of Co(II) and Pb(II), respectively. In addition, the initial adsorption rate of FA/PAN membrane and FA powder for heavy metal ions was significantly faster than that of AC powder.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A cheap, durable and easy-to-use fibrous membrane was fabricated by electrospinning. </LI> <LI> Trapping of heavy metal ions by tested materials followed the order: Pb(II) > Co(II) > Cr(VI). </LI> <LI> Trapping of BTX aromatic hydrocarbons by tested materials followed the order: xylene > toluene > benzene. </LI> <LI> The adsorption mechanisms of fibrous composites were proposed accordingly. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Studies on the influence factors of wind dynamic responses on hyperbolic cooling tower shells

Jun-Feng Zhang,Qing-Shuai LIU,Yao-Jun Ge,Lin Zhao 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.72 No.5

Wind induced dynamic responses on hyperbolic cooling tower (HCT) shells are complicated functions of structure and wind properties, such as the fundamental frequency fmin, damping ratio ζ, wind velocity V, correlationship in meridian direction and so on, but comprehensions on the sensitivities of the dynamic responses to these four factors are still limited and disagree from each other. Following the dynamic calculation in time domain, features of dynamic effects were elaborated, focusing on the background and resonant components σB and σR, and their contributions to the total rms value σT. The σR is always less than σB when only the maximum σT along latitude is concerned and the contribution of σR to σT varies with responses and locations, but the σR couldn’t be neglected for structural design. Then, parameters of the above four factors were artificially adjusted respectively and their influences on the gust responses were illustrated. The relationships of σR and the former three factors were expressed by fitted equations which shows certain differences from the existing equations. Moreover, a new strategy for wind tunnel tests aiming at surface pressures and the following dynamic calculations, which demands less experiment equipment, was proposed according to the influence from meridian correlationship.

Reducing volatile organic compound emissions from diesel engines using canola oil biodiesel fuel and blends

Ge, Jun Cong,Kim, Ho Young,Yoon, Sam Ki,Choi, Nag Jung Elsevier 2018 Fuel Vol.218 No.-

<P><B>Abstract</B></P> <P>Volatile organic compounds (VOCs), a group of environmental pollutants, are emitted in large quantities when fossil fuel is burned in automobiles. This research investigates the VOCs in the exhaust emissions from a common rail diesel engine fueled with canola oil biodiesel fuel (COBF), conventional diesel fuel (CDF), and B20 (20% COBF blended with 80% CDF by volume) at various engine loads (30 Nm, 80 Nm, 130 Nm) and a constant engine speed of 1500 rpm. The results indicate that the regulated emissions (CO, HC, PM) were reduced obviously when COBF and B20 were used in a CRDI diesel engine, and a larger number of VOCs (about 30 types) are emitted with CDF and the quantity emitted is greater than with B20 and COBF. The total VOC emissions (TVOC) of B20 were lower than those with the other test fuels at all experimental conditions. In addition, this paper presents a simple approach for sampling VOC emissions from diesel engines, uses a gas chromatography/mass spectrometry (GC/MS) analysis, and also confirms that COBF blended with CDF in a volume fraction of 20–80 is an excellent alternative fuel based on VOC emissions.</P>

Mathematical explanation on the POD applications for wind pressure fields with or without mean value components

Jun-Feng Zhang,Yao-Jun Ge,Lin Zhao,Huai Chen 한국풍공학회 2016 Wind and Structures, An International Journal (WAS Vol.23 No.4

The influence mechanism of mean value components, noted as P0, on POD applications for complete random fields PC(t) and fluctuating random fields PF(t) are illustrated mathematically. The critical philosophy of the illustration is introduction of a new matrix, defined as the correlation function matrix of P0, which connect the correlation function matrix of PC(t) and PF(t), and their POD results. Then, POD analyses for several different wind pressure fields were presented comparatively as validation. It's inevitable mathematically that the first eigenmode of PC(t) resembles the distribution of P0 and the first eigenvalue of PC(t) is close to the energy of P0, due to similarity of the correlation function matrixs of PC(t) and P0. However, the viewpoint is not rigorous mathematically that the first mode represents the mean pressure and the following modes represent the fluctuating pressure when PC(t) are employed in POD application. When PC(t) are employed, POD results of all modes would be distorted by the mean value components, and it's impossible to identify P0 and PF(t) separately. Consequently, characteristics of the fluctuating component, which is always the primary concern in wind pressure field analysis, can only be precisely identified with P0 excluded in POD.

Fabrication of low-cost and high-performance coal fly ash nanofibrous membranes via electrospinning for the control of harmful substances

Ge, Jun Cong,Kim, Ju Yeon,Yoon, Sam Ki,Choi, Nag Jung Elsevier 2019 Fuel Vol.237 No.-

<P><B>Abstract</B></P> <P>The use of a high-performance and low-cost electrospun nanofiber membrane to remove harmful pollutants from the air is highly valuable in terms of commercial applications. In this paper three functional materials were successfully fabricated into a low-cost, high-performance fibrous mat via a simple and one-step electrospinning technology. These materials included coal fly ash (CFA), which is an industrial waste mainly derived from coal-fired power plants with an adsorption capacity for adsorbing of volatile organic compounds (VOCs); silver nitrate (AgNO<SUB>3</SUB>), which imparts excellent antibacterial ability; and polyacrylonitrile (PAN), which serves as an electrospun substrate with high spin-ability. The binding properties of different amounts of CFA powder, AgNO<SUB>3</SUB> and PAN were observed and analyzed in detail by field emission scanning electron microscopy (FE-SEM), biological transmission electron microscopy (Bio-TEM), X-ray diffraction (XRD) and other experimental analyses. The results show that the PAN nanofibers containing 40 wt% CFA (relative to the weight of PAN) had the highest VOCs adsorption capacity compared with other membranes. Furthermore, 2 wt% AgNO<SUB>3</SUB> (relative to the weight of PAN) and 40 wt% CFA powder can be easily fabricated with and PAN nanofibers, and this electrospun PAN/CFA/AgNO<SUB>3</SUB> composite membrane has excellent antibacterial ability on Gram-negative <I>Escherichia coli</I> (<I>E. coli</I>) (ATCC 52922) and Gram-positive <I>Staphylococcus aureus</I> (<I>S. aureus</I>) (ATCC 29231) bacteria. These electrospun fibrous mats currently stand as an emerging material that has huge development potential for treatment of environmental pollutants.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Multifunctional composite coal fly ash membranes are fabricated via electrospinning. </LI> <LI> VOCs adsorption effect is related to their own molecular structure and weight. </LI> <LI> Antibacterial activity mechanism of PAN/CFA/AgNO<SUB>3</SUB> membranes has been summarized. </LI> <LI> Electrospun coal fly ash membranes have huge potential in further application. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

A Study on Application Characteristics of Canola Oil Biodiesel Fuel in a CRDI Turbocharged Diesel Engine

Jun-Cong Ge,Nag-Jung Choi 한국기계기술학회 2017 한국기계기술학회 학술대회논문집 Vol.2017 No.04

전통적인 화석 에너지 자원의 고갈과 환경오염 악화 등의 관점에서 볼 때 에너지 절약 및 배출가스의 저감은 동시에 해결해야 되는 문제로 대두되고 있다. 바이오연료는 대체연료의 하나로서 이러한 문제들을 효과적으로 해소할 수 있는 대안으로 떠오르고 있다. 따라서 본 연구에서는 커먼레일 터보과급디젤기관에 서 카놀라유 바이오디젤연료의 적용효과를 알아보기 위하여 실험적으로 고찰하였다. 실험에 사용된 연료 는 ULSD(초저황 디젤유), BD20(체적비로 20%인 카놀라유와 80% 디젤유 혼합) 및 PCO(순수한 카놀라 유)를 사용하였다. 카놀라유 바이오디젤연료의 혼합율이 증가함에 따라 입자상물질(PM)과 일산화탄소 (CO)는 크게 감소하였으며, 질소산화물(NOx)은 약간 증가하는 현상을 보였다. With depletion of conventional fossil energy resources and increased pollution, energy-saving and emission reduction problems have to be solved. Biofuels are alternative fuels that can effectively reduce these problems. Therefore, in this study, the application characteristics of canola oil biodiesel in a CRDI Turbocharged Diesel Engine was experimentally investigated. The test fuels were denoted as ULSD (ultra low sulfur diesel), BD20 (20% canola oil blended with 80% ULSD by volume), and PCO (pure canola oil), respectively. By using canola oil biodiesel, the particulate matter (PM) and carbon monoxide (CO) emissions were considerably reduced with increased BMEP. The nitrogen oxide (NOx) emissions increased only slightly due to the inherent presence of oxygen in biodiesel.

Thickness effects of aerosol deposited hygroscopic films on ultra-sensitive humidity sensors

Liang, Jun-Ge,Kim, Eun-Seong,Wang, Cong,Cho, Myung-Yeon,Oh, Jong-Min,Kim, Nam-Young Elsevier 2018 Sensors and actuators. B Chemical Vol.265 No.-

<P><B>Abstract</B></P> <P>Hygroscopic film that has a super mesoporous structure exhibits high sensitivity and fast response/recovery in humidity sensing applications. Aerosol deposition (AD) via a shock-loading-solidification preparation mechanism, which is an unexplored potential hygroscopic film preparation technique, can produce a porous microstructure, and the AD hammering effect creates various interior and surface microstructures in different-thickness films. The objective of our study was to verify the feasibility of using AD as a humidity-sensing film preparation technique, and to investigate the thickness effects of the film on its microstructure and hygroscopic properties. Hygroscopic films with thicknesses ranging from 0.1–10.0 μm were aerosol deposited with BaTiO<SUB>3</SUB> powders before undergoing a 400 °C thermal treatment. The resulting surface morphology exhibited roughness increases for thicknesses from 0.1–6.0 μm, and a decrease at 10.0 μm. The cross-sectional structure was characterized by a transitional-density grain distribution in which higher density small-sized grains could be seen in the bottom layer. Films with thicknesses of 1.5 μm and 3.0 μm achieved excellent sensitivities of 178.6 ± 7.3 pF/%RH and 299.9 ± 5.4 pF/%RH, respectively. Further, the response and recovery time for the 1.5 μm film were both less than 5 s. The current study determined the feasibility of AD-based humidity-sensing film preparation and provided a reference for optimal thickness control. The surface hydrophilicity, pore volume, and open-pore ratio were analyzed as critical factors of the thickness related humidity sensing effects, and physical modeling indicated that AD-prepared films exhibited an expanded humidity detection range, enhanced water vapor adsorption and desorption, and improved sensitivity to humidity.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Aerosol deposition can be used to prepare ultra-sensitive ceramic humidity sensors. </LI> <LI> Film-based sensors were prepared using a shock-loading solidification mechanism of aerosol deposition. </LI> <LI> Their sensitivity depends on the hydrophilicity, pore volume, and open-pore ratio. </LI> <LI> The thickness of the film regularly affects the humidity-sensing properties. </LI> </UL> </P>