Dimensionality reduction for predicting CO conversion in water gas shift reaction over Pt-based catalysts using support vector regression models

Removal of CO in fuel cell applications is an important issue. In this study, models based on support vector regression (SVR) along with several dimensionality reduction methods are utilized for predicting the CO conversion in water–gas shift (WGS) reaction. SVR model parameters are determined with a two-stage grid search method and for dimensionality reduction, principal component analysis (PCA), backward feature elimination (BFE) and simulated annealing (SA) methods are used. PCA reduces the dimension by mapping the input data to a lower dimensional feature space. On the other hand, BFE and SA methods finds a subset of features leading to a higher prediction performance. Influence of these methods on prediction performance is investigated by testing the SVR models with and without reducing the dimension. It is observed that all of these methods reduce the prediction error when an appropriate threshold for final number of features is set. Moreover, identical feature subsets are output by BFE and SA methods. In conclusion, it has been shown that some of the features for CO conversion in WGS reaction are more important and using only these features may improve the prediction performance.     

Investigation of blast-induced ground vibrations in the Tülü boron open pit mine

Blasting, which is widely used in hard rock mining, construction, and quarrying, can have a considerable impact on the surrounding environment. The intensity of the blast-induced ground vibration is affected by parameters such as the physical and mechanical properties of the rock mass, characteristics of the explosive, and the blasting design. The rock characteristics can change greatly from field to field or from one part of a bench to another part, and can have directional variability according to discontinuities in the geological formation and structure. In this study, field measurements were carried out and their results were evaluated to determine blast-induced ground vibrations at the Eti Mine Tülü Boron Mining Facility, Turkey. Our results showed different field constants for the propagating blast vibrations depending on the direction of propagation (K = 211.25–3,671.13 and β = 1.04–1.90) and the damping behavior of the particle velocity. Additionally, we found that the field constants decrease as the rock mass rating (%) values diminishes. A much higher correlation coefficient (R ² = 0. 95) between the predicted and measured peak particle velocity (PPV) values was achieved for our modeling studies for PPV prediction using artificial neural networks compared with classical evaluation methods.     

Supplier selection and purchase problem for multi-echelon defective supply chain system with stochastic demand

In the real production process, some members in the supply chain system sometimes cannot effectively complete their production task because of defects involving the production or purchasing of components. A supply chain system that has defects in at least one echelon is called a multi-echelon defective supply chain (MDSC) system. Most supply chain systems are MDSC systems. Determining parts or components supply quota from different suppliers with limited suppliers, factories and distribution centers capacities in the supply chain system are becoming an important issue for businesses. In this study, we propose a new heuristic (H2) which is an extension of H1 heuristic that was previously presented. The MDSC system was formed with the mixed integer linear programming by LINDO software for calculation of the lower bound. The heuristics and MDSC system were modeled by using ProModel software. The heuristics were applied to a case from the Turkish furniture industry. The heuristics were compared with each other by considering different coefficients of variation, service levels, and deviation from lower bound. Simulation experiments showed that the proposed H2 heuristic outperformed the H1 heuristic.     

Preparation of thin film alloys with electrodeposition from heterotrinuclear M1–M2–M1 complexes (M1: NiII, CuII; M2: CuII, CoII, ZnII, CdII)

M₁ ^II–M₂ ^II–M₁ ^II type linear complexes (where M₁ = Ni²⁺, Cu²⁺ and M₂ = Cu²⁺, Zn²⁺, Co²⁺ and Cd²⁺ were prepared and dissolved in dimethyl sulfoxide. They were then electrodeposited on mild steel surfaces by the use of rotating disc electrodes. The deposition potentials were determined from cyclic voltammetric i-E scans. The metal films deposited on mild steel surfaces were characterized with atomic absorption spectrometer (AAS), X-ray fluorescence (XRF) and ion chromatography (IC) methods. Although the stoichiometric quantity of M₂ metal cation was half of the M₁ metal cation in the complex, the amount of M₂ metal deposited upon the surface was markedly greater. The amount of M₂ ion deposited on the surface was found to increase with the hardness of the ion. The X-ray diffraction (XRD) patterns showed that the excessively deposited metal on the surface was in metallic form as well as alloy. The size of the deposited film particles was investigated by the use of atomic force microscope (AFM) technique and the particles were observed to be bigger than nanoparticle size.     

Development and Cyclic Behavior of U-Shaped Steel Dampers with Perforated and Nonparallel Arm Configurations

Metallic dampers are sacrificial devices (fuses) that dissipate significant energy during earthquakes while protecting other parts of structures from possible damage. In addition to numerous implementation opportunities of other base isolation systems, U-shaped dampers (UD) are one of the widely investigated and used devices in practice especially in Japan. The present study focuses on enhancing seismic performance of these types of dampers by changing their geometric properties. UDs with perforated (i.e. with holes) and/or nonparallel arms are developed for this purpose. For a better comparison, the criterion of equal material volume (or mass) has been utilized. Three dimensional finite element models of the new type of UDs are formed and investigated numerically under selected displacement histories. Based on the obtained hysteretic curves; dissipated energy intensities, effective stiffness ratios, reaction forces, effective damping ratios are evaluated in this parametric study. It is found that both damper types have merits in use of seismic applications and that the selection of the damper configuration is dependent on the design specific issues.     

Multimodal Precipitation in the Superalloy IN738LC

IN738LC is a polycrystalline, nickel-base superalloy, which is used in aggressive environments at high temperatures. The required strength is provided by precipitate strengthening. Both unimodal and multimodal precipitate distributions are observed in IN738LC. After reaching a critical size, a unimodal precipitate microstructure transforms to a bimodal one. This transformation is controlled by the precipitate-matrix interface, which is under compression in IN738LC. As the unimodal precipitates grow, the strained interface, due to differential lattice parameter of the matrix and the precipitate phase, stops solute diffusion into the growing precipitates. Hence, the solute atoms, entrapped in the matrix, saturate the matrix and form new, fine precipitates. Dissolution of some large precipitates also supplies solute to supersaturate the matrix. On the other hand, a multimodal precipitate distribution tends to become unimodal at low aging temperatures and bimodal at high aging temperatures. Interestingly, the activation energy is calculated for the coarsening of large precipitates in multimodal distribution and is found to vary with aging time.     

Microhardness and morphologic characteristics of rapidly solidified Al-12Si-8Ni-5Nd alloy

Al-Si-Ni-Nd alloys with a nominal composition of Al-12 wt.% Si-8 wt.% Ni-5 wt.% Nd alloy are prepared by a conventional casting (ingot) and melt spinning technique at different cooling rates (ν). The effects of the rapid solidification rate on the microstructures and microhardness performances of the specimen alloys are investigated in detail. The results obtained by the XRD, SEM and DSC show that the ingot and melt spun alloys have a multiphase structure. When ν is 5 m/s, the alloy consists of four phases namely α-Al, intermetallic Al₃Ni, Al₁₁Nd₃, and fcc Si. The melt-spun ribbons are completely composed of α-Al and eutectic Si phases, and primary silicon is not observed when ν increases to 20 m/s, 25 m/s, 30 m/s and 35 m/s. The XRD analysis indicated that the solubility of Si in the α-Al matrix increases greatly with the rapid solidification. The change in microhardness is discussed based on the microstructural observations. The microhardness values of the melt spun ribbons are about three times higher than those of ingot counterparts.