Mathematical Optimization Approach for Facility Layout on Several Rows

The facility layout problem is concerned with finding an arrangement of non-overlapping indivisible departments within a facility so as to minimize the total expected flow cost. In this paper we consider the special case of multi-row layout in which all the departments are to be placed in three or more rows, and our focus is on, for the first time, solutions for large instances. We first propose a new mixed integer linear programming formulation that uses continuous variables to represent the departments’ location in both x and y coordinates, where x represents the position of a department within a row and y represents the row assigned to the department. We prove that this formulation always achieves an optimal solution with integer values of y, but it is limited to solving instances with up to 13 departments. This limitation motivates the application of a two-stage optimization algorithm that combines two mathematical optimization models by taking the output of the first-stage model as the input of the second-stage model. This algorithm is, to the best of our knowledge, the first one in the literature reporting solutions for instances with up to 100 departments.publishersversionpublishe

Effect of repeated use on topographical features of protaper next endodontic rotary file

Background: The purpose of this study was to evaluate themorphological alterations of the ProTaper next rotary file (PTN)under scanning electron microscopy (SEM).Materials and Methods: A total of 18 simulated root canals wereallocated to three groups. Six new sets of PTN instruments were used3 times. A #10 K-file was inserted into the working length, followedby ProGlider to create a glide path. Ensuring the manufacturersinstructions with 99% ethyl alcohol for irrigation, all canals wereprepared. Files were photographed in the same position before andafter three canals preparations using a high-resolution SEM.Result: A metal strip appeared on one X1 instrument surfacepreoperatively. Microcrack defects were observed on two X2 filespostoperatively, and the blunt cutting edge was observed on threeX1 files before and after use and one file fractured.Conclusion: Small number of changes appeared on PTN surfaces,yet same PTN file can be used safely 3 times to prepare multi-rootedteeth within the same patient

Selectively boron doped homoepitaxial diamond growth for power device applications

Diamond lateral growth is a powerful technique for the design and fabrication of diamond-based power electronic devices. Growth orientation affects the diamond deposition in terms of growth rate, surface roughness, and impurity incorporation. It has been shown that the finally grown surface of a patterned substrate can be predesigned based on the growth conditions. Thus, simultaneous growth along different surface orientations yields regions with different properties. In line with this, the incorporation of boron in a microwave plasma enhanced chemical vapor deposition laterally deposited epilayer over a mesa patterned {100}-oriented diamond substrate was studied by cathodoluminescence. It was observed that laterally oriented facets were highly boron doped in contrast to the {100}-oriented surfaces, which did not show any bound exciton emission, related to the doping. This study shows that, by designing the initial pattern and tuning the conditions, it is possible to drive a selective incorporation of boron into the grown layer

Recycled hybrid material for use as shielding in operations with ionizing radiation

One of the most efficient measures to prevent gamma radiation is shielding, which can take the form of protection barriers, storage containers, wall coating, bunkers, or many others aimed at minimizing the exposure of people to radiation. The materials used to this end have not changed much since the invention of X-rays, when materials with high attenuation capacity were employed, such as lead, tungsten, or concrete. These are all high-density materials and, therefore, also very heavy, and some of them are expensive and not environmentally friendly, as they do not have many possibilities with regards to their recycling. Circular economy provides an opportunity to reintroduce subproducts and waste in the same production processes that generated them or as raw matters in others. The use of sustainable materials is one of these options; however, there is little research in the field of radiation protection about the use of recycled material to this end, and there are few alternative sustainable options different from conventional materials that show similar behaviour. In our study, we have designed and built shielded panels called Mixlead® for gammagraphy, made of 100 % recyclable materials with sandwich structures combining polymeric fractions of electric cables and lead-alloy protection sheets used in the packaging of radiographic plates. With a methodology combining shielding calculations and a series of thermomechanical-radiological tests, it was possible to accurately determine the thickness of Mixlead® necessary to perform the tests with security guarantees and meeting sustainability requirements for radioactive sources of Iridium (192Ir) and Selenium (75Se), the use of the former being predominant, with an average activity of 1 GBq. In order to reduce this activity 2 and 10 times, the necessary thickness would be 24 and 79 mm respectively, which represents 3 or 4 layers of Mixlead® material.15 página

Patologia em fachadas azulejadas em Aveiro

Mestrado em Engenharia CivilA presente dissertação tem como objetivo principal, o estudo, mapeamento e análise da patologia das fachadas azulejadas existentes na cidade de Aveiro, do seu comportamento ao longo do tempo, da durabilidade e da eventual degradação dos azulejos bem como das suas diversas causas, enquanto revestimentos tendencialmente impermeáveis em fachadas de edifícios, assim como algumas diretrizes sobre a conservação e restauro de azulejaria notável.The main objective of the present dissertation is the study, mapping and analysis of the pathology associated with glazed tile facades in the city of Aveiro. This includes their behaviour over time, the durability and possible deterioration of the tiles as waterproof wall coverings on building facades, as well as the various causes of these occurrences. In addition, the dissertation discusses some guidelines with regard to the conservation and restoration of notable tile work.La présente thèse a comme objectif principal l’étude, la cartographie et l’analyse des pathologie des façades revêtues de carreaux de faïence mosaïque dans la ville de ‘’Aveiro’’, de leur comportement au long des années passées, de leur durabilité et leur éventuelle dégradation et de leurs diverses causes, en tant que revêtements tendanciellement imperméables sur des façades de bâtiments, ainsi que les lignes directrices sur la conservation et la restauration remarquable des carreaux de faïence mosaïque.قطانملا ميسقتو ،ةيليصفت ةسارد ءارجإ وه ةحورطألا هذهل يسيئرلا فدهلا فرخزملا فزخلاب ةاطغملا ينابملا تاهجاو يف ةرهاظلا ضارمألا ليلحتو ةيفارغجلا روهدتلا ةيناكمإ وأ لمحتلا ةوقو ،تاونسلا ىدم ىلع هكولس ،’’ورييفأ’‘ ةنيدم يف ءاملا برست دض يماح ءاطغ مهرابتعاب ،هتاببسم فلتخمو تقولا عم يجيردتلا ميمرتو ظفح نأشب ةيهيجوتلا ئدابملا ضعب ءادتقاو ،ينابملا تاهجاو ىلع نمDas Hauptziel dieser Dissertation ist die Studie, Darstellung und Analyse der Pathologie der Fliesenfassaden, die es in der Stadt Aveiro gibt, ihres Verhaltens im Verlauf der Zeit, ihrer Beständigkeit, des eventuellen Zerfalls der Fliesen sowie der diversen Ursachen hierfür als tendenziell wasserdichte Verkleidung an Fassaden und Gebäuden, sowie einige Leitlinien zur Erhaltung dieser außergewöhnlichen Fliesen

Evidences of exopolysaccharide production by Helicobacter pylori submitted to hydrodynamic stress

Helicobacter pylori is a widespread Gram-negative bacterium that infects the stomach of humans leading to the onset of several gastric disorders, such as gastritis, gastric ulcers, and cancers. The transmission of H. pylori remains unclear but two different pathways have been suggested: faecal-oral and oraloral. It has been reported that H. pylori has the ability to incorporate in biofilms formed on water-exposed surfaces thus providing a route of infection. On the other hand, a polysaccharide-containing biofilm has been observed at the air-liquid interface when H. pylori is grown in a glass fermenter1. Because exopolysaccharides (EPS) play a determinant role in bacterial adhesion by conferring protection against adverse conditions such as starvation and environmental aggressions, EPS production would be expected to be higher if the bacterium is exposed to water. In this work the capability of H. pylori to produce EPS when exposed to water and under hydrodynamic stress has been evaluated. H. pylori was inoculated in autoclaved distilled water and allowed to stand under gentle stirring at room temperature. The significant and continuous increase in the sugar content 192 hours after inoculation suggests the production of exopolysaccharides. This evidence is reinforced by epiflourescence microscopical observation of the bacteria stained with DAPI (4,6-diamidino-2-phenylindole) that revealed the presence of bacterial aggregates 318 hours after inoculation

Portuguese 16th to Early 18th Century tin Glazed Ceramics Found at the Tagus Estuary Saltpans

UID/NAN/50024/2019 M-ERA-MNT/0002/2015 UIDB/04209/2020 UIDP/04209/2020Salt was extracted from saltpans, in the South shore of Tagus River by evaporation of the salted sea water which penetrates into the estuary. The walls and the bottom of those saltpans were made of local clays to retain the sea water, and ceramic sherds have been used to endure those walls and also to allow people to walk on the saltpans’ walls. Those sherds constitute an example of the ceramics production in Lisbon workshops, starting in the mid-16th century and reaching high levels of quality in the 17th and 18th century. A detailed archaeometric study of 14 selected sherds dated from the 16th to the early 18th century has been made and the conjugation of the information provided by the micro-Raman, XRD and XRF experiments for those sherds and clays collected locally, allowed us the characterisation of the Lisbon ceramics in that period. Three main groups could be identified in the ceramic bodies; all made with locally collected clays of Miocene origin. In the first group, the potters used raw materials from the clay sources located at Santa Catarina area in Lisbon, most probably mixed with Lapa clays, which were fired at a high temperatures, ranging from 850ºC to 950ºC. Gehlenite and quartz are the dominant minerals of these ceramic bodies. In the second and third groups of Lisbon ceramic bodies, made with Prazeres clays, diopside was also detected but with variable amounts of gehlenite. Clay formations mineralogy mainly include kaolinite, muscovite/illite, quartz, calcite, and feldspars (albite and microcline).publishersversionpublishe

Characterization of Ni-CNTs Nanocomposites Produced by Ball-Milling

This research focuses on the characterization of a metal matrix nanocomposite (MMNC) comprised of a nickel matrix reinforced by carbon nanotubes (CNTs). The aim of this study was to characterize Ni-CNTs nanocomposites produced by powder metallurgy using ball-milling. CNTs were initially untangled using ultrasonication followed by mixture/dispersion with Ni powder by ball-milling for 60, 180, or 300 min. The mixtures were cold-pressed and then pressureless sintered at 950 degrees C for 120 min under vacuum. Their microstructural characterization was mainly performed by optical microscopy (OM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). The mechanical properties were evaluated by Vickers microhardness. The results indicate that combining ultrasonication and ball-milling can successfully produce Ni-CNTs nanocomposites. The ball-milling time has a significant effect on both the CNT dispersion and the final nanocomposite microstructure

EBSD Analysis of Metal Matrix Nanocomposite Microstructure Produced by Powder Metallurgy

The development of metal nanocomposites reinforced by carbon nanotubes (CNTs) remains a focus of the scientific community due to the growing need to produce lightweight advanced materials with unique mechanical properties. However, for the successful production of these nanocomposites, there is a need to consolidate knowledge about how reinforcement influences the matrix microstructure and which are the strengthening mechanisms promoting the best properties. In this context, this investigation focuses on the study of the reinforcement effect on the microstructure of an Ni-CNT nanocomposites produced by powder metallurgy. The microstructural evolution was analysed by electron backscattered diffraction (EBSD). The EBSD results revealed that the dispersion/mixing and pressing processes induce plastic deformation in the as-received powders. The dislocation structures produced in those initial steps are partially eliminated in the sintering process due to the activation of recovery and recrystallization mechanisms. However, the presence of CNTs in the matrix has a significant effect on the dislocation annihilation, thus reducing the recovery of the dislocation structures

Codelastro. A STEM project for code learning with astronomical ideas

Learning how to use and to be able to program computers and other computer based or artificial intelligence devices is becoming of high importance in today’s modern societies. Micro:bit is a device that can be used to introduce children and students to this world. Micro:bit is a pocket programmable device that allows children and young people to learn how to program in a simple, playful and creative way. On the other hand, astronomy is an important science topic that appeals to the imagination and wonder of children, therefore contributing to their motivation and in promoting interest in science. Based on these two ideas, a STEM project named “Code Learning with Astronomical Ideas”, codename CODELASTRO, was developed and is going to be presented herein. The core project idea was to create a code learning-program based on micro:bit and astronomical topics. The micro:bit integrated sensors allow the development of STEM projects, in which children and young people, almost autonomously and in groups, can learn by going through all phases of design, development, coding, testing and execution. Exploring the relationship of programming and astronomy gave us an opportunity to teach how science can be challenging and attractive to young people. The initial target audience of the CODELASTRO project was students and teachers from developing nations, Mozambique and East Timor in particular. It was proved that this project can be successfully implemented in such countries with limited resources and facing developmental challenge