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In the Yangtze River Economic Belt (YREB), the green economy is an essential to sustainable economic development. In this study, we calculated a comprehensive index of environmental pollution based on the global entropy weight method and used the super slacks-based measure (SBM) model to estimate the green economic efficiency (GEE) of provinces and cities in the YREB from 2005 to 2018. Subsequently, we explored temporal and spatial evolution characteristics combined with the Theil and Moran indexes, and adopted the spatial Dubin model to analyze its influencing factors. We divided the YREB into three watersheds to facilitate the analysis. The results show that the GEE in the YREB initially decreased and then increased, and the difference among the three major watersheds was higher than that within the watershed. We found a positive spatial autocorrelation in the development level of the green economy in the YREB. While industrial structure had a negative effect, economic development, scientific and technological level, and environmental regulation all had a positive effect on GEE. Finally, we offered policy recommendations to improve the level of green development in the YREB.

RGB-based methods have certain disadvantages because they lack 3D information and cannot cope with the pose estimation problem in cluttered scenes. Therefore, we propose a region-level pose estimation network that uses RGB-D images. We first extracted the objects’ color features and geometric features by convolutional neural networks (CNN) and PointNet, respectively, and then performed feature fusion. The fused features were fed into a region-level feature extraction network to obtain the region-level features, which extracted the local geometry features from the point cloud and learned the point set’s semantic information. We used the output of the region-level feature extraction network to perform region-level pose estimation, then selected the pose with the highest confidence level as the output and iteratively optimized the pose to obtain the final results. The experimental results showed that the proposed solution performed well on the LINEMOD data set, which verified the effectiveness of the proposed method in the pose estimation problem and the algorithm’s robustness in severely cluttered scenes.

To fully disclose potential configurations of parallel mechanisms (PMs) that are performance-comparable to the commercially successful Exechon, a family of one translational two rotational (1T2R) over-constrained Exechon inspired PMs is synthesized through the screw theory. The synthesized PMs are further comparatively analyzed in terms of inverse kinematics, singularity occurrence and reachable workspace based on a unified kinematic model. The kinematic analyses indicate that the inherited overconstraints benefit for eliminating the constraint singularity of all synthesized Exechon inspired PMs and the workspace distribution of an Exechon inspired PM is closely related to its topological arrangement. Based on the kinematic evaluations, a preferred configuration of 2U P R-1R P S PM (‘R’: revolute joint, ‘U’: universal joint, ‘S’: spherical joint, ‘ P ’: prismatic actuated joint) is selected as a candidate for 1T2R spindle head. A laboratory prototype is fabricated and experimentally tested to verify the feasibility of the type synthesis and the correctness of the kinematic analyses. By integrating the selected PM with a 2-degree of freedom sliding gantry, a full scale prototype of a novel hybrid kinematic machine tool is developed to perform 5-axis machining tasks. The well match between the machined workpiece and its designed shape fully proves the engineering potential of the synthesized PMs that are expected to be employed as the functional module to construct 5-axis serial-parallel hybrid machining devices.

Origami engineering as an interdisciplinary subject brings thriving progress of mechanisms innovation. In this paper, a construction approach from origami to multiple spherical-integrated mechanisms is proposed and subtly sets up the bridge between origami and Bennett linkage, Bricard linkage. Subsequently, the attention is drawn to a special origami-inspired integrated 8R kinematotropic metamorphic mechanism. The paper applies screw theory to illustrating the reconfigurability of singular configurations with distinct parametric constraints in the 8R mechanism. Two overconstrained linkages, a 4R linkage and a 6R linkage, are evolved under peculiar geometrical constraints respectively. Furthermore, the kaleidocycle and deployable properties of the 8R mechanism are revealed. The paper hence not only presents an interesting work extracted from origami but also sheds light on the promising investigation about the intersection of distinct types of reconfigurable mechanisms. Finally, by using the kinematotropic metamorphic 8R mechanism as the reconfigurable trunk, a novel quadruped robot is built and its characteristics will be investigated in future research.

This paper aims to investigate the effects of parameter uncertainties on kinetostatic behaviors of Exechon-like parallel kinematic machines (PKMs). A general interval kinetostatic model for Exechon-like PKMs is established by using Chebyshev inclusion function. The prediction accuracy and efficiency of the interval model are numerically verified. Based on the interval model, two indexes are formulated to quantify the effects of parameter uncertainties on kinetostatics of the PKM. The gravity-caused elastic displacements of the PKM are computed throughout its workspace when considering design parameters as interval variables. A sensitivity analysis is carried out to identify the most influential design variables when the PKM is under a condition of parameter uncertainties. Based on this, a cost-effective scheme of tolerance allocation is designed for the PKM in a convenient manner. The analyses reveal the interval kinetostatic response of the PKM is strongly position-dependent and nonlinear-related to multiple uncertain parameters. Hence, parameter uncertainties need to be fully considered during early design stage of such PKMs. The proposed interval model can be further applied to similar over-constrained parallel robots with minor modifications.

In this letter, we analyze the identity-based signature with conditional privacy-preserving authentication scheme (short for IBS-CPPA, published in Journal of Systems Architecture, doi: 10.1016/j.sysarc.2019.101692 ) and demonstrate that it cannot provide secure authentication between vehicles. Specifically, in IBS-CPPA, two types of adversaries can launch different attacks to forge a valid signature on any traffic-related message to impersonate a target vehicle, so as to invalidate the authentication between vehicles.

This paper focuses on instantaneous mobility analysis of parallel mechanisms using the twist space intersection approach. In this study, a nullspace-associated approach is first presented to determining the intersection of screw systems based on screw theory and linear algebra. The approach provides a way of investigating the motion-screw system of the platform for parallel mechanisms without constraint analysis. By investigating the order of the motion-screw system of a platform, this paper presents the instantaneous mobility of a 3-revolute-prismatic-spherical (3-RPS) parallel mechanism, that of a Bennett mechanism, that of a revolute-cylindrical-prismatic-prismatic (RCPP) mechanism and that of a 3-prismatic-universal-prismatic (3-PUP) parallel mechanism. This way of examining the mobility is equivalent to the way based on constraint analysis, presenting the validity of the presented approach and the correctness of instantaneous mobility analysis using the twist space intersection approach for parallel mechanisms and for overconstrained mechanisms.

The furcation point in a mechanism is a salient feature of reconfigurable mechanisms and change of a joint from an unconstrained condition to a geometrically constrained condition resulting in naturally link annexing with this geometrical constraint is a typical feature of metamorphic mechanisms. This paper presents a novel 6R metamorphic mechanism by inserting two revolute joints to a Bennett mechanism. From parameters of this novel 6R metamorphic mechanism, the source mechanism before changing is a special case of the Bricard 6R line-symmetric mechanism while the closure equation gives constraint conditions of joints. The geometrically constrained conditions result in variable motion branches of the mechanism. When all joints are unconstrained geometrically, two 6R motion branches can be obtained and when two joints are under geometric constrained, three 4R motion branches can be obtained. Further, three further motion branches with coaxial joints are obtained and motion branch transformation is illustrated with kinematic curves. For each of the motion branches, motion screws of this novel 6R metamorphic mechanism present corresponding geometry morphology and are analysed with screw algebra.

Improving environmental efficiency has been regarded as an objective requirement and an inevitable path to build a resource-saving and environment-friendly society in China. The slacks-based measurement (SBM) model with undesirable output is applied to measure the environmental efficiency of provinces in China from 1998 to 2009. Then, by the Tobit model, we can empirically test the impact of influencing factors on the environmental efficiency. It demonstrates the low value of the environmental efficiency of each province with an essentially descending trend on the whole and the distinct differences between the environmental efficiency of those provinces. Besides, GDP per capita dependent on foreign capital and trade, environmental awareness and population density have obviously positive impacts on environmental efficiency. And the proportion of the secondary industry in the GDP shows a significantly negative impact on the environmental efficiency.

The conceptual design of products is an important stage in the design process. However, how to reuse the existing and successful parts is always the key factor to the success of products in the process. To match the case parts rapidly and accurately, this paper puts forward the case-based reasoning (CBR) technology based on functional mode, which expresses accurately the functional structure through the generalized positioning of parts in products. Also, the scheme of variable-length hierarchical coding of functional mode is proposed, and the analytic hierarchy process (AHP) is adopted to determine matching function. Then, based on the hierarchy retrieval mode, the accurate matching of case parts is realized. The application of instance shows that the matching mode is feasible.

Foreign fibers in cotton have seriously effect on cotton production the quality of cotton products, while image processing algorithms based on machine vision offer an effective measure to deal with the problem. Wavelet is introduced to detecting foreign fibers in cotton as its great potential and excellent feature in signal and image processing. In this paper, the contaminants recognition process is divided into three steps, namely transformation of picture, image processing based on wavelet and image post-processing. On the first step, the format of color image is converted to index from RGB, which is the precondition of wavelet image analysis. A piecewise linear transform model is proposed to enhance the image. Secondly, the best tree analysis structure is calculated contrasting to the initial one. Through optimizing the entropy value, wavelet packet 2-D compresses off about 90% of the original coefficients by deleting the redundant information, while saving 99.13% energy. And image is reconstituted basis on the adjusted wavelet coefficients. In the last part, wiener adaptive filter is employed to smoothing the picture, and then we dichotomize the images after such series of treatments. The effect of the image processing indicated that wavelet packet is an effective method in the foreign fibers inspection combined with some other measures.

In view of the harm of cotton contaminants, the image processing method based on machine vision provides a good solution to eliminating the foreign fibers. After analyzing cotton contaminants characteristics adequately, this paper presents a practical recognition algorithm for cotton foreign fibers images. By converting the collected images from RGB to YCbCr space, gray image Y, blue color component Cb and red color component Cr are obtained, and green color component Cg is constructed. In doing so, it is helpful to distinguish gray information and color information effectively and helpful to use them respectively. For brightness images Y, the image sharpening algorithm based on neighborhood gradient is proposed after contrasting arctangent histogram and automatic histogram enhancement. The algorithm fully considers effects of gray variation level of pixel itself, neighborhood pixel gradient and the distance between neighboring point and the centre point. Iterative threshold segmentation is applied to binarize the image Cr, Cb, Cg and the gradient-sharpened image respectively. The optimum threshold obtained by iterative algorithm is free of the effect of noise. With the increase of iterations the evaluating gray value is tending to the true value. Performing fusion technology to the four binary images can fuse gray image and color image information together. In order to eliminate the noise points and false feature, this paper proposes the shape feature recognition method based on minimum area, the ratio between perimeter and area and objective center distance. Finally the fused image is conducted morphological processing. It is proved by experimental results that the algorithm is effective and credible.