Temperature stress of waste bunker in municipal solid waste incineration power generation plant

With large number of municipal solid waste incineration power generation plants appearing, serious environmental pollution will be caused if temperature cracks appear in waste bunkers. To reveal the interaction between the surrounding soil and bunker walls under the action of temperature, a finite element model is established. Considering the surrounding soil layer, the characteristics and influence laws of the interaction between the municipal solid waste bunker and the soil under different temperature conditions are studied. The simulation results show that the existence of the surrounding soil layer will affect the stress distribution, mainly at the bottom of the bunker and the surface of the bunker wall. Due to the thermal expansion and contraction, the municipal solid waste bunker is pressed during the heating process. In the process of cooling, there will be excessive tensile stress at the bottom of the bunker. To address this problem, expansion belt is arranged at the stress concentration portion to reduce the stress concentration. This measure proves to be effective according to analysis results, which provides a reference for the design of municipal solid waste bunkers

Model-based Reconstruction of Myocardial Perfusion SPECT and PET Images

Myocardial perfusion imaging is an important noninvasive tool in the diagnosis and prognosis of coronary artery disease, the leading cause of death in the United States. Electrocardiographically (ECG) gated acquisition allows combined evaluation of perfusion and left ventricular function within a single study. However, the accuracy of perfusion quantification and functional analysis is reduced by a number of image degrading factors. Particularly, partial volume effects (PVE) resulting from finite spatial resolution cause activity spillover between tissue classes and blur region boundaries. High-resolution anatomical images, such as contrast CT or MRI, can be used for partial volume compensation (PVC), but they are generally not available in clinical practice. The objective of this research is to develop and evaluate a model-based reconstruction method for emission computed tomography applied to myocardial perfusion imaging to improve perfusion quantification and functional assessment without the presence of anatomical images. The idea is to model the left ventricle (LV) using a geometry model and an activity distribution model instead of modeling them using voxels. The geometry model parameterizes the endocardial and epicardial surfaces using a set of rays originating from the long axis of LV. The rays sample the surfaces cylindrically in the basal and mid-ventricular regions and spherically in the apex. The surfaces are obtained by interpolating the corresponding intersection points with the rays using a cubic-spline function. The activity distribution model divides the myocardium into segments similar to those used in standardized myocardial quantitative analysis. The model assumes uniform activity concentrations in the segments as well as the blood pool and body background. The method estimates the parameters of the geometry and activity models instead of the intensities of all voxels, which greatly reduces the number of unknowns to be estimated. The goal of model-based reconstruction method was to estimate the parameters that give the best match between the image generated by the model and the measured data. The input image is contaminated by noise, so the metric for the goodness of fit was a statistical criterion based on the likelihood, i.e., the probability that the image resulted from the given set of model parameters. The image generated by the model includes the effects of resolution and other image degrading factors. A shape constraint was also incorporated into the objective function to regularize the ill-posed reconstruction problem and increase the robustness to perfusion defects and noise. The model parameters were optimized by seeking the maximum of the objective function using a group-wise alternating scheme along with dedicated initial parameter estimation. The hypothesis underlying the work is that resulting geometry parameters produce an accurate segmentation of the LV while the activity parameters are PVE compensated representations of the true activities in the segments. The proposed method integrates prior knowledge about the targeted object and the imaging system into one framework and allows simultaneous LV segmentation and PVC. In the evaluation with simulated myocardial perfusion SPECT images, it improved accuracy and precision in delineating the myocardium in comparison with typical segmentation methods. In addition, it recovered the myocardial activity more effectively compared to deconvolution-based PVC, which also does not require coregistered anatomical images to define regions of interest

Effect of temperature stress on main structure in waste incineration power generation plant

Waste incineration power station includes many functional structures, such as garbage discharge, storage, sorting and feeding units, boiler unit, tail gas treatment unit, leachate treatment unit, and coal storage unit. The structural forms of each part are different. Because of the particularity of garbage, structure units are required to be as close as possible and temperature joints should not be set up for the sake of possible leakage of exhaust gas or effluent liquor, so various structural units are integrated, which leads to the difficulty in structure design, and thermal stress cannot be neglected. In order to understand the effect temperature stress on main plant structures, a finite element model is established to study the distribution of thermal stress of the whole structure under three conditions: heating in summer, cooling in winter and heating in winter. It is found the influence of temperature on frame beam, column and steel space truss can be neglected, and the thermal stress on floor cannot be neglected [1]. The maximum stress is mainly distributed on both edges of floor along the longitude direction of structure. For those regions where stress concentration occurs, reinforcement bands or reinforcement mesh can be used to reduce the tensile stress. The analysis results show that this measure is effective and provides a reference for the design of the main structure of waste incineration power plant. This paper innovatively analyses the structure system of main workshop of refuse incineration power plant, which is composed of steel structure and concrete structure, and describes the skills and key points of complex system modeling. According to different seasons and heating temperature difference, the temperature stress on the surface of the structure is analyzed, which provides a reference for calculating degree stress and temperature difference of the similar structure system. The weak part of resistance to temperature stress in the structure system composed of concrete structure and steel structure is found out, and the corresponding solutions are put forward, which provides guidance for the construction of the main workshop of refuse incineration power station

Comparison on yield mechanism of strong column-weak beam of reinforced concrete frame structure

Ductility is an important aspect of the seismic performance of structures. Strong column and weak beam are important means to ensure the hinge plastic failure mechanism of frame structures. The corresponding provisions on failure mechanism of strong column-weak beam has been specified in design codes of various countries, but their differences are relatively large. This paper takes a plane frame as example which is designed according to the seismic code regulations of various countries, and then the difference in the failure mechanism of the designed frame under seismic actions is compared and analyzed. Finally, some suggestions are given to ensure the realization of strong column-weak beam mechanism

5-year monitoring of the dynamic properties of a 32-story SRC structure

The dynamic properties of the structure are related to many factors, such as mass distribution, component stiffness, material properties. In addition, environmental conditions may also affect the dynamic characteristics. In this paper, the modal identification of 133 strong earthquakes recorded in a 32-story SRC building structure in Tokyo from 2013 to 2018 is performed first, and then the dynamic characteristics (natural frequency, damping ratio) are obtained. The statistical regression analysis is used to analyze the influence of environmental conditions (temperature, humidity) on the dynamic characteristics of the high-rise SRC building structure, and the change trend of its dynamic characteristics. Finally, the results of the analysis are given to provide experience and basis for the design of similar building structures

Liquefaction identification based on instantaneous H/V spectrum ratio

The strong vibration record contains a lot of information on the site during the earthquake, and the dynamic characteristics of the soil layer in the site can be expressed through this information. Currently, the H/V spectral ratio recorded by acceleration is often used to study the seismic effect of the site. Inspired by this, the thesis puts forward the idea of using the instantaneous H/V spectral ratio and its corresponding instantaneous frequency to judge the site liquefaction. The time-varying VARMA model is used to represent the horizontal ground motion component as the output of a time-varying system with vertical ground motion component as input. According to the time-varying VARMA parameters, the instantaneous spectral ratio, instantaneous frequency of the system and instantaneous damping ratio are used to judge the site liquefaction

Mode-superposition response spectrum method for wind-induced vibration analysis of structures

The calculation process of time history analysis method is complicated and time-consuming which is not convenient for wide application and promotion in engineering design. Based on the idea of mode decomposition in structural seismic response analysis, the fluctuating wind response spectrum and the mode decomposition response spectrum method for wind-induced vibration analysis are derived in this paper. Taking a high-rise building structure as an example, this paper uses the method proposed in this paper, the time history analysis method and the method of my country's load code to compare the wind-induced vibration response analysis. The results show that the method proposed in this paper is simple, effective and convenient for engineering application

Computing the numerical scale of the linguistic term set for the 2-tuple fuzzy linguistic representation model

When using linguistic approaches to solve decision problems, we need the techniques for computing with words (CW). Together with the 2-tuple fuzzy linguistic representation models (i.e., the Herrera and Mart&acute;ınez model and the Wang and Hao model), some computational techniques for CW are also developed. In this paper, we define the concept of numerical scale and extend the 2-tuple fuzzy linguistic representation models under the numerical scale.We find that the key of computational techniquesbased on linguistic 2-tuples is to set suitable numerical scale withthe purpose of making transformations between linguistic 2-tuplesand numerical values. By defining the concept of the transitivecalibration matrix and its consistent index, this paper develops an optimization model to compute the numerical scale of the linguistic term set. The desired properties of the optimization model are also presented. Furthermore, we discuss how to construct the transitive calibration matrix for decision problems using linguistic preference relations and analyze the linkage between the consistent index of the transitive calibration matrix and one of the linguistic preference relations. The results in this paper are pretty helpful to complete the fuzzy 2-tuple representation models for CW.<br /