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It is of great practical value to explore the correlation between the vertical curve radius of desert highway and the increase of sand accumulation in local lines, and to select the appropriate vertical curve radius for reducing the risk of sand accumulation. In this study, three-dimensional models of desert highway embankments with different vertical curve radii were constructed, and Fluent software was used to simulate the wind-sand flow field and sand accumulation distribution of vertical curve embankments. The results show that: (1) Along the direction of the road, the concave and the convex vertical curve embankments have the effect of collecting and diverging the wind-sand flow, respectively. When the radius of the concave vertical curve is 3000 m, 5000 m, 8000 m, 10000 m and 20000 m, the wind velocity in the middle of the vertical curve is 31.76%, 22.58%, 10.78%, 10.53% and 10.44%, higher than that at both ends. When the radius of the convex vertical curve is 6500 m, 8000 m, 10000 m, 20000 m and 30000 m, the wind velocity at both ends of the vertical curve is 14.06%, 9.99%, 6.14%, 3.22% and 2.41%, higher than that in the middle. The diversion effect also decreases with the increase of the radius. (2) The conductivity of the concave and convex vertical curve embankments with different radii is greater than 1, which is the sediment transport roadbed. The conductivity increases with the increase of radius and gradually tends to be stable. When the radius of the concave and convex vertical curves reaches 8000 m and 20000 m respectively, the phenomenon of sand accumulation is no longer serious. Under the same radius condition, the concave vertical curve embankment is more prone to sand accumulation than the convex one. (3) Considering the strength of the collection and diversion of the vertical curve embankment with different radii, and the sand accumulation of the vertical curve embankment in the desert section of Wuma Expressway, the radius of the concave vertical curve is not less than 8000 m, and the radius of the convex vertical curve is not less than 20000 m, which can effectively reduce the sand accumulation of the vertical curve embankment. In the desert highway area, the research results of this paper can provide reference for the design of vertical curve to ensure the safe operation of desert highway. [ABSTRACT FROM AUTHOR]

Windblown sand hazards seriously threaten the safe operation of highways in desert areas. Reasonable risk assessment can provide the basis for windblown sand hazards prevention and risk reduction. To facilitate the formulation of better windblown sand hazards prevention and reduction strategies, a new windblown sand hazards risk assessment model along the highways was proposed, in which seven evaluation indicators were selected from danger of the hazard-causing factors, vulnerability of the hazard-forming environment, and the vulnerability of the hazard-bearing body. The model was established based on the combination weighting method of game theory, and the risk map was generated based on the GIS platform. Finally, the model was applied to the windblown sand hazards risk assessment along the Wuhai-Maqin Highway. The result showed that the risk of the windblown sand hazards along the Wuhai-Maqin Highway is mainly medium, low, and very low. High and very high risk windblown sand hazards sections account for only 33% of the total length of the highway. The high and very high risk highway sections of the windblown sand hazards are mainly distributed in the hinterland of shifting dunes area and near the horizontal curve with a small radius in the flat sandy land area. By comparing with the real information of windblown sand hazards along the highway, correlation was up to 85.93%, which verified the accuracy of the model. The model can be applied to windblown sand hazards risk assessment along the highways. [ABSTRACT FROM AUTHOR]

The latticed dunes in the Tengger Desert are widely distributed, and the sand-blocking fence placed here are highly susceptible to local failure due to complex wind-sand activities, posing a serious threat to the safe operation of the highway. To explore the local failure mechanism of sand-blocking fence in the latticed dune area, the local failure of sand-blocking fence in the latticed dune areas along the Wuhai-Maqin Highway in China was observed. Taking the first main ridge of the latticed dune as the placement location, the structure of the wind-sand flow field of sand-blocking fence placed at top, the bottom and the middle of windward slope was analyzed by Computational Fluid Dynamics (CFD). The results show that when placed at top of the first main ridge, the wind speed near the sand-blocking fence is the highest, up to 15.23 m/s. Therefore, the wind load strength on the sand barrier is correspondingly larger, up to 232.61 N·m−2. As the strength of material continues to decrease, the nylon net is prone to breakage. The roots of the angle steel posts are susceptible to hollowing by vortex action, which can cause sand-blocking fence to fall over in strong wind conditions. When placed at the bottom of windward slope, wind speed drop near sand-blocking fence is greatest, with the decrease of 12.48–14.32 m/s compared to the original wind speed. This is highly likely to lead to large-scale deposition of sand particles and burial of the sand-blocking fence. When placed in the middle of windward slope, sand-blocking fence is subjected to less wind load strength (168.61N·m−2) and sand particles are mostly deposited at the bottom of windward slope, with only a small amount of sand accumulating at the root of sand-blocking fence. Based on field observations and numerical modelling results, when the sand-blocking fence is placed in latticed dune area, it should be placed in the middle of the windward slope of the first main ridge as a matter of priority. Besides the sand-blocking fence should be placed at the top of the first main ridge, and sand fixing measures should be added. [ABSTRACT FROM AUTHOR]

After the construction of desert highway, the physiognomy changes caused by surface wind erosion and accumulation not only seriously threaten the stability of road structure, but also have a tremendous impact on the safety of the highway operation and the maintenance work on the highway. The purpose of this paper is to explore the change of sand sedimentation and the law of sand transport along the highway in the moving dune areas, and to clarify the change of sand flow and the formation mechanism of sand damage in the moving dune areas. Taking the test section of Wuhai-Maqin Expressway in the hinterland of Tengger Desert as the research object, the on-site observation of sand accumulation and the recording of wind information by small weather stations were adopted, supplemented by CFD numerical simulation method, in order to provide reference for the construction of sand control system in moving dune areas. The study results show that: (1) Dunes not only obstruct wind-drift sand but are also the sediment source condition for forming road sand. The windward dunes near the road are affected by wind and the deposition of sand will quickly bury the road in the strong wind season. (2) Compared with highways with flat terrain, the existence of dunes affects the flow field structure and the distribution of sand sedimentation on the highway, in which, under the influence of the gathering effect, the flow velocity reaches the maximum at the top of the dune and a large low-speed recirculation zone is formed on the lee side of the dune, easily causing sand accumulation. (3) Sediment accumulates at the windward side of the embankment or dune where sandy air current is easy to saturate. However, with the increase of wind speed, in addition to the grit carried by the sandy air current itself, new sand rolled up on the windward side of the dunes also form deposits on the road surface and the amount of sand-accumulation on highway surface and leeward side tends to increase. As a result, for the highway in drifting sand dunes areas, sediment prevention and control measures should be taken actively. It is necessary to remove sediment from the road in time and reduce the moving speed of sand dunes and the deposition range of wind-sand flow, ultimately for the purpose of reducing the damage wind-sand activity causes to the highway in desert. [ABSTRACT FROM AUTHOR]

Using the plane alignment design of the Wuhai–Maqin highway as the background of this study, based on the Fluent–Euler two-fluid model, the response law of the wind–sand flow to the embankment under different angles, different curve radii, and different surface windward factors were studied. Additionally, the accuracy of the numerical simulation was verified by the distribution of sand accumulation on the embankment site. The results show that when the wind–sand flow passes through the embankment, and when the angle between the wind direction and the straight embankment gradually decreases from 90° (vertical) to 0° (parallel), the speed-division range is correspondingly shortened. Under the influence of plane alignment, the diversion effect leads to a certain difference in the flow-field structure at different positions of the line. The convex windward embankment has the effect of dredging the wind–sand flow outward. The concave windward embankment has the effect of gathering the wind–sand flow inward. The dredging and gathering effects of the flat curve on the wind–sand flow decreases with the increase in the radius. In the plane linear design, line direction should be parallel to the dominant wind direction as much as possible. If a flat curve needs to be set, the convex windward curve should be given priority, and a large radius curve should be selected as much as possible. [ABSTRACT FROM AUTHOR]

Aimed at the fragile ecological environment in desert, once the resources along routes are destroyed, it will be difficult to restore the original ecological equilibrium in a short time. This paper studies the ecological-equilibrium-oriented risk evaluation of desert motorway schemes in order to choose route schemes reasonably and prevent the sandstorm aggravation caused by ecological damage. Having insight into the special geographical environment and road construction characteristics of Tengger Desert, the research establishes an index system for the ecological risk evaluation in desert areas from five aspects: the interference of living environment of animals and plants, the destruction of natural ecological landscapes, the pollution of water and soil resources, the development and utilization of natural resources, and the sand fixation of plants and the subsequent maintenance; then it confirms each evaluation index's weight by using the set-valued statistics method to transform the description of the evaluation indexes to an interval value and furthermore determines the comprehensive ecological risk evaluation level of the route scheme in virtue of the two-dimensional cloud image MATLAB outputs which takes the ecological damage and remediation cost as the basic variables. By constructing the model under the method above, the ecological risk evaluations of two route schemes in Zhongwei sand crossing section of Wuhai-Maqin Expressway have been made. The result shows that the western route scheme's evaluation grade is "good," is better than the southern route scheme, is within the scope of acceptable risk, agrees with the practical project condition, and verifies the applicability and effectiveness of the model for ecological risk evaluation in desert areas. [ABSTRACT FROM AUTHOR]

Owing to the similar physicochemical properties between ethane (C2H6) and ethylene (C2H4), obtaining polymerization-grade C2H4 (≥99.95% pure) is still tricky problem in the petrochemical industry. Here, we report a robust scandium-based metal-organic framework (ScBPDC), which is connected by oxygen-rich phenyl ligand with exceptionally high thermal stability (up to 873 K) and capacity of C2H6 (4.94 mmol/g at 100 kPa and 283 K), exhibiting superior separation performance of C2H6/C2H4 mixture (the IAST selectivity is up to 1.7 at 283 K). Importantly, ScBPDC can produce 8.96 L/kg C2H4 with ≥99.99% purity while the C2H4/C2H6 (50:50, v/v) as the mixture injection and the low isosteric heat of ScBPDC (16.4 kJ/mol for C2H6) validates the facility of adsorbent regeneration. Furthermore, theoretical calculations demonstrate the C2H6 molecules are trapped in the nonpolar pore surface via C-H⋯π and C-H⋯O interactions between multiple hydrogen atoms of C2H6 and the host framework. [ABSTRACT FROM AUTHOR]

A dual circularly polarized (CP) magnetoelectric dipole antenna is presented in this article. The dual-CP antenna was devised to form a circular ring shape and fabricated using 3-D printing technology. To overcome the conflict between high (broadside) gain and wide (half-power) beamwidth, a new beamwidth broadening technique was proposed. Twelve meta-columns were placed evenly along the circumference close to the ring-shaped dipole. A design approach is elaborated, where the number and size of meta-columns were decided according to the design curves. Symmetrical beamwidth of 108° in orthogonal planes with a broadside gain of 6 dBic was achieved across a wide effective bandwidth from 3.2 to 5.4 GHz (51%), sufficiently covering the 5G new radio (NR) bands: $n77, n78, n79$. The antenna owns a compact size of $0.83 \times 0.83 \times 0.18\lambda ^{3}$ at 4.15 GHz. A planar subarray composed of four dual-CP elements was also investigated and compared with the existing arrays. [ABSTRACT FROM AUTHOR]

The separation of acetylene from ethylene is of paramount importance in the purification of chemical feedstocks for industrial manufacturing. Herein, an isostructural series of gallate‐based metal–organic frameworks (MOFs), M‐gallate (M=Ni, Mg, Co), featuring three‐dimensionally interconnected zigzag channels, the aperture size of which can be finely tuned within 0.3 Å by metal replacement. Controlling the aperture size of M‐gallate materials slightly from 3.69 down to 3.47 Å could result in a dramatic enhancement of C2H2/C2H4 separation performance. As the smallest radius among the studied metal ions, Ni‐gallate exhibits the best C2H2/C2H4 adsorption separation performance owing to the strongest confinement effect, ranking after the state‐of‐the‐art UTSA‐200a with a C2H4 productivity of 85.6 mol L−1 from 1:99 C2H2/C2H4 mixture. The isostructural gallate‐based MOFs, readily synthesized from inexpensive gallic acid, are demonstrated to be a new top‐performing porous material for highly efficient adsorption of C2H2 from C2H4. [ABSTRACT FROM AUTHOR]

To thoroughly explore the relationship between concrete pavement texture characteristics and tire/pavement noise of grooving concrete pavement, the surface texture, i.e., roughness, macrotexture, and microtexture, was investigated in numerous highway pavements. The On-Board Sound Intensity (OBSI) method was used to test the pavement/tire noise. The statistical correlation between concrete pavement texture characteristics and tire/pavement noise was quantitatively described by two correlation analysis methods for highway concrete pavement: origin of linear regression and the Pearson two-sided test method. The results indicate that the effect of pavement roughness on tire/pavement noise is significant, while the noise level is minor for the flat pavement. The macro texture depth also has a marked impact on the tire/pavement noise. In addition, a large grooving depth of concrete pavement could cause a high tire/pavement noise level; however, there is no clear correlation between side-way force coefficient (SFC) and tire/pavement noise. [ABSTRACT FROM AUTHOR]

Highly selective capture of methane from nitrogen is considered to be a feasible approach to improve the heating value of methane and mitigate the effects of global warming. In this work, an ultramicroporous squarate‐based metal‐organic framework (MOF), [Co3(C4O4)2(OH)2] (C4O42− = squarate), with enhanced negative oxygen binding sites was synthesized for the first time and used as adsorbent for efficient separation of methane and nitrogen. Adsorption performance of this material was evaluated by single‐component adsorption isotherms and breakthrough experiments. Furthermore, density functional theory calculation was performed to gain the deep insight into the adsorption binding sites. Compared with the other state‐of‐the‐art materials, this material exhibited the highest adsorption selectivity (8.5–12.5) of methane over nitrogen as well as the moderate volumetric uptake of methane (19.81 cm3/cm3) under ambient condition. The unprecedented selectivity and chemical stability guaranteed this MOF as a candidate adsorbent to capture CH4 from N2, especially for the unconventional natural gas upgrading. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3681–3689, 2018 [ABSTRACT FROM AUTHOR]

Moisture susceptibility is one of the key issues of warm mix asphalt (WMA). In this research, the moisture susceptibility of asphalt mixtures and binders containing Sasobit warm mix additive was investigated in comparison to that of hot mixture asphalt (HMA) through laboratory aging experiments. The WMA asphalt mixtures were aged in the laboratory at three aging temperatures and times. The moisture susceptibility of the asphalt mixtures was measured through the laboratory immersed Marshall test and freeze-thaw splitting test. The surface free energy (SFE) of asphalt binders extracted from WMA asphalt mixtures was determined by the sessile drop method. The results show that the aging time and temperature have a significant effect on the improvement in moisture susceptibility in terms of both the freeze-thaw splitting strength ratios and the residual Marshall stability of asphalt mixtures containing Sasobit warm mix additive. The SFE of asphalt binders extracted from Sasobit warm mix increased with the aging time and temperature. The moisture susceptibility of the asphalt mixtures and binders containing Sasobit warm mixes was similar to or even greater than that of HMA aging under certain conditions. [ABSTRACT FROM AUTHOR]

Cover Feature: Adsorptive Separation of Acetylene from Ethylene in Isostructural Gallate-Based Metal-Organic Frameworks (Chem. Eur. J. 68/2019) B An isostructural family of M-gallate (M=Mg, Co, Ni) MOFs b not only afforded excellent separation performances for the removal of C SB 2 sb H SB 2 sb from C SB 2 sb H SB 4 sb , but also a remarkably high C SB 2 sb H SB 4 sb productivity of 85.6 mol L SP -1 sp from an 1/99 C SB 2 sb H SB 2 sb /C SB 2 sb H SB 4 sb mixture. Metal-ion substitution, with different lengths of the metal-oxygen bonds, significantly enhanced the interaction between the C SB 2 sb H SB 2 sb molecules and frameworks as a result of precisely controlling the pore aperture size from 3.69 to 3.47 Å. More information can be found in the Full Paper by Z. Bao, Q. Ren, et al. on page 15516. [Extracted from the article]