Experimental Study on the Effect of Fine-Grained Soil Content on the Freezing Strength of Aeolian Sand-Cement Interface

In cold regions,understanding the freezing strength of the interface between soil and structure is crucial for designing frost-resistant foundations.To investigate how the content of cement powder in aeolian sand affects this strength,we conducted direct shear tests under various conditions such as different fine-grained soil content,normal stress,and initial moisture content of the soil.By analyzing parameters like soil properties,and volume of ice content,and using the Mohr-Coulomb strength theory to define interface strength,we aimed to indirectly measure the cementation strength of the interface.Our findings revealed that as the particle content increased,the interface stress-strain curves became noticeably stiffer.We also observed a positive linear relationship between freezing strength and silt content,while the initial moisture content of the soil did not significantly impact the strengthening effect of fine-grained soil on freezing strength.Moreover,we discovered that as the powder content increased,the force binding the ice to the interface decreased,while the friction angle at the interface increased.However,the cohesion force at the interface remained relatively unchanged.Overall,our analysis suggests that the increase in freezing strength due to fine-grained soil content is primarily due to the heightened friction between aeolian sand and the interface.

Burial depth interval of the shale brittle–ductile transition zone and its implications in shale gas exploration and production

Brittleness and ductility of shale are closely related to shale gas exploration and production. How to predict brittleness and ductility of shale is one of the key issues in the study of shale gas preservation and hydraulic fracturing treatments. The magnitude of shale brittleness was often determined by brittle mineral content(for example, quartz and feldspars) in shale gas exploration.However, the shale brittleness is also controlled by burial depth. Shale brittle/ductile properties such as brittle, semibrittle and ductile can mutually transform with burial depth variation. We established a work flow of determining the burial depth interval of brittle–ductile transition zone for a given shale. Two boundaries were employed to divide the burial depth interval of shale brittle/ductile properties. One is the bottom boundary of the brittle zone(BZ), and the other is the top boundary of the ductile zone(DZ). The brittle–ductile transition zone(BDTZ) is between them.The bottom boundary of BZ was determined by the overconsolidation ratio(OCR) threshold value combined with pre-consolidation stress which the shale experienced over geological time. The top boundary of DZ was determined based on the critical confining pressure of brittle–ductile transition. The OCR threshold value and the critical confining pressure were obtained from uniaxial strain andtriaxial compression tests. The BZ, DZ and BDTZ of the Lower Silurian Longmaxi shale in some representative shale gas exploration wells in eastern Sichuan and western Hubei areas were determined according to the above work flow. The results show that the BZ varies with the maximum burial depth and the DZ varies with the density of the overlying rocks except for the critical confining pressure.Moreover, the BDTZ determined by the above work flow is probably the best burial depth interval for marine shale gas exploration and production in Southern China. Shale located in the BDTZ is semi-brittle and is not prone to be severely naturally fractured but likely to respond well to hydraulic fracturing. The depth interval of BDTZ determined by our work flow could be a valuable parameter of shale gas estimation in geology and engineering.

Dynamic response of cylindrical lined cavity in elastic medium

An analytical solution to the transient dynamic response of a cylindrical lining subjected to an internal loading was presented and the dynamic interaction between the lining and surrounding soil was considered. The lining structure and the soil were treated as a cylindrical elastic shell and an infinite elastic compressible medium, respectively. A two-dimensional axisymmetric wave equation was derived from the governing equation of displacement by introducing the potential functions. Shell equation of motion was established based on continuity conditions. The closed-form solution for dynamic response of the lining due to an impact loading was obtained in Laplace transforms and inverse transforms. Detailed parametric studies were also presented to illustrate the influences of the Poisson ratio of soil, the dynamic shear moduli of both soil and lining and the thickness of lining on dynamic response of the lining.

Removal of a type of endocrine disruptors—di-n-butyl phthalate from water by ozonation

Ozonation of synthetic water containing a type of endocrine disruptor-di-n-butyl phthalate （DBP） was examined. Key impact factors such as pH, temperature, ionic strength, ozone dosage and initial DBP concentration were investigated. In addition, the activities of radicals on uncatalysed and catalysed ozonation were studied. The degradation intermediate products were followed and the kinetic of the ozonation were assessed as well. Results revealed that ozonation of DBP followed two mechanisms. Firstly, the reaction rate of direct ozonation was slower at lower pH, temperature, and ionic strength. Secondly, when these factors were increased for indirect radical reaction, higher percentage of DBP was removed with the increase of the initial ozone dosage and the decrease of the initial DBP concentration. In addition, tea-butanol, humic substances and Fe（Ⅱ） affected DBP ozonation through the radical pathway. It was determined that ozonation was restrained by adding tea-butanol for its radical inhibition effect. Furthermore, humic substances enhanced the reaction to some extent, but a slight negative effect would be encountered if the optimum dosage was exceeded. As a matter of fact, Mn（Ⅱ） affected the ozonation by ＂active sites＂ mechanism. In the experiment, three different kinds of intermediate products were produced during ozonation, but the amount of products for each one of them decreased as pH, temperature, ionic strength and initial ozone dosage increased. A kinetic equation of the reaction between ozone and DBP was obtained.

The Compatibility of Polycarboxylate-Type Superplasticizers with Cement

Four polycarboxylate- type （ PC ） superplasticizers of different functional groups were used ; their dispersing and retaining behaviors were analyzed through ZETA potential measurement, mini-slump test of cement paste and performance test of concrete. The experimental results show that the dispersing and flow-retaining ability of PC was determined by two factors of anionic groups and nonionic groups ： the density of anionic groups - COO^- or - SO3^- acted on the electronic repulsive force. and the length and proportion of nonionic graft groups of PEO in PC chemical stracture affected the steric effect. The compatibility between PC superplasticizers and cement mainly depended on the type of PEO groups ; furtlwrmore, adding mineral powders is good to the compatibility for high performance concretes （ HPCs ）.

Characteristics of Microbial Aerosol Pollution in Pig Houses

[ Objective] To explore the characteristics of microbial aerosol pollution in different pig houses and provide theoretical foundation for risk assessment of microbial aerosols on human and animal health. [Method] Gestation house, nursery house and fattening house in suburb of Beijing were chosen as research objects, and the concentration, size distribution and composition characteristics of the airborne microorganisms were determined. [ Result] The concentrations of airborne microorganisms were completely different in different houses under the influences of ventilation, methods of cleaning manure and pig populations. The highest concentration of airborne microrganisms was the nursery house. The particles with diameter size of 0.65 -2.10 μm carried 26% -27% heterotrophic bacteria and 39% -43% fungi. They could reach alveolus of humans and animals and thus made infectious threat to health of humans and animals. The dominant heterotrophic bacteria genera were composed of Bacil/us and Pseudomonas; and the dominant fungi were Penicillium and Muco. [ Conclusion] Concentrations of airborne microorganisms are completely different in different houses. However. there is no sianificant difference between the microbial composition and tyee of oia houses.

Excitation of Light-Induced Acoustic Waves in Doped Lithium Niobate Crystals

The phenomena of acoustic emission in doped lithium niobate crystals were observed in the process of light-induced quasi-breakdown. It is found that the ultrasonic waves introduce into the crystal have been modulated by the low frequency acoustic waves. Its frequency increases with the rise of the intensity of incident light and its jump period of breakdown is the same as that of the photovoltaic current Ic, the change of light-induced refractive index Δn and the diffracted light intensity L. This effect was explained with the interaction of the three waves and resonant state theory. The experimental results and the theoretical analysis are in conformity.

Performance of the Cement Matrix Composite Material With Rubber Powder

The effect of the deferent rubber content substituted for fine aggregate on the mortar performance was studied.The effects of the rubber coated with the coating materials on the mortar compressive strength,bending strength and impact work were discussed.The optimum rubber powder content and the suitable coating material were found.Through the electrical probe test-BEI,SEI and calcium ion distribution,and the slight crack and the interface between the rubber and cement matrix are analyzed.The results show that the rubber powder coated with the surface treatment materials A,B and C has the capability of absorbing a large amount of energy under the compressive and flexural load and the slight cracks of R-C were controlled and restrained.

Effect of Activator and Curing Mode on Fly Ash-based Geopolymers

The influences of concentration and modulus of sodium silicate solution and curing mode on the phase composition, microstructure and strength development in the geopolymers prepared using Class F fly ash were investigated. X-ray diffraction （XRD）, Fourier transform infrared spec-troscopy （FTIR） and MAS NMR were utilized. Results show that the compressive strength increases as sodium silicate solution modulus increases, but when modulus exceeds 1.4, the compressive strength decreases, and it decreases markedly while the modulus is greater than 2.0. The compressive strength was improved by the increase of sodium silicate solution concentration. When the concentration is 32%, the compressive strength reaches the maximum, then it reduces as concentration increasing. Elevated temperature can increase the strength of samples that synthesized from sodium silicate solution with 32% concentration and modulus 1.2. Compared to the strength of the sample cured at 50 ℃, the strength of the samples cured at 65 ℃ and 80 ℃ are higher at 1 d and 3 d, but the same at 7 d. At high temperature, prolonged curing time will decrease the strength. Long precuring at room temperature before application of heat is beneficial for strength development, and there is about 50% increase in strength of the samples cured at 1 d precuring and 2 d elevated temperature as compared to the strengths of the samples cured for 3 d at elevated temperatures or cured for 28 d at room temperature. The main product of reaction in the geopolymeric material is amorphous alkali aluminosilicate gel.

Dynamic Instability of Tunnel in Blocky Rock Mass

The displacements and geometry of the rock blocks and the properties of the rock struc-ture play an important role in the stability of tunnels.Based on the key block model,the dynamic instability analysis of underground tunnel subjected to intensive short-time compressional wave was conducted.The instability of the tunnel caused by the spallation and the inertial effect was distin-guished.And the influence of the roof contour curvature of tunnel was also determined.

Technology System of Low Energy Housing of Water Town in Southern Bank of Yangze River Based on SI System

Development of new vernacular dwelling of water town in the southern bank of the Yangze River is an important approach to improve rural appearance,infrastructure,quality of life,and to realize new urbanization of this area. How would this process to inherit the quintessence of traditional local-style dwelling as well as integrate with low energy consumption technology is also an important problem due to the valuable Chinese traditional architectural culture in this area. Taking SI system as breaking point,this paper analyzes the green ecological characteristics of traditional residence in the south of the lower reaches of the Yangze River,discusses the current residential technology of low energy consumption, and proposes the low energy consumption residential technology integration system in the south of the lower reaches of the Yangze River.Based on this,this paper takes the SDC 2013 entry "solark"as a practical application case study and further expounds the prospects of this technology system.

Study of optimal discharge pressure of compressor in CO_2 refrigerating trans-critical cycle

In this paper, a carbon dioxide trans-critical refrigerating system which is different from a conventional subcritical refrigerating cycle was studied. The trans-critical carbon dioxide refrigerating systems are based on the Gustav Lorntzen cycle. Emphasis was focused on how to determine the optimal discharge pressure of compressor in CO2 trans-critical cycle. The factors related with the optimal discharge pressure were analyzed. A formula was developed based on cycle simulation, which could be used to predict the optimal discharge pressure of a basic CO2 trans-critical cycle. After further studies on CO2 trans-critical cycles with a regenerator or expander, two more formulas were also developed. These formulas could provide an access to improve the COP of CO2 trans-critical cycle.

一种改进的BP算法在工程造价预测中的应用

针对在神经网络中得到广泛应用的BP算法难以确定隐节点个数的缺点 ,提出了一种动态调整隐节点数的改进的BP算法 ,以恰当确定隐节点数 在收集相似工程有关资料的基础上 ,考虑物价波动的影响 ,应用上述算法对工程造价进行预测 算例结果表明 :该方法所得的工程造价预测值精度令人满意 。

Adaptive Controller for Vehicle Active Suspension Generated Through LMS Filter Algorithms

The least means squares （LMS） adaptive filter algorithm was used in active suspension system. By adjusting the weight of adaptive filter, the minimum quadratic performance index was obtained. For two-degree-of-freedom vehicle suspension model, LMS adaptive controller was designed. The acceleration of the sprung mass,the dynamic tyre load between wheels and road,and the dynamic deflection between sprung mass and unsprung mass were determined as the evaluation targets of suspension performance. For LMS adaptive control suspension, compared with passive suspension, acceleration power spectral density of sprung mass acceleration under the road input model decreased 8-10 times in high frequency resonance band or low frequency resonance band. The simulation results show that LMS adaptive control is simple and remarkably effective. It further proves that the active control suspension system can improve both the riding comfort and handling safety in various operation conditions, and the method is fit for the active control of the suspension system.

ANALYSIS OF YIELD CONDITION FOR ENGINEERING MATERIALS

By analysing the geometric meaning of three stress components σm, τp, and S_2 in stress space and by comparing experimental results, an ideal yield condition suitable for various isotropic materials is obtained.

Membrane action in lateral restraint reinforced concrete slabs

Based on the assumption of additional three-hinge arching action,an analytical method was proposed to predict the additional load of lateral restraint reinforced concrete (RC) slab under compressive membrane action (CMA),and its ultimate load could be obtained by adding pure bending load. The experiment of twelve one-way RC slabs supported by shear-walls was carried out,and the calculations of this proposed method provide good predictions for the experimental evidences. The influence of some design parameters on bearing capacity was also investigated. It is shown that the effect of vertical load on ending shear-wall on the ultimate load capacity can be generally neglected when the bending restraint is satisfied. The additional load capacity also decreases with the increase of the span-to-height ratio of central slab. When reducing the reinforcement area,the additional load capacity is increased,and this method can be used to save steel or enhance the ultimate load capacity of low steel ratio slab.

Light-induced acoustic effect in LiNbO3：Fe：Ce crystals

The phenomena of acoustic emission in LiNbO3：Fe：Ce crystals have been observed in the process of light-induced quasi-breakdown. It is found that the ultra-high frequency acoustic signal introduced into the crystal is modulated by the low frequency acoustic waves. Its frequency increases with the increase of the intensity of incident light and its jump period of breakdown is the same as that of the photovoltaic current Ic, the change of light-induced refractive index △n and the diffracted light intensity L. This phenomenon has been analysed in this paper, which is caused by the inverse piezoelectric strain effect of the jump of space charge field during the quasi-breakdown.

Reinforcing a Dangerous Rock Mass Using the Flexible Network Method

Because the main failure type of a dangerous rock mass is collapse, the treatment of such a mass should focus on controlling collapse failure. When treating dangerous rock masses, disturbing the mass （e. g. by blasting） needs to be avoided, as this new damage could cause collapse. So the self-bearing capacity of the mountain mass must be used to treat the dangerous rock mass. This article is based on a practical example of the control of a dangerous rock mass at Banyan Mountain, Huangshi, Hubei Province. On the basis of an analysis of damage mechanism and the stability of the dangerous rock mass, a flexible network reinforcement method was designed to prevent the collapse of the rock mass. The deformations of section Ⅱ w of the dangerous rock mass before and after the flexible network reinforcement were calculated using the two-dimensional finite element method. The results show that the maximum deformation reduced by 55 % after the application of the flexible network reinforcement, from 45.99 to 20.75 ram, which demonstrates that the flexible network method is effective, and can provide some scientific basis for the treatment of dangerous rock masses.

An Experimental Study on Latent Heat Recovery of Exhaust Wet Flue Gas

The experiment was conducted to investigate the heat transfer performance of wet flue gas in a vertical tube. The factors influencing the convective condensation of wet flue gas were experimentally investigated. The measured results indicate that the convective heat transfer of bulk flow and condensation heat transfer of vapor have significant contribution to the total heat transfer and the dominant transport mechanism is dependent upon the vapor fraction in mixture.

Depressing defocusing effect in microscopy by bi-orthogonal wavelet transform

For different dimensions, heights and irregular shapes, small and large particles cannot be viewed simultaneously as sharp images under the microscope due to optical defocusing effects. Bi-orthogonal wavelet transform is used in this paper to depress such defocusing effect by merging the wavelet coefficients of the image series. The algorithm is presented in detail, using SWE（13,7） and CDF（2,2）, and a few particle images are provided to validate the proposed method.