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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Information modeling in mechanical design: with application to cam mechanical design

Shooter, Steven B. 06 June 2008 (has links)
Good engineering practice requires designers to incorporate knowledge, processes and skills to produce a superior product. Each stage of the product realization process requires that the designer utilize available resources to make sound engineering decisions in a timely manner. Much of the research on engineering design has focused on formulating genera] models for the design process. However, it has been shown that these models are rarely used by engineers in practice. This dissertation advances the concept that useful design models must include methodologies that are particular to a given field or type of design. The inclusion of these knowledge-domain-dependent methodologies provides a complete framework for the greatest utility to the designer. This dissertation describes a general approach to engineering design and proposes a model for developing design assistance tools useful to the practicing designer. The methodology and the model are applied to the domain of cam mechanism design. The model describes the conceptual design process that begins with formulating objectives and establishing specifications and concludes with the actual synthesis of the cam profile. The design model is then incorporated into a comprehensive modular computer tool that is integrated with a PC-based CAD package. This dissertation contributes to both the field of engineering design and cam mechanism design. It provides a design model that incorporates a detailed methodology with information and analytical tools for design. By focusing on the knowledge domain of cam mechanism design it contributes to this field as well. Most prior research focused on techniques for synthesizing the cam profile and provided little assistance for the earlier stages of design. No previous tools have been developed that provide the scope of assistance presented in this dissertation. / Ph. D.
22

A Novel Tension-Member Follower Train for a Generic Cam-Driven Mechanism

LaPierre, Jeffrey A 13 June 2008 (has links)
"Many assembly machines for consumer products suffer from the fact that the mechanisms used to impart the necessary assembly motions to the product are orders of magnitude more massive than the product payloads that they carry. This characteristic subsequently limits the operating speed of the machine. If the follower train could be made less massive without sacrificing accuracy and control, it would therefore allow higher speeds. It is well-known that structures that carry only tensile loads can be much less massive than those that must also carry compressive loads. This concept is demonstrated in many structures, such as the suspension bridge. This master’s project set out to investigate the feasibility of a tension-member follower train for a generic cam-driven pick and place mechanism. This system was first dynamically simulated using a computer model, and then tested by constructing a proof of concept prototype. A cam-driven, low-mass tension member (in this case a spring steel strip over pulleys) under spring preload was used to replace the bellcranks and connecting rods typical of a conventional follower train. The system was determined to be feasible and will allow for increased operating speeds at potentially lower costs as an additional benefit."
23

Hüllkurven-Berechnung der Fräserradienkorrektur von Zylinderkurvenkörpern mit Mathcad / Envelope calculation of the milling cutter radius correction of cylindrical cams with Mathcad

Matthes, Jörg 11 May 2011 (has links) (PDF)
Das Fräsen der Nutkurve von Zylinderkurvenkörpern räumlicher Kurvengetriebe erfolgt durch das Nachstellen des Bewegungsablaufs des Kurvengetriebes. Anstelle der Rolle fährt ein Fräser mit gleichem Durchmesser die Bahnkurve ab und erzeugt so die Nut. Die entstehende Hüllfläche entspricht der Hüllfläche des Kontaktes zwischen Rolle und Kurvenflanke. Durch den Verschleiß des Fräsers wird diese Übereinstimmung nicht mehr gewährleistet. Abhilfe schafft hier nur eine Fertigung mit beliebig kleinerem Fräserradius. Die theoretische Grundlage dieses Problems, die im Zusammenhang mit der Berechnung der Hüllkontur räumlicher Kurvenkörper steht, wird im Beitrag aufgezeigt und unter dem Einsatz von Mathcad realisiert. Die hier vorgestellte Methode benutzt die Hüllfläche als Referenz zur Ermittlung der Fräserbahn. Die in Mathcad notwendigen Berechnungsansätze werden aufgezeigt und die Abfolge mit den Ergebnissen an einem Beispiel demonstriert.
24

Effect of transforming growth factor-β on up/down regulation of integrin-β1 in primary chondrocyte culture

Khaghani, Seyed A., Sefat, Farshid, Youseffi, Mansour, Rehman, R., Soon, Chin Fhong, Akbarova, G. January 2016 (has links)
yes / Regeneration of a damaged or non-functioning tissue requires adhesion of cells to their extracellular matrix (ECM). Thus the investigation of the level of synthesised cell adhesion molecules (CAMs) in cell culture systems play major roles in cell and tissue engineering. Adhesion of chondrocyte to a collagen type-II rich matrix, is dependent on cell adhesion molecules (CAMs) and integrins and cells adhere to ECM through integrins.
25

A CAD-interactive software package for the synthesis of planar disk cams

Payne, Stephen Richard 04 September 2008 (has links)
The objective of this thesis is to provide an interactive system for the graphical design and analysis of planar disk cams. The software written for this thesis, the Cam Design System, operates as an add-on application that runs within the CADKEY® graphical environment and inherits all the CADKEY® software functions. It allows the user to specify different follower and motion curve parameters to synthesize a cam, and will analyze the cam for pressure angle flaws. It will also produce output in a numerical data format, as CAD drawings, as a detailed design report, or as NC data. This thesis first discusses what software is already available to perform similar synthesis and analysis, and the extent of documentation of cain design and the use of conjugate geometry theory in literature. Next, it describes how the C-code integrates with the CADKEY® graphical system. The next sections describe all the design theory used in the software, including all the conjugate geometry theory and full descriptions of each of the motion curve characteristics used in the software. The subsequent section describes the software itself and how it is structured, and provides a few examples of designing a cam. The last section sums up the work of this thesis, and provides some recommendations for future work in this area. / Master of Science
26

A CAD/CAM interface for computer-aided design of cams

Gandhi, Ashit R. 12 March 2013 (has links)
The purpose of this thesis is to provide a complete package for the design and three dimensional modeling display of cams. The software produced as a part of this work will operate as a module of CADAM to produce cam designs and enter the resulting cam as a CAD model and produce the graphical display of the cam. In addition to the introductory material, this thesis is divided into four sections. The section on the graphics packages used in this thesis includes a brief history and capabilities of each of the packages. The second section details the procedure to be adopted in order to design a cam. The next section details ANICAM, the program that has been developed to incorporate the design and display procedure. The fourth section of this thesis contains recommendations for further work in this area. The theoretical work in this project is a combination of original derivations and applications of the theory in the design literature. / Master of Science
27

Theoretical Studies of the Structure and Stability of Metal Chalcogenide CrnTem (1≤n≤6, 1≤m≤8) clusters

Prabha, FNU Sweta 01 January 2019 (has links)
In the presented work, first principle studies on electronic structure, stability, and magnetic properties of metal chalcogenide, CrnTem clusters have been carried out within a density functional framework using generalized gradient functions to incorporate the exchange and correlation effects. The energetic and electronic stability was investigated, and it was found that they are not always correlated as seen in the cluster Cr6Te8 which has smaller gap between its HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital) and a high electron affinity of 3.39 eV indicating lower electronic stability whereas higher fragmentation energy indicating energetic stability. The high electron affinity shows that the stability of Cr6Te8 cluster can be enhanced by adding charge donating ligands including PEt3 to form stable Cr6Te8(PEt3)6 clusters as seen in experiments. The other cluster of interest was Cr4Te6 in which energetic stability was accompanied with electronic inertness marked by its large HOMO-LUMO gap, non-magnetic ground state and high fragmentation energy.
28

Médecine non-conventionnelle et psycho-oncologie : évaluation de l’impact des Médecines Complémentaires et Alternatives (MCA) chez les patients atteints de cancer / Unconventional movement in oncology : the impact of CAM (Complementary and Alternative Medecines) in patients with cancer

Suissa, Veronique 13 September 2017 (has links)
Cette étude porte sur le mouvement non conventionnel en oncologie et tend à évaluer l’impact des MCA conjointement en termes de bénéfices, de risques et de dérives chez les patients atteints de cancer. Notre démarche comparative explore le vécu de 32 patients utilisant ou non les MCA, de façon complémentaire ou alternative aux traitements curatifs. Un entretien semi-directif unique a été mené auprès de chaque patient dans l’objectif d’identifier les processus communs et distincts entre les différents groupes. Un livret de questionnaire leur a également été remis afin de rendre compte des caractéristiques du mouvement hétérodoxe. L’analyse du discours révèle que le recours aux MCA influence positivement le vécu de la maladie sur l’ensemble des dimensions de la personne, mais détériore la représentation de la médecine allopathique et la relation soignant/soigné. Le refus de traitements curatifs chez les utilisateurs de MCA est lié à un univers de croyances invalidantes qu’ils développent. L’analyse des échelles suggère que le recours aux MCA améliore la perception de la santé globale, réduit la symptomatologie dépressive, mais reste sans effet sur l’anxiété. Le recours alternatif aux MCA est lié aux croyances d’attribution causale interne et de contrôle religieux, mais pas à celle d’un contrôle sur l’évolution de la maladie. L’intégration des MCA en oncologie apparaît pertinente et nécessaire pour améliorer la prise en charge des malades, mais doit pouvoir se déployer avec prudence et de façon progressive au regard des risques et des dérives de certaines pratiques hétérodoxes. / This study examines the unconventional movement in Oncology and aim to assess the impact of CAM jointly in terms of benefits, of risks and derivatives in patients with cancer.Our comparative approach explores the experience of 32 patients using or not the CAM of complementary or alternative to curative treatments. A unique semi directive interview was conducted with each patient in order to identify common and distinct processes between differents groups. A questionnaire booklet was also been handed them to end to account characteristics of the unconventional movement.Analysis of the speech shows that the use of CAM affects positively the experience of the illness across the dimensions of the person, but deteriorates the representation of allopathic medicine and the patient-caregiver relationship. The refusal of curative treatments among users of CAM is linked to a universe of disabling beliefs they develop.The analysis of scales suggests that the use of CAM improves the perception of global health, reduces the depressive symptomatology, but has no effect on anxiety. The alternative use of CAM is related to internal causal attribution and control beliefs, but not to control over the course of the disease. The integration of CAM in oncology appears relevant and necessary to improve the care of patients, but should be able to be deployed with caution and progressively in the light of the risks and derivatives of certain heterodox practices.
29

Problematik der Einzweckmaschinen mit elektronischen Kurvenscheiben

Fišer, Pavel, Jirásko, Petr, Václavík, Miroslav 17 May 2018 (has links) (PDF)
Die Firma VÚTS, a.s., beschäftigt sich mit der Konstruktion und Herstellung von speziellen Einzweckmaschinen, die sie mit ihren entwickelten die Umsetzung der zuständigen Technologie ermöglichenden Steuerungssystemen bestückt. Die Abteilung für Mechatronik führt mehr als 10 Jahre die Anwendungsforschung von elektronischen Kurvenscheiben basierend auf HW und SW-Komponenten von Yaskawa (Japan) / 2 / durch. Da die Anwendung von elektronischen Kurvenscheiben mit den eigenen Steuersystemen zusammenhängt, wurde ein allgemeines Steuersystem entwickelt, das auf dem Konzept einer Zustandsmaschine mit manueller und automatischer Betriebsart basiert. Dieses Konzept ist im Bereich der Steuersysteme für Werkzeugmaschinen üblich. Der grundlegende Unterschied liegt jedoch in der automatischen Betriebsart, bei der die Programmlogik der elektronischen Kurvenscheiben zum Steuern einzelner NC-Achsen verwendet wird. Die Bewegung der Arbeitsglieder bzw. einzelner Achsen wird von den Bewegungsgesetzen abgeleitet, einschließlich der ersten und der zweiten Ableitungen, die in den Vorwärtskopplungen der Geschwindigkeit und des Momentes der Kaskadenregelstruktur in dem Servo-Wandler verwendet sind. Das Konzept des Steuersystems mit elektronischen Kurvenscheiben wurde für eine Anzahl von Einzweckmaschinen verwendet, von denen zwei Vertreter erwähnt werden. [... aus der Einleitung]
30

Návrh konstrukce jednoúčelového manipulátoru pro automatickou výměnu nástrojů s třívačkovým generátorem pracovního cyklu / Design of dedicated manipulator for automatic tool change with the three cam generator duty cycle

Bláha, Pavel January 2021 (has links)
This thesis deals with the design of a single-purpose manipulator for automatic tool changing with a three-cams generator of the working cycle. At the beginning of the paper, general background information about tool trays and manipulators for the change of tools is briefly described. The scheme of the kinematic manipulator is proposed in this work as well. The thesis also includes the calculation of the shapes of the grooves in the cams. The result of this work is the design of the manipulator, including an animation of tool changing.

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