Effects of Drip System Uniformity and Irrigation Amount on Water and Salt Distributions in Soil Under Arid Conditions

The dynamics of water and salt in soil were monitored in the 2010 and 2011 growing seasons of cotton to evaluate the salinity risk of soil under drip irrigation in arid environments for different management practices of drip system uniformity and irrigation amount. In the experiments, three Christiansen uniformity coefficients （CU） of approximately 65, 80, and 95% （referred to as low, medium, and high uniformity, respectively） and three irrigation amounts of 50, 75, and 100% of full irrigation were used. The distribution of the soil water content and bulk electrical conductivity （ECb） was monitored continuously with approximately equally spaced frequency domain reflectometry （FDR） sensors located along a dripline. Gravimetric samples of soil were collected regularly to determine the distribution of soil salinity. A great fluctuation in CU of water content and ECb at 60 cm depth was observed for the low uniformity treatment during the irrigation season, while a relatively stable variation pattern was observed for the high uniformity treatment. The ECb CU was substantially lower than the water content CU and its value was greatly related to the water content CU and the initial ECb CU. The spatial variation of seasonal mean soil water content and seasonal mean soil bulk electrical conductivity showed a high dependence on the variation pattern of emitter discharge rate along a dripline for the low and medium uniformity treatments. A greater irrigation amount produced a significantly lower soil salinity at the end of the irrigation season, while the influence of the system uniformity on the soil salinity was insignificant at a probability level of 0.1. In arid regions, the determination of the target drip irrigation system uniformity should consider the potential salinity risk of soil caused by nonuniform water application as the influence of the system uniformity on the distribution of the soil salinity was progressively strengthened during the growing season of crop.

Preparation of Solid Solutions [Li_(3x) La_(0.67-x) Y_y Ti_(1-2y) Nb_y O_3] and Its Lithium-ion Conductivity

Perovskite type lithium fast ion conductors of Li 3 x La 0.67- x Y y Ti 1-2 y Nb y O 3 system were prepared by solid state reaction. X Ray powder diffraction shows that a single phase perovskite solid solution with orthorhombic structure forms in the ranges of x =0.10, y <0.075. Over this composition range the another phase, Y 2O 3 hexagonal phase is found. AC impedance measurements indicate that the bulk conductivities and the total conductivities are of the order of 10 -4 S·cm -1 and 10 -5 S·cm -1 at 25 ℃ respectively. The compositions have low bulk activation energies of about 20 kJ·mol -1 and total activation energies of about 40 kJ·mol -1 in the temperature range of 298～523 K, respectively.

Study on Lithium Fast Ion Conductors of Li_(3x)La_(0.67-x) In_yTi_(1-2y)P_yO_3 System

Perovskite type lithium fast ion conductors of Li 3 x La 0.67- x In y Ti 1-2 y P y O 3 system were prepared by solid state reaction. X ray powder diffraction shows that perovskite solid solution forms in the ranges of x =0.10～0.12, y ≤0.2. AC impedance measurements indicate that the bulk conductivities and the total conductivities are of 1×10 -4 and 1× 10 -5 S·cm -1 at 25 ℃ respectively. The compositions have low bulk activation energies of 20 kJ·mol -1 in the temperature ranges of 298～523 K and total activation energies of 40 kJ·mol -1 in the temperature ranges of 298～623 K.

Conductivity and mechanical properties of conductive adhesive with silver nanowires

The aim of this study was to develop conductive adhesive using silver nanowires prepared via solvothermal method as conductive fillers and epoxymodified organosilicone resin as matrix resin. Effect of the addition of silver nanowires/flakes on the conductive adhesive＇s electrical and mechanical properties was investigated. Compared with conventional conductive adhesive with silver flakes fillers, the percolation threshold of conductive adhesive with silver nanowires fillers is 10 % lower approximately. However, further rise of the content of silver nanowires has no obvious influence on improvement of the electrical conductivity of conductive adhesive. Both conductive and mechanical properties of conductive adhesive can be compatible by adding silver nanowires, which traditional silver conductive adhesives cannot reach.

Influence of interface point defect on the dielectric properties of Y doped CaCu_(3)Ti_(4)O_(12) ceramics

CaCu_(3)Ti_(4-x)Y_(x)O_(12)(0≤x≤0.12)ceramics were fabricated with conventional solid-state reaction method.Phase structure and microstructure of prepared ceramics were characterized by X-ray diffraction(XRD)and scanning electron microscopy(SEM),respectively.The impedance and modulus tests both suggested the existence of two different relaxation behavior,which were attributed to bulk and grain boundary response.In addition,the conductivity and dielectric permittivity showed a step-like behavior under 405 K.Meanwhile,frequency independence of dc conduction became dominant when above 405 K.In CCTO ceramic,rare earth element Y^(3+)ions as an acceptor were used to substitute Ti sites,decreasing the concentration of oxygen vacancy around grainelectrode and grain boundary.The reason to the reduction of dielectric behavior in low frequencies range was associated with the Y doping in CCTO ceramic.

Synergetic variations of active layer soil water and salt in a permafrost-affected meadow in the headwater area of the Yellow River,northeastern Qinghai-Tibet plateau

The coupling effects and mechanisms of water,heat,and salt in frozen soils are considered to be one of the core scientific issues in frozen soil studies.This study was based on in situ observation data of active layer soil volumetric water content(VWC),temperature,and bulk electrical conductivity(EC)obtained at an alpine meadow site from October 2016 to November 2019.The site is located in the headwater area of the Yellow River(HAYR).We analyzed the synergetic variations of active layer soil VWC,temperature,and bulk EC during the freeze and thaw processes and discussed the underlying mechanisms.When the thaw process occurred from 10 to 80 cm depths,the VWC and bulk EC at a 10 cm depth showed syn-chronous high-frequency fluctuations and both increased linearly.The linear decreasing rate of the VWC(bulk EC)at an 80 cm depth in the freeze depths between 0 and 40 cm was 2(1.6e2.3)times that of the VWC(bulk EC)at an 80 cm depth in the freeze depths occurring 0e10 cm.As soil temperature decreased in the frozen layer,unfrozen water content(bulk EC)decreased nonlinearly along with the absolute value of soil temperature(|T|),following a power(logarithmic)function.This study provided data that partly elucidate the interactions among permafrost,meadow,and ecohydrological processes in the HAYR.Also,our results can be used as a scientific basis for decision making on the protection and restoration of alpine grasslands,as well as for soil salinization studies.