Mapping the Impacts of Anthropogenic Activities on Vegetation in the Area Councils of FCT using Remote Sensing

Globally, amongst all the factors threatening the existence of landcover in the biosphere, agriculture and urbanization plays the most potent role aside from the natural factor of climate. The study examines the effect of human factors on vegetal cover and identifies the drivers of the changes within the area councils of the FCT over a period of three decades. The need to conserve limited natural resources is threaten by the effect of increased population and their continuous anthropogenic activities on this limited resource, thus the vegetation cover which represents an important natural resource for both humans and other species is lost due to reckless and unsustainable usage. Using geospatial techniques, the magnitude of human activities of development is assessed as it affects vegetation cover. The results of the analysis show a tremendous impact of anthropogenic activities as the landcover continue to deplete from 1987 – 2016. Human impacts were identified as the major driver of vegetal cover change in all area councils as it increases from 11510.89km2 to 85563.01km2 in AMAC, 765.55km2 to 82820.74km2 in Gwagwalada, 1621.73km2 to 54267km2 in Kwali, 1259.49km2 to 4985.56km2 in Abaji, 6621.80km2 to 34295.20km2 in Kuje and 15678.82km2 to 24925.94km2 in Bwari.The study recommends that continuous inventory of human impacts should be carried out to check mate the unsustainable management practices of human induced activities in the study area. It concludes that anthropogenic activities are on the rise thus measures should be taken to mitigate its effects to ensure better environmental sustainability

Coen Beeker’s ‘Urban Fields’ for Addis Ababa

Cities under rapid urbanization such as Addis Ababa offer a set of challenges for today’s designers and planners. The urgent need for access to affordable and decent living environments presses city administrations, whose primary response tends to be a top-down approach of public housing projects and allocating plots through a bidding process in which only the affluent become beneficiaries. Such socially selective approaches usually segregate urban dwellers into economic classes and fall short of providing affordable housing options. The formal and informal horizontal sprawl of the city has continued unabated since the mid-1970s and has gained even stronger momentum in the past decade. It is important today to consider options that allow integration instead of segregation and to find options for legal and planned urban environments that deal with peripheral urbanisation. Coen Beeker’s ‘step-by-step’ process of urbanization, which allows gradual changes that promote incremental and adaptable formation of ‘urban fields’ in the peripheries of Addis Ababa, illustrates the possibilities. He argues that access to legally tenured plots of land and further urbanization through measured steps is crucial for developing affordable and cohesive communities in these areas. This paper is an analysis of the pertinent challenges faced by the city of Addis Ababa in relation to peripheral urbanisation and an assessment of Coen Beeker’s proposal to deal with these challenges.OLD Woningbou

Addis Ababa's Sefer, Iddir, and Gebbi: Nuanced reading of complex urban forms

This research is motivated by the scholarly calls for new concepts and analytic tools for documenting, analysing, and theorizing complex urban territories such as those of cities in Africa. With implicit comparative intent, it takes the case of Addis Ababa city and its old and typifying places—the sefer, to develop and test a new architectural transdisciplinary research methodology referred to as the trinocular. By way of this methodology, it unearths and introduces sefer, iddir, and gebbi of Addis Ababa as not only socio-spatial phenomena but concepts and vocabulary for a located and nuanced reading of the city itself. Sefer are introduced as flexible boundary conditions that are primarily cognized by their dwellers—results of indigenous and autochthonous foundation and continued processes of self-actualization by communities that construct them. Iddir is unearthed as a form of social capital embedded in sefer that appears in the structures of relations among residents. And the gebbi as an urban spatial typology that constitutes the sefer’s morphology—the last frontier of communality just prior domestic spaces which, in many cases, can be a single multi-functional room.These concepts and vocabulary, it is argued, in both practical and metaphoric sense, should be the starting point of new urban imaginaries for Addis Ababa. Urban planning and housing projections thus, should draw inspiration from these notions, elements, and phenomena. Furthermore, lessons learnt from the trinocular and the findings are presented as new avenues for architectural research in similar, less-known, and complex urban conditions as the sefer of Addis Ababa.Space & Typ

Design of log domain differential class AB universal biquad filter by employing lossy integrators

A new current mode low voltage differential Class AB second order universal biquad filter has been designed in this work. In design process, inspiring from Kerwin-Huelsman-Newcomb circuit, the circuit is realized with lossy integrators. The circuit has fundamental filter outputs namely; low pass, high pass and band pass. All pass and notch filter outputs have also been obtained by using additional circuits. In circuit design process, the state space method and translinear principle have been used. Two of the circuit parameters are electronically tunable which are the quality factor Q and the pole frequency f0. PSpice circuit simulations have been obtained to check the theoretical results' validity. In PSpice simulations, both ideal and AT&T CBIC-R type real transistor models have been used. © 2018 National Institute of Science Communication and Information Resources (NISCAIR). All rights reserved

Second order class a log domain all pass filter design employing lossy integrators

In this study, a new Class A second order log domain all pass filter is designed by using lossy integrators. An all pass filter has unity gain at all frequencies. It also shifts phase at desired value at the given frequency of the input signal. The proposed filter circuit design is based on Kerwin-Huelsman-Newcomb (KHN) block diagram by using lossy integrators. The circuit is synthesized by using state space synthesis method and the translinear principle. The natural frequency f0 of the circuit is electronically tunable by varying amplitudes of the current sources. PSpice simulation results are given to verify the theoretical analysis. The simulations are performed with both ideal transistor models and AT&T CBIC-R type real transistor models. © 2016 IEEE

Design of the third order elliptic filter with seevinck type dummy inputs in the log domain using the state space synthesis method

In this paper, a current mode, third order, elliptic filter is synthesized in the log domain. The state space synthesis method is used for the design procedure. Seevinck type dummy inputs are used in order to realize a Class AB and differential type elliptic filter for the first time. Initially, ideal transistors with infinite forward gain are used for PSpice simulations in order to verify the validity of the mathematical derivations. The AC response of the filter was as predicted. Using CBIC-R type real transistors, the simulations are repeated. Some minor differences between ideal and real transistors' responses are observed and the results are discussed. On the other hand, for the time domain analysis, the circuit is driven by a signal at the filter's comer frequency, i.e. f=100 kHz. This response was also as predicted. © 2005 IEEE

Study of different class AB log domain first order filters

Several different class AB log-domain/translinear filters are compared in terms of their noise and distortion behavior using both analytical and simulation results. A few of the circuit topologies shown have not been considered before and are derived using a new theory for class AB dynamical circuits recently proposed. The study, although approximate, suggests ways in which both noise and distortion performance may be optimized by appropriate choice of circuit topology. Other practical aspects of the designs are also discussed

Fifth order butterworth low pass square-root domain filter design

In this study, two different fifth order square-root domain low pass Butterworth filters are designed. First filter is designed directly from fifth order transfer function. Second filter is obtained by cascading one first order and two second order filters. Both filters are designed by using state space synthesis method and constituted by current mirrors, square-root circuits, current sources and capacitors. Proposed filters are simulated by PSpice using 3V supply voltage and 0.35μm CMOS technology parameters. Both filters simulation results are compared. Ill. 6, bibl. 12 (in English; abstracts in English and Lithuanian)

High frequency log domain all pass filter based on KHN topology

In this study, a current mode Log domain Class AB differential type all pass filter based on KHN structure has been synthesized by using the state space method and by adopting translinear circuits for the first time. The proposed circuit is synthesized for high frequency applications, i.e. around 100 MHz. Varying the values of the current sources of the circuit, the natural frequency of the filter can be tuned electronically. The circuit is simulated in PSpice by using both idealized and real transistors that are suitable for high frequency operations. Simulations showed that amplitude response of the system remains almost constant for 6 decades between 10 kHz and 10 GHz. Moreover, natural frequency of the filter can be set by electronically changing the source currents between 2 mA and 7 mA. In addition to these simulations, THD and noise analysis are carried out. The obtained results are given. © 2008 IEEE

Fully controllable first order current mode universal filter composed of bjts and a grounded capacitor

In this paper, a new BJT based configuration for providing first order current mode high-pass, low-pass and all-pass filter responses from the same configuration is suggested. The proposed circuit called as a universal filter possesses some important advantages such as consisting of low component count BJT and a grounded capacitor, having electronic tunability property of its pole frequency and having electronic controllability feature of filter types. The suggested circuit does not suffer from disadvantages of use of the resistors. Moreover, as an application, second order band-pass filter is also obtained by cascading two proposed filter structure. Simulations by means of PSpice program are accomplished to demonstrate the performance and effectiveness of the developed first-order universal filter. Approximately more than 1 decade tunability range is achieved. Ill. 7, bibl. 14, tabl. 3 (in English; abstracts in English and Lithuanian)