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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.
211

Multi-objective day-ahead scheduling of microgrids using modified grey wolf optimizer algorithm

Javidsharifi, M., Niknam, T., Aghaei, J., Mokryani, Geev, Papadopoulos, P. 10 August 2018 (has links)
Yes / Investigation of the environmental/economic optimal operation management of a microgrid (MG) as a case study for applying a novel modified multi-objective grey wolf optimizer (MMOGWO) algorithm is presented in this paper. MGs can be considered as a fundamental solution in order for distributed generators’ (DGs) management in future smart grids. In the multi-objective problems, since the objective functions are conflict, the best compromised solution should be extracted through an efficient approach. Accordingly, a proper method is applied for exploring the best compromised solution. Additionally, a novel distance-based method is proposed to control the size of the repository within an aimed limit which leads to a fast and precise convergence along with a well-distributed Pareto optimal front. The proposed method is implemented in a typical grid-connected MG with non-dispatchable units including renewable energy sources (RESs), along with a hybrid power source (micro-turbine, fuel-cell and battery) as dispatchable units, to accumulate excess energy or to equalize power mismatch, by optimal scheduling of DGs and the power exchange between the utility grid and storage system. The efficiency of the suggested algorithm in satisfying the load and optimizing the objective functions is validated through comparison with different methods, including PSO and the original GWO. / Supported in part by Royal Academy of Engineering Distinguished Visiting Fellowship under Grant DVF1617\6\45
212

Analogy-based software project effort estimation. Contributions to projects similarity measurement, attribute selection and attribute weighting algorithms for analogy-based effort estimation.

Azzeh, Mohammad Y.A. January 2010 (has links)
Software effort estimation by analogy is a viable alternative method to other estimation techniques, and in many cases, researchers found it outperformed other estimation methods in terms of accuracy and practitioners¿ acceptance. However, the overall performance of analogy based estimation depends on two major factors: similarity measure and attribute selection & weighting. Current similarity measures such as nearest neighborhood techniques have been criticized that have some inadequacies related to attributes relevancy, noise and uncertainty in addition to the problem of using categorical attributes. This research focuses on improving the efficiency and flexibility of analogy-based estimation to overcome the abovementioned inadequacies. Particularly, this thesis proposes two new approaches to model and handle uncertainty in similarity measurement method and most importantly to reflect the structure of dataset on similarity measurement using Fuzzy modeling based Fuzzy C-means algorithm. The first proposed approach called Fuzzy Grey Relational Analysis method employs combined techniques of Fuzzy set theory and Grey Relational Analysis to improve local and global similarity measure and tolerate imprecision associated with using different data types (Continuous and Categorical). The second proposed approach presents the use of Fuzzy numbers and its concepts to develop a practical yet efficient approach to support analogy-based systems especially at early phase of software development. Specifically, we propose a new similarity measure and adaptation technique based on Fuzzy numbers. We also propose a new attribute subset selection algorithm and attribute weighting technique based on the hypothesis of analogy-based estimation that assumes projects that are similar in terms of attribute value are also similar in terms of effort values, using row-wise Kendall rank correlation between similarity matrix based project effort values and similarity matrix based project attribute values. A literature review of related software engineering studies revealed that the existing attribute selection techniques (such as brute-force, heuristic algorithms) are restricted to the choice of performance indicators such as (Mean of Magnitude Relative Error and Prediction Performance Indicator) and computationally far more intensive. The proposed algorithms provide sound statistical basis and justification for their procedures. The performance figures of the proposed approaches have been evaluated using real industrial datasets. Results and conclusions from a series of comparative studies with conventional estimation by analogy approach using the available datasets are presented. The studies were also carried out to statistically investigate the significant differences between predictions generated by our approaches and those generated by the most popular techniques such as: conventional analogy estimation, neural network and stepwise regression. The results and conclusions indicate that the two proposed approaches have potential to deliver comparable, if not better, accuracy than the compared techniques. The results also found that Grey Relational Analysis tolerates the uncertainty associated with using different data types. As well as the original contributions within the thesis, a number of directions for further research are presented. Most chapters in this thesis have been disseminated in international journals and highly refereed conference proceedings. / Applied Science University, Jordan.
213

Androgenetic alopecia: a possible treatment and a relationship with hair greying. Assessment of the herbal mixture Xiantene for the treatment of androgenetic alopecia and a relationship between early hair greying and the progression of androgenetic alopecia

Davies, Paul G. January 2010 (has links)
Hair plays an important role in human social and sexual communication. The androgen-stimulated, patterned loss of hair in cases of androgenetic alopecia (or common baldness) in genetically pre-disposed individuals, is associated with ageing and can cause marked phychological distress. However, it is poorly controlled. To investigate the effectiveness of daily topical application of a Chinese medicine-derived herbal mixture, Xiantene, on balding progression, two double-blind, placebo-controlled studies (3 and 12 months) were carried out on balding men using the trichogram approach. Xiantene significantly increased both the total number of hairs and those in anagen, improving the ratio of anagen:telogen hairs. This suggests that topical Xiantene increased the length of the anagen phase and may promote a cessation, or partial reversal, of the progression of androgenetic alopecia in men. Canities, loss of scalp hair colour, is another mark of ageing. To investigate whether early greying may protect follicles from androgenetic alopecia, the extent of alopecia, assessed using the Hamilton scale, was compared between men who first became grey before, or after, 30. Both alopecia and greying increased with age in 843 men (217 European, 626 Thai) whenever they first started greying. However, men who showed greying before 30 were significantly less bald, though more grey, in both groups. Hair follicle melanocytes synthesise the pigment melanin, producing reactive oxygen species (ROS) and oxidative stress; losing melanocyte pigmentary activity, and therefore these toxic factors, appears to enable hair follicles to maintain their full size for longer, despite the androgen drive to miniaturisation. / Tri-Mill Charitable Trust, Global Beauty International Management Ltd.
214

Design and analysis of Discrete Cosine Transform-based watermarking algorithms for digital images. Development and evaluation of blind Discrete Cosine Transform-based watermarking algorithms for copyright protection of digital images using handwritten signatures and mobile phone numbers.

Al-Gindy, Ahmed M.N. January 2011 (has links)
This thesis deals with the development and evaluation of blind discrete cosine transform-based watermarking algorithms for copyright protection of digital still images using handwritten signatures and mobile phone numbers. The new algorithms take into account the perceptual capacity of each low frequency coefficients inside the Discrete Cosine Transform (DCT) blocks before embedding the watermark information. They are suitable for grey-scale and colour images. Handwritten signatures are used instead of pseudo random numbers. The watermark is inserted in the green channel of the RGB colour images and the luminance channel of the YCrCb images. Mobile phone numbers are used as watermarks for images captured by mobile phone cameras. The information is embedded multiple-times and a shuffling scheme is applied to ensure that no spatial correlation exists between the original host image and the multiple watermark copies. Multiple embedding will increase the robustness of the watermark against attacks since each watermark will be individually reconstructed and verified before applying an averaging process. The averaging process has managed to reduce the amount of errors of the extracted information. The developed watermarking methods are shown to be robust against JPEG compression, removal attack, additive noise, cropping, scaling, small degrees of rotation, affine, contrast enhancements, low-pass, median filtering and Stirmark attacks. The algorithms have been examined using a library of approximately 40 colour images of size 512 512 with 24 bits per pixel and their grey-scale versions. Several evaluation techniques were used in the experiment with different watermarking strengths and different signature sizes. These include the peak signal to noise ratio, normalized correlation and structural similarity index measurements. The performance of the proposed algorithms has been compared to other algorithms and better invisibility qualities with stronger robustness have been achieved.
215

»Cultural Grey-Out« oder »Many Diverse Musics«?: Musikkulturen der Welt in Zeiten der Globalisierung

Grupe, Gerd 23 June 2023 (has links)
While Erich von Hornbostel, pioneer of the early Berlin school of comparative musicology, saw no reason to expect a homogenisation of music around the globe, some later ethnomusicologists feared a cultural greying-out, a loss of diversity of the world’s musics under the impact of Westernisation. More in-depth knowledge of many musical cultures and of the processes at work in present-day societies in Asia and Africa, however, seem to paint a different picture. By discussing several case studies of musical idioms from Nigeria and Zimbabwe, this paper corroborates Peter Manuel’s opinion that it is especially in the domain of popular musics where a dynamic process constantly gives rise to ever new local musical styles. Their success as compared to some transnational genres may in part be attributed to the importance of helping to create local identities. Thus, the effects of the decreasing presence of some more traditional musical idioms and of the almost omnipresent Western pop music are counteracted by new, sometimes hybrid popular styles which often draw substantially from local traditional genres. But the impact of globalisation can also be traced in the domain of non-Western traditional musics and of Western contemporary composers. As a case in point, the attitudes of two Western composers, Kevin Volans and György Ligeti, towards traditional music of sub-Saharan Africa are explored by drawing on two well-known examples, namely Volans’ piece Mbira and Ligeti’s piano etude No. 6. In conclusion we may assume that, in spite of a profound Western influence on the musics of the world, at present there seems to be no reason to fear a musical greying-out.
216

A Multimodal Magnetic Resonance Study of the Effects of Childhood Lead Exposure on Adult Brain Structure

Brubaker, Christopher John 15 September 2009 (has links)
No description available.
217

Influence of Daily Electrical Stimulation of Periaqueductal Grey on Vocalization and Depressive-like Behavior during Separation in Guinea Pigs

Dazey, Jennifer January 2012 (has links)
No description available.
218

Association of Arterial Stiffness and Changes in Brain Structure and Function in the UK Biobank

Allison, Elric Y. 11 1900 (has links)
While evidence suggests there is indeed a relationship between arterial stiffness and changes in brain structure and function cross-sectionally, the longitudinal relationship between arterial stiffness and changes in brain structure and function is unclear. Also unclear is whether a regional effect of arterial stiffness on brain structure exists, or if the effect is homogenous across brain regions. Using a healthy cohort of the UK Biobank study (N = 1858, meanSD: 61  7 years), we investigated the longitudinal association between changes in arterial stiffness index (ASI) and brain structure (grey matter cortical thickness, whole brain grey matter volume, white matter hyperintensity volume) and function (cognitive performance in 6 tests) over 2.5  1 years. We also examined the association between baseline ASI and all structural and functional brain outcomes 8-11 years post-baseline (N = 630). Prior to post-hoc correction, we observed a significant effect of changes in ASI over 2.5  1 years on grey matter cortical thickness in 11 brain regions contributing to reductions between 0.0004-0.0024mm annually, but none of the 11 regions remained significant post-correction. Following correction there was also no effect of changes in ASI on whole brain grey matter volume (p = 0.76), white matter hyperintensity volume (p = 0.84), or cognitive performance in the domains of interest. Baseline ASI was not associated with regional grey matter cortical thickness, white matter hyperintensity volume, or cognitive function, but did have a significant negative association with whole brain grey matter volume 8.5  1.05 (p = 0.015) years later and 11  1.02 (p = 0.03) years later. Our findings suggest that taken with the effect of age, elevations in ASI may have an additive effect to accelerate changes in brain structure beyond the range that is to be expected as a part of normal aging. Our findings also suggest the relationship between ASI and reductions in whole brain grey matter volume may require long-term exposure to elevations in arterial stiffness in otherwise healthy older adults. / Thesis / Master of Science in Kinesiology / Arterial stiffening both accompanies the normal aging process and can progress due to acquired health conditions. As arteries begin to stiffen the ability to buffer high pressure blood flow is impaired and can put microvasculature at risk of damage. Microvascular damage in the brain can disrupt blood and subsequent oxygen delivery to the brain. When delivery to the brain does not meet the metabolic demand, changes in brain structure brain can occur. Changes in brain structure are associated with impaired brain function, as well as potentially accelerating the progression of neurological diseases. What remains unclear is whether arterial stiffness impacts brain structure differently across regions or all regions homogenously. The purpose of this thesis was to examine the relationship between arterial stiffness and structural and functional changes in the brain over time (objective 1: 2-5 years; objective 2: 8-11 years). Our observations suggest that the progression of arterial stiffness had an effect that was equivalent to approximately 30% of the rate of grey matter tissue loss associated with normal healthy aging (~0.25% reduction in grey matter per year). We found no effect of changes in arterial stiffness on the progression of total grey matter volume, white matter lesions or brain function. We did observe a significant negative relationship between arterial stiffness at baseline and total grey matter volume 8-11 years later. We found no relationship between baseline arterial stiffness and brain structure or function 8–11-years post-baseline. Taken with the effects of normal aging, the loss of tissue in select brain regions associated with changes in arterial stiffness may result in grey matter reductions beyond the range associated with what is considered healthy or normal aging. The association of arterial stiffness and total grey matter volume 8-11 years later suggests that changes in whole brain structure are the product of long-term exposure to arterial stiffness.
219

Heat Storage in Buildings : Achieving thermal peak shaving through indoor temperature flexibility

Cederblad, Mathilda, Dahlberg, August January 2022 (has links)
Buildings are currently controlled in a sub optimal way, using a WC controller that is dependent only on the external temperature. A rich amount of real-time data from installed sensors is available within the buildings and the network and can be used to counteract this. To better control the indoor temperature and the heat supply this degree-project develops a model and optimizer for control of the indoor temperature, where industry standard data streams are used as inputs. The model and optimizer can be implemented in a MPC which takes the future external temperature into consideration and enhances the ability to control the heat supply. There are two main reasons why enhanced control is interesting to look at, the economic aspects and the comfort of the occupancies. This degree project is focused on developing a general building model for the purpose of utilizing the building as an energy storage for peak-shaving.  The finalized model is a dynamic grey-box model developed using data from a multifamily building, Building A, located in Västerås Sweden. The training period is set to 408 hours, and the prediction horizon is set to 48 hours as a result of the verification. To demonstrate the utilization possibilities of using the building as a heat storage, an optimizer is constructed to evaluate a peak shaving control strategy. The control objective (Qsupply) is controlled by manipulating the indoor temperature (Tin) within a set interval. By setting a fixed interval for the indoor temperature within the comfort interval, the comfort is still maintained. For the peak shaving different flexibilities within the indoor temperature have been examined with a range from 22 +/- 0.25 degrees Celcius to 22 +/- 2.00 degrees Celcius.  The model is verified in 4 steps: prediction ability on the historic data, parametric verification on the time constant, simulation of heat supply separately from the historic data and model generality by implementing the model on a second multifamily building, Building B. The model has a RRMSE of 8% for Building A and 9% for Building B which is considered excellent.  Due to the lack of access to the real building, the developed model is not validated. Based on peak shaving and energy consumption, the preferred solution is 22+/- 1.25 degrees Celcius. But based on surveys about occupancies attitude toward flexibility in the indoor temperature and economical aspects, an indoor temperature of 22 +/- 0.50 degrees Celcius is considered the best choice with the maximum peak in the heat supplied decreased by 35% and the energy consumption is decreased by 10% compared to the historical case. We suggest allowing the customers to choose their preferred flexibility to ensure comfort.
220

Modeling the Heat Flow Dynamics of a Houses Using Stochastic Differential Equations

Mayo Nardone, Pablo Sabino January 2021 (has links)
This research aims to explore new ways of assessing energy performance within housing units. The mainobjective of this work is to propose a heat dynamics model based on monitoring data, to contribute towardsan energy-efficient transition in the building sector. An extensive study on the available mathematical and statistical tools is described in order to determine aholistic solution, found in grey-box models. This model approach offers the possibility of understandingmultivariate systems, which can be applied to a housing-unit heat flow dynamics. Through the iterative process of testing each possible model, this work determines the one with bestexplanatory power, defining the thermal characteristics of the studied housing unit. This method allows thedetection of underperforming dwellings among constructions with high energy-efficiency standards. This investigation reflects the feasibility of employing grey-box models to predict the dynamics of heatrelated systems. Moreover, it sets the basis for new ways of employing the monitoring data of dwellings. / Denna forskning syftar till att utforska nya sätt att bedöma energiprestanda inom bostäder. Huvudsyftetmed detta arbete är att föreslå en värmedynamikmodell baserad på övervakningsdata för att bidra till enenergieffektiv övergång inom byggsektorn. En omfattande studie av tillgängliga matematiska och statistiska verktyg beskrivs för att bestämma enhelhetslösning, som finns i gråboxmodeller. Denna modellstrategi ger möjlighet att förstå multivariatasystem, som kan tillämpas på en hushålls värmedynamik. Genom den iterativa processen att testa varje möjlig modell bestämmer detta arbete den med bästförklarande kraft, och definierar de studerade husenhetens termiska egenskaper. Denna metod gör detmöjligt att upptäcka underpresterande bostäder bland anläggningar med hög energieffektivitetsstandard. Denna undersökning återspeglar möjligheten att använda gråboxmodeller för att förutsäga dynamiken ivärmerelaterade system. Dessutom lägger den grunden för nya sätt att använda övervakningsdata förbostäder.

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