---

Aims: Reports show that vaccination against influenza could elicit nonspecific immune reactions against coronavirus disease-19 (COVID-19). The present research aimed to evaluate the prevalence of COVID-19 disease among the staff of Shahid Beheshti hospital in Kashan despite vaccination against influenza.
Materials & Methods: This study was performed on 1400 employees of Shahid Beheshti hospital in Kashan from February to August 2020. Personnel whose disease was confirmed by PCR test or CT scan were considered to have COVID-19. In the present research, the relationship between influenza vaccination and the incidence of COVID-19 infection was evaluated. The collected data were analyzed by SPSS software Version 26.
Findings: Out of a total of 1400 hospital personnel participating in this study, 272 people were diagnosed as COVID-19. Among 272 patients, 23 (8.45%) cases were vaccinated. The average age of vaccinated patients was 33.48 ± 12.72 years, of whom 14 (60.87%) patients were female. Vaccination was significantly associated with prevention of COVID-19 infection (p< .05). The study of odds ratio (OR) to evaluate the effect of vaccination showed that the OR was 0.61 (95% CI: 0.39- 0.97). There was a significant difference in SpO₂, type of treatment, and lung involvement based on CT between the two groups of vaccinated and unvaccinated COVID-19 patients (p< .05).
Conclusion: In vaccinated group, COVID-19 was lower than of the no influenza vaccinated group. According to the results, the use of influenza vaccine as an effective vaccine against the new coronavirus strains could be helpful in controlling the disease.

---

Plasma assisted machining (PAM) is a method to improve machinability of hard turning. The process of plasma assisted machining for turning applications utilizes a high-temperature plasma arc to provide a controlled source of localized heat, which softens only that small portion of the work material removed by the cutting tool. The goal of this study is to present a methodology for determination cutting force during plasma enhanced turning of hardened steel AISI 4140. In this regard, a finite differential model was made to estimate the uncut chip temperature under different plasma currents, cutting speeds and feeds during PAM. A mechanistic model developed to estimate cutting force under different PAM conditions by considering shear stresses in the primary, secondary shear zones and force on the tool edge. The proposed model was calibrated with experimental hard turning data, and further validated over practical PAM conditions. Mean errors of predicted values and experimental data is lower than 10 percent. It is shown that PAM can decrease main cutting force in comparison to convectional to 40 percent in turning of hardened steel at high levels of uncut chip temperature due to softening the material.

---

Ultrasonic Assisted Magnetic Abrasive Finishing (UAMAF) is the combination of magnetic abrasive finishing (MAF) and ultrasonic vibrations to finish the surfaces in nanometer scale. In this work, the experimental setup for UAMAF was prepared to finish inner surface of tube workpiec. By using experimental setup, the effect of experimental parameters such as ultrasonic vibrations, mesh number, the type of abrasives (SiC and diamond) and finishing time has been investigated on the changes in the surface roughness of AL6061 tube workpiece. The experimental results showed that the use of ultrasonic vibrations has a significant effect on reducing the surface roughness. The changes in surface roughness increases with the mesh number from 90 to 800 and finishing time from 30s to 5 min. Among two types of abrasives, diamond showed the best performance in finishing. Optical microscopy images showed that the dominant finishing mechanism in MAF for coarse grains (with mesh size of 90 and 120) is two body and for fine grains (with mesh size of 220, 400 and 800) is three body. In UAMAF for both of the coarse and fine grains the dominant finishing mechanism is three body.

---

Metal and especially aluminum mirrors have wide applications in the optical industry due to their desirable properties, hence requiring very high polished surfaces. One of the methods of preparing aluminum mirrors is single-point diamond turning. In this research, the manufacturing process of 6061-grade aluminum mirrors has been studied using diamond turning and consequent polishing process in order to reach surfaces with acceptable optical properties. In the first part, the effective range of turning parameters was determined. The results showed that the feed values less than 5 µm/rev, the cutting-edge radius between 0.2 and 0.8 mm, and the rotational speed of 2250 rpm have a greater effect on the surface roughness. In the second part of the research, initially, the turning process was performed with effective parameters and then the polishing process was applied as the final finishing process. Surface finish is evaluated by surface roughness and surface interferometry parameters. The results showed that the smaller surface roughness after the diamond tool turning process led to higher optical properties after the final polishing process. The lowest PV value equal to 0.293 µm was obtained by diamond turning with 3 µm/rev and a cutting-edge radius of 0.8 mm.
 

---

Metal and especially aluminum mirrors have wide applications in the optical industry due to their desirable properties, hence requiring very high polished surfaces. One of the methods of preparing aluminum mirrors is single-point diamond turning. In this research, the manufacturing process of 6061-grade aluminum mirrors has been studied using diamond turning and consequent polishing process in order to reach surfaces with acceptable optical properties. In the first part, the effective range of turning parameters was determined. The results showed that the feed values less than 5 µm/rev, the cutting edge radius between 0.2 and 0.8 mm, and the rotational speed of 2250 rpm have a greater effect on the surface roughness. In the second part of the research, initially, the turning process was performed with effective parameters and then the polishing process was applied as the final finishing process. Surface finish is evaluated by surface roughness and surface interferometry parameters. The results showed that the smaller surface roughness after the diamond tool turning process led to higher optical properties after the final polishing process. The lowest PV value equal to 0.293 µm was obtained by diamond turning with 1.5 µm/rev and a cutting edge radius of 0.8 mm.