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• Groundwater depth (GT) controlled transpiration dynamics of Populus tomentosa. • Diurnal (Q day) and nocturnal water use (Q night) had different seasonal trends. • Groundwater recharged Q night and reduced the water consumption from the stem. • Q night helped poplars refill the consumption of water stored in the stem (R e). • When GT < 170 cm of the surface, R e / Q night increased with increasing GT. For theories of forest water utilization over day-night cycles, it is important to have a reliable information on plant transpiration behaviors during daytime and nighttime and their environmental controls. With the help of thermal dissipation probes, our study investigated the seasonal variations in the diurnal (Q day) and nocturnal stand water use (Q night) of a Populus tomentosa plantation and explored their responses to groundwater table (GT) fluctuations and the meteorological factors. The results indicated that Q night occurred on most nights during the growing season in the P. tomentosa plantation, but with a different seasonal dynamic from Q day. A distinct increase in the ratio of nocturnal to daily water use appeared at the beginning and the end of the growing season. During the experimental period, stem refilling accounted for 61% of Q night , indicating that P. tomentosa was able to draw on stored water in the stem to support transpiration. The Q day and Q night were positively and negatively related to GT , respectively. When the GT varied within 170 cm of the surface, the proportion of stem refilling accounting for Q night increased with GT. The positive and negative correlations were found in meteorological factors with Q day and Q night , respectively. Among the single meteorological factors except for ET 0 , vapor pressure deficit (VPD) and photosynthetically active radiation (PAR) explained the highest variation in Q day in 2010 and 2011, respectively. In contrast, Q night was dominantly affected by VPD in 2011. Nocturnal stand water-use could help P. tomentosa to recharge the consumption of water stored in the stem and overcome the seasonal drought. The compensation effect of groundwater on the nocturnal stand water-use of P. tomentosa could reduce its consumption of water stored in the stem. As the stand age of P. tomentosa plantation varied, the key meteorological drivers of both Q day and Q night also changed. Our results enable better understanding of the water-use strategies of poplars in the North China Plain and can lead to refinement of current silvicultural techniques. [ABSTRACT FROM AUTHOR]

Highlights • Four different methods were applied to determine the optimal tensiometer placement. • The optimal tensiometer placement location should not change with stand age. • The tensiometer should best be placed 10 cm deep and 15 cm distant from the dripper. • This will optimize the schedule for drip irrigation in different aged Populus tomentosa forests. Abstract Determining the optimal tensiometer placement is crucial for scheduling irrigation based on soil water potential (SWP) in poplar plantations. However, such work has never been done. The stand-age effect on the tensiometer placement is still unknown, hindering the development of a dynamic irrigation regime. In a surface drip irrigated Populus tomentosa , short-rotation plantation on sandy loam soil, the variation of SWP at different positions [hereafter expressed in spatial coordinates (distance from dripper in cm, depth in cm)] within the soil wetting volume (WV), and the daily tree growth rates were continuously monitored in one growing season. Whereas, the transpiration and fine root distribution were measured in two growing seasons. The HYDRUS model was calibrated using soil water and transpiration data from one growing season and validated using data in another growing season. Then the model was applied to simulate sixty scenarios, which were combinations of different SWP measurement positions (ten scenarios), root distribution patterns (three scenarios; mainly using rooting depth as a proxy for trees at different ages), and irrigation thresholds (two scenarios). Based on the simulation results, we estimated the ratio of actual to potential transpiration (T a / T p) and irrigation efficiency (IE; calculated as (T a / T p)/irrigation amount) for each scenario. The absolute value of the mean relative difference of SWP was smaller at (15, 10) than at any other positions within the WV. The proportion of variation in growth (R2 = 0.294) and transpiration rates (R2 = 0.247) explained by root water-uptake was also highest at (15, 10). Fine roots concentrated on both sides of dripper as the trees grew bigger, with the maximal root density finally occurring at about (15, 10) and (−15, 10). Under the (−15, 10), (0, 10), (15, 10) and (0, 30) position scenarios, the T a / T p was at a high level relative to other scenarios, while the IE were at a middle level. As rooting depth increased, the ranks of different tensiometer positions in T a / T p and IE changed only a little, and T a / T p decreased slightly, implying the optimal placement should not vary with stand age. Therefore, tensiometer was recommended to place at 10 cm depth and about 15 cm distance from the dripper to schedule drip irrigation in different-aged P. tomentosa plantations on sandy loam soil. This will bring benefits to minimizing the use of irrigation water and maximizing production. Besides, the comprehensive approach used in this study can be adopted, when determining the optimal soil water measurement positions for scheduling irrigation for other plant species growing on other soil types. [ABSTRACT FROM AUTHOR]

C/ZrC-SiC composites with a density of 3.09 g/cm 3 and a porosity of 4.8% were prepared by reactive melt infiltration and vapour silicon infiltration. The flexural strength and modulus were 235 MPa and 18.3 GPa, respectively, and the fracture toughness was 7.0 MPa m 1/2 . The formation of SiC and ZrSi 2 during vapour silicon infiltration, at the residual cracks and pores in the C/ZrC, enhanced the interface strength and its mechanical properties. The high flexural strength (223 MPa, c . 95% of the original value) after oxidation at 1600 °C for 10 min indicated the excellent oxidation resistance of the composites after vapour silicon infiltration. The mass loss and linear recession rate of the composites were 0.0071 g/s and 0.0047 mm/s, respectively and a fine ablation morphology was obtained. [ABSTRACT FROM AUTHOR]

Carbon fiber-reinforced silicon carbide (C/SiC) nuts and bolts (M8) with different fiber preform structures were prepared by precursor infiltration and pyrolysis. The influences of fiber preform structures on the mechanical properties of C/SiC nuts and bolts, as well as the failure behaviors of threaded joints were studied. A C/SiC nut, which was fabricated by using the preform prepared by stacking 3K carbon fiber cloth followed by stitching, had the highest shearing strength (64.5 MPa). The bolt with the preform prepared by alternatively stacking 3 K carbon fiber cloth and unidirectional layer of carbon fiber tows followed by stitching had the highest extreme tensile strength (243.2 MPa) and shearing strength (106.3 MPa), but low thread tooth bearing ability (3.5 kN) and critical thread engagement length (9 mm). It is suitable for applications emphasizing the extreme tensile or shearing strengths of threaded joints or possessing enough thread engagement length to ensure bolt rupture as the failure mode. The bolt with the perform prepared by stacking 1K carbon fiber cloth followed by stitching had the highest thread tooth bearing ability (5.0 kN) and the lowest critical thread engagement length (6 mm), as well as moderate extreme tensile strength (163.0 MPa) and shearing strength (82.1 MPa). It works effectively for applications concerning thread tooth strength or possessing limited thread engagement length. Therefore, the preform for preparing a C/SiC bolt should be selected according to its application requirements. [ABSTRACT FROM AUTHOR]

Highlights: [•] A design principle of drilling holes on C/SiC substrates and joints is proposed. [•] The theoretical simulation can effectively predict the fracture behavior of the joints. [•] The number increase of pins/bolts improves the reliability of C/SiC joints. [•] The mechanical properties of C/SiC joints with different joining methods are provided. [ABSTRACT FROM AUTHOR]

Abstract: This work is aimed at providing a new joining technology for C/SiC composites and investigating the influence of drilling holes, hole distribution (including ratios of edge distance to diameter (E/D), width to diameter (W/D) and hole distance to diameter (H/D)) and the number of applied pins on the mechanical properties of C/SiC substrates and joints. The mechanical testing results show that drilling holes and hole distribution greatly affects the mechanical properties of C/SiC substrates but when adopting an optimized design principle (E/D ⩾3, W/D ⩾3 and H/D ⩾3) the effect could be neglected. 1D C/SiC pins with higher shearing strength (107.2MPa) are more suitable to join the substrates. With the increase of pins (1, 2 and 4), the bearing loads of the joints increase almost linearly, and the reliability of joints is also improved in that the fracture mode changes from the interlayer damage to the substrate rupture. Besides, the joining process generates uniform and dense joining layer (composition of ZrC and SiC) and a strong bonding without obvious interface. [Copyright &y& Elsevier]

• A specklegram based curvature sensor by a regression model of deep learning. • Specklegrams with various curvatures are got by a motorized translation stage. • CNN trained by specklegrams of less curvatures can predict more untrained curvatures. • Influencing factors on the prediction accuracy of CNN models are analyzed in detail. • The proposed scheme has the merits of simplicity and low cost. An optical fiber curvature sensor based on the detection of specklegrams from the facet of multimode fiber (MMF) is realized by using a deep learning regression model. Since the specklegrams result from mode interference in the MMF, they can be used to characterize the status of the MMF. In the experiment, light from a semiconductor laser source was injected into a section of 10-cm-long step-indexed MMF with a core diameter of 50 μ m. A large number of specklegrams at the facet of the MMF were automatically detected when different curvatures were introduced for the MMF by a controllable moving translation stage. The output specklegrams of the MMF under different curvatures were then fed into a convolutional neural network (CNN) for training, validation and testing. Experimental results demonstrate that after the CNN was well-trained by the specklegrams with specified curvatures, the CNN can effectively predict the curvature from any of the specklegrams obtained from the MMF with a curvature in the trained range. In the experiment, the CNN trained by specklegrams with 20 curvatures successfully predicted the curvatures corresponding to the specklegrams from the MMF under 57 curvatures in the range of 1.55–6.93 m−1. The prediction error for 94.7% of the specklegrams is within an error range of ± 0.3 m - 1 , confirming the feasibility of curvature sensing based on the analysis of specklegrams by CNN. [ABSTRACT FROM AUTHOR]

A field experiment was conducted in 2017 and 2018 to investigate the responses of fine root growth and morphology plasticity to drip irrigation and nitrogen fertigation (DIF) in a young triploid P. tomentosa plantation in the North China Plain. We monitored four DIF treatments (I20F0, I20FH, I45F0, I45FH), which were the combinations of two irrigation thresholds (− 20 kPa and − 45 kPa, denoted as I20 and I45) and two N fertigation amounts (0, denoted as F0; 220 and 260 kg N ha−1 year−1 in 2017 and 2018, denoted as FH). Some soil properties and aboveground growth parameters were also monitored. I20 significantly improved fine root biomass density (FRBD) by 156.92% and induced a significant reduction of specific root length (SRL) by 28.79% in 0–30 cm soil layers than I45, and FH significantly decreased fine root length density (− 62.88%), surface area (− 54.01%), and SRL (− 39.01%) in 30–80 cm soil layers than F0 in 2017. Fine root traits differed little among DIF treatments in 0–30 cm soil layers in 2018, but I20 significantly improved FRBD by 259.98% than I45 and FH significantly improved fine root averaged diameter by 67.14% in 30–80 cm soil layers than F0. These suggested that fine root had a conservative foraging strategy in water- and nitrogen-rich conditions. All the trait plasticity might be due to the changeable soil properties (i.e. soil water content, organic matter, nitrate and ammonium nitrogen, and total phosphorus). Based on the little difference of fine root mass among DIF treatments in two years, we hold the view that fine root distribution pattern and some growth and morphological traits adapted to water-nitrogen heterogeneity more easily than the mass plasticity in young aged P. tomentosa plantations. Yet enhancing our understanding of fine root foraging strategy in response to DIF practices and how it affects tree growth requires more attention to some physiological and biochemical processes and the growth dynamics of the root systems. • Fine root had a conservative foraging strategy in resource-rich conditions. • Key indices affecting fine root trait plasticity were SWC, OM, NO 3- -N, NH 4+ -N, and TP. • Fine root showed higher trait plasticity compared with mass plasticity under DIF practices. [ABSTRACT FROM AUTHOR]

• A bending recognition scheme based on specklegrams with high accuracies. • A motorized translation stage is used to get specklegrams with various bending. • CNN based deep learning is used to classify specklegrams. • The scheme shows potential a single MMF acts as an independent status monitor. Since the curvature induced variations of mode interference in multimode fiber (MMF) can be well represented by the fiber specklegrams, a bending recognition scheme based on the analysis of MMF specklegrams is proposed and verified. Amounts of specklegrams from the facet of MMF under different bendings were detected and used for training and testing in an image recognition algorithm based on deep learning. Good recognition results are provided by the specklegrams from MMF with diameter being 105 and 200 μ m , for which the average accuracies of bending status recognition are respectively 92.8% and 96.6%. Because specklegram can represent the status of the whole section of MMF, such scheme indicates the capability to distinguish the specklegrams even when the MMF is under complicated bending. In this sense, the scheme presents the potential of a single MMF being used as a bending indicator or status monitor independently, which may find applications in distinguishing the status of certain structures, such as robotic arms, mechanical fingers and some disabled auxiliary equipments. [ABSTRACT FROM AUTHOR]

Decabromodiphenyl ethane (DBDPE) is a new and popular type of brominated flame retardant (BFR) with high bromine content, strong thermal stability, and ultraviolet resistance. To evaluated the potential toxicity of this new BFR to soil ecosystem, different concentrations of DBDPE were used to observe effects on earthworms (Eisenia fetida) in artificial soil. The reactive oxygen species (ROS) contents, activities of antioxidase system and detoxify enzyme, levels of malondialdehyde (MDA), as well as DNA damage in earthworms were measured after exposure to 0, 2.5, 5, 10, and 20 mg/kg DBDPE in artificial soil for 7, 14, 21, and 28 days. The results showed that ROS and MDA content significantly increased for all treatments from days 7–21, followed by a decrease. Throughout the experimental period, SOD, POD, and CAT activities increased. The GST activity was stimulated significantly from days 14–28. Besides, the olive tail moment (OTM) value in all treated groups was significantly higher than that in the control and exhibited a concentration-related and exposure time-related response. This is the first study evaluating the biological toxicity of BFR at different concentrations using an integrated biomarker response index. Our results show that DBDPE has biochemical toxicity on earthworms, which sheds some light on the potential risks of DBDPE in the soil environment and provides a basis for the monitoring and diagnosis of soils contaminated with DBDPE. Image 1 • The subchronic toxicity of DBDPE retardant to earthworms was initially investigated. • An Integrated Biomarkers Response (IBR) index was used. • Oxidative stress was detected in earthworms exposed to 2.5–20 mg/kg DBDPE. • DBDPE exposure might cause a potential toxicity for the earthworm (Eisenia fetida). Oxidative stress and genotoxicity were detected in earthworms exposed to 2.5–20 mg/kg DBDPE. This BFR exposure might cause a potential toxicity for earthworm. [ABSTRACT FROM AUTHOR]

• A reflective tactile sensor based on specklegrams from MMF was proposed. • MMF-based optic couplers are used to realize the reflection operation. • Contact force sensing were realized by six algorithms and force range can be 0–30 N. • The periods of four different texture plates can be accurately recognized. • Accurate contact position recognition from 55 cases is achieved. A tactile sensor based on the detection of specklegram was proposed using a multimode fiber (MMF)-based optical coupler (OC) with a reflection configuration. Human-like sensations of multiple tactile information are successfully demonstrated. The laser beam was guided by one arm of the MMF-based OC with a coupling ratio of 50:50 and reflected by a soft mirror embedded in a 3D-printed finger-shaped sensor probe. The specklegram interrogated by a camera was obtained at the reflection end of the MMF-based OC. Contact force sensing was firstly realized by six kinds of processing algorithms and the zero-mean normalized cross-correlation coefficient was further used to make an in-depth investigation. Maximal linear measurement range of 30 N was obtained. To evaluate the texture detection ability, the proposed sensor was tested by scanning four 3D-printed texture plates with different periods, and the period obtained by processing the experimental results was highly consistent with that of the texture plates. In addition, the specklegrams from 55 cases when 11 different contact forces were applied at 5 different positions of the sensor probe can be classified with an accuracy of 98 %, which shows the sensor is capable of recognizing the contact position. Furthermore, three kinds of sensor probes with different shore hardness and three different MMF-based OCs were used for comparative analysis. [ABSTRACT FROM AUTHOR]

• High-level irrigation increased soil water contents during dry months. • High-level irrigation enhanced early stand growth on sandy loam soils. • N fertigation increased mineral N concentration in top 0-20 cm soil layer. • N fertigation had no effect on tree growth in such young stands. • Precipitation influenced tree seasonal growth and mineral N distribution in soils. The patterns of soil water and mineral nitrogen (N min) distribution, stand growth, and N uptake in a triploid Populus tomentosa plantation under two-year drip irrigation and N fertigation (DIF) treatments were investigated. There was a positive relationship between stand growth and the amount of precipitation and irrigation. Precipitation and irrigation affected the content of N min in top 0−20 cm soil layer after fertigation and the redistribution of N min in the soil. There was no significant difference in N uptake in poplar plantation among DIF treatments, and the high-fertigation in the rainy seasons didn't enhance stand growth. Thus, high-level irrigation with lower N fertigation was recommended in the study area. The long-term effects of fertigation on tree stand growth and N min distribution in deep soil layers and underground water remain to be studied further. [ABSTRACT FROM AUTHOR]

Zirconium carbide (ZrC) coatings were deposited on graphite substrates by chemical vapor deposition from the Zr-Br 2 -C 3 H 6 -H 2 -Ar system. The influence of total pressure on the growth of ZrC was investigated in the range of 5–60 kPa. As the total pressure increased, the deposition rate increased evidently, and the preferential orientation of ZrC coatings changed from the (200) plane to the (220) plane. The growth mechanism changed from a mass transport reaction to a surface reaction at the total pressure of 20–40 kPa. At the total pressure below 20 kPa, the deposition was dominated by crystal growth, so the coatings were composed of well-faceted pyramidal-shaped crystals growing along the <001> direction. At the total pressure above 60 kPa, the growth of ZrC coatings was controlled by the nucleation mechanism, so the coatings were cluster-like crystals rapidly growing along the <110> direction. In addition, low pressure was conducive to the formation of near-stoichiometric ZrC without free carbon. These variations of ZrC coatings can mainly be attributed to gas supersaturation and remarkably changed transport diffusion coefficients with increasing total pressure. [ABSTRACT FROM AUTHOR]

C/SiC–ZrC composites were prepared by a combining slurry process with precursor infiltration and pyrolysis, and then annealed from 1200 °C to 1800 °C. With rising annealing temperature, their mass loss rate increased, and the flexural strength and modulus decreased from 227.9 MPa to 41.3 MPa and from 35.3 GPa to 22.7 GPa, respectively. High-temperature annealing, which elevated thermal stress and strengthened interface bonding, was harmful to the flexural properties. However, it improved the ablation properties by increasing the crystallization degree of SiC matrix. The mass loss rate and linear recession rate decreased with increasing annealing temperature and those of the samples annealed at 1800 °C were 0.0074 g/s and 0.0011 mm/s respectively. Taking mechanical and ablation properties into consideration simultaneously, the optimum annealing temperature was 1600 °C. [ABSTRACT FROM AUTHOR]

Abstract: The form and water uptake characteristics of the fine root system in a 5-year-old triploid Populus tomentosa plantation were investigated to make recommendations related to irrigation water management for P. tomentosa plantation. Fine roots for analysis were collected from 2106 soil cores taken around eight trees. Soil moisture, trunk sap flow and evaporation were measured concurrently for four months in two experimental plots using time-domain reflectometry, thermal dissipation sensors and micro-lysimeters, respectively. Nearly half (44%) of fine roots corresponded to 0.2–0.5mm diameter. Generally, lateral root distribution was even, however, the vertical root profile showed an unusual pattern (nearly an ‘S’ shape). Dense fine roots occurred in surface soil and nearly one third (28%) of total fine roots occurred below 100cm depth, indicating the plantation had developed a dimorphic root system. With increasing distance from the tree, root distribution tended to be shallower. Mean fine root diameter was significantly larger (P <0.05) below 120cm, probably due to soil texture change or/and anoxia. Root water uptake in the 0–20cm layer contributed 58% of that within the 0–90cm soil layer, suggesting surface roots played the major water uptake role in shallow soil (<90cm). On average, P. tomentosa extracted 57% of transpired water from deep soil (>90cm), implying deep roots can contribute significantly to the water relations of mature P. tomentosa plantations. This functional significance of deep roots might be determined by their high length density and relatively large diameter. Based on these results, three irrigation management strategies were recommended: (1) irrigation schedules should be devised based on periodic measurement of the depth to water table; (2) water should be mainly provided to and maintained in the surface 40cm soil; and (3) water should be applied to the zone within 1m from the tree. [Copyright &y& Elsevier]

• Specklegrams from different concatenated fibers are compared and analyzed. • Sensor head with MMF housed in enables conversion of force into fiber deformation. • Changes in the ZNCC of fiber specklegrams characterize the fiber deformation. • Concatenated fiber enables good force sensing and is insensitive to disturbance. • Specklegram detection from concatenated fiber applied to tactile sensing is shown. An optical contact force sensor based on specklegram detection was proposed and validated for tactile sensing in this research. The specklegrams from different multimode fiber (MMF) based structures were firstly analyzed and compared in detail. Two of the structures based on the concatenation of MMF and few mode fiber (FMF) were selected. In the experiment, only the section of MMF is housed in a specially designed sensor head by 3D printing and the FMF section is used to lead the light out to the camera. The concatenated fiber structure enables the sensitive response to the applied force and shows insensitivity to the disturbance along the light lead-out part. With a contact force applying to the sensor head, bending of the MMF could be induced, which results in a deformed specklegram. In this way, the zero-mean normalized cross-correlation coefficient of the fiber specklegrams goes down with the increase of the contact force. For the selected fiber structure with different parameters, different sensitivity and different measurement ranges of force are realized, of which the largest linear measurement range of force is 0–23 N. Compared with only adopting MMF, the proposed scheme presents better stability together with a large measurement range and the flexibly adjusted sensitivity by changing the parameters of the fiber or the sensor head. [ABSTRACT FROM AUTHOR]