Influential factors analysis on photoacoustic signal of photoacoustic spectroscopy monitoring trace gases

Photoacoustic spectroscopy (PAS) is a highly sensitive gas analyzing method without the shortcoming of gas consumption, which can be used in transformer oil trace gases dissolved in on line monitoring. The photoacoustic signal is detected with a microphone, which is the only feature in gas concentration analysis. A portable and tunable experimental setup has been developed based on the photoacoustic spectroscopy fundamental. Through the photoacoustic signal stimulate mechanism analysis, this paper thoroughly discusses the influences of gas pressure, temperature, laser power, gas concentration, background gas, chopped frequency and the resonant frequency drift on the gas photoacoustic signal. The theoretical and experimental results supply reference and technical support for further improvements in oil gas photoacoustic spectroscopy of on-line monitoring system.     

Estimation of Earth Work Volume and Design Elevation in Large Earth Work

In this paper,the approximation calculation method based on calculation model of earthwork formula of tetragonal prism is described. The optimization design elevation in large earthwork can be determined by this method. Through introducing a set of different design elevations, the difference between and sum of the total excavation and the total fill can be calculated. An economical analysis is carried out on the design elevation chosen with little value for both cases by numerical values comparison. The elevation with the lowest cost is taken as the optimal design elevation.     

An Unsteady Flow Analysis in Gas Transmission Pipeline Based on Theory of Functional Analysis

Branch -like pipeline is a common structure in gas transmission pipeline. In the light of the constituent properties of natural gas branch - like pipeline system, the system can be divided into fundamental constituent units. This paper presents a realistic unsteady flow model consisting of simple models of pipeline units and connecting conditions, boundary conditions and initial condition associated with units by using system analysis method. The solutions in wide sense are obtained by theory of functional analysis and operator series method, Such a method has the properties of both analytical solution and numerical solution methods. When the divided pipeline unit is larger, an intuitive approximate analytical solution may be obtained; while the one is smaller, a more accurate numerical solution may be acquired. Based on this, a general computer program has been developed for this model and solutions have been used successfully in a local natural gas transmission network in Sichuan. It is proved that the model and algorithm proposed in this paper are of the advantages of convenient calculation, high precision, time saving and wide application range by way of analysis and application.     

Error Analysis between Relative Motion Solving Method and Absolute Displacement Direct Solving Method

Under multi-support earthquake excitation, the damping is proportional to the relative velocity in relative motion method, While the damping is proportional to the absolute velocity in method of direct solving absolute displacement, and the damping assuming difference may cause the calculation errors on structural responses. The structural response errors of the dynamic component of power spectral density between the two solving methods are derived by random vibration theoretical analysis in Rayleigh damping model, which include damping ratio and the ratio between excitation frequency and fundamental frequency of the structures. Based on probability theory, the variation errors of dynamic component response between the two solving methods are also derived by theoretical analysis, and some numerical examples are provided to verify the error analysis. At last, it is pointed out that the calculation errors between the two solving methods decrease with damping ratio, and it is negligible when the damping ratio of structure is less than 5%.     

Simulation for Leaky Water Distribution System Caused by Earthquake

In order to analyze the hydraulic characteristics of the leaky water distribution system (WDS) caused by earthquake, the method to calculate the leakage flow of WDS in a possible earthquake was improved by introducing the formula suggested by Japan Water Works Association (JWWA) to calculate the failure probability of pipes in an earthquake, and the hydraulic model for leaky WDS caused by earthquake was established. A novel method of hydraulic calculation named “two-step iteration” was developed specially to simulate the WDS with deficient operating pressure, so as to realize the quantitative analysis of leakage flow, pressure and flow of WDS in different earthquake intensities. Finally, the proposed model and method were implemented to predict the performance of a sample networks in different earthquake intensities based on the EPANET software. The prediction results indicate that the proposed model can describe the hydraulic characteristics of damaged WDS in a possible earthquake reasonably; the presented method can avoid the iteration divergence and improve the rate of iteration convergence in the process of hydraulic calculation. Furthermore, the model can be solved by the existing calculation software directly.     

A panel model of isotope concentration-flow coupled field in groundwater systems

Several previous general lumped parameter model of radioisotope concentration field in groundwater systems, such as EM, PM and EPM model, are introduced, and the ambiguous physical meaning of response functions within these models are pointed out.And then, based on the radioactive decay principles and mass conservation principle, assuming that 1)the fluid system is in steady state, 2)infiltration rate is constant, and 3)the horizontal transport of water flow rate is constant, a general lumped parameter model of radioisotope concentration-fluid coupled field in groundwater systems is deduced under these conditions, that is, Panel model.Compared with the above mentioned models, this new model is built on a clear physical basis with a definite physical meaning of each parameter, so that it could make accurate interpretations on radioisotope data of the relevant water flow system, and provide more precise mathematical foundation on quantitative analysis and simulation of radioisotope concentration.     

Photoacoustic spectroscopy applied to the detection of SF6decomposition components under partial discharge

The traditional detection methods of SF6 decomposition components under partial discharge have some shortages,including consuming much detected gas,long detecting time,and unsuitable for on-line monitoring. While,photoacoustic spectroscopy has some advantages,including high sensitivity on detecting gas,and without consuming detected gas,etc. According to these reasons,the detection technology used in SF6 decomposition components under partial discharge is studied,and the feature spectrum of SO2,CO2 and CF4by SF6 decomposing is given. Through the photoacoustic spectroscopy device,the relation lines between photoacoustic spectroscopy(PAS) signal and concentration of gas components are obtained. The minimum detection limits of SO2,CO2 and CF4are about 3.8×10 -6,3.1×10 -6 and 4.7×10 -6 respectively. A method of RBF neural network is set up to reduce the crossover response of PAS signals of SO2,CO2 and CF4 mixed gas. It makes the average examination error of three gases reduce to 5.6%,1.6% and 3.3% respectively. Its reliability is checked by comparative testing of gas ehromatography and detector tube. The results indicate that the RBF neural network is useful in improving detection precision and provides a kind of technology to crossover response problem.     

Image-Based Soil Deformation Measurement in Geotechnical Model Test

Deformation measurement and analysis play an important role in geotechnical model tests. Using the concept of quadrilateral isoperimetric element, the strain filed was achieved from the calculation method based on displacement modes, and the verification results show that this measurement technique has a reliable precision. The soil deformation in model test of square shallow foundation was measured by using this technique, and the results show that the measurement system based on digital image correlation method can realize the whole process quantitative measurement of soil displacement field and shear strain filed. This deformation measurement technique provides a tool for the qualitative and quantitative analysis of soil micromechanics characteristics.     

Nonlinear Analysis of Indoor Radon Concentration

Radon is a natural radioactive noble gas that is naturally found in the ground. Exposure (excessive) to radon can pose a threat to the public health and get the public attention wordwide. Requiring the balanced mixing of radon and its daughters in indoor radon and outdoor air, a quantitative calculation model is deduced. The results showed that the indoor radon levels reach a steady value with the increases of ventilation radio and time, resulting in the balance for radon concentration indoor and outdoor air ultimately. Based on the model calculation, radon in door air has a theoretiacl value ranging between 6.35 and 40 Bq/m 3, which are in accordance with the actual measurements（6.0～50 Bq/m 3）by Tianshan Ren and Mei Wang, etc. The established quantitatively model for calculating the change of radon levels in indoor air could provide the technical support for indoor radon control and environmental assessment.     

A fast quantitative identification algorithm of colorimetric visual-sensor-array based on basic units matching

There are many difficulties to process a colorimetric visual-sensor-array by traditional processing methods, such as complicated manual analysis due to many data and hard to finish varieties and concentrations identification simultaneously, etc. In view of colorimetric-sensor-array’s same location response to the same gas, a fast quantitative identification algorithm of colorimetric visual-sensor-array based on basic units matching which can solve these problems is proposed. First, denoising and feature extraction are processed by setting experienced threshold to reduce redundancies and lessen manual analysis. Second, a creative qualitative analysis method based on basic units is put forward, which not only reduces computation, but also increases efficiency and precision. Finally, a ANFIS of NH3 concentration recognition utilizing advantages of fuzzy logic and neural network is used to distinguish low concentration NH3. The advantage of this algorithm is that varieties and concentrations of different gases could be detected successively, solving the problem of recognition errors caused by characteristic data infection when varieties and concentrations of different gases are detected simultaneously.The results of template matching based on basic units show that the classification accuracy of NH3, Cl2 and SO2 are 100%. The low concentration NH3 classification accuracy is also very high after species identification with measurement errors below 5%.     

Defects detection in the inner surface of pipes based on inverse heat conduction problem

It is a typical ill posed inverse heat conduction problem to estimate the geometry boundary of the inner surface of pipe by the temperature of outer surface. With the establishment of a two dimensional steady model for pipe with irregular inner surface, the inverse problem is transformed into a direct problem and an optimization problem. Based on the temperature at the outer surface obtained from the infrared thermography and the variation of the object function, the conjugate gradient method (CGM) is introduced into the geometry problem. With the numerical analysis of three typical defects, the effects of the measurement errors, choice of the initial value, boundary conditions and number of discrete temperature points are discussed and the proposed methodology is approved.     

Design calculation and finite element simulation analysis of stranded wire helical springs

The spatial structure of single wire is analyzed based on the forming process of stranded wire helical springs. Additionally,three parameters are derived from the existing foundation,including distribution circle radius of strand,spiral parameter of single wire and track scanning parameter. The aided design method of stranded wire helical springs based on feature scanning is put forward in which the centerline model of single wire can be obtained through one scanning step and the modeling method is given based on PROE code. The simulation analysis for spring in loading is performed by using ABAQUS code based on the calculation results. The finite element analysis results show the stress-strain ability of wire and the stress distribution of the section. The affects of loading rate on vibration of coils is also found.The results can make up for the deficiency of existing methods and give more beneficial assistance for production processing and performance test of the stranded wire helical springs.     

Analysis on the Feasibility of Desulfurization Wastewater Evaporation Treatment in Flue Gas Duct Without Pollution Discharge

A mathematical model of droplet motion and evaporation in flue gas has been established to analysis the feasibility of desulfurization wastewater evaporation treatment in flue gas duct. The parameters such as the duct structure, the flue gas temperature and the diameter liquid droplet are analyzed; the states of evaporation of liquid droplets are obtained under various working conditions. Moreover, a further comprehensive optimization and quantitative analysis have been carried out on unevaporated liquid quantity with various flue gas temperature and droplet diameters. The results show that this approach of evaporating desulfurization wastewater by flue gas in duct is feasible. The study provides support in further practical application for engineering.     

CALCULATION OF CONTACT PRESSURE UNDER FOUNDATION RESTING ON VISCO-ELASTOPLASTIC SUBGRADE

In this paper, the finite element method(FEM) is carried out for the contact pressure under circular foundation with visco-elastoplastic model and a 8 node finite element program determing parameter. In order to prove the reliability of the theoretical analysis, a circular rigid loading plate test on remolded clay is done. Otherwise, a comparison of the measuring contact pressure under box foundations of highrise buildings in Beijing and Shanghai with the calculated value by different method is made. The result shows the calculated value by the method proposed in this paper is more coincident with practical data.     

Section Optimization Design of Steel-Concrete Continuous Composite Beams Based on the Finite Element Method

This paper introduces the efficient computer aided design method to optimize the section of steel-concrete continuous composite beams by combining FEM for structure analysis with optimization arithmetic and an efficient shearing force link model of steel-concrete composite beams.The authors established a finite element analysis model,optimization parameter model,optimization mathematics model of steel-concrete continuous composite beams and programs analysis file and optimization control file by using the ANSYS parameter design language. The optimum of the steel-concrete continuous composite beams section is obtained after computing and the optimization result indicates that this method is efficient in optimizing the section of steel-concrete continuous composite beams.So it could be applied extensively in the steel-concrete continuous composite beams section optimization design.     

Establishment and analysis of dynamic mathematical model for coal gasifier

Based on the analysis of flowing combustion, gasification reaction, and lumped parameter, a three region model is established to predict the temperature and gas components of Texaco coal gasifier. Using mass balance and energy balance equations to each zone, the model takes account of gas solid two phase flow, coal pyrolysis, radiation heat transfer, and heterogeneous and homogeneous kinetic chemical reactions. Based on the model, a program is developed for dynamic and static simulation. After parameterization and simulation analysis, some important trends and conclusions are attained. Because the model can accurately predict the temperature and gas components in jet region, it has widespread engineering application value.     

Torsional Vibration Simulation Analysis of Drilling String and Rock Bit

In this paper,the method of establishing the torsional vibration model of drilling string and rock bit and the process of simulation analysis are introduced.The interaction between bit and rock and elastic deformation of drilling string in the process of petroleum drilling which caused the torsional vibration of the drilling string and rock bit is main considered in establishing the model.The torsional model is solved by difference method.Based on the models,the simulation analysis software of drilling string and rock bit is designed,and simulation calculation and analysis of the tortional vibration of drilling string and rock bit under different conditions are computed,and the dynamic behavior and kinetics regularity of drilling string and rock bit in drilling are obtained.     

Analysis on stress wave effect during the process ofrock breaking by pulsed jet

A mathematical model of rock breaking under pulsed jet is established by introducing the Johnson-Holmquist-Concrete constitutive relation and the smoothed particle hydrodynamics method. Based on this model, the formation, propagation and attenuation of stress wave during rock breaking by pulsed jet are simulated. The relations between pressure and time at different points on rock surface and the curve of peak stress wave versus distance to action spot are obtained. Destruction behaviors of rock under pulsed jet and effects on stress wave effect from jet velocity and lithology are studied according to the above calculation results, analysis results show that stress wave effect of pulsed jet acts locally and the peak stress wave shrinks sharply as the acting distance increases. The rock breaking mechanism of stress wave is tensile failure during the high speed process of load-unload. Power and effect range of stress wave is in high direct proportion with jet velocity. There is a threshold velocity before the macroscopic failure. Rocks of different lithologies have different destruction types under pulsed stress wave of pulsed jet. Destruction type of low strength rock like sandstone is crack propagation under the tensile stress during the high speed process of load-unload, while the destruction type of high strength brittle rocks like granite and limestone is vertical failure of stress concentration.     

Upper bound solution of reliability for slope based on limit analysis method

In order to reduce errors of reliability for slope in function establishment,parameter estimation and algorithm selection,a new reliability model for slope is established based on the upper-bound theory of limit analysis. The statistical characteristics o     

Nonlinear Forecast System for River Water Pollution Based on GIS

Based on the analysis of the water pollution spatial distribution characters of Yangtze River in Chongqing,a new method based on the integration of BP neural network and genetic arithmetic(GA) is proposed.For some shortcomings existed in the standard BP neural network,this method has ultimately overcome these shortcomings by combining the GA with BP artificial neural network through altering stimulating function,adding momentum factor to power value for BP algorithm and introducing genetic arithmetic to searching for the knots of the hidden layer,momentum factor and learning level.Using this method can easily overcome the difficulty of measuring the water prediction model's parameters.GIS is used as a tool for data management and spatial analysis,and the prediction result of the model for the water pollution spatial distribution characters of Yangtze River in Chongqing is visualized and explored with the precision of more than 78%.