Soil Moisture Determines Horizontal and Vertical Root Extension in the Perennial Grass Lolium perenne L. Growing in Karst Soil

Karst regions are characterized by heterogeneous soil habitats, with shallow wide soil (SW) on hilly slopes and deep narrow soil (DN) in rocky trenches. To make full use of limited water and nutrients, plants have therefore developed a number of root extension strategies. This study investigated the effect of soil moisture on horizontal root extension in SW and vertical root extension in DN by assessing root growth responses, biomass allocation, and root distribution. A full two-way factorial blocked design of soil dimensions by water availability was followed. The perennial grass Lolium perenne L. was grown in SW and DN under high (W100%), moderate (W50%), and low (W30%) water availability, respectively. The main results were as follows: (1) The total biomass of L. perenne was not influenced either by soil habitat or by water application. Root length, root surface area, root biomass and root to shoot ratio all decreased with decreasing water application in SW, but not in DN soil. (2) With decreasing water application, the cumulative percentage of root length, root surface area and root biomass in 4 rings from the center out to 12 cm of SW soil showed a trend of W50% > W30% > W100% in SW, however, the cumulative percentage of root biomass in 4 layers from the surface to a depth of 36 cm was not significantly different between different water treatments in DN. (3) Under all three water treatments, specific root length showed an increase but root length density showed a decreasing trend from the center outward in SW soil or from the surface to bottom in DN soil. Overall, these results suggest that in SW habitat, soil moisture determines horizontal expansion of the roots in L. perenne, although the overall expansion ability was limited in severe drought. However, due to the relatively strong water retention ability, soil moisture changes were less obvious in DN, resulting in no significant vertical extension of the root system. The root response of L. perenne helps our understanding of how herbaceous plants can adjust their belowground morphology to support their growth in harsh karst soil environments

The feasibility study of non-invasive fetal trisomy 18 and 21 detection with semiconductor sequencing platform

Objective: Recent non-invasive prenatal testing (NIPT) technologies are based on next-generation sequencing (NGS). NGS allows rapid and effective clinical diagnoses to be determined with two common sequencing systems: Illumina and Ion Torrent platforms. The majority of NIPT technology is associated with Illumina platform. We investigated whether fetal trisomy 18 and 21 were sensitively and specifically detectable by semiconductor sequencer: Ion Proton. Methods: From March 2012 to October 2013, we enrolled 155 pregnant women with fetuses who were diagnosed as high risk of fetal defects at Xiamen Maternal & Child Health Care Hospital (Xiamen, Fujian, China). Adapter-ligated DNA libraries were analyzed by the Ion Proton??? System (Life Technologies, Grand Island, NY, USA) with an average 0.3 ?? sequencing coverage per nucleotide. Average total raw reads per sample was 6.5 million and mean rate of uniquely mapped reads was 59.0%. The results of this study were derived from BWA mapping. Z-score was used for fetal trisomy 18 and 21 detection. Results: Interactive dot diagrams showed the minimal z-score values to discriminate negative versus positive cases of fetal trisomy 18 and 21. For fetal trisomy 18, the minimal z-score value of 2.459 showed 100% positive predictive and negative predictive values. The minimal z-score of 2.566 was used to classify negative versus positive cases of fetal trisomy 21. Conclusion: These results provide the evidence that fetal trisomy 18 and 21 detection can be performed with semiconductor sequencer. Our data also suggest that a prospective study should be performed with a larger cohort of clinically diverse obstetrics patients.open2

Broprojektering med 3D-cadverktyget Revit Structure

Validerat; 20120514 (anonymous

Structure modification and constant remelting speed control of a 120-t three-phase electroslag furnace

The traditional large electroslag remelting furnaces have many shortages, such as high short-network impedance and inductance, long maintenance time for electrode replacement, low stiffness of driveline, and low control accuracy of remelting speed. The present research was aimed to solve these problems through structure modification and constant remelting speed control for a 120-t electroslag remelting (ESR) furnace. Based on the technique of three-phase double electrodes in series, the short-network system and the structure of the 120-t ESR furnace were improved; and a continuous feeding system for the self-consumption electrode was proposed. A self-designed fully hydraulic driveline system with three degrees of freedom was successfully applied to the 120-t ESR furnace. An electrode auto-replacement system and the S-style speed-control curve of electrode-feeding system were designed on the basis of the soft measurement/sensing model on the remaining electrode length so as to obtain a high accuracy control system for constant remelting speed. The experiment products showed good surface quality and cross-sectional results, indicating good system control, and verifying the effectiveness of the structure modification of the furnace

Effects of electrode immersion depth and remelting rate on electroslag remelting process

In the electroslag remelting process, the electrode molten state is a critical factor determining the ingot quality, while the electrode immersion depth and melting rate are key factors for the stability of the electroslag re-melting process. Studies were carried out to investigate the microscopic and macroscopic effects of electrode immersion depth and melting rate on the potential distribution and heat density in the slag bath, and on the depth and shape of the molten bath. Based on the finite element method and the numerical solution method, the effect of the electrode immersion depth on the slag bath heat density was researched; the relationship between the electrode immersion depth and the slag resistance was obtained; and the unsteady-state model of the solidification process of the re-melting ingot was solved using the finite difference method. The mathematical model and physical model of the electrode melting process were established and solved; and the corresponding curves between the electrode molten-state and slag-bath physical parameters were obtained. The experimental results verified the simulated results studied in this paper

Research on Output Signal Controlling of an Asymmetric Hydraulic Cylinder Based on a Flexible Connection

In industrial production, the structures of hydraulic servo system-connecting device-load systems are often simplified as rigid connections for the ease of calculation. However, this simplification is problematic when applied to flexible connections in hydraulic systems, which generally have multivariable and strong couplings; these characteristics affect the control accuracy of the hydraulic servo system and lead to serious distortion of the output waveform, which cannot be ignored. These problems cause greater lag and attenuation of the actual signal than those of the expected signal, leading to lower credibility. Therefore, it is important to study the waveform distortion caused by flexible connections. In this paper, according to the characteristics of a flexible connection, a corresponding mathematical model is established, and an adaptive controller, whose structure is simple and calculation cost is low, is used to adjust the amplitude and phase of the response signal and improve the accuracy of the system response. Treating the change in the response signal as the error value, the algorithm weights are adjusted until the error value is stable. Then, a more accurate output signal is obtained. Finally, the validity and practicability of the adaptive controller are verified by simulation experiments

Study on the Resonant Suppression of Electrohydraulic Servo Shaking Table of a 2-Mass Dynamic System

Since the load of electrohydraulic servo shaking table is an elastic load, there is a mutual coupling effect that exists between the experimental object and the shaking table, forming the resonance to weaken the dynamic characteristics, and producing resonant peak and resonant valley in the bandwidth required by the system, in which the amplitude is often larger than the stability range of acceleration’s amplitude. In this paper, the mathematical modeling of hydraulic power mechanism in a two-mass dynamic system is established based on electrohydraulic servo shaking table, yielding the frequency characteristic curve in accordance with the transfer function of the model. A multifrequency adaptive notch filter based on the least mean square algorithm is proposed to suppress the resonance, and the suppression effect of the resonance is simulated and verified in line with various values of load stiffness. Finally, the power spectrum is used to demonstrate the effectiveness of the multifrequency adaptive notch filter in the resonant suppression

A comprehensive review of the key technologies for pure electric vehicles

The final publication is available at Elsevier via https://doi.org/10.1016/j.energy.2019.06.077. © 2019. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/Nowadays, the emissions from conventional vehicles significantly contribute to increasingly serious environmental issues. In addition, the energy crisis and the low energy efficiency of conventional vehicles also offer a good opportunity to develop electric vehicles. Hybrid electric vehicles have better fuel economy compared to conventional vehicles, but they are just an interim step in vehicle development and pure electric vehicles are the ultimate goal. Currently, the technologies of hybrid electric vehicles can be found in numerous literature surveys, however there is a lack of published papers to present a comprehensive technical review for pure electric vehicles. In this study, the characteristics and typical models of energy sources of pure electric vehicles are firstly described. Then the existing pure electric vehicle types are depicted and the environmental impacts of the typical pure electric vehicles are evaluated. Moreover, energy management strategies for pure electric vehicles and charging technologies are investigated. The main challenges faced by pure electric vehicles and corresponding solutions are discussed, whilst the latest developments of pure electric vehicles are presented. The awareness of environmental issues and the energy crisis as well as the incentives from the governments of many countries continuously enhance the rapid development of pure electric vehicles

Comparison of compressible and incompressible numerical methods in simulation of a cavitating jet through a poppet valve

The regime of compressible flow generally refers to the super/subsonic case. However, several remarkable cases with low Mach number could not be appropriately described with the incompressible method. It is a similar case for a cavitating jet inside a poppet valve. In order to comprehensively address the discrepancy between incompressible and compressible methods, both non-cavitating and cavitating cases are performed in experiment and calculation based on OpenFOAM. Experiment reveals a transition in flow pattern in both non-cavitating and cavitating flow. For example, for 0.7 mm openness and 30-degree poppet angle, transition happens at approximately 29 and 27 bar pressure drop for the two cases, respectively. In general, results from the compressible method exhibit better agreement with experiment regarding both flow performance and flow structure. By contrast, the incompressible method could not provide an accurate description for the transition process under the applied flow condition. A series of studies are carried out with emphasis on such discrepancy. Firstly, the deviation in flow performance is addressed based on velocity profile and turbulence level. Secondly, the disparity in flow structure is illustrated and the mechanism for cavitation inception is discussed, which combined provide an interpretation of the deficiency of the incompressible method. Thirdly, different inlet boundary conditions are applied, and the results confirm the independence of deficiency of the incompressible method for inlet fluctuation. Finally, a re-examination is proposed concerning traditional notion of compressible flow as well as the applicability of incompressible numerical method