New method to characterize a machining system: application in turning

Many studies simulates the machining process by using a single degree of freedom spring-mass sytem to model the tool stiffness, or the workpiece stiffness, or the unit tool-workpiece stiffness in modelings 2D. Others impose the tool action, or use more or less complex modelings of the efforts applied by the tool taking account the tool geometry. Thus, all these models remain two-dimensional or sometimes partially three-dimensional. This paper aims at developing an experimental method allowing to determine accurately the real three-dimensional behaviour of a machining system (machine tool, cutting tool, tool-holder and associated system of force metrology six-component dynamometer). In the work-space model of machining, a new experimental procedure is implemented to determine the machining system elastic behaviour. An experimental study of machining system is presented. We propose a machining system static characterization. A decomposition in two distinct blocks of the system "Workpiece-Tool-Machine" is realized. The block Tool and the block Workpiece are studied and characterized separately by matrix stiffness and displacement (three translations and three rotations). The Castigliano's theory allows us to calculate the total stiffness matrix and the total displacement matrix. A stiffness center point and a plan of tool tip static displacement are presented in agreement with the turning machining dynamic model and especially during the self induced vibration. These results are necessary to have a good three-dimensional machining system dynamic characterization

Outcomes and Risk Score for Distal Pancreatectomy with Celiac Axis Resection (DP-CAR): An International Multicenter Analysis

Background: Distal pancreatectomy with celiac axis resection (DP-CAR) is a treatment option for selected patients with pancreatic cancer involving the celiac axis. A recent multicenter European study reported a 90-day mortality rate of 16%, highlighting the importance of patient selection. The authors constructed a risk score to predict 90-day mortality and assessed oncologic outcomes. Methods: This multicenter retrospective cohort study investigated patients undergoing DP-CAR at 20 European centers from 12 countries (model design 2000–2016) and three very-high-volume international centers in the United States and Japan (model validation 2004–2017). The area under receiver operator curve (AUC) and calibration plots were used for validation of the 90-day mortality risk model. Secondary outcomes included resection margin status, adjuvant therapy, and survival. Results: For 191 DP-CAR patients, the 90-day mortality rate was 5.5% (95 confidence interval [CI], 2.2–11%) at 5 high-volume (≥ 1 DP-CAR/year) and 18% (95 CI, 9–30%) at 18 low-volume DP-CAR centers (P = 0.015). A risk score with age, sex, body mass index (BMI), American Society of Anesthesiologists (ASA) score, multivisceral resection, open versus minimally invasive surgery, and low- versus high-volume center performed well in both the design and validation cohorts (AUC, 0.79 vs 0.74; P = 0.642). For 174 patients with pancreatic ductal adenocarcinoma, the R0 resection rate was 60%, neoadjuvant and adjuvant therapies were applied for respectively 69% and 67% of the patients, and the median overall survival period was 19 months (95 CI, 15–25 months). Conclusions: When performed for selected patients at high-volume centers, DP-CAR is associated with acceptable 90-day mortality and overall survival. The authors propose a 90-day mortality risk score to improve patient selection and outcomes, with DP-CAR volume as the dominant predictor

The Influence of Communicative Method and Independent Learning Style to the English Learning Outcomes: An Experiment Research to Primary Grade One Level

The aim of this research is to obtain information about the effect of communicative teaching methods and independent learning styles on learning outcomes of Speaking English to the Primary grade 1 students in Al Hikmah School , South Jakarta. The communicative method is an effective learning method applied in the learning process of speaking English, especially for students at the Primary school level. This learning method provides more opportunities for students to express themselves in English, so that the English they learn can be integrated in their personalities and they can feel happier in learning. In this study, researchers used experimental research. The sample in this study amounted to 20 children who were divided into 2 groups of learning styles. Instrument learning outcomes in English are measured through written and oral tests. The results showed that in children with independent learning styles taught by communicative methods achieving higher English-Speaking learning outcomes than not being taught with this method

BRUIT AÉRODYNAMIQUE D'UNE TURBOMACHINE DE TYPE HÉLICO-CENTRIFUGE

L'étude présentée porte sur le calcul du bruit aérodynamique d'une turbomachine (modèle de Lowson (Ref.1)). Le type hélico-centrifuge est plus particulièrement étudié. Les équipements, objets de nos investigations, sont des petites turbomachines qui tournent à vitesse élevée (environ 14000tr/mn), utilisées dans le domaine aéronautique et spatial. Une validation expérimentale et qualitative du modèle est réalisée en vue de réduire le bruit de raies.This study concerns aerodynamic noise calculations of a mixed-flow turbomachine (Lowson model (Ref.1)). The equipment on wich we are working is small with high rotation speed (about 14000 rpm) and is used in aeronautics. An experimental validation is obtained by reducing the discrete frequency sound