Titan Cement (Greece)

Distance teaching process as a result of the sudden, immediate and without prior design implementation of online education in Greece is the subject of this study. The combined use of synchronous and asynchronous teaching, teachers’ insufficient training to efficiently meet the requirements of the new teaching method because of the pandemic and the suspension of the operation of school units, as well as the necessary electronic equipment that teachers and children needed are considered important factors that caused stress, fear, reluctance, discomfort, etc. However, after the participation in the distance teaching process, the question arises: what is the opinion that the involved parties (teachers, children, parents) shaped about distance education? Is it a positive or a negative one? Would they wish to see face-to-face teaching being replaced by distance teaching? Were there any advantages and disadvantages during its implementation? If yes, what were the most important ones in each case? This study attempts to answer these questions.

Multiphase materials are encountered in several areas of science and technology. Their properties are determined by the fraction of the phases (material compounds) constituting the composite material. Therefore, the quantitative characterization of phase fractions is highly demanded and has been the subject of extensive studies. To this end, a widely used technique is the segmentation of top-down back-scattered electron SEM (BSE-SEM) images given that different phases are depicted with pixel collections of different luminosity. Gaussian mixture models (GMM) are one the most popular and easily implemented methods to segment the BSE-SEM images through the deconvolution of their histograms. However, the accuracy and the limitations of their application have not been fully investigated. The aim of this paper is to design a neural-network approach to fill this gap and provide a fast tool for the automatic evaluation of the accuracy of GMM predictions for all material phases based on the inspection of the measured SEM image histogram alone. The proposed tool facilitates the decision-making process of an SEM user concerning the optimum choice of a segmentation method.

Nanostructured transition metal phosphides, in the last few years, have attracted increased scientific interest, due to their unique physicochemical properties. Nickel phosphide nanoparticles, with controllable crystal structures, from metal-rich tetragonal Ni12P5 to phosphorous-rich hexagonal Ni2P, and hexagonal close-packed (hcp) Ni2P-decorated reduced graphene oxide (r-GO) nanohybrid materials have been synthesized via a novel one-step liquid-phase approach in primary–tertiary aliphatic amine mixtures. The nanoparticles are monodispersed, have a spherical shape and a controllable size in the sub-10 nm regime, and uniformly decorate the surface of r-GO, leading to the formation of Ni2P/r-GO hybrid materials. The materials were characterized using powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and Raman spectroscopy and catalytically evaluated for the dibenzothiophene hydro-desulfurization (HDS) reaction. The results clearly demonstrated that the role of the tertiary amine is crucial for the phosphidation process. In addition, r-GO has been proven to be ideal alternative support to the traditional inorganic ones for the immobilization of the catalytically active component, preventing significant sintering effects.

Nanostructured transition metal phosphides gathered last years an elevated scientific interest, due to their unique physical-chemical properties. Nickel phosphide nanoparticles, with the controllable crystal structure, from the metal rich tetragonal Ni<sub>12</sub>P<sub>5</sub> to the phosphorous rich hexagonal Ni<sub>2</sub>P, and <i>hcp</i> Ni<sub>2</sub>P decorated r-GO (reduced graphene oxide), nano-hybrid materials have been synthesized via a novel one step organometallic approach in primary-tertiary aliphatic amines mixture. The nanoparticles are monodispersed, with spherical shape and controllable size in the sub-10 nm regime and decorate uniformly the surface of the r-GO, leading to the formation of Ni<sub>2</sub>P/r-GO hybrid materials. The materials were characterized by powder XRD, TEM and Raman spectroscopy and catalytically evaluated for the dibenzothiophene hydrodesulphurization (HDS) reaction. The results show that the role of the tertiary amine is crucial for the phosphidation process and the r-GO is an ideal alternative, to the traditional inorganic ones, support for the immobilization of the catalytically active component, preventing significantly sintering effects.

Single and few-layers MoS2 were uniformly grown on the surface of chemically reduced graphene oxide (r-GO) via a facile liquid phase approach. The method is based on a simple functionalization of r-GO with oleyl amine which seem to affect significantly the MoS2 way of growth. Scanning transmission electron microscopy (STEM) and Atomic Force Microscopy (AFM) analysis reveal the presence of single-layer MoS2 on the surface of a few-layers r-GO. XPS and Raman spectroscopies were used for in-depth structural characterization. Furthermore, we have successfully applied the method to synthesize MoS2 nanocomposites with multiwall carbon nanotubes (CN) and carbon nanofibers (CNF). The results demonstrate clearly the selective MoS2 growth on both carbon-based supports.

This chapter presents application of FEM as a supporting tool for condition monitoring of existing equipments (technical assessment of condition, determination of best monitoring parameters, setting limits for early corrective actions).

Pervious concrete is a type of concrete with significantly increased water permeability, ensuring increased rates of drainage of rainfall. The high porosity is achieved by removing a large percentage of fine aggregates from the mix. The present paper is an approach for the addition of steel slag as a substitute for coarse aggregates in pervious concrete. More specifically, three types of aggregates have been used: steel slag, construction and demolition wastes and conventional limestone aggregates. The produced pervious concretes are compared for their properties, such as water permeability, compressive strength and abrasion behaviour. Also this paper contains the study of the porosity analysis of these pervious concrete mix designs by using porosity profiles produced from X-ray CT Scanning. According to the results of this paper, it is observed that the incorporation of industry by-products or of Construction and Demolition (C&D) wastes leads to better abrasion behaviour, and to the increase, in some cases, of the compressive strength and of the water permeability.

This study was motivated by the necessity to recycle sludge water resulting from washing out concrete mixing trucks - a problem of both environmental and economic importance for the ready-mixed concrete industry. Sludge water from ready-mixed concrete plants as well as dry sludge, which is derived from the settling of the water, are hazardous for disposal due to their high pH value (pH>11.5). In this work, cement mortars were composed using either sludge water after various treatment, or dry sludge in several ratios. The cement mortars were tested for their workability and strength development. The purpose of this experimental design was to prove that sludge water, as well as sludge in a wet or dry form, can be used in the production of mortars without degrading any of their properties.

There are several types of motors to choose from when selecting motors for large HP (2000 HP - 10.000 HP) cement plant applications including; squirrel cage induction motors, wound rotor induction motors, PAM induction motors, synchronous motors, and DC motors, all of which have their own advantages and disadvantages. This paper will compare the operational characteristics of the induction, synchronous and DC motors to demonstrate how to apply the different speed-torque-current characteristics of each when driving typical cement plant loads. This paper will compare several different starting methods for AC motors such as across the line starting, autotransformer, solid state starting, and Adjustable Speed Drive (ASD) and discuss the limiting factors of each method such as starting current requirements and cage heating. A comparison of the operating characteristics of induction and synchronous motors will demonstrate how the power factor and efficiency advantage of synchronous motors can be applied to lower the energy cost of a cement plant. The variable speed operation of induction and synchronous motors operating on adjustable speed drives will be compared with the operational characteristics of DC motors which vary speed without the use of a drive.