Handling boundary constraints for particle swarm optimization in high-dimensional search space

Despite the fact that the popular particle swarm optimizer (PSO) is currently being extensively applied to many real-world problems that often have high-dimensional and complex fitness landscapes, the effects of boundary constraints on PSO have not attracted adequate attention in the literature. However, in accordance with the theoretical analysis in [11], our numerical experiments show that particles tend to fly outside of the boundary in the first few iterations at a very high probability in high-dimensional search spaces. Consequently, the method used to handle boundary violations is critical to the performance of PSO. In this study, we reveal that the widely used random and absorbing bound-handling schemes may paralyze PSO for high-dimensional and complex problems. We also explore in detail the distinct mechanisms responsible for the failures of these two bound-handling schemes. Finally, we suggest that using high-dimensional and complex benchmark functions, such as the composition functions in [19], is a prerequisite to identifying the potential problems in applying PSO to many real-world applications because certain properties of standard benchmark functions make problems inexplicit.     

Two-dimensional spin coating with a vertical centrifugal force and the effect of artificial gravity on surface leveling

This study focuses on an innovative method for spin coating called the two-dimensional (2D) spin coating method. Using a centrifugal force applied by a rotary machine perpendicular to the wafer surface body, a vertical centrifuge force (VCF) was generated. The VCF allowed controllable artificial gravity acceleration to be generated and caused the coating to face this elevated gravity acceleration to adjust and normalize the high and low surface tension stresses. Previous surface leveling mathematics were analyzed and modified. The modified calculations indicate that the effect of additional gravity exerted on the liquid’s surface can reduce the amplitude of surface leveling. To experimentally investigate this phenomenon, a 2D spin coater was designed and manufactured. Higher artificial gravity overcame some common coating defects, such as cloudiness, edge beading, inner layer bubbling, and unsmooth surface leveling. Photoresist (AZP4620) was used as the coating material. The surface roughness was analyzed by atomic force microscopy (AFM) and the layer properties were also imaged by scanning electron microscopy (SEM). The AFM results (average and root-mean-square roughness) indicated a decrease in surface leveling amplitude by increasing the VCF. SEM images showed condensed layers without any porosity or rupture. The experimental results agreed with the simulations and calculated values.     

Application of self-collimated beams in realizing all-optical photonic crystal-based half-adder

In this paper an all-optical half-adder was proposed by using self-collimation effect in two-dimensional photonic crystals. Self-collimation effect was obtained in XM direction for wavelength 1500 nm by using square lattice rod-type photonic crystal structure. Plane wave expansion and finite-difference time-domain methods were used to obtain the band structure diagram and simulate the optical behavior of the proposed structure, respectively. The maximum delay time and required input intensity are 1 ps and 54 mW/μm², respectively. The normalized power-level margins for logics 0 and 1 were obtained to be about 20 and 70%, respectively. The total footprint of the structure is about 75 μm², which is suitable for all optical integrated circuits.     

All-optical 6- and 8-channel demultiplexers based on photonic crystal multilayer ring resonators in Si/C rods

In this paper, we employed multilayer ring resonators in a silicon rod base structure to realize 6-channel and 8-channel demultiplexers based on two-dimensional photonic crystals. Both the main rings and basic structures are composed of silicon rods, and the interior rings of the multilayer rings are composed of carbon. Employing silicon and carbon rods of different radii in multilayer ring resonators enhanced the coupling efficiency between the rings and waveguides. The average quality factor and power transmission efficiency were 4320 and 93%, respectively. Crosstalk values from \(-11\) to ?46 dB in conjunction with the mentioned characteristics suggest the use of the device for optical communication applications. The compact size of the proposed structure and the materials used make the proposed demultiplexer suitable for optical integrated circuits.     

Anti‐Oxygen Leaking LiCoO2

LiCoO₂ is a prime example of widely used cathodes that suffer from the structural/thermal instability issues that lead to the release of their lattice oxygen under nonequilibrium conditions and safety concerns in Li‐ion batteries. Here, it is shown that an atomically thin layer of reduced graphene oxide can suppress oxygen release from Li_xCoO₂ particles and improve their structural stability. Electrochemical cycling, differential electrochemical mass spectroscopy, differential scanning calorimetry, and in situ heating transmission electron microscopy are performed to characterize the effectiveness of the graphene‐coating on the abusive tolerance of Li_xCoO₂. Electrochemical cycling mass spectroscopy results suggest that oxygen release is hindered at high cutoff voltage cycling when the cathode is coated with reduced graphene oxide. Thermal analysis, in situ heating transmission electron microscopy, and electron energy loss spectroscopy results show that the reduction of Co species from the graphene‐coated samples is delayed when compared with bare cathodes. Finally, density functional theory and ab initio molecular dynamics calculations show that the rGO layers could suppress O₂ formation more effectively due to the strong C? O_cathode bond formation at the interface of rGO/LCO where low coordination oxygens exist. This investigation uncovers a reliable approach for hindering the oxygen release reaction and improving the thermal stability of battery cathodes.     

Synergistic Effect of Graphene Oxide for Impeding the Dendritic Plating of Li

Dendritic growth of lithium (Li) has severely impeded the practical application of Li‐metal batteries. Herein, a 3D conformal graphene oxide nanosheet (GOn) coating, confined into the woven structure of a glass fiber separator, is reported, which permits facile transport of Li‐ions thought its structure, meanwhile regulating the Li deposition. Electrochemical measurements illustrate a remarkably enhanced cycle life and stability of the Li‐metal anode, which is explained by various microscopy and modeling results. Utilizing scanning electron microscopy, focused ion beam, and optical imaging, the formation of an uniform Li film on the electrode surface in the case of GO‐modified samples is revealed. Ab initio molecular dynamics (AIMD) simulations suggest that Li‐ions initially get adsorbed to the lithiophilic GOn and then diffuse through defect sites. This delayed Li transfer eliminates the “tip effect” leading to a more homogeneous Li nucleation. Meanwhile, C? C bonds rupture observed in the GO during AIMD simulations creates more pathways for faster Li‐ions transport. In addition, phase‐field modeling demonstrates that mechanically rigid GOn coating with proper defect size (smaller than 25 nm) can physically block the anisotropic growth of Li. This new understanding is a significant step toward the employment of 2D materials for regulating the Li deposition.     

Theory of micropolar gyroelastic continua

This paper is devoted to the dynamic modeling of micropolar gyroelastic continua and explores some of the modeling and analysis issues related to them. It can be considered as an extension of the previous studies on equivalent continuum modeling of truss structures with or without angular momentum devices. Assuming unrestricted or large attitude changes for the axes of the gyros and utilizing the micropolar theory of elasticity, the energy expressions and equations of motion for undamped micropolar gyroelastic continua are derived. Whereas the micropolar gyroelastic continuum model with extra coefficients and degrees of freedom is primarily developed to account for the asymmetric stress–strain analysis in the gyroelastic continua, it also proves to be beneficial for a more comprehensive representation of the actual gyroelastic structure. The dynamic equations of the general gyroelastic continua are reduced to the case of one-dimensional gyroelastic beams. Simplified micropolar beam torsion and bending theories are used to derive the governing dynamic equations of micropolar gyroelastic beams from Hamilton’s principle. A finite element model corresponding to the micropolar gyrobeams is built in MATLAB\({^{\circledR}}\) and is used in numerical examples to study the spectral and modal behavior of simply supported micropolar gyroelastic beams.     

Design of highly efficient polarization beam splitter based on self-collimation on Si platform

A highly efficient polarization beam splitter based on self-collimation phenomenon in 2D square array of air holes in Si background is presented. For the presented structural parameters, a broad bandwidth of Δω/ω_c = 1.3% for the incidence angle of |θ_in| < 80° is obtained. Here, a maximum deviation angle of |θ_p|_max < 5° from ideal self-collimation is considered. The extinction ratios for TE and TM polarizations exceed 70 and 12 dB, respectively, in the whole frequency range through applying optimized anti-reflections at input and output ports. Structural simplicity and its compatibility with existing fabrication technologies along with the flexibility of the design to match for desired central frequency in IR range using scalability rule of Maxwell equations are outstanding features of the design.     

A structural approach to assessing postponement strategies: construct development and validation

This paper endeavours to introduce and validate constructs and measured variables for postponement strategies. Although empirical researchers have examined postponement, a consistent set of valid, reliable factors has not been developed and used. The lack of valid constructs is a barrier to hypothesis testing and meta-analysis on postponement. Using confirmatory factor analysis (CFA), the validity and reliability of the proposed postponement constructs are examined. This is performed through a pilot study and a large scale survey on a sample of 219 manufacturing firms which represent a wide range of manufacturing operations. The outcomes of this paper establish a set of variables which can measure shipment, manufacturing, purchasing and design postponements.     

A new DEA method for supplier selection in presence of both cardinal and ordinal data

The success of a supply chain is highly dependent on selection of best suppliers. These decisions are an important component of production and logistics management for many firms. Little attention is given in the literature to the simultaneous consideration of cardinal and ordinal data in supplier selection process. This paper proposes a new integrated data envelopment analysis (DEA) model which is able to identify most efficient supplier in presence of both cardinal and ordinal data. Then, utilizing this model, an innovative method for prioritizing suppliers by considering multiple criteria is proposed. As an advantage, our method identifies best supplier by solving only one mixed integer linear programming (MILP). Applicability of proposed method is indicated by using data set includes specifications of 18 suppliers.