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Comparison of foliar nutrient concentrations between natural and artificial forests of Pinus sylvestris var. mongolica on sandy land, China 被引量:7
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作者 ZHU Jiao-jun TAN Hui +1 位作者 KANG Hong-zhang XU Mei-ling 《Journal of Forestry Research》 SCIE CAS CSCD 2006年第3期177-184,共8页
In order to examine the causes of degradation of Pinus sylvestris var. mongolica plantations on sandy land, the foliar concentrations of N, P, K and C were analyzed and compared between the field grown P. sylvestris v... In order to examine the causes of degradation of Pinus sylvestris var. mongolica plantations on sandy land, the foliar concentrations of N, P, K and C were analyzed and compared between the field grown P. sylvestris var. mongolica trees from two provenances (natural forests and plantations). The results indicated that natural tree needles had lower N, P and C concentrations, and higher K concentrations than those of plantation tree needles. For plantation tree needles, ratios of N: P, P. K and N: K increased with tree age before 45 years old; but they were not clear for the natural tree needles. Compared with the conclusions reported on Pinus spp., we found that the foliar N and P concentrations were in the optimal range for both natural and plantation tree needles. This result suggested that N or P might not be the absolute limit factors in plant nutrient for P sylvestris var. mongolica on sandy land. However, foliar K concentrations in both natural and plantation tree needles were much lower than those reported on Pinus spp. (〉4.80 g kg-1).The N: P ratio of natural needles was in the adequate ranges, but N: P ratio of plantation needles was out of the adequate ranges. These results indicated that there was a better balanced nutrition status in the natural forest than in the plantations. If only considering the foliar nutrient concentrations of P sylvestris var. mongolica from different provenances, it might be concluded that the degradation phenomenon of P. sylvestris var. mongolica plantations was not induced by nutrition deficiency of absolute nutrients of N and P, but might be induced by other mineral nutrients or by the effectiveness of N and P nutrients. The unbalanced nutrition status and relatively quick decomposition of needles in the plantations might also contribute to the degradation. 展开更多
关键词 Degradation phenomenon Forest ecosystem on sandy land N: P ratio Natural Mongolian pine Pinus sylvestris var. mongolica Plantation Mongolian pine
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The combined prognostic value of pretreatment neutrophil-to-lymphocyte ratio, lymphocyte-to-monocyte ratio, and platelet-to-lymphocyte ratio in stage IE/IIE extranodal natural killer/T-cell lymphoma 被引量:2
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作者 Xiaoying Quan 《Oncology and Translational Medicine》 2019年第3期137-146,共10页
Objective This study aimed to explore the combined prognostic value of pretreatment neutrophil-tolymphocyte ratio(NLR), lymphocyte-to-monocyte ratio(LMR), and platelet-to-lymphocyte ratio(PLR) in newly diagnosed IE/II... Objective This study aimed to explore the combined prognostic value of pretreatment neutrophil-tolymphocyte ratio(NLR), lymphocyte-to-monocyte ratio(LMR), and platelet-to-lymphocyte ratio(PLR) in newly diagnosed IE/IIE extranodal natural killer/T-cell lymphoma(ENKTL) treated with a P-Gemox regimen combined with radiotherapy or radiotherapy alone.Methods A total of 132 patients from 2009 to 2017 at the Sichuan Cancer Hospital were enrolled in the study. The cutoff values of NLR, LMR, and PLR using overall survival(OS) rate as an endpoint were obtained by the receiver operating curve. Results The cutoff value of NLR was 3.5. Patients with high NLR had significantly shorter progressionfree survival(PFS)(P < 0.001) and OS(P < 0.001) than those with low NLR. Similarly, the cutoff value of LMR was 3.0. The high LMR group had significantly longer PFS(P=0.001) and OS(P < 0.001) than the low LMR group. Similarly, the cutoff value of PLR was 191.7. The high PLR group was significantly associated with poor PFS(P < 0.001) and OS(P < 0.001) than the low PLR group. Furthermore, combining NLR, LMR, and PLR to build a new model to stratify patients into low-, intermediate-, intermediate-high-, and high-risk groups, there were also significant differences in PFS(P < 0.001) and OS(P < 0.001). The univariate analysis showed that presenting B symptoms, stage IIE, local tumor invasion, Eastern Cooperative Oncology Group score ≥ 2, elevated lactate dehydrogenase level, elevated NLR, decreased LMR, and elevated PLR were significantly associated with poor survival. The multivariate analysis demonstrated that PLR was an independent prognostic factor for both PFS(hazard ratio [HR]= 2.073, 95% confidence interval [CI]= 1.080–3.981, P = 0.028) and OS(HR = 2.127, 95% CI = 1.102–4.107, P = 0.025).Conclusion Elevated pretreatment PLR was a novel simple predictor of poor survival in patients with stage IE/IIE ENKTL. Combining NLR, LMR, and PLR could provide additional stratification. 展开更多
关键词 EXTRANODAL natural killer/T-cell neutrophil-to-lymphocyte RATIO lymphocyte-to-monocyte RATIO platelet-to-lymphocyte RATIO prognosis
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Effect of natural and synthetic fibers reinforcement on California bearing ratio and tensile strength of clay 被引量:3
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作者 Mahdi Ghasemi Nezhad Alireza Tabarsa Nima Latifi 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2021年第3期626-642,共17页
Use of environmentally friendly approaches with the purpose of strengthening soil layers along with finding correlations between the mechanical characteristics of fiber-reinforced soils such as indirect tensile streng... Use of environmentally friendly approaches with the purpose of strengthening soil layers along with finding correlations between the mechanical characteristics of fiber-reinforced soils such as indirect tensile strength(ITS)and California bearing ratio(CBR)and as well as the evaluation of shear strength parameters obtained from the triaxial test would be very effective at geotechnical construction sites.This research was aimed at investigating the influence of natural fibers as sustainable ones including basalt(BS)and bagasse(BG)as well as synthetic polyester(PET)fibers on the strength behavior of clayey soil.To this end,the effects of various fiber contents(0.5%,1%and 2%)and lengths(2.5 mm,5 mm and 7.5 mm)were experimentally evaluated.By conducting ITS and CBR tests,it was found that increasing fiber content and length had a significant influence on CBR and ITS values.Moreover,2%of 7.5 mm-long fibers led to the largest values of CBR and ITS.The CBR values of soil reinforced with PET,BS,and BG fibers were determined as 19.17%,15.43%and 13.16%,respectively.The ITS values of specimens reinforced with PET,BS,and BG fibers were reported as 48.57 kPa,60.7 kPa and 47.48 kPa,respectively.The results of the triaxial compression test revealed that with the addition of BS fibers,the internal friction angle increased by about 100%,and with the addition of PET fibers,the cohesion increased by about 70%.Moreover,scanning electron microscope(SEM)analysis was employed to confirm the findings.The relationship between CBR and ITS values,obtained via statistical analysis and used for the optimum design of road pavement layers,demonstrated that these parameters had high correlation coefficients.The outcomes of multiple linear regression and sensitivity analysis also confirmed that the fiber content had a greater effect on CBR and ITS values than fiber length. 展开更多
关键词 Natural fibers Synthetic fibers Indirect tensile strength(ITS) California bearing ratio(CBR) Reinforced soil
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The Natural Probability Distribution of Load and Unload Response Ratio
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作者 Chen Qifu,Yin Xiangchu,and Ma LiCenter for Analysis and Prediction,SSB,Beijing 100036,China 《Earthquake Research in China》 1997年第1期43-49,共7页
In this paper,the Gutenberg-Richter model is used to generate seismic events.The events that satisfy the random distribution are also generated.With those events,the natural probability distribution of Load and Unload... In this paper,the Gutenberg-Richter model is used to generate seismic events.The events that satisfy the random distribution are also generated.With those events,the natural probability distribution of Load and Unload Response Ratio(LURR),which measures quantitatively the degree of instability of a nonlinear system,is discussed.The study is based on stress energy release,which is chosen as the response of nonlinear system F3.The comparative results from the observation catalogue and generating data are also studied.It is revealed that the natural probability of LURR is mostly stable when the sample number is sufficient.The lower the natural probability of LURR,the more the precursory is information it may contain.The influence of Y3 resulting from the sample number and the magnitude range of events is also discussed. 展开更多
关键词 NATURAL PROBABILITY Distribution System EVENT load-unload RESPONSE ratio.
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High-Precision Direct Determination of the ^(87)Sr/^(86)Sr Isotope Ratio of Bottled Sr-Rich Natural Mineral Drinking Water Using MC-ICP-MS
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作者 YANG Yue-heng,WU Fu-yuan,XIE Lie-wen YANG Jin-hui,ZHANG Yan-bin(State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing,100029,China) 《矿物学报》 CAS CSCD 北大核心 2011年第S1期1025-1025,共1页
Strontium has four naturally occurring stable isotopes,84Sr,86Sr,87Sr,and 88Sr,with abundances of 0.56,9.87,approximately 7.04,and 82.53 atomic %,respectively.The 87Sr/86Sr isotope ratio is variable due to the additio... Strontium has four naturally occurring stable isotopes,84Sr,86Sr,87Sr,and 88Sr,with abundances of 0.56,9.87,approximately 7.04,and 82.53 atomic %,respectively.The 87Sr/86Sr isotope ratio is variable due to the addition of radiogenic 87Sr produced by the beta decay of 87Rb with a half-life of 4.88 ± 0.05 Ga.Thus, 展开更多
关键词 Sr Isotope Ratio of Bottled Sr-Rich Natural Mineral Drinking Water Using MC-ICP-MS High-Precision Direct Determination of the TIMS ICP MC
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Development and testing of a detailed kinetic mechanism of natural gas combustion in internal combustion engine 被引量:2
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作者 M.Mansha A.R.Saleemi +1 位作者 Badar M.Ghauri Naveed Ramzan 《Journal of Natural Gas Chemistry》 EI CAS CSCD 2010年第2期97-106,共10页
A detailed chemical mechanism to describe the combustion of natural gas in internal combustion (IC) engine has been developed,which is consisting of 233 reversible reactions and 79 species.This mechanism accounts fo... A detailed chemical mechanism to describe the combustion of natural gas in internal combustion (IC) engine has been developed,which is consisting of 233 reversible reactions and 79 species.This mechanism accounts for the oxidation of methane,ethane,propane and nitrogen.It has been tested using IC engine model of CHEMKIN 4.1.1 and experimental measurements.The performance of the proposed mechanism was evaluated at various equivalence ratios (φ=0.6 to φ=1.3),initial reactor conditions (Tini=500 to 3500 ℃; Pini=1.0 to 10 atm) and engine speed (2000-7000 rpm).The proposed kinetic mechanism shows good concordances with GRI3.0 mechanism especially in the prediction of temperature,pressure and major product species (H2O,CO2) profiles at stoichiometric conditions (φ=1.0).The experimental results of measured cylinder pressure,species fractions were also in agreement with simulation results derived from the proposed kinetic mechanism.The proposed mechanism successfully predicts the formation of gaseous pollutants (CO,NO,NO2,NH3) in the engine exhaust.Although there are some discrepancies among each simulation profile,the proposed detailed mechanism is good to represent the combustion of natural gas in IC engine. 展开更多
关键词 natural gas detailed mechanism equivalence ratio pollutants emission COMBUSTION
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Natural Oscillations of Viscoelastic Lamellar Mechanical Systems with Point Communications 被引量:3
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作者 Safarov Ismail Ibrahimovich Teshaev Muhsin Hudoyberdievich Madjidov Maqsud 《Applied Mathematics》 2014年第19期3018-3025,共8页
We investigated the natural oscillations of dissipative inhomogeneous plate mechanical systems with point connections. Based on the principle of virtual displacements, we equate to zero the sum of all active work forc... We investigated the natural oscillations of dissipative inhomogeneous plate mechanical systems with point connections. Based on the principle of virtual displacements, we equate to zero the sum of all active work force, including the force of inertia which obtain equations vibrations of mechanical systems. Frequency equation is solved numerically by the method of Muller. According to the result of numerical analysis we established nonmonotonic dependence damping coefficients of the system parameters. 展开更多
关键词 Plate VISCOELASTIC Properties NATURAL Frequencies Damping Ratios Structurally HOMOGENEOUS and Structurally Heterogeneous
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Effect of adding natural pozzolana on geotechnical properties of lime-stabilized clayey soil 被引量:5
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作者 Aref al-Swaidani Ibrahim Hammoud Ayman Meziab 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2016年第5期714-725,共12页
Clayey soils in Syria cover a total area of more than 20,000 km2 of the country, most of which are located in the southwestern region. In many places of the country, the clayey soils caused severe damage to infrastruc... Clayey soils in Syria cover a total area of more than 20,000 km2 of the country, most of which are located in the southwestern region. In many places of the country, the clayey soils caused severe damage to infrastructures. Extensive studies have been carried out on the stabilization of clayey soils using lime. Syria is rich in both lime and natural pozzolana. However, few works have been conducted to investigate the influence of adding natural pozzolana on the geotechnical properties of lime-treated clayey soils. The aim of this paper is to understand the effect of adding natural pozzolana on some geotechnical properties of lime-stabilized clayey soils. Natural pozzolana and lime are added to soil within the range of 0%–20% and 0%–8%, respectively. Consistency, compaction, California bearing ratio (CBR) and linear shrinkage properties are particularly investigated. The test results show that the investigated properties of lime-treated clayey soils can be considerably enhanced when the natural pozzolana is added as a stabilizing agent. Analysis results of scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) show significant changes in the microstructure of the treated clayey soil. A better flocculation of clayey particles and further formation of cementing materials in the natural pozzolana-lime-treated clayey soil are clearly observed. 展开更多
关键词 Natural pozzolana Clayey soil stabilization CompactionCalifornia bearing ratio (CBR) Linear shrinkage
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Aortic Dissection Research in China:Analysis of Studies Funded by the National Natural Science Foundation of China 被引量:2
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作者 Zhang YUE Da-shuai WANG +3 位作者 Sheng LE Jia-hong XIA Ping YE Xiao-fan HUANG 《Current Medical Science》 SCIE CAS 2023年第1期206-212,共7页
Objective The National Natural Science Foundation of China(NSFC)has made great progress in promoting the development of aortic dissection research in recent years.This study aimed to examine the development and resear... Objective The National Natural Science Foundation of China(NSFC)has made great progress in promoting the development of aortic dissection research in recent years.This study aimed to examine the development and research status of aortic dissection research in China so as to provide references for future research.Methods The NSFC projects data from 2008 to 2019 were collected from the Internet-based Science Information System and other websites utilized as search engines.The publications and citations were retrieved by Google Scholar,and the impact factors were checked by the InCite Journal Citation Reports database.The investigator’s degree and department were identified from the institutional faculty profiles.Results A total of 250 grant funds totaling 124.3 million Yuan and resulting in 747 publications were analyzed.The funds in economically developed and densely populated areas were more than those in underdeveloped and sparsely populated areas.There was no significant difference in the amount of funding per grant between different departments’investigators.However,the funding output ratios of the grants for cardiologists were higher than those for basic science investigators.The amount of funding for clinical researchers and basic scientific researchers in aortic dissection was also similar.Clinical researchers were better in terms of the funding output ratio.Conclusion These results suggest that the medical and scientific research level of aortic dissection in China has been greatly improved.However,there are still some problems that urgently need to be solved,such as the unreasonable regional allocation of medical and scientific research resources,and the slow transition from basic science to clinical practice. 展开更多
关键词 National Natural Science Foundation of China aortic dissection GRANT FUNDING funding output ratio
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Morphological Effects of Natural Products on Schizosaccharomyces pombe Measured by Imaging Flow Cytometry 被引量:1
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作者 Joel Heisler Lindsay Elvir +3 位作者 Farah Barnouti Erica Charles Tom D.Wolkow Radha Pyati 《Natural Products and Bioprospecting》 CAS 2014年第1期27-35,共9页
Gaining a full understanding of the mechanisms of action of natural products as therapeutic agents includes observing the effects of natural products on cellular morphology,because abnormal cellular morphology is an i... Gaining a full understanding of the mechanisms of action of natural products as therapeutic agents includes observing the effects of natural products on cellular morphology,because abnormal cellular morphology is an important aspect of cellular transformations that occur as part of disease states.In this study a set of natural products was examined in search of small molecules that influence the cylindrical morphology of fission yeast Schizosaccharomyces pombe.Imaging flow cytometry of large populations of S.pombe exposed to natural products captured cell images and revealed changes in mean length and aspect ratio of cells.Several natural products were found to alter S.pombe’s morphology relative to control,in terms of elongating cells,shrinking them,or making them more round.These results may facilitate future investigations into methods by which cells establish and maintain specific shapes. 展开更多
关键词 Schizosaccharomyces pombe MORPHOLOGY Natural products Imaging flow cytometry Aspect ratio Fission yeast
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Genetic types and geochemicai characteristics of natural gases in the Jiyang Depression,China
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作者 Wen-Tao Li Yang Gao Chun-Yan Geng 《Petroleum Science》 SCIE CAS CSCD 2015年第1期81-95,共15页
Natural gases were widely distributed in the Jiyang Depression with complicated component composition, and it is difficult to identify their genesis. Based on investigation of gas composition, carbon isotope ratios, l... Natural gases were widely distributed in the Jiyang Depression with complicated component composition, and it is difficult to identify their genesis. Based on investigation of gas composition, carbon isotope ratios, light hydrocarbon properties, as well as geological analysis, natural gases in the Jiyang Depression are classified into two types, one is organic gas and the other is abiogenic gas. Abiogenic gas is mainly magmatogenic or mantlederived CO2. Organic gases are further divided into coaltype gas, oil-type gas, and biogas according to their kero- gen types and formation mechanisms. The oil-type gases are divided into mature oil-type gas (oil-associated gas) and highly mature oil-type gas. The highly mature oil-type gases can be subdivided into oil-cracking gas and kerogen thermal degradation gas. Identification factors for each kind of hydrocarbon gas were summarized. Based on genesis analysis results, the genetic types of gases buried in different depths were discussed. Results showed that shallow gases (〈1,500 m) are mainly mature oil-type gases, biogas, or secondary gases. Secondary gases are rich in methane because of chromatographic separation during migration and secondary biodegradation. Secondary biodegradation leads to richness of heavy carbon isotope ratios in methane and propane. Genesis of middle depth gases (1,500-3,500 m) is dominated by mature oil-type gases.Deep gases (3,500-5,500 m) are mainly kerogen thermal degradation gas, oil-cracking gas, and coal-type gas. 展开更多
关键词 Genetic types Natural gases Jiyang Depression Light hydrocarbon properties Carbon isotope ratios Identification factors
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Influence of Trailing-Edge Wear on the Vibrational Behavior of Wind Turbine Blades
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作者 Yuanjun Dai Xin Wei +2 位作者 Baohua Li Cong Wang Kunju Shi 《Fluid Dynamics & Materials Processing》 EI 2024年第2期337-348,共12页
To study the impact of the trailing-edge wear on the vibrational behavior of wind-turbine blades,unworn blades and trailing-edge worn blades have been assessed through relevant modal tests.According to these experimen... To study the impact of the trailing-edge wear on the vibrational behavior of wind-turbine blades,unworn blades and trailing-edge worn blades have been assessed through relevant modal tests.According to these experiments,the natural frequencies of trailing-edge worn blades-1,-2,and-3 increase the most in the second to fourth order,thefifth order increases in the middle,and thefirst order increases the least.The damping ratio data indi-cate that,in general,thefirstfive-order damping ratios of trailing-edge worn blades-1 and trailing-edge worn blades-2 are reduced,and thefirstfive-order damping ratios of trailing-edge worn blades-3 are slightly improved.The mode shape diagram shows that the trailing-edge worn blades-1 and-2 have a large swing in the tip and the blade,whereas the second-and third-order vibration shapes of the trailing edge-worn blade-3 tend to be improved.Overall,all these results reveal that the blade’s mass and the wear area are the main fac-tors affecting the vibration characteristics of wind turbine blades. 展开更多
关键词 Wind turbine modal test natural frequency damping ratio mode shape
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Evaluating effectiveness of frequency ratio, fuzzy logic and logistic regression models in assessing landslide susceptibility: a case from Rudraprayag district, India 被引量:7
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作者 Mehebub SAHANA Haroon SAJJAD 《Journal of Mountain Science》 SCIE CSCD 2017年第11期2150-2167,共18页
Rudraprayag in Garhwal Himalayan division is one of the most vulnerable districts to landslides in India. Heavy rainfall, steep slope and developmental activities are important factors for the occurrence of landslides... Rudraprayag in Garhwal Himalayan division is one of the most vulnerable districts to landslides in India. Heavy rainfall, steep slope and developmental activities are important factors for the occurrence of landslides in the district. Therefore, specific assessment of landslide susceptibility and its accuracy at regional level is essential for disaster management and proper land use planning. The article evaluates effectiveness of frequency ratio, fuzzy logic and logistic regression models for assessing landslide susceptibility in Rudraprayag district of Uttarakhand state, India. A landslide inventory map was prepared and verified by field data. Fourteen landslide parameters and generated inventory map were utilized to prepare landslide susceptibility maps through frequency ratio, fuzzy logic and logistic regression models. Landslide susceptibility maps generated through these models were classified into very high, high, medium, low and very low categories using natural breaks classification. Receiver operating characteristics(ROC) curve, spatially agreed area approach and seed cell area index(SCAI) method were used to validate the landslide models. Validation results revealed that fuzzy logic model was found to be more effective in assessing landslide susceptibility in the study area. The landslide susceptibility map generated through fuzzy logic model can be best utilized for landslide disaster management and effective land use planning. 展开更多
关键词 LANDSLIDE SUSCEPTIBILITY Frequency ratio LOGISTIC regression Natural BREAKS classification Remote sensing GEOGRAPHIC information system
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Measurement of Vibrational Stiffness and Air Damping of Damselfly Wings
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作者 Rupan Talukder Kunigal N. Shivakumar 《Journal of Biomaterials and Nanobiotechnology》 2016年第3期127-141,共15页
A simple cantilever beam vibration test method made of biomorph and insect wing, were used to measure the vibrational stiffness and the air damping of insect wings. Vibration tests were performed in vacuum pressures t... A simple cantilever beam vibration test method made of biomorph and insect wing, were used to measure the vibrational stiffness and the air damping of insect wings. Vibration tests were performed in vacuum pressures to atmosphere and the wing stiffness and air damping factor were measured. The test method was found to be a viable method for measuring wing stiffness, natural frequencies and mode shapes. The vibrational deformation of the insect wings was found to be combination of bending and torsion because of unsymmetrical geometry of wing. The measured stiffness (K) of damselfly wings varied from 0.18 to 0.31 N/m and the air damping ratio ranged from 0.72 to 0.79. The undamped natural frequency (f<sub>n</sub>) at 13 kPa varied from 249 to 299 Hz and at atmosphere it varied from 168 to 198 Hz. 展开更多
关键词 VIBRATION Natural Frequency STIFFNESS Damselfly Wing Damping Ratio Biomorph
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The Effect of Tool Construction and Cutting Parameters on Surface Roughness and Vibration in Turning of AISI 1045 Steel Using Taguchi Method
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作者 Rogov Vladimir Aleksandrovich Ghorbani Siamak 《Modern Mechanical Engineering》 2014年第1期8-18,共11页
This paper presents an experimental investigation focused on identifying the effects of cutting conditions and tool construction on the surface roughness and natural frequency in turning of AISI1045 steel. Machining e... This paper presents an experimental investigation focused on identifying the effects of cutting conditions and tool construction on the surface roughness and natural frequency in turning of AISI1045 steel. Machining experiments were carried out at the lathe using carbide cutting insert coated with TiC and two forms of cutting tools made of AISI 5140 steel. Three levels for spindle speed, depth of cut, feed rate and tool overhang were chosen as cutting variables. The Taguchi method L9 orthogonal array was applied to design of experiment. By the help of signal-to-noise ratio and analysis of variance, it was concluded that spindle speed has the significant effect on the surface roughness, while tool overhang is the dominant factor affecting natural frequency for both cutting tools. In addition, the optimum cutting conditions for surface roughness and natural frequency were found at different levels. Finally, confirmation experiments were conducted to verify the effectiveness and efficiency of the Taguchi method in optimizing the cutting parameters for surface roughness and natural frequency. 展开更多
关键词 Surface ROUGHNESS Cutting Condition Natural Frequency VIBRATION TURNING ANOVA Taguchi Method S/N Ratio
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Variations of CO2 Mixing Ratios in the Air near the Ground in the European Territory of Russia
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作者 Felix Kashin 《Journal of Environmental Science and Engineering(A)》 2013年第9期531-536,共6页
The instrumentation, method and measurement results used for measurements of CO2 concentrations in surface air of Obninsk (55.1° N, 36.9° E, 183 m above the sea level) located at a distance of 105 km to th... The instrumentation, method and measurement results used for measurements of CO2 concentrations in surface air of Obninsk (55.1° N, 36.9° E, 183 m above the sea level) located at a distance of 105 km to the south-west of Moscow are presented. Proposed is a method of experimental data filtering allowing one to separate natural and anthropogenic variations of CO2 concentrations. It is shown that minimal concentrations of CO2 registered in Obninsk and at the continental stations of GAW WMO characterize not only the "regional background" but also coincide with the data from GAW WMO background stations located in the oceanic regions. In this connection, one can assume that the excess in measured CO2 concentration over its minimal values, making about 5-6 ppm, is connected with an anthropogenic emission, and the continent should be considered as an anthropogenic source of C02. 展开更多
关键词 Carbon dioxide mixing ratio natural and anthropogenic variations.
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The Most Irrational Number that Shows up Everywhere: The Golden Ratio
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作者 Jiwon Choi Agegnehu Atena Wondimu Tekalign 《Journal of Applied Mathematics and Physics》 2023年第4期1185-1193,共9页
Since the time of the ancient Greeks, humans have been aware of this mathematical idea. Golden ratio is an irrational number that is symbolized by the Greek numeral phi (φ). One can find this ratio everywhere. It is ... Since the time of the ancient Greeks, humans have been aware of this mathematical idea. Golden ratio is an irrational number that is symbolized by the Greek numeral phi (φ). One can find this ratio everywhere. It is in nature, art, architecture, human body, etc. But this symbolism can result in a strong connection with mathematical nature. In this paper we will be discussing the connection between Fibonacci sequence (a series of numbers where every number is equal to the sum of two numbers before it) and Golden ratio. Secondly, how this mathematical idea shows up in a nature, such as sunflower and human DNA. 展开更多
关键词 The Golden Ratio Fibonacci Sequence NATURE
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天然气管道掺氢输送研究现状与分析 被引量:11
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作者 高岳 朱红钧 +3 位作者 唐堂 李佳男 陈泉宇 刘文丽 《低碳化学与化工》 CAS 北大核心 2024年第3期118-128,共11页
天然气管道掺氢输送是实现大规模、远距离和低成本氢气运输的手段之一,但氢气掺入天然气管道给管线运行工况、安全维护等带来了不容忽视的影响,具有一定的安全隐患。为此,围绕国内外天然气管道掺氢输送的技术研究与工程应用现状,讨论了... 天然气管道掺氢输送是实现大规模、远距离和低成本氢气运输的手段之一,但氢气掺入天然气管道给管线运行工况、安全维护等带来了不容忽视的影响,具有一定的安全隐患。为此,围绕国内外天然气管道掺氢输送的技术研究与工程应用现状,讨论了影响天然气管道掺氢安全输送的主要因素,即掺氢引起的天然气物性改变、氢致失效和掺混不均,以及掺氢管道泄漏扩散和燃爆的安全问题。结果表明,天然气掺氢后,对现有管材提出了新要求,需开展相关实验以揭示氢致失效机理,掺氢天然气管道停输后是否发生气体分层与管道是否发生氢致失效密切相关。掺氢天然气管道泄漏扩散及自燃的安全范围、发生燃爆所需的最小掺氢比及燃爆机理尚不明晰,实验研究与实际运营存在差距。针对天然气管道掺氢输送的规范、标准及相关监管政策仍处于发展阶段,需要结合系统的研究数据及实践进一步完善。以上结果明晰了掺氢输送存在的风险,可为大规模掺氢混输的工程推广与实际运营提供参考。 展开更多
关键词 掺氢天然气 管道输送 掺氢比 泄漏扩散 燃爆
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New Class of Almost Unbiased Modified Ratio Cum Product Estimators with Knownparameters of Auxiliary Variables
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作者 Jambulingam Subramani Master Ajith S 《Journal of Mathematics and System Science》 2017年第9期248-260,共13页
This manuscript deals with new class of almost unbiased ratio cum product estimators for the estimation of population mean of the study variable by using the known values auxiliary variable. The bias and mean squared ... This manuscript deals with new class of almost unbiased ratio cum product estimators for the estimation of population mean of the study variable by using the known values auxiliary variable. The bias and mean squared error of proposed estimators are obtained. An empirical study is carried out to assess the efficiency of proposed estimators over the existing estimators with the help of some known natural populations and it shows that the proposed estimators are almost unbiased and it perform better than the existing estimators. 展开更多
关键词 Auxiliary variable BIAS Mean squared error Natural populations Ratio and Productestimators Simple random sampling.
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Analysis of vibration attenuation characteristics of large thickness carbon fiber composite laminates
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作者 Yi-Qi WANG Chaoqun WANG +2 位作者 Pengxiao YANG Ziao WANG Tete CAO 《Mechanical Engineering Science》 2022年第1期22-26,共5页
The vibration attenuation and damping characteristics of carbon fiber reinforced composite laminates with different thicknesses were investigated by hammering experiments under free boundary constraints in different d... The vibration attenuation and damping characteristics of carbon fiber reinforced composite laminates with different thicknesses were investigated by hammering experiments under free boundary constraints in different directions.The dynamic signal testing and analysis system is applied to collect and analyze the vibration signals of the composite specimens,and combine the self-spectrum analysis and logarithmic decay method to identify the fundamental frequencies of different specimens and calculate the damping ratios of different directions of the specimens.The results showed that the overall stiffness of the specimen increased with the increase of the specimen thickness,and when the thickness of the sample increases from 24mm to 32mm,the fundamental frequency increases by 35.1%,the vibration showed the same vibration attenuation and energy dissipation characteristics in the 0°and 90°directions of the specimen,compared with the specimen in the 45°direction,which was less likely to be excited and had poorer vibration attenuation ability,while the upper and lower surfaces of the same specimen showed slightly different attenuation characteristics to the vibration,the maximum difference of damping capacity between top and bottom surfaces of CFRP plates is about 70%. 展开更多
关键词 Carbon fiber composite laminates Logarithmic decay method Damping ratio Natural frequency
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