Influence of confined water on the limit support pressure of tunnel face in weakly water-rich strata

In the process of shield tunneling through soft soil layers,the presence of confined water ahead poses a significant threat to the stability of the tunnel face.Therefore,it is crucial to consider the impact of confined water on the limit support pressure of the tunnel face.This study employed the finite element method(FEM)to analyze the limit support pressure of shield tunnel face instability within a pressurized water-containing layer.Subsequently,a multiple linear regression approach was applied to derive a concise solution formula for the limit support pressure,incorporating various influencing factors.The analysis yields the following conclusions:1)The influence of confined water on the instability mode of the tunnel face in soft soil layers makes the displacement response of the strata not significant when the face is unstable;2)The limit support pressure increases approximately linearly with the pressure head,shield tunnel diameter,and tunnel burial depth.And inversely proportional to the thickness of the impermeable layer,soil cohesion and internal friction angle;3)Through an engineering case study analysis,the results align well with those obtained from traditional theoretical methods,thereby validating the rationality of the equations proposed in this paper.Furthermore,the proposed equations overcome the limitation of traditional theoretical approaches considering the influence of changes in impermeable layer thickness.It can accurately depict the dynamic variation in the required limit support pressure to maintain the stability of the tunnel face during shield tunneling,thus better reflecting engineering reality.

Isolation and Structural Analysis of DRE-Binding Transcription Factor from Maize (Zea mays L.)

Dehydration-responsive element-binding (DREB) proteins specifically binding with dehydration-responsive element (DRE) have been identified as a kind of important transcription activator of plants under drought, high salt and cold stress. The conserved amino, acid residues of Val (14th residue) and Glu (19th residue) in AP2/EREBP domain of DREB1A have been identified to be two key points in determining the binding ability of DREB gene with DRE element. Using the yeast one-hybrid system, we isolated one maize DREB gene named maDREB1 by screening cDNA library. Trans-activation experiment in yeast reporter strain demonstrated that maDREB1 protein could function as a DREB transcription factor activating target gene expression by specifically binding to the DRE cis-element. To assess the functional significance of these two residues in maDREB1, the V14 and E19 were substituted individually or doubly by Ala and Asp. Point mutation analysis showed that V14 substitution made significant loss of binding ability with DRE element, while point mutation of E19 had less effect. If the substitution happened simultaneously to these two residues, it would lead to great loss of the ability of binding with DRE element. It suggested that V14 and E19 were both important in protein-DNA interacting in maDREB1, though 14V was more essential. The copy number and expression pattern of maDREB1 was discussed.

A universal thermodynamic model of calculating mass action concentrations for structural units or ion couples in aqueous solutions and its applications in binary and ternary aqueous solutions

A universal thermodynamic model of calculating mass action concentrations for structural units or ion couples in ternary and binary strong electrolyte aqueous solution was developed based on the ion and molecule coexistence theory and verified in four kinds of binary aqueous solutions and two kinds of ternary aqueous solutions. The calculated mass action concentrations of structural units or ion couples in four binary aqueous solutions and two ternary solutions at 298.15 K have good agreement with the reported activity data from literatures after shifting the standard state and concentration unit. Therefore, the calculated mass action concentrations of structural units or ion couples from the developed universal thermodynamic model for ternary and binary aqueous solutions can be applied to predict reaction ability of components in ternary and binary strong electrolyte aqueous solutions. It is also proved that the assumptions applied in the developed thermodynamic model are correct and reasonable, i.e., strong electrolyte aqueous solution is composed of cations and anions as simple ions, H2O as simple molecule and other hydrous salt compounds as complex molecules. The calculated mass action concentrations of structural units or ion couples in ternary and binary strong electrolyte aqueous solutions strictly follow the mass action law.

Finite element analyses of Wanjiazhai water transmission tunnel excavation and service

This paper is devoted to the nonlinear stress and strain analysis oftunneling and working conditions of Wanjiazhai Division Project No.7 Tunnel in Shanxi province ofChina. The initial geological stress of loess was simulated by grading fill; the theory of unloadingproposed by Duncan and boundary stress of elasticity were used to calculate the excavation of thetunnel; Goodman joint elements were applied to simulate the joints of the liners; both loading andunloading tests have been performed to determine the parameters of Duncan-Chang's model and thecalculated results were compared; Terzaghi' s theory on loosening earth pressure was applied. Manyworking conditions were analyzed and some reasonable results were obtained. Based on the analyses,reparative measures were proposed and completed. The tunnel has functioned well since October, 2001.

即热产水系统功率与流速物理关系及应用研究

泵给水电即热式热水连续生产技术应用前景广泛,出水速度快、水温和水量控制准确、高效节能是技术的核心,但水泵电机和电加热组件等不确定,使得技术推广实现多用途控制成为瓶颈。结合文献和科学原理开展研究,对典型技术应用系统的组成以及即热机理等进行了详细的分析,创新性提出了易于推广的通用策略并应用于技术模型进行实践研究。研究表明,该技术通略可使系统灵活调整选用调功式、调速式等节能方式,实现温量的准确控制。

Finite element analysis of the Taizhou Water Station Site

The Taizhou Water Station Site is an ancient masonry structure ruin built in the Southern Song Dynasty. The main structure was severely damaged. In order to understand its current structural properties and provide a scientific basis for protection design nonlinear finite element analysis and parameter analysis are carried out.The crack patterns deformations and stresses of the main structure under four load cases are analyzed by nonlinear finite element analysis and the effect of the backfill bulk density and modulus on the maximum principal tensile stress and maximum compressive stress are studied by parameter analysis.The results show that the most unfavorable condition for the foundation is the combination of weight＋backfill soil pressure＋additional load the most unfavorable load case to the main structure is weight ＋backfill soil pressure ＋water pressure＋additional heap load the maximum principal tensile stress of the main structure is very sensitive to the changes in the bulk density of the backfill soil.

Kinetics of thermal decomposition of lanthanum oxalate hydrate

Lanthanum oxalate hydrate La2（C2O4）3·10H2O,the precursor of La2O3 ultrafine powders,was prepared by impinging stream reactor method with PEG 20000 as surfactant.Thermal decomposition of La2（C2O4）3·10H2O from room temperature to 900 °C was investigated and intermediates and final solid products were characterized by FTIR and DSC-TG.Results show that the thermal decomposition process consists of five consecutive stage reactions.Flynn-Wall-Ozawa（FWO） and Kissinger-Akahira-Sunose（KAS） methods were implemented for the calculation of energy of activation（E）,and the results show that E depends on α,demonstrating that the decomposition reaction process of the lanthanum oxalate is of a complex kinetic mechanism.The most probable mechanistic function,G（α）=[1-（1＋α）1/3]2,and the kinetic parameters were obtained by multivariate non-linear regression analysis method.The average E-value that is compatible with the kinetic model is close to value which was obtained by FWO and KAS methods.The fitting curve matches the original TG curve very well.

WAVE TRANSFORMATION AND BREAKING OVER A RECTANGULAR STEP

An idealized numerical wave flume has been established by finite element method on the bases of Navier Stokes equations through prescribing the appropriate boundary conditions for the open boundary,incident boundary,free surface and solid boundary in this paper.The characteristics of waves propagating over a step have been investigated by this numerical model.The breaker wave height is determined depending on the kinetic criterion.The numerical model is verified by laboratory experiments,and the empirical formula for the damping of wave height due to breaking is also given by experiments.

论《水经注》对潧(溱)水之误注兼论《水经注》研究的几个问题

北魏郦道元所著《水经注》是记述我国1252条河流之水道源流以及相关自然景物与人文史迹的重要典籍。后代学者在对其进行辑补、校释时也发现或造成了一些错误。本文通过引证前辈学者研究成果并列举新的论据,揭明郦道元将春秋战国时郑国与韩国都城(遗址在今河南省新郑市区)东之溱水误注为黄水河;并进而阐述了对《水经注》再做深入研究与严谨校释之学术意义及实践价值,提出了当前应树立新的研究理念,协调学术力量,撰写《<水经注>简校》、《<水经注>新校》、《新水经》等代表现代学术水平新成果等具体建议。

3D topographic correction of the BSR heat flow and detection of focused fluid flow

The bottom-simulating reflector（BSR） is a seismic indicator of the bottom of a gas hydrate stability zone. Its depth can be used to calculate the seafloor surface heat flow. The calculated BSR heat flow variations include disturbances from two important factors：（1） seafloor topography, which focuses the heat flow over regions of concave topography and defocuses it over regions of convex topography, and（2） the focused warm fluid flow within the accretionary prism coming from depths deeper than BSR. The focused fluid flow can be detected if the contribution of the topography to the BSR heat flow is removed. However, the analytical equation cannot solve the topographic effect at complex seafloor regions. We prove that 3D finite element method can model the topographic effect on the regional background heat flow with high accuracy, which can then be used to correct the topographic effect and obtain the BSR heat flow under the condition of perfectly flat topography. By comparing the corrected BSR heat flow with the regional background heat flow, focused fluid flow regions can be detected that are originally too small and cannot be detected using present-day equipment. This method was successfully applied to the midslope region of northern Cascadia subducting margin. The results suggest that the Cucumber Ridge and its neighboring area are positive heat flow anomalies, about 10%–20% higher than the background heat flow after 3D topographic correction. Moreover, the seismic imaging associated the positive heat flow anomaly areas with seabed fracture–cavity systems. This suggests flow of warm gas-carrying fluids along these high-permeability pathways, which could result in higher gas hydrate concentrations.

Physico-chemical and elemental investigation of aqueous leaching of high sulfur coal and mine overburden from Ledo coalfield of Northeast India

Acid mine drainage （AMD） is one of the major problems in high sulfur coal mining areas generating acidic water. The acidic mine water generated contain hazardous elements in varying concentrations. The Northeastern Indian coalfield produces considerable amounts of AMD. The AMD and metal leaching from coal and mine over burden （OB） are the two important naturally occurring processes. In order to know the AMD potential, the aqueous leaching experiment of a few coal and OB samples from the Ledo colliery of the Northeastern coalfield, Mergherita （India）, at different time periods （1, 3, 5, and 8 h） and at different temperatures （25, 45, 65, and 90℃） were performed in the laboratory. The physico- chemical analysis of the aqueous leachates shows the pH, electrical conductivity （EC）, and total dissolved solid （TDS） in the range of 1.62-3.52, 106-2006 μs/cm, and 106-1003 ppm for the raw coal samples respectively. The OB samples produced pH, EC, and TDS in the range of 3.68-6.92, 48.6-480 μs/cm, and 69.5-240 ppm respectively. From the study, it was revealed that the concentrations of major （Si, A1, K, Na, Fe, Ca, Mg）, minor （Mn） and trace/hazardous elements （As, Ba, Cd, Co, Cr, Cu, Hg, Ni, Pb, Se, Zn） considerably change with leaching time as well as with leaching temperature. Out of these elements As, Cd, Hg, Pb, Cr, and Se are of greater environmental importance. Alteration of the physico-chemical structure of the coal and OB samples resulting from leaching was also studied by field emission scanning electron microscope- energy-dispersive X-ray spectroscopy method. The release of the potentially hazardous elements from the raw coal and OB during leaching time periods to the leachates was detected by inductively coupled plasma-atomic emission spectroscopy and ion-chromatographic analyses. The major minerals found in coal and OB are quartz （SiO2）, pyrite （FeS2）, hematite, marcasite, and kaolinite. The association of different functional groups in minerals and their mode of association were studied by Fourier-transform infrared spectroscopy and X-ray diffraction analytical techniques. The present laboratory study will be useful in relating the characteristics of aqueous leaching from coal and mine OB with the natural weathering condition at the coal mine area.

Preliminary Study on the Accumulation Characteristics of Mineral Elements in Potted Poa crymophila under Drought and Water Stress

[Objective] This study was conducted to explain the mechanism of the accumulation characteristics of mineral elements in alpine grassland plants. [Method] Cultivated alpine grassland plant, Poa crymophila, was treated with drought and wa- ter stress, and then the samples were collected and analyzed. [Result] Compared with the control group, under drought and water stress, multiple mineral elements tended to accumulate and increase, and there were significant differences in the contents of Cu, Mn, Ni and P （P〈0.05）. [Conclusion] Under drought and water stress, mineral elements in potted Poa crymophila tended to accumulate and in- crease, which is the adaption and response of Poa crymophila to drought and water stress, as well as the re-verification of the starvation effect hypothesis of mineral effects. The starvation effect of mineral elements is one of the endogenic forces for the accumulation and differentiation of mineral elements in grassland plants.

Botulinum toxin for chronic anal fissure after biliopancreatic diversion for morbid obesity

AIM: To study the effect of botulinum toxin in patients with chronic anal fissure after biliopancreatic diversion (BPD) for severe obesity. METHODS: Fifty-nine symptomatic adults with chronic anal fissure developed after BPD were enrolled in an open label study. The outcome was evaluated clinically and by comparing the pressure of the anal sphincters before and after treatment. All data were analyzed in univariate and multivariate analysis. RESULTS: Two months after treatment, 65.4% of the patients had a healing scar. Only one patient had mild incontinence to flatus that lasted 3 wk after treatment, but this disappeared spontaneously. In the multivariate analysis of the data, two registered months after the treatment, sex (P = 0.01), baseline resting anal pressure (P = 0.02) and resting anal pressure 2 mo after treatment (P < 0.0001) were significantly related to healing rate.CONCLUSION: Botulinum toxin, despite worse results than in non-obese individuals, appears the best alternative to surgery for this group of patients with a high risk of incontinence.

Recent developments in the use of single-atom catalysts for water splitting

Electrochemical water splitting is regarded as the most promising approach to produce hydrogen.However,the sluggish electrochemical reactions occurring at the anode and cathode,namely,the oxygen evolution reaction(OER)and the hydrogen evolution reaction(HER),respectively,consume a tremendous amount of energy,seriously hampering its wide application.Recently,single-atom catalysts(SACs)have been proposed to effectively enhance the kinetics of these two reactions.In this minireview,we focus on the recent progress in SACs for OER and HER applications.Three classes of SACs have been reviewed,i.e.,alloy-based SACs,carbon-based SACs and SACs supported on other compounds.Different factors affecting the activities of SACs are also highlighted,including the inherent element property,the coordination environment,the geometric structure and the loading amount of metal atoms.Finally,we summarize the current problems and directions for future development in SACs.

COMPARATIVE STUDIES ON NITROGEN BUDGETS OF CLOSED SHRIMP POLYCULTURE SYSTEMS

April to October, 1997 comparative studies on the nitrogen budgets of closed shrimp polyculture systems showed that, in all the studied polyculture systems, nitrogen from feeds and fertilizers were the main input items, which comprised 70.7%-83.9% of the total input nitrogen, 3.2%-7.4% of which was provided by nitrogen fixation. It was in monoculture enclosures (Y 4, Y 11 and Y 12) that the percentage reached the maximum value. The output nitrogen in harvested products comprised 10.8%-24.6% of total input nitrogen, and the highest percentage, 24.6%, was found in shrimp fish tagelus polyculture systems. In shrimp monoculture and shrimp fish polyculture systems, they were 19.1% and 21.9%, respectively. The nitrogen utilization efficiency was different and varied from 12.2% to 20.1%. The highest, 20.1%, was found in shrimp fish tagelus polyculture systems, and the average of 20.0% was found in shrimp tagelus polyculture systems. The lowest, 12.2%, was found in shrimp monoculture systems. All the nitrogen utilization efficiencies in shrimp fish systems or shrimp scallop systems seemed to be higher than that of the monoculture system, but they showed little statistical difference. The main outputs of nitrogen were found in sediment mud, and comprised 48.2%-60.8% of the total input, the lowest percentage was found in shrimp fish tagelus polyculture systems, and the highest percentage in shrimp scallop systems. During the experiment, nitrogen lost through denitrification and ammonia volatilization comprised 1.9%-6.2%, averaged 2.8%, of the total input, and the loss through seepage comprised 5.9%-8.9% of the total. The estimated nitrogen attached to the enclosure wall comprised 3.7%-13.3% of the total, and was highest in shrimp monoculture systems. Compared with the classic shrimp farming industry, the closed shrimp polyculture systems may improve the nitrogen utilization efficiency, and hence reduce the environmental impacts on coastal waters. The nitrogen discharging rates for all the studied polyculture systems ranged from 3.0% to 6.0% of total input nitrogen.

Spatial Variability of Micronutrients in Rice Grain and Paddy Soil

Consumption of rice is the main source of micronutrients to human in Asia. A paddy field with unknown anthro- pogenic contamination in Deqing County, Zhejiang Province, China was selected to characterize the spatial variability and distribution of micronutrients in rice grain and soil. A total of 96 paired soil and rice grain samples were collected at harvest. The micronutrients in the soil samples were extracted by diethylenetriamine pentaacetic acid （DTPA）. The mean micronutrient concentrations in rice grain were 3.85 μg Cu g^-1, 11.6 μg Fe g^-1, 39.7 μg Mn g^-1 and 26.0 μg Zn g^-1 The mean concentrations were 2.54μg g^-1 for DTPA-Cu, 133.5μg g^-1 for DTPA-Fe, 30.6μg g^-1 for DTPA-Mn, and 0.84μg g^-1 for DTPA-Zn. Semivariograms showed that measured micronutrients in rice grain were moderately dependent, with a range distance of about 110 m. The concentrations of the DTPA-extractable micronutrients all displayed strong spatial dependency, with a range distance of about 60 m. There was some resemblance of spatial structure between soil pH and the grain Cu, Fe, Mn, and Zn. By analogy, similar spatial variation was observed between soil organic matter （SOM） and DTPA-extractable table micronutrients in the soil. Kriging estimated maps of the attributes showed the spatial distributions of the variables in the field, which is beneficial for better understanding the spatial variation of micronutrients and for potentially refining agricultural management practices at a field scale.

Influence of array elements’ consistency on SNR of hydrophone array

The influence of array element’s consistency on the hydrophone array’s signal-to-noise ratio (SNR) is studied. The consistency of array elements means the outputs of all the array’s elements are the same, that is to say, the outputs have the same phase and amplitude when their inputs are the same. The relationship between the SNR and the correlation coefficient of signal and the relationship between the SNR and the correlation coefficient of noise are given. Hydrophone array’s gain with the output of elements’ inconsistent phase and amplitude is analyzed theoretically. When the signal is single-frequency, the gain expression of two-elements array is deduced. Then the gain is calculated when the phase difference is 10° and the amplitude difference is 3 dB. The theoretical analysis is verified through simulation. The simulation results show the variation rule of array’s SNR when the consistency changes: the array SNR gain is greatly affected by the consistency of the elements’ output and the gain decreases as the consistency decreases and the gain may be negative when the amplitude response becomes worse.

Light Fraction Carbon and Water-Stable Aggregates in Black Soils

The distribution of light fraction carbon （LF-C） in the various size classes of aggregates and its relationship to water- stable aggregates as well as the influence of cultivation on the organic components in virgin and cultivated black soils were studied by wet sieving and density separation methods. The total organic carbon （TOC） and LF-C were significantly higher （P≤ 0.05） in the virgin soils than in the cultivated soils. The LF-C in aggregates of different size classes varied from 0.9 to 2.5 g kg^-1 in the cultivated soils and from 2.5 to 7.1 g kg^-1 in the virgin soils, whereas the ratio of LF-C to TOC varied from 1.9% to 7.3% and from 5.0% to 12.2%, respectively. After being incubated under constant temperature and controlled humidity for three months, the contribution of LF-C to TOC sharply decreased to an amount （1.7%4.5%） close to the level in soils that had been cultivated for 20 to 25 years （1.3%-8.8%）. As a result, the larger water-stable macro-aggregates （especially 〉 1 mm） decreased sharply, indicating that the LF-C pool in virgin soils declined quickly after cultivation, which reduced the water stability of soil aggregates.

Thermodynamic Consistency Test for Binary Gas ＋ Water Equilibrium Data at Low and High Pressures

Phase equilibrium in binary gas + water mixtures over wide ranges of temperatures and pressures are modeled and tested for thermodynamic consistency. For modeling, the Peng-Robinson equation of state was used and the Wong-Sandler mixing rules were incorporated into the equation of state parameters. In the Wong-Sandler mixing rules the van Laar model for the excess Gibbs energy was applied. In addition, a reasonable and flexible method is applied to test the thermodynamic consistency of pressure-temperature-concentration(P-T-x) data of these binary mixtures.Modeling is found acceptable in all cases, meaning that deviations in correlating the pressure and the gas phase concentration are low. For all cases the thermodynamic consistency method gives a clear conclusion about consistency or inconsistency of a set of experimental P-T-x data.

FEM for Stability Analysis Against Overturning of Portal Water Injection Sheet Pile

Portal water injection sheet pile (PWISP), as a retaining wall, appeared in seashore engineering in 2000. Although there have been many systematic methods addressing the issue, there are very few focusing on the new structure because of the difficulties in defining the earth pressure between the two piles. A new method is proposed in this paper to obtain the earth pressure between the PWISPs. Stability analysis against overturning follows as a consequence. Using Finite Element Analysis (FEA) software ANSYS, both the nonlinear characteristics of the soil and those of the contact elements are taken into account to obtain the earth pressure distribution on the contact surface. Based on the results of the FEA, Rankin’s theory and the slip plane theory, the formula of the earth pressure on the inner surfaces between the piles is given. Assuming the PWISP as the analysis object and the earth pressure as an outside force acting upon it, the equation of stability against overturning of the PWISP is presented. Finally, some parameters are discussed about the stability of the PWISP against overturning, such as the embedded depth of the front pile, the distance between the two rows of piles, the internal friction angle and the cohesion of the earth. The results show that the increase of the cohesion and the internal friction angle will decrease the distance and the embedded depth, and therefore enhance the stability against overturning. Specifically, when the distance is 1/3-2/3 of the maximal excavation depth, the two rows of piles give the best performance in stability.