External Surface Research Articles

Effect of Zn–Brønsted acid in zeolites on ethane dehydrogenation with tandem reverse water gas shift reaction

The abundant hydroxyl groups and tunable Brønsted acid sites (BAS) of MWW zeolites were used to introduce and anchor zinc active sites, preventing the volatilization and deactivation of ZnOx due to its reduction to Zn0. Fabricated Zn/MWW catalysts effectively promoted ethane dehydrogenation (EDH) and tandem complex reaction of dehydroaromatization and CO2 oxidative dehydrogenation at high temperatures. Brønsted Zn/MWW catalysts containing [ZnOH]+ were prepared via incipient wetness impregnation using liquid ion exchange whereas those containing [ZnOx]2+ were prepared via atom planting using the gas dechlorination reaction. Additionally, the different acidic sites in MWW zeolites effectively affected the interaction between ZnCl2 and hydroxyl groups during the dechlorination reaction. The catalytic EDH performance of [ZnOx]2+ active sites generated using stronger BASs was higher than that of [ZnOx]2+ active sites generated via weaker BASs and silanol. The synergetic effect of Zn and BASs in zeolites catalyzed dehydroaromatization can be suppress by control the [ZnOH]+ location in the external surface of zeolite or by homogenous consumption of the BAS by [ZnOx]2+. Furthermore, [ZnOH]+ and [ZnOx]2+ catalyzed the reverse water gas shift reaction, accelerated the rate-limiting step of EDH via the CO2 oxidative EDH reaction, inhibited the selectivity of aromatics, and consumed coke via the Boudouard reaction.

High-performance biochar from Chlorella pyrenoidosa algal biomass for heavy metals removal in wastewater

In this research, a highly porous sodium bicarbonate modified biochar was produced by the fast pyrolysis of Chlorella pyrenoidosa biomass. The biochar without modification showed non-porous material characteristics based on the results of N2 isotherm adsorption–desorption. The modification with sodium bicarbonate successfully enhanced the BET specific surface area of biochar up to 1282 m2/g at a temperature of 750 °C, with microporous surface area of 871 m2/g and external surface area of 411 m2/g. XRD characterization showed broad peak around 24° which indicates amorphous carbon structure that is favorable for adsorption purposes. FTIR characterization after pyrolysis showed an important functional group that should enhance the adsorption process. Following that, a batch adsorption technique of lead synthetic wastewater is used to conduct more tests on its performance. The maximum adsorption capacity of lead (Pb) based on Langmuir model of modified biochar (qmax) is 159.071 ± 23.4008 mg/g. The heterogeneity factor (hf) based on Freundlich model is 0.4671 ± 0.06394, which mainly indicates the physical adsorption. The separation factor (RL) is nearly zero, indicating irreversible nature. The pseudo second order kinetic model showed that the rate of adsorption (k2) for modified biochar is 0.00931 ± 0.00222 g.mg−1 min−1. Overall, the results demonstrated that in terms of technological feasibility, modified biochar from Chlorella pyrenoidosa met the standards of commercial activated carbon, either based on characterization data or performance results.

The influence of biological relatedness on sexual dimorphism and sex classification based on external morphology of the frontal bone.

The most significant sexual differences in the human skull are located in the upper third of the face (the frontal bone), which is a useful research object, mainly in combination with virtual anthropology methods. However, the influence of biological relatedness on sexual dimorphism and frontal bone variability remains unknown. This study was directed at sexual difference description and sex classification using the form and shape of the external surface of the frontal bones from a genealogically documented Central European osteological sample (nineteenth to twentieth centuries). The study sample consisted of 47 cranial CT images of the adult members of several branches of one family group over 4 generations. Three-dimensional virtual models of the frontal bones were analyzed using geometric morphometrics and multidimensional statistics. Almost the entire external frontal surface was significantly different between males and females, especially in form. Significant differences were also found between this related sample and an unrelated one. Sex estimation of the biologically related individuals was performed using the classification models developed on a sample of unrelated individuals from the recent Czech population (Čechová et al. in Int J Legal Med 133: 1285 1294, 2019), with a result of 74.46% and 63.83% in form and shape, respectively. Failure of this classifier was caused by the existence of typical traits found in the biologically related sample different from the usual manifestation of sexual dimorphism. This can be explained as due to the increased degree of similarity and the reduction of variability in biologically related individuals. The results show the importance of testing previously published methods on genealogical data.

Developing a validated simulation model of micro-zonal air-conditioning to evaluate thermal comfort parameters

ABSTRACT Micro-Zonal Occupant-Centric Control (MZOCC) helps in reducing building energy consumption by conditioning only the occupied regions in a room. For this, MZOCC divides a large room such as open-plan offices into virtual micro-zones to allow independent diffuser level control. But, unplanned MZOCC can lead to heavy thermal gradients and deflection of air jets, leading to thermal discomfort. To evaluate thermal comfort at different regions of a room under MZOCC, there is a need to accurately model parameters of thermal comfort. Field studies, exploring the transient variations in air temperature, humidity and velocity at different regions of the room due to MZOCC, are limited. At the same time, developing validated simulation models or digital twins using experimental data helps in exploring micro-zonal strategies to arrive at the best strategy. The aim of this study is to create a digital twin of an open-plan office and model the parameters required to estimate thermal comfort. This study senses transient variations in air temperature, velocity and humidity using a wireless sensor network and develops a computational fluid dynamic (CFD) model that can accurately model the sensed transient variations. Field data, constituting external surface temperatures captured using thermal images, variations in air-conditioning control strategy, dynamic occupancy and location, are periodically updated in the digital twin. The CFD model accurately predicts the trends in variations in indoor temperature, velocity and humidity at different regions of the room. The developed digital twin can be used in future studies to evaluate thermal comfort and plan MZOCC control strategies.

Bifunctional two-dimensional copper-organic framework for high catalytic performance on cycloaddition of CO2 with epoxides and deacetalization-Knoevenagel condensation

Due to the larger external surface areas and more accessible active sites, two-dimensional (2D) metal-organic frameworks (MOFs) have aroused great interest in the catalytic field. Herein, the exquisite combination of Cu2+ and designed flexible tetracarboxylic acid of 1,1′-(1,3-phenylenebis(methylene))bis(1H-benzo[d]imidazole-5,6-dicarboxylic acid) (H4PBDA) under the solvothermal condition offers a highly robust 2D network of [Cu(H2PBDA)(H2O)]n (NUC-130), which are interlaced via hydrogen-bonding interactions to form a 3D skeleton. After removing associated solvent molecules by activation, NUC-130a is a scarcely reported Lewis acid/Brönsted acid mediated host framework, which can serve as a promising multifunctional catalyst due to the plentiful active sites including exposed penta-coordinated Cu2+ ions, Brønsted acidic sites of -COOH, and Lewis basic sites of Nbenzimidazole atoms and C=O groups. Performed experiments confirmed that NUC-130a had the high catalytic performance on the cycloaddition of CO2 with a series of epoxide derivatives under solvent-free mild conditions. Furthermore, for deacetalization-Knoevenagel condensation based on acid-base catalysis, NUC-130a also shows excellent catalytic activity, which should be ascribed to that dimethyl acetal can be more effectively hydrolyzed by free -COOH group into formyl group than simple Lewis acidic metal sites. Hence, this work not only provides a type of promising catalyst for efficient chemical fixation of CO2 and deacetalization-Knoevenagel condensation, but also opens up an avenue to creating multifunctional MOFs with integrating multiple active sites and larger external surface areas.

Manufacturing Accuracy, Intaglio Surface Adaptation, and Survival of Additively and Subtractively Manufactured Definitive Resin Crowns After Cyclic Loading: An In Vitro Study.

To assess the manufacturing accuracy, intaglio surface adaptation, and survival of resin-based CAD/CAM definitive crowns created via additive manufacturing (AM) or subtractive manufacturing (SM). A maxillary right first molar crown was digitally designed and manufactured using AM hybrid resin composite (VarseoSmile Crown Plus, Bego [AM-HRC]), AM glass filler-reinforced resin composite (Crowntec, Saremco Dental [AM-RC]), and SM polymer-infiltrated ceramic (Vita Enamic, VITA Zahnfabrik [SM-PICN]). Manufacturing accuracy (trueness and precision) was assessed by computing the root mean square (RMS) error (in μm; n = 15 per material). Intaglio surface adaptation was assessed by calculating the average gap distance (μm). Ten crowns from each group were cemented on fiberglass-reinforced epoxy resin dies and cyclically loaded to simulate 5 years of functional loading. One-way ANOVA, post hoc Bonferroni comparison tests, and Levene's test were used to analyze the data (α = .05). AM-RC had higher overall trueness than AM-HRC and SM-PICN (P ≤ .05), whereas the trueness of AM-RC on the external surface was similar to that of SM-PICN (P = .99) and higher than AM-HRC (P = .001). SM-PICN had lower precision than AM-RC and AM-HRC overall and at internal occlusal surfaces (P ≤ .05). Overall intaglio surface adaptation was similar between all groups (P = .531). However, for the axial intaglio surface, AM-RC and AM-HRC had higher adaptation than SM-PICN (P ≤ .05). All tested crowns survived the cyclic loading simulation of 5 years clinical use. AM-RC showed high manufacturing accuracy and adaptation. The tested resin-based CAD/CAM materials demonstrated clinically acceptable manufacturing accuracy and simulated medium-term durability, justifying the initiation of clinical investigations to determine their potential implementation in daily clinical practice.

Reducing the Cost of 3D Metal Printing Using Selective Laser Melting (SLM) Technology in the Manufacture of a Drill Body by Reinforcing Thin-Walled Shell Forms with Metal-Polymers

This article describes the technology for manufacturing a metal composite structure of a metal-cutting tool body. The main problem with using metal 3D-printing is its prohibitively high cost. The initial data for carrying out finite element calculations are presented, in particular, the calculation and justification of the selected loads on the drill body arising from metal-cutting forces. The described methodology for designing a digital model of a metal-cutting tool for the purpose of its further production using SLM 3D metal printing methods facilitates the procurement of a digital model characterized by a reduced weight and volume of material. The described design technology involves the production of a thin-walled outer shell that forms the external technological surfaces necessary for the drill body, as well as internal structural elements formed as a result of topological optimization of the product shape. Much attention in this article is paid to the description of the technology for filling internal cavities with a viscous metal polymer, formed as a result of the topological optimization of the original model. Due to this design approach, it is possible to reduce the volume of 3D metal printing by 32%, which amounts to more than USD 135 in value terms.

Exploring the Effects of Process Parameters during W/O/W Emulsion Preparation and Supercritical Fluid Extraction on the Protein Encapsulation and Release Properties of PLGA Microspheres.

In this study, protein-loaded poly(lactic-co-glycolic acid) (PLGA) microspheres were prepared via supercritical fluid extraction of emulsion (SFEE) technology. To understand the correlation between process parameters and the main quality characteristics of PLGA microspheres, a comprehensive prior study on the influence of process variables on encapsulation efficiency (EE), initial drug burst release (IBR), morphology, surface property, and particle size distribution (PSD) was conducted within a wide process condition range of each unit process step, from the double-emulsion preparation step to the extraction step. Bovine serum albumin (BSA), a high-molecular weight-protein that is difficult to control the IBR and EE of PLGA microspheres with, was used as a model material. As double-emulsion manufacturing process parameters, the primary (W/O) and secondary emulsion (W/O/W) homogenization speed and secondary emulsification time were evaluated. In addition, the effect of the SFEE process parameters, including the pressure (70-160 bar), temperature (35-65 °C), stirring rate (50-1000 rpm), and flow rate of supercritical carbon dioxide, SC-CO2 (1-40 mL/min), on PLGA microsphere quality properties were also evaluated. An increase in the homogenization speed of the primary emulsion resulted in an increase in EE and a decrease in IBR. In contrast, increasing the secondary emulsification speed resulted in a decrease in EE and an increase in IBR along with a decrease in microsphere size. The insufficient secondary emulsification time resulted in excessive increases in particle size, and excessive durations resulted in decreased EE and increased IBR. Increasing the temperature and pressure of SFEE resulted in an overall increase in particle size, a decrease in EE, and an increase in IBR. It was observed that, at low stirring rates or SC-CO2 flow rates, there was an increase in particle size and SPAN value, while the EE decreased. Overall, when the EE of the prepared microspheres is low, a higher proportion of drugs is distributed on the external surface of the microspheres, resulting in a larger IBR. In conclusion, this study contributes to the scientific understanding of the influence of SFEE process variables on PLGA microspheres.

Removal of Crystal Violet Dye from Aqueous Solutions through Adsorption onto Activated Carbon Fabrics

The removal of contaminants from aqueous solutions by adsorption onto carbonaceous materials has attracted increasing interest in recent years. In this study, pristine and oxidized activated carbon (AC) fabrics with different surface textures and porosity characteristics were used for the removal of crystal violet (CV) dye from aqueous solutions. Batch adsorption experiments were performed to investigate the CV adsorption performance of the AC fabrics in terms of contact time, temperature, adsorbate concentration and adsorbent amount. Evaluation of the thermodynamic parameters and the adsorption performance of the AC fabrics in ground water and sea water solutions were also carried out. Langmuir isotherm model, pseudo first and pseudo second order kinetics models were utilized to analyze and fit the adsorption data. The introduction of oxygen-based functional groups on the surface of AC fabrics was carried out through a nitric acid treatment. This oxidation process resulted in a significant reduction in the surface area and pore volume, along with a small increase in the average pore size and a significant enhancement in the CV adsorption capacity, indicating that the dye molecules are mainly adsorbed on the external surface of the carbon fabrics. The herein evaluated 428 mg/g adsorption capacity at 55 °C for the oxidized non-woven AC fabric is one of the highest adsorption capacity values reported in the literature for CV removal using AC materials. Thermodynamic studies showed that the adsorption occurs spontaneously and is an endothermic and entropy-driven reaction. Furthermore, pristine and oxidized non-woven AC fabrics displayed more than 90% CV uptake from sea water samples, underlining the great potential these fabrics possess for the removal of dyes from natural/multicomponent waters.

Covalent Post-Synthetic Modification of Metal-Organic Cages: Concepts and Recent Progress.

Metal-organic cages (MOCs) are supramolecular coordination complexes that have internal cavities for hosting guest molecules and exhibiting various properties. However, the functions of MOCs are limited by the choice of the building blocks. Post-synthetic modification (PSM) is a technique that can introduce new functional groups and replace existing ones on the MOCs without changing their geometry. Among many PSM methods, covalent PSM is a promising approach to modify MOCs with tailored structures and functions. Covalent PSM can be applied to either the internal cavity or the external surface of the MOCs, depending on the functionality expected to be customized. However, there are still some challenges and limitations in the field of covalent PSM of MOCs, such as the balance between the stability of MOCs and the harshness of organic reactions involved in covalent PSMs. This concept article introduces the organic reaction types involved in covalent PSM of MOCs, their new applications after modification, and summarizes and provides an outlook of this research field.

Experimental and numerical investigation of the effect of alumina on thermite reation propagation for thermal plug and abandonment of oil wells

Thermite has been considered as a potential alternative for the wellbore plug and abandonment process. This new technology, thermal P&A, may substitute cementation as a cheaper and more compelling material. In this way, different thermite systems and additives are being explored in this scenario. The present study aims to examine the effects of diluting the Fe2O3–2Al thermite system with alumina in search of a more controlled reaction by observing effects on total ejected mass, burning velocity, and temperature levels. Small-scale experiments were conducted where stainless-steel tubes were filled with the thermite system. Thermocouples welded to the tube's external surface allowed us to obtain the temperature profiles at different positions and the overall reaction propagation velocity. The 20 % diluted system suppressed the measured peak temperature, burning rate, and expelled mass of about 10%, 60%, and 45%, respectively, compared to a non-diluted system. Simplified numerical simulation assuming a zero-order kinetics mechanism presented consistent results with the experimental peak temperatures at most positions analyzed. The simulation revealed that the diluted system would not reach the aluminum vaporization temperature as observed in the non-diluted system. Still, instead, it would be limited to the alumina melting temperature of 2327 K. In summary, the diluted system showed substantial reductions in peak temperature, burning rate, and expelled mass, indicating potential cost-effective and controlled applications in Thermal P&A processes.

Porous Silicon Nanoparticles Conjugated Magnetite‐Chitosan Graphene Oxide Nanoparticles for Effective Removal of Complex Pollutants

AbstractThe effective removal of complex pollutants is extremely challenging for environmental and material science, especially pollutants including detergents and pesticides do not decompose or degrade in the aquatic environment which cannot be easily removed. Here, a novel biocompatible superparamagnetic nanocomposite integrating the advantages of porous silicon nanoparticles is developed, the chelation ability of chitosan, and graphene‐oxide‐iron that can simultaneously adsorb complex hydrophobic and hydrophilic pollutants on their internal and external surfaces which have significantly improved pollutant removal efficiency over the current existing methods. A porous silicon nanoparticle (PSi) conjugated magnetite‐chitosan‐reduced graphene oxide (MCRGO) nanoparticles (PSi‐MCRGO) are synthesized for complete removal of detergent, pesticide, and toxic heavy metals cadmium and lead ions from water at a favorable room temperature. The adsorption behavior of the nanocomposites fits well with the Freundlich isotherm and pseudo‐second‐order kinetics model by adsorption mechanism. Moreover, the fresh and recycled nanocomposites are easily separated by an external magnetic field for reusability due to super magnetite response and show high binding capacity for toxic heavy metal ions. Furthermore, the nanocomposites are biocompatible and reusable, and for the fourth time, recycled nanocomposites can completely remove toxic heavy metals. Overall, the novel nanocomposites completely remove complex pollutants which hold great potential for real water treatment.

A natural protein-related biopolymer film and its positive role in pearl brightening

To date, the external micromorphological differences among high-luster pearls and the precise relationship between the organic matrix covered on the external surface of pearl and its luster remain, to a large extent, unknown. Here, using scanning electron microscopy combined with energy-dispersive x-ray spectroscopy, infrared spectroscopy, and Raman spectroscopy, we comparatively investigated the multiscale surface characteristics of representative seawater-cultured pearls with different luster grades. The results showed that a natural protein-related biopolymer film of nano-thickness existed on the surface of high-luster pearls. Moreover, the biopolymer film and the microscale tablets self-assembled by aragonite nanoparticles, which serve as a nanoscale organic film and a microscale plane mirror, respectively, together play key roles in producing the excellent luster. In addition, the higher the content of organic matter covering the external surface of pearls, or the thicker the average thickness of the film, the smoother the surface and the better the luster of pearls. The findings substantially enhance our knowledge of the gemological and morphological characteristics of pearls and their corresponding natural brightening mechanism. Most importantly, this study not only provides some key guidelines on the daily maintenance of pearls and the optimization process for pearl brightening but also inspires optical functional material syntheses.

A Deep Insight into Perfluorooctanoic Acid Photodegradation Using Metal Ion-Exchanged Zeolites.

Treating perfluorooctanoic acid (PFOA) in an aqueous environment is problematic due to its low concentration and its high resistance to biological and chemical degradation. To tackle this challenge, combinations of pre-enrichment and photodegradation processes are promising solutions. In this work, we investigated metal ion-exchanged zeolites as adsorbents and photocatalysts for PFOA treatment. Among various transition metal ion-exchanged BEA zeolites, Fe-exchanged BEA (Fe-BEA) zeolites showed significant activity for the photodegradation of PFOA. The isolated iron species in Fe-BEA zeolite are responsible for PFOA photodegradation, whereas other iron species present from excess iron loading in the zeolite will lower its photocatalytic activity. Furthermore, it was proved via size exclusion tests using branched PFOA isomers that the photodegradation of PFOA took place on the internal surface rather than the external surface of Fe-BEA zeolite. Photodegradation of PFOA was also tested to be effective with Fe-exchanged BEA-type zeolites having various SiO2/Al2O3 ratios, but ineffective with FAU-type zeolites. The optimal Fe-BEA zeolite showed a sorption coefficient Kd of 6.0 × 105 L kg-1 at an aqueous phase PFOA concentration of 0.7 μg L-1 and a PFOA half-life of 1.8 h under UV-A irradiation. The presented study offers a deeper understanding of the use of metal ion-exchanged zeolites for photodegradation of PFOA.

Anisotropic Deformation in a Polymer Slab Subjected to Fluid Adsorption.

Nanoporous adsorbents can mechanically swell or shrink once upon the accumulation of guest fluid molecules at their internal surfaces or in their cavities. Existing theories in this field attribute such sorption-induced swelling to a tensile force, while shrinkage is always associated with a contractive force. In this study, however, we propose that the sorption-induced deformation of a porous architecture is not solely dictated by the stress conditions but can also be largely influenced by its mechanical anisotropy. In more detail, the sorption-induced deformation of a polymeric slab is investigated using a hybrid molecular dynamics and Monte Carlo algorithm. When subjected to water loading, the slab is found to swell along its normal direction and display an overall positive volumetric strain. Moreover, the surface roughness is enhanced as a response to the surface energy decrease induced by the water covering the slab external surface. Unexpectedly, the in-plane deformation of the slab material seems to be highly constrained, so that it is far below its normal counterpart. This anisotropy is enhanced when the slab thickness decreases. With a thickness of around 1.35 nm, an in-plane shrinkage is observed throughout the entire hygroscopic range. A theoretical analysis based on a poromechanical model suggests that the anisotropic mechanical properties, which are common for a slab material, are the essence of the constrained in-plane swelling or even shrinkage under the isotropic sorption-induced tensile forces. This study, unveiling overlooked mechanisms of sorption-induced shrinkage in mechanically anisotropic materials, provides new insights into this field.

Skin histopathological responses of Oreochromis niloticus (Nile tilapia) to transportation in water with and without salt

Oreochromis niloticus (Nile tilapia) is a well-known economic fish species that can thrive under the right environmental circumstances. The transport of live fish, either for food or as companion animals, presents a big issue for animal welfare at the same time it is considered one of stressful conditions. Hence, the present study investigated the skin histopathological responses of O. niloticus that were attributed to stress and salt addition during transportation. Three experimental groups of O. niloticus the 1st is the control non-transported group (CG), the 2nd is transport in water without salt (PT-S) and the 3rd is transport in water containing 5gL− 1salt (PT + S), the last 2 groups were transported in 5 h transport model. Results indicate that the skin of PT-S fish showed a marked decrease in epidermal thickness, decreased number of goblet cells, and an increase in the sub-epidermal and dermal pigments with the presence of large edematous vacuoles. Fish skin from PT + S demonstrated mild hydropic swelling in epidermal cells with normal goblet (mucous) cells density, and more or less normal melanin pigment distribution in sub epidermis and on the dermis layers, however, dermis showed mild edematous spaces. Scanning microscopy of PT-S skin tissue showed few scratched white patches among normal regions that may represent a thickened surface with the decreased number of goblets cell opening, while the PT + S group showed moderate preservation of surface skin architectures with the presence of goblet (mucous) cells opening in spite of presence of slight thickened white patches. The estimated total lesion changes present in PT-S group showed a significant increase (P < 0.001) compared with the control (CG) group. On the other hand, PT + S showed significant (P < 0.001) improvement in the overall previously recorded changes compared with the PT-S group, and a non- significant change in the histological architectures compared with the control group. Our findings underlined the importance of skin and its mucous cover health during transportation. The use 5 gL− 1salt during O. niloticus transportation appears to preserve the surface skin features, and keep the goblet (mucous) cells open to the external surface, and may act as a deterrent for the release of mucus from goblet (mucous) cells in response to stress and lessen the stress of transportation.

Theoretical studies of the expedient radius of thin pipe insulation

Decentralized ventilation systems with exhaust heat recovery are an energy-efficient solution for organizing and maintaining comfortable microclimate parameters in apartments and individual residential buildings. Such supply and exhaust systems do not require additional space for the distribution network of air ducts and significant intervention in the interior of the premises. One such device is the Vents TwinFresh regenerative installation. Twin Fresh install in the structure of the outer wall. The task of follow-up is to increase the efficiency of its work. Studies of heat exchange processes in the thin channels of the heat regenerator carried out. Channels with different thermophysical properties are studied. Experimental uncertainty decreases with better thermal insulation of the investigational stand. It is confirmed by the decrease in overheating and the heat transfer coefficient of the external surface thermal insulation when its thickness increases. Overcoming the critical diameter of the insulation of the experimental installation allows to minimize the measurement error, which takes into account the influence of heat exchange processes of the outer surface of the insulation with the environment. It is necessary to determine not the critical but the expedient diameter of the insulation. When using the appropriate thickness of thermal insulation, the temperatures on the inner and outer surfaces of the pipe have practically the same value. Thus, it is possible to take temperature readings of thin tubes from the outside, not from the inside, with the same accuracy. Accordingly, the design of the test stands for experimental research is simplified. The scope of application of the appropriate diameter of thermal insulation is not limited only to studies of heat transfer. This concept can used in any systems, equipment, and techniques that require insulating materials.

Comparative research on the pipe-soil frictional resistances of circular and rectangular pipe sections during trenchless pipe jacking.

Pipe jacking is a trenchless construction method to achieve forward tunneling and efficient construction of underground structure simultaneously without extensive surface excavation. In the process of pipe jacking construction, the jacking force provided by the hydraulic jacking equipment must overcome the frontal resistance of the cutter head and the frictional resistance between the pipe sections and formation at the same time. In particular, the pipe-soil frictional resistance increases with the increases of jacking distance, buried depth, pipe diameter and the complexity of jacking trajectory. Therefore, it is very important to correctly estimate jacking force in trenchless jacking engineering practice for the smooth implementation of pipe jacking, operation risk and comprehensive cost control. Firstly, the stress states of jacking circular and rectangular pipe sections in the soil are analyzed, and the key influencing factors of their pipe-soil frictional resistance are obtained respectively. Then, the pipe-soil frictional resistance of jacking the circular and rectangular pipe sections with the same external surface area in the dry sandy soil and coal granular layer are tested separately by using the self-developed multifunctional experimental apparatus during trenchless pipe jacking. The results show that the pipe-soil frictional resistances of jacking circular and rectangular pipe sections in the coal granular layer are always smaller than that in the sandy soil under the same experimental conditions, and the corresponding fitting calculation equation of pipe-soil frictional resistances are obtained respectively. Meanwhile, the modified calculation methods of the above pipe-soil frictional resistances are proposed respectively based on the relationship between the lateral pressure coefficient K and the buried depth of pipe section H. Moreover, the disturbed area of soil in the upper part of jacking circular pipe section presents an arc distribution, while the disturbed area of soil in the upper part of jacking rectangular pipe section presents a slightly concave distribution. Due to the different disturbance conditions of soil around the pipe section, the lateral pressure coefficient K should be corrected in the calculation equations of pipe-soil frictional resistance of jacking circular and rectangular pipe sections based on the discrete element numerical simulation analysis by EDEM software. Finally, the pipe-soil frictional resistances obtained by different methods in the sandy soil are compared and analyzed. The calculated values of the modified theoretical calculation method are very close to the experimental test values, while the other methods are smaller than the experimental test values, which makes the rationality of the modified theoretical calculation method of pipe-soil frictional resistance is verified, and some suggestions are also put forward for the value of some coefficients in the relevant empirical estimation equations. The above research achievements systematically compared the states of pipe-soil frictional resistances of jacking circular and rectangular pipe sections based on different research methods, especially for the correct evaluation of jacking force during trenchless pipe jacking, they could provide some valuable references and effective guidance for the subsequent research, engineering practice and further development of trenchless pipe jacking technology.

Towards Amplified Probing of Weak Intermolecular Interactions on the External Surfaces of Molecular Capsules.

We report a sensitive method for comparing weak interactions between aryl rings located on the external surfaces of equilibrating homo- and heterodimeric capsules. Two identical self-complementary resorcin[4]arene tetrabenzoate molecules and one tetramethylammonium cation form in CDCl3 hydrogen-bonded homodimeric capsules whose exteriors are decorated with four tight pairs of weakly interacting aryl rings. The pair wise mixing of six different homodimers establishes their equilibria with the corresponding heterodimeric species in which two types of aryl rings exert on each other some gentle forces. This equilibrium is significantly shifted either towards homo- or heterodimers depending on the nature and location of the substituents in the weakly interacting aryl rings. The thermodynamic favorability or disadvantage of the heterodimerization is determined by stronger or weaker aryl-aryl attractions in the hetero- or homodimeric capsules, respectively. The four-fold amplification of weak aryl-aryl interactions on the external surfaces of the equilibrating capsules is responsible for high sensitiveness of our approach.

Improvement of NH3-SCR Performance by Exposing Different Active Components in a VCeMn/Ti Catalytic System

The physicochemical properties of active components play a key role in enhancing catalytic performance. In multi-component catalysts, different components offer a wide range of structural possibilities and catalytic potential. However, determining the role of specific components in enhancing efficiency may be blurry. This study synthetized a range of catalysts with various metal compositions on their external surfaces to investigate their catalytic activity on NH3-SCR. The V/CeMn/Ti catalysts exhibited exceptional catalytic efficiency and strong tolerance to SO2 during the SCR process. In the system, Mn and Ce facilitated electron transfer during the catalytic removal of NOx. As an assisting agent, increased the number of active species and acidic sites, playing a crucial role in oxidizing NO to NO2 and facilitating the denitrogenation reaction process at low temperatures. Further studies showed that the three ingredients exhibited unique adsorbent behaviors on the reacting gases, which provided different catalytic possibilities. This work modeled the particular catalysis of V and Ce (Mn) species, respectively, and offers experimental instruction for improving the activity and excellent tolerance to SO2 by controlling active ingredients.