Numerical Simulation of Mechanical Characteristics of Roadway Surrounding Rock under Dynamic and Static Loading

Mechanical characteristics of roadway surrounding rock under different stress wave disturbances are the key to design roadway supporting scheme. In this study, the 2802 transportation roadway in Zhangcun Coal Mine is selected as the engineering background. The distribution of stress, displacement, and plastic zone in surrounding rock under the impact of different stress waves is studied. Results show that the stress and displacement of the roof, floor, and coal walls present fluctuating change with time during the stress wave loading process. With the increase of disturbing intensity of stress wave, the resistance ability for stress wave disturbance of the roof is lower than that of the floor, while the resistance ability of two sides is the same. The volume of plastic zone in roadway surrounding rock was calculated by the self-compiled FISH code. The relationship between the plastic zone volume and the stress wave disturbing intensity in different states is explored. The cubic polynomial relationship between the volume and the disturbing intensity in the state of shear_past and tension_past is obtained. Under the simulated condition, the disturbing intensity of stress wave has the greatest influence on the increase of shear_past volume when it equals 11 MPa. While the disturbing intensity of stress wave has the greatest influence on the increase of tension_past volume, it equals 7 MPa. Meanwhile, the relation between stress wave disturbing intensity and surrounding rock stress and displacement is obtained respectively. The achievements provide a theoretical base for roadway surrounding rock support under dynamic and static loading.

Predictive maintenance integrated production scheduling by applying deep generative prognostics models: approach, formulation and solution

To harness the full potential of predictive maintenance (PdM), PdM information has to be used to optimally plan production and maintenance actions. Hence, operation-specific modelling of degradation, i.e. predictions of the health condition under time-varying operational conditions, has to be realized. By utilizing operation-specific degradation information, maintenance and production can be planned with regard to each other and thus, predictive maintenance integrated production scheduling (PdM-IPS) is enabled. This publication proposes a novel PdM-IPS approach consisting of two interacting modules: an operation-specific Prognostics and Health Management (PHM) module and an integrated production scheduling and maintenance planning (IPSMP) module. Specifically, the mathematical problem of the IPSMP module based on an extended version of the maintenance integrated flexible job shop problem is formulated. A two-stage genetic algorithm to efficiently solve this problem is designed and subsequently applied to simulated condition monitoring, as well as real industrial data. Results indicate that the approach is able to find feasible high quality PdM integrated production schedules.

The effect of different work-rest schedules on ergonomic risk in poultry slaughterhouse workers

BACKGROUND: Rest breaks are an organizational measure to reduce the high risk of upper limb work-related musculoskeletal disorders (UL-WMSDs) to which slaughterhouse workers are subject. OBJECTIVE: To analyze the effect of different work-rest schedules on ergonomic risk in poultry slaughterhouse workers. METHODS: A total of 36 repetitive tasks was selected in a Brazilian slaughterhouse. Using the Occupational Repetitive Action (OCRA) Checklist, the level of exposure of workers to risk factors of UL-WMSDs in two work-rest schedules was evaluated. In the real condition, 6 rest breaks of 10 minutes were performed, and in the simulated condition, 3 rest breaks of 20 minutes. RESULTS: The right side of the body presented a higher score on the OCRA Checklist (72%of the tasks) than the left side (p = 0.037) in the real condition. Additionally, the OCRA score (18.3±2.5) was significantly lower (p < 0.001) than the simulated condition (21.9±3.0). It was verified that the risk level in simulated condition remained the same in 13 (36%) tasks, while in 23 (64%) tasks there was an increase in the risk level. CONCLUSIONS: Work-rest schedule of 6 breaks of 10 minutes was better than 3 breaks of 20 minutes to reduce the risk of UL-WMSDs in poultry slaughterhouse workers.

Experimental Study on Chloride Stress Corrosion Cracking Sensitivity of 316L Stainless Steel

The slow–strain-rate tensile test was used to study the chloride stress corrosion cracking (SSC) behavior of 316L stainless steel under the simulated condition of a CO2 gas field in the Tarim Basin, and the effects of CO2, Cl− concentration, and temperature on the sensitivity of SCC were discussed. The results show that the increase of CO2 content has no apparent influence on the chloride SCC sensitivity of 316L stainless steel. With the rise in temperature, chloride SCC’s sensitivity increases, and the change in the SCC sensitivity index Iscc is noticeable. When the concentration of Cl− increases, the sensitivity of chloride SCC also increases. The degree of influence of the three factors on the experimental results can be ranked as follows: temperature>Cl− > CO2. In this experiment, when the partial pressure of CO2 is 0.1 MPa, the temperature is 65°C, the concentration of Cl− is 1,20,000 mg/L, and Iscc of 316L tensile samples has a maximum of 26.8%.

Through The Back Door: Expiratory Accumulation Of SARS-Cov-2 In The Olfactory Mucosa As Mechanism For CNS Penetration

IntroductionSARS-CoV-2 is a respiratory virus supposed to enter the organism through aerosol or fomite transmission to the nose, eyes and oropharynx. It is responsible for various clinical symptoms, including hyposmia and other neurological ones. Current literature suggests the olfactory mucosa as a port of entry to the CNS, but how the virus reaches the olfactory groove is still unknown. Because the first neurological symptoms of invasion (hyposmia) do not correspond to first signs of infection, the hypothesis of direct contact through airborne droplets during primary infection and therefore during inspiration is not plausible. The aim of this study is to evaluate if a secondary spread to the olfactory groove in a retrograde manner during expiration could be more probable.MethodsFour three-dimensional virtual models were obtained from actual CT scans and used to simulate expiratory droplets. The volume mesh consists of 25 million of cells, the simulated condition is a steady expiration, driving a flow rate of 270 ml/s, for a duration of 0.6 seconds. The droplet diameter is of 5 μm.ResultsThe analysis of the simulations shows the virus to have a high probability to be deployed in the rhinopharynx, on the tail of medium and upper turbinates. The possibility for droplets to access the olfactory mucosa during the expiratory phase is lower than other nasal areas, but consistent.DiscussionThe data obtained from these simulations demonstrates the virus can be deployed in the olfactory groove during expiration. Even if the total amount in a single act is scarce, it must be considered it is repeated tens of thousands of times a day, and the source of contamination continuously acts on a timescale of several days. The present results also imply CNS penetration of SARS-CoV-2 through olfactory mucosa might be considered a complication and, consequently, prevention strategies should be considered in diseased patients.

Impact of Microencapsulation on Two Probiotic Strains in Alginate Chitosan and Eudragit S100 Under Gastrointestinal and Normal Conditions

Background: Nanoparticles in biotechnology studies have played a significant role during the recent years and a wide range of them are being applied in food industries to prolong the microorganisms viability for more effective function in food processing and human gut. Methods: The main purpose of this research was evaluating the viability of two bacteria of Lactobacillus casei and Lactobacillus bulgaricus treated through double-coated beads including alginate Chitosan (First coating), and Eudragit S100 (Second coating) in simulated Gastrointestinal (GI) circumstance and yogurt. Free cells were employed as a control test and the results reflected that microencapsulated strains can survive longer than the normal cells. Results: The number of free cells of L. casei and L. bulgaricus respectively decreased from 6.0×106 and 7.2×106 (In the first day) to 4.1×105 and 5.3×106 (In the day 32) in GI condition. Also, in the same intervals of time, the number of double-coated L. casei and L. bulgaricus decreased respectively from 6.9×108 and 7.1×108 to 4.5×107 and 3.1×107 in simulated condition. Furthermore, the pH rate steadily decreased, however, it was more dramatic in the first week, whereas the trend gradually became more moderate in the last two measurements. Conclusion: Results indicated that microencapsulation increases the bacteria viability. Also, the pattern of pH changes was similar for both strains and revealed that the rates of pH and acidity in both double-coated and normal forms are close to the control test in the final measurement.