Plastic deformation of rough rolling contact: An experimental and numerical investigation

Quantifying the surface roughness evolution in contacts is a crucial step in the fatigue prediction process. Surfaces are initially conditioned by the running-in process and later altered by surface fatigue. The aim of this study is to understand and predict the evolution of the micro-geometry in the first few over-rolling cycles. Numerical predictions are validated by experiments. A major difficulty in understanding surface degradation is the measurement of the surface roughness evolution at the relevant scales. A twin disc micro-test rig, called μMag, was specially designed for this kind of analysis. The μMag allows the “in situ” observation of changes in the disc surface during interrupted tests, thus avoiding dismounting the specimens, which is a major cause of inaccuracy. The new method also maintains the relative position of the two discs. The precision of the measurements allows one to use the initial surface micro-geometry as input for the numerical contact calculation. Thus, the plastic deformation of the surfaces can be measured during the first cycles and compared to the numerical prediction. Results show a very good agreement between numerical predictions and experimental measurements

Naturally Occurring Asbestos: the problem of quantification

L'abstract è presente nell'allegato / the abstract is in the attachmen

Comminution effects on mineral grade distribution

Every mining operations is followed by a beneficiation process aimed to deliver quality material to the transformation industry. Most of mineral processing is focused on comminution and grinding of extracted ore that is crucial for the following separation steps in order to divide gangue from valuable minerals. Comminution is the most energy consuming phase and the quality of the results is strictly related to the characteristic of the material under treatment. A preliminary study has been performed to understand the crushing behaviour of a mixed sulphide ore, containing galena and sphalerite, and how target minerals grade distributes among the different sized products of the process. Ore samples have been examined and characterized by means of thin sections observation and SEM analyses for the determination of the grain liberation size, while XRD quantitative analyses have been performed for the definition of the grades. The crushing circuit selected comprises lab-scale impact crusher, jaw crusher, disk mill and rod mill. The products collected are below the free grain size threshold and granulometric analyses have been performed. Comminution products have been divided in size classes suitable for flotation separation, ranging between 0.250 and 0.075mm and XRD analyses showed a variable mineral grade distribution varying with the reduction in dimension of the products. This important trend should be considered for further investigation related to an efficient froth flotation separation

Desert within a city: Exploring the relationship between food security, diet, and body mass index

Background: Food deserts are areas of decreased access to nutritious and affordable foods. Residing within a defined food desert is thought to decrease consumption of produce, dairy, and whole grains and increase consumption of energy-dense foods as well as body mass index (BMI). Objective: The purpose of this study was to determine the effects of the level of food security on consumption of fruits, vegetables, dairy, whole grains, high-sugar foods, high-fat foods, and BMI. Design: A one-time, self-administered data collection packet was sent to residents of a food desert. The Dietary Screener Questionnaire was utilized to determine the average daily consumption of fruit, vegetables, dairy, whole grains, high-sugar foods, and high-fat foods. Additional questions were inquired to determine BMI, education level, income level, employment status, grocery shopping frequency, and vehicle accessibility. Participants: A sample population was recruited from a food desert located in Bloomington, Illinois. Surveys were sent via the United States Postal Service to 953 residents. Inclusion criteria included: at least 18 years of age, reside within the defined food desert tract, and ability to read and understand English. Participants were of any race, ethnicity, education level, or income level. Results: Demographic findings revealed the sample population were predominately food secure individuals with higher education levels and medium to high incomes. Statistical analysis revealed no significant correlations between level of food security, average consumption of fruit, vegetables, dairy, whole grains, energy-dense foods, or BMI. However, significant correlations were exposed between food security and mode of transportation (r = .277, p = .017), grocery shopping frequency (r = .330, p = .000) and income (r = -.345, p = .000). Significant correlations were found between education level and BMI (r = -.253, p = .009) and education level and high fat food intake (r = -.233, p = .004). More significant correlations were found between food groups, revealing dietary patterns and trends. Conclusions: Findings of this study emphasize the importance of continued research of food deserts and food security. Individualized intervention strategies have the ability to address the specific needs of food desert residents, which may vary depending on the food desert. Significant correlations were found between food security and vehicle accessibility, grocery shopping frequency, and income as well as between level of education and BMI. While food insecurity was not found to have a direct correlation to diet or BMI, its correlation to other variables suggest it could have an indirect affect

Evaluation of errors in quantitative determination of asbestos in rock

The quantitative determination of the content of asbestos in rock matrices is a complex operation which is susceptible to important errors. The principal methodologies for the analysis are Scanning Electron Microscopy (SEM) and Phase Contrast Optical Microscopy (PCOM). Despite the PCOM resolution is inferior to that of SEM, PCOM analysis has several advantages, including more representativity of the analyzed sample, more effective recognition of chrysotile and a lower cost. The DIATI LAA internal methodology for the analysis in PCOM is based on a mild grinding of a rock sample, its subdivision in 5-6 grain size classes smaller than 2 mm and a subsequent microscopic analysis of a portion of each class. The PCOM is based on the optical properties of asbestos and of the liquids with note refractive index in which the particles in analysis are immersed. The error evaluation in the analysis of rock samples, contrary to the analysis of airborne filters, cannot be based on a statistical distribution. In fact for airborne filters a binomial distribution (Poisson), which theoretically defines the variation in the count of fibers resulting from the observation of analysis fields, chosen randomly on the filter, can be applied. The analysis in rock matrices instead cannot lean on any statistical distribution because the most important object of the analysis is the size of the of asbestiform fibers and bundles of fibers observed and the resulting relationship between the weights of the fibrous component compared to the one granular. The error evaluation generally provided by public and private institutions varies between 50 and 150 percent, but there are not, however, specific studies that discuss the origin of the error or that link it to the asbestos content. Our work aims to provide a reliable estimation of the error in relation to the applied methodologies and to the total content of asbestos, especially for the values close to the legal limits. The error assessments must be made through the repetition of the same analysis on the same sample to try to estimate the error on the representativeness of the sample and the error related to the sensitivity of the operator, in order to provide a sufficiently reliable uncertainty of the method. We used about 30 natural rock samples with different asbestos content, performing 3 analysis on each sample to obtain a trend sufficiently representative of the percentage. Furthermore we made on one chosen sample 10 repetition of the analysis to try to define more specifically the error of the methodology

Improving Skin Cancer Screening in Primary Care

Skin cancer is one of the most common forms of cancer in the United States, with melanoma having the highest rate of mortality of all forms of skin cancer (CDC, 2019). However, there is hesitancy among primary care providers to perform skin cancer screenings (Oliveria et al., 2011). Prevention and early detection of melanoma is key. Melanoma has been known to be highly curable when found early. This makes early detection even more important in order to prevent metastasis and potential mortality (Bruce et al, 2017). The use of targeted screening tools can potentially save lives when utilized in primary care. This project was carried out in a rural, Midwestern public health clinic. The implementation of the SAMScore questionnaire was completed for adult patients seen during office visits from August 24, 2020 through November 25, 2020. Providers involved in the project reviewed survey answers with patients to determine level of risk. Dermatology referrals were recommended to those found to be high-risk. All patients involved in this project were provided education on skin cancer and preventive measures. Of the 19 patients screened, four were found to be high-risk for melanoma with one patient being diagnosed with melanoma after referral to dermatology. This project provided not only an educational opportunity for patients, but it also brought forth a screening method that is quick, concise, and financially feasible. Although this project consisted of a small sample size, future replications can easily be implemented in a larger and more diverse primary care setting

Comminution Effects on Mineral-Grade Distribution: The Case of an MVT Lead-Zinc Ore Deposit

Every mining operation is followed by a beneficiation process aimed at delivering quality materials to the transformation industry. Mainly, in order to separate valuable minerals from gangue in mineral processing, the crushing and grinding of extracted ore are crucial operations for the following separation steps. Comminution is the most energy-consuming operation in mining, and the quality of the results is strictly related to the characteristic of the material under treatment, the type of equipment used in comminution, and the circuit design adopted. A preliminary study was performed in order to understand the crushing behavior under different comminution forces of a high-grade mixed Zn-Pb sulfide ore sample, collected in a Mississippi-Valley Type (MVT) deposit, and the distribution of the target minerals among the products of the process. Ore samples were examined and characterized through thin section observation and SEM analyses for the determination of grain size and texture features, while X-ray powder diffraction (XRPD) quantitative analyses were performed for the definition of target mineral concentrations of comminuted product samples. The selected crushing and grinding circuit comprised lab-scale equipment. For each stage of the process, products below the estimated free-grain size threshold were collected, and particle size analyses were carried out. Comminution products were divided into size distribution classes suitable for further separation operations, and XRPD analyses showed a mineral-grade distribution varying with the dimensions of the products. Characterization of the ore material after crushing and grinding force applications in terms of the distribution of target minerals among different-sized classes was achieved. The important trends highlighted should be considered for further investigation related to an efficient separation

A multi-model X-FEM strategy dedicated to frictional crack growth under cyclic fretting fatigue loadings.

International audienceA 2D X-FEM/LATIN numerical model (eXtended Finite Element Method/Large Time Increment method) is proposed in this paper for the analysis of fretting fatigue problems and the simulation of the crack propagation under such loadings. The half-analytical two-body contact analysis allows to capture accurately the pressure and the cyclic tractions exerted at the interface that induce non-proportional multi-axial loading. These distributions are then used as input data for determining critical location for crack initiation and crack inclination based on Dang Van's criterion. The frictional contact conditions of the fretting fatigue cracks have an important impact on the crack behaviour. In this respect, contact with friction between the crack faces is finely modeled within the X-FEM frame. The obtained results are compared and validated with a half-analytical reference model. The numerical simulations reveal the robustness and the efficiency of the proposed approach for a wide range of fretting loadings and friction coefficients values along crack faces. The crack growth directions are then predicted accurately based on the use of criteria adapted to multi-axial non-proportional fatigue. Four cases dealing with crack propagation are then presented. It is shown how the crack length, the tangential loading modify the crack path during the propagation process

Bud Fall Induction in Clove (Syzygium Aromaticum)

ABSTRACT The abstract is to be in fully-justifie