123 research outputs found
Manufacturing automation : metal cutting mechanics, machine tool vibrations, and CNC design / Yusuf Altintas.
No full textengineering bookfair2015Includes bibliographical references and index.xii, 366 pages :"Metal cutting is a widely used method of producing manufactured products. The technology of metal cutting has advanced considerably along with new materials, computers, and sensors. This new edition treats the scientific principles of metal cutting and their practical application to manufacturing problems. It begins with metal cutting mechanics, principles of vibration, and experimental modal analysis applied to solving shop floor problems. Notable is the in-depth coverage of chatter vibrations, a problem experienced daily by manufacturing engineers. The essential topics of programming, design, and automation of CNC (computer numerical control) machine tools, NC (numerical control) programming, and CAD/CAM technology are discussed. The text also covers the selection of drive actuators, feedback sensors, modeling and control of feed drives, the design of real time trajectory generation and interpolation algorithms, and CNC-oriented error analysis in detail. Each chapter includes examples drawn from industry, design projects, and homework problems. This book is ideal for advanced undergraduate and graduate students, as well as practicing engineers"--Provided by publisher
Effectiveness of Sedoanalgesia in Percutaneous Liver Biopsy Premedication
No full textABSTRACT
Aim
Percutaneous needle liver biopsy (PLB) is frequently associated with pain and anxiety. This may discourage the patients for biopsy, and rebiopsies, if needed. We planned a study to investigate the efficacy of additional analgesia or sedation for PLB.
Materials and methods
The study has been designed as a single-center, prospective study. The PLB was planned for 18- to 65-year-old consecutive patients who were included in the study. The patients were divided into three premedication groups as control, Meperidine, and Midazolam. Hospital Anxiety and Depression Scale (HADS) was used to measure each subject's anxiety level. Fifteen minutes before the biopsy, 1 mL 0.9% NaCl subcutaneously (sc), 1 mg/kg (max 100 mg) Meperidine sc, or 0.1 mg/kg (max 5 mg) Midazolam intravenously was administered to patients respectively. Then PLB was done with 16 G Menghini needle. The day after, the patients were asked about feelings regarding biopsy.
Results
Groups were similar by gender and age. The HADS scores prior to PLB and on visual analog scale (VAS, 1—10 points) score during PLB were similar. In the three groups, 7, 12, and 7 patients, respectively, experienced no pain. Other patients explained pain as mild or moderate or severe. The number of patients who agreed for possible rebiopsy was higher in Meperidine and Midazolam groups than in the control group.
Conclusion
Premedication with Meperidine or Midazolam in PLB would improve patients' tolerance, comfort, and attitude against a possible repeat PLB.
How to cite this article
Sezgin O, Yaras S, Ates F, Altintas E, Saritas B. Effectiveness of Sedoanalgesia in Percutaneous Liver Biopsy Premedication. Euroasian J Hepato-Gastroenterol 2017;7(2):146-149.
</jats:sec
Method of determining the process applied for feature machining : experimental validation of a slot
No full textIn this paper, we will be evaluating the "manufacturability" levels for several machining processes of "slot" feature. Using the STEP standard, we will identify the slot feature characteristics. Then, using the ascendant generation of process method, we will define the associated milling process. The expertise is based on a methodology relative to the experience plans carried out during the formalization and systematic evaluation of the machining process associated with the feature
Acute Pancreatitis in Turkey: Results of a Nationwide Multicenter Study
No full textALTINTAS, Engin/0000-0003-0796-1456; SAGLAM, Osman/0000-0003-0779-992X; Soyturk, Mujde/0000-0002-2646-639X; tozlu, mukaddes/0000-0002-8534-8027Background: Acute pancreatitis (AP) is the most common gastrointestinal disease requiring hospitalization, with significant mortality and morbidity. We aimed to evaluate the clinical characteristics of AP and physicians ' compliance with international guidelines during its management. Methods: All patients with AP who were hospitalized at 17 tertiary centers in Turkey between April and October 2022 were evaluated in a prospective cohort study. Patients with insufficient data, COVID-19 and those aged below 18 years were excluded. The definitions were based on the 2012 revised Atlanta criteria. Results: The study included 2144 patients (median age:58, 52 % female). The most common etiologies were biliary (n = 1438, 67.1 %), idiopathic (n = 259, 12 %), hypertriglyceridemia (n = 128, 6 %) and alcohol (n = 90, 4.2 %). Disease severity was mild in 1567 (73.1 %), moderate in 521 (24.3 %), and severe in 58 (2.6 %) patients. Morphology was necrotizing in 4.7 % of the patients. The overall mortality rate was 1.6 %. PASS and BISAP had the highest accuracy in predicting severe pancreatitis on admission (AUC:0.85 and 0.81, respectively). CT was performed in 61 % of the patients, with the majority (90 %) being within 72 h after admission. Prophylactic NSAIDs were not administered in 44 % of the patients with post-ERCP pancreatitis (n = 86). Antibiotics were administered to 53.7 % of the patients, and 38 % of those received them prophylactically. Conclusions: This prospective study provides an extensive report on clinical characteristics, management and outcomes of AP in real -world practice. Mortality remains high in severe cases and physicians ' adherence to guidelines during management of the disease needs improvement in some aspects. (c) 2023 IAP and EPC. Published by Elsevier B.V. All rights reserved
Cyclic Variation of Residual Stress Induced by Tool Vibration in Machining Operations
No full textIn machining, due to the tool vibration the forces, temperatures and stresses vary during the cutting process, so as the residual stresses over the machined surface. This variation of the residual stress has never been measured and, therefore, imposes new experimental challenges. The objective of this work is to correlate the variation of the residual stresses along the cutting path with the frequency of the surface geometrical defect generated by the vibration of the tool holding system. In order to perform such correlation a hybrid experimental/analytical approach was applied for an austenitic stainless steel, AISI 316L. Residual stresses were analyzed in the machined specimen along the cutting path using neutron diffraction. The results show a cyclic variation of the residual stresses, which can be detected when considering the frequency of the tool vibration. The frequency of the tool vibration is also correlated with the topology of the surface
Chatter Control by Spindle Speed Variation in High-Speed Milling
No full textHigh-speed milling operations are often limited by regenerative vibrations. The aim of this paper is to analyze the effect of spindle speed variation on machine tool chatter in high-speed milling. The stability analysis of triangular and sinusoidal shape variations is made numerically with the semi-discretization method. Parametric studies show also the influence of the frequency and amplitude variation parameters. This modeling is validated experimentally by variable spindle speed cutting tests with a triangular shape. Stable and unstable tests are analyzed in term of amplitude vibration and surface roughness degradation. This work reveals that stability must be considered at period variation scale. It is also shown that spindle speed variation can be efficiently used to suppress chatter in the flip lobe area
Bouwlogistiek 2.0: Een onderzoek naar de toepasbaarheid van innovatieve bouwlogistieke concepten in binnenstedelijke projecten en de voor- en nadelen van deze concepten vanuit een efficiëntie perspectief
No full textEen onderzoek naar de toepasbaarheid van innovatieve bouwlogistieke concepten in binnenstedelijke projecten en de voor- en nadelen van deze concepten vanuit een efficiëntie perspectief.Design & Construction ManagementReal Estate & HousingArchitectur
Metal cutting modelling SPH approach
No full textThe purpose of this work is to evaluate the use of the smoothed particle hydrodynamics (SPH) method within the framework of high speed cutting modelling. First, a 2D SPH based model is carried out using the LS-DYNA® software. The developed SPH model proves its ability to account for continuous and shear localised chip formation and also correctly estimates the cutting forces, as illustrated in some orthogonal cutting examples. Then, the SPH model is used in order to improve the general understanding of machining with worn tools. At last, a hybrid milling model allowing the calculation of the 3D cutting forces is presented. The interest of the suggested approach is to be
freed from classically needed machining tests: Those are replaced by 2D numerical tests using the SPH model. The developed approach proved its ability to model the 3D cutting forces in ball end milling
- …
