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The separation and purification of xylene isomers is an industrially important but challenging process. Developing highly efficient adsorbents is crucial for the implementation of simulated moving bed technology for industrial separation of these isomers. Herein, we report a stacked one-dimensional coordination polymer {[Mn(dhbq)(H 2 O) 2 ], H 2 dhbq = 2,5-dihydroxy-1,4-benzoquinone} that exhibits an ideal molecular recognition and sieving of xylene isomers. Its distinct temperature-adsorbate–dependent adsorption behavior enables full separation of p -, m -, and o -xylene isomers in both vapor and liquid phases. The delicate stimuli-responsive swelling of the structure imparts this porous material with exceptionally high flexibility and stability, well-balanced adsorption capacity, high selectivity, and fast kinetics at conditions mimicking industrial settings. This study may offer an alternative approach for energy-efficient and adsorption-based industrial xylene separation and purification processes.

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.

A scientific and reasonable sand control engineering can effectively reduce the impact of wind and sand activities on highway. The accurate evaluation of the comprehensive benefits about sand control engineering is the key to judging whether they can achieve the expected protective effect and ensure the smooth operation of desert highway. Through literature surveys and integrated analysis of typical highway sand control engineering in desert areas, a comprehensive benefits evaluation indicator system for highway sand control engineering was constructed from three dimensions: engineering benefits, economic benefits and environmental benefits. Then, the matter-element extension model with variable weight was introduced to calculate the indicator weights and a comprehensive benefit evaluation model for sand control engineering was proposed. The model allows the problem of distortion in evaluation result due to fluctuations in indicator values to be resolved. Combined with sand control engineering in the desert section of the Wuhai-Maqin Highway in China, the verification of the evaluation results was implemented. The research results show that the comprehensive benefits of the sand control engineering in the desert section of the Wuhai-Maqin Highway is in the “good” level, but it is slightly inclined towards the trend of the “medium” level. In this case, the ability to resisting wind and sand, construction quality and growth and restoration of vegetation, the three evaluation indicators of 13 evaluation indicators are the key indicators which make a significant impact on the comprehensive benefits. In the operation and maintenance stage, the growth and recovery ability of vegetation can be enhanced by strengthening the cultivation of vegetation, and the linkage of engineering, economy and environmental benefits can be promoted. The research results can be used as a reference for the evaluation of highway sand control engineering in wind and sand areas.

The effective removal of radioactive 99TcO4- anion from nuclear wastewater remains a very difficult unsolved problem. Functional adsorbent materials with high stability, anion-exchange capacity, excellent selectivity, and recyclability are much needed to solve this problem. In this work, we designed two stable cationic metal-organic frameworks (MOFs)-Zr-tcbp-Me and Zr-tcpp-Me-for possible use as adsorbent materials to remove 99TcO4-. Both compounds were synthesized by solvothermal reactions of the tetracarboxylate ligand with zirconium salt, followed by postsynthetic modification (N-methylation). The crystallinity of both zirconium-based MOFs can be well retained under harsh conditions, and they exhibit high adsorption capacity and selectivity toward ReO4- anion, a nonradioactive analogue of 99TcO4-. Zr-tcbp-Me and Zr-tcpp-Me demonstrate the highest framework stability toward acidity among all previously reported cationic MOFs that have been tested for perrhenate removal from wastewater.

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.

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.

Purification of propylene from the propyne (C3H4)/propylene (C3H6) mixture is a significant and challenging process in the chemical industry. Nowadays, the removal of propyne from propylene mainly ...

Two ultramicroporous metal-organic frameworks, Zn(ox)0.5(trz) and Zn(ox)0.5(atrz) (ox = oxalate, trz = triazolate, and atrz = 3-aminotriazolate), have been synthesized and tested for the adsorptive separation of Xe and Kr. We demonstrate that the Xe/Kr adsorption selectivity relates to the pore size as well as the structure flexibility of the adsorbents.

The pore size of adsorbents plays a vital role in determining the overall separation performance of gas separation and purification by adsorption. In this work, the pore apertures of the coordination pillared layer (CPL) was systematically controlled by adjusting the length of pillared ligands. We used pyrazine, 4,4'-bipyridine, and 1,2-di(4-pyridyl)-ethylene with increased length to synthesize CPL-1 (L = pyrazine), CPL-2 (L = 4,4'-bipyridine), and CPL-5 [L = 1,2-di(4-pyridyl)-ethylene], respectively. The aperture size of these CPLs varies from 4 to 11 A: CPL-1 (4 × 6 A2), CPL-2 (9 × 6 A2), and CPL-5 (11 × 6 A2). Among the three frameworks, CPL-2 exhibits the highest C2H2 uptake at ambient conditions as it has moderate pore size and porosity. However, CPL-1 has the best separation performance in the breakthrough experiments with binary gas mixture of C2H2/C2H4, thanks to the optimal pore size nearly excluding C2H4, which is only observed in the state-of-the-art UTSA-300a so far. The DFT calculations were carried out to elucidate the specific adsorption sites for both acetylene and ethylene among these frameworks. The modeling results suggest that binding strength is highly related to aperture size and that CPL-1 shows the highest adsorption selectivity owing to the optimal pore size. This work demonstrates that engineering pore size enables us to fabricate the highly efficient metal-organic framework (MOF)-based adsorbents for specific gas separation on the basis of the isoreticular chemistry.

The efficient separation of xenon (Xe) and krypton (Kr) is one of the industrially important processes. While adsorptive separation of these two species is considered to be an energy efficient process, developing highly selective adsorbent remains challenging. Herein, a rigid squarate-based metal-organic framework (MOF), having a perfect pore size (4.1 A × 4.3 A) comparable with the kinetic diameter of Xe (4.047 A) as well as pore surface decorated with very polar hydroxyl groups, is able to effectively discriminate Xe atoms, affording a record-high Xe/Kr selectivity. An exceptionally high Xe uptake capacity of 58.4 cm3/cm3 and selectivity of 60.6 at low pressure (0.2 bar) are achieved at ambient temperature. The MOF exhibits the highest Xe Henry coefficient (192.1 mmol/g/bar) and Xe/Kr Henry selectivity (54.1) among all state-of-the-art adsorbents reported so far. Direct breakthrough experiments further confirm the excellent separation performance. The density functional theory calculations reveal that the strong interaction between Xe and the framework is a result of the synergy between optimal pore size and polar porosity.

Ideal metal-organic frameworks (MOFs) are those have not only significant adsorption separation performances but also excellent vapor and/or thermal stability. In this work, a calcium-based metal-organic framework with high vapor-stability and thermostability, Ca(squarate), was prepared using readily available precursor (CaCO3) and squaric acid as starting materials by hydrothermal method. Characterization techniques including PXRD, TGA and BET surface area analysis reveal that this MOF remains stable no matter whether it was soaked in water or exposed to air for as long as 2 weeks. Moreover, the studied MOF material is capable of discriminating C2 hydrocarbon molecules as it has an appropriate pore diameter around 3.4 A. Excellent efficient separation for C2H2/C2H4 mixture (50:50, v/v) with an adsorption selectivity of 8.1 was realized at room temperature and ambient pressure, on the other hand, it also displayed a good separation performance for C2H4/C4H6 mixture (50:50, v/v) with an adsorption selectivity of 5.9. Furthermore, adsorption mechanism of C2 hydrocarbons in this framework was investigated by the DFT-D calculation. The results revealed that this framework discriminated light hydrocarbons as a result of different interaction strength between hydrocarbons and framework that mainly arise from π-π interactions.

The demand for CO2/C2H2 separation, especially the removal of CO2 impurity, continues to grow because of the high-purity C2H2 required for various industrial applications. The adsorption separation of C2H2 and CO2 via porous materials is gaining a considerable attention as it is more energy-efficient compared with cryogenic distillation. The ideal porous materials are those that preferentially adsorb CO2 over C2H2; however, very few adsorbents meet such requirement. Herein, two isostructural cyclodextrin-based CD-MOFs (CD-MOF-1 and CD-MOF-2) were demonstrated to have an inverse ability to selectively capture CO2 from C2H2 by single-component adsorption isotherms and dynamic breakthrough experiments. These two MOFs showed excellent adsorption capacity and benchmark selectivity (118.7) for CO2/C2H2 mixture at room temperature, enabling the pure C2H2 to be obtained in only one step. This work revealed that these materials were promising adsorbents for obtaining high-purity C2H2 via selectively capturing CO2 ...

In this paper, a novel omni-directional antenna with wideband and low cross-polarization for GSM1800/3G/LTE/5G indoor communication systems is proposed. By using the printed log-periodical antenna elements, which are evenly arranged around the center, the proposed antenna achieves the omnidirectional radiation patterns. Moreover, with the cooperation of the log-periodical antenna and the annular parasitic patches, a wide bandwidth and a good omnidirectional radiation performance are achieved simultaneously. Simulated results indicate that an impedance bandwidth of 1.7-3.8 GHz (76.4%) can be achieved with a gain of approximately 1.5 dBi across the whole operating frequency. Low cross-polarization level of less than −30 dB and compact size are also acquired.

This paper presents the results of mutual coupling study into Chinese-character-shaped patch antennas. A number of two-element arrays composed of side-by-side identical and non-identical circularly polarized (CP) antenna elements are investigated. Our results reveal that the Guo-Meng array of nonidentical elements exhibit better coupling reduction with less fluctuation versus frequency as compared with the Guo-Guo and Meng-Guo scenarios. A new reduction technique is also introduced here to suppress the mutual coupling below −20 dB at, and beyond, the separation of 0.75 wavelengths at 2.5 GHz.

A novel magneto-electric (ME) dipole antenna is presented in this paper, which owns the characteristics of low cross polarization level and high front-to-back ratio (FBR) for the Sth-generation (5G) indoor communications is described. By dividing the conventional patches into two pairs of rectangle patches and four pieces of parasitic patches, the current which produces cross-polarization can be offset. Furthermore, the vertical fence can effectively widen the beamwidth of antenna. Experiment results demonstrate that a broad frequency bandwidth of 3.3-4.2 GHz (24%) can be achieved for 5G communications. Besides, a cross - polarization level below −20 dB and a FBR level of approximately 26 dB in the operating bands. Noting that a wide beamwidth of 100° for E-plane and H-plane is also obtained.

The simultaneous capture of trace propyne and propadiene from propylene is one of the important but energy demanding industrial processes because of their similar physicochemical properties as well as the ultralow concentration in the mixtures. Herein, a highly stable Ca-based MOF, constructed from an inexpensive precursor (CaCO3) and rigid squaric acid, is capable of preferentially capturing trace propyne and propadiene with record-high uptake capacities of 2.44 and 2.64 mmol/g at pressures as low as 5 mbar, respectively. Direct multicomponent breakthrough experiments confirm that Ca-based MOF exhibits an excellent performance for simultaneous removal of trace propyne and propadiene from propylene. DFT simulation and in situ single-crystal X-ray diffraction of propadiene- and propyne-adsorbed Ca-based MOFs reveal that the strong affinity of the framework toward two species is ascribed to the multiple types of cooperative binding including π-π stacking and C-H···O interactions. The calcium squarate framework sets a new benchmark for adsorptive purification of propylene, showing great potential in the practical application.

Mg-MOF-74 is one of the most well-known metal–organic frameworks (MOFs) and has been widely studied for gas adsorption and separation. Nevertheless, employment of original Mg-MOF-74 in powder form inevitably leads to a high pressure drop across column and even dust pollution in practical application. In this work, we molded powder Mg-MOF-74 into extrudates and tested its performance on adsorptive separation of ethylene/ethane mixture for the first time, taking commercialized benchmark 13X zeolite as comparison. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), specific surface area measurements, and thermal gravimetric analysis (TGA) were performed to characterize the transformed samples, and adsorption equilibrium of ethylene and ethane on molded Mg-MOF-74 were measured at 273 and 298 K and pressure up to 1 bar. The potential industrial application of molded Mg-MOF-74 was examined through breakthrough and regeneration experiments, revealing that molded Mg-MOF-74 was feasible and stable ...

In this paper, a three-dimensional (3D) printed low-profile wideband antenna for the fifth generation (5G) indoor communications is proposed. To obtain a compact size and wide-beamwidth characteristics, a 3D printed folded annular electrical dipole is designed. Furthermore, a pair of orthogonal -shape strips excited by a 90°-phase difference are arranged in the gaps of vertical plates to acquire the dual-circular polarization (CP) feature. The feeding network that is composed of a modified 3dB-hybrid coupler is printed below the ground to provide wide band and 90°-phase difference traits. Simulated results show that a wide bandwidth of 3.3 GHz-5.0 GHz (41%) with stable gain of approximately 6 dBi can be achieved. Besides, a wide beamwidth of 110° in dual CP directions as well as a low-profile of 0.18 $\lambda_{0}$ can also be obtained.

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 A by metal replacement. Controlling the aperture size of M-gallate materials slightly from 3.69 down to 3.47 A could result in a dramatic enhancement of C2 H2 /C2 H4 separation performance. As the smallest radius among the studied metal ions, Ni-gallate exhibits the best C2 H2 /C2 H4 adsorption separation performance owing to the strongest confinement effect, ranking after the state-of-the-art UTSA-200a with a C2 H4 productivity of 85.6 mol L-1 from 1:99 C2 H2 /C2 H4 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 C2 H2 from C2 H4 .

The demand for CO

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.

peer-reviewed Research on HOFs has been developed for quite a long time; however, those with both established permanent porosities and functional properties are extremely rare due to weak hydrogen-bonding interactions among molecular organic linkers which are much more fragile and difficult to stabilize. Herein, through judiciously combining the superiority of both the moderately stable coordination bonds in MOFs and hydrogen bonds, we have realized a microporous hydrogenbonded metal-complex or metallotecton framework HOF-21, which not only shows permanent porosity but also exhibits highly selective separation performance of C2H2/C2H4 at room temperature. The outstanding separation performance can be ascribed to sieving effect confined by the fine-tuning pores and the superimposed hydrogen-bonding interaction between C2H2 and SiF62- on both ends as validated by both modeling and neutron powder diffraction experiments. More importantly, the collapsed HOF-21 can be restored by simply immersing it into water or salt solution. To the best of our knowledge, such extraordinary water stability and restorability of HOF-21 was observed for the first time in HOFs, underlying the bright perspective of such new HOF materials for their industrial usage.

This study presents an experience case of applications of Polymer Cement Concrete (PCC) as food architecture overlay materials in China. The material composition of PCC is introduced. PCC was designed according with filling index defined. The compressive and flexural strength were tested at 7 d and 28 d. The field performance tests were done including the compaction degree, texture depths, the British pendulum number. The surface appearance and the field core of PCC were observed. Finally, economic benefits were achieved through comparisons of cost of PCC with other surface food architecture overlay material. The result show that the application of polymer concrete overlays with high-strength, fast-curing characteristics and skid resistance which can result in improved safety and reduced maintenance at a lower cost in comparison to asphalt reconstruction.

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.

Improving the compatibility between flame retardant and asphalt is a difficult task due to the complex nature of the materials. This study explores a low dosage compound flame retardant and seeks to improve the compatibility between flame retardants and asphalt. An orthogonal experiment was designed taking magnesium hydroxide, ammonium polyphosphate, and melamine as factors. The oil absorption and activation index were tested to determine the effect of titanate on the flame retardant additive. The pavement performance test was conducted to evaluate the effect of the flame retardant additive. Oxygen index test was conducted to confirm the effect of flame retardant on flame ability of asphalt binder. The results of this study showed that the new composite flame retardant is more effective in improving the compatibility between flame retardant and asphalt and reducing the limiting oxygen index of asphalt binder tested in this study.