Study on the Bearing Characteristics and Application of the Filling Body in Original Roadway Filling and Nonpillar Driving

Original roadway filling and nonpillar driving can effectively solve the difficulty facing mining replacement in the stope of deep mines. As the bearing characteristics of the filling body in the original roadway play a crucial role in the structural stability of the overlying strata, with the recovery and geological conditions of 62210 working face in Xinzhuangzi Coal Mine, Huainan Mining Group, China, as the background, this study analyzed the stability characteristics of the filling body in the original roadway through comprehensive research methods of theoretical analysis, laboratory tests, and onsite monitoring. The results disclose that the filling body in the original roadway should boost early strength, strong bearing capacity, and long-term weakening. When the water-cement ratios are 1 : 1, 1.5 : 1, 2 : 1, 2.5 : 1, and 3 : 1, the strengths of the filling body are 1.12 MPa, 0.93 MPa, 0.57 MPa, 0.33 MPa, and 0.21 MPa at 2 h and 5.63 MPa, 4.66 MPa, 2.87 MPa, 1.65 MPa, and 1.02 MPa at 48 h, respectively. The strengths surge by 5 times within 2 d on the whole and reach the maximum at about 7 d, i.e., 8.12 MPa, 6.91 MPa, 6.60 MPa, 3.95 MPa, and 2.20 MPa, respectively. As time goes, the water content of the filling body gradually decreases and the compressive strength plunges. This demonstrates that the rapid solidification material with a high water content can satisfy the requirements of the bearing characteristics of the original roadway filling body. With reference to numerical simulation and the data monitored onsite, it can be known that the filling body in the original roadway can support the roof effectively and control the surrounding rock deformation of newly excavated roadways in the lower section. The research results provide theoretical guidance for coal mining under similar geological conditions and serve as reference for safe and efficient coal mining.

Preparing Modified Bonding Representations Inventory: Challenges and Solution

Collecting data on learners' performance in different chemistry contents and analysing them to identify their knowledge and understanding in related content areas is a major task of Chemistry Education Research. The data collection process on the learners' content knowledge and understanding of content knowledge requires a standard measuring tool. The preparation of standardized tools for measuring academic achievement requires computer software. All software used in the standardization of a tool comes at a cost and requires training for the researcher involved in handling the situation, which can impede the smooth running of a project. The same was the situation when the author was working on modifying the bonding representations inventory (BRI) for its local use in South Africa. The data analysis laboratory was situated in a different city, 500 km away from the researcher's field of work. Owing to the long distance and communication delay, the author was concerned with delays in the project. It is known that necessity, which can create an opportunity. The Microsoft Excel (MS-Excel) platform was used for standardizing the modified BRI because MS-Excel is available as a standard in MS-Office on the Windows platform. This paper presents a fact. That, a tool can be standardized by using MS-Excel without any complexity.

Granulometric composition research of mine rocks as a material for backfilling the mined-out area in coal mines

Purpose. Determination of the granulometric characteristics and loosening coefficient of mine rocks formed during stope operations from undercutting the bottom rocks as a potential backfill material based on a set of mine and laboratory research. Methods. To do research, a complex methodology is used, which includes a photographic surveying the mass of destroyed rocks from undercutting the bottom rocks in mine conditions, digital processing and determining the granulometric composition in the software package, sampling the mine rocks at the surface complex, and reconstructing the granulometric composition, similar to the full-scale mine conditions in the laboratory. Sieve analysis, laboratory balance and laboratory container are used to determine the granulometric composition and loosening coefficient. Findings. The dependence between the granulometric composition and loosening coefficient of rocks, which increases by 33% within fractions of 0-50 mm and by 8% within fractions of 50-140 mm, has been revealed. It has been determined that the destroyed rocks in the face within fractions of 0-140 mm have a bulk density of 1.28 g/cm3, loosening coefficient of 1.7, the voidness of and the maximum reserve for the backfill mass compaction with mine rocks is 41.9%. An analytical assessment of the volumes of the formed cavities of the mined-out area in the longwall face and gobed mine workings, as well as the prospects and completeness of their filling with mine rocks have been performed. Originality. It has been determined that the loosening coefficient of mine rocks destroyed in the stope face by KA-200 shearer changes according to the logarithmic dependence on their granulometric composition. This makes it possible to control the granulometric characteristics of the backfill material to achieve the maximum density of the backfill mass. Practical implications. Further research can serve as a basis for determining the rational parameters for the formation and placement of backfill masses during complex-mechanized selective mining of coal seams using various methods of backfilling operations.

The influence of social isolation on the incidence of positivity in covid-19 tests in a metropolitan region of São Paulo, Brazil

Introduction: With the arrival of the SARS-CoV-2 (Coronavirus 2 of severe acute respiratory syndrome) pandemic in Brazil, especially in the city of São Paulo, there was a need to apply social isolation policies associated with testing, covering all municipalities. The Clinical Analysis Laboratory of Centro Universitário FMABC was one of the first laboratories to receive certification and qualification to perform RT-PCR (reverse transcriptase reaction followed by polymerase chain reaction) tests in the metropolitan region of São Paulo. Objective: Aim to analyze the influence of adopting social isolation on the incidence of positivity in COVID-19 tests in the metropolitan region of São Paulo, Brazil. Methods: a descriptive study carried out from March to May 2020, epidemiological data were collected from each unit served and organized by the data controllership team of the Clinical Analysis Laboratory of FMABC. Epidemiological, demographic, and laboratory data were extracted from the Matrix® outpatient data management system. Clinically suspected cases and confirmed by laboratory tests (RT-PCR and serological tests) were entered. The tests were divided into serological tests using the RT-PCR molecular test, on samples of nasopharyngeal mucosal scrapings collected with sterile Swab. Results: It were evaluated PCR test and antibody presence (IgA, IgM and IgG) in blood samples of 16.297 patients. 22.718 tests were performed for the diagnosis of COVID-19, both RT-PCR (10.410 tests) and serological tests to detect anti-SARS-CoV-2 antibodies, IgA, IgM and IgG, a total of 16.297 patients were assessed, 63% women and 37% men. It was observed that the social isolation policies adopted during this period contained the massive expansion of contamination, at least while the social isolation rates were above 55%. Conclusion: The data of this study demonstrated the effectiveness of social isolation in containing the positive contamination of SARS-CoV-2 in the metropolitan region of São Paulo, at least for the first three months.

Socioeconomic impacts of sand harvesting along the Sanaga River in Nkol’Ossananga locality (Yaoundé-Cameroon): a vision toward a mechanized operation for sustainable exploitation

This paper presents the impacts of Nkol’Ossananga sand harvesting on social live and local economy based on field investigations and data analysis. Laboratory analysis of sand samples from the site has shown that the cleanliness of the Nkol’Ossananga sand nears 100%. This means that Nkol’Ossananga sand is pure and clean, most appropriate for house constructions and building engineering. The activity produces incomes to all actors of the chain value and government. Incomes generated are used by artisans to build their houses, buy some electronic devices, and take care of their families or to capitalize in their business investigation. In spite of the positive impacts presumed, Nkol’Ossananga sand harvesting also stands as the origin of many negative impacts including cultural brewing, delinquency, precocious abandon of studies and abandon of agriculture. The exploitation is done with rudimentary tools and poor technics thereby exposing artisans to several risks and illnesses. For sustainable exploitation, a mechanized operation has to be implemented. This kind of exploitation is the one that will improve the working conditions, increase production and incomes of workers as similar as that of government, and also reduces negative environmental impacts. Key words: Nkol’Ossananga sand, rudimentary tools and poor technics, incomes, negative impacts, sustainable exploitation, mechanized operation. Cet article présente les impacts sociaux et économiques de l’exploitation artisanale du sable de Nkol’Ossananga sur la base d’enquêtes de terrain et d’analyses de données. L’analyse en laboratoire des échantillons de sable collectés sur le site a montré que la propreté du sable de Nkol’Ossananga avoisine 100%. Ce qui signifie que le sable de Nkol’Ossananga est approprié pour le BTP et le génie civil. L'activité génère des revenus importants à tous les acteurs de la chaîne de production et le gouvernement. Les revenus générés sont utilisés par les artisans pour se faire construire leur maison d’habitation, acheter des appareils électroniques, prendre soin de leur famille ou alors sont capitalisés dans le commerce. Malgré les impacts positifs susmentionnés, l’exploitation artisanale du sable de Nkol’Ossananga est également source du brassage culturel, de la délinquance juvénile et de l’abandon précoce des études. Pour une exploitation durable, l’exploitation semi-mécanisée est envisageable. Ce type d'exploitation est celui qui pourra améliorer les conditions de travail des artisans, augmenter leur production et leurs revenus au même titre que ceux du gouvernement, et réduira par ricochet les impacts négatifs.

Head Accelerations during a 1-on-1 Rugby Tackling Drill Performed by Experienced Rugby Union Players

Rugby Union is a popular sport played by males and females worldwide, from junior to elite levels. The highly physical skill of tackling occurs every few seconds throughout a match and various injuries associated with tackling are relatively common. Of particular interest are head injuries that result in a concussion. Recently, repeated non-injurious head impacts in sport have attracted the attention of researchers interested in brain health. Therefore, this study assessed head movement during repeated rugby tackle drills among experienced Rugby Union players. Experienced male and female participants performed 15 1-on-1 tackles in a motion analysis laboratory to measure the head movements of the ball carrier and tackler during each tackle, using three-dimensional motion capture. The average peak acceleration of the head for ball carriers was 28.9 ± 24.08 g and 36.67 ± 28.91 g for the tacklers. This study found that the type of head impacts common while performing a tackle in Rugby Union are similar to those experienced by soccer players during heading, which has been found to alter brain function that lasts hours after the event. This has important implications for player health and suggests that mitigation strategies should be considered for Rugby Union.

Quality of forage seeds sold in the state of Mato Grosso

The acquisition of high-quality seeds is essential to successfully implant areas with forage. However, to be commercialized, they must meet the minimum quality standards established by law. Inspections are necessary to guarantee the quality and identity of the commercialized seed. Thus, the objective was to evaluate the quality of tropical forage seed species collected in 2018, in the state of Mato Grosso. The survey was based on data from officers’ samples, in commercial establishments and fine consumers, collected during inspections conducted by the Agricultural Defense Institute of the State of Mato Grosso - INDEA-MT and subsequently analyzed by the Guilherme de Abreu Lima Seed Analysis Laboratory (LASGAL). Purity analysis, determination of other seeds by number (DOSN), germination test and tetrazolium test were carried out. The study showed that 75% of the analyzed samples reached the minimum requirements for commercialization in terms of physical purity; 95% of the samples were within the standard for physiological quality determined by law; and 91.9% did not exceed the maximum limits regarding the number of undesirable seeds present in a sample. In general, 36.1% of the total samples analyzed did not conform in some way to quality standards, therefore were not appropriate for commercialization.