Influence of Underlying Surface on Distribution of Hourly Heavy Rainfall over the Middle Yangtze River Valley

The variation of boundary layer circulation caused by the influence of complex underlying surface is one of the reasons why it is difficult to forecast hourly heavy rainfall (HHR) in the middle Yangtze River Valley (YRV). Based on the statistics of high-resolution observation data, it is found that the low resolution data underestimate the frequency of HHR in the mountain that are between the twain-lake basins in the middle YRV (TLB-YRV). The HHR frequency of mountainous area in the TLB-YRV is much higher than that of Dongting Lake on its left and is equivalent to the HHR frequency of Poyang Lake on its right. The hourly reanalysis data of ERA5 were used to study the variation of boundary layer circulation when HHR occurred. It can be found that the boundary layer circulation corresponding to different underlying surfaces changed under the influence of the weather system. Firstly, the strengthening of the weather system in the early morning resulted in the strengthening of the southwest low-level air flow, which intensified the uplift of the windward slope air flow on the west and south slopes of the mountainous areas in the TLB-YRV. As a result, the sunrise HHR gradually increases from the foot of the mountain. The high-frequency HHR period of sunrise occurs when the supergeostrophic effect is weakened, the low-level vorticity and frontal forcing are strengthened, and the water vapor flux convergence begins to weaken. Secondly, the high-frequency HHR period of the sunset is caused by stronger local uplift and more unstable atmospheric stratification, but the enhanced local uplift is caused by the coupling of the terrain forcing of the underlying surface and the enhanced northern subgeostrophic flow, which causes the HHR to start closer to the mountain top at sunset than at sunrise

Manipulation of Microobjects Based on Dynamic Adhesion Control

Due to scale effects, microoperation, especially the releasing of microobjects, has been a long-standing challenge in micromanipulation applications. In this paper a micromanipulation method is presented based on dynamic adhesion control with compound vibration. This adhesion control technique employs inertia force to overcome adhesion force achieving 100% repeatability with releasing accuracy of 4± 0.5μm, which was experimentally quantified through the manipulation of 20–100μm polystyrene spheres under an optical microscope. The micromanipulation system consists of a microgripper and a piezoelectric ceramics module. The compound vibration comes from the electrostatic actuator and the piezoelectrically driven actuator. Surface and bulk micromachining technology is employed to fabricate the microgripper used in the system from a single crystal silicon wafer. Experimental results confirmed that this adhesion control technique is independent of substrate. Theoretical analyses were conducted to understand the picking up and releasing mechanism. Based on this preliminary study, the micromanipulation system proved to be an effective solution for active picking up and releasing of micromanipulation

Dilational Properties of Novel Amphiphilic Dendrimers at Water–Air and Water–Heptane Interfaces

In this work, a series of novel amphiphilic dendrimers taking polyamidoamine dendrimer as the core with different hydrophobic tails QPAMC_m were synthesized and the dilational properties were studied as monolayers by dilational rheological measurements at the water–air and water–<i>n</i>-heptane interfaces to explore the nature of adsorption behaviors. The results showed that the maximum values of the dilational modulus seemed to have no obvious variation in a wide change of hydrophobic chain length at the surface. However, there was considerable variability in the tendency of the influence of bulk concentration on the dilational modulus at the two different interfaces. It was interestingly found that the diffusion-exchange process slowed down with the increase of alkyl chain length leading to more elastic nature of adsorption film, which was contrary to the tendencies of conventional single chain and gemini surfactants. It is reasonable to consider that, in the case of the molecule having short chain length such as QPAMC₈, the alkyl chains are too short to overlap across the headgroup, enable the intermolecular hydrophobic interaction to be predominant with increasing of surface concentration, which enhances the elasticity and shows the slowest diffusion-exchange process. Whereas, when the chain length increases to 12 or 16, the alkyl chains are long enough to act intramolecularly to form intracohesion conformation, which results in enhancing the diffusion-exchange process. In conclusion, the interfacial behaviors are dictated by the size ratio between the tail and headgroup. A reasonable model with respect to the molecular interaction was proposed on the basis of experimental data. The results of interfacial tension relaxation and dynamic light scattering (DLS) experiments, in accord with the proposed mechanism, also present the unusual tendency comparing to the traditional single or gemini surfactants

Low Plant Density Improves Fruit Quality without Affecting Yield of Cucumber in Different Cultivation Periods in Greenhouse

With the development of the economy, the demand for cucumber quality is quickly increasing. The aim of this study was to elucidate the role that plant density plays in leaf photosynthesis, shoot dry matter distribution, yield and quality of cucumber in different cultivation periods under greenhouse conditions. Experimental treatments based on three plant density treatments (2.25, 3.0 and 3.75 plants m−2) were conducted in turn during three growth and harvest periods in a year. The results showed that the changes in photosynthesis and weekly yield per unit area were different and dependent on the harvest time, which was mainly induced by temperature and radiation. Interestingly, we found that reducing plant density did not significantly affect the photosynthesis of leaves and did not decrease weekly yield per unit area and total yield. Low-density treatment had the highest weekly yield per plant and total yield per plant in the three harvest periods, the highest ratio of dry matter being allocated to fruits and the highest contents of soluble sugar, total phenols, flavonoid, soluble protein, vitamin C (Vc), chlorophyll and carotenoids in fruits. Moreover, a relatively low nitrite content was found in fruits following low-density treatment. The study indicated that low-density treatment was associated with a high quality of fruits without reducing the cucumber’s total annual yield under natural light in the greenhouse. Hence, our study suggests that properly reducing cucumber plant density to 2.25 plants m−2 could be a practicable approach for greenhouses in Shanghai, China

Effects of Light Intensity on Growth and Quality of Lettuce and Spinach Cultivars in a Plant Factory

The decreased quality of leafy vegetables and tipburn caused by inappropriate light intensity are serious problems faced in plant factories, greatly reducing the economic benefits. The purpose of this study was to comprehensively understand the impact of light intensity on the growth and quality of different crops and to develop precise lighting schemes for specific cultivars. Two lettuce (Lactuca sativa L.) cultivars—Crunchy and Deangelia—and one spinach (Spinacia oleracea L.) cultivar—Shawen—were grown in a plant factory using a light-emitting diode (LED) under intensities of 300, 240, 180, and 120 μmol m−2 s−1, respectively. Cultivation in a solar greenhouse using only natural light (NL) served as the control. The plant height, number of leaves, and leaf width exhibited the highest values under a light intensity of 300 μmol m−2 s−1 for Crunchy. The plant width and leaf length of Deangelia exhibited the smallest values under a light intensity of 300 μmol m−2 s−1. The fresh weight of shoot and root, soluble sugar, soluble protein, and ascorbic acid contents in the three cultivars increased with the increasing light intensity. However, tipburn was observed in Crunchy under 300 μmol m−2 s−1 light intensity, and in Deangelia under both 300 and 240 μmol m−2 s−1 light intensities. Shawen spinach exhibited leaf curling under all four light intensities. The light intensities of 240 and 180 μmol m−2 s−1 were observed to be the most optimum for Crunchy and Deangelia (semi-heading lettuce variety), respectively, which would exhibit relative balance growth and morphogenesis. The lack of healthy leaves in Shawen spinach under all light intensities indicated the need to comprehensively optimize cultivation for Shawen in plant factories to achieve successful cultivation. The results indicated that light intensity is an important factor and should be optimized for specific crop species and cultivars to achieve healthy growth in plant factories