Acceleration Period Research Articles

Pore connectivity of oil well cement in the early hydration stage by in situ electrical resistivity measurements and low-field nuclear magnetic resonance

The pore connectivity of cement slurry is an important parameter to be considered when investigating short-term gas migration in the cementing engineering of natural gas wells. This study combined electrical resistivity measurements (ERM), low-field nuclear magnetic resonance, and multi-phase phenomenological models to create an in situ evaluation method for the pore connectivity of cement slurry. This method was effective for investigating the porosity, pore size, and pore connectivity of the cement slurry in the early hydration stage. The results showed that the initial formation factor of the cement slurry was determined by the water-to-cement ratio (w/c). In the initial hydration stage, the porosity of the cement slurry (w/c = 0.44) was approximately 58%. Additionally, the pore size ranged from 11 to 75 nm, and the pore connectivity was 0.65–0.70. The small amount of Q1 calcium silicate hydrate (C-S-H) generated during the hydration induction period did not affect the dispersed-particle microstructure of the cement slurry and had little effect on its pore structure. During the hydration acceleration period, numerous Q1 and Q2 SiO4 species were detected, which converted the microstructure of the cement slurry to a cross-linked structure, thereby reducing the pore size and pore connectivity of the cement slurry. The porosity of the cement slurry reduced to 52% after hydration for 12 h at 30 °C. However, the pore size distribution decreased to 4.5–35 nm, and the pore connectivity varied from 0.5 to 0.58.

Numerical evaluation of long-term neutron irradiation damage on reinforced concrete (RC) members

In the long-term operation of nuclear power plants (NPPs), irradiation can adversely affect the behavior of reinforced concrete (RC) members because of the degradation of the constituent materials. Degradation of concrete may be associated with the volume expansion of concrete due to irradiation, which is known as radiation-induced volume expansion (RIVE). As the compressive strength of concrete decreases under irradiation environments, the yield stress increases, and the ductility of steel decreases. Furthermore, the material properties of concrete and reinforcing steel vary within the cross-section of RC members because of the flux attenuation. In this study, such complicated changes in the material characteristics are systematically considered by using a simple fiber modeling approach to analyze the RC member behaviors. The effects of RIVE on the flexural members are computed by employing compatibility and equilibrium conditions. Based on the proposed framework, the behaviors of RC members are investigated under static and seismic loading conditions. The computational results demonstrate that the irradiation on RC members leads to changes in the structural characteristics such as the maximum load capacity, ductility, toughness, and the maximum spectral acceleration and corresponding period. Therefore, the irradiation effects must be carefully considered in RC structural analyses.

Quasi-Periodic Pulsations Detected in Ly $\alpha $ and Nonthermal Emissions During Solar Flares

We report quasi-periodic pulsations (QPPs) with double periods during three solar flares (viz. SOL2011-Feb-15T01:44, SOL2011-Sep-25T04:31, SOL2012-May-17T01:25). The flare QPPs were observed from light curves in Ly$\alpha$, hard X-ray (HXR) and microwave emissions, with the Ly$\alpha$ emission recorded by the Geostationary Operational Environmental Satellite, the HXR emission recorded by the Reuven Ramaty High-Energy Solar Spectroscopic Imager and the Fermi Gamma-ray Burst Monitor, and the microwave emission recorded by the Nobeyama Radio Polarimeters and Radioheliograph. By using the Markov chain Monte Carlo (MCMC) method, QPPs with double periods of about two minutes and one minute were first found in the Ly$\alpha$ emission. Then using the same method, a QPP with nearly the same period of about two minutes was also found in HXR and microwave emissions. Considering the possible common origin (nonthermal electrons) between Ly$\alpha$ and HXR/microwave emission, we suggest that the two-minute QPP results from the periodic acceleration of nonthermal electrons during magnetic reconnections. The ratio between the double periods in the Ly$\alpha$ emission was found to be close to two, which is consistent with the theoretical expectation between the fundamental and harmonic modes. However, we cannot rule out other possible driving mechanisms for the one-minute QPPs in HXR/microwave emissions due to their relatively large deviations.

Multi-attribute seismic data spectrum analysis of tunnel orthogonal underpass landslide shaking table test

To explore the spatial deformation characteristics and dynamic response law of the tunnel's orthogonal underpass landslide under potential seismic action, we carried out the shaking table test for the first time. We measured and obtained the seismic data with various attributes, such as the characteristic image of different probability horizontal seismic action, acceleration, dynamic soil pressure and dynamic strain. Based on the time-domain analysis of multi-attribute data such as deformation characteristics and acceleration, we revealed the spatial dynamic response characteristics of the lining structure at different positions in the annular particle. By Wavelet Transform, we obtained the time-frequency variation relationship between the multi-attribute data. In addition, we discussed in detail the relationship between the frequency and the specific period of acceleration, dynamic soil pressure and dynamic strain at different probabilities of horizontal vibration stages. We then proposed the damage level correlation quantitatively characterized by the spectrum characteristics of multi-attribute data through Fast Fourier Transform and statistical probability scatter-matrix operations. The sensitivity difference of multi-attribute seismic data was significant. The time-history effect of dynamic soil pressure was the most sensitive and the time-history effect of dynamic strain had obvious hysteresis compared with acceleration. In the frequency domain of multi-attribute seismic data signals, the predominant frequencies were mainly concentrated in 1–10 Hz, and their dominant frequencies were significantly different. The singular boundary between low-frequency and high-frequency was 10 Hz, and the structures with frequencies between 15 and 20 Hz were relatively safe. Multi-attribute data response variables were positively correlated, acceleration was highly correlated with dynamic soil pressure response, while acceleration was weakly correlated with dynamic strain response, showing a significant correlation. Due to the spatial location of the tunnel's orthogonal underpass landslide, and the effect of seismic wave amplification and bias effect of mountain tunnel, the lining was damaged in a regional difference, and the inverted arch uplift cracked into a weak area. The research results can provide a theoretical reference for the failure model prediction and engineering safety evaluation of the tunnel's orthogonal underpass landslide in high intensity earthquake area.

RETRACTED ARTICLE: Analysis of drought climate ecology and college students’ entrepreneurial ability based on an ant colony optimization model

This paper first proposes an ant colony optimization model. The model defines the probability that acts on the number of average branch nodes, which always maintains the balance between “exploration” and “use”, so that the algorithm maintains a higher search capability while avoiding mistakes. According to this, the relationship between the drought climate development and the ecological impact of the grassland has summarized the accumulation mechanism of grassland ecological effects by studying the combination characteristics of grassland and ecological effects and the comprehensive response to important ecological elements. The entire life cycle of the arid climate can summarize the initial, developmental acceleration period, stable development period, and the end of development. Its integrated ecological effects of grasslands have time accumulation, spatial extension, and aggregation source, and also have characteristics such as hidden and dominant properties, threshold sensitivity, and ecological recovery. Finally, this paper creates a system for evaluating students’ entrepreneurial capacity. According to the elements collected, the index is obtained by theoretical analysis, and three-level indicators of entrepreneurial quality, entrepreneurial capacity, and entrepreneurship knowledge are extracted. Through professional communication and group exchange, the entrepreneurial capacity elements are classified. Through the questionnaire survey and causal analysis, we are able to check the entrepreneurial capacity index, improve the indicator system, and finally obtain an indicator of evaluating students’ entrepreneurial capacity evaluation, including level III indicators, level 9 II indicators, and 32-level III-level indicators and use them. The method will be described. We also calculated the weight and determined the assessment model by the level process. This paper uses a comprehensive fuzzy evaluation method as an evaluation method to establish an evaluation system to ensure its rationality and availability.

Effect of C-S-H Nucleating Agent on Cement Hydration

This work aims to study the effect of a nucleating agent on cement hydration. Firstly, the C-S-H crystal nucleation early strength agent (CNA) is prepared. Then, the effects of CNA on cement hydration mechanism, early strength enhancement effect, C-S-H content, 28-days hydration degree and 28-days fractal dimension of hydration products are studied by hydration kinetics calculation, resistivity test, BET specific surface area test and quantitative analysis of backscattered electron (BSE) images, respectively. The results show that CNA significantly improves the hydration degree of cement mixture, which is better than triethanolamine (TEA). CNA shortens the beginning time of the induction period by 49.3 min and the end time of the cement hydration acceleration period by 105.1 min than the blank sample. CNA increases the fractal dimension of hydration products, while TEA decreases the fractal dimension. CNA significantly improves the early strength of cement mortars; the 1-day and 3-days strength of cement mortars with CNA are more than the 3-days and 7-days strength of the blank sample. These results will provide a reference for the practical application of the C-S-H nucleating agent.

Effect of the specific surface area of nano-silica particle on the properties of cement paste

Two types of nano-silica with specific surface areas of 100 m2/g (NS-100) and 470 m2/g (NS-470) were used to investigate the effect of the specific surface area on the properties of cement paste. The mercury intrusion porosimetry results show that NS-470 nano-silica is more effective in improving the pore structure, which mainly reduces the gel pores and large pores. The attenuated-total-reflection spectrums illustrate that NS-470 nano-silica can be covered with more Si-OH groups, leading to the higher reactivity to accelerate the hydration reaction. The calorimetry results indicate that NS-470 nano-silica can more effectively prolong the acceleration period, and increase the exothermic rate and late hydration degree. The hydration kinetics simulation indicates that NS-470 nano-silica makes the hydration reaction quickly enter the diffusion stage. Based on the results of microanalysis, the mechanism of how the specific surface area influences the function of nano-silica in cement paste is proposed.

Numerical investigation on spilling upward performance of hydrogen bubbles inside a delivery tube under low-gravity environment

A typical cryogenic upper stage mission requires a reliable liquid–gas phase separation prior to engine restart in space, and auxiliary engines are usually used to provide positive acceleration effect to satisfy vapor-free liquid supplement purpose. To assist thruster logic design for an upper stage, bubble distribution inside a delivery tube and bubble spilling behaviors should be known previously. In the present paper, a CFD approach is adopted to numerically study the bubble generation and bubble movement in liquid hydrogen (LH2) delivery tube under microgravity, and the bubble spilling upward behaviors under different situations are significantly analyzed. The results show that space heat from surroundings brings about liquid evaporation inside the delivery tube, and weak convection effect induced by bubble generation process could result in random bubble distribution in the whole tube range. The maximum bubble reaches the size of tube inner diameter. Under positive acceleration effect, the bubbles spill upward and bring about gas amount decrease in the delivery tube range. Moreover, the bubble spilling upward is not a continuous process, and only the big bubble discharge exerts a significant contribution to the gas amount decrease. In addition, the tube layout and the initial gas amount have slight influence on the bubble discharge performance, but the space acceleration level plays the primary effect on this process. For the present objective, the acceleration with 10−3g0 could drive the bubble to be discharged within 700 s. When the acceleration increases to 10−1g0, the required time correspondingly decreases to less than 100 s. Under the acceleration level of 10−4g0, however, the bubble could not spill upward any more but a vapor amount increase phenomenon is observed. Generally, the present work provides an opportunity to understand the bubble properties inside the cryogenic delivery tube in microgravity, and the results on acceleration influence as well as acceleration period are beneficial to the sequence design of space engine restart.

Adaptive control of movement deceleration during saccades.

As you read this text, your eyes make saccades that guide your fovea from one word to the next. Accuracy of these movements require the brain to monitor and learn from visual errors. A current model suggests that learning is supported by two different adaptive processes, one fast (high error sensitivity, low retention), and the other slow (low error sensitivity, high retention). Here, we searched for signatures of these hypothesized processes and found that following experience of a visual error, there was an adaptive change in the motor commands of the subsequent saccade. Surprisingly, this adaptation was not uniformly expressed throughout the movement. Rather, after experience of a single error, the adaptive response in the subsequent trial was limited to the deceleration period. After repeated exposure to the same error, the acceleration period commands also adapted, and exhibited resistance to forgetting during set-breaks. In contrast, the deceleration period commands adapted more rapidly, but suffered from poor retention during these same breaks. State-space models suggested that acceleration and deceleration periods were supported by a shared adaptive state which re-aimed the saccade, as well as two separate processes which resembled a two-state model: one that learned slowly and contributed primarily via acceleration period commands, and another that learned rapidly but contributed primarily via deceleration period commands.

The kinetic of calcium silicate hydrate formation from silica and calcium hydroxide nanoparticles

HypothesisThe mechanism of calcium silicate hydrate (CSH) formation, a relevant component of cement, the largest used material by mankind, is well documented. However, the effects of nano-sized materials on the CSH formation have not yet been evaluated. To this aim, a kinetic study on CSH formation via the “pozzolanic reaction” of nanosilica and calcium hydroxide nanoparticles, and in the presence of hydroxypropyl cellulose (HPC) as hydration regulator, is reported in this paper. ExperimentsThe reagents were mixed with water and cured at 10, 20, 30 and 40 °C. The reaction kinetics was studied with differential scanning calorimetry (DSC). A Boundary Nucleation and Growth model (BNGM) combined with a diffusion-limited model was used to analyze the data, yielding induction times, reaction rates, activation energies, nucleation and linear growth rates, and the related diffusion coefficients. FindingsThe rate constants kB and kG, which are, respectively, the rate at which the nucleated boundary area transforms, and the rate at which the non-nucleated grains between the boundaries transform, increase with temperature. Their different temperature dependence accounts for the prevailing effect of nucleation over nuclei growth at progressively lower temperatures. The nucleation rate, IB, is strongly enhanced when using nanomaterials, while the linear growth rate, G, is limited by the tightly packed structure of the transforming matrix. HPC influences the kinetics between 10 and 30 °C; at 40 °C the temperature effect becomes predominant. HPC delays induction and acceleration periods, increases Ea(kB), and enhances the reaction efficiency during the diffusion regime, by retaining and delivering water over the matrix, thus allowing a higher water consumption in the hydration reaction of CSH.

Investigation of the effect of waterborne epoxy resins on the hydration kinetics and performance of cement blends

The hydration process and products of polymer-modified cement determine its pore structure and mechanical properties. However, relatively few studies have systematically studied the hydration behavior, microstructure and mechanical properties of waterborne epoxy resin (WER)-modified cement blends. This study aims to investigate the influence of the WER content and curing temperature on the early hydration process and hydration product evolution of cement paste. Moreover, the retardation effect of WER during cement hydration on the microstructure and mechanical properties of cement mortar was also studied. In this investigation, three WER contents in the emulsion (i.e., 3%, 6% and 9%) and two curing temperatures (i.e., 20 °C and 40 °C) were employed. The hydration behavior of WER-modified cement over 72 h was characterized by means of the hydration heat, and the hydration kinetics were calculated by using a model proposed by Krstulović and Dabić. The hydration process of the modified cement paste was characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetric (TG) analysis, and scanning electron microscopy (SEM). The microstructure, pore structure, compressive strength and flexural strength of the modified cement mortar were also investigated. The results showed that the WER-modified cements exhibited a lower hydration rate in the acceleration period and released less hydration heat than the plain cement. The retardation effect of WER was mainly related to the prolonged interactions at phase boundaries (I process). The higher the WER content was, the more significant the retardation effect. As the WER content increased, a decreasing content of CH at various curing ages in the modified cement paste was observed according to the FTIR spectroscopy, XRD, and TG analysis results. However, when the curing temperature was increased from 20 °C to 40 °C, the hydration rate during the acceleration period notably increased, and the CH content also increased, suggesting an increase in the hydration degree. The compressive strength of WER-modified cement mortar decreased as the WER content increased, which may be related to the cement having a lower hydration degree. The use of an optimum WER content (3%) refined the pore structure in the cement mortar, which resulted in an increase in its flexural strength.

Effect of superplasticizers on hydration kinetics of ultrafine sulfoaluminate cement-based grouting material

The effect of naphthalene superplasticizer (FDN) and polycarboxylate superplasticizer (PCE) on hydration kinetics of ultrafine sulfoaluminate cement-based grouting material (USCBGM) was studied. The results showed the hydration process of USCBGM was divided into acceleration, deceleration and stabilization period, being controlled by nucleation (NG), phase boundary reaction (I) and diffusion (D) respectively, which were well simulated through Knudsen and Kondo models. FDN retarded the hydration of USCBGM in acceleration and stabilization period, but promoted the hydration during deceleration period. PCE did not significantly affect the hydration in acceleration period, but also can promote the hydration in deceleration period. However, PCE had less effect on hydration during deceleration period compared with FDN. Moreover, PCE can obviously retard the hydration in stabilization period. The reaction controlled process of USCBGM changed from NG-I-D to NG-D whether FDN or PCE was added according to the fitting results of hydration kinetics.

The influence of degree of loading and load placing on steerability of vehicles

The methodology of research of the influence of the degree of loading, kinematic parameters of movement, and nonlinear power characteristics of elastic elements and shock-absorbers of the suspension system on their steerability on curved sections of the road is developed. The research is based on the equation of kinetostatics of the system of sprung-unsprung part and differential equations that relate the motion of the sprung part of vehicles. Concerning the last, they take into account both loading of a vehicle and nonlinear-elastic characteristics of shock-absorbers. For the case when elastic characteristics of shock-absorbers are described by degree or close to it dependence, the fluctuation of sprung part is described analytically. Their peculiarity is that the frequency and therefore dynamic force of wheels pressure on the bearing surface (road) depends on the amplitude. It is the last value and characteristics of the road surface that determine the main parameters of steerability and stability of the movement of wheeled vehicles along curved sections of the road. Taken together, the mentioned above allowed to obtain the dependence of the critical value of the dynamic angle of rotation of the steered wheels, as a function of the amplitude of longitudinal-angular oscillations, kinematic motion parameters, and the level of loading of a vehicle. It is established: - fluctuation of the sprung part significantly reduce the value of the limiting angle of rotation of the steered wheels along the curved sections of the road; - for the period of acceleration of the vehicle and the closer location of the center of gravity of the cargo transported to the tailgate, the limit value of the dynamic angle of rotation of the steered wheels is less; - the suspension system with the progressive law of change of regenerative force of elastic shock-absorbers in a wider range of change fluctuations amplitude of the suspended part satisfies ergonomic conditions of transportation. The obtained calculated dependencies can simultaneously be basic during the modernization of existing or the creation of new suspension systems in order to improve the main operation characteristics of wheeled vehicles

A LATTICE-BOLTZMANN METHOD SIMULATION OF THE HORIZONTAL OFFSET IN OBLIQUE COLUMN DEPOSITION OF ALUMINUM DROPLETS

The metal droplet deposition manufacturing technology adopts a point-by-point stacking method, which provide an unsupported manufacturing method for oblique column deposition with high flexibility. In this paper, a lattice Boltzmann model is established for simulating the continuous deposition process of the oblique column, and the horizontal displacement of the droplet on the solidification surface is studied. According to the charging and discharging process of surface energy, the deposition process is divided into four stages: falling, rapid expansion, slow expansion, and rebound. The forces on the deposited droplet are analyzed by the trend of surface energy, the gravitational potential energy, the kinetic energy, and the viscous dissipation. The internal flow of droplet is sliding in the expansion stage and rolling in the rebound stage. The internal flow of the droplet shows sliding state in the expansion stage and rolling state in the rebound stage. The acceleration of the deviation mainly occurs in the expansion stage, while the deviation distance occurs in the rebound stage. Combined with the forces in the expansion stage, it is concluded that the main driving forces of displacement are gravity and capillary force. With the increase of the droplet axial distance, the acceleration in expansion stage is shortened, and the peak of velocity is increased, so that the horizontal deviation is first increased and then decreased. This staged feature stems from the competitive relationship between the acceleration period and the maximum speed in the deviate motion. Under different deposition heights and solid-liquid wettability, the deviation distance maintains the same trend. Under a certain axial distance, the deviate distance decreases with the increasing solid-liquid wettability, or the increasing deposition height. The evolution tendency of the horizontal deviation distance is fitted, and the scanning step is optimized to realize the uniform deposition of the inclined column whose inclination angle is consistent with the theoretical result.

Periodicities in an active region correlated with Type III radio bursts observed by Parker Solar Probe.

Context.Periodicities have frequently been reported across many wavelengths in the solar corona. Correlated periods of ~5 min, comparable to solar p-modes, are suggestive of coupling between the photosphere and the corona.Aims.Our study investigates whether there are correlations in the periodic behavior of Type III radio bursts which are indicative of nonthermal electron acceleration processes, and coronal extreme ultraviolet (EUV) emission used to assess heating and cooling in an active region when there are no large flares.Methods.We used coordinated observations of Type III radio bursts from the FIELDS instrument on Parker Solar Probe (PSP), of EUV emissions by the Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA) and white light observations by SDO Helioseismic and Magnetic Image (HMI), and of solar flare X-rays by Nuclear Spectroscopic Telescope Array (NuSTAR) on April 12, 2019. Several methods for assessing periodicities are utilized and compared to validate periods obtained.Results.Periodicities of ~5 min in the EUV in several areas of an active region are well correlated with the repetition rate of the Type III radio bursts observed on both PSP and Wind. Detrended 211 and 171 Å light curves show periodic profiles in multiple locations, with 171 Å peaks sometimes lagging those seen in 211 Å. This is suggestive of impulsive events that result in heating and then cooling in the lower corona. NuSTAR X-rays provide evidence for at least one microflare during the interval of Type III bursts, but there is not a one-to-one correspondence between the X-rays and the Type III bursts. Our study provides evidence for periodic acceleration of nonthermal electrons (required to generate Type III radio bursts) when there were no observable flares either in the X-ray data or the EUV. The acceleration process, therefore, must be associated with small impulsive events, perhaps nanoflares.

Working Mechanisms and Design Principles of Comb-like Polycarboxylate Ether Superplasticizers in Cement Hydration: Quantitative Insights for a Series of Well-Defined Copolymers

Cement and concrete are the most widely used building materials and contain comb copolymers such as polycarboxylate ethers (PCEs) as hydration and setting modifiers. The working mechanisms of these additives in cement hydration have remained uncertain, which limits the rational design of additives and of new cement materials with lower CO2 footprint. We identified quantitative correlations between PCE copolymer structure, adsorption, and cement setting properties for a series of copolymer structures and concentrations, combined with insights into conformations and adsorption mechanisms by atomistic simulations. The PCE copolymers have only a small fraction of polydispersity compared to earlier studies, and molecular dynamics simulations utilize Interface force field models for C-S-H phases that enable order-of-magnitude more accurate insights into the dynamics of the nanoscale polymer interfaces compared to earlier models. Two distinct sets of property correlations were discovered. (1) The carboxylate content of the PCEs, i.e., the molar density of ionic side groups per unit mass, correlates with the adsorbed amount of polycarboxylate ethers onto cement pastes, the conductivity of the cement paste, and the retardation of the acceleration period of cement hydration. (2) The combination of the ionic character of the polymer backbone and the length of non-ionic polyethylene glycol (PEG) side chains correlates with the water-to-cement ratio necessary for processing, zeta potentials, and fluidity of the cement pastes in mini slump tests. Simulations indicate that PCE adsorption onto cement particles involves migration of calcium ions in the acrylate backbone onto the calcium silicate hydrate surface, or calcium hydroxide surfaces, followed by ion pairing of the anionic polymer backbone with the positively charged mineral surface. PEG side chains exhibit no affinity to the mineral surface. The best fluidity and water reduction are achieved using an optimum ratio of the volume of PEG side chains to the volume of the anionic backbone, balancing sufficient surface bonding through the ionic backbone and minimization of interparticle forces by the non-ionic PEG side chains. A charge density too low prevents effective adsorption, and a charge density too high leads to multilayer deposition and ionic agglomeration forces between coated particles that reduce the fluidity and increase the necessary water-to-cement ratio. The proposed mechanism supersedes prior models and provides quantitative metrics for the rational design of polymer additives for cement and related particle dispersions.

Kinematic changes in goal-directed movements in a fear-conditioning paradigm

In individuals with a musculoskeletal disorder, goal-directed reaching movements of the hand are distorted. Here, we investigated a pain-related fear-conditioning effect on motor control. Twenty healthy participants (11 women and 9 men, 21.7 ± 2.7 years) performed a hand-reaching movement task. In the acquisition phase, a painful electrocutaneous stimulus was applied on the reaching hand simultaneous with the completion of reaching. In the subsequent extinction phase, the task context was the same but the painful stimulus was omitted. We divided the kinematic data of the hand-reaching movements into acceleration and deceleration periods based on the movement-velocity characteristics, and the duration of each period indicated the degree of impairment in the feedforward and feedback motor controls. We assessed the wavelet coherence between electromyograms of the triceps and biceps brachii muscles. In the acquisition phase, the durations of painful movements were significantly longer in both the acceleration and deceleration periods. In the extinction phase, painful movements were longer only in the acceleration period and higher pain expectation and fear were maintained. Similarly, the wavelet coherence of muscles in both periods were decreased in both the acquisition and extinction phases. These results indicate that negative emotional modulations might explain the altered motor functions observed in pain patients.

Application programming interface guided QA plan generation and analysis automation.

PurposeLinear accelerator quality assurance (QA) in radiation therapy is a time consuming but fundamental part of ensuring the performance characteristics of radiation delivering machines. The goal of this work is to develop an automated and standardized QA plan generation and analysis system in the Oncology Information System (OIS) to streamline the QA process.MethodsAutomating the QA process includes two software components: the AutoQA Builder to generate daily, monthly, quarterly, and miscellaneous periodic linear accelerator QA plans within the Treatment Planning System (TPS) and the AutoQA Analysis to analyze images collected on the Electronic Portal Imaging Device (EPID) allowing for a rapid analysis of the acquired QA images. To verify the results of the automated QA analysis, results were compared to the current standard for QA assessment for the jaw junction, light‐radiation coincidence, picket fence, and volumetric modulated arc therapy (VMAT) QA plans across three linacs and over a 6‐month period.ResultsThe AutoQA Builder application has been utilized clinically 322 times to create QA patients, construct phantom images, and deploy common periodic QA tests across multiple institutions, linear accelerators, and physicists. Comparing the AutoQA Analysis results with our current institutional QA standard the mean difference of the ratio of intensity values within the field‐matched junction and ball‐bearing position detection was 0.012 ± 0.053 (P = 0.159) and is 0.011 ± 0.224 mm (P = 0.355), respectively. Analysis of VMAT QA plans resulted in a maximum percentage difference of 0.3%.ConclusionThe automated creation and analysis of quality assurance plans using multiple APIs can be of immediate benefit to linear accelerator quality assurance efficiency and standardization. QA plan creation can be done without following tedious procedures through API assistance, and analysis can be performed inside of the clinical OIS in an automated fashion.

Interdecadal changes of summer precipitation dominant mode over East Asia‐Northwest Pacific around late 1990s

AbstractIn this study, we investigate the interdecadal variation characteristics of the dominant mode of summer precipitation over East Asia‐Northwest Pacific (EA‐NWP) before and after late 1990s, reveal the physical mechanism, and address its possible connection with the regional ocean warming background. Study results show that the empirical orthogonal function mode 1 (EOF1) of summer precipitation anomalies over EA‐NWP during the global ocean warming acceleration period (1979–1998) present a more significant dipole pattern between Yangtze River Basin (YRB) and tropical NWP compared with that during the global ocean warming slowdown period (1999–2012). And then we find that the anomalous dipoles of low‐level winds, geopotential height, convection, and associated wave activity fluxes over NWP significantly shift westward (eastward) and enhance (weaken) in 1979–1998 (1999–2012), which are regarded as the direct cause of the adjustment of dipole pattern between YRB and tropical NWP. Further analysis reveals that the negative sea surface temperature (SST) anomalies in the tropical NWP are prominent (not prominent), resulting in the stronger (weaker) Pacific–Japan Teleconnection over Japan and Tropics in NWP during the period 1979–1998 (1999–2012), and ultimately lead to the change of summer precipitation EOF1 in EA‐NWP. By regressing vertical velocity, outgoing longwave radiation, relative vorticity, wave activity fluxes, and precipitation onto the NWP SST in the two periods, the impacts of the SST in the NWP on the interdecadal variation of summer precipitation EOF1 in EA‐NWP are verified. Finally, the mechanism diagram of interdecadal variation of summer precipitation is given, which can be useful for short‐term precipitation prediction of East Asia.

Non-isothermal flow of Sisko fluid in a stenotic tube induced via pulsatile pressure gradient and periodic body acceleration

A theoretical study for pulsatile unsteady blood flow and heat transfer effects via tapered stenotic artery is presented. This study is based upon a non-Newtonian Sisko-fluid model. The order of magnitude analysis is executed for the derivation of momentum and energy equations for the mild constriction model. The coordinate transformation is utilized to transform the computational domain. A finite difference scheme is utilized for the solution of modeled non-linear partial differential equations. The computed results are exhibited in form of graphs for velocity, wall shear stress (WSS), resistive impendence, flow rate, and temperature for appropriate ranges of important physical parameters governing the flow, including the Sisko fluid material parameter power-law index stenosis height the amplitude of body acceleration shape parameter Prandtl number and Brinkman number This investigation deduces that the flow rate and blood velocity rise with the escalation in the amplitude of body acceleration and shape parameter whereas both decrease by varying material parameter, power-law index, and stenosis height. The wall shear stress (WSS) rises with increasing the power-law index, material parameter, and stenosis height, whereas it decreases with the escalation in the amplitude of body acceleration and shape parameter. The resistive impedance increases with the increase of the size of stenosis and power-law index. The temperature field appears to dominate for smaller values of Prandtl number and larger values of Brinkman number.