Experimental study on mechanical and acoustic emission characteristics of sedimentary sandstone under different loading rates

In the field of rock engineering, complexity of stress environment is an important factor affecting its stability. Thus, in view of fracture mechanism of rock under different loading rates within the scope of quasi-static strain rate, four groups of uniaxial compression tests with different strain rates were carried out on sandstone specimens, and strength, deformation, failure modes and acoustic emission characteristics of specimens were compared and analyzed. Furthermore, the fracture mechanism was discussed from the perspective of fracture characteristics based on fractal dimension, crack propagation law inverted through acoustic emission b-value, and micro fracture morphology. The results showed that as the strain rate increased from 10 to 5 s−1 to 10−2 s−1, the fractal dimension of rock fragments increased, and the fractal dimension of rock fragments increased by 9.66%, 7.32%, and 3.77% successively for every 10 times increase in strain rate, which means that the equivalent size of fragments was getting smaller, and the fragmentation feature was becoming increasingly prominent. The crack propagation process based on acoustic emission b-value showed that with the increase of loading rate, the specimen entered the rapid crack propagation stage earlier, in order of 68%, 66%, 29%, and 22% of peak stress. Moreover, the microscopic fracture morphology showed that with the increase of loading rate, transgranular phenomenon was clear, and the fracture morphology changed from smooth to rough. That meant that the fracture of sandstone rock at high loading rates was mainly caused by the propagation of large cracks, which was different from the slow process of initiation, convergence and re-propagation of small cracks at low strain rates

A Facile Synthesis of ZnCo\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e4\u3c/sub\u3e Nanocluster Particles and the Performance as Anode Materials for Lithium Ion Batteries

ZnCo2O4 nanocluster particles (NCPs) were prepared through a designed hydrothermal method, with the assistance of a surfactant, sodium dodecyl benzene sulfonate. The crystalline structure and surface morphology of ZnCo2O4 were investigated by XRD, XPS, SEM, TEM, and BET analyses. The results of SEM and TEM suggest a clear nanocluster particle structure of cubic ZnCo2O4 (~100 nm in diameter), which consists of aggregated primary nanoparticles (~10 nm in diameter), is achieved. The electrochemical behavior of synthesized ZnCo2O4 NCPs was investigated by galvanostatic discharge/charge measurements and cyclic voltammetry. The ZnCo2O4 NCPs exhibit a high reversible capacity of 700 mAh g−1 over 100 cycles under a current density of 100 mA g−1 with an excellent coulombic efficiency of 98.9% and a considerable cycling stability. This work demonstrates a facile technique designed to synthesize ZnCo2O4 NCPs which show great potential as anode materials for lithium ion batteries

COVID-19 in Japan: What could happen in the future? (Recent developments on inverse problems for partial differential equations and their applications)

This paper was finished in February, 2020 and posted in MedRxiv on Feb. 28th, 2020.COVID-19 has been impacting on the whole world critically and constantly Since December 2019. We have independently developed a novel statistical time delay dynamic model on the basis of the distribution models from CCDC. Based only on the numbers of confirmed cases in different regions in China, the model can clearly reveal that the containment of the epidemic highly depends on early and effective isolation. We apply the model on the epidemic in Japan and conclude that there could be a rapid outbreak in Japan if no effective quarantine measures are carried out immediately

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Responses of Nitrogen-Fixing Bacteria Communities to Elevation, Season, and Slope Aspect Variations in Subtropical Forests of Yunnan, China

Nitrogen-fixing bacteria play a significant role in tropical forest ecosystems. However, little is known about the comprehensive effects of altitude gradient (1000–2600 m), seasons (October, January, April, and July), and slope aspects (east and west) on the abundance and diversity of nitrogen-fixing bacteria in subtropical forest. Q-PCR and PCR-DGGE methods were performed to explore the abundance and diversity of nitrogen-fixing bacteria, respectively, in the Ailao Mountain subtropical forest. Our results showed that the abundance of nitrogen-fixing bacteria was highest in October and December, whereas it was lowest in April and July. Moreover, there was no difference in the total number of soil nitrogen-fixing bacteria on the eastern and western slopes. The diversity of soil nitrogen-fixing bacteria is higher at low and medium altitudes, but lower at high and medium altitudes with increasing altitude, and similar variation in the eastern and western slopes as well. Moreover, the most influential factors affecting the abundance of nitrogen-fixing bacteria was NH4+-N and herbal coverage, while those most affecting the diversity of nitrogen-fixing bacteria were NH4+-N and NO3−-N. In addition, permutational multivariate analysis demonstrated that the season had the greatest effects on the abundance of nitrogen-fixing, whereas altitude had the greatest effects on the diversity of nitrogen-fixing bacteria. These findings provide evidence that the variation in nitrogen-fixing bacteria is affected by multiple factors (altitudes, seasons and slope aspects) in the subtropical forests of Yunnan, China

Filter design and power allocation for uplink time-reversal NOMA

The time-reversal division multiple access (TRDMA) system employs multipath channels to realize multi-user transmission via time-reversal filtering. The performance of TRDMA is affected by the correlation among users’ channels. When the correlation is high, inter-user interference (IUI) in the TRDMA system will be serious and the system capacity will be severely restricted. In this paper, we propose an uplink multiple access scheme time-reversal non-orthogonal multiple access (TR-NOMA), wherein TRDMA and power-domain non-orthogonal multiple access are combined. The base station employs a TR filter for each user to suppress IUI and applies successive interference cancellations in the detection process of users’ signals. Users’ transmit power and TR filters are jointly optimized to promote system capacity. The original optimization problem is non-convex. We decompose the optimization problem into two sub-problems: the design of TR filters and the allocation of users’ transmit power, which is solved by utilizing generalized eigenvalue decomposition and successive lower bound convex approximation, respectively. The solution to the original optimization problem is obtained by the iterative solution between the two sub-problems. Simulation results demonstrate that the sum rate of the optimized TR-NOMA system is significantly higher than that of the TRDMA system

Evaluation of aquatic phytoremediation technologies in urban black–odorous water remediation technology using a multi-level fuzzy analysis method

The comprehensive analysis and research on the selection and evaluation of technology for urban black and odorous water remediation have not yet formed a complete system, and the technical analysis and comparison of the remediation technology are not combined with the characteristics of the river and the pollution status, which often could not achieve the expected effect. Combining the multi-level index division and fuzzy weight matrix calculation method, this paper establishes a comprehensive evaluation method for urban black–odorous water treatment technology based on multi-level fuzzy analysis. The proposed method was applied to assess four kinds of in situ purification-aquatic plant remediation technologies. The results showed that the pollutants removal efficiency of a submerged plant was much higher than that of an emergent aquatic plant, floating-leaved water plant and floating plant. Meanwhile, according to the evaluation model, the comprehensive grading order of in situ purification-aquatic plants was as follows: emergent aquatic plant (84.2044) > submerged plant (78.838) > floating-leaved water plant (72.7596) > floating plant (66.4312). The calculations indicated that the ecological restoration project of black and odorous water should build an ecological restoration technology system based on in situ purification-submerged plant remediation technology, supplemented by other three types of aquatic phytoremediation technologies. HIGHLIGHTS This study establishes a comprehensive evaluation method for urban black–odorous water treatment technology based on multi-level index division and fuzzy weight matrix calculation.; The black–odorous water treatment technology was divided into six categories.; The ecological restoration project of black and odorous water should be constructed mainly by in situ purification-submerged plant remediation technology.

Thyroxine Regulates the Opening of the Organ of Corti through Affecting P-Cadherin and Acetylated Microtubule

Different serum thyroxine levels may influence the morphology of the inner ear during development. A well-developed organ of Corti (OC) is considered to be critical to the function of hearing. In our study, we treated mice with triiodothyronine (T3) and found that the opening of the OC occurred sooner than in control mice. We also observed an increased formation of acetylated microtubules and a decrease in the adhesion junction molecule P-cadherin the during opening of the OC. Our investigation indicates that thyroxin affects P-cadherin expression and microtubule acetylation to influence the opening of the OC

Tower Configuration Impacts on the Thermal and Flow Performance of Steel-Truss Natural Draft Dry Cooling System

In recent years, the steel-truss natural draft dry cooling technique has received attention owing to its advantages in better aseismic capability, shorter construction period, and preferable recycling. For cooling towers generating the draft force of air flow, its configuration may impact the thermal and flow performance of the steel-truss natural draft dry cooling system. With regard to the issue, this work explored the thermal and flow characteristics for the steel-truss natural draft dry cooling systems with four typical engineering tower configurations. By numerical simulation, the pressure, flow, and temperature contours were analyzed, then air mass flow rates and heat rejections were calculated and compared for the local air-cooled sectors and overall steel-truss natural draft dry cooling systems with those four tower configurations. The results present that tower 2 with the conical/cylindrical configuration had slightly lower heat rejection compared with tower 1 with the traditional hyperbolic configuration. Tower 3 with the hyperbolic/cylindrical configuration showed better thermo-flow performances than tower 1 at high crosswinds, while tower 4 with the completely cylindrical configuration appeared to have much reduced cooling capability under various crosswind conditions, along with strongly deteriorated thermal and flow behaviors. As for engineering application of the steel-truss natural draft dry cooling system, the traditional hyperbolic tower configuration is recommended for local regions with gentle wind, while for those areas with gale wind yearly, the hyperbolic/cylindrical integrated cooling tower is preferred

Estimating the Light Interception and Photosynthesis of Greenhouse-Cultivated Tomato Crops under Different Canopy Configurations

Understanding the spatial heterogeneity of light and photosynthesis distribution within a canopy is crucial for optimizing plant growth and yield, especially in the context of greenhouse structures. In previous studies, we developed a 3D functional-structural plant model (FSPM) of the Chinese solar greenhouse (CSG) and tomato plants, in which the greenhouse was reconstructed as a 3D mockup and implemented in the virtual scene. This model, which accounts for various environmental factors, allows for precise calculations of radiation, temperature, and photosynthesis at the organ level. This study focuses on elucidating optimal canopy configurations for mechanized planting in greenhouses, building upon the commonly used north–south (N–S) orientation by exploring the east–west (E–W) orientation. Investigating sixteen scenarios with varying furrow distance (1 m, 1.2 m, 1.4 m, 1.6 m) and row spacing (0.3 m, 0.4 m, 0.5 m, 0.6 m), corresponding to 16 treatments of plant spacing, four planting patterns (homogeneous row, double row, staggered row, incremental row) and two orientations were investigated. The results show that in Shenyang city, an E–W orientation with the path width = 0.5 (furrow distance + row distance) = 0.8 m (homogeneous row), and a plant distance of 0.32 m, is the optimal solution for mechanized planting at a density of 39,000 plants/ha. Our findings reveal a nuanced understanding of how altering planting configurations impacts the light environment and photosynthesis rate within solar greenhouses. Looking forward, these insights not only contribute to the field of CSG mechanized planting, but also provide a basis for enhanced CSG planting management. Future research could further explore the broader implications of these optimized configurations in diverse geographic and climatic conditions