Characterization and modeling of long-term stress-strain behavior of water confined pre-saturated gypsum rock in Kurdistan Region,Iraq

In order to understand the effects of soaking time and confined water pressure on the strength of rock due to dissolution of gypsum,rock samples with 96% of gypsum content collected from Kurdistan Region in northern Iraq were investigated.Laboratory tests were then performed on the normal gypsum rock samples under pre-saturated condition to obtain their uniaxial compressive strength(UCS) values.The pre-saturated samples were submerged in distilled water for 35 d,70 d and 105 d,respectively,under confined water pressures of 0-0.5 MPa.The gypsum content decreased by 11% after 105 d of soaking under confined water pressure of 0.5 MPa.The UCS of the normal gypsum rock was 19.6 MPa and it decreased to 6.3 MPa and 2 MPa after 105 d of soaking under confined water pressures of 0 and 0.5 MPa,respectively.A nonlinear constitutive model was used to simulate the experimental stress-strain relationships of rock samples under various conditions.The constitutive model parameters were sensitive to the gypsum content.

COMPARATIVE STUDY ON DROUGHT RESISTANCE OF LARIX OLGENSIS HENRY AND PINUS SYLVESTRIS VAR.MONGOLICA(Ⅰ)──THE INFLUENCE OF SOIL WATER CONTENT ON SEEDLINGS PLANTING IN FLOWERPOT

Water potential (φ w .) and net photosynthetic rate (Pn) of Larix olgensis and Pinns.sylvestris var. mongolica deercased with the deerease of soil water content φw and Pn of L.olgensis changed hardly during the first 9 davs after stopping watering, then deereased sharply at the 10th dav Pn of P sylvestris var mongolica deereased slightly during the lirst 8 days, then deereased sharply at the 9th day Their respiration rate, chlorophyll content and their a/b ratio changed hardly. The tollowing 3 conclusions were obtained and discussed exhaustively . (Ⅰ) φ w can be used to direct watering as a sensitive index of judging whether L. olgensis and P.sylvestris var. mongolica lacking water (2 )The deereasc of Pn of L. olgensis and P. sylvestris var. mongolica when drought had nothing to do with chlorophyll. (3) P. sylvestris var. mongolica had morphological drought resistance . while L,olgensis had physiological drought resistance, and their drought resistance was discnssed comparatively first time.

Influence of soil organic matter contents on soil water characteristics of forests on east slope of Gongga Mountain

By testing soil organic matter （SOM） contents, soil water contents （SWC） within low suctions, and saturated infiltration rates of samples taken from east slope of Gongga Mountain of China, the enhancive effects of SOM contents on SWC within low suctions and saturated infiltration rates were quantified. The simulated functions might be applied on regional experience forest-hydrology model. The improving function of protecting forest floor and increasing SOM contents on forest ecosystem hydrological effects were also embodied.

Characteristic of hyaluronic acid derivative films cross-linked by polyethylene glycol of low water content

Objective:To test the characteristics of hyaluronic acid(HA)derivative cross-linked by polyethylene glycol films of low water content.Methods:The cross-linked HA film with 200μm thickness was got at atmospheric pressure at 25℃for 5 d.After dried,cross-linked films of 10 mm×10 mm were weighed and immersed in phosphate buffered saline (PBS pH 7.45)at 37℃for 24 h.Then the solution fraction and water content were estimated.Meanwhile,cross-linked HA derivative films were immersed in phosphate buffered saline(PBS:pH 7.45)at 37℃for determined time and then implanted subcutaneously in the back of white rats to test in vitro or in vivo degradation characteristic.Results and Conclusion:HA hydrogel cross-linked by polyethylene glycol with water content is as low as 60% and this kind of HA derivative has a slow degradation rate.

Vibration pore water pressure characteristics of saturated fine sand under partially drained condition

Vibration pore water pressure characteristics of saturated fine sand under partially drained condition were investigated through stress-controlled cyclic triaxial tests employed varied fine content of samples and loading frequency. In order to simulate the partially drained condition, one-way drainage for sample was implemented when cyclic loading was applied. The results show that the vibration pore water pressure's response leads the axial stress and axial strain responses, and is lagged behind or simultaneous with axial strain-rate's response for all samples in this research. In addition, the satisfactory linear relationship between vibration pore water pressure amplitude and axial strain-rate amplitude is also obtained. It means that the direct cause of vibration pore water pressure generation under partially drained conditions is not the axial stress or axial strain but the axial strain-rate. The lag-phase between pore water pressure and axial strain-rate increases with the increase of the fine content or the loading frequency.

Effects of Water Stress on Leaf Water and Chlorophyll Fluorescence Parameters of Sugarcane Seedling

[Objective] The aim was to explore the effects of water stress on leaf water and chlorophyll fluorescence parameters of sugarcane seedling,as well as to provide basis for the study on sugarcane production and evaluation. [Method] Seven different sugarcane varieties were studied at the seedling stage under drought stress,and the changes of leaf water and chlorophyll fluorescence parameters under stress conditions were detected. [Result] leaf water potential,leaf relative water content and soil relative water content showed a certain amount of internal relationship,the sugarcane varieties that had more tolerant to drought had higher utilization rate of soil water; the correlation analysis and factor analysis suggested that the survival rate at seedling stage under drought stress,Fv/Fm,leaf water potential and relative water content could be used as drought resistance evaluation indicators. [Conclusion] As a relatively independent influencing factor,water potential had dominating effect on drought resistance,and the reliability of Fv/Fm as drought resistance evaluation indicator had been verified.

Effects of Nitrogen Fertilizer Treatments on Caryopsis Filling and Respiratory Rate of Rice

An experiment was conducted to study the effects of nitrogen （N） rate and application time on grain filling and respiratory trait of caryopsis in two rice varieties, IR36 and Dali. The treatments were consisted of no N application topdressing at both tillering and booting stages （CK）, 6 g/pot of N topdressing at the tillering stage and 2 g/pot of N topdressing at the booting stage, 2 g/pot of N topdressing at the tillering stage and 6 g/pot of N topdressing at the booting stage. The results showed that the proper utilization of N fertilizer can be helpful to maintain the higher water content, higher respiratory rate and higher dehydrogenase activity of rice caryopsis in late filling phase, and prolong the course for filling and maintaining higher respiratory rate and dehydrogenase activity of rice caryopsis. More N application at booting was more effective compared to more N application at tillering.

Preparation of New Cementitious System using Fly Ash and Dehydrated Autoclaved Aerated Concrete

We experimentally studied the interaction between pozzolanic material（fly ash） and dehydrated autoclaved aerated concrete（DAAC）. The DAAC powder was obtained by grinding aerated concrete waste to particles fi ner than 75μm and was then heated to temperatures up to 900 ℃. New cementitious material was prepared by proportioning fly ash and DAAC, named as AF. X-ray diffraction（XRD） was employed to identify the crystalline phases of DAAC before and after rehydration. The hydration process of AF was analyzed by the heat of hydration and non-evaporable water content（Wn）. The experimental results show that the highest reactivity of DAAC can be obtained by calcining the powder at 700 ℃ and the dehydrated products are mainly β-C2 S and CaO. The cumulative heat of hydration and Wn was found to be strongly dependent on the replacement level of fl y ash, increasing the replacement level of fl y ash lowered them in AF. The strength contribution rates on pozzolanic effect of fl y ash in AF are always negative, showing a contrary tendency of that of cement-fl y ash system.

Drying Characteristics of Microwave-assisted Foam Drying of Corn Soaking Water

To improve the industrial utilization of corn soaking water, the yeast protein powder was produced by microwave-assisted foam drying. Firstly, preparation experiments were carded out, which included the foaming characteristic experiments of fermentation broth and that about the effects of carbon and nitrogen ratio on solid content in the fermentation broth. Secondly, the drying characteristics experiment of corn soaking water was studied, which selected the microwave power, material amount and thickness as the influencing factors for the single experiment. The results showed that the final moisture content （d.b.） and drying rate were significantly affected by those factors.

BECK FOUMULA REVISION FOR ^(222)Rn ESCAPE AND WATER CONTENT IN SOIL

This paper points out the limitation of Beck formula and gives a revised formula owing to the water content and 222Rn escape in soil for calculating γ radiation doserate through the experimental fitting from 576 sets of measured values in ZhejiangProvince. When the revised formula is applied to Beijing Municipality, where there is a great difference in the meteorology and soil conditions, the calculated average in general is only 3.5% different from that measured; those of every position deviate only 2.1% averagely; and their dispersion is in the experimental errors. Therefore, the revised formula possesses a high reliability and a broad suitability, and is an effective method to estimate the ac radiation dose rate oil the land.

Short-term Response of Photosynthesis and Chlorophyll Content to Salinity Stress in Two Mangrove Species:Aegiceras corniculatum and Kandelia candel

There were fewer comparative studies on the adaptability of mangrove plants with two different salt secretion mechanisms to salinity stress. In this study,the seedlings of mangrove plants Aegiceras corniculatum and Kandelia candel were selected as the research objects,and the methods of hydroponics with different salinity gradients were used. The salinity of 0‰,10‰,and 30‰ was applied respectively to simulate the adaptability of seedlings at low,moderate,and severe salinity stresses. Based on the results,the short-term responses of photosynthesis and chlorophyll content to salinity stress in two mangrove species with different salt secretion mechanisms were analyzed and discussed. The results show that A. corniculatum was more tolerant to10‰ salinity than K. candel,and the net photosynthetic rate(Pn),transpiration rate(Tr),stomatal conductance( Gs) and water use efficiency(WUE)were also relatively higher;both A. corniculatum and K. candel could acclimate the low salinity(0‰),but showed severe osmotic stress at 30‰ salinity;A. corniculatum was more sensitive to severe salinity(30‰) than K. candel. These results can be of help to provide a theoretical support for the selection of species for mangrove wetlands restoration and seedlings acclimatization in tidal flats.

Root distribution of three co-occurring desert shrubs and their physiological response to precipitation

Root distribution of three desert shrubs,Tamarix ramosissima Ledeb.,Haloxylon ammodendron(C.A.Mey.) Bunge and Reaumuria soongorica(Pall.) Maxim.was investigated under co-occurring conditions using a method for excavating the whole root system.Assimilation shoot water potential and transpiration rates were monitored during the wet-dry cycle.Leaf-specific apparent hydraulic conductance and the index of water stress impact for the three species were calculated from shoot water potential and transpiration rate.The results showed that,along the soil profile,the root system of T.ramosissima mainly distributed at 50 to 310 cm interval,with an average total absorbing root-surface area of 30,249.2 cm2 per plant;the root system of H.ammodendraom distributed at 0 to 250 cm interval with an average total absorbing root-surface area of 12,847.3 cm2 per plant;the root system of R.soongorica distributed at 0-80 cm interval,with an average total absorbing root-surface area of 361.8 cm2.The root distribution shows the following:T.ramosissima uses groundwater as its main water source;H.ammodendraom uses both groundwater and rainwater;and R.soongorica uses rainwater only.During the wet-dry cycle,the hydraulic parameters of T.ramosissima showed no responses to precipitation.R.soongorica responded most significantly,and the responses of H.ammodendraom were intermediate.In conclusion,the plant response to rain events is closely related to their root distribution and plant water-use strategy.

Extraction Process Optimization and Moisturizing Performance of Fucoidan from Sargassum fusiforme

[Objectives] The research aimed to optimize extraction process of fucoidan from Sargassum fusiforme( FSF) and study its moisturizing performance. [Methods]Extracting condition of FSF by cellulase hydrolysis-ultrasonic assisted extraction method was optimized. The influences of solvent p H,enzyme dosage,extraction temperature,cellulose hydrolysis time,ultrasonication time,and the ratio of material to liquid on FSF were investigated by single factor and orthogonal experiments. [Results] The optimum extraction conditions were as followings:p H,4. 5; enzyme dosage,1%; extraction temperature,40℃; cellulose hydrolysis time,2 h; ultrasonic time,15 min; and the ratio of material to liquid,1∶ 10( g∶ m L). Under the optimal condition,the extraction yield of FSF was 8. 50%,RSD = 2. 74%. The short-time hygroscopicity( within 8 h) of crude extract of fucoidan from S. fusiforme( CEFSF) was better than glycerin,butanediol,and sodium alginate,and the moisture retention capacity of 1% CEFSF aqueous solution was better than 1% butanediol or 1% sodium alginate,and was equal to 5% glycerin under relative humidity of 43% and 81%. The determination results of skin moisture content and transepidermal water loss rate( TEWL)showed that: 5% CEFSF solution had good moisturizing effect. [Conclusions]The research could provide certain reference for deep development of S. fusiforme.

Short-term responses to salinity of seabuckthorn (Hippophae rhamnoides L.) seedlings in the extremely cold and saline Qinghai region of China

The investigation of the mechanisms of plant adaptation to stressor action is one of the leading directions of current biological studies. To understand the mechanism of salt tolerance of seabuckthom （Hippophae rhamnoides L.） and identify its ability to cope with the salinity effect in the saline and extremely cold region of Qinghai, China, a test was conducted with two-year-old seedlings subjected to 0, 200, 400 and 600 mmol·L^-1 NaClsolutions for 30 d. The results show that with an increase in salinity, the biomass of H. rhamnoides seedlings clearly decreased. Leaf water potential （ψw） and relative water content （RWC） were significantly reduced under salinity, with severe water shortages appearing in leaves. At the same time, the total chlorophyll content declined markedly. When salinity increased and stress time prolonged, the net CO2 assimilation rate （A） significantly declined. Intercellular CO2 concentration （Ci） declined at first and was then followed by an increase over the stress time. We conclude that H. rhamnoides grown in the extremely cold and saline region of Qinghai has a certain resistance to salt, which can be planted at appropriate salinity levels.

Evaluation of Tomato Genetic Resources for Response to Water Deficit

Water deficit strongly affects plant yield and quality. However, plants can minimize drought injury by adaptation mechanisms that have evolved to escape harmful conditions. The response to water deprivation is a complex trait controlled by several genes. In order to gain a deeper understanding of drought response mechanisms in tomato, a collection of 27 genotypes was studied under different water deficit conditions. Since developmental stages might be differently influenced by drought, analyses were carried out on young plantlets during fruit setting. The only genotype that showed good performances both as water retention and fruit production was the ecotype Siccagno. All the genotypes were analyzed at molecular level with the aim of detecting structural polymorphisms in selected stress-responsive genes. In addition, the expression level of a number of these genes was measured in the genotypes more tolerant to water deficit. Many polymorphisms were detected in six stress-responsive genes, and some could imply significant modifications in the protein structure. Furthermore, the expression analysis by RT-qPCR of three stress-responsive genes allowed arguing that a higher level of expression of the gene erd15 might be related to the better response to water deficit exhibited by Siccagno. Similarly, the lower expression of eight genes in the same genotype analysed through a microarray experiment confirmed the involvement of these stress-related genes in the tomato response to drought. Further investigations are required for a better comprehension of the mechanisms underlying response to water deficit in tomato by exploiting the genetic resource identified as more tolerant. The use of new technologies able to globally analyze structural polymorphism and expression level of genes will succeed to identify crucial genes involved in stress response in the ecotype Siccagno grown under different water regimes.

Influence of water content and shear rate on the mechanical behavior of soil-rock mixtures

Soil-rock mixtures(S-RMs) are widely distributed in the nature. The mesoscopic deformation and failure mechanisms as well as the macro-mechanical behaviors of the S-RMs depend largely upon the rate of deformation, water content and particle sizes. In this research, a series of large-scale direct shear tests with different water contents and different grain-size distributions were conducted to study the influence of the aforementioned factors on the mechanical properties of the S-RMs. Due to the effect of the rock blocks' breakage in the S-RMs, the relationship between the shear strength and the vertical stress of S-RM follows a power law instead of a linear one. It is found that there exists a threshold value for the vertical stress during the shearing process,below which the soil strength is mainly determined by the inter-locking of particles and the re-arrangement of meso-structure,and otherwise large-sized rock blocks are gradually broken into smaller fragments, resulting in a decrease in the soil strength.The shear rate can also significantly influence the degree of particle breakage and the meso-structural rearrangement of the SRMs, namely, under low shear rate, the particles of the samples are fully broken resulting in enhanced macro-strength. As a result, the lower the shear rate, the higher the macroscopic strength. So under unsaturated conditions, the water content will affect the strength of the S-RMs by reducing the strength of rock blocks. As the water content increases, the soil strength decreases gradually, and assumes a moderate value when the water content reaches 8%. At the same water content, the soil strength increases with the sizes of large rock blocks. For the occlusion, breakage and structure re-arrangement of the oversized rock blocks inside S-RM, which have a huge influence on the mechanical characteristics of the samples.

Correlation and Quantitative Trait Loci Analyses of Total Chlorophyll Content and Photosynthetic Rate of Rice(Oryza sativa) under Water Stress and Well-watered Conditions

In order to explore the relevant molecular genetic mechanisms of photosynthetic rate （PR） and chlorophyll content （CC） in rice （Oryza sativa L.）, we conducted a series of related experiments using a population of recombinant inbred lines （Zhenshan97B x IRAT109）. We found a significant correlation between CC and PR （R = 0.19＊＊） in well-watered conditions, but no significant correlation during water stress （r = 0.08）. We detected 13 main quantitative trait loci （QTLs） located on chromosomes 1, 2, 3, 4, 5, 6, and 10, which were associated with CC, including six QTLs located on chromosomes 1, 2, 3, 4, and 5 during water stress, and seven QTLs located on chromosomes 2, 3, 4, 6, and 10 in well-watered conditions. These QTLs explained 47.39% of phenotypic variation during water stress and 56.19% in well-watered conditions. We detected four main QTLs associated with PR; three of them （qPR2, qPR10, qPR11） were located on chromosomes 2, 10, and 11 during water stress, and one （qPR10） was located on chromosome 10 in well-watered conditions. These QTLs explained 34.37% and 18.41% of the phenotypic variation in water stress and well-watered conditions, respectively. In total, CC was largely controlled by main QTLs, and PR was mainly controlled by epistatic QTL pairs.

Effect of vacuum degree and aeration rate on sludge dewatering behavior with the aeration-vacuum method

Due to large-scale dredging operations, a large amount of sludge is inevitably produced. Large areas of land are occupied when the dredged sludge is discarded in the disposal site as waste material. The sludge dewatering with aeration-vacuum (SDAV) method is suit for treating the sludge with high water content and high clay content in the disposal site. The water in the sludge can be discharged out. The volume of the sludge can be reduced quickly, and the recycling of the land can be accelerated by this method. Most importantly, this technique is an efficient way to deal with clogging problems when pumping water from high water content, high clay content dredged sludge. Vacuum degree range tests, the aeration rate range tests, and the influencing factors of sludge dewatering behavior tests were conducted with a self-developed SDAV model test device. Sludge samples were taken from the South-to-North Water Diversion East Line Project in Huai’an White-Horse Lake disposal site, Jiangsu Province, China. The optimal range of vacuum degree and aeration rate were obtained through the test results, and the mechanisms for how the two factors work and how they affect the sludge dewatering behavior were analyzed. The suitable vacuum degree range in SDAV is below 50 kPa, and the suitable aeration rate is about 1.0 m3/h. The low-vacuum degree contributes to reduce the ad-sorption effect of micro-channels on soil particles in filter material and to maintain the arch structures. Aeration has the effects of expansion, disturbance, changing Reynolds number, and dynamic sieve separating. The pump quantity of water per meter of filter tube (m) has different change rules as the vacuum degree changes under different aeration rates. The reason is that the formed arch structures’ conformation and permeability differ greatly under different combined-conditions of vacuum degree and aeration rate. The optimal combined-condition for dewatering the sludge is 35 kPa with 1.0 m3/h.

基于改进Mein-Larson降雨入渗模型的黄土边坡稳定性分析

【目的】降雨是诱发浅层边坡滑动的主要因素,为了使降雨入渗过程更加接近实际,【方法】在传统的Mein-Larson降雨入渗模型基础上,考虑土体初始含水率非均匀分布,以含水率分布函数对传统Mein-Larson降雨入渗模型进行了改进并验证了改进模型的有效性。分别将传统Mein-Larson降雨入渗模型和改进的入渗模型与非饱和无限长边坡稳定分析方法结合,建立考虑边坡倾角、土体初始含水率和降雨形式的降雨诱发型边坡稳定性问题计算模型并对边坡安全系数计算,最后将计算结果与有限元数值模拟结果对比分析。【结果】结果表明:含水率分布函数计算值接近试验值,当参数A取0.375时,拟合优度达到0.995。采用改进的入渗模型计算出的各时段湿润锋深度与传统入渗模型接近,但是湿润锋比传统入渗模型早7.7 h到达地下水位线。【结论】基于改进的降雨入渗模型的边坡稳定计算模型计算的边坡安全系数与有限元数值模拟结果接近,相比于基于传统Mein-Larson降雨入渗模型的边坡稳定计算模型计算结果更精确,接近工程实际,可为降雨诱发型边坡稳定分析提供参考。

Experimental Research on the Mechanical Properties of Gypsum Breccia with Different Water Content

This paper deals with the influence of water content on the mechanical properties of gypsum breccia with different initial water contents. The experimental research was taken on the GDS (geotechnical digital systems) tri-axial experiment system by strain rate control. The mechanical properties,including stress-strain curves,peak deviator stress,relative residual strength,elastic modulus,Poisson's ratio,angle of internal friction and cohesion of gypsum breccia,were studied by experiment. The results showed that the water content has obvious infiuence on the mechanical properties of gypsum breccia. With increasing of water content,the angle of internal friction and cohesion of gypsum breccia decrease linearly. Meanwhile,the stress-strain curves go through from the declining,hump curve to the strain hardening curve. At the same confining pressure,the peak deviator stress and elastic modulus decrease exponentially,while Poisson's ratio increases linearly with the increasing of the water content. At the same water content,with increasing of the confining pressure,the peak deviator stress,elastic modulus and the peak deviator stress increase trend but Poisson's ratio decreases at a lower water content. While at a high water contents,the Poisson's ratio doesn't change much. It shows that water content plays an important role in the process of changing from the brittleness to plastic for the mechanical properties of gypsum breccia.