Measuring Urban Spatial Activity Structures: A Comparative Analysis

Abstract: Human activity recognition has been of interest in the field of urban planning. This paper established a general framework by which expected human activity intensity (HAI) measured by the built environment and factual HAI measured by the Baidu thermal chart were estimated and comparatively analyzed so as to identify abnormal human activities in Hanghzou, China. Three elements of the built environment (i.e., residential density, road connectivity, and land-use mixing degree) from multi-source data with high precision are selected to assess the expected HAI. Results indicate Hangzhou has evolved into a polycentric city with three urban clusters. In addition, a significant positive correlation exists between the two types of HAIs. However, there are areas with spatial mismatches, particularly in the “urban village” and new towns, suggesting human activities are not equally distributed all over the city. Research implications, limitations, and future research needs are discussed

Tailoring mSiO2-SmCox nanoplatforms for magnetic/photothermal effect-induced hyperthermia therapy

Hyperthermia therapy is a hotspot because of its minimally invasive treatment process and strong targeting effect. Herein, a synergistic magnetic and photothermal therapeutic nanoplatform is rationally constructed. The well-dispersive mSiO2-SmCox nanoparticles (NPs) were synthesized through a one-step procedure with the regulated theoretical molar ratio of Sm/Co among 1:1, 1:2, and 1:4 for controlling the dispersion and magnetism properties of SmCox NPs in situ growth in the pore structure of mesoporous SiO2 (mSiO2), where mSiO2 with diverse porous structures and high specific surface areas serving for locating the permanent magnetic SmCox NPs. The mSiO2-SmCox (Sm/Co = 1:2) NPs with highly dispersed and uniform morphology has an average diameter of ∼73.08 nm. The photothermal conversion efficiency of mSiO2-SmCox (Sm/Co = 1:2) NPs was determined to be nearly 41%. The further in vitro and in vivo anti-tumor evaluation of mSiO2-SmCox (Sm/Co = 1:2) NPs present promising potentials for hyperthermia-induced tumor therapy due to magnetic and photothermal effects

Three-dimensional numerical simulation of flow in trapezoidal cutthroat flumes based on FLOW-3D

To solve the common problem of flumes flow-measurement accuracy without sacrificing water head, a new type of trapezoidal cutthroat flume to measure the discharge in terminal trapezoidal channels is presented. Using the computational fluid dynamic method, three-dimensional flow fields in trapezoidal cutthroat flumes were simulated using the RNG k-ε three-dimensional turbulence model along with the TruVOF technique. Simulations were performed for 12 working conditions, with discharges up to 0.075 m3·s−1 to determine hydraulic performance. Experimental data for the trapezoidal cutthroat flume in terminal trapezoidal channel were also obtained to validate the simulation results. Velocity distribution of the flume obtained from simulation analyses were compared with observed results based on time-averaged flow field and comparison yielded a solid agreement between results from the two methods, with relative error below 10%. The results indicated that the Froude number and the longitudinal average velocity increased along the convergence section and decreased in the divergent section. In the upper throat, the Froude number was less than 0.5, which meets the water measurement requirement, and the critical flow appeared near the throat section. The maximum water head loss of the trapezoidal cutthroat flume was less than 9% of the total head, compared to the rectangular cutthroat flume, and head loss of trapezoidal cutthroat flume was significantly less. Regression models developed for upstream depth versus discharge under different working conditions were satisfactory, with a relative error of less than 2.06%, which meets the common requirements of flow measurement in irrigation areas. It was concluded that trapezoidal cutthroat flumes can improve flow-measurement accuracy without sacrificing water head

Effect of Working Pressure on the Anticlogging Performance of Micro-Sprinkling Hose with Different Structures

A micro-sprinkling hose is a new type of water-saving irrigation equipment, which can become clogged when using sand-laden surface water sources for irrigation. To test the clogging process and mechanism of the micro-sprinkling hose, as well as the influence of working pressure and hose structure, an intermittent micro-sprinkling irrigation experiment was performed using four different micro-sprinkling hoses with different folded diameters (45, 45, 48, and 60 mm). The number of orifices in the single-cycle orifice cluster was three, five, five, and five. The results showed that, when the working pressures were 30 and 40 kPa, the micro-sprinkling hose was prone to complete blockage. When the working pressures were 50 and 60 kPa, the micro-sprinkling hose was partially clogged. The structure of the micro-sprinkling hose affected the mass and gradation of the deposited sediment by mediating the flow rate inside the hose. The particle size range and content of sediment under irrigation using the N48-5 (folded diameter = 48 mm, with five orifices) and N60-5 (folded diameter = 60 mm, with five orifices) hoses were much larger than those of the original soil samples. Micro-sprinkling hose N60-5 had the best anticlogging performance in this study. The results of this study can provide technical support for the application of micro-sprinkler irrigation systems with sand-laden water

Droughts and Thermo-Priming Enhance Acclimation to Later Drought and Heat Stress in Maize Seedlings by Improving Leaf Physiological Activity

Early heat and drought priming may increase the plant’s ability to resist later drought and heat stress. However, it remains unclear whether combined heat and drought priming can enhance the acclimation of plants to later combined stress by improving physiological activities. In this study, maize seedlings were first pre-exposed twice to heat, drought, and a combination of stresses followed by recovery, and then subjected to six days of more severe stresses. A considerable reduction in photosynthetic pigment content, stomatal size, and photosynthesis was observed under heat and drought conditions, and the changes in the above indicators were amplified under combined stress conditions. Stress priming improves antioxidant defense and cellular osmoregulation, as indicated by improved superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), glutathione reductase (GR), and ascorbate peroxidase activities, as well as elevated soluble sugar (SS) and proline (Pro) contents. Lower superoxide anion and malondialdehyde contents and injury index in the primed seedlings demonstrated the mitigation of oxidative stress. ROC analysis revealed that SOD and POD had considerable reliability in determining that maize seedlings were experiencing heat stress (AUC = 0.941–0.971); GR and SS were capable of accurately monitoring drought stress that was being experienced by plants (AUC = 0.919–0.958); and SOD, GR, and Pro had more capability for detecting the combination of heat and drought stress (AUC = 0.907–0.958). Collectively, the primed seedlings exhibited better performance than the non-primed seedlings, exhibiting stronger stress acclimation supported by an effective antioxidant defense system and osmoregulatory function

A Prediction Model of Labyrinth Emitter Service Duration (ESD) under Low-Quality (Sand-Laden Water) Irrigation

The reasonable evaluation of emitter service duration and appropriate emitter selection have become an important way to improve the efficiency of drip irrigation systems, and also provide a basis for the wide application of drip irrigation technology in agricultural and landscape irrigation. During field irrigation, both irrigation uniformity (CU) and relative average flow (Dra) play crucial roles in crop growth, so it is not appropriate to evaluate emitters based on one of these factors alone. In this study, a new comprehensive index for measuring the operating life of emitters—the emitter service duration (ESD) was established for selecting emitter products in the field. The indoor drip irrigation experiment was carried out under nine kinds of sand-laden water, and the emitters’ service duration, based on irrigation uniformity and emitter flow, was tested. By analyzing the individual effects and the comprehensive effects of them, the comprehensive measurement index of the ESD was established and the Pearson bivariate correlation analysis was used to explore the influencing factors. The results showed that the lower the quality of the irrigation water, the smaller the value of the ESD, which meant that the emitters were more likely to be blocked. Different irrigation water sources had different effects on the ESD, which were mainly caused by the characteristic size. Two dimensionless characteristic parameters (W/D and A1/2/L) are significantly correlated with ESD. Based on W/D and A1/2/L, the ESD prediction model was obtained and the accuracy could reach 86%. It could provide an accurate method for selecting emitters under different water source conditions, which is beneficial for the safe, efficient, and long-term operation of a drip irrigation systems using a low-quality water source

Numerical Simulation Research on the Diversion Characteristics of a Trapezoidal Channel

Open-channel bifurcations are the most common water diversion structures in irrigation districts. In irrigation water conveyance, water transport efficiency and sedimentation are primary concerns. This study accordingly analyzes the influence of open-channel bifurcations on water delivery in irrigation areas. Herein, the three-dimensional flow at an open-channel bifurcation was studied via numerical simulations using FLOW-3D software and including 15 sets of working conditions. The hydraulic characteristics of the recirculation zone and flow structures in the vicinity of the open-channel bifurcation were analyzed. Equations for the flow diversion width of the surface and bottom layers in the trapezoidal channel were then obtained. The flow diversion widths along the water depth were found to differ between trapezoidal and rectangular channels. The results also show that open-channel bifurcations considerably influence the flow velocity in the main channel. The flow velocity in the recirculation zone of open-channel bifurcations was small, but the pulsation velocity and the turbulent kinetic energy were large. The energy dissipated in this area was relatively large, which was not conducive to channel water delivery. This study provides a reference for channel optimization and operation management in irrigation districts

Weed Strategy Considering the Weed Control Effect and Weed Control Uniformity with Microsprinkler Irrigation

Improper herbicide application without proper personnel protection (PPE) can be harmful. Herbicide application with microsprinkler irrigation reduces direct contact with herbicides with the benefits of being highly efficient, decreasing water and herbicide use, and using precise irrigation and concentration control during agricultural production. Therefore, to propose a reasonable strategy for applying microsprinkler irrigation, a laboratory test was conducted to study the water distribution characteristics, and different herbicide concentrations (1.5 g/L, 2.0 g/L, and 3.0 g/L) were used in a field irrigation experiment with polyethylene microsprinkler hoses. Wheat was selected as the test crop, and the effects of the different herbicide concentrations were compared and analyzed based on the weed control effect and weed control uniformity. The results showed that in comparison to other herbicide concentrations, a higher herbicide application concentration (3.0 g/L) did not have a better application effect. Application concentration and duration influenced each other and synergistically affected the application effect. The weed control effects of the herbicide concentrations at 1.5 g/L and 2.0 g/L were similar and had better application effects than those of the other concentrations. When using this approach, the specific herbicide concentration should be determined according to the crop and soil environmental conditions, and the application concentration and duration should be adjusted reasonably

Different Irrigation Pressure and Filter on Emitter Clogging in Drip Phosphate Fertigation Systems

Irrigation pressures and filters have a significant influence on emitter clogging in drip fertigation systems. Exploring the anti-clogging performance of emitters at different irrigation pressures (80, 90, 100 kPa; 40, 50, 60 kPa) and filters (the disc filter with an aperture of 125 μm, the screen filter with an aperture of 125μm, and the screen filter with an aperture of 200 μm) can provide suitable guidance for the design and operation of drip fertigation systems. The average relative discharge (Dra), the Christiansen uniformity coefficient (CU), and the differential pressure (DP) were analyzed to study the anti-clogging performance of flat emitters (FE) and labyrinth emitters (LE). Meanwhile, the scanning electron microscope and energy dispersive spectrometer were used to observe the surface morphology and chemical composition of clogging substances in filters and emitters. Results showed that the irrigation pressure of 90 and 50 kPa did not cause a significant decrease in Dra, and the Dra of two types of emitters were all great than 95.22%. When the irrigation pressure was 80 and 40 kPa, the Dra decreased significantly (73.48–78.71%, 81.3–83.6% for FE and LE). The CU values of emitters were all greater than 90% except for the irrigation pressures of 80 and 40 kPa. The relative Dra and CU of LE were greater than those of FE, indicating that the LE had a better anti-clogging performance compared with the FE. The decrease in DP reflected an increase in the emitter clogging degree. Meanwhile, irrigation pressures and the interaction between irrigation pressures and filters imposed a significant effect on the CU at a significance level of p < 0.05, p < 0.01, respectively. The clogging process was mainly affected by physical and chemical factors, and the generated clogging substances included phosphate fertilizer, silicate, carbonate, and phosphate precipitations. In conclusion, the best operation mode of phosphate fertilizer in drip fertigation systems was to use the disc filter with an aperture of 125 μm and the LE at the irrigation pressure of 50 kPa. An appropriate irrigation pressure combined with effective filters can reduce emitter clogging while saving water and fertilizer