Average Peak Value Research Articles

Barefoot vs shod walking and jogging on the electromyographic activity of the medial and lateral gastrocnemius

Gastrocnemius weakness is associated with Achilles tendinopathies and muscle strains, with the medial gastrocnemius (MG) more commonly injured than the lateral gastrocnemius (LG). Walking and jogging are common in daily activities and sports, and biomechanical differences between shod and barefoot exercise may influence MG and LG activation. Understanding these activation patterns could help optimize training programs for injury prevention and/or rehabilitation. The aim was to compare MG and LG electromyographic activity during walking and jogging, both shod and barefoot. Twenty-nine participants (25.28 ± 4.53 years, 171.31 ± 0.76 cm, 72.68 ± 6.36 kg) completed a warm-up followed by 1 min of walking (80–99 steps/min) and jogging (130–150 steps/min) in both conditions (barefoot and shod, random order). Electromyographic signals were recorded using wearable devices (mDurance Solutions S.L., Granada, Spain; 1024 Hz sampling rate). We measured the root-mean-square (RMS) amplitudes for an entire stride cycle and digitally filtered the signals. For analysis, we normalized electromyographic values to the average peak values obtained during two sprints. We analyzed differences with a repeated-measures analysis of variance. Significant effects of condition (barefoot-shod) and gastrocnemius (MG-LG) were observed (all p ≤ 0.023, ƞp2 = 0.17–0.39), with higher MG activation compared to LG in the barefoot conditions (p = 0.004–0.027, d = 0.72–0.83), and nonsignificant differences between muscles in the shod conditions (p > 0.05). Shod exercise compared to barefoot resulted in lower MG activation (p = 0.001–0.003, d = 0.62–0.63) and non-significant differences in LG activation. These results indicate that barefoot walking and jogging increase MG activation compared to shod conditions, with no differences in LG activation. Additionally, footwear reduces differences between MG and LG.

Study on the Fire Characteristics of Dual Fire Sources and the Difference in Power Temperature of Different Fire Sources in Tunnel

To investigate the combustion characteristics of multiple fire sources in the tunnel caused by ‘jumping’ discontinuous fire spread, we utilized scaled model experiments, numerical simulation software, and theoretical research. Our study focused on analyzing the influence of different fire source powers on the temperature characteristics of double fire sources in the tunnel. We examined the temperature characteristics, critical wind speed, and change rule under various wind speeds, fire source spacing, and fire source powers. Additionally, we explored the temperature characteristics, critical wind speed, and change rule of different fire source powers under varying wind speed conditions. The mathematical model for roof temperature decay and the temperature decay coefficients of dual source fires were established through the analysis of scale-down model experiments and numerical simulations. In comparison to single-source fires, the temperature variations in the tunnel of dual source fires exhibit a more intricate pattern, with higher average temperature and temperature peak values. These values are influenced by factors such as fire source spacing and power. Numerical simulation software was utilized to investigate the impact of fire source spacing at 10 m, 15 m, and 20 m, as well as the effect of varying fire source power on the temperature distribution within a tunnel under consistent fire source position and growth coefficient. The study revealed that, with consistent double fire source position and ventilation conditions in the tunnel, the upstream fire source exhibited greater power than the downstream fire source, resulting in the lowest average and peak temperatures in the tunnel. This observation could potentially enhance escape and rescue operations within the tunnel. Similarly, the lowest average and peak temperatures in the tunnel were also identified, offering potential benefits for optimizing escape and rescue strategies in tunnel scenarios.

Design Considerations Concerning an Innovative Drive System for a Manual Wheelchair

Manual wheelchairs, which are the basic means of transport for people with disabilities, are usually characterized by an inefficient adaptation to the physical capabilities of their users. For this reason, it is advisable to search for solutions that will allow us to change the parameters of the mechanical power generated by human muscles. For this purpose, mechanical gearing known from other solutions, for example, from bicycles, can be used. The paper describes the design methodology and a number of issues related to the construction of an innovative wheelchair prototype using a chain transmission in its drive system. This solution allows for the implementation of a variable ratio between the wheels and the pushrims. Thus, it effectively allows for matching the demand for driving torque to the movement conditions and the physical capabilities of its user. The use of such a system provides the basis for increasing the efficiency of the manual propulsion process. Initial studies show that changing the gear ratio allows for different speeds of the wheelchair wheel. In the tests conducted, the root mean square of this value varied from 15.2 RPM to 35.5 RPM, which resulted in a change in power from 15.8 W to 40.1 W. Of course, the values of rotational speed and torque show a cyclically changing character, which results from the intermittent nature of generating drive by the wheelchair user. The average peak values of rotational speed were 31.4 ± 1.7 RPM, 44.3 ± 3.4 RPM and 57.9 ± 3.4 RPM, while the torque was 12.1 ± 0.5 Nm, 12.4 ± 0.4 Nm and 14.1 ± 0.6 Nm for Gears 1, 4 and 6, respectively.

The Effect of Grass Juices on The Agricultural Properties of Legumes Grown in Different Root Media

The consumption of grass juices obtained from cereals for health purposes is increasing day by day. For this purpose, research on different plant solutions has gained momentum. In our study, barley (Hordeum vulgare L.) and oat (Avena sativa L.) grass juices grown in hydroponic conditions were used. Obtained grass juices were applied to pea and lupine seeds in 100% soil (control), 100% pumice, 100% perlite, 100% tea waste and 100% cocopeat substrate. Germination percentage, germination rate, average daily germination, peak value, germination value, root dry and fresh weight, stem dry and fresh weight, root and stem length, plant yield, grass yield, plant yield seed rate, macro and micro (N, P, K, Ca, Mg, Fe, Cu, Zn and Mn) mineral substance contents were investigated pea and lupine. Grass juices were obtained by mowing barley and oat seeds sown in 30 × 50 × 7 cm plastic tubs in ten days and passing them through a juicer. Pea and lupine 25 seeds, which were placed in each pot, were grown in different root media (100% soil, 100% cocopeat, 100% pumice, 100% perlite, and 100% tea waste) under in vitro conditions. 150 ml of water (control), barley grass juice, oat grass juice and barley + oat grass juice were applied to the seeds according to their subjects. The experiment was carried out in 400 pots with 10 replications x 2 species x 4 treatments x 5 media, according to the factorial fully randomised design. As a result of the research, germination physiology (germination percentage, germination rate, average daily germination, peak value and germination value), mineral substance content (N, P, K, Ca, Mg, Fe, Cu, Zn and Mn), growth and yield parameters at (root dry and wet weight, stem dry and wet weight, root and stem length, plant yield, grass yield, plant yield seed rate) barley grass juice application was found to be more effective than other applications after control. In all parameters examined in the research, it was determined that the five different medias used as growing media followed the order of soil>cocopeat>pumice>perlite>tea waste, and after the control and the best growing medium was cocopeat.

Microstructure, mechanical properties and multiphase synergistic strengthening mechanisms of LPBF fabricated AlZnMgZr alloy with high Zn content

In this work, a novel aluminum alloy with high Zn content was designed for laser powder bed fusion (LPBF) forming process. Aluminum alloy powder containing 14 wt% Zn and 2 wt% Zr was produced to conduct LPBF experiments with different process parameters. The analysis of the specimens revealed that the up facing surface exhibited an average microhardness peak value of 170.6 HV, achieving the ultimate tensile strength (UTS) of 573 MPa and the elongation of 11.6 %. There was no significant change in grain size and a large amount of plate-like η' (a metastable precipitate MgZn2 phase) phase precipitated within the grains after aging treatment (120°C, 21 h). The specimen reached the average microhardness peak of 181.7 HV and the UTS of 605 MPa. The principal strengthening mechanisms in the LPBF-formed samples were solid solution strengthening and grain refinement strengthening. After aging treatment, the precipitation of the second phase from solute atoms led to grain refinement strengthening and second-phase strengthening becoming the predominant factors to enhance the sample's strength. Al14ZnMgZr alloy have great application prospect in high strength and tough service environment.

A Parameter Assessment of Teaching Quality Indicators Based on Data Class Mining Fuzzy K-Mean Type Clustering

This paper proposes a data-based mining and hesitant fuzzy C-canopy-K mean clustering degree algorithm and uses it in the parameter assessment model of teaching quality indicators. Simulation and training are carried out through data class mining, and information input, followed by combining the hesitant fuzzy K-mean classification assessment method, which involves a hesitant fuzzy type evaluation system, a neural network identification and prediction system, and an application system for module identity verification. The simulation results show that the results of the six simulation conditions are consistent with the actual results, with only slight differences in some amplitudes, and a high degree of consistency in the overall trend, the change rule, and the average peak value. Through the prediction model processing in this paper, the teaching quality index parameter assessment has high accuracy and can reach more than 95.0%, in addition, the development of the law also fits very well. a, b, c, d four kinds of teaching quality parameter assessment of the average calculation of the assessment speed increased by 52.5%. In addition, the assessment test after the integrated design of the module shows that the system can effectively identify the four clustering identification processes that can be seen as excellent, good, medium, and poor; at the same time, the test data show that the system class effectively for teaching quality indicator parameter assessment.

Effect of Filling Ratio-Pattern Parameters on Mechanical Properties of PLA Filaments Used in 3D Printing

This research primarily focuses on the mechanical properties of specimens produced using Polylactic Acid (PLA) through the Fused Deposition Modeling (FDM) technique, a method of 3D printing. Within the scope of this study, specimens were fabricated using various fill percentages and different infill patterns. The simultaneous effect of variable parameters on mechanical properties is a challenging task, and it is aimed to rank the importance of the parameters, model the process, and finally validate the models using tensile and bending experiments. The results show that samples with a Concentric pattern and 95% fill rate exhibited the highest tensile strength with an average of 48.67 MPa. In contrast, the Triangle pattern with 20% infill ratio showed the lowest tensile strength with an average of 14.15 MPa. When evaluating flexural strength values, the Concentric design with a 95% fill ratio stood out once again, recording an average peak value of 79.94 MPa. Meanwhile, the Honeycomb pattern at 20% infill ratio exhibited the lowest strength value measured with an average of 23.3 MPa. Scanning Electron Microscope images taken according to infill rates confirm each other with the voids formed and mechanical performance outputs. These findings underscore that the mechanical attributes of PLA specimens produced using 3D printing technology can significantly vary based on the chosen fill rate and pattern.

A Wearable Upper Limb Exoskeleton System and Intelligent Control Strategy.

Heavy lifting operations frequently lead to upper limb muscle fatigue and injury. In order to reduce muscle fatigue, auxiliary force for upper limbs can be provided. This paper presents the development and evaluation of a wearable upper limb exoskeleton (ULE) robot system. A flexible cable transmits auxiliary torque and is connected to the upper limb by bypassing the shoulder. Based on the K-nearest neighbors (KNN) algorithm and integrated fuzzy PID control strategy, the ULE identifies the handling posture and provides accurate active auxiliary force automatically. Overall, it has the quality of being light and easy to wear. In unassisted mode, the wearer's upper limbs minimally affect the range of movement. The KNN algorithm uses multi-dimensional motion information collected by the sensor, and the test accuracy is 94.59%. Brachioradialis muscle (BM), triceps brachii (TB), and biceps brachii (BB) electromyogram (EMG) signals were evaluated by 5 kg, 10 kg, and 15 kg weight conditions for five subjects, respectively, during lifting, holding, and squatting. Compared with the ULE without assistance and with assistance, the average peak values of EMG signals of BM, TB, and BB were reduced by 19-30% during the whole handling process, which verified that the developed ULE could provide practical assistance under different load conditions.

Forecast of solar cycle 25 based on Hybrid CNN-Bidirectional-GRU (CNN-BiGRU) model and Novel Gradient Residual Correction (GRC) technique

In this study, a hybrid deep-learning(DL) model is proposed, which consists of a Convolution-Neural-Network (CNN) and Bidirectional-Gated-Recurrent-Unit (Bi-GRU) for the prediction of sunspot numbers(SSN) of different frequencies along with novel post-processing techniques of Gradient-Residual-Correction (GRC) to enhance the accuracy of the predictions further. GRC is utilized to reduce the residual present in the forecasted values. The AdaBoost regression model is implemented over the residual obtained from the prediction of training data using a hybrid CNN-BiGRU model with respect to the gradient of the training data points to predict the residual for the test data points. Ultimately, the predicted residual for test data points is summed up with the predicted test data points to achieve the final predictions. The results obtained from the proposed methods are compared with the results obtained from traditional DL models. The validation of the proposed method is carried out based on four performance metrics, namely Root Mean Squared Error(RMSE), Mean Absolute Scaled Error(MASE), Mean Absolute Error(MAE), and Mean Absolute Percentage Error(MAPE). A significant percentage of improvement is observed while using the GRC technique in comparison to all other experimented models for all four variants of SSN data. A maximum improvement of 85.71% has been achieved in comparison to the BiLSTM model over the 13-month smoothed SSN dataset on the basis of MAPE. Friedman Ranking is also performed as a non-parametric statistical test over the results of the performance measures. This model has been utilized for the forecast of solar cycle 25(SC25) over the annual mean of total SSN. It has been observed that the SC25 is expected to reach its peak in the year 2024 with an annual average peak value of 143.641. Comparative analysis of SC25 and the peak of SSN in the ongoing cycle with the previous works are also carried out.

Wet deposition of polycyclic aromatic hydrocarbons in a remote area of Central South China from 2014 to 2017

AbstractIn recent years, there has been a notable increase in the consumption of fossil energy, leading to a significant rise in environmental pollution, particularly in China due to its rapid development. This has resulted in the frequent occurrence of large‐scale fog and haze weather, highlighting the urgent need for environmental protection measures. To gain insights into the atmospheric conditions in China, an analysis was conducted on the wet deposition of polycyclic aromatic hydrocarbons (PAHs) in a remote region of Central South China from 2014 to 2017. The study revealed that the average concentrations and peak values of Ʃ16PAHs in 2014 and 2015 were considerably higher than those observed in 2016 and 2017. Furthermore, it was found that five‐ring PAH species were the predominant components during 2014 and 2015, indicating a shift in the main sources of PAHs. The peaks of Ʃ16PAHs were predominantly detected in samples collected during light rain in the winter, specifically on days without heavy rainfall. This can be attributed to the absence of heavy rain, which would otherwise reduce the concentration of air pollutants. Consequently, contaminants accumulated in the air are easily enriched in rainwater. The concentrations of Ʃ15Alkyl‐PAHs also exhibited a significant correlation with the number of rainfall days. Notably, a much higher annual average concentration of Ʃ15Alkyl‐PAHs was observed in 2017, which experienced fewer rainfall days. Coal combustion, petroleum sources, and vehicular emissions accounted for 58%, 12%, and 30% of the PAHs in the air, respectively. Despite improvements in air quality in China since 2016, it is crucial to address the elevated concentrations of PAHs in the atmosphere, particularly under adverse meteorological conditions characterized by reduced rainfall.

Floor heave mechanism for gob-side entry retaining with concrete blocks and control method: A case study

The issue of significant floor heave deformation in gob-side entry retaining has long been a challenging problem in the context of longwall mining. This paper studies the floor heave failure mechanism and control method for gob-side entry retaining with concrete blocks in Guizhou Faer Coal Mine in China. Based on Rankine’s earth pressure theory, the effective shear stress equation for the plastic slip of roadway floor is established. The deformation mechanism of floor heave in a retaining roadway with a block wall is revealed in this study. The new comprehensive control method is proposed, encompassing roof pre-splitting blasting for pressure relief, reinforcing cables for roof control, double directions control bolts for concrete block, and pliability cushion yielding pressure. FLAC3D numerical calculation model is established, which shows that the new method can effectively reduce the average vertical stress peak value of the entity coal floor by 34.6% and significantly reduce the pressure source causing the roadway floor heave. Besides, a multi-parameter real-time online monitoring system for mine pressure was designed, and field tests were carried out. The results show that the maximum value of roadway floor heave under the new method is 163 mm, reduced by 66.9%, and the roadway floor heave is effectively controlled. These research findings offer a fresh perspective and new ideas for controlling floor heave in mining operations.

Effect of Bacillus sp. application on the germination of coriander (Coriandrum sativum L.) under salt stress

Coriander (Coriandrum sativum L.), one of the annual herbaceous plants widely used as a medicinal and aromatic herb, is used as flavor and aroma, to treat digestive system diseases, as antipyretic, etc. Salinity, which is one of the soil quality index parameters, is one of the most important abiotic stress factors limiting the production of agricultural products. This study examined the effect of Bacillus sp. application on germination rate (%), germination speed (days), average daily germination (days), peak and germination values of coriander at different salt (NaCl) concentrations (0, 50, 100, 150, 200 mM). It was determined that the Bacillus sp. and salt application were significant at the level of 1% in the investigated parameters and that the bacterial application minimized the negative effects of increasing salt concentrations on the germination biology. The germination rate (67%), germination speed (8.4 days), average daily germination (4.5 days), peak (2.33%), and germination values (10.5%) were obtained. It was determined that no Bacillus sp. + 50 mM salt application provided the best germination values in coriander seeds.

Spectrum sensing in cognitive radio networks using an ensemble of machine learning frameworks and effective feature extraction

From the signal received on a particular frequency band, spectrum sensing (SS) is used in cognitive radio (CR) to assess whether the primary user (PU) is using the spectrum and, consequently, whether the secondary user (SU) can utilize the spectrum. The main issue with SS is determining the presence of the primary signal in a low signal-to-noise ratio (SNR). Compared to conventional technologies, machine learning techniques are more effective and accurate at identifying the qualities of input data. This paper proposes a machine learning (ML) based SS model for CR with effective feature extraction and reduction techniques. The proposed work comprises five phases: noise removal, wavelet transform, feature extraction, dimensionality reduction, and classification. Firstly, noise filtering is done on the received signal to remove the noise present in the input signal using the filters such as moving median filter (MMF), Gaussian filter (GF), and Gabor filter (GBF). After that, the filtered signal is transformed into a wavelet domain using Discrete Wavelet Transform (DWT) algorithm. Then the statistical features such as average absolute value, wavelet energy, variance, standard deviation, and peak value features are extracted from the DWT. Next, the dimensionality reduction (DR) is performed using Linear Discriminant Analysis (LDA). Finally, the classification is performed using the ensemble ML classifiers such as Support Vector Machine (SVM), Naive Bayes (NB), and K-Nearest Neighbour (KNN), which classify whether the PU signal is active or not. Simulations are carried out to analyze the efficiency of the presented models for SS. The results proved that SVM obtains the best performance for SS with higher accuracy and lower SNR.

Regulation of Flood Dynamics by a Check Dam System in a Typical Ecological Construction Watershed on the Loess Plateau, China

The check dam is the most important engineering measure in place for controlling water and preventing soil loss in the gully on the Loess Plateau. This study assesses Jiuyuangou, a typical governance watershed of the Loess Plateau, and studies the influence that the check dam system has on the dynamics of sub-storm floods over different return periods by coupling the one-dimensional hydrodynamic MIKE 11 model with the distributed hydrological MIKE SHE model. This research demonstrates the following: The check dam system significantly reduces a flood’s peak flow and total volume in the basin and also increases the flood duration. The former effects are greater than the latter effect. The flood peak’s rate of reduction, the flood volume’s rate of reduction and the flood duration’s rate of increase all increase linearly as the number of check dams increase. Of all dam systems, the check dam has the best linear response to a flood peak’s rate of reduction. The check dam system reduces the flow rate of flood runoff in the basin. After the dam is built, the average flow rate in the basin decreases by 54%. The runoff velocity of the flood is reduced by different degrees over different return periods and the average peak value decreases compared with a scenario lacking any kind of dam. The check dams have a greater impact on the runoff velocity over a shorter return period, with the velocity being 58.56% slower. Finally, the check dam system significantly reduces the intensity of erosion in the middle and lower reaches of the watershed, and it changes the distribution of the intensity compared to the original channel runoff. These findings are expected to provide a scientific basis for guiding the construction and high-quality development of check dams on the Loess Plateau. In addition, check dam construction in basins can trap water, sediment and nutrients, and it can also contribute to ecosystem diversity and maintaining ecosystem imbalances around the world.

Application of 5G Mobile Communication Technology Integrating Robot Controller Communication Method in Communication Engineering

Following the ongoing advancement of the communication industry, data traffic and information have achieved rapid growth. As the core technology of contemporary mobile communication, 5G technology can not only meet the transportation needs of massive data traffic but also be expanded to various industries, expanding the development field of intelligent communication and realizing further improvement of production efficiency. At present, 5G mobile communication technology is widely used in communication engineering, providing effective technical support for engineering construction and operation. However, while the progress of the times brings innovation and refinement in mobile communication technology, it also increases the complexity of market development, in this context, the practical application of 5G technology in communication engineering is limited, which limits the development of both. In order to solve this dilemma, this paper integrated the communication method of the robot controller, and based on the analysis of the characteristics and application status of mobile communication technology, the application of 5G technology in communication engineering was deeply studied. In order to prove the effect of the robot controller communication method, in this paper, simulation experiments were carried out to analyze the application effect of 5G in communication engineering from three aspects of throughput rate, energy efficiency, and signal suppression effect and to compare it with traditional communication methods. The results of the signal suppression experiment showed that the average peak value of the signal under the traditional communication method was 18.134 dB, and the average peak value of the signal under the method in this paper was 11.296 dB, which showed that the 5G technology integrating the communication method of the robot controller is more practical in communication engineering.

Design of Low-SAR Terminal Antenna Using Characteristic Mode Manipulation

A novel specific absorption rate (SAR) reduction method based on the characteristic mode theory (CMT) is proposed for mobile terminal. The CMT is introduced to establish the relationship between the characteristic electric field and the induced electric field in human tissues. The design process and mechanism of a low-SAR antenna are demonstrated. To verify the effectiveness of the proposed SAR reduction method, a low-SAR loop antenna is designed. The measurement results show that the 10 g average SAR peak value of the proposed antenna is reduced by 26.1%. The measured −10 dB bandwidth of the low-SAR antenna is 320 MHz, which is increased by 60% compared with the reference antenna (200 MHz). The measured efficiency of the reference antenna and low-SAR antenna are better than 64% and 73% in the entire operating frequency band. With the advantages of bandwidth enhancement, significant SAR reduction and high antenna efficiency, the proposed SAR reduction method is a good choice for the low-SAR terminal antenna design.

Verification and development of a metamaterial with large bandwidth smooth transmission properties for the thermal properties sensing of Xuan paper

Metamaterial sensors are widely used because of their rich resonance behaviors. However, due to the dependence on resonance properties, many metamaterial sensors are difficult to be applied in measurement of the stationary thermal properties of Xuan paper samples in a wide frequency range. Many important properties of Xuan paper samples are related to thermal resonance properties,. such as folding resistance, tensile strength, ink-run property, whiteness, dry heat and wet heat aging. Here, a metamaterial sensor with smooth transmission performance in the operating frequency band is designed and fabricated. In experiments, by increasing temperature, the time for the thermal response current of the Xuan paper samples to reach the peak value is significantly reduced, and the average peak value is increased. The heat conduction of the Xuan paper samples is increased and the thermal resistance is reduaced. When the thickness of the Xuan paper sample is gradually increased, the time required for the thermal response current to reach the peak value is gradually increased and the average peak value is decreased. When the concentration of alum gelatin solution applied on the surface of the Xuan paper sample is gradually increased, the corresponding thermal response current is enhanced, and the time required to reach the peak is significantly reduced. The results show that the metamaterial sensor can be used to measure the thermal properties of Xuan paper samples.

Real-Time Gait Phase Estimation Based on Neural Network and Assistance Strategy Based on Simulated Muscle Dynamics for an Ankle Exosuit

Soft exosuits have been demonstrated to possess the potential to reduce metabolism and muscle fatigue in human locomotion. How to maximize the user’s metabolic benefit and reduction of muscle fatigue are the primary objectives of assistance patterns optimization. For the exosuit controller, accurate gait phase estimation and appropriate assistance force profile are crucial factors. To gain an accurate real-time gait phase estimation, a neural network algorithm based on multi-modal information fusion was developed. The eigenvector of which was composed of Euler angles and gyroscope data of four Inertial Measurement units fixed on thigh and calf, and gait period estimated by force sensing resistor installed on foot insoles. The mean squared error of the model is below 3 ms and the regression coefficient R exceeds 0.999 when walking at a speed of 1.5 m/s. For the assistance force profile, which was designed based on the characteristics of soleus muscle dynamics. Wherein the biomechanics of walking were derived from simulation with OpenSim software. Compared with wearing an exosuit without assistance and with assistance, the metabolic demand was reduced by an average of 7.5%, and the average peak value and RMS of calf muscles involved in palntarflexion were decreased to different degrees. Our research illustrates the feasibility of neural network-based real-time gait phase estimation and assistance strategy design obtained by simulating muscle dynamics in the OpenSim software.

The newly absorbed atmospheric lead by wheat spike during filling stage is the primary reason for grain lead pollution

Wheat spikes could directly absorb lead (Pb) from atmospheric depositions. However, the mechanism by which the spikes contribute to Pb accumulation in the grain remains unclear. To investigate this mechanism, a field experiment was conducted using three comparative spikes shading treatments: 1) exposed to atmospheric deposition and light (CK), 2) non-exposed to atmospheric deposition and light (T1), and 3) non-exposed to atmospheric deposition but light-transmitting (T2). Spikes shading treatments reduced the average rate and peak value of the accumulation of Pb in grains, which significantly decreased the grain Pb concentration by 57.44 % and 50.26 % in T1 and T2 treatments, respectively. Moreover, Pb isotopic analysis shows that the Pb in spike and grain was mainly from atmospheric deposition, and the percentage of the grain Pb originated from atmospheric Pb decreased from 85.98 % in CK to 72.87 % and 79.59 % in T1 and T2, respectively. In addition, the spikes, rather than the leaves/roots, were the largest wheat tissue source of Pb in grains, and the relative contribution of spikes to grain Pb accumulation increased to 65.57 % at the maturity stage, of which the stored Pb re-translocation of spikes and the newly absorbed Pb by spikes during the filling stage contributed 13.37 % and 52.20 % to the grain Pb, respectively. Thus, the contribution of the spike to the grain Pb was mainly from the newly absorbed Pb from the atmospheric deposition during the grain filling phase, and grain filling phase is the key stage for the absorption of Pb by the grain. In brief, the newly absorbed atmospheric Pb by wheat spike during filling stage is the primary cause of grain Pb contamination, which provided a new insight for effective control of wheat Pb pollution.

Transport of montmorillonite colloid in unsaturated packed column: The combined effects of sand grain size, flow rate and colloid concentration

The transport of colloid in unsaturated porous media affects the migration of contaminants and thus is closely related to groundwater resources protection. To figure out the combined effects of grain size, colloid concentration and injection flow rate on montmorillonite colloid transport characteristics in unsaturated quartz sand, a total of 27 sets of column experiments were conducted with three kinds of quartz sand (20, 40, 60 mesh), three flow rates (1.98, 3.96, 5.94 cm3/min) and three colloid concentrations (300, 600, 900 mg/L), using three packed columns with the inner diameter of 11 cm and the height of 40 cm. The experimental results showed that the transport of Na-montmorillonite colloid particles in the unsaturated quartz sand columnoccurred with significant retention. In the 20 mesh quartz sand column, the average peak values of the penetration curves for low and high concentration colloidal solutions of 300 and 900 mg/L increased by 44% and 27%, respectively, as the flow rate increased from 1.98 to 5.94 cm3/min. The average peak value of the colloidal solution with concentration 300 mg/L increased 17% more than that of the colloidal solution with 900 mg/L for increasing flow rate. When the injection flow rate of the colloidal solution was increased from 1.98 to 5.94 cm3/min, the effect of flow rate on colloidal transport was the most obvious, followed by the effect of media particle size, while the effect of colloidal solution concentration was the least. The calculation based on the total potential energy of Derjaguin-Landau-Verwey-Overbeek (DLVO) and collision efficiency further explained the retention of colloids in unsaturated porous media.