A genetic algorithm-based search space splitting pattern and its application in hydraulic and coastal engineering problems

This article reports a search space splitting pattern that can be applied to genetic algorithms in order to ensure that the entire search space is investigated. Hence, by keeping the genetic algorithm simple, in a reasonable time and with a high degree of accuracy, the initial solutions can be improved toward the global optimum point. The simplicity of the presented method is an advantage that makes it useful for applied hydraulic and coastal engineering problems. The performance of the proposed method was evaluated by a benchmark optimization problem, Levy No. 5, and three hydraulic and coastal engineering problems: inverse problem of Manning’s equation, the equation of equilibrium beach profiles, and the settling velocity equation of natural sediment particles. The results indicated that the nonlinear complex problems can be solved by the proposed method with a high degree of accuracy. The proposed genetic algorithm-based search space splitting pattern can either be used exclusively or alternatively it can be combined with improved operators in the literature.

     

Dielectric and Optical Properties of CdS–Polymer Nanocomposites Prepared by the Successive Ionic Layer Adsorption and Reaction (SILAR) Method

The successive ionic layer adsorption and reaction (SILAR) method has been used to grow epitaxial CdS–polymer nanostructures as thin films with different surface morphology and particle size. The main purpose of the study was to investigate the dielectric properties and a.c. electrical conductivity (σ _a.c.), by a.c. impedance spectroscopy between 1 kHz and 1 MHz, at room temperature, of CdS–polymer nanocomposites produced by use of 2, 6, and 10 cycles of SILAR. The surface morphology and optical absorption of the samples were characterized by scanning electron microscopy (SEM) and UV–visible spectroscopy, respectively. Determination of the energy gaps of CdS–polymer nanocomposites prepared by use of different numbers of cycles of SILAR reveals that the band gap decreases with increasing number of cycles (J. Cryst. Growth 305, 175–180, 2007). This behavior is because of the growth of nanoparticles in the matrix materials, and can be explained by changes in the amount of confinement as a consequence of particle size variation. SEM images also confirm that different numbers of cycles lead to different morphology. Frequency-dependent dielectric properties and a.c. electrical conductivity of the samples prepared by use of different numbers of cycles of SILAR were investigated, and comparative studies on some electrophysical properties of the samples are reported. Experimental results show that values of the dielectric constant (ε′), dielectric loss (ε″), dielectric loss tangent (tanδ), the real (M′) and imaginary (M″) parts of electric modulus, and σ _a.c. are highly dependent on the frequency and the number of cycles. It can be concluded that changing the frequency and the number of cycles substantially alters both the dielectric properties and a.c. electrical conductivity of the samples.     

A particle swarm optimization algorithm for the multiple-level warehouse layout design problem

Warehouse operation and management is one of the essential parts of manufacturing and service operations. The warehouse layout problem is a key to warehouse operations. Generally, warehouse layout design models attempt to optimize different objectives such as the orientation of storage racks, the allocation of space among competing uses, the number of cranes, the overall configuration of the facility, etc. The warehousing strategies can be classified as distribution-type, production-type and contract-type warehouse strategies. In this study, a distribution-type warehouse considered that various type products are collected from different suppliers for storing in the warehouse for a determined period and for delivery to different customers. The aim of the study is to design a multiple-level warehouse shelf configuration which minimizes the annual carrying costs. The turnover rates of the products are classified and they are considered while putting/picking them to/from shelves regarding the distances between the shelves and docks. Since proposed mathematical model was shown to be NP-hard, a particle swarm optimization algorithm (PSO) as a novel heuristic was developed for determining the optimal layout.     

Transport of a soft cargo on a nanoscale ratchet

Surface ratchets can guide droplet transport for microfluidic systems. Here, we demonstrated the actuation of microgels encapsulated in droplets using a unidirectional nanotextured surface, which moves droplets with low vibration amplitudes by a ratcheting mechanism. The nanofilm carries droplets along the ratchets with minimal drop shape deformation to move the encapsulated soft cargo, i.e., microscale hydrogels. The tilted nanorods of the nanofilm produce unidirectional wetting, thereby enabling droplet motion in a single direction. Maximum droplet translation speed on the nanofilm was determined to be 3.5 mm∕s, which offers a pathway towards high throughput microgel assembly applications to build complex constructs.     

Investigation of Effects of Nonlinear Static Analysis Procedures to Performance Evaluation on Low-Rise RC Buildings

The aim of the study is to compare and evaluate structural response demands obtained from nonlinear static analysis procedures (NSPs) which are displacement coefficient method (DCM) recommended in FEMA 356 and capacity spectrum method (CSM) recommended in ATC 40. For these reasons, three of three-dimensional low-rise RC buildings with different characteristics are investigated. In order to determine nonlinear behavior of the buildings under lateral loads, the base shear-roof displacement relationships (capacity curves) are obtained by pushover analysis including P-delta effects. Then by considering four different seismic hazard levels, building performances are determined by using the CSM and by using from DCM results determined in a previous study. In order to determine performance levels of the buildings, maximum beam and column plastic rotation demands and maximum story drift demands are determined in the related maximum displacement demands. Plastic strains in the equivalent diagonal struts, representing the nonstructural infill walls, are also determined, similarly. Comparing structural response quantities (such as plastic rotations, story drifts, etc.) obtained from the NSPs for considered low-rise RC buildings, effects of different NSPs in performance evaluations of the buildings are investigated comparatively, as well.     

Integrating data envelopment analysis and analytic hierarchy for the facility layout design in manufacturing systems

Facility layout design (FLD) has a very important effect on the performance of a manufacturing system. The concept of FLD is usually considered as a multiobjective problem. For this reason, a layout generation and its evaluation are often challenging and time consuming due to their inherent multiple objectives in nature and their data collection process. In addition, an effective facility layout evaluation procedure necessitates the consideration of qualitative criteria, e.g., flexibility in volume and variety and quality related to the product and production, as well as quantitative criteria such as material handling cost, adjacency score, shape ratio, and material handling vehicle utilization in the decision process. This paper presents a decision-making methodology based on data envelopment analysis (DEA), which uses both quantitative and qualitative criteria, for evaluating FLD. The criteria that are to be minimized are viewed as inputs whereas the criteria to be maximized are considered as outputs. A computer-aided layout-planning tool, VisFactory, is adopted to facilitate the layout alternative design process as well as to collect quantitative data by using exact and vague data by means of fuzzy set theory. Analytic hierarchy process (AHP) is then applied to collect qualitative data related to quality and flexibility. The DEA methodology is used to solve the layout design problem by simultaneously considering both the quantitative and qualitative data. The purposed integrated procedure is applied to a real data set of a case study, which consists of 19 FLDs provided of the plastic profile production system.     

Investigation of the effects of plasma arc parameters on the structure variation of AISI 304 and St 52 steels

In this study, AISI 304 stainless steel and St 52 carbon steel have been cut by plasma arc and the variations of structural specifications occurred after cutting has been investigated. According to the experimental results, it has been seen that burning of particulars and distribution amount were increased when the cutting was performed using the speeds which are upper or lower limits of the ideal cutting speeds proposed by the manufacturer of the machine tool. Moreover, it was determined that the hardness from the outer surface to the core decreased, while the hardness near to the outer surface which affected by the high temperature occurred during cutting increased.     

Mean shift spectral clustering

In recent years there has been a growing interest in clustering methods stemming from the spectral decomposition of the data affinity matrix, which are shown to present good results on a wide variety of situations. However, a complete theoretical understanding of these methods in terms of data distributions is not yet well understood. In this paper, we propose a spectral clustering based mode merging method for mean shift as a theoretically well-founded approach that enables a probabilistic interpretation of affinity based clustering through kernel density estimation. This connection also allows principled kernel optimization and enables the use of anisotropic variable-size kernels to match local data structures. We demonstrate the proposed algorithm's performance on image segmentation applications and compare its clustering results with the well-known Mean Shift and Normalized Cut algorithms.