13,195 research outputs found
Assessment of Newspaper Circulation and Readership in Northern Ghana
There is a widespread concern that the print newspaper industry across the world and in Ghana particularly faces an uncertain future and a long-term decline in readership and circulation due to the prevalence of internet mediated News websites, making print newspapers obsolete in their present format. This paper is an assessment of the circulation and readership of printed newspapers in the northern regional capital, Tamale. It investigates preferred News sources among newsreaders and examines consumption pattern of newspapers in the metropolis. It discussed the challenges the print media industry faces in the wake of News websites’ proliferation in the Ghanaian media landscape. The paper is based on exploratory research design. It sampled four leading print newspapers in Ghana (Daily Graphic, Daily Guide, Ghanaian Times and Business and Financial Times) as reference points for data collection. Four newspaper vendors who vend these newspapers in the metropolis were sampled through simple random sampling. The paper finds a sharp decline in circulation and readership of printed newspaper in the metropolis in favour of internet powered News websites. The paper concludes that although newsreaders prefer sourcing News online, they still find the traditional printed media as the most credible and reliable sources for News. The paper recommends that the traditional print media take advantage of the reach of internet powered platforms to create online presence and ensure that they innovate to get newsreaders subscribe to their brands since print newspaper readership is gradually declining in the metropolis
Individual And Ensemble Pattern Classification Models Using Enhanced Fuzzy Min-Max Neural Networks
Pattern classification is one of the major components for the design and development of a computerized pattern recognition system. Focused on computational intelligence models, this thesis describes in-depth investigations on two possible directions to design robust and flexible pattern classification models with high performance. Firstly is by enhancing the learning algorithm of a neural-fuzzy network; and secondly by devising an ensemble model to combine the predictions from multiple neural-fuzzy networks using an agent-based framework. Owing to a number of salient features which include the ability of learning incrementally and establishing nonlinear decision boundary with hyperboxes, the Fuzzy Min-Max (FMM) network is selected as the backbone for designing useful and usable pattern classification models in this research. Two enhanced FMM variants, i.e. EFMM and EFMM2, are proposed to address a number of limitations in the original FMM learning algorithm. In EFMM, three heuristic rules are introduced to improve the hyperbox expansion, overlap test, and contraction processes. The network complexity and noise tolerance issues are undertaken in EFMM2. In addition, an agent-based framework is capitalized as a robust ensemble model to house multiple EFMM-based networks. A useful trust measurement method known as Certified Belief in Strength (CBS) is developed and incorporated into the ensemble model for exploiting the predictive performances of different EFMM-based networks
Interaction of Closely Spaced Shallow Foundations on Sands and Clays: A review
The evaluation of the static interaction of closely spaced footings and its influence in the overall bearing capacity and settlement on sand and clay soils is addressed in this review. The work is accomplished through a comprehensive look into all relevant literature regarding the interaction of sallow foundations, assessments are made, and conclusions are drawn which will ultimately be relevant to future endeavors associated with the design and the evaluation of closely spaced shallow foundations in terms of determining the optimal spacing between footings, enhancing bearing capacity, and controlling deformation. Furthermore, the work is divided to three major approaches: theoretical studies, experimental or field tests, and numerical analysis. Each have been discussed thoroughly in details, with indicating the shortcomings of previous studies and where each approach has reached. The result of this review has showed that nearly all previous research studies explored the effect of the interaction of closely spaced shallow foundations on the bearing capacity at the ultimate failure compared to the settlement behavior which is for some reason not addressed profoundly,even though it is more critical than bearing capacity. Additionally, current regulations and codes have not devoted a major effort toward addressing the influence of closely spaced shallow foundations appropriately, especially today,where the limitation of a site and the placing of footings close together in order to accommodate structural details are becoming a more common issue
Design of discrete time controllers for DC-DC boost converter
06.03.2018 tarihli ve 30352 sayılı Resmi Gazetede yayımlanan “Yükseköğretim Kanunu İle Bazı Kanun Ve Kanun Hükmünde Kararnamelerde Değişiklik Yapılması Hakkında Kanun” ile 18.06.2018 tarihli “Lisansüstü Tezlerin Elektronik Ortamda Toplanması, Düzenlenmesi ve Erişime Açılmasına İlişkin Yönerge” gereğince tam metin erişime açılmıştır.DC-DC dönüştürücüler sahip oldukları yüksek verim, yüksek güç yoğunluğu, yüksek güç seviyeleri, düşük maliyet ve küçük fiziksel yapı özelliklerinden dolayı modern güç elektroniği sistemlerinde yaygın olarak kullanılmaktadırlar. Genel olarak alçaltıcı, yükseltici ve alçaltıcı/yükseltici tipinde olabilen dönüştürücüler çoklu çıkış gerilimine sahip olabilmektedirler. Yükseltici dönüşürücüler, giriş geriliminden daha yüksek bir çıkış gerilimi üreten bir tür anahtarlamalı-modlu dc-dc dönüştürücülerdir. Yükseltici tip DC-DC dönüştürücünün ortalama durum-uzay tekniğine dayalı küçük-sinyal modeli elde edilmiştir. Ayrık-zaman kontrolör iki ayı yöntem, frekans domeni ve durum-uzay yöntemleri, kullanılarak tasarlanmıştır. Kök-yer eğrisi yöntemi ile integral kontrolör tasarlanmıştır. Durum geribesleme kazanç matrisi hem kutup yerleştirme hem de doğrusal optimal kuadratik regülatör yaklaşımları kullanılarak tasarlanmıştır. Kontrolcülü yükseltici dönüştürücünün performansı MATLAB/SIMULINK ortamında yapılan similasyon çalışmaları ile incelenmiş ve doğrulanmıştır. Tasarlanan kontrolör türleri tasarım metodolojisi, uygulama problemleri ve performans açısından karşılaştırılmıştır. Tasarlanan kontrol yöntemlerinin birbirine yakın bir performansa sahip olduğu gözlemlenmiştir. Bu çalışmada, yükseltici tip DC-DC dönüştürücüler için sürekli-hal ve dinamik karakteristik açısından uygun bir performansa sahip kontrolör tasarımı amaçlanmıştır.DC-DC converters are extensively used in modern power electronics devices due to their high efficiency, high power density, high power levels, low cost, and small size. In general, they can be step-up, step-down or step-up/down converters and can have multiple output voltages. Boost converter, (also known as a step-up converter) is a type of switched-mode dc-dc converter which produces output voltage that is greater than input voltage. A small signal modeling based on state space averaging technique for DC-DC Boost converter is carried out. Discrete time controller is designed using two design techniques; frequency domain and state space methods. Root locus technique is used to design an integral controller. A state feedback gain matrix is designed by pole placement technique and Linear Quadratic Optimal Regulator (LQR) methods. The performance of the controlled boost converter are investigated and verified through MATLAB/SIMULINK simulation. Comparison between the designed controllers related to the design methodology, implementation issues and performance is carried out. It is seen that the designed controllers yielded comparable performances. In this study, it is aimed to design a controller for DC-DC boost converter to provide satisfactory performance in term of static, dynamic and steady-state characteristics
Numerical Study of Negative-Refractive Index Ferrite Waveguide
Consider a magnetized ferrite-wire waveguide structure situated between two half free spaces. Ferrites
to provide negative permeability and wire array to provide negative permittivity. The structure form left -
handed material (LHM) with negative refractive index. The transmission of electromagnetic waves
through the structure is investigated theoretically. Maxwell's equations are used to determine the electric
and magnetic fields of the incident waves at each layer. Snell's law is applied and the boundary conditions
are imposed at each layer interface to calculate the reflected and transmitted powers of the structure. Numerical
results are illustrated to show the effect of frequency, applied magnetic fields, angle of incidence
and LHM thickness on the mentioned powers. The analyzed results show that the transmission is very
good when the permeability and permittivity of the structure are both simultaneously negative. The frequency
band corresponding to this transmission can be tuned by changing the applied magnetic fields. The
obtained results are in agreement with the law of conservation of energy.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2489
Maximum and Minimum Transmittance of a Structure Containing N-Identical Pairs of Left- and Right-Handed Materials
The optical transmission properties of a structure consisting of N identical pairs of left- and right-materials are investigated theoretically and numerically. Maxwell's equations are used to determine the electric and magnetic fields of the incident waves at each layer. Snell's law is applied and the boundary conditions are imposed at each layer interface to calculate Fresnel coefficients. Expressions for reflectance and transmittance of the structure are given in terms of these coefficients. In the numerical results the transmittance of the structure is computed and illustrated as a function of frequency under different values of N. Minimum transmittance is achieved by using high and low opposite refractive indices of left and right materials of each pair of the structure. The frequency band of this transmittance is reduced by decreasing N. Maximum transmittance is demonstrated by using two slabs of the same width and opposite refractive indices placed between two dielectric media of the same kind. The effect of frequency and angle of incidence is very weak in these structures as compared to their all-dielectric counterparts. Moreover the obtained results are in agreement with the law of conservation of energy.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3026
Numerical study of a structure containing left-handed material waveguide
In this paper a waveguide structure consisting of a pair of left-handed material (LHM) and dielectric slabs inserted in vacuum is investigated theoretically. Maxwell’s equations are used to determine the electric and magnetic fields of the incident waves at each layer. Snell’s law is applied and the boundary conditions are imposed at each layer interface to calculate the reflected and transmitted powers of the structure. Numerical results are illustrated to show the effects of frequency, angle of incidence and LHM thickness on the transmitted power when the refractive index of the dielectric layer changes. The same procedure is repeated to show the variation of the transmitted power with the change in the mentioned parameters under different values of dissipation factor of the lossy LHM. Consequently, two cases of the LHM are considered, loss-less case and loss case. The results obtained, are in agreement with
Effect of negative permittivity and permeability on the transmission of electromagnetic waves through a structure containing left-handed material
We investigate the characteristics of electromagnetic wave reflection and transmission by multilayered structures consisting of a pair of left-handed material (LHM) and dielectric slabs inserted between two semi-infinite dielectric media. The theoretical aspect is based on Maxwell's equations and matching the boundary conditions for the electric and magnetic fields of the incident waves at each layer interface. We calculate the reflected and transmitted powers of the multilayered structure taking into account the widths of the slabs and the frequency dependence of permittivity and permeability of the LHM. The obtained results satisfy the law of conservation of energy. We show that if the semi-infinite dielectric media have the same refractive index and the slabs have the same width, then the reflected (and transmitted) powers can be minimized (and maximized) and the powers-frequency curves show no ripple. On the other hand if the semi-infinite dielectric media have different values of refractive indices and the slabs have different widths, then under certain conditions the situation of minimum and maximum values of the mentioned powers will be reversed
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