Seismicity Enhances Macrodispersion in Finite Porous and Fractured Domains: A Pore-Scale Perspective

Understanding the effects of oscillating flow field induced by seismicity on the transport process is vital for predicting the fate and transport of solute in many dynamic environments. However, there is prominent discrepancy in arguing with the response of dispersion to the oscillating flow field (i.e., the longitudinal dispersion coefficient would decrease, increase, or maintain unchanged). To unravel the underpinning physics about this controversial response, we simulated two-hundred twenty pore-scale numerical experiments for the seismicity-induced oscillating flow field and associated solute transport in the idealized finite porous (i.e., fluidic plate) and fractured (i.e., parallel plates) domains. The numerically obtained breakthrough curves were fitted to the macroscopic advection-dispersion equation to retrieve the mean velocity and apparent macrodispersion coefficient (DL). We found that DL increases to its maxima when the oscillating flow field resonates with the finite systems, that is, the period (T) of the oscillating flow field or the seismic wave approaches the pore volume (τ) of a finite domain. The resonant effects diminish and DL barely changes when T is much larger or smaller than τ. Moreover, the degree of enhancement in DL increases exponentially with the amplitude of the seismic force. Fundamental understanding of the response of macrodispersion to the oscillating flow field adds value in predicting the fate of solute in transient flow systems via the advection-dispersion equation

Performance analysis of two typical greenhouse lettuce production systems: Commercial hydroponic production and traditional soil cultivation

Introduction: Due to the shortage of land and water resource, optimization of systems for production in commercial greenhouses is essential for sustainable vegetable supply. The performance of lettuce productivity and the economic benefit in greenhouses using a soil-based system (SBS) and a hydroponic production system (HPS) were compared in this study. Methods: Experiments were conducted in two identical greenhouses over two growth cycles (G1 and G2). Three treatments of irrigation volumes (S1, S2, and S3) were evaluated for SBS while three treatments of nutrient solution concentration (H1, H2, and H3) were evaluated for HPS; the optimal levels from each system were then compared. Results and discussion: HPS was more sensitive to the effects of environmental temperature than SBS because of higher soil buffer capacity. Compared with SBS, higher yield (more than 134%) and higher water productivity (more than 50%) were observed in HPS. We detected significant increases in ascorbic acid by 28.31% and 16.67% and in soluble sugar by 57.84% and 32.23% during G1 and G2, respectively, compared with SBS. However, nitrate accumulated in HPS-grown lettuce. When the nutrient solution was replaced with fresh water 3 days before harvest, the excess nitrate content of harvested lettuce in HPS was removed. The initial investment and total operating cost in HPS were 21.76 times and 47.09% higher than those in SBS, respectively. Consideration of agronomic, quality, and economic indicators showed an overall optimal performance of the H2 treatment. These findings indicated that, in spite of its higher initial investment and requirement of advanced technology and management, HPS was more profitable than SBS for commercial lettuce production

Effect of Exogenous Nitric Oxide on Postharvest Storage Quality of Hyacinth Bean

In order to study the effect of nitric oxide (NO) on the storage quality of hyacinth bean after harvest, sodium nitroprusside (SNP) was used as an exogenous NO donor in this study. Hyacinth bean was soaked in 0.2 mmol/L SNP solution or distilled water as control for 10 min and then stored at (20 ± 1) ℃ and 80%–90% relative humidity. Decay incidence, rust incidence, hardness, the contents of total soluble solids (TSS), malondialdehyde (MDA), flavonoids, total phenols and chlorophyll, and the activities of antioxidant enzymes (peroxidase (POD), polyphenol oxidase (PPO), phenylalanine ammoniase (PAL), catalase (CAT) and ascorbate peroxidase (APX)) were observed during the storage period. The results showed that exogenous NO treatment could inhibit the rot and rust, keep the color and hardness, and inhibit the degradation of TSS and chlorophyll in hyacinth bean, so that hyacinth bean could maintain good sensory quality. Exogenous NO treatment could also prevent the accumulation of MDA and increase the contents of total phenols and flavonoids. In addition, exogenous NO treatment maintained the activities of PAL, CAT and APX during storage, and inhibited the increase in the activities of POD and PPO, thereby enhancing the antioxidant capacity and delaying the maturation and senescence of hyacinth bean. In conclusion, exogenous NO treatment can delay the postharvest maturation and senescence, maintain the physiological quality during storage, and effectively prolong the shelf life of hyacinth bean

The Mesozoic along-strike tectono-metamorphic segmentation of Longmen Shan (eastern Tibetan plateau)

The Longmen Shan belt (eastern border of the Tibetan plateau) constitutes a tectonically active region as demonstrated by the occurrence of the unexpected 2008 Mw 7.9 Wenchuan and 2013 Mw 6.6 Lushan earthquakes in the central and southern parts of the belt respectively. These events revealed the necessity of a better understanding of the long‐term geological evolution of the belt and its effect on the present dynamics and crustal structure. New structural and thermobarometric data offer a comprehensive dataset of the paleo‐temperatures across the belt and P‐T estimates for low‐grade metamorphic domains. In the central Longmen Shan, two metamorphic jumps of 150‐200°C, 5‐6 kbar and ~50 °C, 3‐5 kbar acquired during the Early Mesozoic are observed across the Wenchuan and Beichuan faults respectively, attesting to their thrusting movement and unrevealing a major decollement between the allochtonous Songpan‐Garze metasedimentary cover (at T > 500°C) and the autochtonous units and the basement (T < 400°C). In the southern Longmen Shan, the only greenschist‐facies metamorphism is observed both in the basement (360 ± 30°C, 6 ± 2 kbar) and in the metasedimentary cover (350 ± 30°C, 3 ± 1 kbar). Peak conditions were reached at c. 80‐60 Ma in the basement and c. 55‐33 Ma in the cover, c. 50 Ma after the greenschist‐facies metamorphic overprint observed in the central Longmen Shan (c. 150‐120 Ma). This along‐strike metamorphic segmentation coincides well with the present fault segmentation and reveals that the central and southern Longmen Shan experienced different tectono‐metamorphic histories since the Mesozoic

PSR J1926-0652: A Pulsar with Interesting Emission Properties Discovered at FAST

We describe PSR J1926-0652, a pulsar recently discovered with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). Using sensitive single-pulse detections from FAST and long-term timing observations from the Parkes 64-m radio telescope, we probed phenomena on both long and short time scales. The FAST observations covered a wide frequency range from 270 to 800 MHz, enabling individual pulses to be studied in detail. The pulsar exhibits at least four profile components, short-term nulling lasting from 4 to 450 pulses, complex subpulse drifting behaviours and intermittency on scales of tens of minutes. While the average band spacing P3 is relatively constant across different bursts and components, significant variations in the separation of adjacent bands are seen, especially near the beginning and end of a burst. Band shapes and slopes are quite variable, especially for the trailing components and for the shorter bursts. We show that for each burst the last detectable pulse prior to emission ceasing has different properties compared to other pulses. These complexities pose challenges for the classic carousel-type models.Comment: 13pages with 12 figure

Effect of Interfacial Properties on the Characteristics of Non-metallic Inclusions in Steel,,

Non-metallic inclusions have both positive and negative effects on steel mechanical properties, depending on their characteristics, such as composition, number, size, size distribution, morphology, and spatial distribution. Their characteristics depend on their nucleation, growth and evolution processes, which occur uniquely at interfaces. Accumulation of surfactants at the interfaces will modify the interfacial properties and thereby the inclusion characteristics. In the first part of this thesis, the effect of surfactant Te on the characteristics of Al2O3 inclusions in steel was investigated. Without stirring the melt after Al addition, Te decreases the size of the inclusions and narrows the size distribution at early stage of deoxidation by promoting nucleation of the inclusions. Te, however, also favors the clustering of Al2O3 inclusions when stirring the melt, because Te modifies the morphology of Al2O3 inclusions and hence their morphology-dependent clustering. Moreover, Te decreases the spatial distribution homogeneity of Al2O3 inclusions in the iron matrix, indicating that Te facilitates pushing of Al2O3 inclusions by advancing solid-liquid interfaces. This was explained based on the thermodynamics of an asymmetric thin liquid film confined by an advancing solid-liquid interface and a particle. In the second part of this thesis, the effect of surfactant Te on the formation of MnS inclusions in liquid steel was studied. Coarse (d ≥ 1.5 μm) and fine (d ≤ 1.0 μm) MnS inclusions, which were formed respectively during and after solidification, were observed. Both show a chain-like pattern in the interdendritic regions. Te significantly modifies the MnS inclusions into a more globular form. Te also remarkably suppresses the precipitation of both coarse and fine inclusions in the interdendritic regions, suggesting that Te affects the segregation of Mn and S. To explain this, we propose that the presence of a surface active element in liquid steel affects the back diffusion rate of solutes from the solid phase to the liquid phase across advancing solid-liquid interfaces during solidification. Theoretical analysis suggests that Te decreases the S back diffusion rate, alleviating the segregation of S, whereas it increases the Mn back diffusion rate, aggravating the segregation of Mn.status: publishe