Multiple asymmetric traveling salesmen problem with and without precedence constraints: Performance comparison of alternative formulations

In this paper, we investigate the performances of 32 formulations for the multiple asymmetric traveling salesman problem (mATSP) from the viewpoint of their tightness and solvability using commercial software. These formulations are either new or are generalizations of those proposed in the literature for the ATSP, including a transformation of the mATSP to an equivalent ATSP formulation. In particular, our results based on the latter strategy reveal that the superiority of the original mATSP formulation over an equivalent transformed ATSP model depends upon the type of formulation used for conducting such a transformation. We also extend our study to the case where precedence relationships exist among the cities. We address two situations in this context. In the first case, a sequential processing order is enforced between a pair of cities only if they both lie on the tour of a particular salesman. The second case involves a more general precedence in which a sequential processing order between certain pairs of cities is enforced regardless of whether the designated pairs are visited by the same or by different salesmen. Our computational experiments demonstrate that the flow-based models afford the tightest LP relaxations. Additionally, the formulations that model the different variants of the mATSP directly, rather than by transforming them to equivalent ATSP problems, are generally faster to solve and are more robust.     

热分级技术在高速BOPP膜料评价中的应用

海南炼化聚丙烯装置采用非对称外给电子体技术生产高速BOPP膜料。利用连续自成核热分级技术对3个样品进行等规度序列分布表征,结果表明3个样品的片晶厚度分布系数为1.07~1.08,样品的Ipeak1/Ipeak2值为1.36~1.58,说明采用非对称外给电子体技术生产的高速BOPP膜料具有较宽的等规度分布,且高等规度组分含量大于低等规度组分含量。与传统的BOPP膜料相比,采用非对称电子体技术生产的高速BOPP膜料不仅具有良好的成膜性,而且还具有较高的挺度。     

Mixed convective peristaltic flow of Eyring‐Prandtl fluid with chemical reaction and variable electrical conductivity in a tapered asymmetric channel

The influence of inconstant electrical conductivity and chemical reaction on the peristaltic motion of non‐Newtonian Eyring‐Prandtl fluid inside a tapered asymmetric channel is investigated. The system is concerned by a uniform external magnetic field. The heat and mass transfer are considered. The problem is controlled mathematically by a system of nonlinear partial differential equations which describe the velocity, temperature, and nanoparticle concentration of the fluid. By means of long wavelength and low Reynolds numbers, our system is simplified. It is explained by using the multi‐step differential transform method as a semi‐analytical technique. The distributions of velocity, temperature, nanoparticle concentration, as well as pressure gradient and pressure rise are obtained as a function of the physical parameters of the problem. The effects of these parameters on these distributions are deliberated numerically and illustrated graphically through a set of figures. The results indicate that the parameters play a significant role in controlling the velocity, temperature, nanoparticle concentration, pressure gradient, and pressure rise.     

The generalized Dice similarity measures for Pythagorean fuzzy multiple attribute group decision making

The Pythagorean fuzzy set (PFS) is characterized by two functions expressing the degree of membership and the degree of nonmembership, which square sum of them is equal or less than 1. It was proposed as a generalization of a fuzzy set to deal with indeterminate and inconsistent information. In this study, we shall present some novel Dice similarity measures of PFSs and the generalized Dice similarity measures of PFSs and indicates that the Dice similarity measures and asymmetric measures (projection measures) are the special cases of the generalized Dice similarity measures in some parameter values. Then, we propose the generalized Dice similarity measures-based multiple attribute group decision-making models with Pythagorean fuzzy information. Then, we apply the generalized Dice similarity measures between PFSs to multiple attribute group decision making. Finally, an illustrative example is given to demonstrate the efficiency of the similarity measures for selecting the desirable ERP system.     

Influence of the weight ratio of polydimethylsiloxane modified gelatin to silicone rubber on the potential performance of asymmetric bilayer membranes as wound dressings

Asymmetric bilayer membranes have been regarded as ideal wound dressings for skin regeneration. Our previous work reported the potential advantages of polydimethylsiloxane modified gelatin/silicone rubber (PGE/SR) asymmetric bilayer membrane as a wound dressing. However, it is still unknown whether the proportion of the two components of the bilayer membrane has a prominent influence on its relevant performance. Herein, various PGE/SR membranes with different PGE:SR weight ratios (100:25, 100:50 and 100:100) were fabricated through a self‐stratification method driven by surface tension gradients. Subsequently, the effects of the PGE:SR ratios on the relevant performance (i.e. porous structure, mechanical properties, degradability and biocompatibility) of PGE/SR membranes were systematically investigated. The current results demonstrate that the separating force between the PGE and SR components was reduced significantly on increasing the content of SR, and in particular the PGE/SR1 membrane (100:25) exhibited a well‐defined asymmetric bilayer structure with high porosity, appropriate toughness, water uptake, swelling ratio and water permeability. Concomitantly, the maximum weight loss for the PGE/SR1 membrane was ca 70.65% after 9 days of enzymatic degradation, which met the typical healing period of a normal skin wound. In addition, both the original and degraded PGE/SR1 membrane possessed favorable cytocompatibility in vitro, suggesting its potential application as a wound dressing. © 2019 Society of Chemical Industry     

Adaptive control for switched uncertain nonlinear systems with time‐varying output constraint and input saturation

This paper is concerned with adaptive tracking control for switched uncertain nonlinear systems, which contain the time‐varying output constraint (TVOC) and input asymmetric saturation characteristic. In response to the unknown functions, the fuzzy logic systems are adopted. The controller is constructed by the backstepping technique. Based on the Tangent Barrier Lyapunov Function (BLF‐Tan), an adaptive switched control scheme is designed. It is demonstrated that all signals in the resulted system are semiglobally uniformly ultimately bounded with TVOC under arbitrary switchings. Furthermore, the effectiveness of presented control method is validated via the simulation example.     

Significant Role of Al in Ternary Layered Double Hydroxides for Enhancing Electrochemical Performance of Flexible Asymmetric Supercapacitor

The Al effect on the electrochemical properties of layered double hydroxides (LDHs) is not properly probed, although it is demonstrated to notably promote the capacitive behavior of LDHs. Herein, ternary NiCo₂Al_x layered double hydroxides with varying levels of Al stoichiometry are purposely developed, grown directly on mechanically flexible and electrically conducting carbon cloth (CC@NiCo₂Al_x‐LDH). Al plays a significant role in determining the structure, morphology, and electrochemical behavior of NiCo₂Al_x‐LDHs. At an increasing level of Al in NiCo₂Al_x‐LDHs, there is a steady evolution from 1D nanowire to 2D nanosheets. The CC@NiCo₂Al‐LDH at an appropriate level of Al and with the nanowire–nanosheet mixed morphology exhibits both significantly enhanced electrochemical performance and excellent structural stability, with about a 2.3‐fold capacitance of NiCo₂‐OH. When applied as the anode in a flexible asymmetric supercapacitor (ASC), the CC@NiCo₂Al‐LDH gives rise to a remarkable energy density of 44 Wh kg^?1 at the power density of 462 W kg^?1, together with remarkable cyclic stability with 91.2% capacitance retention over 15 000 charge–discharge cycles. The present study demonstrates a new pathway to significantly improve the electrochemical performance and stability of transition metal LDHs, which are otherwise unstable in structure and poorly performing in both rate and cycling capability.     

微量Zr对不对称轧制Al-0.8Mg-0.9Si合金板织构及性能的影响

本文研究了微量Zr对不对称轧制Al-0.8Mg-0.9Si合金板及其相继固溶处理后的微观结构及性能的影响。结果表明：微量Zr在Al-0.8Mg-0.9Si合金中形成Al3Zr相弥散分布在基体中,在不对称轧制过程中,该化合物相对Copper{112}<111>、Brass{011}<211>、S{123}<634>、E{111}<110>和F{111}<112>等形变织构无明显影响；在随后的固溶处理过程中,轧制板材发生的再结晶使得Copper、Brass、S等形变织构的取向密度降低,但不溶的细小Al3Zr相在一定程度上抑制了不连续再结晶行为,反而使轧制过程中形成的E、F剪切织构的取向密度增加。添加微量Zr所形成的上述结构使该合金板材在固溶后获得较好的综合性能,其抗拉强度、屈强比和延伸率分别可达230MPa、0.49和9.5%以上；塑性应变比r值从0.7提高至0.84,杯突值IE由8.94提高至9.84,各向异性度|Δr|由0.15降低至0.04。     

A novel symmetric/asymmetric multilevel current source inverter topology with lower number of components and lowest power rating of switches

A novel multilevel current source inverter (MCSI) configuration is introduced in this paper. The ability of handling with asymmetrical DC sources is one of the substantial advantages of the proposed inverter. In asymmetric mode, by appropriate selection of DC sources magnitude, a considerable increase can be obtained in the number of output levels without any manipulation on inverters’ hardware. In MCSIs, the number of required circuit devices is very important because the overall costs, circuit size, reliability and control complexity are dependent on them directly. The proposed inverter can generate all desired current levels using a lower number of elements. Besides, it is known that reduction of number of switches from conventional inverters imposes an undesired increase in total semiconductor device power (SDP). But, the total SDP of the proposed inverter is kept equal to conventional inverter. To validate the superiority of the proposed inverter, a full comparison is provided. Also, the computer simulation and experimental results are presented.