647 research outputs found
"Free Dawit Isaak"
No full textThe author joined the World Press Freedom Day campaign this year, 2011, to highlight the plight of WAN-IFRA's 2011 Golden Pen of Freedom laureate, Dawit Isaak, incarcerated without charge for nearly a decade in a notorious Eritrean jail. In this editorial Peter Englund explores how the right to dissent and question strengthens a nation, and that this universal right cannot be taken for granted.Isaak, Dawit Isaak, press freedom, World Press Freedom Day, right to dissent, democracy, freedom
Determination of 1-aminopropan-2-one, a dissolved sewage component, in water samples
No full textA new method for the determination of 1-aminopropan-2-one (APR) in water samples was developed. APR was synthesised as its hydrochloride and derivatized with 2,4-dinitrophenylhydrazine (DNPH) for determination by high-pressure liquid chromatography with ultraviolet detection (UV-HPLC). APR was determined in water samples at pH 12 using a gas-stripping chamber, connected to a cartridge containing DNPH. Acidified water samples were injected into the gas-stripping chamber and a solution of NaOH added to bring the solution to pH 12. APR was volatilised and stripped from solution and passed onto the cartridge under a constant stream of nitrogen gas. Gas flow rates were carefully controlled to allow maximum contact of APR with DNPH on the cartridge. When the reaction time had elapsed, the cartridge was disconnected and the derivative eluted with a fixed volume of acetonitrile and injected onto the HPLC, where the APR hydrazone was resolved isocratically with a mobile phase consisting of acetonitrile and water (60 : 40). The HPLC was calibrated using standard solutions of the APR hydrazone. Recoveries of APR from standard samples were 90–100% at the 10 ?M level and the detection limit for the method was calculated as 18 nM. Detection of APR in urine and primary-treated sewage samples (41 nM and 1.225 ?M, respectively) confirmed the applicability of the technique to analysis of environmental samples
Drain Induced Barrier Widening and Reverse Short Channel Effects in Tunneling FETs: Investigation and Analysis
No full textIn this paper, using calibrated TCAD simulations, we demonstrate how the performance of a Tunneling FET (TFET) can be improved by using a new phenomenon called drain induced barrier widening (DIBW) at the source-channel junction. Our results indicate that TFETs in which DIBW dominates exhibit a steep subthreshold swing (≈35 mV/dec) and a low OFF-state current ( ) without affecting the ON-state current. We also show that TFETs exhibit a reverse short channel effect due to an increase in the tunneling width at the source-channel junction
Policies to promote cereal intensification in Ethiopia: A review of evidence and experience
No full textDawit Alemu: DCA, EthiopiaCereal crops, Agricultural development, Agricultural extension work, Fertilizers, Seed industry and trade Developing countries, Public investment, Food policy,
Representation discovery in non-parametric reinforcement learning
No full textThesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2014.Cataloged from PDF version of thesis.Includes bibliographical references (pages 71-73).Recent years have seen a surge of interest in non-parametric reinforcement learning. There are now practical non-parametric algorithms that use kernel regression to approximate value functions. The correctness guarantees of kernel regression require that the underlying value function be smooth. Most problems of interest do not satisfy this requirement in their native space, but can be represented in such a way that they do. In this thesis, we show that the ideal representation is one that maps points directly to their values. Existing representation discovery algorithms that have been used in parametric reinforcement learning settings do not, in general, produce such a representation. We go on to present Fit-Improving Iterative Representation Adjustment (FIIRA), a novel framework for function approximation and representation discovery, which interleaves steps of value estimation and representation adjustment to increase the expressive power of a given regression scheme. We then show that FIIRA creates representations that correlate highly with value, giving kernel regression the power to represent discontinuous functions. Finally, we extend kernel-based reinforcement learning to use FIIRA and show that this results in performance improvements on three benchmark problems: Mountain-Car, Acrobot, and PinBall.by Dawit Zewdie.M. Eng
Performance evaluation of space time trellis coded MIMO for mobile communications
No full textThe major enemy of wireless communication is multipath fading that highly degrades the received signal. Spatial diversity highly reduces deep fades of the wireless communication. Higher signal to noise ratio (SNR) requirement can be reduced by using space time coding. In this paper, the error performance of un-coded MIMO, different diversity combing methods, space time block codes and space time trellis codes are analyzed using different parameters including number of antennas, M-array modulations, trace criteria, rank and determinant. The simulation results have shown that the Bit Error Rate (BER) significantly reduces with increasing number of receiver antennas. However, the number of antennas that a mobile device can have is limited by its size and this is inconvenient for mobile communication. Hence, this paper suggests space time codes to mitigate multipath problems in mobile communication. So, BER performance of space time block codes scheme was evaluated by varying the number of transmitter and receiver antennas along with varying M-array PSK modulation orders. The results have shown that better BER is possible by integrating space time codes with spatial diversity. Finally, the error performance of space time trellis codes was evaluated by using trace, rank and determinant, and the simulation results depicted that better error performance is achieved using the proposed multipath reduction method
Extended Methodology to Determine SRAM Write Margin in Resistance-Dominated Technology Node
No full textAn extended write-ability methodology of static random-access memory (SRAM) in advanced technology nodes is proposed in this article. Increased bitline (BL) resistance in sub-10 nm node has hindered BL from fully discharge during a write operation. Furthermore, the write ability is degraded by an increased leakage current of half-selected bitcells on BL and BL capacitance operated in high frequency. In a realistic write operation, BL parasitics also cause 30% SRAM yield loss in interconnect resistance-dominated technology nodes. Thus, this proposed method analyzes the time-dependent impacts of BL parasitic resistors, capacitors, and pass-gate (PG) transistors on write margin considering the negative BL (NBL) assist technique.status: Publishe
Modelling the spatial distribution of three marine fish species in the southern Benguela
No full textUnderstanding the spatial distribution of species in relationship to climatic and environmental variables is key to conservation and management of important species, as their distribution might change under climate change and variability. Based on presence absence data from scientific trawl surveys, this study used Generalized Additive Model (GAM) and Krigging with External Drift (KED) statistical techniques to determine the spatial distribution of three marine fish species of commercial interest: Merluccius capensis, Merluccius paradoxus, and Thyrsites atun, on the West and South coasts of South Africa. The modelled distributions reflect the previously determined range and habitats of the two species of hake and are in accordance with the common knowledge on the biology of the two species. Presence-absence modelling found depth to be the main factor for explaining hake distribution on both coasts. For the West coast an interaction between sea surface temperature and chlorophyll-a combined with depth as a factor was found to provide the best model. On the South coast depth was the only factor retained. The models for M. capensis and M. paradoxus are potentially useful in mapping and determining future distributions based on environmental factors. The model obtained for the spatial distribution of T. atun has a lower explanatory power than those of the two hake species
Adoption of agricultural technologies visa vis agricultural extension in Ethiopia: Theoretical tenets and empirical evidences
No full textThe author explains different Adoption estimation methods, gives examples about Adoption levels on the field in Ethiopia, discusses Factors affecting adoption, compares Adoption and yield gaps and issues the Implications for research and development during his presentation
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