1,620 research outputs found
The effects of agricultural activities and atmospheric acid deposition on carbonate weathering in a small karstic agricultural catchment, Southwest China
In order to quantify the sources and fluxes of DIC, the effects of the use of N-fertilizers and acid deposition on carbonate weathering have been quantified by hydrochemistry and ÎŽ13CDIC of groundwater in Qingmuguan underground river system (QURS) â a small karstic agricultural catchment of Southwest China. The results show that: (1) the significant temporal variations for major element concentrations and ÎŽ13CDIC of groundwater in different months were observed, especially, of which the groundwater showed significant high concentrations of DIC, Ca2+, Mg2+, NO3â, SO42â and ÎŽ13CDIC in rainy season and fertilizing period in the QURS; (2) the contributions of carbonate dissolution by carbonic acid to total concentrations of (Ca2++Mg2+) and HCO3â of groundwater in different months averaged 68.5 % and 81.0 %, respectively. While the contributions of carbonate dissolution by nitric acid originated from the use of N-fertilizers and atmospheric acid deposition to total concentrations of (Ca2++Mg2+) and HCO3â of groundwater in different months averaged 11.1 % and 6.7 %, respectively, and the contributions of carbonate dissolution by sulphuric acid originated from the atmospheric acid deposition to total concentrations of (Ca2++Mg2+) and HCO3â of groundwater in different months averaged 20.4 % and 12.3 %, respectively; (3) the ÎŽ13CDIC increased obviously with (Ca2++Mg2+)/HCO3â of groundwater in the rainy season and fertilizing period indicated that the use of N-fertilizers and atmospheric acid deposition should be responsible for the elevated the ÎŽ13CDIC and the molar ratio of (Ca2++Mg2+)/HCO3â of groundwater in the QURS.Key words: carbonate weathering, karst groundwater, agricultural activities, atmospheric acid deposition, Qingmuguan, Southwest China
Safety evaluation method of bridge plate rubber bearing based on SVM
In order to comprehensively evaluate the working state and safety performance of the bridge plate rubber bearing (PRB), the basic principle and method of SVM in machine learning theory (Support Vector Machine) was introduced in this paper. Firstly, the performance indices (such as the average compression stress, tangent value of the shear angle and the rotation angle of the PRB) were analyzed and calculated through its finite element model considering the different working conditions (axial compression, shear deformation and the rotation deformation of the PRB). Subsequently, considering the relevant indices affecting the safety performance of the PRB, the Pearson Correlation Coefficients (PCC) were calculated by SVM method for assessing the internal correlation of the performance indices of the PRB for different cases, respectively. The threshold values of the influential factors for different cases considering the PCC and the weight coefficient were obtained for grading the working state of the PRB as five levels. Moreover, in order to verify the validity and suitability of the evaluation of the working state of the plate rubber bearing by the SVM method, three apparent indices for grading the performance level of the PRB such as the crack, the undistributed spalling deformation and the dislocation of the PRB were analyzed and compared with the qualitative descriptions and the quantitative values. Finally, the corresponding threshold values for grading the performance levels of the PRB working states were proposed. It was shown that the SVM based evaluation method for the PRB is feasible and convenient, especially for the bridges with real-time monitoring devices to get the response data of the PRB
Linear convergence of the Collatz method for computing the Perron eigenpair of primitive dual number matrix
Very recently, Qi and Cui extended the Perron-Frobenius theory to dual number
matrices with primitive and irreducible nonnegative standard parts and proved
that they have Perron eigenpair and Perron-Frobenius eigenpair. The Collatz
method was also extended to find Perron eigenpair. Qi and Cui proposed two
conjectures. One is the k-order power of a dual number matrix tends to zero if
and only if the spectral radius of its standard part less than one, and another
is the linear convergence of the Collatz method. In this paper, we confirm
these conjectures and provide theoretical proof. The main contribution is to
show that the Collatz method R-linearly converges with an explicit rate.Comment: arXiv admin note: text overlap with arXiv:2306.16140 by other author
The pc-scale radio structure of MIR-observed radio galaxies
We investigated the relationship between the accretion process and jet
properties by ultilizing the VLBA and mid-infrared (MIR) data for a sample of
45 3CRR radio galaxies selected with a flux density at 178 MHz Jy, 5
GHz VLA core flux density 7 mJy, and MIR observations. The pc-scale
radio structure at 5 GHz are presented by using our VLBA observations for 21
sources in February, 2016, the analysis on the archival data for 16 objects,
and directly taking the measurements for 8 radio galaxies available in
literatures. The accretion mode is constrained from the Eddington ratio with a
dividing value of 0.01, which is estimated from the MIR-based bolometric
luminosity and the black hole masses. While most FRII radio galaxies have
higher Eddington ratio than FRIs, we found that there is indeed no single
correspondence between the FR morphology and accretion mode with eight FRIIs at
low accretion and two FRIs at high accretion rate. There is a significant
correlation between the VLBA core luminosity at 5 GHz and the Eddington ratio.
Various morphologies are found in our sample, including core only, single-sided
core-jet, and two-sided core-jet structures. We found that the higher accretion
rate may be more likely related with the core-jet structure, thus more extended
jet. These results imply that the higher accretion rates are likely able to
produce more powerful jets. There is a strong correlation between the MIR
luminosity at 15 m and VLBA 5 GHz core luminosity, in favour of the tight
relation between the accretion disk and jets. In our sample, the core
brightness temperature ranges from to K with a median
value of K indicating that systematically the beaming effect may
not be significant....Comment: 21 pages, 8 figures, accepted by RA
ELECRec: Training Sequential Recommenders as Discriminators
Sequential recommendation is often considered as a generative task, i.e.,
training a sequential encoder to generate the next item of a user's interests
based on her historical interacted items. Despite their prevalence, these
methods usually require training with more meaningful samples to be effective,
which otherwise will lead to a poorly trained model. In this work, we propose
to train the sequential recommenders as discriminators rather than generators.
Instead of predicting the next item, our method trains a discriminator to
distinguish if a sampled item is a 'real' target item or not. A generator, as
an auxiliary model, is trained jointly with the discriminator to sample
plausible alternative next items and will be thrown out after training. The
trained discriminator is considered as the final SR model and denoted as
\modelname. Experiments conducted on four datasets demonstrate the
effectiveness and efficiency of the proposed approach.Comment: Accepted to SIGIR 202
An Alternative Approach for High Speed Railway Carrying Capacity Calculation Based on Multiagent Simulation
It is a multiobjective mixed integer programming problem that calculates the carrying capacity of high speed railway based on mathematical programming method. The model is complex and difficult to solve, and it is difficult to comprehensively consider the various influencing factors on the train operation. The multiagent theory is employed to calculate high speed railway carrying capacity. In accordance with real operations of high speed railway, a three-layer agent model is developed to simulate the operating process of high speed railway. In the proposed model, railway network agent, line agent, station agent, and train agent are designed, respectively. To validate the proposed model, a case study is performed for BeijingâShanghai high speed railway by using NetLogo software. The results are consistent with the actual data, which implies that the proposed multiagent method is feasible to calculate the carrying capacity of high speed railway
Deciphering Charging Status, Absolute Quantum Efficiency, and Absorption Cross Section of MultiCarrier States in Single Colloidal Quantum Dot
Upon photo- or electrical-excitation, colloidal quantum dots (QDs) are often
found in multi-carrier states due to multi-photon absorption and photo-charging
of the QDs. While many of these multi-carrier states are observed in single-dot
spectroscopy, their properties are not well studied due to random
charging/discharging, emission intensity intermittency, and uncontrolled
surface defects of single QD. Here we report in-situ deciphering the charging
status, and precisely assessing the absorption cross section, and determining
the absolute emission quantum yield of mono-exciton and biexciton states for
neutral, positively-charged, and negatively-charged single core/shell CdSe/CdS
QD. We uncover very different photon statistics of the three charge states in
single QD and unambiguously identify their charge sign together with the
information of their photoluminescence decay dynamics. We then show their
distinct photoluminescence saturation behaviors and evaluated the absolute
values of absorption cross sections and quantum efficiencies of monoexcitons
and biexcitons. We demonstrate that addition of an extra hole or electron in a
QD changes not only its emission properties but also varies its absorption
cross section
Thermal effects on high-frequency magnetic-field-induced martensite reorientation in ferromagnetic shape memory alloys: An experimental and theoretical investigation
Ferromagnetic Shape Memory Alloys (FSMAs) exhibit large strains by the magnetic-field-induced martensite reorientation. But, due to the high-frequency field-induced cyclic frictional martensite twin boundary motion in FSMAs, the dissipation heat can cause a large temperature rise. Thus, the output strain amplitude of FSMAs would decrease significantly if the temperature increases to be high enough to trigger the Martensite-Austenite phase transformation. Such thermal effects on the dynamic responses of FSMAs are unclear in literature because most existing dynamic experiments were performed only for a short-time period (a few seconds) to avoid the temperature rise. In this paper, systematic long-time experiments (>100âŻs) on a Ni-Mn-Ga single crystal are conducted at various levels of magnetic field frequency, initial compressive stress and ambient airflow velocity. It is found that, during the long-time actuation, the specimen temperature increases and then saturates at a certain level (stable temperature) while the strain oscillation evolves to a stable cycle; both the stable temperature and the stable strain amplitude depend on the frequency, the stress level and the heat exchange condition (i.e., ambient airflow velocity). Particularly, when the specimen temperature reaches a critical level to partially transform the martensite to the austenite, the output strain amplitude reduces suddenly because of less martensite reorientation. Changing the ambient heat-exchange condition (by the airflow) can modify the specimen temperature evolution to avoid the phase transformation, but it also changes the behaviors of the martensite reorientation that is sensitive to temperature. Eventually, the output strain amplitude depends on the airflow velocity non-monotonically, i.e., there exists a critical heat exchange condition to achieve the maximum stable strain amplitude. Based on the systematic experiments and a simplified one-dimensional heat-transfer model, the critical condition can be determined. The new experimental phenomena of the thermal effects can be well understood and described by the heat-transfer model. Further, instead of avoiding the temperature rise and the phase transformation, we propose to take advantage of the interaction between the temperature-induced phase transformation and the magnetic-field-induced martensite reorientation to develop a special âisothermalâ FSMA actuator with a tunable output strain amplitude and a constant working temperature. This paper provides systematic experimental data and theoretical analysis for understanding the thermo-magneto-mechanical coupling in FSMAs and developing reliable high-frequency long-time running FSMA-actuators
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