Intercept Of Line Research Articles

Patterns of compound-leaf form and deciduous-leaf habit across forests in China: Their association and key climatic factors

Leaf form (compound vs. simple) and habit (evergreen vs. deciduous) are key functional traits of trees to adapt to various climates and are vital in determining plant response to climate change. However, their association and climatic determinants remain uncertain, especially in East Asian forests in the largest monsoon region on earth. To fill these knowledge gaps, we compiled a dataset comprising 42 intact forests and over 2200 angiosperm tree species across China (spanning 30 latitudes and 47 longitudes). The geographical and climatic patterns of leaf form and habit were analyzed. The association between compound leaf and deciduousness was tested for tropical, subtropical and temperate climatic zones. We found that both the percentage of compound leaf (CT%) and deciduous tree species (DT%) increased with latitude and decreased with mean annual precipitation (MAP). For all forests, DT% was negatively related to mean annual temperature (MAT), whereas CT% was not. Nevertheless, both DT% and CT% increased with increasing MAT in the tropics, possibly owing to the high vapor pressure deficits (VPD) and canopy water deficits associated with high temperatures. A positive linear relationship between CT% and DT% was found across all forests and within different climatic zones except for temperate, and the intercept of the regression line was significantly higher in the tropics than in the subtropics. Overall, as supported by principal component analysis, deciduousness was negatively associated with both temperature and precipitation, while CT negatively with precipitation only across zones and positively with temperature in the tropics. Different relationships in different climatic zones suggest potentially different selective forces. Our findings provide novel insights into the linkage between leaf form and habit, as well as how climate shapes the landscape of broadleaf forests, which has important implications regarding the response of forest composition to climate change.

State Estimation With Heading Constraints for On-Road Vehicle Tracking

In transportation networks, vehicle motions are usually subject to the constraints arising from the roads, preset sea-routes, or preset flight routes. Taking advantage of prior known information of such constraints generally produces better surveillance performance. The problem of state estimation with heading constraints, in which only the direction of the target trajectory is prior known, is considered. When only part of the trajectory information is available, the conventional constrained estimation methods cannot be used to produce constrained estimates. The heading constraints in two typical situations are investigated, one is with a straight line, the other is a circular arc. For the straight trajectory, two augmentation approaches are proposed to formulate the constraints. One, parameter augmentation, augments the base state by the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$y$ </tex-math></inline-formula> -intercept of the constraint straight line. In the other approach, state augmentation, the states at the past time step are used to augment the base state. Two corresponding heading constraints are formulated by the augmented state’s elements and the prior known information about road direction. For a circular trajectory, the heading constraint is formulated using position and velocity components in the base state. Pseudo-measurements are constructed to incorporate the heading constraint into the estimators and result in three heading constraint Kalman filters (HCKFs). They are parameter augmentation HCKF and state augmentation HCKF in case of straight trajectory, and HCKF for circular trajectory. The discrimination of road segments at junctions is also discussed. Furthermore, the proposed constraint filters are integrated into the interacting multiple model estimator to handle on-road maneuvers with possible accelerations. Numerical simulations are conducted to evaluate the performances of the three HCKFs compared with existing methods.

Specific heat of metals and standard electrode potentials

Traditional thermodynamic considerations show that the standard electrode potentials, E0, of metal/metal ion electrodes are linearly related to the Fermi energies of the metal electrons, μ. Expressing E0 in volts, μ in volts/ion, and accounting for the dielectric screening of the solution, the expected slope of the straight line equals 1. Having evaluated μ from the electronic contributions of the specific heats of 11 sp metals in terms of Sommerfeld’s theory, we found a linear relationship between μ and E0. The slope of that line depends on the relative permittivity of water at the metal surface, ɛin. Taking ɛin = 6, in accordance with the general practice in electrochemistry, the expected slope was obtained without any parameter fitting. The intercept of the straight line can be interpreted as the absolute standard potential of the hydrogen electrode finding EH+/H20abs=3.86±0.13V. The calculations being based on equilibrium thermodynamics are independent of any actual mechanism.

A semi-analytical workflow to study dimethyl ether improved water flooding; a fractional flow study

This paper introduces a semi-analytical procedure to study fractional flow (fw) and performance of dimethyl ether improved water flooding (DEW). To this end, the fw-curve of DME/water-oil is discussed and the effect of the K-value on the fractional flow and the oil recovery curve is studied. To achieve proper fw-curves, governing equations are solved using a finite difference approach, and saturation and concentrations are obtained in every time step. Therefore, numerous fw-curves are found; we select a DME-free and a DME-rich fw-curve. Then, an initial point, which is determined using the partition coefficient value (K-value), is chosen to plot a tangential line on the fw-curve. The intercept of the tangential line and the horizontal axis is named pseudo-adsorption point. Upon increase of K-value, the intercept moves toward the origin of the plot. Moreover, results show that with the increase of K-value, the DME-rich fw-curve moves to the right side, which makes a larger horizontal distance between DME-free and DME-rich fw-curves. In addition results indicate that at small K-values, the increase of K-value significantly improves oil recovery, but the further increase does not lead to significant recovery improvements. This workflow can be considered useful to analyze DME-improved water flooding in different conditions.

An examination of the short-time approximation for mixed-controlled adsorption

A new linear approximation for a mixed-controlled adsorption process had been designed for estimating the surfactant diffusivity (Df) and adsorption rate constant (βf) by purely using the dynamic surface tension (ST) data (Moorkanikkara and Blankschtein, 2006). However, the uniqueness and applicability of this linear approximation are yet to be ascertained. Subsequently, a theoretical simulation was conducted to study the uniqueness and robustness of this linear approximation. An adsorption process of nonionic surfactant onto a freshly created planar air-water interface was considered and its mixed-controlled dynamic ST profiles were simulated using the Langmuir model. Linear regions in the simulated ST vs t1/2 profiles do exist, which could be described well by a straight line with an intercept >72 mN/m (representing the linear approximation). Values of Df and βf could then be estimated from the slope and the intercept of this straight line. While the applicability of this linear approximation was confirmed, the results did show a distinct possibility of obtaining multiple sets of Df and βf if different linear regions of the γ vs t1/2 profiles were selected for the fitting. Additionally, the applicability of this linear approximation on experimental dynamic ST data was tested.

Isotopic analysis to quantify the role of the Indian monsoon on water resources of selected river basins in the Himalayas

AbstractWestern disturbances (WDs) and Indian summer monsoon (ISM) led precipitation play a central role in the Himalayan water budget. Estimating their contributions to water resource is although a challenging but essential for hydrologic understanding and effective water resource management. In this study, we used stable water isotope data of precipitation and surface waters to estimate the contribution of ISM and WDs to the water resources in three mountainous river basins ‐ Indus, Bhagirathi and Teesta river basins of western, central and Eastern Himalayas. The study reveals distinct seasonality in isotope characteristics of precipitation and surface waters in each river basin is due to changes in moisture source, hydrometeorology and relief. Despite steady spatial variance in the slope and intercept of regression lines from the Teesta to Indus and the Bhagirathi river basins, the slope and intercept are close to the global meteoric water line and reported local meteoric water line of other regions in the Himalayas and the Tibetan Plateau. The two‐component end‐member mixing method using d‐excess as tracer were used to estimate the contribution from ISM and WD led precipitation to surface water in aforementioned river basins. The results suggest that the influence of the ISM on the water resources is high (&gt;72% to annual river flow) in Teesta river basin (eastern Himalayas), while as the WDs led precipitation is dominantly contributing (&gt;70% average annual river flow) to the surface waters in the Indus river basin (western Himalayas). The contribution of ISM and WD led precipitation in Bhagirathi river basin is 60% and 40%, respectively. The findings demonstrate that the unusual changes in the ISM and WD moisture dynamics have the potential to affect the economy and food security of the region, which is dependent on the availability of water resources. The obtained results are of assistance to policy makers/mangers to make use of the information for better understanding hydrologic response amid unusual behaviour of the dual monsoon system over the region.

Effects of site productive capacity and stand density management on the maximum density line for Eucalyptus pilularis (blackbutt)

ABSTRACT Data were available from two measurements of each stand of a set of stands in native regrowth and plantation forests of Eucalyptus pilularis (blackbutt) in subtropical New South Wales and Queensland. Measurements were made after competition-induced mortality had started in each stand. Most of the regrowth forest had been thinned some time before the measurements. Based on the Reineke model that relates stand stocking density to quadratic mean diameter, a maximum density line was determined for each stand based on methods developed by Vanclay and Sands. It was found that the intercept of the maximum density line increased both with increasing stand site productive capacity and in the thinned regrowth stands. The latter finding does not seem to have been reported for forests before; it is hypothesised to be a result of the delayed redevelopment of inter-tree competitive processes following the major reduction in stand density resulting from thinning. Both effects will have consequences for the structure of density management diagrams commonly used to assist in forest management practice.

Inner changes of Portland cement and metakaolin-based geopolymer in the high-temperature environment

The inner structure of cementitious materials is crucial for the intelligent design and construction in civil engineering. In this work, two kinds of samples made from Portland cement and metakaolin-based geopolymer respectively were prepared to be exposed in high-temperature environment. In the experiments, the samples were placed on a heater with a 400°C surface for 40 minutes. A high-energy X-ray computed tomography (CT) facility was used to detect the macroscopic inner structure of the samples. In addition, the infrared-ray morphology of samples was also tested and compared. Results show that metakaolin-based geopolymer was relatively more resistant to heat compared with Portland cement. However, the cracks development of metakaolin-based geopolymer was severer due to the shrinkage in the high-temperature environment. In addition, based on the X-ray CT images, a method to show the distribution of pores' sizes was proposed. It was found the distribution of pores' volumes and area surfaces can be fitted by power laws which are straight lines in the logarithmic coordinates, and the geopolymer samples have relatively higher goodness of fit. Moreover, a lower intercept of the fitting line indicates the frequency of larger pores in the sample is lower, and a lower slope indicates a tighter distribution range of the pores' sizes. These findings may provide insight for future intelligent design of digital cementitious materials used in hash environment.

Precise prediction of the drag reduction efficiency of polymer in turbulent flow considering diameter effect

One important issue for drag reduction of turbulent flow with polymers is the pipe diameter effect. Although this scale-up effect has been extensively investigated, there are still debates. For instance, when using the traditional scaling law to predict the friction factor in pipe flow of wide pipe diameters, the relative errors between experimental data and predicted values can be up to 1000%. This paper develops a new method to predict the friction factor in pipe flow applicable to a wide range of pipe diameters. The new method developed in this study transforms the Reynolds number (Re) vs friction factor (f) to log10(Ref) vs 1/f in the Prandtl–von Karman coordinate, where the latter two parameters are correlated on straight lines. We find that the slope and intercept of these straight lines can be predicted by empirical correlations involving diameters and polymer concentrations. Thus, if Re and f from a pipe flow of small diameter are known, these two correlations for slope and intercept can predict the cases for large pipe diameters. With our method, most relative errors between the predicted values and experimental data are within 20%, much better than the traditional scaling law. Finally, we point out the physical meaning of the slope and intercept, and make it clear why the previous scaling law becomes not reliable when it is employed to predict the friction factor for pipe flow with a too wide range of pipe diameters.

Differentiation of Hydrogen and Oxygen Isotopes in the Water Source Treatment Wetlands of Stream Networks

To explore the isotopic distribution and differentiation of water along the hydraulic flow gradients and plant-bed/ditch systems in constructed root-channel wetlands, surface and subsurface water samples were collected from four ecological wetlands, namely Shijiuyang and Guanjinggang in Jiaxing, as well as Changshuitang and Taishangang in Haining. All samples were collected along water flow pathways during the wet and rainy summer season in August 2019, except for those from Taishangang, which were collected within the plant-bed/ditch system during the dry and cold winter season in January 2020. The abundance of deuterium (δD) and δ18 O was determined in each functional area of the wetlands to assess the influence of wetlands on water differentiation. Stable isotope technology and mathematical statistics were used to analyze the distribution of δD and δ18 O in constructed root-channel wetlands and to reveal the influence of plant-bed/ditch systems on stable isotopes of water. A variety of data mining methods were used to examine the differentiation of stable isotopes of water, at various dimensions and scales, including nonparametric Kendall's tau-b correlation, stepwise regression, gray relational analysis, and machine learning (random forest) combined with scatter diagrams and model hypothesis diagnosis analysis. The main results were as follows:① The spatiotemporal variations in water isotopes of stream networks were largely affected by different water supply and evaporation enrichment effects. The slope and intercept of the wetland water line in Jiaxing were both significantly lower than the regional precipitation line of the adjacent Changshu Station (CHNIP). This showed that the wetlands area had undergone hydrogen and oxygen isotope enrichment. The δD values in Shijiuyang wetland water ranged from -52.2‰ to -49.4‰, and δ18 O values ranged from -7.6‰ to -6.9‰. In Guanjinggang wetland water samples, δD ranged from -48.1‰ to -45.1‰, and δ18 O ranged from -6.8‰ to -5.8‰. The δD values in Changshuitang wetland water ranged from -49.8‰ to -48.4‰, and δ18 O ranged from -7.2‰ to -6.6‰. The δD values in Taishangang wetland water ranged from -55.3‰ to -51.6‰, and δ18 O ranged from -7.8‰ to -7.2‰. ② Hydrogen and oxygen isotope abundance and composition of water showed complex nonlinear changes in the vertical and horizontal dimensions at different scales. At the regional scale, water level elevation in the vertical dimension had a greater impact on water isotope distribution than the length of the hydraulic flow pathway in the horizontal dimension. Water isotopes tended to be enriched in low-lying areas with low water levels. At the local scale, the influence of hydraulic process often played a greater role in determining water isotope distributions. The spatial variations of water isotopes were comprehensively determined by the evaporation of regional water and meandering hydraulic processes inside the wetland. ③ Compared with other wetland functional areas, the central constructed root-channel area (middle treatment zone) was more enriched in water isotopes. ④ The underground macropore network formed by plants with developed rhizomes or roots (e.g., Phragmites communis Trin. and Typha orientalis Presl), mineral-rich substrate soil, and aquatic plants in the plant bed had a significant influence on the abundance of hydrogen and oxygen isotopes in the plant-bed/ditch system. Therefore, when water passed through the plant-bed/ditch system, the values of δD and δ18 O in the lower ditch (outlet) were lower than those in the higher ditch (inlet). ⑤ The abrupt change in isotopic contents of the plant-bed/ditch system might indicate an inflection point in water quality purification. ⑥ The deuterium excess (d-excess) in subsurface water of the plant-bed/ditch system was significantly higher than that in ditch water, and the coefficient of variation in subsurface water was considerably greater than that in ditch water. The d-excess in the wetland root-channel ecological purification zone showed significant temporal differences and was negative in the summer and positive in the winter, which reflected the seasonal variation in water vapor sources and the spatial variation in isotope fractionation behavior in wetlands. These results provide some understanding of the distribution of water isotopes in constructed wetlands, which will strengthen their operation and management. This study also provides some ideas regarding new technologies for water quality improvement and shows that water isotope technology may be a reliable method for analyzing wetland hydrology.

A probabilistic method for long-term estimation of ice loads on ship hull

Ships navigating in ice-infested regions need strengthened hull to resist the loads arising from the interactions with ice. Correct estimation of the maximum ice loads a ship may encounter during its lifetime is of vital importance for the design of ship structures. Due to the stochastic nature of ice properties and interaction processes, probabilistic approaches are useful to make long-term estimations of local ice loads on the hull. The Event Maximum Method (EMM) is an existing probabilistic approach for the long-term estimation of ice loads on the hull. This paper aims to extend the current EMM, first by introducing a model for the intercept of the linear regression line on the abscissa in order to quantify this value. Moreover, ice concentration is considered in the extended method as the second ice condition parameter in addition to thickness. The proposed method is applied to the full-scale measurement of the ship S.A. Agulhas II using the data obtained from the 2018/19 Antarctic voyage. The obtained model is then validated against six-year measurement data from 2013 to 2019, which shows reasonable similarity.

Ground and excited state masses of Ωc0 , Ωcc+ and Ωccc++ baryons

The masses of ground and excited states of ${\mathrm{\ensuremath{\Omega}}}_{c}^{0}$, ${\mathrm{\ensuremath{\Omega}}}_{cc}^{+}$, and ${\mathrm{\ensuremath{\Omega}}}_{ccc}^{*++}$ baryons are calculated within the framework of Regge phenomenology. Here our attempt is to assign a possible spin parity to these obtained masses. Our calculated masses in the $(J,{M}^{2})$ plane with both natural (${J}^{P}=1/{2}^{+},3/{2}^{\ensuremath{-}},5/{2}^{+},\dots{}$) and unnatural (${J}^{P}=3/{2}^{+},5/{2}^{\ensuremath{-}},7/{2}^{+},\dots{}$) spin parities are in agreement with the experimental observations where available and reasonably close to other theoretical predictions. Further, we fix the slope and intercept of each Regge line in the $(n,{M}^{2})$ plane and estimate the masses of higher excited states of these baryons. The obtained mass relations and the mass value predictions could provide useful information in future experimental searches and the spin-parity assignment of these states.

Energy Absorption Characteristics of PVC Coarse Aggregate Concrete under Impact Load

In this paper, polyvinyl chloride (PVC) coarse aggregate with different mixing contents is used to solve the problems of plastic pollution, low energy absorption capacity and poor damage integrity, which provides an important reference for PVC plastic concrete used in the initial support structures of highway tunnels and coal mine roadway. At the same time, the energy absorption characteristics and their relationship under different impact loads are studied, which provides an important reference for predicting the energy absorption characteristics of concrete under other PVC aggregate content or higher impact speed. This study replaced natural coarse aggregate in concrete with different contents and equal volume of well-graded flaky PVC particles obtained by crushing PVC soft board. Also, slump, compression, and splitting strength tests, a free falling low-speed impact test of steel balls and a high-speed impact compression test of split Hopkinson pressure bar (SHPB) were carried out. Results demonstrate that the static and dynamic compressive strength decreases substantially, and the elastic modulus and slump decrease slowly with the increase of the mixing amount of PVC aggregate (0–30%). However, the energy absorption rate under low-speed impact and the specific energy absorption per MPa under high-speed impact increase obviously, indicating that the energy absorption capacity is significantly enhanced. Regardless of the mixing amount of PVC aggregate, greater strain rate can significantly enhance the dynamic compressive strength and the specific energy absorption per MPa. After the uniaxial compression test or the SHPB impact test, the relative integrity of the specimen is positively correlated with the mixing amount of PVC aggregate. In addition, the specimens are seriously damaged with the increase of the impact strain rate. When the PVC aggregate content is 20%, the compressive strength and splitting strength of concrete are 33.8 MPa and 3.26 MPa, respectively, the slump is 165 mm, the energy absorption rate under low-speed impact is 89.5%, the dynamic compressive strength under 0.65 Mpa impact air pressure is 58.77 mpa, and the specific energy absorption value per MPa is 13.33, which meets the requirements of shotcrete used in tunnel, roadway support and other impact loads. There is a linear relationship between the energy absorption characteristics under low-speed impact and high-speed impact. The greater the impact pressure, the larger the slope of the fitting straight line. The slope and intercept of the fitting line also show a good linear relationship with the increase of impact pressure. The conclusions can be used to predict the energy absorption characteristics under different PVC aggregate content or higher-speed impact pressure, which can provide important reference for safer, more economical, and environmental protection engineering structure design.

Characteristics of Stable Isotopes in Precipitation and Their Moisture Sources in the Guanling Region, Guizhou Province

Environmental prediction is one of the crucial means for social sustainable development. Based on the continuous sampling of atmospheric precipitation in Guanling County, Guizhou Province, China, from March 2016 to February 2017, and combining the reanalyzed data of the National Centre for Environmental Prediction/National Centre for Atmospheric Research with the Hybrid Single-Particle Lagrangian Integrated Trajectory model, this paper analyzed the variations of δ2H and δ18O in precipitation at the synoptic scale in the Guanling region. The results showed that the variations of δ2H, δ18O, and d-excess values in precipitation exhibited remarkable seasonal variability. The stable isotopic values in precipitation in the winter half-year were higher than those in the summer half-year. The meteoric water line of the winter half-year was close to the annual meteoric water line. The results showed that there was more than one fundamental source of moisture. It was affected by the winter monsoon period, which is longer than the summer monsoon period, so the local evaporation of water vapor participating in the water circulation had a greater impact. With the increase of precipitation, the intercept and slope of the meteoric water line gradually decreased, which indicated that the secondary evaporation was weak under the effect of stable isotope subcloud cluster. The correlations of precipitation δ18O with temperature T and precipitation P vary with time scales. As the time scale decreased, the correlation between δ18O and the temperature and precipitation improved. When P ≤ 5 mm and 10°C &lt; T ≤ 30°C, the most sensitive changes in stable isotopes were observed. In the study area, the backward trajectory model showed that the moisture in the winter half of the year was mainly from the transportation of the westerlies wind, replenishment, and local reevaporation of near-source ocean water, while the water in the summer half of the year mainly came from the transportation of water from the ocean at low latitudes.

Correlation of Critical State Strength Properties with Particle Shape and Surface Fractal Dimension of Clinker Ash

Clinker ash is a byproduct obtained from coal-fired electrical generators. It is a type of recycled granular material with a complex particle shape and large surface roughness. Particle shape descriptors and surface fractal dimensions are effective parameters to quantify sand grain morphologies. A simple image analysis approach is employed to determine the aspect ratio, sphericity, roundness, and convexity of 12 types of clinker ash collected from thermal power plants distributed on the western island of Japan. Compared to the majority of sands with other mineralogical components, clinker ash particles have a smaller aspect ratio, sphericity, and roundness. Under similar test conditions, clinker ash exhibits higher shear resistance than natural sands at the critical state. Critical state friction angles tend to decrease with increasing aspect ratio, sphericity, roundness, and convexity. A decreased aspect ratio, roundness, and convexity enhance the slope and intercept of critical state lines in the void ratio and mean stress plane. The mean regularity, which is the average of four particle shape descriptors, is regarded as an effective index to characterize the shear strength of clinker ash at the critical state. The surface fractal dimension could also be decided from digital image analysis. The results also show that the critical state friction angle is well correlated with the surface fractal dimension for different types of clinker ash. The implication is that a rougher surface texture hinders the rotation, frustration, and interlocking of particles at the critical state, resulting in higher shear resistance.

Precipitation Isotopes Linked with High-Level Cloud Cover at Local and Regional Scales in the Asian Monsoon Edge Region

In monsoonal areas, the ocean transports water vapor to inland areas and affects the stable isotopes of precipitation in inland areas, leading to that stable isotopes of precipitation could be used as a medium to study large-scale water vapor cycles. Analysis of the characteristics of δ18O and δ2H indicates that stable isotopes of precipitation in the Shiyang River Basin (SRB) exhibit obvious seasonal changes. The slope and intercept of the local meteoric water line (LMWL) in summer and autumn are lower than those in spring and winter, which is similar to the typical monsoon climate zone, indicating that large-scale monsoon water vapor is the main source of precipitation in the SRB. Regional-scale (equatorial North Pacific) cloud cover and outgoing longwave radiation (OLR) have a stronger impact on the East Asian monsoon edge area, there is a significant negative correlation between cloud cover in the equatorial North Pacific and precipitation stable isotopes in the SRB, and there is a positive correlation between OLR in the equatorial North Pacific and precipitation stable isotopes in the SRB. The cloud cover on the fifth day before precipitation in the equatorial North Pacific has the greatest impact on precipitationδ18O in the SRB. In the region with the highest correlation coefficient (the equatorial North Pacific), the correlation between precipitation δ18O and high cloud cover is greater than that between precipitation δ18O and medium cloud cover or low cloud cover, indicating that cloud cover has the most significant influence on precipitation stable isotopes in the middle troposphere (3–8 km).

Coupling effects of particle shape and cyclic shear history on shear properties of coarse-grained soil–geogrid interface

Accurate measurement of particle shape is necessary to properly investigate the cyclic shear behavior of a soil–geogrid interface. In this study, the particle shapes of crushed limestone, quartz sand, round gravel and spherical granular media were described and quantified in terms of particle regularity. Cyclic direct shear tests were then performed with particles of various shapes for different relative densities and shear displacement amplitudes. Monotonic direct shear tests and post cyclic direct shear tests were performed to compare the relationship between particle regularity and interface friction angle. The test results showed that the interface underwent cyclic shear hardening for relative densities between 0.453 and 0.672. The area of the hysteresis loop, cyclic peak shear strength and maximum vertical displacement increased with increasing shear displacement amplitude, and decreased with increasing particle regularity. In monotonic and post cyclic direct tests, the friction angle decreased linearly as particle regularity increased. Comparing to the monotonic direct shear tests, the slope and intercept of the regression lines increased in the post cyclic direct shear tests after undergoing cyclic shearing. This study shows that it is important to analyze the interface shear behavior in the monotonic, cyclic and post cyclic direct shear tests using parameterized particle shapes.

High Optical Performance of Pseudo-Single-Crystal Semiconductors Formed on Glass Using Layer-Exchanged Ge Seed Layer

Introduction The multi-junction solar cell has continued to update the highest conversion efficiency of solar cells. However, the bulk Ge substrate, has been used as a bottom cell material for multi-junction solar cells, is too expensive for consumer application. One promising approach to reducing the fabrication cost is substituting the bulk Ge substrate with a Ge thin film on an inexpensive glass substrate.We formed a large-grained (> 100 µm) Ge layer on glass by using Al-induced layer exchange (ALILE) at a low temperature of 325 °C [1]. In addition, the resistivity of ALILE-Ge is low enough (< 103 cm-3) to be used as a bottom electrode due to highly Al doping [2]. Here, we adopted the Ge layer formed by ALILE as an epitaxial seed and grow Ge and GaAs as bottom and middle gap absorbing layers, respectively. We demonstrate the highest optical performance among the polycrystalline semiconductors formed on glass without transferring. Experimental Procedure First, the 50-nm-thick Ge seed layer on the glass substrate was prepared using ALILE (Fig. 1(a)). The upper Al layer is removed with HF (1.5%) treatment for 1 min. The resulting ALILE-Ge seed layer is highly (111)-oriented and large-grained (Figs. 1(b),(c)). Then, the Ge or GaAs layers were formed on the ALILE-Ge seed layer by solid phase epitaxy (SPE) or molecular beam epitaxy (MBE), respectively. For the SPE, amorphous-Ge layers (100-500 nm thick) were deposited at room temperature and then annealed at 350 °C in a N2 ambient (Fig. 2(a)). For the MBE, the 500-nm-thick GaAs layers were grown with heating the substrate at T g = 500‒570 °C (Fig. 3(a)). Results and Discussion Figure 2(b) shows that the SPE-Ge layers appear larger minority carrier lifetime, τ eff, than ALILE-Ge. In addition, τ eff increases with the increasing thickness of SPE-Ge, w. The SPE-Ge for w = 500 nm achieves τ eff of more than 1 µs. We calculated the bulk minority carrier lifetime of SPE-Ge, τ bulk, as expressed the equation in Fig. 2(c). From the intercept of the least-squares line in Fig. 2(c), τ bulk is determined to be 5.6 µs. Figure 2(d) shows that this value is close to that of a single-crystal Ge with hole concentration in the latter half of 1017 cm-3 [3]. SIMS measurement revealed that SPE-Ge has 6 × 1017 cm-3 of Al, which is diffused from ALILE-Ge. Assuming that the Al atoms in the SPE-Ge are fully activated as acceptors, τ bulk of the SPE-Ge is mostly limited by impurity scattering.Figure 3(b) shows that the EBSD image of the GaAs sample for T g = 520 °C was very similar to that of ALILE-Ge. Figures 3(c) and 3(d) show the stacked structure of ITO/GaAs/Ge/glass as intended. The SAED pattern in Fig. 3(e) indicates that the GaAs film is epitaxially (111) oriented and single crystalline in this area (800 nm in diameter).The composition of GaAs and the FWHMs of the TO and LO mode peaks were calculated from the EDX and Raman spectra, respectively. Figure 4(a) shows that the FWHMs initially decrease with increasing T g, indicating that the higher T g improves the crystallinity of the GaAs films. Conversely, the FWHMs increase for T g > 550 °C, due to the reduction of the As atomic ratio in the GaAs. Figure 4(b) shows clear photoresponse spectra rising near a wavelength of 900 nm, which corresponds to the bandgap of GaAs. Figure 4(c) shows that internal quantum efficiency (IQE) is maximum at wavelengths of 700–800 nm for all samples. Figure 4(d) shows that the photoresponsivity and IQE initially increase with increasing T g and decrease for T g > 550 °C. This behavior is consistent with the FWHM results. We note that the photoresponsivity and IQE of the ALILE-Ge samples are comparable to those of the single-crystal GaAs which was simultaneously grown on Ge(111) substrate. This is because GaAs on ALILE-Ge is large-grained and behaves like a pseudo-single crystal. Thus, the maximum photoresponsivity (470 mA/W) and IQE (90%) were obtained at T g = 550 °C.In conclusion, we demonstrate the great potential of ALILE-Ge as an epitaxial seed for the Ge and GaAs layers. Their optical performance is highest among the polycrystalline ones formed on glass. This achievement will directly lead to the fabrication of novel high-efficiency multi-junction solar cells based on inexpensive substrates.

Impact of human activities on urban river system and its implication for water-environment risks: an isotope-based investigation in Chengdu, China

To analyze the anthropogenic activities on water-environment conditions, sampling campaigns and isotope measurement for precipitation, river water and groundwater were conducted in Jinjiang River System, Chengdu, China for one year. The results show that runoff is the main factor affecting the isotopic composition in natural-state rivers, while in rivers affected by human activities, the isotopic composition varies greatly due to the influence of impermeable surface and municipal pipe networks on water evaporation and mixing. The warm-and-humid moisture source and "heat island" effect lead to high slope and intercept of local meteoric water line (LMWL), and the characteristics of surface water line (SWL) are closely related to land types. Isotope changes along the flow path indicate significant evaporation effect in wet season, while the operation of municipal pipe networks partially conceals the evaporation effect in dry season. The intensity of river evaporation is positively correlated with the urbanization level along the river. Isotope mixing model shows that precipitation and river water are the recharge sources of groundwater in rain and dry seasons, respectively, and the mixing ratios between Jiangan River and Fuhe River shows significant seasonal variation. The combination of isotopic analysis and pollutant data reveals that the seasonal water contribution is the main factor influencing the water quality. Risks for water safety and environmental health in Chengdu and cities along lower Minjiang River were assessed.

Stable isotope signatures of river and lake water from Poyang Lake, China: Implications for river–lake interactions

Interactions between the Yangtze River and Poyang Lake are undergoing rapid changes due to intensive human activities and ongoing climate change. This study investigates the spatiotemporal variations of isotopic compositions (δ2H and δ18O) in river and lake water to explore the river–lake interactions in combination with water level and discharge in Poyang Lake watershed. The results showed that river and lake water isotopes (δ2H and δ18O) exhibited highly temporal heterogeneity across seasons but their spatial differences were not remarkable, which is closely related with water sources from local precipitation and groundwater, and lake hydrology. The homogeneous patterns of lake water δ2H and δ18O indicated that Poyang Lake is a well-mixed lake in spatial scales. By contrast, the river (10.7‰) and lake (10.8‰) water d-excess and lc-excess (−0.6‰) were close to precipitation d-excess and lc-excess suggesting that precipitation is the main source for the lake and river. The slope and intercept of the river water line were slightly lower than those of the local meteoric water line and lake water line, which could be attributed to a greater evaporative enrichment in river water impacted by water flow regulation in the watershed. Interactions between Poyang Lake and Yangtze River vary seasonally, as evidently shown by the variations of water discharge and isotope compositions in river and lake water. The δ2H and δ18O of the Yangtze River water become more positive in the downstream zone than those in the upstream zone, indicating that the water from Poyang Lake has a great impact on downstream river water. This result can also be demonstrated by the efflux rate from the Poyang Lake to the Yangtze River, ranging from 17.9% to 67.9% across seasons except for the outlier rate in October resulted from the backflow of water from Yangtze River to the Poyang Lake. The complex lake–river interactions between Poyang Lake and Yangtze River mainly resulted from the regulation of Three Gorges Dam and water discharge from Poyang Lake watershed. These findings of the complex lake–river interactions will help to improve understanding of the hydrological processes and transport of pollutants and solutes around the confluence zone of the Yangtze River and Poyang Lake.