A novel intelligent approach for yaw position forecasting in wind energy systems

Yaw control systems orientate the rotor of a wind turbine into the wind direction, optimize the wind power generated by wind turbines and alleviate the mechanical stresses on a wind turbine. Regarding the advantages of yaw control systems, a k-nearest neighbor classifier (k-NN) has been developed in order to forecast the yaw position parameter at 10-min intervals in this study. Air temperature, atmosphere pressure, wind direction, wind speed, rotor speed and wind power parameters are used in 2, 3, 4, 5 and 6-dimensional input spaces. The forecasting model using Manhattan distance metric for k = 3 uncovered the most accurate performance for atmosphere pressure, wind direction, wind speed and rotor speed inputs. However, the forecasting model using Euclidean distance metric for k = 1 brought out the most inconsistent results for atmosphere pressure and wind speed inputs. As a result of multi-tupled analyses, many feasible inferences were achieved for yaw position control systems. In addition, the yaw position forecasting model developed was compared with the persistence model and it surpassed the persistence model significantly in terms of the improvement percent.     

Fatigue in bamboo

This paper describes the results of an experimental programme to determine the fatigue behaviour of bamboo. Bamboo is subjected to cyclic loading, both in the plant itself and subsequently when the material is used in load-bearing applications in the construction industry. However, there is currently no data in the literature describing fatigue in this material. We found that sections of bamboo culm loaded parallel to the culm axis did not undergo fatigue failure: samples either failed on the first loading cycle, or not at all. By contrast, fatigue was readily apparent in samples loaded in compression across the diameter of the culm. The number of cycles to failure increased as the cyclic load range decreased in a manner similar to that found in many engineering materials: fatigue occurred at applied loads as small as 40% of the ultimate strength. Two different species of bamboo were tested and found to have different ultimate strengths but similar high-cycle fatigue strengths. Finite element analysis was used to help understand the progression of fatigue damage and the effect of stress concentration features. Some tentative design rules are proposed to define stress levels for the safe use of bamboo, taking fatigue into account.     

Strength and chemical resistance of mortars containing brick manufacturing clays subjected to different treatments

This paper presents the results of an investigation of the properties of mortar in which a calcined clay was employed as a pozzolan. Mortars were prepared using either heat treated clay or ground waste clay bricks (from the same clay subjected to 1000 °C calcining) as a pozzolanic partial replacement for cement at replacement levels of 10%, 20% and 30%. The compressive strengths of the mortars were monitored up to 90 days and the resistance to sodium sulphate solution and synthetic seawater was monitored up to 300 days. The specimens were also monitored for weight changes. Partially replacing cement by ground brick or heat-treated brick clay gives early strengths that are lower than that of the control. At 90 days, however, the strengths are the same as or are greater than that of the control. Heat-treated clay is effective in reducing expansion during exposure of the mortar to sulphate solution and synthetic seawater. The rapidly cooled clay gives better performance, in terms of strength development and resistance to harmful solutions, than the slow cooled clay.     

DO浓度对SUFR系统同步硝化反硝化的影响

采用螺旋升流式反应器（SUFR）处理生活污水，考察了好氧反应池中DO浓度对其同步硝化反硝化的影响。结果表明，在好氧反应池上部溶解氧浓度为3．0～3．5mg／L时，发生了明显的同步硝化反硝化现象，其对TN的去除量占SUFR系统对TN去除总量的16％左右；好氧反应池中的同步硝化反硝化反应只发生在池的下部，其中、上部只进行了好氧硝化反应；SUFR系统中好氧反应池上部的最佳溶解氧浓度范围为3．0～3．5mg／L，此时系统的硝化和反硝化效果最佳，好氧反应池中的脱氮效果也较好，系统对TN的去除率〉84％。     

A computational model for reinforced concrete members confined with fiber reinforced polymer lamina: Implementation and experimental validation

This study presents a computational model to simulate the behavior of confined concrete in column plastic hinge zones. The model describes the distribution of confining stresses within a circular column cross-section and the hysteretic behavior of concrete under passive confinement. Of particular interest is the ability of the model to predict the maximum circumferential strains and thus estimate the limit state of the confining medium rather than relying on empirical limits such as concrete compressive strain or drift ratio. This is performed with fiber-discretized beam column analysis without the computational expenses of a continuum finite element (FE) model. The confined section and material model are implemented in an object-oriented computational platform for structural analysis. New classes are developed and presented for a confined fiber section, a confined concrete material, and associated hysteretic behavior rules. Finally, the results from two experimental programs on columns strengthened using fiber reinforced polymer (FRP) lamina are reproduced using the developed computational model. Comparison of simulation and experiment shows that the computational model can closely match the observed response characteristics and can adequately predict the deformation level leading to FRP rupture.     

等离子体化学气相法沉积金刚石薄膜

本文介绍和评述了化学气相沉积法制备人造金刚石薄膜及其进展。重点评述了反应机理、发展历史、沉积方法、补底材料、检测手段。论述了有利于形成立方晶系金刚石材料的沉积条件。     

Application of deep learning algorithms in geotechnical engineering: a short critical review

Artificial Intelligence Review - With the advent of big data era, deep learning (DL) has become an essential research subject in the field of artificial intelligence (AI). DL algorithms are...     

弹性半无限空间中矩形孔收缩的复变函数解答

随着城市建设的发展,矩形隧道的应用越来越多,但针对矩形隧道的理论研究却鲜有见闻。针对矩形隧道,建立了半无限空间矩形隧道的弹性理论计算模型,采用最小二乘迭代方法确定共形映射函数的各项系数,并将计算区域映射为复平面上的一个同心圆环;运用Muskhelishvili复变函数方法,将计算区域内的应力函数展开成为Laurant级数的形式,给定了地表零应力边界和矩形孔口径向位移边界,求得了半无限空间矩形隧道在给定位移条件下的应力场和位移场。分析了不同高宽比、不同泊松比、不同埋深对位移场和应力场的影响,总结了矩形隧道位移场和应力场的一般规律。结果表明：高宽比偏小、泊松比偏大、埋深偏小都会使得沉降槽不再是类高斯曲线的形状,这些参数的变化也会在不同程度上影响应力场和位移场的大小和分布。     

Elastic-plastic analytical solution for centric crack loaded by two pairs of point shear forces in finite plate

1 Introduction A great number of cracks exist in metal materials. Their existence and interaction often lead to high stress concentration and become the source of weakening and failure of metal materials[1- 4]. The elastic-plastic analysis for a cracked p…     

Thermodynamic database of the phase diagrams in the Mg-Al-Zn-Y-Ce system

The Mg-Al-Zn-Y-Ce system is one of the key systems for designing high-strength Mg alloys. The purpose of the present article is to develop a thermodynamic database for the Mg-Al-Zn-Y-Ce multicomponent system to design Mg alloys using the calculation of phase diagrams （CALPHAD） method, where the Gibbs energies of solution phases such as liquid, fcc, bcc, and hcp phases were described by the subregular solution model, whereas those of all the compounds were described by the sublattice model. The thermodynamic parameters describing Gibbs energies of the different phases in this database were evaluated by fitting the experimental data for phase equilibria and thermodynamic properties. On the basis of this database, a lot of information concerning stable and metastable phase equilibria of isothermal and vertical sections, molar fractions of constituent phases, the liquidus projection, etc., can be predicted. This database is expected to play an important role in the design of Mg alloys.