Based on experimental results, performed on an instrumented single wire saw, an analytical model for the macroscopic mechanical conditions in the wire sawing process is presented. The model describes ...the influence of important process parameters like wire velocity, feed velocity and tension force as well as geometric relations like ingot size and wire length to the lapping pressure and the shape of the formed wire bow. The model is based on macroscopic, measurable, machining parameters and uses the experimentally determined relation between pressure and removal rate according to Prestons law. The derived equations are used to study the influence of typical process parameters systematically and the results are exemplified for the production line of 6
in solar wafers.
► An analytical model for the macroscopic mechanical conditions in the wire sawing process is presented. ► The influence of important process parameters as well as geometric relations are considered. ► Experimental studies, performed on an instrumented single wire saw, are presented. ► The experimental results are in good agreement with the analytical model. ► The influence of important wire sawing parameters is studied.
The material removal rate in the wire sawing technology depends on several features of the used abrasives and the complex process of particle movement and interaction inside the kerf. To investigate ...these micro-mechanical aspects of the wire sawing process, a numerical model is developed in the present paper. The model is based on the discrete element method adjusted to use sharp edged polygonal particles. The crucial procedure of material removal is implemented through concepts of the fracture mechanics of sharp edged indenters. The model allows to study the influence of essential parameters like wire speed, lapping pressure, particle shape, particle size distribution a.o. on the material removal process. A parametric study towards the influence of wire speed and lapping pressure on the amount of material removal is also presented. The parametric numerical studies carried out confirm the phenomenological law of Preston for the removal rate and enable correlations between the Preston coefficient and micro-mechanical process parameters.
•The micromechanical process of material removal during wire sawing is modeled.•The discrete element method was extended for sharp edged abrasive particles.•Concepts of indentation fracture mechanics are applied to micro-cracking processes.•The results agree well with experiments and confirm the classical Preston law for the removal rate.•The influence of many technological parameters of wire sawing is examined.
The aim of the study is to clarify how far it is possible to describe the mechanical behavior of novel TRIP‐Steel/Mg‐PSZ composite open‐cell foam structures using beam networks generated from random ...tessellations. Conventional compression tests were performed with various foam samples. Furthermore, the deformation of open‐cell composite foams was observed as well by X‐ray computed tomography (XCT). Up to a compressive strain of 20% different stages of deformation could be observed. Respective bulk samples were manufactured by powder metallurgy and tested in order to determine the mechanical properties of the bulk material. Numerical simulations were employed based on the suitable modeling of foams exposed to mechanical loading. The predictions of the simulation are compared with the results of the deformation experiments.
Abstract
The aim of the study is to clarify how far it is possible to describe the mechanical behavior of novel TRIP‐Steel/Mg‐PSZ composite open‐cell foam structures using beam networks generated ...from random tessellations. Conventional compression tests were performed with various foam samples. Furthermore, the deformation of open‐cell composite foams was observed as well by X‐ray computed tomography (XCT). Up to a compressive strain of 20% different stages of deformation could be observed. Respective bulk samples were manufactured by powder metallurgy and tested in order to determine the mechanical properties of the bulk material. Numerical simulations were employed based on the suitable modeling of foams exposed to mechanical loading. The predictions of the simulation are compared with the results of the deformation experiments.
Investigations on the wire sawing process Liedke, T.; Ams, A.; Kuna, M.
Proceedings in applied mathematics and mechanics,
12/2007, Letnik:
7, Številka:
1
Journal Article
Purpose: This study investigated the prevalence of developmental and acquired pathologic conditions associated with impacted third molars (3Ms) in a Southern Brazilian population and evaluated ...whether demographic and tooth characteristics were correlated with the presence of bone or tooth lesions. Materials and Methods: Panoramic radiographs were assessed for developmental (bone-related) or acquired (tooth-related) pathoses associated with impacted upper or lower 3Ms. Data on tooth positioning, tooth development, and patient demographics were collected. A trained, calibrated postgraduate student evaluated all images. Binary and multivariate logistic regression models were used to assess associations between outcomes and the demographic and radiographic variables. The threshold for statistical significance was set at 5% (P<0.05). Results: The sample comprised panoramic radiographs from 2054 patients, predominantly female (59.2%), with a mean age of 27.2±11.5 years. Overall, 4066 impacted 3Ms were evaluated, revealing 471 (11.6%) developmental and 710 (17.5%) acquired pathoses. Among the developmental pathoses, 460 (95.2%) were indicative of dentigerous cysts. Male sex, lower 3M location, vertical or distoangular positioning, and incomplete root formation were associated with an elevated likelihood of developmental pathology. Lower tooth position, complete root formation, and partial eruption were linked to an increased probability of an acquired pathology in the third or second molar. Conclusion: The prevalence of pathologic conditions associated with impacted 3Ms was low. Male sex, lower 3M placement, horizontal or distoangular positioning, and incomplete root formation were associated with developmental pathoses, while lower tooth position, complete root formation, and partial eruption were related to acquired pathoses.
In patients with hormone-dependent postmenopausal breast cancer, standard adjuvant therapy involves 5 years of the nonsteroidal aromatase inhibitors anastrozole and letrozole. The steroidal inhibitor ...exemestane is partially non-cross-resistant with nonsteroidal aromatase inhibitors and is a mild androgen and could prove superior to anastrozole regarding efficacy and toxicity, specifically with less bone loss.
We designed an open-label, randomized, phase III trial of 5 years of exemestane versus anastrozole with a two-sided test of superiority to detect a 2.4% improvement with exemestane in 5-year event-free survival (EFS). Secondary objectives included assessment of overall survival, distant disease-free survival, incidence of contralateral new primary breast cancer, and safety.
In the study, 7,576 women (median age, 64.1 years) were enrolled. At median follow-up of 4.1 years, 4-year EFS was 91% for exemestane and 91.2% for anastrozole (stratified hazard ratio, 1.02; 95% CI, 0.87 to 1.18; P = .85). Overall, distant disease-free survival and disease-specific survival were also similar. In all, 31.6% of patients discontinued treatment as a result of adverse effects, concomitant disease, or study refusal. Osteoporosis/osteopenia, hypertriglyceridemia, vaginal bleeding, and hypercholesterolemia were less frequent on exemestane, whereas mild liver function abnormalities and rare episodes of atrial fibrillation were less frequent on anastrozole. Vasomotor and musculoskeletal symptoms were similar between arms.
This first comparison of steroidal and nonsteroidal classes of aromatase inhibitors showed neither to be superior in terms of breast cancer outcomes as 5-year initial adjuvant therapy for postmenopausal breast cancer by two-way test. Less toxicity on bone is compatible with one hypothesis behind MA.27 but requires confirmation. Exemestane should be considered another option as up-front adjuvant therapy for postmenopausal hormone receptor-positive breast cancer.
Nanotechnology has introduced a new quality and has definitely developed the possibilities of treating and diagnosing various diseases. One of the scientists' interests is liposomes and metallic ...nanoparticles (LipoMNPs)-the combination of which has introduced new properties and applications. However, the field of creating hybrid nanostructures consisting of liposomes and metallic nanoparticles is relatively little understood. The purpose of this review was to compile the latest reports in the field of treatment and medical imaging using of LipoMNPs. The authors focused on presenting this issue in the direction of improving the used conventional treatment and imaging methods. Most of all, the nature of bio-interactions between nanostructures and cells is not sufficiently taken into account. As a result, overcoming the existing limitations in the implementation of such solutions in the clinic is difficult. We concluded that hybrid nanostructures are used in a very wide range, especially in the treatment of cancer and magnetic resonance imaging. There were also solutions that combine treatments with simultaneous imaging, creating a theragnostic approach. In the future, researchers should focus on the description of the biological interactions and the long-term effects of the nanostructures to use LipoMNPs in the treatment of patients.
Objectives: This study aimed to evaluate the success rate of endodontic treatments performed by undergraduate students and the factors associated with the outcome. Materials and Methods: A follow-up ...of 3 to 8 years after root canal filling was carried out in 91 patients. At the follow-up visits, medical and dental history questionnaires were applied along with clinical and radiographic examinations. Data collected in the clinical exam included: the presence of pain, swelling, sinus tract, mobility, tenderness to palpation and percussion, periodontal probing profile, and type/quality of coronal restoration. Postoperative and follow-up radiographs were digitalized and analyzed by 2 trained and calibrated examiners to assess periapical healing. The treatment outcome was based on strict clinical and radiographic criteria and classified as success (absence of any clinical and radiographic sign of apical periodontitis) or failure (other combination). Logistic regression was used to investigate the impact of clinical and radiographic variables on endodontic treatment outcomes at a 5% significance level. Results: The success rate of endodontic treatments was 60.7%. The only risk factor significantly associated with failure was the presence of a periapical lesion on the postoperative radiograph (odds ratio, 3.35; 95% confidence interval, 1.17-9.54). Conclusions: The success rate of endodontic treatments performed by undergraduate students was low and was jeopardized by the presence of a periapical lesion on the postoperative radiograph.
Abstract
Magneto-ionics, understood as voltage-driven ion transport in magnetic materials, has largely relied on controlled migration of oxygen ions. Here, we demonstrate room-temperature ...voltage-driven nitrogen transport (
i.e
., nitrogen magneto-ionics) by electrolyte-gating of a CoN film. Nitrogen magneto-ionics in CoN is compared to oxygen magneto-ionics in Co
3
O
4
. Both materials are nanocrystalline (face-centered cubic structure) and show reversible voltage-driven ON-OFF ferromagnetism. In contrast to oxygen, nitrogen transport occurs uniformly creating a plane-wave-like migration front, without assistance of diffusion channels. Remarkably, nitrogen magneto-ionics requires lower threshold voltages and exhibits enhanced rates and cyclability. This is due to the lower activation energy for ion diffusion and the lower electronegativity of nitrogen compared to oxygen. These results may open new avenues in applications such as brain-inspired computing or iontronics in general.
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