Central Point Method Research Articles

Statistical machine learning model for capacitor planning considering uncertainties in photovoltaic power

New energy integration and flexible demand response make smart grid operation scenarios complex and changeable, which bring challenges to network planning. If every possible scenario is considered, the solution to the planning can become extremely time-consuming and difficult. This paper introduces statistical machine learning (SML) techniques to carry out multi-scenario based probabilistic power flow calculations and describes their application to the stochastic planning of distribution networks. The proposed SML includes linear regression, probability distribution, Markov chain, isoprobabilistic transformation, maximum likelihood estimator, stochastic response surface and center point method. Based on the above SML model, capricious weather, photovoltaic power generation, thermal load, power flow and uncertainty programming are simulated. Taking a 33-bus distribution system as an example, this paper compares the stochastic planning model based on SML with the traditional models published in the literature. The results verify that the proposed model greatly improves planning performance while meeting accuracy requirements. The case study also considers a realistic power distribution system operating under stressed conditions.

A Method for Calculating the Reliability of Welded Metal Bellows for Mechanical Seals

Welded metal bellows are an elastic element widely used in the field of mechanical seals. The main objective of the present study was to investigate the reliability of welded metal bellows in mechanical seals under specified working conditions. To this end, a stress relaxation test bench was built to obtain the residual elastic force data of welded metal bellows under different compression loads in high-temperature environments. Then, the elastic force loss equation of the bellows was fitted. Moreover, a failure judgment form of welded metal bellows in the mechanical seal is proposed. According to the calculation relationship between the seal face pressure and the welded metal bellows’ elastic force, the elasticity force loss range of the bellows was 556–708 N. Finally, according to the elastic force loss equation, elastic force loss was determined. The maintenance time of the welded metal bellows, and the bellow’s failure limit state equation were determined, and the limit state equation was substituted into the center point method. The reliability of the welded metal bellows was 0.9958. The results show that the new failure criterion and the center point reliability calculation method proposed in this paper have certain practical value for the rapid reliability prediction of welded metal bellows.

A New Stopping Sight Distance Model and Fuzzy Reliability Analysis Comparison

Aiming at the research on the stopping sight distance of the highway, on the basis of calculating the stopping sight distance in the current specification, the actual braking process of the car is divided into three stages: the driver’s reaction stage, the braking force rising stage and the continuous braking stage. The calculation model of the complete braking stage is analyzed by MATLAB, and then the calculation model of the stopping sight distance of the ESC system is proposed. Considering the ambiguity of the operating speed, the fuzzy reliability theory is introduced to establish the function of the fuzzy reliability of the stopping sight distance. Using the Gaussian fuzzy number and the center point method, the reliability index and failure probability of the stopping sight distance are obtained, and the safety of the stopping sight distance is evaluated. According to the "Uniform Standard for Reliability Design of Highway Engineering Structures", the traditional reliability calculation method and the fuzzy reliability calculation method are used to calculate the stopping sight distance value that meets the corresponding reliability index of the highway safety level. The calculated value of the system stopping sight distance model is used as a reference, and the reliability index and failure probability of the two reliability calculation methods are calculated. The calculation results show that: compared with the traditional reliability calculation method, the fuzzy reliability calculation method calculates the stopping sight distance value with higher reliability index, lower failure probability and higher calculation accuracy. Implementing the road design based on the stopping sight distance value calculated by the fuzzy reliability theory can improve the road safety.

Study on Structural Reliability of Prestressed Reinforced Concrete Beam Bridges Based on Full Probability Analysis

A three dimensional(3D) finite element model is established for a prestressed concrete girder bridge, list the limit state equation and variable probability distribution model, obtain the failure probability and reliability index of the limit state equation based on the Monte-Carlo method, investigate the reliability index’s sensitivity to random variables for limit state equations of bridge bearing capacity. The specific method of the research on the structure reliability index calculation is to select a suitable way that can fit the research’s object among the center point method, the checking-point method, the Monte-Carlo method, the importance sampling method, and so on. Authors use finite element software ANSYS to build model and perform 3D force analysis. According to the results, authors can determine the bridges’ failure modes under the state of 3D stress. Then, authors can list the possible limit state equations related to Stiffness, strength, function, durability, and some character else. After determining the bridge’s structural limit state equation and the probability distribution model of the variables, determine the distribution function of each impact factor and its characteristic parameters through the site survey data and other related data surveys. Then, use the Monte-Carlo method for the calculation of bridge reliability index, obtain the failure probability and reliability index of each limit state equation, analyze the sensitivity of each variable to the reliability index under the ultimate state of the bridge’s bearing capacity. At last, authors give construction quality control plans and suggestions according to the data above.

Design of a new low-cost unmanned aerial vehicle and vision-based concrete crack inspection method

With the explosive development of the computer vision technology, more and more vision-based inspection methods enabled by unmanned aerial vehicle technologies have been researched on the crack inspection of the sundry concrete structures. However, because of the limitation of the low-cost unmanned aerial vehicle hardware, whose cost is around US$500, most of the vision-based methods are difficult to be implemented on the low-cost unmanned aerial vehicle for real-time crack inspection. To address this challenge, in this article, a new computationally efficient vision-based crack inspection method is designed and successfully implemented on a low-cost unmanned aerial vehicle. Furthermore, to reduce the acquired data samples, a new algorithm entitled crack central point method is designed to extract the effective information from the pre-processed images. The proposed vision-based crack detection method includes the following three major components: (1) the image pre-processing algorithm, (2) crack central point method, and (3) the support vector machine model–based classifier. To demonstrate the effectiveness of the new inspection method, a concrete structure inspection experiment is implemented. The experimental results indicate that this new method is able to accurately and rapidly inspect the cracks of concrete structure in real time. This new vision-based crack inspection method shows great promise for the practical application.

Reliability analysis for stability of the gravity retaining wall under mountain torrent

The damage of roadbed retaining wall caused by mountain torrent is the most common disaster in geotechnical engineering. Based on the central point method, a reliability analysis model of the gravity retaining wall under mountain torrent load was established in this paper, and the performance functions of the anti-sliding and anti-overturning stability were derived. Finally, the reliability indexes of the anti-slip stability and overturning stability of the gravity retaining wall were obtained. We also analysed the sensitivity of stability reliability by changing the values of five variables which were the angle of mountain torrent load , internal friction angle , included angle between the retaining wall and the straight surface , friction angle , friction coefficient f. For the anti- sliding reliability, f, ϵ and ϕ have the greatest influences on the stability of the retaining wall. The increases of the other two variables have positive impacts on the anti-sliding stability. For the anti-overturning stability, the index coefficient increases with the increases of θ and ϵ, and decreases with the increase of ϕ until stability. The calculation method proposed in this paper considered the influence of mountain torrent, therefore it has a good practical application value in engineering.

Statistical characteristics of naturally aged PVDF-coated fabrics’ mechanical properties and structural reliability index

Membrane structures deteriorate with time. This results in reduction of their resistance, and consequently, of their reliability. Material aging is one of the main causes of structure deterioration. This paper investigates statistical characteristics of naturally aged polyvinylidene fluoride PVDF-coated fabrics' mechanical properties and calculates reliability indexes on the basis of Central Point Method and Rackwitz-Fiessler Method. Five groups of experimental fabrics were taken from different existing engineering structures or indoor warehouse in China, which have been naturally aged for more than 10 years. First, series of tearing tests, uniaxial and biaxial tensile tests were carried out to study the mechanical properties. Then, the uncertainties of material properties, material's dimension, computational model and load effects were discussed and the reliability indexes were studied by two methods according to the ultimate limit state. Finally, reliability indexes of aged PVDF-coated fabrics were compared with that of unaged coated fabrics. Results show that the impact of natural ageing on the properties of PVDF-coated fabric can not be ignored in reliability analysis and membrane structures design. These data offer a further understanding of aged PVDF-coated fabrics' mechanical properties and provide references for the durability analysis of tensioned membrane structures.

Reliability analysis of buried polyethylene pipeline subject to traffic loads

Due to the increasing number of vehicles in urban areas and the degradation of pavement performance, the failure rate of polyethylene pipeline, across roads, has increased rapidly. Based on relevant data, the traffic loads are regarded as a random variable; also its distribution is determined. First, the nonlinear contact interaction model was established, among traffic loads, soil and buried polyethylene pipeline, using finite element analysis software. Second, considering the decline of the pavement performance, the mechanical characteristics of buried gas pipeline suffering from different traffic loads were analyzed. Based on statistics of vehicle load, the distribution law of its maximum equivalent stress was determined by numerical simulation. Particularly, the strength distribution law of polyethylene pipeline was obtained through experiments. The reliability index of polyethylene pipeline was calculated using central point method and Monte Carlo method. Finally, based on the degradation curve of pavement performance, the remaining life of buried polyethylene pipeline was assessed.

Solving fully interval assignment problems

A new method namely, center point method is proposed to find an optimal interval assignment solution for fully interval assignment problems (FIAP). In the proposed method, the given FIAP is decomposed into a crisp assignment problem (AP) with the help of midpoint technique, solving it with the existing technique and by using its optimal solutions; an optimal interval assignment solution to the given FIAP is obtained. Comparison of intervals and partial ordering techniques were not used and there is no restriction on the elements of coefficient interval matrix in the proposed method. The proposed method is easier and also, simply because of the CA techniques. Using numerical examples the above method is illustrated.

An algorithm for accurate needle orientation.

For the early diagnosis and treatment, a needle insertion for biopsy and treatment is a common and important means. To solve the low accuracy and high probability of repeat surgery in traditional surgical procedures, a computer-assisted system is an effective solution. In such a system, how to acquire the accurate orientation of the surgical needle is one of the most important factors. This paper proposes a "Center Point Method" for needle axis extraction with high accuracy. The method makes full use of edge points from two sides of the needle in image and creates center points through which an accurate axis is extracted. Experiments show that the proposed method improves needle orientation accuracy by approximately 70% compared to related work in binocular stereovision system.

Statistical Characteristics of Ethylene Tetrafluoroethylene Foil’s Mechanical Properties and Its Partial Safety Factors

AbstractThis paper investigates the statistical characteristics of ethylene tetrafluoroethylene (ETFE) foils’ uniaxial and biaxial mechanical properties and suggests optimal partial safety factors of this material. Ten groups of uniaxial tensile tests and nine groups of biaxial tensile tests were performed. The test results indicated that two yield points of ETFE foils were more stable than the ultimate yield point, and then these two yield points were recommended as the reference points for single-layer pretensioned and cushion foil types. Moreover, a probabilistic limit state design method was adopted to calculate partial safety factors of ETFE foils. The statistical characteristics of an ETFE foil’s resistance and the partial safety factors of this material under three load effect combinations were determined. Reliability indexes were finally checked on the basis of the central point method and the Rackwitz–Fiessler method, whose results showed that the suggested partial safety factors could satisfy th...

Research on Categorization of Animation Effect Based on Data Mining

Nowadays, the production process of animation effect is increasingly developed, and its effect is also growing better. But in most cases, the categorization of special effect added to the animation is confusing due to excessive variations. Data mining will desirably solve the problem of animation effect categorization, so the application of data mining in the animation effect categorization becomes the hot spot in research and analy- sis at present. This article makes a detailed analysis on relevant algorithm of data mining technology, that is, the k application of averaging method, k central point method and relational degree algorithm in problem of animation effect categorization. It provides a clear method of categorization for animation effect. Thereafter, it also concludes the accuracy of animation effect categorization can be greatly improved through reasonable algo- rithm integration in the treatment of animation effect categorization by data mining.

Analysis of the Ground Surface Settlement of Metro Tunnel by Using Peck Formula

Based on the peck formula, this paper has analyzed measured data of ground surface subsidence, and get the regression curve of ground surface subsidence. Expression for degree of reliability of the maximum ground surface settlement is derived analytically by using central-point method. On the basis of a certain section of tunnel of Guangzhou subway constructed by mining excavation method, linear regression method can be effectively fitting the ground surface deformation data due to tunnel excavation. The central-point method provides a new way for reliability analysis of the ground surface settlement of shield construction.

The New Approximate Calculation Method for the First Order Reliability

One new method is presented for computing engineering structure reliability by accelerating convergence based on the analysis of errors in the center point method and borrowing ideas form the merits of the other First-Order Second Moment (FOSM) methods. The accelerating convergence method is based on the first class Chebyshev polynomials. Firstly, the transformation relation of the first class Chebyshev polynomials and the power polynomials is given and expanded to vector formula. Secondly, the outstanding function approximate character of the first class Chebyshev polynomials can supply the high order information for the choosing of approximately surface. An example shows that the method presented in this article has well precision. Although the accelerating convergence method needs choose the format of the structural function properly for get the high precision results, the method can serve as an effective for engineering estimate owing to non-iterative formula and convenience.

The New Approximate Calculation Method for the First Order Reliability

The new method is presented for computing engineering structure reliability by direct searching the next checking point and accelerating convergence based on the analysis of errors in the center point method and borrowing ideas form the merits of the other First-Order Second Moment (FOSM) methods. The idea of the direct searching method is constructing a new explicit searching formula to make the new checking point being more closed to the failure surface based on the results of the center point method. The new checking point has steepest descent character because the searching path is the gradient of the approximate surface. An example shows that the method presented in this article has well precision. Although the direct searching formula may not reach the globally optimal point, the error can be controlled owing to the locally optimal plan at each searching step.

MCDB Monte Carlo Code with Fast Track Technique and Mesh Tally Matrix for BNCT

The MCDB Monte Carlo Dosimetry Code for Brain Tumors has been developed for Boron Neutron Capture Therapy (BNCT). This code system includes a medical preprocessor, a Monte Carlo dose calculation and a postprocessor. The center point method is used to determine the material and density in each voxel. For dose calculations, a fast particle track technique is developed for the voxel model. This technique is valid for the single-voxel model as well as the multivoxel model. The material matrix and mesh tally matrix are designed for reducing the initialization and tally times. The same dose results as MCNP are achieved. MCDB is faster by a factor of 2:7~3:5 in computational speed with respect to MCNP. Furthermore, MCDB can do parallel computation. It meets the clinical requirements for precision and time.

MCDB Monte Carlo Code with Fast Track Technique and Mesh Tally Matrix for BNCT

The MCDB Monte Carlo Dosimetry Code for Brain Tumors has been developed for Boron Neutron Capture Therapy (BNCT). This code system includes a medical preprocessor, a Monte Carlo dose calculation and a postprocessor. The center point method is used to determine the material and density in each voxel. For dose calculations, a fast particle track technique is developed for the voxel model. This technique is valid for the single-voxel model as well as the multivoxel model. The material matrix and mesh tally matrix are designed for reducing the initialization and tally times. The same dose results as MCNP are achieved. MCDB is faster by a factor of 2:7~3:5 in computational speed with respect to MCNP. Furthermore, MCDB can do parallel computation. It meets the clinical requirements for precision and time.

Determination of the Locations of Ground Water Table Anomalies by the Ring and Central Point Method Study of Three Areas in Iraq

The groundwater table is observed in three areas in Iraq. Many wells are used to construct the ground water table maps in these areas. These maps are reflecting the irregularity in the water table. The observed values of groundwater table are converted to a regular grid of water table points, with different spacing interval from area to another. The regional groundwater table is calculated, using the ring and central point method, in each observation point. The residual (local) anomalies in the ground water table values for the grid points are obtained by the subtracting of the regional (average values) of ground water table from the observed values. The griding of water table and the calculations of regional and residual anomalies are done using QBASIC computer program build for this purpose. The regional ground water table and residual anomaly of groundwater table are mapped, the regional maps show the main water table level in the studied areas. The residual maps show many positive and negative anomalies of groundwater table. These maps reflect that the positive anomalies related to the leakage of water from the subsurface pipelines and drainage channels in the studied areas, while the negative anomaly related to the high pumping or discharge rate. This method can be used to determine the locations of leakage from pipelines and drainage channels

Direct integration of Stokes' Undulation and Vening Meinesz's Deflection Equations for geographically defined gravity anomaly blocks

We give here a direct solution of this problem by converting, in an indirect way, the relevant integral equations over each block to their equivalent line integrals taken along and around the boundary curves of the block. Results of sample computations given clearly demonstrate the convergence and stability of these line integrals. We also computed geoidal parameters due to a 30°×30° inner zone alone at 71 grid locations in Cameroon, using 1°×1° anomalies and integration steps of 30″ for the four innermost blocks and 180″ for the rest of the blocks and compared these with equivalent values from the midpoint method. This comparison yielded significant differences—rms ΔN = 2.2 m, ΔNmax = 4 m; rms Δξ = 2.9″, Δξmax = 10.5″; rms Δη = 2.0″, Δηmax = 6.7″—that reflect the poor accuracy of the center point method, especially for 1°×1° blocks near the computation point.