Vibration monitoring for defect diagnosis of rolling element bearings as a predictive maintenance tool: Comprehensive case studies

Vibration monitoring and analysis in rotating machineries offer very important information about anamolies formed internal structure of the machinery. The information gained by vibration analysis enable to plan a maintenance action. In this study, the vibration monitoring and analysis case studies were presented and examined in machineries that were running in real operating conditions. Failures formed on the machineries in the course of time were determined in its early stage by the spectral analysis. It was shown that the vibration analysis gets much advantage in factories as a predictive maintenance technique.     

Comparison of radioactive transmission and mechanical properties of Portland cement and a modified cement with trommel sieve waste

In this study, it was aimed to stabilize trommel sieve waste (TSW) occurring during manufacture of borax from tincal. The effects of TSW added on the mechanical properties and radioactive transmission of modified cement prepared by adding TSW to clinker was investigated. The properties which TSW as additive caused the cement to gain were tested and compared with normal Portland cement.Measurements have been made to determine variation of mass attenuation coefficients of TSW and cement by using an extremely narrow-collimated-beam transmission method in the energy range 15.746-40.930 keV with X-ray transmission method. The characteristic Kα and Kβ X-rays of the different elements (Zr, Mo, Ag, In, Sb, Ba and Pr) passed through TSW and cement were detected with a high-resolution Si(Li) detector. Results are presented and discussed in this paper.     

Investigation on the ballistic impact behavior of various alloys against 7.62 mm armor piercing projectile

In this study, impact behavior of the aluminum alloys of 7075 and 5083 and the high-strength low-alloy steel, AISI 4140 was investigated under 7.62 mm armor piercing (AP) projectile experimentally. Various heat treatments were applied to the alloys AISI 4140 and 7075 to see the effect of hardness and strength on their ballistic behaviors. Experimental results showed that among the investigated materials, the best ballistic performance was attained with the alloy, 7075-T651 which maintained the ballistic protection with the areal density 85 kg/m².     

Borosilicate nanoparticles prepared by exothermic phase separation

Nanoparticles play an important role in chemical and biological sciences due to their ability to bind and concentrate many molecules on their surface. Polymers and silica are widely used to make nanoparticles, but efforts to make nanoparticles from borosilicate glass--which exhibits high tolerance to chemicals and solvents, combined with excellent mechanical and thermal stability--have proved unsuccessful. Here we show that borosilicate nanoparticles (100-500 nm in size) can be synthesized by simply mixing a silicon-boron binary oxide solution, prepared using non-aqueous organic solvents, with water. This induces a vigorous exothermic phase separation in which borosilicate nanoparticles burst out of a silica phase. In addition to potential applications in the life sciences, monodisperse borosilicate particles could also have applications in the production of photonic bandgap devices with high optical contrast, contrast agents for ultrasonic microscopy or chemical filtration membranes.     

Statistical and neural network assessment of the compression index of clay-bearing soils

The compression index is used to estimate the consolidation settlement of clay-bearing soils. As the determination of compression index from oedometer tests is relatively time-consuming, empirical equations based on index properties can be useful. In this study the performance of widely used single and multi-variable empirical equations was evaluated using a database consisting of 135 test data. New empirical equations were developed utilizing least square regression analysis. In addition, an artificial neural network (ANN) with eight input variables was also developed to estimate the compression index. It was concluded that ANN provides the best results.      

Decoding of LT‐Like Codes in the Absence of Degree‐One Code Symbols

Luby transform (LT) codes were the first practical rateless erasure codes proposed in the literature. The performances of these codes, which are iteratively decoded using belief propagation algorithms, depend on the degree distribution used to generate the coded symbols. The existence of degree‐one coded symbols is essential for the starting and continuation of the decoding process. The absence of a degree‐one coded symbol at any instant of an iterative decoding operation results in decoding failure. To alleviate this problem, we proposed a method used in the absence of a degree‐one code symbol to overcome a stuck decoding operation and its continuation. The simulation results show that the proposed approach provides a better performance than a conventional LT code and memory‐based robust soliton distributed LT code, as well as that of a Gaussian elimination assisted LT code, particularly for short data lengths.     

A Photoluminescent Polymeric 2D Silver(I) Complex Exhibits a Fishbone-like 1D Silver Cluster and New Coordination Mode of the Pyridine-2,3-Dicarboxylate

In this study, a novel organic–inorganic hybrid compound with AgNO₃ and 2,3-pyridinedicarboxylic acid (H₂pydc), [Ag₂(μ₆-pydc)]_n (1) has been synthesized. The molecular structure of complex has been determined by the single crystal X-ray diffraction. The complex has been observed to crystallize in the monoclinic space group P2₁/c. The asymmetric unit of compound consists of two crystallographically different Ag(I) centers and one pydc ligand. The Ag1 and Ag2 adopt tetrahedral and T-shaped geometries, respectively. At the same time, the silver(I) compound consists of a fish bone similar to the 1D silver cluster. Furthermore, novel coordination mode shown by H₂pydc indicates that the crystal exhibits photoluminescence in the solid state at room temperature.     

Viscous-dissipation effects on the heat transfer in a Poiseuille flow

In this study, laminar heat-convection in a Poiseuille flow of a Newtonian fluid with constant properties is analyzed by taking the viscous dissipation into account. At first, both hydrodynamically and thermally fully-developed flow case is investigated. Then, consideration is given to thermally-developed laminar forced-convection. The axial heat-conduction in the fluid is neglected. Two different thermal boundary-conditions are considered: the constant heat-flux and the constant wall-temperature. Both the hot-wall and the cold-wall cases are considered. In the literature, the viscous-dissipation effect is commonly represented by the Brinkman number. Several different definitions of the Brinkman number arise depending on the thermal boundary conditions. Either for the thermally fully-developed case or the thermally-developing case (the Graetz problem), temperature distributions and the Nusselt numbers are analytically determined as functions of the Brinkman number.     

Experimental and Computational Studies on the Thermal Degradation of Nitroazidobenzenes

In this combined experimental and theoretical study the thermal degradation of 2‐nitroazidobenzene ( I ), 2,4‐dinitroazidobenzene ( II ) and 2,4,6‐trinitroazidobenzene ( III ) to yield benzofuroxan ( IV ), 4‐nitrobenzofuroxan ( V ), and 4,6‐dinitrobenzofuroxan ( VI ) were investigated by thermoanalytical (TG, DSC) and computational methods. In contrast, furoxan formation was not observed for 4‐nitroazidobenzene ( VII ) under heating due to the para position of the nitro group in the benzene ring. All compounds were characterized by elemental analysis, vibrational (IR) spectroscopy and mass spectrometry. The crystal structure of compound III was determined by single‐crystal X‐ray diffraction. DFT‐based structure optimizations and frequency analyses were performed at the B3LYP/cc‐pVDZ level of theory. The structural parameters of the fully optimized compound III showed very good agreement with the single‐crystal X‐ray data. The enthalpies of formation for compounds I , II , III , IV , V , and VI were calculated using the complete basis set (CBS‐4M) method of Petersson and co‐workers in order to obtain accurate energies. The enthalpies of degradation for compounds I , II , and III were obtained from calculated enthalpies of formation according to the Hess Law and were compared with the experimental values, which were available from DSC analysis and were found to be in very good agreement.     

Profiling of in vitro neurobiological effects and phenolic acids of selected endemic Salvia species

The ethyl acetate and methanol extracts from 16 Salvia L. species were screened for their inhibitory activity against acetylcholinesterase, butyrylcholinesterase, lipoxygenase, and tyrosinase; the enzymes linked to neurodegeneration. Their antioxidant activity was also tested using DPPH radical scavenging, metal-chelation, and ferric-reducing antioxidant power (FRAP) assays. Total flavonoid content of the extracts was determined by AlCl₃ reagent, while HPLC technique was applied for analysis of various phenolic acids in the extracts. The extracts exerted weak cholinesterase and tyrosinase inhibition, and remarkable inhibition against lipoxygenase (13.07 ± 2.73-74.21 ± 5.61%) at 100 μg ml⁻¹. The methanol extracts showed higher antioxidant activity in DPPH radical scavenging and FRAP assays. The extracts were analyzed for their gallic, protocateuchic, p-hydroxy-benzoic, vanillic, caffeic, chlorogenic, syringic, o- and p-coumaric, ferulic, rosmarinic, and tr-cinnamic acid contents and the methanol extract of Salvia ekimiana (153.50 mg 100 g⁻¹) was revealed to be the richest in terms of rosmarinic acid.