Search results for " Forming"
showing 10 items of 127 documents
Recent Developments in the Design and Control of Cold Forming Processes
1999
In the paper some problems of process design and control in metal forming are taken into account. In particular as far as the former aspect is concerned, the problem of the preform design in cold forging is analyzed: the contributions offered by several researchers are presented and an innovative design procedure is proposed. As well, the suitability of closed-loop control systems for metal forming applications is discussed with particular reference to sheet stamping operations; again, after an overview of the state of the art, the advantages offered by the application in this field of Artificial Intelligence techiniques is pointed out.
An Ovalbumin Peptide-Specific Cytotoxic T Cell Clone with Antigen Self-Presentation Capacity Uses Two Distinct Mechanisms to Kill Target Cells
1993
Abstract Cloned 10BK.1 T cells with specificity for the ovalbumin peptide OVA257-264 are representative of a novel cell type within the CD8 + subset of T cells. In the presence and in the absence of added antigen presenting cells these T cells react toward antigen (Ag) by proliferation and lymphokine production. These data suggest self-presentation of the Ag by 10BK.1 cells. Here we present evidence that 10BK.1 cells exhibit cytotoxic activity that involves two different cytotoxic effector mechanisms. (i) One mechanism is fast killing activity, apparent within 4 hr. Constitutive mouse T cell-specific proteinase-1 (MTSP-1) activity, constitutive expression of MTSP-1 RNA, increased by Ag chal…
Vibrio cholerae cytolysin: assembly and membrane insertion of the oligomeric pore are tightly linked and are not detectably restricted by membrane fl…
2000
AbstractHemolytic strains of Vibrio cholerae secrete a cytolysin that, upon binding as a monomer, forms pentameric pores in animal cell membranes. Pore formation is inhibited at low temperature and in the absence of cholesterol. We here posed the following questions: firstly, can oligomerization be observed in the absence of pore formation? Secondly, is membrane fluidity responsible for the effect of temperature or of cholesterol upon pore formation? The first issue was approached by chemical cross-linking, by electrophoretic heteromer analysis, and by electron microscopy. None of these methods yielded any evidence of a non-lytic pre-pore oligomer. The second question was addressed by the u…
In-situ forming gel-like depot of a polyaspartamide-polylactide copolymer for once a week administration of Sulpiride
2015
Abstract Objectives An in-situ forming gel-like depot, prepared by using an appropriate polyaspartamide-polylactide graft copolymer, has been employed to release in a sustained way sulpiride. Methods α,β-poly(N-2-hydroxyethyl)-D,L-aspartamide-g-polylactic acid (PHEA-g-PLA) has been used as a polymer component. Its physicochemical properties make possible to dissolve it in N-methyl-2-pyrrolidone, with the obtainment of a solution able to form a gel-like depot once injected into a physiological medium. Cell compatibility of PHEA-g-PLA depot has been investigated, using murine dermal fibroblasts as cell model. 3-(4,5-Dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazo…
An Intelligent Tool to Predict Fracture in Sheet Metal Forming Operations
2007
One of the main issues in sheet metal forming operations design is the determination of formability limits in order to prevent necking and fracture. In fact, the ability to predict fracture represents a powerful tool to improve the production quality in mechanical industry. Many researchers investigated the problem here addressed, mainly studying forming limit diagrams (FLD) or developing fracture criteria which are able to foresee fracture defects for different processes. In this paper, the author present some early results of a research project focused on the application of artificial intelligence (AI) for ductile fracture prediction in sheet metal forming operations. The main advantage o…
Dielectric relaxation models applied of the dynamics of myoglobin as determined by Mössbauer spectroscopy
1996
Abstract Protein specific modes of motions are found in myoglobin crystals above 180 K. In this contribution we show that this type of motions can be analyzed by a Davidson-Cole, a Cole-Cole or a Havriliak-Negami distribution in analogy to dielectric relaxation. However, the temperature dependence of the obtained parameters is quite unusual indicating a broadening of the distributions with temperature instead of motional narrowing. This can be understood from the picture of conformational substates if one assumes that more and more substates become accessible with increasing temperature. The result shows that the analogy between glass forming organic liquids and proteins should not be exagg…
Primary culture of avian embryonic heart forming region cells to study the regulation of vertebrate early heart morphogenesis by vitamin A
2014
Background: Important knowledge about the role of vitamin A in vertebrate heart development has been obtained using the vitamin A-deficient avian in ovo model which enables the in vivo examination of very early stages of vertebrate heart morphogenesis. These studies have revealed the critical role of the vitamin A-active form, retinoic acid (RA) in the regulation of several developmental genes, including the important growth regulatory factor, transforming growth factor-beta2 (TGFβ2), involved in early events of heart morphogenesis. However, this in ovo model is not readily available for elucidating details of molecular mechanisms determining RA activity, thus limiting further examination o…
Energy Efficiency of Sheet Metal Working Processes: Where do we stand today?/Energieeffizienz in Prozessen der Blechumformung – eine aktuelle Standor…
2014
Due to increasing energy and resource costs at the one hand and upcoming regulations on energy and resource efficiency at the other, a growing interest of machine tool builders to the environmental performance of their machine tools can be observed today. The last decade, academic as well as industrial research groups started to assess the energy demand of discrete part manufacturing processes and indicated a significant potential for improvement [1]. In contrast to conventional machining processes (e.g. milling, turning…), (sheet) metal forming processes are still less well documented in terms of their energy demand [2]. In consequence, potential energy efficiency improvement measures for …
ROUGHNESS CONTROL OF PARTS OBTAINED THROUGH INCREMENTAL SHEET FORMING
2007
Abstract The present paper adresses the issue of controlling the quality of surface in the case of a new sheet metal forming process by which various curved shells are formed without the help of expensive dies. The roughness of the surface which comes in direct contact with the punch at incremental sheet forming suffers an obvious worsening compared to the initial blank surface roughness. The present paper discusses the measuring of the roughness of parts obtained through the previously mentioned process and highlights the factors that influence it. There were taken into account the initial roughness of the punch, the punch diameter and the friction coefficient between the punch and the bla…
Contributions Regarding Incremental Forming Process of Bimetallic Sheets
2014
Incremental forming is a process with a high degree of novelty, so this paper describes first of all a series of theoretical principles of the incremental forming process. A main objective of the paper was the usage, as blanks in incremental forming process of bimetallic sheets. So the experimental researches have targeted the realising of parts with different shapes made from such type of blank. In the experimental researches was chosen as technological equipment for incremental forming the numerical controlled milling centre. The paper also present the tools used in incremental forming in order to obtain a hemispherical parts.