Dynamic Characteristics of Functionally Graded Timoshenko Beams by Improved Differential Quadrature Method

This study proposes an effective method to enhance the accuracy of the Differential Quadrature Method(DQM)for calculating the dynamic characteristics of functionally graded beams by improving the form of discrete node distribution.Firstly,based on the first-order shear deformation theory,the governing equation of free vibration of a functionally graded beam is transformed into the eigenvalue problem of ordinary differential equations with respect to beam axial displacement,transverse displacement,and cross-sectional rotation angle by considering the effects of shear deformation and rotational inertia of the beam cross-section.Then,ignoring the shear deformation of the beam section and only considering the effect of the rotational inertia of the section,the governing equation of the beam is transformed into the eigenvalue problem of ordinary differential equations with respect to beam transverse displacement.Based on the differential quadrature method theory,the eigenvalue problem of ordinary differential equations is transformed into the eigenvalue problem of standard generalized algebraic equations.Finally,the first several natural frequencies of the beam can be calculated.The feasibility and accuracy of the improved DQM are verified using the finite element method(FEM)and combined with the results of relevant literature.

Enhancing pose accuracy of space robot by improved differential evolution

Due to the intense vibration durirLg launching and rigorous orbital temperature environment, the kinematic parameters of space robot may be largely deviated from their nominal parameters. The disparity will cause the real pose （including position and orientation） of the end effector not to match the desired one, and further hinder the space robot from performing the scheduled mission. To improve pose accuracy of space robot, a new self-calibration method using the distance measurement provided by a laser-ranger fixed on the end-effector is proposed. A distance-measurement model of the space robot is built according to the distance from the starting point of the laser beam to the intersection point at the declining plane. Based on the model, the cost function about the pose error is derived. The kinematic calibration is transferred to a non-linear system optimization problem, which is solved by the improved differential evolution （DE） algoritlun. A six-degree of freedom （6-DOF） robot is used as a practical simulation example, and the simulation results show： 1） A significant improvement of pose accuracy of space robot can be obtained by distance measurement only; 2） Search efficiency is increased by improved DE; 3） More calibration configurations may make calibration results better.

Glypican 4 down-regulation in pluripotent stem cells as a potential strategy to improve differentiation and to impair tumorigenicity of cell transplants

Recent advances in stem cell technologies have opened new avenues for the treatment of a number of diseases still lacking effective therapeutic options.Cell transplantation has emerged as among the most promising clinical intervention for disorders such as injuries,diabetes,liver diseases, neurodegeneration and heart failure （Lee et al., 2013; Forbes and Rosenthal, 2014; Tabar and Studer, 2014）.

Cluster voltage control method for “Whole County” distributed photovoltaics based on improved differential evolution algorithm

China is vigorously promoting the “whole county promotion” of distributed photovoltaics (DPVs). However, the high penetration rate of DPVs has brought problems such as voltage violation and power quality degradation to the distribution network, seriously affecting the safety and reliability of the power system. The traditional centralized control method of the distribution network has the problem of low efficiency, which is not practical enough in engineering practice. To address the problems, this paper proposes a cluster voltage control method for distributed photovoltaic grid-connected distribution network. First, it partitions the distribution network into clusters, and different clusters exchange terminal voltage information through a “virtual slack bus.” Then, in each cluster, based on the control strategy of “reactive power compensation first, active power curtailment later,” it employs an improved differential evolution (IDE) algorithm based on Cauchy disturbance to control the voltage. Simulation results in two different distribution systems show that the proposed method not only greatly improves the operational efficiency of the algorithm but also effectively controls the voltage of the distribution network, and maximizes the consumption capacity of DPVs based on qualified voltage.

Exploring differentiated improvement strategies of cultivated land quality in China

Quality is the core feature of cultivated land. In the face of deteriorating cultivated land quality and growing food demand, improving cultivated land quality is a top priority for guaranteeing the sustainable use of resources and national food security. Cultivated land quality in the new era can be considered in four dimensions: suitability, contiguity, resistance and ecological stress. Cultivated land suitability in China shows a decreasing trend from east to west, cultivated land contiguity is high in the north-east and low in the south-west. In terms of cultivated land resistance, the number of strongly and weakly resistant cropping fields is small and spatially clustered. Cultivated land with ecological stress is mainly located in the northern region. Based on the current situation of cultivated land quality and the strategic needs of national high-quality development, China's future goals for improving cultivated land quality include four aspects: promoting the sustainable use of resources,improving the economic benefits of farming, coping with extreme meteorological disasters and meeting the transition of the food system.Against the backdrop of a volatile international environment and high domestic demand for food, China should guarantee a safe supply of staples, a stable supply of animal feed and a moderate supply of high-nutrient food. In the future, China should create three major food production spaces: highstandard, low-to medium-yield, and marginal cultivated land. China urgently needs to construct three paths to implement the goal of improving cultivated land quality, namely the development of high-standard cultivated land with the core of spatial optimization, resilience enhancement and scale coupling,the transformation of low-to medium-yield cultivated land with the core of obstacle elimination, tenure adjustment, ecological sustainable, and the conservation development of marginal cultivated land with a focus on sustainable use.

Multi-angle Face Detection Based on DP-Adaboost

Although important progresses have been already made in face detection,many false faces can be found in detection results and false detection rate is influenced by some factors,such as rotation and tilt of human face,complicated background,illumination,scale,cloak and hairstyle.This paper proposes a new method called DP-Adaboost algorithm to detect multi-angle human face and improve the correct detection rate.An improved Adaboost algorithm with the fusion of frontal face classifier and a profile face classifier is used to detect the multi-angle face.An improved horizontal differential projection algorithm is put forward to remove those non-face images among the preliminary detection results from the improved Adaboost algorithm.Experiment results show that compared with the classical Adaboost algorithm with a frontal face classifier,the textual DP-Adaboost algorithm can reduce false rate significantly and improve hit rate in multi-angle face detection.

Optimal Energy-Efficient Operation of a Metro Train on a Long and Steep Downhill Segment

Because the standard four-stage operation and con-trol strategy cannot fully utilize the gravitational potential energy of a train operating on a long and steep downhill segment,this paper further improves the method for train operation and control strategy.The improved operation includes three stages of acceleration,coasting-speed limit cruising,and brak-ing.Taking the speed limit,time limit,and distance limit as the constraints,the coasting condition switching point,braking condition switching point,traction coefficient,and braking force coefficient are used as the decision variables.Then,an improved train traction energy consumption model is constructed,and an improved differential evolution algorithm is designed to solve this model.The improved method is used to simulate two long and steep downhill segments of the Nanning metro.The results show that the improved method can meet the requirements of speed limit,time limit,and distance limit.Compared with the standard four-stage operation,the improved train operation and control strategy can reduce train energy consumption by more than 40%on the two long and steep downhill segments;compared with other similar algorithms,the improved algorithm is more suitable for solving the model.