Hydraulic resistance partitioning between shoot and root system and plant water status of Haloxyolon ammodendron growing at sites of contrasting soil texture

Hydraulic resistance components and water relations were studied on Haloxyolon ammoden-dron,a small xeric tree,growing at sites significantly differed in soil texture.Soil water content,leaf water potential(ψl),xylem water potential(ψx),root water potential(ψroot),leaf transpiration rate(TR) and stomatal conductance(gs) were measured at the two sites during the growing season of 2005 and 2006.Leaf spe-cific hydraulic resistance(Rplant) during the whole growing season,hydraulic resistance of plants(Rp),shoots(Rshoot) and roots(Rroot) in the August of both years were calculated and expressed on leaf area basis.The results showed the proportion of the hydraulic resistance of the aerial part(Rshoot) to the Rp was the same to the proportion of the hydraulic resistance of the soil part(Rroot) to the Rp,indicating that both parts were equivalent important to plant water hydraulic system from soil to leaf.Positive significant corre-lations were found between Rp and Rroot,suggesting that root hydraulics resistance was a major determinant of plant hydraulic resistance(Rp) and transpiration rate.The integrated effect of stomatal control,hy-draulic regulation and morphology adjustment enabled plants at heavy soil site surviving the extreme water deficit period.

Effects of simulated submerged and rigid vegetation and grain roughness on hydraulic resistance to simulated overland flow

Better understanding of the role of vegetation and soil on hydraulic resistance of overland flow requires quantitative partition of their interaction. In this paper, a total of 144 hydraulic flume experiments were carried out to investigate the hydraulic characteristics of overland flow. Results show that hydraulic resistance is negatively correlated with Reynolds number on non-simulated vegetated slopes, while positively on vegetated slopes. The law of composite resistance agrees with the dominant resistance, depending on simulated vegetation stem,surface roughness, and discharge. Surface roughness has greater influence on overland flow resistance than vegetation stem when unit discharge is lower than the low-limited critical discharge, while vegetation has a more obvious influence when unit discharge is higher than the upper-limited critical discharge. Combined effects of simulated vegetation and surface roughness are unequal to the sum of the individual effects through t-test, implying the limitation of using linear superposition principle in calculating overland flow resistances under combined effect of roughness elements.

HYDRAULIC RESISTANCE OF SUBMERGED VEGETATION RELATED TO EFFECTIVE HEIGHT

Submerged vegetation has a significant impact on water flow velocity.Current investigations include the impact through adding drag resistance and increasing bottom roughness coefficient,which cannot elucidate the characters of real submerged vegetation.To evaluate the effects of submerged vegetation on water currents at different velocities,a laboratory experiment was conducted using three kinds of vegetations.The effective heights of these vegetations on varying flow velocities were evaluated.An equation describing the relationship between the normalized resistance of the submerged plants and the Reynolds number based on the plant effective height was then established and used to calculate the hydraulic resistance parameters of submerged plants in different stages of growth.

Understanding Qi Running in the Meridians as Interstitial Fluid Flowing via Interstitial Space of Low Hydraulic Resistance

Qi, blood and the meridians are fundamental concepts in Chinese medicine（CM）, which are components of the human body and maintain physiological function. Pathological changes of qi, blood and meridians may lead to discomfort and disease. Treatment with acupuncture or herbal medicine aims to regulate qi and blood so as to recover normal function of the meridians. This paper explores the nature of qi as well as compares and correlates them with the structures of the human body. We propose a conceptualization of qi as being similar to the interstitial fluid, and the meridians as being similar to interstitial space of low hydraulic resistance in the body. Hence, qi running in the meridians can be understood as interstitial fluid flowing via interstitial space of low hydraulic resistance.

A discovery of low hydraulic resistance channels along meridians in rats

Background:Continuous and porous low hydraulic resistance channels(LHRCs)are important structures of meridians in traditional Chinese medicine(TCM).In this study,based on the previous research on LHRCs along meridian paths(LHRCMs)in mini-pig,we aimed to detect the low hydraulic resistance point(LHRP)and display the LHRCMs in rats.Methods:A technique for measuring interstitial hydraulic resistance(Rh)in rats was established to detect and measure the Rh along the conception vessel(CV)in TCM,and Alcian Blue(AB)solution was injected into the LHRP along the CV.The interstitial fluid pressure(IFP)of the LHRP was measured before and after AB injection.Then,the distribution characteristics of the AB solution were investigated to explore the relationship between AB tracks and meridian paths in TCM.Results:The positions of the LHRPs coincided with the low impedance points(LIPs)of the rat skin along the CV.The Rh value along the CV(10.37,1.26,×10^(6)dyne s cm^(-5))was significantly lower than that in the non-meridian area(19.13±1.37,×10^(6)dyne s cm^(-5),P<0.01).After AB injection,the IFP of the LHRP was 2.52 mmHg,which was higher than that before AB injection.The AB tracks(ABT)along the CV,spleen meridian,and kidney meridian appeared in one or two directions,with single or multiple paths and uneven thickness and length.The appearance rate was 73.33%.Conclusions:LHRCMs existed not only in minipigs but also in rats.The LHRCMs could be observed after AB injection into the LHRP in the subcutaneous connective tissues of rats.

Study on Hydraulic System Efficiency of Heaving-Buoy Wave Energy Converter

The hydraulic system is the key component in the widely used wave energy converters(WEC).In this paper,we theoretically analyze and describe our investigation of the efficiency of the hydraulic system by simulation and model testing of the combined heaving-buoy WEC.We derive a new governing equation that includes nonlinear hydraulic resistance in the power take-off(PTO).We conducted a physical model experiment based on a 100-kW prototype and applied a hydraulic system with an energy accumulator.The model test results reveal an important parameter related to efficiency with respect to nonlinear hydraulic resistance.We also studied the relationship between the efficiency and the initial conditions.Finally,based on our numerical simulation results,we discuss the effect on efficiency of the gas content of the hydraulic fluid and ways to reduce its impact.

DESIGN THEORY FOR G-π BRIDGE RELIEF VALVE WITH ZERO OVERRIDE

A new construction of the relief valve is presented with pilot G-pi bridghydraulic resistances network. The design theory of G-pi bridge relief valve is studied and theformulas for designing the relief valve with zero static pressure override are obtained. The staticperformances of the relief valve are experimentally investigated. The theoretical and experimentalresults show that the static pressure override of the developed relief valve can be zero, i.e. whenthe overflow increases the control pressure is kept constant.

Behaviours of Soil-Root Interface and Their Variations with Wheat Varieties

Water movement into and out of roots depends on the water potential difference between the bulk soiland the root xylem and the total hydraulic conductance of the pathway, which can be divided into three parts,i.e. soil conductance, soil-root conductance and root conductance. The vaues and relative importance varywith soil water content. The general rule is that water uptake by roots is mainly limited by radial hydraulicconductance of roots in wet soils, the soil-root interfaCe becomes a major limiting factor to water uptake inmoderately dry soils, and the water uptake is limited by the rapidly decreasing soil hydraulic conductance inseriously dry soils. Meanwhile these limiting factors vary with crop variety, and these variations can be usedto evaluate the drought-resistance and water use efficiency of crops.

Assessing the Connectivity of a Regional Fractured Aquifer Based on a Hydraulic Conductivity Field Reversed by Multi-Well Pumping Tests and Numerical Groundwater Flow Modeling

Aquifer connectivity could greatly affect groundwater flow and further control the contaminant transport in fractured medium.However,assessing connectivity of fractured aquifer at regional scales is still a challenge because such connectivity is difficult to be measured directly.This study proposes a framework for assessing connectivity of a fractured aquifer,with Qitaihe area,Heilongjiang Province,northeastern China as an illustrating study area.The 3-D finite difference numerical models were established to interpret the results of three multi-well pumping tests and inversely estimate the distribution of hydraulic conductivity(K)in the fractured aquifer.A static connectivity metric of the minimum hydraulic resistance(MHR)was calculated,based on the optimized K-field,to evaluate the hydraulic connectivity in the aquifer,and the corresponding least resistance paths(LRPs)were identified.The results indicate a better horizontal connectivity in the fractured aquifer in the northeastern and middle parts than in the southwestern part of the study area.The identified LRP indicated that the preferential flow channels at regional scales were controlled mainly by aquifer connectivity instead of local high-K zones.The results of this study can provide a method for aquifer connectivity estimation at regional scales.

Resistance of large caisson in floating transport considering the influence of air

This paper deals with the floating resistance of super large caisson by numerical simulation,and the influence of air resistance on the caisson,which is often ignored by previous researchers,is considered.The floating caisson of Taizhou Highway Bridge’s middle tower pier is investigated,and the software package FLUENT is used to simulate the floating process of largescale rounded rectangular steel caisson.This simulation adopts the volume of fluid(VOF)model with water-air two-phase flow,which can take both the hydraulic resistance and air resistance into account.Subsequently,the analyses on hydraulic resistance and air resistance under different working conditions,such as different flow velocities and different draughts of water are performed,and the results are compared with those calculated by related empirical formula.The comparison shows that the air resistance takes up notable portion in the total resistance on the floating caisson,and the effect of air resistance on the safety of caisson should be paid sufficient attention to rather than be ignored.

NUMERICAL MODEL FOR FLOW THROUGH SUBMERGED VEGETATION REGIONS IN A SHALLOW LAKE

Aquatic vegetation has a significant impact on water currents. To evaluate the effects of changes in the aquatic vegetation on water currents of different velocity, a 3-D hydrodynamic model was then developed by taking into consideration of the additional hydraulic resistance of the aquatic plants. The Navier- Stokes equations were then solved using the SIMPLE method and the k - e＂ turbulence model. Calculations using the established models were used to forecast the vertical distribution of the horizontal velocity and horizontal flow under the transmission conditions of the South-North Water Diversion in the Nansi Lake. And comparative calculation for the flow velocity was also performed using the simplified method of assigning a high roughness coefficient to the lake bed in the same area. Results suggest that adding additional hydraulic resistance of the aquatic plants is feasible. The calculation errors between simulation result and the field observed data are smaller than 15%, while, those errors are up to 35% if the influence of aquatic vegetation is dealt with the simplified method.

Understanding Propagated Sensation along Meridians by Volume Transmission in Peripheral Tissue

Propagated sensation along meridians （PSM） is a phenomenon that a sensation moves along meridians during stimulation of an acupoint. PSM has an appearance rate of 1.3% among people and have characteristics of low speed, going toward afflicted sites and being blocked by physical pressure which is difficult to be explained by known neural and blood transmission. Volume transmission （VT） is a widespread mode of intercellular communication in the central nervous system that occurs in the extracellular fluid and in the cerebrospinal fluid. VT signals moves from source to target cells via energy gradients leading to diffusion and convection （flow） which is slow, long distance and much less space filling. VT channel diffuse forming a plexus in the extracellular space with two parameters of volume fraction and tortuosity. Some experiments showed an information transmission between adjacent and distant acupoints along meridians cross spinal segments. This process is a cross-excitation between peripheral nerve terminals which is related to nonsynaptic transmission. Some neurotransmitters or neuropeptides such as glutamate, adenosine triphosphate （ATP） and neuropeptide such as substance P, neurokinin A and calcitonin gene-related peptide relate with the cross-excitation which can be regards as VT signals. Comparing the characteristics of PSM and VT, many similar aspects can be found leading to an assumption that PSM is a process of VT in peripheral tissue along meridians. The reason why VT signals transmit along meridians is that the meridian is rich in interstitial fluid under the condition of low hydraulic resistance which has been proven experimentally. According to Darcy＇s law which descript the flow of interstitial fluid and conservation equation, interstitial fluid will move toward meridians and flow along meridians that restrict the VT signals within the channel and accelerate the flow according to Fick＇s diffusion law. During the process, a degranulation of histamine from mast cells happens on the route which can expand capillary and increase the blood perfusion and interstitial fluid which had already been observed. The mechanism of PSM is featured by alternative axon reflex （wired transmission, WT） and VT in peripheral tissue along meridians, sending simultaneously a continuous sensate signal to control nerve system which can be felt like a PSM.

ROUGHNESS COEFFICIENT FOR UNSUBMERGED AND SUBMERGED REED

The characteristics of the roughness coefficient are very important for practical application. Some experiments are conducted to study the variation of Manning＇s n with flow depth, mean velocity, and density of vegetation,. An assumed velocity distribution to describe the vegetative flow of submerged vegetation is confirmed by experimental results. The measured velocities in this study seem to have little effect on the curve of n ~ h, and a new linear relationship between Manning＇s n and flow depths is observed clearly. According to the arguments that the flow resistance of densely unsubmerged vegetation is dominated by the resistance exerted on vegetations, the influence of the density of vegetation on Manning＇s n is estimated. On the basis of the velocity distribution, the n - h curve under submerged condition is theoretically obtained from the n - h curve under unsubmerged condition. These results are also well confirmed by experimental results and very significant for practical applications.