Ceramic Floor Research Articles

Experimental and numerical analysis of the energy performance of a large scale intensive green roof system installed on an office building in Athens

The aim of this study is to investigate the thermal behaviour and the energy efficiency of an intensive green roof system composed of indigenous aromatic plants with low irrigation needs, installed in the 10,000m2 roof of a fully insulated, low energy office building in Athens, Greece. It consists of almost 16,000 Mediterranean plants of at least 14 different kinds and a running track of a stabilized ceramic floor. The urban heat island mitigation potential of the green roof as well as its energy contribution is investigated using experimental and theoretical methodologies. The surface temperature of the green roof is found to be up to 15K lower than that of a conventional roof. Plants having a low absorptivity to solar radiation together with a dense foliage are found to present a much lower surface temperature and a higher mitigation potential. The surface temperature of the plants is found to be highly influenced by the ambient air temperature. Using simulation techniques it is calculated that such a type of green roofs can decrease the average indoor temperature of a non air conditioned building up to 0.7K, while it may decrease substantially its annual cooling and heating needs.

Characterization of Sugarcane Bagasse ash Waste for Its Use in Ceramic Floor Tile

In Brazil, the sugarcane industry generates large amounts of sugarcane bagasse ash, and a key issue is to find a proper use of this solid waste material. The aim of this study is to determine the chemical, physical and mineralogical characteristics of a sugarcane bagasse ash sample from south-eastern Brazil, and to investigate its use in the production of ceramic floor tile. The sample of this waste material was analyzed regarding chemical composition, mineralogical analysis, particle size distribution, morphology, particle density, and organic matter. Floor tile pieces containing up to 2.5 wt% sugarcane bagasse ash waste as a partial replacement of quartz were prepared by uniaxial pressing and sintered at 1190°C. The following technological properties were determined using standard procedures: flexural strength, apparent density, linear shrinkage, and water absorption. The experimental results indicated that the sugarcane bagasse ash waste is rich in quartz particles, and has potential to be used as an alternative raw material for the production of ceramic floor tile.

Influence of Glassy Additives on the Formation of Crystalline Phases in Sintered Red Ceramic Bodies

ABSTRACTThe main objective of this research work was to study the influence of glassy additives on the formation of crystalline phases in sintered red ceramic bodies used for the fabrication of ceramic floor tiles, whose composition is a mixture of quartz (SiO2), kaolinite [Al2Si2O5(OH)4], albite (NaAlSi3O8), muscovite [KAl2(Si3Al)O10(OH)2] and calcite (CaCO3). The additives used were: fly ash, soda-lime glass, borosilicate glass, glass frit, Na2P3O10 and cryolite (Na3AlF6). These were added in variable proportions to the nominal composition of the red ceramic bodies, either as single or as combined additions, aiming to accelerate the densification of the materials during their sintering process. For all the additive types used, the crystalline phases formed in the samples sintered using a peak temperature ranging from 950 to 1030 °C were: quartz (SiO2), anorthite (CaAl2Si2O8), and hematite (Fe2O3). It is known that the presence of anorthite is particularly beneficial for the mechanical properties, chemical stability and densification of the sintered red ceramic bodies. However, some of the considered additions tended to be detrimental for the formation of this phase in the studied materials, especially at the lowest peak sintering temperature employed. This was verified by means of XRD and SEM analysis.

A Pilot Recycling of Plastic Pure Water Sachets/Bottles into Composite Floor Tiles: A Case Study from Selected Dumping Site in Ogbomoso

The adverse effect associated with the surge in uses of non-biodegradable plastic products include the blockage of drains, suffocating some animal life, who accidentally take them as food, grounds impermeable to water and several other hazards. The need then arises to finding a safe means converting these plastic waste products into other useful and harmless items. The method adopted involves the collection of the plastic materials from trenches, drainages, streets, dump sites and from eateries around Ogbomoso metropolis. These were sorted and washed before the Shredding Process was carried. Melting of the Shredded Plastics and poured into a dimensioned wooden mould and Cured for some days. It could be shown from the crushing test that the conventional tiles fail under slight heavier loads of 34 kN as comparable to the 29 kN failure load of the composite tiles. However the water absorption test has no effect on both the conventional and the composite tiles respectively. Furthermore, the flammability test carried out on the conventional tiles shows a slight change as compared to the composite tiles which split under the effect of flame. Moreover the composite tiles recorded a higher value than that of the conventional tiles. The tests show that the composite floor tiles are cheaper, durable, and affordable as compared to the ceramic tile. Hence, the performances of the composite floor tiles though are a little less than that of the commercial ceramic floor tiles yet appear a reasonably good substitute at more reasonable rate.

Recycling of Malaysia’s electric arc furnace (EAF) slag waste into heavy-duty green ceramic tile

Recently, various solid wastes from industry such as glass waste, fly ash, sewage sludge and slag have been recycled into various value-added products such as ceramic tile. The conventional solutions of dumping the wastes in landfills or incineration, including in Malaysia are getting obsolete as the annual huge amount of the solid wastes would boost-up disposal cost and may cause permanent damage to the flora and fauna. This recent waste recycling approach is much better and greener as it can resolve problems associated with over-limit storage of industrial wastes and reduce exploration of natural resources for ceramic tile to continuously sustain the nature. Therefore, in this project, an attempt was made to recycle electric arc furnace (EAF) slag waste, obtained from Malaysia’s steel making industry, into ceramic tile via conventional powder compaction method. The research work was divided into two stages. The first stage was to evaluate the suitability of EAF slag in ceramic tile by varying weight percentage of EAF slag (40wt.%, 50wt.% and 60wt.%) and ball clay (40wt.%, 50wt.% and 60wt.%), with no addition of silica and potash feldspar. In the second stage, the weight percentage of EAF slag was fixed at 40wt.% and the percentage of ball clay (30wt.% and 40wt.%), feldspar (10wt.% and 20wt.%) and silica (10wt.% and 20wt.%) added was varied accordingly. Results obtained show that as weight percentage of EAF slag increased up to 60wt.%, the percentage of apparent porosity and water absorption also rose, with a reduction in tile flexural strength and increased porosity. On the other hand, limiting the weight percentage of EAF slag to 40wt.% while increasing the weight percentage of ball clay led to a higher total percentage of anorthite and wollastonite minerals, resulting in higher flexural strength. It was found that introduction of silica and feldspar further improved the flexural strength due to optimization of densification process. The highest flexural strength, lowest apparent porosity and water absorption of EAF slag based tile was attained at the composition of 40wt.% EAF slag – 30wt.% ball clay – 10wt.% feldspar – 20wt.% silica. The properties of ceramic tile made with EAF slag waste (up to 40wt.%), especially flexural strength are comparable to those of commercial ceramic tile and are, therefore, suitable as high flexural strength and heavy-duty green ceramic floor tile. Continuous development is currently underway to improve the properties of tile so that this recycling approach could be one of the potential effective, efficient and sustainable solutions in sustaining our nature.

Distribution of contact pressure over the surface of ceramic floor tiles during the polishing process

Abstract Assisted with computational simulation this work quantitatively determined the distribution of contact pressure over the surface of porcelain stoneware tiles during the industrial polishing process. In modern polishing lines there are basically three movements responsible for the scratching velocity and the position of the abrasives. Combining the kinematic equations obtained by these movements with a pre-existing model the contact pressure between abrasive tool and tile surface could be determined as function of time. The spatial distribution of average, standard deviation and maximum values of contact pressure were then obtained and mapped over the entire surface. The simulation results showed that the contact pressure tends to be 50% higher near to the center, in regions worked by the innermost abrasives. Additionally, periodical variations of up to 10% were found to occur due to the partial retreat of the abrasive tool.

Cue-induced renewal of heroin place preference

It is well established that re-exposure to a context paired with the effects of drugs of abuse can renew extinguished drug seeking behavior. A context, however, typically includes several stimuli, which may differ in their ability to control drug-oriented behaviors. Hence, the primary objective of this study was to assess whether a heroin-induced place preference could be recovered by re-exposure to a contextual stimulus that was part of the conditioning context before extinction. The second objective was to explore the role of the basolateral nucleus of the amygdala (BLA) in this conditioned effect. Male Sprague-Dawley rats were injected with 3 mg/kg heroin and confined in a compartment that was distinguished by a variety of contextual stimuli, including a ceramic floor tile. During extinction, the floor stimulus was removed, and it was reintroduced for a drug-free test of preference. A control experiment evaluated the unconditioned preference for the floor stimulus. It was found that reintroduction of the floor stimulus caused the recovery of heroin place preference. This effect was not observed in rats infused in the BLA with muscimol (0.03 nmol) and baclofen (0.3 nmol) just prior to the test. These data suggest that an extinguished heroin place preference can be renewed by a contextual tactual stimulus that was part of the conditioning context, and that this process requires an intact BLA.

Paper 6: Grouting Mortars for Fragmented Bricks and Repair Mortars for Tiles in the Archaeological Site Coudenberg

Different grouting and repair mortars were developed and evaluated for the conservation and restoration of fragmented bricks in the walls and floors of the remaining cellars underneath the Aula Magna, the palace’s main banqueting hall, and to fill the lacunae and perform edge repairs of red and blue-grey ceramic floor tiles in the remaining cellars underneath the chapel of the former Palace of Coudenberg in Brussels, Belgium.To prevent the deposition of lime bloom at the surface of the masonry and to achieve an acceptable colour match of the grout in harmony with the bricks of the Aula Magna, the effect of brick powder added to natural hydraulic lime was studied. The pozzolanic properties and colour match of several historic and modern powdered bricks were investigated. Surprisingly, ancient bricks do not seem to possess higher pozzolanic properties than the more modern ones, although it is supposed that they were fired at lower temperatures. Additional evidence for the pozzolanic reaction of the different brick powder materials was obtained from a simple visual observation of stored samples. After eight weeks all of the samples containing brick powders, fired at low and high temperatures, added to putty lime had hardened under water and were transformed into a remarkably tough material. These results are important, as modern bricks are readily available in large quantities and different colours, which are hence in favour of being used instead of historical material from the site.For the repair of the ceramic floor tiles different mortars were investigated with mixtures containing talcum, stone or brick powder, pigments, and chalk added to an epoxy binder. The mortars were tested in the laboratory and in situ for their workability and resemblance with the historic floor tiles. The finished mortars showed excellent aesthetic properties with the tiles in situ and good properties to prevent further loss due to human interaction.

Dual functions of novel glass–ceramic floor tile design and preparation

A novel glass–ceramic floor tile with both decorative and microwave absorption properties was successfully obtained through the sintering process from frits with coarse grain sizes (2.0mm average particle size) using commercial raw materials (purity range of 73–99%). The tile consists of two glass–ceramic layers, i.e., decorative top layer and functional middle layer, atop flat ceramic substrate (as a sandwich). The sandwich was subjected to sintering at 1200°C for 15min to achieve the desired esthetic appearance and magnetic properties. The sintered samples were investigated by X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), physical property measurement system (PPMS) and vector network analyzer (VNA) Esthetic appearance was attributed to the formation of crystalline phases among decorative layer where hematite, magnetite, zircon and monoclinic zirconia are being indexed. Electromagnetic wave absorption in 2–18GHz frequency range was calculated based on the experimental data due to the formation of magnetite in the middle layer. Our analysis showed that peak reflection loss of −11.23dB (92% microwave absorption) is appeared at 10.72GHz. Bandwidth of 2.16GHz is attainted for reflection loss value less than −10dB (i.e. more than 90% microwave absorption).

Modifying action sounds influences people's emotional responses and bodily sensations.

We report an experiment designed to investigate the effect of modifying the sound of high-heeled shoes on women's self-reported valence, arousal, and dominance scores, as well as any changes to a variety of measures of bodily sensation. We also assessed whether self-evaluated personality traits and the enjoyment associated with wearing heels were correlated with these effects. Forty-eight women walked down a “virtual runway” while listening to four interaction sounds (leather- and polypropylene-soled high-heeled shoes contacting ceramic flooring or carpet). Analysis of the questionnaires that the participants completed indicated that the type of sonic interaction impacted valence, arousal, and dominance scores, as well as the evaluated bodily sensations. There were also correlations between these scores and both self-evaluated personality traits and the reported enjoyment associated with wearing high heels. These results demonstrate the effect that the sound of a woman's physical interaction with the environment can have, especially when her contact with the ground while walking makes a louder sound. More generally, these results demonstrate that the manipulation of product extrinsic sounds can modify people's evaluation of their emotional outcomes (valence, arousal, and dominance), as well as their bodily sensations.

Contatc Analysis on Thread Connections of 32.8MN PRESS Columns

Automatic hydraulic press is widely used for pressing ceramic wall and floor tiles, the four columns of its frame withstand the all work force when it works, so the columns are the key compartments of the frame, and its work performance has an important impact on the structural performance of the entire automatic hydraulic press. Took the column thread connection of 32.8MN automatic hydraulic press as research object, established axisymmetric finite element model and carried on contact finite element analysis for it by using the large commercial finite element software ANSYS to gain the stress distribution of the column’s thread connection. The results and discussion can provide reference for designing automatic hydraulic press columns . DOI: http://dx.doi.org/10.11591/telkomnika.v11i7.2847 Full Text: PDF

The unusual appearance of black esophagus in a case of fatal hypothermia: a possible underlying mechanism

Acute esophageal necrosis is characterized by a full length, circumferential black discoloration of the entire mucosa of the esophagus that ends abruptly at the esophagogastric junction [1]. The clinical presentation of cases is almost universally related to upper gastrointestinal bleeding [2]. Although unclear, the etiology is likely to be multifactorial [1, 2]. Case history: A 61-year-old male, alcoholic with liver cirrhosis was found lying unconscious on a cold bathroom floor. The patient was in a deep coma, hypotensive with accompanying metabolic acidosis, slight hyperglycemia, significantly elevated urea, creatinine, and liver enzymes levels, and had progressing secondary anemia. The patient died approximately 46 h after he was initially found in his house. The autopsy found that the distal third of the esophagus contained blackish necrotic mucosa, which ended abruptly at the esophagogastric junction. The stomach mucosa had numerous red-brownish erosions— Wischnewski spots (Fig. 1). The entire length of the intestine was filled with dark-red blood. Microscopic examination revealed an acute full-thickness necrosis of the esophagus mucosa in which the epithelium was almost completely consumed, and acute inflammatory cells in the submucosa and mucosa. The cause of death was fatal blood loss from the upper gastrointestinal tract. Hypothermia stimulates profound vasoconstriction, especially in the splanchnic region, and alterations in microcirculation, which leads to ischemic organ damage [3]. A somewhat atypical presentation of a black esophagus as seen in this case, where only the lower third of the organ is affected, is most likely related to its segmental vascular supply. The distal esophagus receives its blood flow from branches of the left gastric artery or left inferior phrenic artery, and is the least vascularized section of the esophagus. Therefore, the first signs of an ischemic injury to the esophagus typically appear in the distal section [2]. Although the black esophagus in this case could perhaps be related to acute alcohol intoxication, or liver cirrhosis, the most probable cause has been considered to be the vasoconstriction of the common arteries of the stomach and the distal section of the esophagus due to hypothermia. Wischnewski spots would seem to occur more frequently in the elderly after having been exposed to cold stress for an extended period of time [4, 5]. The presence of them in this case indicates that the cooling of the body was not rapid, that is, the patient had most probably been lying on the cold ceramic floor for some time before being found, loosing body heat via conduction during that time. The microscopic appearance of acute esophagitis with a sharp demarcation of mucosal necrosis by predominantly neutrophilic granulocytes places the noxious mucosal injury within a time frame of approximately 24–72 h prior to death [1]. The microscopic picture of the black esophagus in this case is consistent with this finding, as the patient died approximately 46 h after he was admitted to hospital. The cause of death in this case has been attributed to fatal exsanguination from the upper gastrointestinal tract. All other potential sources of bleeding from the gastrointestinal tract were excluded by autopsy. The fatal blood loss was facilitated by coagulopathy due to the preexisting alcoholic liver cirrhosis, as well as liver failure caused by re-warming [3]. The mucosal necrosis of the distal section of the esophagus may represent a delayed complication of V. Živkovic S. Nikolic (&) Institute of Forensic Medicine, University of Belgrade School of Medicine, 31a Deligradska str., 11000 Belgrade, Serbia e-mail: bobanvladislav@yahoo.com; slobodan.nikolic@mfub.bg.ac.rs

Properties of Plastic Bonded Agricultural – Waste Composites, I: Charcoal and Wood-Dust Separately Bonded Composites

Eleven (11) composites, are unfilled and five each filled with varying contents of charcoal and wood dust separating bonded with melted spent thermoplastics have been compounded and their compressive strength, density, specific gravity, percentage shrinkage and percentage absorption determined.Composite density ranges (0.83-0.94)g/cm 3 , compressive strength from (6.92-16.14)n/mm 2 , percentage shrinkage from (1.01-4.76)% and percentage water absorption from (1.75-15.75)%. These results suggest that these composites (i) meet the allowable American standard for test and measurement (ASTM) for ceramic floor and wall tiles in compressor strength (0.2-22.1)minimum, % shrinkage (maximum 15%) and water absorption (maximum 16%) (ii)are appreciably strong compare to the gmelina-wood/cement composite and (iii) if comprehensively examined, composites may be useful in the building industry for the manufacture of tiles and boards and even compete favorably with the wood cement composites. Keywords: Compressive strength, % shrinkage, % absorption, thermoplastic,tiles. I. Introduction The reinforcement of inorganic matrices for improved structural integrity with linigocellulose fluids materials is an old option. Inorganic builders such as Portland cement have been used in building elements. Example of the different types of inorganic bonded wood composite industrially produced are magnesium bonded composite panel (1,2). They are used as particle partitioning, cladding, wall lining and paneling and roofing of floor base (3-5) The use of cement builder in the production of particle boards has aroused interest lately probably because of the shortage and increase in the price of synthetic resin and the desire of develop boards that are suitable foe the exterior applications. The needed raw materials (cement and wood) are readily available in developing countries and the production technology is relatively simple. The cement bonded particle boards is reported (2, 6-8) to have better resistance to impact loading when compared with asbestos board stiffer than the unbound with a bond strength that increase progressively with period of exposure to structural weathering. One of the many problems with cement bonded particle is that of which relates to the weight of the board. Commercially, the board is manufactured within the density range of 1100-1300kg/m 3 and with cement wood ratios ranging between 2.75 -3.00 cement to 1.00 of wood on weight basis (9). The large quality of cement per unit weight of wood employed in the board manufacture makes the resultant board to be heavy. It has been noted that the characteristically high density of the board is a possible limitation to the boards use particular in the areas where weight saving is essential. Deppe (10) noted the need for research effort directed towards finding ways of reducing density of the board while at the same time improving the strength of the board.This need is the aim of the present work. The sale of pure water in plastic sachets without effective management of the sachet after the consumption of the water contains has resulted in environmental pollution caused by the non-biodegradable spent purer water sachet particularly in our cities in this country. In an attempt to control the menace, the spent sachet has been used as a binder in the production of particle boards separately consisting of charcoal and wood dust. The compressive strength, % absorption and % shrinkage of the composites are reported in this write up. EXPERIMENTAL Materials spent pure sachet were collected from restaurants, washed and sun dried. Filters: (a) Charcoal was bought at the Erekesan market Akure, washed, sun dried, crushed and sieved with endecotte sieve into an appropriate particle size and stored at 105

Influência da incorporação de resíduo de rocha ornamental sobre as propriedades e microestrutura sinterizada de piso cerâmico

O Brasil é um dos maiores produtores e consumidores de rochas ornamentais no mundo. No entanto, a indústria de rochas ornamentais gera enormes quantidades de resíduos sólidos na forma de pó fino não biodegradável. No século XXI o grande desafio do setor de rochas ornamentais é o descarte final deste abundante resíduo de forma ambientalmente correta. Os resíduos de rochas ornamentais são ricos em materiais fundentes, que promovem a formação de fase líquida e auxiliam na densificação de materiais cerâmicos tradicionais. Neste trabalho foi avaliada a possibilidade de utilização de resíduo de rocha ornamental como um material de fluxo em composição para fabricação de piso cerâmico vitrificado de alta qualidade. As massas cerâmicas contendo até 45 % em peso de resíduo de rocha ornamental foram preparadas pelo processo via seca. Peças cerâmicas prismáticas foram preparadas por prensagem uniaxial a 50 MPa e sinterizadas a 1230 ºC usando um ciclo de queima rápida. As seguintes propriedades física e mecânica foram determinadas: retração linear, absorção de água, massa específica aparente, porosidade aparente e tensão de ruptura a flexão. A microestrutura sinterizada foi acompanhada por microscopia eletrônica de varredura e as fases cristalinas foram identificadas por difração de raios-X. Os resultados mostram que o efeito da adição do resíduo de rocha ornamental foi o de promover maior densificação e propriedades melhoradas dos pisos cerâmicos vitrificados.

基于机器视觉的大幅面陶瓷地砖尺寸测量研究

基于机器视觉的大幅面陶瓷地砖尺寸测量研究

Microanalytical characterization of decorations in handmade ancient floor tiles using inductively coupled plasma optical emission spectrometry (ICP-OES)

In this study a total of 114 glazed decorations of 42 ceramic floor tiles, manufactured in Sicily from the 16th to the 21th AD, were investigated. The micro sampling method, proposed by us, using a cotton swab soaked in hydrofluoric acid, includes advantages of high sensitivity, high selectivity, simplicity, speed, not expensive and can be considered non-destructive because the point of sampling remains invisible to the human eye. ICP-OES technique was used in this study. Twenty-four elements (Al, As, B, Be, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Ni, Pb, Sb, Se, Si, Sn, Ti, V and Zn) were determined in each colored enamel.Enameled decorations in Sicilian tiles were varied in tones and chromatic effects, obtained with a limited number compounds of cobalt, copper, iron, manganese, tin, and in the artifacts following the year 1920, also titanium. An important remark is that some of the colors, such as black, orange, purple and brown were prepared using the same metals, while white, light blue, blue and green were obtained with different elements. The adoption of different recipes for the same color suggests the presence of several laboratories of ceramists working in Sicily who had preferences for different methods for the production of their enameled artifacts.Concerning the opacifier, the high amounts of lead and antimony, only in a case, indicate the use of lead antimonate (Pb2Sb2O7). Black decorations were present in several of the analyzed samples and in most of them were identified mixtures of black iron and manganese oxides. The green decorations appear to have been prepared with copper oxide; lighter hue samples contained additional amounts of zinc and/or barium compounds. Considering all the samples, meanly, iron predominates in yellow decorations, only a sample contains large amounts of Cd, Zn and very little Sb, which suggests the use of the pigments ZnO (as white) and CdS as cadmium yellow. For all samples, except one, we can exclude the use of pigments containing chromium.

Study on the Fatigue Life of Fully-Automatic Hydraulic Press Pull Rods Based on Finite Element and Mechanical Materials

Fully-automatic hydraulic press is one of the key mechanical equipments of ceramic wall and floor tiles production line. The four pull rods of the frame withstand the all work force when it works, so took a type of fully-automatic hydraulic press as the object of study, established the 3D model of its pull rods by CAD software Pro-E, and then import them into finite element analysis software to analysis the value and distribution of the stress and strain, finnly studied the fatigue life of the pull rods according to the finite element static analysis result and the S-N curve of the pull rods material by using ANSYS fatigue analysis module. The methods and conclusions have practical significance to understand the hydraulic press structure and improve on the structure design and life assessment of the fully-automatic hydraulic press beam.

Utilization of granodiorite in the production of porcelain stoneware tiles

In the present study, the use of granodiorite, as fluxing agent in a body mix for stoneware ceramic tiles production, was assessed. Four batches were formulated using clay from Khaboba, and natural granodiorite from Saint Katherine, Sinai, Egypt. The batches were tailored to completely replace both feldspatic and inert components of stoneware ceramic tiles. Densification was studied according to ISO rules, while sinterability was estimated by optical dilatometry. The dependence of microstructure and mechanical properties of stoneware ceramic tiles on granodiorite content was discussed. Strength measurements showed that increasing granodiorite content the bending strength of the bodies increased. In particular the studied batches can be used for the production of industrial fast firing tiles. The obtained ceramic tiles possess properties similar to commercial ceramic floor and/or wall tiles.

Relationship between Young's modulus and temperature in porcelain tiles

Abstract A focused research was conducted on samples prepared from an industrial porcelain tile composition containing quartz, used to produce ceramic floor tiles, with the aim of evaluating the variation of fired specimens’ Young's modulus with temperature. These samples were fired in controlled laboratory conditions so that specimens with pre-existing cracks were obtained and subject to non-destructive in situ thermo-mechanical measurements (impulse excitation technique) in the 22–700 °C temperature range during heating and cooling processes in order to find evidences to explain the hysteresis phenomenon in the Young's modulus versus temperature curve. The observed irreversible Young's modulus may be directly related to the pre-existent cracks that on heating and cooling are closed and opened up respectively, changing thus the Young's modulus which is well characterized by a hysteresis cycle.

Non-accidental collision followed by dental trauma: associated factors

The aim of the present cross-sectional survey was to assess factors associated with non-accidental collision followed by dental trauma among adolescents in the city of Diamantina, Brazil. A total of 387 students from 12 to 15 years of age (mean = 14 SD = 0.9) were randomly selected. The study was carried out in two stages. Firstly, data were collected through dental examinations of permanent incisors. Secondly, a thorough interview was held with 85 adolescents who exhibited dental trauma in the dental examinations. The interview consisted of a detailed description of the incident and physical environment in which it occurred. Descriptive analysis and the chi-square test (P < 0.05) were performed. The prevalence of dental injury was 22% (n = 85). Dental trauma was more prevalent in boys (P = 0.001) and individuals with overjet >3 mm (P = 0.007) and inadequate lip coverage (P = 0.013). Analysis of the event revealed that 22.3% of the cases of dental trauma occurred because of non-accidental collision. Non-accidental collision followed by injury occurred mainly at school (P < 0.001) and in an environment with a concrete, tiled or ceramic floor (P = 0.001). No statistically significant associations were found between non-accidental collision and gender, age or mother's schooling. It was concluded that the non-accidental collisions happened especially at school and in indoor environments with a concrete, tiled or ceramic floor.