718 research outputs found
In the Milieu of Planning: The Micro and Meso Scales Climatic Effects in Urban Neighbourhoods in Nigeria
In several developing countries, urban centres are emerging at rapid rates. These urban centres are associated with increase in population as well as increase in social and economic activities resulting in the generation of huge wastes. They are also known as areas of intense constructions especially of buildings and roads. Most of these activities result in the cutting down of trees and deforestation thereby making surfaces to be bare or at best paved with bitumen or concrete. All these result in increase in temperature especially in areas within the urban centres without vegetal cover (treeless). This very much is the situation in many Nigerian urban centres including Lokoja North Central Nigeria. This paper posits and shows the contrast in temperature between neighbourhoods that have vegetal covers (tree communities) and those that do not have. It therefore highlights the benefit of the micro scale climatic effect of tree(s) on the meso scale climatic effect of a city or urban centre on itself. It further advocates for the greening of the study area (Lokoja) through the planting of trees, establishment of lawns, urban parks and gardens and the use of green roof options. This position is supported and based on the survey of local resilience strategies and measures used by the respondents and inhabitants of the study area in which 59% of the respondents make use of urban greening options among other coping measures such as lifestyle modification and building modification. Keywords: Micro and Meso-Scales Climatic Effects, Temperature, Urban Heat Island, Thermal Discomfort and Resilience
A Bedside Measure of Body Composition in Duchenne Muscular Dystrophy
Background In clinical practice, monitoring body composition is a critical component of nutritional assessment and weight management in boys with Duchenne muscular dystrophy. We aimed to evaluate the accuracy of a simple bedside measurement tool for body composition, namely bioelectrical impedance analysis, in boys with Duchenne muscular dystrophy. Methods Measures of fat-free mass were determined using a bioelectrical impedance analysis machine and compared against estimations obtained from a reference body composition model. Additionally, the use of raw impedance values was analyzed using three existing predictive equations for the estimation of fat-free mass. Accuracy of bioelectrical impedance analysis was assessed by comparison against the reference model by calculation of biases and limits of agreement. Results Body composition was measured in 10 boys with Duchenne muscular dystrophy, mean age 9.01 ± 2.34 years. The bioelectrical impedance analysis machine values of fat-free mass were on average 2.3 ± 14.1 kg higher than reference values. Limits of agreement (based on 95% confidence interval of the mean) were -7.4 to 2.9 kg. There was a significant correlation between the mean fat-free mass and difference in fat-free mass between the bioelectrical impedance analysis machine and the reference model (r = -0.86; P = 0.02) suggesting that the bias was not consistent across the range of measurements. The most accurate predictive equation for the estimation of fat-free mass using raw impedance values was the equation by Pietrobelli et al. (mean difference, -0.7 kg; 95% limits of agreement, -3.5 to 2.0 kg). Conclusions In a clinical setting, where a rapid assessment of body composition is advantageous, the use of raw impedance values, combined with the equation by Pietrobelli et al., is recommended for the accurate estimation of fat-free mass, in boys with Duchenne muscular dystrophy
Relations Between NC and CC Neutrino Structure Functions for Nucleons and Nuclei
The relations between neutrino NC and CC structure functions and cross
sections, which are driven by isospin symmetry, are discussed for nucleons and
nuclei.Comment: 6 pages, 2 figures, more references added, typos corrected. Talk at
3rd International Workshop On Neutrino Nucleus Interactions In The Few GeV
Region (NuInt04), 17-21 Mar 2004, Gran Sasso, Assergi, Ital
Analytic Estimates of the QCD Corrections to Neutrino-Nucleus Scattering
We study the QCD corrections to neutrino deep-inelastic scattering on a
nucleus, and analytically estimate their size. For an isoscalar target, we show
that the dominant QCD corrections to the ratio of the neutral- to
charged-current events are suppressed by sin^4 theta_W, where theta_W is the
weak mixing angle. We then discuss the implications for the NuTeV determination
of sin^2 theta_W.Comment: 16 pages, Late
Evaluation of silicon MOSFETs and GaN HEMTs in softâswitched and hardâswitched DCâDC boost converters for domestic PV applications
Hardâswitched highâgain DCâDC converters such as the boost converter play an important role in renewable energy systems. Research to increase their efficiency is important and can be achieved using softâswitching techniques; however, that approach requires an auxiliary circuit. The auxiliary circuit decreases power density and reliability while increasing the cost. Moreover, softâswitching topologies usually cannot improve the efficiency for all power and voltage ranges. Wide bandgap (WBG) devices, such as gallium nitride (GaN), result in lower switching losses than silicon (Si), can be used while retaining the simple structure of a hardâswitched topology. However, the high cost of these devices is problematic for their frequently costâsensitive applications. To quantify the cost and efficiency, this study compares softâswitching techniques and WBGâbased switches in DCâDC boost converters for a photovoltaic (PV) energy application. The performance of four prototypes including the softâswitched and hardâswitched DCâDC converters with both stateâofâtheâart Si and GaN switches are evaluated in terms of cost, power density, efficiency, and reliability using theoretical analysis, simulation and experimental results. It is shown that the GaNâbased hardâswitched converter provides higher efficiency and power density; it is more expensive than its Siâbased counterpart, yet is cheaper than softâswitched converters
Analysis, design and modelling of two fully- integrated transformers with segmental magnetic shunt for LLC resonant converters
To achieve a precise, high leakage inductance for an integrated magnetic transformer, a magnetic shunt (based on low- permeability materials) is usually added to the planar transformer. However, high-performance low-permeability power materials are not readily available in the market. Therefore, two new topologies for shunt-inserted planar transformer are proposed in this paper. In the proposed topologies, the magnetic shunts are based on high-permeability materials like ferrite, which is widely available, and use multiple small gaps to approximate a low-permeability material as an alternative to a low-permeability magnetic shunt. The analysis, design and modelling of the proposed planar transformers are presented in detail. It is shown that the magnetizing inductance can be controlled by vertical air gaps and the leakage inductance value can be controlled by the thickness of the shunt. Hence, the desirable leakage inductance and magnetizing inductance values for the integrated transformer can be obtained for use in LLC resonant converters. The theoretical analyses are verified by finite element analysis (FEA) and the AC resistance for the proposed topologies is discussed
Charge Symmetry Violation Corrections to Determination of the Weinberg Angle in Neutrino Reactions
We show that the correction to the Paschos-Wolfenstein relation associated
with charge symmetry violation in the valence quark distributions is
essentially model independent. It is proportional to a ratio of quark momenta
that is independent of Q^2. This result provides a natural explanation of the
surprisingly good agreement found between our earlier estimates within several
different models. When applied to the recent NuTeV measurement, this effect
significantly reduces the discrepancy with other determinations of the Weinberg
angle.Comment: 7 pages, no figures; expanded discussion of N.ne.Z correction
Locating Community among People with Schizophrenia living in a Diverse Urban Environment
Increasing the community participation of people with severe mental illness is a primary goal of recovery-oriented services. Despite this emphasis, the construct of community remains understudied and poorly articulated. This study provides an in-depth examination of the experiences, beliefs, behaviors, and spaces that constitute community participation for a highly diverse group of people with schizophrenia who are urban dwellers. An in-depth, longitudinal qualitative design was employed with 30 individuals with schizophrenia residing in inner-city neighborhoods in Canadaâs largest city. For these individuals, community participation is a dynamic process, shaped by illness and non-illness-associated social relationships and spaces, self-concept, and the resources accessible to the person. The complexity of factors that are associated with âcommunityâ for people with schizophrenia, with overlays of culture, poverty, victimization, and discrimination, calls for a critical examination of the community rhetoric employed in practice and policy contexts
Singleâactive switch highâvoltage gain DCâDC converter using a nonâcoupled inductor
A singleâactive switch highâvoltage gain nonâcoupled inductor DCâDC converter is presented. The introduced converter achieves high stepâup gain without using any coupled inductors or transformers, provides high efficiency, and has a simple control system. The converter also achieves low voltage stress on the switch and diodes without clamping circuits, reducing cost, conduction losses, and complexity. The input current of the introduced converter is continuous with low ripple, and is therefore suitable for renewable energy applications in which the fast dynamic response of the converter is necessary. The principle of operation and design considerations of the introduced converter are investigated. A 200 W prototype circuit with 40 kHz switching frequency, 40 V input voltage, and 250 V output voltage is implemented. The prototype operates at 93.2% efficiency, with voltage and current error of less than 4% compared to theoretical values
Application of B-splines to determining eigen-spectrum of Feshbach molecules
The B-spline basis set method is applied to determining the rovibrational
eigen-spectrum of diatomic molecules. A particular attention is paid to a
challenging numerical task of an accurate and efficient description of the
vibrational levels near the dissociation limit (halo-state and Feshbach
molecules). Advantages of using B-splines are highlighted by comparing the
performance of the method with that of the commonly-used discrete variable
representation (DVR) approach. Several model cases, including the Morse
potential and realistic potentials with 1/R^3 and 1/R^6 long-range dependence
of the internuclear separation are studied. We find that the B-spline method is
superior to the DVR approach and it is robust enough to properly describe the
Feshbach molecules. The developed numerical method is applied to studying the
universal relation of the energy of the last bound state to the scattering
length. We numerically illustrate the validity of the quantum-defect-theoretic
formulation of such a relation for a 1/R^6 potential.Comment: submitted to can j phys: Walter Johnson symposu
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