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Wojciech Stachurski,Jacek Sawicki,Krzysztof Krupanek,Krzysztof Nadolny 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.8 No.4
This article presents the results of experiments concerning a computational fluid dynamics (CFD)/numerical analysis of the flow of air in the grinding zone during the sharpening of the face surface of hob cutters while using the MQL method. The carrying out of a simulation allows one to determine the influence of various settings of the angle of the spray nozzle on the amount of air directly reaching the zone of contact of the grinding wheel with the workpiece, as well as the grinding wheel active surface (GWAS). In the numerical analysis, the ‘SST k-ω ’ model available in the Ansys CFX program was used, and to which the Kato and Lander’s modification was applied. With the aim of verifying the results obtained from the basis of the numerical simulations, experimental testing was conducted. As a verification parameter, the percentage rate of grinding wheel clogging was used. The measurement of clogging was conducted by the optical method taking microscopic images of the grinding wheel active surface (GWAS) and then analysing it which the use of digital processing and image analysis. As a result of the numerical simulations, it was confirmed that the greatest effectiveness in delivering air to the contact zone of the grinding wheel with the workpiece being machined was achieved by setting the nozzle at the lowest of the angles tested (90°). At the same time, the greatest efficiency in delivering air to the grinding wheel active surface was achieved by setting the nozzle at the largest of the angles tested (90°). The experimental tests allowed one to state that the change in the inclination of the spray nozzle does not significantly influence the effectiveness of chip removal from the surface of the intergranular spaces of the grinding wheel. By setting the nozzle at a 90° angle, wall shear stresses τ w have a decisive influence on cleaning the GWAS, while at an angle of 30° the cleaning function is taken on by air being delivered directly into the contact zone of the grinding wheel with the face surface of the hob cutter being sharpened. A comparison of the percentage rates of grinding wheel clogging obtained from using the flood method (WET), as well as the MQL method, indicates the insufficient cleaning ability of the MQL method. A solution to this problem may be the application of additional cleaning nozzles employing streams of compressed air (CA) or cold compressed air (CCA).
Z. GAWRONSKI,A. MALASINSKI,J. SAWICKI 한국자동차공학회 2010 International journal of automotive technology Vol.11 No.1
Recent developments in the aerospace and automotive industries have significantly affected the progress of modern manufacturing technologies, including the heat treatment of gear wheels. This view has been expressed in the works of Gräfen and Edenhofer (1999), Herring and Houghton (1995), Preisser et al. (1998) and Sugiyama et al. (1999). For ecological and economic reasons, however, traditional treatments are still in use. Additionally, the implementation of a new process in the aerospace industry is very difficult due to the safety precautions that are involved in this kind of production. In order to protect the surfaces of components from disadvantageous structural changes related to the hardening process (oxidation, decarburization and carburizing) galvanic copper plating is widely used even though the process is known to be harmful to the environment. On the other hand, as pointed out by Dawes and Cooksey (1965), it is commonly known that the most effective protection of a batch against these undesirable effects is a protective atmosphere applied during the heating. Therefore, the development of a fully controlled and repeatable process of gear wheel heat treatment under a protective atmosphere will reduce the global emission of toxic substances originating from galvanic copper plating and cooper stripping processes, while at the same time providing more effective protection of the parts.
Colossal Magnetoresistance in (Cd,Mn)Te heterostructures
T. Andrearczyk,W. Zaleszczyk,M. Wiater,T. Wojtowicz,M. Sawicki,G. Karczewski,T. Dietl,Dragana Popovic,J. Jaroszynski 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.1
We report on magnetotransport in diluted magnetic 2D modulation doped (Cd,Mn)Te quantum wells and 3D bulk (Cd,Mn)Se samples. The application of magnetic elds reveals features commonly observed in colossal magnetoresistant (CMR) materials, such as a strong negative magnetoresistance and dramatic and nonmonotonic changes in the zero-eld resistance, which coincide with the fer- romagnetic ordering. These phenomena are present near the metal-insulator transition (MIT), yet another common property of CMR systems. Most likely, the observed CMR-like features re ect nanoscale phase separation of the electron uid and the emergence of ferromagnetic clusters in an intermediate density region. Our results suggest that the clustering around the MIT is ubiquitous not only in CMR manganites and underdoped cuprates but also in disordered semiconductors. We report on magnetotransport in diluted magnetic 2D modulation doped (Cd,Mn)Te quantum wells and 3D bulk (Cd,Mn)Se samples. The application of magnetic elds reveals features commonly observed in colossal magnetoresistant (CMR) materials, such as a strong negative magnetoresistance and dramatic and nonmonotonic changes in the zero-eld resistance, which coincide with the fer- romagnetic ordering. These phenomena are present near the metal-insulator transition (MIT), yet another common property of CMR systems. Most likely, the observed CMR-like features re ect nanoscale phase separation of the electron uid and the emergence of ferromagnetic clusters in an intermediate density region. Our results suggest that the clustering around the MIT is ubiquitous not only in CMR manganites and underdoped cuprates but also in disordered semiconductors.
Sirtuin 2 regulates cellular iron homeostasis via deacetylation of transcription factor NRF2
Yang, Xiaoyan,Park, Seong-Hoon,Chang, Hsiang-Chun,Shapiro, Jason S.,Vassilopoulos, Athanasios,Sawicki, Konrad T.,Chen, Chunlei,Shang, Meng,Burridge, Paul W.,Epting, Conrad L. American Society for Clinical Investigation 2017 The Journal of clinical investigation Vol.127 No.4
Guberina Nika,Gäckler Anja,Grueneisen Johannes,Wetter Axel,Witzke Oliver,Herrmann Ken,Rischpler Christoph,Fendler Wolfgang,Umutlu Lale,Sawicki Lino Morris,Forsting Michael,Rohn Hana 대한핵의학회 2020 핵의학 분자영상 Vol.54 No.4
Purpose To study the value of 2-deoxy-2-[18F]fluoro-D-glucose([18F]FDG) positron emission tomography/computed tomography (PET/CT) and [18F]FDG positron emission tomography/magnetic resonance imaging (PET/MRI) in assessing immunocompromised patients with suspected malignancy or infection. Methods [18F]FDG-PET/CT and [18F]FDG-PET/MRI examinations of patients who were immunocompromised after receiving lung, heart, pancreas, kidney, liver, or combined kidney-liver transplants were analyzed in this retrospective study. Patients underwent whole-body hybrid-imaging because of clinical signs of malignancy and/or infection. Findings were assessed by molecular features ([18F]FDG-uptake) and morphological changes. The final diagnosis, which was arrived at after review of clinical, laboratory, and histopathologic analyses and follow-up imaging studies, served as the reference standard. Results Altogether, (i) 28 contrast-enhanced [18F]FDG-PET/CT scans (CE-PET/CT), (ii) 33 non-contrast [18F]FDG-PET/CT scans (NC-PET/CT), and (iii) 18 [18F]FDG-PET/MRI scans were included. Additionally, 12/62 patients underwent follow-up PET imaging to rule out vital tumor ormetabolic active inflammatory processes. CE-PET/CT exhibited 94.4%sensitivity, 80.0% specificity, 89.5% positive predictive value (PPV), 88.9% negative predictive value (NPV), and 89.3% accuracy with regard to the reference standard. NC-PET/CT exhibited 91.3% sensitivity, 80.0% specificity, 91.3% PPV, 80.0% NPV, and 87.9% accuracy. PET/MRI exhibited 88.6% sensitivity, 99.2% specificity, 99.6% PPV, 81.3% NPV, and 94.4% accuracy. Exact McNemar statistical test (one-sided) showed significant difference between the CT-/MR-component alone and the integrated PET/CT and PET/MRI for diagnosis of malignancy or infection (p value < 0.001). Radiation exposure was 4- to 7-fold higher with PET/CT than with PET/MRI. Conclusion For immunocompromised patients with clinically unresolved symptoms, to rule out vital tumor manifestations or metabolic active inflammation, [18F]FDG-PET/MRI, CE-[18F]FDG-PET/CT, and NC-[18F]FDG-PET/CT exhibit excellent performance in diagnosing malignancy or infection. The main strength of PET/MRI is its considerably lower level of radiation exposure than that associated with PET/CT.