Due to the influence of the background of the era and its ideological and cognitive factors, some college students lack independent labor ability and awareness, and it is necessary to build a labor ...education system that meets the requirements of the new era to further improve the effectiveness of educating people. By updating the pheromone, the ant colony algorithm is introduced to improve the convergence speed of the basic clustering algorithm. A linear combination of average similarity and cosine distance function is used to cluster labor education-related data, and the probability conversion function is used to increase the accuracy of clustering. The dilemmas that confront labor education in colleges and universities become clustered after a finite number of iterations. And quantitative analysis is carried out from the two aspects of learning quality of labor education in colleges and the influence of learner characteristics on learning effect to explore the innovative road of labor education in colleges and universities. The results show that: in the analysis of learning quality, learners’ average learning readiness is the highest (M=3.89, S=0.49), and the cluster centers corresponding to the sub-dimensions of “knowledge reserve”, “learning attitude” and “learning skills” are 3.66, 4.33 and 3.98. The mean value of “learning skills” is the highest, with 0.875 learners above the medium level, indicating that most of the learners think they can conduct independent learning in labor technology. The development of a labor education model is given an innovative direction by this study.
This paper analyzes the factors that affect the mental health of college students, and the focus of this analysis is on emotional-emotional factors. The extroverted presentation of emotional affects ...is used as visual information to study the mental health status of college students. Based on the advantages of long and short memory neural networks based on deep learning models in processing two-dimensional images, a computer vision task is used to perform visual recognition, target detection, and expression image classification of college students’ facial expressions. The use of video facial expression recognition with multi-feature fusion is utilized to effectively identify the facial expression machine of college students in both laboratory-controlled and outdoor environments. The mental health status of college students was analyzed in terms of facial expression recognition and feature extraction. The recognition rate for general features was 80.3%, 89.3% for six specific facial emotions, and 84.4% for LBP features.
The kaleidoscopic applications of zeolite catalysts (zeo-catalysts) in petrochemical processes has been considered as one of the major accomplishments in recent decades. About twenty types of zeolite ...have been industrially applied so far, and their versatile porous architectures have contributed their most essential features to affect the catalytic efficiency. This review depicts the evolution of pore models in zeolite catalysts accompanied by the increase in industrial and environmental demands. The indispensable roles of modulating pore models are outlined for zeo-catalysts for the enhancement of their catalytic performances in various industrial processes. The zeolites and related industrial processes discussed range from the uni-modal micropore system of zeolite Y (12-ring micropore, 12-R) in fluid catalytic cracking (FCC), zeolite ZSM-5 (10-R) in xylene isomerization and SAPO-34 (8-R) in olefin production to the multi-modal micropore system of MCM-22 (10-R and 12-R pocket) in aromatic alkylation and the hierarchical pores in FCC and catalytic cracking of C4 olefins. The rational construction of pore models, especially hierarchical features, is highlighted with a careful classification from an industrial perspective accompanied by a detailed analysis of the theoretical mechanisms.
Recent advances in zeolite-catalyzed industrial processes have been comprehensively reviewed with a careful classification and a detailed theoretical analysis.
This article is a detailed review of the measures to modify the high-temperature mechanical properties of silicon carbide ceramic matrix composites (SiC CMCs), namely toughness, high-temperature ...stability and wear resistance. Additionally, it briefly describes the common processing methods of the SiC CMCs and their application in the high-temperature field of aerospace. The advantages and disadvantages of various existing processing and molding methods for the SiC CMCs are also discussed. The high-temperature mechanical properties of the SiC CMCs are mainly affected by the properties of the matrix, added phase and interface. It is crucial to reduce the crystal defects of the matrix and select a suitable enhancement phase for an elevated performance. Moreover, it is important to improve the bonding at the interface between the enhancement phase and the matrix. This review is expected to provide useful information for the subsequent development of complex SiC CMCs for high-temperature applications.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Hierarchical zeolites combine the intrinsic catalytic properties of microporous zeolites and the enhanced access and transport of the additional meso- and/or macroporous system. These materials are ...the most desirable catalysts and sorbents for industry and become a highly evolving field of important current interests. In addition to the enhanced mass transfer leading to high activity, selectivity, and cycle time, another essential merit of the hierarchical structure in zeolite materials is that it can significantly improve the utilization effectiveness of zeolite materials resulting in the minimum energy, time, and raw materials consumption. Substantial progress has been made in the synthesis, characterization, and application of hierarchical zeolites. Herein, we provide an overview of recent achievements in the field, highlighting the significant progress in the past decade on the development of novel and remarkable strategies to create an additional pore system in zeolites. The most innovative synthesis approaches are reviewed according to the principle, versatility, effectiveness, and degree of reality while establishing a firm link between the preparation route and the resultant hierarchical pore quality in zeolites. Zeolites with different hierarchically porous structures, i.e., micro-mesoporous structure, micro-macroporous structure, and micro-meso-macroporous structure, are then analyzed in detail with concrete examples to illustrate their benefits and their fabrications. The significantly improved performances in catalytic, environmental, and biological applications resulting from enhanced mass transport properties are discussed through a series of representative cases. In the concluding part, we envision the emergence of “material-properties-by-quantitative and real rational design” based on the “generalized Murray’s Law” that enables the predictable and controlled productions of bioinspired hierarchically structured zeolites. This Review is expected to attract important interests from catalysis, separation, environment, advanced materials, and chemical engineering fields as well as biomedicine for artificial organ and drug delivery systems.
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A water-filled cave can easily result in the deterioration of the surrounding rock when a shield tunnel passes through the urban karst area, resulting in engineering disasters such as water inrush, ...ground collapse, and shield machine malfunction. To study the surrounding rock stability due to the proximity of a cave with confined water, we carried out a large-scale three-dimensional geo-mechanical model test on a tunnel that was excavated by a compound EPB (Earth Pressure Balance) shield machine based on the metro tunnel in the “spring city” of Jinan. We developed a new 3D printing technology for a water-filled cave and a new method for the 3D laser reconstruction of surface settlement monitoring. The multi-physics evolution information, including the soil moisture content of the muck, the displacement, the stress, and the seepage pressure, were obtained and proven consistent with each other. The results showed that the water inrush mainly resulted from a shield tunneling disturbance in conjunction with the confined water in the cave. The process of water inrush in the surrounding rock could be divided into three stages, which included the initial stable period, the variation period with the shield tail passing through, and the final stable period. The rock ahead of the excavation face was characterized by two stages, which included the initial stable period and the sudden collapse of the water-resistant slab. Compared with the tunnel excavated by drilling and with the blasting method, the water inrush triggered by the EPB shield machine tunneling was observed to be more hidden and catastrophic. The displacement and the seepage pressure comprised the most intuitive precursor information. These test results can provide a theoretical basis and guidance for the water inrush prediction for being triggered by a single confined cave with no inter-connections.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Following the excavation of the rectangular tunnel faces with deep harder rock, spalling often occurs on both sidewalls of the tunnel, which affects the tunnel support and stability. To investigate ...the spalling phenomenon of the harder rock under the deep initial three-dimensional (3D) stress conditions, true triaxial loading tests of different depths (250, 500, 750, and 1000 m) and different stress combinations (four different horizontal stresses at the same depth 1000 m) were designed on plastic fine grain marble. The overall failure process of the surrounding rock was monitored and recorded by a wireless micro-camera. The results show that, under the shallow stress condition (250 and 500 m), the V-shaped bands will appear on the both sidewall due to the overall shear failure of the specimen. Under the deep stress condition (750 and 1000 m), the obvious spalling was observed on the hole sidewalls of all marble specimens. Moreover, at the time of hole sidewall spalling, the vertical stress is the maximum principal stress. The spalling process of the hole sidewall can be divided into four stages: the microcrack initiation, the appearance of thin rock slabs, the formation of arc-shaped notches, and the expansion to V-shaped notches. If the excavation depth remains the same (1000 m) when the maximum principal stress is perpendicular to the tunnel axis, excavation along the minimum principal stress direction is beneficial to reducing the spalling damage degree. Compared to the brittle granite specimens with rectangular holes under the same 3D stress conditions, the influence of brittleness and plasticity of rock materials on spalling failure was analysed. (1) Spalling failure mode of hole sidewalls: the plastic-marble is static failure without fine particle ejection, while the brittle granite will break dynamically with fine particle ejection. (2) Spalling failure process and zones of sidewall: the cracks on the plastic marble sidewalls develop parallel to the axial direction, and run through the whole hole sidewall along the axis, while the cracks on the brittle granite hole sidewalls propagate perpendicular to the axial direction, and the sidewalls first break locally and then break through the whole hole. Failure zones on both sidewalls of the two kinds of rock specimens will transit from arc-shaped notch to V-shape notch. Those failure notches are symmetrical and finally penetrate the sidewalls. (3) Microscopic failure mode: scanning electron microscope (SEM) shows that the plastic and brittle rock materials are tensile failure during the spalling under 3D stress conditions. The plastic marble is characterized by fracture tension failure, while the brittle granite is characterized by layered tension failure. Some suggestions are given finally, under the condition that the vertical stress is the maximum principal stress, when the tunnel is excavated along the horizontal direction, the resistant ability of the tunnel sidewall in the plastic and brittle surrounding rock should be strengthened by supporting the sidewall, which can effectively reduce the degree of spalling damage.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In the Qinghai-Tibet Plateau, fractures and fault zones have developed in this area, where earthquakes and extreme rainfall frequently induce debris flow disasters, which seriously threaten the ...safety of the people and properties. In this study, Zhujiagou, Minxian County, Gansu Province in China, has a typical debris flow channel in a small watershed on the northeastern edge of the Qinghai-Tibet Plateau, which has been used as the case study for risk assessment. A debris flow-risk assessment method has been developed in this study. The fusion algorithm of entropy weight and coefficient of variation has been used to evaluate the susceptibility of debris flow in each tributary channel in the watershed. Further, numerical simulation of the debris flow events at the main channel and at the high-prone debris flow tributary channel has been carried out. The "7.18" Zhujiagou debris flow event has been used to verify that the accuracy of the numerical simulation is higher than 74.12%. This method has been applied to design the Zhujiagou debris flow-risk zoning under extreme rainfall conditions, aimed at forming a set of debris flow-risk evaluation system suitable for this type of small watershed. The results show that the peak single-width clear water flow at the mouth of the channel, the length of the channel, and the shallow surface rock formation are the main factors influencing the susceptibility of debris flow. The main tributaries of the watershed are Hagu channel, Zhuling channel, Songshu channel, and Langjia channel which are all high-prone debris flow channels. The Zhujiagou debris flow accumulation fan under the designed 1% rainfall frequency will block the Taohe, which will threaten the safety of the residents and properties near the channel, at the mouth of the channel and in the urban area on the opposite bank of the Taohe. Compared with Hagugou, Zhulinggou, and Songshugou, the low-risk area is Langjiagou. The research results of this study can be used for evaluation methods and as a basis for preventing debris flow disasters on the northeastern edge of the Qinghai-Tibet Plateau.
We propose a surface atom engineering strategy to obtain a well-dispersed Co-incorporated MoS2 nanomaterial, which maximizes the Co–Mo–S phase and achieves high activity in hydrodeoxygenation (HDO) ...of lignin-derived phenolic compounds. It was shown by X-ray diffraction, transmission electron microscopy, Ramanspectroscopy, high-sensitivity low-energy ion scattering, and X-ray photoelectron spectroscopy that plenty of accessible Co–Mo–S phase were generated on the catalyst surface, which could accelerate the hydrodeoxygenation (HDO) reaction. Notably, most of the Co–Mo–S phases were located at the top surface of MoS2, which explained the full deoxygenation performance of the CoMoS catalyst. Moreover, among the diverse lignin-derived oxygenated compounds, phenolic hydroxyl HDO was structure-sensitive relative to diphenyl ether over Co-doped MoS2 catalysts. Effective conversion of mixed phenols to corresponding arenes such as BTX (benzene, toluene, and xylene) with high yield (>85%) and stable recyclability was exhibited by using the CoMoS catalyst with highly dispersed Co–Mo–S phase.
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In this study, polyethylene (PP)/polyethylene terephthalate (PET)/multiwalled carbon nanotube (MWCNT) nanocomposites with nanofibrillary structure were processed by hot drawing‐assisted extrusion ...technology, and nonfoaming and microfoaming samples were processed by injection molding machine. Scanning electron microscope micrographs showed that when PET content was 2.5 wt%, PET fibers had a larger aspect ratio, which brought an outstanding promotion on microfoaming of PP matrix, and further details were provided by DSC and rheology analysis. When foaming sample loaded with 2.5 wt% PET and 3 wt% MWCNT, the best shielding effectiveness achieved 29.91 dB·cm3·g−1 in the test frequency range about 8.2–12.4 GHz. The results proved that the introduction of PET fibers optimized the microfoaming effect, and the uniform cell structure promoted the MWCNT dispersion and internal reflection of electromagnetic wave. Therefore, the shielding property is absorption‐dominated type and meets the requirements of lightweight and ultraefficient shielding demand of industry.
Experimental consideration.
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