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Experimental Investigation of Multi-Mode Vortex-Induced Vibration of Flexible Risers with Different mass ratios

China Ocean Engineering 2023年第1期37卷 1-15页

作者： WANG Yu LOU Min REN Xiao-hui LIANG Wei-xing LI Xiang DANG Peng-bo School of Petroleum Engineering China University of Petroleum(East China)Qingdao 266580China Key Laboratory of Unconventional Oil&Gas Development(China University of Petroleum(East China)) Ministry of EducationQingdao 266580China College of Civil Engineering and Architecture Shandong University of Science and TechnologyQingdao 266590China

Experiments were conducted on risers with different mass ratios to study the effect of mode conversion and spanwise correlation. The slenderness ratio of the riser model was set as 169, and the Reynolds numbers are 1600-14400. The dynamic responses of riser models versus reduced velocity were analyzed, and the spanwise displacement, frequency,and trajectory of the mode conversion from the lower to the higher mode were explored. The results revealed that the riser model with a higher mass ratio excites a higher number of modes. The conversion region of multi-mode competition exists and narrows with the increasing mass ratio. Mode conversion is continuous and manifests as the transmission of peaks and troughs in mode shape: the peaks and troughs of mode shape move up in the mode stable development region and move down in the mode conversion region. The single-mode dominating vibration exhibits a standing wave feature, and the traveling wave feature is significant in the mode conversion region. Furthermore, the frequency jump is always transmitted from the trough to the peak of the mode shape, and finally, all the axial positions vibrate at the same frequency. The trajectory in the mode conversion region deviates from the 8-shape and recovers the standard8-shape at the middle and late stages of the mode stable development region.

关键词： vortex-induced vibration dynamic response mode conversion mass ratio mode weight

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Functional composition of tall-statured trees underpins aboveground biomass in tropical forests

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Journal of Forestry Research 2023年第2期34卷 333-344页

作者： Suwash Kunwar Li-Qiu Wang Maryam Kazempour Larsary Rajeev Chaudhary Puspa Raj Joshi Arshad Ali Department of Forest Resources Management College of ForestryNanjing Forestry UniversityNanjing 210037JiangsuPeople’s Republic of China Forest Ecology Research Group College of Life SciencesHebei UniversityBaoding 071002HebeiPeople’s Republic of China Division Forest Offi ce DadeldhuraMinistry of ForestDhangadhiSudurpashchim ProvinceNepal Department of Forestry Faculty of Natural ResourcesUniversity of Guilan43619-96196 SomehsaraIran Division Forest Offi ce PahalmanpurMinistry of ForestDhangadhiSudurpashchim ProvinceNepal Institute of Forestry Tribhuvan UniversityHetauda CampusHetauda 44107Nepal

The influences of trait diversity(i.e.,the niche complementarity effect)and functional composition(i.e.,the mass ratio effect)on aboveground biomass(AGB)is a highly debated topic in forest ***,further studies are needed to explore these mechanisms in unstudied forest ecosystems to enhance our understanding,and to provide guidelines for specific forest ***,we hypothesized that functional composition would drive AGB better than trait diversity and stem size inequality in the(sub-)tropical forests of *** data from 101 forest plots,we tested 25 structural equation models(SEMs)to link elevation,stem DBH inequality,trait diversity(i.e.,trait richness,evenness,dispersion and divergence),functional composition[i.e.,community-weighted of maximum height mean(CWM of Hmax),specific leaf area(CWM of SLA),leaf dry matter content(CWM of LDMC),and wood density(CWM of WD)]and *** best-fitted SEMs indicated that CWM of Hmax promoted AGB while overruling the impacts of trait diversity indices on ***,low trait diversity indices were linked with higher AGB while overruling the effects of CWM of SLA,LDMC and WD on *** addition,AGB decreased with increasing elevation,whereas stem size inequality did not influence *** results suggest that divergent species’functional strategies could shape AGB along an altitudinal gradient in tropical *** argue that forest management practices should include plant functional traits in the management plan for the co-benefits of biodiversity conservation and carbon sequestration that underpins human wellbeing.

关键词： Functional traits mass ratio Niche complementarity Niche overlap Topography

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Mineralogical and sink-float studies of Jajarm low-grade bauxite

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International Journal of Minerals,Metallurgy and Materials 2010年第3期17卷 251-256页

作者： Mohammad Zarbayani Esmaeil Jorjani Mirsaleh Mirmohammadi Mohammad Taghi Shadloo Mohammad Noaparast Science and Research Branch Islamic Azad University School of Mining Engineering University of Tehran Jajarm Alumina Company

Jajarm＇s bauxite deposits are mainly diasporic, and they have a low mass ratio of Al2O3/SiO2. It is necessary to increase the run-of-mine mass ratio before feeding the material to the Bayer process. Chemical analysis indicated that the low-grade bauxite sample from Jajarm contained 43.9wt% Al2O3 and 13.35wt% SiO2, resulting in a mass ratio of 3.29. According to mineralogical studies, the presence of aluminosilicate minerals such as kaolinite, illite, and quartz was the main reason for the decrease of the mass ratio. Microscopic observations revealed that, with the size reduction from -1000＋710 to -38 μm, the liberation degree of diaspore increased from 10% to 60%, and that of aluminosilicates increased from 20% to 85%. Heavy liquids with the densities of 2.8, 3.0, 3.2, and 3.4 g/cm3 were used to evaluate the heavy media separation in three sizes, i.e., -3350＋710, -710＋212, and -212＋125 μm. Laboratory studies confirm that the density of 3.2 g/cm3 can produce the concentrates （in sunk fractions） with recoveries of 89.09%, 91.24%, and 84.68% with the Al2O3/SiO2 mass ratios of 5.03, 5.16, and 5.15 for the -3350＋710, -710＋212, and -212＋ 125 μ m sizes, respectively.

关键词： bauxite diaspore aluminosilicate mass ratio heavy media

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Variation of Added mass and Its Application to the Calculation of Amplitude Response for A Circular Cylinder

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China Ocean Engineering 2007年第3期21卷 429-437页

作者：王艺陈伟民林缅 Institute of Mechanics Chinese Academy of Sciences

In the present study, analyzed are the variation of added mass for a circular cylinder in the lock-in （synchronization） range of vortex-induced vibration （VIV） and the relationship between added mass and natural frequency. A theoretical minimum value of the added mass coefficient for a circular cylinder at lock-in is given. Developed are semi-empirical formulas for the added mass of a circular cylinder at lock-in as a function of flow speed and mass ratio. A comparison between experiments and numerical simulations shows that the semi-empirical formulas describing the variation of the added mass for a cireular cylinder at lock-in are better than the ideal added mass. In addition, computation models such as the wake oscillator model using the present formulas can predict the amplitude response of a circular cylinder at lock-in more accurately than those using the ideal added mass.

关键词： vortex-induced vibration added mass lock-in mass ratio natural frequency

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Physical Modeling and Parametric Study on Two-Degree-of-Freedom VIV of A Cylinder near Rigid Wall

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China Ocean Engineering 2009年第1期23卷 119-132页

作者：杨兵高福平李东晖吴应湘 Institute of Mechanics Chinese Academy of Sciences

Unlike most previous studies on the transverse vortex-induced vibration（VlV） of a cylinder mainly under the wallfree condition （Williamson ＆ Govardhan, 2004）, this paper experimentally investigates the vortex-induced vibration of a cylinder with two degrees of freedom near a rigid wall exposed to steady flow. The amplitude and frequency responses of the cylinder are discussed. The lee wake flow patterns of the cylinder undergoin^g VIV were visualized by employing the hydrogen bubble technique. The effects of the gap-to-diameter ratio （eo/D） and the mass ratio on the vibration amplitude and frequency are analyzed. Comparisons of VIV response of the cylinder are made between one degree （only transverse） and two degrees of freedom （streamwise and transverse） and those between the present study and previous ones. The experimental observation indicates that there are two types of streamwise vibration, i.e. the first streamwise vibration （FSV） with small amplitude and the second streamwise vibration （SSV） which coexists with transverse vibration. The vortex shedding pattern for the FSV is approximately syrmnetric and that for the SSV is ahernate. The first streamwise vibration tends to disappear with the decrease of eo/D. For the case of large gap-to-dianeter ratios （ e.g. eo/D = 0. 54 ～ 1.58）, the maximum amplitudes of the second streamwise vibration and transverse one increase with the increasing gap- to-diameter ratio. But for the case of small gap-to-diameter ratios （e. g. eo/D= 0. 16, 0.23）, the vibration amplitude of the cylinder increases slowly at the initial stage （i.e. at small reduced velocity Vr）, and across the maximum amplitude it decreases quickly at the last stage （i.e. at large Vr）. Within the range of the examined small mass ratio （m 〈 4）, both streamwise and transverse vibration amplitude of the cylinder decrease with the increase of mass ratio for the fixed value of Vr- The vibration range （ in terms of Vr） tends to widen with the decrease of the mass

关键词： vortex-induced vibration cylinder near a wall two degrees of freedom steady flow gap-to-diameter ratio mass ratio

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Preparation and Properties of Cereal-Metal Complex Films

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复旦学报（自然科学版） 2007年第5期46卷 770-页

作者： Xian-Hua He, Si-Qian Wang, Mei-Yu Huang, Ying-Yan Jiang(4060 Group,Institute of Chemistry,The Chinese Academy of Sciences Zhongguancun Beijing 100080,China) 4060 Group Institute of ChemistryThe Chinese Academy of Sciences Beijing Zhongguancun 100080

1 Results Various kinds of biodegradable polymer materials have been researched[1]. In our previous papers,cereals such as wheat,buckwheat,glutinous rice and nonglutinous rice were polycondenced with citric acid and polysilicic acid to prepare copolymer films respectively[2,3].These copolymer fims have relatively good mechanical properties but the water proofness is not so ***,some cereals such as wheat,glutinous rice,nonglutinous rice,kaoliang,millet and maize were reacted with copper chlorid...

关键词： cereal-metal complex film metal chloride mass ratio

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