6,293 research outputs found
Micromechanical Analysis on the Failure Criterion of Ductile Material
AbstractBased on finite element simulation, the void growth behavior in a 3D cell model subjected to low stress triaxiality was studied. The distribution rule of stress-strain near the void was investigated, as well as the developing trend of volume of void. The analysis results indicated that it is not appropriate to regard void volume fraction as a damage parameter under the low stress triaxiality condition. Further research was carried out to verify the reliability of the fracture strain as element failure criterion by comparing the uniaxial tension simulation and experiment results. More studies were conducted to analyze the void growth under low stress triaxiality by introducing the critical equivalent plastic strain as the material failure parameter
Evaluation of agricultural ecosystem services in fallowing land based on farmers' participation and model simulation
Fallowing with green fertilizer can benefit agricultural ecosystem services (AES). Farmers in Taiwan do not implement fallow practices and plant green fertilizer because the current subsidy level (46,000 NTperha)istoolowtomanagefallowingThispaperdefinestheobjectiveofgovernmentagriculturepolicyorthefarmerâsobjectiveasmaximizationoffarmproductivityapproximatedtothevalueofsocialwelfareandAESFarmswhichdonotfollowproperfallowingpracticesoftenhavepoorlymaintainedfallowlandorleftfarmlandabandonedThisresultsinnegativeenvironmentalconsequencessuchascutworminfestationsinabandonedlandwhichinturncanaffectcropsinadjacentfarmlandsTheobjectivesofthisstudyaretwofoldFirstitdeterminestheproperfallowingsubsidybasedontheconceptofpaymentforecosystemservicestoenticemorefarmerstoparticipateinfallowingSeconditsimulatesthebenefitofplantinggreenmanureinfallowlandtothesupplyofAESbasedontherateoffarmerswhoarewillingtoparticipateinfallowlandpracticesandessentialparametersthatcanaffectsoilfertilitychangeTheapproachinvolvesaseriesofinterviewsandadevelopedempiricalmodelThevalueofAESwhentherateoffarmerparticipationis100 ) over the value at the current participation rate of 14%. This study further concludes that the appropriate fallowing subsidy has a large positive impact on AES and social welfare (e.g., benefit from food and biofuel supplies) and is seen as a basis of ecological governance for sustainable agro-ecosystems
Prediction of Roughness Heights of Milled Surfaces for Product Quality Prediction and Tool Condition Monitoring
The objective of this research is to predict the roughness heights of milled surfaces, which indicates product quality and tool conditions. Two experiments are carried out to evaluate relevant factors such as vibration, force, and surface roughness. The purpose of the first experiment is to find out the limits of the machining variables compared to the constraints of the materials. The purpose of the second experiment is to identify, collect, and compare how each factor affects product quality and tool conditions. Based on this study, the vibration, force, and surface roughness are good indicators for tool conditions. When the magnitudes of the vibration and force increase, the surface roughness also increases. The increase in surface roughness with constant cutting parameters indicates the degrading of product quality and the decrease of the tool life. Thus, the variables, such as vibration and forces, are used as the inputs, and the surface roughness is used as the output of neural networks. By optimizing the network variables, it has been found that a 4,4,8,1 neural network can achieve the least absolute error, and accurately predict the actual roughness heights collected from the experiment. The minimum error of the prediction of surface roughness is 0.11%, the average error is 2.11%, and the maximum error is 6.98%. The prediction of surface roughness of milled surfaces is very important for the product quality prediction and tool condition monitoring
Occurrence and risk assessment of polycyclic aromatic hydrocarbons in soil from the Tiefa coal mine district, Liaoning, China.
In order to evaluate soil-associated polycyclic aromatic hydrocarbons (PAHs) pollution from coal mine activities in Tiefa coal mine, Northeast China, 16 PAHs identified as priority pollutants by US Environmental Pollution Agency were determined in mining zone soil (MZS), agricultural soil (AS), local lake bank soil (LBS), a vertical soil profile and three coal gangue samples. The total concentration of 16 PAHs (defined as Σ(16)PAH, dry weight) in surface soil ranged from 5.1 to 5642.3 ng g(-1), with an arithmetic mean of 1118.3 ng g(-1). Σ(16)PAH values at the sites from MZS are significantly higher than those found in AS and LBS. The vertical distribution of PAHs indicated that these compounds can penetrate the deeper layers of the soil, especially the low-rings compounds. A complex of petrogenic origin and pyrolytic sources was found within the study area, as suggested by the isomeric ratios of PAHs. According to principal component analysis (PCA), four factors were identified in the source contribution, including coal combustion, unburned coal particulates, coal gangue and vehicular emissions. The degree of contamination and the PAH toxicity assessment suggested that the soils of the study area have been seriously polluted and pose a high potential health risk.</span
Combinatorial Voter Control in Elections
Voter control problems model situations such as an external agent trying to
affect the result of an election by adding voters, for example by convincing
some voters to vote who would otherwise not attend the election. Traditionally,
voters are added one at a time, with the goal of making a distinguished
alternative win by adding a minimum number of voters. In this paper, we
initiate the study of combinatorial variants of control by adding voters: In
our setting, when we choose to add a voter~, we also have to add a whole
bundle of voters associated with . We study the computational
complexity of this problem for two of the most basic voting rules, namely the
Plurality rule and the Condorcet rule.Comment: An extended abstract appears in MFCS 201
Penta-quark states with hidden charm and beauty
More and more hadron states are found to be difficult to be accommodated by
the quenched quark models which describe baryons as 3-quark states and mesons
as antiquark-quark states. Dragging out an antiquark-quark pair from the gluon
field in hadrons should be an important excitation mechanism for hadron
spectroscopy. Our recent progress on the penta-quark states with hidden charm
and beauty is reviewed.Comment: Plenary talk at the 5th Asia-Pacific Conference on Few-Body Problems
in Physics 2011 (APFB2011), 22-26 Aug., 2011, Seoul, Kore
Using in situ technique to estimate nutrient availability of six barley varieties for ruminants
Non-Peer ReviewedBarley grains are as a main source of feed for ruminants in Canada. Although barley varieties have similar chemical composition, they exhibit different rumen degradation characteristics and nutrient availability. The objective of this study was to estimate nutrient availability of the six barley varieties using nylon bags incubated for 0, 2, 4, 8, 12, 24 and 48 h in the rumen of dairy cow and determine the rumen degradation parameters of DM, CP and starch according to the first order degradation kinetics equation. The results indicated that the barley varieties showed different degradation rate (Kd) of DM, CP and starch during incubation period. CDC Trey was the highest (P<0.05) in effective degradability of DM (498.04g/kg) while AC Metcalfe showed the highest (P<0.05) effective degradability of CP (63.06g/kg) and starch (344.82g/kg) compared with other barley varieties. CDC Helgason had the largest size of rumen undegradable fraction of DM (640.21g/kg), CP (83.85g/kg, NRC 2001 model) and starch (321.85g/kg). Feeds degradation features from this study involved nutrients utilization in ruminant digestive systems. Further study to investigate and compare the structural/chemical make-up characteristics between barley varieties may provide more information as to why barley varieties exhibit different biodegradation behaviors
Timing of closure of the Mesozoic-Tethys Ocean: Constraints from remnants of a 141-135 ocean island within the Bangong-Nujiang suture zone, Tibetan Plateau
Knowledge of the timing of the closure of the Meso-Tethys Ocean as represented by the BangongâNujiang Suture Zone, i.e., the timing of the Lhasa-Qiangtang collision, is critical for understanding the Mesozoic tectonics of the Tibetan Plateau. But this timing is hotly debated; existing suggestions vary from the Middle Jurassic (ca. 166 Ma) to Late Cretaceous (ca. 100 Ma). In this study, we describe the petrology of the Zhonggang igneousâsedimentary rocks in the middle segment of the BangongâNujiang Suture Zone and present results of zircon UâPb geochronology, whole-rock geochemistry, and SrâNd isotope analysis of the Zhonggang igneous rocks. The Zhonggang igneousâsedimentary rocks have a thick basaltic basement (>2 km thick) covered by limestone with interbedded basalt and tuff, trachyandesite, chert, and poorly sorted conglomerate comprising limestone and basalt debris. There is an absence of terrigenous detritus (e.g., quartz) within the sedimentary and pyroclastic rocks. These observations, together with the typical exotic blocks-in-matrix structure between the Zhonggang igneousâsedimentary rocks and the surrounding flysch deposits, lead to the conclusion that the Zhonggang igneousâsedimentary rocks are remnants of an ocean island within the Meso-Tethys Ocean. This conclusion is consistent with the ocean island basalt-type geochemistry of the Zhonggang basalts and trachyandesites, which are enriched in light rare earth elements (LaN/YbN = 4.72â18.1 and 5.61â13.7, respectively) and have positive NbâTa anomalies (NbPM/ThPM > 1, TaPM/UPM > 1), low initial 87Sr/86Sr ratios (0.703992â0.705428), and positive mantle ΔNd(t) values (3.88â5.99). Zircon UâPb dates indicate that the Zhonggang ocean island formed at 141â135 Ma; therefore, closure of the Meso-Tethys Ocean and collision of the Lhasa and Qiangtang terranes must have happened after ca. 135 Ma
Using synchrotron-based FTIR microspectroscopy (SFTIRM) to reveal the differences of endosperm structural and chemical make-up among six barley varieties
Non-Peer ReviewedBarley grains are widely used for malting and feeding purposes in Canada. Although barley varieties have similar chemical composition, they exhibit different rumen degradation characteristics and nutrient availability. The objectives of this study was to determine structural make-up features and identify the structural differences in chemical functional groups in endosperm tissue among the six barley varieties using ultra-spatially resolved synchrotron-based FTIR microspectroscopy (SFTIRM). The results indicated that the barley varieties showed significant differences in terms of peak area intensities and the peak ratios of the amide I (1650 cm-1) and amide II (1550 cm-1), cellulosic compounds (ca. 1240 cm-1), and non-structural carbohydrates (NSC, starch) peak (1025 cm-1). The synchrotron-based FTIR spectroscopic information associated with structural and chemical make-up characteristics of barley grains may provide more information as to why barley varieties exhibit different biodegradation behaviors
Effects of Boundary Conditions on Single-File Pedestrian Flow
In this paper we investigate effects of boundary conditions on one
dimensional pedestrian flow which involves purely longitudinal interactions.
Qualitatively, stop-and-go waves are observed under closed boundary condition
and dissolve when the boundary is open. To get more detailed information the
fundamental diagrams of the open and closed systems are compared using
Voronoi-based measurement method. Higher maximal specific flow is observed from
the pedestrian movement at open boundary condition
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