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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.
271

Early polymeric materials encountered in furniture, 1880-1920 : their chemistry, conservation, history and manufacture

Kaner, Jake January 2001 (has links)
No description available.
272

Ratings of female genital attractiveness pre- and post-genital cosmetic surgery differ by age and gender

Pallatto, Corey Ann 06 October 2011 (has links)
To understand how genital self-image affects sexual well-being, it is important to consider its influence on sexual function and distress. It is also important to learn what type of genital appearance is considered visually appealing to men and women, and whether genitalia modified by cosmetic surgery are judged as more attractive compared to unmodified genitalia. The present study assessed women’s genital self-image, sexual functioning and sexual distress in order to elucidate the relationship between these three elements of sexual well-being. Additionally, genital photographs were presented to men and women in order to assess conceptions of female genital attractiveness relative to surgical status (i.e. before and after). Four hundred and seventy-six women (M age=24.38) completed online questionnaires to assess genital self-image, sexual satisfaction, functioning and distress. The female sample along with 429 men (M age = 27.47) also reviewed pictures of pre- and post-surgery genitalia and rated them on levels of attractiveness. The Female Genital Self-Image Scale, the Relational Concern and Personal Concern subscales of the Sexual Satisfaction Scale – Women, and the Female Sexual Functioning Index were administered. Genital self-image was positively correlated with functioning variables including arousal, lubrication, orgasm, satisfaction and pain, and negatively correlated with sexual distress. Men rated unaltered and altered genitalia as more attractive than women; older participants rated unaltered and altered genitalia as more attractive than younger participants, and men and women of all ages found altered genitalia more attractive than unaltered genitalia.Women with positive genital self-image experience higher levels of sexual functioning and lower levels of sexual distress. Female genitalia modified by genital cosmetic surgery are considered more attractive regardless of age and gender. / text
273

Modeling and analysis of dual hydroforming process

Jain, Nishant 30 September 2004 (has links)
The tube hydroforming process has gained increasing attention in recent years. Coordination of the internal pressurization and axial feeding curves is critical in the tube hydroforming process to generate successful parts without fracture or wrinkling failure. The stress state at a given time and location varies with the process history and the design and control of the load paths. A new process parameter, counter-pressure, is introduced to achieve a favorable tri-axial stress state during the deformation process. The new process is referred to as dual hydroforming. The benefits offered by dual hydroforming will be characterized based upon the amount of wall thinning, plastic instability limit and final bulged configuration. An analytical model is developed to analyze the stress and strain state in the part (tube) during the dual hydroforming process. The stress-strain condition analyzed will be used to evaluate and compare thinning for tube hydroforming and dual hydroforming. The effect of applying counter-pressure on the plastic instability of thin-walled tubes with only internal pressure and combination of internal pressure and independent axial loading is considered. Finite element analysis is used to quantify the merits of dual hydroforming in terms of final bulged configuration. A parametric study has been conducted to investigate the effectiveness of dual hydroforming based on the various material properties and process conditions. Dual hydroforming results in different stress and strain states compared to tube hydroforming. The counter-pressure enabled favorable tri-axial stress state during deformation that resulted in different thickness and percentage thinning. Finite element analysis showed that for a particular amount of wall thinning there is an increase of around 8% in bulge height for dual hydroforming. Dual hydroforming delays the onset of plastic instability. This increase in the value of effective strain to failure results in an increase of around 12% in bulge height for dual hydroforming as shown by finite element simulations. Results of this study indicate that dual hydroforming can increase expansion i.e. more difficult parts can be designed and manufactured. Also, for a given part geometry, higher strength and less formable materials can be used.
274

Crystallization and melting behavior studies of un-nucleated and silica-nucleated isotactic polystyrene and isotactic poly(propylene oxide)

Kennedy, Mary A. January 1988 (has links)
The effect of silica on the crystallization and melting behavior of a highly isotactic, well characterized isotactic polystyrene (i-PS) have been investigated. The origins of the various endotherms obtained upon heating have been defined by partial scanning experiments and by a study of the effect of heating rate using differential scanning calorimetry (DSC). The presence of 1 part silica in 100 parts polymer (1 pph) decreases the maximum degree of crystallinity considerably but has a minimal effect on the rate of crystallization. Analysis by the Avrami method shows that the silica does not affect the overall rate of crystallization significantly. The decrease in the crystallinity indicates that silica affects the level of secondary crystallization, thus the crystal perfection. / The surface morphologies and growth rates of i-PS spherulites, as studied by photomicroscopy, were not affected by 1 pph of silica. The experimental data were fitted to a modified form of the Hoffman-Lauritzen equation. / The effect of silica on spherulite growth rates and surface morphologies of isotactic poly(propylene oxide) (i-PPO) have also been investigated by optical microscopy. Two distinct i-PPO samples of different molecular weights were used, each of which was highly isotactic. The addition of silica has a pronounced effect on the morphology of the spherulites, producing dendritic type morphology. Upon step-crystallization, the spherulites exhibited mixed morphologies, i.e., fibrillar and ringed. Silica depresses the spherulite growth rates throughout the entire temperature range. The effects were more profound as the quantity of filler increased. The growth rate-temperature behavior was analysed in terms of the classical Hoffman-Lauritzen equation and a modified version to take into account the polymer-filler interaction.
275

Beyond the disposable plastic grocery bag : the opportunity of bagless retail as seen through the lenses of morality, economics, and the environment

Tucker, Norel G. 30 November 2010 (has links)
This paper has attempted to accurately assess the impact of the disposable plastic grocery bag on the planet. Based on the research findings, it has been concluded that disposable plastic grocery bags are not a necessity, are not justifiable on many reasonable grounds, are costly, and are a toxic detriment to our health and our environment. The distribution of an educational executive briefing package attempted to influence retailers to avail of the opportunity (outlining potential profit, corporate image, and environmental benefits) of going bagless at the checkout, and to cease the use of disposable plastic bags in favour of the non-woven, polypropylene green bag. A shift to this reusable green bag appears to represent an important and effective interim measure towards more noble and sustainable living. Throughout this paper, the disposable plastic grocery bag will be considered through the lenses of morality, economics and the environment.
276

Popcorn for cushioning purpose

Cheng, Hoi Po, 1975- January 2005 (has links)
In the packaging industry, cushioning products are usually made of plastic materials, such as polystyrene. The insulation and lightweight character make it more popular and convenient to use. However, the extensive use of it creates more waste leading to an environmental problem. Usually the cushioning foams are discarded after being used for inbox protection as packaging material; eventually they end up in a landfill. Most plastic foams are not biodegradable, which cannot be composted and will create more and more waste that affects the ecological system. In the mean time, foams made up of bio-degradable materials are considered. In general, biodegradable plastics are starch-based or cellulose-based, and the biodegradable components can be found in corn (e.g. corn starch, and corn cob). Instead of extracting the corn component, here popped corn kernel will be investigated for its suitability in packaging applications.
277

State variable analysis of flow localization in work hardening materials

Christodoulou, Nicholas C. January 1982 (has links)
Large strain tensile tests were carried out on OFHC Cu and 99.99% Al with the aim of determining the first and second order work hardening and rate sensitivity coefficients. The tests were performed at room temperature and 473 K and at constant true strain rates in the range 5 x 10('-4) to 10('-1) s('-1). With the aid of a diameter transducer, which was set up to measure and control the rate of reduction of the diameter of the tensile specimen, the strain rate at the minimum cross-section was held constant well beyond the point of maximum load. A second diametral sensor was constructed for use at elevated temperatures. In order to extend the range of conditions covered, constant strain rate compression tests were also performed on Cu at 698 K. In a further series of experiments, tensile tests were carried out on Cu and Al samples at 293 and on Al specimens at 473 K in which the flow localization process was followed by photographic means. / It was observed that the values of the rate sensitivity of the work hardening rate B(,(sigma)) beyond the maximum load are not negligible, but that they are less than 1, in opposition to the theoretical predictions of Kocks et al('(47)). Furthermore, it is shown that, contrary to the suggestion of these workers, the rate sensitivity at constant work hardening rate N is not the material coefficient that controls the growth of strain rate gradients at large strains. / The material coefficients determined using the diametral transducer were employed for the numerical integration of the second order differential equation describing flow localization proposed by Kocks et al('(47)). This equation was integrated at the minimum cross-section of the sample, and the solution is compared with the one calculated by integrating the first order differential equation proposed earlier by Jonas et al('(10)). As expected, the strain measurements obtained from the flow localization experiments are reproduced more closely by the second order solution than by the first order one largely because of the non-negligible values of B(,(sigma)). However, at large deformations, there is a discrepancy between the experimental observations and the predictions of the second order theory. This is attributed to the development of triaxial stresses at these strains. A possible modification of the second order treatment is suggested, based on the gradient in the Bridgman correction term.
278

Cutaneous malignant melanoma in the Natal province : an epidemiologic study : reflections upon its aetiology.

Flamment, A. H. January 1985 (has links)
The purpose of the study has been primarily to draw a profile of malignant melanoma in the different population groups inhabiting the Natal Province and Kwa-Zulu, to compare the presentation and incidence of the disease between these groups as well as with similar racial groups in different countries. The data collected then permitted to estimate which parameters were relevant in predicting the course of the disease, as well as the results of surgical and adjuvant therapy, and was utilized in a search for the aetiology of the tumour. / Thesis (M.D.)-University of Natal, Durban, 1985.
279

Novel methods for determining the optical constants of anisotropic polymer films -- new application of prism wave-guide coupling

Liu, Tao January 2001 (has links)
No description available.
280

Elastic-plastic instability of plane frames

Mohamed, Salah-Eldin A. 08 1900 (has links)
No description available.

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