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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.
441

DISCRETE COMPLIANT MOTION PLANNING SYSTEM FOR ROBOTIC ASSEMBLY

Yang, Fan January 2009 (has links)
This dissertation focuses on compliant motion planning designed for robotic assembly. A Discrete Complaint Motion Planner (DCMP) reacts to detected discrete contact state transitions and issues compliant motion command to the underlying continuous robot system. It consists of a Qualitative Contact Model, a Compliant Motion Strategy Planner (CMSP) and a Compliant Motion Command Planner (CMCP).How to model and characterize a contact state is a major issue. In this dissertation, contact states are described using the qualitative configuration representation called Feature Interaction Matrix (FIM). A FIM encodes not only the contact information but also the relative configuration between two polyhedral parts. This FIM-based qualitative contact state model has several contributions: 1) an optimization-based approach is developed to verify the hypothetical states in FIM; 2) penetration check for hypothetical contact states through constraint satisfaction is simple and fast; 3) spatial adjacency can be easily determined using convex cone techniques; 4) a generate-and-test method is proposed to expand qualitative states in FIM; 5) compliant motion parameters are derived by an optimization method.The qualitative contact states and how they are connected is modeled with an adjacency graph/sub-graph, where nodes represent qualitative contact states and spatially adjacent contact states are connected by arcs. Each arc represents a desired contact state transition. The CMSP receives contact state transition event from an on-line estimator, then computes/checks the assembly strategy and issues the next desired contact state transition to the CMCP. The compliant motion strategy is computed using graph-search techniques with the automatic construction of the adjacency graph/sub-graph. The CMSP integrate hypotheses generation, hypotheses verification, spatial adjacency and graph search algorithms.When the next desired contact state transition is received, the CMCP computes the compliant motion parameters that are issued to the underlying continues robot system to achieve the desired contact state transition. The generation of motion parameters is defined as an optimization problem and an algorithm is developed to solve it.The DCMP in this dissertation considers both 3D translational and 3D rotational motions. Experiments are carried out to demonstrate the feasibility of the approach for the automatic assembly of polyhedral parts.
442

The Universal Similarity Metric, Applied to Contact Maps Comparison in A Two-Dimensional Space

Rahmati, Sara 27 September 2008 (has links)
Comparing protein structures based on their contact maps is an important problem in structural proteomics. Building a system for reconstructing protein tertiary structures from their contact maps is one of the motivations for devising novel contact map comparison algorithms. Several methods that address the contact map comparison problem have been designed which are briefly discussed in this thesis. However, they suggest scoring schemes that do not satisfy the two characteristics of “metricity” and “universality”. In this research we investigate the applicability of the Universal Similarity Metric (USM) to the contact map comparison problem. The USM is an information theoretical measure which is based on the concept of Kolmogorov complexity. The ultimate goal of this research is to use the USM in case-based reasoning system to predict protein structures from their predicted contact maps. The fact that the contact maps that will be used in such a system are the ones which are predicted from the protein sequences and are not noise-free, implies that we should investigate the noise-sensitivity of the USM. This is the first attempt to study the noise-tolerance of the USM. In this research, as the first implementation of the USM we converted the two-dimensional data structures (contact maps) to one-dimensional data structures (strings). The results of this implementation motivated us to circumvent the dimension reduction in our second attempt to implement the USM. Our suggested method in this thesis has the advantage of obtaining a measure which is noise tolerant. We assess the effectiveness of this noise tolerance by testing different USM implementation schemes against noise-contaminated versions of distinguished data-sets. / Thesis (Master, Computing) -- Queen's University, 2008-09-27 05:53:31.988
443

Evaluation of Mitigative Techniques for Non-Contact Lap Splices in Concrete Block Construction

2014 April 1900 (has links)
A previously completed study in the field of concrete block construction by Ahmed and Feldman (2012) indicated that, on average, the reinforcing bars in non-contact lap splices, where the lapped bars are located in adjacent cells, only develop 71% of the tensile resistance of spliced bars which are in contact. An experimental program was therefore initiated to design and evaluate remedial measures which can potentially increase the tensile resistance of non-contact lap splices to that of contact lap splice of the same lap length. Implementation of the proposed measures in various field situations was also analyzed. Six unique remedial splice details, along with standard contact and unaltered non-contact lap splices were evaluated and compared. The mitigative details included providing additional confinement, installing knock-out webs, placing splice reinforcement between the lapped bars, and combinations of these aforementioned details. Three replicates of each splice detail were constructed for a total of 24 wall splice specimens. Each wall splice specimen was reinforced with No. 15 Grade 400 deformed steel reinforcing bars with 200 mm lap splice lengths at located the midspan. The specimens were tested in a horizontal position under a monotonic, four-point loading geometry. Load and deflection data were collected throughout testing and were subsequently used in an iterative moment-curvature analysis to calculate the maximum tensile resistance of the spliced reinforcement. This was then used to compare the structural performance of each remedial splice detail to the standard contact and non-contact lap splices. The wall splice specimens which contained non-contact lap splices with knock-out webs, s-shaped, and transverse reinforcement in the splice region achieved similar tensile capacities as the wall splice specimens with standard contact lap splices. Industry professionals have indicated that the installation of the remedial measures evaluated in this study would not affect the constructability of masonry assemblages in field situations. The splice detail with knock-out webs confined within the lap splice length was determined to be the most viable procedure as it can be installed to increase the resistance of non-contact lap splices in almost all construction situations. This remedial procedure was able to improve the tensile resistance of the lapped reinforcement by 63% compared to the wall splice specimens with standard non-contact lap splices.
444

Branched covers of contact manifolds

Casey, Meredith Perrie 13 January 2014 (has links)
We will discuss what is known about the construction of contact structures via branched covers, emphasizing the search for universal transverse knots. Recall that a topological knot is called universal if all 3-manifold can be obtained as a cover of the 3-sphere branched over that knot. Analogously one can ask if there is a transverse knot in the standard contact structure on S³ from which all contact 3-manifold can be obtained as a branched cover over this transverse knot. It is not known if such a transverse knot exists.
445

Dermatitu sergančių pacientų įsijautrinimo kontaktiniams alergenams ir su juo susijusių veiksnių tyrimas / Investigation on contact sensitization and its associated factors in dermatitis patients

Beliauskienė, Aistė 14 February 2012 (has links)
Darbo tikslas – įvertinti dermatitu sergančių pacientų įsijautrinimą kontaktiniams alergenams ir su juo susijusius veiksnius. Darbo uždaviniai: 1. Nustatyti įsijautrinimo kontaktiniams alergenams dažnumą tarp dermatitu sergančių pacientų. 2. Įvertinti įsijautrinimo kontaktiniams alergenams dažnumo sąsajas su tiriamųjų amžiumi, lytimi ir profesija. 3. Nustatyti įsijautrinimo kontaktiniams alergenams klinikos ypatumus. 4. Įvertinti įsijautrinimo kontaktiniams alergenams sąsajas su atopiniu dermatitu, lėtine (-ėmis) kojos (-ų) opa (-omis) ir kitais veiksniais. Išvados: 1. Kontaktiniams alergenams įsijautrinę pusė dermatitu sergančių pacientų, dažniausiai – metalui nikeliui (17,1 proc.). Iš aromatinių medžiagų dažniausias yra įsijautrinimas Peru balzamui (8 proc.). Į pagrindinį alergenų rinkinį neįtrauktini retai (0,1 proc.) nustatyti alergenai: gumų medžiagos merkaptobenzotiazolas ir N-zopropil-N’-fenil-parafenilendiaminas. 2. Įsijautrinimas kontaktiniams alergenams jaunesniems nei 40 metų dermatitu sergantiems pacientams pasireiškia du kartus dažniau nei vyresniems, o moterims – du kartus dažniau nei vyrams. Žemės ūkio ir miškininkystės darbuotojai kontaktiniams alergenams įsijautrinę tris kartus dažniau nei kiti dirbantieji. Vertinant atskirus alergenus, jaunesni nei 40 metų pacientai dažniau nei vyresni yra įsijautrinę nikeliui, kobaltui ir kvaterniumui-15, o 40 metų ir vyresni – Peru balzamui, kanifolijai, aromatų mišiniui I, lanolinui, seskviterpenlaktonams ir... [toliau žr. visą tekstą] / The aim of the study: To evaluate contact sensitization and its associated factors in patients with dermatitis. The objectives of the study: 1. To determine the frequency of sensitization to contact allergens in patients with dermatitis. 2. To evaluate associations between the frequency of sensitization to contact allergens and age, sex and occupation in patients with dermatitis. 3. To determine clinical features of contact sensitization. 4. To evaluate associations between sensitization to contact allergens and atopic dermatitis, chronic leg ulcers and other factors. CONCLUSIONS 1.Half of the patients with dermatitis were sensitized to contact allergens, most frequently to metal nickel (17.1%). From the fragrances, bal¬sam of Peru was the most frequent contact allergen (8%). Rare allergens that should not be included in the baseline series are the substances present in the composition of rubber – mercaptobenzothiazole and N-isopropyl-N'-phenyl-p-phenylene diamine (IPPD). 2.Patients under 40 years of age are two times more frequently sensitized than the older ones. In women contact allergy is twice as more frequent as in men. Agricultural and forestry workers are sensitized to contact allergens three times as more often as other employees. What regards individual allergens, among patients under 40 years of age sensitization to nickel, cobalt and quaternium-15 is more prevalent than in the older ones. Among patients who are 40 years of age and over contact sensitization to... [to full text]
446

Contact Mechanics Of A Graded Surface With Elastic Gradation In Lateral Direction

Ozatas, Cihan A. 01 January 2003 (has links) (PDF)
Today, nonhomogeneous materials are used in many technological applications. Nonhomogeneity can be introduced intentionally in order to improve the thermomechanical performance of material systems. The concept of functionally graded materials (FGMs) is an example of such an application. Nonhomogeneity can also be an intrinsic property of some of the natural materials such as natural soil. The main interest in this study is on the contact mechanics of nonhomogeneous surfaces. There is an extensive volume of literature on the contact mechanics of nonhomogeneous materials. In most of these studies, the elastic gradation is assumed to exist in depth direction. But, it is known that elastic gradation may also exist laterally. This may either occur naturally as in the case of natural soil or may be induced as a result of the applied processing technique as in the case of FGMs. The main objective in this study is therefore to examine the effect of the lateral nonhomogeneities on the contact stress distribution at the surface of an elastically graded material. In the model developed to examine this problem, a laterally graded surface is assumed to be in sliding contact with a rigid stamp of arbitrary profile. The problem is formulated using the theory of elasticity and reduced to a singular integral equation. The integral equation is solved numerically using a collocation approach. By carrying out parametric studies, the effects of the nonhomogeneity constants, coefficient of friction and stamp location on the contact stress distribution and on the required contact forces are studied.
447

Contact Mechanics Of Graded Materials With Two Dimensional Material Property Variations

Gokay, Kemal 01 September 2005 (has links) (PDF)
ABSTRACT CONTACT MECHANICS OF GRADED MATERIALS WITH TWODIMENSIONAL MATERIAL PROPERTY VARIATIONS G&ouml / kay, Kemal M.S., Department of Mechanical Engineering Supervisor: Asst. Prof. Dr. Serkan Dag September 2005, 62 pages Ceramic layers used as protective coatings in tribological applications are known to be prone to cracking and debonding due to their brittle nature. Recent experiments with functionally graded ceramics however show that these material systems are particularly useful in enhancing the resistance of a surface to tribological damage. This improved behavior is attributed to the influence of the material property gradation on the stress distribution that develops at the contacting surfaces. The main interest in the present study is in the contact mechanics of a functionally graded surface with a two &ndash / dimensional spatial variation in the modulus of elasticity. Poisson&rsquo / s ratio is assumed to be constant due to its insignificant effect on the contact stress distribution [30]. In the formulation of the problem it is assumed that the functionally graded surface is in frictional sliding contact with a rigid flat stamp. Using elasticity theory and semi-infinite plane approximation for the graded medium, the problem is reduced to a singular integral equation of the second kind. Integral equation is solved numerically by expanding the unknown contact stress distribution into a series of Jacobi polynomials and using suitable collocation points. The developed method is validated by providing comparisons to a closed form solution derived for homogeneous materials. Main numerical results consist of the effects of the material nonhomogeneity parameters, coefficient of friction and stamp size and location on the contact stress distribution.
448

Högstadieelevers kontaktorsaker och kontaktsätt med skolsköterska : - En enkätstudie

Nyström, Fabian, Öqvist, Pia-Maria January 2013 (has links)
Syfte: Syftet med examensarbetet var att undersöka hur och varför högstadieelever kontaktar skolsköterskan. Vidare var syftet att undersöka om det förelåg någon skillnad mellan könen samt årskurser i relation till antal kontakter med skolsköterskan samt antal gånger de sökt för fysiska respektive psykiska orsaker. Metod: Kvantitativ deskriptiv studiedesign via enkäter. 151 elever i årskurs 7-9 tillfrågades om att besvara en enkät, 74 % (n=112) av populationen deltog. Resultat: Majoriteten av eleverna kontaktade skolsköterskan via den öppna mottagningen. 67,9 % hade kontaktat för fysiska orsaker där ”längd och vikt”, ”gjort mig illa” och ”huvudvärk” var vanligast. För psykisk ohälsa var siffran 10,7 % och ”stress” vanligast förekommande. Ingen skillnad mellan könen kunde påvisas i antalet kontakter samt kontakter för fysiska respektive psykiska orsaker. Mellan årskurserna finns det en skillnad gällande i antalet besök (p = 0,02) och antalet besök för fysiska orsaker (p = 0,005), där årskurs 7 är mest frekvent att söka. Majoriteten (64,2%) av deltagarna ville helst kontakta skolsköterskan direkt via den öppna mottagningen. Slutsats: Det är främst via den öppna mottagningen som elever tar och vill kunna komma i kontakt med skolsköterskan. Det finns en skillnad mellan årskurser i antalet besök hos skolsköterskan samt antalet besök för fysiska orsaker. / Aim: The aim of this bachelor thesis was to examine how and why high school students contacted their school nurse. Furthermore the aim was to examine if there was a difference between genders and grades pertaining to number of contacts with the school nurse and number of contacts because of physical respectively mental reasons. Method: Quantitative descriptive study design using questionnaires. 151 students in grades 7-9 were asked to answer a questionnaire, 74% (n = 112) of the population participated. Results: The majority of the students contacted the school nurse through the nurse’s office. 67.9% had contacted concerning physical health issues which "height and weight", "hurt me" and "headache" was the most common. For mental issues the same number was 10.7 % and “stress” most common. There was no significant difference between genders in relation to number of contacts with the school nurse or physical or mental reasons for contact. However there was a significant difference (p = 0.02) between grades pertaining to relation to number of contacts and to physical reasons for contact (p = 0.005), which grade 7 is most frequently. Most (64.2 %) pupils would like to contact the school nurse through the nurse’s office. Conclusion: The students prefer to have direct contact with the school nurse at the nurse´s office. There is a difference between grades in the number of visits to the school nurse and the number of visits for physical reasons.
449

Skin sensitivity testing : a biophysical approach /

Nyrén, Miruna, January 2002 (has links)
Diss. (sammanfattning) Stockholm : Karol. inst., 2002. / Härtill 5 uppsatser.
450

Influence of crystallographic orientation in normal and sliding contacts

Dawkins, Jeremy James January 2008 (has links)
Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Rick Neu; Committee Member: Itzhak Green; Committee Member: Jeffrey Streator

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